AP-42
Edition
September 1985
COMPILATION
OF
AIR POLLUTANT
EMISSION FACTORS
Volume I:
Stationary Point
And Area Sources
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office Of Air And Radiation
Office Of Air Quality Planning And Standards
Research Triangle Park, North Carolina 27711
September 1985
For sale by the Superintendent of Documents, U.S. Government Printing Office
Washington, DC 20402
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This report has been reviewed by The Office of Air Quality Planning And Standards, U. S. Environmental
Protection Agency, a nd has been approved for publication. Mention of trade names or commercial products is
not intended to constitute endorsement or recommendation for use.
Volume I
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PUBLICATIONS IN SERIES
Issue Date
COMPILATION OF AIR POLLUTANT EMISSION FACTORS
(Fourth Edition) 9/85
iii 9/85
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PREFACE TO THE FOURTH EDITION
VOLUME I: STATIONARY POINT AND AREA SOURCES
Compilation of Air Pollutant Emission Factors, AP-42, reports data on
emissions of atmospheric pollutants for which sufficient information exists
to establish realistic emission factors. The information herein is based on
Public Health Service Publication 999-AP-42, Compilation Of Air Pollutant
EmigsjLon Factors, by R. L. Duprey, and on three ensuing revised and expanded
editions of Compilation Of Air Pollutant Emission Factors as published by the
U. S. Environmental Protection Agency in February 1972, April 1973 and February
1976.
The present document comprises the Third Edition and all Supplements issued
since it appeared in February 1976. Also included here are seven newly revised
Sections of AP-42, with information recently developed for AP-42 users. These
new data will be found in the following:
Section 4.3 Storage Of Organic Liquids
Section 4.4 Transportation And Marketing Of Petroleum Liquids
Section 8.11 Glass Fiber Manufacturing
Section 8.19 Construction Aggregate Processing
Section 11.2.1 Unpaved Roads
Section 11.2.5 Paved Urban Roads
Section 11.2.6 Industrial Paved Roads
Chapters and Sections of this document are arranged in a format that
permits easy and convenient replacement of material, whenever information
reflecting more accurate and refined emission factors should be published and
distributed. For easy addition of any future materials, the loose leaf format
continues to be used. This approach permits the document to be placed in a
ring binder or to be secured by rings, rivets or other fasteners. A bottom
corner of each page bears the date the information was issued.
For the Fourth Edition, stationary point and area sources have been
collected as Volume I. Mobile sources, formerly in Chapter 3.0, are now
separated Into Volume II. Also, commensurate with the designation of lead as
a criteria pollutant, lead emission factors formerly in Appendix E have been
incorporated into the appropriate Sections. For persons unfamiliar with the
contents of AP—42, an alphabetic cross reference index has been added following
the Contents.
Comments and suggestions regarding this document are appreciated and should
be sent to the Director, Monitoring And Data Analysis Division, MD-14, U. S,
Environmental Protection Agency, Research Triangle Park, NC 27711.
IV
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CONTENTS
Page
INTRODUCTION 1
1. EXTERNAL COMBUSTION SOURCES 1.1-1
1.1 Bituminous Coal Combustion 1.1-1
1.2 Anthracite Coal Combustion 1.2-1
1.3 Fuel Oil Combustion 1.3-1
1.4 Natural Gas Combustion 1.4-1
1.5 Liquified Petroleum Gas Combustion 1.5-1
1.6 Wood Waste Combustion In Boilers 1.6-1
1.7 Lignite Combustion 1.7-1
1.8 Bagasse Combustion In Sugar Mills 1.8-1
1.9 Residential Fireplaces 1.9-1
1.10 Residential Wood Stoves 1.10-1
1.11 Waste Oil Combustion 1.11-1
2. SOLID WASTE DISPOSAL 2.0-1
2.1 Refuse Combustion 2.1-1
2.2 Automobile Body Incineration 2.2-1
2.3 Conical Burners 2.3-1
2.4 Open Burning 2.4-1
2.5 Sewage Sludge Incineration 2.5-1
3. STATIONARY INTERNAL COMBUSTION SOURCES 3.0-1
Glossary Of Terms Vol. II
Highway Vehicles Vol. II
Off Highway Mobile Sources Vol. II
3.1 Off Highway Stationary Sources 3.1-1
4. EVAPORATION LOSS SOURCES 4.1-1
4.1 Dry Cleaning 4.1-1
4.2 Surface Coating 4.2-1
4.3 Storage Of Organic Liquids 4.3-1
4.4 Transportation And Marketing Of Petroleum Liquids 4.4-1
4.5 Cutback Asphalt, Emulsified Asphalt And Asphalt Cement .. 4.5-1
4.6 Solvent Degreasing 4.6-1
4.7 Waste Solvent Reclamation . . . 4.7-1
4.8 Tank And Drum Cleaning 4.8-1
4.9 Graphic Arts 4.9-1
4.10 Commercial/Consumer Solvent Use 4.10-1
4.11 Textile Fabric Printing 4.11-1
5. CHEMICAL PROCESS INDUSTRY 5.1-1
5.1 Adipic Acid 5.1-1
5.2 Synthetic Ammonia 5.2-1
5.3 Carbon Black 5.3-1
5.4 Charcoal 5.4-1
5.5 Chlor-Alkali 5.5-1
5.6 Explosives 5.6-1
5.7 Hydrochloric Acid 5.7-1
5.8 Hydrofluoric Acid 5.8-1
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Page
5.9 Nitric Acid 5.9-1
5 .10 Paint And Varnish 5.10-1
5.11 Phosphoric Acid 5.11-1
5.12 Phthalic Anhydride 5.12-1
5.13 Plastics 5.13-1
5 .14 Printing Ink 5 .14-1
5.15 Soap And Detergents 5.15-1
5.16 Sodium Carbonate 5.16-1
5.17 Sulfuric Acid 5.17-1
5.18 Sulfur Recovery 5.18-1
5.19 Synthetic Fibers 5.19-1
5.20 Synthetic Rubber ; 5.20-1
5 . 21 Terephthalic Acid 5.21-1
5.22 Lead Alkyl 5.22-1
5.23 Pharmaceuticals Production 5 . 23-1
5.24 Maleic Anhydride 5.24-1
6. FOOD AND AGRICULTURAL INDUSTRY 6.1-1
6.1 Alfalfa Dehydrating 6.1-1
6.2 Coffee Roasting 6.2-1
6.3 Cotton Ginning 6.3-1
6.4 Grain Elevators And Processing Plants 6.4-1
6.5 Fermentation 6.5-1
6.6 Fish Processing 6.6-1
6.7 Meat Smokehouses 6.7-1
6.8 Ammonium Nitrate Fertilizers 6.8-1
6.9 Orchard Heaters 6.9-1
6 .10 Phosphate Fertilizers 6.10-1
6.11 Starch Manufacturing 6.11-1
6.12 Sugar Cane Processing 6.12-1
6.13 Bread Baking 6.13-1
6.14 Urea 6.14-1
6 .15 Beef Cattle Feedlots 6 .15-1
6.16 Defoliation And Harvesting Of Cotton 6.16-1
6.17 Harvesting Of Grain 6.17-1
6.18 Ammonium Sulfate 6.18-1
7. METALLURGICAL INDUSTRY 7.1-1
7.1 Primary Aluminum Production 7.1-1
7.2 Coke Production 7.2-1
7.3 Primary Copper Smelting 7.3-1
7.4 Ferroalloy Production 7.4-1
7.5 Iron And Steel Production 7.5-1
7.6 Primary Lead Smelting 7.6-1
7.7 Zinc Smelting 7.7-1
7.8 Secondary Aluminum Operations 7.8-1
7.9 Secondary Copper Smelting And Alloying 7.9-1
7.10 Gray Iron Foundries 7.10-1
7.11 Secondary Lead Processing 7.11-1
7.12 Secondary Magnesium Smelting 7.12-1
7.13 Steel Foundries 7.13-1
VI
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Page
7.14 Secondary Zinc Processing 7.14-1
7.15 Storage Battery Production 7.15-1
7.16 Lead Oxide And Pigment Production 7.16-1
7.17 Miscellaneous Lead Products 7.17-1
7.18 Leadbearing Ore Crushing And Grinding /. 7.18-1
8. MINERAL PRODUCTS INDUSTRY 8.1-1
8.1 Asphaltic Concrete Plants 8.1-1
8.2 Asphalt Roofing 8.2-1
8.3 Bricks And Related Clay Products 8.3-1
8.4 Calcium Carbide Manufacturing 8.4-1
8.5 Castable Refractories 8.5-1
8.6 Portland Cement Manufacturing 8.6-1
8.7 Ceramic Clay Manufacturing 8.7-1
8.8 Clay And Fly Ash Sintering 8.8-1
8.9 Coal Cleaning 8.9-1
8.10 Concrete Batching 8.10-1
8.11 Glass Fiber Manufacturing 8.11-1
8.12 Frit Manufacturing 8.12-1
8.13 Glass Manufacturing 8.13-1
8.14 Gypsum Manufacturing 8.14-1
8;15 Lime Manufacturing 8.15-1
8.16 Mineral Wool Manufacturing 8.16-1
8.17 Perlite Manufacturing 8.17-1
8.18 Phosphate Rock Processing 8.18-1
8.19 Construction Aggregate Processing 8.19-1
8.20 [Reserved] 8.20-1
8.21 Coal Conversion 8.21-1
8.22 Taconite Ore Processing 8.22-1
8.23 Metallic Minerals Processing 8.23-1
8.24 Western Surface Coal Mining 8.24-1
9. PETROLEUM INDUSTRY 9.1-1
9.1 Petroleum Refining 1 9.1-1
9.2 Natural Gas Processing 9.2-1
10. WOOD PRODUCTS INDUSTRY 10.1-1
10.1 Chemical Wood Pulping 10.1-1
10.2 Pulpboard 10.2-1
10.3 Plywood.Veneer And Layout Operations 10.3-1
10.4 Woodworking Waste Collection Operations 10.4-1
.11. MISCELLANEOUS SOURCES 11.1-1
11.1 Wildfires And Prescribed Burning 11.1-1
11.2 Fugitive Dust Sources 11.2-1
11.3 Explosives Detonation 11.3-1
APPENDIX A Miscellaneous Data And Conversion Factors A-l
vii
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KEY WORD INDEX
Acid
Adipic 5.1
Hydrochloric 5.7
Hydrofluoric 5.8
Phosphoric 5.11
Sulfuric 5.17
Terephthalic 5.21
Adipic Acid 5.1
Aggregate, Construction 8.19
Aggregate Storage Piles
Fugitive Dust Sources 11.2
Agricultural Tilling
Fugitive Dust Sources 11.2
Alfalfa Dehydrating 6.1
Alkali, Chlor- 5.5
Alloys
Ferroalloy Production 7.4
Secondary Copper Smelting And Alloying 7.9
Aluminum
Primary Aluminum Production 7.1
Secondary Aluminum Operations 7.8
Ammonia, Synthetic 5.2
Ammonium Nitrate Fertilizers 6.8
Anhydride, Phthalic 5.12
Anthracite Coal Combustion 1.2
Ash
Fly Ash Sintering 8.8
Asphalt
Cutback Asphalt, Emulsified Asphalt And Asphalt Cement 4.5
Roofing 8.2
Asphaltic Concrete Plants 8.1
Automobile Body Incineration 2.2
Bagasse Combustion In Sugar Mills 1.8
Baking, Bread 6.13
Bark
Wood Waste Combustion In Boilers 1.6
Batching, Concrete • 8.10
Battery
Storage Battery Production 7 .15_
Beer Production
Fermentation 6.5
Bituminous Coal Combustion 1*1
Bread Baking 6 .13
Bricks And Related Clay Products • • 8.3
Burners, Conical (Teepee) -• 2.3"~
Burning, Open 2.4
ix
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Calcium Carbide Manufacturing 8.4
Cane
Sugar Cane Processing 6.12
Carbon Black 5.3
Carbonate
Sodium Carbonate Manufacturing 5.16
Castable Refractories 8.5
Cattle
Beef Cattle Feedlots 6.15
Cement
Asphalt 4.5
Portland Cement Manufacturing 8.6
Ceramic Clay Manufacturing 8.7
Charcoal 5.4
Chemical Wood Pulping 10.1
Chlor-Alkali 5.5
Clay
Bricks And Related Clay Products. 8.3
Ceramic Clay Manufacturing 8.7
Clay And Fly Ash Sintering.. ;..... 8.8
Cleaning
Coal 8.9
Dry 4.1
Tank And Drum 4.8
Coal
Anthracite Coal Combustion 1.2
Bituminous Coal Combustion 1.1
Cleaning 8.9
Conversion 8.21
Coating, Surface 4.2
Coffee Roasting 6.2
Coke Manufacturing 7.2
Combustion
Anthracite Coal 1.2
Bagasse, In Sugar Mills 1.8
Bituminous Coal 1.1
Fuel Oil 1.3
Internal Vol. II
Lignite 1.7
Liquified Petroleum Gas 1.5
Natural Gas 1.4
Orchard Heaters 6.9
Residential Fireplaces 1.9
Waste Oil 1-11
Wood Stoves 1.10
Concrete
Asphaltic Concrete Plants 8.1
Concrete Batching 8.10
Conical (Teepee) Burners 2.3
Construction Aggregate 8.19
Construction Operations
Fugitive Dust Sources 11.2
Conversion, Coal 8 .21
Wood Waste In Boilers 1-6
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Copper
Primary Copper Smelting 7.3
Secondary Copper Smelting And Alloying 7.9
Cotton
Defoliation And Harvesting 6.16
Ginning 6.3
Dacron
Synthetic Fibers 5.19
Defoliation, Cotton 6.16
Degreasing, Solvent 4.6
Dehydrating, Alfalfa 6.1
Detergents
Soap And Detergents 5.15
Detonation, Explosives 11.3
Drum
Tank And Drum Cleaning 4.8
Dry Cleaning 4.1
Dust
Fugitive Dust Sources 11.2
Elevators, Feed and Grain Mills 6.4
Explosives 5.6
Explosives Detonation 11.3
Feed
Beef Cattle Feedlots 6.15
Feed And Grain Mills And Elevators 6.4
Fermentation 6.5
Fertilizers
Ammonium Nitrate 6.8
Phosphate 6.10
Ferroalloy Production 7.4
Fiber
Glass Fiber Manufacturing 8.11
Fiber, Synthetic 5.19
Fires
Forest Wildfires 11.1
Fireplaces, Residential 1.9
Fish Processing 6.6
Fly Ash
Clay And Fly Ash Sintering '. 8.8
Foundries
Gray Iron Foundries 7 .10
Steel Foundries 7.13
Frit Manufacturing 8.12
Fuel Oil Combustion 1.3
Fugitive Dust Sources 11.2
Gas Combustion, Liquified Petroleum 1.5
Gas, Natural
Natural Gas Combustion 1.4
Natural Gas Processing 9.2
Ginning, Cotton 6.3
xi
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Glass Manufacturing 8.13
Glass Fiber Manufacturing 8.11
Grain
Feed And Grain Mills And Elevators 6.4
Harvesting Of Grain 6.17
Gravel
Sand And Gravel Processing 8.19
Gray Iron Foundries 7.10
Gypsum Manufacturing 8.14
Harvesting
Cotton 6.16
Grain 6.17
Heaters, Orchard 6.9
Hydrochloric Acid 5.7
Hydrofluoric Acid •. 5.8
Incineration
Automobile Body 2.2
Conical (Teepee) 2.3
Refuse 2.1
Sewage Sludge 2.5
Ink, Printing 5.14
Internal Combustion Engines
Highway Vehicles Vol. II
Off Highway Mobile Sources Vol. II
Off Highway Stationary Sources 3.3
Iron
Ferroalloy Production 7.4
Gray Iron Foundries 7.10
Iron And Steel Mills 7.5
Taconite Ore Processing 8.22
Lead
Leadbearing Ore Crushing And Grinding 7 .18
Miscellaneous Lead Products 7.17
Primary Lead Smelting 7.6
Secondary Lead Smelting 7.11
Lead Alkyl 5.22
Lead Oxide And Pigment Production 7.16
Leadbearing Ore Crushing And Grinding 7.18
Lignite Combustion. 1.7
Lime Manufacturing 8.15
Liquified Petroleum Gas Combustion 1.5
Magnesium
Secondary Magnesium Smelting 7.12
Maleic Anhydride 5.24
Marketing
Transportation And Marketing Of Petroleum Liquids 4.4
Meat Smokehouses 6.7
Mineral Wool Manufacturing 8.16
xii
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Mobile Sources
Highway Vol. II
Off Highway Vol. II
Natural Gas Combustion 1.4
Natural Gas Processing 9.2
Nitric Acid Manufacturing 5.9
Off Highway Mobile Sources Vol. II
Off Highway Stationary Sources 3.3
Oil
Fuel Oil Combustion 1.3
Waste Oil Combustion 1.11
Open Burning 2.4
Orchard Heaters 6.9
Ope Processing
Leadbearing Ore Crushing And Grinding 7 .18
Taconite 8.22
Organic Liquids, Storage 4.3
Paint And Varnish Manufacturing 5.10
Paved Roads
Fugitive Dust Sources 11.2
Perlite Manufacturing 8.17
Petroleum
Liquified Petroleum Gas Combustion 1.5
Refining 9.1
Storage Of Organic Liquids 4.3
Transportation And Marketing Of Petroleum Liquids 4.4
Pharmaceuticals Production 5.23
Phosphate Fertilizers 6.10
Phosphate Rock Processing 8.18
Phosphoric Acid 5.11
Phthalic Anhydride 5 .12
Pigment
Lead Oxide And Pigment Production 7 .16
Plastics 5 .13
Plywood Veneer And Layout Operations 10.3
Portland Cement Manufacturing 8.6
Printing Ink 5 .14
Pulpboar d 10.2
Pulping, Chemical Wood 10.1
Reclamation, Waste Solvent 4.7
Recovery, Sulfur 5.18
Refractories, Castable 8.5
Residential Fireplaces 1.9
Roads, Paved
Fugitive Dust Sources 11.2
Roads, Unpaved
Fugitive Dust Sources 11.2
Roasting Coffee 6.2
Rock
Phosphate Rock Processing 8.18
xiii
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Roofing, Asphalt 8.2
Rubber, Synthetic 5.20
Sand And Gravel Processing 8,19
Sewage Sludge Incineration 2.5
Sintering, Clay And Fly Ash 8.8
Smelting
Primary Copper Smelting 7.3
Primary Lead Smelting 7.6
Secondary Copper Smelting And Alloying 7.9
Secondary Lead Smelting 7.11
Secondary Magnesium Smelting 7.12
Zinc Smelting 7.7
Smokehouses, Meat 6.7
Soap And Detergent Manufacturing 5.15
Sodium Carbonate Manufacturing 5.16
Solvent
Commercial/Consumer Use 4.10
Solvent Degreasing 4.6
Waste Solvent Reclamation 4.7
Starch Manufacturing 6.11
Stationary Sources, Off Highway 3.3
Steel
Iron And Steel Mills 7.5
Steel Foundries 7.13
Storage Battery Production 7.15
Storage Of Organic Liquids 4.3
Sugar Cane Processing 6.12
Sugar Mills, Bagasse Combustion In 1.8
Sulfur Recovery 5.18
Sulf uric Acid 5.17
Surface Coating 4.2
Synthetic Ammonia 5.2
Synthetic Fiber 5.19
Synthetic Rubber 5.20
Taconite Ore Processing 8.22
Tank And Drum Cleaning 4.8
Terephthalic Acid 5.21
Tilling, Agricultural
Fugitive Dust Sources 11.2
Transportation And Marketing Of Petroleum Liquids 4.4
Unpaved Roads
Fugitive Dust Sources 11.2
Urea 6.14
Varnish
Paint And Varnish Manufacturing 5.10
Vehicles, Highway And Off Highway Vol. II
Waste Solvent Reclamation 4.7
Waste Oil Combustion 1.11
xiv
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Whiskey Production
Fermentation 6.5
Wildfires, Forest 11.1
Wine Making
Fermentation. 6.5
Wood Pulping, Chemical.. 10.1
Wood Stoves 1.10
Wood Waste Combustion In Boilers 1.6
Woodworking Waste Collection Operations 10.4
Zinc
Secondary Zinc Processing 7.14
Smelting 7.7
xv
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COMPILATION OF AIR POLLUTANT EMISSION FACTORS
VOLUME I:
STATIONARY POINT AND AREA SOURCES
Introduction
What is an emission factor?
An emission factor is an average value which relates the quantity of a
pollutant released to the atmosphere with the activity associated with the
release of that pollutant. It is usually expressed as the weight of pollutant
divided by a unit weight, volume, distance or duration of the activity that
emits the pollutant (e. g., kilograms of particulate emitted per megagrams of
coal combusted). Using such factors permits the estimation of emissions from
various sources of air pollution. In most cases, these factors are simply
averages of all available data of acceptable quality, generally without consid-
eration for the influence of various process parameters such as temperature,
reactant concentrations, etc. For a few cases, however, such as in the estima-
tion of volatile organic emissions from petroleum storage tanks, this document
contains empirical formulae which can relate emissions to such variables as
tank diameter, liquid temperature and wind velocity. Emission factors corre-
lated with such variables tend to yield more precise estimates than would fac-
tors derived from broader statistical averages.
Recommended uses of emission factors
Emission factors are very useful tools for estimating air pollutants
from sources. However, because such factors are averages obtained from data
of wide range and varying degrees of accuracy, emissions calculated this way
for a given facility are likely to be different from th^t facility's actual
emissions. Because they are averages, the emission factor will be higher than
actual emissions for some sources and lower than for otherk. Only an onsite
source test can determine the actual pollutant contribution from a source,
under the cbnditions existing at the time of the test. For the most accurate
emissions estimation, It is recommended that source specific data be obtained
whenever possible. Factors are more appropriately used to estimate the collec-
tive emissions of a number of sources, such as is done in emissions inventory
efforts.
If factors are used to predict emissions from new or proposed sources,
the user should review the latest literature and technology to determine if
such sources are likely to exhibit emission characteristics different from
those of typical existing sources.
In a few AP-42 Sections, emission factors are presented for facilities
having air pollution control equipment in place. These factors generally are
not intended to represent best available or state of the art control techno-
logy, rather they relate to the level of control commonly found on existing
facilities. The usefulness of this information should be considered carefully,
in light of changes in air pollution control technology. The user should
consider the age, level cf maintenance and other aspects which may influence
equipment efficacy.
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Examples of various factor applications
Calculating carbon monoxide (CO) emissions from distillate oil combustion
serves as an example of the simplest use of emission factors. Consider an
industrial boiler which burns 90,000 liters of distillate oil per day. In
Section 1.3 of AP-42, the CO emission factor for industrial boilers burning
distillate oil is 0.6 kg CO per 103 liters of oil burned.
Then CO emissions
= CO emission factor x distillate oil burned/day
= 0.6 x 90
= 54 kg/day
In a somewhat more complex case, suppose a sulfuric acid (112804) plant
produces 200 Mg of 100% H2S04 per day by converting sulfur dioxide (S02) into
sulfur trioxide (803) at 97.5% efficiency. In Section 5.17, the S02 emission
factors are listed according to S02 to 803 conversion efficiencies, in whole
numbers. The reader is directed to Footnote b, an interpolation formula which
may be used to obtain the emission factor for 97.5% S02 to 503 conversion.
Emission factor for kg S02/Mg 100% H2S04
= 682 - [(6.82)(% S02 to 803 conversion)]
- 682 - [(6.82)(97.5)]
= 682 - 665
= 17
For production of 200 Mg of 100% H2S04 per day, S02 emissions are calculated as
S02 emissions
= 17 kg S02 emissions/Mg 100% H2S04 x 200 Mg 100% H2S04/day
=3400 kg/day
Emi s s i on Factor Rat ing s
To help users understand the reliability and accuracy of AP-42 emission
factors, each Table (and sometimes individual factors within a Table) is given
a rating (A through E, with A being the best) which reflects the quality and
the amount of data on which the factors are based. In general, factors based on
many observations or on more widely accepted test procedures are assigned higher
rankings. For instance, an emission factor based on ten or more source tests on
different plants would likely get an A rating, if all tests were conducted using
a single valid reference measurement method or equivalent techniques. Conversely,
a factor based on a single observation of questionable quality, or one extrapo-
lated from another factor for a similar process, would probably be labeled D or
E. Several subjective schemes have been used in the past to assign these ratings,
depending upon data availability, source characteristics, etc. Because these
ratings are subjective and take no account of the inherent scatter among the
data used to calculate factors, they should be used only as approximations, to
infer error bounds or confidence intervals about each emission factor. At
most, a rating should be considered an Indicator of the accuracy and precision of
a given factor used to estimate emissions from a large number of sources. This
indicator will largely reflect the professional judgement of the authors and
reviewers of AP-42 Sections concerning the reliability of any estimates derived
with these factors.
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1. EXTERNAL COMBUSTION SOURCES
External combustion sources include steam/electric generating plants,
industrial boilers, and commercial and domestic combustion units. Coal,
fuel oil and natural gas are the major fossil fuels used by these sources.
Other fuels, used in relatively small quantities, are liquefied petroleum
gas, wood, coke, refinery gas, blast furnace gas and other waste or byproduct
fuels. Coal, oil and natural gas currently supply about 95 percent of the
total thermal energy consumed in the United States. 1980 saw nationwide
consumption1 of over 530 x 106 megagrams (585 million tons) of bituminous
coal, nearly 3.6 x 106 megagrams (4 million tons) of anthracite coal,
91 x 109 liters (24 billion gallons) of distillate oil, 114 x 109 liters
(37 billion gallons) of residual oil, and 57 x 1012 cubic meters (20 trillion
cubic feet) of natural gas.
Power generation, process heating and space heating are some of the
largest fuel combustion sources of sulfur oxides, nitrogen oxides and
particulate emissions. The following Sections present emission factor data
on the major fossil fuels - coal, fuel oil and natural gas - and for other
fuels as well.
National Emissions Data System (NEDS) Fuel Use Report. EPA-450/4-82-011,
U. S. Environmental Protection Agency, Research Triangle Park, NC,
August 1982.
8/82
External Combustion Sources
1.0-1
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1.1. BITUMINOUS AND SUBBITUMINOUS COAL COMBUSTION
1.1.1 General:
Coal is a complex combination of organic matter and inorganic ash
formed over eons from successive layers of fallen vegetation. Coal types
are broadly classified as anthracite, bituminous, subbituminous or lignite,
and classification is made by heating values and amounts of fixed carbon,
volatile matter, ash, sulfur and moisture. Formulas for differentiating
coals based on these properties are given in Reference 1. See Sections 1.2
and 1.7 for discussions of anthracite and lignite, respectively.
There are two major coal combustion techniques, suspension firing and
grate firing. Suspension firing is the primary combustion mechanism in
pulverized coal and cyclone systems. Grate firing is the primary mechanism
in underfeed and overfeed stokers. Both mechanisms are employed in spreader
stokers.
Pulverized coal furnaces are used primarily in utility and large
industrial boilers. In these systems, the coal is pulverized in a mill to
the consistency of talcum powder (i.e., at least 70 percent of the particles
will pass through a 200 mesh sieve). The pulverized coal is generally
entrained in primary air before being fed through the burners to the combus-
tion chamber, where it is fired in suspension. Pulverized coal furnaces are
classified as either dry or wet bottom, depending on the ash removal tech-
nique. Dry bottom furnaces fire coals with high ash fusion temperatures,
and dry ash removal techniques are used. In wet bottom (slag tap) furnaces,
coals with low ash fusion temperatures are used, and molten ash is drained
from the bottom of the furnace. Pulverized coal furnaces are further clas-
sified by the firing position of the burners, i.e., single (front or rear)
wall, horizontally opposed, vertical, tangential (corner fired), turbo or
arch fired.
Cyclone furnaces burn low ash fusion temperature coal crushed to a 4
mesh size. The coal is fed tangentially, with primary air, to a horizontal
cylindrical combustion chamber. In this chamber, small coal particles are
burned in suspension, while the larger particles are forced against the
outer wall. Because of the high temperatures developed in the relatively
small furnace volume, and because of the low fusion temperature of the coal
ash, much of the ash forms a liquid slag which is drained from the bottom of
the furnace through a slag tap opening. Cyclone furnaces are used mostly in
utility and large industrial applications.
In spreader stokers, a flipping mechanism throws the coal into the
furnace and onto a moving fuel bed. Combustion occurs partly in suspension
and partly on the grate. Because of significant carbon in the particulate,
8/82 External Combustion Sources
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flyash reinjection from mechanical collectors is commonly employed to improve
boiler efficiency. Ash residue in the fuel bed is deposited in a receiving
pit at the end of the grate.
In overfeed stokers, coal is fed onto a traveling or vibrating grate,
and it burns on the fuel bed as it progresses through the furnace. Ash
particles fall into an ash pit at the rear of the stoker. The term "over-
feed" applies because the coal is fed onto the moving grate under an adjust-
able gate. Conversely, in "underfeed" stokers, coal is fed into the firing
zone from underneath by mechanical rams or screw conveyers. The coal moves
in a channel, known as a retort, from which it is forced upward, spilling
over the top of each side to form and to feed the fuel bed. Combustion is
completed by the time the bed reaches the side dump grates from which the
ash is discharged to shallow pits. Underfeed stokers include single retort
units and multiple retort units, the latter having several retorts side by
side.
1.1.2 Emissions and Controls
The major pollutants of concern from external coal combustion are
particulate, sulfur oxides and nitrogen oxides. Some unburnt combustibles,
including numerous organic compounds and carbon monoxide, are generally
emitted even under proper boiler operating conditions.
Particulate2^ - Particulate composition and emission levels are a
complex function of firing configuration, boiler operation and coal pro-
perties. In pulverized coal systems, combustion is almost complete, and
thus particulate is largely comprised of inorganic ash residue. In wet
bottom pulverized coal units and cyclones, the quantity of ash leaving the
boiler is less than in dry bottom units, since some of the ash liquifies,
collects on the furnace walls, and drains from the furnace bottom as molten
slag. In an effort to increase the fraction of ash drawn off as wet slag
and thus to reduce the flyash disposal problem, flyash is sometimes rein-
jected from collection equipment into slag tap systems. Ash from dry bottom
units may also be reinjected into wet bottom boilers for this same purpose.
Because a mixture of fine and coarse coal particles is fired in spreader
stokers, significant unburnt carbon can be present in the particulate. To
improve boiler efficiency, flyash from collection devices (typically multi-
ple cyclones) is sometimes reinjected into spreader stoker furnaces. This
practice can dramatically increase the particulate loading at the boiler
outlet and, to a lesser extent, at the mechanical collector outlet. Flyash
can also be reinjected from the boiler, air heater and economizer dust
hoppers. Flyash reinjection from these hoppers does not increase particulate
loadings nearly so much as from multiple cyclones.5
Particulate emissions from uncontrolled overfeed and underfeed stokers
are considerably lower than from pulverized coal units and spreader stokers,
since combustion takes place in a relatively quiescent fuel bed. Flyash
reinjection is not practiced in these kinds of stokers.
Other variables than firing configuration and flyash reinjection can
affect emissions from stokers. Particulate loadings will often increase as
1.1-2 EMISSION FACTORS 8/82
-------
load increases (especially as full load is approached) and with sudden load
changes. Similarly, particulate can increase as the ash and fines contents
increase. ("Fines" are defined in this context as coal particles smaller
than one sixteenth inch, or about 1.6 millimeters, in diameter.) Converse-
ly, particulate can be reduced significantly when overfire air pressures are
increased.5
The primary kinds of particulate control devices used for coal combus-
tion include multiple cyclones, electrostatic precipitators, fabric filters
(baghouses) and scrubbers. Some measure of control will even result due to
ash settling in boiler/air heater/economizer dust hoppers, large breeches
and chimney bases. To the extent possible from the existing data base, the
effects of such settling are reflected in the emission factors in
Table 1.1-1.
Electrostatic precipitators (ESP) are the most common high efficiency
control device used on pulverized coal and cyclone units, and they are being
used increasingly on stokers. Generally, ESP collection efficiencies are a
function of collection plate area per volumetric flow rate of flue gas
through the device. Particulate control efficiencies of 99.9 weight percent
are obtainable with ESPs. Fabric filters have recently seen increased use
in both utility and industrial applications, generally effecting about 99.8
percent efficiency. An advantage of fabric filters is that they are un-
affected by high flyash resistivities associated with low sulfur coals.
ESPs located after air preheaters (i.e., cold side precipitators) may operate
at significantly reduced efficiencies when low sulfur coal is fired. Scrub-
bers are also used to control particulate, although their primary use is to
control sulfur oxides. One drawback of scrubbers is the high energy require-
ment to achieve control efficiencies comparable to those of ESPs and
baghouses.2
Mechanical collectors, generally multiple cyclones, are the primary
means of control on many stokers and are sometimes installed upstream of
high efficiency control devices in order to reduce the ash collection burden.
Depending on application and design, multiple cyclone efficiencies can vary
tremendously. Where cyclone design flow rates are not attained (which is
common with underfeed and overfeed stokers), these devices may be only
marginally effective and may prove little better in reducing particulate
than large breeching. Conversely, well designed multiple cyclones, oper-
ating at the required flow rates, can achieve collection efficiencies on
spreader stokers and overfeed stokers of 90 to 95 percent. Even higher
collection efficiencies are obtainable on spreader stokers with reinjected
flyash because of the larger particle sizes and increased particulate load-
ings reaching the_controls.5~6
Sulfur Oxides7"^ - Gaseous sulfur oxides from external coal combustion
are largely sulfur dioxide (S02) and much lesser quantities of sulfur tri-
oxide (303) and gaseous sulfates. These compounds form as the organic and
pyritic sulfur in the coal is oxidized during the combustion process. On
average, 98 percent of the sulfur present in bituminous coal will be emitted
as gaseous sulfur oxides, whereas somewhat less will be emitted when subbitu-
minous coal is fired. The more alkaline nature of the ash in some subbitu-
minous coals causes some of the sulfur to react to form various sulfate
8/82
External Combustion Sources
1.1-3
-------
TABLE 1.1-1. EMISSION FACTORS FOR EXTERNAL BITUMINOUS AND SUBBITUMINOUS COAL COMBUSTION3
Firing Configuration
Pulverized coal fired
Dry bottom
Wet bat ton
Cyclone furnace
Spreader stoker
Uncontrolled
After multiple cyclone
With fly ash reinjection
from multiple cyclone
Ho fly ash reinjection
from multiple cyclone
Overfeed stoker'1
Uncontrolled
After multiple cyclone
underfeed stoker
Uncontrolled
After multiple cyclone
Handf ired units
Particulate0
kg /Kg
5A
3.5An
lAh
30J
a. 5
6
S"
4.5*
7.5P
5.5"
7.5
Ib/ton
10A
7Ab
2A"
60J
•17
12
16°
9"
15P
Hi
15
Sulfur Oiide BC
kg/Mg
19.58(17 .53)
19.5S<17.5S)
19.5S(17.5S)
19.55(17.55)
19 .55(17.55)
19.53(17.55)
19.5S<17.55)
19.55(17.55)
15.55
15. 5S
15 .5S
Ib/ton
39S(35S)
393(355)
39S(35S)
395(355)
39S(35S)
39S(35S)
398(355)
395(355)
315
315
315
Nitrogen Oxides11
kg/Mg
10.5(7.5)8
17
18.5
7
7
7
3.25
3.25
4.75
4,75
1.5
Ib/ton
21(15)8
34
37
14
14
14
7.5
7.5
9.5
9.5
3
Carbon Monoxide^
kg /HE
0.3
0.3
0.3
2.5
2.5
2.5
3
3
5.5
5.5
45
Ib/ton
0.6
0.6
0.6
5
5
5
6
6
11
11
90
Nom»thane VOCe.£
kg/Mg
0.04
0.04
0.04
0.04
0.04
0.04
0.04
0.04
0.65
0.65
5
Ib/ton
0.07
0.07
0.07
0.07
0.07
0.07
0.07
0.07
1.3
1.3
10
Methane'
ie/Mg
0.015
0.015
0.015
0.015
0.015
0.015
0.015
0.015
0.4
0.4
4
Ib/toa
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.03
0.8
0.8
3
CO
00
NJ
^Factors represent uncontrolled emissions unices otherwise specified and should be applied Co coal consumption as fired.
teased an EPA Hethod 5 (front half catch) as described In Reference 12. Where participate Is expressed In terns of coal
ash content, A, factor Is determined by Multiplying weight I ash content of coal (as fired) by the numerical value
preceding, the "A". For example, if coal having 81 ash ia fired In a dry bottom unit, the particulate emission factor
would be 5 x Bt or 40 kg/Mg (80 Ib/ton). The " c c nde as ible " natter collected in back half catch of EPA Method 5 averages
<5S of front half, or "filterable", catch for pulverized coal and cyclone furnaces; 101 for epreader stokers; 151 for
other stokers; and 50E for handfired units (References 6, 19, 49).
cExpreseed as 502> including SO^, SQu and gaseous sulfates. Factors In parentheses should be used to estimate gaseous
SOj emissions for subblturn!nous coal. In all cases, "S" is weight Z sulfur content of coal aa fired. See Footnote b for
example calculation. On average for bituminous coal, 97X of fuel sulfur is emitted as SO;, and only about 0.71 of fuel
sulfur is emitted as SOj and gaseous sulfate. An equally small percent of fuel sulfur Is emitted as particulate sulfate
(References 9, 13). Snail quantities of sulfur are also retained in bottom ash. With subbiluminous coal generally about
10X more fuel sulfur is retained in the bottom ash and particulate because of the more alkaline nature of the coal ash.
Conversion to gaseous sulfate appears about the same as for bituminous coal.
"Expressed as NO,- Generally, 95 - 99 volume I of nitrogen oxides present In com boatIon exhaust will be In the form of
HO, the rest N02 (Reference 11). To express factors as NO, multiply by factor of 0.66. All factors represent emission
at baseline operation (i.e., 60 - 1101 load and no NOK control measures, as discussed In text).
^Nominal values achieveable under normal operating conditions. Values one or two orders of magnitude higher can occur
when combustion la not complete.
f No methane volatile organic compounds (VOC), expressed as C2 to C,g n-alkane equivalents (Reference 58). Because of
limited data on HHVOC available to distinguish the effects of firing configuration, all data were averaged
collectively to develop a single average for pulverized coal units, cyclones, spreaders and overfeed stokers.
^Parenthetic value is for tangentially fired boilers.
^Uncontrolled particulate emissions, when no fly ash reinjection is employed.. TJhen control device is installed, and
collected fly ash is reinjected to boiler, particulate from boiler reaching, control equipment can increase by up to a
factor of two.
JAccounts for fly ash settling in an economizer, air heater or breeching upstream of control device or stack.
(Farticulate directly at boiler outlet typically will be twice this level.) Factor should be applied even when fly
ash is reinjected to boiler from boiler, air heater or economizer dust hoppers.
^Includes traveling grate, vibrating grate and chain grate stokers.
"Accounts for fly ash settling in breeching or stack base. Particulate loadings directly at boiler outlet typically
can be 50X higher.
DSee text for discussion of apparently low multiple cyclone control efficiencies, regarding uncontrolled emissions.
PAccounts for fly ash settling in breeching downstream of boiler outlet.
-------
00
oa
NJ
TABLE 1.1-2. EMISSION FACTOR RATINGS AND REFERENCES FOR BITUMINOUS AND SUBBITUMINOUS COAL COMBUSTION
CU
M
O
01
rt
H-
O
3
t-f
O
rc
tn
Firing Configuration
Pulverized coal fired
Dry bottom
Wet bottom
Cyclone furnace
Spreader atoker
Uncontrolled
After multiple cyclone
With flyash rein ject Ion
from cyclone
Ho flyaah re Inject ion
from cyclone
Overfeed stoker
Uncontrolled
After multiple cyclone
Underfeed stoker
Uncontrolled
After multiple cyclone
Hand fired unit a
Particulate
Rating
A
D
D
B
B
A
B
B
B
C
D
Kef.
14-25
14,16,26
14,19,22,
27-29
17,30-35
14,32,36-38
17,31-35,
39,40.59
6,17,41-43,
45-47
6,41,44-45
6,19,47-48
6
49-50
Sulfur Oxides Nitrogen Oxides
Rating Ref. Rating Ref.
A 9,16-19,21, A 11,14,16-17,
31-37,39, 21,46,56
41-46,51-55
A " C 14,16
A " B 11
A "A 11,17,31-37
39-40,46
A A "
A A
A "A 11,17,19,
41-45
A A
B 19,48 B 19,47-48
B B
D " D 50
Carbon Monoxide
Rating Ref.
A 16,18-19,21
47,57
A "
A
A 17,19,31-34,
36,47,51
*
A
B 17,41-42,45,
47,51
B "
B 19,47-48
B
D 50
Nonme thane VOC
Rating Ref.
A 55,58
A 58
A "
A
A
A "
A
A
A 47,58
A
D 50,58
Methane
Ratine Ref.
A 58
A "
A
A "
A "
X
A "
A "
A 47,58
A
D 50,58
These ratings, in the context of this Section, refer to the number of test data on which each emission factor is based. An "A" rating Beans the
factor Is based on tests at ten or more boilers, a "B" rating on six to nine teat data, and a "C" rating on test data for two to five boilers.
A "D" rating Indicates the factor la based on only a single datum or extrapolated from a secondary reference. These ratings are not a neasure of
the scatter In the underlying test data. However, a higher rating will generally Increase confidence that a given factor will better approximate
the average emissions for a particular boiler category.
t-1
-------
salts that are retained in the boiler or in the flyash. Generally, boiler
size, firing configuration and boiler operation have little impact on the
percent conversion of fuel sulfur to sulfur oxides.
Several techniques are used to reduce sulfur oxides from coal combus-
tion. One way is to switch to lower sulfur coals, since sulfur oxide emis-
sions are proportional to the sulfur content of the coal. This alternative
may not be possible where lower sulfur coal is not readily available or
where a different grade of coal cannot be satisfactorily fired. In some
cases, various cleaning processes may be employed to reduce the fuel sulfur
content. Physical coal cleaning removes mineral sulfur such as pyrite but
is not effective in removing organic sulfur. Chemical cleaning and solvent
refining processes are being developed to remove organic sulfur.
Many flue gas desulfurization techniques can remove sulfur oxides
formed during combustion. Flue gases can be treated through wet, semidry or
dry desulfurization processes of either the throwaway type, in which all
waste streams are discarded, or the recovery (regenerable) type, in which
the SOx absorbent is regenerated and reused. To date, wet systems are the
most commonly applied. Wet systems generally use alkali slurries as the SOx
absorbent medium and can be designed to remove well in excess of 90 percent
of the incoming SOX. Particulate reduction of up to 99 percent is also
possible with wet scrubbers, but flyash is often collected by upstream ESPs
or baghouses to avoid erosion of the desulfurization equipment and possible
interference with the process reactions.7 Also, the volume of scrubber
sludge is reduced with separate flyash removal, and contamination of the
reagents and byproducts is prevented. References 7 and 8 give more details
on scrubbing and other SOX removal techniques.
Nitrogen Oxides 10-11 _ Nitrogen oxides (NOX) emissions from coal
combustion are primarily nitrogen oxide (NO). Only a few volume percent are
comprised of nitrogen dioxide (N02). NO results from thermal fixation of
atmospheric nitrogen in the combustion flame and from oxidation of the
nitrogen bound in the coal. Typically, only 20 to 60 percent of the fuel
nitrogen is converted to nitrogen oxides. Bituminous and subbituminous
coals usually contain from 0.5 to 2 weight percent nitrogen, present mainly
in aromatic ring structures. Fuel nitrogen can account for up to 80 percent
of total NOX from coal combustion.
A number of combustion modifications can be made to reduce NOX emis-
sions from boilers. Low excess air (LEA) firing is the most widespread
control modification, because it can be practiced in both old and new units
and in all sizes of boilers. LEA firing is easy to implement and has the
added advantage of increasing fuel use efficiency. LEA firing is generally
only effective above 20 percent excess air for pulverized coal units and
above 30 percent excess air for stokers. Below these levels the NOX reduc-
tion due to decreased 02 availability is offset by increased NOX due to
increased flame temperature. Another NOX reduction technique is simply to
switch to a coal having a lower nitrogen content, although many boilers may
not properly fire coals of different properties.
Off-stoichiometric (staged) combustion is also an effective means of
controlling NOx from coal fired equipment. This can be achieved by using
1.1-6
EMISSION FACTORS
8/82
-------
overfire air or low NOX burners designed to stage combustion in the flame
zone. Other NOX reduction techniques include flue gas recirculation, load
reduction, and steam or water injection. However, these techniques are not
very effective for use on coal fired equipment because of the fuel nitrogen
effect. Ammonia injection is another technique which can be used, but it is
costly. The net reduction of NOX from any of these techniques or combin-
ations thereof varies considerably with boiler type, coal properties and
existing operating practices. Typical reductions will range from 10 to 60
percent. References 10 and 60 should be consulted for a detailed discussion
of each of these NOX reduction techniques. To date, flue gas treatment is
not used to reduce nitrogen oxide emissions due to its higher cost.
Volatile Organic Compounds and Carbon Monoxide - Volatile organic com-
pounds (VOC) and carbon monoxide (CO) are unburnt gaseous combustibles which
are generally emitted in quite small amounts. However, during startups,
temporary upsets or other conditions preventing complete combustion, unburnt
combustible emissions may increase dramatically. VOC and CO emissions per
unit of fuel fired are normally lower from pulverized coal or cyclone
furnaces than from smaller stokers and handfired units where operating
conditions are not as well controlled. Measures used for NOX control can
increase CO emissions, so to minimize the risk of explosion, such measures
are applied only to the point at which CO in the flue gas reaches a maximum
of about 200 parts per million. Control measures, other than maintaining
proper combustion conditions, are not applied to control VOC and CO.
Emission Factors and References - Average emission factors for
bituminous and subbituminous coal combustion in boilers are presented in
Table 1.1-1. The factors for underfeed stokers and handfired units also may
be applied to hot air furnaces. In addition to factors for uncontrolled
emissions, factors are also presented for emissions after multiple cyclones.
Emission factor ratings and references are presented in Table 1.1-2.
Further general information on coal, combustion practices, emissions and
controls is available in the references cited above.
8/82
External Combustion Sources
1.1-7
-------
References for Section 1.1
1. Steam. 38th Edition, Babcock and Wilcox, New York, 1975.
2. Control Techniques for Particulate Emissions from Stationary Sources,
Volume I, EPA-450/ 3-81-005a, U.S. Environmental Protection Agency,
Research Triangle Park, NC, April 1981.
3. ibidem, Volume II. EPA-450/ 3-81-005b.
4. Electric Utility Steam Generating Units: Background Information for
Proposed Particulate^ Matter Emission Standards, EPA-450/2-78-006a, U.S.
Environmental Protection Agency, Research Triangle Park, NC, July 1978.
5. William Axtman and Mark A. Eleniewski, "Field Test Results of Eighteen
Industrial Coal Stoker Fired Boilers for Emission Control and Improved
Efficiency", Presented at the 74th Annual Meeting of the Air Pollution
Control Association, Philadelphia, PA, June 1981.
6 . Field Tests of Industrial Stoker Coal Fir_ed Boilers _ f _or ^Emission Control
and Efficiency Improvement - Sites L1-L7, EPA-600/7-81-020a, U.S.
Environmental Protection Agency, Washington, DC, February 1981.
7 . Control Techniques^fpr Sulfur Dioxide Emissions f rom jtationary^ Sources ,
2nd Edition, EPA-450/ 3-81-004, U.S. Environmental Protection Agency,
Research Triangle Park, NC, April 1981.
8. Electric Utility Steam Generating Units: Background Information for
Proposed S02 Emission Standards, EPA-450/2-78-007a, U.S. Environmental
Protection Agency, Research Triangle Park, NC, July 1978.
9. Carlo Castaldini and Meredith Angwin, Boiler Design and Operating
Variables Affecting Uncontrolled Sulfur Emissions from Pulverized Coal
Fired Steam Generators, EPA-450/ 3-77-047, U.S. Environmental Protection
Agency, Research Triangle Park, NC, December 1977.
10. Control Techniques for Nitrogen Oxides Emissions from Stationary
Sources, 2nd Edition, EPA-450/1-78-001, U.S. Environmental Protection
Agency, Research Triangle Park, NC, January 1978.
11. Review of^ NOjc Emission Factors for Stationary Fossil Fuel Combustion
Sources, EPA-450/4-79-021, U.S. Environmental Protection Agency,
Research Triangle Park, NC, September 1979.
12. Standards of Performance for New Stationary Sources , 36 FR 24876,
December 23, 1971.
13. Lou Scinto, Primary Sulfate Emissions from Coal and Oil Combustion,
EPA Contract Number 68-02-3138, TRW Inc., Redondo Beach, CA, February
1980.
1.1-8 EMISSION FACTORS 8/82
-------
14. Stanley T. Cuffe and Richard W. Gerstle, Emissions from Coal Fired
Power Plants: A Comprehensive Summary, 999-AP-35, U.S. Department of
Health, Education and Welfare, Durham, NC, 1967.
15. Field Testing: Application of Combustion Modifications To Control NQx
Emissions from Utility Boilers, EPA-650/2-74-066, U.S. Environmental
Protection Agency, Washington, DC, June 1974.
16. Control of Utility Boiler and Gas Turbine Pollutant Emissions by
Combustion Modification - Phase I, EPA-600/7-78-036a, U.S. Environmental
Protection Agency, Washington, DC, March 1978.
17. Low-sulfur Western Coal Use in Existing Small and Intermediate Size
Bjoilers, EPA-600/7-78-153a, U.S. Environmental Protection Agency,
Washington, DC, July 1978.
18. Hazardous Emission Characterization of Utility Boilers,
EPA-650/2-75-066, U.S. Environmental Protection Agency, Washington, DC,
July 1975.
19. Application of Combustion Modifications To Control Pollutant Emissions
from Industrial Boilers - Phase I, EPA-650/2-74-078a, U.S. Environmental
Protection Agency, Washington, DC, October 1974.
20. Field Study To Obtain Trace Element Mass Balances at a Coal^ Fired
Utility Boiler, EPA-600/7-80-171, U.S. Environmental Protection Agency,
Washington, DC, October 1980.
21. Environmental^ Assessment of Coal- and Oil-firing in a Controlled
Industrial Boiler. Volume II, EPA-600/7-78-164b, U.S. Environmental
Protection Agency, Washington, DC, August 1978.
22. Coal Fired Power Plant Trace Element Study, U.S. Environmental
Protection Agency, Denver, CO, September 1975.
23. Source Testing of Duke Power Company, Plezer, SC. EMB-71-CI-01, U.S.
Environmental Protection Agency, Research Triangle Park, NC, February,
1971.
24. John W. Kaakinen, gt__al_., "Trace Element Behavior in Coal-fired Power
Plants", Environmental Science and Technology, 9_(9) : 862-869, September
1975.
25. Five Field Performance Tests on Koppers Company Precipitator, Docket
Number OAQPS-78-1, Office of Air Quality Planning and Standards, U.S.
Environmental Protection Agency, Research Triangle Park, NC, February-
March 1974.
26. H. M. Rayner and L. P. Copian, Slag Tap Boiler Performance Associated
with^ Power Plant Flyash Disposal, Western Electric Company, Hawthorne
Works, Chicago, IL, undated.
8/82
External Combustion Sources
1.1-9
-------
27. A. B. Walker, "Emission Characteristics for Industrial Boilers", Air
Engineering, 9^(8): 17-19, August 1967.
28. Environmental Assessment of Coal-fired Controlled Utility Boiler,
EPA-600/7-80-086, U.S. Environmental Protection Agency, Washington, DC,
April 1980.
29. Steam, 37th Edition, Babcock and Wilcox, New York, 1963.
30. Industrial Boiler; Emission Test Report, Formica Corporation,
Cincinnati, Ohio, EMB-80-IBR-7, U.S. Environmental Protection Agency,
Research Triangle Park, NC, October 1980.
31. Field Tests of Industrial Stoker Coal-fired Boilers for Emissions
Control and Efficiency Improvement - Site A, EPA-600/7-78-136a, U.S.
Environmental Protection Agency, Washington, DC, July 1978.
32. ibidem-Site C, EPA-600/7-79-130a, May 1979.
33. ibidem-Site E. EPA-600/7-80-064a, March 1980.
34. ibidem-Site F. EPA-600/7-80-065a, March 1980.
35• ibidem-Site G, EPA-600/7-80-082a, April 1980.
36. ibidem-Site B, EPA-600/7-79-041a, February 1979.
37. Industrial Boilers; Emission Test Report, Genera^JMotors Corporation,
Parma, Ohio, Volume I, EMB-80-IBR-4, U.S. Environmental Protection
Agency, Research Triangle Park, NC, March 1980.
38. AJField Test Using Coal: dRDF Blends in Spreader Stoker-fired Boilers,
EPA-600/2-80-095, U.S. Environmental Protection Agency, Cincinnati, OH,
August 1980.
39. Industrial Boilers; Emission Test Report, Rickenbacker Air Force Base,
Columbus, Ohio, EMB-80-IBR-6, U.S. Environmental Protection Agency,
Research Triangle Park, NC, March 1980.
40. Thirty-day Field Tests of Industrial Boilers: Site 1,
EPA-600/7-80-085a, U.S. Environmental Protection Agency, Washington,
DC, April 1980.
41. Field Tests of Industrial Stoker Coal-fired Boilers for Emissions
Control and Efficiency Improvement - Site D, EPA-600/7-79-237a, U.S.
Environmental Protection Agency, Washington, DC, November 1979.
42. ibidem-Site H, EPA-600/7-80-112a, May 1980.
43. ibidem-Site I, EPA-60C/7-80-136a, May 1980.
44. ibidem-Site J, EPA-600/7-80-137a, May 1980.
1.1-10
EMISSION FACTORS
8/82
-------
45. ibidem-Site K. EPA-600/7-80-138a, May 1980.
46. Regional Air Pollution Study; Point Source Emission Inventory,
EPA-600/4-77-014, U.S. Environmental Protection Agency, Research
Triangle Park, NC, March 1977.
47. R. P. Hangebrauck, et al., "Emissions of Polynuclear Hydrocarbons and
Other Pollutants from Heat Generation and Incineration Process",
Journal of the Air Pollution Control Association, 14_(7) :267-278, July
1964.
48. Source Assessment: Goal-fired Industrial Combustion Equipment^ Field
Tests, EPA-600/2-78-004o, U.S. Environmental Protection Agency,
Washington, DC, June 1978.
49. Source Sampling Residential Fireplaces for Emission Factor Development,
EPA-450/3-76-010, U.S. Environmental Protection Agency, Research
Triangle Park, NC, November 1975.
50. Atmospheric Emissions from Coal Combustion: An Inventory Guide,
999-AP-24, U.S. Department of Health, Education and Welfare, Cincinnati,
OH, April 1966.
51. Application of Combustion Modification To Control Pollutant Emissions
from Industrial Boilers - Phase II, EPA-600/2-76-086a, U.S.
Environmental Protection Agency, Washington, DC, April 1976.
52. Continuous Emission Monitoring for Industrial Boiler, General Motors
Corporation, St. Louis, Missouri, Volume 1, EPA Contract Number
68-02-2687, GCA Corporation, Bedford, MA, June 1980.
53. Survey of Flue Gas Desulfurization Systems: Cholla Station, Arizona
Public Service Company, EPA-600/7-78-048a, U.S. Environmental Protection
Agency, Washington, DC, March 1978.
54. ibidem: La Cygne Station, Kansas City Power and Light,
EPA-600/7-78-048d, March 1978.
55. Source Assessment: Dry Bottom Utility Boilers Firing Pulverized
Bituminous Coal, EPA-600/2-79-019, U.S. Environmental Protection Agency,
Washington, DC, August 1980.
56. Thirty-day Field Tests of Industrial Boilers: Site 3 - Pulverized-
coal-fired Boiler, EPA-600/7-80-085c, U.S. Environmental Protection
Agency, Washington, DC, April 1980.
57. Systematic Field Study of Nitrogen Oxide Emission Control Methods for
Utility Boilers, APTD-1163, U.S. Environmental Protection Agency,
Research Triangle Park, NC, December 1971.
8/82
External Combustion Sources
1.1-11
-------
58. Emissions of Reactive Volatile Organic Compounds from Utility Boilers,
EPA-600/7-80-111, U.S. Environmental Protection Agency, Washington, DC,
May 1980.
59. Industrial Boilers: Emission Test Report, "-£)uPont Corporation,
Parkersburg, West Virginia, EMB-80-IBR-12, U.S. Environmental
Protection Agency, Research Triangle Park, NC, February 1982.
60. Technology Assessment Report for Industrial Boiler Applications:
Combustion Modification, EPA-600/7-79-178f, U.S. Environmental
Protection Agency, Research Triangle Park, NC, December 1979.
NOx
1.1-12
EMISSION FACTORS
8/82
-------
1.2 ANTHRACITE COAL COMBUSTION
1.2.1 General1"2
Anthracite coal is a high rank coal with a high fixed carbon content and
low volatile matter content, relative to bituminous coal and lignite, and it
has higher ignition and ash fusion temperatures. Because of its low volatile
matter content and slight clinkering, anthracite is most commonly fired in
medium sized traveling grate stokers and small hand fired units. Some
anthracite (occasionally along with petroleum coke) is used in pulverized coal
fired boilers. It is also blended with bituminous coal. None is fired in
spreader stokers. Because of its low sulfur content (typically less than 0.8
weight percent) and minimal smoking tendencies, anthracite is considered a
desirable fuel where readily available.
In the United States, all anthracite is mined in Northeastern Pennsylvania
and is consumed mostly in Pennsylvania and several surrounding states. The
largest use of anthracite is for space heating. Lesser amounts are employed
for steam/electric production; coke manufacturing, sintering and pelletizing;
and other industrial uses. Anthracite combustion currently is only a small
fraction of the total quantity of coal combusted in the United States.
1.2.2 Emissions and Controls
2-14
Particulate emissions from anthracite combustion are a function of furnace
firing configuration, firing practices (boiler load, quantity and location of
underfire air, sootblowing, flyash reinjection, etc.)» and the ash content of
the coal. Pulverized coal fired boilers emit the highest quantity of participate
per unit of fuel because they fire the anthracite in suspension, which results
in a high percentage of ash carryover into the exhaust gases. Pulverized
anthracite fired boilers operate in the dry tap or dry bottom mode because of
anthracite's characteristically high ash fusion temperature. Traveling grate
stokers and hand fired units produce much less particulate per unit of fuel
fired, because combustion takes place in a quiescent fuel bed without significant
ash carryover into the exhaust gases. In general, particulate emissions from
traveling grate stokers will increase during sootblowing and flyash reinjection
and with higher fuel bed underfeed air from forced draft fans. Smoking is
rarely a problem because of anthracite's low volatile matter content.
Limited data are available on the emission of gaseous pollutants from
anthracite combustion. It is assumed from bituminous coal combustion data
that a large fraction of the fuel sulfur is emitted as sulfur oxides. Also,
because combustion equipment, excess air rates, combustion temperatures, etc.,
are similar between anthracite and bituminous coal combustion, nitrogen oxide
and carbon monoxide emissions are assumed to be similar, too. Volatile organic
compound (VOC) emissions, however, are expected to be considerably lower
because the volatile matter content of anthracite is significantly less than
that of bituminous coal.
5/83
External Combustion Sources
1.2-1
-------
1-0
NJ
TABLE 1.2-1. UNCONTROLLED EMISSION FACTORS FOR ANTHRACITE COMBUSTION0
w
00
OJ
Sulfur Nitrogen Carbon VOC
Particulates Oxides Oxides Monoxide Nonme thane Methane
kg/Mg Ib/ton kg/Mg
Ib/ton kg/Mg Ib/ton kg/Mg Ib/ton
Pulverized coal
fired f
19. 5S
39S
18
* Traveling grate
SSION FACTORS
stoker
Hand fed units
Q
.Factors are for
Rnco^ r\n KPA Vlai
4.6° 9.1B
5h 10h
uncontrolled
Uhnr1 *\ ffrnni-
19
19
.53
.53
emissions
hal f 1^3 tr*\
39S
39S
and should
-,^
5
1.
be
10
5 3
applied
0.
f
to coal
3 0.6
f
consumption as
f
f
fired.
f
f
Based on the assumption that, as with bituminous coal combustion, most of the fuel sulfur is emitted as
sulfur oxides. Limited data in Reference 5 verify this assumption for pulverized anthracite fired
boilers. Most of these emissions are S02, with 1-3% S03. S indicates that the weight percent of
,sulfur in the oil should be multiplied by the value given.
For pulverized anthracite fired boilers and hand fed units, assumed to be similar to bituminous coal
combustion. For traveling grate stokers, see References 8 and 11.
May increase by several orders of magnitude if a boiler is not properly operated or maintained. Factors
for traveling grate stokers are based on limited information in Reference 8. Factors for pulverized
..coal fired boilers substantiated by additional data in Reference 14.
Emission factor reported in Table 1.1-1 may be used, based on the similarity of anthracite and bituminous
coal.
g
References 12-13, 15-18. Accounts for limited fallout that may occur in fallout chambers and stack
breeching. Emission factors for individual boilers may range from 2.5 - 25 kg/Mg (5 - 50 Ib/ton) and as
.high as 25 kg/Mg (50 Ib/ton) during sootblowing.
"Reference 2.
-------
Control of emissions from anthracite combustion has mainly been limited
to particulate matter. The most efficient particulate controls - fabric
filters, scrubbers and electrostatic precipitators - have been installed on
large pulverized anthracite fired boilers. Fabric filters and venturi scrubbers
can effect collection efficiencies exceeding 99 percent. Electrostatic
precipitators, on the other hand, are typically only 90 to 97 percent efficient,
because of the characteristic high resistivity of low sulfur anthracite flyash.
It is reported that higher efficiencies can be achieved using larger precipitators
and flue gas conditioning. Mechanical collectors are frequently employed
upstream from these devices for large particle removal.
Traveling grate stokers are often uncontrolled. Indeed, particulate
control has often been considered unnecessary because of anthracite's low
smoking tendencies and of the fact that a significant fraction of large size
flyash from stokers is readily collected in flyash hoppers as well as in the
breeching and b;-ise of the stack. Cyclone collectors have been employed on
traveling grate stokers, and limited information suggests these devices may be
up to 75 percent efficient on particulate. Flyash reinjection, frequently
used in traveling grate stokers to enhance fuel use efficiency, tends to
increase particulate emissions per unit of fuel combusted.
Emission factors for anthracite combustion are presented in Table 1.2.1,
and emission factor ratings in Table 1.2-2.
TABLE 1.2-2. ANTHRACITE COAL EMISSION FACTOR RATING3
Furnace Type
Sulfur Nitrogen Carbon VOC
Particulates Oxides Oxides Monoxide Nonmethane Methane
Pulverized coal
Traveling grate
Hand fed units
B
B
B
B
B
B
B
B
8
B
B
B
C
C
D
C
C
D
The emission factor rating is explained in the Introduction to this volume.
References for Section 1.2
1. Minerals Yearbook, 1978-79, Bureau of Mines, U. S. Department of the
Interior, Washington, DC, 1981.
2. Air Pollutant Emission Factors, HEW Contract No. CPA-22-69-119, TRW Inc.,
Reston, VA, April 1970.
3. Steam, 38th Edition, Babcock and Wilcox, New York, NY, 1975.
4. Fossil Fuel Fired Industrial Boilers - Background Information for Proposed
Standard^, Draft, Office of Air Quality Planning and Standards, U. S.
Environmental Protection Agency, Research Triangle Park, NC, June 1980.
5. R. W. Cass and R. M. Bradway, Fractional Efficiency of a Utility Boiler
Baghousej Sunbury Steam Electric Station, EPA-600/2-76-077a, U. S. Envi-
ronmental Protection Agency, Research Triangle Park, NC, March 1976.
5/83
External Combustion Sources
1.2-3
-------
6. R. P. Janaso, "Baghouse Dust Collectors on a Low Sulfur Coal Fired Utility
Boiler", Presented at the 67th Annual Meeting of the Air Pollution Control
Association, Denver, CO, June 1974.
7. J. H. Phelan, e t al . , Design and Operation Experience with_Ba_ghpuse Dust
Collectors for Pulverized Coal Fired Utility Boilers - Sunbury Station,
Holtwood Station, Proceedings of the American Power Conference, Denver,
CO, 1976.
8. Source Test Data^on^ Anthracite^ Fired Traveling Grate Stokers, Office of
Air Quality Planning and Standards, U. S. Environmental Protection Agency,
Research Triangle Park, NC, 1975.
9. Source and Emissions Information on Anthracite Fired Boilers, Pennsylvania
Department of Environmental Resources, Harrisburg, PA, September 27, 1974.
10. R. J. Milligan, et al . , Review of NOX Emission Factors for Stationary
Fossil Fuel Combustion Sources, EPA-450/4-79-021, U. S. Environmental
Protection Agency, Research Triangle Park, NC, September 1979.
11. N. F. Suprenant, et al., Emissions Assessment of Conventional Stationary
Combustion Systems, yplume^TV; Commercial/ Institutional Combustion
Sources , EPA Contract No. 68-02-2197, GCA Corporation, Bedford, MA,
October 1980.
12. Source Sampling of Anthracite Coal Fired Boilers, RCA-Electronic Components,
Lancaster, Pennsyrvania^, Final Report, Scott Environmental Technology,
Inc., Plumsteadville, PA, April 1975.
13. Source Sampling of Anthracite Coal Fired Boilers, Shippensburg State
College, Shippensburg , Pennsylvania, Final Report, Scott Environmental
Technology, Inc., Plumsteadville, PA, May 1975.
14. W. Bartok, et al., Systematic Field Study of NOx Emission Control
Methods for Utility Boilers, APTD-1163, U. S. Environmental Protection
Agency, Research Triangle Park, NC, December 1971.
15. Source Sampling of Anthracite Coal Fired Boilers, Ashland State
General Hp_sp_italjT AsTiland, Pennsylvania, Final ReporT, Pennsy 1 vania
Department of Environmental Resources, Harrisburg, PA, March 16, 1977.
16. Source Sampling of Anthracite Coal Fired Boilers, Norristown State
Hospital, Norristown, Pennsylvania, Final Reporl:, Pennsylvania Department
of Environmental Resources, Harrisburg, PA, January 29, 1980.
1 7 . Source Sampling of Anthracite Coal Fired Boilers, Pennhurst Center,
Spring City, Pennsy Ivaniaj Final Report, TRC Environmental Consultants,
Inc., Wethersfield, CT, January 23, 1980.
18. Source Sampling of Anthracite Coal Fired Boilers, We^tChesJ^er State,
West Chester, Pennsylvania, Final Report, Roy Weston, Inc., West Chester,
PA, April 4, 1977.
1.2-4 EMISSION FACTORS 5/83
-------
1.3 FUEL OIL COMBUSTION
1222
1.3.1 General ''
Fuel oils are broadly classified into two major types, distillate
and residual. Distillate oils (fuel oil grade Nos. 1 and 2) are
used mainly in domestic and small commercial applications in which
easy fuel burning is required. Distillates are more volatile and
less viscous than residual oils, having negligible ash and nitrogen
contents and usually containing less than 0.3 weight percent sulfur.
Residual oils (grade Nos. 4, 5 and 6), on the other hand, are used
mainly in utility, industrial and large commercial applications
with sophisticated combustion equipment. No. 4 oil is sometimes
classified as a distillate, and No. 6 is sometimes referred to as
Bunker C. Being more viscous and less volatile than distillate
oils, the heavier residual oils (Nos. 5 and 6) must be heated to
facilitate handling and proper atomization. Because residual oils
are produced from the residue left after lighter fractions (gasoline,
kerosene and distillate oils) have been removed from the crude oil,
they contain significant quantities of ash, nitrogen and sulfur.
Properties of typical fuel oils are given in Appendix A.
1.3.2 Emissions
Emissions from fuel oil combustion are dependent on the grade
and composition of the fuel, the type and size of the boiler, the
firing and loading practices used, and the level of equipment
maintenance. Table 1.3-1 presents emission factors for fuel oil
combustion in units without control equipment. The emission factors
for industrial and commercial boilers are divided into distillate
and residual oil categories because the combustion of each produces
significantly different emissions of particulates, SO and NO .
The reader is urged to consult the references for a detailed
discussion of the parameters that affect emissions from oil combustion.
. , ^ „ 3-7,12-13,24,26-27 . 1 . .
Particulate Matter - Particulate emissions are most
dependent on the grade of fuel fired. The lighter distillate oils
result in significantly lower particulate formation than do the
heavier residual oils. Among residual oils, Nos. 4 and 5 usually
result in less particulate than does the heavier No. 6.
In boilers firing No. 6, particulate emissions can be described,
on the average, as a function of the sulfur content of the oil. As
shown in Table 1.3—1 (Footnote g), particulate emissions can be
reduced considerably when low—sulfur grade 6 oil is fired. This is
because low sulfur No. 6, whether refined from naturally occurring
low sulfur crude oil or desulfurized by one of several current
processes, exhibits substantially lower viscosity and reduced
asphaltene, ash and sulfur - all of which results in better
atomization and cleaner combustion.
8/82 External Combustion Sources 1.3-1
-------
TABLE 1.3-1. UNCONTROLLED EMISSION FACTORS FOR FUEL OIL COMBUSTION
EMISSION FACTOR RATING: A
N5
M
c/;
en
H
O
PO
oo
oo
Particulate
Matter
Sulfur Dioxide
Sulfur
Trloxide
Carbon Hitrogen Oxide
Monoxide
Volatile Organics
Nonmethane Methane
Boiler Type
kg/10 1 lh/10
•3gal kg/103! lb/103gal kg/103l lb/103gal kg/103l lb/103gal kg/103l lb/103gal kg/103l lb/103gal kg/103l lb/103gal
Utility Boilers
Residual Oil
Industrial Boilers
Residual Oil
Distillate Oil
g
0.24
Commercial Boilers
Residual Oil g
Distillate Oil 0.24
Residential Furnaces
Distillate Oil
19S
19S
17S
195
17E
157S 0.34Sh 2.9Sh
157S
142S
157S
142S
0.24S
0. 24S
0.24S
0.24S
23
2S
2S
25
0,6
0.6
0.6
0.6
0.6
8.0 67
(12.&H5)1 (105H42)1
2.4
6.6
2.4
2.2
55J
20
55
20
18
0.09 0.76
0.034 0.28
0.024 0.2
0.14 1.13
0.04 0.34
0.085 0.713
0.03
0.12
0.006
0.057
0.026
0.214
0.28
1.0
0.052
0.475
0.216
1.78
Distillate Oil 0.3 2.5 17S 142B 0.24S 2S 0.6 5
aBoilers can be approximately classified according to their gross (higher) heat rate as shown helov:
Utility (oower olant) boilers: >106 x 10* J/hr (MOO x 106 Btu/hr)
;rs: 10.6 x 10* to 106 x 109 J/hr (10 x 106 to 100 x 106 Btu/hr)
:rs: 0.5 x 10'* to 10.6 x 109 J/hr (0.5 x 106 to 10 x 106 Btu/hr)
.««^^. jT\ R -u- 1 n9 1 M,- tjrf\ R „ t flfc llt.n JUi-'l
Expressed as N02, References 1-5, B-1L, 17 and 26, Test results indicate that at least 95s by weight of HOK Is HO for all boiler types except residential
furnaces, where about 75% Is NO.
References 18-21. Volatile organic compound emiss Ions are genera11y negligible unions boiler Is improperly operated or not wel 1 maintained, in which case
emissions may increase by several orders of mn^nitude.
Particulate emission factors for residual oil combustIon are, on average, a function of fuel oil grade and sulfur content:
Grade 6 oil: 1.25(S) + 0.38 kg/103 liter [10(3) + 3 lb/103 gal] where S in tlie weight % of sulfur in the oil. This relations
basttd on 31 Individual tes ts and lias a correlr-j tion coefficient of 0.65.
f ]„ c „ j i . i TC i, „ n n3 i t t-r.~ /in i u Mn3 ,,^i\
nship
(irade 5 oil:
Grade 4 oil:
1.25 kg/103 liter (10 lb/103 gal)
0.88 kg/103 liter (7 lb/103 gal)
Jse 5 kg/103 liters (42 lb/103 gal) for tangentially fir
ccurately by the empirical relationship:
kg H02/103 liters - 2.75 +• 500,5 weight %) nitrogen content, use 15 kg N02/103 liter (120 Ib NG2/lU3gal) as an emission factor*
-------
Boiler load can also affect particulate emissions in units
firing No. 6 oil. At low load conditions, particulate emissions
may be lowered by 30 to 40 percent from utility boilers and by as
much as 60 percent from small industrial and commercial units. No
significant particulate reductions have been noted at low loads
from boilers firing any of the lighter grades, however. At too low
a load condition, proper combustion conditions cannot be maintained,
and particulate emissions may increase drastically. It should be
noted, in this regard, that any condition that prevents proper
boiler operation can result in excessive particulate formation.
1-5 25 27
Sulfur Oxides (SOX) ' ' - Total sulfur oxide emissions are
almost entirely dependent on the sulfur content of the fuel and are
not affected by boiler size burner design, or grade of fuel being
fired. On the average, more than 95 percent of the fuel sulfur is
emitted as S02, about 1 to 5 percent as S03 and about 1 to 3 percent
as particulate sulfates. Sulfur trioxide readily reacts with water
vapor (both in air and in flue gases) to form a sulfuric acid mist.
Nitrogen Oxides (NOX) ' ' ' * - Two mechanisms form nitrogen
oxides, oxidation of fuelbound nitrogen and thermal fixation of
the nitrogen in combustion air. Fuel NOX are primarily a function
of the nitrogen content of the fuel and the available oxygen (on
the average, about 45 percent of the fuel nitrogen is converted to
NOX, but this may vary from 20 to 70 percent). Thermal NOX, on the
other hand, are largely a function of peak flame temperature and
available oxygen - factors which depend on boiler size, firing
configuration and operating practices.
Fuel nitrogen conversion is the more important NOX forming
mechanism in residual oil boilers. Except in certain large units
having unusually high peak flame temperatures, or in units firing a
low nitrogen residual oil, fuel NOX will generally account for over
50 percent of the total NOX generated. Thermal fixation, on the
other hand, is the dominant NOX forming mechanism in units firing
distillate oils, primarily because of the negligible nitrogen
content in these lighter oils. Because distillate oil fired boilers
usually have low heat release rates, however, the quantity of
thermal NOX formed in them is less than that of larger units.
A number of variables influence how much NOX is formed by
these two mechanisms. One important variable is firing configuration.
Nitrogen oxide emissions from tangentially (corner) fired boilers
are, on the average, less than those of horizontally opposed units.
Also important are the firing practices employed during boiler
operation. Limited excess air firing, flue gas recirculation,
staged combustion, or some combination thereof may result in NOX
reductions from 5 to 60 percent. See Section 1.4 for a discussion
of these techniques. Load reduction can likewise decrease NOX
production. Nitrogen oxides emissions may be reduced from 0.5 to 1
percent for each percentage reduction in load from full load operation.
It should be noted that most of these variables, with the exception
8/82
External Combustion Sources
1.3-3
-------
of excess air, influence the NOX emissions only of large oil fired
boilers. Limited excess air firing is possible in many small
boilers, but the resulting NOX reductions are not nearly as significant.
18—21
Other Pollutants - As a rule, only minor amounts of volatile
organic compounds (VOC) and carbon monoxide will be emitted from
the combustion of fuel oil. The rate at which VOCs are emitted
depends on combustion efficiency. Emissions of trace elements from
oil fired boilers are relative to the trace element concentrations
of the oil.
Organic compounds present in the flue gas streams of boilers
include aliphatic and aromatic hydrocarbons, esters, ethers, alcohols,
carbonyls, carboxylic acids and polycylic organic matter. The last
includes all organic matter having two or more benzene rings.
Trace elements are also emitted from the combustion of fuel oil.
The quantity of trace elements emitted depends on combustion
temperature, fuel feed mechanism and the composition of the fuel.
The temperature determines the degree of volatilization of specific
compounds contained in the fuel. The fuel feed mechanism affects
the separation of emissions into bottom ash and fly ash.
If a boiler unit is operated improperly or is poorly maintained,
the concentrations of carbon monoxide and VOCs may increase by several
orders of magnitude.
1.3.3 Controls
The various control devices and/or techniques employed on
oil fired boilers depend on the type of boiler and the pollutant
being controlled. All such controls may be classified into three
categories, boiler modification, fuel substitution and flue gas
cleaning.
Boiler Modification ' ' * - Boiler modification includes
any physical change in the boiler apparatus itself or in its opera-
tion. Maintenance of the burner system, for example, is important
to assure proper atomization and subsequent minimization of any
unburned combustibles. Periodic tuning is important in small units
for maximum operating efficiency and emission control, particularly
of smoke and CO. Combustion modifications, such as limited excess
air firing, flue gas recirculation, staged combustion and reduced
load operation, result in lowered NOX emissions in large facilities.
See Table 1.3-1 for specific reductions possible through these
combustion modifications.
OC 1O 9tt
Fuel Substitution ' ' ' - Fuel substitution, the firing of
"cleaner" fuel oils, can substantially reduce emissions of a number
of pollutants. Lower sulfur oils, for instance, will reduce SOX
emissions in all boilers, regardless of size or type of unit or
1.3-4 EMISSION FACTORS 8/82
-------
grade of oil fired. Particulates generally will be reduced when a
lighter grade of oil is fired. Nitrogen oxide emissions will be
reduced by switching to either a distillate oil or a residual oil
with less nitrogen. The practice of fuel substitution, however,
may be limited by the ability of a given operation to fire a better
grade of oil and by the cost and availability thereof.
1 C_1 f. O O
Flue Gas Cleaning ' - Flue gas cleaning equipment generally
is employed only on large oil fired boilers. Mechanical collectors,
a prevalent type of control device, are primarily useful in con-
trolling particulates generated during soot blowing, during upset
conditions, or when a very dirty, heavy oil is fired. During these
situations, high efficiency cyclonic collectors can effect up to 85
percent control of particulate. Under normal firing conditions or
when a clean oil is combusted, cyclonic collectors will not be nearly
as effective due to a high percentage of small particles (less than
3 microns diameter) being emitted.
Electrostatic precipitators are commonly used in oil fired power
plants. Older precipitators which are also small precipitators
generally remove 40 to 60 percent of the particulate matter emissions.
Due to the low ash content of the oil, greater collection efficiency
may not be required. Today, new or rebuilt electrostatic precipitators
have collection efficiencies of up to 90 percent.
Scrubbing systems have been installed on oil-fired boilers,
especially of late, to control both sulfur oxides and particulate.
These systems can achieve S02 removal efficiencies of up to 90 to
95 percent and provide particulate control efficiencies on the
order of 50 to 60 percent.
1. W. S. Smith, Atmospheric Emissions from Fuel Oil Combustion;
An Inventory Guide, 999-AP-2, U.S. Department of Health,
Education and Welfare, Cincinnati, OH, November 1962.
2. J. A. Danielson (ed.)» Air Pollution Engineering Manual, Second
Edition, AP-40, U.S. Environmental Protection Agency, Research
Triangle Park, NC, 1973. Out of Print.
3. A. Levy,
A Field Investigation of Emissions from Fuel
Oil Combustion for Space Heating, API Bulletin 4099, Battelle
Columbus Laboratories, Columbia, OH, November 1971.
4. R. E. Barrett, et al., Field Investigation of Emissions from
Combustion Equipment for Space Heating, EPA-R2-73-084a, U.S.
Environmental Protection Agency, Research Triangle Park, NC,
June 1973.
5. G. A. Cato, et al. , Field Testing: Application of Combustion
Modifications To Control Pollutant Emissions from Industrial
Boilers - Phase_I, EPA-650/2-74-078a, U.S. Environmental
Protection Agency, Research Triangle Park, NC, October 1974.
8/82
External Combustion Sources
1.3-5
-------
6. G. A. Cato, et al., Field Testing; Application of Combustion
Modifications To Control Pollutant Emissions from Industrial
Boilers - Phase II, EPA-600/2-76-086a, U.S. Environmental
Protection Agency, Research Triangle Park, NC, April 1976.
7. Particulate Emission Control Systems for Oil-Fired Boilers,
EPA-450/3-74-063, U.S. Environmental Protection Agency, Research
Triangle Park, NC, December 1974.
8. W. Bartok, et al., Systematic Field Study of NOX Emission
Control Methods for Utility Boilers, APTD-1163, U.S. Environmental
Protection Agency, Research Triangle Park, NC, December 1971.
9. A. R. Crawford, et al., Field Testing: Application of Combustion
Modifications To Control NOX Emissions from Utility Boilers,
EPA-650/2-74-066, U.S. Environmental Protection Agency, Research
Triangle Park, NC, June 1974.
10. J. F. Deffner, et al., Evaluation of Gulf Econojet Equipment with
Respect to Air Conservation, Report No. 731RC044, Gulf Research
and Development Company, Pittsburgh, PA, December 18, 1972.
11. C. E. Blakeslee and H. E. Burbach, "Controlling NOX Emissions
from Steam Generators", Journal of the Air Pollution Control
Association, 23_: 37-42, January 1973.
12. C. W. Siegmund, "Will Desulfurized Fuel Oils Help?", American
Society of Heating, Refrigerating and Air Conditioning Engineers
Journal, LU 29-33, April 1969.
13, F. A. Govan, et al., "Relationships of Particulate Emissions
Versus Partial to Full Load Operations for Utility-sized
Boilers", Proceedings of Third Annual Industrial Air Pollution
Control Conference, Knoxville, TN, March 29-30, 1973.
14. R. E. Hall, et al., A^jtudy of Air Pollutant Emissions from
Residential Heating Systems, EPA-650/2-74-003, U.S. Environmental
Protection Agency, Research Triangle Park, NC, January 1974.
15. Flue Gas Desulfurization: Installations and Operations, U.S.
Environmental Protection Agency, Washington, DC, September
1974.
16. Proceedings; Flue Gas Desulfurization Symposium - 1973,
EPA-650/2-73-038, U.S. Environmental Protection Agency, Research
Triangle Park, NC, December 1973.
17. R. J. Milligan, et al., Review of NOx Emission Factors for
Stationary Fossil Fuel Combustion Sources, EPA-450/4-79-021,
U.S. Environmental Protection Agency, Research Triangle Park,
NC, September 1979.
1.3-6
EMISSION FACTORS
8/82
-------
18. N. F. Suprenant, et al., Emissions Assessment of Conventional
Stationary Combustion Systems: Volume I. Gas and Oil-Fired
Residential Heating Sources, EPA-600/7-79-029b, U.S. Environmental
Protection Agency, Research Triangle Park, NC, May 1979.
19. C. C. Shih, et al., Emissions Assessment of Conventional
Stationary Combustion Systems: Volume III. External Combustion
Sources for Electricity Generation. EPA Contract No. 68-02-2197,
TRW Inc., Redondo Beach, CA, November 1980.
20. N. F. Suprenant, et al.. Emissions Assessment of Conventional
Stationary Combustion Systems'. Volume IV. Commercial
Institutional Combustion Sources, EPA Contract No. 68-02-2197,
GCA Corporation, Bedford, MA, October 1980.
21. N. F. Suprenant, et al., Emissions Assessment of Conventional
Stationary Combustion Systems; Volume V. Industrial Combustion
Sources, EPA Contract No. 68-02-2197, GCA Corporation, Bedford,
MA, October 1980.
22. Fossil Fuel Fired Industrial Boilers - Background Information
for Proposed Standards (Draft EIS), Office of Air Quality
Planning and Standards, U.S. Environmental Protection Agency,
Research Triangle Park, NC, June 1980.
23. K. J. Lim, et al., Technology Assessment Report for Industrial
Boiler Applications: NOX Combustion Modification, EPA-600/
7-79-178f, U.S. Environmental Protection Agency, Research
Triangle Park, NC, December 1979.
24. Emission Test Reports, Docket No. OAQPS-78-1, Category II-I-257
through 265, U.S. Environmental Protection Agency, Research
Triangle Park, NC, 1972 through 1974.
25. Primary Sulfate Emissions from Coal and Oil Combustion, Industrial
Environmental Research Laboratory, U.S. Environmental Protection
Agency, Research Triangle Park, NC, February 1980.
26. C. Leavitt, et al., Environmental Assessment of an Oil-Fired
Controlled Utility Boiler, EPA-600/7-80-087, U.S. Environmental
Protection Agency, Research Triangle Park, NC, April 1980.
27. W. A. Carter and R. J. Tidona, Thirty-day Field Tests of
Industrial Boilers; Site 2 - Residual-oil-fired Boiler,
EPA-600/7-80-085b, U.S. Environmental Protection Agency,
Research Triangle Park, NC, April 1980.
28. G. R. Offen, et al., Control of Particulate Matter from Oil
Burners and Boilers, EPA-450/3-76-005, U.S. Environmental
Protection Agency, Research Triangle Park, NC, April 1976.
8/82
External Combustion Sources
1.3-7
-------
-------
1.4 NATURAL GAS COMBUSTION
1.4.1 General1'2
Natural gas is one of the major fuels used throughout the
country. It is used mainly for power generation, for industrial
process steam and heat production, and for domestic and commercial
space heating. The primary component of natural gas is methane,
although varying amounts of ethane and smaller amounts of nitrogen,
helium and carbon dioxide are also present. Gas processing plants
are required for recovery of liquefiable constituents and removal
of hydrogen sulfide (H2S) before the gas is used (see Natural Gas
Processing, Section 9.2). The average gross heating value of
natural gas is approximately 9350 kilocalories per standard cubic
meter (1050 British thermal units/standard cubic foot), usually
varying from 8900 to 9800 kcal/scm (1000 to 1100 Btu/scf).
Because natural gas in its original state is a gaseous,
homogenous fluid, its combustion is simple and can be precisely
controlled. Common excess air rates range from 10 to 15 percent,
but some large units operate at lower excess air rates to increase
efficiency and reduce nitrogen oxide (NOX) emissions.
o_o A
1.4.2 Emissions and Controls
Even though natural gas is considered to be a relatively clean
fuel, some emissions can occur from the combustion reaction. For
example, improper operating conditions, including poor mixing,
insufficient air, etc., may cause large amounts of smoke, carbon
monoxide and hydrocarbons to be produced. Moreover, because a
sulfur containing mercaptan is added to natural gas for detection
purposes, small amounts of sulfur oxides will also be produced in
the combustion process.
Nitrogen oxides are the major pollutants of concern when
burning natural gas. Nitrogen oxide emissions are functions of
combustion chamber temperature and combustion product cooling rate.
Emission levels vary considerably with the type and size of unit
and with operating conditions.
In some large boilers, several operating modifications may be
employed for NO control. Staged combustion for example, including
off-stoichiometric firing and/or two stage combustion, can reduce
NO emissions by 5 to 50 percent.2° In off-stoichiometric firing,
also called "biased firing", some burners are operated fuel rich,
some fuel lean, and others may supply air only. In two stage
combustion, the burners are operated fuel rich (by introducing only
70 to 90 percent stoichiometric air), with combustion being completed
by air injected above the flame zone through second stage "NO-ports".
In staged combustion, NOX emissions are reduced because the bulk of
combustion occurs under fuel rich conditions.
8/82 External Combustion Sources 1.4-1
-------
Other NOX reducing modifications include low excess air firing
and flue gas recirculation. In low excess air firing, excess air
levels are kept as low as possible without producing unacceptable
levels of unburned combustibles (carbon monoxide, volatile organic
compounds and smoke) and/or other operational problems. This
technique can reduce NOX emissions by 5 to 35 percent, primarily
because of lack of oxygen during combustion. Flue gas recirculation
into the primary combustion zone, because the flue gas is relatively
cool and oxygen deficient, can also lower NOX emissions by 4 to
85 percent, depending on the amount of gas recirculated. Flue gas
recirculation is best suited for new boilers. Retrofit application
would require extensive burner modifications. Initial studies
indicate that low NOX burners (20 to 50 percent reduction) and
ammonia injection (40 to 70 percent reduction) also offer NOX
emission reductions.
Combinations of the above combustion modifications may also be
employed to reduce NOX emissions further. In some boilers, for
instance, NOX reductions as high as 70 to 90 percent have been
produced by employing several of these techniques simultaneously.
In general, however, because the net effect of any of these
combinations varies greatly, it is difficult to predict what the
reductions will be in any given unit.
Emission factors for natural gas combustion are presented in
Table 1.4-1, and factor ratings in Table 1.4-2.
U
0.6
0.4
0.2
I
40
60
80
LOAD, percent
100
110
Figure 1.4-1, Load reduction coefficient as function of boiler
load. (Used to determine NOX reductions at reduced loads in
large boilers.)
1.4-2 EMISSION FACTORS
8/82
-------
00
CO
KJ
TABLE 1.4-1. UNCONTROLLED EMISSION FACTORS FOR NATURAL GAS COMBUSTION5
X
ft-
a
EU
i—>
n
en
H-
O
cn
O
n
ft
CO
Furnace Size & Type
(106 Btu/hr
heat input)
Utility boilers
(MOO)
Industrial boilers
(10 - 100)
Domestic and
commercial boilers
(< £0)
Particulates
kg/106m3 lb/10fift3
16-80
16-80
16-80
1-5
1-5
1-5
Sulfurc
Dioxide
kg/106m3 lb/106ft3
9.6 0,6
9.6 0.6
9.6 0.6
ITJ d , e
Nitrogen
Oxide
kg/106m3 Ib/lO^ft
8800h 550h
2240 140
1600 100
f E
Carbon
Monoxide
3 kg/106ra3 lb/106ft3
640
560
320
40
35
20
Volatile
Nonme thane
kg/loV lb/lQ6ft3
23
44
34
1.4
2.8
5.3
OrganicB
Methane
kg/106m3 lb/106ft3
4.8
48
43
0.3
3
2.7
All emission factors are expressed as weight per volume fuel fired.
References 15-18.
Reference 4 (bnsed on an average sulfur content of natural gas of 4600 g/10 Nm (2000 gr/10 scf).
dReferences 4-5,7-8,11,14,18-19,21.
^Expressed as NOj. Test results indicate that about 95 weight Z of NOX IB NO.
References 4,7-8,16,18,22-25.
^References 16 and 18. Kay increase 10 to 100 times with improper operation or maintenance.
Use 4400 kg/10 m3 {275 lb/10 ft3) for tangentially fired units. At reduced loads, multiply this factor by the load reduction coefficient
given in Figure 1,4-1. See text for potential NOX reductions by combustion modifications.
modifications will also occur at reduced load conditions.
Note that the NOX reduction from these
-------
TABLE 1.4-2. FACTOR RATINGS FOR NATURAL GAS COMBUSTION
Furnace Type
Utility boiler
Industrial boiler
Commercial boiler
Residential furnace
Particulates
B
B
B
B
Sulfur
Oxides
A
A
A
A
Nitrogen
Oxides
A
A
A
A
Carbon
Monoxides
A
A
A
A
VOC
Nonmethane Methane
C
c
D
D
C
C
D
D
References for Section 1.4
1. D. M. Hugh, et al., Exhaust Gases from Combustion and Industrial
Processes, EPA Contract No. EHSD 71-36, Engineering Science,
Inc., Washington, DC, October 2, 1971.
2. J. H. Perry (ed.), Chemical Engineer's Handbook, 4th Edition,
McGraw-Hill, New York, NY, 1963.
3. H. H. Hovey, et al., The Development of Air Contaminant Emission
Tables for Non-process Emissions, New York State Department of
Health, Albany, NY, 1965.
4. W. Bartok, et al., Systematic Field Study of NOX Emission
Control Methods^ for Utility Boilers, APTD-1163, U.S. Environ-
mental Protection Agency, Research Triangle Park, NC, December
1971.
5. F. A. Bagwell, et al., "Oxides of Nitrogen Emission Reduction
Program for Oil and Gas Fired Utility Boilers", Proceedings
of the American Power Conference, j.4_: 683-693, April 1970.
6. R. L. Chass and R. E. George, "Contaminant Emissions from the
Combustion of Fuels", Journal of the Air Pollution Control
Association JJD-.34-42. February 1980.
7. H. E. Dietzmann, A Study of Power Plant Boiler Emissions,
Final Report No. AR-837, Southwest Research Institute, San
Antonio, TX, August 1972.
8. R. E. Barrett, et al., Field Investigation of Emissions from
Combustion Equipment for Space Heating, EPA-R2-73-084, U.S.
Environmental Protection Agency, Research Triangle Park, NC,
June 1973.
9. Private communication with the American Gas Association
Laboratories, Cleveland, OH, May 1970.
1.4-4 EMISSION FACTORS 8/82
-------
I
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
Unpublished data on domestic gas fired units, National Air
Pollution Control Administration, U.S. Department of Health,
Education and Welfare, Cincinnati, OH, 1970.
C. E. Blakeslee and H. E. Burbock, "Controlling NOX Emissions
from Steam Generators", Journal of the Air Pollution Control
Association, 23:37-42, January 1979.
L. K. Jain, et al., "State of the Art" for Controlling NOX
Emissions: Part 1, Utility Boilers, EPA Contract No. 68-02-0241,
Catalytic, Inc., Charlotte, NC, September 1972.
J. W. Bradstreet and R. J. Fortman, "Status of Control Techniques
for Achieving Compliance with Air Pollution Regulations by the
Electric Utility Industry", Presented at the 3rd Annual Industrial
Air Pollution Control Conference, Knoxville, TN, March 1973.
Study of Emissions of NOX from Natural Gas-Fired Steam Electric
Power Plants in Texas, Phase II, Vol. 2, Radian Corporation,
Austin, TX, May 8, 1972.
N. F. Suprenant, et al., Emissions Assessment of Conventional
Stationary Combustion Systems: Volume I. Gas and Oil-Fired
Residential Heating Sources, EPA-600/7-79-029b, U.S. Environ-
mental Protection Agency, Research Triangle Park, NC, May
1979.
C. C. Shih, et al., Emissions Assessment of Conventional
Stationary Combustion Systems: Volume III. External
Combustion Sources for Electricity Generation, EPA Contract
No. 68-02-2197, TRW, Inc., Redondo Beach, CA, November 1980.
N. F. Suprenant, et al., Emissions Assessment of Conventional
Stationary Combustion Systems: Volume IV. Commercial
Institutional Combustion Sources, EPA Contract No. 68-02-2197,
GCA Corporation, Bedford, MA, October 1980.
N. F. Suprenant, et al., Emissions Assessment of Conventional
Stationary Combustion Systems: Volume V. Industrial Combustion
Sources, EPA Contract No. 68-02-2197, GCA Corporation, Bedford,
MA, October 1980.
R. J. Milligan, et al., Review of NOX Emission Factors for
Stationary Fossil Fuel Combustion Sources, EPA-450/4-79-021,
U.S. Environmental Protection Agency, Research Triangle Park,
NC, September 1979.
W. H. Thrasher and D. W. Dewerth, Evaluation of the Pollutant
Emissions from Gas-Fired Water Heaters, Research Report No.
1507, American Gas Association, Cleveland, OH, April 1977.
8/82
External Combustion Sources
1.4-5
-------
21. W. H. Thrasher and D. W. Dewerth, Evaluation of the Pollutant
Emissions from Gas-Fired Forced Air Furnaces, Research Report
No. 1503, American Gas Association, Cleveland, OH, May 1975.
22. G. A. Cato, et al., Field Testing: Application of Combustion
Modification To Control Pollutant Emissions from Industrial
Boilers, Phase I, EPA-650/2-74-078a, U.S. Environmental Protection
Agency, Washington, DC, October 1974.
23. G. A. Cato, et al., Field Testing: Application of Combustion
Modification To Control Pollutant Emissions from Industrial
Boilers, Phase II, EPA-600/2-76-086a, U.S. Environmental Pro-
tection Agency, Washington, DC, April 1976.
24. W. A. Carter and H. J. Buening, Thirty-day Field Tests of
Industrial Boilers - Site 5, EPA Contract No. 68-02-2645, KVB
Engineering, Inc., Irvine, CA, May 1981.
25. W. A. Carter and H. J. Buening, Thirty-day Field Tests of
Industrial Boilers - Site 6. EPA Contract No. 68-02-2645,
KVB Engineering, Inc., Irvine, CA, May 1981.
26. K. J. Lim, et al., Technology Assessment Report forIndustrial
Boiler Applications: NOx Combustion Modification, EPA Contract
No. 68-02-3101, Acurex Corporation, Mountain View, CA, December
1979.
1.4-6
EMISSION FACTORS
8/82
-------
1.5 LIQUEFIED PETROLEUM GAS COMBUSTION
1.5.1 General
Liquefied petroleum gas (LPG) consists of butane, propane, or
a mixture of the two, and of trace amounts of propylene and butylene.
This gas, obtained from oil or gas wells as a gasoline refining
byproduct, is sold as a liquid in metal cylinders under pressure
and, therefore, is often called bottled gas. LPG is graded according
to maximum vapor pressure, with Grade A being mostly butane, Grade F
mostly propane, and Grades B through E being varying mixtures of
butane, and propane. The heating value of LPG ranges from 6,480
kcal/liter (97,400 Btu/gallon) for Grade A to 6,030 kcal/liter
(90,500 Btu/gallon) for Grade F. The largest market for LPG is the
domes tic/commercial market, followed by the chemical industry and
the internal combustion engine.
1.5.2 Emissions
LPG is considered a "clean" fuel because it does not produce
visible emissions. However, gaseous pollutants such as carbon
monoxide, volatile organic compounds (VOC's) and nitrogen oxides do
occur. The most significant factors affecting these emissions are
burner design, adjustment and venting. Improper design, blocking
and clogging of the flue vent, and lack of combustion air result in
improper combustion and the emission of aldehydes, carbon monoxide,
hydrocarbons and other organics. Nitrogen oxide emissions are a
function of a number of variables including temperature, excess
air and residence time in the combustion zone. The amount of
sulfur dioxide emitted is directly proportional to the amount of
sulfur in the fuel. Emission factors for LPG combustion are presented
in Table 1.5-1.
8/82
External Combustion Sources
1.5-1
-------
Ul
NJ
cn
en
t-i
i
H
O
oo
oo
NJ
TABLE 1.5-1. EMISSION FACTORS FOR LPG COMBUSTION3
EMISSION FACTOR RATING: C
Furnace
Type and
fuel
Industrial
Butane
Propane
Domestic/
commercial
Butane
Propane
Participates
Sulfur
Oxides"
kg/103!
0.01-0.06
0.01-0.05
0.01-0.06
0.01-0.05
lb/10'gnl
U, 10-0. 47
U. 09-0. 44
0.10-0.47
0.09-0.44
kg/103]
0.01S
0.01S
0.01S
0.01S
lt>/103gal
0.09S
0.09S
0.09S
0.09S
Nitrogen
Oxides0
kg/103l
1.58
1.49
1.13
1.05
lb/103gal
13.2
12.4
9.4
8.8
Carbon
Monox ide
kg/103l
0.4
0.37
0.23
0.22
Ib/103gal
3.3
3.1
1.9
i.a
Volatile
No nine thane
kg/103l
0.03
0.03
0.06
0.06
lb/103gal
0.26
0.25
0.5
0.47
Organ ics
Methane
kg/103l
0.03
0.03
0.03
0.03
Ib/lO'gal
0.28
0.27
0.25
0.24
Assumes emissions (except sit 1 fur oxides) are the name, on n heat input basis, as for natural gas combust Ion.
Expressed as S02- S equals the sulfur content expressed in g/100 m3 gas vapor. For example, if sulfur content is 0.366 g/lOOm3 (0.16 gr/100ft3) vapor,
the S0a emission factor would be 0.01 x 0.366 or 0.0037 kg S02/103 liters (0.09 x 0.16 or 0.014 Ib of SO2/1000 pfal) butane burned.
Expressed as H03.
-------
References for Section 1.5
1. Air Pollutant Emission Factors, Final Report, Contract No.
CPA-22-69-119, Resources Research, Inc., Reston, VA, Durham,
NC, April 1970.
2. E. A. Clifford, A Practical Guide to Liquified Petroleum Gas
Utilization, New York, Moore Publishing Co., 1962.
8/82 External Combustion Sources 1.5-3
-------
-------
1.6 WOOD WASTE COMBUSTION IN BOILERS
1.6.1 General
The burning of wood waste in boilers is mostly confined to
those industries where it is available as a byproduct. It is
burned both to obtain heat energy and to alleviate possible solid
waste disposal problems. Wood waste may include large pieces like
slabs, logs and bark strips as well as cuttings, shavings, pellets
and sawdust, and heating values for this waste range from about
4,400 to 5,000 kilocalories per kilogram of fuel dry weight (7,940 to
9,131 Btu/lb). However, because of typical moisture contents of
40 to 75 percent, the heating values for many wood waste materials
as fired range as low as 2,200 to 3,300 kilocalories per kilogram
of fuel. Generally, bark is the major type of waste burned in pulp
mills, and a varying mixture of wood and bark waste, or wood waste
alone, are most frequently burned in the lumber, furniture and
plywood industries.
1.6.2 Firing Practices
1-3
A variety of boiler firing configurations is used for burning
wood waste. One common type in smaller operations is the dutch
oven, or extension type of furnace with a flat grate. This unit is
widely used because it can burn fuels with a very high moisture
content. Fuel is fed into the oven through apertures at the top of
a firebox and is fired in a cone shaped pile on a flat grate. The
burning is done in two stages, drying and gasification, and combustion
of gaseous products. The first stage takes place in a cell separated
from the boiler section by a bridge wall. The combustion stage
takes place in the main boiler section. The dutch oven is not
responsive to changes in steam load, and it provides poor combustion
control.
In a fuel cell oven, the fuel is dropped onto suspended fixed
grates and is fired in a pile. Unlike the dutch oven, the fuel
cell also uses combustion air preheating and repositioning of the
secondary and tertiary air injection ports to improve boiler efficiency.
In many large operations, more conventional boilers have been
modified to burn wood waste. These units may include spreader
stokers with traveling grates, vibrating grate stokers, etc., as
well as tangentially fired or cyclone fired boilers. The most
widely used of these configurations is the spreader stoker. Fuel
is dropped in front of an air jet which casts the fuel out over a
moving grate, spreading it in an even thin blanket. The burning is
done in three stages in a single chamber, (1) drying, (2) distillation
and burning of volatile matter and (3) burning of carbon. This
type of operation has a fast response to load changes, has improved
combustion control and can be operated with multiple fuels. Natural
gas or oil are often fired in spreader stoker boilers as auxiliary
fuel. This is done to maintain constant steam when the wood waste
8/82
External Combustion Sources
1.6-1
-------
supply fluctuates and/or to provide more steam than is possible
from the waste supply alone.
Sander dust is often burned in various boiler types at plywood,
particle board and furniture plants. Sander dust contains fine
wood particles with low moisture content (less than 20 weight
percent). It is fired in a flaming horizontal torch, usually with
natural gas as an ignition aid or supplementary fuel.
A—7 ft
1.6.3 Emissions and Controls
The major pollutant of concern from wood boilers is particulate
matter, although other pollutants, particularly carbon monoxide,
may be emitted in significant amounts under poor operating conditions,
These emissions depend on a number of variables, including (1) the
composition of the waste fuel burned, (2) the degree of flyash
reinjection employed and (3) furnace design and operating conditions.
The composition of wood waste depends largely on the industry
whence it originates. Pulping operations, for example, produce
great quantities of bark that may contain more than 70 weight
percent moisture and sand and other noncombustibles. Because of
this, bark boilers in pulp mills may emit considerable amounts of
particulate matter to the atmosphere unless they are well controlled.
On the other hand, some operations such as furniture manufacture
produce a clean dry (5 to 50 weight percent moisture) wood waste
that results in relatively few particulate emissions when properly
burned. Still other operations, such as sawmills, burn a variable
mixture of bark and wood waste that results in particulate emissions
somewhere between these two extremes.
Furnace design and operating conditions are particularly
important when firing wood waste. For example, because of the high
moisture content that can be present in this waste, a larger than
usual area of refractory surface is often necessary to dry the fuel
before combustion. In addition, sufficient secondary air must be
supplied over the fuel bed to burn the volatiles that account for
most of the combustible material in the waste. When proper drying
conditions do not exist, or when secondary combustion is incomplete,
the combustion temperature is lowered, and increased particulate,
carbon monoxide and hydrocarbon emissions may result. Lowering of
combustion temperature generally results in decreased nitrogen
oxide emissions. Also, emissions can fluctuate in the short term
due to significant variations in fuel moisture content over short
periods of time.
Flyash reinjection, which is common in many larger boilers to
improve fuel efficiency, has a considerable effect on particulate
emissions. Because a fraction of the collected flyash is reinjected
into the boiler, the dust loading from the furnace, and consequently
from the collection device, increases significantly per unit of
wood waste burned. It is reported that full reinjection can cause
1.6-2 EMISSION FACTORS 8/82
-------
00
oo
ro
TABLE 1.6-1. EMISSION FACTORS FOR WOOD AND BARK COMBUSTION IN BOILERS
Pollutant/Fuel Type/Control
Partlculatea>b
Bark<=
Multiclone, with fly ash
reinfection1*
Multiclone, without fly ash
reinjeetion11
Uncontrolled
Hood/bark mixture6
Multiclone, with fly ash
relnjectionf
Multiclone, without fly ash
reinjectionf
Uncontrolled^
Uncontrolled
Sulfur DioxldeJ
Nitrogen Oxides (as N02)k
50,000 - 400,000 Ib steam/hr
<50,000 Ib steam/hr
Carbon Monoxide111
VOC
Nonme thanen
MethaneP
tg/Mg
7
4.5
24
3
2.7
3.6
4.4
0.075
(0.01 - 0.2)
1,4
0.34
2-24
0.7
0.15
Ib/ton
14
9
47
6
5.3
7.2
8.8
0.15
(0.02 - 0.4)
2.8
0.68
4-47
1.4
0.3
Rating
B
B
B
C
C
c
c
B
B
B
C
D
E
References 2, 4, 9, 17-18. For boilers burning gas or oil as
an auxiliary fuel, all particulates are assumed to reault
from only wood waste fuel.
"May Include condensible hydrocarbons consisting of pitches
and tars, mostly from back half catch of EPA Method 5.
Tests reported In Reference 20 indicate that condensible
hydrocarbons account for 41 of total particulate weight.
cBased on fuel moisture content of about 501.
dAfter control equipment, assuming an average collection
efficiency of 801. Data from References 4, 7-8 indicate
that 501 fly ash reinfection increases the dust load at
the cyclone inlet 1.2 to 1.5 times, while 1001 fly ash
relnjection increases the load 1.5 to 2 times without
reinjeetion.
eBased on fuel noiature content of 331.
Based on large dutch ovens and spreader stokers (averaging
23,430 kg steam/hr) with steam preasures from 20 - 75 kna
(140 - 530 psi).
BBased on small dutch ovens and spreader stokers (usually
operating <9075 kg steam/hr), with pressures from 5-30 kpa
(35 - 230 psi). Careful air adjustments and improved fuel
separation and firing were used on some units, but the
effects cannot be isolated.
nReferences 12-13, 19, 27. Wood waste includes cuttings,
shavings, sawdust and chips, but not bark. Moisture content
ranges from 3-50 weight X. Based on small units
(<3000 kg steam/hr) in New York and North Carolina.
^Reference 23. Based on tests of fuel sulfur content and
sulfur dioxide emissions at four mills burning bark. The
lower limit of the range (in parentheses) should be used for
wood, and higher values for bark. A heating value of 5000
kcal/kg (9000 BTU/lb) is assumed. The factors are based on
the dry weight of fuel,
""References 7, 24-26. Several factors can influence emission
rates, including combustion zone temperatures, excess air,
boiler operating conditions, fuel moisture and fuel nitrogen
content. Factors on a dry weight basis.
"Reference 30. Factors on a dry weight basis.
"References 20, 30. Nonmethane VOC reportedly consists of
compounds with a high vapor pressure such as alpha pinene.
PReference 30. Based on an approximation of aethane/non-
methane ratio, which is very variable. Methane, expressed as
a X of total volatile organic compounds, varied from 0-74
weight X.
Ul
-------
a tenfold increase in the dust loadings of some systems, although
increases of 1.2 to 2 times are more typical for boilers using 50
to 100 percent reinjection. A major factor affecting this dust
loading increase is the extent to which the sand and other noncom-
bustibles can successfully be separated from the flyash before
reinjection to the furnace.
Although reinjection increases boiler efficiency from 1 to
4 percent and minimizes the emissions of uncombusted carbon, it
also increases boiler maintenance requirements, decreases average
flyash particle size and makes collection more difficult. Properly
designed reinjection systems should separate sand and char from the
exhaust gases, to reinject the larger carbon particles to the
furnace and to divert the fine sand particles to the ash disposal
system.
Several factors can influence emissions, such as boiler size
and type, design features, age, load factors, wood species and
operating procedures. In addition, wood is often cofired with
other fuels. The effect of these factors on emissions is difficult
to quantify. It is best to refer to the references for further
information.
The use of multitube cyclone mechanical collectors provides
the particulate control for many hogged boilers. Usually, two
multicyclones are used in series, allowing the first collector to
remove the bulk of the dust and the second collector to remove
smaller particles. The collection efficiency for this arrangement
is from 65 to 95 percent. Low pressure drop scrubbers and fabric
filters have been used extensively for many years. On the West
Coast, pulse jets have been used.
Emission factors for wood waste boilers are presented in
Table 1.6-1.
References for Section 1.6
1. Steam, 38th Edition, Babcock and Wilcox, New York, NY, 1972.
2. Atmospheric Emissions from the Pulp and Paper Manufacturing
Industry, EPA-450/1-73-002, U.S. Environmental Protection
Agency, Research Triangle Park, NC, September 1973.
3. C-E Bark Burning Boilers, C-E Industrial Boiler Operations,
Combustion Engineering, Inc., Windsor, CT, 1973.
4. A. Barron, Jr., "Studies on the Collection of Bark Char throughout
the Industry", journal of the Technical Association of the Pulp
and Paper Industry, 53_(_8); 1441-1448, August 1970.
5. H. Kreisinger, "Combustion of Wood " ", Mechanical
Engineering, 61:115-120, February li ,
1.6-4 EMISSION FACTORS 8/82
-------
6. Air Pollution Handbook, P.L. Magill (ed.), McGraw-Hill Book
Co., New York, NY, 1956.
7. Air Pollutant Emission Factojcs, HEW Contract No. CPA-22-69-119,
Resources Research, Inc., Reston, VA, April 1970.
8. J.F. Mullen, A Method for Determining Combustible Loss, Dust
Emissions, and Recirculated Refuse for a Solid Fuel Burning
System, Combustion Engineering, Inc., Windsor, CT, 1966.
9. Source test data, Alan Lindsey, U.S. Environmental Protection
Agency, Atlanta, GA, May 1973.
10. H.K. Effenberger, et al., "Control of Hogged Fuel Boiler
Emissions: A Case History", Journal of the Technical Associa-
tion of the Pulp and Paper Industry, 56(2):111-115,
February 1973.
11. Source test data, Oregon Department of Environmental Quality,
Portland, OR, May 1973.
12. Source test data, Illinois Environmental Protection Agency,
Springfield, IL, June 1973.
13. J.A. Danielson (ed.), Air Pollution Engineering Manual (2nd Ed.),
AP-40, U.S. Environmental Protection Agency, Research Triangle
Park, NC, 1973. Out of Print.
14. H. Droege and G. Lee, "The Use of Gas Sampling and Analysis
for the Evaluation of Teepee Burners", presented at the Seventh
Conference on the Methods in Air Pollution Studies, Los Angeles,
CA, January 1967.
15. B.C. Junge and K. Kwan, "An Investigation of the Chemically
Reactive Constituents of Atmospheric Emissions from Hog-Fuel
Boilers in Oregon", Paper No. 73-AP-21, presented at the Annual
Meeting of the Pacific Northwest International Section of the
Air Pollution Control Association, November 1973.
16. S.F. Galeano and K.M. Leopold, "A Survey of Emissions of
Nitrogen Oxides in the Pulp Mill", Journal of the Technical
Association of the Pulp and Paper Industry, 56_(3_)_; 74-76,
March 1973.
17. P.B. Bosserman, "Wood Waste Boiler Emissions in Oregon State",
Paper No. 76-AP-23, presented at the Annual Meeting of the
Pacific Northwest International Section of the Air Pollution
Control Association, September 1976.
18. Source test data, Oregon Department of Environmental Quality,
Portland, OR, September 1975.
8/82
External Combustion Sources
1.6-5
-------
19. Source test data, New York State Department of Environmental
Conservation, Albany, NY, May 1974.
20. P.B. Bosserman, "Hydrocarbon Emissions from Wood Fired Boilers",
Paper No. 77-AP-22, presented at the Annual Meeting of the
Pacific Northwest International Section of the Air Pollution
Control Association, November 1977.
21. Control of Particulate Emissions from Wood Fired Boilers,
EPA-340/1-77-026, U.S. Environmental Protection Agency,
Washington, DC, 1978.
22. Wood Residue Fired Steam Generator Particulate Matter Control
Technology Assessment* EPA-450/2-78-044, U.S. Environmental
Protection Agency, Research Triangle Park, NC, October 1978.
23. H.S. Oglesby and R.O. Blosser, "Information on the Sulfur
Content of Bark and Its Contribution to S02 Emissions When
Burned as a Fuel", Journal of the Air Pollution Control
Association, 30(7);769-772, July 1980.
24. A Study of Nitrogen Oxides Emissions from Wood Residue Boilers,
Technical Bulletin No. 102, National Council of the Paper
Industry for Air and Stream Improvement, New York, NY,
November 1979.
25. R.A. Kester, Nitrogen OxideJEmissions from a Pilot Plant
Spreader Stoker Bark Fired Boiler, Department of Civil
Engineering, University of Washington, Seattle, WA,
December 1979.
26. A. Nunn, NOv Emission Factors for Wood Fired Boilers,
EPA-600/7-79-219, U.S. Environmental Protection Agency,
Research Triangle Park, NC, September 1979.
27. C.R. Sanborn, Evaluation of Wood Fired Boilers and WideJSodied
Cyclones in the State of Vermont, U.S. Environmental Protection
Agency, Boston, MA, March 1979.
28. Source test data, North Carolina Department of Natural Resources
and Community Development, Raleigh, NC, June 1981.
29. Nonfossil Fueled Boilers - Emission Test Report: Weyerhaeuser
Company, Longview, Washington, EPA-80-WFB-10, U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards,
Research Triangle Park, NC, March 1981.
30. A Study of Wood-Residue Fired Power Boiler Total Gaseous
Nonmethane Organic Emissions in the^ Pacific Northwest, Technical
Bulletin No. 109, National Council of the Paper Industry for Air
and Stream Improvement, New York, NY, September 1980.
1.6-6
EMISSION FACTORS
8/82
-------
1.7 LIGNITE COMBUSTION
1.7.1 General1"4
Lignite is a relatively young coal with properties intermediate
to those of bituminous coal and peat. It has a high moisture
content (35 to 40 weight percent) and a low wet basis heating value
(1500 to 1900 kilocalories) and generally is burned only close to
where it is mined, in some midwestern States and in Texas. Although
a small amount is used in industrial and domestic situations,
lignite is mainly used for steam/electric production in power
plants. In the past, lignite was burned mainly in small stokers,
but today the trend is toward use in much larger pulverized coal
fired or cyclone fired boilers.
The major advantages of firing lignite are that, in certain
geographical areas, it is plentiful, relatively low in cost and low
in sulfur content (0.4 to 1 wet basis weight percent). Disadvantages
are that more fuel and larger facilities are necessary to generate
a unit of power than is the case with bituminous coal. There are
several reasons for this. First, the higher moisture content means
that more energy is lost in the gaseous products of combustion,
which reduces boiler efficiency. Second, more energy is required
to grind lignite to the combustion specified size, especially in
pulverized coal fired units. Third, greater tube spacing and
additional soot blowing are required because of the higher ash
fouling tendencies. Fourth, because of its lower heating value,
more fuel must be handled to produce a given amount of power, since
lignite usually is not cleaned or dried before combustion (except
for some drying that may occur in the crusher or pulverizer and
during transfer to the burner). Generally, no major problems exist
with the handling or combustion of lignite when its unique
characteristics are taken into account.
2-11
1.7.2 Emissions and Controls
The major pollutants of concern when firing lignite, as with
any coal, are particulates, sulfur oxides, and nitrogen oxides.
Volatile organic compound (VOC) and carbon monoxide emissions are
quite low under normal operating conditions.
Particulate emission levels appear most dependent on the
firing configuration in the boiler. Pulverized coal fired units
and spreader stokers, which fire all or much of the lignite in
suspension, emit the greatest quantity of flyash per unit of fuel
burned. Cyclones, which collect much of the ash as molten slag in
the furnace itself, and stokers (other than spreader), which retain
a large fraction of the ash in the fuel bed, both emit less particulate
matter. In general, the relatively high sodium content of lignite
lowers particulate emissions by causing more of the resulting
flyash to deposit on the boiler tubes. This is especially so in
pulverized coal fired units wherein a high fraction of the ash is
8/82 External Combustion Sources 1.7-1
-------
I
N;
TABLE 1.7-1. EMISSION FACTORS FOR EXTERNAL COMBUSTION OF LIGNITE COAL£
to
§
H
O
ye
en
Firing Configuration
Pulverized Coal Fired
Dry Bottom
Cyclone Furnace
Spreader Stoker
Other Stokers
Particulates
kg/Mg
3.1A
3.3A
3.4A
1.5A
Ib/ton
6.3A
6.7A
6.8A
2.9A
Sulfur
dioxide0
kg/Mg
15S
153
15S
15S
Ib/ton
30S
30S
30S
30S
Nitrogen
oxides
kg/Mg Ib/ton
6e*f
8.5
3
3
12e,f
17
6
6
Carbon
Monoxide
g
g
g
g
voc
Konme thane Methane
*"
g
g
g
g
g
g
g
g
For uncontrolled emissions, and should be applied to lignite consumption as fired.
References 5-6,9,12. A is the wet basis percent ash content of the lignite.
References 2,5-6. S is the wet basis percent sulfur content of the lignite by weight. For a high sodium/ash lignite
(Na20 >8%), use 8.53 kg/Mg (17S Ib/ton); for a low sodium/ash lignite (Na20 <22), use 17.5S kg/Mg (35S Ib/ton). When
the sodium/ash content is unknown, use 15S kg/Mg (30S Ib/ton). The conversion of sulfur to sulfur dioxide is shown as
,a function of alkali ash constituents in References 10-11.
References 2,5,7-8. Expressed as N02.
eUse 7 kg/Mg (14 Ib/ton) for front wall fired and horizontally opposed wall fired units, and 4 kg/Mg (8 Ib/ton) for
ftangenttally fired units.
May be reduced 20 - 40% with low excess air firing and/or staged combustion in front fired and opposed wall fired units and
cyclones.
^Factors reported in Table 1.1-t may be used, based on the similarity of lignite combustion and bituminous coal combustion.
00
-------
suspended in the combustion gases and can readily come into contact
with the boiler surfaces.
Nitrogen oxide emissions are mainly a function of the boiler
firing configuration and excess air. Stokers produce the lowest NO
levels, mainly because most existing units are much smaller than
the other firing type and have lower peak flame temperatures. In
most boilers, regardless of firing configuration, lower excess air
during combustion results in lower NO emissions.
Sulfur oxide emissions are a function of the alkali (especially
sodium) content of the lignite ash. Unlike most fossil fuel
combustion, in which over 90 percent of the fuel sulfur is emitted
as S02, a significant fraction of the sulfur in lignite reacts with
the ash components during combustion and is retained in the boiler
ash deposits and flyash. Tests have shown that less than 50 percent
of the available sulfur may be emitted as SOa when a high sodium
lignite is burned, whereas more than 90 percent may be emitted from
low sodium lignite. As a rough average, about 75 percent of the
fuel sulfur will be emitted as S02, the remainder being converted
to various sulfate salts.
Newer lignite fired utility boilers are equipped with large
electrostatic precipitators that may achieve as high as 99.5 percent
particulate control. Older and smaller electrostatic precipitators
operate at about 95 percent efficiency. Older industrial and
commercial units use cyclone collectors that normally achieve 60 to
80 percent collection efficiency on lignite flyash. Flue gas
desulfurization systems currently are in operation on several
lignite fired utility boilers. These systems are identical to
those used on bituminous coal fired boilers (see Section 1.1).
Nitrogen oxide reductions of up to 40 percent can be achieved
by changing the burner geometry, controlling excess air and making
other changes in operating procedures. The techniques are identical
for bituminous and lignite coal.
TABLE 1.7-2. RATINGS OF EMISSION
FACTORS FOR LIGNITE COMBUSTION
Firing Configuration
Pulverized Coal Fired
Dry Bottom
Cyclone Furnace
Spreader Stoker
Other Stokers
Particulates
A
C
B
B
Sulfur
Dioxide
A
A
B
C
Nitrogen
Dioxide
A
A
C
D
8/82
External Combustion Sources
1.7-3
-------
Emission factors for participates, sulfur dioxide and nitrogen
oxides are presented in Table 1.7-1. Based on the similarity of
lignite combustion and bituminous coal combustion, emission factors
for carbon monoxide and volatile organic compounds reported in
Table 1.1-1 may be used.
References for Section 1.7
1. Kirk-Othmer Encyclopedia of Chemical Technology, Volume 12,
Second Edition, John Wiley and Sons, New York, NY, 1967.
2. G.H. Gronhovd, et al., "Some Studies on Stack Emissions from
Lignite Fired Powerplants", Presented at the 1973 Lignite
Symposium, Grand Forks, ND, May 1973.
3. Standards Support and Environmental Impact Statement:
Promulgated Standards of Performance for Lignite Fired Steam
Generators: Volumes I and II, EPA-450/2-76-030a,b, U.S.
Environmental Protection Agency, Research Triangle Park, NC,
December 1976.
4. 1965 Keystone Coal Buyers Manual, McGraw-Hill, Inc., New York,
NY, 1965.
5. Source test data on lignite fired power plants, North Dakota
State Department of Health, Bismarck, ND, December 1973.
6. G.H. Gronhovd, et al., "Comparison of Ash Fouling Tendencies
of High and Low Sodium Lignite from a North Dakota Mine",
Proceedings of the American Power Conference, Volume XXVIII,
1966.
7. A.R. Crawford, et al., Field Testing: Application of Combustion
Modification To Control NO Emissions from Utility Boilers,
EPA-650/2-74-066, U.S. Environmental Protection Agency, Research
Triangle Park, NC, June 1974.
8. "Nitrogen Oxides Emission Measurements for Lignite Fired Power
Plants", EPA Project Report No. 75-LSG-3, Office of Air Quality
Planning and Standards, U.S. Environmental Protection Agency,
Research Triangle Park, NC, 1974.
9. Coal Fired Power Plant Trace Element Study, A Three Station
Comparison, U.S. Environmental Protection Agency, Denver, CO,
September 1975.
10. C. Castaldini and M. Angwin, Boiler Design and Operating
Variables Affecting Uncontrolled Sulfur Emissions from
Pulverized Coal Fired Steam Generators, EPA-450/3-77-047, U.S.
Environmental Protection Agency, Research Triangle Park, NC,
December 1977.
1.7-4
EMISSION FACTORS
8/82
-------
11. C.C. Shin, e t al.» Emissions Assessment of Conventional
Stationary Combustion Systems, Volume III; External
Combustion Sources for Electricity Generation, EPA Contract
No. 68-02-2197r"TRW Inc., Redondo Beach, CA, November 1980.
12. Source test data on lignite fired cyclone boilers, North Dakota
State Department of Health, Bismarck, ND, March 1982.
External Combustion Sources 1.7-5
-------
-------
1.8 BAGASSE COMBUSTION IN SUGAR MILLS
1.8.1 General1
Bagasse is the fibrous residue from sugar cane that has been processed in a sugar mill. (See Section
6.12 for a brief general description of sugar cane processing.) It is fired in boilers to eliminate a large
solid waste disposal problem and to produce steam and electricity to meet the mill's power require-
ments. Bagasse represents about 30 percent of the weight of the raw sugar cane. Because of the high
moisture content (usually at least 50 percent, by weight) a typical heating value of wet bagasse will
range from 3000 to 4000 Btu/lb (1660 to 2220 kcal/kg). Fuel oil may be fired with bagasse when the
mill's power requirements cannot be met by burning only bagasse or when bagasse is too wet to support
combustion.
The United States sugar industry is located in Florida, Louisiana, Hawaii, Texas, and Puerto Rico.
Except in Hawaii, where raw sugar production takes place year round, sugar mills operate seasonally,
from 2 to 5 months per year.
Bagasse is commonly fired in boilers employing either a solid hearth or traveling grate. In the for-
mer, bagasse is gravity fed through chutes and forms a pile of burning fibers. The burning occurs on
the surface of the pile with combustion air supplied through primary and secondary ports located in
the furnace walls. This kind of boiler is common in older mills in the sugar cane industry. Newer boil-
ers, on the other hand, may employ traveling-grate stokers. Underfire air is used to suspend the ba-
gasse, and overf ired air is supplied to complete combustion. This kind of boiler requires bagasse with a
higher percentage of fines, a moisture content not over 50 percent, and more experienced operating
personnel.
1.8.2 Emissions and Controls1
Particulate is the major pollutant of concern from bagasse boilers. Unless an auxiliary fuel is fired,
few sulfur oxides will be emitted because of the low sulfur content (<0.1 percent, by weight) of ba-
gasse. Some nitrogen oxides are emitted, although the quantities appear to be somewhat lower (on an
equivalent heat input basis) than are emitted from conventional fossil fuel boilers.
Particulate emissions are reduced by the use of multi-cyclones and wet scrubbers. Multi-cyclones
are reportedly 20 to 60 percent efficient on particulate from bagasse boilers, whereas scrubbers (either
venturi or the spray impingement type) are usually 90 percent or more efficient. Other types of con-
trol equipment have been investigated but have not been found to be practical.
Emission factors for bagasse fired boilers are shown in Table 1.8-1.
4/77
External Combustion Sources
1.8-1
-------
Table 1.8-1. EMISSION FACTORS FOR UNCONTROLLED BAGASSE BOILERS
EMISSION FACTOR RATING: C
Particulatec
Sulfur oxides
Nitrogen oxides6
Emission factors
lb/103lb steam3
4
d
0.3
g/kg steam3
4
d
0.3
Ib/ton bagasse"
16
d
1.2
kg/MT bagasse'-'
8
d
0.6
Emission factors are expressed in terms of the amount of Steam produced, as most mills do not monitor the
amount of bagasse fired. These factors should be applied only to that fraction of steam resulting from bagasse
combustion. If a significant amount (>25% of total Btu input) of fuel oil is fired with the bagasse, the appropriate
emission factors from Table 1.3-1 should be used to estimate the emission contributions from the fuel oil.
^Emissions are expressed in terms of wet bagasse, containing approximately 50 percent moisture, by weight.
As a rule of thumb, about 2 pounds (2 kg) of steam are produced from 1 pound (1kg) of wet bagasse.
cMulti-cyclones are reportedly 20 to 60 percent efficient on particulate from bagasse boilers. Wet scrubbers
are capable of effecting 90 or more percent particulate control. Based on Reference 1.
"^Sulfur oxide emissions from the firing of bagasse alone would be expected to be negligible as bagasse typically
contains less than 0.1 percent sulfur, by weight. If fuel oil is fired with bagasse, the appropriate factors from
Table 1.3-1 should be used to estimate sulfur oxide emissions.
e Based on Reference 1.
Reference for Section 1.8
1. Background Document: Bagasse Combustion in Sugar Mills. Prepared by Environmental Science
and Engineering, Inc., Gainesville, Fla., for Environmental Protection Agency under Contract
No. 68-02-1402, Task Order No. 13. Document No. EPA-450/3-77-007. Research Triangle Park, N.C.
October 1976.
1.8-2
EMISSION FACTORS
4/77
-------
1.9 RESIDENTIAL FIREPLACES
1.9.1 General1"
Fireplaces are used mainly in homes, lodges, etc., for supplemental
heating and for aesthetic effects. Wood is the most common fuel for
fireplaces, but, coal, compacted wood waste "logs", paper and rubbish may
also be burned. Fuel is intermittently added to the fire by hand.
Fireplaces can be divided into two broad categories, 1) masonry,
generally brick fireplaces, assembled on site integral to a structure and
2) prefabricated, usually metal, fireplaces installed on site as a package
with appropriate ductwork.
Masonry fireplaces typically have large fixed openings to the firebed
and dampers above the combustion area in the chimney to limit room air and
heat losses when the fireplace is not being used. Some masonry fireplaces
are designed or retrofitted with doors and louvers to reduce the intake of
combustion air during use.
Many varieties of prefabricated fireplaces are now available on the
market. One general class is the freestanding fireplace. The most common
freestanding fireplace models consist of an inverted sheet metal funnel and
stovepipe directly above the fire bed. Another class is the "zero clearance"
fireplace, an iron or heavy gauge steel firebox lined with firebrick on the
inside and surrounded by multiple steel walls spaced for air circulation.
Zero clearance fireplaces can be inserted into existing masonry fireplace
openings, thus they are sometimes called "inserts". Some of these units are
equipped with close fitting doors and have operating and combustion character-
istics similar to wood stoves (see Section 1.10, Residential Wood Stoves).
Prefabricated fireplaces are commonly equipped with louvers and glass doors
to reduce the intake of combustion air, and some are surrounded by ducts
through which floor level air is drawn by natural convection and is heated
and returned to the room.
Masonry fireplaces usually heat a room by radiation, with a significant
fraction of the combustion heat lost in the exhaust gases or through the
fireplace walls. Moreover, some of the radiant heat entering the room must
go toward warming the air that is pulled into the residence to make up for
the air drawn up the chimney. The net effect is that masonry fireplaces are
usually inefficient heating devices. Indeed, in cases where combustion is
poor, where the outside air is cold, or where the fire is allowed to smolder
(thus drawing air into a residence without producing appreciable radiant
heat energy), a net heat loss may occur in a residence from use of a fireplace.
Fireplace heating efficiency may be improved by a number of measures that
either reduce the excess air rate or transfer some of the heat back into the
residence that would normally be lost in the exhaust gases or through the
fireplace walls. As noted above, such measures are commonly incorporated
into prefabricated units. As a result, the energy efficiencies of prefabri-
cated fireplaces are slightly higher than those of masonry fireplaces.
5/83 External Combustion Sources 1.9—1
-------
1.9.2 Emissions
-i n
The major pollutants of concern from fireplaces are unburnt combustibles,
including carbon monoxide, gaseous organics and particulate matter (i.e.,
smoke). Significant quantities of unburnt combustibles are produced because
fireplaces are inefficient combustion devices, because of high uncontrolled
excess air rates and the absence of any sort of secondary combustion. The
latter is especially important in wood burning because of its high volatile
matter content, typically 80 percent on a dry weight basis. In additon to
unburnt combustibles, lesser amounts of nitrogen oxides and sulfur oxides
are emitted.
Polycyclic organic material (POM), a minor but potentially important
component of wood smoke, is a group of organic compounds which includes
potential carcinogens such as benzo (a)pyrene (BaP) . POM results from the
combination of free radical species formed in the flame zone, primarily as a
consequence of incomplete combustion. Under reducing conditions, radical
chain propagation is enhanced, allowing the buildup of complex organic
material such as POM. POM is generally found in or on smoke particles,
although some sublimation into the vapor phase is probable.
Another important constituent of wood smoke is creosote. This tar-like
substance will burn if the fire is sufficiently hot, but at lower tempera-
tures, it may deposit on cool surfaces in the exhaust system. Creosote
deposits are a fire hazard in the flue, but they can be reduced if the
exhaust ductwork is insulated to prevent creosote condensation or the exhaust
system is cleaned regularly to remove any buildup.
Fireplace emissions are highly variable and are a function of many wood
characteristics and operating practices. In general, conditions which
promote a fast burn rate and a higher flame intensity will enhance secondary
combustion and thereby lower emissions. Conversely, higher emissions will
result from a slow burn rate and a lower flame intensity. Such generali-
zations apply particularly to the earlier stages of the burning cycle, when
significant quantities of combustible volatile matter are being driven out
of the wood. Later in the burning cycle, when all of the volatile matter
has been driven out of the wood, the charcoal that remains burns with
relatively few emissions.
1.9-2
EMISSION FACTORS
5/83
-------
Emission factors and corresponding factor ratings for wood combustion
in residential fireplaces are given in Table 1.9-1.
TABLE 1.9-1. EMISSION FACTORS FOR RESIDENTIAL FIREPLACES
Pollutant
Particulate
Q
Sulfur oxides
Nitrogen oxides
Carbon monoxide
Wood
g/kg
14
0.2
1.7
85
Ib/ton
28
0.4
3.4
170
Emission
Factor
Ratings
C
A
C
C
voc
Methane
No nme thane
13
26
Based on tests burning primarily oak, fir or pine, with moisture
.content ranging from 15 - 35%.
References 1, 3-4, 8-10. Includes condensible organics (back
half catch of EPA Method 5 or similar test method), which alone
accounts for 54 - 76% of the total mass collected by both the
front and back half catches (Reference 4). POM is carried by
suspended particulate matter and has been found to range from
0.017 - 0.044 g/kg (References 1, 4) which may include BaP of up
to 1.7 mg/kg (Reference 1).
,References 2, 4.
Expressed as N02. References 3-4, 8, 10.
^References 1, 3-4, 6, 8-10.
References 1, 3-4, 6, 10. Dash = no data available.
References for Section 1.9
1. W. D. Snowden, et al., Source Sampling of Residential Fireplaces
for Emission Factor Development, EPA-450/3-76-010, U. S. Environmental
Protection Agency, Research Triangle Park, NC, November 1975.
2. D. G. DeAngelis, et al., Source Assessment: Residential Combustion
of Wood, EPA-600/2-80-042b, U. S. Environmental Protection Agency,
Washington, DC, March 1980.
3. P. Kosel, _e_ta^U, "Emissions from Residential Fireplaces", CARB Report
C-80-027, California Air Resources Board, Sacramento, CA, April 1980.
5/83
External Combustion Sources
1.9-3
-------
4. D. G. DeAngelis, e t al., Preliminary Characterization of Emissions from
Wood Fired Residential Combustion Equipment. EPA-600/7-80-040, U. S.
Environmental Protection Agency, Washington, DC, March 1980.
5. H. I. Lips and K. J. Lim, Assessment of Emissions from Residential and
Industrial Wood Combustion, EPA Contract No. 68-02-3188, Acurex
Corporation, Mountain View, CA, April 1981.
6. A. C. S. Hayden and R. W. Braaten, "Performance of Domestic Wood Fired
Appliances", Presented at the 73rd Annual Meeting of the Air Pollution
Control Association, Montreal, Canada, June 1980.
7. J. A. Peters, POM Emissions from Residential Woodburning: An Environmental
Assessment, Monsanto Research Corporation, Dayton, OH, May 1981.
8. L. Clayton, et al., "Emissions from Residential Type Fireplaces", Source
Tests 24C67, 26C, 29C67, 40C67, 41C67, 65C67 and 66C67, Bay Area Air
Pollution Control District, San Francisco, CA, January 31, 1968.
9. Source Testing for Fireplaces, Stoves, and Restaurant Grills in Vail,
Colorado (Draft), EPA Contract No. 68-01-1999, Pedco Environmental, Inc.,
December 1977.
10. J. L. Muhlbaier, "Gaseous and Particulate Emissions from Residential
Fireplaces," Publication GMR-3588, General Motors Research Laboratories,
Warren, MI, March 1981.
1.9-4 EMISSION FACTORS 5/83
-------
1.10 RESIDENTIAL WOOD STOVES
1.10.1 General1"2
Wood stoves are used primarily as domestic space heaters to supplement
conventional heating systems. The two basic designs for wood stoves are
radiating and circulating. Common construction materials include cast
iron, heavy gauge sheet metal and stainless steel. Radiating type stoves
transfer heat to the room by radiation from the hot stove walls. Circulating
type stoves have double wall construction with louvers on the exterior wall
to permit the conversion of radiant energy to warm convection air. Properly
designed, these stoves range in heating efficiency from 50 to 70 percent.
Radiant stoves have proven to be somewhat more efficient than the circulating
type.
The thoroughness of combustion and the amount of heat transferred from a
stove, regardless of whether it is a radiating or circulatory model, depend
heavily on firebox temperature, residence time and turbulence (mixing). The
"three Ts" (temperature, time and turbulence) are affected by air flow
patterns through the stove and by the mode of stove operation. Many stove
designs have internal baffles that increase the residence time of flue
gases, thus promoting heat transfer. The use of baffles and secondary
combustion air may also help to reduce emissions by promoting nixing and
more thorough combustion. Unless the secondary air is adequately preheated,
it may serve to quench the flue gas, thus retarding, rather than enhancing,
secondary combustion. Secondary combustion air systems should be designed
to deliver the proper amount of secondary air at the right location with
adequate turbulence and sufficient temperature to promote true secondary
combustion.
Stoves are further categorized by the air flow pattern through the
burning wood within the stoves. Example generic designs - updraft, downdraft,
crossdraft and "S-flow" - are shown schematically in Figure 1.10-1.
In the updraft air flow type of stove, air enters at the base of the
stove and passes through the wood to the stovepipe at the top. Secondary
air enters above the wood to assist in igniting unburned volatiles in the
combustion gases. Updraft stoves provide very little gas phase residence
time, which is needed for efficient transfer of heat from the gases to the
walls of the stove and/or stovepipe.
The downdraft air flow type of stove initially behaves like an updraft.
A vertical damper is opened at the top rear to promote rapid combustion.
When a hot bed of coals is developed, the damper is closed, and the flue
gases are then forced back down through the bed of coals before going out
the flue exit.
The side or cross draft is equipped with a vertical baffle (open at the
bottom) and an adjustable damper at the top, similar to the downdraft. The
damper is open when combustion is initiated, to generate hot coals and
adequate draft. The damper is then closed. The gases must then move down
5/83
External Combustion Sources
1.10-1
-------
under the vertical baffle, the flame is developed horizontally to the fuel
bed, and ideally the gases and flame come in contact at the baffle point
before passing out the flue exit.
M
v-~ >-'
B B B
sc
UndttflnAIr
OrUpDnft
Down Draft
P - Priflwy Air Supply
I - Smndvy Air Supply
E - ElhMMt la Slvk
B - Primary Bumtnt
SC- SMondvv Combuldon
sc
J
^
-\
X
Stile or Cross Drift
S-Flow
Figure 1.10-1. Generic designs of wood stoves based on flow paths
The S-flow, or horizontal baffle, stove is equipped with both a primary
and a secondary air inlet, like the updraft stove. Retention time within
the stove is a function of both the rate of burn and the length of the smoke
.path. To lengthen the retention time, gases are kept from exiting directly
up the flue by a metal baffle plate located several inches above the burning
wood. The baffle plate absorbs a considerable amount of heat and reflects
and radiates much of it back to the firebox. The longer gas phase residence
time results in improved combustion when the proper amounts of air are
provided, and it enhances heat transfer from the gas phase.
Softwoods and hardwoods are the most common fuels for residential
stoves. Coal and waste fuels, which burn at significantly higher temperature
than cordwood, are not included in computing emission factors because of the
relative scarcity of test data available. The performance of various heaters
within a given type will vary, depending on how a particular design uses its
potential performance advantages. Much of the available emissions data came
from studies conducted on stoves designed for woodburning.
1.10.2 Emissions and Controls
3-25
Residential combustion of wood produces atmospheric emissions of
particulates, sulfur oxides, nitrogen oxides, carbon monoxide, organic
materials including polycyclic organic matter (POM), and mineral constituents.
Organic species, carbon monoxide and, to a large extent, the particulate
1.10-2
EMISSION FACTORS
5/83
-------
matter emissions result frora incomplete combustion of the fuel. Efficient
combustion tends to limit emissions of carbon monoxide and volatile organic
compounds by oxidizing these compounds to carbon dioxide and water. Sulfur
oxides arise from oxidation of fuel sulfur, while nitrogen oxides are formed
both from fuel nitrogen and by the combination of atmospheric nitrogen with
oxygen in the combustion zone. Mineral constituents in the particulate
emissions result from minerals released from the wood matrix during combustion
and entrained in the combustion gases.
Wood smoke is composed of unburned fuel - combustible gases, droplets
and solid particulates. Part of the organic compounds in smoke often condenses
in the chimney or flue pipe. This tar-like substance is called creosote.
If the combustion zone temperature is sufficiently high, creosote burns with
the other organic compounds in the wood. However, creosote burns at a
higher temperature than other chemicals in the wood, so there are times when
it is not burned with the other products. Creosote deposits are a fire
hazard, but they can be reduced if the exhaust ductwork is insulated to
prevent creosote condensation, or the exhaust system is cleaned regularly to
remove any buildup.
Polycyclic organic material (POM), a minor but potentially important
component of wood smoke, is a group of organic compounds which includes
potential carcinogens such as benzo(a)pyrene (BaP). POM results from the
combination of free radical species formed in the flame zone, primarily as a
consequence of incomplete combustion. Under reducing conditions, radical
chain propagation is enhanced, allowing the buildup of complex organic
material such as POM. POM is generally found in or on smoke particles,
although some sublimation into the vapor phase is probable.
Emissions from any one stove are highly variable, and they correspond
directly to different stages in the burning cycle. A new charge of wood
produces a quick drop in firebox temperature and a dramatic increase in
emissions, primarily organic matter. When all of the volatiles have been
driven off, the charcoal stage of the burn is characterized by relatively
clean emissions.
Emissions of particulate, carbon monoxide and volatile organic compounds
were found to depend on burn rate. Emissions increase as burn rates decrease,
for the great majority of the closed combustion devices currently on the
market. A burn rate of approximately three kilograms per hour has been
determined representative of actual woodstove operation.
Wood is a complex fuel, and the combined processes of combustion and
pyrolysis which occur in a wood heater are affected by changes in the
composition of the fuel, moisture content and the effective burning surface
area. The moisture content of wood depends on the type of wood and the
amount of time it has been dried (seasoned). The water in the wood increases
the amount of heat required to raise the wood to its combustion point, thus
reducing the rate of pyrolysis until moisture is released. Wood moisture
has been found to have little affect on emissions. Dry wood (less than
15 percent moisture content) may produce slightly higher emissions than the
commonly occurring 30 to 40 percent moisture wood. However, firing very wet
wood may produce higher emissions due to smoldering and reduced burn rate.
The size of the wood also has a large effect on the rate of pyrolysis. For
5/83
External Combustion Sources
1.10-3
-------
smaller pieces of wood, there is a shorter distance for the pyrolysis products
to diffuse, a larger surface area-to-mass ratio, and a reduction in the time
required to heat the entire piece of wood. One effect of log size is to
change the distribution of organics among the different effluents (creosote,
particulate matter and condensible organics) for a given burn rate. These
results also indicate that the distribution of the total organic effluent
among creosote, particulate matter and condensibles is a function of firebox
and sample probe temperatures.
Results of ultimate analysis (for carbon, hydrogen and oxygen) of dry
wood types are within one to two percent for the majority of all species.
The inherent difference between softwood and hardwood is the greater amount
of resins in softwoods, which increases their heating value by weight.
Several combustion modification techniques are available to reduce
emissions from wood stoves, with varying degrees of effectiveness. Some
techniques relate to modified stove design and others to operator practices.
Proper modifications of stove design (1) will reduce pollutant formation in
the fuel magazine or in the primary combustion zone or (2) will cause
previously formed emissions to be destroyed in the primary or secondary
combustion zones.
A recent wood stove emission control development is the catalytic
converter, a transfer technology from the automobile. The catalytic converter
is a noble metal catalyst, such as palladium, coated on ceramic honeycomb
substrates and placed directly in the exhaust gas flow, where it reduces the
ignition temperature (flash point) of the unburnt hydrocarbons and carbon
monoxide. Retrofit catalysts tend to be installed in the flue pipe farther
downstream of the woodstove firebox than built-in catalysts. Thus, adequate
catalyst operating temperatures may not be achieved with the add on type,
resulting in potential flue gas blockage and fire hazards. Limited testing
of built-in designs indicates that carbon monoxide and total hydrocarbon
emissions are reduced considerably, and efficiency is improved, by the
catalyst effect. Some initial findings also indicate that emissions of
nitrogen oxides may be increased by as much as a factor of three.
Additionally, there is concern that combustion temperatures achieved in
stoves operating at representative burn rates (approximately 3 kilograms per
hour or less) are not adequate to "light off" the catalyst. Thus, the
catalytic unit might reduce emissions but not under all burning conditions.
1.10-4 EMISSION FACTORS 5/83
-------
Emission factors and corresponding emission factor ratings for wood
combustion in residential wood stoves are presented in Table 1.10-1.
TABLE 1.10-1. EMISSION FACTORS FOR RESIDENTIAL WOOD STOVES
Pollutant
b c
Particulate '
Sulfur oxides
Nitrogen oxides
f c
Carbon monoxide '
g/kg
21
0.2
1.4
130
Wood3
Ib/ton
42
0.4
2.8
260
Emission
Factor
Ra tings
C
A
C
C
voc
g,c
Methane
No nine thane
0.5
51
1.0
100
D
D
Based on tests burning primarily oak, fir or pine, with moisture
, content ranging from 15 - 35%.
References 3-6, 8-10, 13-14, 17, 22, 24-25. Includes condensible
organics (back half catch of EPA Method 5 or similar test
method), which alone account for 54 - 76% of the total mass
collected by both front and back half catches (Reference 4).
POM is carried by suspended particulate matter and has been
found to range from 0.19 - 0.37 g/kg (References 4, 14-15,
^22-23) which may include BaP of up to 1.4 mg/kg (Reference 15).
Emissions were determined at burn rates of 3 kg/hr or less. If
>3 kg/hr, emissions may decrease by as much as 55 - 60% for
,particulates and VOC, and 25% for carbon monoxide.
References 2, 4.
^Expressed as NO . References 3-4, 15, 17, 22-23.
References 3-4, 10-11, 13, 15, 17, 22-23.
References 3-4, 11, 15, 17, 22-23.
References for Section 1.10
1. H. I. Lips and K. J. Lim, Assessment of Emissions from Residential and
Industrial Wood Combustion, EPA Contract No. 68-02-3188, Acurex
Corporation, Mountain View, CA, April 1981.
2. D. G. DeAngelis, et al., Source Assessment: Residential Combustion of
Wood, EPA-600/2-80-042b, U. S. Environmental Protection Agency,
Washington, DC, March 1980.
3. J. A. Cooper, "Environmental Impact of Residential Wood Combustion
Emissions and Its Implications", Journal of the Air Pollution Control
Association, 30(8):855-861, August 1980.
5/83
External Combustion Sources
1.10-5
-------
4. D. G. DeAngelis, et al., Preliminary Characterization of Emissions from
Wood-fired Residential Combustion Equipment, EPA-600/7-80-040, U. S.
Environmental Protection Agency, Washington, DC, March 1980.
5. S. S. Butcher and D. I. Buckley, "A Preliminary Study of Particulate
Emissions from Small Wood Stoves", Journal of the Air Pollution Control^
Association, 27^(4):346-348, April 1977.
6. S. S. Butcher and E. M. Sorenson, "A Study of Wood Stove Particulate
Emissions", Journal of the Air Pollution Control Association,
_24(9): 724-728, July 1979.
7. J. W. Shelton, et al., "Wood Stove Testing Methods and Some Preliminary
Experimental Results", Presented at the American Society of Heating,
Refrigeration and Air Conditioning Engineers (ASHRAE) Symposium, Atlanta,
GA, January 1978.
8. D. Rossman, et al., "Evaluation of Wood Stove Emissions", Oregon
Department of Environmental Quality, Portland, OR, December 1980.
9. P. Tiegs, et al., "Emission Test Report on Four Selected Wood Burning
Home Heating Devices", Oregon Department of Energy, Portland, OR,
January 1981.
10. J. A. Peters and D. G. DeAngelis, High Altitude Testing of 'Residential
Wood-fired Combustion Equipment, EPA-600/2-81-12~7, U. S. Environmental
Protection Agency, Washington, DC, September 1981.
11. A. C. S. Hayden and R. W. Braaten, "Performance of Domestic Wood-fired
Appliances", Presented at 73rd Annual Meeting of the Air Pollution
Control Association, Montreal, Canada, June 1980.
12. R. J. Brandon, "An Assessment of the Efficiency and Emissions of Ten
Wood-fired Furnaces", Presented at the Conference on Wood Combustion
Environmental Assessment, New Orleans, LA, February 1981.
13. B. R. Hubble and J. B. L. Harkness, "Results of Laboratory Tests on
Wood-stove Emissions and Efficiencies", Presented at the Conference on
Wood Combustion Environmental Assessment, New Orleans, LA, February
1981.
14. B. R. Hubble, et al., "Experimental Measurements of Emissions from
Residential Wood-burning Stoves", Presented at the International
Conference on Residential Solid Fuels, Portland, OR, June 1981.
15. J. M. Allen and W. M. Cooke, "Control of Emissions from Residential
Wood Burning by Combustion Modification", EPA Contract No. 68-02-2686,
Battelle Laboratories, Columbus, OH, November 1980.
16. J. R. Duncan, et al., "Air Quality Impact Potential from Residential
Wood-burning Stoves", TVA Report 80-7.2, Tennessee Valley Authority,
Muscle Shoals, AL, March 1980.
1.10-6 EMISSION FACTORS 5/83
-------
17. P. Kosel, et al., "Emissions from Residential Fireplaces", CARB Report
C-80-027, California Air Resources Board, Sacramento, CA, April 1980.
18. S. G. Barnett and D. Shea, "Effects of Wood Burning Stove Design on
Particulate Pollution", Oregon Department of Environmental Quality,
Portland, OR, July 1980.
19. J. A. Peters, POM Emissions from Residential Wood-burning: An_Eny_iron-
mental Assessment, Monsanto Research Corporation, Dayton, OH, May 1981.
20. Source Testing for Fireplaces, Stoves, and Resta_u_rau_^ Gjrills in Vail,
Colorado (Draft), EPA Contract No. 68-01-1999, Pedco Environmental,
Inc., December 1977.
21. A. C. S. Hayden and R. W. Braaten, "Effects of Firing Rate and Design
on Domestic Wood Stove Performance", Presented at the Residential Wood
and Coal Combustion Specialty Conference, Louisville, KY, March 1982.
22. C. V. Knight and M. S. Graham, "Emissions and Thermal Performance
Mapping for an Unbaffled, Airtight Wood Appliance and a Box Type Catalytic
Applicance", Proceedings of 1981 International Conference on Residential
Solid Fuels, Oregon Graduate Center, Portland, OR, June 1981.
23. C. V. Knight et al., "Tennessee Valley Authority Residential Wood
Heater Test Report: Phase I Testing", Tennessee Valley Authority,
Chattanooga, TN, November 1982.
24. Richard L. Poirot and Cedric R. Sanborn, "Improved Combustion Efficiency
of Residential Wood Stoves", U. S. Department of Energy, Washington,
DC, September 1981.
25. Cedric R. Sanborn, et al., "Waterbury, Vermont: A Case Study of
Residential Woodburning", Vermont Agency of Environmental Conservation,
Montpelier, VT, August 1981.
5/83
External Combustion Sources
1.10-7
-------
-------
1.11 WASTE OIL COMBISTION
1.11.1 General
The largest source of waste oil is used automotive crankcasc oil, originating mostly from automo-
bile service stations, and usually being found with small amounts of other automotive fluids. Other
sources of waste oil include metal working lubricants, heavy hydrocarbon fuels, animal and vegetable
oils and fats, and industrial oil materials.
In 1975. 57 percent of waste crankcase oil \vas consumed as alternative fuel in conventional hoiler
equipment (Section 1.3). The remainder was refined (15 percent), blended into road oil or asphalt
(15 percent), or used for other nonfuel purposes (13 percent).1
1.11.2 Emissions and Controls
Lead emissions from burning waste oil depend on the lead conte.nt.of the oil and on operating
conditions. Lead content may \ary from 800 to 11.200 ppm.- Average concentrations have been sug-
gested as 6,000' and as 10,000 ppm:>. During normal operation, about 50 percent of the lead is emitted
as participate willi flue gas.V Combustion of fuel containing 10 percent waste oil gives parliculalc
ranging from 14 to 19 percent lead. Ash content from combustion of fuels containing waste oil is higher
than that for distillate or residual fuel oil. ranging from 0.03 to 3.78 weight percent, and lead accounts
for about 35 percent of the ash produced in such combustion.-
Currently, controls are not usually applied to oil fired combustion sources. An exception is utility
boilers, especially in the northeastern I nited Slates, Pretrealment by vacuum distillation, solvent
extraction, settling and/or ceulrifuging minimizes lead emissions but max make waste oil use uneco-
nomical.- High efficiency parliculate control b> means of properly operated and maintained fabric
fillers is 99 percent effective lor 0.5-1 jim diameter lead and other submicron-si/ed parliculate. hut
s-uch a degree of control is infrcquenllv used."
Table 1.11-1. WASTE OIL COMBUSTION EMISSION FACTORS
EMISSION FACTOR RATING: B
Pollutant
Paniculate3
Leadb
Emission.factor
(kg/m3)
9.0 (A)
9.0 (P)
(lb/103gal)
75 (A)
75 (P)
References
5
1,2,3
letter A is for weight % of ash in the waste oil. To calculate the
particulate emission factor, multiply the ash in the oil by 9.0 to get
kilograms of particulate emitted per m^ waste oil burned. Example:
ash of waste oil is 0.5% the emission factor is 0.5 x 9.0 = 4.5 kg
particulate per m3 waste oil burned.
''The letter P indicates that the percent lead in the waste oil being pro-
cessed should be multiplied by the value given in the table in order to
obtain the emission factor. Average P= 1.0% (10,000 ppm). Refer to
Reference 5.
7/79
External Combustion Sources
1.11-1
-------
References for Section 1.11
1 S. Wyatt, et «/., Preferred Standards Path Analysis on Lead Emissions from Stationary Sources,
Of fire of Air Quality Planning and Standards. I '.S. Environmental Protection Agency. Research
Triangle Park, NC, September 1974.
2. S. Chansky, et a/., Waste Automotive Lubricating Oil Reuse as a Fuel, EPA-600/5-74-032, U.S.
Environmental Protection Agency. Washington. DC. September 1974.
3. Final Report of the API Task Force on Oil Disposal, American Petroleum Institute, New York,
!SV, May 1970.
4. Background Information in Support of the Development of Performance Standards for the
Lead Additive Industry, EPA Contract No. 68-02-2085, PEDCo-Environmental Specialists, Inc.,
Cincinnati, OH, January 1976
5. Control Techniques for Lead Air Emissions, EPA-450/2-77-012, U.S. Environmental Protection
Agency, Research Triangle Park, NC, December 1977.
1.11-2 EMISSION FACTORS 7/79
-------
2. SOLID WASTE DISPOSAL
As defined in the Solid Waste Disposal Act of 1965, the term "solid waste" means garbage, refuse, and other
discarded solid materials, including solid-waste materials resulting from industrial, commercial, and agricultural
operations, and from community activities. It includes both combustibles and noncombustibles.
Solid wastes may be classified into four general categories: urban, industrial, mineral, and agricultural.
Although urban wastes represent only a relatively small part of the total solid wastes produced, this category has
a large potential for air pollution since in heavily populated areas solid waste is often burned to reduce the bulk
of material requiring final disposall The following discussion will be limited to the urban and industrial waste
categories.
An average of 5.5 pounds (2.5 kilograms) of urban refuse and garbage is collected per capita per day in the
United States.2 This figure does not include uncollected urban and industrial wastes that are disposed of by other
means. Together, uncollected urban and industrial wastes contribute at least 4.5 pounds (2.0 kilograms) per
capita per day. The total gives a conservative per capita generation rate of 10 pounds (4.5 kilograms) per day of
urban 'and industrial wastes. Approximately 50 percent of all the urban and industrial waste generated .in the
United States is burned, using a wide variety of combustion methods with both enclosed and open
burning3. Atmospheric emissions, both gaseous and paniculate, result from refuse disposal operations that use
combustion to reduce the quantity of refuse. Emissions from these combustion processes cover a wide range
because of their dependence upon the refuse burned, the method of combustion or incineration, and other
factors. Because of the large number of variables involved, it is not possible, in general, to delineate when a higher
or lower emission factor, or an intermediate value should be used. For this reason, an average emission factor has
been presented.
References
1. Solid Waste - It Will Not Go Away. League of Women Voters of the United States. Publication Number 675.
April 1971.
2. Black, R.J., H.L. Hickman, Jr., A.J. Klee, A.J. Muchick, and R.D. Vaughan. The National Solid Waste
Survey: An Interim Report. Public Health Service, Environmental Control Administration. Rockville, Md.
1968.
3. Nationwide Inventory of Air Pollutant Emissions, 1968. U.S. DHEW, PHS, EHS, National Air Pollution
Control Administration. Raleigh, N.C. Publication Number AP-73. August 1970.
12/77
Solid Waste Disposal
2.0-1
-------
-------
2.1 REFUSE INCINERATION
2.1.1 Process Description1'4
The most common types of incinerators consist of a refractory-lined chamber with a grate upon which refuse
is burned. In some newer incinerators water-walled furnaces are used. Combustion products are formed by
heating and burning of refuse on the grate. In most cases, since insufficient underfire (undergrate) air is provided
to enable complete combustion, additional over-fire air is admitted above the burning waste to promote complete
gas-phase combustion. In multiple-chamber incinerators, gases from the primary chamber flow to a small
secondary mixing chamber where more air is admitted, and more complete oxidation occurs. As much as 300
percent excess air may be supplied in order to promote oxidation of combustibles. Auxiliary burners are
sometimes installed in the mixing chamber to increase the combustion temperature. Many small-size incinerators
are single-chamber units in which gases are vented from the primary combustion chamber directly into the
exhaust stack. Single-chamber incinerators of this type do not meet modern air pollution codes.
2.1.2 Definitions of Incinerator Categories1
No exact definitions of incinerator size categories exist, but for this report the following general categories
and descriptions have been selected:
1. Municipal incinerators — Multiple-chamber units often have capacities greater than 50 tons (45.3 MT) per
day and are usually equipped with automatic charging mechanisms, temperature controls, and movable
grate systems. Municipal incinerators are also usually equipped with some type of paniculate control
device, such as a spray chamber or electrostatic precipitator.
2, Industrial/commercial incinerators — The capacities of these units cover a wide range, generally between
50 and 4,000 pounds (22.7 and 1,800 kilograms) per hour. Of either single- or multiple-chamber design,
these units are often manually charged and intermittently operated. Some industrial incinerators are
similar to municipal incinerators in size and design. Better designed emission control systems include gas •
fired afterburners or scrubbing, or both.
3. Trench incinerators — A trench incinerator is designed for the combustion of wastes having relatively high
heat content and low ash content. The design of the unit is simple: a U-shaped combustion chamber is
formed by the sides and bottom of the pit and air is supplied from nozzles along the top of the pit. The
nozzles are directed at an angle below the horizontal to provide a curtain of air across the top of the pit and
to provide air for combustion in the pit. The trench incinerator is not as efficient for burning wastes as the
municipal multiple-chamber unit, except where careful precautions are taken to use it for disposal of low-
ash, high-heat-content refuse, and where special attention is paid to proper operation. Low construction
and operating costs have resulted in the use of this incinerator to dispose of materials other than those tor
which it was originally designed. Emission factors for trench incinerators used to burn thr<*e such
materials7 are included in Table 2.1-1.
4. Domestic incinerators — This category includes incinerators marketed for residential use. Fairly simple in
design, they may have single or multiple chambers and usually are equipped with an auxiliary burner to
aid combustion.
5. Flue-fed incinerators — These units, commonly found in large apartment houses, are characterized by the
charging method of dropping refuse down the incinerator flue and into the combustion chamber. Modified
flue-fed incinerators utilize afterburners and draft controls to improve combustion efficiency and reduce
emissions.
12/77
Solid Waste Disposal
2.1-1
-------
Cfl
H
O
H
O
pa
TABLE 2.1-1. EMISSION FACTORS FOR REFUSE INCINERATORS WITHOUT CONTROLS3
EMISSION FACTOR RATING: A
Participates
Municipal^
Multiple chanber , uncontrolled
With settling chamber and
water spray system
Industrial/ c come r ci a 1
Multiple chanber1
Single chamber''
Trench ^
Wood
Rubber tires
Municipal refuse
Controlled air"
Flue- fed single chamber0
Flue-fed (modified) P -I
Domestic single chamber
Without primary burnerr
With primary burner8
Pathological
kg/Mg
15
7
3.5
7.5
6.5
69
18.5
0.7
15
1
17.5
3.5
4
Ib/ton
30
14
7
15
13
138
37
1.4
30
6
35
7
8
Sulfur
kg/Mg
L.25
1.25
L.25J
1.25J
0.05
-
i.2sJ
0.75
0.25
0.25
0.25
0.25
Nag
Oxidesc
Ib/ton
2.5
2.5
2.5J
2.5J
O.I111
-
2.5J
1.5
0.5
0.5
0.5
0.5
Neg
Carbon n
kg/Mg
17.5
17.5
5
10
-
-
-
Neg
10
5
150
Neg
Neg
oonoxide
Ib/ton
35
35
10
20
-
-
Neg
20
10
300
Neg
Neg
Organic s<*
kg/Mg
0.75
0.75
1.5
7.5
-
-
-
Neg
7.5
1.5
50
1
Neg
Ib/ton
1.5
1.5
3
15
-
_
-
Neg
15
3
100
2
Neg
Nitrogen oxides6 Leadf
kg/Hg
1.5
1.5
1.5
1
2
_
-
5
1.5
5
0.5
1
1.5
Ib/ton kg/ Kg Ib/ton
3 0.2 0.4
3 - -
3
2 - -
4 - -
- _ _
-
10
3
10
1 - -
2
3 - -
aEmission factors are based on weight per unit weight of refuse
charged. Dash indicates no available data.
bAverage factors given based on EPA procedures for incinerator
stack testing.
cExpressed as sulfur dioxide.
^Expressed as methane.
eExpressed as nitrogen dioxide.
fReferences 5, 8-14, 24-28.
SReferences 5, 8-14.
"Most municipal incinerators are equipped with at least this much
control; see Table 2.1-2 for appropriate efficiencies for other
controls.
iReferences 3, 5, 10, 13, 15.
JBased on municipal incinerator data.
^References 3, 5, 10, 15.
^•Reference 7.
mBased on data for wood combustion in conical burners
"Reference 9.
"References 3, 10, 11, 13, 15, 16.
Pwith afterburners and draft controls.
^References 3, 11, 15.
References 5, 10.
sReference 5.
Reference 3, 9.
CO
ho
-------
6. Pathological incinerators — These are incinerators used to dispose of animal remains and other organic
material of high moisture content. Generally, these units are in a size range of 50 to 100 pounds (22.7 to
45.4 kilograms) per hour. Wa§tes are burned on the hearth in the combustion chamber. The units are
equipped with combustion controls and afterburners to ensure good combustion and minimal emissions.
7. Controlled air incinerators — These units operate on a controlled combustion principle in which the waste
is burned in the absence of sufficient oxygen for complete combustion in the main chamber. This process
generates a highly combustible gas mixture that is then burned with excess air in a secondary chamber,
resulting in efficient combustion. These units are usually equipped with automatic charging mechanisms
and are characterized by the high effluent temperatures reached at the exit of the incinerators.
2.1.3 Emissions and Controls1
Operating conditions, refuse composition, and basic incinerator design have a pronounced effect on
emissions. The manner in which air is supplied to the combustion chamber or chambers has, among all the
parameters, the greatest effect on the quantity of particulate emissions. Air may be introduced from beneath the
chamber, from the side, or from the top of the combustion area. As underfire air is increased, and increase in fly-
ash emissions occurs. Erratic refuse charging causes a disruption of the combustion bed and a subsequent release
of large quantities oLparticulates. Large quantities of uncombusted particulate matter and carbon monoxide are
also emitted for an extended period after charging of batch-fed units because of interruptions in the combustion
process. In continuously fed units, furnace particulate emissions are strongly dependent upon grate type. The use
of rotary kiln and reciprocating grates results in higher particulate emissions than the use of rocking or traveling
grates.14 Emissions of oxides of sulfur are dependent on the sulfur content of the refuse. Carbon monoxide and
unburned hydrocarbon emissions may be significant and are caused by poor combustion resulting from improper
incinerator design or operating conditions. Nitrogen oxide emissions increase with an increase in the temperature
of the combustion zone, an increase in the residence time in the combustion zone before quenching, and an
increase in the excess air rates to the point where dilution cooling overcomes the effect of increased oxygen
concentration.14
Hydrochloric acid emissions were found to approximate 1.0 Ib/ton of feed in early work14 and 1.8 Ib/ton in
more recent work.23 The level can be sharply increased in areas where large quantities of plastics are consumed.
Methane levels found in recent work" range from 0.04 to 0.4 Ib/ton of feed.
Table 2.1-2 lists the relative collection efficiencies of particulate control equipment used for municipal
incinerators. This control equipment has little effect on gaseous emissions. Table 2.1-1 summarizes the
uncontrolled emission factors for the various types of incinerators previously discussed.
Table 2.1-2. COLLECTION EFFICIENCIES FOR VARIOUS TYPES OF
MUNICIPAL INCINERATION PARTICULATE CONTROL SYSTEMS1
Type of system
Settling chamber
Settling chamber and water spray
Wetted baffles
Mechanical collector
Scrubber
Electrostatic precipitator
Fabric filter
Efficiency, %
0 to30
30 to 60
60
30 to 80
80 to 95
90 to 96
97 to 99
aReferences 3, 5, 6, and 17 through 21.
12/77
Solid Waste Disposal
2.1-3
-------
References for Section 2.1
1. Air Pollutant Emission Factors, Fina^ Report, Resources Research, In-
corporated, Reston, VA, prepared for National Air Pollution Control Ad-
ministration, Durham, NC, under Contract Number CPA-2269-119, April
1970.
2. Control Techniques for Carbon^MpnoxjLdeEmissions frorn^ Stationary Sources,
U.S. DREW, PHS, EHS, National Air Pollution Control Administration,
Washington, DC, Publication Number AP-65, March 1970.
3. Air Pollution Engineering Manual, U.S. DHEW, PHS, National Center for
Air Pollution Control, Cincinnati, OH, Publication Number 999-AP-40,
1967, p. 413-503.
4. J. DeMarco. et al., Incinerator Guidel.±nes 19^9, U.S. DHEW, Public
Health Service, Cincinnati, OH, SW. 13TS, 1969, p. 176.
5. C. V. Kanter, R. G. Lunche, and A. P. Fururich, Techniques for Testing
Air Contaminants from Combustion Sources, J. Air Pol. Control Assoc.,
JK4): 191-199, February 1957.
6. W. Jens, and F. R. Rehm, Municipal Incineration and Air Pollution Con-
trol , 1966 National Incinerator Conference, American Society of Mech-
anical Engineers, New York, NY, May 1966.
7. J. 0. Burkle, J. A. Dorsey, and B. T. Riley, The Effects of Operating
Variables and Refuse Types on Emissions from a Pilot-Scale Trench In-
cinerator, Proceedings of the 1968 Incinerator Conference^ American
Society of Mechanical Engineers, New York, NY, May 1968, p. 34-41.
8. J. H. Fernandes, Incinerator Air Pollution Control, Proceedings of
1968 National Incinerator Conference, American Society of Mechanical
Engineers, New York, NY, May 1968, p. 111.
9. Unpublished data on incinerator testing. U.S. DHEW, PHS, EHS, National
Air Pollution Control Administration, Durham, NC, 1970.
10. J. L. Stear, Municipal Incineration: A Review of Literature, U.S.
Environmental Protection Agency, Office of Air Programs, Research
Triangle Park, NC, GAP Publication Number AP-79, June 1971.
11. E. R. Kaiser, et al., Modifications to Reduce Emissions^ from a Flue-
f_ed_ Incinerator, New York University, College of Engineering, Report
Number 552.2, June 1959, p. 40 and 49.
12. Unpublished data on incinerator emissions. U.S. DHEW, PHS, Bureau of
Solid Waste Management, Cincinnati, OH, 1969.
2.1-4 EMISSION FACTORS 12/77
-------
13. E. R. Kaiser, Refuse Reduction Processes in Proceedings of Surgeon
Gener al' s Conf erence on Solid Waste_jlanagemen±, Public Health Service,
Washington, DC, PHS Report Number 1729, July~TO-20, 1967.
14. Walter R. Nissen, Systems Study of Air Follution from Municipal Incin-
eration, Arthur D. Little, Inc. Cambridge, MA, prepared for National
Air Pollution Control Administration, Durham, NC, under Contract Number
CPA-22-69-23, March 1970.
15. Unpublished source test data on incinerators, Resources Research, In-
corporated, Reston, VA, 1966-1969.
16. Communication between Resources Research, Incorporated, Reston, VA,
and Maryland State Department of Health, Division of Air Quality Con-
trol, Baltimore, MD, 1969.
17. F. R. Rehm, Incinerator Testing and Test Results, J. Air Po 1. Contro1
Assoc. 6_: 199-204, February 1957.
18. R. L. Stenburg, et aJU , Field Evaluation of Combustion Air Effects on
Atmospheric Emissions from Municipal Incinerations, J. Air Pol. Control
Assoc. 12:83-89, February 1962.
19. E. E. Smauder, Problems of Municipal Incineration, Pjroceedings of Air
Pollution Control Association, West Coast Section, Los Angeles, CA,
March 1957.
20. R. W. Gerstle, Unpublished data: revision of emission factors based
on recent stack tests, U.S. DHEW, PHS, National Center for Air Pollu-
tion Control, Cincinnati, OH, 1967.
21. A Field Study of Performance of Three Municipal Incinerators, University
of California, Berkeley, Technical Bulletin ^:41, November 1957.
22. J. Driscol, et al., Evaluation of MonitorIng Methods ana" Instrumentation
for Hydrocarbons and Carbon Monoxide in Stationary Source Emissiojis,
Publication No. EPA-R2-72-106, November 1977.
23. J. A. Jahnke, J. L. Chaney, R. Rollins, and C. R. Fortune, A Research
Study of Gaseous Emissions from a Municipal Incinerator, J.^Air Polltit.
Control Assoc. 27:747-753, August 1977.
24. Control Techniques^ fojr jLead Air Emissions^ EPA-450/2-77-012, U.S. Envir-
onmental Protection Agency, Research Triangle Park, NC, December 1977.
25. W. E. Davis, Emissions Study of Industrial Source of Lead Air Pollutants,
1970, EPA APTD-1543, W. E. Davis and Associates, Leawood, KS, April
1973.
12/81 Solid Waste Disposal 2.1-5
-------
26. Emission Tests Nos. 71-CI-05 and 71-CI-ll, Office of Air Quality Planning
and Standards, U.S. Environmental Protection Agency, Research Triangle
Park, NC, September 1971.
27. K. J. Yost, The Environmental Flow of Cadmium and Other Trace Metals; Pro-
gress Report for July 1, 1973 to June 30, 1^974, Purdue University, West
Lafayette, IN.
28. F. L. Gloss, et al., "Metal and Particulate Emissions from Incinerators
Burning Sewage Sludge", Proceedings of the 1970 National Incinerator Con-
ference of ASME, 1970.
2.1-6
EMISSION FACTORS
12/81
-------
2.2 AUTOMOBILE BODY INCINERATION
2.2.1 Process Description
Auto incinerators consist of a single primary combustion chamber in which one or several partially stripped
cars are burned. (Tires are removed.) Approximately 30 to 40 minutes is required to burn two bodies
simultaneously.2 As many as 50 cars per day can be burned in this batch-type operation, depending on the
capacity of the incinerator. Continuous operations in which cars are placed on a conveyor belt and passed
through a tunnel-type incinerator have capacities of more than 50 cars per 8-hour day.
2.2.2 Emissions and Controls •
Both the degree of combustion as determined by the incinerator design and the amount of combustible
material left on the car greatly affect emissions. Temperatures on the order of 1200°F (650°C) are reached during
auto body incineration.2 This relatively low combustion temperature is a result of the large incinerator volume
needed to contain the bodies as compared with the small quantity of combustible material. The use of overfire air
jets in the primary combustion chamber increases combustion efficiency by providing air and increased
turbulence.
In an attempt to reduce the various air pollutants produced by this method of burning, some auto incinerators
are equipped with emission control devices. Afterburners and low-voltage electrostatic precipitators have been
used to reduce paniculate emissions; the former also reduces some of the gaseous emissions.3-4 When
afterburners are used to control emissions, the temperature in the secondary combustion chamber should be at
least 1500°F (815°C). Lower temperatures result in higher emissions. Emission factors for auto body incinerators
are presented in Table 2.2-1.
4/73
Table 2.2-1. EMISSION FACTORS FOR AUTO BODY INCINERATION8
EMISSION FACTOR RATING: B
Pollutants
Particulatesb
Carbon monoxide0
Hydrocarbons (CH4)C
Nitrogen oxides (N02)d
Aldehydes (HCOH)d
Organic acids (acetic)d
Uncontrolled
Ib/car
2
2.5
0.5
0.1
0.2
0.21
kg/car
0.9
1.1
0.23
0.05
0.09
0.10
With afterburner
Ib/car
1.5
Neg
Neg
0.02
0.06
0.07
kg/car
0.68
Neg
Neg
0.01
0.03
0.03
aBased on 250 Ib (113 kg) of combustible material on stripped car body.
bReferences 2 and 4.
GBased on data for open burning and References 2 and 5.
dReference 3.
Solid Waste Disposal
2.2-1
-------
References for Section 2.2
1. Air Pollutant Emission Factors. Final Report. Resources Research Inc. Reston, Va. Prepared for National Air
Pollution Control Administration, Durham, N.C., under Contract Number CPA-22-69-119. April 1970.
2. Kaiser, E.R. and J. Tolcias. Smokeless Burning of Automobile Bodies. J. Air Pol. Control Assoc. 72:64-73,
February 1962.
3. Alpiser, F.M. Air Pollution from Disposal of Junked Autos. Air Engineering. 10:18-22, November 1968.
4. Private communication with D.F. Walters, U.S. DHEW, PHS, Division of Air Pollution. Cincinnati, Ohio. July
19, 1963.
5. Gerstle, R.W. and D.A. Kemnitz. Atmospheric Emissions from Open Burning. J. Air Pol. Control Assoc.
17:324-327. May 1967.
2.2-2 EMISSION FACTORS 4/73
-------
2.3 CONICAL BURNERS
2.3.1 Process Description1
Conical burners are generally a truncated metal cone with a screened top vent. The charge is placed on a
raised grate by either conveyor or bulldozer; however, the use of a conveyor results in more efficient burning. No
supplemental fuel is used, but combustion air is often supplemented by underfire air blown into the chamber
below the grate and by overfire air introduced through peripheral openings in the shell.
2.3.2 Emissions and Controls
The quantities and types of pollutants released from conical burners are dependent on the composition and
moisture content of the charged material, control of combustion air, tvpe of charging system used, and the
condition in which the incinerator is maintained. The most criucal ot tnese factors seems to be the level of
maintenance on the incinerators. It is not uncommon for conical burners to have missing doors and numerous
holes in the shell, resulting in excessive combustion air, low temperatures, and, therefore, high emission rates of
combustible pollutants.2
Particulate control systems have been adapted to conical burners with some success. These control systems
include water curtains (wet caps) and water scrubbers. Emission factors for conical burners are shown in Table
2.3-1.
4/73
Solid Waste Disposal
2.3-1
-------
K)
Table 2.3-1. EMISSION FACTORS FOR WASTE INCINERATION IN CONICAL BURNERS
WITHOUT CONTROLS3
EMISSION FACTOR RATING: B
Type of
waste
Municipal
refuse*3
Wood refuse6
Particulates
Ib/ton
20(10 to 60)c-d
If
79
20n
kg/MT
10
0.5
3,5
10
Sulfur oxides
Ib/ton
2
0.1
kg/MT
1
0.05
Carbon monoxide
!b/ton
60
130
kg/MT
30
65
Hydrocarbons
Ib/ton
20
11
kg/MT
10
5.5
Nitrogen oxides
Ib/ton
5
1
kg/MT
2.5
0.5
E
1—I
cw
cw
O
z
*n
>
?8
w
aMoisture content as fired is approximately 50 percent for wood waste.
Except for participates, factors are based on comparison with other waste disposal practices.
cUse high side of range for intermittent operations charged with a bulldozer.
Based on Reference 3.
References 4 through 9.
Satisfactory operation: properly maintained burner with adjustable underfireair supply and adjustable, tangential overfireair inlets, approximately 500 percent
excess air and 7QQ°F (370°C) exit gas temperature.
9 Unsatisfactory operation: properly maintained burner with radial overfireair supply near bottom of shell, approximately 1200 percent excess air and 400° F (204°C)
exit gas temperature.
"Very unsatisfactory operation: improperly maintained burner with radial overfire air supply near bottom of shell and many gaping holes in shell, approximately 1500
percent excess air and 400°F (204°C) exit gas temperature.
-------
References for Section 2.3
1. Air Pollutant Emission Factors. Final Report. Resources Research Inc. Reston, Va. Prepared for National Air
Pollution Control Administration, Durham, N.C., under Contract Number CPA-22-69-119. April 1970.
2. Kreichelt, I.E. Air Pollution Aspects of Teepee Burners. U.S. DHEW, PHS, Division of Air Pollution.
Cincinnati, Ohio. PHS Publication Number 999-AP-28. September 1966.
3. Magill, P.L. and R.W. Benoliel. Air Pollution in Los Angeles County: Contribution of Industrial Products.
Ind. Eng. Chem. 44:1347-1352, June 1952.
4. Private communication with Public Health Service, Bureau of Solid Waste Management, Cincinnati, Ohio.
October 31, 1969.
5. Anderson, D.M., J. Lieben, and V.H. Sussman. Pure Air for Pennsylvania. Pennsylvania State Department of
Health, Harrisburg. November 1961. p.98.
6, Boubel, R.W. et al. Wood Waste Disposal and Utilization. Engineering Experiment Station, Oregon State
University, Corvallis. Bulletin Number 39. June 1958. p.57.
7. Netzley, A.B. and J.E. Williamson. Multiple Chamber Incinerators for Burning Wood Waste. In: Air Pollution
Engineering Manual, Danielson, J.A. (ed.). U.S. DHEW, PHS, National Center for Air Pollution Control.
Cincinnati, Ohio. PHS Publication Number 999-AP-40. 1967. p.436-445.
8. Droege, H. and G. Lee. The Use of Gas Sampling and Analysis for the Evaluation of Teepee Burners. Bureau
of Air Sanitation, California Department of Public Health. (Presented at the 7th Conference on Methods in
Air Pollution Studies, Los Angeles. January 1965.)
9. Boubel R.W. Particulate Emissions from Sawmill Waste Burners. Engineering Experiment Station, Oregon
State University, Corvallis. Bulletin Number 42. August 1968. p.7,8.
4/73
Solid Waste Disposal
2.3-3
-------
-------
2.4 OPEN BURNING
2.4.1 General1
Open burning can be done in open drums or baskets, in fields and yards, and in large open dumps or pits.
Materials commonly disposed of in this manner are municipal waste, auto body components, landscape refuse,
agricultural field refuse, wood refuse, bulky industrial refuse, and leaves.
2.4.2 Emissions1-19
Ground-level open burning is affected by many variables including wind, ambient temperature, composition
and moisture content of the debris burned, and compactness of the pile. In general, the relatively low
temperatures associated with open burning increase the emission of particulates, carbon monoxide, and
hydrocarbons and suppress the emission of nitrogen oxides. Sulfur oxide emissions are a direct function of the
sulfur content of the refuse. Emission factors are presented in Table 2.4-1 for the open burning of municipal
refuse and automobile components.
Table 2.4-1. EMISSION FACTORS FOR OPEN BURNING OF NONAGRICULTURAL MATERIAL
EMISSION FACTOR RATING: B
Source
Municipal refuse*3
kg/Mg
Ib/ton
Automobile
components'^
kg/Mg
Ib/ton
Particulate
8
16
50
100
Sulfur
oxides
0.5
1
Neg.
Neg.
Carbon
monoxide
42
85
62
125
voca
methane nonme thane
6.5 15
13 30
5 16
10 32
Nitrogen
oxides
3
6
2
4
aData indicate that VOC emissions are approximately 25% methaae, 8% other saturates,
18% olefins, 42% others (oxygenates, acetylene, aromatics, trace formaldehyde).
^References 2, 7.
cReferences 2. Upholstery, belts, hoses and tires burned together.
Emissions from agricultural refuse burning are dependent mainly on the moisture con tent of the refuse and,
in the case of the field crops, on whether the refuse is burned in a headfire or a backfire. (Headfires are started at
the upwind side of a field and allowed to progress in the direction of the wind, whereas backfires are started at the
downwind edge and forced to progress in a direction opposing the wind.) Other variables such as fuel loading (how-
much refuse material is burned per unit of land area) and how the refuse is arranged (that is, in piles, rows, or
spread out) are also important in certain instances. Emission factors for open agricultural burning are presented
in Table 2.4-2 as a function of refuse type and also, in certain instances, as a function of burning techniques
and/or moisture content when these variables are known to significantly affect emissions. Table 2.4-2 also
presents typical fuel loading values associated with each type of refuse. These values can be used, along with the
corresponding emission factors, to estimate emissions from certain categories of agricultural burning when the
specific fuel loadings for a given area are not known.
Emissions from leaf burning are dependent upon the moisture content, density, and ignition location of the
leaf piles. Increasing the moisture content of the leaves generally increases the amount of carbon monoxide,
5/83
Solid Waste Disposal
2.4-1
-------
to
i*
INS
Table 2.4-2. EMISSION FACTORS AND FUEL LOADING FACTORS FOR OPEN BURNING
OF AGRICULTURAL MATERIALS*
EMISSION FACTOR RATING: B
cn
C/5
O
o
3
Partlculateb
Refuse Category kg/Mg Ib/ton
Field Cropsd
Unspecified 11 21
Burning techniques not
algnlf i<:ante 1
Asparagusf 20 40
Barley 11 22
Carbon
Monoxide
kg/Mg
58
75
78
Corn ] 7 14 54
Cotton 4 8 88
Grasses S 16
Pineapple^ ! 4 8
Rice" 4 9
Safflower 9 18
50
56
41
72
Sorghum <3 18 38
Sugar i:anel ' 2.5-3.5 6-8.4 30-41
1
Hendfire burning J |
Alfalfa 23 45 53
BcFiii (red) 22 43 93
Hay (uilrt) IT 32 ] 70
Oils 22 44 68
P,j;t 16 31 74
WhiMt ! 11 22 64
1
Backfire burning^ |
Alfalfa | 14 29 60
Bean (r."D, ?e;i 7 14 72
ilay (wi Id) 8 17
Oats 11 21
Whoat 6 13
75
68
54
Vine Crops 3 5 26
Weeds '
L'nspeL-i fl.-d H 15 42
r-l'i-^Un rliistU Ctumblewecd) ' 11 22 j 154
T'lL.'S (wiH reeds) [3 5 17
! !
Ib/ton
117
150
vocc
Methane
kg/Mg
2.7
10
157 2.2
108
176
101
112
83
144
77
60-81
106
136
139
137
147
128
2
0.7
2.2
1
1.2
3
I
0.6-2
4.2
5.5
2.5
4
4.5
2
119
4.5
148 3
150 2
136 2
108
51
1.3
0.8
85 | 1.5
309 0.2
34 3.2
1
Ib/ton
5.4
20
4.5
4
1.4
4.5
2
2.4
6
2
1.2-3.8
S.5
11
Nonme thane
kg/Mg
9
33
7.5
6
2.5
7.5
3
4
10
3.5
2-6
14
18
5 8.5
7.8
9
4
9
6
13
15
6.5
14
10
4 6.5
4 7
2.6
1.7
4.5
3
3 J 4.5
0.5 ' 0.8
6.5 10
1
Ib/ton
18
66
15
12
5
15
6
8
20
7
Fuel Loading Factors
(waste production)
Mg/hectare ton/acre
4.5
3.4
3.8
9.4
3.8
6.7
2.9
6.5
4-12 1 8-46
1
i
28 ' 1.8
36 5.6
17
26
2.2
3.6
29 5.6
13 4.3
29 1.8
19 ' 5.6
13 2.2
14 3.6
9
5
9
1.5
21
4.3
5.6
7.2
0.'
2
1.5
1.7
4.2
1.7
3.0
1.3
2.9
3-17
0.8
2.5
1.0
1.6
2.5
1.9
0.8
2.5
1.0
1.6
1.9
2.5
3.2
0.1
s
-------
0_
a
SI
V!
13
O
ft!
Orchard Crops*1'1!1"
l.lnspec i f led
Almond
Appl e
Apricot
Avocado
Cherry
Citrus (orange, lemon)
Date palm
Fig
^ecta r i lie
01 ive
Peach
Pear
Prune
Wai -.it
Forest Residues11
Inspect fled
Hemlock, Doug lus Ft**, cedarP
Pond ero sa p Inel
3 6
3 6
2 4
3 6
10 21
4 8
3 6
5 10
4 7
2 4
6 12
3 6
it 9
2 3
3 6
8 17
2 4
6 12
26 52
23 46
21 42
24 49
58 116
22 44
40 81
28 56
28 57
16 33
57 114
21 42
28 57
21 42
24 47
70 140
45 90
98 195
1.2 2.5
1 2
0.5 1
1 2
3.8 7.5
1.2 2.5
1.5 3
0.8 1.7
1,2 2.5
0.5 1
2 4
0.6 1.2
1 2
0.4 0.7
1 2
2.8 5.7
0.6 1.2
1.7 3.3
4 8
3 6
1.5 3
3 6
12 25
4 8
5 9
3 5
4 8
1.5 3
7 14
2 4
3.5 7
1 2
3 6
9 19
2 4
5.5 11
3.6 1.6
3.6 1.6
5.2 2.3
4 1.8
3.4 1.5
2.2 1.0
2,2 1.0
2.2 1,0
4.9 2.2
4.5 2,0
2.7 1.2
5.6 2,5
5.8 2.6
2.7 1.2
2.7 1.2
157 70
to
f
w
^Expressed .\-i weight of pollutant emitted/weight of refuse material burned.
^KcFerenoe 12. Particulate matter from most agricultural re fuse burning has been found to be in the submic romete r
siz^ range.
cD.it.i indicate that VOC emissions average 22^ methane, 7.5? other saturates, 17% olefins, 1531 acetylene, 38.5?
unidentified. Unidentified VOC are expected to include aldehydes, ketones, aromatics, cycloparaffins.
'-1-t^ FH rences 12-13 for emission factors, Reference 14 For fuel loading factors*
11V fir these refuse materials, no significant difference exists between emissions from headfiring or backfiring.
f r;u' to rs represent emissions under typical high moisture conditions. If ferns are dried to \ Ib/ton).
^Reference 20. See Section 8.12 for discussion of sugar cane burning, The following fuel loading factors are to be
used in the corresponding states: Louisiana, 8 - 13.6 Mg/hectare (3-5 ton/acre); Florida, 11 - 19 Mg/hectare
(4-7 ton/acre); Hawaii, 30 - 48 Mg/hectare (11 - 17 ton/acre). For other areas, values generally Increase with length
of growing season. Use the larger end of the emission factor range for lower loading factors.
JSee text for definition of headfiring.
kSee text for definition of backfiring. This category, for emission estimation purposes, includes another technique
used occasionally to limit emissions, called into-the-wind strtpllghtlng, which is lighting fields in strips into the
wind at 100 - 200 ra (300 - n )0 ft) intervals.
T-Orchdrd prunings are usually burned in piles. There are no significant differences in emissions between burning a
"cold pile" and using a roll-on technique, where prunings are bulldozed onto the embers of a preceding fire.
mlf orchard removal is the purpose of a burn, 66 Mg/hectare (30 ton/acre) of waste will be produced.
•Reference 10. NOX emissions estimated at 2 kg/Mg (4 Ib/ton).
PRe ferenoe 15.
IRe-Feretice 16,
-------
hydrocarbon, and particulate emissions. Increasing the density of the piles increases the amount of hydrocarbon
and particulate emissions, but has a variable effect on carbon monoxide emissions. Arranging the leaves in
conical piles and igniting around the periphery of the bottom proves to the least desirable method of burning.
Igniting a single spot on the top of the pile decreases the hydrocarbon and particulate emissions. Carbon
monoxide emissions with top ignition decreases if moisture content is high but increases if moisture content is
low. Particulate, hydrocarbon, and carbon monoxide emissions from windrow ignition (piling the leaves into a
long row and igniting one end, allowing it to burn toward the other end) are intermediate between top and bottom
ignition. Emission factors for leaf burning are presented in Table 2.4-3.
For more detailed information on this subject, the reader should consult the references cited at the end of
this section.
Table 2.4-3. EMISSION FACTORS FOR LEAF BURNING18'19
EMISSION FACTOR RATING: B
Leaf Species
Black Ash
Modesto Ash
White Ash
Catalpa
Horse Chestnut
Cottonvjood
American Kim
Eucalyptus
Sweet Gam
Black. Locust
Magnolia
Silver Maple
American Sycamore
California Sycamore
Tulip
Red Oak
Sugar Maple
Unspecified
Particulateb
kg/Mg Ib/ton
18 36
16 32
21.5 43
8.5 17
27 54
19 38
13 26
18 36
16.5 33
35 70
6.5 13
33 66
7.5 15
5 10
10 20
46 92
26.5 53
19 38
Carbon monoxide
kg/Mg Ib/ton
63.5 127
81.5 163
57 113
44.5 89
73.5 147
45 90
59.5 119
45 90
70 140
65 130
27.5 55
51 102
57.5 115
52 104
38.5 77
68.5 137
54 108
56 112
VOCC
Methane
kj>/Mg Ib/ton
5.5 11
5 10
6.5 13
2.5 5
8 17
6 12
4 B
5.5 11
5 10
11 22
2 4
10 20
2.5 5
1.5 3
3 6
14 28
8 16
6 12
Nonmethane
kg/Mg Ib/ton
13.5 27
12 24
16 32
6.5 13
20 40
14 28
9.5 19
13.5 27
12.5 25
. 26 52
5 10
24 . 5 49
5.5 11
3.5 7
7.5 15
34 69
20 40
14 28
aReferences 18-19. Factors are an arithmetic average of results obtained by burning high and low moisture
content conical piles, ignited either at the top or around the periphery of the bottom. The windrow
arrangement was only tested on Modesto Ash, Catalpa, American Elm, Sweet Gum, Silver Maple and Tulip, and
results are included In the averages for these species.
"The majority of particulate is submicron in size.
cTests indicate that VOC emissions average 29% methane, 11% other saturates, 33% oleflns, 27% other
(aromatics, acetylene, oxygenates).
References for Section 2.4
1. Air Pollutant Emission Factors. Final Report. Resources Research, Inc., Reston, Va. Prepared for National
Air Pollution Control Administration, Durham, N.C. under Contract Number CPA-22-69-119. April 1970.
2. Gerstle, R. W. and D. A. Kemnitz. Atmospheric Emissions from Open Burning. J. Air Pol. Control Assoc.
^2:324-327. May 1967.
2.4-4
EMISSION FACTORS
5/83
-------
3. Burkle, J. 0., J.A. Dorsey, and B. T. Riley. The Effects of Operating Variables and Refuse Types on
Emissions from a Pilot-Scale Trench Incinerator. In: Proceedings of 1968 Incinerator Conference,
American Society of Mechanical Engineers. New \ork. May 1968. p. 34-41.
4. Weisburd, M. I. and S. S. Griswold (eds.). Air Pollution Control Field Operations Guide: A Guide for
Inspection and Control. U.S. DHEW, PHS, Division of Air Pollution, Washington, D.C.,PHS Publication
No. 937. 1962.
5. Unpublished data on estimated major air contaminant emissions. State of New York Department of Health.
Albany. April 1, 1968.
6. Darley, E. F. et al. Contribution of Burning of Agricultural Wastes to Photochemical Air Pollution J. Air
Pol. Control Assoc. 76:685-690, December 1966.
7. Feldstein, M. et al. The Contribution of the Open Burning of Land Clearing Debris to Air Pollution. J. Air
Pol. Control Assoc. 73:542-545, November 1963.
8. Boubel, R. W., E. F. Darley, and E. A. Schuck. Emissions from Burning Grass Stubble and Straw. J. Air Pol.
Control Assoc. 79:497-500, July 1969.
9. Waste Problems of Agriculture and Forestry. Environ. Sci. and Tech. 2:498, July 1968.
10. Yamate, G. et al. An Inventory of Emissions from Forest Wildfires, Forest Managed Burns, and Agricultural
Burns and Development of Emission Factors for Estimating Atmospheric Emissions from Forest Fires.
(Presented at 68th Annual Meeting Air Pollution Control Association. Boston. June 1975.)
11. Darley, E. F. Air Pollution Emissions from Burning Sugar Cane and Pineapple from Hawaii. University of
California, Riverside, Calif. Prepared for Environmental Protection Agency, Research Triangle Park, N. C.
as amendment to Research Grant No. R800711. August 1974.
12. Darley, E. F. et al. Air Pollution from Forest and Agricultural Burning. California Air Resources Board
Project 2-017-1, University of California. Davis, Calif. California Air Resources Board Project No. 2-017-1.
April 1974.
13. Darley, E. F. Progress Report on Emissions from Agricultural Burning. California Air Resources Board
Project 4-011. University of California, Riverside, Calif. Private communication with permission of Air
Resources Board, June 1975.
14. Private communication on estimated waste production from agricultural burning activities. California Air
Resources Board, Sacramento, Calif. September 1975.
15. Fritschen, L. et al. Flash Fire Atmospheric Pollution. U.S. Department of Agriculture, Washington, D.C.
Service Research Paper PNW-97. 1970.
16. Sandberg, D. V., S. G. Pickford, and E. F. Darley. Emissions from Slash Burning and the Influence of Flame
Retardant Chemicals. J. Air Pol. Control Assoc. 25:278, 1975.
17. Wayne, L. C. and M. L. McQueary. Calculation of Emission Factors for Agricultural Burning Activities.
Pacific Environmental Services, Inc., Santa Monica, Calif. Prepared for Environmental Protection Agency,
Research Triangle Park, N. C., und. Contract No. 68-02-1004, TasK Order No. 4. Publication No. EPA-
450/3-75-087. November 1975.
5/83
Solid Waste Disposal
2.4-5
-------
18. Darley, E.F. Emission Factor Development lor Leal' Burning. I ni\ersil\ of California. Rhcrside.
Calif. Prepared for Environmental Protection Agenc\. Research Triangle Park. N.C.. under
Purchase Order No. 5-02-6876-1. September 1976.
19. Darle\, E.F. Evaluation of the Impact of Leaf Burning - IMiase I: Emission Factors for Illinois
Leaves. University of California. Riverside. Calif. Prepared for Stale of Illinois. Institute for
Environmental Quality. August 1975.
20, Southerland, J.H. and A. McBath, Emission Factors and Field Loading for Sugar Cane Burning.
MDAD, OAQPS, U.S. Environmental Protection Agency, Research Triangle Park, N.C. January
1978.
2.4-6
EMISSION FACTORS
5/83
-------
2.5 SEWAGE SLUDGE INCINERATION
2.5.1 Process Description *-3
Incineration is becoming an important means of disposal for the increasing amounts of sludge being produced
in sewage treatment plants. Incineration has the advantages of both destroying the organic matter present in
sludge, leaving only an odorless, sterile ash, as well as reducing the solid mass by about 90 percent. Disadvantages
include the remaining, but reduced, waste disposal problem and the potential for air pollution. Sludge inciner-
ation systems usually include a sludge pretreatment stage to thicken and dewater the incoming sludge, an inciner-
ator, and some type of air pollution control equipment (commonly wet scrubbers).
The most prevalent types of incinerators are multiple hearth and fluidized bed units. In multiple hearth
units the sludge enters the top of the furnace where it is first dried by contact with the hot, rising, combustion
gases, and then burned as it moves slowly down through the lower hearths. At the bottom hearth any residual
ash is then removed. In fluidized bed reactors, the combustion takes place in a hot, suspended bed of sand with
much of the ash residue being swept out with the flue gas. Temperatures in a multiple hearth furnace are 600°F
(320°C) in the lower, ash cooling hearth; 1400 to 2000°F (760 to 1100°C) in the central combustion hearths,
and 1000 to 1200°F (540 to 650°C) in the upper, drying hearths. Temperatures in a fluidized bed reactor are
fairly uniform, from 1250 to 1500°F (680 to 820°C). In both types of furnace an auxiliary fuel may be required
either during startup or when the moisture content of the sludge is too high to support combustion.
2.5.2 Emissions and Controls 1,2,4-7
Because of the violent upwards movement of combustion gases with respect to the burning sludge, particu-
lates are the major emissions problem in both multiple hearth and fluidized bed incinerators. Wet scrubbers are
commonly employed for particulate control and can achieve efficiencies ranging from 95 to 99+ percent.
Although dry sludge may contain from 1 to 2 percent sulfur by weight, sulfur oxides are not emitted in signif-
icant amounts when sludge burning is compared with many other combustion processes. Similarly, nitrogen
oxides, because temperatures during incineration do not exceed 1500°F (820°C) in fluidized bed reactors or
1600 to 2000°F (870 to 1100°C) in multiple hearth units, are not formed in great amounts.
Odors can be a problem in multiple hearth systems as unburned volatiles are given off in the upper, drying
hearths, but are readily removed when afterburners are employed. Odors are not generally a problem in fluid-
ized bed units as temperatures are uniformly high enough to provide complete oxidation of the volatile com-
pounds. Odors can also emanate from the pretreatment stages unless the operations are properly enclosed.
Emission factors for sludge incinerators are shown in Table 2.5-1. It should be noted that most sludge incin-
erators operating today employ some type of scrubber.
5/74
Solid Waste Disposal
2.5-1
-------
oo
to
Ul
NS
TABLE 2.5-1. EMISSION FACTORS FOR SEWAGE SLUDGE INCINERATORS3
EMISSION FACTOR RATING: B
Uncontrolled*5
EMISS]
o
FACTORS
Pollutant
Particulatec
Sulfur dioxided
Carbon monoxide6
d
Nitrogen oxides (as N02.
Hydrocarbons^
Hydrogen chloride gas
Leadf
After scrubber
Multiple hearth
kg/Mg
50
0.5
Neg
) 3
0.75
0.75
-
Ib/ton
100
1
Neg
6
1.5
1.5
-
kg/Mg
1.5
0.4
Neg
2.5
0.5
0.15
0.015
(0.01-0.2)
Ib/ton
3
0.8
Neg
5
1
0.3
0.025
(0.02-0.03)
Fluidized bed
kg/Mg
1.5
0.4
Neg
2.5
0.5
0.15
0.001
(0.005-0.002)
Ib/ton
3
0.8
Neg
5
1
0.3
0.002
(0.001-0.003)
aEraission factors expressed as weight per unit weight of dried sludge. Dash indicates
no data available.
^Estimated from emission factors after scrubbers.
References 6-9.
^Reference 8.
References 6, 8.
fReferences 10-11.
-------
References for Section 2.5
1. R. R. Calaceto, Advances in Fly Ash Removal with Gas-Scrubbing Devices,
Filtration Engineering, J.(7):12-15, March 1970.
2. S. Balakrishnam, gt ajU , State of the Art Review on Sludge Incineration
Practices, U.S. Department of the Interior, Federal Water Quality Adminis-
tration, Washington, DC, FWQA-WPC Research Series.
3. Canada's Largest Sludge Incinerators Fired Up and Running, Water and
Pollution Control, ^07(1):20-21, 24, January 1969.
4. R. R. Calaceto, Sludge Incinerator Fly Ash Controlled by Cyclonic Scrub-
ber, Public Works, 94(2):113-114, February 1963.
5. I. M. Schuraytz, et al. , Stainless Steel Use In Sludge Incinerator Gas
Scrubbers, Public Works 103(2):55-57, February 1972.
6. P. Liao, Design Method for Fluidized Bed Sewage Sludge Incinerators,
PhD. Thesis, University of Washington, Seattle, WA, 1972.
7. Source test data supplied by the Detroit Metropolitan Water Department,
Detroit, MI, 1973.
8. Source test data from Office of Air Quality Planning and Standards, U.S.
Environmental Protection Agency, Research Triangle Park, NC, 1972.
9. Source test data from Dorr-Oliver, Inc., Stamford, CT, 1973.
10. W. E. Davis, Emissions Study of Industrial Sources of Lead Air Pollutants,
1970, EPA APTD-1543, W. E. Davis and Associates, Leawood, KS, April 1973.
1973.
11. Sewage Sludge Incineration, EPA-R2-72-040, U.S. Environmental Protection
Agency, Research Triangle Park, NC, August 1972.
2.5-3
Solid Waste Disposal
12/81
-------
-------
3.0 STATIONARY INTERNAL COMBUSTION SOURCES
Internal combustion engines Included in this category generally are used
in applications similar to those associated with external combustion sources.
The major engines within this category are gas turbines and large heavy duty
general utility reciprocating engines. Most stationary internal combustion
engines are used to generate electric power, to pump gas or other fluids, or
to compress air for pneumatic machinery.
9/85
3.0-1
-------
-------
3.1 Stationary Gas Turbines for Electric Utility Power Plants
3.1.1 General - Stationary gas turbines find application in electric power generators, in gas pipeline pump and
compressor drives, and in various process industries. The majority of these engines are used in electrical generation
for continuous, peaking, or standby power.1 The primary fuels used are natural gas and No, 2 (distillate) fuel oil,
although residual oil is used in a few applications.
3.1.2 Emissions — Data on gas turbines were gathered and summarized under an EPA contract.2 The contractor
found that several investigators had reported data on emissions from gas turbines used in electrical generation but
that little agreement existed among the investigators regarding the terms in which the emissions were expressed.
The efforts represented by this section include acquisition of the data and their conversion to uniform terms.
Because many sets of measurements reported by the contractor were not complete, this conversion often involved
assumptions on engine air flow or fuel flow rates (based on manufacturers' data). Another shortcoming of the
available information was that relatively few data were obtained at loads below maximum rated (or base) load.
Available data on the population and usage of gas turbines in electric utility power plants are fairly extensive,
and information from the various sources appears to be in substantial agreement. The source providing the most
complete information is the Federal Power Commission, which requires major utilities (electric revenues of $1
million or more) to submit operating and financial data on an annual basis. Sawyer and Farmer3 employed these
data to develop statistics on the use of gas turbines for electric generation in 1971. Although their report involved
only the major, publicly owned utilities (not the private or investor-owned companies), the statistics do appear to
include about 87 percent of the gas turbine power used for electric generation in 1971.
Of the 253 generating stations listed by Sawyer and Farmer, 137 have more than one turbine-generator unit.
From the available data, it is not possible to know how many hours each turbine was operated during 1971 for
these multiple-turbine plants. The remaining 116 (single-turbine) units, however, were operated an average of 1196
hours during 1971 (or 13.7 percent of the time), and their average load factor (percent of rated load) during
operation was 86.8 percent. This information alone is not adequate for determining a representative operating
pattern for electric utility turbines, but it should help prevent serious errors.
Using 1196 hours of operation per year and 250 starts per year as normal, the resulting average operating day is
about 4.8 hours long. One hour of no-load time per day would represent about 21 percent of operating time, which
is considered somewhat excessive. For economy considerations, turbines are not run at off-design conditions any
longer than necessary, so time spent at intermediate power points is probably minimal. The bulk of turbine
operation must be at base or peak load to achieve the high load factor already mentioned.
If it is assumed that time spent at off-design conditions includes 15 percent at zero load and 2 percent each at
25 percent, 50 percent, and 75 percent load, then the percentages of operating time at rated load (100 percent)
and peak load (assumed to be 125 percent of rated) can be calculated to produce an 86.8 percent load factor.
These percentages turn out to be 19 percent at peak load and 60 percent at rated load; the postulated cycle based
on. this line of reasoning is summarized in Table 3.1-1.
1/75 3.1-1
-------
Table 3.1-1. TYPICAL OPERATING CYCLE FOR ELECTRIC
UTILITY TURBINES
Condition,
% of rated
power
0
25
50
75
100 (base)
125 (peak)
Percent operating
time spent
at condition
15
2
2
2
60
19
Time at condition
based on 4.8-hr day
hours
0.72
0.10
0.10
0.10
2.88
0.91
4.81
minutes
43
6
6
6
173
55
289
Contribution to load
factor at condition
0.00x0.15 = 0.0
0.25 x 0.02 = 0.005
0.50x0.02 = 0.010
0.75x0.02 = 0.015
1.0 x 0.60 = 0.60
1.25x0.19 = 0.238
Load factor = 0.868
The operating cycle in Table 3.1-1 is used to compute emission factors, although it is only an estimate of actual
operating patterns.
Table 3.1-2. COMPOSITE EMISSION FACTORS FOR 1971
POPULATION OF ELECTRIC UTILITY TURBINES
EMISSION FACTOR RATING: B
Time basis
Entire population
Ib/hr rated loada
kg/hr rated load
Gas-fired only
Ib/hr rated load
kg/hr rated load
Oil-fired only
Ib/hr rated load
kg/hr rated load
Fuel basis
Gas-fired only
Ib/I06ft3gas
kg/106m3 gas
Oil-fired only
Ib/I03gal oil
kg/103 liter oil
Nitrogen
oxides
8.84
4.01
7.81
3.54
9.60
4.35
413.
6615.
67.8
8.13
Hydro-
carbons
0.79
0.36
0.79
0.36
0.79
0.36
42.
673.
5.57
0.668
Carbon
Monoxide
2.18
0.99
2.18
0.99
2.18
0.99
115.
1842.
15.4
1.85
Partic-
ulate
0.52
0.24
0.27
0.12
0.71
0.32
14.
224.
5.0
0.60
Sulfur
oxides
0.33
0.15
0.098
0.044
0.50
0.23
940Sb
15,0005
140S
16.8S
Rated load expressed in megawatts.
bS is the percentage sulfur. Example: If the factor is 940 and the sulfur content is 0.01 percent, the sulfur oxides emitted would
be 940 times 0.01, or 9.4 lb/106 ft3 gas.
Table 3.1-2 is the resultant composite emission factors based on the operating cycle of Table 3.1-1 and the
1971 population of electric utility turbines.
3.1-;
EMISSION FACTORS
1/75
-------
Different values for time at base and peak loads are obtained by changing the total time at lower loads (0
through 75 percent) or by changing the distribution of time spent at lower loads. The cycle given m Table 3 1-1
ms reasonable, however, considering the fixed load factor and the economies of turbine ^^* ^
cycle determines only the importance of each load condition in computing composite emission factors for each
type of turbine, not overall operating hours.
The top portion of Table 3 .1-2 gives separate factors for gas-fired and oil-fired units, and the bottom portion
give fuelPbaPsed actor that can be'used to estimate emiss.on rates when overall fuel consumption data are
Sable. Fuel-based emission factors on a mode basis would also be useful but present fuel consumption data are
not adequate for this purpose.
References for Section 3.1
3.
.O'Keefe, W. and R. G. Schwieger. Prime Movers. Power. 77.5(11): 522-531. November 1971.
Hare C T and K J Springer. Exhaust Emissions from Uncontrolled Vehicles and Related Equipment Using
Sinai' Combustion Engines. Final Report. Part 6: Gas Turbine Electric Utility Power Plants. Southwest
Research Institute, San Antonio, Tex. Prepared for Environmental Protection Agency, Research Triangle r-aik,
N.C., under Contract No. EHS 70-108, February 1974.
Sawyer, V. W. and R. C. Farmer. Gas Turbines in U.S. Electric Utilities. Gas Turbine International. January -
April 1973.
1/75
3.1-3
-------
-------
3.2 Heavy Duty Natural Gas Fired Pipeline Compressor Engines
3.2.1 General1 — Engines in the natural gas industry are used primarily to power compressors used for pipeline
transportation, field gathering (collecting gas from wells), underground storage, and gas processing plant
applications. Pipeline engines are concentrated in the major gas producing states (such as those along the Gulf
Coast) and along the major gas pipelines. Both reciprocating engines and gas turbines are utilized, but the trend
has been toward use of large gas turbines. Gas turbines emit considerably fewer pollutants than do reciprocating
engines; however, reciprocating engines are generally more efficient in their use of fuel.
3.2.2 Emissions and Controls1'2 — The primary pollutant of concern is NOX, which readily forms in the high
temperature, pressure, and excess air environment found in natural gas fired compressor engines. Lesser amounts
of carbon monoxide and hydrocarbons are emitted, although for each unit of natural gas burned, compressor
engines (particularly reciprocating engines) emit significantly more of these pollutants than do external
combustion boilers. Sulfur oxides emissions are proportional to the sulfur content of the fuel and will usually be
quite low because of the negligible sulfur content of most pipeline gas.
The major variables affecting NOX emissions from compressor engines include the air fuel ratio, engine load
(defined as the ratio of the operating horsepower divided by the rated horsepower), intake (manifold) air
temperature, and absolute humidity. In general, NOX emissions increase with increasing load and intake air
temperature and decrease with increasing absolute humidity and air fuel ratio. (The latter already being, in most
compressor engines, on the "lean" side of that air fuel ratio at which maximum NOX formation occurs.)
Quantitative estimates of the effects of these variables are presented in Reference 2.
Because NOX is the primary pollutant of significance emitted from pipeline compressor engines, control
measures to date have been directed mainly at limiting NOX emissions. For gas turbines, the most effective
method of controlling NOX emissions is the injection of water into the combustion chamber. Nitrogen oxides
reductions as high as 80 percent can be achieved by this method. Moreover, water injection results in only
nominal reductions in overall turbine efficiency. Steam injection can also be employed, but the resulting NOX
reductions may not be as great as with water injection, and it has the added disadvantage that a supply of steam
must be readily available. Exhaust gas recirculation, wherein a portion of the exhaust gases is recircuiated back
into the intake manifold, may result in NOX reductions of up to 50 percent. This technique, however, may not be
practical in many cases because the recircuiated gases must be cooled to prevent engine malfunction. Other
combustion modifications, designed to reduce the temperature and/or residence time of the combustion gases,
can also be effective in reducing NOX emissions by 10 to 40 percent in specific gas turbine units.
For reciprocating gas-fired engines, the most effective NOX control measures are those that change the air-fuel
ratio. Thus, changes in engine torque, speed, intake air temperature, etc., that in turn increase the air-fuel ratio,
may all result in lower NOX emissions. Exhaust gas recirculation may also be effective in lowering NOX emissions
although, as with turbines, there are practical limits because of the large quantities of exhaust gas that must be
cooled. Available data suggest that other NOX control measures, including water and steam injection, have only
limited application to reciprocating gas fired engines.
Emission factors for natural gas fired pipeline compressor engines are presented in Table 3.2-1.
4/76
3.2-1
-------
Table 3.2-1. EMISSION FACTORS FOR HEAVY DUTY NATURAL
GAS FIRED PIPELINE COMPRESSOR ENGINES3
EMISSION FACTOR RATING: A
Reciprocating engines
lb/103hp-hr
g/hp-hr
g/kW-hr
lb/106scff
kg/106Nm3f
Gas turbines
lb/103hp-hr
g/hp-hr
g/kW-hr
Ib/106scf9
kg/106Nm39
Nitrogen oxides
(as NO2)b
24
11
15
3,400
55,400
2.9
1.3
1.7
300
4,700
Carbon
monoxide
3.1
1.4
1.9
430
7,020
1.1
0.5
0.7
120
1,940
Hydrocarbons
(as C>c
9.7
4.4
5.9
1,400
21,800
0.2
0.1
0.1
23
280
Sulfur
dioxide"
0.004
0.002
0.003
0.6
9.2
0.004
0.002
0.003
0.6
9.2
Paniculate6
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
aAII factors based on References 2 and 3.
''These factors are for compressor engines operated at rated load. In general, NOX emissions will increase with increasing
load and intake (manifold) air temperature and decrease with increasing air-fuel ratios (excess air rates) and absolute
humidity. Quantitative estimates of the effects of these variables are presented in Reference 2.
°These factors represent total hydrocarbons. Nonmethane hydrocarbons are estimated to make up to 5 to 10 percent of
these totals, on the average.
dEased on an assumed sulfur content of pipeline gas of 2000 gr/10" scf (4600 g/j^m3). If pipeline quality natural gas is
not fired, a material balance should be performed to determine SC>2 emissions based on the actual sulfur content.
eNot available from existing data.
fThese factors are calculated from the above factors for reciprocating engines assuming a heating value of 1050 Btu/scf
(9360 kcal/Nm3) for natural gas and an average fuel consumption of 7500 Btu/hp-hr (2530 kcal/kW-hr).
Sjhese factors are calculated from the above factors for gas turbines assuming a heating value of 1,050 Btu/scf (9,360 kcal/
Nm3) of natural gas and an average fuel consumption of 10,000 Btu/hp-hr (3.380 kcal/kW-hr).
References for Section 3.2
1. Standard Support Document and Environmental Impact Statement - Stationary Reciprocating Internal
Combustion Engines. Aerotherm/Acurex Corp., Mountain View, Calif. Prepared for Environmental Protection
Agency, Research Triangle Park, N.C. under Contract No. 68-02-1318, Task Order No. 7, November 1974.
2. Urban, C.M. and K.J. Springer. Study of Exhaust Emissions from Natural Gas Pipeline Compressor Engines.
Southwest Research Institute, San Antonio, Texas. Prepared for American Gas Association, Arlington, Va.
February 1975.
3. Dietzmann, H.E. and KJ. Springer. Exhaust Emissions from Piston and Gas Turbine Engines Used in Natural
Gas Transmission. Southwest Research Institute, San Antonio, Texas. Prepared for American Gas Association,
Arlington, Va. January 1974.
3.2-2
EMISSION FACTORS
4/76
-------
I
3.3 Gasoline and Diesel Industrial Engines
3.3.1 General - This engine category covers a wide variety of industrial applications of both gasoline and diesel
internal combustion power plants, such as fork lift trucks, mobile refrigeration units, generators, pumps, and
portable well-drilling equipment. The rated power of these engines covers a rather substantial range-from less than
15 kW to 186 kW (20 to 250 hp) for gasoline engines and from 34 kW to 447 kW (45 to 600 hp) for diesel engines.
Understandably, substantial differences in both annual usage (hours per year) and engine duty cycles also exist. It
was necessary, therefore, to make reasonable assumptions concerning usage in order to formulate emission
factors.1
3.3.2 Emissions - Once reasonable usage and duty cycles for this category were ascertained, emission values
from each of the test engines l were aggregated (on the basis of nationwide engine population statistics) to arrive at
the factors presented in Table 3.3-1. Because of their aggregate nature, data contained in this table must be
applied to a population of industrial engines rather than to an individual power plant.
The best method for calculating emissions is on the basis of "brake specific" emission factors (g/kWh or
Ib/hphr). Emissions are calculated by taking the product of the brake specific emission factor, the usage in hours
(that is, hours per year or hours per day), the power available (rated power), and the load factor (the power
actually used divided by the power available).
Table 3.3-1. EMISSION FACTORS FOR GASOLINE
AND DIESEL POWERED INDUSTRIAL EQUIPMENT
EMISSION FACTOR RATING: C
Pollutant3
Carbon monoxide
9/hr
Ib/hr
g/kWh
g/hphr
kg/103 liter
lb/103 gal
Exhaust hydrocarbons
9/hr
Ib/hr
g/kWh
g/hphr
kg/103 liter
lb/103 gal
Evaporative hydrocarbons
g/hr
Ib/hr
Crankcase hydrocarbons
g/hr
Ib/hr
Engine category
Gasoline
5700.
12.6
267.
199.
472.
3940.
191.
0.421
8.95
6.68
15.8
132.
62.0
0.137
38.3
0.084
Diesel
197.
0.434
4,06
3.03
12.2
102.
72.8
0.160
1.50
1.12
4.49
37.5
—
-
—
—
1/75
3.3-1
-------
Table 3.3-1 (continued). EMISSION FACTORS FOR GASOLINE
AND DIESEL POWERED INDUSTRIAL EQUIPMENT
EMISSION FACTOR RATING: C
Pollutant3
Nitrogen oxides
g/hr
Ib/hr
g/kWh
g/hphr
kg/103 liter
lb/103 gal
Aldehydes
g/hr
Ib/hr
g/kWh
g/hphr
kg/103 liter
lb/103 gal
Sulfur oxides
g/hr
Ib/hr
g/kWh
g/hphr
kg/103 liter
lb/103 gal
Paniculate
g/hr
Ib/hr
g/kWh
g/hphr
kg/103 liter
lb/103 gal
Engine category"
Gasoline
148.
0.326
6.92
5.16
12.2
102.
6.33
0.014
0.30
0.22
0.522
4.36
7.67
0.017
0.359
0,268
0.636
5.31
9.33
0.021
0.439
0.327
0.775
6.47
Diesel
910.
2.01
18.8
14.0
56.2
469.
13.7
0.030
0.28
0.21
0.84
7.04
60.5
0.133
1.25
0.931
3.74
31.2
65.0
0.143
1.34
1.00
4.01
33.5
References 1 and 2.
As discussed in the text, the engines used to determine the results in this
table cover a wide range of uses and power. The listed values do not,
however, necessarily apply to some very large stationary diesel engines.
References for Section 3.3
1. Hare, C. T. and K. J. Springer. Exhaust Emissions from Uncontrolled Vehicles and Related Equipment Using
Internal Combustion Engines. Final Report. Part 5: Heavy-Duty Farm, Construction, and Industrial Engines.
Southwest Research Institute. San Antonio, Texas. Prepared for Environmental Protection Agency, Research
Triangle Park, N.C., under Contract No. EHS 70-108. October 1973. 105 p.
2. Hare, C. T. Letter to C. C. Masser of the Environmental Protection Agency concerning fuel-based emission
rates for farm, construction, and industrial engines. San Antonio, Tex. January 14, 1974.
3.3-2
EMISSION FACTORS
1/75
-------
3.4 STATIONARY LARGE BORE DIESEL AND DUAL FUEL ENGINES
3.4.1 General
The primary domestic use of large bore diesel engines, i.e., those
greater than 560 cubic inch displacement per cylinder (CID/CYL), is in oil
and gas exploration and production. These engines, in groups of three to
five, supply mechanical power to operate drilling (rotary table), mud pump-
ing and hoisting equipment, and may also operate pumps or auxiliary power
generators. Another frequent application of large bore diesels is elec-
tricity generation for both base and standby service. Smaller uses include
irrigation, hoisting and nuclear power plant emergency cooling water pump
operation.
Dual fuel engines were developed to obtain compression ignition
performance and the economy of natural gas, using a minimum of 5 to 6 percent
diesel fuel to ignite the natural gas. Dual fuel large bore engines (greater
than 560 CID/CYL) have been used almost exclusively for prime electric power
generation.
3.4.2 Emissions and Controls
The primary pollutant of concern from large bore diesel and dual fuel
engines is NOx, which readily forms in the high temperature, pressure and
excess air environment found in these engines. Lesser amounts of carbon
monoxide and hydrocarbons are also emitted. Sulfur dioxide emissions will
usually be quite low because of the negligible sulfur content of diesel
fuels and natural gas.
The major variables affecting NOX emissions from diesel engines are
injection timing, manifold air temperature, engine speed, engine load and
ambient humidity. In general, NOX emissions decrease with increasing
humidity.
Because NOx is the primary pollutant from diesel and dual fuel engines,
control measures to date have been directed mainly at limiting NOX emis-
sions. The most effective NOx control technique for diesel engines is fuel
injection retard, achieving reductions (at eight degrees of retard) of up to
40 percent. Additional NOx reductions are possible with combined retard and
air/fuel ratio change. Both retarded fuel injection (8°) and air/fuel ratio
change of five percent are also effective in reducing NOx emissions from
dual fuel engines, achieving nominal NOx reductions of about 40 percent and
maximum NOx reductions of up to 70 percent.
Other NOX control techniques exist but are not considered feasible
because of excessive fuel penalties, capital cost, or maintenance or opera-
tional problems. These techniques include exhaust gas recirculation (EGR),
combustion chamber modification, water injection and catalytic reduction.
8/82
3.4-1
-------
TABLE 3.4-1. EMISSION FACTORS FOR STATIONARY LARGE BORE DIESEL
AND DUAL FUEL ENGINESa
EMISSION FACTOR RATING: C
Engine type
Diesel
lb/103 hph
g/hph
g/kWh
lb/103 galf
8/1
Dual fuel
lb/103 hph
g/hph
g/kWh
Particulateb
2.4
1.1
1.5
50
6
NA
HA
NA
Nitrogen
oxidesc
24
11
15
500
60
18
8
11
Carbon
monoxide
6.4
2.9
3.9
130
16
5.9
2.7
3.6
VOCd
Methane
0-07
0.03
0.04
1
0.2
4.7
2.1
2.9
Nonroethane
0.63
0.29
0.4
13
1.6
1.5
0.7
0.9
Sulfur
dioxide*
2.8
1.3
1.7
60
7.2
0.70
0.32
0.43
aRepresentative uncontrolled levels for each fuel, determined by weighting data from
several manufacturers. Weighting based on Z of total horsepower sold by each manu-
facturer during a five year period. NA - not available.
^Emission Factor Rating: E. Approximation based on test of a medium bore dleael.
Emissions are minimum expected for engine operating at 50 - 100Z full rated load.
At 01 load, emissions would increase to 30 g/1. Reference 2.
cMeasured as NC^. Factors are for engines operated at rated load and speed.
dNonmethane VOC is 90X of total VOC from diesel engines but only 25Z of total VOC
emissions from dual fuel engines. Individual chemical species within Che non-
methane fraction are not identified. Molecular weight of nonmethane gas stream la
assumed to be that of methane.
efiased on assumed sulfur content of 0.4 weight % for diesel fuel and 0.46 g/scm
(0.20 gr/scf) for pipeline quality natural gas. Dual fuel S02 emissions based on
5Z oil/953; gas mix. Emissions should be adjusted for other fuel ratios.
fThese factors calculated from the above factors, assuming heating values of 40
MJ/1 (145,000 Btu/gal) for oil and 41 MJ/scm (1100 Btu/scf) for natural gas, and
an average fuel consumption of 9.9 MJ/kWh (7000 Btu/hph).
References for Section 3.4
1. Standards Support And Environmental Impact Statement, Volume I;
sTationary Internal Combustion Engines, EFA-450/2-78-125a, U. S.
Environmental Protection Agency, Research Triangle Park, NC, July 1979.
2. Telephone communication between William H. Lamason, Office Of Air
Quality Planning And Standards, U. S. Environmental Protection Agency,
Research Triangle Park, NC, and John H. Wasser, Office Of Research And
Development, U. S. Environmental Protection Agency, Research Triangle
Park, NC, July 15, 1983-
3.4-2
EMISSION FACTORS
8/84
-------
4. EVAPORATION LOSS SOURCES
Evaporation losses include the organic solvents emitted from
dry cleaning plants and surface coating operations, and the volatile
matter in petroleum products. This chapter presents the volatile
organic emissions from these sources, including liquid petroleum
storage and marketing. Where possible, the effect is shown of
controls to reduce the emissions of organic compounds.
4.1 DRY CLEANING
4.1.1 General1'2
Dry cleaning involves the cleaning of fabrics with nonaqueous
organic solvents. The dry cleaning process requires three steps:
(1) washing the fabric in solvent, (2) spinning to extract excess
solvent and (3) drying by tumbling in a hot air stream.
Two general types of cleaning fluids are used in the industry,
petroleum solvents and synthetic solvents. Petroleum solvents,
such as Stoddard or 140-F, are inexpensive combustible hydrocarbon
mixtures similar to kerosene. Operations using petroleum solvents
are known as petroleum plants. Synthetic solvents are nonflammable
but more expensive halogenated hydrocarbons. Perchloroethylene and
trichlorotrifluoroethane are the two synthetic dry cleaning solvents
presently in use. Operations using these synthetic solvents are
respectively called "perc" plants and fluorocarbon plants.
There are two basic types of dry cleaning machines, transfer
and dry-to-dry. Transfer machines accomplish washing and drying in
separate machines. Usually, the washer extracts excess solvent
from the clothes before they are transferred to the dryer, but some
older petroleum plants have separate extractors for this purpose.
Dry-to-dry machines are single units that perform all of the washing,
extraction and drying operations. All petroleum solvent machines
are the transfer type, but synthetic solvent plants can be either
type.
The dry cleaning industry can be divided into three sectors,
coin operated facilities, commercial operations and industrial
cleaners. Coin operated facilities are usually part of a laundry
supplying "self-service" dry cleaning for consumers. Only synthetic
solvents are used in coin operated dry cleaning machines. Such
machines are small, with a capacity of 3.6 to 11.5 kg (8 to 25 Ib)
of clothing.
4/81
Evaporation Loss Sources
4.1-1
-------
EXHAUST GAS/SOLVENT
N)
-P-
--^
00
WATER
> CONDENSER
DETERGENT
SEPARATOR
WATER
•< MUCK
-* GASES
-^ SOLVENT
EMISSIONS
CARBON
ADSORBER
, 1
\JL
.
STILL
tESIDUE
TORAGE
MUCK
COOKER
1
1
MUCK) r-
1
'-*
\
DISPOSAL
HEAT
^
FILTER
MUCK
STORAGE
CONDENSER
\
DISPOSAL
[DESORBEDSOLVENT
' AND STEAM
WATER
Figure 4.1-1. Perchloroethylene dry cleaning plant flow diagram.
-------
Commercial operations, such as small neighborhood or franchise
dry cleaning shops, clean soiled apparel for the consumer. Generally,
perchloroethylene and petroleum solvents are used in commercial
operations. A typical "perc" plant operates a 14 to 27 kg (30 to
60 Ib) capacity washer/extractor and an equivalent size reclaiming
dryer.
Industrial cleaners are larger dry cleaning plants which
supply rental service of uniforms, mats, mops, etc., to businesses
or industries. Perchloroethylene is used by approximately 50 percent
of the industrial dry cleaning establishments. A typical large
industrial cleaner has a 230 kg (500 Ib) capacity washer/extractor
and three to six 38 kg (100 Ib) capacity dryers.
A typical perc plant is shown in Figure 4.1—1. Although one
solvent tank may be used, the typical perc plant uses two tanks for
washing. One tank contains pure solvent, and the other contains
"charged" solvent (used solvent to which small amounts of detergent
have been added to aid in cleaning). Generally, clothes are cleaned
in charged solvent and rinsed in pure solvent. A water bath may
also be used.
After the clothes have been washed, the used solvent is filtered,
and part of the filtered solvent is returned to the charged solvent
tank for washing the next load. The remaining solvent is then
distilled to remove oils, fats, greases, etc., and is returned to
the pure solvent tank. The resulting distillation bottoms are
typically stored on the premises until disposed of. The filter
cake and collected solids (muck) are usually removed from the
filter once a day. Before disposal, the muck may be "cooked" to
recover additional solvent. Still and muck cooker vapors are
vented to a condenser and separator, where more solvent is reclaimed.
In many perc plants, the condenser offgases are vented to a carbon
adsorption unit for additional solvent recovery.
After washing, the clothes are transferred to the dryer to be
tumbled in a heated air stream. Exhaust gases from the dryer,
along with a small amount of exhaust gases from the washer/extractor,
are vented to a water cooled condenser and water separator.
Recovered solvent is returned to the pure solvent storage tank. In
30 to 50 percent of the perc plants, the condenser offgases are
vented to a carbon adsorption unit for additional solvent recovery.
To reclaim this solvent, the unit must be periodically desorbed
with steam, usually at the end of each day. Desorbed solvent and
water are condensed and separated, and recovered solvent is returned
to the pure solvent tank.
A petroleum plant would differ from Figure 4.1-1 chiefly in
that there would be no recovery of solvent from the washer and
dryer and no muck cooker, A fluorocarbon plant would differ in
that an unvented refrigeration system would be used in place of a
carbon adsorption unit. Another difference is that a typical
4/81 Evaporation Loss Sources 4.1-3
-------
fluorocarbon plant could use a cartridge filter which is drained
and disposed of after several hundred cycles.
Emissions and Controls
1-3
The solvent itself is the primary emission from dry cleaning
operations. Solvent is given off by washer, dryer, solvent still,
muck cooker, still residue and filter muck storage areas, as well
as by leaky pipes, flanges and pumps.
Petroleum plants have not generally employed
because of the low cost of petroleum solvents and
associated with collecting vapors. Some emission
can be obtained by maintaining all equipment (e.g.
accumulation, solvent leakage, etc.) and by using
practices (e.g., not overloading machinery). Both
and incineration appear to be technically feasible
petroleum plants, but costs are high.
solvent recovery,
the fire hazards
control, however,
, preventing lint
good operating
carbon adsorption
controls for
Solvent recovery is necessary in perc plants due to the higher
cost of perchloroethylene. As shown in Figure 4.1-1, recovery is
effected on the washer, dryer, still and muck cooker through the
use of condensers, water/solvent separators and carbon adsorption
units. Typically once a day, solvent in the carbon adsorption unit
is desorbed with steam, condensed, separated from the condensed
water and returned to the pure solvent storage tank. Residual
solvent emitted from treated distillation bottoms and muck is not
recovered. As in petroleum plants, good emission control can be
obtained by good housekeeping (maintaining all equipment and using
good operating practices).
All fluorocarbon machines are of the dry-to-dry variety to
conserve solvent vapor, and all are closed systems with built in
solvent recovery. High emissions can occur, however, as a result
of poor maintenance and operation of equipment. Refrigeration
systems are installed on newer machines to recover solvent from the
washer/dryer exhaust gases.
Emission factors for dry cleaning operations are presented in
Table 4.1-1.
, Typical coin operated and commercial plants emit less than
10 grams (one ton) per year. Some applications of emission estimates
are too broad to identify every small facility. For estimates over
large areas, the factors in Table 4.1-2 may be applied for coin
operated and commercial dry cleaning emissions.
4.1-4
EMISSION FACTORS
4/81
-------
.p-
CO
TABLE 4.1-1. SOLVENT LOSS EMISSION FACTORS FOR DRY CLEANING OPERATIONS
EMISSION FACTOR RATING: B
Solvent Type
(Process used)
Emission Rate
a
Source
Typical system
kg/100 kg (ib/lbO lb)
Well controlled system
kg/100 kg (lb/100 lb)
Petroleum
(transfer process)
washer /dryer
filter disposal
uncooked (drained)
centriEuged
still residue .disposal
miscellaneous
18
8
1
1
2C
0.5 -
0.5 -
1
1
1
"O
O
i-i
O
P
I-1
O
en
o
H
o
(B
cn
PercViloroethy lene
(transfer process)
Tr Ichlo rot r If luoroe thane
(dry- to-dry process)
washer/dryer/still/muck cooker
filter disposal
uncooked muck
cooked muck
cartridge filter
still residue .disposal
miscellaneous
washer /dryer /still
cartridge filter disposal
still residue .disposal
miscellaneous
8C
14
1.3
1.1
1.6
1.5
0
1
0.5
1 - 3
0.3"
0.5 -
0.5 -
0.5 -
1
0
1
0.5
1 - 3
1.3
l.l
1.6
I
Ul
References 1-4. Units are in terms of weight solvent per weight of clothes cleaned (capacity x loads).
Emissions also may be estimated by determining the amount of solvent consumed. Assuming that all
solvent input is eventually evaporated to the atmosphere, an emission factor of 2000 Ib/ton (1000 kg/Hg)
, of solvent consumed can he applied.
Different material In wash retains a different amount of solvent (synthetics, 10 kg/100 kg; cotton,
c20 kg/100 kg; leather, 40 kg/100 kg).
.Emissions from washer, dryer, still and muck cooker are passed collectively through a carbon adsorber.
Miscellaneous sources Include fugitives from flanges, pumps, pipes and storage tanks, and fixed losses
such as opening and closing dryers, etc.
Uncontrolled emissions from washer, dryer, still and muck cooker average about 8 kg/100 kg (8 lb/100 lb)
,About 15% of solvent emitted Is from washer, 75% dryer, 5% each from still and muck cooker.
Based on the typical refrigeration system Installed In fluorocarbon plants.
-------
TABLE 4.1-2. PER CAPITA SOLVENT LOSS EMISSION
FACTORS FOR DRY CLEANING PLANTS3
EMISSION FACTOR RATING: B
Operation
Emission Factors ,
kg/yr/capita g/day/capita
(Ib/year/cap) (Ib/day/cap)
Commercial
Coin operated
0.6
(1.3)
0.2
(0.4)
1.9
(0.004)
0.6
(0.001)
*5
, References 2-4. All nonmethane VOC.
Assumes a 6 day operating week (313 days/yr).
References for Section 4.1
1. Study To Support New Source Performance Standards for the
Dry Cleaning Industry, EPA Contract No. 68-02-1412, TRW, Inc.,
Vienna, VA, May 1976.
2. Perchloroethylene Dry Cleaners - Background Information for
Proposed Standards, EPA-450/3-79-029a, U.S. Environmental
Protection Agency, Research Triangle Park, NC, August 1980.
3. Control of Volatile Organic Emissions from Perchloroethylene
Dry Cleaning Systems, EPA-450/2-78-050, U.S. Environmental
Protection Agency, Research Triangle Park, NC, December 1978.
4. Control of Volatile Organic Emissions from Petroleum Dry
Cleaners (Draft), Office of Air Quality Planning and Standards,
U.S. Environmental Protection Agency, Research Triangle Park,
NC, February 1981.
4.1-6
EMISSION FACTORS
4/81
-------
4.2 SURFACE COATING
Surface coating operations involve the application of paint, varnish,
lacquer or paint primer, for decorative or protective purposes. This is
accomplished by brushing, rollings, spraying, flow coating and dipping oper-
ations. Some industrial surface coating operations include automobile assembly,
job enameling, and manufacturing of aircraft, containers, furniture, appliances
and plastic products. Nonindustrial applications of surface coatings include
automobile refinishing and architectural coating of domestic, industrial,
government and institutional structures, including building interiors and
exteriors and exteriors and signs and highway markings. Nonindustrial Surface
Coating is discussed below in Section 4.2.1, and Industrial Surface Coating
in Section 4.2.2.
Emissions of volatile organic compounds (VOC) occur in surface coating
operations because of evaporation of the paint vehicle, thinner or solvent
used to facilitate the application of coatings. The major factor affecting
these emissions is the amount of volatile matter contained in the coating.
The volatile portion of most common surface coatings averages about 50 per-
cent, and most, if not all, of this is emitted during the application of
coatings. The major factor affecting these emissions is the amount of
volatile matter contained in the coating. The volatile portion of most com-
mon surface coatings averages about 50 percent, and most, if not all, of this
is emitted during the application and drying of the coating. The compounds
released include aliphatic and aromatic hydrocarbons, alcohols, ketones,
esters, alkyl and aryl hydrocarbon solvents, and mineral spirits. Table
4.2-1 presents emission factors for general surface coating operations.
TABLE 4.2-1. EMISSION FACTORS FOR GENERAL SURFACE COATING APPLICATIONS3
EMISSION FACTOR RATING: B
Coating Type
Paint
Varnish and Shellac
Lacquer
Enamel
Primer (zinc chromate)
Emissions^
kg/Mg
560
500
770
420
660
Ib/ton
1120
1000
1540
840
1320
aReference
^Reference 2. Nonmethane VOC.
References for Section 4.2
1. Products Finishing. 4jL(6A):4-54, March 1977.
2. Air Pollution Engineering Manual, Second Edition, AP-40, U. S.
Environmental Protection Agency, Research Triangle Park, NC, May 1973.
Out of Print.
4/81
Evaporation Loss Sources
4.2-1
-------
-------
4.2.1 NONINDUSTRIAL SURFACE COATING1'3'5
Nonindustrial surface coating operations are nonmanufacturing
applications of surface coating. Two major categories are architectural
surface coating and automobile refinishing. Architectural uses are
considered to include both industrial and nonindustrial structures.
Automobile refinishing pertains to the painting of damaged or worn
highway vehicle finishes and not the painting of vehicles during
manufacture.
Emissions from a single architectural structure or automobile
refinishing are calculated by using total volume and content and
weight of volatile constituents for the coating employed in the
specific application. Estimating emissions for a large area which
includes many major and minor applications of nonindustrial surface
coatings requires that area source estimates be developed. Archi-
tectural surface coating and auto refinishing emissions data are
often difficult to compile for a large geographical area. In cases
where a large inventory is being developed and/or resources are
unavailable for detailed accounting of actual volume of coatings
for these applications, emissions may be assumed proportional to
population or number of employees. Table 4.2.1-1 presents factors
from national emission data and emissions per population or employee
for architectural surface coating and automobile refinishing.
TABLE 4.2.1-1. NATIONAL EMISSIONS AND EMISSION FACTORS
FOR VOC FROM ARCHITECTURAL SURFACE COATING
AND AUTOMOBILE REFINISHING*
EMISSION FACTOR RATING: C
Emissions
National
Mg/yr
ton/yr
Architectural Surface
Coating
446,000
491,000
Automobile
Refinishing
181,000
199,000
Per capita
kg/yr (Ib/yr)
g/day (Ib/day)
Per employee
Mg/yr (ton/yr)
kg/day (Ib/day)
21.4 (4.6)
5.8 (0.013)
0.84 (1.9)
2.7 (0.006)
2.3 (2.6)
7.4 (16.3)
.References 3 and 5-8. All nonmethane organics.
Reference 8. Calculated by dividing kg/yr (Ib/yr) by 365 days and
converting to appropriate units. Assumes that 75% of annual
emissions occurs over a 9 month ozone season. For shorter ozone
seasons, adjust accordingly.
Assumes a 6 day operating week (313 days/yr).
4/81 Evaporation Loss Sources 4.2.1-1
-------
The use of waterborne architectural coatings reduces volatile
organic compound emissions. Current consumption trends indicate
increasing substitution of waterborne architectural coatings for
those using solvent. Automobile refinishing often is done in areas
only slightly enclosed, which makes control of emissions difficult.
Where automobile refinishing takes place in an enclosed area,
control of the gaseous emissions can be accomplished by the use of
adsorbers (activated carbon) or afterburners. The collection
efficiency of activated carbon has been reported at 90 percent or
greater. Water curtains or filler pads have little or no effect on
escaping solvent vapors, but they are widely used to stop paint
particulate emissions.
References for Section 4.2.1
1. Air Pollution Engineering Manual, Second Edition, AP-40, U.S.
Environmental Protection Agency, Research Triangle Park, NC,
May 1973. Out of Print.
2. Control Techniques for Hydrocarbon and Organic Gases from
Stationary Sources, AP-68, U.S. Environmental Protection
Agency, Research Triangle Park, NC, October 1969.
3. Control Techniques Guideline for Architectural Surface Coatings
(Draft), Office of Air Quality Planning and Standards, U.S.
Environmental Protection Agency, Research Triangle Park, NC,
February 1979.
4. Air Pollutant Emission Factors, HEW Contract No. CPA-22-69-119,
Resources Research Inc., Reston, VA, April 1970.
5. Procedures for the Preparation of Emission Inventories for
Volatile Organic Compounds, Volume I, Second Edition,
EPA-450/2-77-028, U.S. Environmental Protection Agency, Research
Triangle Park, NC, September 1980.
6. W.H. Lamason, "Technical Discussion of Per Capita Emission
Factors for Several Area Sources of Volatile Organic Compounds",
Monitoring and Data Analysis Division, U.S. Environmental
Protection Agency, Research Triangle Park, NC, March 15, 1981.
Unpublished.
7. End Use of Solvents Containing Volatile Organic Compounds,
EPA-450/3-79-032, U.S. Environmental Protection Agency, Research
Triangle Park, NC, May 1979.
8. Written communications between Bill Lamason and Chuck Mann,
Monitoring and Data Analysis Division, U.S. Environmental
Protection Agency, Research Triangle Park, NC, October 1980
and March 1981.
4.2.1-2
EMISSION FACTORS
4/81
-------
9- Final Emission Inventory Requirements for 1982 Ozone State
Implementation Plans. EPA-450/4-80-016. U.S. Environmental
Protection Agency, Research Triangle Park, NC, December 1980.
4/81 Evaporation Loss Sources 4.2.1-3
-------
-------
4.2.2 INDUSTRIAL SURFACE COATING
4.2.2.1 GENERAL INDUSTRIAL SURFACE COATING1'4
Process Description - Surface coating is the application of decorative or
protective materials In liquid or powder form to substrates. These coatings
normally include general solvent type paints, varnishes, lacquers and water
thinned paints. After application of coating by one of a variety of methods
such as brushing, rolling, spraying, dipping and flow coating, the surface is
air and/or heat dried to remove the volatile solvents from the coated surface.
Powder type coatings can be applied to a hot surface or can be melted after
application and caused to flow together. Other coatings can be polymerized
after application by thermal curing with infrared or electron beam systems.
Coating Operations - There are both "toll" ("independent") and "captive"
surface coating operations. Toll operations fill orders to various manufac-
turer specifications, and thus change coating and solvent conditions more
frequently than do captive companies, which fabricate and coat products within
a single facility and which may operate continuously with the same solvents.
Toll and captive operations differ in emission control systems applicable to
coating lines, because not all controls are technically feasible In toll
situations.
Coating Formulations - Conventional coatings contain at least 30 volume
percent solvents to permit easy handling and application. They typically con-
tain 70 to 85 percent solvents by volume. These solvents may be of one com-
ponent or of a mixture of volatile ethers, acetates, aromatics, cellosolves,
aliphatic hydrocarbons and/or water. Coatings with 30 volume percent of
solvent or less are called low solvent or "high solids" coatings.
Waterborne coatings, which have recently gained substantial use, are of
several types: water emulsion, water soluble and colloidal dispersion, and
electrocoat. Common ratios of water to solvent organlcs In emulsion and dis-
persion coatings are 80/20 and 70/30.
Two part catalyzed coatings to be dried, powder coatings, hot melts, and
radiation cured (ultraviolet and electron beam) coatings contain essentially
no volatile organic compounds (VOC), although some monomers and other lower
molecular weight organics may volatilize.
Depending on the product requirements and the material being coated, a
surface may have one or more layers of coating applied. The first coat may be
applied to cover surface imperfections or to assure adhesion of the coating.
The intermediate coats usually provide the required color, texture or print,
and a clear protective topcoat is often added. General coating types do not
differ from those described, although the intended use and the material to be
coated determine the composition and resins used in the coatings.
Coating Application Procedures - Conventional spray, which is air atomized
and usually hand operated, is one of the most versatile coating methods. Colors
can be changed easily, and a variety of sizes and shapes can be painted under
4/81
Evaporation Loss Sources
4.2.2.1-1
-------
many operating conditions. Conventional, catalyzed or waterborne coatings can
be applied with little modification. The disadvantages are low efficiency from
overspray and high energy requirements for the air compressor.
In hot airless spray, the paint is forced through an atomizing nozzle.
Since volumetric flow is less, overspray is reduced. Less solvent is also
required, thus reducing VOC emissions. Care must be taken for proper flow of
the coating, to avoid plugging and abrading of the nozzle orifice. Electro-
static spray Is most efficient for low visocity paints. Charged paint par-
ticles are attracted to an oppositely charged surface. Spray guns, spinning
discs or bell shaped atomizers can be used to atomize the paint. Application
efficiencies of 90 to 95 percent are possible, with good "wraparound" and edge
coating. Interiors and recessed surfaces are difficult to coat, however.
Roller coating is used to apply coatings and inks to flat surfaces. If
the cylindrical rollers move in the same direction as the surface to be coated,
the system is called a direct roll coater. If they rotate in the opposite
direction, the system is a reverse roll coater. Coatings can be applied to any
flat surface efficiently and uniformly and at high speeds. Printing and deco-
rative graining are applied with direct rollers. Reverse rollers are used to
apply fillers to porous or Imperfect substrates, including papers and fabrics,
to give a smooth uniform surface.
Knife coating is relatively Inexpensive, but it is not appropriate for
coating unstable materials, such as some knit goods, or when a high degree of
accuracy In the coating thickness is required.
Rotogravure printing is widely used In coating vinyl imitation leathers
and wallpaper, and in the application of a transparent protective layer over
the printed pattern. In rotogravure printing, the image area is recessed, or
"Intaglio", relative to the copper plated cylinder on which the image is
engraved. The Ink is picked up on the engraved area, and excess ink is scraped
off the nonimage area with a "doctor blade". The image is transferred directly
to the paper or other substrate, which is web fed, and the product is then
dried.
Dip coating requires that the surface of the subject be immersed in a bath
of paint. Dipping is effective for coating irregularly shaped or bulky items
and for priming. All surfaces are covered, but coating thickness varies, edge
blistering can occur, and a good appearance is not always achieved.
In flow coating, materials to be coated are conveyed through a flow of
paint. Paint flow is directed, without atomization, toward the surface through
multiple nozzles, then is caught in a trough and recycled. For flat surfaces,
close control of film thickness can be maintained by passing the surface
through a constantly flowing curtain of paint at a controlled rate.
Emissions and Controls - Essentially all of the VOC emitted from the sur-
face coating industry is from the solvents which are used In the paint formu-
lations, used to thin paints at the coating facility or used for cleanup. All
unrecovered solvent can be considered potential emissions. Monomers and low
molecular weight organics can be emitted from those coatings that do not include
solvents, but such emissions are essentially negligible.
4.2.2.1-2 EMISSION FACTORS 4/81
-------
Emissions from surface coating for an uncontrolled facility can be esti-
mated by assuming that all VOC in the coatings is emitted. Usually, coating
consumption volume will be known, and some information about the types of
coatings and solvents will be available. The choice of a particular emission
factor will depend on the coating data available. If no specific information
is given for the coating, it may be estimated from the data in Table 4.2.2.1-2,
TABLE 4.2.2.1-1. VOC EMISSION FACTORS FOR UNCONTROLLED SURFACE COATING3
EMISSION FACTOR RATING: B
Available Information on coating
Conventional or waterborne
paints
VOC, wt % (d)
VOC, vol % (V)
Waterborne paint
VOC as weight % of total
volatiles - including water
(X); total volatiles as
weight % of coating (d)
VOC as volume % of total
volatiles - Including water
(Y); total volatiles as
volume % of coating (V)
Emissions of VOCb
kg/liter of coating Ib/gal of coating
d'coating density0
100
V'O.
100
d'X'coating densityc
100
100
d•abating densi ty°
100
V7.36d
100
d'X'coating density0
100
V-Y-7.36d
100
aMaterial balance, when coatings volume use is known.
t>For special purposes, factors expressed kg/1 of coating less water may be
desired. These may be computed as follows:
Factor as kg/1 of coating
= Factor as kg/1 of coating less water ^ _ volume % water
100
°If coating density Is not known, it can be estimated from the information
In Table 4.2.2.1-2.
dThe values 0.88 (kg/1) and 7.36 (Ib/gal) use the average density of
solvent In coatings. Use the densities of the solvents in the coatings
actually used by the source, if known.
4/81
Evaporation Loss Source
4.2.2.1-3
-------
TABLE 4.2.2.1-2. TYPICAL DENSITIES AND SOLIDS CONTENTS OF COATINGS
Type of coating
Enamel, air dry
Enamel , baking
Acrylic enamel
Alkyd enamel
Primer surfacer
Primer, epoxy
Varnish, baking
Lacquer, spraying
Vinyl, roller coat
Polyur ethane
Stain
Sealer
Magnet wire enamel
Paper coating
Fabric coating
Density
kg/liter
0.91
1.09
1.07
0.96
1.13
1.26
0.79
0.95
0.92
1.10
0.88
0.84
0.94
0.92
•.. 0.92
Ib/gal
7.6
9.1
8.9
8.0
9.4
10.5
6.6
7.9
7.7
9.2
7.3
7.0
7.8
7.7
7.7
Solids
(volume %)
39.6
42.8
30.3
47.2
49.0
57.2
35.3
26.1
12.0
31.7
21.6
11.7
25.0
22.0
22.0
aReference 1.
All solvents separately purchased as solvent that are used in surface
coating operations and are not recovered subsequently can be considered
potential emissions. Such VOC emissions at a facility can result from onsite
dilution of coatings with solvent, from "makeup solvents" required in flow
coating and, in some Instances, dip coating, and from the solvents used for
cleanup. Makeup solvents are added to coatings to compensate for standing
losses, concentration or amount, and thus to bring the coating back to working
specifications. Solvent emissions should be added to VOC emissions from
coatings to get total emissions from a coating facility.
Typical ranges of control efficiencies are given In Table 4.2.2.1-3.
Emission controls normally fall under one of three categories - modification in
paint formula, process changes, or addon controls. These are discussed further
in the specific subsections which follow.
TABLE 4.2.2.1-3. CONTROL EFFICIENCIES FOR
SURFACE COATING OPERATIONS3
Control option
Substitute waterborne coatings
Substitute low solvent coatings
Substitute powder coatings
Add afterburners/incinerators
Reduction15
60-95
40-80
92-98
95
aReferences 2-4.
^Expressed as % of total uncontrolled emission load-
4.2.2.1-4 EMISSION FACTORS
4/81
-------
References for Section 4.2.2.1
1• Controlling Pollution from the Manufacturing and Coatingof Metal
Products; Metal Coating Air Pollution Control, EPA-625/3-77-009, U. S,
Environmental Protection Agency, Cincinnati, OH, May 1977.
2. H. R. Powers, "Economic and Energy Savings through Coating Selection",
The Sherwin-Williams Company, Chicago, 1L, February 8, 1978.
3. Air Pollution Engineering Manual, Second Edition, AP-40, U. S.
Environmental Protection Agency, Research Triangle Park, NC, May 1973.
Out of Print.
4. Products Finishing. 41(6A):4-54, March 1977.
4/81 Evaporation Loss Sources 4.2.2.1-5
-------
-------
4.2.2.2 CAN COATING1"4
Process Description - Cans may be made from a rectangular sheet (body blank)
and two circular ends (three piece cans), or they can be drawn and wall ironed
from a shallow cup to which an end is attached after the can is filled (two
piece cans). There are major differences In coating practices, depending on
the type of can and the product packaged in It. Figure 4.2.2.2-1 depicts a
three piece can sheet printing operation.
There are both "toll" and "captive" can coating operations. The former
fill orders to customer specifications, and the latter coat the metal for pro-
ducts fabricated within one facility. Some can coating operations do both
toll and captive work, and some plants fabricate just can ends.
Three piece can manufacturing involves sheet coating and can fabricating.
Sheet coating includes base coating and printing or lithographing, followed by
curing at temperatures of up to 220°C (425°F). When the sheets have been
formed Into cylinders, the seam Is sprayed, usually with a lacquer, to protect
the exposed metal. If they are to contain an edible product, the interiors are
spray coated, and the cans baked up to 220°C (425°F).
Two piece cans are used largely by beer and other beverage industries.
The exteriors may be reverse roll coated in white and cured at 170 to 200°C
(325 to 400°F). Several colors of ink are then transferred (sometimes by
lithographic printing) to the cans as they rotate on a mandrel. A protective
varnish may be roll coated over the Inks. The coating is then cured in a
single or multipass oven at temperatures of 180 to 200°C (350 to 400°F). The
cans are spray coated on the Interior and spray and/or roll coated on the
exterior of the bottom end. A final baking at 110 to 200°C (225 to 400°F)
completes the process.
Emissions and Controls - Emissions from can coating operations depend on
composition of the coating, coated area, thickness of coat and efficiency of
application. Post-application chemical changes, and nonsolvent contaminants
like oven fuel combustion products, may also affect the composition of emis-
sions. All solvent used and not recovered can be considered potential
emissions*
Sources of can coating VOC emissions include the coating area and the oven
area of the sheet base and lithographic coating lines, the three piece can side
seam and interior spray coating processes, and the two piece can coating and
end sealing compound lines. Emission rates vary with line speed, can or sheet
size, and coating type. On sheet coating lines, where the coating is applied
by rollers, most solvent evaporates In the oven. For other coating processes,
the coating operation itself is the major source. Emissions can be estimated
from the amount of coating applied by using the factors in Table 4.2.2.1-1 or,
if the number and general nature of the coating lines are known, from Table
4.2.2.2-1.
Incineration and the use of waterborne and low solvent coatings both
reduce organic vapor emissions. Other technically feasible control options,
such as electrostatically sprayed powder coatings, are not presently applicable
to the whole Industry. Catalytic and thermal incinerators both can be used,
4/81 Evaporation Loss Sources 4.2.2.2-1
-------
°
NJ
N>
m
^
en
en
o
o
33
C/5
INK APPLICATORS
SHEET (PLATE)
FEEDER
SHEET (PLAT€)
STACKER
oo
figure 4.2.2.2-1. Three piece can sheet printing operation.7
-------
00
TABLE 4.2.2.2-1. VOC EMISSION FACTORS FOR CAN COATING PROCESSES3
EMISSION FACTOR RATING: B
Process
Three piece can sheet base coating line
Three piece can sheet lithographic
coating line
Three piece beer and beverage can - side
seam spray coating process
Three piece beer and beverage can -
interior body spray coating process
Two piece can coating line
Two piece can end sealing compound line
Typical emissions
from coating line^
Ib/hr
112
65
12
54
86
8
kg/hr
51
30
5
25
39
4
Estimated
fraction
from coater
area (%)
9-12
8-11
100
75-85
NA
100
Estimated
fraction
from oven
<*)
88-91
89-92
air dried
15-25
NA
air dried
Typical organic
emissions0
Mg/yr
160
50
18
80
260
14
ton/yr
176
55
20
88
287
15
rt
H-
O
O
tn
to
CO
O
c
H
O
0>
0)
aReference 3. NA = not available.
"Organic solvent emissions will vary according to line speed, size of can or sheet being coated, and
type of coating used.
cBased upon normal operating conditions.
N>
NJ
I
-------
TABLE 4.2.2.2-2. CONTROL EFFICIENCIES FOR CAN COATING LINESa
Affected facility^
Control option
Reduction0
Two Piece Can Lines
Exterior coating
Interior spray
coating
Three Piece Can Lines
Sheet coating lines
Exterior coating
Interior spray
coating
Can fabricating lines
Side seam spray
coating
Interior spray
coating
End Coating Lines
Sealing compound
Sheet coating
Thermal and catalytic incineration
Waterborne and high solids coating
Ultraviolet curing
Thermal and catalytic incineration
Waterborne and high solids coating
Powder coating
Carbon adsorption
Thermal and catalytic incineration
Waterborne and high solids coating
Ultraviolet curing
Thermal and catalytic incineration
Waterborne and high solids coating
Waterborne and high solids coating
Powder (only for uncemented seams)
Thermal and catalytic incineration
Waterborne and high solids coating
Powder (only for uncemented seams)
Carbon adsorption
Waterborne and high solids coating
Carbon adsorption
Thermal and catalytic incineration
Waterborne and high solids coating
90
60-90
<100
90
60-90
100
90
90
60-90
<100
90
60-90
60-90
100
90
60-90
100
90
70-95
90
90
60-90
aReference 3.
bCoil coating lines consist of coaters, ovens and quench areas. Sheet, can
and end wire coating lines consist of coaters and ovens.
cCompared to conventional solvent base coatings used without any added
4.2.2.2-4
EMISSION FACTORS
4/81
-------
primers, backers (coatings on the reverse or backside of the coil), and some
waterborne low to medium gloss topcoats have been developed that equal the
performance of organic solventborne coatings for aluminum but have not yet been
applied at full line speed in all cases. Waterborne coatings for other metals
are being developed .
Available control technology Includes the use of addon devices like
Incinerators and carbon adsorbers and a conversion to low solvent and ultra-
violet curable coatings. Thermal and catalytic incinerators both may be used
to control emissions from three piece can sheet base coating lines, sheet
lithographic coating lines, and interior spray coating. Incineration Is appli-
cable to two piece can coating lines. Carbon adsorption is most acceptable to
low temperature processes which use a limited number of solvents. Such pro-
cesses include two and three piece can interior spray coating, two piece can
end sealing compound lines, and three piece can side seam spray coating.
Low solvent coatings are not yet available to replace all the organic
solventborne formulations presently used in the can Industry. Waterborne
basecoats have been successfully applied to two piece cans. Powder coating
technology Is used for side seam coating of noncemented three piece cans.
Ultraviolet curing technology is available for rapid drying of the first
two colors of Ink on three piece can sheet lithographic coating lines.
References for Section 4.2.2.2
1. T. W. Hughes, e t jil_^, Source Assessment! Prlorltizatlon jaf Air Pollution
from Industrial Surface Coating Operations, EPA-650/2-75-019a, U. S.
Environmental Protection Agency, Research Triangle Park, NC, November 1975.
2. Control of Volatile Organic Emissions from Existing Stationary Sources,
Volume I: Control Methods for Surface Coating Operations, EPA-450/2-76-
028, U. S. Environmental Protection Agency, Research Triangle Park, NC,
May 1977.
3 . Control of Volatile Organic Emissions from Existing Stationary Sources,
Volume II: Surface Coating of Cans, Colls, Paper Fabrics, Automobiles,
and Light Duty Trucks, EPA-450/2-77-OQ8, U. S . Environmental Protection
Agency, Research Triangle Park, NC, May 1977.
4. Air Pollution Control Technology Applicable to 26 Source of Volatile
Organic Compounds, Office of Air Quality Planning and Standards, U. S.
Environmental Protection Agency, Research Triangle Park, NC, May 27, 1977.
Unpublished.
4/81
Evaporation Loss Sources
4.2.2.2-5
-------
-------
4.2.2.3 MAGNET WIRE COATING1
Process Description - Magnet wire coating is applying a coat of electrically
Insulating varnish or enamel to aluminum or copper wire used In electrical
machinery. The wire is usually coated in large plants that both draw and
insulate It and then sell It to electrical equipment manufacturers. The wire
coating must meet rigid electrical, thermal and abrasion specifications.
Figure 4.2.2.3-1 shows a typical wire coating operation. The wire is
unwound from spools and passed through an annealing furnace. Annealing softens
the wire and cleans it by burning off oil and dirt. Usually, the wire then
passes through a bath in the coating applicator and is drawn through an orifice
or coating die to scrape off the excess. It is then dried and cured in a two
zone oven first at 200°, then 430°C (400 and 806°F). Wire may pass through the
coating applicator and the oven as many as twelve times to acquire the necessary
thickness of coating.
Emissions and Controls - Emissions from wire coating operations depend on
composition of the coating, thickness of coat and efficiency of application.
Postapplication chemical changes, and nonsolvent contaminants such as oven fuel
combustion products, may also affect the composition of emissions. All solvent
used and not recovered can be considered potential emissions.
The exhaust from the oven Is the most important source of solvent emissions
in the wire coating plant. Emissions from the applicator are comparatively low,
because a dip coating technique is used. See Figure 4.2.2.3-1.
Volatile organic compound (VOC) emissions may be estimated from the factors
In Table 4.2.2.1-1, if the coating usage Is known and if the coater has no
controls. Most wire coaters built since 1960 do have controls, so the infor-
mation in the following paragraph may be applicable. Table 4.2.2.3-1 gives
estimated emissions for a typical wire coating line.
TABLE 4.2.2.3-1
ORGANIC SOLVENT EMISSIONS FROM A TYPICAL WIRE
COATING LINE3
Coating Llneb
kg/hr Ib/hr
12 26
Annual Totalsc
Mg/yr ton/yr
84 93
aReference 1.
^Organic solvent emissions vary from line to line by size and
speed of wire, number of wires per oven, and number of passes
through oven. A typical line may coat 544 kg (1,200 Ib) wire/day.
A plant may have many lines.
cBased upon normal operating conditions of 7,000 hr/yr for one line
without incinerator.
4/81
Evaporation Loss Sources
4.2.2.3-1
-------
NJ
k)
00
I
to
m
cn
co
o
O
zo
CO
DRYING AND
CURING
OVEN
Figure 4.2.2.3-1. Wire coating line emission points.^
oo
-------
Incineration is the only commonly used technique to control emissions from
wire coating operations. Since about I960, all major wire coating designers
have Incorporated catalytic incinerators into their oven designs, because of
the economic benefits. The Internal catalytic incinerator burns solvent fumes
and circulates heat back Into the wire drying zone. Fuel otherwise needed to
operate the oven is eliminated or greatly reduced, as are costs. Essentially
all solvent emissions from the oven can be directed to an incinerator with a
combustion efficiency of a least 90 percent.
Ultraviolet cured coatings are available for special systems. Carbon
adsorption is not practical. Use of low solvent coatings is only a potential
control, because they have not yet been developed with properties that meet
industry's requirements.
References for Section 4.2.2.3
1. Control of Volatile Organic Emissions from Existing Statjlonary Sources,
Volume IV: JjSur'face Coating for Insulationofr MagnetrwireTEPA-450/2-77-
033, U. S. Environmental Protection Agency, Research Triangle Park, NC,
December 1977.
2. Controlled jind Uncontrolled Emission Rates and Applicable Limitations for
Eighty Processes, EPA Contract Number 68-02-1382, TRC of New England,
Wethersfield, CT, September 1976.
4/81
Evaporation Loss Sources
4.2.2.3-3
-------
-------
4.2.2.4 OTHER METAL COATING1"3
Process Description - Large appliance, metal furniture and miscellaneous metal
part and product coating lines have many common operations, similar emissions
and emission points, and available control technology. Figure 4.2.2.4-1 shows
a typical metal furniture coating line.
Large appliances include doors, cases, lids, panels and interior support
parts of washers, dryers, ranges, refrigerators, freezers, water heaters, air
conditioners, and associated products. Metal furniture includes both outdoor
and indoor pieces manufactured for household, business or institutional use.
"Miscellaneous parts and products" herein denotes large and small farm machin-
ery, small appliances, commercial and industrial machinery, fabricated metal
products and other industries that coat metal under Standard Industrial
Classification (SIC) codes 33 through 39.
Large Appliances - The coatings applied to large appliances are usually
epoxy, epoxy/acrylic or polyester enamels for the primer or single coat, and
acrylic enamels for the topcoat. Coatings containing alkyd resins are also
used. Prime and interior single coats are applied at 25 to 36 volume percent
solids. Topcoats and exterior single coats are applied at 30 to 40 volume
percent. Lacquers may be used to touch up any scratches that occur during
assembly. Coatings contain 2 to 15 solvents, typical of which are esters,
ketones, apliphatics, alcohols, aromatics, ethers and terpenes.
Small parts are generally dip coated, and flow or spray coating is used
for larger parts. Dip and flow coating are performed in an enclosed room
vented either by a roof fan or by an exhaust system adjoining the drain board
or tunnel. Down or side draft booths remove overspray and organic vapors from
prime coat spraying. Spray booths are also equipped with dry filters or a
water wash to trap overspray.
Parts may be touched up manually with conventional or airless spray equip-
ment. Then they are sent to a flashoff area (either open or tunneled) for
about 7 minutes and are baked in a multipass oven for about 20 minutes at 180
to 230°C (350 to 450°F). At that point, large appliance exterior parts go on
to the topcoat application area, and single coated interior parts are moved to
the assembly area of the plant.
The topcoat, and sometimes primers, are applied by automated electrostatic
disc, bell or other types of spray equipment. Topcoats often are more than one
color, changed by automatically flushing out the system with solvent. Both the
topcoat and touchup spray areas are designed with side or down draft exhaust
control. The parts go through about a 10 minute flashoff period, followed by
baking in a multipass oven for 20 to 30 minutes at 140 to 180°C (270 to 350°F).
Metal Furniture - Most metal furniture coatings are enamels, although some
lacquers are used. The most common coatings are alkyds, epoxies and acrylics,
which contain the same solvents used in large appliance coatings, applied at
about 25 to 35 percent solids.
On a typical metal furniture coating line (see Figure 4.2.2.4-1), the
prime coat can be applied with the same methods used for large appliances, but
it may be cured at slightly lower temperatures, 150 to 200°C (300 to 400°F).
4/81 Evaporation Loss Sources 4.2.2.4-1
-------
1°
°
m
en
en
o
O
3J
en
FROM
MACHINE
SHOP
CONVENTIONAL
OR ELECTROSTATIC,
AIR OR AIRLESS,
SPRAY COATING
TO FINAL
' ASSEMBLY
rtn
CLEANING
AND
PREPARATION
PRIME COATING
(OPTIONAL — USED
ONLY IN TWO COAT
OPERATION)
FLOW COATING
TOP COATING
OR SINGLE COAT
OPERATION
CD
Figure 4.2.2.4-1 Metal product coating line emission points.
-------
The topcoat, usually the only coat, Is applied with electrostatic spray or with
conventional airless or air spray. Most spray coating is manual, In contrast
to large appliance operations. Flow coating or dip coating is done, if the
plant generally uses only one or two colors on a line.
The coated furniture is usually baked, but In some cases It Is air dried.
If it is to be baked, it passes through a flashoff area into a multizone oven
at temperatures ranging from 150 to 230°C (300 to 450°F).
Miscellaneous Metal Parts and Products - Both enamels (30 to 40 volume
percent solids) and lacquers (10 to 20 volume percent solids) are used to coat
miscellaneous metal parts and products, although enamels are more common.
Coatings often are purchased at higher volume percent solids but are thinned
before application (frequently with aromatic solvent blends). Alkyds are
popular with Industrial and farm machinery manufacturers. Most of the coatings
contain several (up to 10) different solvents, including ketones, esters,
alcohols, aliphatics, ethers, aromatics and terpenes.
Single or double coatings are applied in conveyored or batch operations.
Spraying Is usually employed for single coats. Flow and dip coating may be
used when only one or two colors are applied. For two coat operations, primers
are usually applied by flow or dip coating, and topcoats are almost always
applied by spraying. Electrostatic spraying is common. Spray booths and areas
are kept at a slight negative pressure to capture overspray.
A manual two coat operation may be used for large items like industrial
and farm machinery. The coatings on large products are often air dried rather
than oven baked, because the machinery, when completely assembled, includes
heat sensitive materials and may be too large to be cured in an oven. Miscel-
laneous parts and products can be baked In single or multipass ovens at 150 to
230°C (300 to 450°F).
Emissions and Controls - Volatile organic compounds (VOC) are emitted
from application and flashoff areas and the ovens of metal coating lines. See
Figure 4.2.2.4-1. The composition of emissions varies among coating lines
according to physical construction, coating method and type of coating applied,
but distribution of emissions among individual operations has been assumed to
be fairly constant, regardless of the type of coating line or the specific pro-
duct coated, as Table 4.2.2.4-2 indicates. All solvent used can be considered
potential emissions. Emissions can be calculated from the factors In Table
4.2.2.1-1 if coatings use Is known, or from the factors in Table 4.2.2.4-2 if
only a general description of the plant Is available. For emissions from the
cleansing and pretreatment area, see Section 4.6, Solvent Degreasing.
When powder coatings, which contain almost no VOC, are applied to some
metal products as a coating modification, emissions are greatly reduced.
Powder coatings are applied as single coats on some large appliance interior
parts and as topcoat for kitchen ranges. They are also used on metal bed and
chair frames, shelving and stadium seating, and they have been applied as
single coats on small appliances, small farm machinery, fabricated metal pro-
duct parts and industrial machinery components. The usual application methods
are manual or automatic electrostatic spray.
4/81 Evaporation Loss Sources 4.2.2.4-3
-------
NJ
*
K)
TABLE 4.2.2.4-1. ESTIMATED CONTROL TECHNOLOGY EFFICIENCIES FOR METAL COATING LINES3
en
o>
H
O
a
g
H
O
P«
CO
Control
Technology
Powder
Water borne (spray,
dip, flowcoat)
Waterborne (elec-
trode posit Ion)
Higher solids
(spray)
Carbon absorption
Incineration
Application
Large appliances
Top, exterior or
Interior single
coat
All applications
Prime or Interior
single coat
Top or exterior
single coat and
sound deadener
Prime, single
or topcoat
application and
flashoff areas
Prime , top or
or single coat
ovens
Metal furniture
Top or single
coat
Prime , top or
single coat
Prime or single
coat
Top or single
coat
Prime, top or
single coat
application
and flashoff
areas
Ovens
Miscellaneous
Oven baked single
coat or topcoat
Oven baked single
coat, primer and
topcoat; air
dried primer and
topcoat
Oven baked single
coat and primer
Oven baked single
coat and topcoat;
air dried primer
and topcoat
Oven baked single
coat, primer and
topcoat applica-
tion and flash-
off areas; air
dried primer and
topcoat applica-
tion and drying
areas
Ovens
Organic Emissions Reduction (I)
Large
appliances
95-99b
70-90b
90-95b
60-80b
90^
90d
Metal
f urnl ture
95-99b
60-90*>
90-95b
50-80b
90-1
90d
Miscellaneous
95-98c
60-9QC
90-95C
50-8QC
9Qd
90+d
00
aReferences 1-3.
bthe base case against which these Z reductions were calculated Is a high organic solvent coating which
contains 25 volume Z solids and 75 volume X organic solvents. Transfer efficiencies for liquid coatings
are assumed to be about 801 for spray and 901 for dip or flowcoat, for powders about 931, and for electro-
deposition, 99Z.
cFlgures reflect the range of reduction possible. Actual reduction achieved depends on compositions of the
conventional coating originally used and replacement low organic solvent coating, on transfer efficiency,
and on relative film thicknesses of the two coatings.
d Reduce ion is only across the control device and does not account for capture efficiency.
-------
00
TABLE 4.2.2.4-2. EMISSION FACTORS FOR TYPICAL METAL COATING PLANTS3
EMISSION FACTOR RATING: B
w
O
H
H-
O
0
t-1
O
en
o
c
N
n
(0
en
•P-
I
Ul
Type of Plant
Large appliances
Prime and topcoat spray
Metal furniture*1
Single sprayc
Single dlpd
Miscellaneous metal*5
Conveyor single flow"
Conveyor dip
Conveyor single spray6
Conveyor two coat, flow and
spray
Conveyor two coat, dip and
spray
Conveyor two coat, spray
Manual two coat, spray
and air dry
Production Rate
768,000 unlts/yr
48 x 106 ft2/yr
23 x 106 ft2/yr
16 x 106 ft2/yr
16 x 106 ft2/yr
16 x 106 ft2/yr
16 x 106 ft2/yr
16 x 106 ft2/yr
16 x 106 ft2/yr
8.5 x 106 ft2/yr
Emissions
Mg/yr
315
500
160
111
111
200
311
311
400
212
ton/yr
347
550
176
122
122
220
342
342
440
233
Estimated Emissions (Z)
Application
and Flashoff
80
65 - 80
50 - 60
50-60
40 - 50
70 - 80
60 - 70
60 - 70
70 - 80
100
Ovens
20
20 - 35
40 - 50
40 - 50
50 - 60
20 - 30
30 - 40
30 - 40
30 - 30
0
aReferences 1-4.
^Estimated from area coated, assumed dry coating thickness of 1 nil, coating of 75% solvent by volume and
25% solids by volime, appropriate transfer efficiency (TE), and solvent density of 0.88 kg/liter
(7.36 Ib/gal). The equation to be used is:
E (tons/yr) - 2.29 x 10~6 area coated (ft2) V
1
TE
E (Mg/yr)
where V • VOC as volume %.
- 2.09 x 10~6 area coated (ft2) V
cTransfer efficiency assumed to be 60IS, presuming the coater uses manual electrostatic equipment.
^Flow and dip coat transfer efficiencies assumed to be 90%.
eTranafer efficiency assumed to be 50%, presuming the coater uses electrostatic equipment but coats a
wide range of product sizes and configurations.
-------
Improving transfer efficiency Is a method of reducing emissions. One
such technique is the electrostatic application of the coating, and another
is dip coating with waterborne paint. For example, many makers of large
appliances are now using electrodeposition to apply prime coats to exterior
parts and single coats to Interiors, because this technique increases corrosion
protection and resistance to detergents. Electrodeposition of these waterborne
coatings is also being used at several metal furniture coating plants and at
some farm, commercial machinery and fabricated metal products facilities.
Automated electrostatic spraying is most efficient, but manual and
conventional methods can be used, also. Roll coating is another option on some
miscellaneous parts. Use of higher solids coatings is a practiced technique
for reduction of VOC emissions.
Carbon adsorption is technically feasible for collecting emissions from
prime, top and single coat applications and flashoff areas. However, the
entrained sticky paint particles are a filtration problem, and adsorbers are
not commonly used.
Incineration is used to reduce organic vapor emissions from baking ovens
for large appliances, metal furniture and miscellaneous products, and It is an
option for control of emissions from application and flashoff areas.
Table 4.2.2.4-1 gives estimated control efficiencies for large appliance,
metal furniture and miscellaneous metal part and product coating lines, and
Table 4.2.2.4-2 gives their emission factors.
References for Section 4.2.2.4
1. Control of Volatile OrganicJEndssions from Existing Stationary Sources,
Volume III; Surface Coating of Metal Furniture, EPA-450/2-77-032, U. S.
Environmental Protection Agency, Research Triangle Park, NC, December 1977.
2. Control of Volatile Organic Emissions from Existing Stationary Sources,
Volume V; Surface Coating of Large Appliances. EPA-450/2-77-034, U. S.
Environmental Protection Agency, Research Triangle Park, NC, December 1977.
3. Control of Volatile Organic Emissions from Existing Stationary Sources,
Volume V; Surface Coating of Miscellaneous Metal Parts and Products,
EPA-450/2-78-015, U. S. Environmental Protection Agency, Research Trlangle
Park, NC, June 1978.
4. G. T. Helms, "Appropriate Transfer Efficiencies for Metal Furniture and
Large Appliance Coating", Memorandum, Office of Air Quality Planning and
Standards, U. S. Environmental Protection Agency, Research Triangle Park,
NC, November 28, 1980.
4.2.2.4-6 EMISSION FACTORS 4/81
-------
4.2.2.5 FLAT WOOD INTERIOR PANEL COATING
Process Description^ - Finished flat wood construction products are interior
panels made of hardwood plywoods (natural and lauan), particle board, and
hardboard.
Fewer than 25 percent of the manufacturers of such flat wood products
coat the products in their plants, and in some of the plants that do coat, only
a small percentage of total production is coated. At present, most coating is
done by toll coaters who receive panels from manufacturers and undercoat or
finish them according to customer specifications and product requirements.
Some of the layers and coatings that can be factory applied to flat woods
are filler, sealer, groove coat, primer, stain, basecoat, ink, and topcoat.
Solvents used in organic base flat wood coatings are usually component mix-
tures, including methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene,
butyl acetates, propanol, ethanol, butanol, naphtha, methanol, amyl acetate,
mineral spirits, SoCal I and II, glycols, and glycol ethers. Those most often
used in waterborne coatings are glycol, glycol ethers, propanol and butanol.
Various forms of roll coating are the preferred techniques for applying
coatings to flat woods. Coatings used for surface cover can be applied with
a direct roller coater, and reverse roll coaters are generally used to apply
fillers, forcing the filler into panel cracks and voids. Precision coating
and printing (usually with offset gravure grain printers) are also forms of
roll coating, and several types of curtain coating may be employed, also
(usually for topcoat application). Various spray techniques and brush coating
may be used, too.
Printed Interior panellngs are produced from plywoods with hardwood
surfaces (primarily lauan) and from various wood composition panels, including
hardboard and particle board. Finishing techniques are used to cover the
original surface and to produce various decorative effects. Figure 4.2.2.5-1
Is a flow diagram showing some, but not all, typical production line variations
for printed interior paneling.
Groove coatings, applied in different ways and at different points In the
coating procedure, are usually pigmented low resin solids reduced with water
before use, therefore yielding few, if any, emissions. Fillers, usually applied
by reverse roll coating, may be of various formulations: (1) polyester (which
Is ultraviolet cured), (2) water base, (3) lacquer base, (4) polyurethane and
(5) alkyd urea base. Water base fillers are in common use on printed paneling
lines.
Sealers may be of water or solvent base, usually applied by airless spray
or direct roll coating, respectively. Basecoats, which are usually direct roll
coated, generally are of lacquer, synthetic, vinyl, modified alkyd urea,
catalyzed vinyl, or water base.
Inks are applied by an offset gravure printing operation similar to direct
roll coating. Most lauan printing inks are pigments dispersed In alkyd resin,
with some nitrocellulose added for better wipe and printability. Water base
4/81
Evaporation Loss Sources
4.2.2-5-1
-------
inks have a good future for clarity, cost and environmental reasons. After
printing, a board goes through one or two direct or precision roll coaters
for application of the clear protective topcoat. Some topcoats are synthetic,
prepared from solvent soluble alkyd or polyester resins, urea formaldehyde
cross linkings, resins, and solvents.
Natural hardwood plywood panels are coated with transparent or clear
finishes to enhance and protect their face ply of hardwood veneer. Typical
production lines are similar to those for printed interior paneling, except
that a primer sealer is applied to the filled panel, usually by direct roll
coating. The panel is then embossed and "valley printed" to give a "dis-
tressed" or antique appearance. No basecoat is required. A sealer Is also
applied after printing but before application of the topcoat, which may be
curtain coated, although direct roll coating remains the usual technique.
Emissions and Controls^-"^ - Emissions of volatile organic compounds (VOC) at
flat wood coating plants occur primarily from reverse roll coating of filler,
direct roll coating of sealer and basecoat, printing of wood grain patterns,
direct roll or curtain coating of topcoat(s), and oven drying after one or
more of those operations (see Figure 4.2.2.5-1). All solvent used and not
recovered can be considered potential emissions. Emissions can be calculated
from the factors in Table 4.2.2.1-1, if the coating use is known. Emissions
for interior printed panels can be estimated from the factors in Table
4.2.2.5-1, If the area of coated panels is known.
Waterborne coatings are Increasingly used to reduce emissions. They can
be applied to almost all flat wood except redwood and, possibly, cedar. The
major use of waterborne flat wood coatings is in the filler and basecoat
applied to printed interior paneling. Limited use has been made of waterborne
materials for inks, groove coats, and topcoats with printed paneling, and for
inks and groove coats with natural hardwood panels.
Ultraviolet curing systems are applicable to clear or semitransparent
fillers, topcoats on particle board coating lines, and specialty coating oper-
ations. Polyester, acrylic, urethane and alkyd coatings can be cured by this
method.
Afterburners can be used to control VOC emissions from baking ovens, and
there would seem to be ample recovered heat to use. Extremely few flat wood
coating operations have afterburners as addon controls, though, despite the
fact that they are a viable control option for reducing emissions where product
requirements restrict the use of other control techniques.
Carbon adsorption Is technically feasible, especially for specific
applications (e. g., redwood surface treatment), but the use of multicomponent
solvents and different coating formulations in several steps along the coating
line has thus far precluded its use to control flat wood coating emissions and
to reclaim solvents. The use of low solvent coatings to fill pores and to seal
wood has been demonstrated.
4.2.2.5-2
EMISSION FACTORS
4/81
-------
00
m
CD
o
—1
Q)
O
(/)
to
cn
O
c
o
Q
\
FEEDER
*-
TEMPERING
}
BRUSHER
SANDER
OVEN
INKS (OFFSET
GflAVUHE)
INSPECTION
PACKAGING
SHIPMENT
NJ
O1
1
to
Figure 4.2.2.5-1. Flat Wood interior panel coating line emission points.
RRC - REVERSE ROLL COATING
OftC - DIRECT ROLL COATING
-------
NJ
*
K)
Ln
TABLE 4.2.2.5-1. VOC EMISSION FACTORS FOR INTERIOR PRINTED PANELS3
EMISSION FACTOR RATING: B
Paint
Category
Filler
Sealer
Basecoat
Ink
Topcoat
Coverage**
liter/lOOm2
Water
borne
6.5
1.4
2.6
0.4
2.6
Conven-
tional
6.9
1.2
3.2
0.4
2.8
gal/1,000 ft2
Water
borne
1.6
0.35
3.2
0.1
0.65
Conven-
tional
1.7
0.3
0.65
0.1
0.7
Uncontrolled VOC Emissions
kg/100m2 coated
Water
borne
0.3
0.2
0.8
0.1
0.4
Conven-
tional
3.0
0.5
0.2
0.3
1.8
Ultra-
violet0
Neg
0
0.24
0.10
Neg
lb/1,000 ft2 coated
Water
borne
0.6
0.4
0.5
0.2
0.8
Conven-
tional
6.1
1.1
5.0
0.6
3.7
Ultra-
violet0
Neg
0
0.5
0.2
Neg
TOTAL 13.5 14.5 3.4 3.6 1.2 8.0 0.4 2.5 16.5 0.8
H
CO
§
I
H
CO
aReference 1. Organics are all nuiiuic i_uanc. «^5 - i.^6^...6.* ^^-^ •
^Reference 3. From Abitibi Corp., Cucamonga, CA. Adjustments between water and conventional paints made
using typical nonvolatiles content.
CUV line uses no sealer, uses waterborne basecoat and ink. Total adjusted to cover potential emissions
from UV coatings.
00
-------
References for Section 4.2.2.5
1. Control of Volatile Organic Emissions from Existing Stationary Sources,
Volume VII; Factory Surface Coating of Flat Wood Interior Paneling, EPA-
450/2-78-032, U. S. Environmental Protection Agency, Research Triangle
Park, NC, June 1978.
2. Air Pollution Control Technology Applicable to 26 Sources of Volatile
Organic Compounds, Office of Air Quality Planning and Standards, U. S.
Environmental Protection Agency, Research Triangle Park, NC, May 27, 1977.
Unpublished*
3. Products Finishing, 41(6A):4-54, March 1977.
4/81
Evaporation Loss Sources
4.2.2.5-5
-------
-------
4.2.2.6 PAPER COATING
Process Description^"^ - Paper is coated for various decorative and functional
purposes with waterborne, organic solventborne, or solvent free extruded mate-
rials. Paper coating is not to be confused with printing operations, which
use contrast coatings that must show a difference in brightness from the paper
to be visible. Coating operations are the application of a uniform layer or
coating across a substrate. Printing results in an image or design on the
substrate.
Waterborne coatings improve printabllity and gloss but cannot compete
with organic solventborne coatings in resistance to weather, scuff and chem-
icals. Solventborne coatings, as an added advantage, permit a wide range of
surface textures. Most solventborne coating is done by paper converting com-
panies that buy paper from mills and apply coatings to produce a final product.
Among the many products that are coated with solventborne materials are adhesive
tapes and labels, decorated paper, book covers, zinc oxide coated office copier
paper, carbon paper, typewriter ribbons, and photographic film.
Organic solvent formulations generally used are made up of film forming
materials, plastlcizers, pigments and solvents. The main classes of film
formers used in paper coating are cellulose derivatives (usually nitrocellu-
lose) and vinyl resins (usually the copolymer of vinyl chloride and vinyl
acetate). Three common plastlcizers are dioctyl phthalate, tricresyl phos-
phate and castor oil. The major solvents used are toluene, xylene, methyl
ethyl ketone, isopropyl alcohol, methanol, acetone, and ethanol. Although a
single solvent is frequently used, a mixture Is often necessary to obtain the
optimum drying rate, flexibility, toughness and abrasion resistance.
A variety of low solvent coatings, with negligible emissions, has been
developed for some uses to form organic resin films equal to those of con-
ventional solventborne coatings. They can be applied up to 1/8 inch thick
(usually by reverse roller coating) to products like artificial leather goods,
book covers and carbon paper. Smooth hot melt finishes can be applied over
rough textured paper by heated gravure or roll coaters at temperatures from 65
to 230°C (150 to 450°F).
Plastic extrusion coating is a type of hot melt coating in which a molten
thermoplastic sheet (usually low or medium density polyethylene) is extruded
from a slotted die at temperatures of up to 315°C (600°F). The substrate and
the molten plastic coat are united by pressure between a rubber roll and a
chill roll which solidifies the plastic. Many products, such as the polyeth-
ylene coated milk carton, are coated with solvent free extrusion coatings.
Figure 4.2.2.6-1 shows a typical paper coating line that uses organic
solventborne formulations. The application device is usually a reverse roller,
a knife or a rotogravure printer. Knife coaters can apply solutions of much
higher viscosity than roll coaters can, thus emitting less solvent per pound of
solids applied. The gravure printer can print patterns or can coat a solid
sheet of color on a paper web.
4/81
Evaporation Loss Sources
4.2.2.6-1
-------
Ovens may be divided into from two to five temperature zones. The first
zone is usally at about 43°C (110°F) , and other zones have progressively higher
temperatures to cure the coating after most solvent has evaporated. The typi-
cal curing temperature is 120°C (250°F) , and ovens are generally limited to
200°C (400°F) to avoid damage to the paper. Natural gas is the fuel most often
used in direct fired ovens, but fuel oil is sometimes used. Some of the hea-
vier grades of fuel oil can create problems, because SO and particulate may
contaminate the paper coating. Distillate fuel oil usually can be used satis-
factorily. Steam produced from burning solvent retrieved from an adsorber or
vented to an Incinerator may also be used to heat curing ovens.
f\
Emissions and Controls - The main emission points from paper coating lines are
the coating applicator and the oven (see Figure 4.2.2.6-1). In a typical paper
coating plant, about 70 percent of all solvents used are emitted from the coat-
Ing lines, with most coming from the first zone of the oven. The other 30 per-
cent are emitted from solvent transfer, storage and mixing operations and can
be reduced through good housekeeping practices. All solvent used and not
recovered or destroyed can be considered potential emissions.
TABLE 4.2.2.6-1. CONTROL EFFICIENCIES FOR
PAPER COATING LINES3
Affected facility
Coating line
Control method
Incineration
Carbon adsorption
Low solvent coating
Efficiency (%)
95
90+
80 - 99b
aReference 2.
^Based on comparison with a conventional coating containing 35%
solids and 65% organic solvent, by volume.
Volatile organic compounds (VOC) emissions from individual paper coating
plants vary with size and number of coating lines, line construction, coating
formulation, and substrate composition, so each must be evaluated individually.
VOC emissions can be estimated from the factors in Table 4.2.2.1-1, if coating
use is known and sufficient information on coating composition is available.
Since many paper coating formulas are proprietary, it may be necessary to have
information on the total solvent used and to assume that, unless a control
device is used, essentially all solvent is emitted. Rarely would as much as 5
percent be retained in the product.
Almost all solvent emissions from the coating lines can be collected and
sent to a control device. Thermal incinerators have been retrofitted to a large
number of oven exhausts, with primary and even secondary heat recovery systems
heating the ovens. Carbon adsorption is most easily adaptable to lines which
use single solvent coating. If solvent mixtures are collected by adsorbers,
they usually must be distilled for reuse.
Although available for some products, low solvent coatings are not yet
available for all paper coating operations. The nature of the products, such
4.2.2.6-2
EMISSION FACTORS
4/81
-------
CO
BLADE COATED
EXCESS » WEB
COATING -~A
PAPER WEB
01
O
-1
OJ
5'
D
O
CO
o
c
o
CD
REVERSE ROLL
COATER
HEATED AIR FROM
BURNER, BOILER OR
HEAT RECOVERY
ZONE 1
EXHAUST
(MAJOR
EMISSION
POINT)
ZONE 2
EXHAUST
it if \r
0 O
— If —
o
^r 1< TI ir
0 O C
HOT AIR MANIFOLD
OVEN
TENSION ROLLS
D _\
UNWIND
REWIND
o
0>
CO
Figure 4.2.2.6.-1. Paper coating line emission points.
-------
as some types of photographic film, may preclude development of a low solvent
option. Furthermore, the more complex the mixture of organic solvents in the
coating, the more difficult and expensive to reclaim them for reuse with a
carbon adsorption system.
References for Section 4.2.2.6
1. T. W. Hughes, e t al., Source Assessment: Prioritlzatlon of Air Pollution
from Industrial Surface Coating Operations, EPA-650/2-75-019a, U. S.
Environmental Protection Agency, Research Triangle Park, NC, February 1975,
2. Control of Volatile Organic Emissions from Existing Stationary Sources,
Volume II; Surface Coating of Cans, Colls, Paper Fabrics, Automobiles,
and Light Duty Trucks, EPA-450/2-77-008, U. S. Environmental Protection
Agency, Research Triangle Park, NC, May 1977.
4.2.2.6-4 EMISSION FACTORS 4/81
-------
4.2.2.7 FABRIC COATING1"3
Process Description - Fabric coating imparts to a fabric substrate properties
such as strength, stability, water or acid repellence, or appearance. Fabric
coating is the uniform application of an elastomeric or thermoplastic polymer
solution, or a vinyl plastisol or organosol, across all of at least one side
of a supporting fabric surface or substrate. Coatings are applied by blade,
roll coater, reverse roll coater, and in some instances, by rotogravure coater.
Fabric coating should not be confused with vinyl printing and top coating,
which occur almost exclusively on rotogravure equipment. Textile printing also
should not be considered a fabric coating process.
Products usually fabric coated are rainwear, tents, tarpaulins, substrates
for industrial and electrical tape, tire cord, seals, and gaskets. The industry
is mostly small to medium size plants, many of which are toll coaters, rather
than specialists in their own product lines.
Figure 4.2.2.7-1 is of a typical fabric coating operation. If the fabric
is to be coated with rubber, the rubber is milled with pigments, curing agents
and fillers before being dissolved (mixed) in a suitable solvent. When other
than rubber coatings are used, milling is rarely necessary.
Emissions and Controls1 - The volatile organic compounds (VOC) emissions in a
fabric coating plant originate at the mixer, the coating applicator and the
oven (see Figure 4.2.2.7-1). Emissions from these three areas are from 10 to
25 percent, 20 to 30 percent and 40 to 65 percent, respectively. Fugitive
losses, amounting to a few percent, escape during solvent transfer, storage
tank breathing, agitation of mixing tanks, waste solvent disposal, various
stages of cleanup, and evaporation from the coated fabric after it leaves the
line.
The most accurate method of estimating VOC emissions from a fabric coating
plant is to obtain purchase or use records of all solvents in a specified time
period, add to that the amount of solvent contained in purchased coating solu-
tions, and subtract any stockpiled solvent, such as cleanup solvent, that is
recovered and disposed of in a nonpolluting manner. Emissions from the actual
coating line, without any solvent recovery, can be estimated from the factors
In Section 4.2.2.1, General Industrial Surface Coating, if coating use Is known
and sufficient information on coating composition Is available. Because many
fabric coatings are proprietary, it may be necessary for the user to supply
information on the total solvent used and to assume that, unless a control
device is used, all solvent Is emitted. To calculate total plant emissions,
the coatings mixing losses must be accounted. These losses can be estimated
from the printline losses by using the relative split of plant emissions bet-
ween the mixing area and the printline. For example,
Emissions, = Emissions, /10% loss from mixing N
mixing printline \85% loss from printline'
Incineration Is probably the best way to control coating application and
curing emissions on coating lines using a variety of coating formulations.
Primary and secondary heat recovery are likely to be used to help reduce the
fuel requirements of the coating process and, therefore, to increase the economy
4/81 Evaporation Loss Sources 4.2.2.7-1
-------
o
jo
^
to
m
V)
en
CURING
PIGMENTS RUBBER AGENTS
SOLVENT
' J =
MILLING
MIXING
COATING APPLICATION
(KNIFE, ROLLER,
ROTOGRAVURE)
DRYING AND
CURING OVENS
COATED
PRODUCT
Figure 4.2.2.7-1. Fabric coating plant emission points.7
-------
of incineration. As with other surface coating operations, carbon adsorption
is most easily accomplished by sources using a single solvent that can be
recovered for reuse. Mixed solvent recovery is, however, in use in other web
coating processes. Fugitive emissions controls include tight covers for open
tanks, collection hoods for cleanup areas, and closed containers for storage
of solvent wiping cloths. Where high solids or waterborne coatings have been
developed to replace conventional coatings, their use may preclude the need for
a control device.
References for Section 4.2.2.7
1. Control of Volatile Organic Emissions from Existing Stationary Sources,
Volume II; Surface Coating of Cans, Coils, Paper Fabrics, Automobiles,
and Light Duty Trucks, EPA-450/2-77-008, U. S. Environmental Protection
Agency, Research Triangle Park, NC, May 1977.
2. B. H. Carpenter and G. K. Hilliard, Environmental Aspects of Chemical Use
in Printing Operations, EPA-560/1-75-005, U. S. Environmental Protection
Agency, Washington, DC, January 1976.
3. J. C. Berry, "Fabric Printing Definition", Memorandum, Office of Air Quality
Planning and Standards, U. S. Environmental Protection Agency, Research
Triangle Park, NC, August 25, 1980.
4/81
Evaporation Loss Sources
4.2.2.7-3
-------
-------
4.2.2.8 AUTOMOBILE AND LIGHT DUTY TRUCK SURFACE COATING OPERATIONS
General - Surface coating of an automobile body is a multistep operation
carried out on an assembly line conveyor system. Such a line operates at a
speed of 3 to 8 meters (9 to 25 feet) per minute and usually produces 30 to
70 units per hour. An assembly plant may operate up to two 8 hour production
shifts per day, with a third shift used for cleanup and maintanance. Plants
may stop production for a vacation of one and a half weeks at Christmas
through New Year's Day and may stop for several weeks in Summer for model
changeover.
Although finishing processes vary from plant to plant, they have some
common characteristics. Major steps of such processes are:
Solvent wipe
Phosphating treatment
Application of prime coat
Curing of prime coat
Application of guide coat
Curing of guide coat
Application of topcoat(s)
Curing of topcoat(s)
Final repair operations
A general diagram of these consecutive steps is presented in Figure
4.2.2.8-1. Application of a coating takes place in a dip tank or spray
booth, and curing occurs in the flashoff area and bake oven. The typical
structures for application and curing are contiguous, to prevent exposure
of the wet body to the ambient environment before the coating is cured.
The automobile body is assembled from a number of welded metal sections.
The body and the parts to be coated all pass through the same metal
preparation process.
First, surfaces are wiped with solvent to eliminate traces of oil and
grease. Second, a phosphating process prepares surfaces for the primer
application. Since iron and steel rust readily, phosphate treatment is nec-
essary to retard such. Phosphating also improves the adhesion of the primer
and the metal. The phosphating process occurs in a multistage washer, with
detergent cleaning, rinsing, and coating of the metal surface with zinc
phosphate. The parts and bodies pass through a water spray cooling process.
If solventborne primer is to be applied, they are then oven dried.
A primer is applied to protect the metal surface from corrosion and
to assure good adhesion of subsequent coatings. Approximately half of all
assembly plants use solventborne primers with a combination of manual and
automatic spray application. The rest use waterborne primers. As new plants
are constructed and exiting plants modernized, the use of waterborne primers
is expected to increase.
The term "solvent" here means organic solvent.
8/82
Evaporation Loss Sources
4.2.2.8-1
-------
OO
H
§
n
H
00
00
Body welded, \
solder applied >
and ground /
Solvent
(kerosene)
wipe
A
Topcoat cured
Topcoat
sprayed*
A
A
Second topcoat and
touchup sprayed
Paint repair
cured or
air dried
7 stage
phosphating
T
^ Sealants applied "^> ^ _ _ _ _
i A ^^
Prime coat *—
(and sealant)
cured
\^^
Prime coat * *
applied (spray
or dip)
Prime coat
sanded
<
^
Water spray
cooling
1 y
Guide coat L
sprayed
!
^
^
i A
L — i
Guide coat
cured
A
Second topcoat
cured
Potential A
emission *—*
points
*To get sufficient film build, for two colors or a base coat/clear coat,
there may be multiple topcoats.
Figure 4.2.2.8-1. Typical automobile and light duty truck surface coating line.
-------
Waterborne primer is most often applied in an electrodeposition (EDP)
bath. The composition of the bath is about 5 to 15 volume percent solids,
2 to 10 percent solvent and the rest water. The solvents used are typically
organic compounds of higher molecular weight and low volatility, like
ethylene glycol monobutyl ether.
When EDP is used, a guide coat (also called a primer surfacer) is
applied between the primer and the topcoat to build film thickness, to fill
in surface imperfections and to permit sanding between the primer and top-
coat. Guide coats are applied by a combination of manual and automatic
spraying and can be solventborne or waterborne. Powder guide coat is used
at one light duty truck plant.
The topcoat provides the variety of colors and surface appearance to
meet customer demand. Topcoats are applied in one to three steps to assure
sufficient coating thickness. An oven bake may follow each topcoat appli-
cation, or the coating may be applied wet on wet. At a minimum, the final
topcoat is baked in a high temperature oven.
Topcoats in the automobile industry traditionally have been solventborne
lacquers and enamels. Recent trends have been to higher solids content.
Powder topcoats have been tested at several plants.
The current trend in the industry is toward base coat/clear coat
(BC/CC) topcoating systems, consisting of a relatively thin application of
highly pigmented metallic base coat followed by a thicker clear coat. These
BC/CC topcoats have more appealing appearance than do single coat metallic
topcoats, and competitive pressures are expected to increase their use by
U. S. manufacturers.
The VOC content of most BC/CC coatings in use today is higher than that
of conventional enamel topcoats. Development and testing of lower VOC
content (higher solids) BC/CC coatings are being done, however, by automobile
manufacturers and coating suppliers.
Following the application of the topcoat, the body goes to the trim
operation area, where vehicle assembly is completed. The final step of the
surface coating operation is generally the final repair process, in which
damaged coating is repaired in a spray booth and is air dried or baked in a
low temperature oven to prevent damage of heat sensitive plastic parts added
in the trim operation area.
Emissions and Controls - Volatile organic compounds (VOC) are the major
pollutants from surface coating operations. Potential VOC emitting oper-
ations are shown in Figure 4.2.2.8-1. The application and curing of the
prime coat, guide coat and topcoat account for 50 to 80 percent of the VOC
emitted from assembly plants. Final topcoat repair, cleanup, and miscella-
neous sources such as the coating of small component parts and application
of sealants, account for the remaining 20,percent. Approximately 75 to 90
percent of the VOC emitted during the application and curing process is
emitted from the spray booth and flasjioff area, and 10 to 25 percent from
the bake oven. This emissions split is heavily dependent on the types of
8/82
Evaporation Loss Sources
4.2.2.8-3
-------
TABLE 4.2.2.8-1. EMISSION FACTORS FOR AUTOMOBILE AND LIGHT DUTY
TRUCK SURFACE COATING OPERATIONS21
EMISSION FACTOR RATING: C
Automobile
Coating kg(lb)
per vehicle
Prime Coat
Solventborne
spray
Cathodic
electrodeposition
Guide Coat
Solventborne spray
Waterborne spray
Topcoat
Lacquer
Dispersion lacquer
Enamel
Basecoat/ clear coat
Waterborne
6.61
(14.54)
.21
(-45)
1.89
(4.16)
.68
(1.50)
21.96
(48.31)
14.50
(31.90)
7.08
(15.58)
6.05
(13.32)
2.25
(4.95)
of VOC b
per hour
363
(799)
12
(25)
104
229
38
(83)
1208
(2657)
798
(1755)
390
(857)
333
(732)
124
(273)
Light Duty Truck
kg(lb)
per vehicle
19.27
(42.39)
.27
(.58)
6.38
(14.04)
2.3
(5.06)
NA
NA
17.71
(38.96)
18.91
(41.59)
7.03
(15.47)
of VOC
^
per hour
732
(1611)
10
(22)
243
(534)
87
(192)
NA
NA
673
(1480)
719
(1581)
267
(588)
All nonmethane VOC. Factors are calculated using the following equation
and the typical values of parameters presented in Tables 4.2.2.8-2 and
4.2.2.8-3. NA - Not applicable.
A
E = v
v
T, V c2
f c L
Where: E = emission factor for VOC, mass per vehicle (Ib/vehicle)
(exclusive of any addon control devices)
A = area coated per vehicle (ft /vehicle)
GI = conversion factor: 1 ft/12,000 mil
T, = thickness of the dry coating film (mil)
V = VOC (organic solvent) content of coating as applied, less water
c (Ib VOC/gal coating, less water)
C2 = conversion factor: 7.48 gallons/ft3
S = solids in coating as applied, volume fraction (gal solids/gal
coating)
e_, = transfer efficiency fraction (fraction of total coating solids
used which remains on coated parts)
Example: The VOC emissions per automobile from a cathodic electrodeposited
prime coat.
(850 ftz)(1/12000)(0.6 mil)(1.2 lb/gal-H20)
(-84 gal/gal)(1.00)
- .45 Ib VOC/vehicle (.21 kg VOC/vehicle)
Base on an average line speed of 55 automobiles/hr.
cBased on an average line speed of 38 light duty trucks/hr.
E mass of VOC
v
4.2.2.8-4
EMISSION FACTORS
8/82
-------
solvents used and on transfer efficiency. With improved transfer effi-
ciencies and the newer coatings, it is expected that the percent of VOC
emitted from the spray booth and the flashoff area will decrease, and the
percent of VOC emitted from the bake oven will remain fairly constant.
Higher solids coatings, with their slower solvents, will tend to have a
greater fraction of emissions from the bake oven.
Several factors affect the mass of VOC emitted per vehicle from surface
coating operations in the automotive industry. Among these are:
VOC content of coatings (pounds of coating, less water)
Volume solids content of coating
Area coated per vehicle
Film thickness
Transfer efficiency
The greater the quantity of VOC in the coating composition, the greater will
be the emissions. Lacquers having 12 to 18 volume percent solids are higher
in VOC than enamels having 24 to 33 volume percent solids. Emissions are
also influenced by the area of the parts being coated, the coating thickness,
the configuration of the part and the application technique.
The transfer efficiency (fraction of the solids in the total consumed
coating which remains on the part) varies with the type of application tech-
nique. Transfer efficiency for typical air atomized spraying ranges from 30
to 50 percent. The range for electrostatic spraying, an application method
that uses an electrical potential to increase transfer efficiency of the
coating solids, is from 60 to 95 percent. Both air atomized and electro-
static spray equipment may be used in the same spray booth.
Several types of control techniques are available to reduce VOC
emissions from automobile and light duty truck surface coating operations.
These methods can be broadly categorized as either control devices or new
coating and application systems. Control devices reduce emissions by either
recovering or destroying VOC before it is discharged into the ambient air.
Such techniques include thermal and catalytic incinerators on bake ovens,
and carbon adsorbers on spray booths. New coatings with relatively low VOC
levels can be used in place of high VOC content coatings. Such coating
systems include electrodeposition of waterborne prime coatings, and for top
coats, air spray of waterborne enamels and air or electrostatic spray of
high solids, solventborne enamels and powder coatings. Improvements in the
transfer efficiency decrease the amount of coating which must be used to
achieve a given film thickness, thereby reducing emissions of VOC to the
ambient air.
Calculation of VOC emissions for representative conditions provides the
emission factors in Table A.2.2.8-1. The factors were calculated with the
typical value of parameters presented in Tables 4.2.2.8-2 and 4.2.2.8-3.
The values for the various parameters for automobiles and light duty trucks
represent average conditions existing in the automobile and light duty truck
industry in 1980. A more accurate estimate of VOC emissions can be calcu-
lated with the equation in Table 4.2.2.8-1 and with site-specific values for
the various parameters.
8/82
Evaporation Loss Sources
4.2.2.8-5
-------
KJ
TABLE 4.2.2.8-2. PARAMETERS FOR THE AUTOMOBILE SURFACE COATING INDUSTRY*
00
Oi
2
Tl
O
H
C
Application
Prime Coat
Solventborne spray
Cathodic electrodeposition
Guide Coat
Solventborne spray
Waterborne spray
Topcoat
Solventborne spray
Lacquer
Dispersion lacquer
Enamel
Base coat/clear coat
Base coat
Clear coat
Waterborne spray
Area Coated
per vehicle,
ft2
450
{220-570)
850
(660-1060)
200
(170-280)
200
(170-280)
240
(170-280)
240
(170-280)
240
(170-280)
240
240
(170-280)
240
(170-280)
240
(170-280)
Film
Thickness,
mil
0.8
(0.3-2.5)
0.6
(0.5-0.8)
0.8
(0.5-1.5)
0.8
(0.5-2.0)
2.5
(1.0-3.0)
2.5
(1.0-3.0)
2.5
(1.0-3.0)
2.5
1.0
(0.8-1.0)
1.5
(1.2-1.5)
2.2
(1.0-2.5)
VOC Content,
lb/gal-H20
5.7
(4.2-6.0)
1.2
(1.2-1.5)
5.0
(3.0-5.6)
2.8
(2.6-3.0)
6.2
(5,8-6.6)
5.8
(4.9-5.8)
5.0
(3.0-5.6)
4.7
5.6
(3.4-6.4)
4.0
(3.0-5.1)
2.8
(2.6-3.0)
Volume Fraction Solids,
gal/gal-H20
0.22
(.20-. 35)
0.84
(.84-. 87)
0.30
(.25-. 55)
0.62
(.60-. 65)
0.12
(.10-. 13)
0.17
(.17-. 27)
0.30
(.25-. 55)
0.33
0.20
(.13-. 48)
0.42
(.30-. 54)
0.62
(.60-. 65)
Transfer
Efficiency,
%
40
(35-50)
100
(85-100)
40
(35-65)
30
(25-40)
40
(30-65)
40
(30-65)
40
(30-65)
40
40
(30-50)
40
(30-65)
30
(25-40)
00
00
All values for coatings as applied, except for VOC content and volume fraction solids which are for coatings as applied minus water.
Ranges in parentheses. Low VOC content (high solids) base coat/clear coats are still undergoing testing and development.
Composite of base coat and clear coat.
-------
TABLE 4.2.2.8-3. PARAMETERS FOR THE LIGHT DUTY TRUCK SURFACE COATING INDUSTRY*
00
j:
r.
-p-
f
K)
M
00
Application
Prime Coat
Solventborne spray
Cathodic electrodeposition
Guide Coat
Solventborne spray
Waterbome spray
Topcoat
Solventborne spray
Enamel
Base coat/clear coat
Base coat
Clear coat
Waterbome spray
Area Coated
per vehicle,
ft2
875
(300-1000)
1100
(850-1250)
675
(180-740)
675
(180-740)
750
(300-900)
750
750
(300-900)
750
(300-900)
750
(300-900)
Film
Thickness ,
mil
1.2
(0.7-1.7)
0.6
(0.5-0.8)
0.8
(0.7-1.7)
0.8
(0.5-2.0)
2.0
(1.0-2.5)
2.5
1.0
(0.8-1.0)
1.5
(1.2-1.5)
2.2
(1.0-2.5)
VOC Content,
lb/gal-H20
5.7.
(4.2-6.0)
1.2
(1.2-1.5)
5.0
(3.0-5.6)
2.8
(2.6-3.0)
5.0
(3.0-5.6)
4.7
5.6
(3.4-6.4)
4.0
(3.0-5.1)
2.8
(2.6-3.0)
Volume Fraction Solids,
gal/gal-H20
0.22
(0.20-.35)
0.84
(.84-. 87)
0.30
(.25-. 55)
0.62
(.60-. 65)
0.30
(.25-. 55)
0.33
0.20
(.13-. 48)
0.42
(.30-. 54)
0.62
(.60-. 65)
Transfer
Efficiency,
%
40
(35-50)
100
(85-100)
40
(35-65)
30
(25-40)
40
(30-65)
40
40
(30-50)
40
(30-65)
30
(25-40)
All values are for coatings as applied, except for VOC content and volume fraction solids which are for coatings as applied minus water.
bRanges in parenthesis. Low VOC content (high solids) base coat/clear coats are still undergoing testing and development.
Composite of typical base coat and clear coat.
-------
Emission factors are not available for final topcoat repair, cleanup,
coating of small parts and application of sealants.
References for Section 4.2.2.8
1. Control of Volatile Organic Emissions from Existing Stationary
Sources - Volume II: Surface Coating of Cans, Coils, Paper Fabrics,
Automobiles, and Light Duty Trucks, EPA-450/2-77-008, U.S. Environmental
Protection Agency, Research Triangle Park, NC, May 1977.
2. Study To Determine Capabilities To Meet Federal^ ^EPA Guidelines for
Volatile Organic Compound Emissions^, General Motors Corporation,
Detroit, MI, November 1978.
3. Automobile and Light Duty Truck Surfa^ce Coating Operations - Background
Information for Proposed Standards, EPA-450/3-79-030, U.S. Environmental
Protection Agency, Research Triangle Park, NC, September 1979.
4. Written communication from D. A. Frank, General Motors Corporation,
Warren, MI, to H. J. Modetz, Acurex Corporation, Morrisville, NC,
April 14, 1981.
4.2.2.8-8 EMISSION FACTORS 8/82
-------
4.2.2.9 PRESSURE SENSITIVE TAPES AND LABELS
General - The coating of pressure sensitive tapes and labels
(PSTL) is an operation in which some backing material (paper, cloth
or film) is coated to create a tape or label product that sticks on
contact. The term "pressure sensitive" indicates that the adhesive
bond is formed on contact, without wetting, heating or adding a
curing agent.
The products manufactured by the PSTL surface coating industry
may have several different types of coatings applied to them. The
two primary types of coatings are adhesives and releases. Adhesive
coating is a necessary step in the manufacture of almost all PSTL
products. It is generally the heaviest coating (typically 0.051 kg/m^,
or 0.011 Ib/ft2) and therefore has the highest level of solvent
emissions (generally 85 to 95 percent of total line emissions).
Release coatings are applied to the backside of tape or to the
mounting paper of labels. The function of release coating is to
allow smooth and easy unrolling of a tape or removal of a label
from mounting paper. Release coatings are applied in a very thin
coat (typically 0.00081 kg/m2, or 0.00017 Ib/ft2). This thin
coating produces less emissions than does a comparable size adhesive
coating line.
Five basic coating processes can be used to apply both adhesive
and release coatings:
solvent base coating
waterborne (emulsion) coating
100 percent solids (hot melt) coating
calender coating
prepolymer coating
A solvent base coating process is used to produce 80 to 85
percent of all products in the PSTL industry, and essentially all
of the solvent emissions from the industry result from solvent base
coating. Because of its broad application and significant emissions,
solvent base coating of PSTL products is discussed in greater
detail.
1—2 5
Process Description ' - Solvent base surface coating is conceptually
a simple process. A continuous roll of backing material (called
the web) is unrolled, coated, dried and rolled again. A typical
solvent base coating line is shown in Figure 4.2.2.9-1. Large
lines in this industry have typical web widths of 152 centimeters
(60 in), while small lines are generally 48 centimeters (24 in).
Line speeds vary substantially, from three to 305 meters per
8/82
Evaporation Loss Sources
4.2.2.9-1
-------
oo
00
to
a Clean Exhaust Gas
%
p
rt
H-
O
co
CO
o
H
n
n>
co
NJ
NJ
VD
ts)
Heated Air
from Burner
Fugitive So1vent
Emissions bolvent
n
Control Device
Drying Oven Exhausts
Hot Air Nozzles
u o o u o
Adhesive or
Release Coater
Fugitive Solvent
Emissions
Solvent in the Web
Rewind
Figure 4.2.2.9-1. Diagram of a Pressure Sensitive Tape and Label Coating Line
-------
minute (10 - 1000 ft/min). To initiate the coating process the
continuous web material is unwound from its roll. It travels to a
coating head, where the solvent base coating formulation is applied.
These formulations have specified levels of solvent and coating
solids by weight. Solvent base adhesive formulations contain
approximately 67 weight percent solvent and 33 weight percent
coating solids. Solvent base releases average about 95 weight
percent solvent and 5 weight percent coating solids. Solvents used
include toluene, xylene, heptane, hexane and methyl ethyl ketone.
The coating solids portion of the formulations consists of elastomers
(natural rubber, styrene-butadiene rubber, polyacrylates), tackifying
resins (polyterpenes, rosins, petroleum hydrocarbon resins, asphalts),
plasticizers (phthalate esters, polybutenes, mineral oil), and
fillers (zinc oxide, silica, clay).
The order of application is generally release coat, primer
coat (if any) and adhesive coat. A web must always have a release
coat before the adhesive can be applied. Primer coats are not
required on all products, generally being applied to improve the
performance of the adhesive.
Three basic categories of coating heads are used in the PSTL
industry. The type of coating head used has a great effect on the
quality of the coated product, but only a minor effect on overall
emissions. The first type operates by applying coating to the web
and scraping excess off to a desired thickness. Examples of this
type of coater are the knife coater, blade coater and metering rod
coater. The second category of coating head meters on a specific
amount of coating. Gravure and reverse roll coaters are the most
common examples. The third category of coating head does not
actually apply a surface coating, but rather it saturates the web
backing. The most common example in this category is the dip and
squeeze coater.
After solvent base coatings have been applied, the web moves
into the drying oven where the solvents are evaporated from the
web. The important characteristics of the drying oven operation
are:
source of heat
temperature profile
residence time
allowable hydrocarbon concentration In the dryer
oven air circulation
Two basic types of heating are used in conventional drying
ovens, direct and indirect. Direct heating routes the hot combustion
gases (blended with ambient air to the proper temperature) directly
8/82
Evaporation Loss Sources
4.2.2.9-3
-------
into the drying zone. With indirect heating, the incoming oven air
stream is heated in a heat exchanger with steam or hot combustion
gases but does not physically mix with them. Direct fired ovens
are more common in the PSTL industry because of their higher
thermal efficiency. Indirect heated ovens are less energy efficient
in both the production of steam and the heat transfer in the
exchanger.
Drying oven temperature control is an important consideration
in PSTL production. The oven temperature must be above the boiling
point of the applied solvent. However, the temperature profile
must be controlled by using multizoned ovens. Coating flaws known
as "craters" or "fish eyes" will develop if the initial drying
proceeds too quickly. These ovens are physically divided into
several sections, each with its own hot air supply and exhaust. By
keeping the temperature of the first zone low, and then gradually
increasing it in subsequent zones, uniform drying can be accomplished
without flaws. After exiting the drying oven, the continuous web
is wound on a roll, and the coating process is complete.
Emissions ' - The only pollutants emitted in significant
quantities from solvent base coating of pressure sensitive tapes
and labels are volatile organic compounds (VOC) from solvent
evaporation. In an uncontrolled facility, essentially all of the
solvent used in the coating formulation is emitted to the atmosphere.
Of these uncontrolled emissions, 80 to 95 percent are emitted with
the drying oven exhaust. Some solvent (from zero to five percent)
can remain in the final coated product, although this solvent will
eventually evaporate into the atmosphere. The remainder of applied
solvent is lost from a number of small sources as fugitive emissions.
The major VOC emission points in a PSTL surface coating operation
are indicated in Figure 4.2.2.9-1.
There are also VOC losses from solvent storage and handling,
equipment cleaning, miscellaneous spills, and coating formulation
mixing tanks. These emissions are not addressed here, as these
sources have a comparatively small quantity of emissions.
Fugitive solvent emissions during the coating process come
from the evaporative loss of solvent around the coating head and
from the exposed wet web prior to its entering the drying oven.
The magnitude of these losses is determined by the width of the
web, the line speed, the volatility and temperature of the solvent,
and the air turbulence in the coating area.
Two factors which directly determine total line emissions are
the weight (thickness) of the applied coating on the web and the
solvent/solids ratio of the coating formulations. For coating
4.2.2.9-4 EMISSION FACTORS 8/82
-------
formulations with a constant solvent/solids ratio during coating,
any increases in coating weight would produce higher levels of VOC
emissions. The solvent/solids ratio in coating formulations is not
constant industrywide. This ratio varies widely among products.
If a coating weight is constant, greater emissions will be produced
by increasing the weight percent solvent of a particular formulation.
These two operating parameters, combined with line speed, line
width and solvent volatility, produce a number of potentional mass
emission situations. Table 4.2.2.9-1 presents emission factors for
controlled and uncontrolled PSTL surface coating operations. The
potential amount of VOC emissions from the coating process is equal
to the total amount of solvent applied at the coating head.
I f -| Q
Controls ' - The complete air pollution control system for a
modern pressure sensitive tape or label surface coating facility
consists of two sections, the solvent vapor capture system and the
emission control device. The capture system collects VOC vapors
from the coating head, the wet web and the drying oven. The captured
vapors are directed to a control device to be either recovered (as
liquid solvent) or destroyed. As an alternate emission control
technique, the PSTL industry is also using low-VOC content coatings
to reduce their VOC emissions. Waterborne and hot melt coatings
and radiation cured prepolymers are examples of these low-VOC
content coatings. Emissions of VOC from such coatings are negligible
or zero. Low-VOC content coatings are not universally applicable
to the PSTL industry, but about 25 percent of the production in
this industry is presently using these innovative coatings.
Capture Systems - In a typical PSTL surface coating facility,
80 to 95 percent of VOC emissions from the coating process is
captured in the coating line drying ovens. Fans are used to
direct drying oven emissions to a control device. In some facilities
a portion of the drying oven exhaust is recirculated into the oven
instead of to a control device. Recirculation Is used to increase
the VOC concentration of the drying oven exhaust gases going to the
control device.
Another important aspect of capture in a PSTL facility
involves fugitive VOC emissions. Three techniques can be used to
collect fugitive VOC emissions from PSTL coating lines. The first
involves the use of floor sweeps and/or hooding systems around the
coating head and exposed coated web. Fugitive emissions collected
in the hoods can be directed into the drying oven and on to a
control device, or they can be sent directly to the control device.
The second capture technique involves enclosing the entire coating
line or the coating application and flashoff areas. By maintaining
8/82 Evaporation Loss Sources 4.2.2.9-5
-------
TABLE 4.2.2.9-1. EMISSION FACTORS FOR PRESSURE SENSITIVE
TAPE AND LABEL SURFACE COATING OPERATIONS
EMISSION FACTOR RATING: C
Nonme thane VOCa
Emission Points
Drying Oven Exhaust
Fugitives0
Product Retention
Control Device6
Total Emissions
Uncontrolled
kg/kg
db/lb)
0.30-0.95
0.01-0.15
0.01-0.05
1.0
85% Control
kg/kg
(Ib/lb)
0.01-0.095
0.01-0.05
0.045
0.15
90% Control
kg/kg
Clb/lb)
0.0025-0.0425
0.01-0.05
0.0475
0.10
Expressed as the mass of volatile organic compounds (VOC) emitted per
mass of total solvent used. Solvent is assumed to consist entirely of VOC.
b
References 1, 6-7, 9. Dryer exhaust emissions depend on coating line
operating speed, frequency of line downtime, coating composition and
oven design.
jJetermined by difference between total emissions and other point
sources. Magnitude is determined by size of the line equipment,
line speed, volatility and temperature of the solvents, and air
turbulence in the coating area.
References 6-3. Solvent in the product eventually evaporates into
the atmosphere.
References 1, 10, 17-13. Emissions are residual content In captured
solvent laden air vented after treatment. Controlled coating line
emissions are based on an overall reduction efficiency which is equal
to capture efficiency times control device efficiency. For 852
control, capture efficiency is 901 with a 95% efficient control device.
For 90Z control, capture efficiency is 95% with a 95% efficient control
device.
Values assume that uncontrolled coating lines eventually emit 100%
of all solvents used.
4.2.2.9-6
EMISSION FACTORS
8/82
-------
a slight negative pressure within the enclosure, a capture efficiency
of 100 percent is theoretically possible. The captured emissions
are directed by fans into the oven or to a control device. The
third capture technique is an expanded form of total enclosure.
The entire building or structure which houses the coating line acts
as an enclosure. The entire room air is vented to a control
device. The maintenance of a slight negative pressure ensures that
very few emissions escape the room.
The efficiency of any vapor capture system is highly dependent
on its design and its degree of integration with the coating line
equipment configuration. The design of any system must allow safe
and adequate access to the coating line equipment for maintenance.
The system must also be designed to protect workers from exposure
to unhealthy concentrations of the organic solvents used in the
surface coating processes. The efficiency of a well designed
combined dryer exhaust and fugitive capture system is 95 percent.
Control Devices - The control devices and/or techniques that
may be used to control captured VOC emissions can be classified
into two categories, solvent recovery and solvent destruction.
Fixed bed carbon adsorption is the primary solvent recovery technique
used in this industry. In fixed bed adsorption, the solvent
vapors are adsorbed onto the surface of activated carbon, and the
solvent is regenerated by steam. Solvent recovered in this manner
may be reused in the coating process or sold to a reclaimer. The
efficiency of carbon adsorption systems can reach 98 percent, but a
95 percent efficiency is more characteristic of continuous long
term operation.
The primary solvent destruction technique used in the PSTL
industry is thermal incineration, which can be as high as 99
percent efficient. However, operating experience with incineration
devices has shown that 95 percent efficiency is more characteristic.
Catalytic incineration could be used to control VOC emissions with
the same success as thermal incineration, but no catalytic devices
have been found in the industry.
The efficiencies of carbon adsorption and thermal incineration
control techniques on PSTL coating VOC emissions have been determined
to be equal. Control device emission factors presented in Table
4.2.2.9-1 represent the residual VOC content in the exhaust air
after treatment.
The overall emission reduction efficiency for VOC emission
control systems is equal to the capture efficiency times the
control device efficiency. Emission factors for two control
levels are presented in Table 4.2.2.9-1. The 85 percent control
8/82
Evaporation Loss Sources
4.2.2.9-7
-------
level represents 90 percent capture with a 95 percent efficient
control device. The 90 percent control level represents 95 percent
capture with a 95 percent efficient control device.
References for Section 4.2.2.9
1. The Pressure Sensitive Tape^jmd^ Label Surface Coating Industry -
Background Information Document, EPA-450/3-80-003a, U. S.
Environmental Protection Agency, Research Triangle Park, NC,
September 1980.
2. State of California Tape and Label Coaters Survey, California
Air Resources Board, Sacramento, CA, April 1978. Confidential.
3. M. R. Rifi, "Water Based Pressure Sensitive Adhesives, Structure
vs. Performance", presented at Technical Meeting on Water Based
Systems, Chicago, IL, June 21-22, 1978.
4. Pressure Sensitive Products and Adhesives Market, Frost and
Sullivan Inc., Publication No. 614, New York, NY, November
1978.
5. Silicone Release Questionnaire, Radian Corporation, Durham,
NC, May 4, 1979. Confidential.
6. Written communication from Frank Phillips, 3M Company, to G.
E. Harris, Radian Corporation, Durham, NC, October 5, 1978.
Confidential.
7. Written communication from R. F. Baxter, Avery International,
to G. E. Harris, Radian Corporation, Durham, NC, October 16,
1978. Confidential.
8. G. E. Harris, "Plant Trip Report, Shuford Mills, Hickory, NC",
Radian Corporation, Durham, NC, July 28, 1978.
9. T. P. Nelson, "Plant Trip Report, Avery International, Painesville,
OH", Radian Corporation, Durham, NC, July 26, 1979.
10. Control of Volatile Organic Emissions from Existing Stationary
Sources - Volume II; Surface Coating of Cans, Coils, Paper,
Fabrics, Automobiles, and Light Duty Trucks, EPA-450/2-77-008,
U. S. Environmental Protection Agency, Research Triangle Park,
NC, May 1977.
11. Ben Milazzo, "Pressure Sensitive Tapes", Adhesives Age,
22:27-28, March 1979.
4.2.2.9-5
EMISSION FACTORS
8/82
-------
12. T. P. Nelson, "Trip Report for Pressure Sensitive Adhesives -
Adhesives Research, Glen Rock, PA", Radian Corporation, Durham,
NC February 16, 1979.
13. T. P. Nelson, "Trip Report for Pressure Sensitive Adhesives -
Precoat Metals, St. Louis, MO", Radian Corporation, Durham, NC
August 28, 1979.
14. G. W. Brooks, "Trip Report for Pressure Sensitive Adhesives -
E. J. Gaisser, Incorporated, Stamford, CT", Radian Corporation,
Durham, NC, September 12, 1979.
15. Written communication from D. C. Mascone to J. R. Farmer,
Office of Air Quality Planning and Standards, U. S. Environmental
Protection Agency, Research Triangle Park, NC, June 11, 1980.
16. Written communication from R. E. Miller, Adhesives Research,
Incorporated, to T. P. Nelson, Radian Corporation, Durham, NC,
June 18, 1979.
17. A. F. Sidlow, Source Test Report Conducted at Fasson Products,
Division of Avery Corporation, Cucamonga, CA, San Bernardino
County Air Pollution Control District, San Bernardino, CA,
January 26, 1972.
18. R. Milner, et al., Source Test Report Conducted at Avery
Label Company, Monrovia, CA, Los Angeles Air Pollution Control
District, Los Angeles, CA, March 18, 1975.
8/82
Evaporation Loss Sources
4.2.2.9-9
-------
-------
4.2.2.10 METAL COIL SURFACE COATING
General^~2 - Metal coil surface coating (coil coating) is the linear process
by which protective or decorative organic coatings are applied to flat metal
sheet or strip packaged in rolls or coils. Although the physical
configurations of coil coating lines differ from one installation to another,
the operations generally follow a set pattern. Metal strip is uncoiled at the
entry to a coating line and is passed through a wet section, where the metal
is thoroughly cleaned and is given a chemical treatment to inhibit rust and to
promote coatings adhesion to the metal surface. In some installations, the
wet section contains an electrogalvanizing operation. Then the metal strip is
dried and sent through a coating application station, where rollers coat one
or both sides of the metal strip. The strip then passes through an oven where
the coatings are dried and cured. As the strip exits the oven, it is cooled
by a water spray and again dried. If the line is a tandem line, there is
first the application of a prime coat, followed by another of top or finish
coat. The second coat is also dried and cured in an oven, and the strip is
again cooled and dried before being rewound into a coil and packaged for
shipment or further processing. Most coil coating lines have accumulators at
the entry and exit that permit continuous metal strip movement through the
coating process while a new coil is mounted at the entry or a full coil
removed at the exit. Figure 4.2.2.10-1 is a flow diagram of a coil coating
line.
Coil coating lines process metal in widths ranging from a few centimeters
to 183 centimeters (72 inches), and in thicknesses of from 0.018 to 0.229
centimeters (0.007 to 0.090 inches). The speed of the metal strip through the
line is as high as 3.6 meters per second (700 feet per minute) on some of the
newer lines.
A wide variety of coating formulations is used by the coil coating
industry. The more prevalent coating types include polyesters, acrylics,
polyfluorocarbons, alkyds, vinyls and plastisols. About 85 percent of the
coatings used are organic solvent base and have solvent contents ranging from
near 0 to 80 volume percent, with the prevalent range being 40 to 60 volume
percent. Most of the remaining 15 percent of coatings are waterborne, but
they contain organic solvent in the range of 2 to 15~volume percent. High
solids coatings, in the form of plastisols, organosols and powders, are also
used to some extent by the industry, but the hardware is different for powder
applications.
The solvents most often used in the coil coating industry include xylene,
toluene, methyl ethyl ketone, Cellosolve Acetate (TM), butanol, diacetone
alcohol, Cellosolve (TM), Butyl Cellosolve (TM), Solvesso 100 and 150 (TM),
isophorone, butyl carbinol, mineral spirits, ethanol, nitropropane,
tetrahydrofuran, Panasolve (TM), methyl isobutyl ketone, Hisol 100 (TM),
Tenneco T-125 (TM), isopropanol, and diisoamyl ketone.
Coil coating operations can be classified in one of two operating
categories, toll coaters and captive coaters. The toll coater is a service
coater who works for many customers according to the needs and specifications
8/82
Evaporation Loss Sources
4.2.2.10-1
-------
•p-
•
to
•
to
o
NJ
*
i
SOLVENT LOSS |
FROM PRIME J
COATING AREA 1
SOLVENT LOSS
FROM TOPCOAT
COATING AREA
W
S
M
00
on
H
O
on
ACCUMULATOR
SPLICER
n
V IN
/
UNCOILING
METAL
i
I
i AIR 1
\
\
\ PRIME
N COATING
\K
WET SECTION
*cfe
PRIME
COATING
AREA
\
»
\
\
N
NATUHA
GAS
i
-I
N
\
X
JL,
PRIME
OVEN
'
TO CONTROL
EQUIPMENT
,4 AIR
PNATURAL
\ GAS
" ~ V
\ TOPCOAT
1 -V1
ACCUMULATOR
Tl M
"A
E
III
SHEAR
?
PRIME TOPCOAT TOPCOAT TOPCOAT RECOILING
QUENCH COATING OVEN QUENCH METAL
AREA
00
CO
10
Figure 4.2.2,10-1. Flow Diagram of model coil coating line.
-------
of each. The coated metal is delivered to the customer, who forms the end
products. Toll coaters use many different coating formulations and normally
use mostly organic solvent base coatings. Major markets for toll coating
operations include the transportation industry, the construction industry and
appliance, furniture and container manufacturers. The captive coater is
normally one operation in a manufacturing process. Many steel and aluminum
companies have their own coil coating operations, where the metal they produce
is coated and then formed into end products. Captive coaters are much more
likely to use water base coatings because the metal coated is often used for
only a few end products. Building products such as aluminum siding are one of
the more important uses of waterborne metal coatings.
Emission and Controls-*-"^ _ Volatile organic compounds (VOC) are the major
pollutants emitted from metal coil surface coating operations. Specific
operations that emit VOC are the coating application station, the curing oven
and the quench area. These are identified in Figure 4.2.2,10-1. VOC
emissions result from the evaporation of organic solvents contained in the
coating. The percentage of total VOC emissions given off at each emission
point varies from one installation to another, but, on the average, about 8
percent is given off at the coating application station, 90 percent the oven
and 2 percent the quench area. On most coating lines, the coating application
station is enclosed or hooded to capture fugitive emissions and to direct them
into the oven. The quench is an enclosed operation located immediately
adjacent to the exit end of the oven so that a large fraction of the emissions
given off at the quench is captured and directed into the oven by the oven
ventilating air. In operations such as these, approximately 95 percent of the
total emissions is exhausted by the oven, and the remaining 5 percent escapes
as fugitive emissions.
The rate of VOC emissions from individual coil coating lines may vary
widely from one installation to another. Factors that affect the emission
rate include VOC content of coatings as applied, VOC density, area of metal
coated, solids content of coatings as applied, thickness of the applied
coating and number of coats applied. Because the coatings are applied by
roller coating, transfer efficiency is generally considered to approach 100
percent and therefore does not affect the emission rate.
Two emission control techniques are widespread in the coil coating
industry, incineration and use of low VOC content coatings. Incinerators may
be either thermal or catalytic, both of which have been demonstrated to
achieve consistently a VOC destruction efficiency of 95 percent or greater.
When used with coating rooms or hoods to capture fugitive emissions,
incineration systems can reduce overall emissions by 90 percent or more.
Waterborne coatings are the only low VOC content coating technology that
is used to a significant extent in the coil coating industry. These coatings
have substantially lower VOC emissions than most of the organic solventborne
coatings. Waterborne coatings are used as an emission control technique most
often by installations that coat metal for only a few products, such as
building materials. Many such coaters are captive to the firm that produces
and sells the products fabricated from the coated coil. Because waterborne
8/82
Evaporation Loss Sources
4.2.2.10-3
-------
TABLE 4.2.2.10-1. VOC EMISSION FACTORS FOR COIL COATING3
EMISSION FACTOR RATING: C
Coatings
kg/hr (Ib/hr)
Average Normal range
kg/m2 (Ib/ft2)
Average
Normal range
Solventborne
uncontrolled
controlled
Waterborne
303
(669)
30
( 67)
50
(111)
50
(110
5
(11
3
(7
- 1,798
- 3,964)
- 180
- 396)
- 337
- 743)
0.060
(0.012)
0.0060
(0.0012)
0.0108
(0.0021)
0.027
(0.006
0.0027
(0.0006
0.0011
(0.0003
- 0.160
- 0.033)
- 0.0160
- 0.0033)
- 0.0301
- 0.0062)
aAll nonmethane VOC, Factors are calculated using the following equations and
the operating parameters given in Table 4.2.2.10-2.
(1)
0.623 ATVD
where
E = mass of VOC emissions per hour (Ib/hr)
A = Area of metal coated per hour (ft^)
= Line speed (ft/min) x strip width (ft) x 60 min/hr
V = VOC content of coatings (fraction by volume)
D = VOC Density (assumed to be 7.36 Ib/gal)
S = Solids content of coatings (fraction by volume)
T = Total dry film thickness of coatings applied (in).
The constant 0.623 represents conversion factors of 7.48 gal/ft^ divided
by the conversion factor of 12 in/ft.
(2)
E
M = -
A
where
M = mass of VOC emissions per unit area coated.
^Computed by assuming a 90 percent overall control efficiency (95 percent
capture and 95 percent removal by the control device).
4.2.2.10-4
EMISSION FACTORS
8/82
-------
TABLE 4.2.2.10-2. OPERATING PARAMETERS FOR SMALL, MEDIUM AND
LARGE COIL COATING LINESa
Solventborne coatings
Line
size
Small
Medium
Large
Line
speed
(ft/min)
200
300
500
Strip
width
(ft)
1.67
3
4
Total
dry film
thickness^
(in)
0.0018
0.0018
0.0018
VOC
content0
(fraction)
0.40
0.60
0.80
Solids
content0
(fraction)
0.60
0.40
0.20
VOC
densityb
(Ib/gal)
7.36
7.36
7.36
Waterborne coatings
Small
Medium
Large
200
300
500
1.67
3
4
0.0018
0.0018
0.0018
0.02
0.10
0.15
0.50
0.40
0.20
7.36
7.36
7.36
aObtained from Reference 3.
"Average value assumed for emission factor calculations. Actual values should
be used to estimate emissions from individual sources.
CA11 three values of VOC content and solids content were used in the
calculation of emission factors for each plant size to give maximum, minimum
and average emission factors.
coatings have not been developed for many coated metal coil uses, most toll
coaters use organic solventborne coatings and control their emissions by
incineration. Most newer incincerator installations use heat recovery to
reduce the operating cost of an incineration system.
Emission factors for coil coating operations and the equations used to
compute them are presented in Table 4.2.2.10-1. The values presented therein
represent maximum, minimum and average emissions from small, medium and large
coil coating lines. An average film thickness and an average solvent content
are assumed to compute the average emission factor. Values for the VOC
content near the maximum and minimum used by the industry are assumed for the
calculations of maximum and minimum emission factors.
The emission factors in Table 4.2.2.10-1 are useful in estimating VOC
emissions for a large sample of coil coating sources, but they may not be
8/82
Evaporation Loss Sources
4.2.2.10-5
-------
applicable to individual plants. To estimate the emissions from a specific
plant, operating parameters of the coil coating line should be obtained and
used in the equation given in the footnote to the Table. If different
coatings are used for prime and topcoats, separate calculations must be made
for each coat. Operating parameters on which the emission factors are based
are presented in Table 4.2.2.10-2.
References for Section 4.2.2.10
1. Metal Coil Surface Coating Industry - Background Information for Proposed
Standards, EPA-450/3-80-035a, U.S. Environmental Protection Agency,
Research Triangle Park, NC, October 1980.
2. Control of Volatile Organic Emissions from Existing Stationary Sources,
Volume II: Surface Coating of Cans, Coils, Paper, Fabrics, Automobiles,
and Light Duty Trucks, EPA-450/2-77-008, U.S. Environmental Protection
Agency, Research Triangle Park, NC, May 1977.
3. Unpublished survey of the Coil Coating Industry, Office of Water and
Waste Management, U.S. Environmental Protection Agency, Washington, DC,
1978.
4. Communication between Milton Wright, Research Triangle Institute,
Research Triangle Park, NC, and Bob Morman, Glidden Paint Company,
Strongville, OH, June 27, 1979.
5. Communication between Milton Wright, Research Triangle Institute,
Research Triangle Park, NC, and Jack Bates, DeSoto, Incorporated, Des
Plaines, IL, June 25, 1980.
6. Communication between Milton Wright, Research Triangle Institute,
Research Triangle Park, NC, and M. W. Miller, DuPont Corporation,
Wilmington, DE, June 26, 1980.
7. Communication between Milton Wright, Research Triangle Institute,
Research Triangle Park, NC, and H. B. Kinzley, Cook Paint and Varnish
Company, Detroit, MI, June 27, 1980.
8. Written communication from J. D. Pontius, Sherwin Williams, Chicago, IL,
to J. Kearney, Research Triangle Institute, Research Triangle Park, NC,
January 8, 1980.
9. Written communication from Dr. Maynard Sherwin, Union Carbide,
South Charleston, WV, to Milton Wright, Research Triangle Institute,
Research Triangle Park, NC, January 21, 1980.
10. Written communication from D. 0. Lawson, PPG Industries, Springfield, PA,
to Milton Wright, Research Triangle Institute, Research Triangle Park,
NC, February 8, 1980.
4.2.2.10-6
EMISSION FACTORS
8/82
-------
11. Written communication from National Coil Coaters Association,
Philadelphia, PA, to Office of Air Quality Planning and Standards, U.S.
Environmental Protection Agency, Research Triangle Park, NC, May 30,
1980.
12, Written communication from Paul Timmerman, Hanna Chemical Coatings
Corporation, Columbus, OH, to Milton Wright, Research Triangle Institute,
Research Triangle Park, NC, July 1, 1980.
8/82 Evaporation Loss Sources 4.2.2.10-7
-------
-------
4.2.2.11 LARGE APPLIANCE SURFACE COATING
General^ - Large appliance surface coating is the application of protective or
decorative organic coatings to preformed large appliance parts. For this
discussion, large appliances are defined as any metal range, oven, microwave
oven, refrigerator, freezer, washing machine, dryer, dishwasher, water heater
or trash compactor.
Regardless of the appliance, similar manufacturing operations are
involved. Coiled or sheet metal Is cut and stamped Into the proper shapes,
and the major parts welded together. The welded parts are cleaned with
organic degreasers or a caustic detergent (or both) to remove grease and mill
scale accumulated during handling, and the parts are then rinsed in one or
more water rinses. This Is often followed by a process to improve the grain
of the metal before treatment In a phosphate bath. Iron or zinc phosphate is
commonly used to deposit a microscopic matrix of crystalline phosphate on the
surface of the metal. This process provides corrosion resistance and
increases the surface area of the part, thereby allowing superior coating
adhesion. Often the highly reactive metal is protected with a rust Inhibitor
to prevent rusting prior to painting.
Two separate coatings have traditionally been applied to these prepared
appliance parts, a protective prime coating that also covers surface
imperfections and contributes to total coating thickness, and a final,
decorative top coat. Single coat systems, where only a prime coat or only a
top coat is applied, are becoming more common. For parts not exposed to
customer view, a prime coat alone may suffice. For exposed parts, a
protective coating may be formulated and applied so as to act as the top coat.
There are many different application techniques in the large appliance
industry, including manual, automatic and electrostatic spray operations, and
several dipping methods. Selection of a particular method depends largely
upon the geometry and use of the part, the production rate, and the type of
coating being used. Typical application of these coating methods is shown in
Figure 4.2.2.11-1.
A wide variety of coating formulations is used by the large appliance
industry. The prevalent coating types include epoxies, epoxy/acrylics,
acrylics and polyester enamels. Liquid coatings may use either an organic
solvent or water as the main carrier for the paint solids.
Waterborne coatings are of three major classes, water solutions, water
emulsions and water dispersions. All of the waterborne coatings, however,
contain a small amount (up to 20 volume percent) of organic solvent that acts
as a stabilizing, dispersing or emulsifying agent. Waterborne systems offer
some advantages over organic solvent systems. They do not exhibit as great an
increase In viscosity with increasing molecular weight of solids, they are
nonflammable, and they have limited toxicity. But because of the relatively
slow evaporation rate of water, it is difficult to achieve a smooth finish
with waterborne coatings. A bumpy "orange peel" surface often results. For
this reason, their main use in the large appliance industry is as prime coats.
5/83 Evaporation Loss Sources 4.2.2.11-1
-------
*•
•
SS
KJ
Direct-To-Metal Top Coat
o
V)
W
H
»
I *
H 03
O 3
8 I
Exterior
Parts
Interior
Parts
Cleansing and
Pretreatment
Section
Flowcoat
or
Dip Coat
VOC
VOC
(flashoff)
VOC
Prime Coat
To Assembly
Figure 4.2.2.11-1. Typical coating application methods in the large appliance industry.
-------
While conventional organic solventborne coatings also are used for prime
coats, they predominate as top coats. This is due in large part to the
controllability of the finish and the amenability of these materials to
application by electrostatic spray techniques. The most common organic
solvents are ketones, esters, ethers, aromatics and alcohols. To obtain or
maintain certain application characteristics, solvents are often added to
coatings at the plant. The use of powder coatings for top coats is gaining
acceptance in the industry. These coatings, which are applied as a dry powder
and then fused into a continuous coating film through the use of heat, yield
negligible emissions.
Emissions and Controlsl~2 - Volatile organic compounds (VOC) are the major
pollutants emitted from large appliance surface coating operations. VOC from
evaporation of organic solvents contained in the coating are emitted in the
application station, the flashoff area and the oven. An estimated 80 percent
of total VOC emissions is given off in the application station and flashoff
area. The remaining 20 percent occurs in the oven. Because the emissions are
widely dispersed, the use of capture systems and control devices is not an
economically attractive means of controlling emissions. While both
incinerators and carbon adsorbers are technically feasible, none is known to
be used in production, and none is expected. Improvements in coating
formulation and application efficiency are the major means of reducing
emissions.
Factors that affect the emission rate include the volume of coating used,
the coating's solids content, the coating's VOC content, and the VOC density.
The volume of coating used is a function of three additional variables, 1) the
area coated, 2) the coating thickness and 3) the application efficiency.
While a reduction in coating VOC content will reduce emissions, the
transfer efficiency with which the coating is applied (i.e., the volume
required to coat a given surface area) also has a direct bearing on the
emissions. A transfer efficiency of 60 percent means that 60 percent of the
coating solids consumed is deposited usefully onto appliance parts. The other
40 percent is wasted overspray. With a specified VOC content, an application
system with a high transfer efficiency will have lower emission levels than
will a system with a low transfer efficiency, because a smaller volume of
coating will coat the same surface area. Since not every application method
can be used with all parts and types of coating, transfer efficiencies in this
industry range from 40 to over 95 percent.
Although waterborne prime coats are becoming common, the trend for top
coats appears to be toward use of "high solids" solventborne material,
generally 60 volume percent or greater solids. As different types of coatings
are required to meet different performance specifications, a combination of
reduced coating VOC content and improved transfer efficiency is the most
common means of emission reduction.
In the absence of control systems that remove or destroy a known fraction
of the VOC prior to emission to the atmosphere, a material balance provides
the quickest and most accurate emissions estimate. An equation to calculate
5/83
Evaporation Loss Sources
4.2.2.11-3
-------
emissions is presented below. To the extent that the parameters of this
equation are known or can be determined, its use is encouraged. In the event
that both a prime coat and a top coat are used, the emissions from each must
be calculated separately and added to estimate total emissions. Because of
the diversity of product mix and plant sizes, it is difficult to provide
emission factors for "typical" facilities. Approximate values for several of
the variables in the equation are provided, however.
(6.234 x 10-*) P A t V0 DQ
E = + Ld Dd
VST
where
E = mass of VOC emissions per unit time (Ib/unit time)
P = units of production per unit time
A = area coated per unit of production (ft^)
t = dry coating thickness (mils)
V0 = proportion of VOC in the coating (volume fraction), as received*
DQ = density of VOC solvent in the coating (Ib/gal), as received*
Vg = proportion of solids in the coating (volume fraction), as received*
T = transfer efficiency (fraction - the ratio of coating solids
deposited onto appliance parts to the total amount of coating solids
used. See Table 4.2.2.11-1).
Ld = volume of VOC solvent added to the coating per unit time (gal/unit
time).
Dd = density of VOC solvent added (Ib/gal).
The constant 6.234 x 10~* is the product of two conversion factors:
8.333 x 10-5 ft 7.48i gai
and .
mil ft3
If all the data are not available to complete the above equation, the
following may be used as approximations:
VQ - 0.38
DQ = 7.36 Ib/gal
Vs - 0.62
Ld = 0 (assumes no solvent added at the plant).
*
If known, Vo, DQ and Vg for the coating as applied (i.e., diluted) may be
used in lieu of the values for the coating as received, and the term LdDd
deleted.
4.2.2.11-4 EMISSION FACTORS 5/83
-------
TABLE 4.2.2.11-1. TRANSFER EFFICIENCIES
Application Method
Air atomized spray
Airless spray
Manual electrostatic spray
Flow coat
Dip coat
Nonrotational automatic electrostatic spray
Rotating head automatic electrostatic spray
Electrodeposltion
Powder
Transfer
Efficiency (T)
0.40
0.45
0.60
0.85
0.85
0.85
0.90
0.95
0.95
TABLE 4.2.2.11-2. AREAS COATED AND COATING THICKNESS
Appliance
Compactor
Dishwasher
Dryer
Freezer
Microwave oven
Range
Refrigerator
Washing machine
Water heater
Prime
A(ft2)
20
10
90
75
8
20
75
70
20
Coat
t(mils)
0.5
0.5
0.6
0.5
0.5
0.5
0.5
0.6
0.5
Top
20
10
30
75
8
30
75
25
20
Coat
t(mils)
0.8
0.8
1.2
0.8
0.8
0.8
0.8
1.2
0.8
5/83
Evaporation Loss Sources
4.2.2.11-5
-------
In the absence of all operating data, an emission estimate of 49.9 Mg (55
tons) of VOC per year may be used for the average appliance plant. Because of
the large variation in emissions among plants (from less than 10 to more than
225 Mg [10 to 250 tons] per year), caution is advised when this estimate is
used for anything except approximations for a large geographical area. Most
of the known large appliance plants are in localities considered nonattainment
areas for achieving the national ambient air quality standard (NAAQS) for
ozone. The 49.9-Mg-per-year average is based on an emission limit of 2,8
Ib/VOC per gallon of coating (minus water), which is the limit recommended by
the Control Techniques Guideline (CTG) applicable in those areas. For a plant
operating in an area where there are no emission limits, the emissions may be
four times greater than from an identical plant subject to the CTG recommended
limit.
References for Section 4.2.2.11
1. Industrial Surface Coating; Appliances - Background Information for
Proposed Standards, EPA-450/3-80-037a, U. S. Environmental Protection
Agency, Research Triangle Park, NC, November 1980.
2. Industrial Surface Coating: Large Appliances - Background Information
for Promulgated Standards, EPA 450/3-80-037b, U. S. Environmental
Protection Agency, Research Triangle Park, NC, 27711, October 1982.
4.2.2.11-6 EMISSION FACTORS 5/83
-------
4.2.2.12 METAL FURNITURE SURFACE COATING
4.2.2.12.1 General
The metal furniture surface coating process is a multistep operation
consisting of surface cleaning and coatings application and curing. Items
such as desks, chairs, tables, cabinets, bookcases and lockers are normally
fabricated from raw material to finished product in the same facility. The
industry uses primarily solventborne coatings, applied by spray, dip or flow
coating processes. Spray coating is the most common application technique
used. The components of spray coating lines vary from plant to plant but
generally consist of the following:
Three to five stage washer
Dryoff oven
Spray booth
Flashoff area
Bake oven
Items to be coated are first cleaned in the washer to remove any grease,
oil or dirt from the surface. The washer generally consists of an alkaline
cleaning solution, a phosphate treatment to improve surface adhesion charac-
teristics, and a hot water rinse. The items are then dried in an oven and
conveyed to the spray booth, where the surface coating is applied. After this
application, the items are conveyed through the flashoff area to the bake
oven, where the surface coating is cured. A diagram of these consecutive
steps is presented in Figure 4.2.2.12-1. Although most metal furniture products
receive only one coat of paint, some facilities apply a prime coat before the
top coating to improve the corrosion resistance of the product. In these
cases, a separate spray booth and bake oven for application of the prime coat
are added to the line, following the dryoff oven.
The coatings used in the industry are primarily solventborne resins,
including acrylics, amines, vinyls and cellulosics. Some metallic coatings
are also used on office furniture. The solvents used are mixtures of aliphatics,
xylene, toluene and other aromatics. Typical coatings that have been used in
the industry contain 65 volume percent solvent and 35 volume percent solids.
Other types of coatings now being used in the industry are waterborne, powder
and solventborne high solids coatings.
4.2.2.12.2 Emissions and Controls
Volatile organic compounds (VOC) from the evaporation of organic solvents
in the coatings are the major pollutants from metal furniture surface coating
operations. Specific operations that emit VOC are the coating application
process, the flashoff area and the bake oven. The percentage of total VOC
emissions given off at each emission point varies from one installation to
another, but on the average spray coating line, about 40 percent is given off
at the application station, 30 percent in the flashoff area, and 30 percent in
the bake oven.
5/83
Evaporation Loss Sources
4.2.2.12-1
-------
10
ro
10
U)
s
Three stage washer
Dryoff oven
Conveyor
Bake oven
Spray booth
Manual touchup spra^ booth
t
Flashoff
00
00
Figure 4.2.2.12-1. Example automated spray coating lines, with manual touchup.
-------
Factors affecting the quantity of VOC emitted from metal furniture surface
coating operations are the VOC content of the coatings applied, the solids
content of coatings as applied and the transfer efficiency. Knowledge of both
the VOC content and solids content of coatings is necessary in cases where the
coating contains other components, such as water.
The transfer efficiency (volume fraction of the solids in the total
consumed coating that remains on the part) varies with the application technique.
Transfer efficiency for standard (or ordinary) spraying ranges from 25 to
50 percent. The range for electrostatic spraying, a method that uses an
electrical potential to increase transfer efficiency of the coating solids, is
from 50 to 95 percent, depending on part size and shape. Powder coating
systems normally capture and recirculate overspray material and, therefore,
are considered in terms of a "utilization rate" rather than a transfer efficiency.
Most facilities achieve a powder utilization rate of 90 to 95 percent.
Typical values for transfer efficiency with various application devices
are in Table 4.2.2.12-1.
Two types of control techniques are available to reduce VOC emissions
from metal furniture surface coating operations. The first technique makes
use of control devices such as carbon adsorbers and thermal or catalytic
incinerators to recover or destroy VOC before it is discharged into the ambient
air. These control methods are seldom used in the industry, however, because
the large volume of exhaust air and low concentrations of VOC in the exhaust
reduce their efficiency. The more prevalent control technique involves reducing
the total amount of VOC likely to be evaporated and emitted. This is accomplished
by use of low VOC content coatings and by improvements in transfer efficiency.
New coatings with relatively low VOC levels can be used instead of the traditional
high VOC content coatings. Examples of these new systems include waterborne
coatings, powder coatings, and higher solids coatings. Improvements in coating
transfer efficiency decrease the amount that must be used to achieve a given
film thickness, thereby reducing emissions of VOC to the ambient air. By
using a system with increased transfer efficiency (such as electrostatic
spraying) and lower VOC content coatings, VOC emission reductions can approach
those achieved with control devices.
The data presented in Tables 4.2.2.12-2 and 4.2.2.12-3 are representative
of values which might be obtained from existing plants with similar operating
characteristics. Each plant has its own combination of coating formulations,
application equipment and operating parameters. It is recommended that,
whenever possible, plant specific values be obtained for all variables when
calculating emission estimates.
Another method that also may be used to estimate emissions for metal
furniture coating operations involves a material balance approach. By assuming
that all VOC in the coatings applied are evaporated at the plant site, an
estimate of emissions can be calculated using only the coating formulation and
data on the total quantity of coatings used in a given time period. The
percentage of VOC solvent in the coating, multiplied by the quantity of coatings
used yields the total emissions. This method of emissions estimation avoids
the requirement to use variables such as coating thickness and transfer
efficiency, which are often difficult to define precisely.
5/83
Evaporation Loss Sources
4.2.2.12-3
-------
TABLE 4.2.2.12-1. COATING METHOD TRANSFER EFFICIENCIES
Application Methods Transfer Efficiency
(Te)
Air atomized spray 0.25
Airless spray 0.25
Manual electrostatic spray 0.60
Nonrotational automatic
electrostatic spray
Rotating head electrostatic fi „
spray (manual and automatic)
Dip coat and flow coat 0.90
Electrodeposition 0.95
TABLE 4.2.2.12-2. OPERATING PARAMETERS FOR COATING OPERATIONS
Plant Operating Number of lines Line speed Surface area Liters of ,
size schedule (m/min) coated/yr coating used
(hr/yr) (m2)
Small 2,000
Medium 2,000
Large 2,000
1
(1 spray booth)
2
(3 booths/line)
10
(3 booths/line)
2.5
2.4
4.6
45,000
780,000
4,000,000
5,000
87,100
446,600
aLine speed is not used to calculate emissions, only to characterize
plant operations.
Using 35 volume % solids coating, applied by electrostatic spray at
65 % transfer efficiency.
4.2.2.12-4 EMISSION FACTORS 5/83
-------
TABLE 4.2.2.12-3. EMISSION FACTORS
FOR VOC FROM SURFACE COATING OPERATIONS3'
Plant Size and Control Techniques
VOC Emissions
kg/m2 coated kg/year kg/hour
Small
Uncontrolled emissions
65 volume % high solids coating
Waterhorne coating
Medium
Uncontrolled emissions
65 volume % high solids coating
Waterhorne coating
Large
Uncontrolled emissions
65 volume % high solids coating
Waterborne coating
.064
.019
.012
.064
.019
.012
.064
.019
.012
2,875
835
520
49,815
14,445
8,970
255,450
74,080
46,000
1.44
.42
.26
24.90
7.22
4.48
127.74
37.04
23.00
Calculated using the parameters given in Table 4.2-2.12-2 and the
following equation. Values have been rounded off.
E =
0.0254 A T V D
S Te
where E = Mass of VOC emitted per hour (kg)
A = Surface area coated per hour (m2)
T = Dry film thickness of coating applied (mils)
V = VOC content of coating; including dilution
solvents added at the plant (fraction by volume)
D = VOC density (assumed to be 0.88 kg/1)
S = Solids content of coating (fraction by volume)
Te = Transfer efficiency (fraction)
The constant 0.0254 converts the volume of dry film applied per m2
to liters.
Example: The VOC emission from a medium size plant applying 35
volume % solids coatings and the parameters given in
Table 4.2.2.12-3.
Kilograms of VOC/hr -
_ 0.0254(390m2/hr)(l mil)(0.65)(0.88 kg/1)
(0.35)(0.65)
=24.9 kilograms of VOC per hour
^Nominal values of T, V, S and Te:
T = 1 mil (for all cases)
V =0.65 (uncontrolled), 0.35 (65 volume % solids), 0.117 (waterborne)
S = 0.35 (uncontrolled, 0.65 (65 volume % solids), 0.35 (waterborne)
Te = 0.65 (for all cases)
5/83
Evaporation Loss Sources
4.2.2.12-5
-------
Reference for Section 4.2.2.12
1- Surface Coating of Metal Furniture - Background Information for Proposed
Standards, EPA-450/3-80-007a, U. S. Environmental Protection Agency Research
Triangle Park, NC, September 1980.
4.2.2.12-6 EMISSION FACTORS 5/83
-------
4.3 STORAGE OF ORGANIC LIQUIDS
4.3.1 Process Description
Storage vessels containing organic liquids can be found in many
industries, including (l) petroleum producing and refining, (2) petro-
chemical and chemical manufacturing, (3) bulk storage and transfer
operations, and (4) other industries consuming or producing organic liquids.
Organic liquids in the petroleum industry, usually called petroleum liquids,
generally are mixtures of hydrocarbons having dissimilar true vapor pressures
(for example, gasoline and crude oil). Organic liquids in the chemical
industry, usually called volatile organic liquids, are composed of pure
chemicals or mixtures of chemicals with similar true vapor pressures (for
example, benzene or a mixture of isopropyl and butyl alcohols).
Five basic tank designs are used for organic liquid storage vessels,
fixed roof, external floating roof, internal floating roof, variable vapor
space, and pressure (low and high).
Fixed Roof Tanks - A typical fixed roof tank is shown in Figure 4.3-1.
This type of tank consists of a cylindrical steel shell with a permanently
affixed roof, which may vary in design from cone or dome shaped to flat.
Fixed roof tanks are commonly equipped with a pressure/vacuum vent
that allows them to operate at a slight internal pressure or vacuum to
prevent the release of vapors during very small changes in temperature,
pressure or liquid level. Of current tank designs, the fixed roof tank is
the least expensive to construct and is generally considered the minimum
acceptable equipment for storage of organic liquids.
Fresoure/vacuuB
Valve
Gauge Hatch
Manhole
ManlMlc
Nozzle (For
submerged fill
or drainage)
9/85
Figure 4.3-1. Typical fixed roof tank.1
Evaporation Loss Sources
4.3-1
-------
External Floating Roof Tanks - A typical external floating roof tank is
shown in Figure 4.3-2. This type of tank consists of a cylindrical steel
shell equipped with a roof which floats on the surface of the stored liquid,
rising and falling with the liquid level. The liquid surface is completely
covered by the floating roof, except at the small annular space between the
roof and the tank wall. A seal (or seal system) attached to the roof
contacts the tank wall (with small gaps, in some cases) and covers the
annular space. The seal slides against the tank wall as the roof is raised
or lowered. The purpose of the floating roof and the seal (or seal system)
is to reduce the evaporation loss of the stored liquid.
Internal Floating Roof Tanks - An internal floating roof tank has both a
permanent fixed roof and a deck inside. The deck rises and falls with the
liquid level and either floats directly on the liquid surface (contact
deck) or rests on pontoons several inches above the liquid surface (non-
contact deck). The terms "deck" and "floating roof" can be used
interchangeably in reference to the structure floating on the liquid inside
the tank. There are two basic types of internal floating roof tanks, tanks
in which the fixed roof is supported by vertical columns within the tank,
and tanks with a self-supporting fixed roof and no internal support columns.
Fixed roof tanks that have been retrofitted to employ a floating deck are
typically of the first type, while external floating roof tanks typically
have a self-supporting roof when converted to an internal floating roof
tank. Tanks initially constructed with both a fixed roof and a floating
deck may be of either type.
The deck serves to restrict evaporation of the organic liquid stock.
Evaporation losses from decks may come from deck fittings, nonwelded deck
seams, and the annular space between the deck and tank wall. Typical
contact deck and noncontact deck internal floating roof tanks are shown in
4.3-2
Figure 4.3-2. External floating roof tank.1
EMISSION FACTORS
9/85
-------
Figure 4.3-3. Contact decks can be aluminum sandwich panels with a honey-
comb aluminum core floating in contact with the liquid, or pan steel decks
floating in contact with the liquid, with or without pontoons. Typical
noncontact decks have an aluminum deck or an aluminum grid framework
supported above the liquid surface by tubular aluminum pontoons or other
bouyant structures. Both types of deck incorporate rim seals, which slide
against the tank wall as the deck moves up and down. In addition, these
tanks are freely vented by circulation vents at the top of the fixed roof.
The vents minimize the possibility of organic vapor accumulation in con-
centrations approaching the flammable range. An internal floating roof
tank not freely vented is considered a pressure tank.
Pressure Tanks - There are two classes of pressure tanks in general use,
low pressure (2.5 to 15 psig) and high pressure (higher than 15 psig).
Pressure tanks generally are used for storage of organic liquids and gases
with high vapor pressures and are found in many sizes and shapes, depending
on the operating pressure of the tank. Pressure tanks are equipped with a
pressure/vacuum vent that is set to prevent venting loss from boiling and
breathing loss from daily temperature or barometric pressure changes. High
pressure storage tanks can be operated so that virtually no evaporative or
working losses occur. In low pressure tanks, working losses can occur with
atmospheric venting of the tank during filling operations.
Variable Vapor Space Tanks - Variable vapor space tanks are equipped with
expandable vapor reservoirs to accomodate vapor volume fluctuations attribut-
able to temperature and barometric pressure changes. Although variable
vapor space tanks are sometimes used independently, they are normally
connected to the vapor spaces of one or more fixed roof tanks. The two
most common types of variable vapor space tanks are lifter roof tanks and
flexible diaphragm tanks.
Lifter roof tanks have a telescoping roof that fits loosely around the
outside of the main tank wall. The space between the roof and the wall is
closed by either a wet seal, which is a trough filled with liquid, or a dry
seal, which uses a flexible coated fabric.
Flexible diaphragm tanks use flexible membranes to provide expandable
volume. They may be either separate gasholder units or integral units
mounted atop fixed roof tanks.
4.3.2 Emissions And Controls
Emission sources from organic liquids in storage depend upon the tank
type. Fixed roof tank emission sources are breathing loss and working
loss. External or internal floating roof tank emission sources are standing
storage loss and withdrawal loss. Standing storage loss includes rim seal
loss, deck fitting loss and deck seam loss. Pressure tanks and variable
vapor space tanks are also emission sources.
Fixed Roof Tanks - Two significant types of emissions from fixed roof tanks
are breathing loss and working loss. Breathing loss is the expulsion of
vapor from a tank through vapor expansion and contraction, which are the
results of changes in temperature and barometric pressure. This Idss
occurs without any liquid level change in the tank.
9/85 Evaporation Loss Sources 4.3-3
-------
Canter Vant
V*nt -,
Manhole
Tank Support Col1
with Column Well
Contact Deck Type
Center Vent
Vent
Rim
Pontoon*
Manhole
Rln Plate
Rim Pontoon*
Tank Support Colinan
with Column Well
Vapor Space
Noncontact Deck Type
4.3-4
Figure 4.3-3. Internal floating roof tanks.1
EMISSION FACTORS
9/85
-------
The combined loss from filling and emptying is called working loss.
Filling loss comes with an increase of the liquid level in the tank, when
the pressure inside the tank exceeds the relief pressure and vapors are
expelled from the tank. Emptying loss occurs when air drawn into the tank
during liquid removal becomes saturated with organic vapor and expands,
thus exceeding the capacity of the vapor space.
The following equations, provided to estimate emissions, are applicable
to tanks with vertical cylindrical shells and fixed roofs. These tanks
must be substantially liquid and vapor tight and must operate approximately
at atmospheric pressure. Fixed roof tank breathing losses can be estimated
from2:
D1.73HO.S1AT0.50F CK (1)
t VJ
where:
L_ = fixed roof breathing loss (Ib/yr)
is
MV — molecular weight of vapor in storage tank (Ib/lb mole), see
Note 1
P. = average atmospheric pressure at tank location (psia)
P - true vapor pressure at bulk liquid conditions (psia), see Note 2
D = tank diameter (ft)
H - average vapor space height, including roof volume correction
(ft), see Note 3
AT = average ambient diurnal temperature change (°F)
Fp = paint factor (dimensionless), see Table 4.3-1
C — adjustment factor for small diameter tanks (dimensionless), see
Figure 4.3-4
Kp = product factor (dimensionless), see Note 4
V_j
Notes: (1) The molecular weight of the vapor, MV, can be determined by
Table 4.3-2 for selected petroleum liquids and volatile
organic liquids or by analysis of vapor samples. Where
mixtures of organic liquids are stored in a tank, M,, can be
estimated from the liquid composition. As an example of the
latter calculation, consider a liquid known to be composed
of components A and B with mole fractions in the liquid X
and X, , respectively. Given the vapor pressures of the pure
9/85 Evaporation Loss Sources 4.3-5
-------
TABLE 4.3-1. PAINT FACTORS FOR FIXED ROOF TANKS'
Tank color
Roof
Shell
Paint factors (Fp)
Paint condition
Good
Poor
White
Aluminum (specular)
White
Aluminum (specular)
White
Aluminum (diffuse)
White
Light gray
Medium gray
White
White
Aluminum (specular)
Aluminum (specular)
Aluminum (diffuse)
Aluminum (diffuse)
Gray
Light gray
Medium gray
1.00
1.04
1.16
1.20
1.30
1.39
1.30
1.33
1.40
Reference 2.
Estimated from the ratios of the seven preceding paint factors.
1.0
,
o
•
00
< 0.6
o
*
*»
o
•
10 20
TANK DIAMETER, ft
30
1.15
1.18
1.24
1.29
1.38
1.46
1.38
1.44h
1.58*
Figure 4.3-4. Adjustment factor (C) for small diameter tanks.2
4.3-6 EMISSION FACTORS 9/85
-------
oo
Ul
TABLE 4.3-2. PHYSICAL PROPERTIES OF TYPICAL ORGANIC LIQUIDS£
•n
o
o
B
O
tn
en
CO
O
n
re
en
Organic liquid
Petroleum Liquids
Gasoline RVP 13
Gasoline RVP 10
Gasoline RVP 7
Crude oil RVP 5
Jet naphtha (JP-4)
Jet kerosene
Distillate fuel no. 2
Residual oil no. 6
Volatile Organic Liquids
Acetone
Acrylonitrile
Benzene
Carbon disulfide
Carbon tetrachloride
Chloroform
Cyclohexane
1,2-Dichloroethane
Ethylacetate
Ethyl alcohol
Isopropyl alcohol
He thy 1 alcohol
Hethylene chloride
Hethylethyl ketone
Hethylmetha cry late
1,1, 1-Trichlo roe thane
Trichloroethylene
Toluene
Vinylacetate
Vapor
molecular
weight
& 60°F
62
66
68
50
80
130
130
190
58
53
78
76
154
119
84
99
88
46
60
32
85
72
100
133
131
92
86
Product
density (d) ,
Ib/gal
g 60°F
5.
5.
5.
7.
6.
7,
7.
7.
6.
6.
7.
10.
13.
12.
6.
10.
7.
6.
6.
6.
11.
6.
7.
11.
12.
7.
7.
6
6
6
1
4
0
1
9
6
8
4
6
4
5
5
5
6
6
6
6
1
7
9
2
3
3
8
Condensed
vapor
density (w) ,
Ib/gal
@ 60°F
4.9
5.1
5.2
4.5
5.4
6.1
6.1
6.4
6.6
6.8
7.4
10.6
13.4
12.5
6.5
10.5
7.6
6.6
6.6
6.6
11.1
6.7
7.9
11.2
12.3
7.3
7.8
t
40°F
4.7
3.4
2.3
1.8
0.8
0.0041
0.0031
0.00002
1.7
0.8
0.6
3.0
0.8
1.5
0.7
0.6
0.6
0.2
0.2
0.7
3.1
0.7
0.1
0.9
0.5
0.2
0.7
True vapor
50°F
5.7
4.2
2.9
2.3
1.0
0.0060
0.0045
0.00003
2.2
1.0
0.9
3.9
1.1
1.9
0.9
0.8
0.8
0.4
0.3
1.0
4.3
0.9
0.2
1.2
0.7
0.2
1.0
60°F
6.9
5.2
3.5
2.8
1.3
0.0085
0.0074
0.00004
2.9
1.4
1.2
4.8
1.4
2.5
1.2
1.0
1.1
0.6
0.6
1.4
5.4
1.2
0.3
1.6
0.9
0.3
1.3
pressure in psia at:
70°F
8.3
6.2
4.3
3.4
1.6
0.011
0.0090
0.00006
3.7
1.8
1.5
6.0
1.8
3.2
1.6
1.4
1.5
0.9
0.7
2,0
6.8
1.5
0.6
2.0
1.2
0.4
1.7
80°F
9.9
7.4
5.2
4.0
1.9
0.015
0.012
0,00009
4.7
2.4
2.0
7.4
2.3
4.1
2. 1
1.7
1.9
1.2
0.9
2.6
8.7
2.1
0.8
2.6
1.5
0.6
2.3
90°F
11.7
8.8
6.2
4.8
2.4
0.021
0.016
0.00013
5.9
3.1
2.6
9.2
3.0
5.2
2.6
2.2
2.5
1.7
1.3
3.5
10.3
2.7
1.1
3.3
2.0
0.8
3.1
100°F
13.8
10.5
7.4
5.7
2.7
0.029
0.022
0.00019
7.3
4.0
3.3
11.2
3.8
6.3
3.2
2.8
3.2
2.3
1.8
4.5
13.3
3.3
1.4
4.2
2.0
1.0
4.0
.References 3-4.
For a more comprehensive listing of volatile organic liquids, see Reference 3.
RVP = Reid vapor pressure in psia.
Oo
I
—I
-------
components, Pa and P, , and the molecular weights of the pure
components, Mfl and Mb> My is calculated:
-M
where: P , by Raoult's law, is:
P. = P X + P, X,
t a a bo
Pt
(2) True vapor pressures for organic liquids can be determined
from Figures 4.3-5 or 4.3-6, or Table 4.3-2. In order to
use Figures 4.3-5 or 4.3-6, the stored liquid temperature, T_,
must be determined in degrees Fahrenheit. T_ is deter-
mined from Table 4.3-3, given the average annual ambient
temperature, T , in degrees Fahrenheit. True vapor pressure
is the equilibrium partial pressure exerted by a volatile
organic liquid, as defined by ASTM-D-2879 or as obtained
from standard reference texts. Reid vapor pressure is the
absolute vapor pressure of volatile crude oil and volatile
nonviscous petroleum liquids, except liquified petroleum
gases, as determined by ASTM-D-323.
(3) The vapor space in a cone roof is equal in volume to a
cylinder, which has the same base diameter as the cone and is
one third the height of the cone. If information is not
available, assume H equals one half tank height.
(4) For crude oil, K_ = 0.65. For all other organic liquids,
Kc = 1.0.
Fixed roof tank working losses can he estimated from2:
Ly = 2.40 x io-s MVPVNKNKC (2)
where:
L.; = fixed roof working loss (Ib/year)
My = molecular weight of vapor in storage tank (Ib/lb mole), see Note 1
to Equation 1
P = true vapor pressure at bulk liquid temperature (psia) , see Note 2
to Equation 1
V = tank capacity (gal)
N" = number of turnovers per year (dimensionless)
V - Total throughput per year (gal)
Tank capacity, V (gal)
4.'i-S EMISSION FACTORS 9/85
-------
I— 0.5
>
w
IE
• 8
• 9
10
11
12
13
14
IS
20
25
1
M
Ul
a
,— 2
_ 3
_ 4
— S
— 10
1—15
1
130 — =
120
110
100 — =
90
80
-I s
—I 111
70
60
SO
40
30
20 —-
10
0 —^
^ S
II
•3 3
-t GC
"3 o
I IS
Figure 4.3-5. True vapor pressure (P) of crude oils (2-15 psi RVP).1
9/85
Evaporation Loss Sources
4.3-9
-------
0.20
0.30
0.40
120 —
j— 0.50
— 0.60
— 0.70
— 0.80
£- 0.90
1— 1.00
p
i-
tt .
3 ~
"1 L~
tf\ r-
1.50
2.00
2.50
110
100-
90 —
I | 3,0
^ P- 3.50
X tr
I- b_ 4.00
5-
u
-------
KN
KC
Note:
turnover factor (dimensionless), see Figure 4.3-7
product factor (dimensionless), see Note 1
(1) For crude oil, Kr - 0.84. For all other organic liquids,
Kc=1.0.
TABLE 4.3-3. AVERAGE STORAGE TEMPERATURE (Tq)
AS A FUNCTION OF TANK PAINT COLORa
Tank color
Average storage temperature,
S
White
Aluminum
Gray
Black
2.5
3.5
5.0
.Reference 5.
T. is the average annual ambient temperature in
degrees Fahrenheit.
TURNOVER FACTOR, KN
O O O O Hi
• * * • •
D 10 -P* ON 00 O
I
\
\
V
^,
— — __
• —
0 100
TURNOVERS PER YEAR -
200 300 400
ANNUAL THROUGHPUT
TANK CAPACITY
Note: For 36 turnovers per year or less, KN - 1.0
Figure 4.3-7. Turnover factor (Kj for fixed roof tanks.
9/85 Evaporation Loss Sources 4.3-11
-------
Several methods are used to control emissions from fixed roof tanks.
Emissions from fixed roof tanks can be controlled by the installation of an
internal floating roof and seals to minimize evaporation of the product
being stored. The control efficiency of this method ranges from 60 to
99 percent, depending on the type of roof and seals installed and on the
type of organic liquid stored.
The vapor recovery system collects emissions from storage vessels and
converts them to liquid product. Several vapor recovery procedures may be
used, including vapor/liquid absorption, vapor compression, vapor cooling,
vapor/solid adsorption, or a combination of these. The overall control
efficiencies of vapor recovery systems are as high as 90 to 98 percent,
depending on the method used, the design of the unit, the composition of
vapors recovered, and the mechanical condition of the system.
Another method of emission control on fixed roof tanks is thermal
oxidation. In a typical thermal oxidation system, the air/vapor mixture is
injected through a burner manifold into the combustion area of an incin-
erator. Control efficiencies for this system can range from 96 to
99 percent.
External And Internal Floating Roof Tanks - Total emissions from floating
roof tanks are the sum of standing storage losses and withdrawal losses.
Standing storage loss from internal floating roof tanks includes rim seal,
deck fitting, and deck seam losses. Standing storage loss from external
floating roof tanks, as discussed here, includes only rim seal loss, since
deck fitting loss equations have not been developed. There is no deck seam
loss, because the decks have welded sections.
Standing storage loss from external floating roof tanks, the major
element of evaporative loss, results from wind induced mechanisms as air
flows across the top of an external floating roof tank. These mechanisms
may vary, depending upon the type of seals used to close the annular vapor
space between the floating roof and the tank wall. Standing storage emis-
sions from external floating roof tanks are controlled by one or two separate
seals. The first seal is called the primary seal, and the other, mounted
above the primary seal, is called the secondary seal. There are three basic
types of primary seals used on external floating roofs, mechanical (metallic
shoe), resilient (nonmetallic), and flexible wiper. The resilient seal can
be mounted to eliminate the vapor space between the seal and liquid surface
(liquid mounted), or to allow a vapor space between the seal and liquid
surface (vapor mounted). A primary seal serves as a vapor conservation
device by closing the annular space between the edge of the floating roof
and the tank wall. Some primary seals are protected by a metallic weather
shield. Additional evaporative loss may be controlled by a secondary seal.
Secondary seals can be either flexible wiper seals or resilient filled
seals. Two configurations of secondary seal are currently available, shoe
mounted and rim mounted. Although there are other seal system designs, the
systems described here compose the majority in use today. See Figure 4.3-8
for examples of primary and secondary seal configurations.
Typical internal floating roofs generally incorporate two types of
primary seals, resilient foam filled seals and wipers. Similar in design
4.3-12 EMISSION FACTORS 9/85
-------
/I
TANK
WALL
METALLIC WEATHER
SHIELD
'FLOATING ROOF
SEAL FABRIC
RESILIENT FOAM
ELASTOMERIC WIPER SEAL
a. Liquid mounted seal with
weather shield.
RIM-MOUNTED
' SECONDARY SEAL
c. Vapor mounted seal with
rim mounted secondary seal.
NONCONTACT INTERNAL
/ FLOATING ROOF
PONTOON
METAL SEAL RING
PONTOON'
b. Elastomeric wiper seal.
RIM-MOUNTED
SECONDARY SEAL
d. Metallic shoe seal with shoe
mounted secondary seal.
Figure 4.3-8. Primary and secondary seal configurations.1
9/85 Evaporation Loss Sources
4.3-13
-------
to those in external floating roof tanks, these seals close the annular
vapor space between the edge of the floating roof and the tank wall.
Secondary seals are not commonly used with internal floating roof tanks.
Deck fitting loss emissions from internal floating roof tanks result
from penetrations in the roof by deck fittings, fixed roof column supports
or other openings. There are no procedures for estimating emissions from
external roof tank deck fittings. The most common fittings with relevance
to controllable vapor losses are described as follows:1
1. Access Hatch. An access hatch is an opening in the deck with a
peripheral vertical well that is large enough to provide passage of workers
and materials through the deck for construction or servicing. Attached to
the opening is a removable cover which may be bolted and/or gasketed to
reduce evaporative loss. On noncontact decks, the well should extend down
into the liquid to seal off the vapor space below the deck.
2. Automatic Gauge Float Well. A gauge float is used to indicate the
level of liquid within the tank. The float rests on the liquid surface,
inside a well that is closed by a cover. The cover may be bolted and/or
gasketed to reduce evaporation loss. As with other similar deck penetra-
tions, the well extends fixed into the liquid on noncontact decks.
3. Column Well. For fixed roofs that are column-supported, the
columns pass through deck openings with peripheral vertical wells. On
noncontact decks, the well should extend down into the liquid. The wells
are equipped with closure devices to reduce evaporative loss and may be
gasketed or ungasketed to further reduce the loss. Closure devices are
typically sliding covers or flexible fabric sleeve seals.
4. Ladder Well. Some tanks are equipped with internal ladders that
extend from a manhole in the fixed roof to the tank bottom. The deck
opening through which the ladder passes has a peripheral vertical well. On
noncontact decks, the well should extend down into the liquid. The wells
are typically covered with a gasketed or ungasketed sliding cover.
5. Roof Leg or Hanger Well. To prevent damage to fittings underneath
the deck and to allow for tank cleaning or repair, supports are provided to
hold the deck a predetermined distance off the tank bottom. These supports
consist of adjustable or fixed legs attached to the floating deck or hangers
suspended from the fixed roof. For adjustable legs or hangers, the load-
carrying element passes through a well or sleeve into the deck. With
noncontact decks, the well should extend into the liquid.
6. Sample Pipe or Well. A funnel-shaped sample well may be provided
to allow for sampling of the liquid with a sample thief. A closure is
typically located at the lower end of the funnel and frequently consists of
a horizontal piece of fabric slit radially to allow thief entry. The well
should extend into the liquid on noncontact decks. Alternatively, a sample
well may consist of a slottled pipe extending into the liquid, equipped
with a gasketed or ungasketed sliding cover.
4.3-14
EMISSION FACTORS
9/85
-------
7- Vacuum Breaker. A vacuum breaker equalizes the pressure of the
vapor space across the deck as the deck is either being landed on or floated
off its legs. The vacuum breaker consists of a well with a cover. Attached
to the underside of the cover is a guided leg of such length that it contacts
the tank bottom as the internal floating deck approaches. When in contact
with the tank bottom, the guided leg mechanically opens the breaker by
lifting the cover off the well; otherwise, the cover closes the well. The
closure may be gasketed or ungasketed. Because the purpose of the vacuum
breaker is to allow the free exchange of air and/or vapor, the well does
not extend appreciably below the deck.
The decks of internal floating roofs typically are made by joining
several sections of deck material, resulting in seams in the deck. To the
extent that these seams are not completely vapor tight, they become a
source of emissions. It should be noted that external floating roof tanks
and welded internal floating roofs do not have deck seam losses.
Withdrawal loss is another source of emissions from floating roof
tanks. This loss is the vaporization of liquid that clings to the tank
wall and is exposed to the atmosphere when a floating roof is lowered by
withdrawal of liquid. There is also clingage of liquid to columns in
internal floating roof tanks which have a column supported fixed roof.
Total Losses From Floating Roof Tanks - Total floating roof tank emissions
are the sum of rim seal, withdrawal, deck fitting, and deck seam losses.
It should be noted that external floating roof tanks and welded internal
floating roofs do not have deck seam losses. Also, there are no procedures
for estimating emissions from external floating roof tank deck fittings.
The equations provided in this Section are applicable only to freely vented
internal floating roof tanks or external floating roof tanks. The equations
are not intended to be used in the following applications: to estimate
losses from closed internal floating roof tanks (tanks vented only through
a pressure-vacuum vent); to estimate losses from unstabilized or boiling
stocks or from mixtures of hydrocarbons or petrochemicals for which the
vapor pressure is not known or cannot be readily predicted; or to estimate
losses from tanks in which the materials used in the seal system and/or
deck construction are either deteriorated or significantly permeated by the
stored liquid.6 Total losses may be written as:
where:
- LR + LW + L
F LD
(3)
LT = total loss (Ib/yr)
LR = rim seal loss (see Equation 4)
Lt7 = withdrawal loss (see Equation 5)
w
L-p, = deck fitting loss (see Equation 6)
Ln = deck seam loss (see Equation 7)
9/85 Evaporation Loss Sources
4.3-15
-------
Rim Seal Loss - Rim seal loss from floating roof tanks can be estimated
by the following equation5-6:
LR = KgVVDM^ (4)
where :
L_ = rim seal loss (Ib/yr)
K_ = seal factor (lb-mole/(ft (mi/hr)n yr)), see Table 4.3-4
L>
V = average wind speed at tank site (mi/hr) , see Note 1
n = seal related wind speed exponent (dimensionless) , see Table 4.3-4
P* = vapor pressure function (dimensionless), see Note 2
_P
P* = PA
where:
P = true vapor pressure at average actual liquid storage
temperature (psia), see Note 2 to Equation 1
P = average atmospheric pressure at tank location (psia)
D = tank diameter (ft)
iLj = average vapor molecular weight (Ib/lb-mole), see Note 1 to
Equation 1
Kr = product factor (dimensionless), see Note 3
c
Notes: (1) If the wind speed at the tank site is not available, wind
speed data from the nearest local weather station may be
used as an approximation.
(2) P* can be calculated or read directly from Figure 4.3-9.
(3) For all organic liquids except crude oil, KC = 1.0. For
crude oil, K-, = 0.4.
Withdrawal Loss - The withdrawal loss from floating roof storage tanks
can be estimated using Equation 5-5-6
Lw =
(0.943)QCW
T
•C*)
(5)
4.3-16 EMISSION FACTORS 9/85
-------
TABLE 4.3-4. SEAL RELATED FACTORS FOR FLOATING ROOF TANKS'
Tank and seal type
Welded Tank
n
Riveted Tank
K,, n
External floating roof tanks
Metallic shoe seal
Primary seal only 1.2 1.5 1.3 1.5
With shoe mounted secondary seal 0.8 1.2 1.4 1.2
With rim mounted secondary seal 0.2 1.0 0.2 1.6
Liquid mounted resilient seal
Primary seal only 1.1 1.0 NAC NA
With weather shield 0.8 0.9 NA NA
With rim mounted secondary seal 0.7 0.4 NA NA
Vapor mounted resilient seal
Primary seal only 1.2 2.3 NA NA
With weather shield 0.9 2.2 NA NA
With rim mounted secondary seal 0.2 2.6 NA NA
Internal floating roof tanks
Liquid mounted resilient seal
Primary seal only 3.0 0 NA NA
With rim mounted secondary seal 1.6 0 NA NA
Vapor mounted resilient seal
Primary seal only 6.7 0 NA NA
With rim mounted secondary seal6 2.5 0 NA NA
Based on emissions from tank seal systems in reasonably good working
condition, no visible holes, tears, or unusually large gaps between
the seals and the tank wall. The applicability of K decreases in
cases where the actual gaps exceed the gaps assumed during develop-
-ment of the correlation.
Reference 5.
|jNA = Not Applicable.
Reference 6.
If tank specific information is not available about the secondary
seal on an internal floating roof tank, then assume only a primary
seal is present.
9/85
Evaporation Loss Sources
4.3-17
-------
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§
i
4500
4000
3500
3000
2500
2000
1500
1000
500
BOLTED DECK
F, - (0.0228) 0s + (0.79) 0 + 105.2
\
7
WELDED DECK (See Note)
F, = (0.0132) & -t- (0.79) D + 105.2
50 100 150 200 250
TANK DIAMETER. 0 (ft)
300
350
400
BASIS: Finings include: (1) access hatch, with ungasketed, unbolted cover, (2) adjustable deck legs; (3) gauge
float well, with ungasketed, unbolted cover; (4) sample well, with slit fabric seal (10 percent open area); (5) 1-
inch diameter stub drains (only on bolted deck); and (6) vacuum breaker, with gasketed weighted mechanical
actuation. This basis was derived from a survey of users and manufacturers. Other fittings may be typically used
within particular companies or organizations to reflect standards and/or specifications of that group. This figure
should not supersede information based on actual tank data.
NOTES: If no specific information is available, assume welded decks are the most common/typical type currently
in use in tanks with self-supporting fixed roofs.
Figure 4.3-11. Approximated total deck fitting loss factors (F ) for
typical deck fittings in tanks with self-supporting fixed roofs and
either a bolted deck or a welded deck.6 This figure is to be used only
when tank specific data on the number and kind of deck fittings are
unavailable.
4.3-24
EMISSION FACTORS
9/85
-------
where:
L = total length of deck seams (ft)
seam 6 v '
A, , - area of deck (ft2) - n D2/4
D, P*, MV, Kp - as defined for Equation 4
If the total length of the deck seam is not known, Table 4.3-8 can be
used to determine S_.. Where tank specific data concerning width of deck
sheets or size of deck panels are unavailable, a default value for S^ can
be assigned. A value of 0.20 (ft/ft2) can be assumed to represent the most
common bolted decks currently in use.
TABLE 4.3-8. DECK SEAM LENGTH FACTORS (SD) FOR TYPICAL
DECK CONSTRUCTIONS FOR INTERNAL FLOATING ROOF TANKS3
Typical deck seam
length factor,
Deck construction Sn (ft/ft2)
Continuous sheet construction
5 ft wide 0.20C
6 ft wide 0.17
7 ft wide 0.14
Panel construction
5 x 7.5 ft rectangular 0.33
5 x 12 ft rectangular 0.28
Reference 6. Deck seam loss applies to bolted decks only.
b 1
Sn = -, where W = sheet width (ft)
c W
If no specific information is available, these
factors can be assumed to represent the most common bolted
decks currently in use.
d (L+W)
Sn = TT7 , where W = panel width (ft) and L = panel
U LW length (ft)
Pressure Tanks - Losses occur during withdrawal and filling operations in
low pressure (2.5 to 15 psig) tanks when atmospheric venting occurs. High
pressure tanks are considered closed systems, with virtually no emissions.
Vapor recovery systems are often found on low pressure tanks. Fugitive
losses are also associated with pressure tanks and their equipment, but
9/85 Evaporation Loss Sources 4.3-25
-------
with proper system maintenance, these losses are considered insignificant.
No appropriate correlations are available to estimate vapor losses from
pressure tanks.
Variable Vapor Space Tanks - Variable vapor space filling losses result
when vapor is displaced by liquid during filling operations. Since the
variable vapor space tank has an expandable vapor storage capacity, this
loss is not as large as the filling loss associated with fixed roof tanks.
Loss of vapor occurs only when the tank's vapor storage capacity is
exceeded.
Variable vapor space system filling losses can be estimated from:3-7
V
Lv = (2.40 x 10-2) ^- ((VO - (0.25 V2N2)) (8)
where:
L.. = variable vapor space filling loss (lb/103 gal throughput)
My = molecular weight of vapor in storage tank (Ib/lb-mole), see Note 1
to Equation 1
P = true vapor pressure at bulk liquid conditions (psia), see Note 2
to Equation 1
Vi = volume of liquid pumped into system, throughput (bbl)
V2 = volume expansion capacity of system (bbl), see Note 1
N£ = number of transfers into system (dimensionless), see Note 2
Notes: (1) V2 is the volume expansion capacity of the variable vapor
space achieved by roof lifting or diaphragm flexing.
(2) N2 is the number of transfers into the system during the
time period that corresponds to a throughput of Vi.
The accuracy of Equation 8 is not documented. Special tank operating
conditions may result in actual losses significantly different from the
estimates provided by Equation 8. It should also be noted that, although
not developed for use with heavier petroleum liquids such as kerosenes and
fuel oils, the equation is recommended for use with heavier petroleum
liquids in the absence of better data.
4.3.3 Sample Calculations
Three sample calculations to estimate emission losses are provided,
fixed roof tank, external floating roof tank, and internal floating roof
4.3-26 EMISSION FACTORS 9/85
-------
tank. Note that the same tank size, tank painting, stored product, and
ambient conditions are employed in each sample calculation. Only the type
of roof varies.
Problem I - Estimate the total loss from a fixed roof tank for 3 months
based on data observed during the months of March, April and May and given
the following information:
Tank description: Fixed roof tank; 100 ft diameter; 40 ft height;
tank shell and roof painted specular aluminum
color.
Stored product: Motor gasoline (petroleum liquid); Reid vapor
pressure (RVP), 10 psia; 6.1 Ib/gal liquid
density; no vapor or liquid composition given;
375,000 bbl throughput for the 3 months.
Ambient conditions: 60°F average ambient temperature for the 3 months;
10 mi/hr average wind speed at the tank site for
the 3 months; assume 14.7 psia atmospheric pres-
sure; average maximum daily temperature, 68°F;
average minimum daily temperature, 47°F.
Calculation: Total loss = breathing loss + working loss.
(a) Breathing Loss - Calculate using Equation 1.
, ^).68
L = 2.26 x 10-2 M.. L Pp 1 D1-73H0-51AT°-50FDCK (1)
B T ^PA-P J PC
where:
L_ = breathing loss (Ib/yr)
D
My = 66 Ib/lb-mole (from Table 4.3-2 and RVP 10 gasoline)
TA = 60°F (given)
T = 62.5°F (from Table 4.3-3, for an aluminum color tank in good
condition and T = 60°F)
RVP = 10 psia (given)
P =14.7 psia (assumed)
P - 5.4 psia (from Figure 4.3-6, for 10 psia Reid vapor pressure
gasoline and Tc = 62.5°F)
D
D = 100 ft (given)
H = 20 ft (assumed H = \ tank height)
9/85 Evaporation Loss Sources 4.3-27
-------
AT = 21°F (average daily maximum, 68°F, minus average daily
minimum, 47°F)
Fp = 1.20 (from Table 4.3-1 and given specular aluminum tank color)
C = 1.0 (tank diameter is larger than 30 ft)
KC = 1'" Cvalue appropriate for all organic liquids except crude oil)
LB (Ib/yr) =
/ \ °-68
(2.26 x 10-2)(66)L J (100)1-73(20)°-51(21)°-50(1.20)(1.0)(1.0)
75,323 Ib/yr
7S ^7^
For the 3 months, Lfi = J'^ ° = 18,831 Ib
(b) Working Loss - Calculate using Equation 2.
LW = 2.40 x io-5 MVFVMKNKC (2)
where:
L = working loss (Ib/yr)
MV = 66 Ib/lb-mole (from Table 4.3-1 and RVP 10 gasoline)
P = 5.4 psia (calculated for breathing loss above)
V = 2,350,000 gal
where: V (cubic feet) = - r —
4
7i = 3.141
D = 100 ft
h = 40 ft
_ 3.141(100)2(4Q)
4
= 314,100 cubic ft
V (gal) = (7.48 gal/ft3) V (ft3)
V (gal) = 7.48 (314,100) = 2,349,468 gal, round to 2,350,000 gal
\r = throughput/year
tank volume
_ (375,000 bbl)(4)(42 gal/bbl)
2,350,000 gal
4.3-28 EMISSION FACTORS 9/85
-------
KJJ = 1.0 (from Figure 4.3-7 and N = 26.8)
KC = 1.0 (value appropriate for all organic liquids except crude oil)
Lw (Ib/yr) =
2.40 x 10-5 (66)(5.4)(2.35xl06)(26.8)(l.0)(1.0) = 538,705 Ib/yr
For the 3 months, LY, = 538'705 = 134,676 Ib
W 4
(c) Total Loss for the 3 months -
LT "" LB + LW
= 18,831 + 134,676
= 153,507 Ib
Problem II - Estimate the total loss from an external floating roof tank
for 3 months, based on data observed during the months of March, April and
May and given the following information:
Tank description: External floating roof tank with a mechanical
(metallic) shoe primary seal in good condition;
100 ft diameter; welded tank; shell and roof
painted aluminum color.
Stored product: Motor gasoline (petroleum liquid); Reid vapor
pressure, 10 psia; 6.1 Ib/gal liquid density; no
vapor or liquid composition given; 375,000 bbl
throughput for the 3 months.
Ambient conditions: 60°F average ambient temperature for the 3 months;
10 mi/hr average wind speed at tank site for the
3 months; assume 14.7 psia atmospheric pressure.
Calculation: Total loss = rim seal loss + withdrawal loss +
deck fitting loss + deck seam loss.
(a) Rim Seal Loss - Calculate the yearly rim seal loss from Equation 4.
LR = KsVnP*DMvKc (4)
where:
= rim seal loss (Ib/yr)
= 1.2 (from Table 4.3-4, for a welded tank with a mechanical shoe
primary seal; note that external floating roofs have welded decks
only)
9/85 Evaporation Loss Sources 4.3-29
-------
n = 1.5 (from Table 4.3-4, for a welded tank with a mechanical shoe
primary seal)
V = 10 mi/hr (given)
T = 60°F (given)
A
T = 62.5°F (from Table 4.3-3, for an aluminum color tank in good
condition and T. = 60°F)
A
RVP = 10 psia (given)
P = 5.4 psia (from Figure 4.3-6, for 10 psia Reid vapor pressure
gasoline and Tc = 62.5°F)
L>
P = 14.7 psia (assumed)
A
^ = 0.114
Q-5
(can also be determined from Figure 4.3-9 for P = 5.4 psia)
D = 100 ft (given)
*L = 66 Ib/lb-mole (from Table 4.3-2 and RVP 10 gasoline)
Kp = 1.0 (value appropriate for all organic liquids except crude oil)
\j
To calculate yearly rim seal loss based on the 3 month data, multiply
the K , K , P", D, M^, and Vn values, as in Equation 4.
LR = (
= 28,551 Ib/yr
For the 3 months, L = (^'551') = 7,138 Ib
(b) Withdrawal Loss - Calculate the withdrawal loss from Equation 5.
Lw =(0.943)^ 1+V^J (5)
where:
L = withdrawal loss (Ib/yr)
w
4.3-30 EMISSION FACTORS 9/85
-------
Q ~ 3.75 x 10s bbl for 3 months = 1.5 x 106 bbl/yr (given)
C = 0.0015 bbl/1,000 ft2 (from Table 4.3-5, for gasoline in a steel
tank with light rust assumed for tank in good condition as given)
W = 6.1 Ib/gal (given)
Jj
D = 100 ft (given)
N = 0 (value for external floating roof tanks)
\j
F = 1.0 (default value when column diameter is unknown; however,
there are no columns in this tank, and an F value is used only
for calculation purposes)
To calculate yearly withdrawal loss, use Equation 5.
_ (0.943)(1.5 x 106)(0.0015X6.1) (0.0)(l.O)
100 100
= 129 Ib/yr
To calculate withdrawal loss for 3 months, divide by 4.
For the 3 months, L = 129/4 = 32 Ib
(c) Deck Fitting Loss - As stated, deck fitting loss estimation procedures
for external floating roof tanks are not available. The deck fitting
loss for the 3-month period is unknown and will be assumed to 0.
(d) Deck Seam Loss - External floating roof tanks have welded decks;
therefore, there are no deck seam losses.
(e) Total Loss for the 3 months - Calculate the total loss using Equation 3.
LT = LR + LW + LF + LD (3)
where:
L - total loss (lb/3 mo)
LR = 7,138 lb/3 mo
L = 32 lb/3 mo
W
L,., ~ 0 (assumed)
LD = °
LT = 7,138 + 32 + 0 + 0
= 7,170 lb/3 mo
9/85 Evaporation Loss Sources 4.3-31
-------
Problem III - Estimate the total loss for 3 months from an internal
floating roof tank based on data observed during the months of March, April
and May and given the following information:
Tank description: Freely vented internal floating roof tank;
contact deck made of welded 5 ft wide continuous
sheets, with vapor mounted resilient seal; the
fixed roof is supported by 6 pipe columns; tank
shell and roof painted aluminum; 100 ft diameter.
Stored product: Motor gasoline (petroleum liquid); Reid vapor
pressure of 10 psia; 6.1 Ib/gal liquid density;
no vapor or liquid composition given; 375,000 bbl
throughput for the 3 months.
Ambient conditions: 60°F average ambient temperature for the 3 months;
10 mi/hr average wind speed at the tank site for
the 3 months; assume 14.7 psia atmospheric
pressure.
Calculation: Total loss = rim seal loss + withdrawal loss +
deck fitting loss + deck seam loss.
(a) Rim Seal Loss - Calculate yearly rim seal loss using Equation 4.
LR = KsvVDMvKc (4)
where:
L = rim seal loss (Ib/yr)
Kg = 6.7 (from Table 4.3-4; for a welded tank with a vapor mounted
resilient seal and no secondary seal)
V = 10 mi/hr (given)
n = 0 (from Table 4.3-4 for a welded tank with a vapor mounted
resilient seal and no secondary seal)
P* = 0.114 (calculated in Problem II)
D = 100 ft (given)
My = 66 Ib/lb-mole (from Table 4.3-2 and RVP 10 gasoline)
KQ = 1-0 (value appropriate for all organic liquids except crude oil)
LR = 6.7(10)°(0.114)(100)(66)(1.0)
= 5,041 Ib/yr
For the 3 months, LR = 5^41 = 1,260 Ib
4.3-32 EMISSION FACTORS 9/85
-------
(b) Withdrawal Loss - Calculate using Equation 5.
QCWT
LW •=• (0.943)
where:
•('-*)]
!„ = withdrawal loss (Ib/yr)
Q = 1.5 x 106 bbl/yr (calculated in Problem II)
C = 0.0015 bbl/1,000 ft2 (from Table 4.3-5, light rust)
WT = 6.1 Ib/gal (given)
_LJ
D - 100 ft (given)
N = 6 (given)
Fp = 1.0 (default value since column construction details are unknown)
T - (0.943)(l.5xl06)(0.0015)(6.1) f .f(6)(1.0)-\1
LW - joe|^1 H 100 JJ
- 137 Ib/yr
137
For the 3 months, LW = —j— - 34 Ib
(c) Deck Fitting Loss - Calculate using Equation 6.
LF = FFP*MVKC (6)
where:
L^ = deck fitting loss (Ib/yr)
Fp = 700 Ib-mole/yr (interpreted from Figure 4.3-10, given tank diameter
of 100 ft)
P* - 0.114 (calculated in Problem II)
M = 66 Ib/lb-mole (from Table 4.3-2 and RVP 10 gasoline)
K- = 1.0 (value appropriate for all liquid organics except crude oil)
L_ = 700(0.114)(66)(1.0)
r
= 5,267 Ib/yr
For the 3 months, !„ = 5>267 = 1,317 Ib
* 4
9/85 Evaporation Loss Sources 4.3-33
-------
(d) Deck Seam Loss - Calculate using Equation 7.
LD = I
where:
L~ = deck seam loss (Ib/yr)
K_ = 0 for welded seam deck, therefore
(e) Total Loss for 3 months - Calculate from Equation 3.
LT = LR + Lw + Lr + LD (3)
where:
L - total loss (Ib/yr)
LR = 1,260 lb/3 mo
LW — 34 lb/3 mo
LF = 1,317 lb/3 mo
LT = 1,260 + 34 + 1,317 + 0
For the 3 months, LT = 2,611 Ib
References for Section 4.3 —
1. VOC Emissions From Volatile Organic Liquid Storage Tanks - Background
Information for Proposed Standards, EPA-450/3-81-003a, U. S. Environ-
mental Protection Agency, Research Triangle Park, NC, July 1984.
2. Background Documentation for Storage of Organic Liquids, EPA Contract
No. 68-02-3174, TRW Environmental, Inc., Research Triangle Park, NC,
May 1981.
3. Petrochemical Evaporation Loss From Storage Tanks, Bulletin No. 2523,
American Petroleum Institute, New York, NY, 1969.
4. Henry C. Barnett, et al., Properties of Aircraft Fuels, NACA-TN 3276,
Lewis Flight Propulsion Laboratory, Cleveland, OH, August 1956.
5. Evaporation Loss From External Floating Roof Tanks, Second Edition,
Bulletin No. 2517, American Petroleum Institute, Washington, D. C.,
1980.
4.3-34 EMISSION FACTORS 9/85
-------
6. Evaporation Loss From Internal Floating Roof Tanks, Third Edition,
Bulletin No. 2519, American Petroleum Institute, Washington, D. C.,
1983.
7. Use of Variable Vapor Space Systems To Reduce Evaporation Loss,
Bulletin No. 2520, American Petroleum Institute, New York, NY, 1964.
9/85 Evaporation Loss Sources 4.3-35
-------
-------
4.4 TRANSPORTATION AND MARKETING OF PETROLEUM LIQUIDS1 3
4.4.1 General
The transportation and marketing of petroleum liquids involve many
distinct operations, each of which represents a potential source of evapo-
ration loss. Crude oil is transported from production operations to a
refinery by tankers, barges, rail tank cars, tank trucks and pipelines.
Refined petroleum products are conveyed to fuel marketing terminals and
petrochemical industries by these same modes. From the fuel marketing
terminals, the fuels are delivered by tank trucks to service stations,
commercial accounts and local bulk storage plants. The final destination
for gasoline Is usually a motor vehicle gasoline tank. Similar distri-
bution paths exist for fuel oils and other petroleum products. A general
depiction of these activities is shown in Figure 4.4-1.
4.4.2 Emissions and Controls
Evaporative emissions from the transportation and marketing of
petroleum liquids may be separated, by storage equipment and mode of
transportation used, into four categories:
1. Rail tank cars, tank trucks and marine vessels: Loading, transit
and ballasting losses.
2. Service stations: Bulk fuel drop losses and underground tank
breathing losses.
3. Motor vehicle tanks: Refueling losses.
4. Large storage tanks: Breathing, working and standing storage
losses. These are discussed in Section 4.3.
Evaporative and exhaust emissions are also associated with motor
vehicle operation, and these topics are discussed in AP-42, Volume II:
Mobile Sources.
Rail Tank Cars, Tank Trucks and Marine Vessels - Emissions from these
sources are due to loading losses, ballasting losses and transit losses.
Loading Losses - Loading losses are the primary source of evaporative
emissions from rail tank car, tank truck and marine vessel operations.
Loading losses occur as organic vapors in "empty" cargo tanks are
displaced to the atmosphere by the liquid being loaded into the tanks.
These vapors are a composite of (1) vapors formed in the empty tank by
evaporation of residual product from previous loads, (2) vapors transferred
to the tank in vapor balance systems as product is being unloaded, and
(3) vapors generated in the tank as the new product is being loaded. The
quantity of evaporative losses from loading operations is, therefore, a
function of the following parameters.
9/85
Evaporation Loss Sources
4.4-1
-------
-p-
I
to
o
a
g.
H
O
pa
en
i
OIL FIELD
CRUDE
STORAGE
TANKS
CRUDE OIL PRODUCTION
f
PRODUCT
STORAGE
TANKS
REFINERY
MARKETING
TERMINAL
STORAGE
TANKS
TANK CAR
i
BULK
PLANT
STORAGE
TANKS
TANK TRUCK
COMMERCIAL
ACCOUNTS
STORAGE
TANKS
PETROCHEMICALS
SERVICE
STATIONS
00
Ln
AUTOMOBILES
AND
OTHER MOTOR
VEHICLES
Figure 4.4-1. Flowsheet of petroleum production, refining, and distribution systems. (Sources of organic evaporative
emissions are indicated by vertical arrows.)
-------
• Physical and chemical characteristics of the previous cargo.
• Method of unloading the previous cargo.
• Operations to transport the empty carrier to a loading terminal.
• Method of loading the new cargo.
• Physical and chemical characteristics of the new cargo.
The principal methods of cargo carrier loading are illustrated in
Figures 4.4-2 through 4.4-4. In the splash loading method, the fill pipe
dispensing the cargo is lowered only partway into the cargo tank. Signifi-
cant turbulence and vapor/liquid contact occur during the splash loading
operation, resulting in high levels of vapor generation and loss. If the
turbulence is great enough, liquid droplets will be entrained in the vented
vapors.
A second method of loading Is submerged loading. Two types are the
submerged fill pipe method and the bottom loading method. In the submerged
fill pipe method, the fill pipe extends almost to the bottom of the cargo
tank. In the bottom loading method, a permanent fill pipe is attached to
the cargo tank bottom. During most of both methods of submerged loading,
the fill pipe opening is below the liquid surface level. Liquid turbulence
is controlled significantly during submerged loading, resulting in much
lower vapor generation than encountered during splash loading.
The recent loading history of a cargo carrier is just as important a
factor in loading losses as the method of loading. If the carrier has
carried a nonvolatile liquid such as fuel oil, or has just been cleaned,
it will contain vapor free air. If it has just carried gasoline and has
not been vented, the air in the carrier tank will contain volatile organic
vapors, which are expelled during the loading operation along with newly
generated vapors.
Cargo carriers are sometimes designated to transport only one product,
and in such cases are practicing "dedicated service". Dedicated gasoline
cargo tanks return to a loading terminal containing air fully or partially
saturated with vapor from the previous load. Cargo tanks may also be
"switch loaded" with various products, so that a nonvolatile product being
loaded may expel the vapors remaining from a previous load of a volatile
product such as gasoline. These circumstances vary with the type of cargo
tank and with the ownership of the carrier, the petroleum liquids being
transported, geographic location, and season of the year.
One control measure for gasoline tank trucks Is called "vapor balance
service", in which the cargo tank retrieves the vapors displaced during
product unloading at bulk plants or service stations and transports the
vapors back to the loading terminal. Figure 4.4-5 shows a tank truck in
vapor balance service filling a service station underground tank and taking
on displaced gasoline vapors for return to the terminal. A cargo tank
in vapor balance service normally is saturated with organic vapors, and the
presence of these vapors at the start of submerged loading results in
greater loading losses than encountered during nonvapor balance, or
"normal", service. Vapor balance service is usually not practiced with
9/85
Evaporation Loss Sources
4.4-3
-------
FILL PIPE
VAPOR EMISSIONS
-HATCH COVER
CARGO TANK
Figure 4.4-2. Splash loading method.
VAPOR EMISSIONS
FILL PIPE
HATCH COVER
CARGO TANK
Figure 4.4-3. Submerged fill pipe.
4.4-4
VAPOR VENT
TO RECOVERY
OR ATMOSPHERE
HATCH CLOSED
VAPORS
Figure 4.4-4. Bottom loading.
EMISSION FACTORS
CARGO TANK
FILL PIPE
9/85
-------
r
marine vessels, although some vessels practice emission control by means of
vapor transfer within their own cargo tanks during ballasting operations (see
page 4.4-10).
MANIFOLD FOR RETURNING VAPORS
VAPOR VENT LINE
TRUCKSTORAGE\ I
COMPARTMENTS
PRESSURE RELIEF VALVES
/Htt\ltttttttflwr
t
UNDERGROUND
vSTORAGETANK
Figure 4.4-5. Tank truck unloading into a service station
underground storage tank and practicing "vapor balance"
form of emission control.
Emissions from loading petroleum liquid can be estimated (with a
probable error of ±30 percent)4 using the following expression:
LL = 12.46 SPM
(1)
where:
M
P
T
S
Loading loss, lb/103 gal of liquid loaded
Molecular weight of vapors, Ib/lb-raole (see Table 4.3-2)
True vapor pressure of liquid loaded, psia (see Figures
4.3-5 and 4.3-6 and Table 4.3-2)
Temperature of bulk liquid loaded, °R (°F + 460)
A saturation factor (see Table 4.4-1)
9/85
Evaporation Loss Sources
4.4-5
-------
The saturation factor, S, represents the expelled vapor's fractional approach
to saturation, and it accounts for the variations observed in emission rates
from the different unloading and loading methods. Table 4.4-1 lists suggested
saturation factors.
TABLE 4.4-1. SATURATION (S) FACTORS FOR CALCULATING
PETROLEUM LIQUID LOADING LOSSES
Cargo carrier
Mode of operation
S factor
Tank trucks and
rail tank cars
Marine vessels3
Submerged loading of a clean
cargo tank 0.50
Submerged loading: dedicated
normal service 0.60
Submerged loading: dedicated
vapor balance service 1.00
Splash loading of a clean
cargo tank 1.45
Splash loading: dedicated
normal service 1.45
Splash loading: dedicated
vapor balance service 1.00
Submerged loading: ships 0.2
Submerged loading: barges 0.5
aFor products other than gasoline and crude oil. Use factors
from Table 4.4-2 for marine loading of gasoline. Use Equations
2 and 3 and Table 4.4-3 for marine loading of crude oil.
Emissions from controlled loading operations can be calculated by multi-
plying the uncontrolled emission rate calculated in Equation 1 by the control
efficiency term:
- eff
100
Measures to reduce loading emissions include selection of alternate
loading methods and application of vapor recovery equipment. The latter
captures organic vapors displaced during loading operations and recovers
4.4-6
EMISSION FACTORS
9/85
-------
the vapors by the use of refrigeration, absorption, adsorption and/or com-
pression. The recovered product is piped back to storage. Vapors can also
be controlled through combustion in a thermal oxidation unit, with no
product recovery. Figure 4.4-6 demonstrates the recovery of gasoline vapors
from tank trucks during loading operations at bulk terminals. Control
efficiencies of modern units range from 90 to over 99 percent, depending on
the nature of the vapors and the type of control equipment used.5"6
VAPOR RETURN LINE
VAPOR-FREE
AIR VENTED
TO
ATMOSPHERE
VAPOR
RECOVERY
UNIT
RECOVERED PRODUCT
TO STORAGE
PRODUCT FROM
LOADING TERMINAL
STORAGE TANK
Figure 4.4-6. Tank truck loading with vapor recovery.
Sample Galculation - Loading losses (Lj_,) from a gasoline tank truck in
dedicated vapor balance service and practicing vapor recovery would be calcu-
lated as follows, using Equation 1:
Design basis -
Cargo tank volume is 8,000 gallons
Gasoline RVP is 9 psia
Product temperature is 80°F
Vapor recovery efficiency is 95%
Loading loss equation -
LL
12.46 SPM h _ eff
T \ 100
where: S = Saturation factor (see Table 4.4-1) = 1.00
P = True vapor pressure of gasoline (see Figure 4.3-6) = 6.6 psia
M = Molecular weight of gasoline vapors (see Table 4.3-2) = 66
T = Temperature of gasoline = 540°R
eff = Control efficiency = 95%
9/85
Evaporation Loss Sources
4.4-7
-------
L = 12*46 (1.00)(6.6)(66) h - 95 \
L 540 \ 100 /
= 0.50 lb/103 gal
Total loading losses are:
(0.50 lb/103 gal)(8.0 x 103 gal) = 4.0 Ib
Measurements of gasoline loading losses from ships and barges have led
to the development of emission factors for these specific loading operations.7
These factors are presented in Table 4.4-2 and, for gasoline loading oper-
ations at marine terminals, should be used instead of Equation 1.
In addition to Equation 1, which estimates emissions from the loading
of petroleum liquids, Equation 2 has been developed specifically for esti-
mating the emissions from the loading of crude oil into ships and ocean
barges:
CL - cA + CG (2)
where: CL = Total loading loss, lb/103 gal of crude oil loaded
CA = Arrival emission factor, contributed by vapors in the empty
tank compartment prior to loading, lb/103 gal loaded (see
Note)
CG = Generated emission factor, contributed by evaporation
during loading, lb/103 gal loaded
This equation was developed empirically based on test measurements of
several vessel compartments.7 The quantity CQ can be calculated using
Equation 3:
CG = 1.84 (0.44 P - 0.42) M G (3)
T
where: P = True vapor pressure of loaded crude oil, psia (see
Figure 4.3-5 and Table 4.3-2)
M = Molecular weight of vapors, Ib/lb-mole (see Table 4.3-2)
G = Vapor growth factor = 1.02 (dimension!ess)
T = Temperature of vapors, °R (°F + 460)
Note - Values of C^ for various cargo tank conditions are listed in
Table 4.4-3.
Emission factors derived from Equation 3 and Table 4.4-3 represent
total organic compounds. Nonmethane-nonethane volatile organic compound
(VOC) emission factors for crude oil vapors have been found to range from
approximately 55 to 100 weight percent of these total organic factors.
When specific vapor composition information is not available, the VOC
emission factor can be estimated by taking 85 percent of the total organic
factor.3
4.4-8 EMISSION FACTORS 9/85
-------
TABLE 4.4-2. VOLATILE ORGANIC COMPOUND EMISSION FACTORS FOR
GASOLINE LOADING OPERATIONS AT MARINE TERMINALS3
Vessel
tank
condition
Uncleaned
Ballasted
Cleaned
Gas-freed
Any con-
dition
Gas-freed
Typical
overall
situation^
Previous
cargo
Volatilec
Volatile
Volatile
Volatile
Nonvolatile
Any cargo
Any cargo
Total organic
Ships/ocean barges'5
nig/liter lb/103 gal
transferred transferred
315 2.6
205 1.7
180 1.5
85 0.7
85 0.7
e e
215 1.8
emission factors
Bargesb
rag/liter lb/103
gal
transferred transferred
465 3.9
d d
e e
e e
e e
245 2.0
410 3.4
References 2, 8. Factors represent nonmethane-nonethane VOC emissions because
methane and ethane have been found to constitute a negligible weight fraction of
the evaporative emissions from gasoline.
"Ocean barges (tank compartment depth about 40 feet) exhibit emission levels similar
to tank ships. Shallow draft barges (compartment depth 10 to 12 feet) exhibit
higher emission levels.
cVolatile cargoes are those with a true vapor pressure greater than 1.5 psia.
^Barges are not usually ballasted.
Unavailable.
^Based on observation that 41% of tested ship compartments were uncleaned, lit
ballasted, 24Z cleaned, and 24Z gas-freed. For barges, 762 were uncleaned.
TABLE 4.4-3.
AVERAGE ARRIVAL EMISSION FACTORS, CA, FOR CRUDE
OIL LOADING EMISSION EQUATION^
Ship/ocean barge
tank condition
Previous
cargo
Arrival emission
factor, lb/103 gal
Uncleaned
Ballasted
Cleaned or
gas-freed
Any condition
Volatile^
Volatile
Volatile
Nonvolatile
0.86
0.46
0.33
0.33
aArrival emission factors (CA) to be added to generated emission
factors calculated in Equation 3 to produce total crude oil
loading loss. These factors represent total organic compounds;
nonmethane-nonethane VOC emission factors average about 15% lower.
^Volatile cargoes are those with a true vapor pressure greater
than 1.5 psia.
9/85
Evaporation Loss Sources
4.4-9
-------
Ballasting Losses - Ballasting operations are a major source of
evaporative emissions associated with the unloading of petroleum liquids at
marine terminals. It is common practice to load several cargo tank compart-
ments with sea water after the cargo has been unloaded. This water, termed
"ballast", Improves the stability of the empty tanker during the subsequent
voyage. Although ballasting practices vary, individual cargo tanks are
ballasted typically about 80 percent, and the total vessel is ballasted 15 to
40 percent, of capacity. Ballasting emissions occur as vapor laden air in
the "empty" cargo tank is displaced to the atmosphere by ballast water being
pumped into the tank. Upon arrival at a loading port, the ballast water is
pumped from the cargo tanks before the new cargo is loaded. The ballasting
of cargo tanks reduces the quantity of vapors returning in the empty tank,
thereby reducing the quantity of vapors emitted during subsequent tanker
loading. Regulations administered by the U. S. Coast Guard require that, at
marine terminals located in ozone nonattainment areas, large tankers with
crude oil washing systems contain organic vapors from ballasting.9 This is
accomplished principally by displacing the vapors during ballasting into a
cargo tank being simultaneously unloaded. Marine vessels in other areas emit
organic vapors directly to the atmosphere.
Equation 4 has been developed from test data to calculate the ballasting
emissions from crude oil ships and ocean barges7:
LB = 0.31 + 0.20 P + 0.01 PUA (4)
where: Lg = Ballasting emission factor, lb/103 gal of ballast water
P = True vapor pressure of discharged crude oil,
psia (see Figure 4.3-5 and Table 4.3-2)
UA = Arrival cargo true ullage, prior to dockside discharge,
measured from the deck, feet. The term "ullage" refers to
the distance between the cargo surface level and the deck
level
Table 4.4-4 lists average total organic emission factors for ballasting
into uncleaned crude oil cargo compartments. The first category applies to
"full" compartments wherein the crude oil true ullage just prior to cargo
discharge is less than 5 feet. The second category applies to lightered, or
short-loaded, compartments (part of cargo previously discharged or original
load a partial fill), with an arrival true ullage greater than 5 feet. It
should be remembered that these tabulated emission factors are examples
only, based on average conditions, to be used when crude oil vapor pressure
is unknown. Equation 4 should be used when information about crude oil
vapor pressure and cargo compartment condition is available. The sample
calculation illustrates the use of Equation 4.
S ample Galculat ion - Ballasting emissions from a crude oil cargo ship
would be calculated as follows, using Equation 4:
Design basis -
Vessel and cargo description:
80,000 dead-weight-ton tanker, crude oil capacity 500,000 barrels;
20 percent of the cargo capacity Is filled with ballast water after
4.4-10
EMISSION FACTORS
9/85
-------
TABLE 4.4-4. TOTAL ORGANIC EMISSION FACTORS
FOR CRUDE OIL BALLASTING3
Average emission factors
By category Typical overall *>
Compartment mg/liter lb/103 gal mg/liter lb/103 gal
condition before ballast ballast ballast ballast
cargo discharge water water water water
Fully loadedc 111 0.9
Lightered or
previously
short-loadedd 171 1.4
129 1.1
aAssumes crude oil temperature of 60°F and RVP of 5 psia. Nonmethane-
nonethane VOC emission factors average about 85% of these total
organic factors.
t>Based on observation that 70% of tested compartments had been fully
loaded before ballasting. May not represent average vessel practices.
cAssumed typical arrival ullage of 2 ft.
•^Assumed typical arrival ullage of 20 ft.
cargo discharge. The crude oil has an RVP of 6 psia and is discharged at
75°F.
Compartment conditions:
70 percent of the ballast water is loaded into compartments that had
been fully loaded to 2 feet ullage, and 30 percent is loaded into
compartments that had been lightered to 15 feet ullage before arrival
at dockside.
Ballasting emission equation -
LB = 0.31 + 0.20 P + 0.01 PUA
where: P = True vapor pressure of crude oil (see Figure 4.3-5)
= 4.6 psia
UA = True cargo ullage for the full compartments = 2 feet, and
true cargo ullage for the lightered compartments = 15 feet
LB = 0.70 [0.31 + (0.20)(4.6) + (0.01)(4.6)(2)]
+ 0.30 [0.31 + (0.20)(4.6) + (0.01X4.6X15)]
= 1.5 lb/103 gal
Total ballasting emissions are:
(1.5 lb/103 gal)(0.20)(500,000 bbl)(42 gal/bbl) = 6,300 Ib
Since VOC emissions average about 85% of these total organic emissions,
emissions of VOC are about: (0.85)(6,300 Ib) = 5,360 Ib
9/85 Evaporation Loss Sources 4.4-11
-------
Transit Losses - In addition to loading and ballasting losses, losses
occur while the cargo is in transit. Transit losses are similar in many
ways to breathing losses associated with petroleum storage (see Section 4.3).
Experimental tests on ships and barges have indicated that transit losses
can be calculated using Equation 54:
LT = 0.1 PW (5)
where: LT = Transit loss from ships and barges, lb/week-103 gal transported
P = True vapor pressure of the transported liquid, psia
(see Figures 4.3-5 and 4.3-6 and Table 4.3-2)
W = Density of the condensed vapors, Ib/gal (see Table 4.3-2)
Emissions from gasoline truck cargo tanks during transit have been studied
by a combination of theoretical and experimental techniques, and typical
emission values are presented in Table 4.4—5. ~ Emissions depend on the
extent of venting from the cargo tank during transit, which in turn depends
on the vapor tightness of the tank, the pressure relief valve settings, the
pressure in the tank at the start of the trip, the vapor pressure of the
fuel being transported, and the degree of fuel vapor saturation of the
space in the tank. The emissions are not directly proportional to the time
spent in transit. If the vapor leakage rate of the tank increases, emissions
increase up to a point, and then the rate changes as other determining
factors take over. Truck tanks in dedicated vapor balance service usually
contain saturated vapors, and this leads to lower emissions during transit,
because no additional fuel evaporates to raise the pressure in the tank to
cause venting. Table 4.4-5 lists "typical" values for transit emissions and
"extreme" values that could occur in the unlikely event that all determining
factors combined to cause maximum emissions.
In the absence of specific inputs for Equations 1 through 5, the
typical evaporative emission factors presented in Tables 4.4-5 and 4.4-6
should be used. It should be noted that, although the crude oil used to
calculate the emission values presented in these tables has an RVP of 5,
the RVP of crude oils can range from less than 1 up to 10. Similarly, the
RVP of gasolines has a range of approximately 7 to 13. In areas where
loading and transportation sources are major factors affecting air quality,
it is advisable to obtain the necessary parameters and calculate emission
estimates using Equations 1 through 5.
Service Stations - Another major source of evaporative emissions is the
filling of underground gasoline storage tanks at service stations. Gaso-
line is usually delivered to service stations in large (8,000 gallon) tank
trucks or smaller account trucks. Emissions are generated when gasoline
vapors in the underground storage tank are displaced to the atmosphere by
the gasoline being loaded into the tank. As with other loading losses, the
quantity of the service station tank filling loss depends on several vari-
ables, including the method and rate of filling, the tank configuration,
and the gasoline temperature, vapor pressure and composition. Using Equa-
tion (1), an average emission rate for submerged filling is 880 milligrams
per liter of transferred gasoline, and the rate for splash filling is 1,380
milligrams per liter of transferred gasoline (see Table 4.4-7).
4.4-12 EMISSION FACTORS 9/85
-------
TABLE 4.4-5 TOTAL ORGANIC EMISSION FACTORS FOR PETROLEUM
LIQUID RAIL TANK CARS AND TANK TRUCKS
Emission source
Loading operations c
Submerged loading -
dedicated normal service
mg/liter transferred
lb/103 gal transferred
Submerged loading -
vapor balance service"
mg/liter transferred
lb/103 gal transferred
Splash loading -
dedicated normal service
mg/liter transferred
lb/103 gal transferred
Splash loading -
vapor balance service
mg/liter transferred
lb/103 gal transferred
Transit losses
Loaded with product
mg/liter transported
typical
extreme
lb/103 gal transported
typical
extreme
Return with vapor
mg/liter transported
typical
extr erne
lb/103 gal transported
typical
extreme
Jet Distillate Residual
Crude naphtha Jet oil oil
Gasoline8 oilb (JP-4) kerosene No. 2 No. 6
590 240 180 1.9 1.7 0.01
5 2 1.5 0.16 0.014 0.0001
980 400 300 e e e
83 2.5 e e e
1,430 580 430 5 4 0.03
12 5 4 .0.04 0.03 0.0003
980 400 300 e e e
83 2.5 e e e
0-1.0 f f f f f
0-9.0 f f f f f
0 - 0.01 f f f f f
0 - 0.08 f f f f f
0 - 13.0 f f f f f
0 - 44.0 f f f f f
0 - 0.11 f f f f f
0 - 0.37 f f f f f
aRefetence 2. Gasoline factors represent emissions of nonmethane-nonethane VOC, since methane
and ethane constitute a negligible weight fraction of the evaporative emissions from gasoline.
The example gasoline has an RVP of 10 psia.
bThe example crude oil has an RVF of 5 psla.
cLoading emission factors are calculated using Equation 1 for a dispensed product temperature of
60 °F.
Reference 2.
eNot normally used.
rUnava liable.
9/85
Evaporation Loss Sources
4.4-13
-------
TABLE 4.4-6.
TOTAL ORGANIC EMISSION FACTORS FOR PETROLEUM
MARINE VESSEL SOURCES3
Emission source
Crude
Gasoline*5 oilc
Jet
naphtha
(JP-4)
Jet
kerosene
Distillate
oil
No. 2
Residual
oil
No. 6
Loading operations
Ships/ocean barges
rag/liter transferred d 73 60
lb/103 gal transferred d 0.61 0.50
Barges
rag/liter transferred d 120 150
lb/103 gal transferred d 1.0 1.2
Tanker ballasting
mg/liter ballast water 100 e f
lb/103 gal ballast water 0.8 e f
Transit
mg/week-liter transported 320 150 84
lb/week-103 gal transported 2,7 1.3 0.7
0.63
0.005
1.60
0.013
0.60
0.005
0.55
0.005
1.40
0.012
0.54
0.005
0.004
0.00004
0.011
0.00009
0.003
3 x 10
-5
3Emission factors are calculated for a dispensed product temperature of 60°F.
''Factors shown for gasoline represent nonmethane-nonethane VOC emissions. The example
gasoline has an RVP of 10 psia.
cNonmethane-nonethane VOC emission factors for a typical crude oil are 15% lower than
the total organic factors shown. The example crude oil has an RVP of 5 psia.
dSee Table 4.4-2 for these emission factors.
eSee Table 4.4-4 for these emission factors.
f Unavailable.
Emissions from underground tank filling operations at service stations
can be reduced by the use of a vapor balance system such as in Figure 4.4-5
(termed Stage I vapor control). The vapor balance system employs a hose that
returns gasoline vapors displaced from the underground tank to the tank truck
cargo compartments being emptied. The control efficiency of the balance system
ranges from 93 to 100 percent. Organic emissions from underground tank
filling operations at a service station employing a vapor balance system and
submerged filling are not expected to exceed 40 milligrams per liter of
transferred gasoline.
A second source of vapor emissions from service stations is under-
ground tank breathing. Breathing losses occur daily and are attributable
to gasoline evaporation and barometric pressure changes. The frequency
with which gasoline is withdrawn from the tank, allowing fresh air to
enter to enhance evaporation, also has a major effect on the quantity of
these emissions. An average breathing emission rate is 120 milligrams
per liter of throughput.
4.4-14
EMISSION FACTORS
9/85
-------
TABLE 4.4-7. EVAPORATIVE EMISSIONS FROM GASOLINE
SERVICE STATION OPERATIONS
Emission rate
Emission source
mg/liter
throughput
lb/103 gal
throughput
Filling underground tank
Submerged filling*1 880
Splash filling3 1,380
Balanced submerged filling 40
Underground tank breathing
and emptying^ 120
Vehicle refueling operations
Displacement losses
(uncontrolled) 1,320
Displacement losses
(controlled) 132
Spillage 80
7.3
11.5
0.3
1.0
11.0
1.1
0.7
aThese factors are calculated using Equation 1 for a gasoline
temperature of 60°F and RVP of 10 psia-
^Includes any vapor loss between underground tank and gas pump.
Motor Vehicle Refueling - Service station vehicle refueling activity also
produces evaporative emissions. Vehicle refueling emissions come from vapors
displaced from the automobile tank by dispensed gasoline and from spillage.
The quantity of displaced vapors depends on gasoline temperature, auto tank
temperature, gasoline RVP and dispensing rate. It is estimated that the
uncontrolled emissions from vapors displaced during vehicle refueling average
1,320 milligrams per liter of dispensed gasoline.5'12
Spillage loss Is made up of contributions from prefill and postfill
nozzle drip and from spit-back and overflow from the vehicle's fuel tank
filler pipe during filling. The amount of spillage loss can depend on several
variables, including service station business characteristics, tank configur-
ation, and operator techniques. An average spillage loss is 80 milligrams
per liter of dispensed gasoline.5'
Control methods for vehicle refueling emissions are based on conveying
the vapors displaced from the vehicle fuel tank to the underground storage
tank vapor space through the use of a special hose and nozzle, as depicted
in Figure 4.4-7 (termed Stage II vapor control). In "balance" vapor control
systems, the vapors are conveyed by natural pressure differentials established
during refueling. In "vacuum assist" systems, the conveyance of vapors from
the auto fuel tank to the underground storage tank is assisted by a vacuum
pump. Although vapor control systems for vehicle refueling activity are not
currently in widespread operation at service stations, tests on a few systems
have indicated overall system control efficiencies in the range of 88 to 92
percent. '
9/85
Evaporation Loss Sources
4.4-15
-------
Figure 4.4-7. Automobile refueling vapor recovery system.
References for Section 4,4
1. C. E. Burklin and R. L. Honercamp, Revision of\ Evaporative Hydrocarbon
Emission Factors, EPA-450/3-76-039, U. S. Environmental Protection
Agency, Research Triangle Park, NC, August 1976.
2. G. A. LaFlam, S. Osbourn and R. L. Norton, Revision of Tank Truck
Loading Hydrocarbon Emission Factors, Pacific Environmental Services,
Inc., Durham, NC, May 1982.
3. G. A. LaFlam, Revision of Marine Vessel Evaporative Emission Factors,
Pacific Environmental Services, Inc., Durham, NC, November 1984.
4. Evaporation Loss from Tank Cars, Tank Trucks and Marine Vessels,
Bulletin No. 2514, American Petroleum Institute, Washington, DC, 1959.
5. C. E. Burklin, et al., A Study of Vapor Control Methods for Gasoline
Marketing Operations, EPA-450/3-75-046A and -046B, U. S. Environmental
Protection Agency, Research Triangle Park, NC, May 1975.
6. Bulk Gasoline Terminals - Background Information for Promulgated
Standards, EPA-450/3-80-038b, U. S. Environmental Protection Agency,
Research Triangle Park, NC, August 1983.
7. Atmospheric Hydrocarbon Emissions from Marine Vessel Transfer Opera-
tions , Publication 2514A, American Petroleum Institute, Washington, DC,
1981.
4.4-16
EMISSION FACTORS
9/85
-------
8. C. E. Burklin, et al., Background Information on Hydrocarbon Emissions
from Marine Terminal Operations. EPA-450/3-76-038a and -038b, U. S.
Environmental Protection Agency, Research Triangle Park, NC,
November 1976.
9. Rules for the Protection of the Marine Environment Relating tq^Tank
Vessels Carrying Oil in Bulk, 45 FR 43705, June 30, 1980.
10. R. A. Nichols, Analytical Calculation of Fuel Transit Breathing Loss,
Chevron USA, Inc., San Francisco, CA, March 21, 1977.
11. R. A. Nichols, Tank Truck Leakage Measurements, Chevron USA, Inc.,
San Francisco, CA, June 7, 1977.
12. Investigation of Passenger Car Refueling Losses: Final Report,
2nd Year Program, APTD-1453, U. S. Environmental Protection Agency,
Research Triangle Park, NC, September 1972.
9/85
Evaporation Loss Sources
4.4-17
-------
-------
4.5 CUTBACK ASPHALT, EMULSIFIED ASPHALT AND ASPHALT
CEMENT
4.5.1 General1-3
Asphalt surfaces and pavements are composed of compacted aggregate and an asphalt binder. Aggregate
material* are produced from rock quarries as manufactured stone or are obtained from natural gravel or soil
deposits. Metal ore refining processes produce artificial aggregates as a byproduct. In asphalt, the
aggregate performs three functions. It transmits the load from the surface to the base course, takes the
abrasive wear of traffic, and provides a nonskid surface. The asphalt binder holds the aggregate together,
preventing displacement and loss of aggregate and providing a waterproof cover for the base.
Asphalt binders take the form of asphalt cement (the residue of the distillation of crude oils) and liquified
asphalts. To be used for pavement, asphalt cement, which is semisolid, must be heated prior to mixing with
aggregate. The resulting hot mix asphalt concrete is generally applied in thicknesses of from two to six
inches. Liquified asphalts are (1) asphalt cutbacks (asphalt cement thinned or "cutback" with volatile
petroleum distillates such as naptha, kerosene, etc.) and (2) asphalt emulsions (nonflammable liquids pro-
duced by combining asphalt and water with an emulsifying agent, such as soap). Liquified asphalts are used
in tack and seal operations, in priming roadbeds for hot mix application, and for paving operations up to
several inches thick.
Cutback asphalts fall into three broad categories: rapid cure (RC), medium cure (MC), and slow cure
(SC) road oils. SC, MC and RC cutbacks are prepared by blending asphalt cement with heavy residual oils,
kerosene-type solvents, or naptha and gasoline solvents, respectively. Depending on the viscosity desired.
the proportions of solvent added generally range from 25 to 45 percent by volume.
Emulsified asphalts are of two basic types. One type relies on water evaporation to cure. The other type
(cationic emulsions) relies on ionic bonding of the emulsion and the aggregate surface. Emulsified asphalt
can substitute for cutback in almost any application. Emulsified asphalts are gaining in popularity, because
of the energy and environmental problems associated with the use of cutback asphalts.
4.5.2 Emissions!*2
The primary pollutants of concern from asphalts and asphalt paving operations are volatile organic
compounds (VOC). Of the three types of asphalts, the major source of VOC is cutback. Only minor
amounts of VOC are emitted from emulsified asphalts and asphalt cement.
VOC emissions from cutback asphalts result from the evaporation of the petroleum distillate solvent, or
diluent, used to liquify the asphalt cement. Emissions occur at both the job site and the mixing plant. At the
job site, VOCs are emitted from the equipment used to apply the asphaltic product and from the road
surface. At the mixing plant, VOCs are released during mixing and stockpiling. The largest source of
emissions, however, is the road surface itself.
For any given amount of cutback asphalt, total emissions are believed to be the same, regardless of
stockpiling, mixing and application times. The two major variables affecting both the quantity of VOC
emitted and the time over which emissions occur are the type and the quantity of petroleum distillate used
as a diluent. As an approximation, long term emissions from cutback asphalts can be estimated by
assuming that 95 percent of the diluent evaporates from rapid cure (RC) cutback asphalts, 70 percent from
medium cure (MC) cutbacks, and about 25 percent from slow cure (SC) asphalts, by weight percent. Some
of the diluent appears to be retained permanently in the road surface after application. Limited test data
suggest that, from rapid cure (RC) asphalt, 75 percent of the total diluent loss occurs on the first day after
7/79
Evaporation Loss Sources
4.5-1
-------
application, 90 percent occurs within the first month, and 95 percent in three to four months. Evaporation
takes place more slowly from medium cure (MC) asphalts, with roughly 20 percent of the diluent being
emitted during the first day, 50 percent during the first week, and 70 percent after three to four months. No
measured data are available for slow cure (SC) asphalts, although the quantity emitted is believed to be
considerably less than with either rapid or medium cure asphalts, and the time during which emissions take
place is expected to be considerably longer (Figure 4.5-1). An example calculation for determining VOC
emissions from cutback asphalts is given below:
Example: Local records indicate that 10,000 kg of RC cutback asphalt (containing 45 percent
diluent, by volume) was applied in a given area during the year. Calculate the mass of VOC
emitted during the year from this application.
To determine VOC emissions, the volume of diluent present in the cutback asphalt must
first be determined. Because of density of naptha (0.7 kg/1) differs from that of asphalt
cement (1.1 kg/1), the following equations should be solved to determine the volume of
diluent (x) and the volume of asphalt cement (y) in the cutback asphalt:
10,000 kg cutback asphalt = (x liter, diluent)
+ (y liter, asphalt cement)
and
x liter, diluent « 0.45 (x liter, diluent + y liter, asphalt cement)
From these equations, the volume of diluent present in the cutback asphalt is determined
to be about 4900 liters, or about 3400 kg. Assuming that 95 percent of this is evaporative
VOC, emissions are then: 3400 kg x 0.95 = 3200 kg (i.e., 32<^. by weight, of the cutback
asphalt eventually evaporates).
These equations can be used for medium cure and slow cure asphalts by assuming typical diluent densities
of 0.8 and 0.9 kg/liter, respectively. Of course, if actual density values are known from local records, they
should be used in the above equations rather than typical values. Also, if different diluent contents are
used, they should also be reflected in the above calculations. If actual diluent contents are not known, a
typical value of 35 percent may be assumed for inventory purposes.
In lieu of solving the equations in the above example, Table 4.5-1 may be used to estimate long term
emissions from cutback asphalts. Table 4.5-1 directly yields long term emissions as a function of the
volume of diluent added to the cutback and of the density of the diluents and asphalt cement used in the
cutback asphalt. If short term emissions are to be estimated, Figure 4.5-1 should be used in conjunction
with Table 4.5-1.
No control devices are employed to reduce evaporative emissions from cutback asphalts. Asphalt
emulsions are typically used in place of cutback asphalts to eliminate VOC emissions.
4.5-2 EMISSION FACTORS 7/79
-------
1 DAY 1 WEEK
1 MONTH 4 MONTHS
Figure 4.5-1. Percent of diluent evaporated
from cutback asphalt over time.
TABLE 4.5-1. EVAPORATIVE VOC
EMISSIONS FROM CUTBACK ASPHALTS
AS A FUNCTION OF DILUENT CONTENT
AND CUTBACK ASPHALT TYPE3
EMISSION FACTOR RATING: C
Type of Cutback*3
Rapid cure
Medium cure
Slow cure
Percent, by Volume,
of Diluent in Cutback0
25%
17
14
5
35%
24
20
8
45%
32
26
10
7/79
aThese numbers represent the percent, by weight, of
cutback asphalt evaporated- Factors are based on
References 1 and 2.
bTypical densities assumed for diluents used in RC, MC
and SC cutbacks are 0.7, 0.8 and 0,9 kg/liter,
respectively.
cDiluent contents typically range between 25-45%, by
volume. Emissions may be linearly interpolated for any
given type of cutback between these values.
Evaporation Loss Sources
4.5-3
-------
References for Section 4.5
1. R. Keller and R, Bohn, Nonmethane Volatile Organic Emissions from Asphalt Cement and Liquified
Asphalts, EPA-450/3-78-124, U.S. Environmental Protection Agency, Research Triangle Park, NC,
December 1978.
2, F. Kirwan and C. Maday, Air Quality and Energy Conservation Benefits from Using Emulsions To
Replace Asphalt Cutbacks in Certain Paving Operations, EPA-450/2-78-004. U.S. Environmental
Protection Agency, Research Triangle Park. NC, January 1978,
3, David W, Markwordt, Control of Volatile Organic Compounds from Use of Cutback Asphalt, EPA-
450/2-77-037, U.S. Environmental Protection Agency, Research Triangle Park. NC, December 1977.
4.5-4 EMISSION FACTORS 7/79
-------
4.6 SOLVENT DECREASING
4.6.1 General1'2
Solvent degreasing (or solvent cleaning) Is the physical
process of using organic solvents to remove grease, fats, oils, wax
or soil from various metal, glass or plastic items. The types of
equipment used in this method are categorized as cold cleaners,
open top vapor degreasers, or conveyorized degreasers. Nonaqueous
solvents such as petroleum distillates, chlorinated hydrocarbons,
ketones and alcohols are used. Solvent selection is based on the
solubility of the substance to be removed and on the toxicity,
flammability, flash point, evaporation rate, boiling point, cost
and several other properties of the solvent.
The metalworking industries are the major users of solvent
degreasing, i.e., automotive, electronics, plumbing, aircraft,
refrigeration and business machine industries. Solvent cleaning is
also used in industries such as printing, chemicals, plastics,
rubber, textiles, glass, paper and electric power. Most repair
stations for transportation vehicles and electric tools use solvent
cleaning at least part of the time. Many industries use water
based alkaline wash systems for degreasing, and since these systems
emit no solvent vapors to the atmosphere, they are not included in
this discussion.
Cold Cleaners - The two basic types of cold cleaners are maintenance
and manufacturing. Cold cleaners are batch loaded, nonbolling
solvent degreasers, usually providing the simplest and least
expensive method of metal cleaning. Maintenance cold cleaners are
smaller, more numerous and generally using petroleum solvents as
mineral spirits (petroleum distillates and Stoddard solvents).
Manufacturing cold cleaners use a wide variety of solvents, which
perform more specialized and higher quality cleaning with about
twice the average emission rate of maintenance cold cleaners. Some
cold cleaners can serve both purposes.
Cold cleaner operations include spraying, brushing, flushing
and immersion. In a typical maintenance cleaner (Figure 4.6-1),
dirty parts are cleaned manually by spraying and then soaking in
the tank. After cleaning, the parts are either suspended over the
tank to drain or are placed on an external rack that routes the
drained solvent back into the cleaner. The cover Is intended to be
closed whenever parts are not being handled in the cleaner. Typical
manufacturing cold cleaners vary widely in design, but there are
two basic tank designs, the simple spray sink and the dip tank. Of
these, the dip tank provides more thorough cleaning through
immersion, and often Is made to improve cleaning efficiency by
agitation. Small cold cleaning operations may be numerous in urban
areas. However, because of the small quantity of emissions from
each operation, the large number of individual sources within an
urban area, and the application of small cold cleaning to industrial
4/81
Evaporation Loss Sources
4.6-1
-------
I
ro
H
cn
tn
H
§
H
O
DIFFUSION AND
CONVECTION
J-J ^r-AGITATIONS' • •;:•.
CARRY OUT
COLD CLEANER
OPEN TOP VAPOR DEGREASER
00
Figure 4.6-1. Degreaser emission points.
-------
uses not directly associated with degreasing, it is difficult to
identify individual small cold cleaning operations. For these
reasons, factors are provided in Table 4.6-1 to estimate emissions
from small cold cleaning operations over large urban geographical
areas. Factors in Table 4.6—1 are for nonmethane VOC and include
25 percent 1,1,1 - trichloroethane, methylene chloride and
trichlorotrifluoroethane.
TABLE 4.6-1. NONMETHANE VOC EMISSIONS FROM SMAIL
COLD CLEANING DEGREASING OPERATIONS*1
EMISSION FACTOR RATING: C
Per capita
Operating period emission factor
Annual 1.8 kg
4.0 Ib
Diurnal 5.8 g
0.013 Ib
Reference 3.
Assumes a 6 day operating week (313 days/yr).
Open Top Vapor Systems - Open top vapor degreasers are batch loaded
boiling degreasers that clean with condensation of hot solvent
vapor on colder metal parts. Vapor degreasing uses halogenated
solvents (usually perchloroethylene, trichloroethylene, or 1,1,1-tri-
chloroethane), because they are not flammable and their vapors are
much heavier than air.
A typical vapor degreaser (Figure 4.6-1) is a sump containing
a heater that boils the solvent to generate vapors. The height of
these pure vapors is controlled by condenser coils and/or a water
jacket encircling the device. Solvent and moisture condensed on
the coils are directed to a water separator, where the heavier
solvent is drawn off the bottom and is returned to the vapor degreaser.
A "freeboard" extends above the top of the vapor zone to minimize
vapor escape. Parts to be cleaned are immersed in the vapor zone,
and condensation continues until they are heated to the vapor
temperature. Residual liquid solvent on the parts rapidly evaporates
as they are slowly removed from the vapor zone. lip mounted exhaust
systems carry solvent vapors away from operating personnel. Cleaning
action is often increased by spraying the parts with solvent below
the vapor level or by immersing them in the liquid solvent bath.
Nearly all vapor degreasers are equipped with a water separator
which allows the solvent to flow back into the degreaser.
Emission rates are usually estimated from solvent consumption
data for the particular degreasing operation under consideration.
4/81 Evaporation Loss Sources 4.6-3
-------
Solvents are often purchased specifically for use in degreasing and
are not used in any other plant operations. In these cases, purchase
records provide the necessary information, and an emission factor
of 1,000 kg of volatile organic emissions per metric ton of solvent
purchased can be applied, based on the assumption that all solvent
purchased is eventually emitted. When information on solvent
consumption is not available, emission rates can be estimated if
the number and type of degreasing units are known. The factors in
Table 4.6-2 are based on the number of degreasers and emissions
produced nationwide and may be considerably in error when applied
to one particular unit.
The expected effectiveness of various control devices and
procedures is listed in Table 4.6-3. As a first approximation,
this efficiency can be applied without regard for the specific
solvent being used. However, efficiencies are generally higher for
more volatile solvents. These solvents also result in higher
emission rates than those computed from the "average" factors
listed in Table 4.6-2.
Gonveyorized Degreasers - Conveyorized degreasers may operate with
either cold or vaporized solvent, but they merit separate
consideration because they are continuously loaded and are almost
always hooded or enclosed. About 85 percent are vapor types, and
15 percent are nonboiling.
1-3
4.6.2 Emissions and Controls
Emissions from cold cleaners occur through (1) waste solvent
evaporation, (2) solvent carryout (evaporation from wet parts),
(3) solvent bath evaporation, (4) spray evaporation, and (5) agitation
(Figure 4.6-1). Waste solvent loss, cold cleaning's greatest
emission source, can be reduced through distillation and transport
of waste solvent to special incineration plants. Draining cleaned
parts for at least 15 seconds reduces carryout emissions. Bath
evaporation can be controlled by using a cover regularly, by allowing
an adequate freeboard height and by avoiding excessive drafts in
the workshop. If the solvent used is insoluble in, and heavier
than, water, a layer of water two to four inches thick covering the
halogenated solvent can also reduce bath evaporation. This is
known as a "water cover". Spraying at low pressure also helps to
reduce solvent loss from this part of the yrocess. Agitation
emissions can be controlled by using a cover, by agitating no
longer than necessary, and by avoiding the use of agitation with
low volatility solvents. Emissions of low volatility solvents
increase significantly with agitation. However, contrary to what
one might expect, agitation causes only a small increase in emissions
of high volatility solvents. Solvent type is the variable which
most affects cold cleaner emission rates, particularly the volatility
at operating temperatures.
4.6-4 EMISSION FACTORS 4/81
-------
00
TABLE 4.6-2. SOLVENT LOSS EMISSION FACTORS FOR DECREASING OPERATIONS
MISSION FACTOR RATING: C
*d
o
H
fu
r+
P-
O
3
f
O
(0
en
to
o
S
o
-------
TABLE 4.6-3. PROJECTED EMISSION REDUCTION FACTORS FOR SOLVENT DECREASING
System
Control devices
Cover or enclosed design
Drainage facility
Water cover, refrigerated chiller, carbon
adsorption or high freeboard
Solid, fluid spray stream
Safety switches and thermostats
Cold
cleaner
A
X
X
B
X
X
X
X
Vapor
degreaser
A B
X X
X
X
X
X
Conveyorized
degreaser
A
X
B
X
X
X
X
Emission reduction from control devices (%)
Operating procedures
Proper use of equipment
Use of high volatility solvent
Waste solvent reclamation
Reduced exhaust ventilation
Reduced conveyor or entry speed
Emission reduction from operating
procedures(%)
Total emission reduction(%)
13-38 NA
20-40 30-60
X
X
X
40-60
X
X
X
15-45 NA
15-35 20-40 20-30 20-30
28-33e 55-69f 30-60 45-75 20-30 50-70
Reference 2. Ranges of emission reduction present poor to excellent compliance.
X indicates devices or procedures which will effect the given reductions. Letters
A and B indicate different control device circumstances. See Appendix B of
bReference 2.
Only one of these major control devices would be used in any degreasing system. System B
could employ any of them. Vapor degreaser system B could employ any except water cover,
Conveyorized degreaser system B could employ any except water cover and high freeboard.
,If agitation by spraying is used, the spray should not be a shower type.
Breakout between control equipment and operating procedures is not available.
A manual or mechanically assisted cover would contribute 6-18% reduction; draining
parts 15 seconds within the degreaser, 7-20X; and storing waste solvent in containers,
fan additional 15-45%.
Percentages represent average compliance.
As with cold cleaning, open top vapor degreasing emissions
relate heavily to proper operating methods. Most emissions are due
to (6) diffusion and convection, which can be reduced by using an
automated cover, by using a manual cover regularly, by spraying
below the vapor level, by optimizing work loads or by using a
refrigerated freeboard chiller (for which a carbon adsorption unit
would be substituted on larger units). Safety switches and
thermostats that prevent emissions during malfunctions and abnormal
operation also reduce diffusion and convection of the vaporized
solvent. Additional sources are (7) solvent carryout, (8) exhaust
systems and (9) waste solvent evaporation. Carryout is directly
affected by the size and shape of the workload, by racking of parts
and by cleaning and drying time. Exhaust emissions can be nearly
eliminated by a carbon adsorber that collects the solvent vapors
for reuse. Waste solvent evaporation is not so much a problem with
4.6-6
EMISSION FACTORS
4/81
-------
vapor degreasers as it is with cold cleaners, because the halogenated
solvents used are often distilled and recycled by solvent recovery
systems.
Because of their large workload capacity and the fact that
they are usually enclosed, conveyorized degreasers emit less solvent
per part cleaned than do either of the other two types of degreaser.
More so than operating practices, design and adjustment are major
factors affecting emissions, the main source of which is carryout
of vapor and liquid solvents.
References for Section 4.6
1. P.J. Marn, et al., Source Assessment: Solvent Evaporation -
Oegreasinj*, EPA Contract No. 68-02-1874. Monsanto Research
Corporation, Dayton, OH, January 1977.
2. Jeffrey Shumaker, Control of Volatile Organic Emissions from
Solvent Metal Cleaning, EPA-450/2-77-022, U.S. Environmental
Protection Agency, Research Triangle Park, NC, November 1977.
3. W.H. Lamason, "Technical Discussion of Per Capita Emission
Factors for Several Area Sources of Volatile Organic Compounds",
Office of Air Quality Planning and Standards, U.S. Environmental
Protection Agency, Research Triangle Park, NC, March 15, 1981,
unpublished.
4. K.S. Suprenant and D.W. Richards, Study To Support New Sjource
Performance Standards for Solvent Metal Cleaning Operations,
EPA Contract No. 68-02-1329, Dow Chemical Company, Midland,
MI, June 1976.
4/81
Evaporation Loss Sources
4.6-7
-------
-------
4.7 WASTE SOLVENT RECLAMATION
1-4
4.7 .1 Process Description
Waste solvents are organic dissolving agents that are contaminated
with suspended and dissolved solids, organics, water, other solvents,
and/or any substance not added to the solvent during its manufacture.
Reclamation is the process of restoring a waste solvent to a condition
that permits its reuse, either for its original purpose or for other
industrial needs. All waste solvent is not reclaimed, because the cost
of reclamation may exceed the value of the recovered solvent.
Industries that produce waste solvents include solvent refining,
polymerization processes, vegetable oil extraction, metallurgical
operations, pharmaceutical manufacture, surface coating, and cleaning
operations (dry cleaning and solvent degreasing). The amount of solvent
recovered from the waste varies from about 40 to 99 percent, depending
on the extent and characterization of the contamination and on the
recovery process employed.
Design parameters and economic factors determine whether solvent
reclamation is accomplished as a main process by a private contractor,
as an integral part of a main process (such as solvent refining), or as
an added process (as in the surface coating and cleaning industries).
Most contract solvent reprocessing operations recover halogenated hydro-
carbons (e.g., methylene chloride, trichlorotrifluoroethane, and trich-
loroethylene) from degreasing, and/or aliphatic, aromatic, and naphthenic
solvents such as those used in the paint and coatings industry. They
may also reclaim small quantities of numerous specialty solvents such as
phenols, nitriles, and oils.
The general reclamation scheme for solvent reuse is illustrated in
Figure 4.7-1. Industrial operations may not incorporate all of these
steps. For instance, initial treatment is necessary only when liquid
waste solvents contain dissolved contaminants.
4.7.1.1 Solvent Storage and Handling - Solvents are stored before and
after reclamation in containers ranging in size from 55 gallon (0.2 m3)
drums to tanks with capacities of 20,000 gallons (75 m ) or more.
Storage tanks are of fixed or floating roof design. Venting systems
prevent solvent vapors from creating excessive pressure or vacuum inside
fixed roof tanks.
Handling includes loading waste solvent into process equipment and
filling drums and tanks prior to transport and storage. The filling is
most often done through submerged or bottom loading.
2/80 Kvuporalion Loss Sources 4.7-1
-------
STOW
TANK \
Q
WASTE ^B
SOLVENTS
iGE
™
)
FUG
T EMIS
STORAGE
AND
HANDLING
ITIVE FUGITIVE CONDENSER FUGITIVE FUGITIVE STORAGE E
SIONS EMISSIONS VENT A EMISSIONS EMISSIONS TANK VENT E
1 f A /I rt
1
! o ; : o
INITIAL DISTILLATION PURIFI-
.. ....- TREATMENT .. .... 3 -j CATION ^
0
STORAGE
AND
HANDLI
UGITIVE
MISSIONS
A
[
I
. RECLAIMED
„ SOL VENT
NG
WASTE — — ^-INCINERATOR STACK
— - > DISPOSAL - — -^FUGITIVE EMISSIONS
Figure 4.7-1. General waste solvent reclamation scheme and emission points. 1
PROCESS H1.QWER
Figure 4.7-2. Typical fixed bed activated carbon solvent recovery system.6
1,7-2
EMISSION FACTORS
2/80
-------
Table 4.7-1. EMISSION FACTORS FOR SOLVENT RECLAIMING
EMISSION FACTOR RATING: D
a
Source
Storage tank
vent
Condenser
vent
Incinerator
Q
stack
Incinerator
stack
Fugitive
emissions
Spillage0
Loading
Leaks
Open
sources
Criteria
pollutant
Volatile
organic s
Volatile
organics
Volatile
organics
Particulates
Volatile
organics
Volatile
organics
Volatile
organics
Volatile
organics
Emission
Ib/ton
0.02
(0.004-0.09)
3.30
(0.52-8.34)
0.02
1.44
(1.1-2.0)
0.20
0.72
(0.00024-1.42)
NA
NA
factor average
kg/MT
0.01
(0.002-0.04)
1.65
(0.26-4.17)
0.01
0.72
(0.55-1.0)
0.10
0.36
(0.00012-0.71)
NA
NA
Reference 1. Data obtained from state air pollution control agencies
and presurvey sampling. All emission factors are for uncontrolled
process equipment, except those for the incinerator stack. (Reference
1 does not, however, specify what the control is on this stack.)
Average factors are derived from the range of data points available.
Factors for these sources are given in terms of pounds per ton and
kilograms per metric ton of reclaimed solvent. Ranges in parentheses.
, NA - not available.
Storage tank is of fixed roof design.
Only one value available.
4.7 .1.2 Initial Treatment - Waste solvents are initially treated by
vapor recovery or mechanical separation. Vapor recovery entails removal
of solvent vapors from a gas stream in preparation for further reclaim-
ing operations. In mechanical separation, undissolved solid contaminants
are removed from liquid solvents.
2/80
Evaporation Loss Sources
4.7-3
-------
Vapor recovery or collection methods employed include condensation,
adsorption and absorption. Technical feasibility of the method chosen
depends on the solvent's miscibility, vapor composition and concentration,
boiling point, reactivity, and solubility, as well as several other
factors.
Condensation of solvent vapors is accomplished by water cooled
condensers and refrigeration units. For adequate recovery, a solvent
vapor concentration well above 0.009 grains per cubic foot (20 mg/m3) is
required. To avoid explosive mixtures of a flammable solvent and air in
the process gas stream, air is replaced with an inert gas, such as
nitrogen. Solvent vapors that escape condensation are recycled through
the main process stream or recovered by adsorption or absorption.
Activated carbon adsorption is the most common method of capturing
solvent emissions. Adsorption systems are capable of recovering solvent
vapors in concentrations below 0.002 grains per cubic foot (4 mg/m3) of
air. Solvents with boiling points of 290°F (200°C) or more do not
desorb effectively with the low pressure steam commonly used to regen-
erate the carbon beds. Figure 4.7-2 shows a flow diagram of a typical
fixed bed activated carbon solvent recovery system. The mixture of
steam and solvent vapor passes to a water cooled condenser. Water
immiscible solvents are simply decanted to separate the solvent, but
water miscible solvents must be distilled, and solvent mixtures must be
both decanted and distilled. Fluidized bed operations are also in use.
Absorption of solvent vapors is accomplished by passing the waste
gas stream through a liquid in scrubbing towers or spray chambers.
Recovery by condensation and adsorption results in a mixture of water
and liquid solvent, while absorption recovery results in an oil and
solvent mixture. Further reclaiming procedures are required, if solvent
vapors are collected by any of these three methods.
Initial treatment of liquid waste solvents is accomplished by
mechanical separation methods. This includes both removing water by
decanting and removing undissolved solids by filtering, draining,
settling, and/or centrifuging. A combination of initial treatment
methods may be necessary to prepare waste solvents for further
processing.
4.7 .1.3 Distillation - After initial treatment, waste solvents are
distilled to remove dissolved impurities and to separate solvent mix-
tures. Separation of dissolved impurities is accomplished by simple
batch, simple continuous, or steam distillation. Mixed solvents are
separated by multiple simple distillation methods, such as batch or
continuous rectification. These processes are shown in Figure 4.7-3.
In simple distillation, waste solvent is charged to an evaporator.
Vapors are then continuously removed and condensed, and the resulting
sludge or still bottoms are drawn off. In steam distillation, solvents
1,7-1 EMISSION FACTORS 2/80
-------
are vaporized by direct contact with steam which is injected into the
evaporator. Simple batch, continuous, and steam distillations follow
Path I in Figure 4.7-3.
The separation of mixed solvents requires multiple simple distil-
lation or rectification. Batch and continuous rectification are repre-
sented by Path II in Figure 4.7-3. In batch rectification, solvent
vapors pass through a fractionating column, where they contact condensed
solvent (reflux) entering at the top of the column. Solvent not returned
as reflux is drawn off as overhead product. In continuous rectification,
the waste solvent feed enters continuously at an intermediate point in
the column. The more volatile solvents are drawn off at the top, while
those with higher boiling points collect at the bottom.
Design criteria for evaporating vessels depend on waste solvent
composition. Scraped surface stills or agitated thin film evaporators
are the most suitable for heat sensitive or viscous materials. Conden-
sation is accomplished by barometric or shell and tube condensers.
Azeotropic solvent mixtures are separated by the addition of a third
solvent component, while solvents with higher boiling points, e.g., in
the range of high flash naphthas (310°F, 155°C), are most effectively
distilled under vacuum. Purity requirements for the reclaimed solvent
determine the number of distillations, reflux ratios and processing time
needed.
WASTE SOLVENT
STREAM _
EVAPORATION
SOLVENT VAPOR
REFLUX
SOLVENT
VAPOR
II
SLUDGE
I
! FRACTIONATION !
I
1
CONDENSATION
1
DISTILLED SOLVENT
Figure 4*7-3. Distillation process for solvent reclaiming.
4.7.1.4 Purification - After distillation, water is removed from
solvent by decanting or salting. Decanting is accomplished with immis-
cible solvent and water which, when condensed, form separate liquid
layers, one or the other of which can be drawn off mechanically. Addi-
tional cooling of the solvent/water mix before decanting increases the
separation of the two components by reducing their solubility. In
salting, solvent is passed through a calcium chloride bed, and water is
removed by absorption.
2/80
Evaporation Los,* Sources
4.7-5
-------
During purification, reclaimed solvents are stabilized, if neces-
sary. Buffers are added to virgin solvents to ensure that pH level is
kept constant during use. To renew it, special additives are used
during purification. The composition of these additives is considered
proprietary.
4.7.1.5 Waste Disposal - Waste materials separated from solvents during
initial treatment and distillation are disposed of by incineration,
landfilling or deep well injection. The composition of such waste
varies, depending on the original use of the solvent. But up to 50
percent is unreclaimed solvent, which keeps the waste product viscous
yet liquid, thus facilitating pumping and handling procedures. The
remainder consists of components such as oils, greases, waxes, deter-
gents, pigments, metal fines, dissolved metals, organics, vegetable
fibers, and resins.
About 80 percent of the waste from solvent reclaiming by private
contractors is disposed of in liquid waste incinerators. About 14
percent is deposited in sanitary landfills, usually in 55 gallon drums.
Deep well injection is the pumping of wastes between impermeable geologic
strata. Viscous wastes may have to be diluted for pumping into the
desired stratum level.
1 3-5
4.7.2 Emissions and Controls '
Volatile organic and particulate emissions result from waste solvent
reclamation. Emission points include storage tank vents [1], condenser
vents [2], incinerator stacks [3], and fugitive losses (numbers refer to
Figures 4.7-1 and -3). Emission factors for these sources are given in
Table 4.7-1.
Solvent storage results in volatile organic compound (VOC)
emissions from solvent evaporation (Figure 4.7-1, emission point 1).
The condensation of solvent vapors during distillation (Figure 4.7-3)
also involves VOC emissions, and if steam ejectors are used, emission of
steam and noncondensables as well (Figures 4.7-1 and -3, point 2).
Incinerator stack emissions consist of solid contaminants that are
oxidized and released as particulates, unburned organics, and combustion
stack gases (Figure 4.7-1, point 3).
VOC emissions from equipment leaks, open solvent sources (sludge
drawoff and storage from distillation and initial treatment operations),
solvent loading, and solvent spills are classifed as fugitive. The
former two sources are continuously released, and the latter two,
intermittently.
Solvent reclamation is viewed by industry as a form of control in
itself. Carbon adsorption systems can remove up to 95 percent of the
solvent vapors from an air stream. It is estimated that less than 50
percent of reclamation plants run by private contractors use any control
technology.
4,7-6 EMISSION FACTORS 2/80
-------
Volatile organic emissions from the storage of solvents can be
reduced by as much as 98 percent by converting from fixed to floating
roof tanks, although the exact percent reduction also depends on solvent
evaporation rate, ambient temperature, loading rate, and tank capacity.
Tanks may also be refrigerated or equipped with conservation vents which
prevent air inflow and vapor escape until some preset vacuum or pressure
develops.
Solvent vapors vented during distillation are controlled by scrub-
bers and condensers. Direct flame and catalytic afterburners can also
be used to control noncondensables and solvent vapors not condensed
during distillation. The time required for complete combustion depends
on the flamtnability of the solvent. Carbon or oil adsorption may be
employed also, as in the case of vent gases from the manufacture of
vegetable oils.
Wet scrubbers are used to remove particulates from sludge incin-
erator exhaust gases, although they do not effectively control submicron
particles.
Submerged rather than splash filling of storage tanks and tank cars
can reduce solvent emissions from this source by more than 50 percent.
Proper plant maintenance and loading procedures reduce emissions from
leaks and spills. Open solvent sources can be covered to reduce these
fugitive emissions.
References for Section 4.7
1. D. R. Tierney and T. W. Hughes, Source Assessment: Reclaiming_of_
Waste Solvents _- State of the Art, EPA-600/2-78/004f, U.S.
Environmental Protection Agency, Cincinnati, OH, April 1978.
2. J. E. Levin and F. Scofield, "An Assessment of the Solvent
Reclaiming Industry". Proceedings of the 170th Meeting of the
American Chemical Society, Chicago, IL, 35_(_2) :416-418,
August 25-29, 1975.
3. H. M. Rowson, "Design Considerations in Solvent Recovery".
Proceedings of the Metropolitan Engineers' Council on Air Resouces
(MECAR) Symposium on New Developments in Air Pollutant Control, New
York, NY, October 23, 1961, pp. 110-128.
4. J. C. Cooper and F. T. Cuniff, "Control of Solvent Emissions".
Proceedings of the Metropolitan Engineers' Council on Air Resources
(MECAR) Symposium on New Developments in Air Pollution Control, New
York, NY, October 23, 1961, pp. 30-41.
2/80 Kva|iorution Loss Sources 1.7-7
-------
5. W. R. Meyer, "Solvent Broke", Proceedings of TAPPI Testing Paper
Synthetics Conference, Boston, MA, October 7-9, 1974, pp. 109-115.
6. Nathan R. Shaw, "Vapor Adsorption Technology for Recovery of
Chlorinated Hydrocarbons and Other Solvents", Presented at the 80th
Annual Meeting of the Air Pollution Control Association, Boston,
MA, June 15-20, 1975.
4.7.8 EMISSION FACTORS 2/80
-------
4.8 TANK AND DRUM CLEANING
4.8.1 General
Rail tank cars, tank trucks and drums are used to transport about
700 different commodities. Rail tank cars and most tank trucks and
drums are in dedicated service (carrying one commodity only) and, unless
contaminated, are cleaned only prior to repair or testing. Nondedicated
tank trucks (about 20,000, or 22 percent of the total in service) and
drums (approximately 5.6 million, or 12.5 percent of the total) are
cleaned after every trip.
4.8.1.1 Rail Tank Cars - Most rail tank cars are privately owned. Some
cars, like those owned by the railroads, are operated for hire. The
commodities hauled are 35 percent petroleum products, 20 percent organic
chemicals, 25 percent inorganic chemicals, 15 percent compressed gases,
and 5 percent food products. Petroleum products considered in this
study are glycols, vinyls, acetones, "benzenes, creosote, etc. Not
included in these figures are gasoline, diesel oil, fuel oils, jet
fuels, and motor oils, the greatest portion of these being transported
in dedicated service.
Much tank car cleaning is conducted at shipping and receiving
terminals, where the wastes go to the manufacturers' treatment systems.
However, 30 to 40 percent is done at service stations operated by tank
car owner/lessors. These installations clean waste of a wide variety of
commodities, many of which require special cleaning methods.
A typical tank car cleaning facility cleans 4 to 10 cars per day.
Car capacity varies from 10,000 to 34,000 gallons (40 - 130 rn3). Clean-
ing agents include steam, water, detergents and solvents, which are
applied using steam hoses, pressure wands, or rotating spray heads
placed through the opening in the top of the car. Scraping of hardened
or crystallized products is often necessary. Cars carrying gases and
volatile materials, and those needing to be pressure tested, must be
filled or flushed with water. The average amount of residual material
cleaned from each car is estimated to be 550 Ib (250 kg). Vapors from
car cleaning not flared or dissolved in water are dissipated to the
atmosphere.
4.8.1.2 Tank Trucks - Two thirds of the tank trucks in service in the
United States are operated for hire. Of these, 80 percent are used to
haul bulk liquids. Most companies operate fleets of five trucks or
less, and whenever possible, these trucks are assigned to dedicated
service. Commodities hauled and cleaned are 15 percent petroleum pro-
ducts (except as noted in 4.8.1.1), 35 percent organic chemicals, 5
percent food products, and 10 percent other products.
Interior washing is carried out at many tank truck dispatch ter-
minals. Cleaning agents include water, steam, detergents, bases, acids
and solvents, which are applied with hand-held pressure wands or by
2/80 Evaporation Lost* Sources 1.8-1
-------
Turco or Butterworth rotating spray nozzles. Detergent, acidic or basic
solutions are usually used until spent and then sent to treatment facil-
ities. Solvents are recycled in a closed system, with sludges either
incinerated or landfilled. The average amount of material cleaned from
each trailer is 220 Ib (100 kg). Vapors from volatile material are
flared at a few terminals but most commonly are dissipated to the atmos-
sphere. Approximately 60 gallons (0.23 m3) of liquid are used per tank
truck steam cleaning and 5500 gallons (20.9 m3) for full flushing.
Table 4.8-1. EMISSION FACTORS FOR RAIL TANK CAR CLEANING3
EMISSION FACTOR RATING: D
Chemical Class
Compound
Ethylene glycol
Chlorobenzene
o-Dichlorobenzene
Creosote
Vapor
pressure
low
medium
low
low
Total
Viscosity
high
medium
medium
high
emissions
Ib/car
0.0007
0.0346
0.1662
5.1808
g/car
0.3
15.7
75.4
2350
a
Reference 1. Emission factors are in terms of average weight of
pollutant released per car cleaned.
Two hour test duration.
Q
Eight hour test duration.
4.8.1.3 Drums - Both 55 and 30 gallon (0.2 and 0.11 m3) drums are used
to ship a vast variety of commodities, with organic chemicals (including
solvents) accounting for 50 percent. The remaining 50 percent includes
inorganic chemicals, asphaltic materials, elastromeric materials, printing
inks, paints, food additives, fuel oils and other products.
Drums made entirely of 18 gauge steel have an average life, with
total cleaning, of eight trips. Those with 20 gauge bodies and 18 gauge
heads have an average life of three trips. Not all drums are cleaned,
especially those of thinner construction.
Tighthead drums which have carried materials that are easy to clean
are steamed or washed with base. Steam cleaning is done by inserting a
nozzle into the drum, with vapors going to the atmosphere. Base washing
is done by tumbling the drum with a charge of hot caustic solution and
some pieces of chain.
Drums used to carry materials that are difficult to clean are
burned out, either in a furnace or in the open. Those with tightheads
have the tops cut out and are reconditioned as open head drums. Drum
burning furnaces may be batch or continuous. Several gas burners bathe
the drum in flame, burning away the contents, lining and outside paint
in a nominal 4 minute period and at a temperature of at least 900° but
I.K-2
EMISSION FACTORS
2/80
-------
not more than 1000°F (480 - 540°C) to prevent warping of the drum.
Emissions are vented to an afterburner or secondary combustion chamber,
where the gases are raised to at least 1500°F (760°C) for a minimum of
0.5 seconds. The average amount of material removed from each drum is
4.4 Ib (2 kg).
Table 4.8-2. EMISSION FACTORS FOR TANK TRUCK CLEANING0
EMISSION FACTOR RATING: D
Chemical Class
Compound
Acetone
Perchloroethylene
Methyl methacrylate
Phenol
Propylene glycol
Vapor
pressure
high
high
medium
low
low
Viscosity
low
low
medium
low
high
Total
emissions
Ib/truck
0.686
0.474
0.071
0.012
0.002
K/ truck
311
215
32.4
5.5
1.07
Reference 1. One hour test duration.
4.8.2 Emissions and Controls
4,8.2.1 Rail Tank Cars and Tank Trucks - Atmospheric emissions from
tank car and truck cleaning are predominantly volatile organic chemical
vapors. To achieve a practical but representative picture of these
emissions, the organic chemicals hauled by the carriers must be broken
down into classes of high, medium and low viscosities and high, medium
and low vapor pressures. This is because high viscosity materials do
not drain readily, affecting the quantity of material remaining in the
tank, and high vapor pressure materials volatilize more readily during
cleaning and tend to lead to greater emissions.
Practical and economically feasible controls of atmospheric
emissions from tank car and truck cleaning do not exist, except for
containers transporting commodities that produce combustible gases and
water soluble vapors (such as ammonia and chlorine). Gases which are
displaced as tanks are filled are sent to a flare and burned. Water
soluble vapors are absorbed in water and sent to the wastewater system.
Any other emissions are vented to the atmosphere.
Tables 4.8-1 and 4.8-2 give emission factors for representative
organic chemicals hauled by tank cars and trucks.
4.8.2.2 Drums - There is no control for emissions from steaming of
drums. Solution or caustic washing yields negligible air emissions,
because the drum is closed during the wash cycle. Atmospheric emissions
from steaming or washing drums are predominantly organic chemical vapors.
2/80
Evaporation Loss Sources
1,8-3
-------
Air emissions from drum burning furnaces are controlled by proper
operation of the afterburner or secondary combustion chamber, where gases
are raised to at least 1400°F (760°C) for a minimum of 0.5 seconds. This
normally ensures complete combustion of organic materials and prevents the
formation, and subsequent release, of large quantities of NOX, CO and
particulates. In open burning, however, there Is no feasible way of con-
trolling the release of incomplete combustion products to the atmosphere.
Conversion of open cleaning operations to closed cycle cleaning and elim-
ination of open air drum burning seem to be the only control alternatives
immediately available.
Table 4.8-3 gives emission factors for representative criteria
pollutants emitted from drum burning and cleaning.
TABLE 4.8-3. EMISSION FACTORS FOR DRUM BURNING3
EMISSION FACTOR RATING: E
Pollutant
Particulate
NOX
voc
Total Emissions
Controlled
Ib/drum g/drum
0.02646 12b
0.00004 0.018
negligible
Uncontrolled
Ib/drum g/drum
0.035 16
0.002 0.89
negligible
aReference 1. Emission factors are in terms of weight of pollutant
released per drum burned, except for VOC, which are per drum washed.
^Reference 1, Table 17 and Appendix A.
Reference for Section 4.8
1. T. R. Blackwood , et al., Source Assessment; Rail Tank Car, Tank Truck,
and Drum Cleaning, State of the Art, EPA-600/2-78-004g, U. S. Environ-
mental Protection Agency, Research Triangle Park, NC, April 1978.
4.8-4
EMISSION FACTORS
2/80
-------
4.9 GRAPHIC ARTS
4.9.1 General
Process Description - The term "graphic arts" as used here means
four basic processes of the printing industry: web offset lithography,
web letterpress, rotogravure and flexography. Screen printing and
manual and sheet fed techniques are not included in this discussion.
Printing may be performed on coated or uncoated paper and on
other surfaces, as in metal decorating and some fabric coating
(see Section 4.2, Industrial Surface Coating). The material to
receive the printing is called the substrate. The distinction
between printing and paper coating, which may employ rotogravure or
lithographic methods, is that printing invariably involves the
application of ink by a printing press. However, printing and
paper coating have these elements in common: application of a
relatively high solvent content material to the surface of a moving
web or film, rapid solvent evaporation by movement of heated air
across the wet surface, and solvent laden air exhausted from the
system.
Printing inks vary widely in composition, but all consist of
three major components: pigments, which produce the desired colors
and are composed of finely divided organic and inorganic materials;
binders, the solid components that lock the pigments to the substrate
and are composed of organic resins and polymers or, in some inks,
oils and rosins; and solvents, which dissolve or disperse the
pigments and binders and are usually composed of organic compounds.
The binder and solvent make up the "vehicle" part of the ink. The
solvent evaporates from the ink into the atmosphere during the
drying process.
Web Offset Lithography - Lithography, the process used to produce
about 75 percent of books and pamphlets and an increasing number of
newspapers, is characterized by a planographic image carrier
(i.e., the image and nonimage areas are on the same plane). The
image area is ink wettable and water repellant, and the nonimage
area is chemically repellant to ink. The solution used to dampen
the plate may contain 15 to 30 percent isopropanol, if the Dalgren
dampening system is used.8 When the image is applied to a rubber
covered "blanket" cylinder and then transferred onto the substrate,
the process is known as "offset" lithography. When a web (i.e., a
continuous roll) of paper is employed with the offset process, this
is known as web offset printing. Figure 4.9-1 illustrates a web
offset lithography publication printing line. A web newspaper
printing line contains no dryer, because the ink contains very
little solvent, and somewhat porous paper is generally used.
Web offset employs "heatset" (i.e., heat drying offset) inks
that dry very quickly. For publication work the inks contain about
40 percent solvent, and for newspaper work 5 percent solvent is
used. In both cases, the solvents are usually petroleum derived
4/81 Evaporation Loss Sources 4.9-1
-------
GAS-
I THERMAL OR '
CATALYTIC
i i ncmvmL. un .
•i CATALYTIC |NK
[INCINERATOR' JHERM
L- r--J—L —
INK SOLVENT AND
THERMAL DEGRADATION
PRODUCTS
Z.~_._L.
1 HEAT 1
1 EXCHANGER 1
1 #1 1
* 1
1 .
i
1
1
\ 1
| 1 b.
| SHELL AND
| FLAT TUBE
• HEAT
j EXCHANGER
* \ #2
COMBUSTION
PRODUCTS,
UNBURNED
ORGANICS,
O, DEPLETED
AIR
FRESH AIR
EXHAUST FAN
| FILTER || FILTER
HEATSET
INK
WASHUP -
SOLVENTS.
WEB
INK SOLVENT AND
THERMAL DEGRADATION
PRODUCTS
AIR AND SMOKE
WATER AND
ISOPROPANOL
VAPOR
t
PRINTED WEB
TT
—»• WATER AND
ISOPROPANOL VAPOR
AIR
AIR
WATER ISOPROPANOL
(WITH DALGREN
DAMPENING SYSTEM)
Figure 4.9-1. Web offset lithography publication printing line emission points
11
4.9-2
EMISSION FACTORS
4/81
-------
hydrocarbons. In a publication web offset process, the web is
printed on both sides simultaneously and passed through a tunnel or
floater dryer at about 200-290°C (400-500°F). The dryer may be hot
air or direct flame. Approximately 40 percent of the incoming
solvent remains in the ink film, and more may be thermally degraded
in a direct flame dryer. The web passes over chill rolls before
folding and cutting. In newspaper work no dryer is used, and most
of the solvent is believed to remain in the ink film on the paper.11
Web Letterpress - Letterpress is the oldest form of moveable type
printing, and it still dominates in periodical and newspaper publish-
ing, although numerous major newspapers are converting to web offset.
In letterpress printing, the image area is raised, and the ink is
transferred to the paper directly from the image surface. The
image carrier may be made of metal or plastic. Only web presses
using solventborne inks are discussed here. Letterpress newspaper
and sheet fed printing use oxidative drying inks, not a source of
volatile organic emissions. Figure 4.9-2 shows one unit of a web
publication letterpress line.
Publication letterpress printing uses a paper web that is
printed on one side at a time and dried after each color is applied.
The inks employed are heatset, usually of about 40 volume percent
solvent. The solvent in high speed operations is generally a
selected petroleum fraction akin to kerosene and fuel oil, with a
boiling point of 200-370°C (400-700°F),13
Rotogravure - In gravure printing, the image area is engraved, or
"intaglio" relative to the surface of the image carrier, which is a
copper plated steel cylinder that is usually also chrome plated to
enhance wear resistance. The gravure cylinder rotates in an ink
trough or fountain. The ink is picked up in the engraved area, and
ink is scraped off the nonimage area with a steel "doctor blade".
The image is transferred directly to the web when it is pressed
against the cylinder by a rubber covered impression roll, and the
product is then dried. Rotary gravure (web fed) systems are known
as "rotogravure" presses.
Rotogravure can produce illustrations with excellent color
control, and it may be used on coated or uncoated paper, film, foil
and almost every other type of substrate. Its use is concentrated
in publications and advertising such as newspaper supplements,
magazines and mail order catalogues; folding cartons and other
flexible packaging materials; and specialty products such as wall
and floor coverings, decorated household paper products and vinyl
upholstery. Figure 4.9-3 illustrates one unit of a publication
rotogravure press. Multiple units are required for printing multiple
colors.
The inks used in rotogravure publication printing contain from
55 to 95 volume percent low boiling solvent (average is 75 volume
percent), and they must have low viscosities. Typical gravure
4/81
Evaporation Loss Sources
4.9-3
-------
1 1
1 THERMAL
WEB
"*! INCINERATOR C*
1 j
J i
GAS HEAT 1
1 EXCHANGER
| #1
* I
i— — —
EXHAUST FAN r
I
FAN ^J
_/
HEATSET INK
COMBUSTION
' PRODUCTS,
~J UNBURNED
Dm" A O V 1 O Ru AIM IU%* ,
»• HbAU 1 ^n.RFPIFTcp
"#2° i ^ AIR
> j < _.._,,__ Uf FRESH AIR
FILTER | | FILTERJ ' '
1 '
S"\ CAM rA<: 1 ONLY WHEN
(J FAN GAS CATALYTIC
^^ 1 UNIT IS
t t_ USED HERE
"~ r "i
AIR HEATER ^i CATALYTIC |
FOR DRYER j INCINERATOR!
i _ _!
t /k~* '
GAS f ' ) SUPPLY FAN
SOLVENT AND THERMAL AIR AND SMOKE
DEGRADATION
PRODUCTS
TUNNEL OR rm. .
T^r, _, t-HILL k^ PRINTED WEB
— "-WASHUP DRYER
*— SOLVENTS
AIR
COOL WATER
:„+, 11
Figure 4.9-2. Web letterpress publication printing line emission points,
4.9-4
EMISSION FACTORS
4/81
-------
solvents include alcohols, aliphatic naphthas, aromatic hydrocarbons,
esters, glycol ethers, ketones and nitroparaffins. Water base
inks are in regular production use in some packaging and specialty
applications, such as sugar bags.
Rotogravure is similar to letterpress printing in that the web
is printed on one side at a time and must be dried after application
of each color. Thus, for four color, two sided publication printing,
eight presses are employed, each including a pass over a steam drum
or through a hot air dryer at temperatures from ambient up to 120°C
(250°F) where nearly all of the solvent is removed. For further
information, see Section 4.9.2.
Flexography - In flexographic printing, as in letterpress, the image
area is above the surface of the plate. The distinction is that
flexography uses a rubber image carrier and alcohol base inks. The
process is usually web fed and is employed for medium or long
multicolor runs on a variety of substrates, including heavy paper,
fiberboard and metal and plastic foil. The major categories of the
flexography market are flexible packaging and laminates, multiwall
bags, milk cartons, gift wrap, folding cartons, corrugated paperboard
(which is sheet fed), paper cups and plates, labels, tapes and
envelopes. Almost all milk cartons and multiwall bags and half of
all flexible packaging are printed by this process.
Steam set inks, employed in the "water flexo" or "steam set
flexo" process, are low viscosity inks of a paste consistency that
are gelled by water or steam. Steam set inks are used for paper
bag printing, and they produce no significant emissions. Water
base inks, usually pigmented suspensions in water, are also available
for some flexographic operations, such as the printing of multiwall
bags.
Solvent base inks are used primarily in publication printing,
as shown in Figure 4.9-3. As with rotogravure, flexography publi-
cation printing uses very fluid inks of about 75 volume percent
organic solvent. The solvent, which must be rubber compatible, may
be alcohol, or alcohol mixed with an aliphatic hydrocarbon or
ester. Typical solvents also include glycols, ketones and ethers.
The inks dry by solvent absorption into the web and by evaporation,
usually in high velocity steam drum or hot air dryers, at temper-
atures below 120°C (250°F).3'13 As in letterpress publishing, the
web is printed on only one side at a time. The web passes over
chill rolls after drying.
Emissions and Controls - Significant emissions from printing
operations consist primarily of volatile organic solvents. Such
emissions vary with printing process, ink formulation and coverage,
press size and speed, and operating time. The type of paper (coated
or uncoated) has little effect on the quantity of emissions, although
low levels of organic emissions are derived from the paper stock
4/81
Evaporation Loss Sources
4.9-5
-------
TO ATM(
i
DSPHERE
TRACES OF
WATER
AND
SOLVENT
HOI
1
JCON
x 1
COO
STEAM PLUS
SOLVENT
VAPOR I
Y i
\ \
1
i^
|
X '
* 1
WATER
l._,
1
DENSER |
r*
L WATER
ACTIVATEC
ADSOI
(ACTIVE
i DECANTER
> CARBON i \
1BER |
MODE)
i
ACTIVATED CARBON j-*-'
ADSORBER '
(REGENERATING) l~)f-
J
1 j ^
SOLVENTJ 1 SOLVENTS
.MIXTURE. 1 *"
f JSTIIII
i i !
1 *" 1 1 *• WATER
1 WARM ! |
WATER
/ COMBUSTION
C PRODUCTS
r_J ,
r i
1 i i
STEAM ' STEAM BOILER |
'^— < "-*— — — 1 i
urrr
GAS AIR 1
WATER
SOLVENT LADEN AIR
WEB-
INK
! -
INK
FOUNTAIN
*—
PRESS
(ONE UNIT)
STEAM DRUM OR
HOT AIR DRYER
-*-
CHILL
ROLLS
i i i
PRINTED WEB
1 MT 171
AIR AIR HEAT COOL i
HEAT
FROM STEAM,
HOT WATER,
OR HOT AIR
COOL WATER
Figure 4.9-3. Rotogravure and flexography printing line emission points (chill rolls not
used in rotogravure publication printing).''
4.9-6
EMISSION FACTORS
4/81
-------
1 3
during drying. High volume web fed presses such as those discussed
above are the principal sources of solvent vapors. Total annual
emissions from the industry in 1977 were estimated to be 380,000 Mg
(418,000 tons). Of this total, lithography emits 28 percent, letter-
press 18 percent, gravure 41 percent and flexography 13 percent.-^
Most of the solvent contained in the ink and used for dampening
and cleanup eventually finds its way into the atmosphere, but some
solvent remains with the printed product leaving the plant and is
released to the atmosphere later. Overall solvent emissions can be
computed from Equation 1 using a material balance concept, except
in cases where a direct flame dryer is used and some of the solvent
is thermally degraded.
The density of naphtha base solvent at 21°C (70°F) is
6.2 pounds per gallon.
total
= T
(1)
where
E , = total solvent emissions including those from the
printed product, kg (Ib)
T = total solvent use including solvent contained in
ink as used, kg (Ib)
The solvent emissions from the dryer and other printline
components can be computed from Equation 2. The remaining solvent
leaves the plant with the printed product and/or is degraded in the
dryer.
ISd (100 - P)
100 100
(2)
where
E = solvent emissions from printline, kg (Ib)
I = ink use, liters (gallons)
d = solvent density, kg/liter (Ib/gallon)
S and P = factors from Table 4.9-1
Per Capita Emission Factors - Although major sources contribute
most of the emissions for graphic arts operations, considerable
emissions also originate from minor graphic arts applications,
including inhouse printing services in general industries. Small
sources within the graphic arts industry are numerous and difficult
to identify, since many applications are associated with nonprinting
4/81
Evaporation Loss Sources
4.9-7
-------
TABLE 4.9-1.
TYPICAL PARAMETERS FOR COMPUTING SOLVENT EMISSIONS
FROM PRINTING LINES a'b
Process
Solvent
Content of Ink
(Volume %) [S]
Solvent Remaining
in Product and
Destroyed in Dryer
(%) [P]°
Emission
Factor
Rating
Web Offset
Publication
Newspaper
Web Letterpress
Publication
Newspaper
Rotogravure
Flexography
40
40
0
75
75
40 (hot air dryer)
60 (direct flame dryer)
100
40
(not applicable)
2-7
2-7
C
C
References 1 and 14.
Values for S and P are typical. Specific values for S and P
^should be obtained from a source to estimate its emissions.
"For certain packaging products, amount of solvent retained is
regulated by FDA.
TABLE 4.9-2. PER CAPITA NONMETHANE VOC EMISSION
FACTORS FOR SMALL GRAPHIC ARTS APPLICATIONS
EMISSION FACTOR RATING: D
Units
Emission Factor
kg/year/cap ita
Ib/year/capita
g/day/capita
Ib/day/capita
0.4
0.8
1
0.003
All nonmethane VOC.
Reference 15.
Assumes a 6 day operating week (313 days/yr).
industries. Table 4.9-2 presents per capita factors for estimating
emissions from small graphic arts operations. The factors are
entirely nonmethane VOC and should be used for emission, estimates
over broad geographical areas.
Web Offset Lithography - Emission points on web offset lithography
publication printing lines include (1) the ink fountains, (2) the
4.9-8
EMISSION FACTORS
4/81
-------
dampening system, (3) the plate and blanket cylinders, (4) the
dryer, (5) the chill rolls and (6) the product (see Figure 4.9-1).
Alcohol is emitted from Points 2 and 3. Washup solvents are a
small source of emissions from Points 1 and 3. Drying (Point 4) is
the major source, because 40 to 60 percent of the ink solvent is
removed from the web during this process.
The quantity of web offset emissions may be estimated from
Equation 1, or from Equation 2 and the appropriate data from
Table 4.9-1.
Web Letterpress - Emission points on web letterpress publication
printing lines are: the press (includes the image carrier and
inking mechanism), the dryer, the chill rolls and the product (see
Figure 4.9-2).
Web letterpress publication printing produces significant
emissions, primarily from the ink solvent, about 60 percent of
which is lost in the drying process. Washup solvents are a small
source of emissions. The quantity of emissions can be computed as
described for web offset.
Letterpress publication printing uses a variety of papers and
inks that lead to emission control problems, but losses can be
reduced by a thermal or catalytic incinerator, either of which may
be coupled with a heat exchanger.
Rotogravure - Emissions from rotogravure printing occur at the ink
fountain, the press, the dryer and the chill rolls (see Figure 4.9-3).
The dryer is the major emission point, because most of the VOC in
the low boiling ink is removed during drying. The quantity of
emissions can be computed from Equation 1, or from Equation 2 and
the appropriate parameters from Table 4.9-1.
Vapor capture systems are necessary to minimize fugitive
solvent vapor loss around the ink fountain and at the chill rolls.
Fume incinerators and carbon adsorbers are the only devices that
have a high efficiency in controlling vapors from rotogravure
operations.
Solvent recovery by carbon adsorption systems has been quite
successful at a number of large publication rotogravure plants.
These presses use a single water immiscible solvent (toluene) or a
simple mixture that can be recovered in approximately the propor-
tions used in the ink. All new publication gravure plants are
being designed to include solvent recovery.
Some smaller rotogravure operations, such as those that print
and coat packaging materials, use complex solvent mixtures in which
many of the solvents are water soluble. Thermal incineration with
heat recovery is usually the most feasible control for such operations.
4/81
Evaporation Loss Sources
4.9-9
-------
TABLE 4.9-3. ESTIMATED CONTROL TECHNOLOGY EFFICIENCIES
FOR PRINTING LINES
Reduction in
Method Application Organic Emissions
CO
Carbon adsorption Publication rotogravure
operations 75
b c
Incineration Web offset lithography 95,
Web letterpress 95
Packaging rotogravure
printing operations 65
Flexography printing
operations 60
Waterborne inks Some packaging rotogravure
printing operations^ 65-75
Some flexography packaging
printing operations 60
Q
Reference 3. Overall emission reduction efficiency (capture
.efficiency multiplied by control device efficiency).
Direct flame (thermal) catalytic and pebble bed. Three or more
pebble beds in a system have a heat recovery efficiency of 85%.
Reference 12. Efficiency of volatile organic removal - does not
.consider capture efficiency.
Reference 13. Efficiency of volatile organic removal - does not
consider capture efficiency.
Solvent portion consists of 75 volume % water and 25 volume %
..organic solvent.
With less demanding quality requirements.
With adequate primary and secondary heat recovery, the amount of
fuel required to operate both the incinerator and the dryer system
can be reduced to less than that normally required to operate the
dryer alone.
In addition to thermal and catalytic incinerators, pebble bed
incinerators are also available. Pebble bed incinerators combine
the functions of a heat exchanger and a combustion device, and can
achieve a heat recovery efficiency of 85 percent.
VOC emissions can also be reduced by using low solvent inks.
Waterborne inks, in which the volatile portion contains up to
20 volume percent water soluble organic compounds, are used
extensively in rotogravure printing of multiwall bags, corrugated
paperboard and other packaging products, although water absorption
into the paper limits the amount of waterborne ink that can be
printed on thin stock before the web is seriously weakened.
4.9-10 EMISSION FACTORS 4/81
-------
Flexography - Emission points on flexographic printing lines are
the ink fountain, the press, the dryer and the chill rolls (see
Figure 4.9-3). The dryer is the major emission point, and emissions
can be estimated from Equation 1, or from Equation 2 and the
appropriate parameters from Table 4.9-1.
Vapor capture systems are necessary to minimize fugitive
solvent vapor loss around the ink fountain and at the chill rolls.
Fume incinerators are the only devices proven highly efficient in
controlling vapors from flexographic operations. VOC emissions can
also be reduced by using waterborne inks, which are used extensively
in flexographic printing of packaging products.
Table 4.9-3 shows estimated control efficiencies for printing
operations.
References for Section 4.9
1. "Air Pollution Control Technology Applicable to 26 Sources of
Volatile Organic Compounds", Office of Air Quality Planning
and Standards, U.S. Environmental Protection Agency, Research
Triangle Park, NC, May 27, 1977. Unpublished.
2. Peter N. Formica, Controlled and Uncontrolled Emission Rates
and Applicable Limitations for Eighty Processes, EPA-340/1-78-004,
U.S. Environmental Protection Agency, Research Triangle Park,
NC, April 1978.
3. Edwin J. Vincent and William M. Vatavuk, Control of Volatile^
Organic jSmissjLons from Existing Stationary Sources^ Volume VIII:
Graphic Arts - Rotogravure and Flexography, EPA-450/2-78-033,
U.S. Environmental Protection Agency, Research Triangle Park,
NC, December 1978.
4. Telephone communication with C.M. Higby, Gal/Ink, Berkeley, CA,
March 28, 1978.
5. T.W. Hughes, et al., Prioritization of Air Pollution from
Industrial Surface Coating Operations, EPA-650/2-75-019a, U.S.
Environmental Protection Agency, Research Triangle Park, NC,
February 1975.
6. Harvey F. George, "Gravure Industry's Environmental Program",
Environmental Aspects of Chemical Use in Printing Operations,
EPA-560/1-75-005, U.S. Environmental Protection Agency, Research
Triangle Park, NC, January 1976.
K.A. Bownes, "Material of Flexography", ibid.
Ben H. Carpenter and Garland R. Hilliard, "Overview of Printing
Processes and Chemicals Used", ibid.
7.
8.
4/81
Evaporation Loss Sources
4.9-11
-------
9. R.L. Harvin, "Recovery and Reuse of Organic Ink Solvents",
ibid.
10. Joseph L. Zborovsky, "Current Status of Web Heatset Emission
Control Technology", ib id .
11. R.R. Gadomski, et al., Evaluations of Emission and Control
Technologies in the Graphic Arts T-ndustries, Phase I; Final
APTD-0597, National Air Pollution Control Administration,
Cincinnati, OH, August 1970.
12. R.R. Gadomski, et al . , Evaluations of Emissions and__Cp_ntrpl
Technologies in the Graphic Art% Industries, Phase _!_!;_ __W_eb
Offset and _ Metal Decorating Processess, APTD-1463, U.S.
Environmental Protection Agency, Research Triangle Park, NC,
May 1973.
13. Control Techniques for Volatile Organic Emissions from
Stationary Sources, EPA-450/2-78-022, U.S. Environmental
Protection Agency, Research Triangle Park, NC, May 1978.
14. Telephone communication with Edwin J. Vincent, Office of Air
Quality Planning and Standards, U.S. Environmental Protection
Agency, Research Triangle Park, NC, July 1979.
15. W.H. Lamason, "Technical Discussion of Per Capita Emission
Factors for Several Area Sources of Volatile Organic Compounds",
Office of Air Quality Planning and Standards, U.S. Environmental
Protection Agency, Research Triangle Park, NC, March 15, 1981.
Unpublished .
4.9-12 EMISSION FACTORS 4/81
-------
4.9.2 PUBLICATION GRAVURE PRINTING
1-2
Process Description - Publication gravure printing is the printing
by the rotogravure process of a variety of paper products such as
magazines, catalogs, newspaper supplements and preprinted inserts,
and advertisements. Publication printing is the largest sector
involved in gravure printing, representing over 37 percent of the
total gravure product sales value in a 1976 study.
The rotogravure press is designed to operate as a continuous
printing facility, and normal operation may be either continuous or
nearly so. Normal press operation experiences numerous shutdowns
caused by web breaks or mechanical problems. Each rotogravure
press generally consists of eight to sixteen individual printing
units, with an eight unit press the most common. In publication
printing, only four colors of ink are used, yellow, red, blue and
black. Each unit prints one ink color on one side of the web, and
colors other than these four are produced by printing one color
over another to yield the desired product.
In the rotogravure printing process, a web or substrate from a
continuous roll is passed over the image surface of a revolving
gravure cylinder. For publication printing, only paper webs are
used. The printing images are formed by many tiny recesses or
cells etched or engraved into the surface of the gravure cylinder.
The cylinder Is about one fourth submerged in a fountain of low
viscosity mixed ink. Raw ink Is solvent diluted at the press and
is sometimes mixed with related coatings, usually referred to as
extenders or varnishes. The ink, as applied, is a mixture of
pigments, binders, varnish and solvent. The mixed Ink is picked up
by the cells on the revolving cylinder surface and is continuously
applied to the paper web. After impression is made, the web travels
through an enclosed heated air dryer to evaporate the volatile
solvent. The web is then guided along a series of rollers to the
next printing unit. Figure 4.9.2-1 illustrates this printing
process by an end (or side) view of a single printing unit.
At present, only solventborne Inks are used on a large scale
for publication printing. Waterborne inks are still in research
and development stages, but some are now being used in a few limited
cases. Pigments, binders and varnishes are the nonvolatile solid
components of the mixed ink. For publication printing, only ali-
phatic and aromatic organic liquids are used as solvents. Presently,
two basic types of solvents, toluene and a toluene-xylene-naphtha
mixture, are used. The naphtha base solvent is the more common.
Benzene is present in both solvent types as an Impurity, in concen-
trations up to about 0.3 volume percent. Raw inks, as purchased,
have 40 to 60 volume percent solvent, and the related coatings
typically contain about 60 to 80 volume percent solvent. The
applied mixed ink consists of 75 to 80 volume percent solvent,
required to achieve the proper fluidity for rotogravure printing.
4/81
Evaporation Loss Sources
4.9.2-1
-------
1 o /
Emissions and Controls ' - Volatile organic compound (VOC) vapors
are the only significant air pollutant emissions from publication
rotogravure printing. Emissions from the printing presses depend
on the total amount of solvent used. The sources of these VOC
emissions are the solvent components in the raw inks, related
coatings used at the printing presses, and solvent added for dilu-
tion and press cleaning. These solvent organics are photochemically
reactive. VOC emissions from both controlled and uncontrolled publi-
cation rotogravure facilities in 1977 were about 57,000 megagrams
(63,000 tons), 15 percent of the total from the graphic arts industry.
Emissions from ink and solvent storage and transfer facilities are
not considered here.
Table 4.9-1 presents emission factors for publication printing
on rotogravure presses with and without control equipment. The
potential amount of VOC emissions from the press is equal to the
total amount of solvent consumed in the printing process (see
Footnote f). For uncontrolled presses, emissions occur from the
dryer exhaust vents, printing fugitive vapors, and evaporation of
solvent retained in the printed product. About 75 to 90 percent
of the VOC emissions occur from the dryer exhausts, depending on
press operating speed, press shutdown frequency, ink and solvent
composition, product printed, and dryer designs and efficiencies.
The amount of solvent retained by the various rotogravure printed
products is three to four percent of the total solvent in the ink
used. The retained solvent eventually evaporates after the printed
product leaves the press.
There are numerous points around the printing press from
which fugitive emissions occur. Most of the fugitive vapors result
from solvent evaporation in the ink fountain, exposed parts of the
gravure cylinder, the paper bath at the dryer inlet, and from the
paper web after exiting the dryers between printing units. The
quantity of fugitive vapors depends on the solvent volatility, the
temperature of the ink and solvent in the ink fountain, the amount
of exposed area around the press, dryer designs and efficiencies,
and the frequency of press shutdowns.
The complete air pollution control system for a modern
publication rotogravure printing facility consists of two sections,
the solvent vapor capture system and the emission control device.
The capture system collects VOC vapors emitted from the presses and
directs them to a control device where they are either recovered or
destroyed. Low-VOC waterborne ink systems to replace a significant
amount of solventborne inks have not been developed as an emission
reduction alternative.
Capture Systems - Presently, only the concentrated dryer
exhausts are captured at most facilities. The dryer exhausts
contain the majority of the VOC vapors emitted. The capture
efficiency of dryers is limited by their operating temperatures and
4.9.2-2 EMISSION FACTORS 4/81
-------
.c-
*~-
00
TO NEXT UNIT
XI
o
H
01
rt
H-
§
b
ifi
CO
o
c
n
o
(C
en
ADJUSTABLE
COMPENSATING
ROLLER
DRYER EXIT AIR FLOW
REC1RCULATION
FAN
TO DRYER
EXHAUST
HEADER
PRESSURE
CYLINDER/RUBBER
ROLLER
CIRCULATION
PUMP
M LIQUID VOLUME METERS
*-
v£j
Figure 4.9,2-1. Diagram of a rotogravure printing unit.
-------
ro
H
3.
•P-
03
TABLE 4.9.2-1. EMISSION FACTORS FOR PUBLICATION ROTOGRAVURE PRINTING PRESSES
EMISSION FACTOR RATING: C
Kml ss Jem
I'll LlltS
Dryer exhausts
Fugi t Ives
Printed product
Cont rol device
Totnl emissions
Dnconlrol led
Total
solvent Daw Ink
kg/kg kg Ib
(Ib/lb) liter gal
0.34 1.24 10.42
0. 13 0.19 t.61
U.01 0.05 0.17
1.0 1.48 12.40
VUC Emissions"
753! Control
Total
solvent Daw Ink
kg/kg kg Ib
, the density
of the most common mixed solvent used is 0.742 kg/liter (6.2 Ib/gal); density of toluene
solvent used Is 0.863 kg/liter (7.2 Ib/gal). See Reference I.
• Mass of VOC emitted/raw Ink (and coating) volume ratio determined from the mass emission
factor ratio, the solvent/Ink volume ratto, and the solvent density,
kg/IHur = kg/kg it liter/liter x I)
[Ih/gal = Ih/lh x gal/gal x I) ] s
Reference 3 and test
-------
other factors that affect the release of the solvent vapors from
the print and web to the dryer air. Excessively high temperatures
impair product quality. The capture efficiency of older design
dryer exhaust systems is about 84 percent, and modern dryer systems
can achieve 85 to 89 percent capture. For a typical press, this
type capture system consists of ductwork from each printing unit's
dryer exhaust joined in a large header. One or more large fans are
employed to pull the solvent laden air from the dryers and to
direct it to the control device.
A few facilities have increased capture efficiency by gathering
fugitive solvent vapors along with the dryer exhausts. Fugitive
vapors can be captured by a hood above the press, by a partial
enclosure around the press, by a system of multiple spot pickup
vents, by multiple floor sweep vents, by total pressroom ventila-
tion capture, or by various combinations of these. The design of
any fugitive vapor capture system needs to be versatile enough to
allow safe and adequate access to the press in press shutdowns.
The efficiencies of these combined dryer exhaust and fugitive
capture systems can be as high as 93 to 97 percent at times, but
the demonstrated achievable long term average when printing several
types of products is only about 90 percent.
Control Devices - Various control devices and techniques may
be employed to control captured VOC vapors from rotogravure presses.
All such controls are of two categories, solvent recovery and
solvent destruction.
Solvent recovery is the only present technique to control VOC
emissions from publication presses. Fixed bed carbon adsorption by
multiple vessels operating in parallel configuration, regenerated
by steaming, represents the most used control device. A new
adsorption technique using a fluidized bed of carbon might be
employed in the future. The recovered solvent can be directly
recycled to the presses.
There are three types of solvent destruction devices used to
control VOC emissions, conventional thermal oxidation, catalytic
oxidation and regenerative thermal combustion. These control
devices are employed for other rotogravure printing. At present,
none are being used on publication rotogravure presses.
The efficiency of both solvent destruction and solvent recovery
control devices can be as high as 99 percent. However, the
achievable long term average efficiency for publication printing is
about 95 percent. Older carbon adsorber systems were designed to
perform at about 90 percent efficiency. Control device emission
factors presented in Table 4.9-1 represent the residual vapor
content of the captured solvent laden air vented after treatment.
Overall Control - The overall emissions reduction efficiency
for VOC control systems is equal to the capture efficiency times
4/81 Evaporation Loss Sources 4.9.2-5
-------
the control device efficiency. Emission factors for two control
levels are presented in Table 4.9.2-1. The 75 percent control level
represents 84 percent capture with a 90 percent efficient control
device. (This is the EPA control techniques guideline recommenda-
tion for State regulations on old existing presses.) The 85 percent
control level represents 90 percent capture with a 95 percent effi-
cient control device. This corresponds to application of best
demonstrated control technology for new publication presses.
References for Section 4.9.2
1. Publication Rotogravure Printing - Background Information for
Proposed Standards, EPA-450/3-80-031a, U.S. Environmental
Protection Agency, Research Triangle Park, NC, October 1980.
2. Publication Rotogravure Printing - Background Information for
Promulgated Standards, EPA-450/3-80-031b, U.S. Environmental
Protection Agency, Research Triangle Park, NC. Expected
November 1981.
3. Control of Volatile Organic Emissions from Existing Stationary
Sources, Volume VIII; Graphic Arts - Rotogravure and Flexography,
EPA-450/2-78-033, U.S. Environmental Protection Agency, Research
Triangle Park, NC, December 1978.
4. Standards of Performance for New Stationary Sources: Grapjiic
Arts - Publication Rotogravure Printing, 45 FR 71538, October 28,
1980.
5. Written communication from Texas Color Printers, Inc., Dallas,
TX, to Radian Corp., Durham, NC, July 3, 1979.
6. Written communication from Meredith/Burda, Lynchburg, VA, to
Edwin Vincent, Office of Air Quality Planning and Standards,
U.S. Environmental Protection Agency, Research Triangle Park,
NC, July 6, 1979.
7. W.R. Feairheller, Graphic Arts Emission Test Report, Meredith/
Burda, Lynchburg, VA, EPA Contract No. 68-02-2818, Monsanto
Research Corp., Dayton, OH, April 1979-
8. W.R. Feairheller, Graphic Arts Emission Test Report, Texas
Color Printers, Dallas, TX, EPA Contract No. 68-02-2818,
Monsanto Research Corp., Dayton, OH, October 1979.
4.9.2-6 EMISSION FACTORS 4/81
-------
4.10 COMMERCIAL/CONSUMER SOLVENT USE
4.10.1 General1"2
Commercial and consumer use of various products containing
volatile organic compounds (VOC) contributes to formation of tropo-
spheric ozone. The organics in these products may be released
through immediate evaporation of an aerosol spray, evaporation
after application, and direct release in the gaseous phase. Organics
may act either as a carrier for the active product ingredients or
as active ingredients themselves. Commercial and consumer products
which release volatile organic compounds include aerosols, household
products, toiletries, rubbing compounds, windshield washing fluids,
polishes and waxes, nonindustrial adhesives, space deodorants, moth
control applications, and laundry detergents and treatments.
4.10.2 Emissions
Major volatile organic constituents of these products which
are released to the atmosphere include special naphthas, alcohols
and various chloro- and fluorocarbons. Although methane is not
included in these products, 31 percent of the volatile organic
compounds released in the use of these products is considered
nonreactive under EPA policy.^'^
National emissions and per capita emission factors for commercial
and consumer solvent use are presented in Table 4.10-1. Per capita
emission factors can be applied to area source inventories by
multiplying the factors by inventory area population. Note that
adjustment to exclude the nonreactive emissions fraction cited
above should be applied to total emissions or to the composite
factor. Care is advised in making adjustments, in that substitution
of compounds within the commercial/consumer products market may
alter the nonreactive fraction of compounds.
References for Section 4,10
1. W.H. Lamason, "Technical Discussion of Per Capita Emission
Factors for Several Area Sources of Volatile Organic Compounds",
Monitoring and Data Analysis Division, U.S. Environmental
Protection Agency, Research Triangle Park, NC, March 15, 1981.
Unpublished.
2. End Use of Solvents ContainingJVolatile Organic Compounds,
EPA-450/3-79-032, U.S. Environmental Protection Agency,
Research Triangle Park, NC, May 1979.
3. Final Emission Inventory Requirements for 1982 Ozone State
Implementation Plans, EPA-450/4-80-016, U.S. Environmental
Protection Agency, Research Triangle Park, NC, December 1980.
4/81
Evaporation Loss Sources
4.10-1
-------
o
TABLE 4.10-1. EVAPORATIVE EMISSIONS FROM COMMERCIAL/CONSUMER SOLVENT USE
EMISSION FACTOR RATING: C
No rune thane
National Emissions
§
(— i
en
en
ON FACTORS
•P-
00
Use
Aerosol products
Household products
Toiletries
Rubbing compounds
Windshield washing
Polishes and waxes
Non industrial
Space deodorant
Moth control
Laundry detergent
TotalC
References 1 and 2.
103Mg/yr
342
183
132
62
61
48
29
18
16
4
895
10 tons/yr
376
201
145
68
67
53
32
20
18
4
984
voca
Per Capita
kg/yr
1.6
0.86
0.64
0.29
0.29
0.22
0.13
0.09
0.07
0.02
4.2
lb/yr
3.5
1.9
1.4
0.64
0.63
0.49
0.29
0.19
0.15
0.04
9.2
Emission Factors
g/day
4.4
2.4
1.8
0.80
0.77
0.59
0.36
0.24
0.19
0.05
11.6
10~3lb/day
9.6
5.2
3.8
1.8
1.7
1.3
0.79
0.52
0.41
0.10
25.2
Calculated by dividing kg/yr (Ib/yr) by 365 and converting to appropriate units.
Totals may not be additive because of rounding.
-------
4. Procedures for the preparation of Emission Inventories for
Volatile Organic Compounds, Volume I, Second Edition, EPA-450/
2-77-028, U.S. Environmental Protection Agency, Research
Triangle Park, NC, September 1980.
4/81 Evaporation Loss Sources 4.10-3
-------
-------
4.11 TEXTILE FABRIC PRINTING
i _2
4.11.1 Process Description
Textile fabric printing is part of the textile finishing
Industry. In fabric printing, a decorative pattern or design is
applied to constructed fabric by roller, flat screen or rotary
screen methods. Pollutants of interest In fabric printing are
volatile organic compounds (VOC) from mineral spirit solvents in
print pastes or inks. Tables 4.11-1 and 4.11-2 show typical
printing run characteristics and VOC emission sources, respectively,
for roller, flat screen and rotary screen printing methods.
In the roller printing process, print paste is applied to an
engraved roller, and the fabric is guided between it and a central
cylinder. The pressure of the roller and central cylinder forces
the print paste into the fabric. Because of the high quality It can
achieve, roller printing is the most appealing method for printing
designer and fashion apparel fabrics.
In flat screen printing, a screen on which print paste has been
applied is lowered onto a section of fabric. A squeegee then moves
across the screen, forcing the print paste through the screen and
Into the fabric. Flat screen machines are used mostly in printing
terry towels.
In rotary screen printing, tubular screens rotate at the same
velocity as the fabric. Print paste distributed inside the tubular
screen is forced into the fabric as It is pressed between the screen
and a printing blanket (a continuous rubber belt) . Rotary screen
printing machines are used mostly but not exclusively for bottom
weight apparel fabrics or fabric not for apparel use. Most knit
fabric is printed by the rotary screen method, because it does not
stress (pull or stretch) the fabric during the process.
Major print paste components include clear and color
concentrates, a solvent, and in pigment printing, a low crock or
binder resin. Print paste color concentrates contain either
pigments or dyes. Pigments are insoluble particles physically bound
to fabrics. Dyes are In solutions applied to impart color by
becoming chemically or physically incorporated into individual
fibers. Organic solvents are used almost exclusively with pigments.
Very little organic solvent is used in nonpigment print pastes.
Clear concentrates extend color concentrates to create light and
dark shades. Clear and color concentrates do contain some VOC but
contribute less than 1 percent of total VOC emissions from textile
printing operations. Defoamers and resins are included In print
paste to increase color fastness. A small amount of thickening
8/82
Evaporation Loss Sources
4.11-1
-------
TABLE 4.11-1. TYPICAL TEXTILE FABRIC PRINTING RUN CHARACTERISTICS'
CO
CO
H
n
H
o
00
*•*
00
Characteristic
Roller
Rotary screen
Flat screen
Range
Average
Range
Average
Range
Average
Wet pickup rate, kg (lb)b
print paste consumed/kg
Clb) of fabricc
0.51 - 0.58 0.56
OilO - 1.89
0.58
0.22 - 0.83
0.35
Fabric weight kg/e2 (Ib/yd2)d 0.116
g ' 8 y (0.213
0.116 0.116 0.116 - 0.116 0.116 0.314 - 0.314 0.314
0.213) (0.213) (0.213-0.213) (0.213) (0.579 - 0.579) (0.579)
Mineral spirits added to
print paste, weight %
Print paste used per fabric
area, kg/m2 (Ib/yd2)e
Mineral spirits used per
fabric area, kg/m2 (Ib/yd2)f
Print paste used in run,
kg (lb)8
0-60
26
0-50
23 - 23
23
0.059
(0.109
0
(0
673
(1,490
0.067 0.065 0.012 - 0.219 0.067 0.069 - 0.261 0.110
0.124) (0.119) (0.021 - 0.403) (0.124) (0.127 - 0.481) (0.203)
0.040 0.017
0.074} (0.031)
764 741
1,695) (1,627)
0 - 0.109 0.0002 0.016 - 0.060 0.025
(0 - 0.201) (0.0004)(0.030 - 0.111) (0.046)
137 - 2,497 764 787 - 2,975 1,254
(287 - 5,509) (1,695) (1,736 - 6,575) (2,775)
aLength of run = 10,000 m (10,936 yd); fabric width = 1.14 m (1.25 yd); total fabric area = 11,400 m
(13,634 yd2); line speed - 40 m/min (44 yd/min)j distance, printer to oven = 5 m (5.5 yd).
Net pickup ratio is a method of yield calculation in which mass of print paste consumed is divided by
mass of fabric used.
cReference 3.
dOnly average fabric weight is presented.
eFabric weight multiplied by wet pickup rate.
fFabric weight multiplied by wet pickup multiplied by percent mineral spirits in formulation.
SPrint paste used per fabric area multiplied by area of fabric printed.
-------
00
oo
to
-------
agent is also added to each print paste to control print paste
viscosity. Print defoamers, resins and thickening agents do not
contain VOC.
The majority of emissions from print paste are from the
solvent, which may be aqueous, organic (mineral spirits) or both.
The organic solvent concentration in print pastes may vary from 0 to
60 weight percent, with no consistent ratio of organic solvent to
water. Mineral spirits used in print pastes vary widely in physical
and chemical properties. See Table 4.11-3.
TABLE 4.11-3. TYPICAL INSPECTION VALUES FOR MINERAL SPIRITS'
Parameter
References 2,4.
Range
Specific gravity at 15 ° C (60° F)
Viscosity at 25 ° C (77° F)
Flash point (closed cup)
Aniline point
Kauri- Butanol number
Distillation range
Initial boiling points
50 percent value
Final boiling points
Composition (%)
Total saturates
Total aromatics
CQ and higher
0.778
0.83
41
43
32
157
168
199
81.5
7.7
7.5
- 0.805
- 0.95 cP
- 45° C (105 -
- 62° C (110 -
- 45
- 166° C (315
- 178° C (334
- 201° C (390
- 92.3
-18.5
-18.5
113°
144°
- 330
- 348
- 394
F)
F)
°F)
°F)
0 F)
Although some mineral spirits evaporate in the early stages of
the printing process, the majority of emissions to the atmosphere is
from the printed fabric drying process, which drives off volatile
compounds (see Table 4.11-2 for typical VOC emission splits). For
some specific print paste/fabric combinations, color fixing occurs
in a curing process, which may be entirely separate or merely a
separate segment of the drying process.
Two types of dryers are used for printed fabric - steam coil or
natural gas fired dryers, through which the fabric is conveyed on
belts, racks, etc., and steam cans, with which the fabric makes
direct contact. Most screen printed fabrics and practically all
printed knit fabrics and terry towels are dried with the first type
of dryer, not to stress the fabric. Roller printed fabrics and
4.11-4
EMISSION FACTORS
-------
apparel fabrics requiring soft handling are dried on steam cans, which
have lower installation and operating costs and which dry the fabric
more quickly than other dryers.
Figure A.11-1 is a schematic diagram of the rotary screen printing
process, with emission points indicated. The flat screen printing
process is virtually identical. The symbols for fugitive VOC emissions
to the atmosphere indicate mineral spirits evaporating from print paste
during application to fabric before drying. The largest VOC emission
source is the drying and curing oven stack, which vents evaporated
solvents (mineral spirits and water) to the atmosphere. The symbol for
fugitive VOC emissions to the waste water indicates print paste mineral
spirits washed with water from the printing blanket (continuous belt)
and discharged in waste water.
Figure 4.11-2 is a schematic diagram of a roller printing process
in which all emissions are fugitive. Fugitive VOC emissions from the
"back grey" (fabric backing material that absorbs excess print paste) in
the illustrated process are emissions to the atmosphere because the back
grey is dried before being washed. In processes where the back grey is
washed before drying, most of the fugitive VOC emissions from the back
grey will be discharged into the waste water. In some roller printing
processes, steam cans for drying printed fabric are enclosed, and drying
process emissions are vented directly to the atmosphere.
4.11.2 Emissions and Controls 1,3-12
Presently there is no addon emission control technology for organic
solvent used in the textile fabric printing industry. Thermal incinera-
tion of oven exhaust has been evaluated in the Draft Background Informa-
tion document for New Source Performance Standard development , and has
been found unaffordable for some fabric printers. The feasibility of
using other types of addon emission control equipment has not been fully
evaluated. Significant organic solvent emissions reduction has been
accomplished by reducing or eliminating the consumption of mineral
spirit solvents. The use of aqueous or low organic solvent print pastes
has increased during the past decade, because of the high price of
organic solvents and higher energy costs associated with the use of
higher solvent volumes. The only fabric printing applications presently
requiring the use of large quantities of organic solvents are pigment
printing of fashion or designer apparel fabric and terry towels.
Table 4.11-4 presents average emission factors and ranges for each
type of printing process and an average annual emission factor per print
line, based on estimates submitted by individual fabric printers. No
emission tests were done. VOC emission rates involve three parameters,
organic solvent content of print pastes, consumption of print paste
8/82 Evaporation Loss Sources 4.11-5
-------
CFi
t-H
en
en
H
O
53
g
en
FUGtTIVE VOC EMISSIONS TO
ATMOSPHERE
STACK VOC EMISSIONS
FUGITIVE VOC EMISSIONS TO
WASTEWATER
VENT TO
ATMOSPHERE
I
DRYING AND CURING
OVEN
BLEACHED
FABRIC
\
CONTINUOUS BELT
PRINT PASTE
PUMP
DRY PRINTED
FABRIC
t»
CO
ho
Figure 4.11-1. Schematic diagram of the rotary screen printing process,
with fabric drying in a vented oven.
-------
STEAM CANS
oo
00
ro
o
H
&
rt
H-
3
CO
CO
C/3
O
C
FUGITIVE VOC EMISSIONS
TO ATMOSPHERE
PRINTED
FABRIC
DRY PRINTED FABRIC
PRINT
PASTE
BLEACHED
FABRIC
DRY BACK GREY
GRAVURE ROLLER
LINT DOCTOR
BRUSH ROLLER
TROUGH
Figure 4.11-2. Schematic diagram of the roller printing process,
with fabric drying on steam cans.
-------
(a function of pattern coverage and fabric weight), and rate of
fabric processing. With the quantity of fabric printed held
constant, the lowest emission rate represents minimum organic
solvent content print paste and minimum print paste consumption, and
the maximum emission rate represents maximum organic solvent content
print paste and maximum print paste consumption. The average
emission rates shown for roller and rotary screen printing are based
on the results of a VOC usage survey conducted by the American
Textile Manufacturers Institute, Inc. (ATMI), in 1979. The average
flat screen printing emission factor is based on information from
two terry towel printers.
TABLE 4.11-4. TEXTILE FABRIC PRINTING ORGANIC EMISSION FACTORS3
EMISSION FACTOR RATING: C
Roller Rotary screen Flat screen"
VOC Range Average Range Average Range Average
kg(lb)/l,000 kg
Clb) fabric 0 - 348<= I42d 0 - 945C 23d 51 - 191C 79e
Mg(ton)/yr/print
linec
130C
(139)
29C
(31)
29C
(31)
aTransfer printing, carpet printing, and printing of vinyl
coated cloth are specifically excluded from this
compilation.
kplat screen factors apply to terry towel printing. Rotary screen
factors should be applied to flat screen printing of other types of
fabric (e.g., sheeting, bottom weight apparel, etc.).
cReference 13.
^Reference 5.
eReference 6.
Although the average emission factors for roller and rotary
screen printing are representative of the use of medium organic
solvent content print pastes at average rates of print paste
consumption, very little printing is actually done with medium
organic solvent content pastes. The distribution of print paste
use is bimodal, with the arithmetic average falling between the
modes. Most fabric is printed with aqueous or low organic solvent
print pastes. However, in applications where the use of organic
solvents is beneficial, high organic solvent content print pastes
4.11-8 EMISSION FACTORS 8/82
-------
are used to derive the full benefit of using organic solvents. The
most accurate emissions data can be generated by obtaining organic
solvent use data for a particular facility. The emission factors
presented here should only be used to estimate actual process
emissions.
References for Section 4.11
1. Fabric Printing Industry; Background Information for Proposed
Standards (Draft), EPA Contract No. 68-02-3056, Research
Triangle Institute, Research Triangle Park, NC, April 21,
1981.
2. Exxon Petroleum Solvents, Lubetext DC-IP, Exxon Company,
Houston, TX, 1979.
3. Memorandum from S. B. York, Research Triangle Institute, to
Textile Fabric Printing AP-42 file, Office of Air Quality
Planning and Standards, U.S. Environmental Protection Agency,
Research Triangle Park, NC, March 25, 1981.
4. C. Marsden, Solvents Guide, Interscience Publishers, New York,
NY, 1963, p. 548.
5. Letter from W. H. Steenland, American Textile Manufacturers
Institute, Inc., to Dennis Grumpier, U.S. Environmental
Protection Agency, Research Triangle Park, NC, April 8, 1980.
6. Memorandum from S. B. York, Research Triangle Institute, to
textile fabric printing AP-42 file, Office of Air Quality
Planning and Standards, U.S. Environmental Protection Agency,
Research Triangle Park, NC, March 12, 1981.
7. Letter from A. C. Lohr, Burlington Industries, to James Berry,
U.S. Environmental Protection Agency, Research Triangle Park,
NC, April 26, 1979.
8. Trip Report/Plant Visit to Fieldcrest Mills, Foremost Screen
Print Plant, memorandum from S. B. York, Research Triangle
Institute, to G. Gasperecz, U.S. Environmental Protection
Agency, Research Triangle Park, NC, January 28, 1980.
9. Letter from T. E. Boyce, Fieldcrest Corporation, to S. B. York,
Research Triangle Institute, Research Triangle Park, NC,
January 23, 1980.
10. Telephone conversation, S. B. York, Research Triangle
Institute, with Tom Boyce, Foremost Screen Print Plant,
Stokesdale, NC, April 24, 1980.
8/82 Evaporation Loss Sources 4.11-9
-------
11 "Average Weight and Width of Broadwoven Fabrics (Gray)",
Current Industrial Report. Publication No. MC-22T (Supplement),
Bureau of the Census, U.S. Department of Commerce, Washington,
DC, 1977.
12. "Sheets, Pillowcases, and Towels", Current Industrial Report,
Publication No. MZ-23X, Bureau of the Census, U.S. Department
of Commerce, Washington, DC, 1977.
13. Memorandum from S. B. York, Research Triangle Institute, to
Textile Fabric Printing AP-42 file, Office of Air Quality
Planning and Standards, U.S. Environmental Protection Agency,
Research Triangle Park, NC, April 3, 1981.
14. "Survey of Plant Capacity, 1977", Current Industrial Report.
Publication No. DQ-Cl(77)-l, Bureau of the Census, U.S.
Department of Commerce, Washington, DC, August 1978.
4.11-10 EMISSION FACTORS 8/82
-------
5.0 CHEMICAL PROCESS INDUSTRY
This Chapter deals with emissions from the manufacture and use of chemicals
or chemical products. Potential emissions from many of these processes are
high, but because of economic necessity, they are usually recovered. In some
cases, the manufacturing operation is run as a closed system, allowing little
or no emissions to escape to the atmosphere.
The emissions that reach the atmosphere from chemical processes are
generally gaseous and are controlled by incineration, adsorption or absorption.
Particulate emissions may also be a problem, since the particulates emitted
are usually extremely small, requiring very efficient treatment for removal.
Emissions data from chemical processes are sparse. It has been, therefore,
frequently necessary to make estimates of emission factors on the basis of
material balances, yields or similar processes.
5/83
Chemical Process Industry
5.0-1
-------
-------
5.1 ADIPIC ACID
5.1.1 General1"2
Adipic acid, HOOC(CH2)4 COOH, is a white crystalline solid used in the
manufacture of synthetic fibers, coatings, plastics, urethane foams, elastomers
and synthetic lubricants. Ninety percent of all adipic acid produced in the
United States is used in manufacturing Nylon 6,6. Cyclohexane is the basic
raw material generally used to produce adipic acid, however, one plant uses
cyclohexanone, a byproduct of another process. Phenol has also been used but
has proven to be more expensive and less readily available than cyclohexane.
5.1.2 Process Description
1-4
During adipic acid production, the raw material, cyclohexane or
cyclohexanone, is transferred to a reactor, where it is oxidized at 130
to 170°C (260 - 330°F) to form a cyclohexanol/cyclohexanone mixture. The
mixture is then transferred to a second reactor and is oxidized with nitric
acid and a catalyst (usually a mixture of cupric nitrate and ammonium
metavanadate) at 70 to 100°C (160 - 220°F) to form adipic acid. The chemistry
of these reactions is shown below.
0
C C
- CH,, - COOH
+ (a) HNO,
- COOH
+(b)NO + (c)H 0
X £
Cyclohexanone + Nitric acid
-Adipic acid + Nitrogen oxides + Water
HOH
A
HC C H
C
+ (x) HNO,
- COOH
COOH
+(y) NO +(z)H 0
X ^
Cyclohexanol + Nitric acid
-*-Adipic acid + Nitrogen oxides + Water
An alternate route for synthesizing adipic acid from cyclohexane (I. G.
Farben process) involves two air oxidation steps: cyclohexane is oxidized to
cyclohexanol and cyclohexanone; cyclohexanone and cyclohexanol are then oxidized
to adipic acid, with a mixed manganese/barium acetate used as the catalyst.
5/83
Chemical Process Industry
5.1-1
-------
VOC,
I-1
ro
o
0>
3
H-
CD
O
n
ro
en
en
H
P
en
el-
VOC
J
VOC,
CARBON MONOXIDE
1
NITROGEN OXIDE
HMOs
CYCLOHEXANE
STORAGE
VOC
RECOVERY
1
-*~
RECYCLE
REACTOR
NO. 1
*
i
1
NOX
AdbUHbtK
REACTOR
NO. 2
1
J
1
STRIPPER
J
1
NITROGEN OXIDE
i
CRYSTALLIZER/
CENTRIFUGE/
PRODUCT
STILL
PARTICULATE
1
DRYING,
COOLING
PARTIC
J
ULATE
PRODUCT
STORAGE
AIR
CATALYST NITRIC
ACID
AIR
STEAM
RAW MATERIAL
STORAGE
CYCLOHEXANE
OXIDATION
NITRIC ACID
REACTION
ADIPIC ACID
REFINING
DRYING,
COOLING
STORAGE
Ui
00
Figure 5.1-1. General Flow diagram of adipic acid manufacturing process.
-------
Another possible synthesis method is a direct one stage air oxidation of
cyclohexane to adipic acid with a cobaltous acetate catalyst.
The product from the second reactor enters a bleacher, in which the
dissolved nitrogen oxides are stripped from the adipic acid/nitric acid solution
with air and steam. Various organic acid byproducts, namely acetic acid,
glutaric acid and succinic acid, are also formed and may be recovered and sold
by some plants.
The adipic acid/nitric acid solution is chilled and sent to a vacuum
crystallizer, where adipic acid crystals are formed, and the solution is
then centrifuged to separate the crystals. The remaining solution is sent to
another vacuum crystallizer, where any residual adipic acid is crystallized
and centrifugally separated. Wet adipic acid from the last crystallization
stage is dried and cooled and then is transferred to a storage bin. The
remaining solution is distilled to recover nitric acid, which is routed back
to the second reactor for reuse. Figure 5.1-1 presents a general scheme of
the adipic acid manufacturing process.
5.1.3 Emissions and Controls
1,5
Nitrogen oxides (NOX), volatile organic compounds (VOC) and carbon
monoxide (CO) are the major pollutants from adipic acid production. The
cyclohexane reactor is the largest source of CO and VOC, and the nitric acid
reactor is the dominant source of NOX. Drying and cooling of the adipic acid
product create particulate emissions, which are generally low because baghouses
and/or wet scrubbers are employed for maximum product recovery and air pollution
control. Process pumps and valves are potential sources of fugitive VOC
emissions. Secondary emissions occur only from aqueous effluent discharged
from the pl^nt by pipeline to a holding pond. Aqueous effluent from the
adipic acid manufacturing process contains dibasic organic acids, such as
succinic and glutaric. Since these compounds are not volatile, air emissions
are negligible compared to other emissions of VOC from the plant. Figure
5.1-1 shows the points of emission of all process pollutants.
The most significant emissions of VOC and CO come from the cyclohexane
oxidation unit, which is equipped with high and low pressure scrubbers.
Scrubbers have a 90 percent collection efficiency of VOC and are used for
economic reasons, to recover expensive volatile organic compounds as well as
for pollution control. Thermal incinerators, flaring and carbon adsorbers can
all be used to limit VOC emissions from the cyclohexane oxidation unit with a
greater than 90 percent efficiency. CO boilers control CO emissions with
99.99 percent efficiency and VOC emissions with practically 100 percent efficiency.
The combined use of a CO boiler and a pressure scrubber results in nearly
complete VOC and CO control.
Three methods are presently used to control emissions from the NOX absorber:
water scrubbing, thermal reduction, and flaring or combustion in a powerhouse
boiler. Water scrubbers have a low collection efficiency, approximately
70 percent, because of the extensive time needed to remove insoluble NO in the
absorber offgas stream. Thermal reduction, in which offgases containing NO
are heated to high temperatures and are reacted with excess fuel in a reducing
atmosphere, operates at up to 97.5 percent efficiency and is believed to be
5/83
EMISSION FACTORS
5.1-3
-------
the most effective system of control. Burning offgas in a powerhouse or
flaring has an estimated efficiency of 70 percent.
TABLE 5.1-1.
EMISSION FACTORS FOR ADIPIC ACID MANUFACTURE
EMISSION FACTOR RATING: B
Process
Raw material storage
Uncontrolled
Adipic acid
particulate
kg/Mg Ib/ton
0 0
Nitrogen
oxidesb
kg/Mg Ib/ton
0 0
Nonme thane
volatile organic
compounds
kg/Mg Ib/ton
1.1 2.2
Carbon monoxide
kg/Mg Ib/ton
0 0
Cyclohexane oxidation
UncontrolledC 0 0 0 0 20 40 58 115
W/boiler ,0 0 0 0 Neg Neg 0.5 1
W/thermal incinerator 0 0 0 0 Neg Neg Neg Neg
W/flaringe 00002 4 6 12
W/carbon absorber 0 0 0 0 1 2 58 115
W/scrubber plus boiler 0000 Neg Neg Neg Neg
Nitric acid reaction
Uncontrolled8 00 27 53 0 0 00
W/water scrubber 0 0 816 0 0 0 0
W/thermal reduction 0 0 0.5 1 0 0 00
W/flaring or combustion 008 16 0 0 00
Adipic acid refining-1 ,
Uncontrolled 0.1 0.1 0.3 0.6 0.3 0.5 0 0
Adipic acid drying, cooling . .
and storage 0.4 0.8 0 00 0 0 0
aReference 1. Factors are in Ib of pollutant/ton and kg of pollutant/Mg of adipic acid produced.
bNeg = Negligible.
NOX is in the form of NO and NO^. Although large quantities of NjO are also produced, N20 is
not a criteria pollutant and is not, therefore, included here.
cFactors are after scrubber processing, since hydrocarbon recovery using scrubbers is an
.integral part of adipic acid manufacturing.
A thermal incinerator is assumed to reduce VOC and CO emissions by approximately 99.99%.
^A flaring system is assumed to reduce VOC and CO emissions by 90%.
A carbon adsorber is assumed to reduce VOC emissions by 94% and to be ineffective in reducing
CO emissions.
^Uncontrolled emission factors are after NOX absorber, since nitric acid recovery is an integral
.part of adipic acid manufacturing.
Estimated 70% control.
.Estimated 97.5% control.
^Includes chilling, crystallization and centrifuging.
T'actors are after baghouse control device.
5.1-4
Chemical Process Industry
5/83
-------
References for Section 5.1
1. Screening Study To Determine Need for Standards of Performance for
New Adipic Acid Plants, EPA Contract No. 68-02-1316, GCA/Technology
Division, Bedford, MA, July 1976.
2. Kirk-Othmer Encyclopedia of Chemical Technology, "Adipic Acid", Vol. 1,
2nd Ed, New York, Interscience Encyclopedia, Inc, 1967.
3. M. E. O'Leary, "CEH Marketing Research Report on Adipic Acid",
Chemical Economics Handbook, Stanford Research Institute, Menlo Park, CA,
January 1974.
4. K. Tanaka, "Adipic Acid by Single Stage", Hydrocarbon Processing, 55(11),
November 1974.
5. H. S. Bosdekis, Adipic Acid in Organic Chemical Manufacturing, Volume 6,
EPA-450/3-80-028a, U. S. Environmental Protection Agency, Research Triangle
Park, NC, December 1980.
5/83
EMISSION FACTORS
5.1-5
-------
-------
5.2 SYNTHETIC AMMONIA
5.2.1 General
Anhydrous ammonia is synthesized by reacting hydrogen with nitrogen at a
molar ratio of 3:1, then compressing the gas and cooling it to -33°C. Nitrogen
Is obtained from the air, while hydrogen Is obtained from either the catalytic
steam reforming of natural gas (methane) or naphtha, or the electrolysis of
brine at chlorine plants. In the United States, about 98 percent of synthetic
ammonia is produced by catalytic steam reforming of natural gas (Figure 5.2-1).
NATURAL GAS-
FEEDSTOCK
DESULFURIZATION
FUEL
STEAM-
AIR-
EMISSIONS DURING
REGENERATION
A
PRIMARY REFORMER
FUEL COMBUSTION
EMISSIONS
_J
SECONDARY REFORMER
EMISSIONS
HIGH TEMPERATURE
SHIFT
EMISSIONS
rrujv-cao
CONDENSATE
1
EAM
IPPER
i
SHIFT
1
C02 ABSORBER
1
METHANATION
CO2 SOLUTION
REGENERATION
STEAM
EFFLUENT
AMMONIA SYNTHESIS
I
NH3
PURGE GAS VENTED TO
PRIMARY REFORMER
FOR FUEL
5/83
Figure 5.2-1. General process flow diagram of a typical ammonia plant.
Chemical Process Industry
5.2-1
-------
Seven process steps are required to produce synthetic ammonia by the
catalytic steam reforming method:
Natural gas desulfurization
Primary reforming with steam
Secondary reforming with air
Carbon monoxide shift
Carbon dioxide removal
Methanation
Ammonia synthesis
The first, fourth, fifth and sixth steps are to remove impurities such as
sulfur, CO, C02 and water from the feedstock, hydrogen and synthesis gas
streams. In the second step, hydrogen is manufactured, and in the third step,
additional hydrogen is manufactured and nitrogen is introduced into the process.
The seventh step produces anhydrous ammonia from the synthetic gas. While all
ammonia plants use this basic process, details such as pressures, temperatures
and quantities of feedstock will vary from plant to plant.
5.2.2 Emissions
Pollutants from the manufacture of synthetic anhydrous ammonia are emitted
from four process steps:
Regeneration of the desulfurization bed
Heating of the primary reformer
Regeneration of carbon dioxide scrubbing solution
Steam stripping of process condensate
More than 95 percent of the ammonia plants in the U. S. use activated carbon
fortified with metallic oxide additives for feedstock desulfurization. The
desulfurization bed must be regenerated about once every 30 days for a 10-hour
period. Vented regeneration steam contains sulfur oxides and/or hydrogen
sulfide, depending on the amount of oxygen in the steam. Regeneration also
emits volatile organic compounds (VOC) and carbon monoxide. The primary
reformer, heated with natural gas or fuel oil, emits the combustion products
NO , CO, SO , VOC and particulates.
A X
Carbon dioxide is removed from the synthesis gas by scrubbing with
monoethanolamine or hot potassium carbonate solution. Regeneration of this C02
scrubbing solution with steam produces emissions of VOC, NH3, CO, C02 and
monoethanolamine.
Cooling the synthesis gas after low temperature shift conversion forms a
condensate containing quantities of NH3, C02, methanol and trace metals.
Condensate steam strippers are used to remove NH3 and methanol from the water,
and steam from this is vented to the atmosphere, emitting NH3, C02 and methanol!
5.2-2 EMISSION FACTORS 5/83
-------
Table 5.2-1 presents emission factors for the typical ammonia plant.
Control devices are not used at such plants, so the values in Table 5.2—1
represent uncontrolled emissions.
5.2.3 Controls
Add-on air pollution control devices are not used at synthetic ammonia
plants, because their emissions are below state standards. Some processes
have been modified to reduce emissions and to improve utility of raw materials
and energy. Some plants are considering techniques to eliminate emissions
from the condensate steam stripper, one such being the injection of the
overheads into the reformer stack along with the combustion gases.
TABLE 5.2-1. UNCONTROLLED EMISSION FACTORS FOR TYPICAL AMMONIA PLANT3
EMISSION FACTOR RATING: A
Emission Point
Desulfurization unit regeneration
Primary reformer, heater fuel combustion
Natural gas
Distillate oil
Carbon dioxide regenerator
Condensate steam stripper
Pollutant
Total sulfur0'
CO
Nonme thane VOC£
NO
sox
cox
Particulates
Methane
Nonme thane VOC
NO
SOX
CO*
Particulates
Methane
Nonme thane VOC
Ammonia
CO
CO,
Nonme thane VOC
Ammonia
CO
Nonmethane VOCS
kg/Mg
0.0096
6.9
3.6
2.7
0.0024
0.068
0.072
0.0063
0.0061
2.7
1.3
0.12
0.45
0.03
0.19
1.0
1.0
1220
0.52
1.1
3.4
0.6
Ib/ton
0.019
13.8
7.2
5.4
0.0048
0.136
0.144
0.0125
0.0122
5.4
2.6
0.24
0.90
0.06
0.38
2.0
2.0
2440
1.04
2.2
6.8
1.2
Emission factors are expressed in weight of emissions per unit weight of ammonia produced.
Intermittent source, average 10 hours once every 30 days.
Wors t case assumption., that all sulfur entering tank is emitted during regeneration.
Normalized to a 24 hour emission factor.
e
Reference 2.
0.05 kg/MT (0.1 Ib/ton) is monoethanolamine.
^ios tly me thanol.
5/83
Chemical Process Industry
5.2-3
-------
References for Section 5.2
1. G. D. Rawlings and R. B. Reznik, Source Assessment: Synthetic Ammonia
Production, EPA-600/2-77-107m, U. S. Environmental Protection Agency,
Research Triangle Park, NC, November 1977.
2. Source Category Survey; Ammonia Manufacturing Industry, EPA-450/3-80-014,
U. S. Environmental Protection Agency, Research Triangle Park, NC, August
1980.
5.2-4 EMISSION FACTORS 5/83
-------
5.3 CARBON BLACK
5.3.1 Process Description
Carbon black is produced by the reaction of a hydrocarbon fuel such as
oil or gas with a limited supply of combustion air at temperatures of 1320
to 1540°C (2400 to 2800°F). The unburned carbon is collected as an extremely
fine black fluffy particle, 10 to 500 nm diameter. The principal uses of
carbon black are as a reinforcing agent in rubber compounds (especially
tires) and as a black pigment in printing inks, surface coatings, paper and
plastics. Two major processes are presently used in the United States to
manufacture carbon black, the oil furnace process and the thermal process.
The oil furnace process accounts for about 90 percent of production, and the
thermal about 10 percent. Two others, the lamp process for production of
lamp black and the cracking of acetylene to produce acetylene black, are
each used at one plant in the U. S. However, these are small volume specialty
black operations which constitute less than 1 percent of total production in
this country. The gas furnace process is being phased out, and the last
channel black plant in the U. S. was closed in 1976,
5.3.1.1 Oil Furnace Process - In the oil furnace process (Figure 5.3-1 and
Table 5.3-1), an aromatic liquid hydrocarbon feedstock is heated and injected
continuously into the combustion zone of a natural gas fired furnace, where
it is decomposed to form carbon black. Primary quench water cools the gases
to 500°C (1000°F) to stop the cracking. The exhaust gases entraining the
carbon particles are further cooled to about 230°C (450°F) by passage through
heat exchangers and direct water sprays. The black is then separated from
the gas stream, usually by a fabric filter. A cyclone for primary collection
and particle agglomeration may precede the filter. A single collection
system often serves several manifolded furnaces.
The recovered carbon black is finished to a marketable product by
pulverizing and wet pelletizing to increase bulk density. Water from the
wet pelletizer is driven off in a gas fired rotary dryer. Oil or process
gas can be used. From 35 to 70 percent of the dryer combustion gas is
charged directly to the interior of the dryer, and the remainder acts as an
indirect heat source for the dryer. The dried pellets are then conveyed to
bulk storage. Process yields range from 35 to 65 percent, depending on the
feed composition and the grade of black produced. Furnace designs and
operating conditions determine the particle size and the other physical and
chemical properties of the black. Generally, yields are highest for large
particle blacks and lowest for small particle blacks.
5.3.1.2 Thermal Process - The thermal process is a cyclic operation in
which natural gas is thermally decomposed (cracked) into carbon particles,
hydrogen and a mixture of other organics. Two furnaces are used in normal
operation. The first cracks natural gas and makes carbon black and hydrogen.
The effluent gas from the first reactor is cooled by water sprays to about
125°C (250°F), and the black is collected in a fabric filter. The filtered
gas (90 percent hydrogen, 6 percent methane and 4 percent higher hydrocarbons)
5/83 Chemical Process Industry 5.3-1
-------
w
H
CB
cc
ft
H
O
»
Cfl
ATMOSPHtRIC EMISSIONS
OILSTORADE TANK
VENT GAS
MAIN PROCESS VENT GAS
INCINERATOR STACK GAS
TORAGE
BIN
L
/
©
BAGGING
SYSTEM
-TO STORAGE
FUEL OIL
FUGITIVE EMISSIONS
*• PNEUMATIC SYSTEM
VENT GAS
COMBINED DRVER
VENT GAS
VACUUM CLEANUP
SYSTEM VENT GAS
---- OPTIONAL STREAM
Figure 5.3-1. Flow diagram for the oil furnace carbon black process.
-------
TABLE 5.3-1. STREAM IDENTIFICATION FOR THE
OIL FURNACE PROCESS (Figure 5.3-1)
Stream
Identification
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
Oil feed
Natural gas feed
Air to reactor
Quench water
Reactor effluent
Gas to oil preheater
Water to quench tower
Quench tower effluent
Bag filter effluent
Vent gas purge for dryer fuel
Main process vent gas
Vent gas to incinerator
Incinerator stack gas
Recovered carbon black
Carbon black to micropulverizer
Pneumatic conveyor system
Cyclone vent gas recycle
Cyclone vent gas
Pneumatic system vent gas
Carbon black from bag filter
Carbon black from cyclone
Surge bin vent
Carbon black to pelletizer
Water to pelletizer
Pelletizer effluent
Dryer direct heat source vent
Dryer heat exhaust after bag filter
Carbon black from dryer bag filter
Dryer indirect heat source vent
Hot gases to dryer
Dried carbon black
Screened carbon black
Carbon black recycle
Storage bin vent gas
Bagging system vent gas
Vacuum cleanup system vent gas
Combined dryer vent gas
Fugitive emissions
Oil storage tank vent gas
5/83
Chemical Process Industry
5.3-3
-------
is used as a fuel to heat a second reactor. When the first reactor becomes
too cool to crack the natural gas feed, the positions of the reactors are
reversed, and the second reactor is used to crack the gas while the first is
heated. Normally, more than enough hydrogen is produced to make the thermal
black process self-sustaining, and the surplus hydrogen is used to fire
boilers that supply process steam and electric power.
The collected thermal black is pulverized and pelletized to a final
product in much the same manner as is furnace black. Thermal process yields
are generally high (35 to 60 percent), but the relatively coarse particles
produced, 180 to 470 nm, do not have the strong reinforcing properties
required for rubber products.
5.3.2 Emissions and Controls
5.3.2.1 Oil Furnace Process - Emissions from carbon black manufacture
include particulate matter, carbon monoxide, organics, nitrogen oxides,
sulfur compounds, polycyclic organic matter (POM) and trace elements.
The principal source of emissions in the oil furnace process is the
main process vent. The vent stream consists of the reactor effluent and the
quench water vapor vented from the carbon black recovery system. Gaseous
emissions may vary considerably, according to the grade of carbon black
being produced. Organic and CO emissions tend to be higher for small particle
production, corresponding with the lower yields obtained. Sulfur compound
emissions are a function of the feed sulfur content. Tables 5.3-2 and 5.3-3
show the normal emission ranges to be expected, with typical average values.
The combined dryer vent (stream 37 in Figure 5.3-1) emits carbon black
from the dryer bag filter and contaminants from the use of the main process
vent gas if the gas is used as a supplementary fuel for the dryer. It also
emits contaminants from the combustion of impurities in the natural gas fuel
for the dryer. These contaminants include sulfur oxides, nitrogen oxides,
and the unburned portion of each of the species present in the main process
vent gas (see Table 5.3-2). The oil feedstock storage tanks are a source of
organic emissions. Carbon black emissions also occur from the pneumatic
transport system vent, the plantwide vacuum cleanup system vent, and from
cleaning, spills and leaks (fugitive emissions).
Gaseous emissions from the main process vent may be controlled with CO
boilers, incinerators or flares. The pellet dryer combustion furnace, which
is, in essence, a thermal incinerator, may also be employed in a control
system. CO boilers, thermal incinerators or combinations of these devices
can achieve essentially complete oxidation of organics and can oxidize
sulfur compounds in the process flue gas. Combustion efficiencies of.
99.6 percent for hydrogen sulfide and 99.8 percent for carbon monoxide have
been measured for a flare on a carbon black plant. Particulate emissions
may also be reduced by combustion of some of the carbon black particles, but
emissions of sulfur dioxide and nitrogen oxides are thereby increased.
5.3.2.2 Thermal Process - Emissions from the furnaces in this process
are, very low because the offgas is recycled and burned in the next furnace
to provide heat for cracking, or sent to a boiler as fuel. The carbon black
is recovered in a bag filter between the two furnaces.
5.3-4 EMISSION FACTORS 5/83
-------
The rest is recycled in the offgas. Some adheres to the surface of the
checkerbrick where it is burned off in each firing cycle.
Emissions from the dryer vent, the pneumatic transport system vent, the
vacuum cleanup system vent, and fugitive sources are similar to those for
the oil furnace process, since the operations which give rise to these
emissions in the two processes are similar. There is no emission point in
the thermal process which corresponds to the oil storage tank vents in the
oil furnace process. Also in the thermal process, sulfur compounds, POM,
trace elements and organic compound emissions are negligible, because low
sulfur natural gas is used, and the process offgas is burned as fuel.
TABLE 5.3-2. EMISSION FACTORS FOR CHEMICAL
SUBSTANCES FROM OIL FURNACE CARBON
BLACK MANUFACTURE3
Chemical substance
Main process vent gas
Carbon disulfide
Carbonyl sulfide
Methane
Nonmethane VOC
Acetylene
kg/Mg
30
10
25
(10-60)
45
Ib/ton
60
20
50
(20-120)
90
POM
Trace
Ethane
Ethylene
Propylene
Pr op ane
Isobutane
n- Butane
n-Pentane
elements
(5-130)
Oc
1.6
oc
0.23
0.10
0.27
0
0.002
<0.25
(10-260)
oc
3.2
oc
0.46
0.20
0.54
0
0.004
<0.50
Expressed in terms of weight of emissions per unit weight of
.carbon black produced.
These chemical substances are emitted only from the main process
vent. Average values are based on six sampling runs made at a
representative plant (Reference 1). Ranges given in parentheses
are based on results of a survey of operating plants (Reference ^
,Below detection limit of 1 ppm.
Beryllium, lead, mercury, among several others.
5/83
Chemical Process Industry
5.3-5
-------
TABLE 5.3-3. EMISSION FACTORS
EMISSION FACTOR
Particulate Carbon Monoxide
Process
Oil furnace process
Main process vent
Flare
CO boiler and incinerator
Combined Dryer vent
Bag filter11
Scrubber
Pneumatic system vent
Bag filter
kg/Mg
3.27d
(0.1-5)
1.35
(1.2-1.5)
1.04
0.12
(0.01-0.40)
0.36
(0.01-0.70)
0.29
(0.06-0.70)
Ib/ton kg/Mg Ib/ton
6.53d l,400e 2,800e
(0.2-10) (700-2,200) (1,400-4,400)
2.70 122 245
(2.4-3) (108-137) (216-274)
2.07 0.88 1.75
0.24
(0.02-0.80)
0.71
(0.02-1.40)
0.58
(0.12-1.40)
Nitrogen Oxides
kg/Mg
0.28e
(1-2.8)
NA
4.65
0.36
(0.12-0.61)
1.10
Ib/ton
0.56e
(2-5.6)
NA
9.3
0.73
(0.24-1.22)
2.20
Oil storage tank vent
Uncontrolled
Vacuum, cleanup system
vent
Bag filter
Fugitive emissions
Solid waste incinerator-'
^
Thermal process
0.03
(0.01-0.05)
0.10
0.12
Neg
0.06
(0.02-0.10)
0.20
0.24
Neg
0.01
Neg
0.02
Neg
0.04
Unknown
0.08
Unknown
Expressed in terms of weight of emissions per unit weight of carbon black produced. Blanks indicate no emissions.
Most plants use bag filters on all process trains for product recovery except solid waste incineration. Some
plants may use scrubbers on at least one process train. NA - not available.
The partlculate matter Is carbon black.
CEmisslon factors do not include organic sulfur compounds which are reported separately in Table 5.3-2. Individual
organic species comprising the nonmethane VOC emissions are included in Table 5.3-.2
Average values based on surveys of plants (References 4-5).
eAverage values based on results of 6 sampling runs conducted at a representative plant with a mean production
rate of 5.1 x 10 Mg/yr (5.6 x 10 ton/yr). Ranges of values are based on a survey of 15 plants (Reference 4).
Controlled by bag filter.
Not detected at detection limit of 1 ppm.
5.3-6
EMISSION FACTORS
5/83
-------
FOR CARBON BLACK MANUFACTURE
RATING: C
Sulfur
kg/Mg
oe'f
(0-12)
25
(21.9-28)
Oxides
Ib/ton
(0-24)
50
(44-56)
Methane
kg/Mg Ib/ton
25e 50e
(10-60) (20-120)
Nonmethane
kg/Mg
50e
(10-159)
1.85
(1.7-2)
VOCC
Ib/ton
iooe
(20-300)
3.7
(3.4-4)
Hydrogen
kg/Mg
30e
5S-13S8
1
Sulfide
Ib/ton
60e
10S-26S6
2
17.5
35.2
0.99
1.98
0.11
0.22
0.26 0.52
(0.03-0.54) (0,06-1.08)
0.20 0.40
0.72
1.44
0.01
Neg
0.02
Neg
0.01
Neg
0.02
Neg
Neg
*S is the weight percent eulfur in the feed.
Average values and corresponding ranges of values are based on a survey of plants (Reference 4) and on the
public files of Louisiana Air Control Commission.
Emission factor calculated using empirical correlations for petrochemical losses from storage tanks (vapor
pressure - 0.7 kPa). Emissions are mostly aromatic oils.
Based on emission rates obtained from the National Emissions Data System. All plants do not use solid vaste
incineration. See Section 2.1.
emissions from the furnaces are negligible. Emissions from the dryer vent, pneumatic system vent and vacuum
cleanup system and fugitive sources are similar to those for the oil furnace process.
Data are not available.
5/83
Chemical Process Industry
5.3-7
-------
References for Section 5.3
1. R. W. Serth and T. W. Hughes, Source Assessment: Carbon Black
Manufacture, EPA-600/2-77-107k, U. S. Environmental Protection Agency,
Research Triangle Park, NC, October 1977.
2. Air Pollutant Einls_si_on_JJ'actors, APTD-0923, U. S. Environmental Protection
Agency, Research Triangle Park, NC, April 1970.
3. I. Drogin, "Carbon Black", Journal of the Air Pollution Control
Association, _18_:216-228, April 1968.
4. Engineering and Cost Study of Air Pollution Control for the
Petrochemical Industry, Vol. 1; Carbon Black Manufacture by the
Furnace Process, EPA-450/3-73-006a, U. S. Environmental Protection
Agency, Research Triangle Park, NC, June 1974.
5. K. C. Hustvedt and L. B. Evans, Standards Support and Emission Impact
Statement: An Investigation of the Best Systems of Emission Reduction
for Furnace Process Carbon Black Plants in the Carbon Black Industry
(Draft), U. S. Environmental Protection Agency, Research Triangle Park,
NC, April 1976.
6. Source Testing of a Waste Heat Boiler, EPA-75-CBK-3, U. S. Environmental
Protection Agency, Research Triangle Park, NC, January 1975.
7. R. W. Gerstle and J. R. Richards, Industrial Process Profiles for
Environmental Use, Chapter 4; Carbon Black Industry, EPA-600-2-77-023d,
U. S. Environmental Protection Agency, Cincinnati, OH, February 1977.
8. G. D. Rawlings and T. W. Hughes, "Emission Inventory Data for
Acrylonitrile, Phthalic Anhydride, Carbon Black, Synthetic Ammonia,
and Ammonium Nitrate", Proceedings of APCA Specialty Conference on
Emission Factors and Inventories, Anaheim, CA, November 13-16, 1978.
5.3-8 EMISSION FACTORS 5/83
-------
5.4 CHARCOAL
5.4.1 Process Description
1-3
Charcoal is the solid carbon residue following the pyrolysis
(carbonization or destructive distillation) of carbonaceous raw materials.
Principal raw materials are medium to dense hardwoods such as beech, birch,
hard maple, hickory and oak. Others are softwoods (primarily long leaf and
slash pine), nutshells, fruit pits, coal, vegetable wastes and paper mill
residues. Charcoal is used primarily as a fuel for outdoor cooking. In
some instances, its manufacture may be considered as a solid waste disposal
technique. Many raw materials for charcoal manufacture are wastes, as
noted, and charcoal manufacture is also used in forest management for disposal
of refuse.
Recovery of acetic acid and methanol byproducts was initially responsible
for stimulation of the charcoal industry. As synthetic production of these
chemicals became commercialized, recovery of acetic acid and methanol became
uneconomical.
Charcoal manufacturing can be generally classified into either batch
(45 percent) or continuous operations (55 percent). Batch units such as the
Missouri type charcoal kiln (Figure 5.4-1) are small manually loaded and
unloaded kilns producing typically 16 megagrams (17,6 tons) of charcoal
during a three week cycle. Continuous units (i.e., multiple hearth furnaces)
produce an average of 2.5 megagrams (2.75 tons) per hour of charcoal.
During the manufacturing process, the wood is heated, driving off water and
highly volatile organic compounds (VOC). Wood temperature rises to approxi-
mately 275°C (527°F), and VOC distillate yield increases. At this point,
external application of heat is no longer required, since the carbonization
reactions become exothermic. At 350°C (662°F), exothermic pyrolysis ends,
and heat is again applied to remove the less volatile tarry materials from
the product charcoal.
Fabrication of briquets from raw material may be either an integral
part of a charcoal producing facility, or an independent operation, with
charcoal being received as raw material. Charcoal is crushed, mixed with a
binder solution, pressed and dried to produce a briquet of approximately
90 percent charcoal.
3-9
5.4.2 Emissions and Controls
There are five types of charcoal products, charcoal; noncondensible
gases (carbon monoxide, carbon dioxide, methane and ethane); pyroacids
(primarily acetic acid and methanol); tars and heavy oils; and water.
Products and product distribution are varied, depending on raw materials and
carbonization parameters. The extent to which organics and carbon monoxide
are naturally combusted before leaving the retort varies from plant to
plant. If uncombusted, tars may solidify to form particulate emissions, and
pyroacids may form aerosol emissions.
5/83
Chemical Process Industry
5.4-1
-------
N)
H
O
H
O
AIR PIPES
STEEL DOORS
ROOF VENTILATION
PORTS
CONCRETE WALLS
PYROLYSIS
GASES "
WASTE COOLING AIR
TO ATMOSPHERE
7
PRODUCT
CHARCOAL
COOLING AND
COMBUSTION AIR
FEED MATERIAL
CO
Figure 5.4-1. The Missouri type charcoal kiln (left) and the multiple hearth furnace (right).
-------
Control of emissions from batch type charcoal kilns is difficult because
of the cyclic nature of the process and, therefore, its emissions. Throughout
a cycle, both the emission composition and flow rate change. Batch kilns do
not typically have emission control devices, but some may use afterburners.
Continuous production of charcoal is more amenable to emission control than
are batch kilns, since emission composition and flow rate are relatively
constant. Afterburning is estimated to reduce emissions of particulates,
carbon monoxide and VOC by at least 80 percent.
Briquetting operations can control particulate emissions with centrifugal
collection (65 percent control) or fabric filtration (99 percent control).
Uncontrolled emission factors for the manufacture of charcoal are shown
in Table 5.4-1.
TABLE 5.4-1. UNCONTROLLED EMISSION FACTORS
FOR CHARCOAL MANUFACTURING3
EMISSION FACTOR RATING: C
Pollutant
Charcoal Manufacturing
Briquetting
Particulate
Carbon monoxide
Nitrogen oxides
VOC
kg/Mg
133
172
12
Ib/ton
266
344
24
kg/Mg
28
Ib/ton
56
Me thane
Nonme thane
52
157
104
314
Expressed as weight per unit charcoal produced. Dash = not
applicable. Reference 3. Afterburning is estimated to reduce
emissions of particulates, carbon monoxide and VOC >80%. Briquetting
operations can control particulate emissions with centrifugal
.collection (65% control) or fabric filtration (99% control).
Includes tars and heavy oils (References 1, 5-9). Polycyclic
organic matter (POM) carried by suspended particulates was deter-
mined to average 4.0 mg/kg (Reference 6).
..References 1, 5, 9.
Reference 3 (Based on 0.14% wood nitrogen content).
..References 1, 5, 7, 9.
References 1, 3, 5, 7. Consists of both noncondensibles (ethane,
formaldehyde, unsaturated hydrocarbons) and condensibles (methanol,
acetic acid, pyroacids).
5/83
Chemical Process Industry
5.4-3
-------
References for Section 5.4
1. Air Pollutant Emission Factors, APTD-0923, U. S. Environmental Protection
Agency, Research Triangle Park, NC, April 1970.
2. R. N. Shreve, Chemical Process Industries, Third Edition, McGraw-Hill
Book Company, New York, 1967.
3. C. M. Moscowitz, Source Assessment; Charcoal Manufacturing State of
the Art, EPA-600/2-78-004z, U. S. Environmental Protection Agency,
Cincinnati, OH, December 1978.
4. Riegel's Handbook of Industrial Chemistry, Seventh Edition, J. A. Kent,
ed., Van Nostrand Reinhold Company, New York, 1974.
5. J. R. Hartwig, "Control of Emissions from Batch-type Charcoal Kilns",
Forest Products Journal, 21(9):49-50, April 1971.
6. W. H. Maxwell, Stationary Source Testing of a Missouri-type Charcoal Kiln,
EPA-907/9-76-001, U. S. Environmental Protection Agency, Kansas City,
MO, August 1976.
7. R. W. Rolke, et al., Afterburner Systems Study, EPA-RZ-72-062, U. S.
Environmental Protection Agency, Research Triangle Park, NC, August
1972.
8. B. F. Keeling, Emission Testing the Missouri-type Charcoal Kiln, Paper
76-37.1, Presented at the 69th Annual Meeting of the Air Pollution
Control Association, Portland, OR, June 1976.
9. P. B. Hulman, et a^., Screening Study on Feasibility of Standards of
Performance for Wood Charcoal Manufacturing, EPA Contract No. 68-02-2608,
Radian Corporation, Austin, TX, August 1978.
5.4-4
EMISSION FACTORS
5/83
-------
5.5 CHLOR-ALKALI
5.5.1 Process Description1
Chlorine and caustic are produced concurrently by the electrolysis of brine in either the diaphragm or mercury
cell. In the diaphragm cell, hydrogen is liberated at the cathode and a diaphragm is used to prevent contact of the
chlorine produced at the anode with either the alkali hydroxide formed or the hydrogen. In the mercury cell,
liquid mercury is used as the cathode and forms an amalgam with the alkali metal. The amalgam is removed from
the cell and is allowed to react with water in a separate chamber, called a denuder, to form the alkali hydroxide
and hydrogen.
Chlorine gas leaving the cells is saturated with water vapor and then cooled to condense some of the water.
The gas is further dried by direct contact with strong sulfuric acid. The dry chlorine gas is then compressed for
in-plant use or is cooled further by refrigeration to liquefy the chlorine.
Caustic as produced in a diaphragm-cell plant leaves the cell as a dilute solution along with unreacted brine.
The solution is evaporated to increase the concentration to a range of 50 to 73 percent; evaporation also
precipitates most of the residual salt, which is then removed by filtration. In mercury-cell plants, high-purity
caustic can be produced in any desired strength and needs no concentration.
5.5.2 Emissions and Controls1
Emissions from diaphragm- and mercury-cell chlorine plants include chlorine gas, carbon dioxide, carbon
monoxide, and hydrogen. Gaseous chlorine is present in the blow gas from liquefaction, from vents in tank cars
and tank containers during loading and unloading, and from storage tanks and process transfer tanks. Other
emissions include mercury vapor from mercury cathode cells and chlorine from compressor seals, header seals,
and the air blowing of depleted brine in mercury-cell plants.
Chlorine emissions from chlor-alkali plants may be controlled by one of three general methods: (1) use of the
gas in other plant processes, (2) neutralization in alkaline scrubbers, and (3) recovery of chlorine from effluent gas
streams. The effect of specific control practices is shown to some extent in the table on emission factors (Table
5.5-1).
References for Section 5.5
1. Atmospheric Emissions from Chlor-Alkali Manufacture. U.S. EPA, Air Pollution Control Office. Research
Triangle Park, N.C. Publication Number AP-80. January 1971.
2. Duprey, R.L. Compilation of Air Pollutant Emission Factors. U.S. DHEW, PHS, National Center for Air
Pollution Control. Durham, N.C. PHS Publication Number 999-AP-42. 1968. p. 49.
2/72 Chemical Process Industry 5.5-1
-------
Table 5.5-1. EMISSION FACTORS FOR CHLOR-ALKALI PLANTS3
EMISSION FACTOR RATING: B
Type of source
Liquefaction blow gases
Diaphragm cell
Mercury cellb
Water absorber0
Caustic or lime scrubber0
Loading of chlorine
Tank car vents
Storage tank vents
Air blowing of mercury cell brine
Chlorine gas
lb/100 tons
2,000 to 10,000
4,000 to 16,000
25 to 1,000
1
450
1,200
500
kg/1 00 MT
1,000 to 5,000
2,000 to 8,000
12.5 to 500
0.5
225
600
250
References 1 and 2.
^Mercury calls lose about 1.5 pounds mercury per 100 tons (0.75 kg/100 MT) of chlorine liquefied.
cControl devices.
5.5-2
EMISSION FACTORS
2/72
-------
5.6 EXPLOSIVES
5.6.1 General
An explosive is a material that, under the influence of thermal or
mechanical shock, decomposes rapidly and spontaneously with the evolution of
large amounts of heat and gas. There are two major categories, high
explosives and low explosives. High explosives are further divided into
initiating, or primary, high explosives and secondary high explosives.
Initiating high explosives are very sensitive and are generally used in small
quantities in detonators and percussion caps to set off larger quantities of
secondary high explosives. Secondary high explosives, chiefly nitrates, nitro
compounds and nitramines, are much less sensitive to mechanical or thermal
shock, but they explode with great violence when set off by an initiating
explosive. The chief secondary high explosives manufactured for commercial
and military use are ammonium nitrate blasting agents and 2,4,6,-trinitro-
toluene (TNT). Low explosives, such as black powder and nitrocellulose,
undergo relatively slow autocombustion when set off and evolve large volumes
of gas in a definite and controllable manner. Many different types of
explosives are manufactured. As examples of high and low explosives, the
production of TNT and nitrocellulose (NC) are discussed below.
5.6.2 TNT Production1"3'6
TNT may be prepared by either a continuous or a batch process, using
toluene, nitric acid and sulfuric acid as raw materials. The production of
TNT follows the same chemical process, regardless of whether batch or
continuous method is used. The flow chart for TNT production is shown in
Figure 5.6-1. The overall chemical reaction may be expressed as:
3HON0
Toluene Nitric
Acid
Sulfuric TNT
Acid
Water
Sulfuric
Acid
The production of TNT by nitration of toluene is a three stage process
performed in a series of reactors, as shown in Figure 5.6-2. The mixed acid
stream is shown to flow counter current to the flow of the organic stream.
Toluene and spent acid fortified with a 60 percent HN03 solution are fed Into
the first reactor. The organic layer formed in the first reactor is pumped
into the second reactor, where it is subjected to further nitration with acid
from the third reactor fortified with additional HN03. The product from the
second nitration step, a mixture of all possible isomers of dinitrotoluene
(DNT), is pumped to the third reactor. In the final reaction, the DNT is
treated with a fresh feed of nitric acid and oleum (a solution of 803[sulfur
trioxide] in anhydrous sulfuric acid). The crude TNT from this third
nitration consists primarily of 2,4,6-trinitrotoluene. The crude TNT is
5/83
Chemical Process Industry
5.6-1
-------
tjl
N)
cn
en
M
i
O
!*
CO
TOLUENE
MIXED ACID
»
3'2
TO DISPOSAL TO DISPOSAL TO STORAGE
GASEOUS EMISSIONS
•NEGLIGIBLE AMOUNT
00
Figure 5.6-1. TNT production.
-------
washed to remove free acid, and the wash water (yellow water) is recycled to
the early nitration stages. The washed TNT is then neutralized with soda ash
and treated with a 16 percent aqueous sodium sulfite (Sellite) solution to
remove contaminating isomers. The Sellite waste solution (red water) from the
purification process is discharged directly as a liquid waste stream, is
collected and sold, or is concentrated to a slurry and incinerated. Finally,
the TNT crystals are melted and passed through hot air dryers, where most of
the water is evaporated. The dehydrated product is solidified, and the TNT
flakes packaged for transfer to a storage or loading area.
TOLUENE
SPENT ACID
1st
NITRATION
NITRO-
TOLUENE_
t
60%HN03
OLEUM
t
2nd
NITRATION
DNT
I
60%HN03
3rd
NITRATION
^" 1 l\l I
PRODUCT
97%HN03
Figure 5.6-2. Nitration of toluene to form trinitrotoluene.
5.6.3 Nitrocellulose Production
1,6
Nitrocellulose is commonly prepared by the batch type mechanical dipper
process. A newly developed continuous nitration processing method is also
being used. In batch production, cellulose in the form of cotton linters,
fibers or specially prepared wood pulp is purified by boiling and bleaching.
The dry and purified cotton linters or wood pulp are added to mixed nitric and
sulfuric acid in metal reaction vessels known as dipping pots. The reaction
is represented by:
) + 3HON0 + ISO(GO
Cellulose Nitric Sulfuric Nitrocellulose
Acid Acid
Water
Sulfuric
Acid
Following nitration, the crude NC is cent,rifuged to remove most of the spent
nitrating acids and is put through a series of water washing and boiling
treatments to purify the final product.
TABLE 5.6-1.
EMISSION FACTORS FOR THE OPEN BURNING OF TNT
(Ib pollution/ton TNT burned)
a,b
Type of
Explosive
Particulates Nitrogen
Oxides
Carbon
Monoxide
Volatile
Organic
Compounds
TNT
180.0
150.0
56.0
1.1
5/83
aReference 7. Particulate emissions are soot. VOC is nonmethane.
The burns were made on very small quantities of TNT, with test
apparatus designed to simulate open burning conditions. Since
such test simulations can never replicate actual open burning, it
la advisable to use the factors in this Table with caution.
Chemical Process Industry
5.6-3
-------
Process
TABLE 5.6-2. EMISSION FACTORS FOR
EMISSION FACTOR
Particulates
kg/Mg
Ib/ton
Sulfur oxides
(S02)
kg/Mg
Ib/ton
TNT - Batch Process
Nitration reactors
Fume recovery
Acid recovery
Nitric acid concentrators
Sulfuric acid concentrators
Electrostatic
precipator (exit)
Electrostatic precipitator
w/ scrubber
Red water incinerator
Uncontrolled
®
Wet scrubber
Sellite exhaust
TNT - Continuous Process
Nitration reactors
Fume recovery
Acid recovery
12.5
CO.015 - 63)
0.5
25
(0.03 - 126)
1
(2 - 20)
Neg.
(0.025 - 1.75)
1
(0.025 - 1.75)
29.5
(0.005 - 88)
14
(4 - 40)
Neg.
2
(0.05 - 3.5)
2
(0.05 - 3.5)
59
(0.01 - 177)
Red water incinerator 0.13 0.25
(0.015 - 0.25) (0.03 - 0.5)
Nitrocellulose
Nitration reactors — —
Nitric acid concentrator — —
Sulfuric acid concentrator — —
Boiling tubs — —
0.12
(0.025 - 0.22)
0.7
(0.4 - 1)
— •
34
(0.2 - 67)
~
0.24
(0.05 - 0
1.4
(0.8 - 2)
—
68
(0.4-135)
~~
.43)
For some processes, considerable variations in emissions have been reported. Average of reported values
is shown first, ranges in parentheses. Where only one number is given, only one source test was
available. Emission factors are in units of kg of pollutant per Mg and pounds of pollutant per ton of TNT
.or Nitrocellulose produced.
Significant emissions of volatile organic compounds have not been reported for the explosives industry.
However, negligible emissions of toluene and trinitromethane (TNM) from nitration
reactors have been reported in TNT manufacture. Also, fugitive VOC emissions may result from
various solvent recovery operations. See Reference 6.
cReference 5.
dAcid mist emissions influenced by nitrobody levels and type of furnace fuel.
eNo data available for NO emissions after scrubber. NO emissions are assumed unaffected by scrubber.
*
5,6-4
EMISSION FACTORS
5/83
-------
EXPLOSIVES MANUFACTURING
RATING: C
,a,b
Nitrogen oxides
(NO )
kg/Mg Ib/ton
Nitric acid rots t
(100% HNO )
kg/Mg Ib/ton
Sulfuric acid mist
(1003: H,S04)
kg/ton Ib/ton
12.5
(3 - 19)
27.5
(0.5 - 68)
18.5
(8 - 36)
20
(1 - 40)
20
(1 - 40)
25
(6 - 38)
55
(1 - 136)
37
(16 - 72)
40
(2 - 80)
40
(2 - 80)
0.5
(0.15 - 0.95)
46
(0.005 - 137)
CO.3 - 1.9)
92
(0.02 - 275)
4.5
(0.15 - 13.5)
(0.3 - 27)
32.5 65
(0.5 - 94) (1 - 188)
2.5 5
(2 - 3) (4 - 6)
13
(0.75 - 50)
2.5
26
(1.5 - 101)
5
(0.3 - 8)
(0.6 - 16)
(3.35 - 5)
1.5
(0.5 - 2.25)
3.5
(3 - 4.2)
(1.85 - 17)
7
(5 - 9)
8
(6.7 - 10)
3
(1 - 4.5)
7
(6.1 - 8.4)
14
(3.7 - 34)
14
(10 - 18)
0.5
(0.15 - 0.95
0.01
(0.005 - 0.015)
9.5
(0.25 - 18)
(0.3 - 1.9)
0.02
(0.01 - 0.03)
19
(0.5 - 36)
0.3
0. 6
Use lav end of range for modern efficient units, high end for less efficient units.
^Apparent reductions in NO and participate after control may not he significant, because these values are
baaed on only one test result.
^Reference 4.
For product with low nitrogen content (12%), use high end of range. For products with higher
nitrogen content, use lower end of range.
5/83
Chemical Process Industry
5.6-5
-------
2-3 5-7
j.6.4 Emissions and Controls '
Oxides of nitrogen (NOX) and sulfur (SOX) are the major emissions from
the processes involving the manufacture, concentration and recovery of acids
in the nitration process of explosives manufacturing. Emissions from the
manufacture of nitric and sulfuric acid are discussed in other Sections of
this publication. Trinitromethane (TNM) is a gaseous byproduct of the
nitration process of TNT manufacture. Volatile organic compound emissions
result primarily from fugitive vapors from various solvent recovery
operations. Explosive wastes and contaminated packaging material are
regularly disposed of by open burning, and such results in uncontrolled
emissions, mainly of NOX and particulate matter. Experimental burns of
several explosives to determine "typical" emission factors for the open
burning of TNT are presented in Table 5.6-1.
In the manufacture of TNT, emissions from the nitrators containing NO,
N02, N20, trinitromethane (TNM) and some toluene are passed through a fume
recovery system to extract NOX as nitric acid, and then are vented through
scrubbers to the atmosphere. Final emissions contain quantities of unabsorbed
NOX and TNM. Emissions may also come from the production of Sellite solution
and the incineration of red water. Red water incineration results in
atmospheric emissions of NO , SO and ash (primarily Na SO .)
In the manufacture of nitrocellulose, emissions from reactor pots and
centrifuge are vented to an NOX water absorber. The weak 11N03 solution is
transferred to the acid concentration system. Absorber emissions are mainly
NOX. Another possible source of emissions is the boiling tubs, where steam
and acid vapors vent to the absorber.
The most important fact affecting emissions from explosives manufacture
is the type and efficiency of the manufactaring process. The efficiency of
the acid and fume recovery systems for TNT manufacture will, directly affect
the atmospheric emissions. In addition, the degree to which acids are exposed
to the atmosphere during the manufacturing process affects the NOX and SOX
emissions. For nitrocellulose production, emissions are influenced by the
nitrogen content and the desired product quality. Operating conditions will
also affect emissions. Both TNT and nitrocellulose can be produced in batch
processes. Such processes may never reach steady state,, and emission
concentrations may vary considerably with time, and fluctuations in emissions
will, influence the efficiency of control methods.
Several measures may be taken to reduce emissions from explosive
manufacturing. The effects of various control devices and process changes,
along with emission factors for explosives manufacturing, are shown in
Table 5.6-2. The emission factors are all related to the amount of product
produced and are appropriate either for estimating long term emissions or for
evaluating plant operation at full production conditions. For short time
periods, or for plants with intermittent operating schedules, the emission
5.. 6-6 EMISSION FACTORS 5/83
-------
factors in Table 5.6-2 should be used with caution, because processes not
associated with the nitration step are often not in operation at the same time
as the nitration reactor.
References for Section 5.6
1. R. N. Shreve, Chemical Process Industries, 3rd Ed., McGraw-Hill Book
Company, New York, 1967.
2. Unpublished data on emissions from explosives manufacturing, Office of
Criteria and Standards, National Air Pollution Control Administration,
Durham, NC, June 1970.
3. F. B. Higgins, Jr., et al., "Control of Air Pollution From TNT
Manufacturing", Presented at 60th annual meeting of Air Pollution Control
Association, Cleveland, OH, June 1967.
4. Air Pollution Engineering Source Sampling Surveys, Radford Army
Ammunition Plant, U. S. Army Environmental Hygiene Agency, Edgewood
Arsenal, MD, July 1967, July 1968.
5. Air Pollution Engineering Source Sampling Surveys, Volunteer Army
Ammunition Plant and Joliet Army Ammunition Plant, U. S. Army Environmental
Hygiene Agency, Edgewood Arsenal, MD, July 1967, July 1968.
6. Industrial Process Profiles for Environmental Use; The Explosives Industry,
EPA-600/2-77-0231, U. S. Environmental Protection Agency, Research Triangle
Park, NC, February 1977.
7. Specific Air Pollutants from Munitions Processing and Their Atmospheric
Behavior, Volume 4: Open Burning and Incineration of Waste Munitions,
Research Triangle Institute, Research Triangle Park, NC, January 1978.
5/83
Chemical Process Industry
5.6-7
-------
-------
5.7 HYDROCHLORIC ACID
Hydrochloric acid is manufactured by a number of different chemical processes. Approximately 80 percent of
the hydrochloric acid, however, is produced by the by-product hydrogen chloride process, which will be the only
process discussed in this section. The synthesis process and the Mannheim process are of secondary importance.
5.7.1 Process Description1
By-product hydrogen chloride is produced when chlorine is added to an organic compound such as benzene,
toluene, and vinyl chloride. Hydrochloric acid is produced as a by-product of this reaction. An example of a
process that generates hydrochloric acid as a by-product is the direct chlorination of benzene. In this process
benzene, chlorine, hydrogen, air, and some trace catalysts are the raw materials that produce chlorobenzene. The
gases from the reaction of benzene and chlorine consist of hydrogen chloride, benzene, chlorobenzenes, and air.
These gases are first scrubbed in a packed tower with a chilled mixture of monochlorobenzene and
dichlorobenzene to condense and recover any benzene or chlorobenzene. The hydrogen chloride is then absorbed
in a falling film absorption plant.
5.7.2 Emissions
The recovery of the hydrogen chloride from the chlorination of an organic compound is the major source of
hydrogen chloride emissions. The exit gas from the absorption or scrubbing system is the actual source of the
hydrogen chloride emitted. Emission factors for hydrochloric acid produced as by-product hydrogen chloride are
presented in Table 5.7-1.
Table 5.7-1. EMISSION FACTORS FOR HYDROCHLORIC
ACID MANUFACTURING3
EMISSION FACTOR RATING: B
Type of process
By-product hydrogen chloride
With final scrubber
Without final scrubber
Hydrogen chloride emissions
Ib/ton
0.2
3
kg/MT
0.1
1.5
aReference 1.
Reference for Section 5.7
1. Atmospheric Emissions from Hydrochloric Acid Manufacturing Processes. U.S. DHEW, PHS, CPEHS,
National Air Pollution Control Administration. Durham, N.C. Publication Number AP-54. September 1969.
2/72
Chemical Process Industry
5.7-1
-------
-------
5.8 HYDROFLUORIC ACID
1-3
5.8.1 Process Description
Nearly all of the hydrofluoric acid, or hydrogen fluoride, currently
produced in the United States is manufactured by the reaction of acid-
grade fluorospar with sulfuric acid in the reaction:
CaF2
Calcium
Fluoride
(Fluorospar)
Sulfuric
Acid
Calcium
Sulfate
(Anhydrite)
+ 2 HF
Hydrogen
Fluoride
(Hydrofluoric
Acid)
The fluorospar typically contains 97.5 percent or more calcium fluoride,
1 percent or less silicon dioxide (Si02), and 0.05 percent or less
sulfur, with calcium carbonate (CaCOs) as the principal remainder. See
Figure 5.8-1 for a typical process flow diagram.
The reaction to produce the acid is endothermic and is usually
carried out in externally heated horizontal rotary kilns for 30 to 60
minutes at 390 to 480°F (200-250°C). Dry fluorospar and a slight excess
of sulfuric acid are fed continuously to the front end of the kiln.
Anhydrite is removed through an air lock at the opposite end. The
gaseous reaction products - hydrogen fluoride, excess sulfuric acid from
the primary reaction, silicon tetrafluoride, sulfur dioxide, carbon
dioxide, and water produced in secondary reactions - are removed from
the front end of the kiln with entrained particulate materials. The
particulates are removed from the gas stream by a dust separator, and
the sulfuric acid and water are removed by a precondenser. The hydrogen
fluoride vapors are condensed in refrigerant condensers and are delivered
to an intermediate storage tank. The uncondensed gases are passed
through a sulfuric acid absorption tower to remove most of the remaining
hydrogen fluoride, which is also delivered with the residual sulfuric
acid to the intermediate storage tank. The remaining gases are passed
through water scrubbers, where the silicon tetrafluoride and remaining
hydrogen fluoride are recovered as fluosilicic acid (H2SiF5). The
hydrogen fluoride and sulfuric acid are delivered to distillation
columns, where the hydrofluoric acid is extracted at 99.98 percent
purity. Weaker concentrations (typically 70-80 percent) are prepared by
dilution with water.
124
5.8.2 Emissions and Controls * "
Air polluting emissions are suppressed to a great extent by the
condensing, scrubbing and absorption equipment used in the recovery and
purification of the hydrofluoric and fluosilicic acid products. Partic-
ulate material in the process gas stream is controlled by a dust separator
near the outlet of the kiln and is recycled to the kiln for further
2/80
Chemical Process Industry
5.8-1
-------
Figure 5,8-1. Process flow diagram of a typical hydrofluoric acid plant.
PARTICIPATES
PARTICULATES
t
T
SPAR
STORAGE
SILO
A P ARTICULATES
~r— _
*
\
M DRYING KILN " '
(/)
o
q
0
U3
/
SPAR
tUSE
SILO
ACID
SCRUBBER
iI2SOl(
^
r-*
J
X— /
^1*1
' ^\
ROTARY
KILN
f
P
t
- — ^.
^
^
*
T.
T DUST
^ SEPARA-
TOR
HF
StFi,
S09
1
-ri
J
|
T
CONDENSERS
\
T
r
j.
INTERMEDIATE
STORAGE
t
A PRINCIPAL EMISSION LOCATIONS
11,80,. H20 H20 CAUSTIC
SCRUB iER HF
ACID WATER [ WATER A S1F
SCRUBBER SCRUBBER [ SCRUBBER M so
I
t
.... } j_ . T- »* VENT
L^ L» i> | ^ i (TAIL GASJ
^ •-!« ^ ™^ «»ft» 1 ^ 1
rr TT j ^^
1 f
-fc T' r^*n
30-35% H2Sil'6 ,
nunniirr <5TniJAf:ir
\
1 ' 99.98% 1IF
1'POnUfT STORAGE
DESORBER STILL
CaSOi,
to
05
-------
Table 5.8-1. EMISSION FACTORS FOR HYDROFLUORIC ACID MANUFACTURE
wl
ic
Type of Operation
and Control
Spar drying
Uncontrolled
Fabric filter
Spar handling
silos'5
Uncontrolled
Fabric filter
Transfer operations
Uncontrolled
Covers, additives
Tail gasC
Uncontrolled
Caustic scrubber
Control
efficiency
U)
0
99
0
99
0
80
0
99
Emissions
Gases
Ib/ton acid
25.0 (HF)
30.0 (SiFt,)
45.0 (S02)
0.2 (HF)
0.3 (SiF4)
0.5 (S02)
kg/MT acid
12.5 (HF)
15.0 (SiFi,)
22.5 (S02)
0.1 (HF)
0.2 (SiF^)
0.3 (S02)
Participates (Spar)
Ib/ton
Fluorospar
75.0
0.8
60.0
0.6
6.0
1.2
kg/MT
Fluorospar
37.5
0.4
30.0
0.3
3.0
0.6
Emission
Factor
Rating
C
D
E
D
Reference 1. Averaged from information provided by four plants. Hourly fluorospar input calculated
from reported 1975 year capacity, assuming stoichiometric amount of calcium fluoride and 97.5%
content in fluorospar. Hourly emission rates calculated from reported baghouse controlled rates.
Values averaged were:
Plant 1975 capacity Emissions Ib/Ton Fluorospar
1
2
3
4
Information as in Note a.
emissions.
Information as in Note a.
in Reference 4.
15,000 ton HF
20,000 ton HF
50,000 ton HF
11,000 ton HF
106
130
42
30
Four plants averaged for silo emissions, two plants for transfer operations
Three plants averaged. HF and SiFt, emission factors verified by information
-------
processing. The precondenser removes water vapor and sulfuric acid
mist, and the condenser, acid scrubber and water scrubbers remove all
but small amounts of hydrogen fluoride, silicon tetrafluoride, sulfur
dioxide and carbon dioxide from the tail gas. A caustic scrubber is
employed to reduce further the levels of these pollutants in the tail
gas.
Dust emissions result from the handling and drying of the fluorospar,
and they are controlled with bag filters at the spar storage silos and
drying kilns, their principal emission points.
Hydrogen fluoride emissions are minimized by maintaining a slight
negative pressure in the kiln during normal operations. Under upset
conditions, a standby caustic scrubber or a bypass to the tail gas
caustic scrubber are used to control hydrogen fluoride emissions from
the kiln.
Fugitive dust emissions from spar handling and storage are con-
trolled with flexible coverings and chemical additives.
Table 5.8-1 lists the emission factors for the various process
operations. The principal emission locations are shown in the process
flow diagram, Figure 5.8-1.
References for Section 5.8
1. Screening Studyon Feasibility of Standards of Performance for
Hydrofluoric Acid Manufacture, EPA-450/3-78-109, U.S. Environmental
Protection Agency, Research Triangle Park, NC, October 1978.
2. "Hydrofluoric Acid", Kirk-Othmer Encyclopedia of Chemical
Technology, Vol. 9, Interscience Publishers, New York, 1965.
3. W. R. Rogers and K. Muller, "Hydrofluoric Acid Manufacture",
Chemical Engineering Progress, 59(5);85-8. May 1963.
4. J.-.M. Robinson, et al., Engineering and Cost Effectiveness Study
of Fluoride Emissions Control, Vol. 1, PB 207 506, National Technical
Information Service, Springfield, VA, 1972.
5.8-4 EMISSION FACTORS 2/80
-------
5.9 NITRIC ACID
5.9.1 Process Description
Weak Acid Production - Nearly all the nitric acid produced in the
United States is manufactured by the catalytic oxidation of ammonia
(Figure 5.9-1). This process typically consists of three steps, each of
which corresponds to a distinct chemical reaction. First, a 1:9 ammonia/
air mixture is oxidized at high temperature (1380 - 1470°F or
750 - 800°C) as it passes through a platinum/rhodium catalyst, according
to the reaction:
4NH3
Ammonia
502
Oxygen
4NO
Nitric
oxide
6H20
Water
CD
After the process stream is cooled to 100°F (38°C) or less by passage
through a cooler/condenser, the nitric oxide reacts with residual oxygen
to form nitrogen dioxide:
2NO
2N02
Nitrogen
dioxide
Nitrogen
tetroxide
(2)
Finally, the gases are introduced into a bubble cap plate absorption
column for contact with a countercurrent stream of water. The exothermic
reation that occurs is:
3N02
H20
2HN03
NO
(3)
The production of nitric oxide in Reaction 3 necessitates the intro-
duction of a secondary air stream into the column to oxidize it into
nitrogen dioxide, thereby perpetuating the absorption operation.
In the past, nitric acid plants have been operated at a single
pressure, ranging from 14.7 to 176 pounds per square inch (100 - 1200 kPa),
However, since Reaction 1 is favored by low pressures and Reactions 2
and 3 are favored by higher pressures, newer plants tend to be operating
two pressure systems, incorporating a compressor between the oxidizer
and the condenser.
The spent gas flows from the top of the absorption tower to an
entrainment separator for acid mist removal, through a heat exchanger in
the ammonia oxidation unit for energy absorption by the ammonia stream,
through an expander for energy recovery, and finally to the stack. In
most plants, however, the tail gas is treated to remove residual nitrogen
oxides before release to the atmosphere.
High Strength Acid Production - The nitric acid concentration
process consists of feeding strong sulfuric acid and 50 - 70 percent
nitric acid to the top of a packed dehydrating column at approximately
atmospheric pressure. The acid mixture flows downward counter to ascend-
ing vapors. Concentrated nitric acid leaves the top of the column as 98
10/80
Chemical Process Industry
5.9-1
-------
AIR
EMISSION
POINT
COMPRESSOR
EXPANDER
EFFLUENT
STACK
AMMONIA
VAPOR
AIR
— NOX EMISSIONS
CONTROL
CATALYTIC REDUCTION
NIT
2
AIR
,PREHEATER
WASTE
HEAT
BOILER
STEAM
NITRIC OXIDE
GAS
AIR
ENTRAINED
MIST
SEPARATOR
PLATINUM
FILTER
AIR
NITRIC
ACID
COOLING
WATER
J
SECONDARY AIR
COOLER
CONDENSER
NO 2
ABSORPTION
TOWER
PRODUCT
(50 - 70%
HN03)
Figure 5.9-1. Flow diagram of typical nitric acid plant using pressure process (high strength
acid unit not shown).
5.9-2
EMISSION FACTORS
10/80
-------
percent vapor, containing a small amount of N0£ and 02 from dissociation
of nitric acid. The concentrated acid vapor leaves the column and goes
to a bleacher and countercurrent condenser system to effect the conden-
sation of strong nitric acid and the separation of oxygen and nitrogen
oxide byproducts. These byproducts then flow to an absorption column
where the nitric oxide mixes with auxiliary air to form NC>2, which is
recovered as weak nitric acid. Unreacted gases are vented to the atmo-
sphere from the top of the absorption column.
TABLE 5.9-1. NITROGEN OXIDE EMISSIONS FROM NITRIC ACID PLANTS3
EMISSION FACTOR RATING: B
Source
Weak Acid Plant Tail Gas
Uncontrolled
Efficiency^ %
0
Ib/ton Acid
43
(14 - 86)
kg/MT Acid
22
(7 - 43)
Catalytic reduction
Natural gas 99.1 0.4 0.2
(0.05 - 1.2) (0.03 - 0.6)
Hydrogen0 97 - 99.8 0.8 0.4
(0 - 1.5) (0 - 0.8)
Natural gas/hydrogen
(25%/75%) 98 - 98.5 1.0 0.5
(0.8 - 1.1) (0.4 - 0.6)
Extended absorption 95.8 1.8 0.9
(0.8 - 2.7) (0.4 - 1.4)
High Strength Acid Plant6 NAf 10 5
Based on 100% acid. Production rates are in terms of total weight of
product (water and acid). A plant producing 500 tons (454 MT)/day of
55 wt. % nitric acid is calculated as producing 275 tons (250 MT)/day
,of 100% acid. Ranges in parentheses. NA: Not Applicable.
Reference 3. Based on a study of 18 plants.
References 1 and 2. Based on data from 2 plants with these process
conditions: production rate, 130 tons (118 MT)/day at 100% rated
capacity; absorber exit temperature, 90°F (32°C); absorber exit
,pressure, 87 psig (600 kPa); acid strength, 57%.
References 1 and 2. Based on data from 2 plants with these process
conditions: production rate, 208 tons (188 MT)/day at 100% rated
capacity; absorber exit temperature, 90°F (32°C); absorber exit
presure, 80 psig (550 kPa); acid strength, 57%.
References 1 and 2. Based on a unit that produces 3000 Ib/hr (6615
kg/hr) at 100% rated capacity, of 98% nitric acid.
10/80 Chemical Process Industry 5.9-3
-------
The two most common techniques used to control absorption tower
tail gas emissions are extended absorption and catalytic reduction. The
extended absorption technique reduces emissions by increasing the effi-
ciency of the absorption tower. This efficiency increase is achieved by
increasing the number of absorber trays, operating the absorber at
higher pressures, or cooling the weak acid liquid in the absorber.
In the catalytic reduction process (often termed catalytic oxidation),
tail gases are heated to ignition temperature, mixed with fuel (natural
gas, hydrogen, carbon monoxide or ammonia) and passed over a catalyst.
In the presence of the catalyst, the fuels are oxidized, and the nitrogen
oxides are reduced to N2. The extent of reduction of NC>2 and NO to N2
is a function of plant design, fuel type operating temperature and
pressure, space velocity through the reduction catalytic reactor, type
of catalyst, and reactant concentration. See Table 5.9-1.
Two seldom used alternative control devices for absorber tail gas
are molecular sieves and wet scrubbers. In the molecular sieve technique,
tail gas is contacted with an active molecular sieve which catalyticly
oxidizes NO to N02 and selectively adsorbs the N02. The N02 is then
thermally stripped from the molecular sieve and returned to the absorber.
In the scrubbing technique, absorber tail gas is scrubbed with an aqueous
solution of alkali hydroxides or carbonates, ammonia, urea or potassium
permanganate. The NO and N02 are absorbed and recovered as nitrate or
nitrite salts.
Comparatively small amounts of nitrogen oxides are also lost from
acid concentrating plants. These losses (mostly N02) are from the
condenser system, but the emissions are small enough to be controlled
easily by inexpensive absorbers.
Acid mist emissions do not occur from the tail gas of a properly
operated plant. The small amounts that may be present in the absorber
exit gas streams are removed by a separator or collector prior to entering
the catalytic reduction unit or expander.
Emissions from acid storage tanks may occur during tank filling.
The displaced gases are equal in volume to the quantity of acid added to
the tanks.
Nitrogen oxide emissions (expressed as N02) are presented for weak
nitric acid plants in Table 5.9-1. The emission factors vary consider-
ably with the type of control employed and with process conditions. For
comparison purposes, the EPA New Source Performance Standard for both
new and modified plants is 3.0 pounds per ton (1.5 kg/MT) of 100 percent
acid produced, maximum 3 hour average, expressed as N02.
5.9-4 EMISSION FACTORS 10/80
-------
5.9.2 Emissions and Controls
Emissions from nitric acid manufacture consist primarily of nitric
oxide, nitrogen dioxide (which accounts for visible emissions) and trace
amounts of nitric acid mist. By far, the major source of nitrogen
oxides is the tail gas from the acid absorption tower (Table 5.9-1). In
general, the quantity of NOjj emissions is directly related to the
kinetics of the nitric acid formation reaction and absorption tower
design.
The two most common techniques used to control absorption tower
tail gas emissions are extended absorption and catalytic reduction. The
extended absorption technique reduces emissions by increasing the effi-
ciency of the absorption tower. This efficiency increase is achieved by
increasing the number of absorber trays, operating the absorber at
higher pressures, or cooling the weak acid liquid in the absorber.
In the catalytic reduction process (often termed catalytic oxidation),
tail gases are heated to ignition temperature, mixed with fuel (natural
gas, hydrogen, carbon monoxide or ammonia) and passed over a catalyst.
In the presence of the catalyst, the fuels are oxidized, and the nitrogen
oxides are reduced to N£. The extent of reduction of N02 and NO to N£
is a function of plant design, fuel type operating temperature and
pressure, space velocity through the reduction catalytic reactor, type
of catalyst, and reactant concentration. See Table 5.9-1.
Two seldom used alternative control devices for absorber tail gas
are molecular sieves and wet scrubbers. In the molecular sieve technique,
tail gas is contacted with an active molecular sieve which catalyticly
oxidizes NO to N02 and selectively adsorbs the N0£. The N02 is then
thermally stripped from the molecular sieve and returned to the absorber.
In the scrubbing technique, absorber tail gas is scrubbed with an aqueous
solution of alkali hydroxides or carbonates, ammonia, urea or potassium
permanganate. The NO and N0£ are absorbed and recovered as nitrate or
nitrite salts.
Comparatively small amounts of nitrogen oxides are also lost from
acid concentrating plants. These losses (mostly N0£) are from the
condenser system, but the emissions are small enough to -be controlled
easily by inexpensive absorbers.
Acid mist emissions do not occur from the tail gas of a properly
operated plant. The small amounts that may be present in the absorber
exit gas streams are removed by a separator or collector prior to entering
the catalytic reduction unit or expander.
Emissions from acid storage tanks may occur during tank filling.
The displaced gases are equal in volume to the quantity of acid added to
the tanks.
Nitrogen oxide emissions (expressed as N0£) are presented for weak
nitric acid plants in Table 5.9-1. The emission factors vary consider-
ably with the type of control employed and with process conditions. For
comparison purposes, the EPA New Source Performance Standard for both
10/80 Chemical Process Industry 5.9-5
-------
new and modified plants is 3.0 pounds per ton (1.5 kg/MT) of 100 percent
acid produced, maximum 3 hour average, expressed as N02.
References for Section 5.9
1. Control of Air Pollution from Nitric Acid Plants. Office of Air
Quality Planning and Standards, U.S. Environmental Protection
Agency, Research Triangle Park, NC, August 1971. Unpublished.
2. Atmospheric Emissions from Nitric Acid Manufacturing Processes,
999-AP-27, U.S. Department of Health, Education and Welfare,
Cincinnati, OH, 1966.
3. Marvin Drabkin, A Reviewof Standards of Performance for New
Stationary Sources - Nitric Acid Plants. EPA-450/3-79-013, U.S.
Environmental Protection Agency, Research Triangle Park, NC, March
1979.
4. "Standards of Performance for Nitric Acid Plants", 40 CFR 60. G.
5.9-6 EMISSION FACTORS 10/80
-------
5.10 PAINT AND VARNISH
5.10.1 Paint Manufacturing
The manufacture of paint involves the dispersion of a colored oil or
pigment in a vehicle, usually an oil or resin, followed by the addition of an
organic solvent for viscosity adjustment. Only the physical processes of
weighing, mixing, grinding, tinting, thinning and packaging take place. No
chemical reactions are involved.
These processes take place in large mixing tanks at approximately room
temperature.
The primary factors affecting emissions from paint manufacture are care
in handling dry pigments, types of solvents used and mixing temperature.
About 1 or 2 percent of the solvent is lost even under well controlled
conditions. Particulate emissions amount to 0.5 to 1.0 percent of the pigment
handled.
Afterburners can reduce emitted volatile organic compounds (VOC) by
99 percent and particulates by about 90 percent. A water spray and oil filter
system can reduce particulate emissions from paint blending by 90 percent.
5.10.2 Varnish Manufacturing
1-3,5
the
The manufacture of varnish also involves the mixing and blending of
various ingredients to produce a wide range of products. However in this
case, chemical reactions are initiated by heating. Varnish is cooked in
either open or enclosed gas fired kettles for periods of 4 to 16 hours at
temperatures of 93 to 340°C (200 to 650°F).
Varnish cooking emissions, largely in the form of volatile organic
compounds, depend on the cooking temperatures and times, the solvent used,
degree of tank enclosure and the type of air pollution controls used.
Emissions from varnish cooking range from 1 to 6 percent of the raw material.
To reduce organic compound emissions from the manufacture of paint and
varnish, control techniques include condensers and/or adsorbers on solvent
handling operations, and scrubbers and afterburners on cooking operations.
Afterburners can reduce volatile organic compounds by 99 percent. Emission
factors for paint and varnish are shown in Table 5.10-1.
5/83
Chemical Process Industry
5.10-1
-------
TABLE 5;10-1. UNCONTROLLED EMISSION FACTORS FOR PAINT AND
VARNISH MANUFACTURING3'
EMISSION FACTOR RATING: C
Particulate
Type of
product
Paintd
Varnish
Bodying oil
Oleoresinous
Alkyd
Acrylic
kg/Mg
pigment
10
-
-
-
—
Ib/ton
pigment
20
-
-
-
—
Nonmethane VOCC
kg/Mg
of product
15
20
75
80
10
Ib/ton
of product
30
40
150
160
20
References 2, 4-8.
Afterburners can reduce VOC emissions by 99% and
particulates by about 90%. A water spray and oil filter
system can reduce particulates by about 90%.
Q
Expressed as undefined organic compounds whose composition depends
upon the type of solvents used in the manfacture of paint and
varnish.
Reference 4. Particulate matter (0.5 - 1.0 %) is emitted from
pigment handling.
References for Section 5.10
1. Air Pollutant Emission Factors, APTD-0923, U. S. Environmental Protection
Agency, Research Triangle Park, NC, April 1970.
2. R. L. Stenburg, "Controlling Atmospheric Emissions from Paint and Varnish
Operations, Part I", Paint and Varnish Production, September 1959.
3. Private Communication between Resources Research, Inc., Reston, VA, and
National Paint, Varnish and Lacquer Association, Washington, DC.,
September 1969.
4. Unpublished engineering estimates based on plant visits in Washington,
DC, Resources Research, Inc., Reston, VA, October 1969.
5. Air Pollution Engineering Manual, Second Edition, AP-40, U. S.
Environmental Protection Agency, Research Triangle Park, NC, May 1973.
6. E, G. Lunche, et al., "Distribution Survey of Products Emitting Organic
Vapors in Los Angeles County", Chemical Engineering Progress,
53(8):371-376, August 1957.
5.10-2
EMISSION FACTORS
5/83
-------
7. Communication on emissions from paint and varnish operations between
Resources Research, Inc., Reston, VA, and G. Sallee, Midwest Research
Institute, Kansas City, MO, December 17, 1969.
8. Communication between Resources Research, Inc., Reston, VA, and Roger
Higgins, Benjamin Moore Paint Company, June 25, 1968.
5/83 Chemical Process Industry 5.10-3
-------
-------
5.11 PHOSPHORIC ACID
Phosphoric acid is produced by two principal methods, the wet
process and the thermal process. The wet process is employed when the
acid is to be used for fertilizer production. Thermal process phos-
phoric acid is of higher purity and is used in the manufacture of high
grade chemical and food products.
1 2
5.11.1 Process Description "
5.11.1.1 Wet Process Acid Production - In modern wet process phosphoric
acid plants, as shown in Figure 5.11-1, finely ground phosphate rock,
which contains 31 to 35.5 percent phosphorus pentoxide ^205), is
continuously fed into a reactor with sulfuric acid which decomposes the
phosphate rock. In order to ma"ke the strongest phosphoric acid possible
and to decrease later evaporation costs, 93 or 98 percent sulfuric acids
are normally used. Because the proper ratio of acid to rock in the
reactor must be maintained as closely as possible, precise automatic
process control equipment is employed in the regulation of these two
feed streams.
Gypsum crystals (CaSOij . 2^0) are precipitated by the phosphate
rock and sulfuric acid reaction. There is little market for the gypsum,
so it is handled as waste, filtered out of the acid and sent to settling
ponds. Approximately 0.7 acres of cooling and settling pond are required
for every ton of daily P205 production.
Considerable heat is generated in the reactor, which must be
removed. In older plants, this is done by blowing air over the hot
slurry surface. Modern plants use vacuum flash cooling of part of the
slurry, then sending it back into the reactor.
The reaction slurry is held in the reactor for periods of up to
eight hours, depending on the rock and reactor design, and is then sent
to be filtered. This produces a 32 percent acid solution, which gener-
ally needs concentrating for further use. Current practice is to
concentrate it in two or three vacuum evaporators to about 54 percent
P205.
5.11.1.2 Thermal Process Acid Production - Raw materials for the
production of phosphoric acid by the thermal process are elemental
(yellow) phosphorus, air and water. Thermal process phosphoric acid
manufacture, as shown in Figure 5.11—2, typically involves three steps.
First, the liquid elemental phosphorus is burned (oxidized) in a
combustion chamber at temperatures of 3000 to 5000°F (1650 - 2760°C) to
form phosphorus pentoxide. Then, the phosphorus pentoxide is hydrated
with dilute acid or water to produce phosphoric acid liquid and mist.
The final step is to remove the phosphoric acid mist from the gas
stream.
2/80 Chemical Process Industry
-------
QFiN
GROUND
PHOSPHATE-
ROCK
'TO SCRUBBER
HYDROFLU05IUCIC ACID
Figure 5.11-1. Flow diagram of wet process phosphoric acid plant.
AIR
STACK
EFFLUENT
(AIR + H3P04 MIST)
ACID TREATING PLANT
STACK EFFLUENT
(AIR + H S)
HYDROGEN SULFIDE,
SODIUM HYDROSJLFIDE,
OR SODIUM SULFIDE
PHOSPHORUS
COMBUSTION
CHAMBER
HYDRATOR-
ABSORBER COOLING WATER
iT^l PRODUCT
BURNING AND HYDRATION SECTION
BLOWER PUMP
ACID TREATING SECTION
(USED IN THE MANUFACTURE OF ACID
FOR FOOD AND SPECIAL USES)
Figure 5.11-2, Flow diagram of thermal process phosphoric acid plant.
5.1 1 -2
EMISSION FACTORS
2/80
-------
The reactions involved are:
Pi* + 5 02 •
+ 6 H20
Thermal process acid normally contains 75 to 85 percent phosphoric
acid (HsPOif). In efficient plants, about 99.9 percent of the phosphorus
burned is recovered as acid.
1-3
5.11.2 Emissions and Controls
5.11.2.1 Wet Process Emissions and Controls - Gaseous fluorides, mostly
silicon tetrafluoride and hydrogen fluoride, are the major emissions
from wet process acid. Phosphate rock contains 3.5 to 4.0 percent
fluorine, and the final distribution of this fluorine in wet process
acid manufacture varies widely. In general, part of the fluorine goes
with the gypsum, part with the phosphoric acid product, and the rest is
vaporized in the reactor or evaporator. The proportions and amounts
going with the gypsum and acid depend on the nature of the rock and
process conditions. Disposition of the volatilized fluorine depends on
the design and operation of the plant. Substantial amounts can pass off
into the air, unless effective scrubbers are used. Some of the fluorine
which is carried to the settling ponds with the gypsum will get into the
atmosphere, once the pond water is saturated with fluorides.
The reactor, where phosphate rock is decomposed by sulfuric acid,
is the main source of atmospheric contaminants. Fluoride emissions
accompany the air used to cool the reactor slurry. Vacuum flash cooling
has replaced the air cooling method to a large extent, since emissions
are minimized in the closed system.
Acid concentration by evaporation provides another source of
fluoride emissions. It has been estimated that 20 to 40 percent of the
fluorine originally present in the rock vaporizes in this operation.
Total particulate emissions directly from process equipment were
measured for one digester and for one filter. As much as 11 pounds of
particulates per ton of PaOs were produced by the digester, and approxi-
mately 0.2 pounds per ton of "^2^5 were released by the filter. Of this
particulate, 3 to 6 percent was fluorides.
Particulate emissions occurring from phosphate rock handling are
covered in Section 8.18.
5.11.2.2 Thermal Process Emissions and Controls - The principal
atmospheric emission from the thermal process is phosphoric acid mist
(HsPOit) contained in the gas stream from the hydrator. The particle
size of the acid mist ranges from 0.4 to 2.6 micrometers. It is not
uncommon for as much as half of the total phosphorus pentoxide to be
present as liquid phosphoric acid particles suspended in the gas stream.
2/80 Chemical Process Industry 5.11-3
-------
Economical operation of the process demands that this potential loss be
controlled, so all plants are equipped with some type of emission
control equipment.
Control equipment commonly used in thermal process phosphoric acid
plants includes venturi scrubbers, cyclonic separators with wire mesh
mist eliminators, fiber mist eliminators, high energy wire mesh contactors,
and electrostatic precipitators.
Table 5.11-1. EMISSION FACTORS FOR PHOSPHORIC
ACID PRODUCTION
EMISSION FACTOR RATING: B
Source Particulatesa Fluorineb
Ib/ton kg/MT Ib/ton kg/MT
Wet Process
Reactor, uncontrolled - - 56.4 28.2
Gypsum settling and
cooling ponds0 - - 1.12 0.56
Condenser, uncontrolled - - 61.2 30.6
Typical controlled
emissions
Thermal Process *
Packed tower (95.5%)
Venturi scrubber (97.5%)
Glass fiber mist
eliminator
(96.0 - 99.9%)
Wire mesh mist eliminator
(95.0%)
High pressure drop mist
eliminator (99.9%)
Electrostatic precipitator
(98 - 99%)
-
2.14
2.53
0.69
5.46
0.11
1.66
,02-. 07 .01-. 04
1.07
1.27
0.35
2.73
0.06
0.83
£i
Acid mist particulates (0.4 - 2.6 ym).
References 1 and 3. Pounds of fluorine (as gaseous fluorides) per
ton of PaOs produced. Based on a material balance of fluorine from
phosphate rock of 3.9% fluorine and 33% P205.
Approximately 0.7 acres (0.3 hectares) of cooling and settling pond are
required to produce 1 ton of P20s daily. Emissions in terms of pond
,area would be 1.60 Ib/acre per day (1.79 kg/hectare per day).
Reference 5.
g
Reference 3. Pounds of particulate per ton of P205.
Numbers in parentheses indicate the control efficiency associated with
each device.
5.11-4 EMISSION FACTORS 2/80
-------
References for Section 5.11
1. Atmospheric Emissions from Wet Process Phosphoric Acid
Manufacture, AP-57, National Air Pollution Control Administration,
Raleigh, NC, April 1970.
2. Atmospheric Emissions from Thermal Process Phosphoric Acid
Manuf ac ture, AP-48, National Air Pollution Control Administration,
Durham, NC, October 1968.
3. Control Techniques for Fluoride Emissions, Unpublished, U.S. Public
Health Service, Research Triangle Park, NC, September 1970.
4. W.R. King, "Fluorine Air Pollution from Wet Process Phosphoric Acid
Plants - Water Ponds", Doctoral Thesis, Supported by EPA Research
Grant No. R-800950, North Carolina State University, Raleigh, NC,
1974.
5. Final GuidelineLDocument: Control of Fluoride Emissions from
Existing Phosphate Fertilizer Plants, EPA-450/2-77-005, U.S.
Environmental Protection Agency, Research Triangle Park, NC, March
1977.
2/80 Chemical Process Imluslrv 5.11-5
-------
-------
5.12 PHTHALIC ANHYDRIDE
5.12.1 General1
Phthalic anhydride (PAN) production in the United States in 1972 wa§ 0.9 billion pounds per year;
this total is estimated to increase to 2.2 billion pounds per year by 1985. Of the current production, 50
percent is used for plasticizers, 25 percent for alkyd resins, 20 percent for unsaturated polyester resins,
and 5 percent for miscellaneous and exports. PAN is produced by catalytic oxidation of either ortho-
xylene or naphthalene. Since naphthalene is a higher priced feedstock and has a lower feed utilization
(about 1.0 Ib PAN/lb o-xylene versus 0.97 Ib PAN/lb naphthalene), future production growth is pre-
dicted to utilize o-xylene. Because emission factors are intended for future as well as present applica-
tion, this report will focus mainly on PAN production utilizing o-xylene as the main feedstock.
The processes for producing PAN by o-xylene or naphthalene are the same except for reactors,
catalyst handling, and recovery facilities required for fluid bed reactors.
In PAN production using o-xylene as the basic feedstock, filtered air is preheated, compressed, and
mixed with vaporized o-xylene and fed into the fixed-bed tubular reactors. The reactors contain the
catalyst, vanadium pentoxide, and are operated at 650 to 725° F (340 to 385° C). Small amounts of
sulfur dioxide are added to the reactor feed to maintain catalyst activity. Exothermic heat is removed
by a molten salt bath circulated around the reactor tubes and transferred to a steam generation system.
Naphthalene-based feedstock is made up of vaporized naphthalene and compressed air. It is
transferred to the fluidized bed reactor and oxidized in the presence of a catalyst, vanadium pent-
oxide, at 650 to 725° F (340 to 385° C). Cooling tubes located in the catalyst bed remove the exothermic
heat which is used to produce high-pressure steam. The reactor effluent consists of PAN vapors, en-
trained catalyst, and various by-products and non-reactant gas. The catalyst is removed by filtering and
returned to the reactor.
The chemical reactions for air oxidation of o-xylene and naphthalene are as follows.
302
3H20
o-xylene + oxygen
phthalic water
anhydride
naphthalene
+ VA 02
oxygen
0
phthalic
anhydride
5/83
Chemical Process Industry
ZH20 + 2C02
water + carbon
dioxide
-------
The reactor effluent containing crude PAN plus products from side reactions and excess oxygen passes
to a series of switch condensers where the crude PAN cools and crystallizes. The condensers are alter-
nately cooled and then heated, allowing PAN crystals to form and then melt from the condenser tube
fins.
The crude liquid is transferred to a pretreatment section in which phthalic acid is dehydrated to
anhydride. Water, maleic anhydride, and benzole acid are partially evaporated. The liquid then goes
to a vacuum distillation section where pure PAN (99.8 wt. percent pure) is recovered. The product can
be stored and shipped either as a liquid or a solid (in which case it is dried, flaked, and packaged in
multi-wall paper bags). Tanks for holding liquid PAN are kept at 300° F (150° C) and blanketed with
dry nitrogen to prevent the entry of oxygen (fire) or water vapor (hydrolysis to phthalic acid).
Maleic anhydride is currently the only by-product being recovered.
Figures 1 and 2 show the process flow for air oxidation of o-xylene and naphthalene, respectively.
5.12.2 Emissions and Controls1
Emissions from o-xylene and naphthalene storage are small and presently are not controlled.
The major contributor of emissions is the reactor and condenser effluent which is vented from the
condenser unit. Particulate, sulfur oxides (for o-xylene-based production), and carbon monoxide
make up the emissions, with carbon monoxide comprising over half the total. The most efficient (96
percent) system of control is the combined usage of a water scrubber and thermal incinerator. A
thermal incinerator alone is approximately 95 percent efficient in combustion of pollutants for o-
xylene-based production, and 80 percent efficient for naphthalene-based production. Thermal incin-
erators with steam generation show the same efficiencies as thermal incinerators alone. Scrubbers
have a 99 percent efficiency in collecting particulates, but are practically ineffective in reducing car-
bon monoxide emissions. In naphthalene-based production, cyclones can be used to control catalyst
dust emissions with 90 to 98 percent efficiency.
Pretreatment and distillation emissions—particulates and hydrocarbons—are normally processed
through the water scrubber and/or incinerator used for the main process stream (reactor and con-
denser) or scrubbers alone, with the same efficiency percentages applying.
Product storage in the liquid phase results in small amounts of gaseous emissions. These gas
streams can either be sent to the main process vent gas control devices or first processed through
sublimation boxes or devices used to recover escaped PAN. Flaking and bagging emissions are negli-
gible, but can be sent to a cyclone for recovery of PAN dust. Exhaust from the cyclone presents no
problem.
Table 5.12-1 gives emission factors for controlled and uncontrolled emissions from the production
5.12-2 EMISSION FACTORS 5/83
-------
(Jl
00
OJ
PARTICULATE
SULFUR OXIDE
CARBON MONOXIDE
AIR
n
sr
SALT COOLER AND
STEAM GENERATION
HOT AND COOL
CIRCULATING
OIL STREAMS/
WATER AND STEAM
^BOILER FEED
WATER
m
i
i j
i
SWITCH
CONDENSERS
^^^
CRUDE
PRODUCT
STORAGE
o
o
ffi
oo
oo
HH
9
g-
PARTICULATE
PARTICULATE
HYDROCARBON
PRETREAT
MENT
STEAM'
PARTICULATE
STRIPPER
COLUMN
REFINING
COLUMN
•STEAM
PHTHALIC
'ANHYDRIDE
PARTICULATE
HYDROCARBON
to
Figure 5.12-1. Flow diagram for phthalic anhydride using o-xylene as basic feedstock.^
-------
en
M
00
UJ
HOT AND COOL CIRCULATING
OIL STREAMS OR
WATER AND STEAM
ttu
PARTICULATE
CARBON MONOXIDE
SWITCH
CONDENSERS
NAPHTHALENE
>
FLUID
BED
REACTOR
CATAIIYST
1 RECYCLE
1
STEAM
DRUM
^ '
BO
HIGH
PRESSURE
STEAM
AIR.
BOILER FEED
WATER
COMPRESSOR
. PARTICULATE
HYDROCARBON
COOLING
PRODUCT
STILL
PRODUCT
STORAGE
(MOLTEN)
FLAKING AND
BAGGING
OPERATION
(OPTIONAL)
PARTICULATE
*-PHTHALIC ANHYDRIDE
PARTICULATE
HYDROCARBON
Figure 5.12-2. Flow diagram for phthalic anhydride using naphthalene as basic feedstock.'
-------
TABLE 5.12-1. EMISSION FACTORS FOR PHTHALIC ANHYDRIDE
a
EMISSION FACTOR RATING: B
Particulate SO
Process
Oxidation of o-xylene
Main process stream
Uncontrolled
W/scrubber and thermal
incinerator
W/ thermal incinerator
W/inctnerator with
Pre treatment
Uncontrolled
W/scrubber and thermal
incinerator
W/ thermal incinerator
Distillation
Uncontrolled
W/scrubber and thermal
incinerator
W/ thermal incinerator
Oxidation of naphthalene0
Main process stream
Uncontrolled
W/ thermal incinerator
W/ scrubber
Pretreatment
Uncontrolled
W/ thermal incinerator
W/sc rubber
Distillation
Uncontrol led
W/ thermal incinerator
W/scrubber
kg/Mg
69e
3
4
A
H
6.48
0.3
0.4
45e
2
2
-t Ic
28llk
6
0.3
2.5^
0.5
<0.1
191
4
0.2
Ib/ton
138e
6
7
13*
0.5
0.7
89e
4
4
•1 lr
561>k
11
0.6
5J
1
<0.1
381
8
0.4
kg/Mg
f
4.7f
4.7
4.7
4.7
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Ib/ton
9.4f
9.4
9.4
Q A
3 * H
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Nontne thane
vocb
CO
kg/Mg Ib/ton kg/Mg
0
0
0
Q
0
0
0
1.2e'h
<0.1
<0.1
0
0
0
0
0
0
5h,i
1
<0.1
0
0
0
Q
0
0
0
2.4e'h
< 0.1
0.1
0
0
0
0
0
0
10*1'1
2
0.1
151
6
8
0
0
0
0
0
0
50
10
50
0
0
0
0
0
0
Ib/ton
301
12
15
0
0
0
0
0
0
100
20
100
0
0
0
0
0
0
^Reference 1. Factors are in kg of pollutant/Mg (Ib/ton) of phthalic anhydride produced.
Emissions contain no methane.
cControl devices listed are those currently being used by phthalic anhydride plants.
Main process stream includes reactor and multiple switch condensers as vented through condenser unit.
eConsists of phthalic anhydride, maleic anhydride, benzole acid.
Value shorn corresponds to relatively fresh catalyst, which can change with catalyst age. Can be 9.5 - 13 kg/Mg
(19 - 25 Ib/ton) for aged catalyst.
^Consists of phthalic anhydride and maleic anhydride.
Normally a vapor, but can be present as a particulate at lov temperature.
Consists of phthalic anhydride, maleic anhydride, naphthaqulnone.
J
Particulate is phthalic anhydride.
i.
Does not include catalyst dust, controlled by cyclones with efficiency of 90 - 98X.
Reference for Section 5.12
1. Engineering and Cost Study of Air Pollution Control for the
Petrochemical Industry, Vol. 7; Phthalic Anhydride Manufacture
from Ortho-xylene, EPA-450/3-73-006g, U. S. Environmental Protection
Agency, Research Triangle Park, NC, July 1975.
5/83
Chemical Process Industry
5.12-5
-------
-------
5.13 PLASTICS
5.13.1 Process Description1
The manufacture of most resins or plastics begins with the polymerization or linking of the basic compound
(monomer), usually a gas or liquid, into high molecular weight noncrystalline solids. The manufacture of the
basic monomer is not considered part of the plastics industry and is usually accomplished at a chemical or
petroleum plant.
The manufacture of most plastics involves an enclosed reaction or polymerization step, a drying step, and a
final treating and forming step. These plastics are polymerized or otherwise combined in completely enclosed
stainless steel or glass-lined vessels. Treatment of the resin after polmerization varies with the proposed use.
Resins for moldings are dried and crushed or ground into molding powder. Resins such as the alkyd resins that are
to be used for protective coatings are normally transferred to an agitated thinning tank, where they are thinned
with some type of solvent and then stored in large steel tanks equipped with water-cooled condensers to prevent
loss of solvent to the atmosphere. Still other resins are stored in latex form as they come from the kettle.
5.13.2 Emissions and Controls1
The major sources of air contamination in plastics manufacturing are the emissions of raw materials or
monomers, emissions of solvents or other volatile liquids during the reaction, emissions of sublimed solids such as
phthalic anhydride in alkyd production, and emissions of solvents during storage and handling of thinned resins.
Emission factors for the manufacture of plastics are shown in Table 5.13-1.
Table 5.13-1. EMISSION FACTORS FOR PLASTICS
MANUFACTURING WITHOUT CONTROLS8
EMISSION FACTOR RATING: E
Type of plastic
Polyvinyl chloride
Polypropylene
General
Particulate
Ib/ton
35b
3
5 to 10
kg/MT
17.5b
1.5
2.5 to 5
Gases
Ib/ton
17C
0.7d
—
kg/MT
8.5C
0.35d
—
References 2 and 3.
bUsually controlled with a fabric filter efficiency of 98 to 99
percent.
cAs vinyl chloride.
dAs propylene.
Much of the control equipment used in this industry is a basic part of the system and serves to recover a
reactant or product. These controls include floating roof tanks or vapor recovery systems on volatile material,
storage units, vapor recovery systems (adsorption or condensers), purge lines that vent to a flare system, and
recovery systems on vacuum exhaust lines.
2/72
Chemical Process Industry
5.13-1
-------
References for Section 5.13
1. Air Pollutant Emission Factors. Final Report. Resources Research, Inc. Reston, Va. Prepared for National
Air Pollution Control Administration, Durham, N.C., under Contract Number CPA-22-69-119. April 1970,
2. Unpublished data from industrial questionnaire. U.S. DHEW, PHS, National Air Pollution Control
Administration, Division of Air Quality and Emissions Data. Durham, N.C. 1969.
3. Private Communication between Resources Research, Incorporated, and Maryland State Department of
Health, Baltimore, Md. November 1969.
5.13-2 EMISSION FACTORS 2/72
-------
5.14 PRINTING INK
5.14.1 Process Description1
There are four major classes of printing ink: letterpress and lithographic inks, commonly called oil or paste
inks; and flexographic and rotogravure inks, which are referred to as solvent inks. These inks vary considerably in
physical appearance, composition, method of application, and drying mechanism. Flexographic and rotogravure
inks have many elements in common with the paste inks but differ in that they are of very low viscosity, and they
almost always dry by evaporation of highly volatile solvents,2
There are three general processes in the manufacture of printing inks: (1) cooking the vehicle and adding dyes,
(2) grinding of a pigment into the vehicle using a roller mill, and (3) replacing water in the wet pigment pulp by
an ink vehicle (commonly known as the flushing process).3 The ink "varnish" or vehicle is generally cooked in
large kettles at 200° to 600°F (93° to 31S°C) for an average of 8 to 12 hours in much the same way that regular
varnish is made. Mixing of the pigment and vehicle is done in dough mixers or in large agitated tanks. Grinding is
most often carried out in three-roller or five-roller horizontal or vertical mills.
5.14.2 Emissions and Controls1-4
Varnish or vehicle preparation by heating is by far the largest source of ink manufacturing emissions. Cooling
the varnish components — resins, drying oils, petroleum oils, and solvents - produces odorous emissions. At
about 350°F (175°C) the products begin to decompose, resulting in the emission of decomposition products
from the cooking vessel. Emissions continue throughout the cooking process with the maximum rate of emissions
occuring just after the maximum temperature has been reached. Emissions from the cooking phase can be
reduced by more than 90 percent with the use of scrubbers or condensers followed by afterburners.4'5
Compounds emitted from the cooking of oleoresinous varnish (resin plus varnish) include water vapor, fatty
acids, glycerine, acrolein, phenols, aldehydes, ketones, terpene oils, terpenes, and carbon dioxide. Emissions of
thinning solvents used in flexographic and rotogravure inks may also occur.
The quantity, composition, and rate of emissions from ink manufacturing depend upon the cooking
temperature and time, the ingredients, the method of introducing additives, the degree of stirring, and the extent
of air or inert gas blowing. Particulate emissions resulting from the addition of pigments to the vehicle are
affected by the type of pigment and its particle size. Emission factors for the manufacture of printing ink are
presented in Table 5.14-1.
5/83
Chemical Process Industry
5.14-1
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TABLE 5.14-1. EMISSION FACTORS FOR PRINTING INK
MANUFACTURING3
EMISSION FACTOR RATING: E
Nonme thane
volatile organic compounds
Type of process
Vehicle cooking
General
Oils
Oleoresinous
Alkyds
Pigment mixing
kg/Mg
of product
60
20
75
80
NA
Ib/ton
of product
120
40
150
160
NA
Particulates
kg/Mg
of pigment
NA
NA
NA
NA
1
Ib/ton
of pigment
NA
NA
NA
NA
2
Based on data from Section 5.10, Paint and Varnish. NA = not applicable.
The nonmethane VOC emissions are a mix of volatilized vehicle components,
cooking decomposition products and ink solvent.
References for Section 5.14
1. Air Pollutant Emission Factors, APTD-0923, U. S. Environmental
Protection Agency, Research Triangle Park, NC, April 1970.
2. R. N. Shreve, Chemical Process Industries, 3rd Ed., New York, McGraw
Hill Book Co., 1967.
3. L. M. Larsen, Industrial Printing Ijiks, New York, Reinhold Publishing
Company, 1962.
4. Air Pollution Engineering Manual, 2nd Edition, AP-40, U. S. Environmental
Protection Agency, Research Triangle Park, NC, May 1973.
5. Private communication with Ink Division of Interchemical Corporation,
Cincinnati, Ohio, November 10, 1969.
5.14-2
EMISSION FACTORS
5/83
-------
5.15 SOAP AND DETERGENTS
5.15.1 Soap Manufacture
Process Description * - Soap may be manufactured by either a batch or
continuous process, using either the alkaline saponification of natural fats
and oils or the direct saponification of fatty acids. The kettle, or full
boiled, process is a batch process of several steps in either a single kettle
or a series of kettles. Fats and oils are saponified by live steam boiling in
a caustic solution, followed by "graining", or precipitating, the soft curds
of soap out of the aqueous lye solution by adding sodium chloride (salt). The
soap solution then is washed to remove glycerine and color body impurities, to
leave the "neat" soap to form during a settling period. Continuous alkaline
saponification of natural fats and oils follows the same steps as batch
processing, but it eliminates the need for a lengthy process time. Direct
saponification of fatty acids is also accomplished in continuous processes.
Fatty acids obtained by continuous hydrolysis usually are continuously
neutralized with caustic soda in a high speed mixer/neutralizer to form soap.
All soap is finished for consumer use in such various forms as liquid,
powder, granule, chip, flake or bar.
Emissions and Controls - The main atmospheric pollution problem in the
manufacture of soap is odor. Vent lines, vacuum exhausts, product and raw
material storage, and waste streams are all potential odor sources. Control
of these odors may be achieved by scrubbing all exhaust fumes and, if
necessary, incinerating the remaining compounds. Odors emanating from the
spray drier may be controlled by scrubbing with an acid solution.
Blending, mixing, drying, packaging and other physical operations are
subject to dust emissions. The production of soap powder by spray drying is
the largest single source of dust in the manufacture of soap. Dust emissions
from finishing operations other than spray drying can be controlled by dry
filters and baghouses. The large size of the particulates in soap drying
means that high efficiency cyclones installed in series can be satisfactory in
controlling emissions.
5.15.2 Detergent Manufacture
1 7—8
Process Description ' - The manufacture of spray dried detergent has three
main processing steps, slurry preparation, spray drying and granule handling.
Figure 5.15-1 illustrates the various operations. Detergent slurry is produced
by blending liquid surfactant with powdered and liquid materials (builders and
other additives) in a closed mixing tank called a crutcher. Liquid surfactant
used in making the detergent slurry is produced by the sulfonation or sulfation
by sulfuric acid of a linear alkylate or a fatty acid, which is then neutralized
with caustic solution (NaOH). The blended slurry is held in a surge vessel
for continuous pumping to the spray dryer. The slurry is sprayed at high
pressure through nozzles into a vertical drying tower having a stream of hot
air of from 315° to 400"C (600° to 750°F). Most towers designed for detergent
production are countercurrent, with slurry introduced at the top and heated
5/83
Chemical Process Industry
5.15-1
-------
ho
RECEIVING,
STORAGE,
TRANSFER
SLURRY PREPARATION
SPRAY DRYING
BLENDING
AND
PACKING
M
C/5
Cfl
H
O
H
O
DRY DUST
COLLECTORS
SURFACTANTS:
SLURRY
ALCOHOLS
ETHOXYLATES
BUILDERS:
PHOSPHATES
SILICATES
CARBONATES
WATER
ADDITIVES:
PERFUMES
DYES
ANTICAKING AGENTS
MIXER
CRUTCHER
i
SURGE
VESSEL
TO CRUTCHER
AND POST-
ADDITION MIXER
CONTROL
DEVICE
HIGH
PRESSURE
PUMP
HOT AIR
SPRAY
DRYING
TOWER
|FURNACE
[CONVEYOR
DRY DUST
COLLECTORS
POST-
ADDITION
MIXER
GRANULE
STORAGE
PACKAGING
EQUIPMENT
FINISHED
DETERGENTS TO
WAREHOUSE
Figure 5.15-1. Manufacture of spray dried detergents.
-------
air introduced at the bottom. A few towers are concurrent and have hoth hot
air and slurry introduced at the top. The detergent granules are mechanically
or air conveyed from the tower to a mixer to incorporate additional dry or
liquid ingredients and finally sent to packaging and storage.
•J Q
Emissions and Controls - In the batching and mixing of fine dry ingredients
to form slurry, dust emissions are generated at scale hoppers, mixers and the
crutcher. Baghouses and/or fabric filters are used not only to reduce or to
eliminate the dust emissions but to recover raw materials. The spray drying
operation is the major source of particulate emissions from detergent manu-
facturing. Particulate emissions from spray drying operations are shown in
Table 5.15-1. There is also a minor source of volatile organlcs when the
product being sprayed contains organic materials with low vapor pressures.
These vaporized organic materials condense in the tower exhaust air stream
into droplets or particles. Dry cyclones and cyclonic impingement scrubbers
are the primary collection equipment employed to capture the detergent dust in
the spray dryer exhaust for return to process. Dry cyclones are used in
parallel or in series, to collect particulate (detergent dust) and to recycle
the dry product back to the crutcher. Cyclonic impinged scrubbers are used in
parallel to collect the particulate in a scrubbing slurry which is recycled
back to the crutcher. Secondary collection equipment is used to collect the
fine particulates that have escaped from the primary devices. Cyclonic
impingement scrubbers are often followed by mist eliminators, and dry cyclones
are followed by fabric filters or scrubber/electrostatic precipitator units.
Conveying, mixing and packaging of detergent granules can cause dust emissions.
Usually baghouses and/or fabric filters provide the best control.
TABLE 5.15-1. PARTICULATE EMISSION FACTORS FOR SPRAY DRYING
DETERGENTS3
EMISSION FACTOR RATING: B
Particulate Emissions
Control
Device
Uncontrolled
b
Cyclone
Cyclone
w/Spray chamber
w/Packed scrubber
w/Venturi scrubber
Overall
Efficiency, %
_
85
92
95
97
kg/Mg of
product
45
7
3.5
2.5
1.5
Ib/ton of
product
90
14
7
5
3
a
References 2-6. Emissions data for volatile organic compounds has
.not been reported in the literature.
Some type of primary collector, such as a cyclone, is considered
an integral part of the spray drying system.
5/83 Chemical Process Industry 5.15-3
-------
References for Section 5.15
1. Air _Pol_lutant JEmlssion Factors. APTD-0923, U. S. Environmental Protection
Agency, Research Triangle Park, NC, April 1970.
2. A. H. Phelps, "Air Pollution Aspects of Soap and Detergent Manufacture",
Journal ^f the Air Pollution Control Association, 17_(8): 505-507, August
1967.
3. R. N. Shreve, Chemical Process Industries, Third Edition, New York,
McGraw-Hill Book Company, 1967.
4. G. P. Larsen, et al^, "Evaluating Sources of Air Pollution", Industrial
and Engineering Chemistry, 45_: 1070-1074, May 1953.
5. P. Y. McCormick, et al^, "Gas-solid Systems", Chemical Engineer's Handbook,
J. H. Perry (ed.), New York, McGraw-Hill Book Company, 1963.
6. Communication with Maryland State Department of Health, Baltimore, MD,
November 1969.
7. J. A. Danielson, Air Pollution Engineering Manual, AP-40, U. S.
Environmental Protection Agency, May 1973.
8. Source Category Survey; Detergent Industry, EPA-450/3-80-030, U. S.
Environmental Protection Agency, Research Triangle Park, NC, June 1980.
5.15-4 EMISSION FACTORS 5/83
-------
5.16 SODIUM CARBONATE
5.16.1 General1'2
Processes used to produce sodium carbonate (Na2C03), or soda ash, are
classified as either natural or synthetic. Natural processes recover sodium
carbonate from naturally occurring deposits of trona ore (sodium sesquicar-
bonate) or from brine containing sodium sesquicarbonate and sodium carbonate.
The synthetic process (Solvay process) produces sodium carbonate by reacting
ammoniated sodium chloride with carbon dioxide. For about a century, almost
all sodium carbonate production was by the Solvay process. However, since
the mid-1960s, Solvay process production has declined substantially, and
natural production has grown by 500 percent. Only one plant in the U.S. now
uses the Solvay process. Available data on emissions from the Solvay process
are also presented, but because the natural processes are more prevalent in
this country, this discussion will focus on emissions from the natural
processes.
Three different natural processes are currently in use. These are the
monohydrate, sesquicarbonate and direct carbonation processes. The sesqui-
carbonate process was the first natural process used, but it is used at only
one plant and is not expected to be used at future plants. And since data
on uncontrolled emissions from this process are not available, emissions
from the sesquicarbonate process are not discussed. The monohydrate and
direct carbonation processes and emissions are described below, the differ-
ences in these two processes being in raw materials processing.
In the monohydrate process, sodium carbonate is produced from trona
ore, which consists of 86 to 95 percent sodium sesquicarbonate
(Na2C03 • NaHC03 • 2H20), 5 to 12 percent gangues (clays and other insoluble
impurities) and water. The mined trona ore is crushed and screened and
calcined to drive off carbon dioxide and water, forming crude sodium carbon-
ate. Rotary gas fired calciners currently are most commonly used, but the
newest plants use coal fired calciners, and future plants are also likely to
use coal fired calciners because of the economics and the limited avail-
ability of natural gas.
The crude sodium carbonate is dissolved and separated from the insoluble
impurities. Sodium carbonate monohydrate (Na£C03 • H20) is crystallized
from the purified liquid by multiple effect evaporators. The sodium carbon-
ate monohydrate is then dried, to remove the free and bound water and to
produce the final product. Rotary steam tube, fluid bed steam tube, and
rotary gas fired dryers are used, with steam tube dryers more likely in
future plants.
In the direct carbonation process, sodium carbonate is produced from
brine containing sodium sesquicarbonate, sodium carbonate and other salts.
The brine is prepared by pumping liquor into salt deposits, where the salts
8/82
Chemical Process Industry
5;16-1
-------
are dissolved into a liquor. The recovered brine is carbonated by contact
with carbon dioxide to convert all of the sodium carbonate that is present
to sodium bicarbonate. The sodium bicarbonate is then recovered from the
brine by vacuum crystallizers. The crystal slurry is filtered, and the
crystals enter steam heated predryers to evaporate some of the moisture.
The partially dried sodium bicarbonate goes to a steam heated calciner where
carbon dioxide and the remaining water are driven off, forming impure sodium
carbonate. The carbon dioxide evolved is recycled to the brine carbonators.
The impure sodium carbonate is bleached with sodium nitrate in a gas fired
rotary bleacher to remove discoloring impurities. The bleached sodium
carbonate is then dissolved and recrystallized. The resulting crystals of
sodium carbonate monohydrate are dried, as in the monohydrate process.
In the Solvay process, ammonia, calcium carbonate (limestone), coal and
sodium chloride (brine) are the basic raw materials. The brine is purified
in a series of reactors and clarifiers by precipitating the magnesium and
calcium ions with soda ash and sodium hydroxide. Sodium bicarbonate is
formed by carbonating a solution of ammonia and purified brine which is fed
to either steam or gas rotary dryers where it is converted (calcined) to
sodium carbonate.
5.16.2 Emissions and Controls
The principal emission points in the monohydrate and direct carbonation
processes are shown in Figures 5.16-1 and 5.16-2. The major emission sources
in the monohydrate process are calciners and dryers, and the major sources
in the direct carbonation process are bleachers, dryers and predryers.
Emission factors for the emission sources are presented in Table 5.16-1, and
emission factors for the Solvay process are presented in Table 5.16-2.
In addition to the major emission points, emissions may also arise from
crushing and dissolving operations, elevators, conveyor transfer points,
product loading and storage piles. Emissions from these sources have not
been quantified.
Particulate matter is the only pollutant of concern from sodium carbon-
ate plants. Emissions of sulfur dioxide (S02) arise from calciners fired
with coal, but reaction of the evolved S02 with the sodium carbonate in the
calciner keeps SC>2 emissions low. Small amounts of volatile organic com-
pounds (VOC) may also be emitted from calciners, possibly from oil shale
associated with the trona ore, but these emissions have not been quantified.
The particulate matter emission rates from calciners, dryers, predryers
and bleachers are affected by the gas velocity through the unit and by the
particle size distribution of the feed material. The latter affects the
emission rate because small particles are more easily entrained in a moving
stream of gas than are large particles. Gas velocity through the unit
affects the degree of turbulence and agitation. As the gas velocity
increases, so does the rate of increase in total particulate matter emis-
sions. Thus, coal fired calciners may have higher particulate emission
factors than gas fired calciners because they have higher gas flow rates.
The additional particulate emissions contributed by the coal fly ash repre-
sent less than one percent of total particulate emissions, and the emission
5.16-2 EMISSION FACTORS
8/82
-------
00
KJ
H-
O
o
O
(T>
cn
en
H
3
^
(n
rt
Figure 5.16-1. Sodium carbonate production by monohydrate process.
I
OJ
Figure 5.16-2. Sodium carbonate production by direct carbonation process,
-------
TABLE 5.16-1. UNCONTROLLED EMISSION FACTORS FOR NATURAL PROCESS
SODIUM CARBONATE PLANTS3
EMISSION FACTOR RATING:
B
Source
Particulate emissions
kg/Mg Ib/ton
Gas fired calciner
Coal fired calciner
Rotary steam tube dryer°
Fluid bed steam tube dryer
Rotary steam heater predryer
Rotary gas fired bleacher
184.0
195.0
33.0
73.0
1.0
155.0
368.0
390.0
67.0
146.0
3.1
311.0
References 3-5. Values are averages of 2 - 3 test runs.
Factor is in kg/Mg (Ib/ton) of ore fed to calciner. Includes particulate
emissions from coal fly ash. These represent < 1% of the total emissions.
Emissions of S02 from the coal are roughly 0.0007 kg/Mg (0.014 Ib/ton) of
ore feed.
.Factor is in kg/Mg (Ib/ton) of dry product from dryer.
Factor is in kg/Mg (Ib/ton) of dry NaHCOs feed.
Factor is in kg/Mg (Ib/ton) of dry feed to bleacher.
TABLE 5.16-2.
UNCONTROLLED EMISSION FACTORS FOR A SYNTHETIC
SODA ASH (SOLVAY) PLANTa
EMISSION FACTOR RATING: D
Emissions
Ammonia losses
Particulate
kg/Mg
2
25
Ib/ton
4
50
Reference 6.
""Calculated by subtracting measured ammonia effluent discharges from ammonia
^purchases.
"Maximum uncontrolled emissions, from New York State process certificates to
operate. Does not include emissions from fugitive or external combustion
sources.
5.16-4
EMISSION FACTORS
8/82
-------
factor for coal fired calciners is about 6 percent higher than that for gas
fired calciners. Fluid bed steam tube dryers have higher gas flow rates and
particulate emission factors than do rotary steam tube dryers. No data on
uncontrolled particulate emissions from gas fired dryers are available, but
these dryers also have higher gas flow rates than do rotary steam tube
dryers and would probably have higher particulate emission factors.
The particulate emission factors presented in Table 5.16-1 represent
emissions measured at the inlet to the control devices. However, even in
the absence of air pollution regulations requiring emission control, these
emissions should be controlled to some degree to prevent excessive loss of
product. Because the level of control needed for product recovery is
difficult to define, the emission factors do not account for this recovery.
Cyclones in series with electrostatic precipitators (ESP) are most
commonly used to control particulate emissions from calciners and bleachers.
Venturi scrubbers are also used, but they are not as effective. Cyclone/ESP
combinations have achieved removal efficiencies ranging from 99.5 to 99.96
percent for new coal fired calciners, and 99.99 percent for bleachers. Com-
parable efficiencies should be possible for new gas fired calciners. Venturi
scrubbers are most commonly used to control emissions from dryers and pre-
dryers, because of the high moisture content of the exit gas. Cyclones are
used in series with the scrubbers for predryers and fluid bed steam tube
dryers. Removal efficiencies averaging 99.88 percent have been achieved for
venturi scrubbers on rotary steam tube dryers at a pressure drop of 6.2 kPa
(25 inches water), and acceptable collection efficiences may be achieved
with lower pressure drops. Efficiencies of 99.9 percent have been achieved
for a cyclone/venturi scrubber on a fluid bed steam tube dryer at a pressure
drop of 9.5 kPa (38 inches water). Efficiencies over 98 percent have been
achieved for a cyclone/venturi scrubber on a predryer.
Fugitive emissions originating from limestone handling/processing oper-
ations, product drying operations and dry solids handling (conveyance and
bulk loading) are a significant source of emissions from the manufacture of
soda ash by the Solvay process. These fugitive emissions have not been
quantified. Ammonia losses also occur because of leaks at pipe fittings,
gasket flanges, pump packing glands, discharges of absorber exhaust, and
exposed bicarbonate cake on filter wheels and on feed floor prior to
calcifying.
References for Section 5.16
1. Sodium Carbonate Industry - Background Information for Proposed
Standards, EPA-450/3-80-029a, U. S. Environmental Protection Agency,
Research Triangle Park, NC, August 1980.
2. Air Pollutant Emission Factors, Final Report, HEW Contract Number
CPA-22-69-119, Resources Research, Inc., Reston, VA, April 1970.
3. SodjLum Carbonate Manufacturing Plant, EPA-79-SOD-1, U. S. Environ-
mental Protection Agency, Research Triangle Park, NC, August 1979.
8/82
Chemical Process Industry
5.16-5
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4. Sodium Carbonate Manufacturing Plant, EPA-79-SOD-2, U. S. Environ-
mental Protection Agency, Research Triangle Park, NC, March 1980.
5. Particulate Emissions from the Kerr-McGee Chemical Corporation Sodium
Carbonate Plant, EPA-79-SOD-3, U. S. Environmental Protection Agency,
Research Triangle Park, NC, March 1980.
6. Written communication from W. S. Turetsky, Allied chemical Company,
Morristown, NJ, to Frank Noonan, U.S. Environmental Protection Agency,
Research Triangle Park, NC, June 17, 1982.
5.16-6 EMISSION FACTORS 8/82
-------
5.17 SULFURIC ACID
5.17.1 General
All sulfuric acid is made by either the lead chamber process
or the contact process. Because the contact process accounts for
more than 97 percent of the total sulfuric acid production in the
United States, it is the only process discussed in this Section.
Contact plants are generally classified according to the raw materials
charged to them - (1) elemental sulfur burning, (2) spent acid and
hydrogen sulfide burning, and (3) sulfide ores and smelter gas
burning. The contributions from these plants to the total acid
production are 68, 18.5 and 13.5 percent respectively.
All contact processes incorporate three basic operations, each
of which corresponds to a distinct chemical reaction. First, the
sulfur in the feedstock is burned to sulfur dioxide:
S
Sulfur
02 —
Oxygen
S02
Sulfur
dioxide
(1)
Then, the sulfur dioxide is catalytically oxidized to sulfur trioxide:
(2)
2S02 H
Sulfur
dioxide
02 -
Oxygen
2S03
Sulfur
trioxide
Finally, the sulfur trioxide is absorbed in a strong aqueous solution
of sulfuric acid:
S03 +
Sulfur
trioxide
H20 —
Water
1.2
H2S04
Sulfuric
acid
(3)
Elemental Sulfur Burning Plants"'" - Elemental sulfur, such as
Frasch process sulfur from oil refineries, is melted, settled or
filtered to remove ash and is fed into a combustion chamber. The
sulfur is burned in clean air that has been dried by scrubbing with
93 - 99 percent sulfuric acid. The gases from the combustion chamber
cool and then enter the solid catalyst (vanadium pentoxide) con-
verter. Usually, 95 - 98 percent of the sulfur dioxide from the
combustion chamber is converted to sulfur trioxide, with an accompany-
ing large evolution of heat. After being cooled, the converter exit
gas enters an absorption tower, where the sulfur trioxide is absorbed
with 98 - 99 percent sulfuric acid. The sulfur trioxide combines
with the water in the acid and forms more sulfuric acid.
If oleum, a solution of uncombined 803 in 112804, is produced,
803 from the converter is first passed to an oleum tower that is
fed with 98 percent acid from the absorption system. The gases
4/81
Chemical Process Industry
5.17-1
-------
Ui
JO
CXI
DRYING
TOWER
AIR
BLOWER
LIQUID
SULFUR'
STEAM DRUM
BLOW DOWN -•-
-SJ
STORAGE
SULFUR
PUMP
<~r( V.-*.
H ;
FURNACE
TT
COOLER t ;
Illllllllllllll
-o — o
-o — o
STEAM
BOILER
BOILER CONVERTER
BOILER FEED WATER.
TO
ATMOSPHERE
ECONOMIZER
ABSORPTION
TOWER
•WATER
ACID
COOLER
ACID PUMP
TANK
PRODUCT
00
Figure 5.17-1. Basic flow diagram of contact process sulfuric acid plant burning elemental sulfur.
-------
•AIR
;PENTACID
SULFUR
FUEL OIL
FURNACE
DUST
COLLECTOR
WATER
A
\\\\\>
GAS
COOLEF
\\\\V
>
i
<
>
, 1
1
_^,
i
r
i
i i
1 !
ELECTROSTATIC
PRECIPITATORS
• III ill
1 r*H
--' 1 L
v_J 1
1 *
/
L
1
1
1
/
\V^
cm
;TC
NS^
TOWER N
\
A\\\\\\
so?
STRIPPER
.\V\\\VM
BLOWER
ATMOS- A MIST
PHERE^L ELIMINATOR
ABSORPTION
TOWER
WATER
_ 98% ACID _
PUMP TANK
1
A S
f
A A
f
( ACID COOLERS )
"") 1 ")
PRODUCT
PRODUCT*
93% ACID
PUMP TANK'
Figure 5.17-2. Basic flow diagram of contact process sulfuric acid plant burning spent acid.
4/81
Chemical Process Industry
5.17-3
-------
from the oleum tower are then pumped to the absorption column where
the residual sulfur trioxide is removed.
A schematic diagram of a contact process sulfuric acid plant
that burns elemental sulfur is shown in Figure 5.17-1.
1 2
Spent Acid and Hydrogen Sulfide Burning Plants ' - Two types of
plants are used to process this type of sulfuric acid. In one, the
sulfur dioxide and other combustion products from the combustion of
spent acid and/or hydrogen sulfide with undried atmospheric air are
passed through gas cleaning and mist removal equipment. The gas
stream next passes through a drying tower. A blower draws the gas
from the drying tower and discharges the sulfur dioxide gas to the
sulfur trioxide converter. A schematic diagram of a contact process
sulfuric acid plant that burns spent acid is shown in Figure 5.17-2.
In a "wet gas plant", the wet gases from the combustion chamber
are charged directly to the converter with no intermediate treatment.
The gas from the converter flows to the absorber, through which
93 - 98 percent sulfuric acid is circulating.
Sulfide Ores and Smelter Gas Plants - The configuration of this
type of plant is essentially the same as that of a spent acid plant
(Figure 5.17-2), with the primary exception that a roaster is used
in place of the combustion furnace.
The feed used in these plants is smelter gas, available from
such equipment as copper converters, reverberatory furnaces,
roasters and flash smelters. The sulfur dioxide in the gas is con-
taminated with dust, acid mist and gaseous impurities. To remove
the impurities, the gases must be cooled and passed through purifi-
cation equipment consisting of cyclone dust collectors, electrostatic
dust and mist precipitators, and scrubbing and gas cooling towers.
After the gases are cleaned and the excess water vapor is removed,
they are scrubbed with 98 percent acid in a drying tower. Beginning
with the drying tower stage, these plants are nearly identical to
the elemental sulfur plants shown in Figure 5.17-1.
5.17.2 Emissions and Controls
1-3
Sulfur Dioxide - Nearly all sulfur dioxide emissions from
sulfuric acid plants are found in the exit gases. Extensive testing
has shown that the mass of these SO2 emissions is an inverse func-
tion of the sulfur conversion efficiency (S02 oxidized to 803).
This conversion is always incomplete, and is affected by the number
of stages in the catalytic converter, the amount of catalyst used,
temperature and pressure, and the concentrations of the reactants
(sulfur dioxide and oxygen). For example, if the inlet S02 concen-
tration to the converter were 8 percent by volume (a representative
value), and the conversion temperature were 473°C (883°F), the con-
version efficiency would be 96 percent. At this conversion, the
5.17-4 EMISSION FACTORS 4/81
-------
uncontrolled emission factor for S02 would be 27.5 kg/Mg (55 pounds
per ton) of 100 percent sulfuric acid produced, as shown in
Table 5.17-1. For purposes of comparison, note that the Environ-
mental Protection Agency performance standard for new and modified
plants is 2 kg/Mg (4 pounds per ton) of 100 percent acid produced,
maximum 2 hour average.^ As Table 5.17-1 and Figure 5.17-3 indicate,
achieving this standard requires a conversion efficiency of 99.7
percent in an uncontrolled plant or the equivalent S02 collec-
tion mechanism in a controlled facility. Most single absorption
plants have S0~ conversion efficiencies ranging from 95 - 98 percent.
In addition to exit gases, small quantities of sulfur oxides
are emitted from storage tank vents and tank car and tank truck vents
during loading operations, from sulfuric acid concentrators, and
through leaks in process equipment. Few data are available on the
quantity of emissions from these sources.
Of the many chemical and physical means for removing S02 from
gas streams, only the dual absorption and the sodium sulfite/bisul-
fite scrubbing processes have been found to increase acid production
without yielding unwanted byproducts.
TAB1E 5.17-1.
EMISSION FACTORS FOR SULFURIC
ACID PLANTS3
EMISSION FACTOR RATING: A
S02 Emissions
Conversion of SO 2
to S03 (%)
93
94
95
96
97
98
99
99.5
99.7
100
kg/Mg of 100%
H2S04
48.0
41.0
35.0
27.5
20.0
13.0
7.0
3.5
2.0
0.0
Ib/ton of 100%
H2S04
96
82
70
55
40
26
14
7
4
0
.Reference 1.
This linear interpolation formula can be used for calculating
emission factors for conversion efficiencies between 93 and 100%:
emission factor =-13.65 (% conversion efficiency) + 1365.
4/81
Chemical Process Industry
5.17-5
-------
1
99.92
10,000
too
SULFUR CONVERSION, % feedstock sulfur
99-7 99.0 98.0
97.0 96,0 95.0
2 2.S 3
40 50 60 70 80 90100
4 5 6 7 8 9 10 15 20 25 30
S02EMISSIONS, ib/ton of 100% H2$04 produced
Figure 5.17-3. Sulfuric acid plant feedstock sulfur conversion versus volumetric and
mass S02 emissions at various inlet SC>2 concentrations by volume.
5.17-6
EMISSION FACTORS
4/81
-------
In the dual absorption process, the 863 gas formed in the
primary converter stages is sent to a primary absorption tower where
most of the 803 is removed to form E^SO^. The remaining unconverted
sulfur dioxide is forwarded to the final stages in the converter to
remove much of the remaining SO2 by oxidation to 803, from whence
it is sent to the secondary absorber for final sulfur trioxide
removal. The result is the conversion of a much higher fraction of
S02 to S03 (a conversion of 99.7 percent or higher, on the average,
which meets the performance standard). Furthermore, dual absorption
permits higher converter inlet sulfur dioxide concentrations than
are used in single absorption plants, because the secondary conver-
sion stages effectively remove any residual sulfur dioxide from the
primary absorber.
Where dual absorption reduces sulfur dioxide emissions by
increasing the overall conversion efficiency, the sodium sulfite/
bisulfite scrubbing process removes sulfur dioxide directly from
the absorber exit gases. In one version of this process, the sul-
fer dioxide in the waste gas is absorbed in a sodium sulfite solution,
Is separated, and is recycled to the plant. Test results from a
680 Mg (750 ton per day) plant equipped with a sulfite scrubbing
system indicated an average SO emission factor of 1.35 kg/Mg
(2.7 pounds per ton) of 100 percent acid.
1-3
Acid Mist - Nearly all the acid mist emitted from sulfuric acid
manufacturing can be traced to the absorber exit gases. Acid mist
is created when sulfur trioxide combines with water vapor at a
temperature below the dew point of sulfur trioxide. Once formed
within the process system, this mist is so stable that only a small
quantity can be removed in the absorber.
In general, the quantity and particle size distribution of
acid mist are dependent on the type of sulfur feedstock used, the
strength of acid produced, and the conditions in the absorber.
Because it contains virtually no water vapor, bright elemental
sulfur produces little acid mist when burned. However, the hydro-
carbon impurities in other feedstocks - dark sulfur, spent acid
and hydrogen sulfide - oxidize to water vapor during combustion.
The water vapor, in turn, combines with sulfur trioxide as the gas
cools in the system.
The strength of acid produced - whether oleum or 99 percent
sulfuric acid - also affects mist emissions. Oleum plants produce
greater quantities of finer more stable mist. For example, uncon-
trolled mist emissions from oleum plants burning spent acid range
from 0.5 to 5.0 kg/Mg (1.0 to 10.0 pounds per ton), while those
from 98 percent acid plants burning elemental sulfur range from
0.2 to 2.0 kg/Mg (0.4 to 4.0 pounds per ton). Furthermore,
85 - 95 weight percent of the mist particles from oleum plants are
less than 2 microns in diameter, compared with only 30 weight
percent that are less than 2 microns in diameter from 98 percent
acid plants.
4/81
Chemical Process Industry
5.17-7
-------
The operating temperature of the absorption column directly
affects sulfur trioxide absorption and, accordingly, the quality of
acid mist formed after exit gases leave the stack. The optimum
absorber operating temperature depends on the strength of the acid
produced, throughput rates, inlet sulfur trioxide concentrations,
and other variables peculiar to each individual plant. Finally,
it should be emphasized that the percentage conversion of sulfur
trioxide has no direct effect on acid mist emissions. In
Table 5.17-2, uncontrolled acid mist emissions are presented for
various sulfuric acid plants.
TABLE 5.17-2. ACID MIST EMISSION FACTORS FOR SULFURIC
ACID PIANTS WITHOUT CONTROLS3
EMISSIONS FACTOR RATING: B
Emissions
Oleum produced,
Raw material % total output kg/Mg acid Ib/ton acid
Recovered sulfur
Bright virgin sulfur
Dark virgin sulfur
Sulfide ores
Spent acid
0
33
0
0
to
0
to
to
to
43
100
25
77
0.
0.
0.
1.
175
0.
16
6 -
1 -
_
85
- 3
3.
1.
0
7
2
.4
15
0.
0.
1.
2.
35
32
2
2
- 0.8
1.7
- 6.3
- 7.4
- 2.4
. Reference 1.
Emissions are proportional to the percentage of oleum in the total
product. Use low end of ranges for low oleum percentage and high
end of ranges for high oleum percentage.
Two basic types of devices, electrostatic precipitators and
fiber mist eliminators, effectively reduce the acid mist concentra-
tion from contact plants to less than the EPA New Source Performance
Standard, which is 0.075 kg/Mg (0.15 pound per ton) of acid. Pre-
cipitators, if properly maintained, are effective in collecting the
mist particles at efficiencies up to 99 percent (see Table 5.17-3).
The three most commonly used fiber mist eliminators are the
vertical tube, vertical panel, and horizontal dual pad types. They
differ from one another in the arrangement of the fiber elements,
which are composed of either chemically resistant glass or fluoro-
carbon, and in the means employed to collect the trapped liquid.
The operating characteristics of these three types are compared with
electrostatic precipitators in Table 5.17-3.
5.17-8 EMISSION FACTORS 4/81
-------
TABLE 5.17-3. EMISSION COMPARISON AND COLLECTION EFFICIENCY OF
TYPICAL ELECTROSTATIC PRECIPITATOR AND FIBER MIST ELIMINATORS&
Control device
Particle size
collection
efficiency, %
>3 (j.m <3^m
Acid
98% acid plants
kg/Mg Ib/ton
mist emissions
Oleum plants
kg/Mg Ib/ton
Electrostatic
precipitator
Fiber mist
eliminator
99
100
0.05
0.10
0.06
0.12
Tabular
Panel
Dual pad
100
100
100
95-99
90-98
93-99
0.01
0.05
0.055
0.02
0.10
0,11
0.01
0.05
0.055
0.02
0.10
0.11
.Reference 2.
Based on manufacturers' generally expected results. Calculated for i
SO concentration in gas converter.
References for Section 5.17
1. Atmospheric Emissions from Sulfuric Acid Manufacturing Processes,
999-AP-13, U.S. Department of Health, Education and Welfare,
Washington, DC, 1966.
2. Unpublished report on control of air pollution from sulfuric
acid plants, U.S. Environmental Protection Agency, Research
Triangle Park, NC, August 1971.
3. Standards of Performance for New Stationary Sources, 36 FR 24875,
December 23, 1971.
4. M. Drabkin and Kathryn J. Brooks, A Review of Standards of
Performance for New Stationary Sources - Sulfuric Acid Plants,
EPA Contract No. 68-02-2526, Mitre Corporation, McLean, VA,
June 1978.
5. Final Guideline Document: Control of Sulfuric Acid Mist
Emissions from Existing Sulfuric Acid Production Units,
EPA 450/2-77-019, U.S. Environmental Protection Agency,
Research Triangle Park, NC, September 1977.
4/81
Chemical Process Industry
5.17-9
-------
1
-------
5.18 SULFUR RECOVERY
1 2
5.18.1 Process Description '
Most of the elemental sulfur produced from hydrogen sulfide (H2S)
is made by the modified Claus process. A simplified flow diagram of
this process is shown in Figure 5.18-1. The process consists of the
multistage catalytic oxidation of hydrogen sulfide according to the
following overall Reaction:
2H2S + 02 + 2S + 2H20
In the first step, one third of the H2S is reacted with air in a furnace
and combusted to S02 according to Reaction (2):
H2S + 1.502 •*• S02 + H20 (2)
The heat of the reaction is recovered in a waste heat boiler or sulfur
condenser.
For gas streams with low concentrations of H2S (20 - 60%), approxi-
mately one third of the gas stream is fed to the furnace and the H2S is
nearly completely combusted to S02, while the remainder of the gas is
bypassed around the furnace. This is the "split stream" configuration.
For gas streams with higher H2S concentrations, the entire gas stream is
fed to the furnace with just enough air to combust one third of the H2S
to S02. This is the "partial combustion" configuration. In this
configuration, as much as 50 to 60 percent conversion of the hydrogen
sulfide to elemental sulfur takes place in the initial reaction chamber
by Reaction (1). In extremely low concentrations of H2S (<25 - 30%), a
Claus process variation known as "sulfur recycle" may be used, where
product sulfur is recycled to the furnace and burned, raising the
effective sulfur level where flame stability may be maintained in the
furnaces.
After the reaction furnace, the gases are cooled to remove
elemental sulfur and then reheated. The remaining H2S in the gas stream
is then reacted with the S02 over a bauxite catalyst at 500 - 600°F
(260 - 316°C) to produce elemental sulfur according to Reaction 3:
2H2S + S02 + 3S + 2H20 (3)
Because this is a reversible reaction, equilibrium requirements limit
the conversion. Lower temperatures favor elemental sulfur formation,
but at too low a temperature, elemental sulfur fouls the catalyst.
Because the reaction is exothermic, the conversion attainable in one
stage is limited. Therefore, two or more stages are used in series,
with interstage cooling to remove the heat of reaction and to condense
the sulfur.
2/80 Chomiral Prorrss Imlu.sirv 5.18-1
-------
I SULFUR
! CONDENSER
I
t 1
^
REACTION
FURNACE
SULFUR
CONDENSER
SULFUR
CONDENSER
AIR
B
REHEATER
*^
CATALYTIC
CONVERTER
NOTES:
n
H
O
a
tfi
SOLID LINES INDICATE FLOW PATHS
FOR PARTIAL COMBUSTION PROCESS
CONFIGURATION
DASHED LINE INDICATES ADDITIONAL
STREAM PRESENT IN THE SPLIT
STflEAM PROCESS CONFIGURATION
ADDITIONAL CONVERTERS/CONDENSERS
TO ACHIEVE ADDITIONAL RECOVERY OF
ELEMENTAL SULFUB ARE OPTIONAL AT
THI3 POINT
TAIL GAS
SPENT CATALYST
SULFUH
CO
o
Figure 5.18-1. Typical flow diagram - Glaus Process sulfur recovery.
-------
Carbonyl sulfide (COS) and carbon disulfide (CS2) are formed in the
reaction furnace in the presence of carbon dioxide and hydrocarbons:
C02
COS
H2S
H2S
4S
H20
H20
CS2
COS
CS2
2H2S
(4)
(5)
(6)
About 0.25 to 2.5 percent of the sulfur fed may be lost in this way.
Additional sulfur may be lost as vapor, mist or droplets.
5.18.2 Emissions and Controls
Tail gas from a Glaus sulfur recovery unit contains a variety of
pollutants, including sulfur dioxide, hydrogen sulfide, other reduced
sulfur compounds (such as COS and CS2), carbon monoxide, and volatile
organic compounds. If no other controls are used, the tail gas is
incinerated, so that the emissions consist mostly of sulfur dioxide.
Smaller amounts of carbon monoxide are also emitted.
The emissions of S02 (along with H2S and sulfur vapor) depend
directly on the sulfur recovery efficiency of the Glaus plant. This
efficiency is dependent upon many factors, including the following:
- Number of catalytic conversion stages
- Inlet feed stream composition
- Operating temperatures and catalyst maintenance
- Maintenance of the proper stoichiometric ratio of H2S/S02
- Operating capacity factor
Recovery efficiency increases with the number of catalytic stages
used. For example, for a Claus plant fed with 90 percent H2S, sulfur
recovery is approximately 85 percent for one catalytic stage and 95
percent for two or three stages.
Recovery efficiency also depends on the inlet feed stream compo-
sition. Sulfur recovery increases with increasing H2S concentration in
the feed stream. For example, a plant having two or three catalytic
stages would have a sulfur recovery efficiency of approximately 90
percent when treating a 15 mole percent H2S feed stream, 93 percent for
a 50 mole percent H2S stream, and 95 percent for a 90 mole percent H2S
stream. Various contaminants in the feed gas reduce Claus sulfur
recovery efficiency. Organic compounds in the feed require extra air
for combustion, and added water and inert gas from burning these organics
decrease sulfur concentrations and thus lower sulfur recovery. Higher
molecular weight organics also reduce efficiencies because of soot
formation on the catalyst. High concentrations of C02 in the feed gas
reduce catalyst life.
2/80
Chemical Process Industry
5.18-3
-------
Since the Glaus reactions are exothermic, sulfur recovery is
enhanced by removing heat and operating the reactors at as low a tem-
perature as practicable without condensing sulfur on the catalyst.
Recovery efficiency also depends on catalyst performance. One to 2
percent loss in recovery efficiency over the period of catalyst life has
been reported. Maintenance of the 2:1 stoichiometric ratio of H2S and
S02 is essential for efficient sulfur recovery. Deviation above or
below this ratio results in a loss of efficiency. Operation of a Glaus
plant below capacity may also impair Glaus efficiency somewhat.
Removal of sulfur compounds from Glaus plant tail gas is possible
by three general schemes:
1) Extension of the Glaus reaction to increase overall sulfur
recovery,
2) Conversion of sulfur gases to S02, followed by S02 removal
technology,
3) Conversion of sulfur gases to I^S, followed by H2S removal
technology.
Processes in the first scheme remove additional sulfur compounds by
carrying out the Glaus reaction at lower temperatures to shift equi-
librium of the Glaus reactions toward formation of additional sulfur.
The IFP-1, BSR/Selectox, Sulfreen, and Amoco CBA processes use this
technique to reduce the concentration of tail gas sulfur compounds to
1500 - 2500 ppm, thus increasing the sulfur recovery of the Glaus plant
to 99 percent.
In the second class of processes, the tail gas is incinerated to
convert all sulfur compounds to S02. The S02 is then recovered by one
of several processes, such as the Wellman-Lord, In the Wellman-Lord and
certain other processes, the S02 absorbed from the tail gas is recycled
to the Glaus plant to recover additional sulfur. Processes in this
class can reduce the concentration of sulfur compounds in the tail gas
to 200 - 300 ppm or less, for an overall sulfur recovery efficiency
(including the Glaus plant) of 99.9+ percent.
The third method for removal of sulfur compounds from Glaus tail
gas involves converting the sulfur compounds to ^S by mixing the tail
gas with a reducing gas and passing it over a reducing catalyst. The
H2S is then removed, by the Stretford process (in the Beavon and Clean
Air processes) or by an amine absorption system (SCOT process). The
Beavon and Clean Air processes recover the I^S as elemental sulfur, and
the SCOT process produces a concentrated I^S stream which is recycled to
the Glaus process. These processes reduce the concentration of sulfur
compounds in the tail gas to 200 - 300 ppm or less and increase the
overall recovery efficiency of the Glaus plant to 99.9+ percent.
5.18-4 EMISSION FACTORS 2/80
-------
A New Source Performance Standard for Glaus sulfur recovery plants
In petroleum refineries was promulgated in March 1978. This standard
limits emissions to 0.025 percent by volume (250 ppm) of S02 on a dry
basis and at zero percent oxygen, or 0.001 percent by volume of H2S and
0.03 percent by volume of B^S, COS, and CS2 on a dry basis and at zero
percent oxygen.
Table 5.18-1.
EMISSION FACTORS FOR MODIFIED CLAUS SULFUR RECOVERY
PLANTS
EMISSION FACTOR RATING: D
Number of Catalytic Stages
Two , uncontrolled
Three, uncontrolled
Four, uncontrolled
Controlled
Typical
Recovery
of Sulfur, %a
92 to 95
95 to 97.5
96 to 99
99 to 99.9
S0_ Emissions
Ib/ton
348 to 211
211 to 167
167 to 124
40 to 4
kg/MT
174 to 105
106 to 84
84 to 62
20 to 2
Efficiencies are for feed gas streams with high H2S concentrations.
Gases with lower H2S concentrations would have lower efficiencies.
For example, a 2 or 3 stage plant could have a recovery efficiency of
b95% for a 90% H2S stream, 93% for 50% H2S, and 90% for 15% H2S.
Based on net weight of pure sulfur produced. The range in emission
fractors corresponds to the range in percentage recovery of sulfur.
S02 emissions calculated from percentage sulfur recovery by following
equation:
c-n j /i /vfrr,\ (100-% recovery)
SOo emissions (kg/MT) = -—•;. •LL-
* % recovery
X 2000
Lower percent recovery is for control by extended Glaus, and higher
percent is for conversion to and removal of H2S or S02.
References for Section 5.18
1. E. C. Cavanaugh, et
Environmental Assessment Data Base for
2.
3.
Low/Medium Btu Gasification Technology, Volume II, EPA Contract No.
68-02-2147, Radian Corporation, Austin, TX, September 1977.
Standards Support and Environmental Impact Statement, Volume 1;
Proposed Standards of Performance for Petroleum Refinery Sulfur
Recovery Plants. EPA-450/2-76-016a, U. S. Environmental Protection
Agency, Research Triangle Park, NC, September 1976.
B. Goar and T. Arrington, "Guidelines for Handling Sour Gas",
Oil and Gas Journal. 76(26) : 160-164, June 26, 1978.
2/80
Chemical Process Industry
5.18-5
-------
-------
5.19 SYNTHETIC FIBERS
5.19.1 Process Descripti on'
Synthetic fibers are classified into two major categories, semi-synthetic and "true" synthetic. Semi-synthetics,
such as viscose rayon and acetate fibers, result when natural polymeric materials such as cellulose are brought into
a dissolved or dispersed state and then spun into fine filaments. True synthetic polymers, such as Nylon, * Orion,
and Dacron, result from addition and other polymerization reactions that form long chain molecules.
True synthetic fibers begin with the preparation of extremely long, chain-like molecules. The polymer is spun
in one of four ways:2 (1) melt spinning, in which molten polymer is pumped through spinneret jets, the polymer
solidifying as it strikes the cool air; (2) dry spinning, in which the polymer is dissolved in a suitable organic
solvent, and the resulting solution is forced through spinnerets; (3) wet spinning, in which the solution is
coagulated in a chemical as it emerges from the spinneret; and (4) core spinning, the newest method, in which a
continuous filament yarn together with short-length "hard" fibers is introduced onto a spinning frame in such a
way as to form a composite yarn.
5.19.2 Emissions and Controls1
In the manufacture of viscose rayon, carbon disulfide and hydrogen sulfide are the major gaseous emissions.
Air pollution controls are not normally used to reduce these emissions, but adsorption in activated carbon at an
efficiency of 80 to 95 percent, with subsequent recovery of the C$2 can be accomplished.3 Emissions of gaseous
hydrocarbons may also occur from the drying of the finished fiber. Table 5.19-1 presents emission factors for
semi-synthetic and true synthetic fibers.
Table 5.19-1. EMISSION FACTORS FOR SYNTHETIC FIBERS MANUFACTURING
EMISSION FACTOR RATING: E
Type of fiber
Semi-synthetic
Viscose rayon3'*-"
True synthetic0
Nylon
Dacron
Hydrocarbons
Ib/ton
7
—
kg/MT
3.5
—
Carbon
disulfide
Ib/ton
55
-
—
kg/MT
27.5
-
—
Hydrogen
sulfide
Ib/ton
6
-
—
kg/MT
3
-
—
Oil vapor
or mist
Ib/ton
15
7
kg/MT
7.5
3.5
aReference 4.
May be reduced by 80 to 95 percent adsorption in activated charcoal.
GReference 5.
*Mention of company or product names does not constitute endorsement by the Environmental Protection
Agency.
2/72
Chemical Process Industry
5.19-1
-------
References for Section 5.19
1. Air Pollutant Emission Factors. Final Report. Resources Research, Inc. Reston, Va. Prepared for National
Air Pollution Control Administration, Durham, N.C., under Contract Number CPA-22-69-119. April 1970.
2. Fibers, Man-Made. In: Kirk-Othmer Encyclopedia of Chemical Technology. New York, John Wilev and Sons
Inc. 1969.
3. Fluidized Recovery System Nabs Carbon Disulfide. Chem, Eng. 70(8):92-94, April 15,1963.
4. Private communication between Resources Research, Incorporated, and Rayon Manufacturing Plant
December 1969.
5. Private communication between Resources Research, Incorporated, and E.I. Dupont de Nemours and
Company. January 13,1970.
5.19-2 EMISSION FACTORS 2/72
-------
5.20 SYNTHETIC RUBBER
5.20.1. Emulsion Styrene-Butadiene Copolymers
General - Two types of polymerization reaction are used to produce styrene-
butadiene copolymers, the emulsion type and the solution type. This Section
addresses volatile organic compound (VOC) emissions from the manufacture of
copolymers of styrene and butadiene made by emulsion polymerization processes.
The emulsion products can be sold in either a granular solid form, known as
crumb, or in a liquid form, known as latex.
Copolymers of styrene and butadiene can be made with properties ranging
from those of a rubbery material to those of a very resilient plastic.
Copolymers containing less than 45 weight percent styrene are known as
styrene-butadiene rubber (SBR). As the styrene content is increased over 45
weight percent, the product becomes increasingly more plastic.
Emulsion Crumb Process - As shown in Figure 5.20-1, fresh styrene and
butadiene are piped separately to the manufacturing plant from the storage
area. Polymerization of styrene and butadiene proceeds continuously though
a train of reactors, with a residence time in each reactor of approximately
1 hour. The reaction product formed in the emulsion phase of the reaction
mixture is a milky white emulsion called latex. The overall polymerization
reaction ordinarily is not carried out beyond a 60 percent conversion of
monomers to polymer, because the reaction rate falls off considerably beyond
this point and product quality begins to deteriorate.
Because recovery of the unreacted monomers and their subsequent purifi-
cation are essential to economical operation, unreacted butadiene and styrene
from the emulsion crumb polymerization process normally are recovered. The
latex emulsion is introduced to flash tanks where, using vacuum flashing, the
unreacted butadiene is removed. The butadiene is then compressed, condensed
and pumped back to the tank farm storage area for subsequent reuse. The
condenser tail gases and noncondensibles pass through a butadiene adsorber/
desorber unit, where more butadiene is recovered. Some noncondensibles and
VOC vapors pass to the atmosphere or, at some plants, to a flare system.
The latex stream from the butadiene recovery area is then sent to the styrene
recovery process, usually taking place in perforated plate steam stripping
columns. From the styrene stripper, the latex is stored in blend tanks.
From this point in the manufacturing process, latex is. processed
continuously. The latex is pumped from the blend tanks to coagulation
vessels, where dilute sulfuric acid (I^SO^ of pH 4 to 4.5) and sodium
chloride solution are added. The acid and brine mixture causes the emulsion
to break, releasing the styrene-butadiene copolymer as crumb product. The
coagulation vessels are open to the atmosphere.
8/82
Chemical Process Industry
5.20-1
-------
l-n
O
I
§
H
O
CO
00
to
Figure 5.20-1. Typical process for crumb production by emulsion polymerization.
-------
00
CO
to
n
H-
O
O
O
n>
(0
(0
3
P.
ho
O
I
U)
Figure 5.20-2. Typical process for latex production by emulsion polymerization,
-------
TABLE 5.20-1. EMISSION FACTORS FOR EMULSION STYRENE-BUTADIENE
COPOLYMER PRODUCTION3
EMISSION FACTOR RATING: B
Process Volatile Organic Emissions
g/kg _ Ib/ton
Emulsion Crumb
Monomer recovery, uncontrolled 2.6 5.2
Absorber vent 0.26 0.52
Blend/ coagulation tank, uncontrolled 0.42 0.84
Dryers6 2.51 5.02
Emulsion Latex
Monomer removal f
Condenser vent
Blend tanks ,.
Uncontrolled
8.
0
45
.1
16.9
0.2
Nonmethane VOC, mainly styrene and butadiene. For emulsion crumb and
emulsion latex processes only. Factors for related equipment and
operations (storage, fugitives, boilers, etc.) are presented in other
Sections of AP-42.
Expressed as units per unit of copolymer produced.
Average of 3 industry supplied stack tests .
Average of 1 industry stack test and 2 industry supplied emission
estimates.
No controls available. Average of 3 industry supplied stack tests and 1
-industry estimate.
EPA estimates from industry supplied data, confirmed by industry.
Leaving the coagulation process, the crumb and brine acid slurry is
separated by screens into solid and liquid. The crumb product is processed
in rotary presses that squeeze out most of the entrained water. The liquid
(brine/acid) from the screening area and the rotary presses is cycled to the
coagulation area for reuse.
The partially dried crumb is then processed in a continuous belt dryer
which blows hot air at approximately 93°C (200°F) across the crumb to com-
plete the drying of the product. Some plants have installed single pass
dryers, where space permits, but most plants still use the triple pass dryers
which were installed as original equipment in the 1940s. The dried product
is baled and weighed before shipment.
Emulsion Latex Process - Emulsion polymerization can also be used to
produce latex products. These latex products have a wider range of pro-
perties and uses than do the crumb products, but the plants are usually much
smaller. Latex production, shown in Figure 5.20-2, follows the same basic
processing steps as emulsion crumb polymerization, with the exception of
final product processing.
5.20-4 EMISSION FACTORS 8/82
-------
As in emulsion crumb polymerization, the monomers are piped to the
processing plant from the storage area. The polymerization reaction is
taken to near completion (98 to 99 percent conversion), and the recovery of
unreacted monomers is therefore uneconomical. Process economy is directed
towards maximum conversion of the monomers in one process trip.
Because most emulsion latex polymerization is done in a batch process,
the number of reactors used for latex production is usually smaller than for
crum production. The latex is sent to a blowdown tank where, under vacuum,
any unreacted butadiene and some unreacted styrene are removed from the
latex. If the unreacted styrene content of the latex has not been reduced
sufficiently to meet product specifications in the blowdown step, the latex
is introduced to a series of steam stripping steps to reduce the content
further. Any steam and styrene vapor from these stripping steps is taken
overhead and is sent to a water cooled condenser. Any uncondensibles leaving
the condenser are vented to the atmosphere.
After discharge from the blowdown tank or the styrene stripper, the
latex is stored in process tanks. Stripped latex is passed through a series
of screen filters to remove unwanted solids and is stored in blending tanks,
where antioxidants are added and mixed. Finally, latex is pumped from the
blending tanks to be packaged into drums or to be bulk loaded into railcars
or tank trucks.
Emissions and Controls - Emission factors for emulsion styrene-butadiene
copolymer production processes are presented in Table 5.20-1.
In the emulsion crumb process, uncontrolled noncondensed tail gases
(VOC) pass through a butadiene absorber control device, which is 90 percent
efficient, to the atmosphere or, in some plants, to a flare stack.
No controls are presently employed for the blend tank and/or coagul-
ation tank areas, on either crumb or latex facilities. Emissions from
dryers in the crumb process and the monomer removal part of the latex
process do not employ control devices.
Individual plant emissions may vary from the average values listed in
Table 5.20-1 with facility age, size and plant modification factors.
References for Section 5.20
1. Control Techniques Guideline (Draft), EPA Contract No. 68-02-3168,
GCA, Inc., Chapel Hill, NC, April 1981.
2. Emulsion Styrene-Butadiene Copolymers: Background^Document , EPA
Contract No. 68-02-3063, TRW Inc., Research Triangle Park, NC, May 1981.
3. Confidential written communication from C. Fabian, U.S. Environmental
Protection Agency, Research Triangle Park, NC, to Styrene-Butadiene
Rubber File (76/15B), July 16, 1981.
8/82 Chemical Process Industry 5.20-5
-------
-------
5.21 Terephthalic Acid
5.21.1 Process Description
Terephthalic acid (TPA) is made by air oxidation of £-xylene and requires
purification for use in polyester fiber manufacture. A typical continuous
process for the manufacture of crude terephthalic acid (C-TPA) is shown in
Figure 5.21-1. The oxidation and product recovery portion essentially
consists of the Mid-Century oxidation process, whereas the recovery and
recycle of acetic acid and recovery of methyl acetate are essentially as
practiced by dimethyl terephthalate (DMT) technology. The purpose of the
DMT process is to convert the terephthalic acid contained in C-TPA to a form
that will permit its separation from impurities. C-TPA is extremely insoluble
in both water and most common organic solvents. Additionally, it does not
melt, it sublimes. Some products of partial oxidation of £-xylene, such as
£-toluic acid and £-formyl benzoic acid, appear as impurities in TPA.
Methyl acetate is also formed in significant amounts in the reaction.
OCAT " /—\ I'
CH3 + 302 f HO—C_/ \_C-OH + 2H20
(ALtllUAUlU \. ^ '
SOLVENT) (p-XYLENE) (AIR) \. (TEREPHTHALIC ACID) (WATER)
>/ CO + C02 + H20
(MINOR REACTION) (CARBON (CARBON (WATER)
MONOXIDE) DIOXIDE)
C-TPA Production
Oxidation of ^-xylene - _P_-xylene (stream 1 of Figure 5.21-1), fresh acetic
acid (2), a catalyst system, such as manganese or cobalt acetate and sodium
bromide (3), and recovered acetic acid are combined into the liquid feed
entering the reactor (5). Air (6), compressed to a reaction pressure of
about 2000 kPa (290 psi), is fed to the reactor. The temperature of the
exothermic reaction is maintained at about 200°C (392°F) by controlling the
pressure at which the reaction mixture is permitted to boil and form the
vapor stream leaving the reactor (7).
Inert gases, excess oxygen, CO, C02, and volatile organic compounds
(VOC) (8) leave the gas/liquid separator and are sent to the high pressure
absorber. This stream is scrubbed with water under pressure, resulting in a
gas stream (9) of reduced VOC content. Part of the discharge from the
high pressure absorber is dried and is used as a source of inert gas (IG),
and the remainder is passed through a pressure control valve and a noise
silencer before being discharged to the atmosphere through process vent A.
The underflow (23) from the absorber is sent to the azeotrope still for
recovery of acetic acid.
Crystallization and Separation - The reactor liquid containing TPA (10)
flows to a series of crystallizers, where the pressure is relieved and the
5/83 Chemical Process Industry 5.21-1
-------
Ul
•
NJ
I
ro
cn
O
a
H
O
oo
OJ
Figure 5.21-1. Crude Terephthalic Acid Process.
-------
liquid is cooled by the vaporization and return of condensed VOC and water.
The partially oxidized impurities are more soluble in acetic acid and tend
to remain in solution, while TPA crystallizes from the liquor. The inert
gas that was dissolved and entrained in the liquid under pressure is
released when the pressure is relieved and is subsequently vented to the
atmosphere along with the contained VOC (B). The .slurry (11) from the
crystallizers is sent to solid/liquid separators, where the TPA is recovered
as a wet cake (14). The mother liquor (12) from the solid/liquid separators
is sent to the distillation section, while the vent gas (13) is discharged
to the atmosphere (B).
Drying, Handling and Storage - The wet cake (14) from solid/liquid
separation is sent to dryers, where with the use of heat and IG, the
moisture, predominately acetic acid, is removed, leaving the product, C-TPA,
as dry free flowing crystals (19). IG is used to convey the product (19) to
storage silos. The transporting gas (21) is vented from the silos to bag
dust collectors to reduce its particulate loading, then is discharged to the
atmosphere (D). The solids (S) from the bag filter can be forwarded to
purification or can be incinerated.
Hot VOC laden IG from the drying operation is cooled to condense and
recover VOC (18). The cooled IG (16) is vented to the atmosphere (B), and
the condensate (stream 18) is sent to the azeotrope still for recovery of
acetic acid.
Distillation and Recovery - The mother liquor (12) from solid/liquid
separation flows to the residue still, where acetic acid, methyl acetate and
water are recovered overhead (26) and product residues are discarded. The
overhead (26) is sent to the azeotrope still where dry acetic acid is
obtained by using n-propyl acetate as the water removing agent.
The aqueous phase (28) contains saturation amounts of ji-propyl acetate and
methyl acetate, which are stripped from the aqueous matter in the wastewater
still. Part of the bottoms product is used as process water in absorption,
and the remainder (N) is sent to wastewater treatment. A purge stream of
the organic phase (30) goes to the methyl acetate still, where methyl
acetate and saturation amounts of water are recovered as an overhead product
(31) and are disposed of as a fuel (M). iv-propyl acetate, obtained as the
bottoms product (32), is returned to the azeotrope still. Process losses of
n-propyl acetate are made up from storage (33). A small amount of inert
gas, which is used for blanketing and instrument purging, is emitted to the
atmosphere through vent C.
C-TPA Purification
The purification portion of the Mid-Century oxidation process involves
the hydrogenation of C-TPA over a palladium containing catalyst at about
232°C (450°F). High purity TPA is recrystallized from a high pressure water
solution of the hydrogenated material.
The Olin-Mathieson manufacturing process is similar to the Mid-Century
process except the former uses 95 percent oxygen, rather than air, as the
oxidizing agent. The final purification step consists essentially of a
5/83 Chemical Process Industry 5.21—3
-------
continuous sublimation and condensation procedure. The C-TPA is combined
with small quantities of hydrogen and a solid catalyst, dispersed in steam,
and transported to a furnace. There the C-TPA is vaporized and certain of
the contained impurities are catalytically destroyed. Catalyst and non-
volatile impurities are removed in a series of filters, after which the pure
TPA is condensed and transported to storage silos.
1-3
5.21.2 Emissions and Controls
A general characterization of the atmospheric emissions from the
production of C-TPA is difficult, because of the variety of processes.
Emissions vary considerably, both qualitatively and quantitatively. The
Mid-Century oxidation process appears to be one of the lowest polluters, and
its predicted preeminence will suppress future emissions totals.
The reactor gas at vent A normally contains nitrogen (from air oxidation);
unreacted oxygen; unreacted £-xylene; acetic acid (reaction solvent); carbon
monoxide, carbon dioxide, and methyl acetate from oxidation of jv-xylene and
acetic acid not recovered by the high pressure absorber; and water. The
quantity of VOC emitted at vent A can vary with absorber pressure and the
temperature of exiting vent gases. During crystallization of terephthalic
acid and separation of crystalized solids from the solvent (by centrifuge or
filters), noncondensible gases carrying VOC are released. These vented
gases and the C-TPA dryer vent gas are combined and released to the atmosphere
at vent B. Different methods used in this process can affect the amounts of
noncondensible gases and accompanying VOC emitted from this vent.
Gases released from the distillation section at vent C are the small
amount of gases dissolved in the feed stream to distillation; the inert gas
used in inert blanketing, instrument purging pressure control; and the VOC
vapors carried by the noncondensable gases. The quantity of this discharge
is usually small.
The gas vented from the bag filters on the product storage tanks (silos)
(D) is dry, reaction generated inert gas containing the VOC not absorbed in
the high pressure absorber. The vented gas stream contains a small quantity
of TPA particulate that is not removed by the bag filters.
Performance of carbon adsorption control technology for a VOC gas
stream similar to the reactor vent gas (A) and product transfer vent gas (D)
has been demonstrated, but, carbon monoxide (CO) emissions will not be
reduced. An alternative to the carbon adsorption system is a thermal oxidizer
which provides reduction of both CO and VOC.
Emission sources and factors for the C-TPA process are presented in
Table 5.21-1.
5.21-4 EMISSION FACTORS 5/83
-------
TABLE 5.21-1. UNCONTROLLED EMISSION FACTORS FOR
CRUDE TEREPHTHALIC ACID MANUFACTURE3
EMISSION FACTOR RATING: C
Emissions (g/kg)
Emission Source
Stream
Designation
(Figure 5.21-1) Nonmethane VOC
b,c
CO1
Reactor vent
Crystallization,
separation, drying vent
Distillation and
recovery vent
Product transfer
vent
A
B
C
D
15
1.9
1.1
1.8
17
-
-
2
Factors are expressed as g of pollutant/kg of product produced.
.Dash = not applicable.
Reference 1. VOC gas stream consists of methyl acetate, _p_-xylene,
and acetic acid. No methane was found.
f^
Reference 1. Typically, thermal oxidation results in >99% reduction
of VOC and CO. Carbon adsorption gives a 97% reduction of VOC
.only (Reference 1).
Stream contains 0.7 g of TPA particulates/kg. VOC and CO emissions
originated in reactor offgas (IG) used for transfer.
References for Section 5.21
1. S. W. Dylewski, Organic Chemical Manufacturing, Volume 7: Selected
Processes, EPA-450/3-80-028b, U. S. Environmental Protection Agency,
Research Triangle Park, NC, January 1981.
2. D. F. Durocher, et al., Screening_Study To Determine Need for Standards
of Performance for New Sources of Dimethyl Terephthalate and Terephthalic
Ac id Manufac turing, EPA Contract No. 68-02-1316, Radian Corporation,
Austin, TX, July 1976.
3. J. W. Pervier, et al., Survey Reports on Atmosp_h_e_ric__Emi_ssions from the
Petrochemical Indus try_,_ Volume II, EPA-450/3-73-005b, U. S. Environmental
Protection Agency, Research Triangle Park, NC, April 1974.
5/83
Chemical Process Industry
5.21-5
-------
-------
5.22 LEAD ALKYL
5.22.1 Process Description^
Two alkyl lead compounds, tetraethyl lead (TEL) and tetramethyl lead
(TML), are used as antiknock gasoline additives. Over 75 percent of the 1973
additive production was TEL, more than 90 percent of which was made by alkyl-
ation of sodium/lead alloy.
Lead alkyl is produced in autoclaves by the reaction of sodium/lead
alloy with an excess of either ethyl (for TEL) or methyl (for TML) chloride in
the presence of acetone catalyst. The reaction mass is distilled to separate
the product, which is then purified, filtered and mixed with chloride/bromide
additives. Residue is sluiced to a sludge pit, from which the bottoms are
sent to an indirect steam dryer, and the dried sludge is fed to a reverberatory
furnace to recover lead.
Gasoline additives are also manufactured by the electrolytic process, ir
tfhich a solution of ethyl (or methyl) magnesium chloride and ethyl (or methyl)
chloride is electrolysed, with lead metal as the anode.
5.22 Emissions and Controls-^
Lead emissions from the sodium/lead alloy process consist of particulate
lead oxide from the recovery furnace (and, to a lesser extent, from the melting
furnace and alloy reactor), alkyl lead vapor from process vents, and fugitive
emissions from the sludge pit.
Emissions from the lead recovery furnace are controlled by fabric filters
or wet scrubbers. Vapor streams rich in lead alkyl can either be incinerated
and passed through a fabric filter or be scrubbed with water prior to incinera-
ting.
Emissions from electrolytic process vents are controlled by using an elev-
ated flare and a liquid incinerator, while a scrubber with toluene as the scrubb-
ing medium controls emissions from the blending and tank car loading/unloading
systems.
12/81 Chemical Process Industry 5.22-1
-------
TABLE 5.22-1. LEAD ALKYL MANUFACTURE LEAD EMISSION FACTORS3
EMISSION FACTOR RATING: B
Process
Electrolyticb
Sodium/lead alloy
Recovery furnace0
Process vents, TEL<*
Process vents, TML^
Sludge pitsd
kg/Mg
0.5
28
2
75
0.6
Lead
Ib/ton
1.0
55
4
150
1.2
aNo information on other emissions from lead alkyl
manufacturing is available. Emission factors are
expressed as weight per unit weight of product.
^References .1-3.
References 1-2, 4.
^Reference 1.
TABLE 5.22-2. LEAD ALKYL MANUFACTURE CONTROL EFFICIENCIES3
Process Control Percent reduction
Sodium/lead alloy Fabric filter 99+
Low energy wet scrubber 80-85
High energy wet scrubber 95-99
aReference 1.
References for Section 5.22
1. Background Information in Support of the Development of Performance
Standards for the j^ead Additive Industry, EPA Contract No. 68-02-2085,
PEDCo-Environmental Specialists, Inc., Cincinnati, OH, January 1976.
2. Control Techniques for Lead Air Emissions, EPA-450/2-77-012, U. S. En-
vironmental Protection Agency, Research Triangle Park, NC, December 1977.
3. W. E. Davis, Emissions Study of Industrial Sources of Lead Air Pollutants,
1970, EPA Contract No. 68-02-0271, W. E. Davis and Associates, Leawood,
KS, April 1973.
4. R. P. Betz, et al. , Economics^ of Lead Removal in Selected Industries,
EPA Contract No. 68-02-0611, Batelle Columbus Laboratories, Columbus,
OH, August 1973.
5.22-2 EMISSION FACTORS 12/81
-------
5.23 PHARMACEUTICALS PRODUCTION
5.23.1 Process Description
Thousands of individual products are categorized as Pharmaceuticals.
These products usually are produced in modest quantities in relatively
small plants using batch processes. A typical pharmaceutical plant will
use the same equipment to make several different products at different
times. Rarely is equipment dedicated to the manufacture of a single
product.
Organic chemicals are used as raw materials and as solvents, and
some chemicals such as ethanol, acetone, isopropanol and acetic anhyd-
ride are used in both ways. Solvents are almost always recovered and
used many times.
In a typical batch process, solid reactants and solvent are charged
to a reactor where they are held (and usually heated) until the desired
product is formed. The solvent is distilled off, and the crude residue
may be treated several times with additional solvents to purify it. The
purified material is separated from the remaining solvent by centrifuge
and finally is dried to remove the last traces of solvent. As a rule,
solvent recovery is practiced for each step in the process where it is
convenient and cost effective to do so. Some operations involve very
small solvent losses, and the vapors are vented to the atmosphere through
a fume hood. Generally, all operations are carried out inside buildings,
so some vapors may be exhausted through the building ventilation system.
Certain Pharmaceuticals - especially antibiotics - are produced by
fermentation processes. In these instances, the reactor contains an
aqueous nutrient mixture with living organisms such as fungi or bacteria.
The crude antibiotic is recovered by solvent extraction and is purified
by essentially the same methods described above for chemically synthe-
sized pharmaceuticals. Similarly, other Pharmaceuticals are produced by
extraction from natural plant or animal sources. The production of
insulin from hog or beef pancreas is an example. The processes are not
greatly different from those used to isolate antibiotics from fermen-
tation broths.
5.23.2 Emissions and Controls
Emissions consist almost entirely of organic solvents that escape
from dryers, reactors, distillation systems, storage tanks and other
operations. These emissions are exclusively nonmethane organic compounds,
Emissions of other pollutants are negligible (except for particulates in
unusual circumstances) and are not treated here. It is not practical to
attempt to evaluate emissions from individual steps in the production
process or to associate emissions with individual pieces of equipment,
because of the great variety of batch operations that may be carried out
10/80
Chemical Process Industry
5.23-1
-------
at a single production plant. It is more reasonable to obtain data on
total solvent purchases by a plant and to assume that these represent
replacements for solvents lost by evaporation. Estimates can be refined
by subtracting the materials that do not enter the air because of being
incinerated or incorporated into the pharmaceutical product by chemical
reaction.
If plant-specific information is not available, industrywide data
may be used instead. Table 5.23-1 lists annual purchases of solvents by
U.S. pharmaceutical manufacturers and shows the ultimate disposition of
each solvent. Disposal methods vary so widely with the type of solvent
that it is not possible to recommend average factors for air emissions
from generalized solvents. Specific information for individual solvents
must be used. Emissions can be estimated by obtaining plant-specific
data on purchases of individual solvents and computing the quantity of
each solvent that evaporates into the air, either from information in
Table 5.23-1 or from information obtained for the specific plant under
consideration. If solvent volumes are given, rather than weights,
liquid densities in Table 5.23-1 can be used to compute weights.
Table 5.23-1 gives for each plant the percentage of each solvent
that is evaporated into the air and the percentage that is flushed into
the sewer. Ultimately, much of the volatile material from the sewer
will evaporate and will reach the air somewhere other than the pharma-
ceutical plant. Thus, for certain applications it may be appropriate to
include both the air emissions and the sewer disposal, in an emissions
inventory that covers a broad geographic area.
Since solvents are expensive and must be recovered and reused for
economic reasons, solvent emissions are controlled as part of the normal
operating procedures in a pharmaceutical industry. In addition, most
manufacturing is carried out inside buildings, where solvent losses must
be minimized to protect the health of the workers. Water or brine
cooled condensers are the most common control devices, with carbon
adsorbers in occasional use. With each of these methods, solvent can be
recovered. Where the main objective is not solvent reuse but is the
control of an odorous or toxic vapor, scrubbers or incinerators are
used. These control systems are usually designed to remove a specific
chemical vapor and will be used only when a batch of the corresponding
drug is being produced. Usually, solvents are not recovered from
scrubbers and reused, and of course, no solvent recovery is possible
from an incinerator.
It is difficult to make a quantitative estimate of the efficiency
of each control method, because it depends on the process being con-
trolled, and pharmaceutical manufacture involves hundreds of different
processes. Incinerators, carbon adsorbers and scrubbers have been
reported to remove greater than 90 percent of the organics in the
control equipment inlet stream. Condensers are limited, in that they
can only reduce the concentration in the gas stream to saturation at the
5.23-2 EMISSION FACTORS 10/80
-------
condenser temperature, but not below that level. Lowering the temper-
ature will, of course, lower the concentration at saturation, but it is
not possible to operate at a temperature below the freezing point of one
of the components of the gas stream.
TABLE 5.23-1.
SOLVENT PURCHASES AND ULTIMATE DISPOSITION BY
PHARMACEUTICAL MANUFACTURERS3
Solvent
Acetic Add
Acetic Anhydride
Acetone
Aceton1tr11e
Amyl Acetate
Amyl Alcohol
Benzene
Blendan (AMOCO)
Butanol
Carbon Tetrachloride
Chloroform
Cyclohexylamine
o-DI chl ore benzene
Dlethylamine
Diethyl Carbonate
Dimethyl Acetamide
Dimethyl Formamide
D1methylsulfo)dde
1 ,4-D1oxane
Ethanol
Ethyl Acetate
Ethyl Bromide
Ethyl ene Glycol
Ethyl Ether
Formaldehyde
Formamide
Freons
Hexane
Isobutyraldehyde
Isopropanol
Isopropyl Acetate
Isopropyl Ether
Methanol
Methyl Cellosolve
Methylene Chloride
Methyl Ethyl Ketone
Methyl Formate
Methyl Isobutyl Ketone
Polyethylene Glycol 600
Pyrldlne
Skelly Solvent B (hcxanes)
Tetr«hydrofur»n
Toluene
Trlchloroethane
Xylene
Annual
Purchase
(metric tons)
930
1,265
12,040
35
285
1,430
1.010
530
320
1,850
500
3,930
60
50
30
95
1,630
750
43
13,230
2,380
45
60
280
30
440
7.150
530
85
3,850
480
25
7,960
195
10,000
260
415
260
3
3
1,410
4
6.010
135
3,090
Ultimate Disposition (percent).
Air
Emissions
1
1
14
83
42
99
29
-
24
11
57
-
2
94
4
7
71
1
5
10
30
,
.
85
19
-
0.1
17
50
14
28
50
31
47
53
65
-
80
-
-
29
-
31
100
6
Sewer
82
57
22
17
58
-
37
_
8
7
5
-
98
6
71
-
3
28
.
6
47
100
100
4
77
67
-
-
SO
17
11
50
45
53
5
12
74
-
-
100
2
-
14
,
19
Incineration
_
38
_
-
~
16
_
1
82
-
,
-
.
-
-
20
71
_
7
20
-
.
-
-
-
_
15
-
17
61
.
14
_
20
23
-
-
-
.
69
100
26
.
70
Solid Waste or
Contract Haul
_
7
_
-
-
8
36
.
38
„
-
.
_
93
6
.
95
1
3
.
.
11
-
26
.
68
-
7
-
-
6
.
22
-
12
29
.
5
Product
17
42
19
„
„
1
10
100
31
_
_
100
_
-
25
_
.
_
_
76
-
_
.
,
4
7
99.9
..
-
45
-
-
4
_
-
-
14
20
100
Liquid Density
Ib/gal ? 68"F
8.7
9.0
6.6
6.6
7.3
6.8
7.3
NA
6.8
13.3
12.5
7.2
10.9
5.9
8.1
7.9
7.9
11.1
8.6
6.6
7.5
12. 1
9.3
6.0
b
9.5
c
5.5
6.6
6.6
7.3
6.0
6.6
8.7
11.1
6.7
8.2
6.7
9.5
8.2
5.6
7.4
7.2
11.3
7.2
These data were reported by 26 member companies of the Pharmaceutical
Manufacturers Association, accounting for 53 percent of pharmaceutical
sales in 1975.
Sold as aqueous solutions containing 37% to 50% formaldehyde by weight.
Some Ereons are gases, and others are liquids weighing 12 - 14 Ib/gal.
10/80
Chemical Process Industry
5.23-3
-------
Reference for Section 5.23
1. Control of Volatile Organic Emissions from Manufacture of
Synthesized Pharmaceutical Products, EPA-450/2-78-029, U. S.
Environmental Protection Agency, Research Triangle Park, NC,
December 1978.
5.23-4 EMISSION FACTORS 10/80
-------
5.24 MALEIC ANHYDRIDE
5.24.1 General1
The dominant end use of maleic anhydride (MA) is in the production of
unsaturated polyester resins. These laminating resins, which have high
structural strength and good dielectric properties, have a variety of
applications in automobile bodies, building panels, molded boats, chemical
storage tanks, lightweight pipe, machinery housings, furniture, radar
domes, luggage and bathtubs. Other end products are fumaric acid,
agricultural chemicals, alkyd resins, lubricants, copolymers, plastics,
succinic acid, surface active agents, and more. In the United States, one
plant uses only n-butane and another uses n-butane for 20 percent of its
feedstock, but the primary raw material used in the production of MA is
benzene. The MA industry is converting old benzene plants and building new
plants to use n-butane. MA also is a byproduct of the production of
phthalic anhydride. It is a solid at room temperature but is a liquid or
gas during production. It is a strong irritant to skin, eyes and mucous
membranes of the upper respiratory system.
The model MA plant, as described in this Section, has a benzene to MA
conversion rate of 94.5 percent, has a capacity of 22,700 megagrams
(25,000 tons) of MA produced per year, and runs 8000 hours per year.
Because of a lack of data on the n-butane process, this discussion
covers only the benzene oxidation process.
2
5.24.2 Process Description
Maleic anhydride is produced by the controlled air oxidation of
benzene, illustrated by the following chemical reaction:
V2°5
2 C,H, +90. » 2 C.H.CL + BLO + 4 C0_
00 L 4 Z j 2 2
MoO
Benzene Oxygen Maleic Water Carbon
anhydride dioxide
Vaporized benzene and air are mixed and heated before entering the
tubular reactor. Inside the reactor, the benzene/air mixture is reacted in
the presence of a catalyst which contains approximately 70 percent vanadium
pentoxide (V 0 ), with usually 25 to 30 percent molybdenum trioxide (Mo03),
forming a vapor of MA, water and carbon dioxide. The vapor, which may also
contain oxygen, nitrogen, carbon monoxide, benzene, maleic acid,
formaldehyde, formic acid and other compounds from side reactions, leaves
the reactor and is cooled and partially condensed so that about 40 percent
of the MA is recovered in a crude liquid state. The effluent is then passed
through a separator which directs the liquid to storage and the remaining
vapor to the product recovery absorber. The absorber contacts the vapor
with water, producing a liquid of about 40 percent maleic acid. The
5/83 Chemical Process Industry 5.24-1
-------
JS
NJ
cn
§
Is
H
O
PC
CO
CO
LO
AIR
MAKEUP
WATER
XYLENE ® WATER
STRIPPER loUT
DEHYDRATION
COLUMN
AGED ANHYDRIDE
STORAGE
KEY
A - PRODUCT RECOVERY ABSORBER VENT
B - VACUUM SYSTEM VENT
C -STORAGE AND HANDLING EMISSIONS
D - SECONDARY EMISSION POTENTIAL
^. EXCESS
WATER
Figure 5.24-1. Process flow diagram for uncontrolled model plant
-------
40 percent mixture is converted to MA, usually by azeotropic distillation
with xylene. Some processes may use a double effect vacuum evaporator at
this point. The effluent then flows to the xylene stripping column where
the xylene is extracted. This MA is then combined in storage with that from
the separator. The molten product is aged to allow color forming impurities
to polymerize. These are then removed in a fractionation column, leaving
the finished product. Figure 5.24-1 represents a typical process.
MA product is usually stored in liquid form, although it is sometimes
flaked and pelletized into briquets and bagged.
2
5.24.3 Emissions and Controls
Nearly all emissions from MA production are from the main process vent
of the product recovery absorber, the largest vent in the process. The
predominant pollutant is unreacted benzene, ranging from 3 to 10 percent of
the total benzene feed. The refining vacuum system vent, the only other
exit for process emissions, produces 0.28 kilograms (0.62 Ib) per hour of MA
and xylene.
Fugitive emissions of benzene, xylene, MA and maleic acid also arise
from the storage (see Section 4.3) and handling (see Section 9.1.3) of
benzene, xylene and MA. Dust from the briquetting operations can contain
MA, but no data are available on the quantity of such emissions.
TABLE 5.24-1.
COMPOSITION OF UNCONTROLLED EMISSIONS FROM PRODUCT
RECOVERY ABSORBER3
Component
Wt 7
W 1_ . A>
kg/Mg
Ib/ton
Nitrogen
Oxygen
Water
Carbon dioxide
Carbon monoxide
Benzene
Formaldehyde
Maleic acid
Formic acid
73.37
16.67
4.00
3.33
2.33
0.33
0.05
0.01
0.01
21,406.0
4,863.0
1,167.0
972.0
680.0
67.0
14.4
2.8
2.8
42,812.0
9,726.0
2,334.0
1,944.0
1,360.0
134.0
28.8
5.6
5.6
Total
29,175.0
58,350.0
Reference 2.
Potential sources of secondary emissions are spent reactor catalyst,
excess water from the dehydration column, vacuum system water, and
fractionation column residues. The small amount of residual organics in the
spent catalyst after washing has low vapor pressure and produces a small
percentage of total emissions. Xylene is the principal organic contaminant
in the excess water from the dehydration column and in the vacuum system
water. The residues from the fractionation column are relatively heavy
5/83
Chemical Process Industry
5.24-3
-------
organics, with a molecular weight greater than 116, and they produce
a small percentage of total emissions.
Benzene oxidation process emissions can be controlled at the main vent
by means of carbon adsorption, thermal incineration or catalytic incineration.
Benzene emissions can be eliminated by conversion to the n-butane process.
Catalytic incineration and conversion from the benzene process to the n-butane
process are not discussed for lack of data. The vent from the refining
vacuum system is combined with that of the main process, as a control for
refining vacuum system emissions. A carbon adsorption system or an incine-
ration system can be designed and operated at a 99.5 percent removal
efficiency for benzene and volatile organic compounds with the operating
parameters given in Appendix D of Reference 2.
TABLE 5.24-2.
EMISSION FACTORS FOR MALEIC ANHYDRIDE PRODUCTION'
EMISSION FACTOR RATING: C
Source
Nonmethane VOC
kg/Mg
Ib/ton
Benzene
kg/Mg
Ib/ton
Product vents
(recovery absorber and
refining vacuum system
combined vent)
Uncontrolled 87
C
With carbon adsorption 0.34
With incineration 0.43
Storage and handling
emissions
e
Fugitive emissions
Secondary emissions N/A
174
0.68
0.86
67.0
0.34
0.34
134.0
0.68
0.68
N/A
N/A
N/A
No data are available for catalytic incineration or for plants producing MA
from n-butane. Dash: see footnote. N/A: not available.
VOC also includes the benzene. For recovery absorber and refining vacuum,
VOC can be MA and xylene; for storage and handling, MA, xylene and dust
from briquetting operations; for secondary emissions, residual organics
from spent catalyst, excess water from dehydration column, vacuum system
water, and fractionation column residues. VOC contains no methane.
Q
Before exhaust gas stream goes into carbon adsorber, it is scrubbed with
caustic to remove organic acids and water soluble organics. Benzene is the
only likely VOC remaining.
See Section 4.3.
£See Section 9.1.3.
Secondary emission sources are excess water from dehydration column, vacuum
system water, and organics from fractionation column. No data are available
on the quantity of these emissions.
5.24-4
EMISSION FACTORS
5/83
-------
Fugitive emissions from pumps and valves may be controlled by an
appropriate leak detection system and maintenance program. No control
devices are presently being used for secondary emissions.
References for Section 5.24
1. B. Dmuchovsky and J. E. Franz, "Maleic Anhydride", Kirk-Othmer
Encyclopedia of Chemical Technology, Volume 12, John Wiley and
Sons, Inc., New York, NY, 1967, pp. 819-837.
2. J. F. Lawson, Emission Control Options for the Synthetic Organic
Chemicals Manufacturing Industry; Maleic Anhydride Product Report,
EPA Contract No. 68-02-2577, Hydroscience, Inc., Knoxville, TN,
March 1978.
5/83
Chemical Process Industry
5.24-5
-------
-------
6. FOOD AND AGRICULTURAL INDUSTRY
Before food and agricultural products are used by the consumer they undergo a number of processing steps,
such as refinement, preservation, and product improvement, as well as storage and handling, packaging, and
shipping. This section deals with the processing of food and agricultural products and the intermediate steps that
present air pollution problems. Emission factors are presented for industries where data were available. The
primary pollutant emitted from these processes is particulate matter.
6.1 ALFALFA DEHYDRATING
6.1.1 General13
Dehydrated alfalfa is a meal product resulting from the rapid drying of alfalfa by artifical means at
temperatures above 212°F (100°C). Alfalfa meal is used in chicken rations, cattle feed, hog rations, sheep feed,
turkey mash, and other formula feeds. It is important for its protein content, growth and reproductive factors,
pigmenting xanthophylls, and vitamin contributions.
A schematic of a generalized alfalfa dehydrator plant is given in Figure 6.1-1. Standing alfalfa is mowed and
chopped in the field and transported by truck to a dehydrating plant, which is usually located within 10 miles of
the field. The truck dumps the chopped alfalfa (wet chops) onto a self-feeder, which carries it into a direct-fired,
rotary drum. Within the drum, the wet chops are dried from an initial moisture content of about 60 to 80 percent
(by weight) to about 8 to 16 percent. Typical combustion gas temperatures within the oil- or gas-fired drums
range from 1800 to 2000°F (980 to 1092°C) at the inlet to 250 to 300°F (120 to 150°C) at the outlet.
From the drying drum, the dry chops are pneumatically conveyed into a primary cyclone that separates them
from the high-moisture, high-temperature exhaust stream. From the primary cyclone, the chops are fed into a
hammermill, which grinds the dry chops into a meal. The meal is pneumatically conveyed from the hammermill
into a meal collector cyclone in which the meal is separated from the airstream and discharged into a holding bin.
Meal is then fed into a pellet mill where it is steam conditioned and extruded into pellets.
From the pellet mill, the pellets are either pneumatically or mechanically conveyed to a cooler, through which
air is drawn to cool the pellets and, in some cases, remove fines. Fines removal is more commonly effected in
shaker screens following or ahead of the cooler, with the fines being conveyed back into the meal collector
cyclone, meal bin, or pellet mill. Cyclone separators may be employed to separate entrained fines in the cooler
exhaust and to collect pellets when the pellets are pneumatically conveyed from the pellet mill to the cooler.
Following cooling and screening, the pellets are transferred to bulk storage. Dehydrated alfalfa is most often
stored and shipped in pellet form; however, in some instances, the pellets may be ground in a hammermill and
shipped in meal form. When the finished pellets or ground pellets are pneumatically transferred to storage or
loadout, additional cyclones may be employed for product airstream separation at these locations.
6.1.2 Emissions and Controlsl'3
Particulate matter is the primary pollutant of concern from alfalfa dehydrating plants although some odors
arise from the organic volatiles driven off during drying. Although the major source is the primary cooling
cyclone, lesser sources include the downstream cyclone separators and the bagging and loading operations.
4/76
6.1-1
-------
Emission factors for the various cyclone separators utilized in alfalfa dehydrating plants are given in Table
6.1-1. Note that, although these sources are common to many plants, there will be considerable variation from
the generalized flow diagram in Figure 6.1-1 depending on the desired nature of the product, the physical layout
of the plant, and the modifications made for air pollution control. Common variations include ducting the
exhaust gas stream from one or more of the downstream cyclones back through the primary cyclone and ducting
a portion of the primary cyclone exhaust back into the furnace. Another modification involves ducting a part of
the meal collector cyclone exhaust back into the hammermill, with the remainder ducted to the primary cyclone
or discharged directly to the atmosphere. Also, additional cyclones may be employed if the pellets are
pneumatically rather than mechanically conveyed from the pellet mill to the cooler or if the finished pellets or
ground pellets are pneumatically conveyed to storage or loadout.
Table 6.1-1. PARTICULATE EMISSION FACTORS FOR ALFALFA DEHYDRATING PLANTS
EMISSION FACTOR RATING: PRIMARY CYCLONES: A
ALL OTHER SOURCES: C
Sources3
Primary cyclone
Meal collector cyclone^
Pellet collector cyclone6
Pellet cooler cyclone^
Pellet regrind cycloneS
Storage bin cyclone^1
Emissions
Ib/ton of product'-1
10C
2.6
Not available
3
8
Neg.
kg/MT of product13
5C
1.3
Not available
1.5
4
Neg.
aThe cyclones used for product/airstream separation are the air pollution sources in alfalfa dehydrating plants.
All factors are based on References 1 and 2.
'-'Product consists of meal or pellets. These factors can be applied to the quantity of incoming wet chops by
dividing by a factor of four.
cThis average factor may be used even when other cyclone exhaust streams are ducted back into the primary
cyclone. Emissions from primary cyclones may range from 3 to 35 Ib/ton (1.5 to 17.5 kg/MT) of product
and are more a function of the operating procedures and process modifications made for air pollution control
than whether other cyclone exhausts are ducted back through the primary cyclone. Use 3 to 15 Ib/ton (1.5 to
7.5 kg/MT) for plants employing good operating procedures and process modifications for air pollution control.
Use higher values for older, unmodified, or less well run plants.
^This cyclone is also called the air meal separator or hammermill cyclone. When the meal collector exhaust is
ducted back to the primary cyclone and/or the hammermill, this cyclone is no longer a source.
^This cyclone will only be present if the pellets are pneumatically transferred from the pellet mill to the pellet
cooler.
fThis cyclone is also called the pellet meal air separator or pellet mill cyclone. When the pellet cooler cyclone
exhaust is ducted back into the primary cyclone, it is no longer a source.
9"This cyclone is also called the pellet regrind air separator. Regrind operations are more commonly found at
terminal storage facilities than at dehydrating plants.
"Small cyclone collectors may be used to collect the finished pellets when they are pneumatically transferred
to storage.
Air pollution control (and product recovery) is accomplished in alfalfa dehydrating plants in a variety of ways.
A simple, yet effective technique is the proper maintenance and operation of the alfalfa dehydrating equipment.
Particulate emissions can be reduced significantly if the feeder discharge rates are uniform, if the dryer furnace is
operated properly, if proper airflows are employed in the cyclone collectors, and if the hammermill is well
maintained and not overloaded. It is especially important in this regard not to overdry and possibly burn the
chops as this results in the generation of smoke and increased fines in the grinding and pelletizing operations.
6.1-2
EMISSION FACTORS
4/76
-------
^
Xi
o
o
§
CL
FRESH-CUT
ALFALFA {WET CHOPS)
FROM FIELD
I
VJ
TRUCK DUMP
AND LIFT
PELLET
COOLER
CYCLONE
SECONDARY
MEAL
COLLECTO
NATURAL
GAS
BURNERS
STORAGE-
LOADOUT
ON
.Figure 6.1-1. Generalized flow diagram for alfalfa dehydration plant.
-------
Equipment modification provides another means of particulate control. Existing cyclones can be replaced with
more efficient cyclones and concomitant air flow systems. In addition, the furnace and burners can be modified
or replaced to minimize flame impingement on the incoming green chops. In plants where the hammermill is a
production bottleneck, a tendency exists to overdry the chops to increase throughput, which results in increased
emissions. Adequate hammermill capacity can reduce this practice.
Secondary control devices can be employed on the cyclone collector exhaust streams. Generally, this practice
has been limited to the installation of secondary cyclones or fabric filters on the meal collector, pellet collector,
or pellet cooler cyclones. Some measure of secondary control can also be effected on these cyclones by ducting
their exhaust streams back into the primary cyclone. Primary cyclones are not controlled by fabric filters because
of the high moisture content in the resulting exhaust stream. Medium energy wet scrubbers are effective in
reducing particulate emissions from the primary cyclones, but have only been installed at a few plants.
Some plants employ cyclone effluent recycle systems for particulate control. One system skims off the
particulate-laden portion of the primary cyclone exhaust and returns it to the furnace for incineration. Another
system recycles a large portion of the meal collector cyclone exhaust back to the hammermill. Both systems can
be effective in controlling particulates but may result in operating problems, such as condensation in the recycle
lines and plugging or overheating of the hammermill.
References for Section 6.1
1. Source information supplied by Ken Smith of the American Dehydrators Association, Mission, Kan.
December 1975.
2. Gorman, P.G. et al. Emission Factor Development for the Feed and Grain Industry. Midwest Research
Institute, Kansas City, Mo. Prepared for Environmental Protection Agency, Research Triangle Park, N.C.
under Contract No. 68-02-1324. Publication No. EPA-450/3-75-054. October 1974.
3. Smith, K.D, Particulate Emissions from Alfalfa Dehydrating Plants - Control Costs and Effectiveness. Final
Report. American Dehydrators Association. Mission, Kan. Prepared for Environmental Protection Agency,
Research Triangle Park, N.C. Grant No. R801446. Publication No, 650/2-74-007. January 1974,
6.1-4 EMISSION FACTORS 4/76
-------
6.2 COFFEE ROASTING
6.2.1 Process Description1'2
Coffee, which is imported in the form of green beans, must be cleaned, blended, roasted, and packaged befoie
being sold. In a typical coffee roasting operation, the green coffee beans are freed of dust and chaff by dropping
the beans into a current of air. The cleaned beans are then sent to a batch or continuous roaster. During the
roasting, moisture is driven off, the beans swell, and chemical changes take place that give the roasted beans their
typical color and aroma. When the beans have reached a certain color, they are quenched, cooled, and stoned.
6.2.2 Emissions1'2
Dust, chaff, coffee bean oils (as mists), smoke, and odors are the principal air contaminants emitted from
coffee processing. The major source of particulate emissions and practically the only source of aldehydes,
nitrogen oxides, and organic acids is the roasting process. In a direct-fired roaster, gases are vented without
recirculation through the flame. In the indirect-fired roaster, however, a portion of the roaster gases are
recirculated and particulate emissions are reduced. Emissions of both smoke and odors from the roasters can be
almost completely removed by a properly designed afterburner.1 '2
Particulate emissions also occur from the stoner and cooler. In the stoner, contaminating materials heavier
than the roasted beans are separated from the beans by an air stream. In the cooler, quenching the hot roasted
beans with water causes emissions of large quantities of steam and some particulate matter.3 Table 6.2-1
summarizes emissions from the various operations involved in coffee processing.
Table 6.2-1. EMISSION FACTORS FOR ROASTING PROCESSES WITHOUT CONTROLS
EMISSION FACTOR RATING: B
Type of process
Roaster
Direct-fired
Indirect -fired
Stoner and cooler0
Instant coffee spray dryer
Pollutant
Particulates3
Ib/ton
7.6
4.2
1.4
1.4d
kg/MT
3.8
2.1
0.7
0.7d
N0xb
Ib/ton
0.1
0.1
—
-
kg/MT
0.05
0.05
—
-
Aldehydes0
Ib/ton
0.2
0.2
—
-
l
-------
References for Section 6.2
%"$**?> R-L. Compilation of Air Pollutant Emission Factors. U.S. DHEW, PHS, National Center for Air
Pollution Control. Durham, N.C. PHS Publication Number 999-AP-42. 1 968. p. 1 9-20.
3" a6 FVAir PoUution in the Coffee RoastinS Industry. Revised Ed. U.S. DHEW, PHS, Division of Air
n. Cincinnati, Ohio. Publication Number 999-AP-9. 1966. WIVIMOU OI Air
6-2-2 EMISSION FACTORS 2/72
-------
6.3 COTTON GINNING
6.3.1 General1
The primary function of a cotton gin is to separate seed from the lint of raw seed cotton. Approximately one
500-pound bale of cotton can be produced from 1 ton of seed cotton. During ginning, lint dust, fine leaves, and
other trash are emitted into the air. The degree of pollution depends on the seed cotton trash content, which
depends on the method used to harvest the cotton. Handpicked cotton has a lower trash content than machine-
stripped cotton.
6.3.2 Process Description2
Figure 6.3-1 is a flow diagram of the typical cotton ginning process. Each of the five ginning steps and
associated equipment is described in the following sections.
6.3.2.1 Unloading System — Trucks and trailers transport seed cotton from the field to the gin. Pneumatic
systems convey the seed cotton from the vehicles or storage houses to a separator and feed control unit. (Some
gins utilize a stone and green boll trap for preliminary trash removal.) The screen assembly in the separator
collects the seed cotton and allows it to fall into the feed control unit. The conveying air flows from the separator
to a cyclone system where it is cleaned and discharged to the atmosphere.
6.3.2.2 Seed Cotton Cleaning System — Seed cotton is subjected to three basic conditioning processes — drying,
cleaning, and extracting — before it enters the gin stand for separation of lint from seed. To ensure adequate
conditioning, cotton gins typically use two conditioning systems in series (see Figure 6.3-1).
Cotton dryers are designed to reduce the moisture content of the seed cotton to an optimum level of 6.5 to 8.0
percent. A push-pull high-pressure fan system conveys seed cotton through the tower dryer to the cleaner, which
loosens the cotton and removes fine particles of foreign matter such as leaf trash, sand, and dirt. Large pieces of
foreign matter (e.g., sticks, stems, and burrs) are removed from the seed cotton by a different process, referred to
as "extracting." Several types of extractors are used at cotton gins: burr machines, stick machines, stick and burr
machines, stick and green leaf extractors, and extractor-feeders. The burr machine removes burrs and
pneumatically conveys them to the trash storage area. The seed cotton then enters a stick (or a stick and green
leaf) machine, which removes sticks, leaves, and stems. Afterwards, the seed cotton is pneumatically conveyed to
the next processing step.
6.3,2.3 Overflow System — From the final conditioning unit, the seed cotton enters a screw conveyor distributor,
which apportions the seed cotton to the extractor-feeders at a controlled rate. When the flow of seed cotton
exceeds the limit of the extractor-feeders, the excess seed cotton flows into the overflow hopper. A pneumatic
system transfers seed cotton from the overflow hopper back to the extractor-feeder as required.
6.3.2.4 Lint Cotton Handling System — Cotton enters the gin stand through a "huller front," which performs
some cleaning. A saw grasps the locks of cotton and draws them through a widely spaced set of "huller ribs,"
which strip off hulls and sticks. The cotton locks are then drawn into the roll box, where seeds are separated from
the fibers. As the seeds are removed, they slide down the face of the ginning ribs and fall to the bottom of the gin
stand for subsequent removal to storage. Cotton lint is removed from the saw by a brush or a blast of air and
conveyed pneumatically to the lint cleaning system for final cleaning and combing. The lint cotton is separated
from the conveying air stream by a separator that forms the lint into a batt. This batt is fed into the first set of lint
cleaners, where saws comb the lint cotton and remove leaf particles, grass, and motes.
12/77 Food and Agricultural Industry 6.3-1
-------
w
w
i
Pfl
Cfl
to
SEED COTTON CLEANING SYSTEM
LINT-COTTON HANDLING SYSTEM
r
(\ SCREW
V/CO«VEYOR
L ___ ' _____ L ___________ , L ___ ; __
Figure 6.3-1 . Flow diagram of cotton ginning process.^
A • AIR
T •TRASH
S -SEEDCOTTDN
C - COTTONSEED
L -LINT COTTON
NG • NATURAL GAS
-------
6.3.2.5 Battery Condenser and Baling System — Lint cotton is pneumatically transported from the lint cleaning
system to a battery condenser, which consists of drums equipped with screens that separate the lint cotton from
the conveying air. The conveying air is then discharged through an in-line filter or cyclones before being
exhausted to the atmosphere. The batt of lint cotton is then fed into the baling press, which packs it into uniform
bales of cotton,
6.3.3 Emissions and Controls
The major sources of particulates from cotton ginning can be arranged into 10 emission source
categories based on specific ginning operations (Figure 6.3-2). Three primary methods of participate
control are in use: (1) high efficiency cyclones on the high-pressure fan discharges with collection
efficiencies greater than 99 percent,2 (2) in-line filters on low-pressure fan exhaust vents with
efficiencies of approximately 80 percent, and (3) fine screen coverings on condenser drums in the low-
pressure systems with efficiencies of approximately 50 percent.*'4 The unifilter is a new concept for
collecting all wastes from cotton gins. It is designed to replace all cyclones, in-line filters, and covered
condenser drums, and has a collection efficiency of up to 99 percent.5
Table 6.3-1 presents emission factors from uncontrolled cotton ginning operations.1
Table 6.3-2 presents emission factors for a typical cotton gin equipped with available control
devices; the data base involved cotton gins with a variety of different control devices, including
cyclones, in-line filters, screen coverings, and unifilters.2'6-9 The total emission factor can be expected
to vary by roughly a factor of two, depending on the type of seed cotton, the trash content of the seed
cotton, the maintenance of control devices, and the plant operation procedures.
12/77 Food and Agricultural Industry 6.3-3
-------
(REMISSIONS
(8) EMISSIONS
(10) EMISSIONS-*
UNLOADING
SYSTEM
I SEED COTTON
CLEANING
NO. 1 DRYER AND
CLEANER
NO. 2 DRYER AND
CLEANER
EXTRACTOR/FEEDER
DISTRIBUTOR
nio.i LINT
CLEANER
NO. Z LINT
CLEANER
BATTERY CONDENSER
AND
BALING PRESS
TRASH STORAGE
*• EMISSIONS (1)
*- EMISSIONS (2)
REMISSIONS (3)
EMISSIONS (5)
REMISSIONS (6)
REMISSIONS (7)
REMISSIONS (9)
6.3-4
Figure 6.3-2. Emissions from a typical ginning operation.
EMISSION FACTORS 12/77
-------
Table 6.3-1. EMISSION FACTORS FOR COTTON GINNING
OPERATIONS WITHOUT CONTROL" b
EMISSION FACTOR RATING: C
Process
Unloading fan
Seed cotton
cleaning system
Cleaners
and dryersd
Stick and burr
machine
Miscellaneous6
Total
Estimated total
particulate
Ib/bale
5
1
3
3
12
kg/bale
2.27
0.45
1.36
1.36
5.44
Particulates
>100(im
settled out, %c
0
70
95
50
—
Estimated emission
factor (released
to atmosphere)
Ib/bale
5.0
0.3
0.2
1.5
7.0
kg/bale
2.27
0.14
0.09
0.68
3.2
"Reference 1.
'•'One bale weighs 500 pounds (226 kilograms).
Percentage of the particles that settle out in the plant.
dCorresponds to items 1 and 2 in Table 6.3-2.
Corresponds to items 4 through 9 in Table 6.3-2.
12/77
Table 6.3-2. PARTICULATE EMISSION FACTORS
FOR COTTON GINS WITH CONTROLS*
EMISSION FACTOR RATING: C
Emission sourceb
1. Unloading fan
2. No. 1 dryer and cleaner
3. No. 2 dryer and cleaner
4. Trash fan
5. Overflow fan
6. No. 1 lint cleaner condenser
7. No. 2 lint cleaner condenser
8. Mote fan
9. Battery condenser
10. Master trash fan
Total
lb/balec
0.32
0.18
0.10
0.04
0.08
0.81
0.15
0.20
0.19
0.17
2.24
9/k9
0.64
0.36
0.20
0.08
0.16
1.62
0.30
0.40
0.38
0.34
4.48
Emission factor
"References 2,6-9.
Numbers correspond to those in Figure 6.3-2.
CA bale of cotton weighs 500 pounds (227 Kilograms).
Food and Agricultural Industry
6.3-5
-------
References for Section 6.3
1. Air-borne Paniculate Emissions from Cotton Ginning Operations. U.S. Department of Health,
Education and Welfare, Public Health Service, Taft Sanitary Engineering Center. Cincinnati,
Oh. 1960.
2. Source Assessment Document No. 27, Cotton Gins. Monsanto Research Corporation. Dayton, Oh.
Prepared for U.S. Environmental Protection Agency, Research Triangle Park, N.C. Publication
No. EPA-600/2-78-004a. December 1975.
3. McCaskill, O.L. and R. A. Wesley. The Latest in Pollution Control. Texas Cotton Ginners' Journal
and Yearbook. 1974.
4. Baker, Roy. F.|and;Calvin B. Parnell, Jr. Three Types of Condenser Filters for Fly Lint and Dust
Control at Cotton Gins. U.S. Department of Agriculture, Agriculture Research Service. Beltsville,
Md. ARS-42-192. September 1971.
5. McCaskill, O.L. and R.A. Wesley. Unifilter Collecting System for Cotton-gin Waste Materials.
U.S. Department of Agriculture, Agriculture Research Service. New Orleans, La. ARS-S-144.
September 1976.
6. Parnell, C.B., Jr. and Roy V. Baker. Particulate Emissions of a Cotton Gin in the Texas Stripper
Area. U.S. Department of Agriculture, Agriculture Research Service. Washington, D.C.
Production Research Report No. 149. May 1973.
7. Kirk, I.W., T.E. Wright, and K.H. Read. Particulate Emissions from Commercial Cotton Ginning
Operations. Southwestern Cotton Ginning Research Laboraory, Mesilla Park, New Mexico.
Presented at ASAE 1976 Winter Meeting, Chicago, Illinois. December 1976.
8. Cotton Gin Emission Tests, Marana Gin, Producers Cotton Oil Company, Marana, Arizona.
National Enforcement Investigations Center, Denver, Colo, and EPA Region IX. Publication No.
EPA-330/2-78-008. May 1978.
9. Emission Test Report, Westside Farmers' Cooperative Gin #5, Tranquility, California. PEDCo
Environmental, Inc., Cincinnati, Ohio. Prepared for U.S. EPA Division of Stationary Source
Enforcement, Contract No. 68-01-4147, Task No. 47, PN 3370-2-D. February 1978.
6.3-6
EMISSION FACTORS
12/77
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6.4 FEED AND GRAIN MILLS AND ELEVATORS
6.4.1 General1"3
Grain elevators are buildings in which grains are gathered, stored, and discharged for use, further
processing, or shipping. They are classified as "country," "terminal," and "export" elevators, according
to their purpose and location. At country elevators, grains are unloaded, weighed, and placed in
storage as they are received from farmers residing within about a 20-mile radius of the elevator. In
addition, country elevators sometimes dry or clean grain before it is shipped to terminal elevators or
processors.
Terminal elevators receive most of their grain from country elevators and ship to processors, other
terminals, and exporters. The primary functions of terminal elevators are to store large quantities of
grain without deterioration and to dry, clean, sort, and blend different grades of grain to meet buyer
specifications.
Export elevators are similar to terminal elevators except that they mainly load grain on ships for]
export.
Processing of grain in mills and feed plants ranges" from very simple mixing steps to complex!
industrial processes. Included are such diverse processes as: (1) simple mixing operations in feed mills,
(2) grain milling in flour mills, (3) solvent extracting in soybean processing plants, and (4) a complex
. series of processing steps in a corn wet-milling plant. j
6.4.2 Emissions and Controls
Grain handling, milling, and processing include a variety of operations from the initial receipt of
the grain at either a country or terminal elevator to the delivery of a finished product. Flour, livestock
feed, soybean oil, and corn syrup are among the products produced from plants in the grain and feed
industry. Emissions from the feed and grain industry can be separated into two general areas, those
occurring at grain elevators and those occurring at grain processing operations.
6.4.2.1 Grain Elevators - Grain elevator emissions can occur from many different operations in the
elevator including unloading (receiving), loading (shipping), drying, cleaning, headhouse (legs),
tunnel belt, gallery belt, and belt trippers. Emission factors for these operations at terminal, country,
and export elevators are presented in Table 6.4-1. All of these emission factors are approximate average
values intended to reflect a variety of grain types. Actual emission factors for a specific source may be
considerably different, depending on the type of grain, i.e., corn, soybeans, wheat, and other factors
such as grain quality.
The emission factors shown in Table 6.4-1 represent the amount of dust generated per ton of grain
processed through each of the designated operations (i.e., uncontrolled emission factors). Amounts of
grain processed through each of these operations in a given elevator are dependent on such factors as
the amount of grain turned (interbin transfer), amount dryed, and amount cleaned, etc. Because the
amount of grain passing through each operation is often difficult to determine, it may be more useful
to express the emission factors in terms of the amount of grain shipped or received, assuming these
amounts are about the same over the long term. Emission factors from Table 6.4-1 have been modified
accordingly and are shown in Table 6.4-2 along with the appropriate multiplier that was used as repre-
sentative of typical ratios of throughput at each operation to the amount of grain shipped or received.
This ratio is an approximate value based on average values for turning, cleaning, and drying in each
4/77 Food and Agricultural Industry 6.4-1
-------
type of elevator. However, because operating practices in individual elevators are different, these)
ratios, like the basic emission factors themselves, are more valid when applied to a group of elevators
rather than individual elevators.
Table 6.4-1. PARTICULATE EMISSION FACTORS
FOR UNCONTROLLED GRAIN ELEVATORS
EMISSION FACTOR RATING: B
Type of source
Terminal elevators
Unloaded (receiving)
Loading (shipping)
Removal from bins (tunnel belt)
Drying"
Cleaning0
Headhouse (legs)
Tripper (gallery belt)
Country elevators
Unloading (receiving)
Loading (shipping)
Removal from bins
Dryingb
Cleaning0
Headhouse (legs)
Export elevators
Unloading (receiving)
Loading (shipping)
Removal from bins (tunnel belt)
Drying"
Cleaning0
Headhouse (legs)
Tripper (gallery belts)
Emission factor3
Ib/ton
1.0
0.3
1.4
1.1
3.0
1.5
1.0
0.6
0.3
1.0
0.7
3.0
1.5
1.0
1.0
1.4
1.1
3.0
1.5
1.0
kg/MT
0.5
0.2
1.7
0.6
1.5
0.8
0.5
0.3
0.2
0.5
0.4
1.5
0.8
0.5
0.5
0.7
0.5
1.5
0.8
0.5
aEmission factors are in terms of pounds of dust emitted per ton of
grain processed by each operation. Most of the factors for terminal
and export elevators are based on Reference 1. Emission factors
for drying are based on References 2 and 3. The emission factors
for country elevators are based on Reference 1 and specific country
elevator test data in References 4 through 9.
"Emission factors for drying are based on 1.8 Ib/ton for rack dryers
and 0.3 Ib/ton for column dryers prorated on the basis of distribu-
tion of these two types of dryers in each elevator category, as
discussed in Reference 3.
cEmission factor of 3.0 for cleaning is an average value which may
range from <0.5 for wheat up to 6.0 for corn.
The factors in Tables 6.4-1 or 6.4-2 should not be added together in an attempt to obtain a single
emission factor value for grain elevators because in most elevators some of the operations are
equipped with control devices and some are not. Therefore, any estimation of emissions must be
directed to each operation and its associated control device, rather than the elevator as a whole, unless
the purpose was to estimate total potential (i.e., uncontrolled) emissions. An example of the use of
emission factors in making an emission inventory is contained in Reference 3.
6.4-2
EMISSION FACTORS
4/77
-------
Table 6.4-2. PARTICULATE EMISSION FACTORS FOR GRAIN ELEVATORS BASED ON
AMOUNT OF GRAIN RECEIVED OR SHIPPED3
Type of source
Terminal elevators
Unloading (receiving)
Loading (shipping)
Removal from bins (tunnel belt)
Drying13
Cleaning0
Headhouse (legs)
Tripper (gallery belt)
Country elevators
Unloading (receiving)
Loading (shipping)
Removal from bins
Drying13
Cleaning1-
Headhouse (legs)
Export elevators
Unloading (receiving)
Loading (shipping)
Removal from bins (tunnel belt)
Dryingb
Cleaning0
Headhouse (legs)
Tripper (gallery belt)
Emission factor,
Ib/ton processed
1.0
0.3
1,4
1.1
3.0
1.5
1.0
0.6
0.3
1.0
0.7
3.0
1.5
1.0
1.0
1.4
1.1
3.0
1.5
1.0
X
Typical ratio of tons processed
to tons received or shipped^
1.0
1.0
2.0
0.1
0.2
3.0
1.7
1.0
1.0
2.1
0.3
0.1
3.1
1.0
1.0
1.2
0.01
0.2
2.2
1.1
=
Emission factor,
Ib/ton received or shipped
1.0
0.3
2.8
0.1
0.6
4.5
1.7
0.6
0.3
2.1
0.2
0.3
4.7
1.0
1.0
1.7
0.01
0.6
3.3
1.1
3Assume that over the long term the amount received is approximately equal to amount shipped.
bSee Noteb in Table 6.4-1.
cSee Notec in Table 6.4-1.
"Ratios shown are average values taken from a survey of many elevators across the U.S.^ These ratios can be considerably different
for any individual elevator or group of elevators in the same locale.
Some of the operations listed in the table, such as the tunnel belt and belt tripper, are internal or
in-house dust sources which, if uncontrolled, might show lower than expected atmospheric emissions
because of internal settling of dust. The reduction in emissions via internal settling is not known,
although it is possible that all of this dust is eventually emitted to the atmosphere due to subsequent
external operations, internal ventilation, or other means.
Many elevators utilize control devices on at least some operations. In the past, cyclones have com-
monly been applied to legs in the headhouse and tunnel belt hooding systems. More recently, fabric
filters have been utilized at many elevators on almost all types of operations. Unfortunately, some
sources in grain elevators present control problems. Control of loadout operations is difficult because
of the problem of containment of the emissions. Probably the most difficult operation to control,
because of the large flow rate and high moisture content of the exhaust gases, is the dryers. Screen-
houses or continuously vacuumed screen systems are available for reducing dryer emissions and have
been applied at several facilities. Detailed descriptions of dust control systems for grain elevator oper-
ations are contained in Reference 2.
6.4.2.2 Grain Processing Operations - Grain processing operations include many of the operations
performed in a grain elevator in addition to milling and processing of the grain. Emission factors for
different grain milling and processing operations are presented in Table 6.4-3, Brief discussions of
these different operations and the methods used for arriving at the emission factor values shown in
Table 6.4-3 are presented below.
4/77
Food and Agricultural Industry
6.4-3
-------
Table 6.4-3. PARTICULATE EMISSION FACTORS
FOR GRAIN PROCESSING OPERATIONSl-2,3
EMISSION FACTOR RATING: D
Type of source
Feed mills
Receiving
Shipping
Handling
Grinding
Pellet coolers
Wheat mills
Receiving
Precleaning and handling
Cleaning house
Millhouse
Durum mills
Receiving
Precleaning and handling
Cleaning house
Millhouse
Rye milling
Receiving
Precleaning and handling
Cleaning house
Millhouse
Dry corn milling
Receiving
Drying
Precleaning and handling
Cleaning house
Degerming and milling
Oat milling
Total
Rice milling
Receiving
Handling and precleaning
Drying
Cleaning and millhouse
Soybean mills
Receiving
Handling
Cleaning
Drying
Cracking and dehulling
Hull grinding
Emission factor3-'3
(uncontrolled except where indicated)
Ib/ton
1.30
0.50
3.00
0.1 Oc
0.1 QC
1.00
5.00
70.00
1.00
5.00
1.00
.5.00
70.00
1.00
0.50
5.00
6.00
2.5Qd
0.64
5.00
1.60
5.00
7.20
3.30
2.00
kg/MT
0.65
0.25
1.50
0.05C
0.05C
0.50
2.50
35.00
0.50
2.50
0.50
2.50
35.00
0.50
0.25
2.50
3.00
1.25d
0.32
2.50
0.80
2.50
3.60
1.65
1.00
6.4-4
EMISSION FACTORS
4/77
-------
Table 6.4-3 (continued). PARTICULATE EMISSION FACTORS
FOR GRAIN PROCESSING OPERATIONS1,2,3
EMISSION FACTOR RATING: D
Type of source
Bean conditioning
Flaking
Meal dryer
Meal cooler
Bulk loading
Corn wet milling
Receiving
Handling
Cleaning
Dryers
Bulk loading
Emission factora.b
(uncontrolled except where indicated)
Ib/ton
0.10
0.57
1.50
1.80
0.27
1.00
5.00
6.00
-
-
kg/MT
0.05
0.29
0.75
0.90
0.14
0.50
2.50
3.00
-
-
aEmission factors are expressed in terms of pounds of dust emitted per ton of grain
entering the plant (i.e., received), which is not necessarily the same as the amount
of material processed by each operation.
"Blanks indicate insufficient information.
"-Controlled emission factor (controlledwith cyclones).
Controlled emission factor.(This represents several sources in one plant; some
controlled with cyclones and others controlled with fabric filters.)
Emission factor data for feed mill operations are sparse. This is partly due to the fact that many
ingredients, whole grain and other dusty materials (bran, dehydrated alfalfa, etc.), are received by
both truck and rail and several unloading methods are employed. However, because some feed mill
operations (handling, shipping, and receiving) are similar to operations in a grain elevator, an emis-
sion factor for each of these different operations was estimated on that basis. The remaining
operations are based on information in Reference 2.
Three emission areas for wheat mill processing operations are grain receiving and handling, clean-
ing house, and milling operations. Data from Reference 1 are used to estimate emissions factors for
grain receiving and handling. Data for the cleaning house are insufficient to estimate an emission
factor, and information contained in Reference 2 is used to estimate the emission factor for milling
operations. The large emission factor for the milling operation is somewhat misleading because almost
all of the sources involved are equipped with control devices to prevent product losses; fabric filters
are widely used for this purpose.
Operations for durum mills and rye milling are similar to those of wheat milling. Therefore, most
of these emission factors are assumed equal to those for wheat mill operations.
The grain unloading, handling, and cleaning operations for dry corn milling are similar to those in
other grain mills, but the subsequent operations are somewhat different. Also, some drying of corn
received at the mill may be necessary prior to storage. An estimate of the emission factor for drying is
obtained from Reference 2. Insufficient information is available to estimate emission factors for
degerming and milling.
Information necessary to estimate emissions from oat milling is unavailable, and no emission
factor for another grain is considered applicable because oats are reported to be dustier than many
other grains. The only emission factor data available are for controlled emissions.2 An overall con-
trolled emission factor of 2.5 Ib/ton is calculated from these data.
4/77
Food and Agricultural Industry
6.4-5
-------
Emission factors for rice milling are based on those for similar operations in other grain handling
facilities. Insufficient information is available to estimate emission factors for drying, cleaning, and
mill house operations.
Information contained in Reference 2 is used to estimate emission factors for soybean mills.
Emissions information on corn wet-milling is unavailable in most cases due to the wide variety of
products and the diversity of operations. Receiving, handling, and cleaning operations emission
factors are assumed to be similar to those for dry corn milling.
Many of the operations performed in grain milling and processing plants are the same as those in
grain elevators, so the control methods are similar. As in the case of grain elevators, these plants often
use cyclones or fabric filters to control emissions from the grain handling operations (e.g.', unloading,
legs, cleaners, etc.). These same devices are also often used to control emissions from other processing
operations; a good example of this is the extensive use of fabric filters in flour mills. However, there are
also certain operations within some milling operations that are not amenable to use of these devices.
Therefore, wet scrubbers have found some application, particularly where the effluent gas stream has
a high moisture content. Certain other operations have been found to be especially difficult to control,
such as rotary dryers in wet corn mills. Descriptions of the emission control systems that have been
applied to operations within the grain milling and processing industries are contained in Reference 2.
This section was prepared for EPA by Midwest Research Institute.10
References for Section 6.4
1. Gorman, P.G. Potential Dust Emission from a Grain Elevator in Kansas City, Missouri. Prepared
by Midwest Research Institute for Environmental Protection Agency, Research Triangle Park,
N.C. under Contract No. 68-02-0228, Task Order No. 24. May 1974.
2. Shannon, L.J. et al. Emission Control in the Grain and Feed Industry , Volume I - Engineering
and Cost Study. Final Report. Prepared for Environmental Protection Agency by Midwest
Research Institute. Document No. EPA-450/3-73-003a. Research Triangle Park, N.C. December
1973.
3. Shannon, L.J. et al. Emission Control in the Grain and Feed Industry, Volume II - Emission
Inventory. Final Report. Prepared by Midwest Research Institute for Environmental Protection
Agency, Research Triangle Park, N.C. Report No. EPA-450/3-73-003b. September 1974
4. Maxwell, W.H. Stationary Source Testing of a Country Grain Elevator at Overbrook, Kansas.
Prepared by Midwest Research Institute for Environmental Protection Agency under EPA
Contract No. ' 02-1403. Research Triangle Park, N.C. February 1976.
5. Maxwell, W.H. Stationary Source Testing of a Country Grain Elevator at Great Bend, Kansas.
Prepared by Midwest Research Institute for Environmental Protection Agency under EPA
Contract No. 68-02-1403. Research Triangle Park, N.C. April 1976.
6. Belgea, F.J. Cyclone Emissions and Efficiency Evaluation. Report submitted to North Dakota
State Department of Health on tests at an elevator in Edenburg, North Dakota, by Pollution
Curbs, Inc. St. Paul, Minnesota. March 10, 1972.
7. Trowbridge, A.L. Particulate Emission Testing - ERC Report No. 4-7683. Report submitted to
North Dakota State Department of Health on tests at an elevator in Egeland, North Dakota, by
Environmental Research Corporation. St. Paul, Minnesota. January 16, 1976.
6.4-6 EMISSION FACTORS 4/77
-------
9.
10.
Belgea, F J. Grain Handling Dust Collection Systems Evaluation for Farmers Elevator Company
Mmot, North Dakota. Report submitted to North Dakota State Department of Health, by
Pollution Curbs, Inc. St. Paul, Minnesota. August 28, 1972.
Belgea, FJ. Cyclone Emission and Efficiency Evaluation. Report submitted to North Dakota
State Department of Health on tests at an elevator in Thompson, North Dakota, by Pollution
Curbs, Inc. St. Paul, Minnesota. March 10, 1972.
Schrag, M.P. et al. Source Test Evaluation for Feed and Grain Industry. Prepared by Midwest
Research Institute, Kansas City, Mo., for Environmental Protection Agency, Research Triangle
Park, N.C., under Contract No. 68-02-1403, Task Order No. 28. December 1976. Publication No
EPA-450/3-76-043.
4/77
Food and Agricultural Industry
6.4-7
-------
-------
6.5 FERMENTATION
6.5.1 Process Description'
For the purpose of this report only the fermentation industries associated with food will be considered. This
includes the production of beer, whiskey, and wine.
The manufacturing process for each of these is similar. The four main brewing production stages and their
respective sub-stages are: (1) brewhouse operations, which include (a) malting of the barley, (b) addition of
adjuncts (corn, grits, and rice) to barley mash, (c) conversion of starch in barley and adjuncts to maltose sugar by
enzymatic processes, (d) separation of wort from grain by straining, and (e) hopping and boiling of the wort; (2)
fermentation, which includes (a) cooling of the wort, (b) additional yeast cultures, (c) fermentation tor 7 to 10
days, (d) removal of settled yeast, and (e) filtration and carbonation; (3) aging, which lasts from 1 to 2 months
under refrigeration; and (4) packaging, which includes (a) bottling-pasteurization, and (b) racking draft beer.
The major differences between beer production and whiskey production are the purification and distillation
necessary to obtain distilled liquors and the longer period of aging. The primary difference between wine making
and beer making is that grapes are used as the initial raw material in wine rather than grains.
Food and Agricultural Industry 6.5-1
-------
Table 6.5-1. EMISSION FACTORS FOR FERMENTATION PROCESSES
EMISSION FACTOR RATING: E
Type of
product
Partlculates
Ib/ton
kg/MT
Hydrocarbons
Ib/ton
kg/MT
Beer
Grain handling3
Drying spent grains, etc.3
Whiskey
Grain handling3
Drying spent grains, etc.3
Aging
Wine
See Subsection 6.5.1
3
5
-
1.5
2.5
—
j •
I _
j NA
j 10=
—
NA
0.024d
See Subsection 6.5.2
aBased on section on grain processing.
bNo emission factor available, but emissions do occur.
cPounds per year per barrel of whiskey stored.
dKilograms per year per liter of whiskey stored.
eNo significant emissions.
References for Section 6.5
1 Air pollutant Emission Factors. Final Report. Resources Research, Inc. Reston, Va. Prepared for National
Air Pollution Control Administration, Durham, N.C., under Contract Number CPA-22-69-119. April 1970.
2. Shreve, R.N. Chemical Process Industries, 3rd Ed. New York, McGraw-Hill Book Company. 1967. p.
591-608.
6.5-2
EMISSION FACTORS
2/72
-------
6.5.1. BEER MAKING
6.5.1.1 General1"
Beer is a beverage of low alcoholic content (2-7 percent)
made by the fermentation of malted starchy cereal grains. Barley
is the principal grain used. The production of beer is carried out
in four major stages, brewhouse operations, fermentation, aging and
packaging. These processes are shown in Figure 6.5.1-1.
Brewhouse operations include malting of the barley, addition
of adjuncts to the barley mash, conversion of the starch in the
barley and adjuncts to maltose sugar, separation of wort from the
grain, and hopping and boiling of the wort.
In malting, barley is continuously moistened to cause it to
germinate. With germination, enzymes are formed which break down
starches and proteins to less complex water soluble compounds. The
malted barley is dried to arrest the enzyme formation and is ground
in a malt or roll mill. Adjuncts, consisting of other grains
(ground and unmalted), sugars and syrups, are added to the ground
malted barley and, with a suitable amount of water, are charged to
the mash tun (tank-like vessel). Conversion of the complex
carbohydrates (starch and sugars) and proteins to simpler water
soluble fermentable compounds by means of enzyme action takes
place in the mash tun, a process called mashing. The mash is sent
to a filter press or straining tub (lauter tun) where the wort
(unfermented beer) is separated from the spent grain solids. Hops
are added to the wort in a brew kettle, where the wort is boiled
one and a half to three hours to extract essential substances from
the hops, to concentrate the wort, and to destroy the malt enzymes.
The wort is strained to remove hops, and sludge is removed by a
filter or centrifuge.
Wort is cooled to 10°C (50°F) or lower. During cooling, it
absorbs air necessary to start fermentation. The yeast is added
and mixed with the wort in line to the fermentation starter tanks.
Fermentation, the conversion of the simple sugars in the wort to
ethanol and carbon dioxide, is completed in a closed fermenter.
The carbon dioxide gas released by the fermentation is collected
and later used for carbonating the beer. Cooling to maintain
proper fermentation temperature is required because the reaction is
exothermic.
After fermentation is complete, beer is stored to age for
several weeks at 0°C (32°F) in large closed tanks. It is recar-
bonated, pumped through a pulp filter, pasteurized at 60°C (140°F)
to make it biologically stable, and packaged in bottles and cans.
Beer put in kegs for draft sale is not pasteurized.
4/81 Food and Agricultural Industry 6.5.1-1
-------
c
Teast
starter
tub
f >b
( tfermenter 11^
v
(storage )
77
--^ 1
C02
L-- —
^Filter J
[Pasteurizer
/ Packager /
)
Figure 6.5.1-1. Flow diagram of a beer making process,
2-7
6.5.1.2 Emissions and Controls
The major emissions from beer making and their sources are
particulates and volatile organics, mainly ethanol, from spent
grain drying, and particulates from grain handling. Volatile
organics (VOC) from fermentation are negligible, and they are
fugitive because the fermenters are closed to provide for collecting
carbon dioxide. Other brewery processes are minor sources of
volatile organics, ethanol and related compounds, such as boiling
6.5.1-2
EMISSION FACTORS
4/81
-------
wort in the brew kettle and malt drying. An estimate of these
emissions is not available.
Fugitive particulate emissions from grain handling and milling
at breweries are reduced by operating in well ventilated, low
pressure conditions. At grain handling and milling operations,
fabric filters are most often used for dust collection. Organics
and organic particulate matter from spent grain drying can be
controlled by mixing the dryer exhaust with the combustion air of a
boiler. A centrifugal fan wet scrubber is the most commonly used
control.
TABLE 6.5.1-1. EMISSION FACTORS FOR BEER BREWING3
EMISSION FACTOR RATING: D
Source
Grain handling
Brew kettle
Spent grain drying
Cooling units
Fermentation
Particulate
1.5 (3)b
2.5 (5)b
Volatile Organic Compounds
c
NA
1.31 (2.63)d
NAC
Neg
a 6
Expressed in terms of kg/10 g (Ib/ton) of grain handled. Blanks
.indicate no emissions.
Reference 6.
£
Factors not available, but negligible amounts of ethanol emissions
,are suspected.
Reference 4. Mostly ethanol.
Negligible amounts of ethanol, ethyl acetate, isopropyl alcohol,
n-propyl alcohol, isoamyl alcohol, and isoamyl acetate emissions
are suspected.
References for Section 6.5.1
1. H.E. Htfyrup, "Beer and Brewing", Kirk-Othmer Encyclopedia of
Chemical Technology, Volume 3, John Wiley and Sons, Inc.,
New York, 1964, pp. 297-338.
2. R. Norris Shreve, Chemical Process Industries, 3rd Ed.,
McGraw-Hill Book Company, New York, 1967, pp. 603-605.
3. E.G. Cavanaugh, et al., Hydrocarbon Pollutants from Stationary
Sources, EPA-600/7-77-110, U.S. Environmental Protection Agency,
Research Triangle Park, NC, September 1977.
4/81
Food and Agricultural Industry
6.5.1-3
-------
4. H.W. Bucon, et al., Volatile Organic Compound (VOC) Species
Data Manual, Second Edition, EPA-450/4-80-015, U.S. Environmental
Protection Agency, Research Triangle Park, NC, December 1978.
5. Melvin W. First, et al., "Control of Odors and Aerosols from
Spent Grain Dryers", Journal of the Air Pollution Control
Association. 24_(7): 653-659, July 1974.
6. AEROS Manual Series, Volume V; AEROS Manual of Codes,
EPA-450/2-76-005, U.S. Environmental Protection Agency, Research
Triangle Park, NC, April 1976.
7. Peter N. Formica, Controlled and Uncontrolled Emission Rates
and Applicable Limitations for Eighty Processes, EPA-340/1-78-004,
U.S. Environmental Protection Agency, Research Triangle Park,
NC, April 1978.
6.5.1-4
EMISSION FACTORS
4/81
-------
6.5.2 WINE MAKING
6.5.2.1 General1"4
Wine is made by the fermentation of the juice of certain fruits,
chiefly grapes. The grapes are harvested when the sugar content is
right for the desired product, generally around 20 percent sugar by
weight. The industry term for grape sugar content is Degrees Brix, with
1 °Brix equal to 1 gram of sugar per 100 grams of juice.
The harvested grapes are stemmed and crushed, and the juice is
extracted. Sulfurous acid, potassium metabisulfite or liquefied SC>2 is
used to produce 50 to 200 mg of S02, which is added to inhibit the
growth of undesirable bacteria and yeasts. For the making of a white
wine, the skins and solids are removed from the juice before fermen-
tation. For a red wine, the skins and solids, which color the wine, are
left in the juice through the fermentation stage. The pulpy mixture of
juice, skins and solids is called a "must".
White wine is generally fermented at about 52°F (11°C), and red
wine at about 80°F (27°C). Fermentation takes a week to ten days for
white wine and about two weeks for red. Fermentation is conducted in
tanks ranging in size from several thousand gallons to larger than
500,000 gallons.
The sugar of the fruit juice is converted into ethanol by the
reaction:
C6Hi206 -> 2 C2H5OH + 2 C02
(sugar) (ethanol)
This process takes place in the presence of a specially cultivated
yeast. Theoretically, the yield of ethanol should be 51.1 percent by
weight of the initial sugar. The actual yield is found to be around 47
percent. The remaining sugar is lost as alcohol or byproducts of complex
chemical mechanisms, or it remains in the wine as the result of incomplete
fermentation.
When fermentation is complete, the wine goes through a finishing
process for clarification. Common clarification procedures are filtr-
ation, fining refrigeration, pasteurization and aging. The wine is then
bottled, corked or capped, labeled and cased. The finer red and white
table wines are aged in the bottle.
1 2
6.5.2.2 Emissions and Controls '
Large amounts of C02 gas are liberated by the fermentation process.
The gas is passed into the atmosphere through a vent in the top of the
tank. Ethanol losses occur chiefly as a result of entrainment in the
2/80 Food and Agricultural Industry 6.5.2-1
-------
C02. Factors which affect the amount of ethanol lost during fermen-
tation are temperature of fermentation, initial sugar content, and
whether a juice or a must is being fermented (i.e., a white or red wine
being made).
Emission factors for wine making are given in Table 6.5.2-1.
These emission factors are for juice fermentation (white wine) with an
initial sugar content of 20 °Brix. Emission factors are given for two
temperatures commonly used for fermentation.
Table 6.5.2-1. ETHANOL EMISSION FACTORS FOR UNCONTROLLED WINE
FERMENTATION
EMISSION FACTOR RATING: B
Ethanol Emissions '
Fermentation
temperature
52°F (11.1°C)C
80°F (26.7°C)C)d
Other conditions
lb/103 gal
fermented
1.06
4.79
e
g/kl
fermented
127.03
574.04
e
Due primarily to entrainment in C02, not evaporation. I^S, mercaptans
and other componments may be emitted in limited quantities, but no
, test or other information is available.
lost in production.
.References 1 and 2. For white wine with initial 20° Brix.
For red wine, add correction term for must fermentation (2.4 lb/103 gal
eor 287.62 g/kl).
See Equation 1.
Emission factors for wines produced under other conditions can be
approximated with the following equation:
EF = [0.136T - 5.91] + [(B - 20.4)(T - 15.21)(0.00685)] + [C] (1)
where: EF = emission factor, pounds of ethanol lost per
thousand gallons of wine made
T = fermentation temperature, °F
B = initial sugar content, °Brix
C = correction term, 0 (zero) for white wine or
2.4 lb/103 gal for red wine
Although no testing has been done on emissions from wine fermen-
tation without grapes, it is expected that ethanol is also emitted from
these operations.
6.5.2-2 EMISSION FACTORS 2/80
-------
There is potential alcohol loss at various working and storage
stages in the production process. Also, fugitive alcohol emissions
could occur from disposal of fermentation solids. Ethanol is considered
to be a reactive precursor of photochemical oxidants (ozone). Emissions
would be highest during the middle of the fermentation season and would
taper off towards the end. Since wine facilities are concentrated in
certain areas, these areas would be more affected.
Currently, the wine industry uses no means to control the ethanol
lost during fermentation.
References for Section 6.5.2
1. Source Test Report and Evaluation on Emissions from a
Fermentation Tank at E. & J. Gallo Winery, C-8-050, California Air
Resources Board, Sacramento, CA, October 31, 1978.
2. H. W. Zimmerman, et al., "Alcohol Losses from Entrainment in
Carbon Dioxide Evolved during Fermentation", American Journal
of Enology. 15:63-68, 1964.
3. R. N. Shreve, Chemical Process Industries, 3rd Ed.,
McGraw-Hill Book Company, New York, 1967, pp. 591-608.
4. M. A. Amerine, "Wine", Kirk-Qthmer Encyclopedia of Chemical
Technology, Volume 22, John Wiley and Sons, Inc., New York, 1970,
pp. 307-334.
2/80 Food and Agricultural Industry 6.5.2-3
-------
-------
* 6.6 FISH PROCESSING
6.6.1 Process Description
Fish processing includes the canning of fish and the manufacturing of by-products such as fish oil'
and fish meal. The manufacturing of fish oil and fish meal are known as reduction processes. A general-1
ized fish processing operation is presented in Figure 6.6-1 .
Two types of canning operations are used. One is the "wet fish" method in which trimmed and,
eviscerated fish are cooked directly in open cans. The other operation is the "pre-cooked" process in
which eviscerated fish are cooked whole and portions are hand selected and packed into cans. The pre-
cooked process is used primarily for larger fish such as tuna.
By-product manufacture of rejected whole fish and scrap requires several steps. First, the fish scrap
mixture from the canning line is charged to a live steam cooker. After the material leaves the cooker,
it is pressed to remove water and oil. The resulting press cake is broken up and dried in a rotary drier.
Two types of driers are used to dry the press cake: direct-fired and steam-tube driers. Direct-fired
driers contain a stationary firebox ahead of the rotating section. The hot products of combustion from
the firebox are mixed with air and wet meal inside the rotating section of the drier. Exhaust gases are
generally vented to a cyclone separator to recover much of the entrained fish meal product. Steam-
tube driers contain a cylindrical bank of rotating tubes through which hot, pressurized steam is
passed. Heat is indirectly transferred to the meal and the air from the hot tubes. As with direct-fired
driers, the exhaust gases are vented to a cyclone for product recovery.
6.6.2 Emissions and Controls
Although smoke and dust can be a problem, odors are the most objectionable emissions from fish
processing plants. By-product manufacture results in more of these odorous contaminants than
cannery operations because of the greater state of decomposition of the materials processed. In gener-
al, highly decayed feedstocks produce greater concentrations of odors than do fresh feedstocks.
The largest odor sources are the fish meal driers. Usually, direct-fired driers emit more odors than
steam-tube driers. Direct-fired driers will also emit smoke, particularly if the driers are operated
under high temperature conditions. Cyclones are frequently employed on drier exhaust gases for
product recovery and particulate emission control.
Odorous gases from reduction cookers consist primarily of hydrogen sulfide [H2S] and trimethyl-
amine [(CH3),Nj. Odors from reduction cookers are emitted in volumes appreciably less than from fish
meal driers. There are virtually no particulate emissions from reduction cookers.
Some odors are also produced by the canning processes. Generally, the pre-cooked process emits
less odorous gases than the wet-fish process. This is because in the pre-cooked process, the odorous
exhaust gases are trapped in the cookers, whereas in the wet-fish process, the steam and odorous
offgases are commonly vented directly to the atmosphere.
Fish cannery and fish reduction odors can be controlled with afterburners, chlorinator-scrubbers,
and condensers. Afterburners are most effective, providing virtually 100 percent odor control; how-
ever they are costly from a fuel-use standpoint. Chl'orinator-scrubbers have been found to be 95 to 99
percent effective in controlling odors from cookers and driers. Condensers are the least effective
control device. Generally, centrifugal collectors are satisfactory for controlling excessive dust emis-
sions from driers.
Emission factors for fish processing are presented in Table 6.6-1.
4/77 Food and Agricultural Industry 6.6-1
-------
\
FISH.
ODORS
i
CANNING
COOKERS
CANNED
FISH
ODORS
FISH SCRAP
M
S!
ft
STEAM
1
CAHH
LIVE STEAM COOKER
COOKED
SCRAP
*
uai UHSts
CONDENSER
J_ WATER AND
SOLUABLES
¥
PRESS
CENTRIFUGE
PRESS / \ PRESS
CAKEY \ WATER
GRINDER
i
ROTARY FISH ME
DRYER
SOLIDS
SEPARATION
SOLIDS
EXHAUST
GAS
LIQUIDS
ESAND
ENTRAINED FISH MEAL
DRIED
WATER AND
* SULUBLtS
PARTICULATE )
AND ODORS C
REC
FISH MEAL
CYCLONE
V
OVERED FISH MEAL
TO FISH MEAL
GRINDER STDRAG*
Figure 6.6-1. A generalized fish processing flow diagram.
-------
TABLE 6.6-1. EMISSION FACTORS FOR FISH PROCESSING PLANTS
EMISSION FACTOR RATING: C
Emission source
Cookers , canning
Cookers, fish scrap
Fresh fish
Stale fish
Steam tube dryers
Direct fired dryers
Particulates
kg/Mg
Nega
Nega
Nega
2.5
4d
Ib/ton
Nega
Nega
Nega
5d
8*
Trimethylamine
[(C*OiN]
kg/Mg
NAb
0.15C
1.75C
NAd
NAd
Ib/ton
NAb
0.3C
3.5C
NAd
NAd
Hydrogen sulfide
[H?S]
kg/Mg
NAb
0.005C
0.10C
NAd
NAd
Ib/ton
NAb
0.01C
0.2C
NAd
NAd
aReference 1. Factors are for uncontrolled emissions, before cyclone.
Neg = negligible. NA = not available.
bAlthough it is known that odors are emitted from canning cookers,
quantitative estimates are not available.
Reference 2.
dReference 1.
References for Section 6.6
1. Air Pollution Engineering Manual, Second Edition, AP-40, U. S. Environ-
mental Protection Agency, Research Triangle Park, NC, May 1973. Out of
Print.
2. W. Summer, Methods of Air Deodorization, New York, Elsevier Publishing
Company, 1963.
4/77
Food and Agricultural Industry
6.6-3
-------
-------
6.7 MEAT SMOKEHOUSES
6.7.1 Process Description1
Smoking is a diffusion process in which food products are exposed 10 an atmosphere of hardwood smoke,
causing various organic compounds to be absorbed by the food. Smoke is produced commerically in the United
States by three major methods: (1) by burning dampened sawdust (20 to 40 percent moisture), (2) by burning
dry sawdust (5 to 9 percent moisture) continuously, and (3) by friction. Burning dampened sawdust and
kiln-dried sawdust are the most widely used methods. Most large, modern, production meat smokehouses are the
recirculating type, in which smoke is circulated at reasonably high temperatures throughout the smokehouse.
6.7.2 Emissions and Controls1
Emissions from smokehouses are generated from the burning hardwood rather than from the cooked product
itself. Based on approximately 110 pounds of meat smoked per pound of wood burned (110 kilograms of meat
per kilogram of wood burned), emission factors have been derived for meat smoking and are presented in Table
6.7-1.
Emissions from meat smoking are dependent on several factors, including the type of wood, the type of smoke
generator, the moisture content of the wood, the air supply, and the amount of smoke recirculated. Both
low-voltage electrostatic precipitators and direct-fired afterburners may be used to reduce particulate and organic
emissions. These controlled emission factors have also been shown in Table 6.7-1.
Table 6.7-1. EMISSION FACTORS FOR MEAT SMOKINGa-b
EMISSION FACTOR RATING: D
Pollutant
Particulates
Carbon monoxide
Hydrocarbons (CH4)
Aldehydes (HCHO)
Organic acids (acetic)
Uncontrolled
Ib/ton of meat
0.3
0.6
0.07
0.08
0.2
kg/MT of meat
0.15
0.3
0.035
0.04
0.10
Controlled0
Ib/ton of meat
0.1
Negd
Neg
0.05
0.1
kg/MT of meat
0.05
Neg
Neg
0.025
0.05
3Based on 110 pounds of meat smoked per pound of wood burned (110 kg meat/kg wood burned).
References 2, 3, and section on charcoal production.
cControls consist of either a wet collector and low-voltage precipitator in series or a direct-fired afterburner.
dWith afterburner.
2/72
Food and Agricultural Industry
6.7-1
-------
References for Section 6.7
1. Air Pollutant Emission Factors. Final Report. Resources Research, Inc. Reston, Va. Prepared for National
Air Pollution Control Administration, Durham, N.C., under Contract Number CPA-22-69-119. April 1970
2. Carter, E. Private communication between Maryland State Department of Health and Resources Research
Incorporated. November 21,1969.
3. Polglase, W.L. RF Gey and R.T. Walsh. Smokehouses. In: Air Pollution Engineering Manual. Danielson, J.
OQQ AB „? i «2? 4/ ' Natlonal Center for Air Pollution Control. Cincinnati, Ohio. Publication Number
yyy-Ar-40. 1967. p. 750-755.
6-7-2 EMISSION FACTORS 2/72
-------
6.8 AMMONIUM NITRATE
6.8.1 General1"2
Ammonium nitrate (NHi^NOs) is produced by neutralizing nitric acid with
ammonia. The reaction can be carried out at atmospheric pressure or at
pressures up to 410 kPa (45 psig) and at temperatures between 405 and 458K
(270 - 365°F). An 83 weight percent solution of ammonium nitrate product
is produced when concentrated nitric acid (56 - 60 weight percent) is
combined with gaseous ammonia in a ratio of from 3.55 to 3.71 to 1, by
weight. When solidified, ammonium nitrate is a hygroscopic colorless
solid.
Ammonium nitrate is marketed in several forms, depending upon its use.
The solution formed from the neutralization of acid and ammonia may be sold
as a fertilizer, generally in combination with urea. The solution may be
further concentrated to form a 95 to 99.5 percent ammonium nitrate melt for
use in solids formation processes. Solid ammonium nitrate may be produced
by prilling, graining, granulation or crystallization. In addition, prills
can be produced in either high or low density form, depending on the
concentration of the melt. High density prills, granules and crystals are
used as fertilizer. Ammonium nitrate grains are used solely in explosives.
Low density prills can be used as either.
The process for manufacturing ammonium nitrate can contain up to seven
major unit operations. These operating steps, shown in Figure 6.8-1, are
solution formation or synthesis, solution concentration, solids formation,
solids finishing, solids screening, solids coating, and bagging and/or bulk
shipping. In some cases, solutions may be blended for marketing as liquid
fertilizers.
AMMONIA—*-
NITRIC ACID — «*
1
SOLUTION t
FORMATION f*"
nuunivt
t
SOLUTION
CONCENTRATION
' SOLIDS
FORMATION
| OFFSIZE RECYCLE
SOLUTIONS
SOLIDS 1
FINISHING r"^
SOLIDS
SCREENING2
1
SOLIDS
COATING
*.
•*
1 BLENDING i
BAGGING
BULK
SHIPPING
BULK
SHIPPING
'ADDITIVE MAY BE ADDED BEFORE, DURING. OR AFTER CONCENTRATION
SCREENING MAY BE BEFORE OR AFTER SOLIDS FINISHING
Figure 6.8-1. Ammonium nitrate manufacturing operations.
The number of operating steps employed is determined by the desired
end product. For example, plants producing ammonium nitrate solutions
alone use only the solution formation, solution blending and bulk shipping
1/84
Food and Agricultural Industry
6.8-1
-------
operations. Plants producing a solid ammonium nitrate product can employ
all of the operations.
All ammonium nitrate plants produce an aqueous ammonium nitrate
solution through the reaction of ammonia and nitric acid in a neutralizer.
To produce a solid product, the ammonium nitrate solution is concentrated
in an evaporator or concentrator heated to drive off water. A melt is
produced containing from 95 to 99.8 percent ammonium nitrate at
approximately 422K (300°F). This melt is then used to make solid ammonium
nitrate products.
Of the various processes used to produce solid ammonium nitrate,
prilling and granulation are the most common. To produce prills, concen-
trated melt is sprayed.into the top of a prill tower. Ammonium nitrate
droplets form in the tower and fall countercurrent to a rising air stream
that cools and solidifies the falling droplets into spherical prills.
Prill density can be varied by using different concentrations of ammonium
nitrate melt. Low density prills are formed from a 95 to 97.5 percent
ammonium nitrate melt, and high density prills are formed from a 99.5 to
99.8 percent melt. High density prills are less porous than low density
prills.
In the prilling process, an additive may be injected into the melt
stream. This additive serves three purposes, to raise the crystalline
transition temperature of the solid final product; to act as a desiccant,
drawing water into the final product prills to reduce caking; and to allow
prilling to be conducted at a lower temperature by reducing the freezing
point of molten ammonium nitrate. Magnesium nitrate or magnesium oxide are
examples of additives to the melt stream. Such additives account for 1 to
2.5 weight percent of the final product. While these additives are
effective replacements for conventional coating materials, their use is not
widespread in the industry.
Rotary drum granulators produce granules by spraying a concentrated
ammonium nitrate melt (99.0 to 99.8 percent) onto small seed particles in a
long rotating cylindrical drum. As the seed particles rotate in the drum,
successive layers of ammonium nitrate are added to the particles, forming
granules. Granules are removed from the granulator and screened. Offsize
granules are crushed and recycled to the granulator to supply additional
seed particles or are dissolved and returned to the solution process. Pan
granulators operate on the same principle as drum granulators and produce a
solid product with physical characteristics similar to those of drum
granules, except the solids are formed in a large, rotating circular pan.
The temperature of the ammonium nitrate product exiting the solids
formation process is approximately 339 - 397K (150 - 255°F). Rotary drum
or fluidized bed cooling prevents deterioration and agglomeration of solids
before storage and shipping. Low density prills, which have a high mois-
ture content because of a lower melt concentration, require drying before
cooling, usually in rotary drums or fluidized beds.
Since the solids are produced in a wide variety of sizes, they must be
screened for consistently sized prills or granules. Cooled prills are
screened, and offsize prills are dissolved and recycled to the solution
concentration process. Granules are screened before cooling, undersize
6-8-2 EMISSION FACTORS 1/84
-------
particles are returned directly to the granulator, and oversize granules
may be either crushed and returned to the granulator or sent to the
solution concentration process.
Following screening, products can be coated in a rotary drum to
prevent agglomeration during storage and shipment. The most common coating
materials are clays and diatomaceous earth. However, the use of additives
in the ammonium nitrate melt before prilling may preclude the use of
coatings.
Solid ammonium nitrate is stored and shipped in either bulk or bags.
Approximately 10 percent of solid ammonium nitrate produced in the United
States is bagged.
6.8.2 Emissions and Controls
Emissions from ammonium nitrate production plants are particulate
matter (ammonium nitrate and coating materials), ammonia and nitric acid.
Ammonia and nitric acid are emitted primarily from solution formation and
concentration processes, with ammonia also being emitted from prill towers
and granulators. Particulate matter (largely as ammonium nitrate) is
emitted from most of the process operations and is the primary emission
addressed here.
The emission sources in solution formation and concentration processes
are neutralizers and evaporators, primarily emitting nitric acid and
ammonia. Specific plant operating characteristics, however, make these
emissions vary depending upon use of excess ammonia or acid in the
neutralizer. Since the neutralization operation can dictate the quantity
of these emissions, a range of emission factors is presented in
Table 6.8-1. Particulate emissions from these operations tend to be
smaller in size than those from solids production and handling processes
and generally are recycled back to the process.
Emissions from solids formation processes are ammonium nitrate
particulate matter and ammonia. The sources of primary importance are
prill towers (for high density and low density prills) and granulators
(rotary drum and pan). Emissions from prill towers result from carryover
of fine particles and fume by the prill cooling air flowing through the
tower. These fine particles are from microprill formation, attrition of
prills colliding with the tower or one another, and from rapid transition
of the ammonium nitrate between crystal states. The uncontrolled parti-
culate emissions from prill towers, therefore, are affected by tower
airflow, spray melt temperature, condition and type of melt spray device,
air temperature, and crystal state changes of the solid prills. The amount
of microprill mass that can be entrained in the prill tower exhaust is
determined by the tower air velocity. Increasing spray melt temperature
causes an increase in the amount of gas phase ammonium nitrate generated.
Thus, gaseous emissions from high density prilling are greater than from
low density towers. Microprill formation resulting from partially plugged
orifices of melt spray devices can increase fine dust loading and
emissions. Certain designs (spinning buckets) and practices (vibration of
spray plates) help reduce microprill formation. High ambient air
temperatures can cause increased emissions because of entrainment as a
1/84 Food and Agricultural Industry 6.8-3
-------
0\
00
I
js
TABLE 6.8-1.
EMISSION FACTORS FOR PROCESSES IN AMMONIUM NITRATE MANUFACTURING PLANTS1
kg/Mg (Ib/ton)
cn
CO
M
i
n
3
Particulate
Process
Neutralizer
Uncontrolled
0
.045
(0.09
Evap oration /cone en (ration Operations
Solids Formation Operations
High density prill towers
Low density prill towers
Rotary drum granule tor 6
Pan granule tors
Coolers and Dryers
High density prill coolers
Low density prill coolers6
Low density prill dryers
Rotary drum granulator coolers
Fan granulator coolers
Coating Operations
Bulk Loading Operations
0.26
1
0
146
1
0
.59
.46
- 4
- 8
(0
(3.
(0.
.3
.6)
-52)
18)
92)
(292)
.34
.8
25.8
57
e
IB
<2
1°
(2.
(1.
(51.
68)
6)
6)
.2 (114.4)
.1
.3
.0
.01
(16.
(36.
(<4.
(<0.
2)
6)
0)
02)
Matter
Controlled
0.002
(0.004
0
0
0
0
.60
.26
.22
.02
0.01
0
0
0
0
<0
.26
.57
.08
.18
.02
- 0
- 0
-
(1
(0
(0
(0
(0
(0
.22
.43)
.20)
.52)
.44)
.04)
.02)
.52)
(1.14)
(0
(0
(<0
-
.16)
.36)
,04)
Ammonia
0 aeon trolled
Kltric Acid
0.43 - 18.0 (0.86 - 36.0) 0.042 - ld
0.27 - 16.7 (0.54 -
28.6 (57.
0.13 (0.
29.7 (59.
0.07 (0.
0.02 (0.
0.15 (0.
0-1.59 (0 -
0.59 (1.
0 (0)
-
-
(0.084 - 2)d
33.4)
2)
26)
4)
14)
04)
30)
3.18)
188)
-
-
-
.mission Factor
Rating
B
A
A
A
B
B
^Factors are g/kg (kg/Mg) and Ib/ton of ammonium nitrate fertilizer produced. Some ammonium nitrate emission factors are based on data gathered
using a modification to EPA Method 5 (See Reference 1). Dash - no data.
Based on the following control efficiencies for wet scrubbers, applied to uncontrolled emissions: neutralizers, 951; high density prill towers,
62%; low density prill towers, 43X; rotary drum granulators, 99.931; pan granulators, 98.5%; coolers, dryers and coacers, 99X.
cGiven as ranges because of variation in data and plant operations. Factors for controlled emissions not presented due to conflicting results
on control efficiency.
Based on 951 recovery in a granulator recycle scrubber.
eFactors for coolers represent combined precooler and cooler emissions, and factors for dryers represent combined predryer and dryer emissions.
Fugitive particulate emissions arise from coating and bulk loading operations.
-------
result of the higher air flow required to cool prills and because of
increased fume formation at the higher temperatures.
The granulation process in general provides a larger degree of control
in product formation than does prilling. Granulation produces a solid
ammonium nitrate product that, relative to prills, is larger and has
greater abrasion resistance and crushing strength. The air flow in
granulation processes is lower than that in prilling operations. Granu-
lators, however, cannot produce low density ammonium nitrate economically
with current technology. The design and operating parameters of granula-
tors may affect emission rates. For example, the recycle rate of seed
ammonium nitrate particles affects the bed temperature in the granulator.
An increase in bed temperature resulting from decreased recycle of seed
particles may cause an increase in dust emissions from granule
disintegration.
Cooling and drying are usually conducted in rotary drums. As with
granulators, the design and operating parameters of the rotary drums may
affect the quantity of emissions. In addition to design parameters, prill
and granule temperature control is necessary to control emissions from
disintegration of solids caused by changes in crystal state.
Emissions from screening operations are generated by the attrition of
the ammonium nitrate solids against the screens and against one another.
Almost all screening operations used in the ammonium nitrate manufacturing
industry are enclosed or have a cover over the uppermost screen. Screening
equipment is located inside a building, and emissions are ducted from the
process for recovery or reuse.
Prills and granules are typically coated in a rotary drum. The
rotating action produces a uniformly coated product. The mixing action
also causes some of the coating material to be suspended, creating particu-
late emissions. Rotary drums used to coat solid product are typically kept
at a slight negative pressure, and emissions are vented to a particulate
control device. Any dust captured is usually recycled to the coating
storage bins.
Bagging and bulk loading operations are a source of particulate
emissions. Dust is emitted from each type of bagging process during final
filling when dust laden air is displaced from the bag by the ammonium
nitrate. The potential for emissions during bagging is greater for coated
than for uncoated material. It is expected that emissions from bagging
operations are primarily the kaolin, talc or diatomaceous earth coating
matter. About 90 percent of solid ammonium nitrate produced domestically
is bulk loaded. While particulate emissions from bulk loading are not
generally controlled, visible emissions are within typical state regulatory
requirements (below 20 percent opacity).
Table 6.8-1 summarizes emission factors for various processes involved
in the manufacture of ammonium nitrate. Uncontrolled emissions of particu-
late matter, ammonia and nitric acid are given in the Table. Emissions of
ammonia and nitric acid depend upon specific operating practices, so ranges
of factors are given for some emission sources.
1/84 Food and Agricultural Industry 6.8-5
-------
Emission factors for controlled particulate emissions are also in
Table 6.8-1, reflecting wet scrubbing particulate control techniques. The
particle size distribution data presented in Table 6.8-2 indicate the
applicability of wet scrubbing to control ammonium nitrate particulate
emissions. In addition, wet scrubbing is used as a control technique
because the solution containing the recovered ammonium nitrate can be sent
to the solution concentration process for reuse in production of ammonium
nitrate, rather than to waste disposal facilities.
TABLE 6.8-2.
PARTICLE SIZE DISTRIBUTION DATA FOR UNCONTROLLED EMISSIONS
FROM AMMONIUM NITRATE MANUFACTURING FACILITIES3
CUMULATIVE WEIGHT %
< 2.5 vm < 5 um < 10 ym
Solids Formation Operations
Low density prill tower
Rotary drum granulator
Coolers and Dryers
Low density prill cooler
Low density prill predryer
Low density prill dryer
Rotary drum granulator cooler
Pan granulator precooler
56
0.07
0.03
0.03
0.04
0.06
0.3
73
0.3
0.09
0.06
0.04
0.5
0.3
83
2
0.4
0.2
0.15
3
1.5
References 4, 11-12, 22-23. Particle size determinations were not done in
strict accordance with EPA. Method 5. A modification was used to handle the
high concentrations of soluble nitrogenous compounds (See Reference 1).
Particle size distribution-s were not determined for controlled particulate
emissions.
References for Section 6.8
1. Ammonium Nitrate Manufacturing Industry - Technical Document,
EPA-450/3-81-002, U. S. Environmental Protection Agency, Research
Triangle Park, NC, January 1981.
2. W. J. Search and R. B. Reznik, Source Assessment: Ammonium Nitrate
Production, EPA-600/2-77-1071, U. S. Environmental Protection Agency,
Research Triangle Park, NC, September 1977.
3. Memo from C. D. Anderson, Radian Corporation, Durham, NC, to Ammonium
Nitrate file, July 2, 1980.
4. D. P. Becvar, et al., Ammonium Nitrate Emission Test Report: Union
Oil Company of California, EMB-78-NHF-7, U. S. Environmental
Protection Agency, Research Triangle Park, NC, October 1979.
5. K. P. Brockman, Emission Tests for Particulates. Cominco American,
Beatrice, NE, 1974.
6. Written communication from S. V. Capone, GCA Corporation, Chapel Hill,
NC, to E. A. Noble, U. S. Environmental Protection Agency, Research
Triangle Park, NC, September 6, 1979.
6.8-6
EMISSION FACTORS
1/84
-------
7. Written communication from D. E. Cayard, Monsanto Agricultural
Products Company, St. Louis, MO, to E. A. Noble, U. S. Environmental
Protection Agency, Research Triangle Park, NC, December 4, 1978.
8. Written communication from D. E. Cayard, Monsanto Agricultural
Products Company, St. Louis, MO, to E. A. Noble, U. S. Environmental
Protection Agency, Research Triangle Park, NC, December 27, 1978.
9. Written communication from T. H. Davenport, Hercules Incorporated,
Donora, PA, to D. R. Goodwin, U. S. Environmental Protection Agency,
Research Triangle Park, NC, November 16, 1978.
10. R. N. Poster and D. J. Grove, Source Sampling Report: Atlas Powder
Company, Entropy Environmentalists, Inc., Research Triangle Park, NC,
August 1976.
11. M. D. Hansen, et al., Ammonium Nitrate Emission Test Report: Swift
Chemical Company, EMB-79-NHF-11, U. S. Environmental Protection
Agency, Research Triangle Park, NC, July 1980.
12. R. A. Kniskern, et al., Ammonium Nitrate Emission Test Report:
Cominco American, Inc., Beatrice, Nebraska, EMB-79-NHF-9,
U. S. Environmental Protection Agency, Research Triangle Park, NC,
April 1979.
13. Written communication from J. A. Lawrence, C. F. Industries, Long
Grove, IL, to D. R. Goodwin, U. S. Environmental Protection Agency,
Research Triangle Park, NC, December 15, 1978.
14. Written communication from F. D. McCauley, Hercules Incorporated,
Louisiana, MO, to D. R. Goodwin, U. S. Environmental Protection
Agency, Research Triangle Park, October 31, 1978.
15. W. E. Misa, Report of Source Test: Collier Carbon and Chemical
Corporation (Union Oil), Test No. 5Z-78-3, Anaheim, CA,
January 12, 1978.
16. Written communication from L. Musgrove, Georgia Department of Natural
Resources, Atlanta, GA, to R. Rader, Radian Corporation, Durham, NC,
May 21, 1980.
17. Written communication from D. J. Patterson, N-ReN Corporation,
Cincinnati, OH, to E. A. Noble, U. S. Environmental Protection Agency,
Research Triangle Park, NC, March 26, 1979.
18. Written communication from H. Schuyten, Chevron Chemical Company, San
Francisco, CA, to D. R. Goodwin, U. S. Environmental Protection Agency,
March 2, 1979.
19. Emission Test Report; Phillips Chemical Company, Texas Air Control
Board, Austin, TX, 1975.
20. Surveillance Report: Hawkeye Chemical Company, U. S. Environmental
Protection Agency, Research Triangle Park, NC, December 29, 1976.
1/84 Food and Agricultural Industry 6.8-7
-------
21. W. A. Wade and R. W. Cass, Ammonium Nitrate Emission Test Report;
C. F. Industries, EMB-79-NHF-10, U. S. Environmental Protection
Agency, Research Triangle Park, NC, November 1979.
22. W. A. Wade, et al.» Ammonium Nitrate Emission Test Report; Columbia
Nitrogen Corporation, EMB-80-NHF-16, U. S. Environmental Protection
Agency, Research Triangle Park, NC, January 1981.
23. York Research Corporation, Ammonium Nitrate Emission Test Report:
N-ReN Corporation, EMB-78-NHF-5, U. S. Environmental Protection
Agency, Research Triangle Park, NC, May 1979.
6.8-8
EMISSION FACTORS
1/84
-------
6.9 ORCHARD HEATERS
6.9.1 General1-*
Orchard heaters are commonly used in various areas of the United States to prevent frost damage to fruit and
fruit trees. The five common types of orchard heaters—pipeline, lazy flame, return stack, cone, and solid fuel—are
shown in Figure 6.9-1. The pipeline heater system is operated from a central control and fuel is distributed by a
piping system from a centrally located tank. Lazy flame, return stack, and cone heaters contain integral fuel
reservoirs, but can be converted to a pipeline system. Solid fuel heaters usually consist only of solid briquettes,
which are placed on the ground and ignited.
The ambient temperature at which orchard heaters are required is determined primarily by the type of fruit
and stage of maturity, by the daytime temperatures, and by the moisture content of the soil and air.
During a heavy thermal inversion, both convective and radiant heating methods are useful in preventing frost
damage; there is little difference in the effectiveness of the various heaters. The temperature response for a given
fuel rate is about the same for each type of heater as long as the heater is clean and does not leak. When there is
little or no thermal inversion, radiant heat provided by pipeline, return stack, or cone heaters is the most effective
method for preventing damage.
Proper location of the heaters is essential to the uniformity of the radiant heat distributed among the trees.
Heaters are usually located in the center space between four trees and are staggered from one row to the next.
Extra heaters are used on the borders of the orchard.
6.9.2 Emissions1'6
Emissions from orchard heaters are dependent on the fuel usage rate and the type of heater. Pipeline heaters
have the lowest particulate emission rates of all orchard heaters. Hydrocarbon emissions are negligible in the
pipeline heaters and in lazy flame, return stack, and cone heaters that have been converted to a pipeline system.
Nearly all of the hydrocarbon losses are evaporative losses from fuel contained in the heater reservoir. Because of
the low burning temperatures used, nitrogen oxide emissions are negligible.
Emission factors for the different types of orchard heaters are presented in Table 6.9-1 and Figure 6.9-2.
4/73 Food and Agricultural Industry 6.9-1
-------
PIPELINE HEATER
LAZY FLAME
RETURN STACK
SOLID FUEL
CONESTACK
6.9-2
Figure 6.9-1. Types of orchard heaters.
EMISSION FACTORS
4/73
-------
11
o
o
a
I
£
4.0
5.0
6.0
9.0
7.0 8.0
FUEL USAGE RATE, Ib/titr-hr
Figure 6.9-2. Participate emissions from orchard heaters.3,6
10.0
11.0
-------
Table 6.9-1. EMISSION FACTORS FOR ORCHARD HEATERS3
EMISSION FACTOR RATING: C
Pollutant
Part icu late
Ib/htr-hr
kg/htr-hr
Sulfur oxidesc
Ib/htr-hr
kg/htr-hr
Carbon monoxide
Ib/htr-hr
kg/htr-hr
Hydrocarbons*
Ib/htr-yr
kg/htr-yr
Nitrogen oxides'1
Ib/htr-hr
kg/htr-hr
Type of heater
Pipeline
b
b
0.1 3Sd
0.06S
6.2
2.8
NegS
Neg
Neg
Neg
Lazy
flame
b
b
0.11S
0.05S
NA
NA
16.0
7.3
Neg
Neg
i
Return
stack
b
b
0.1 4S
0.06S
NA
NA
16.0
7.3
Neg
Neg
Cone
b
b
0.1 4S
0.06S
NA
NA
16.0
7.3
Neg
Neg
Solid
fuel
0.05
0.023
NAe
NA
NA
NA
Neg
Neg
Neg
Neg
a References 1,3,4, and 6.
bParticulate emissions for pipeline, lazy flame, return stack, and cone heaters are
shown in Figure 6.9-2.
cBased on emission factors for fuel oil combustion in Section 1.3.
dS - sulfur content.
eNot available.
Reference 1. , Evaporative losses only. Hydrocarbon emissions from combustion
are considered negligible. Evaporative hydrocarbon losses for units that are
part of a pipeline system are negligible.
Negligible.
"Little nitrogen oxide is formed because of the relatively low combustion
temperatures.
References for Section 6.9
1. Air Pollution in Ventura County. County of Ventura Health Department, Santa Paula, CA, June 1966.
2. Frost Protection in Citrus. Agricultural Extension Service, University of California, Ventura, C A, November
1967.
3. Personal communication with Mr. Wesley Snowden. Valentine, Fisher, and Tomlinson, Consulting Engineers,
Seattle ,WA, May 1971.
4. Communication with the Smith Energy Company, Los Angeles, CA, January 1968.
5. Communication with Agricultural Extension Service, University of California, Ventura, CA, October 1969.
6. Persona] communication with Mr. Ted Wakai. Air Pollution Control District, County of Ventura, Ojai, CA,
May 1972.
6.9-4
EMISSION FACTORS
7/79
-------
6.10 PHOSPHATE FERTILIZERS
6.10.1 NORMAL SUPERPHOSPHATES1
6.10.1.1 General
The term "normal superphosphate" is used to designate a fertilizer
material containing 15 - 21 percent P2°5- !t is prepared by reacting
ground phosphate rock with 65 - 75 percent sulfuric acid. Rock and acid
are mixed in a reaction vessel, held in an enclosed area (den) while the
reaction mixture solidifies, and transferred to a storage pile for
curing. Following curing, the product is most often ground and bagged
for sale as run-of-the-pile product. It can also be granulated, for
sale as granulated superphosphate or granular mixed fertilizer. However,
this accounts for less than 5 percent of total production. To produce a
granular normal superphosphate material, run-of-the-pile material is
first fed to a pulverizer to be crushed, ground, and screened. Screened
material is sent to a rotary drum granulator and then through a rotary
dryer. The material goes through a rotary cooler and on to storage bins
for sale as bagged or bulk product. Superphosphate fertilizers are
produced at 79 plants in the United States. A generalized flow diagram
of the process for the production of normal superphosphate is shown in
Figure 6.10.1-1.
6.10.1.2 Emissions and Controls
Sources of emissions at a normal superphosphate plant include rock
unloading and feeding, mixer (reactor), den, curing building, and fertil-
izer handling operations. Rock unloading, handling and feeding generate
particulate emissions of phosphate rock dust. The mixer, den and
curing building emit gaseous fluorides (HF and SiFit) and particulates
composed of fluoride and phosphate material. Fertilizer handling oper-
ations release fertilizer dust.
At a typical normal superphosphate plant, the rock unloading,
handling and feeding operations are controlled by a baghouse. The mixer
and den are controlled by a wet scrubber. The curing building and
fertilizer handling operations normally are not controlled.
Emission factors for the production of normal superphosphate are
presented in Table 6.10.1-1. These emission factors are averages based
on recent source test data from controlled phosphate fertilizer plants
in Florida.
10/80 Food and Agricultural Industry 6.10.1-1
-------
1
PARTICULATE
EMISSIONS
BAG HOUSE
GROUND
PHOSPHATE ROCK
ROCK BIN pARTICULATE
EMISSIONS
*
DUST
I BAGHOUSE
TO GYPSUM
POND
PARTICULAR
AND FLUORIDE
-••EMISSIONS
( UNCONTROLLED I
PARTICULAR
AND FLUORIDE
EMISSIONS
PRODUCT
Figure 6.10.1-1. Normal superphosphate process flow diagram.
6.10.1-2
EMISSION FACTORS
10/80
-------
TABLE 6.10.1-1.
EMISSION FACTORS FOR THE PRODUCTION OF
NORMAL SUPERPHOSPHATE*1
EMISSION FACTOR RATING: A
Emission point
Emission factor
Pollutant
Ib/ton
kg/MT
Rock unloading
Rock feeding
Q
Mixer and den
Curing building
Particulate
Particulate
Particulate
Fluoride
Particulate
Fluoride
0.56
0.11
0.52
0.20
7.20
3.80
0.28
0.06
0.26
0.10
3.60
1.90
Reference 1, pp. 74-77, 169.
Factors are for emissions from baghouse with an estimated collection
efficiency of 99%.
Factors are for emissions from wet scrubbers with a reported 97%
control efficiency.
Uncontrolled.
Particulate emissions from ground rock unloading, storage and
transfer systems are controlled by baghouse collectors. These cloth
filters have reported efficiencies of over 99 percent. Collected solids
are recycled to the process.
Silicon tetrafluoride and hydrogen fluoride emissions, and partic-
ulate from the mixer, den and curing building are controlled by scrubbing
the offgases with recycled water. Gaseous silicon tetrafluoride in the
presence of moisture reacts to form gelatinous silica which has the
tendency to plug scrubber packings. The use of conventional packed
countercurrent scrubbers and other contacting devices with small gas
passages for emissions control is therefore limited. Scrubber types
that can be used are cyclonic, venturi, impingement, jet ejector and
spray crossflow packed. Spray towers also find use as precontactors for
fluorine removal at relatively high concentration levels (greater than
3,000 ppm, or 4.67 g/m3).
Air pollution control techniques vary with particular plant designs.
The effectiveness of abatement systems in removal of fluoride and
particulate also varies from plant to plant, depending on a number of
factors. The effectiveness of fluorine abatement is determined by (1)
inlet fluorine concentration, (2) outlet or saturated gas temperature,
(3) composition and temprature of the scrubbing liquid, (4) scrubber
type and transfer units, and (5) effectiveness of entrainment separation.
Control efficiency is enhanced by increasing the number of scrubbing
10/80
Food and Agricultural Industry
6.10.1-3
-------
stages in series and by using a fresh water scrub in the final stage.
Reported efficiencies for fluoride control range from less than 90
percent to over 99 percent, depending on inlet fluoride concentrations
and the system employed. An efficiency of 98 percent for particulate
control is achievable.
Reference for Section 6.10.1
1, J. M. Nyers, et al., Source Assessment: Phosphate Fertilizer
Industry, EPA-600/2-79-019c, U. S. Environmental Protection Agency,
Research Triangle Park, NC, May 1979.
6.10.1-4 EMISSION FACTORS 10/80
-------
6.10.2 TRIPLE SUPERPHOSPHATES
6.10.2.1 General
Triple superphosphate is a fertilizer material of ¥2®$ content over
40 percent, made by reacting phosphate rock and phosphoric acid. The
two principal types of triple superphosphate are run-of-the-pile (40
percent of total production) and granular (60 percent of total produc-
tion) . Run-of-the-pile material is essentially a pulverized mass of
variable particle size produced in a manner similar to normal super-
phosphate. Thus, phosphoric acid (50 percent P20s) is reacted in a cone
mixer with ground phosphate rock. The resultant slurry begins to
solidify on a slow moving conveyer (den) en route to the curing area.
At the point of discharge from the den, the material passes through a
rotary mechanical cutter that breaks up the solid mass. Coarse run-of-
the-pile product is sent to a storage pile and cured for a period of 3
to 5 weeks. The final product is then mined from the "pile" in the
curing shed, and then crushed, screened, and shipped in bulk. Granular
triple superphosphate yields larger, more uniform particles with improved
storage and handling properties. Most of this material is made with the
Dorr-Oliver slurry granulation process, illustrated in Figure 6.10.2-1.
In this process, ground phosphate rock is mixed with phosphoric acid in
a reactor or mixing tank. The phosphoric acid used in this process is
appreciably lower in concentration (40 percent '?205^ tnan that used to
manufacture run-of-the-pile product, because the lower strength acid
maintains the slurry in a fluid state during a mixing period of 1 to 2
hours. A thin slurry is continuously removed and distributed onto
dried, recycled fines, where it coats the granule surfaces and builds up
its size.
Pugmills and rotating drum granulators are used in the granulation
process. A pugmill is composed of a u-shaped trough carrying twin
contrarotating shafts, upon which are mounted strong blades or paddles.
Their action agitates, shears and kneads the solid/liquid mix and trans-
ports the material along the trough. The basic rotary drum granulator
consists of an open ended slightly inclined rotary cylinder, with retain-
ing rings at each end and a scraper or cutter mounted inside the drum
shell. A rolling bed of dry material is maintained in the unit while
the slurry is introduced through distributor pipes set lengthwise in the
drum under the bed. Slurry-wetted granules then discharge onto a
rotary dryer, where excess water is evaporated and the chemical reaction
is accelerated to completion by the dryer heat. Dried granules are then
sized on vibrating screens. Oversize particles are crushed and recircu-
lated to the screen, and undersize particles are recycled to the granu-
lator. Product size granules are cooled in a countercurrent rotary
drum, then sent to a storage pile for curing. After a curing period of
3 to 5 days, granules are removed from storage, screened, bagged and
shipped.
10/80 Food and Agricultural Industry 6.10.2-1
-------
O
ro
w
n
H
o
o
o
CURING BUILDING
I STORAGE S SHI PP INC)
Figure 6.10.2-1. Dorr-Oliver process flow diagram for
granular triple superphosphate production.
-------
6.10.2.2 Emissions and Controls
Emissions of fluorine compounds and dust particles occur during the
production of granular triple superphosphate. Silicon tetrafluoride and
hydrogen fluoride are released by the acidulation reaction and they
evolve from the reactors, den, granulator, dryer and cooler. Evolution
of fluorides continues at a lower rate in the curing building, as the
reaction preceeds. Sources of particulate emissions include the reactor,
granulator, dryer, cooler, screens, mills, and transfer conveyors.
Additional emissions of particulate result from the unloading, storage
and transfer of ground phosphate rock.
At a typical plant, emissions from the reactor, den and granulator
are controlled by scrubbing the effluent gas with recycled gypsum pond
water. Emissions from the dryer, cooler, screens, mills, product trans-
fer systems, and storage building are sent to a cyclone separator for
removal of a portion of the dust before going to wet scrubbers. Bag-
houses are used to control the fine rock particles generated by the
preliminary ground rock handling activities.
Emission factors for the production of run-of-the-pile and granular
triple superphosphate are given in Table 6.10.2-1. These emission
factors are averages based on recent source test data from controlled
phosphate fertilizer plants in Florida.
Particulate emissions from ground rock unloading, storage and
transfer systems are controlled by baghouse collectors. These cloth
filters have reported efficiencies of over 99 percent. Collected solids
are recycled to the process. Emissions of silicon tetrafluoride, hydrogen
fluoride, and particulate from the production area and curing building
are controlled by scrubbing the offgases with recycled water. Exhausts
from the dryer, cooler, screens, mills, and curing building are sent
first to a cyclone separator and then to a wet scrubber.
Gaseous silicon tetrafluoride in the presence of moisture reacts to
form gelatinous silica, which has the tendency to plug scrubber packings.
The use of conventional packed countercurrent scrubbers and other con-
tacting devices with small gas passages for emissions control is there-
fore limited. Scrubber types that can be used are (1) spray tower, (2)
cyclonic, (3) venturi, (4) impingement, (5) jet ejector, and (6) spray-
crossflow packed.
Spray towers are used as precontactors for fluorine removal at
relatively high concentration levels (greater than 3,000 ppm, or 4.67
g/m3).
Air pollution control techniques vary with particular plant designs.
The effectiveness of abatement systems for the removal of fluoride and
particulate also varies from plant to plant, depending on a number of
factors. The effectiveness of fluorine abatement is determined by (1)
10/80 Food and Agricultural Industry 6.10.2-3
-------
to
TABLE 6.10.2-1. CONTROLLED EMISSION FACTORS FOR THE PRODUCTION OF TRIPLE SUPERPHOSPHATES*
EMISSION FACTOR RATING: A
Controlled emission factor
M
H
cn
H
O
£
O
H
O
W
Process
Run-of-the-pile triple
sup erphospha te
Granular triple
superphosphate
Emission point
Rock unloading
Rock feeding
Cone mixer, den
and curing building
Rock unloading
Rock feeding
Reactor, granulator^
dryer, cooler and
screens
Curing building
Pollutant
Particulate
Particulate
Particulate
Fluoride
Particulate
Particulate
Particulate
Fluoride
Particulate
Fluoride
Ib/ton P?0,.
0.14
0.03
0.03
0.20
0.18
0.03
0.10
0.24
0.20
0.04
kg/MT P205
0.07
0.01
0.02
0.10
0.09
0.02
0.05
0.12
0.10
0.02
00
O
^Reference 1, pp. 77-80, 168, 170-171.
Factors are for emissions from baghouses with an estimated collection efficiency of 99%.
Factors are for emissions from wet scrubbers with an estimated 97% control efficiency.
-------
inlet fluorine concentration, (2) outlet or saturated gas temperature,
(3) composition and temperature of the scrubbing liquid, (4) scrubber
type and transfer units, and (5) effectiveness of entrainment separation.
Control efficiency is enhanced by increasing the number of scrubbing
stages in series and by using a fresh water scrub in the final stage.
Reported efficiencies for fluoride control range from less than 90
percent to over 99 percent, depending on inlet fluoride concentrations
and the system employed. An efficiency of 98 percent for particulate
control is achievable.
Reference for Section 6.10.2
1. J. M. Nyers, et al., Source Assessment: Phosphate Fertilizer
Industry, EPA-600/2-79-019c, U. S. Environmental Protection Agency,
Research Triangle Park, NC, May 1979.
10/80
Food and Agricultural Industry
6.10.2-5
-------
-------
6.10.3 AMMONIUM PHOSPHATES
6.10.3.1 General1
Ammonium phosphates are produced by reacting phosphoric acid with
anhydrous ammonia. Both solid and liquid ammonium phosphate fertilizers
are produced in the United States. Ammoniated superphosphates are also
produced, by adding normal superphosphate or triple superphosphate to
the mixture. This discussion covers only the granulation of phosphoric
acid with anhydrous ammonia to produce granular fertilizers. The produc-
tion of liquid ammonium phosphates and ammoniated superphosphates in
fertilizer mixing plants is considered a separate process. Two basic
mixer designs are used by ammoniation-granulation plants, the pugmill
amraoniator and the rotary drum ammoniator. Approximately 95 percent of
ammoniation-granulation plants in the United States use a rotary drum
mixer developed and patented by the Tennessee Valley Authority (TVA) .
In the TVA process, phosphoric acid is mixed in an acid surge tank with
93 percent sulfuric acid (used for product analysis control) and with •
recycle and acid from wet scrubbers (see Figure 6.10.3-1). Mixed acids
are then partially neutralized with liquid or gaseous anhydrous ammonia
in a brick lined acid reactor. All phosphoric acid and approximately 70
percent of ammonia are introduced into this vessel.
A slurry of NH^^POi^ and 22 percent water is produced and sent
through steam-traced lines to the ammoniator-granulator. Ammonia rich
offgases from the reactor are wet scrubbed before exhausting to the
atmosphere. Primary scrubbers use raw material-mixed acids as scrubbing
liquor, and secondary scrubbers use gypsum pond water.
The basic rotary drum ammoniator-granulator consists of a slightly
inclined open end rotary cylinder with retaining rings at each end, and
a scraper or cutter mounted inside the drum shell. A rolling bed of
recycled solids is maintained in the units. Slurry from the reactor is
distributed on the bed, and the remaining ammonia (approximately 30
percent) is sparged underneath. Granulation, by agglomeration and by
coating particules with slurry, takes place in the rotating drum and is
completed in the dryer. Ammonia rich offgases pass through a wet
scrubber before exhausting to the atmosphere.
Moist ammonium phosphate granules are transferred to a rotary
cocurrent dryer and then to a cooler. Before exhausting to the atmo-
sphere, these offgases pass through cyclones and wet scrubbers. Cooled
granules pass to a double deck screen, in which oversize and undersize
particles are separated from product particles.
6.10.3.2 Emissions and Controls
Air emissions from production of ammonium phosphate fertilizers by
ammoniation granulation of phosphoric acid and ammonia result from five
process operations. The reactor and ammoniator granulator produce
10/80 Food and Agricultural Industry 6.10.3-1
-------
U>
H
-
on
to
O
H
O
ftf
C/3
pftooun ID sicmwE,
BKGIHG OR IU1X SHIFWCNT
UKDUSIZE
Figure 6.2.3-1. Ammonium phosphate process flow diagram.
CO
O
-------
emissions of gaseous ammonia, gaseous fluorides (HF and SiFi^.) and partic-
ulate ammonium phosphates. These two exhaust streams generally are
combined and passed through primary and secondary scrubbers.
Exhaust gases from the dryer and cooler also contain ammonia,
fluorides and particulates, and these streams commonly are combined and
passed through cyclones and primary and secondary scrubbers. Partic-
ulate emissions and low levels of ammonia and fluorides from product
sizing and material transfer operations are controlled the same way.
Emission factors for ammonium phosphate production are summarized
in Table 6.10.3-1. These emission factors are averages based on recent
source test data from controlled phosphate fertilizer plants in Florida.
Exhaust streams from the reactor and ammoniator-granulator pass
through a primary scrubber, in which phosphoric acid recovers ammonia
and particulate. Exhaust gases from the dryer, cooler and screen go
first to cyclones for particulate recovery, and from there to primary
scrubbers. Materials collected in the cyclone and primary scrubbers are
returned to the process. The exhaust is sent to secondary scrubbers,
where recycled gypsum pond water is used as a scrubbing liquid to control
fluoride emissions. The scrubber effluent is returned to the gypsum
pond.
Primary scrubbing equipment commonly includes venturi and cyclonic
spray towers, while cyclonic spray towers, impingement scrubbers, and
spray-crossflow packed bed scrubbers are used as secondary controls.
Primary scrubbers generally use phosphoric acid of 20 to 30 percent as
scrubbing liquor, principally to recover ammonia. Secondary scrubbers
generally use gypsum and pond water, for fluoride control.
Throughout the industry, however, there are many combinations and
variations. Some plants use reactor-feed concentration phosphoric acid
(40 percent P20s) in both primary and secondary scrubbers, and some use
phosphoric acid near the dilute end of the 20 to 30 percent ^2.05 range
in only a single scrubber. Existing plants are equipped with ammonia
recovery scrubbers on the reactor, ammoniator-granulator and dryer, and
particulate controls on the dryer and cooler. Additional scrubbers for
fluoride removal are common but not typical. Only 15 to 20 percent of
installations contacted in an EPA survey were equipped with spray-
crossflow packed bed scrubbers or their equivalent for fluoride removal.
Emission control efficiencies for ammonium phosphate plant control
equipment have been reported as 94 - 99 percent for ammonium, 75 - 99.8
percent for particulates, and 74 - 94 percent for fluorides.
10/80 Food and Agricultural Industry 6.10.3-3
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TABLE 6.10.3-1. AVERAGE CONTROLLED EMISSION FACTORS FOR THE
PRODUCTION OF AMMONIUM PHOSPHATES3
EMISSION FACTOR RATING: A
Emission Point
Reactor/ammoniator-granulator
Fluoride (as F)
Particulates
Ammonia
Dryer/ cooler
Fluoride (as F)
Particulates
Ammonia
Product sizing and material transfer
Fluoride (as F)c
Q
Particulates
Ammonia
Total plant emissions
Fluoride (as F)
Particulates
Ammonia
Controlled
Ib/ton P20,
0.05
1.52
b
0.03
1.50
b
0.01
0.06
b
0.08
0.30
0.14
Emission Factors
j kg/MT P205
0.02
0.76
b
0.02
0.75
b
0.01
0.03
b
0.04
0.15
0.07
^Reference 1, pp. 80-83, 173.
No information available. Although ammonia is emitted from these unit
operations, it is reported as a total plant emission.
^Represents only one sample.
EPA has promulgated a fluoride emission guideline of 0.03 g/kg P^
input.
eBased on limited data from only 2 plants.
Reference for Section 6.10.3
1. J. M. Nyers, et al., Source Assessment: Phosphate Fertilizer
Industry, EPA-600/2-79-Ol9c, U.S. Environmental Protection Agency,
Research Triangle Park, NC, May 1979.
6.10.3-4 l EMISSION FACTORS 10/80
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6.11 STARCH MAN UFACTURING
6.11.1 Process Description1
The basic raw material in the manufacture of starch is dent corn, which contains starch. The starch in the
corn is separated from the other components by "wet milling."
The shelled grain is prepared for milling in cleaners that remove both the light chaff and any heavier foreign
material. The cleaned corn is then softened by soaking (steeping) it in warm water acidified with sulfur dioxide.
The softened corn goes through attrition mills that tear the kernels apart, freeing the germ and loosening the hull.
The remaining mixture of starch, gluten, and hulls is finely ground, and the coarser fiber particles are removed by
screening. The mixture of starch and gluten is then separated by centrifuges, after which the starch is filtered and
washed. At this point it is dried and packaged for market.
6.11.2 Emissions
The manufacture of starch from corn can result in significant dust emissions. The various cleaning, grinding,
and screening operations are the major sources of dust emissions. Table 6.11-1 presents emission factors for starch
manufacturing.
Table 6.11-1. EMISSION FACTORS
FOR STARCH MANUFACTURING3
EMISSION FACTOR RATING: D
Type of operation
Uncontrolled
Controlled13
Particulates
Ib/ton
8
0.02
kg/MT
4
0.01
Reference 2.
bBased on centrifugal gas scrubber.
References for Section 6.11
1. Starch Manufacturing. In: Kirk-Othmer Encyclopedia of Chemical Technology, Vol. IX. New York, John
Wiley and Sons, Inc. 1964.
2. Storch, H. L. Product Losses Cut with a Centrifugal Gas Scrubber. Chem. Eng. Progr. 62:51-54. April 1966.
2/72 Food and Agricultural Industry 6.11-1
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6.12 SUGAR CANE PROCESSING
6.12.1 General ' 3
Sugar cane is burned in the field prior to harvesting to remove unwanted foliage as well as to control rodents
and insects. Harvesting is done by hand or, where possible, by mechanical means.
After harvesting, the cane goes through a series of processing steps for conversion to the final sugar product. It
is first washed to remove dirt and trash; then crushed and shredded to reduce the size of the stalks. The juice is
next extracted by one of two methods, milling or diffusion. In milling, the cane is pressed between heavy rollers
to squeeze out the juice; in diffusion, the sugar is leached out by water and thin juices. The raw sugar then goes
through a series of operations including clarification, evaporation, and crystallization in order to produce the final
product. The fibrous residue remaining after sugar extraction is called bagasse.
All mills fire some or all of their bagasse in boilers to provide power necessary in their milling operation. Some,
having more bagasse than can be utilized internally, sell the remainder for use in the manufacture of various
chemicals such as furfural.
6.12.2 Emissions 2'3
The largest sources of emissions from sugar cane processing are the openfield burning in the harvesting of the
crop and the burning of bagasse as fuel. In the various processes of crushing, evaporation, and crystallization,
relatively small quantities of particulates are emitted. Emission factors for sugar cane field burning are shown in
Table 2.4-2. Emission factors for bagasse firing in boilers are included in Chapter 1.
References for Section 6.12
1. Sugar Cane, In: Kirk-Othmer Encyclopedia of Chemical Technology, Vol. IX. New York, John Wiley and
Sons, Inc. 1964.
2. Darley, E. F. Air Pollution Emissions from Burning Sugar Cane and Pineapple from Hawaii. In: Air Pollution
from Forest and Agricultural Burning. Statewide Air Pollution Research Center, University of California,
Riverside, Calif. Prepared for Environmental Protection Agency, Research Triangle Park, N.C. under Grant
No. R800711. August 1974.
3. Background Information for Establishment of National Standards of Performance for New Sources. Raw Cane
Sugar Industry. Environmental Engineering, Inc. Gainesville, Fla. Prepared for Environmental Protection
Agency, Research Triangle Park, N.C. under Contract No. CPA 70-142, Task Order 9c. July 15, 1971.
4/76
Food and Agricultural Industry
6.12-1
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6.13 BREAD BAKING
6.13.1 General1'2
Bakery products generally can be divided into two groups—products leavened by yeast and products
chemically leavened by baking powder. Other than yeast bread, which comprises the largest fraction of
all yeast leavened baking production, leavened products include sweet rolls, crackers, pretzels, etc.
Examples of chemically leavened baking products are cakes, cookies, cake doughnut*, corn bread and
baking powder biscuits.
Brea.d is generally produced by either the straight-dough process or the sponge-dough process. In the
straight-dough process, the ingredients are mixed, allowed to ferment, and then baked. In the sponge-
dough process, only part of the ingredients are initially mixed and allowed to ferment, with the remainder
added to the mix and fermented just prior to baking. The sponge-dough process is more often used by
commercial bakeries.
In a commercial bakery, bread dough is fermented from two to four hours prior to baking at about
450T (232°C). The temperature inside the bread does not exceed 212°F (100°C). The ovens used are pre-
dominately direct fired by natural gas. In such ovens, any vapors driven off the bread and any combustion
product gases are removed through the same exhaust vent.
6.13.2 Emissions1'2
In the leavening process, yeast metabolizes the sugars and starches in the bread dough. During this
fermentation stage, various chemical reactions take place, with the end products being primarily carbon
dioxide (COjj) and ethanol (C2H5OH). The carbon dioxide is necessary to leaven the dough, thereby in-
creasing its volume. The byproduct ethanol, however, evaporates and leaves the dough. The rate of ethanol
production depends on dough temperature, quantity of sweetner and type of yeast.
Laboratory experiments1 and theoretical estimates2 suggest that ethanol emissions from the sponge-
dough process may range from 5 to 8 pounds per 1000 pounds of bread produced, whereas ethanol
emissions from the straight-dough process are only 0.5 pounds per 1000 pounds produced. These factors
include ethanol evaporation from all phases of bread production, although most of the emissions occur
during baking. Negligible quantities of ethanol remain in the bread following baking. Several other non-
methane volatile organic compounds are also emitted from bread production, but in much smaller amounts.
The reader should consult References 1 and 2 for details on how these emission factors are derived.
No controls or process modifications are employed to reduce ethanol emissions from bakeries. Some
fraction of the ethanol emitted during baking could potentially be destroyed in the direct fired gas ovens,
but since the ethanol does not come into contact with the flame zone, this fraction is thought to be in-
significant.
References for Section 6.13
1. R.M. Keller, \orimethane Organic Emissions from Bread Producing Operations. EPA-450/4-79-001. U.S.
Environmental Protection Agency. Research Triangle Park. NC. December 1978.
2. D.C. Henderson, "Commercial Bakeries as a Major Source of Reactive Volatile Organic Gases", Emission
lni-entor\-IF actor Workshop: Volume I, EPA-450/3-78-042a. U.S. Environmental Protection Agency. Research
Triangle Park. NC. August 1978.
7/79
Food and Agricultural Industry
6.13-1
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6.14 UREA
6.14.1 General1
Urea (CO[NH2]2)» also known as carbamide or carbonyl diamide, is
produced by reacting ammonia and carbon dioxide at 448 - 473K (347 - 392°F)
and 13.7 - 23.2 MPa (2,0002 - 3,400 psi) to form ammonium carbamate
(NH2C02NHit) . Pressure may be as high as 41.0 MPa (6,000 psi).3 Urea is
formed by a dehydration decomposition of ammonium carbamate.
Urea is marketed as a solution or in a variety of solid forms. Most
urea solution produced is used in fertilizer mixtures, with a small amount
going to animal feed supplements. Most solids are produced as prills or
granules, for use as fertilizer or protein supplement in animal feeds, and
use in plastics manufacturing. Five U. S. plants produce solid urea in
crystalline form.
The process for manufacturing urea involves a combination of up to
seven major unit operations. These operations, illustrated by the flow
diagram in Figure 6.14-1, are solution synthesis, solution concentration,
solids formation, solids cooling, solids screening, solids coating, and
bagging and/or bulk shipping.
AMMONIA-
CARDONm
DIOXIDE
SOLUTION
SVN THESIS
ADDITIVE"
1
^ SOLUTION
CONCENTflATION
SOLIDS
FORMATION
SOLIDS
COOLING
COATING*
t
SCREENING
1
"
SOLUTIONS
L_
OFFSIZE RECYCLE
OPTIONAL WITH INDIVIDUAL MANUFACTURING PRACTICES
Figure 6.14-1. Major urea manufacturing operations.
The combination of processing steps is determined by the desired end
products. For example, plants producing urea solution use only the solution
formulation and bulk shipping operations. Facilities producing solid urea
employ these two operations and various combinations of the remaining five
operations, depending upon the specific end product being produced.
In the solution synthesis operation, ammonia and C02 are reacted to
form ammonium carbamate. The carbamate is then dehydrated to yield 70 to
77 percent aqueous urea solution. This solution can be used as an
1/84
Food and Agricultural Industry
6.14-1
-------
ingredient of nitrogen solution fertilizers, or it can be concentrated
further to produce solid urea.
The concentration process furnishes urea melt for solids formation.
The three methods of concentrating the urea solution are vacuum concentra-
tion, crystallization and atmospheric evaporation. The method chosen
depends upon the level of biuret (NH2CONHCONH2> impurity allowable in the
end product. The most common method of solution concentration is
evaporation.
Urea solids are produced from the urea melt by two basic methods,
prilling and granulation. Prilling is a process by which solid particles
are produced from molten urea. Molten urea is sprayed from the top of a
prill tower, and as the droplets fall through a countercurrent air flow,
they cool and solidify into nearly spherical particles. There are two types
of prill towers, fluidized bed and nonfluidized bed. The major difference
between these towers is that a separate solids cooling operation may be
required to produce agricultural grade prills in a nonfluidized bed prill
tower.1*
Granulation is more popular than prilling in producing solid urea for
fertilizer. There are two granulation methods, drum granulation and pan
granulation. In drum granulation, solids are built up in layers on seed
granules in a rotating drum granulator/cooler approximately 14 feet in
diameter. Pan granulators also form the product in a layering process, but
different equipment is used, and pan granulators are not common in this
country.
The solids cooling operation generally is accomplished during solids
formation, but for pan granulation processes and for some agricultural grade
prills, some supplementary cooling is provided by auxiliary rotary drums.
The solids screening operation removes offsize product from solid urea.
The offsize material may be returned to the process in the solid phase or be
redissolved in water and returned to the solution concentration process.
Clay coatings are used in the urea industry to reduce product caking
and urea dust formation, even though they also reduce the nitrogen content
of the product, and the coating operation creates clay dust emissions. The
popularity of clay coating has diminished considerably because of the
practice of injecting formaldehyde additives into the liquid or molten urea
before solids formation.5"6 Additives reduce solids caking during storage
and urea dust formation during transport and handling.
The majority of solid urea product is bulk shipped in trucks, enclosed
railroad cars, or barges, but approximately 10 percent is bagged.
6.14.2 Emissions and Controls
Emissions from urea manufacture include ammonia and particulate matter.
Ammonia is emitted during the solution synthesis and solids production
processes. Particulate matter is the primary emission being addressed here.
There have been no reliable measurements of free gaseous formaldehyde
emissions. The chromotropic acid procedure that has been used to measure
6.14-2 EMISSION FACTORS 1/84
-------
formaldehyde is not capable of distinguishing between gaseous formaldehyde
and methylenediurea, the principle compound formed when the formaldehyde
additive reacts with hot urea.7"8
In the synthesis process, some emission control is inherent in the
recycle process where carbamate gases and/or liquids are recovered and
recycled. Typical emission sources from the solution synthesis process are
noncondensable vent streams from ammonium carbamate decomposers and
separators. Emissions from synthesis processes are generally combined with
emissions from the solution concentration process and are vented through a
common stack. Combined particulate emissions from urea synthesis and
concentration are much less than particulate emissions from a typical solids
producing urea plant. The synthesis and concentration operations are
usually uncontrolled except for recycle provisions to recover ammonia. For
these reasons, no factor for controlled emissions from synthesis and
concentration processes is given in this section.
Uncontrolled emission rates from prill towers may be affected by the
following factors:
- product grade being produced
- air flow rate through the tower
type of tower bed
- ambient temperature and humidity
The total of mass emissions per unit is usually lower for feed grade prill
production than for agricultural grade prills, due to lower airflows.
Uncontrolled particulate emission rates for fluidized bed prill towers are
higher than those for nonfluidized bed prill towers making agricultural
grade prills and are approximately equal to those for nonfluidized bed feed
grade prills.1* Ambient air conditions can affect prill tower emissions.
Available data indicate that colder temperatures promote the formation of
smaller particles in the prill tower exhaust.9 Since smaller particles are
more difficult to remove, the efficiency of prill tower control devices
tends to decrease with ambient temperatures. This can lead to higher
emission levels for prill towers operated during cold weather. Ambient
humidity can also affect prill tower emissions. Air flow rates must be
increased with high humidity, and higher air flow rates usually cause higher
emissions.
The design parameters of drum granulators and rotary drum coolers may
affect emissions.10"11
Drum granulators have an advantage over prill towers in that they are
capable of producing very large particles without difficulty. Granulators
also require less air for operation than do prill towers. A disadvantage of
granulators is their inability to produce the smaller feed grade granules
economically. To produce smaller granules, the drum must be operated at a
higher seed particle recycle rate. It has been reported that, although the
increase in seed material results in a lower bed temperature, the
corresponding increase in fines in the granulator causes a higher emission
rate,10 Cooling air passing through the drum granulator entrains
approximately 10 to 20 percent of the product. This air stream is
1/84 Food and Agricultural Industry 6.14-3
-------
controlled with a wet scrubber which is standard process equipment on drum
granulators.
In the solids screening process, dust is generated by abrasion of urea
particles and the vibration of the screening mechanisms. Therefore, almost
all screening operations used in the urea manufacturing industry are
enclosed or are covered over the uppermost screen. This operation is a
small emission source, and particulate emissions from solids screening are
not treated here.12~13
Emissions attributable to coating include entrained clay dust from
loading, inplant transfer, and leaks from the seals of the coater. No
emissions data are available to quantify this fugitive dust source.
Bagging operations are a source of particulate emissions. Dust is
emitted from each bagging method during the final stages of filling, when
dustladen air is displaced from the bag by urea. Bagging operations are
conducted inside warehouses and are usually vented to keep dust out of the
workroom area, according to OSHA regulations. Most vents are controlled
with baghouses. Nationwide, approximately 90 percent of urea produced is
bulk loaded. Few plants control their bulk loading operations. Generation
of visible fugitive particles is slight.
Table 6.14-1 summarizes the uncontrolled and controlled emission
factors, by processes, for urea manufacture. Table 6.14-2 summarizes
particle sizes for these emissions.
TABLE 6.14-2. UNCONTROLLED PARTICLE SIZE DATA FOR UREA PRODUCTION3
OPERATION
PARTICLE SIZE
(Cummulative Weight %)
10 urn < 5 ym < 2.5
urn
Solution Formation and Concentration
Solids Formation
Nonfluidized bed prilling
agricultural grade
feed grade
Fluidized bed prilling
agricultural grade
feed grade
Drum granulation
Rotary Drum Cooler
Bagging
Bulk Loading
NA
90
85
60
24
b
0.70
NA
NA
HA
84
74
52
13
b
0.15
NA
NA
NA
79
50
43
14
b
0.04
NA
NA
NA = not available. No data were available on particle sizes of controlled
emissions. Particle size information was collected uncontrolled in the
ducts and may not reflect particle size in the ambient air.
All particulate matter ^.5.7 um was collected in the cyclone precollector
sampling equipment.
6.14-4
EMISSION FACTORS
1/84
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TABLE 6.14-1. EMISSION FACTORS FOR UREA PRODUCTION*1
EMISSION FACTOR RATING: Ab
Farticulates
Operation
Solution formation ,
and concentration
Solids formation
Nonfluidized
bed prilling
agricultural grade**
feed grade''
Fluidized bed prilling
agricultural grade-1
feed grade-1
fc
Drum granulation
Rotary drum cooler
Bagging
Uncontrolled
kg/Mg
0.0105s
1.9h
1.8
3.1
1.8
120
3.72
0.09511
Ib/ton
0.021e
3.8h
3.6
6.2
3.6
241
7.45
0.19n
Ammonia
Controlled Uncontrolled
kg/Mg Ib/ton kg/Mg
9.!2£
0.032 0.064 0.43
NA NA NA
0.39 0.78 1.46
0.24 0.48 2.07
0.115 0.234 1.071
0.10° 0.20™ 0.0256
NA NA NA
Ib/ton
18.24f
0.87
NA
2.91
4.14
2.151
0.051
NA
Exiting Control Device
kg/Mg
-
i
NA
1
1.04
h
NA
NA
Ib/ton
-
i
NA
i
2.08
h
NA
NA
Based on emissions per unit of production output. Dash - not applicable. NA = not available.
Emission Factor Rating is C for controlled particulate emissions from rotary drum coolers
and uncontrolled particulate emissions from bagging.
Cparticulate teat data were collected using a modification of EPA Reference Method 5. Reference 1,
Appendix B explains these modifications.
References 14 - 16, 19. Emissions from the synthesis process are generally combined with emissions
from the solution concentration process and vented through a common stack. In the synthesis
process, some emission control is inherent in the recycle process where carbamate gases and/or
liquids are recovered and recycled.
eEFA test data indicated a range of 0.0052 - 0.0150 kg/Mg (0.0104 - 0.0317 Ib/ton).
f£PA test data indicated a range of 3.79 - 14.44 kg/Mg (7.58 - 28.89 Ib/ton).
^Reference 20. These factors were determined at an ambient temperature of 288K - 294K
(57T - 69°F), The controlled emission factors are based on ducting exhaust through a downcomer
and then a wetted fiber filter scrubber achieving a 98.3 percent efficiency. This represents a
higher degree of control than is typical in this Industry,
t'igures are based on EPA test data. Industry test data ranged from 0.39 - 1.79 kg/hg
(0.78 - 3.58 Ib/ton).
No ammonia control demonstrated by scrubbers installed for particulate control. Some increase in
ammonia emissions exiting the control device was noted.
^Reference 19. Feed grade factors were determined at an ambient temperature of 302K (85°F) and
agricultural grade factors at an ambient temperature of 299K (80°F). For fluidized bed prilling,
controlled emission factors are based on use of an entrainment scrubber.
References 14 - 16. Controlled emission factors are based on use of a wet entrainment scrubber.
Wet scrubbers are standard process equipment on drum granulators. Uncontrolled emissions were
measured at the scrubber inlet.
^FA test data indicated a range of 0.955 - 1.20 kg/Mg (1.91 - 2.40 Ib/ton).
"EMISSION FACTOR RATING: C; Reference 1.
DEMISSION FACTOR RATING: C; Reference 1.
1/84
Food and Agricultural Industry
6.14-5
-------
Urea manufacturers presently control particulate matter emissions from
prill towers, coolers, granulators and bagging operations. With the
exception of bagging operations, urea emission sources usually are
controlled with wet scrubbers. The preference of scrubber systems over dry
collection systems is primarily for the easy recycling of dissolved urea
collected in the device. Scrubber liquors are recycled to the solution
concentration process to eliminate waste disposal problems and to recover
the urea collected.1
Fabric filters (baghouses) are used to control fugitive dust from
bagging operations, where humidities are low and blinding of the bags is not
a problem. However, many bagging operations are uncontrolled.1
References for Section 6.14
1. Urea Manufacturing Industry - Technical Document, EPA-450/3-81-001,
U. S. Environmental Protection Agency, Research Triangle Park, NC,
January 1981.
2. D. F. Bress, M. W. Packbier, "The Startup of Two Major Urea Plants/'
Chemical Engineering Progress, May 19777 p. 80.
3. A. V. Slack, "Urea/1 Fertilizer Development Trends. Noyes Development
Corporation, Park Ridge, NJ, 1968, p. 121.
4. Written communication from J. M. Killen, Vistron Corporation, Lima, OH,
to D. R. Goodwin, U. S. Environmental Protection Agency, Research
Triangle Park, NC, December 21, 1978.
5. Written communication from J. P. Swanburg, Union Oil of California,
Brea, CA, to D. R. Goodwin, U. S. Environmental Protection Agency,
Research Triangle Park, NC, December 20, 1978.
6. Written communication from M. I. Bornstein and S. V. Capone, GCA
Corporation, Bedford, MA, to E. A. Noble, U. S. Environmental
Protection Agency, Research Triangle Park, NC, June 22, 1978.
7. Written communication from Gary McAlister, U. S. Environmental
Protection Agency, Emission Measurement Branch, to Eric Noble, U. S.
Environmental Protection Agency, Industrial Studies Branch, Research
Triangle Park, NC, July 28, 1983.
8. Formaldehyde Use in Urea-Based Fertilizers, Report of the Fertilizer
Institute's Formaldehyde Task Group, The Fertilizer Institute,
Washington, D. C., February 4, 1983.
9. J. H. Cramer, "Urea Prill Tower Control Meeting 20% Opacity,"
Presented at the Fertilizer Institute Environmental Symposium,
New Orleans, LA, April 1980.
10. Written communication from M. I. Bornstein, GCA Corporation, Bedford,
MA, to E. A. Noble, U. S. Environmental Protection Agency, Research
Triangle Park, NC, August 2, 1978.
6-14-6 EMISSION FACTORS
1/84
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11. Written communication from M. I. Bornstein and S. V. Capone, GCA
Corporation, Bedford, MA, to E. A. Noble, U. S. Environmental
Protection Agency, Research Triangle Park, NC, June 23, 1978.
12. Written communication from J. P. Alexander, Agrico Chemical Company,
Donaldsonville, LA, to D. R. Goodwin, U. S. Environmental Protection
Agency, NC, December 21, 1978.
13. Written communication from N. E. Picquet, W. R. Grace and Company,
Memphis, TN, to D. R. Goodwin, U. S. Environmental Protection Agency,
Research Triangle Park, NC, December 14, 1978.
14. Urea Manufacture: ^Agrico Chemical Company Emission Test Report, EMB
Report 79-NHF-13a, U. S. Environmental Protection Agency, Research
Triangle Park, NC, September 1980.
15. Urea Manufacture: Agrico Chemical Company Emission Test Report, EMB
Report 78-NHF-4, U. S. Environmental Protection Agency, Research
Triangle Park, NC, April 1979.
16. Urea Manufacture: CF Industries Emission Test Report, EMB Report
78-NHF-8, U. S. Environmental Protection Agency, Research Triangle
Park, NC, May 1979.
17. Urea Manufacture: Union Oil of California Emission Test Report, EMB
Report 78-NHF-7, U. S. Environmental Protection Agency, Research
Triangle Park, NC, October 1979.
18. Urea Manufacture: Union Oil of California Emission Test Report. EMB
Report 80-NHF-15, U. S. Environmental Protection Agency, Research
Triangle Park, NC, September 1980.
19. Urea Manufacture: W. R. Grace and Company Emission Test Report, EMB
Report 78-NHF-3, U. S. Environmental Protection Agency, Research
Triangle Park, NC, December 1979.
20. Urea Manufacture: Reichhold Chemicals Emission Test Report, EMB Report
80-NHF-14, U. S. Environmental Protection Agency, Research Triangle
Park, NC, August 1980.
1/84 Food and Agricultural Industry 6.14-7
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6.15 BEEF CATTLE FEEDLOTS
6.15.1 General1
A beef cattle feedlot is an area in which beef animals are confined for fattening prior to marketing.
This fattening, or finish feeding, typically lasts four to five months, during which time the cattle are fed
a high energy ration of feed grains and/or forage.
Cattle feedlots range in capacity from several head up to 100,000 cattle. Of the 146,000 beef cattle feed-
lots in the U.S. in 1973, 2,040 feedlots had a capacity of more than 1,000 head, marketing 65 percent of all
finish fed beef cattle. Animal density in feedlots is generally in the range of 12,500 to 125,000 head/km2.
During its stay in a feedlot, a beef animal will produce over 450 kg of manure (dry weight). Wet manure
production is typically about 27 kg per day per head, usually deposited on less than 20 m2 of surface.
Because of the prodigious quantity of manure produced in a feedlot, periodic removal is necessary to
prevent unacceptable accumulations. Most cattle manure is applied to nearby land as fertilizer for feed
grain production, while some is lagooned, dumped on wastelands, or disposed of through incineration,
liming, or pitting. Manure removal frequencies are dictated in part by climatic conditions, animal comfort.
labor scheduling, and air and water pollution control potentials. TypicaJly, manure removal is conducted
from one to three times per year. When disposal is not immediately possible after removal, the manure may
be stockpiled on a nearby open site.
The leading states in the industry are Texas, Nebraska, Iowa, Kansas, Colorado, California, and
Illinois. These states contribute 75 percent of all feed cattle marketed and contain 72 percent of the feedlots
greater than 1000 head capacity. Feedlots are generally located in low population density regions with
access to major transportation routes.
6.15.2 Emissions and Controls1
Air pollution from feedlots originates from several points in a feedlot operation, including the holding
pens, runoff holding ponds, and alleyways among pens. Major pollutants of concern include fugitive par-
ticulate, ammonia and various malodorous gases.
Fugitive particulate is generated several ways. Cattle movement within the holding pens is a primary
source. Dust is also generated by wind acting on the dried surfaces and by vehicular traffic on alleyways
among the pens. Fugitive particulate emissions from feedlots are composed largely of soil dust and dried
manure. The potential for dust generation is greatly increased during prolonged dry periods (e.g., from late
spring to midsummer in the Southwest), and when a loose, dry pad of soil and manure is allowed to build
up in the pens.
Ammonia is the predominant gaseous pollutant emitted from feedlots. Ammonia is a result of anaerobic
decomposition of feedlot surfaces as well as volatilization from urine. Ammonia emissions are generally
increased when conditions favor anaerobic decay. For example, although 25 to 40 percent moisture levels
are necessary on feedlot surfaces for aerobic decomposition (which is odorless), too much rain or
watering, resulting in puddling and wet spots, can trigger increased ammonia production. Ammonia forma-
tion may also occur when anaerobic conditions exist in the manure stockpiles and runoff holding ponds.
In general, higher ammonia emissions are associated with higher temperatures and humidity, overly wet
conditions, and feedlot disturbances such as mounding or manure removal.
A number of extremely odorous compounds (amines, sulfides. mercaptans) may also result from
anaerobic decomposition of solid manure beneath the feedlot surface as well as in the runoff holding ponds.
7/79 Food and Agricultural Industry 6.15-1
-------
Generally, the same conditions that favor ammonia production will enhance the evolution of these other
gases, as well.
No air pollutant control devices are applied to feedlots because of the fugitive nature of the emissions.
The most effective controls involve various housekeeping mea
sures designed to eliminate conditions that
favor the generation of dust and odors. For example, measures that help to maintain sufficient moisture
levels in the feedlot surface areas and manure stockpiles will reduce the generation of dust. One of the most
effective dust control techniques is periodic application of water to the dry feedlot surface, by either per-
manent sprinkling systems or mobile tank trucks. However, care must be taken to avoid overwatering,
which can cause wet spots conducive to anaerobic decay and subsequent malodors. Increasing the cattle
density in the pens may also help maintain high enough moisture levels to limit particulate generation.
In addition, some dust control is effected by minimizing the accumulation of dry and pulverized manure on
the surfaces of the feedlots. A maximum depth of 2 to 8 cm of loose, dry manure is recommended for
increasing the effectiveness of dust control procedures.
Odor and ammonia control are best effected by housekeeping measures that enhance aerobic rather
than anaerobic decomposition of the cattle waste*. For example, besides reducing dust emissions,
sprinkling provides moisture for aerobic biodegradation of the manure. Good drainage must be provided,
however, and overwatering must be avoided. Deep accumulations of manure of slurry consistency can
optimize anaerobic conditions. Hence, feedlot surfaces should be periodically scraped to remove such
accumulations. Scraping should be done carefully, so that only the surface layer is disturbed. Manure
stockpiles should not be allowed to get too large, too wet, or encrusted, and they should be disposed of
within four or five days. If the stockpiles are composted, the manure should be piled in long narrow win-
drows tu allow access for turning the piles to promote aerobic conditions and to enable rapid control of
spontaneous combustion fires. Anaerobic conditions can be reduced in runoff holding ponds by removing
solids from the runoff, by adding more water to the ponds to dilute the nutrient content, and by aeration
of the surface. Runoff water also may be treated chemically to suppress the release of malodorous gases.
Emission factors for feedlot operations are shown in Table 6.15-1. These factors should be considered
at best to be crude estimates of potential emissions from feedlots where no measures are employed to
control dust or odors. The limitations of these factors are more fully discussed in the footnote to Table
6.15-1. The reader should consult Reference 1 for a detailed discussion of the emissions and control
information available on beef cattle feedlots.
6.13-2
EMISSION FACTORS
7/79
-------
Table 6.15-1. EMISSION FACTORS FOR BEEF CATTLE FEEDLOTS8
EMISSION FACTOR RATING: E
Pollutant
Particulateb
Ammonia0
Amines0
Total sulfur compounds0
Feedlot capacity basis
Ib (kg) per day per
1000 head capacity
280 (130)
11 (5)
0.4 (0.2)
1.7 (0.8)
Feedlot throughput basis
ton (metric ton) per
1000 head throughput
27 (25)
1.1 (1)
0.044 (0.04)
0.15 (0.14)
aThese factors represent general feedlot operations with no housekeeping measures for air pollution control.
Because of the limited data available on emissions and the nature of the techniques utilized to develop emission
factors, Table 6.15-1 should only be used to develop order-of-magnitude estimates of feedlot emissions. AN factors
are based on information compiled in Reference 1.
bThese factors represent emissions during a dry season at a feedlot where watering as a dust control measure would
not be a common practice. No data are available to estimate emission factors for feed lots during periods of abundant
precipitation or where watering and other housekeeping measures are employed for dust control.
cThese factors represent emission factors for feedlots that have not been chemically treated and where no special
housekeeping measures are employed for odor control.
Reference for Section 6.15
1. J.A. Peters and T.R. Blackwood, Source Assessment: Beef Cattle Feedlots, EPA-600/2-77-107, U.S. Environ-
mental Protection Agency. Research Triangle Park, NC. June 1977.
7/79
Food and Agricultural Industry
6.13-3
-------
-------
6.16 DEFOLIATION AND HARVESTING OF COTTON
6.16.1 General
Wherever it is grown in the U.S., cotton is defoliated or disiccated prior to harvest. Defoliants are used
on the taller varieties of cotton which are machine picked for lint and seed cotton, while desiccants usually
are used on short, stormproof cotton varieties of lower yield that are harvested by mechanical stripper
equipment. More than 99 percent of the national cotton area is harvested mechanically. The two principal
harvest methods are machine picking, with 70 percent of the harvest from 61 percent of the area, and
machine stripping, with 29 percent of the harvest from 39 percent of the area. Picking is practiced through-
out the cotton regions of the U.S., while stripping is limited chiefly to the dry plains of Texas and Oklahoma.
Defoliation may be defined as the process by which leaves are abscised from the plant. The process may
be initiated by drought stress, low temperatures or disease, or it may be chemically induced by topically
applied defoliant agents or by overfertilization. The process helps lodged plants to return to an erect posi-
tion, removes the leaves which can clog the spindles of the picking machine and strain the fiber, accelerates
the opening of mature bolls, and reduces boll rots. Desiccation by chemicals is the drying or rapid killing
of the leaf blades and petioles, with the leaves remaining in a withered state on the plant. Harvest-aid
chemicals are applied to cotton as water-based spray, either by aircraft or by a ground machine.
Mechanical cotton pickers, as the name implies, pick locks of seed cotton from open cotton bolls and
leave the empty burs and unopened bolls on the plant. Requiring only one operator, typical modern pickers
are self propelled and can simultaneously harvest two rows of cotton at a speed of 1.1 to 1.6 meters per
second (2.5.- 3,6 mph). When the picker basket gets filled with seed cotton, the machine is driven to a
cotton trailer at the edge of the field. As the basket is fiydraulically raised and tilted, the top swings open.
allowing the cotton to fall into the trailer. When the trailer is full, it is pulled from the field, usually by pick-
up truck, and taken to a cotton gin.
Mechanical cotton strippers remove open and unopened bolls, along with burs, leaves and stems from
cotton plants, leaving only bare branches. Tractor-mounted, tractor-pulled or self propelled, strippers
require only one operator. They harvest from one to four rows of cotton at speeds of 1.8 to 2.7 m/s (4.0 -
6.0 mph). After the cotton is stripped, it enters a conveying system that carries it from the stripping unit to
an elevator. Most conveyers utilize either augers or a series of rotating spike-toothed cylinders to move the
cotton, accomplishing some cleaning by moving the cotton over perforated, slotted or wire mesh screen.
Dry plant material (burs, stems and leaves) is crushed and dropped through openings to the ground. Blown
air is sometimes used to assist cleaning.
6.16.2 Emissions and Controls
Emission factors for the drifting of major chemicals applied to cotton are compiled from literature and
reported in Reference 1. In addition, drift losses from arsenic acid spraying were developed by field
testing. Two off-target collection stations, with six air samplers each, were located downwind from the
ground spraying operations. The measured concentration was applied to an infinite line source atmosphere
diffusion model (in reverse) to calculate the drift emission rate. This was in turn used for the final emission
factor calculation. The emissions occur from July to October, preceding by two weeks the period of harvest
in each cotton producing region. The drift emission factor for arsenic acid is eight times lower than pre-
viously estimated, since Reference 1 used aground rig rather than an airplane, and because of the low vola-
tility of arsenic acid. Various methods of controlling drop size, proper timing of application, and modifica-
tion of equipment are practices which can reduce drift hazards. Fluid additives have been used that in-
crease the viscosity of the spray formulation, and thus decrease the number of fine droplets XlOO /j.rn).
~/"9 Food and Agricultural Industry 6.16-1
-------
Spray nozzle design and orientation also control the droplet size spectrum. Drift emission factors for the
defoliation of desiccation of cotton are listed in Table 6.16-1.
Table 6.16-1. EMISSION FACTORS FOR
DEFOLIATION OR DESICCATION OF COTTON3
EMISSION FACTOR RATING: C
Pollutant
Sodium chlorate
DEF
Arsenic acid
Paraquat
Emission factorb
Ib/ton
20.0
20.0
12.2
20.0
9/kg
10,0
10.0
6.1
10.0
aReference 1
bFactor is in terms of quantity of drift per quantity applied.
Three unit operations are involved in mechanical harvesting of cotton: harvesting, trailer loading (basket
dumping) and transport of trailers in the field. Emissions from these operation? are in the form of solid
particulates. Particulate emissions (<7 /u.m mean aerodynamic diameter) from these operations were de-
veloped in Reference 2. The particulates are composed mainly of raw cotton dust and solid, dust,, which
contains free silica. Minor emissions include small quantities of pesticide, defoliant and desiccant residues
that are present in the emitted particulates. Dust concentrations from harvesting were measured by
following each harvesting machine through the field at a constant distance directly downwind from the
machine, while staying in the visible plume centerline. The procedure for trailer loading was the same,
but since the trailer is stationary while being loaded, it was necessary only to stand a fixed distance
directly downwind from the trailer while the plume or puff passed over. Readings were taken upwind of all
field activity to get background concentrations. Particulate emission factors for the principal types of
cotton harvesting operations in the U.S. are shown in Table 6.16-2. The factors are based on average
machine speed of 1.34 m/s (3,0 mph) for pickers' and 2.25 m/s (5.03 mph) for strippers, on a basket capacity
of 109 kg (240 Ib), on a trailer capacity of 6 baskets, on a lint cotton yield of 63.0 metric tons/km2 (1.17 bale/
acre) for pickers and 41.2 metric tons/km2 (.77 bale/acre) for strippers, and on a transport speed of 4.47 rn/s
(10.0 mph). Analysis of particulate samples showed average free silica content of 7.9 percent for mechan-
ical cotton picking and 2.3 percent for mechanical cotton stripping. Estimated maximum percentages for
pesticides, defoliants and desiccants from harvesting are also noted in Table 6.16-2. No current cotton
harvesting equipment or practices provide for control of emissions. In fact, equipment design and operat-
ing practices tend to maximize emissions. Preharvest treatment (defoliation and desiccation) and harvest
practices are timed to minimize moisture and trash content, so they also tend to maximize emissions. Soil
dust emissions from field transport can be reduced by lowering vehicle speed.
6.16-2
EMISSION FACTORS
7/79
-------
Table 6.16-2. PARTICULATE EMISSION FACTORS FOR COTTON HARVESTING OPERATIONS8
EMISSION FACTOR RATING: C
Type of harvester
Picker0
Two-row, with basket
Stripped
Two-row, pulled trailer
Two-row, with basket
Four-row, with basket
Weighted average6
Harvesting
JS9_
km2
.46
7.4 .
2.3
2.3
4.3
Ib
ml2
2.6
42
13
13
24
Trailer
loading
kg
km2
.070
_b
.092
.092
.056
Ib
"ml5'
.40
.52
.52
.32
Transport
-^
km5
.43
.28
.28
.28
.28
Ib
TriF"
2.5
1.6
1.6
1.6
1.6
Total
•^
krrF
.96
7.7
2.7
2.7
4.6
.Ib
TriF
5.4
44
15
15
26
aEmission factors are from Reference 2 for participate of <7 ^m mean aerodynamic diameter.
bNot applicable
GFree silica content is 7.9%; maximum content of pesticides and defoliants is 0.02%.
dFree silica content is 2.3%; maximum content of pesticides and desiccants is 0.2%.
eThe weighted average stripping factors are based on estimates that 2% of all strippers are four-row .models with
baskets, and of the remainder, 40% are two-row models pulling trailers and 60% are two-row models with mounted
baskets.
References for Section 6.16
1. J. A. Peters and T. R. Blaekwood, Source Assessment: Defoliation of Cotton-State of the Art, EPA-600/2-77-107g.
U.S. Environmental Protection Agency, Research Triangle Park. NC. July 1977.
2. J.' W. Snyder and T. R. Blaekwood, Source Assessment: Mechanical Harvesting of Cotton-State of the Art, EPA-
600/2-77-107d, U. S. Environmental Protection Agency, Research Triangle Park, NC, July 1977.
7/79
Food and Agricultural Industry
6.16-3
-------
6.17 HARVESTING OF GRAIN
6.17.1 General1
Harvesting of grain refers to the activities performed to obtain
the cereal kernels of the plant for grain or the entire plant for forage
and/or silage uses. These activities are accomplished by machines that
cut, thresh, screen, clean, bind, pick, and shell the crops in the
field. Harvesting also includes loading harvested crops into trucks and
transporting crops on the grain field.
Crops harvested for their cereal kernels are cut as close as
possible to the inflorescence (the flowering portion containing the
kernels). This portion is threshed, screened and cleaned to separate
the kernels. The grain is stored in the harvest machine while the
remainder of the plant is discharged back onto the field.
Combines perform all of the above activities in one operation.
Binder machines only cut the grain plants and tie them into bundles or
leave them in a row in the field (called a windrow). The bundles are
allowed to dry for threshing later by a combine with a pickup
attachment.
Corn harvesting requires the only exception to the above
procedures. Corn is harvested by mechanical pickers, picker/shellers,
and combines with corn head attachments. These machines cut and husk
the ears from the standing stalk. The sheller unit also removes the
kernels from the ear. After husking, a binder is sometimes used to
bundle entire plants into piles (called shocks) to dry.
For forage and/or silage, mowers, crushers, windrowers, field
choppers, binders, and similar cutting machines are used to harvest
grasses, stalks and cereal kernels. These machines cut the plants as
close to the ground as possible and leave them in a windrow. The plants
are later picked up and tied by a baler.
Harvested crops are loaded onto trucks in the field. Grain kernels
are loaded through a spout from the combine, and forage and silage bales
are manually or mechanically placed in the trucks. The harvested crop
is then transported from the field to a storage facility.
6.17.2 Emissions and Controls
Emissions are generated by three grain harvesting operations,
(1) crop handling by the harvest machine, (2) loading of the harvested
crop into trucks, and (3) transport by trucks on the field. Particulate
matter, composed of soil dust and plant tissue fragments (chaff) may be
entrained by wind. Particulate emissions from these operations (<7um
mean aerodynamic diameter) are developed in Reference 1. For this
study, collection stations with air samplers were located downwind
(leeward) from the harvesting operations, and dust concentrations were
2/80 Food and Agricultural Industry 6.17-1
-------
measured at the visible plume centerline and at a constant distance
behind the combines. For product loading, since the trailer is station-
ary while being loaded, it was necessary only to take measurements a
fixed distance downwind from the trailer while the plume or puff passed
over. The concentration measured for harvesting and loading was applied
to a point source atmospheric diffusion model to calculate the source
emission rate. For field transport, the air samplers were again placed
a fixed distance downwind from the path of the truck, but this time the
concentration measured was applied to a line source diffusion model.
Readings taken upwind of all field activity gave background concen-
trations. Particulate emission factors for wheat and sorghum harvesting
operations are shown in Table 6.17-1.
There are no control techniques specifically implemented for the
reduction of air pollution emissions from grain harvesting. However,
several practices and occurences do affect emission rates and concen-
tration. The use of terraces, contouring, and stripcropping to inhibit
soil erosion will suppress the entrainment of harvested crop fragments
in the wind. Shelterbelts, positioned perpendicular to the prevailing
wind, will lower emissions by reducing the wind velocity across the
field. By minimizing tillage and avoiding residue burning, the soil
will remain consolidated and less prone to disturbance from transport
activities.
Table 6.17-1. EMISSION RATES/FACTORS FROM THE HARVESTING
GRAIN3
EMISSION FACTOR RATING: D
Operation
Harvest
machine
Truck
loading
Field
transport
Emission rate
Wheat Sorghum
Ib/hr
0.027
0.014
0.37
mg/sec
3.4
1.8
47.0
Ib/hr mg/sec
0.18 23.0
0.014 1.8
0.37 47.0
Q
Emission factor
Wheat Sorghum
lb/mi2
0.96
0.07
0.65
g/km
170.0
12.0
110.0
2 2
lb/mi g/km
6.5 1100.0
0.13 22.0
1.2 200.0
Reference 1.
Assumptions from Reference 1 are an average combine speed of 3.36
meters per second, combine swath width of 6.07 meters, and a field
transport speed of 4.48 meters per second.
In addition to Note b, assumptions are a truck loading time of six
minutes, a truck capacity of .052 km2 for wheat and .029 km2 for
sorghum, and a filed truck travel time of 125 seconds per load.
6.17-2
EMISSION FACTORS
2/«0
-------
Reference for Section 1.14
1. R. A. Wachten and T. R. Blackwood, Source Assessment; Harvesting
of Grain. State of the Art. EPA-600/2-79-107f, U. S. Environmental
Protection Agency, Research Triangle Park, NC, July 1977.
2/80 Food ami .\grioullural Iiuluslry
-------
-------
6.18 AMMONIUM SULFATE MANUFACTURE
6.18.1 General
Ammonium sulfate, [NH4]2S04, is commonly used as a fertilizer.
About 90 percent of ammonium sulfate is produced by three types of
facilities, caprolactam byproduct, synthetic, and coke oven byproduct
plants. The remainder is produced as a byproduct of nickel manu-
facture from ore concentrates, methyl methacrylate manufacture, and
ammonia scrubbing of tail gas at sulfuric acid plants.
During the manufacture of caprolactam, [Cl^^COHN, ammonium
sulfate is produced from the oximation process stream and the
rearrangement reaction stream. Synthetic ammonium sulfate is
produced by the direct combination of ammonia and sulfuric acid in
a reactor. Coke oven byproduct ammonium sulfate is produced by
reacting ammonia recovered from coke oven offgas with sulfuric
acid. Figure 6.18-1 is a process flow diagram for each of the
three primary commercial processes.
After formation of the ammonium sulfate solution, operations
of each process are similar. Ammonium sulfate crystals are formed
by continuously circulating an ammonium sulfate liquor through an
evaporator to thicken the solution. Ammonium sulfate crystals are
separated from tbe liquor in the centrifuge. The saturated liquor
is returned to the dilute ammonium sulfate brine of the evaporator.
The crystals, with about 1 to 2.5 percent moisture by weight after
the centrifuge, are fed to either a fluidized bed or rotary drum
dryer. Fluidized bed dryers are continuously steam heated, and
rotary dryers are either directly fired with oil or natural gas, or
they use steam heated air. At coke oven byproduct plants, rotary
drum dryers may be used in place of a centrifuge and dryer. On the
filter of these dryers, a crystal layer is deposited which is
removed from the drum by a scraper or a knife.
The volume of ammonium sulfate in the dryer exhaust gas varies
according to production process and dryer type. A gas flow rate of
620 scm/Mg of product (20,000 scf/ton) is considered representative
of a direct fired rotary drum dryer. A gas flow of 2,500 scm/Mg of
product (80,000 scf/ton) is considered representative of a steam
heated fluidized bed dryer. Dryer exhaust gases are passed through
a particulate collection device, usually a wet scrubber, for product
recovery and for pollution control.
The ammonium sulfate crystals are conveyed from the dryer to
an enclosure where they are screened to product specifications,
generally to coarse and fine products. The screening is enclosed
to control dust in the building.
4/81 Food and Agricultural Industry 6.18-1
-------
00
a
g
Caprolactum Byproduct
35-40%
AS Solution
Generation
Heater
t^T
Steam Cond.
Crystallizer
Synthetic AS
NH3
Oo~
Reactor
(Saturator)
.— >
To Atm.
Vacuum
System
Cond .
Vacuum
System
t
To Atm.
Steam Cond.
Particulate and VOC Emissions
t
Scrubber
or
Baghouse
Coke Oven Byproduct
_
Oven
Ammonia
Absorber
Ammonia
Still
Steam
- ' 1— >
Reactor
(Saturator)
Cond.
Vacuum
Filter
Dryer
Steam
- ' ' — >•
- Air
Cond.
Figure 6.18-1. Diagram of Ammonium Sulfate (AS) processes.
-------
6,18.2 Emissions and Controls
Ammonium sulfate particulate is the principal pollutant emitted
to the atmosphere from the manufacturing plants, nearly all of it
being contained in the gaseous exhaust of the dryers. Other plant
processes, such as evaporation, screening, and materials handling,
are not significant sources of emissions.
The particulate emission rate of a dryer depends on the gas
velocity and the particle size distribution. Since gas velocity
varies according to the dryer type, emission rates also vary.
Generally, the gas velocity of fluidized bed dryers is higher than
for most rotary drum dryers, and particulate emission rates are
also higher. The smaller the particle, the easier it is removed by
the gas stream of either type of dryer.
At caprolactam byproduct plants, volatile organic compounds
(VOC) are emitted from the dryers. Emissions of caprolactam vapor
are at least two orders of magnitude lower than the particulate
emissions.
Wet scrubbers, such as venturi and centrifuge, are most suitable
for reducing particulate emissions from the dryers. Wet scrubbers
use process streams as the scrubbing liquid. This allows the
collected particulate to be recycled easily to the production
system.
Table 6.18-1 shows the uncontrolled and controlled emission
factors for the various dryer types. The VOC emissions shown in
Table 6.18-1 apply only to caprolactam byproduct plants which may
use either a fluidized bed or rotary drum dryer.
TABLE 6.18-1. EMISSION FACTORS FOR AMMONIUM SULFATE MANUFACTURE3
EMISSION FACTOR RATING: B
Particulates Volatile Organic Compounds
Dryer Type & Controls kg/MgIb/ton kg/Mglb/ton
Rotary dryers
Uncontrolled 23 46 0.74 1.48
Wet scrubber 0.12 0.24 0.11 0.22
Fluidized bed dryers
Uncontrolled
Wet scrubber
109
0.14
218
0.28
0.74
0.11
1.48
0.22
•a
Expressed as emissions by weight per unit of ammonium sulfate
.production by weight.
VOC emissions occur only at caprolactam plants using either type
of dryer. The emissions are caprolactam vapor.
4/81 Food and Agricultural Industry 6.18-3
-------
Reference for Section 6.18
Sulfate Manufacture - Background Information for Proposed
Emission Standards, EPA-450/3-79-034a, U.S. Environmental Protection
Agency, Research Triangle Park, NC, December 1979.
6.18-4 EMISSION FACTORS 4/81
-------
7.1 PRIMARY ALUMINUM PRODUCTION
7.1.1 Process Description1""^
The base ore for primary aluminum production Is bauxite, a hydrated
oxide of aluminum consisting of 30 to 70 percent alumina (A1203) and lesser
amounts of iron, silicon and titanium. The bauxite ore is first purified to
alumina by the Bayer process, and this is then reduced to elemental aluminum.
The production of alumina and the reduction of alumina to aluminum are seldom
accomplished at the same facility. A schematic diagram of the primary
production of aluminum is shown at Figure 7.1-1.
In the Bayer process, the ore is dried, ground in ball mills and mixed
with a leaching solution of sodium hydroxide at an elevated temperature and
pressure, producing a sodium aluminate solution which is separated from the
bauxite impurities and cooled. As the solution cools, the hydrated aluminum
oxide (A1203 . 3H20) precipitates. Following separation and washing to
remove iron oxide, silica and other impurities, the hydrated aluminum oxide
is dried and calcined to produce a crystalline form of alumina ^1303),
advantageous for electrolysis.
Aluminum metal is manufactured by the Hall-Heroult process, which
involves the electrolytic reduction of alumina dissolved in a molten salt
bath of cryolite (Na3AlFg) and various salt additives:
2A1203 Electrolysis 4A1 + 302 d)
Alumina * Aluminum Oxygen
(reduction)
The electrolytic reduction occurs in shallow rectangular cells, or "pots",
which are steel shells lined with carbon. Carbon electrodes extend into the
pot and serve as the anodes, and the carbon lining the steel shell is the cathode.
Molten cryolite functions as both the electrolyte and the solvent for the
alumina. Electrical resistance to the current passing between the electrodes
generates heat that maintains cell operating temperatures between 950° and
1000°C (1730° and 1830°F). Aluminum Is deposited at the cathode, where it
remains as molten metal below the surface of the cryolite bath. The carbon
anodes are continuously depleted by the reaction of oxygen (formed during the
reaction) and anode carbon, to produce carbon monoxide and carbon dioxide.
Carbon consumption and other raw material and energy requirements for aluminum
production are summarized In Table 7.1-1. The aluminum product is period-
ically tapped beneath the cryolite cover and is fluxed to remove trace
impurities.
Aluminum reduction cells are distinguished by the anode type and
configuration used in the pots. Three types of pots are currently used,
prebaked (PB), horizontal stud Soderberg (HSS), and vertical stud Soderberg
(VSS). Most of the aluminum produced in the U. S. Is processed in PB cells.
Anodes are produced as an ancillary operation at the reduction plant.
In the paste preparation plant, petroleum coke Is mixed with a pitch binder
4/81 Metallurgical Industry 7.1-1
-------
BAUXITE
TO CONTROL DEVICE
I
SODIUM
HYDROXIDE
SETTLING
CHAMBER
DILUTION
WATER
RED MUD
(IMPURITIES)
I
DILUTE
SODIUM
HYDROXIDE
TO CONTROL
DEVICE
CRYSTALLIZER
AQUEOUS SODIUM
ALUMINATE
TO CONTROL DEVICE
I
BAKING
FURNACE
BAKED
ANODES
, TO CONTROL DEVICE
PREBAKE
REDUCTION
CELL
ANODE PASTE
TO CONTROL DEVICE
HORIZONTAL
OR VERTICAL
SODERBERG
REDUCTION CELL
MOLTEN
ALUMINUM
Figure 7.1-1. Schematic diagram of primary aluminum production process.
7.1-2
EMISSION FACTORS
4/81
-------
to form a paste which is used for Soderberg cell anodes, and for green anodes
for prebake cells. Paste preparation includes crushing, grinding and screen-
ing of coke and cleaned spent anodes (butts), and blending with a pitch binder
in a steam jacketed mixer. For Soderberg anodes, the thick paste mixture is
transferred directly to the potroom for addition to the anode casings. In
prebake anode preparation, the paste mixture is molded to form self supporting
green anode blocks. The blocks are baked in a direct fired ring furnace or an
indirect fired tunnel kiln. Baked anodes are then transferred to the rodding
room, where the electrodes are attached- Volatile organic vapors from the pitch
paste are emitted during anode baking, and most are destroyed in the baking
furnace. The baked anodes, typically 14 to 24 per cell, are attached to metal
rods and serve as replaceable anodes.
TABLE 7.1-1. RAW MATERIAL AND ENERGY REQUIREMENTS FOR ALUMINUM PRODUCTION
Parameter
Typical value
Cell operating temperature
Current through pot line
Voltage drop per cell
Current efficiency
Energy required
Weight alumina consumed
Weight electrolyte
fluoride consumed
Weight carbon electrode
consumed
~ 950°C (~ 1740°F)
60,000 - 125,000 amperes
4.3 - 5.2
85 - 90%
13.2 - 18.7 kwh/kg aluminum
(6-0 - 8.5 kwh/lb aluminum)
1.89 - 1.92 kg(lb) Al203/kg(lb) aluminum
0.03 - 0.10 kg(lb) fluoride/kg(lb) aluminum
0.45 - 0.55 kg(lb) electrode/kg(lb) aluminum
In the electrolytic reduction of alumina, the carbon anodes are lowered
into the cell and consumed at a rate of about 2.5 centimeters (1 inch) per day.
Prebaked cells are preferred over Soderberg cells for their lower power require-
ments, reduced generation of volatile pitch vapors from the carbon anodes,
and provision for better cell hooding to capture emissions.
The second most commonly used reduction cell is the horizontal stud
Soderberg (HSS). This type of cell uses a "continuous" carbon anode. Green
anode paste is periodically added at the top of the anode casing of the pot
and Is baked by the heat of the cell to a solid carbon mass as the material
moves down the casing. The cell casing consists of aluminum sheeting and
perforated steel channels, through which electrode connections (studs) are
inserted horizontally into the anode paste. During reduction, as the baking
anode is lowered, the. lower row of studs and the bottom channel are removed,
and the flexible electrical connectors are moved to a higher row of studs.
High molecular weight organics from the anode paste are released, along with
other cell emissions. The heavy tars can cause plugging of exhaust ducts,
fans and emission control equipment.
The vertical stud Soderberg (VSS) cell is similar to the HSS cell, except
that the studs are mounted vertically in the anode paste. Gases from the VSS
4/81
Metallurgical Industry
7.1-3
-------
cells can be ducted to gas burners, and the tar and oils combusted. The con-
struction of the HSS cell prevents the installation of an integral gas collection
device, and hooding is restricted to a canopy or skirt at the base of the cell,
where the hot anode enters the cell bath.
Casting involves pouring molten aluminum into molds and cooling it with
water. At some plants, before casting, the molten aluminum may be batch treated
in furnaces to remove oxide, gaseous impurities and active metals such as
sodium and magnesium. One process consists of adding a flux of chloride and
fluoride salts and then bubbling chlorine gas, usually mixed with an inert
gas, through the molten mixture. Chlorine reacts with the impurities to form
HC1, A1203 and metal chloride emissions. A dross forms and floats on the
molten aluminum and is removed before casting.H
7.1.2 Emissions and Controls1"-^ '^
Controlled and uncontrolled emission factors for total particulate
matter, fluoride and sulfur oxides are presented in Table 7.1-2. Fugitive
particulate and fluoride emission factors for reduction cells are also pre-
sented in this Table.
In the preparation of refined alumina from bauxite, large amounts of
particulates are generated during the calcining of hydrated aluminum oxide,
but the economic value of this dust is such that extensive controls are
employed to reduce emissions to relatively small quantities. Small amounts
of particulates are emitted from the bauxite grinding and materials handling
processes.
Emissions from aluminum reduction processes consist primarily of gaseous
hydrogen fluoride and particulate fluorides, alumina, carbon monoxide, vola-
tile organics, and sulfur dioxide from the reduction cells, and fluorides,
vaporized organics and sulfur dioxide from the anode baking furnaces.
The source of fluoride emissions from reduction cells is the fluoride
electrolyte, which contains cryolite, aluminum fluoride (A1F3), and fluorspar
(CaF2)* For normal operation, the weight, or "bath", ratio of sodium fluo-
ride (NaF) to A1F3 is maintained between 1.36 and 1-43 by the addition of A1F3.
This increases the cell current efficiency and lowers the bath melting point,
permitting lower operating temperature in the cell. Cell fluoride emissions
are decreased by lowering the operating temperature. The ratio of gaseous
(mainly hydrogen fluoride and silicon tetrafluoride) to particulate fluorides
varies from 1.2 to 1.7 with PB and HSS cells, but attains a value of approx-
imately 3.0 with VSS cells.
Particulate emissions from reduction cells consist of alumina and carbon
from anode dusting, cryolite, aluminum fluoride, calcium fluoride, chiolite
(Na5Al3Fi4) and ferric oxide. Representative size distributions for partic-
ulate emissions from PB cells and HSS cells are presented in Table 7.1-3.
Particulates less than 1 micron in diameter represent the largest fraction
(35 - 44 percent) for uncontrolled emissions. In one HSS cell, uncontrolled
particulate emissions from one HSS cell had a mass mean particle diameter of 5.5
microns. Thirty percent by mass of the particles were submicron, and 16 percent
were less than 0.2 microns in diameter.'
7.1-4 EMISSION FACTORS 4/81
-------
oo
TABLE 7.1-2. EMISSION FACTORS FOR PRIMARY ALUMINUM PRODUCTION PROCESSES .
EMISSION FACTOR RATING: A
en
p.
o
OJ
M
H
a
g
~-J
•
I-1
I
Operation
Bauxite grinding
Uncontrolled
Spray tower
Floating bed scrubber
Quench Cover and
spray screen
Electrostatic
precipltator (ES?)
Aluminum hydroxide
Calcining
Uncontrolled
Spray tower
Floating bed scrubber
Quench tower
ESP
Anode baking furnace
Uncontrolled
Fugitive
Spray tower
ESP
Dry alimina scrubber
Prebake cell
Uncontrolled
Fugitive
Emissions to collector
Multiple cyclones
Dry alumina scrubber
Dry ESP + spray tower
Spray tower
Floating bed scrubber
Coated bag filter dry
scrubber
Cross flow packed bed
Dry + second scrubber
Total
Participate1*
Kg/Ms Ib/ton
3.0 6.0
0.9 1.8
0.85 1.7
0.5 1.0
0.06 0.12
100.0 200.0
30.0 60.0
28.0 56.0
17.0 34.0
2.0 4.0
1.5 3.0
NA NA
0.375 0.75
0.375 0.75
0.03 0.06
47.0 94.0
2.5 5.0
44.5 89.0
9.8 19.6
0.9 1.8
2.25 4.5
8.9 17.8
8.9 17.8
0.9 1.8
13.15 26.3
0.35 0.7
Gaseous
Fluoride
-------
•vj
•
t->
I
TABLE 7.1-2 (CONT.). EMISSION FACTORS FOR PRIMARY ALUMINUM PRODUCTION PROCESSES'
EMISSION FACTOR RATING: A
I
co
co
M
§
I
CO
Operation
Vertical Soderberg stud cell
Uncontrolled
Fugitive
Emissions to collector
Spray tower
Venturl scrubber
Multiple cyclones
Dry alumina scrubber
Scrubber + ESP + spray
screen + scrubber
Horizontal Soderberg stud cell
Uncontrolled
Fugitive
Emissions to collector
Spray tower
Floating bed scrubber
Scrubber + wet ESP
Web ESP
Dry alumina scrubber
Total
Participate^
Kg/Mg Ib/ton
39.0 78.0
6.0 12.0
33.0 66.0
8.25 16.5
1.3 2.6
16.5 33.0
0.65 1.3
3.85 7.7
49.0 98.0
5.0 10.0
44.0 88.0
11.0 22.0
9.7 19.4
0.9 1.8
0.9 1.8
0.9 1.8
Gaseous
Fluoride (HP)
kg/Mg Ib/ton
16.5 33.0
2.45 4,9
14.05 28.1
0.15 0.3
0.15 0.3
14.05 28.1
0.15 0.3
0.75 1.5
11.0 22.0
1.1 2.2
9.9 19.8
3.75 7.5
0.2 0.4
0.1 0.2
0.5 1.0
0.2 0.4
Partlculate
Fluoride (P)
kg/Mg Ib/ton
5.5 11.0
0.85 1.7
4.65 9.3
1.15 2.3
0.2 0.4
2.35 4.7
0.1 0.2
0.65 1.3
6.0 12.0
0.6 1.2
5.4 10.8
1.35 2.7
1.2 2.4
0.1 0.2
0.1 0.2
0.1 0.2
Sulfur
Oxides
kg/Mg Ib/ton
NA NA
NA NA
NA NA
NA NA
NA NA
NA NA
NA NA
NA NA
NA NA
NA NA
NA NA
NA NA
NA NA
NA NA
NA NA
NA NA
References
2,9
9
9
2
2
2
2
2,9
2,9
2,9
2,9
2
2,9
9
9
aFor bauxite grinding, expressed as kg/Mg (Ib/ton) of bauxite processed. For calcining of aluminum hydroxide,
expressed as kg/Mg (Ib/ton) of alumina produced. All other factors are per Mg (ton) of molten aluminum
product. Emission factors for sulfur oxides have C ratings. NA " not available.
^Includes partlculate fluorides.
c Anode baking furnace, uncontrolled SO, emissions (excluding furnace fuel combustion emissions):
20(C)(S)tl--°l K) kg/Mg [40{C)(S)(1-.01 K) Ib/ton]
oo
Prebake (reduction) cell, uncontrolled SOj emissions:
0.2(C)(S)(K) kg/Mg [0.4(C)(S)(K) Ib/ton]
Where: C - Anode consumption* during electrolysis, Ib anode consumed /lb Al produced
S - 2 sulfur In anode before baking
K - Z of total S02 emitted by prebake (reduction) cells
* Anode consumption weight is weight of anode paste (coke + pitch) before baking.
-------
TABLE 7.1-3. REPRESENTATIVE PARTICLE SIZE DISTRIBUTIONS OF UNCONTROLLED
EMISSIONS FROM PREBAKED AND HORIZONTAL STUD SODERBERG CELLSa
Size range (yV
<1
1 to 5
5 to 10
10 to 20
20 to 44
>44
Particles
PB
35
25
8
5
5
(wt %)
HSS
44
26
8
6
4
aReference
Emissions from reduction cells also include hydrocarbons or organics,
carbon monoxide and sulfur oxides. Small amounts of hydrocarbons are
released by PB pots, and larger amounts are emitted from HSS and VSS pots.
In vertical cells, these organics are Incinerated in integral gas burners-
Sulfur oxides originate from sulfur in the anode coke and pitch. The con-
centrations of sulfur oxides in VSS cell emissions range from 200 to 300 parts
per million. Emissions from PB plants usually have S02 concentrations ranging
from 20 to 30 parts per million.
Emissions from anode bake ovens Include the products of fuel combustion;
high boiling organics from the cracking, distillation and oxidation of paste
binder pitch; sulfur dioxide from the sulfur In carbon paste, primarily from
the petroleum coke, fluorides from recycled anode butts; and other partlc-
ulate matter. The concentrations of uncontrolled S02 emissions from anode
baking furnaces range from 5 to 47 parts per million (based on 3 percent sulfur
in coke.)8
A variety of control devices has been used to abate emissions from
reduction cells and anode baking furnaces. To control gaseous and partic-
ulate fluorides and particulate emissions, one or more types of wet scrub-
bers (spray tower and chambers, quench towers, floating beds, packed beds,
Venturis, and self induced sprays have been applied to all three types of
reduction cells and to anode baking furnaces. Also, particulate control
methods such as electrostatic precipitators (wet and dry), multiple cyclones
and dry alumina scrubbers (fluid bed, Injected, and coated filter types) are
employed with baking furnaces and on all three cell types. Also, the alumina
adsorption systems are being used on all three cell types to control both
gaseous and particulate fluorides by passing the pot offgases through the
entering alumina feed, which adsorbs the fluorides. This technique has an
overall control efficiency of 98 to 99 percent. Baghouses are then used to
collect residual fluorides entrained in the alumina and to recycle them to
the reduction cells. Wet electrostatic precipitators approach adsorption in
particulate removal efficiency but must be coupled to a wet scrubber or
coated baghouse to catch hydrogen fluoride.
Scrubber systems also remove a portion of the S02 emissions. These
emissions could be reduced by wet scrubbing or by reducing the quantity of
sulfur In the anode coke and pitch, i. e., calcining the coke.
4/81
Metallurgical Industry
7.1-7
-------
In the hydrated aluminum oxide calcining, bauxite grinding and materials
handling operations, various dry dust collection devices (centrifugal collec-
tors, multiple cyclones, or electrostatic precipitators and/or wet scrubbers)
have been used.
Potential sources of fugitive particulate emissions in the primary
aluminum industry are bauxite grinding, materials handling, anode baking and
three types of reduction cells (see Table 7.1-2). These fugitives probably
have particle size distributions similar to those presented in Table 7.1-3.
References for Section 7.1
1. Engineering and Cost Effectiveness Study of Fluoride Emissions Control,
Volume I, APTD-0945, U. S. Environmental Protection Agency, Research
Triangle Park, NC, January 1972.
2. Air Pollution Control in the Primary Aluminum Industry, Volume I,
EPA-450/3-73-004a, U. S. Environmental Protection Agency, Research
Triangle Park, NC, July 1973.
3. Particulate Pollutant System Study. Volume I, APTD-0743, U. S. Environ-
mental Protection Agency, Research Triangle Park, NC, May 1971.
4. Emissions from Wet Scrubbing System, Report Number Y-7730-E, York
Research Corp., Stamford, CT, May 1972.
5. Emissions from Primary Aluminum Smelting Plant, Report Number Y-7730-B,
York Research Corp., Stamford, CT, June 1972.
6. Emissions from the Wet Scrubber System, Report Number Y-7730-F, York
Research Corp., Stamford, CT, June 1972.
7. T. R. Hanna and M. J. Pilat, "Size Distribution of Particulates Emitted
from a Horizontal Spike Soderberg Aluminum Reduction Cell", Journal of
the Air Pollution Control Association, 22_: 533-536, July 1972.
8. Background Information for Standards of Performance: Primary Aluminum
Industry, Volume 1: Proposed Standards, EPA-450/2-74-020a, U. S.
Environmental Protection Agency, Research Triangle Park, NC, October
1974.
9. Primary Aluminum: Guidelines for Control of Fluoride Emissions from
Existing Primary Aluminum Plants, EPA-450/2-78-049b, U. S. Environmental
Protection Agency, Research Triangle Park, NC, December 1979.
10. Written communication from T. F. Albee, Reynolds Aluminum, Richmond, VA,
to A. A. MacQueen, U. S. Environmental Protection Agency, Research
Triangle Park, NC, October 20, 1982.
11- Environmental Assessment; Primary Aluminum, Interim report, U. S.
Environmental Protection Agency, Cincinnati, OH, October 1979.
7.1-8 EMISSION FACTORS 4/81
-------
7.2 COKE MANUFACTURING
7.2.1 Process Description
Coking is the process of destructive distillation, or the heating
of coal in an atmosphere of low oxygen content. During this process,
organic compounds in the coal break down to yield gases and a relatively
involatile residue. The primary method for the manufacture of coke is
the byproduct method, which accounts for more than 98 percent of U.S.
coke production.
The byproduct method is oriented to the recovery of gases produced
during the coking cycle. Narrow rectangular slot-type coking ovens are
constructed of silica brick, and a battery is commonly made up of a
series of 40 to 70 of these ovens interspaced with heating flues. A
larry car runs along the top of the coke battery, charging the ovens
with coal through ports. After each charging, the ports are sealed, and
heat is supplied to the ovens by combustion of gases passing through the
flues between the ovens. The fuels used in the combustion process are
natural gas, coke oven gas or blast furnace gas. In the ovens, coke is
formed first near the brick walls and then toward the center, where
temperatures are 2000° - 2100°F (1100° - 1150°C). After a period of
16 - 20 hours, the coking process is complete. Coke is pushed by a ram
from the oven into a quenching car. The quenching car of hot coke is
moved by rail to the quench tower, where several thousand gallons of
water are used to cool the coke. The coke is allowed to dry and is
separated into various sizes for future use. See Figure 7.5-1 of this
document for a flow diagram of an integrated iron and steel plant which
contains the coking operations.
7.2.2 Emis sions
Particulates, volatile organic compounds, carbon monoxide and other
emissions originate from the following byproduct coking operations: (1)
coal preheating (if used), (2) charging of coal into the incandescent
ovens, (3) oven leakage during the coking period, (4) pushing the coke
out of the ovens, (5) quenching the hot coke and (6) combustion stacks.
Gaseous emissions from the byproduct ovens during the coking process are
drawn off to a collecting main and are subjected to various operations
for separating ammonia, coke oven gas, tar, phenol, light oil (benzene,
toluene, xylene) and pyridine. These unit operations are potential
sources of volatile organic compounds.
Oven charging operations and leakage around poorly sealed coke oven
doors and lids are major sources of emissions from byproduct ovens.
Emissions also occur when finished coke is pushed into the quench cars
and during the quenching operation. The combustion process is also a
source of pollutant emissions. As the combusting gases pass through the
coke oven heating flues, emissions from the ovens may leak into the
stream. Also, if the coke oven gas is not desulfurized, the combustion
process will emit sulfur dioxide. Figure 7.2-1 is a depiction of a coke
oven battery showing the major air pollution sources.
10/80 Metallurgical Industry 7.2-1
-------
^J
•
NJ
t-o
M
t/i
cn
n
H
o
o
CO
o
TYPES OF AIR POLLUTION EMISSIONS
FROM COKE-OVEN BATTERIES
(T) Pushing emissions
(2) Charging emissions
(3) Door emissions
(4) Topside emissions
(5) Battery underfire emissions
(Courtesy of the Western
Pennsylvania Air Pollution
Control Association)
-------
00
to
TABLE 7.2-1. EMISSION FACTORS FOR COKE MANUFACTURE3
EMISSION FACTOR RATING: D (except participates)
8=
rt
P.
h->
1-1
H
&
ID
rt
i-t
Part-
icula te
emission
factor Sulfur Carbon Volatile Nitrogen
Partlculates^ rating dioxirtec monoxidec organicsc> oxides (NO-)C Ammonia0 Lead6
Type of operation
Coal Preheaters
Uncontrolled
Controlled by scrubber
Coal Charging
Uncontrolled
Controlled larry car
vented to scrubber
Sequential charging
Door Leaks (Uncontrolled)
Coke Pushing
Suspended particulates
Uncontrolled (measured in duct
venting coke side shed )
Controlled (water sprays)
Total particulars
(suspended plus dust fall)
Uncontrolled
Controlled (water sprays)
Controlled (enclosed coke car
and guide vented to scrubber)
Quenching (Controlled by battles)
Combustion Stacks (uncontrolled)
Combined Operations (uncontrolled)
kg/Mg
3.5
0.325
0.425
0.01
0.008
0.255
0.235
0.195
1.0
O.ii
0.012
0.5
0.29
-
Ib/ton
7.H C
O.b5 C
O.B5 C
0.02 C
0.016 C
0.51 B
0.47 A
0.31 A
2.0 B
1.2 B
0.024 C
1.0 A
0.58 B
-
kg/rig Ib/ton kg/Mg Ib/ton kg/«g Ib/ton kg/Mg Ib/ton kg/Mg Ib/ton kg/Mg Ib/ton
_ _ _ _ _- -----
---- - - _____
0.01 0.02 0.3 0.6 1.25 2.5 0.015 0.03 0,01 0.02
__-. __ _____
_-_ __ _____
0.3 0.6 0,75 1,5 0.005 0.01 0.03 0.06
----- -- _____
--- - - _____
0.035 0.07 0.1 0.2 - - 0.05 0.1
---- __ _____
----- -- _____
_
2.0f 4.0£ -- - - _____
- - - 0.00018 0.00035
OJ
aEmlssion factors expressed as weight per unit weight of coal charged. Dash indicates no available data.
^Reference 1.
eReferences 2-3.
^Expressed as methane.
°References 4-6.
Reference 7. The sulfur dioxide factor is based on the following representative conditions: (1) sulfur content of coal
charged to oven Is O.B weight!!; (2) about 33 weight X of total sulfur in the coal charged to oven is transferred to the
coke oven gas; (3) about 40% of coke oven gas is burned during the underfiring operation, and the remainder is used in
other parts of the steel operation, where the rest of the .sulfur dioxide is discharged - about 3 Jcg/Mg (6 Ib/ton) of
coal charged; and (4) gas used In underfiring has not been desulfurized.
-------
Associated with the byproduct coke oven process are open source fugit-
ive dust operations. These include material handling operations of unload-
ing, storing, grinding and sizing of coal, and the screening, crushing,
storing and loading of coke. Fugitive emissions also come from vehicles
traveling on paved and unpaved surfaces. These emissions and the parameters
that influence them are discussed in more detail in Section 7.5 and Chapter
11 of this document. The emission factors for coking operations are summar-
ized in Table 7.2-1. Extensive information on the data used to develop the
particulate emission factors is found in Reference 1.
References for Section 7.2
1. Particulate Emission Factors Applicable to the Iron and Steel In-
dustry, EPA-450/4-79-028, U.S. Environmental Protection Agency,
Research Triangle Park, NC, September 1979.
2. Air Pollution by Coking Plants, United Nations Report: Economic Com-
mission for Europe, ST/ECE/Coal/26, 1968.
3. R. W. Fullerton, "Impingement Baffles To Reduce Emissions from Coke
Quenching", Journal^of the Air Pollution Control Association,
_17:807-809, December 1967.
4. R. B. Jacko, et al., By-product Coke Oven Pushing Operation; Total
and Trace Metal Particulate Emissions, Purdue University, West
Lafayette, IN, June 27, 1976.
5. Control Techniques for Lead Air Emissions, EPA-450/2-770-012, U.S.
Environmental Protection Agency, Research Triangle Park, NC, December
1977.
6. Mineral Industry Surveys: Weekly Coal Report No. 3056, Bureau of
Mines, U.S. Department of the Interior, Washington, DC, undated.
7. J. Varga and H. W. Lownie, Jr., Final Technological Report on: A
Systems Analysis Study of the Integrated Iron and Steel Industry,
HEW Contract No. PH 22-68-65, Battelle Memorial Institute, Columbus,
OH, May 1969.
7.2-4 EMISSION FACTORS 12/81
-------
7.3 PRIMARY COPPER SMELTING
7.3.1 Process Description^'^
In the United States, copper is produced from sulfide ore concentrates
principally by pyrometallurgical smelting methods. Because the copper ores
usually contain less than 1 percent copper, they must be concentrated before
transport to a smelter. Concentrations of 15 to 35 percent copper are
accomplished at the mine site by crushing, grinding and flotation. Sulfur
content of the concentrate ranges from 25 to 35 percent, and most of the
remainder is iron (25 percent) and water (10 percent). Some concentrates also
contain significant quantities of arsenic, cadmium, lead, antimony and other
heavy metals.
The conventional pyrometallurgical copper smelting process Is illustrated
In Figure 7.3-1. The process includes roasting of ore concentrates to produce
calcine, smelting of roasted (calcine feed) or unroasted (green feed) ore
concentrates to produce matte, and converting of the matte to yield blister
copper product (about 99 percent pure). Typically, the blister copper is fire
refined in an anode furnace, cast Into "anodes" and sent to an electrolytic
refinery for further impurity elimination.
In roasting, charge material of copper concentrate mixed with a siliceous
flux (often a low grade ore) is heated in air to about 650°C (1,200°F),
eliminating 20 to 50 percent of the sulfur as sulfur dioxide (S02). Portions
of such impurities as antimony, arsenic and lead are driven off, and some of
the iron is converted to oxide. The roasted product, called calcine, serves
as a dried and heated charge for the smelting furnace. Either multiple
hearth or fluidized bed roasters are used for roasting copper concentrate.
The fluid bed roaster is similar in appearance to a multihearth roaster but has
fewer intricate internal mechanical systems. Multihearth roasters accept
moist concentrate, whereas fluid bed roasters are fed finely ground material
(60 percent minus 200 mesh). With both of these types, the roasting is
autogenous. Because there is less air dilution, higher S02 concentrations
are present in fluidized bed roaster gases than in multiple hearth roaster
gases.
In the smelting process, either hot calcines from the roaster or raw
unroasted concentrate are melted with siliceous flux in a smelting furnace to
produce copper matte, a molten mixture of cuprous sulfide (Cu2§) and ferrous
sulfide (FeS) and some heavy metals. The required heat comes from partial
oxidation of the sulfide charge and from burning external fuel. Most of the
iron and some of the impurities In the charge oxidize and combine with the
fluxes to form a slag on top of the molten bath, which is periodically removed
and discarded. Copper matte remains in the furnace until tapped. Mattes
produced by the domestic Industry range from 35 to 65 percent copper, with
about 45 percent the most common. This copper content percentage is referred
to as the matte grade. Currently, four smelting furnace technologies are
used in the U.S., reverberatory, electric, Noranda and Outokumpu (flash).
1/84 Metallurgical Industry 7.3-1
-------
ORE CONCENTRATES WITH SILICA FLUXES
FUEL.
AIR-
ROASTING
CONVERTER SLAG (2% Cu)
FUEL-
AIR-
CALCINE
SMELTING
SLAG TO DUMP
(0.5% Cu)
AIR-
MATTE (-40% Cu)
CONVERTING
GREEN POLES OR GAS-
FUEL-
AIR-
BLISTER COPPER
(98.^% Cu)
FIRE REFINING
SLAG TO CONVERTER-
ANODE COPPER (99.5% Cu)
TO ELECTROLYTIC REFINERY
--OFFGAS
OFFGAS
•OFFGAS
OFFGAS
7.3-2
Figure 7.3-1. A conventional copper smelting process.
EMISSION FACTORS
-------
Reverberatory furnace operation is a continuous process, with frequent
charging of input materials and periodic tapping of matte and skimming of
slag. Reverberatory furnaces typically process from 800 to 1,200 Mg (900 to
1,300 tons) of charge per day. Heat is supplied by combustion of oil, gas or
pulverized coal. Furnace temperatures may exceed 1,500°C (2,730°F).
For smelting in electric arc furnaces, heat is generated by the flow of
an electric current in submerged carbon electrodes lowered through
the furnace roof into the slag layer of the molten bath. The feed generally
consists of dried concentrates or calcines, and charging wet concentrates is
avoided. The chemical and physical changes occurring in the molten bath
are similar to those occurring in the molten bath of a reverberatory furnace.
Also, the matte and slag tapping practices are similar at both furnaces.
Electric furnaces do not produce fuel combustion gases, so flow rates are
lower and S02 concentrations higher in effluent gas than in that of reverber-
atory furnaces.
Flash furnace smelting combines the operations of roasting and smelting
to produce a high grade copper matte from concentrates and flux. In flash
smelting, dried ore concentrates and finely ground fluxes are injected together
with oxygen, preheated air, or a mixture of both into a furnace of special
design, where temperature is maintained at approximately 1,000°C (1,830°F).
Flash furnaces, in contrast to reverberatory and electric furnaces, use the
heat generated from partial oxidation of their sulfide sulfur charge to
provide much or all of the energy (heat) required for smelting. They also
produce offgas streams containing high concentrations of SC^.
Slag produced by flash furnace operations contains significantly higher
amounts of copper than does that from reverberatory or electric furnace
operations. As a result, the flash furnace and converter slags produced at
flash smelters are treated in a slag cleaning furnace to recover the copper.
Slag cleaning furnaces usually are small electric arc furnaces. The flash
furnace and converter slags are charged to a slag cleaning furnace and are
allowed to settle under reducing conditions with the addition of coke or iron
sulfide. The copper, which is in oxide form in the slag, is converted to
copper sulfide, subsequently removed from the furnace and charged to a
converter with the regular matte.
The Noranda process, as originally designed, allowed the continuous
production of blister copper in a single vessel, by effectively combining
roasting, smelting and converting into one operation. Metallurgical problems,
however, led to the operation of these reactors for the production of copper
matte. As in flash smelting, the Noranda process takes advantage of the heat
energy available from the copper ore. The remaining thermal energy required
is supplied by oil burners or by coal mixed with the ore concentrates.
The final step in the production of blister copper is converting. The
purpose of converting is to eliminate the remaining iron and sulfur present
in the matte, leaving molten "blister" copper. All but one U. S. smelter use
Fierce-Smith converters, which are refractory lined cylindrical steel shells
mounted on trunnions at either end and rotated about the major axis for
charging and pouring. An opening in the center of the converter functions as
1/84 Metallurgical Industry 7.3-3
-------
a mouth, through which molten matte, siliceous flux and scrap copper are
charged and gaseous products are vented. Air or oxygen rich air is blown
through the molten matte. Iron sulfide (FeS) is oxidized to iron oxide (FeO)
and 502, anc^ tne ^e<"* combines with the flux to form a slag on the surface.
At the end of this segment of the converter operation, termed the slag blow,
the slag is skimmed and generally recycled back to the smelting furnace. The
process of charging, blowing and slag skimming is repeated until an adequate
amount of relatively pure Cu2S, called "white metal", accumulates in the
bottom of the converter. A renewed air blast oxidizes the remaining copper
sulfide sulfur to S02, leaving blister copper in the converter. The blister
copper is subsequently removed and transferred to refining facilities. This
segment of converter operation is termed the finish blow. The S(>2 produced
throughout the operation is vented to pollution control devices.
One smelter uses Hoboken converters, the primary advantage of which lies
in emission control. The Hoboken converter is essentially like a conventional
Pierce—Smith converter, except that this vessel is fitted with a side flue at
one end shaped as an inverted U. This flue arrangement permits siphoning of
gases from the interior of the converter directly to offgas collection,
leaving the converter mouth under a slight vacuum.
Blister copper usually contains from 98.5 to 99.5 percent pure copper.
Impurities may include gold, silver, antimony, arsenic, bismuth, iron, lead,
nickel, selenium, sulfur, tellurium and zinc. To purify blister copper further,
fire refining and electrolytic refining are used. In fire refining, blister
copper is placed in a fire refining furnace, a flux is usually added, and
air is blown through the molten mixture to oxidize remaining impurities,
which are removed as a slag. The remaining metal bath is subjected to a
reducing atmosphere to reconvert cuprous oxide to copper. Temperature in the
furnace is around 1,100°C (2,010°F). The fire refined copper is cast into
anodes and further refined electrolytically. Electrolytic refining separates
copper from impurities by electrolysis in a solution containing copper sulfate
and sulfuric acid. Metallic impurities precipitate from the solution and
form a sludge that is removed and treated to recover precious metals. Copper
is dissolved from the anode and deposited at the cathode. Cathode copper is
remelted and made into bars, ingots or slabs for marketing purpose. The
copper produced is 99.95 to 99.97 percent pure.
7.3.2 Emissions and Controls
Particulate matter and sulfur dioxide are the principal air contaminants
emitted by primary copper smelters. These emissions are generated directly
from the processes involved, as in the liberation of S02 from copper concen-
trate during roasting or in the volatilization of trace elements as oxide fumes.
Fugitive emissions are generated by leaks from major equipment during material
hand1ing op erati ons.
Roasters, smelting furnaces and converters are sources of both particulate
matter and sulfur oxides. Copper and iron oxides are the primary constituents
of the particulate matter, but other oxides such as arsenic, antimony, cadmium,
lead, mercury and zinc may also be present, with metallic sulfates and sulfuric
7.3-4 EMISSION FACTORS 1/84
-------
acid mist. Fuel combustion products also contribute to particulate emissions
from multihearth roasters and reverberatory furnaces.
Single stage electrostatic precipitators (ESP) are widely used in the primary
copper industry for the control of particulate emissions from roasters, smelting
furnaces and converters. Many of the existing ESPs are operated at elevated
temperatures, usually at 200 to 340°C (400 to 650°F) and are termed "hot
ESPs". If properly designed and operated, these ESPs remove 99 percent or
more of the condensed particulate matter present in gaseous effluents. However,
at these elevated temperatures, a significant amount of volatile emissions
such as arsenic trioxide (As2C>3) and sulfuric acid mist is present as vapor in
the gaseous effluent and thus can not be collected by the particulate control
device at elevated temperatures. At these temperatures, the arsenic trioxide
in the vapor state will pass through an ESP. Therefore, the gas stream to be
treated must be cooled sufficiently to ensure that most of the arsenic present
is condensed before entering the control device for collection. At some
smelters, the gas effluents are cooled to about 120°C (250°F) temperature
before entering a particulate control system, usually an ESP (termed "cold
ESP"). Spray chambers or air infiltration are used for gas cooling. Fabric
filters can also be used for particulate matter collection.
Gas effluents from roasters are usually sent to an ESP or spray chamber/ESP
system or are combined with smelter furnace gas effluents before particulate
collection. Overall, the hot ESPs remove only 20 to 80 percent of the total
particulate (condensed and vapor) present in the gas. The cold ESPs may
remove more than 95 percent of the total particulate present in the gas.
Particulate collection systems for smelting furnaces are similar to those for
roasters. Reverberatory furnace offgases are usually routed through waste
heat boilers and low velocity balloon flues to recover large particles and
heat, then are routed through an ESP or spray chamber/ESP system.
In the standard Pierce—Smith converter, flue gases are captured during
the blowing phase by the primary hood over the converter mouth. To prevent
the hood's binding to the converter with splashing molten metal, there is a
gap between the hood and the vessel. During charging and pouring operations,
significant fugitives may be emitted when the hood is removed to allow
crane access. Converter offgases are treated in ESPs to remove particulate
matter and in sulfuric acid plants to remove S02-
Remaining smelter processes handle material that contains very little
sulfur, hence S02 emissions from these processes are insignificant.
Particulate emissions from fire refining operations, however, may be of concern.
Electrolytic refining does not produce emissions unless the associated sulfuric
acid tanks are open to the atmosphere. Crushing and grinding systems used in
ore, flux and slag processing also contribute to fugitive dust problems.
Control of S02 emissions from smelter sources is most commonly performed
in a single or double contact sulfuric acid plant. Use of a sulfuric acid
plant to treat copper smelter effluent gas streams requires that gas be free
from particulate matter and that a certain minimum inlet S02 concentration be
maintained. Practical limitations have usually restricted sulfuric acid plant
application to gas streams that contain at least 3.0 percent SC>2. Table 7.3-1
shows typical average S02 concentrations for the various smelter unit offgases.
1/84 Metallurgical Industry 7.3-5
-------
TABLE 7.3-1. TYPICAL SULFUR DIOXIDE CONCENTRATIONS IN
OFFGASES FROM PRIMARY COPPER SMELTING SOURCES
S02 concentration
Unit Volume %
Multiple hearth roaster
Fluidized bed roaster
Reverberatory furnace
Electric arc furnace
Flash smelting furnace
Continuous smelting furnace
Fierce-Smith converter
Hoboken converter
Single contact H2S04 plant
Double contact H2S04 plant
1.5
10
0.5
4
10
5
4
0.2
- 3
- 12
- 1.5
- 8
- 20
- 15
- 7
8
- 0.26
0.05
Currently, converter gas effluents at most of the smelters are treated
for S02 control in sulfuric acid plants. Gas effluents from some multihearth
roaster operations and all fluid bed roaster operations are also treated in
sulfuric acid plants. The weak S02 content gas effluents from the reverberatory
furnace operations are usually released to the atmosphere with no reduction of
S02- The gas effluents from the other types of smelter furnaces, due to their
higher contents of S02, are treated in sulfuric acid plants before being
vented. Typically, single contact acid plants achieve 92.5 to 98 percent
conversion of S02 to acid, with approximately 2000 ppm S02 remaining in the
acid plant effluent gas. Double contact acid plants collect from 98 to more
than 99 percent of the S02 and emit about 500 ppm S02« Absorption of the S02
in dimethylaniline (DMA) solution has also been used in U. S. smelters to
produce liquid S02-
Emissions from hydrometallurgical smelting plants generally are small in
quantity and are easily controlled. In the Arbiter process, ammonia gas
escapes from the leach reactors, mixer/settlers, thickeners and tanks. For
control, all of these units are covered and vented to a packed tower scrubber
to recover and recycle the ammonia.
Actual emissions from a particular smelter unit depend upon the configuration
of equipment in that smelting plant and its operating parameters. Table 7.3-2
gives emission factors for the major units for various smelter configurations.
7.3.3 Fugitive Emissions
The process sources of particulate matter and S02 emissions are also the
potential fugitive sources of these emissions, roasting, smelting, converting,
fire refining and slag cleaning. Table 7.3-3 presents the potential fugitive
emission factors for these sources. The actual quantities of emissions
from these sources depend on the type and condition of the equipment and on
the smelter operating techniques. Although emissions from many of these
sources are released inside a building, ultimately they are discharged to the
atmosphere.
Fugitive emissions are generated during the discharge and transfer of hot
calcine from multihearth roasters, and negligible amounts of fugitive emissions
7.3-6 EMISSION FACTORS 1/84
-------
TABLE 7.3-2. EMISSION FACTORS FOR PRIMARY COPPER SMELTERS3>b
EMISSION FACTOR RATING: B
Conf iguraCionc
Unit
Particulars matter SO,
Kg/Mg lb/ton Kg/Mg Ib/ton
Ref erences
Reverberatory furnace (RF)
followed by converters (C)
Multlhearth roaster (MHR)
followed by reverberatory
furnace (W) and converters (C)
Fluid bed roaster (FBR) followed
by reverberatory furnace (RF)
and converters (C)
Concentrate dryer (CD) followed
by electric furnace (EF) and
converters (C)
Fluid bed roaster (FBR) followed
by electric furnace (EF) and
converters (C)
Concentrate dryer (CD) followed
by flash furnace (FF) ,
cleaning furnace (SS) and
converters (C)
Concentrate dryer (CD) followed
by Noranda reactors (MR) and
converters (C)
RF
C
MHR
RF
C
FBR
RF
C
CD
EF
C
FBR
EF
C
CD
FF
ssf
Ce
CD
NR
C
25
18
22
25
18
NA
25
18
5
50
18
NA
50
18
5
70
5
NAg
5
NA
NA
50
36
45
50
36
NA
50
36
10
100
36
NA
100
36
10
140
10
NAg
10
NA
NA
160
370
140
90
300
180
90
270
0.5
120
410
180
45
300
0.5
410
0.5
120
0.5
NA
NA
320
740
280
180
600
360
160
540
1
240
820
360
90
600
1
820
1
240
1
NA
NA
4-10,
9, 11-15
4-5, 16-17
4-9, 18-19
8, 11-13
20
e
e
21-22
15
8, 11-13, 15
20
15, 23
e
21-22
24
22
22
21-22
aExpressed as units per unit weight of concentrated ore processed by the smelter. Approximately
4 unit weights of concentrate are required to produce 1 unit weight of blister copper. NA »
not available.
"For particulate matter removal, gaseous effluents from roasters, smelting furnaces and converters
are usually treated in hot ESPs at 200 - 340°C (400 - 65Q°F) or in cold ESPs with gases cooled to
about 120°C (25QQF) before ESP, Particulate emissions from copper smelters contain volatile metallic
oxides which remain in. vapor form at higher temperatures and which condense to solid particulate at
lower temperatures (120°C or 250DF). Therefore, overall particulate removal in hot ESPs may range
from 20 - 80%, and overall particulate removal in cold ESPs may be 99%. Converter gas effluents
and, at some smelters, roaster gas effluents are treated in single contact acid plants (SCAP) or
double contact acid plant's (DCAP) for S02 removal. Typical SCAPs are about 96% efficient, and DCAPs
are up to 99.8 % efficient in S02 removal. They also remove over 99% of particulate matter.
cln addition to sources Indicated, each smelter configuration contains fire refining anode furnaces
after the converters. Anode furnaces emit negligible S02• No particulate emission data are available
for anode furnaces.
dFactors for all configurations except reverberatory furnace followed by converters were developed by
normalising test data for several smelters to represent 30% sulfur content in concentrated ore.
eBased on the test data for the configuration raultihearth roaster followed by reverberatory furnace
and converters.
^Used to recover copper from furnace slag and converter slag.
SSInce the converters at flash furnace and Noranda furnace smelters treat high copper content matte,
converter particulate emissions from flash furnace smelters are expected to be lower than corresponding
emissions from conventional smelters consisting of multihearth roasters, reverberatory furnace, and converters.
may also come from the charging of these roasters. Fluid bed roasting, a
closed loop operation, has negligible fugitive emissions.
Matte tapping and slag skimming operations are sources of fugitive emissions
from smelting furnaces. Fugitive emissions can also result from charging of a
1/84
Metallurgical Industry
7.3-7
-------
TABLE 7.3-3. FUGITIVE EMISSION FACTORS FOR PRIMARY COPPER SHELTERS3
EMISSION FACTOR RATING: B
Source
Partieulate matter
Kg/Mg Ib/ton
S02
Kg/Mg
Ib/ton
Roaster calcine discharge
Smelting furnace*5
Converters
Converter slag return
Anode furnace
Slag cleaning furnacec
1.3
0.2
2.2
NA
0.25
4
2.6
0.4
4.4
NA
0.5
8
0.5
2
65
0.05
0.05
3
• 1
4
130
0.1
0.1
6
References 16, 22, 25-31. Expressed as mass units per unit weight
of concentrated ore processed by the smelter. Approximately 4 unit
weights of concentrate are required to produce 1 unit weight of copper
metal. Factors for flash furnace smelters and Noranda furnace smelters
may be slightly lower than reported values. NA = not available.
"Includes fugitive emissions from matte tapping and slag skimming
operations. About 50% of fugitive partlculate matter emissions and
about 90% of total S02 emissions are from matte tapping operations.
The remainder is from slag skimming.
cUsed to treat slags from smelting furnaces and converters at the flash
furnace smelter.
smelting furnace or from leaks, depending upon the furnace type and condition.
A typical single matte tapping operation lasts from 5 to 10 minutes, and a
single slag skimming operation lasts from 10 to 20 minutes. Tapping frequencies
vary with furnace capacity and type. In an 8 hour shift, matte is tapped 5 to
20 times, and slag is skimmed 10 to 25 times.
Each of the various stages of converter operation, the charging, blowing,
slag skimming, blister pouring, and holding, is a potential source of fugitive
emissions. During blowing, the converter mouth Is in stack (i. e., a close
fitting primary hood is over the mouth to capture offgases). Fugitive emissions
escape from the hoods. During charging, skimming and pouring operations, the
converter mouth is out of stack (i. e., the converter mouth is rolled out of
its vertical position, and the primary hood is isolated). Fugitive emissions
are discharged during the rollout.
At times during normal smelting operations, slag or blister copper can
not be transferred immediately from or to the converters. This condition, the
holding stage, may occur for several reasons, including insufficient matte in
the smelting furnace, the unavailability of a crane, and others. Under these
conditions, the converter is rolled out of vertical position and remains in a
holding position, and fugitive emissions may result.
Fugitive emissions from primary copper smelters are captured by applying
either local or general ventilation techniques. Once captured, emissions may
7.3-8
EMISSION FACTORS
1/84
-------
be vented directly to a collection device or be combined with process offgases
before collection. Close fitting exhaust hood capture systems are used for
multihearth roasters, and hood ventilation systems for smelter matte tapping
and slag skimming operations. For converters, secondary hood systems or building
evacuation systems are used.
7.3.4 Lead Emission Factors
Both the process and the fugitive particulate matter emissions from
various equipment at primary copper smelters contain oxides of many inorganic
elements, including lead. The lead content of particulate matter emissions
depends upon both the lead content of concentrate feed into the smelter and
the process offgas temperature. Lead emissions are effectively removed in
particulate control systems operating at low temperatures of about 120°C (250°F).
Table 7.3-4 presents lead emission factors for various operations of
primary copper smelters. These emission factors represent totals of both
process and fugitive emissions.
TABLE 7.3-4. LEAD EMISSION FACTORS FOR PRIMARY COPPER SMELTERSa
EMISSION FACTOR RATING: C
Lead emissions'*
Operation
kg/Mg
lb/ton
Roasting0
Smeltingd
Converting6
Refining
0.075
0.036
0.13
NA
0.15
0.072
0.27
NA
Reference 32. Expressed as units per unit weight of concentrated ore
processed by the smelter. Approximately 4 unit weights of concentrate
are required to produce 1 unit weight of copper metal. Based on test
data for several smelters containing from 0.1 to 0.4% lead in feed
throughput. NA = not available.
bFor process and fugitive emissions totals.
cBased on test data on multihearth roasters. Includes the total of
process emissions and calcine transfer fugitive emissions. Calcine
transfer fugitive emissions constitute about 10 percent of the total of
process and fugitive emissions.
"Based on test data on reverberatory furnaces. Includes total process
emissions and fugitive emissions from matte tapping and slag skimming
operations. Fugitive emissions from matte tapping and slag skimming
operations amount to about 35% and 21, respectively.
elncludes the total of process and fugitive emissions. Fugitive emissions
constitute about 50 percent of the total.
1/84
Metallurgical Industry
7.3-9
-------
References for Section 7.3
1. Background Information for New Source Performance Standards: Primary
Copper, Zinc, and Lead Smelters, Volume I, Proposed Standards,
EPA-450/2-74-002a, U. S. Environmental Protection Agency, Research Triangle
Park, NC, October 1974.
2. Arsenic Emissions from Primary Copper Smelters - Background Information
for Proposed Standards, Preliminary Draft, EPA Contract No. 68-02-3060,
Pacific Environmental Services, Durham, NC, February 1981.
3. Background Information Document for Revision of New Source Performance
Standards for Primary Copper Smelters, Draft Chapters 3 through 6, EPA
Contract Number 68-02-3056, Research Triangle Institute, Research Triangle
Park, NC, March 31, 1982.
4. Air Pollution Emission Test: ASARCO Copper Smelter, El Paso, Texas.
EMB-77-CUS-6, U. S. Environmental Protection Agency, Research Triangle
Park, NC, June 1977.
5. Written communication from W. F. Cummins, ASARCO, Inc., El Paso, TX, to
A. E. Vervaert, U. S. Environmental Protection Agency, Research Triangle
Park, NC, August 31, 1977.
6. AP-42 Background Files, Office of Air Quality Planning and Standards,
U. S. Environmental Protection Agency, Research Triangle Park, NC.
7. Source Emissions Survey of Kennecott Copper Corporation, Copper Smelter
Converter Stack Inlet and Outlet and Reverberatory Electrostatic
Precipitator Inlet and Outlet, Hurley, New Mexico, File Number EA-735-09,
Ecology Audits, Inc., Dallas, TX, April 1973.
8- Trace Element Study at a Primary Copper Smelter, EPA-600/2-78-065a
and -065b, U. S. Environmental Protection Agency, Research Triangle Park,
NC, March 1978.
9. Systems Study for Control of Emissions, Primary Nonferrous Smelting
Industry, Volume II: Appendices A and B, PB-184885, National Technical
Information Service, Springfield, VA, June 1969.
10. Design and Operating Parameters For Emission Control Studies: White
Pine Copper Smelter, EPA-600/2-76-036a, U. S. Environmental Protection
Agency, Washington, DC, February 1976.
11. R. M. Statnick, Measurement of Sulfur Dioxide, Particulate and Trace
Elements in Copper Smelter Converter and Roaster/Reverberatory Gas Streams,
PB-238095, National Technical Information Service, Springfield, VA,
October 1974.
12. AP-42 Background Files, Office of Air Quality Planning and Standards,
U. S. Environmental Protection Agency, Research Triangle Park, NC.
7.3-10 EMISSION FACTORS 1/84
-------
13. Design and Operating Parameters For Emission Control Studies, Kennecott -
McGill Copper Smelter, EPA-600/2-76-036c, U. S. Environmental Protection
Agency, Washington, DC, February 1976.
14. Emission Test Report (Acid Plant) of Phelps Dodge Copper Smelter, AJo,
Arizona, EMB-78-CUS-11, U. S. Environmental Protection Agency, Research
Triangle Park, NC, March 1979.
15. S. Dayton, "Inspiration's Design for Clean Air", Engineering and Mining
Journal, 175:6, June 1974.
16. Emission Testing of ASARCO Copper Sjnelter, Tacoma, Washington, EMB 78-CUS-
12, U. S. Environmental Protection Agency, Research Triangle Park, NC,
April 1979.
17. Written communication from A. L. Labbe, ASARCO Inc., Tacoma, WA, to S. T.
Cuffe, U. S. Environmental Protection Agency, Research Triangle Park, NC,
November 20, 1978.
18. Design and Operating Parameters for Emission Control Studies: ASARCQ -
Hayden Copper Smelter, EPA-600/2-76-036J, U. S. Environmental Protection
Agency, Washington, DC, February 1976.
19. Pacific Environmental Services, Incorporated, Design and Operating
Parameters for Emission Control Studies; Kennecott, Hayden Copper
Smelter, EPA-600/2-76-036b, U. S. Environmental Protection Agency,
Washington, DC, February 1976.
20. R. Larkin, Arsenic Emissions at Kennecott Copper Corporation, Hayden, AZ,
EPA-76-NFS-1, U. S. Environmental Protection Agency, Research Triangle
Park, NC, May 1977.
21. Emission Compliance Status, Inspiration Consolidated Copper Company,
Inspiration, AZ, U. S. Environmental Protection Agency, San Francisco,
CA, 1980.
22. Written communication from M. P. Scanlon, Phelps Dodge Corporation, to
D. R. Goodwin, U. S. Environmental Protection Agency, Research Triangle
Park, NC, October 18, 1978.
23. Written communication from G. M. McArthur, The Anaconda Company, to
D. R. Goodwin, U. S. Environmental Protection Agency, Research Triangle
Park, NC, June 2, 1977.
24. Telephone communication from V. Katari, Pacific Environmental Services,
Inc., Durham, NC, to R. Winslow, Hidalgo Smelter, Phelps Dodge
Corporation, Hidalgo, AZ, April 1, 1982.
25. Emission Test Report, Phelps Dodge Copper Smelter, Douglas, Arizona,
EMB-78-CUS-8T"u.~sTl:nvironmental Protection Agency, Research Triangle
Park, NC, February 1979.
1/84
Metallurgical Industry
7.3-11
-------
26. Emission Testing of Kennecott Copper Smelter, Magna, Utah, EMB-78-CUS-13,
U. S. Environmental Protection Agency, Research Triangle Park, NC,
April 1979.
27. Emission Test Report, Phelps Dodge Copper Smelter, Ajo, Arizona,
EMB-78-CUS-9, U. S. Environmental Protection Agency, Research Triangle
Park, NC, February 1979.
28. Written communication from R. D. Putnam, ASARCO, Inc., to M. 0. Varner,
ASARCO, Inc., Salt Lake City, UT, May 12, 1980.
29. Emission Test Report, Phelps Dodge Copper Smelter, Piayas, New Mexico,
EMB-78-CUS-10, U. S. Environmental Protection Agency, Research Triangle
Park, NC, March 1979.
30. ASARCQ Copper Smelter, El Paso, Texas, EMB-78-CUS-7, U. S. Environmental
Protection Agency, Research Triangle Park, NC, April 25, 1978.
31. A. D. Church, et al., "Measurement of Fugitive Particulate and Sulfur
Dioxide Emissions at Inco's Copper Cliff Smelter", Paper A-79-51, The
Metallurgical Society of American Institute of Mining, Metallurgical,
and Petroleum Engineers (AIME), New York, NY.
32. Copper Smelters, Emission Test Report - Lead Emissions, EMB-79-CUS-14,
U. S. Environmental Protection Agency, Research Triangle Park, NC,
September 1979.
7.3-12
EMISSION FACTORS
1/84
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7.4 FERROALLOY PRODUCTION
7.4.1 Process Description1 >2
Ferroalloy is the generic term for alloys consisting of iron and one or more other metals. Ferroalloys are used
in steel production as alloying elements and deoxidants. There are three basic types of ferroalloys: (1)
silicon-based alloys, including ferrosilicon and calciurnsilicon; (2) manganese-based alloys, including fer-
romanganese and silicomanganese; and (3) chromium-based alloys, including ferrochromium and ferrosilico-
chrome.
The four major procedures used to produce ferroalloy and high-purity metallic additives for steelmaking are:
(1) blast furnace, (2) electrolytic deposition, (3) alumina silico-thermic process, and (4) electric smelting furnace.
Because over 75 percent of the ferroalloys are produced in electric smelting furnaces, this section deals only with
that type of furnace.
The oldest, simplest, and most widely used electric furnaces are the submerged-arc open type, although
semi-covered furnaces are also used. The alloys are made in the electric furnaces by reduction of suitable oxides.
For example, in making ferrochromium the charge may consist of chrome ore, limestone, quartz (silica), coal and
wood chips, along with scrap iron.
7.4.2 Emissions3
The production of ferroalloys has many dust- or fume-producing steps. The dust resulting from raw material
handling, mix delivery, and crushing and sizing of the solidified product can be handled by conventional
techniques and is ordinarily not a pollution problem. By far the major pollution problem arises from the
ferroalloy furnaces themselves. The conventional submerged-arc furnace utilizes carbon reduction of metallic
oxides and continuously produces large quantities of carbon monoxide. This escaping gas carries large quantities
of particulates of submicron size, making control difficult.
In an open furnace, essentially all of the carbon monoxide burns with induced air at the top of the charge, and
CO emissions are small. Particulate emissions from the open furnace, however, can be quite large. In the
semi-closed furnace, most or all of the CO is withdrawn from the furnace and burns with dilution air introduced
into the system. The unburned CO goes through particulate control devices and can be used as boiler fuel or can
be flared directly. Particulate emission factors for electric smelting furnaces are presented in Table 7.4-1. No
carbon monoxide emission data have been reported in the literature.
2/72
Metallurgical Industry
7.4-1
-------
TABLE 7.4-1. EMISSION FACTORS FOR FERROALLOY PRODUCTION IN
ELECTRIC SMELTING FURNACES3
EMISSION FACTOR RATING: C
Type of furnace and
product
Open furnace
50% FeSic
75% FeSid
90% FeSic
Silicon metal6
Silicomanganese*
Ferrochr erne-Silicon
High Carbon ferro chrome
Semi-covered furnace
Ferromanganesef
Particulates
kg/Mg
100
157.5
282.5
312.5
97.5
-
—
22.5
Ib/ton
200
315
565
625
195
-
—
45
Leadb
kg/Mg
0.15
0.0015
-
0.0015
0.0029
0.04
0.17
0.06
Ib/ton
0.29
0.0031
-
0.0031
0.0057
0.08
0.34
0.11
aEmission factors expressed as weight per unit weight of specified
product. Dash indicates no available data.
^References 1-5.
cReference 8.
References 10-11.
References 9, 12.
fReference 11.
REFERENCES FOR SECTION 7.4
1. R. A. Pearson, "Control of Emissions from Ferroalloy Furnace Processing",
presented at the 27th Electric Furnace Conference, Detroit, MI, December
1969.
2. J. 0. Dealy and A. M. Killin, Air Pollution Control Engineering and Cost
Study of the Ferroalloy Industry, EPA-450/2-74-008, U.S.Environmental
Protection Agency, Research Triangle Park, NC, May 1974.
3. A. E. Vandergrift, et al., Particulate Pollutant System Study - Mass
Emissions, PB-203-128, PB-203-522 and PB-203-521, U.S. Environmental
Protection Agency, Research Triangle Park, NC, May 1971.
4. Control Techniques for Lead Air Emissions, EPA-450/2-77-012, U.S. Environ-
mental Protection Agency, Research Triangle Park, NC, December 1977.
5. W. E. Davis, Emissions Study of Industrial Sources of Lead Air Pollutants,
1970, EPA-APTD-1543, W. E. Davis and Associates, Leawood, KS, April 1973.
6. Air Pollutant Emission Factors, Final Report, Resources Research, Inc.,
Reston, VA, prepared for National Air Pollution Control Administration,
Durham, NC, under Contract Number CPA-22-69-119, April 1970.
7.4-2
EMISSION FACTORS
12/81
-------
7. Ferroalloys: Steel's All-purpose Additives, The Magazine of Metals
Producing, February 1967.
8. R. A. Person, Control of Emissions from Ferroalloy Furnace Processing,
Niagara Falls, NY, 1969.
9. Unpublished stack test results, Resources Research, Incorporated,
Reston, VA.
10. R. Ferrari, Experiences in Developing an Effective Pollution Control
System for a Submerged-Arc Ferroalloy Furnace Operation, J. Metals,
p. 95-104, April 1968.
11. Fredrlksen and Nestaas, Pollution Problems by Electric Furnace
Ferroalloy Production, United Nations Economic Commission for Europe,
September 1968.
12. R. W. Gerstle and J. L. McGinnity, Plant Visit Memorandum, U.S.
DHEW, PHS, National Center for Air Pollution Control, Cincinnati,
OH, June 1967.
12/81 Metallurgical Industry 7.4-3
-------
-------
7.5 IRON AND STEEL PRODUCTION
1-2
7.5.1 Process Description and Emissions
Iron and steel manufacturing may be grouped into eight generic process
operations: 1) coke production, 2) sinter production, 3) iron production,
4) steel production, 5) semifinished product preparation, 6) finished prod-
uct preparation, 7) heat and electricity supply and 8) handling and trans-
port of raw, intermediate and waste materials. Figure 7.5-1, a general
flow diagram of the iron and steel industry, interrelates these categories.
Coke production is discussed in detail in Section 7.2 of this publication,
and more information on the handling and transport of materials is found in
Chapter 11.
Sinter Production - The sintering process converts fine raw materials like
fine iron ore, coke breeze, fluxstone, mill scale and flue dust into an ag-
glomerated product of suitable size for charging into a blast furnace. The
materials are mixed with water to provide cohesion in a mixing mill and are
placed on a continuous moving grate called the sinter strand. A burner
hood above the front third of the sinter strand ignites the coke in the
mixture. Once ignited, combustion is self supporting and provides suffi-
cient heat, 1300 to 1480°C (2400 to 2700°F), to cause surface melting and
agglomeration of the mix. On the underside of the sinter machine lie wind-
boxes that draw the combusted air through the material bed into a common
duct to a particulate control device. The fused sinter is discharged at
the end of the sinter machine, where it is crushed and screened, and any
undersize portion is recycled to the mixing mill. The remaining sinter is
cooled in open air by water spray or by mechanical fan to draw off the heat
from the sinter. The cooled sinter is screened a final time, with the
fines being recycled and the rest being seat to charge the blast furnaces.
Emissions occur at several points in the sintering process. Points of
particulate generation are the windbox, the discharge (sinter crusher and
hot screen), the cooler and the cold screen. In addition, inplant transfer
stations generate emissions which can be controlled by local enclosures.
All the above sources except the cooler normally are vented to one or two
control systems.
Iron Production - Iron is produced in blast furnaces, which are large re-
fractory lined chambers into which iron (as natural ore or as agglomerated
products such as pellets or sinter, coke and limestone) is charged and al-
lowed to react with large amounts of hot air to produce molten iron. Slag
and blast furnace gases are byproducts of this operation. The average
charge to produce one unit weight of iron requires 1.7 unit weights of iron
bearing charge, 0.55 unit weights of coke, 0.2 unit weights of limestone,
and 1.9 unit weights of air. Average blast furnace byproducts consist of
0.3 unit weights of slag, 0.05 unit weights of flue dust, and 3.0 unit
weights of gas per unit of iron produced. The flue dust and other iron ore
fines from the process are converted into useful blast furnace charge by
the sintering operation.
5/83 Metallurgical Industry 7.5-1
-------
01
N)
tn
oo
CO
i — i
i
o
•H
O
50
TO Brim f i»m
Figure 7.5-1. General flow diagram for the iron and steel industry.
-------
Because of its high carbon monoxide content, this blast furnace gas
has a low heating value, about 2790 to 3350 joules per cubic liter (75 to
90 BTU/ft3) and is used as a fuel within the steel plant. Before it can be
efficiently oxidized, however, the gas must be cleaned of particulate.
Initially, the gases pass through a settling chamber or dry cyclone to re-
move about 60 percent of the particulate. Next, the gases undergo a one or
two stage cleaning operation. The primary cleaner is normally a wet scrub-
ber, which removes about 90 percent of the remaining particulate. The sec-
ondary cleaner is a high energy wet scrubber (usually a venturi) or an
electrostatic precipitator, either of which can remove up to 90 percent of
the particulate that eludes the primary cleaner. Together these control
devices provide a clean fuel of less than 0.05 grams per cubic meter (0.02
gr/ft3) for use in the steel plant.
Emissions occur during the production of iron when there is a blast
furnace "slip" and during hot metal transfer operations in the cast house.
All gas generated in the blast furnace is normally cleaned and used for
fuel. Conditions such as "slips", however, can cause instant emissions of
carbon monoxide and particulates. Slips occur when a stratum of the mate-
rial charged to a blast furnace does not settle with the material below it,
thus leaving a gas filled space between the two portions of the charge.
When this unsettled stratum of charge collapses, the displaced gas may
cause the top gas pressure to increase above the safety limit, thus opening
a counter weighted bleeder valve to the atmosphere.
Steel Production (Basic Oxygen Furnace) - The basic oxygen process is used
to produce steel from a furnace charge typically composed of 70 percent
molten blast furnace metal and 30 percent scrap metal by use of a stream of
commercially pure oxygen to oxidize the impurities, principally carbon and
silicon. Most of the basic oxygen furnaces (EOF) in the United States have
oxygen blown through a lance in the top of the furnace. However, the
Quelle Basic Oxygen Process (QBOP), which is growing in use, has oxygen
blown through tuyeres in the bottom of the furnace. Cycle times for the
basic oxygen process range from 25 to 45 minutes.
The large quantities of carbon monoxide (CO) produced by the reactions
in the EOF can be combusted at the mouth of the furnace and then vented to
gas cleaning devices, as with open hoods, or the combustion can be sup-
pressed at the furnace mouth, as with closed hoods. The term "closed hood"
is actually a misnomer, since the opening at the furnace mouth is large
enough to allow approximately 10 percent of theoretical air to enter. Al-
though most furnaces installed before 1975 are of the open hood design,
nearly all the QBOPs in the United States have closed hoods, and most of
the new top blown furnaces are being designed with closed hoods.
There are several sources of emissions in the basic oxygen furnace
steel making process, 1) the furnace mouth during refining - with collec-
tion by local full (open) or suppressed (closed) combustion hoods, 2) hot
metal transfer to charging ladle, 3) charging scrap and hot metal, 4) dump-
ing slag and 5) tapping steel.
Steel Production (Electric Arc Furnaces) - Electric arc furnaces (EAF) are
used to produce carbon and alloy steels. The charge to an EAF is nearly
5/83 Metallurgical Industry 7.5-3
-------
always 100 percent scrap. Direct arc electrodes through the roof of the
furnace melt the scrap. An oxygen lance may or may not be used to speed
the melting and refining process. Cycles range from 1-1/2 to 5 hours for
carbon steel and from 5 to 10 hours for alloy steel.
Sources of emissions in the electric arc furnace steel making process
are l) emissions from melting and refining, often vented through a hole in
the furnace roof, 2) charging scrap, 3) dumping slag and 4) tapping steel.
In interpreting and using emission factors for EAFs, it is important to
know what configuration one is dealing with. For example, if an EAF has a
building evacuation system, the emission factor before the control device
would represent all melting, refining, charging, tapping and slagging emis-
sions which ascend to the building roof. Reference 2 has more details on
various configurations used to control electric arc furnaces.
Steel Production (Open Hearth Furnaces) - In the open hearth furnace (OHF),
a mixture of iron and steel scrap and hot metal (molten iron) is melted in
a shallow rectangular basin or "hearth". Burners producing a flame above
the charge provide the heat necessary for melting. The mixture of scrap
and hot metal can vary from all scrap to all hot metal, but a half and half
mixture is a reasonable industry average. The process may or may not be
oxygen lanced, with process cycle times approximately 8 hours and 10 hours,
respectively.
Sources of emissions in the open hearth furnace steel making process
are 1) transferring hot metal, 2) melting and refining the heat, 3) charg-
ing of scrap and/or hot metal, 4) dumping slag and 5) tapping steel.
Semifinished Product Preparation - After the steel has been tapped, the
molten metal is teemed into ingots which are later heated to form blooms,
billets or slabs. (In a continuous casting operation, the molten metal may
bypass this entire process.) The product next goes through a process of
surface preparation of semifinished steel (scarfing). A scarfing machine
removes surface defects before shaping or rolling of the steel billets,
blooms and slabs by applying jets of oxygen to the surface of the steel,
which is at orange heat, thus removing a thin layer of the metal by rapid
oxidation. Scarfing can be performed by machine on hot semifinished steel
or by hand on cold or slightly heated semifinished steel. Emissions occur
during teeming as the molten metal is poured, and when the semifinished
steel products are manually or machine scarfed to remove surface defects.
Miscellaneous Combustion Sources - Iron and steel plants require energy
(heat or electricity) for every plant operation. Some energy operations on
plant property that produce emissions are boilers, soaking pits and slab
furnaces which burn coal, No. 2 fuel oil, natural gas, coke oven gas or
blast furnace gas. In soaking pits, ingots are heated until the tempera-
ture distribution over the cross section of the ingots is acceptable and
the surface temperature is uniform for further rolling into semifinished
products (blooms, billets and slabs). In slab furnaces, a slab is heated
before being rolled into finished products (plates, sheets or strips). The
emissions from the combustion of natural gas, fuel oil or coal for boilers
7.5-4 EMISSION FACTORS 5/83
-------
can be found in Chapter 1 of this document. Estimated emissions from these
same fuels used in soaking pits or slab furnaces can be the same as those
for boilers, but since it is estimation, the factor rating drops to D.
Emission factor data for blast furnace gas and coke oven gas are not
available and must be estimated. There are three facts available for mak-
ing the estimation. First, the gas exiting the blast furnace passes
through primary and secondary cleaners and can be cleaned to less than 0.05
grams per cubic meter (0.02 gr/ft3). Second, nearly one third of the coke
oven gas is methane. Third, there are no blast furnace gas constituents
that generate particulate when burned. The combustible constituent of
blast furnace gas is CO, which burns clean. Based on facts one and three,
the emission factor for combustion of blast furnace gas is equal to the
particulate loading of that fuel, 0.05 grams per cubic meter (2.9 lb/10e
ft3).
Emissions for combustion of coke oven gas can be estimated in the same
fashion. Assume that cleaned coke oven gas has as much particulate as
cleaned blast furnace gas. Since one third of the coke oven gas is meth-
ane, the main component of natural gas, it is assumed that the combustion
of this methane in coke oven gas generates 0.06 grams per cubic meter (3.3
lb/106 ft3) of particulate. Thus, the emission factor for the combustion
of coke oven gas is the sum of the particulate loading and that generated
by the methane combustion, or 0.1 grams per cubic meter (6.2 lb/10e ft3).
Open Dust Sources - Like process emission sources, open dust sources con-
tribute to the atmospheric particulate burden. Open dust sources include
1) vehicle traffic on paved and unpaved roads, 2) raw material handling
outside of buildings and 3) wind erosion from storage piles and exposed
terrain. Vehicle traffic consists of plant personnel and visitor vehicles;
plant service vehicles; and trucks handling raw materials, plant deliver-
ables, steel products and waste materials. Raw materials are handled by
clamshell buckets, bucket/ladder conveyors, rotary railroad dumps, bottom
railroad dumps, front end loaders, truck dumps, and conveyor transfer sta-
tions, all of which disturb the raw material and expose fines to the wind.
Even fine materials resting on flat areas or in storage piles are exposed
and are subject to wind erosion. It is not unusual to have several million
tons of raw materials stored at a plant and to have in the range of 10 to
100 acres of exposed area there.
Open dust source emission factors for iron and steel production are
presented in Table 7.5-1. These factors were determined through source
testing at various integrated iron and steel plants.
As an alternative to the single valued open dust emission factors
given in Table 7.5-1, empirically derived emission factor equations are
presented in Chapter 11 of this document. Each equation was developed for
a source operation defined on the basis of a single dust generating mecha-
nism which crosses industry lines, such as vehicle traffic on unpaved
roads. The predictive equation explains much of the observed variance in
measured emission factors by relating emissions to parameters which charac-
terize source conditions. These parameters may be grouped into three cate-
gories: 1) measures of source activity or energy expended (e.g., the speed
5/83 Metallurgical Industry 7.5-5
-------
TABLE 7.5-1. UNCONTROLLED PARTICULATE EMISSION FACTORS FOR
OPEN DUST SOURCES AT IRON AND STEEL MILLS3
Operation
Continuous drop
Conveyor transfer station
Sinter
Pile formation -
stacker
Pellet orec
Lump orec
A
Coal"
Batch drop
Front end loader/truck0
High silt slag
Low silt slag
Vehicle travel on.
unpaved roads
Light duty vehicle
j
Medium duty vehicle
Heavy duty vehicle
Vehicle travel on
paved roads
Light/heavy vehicle mix
Emissions by particle size range (aerodynamic
< 30 \m
13
0.026
1.2
0.0024
0.15
0.00030
0.055
0.00011
13
0.026
4.4
0.0088
0.51
1.8
2.1
7.3
3.9
14
0.22
0.78
< 15 (Jrn
9.0
0.018
0.75
0.0015
0.095
0.00019
0.034
0.000069
8.5
0.017
2.9
0.0058
0.37
1.3
1.5
5.2
2.7
9.7
0.16
0.56
< 10 )M
6.5
0.013
0.55
0.0011
0.07S
0.00015
0.026
0.000052
6.5
0.013
2.2
0.0043
0.28
1.0
1.2
4.1
2.1
7.6
0.12
0.44
< 5 (Jm
4.2
0.0084
0.32
0.00064
0.040
o.oooos:
0.014
0.000029
4.0
0.0080
1.4
0.0028
0.18
0.64
0.70
2.5
1.4
4.8
0.079
0.28
diameter)
< 2.5 pm
2.3
0.0046
0.17
0.00034
0.022
0.000043
0.0075
0.000015
2.3
0.0046
0.80
0.0016
0.10
0.37
0.42
1.5
0.76
2.7
0.042
0.15
Unitsb
g/Mg
Ib/T
g/Mg
Ib/T
g/Mg
Ib/T
g/Mg
Ib/T
g/Mg
Ib/T
g/Mg
Ib/T
kg/VKT
Ib/VMT
kg/VKT
Ib/VMT
kg/VKT
Ib/VMT
kg/VKT
Ib/VMT
Emission
Factor
Rating
D
D
B
B
C
C
E
E
C
C
C
C
C
C
C
C
B
B
C
C
Predictive emission factor equations, which generally provide more accurate estimates of emissions, are pre-
sented in Chapter 11.
Units/unit of material transferred. Units/unit of distance traveled.
Reference 3. Interpolation to other particle sizes will be approximate.
Reference 4. Interpolation to other particle sizes will be approximate.
and weight of a vehicle traveling on an unpaved road), 2) properties of the
material being disturbed (e.g., the content of suspendible fines in the
surface material on an unpaved road) and 3) climatic parameters (e.g., num-
ber of precipitation free days per year, when emissions tend to a maximum).
Because the predictive equations allow for emission factor adjustment
to specific source conditions, the equations should be used in place of the
factors in Table 7.5-1, if emission estimates for sources in a specific
iron and steel facility are needed. However, the generally higher quality
ratings assigned to the equations are applicable only if 1) reliable values
of correction parameters have been determined for the specific sources of
interest and 2) the correction parameter values lie within the ranges
tested in developing the equations. Chapter 11 lists measured properties
of aggregate process materials and road surface materials in the iron and
steel industry, which can be used to estimate correction parameter values
for the predictive emission factor equations, in the event that site spe-
cific values are not available. Use of mean correction parameter values
from Chapter 11 reduces the quality ratings of the emission factor equation
by one level.
7.5-6
EMISSION FACTORS
5/83
-------
Particulate emission factors for iron and steel plant processes are in
Table 7.5-2. These emission factors are a result of an extensive investi-
gation by EPA and the American Iron and Steel Institute.2 Carbon monoxide
emission factors are in Table 7.5-S.5
TABLE 7.5-2. PARTICULATE EMISSION FACTORS FOR IRON AND STEEL MILLS&
Source
Blast furnaces
Slips
Uncontrolled cast house emissions
Monitor
Tap hole and trough (not runners)
Sintering
Windbox emissions
Uncontrolled
Leaving grate
After coarse particulate removal
Controlled by dry ESP
Controlled by wet ESP
Controlled by scrubber
Controlled by cyclone
Sinter discharge (breaker and hot
screens)
Uncontrolled
Controlled by baghouse
Controlled by orifice scrubber
V/indbox and discharge
Controlled by baghouse
Bapic oxygen furnaces
Top blown furnace melting and refining
Uncontrolled
Controlled by open hood vented to:
ESP
Scrubber
Controlled by closed hood vented to:
Scrubber
QBOP melting and refining
Controlled by scrubber
Charging
At source
At building monitor
Tapping
At source
At building monitor
Hot metal transfer
At source
At building monitor
EOF monitor (all sources)
Electric arc furnaces
Melting and refining
Uncontrolled
Carbon steel
Charging, tapping and slagging
Uncontrolled emissions escaping
monitor
Melting, refining, charging, tapping
and slagging
Uncontrolled
Alloy steel
Carbon steel
Controlled by:
Configuration 1
(building evacuation to baghouse
for alloy steel)
Configuration 2
(DSE plus charging hood vented
to common baghouse for carbon
steel)
Units
kg (lb)/slip
kg/Mg (Ib/ton) hot metal
Emissions Emission Factor
Rating
39.
5
0.3
kg/Sg
(Ib/toa) finished
0.
15
(87)
(0.6)
(0.3)
D
B
B
sinter
kg/Mg
(Ib/ton) finished
5.
4.
0.
0.
0.
0.
56
35
8
085
235
5
(11.1)
(8.7)
(1.6)
(0.17)
(0.47)
CD
B
A
B
B
B
B
sinter
kg/Mg
(Ib/ton) finished
sinter
kg/Mg
kg/Mg
kg/Mg
(Ib/ton) steel
(Ib/ton) steel
(Ib/ton) hot metal
3.
0.
0.
0.
14.
0.
0.
0.
0.
0.
it
05
295
15
25
065
045
0034
028
3
D.071
kg/Mg
kg/Mg
kg/Mg
kg/Mg
kg/Mg
kg/Mg
(Ib/ton) steel
(Ib/ton) hot metal
(Ib/ton) steel
(Ib/ton) steel
(Ib/ton) steel
(Ib/ton) steel
0.
0.
0.
0.
0.
19
0.
5.
25
0.
0.
46
145
095
028
25
7
65
15
0215
(6.8)
(0.1)
(0.59)
(0.3)
(28.5)
(0.13)
(0.09)
(0.0068)
(0.056)
(0.6)
(0.142)
(0.92)
(0.29)
(0.19)
(0.056)
(0.5)
(38)
(1.4)
(11.3)
(50)
(0.3)
(0.043)
B
B
A
A
B
A
B
A
A
A
B
A
B
A
B
B
C
C
A
C
A
C
(continued)
5/83
Metallurgical Industry
7.5-7
-------
TABLE 7.5-2.
PARTICULATE EMISSION FACTORS FOR IRON AND
STEEL MILLSa (continued)
Source Units
Open hearth furnaces
Melting and refining kg/Mg (Ib/ton) steel
Uncontrolled
Controlled by ESP
Roof monitor emissions
Teeming
Leaded steel kg/Mg (Ib/ton) steel
Uncontrolled (as measured at the
source)
Controlled by side draft hood vented
to baghouse
Unleaded steel
Uncontrolled (as measured at the
source)
Controlled by side draft hood vented
to baghouse
Machine scarfing
Uncontrolled kg/Mg (Ib/ton) metal
through scarfer
Controlled by ESP
Miscellaneous combustion sources
Boilers, soaking pits and slab reheat kg/10s J (lb/10e BTU)
furnaces
Blast furnace gas
Coke oven gae
Emissions Emission Factor
Rating
10.55
0.14
0.084
0.405
0.0019
0.035
0.0008
0.05
0.0115
0.015
0.0052
(21.1)
(0.28)
(0.168)
(0.81)
(0.0038)
(0.07)
(0.0016)
(0.1)
(0.023)
(0.035)
(0.012)
A
A
C
A
A
A
A
£
A
D
D
, Reference 2. ESP = electrostatic precipitator, DSE = direct shell evacuation.
For fuels such as coal, fuel oil and natural gas, use the emission factors presented in Chapter 1. of
this document. The factor rating for these fuels in boilers is A, and in soaking pits and slab re-
heat furnaces is D.
TABLE 7.5-3. UNCONTROLLED CARBON MONOXIDE
EMISSION FACTORS FOR IRON
AND STEEL MILLS3
EMISSION FACTOR RATING: C
Source
kg/Mg
Ib/ton
Sintering windbox
Basic oxygen furnace
Electric arc furnace
22
69
9
44
138
18
, Reference 5.
of finished sinter.
7.5-8
EMISSION FACTORS
5/83
-------
References for Section 7.5
1. H. E. McGannon, ed. , The Making, Shaping and Treating of Steel, U. S.
Steel Corporation, Pittsburgh, PA, 1971.
2. T. A. Cuscino, Jr., Particulate Emission Factors Applicable to the
Iron and Steel Industry, EPA-450/4-79-029 , U. S. Environmental Protec-
tion Agency, Research Triangle Park, NC, September 1979.
3. R. Bonn, et al. , Fugitive Emissions from Integrated Iron and Steel
Plants, EPA-600/2-78-050, U. S. Environmental Protection Agency,
Research Triangle Park, NC, March 1978.
4. C. Cowherd, Jr., et al. , Iron and Steel Plant Open Source Fugitive
Emission Evaluation, EPA-600/2-79-1Q3, U. S. Environmental Protection
Agency, Research Triangle Park, NC, May 1979.
5 . Control Techniques fo^ Carbon Monoxide Emissions from Stationary
Sources , AP-65, U. S. Department of Health, Education and Welfare,
Washington, DC, March 1970.
5/83 Metallurgical Industry 7.5-9
-------
-------
7.6 PRIMARY LEAD SMELTING
7.6.1 Process Description
1-3
Lead is usually found naturally as a sulfide ore containing small
amounts of copper, iron, zinc and other trace elements. It is normally
concentrated at the mine from an ore of 3 to 8 percent lead to an ore
concentrate of 55 to 70 percent lead, containing from 13 to 19 percent,
by weight, free and uncombined sulfur. A typical flow sheet for the
production of lead metal from ore concentrate is shown in Figure 7.6-1.
Processing involves three major steps:
- Sintering, in which the concentrated lead and sulfur are
oxidized to produce lead oxide and sulfur dioxide. (Simulta-
neously, the charge concentrates, recycled sinter, sand and other
inert materials are agglomerated to form a dense, permeable
substance called sinter.)
- Reducing the lead oxide contained in the sinter to produce
molten lead bullion.
- Refining the lead bullion to eliminate any impurities.
7.6.1.1 Sintering - Sinter is produced by a sinter machine, a contin-
uous steel pallet conveyor belt moved by gears and sprockets. Each
pallet consists of perforated or slotted grates, beneath which are
windboxes connected to fans that provide a draft through the moving
sinter charge. Depending on the direction of this draft, the sinter
machine is either of the updraft or downdraft type. Except for the
draft direction, however, all machines are similar in design,
construction and operation.
The sintering reaction is autogenous, occuring at a temperature of
approximately 1800°F (1000°C):
2PbS
302
2PbO
2S02
(1)
Operating experience has shown that system operation and product quality
are optimum when the sulfur content of the sinter charge is between 5
and 7 percent by weight. To maintain this desired sulfur content,
sulfide-free fluxes such as silica and limestone, plus large amounts of
recycled sinter and smelter residues, are added to the mix. The quality
of the product sinter is usually determined by its Ritter Index hardness,
which is inversely proportional to the sulfur content. Hard quality
sinter (low sulfur content) is preferred, because it resists crushing
during discharge from the sinter machine. Undersized sinter usually
results from insufficient desulfurization and is recycled for further
processing.
2/80
Metallurgical Industry
r.6-1
-------
Of the two kinds of sintering machines used, the updraft design is
superior for many reasons. First, the sinter bed thickness is more
permeable (and hence can be larger), thereby permitting a higher pro-
duction rate than that of a downdraft machine of similar dimensions.
Secondly, the small amounts of elemental lead that form during sintering
will solidify at their point of formation in updraft machines, whereas,
in downdraft operation, the metal tends to flow downward and collect on
the grates or at the bottom of the sinter charge, thus causing increased
pressure drop and attendant reduced blower capacity. In addition, the
updraft system exhibits the capability of producing sinter .of higher
lead content and requires less maintenance than the downdraft machine.
Finally, and most important from an air pollution control standpoint,
updraft sintering can produce a single strong SC>2 effluent stream from
the operation, by use of weak gas recirculation. This, in turn, permits
more efficient and economical use of control methods such as sulfuric
acid recovery devices.
7.6.1.2 Reduction - Lead reduction is carried out in a blast furnace,
basically a water jacketed shaft furnace supported by a refractory base.
Tuyeres, through which combustion air is admitted under pressure, are
located near the bottom and are evenly spaced on either side of the
furnace.
The furnace is charged with a mixture of sinter (80 - 90 percent of
charge), metallurgical coke (8 - 14 percent of charge), and other
materials, such as limestone, silica, litharge, slag-forming constit-
uents, and various recycled and cleanup materials. In the furnace, the
sinter is reduced to lead bullion by reactions (2) through (6).
PbO + CO •> Pb + C02 (2)
C + 02 -> C02 (3)
C + C02 ->- 2CO (4)
2PbO + PbS -»- 3Pb + S02 (5)
PbSO^ + PbS •> 2Pb + 2S02 (6)
Carbon monoxide and heat required for reduction are supplied by the
combustion of coke. Most of the impurities are eliminated in the slag.
Solid products from the blast furnace generally separate into four
layers: speiss, the lightest material (basically arsenic and antimony),
matte (copper sulfide and other metal sulfides), slag (primarily
silicates), and lead bullion. The first three layers are combined as
slag, which is continually collected from the furnace and either processed
at the smelter for its metal content or shipped to treatment facilities.
r.A-2 EMISSION FACTORS 2/80
-------
Sulfur oxides are also generated in blast furnaces from small
quantities of residual lead sulfide and lead sulfates in the sinter
feed. The quantity of these emissions is a function not only of the
residual sulfur content in the sinter, hut also of the amount of sulfur
that is captured by copper and other impurities in the slag.
Rough lead bullion from the blast furnace usually requires pre-
liminary treatment (dressing) in kettles before undergoing refining
operations. First, the bullion is cooled to 700 to 800°F (370 - 430°C).
Copper and small amounts of sulfur, arsenic, antimony and nickel are
removed from solution, collecting on the surface as a dross. This
dross, in turn, is treated in a reverberatory furnace where the copper
and other metal impurities are further concentrated before being routed
to copper smelters for their eventual recovery. Drossed lead bullion is
treated for further copper removal by the addition of sulfurbearing
material and zinc, and/or aluminum, to lower the copper content to
approximately 0.01 percent.
7.6.1.3 Refining - The third and final phase of smelting, the refining
of the bullion in cast iron kettles, occurs in five steps:
- Removal of antimony, tin and arsenic.
- Removal of precious metals by Parke's Process, in which zinc
combines with gold and silver to form an insoluble intermetallic at
operating temperatures.
- Vacuum removal of zinc.
- Removal of bismuth using the Betterson Process, which is the
addition of calcium and magnesium to form an insoluble compound
with the bismuth that is skimmed from the kettle.
- Removal of remaining traces of metal impurities by addition
of NaOH and NaN03.
The final refined lead, commonly of 99.990 to 99.999 percent purity,
is then cast into 100 pound pigs for shipment.
1 2
7.6.2 Emissions and Controls '
Each of the three major lead smelting process steps generates
substantial quantities of particulates and/or sulfur dioxide.
Nearly 85 percent of the sulfur present in the lead ore concentrate
is eliminated in the sintering operation. In handling process offgases,
either a single weak stream is taken from the machine hood at less than
2 percent S02, or two streams are taken, one strong stream (5-7
percent 802) from the feed end of the machine and one weak stream (<0.5
percent 802) from the discharge end. Single stream operation has been
2/80 Metallurgical Industry
-------
used when there is little or no market for recovered sulfur, so that the un-
controlled weak SC>2 stream is emitted to the atmosphere. When sulfur removal
is required, however, dual stream operation is preferred. The strong stream
is sent to a sulfuric acid plant\ and the weak stream is vented to the atmos-
phere after removal of particulates.
TABLE 7.6-1. EMISSION FACTORS FOR PRIMARY LEAD SMELTING
PROCESSES WITHOUT CONTROLS3
EMISSION FACTOR RATING: B
Process
Ore crushing'5
Sintering (updraft)c
Blast furnace"1
Dross reverberatory
furnace6
Total
Participates
kg/Mg Ib/ton
1.0 2.0
106.5 213.0
180.5 361.0
10.0 20.0
Sulfur
kg/Mg
-
275.0
22.5
Neg
dioxide
Ib/ton
-
550.0
45.0
Neg
kg/Mg
0.15
87
(4.2-170)
29
(8.7-50)
2.4
(1.3-3.5)
Lead
Ib/ton
0.3
174
(8.4-340)
59
(17.5-100)
4.8
(2.6-7.0)
Materials handlingf 2.5 5.0
aOre crushing emission factors expressed as kg/Mg (Ib/ton) of crushed ore. All other
emission factors expressed as kg/Mg (Ib/ton) of lead product. Dash indicates no
available data.
References 2, 13.
References 1, 4-6, 11, 14-17, 21-22.
References 1-2, 7, 12, 14, 16-17, 19.
eReferences 2, 11-12, 14, 18, 20.
fReference 2.
When dual gas stream operation is used with updraft sinter machines, the
weak gas stream can be recirculated through the bed to mix with the strong gas
stream, resulting in a single stream with an S02 concentration of about 6 per-
cent. This technique has the overall effect of decreasing machine production
capacity, but permits a more convenient and economical recovery of the S02
by sulfuric acid plants and other control methods.
Without weak gas recirculation, the latter portion of the sinter machine
acts as a cooling zone for the sinter and, consequently, assists in the reduc-
tion of dust formation during product discharge and screening. However,
when recirculation is used, the sinter is usually discharged in a relatively
hot state, 400 - 500°C (745 to 950°F), with an attendant increase in partic-
ulates. Methods for reducing these dust quantities include recirculation of
offgases through the sinter bed, relying upon the filtering effect of the
bed or the ducting of gases from the discharge through a partlculate collection
device and then to the atmosphere. Because reaction activity has ceased in
the discharge area, these latter gases contain little S02-
7.6-4 EMISSION FACTORS 12/81
-------
The particulate emissions from sinter machines range from 5 to 20
percent of the concentrated ore feed. When expressed in terms of
product weight, a typical emission is estimated to be 213 Ib/ton (106.5
kg/MT) of lead produced. This value, along with other particulate and
S02 factors, appears in Table 7.6-1.
Table 7.6-2. PARTICLE SIZE DISTRIBUTION OF FLUE DUST
FROM UPDRAFT SINTERING MACHINES
Size (urn)
20 - 40
10 - 20
5-10
<5
Percent by weight
15 - 45
9-30
4-19
1-10
Typical material balances from domestic lead smelters indicate that
about 15 percent of the sulfur in the ore concentrate fed to the sinter
machine is eliminated in the blast furnace. However, only half of this
amount (about 7 percent of the total sulfur in the ore) is emitted as
S02- The remainder is captured by the slag. The concentration of this
S02 stream can vary from 500 to 2500 ppm, by volume (1.4 - 7.2 g/m3),
depending on the amount of dilution air injected to oxidize the carbon
monoxide and to cool the stream before baghouse particulate removal.
Particulate emissions from blast furnaces contain many different
kinds of material, including a range of lead oxides, quartz, limestone,
iron pyrites, iron-lime-silicate slag, arsenic, and other metal-containing
compounds associated with lead ores. These particles readily agglom-
erate and are primarily submicron in size, difficult to wet, and cohesive.
They will bridge and arch in hoppers. On the average, this dust loading
is quite substantial (see Table 7.6-1).
Virtually no sulfur dioxide emissions are associated with the
various refining operations. However, a small amount of particulate is
generated by the dross reverberatory furnace, about 20 Ib/ton (10 kg/MT)
of lead.
Finally, minor quantities of particulates are generated by ore
crushing and materials handling operations. These emission factors are
also presented in Table 7.6-1.
Table 7.6-2 is a listing of size distributions of flue dust from
updraft sintering machine effluent. Though these are not fugitive
emissions, the size distributions may closely resemble those of the
fugitive emissions. Particulate fugitive emissions from the blast
furnace consist basically of lead oxides, 92 percent of which are less
than 4 urn in size. Uncontrolled emissions from a lead dross rever-
beratory furnace are mostly less than 1 urn, and this may also be the
case with the fugitive emissions.
2/80 MolalliirfiM-al Industry 7.6-.»
-------
OS
o
Table 7.6-3. EFFICIENCIES OF REPRESENTATIVE CONTROL DEVICES USED WITH
PRIMARY LEAD SMELTING OPERATIONS
Control method
Efficiency range,
Particulates
Sulfur dioxide
2
M
(/)
(/)
O
o
3
Centrifugal collector
Q
Electrostatic precipitator
Fabric filter3
Tubular cooler (associated with waste heat boiler)'
b c
Sulfuric acid plant (single contact) '
b c
Sulfuric acid plant (dual contact) *
,b,d
Elemental sulfur recovery plant
Dimethylaniline (DMA) absorption process
Ammonia absorption process *
b,e
80 to 90
95 to 99
95 to 99
70 to 80
99.5 to 99.9
99.5 to 99.9
96 to 97
96 to 99.9
90
95 to 99
92 to 95
Reference 2.
Reference 1.
High particulate control efficiency due to action of acid plant gas cleaning system. Based on S02
inlet concentrations of 5-7^ typical outlet emission levels are 2000 ppm (5.7 g/m3) for single
contact and 500 ppm (1.4 g/m3) for dual contact.
Collection efficiency for a two stage uncontrolled Glaus type plant. Refer to Section 5.18 for more
information.
Based on SC>2 inlet concentrations of 4-6%, typical outlet emission levels range from
500-3000 ppm (1.4-8.6 g/m3).
Based on SOg inlet concentrations of 1.5-2.5%, typical outlet emission level is
1200 ppm (3.4 g/m3).
-------
Table 7.6-4. POTENTIAL FUGITIVE EMISSION FACTORS FOR PRIMARY
LEAD SMELTING PROCESSES WITHOUT CONTROLS3'b
EMISSION FACTOR RATING: E
Particulates
Process
Ib/ton
Ore mixing and palletizing (crushing) 2.26
Car charging (conveyor loading and
transfer) of sinter 0.50
Sinter machine leakage 0.68
Sinter return handling 9.00
Sinter machine discharge, sinter crushing
Q
and screening 1.50
Sinter transfer to dump area 0.20
Sinter product dump area 0.01
Blast furnace (charging, blow condition,
tapping) 0.16
Lead pouring to ladle, transferring, and
kg/MT
1.13
0.25
0.34
4.50
0.75
0.10
0.005
0.08
slag pouring
Slag cooling
Zinc fuming furnace vents
Dross kettle
Reverberatory furnace leakage
Silver retort building
Lead casting
0.93
0.47
4.60
0.48
3.00
1.80
0.87
0.47
0.24
2.30
0.24
1.50
0.90
0.44
All factors are expressed in units per end product lead produced,
except sinter operations, which are expressed in units per sinter or
, sinter handled/transferred/charged.
Reference 8, except where noted.
References 9 and 10. Engineering judgement using steel sinter machine
, leakage emission factor.
Reference 2.
Reference 2. Engineering judgement, estimated to be half the magnitude
of lead pouring and ladling operations.
2/80
Metallurgical Industry
r.6-r
-------
I
Emission controls on lead smelter operations are for particulates
and sulfur dioxide. The most commonly employed high efficiency parti-
culate control devices are fabric filters and electrostatic precip-
itators, which often follow centrifugal collectors and tubular coolers
(pseudogravity collectors). Three of the 6 lead smelters presently
operating in the United States use single absorption sulfuric acid
plants for control of sulfur dioxide emissions from sinter machines and,
occasionally, from blast furnaces. Single stage plants can attain SO
levels of 2000 ppm (5.7 g/m3), and dual stage plants can attain levels
of 550 ppm (1.6 g/m3). Typical efficiencies of dual stage sulfuric acid
plants in removing sulfur oxides can exceed 99 percent. Other techni-
cally feasible S02 control methods are elemental sulfur recovery plants
and dimethylaniline (DMA) and ammonia absorption processes. These
methods and their representative control efficiencies are listed in
Table 7.6-3.
References for Section 7.6
1. Charles Darvin and Fredrick Porter, Background Information for New
Source Peformance Standards: Primary Copper, Zinc, and Lead
Smelters, Volume I, EPA-450/2-74-002a, U.S. Environmental
Protection Agency, Research Triangle Park, NC, October 1974.
2. A. E. Vandergrift, et a.1., Handbook of Emissions, Effluents, and
Control Practices for Stationary Particulate Pollution Sources,
Three volumes, HEW Contract No. CPA 22-69-104, Midwest Research
Institute, Kansas City, MO, November 1970 - May 1971.
3. A. Worcester and D. H. Beilstein, "The State of the Art: Lead
Recovery", Presented at the 10th Annual Meeting of the Metallurgical
Society, AIME, New York, March 1971.
4. T. J. Jacobs, "Visit to St. Joe Minerals Corporation Lead Smelter,
Herculaneum, MO", Memorandum to Emission Standards and Engineering
Division, Office of Air Quality Planning and Standards, U.S.
Environmental Protection Agency, Research Triangle Park, NC,
October 21, 1971.
5. T. J. Jacobs, "Visit to Amax Lead Company, Boss, MO", Memorandum to
Emission Standards and Engineering Division, Office of Air Quality
Planning and Standards, U.S. Environmental Protection Agency,
Research Triangle Park, NC, October 28, 1971.
6. Written Communication from R. B. Paul, American Smelting and
Refining Co., Glover, MO, to Regional Administrator, U.S.
Environmental Protection Agency, Kansas City, MO, April 3, 1973.
r.6-8 EMISSION FACTORS 2/80
-------
7. Emission Test No. 72-MM-14, Office of Air Quality Planning and Standards,
U. S. Environmental Protection Agency, Research Triangle Park, NC, May
1972.
8. Silver Valley/Bunker Hill Smelter Environmental Investigation (Interim
Report), EPA Contract No. 68-02-1343, PEDCo Environmental, Specialists,
Inc., Cincinnati, OH, February 1975.
9. R. E. Iversen, "Meeting with U. S. Environmental Protection Agency and
AISI on Steel Facility Emission Factors", Memorandum, Office of Air
Quality Planning and Standards, U. S. Environmental Protection Agency,
Research Triangle Park, NC, June 7, 1976.
10. G. E. Spreight, "Best Practical Means in the Iron and Steel Industry",
The Chemical Engineer, London, 271:132-139, March 1973.
11. Control Techniques for Lead Air Emissions. EPA-450/2-77-012, U. S. En-
vironmental Protection Agency, Research Triangle Park, NC, January 1978.
12. System^ Study for__Control of Emissions: Primary Nonferrous Smelting In-
dustry, U. S. Department of Health, Education and Welfare, Washington,
DC, June 1969.
13. Environmental Assessment of the Domestic Primary Copper, Lead, and Zinc
Industry, EPA Contract No. 68-02-1321, PEDCo-Environmental Specialists,
Inc., Cincinnati, OH, September 1976.
14. H. R. Jones, Pollution Control in the Nonferrous Metals Industry, Noyes
Data Corporation, Park Ridge, NJ, 1972.
15. L. J. Duncan and E. L. Keitz, "Hazardous Particulate Pollution from Typi-
cal Operations in the Primary Nonferrous Smelting Industry", presented
at the 67th Annual Meeting of the Air Pollution Control Association,
Denver, CO, June 1974.
16. E. P. Shea, Source Sampling Report: Emissions from Lead^ Smelters, EPA
Contract No. 68-02-0228, Midwest Research Institute, Kansas City, MO,
1973.
17. R. C. Hussy, Source Testing: Emissions from a Primary Lead Smelter, EPA
Contract No. 68-02-0228, Midwest Research Institute, Kansas City, MO,
1973.
18. Emission Test No. 73-PLD-l, Office of Air Quality Planning and Standards,
U. S. Environmental Protection Agency, Research Triangle Park, NC, Octo-
ber 1973.
19. Interim Report on Control Techniques for Lead Air Emissions, Development
of Lead Emission Factors, and 1975 National Lead Emission Inventory, EPA
Contract No.68-02-1375, PEDCo-Environmental Specialists, Inc., Cincin-
nati, OH, June 1976.
12/81
Metallurgical Industry
7.6-9
-------
20. S. Wyatt, et al., Preferred Standards Path Analysis on Lead Emissions
from Stationary Sources, Office of Air Quality Planning and Standards,
Research Triangle Park, NC, September 1974.
21. A. E. Vandergrift, et^al^, Particulate Pollutant System Stu_dy_ -__Masg
Emissions, PB-203-128, PB-203-522 and PB-203-521, U. S. Environmental
Protection Agency, Research Triangle Park, NC, May 1971.
22. V. S. Katari, et al., Trace Pollutant Emissions from the Processing of
Metallic Ores, EPA-650/2-74-115, U. S. Environmental Protection Agency,
Research Triangle Park, NC, October 1974.
7.6-10
EMISSION FACTORS 12/81
-------
7.7 ZINC SMELTING
7.7.1 Process Description^ ^
As stated previously, most domestic zinc comes from zinc and lead ores.
Another important source of raw material for zinc metal has been zinc oxide
from fuming furnaces. For efficient recovery of zinc, sulfur must be removed
from concentrates to a level of less than 2 percent. This is done by fluid-
ized beds or multiple-hearth roasting occasionally followed by sintering.
Metallic zinc can be produced from the roasted ore by the horizontal or
vertical retort process or by the electrolytic process if a high-purity zinc
is needed.
7.7.2 Emissions and Controls^>2
Dust, fumes, and sulfur dioxide are emitted from zinc concentrate roast-
ing or sintering operations. Particulates may be removed by electrostatic
precipitators or baghouses. Sulfur dioxide may be converted directly into
sulfuric acid or vented. Emission factors for zinc smelting are presented
in Table 7.7-1.
TABLE 7.7-1. EMISSION FACTORS FOR PRIMARY ZINC
SMELTING WITHOUT CONTROLS3
EMISSION FACTOR RATING: B
Type of operation
Particulates Sulfur oxides
kg/Mg Ib/ton kg/Mg Ib/ton
Leadb
kg/Mg
Ib/ton
Ore unloading, storage
and transfer
Roasting (multiple-
1.95 3.85
(1-2.9) (2.0-5.7)
hearth)0
S inter ingd
Horizontal retorts^
Vertical retorts^
Electrolytic process
60
45
4
50
1.5
120
90
8
100
3
550 1100
e e
— _
- -
— —
19.25
(13.5-25)
1.2
2.25
(2-2.5)
—
38.5
(27-50)
2.4
4.5
(4-5)
—
Approximately 2 unit weights of concentrated ore are required to produce
1 unit weight of zinc metal. Emission factors expressed as units per unit
weight of concentrated ore produced. Dash indicates no available data.
^References 1-3.
References 4-5.
^References 5-6.
elncluded in S02 losses from roasting.
fReference 3.
12/81
Metallurgical Industry
7.7-1
-------
References for Section 7.7
1- Cpjntrol Techniques for Lead Air Emissions, EPA-450/2-77-012, U. S. Envi-
ronmental Protection Agency, Research Triangle Park, NC, December 1977.
2. H. R. Jones, Pollution Control in the Nonferrous Metals Industry, Noyes
Data Corporation, Park Ridge, NJ, 1972.
3. G. B. Carne, Control Techniques for Lead Emissions, Draft Report, U. S.
Environmental Protection Agency, Research Triangle Park, NC, February
1971.
4. R. L. Duprey, Compilation of Air Pollutant Emission Factors, U. S. DHEW,
PHS, National Center for Air Pollution Control, Durham, NC, PHS Pub-
lication Number 999-AP-42, 1968, p. 26-28.
5. A. Stern (ed), "Sources of Air Pollution and Their Control, Air Pollution,
Vol III, 2nd Ed., New York, NY, Academic Press, 1968, p. 182-186.
6. G. Bailee, Private communication on Particulate Pollutant Study, Midwest
Research Institute, Kansas City, MO, prepared for National Air Pollution
Control Administration, Durham, NC, under Contract Number 22-69-104,
June 1970.
7. Systems Study for Control of Emissions in the Primary Nonferrous Smelting
Industry, 3 Volumes, San Francisco, Arthur G. McKee and Company, June
7.7-2 EMISSION FACTORS 12/81
-------
7.8 SECONDARY ALUMINUM OPERATIONS
7.8.1 General
Secondary aluminum operations involve the cleaning, melting,
refining and pouring of aluminum recovered from scrap. The processes
used to convert scrap aluminum to secondary aluminum products such
as lightweight metal alloys for industrial castings and ingots are
presented in Figure 7.8-1. Production involves two general classes
of operation, scrap treatment and smelting/refining.
Scrap treatment involves receiving, sorting and processing
scrap to remove contaminants and to prepare the material for smelting.
Processes based on mechanical, pyrometallurgical and hydrometal-
lurgical techniques are used, and those employed are selected to
suit the type of scrap processed.
The smelting/refining operation generally involves the following
steps:
charging
melting
fluxing
alloying
mixing
demagging
degassing
skimming
pouring
All of these steps may be involved in each operation, with process
distinctions being in the furnace type used and in emission charac-
teristics. However, as with scrap treatment, not all of these
steps are necessarily incorporated into the operations at a
particular plant. Some steps may be combined or reordered, depending
on furnace design, scrap quality, process inputs and product
specifications.
Scrap treatment - Purchased aluminum scrap undergoes inspection
upon delivery. Clean scrap requiring no treatment is transported
to storage or is charged directly into the smelting furnace. The
bulk of the scrap, however, must be manually sorted as it passes
along a steel belt conveyor. Free iron, stainless steel, zinc,
brass and oversized materials are removed. The sorted scrap then
goes to appropriate scrap treating processes or is charged directly
to the smelting furnace.
Sorted scrap is conveyed to a ring crusher or hammer mill,
where the material is shredded and crushed, with the iron torn away
from the aluminum. The crushed material is passed over vibrating
screens to remove dirt and fines, and tramp iron is removed by
magnetic drums and/or belt separators. Baling equipment compacts
bulky aluminum scrap into 1x2 meter (3x6 foot) bales.
4/81
Metallurgical Industry
7.8-1
-------
PHETHEATMENT
to
BULL .
SCRAP
US
CO
H
O
a
g
H
i
cn
oo
OLD
SHEET,
CASTINGS,
CLIPPINGS
SMELTING/REFINING
pCHLORINE
rFLUX
REVERBERATORY
(CHLORINE)
SMELTING/REFINING
p FLUORINE FUEL
REVEHBERATORV
(FLUORINE)
SMELTING/REFINING
FLUX-
I
FUEL
CRUCIBLE
SMELTING/REFINING
ELECTRICITY ,-FLUX
INDUCTION
SMELTING/REFINING
Figure 7.8-1. Process flow diagram for the secondary aluminum processing industry.
-------
Pure aluminum cable with steel reinforcement or insulation is
cut by alligator type shears and granulated or further reduced in
hammer mills, to separate the iron core and the plastic coating
from the aluminum. Magnetic processing accomplishes iron removal,
and air classification separates the insulation.
Borings and turnings, in most cases, are treated to remove
cutting oils, greases, moisture and free iron. The processing
steps involved are (a) crushing in hammer mills or ring crushers,
(b) volatilizing the moisture and organics in a gas or oil fired
rotary dryer, (c) screening the dried chips to remove aluminum
fines, (d) removing iron magnetically and (e) storing the clean
dried borings in tote boxes.
Aluminum can be recovered from the hot dross discharged from a
refining furnace by batch fluxing with a salt/cryolite mixture in a
mechanically rotated, refractory lined barrel furnace. The metal
is tapped periodically through a hole in its base. Secondary
aluminum recovery from cold dross and other residues from primary
aluminum plants is carried out by means of this batch fluxing in a
rotary furnace. In the dry milling process, cold aluminum laden
dross and other residues are processed by milling, screening and
concentrating to obtain a product containing at least 60-70 percent
aluminum. Ball, rod or hammer mills can be used to reduce oxides
and nonmetallics to fine powders. Separation of dirt and other
unrecoverables from the metal is achieved by screening, air
classification and/or magnetic separation.
Leaching involves (a) wet milling, (b) screening, (c) drying
and (d) magnetic separation to remove fluxing salts and other non-
recoverables from drosses, skimmings and slags. First, the raw
material is fed into a long rotating drum or an attrition or ball
mill where soluble contaminants are leached. The washed material
is then screened to remove fines and dissolved salts and is dried
and passed through a magnetic separator to remove ferrous materials.
The nonmagnetics then are stored or charged directly to the smelting
furnace.
In the roasting process, carbonaceous materials associated
with aluminum foil are charred and then separated from the metal
product.
Sweating is a pyrometallurgical process used to recover
aluminum from high iron content scrap. Open flame reverberatory
furnaces may be used. Separation is accomplished as aluminum and
other low melting constituents melt and trickle down the hearth,
through a grate and into air cooled molds or collecting pots. This
product is termed "sweated pig". The higher melting materials,
including iron, brass and oxidation products formed during the
sweating process, are periodically removed from the furnace.
4/81 Metallurgical Industry 7.8-3
-------
Smelting/refining - In reverberatory (chlorine) operations,
reverberatory furnaces are commonly used to convert clean sorted
scrap, sweated pigs or some untreated scrap to specification ingots,
shot or hot metal. The scrap is first charged to the furnace by
some mechanical means, often through charging wells designed to
permit introduction of chips and light scrap below the surface of a
previously melted charge ("heel"). Batch processing is generally
practiced for alloy ingot production, and continuous feeding and
pouring are generally used for products having less strict
specifications.
Cover fluxes are used to prevent air contact with and consequent
oxidation of the melt. Solvent fluxes react with nonmetallics such
as burned coating residues and dirt to form insolubles which float
to the surface as part of the slag.
Alloying agents are charged through the forewell in amounts
determined by product specifications. Injection of nitrogen or
other inert gases into the molten metal can be used to aid in
raising dissolved gases (typically hydrogen) and intermixed solids
to the surface.
Demagging reduces the magnesium content of the molten charge
from approximately 0.3 to 0.5 percent (typical scrap value) to
about 0.1 percent (typical product line alloy specification). When
demagging with chlorine gas, chlorine is injected under pressure
through carbon lances to react with magnesium and aluminum as it
bubbles to the surface. Other chlorinating agents, or fluxes, are
sometimes used, such as anhydrous aluminum chloride or chlorinated
organics.
In the skimming step, contaminated semisolid fluxes (dross,
slag or skimmings) are ladled from the surface of the melt and
removed through the forewell. The melt is then cooled before
pouring.
The reverberatory (fluorine) process is similar to the
reverberatory (chlorine) smelting/refining process, except that
aluminum fluoride (AlF^) is employed in the demagging step instead
of chlorine. The AlF^ reacts with magnesium to produce molten
metal aluminum and solid magnesium fluoride salt which floats to
the surface of the molten aluminum and is skimmed off.
The crucible smelting/refining process is used to melt small
batches of aluminum scrap, generally limited to 500 kg (1000 Ib) or
less. The metal treating process steps are essentially the same as
those of reverberatory furnaces.
The induction smelting/refining process is designed to produce
hardeners by blending pure aluminum and hardening agents in an
electric induction furnace. The process steps include charging
scrap to the furnace, melting, adding and blending the hardening
agent, skimming, pouring and casting into notched bars.
7.8-4 EMISSION FACTORS 4/81
-------
7.8.2 Emissions and Controls
Table 7.8-1 presents emission factors for the principal
emission sources in secondary aluminum operations. Although each
step in scrap treatment and smelting/refining is a potential source
of emissions, emissions from most of the processing operations are
either not characterized here or emit only small amounts of
pollutants.
Crushing /screening produces small amounts of metallic and
nonmetallic dust. Baling operations produce particulate emissions,
primarily dirt and alumina dust resulting from aluminum oxidation.
Shredding/classifying also emits small amounts of dust. Emissions
from these processing steps are normally uncontrolled.
Burning/drying operations emit a wide range of pollutants.
Afterburners are used generally to convert unburned hydrocarbons to
C02 and 1^0 . Other gases potentially present, depending on the
composition of the organic contaminants, include chlorides, fluo-
rides and sulfur oxides. Oxidized aluminum fines blown out of the
dryer by the combustion gases comprise particulate emissions. Wet
scrubbers are sometimes used in place of afterburners.
Mechanically generated dust from the rotating barrel dross
furnace constitutes the main air emission of hot dross processing.
Some fumes are produced from the fluxing reactions. Fugitive emis-
sions are controlled by enclosing the barrel in a hood system and
by ducting the stream to a baghouse. Furnace off gas emissions,
mainly fluxing salt fume, are controlled by a venturi scrubber.
In dry milling, large amounts of dust are generated from the
crushing, milling, screening, air classification and materials
transfer steps. Leaching operations may produce particulate emis-
sions during drying. Emissions from roasting are particulates from
the charring of carbonaceous materials.
Emissions from sweating furnaces vary with the feed scrap
composition. Smoke may result from incomplete combustion of organic
contaminants (e.g., rubber, oil and grease, plastics, paint, card-
board, paper) which may be present. Fumes can result from oxidation
of magnesium and zinc contaminants and from fluxes in recovered
drosses and skims.
Atmospheric emissions from reverberatory (chlorine) smelting/
refining represent a significant fraction of the total particulate
and gaseous effluents generated in the secondary aluminum industry.
Typical furnace effluent gases contain combustion products, chlorine,
hydrogen chloride and metal chlorides of zinc, magnesium and aluminum,
aluminum oxide and various metals and metal compounds , depending on
the quality of scrap charged. Particulate emissions from one
secondary aluminum smelter have a size distribution of D^Q = 0.4M-.
4/81 Metallurgical Industry 7.8-5
-------
1
TABLE 7.8-1. PARTICULATE EMISSION FACTORS FOR SECONDARY
ALUMINUM OPERATIONS3
Electrostatic Emission
Uncontrolled
Operation
Sweating furnace
Smelting
Crucible furnace
Reverberatory furnace
Chlorination station
kg/Mg
7.25
0.95
C 2.15
500
Ib/ton
14.5
1.9
4.3
1000
Baghouse precipltator Factor
kg/Mg Ib/ton kg/Mg
1.65 3.3
_
0.65e 1.3e 0.65
25 50
Ib/ton Rating
" C
C
1.3 B
B
Reference 2. Emission factors expressed as units per unit weight of metal
.processed. Factors apply only to Al metal recovery operations.
Based on averages of two source tests.
Based on averages of ten source tests. Standard deviation of uncontrolled
emission factor is 17.5 kg/Mg (3.5 Ib/ton), that of controlled factor is 0.15 kg/Mg
d(0.3 Ib/ton).
Expressed as kg/Mg (Ib/ton) of chlorine used. Based on averages of ten source tests.
Standard deviation of uncontrolled emission factor is 215 kg/Mg (430 Ib/ton), of
controlled factor, 18 kg/Mg (36 Ib/ton),
This factor may be lower if a coated baghouse Is used.
Emissions from reverberatory (fluorine) smelting/refining are
similar to those from reverberatory (chlorine) smelting/refining.
The use of AlF^ rather than chlorine in the demagging step reduces
demagging emissions. Fluorides are emitted as gaseous fluorides
(hydrogen fluoride, aluminum and magnesium fluoride vapors, and
silicon tetrafluoride) or as dusts. Venturi scrubbers are usually
used for fluoride emission control.
References for Section 7.8
1. W.M. Coltharp, et al., Multimedia Environmental Assessment of
the Secondary Nonferrous Metal Industry, Draft Final Report,
2 vols., EPA Contract No. 68-02-1319, Radian Corporation,
Austin, TX, June 1976.
2. W.F. Hammond and S.M. Weiss, Unpublished report on air
contaminant emissions from metallurgical operations in Los
Angeles County, Los Angeles County Air Pollution Control
District, July 1964.
3. R.A, Baker, et al., Evaluation of a Coated Baghouse at a
Secondary Aluminum Smelter, EPA Contract No. 68-02-1402,
Environmental Science and Engineering, Inc., Gainesville, FL,
October 1976.
4. Air Pollution Engineering Manual, 2d Edition, AP-40, U.S.
Environmental Protection Agency, Research Triangle Park, NC,
May 1973. Out of Print.
7.8-6 EMISSION FACTORS 4/81
-------
5. E.J. Petkus, "Precoated Baghouse Control for Secondary Aluminum
Smelting", Presented at the 71st Annual Meeting of the Air
Pollution Control Association, Houston, TX, June 1978.
4/81 Metallurgical Industry 7.8-7
-------
-------
7.9 SECONDARY COPPER SMELTING AND ALLOYING
7.9.1 Process Description1'2
The secondary copper industry processes scrap metals for the recovery of copper. Products include
refined copper or copper alloys in forms such as ingots, wirebar, anodes, and shot. Copper alloys are combinations
of copper with other materials, notably, tin, zinc, and lead. Also, for special applications, combinations include
such metals as cobalt, manganese, iron, nickel, cadmium, and beryllium and nonmetals such as arsenic and
silicon.
The principal processess involved in copper recovery are scrap metal pretreatment and smelting.
Pretreatment includes cleaning and concentration to prepare the material for the smelting furnace. Smelting
involves heating and treating the scrap to achieve separation and purification of specific metals.
The feed material used in the recovery process can be any metallic scrap containing a useful amount of
copper, bronze (copper and tin), or brass (copper and zinc). Traditional forms are punchings, turnings and
borings, defective or surplus goods, metallurgical residues such as slags, skimmings, and drosses, and obsolete,
worn out, or damaged articles including automobile radiators, pipe, wire, bushings, and bearings.
The type and quality of the feed material determines the processes the smelter will use. Due to the large
variety of possible feed materials available, the method of operation varies greatly between plants. Generally, a
secondary copper facility deals with less pure raw materials and produces a more refined product, whereas brass
and bronze alloy processors take cleaner scrap and do less purification and refining. Figure 7.9-1 is a flowsheet
depicting the major processes that can be expected in a secondary copper smelting operation. A brass and bronze
alloying operation is shown in Figure 7.9-2.
Pretreatment of the feed material can be accomplished using several different procedures, either
separately or in combination. Feed scrap is concentrated by manual and mechanical methods such as sorting,
stripping, shredding, and magnetic separation. Feed scrap is sometimes briquetted in a hydraulic press.
Pyrometallurgical pretreatment may include sweating, burning of insulation (especially from wire scrap), and
drying (burning off oil and volatiles) in rotary kilns, Hydrometallurgical methods include flotation and leaching,
with chemical recovery.
In smelting, low-grade scrap is melted in a cupola furnace, producing "black copper" (70 to 80 percent Cu)
and slag; these are often separated in a reverberatory furnace, from which the melt is transferred to a converter or
electric furnace to produce "blister" copper, which is 90 to 99 percent Cu.
Blister copper may be poured to produce shot or castings, but is often further refined electrolytically or by
fire refining. The fire-refining process is essentially the same as that described for the primary copper smelting
industry (Section 7.3.1). The sequence of events in fire-refining is (1) charging, (2) melting in an oxidizing
atmosphere, (3) skimming the slag, (4) blowing with air or oxygen, (5) adding fluxes, (6) "poling" or otherwise
providing a reducing atmosphere, (7) reskimming, and (8) pouring.
To produce bronze or brass rather than copper, an alloying operation is required. Clean, selected bronze
and brass scrap is charged to a melting furnace with alloys to bring the resulting mixture to the desired final
composition. Fluxes are added to remove impurities and to protect the melt against oxidation by air. Air or oxygen
may be blown through the melt to adjust the composition by oxidizing excess zinc.
With zinc-rich feed such as brass, the zinc oxide concentration in the exhaust gas is sometimes high
enough to make recovery for its metal value desirable. This process is accomplished by vaporizing the zinc from
the melt at high temperature and capturing the oxide downstream in a process baghouse.
12/77 Metallurgical Industry 7.9-1
-------
I
ENTERING THE SYSTEM
LOW-GRADE SCRAP
(SLAGS, SKIMMINGS,
DROSSES, CHIPS,
BORINGS)
AIR
PYROMETALLURGICAL
PRETREATMENT
(DRYING)
LEAVING THE SYSTEM
GASES, DUST, METAL OXIDES
•*" TO CONTROL EQUIPMENT
TREATED
SCRAP
t
CUPOLA
BLACK 1
COPPER T
CARBON MONOXIDE. PARTICULATE DUST
»- METAL OXIDES, TO AFTERBURNER AND
PARTICULATE CONTROL
FLUX-
FUEL-
AIR —
SLAG
SMELTING FURNACE
(REVERBERATORY)
GASES AND METAL OXIDES
TO CONTROL EQUIPMENT
SEPARATED
COPPER
SLAG
FLUX-
FUEL-
AIR—
CONVERTER
BLISTER
COPPER
AIR.
FUEL-
REDUCING MEDIUM,
(POLING)
GASES AND METAL OXIDES
TO CONTROL EQUIPMENT
BLISTER
COPPER
CASTINGS AND SHOT
PRODUCTION
FUGITIVE METAL OXIDES FROM
. POURING TO EITHER HOODING
OR PLANT ENVIRONMENT
SLAG
FIRE REFINING
GASES, METAL DUST,
'TO CONTROL DEVICE
7.9-2
REFINED
COPPER
7.9-1. Low-grade copper recovery.
EMISSION FACTORS
12/77
-------
ENTERING THE SYSTEM
LEAVING THE SYSTEM
HIGH-GRADE SCRAP
(WIRE, PIPE, BEARINGS,
PUNCHINGS, RADIATORS)
MANUAL AND MECHANICAL
PRETREATMENT
(SORTING)
->- FUGITIVE DUST TO ATMOSPHERE
-*-UNDESIRED SCRAP TO SALE
DESIRED
COPPER SCRAP
DESIRED BRASS
AND BRONZE SCRAP
FUEL-
AIR -
r
SWEATING
>-LEAD,
GASES, METAL OXIDES TO
CONTROL EQUIPMENT
LEAD, SOLDER, BABBITT METAL
T
BRASS AND
BRONZE
WIRE BURNER
COPPER
FLUX
FUEL
ALLOY MATERIAL
(ZINC, TIN, ETC)
-PARTICULATES, HYDROCARBONS,
ALDEHYDES, FLUORIDES, AND
CHLORIDES TO AFTERBURNER
AND PARTICULATE CONTROL
MELTING AND
ALLOYING FURNACE
—»-METAL OX IDES TO
CONTROL EQUIPMENT
-*-SLAG TO DISPOSAL
ALLOY
MATERIAL
CASTING
-FUGITIVE METAL OXIDES GENERATED
DURING POURING TO EITHER PLANT
ENVIRONMENT OR HOODING
12/77
7.9-2. High-grade brass and bronze alloying.
Metallurgical Industry
7.9-3
-------
The final step is always casting of the suitably alloyed or refined metal into a desired form, i.e, shot, wirebar,
anodes, cathodes, ingots, or other cast shapes. The metal from the melt is usually poured into a ladle or a small
pot, which serves the functions of a surge hopper and a flow regulator, then into a mold.
7.9.2 Emissions and Controls
The principal pollutants emitted from secondary copper smelting activities are particulate matter in
various forms. Removal of insulation from wire by burning causes particulate emissions of metal oxides and
unburned insulation. Drying of chips and borings to remove excess oils and cutting fluids can cause discharges of
large amounts of dense smoke consisting of soot and unburned hydrocarbons. Particulate emissions from the top
of a cupola furnace consist of metal oxide fumes, dirt, and dust from limestone and coke.
The smelting process utilizes large volumes of air to oxidize sulfides, zinc, and other undesirable consti-
tuents of the feed. This procedure generates much particulate matter in the exit gas stream. The wide variation
among furnace types, charge types, quality, extent of pretreatment, and size of charge is reflected in a broad spec-
trum of particle sizes and variable grain loadings in the escaping gases. One major factor contributing to differ-
ences in emission rates is the amount of zinc present in scrap feed materials; the low-boiling zinc evaporates and
combines with air oxygen to give copious fumes of zinc oxide.
Metal oxide fumes from furnaces used in secondary smelters have been controlled by baghouses,
electrostatic precipitators, or wet scrubbers. Efficiency of control by baghouses may be better than 99 percent,
but cooling systems are needed to prevent the hot exhaust gases from damaging or destroying the bag filters. A
two-stage system employing both water jacketing and radiant cooling is common. Electrostatic precipitators are
not as well suited to this application, having a low collection efficiency for dense particulates such as oxides of
lead and zinc. Wet scrubber installations are also relatively ineffective in the secondary copper industry.
Scrubbers are useful mainly for particles larger than 1 micron, (jum) but the metal oxide fumes generated are
generally submicron in size.
Particulate emissions associated with drying kilns can be similarly controlled. Drying temperatures up to
15CPC (300° F) produce relatively cool exhaust gases, requiring no precooling for control by baghouses.
Wire burning generates much particulate matter, largely unburned combustibles. These emissions can be
effectively controlled by direct-flame afterburners, with an efficiency of 90 percent or better if the afterburner
combustion temperature is maintained above 1000° C (1800° F). If the insulation contains chlorinated organics
such as polyvinyl chloride, hydrogen chloride gas will be generated and will not be controlled by the afterburner.
One source of fugitive emissions in secondary smelter operations is charging of scrap into furnaces
containing molten metals. This often occurs when the scrap being processed is not sufficiently compact to allow a
full charge to fit into the furnace prior to heating. The introduction of additional material onto the liquid metal
surface produces significant amounts of volatile and combustible materials and smoke, which can escape through
the charging door. Briquetting the charge offers a possible means of avoiding the necessity of such fractional
charges. When fractional charging cannot be eliminated, fugitive emissions are reduced by turning off the
furnace burners during charging. This reduces the flow of exhaust gases and enhances the ability of the exhaust
control system to handle the emissions.
Metal oxide fumes are generated not only during melting, but also during pouring of the molten metal into
the molds. Other dusts may be generated by the charcoal, or other lining, used in association with the mold.
Covering the metal surface with ground charcoal is a method used to make "smooth-top" ingots. This process
creates a shower or sparks, releasing emissions into the plant environment at the vicinity of the furnace top and
the molds being filled.
Emission factor averages and ranges for six different types of furnaces are presented in Table 7.9-1.
7.9-4 EMISSION FACTORS 12/77
-------
TABLE 7.9-1.
PARTICULATE EMISSION FACTORS FOR FURNACES USED IN SECONDARY
COPPER SMELTING AND ALLOYING PROCESSESa'b
EMISSION FACTOR RATING: B
Particulate Lead11
Control kg/Ms Ib/ton kg/Mg Ib/ton
Furnace and charge type .equipment average
range average range
Cupola
Scrap Iron
Insulated copper wire
Scrap copper and brass
Reverberatory
High lead alloy (58%
Lead
Red/yellow brass (15%
Lead
Other alloys (7% lead)
Copper
Brass and bronze
Rotary
Brass and bronze
Crucible and pot
Brass and bronze
Electric Arc
Copper
Brass and bronze
Electric induction
Copper
Brass and bronze
None
None
ESPC
None
ESP
None
None
None
None
Baghouse
None
•Baghouse
None
ESP
None
ESP
None
Baghouse
None
Baghouse
None
Baghouse
None
Baghouse
0.002
120
V5
3-5
•i.2
30-40
1-1.4
0.003
230
10
70
2.4
60-80
2-2.a
25
6.6
2.5
2.6
0.2
18
•1.3
150
7
11
0.5
2.5
0.5
5.5
3
3.5
0.25
10
0.35
0.4-15
0.1-0.3
0.3-35
0.3-2.5
50-250
3-10
1-20
3-10
1-4
0.02-1
2-9
0.3-20
0.01-0.65
5.1
0.4
36
2.6
300
13
21
1
5
1
11
6
0.5
20
0.7
0.8-30
0.3-0.6
0.6-70
0.6-5
100-500
6-19
2-40
6-19
2-8
0.04-2
4,-18
0.5-40
0.01-1.3
50
13.2
5.0
aFactors for high lead alloy (58 percent lead), red and yellow brass (15 percent lead), and other
alloys (7 percent lead) produced in the reverberatory furnace are based on unit weight produced.
All other factors given in terms of raw materials charged to unit. Dash indicates no available
information.
^The information for particulate in Table 7.9-1 was based on unpublished data furnished by the
following:
Philadelphia Air Management Services, Philadelphia, PA.
New Jersey Department of Environmental Protection, Trenton, NJ.
New Jersey Department of Environmental Protection, Metro Field Office, Springfield, NJ.
New Jersey Department of Environmental Protection, Newark Field Office, Newark, NJ.
New York State Department of Environmental Conservation, New York, NY.
The City of New York Department of Air Resources, New York, NY.
Cook County Department of Environmental Control, Maywood, IL.
Wayne County Department of Health, Air Pollution Control Division, Detroit, MI.
City of Cleveland Department of Public Health and Welfare, Division of Air Pollution
Control, Cleveland, OH.
State of Ohio Environmental Protection Agency, Columbus, OH.
City of Chicago Department of Environmental Control, Chicago, IL.
South Coast Air Quality Management District, Los Angeles, CA.
CESP equals electrostatic precipitator.
References 1, 5-6.
10/80
Metallurgical Industry
7.9-5
-------
1
References for Section 7.9
I. Air Pollution Aspects of Brass and Bronze Smelting and Refining Industry,
U.S. Department of Health, Education and Welfare, National Air Pollution
Control Administration, Raleigh, NC, Publication No. AP-58, November 1969.
2. J. A. Danielson (ed.), Air Pollution Engineering Manual (2nd Ed.), AP-40,
U.S. Environmental Protection Agency, Research Triangle Park, NC, 1973.
Out of Print.
3. Emission Factors and Emission Source Information for Primary and Secondary
Copper Smelters, U.S. Environmental Protection Agency, Research Triangle
Park, NC, Publication No. EPA-450/3-77-051, December 1977.
4. Control Techniques for Lead Air Emissions, EPA-450-2/77-012, U.S. Environ-
mental Protection Agency, Research Triangle Park, NC, December 1977.
5. H. H. Fukubayashi, et al., Recovery of Zinc and Lead from Brass Smelter
Dust, Report of Investigation No. 7880, Bureau of Mines, U.S. Department
of the Interior, Washington, DC, 1974.
6. "Air Pollution Control in the Secondary Metal Industry", Presented at the
First Annual National Association of Secondary Materials Industries Air
Pollution Control Workshop, Pittsburgh, PA, June 1967.
7.9-6
EMISSION FACTORS
12/81
-------
7.10 GRAY IRON FOUNDRIES
7.10.1 General
Gray iron foundries produce gray iron castings by melting,
alloying and molding pig iron and scrap iron. The process flow
diagram of a typical gray iron foundry is presented in Figure 7.10-1.
The four major processing operations of the typical gray iron
foundry are raw materials handling, metal melting, mold and core
production, and casting and finishing.
Raw Materials Handling - The raw material handling operations
include the receiving, unloading, storage and conveying of all raw
materials for the foundry. The raw materials used by gray iron
foundries are pig iron, iron and steel scrap, foundry returns,
metal turnings, alloys, carbon additives, coke, fluxes (limestone,
soda ash, fluorspar, calcium carbide), sand, sand additives, and
binders. These raw materials are received in ships, railcars,
trucks and containers, transferred by truck, loaders and conveyers
to both open piles and enclosed storage areas, and then transferred
by similar means from storage to the processes.
Metal Melting - Generally the first step in the metal melting
operations is scrap preparation. Since scrap is normally purchased
in the proper size for furnace feed, scrap preparation primarily
consists of scrap degreasing. This is very important for electric
induction furnaces, as organics on scrap can cause an explosion.
Scrap may be degreased with solvents, by centrifugation or by
combustion in an incinerator or heater, or it may be charged with-
out treatment, as is often the case with cupola furnaces. After
preparation, the scrap, iron, alloy and flux are weighed and charged
to the furnace.
The cupola furnace is the major type of furnace used in the
gray iron industry today. It is typically a vertical refractory
lined cylindrical steel shell, charged at the top with alternate
layers of metal, coke and flux. larger cupolas are water cooled
instead of refractory lined. Air introduced at the bottom of the
cupola burns the coke to melt the metal charge. Typical melting
capacities range from 0.5 to 14 Mg (1 - 27 tons) per hour, with a
few larger units approaching 50 Mg (100 tons) per hour. Cupolas
can be tapped either continuously or intermittently from a side
tap hole at the bottom of the furnace.
Electric arc furnaces, used to a lesser degree in the gray
iron industry, are large refractory lined steel pots fitted with a
refractory lined roof through which three graphite electrodes are
inserted. The metal charge is heated to melting by electrical arcs
produced by the current flowing between the electrodes and the
charge. Electric arc furnaces are charged with raw material through
the removed lid, by a chute through the lid, or through a door in
4/81
Metallurgical Industry
7.10-1
-------
RAW MATERIALS
UNLOADING, STORAGE,
TRANSFER
• FLUX
• METALLICS
• CARBON SOURCES
• SAND
• BINDER
FUGITIVE
DUST
A
r—^HYDROCARBONS
J AND SMOKE
SCRAP
PREPARATION
SAND
1 FUMESAND-*-
FUGITIVE
-FURNANCE
VENT
FUGITIVE
DUST
A
i
MIXING
*" PREPARATION
Ir
MOLD
MAKING
DUST
•*-FUGITIVE
DUST
FURNANCE
•CUPOLA
• ELECTRIC ARC
• INDUCTION
•OTHER
i
TAPPING,
TREATING
-*- FUGITIVE FUMES
AND DUST
tj— --^FUGITIVE FUMES
i AND DUST
SAND
MOLD POURING,
COOLING
i
CASTING
SHAKEOUT
DUST
• SAND
• BINDER
1
i
CORE MAKING
,
f r
CORE BAKING
---^-FUGITIVE
DUST
-OVEN VENT
COOLING
FUMES AND
FUGITIVE
DUST
CLEANING,
FINISHING
•FUGITIVE
DUST
SHIPPING
Figure 7.10-1. Typical flow diagram of a grey iron foundry.
7.10-2
HUSSION FACTORS
4/81
-------
the side. The molten metal is tapped by tilting and pouring through
a hole in the side. Melting capacities range up to 10 Mg (20 tons)
per hour.
A third furnace type used in the gray iron industry is the
electric induction furnace. Induction furnaces are vertical refrac-
tory lined cylinders surrounded by electrical coils energized with
alternating current. The resulting fluctuating magnetic field
heats the metal. Induction furnaces are kept closed except when
charging, skimming and tapping. The molten metal is tapped by
tilting and pouring through a hole in the side. Induction furnaces
are also used with other furnaces to hold and superheat the charge
after melting and refining in another furnace.
A small percentage of melting in the gray iron industry is
also done in air furnaces, reverberatory furnaces, pot furnaces and
indirect arc furnaces.
The basic melting process operations are 1) furnace charging,
in which the metal, scrap, alloys, carbon and flux are added to the
furnace, 2) melting, during which the furnace remains closed,
3) backcharging, which involves the addition of more metal and,
possibly, alloys, 4) refining and treating, during which the chemis-
try is adjusted, 5) slag removing, and 6) tapping molten metal into
a ladle or directly into molds.
Mold and Core Production - Cores are molded sand shapes used to
make the internal voids in castings, and molds are forms used to
shape the exterior of castings. Cores are made by mixing sand with
organic binders, molding the sand into a core, and baking the core
in an oven. Molds are prepared by using a mixture of wet sand,
clay and organic additives to make the mold shapes, and then by
drying with hot air. Increasingly, cold setting binders are being
used in both core and mold production. Used sand from shakeout
operations is recycled to the sand preparation area to be cleaned,
screened and reused to make molds.
Casting and Finishing - When the melting process is complete, the
molten metal is tapped and poured into a ladle. At this point, the
molten metal may be treated by addition of magnesium to produce
ductile iron by the addition of soda ash or lime to remove sulfur.
At times, graphite may be innoculated to adjust carbon levels. The
treated molten metal is then poured into molds and allowed partially
to cool. The partially cooled castings are placed on a vibrating
grid where the mold and core sand is shaken away from the casting.
The sand is returned to the mold manufacturing process, and the
castings are allowed to cool further in a cooling tunnel.
In the cleaning and finishing process, burrs, risers and gates
are broken off or ground off to match the contours of the castings,
after which the castings are shot blasted to remove remaining mold
sand and scale.
4/81 Metallurgical Industry 7.10-3
-------
TABLE 7.10-1. EMISSION FACTORS FOR GRAY IRON FURNACES
EMISSION FACTOR RATING: B
a
o
Partlculates Carbon Monoxide Sulfur Dioxide Nitrogen Oxides VOC Lead
S
cn
M
0
13
52
o
H
0
cn
Furnace Type
Cupola '
Uncontrolled
Wet cap
Impingement scrubber
High energy scrubber
kg/Mg
8.5
o-me
4
2.5
0.4
Electrostatic preclpitator 0.3
Bag filter
Electric Arch
Electric Induction
Reverberatory
.Expressed as weight of
0.1
5 „
(3-10)6
0.75
1
pollutant per
lb/ ton kg/Mg lb/ ton kg/Mg lb/ ton kg/Mg lb/ ton kg/Mg lb/ ton kg/Mg lb/ ton
17 H5f 73f 0.6S8 1.25S8 - - 0.05-0.6 0.1-1.1
(5-34 )e
8 - - - _____ _ _
5--_ _____ __
0.8 - - 0.3Sg 0.6S8 - -
0.6--- _____ __
0.2--- _____ __
10 0.5-19 1-37 neg neg .02-. 3 .04-. 6 .03-. 15 .06-. 3
(5-20)6
1.5 neg neg neg neg - - .005-. 05 .009-0.1
2-------- .006-. 07 .012-0.14
weight of gray Iron produced. Neg = negligible.
^References 2-5.
Approximately 85% of the total charge Is metal. For every unit weight of coke in the charge, 7 units of gray iron are produced.
-Values in parentheses represent the range of expected values.
Reference 6.
^Reference 1. S represents % sulfur In the coke. This factor assumes 30% of the sulfur Is converted to SO .
References 1 and 8.
00
-------
TABLE 7.10-2. MISSION FACTORS FOR FUGITIVE PARTICIPATES FROM GRAY IRON FOUNDRIES*
EMISSION FACTOR RATING: D
*-
00
s
E
^
n
OQ
h*
O
IB
H1
51
en
f_L
1 '
1 L
0
Ui
Emissions
Process kg/Mg Ib/ton
Scrap and Charge Handling, 0.3 0.6
Heatingb
Magnesium Treatment 2,5 5
Innoculation0 1.5-2.5 3-5
Pouringb 2.5 5
Coolingb 5 10
Shakeoutb 16 32
Cleaning, Finishing 8.5 17
Sand Handling, Preparation, 20 40
Mullingb
b
Core Making, Baking 0.6 1.1
.Expressed as weight oE pollutant per weight oE metal melted.
Reference 1, p. Ill- 13.
CReference 7, p. 2-83.
Emitted to
Work Environment
kg/Mg Ib/ton
0.25 0.5
2.5 5
— —
2.5 5
4.5 9
6.5 13
0.15 0.3
13 26
0.6 1.1
Emitted to
Atmosphere
kg/Mg Ib/ton
0.1 0.2
0.5 1
_ _
1 2
0.5 1
0.5 1
0.05 0.1
1.5 3
0.6 1.1
-------
7.10.2 Emissions and Controls
Emissions from the raw materials handling operations consist
of fugitive particulates generated from the receiving, unloading,
storage and conveying of all raw materials for the foundry. These
emissions are controlled by enclosing the major emission points and
routing the air from the enclosures through fabric filters or wet
collectors.
Scrap preparation using heat will emit smoke, organics and
carbon monoxide, and preparation using solvent degreasers will emit
organics. (See Section 4.6, Solvent Degreasing.) Catalytic incinera-
tors and afterburners can be applied to control about 95 percent of
the organics and carbon monoxide.
Emissions from melting furnaces consist of particulates,
carbon monoxide, organics, sulfur dioxide, nitrogen oxides and
small quantities of chlorides and fluorides. The particulates,
chlorides and fluorides are generated by flux, incomplete combustion
of coke, carbon additives, and dirt and scale on the scrap charge.
Organics on the scrap and the reactivity of the coke effect carbon
monoxide emissions. Sulfur dioxide emissions, characteristic of
cupola furnaces, are attributable to sulfur in the coke.
The highest concentration of furnace emissions occurs during
charging, backcharging, alloying, slag removal, and tapping opera-
tions, when the furnace lids and doors are opened. Generally,
these emissions have escaped into the furnace building and have
been vented through roof vents. Controls for emissions during the
melting and refining operations usually concern venting the furnace
gases and fumes directly to a collection and control system.
Controls for fugitive furnace emissions involve the use of roof
hoods or special hoods in the proximity of the furnace doors, and
of tapping ladles to capture emissions and to route them to emission
control systems.
High energy scrubbers and bag filters with respective effi-
ciencies greater than 95 percent and 98 percent are used to control
particulate emissions from cupolas and electric arc furnaces in the
U.S. Afterburners achieving 95 percent control are used for reducing
organics and carbon monoxide emissions from cupolas. Normally,
induction furnaces are uncontrolled.
The major pollutants from mold and core production are particu-
lates from sand reclaiming, sand preparation, sand mixing with
binders and additives, and mold and core forming. There are organics,
CO and particulate emissions from core baking, and organic emissions
from mold drying. Bag filters and high energy scrubbers can be
used to control particulates from mold and core production.
Afterburners and catalytic incinerators can be used to control
organics and carbon monoxide emissions.
7.10-6 EMISSION FACTORS 4/81
-------
TABLE 7.10-3. SIZE DISTRIBUTION FOR PARTICULATE EMISSIONS FROM
THREE ELECTRIC ARC FURNACE INSTALLATIONS51
Particle Size (n)
<1
<2
<5
<10
<15
<20
<50
Foundry A
5
15
28
41
55
68
98
Foundry B
8
54
80
89
93
96
99
Foundry C
18
61
84
91
94
96
99
Reference 1, p. 111-39.
TABLE 7.10-4. SIZE DISTRIBUTION FOR PARTICULATE
EMISSIONS FROM EIGHTEEN CUPOLA FURNACE INSTALLATIONS3
Cumulative % Less
Particle Size ()-i) Than Indicated Size
<2
<5
<10
<20
<50
<100
<200
14
24
34
44
61
78
93
Reference 1, p. 111-33.
4/81 Metallurgical Industry 7.10-7
-------
In the casting operations, large quantities of particulates
can be generated in the treating and innoculation steps before
pouring. Emissions from pouring consist of fumes, carbon monoxide,
organics, and particulates evolved from the mold and core materials
when contacted with molten iron. These emissions continue to
evolve as the mold cools. A significant quantity of particulate
emissions is also generated during the casting shakeout operation.
Particulate emissions from shakeout can be controlled by either
high energy scrubbers or bag filters. Emissions from pouring are
normally uncontrolled or are ducted into other exhaust streams.
Emissions from finishing operations are of large particulates
emitted during the removal of burrs, risers and gates, and during
the blasting process. Particulates from finishing operations are
usually large in size and are easily controlled by cyclones.
Emission factors for melting furnaces are presented in
Table 7.10-1, and emission factors for fugitive particulates are
presented in Table 7.10-2. Typical particle size distributions for
emissions from electric arc and cupola furnaces are presented in
Table 7.10-3 and Table 7.10-4.
References for Section 7.10
1. J.A. Davis, et al., Screening Study on Cupolas and Electric
Furnaces in Gray Iron Foundries, EPA Contract No. 68-01-0611,
Battelle Laboratories, Columbus, OH, August 1975.
2. W.F. Hammond and S.M. Weiss, "Air Contaminant Emissions from
Metallurgical Operations in Los Angeles County", Presented at
Air Pollution Control Institute, Los Angeles, CA, July 1964.
3. H.R. Crabaugh, et al., "Dust and Fumes from Gray Iron Cupolas:
How They Are Controlled in Los Angeles County", Air Repair,
4_(3): 125-130, November 1954.
4. Air Pollution Engineering Manual, Second Edition, AP-40, U.S.
Environmental Protection Agency, Research Triangle Park, NC,
May 1973. Out of Print.
5. J.M. Kane, "Equipment for Cupola Control", American Foundryman's
Society Transactions, £4_:525-531, 1956.
6. Air Pollution Aspects of the Iron Foundry Industry, APTD-0806,
U.S. Environmental Protection Agency, Research Triangle Park,
NC, February 1971.
7. John Zoller, et^ al., Assessment of Fugitive Particulate Emission
Factors for Industrial Processes, EPA-450/3-78-107, U.S.
Environmental Protection Agency, Research Triangle Park, KG,
September 1978.
7.10-8 EMISSION FACTORS 4/81
-------
8. P.P. Fennelly and P.O. Spawn, Air Pollutant Control Technl(][ues
for Electric Arc Furnaces in the Iron and Steel Foundry Industry,
EPA 450/2-78-024, U.S. Environmental Protection Agency, Research
Triangle Park, NC, June 1978.
9. Control Techniques for lead Air Emissions, Volumes 1 and 2,
EPA-450/2-77-012, U.S. Environmental Protection Agency, Research
Triangle Park, NC, December 1977.
10. W.E. Davis, Emissions Study of Industrial Sources of lead Air
1 970 , APTD-1543, U.S. Environmental Protection
_^
Agency, Research Triangle Park, NC, April 1973.
11. Emission Test No. 71-CI-27, Office of Air Quality Planning and
Standards, U.S. Environmental Protection Agency, Research
Triangle Park, NC, February 1972.
12. Emission Test No. 71-CI-30, Office of Air Quality Planning
and Standards, U.S. Environmental Protection Agency, Research
Triangle Park, NC, March 1972.
4/81 Metallurgical Industry 7.10-9
-------
-------
7.11 SECONDARY LEAD PROCESSING
7.11.1 Process Description
The secondary lead industry processes a variety of leadbearing
scrap and residue to produce lead and lead alloy ingots, battery lead
oxide, and lead pigments (Pb30it and PbO). Processing may involve scrap
pretreatment, smelting and refining/casting. Processes typically used
in each operation are shown in Figure 7.11-1.
7.11.1.1 Scrap pretreatment is the partial removal of metal and non-
metal contaminants from leadbearing scrap and residue. Processes used
for scrap pretreatment include battery breaking, crushing and sweating.
Battery breaking is the draining and crushing of batteries followed by
manual screening to separate the lead from nonmetallic materials. This
separated lead scrap is then mixed with other scraps and smelted in
reverberatory or blast furnaces. Oversize pieces of scrap and residues
are usually crushed by jaw crushers. Sweating separates lead from high-
melting metals in direct gas or oil fired rotary or reverberatory
furnaces. Rotary furnaces are typically used to process low lead content
scrap and residue, while reverberatory furnaces are used to process high
lead content scrap. The partially purified lead is periodically tapped
for further processing in smelting furnaces or pot furnaces.
7.11.1.2 Smelting is the production of purified lead by melting and
separating lead from metal and nonmetallic contaminants and by reducing
oxides to elemental lead. Reverberatory smelting furnaces are used to
produce a semisoft lead product that typically contains 3-4 percent
antimony. Blast furnaces produce hard or antimonial lead containing
about 10 percent antimony.
A reverberatory furnace produces semisoft lead from a charge of
lead scrap, metallic battery parts, oxides, drosses and other residues.
The furnace consists of a rectangular shell lined with refractory brick
and fired directly with oil or gas to a temperature of 2300°F (1250°C).
The material to be melted is heated by direct contact with combustion
gases. The furnace can process about 50 tons per day (45 MT/day).
About 47 percent of the charge is typically recovered as lead product
and is periodically tapped into molds or holding pots. Forty-six
percent of the charge is removed as slag and subsequently processed in
blast furnaces. The remaining 7 percent of the furnace charge escapes
as dust or fume.
Blast furnaces produce hard lead from charges containing siliceous
slag from previous runs (typically about 4.5 percent of the charge),
scrap iron (about 4.5 percent), limestone (about 3 percent), coke (about
5.5 percent), and oxides, pot furnace refining drosses, and reverberatory
slag (comprising the remaining 82.5 percent of the charge). The propor-
tions of rerun slags, limestone and coke vary respectively to as high as
8 percent, 10 percent, and 8 percent of the charge. Processing capacity
of the blast furnace ranges from 20 - 80 tons per day (18 - 73 MT/day).
10/80 Metallurgical Industry 7.11-1
-------
Similar to iron cupolas, the furnaces consist of vertical steel cyl-
inders lined with refractory brick. Combustion air at 0.5 - 0.75 psig
is introduced at the bottom of the furnace through tuyeres. Some of the
coke combusts to melt the charge, while the remainder reduces lead
oxides to elemental lead. The furnace exhausts at temperatures of
1200 - 1350°F (650 - 730°C).
As the lead charge melts, limestone and iron float to the top of
the molten bath and form a flux that retards oxidation of the product
lead. The molten lead flows from the furnace into a holding pot at a
nearly continuous rate. The product lead constitutes roughly 70 percent
of the charge. From the holding pot, the lead is usually cast into
large ingots, called pigs or sows.
About 18 percent of the charge is recovered as slag, with about 60
percent of this being a sulfurous slag called matte. Roughly 5 percent
of the charge is retained for reuse, and the remaining 7 percent of the
charge escapes as dust or fume.
7.11.1.3 Refining/casting is the use of kettle type furnaces in remelt-
ing, alloying, refining and oxidizing processes. Materials charged for
remelting are usually lead alloy ingots which require no further process-
ing before casting. The furnaces used for alloying, refining and oxidiz-
ing are usually gas fired, and operating temperatures range from
700 - 900°F (375 - 485°C).
Alloying furnaces simply melt and mix ingots of lead and alloy
material. Antimony, tin, arsenic, copper and nickel are the most common
alloying materials.
Refining furnaces remove copper and antimony to produce soft lead,
and they remove arsenic, copper and nickel to produce hard lead. Sulfur
may be added to the molten lead bath to remove copper. Copper sulfide
skimmed off as dross may subsequently be processed in a blast furnace to
recover residual lead. Aluminum chloride flux may be used to remove
copper, antimony and nickel. The antimony content can be reduced to
about 0.02 percent by bubbling air through the molten lead. Residual
antimony can be removed by adding sodium nitrate and sodium hydroxide to
the bath and skimming off the resulting dross. Dry dressing consists of
adding sawdust to the agitated mass of molten metal. The sawdust
supplies carbon to help separate globules of lead suspended in the dross
and to reduce some of the lead oxide to elemental lead.
Oxidizing furnaces are either kettle or reverberatory furnaces
which oxidize lead and entrain the product lead oxides in the combustion
air stream. The product is subsequently recovered in baghouses at high
efficiency.
7.H-2 EMISSION FACTORS 10/80
-------
7.11.2 Emissions and Controls
1,4,5
Emission factors for uncontrolled processes and fugitive partic-
ulate emissions are in Tables 7.11-1 and 7.11-2, respectively.
Reverberatory and blast furnaces account for about 88 percent of
the total lead emissions from the secondary lead industry. Most of the
remaining processes are small emission sources with undefined emission
characteristics.
Emissions from battery breaking mainly consist of sulfuric acid
mist and dusts containing dirt, battery case material and lead com-
pounds. Emissions from crushing are also mainly dusts.
Emissions from sweating operations consist of fume, dust, soot
particulates and combustion products, including sulfur dioxide. The
sulfur dioxide emissions are from the combustion of sulfur compounds in
the scrap and fuel. Dusts range in size from 5-20 ym, while unagglom-
erated lead fumes range in size from 0.07 - 0.4 ym, with an average
diameter of 0.3 ym. Particulate loadings in the stack gas from rever-
beratory sweating range from 1.4 - 4.5 grains per cubic foot (3.2 - 10.3
g/m^). Baghouses usually control sweating emissions, with removal
efficiencies exceeding 99 percent. The emission factors for lead sweat-
ing in Table 7.11-1 are based on measurements at similar sweating furnaces
in other secondary metals processing industries, and are not based on
measurements at lead sweating furnaces.
Reverberatory smelting furnaces emit particulates and oxides of
sulfur and nitrogen. Particulates consist of oxides, sulfides and
sulfates of lead, antimony, arsenic, copper and tin, as well as unagglom-
erated lead fume. Particulate loadings range from 7-22 grains per
cubic foot (16 - 50 g/m3). Emissions are generally controlled with
settling and cooling chambers followed by a baghouse. Control efficien-
cies generally exceed 99 percent, as shown in Table 7.11-3. Wet scrub-
bers are sometimes used to reduce sulfur dioxide emissions. However,
because of the small particles emitted, scrubbers are not as widely used
as baghouses for particulate control.
Two chemical analyses by electron spectroscopy showed the part-
iculates to consist of 38 - 42 percent lead, 20 - 30 percent tin, and
about 1 percent zinc.16 Typically, particulates from reverberatory
smelting furnaces comprise about 20 percent lead.
Emissions from blast furnaces occur at charging doors, the slag
tap, the lead well, and the furnace stack. The emissions are combustion
gases (including carbon monoxide, hydrocarbons, and oxides of sulfur and
nitrogen) and particulates. Emissions from the charging doors and the
slag tap are hooded and routed to the devices treating the furnace stack
emissions. Reverberatory furnace particulates are larger than those
emitted from blast furnaces and are thus suitable for control by scrubbers
10/80
Metallurgical Industry
7.11-3
-------
PRETREATMEMT
SMELTING
REFINING/CASTING
H1
H
H
tn
w
H
i
g
H
§
H1
O
CO
O
_^/ SEMISOFT \
^ LEAD J
BATTERIES
DROSSES, RESIDUES,
OVERSIZE SCRAP
RESIDUES, DIE SCRAP
LEAD-SHEATHED
CABLE AND WIRE
HIGH LEAD SCRAP
OXIDES, FLUE DUSTS
MIXED SCRAP
PURE SCRAP
COLLECTED
PARTICULATE1-*
MATTER
REVERBERATORY
SMELTING
BATTERY
BREAKING
KETTLE(SOFTENING)
REFINING
SOFT LEAD
INGOTS
ALLOYING
FLUX AGENT
FUEL
KETTLE(ALLOYING)
REFINING
PRETREATED
SCRAP
BLAST(CUPOLA)
FURNACE SMELTING
ROTARY/TUBE
SWEATING
KETTLE
OXIDATION
REVERBERATORY
SWEATING
(Pb ANDPbO)
REVERBERATOHY
OXIDATION
RED
LEAD OXIDE
Figure 7.11-1, Flow scheme of secondary lead processing.
-------
Table 7.11-2. FUGITIVE EMISSION FACTORS FOR SECONDARY LEAD PROCESSING
EMISSION FACTOR RATING: E
Particulates
Source
Sweating
Smelting
Kettle
Refining
Casting
Ib/ton
1.6 - 3.5
2.8 - 15.7
0.04
0.88
kg/MT
0.8 - 1.8
1.4 - 7.9
0.02
0.44
Ib/ton
0.4 - 1.
0.6 - 3.
0.01
0.2
Lead
kg/MT
8 0.2 - 0.4
6 0.3 - 1.8
0.005
0.1
ci
Based on an engineering estimate that fugitive emissions equal
of the uncontrolled stack emissions. All factors except that for
casting are based on the amount of charge to the process. The casting
factor is based on the amount of lead cast. Reference 14.
Factors are based on an approximation that particulate emissions
^contain 23% lead. References 3 and 5.
'Factors based on limited tests of a roof monitor over casting operations
at a primary smelter.
10/80
Metallurgical Industry
7.11-5
-------
or fabric filters downstream of coolers. Efficiencies for various
control devices are shown in Table 7.11-3. In one application, fabric
filters alone captured over 99 percent of the blast furnace particulate
emissions.
Table 7.11-3. EFFICIENCIES OF PARTICULATE CONTROL EQUIPMENT
ASSOCIATED WITH SECONDARY LEAD SMELTING FURNACES
Control device
a
Fabric filter
Dry cyclone plus fabric filter
Wet cyclone plus fabric filter
Settling chamber plus dry
cyclone plus fabric filter
Venturi scrubber plus demister
Furnace Particulate control
type efficiency, %
Blast
Reverberatory
Blast
Reverberatory
Reverberatory
Blast
98.4
99.2
99.0
99.7
99.8
99.3
Reference 8.
Reference 9.
c
, Reference 10.
Reference 12.
The size distribution for blast furnace particulates recovered by
an efficient fabric filter is reported in Table 7.11-4. Particulates
recovered from another blast furnace contained about 80 - 85 percent
lead sulfate and lead chloride, 4 percent tin, 1 percent cadmium, 1
percent zinc, 0.5 percent each antimony and arsenic, and less than 1
percent organic matter.17
Kettle furnaces for melting, refining and alloying are relatively
minor emission sources. The kettles are hooded, with fumes and dusts
typically vented to baghouses and recovered with efficiencies exceeding
99 percent. Twenty measurements of the uncontrolled particulates from
kettle furnaces showed a mass median aerodynamic particle diameter of
18.9 ym, with particle size ranging from 0.05 - 150 ym. Three chemical
analyses by electron spectroscopy showed the composition of particulates
to vary from 12 - 17 percent lead, 5-17 percent tin, and 0.9 - 5.7
percent zinc.16
Emissions from oxidizing furnaces are economically recovered with
baghouses. The particulates are mostly lead oxide, but they also
contain amounts of lead and other metals. The oxides range in size from
0.2 - 0.5 ym. Controlled emissions have been reported to be as low as
0.2 - 2.8 pounds per ton (0.1 - 1.4 kg/MT).
7.11-6 EMISSION FACTORS 10/80
-------
o
o
Table 7.11-1. EMISSION FACTORS FOR SECONDARY LEAD PROCESSING*1
Particulates
S
(D
rt
fu
| I
e
OP
o
i-1
M
a
c
it
Source
Battery breaking
Crushing
Sweating
Leaching
Smelting
Reverberatory
Blast (cupola)
Kettle refining
Oxidation11
Kettle
Reverberatory
Ib/ton
NA
NA
32-70
Neg
147 (56-313)6
193 (21-381)£
0.8s
<401
NA
kg/MT
NA
NA
16-35
Neg
74 (28-157)6
97 (11-191)£
0.4g
<201
HA
Lead
Ib/ton
NA
NA
7-16C
Neg
34 (13-72)c
44 (5-88)c
0.2C
NA
NA
kg/MT
NA
NA
4-8c
Neg
17 (6-36)c
22 (2-44)c
o.ic
NA
NA
Sulfur Dioxide Emission Factor
Ib/ton
NA
NA
NA
Neg
80 (71-88)e
53 (18-110)£
NA
NA
NA
kg/MT
NA
NA
NA
Neg
40 (36-44)e
27 (9-55)£
NA
NA
NA
Rating
E
B
B
B
E
All emission factors are based on the quantity of material charged to the furnace (except particulate kettle oxidation).
NA = data not available. Neg = negligible.
Reference 1.
Emission factor rating of E. Emission factors for lead emissions are based on an approximation that particulate emissions contain 24%
lead. References 3 and 5.
Numbers in parentheses represent ranges of values obtained.
References 8 - 11.
References 11 - 13.
Reference 11.
References 1 and 2.
Essentially all of the product lead oxide is entrained in an air stream and subsequently recovered by a baghouse with average collection
efficiencies in excess of 99%. The reported value represents emissions of lead oxide that escape a baghotise used to collect the
lead oxide product. The emission factor is based on the amount of lead oxide produced and represents an approximate upper limit for
emissions.
-------
Table 7.11-4. PARTICLE SIZE DISTRIBUTION OF PARTICIPATES
RECOVERED FROM A COMBINED BLAST AND REVERBERATORY
FURNACE GAS STREAM WITH BAGHOUSE CONTROL
a
Particle Size Range, ym
Fabric filter catch, wt
0 to
1 to
2 to
3 to
4 to
1
2
3
4
16
13.
45.
19.
14.
8.
3
2
1
0
4
Reference 4, Table 86.
References for Section 7.11
1. William M. Coltharp, et al., Multimedia Environmental Assessment.
of the Secondary Nonf errjpus_ jfetal_ Indus try (Draft) , 2 Volumes, EPA
Contract No. 68-02-1319, Radian Corporation, Austin, TX, June 1976.
2. H. Nack, et al., Development of an Approach to Identification of
Emerging Technology and Demonstration Opportunities, EPA-650/2-74-
048, U.S. Environmental Protection Agency, Research Triangle Park,
NC, May 1974.
3. J. M. Zoller, et al., A Method of Characterization and Quantifi-
cation of Fugitive Lead Emissions from Secondary Lead Smelters,
Ferroalloy Plants and Gray Iron Foundries^Revised), EPA-450/3-78-
003 (Revised), U.S. Environmental Protection Agency, Research
Triangle Park, NC, August 1978.
4. John A. Danielson, editor, Air Pollution Engineering Manual, Second
Edition, AP-40, U.S. Environmental Protection Agency, Research
Triangle Park, NC, May 1973, pp. 299-304. Out of Print.
5. Control Techniques for Lead Air Emissions. EPA-450/2-77-012, U.S.
Environmental Protection Agency, Research Triangle Park, NC,
January 1978.
6. Background Information for Proposed New Source Performance Standards,
Volume I; Secondary Lead Smelters and Refineries, APTD-1352, U.S.
Environmental Protection Agency, Research Triangle Park, NC, June
1973.
7.11-8
EMISSION FACTORS
10/80
-------
7. J. W. Watson and K. J. Brooks, A Review of Standards of Performance
for New Stationary Sources - Secondary Lead Smelters (Draft), EPA
Contract No. 68-02-2526, The Mitre Corporation, McLean, VA, June
1978.
8. John E. Williamson, et al., A Study of Five Source Tests on Emissions
from Secondary Lead Smelters. EPA Order No. 2PO-68-02-3326, County
of Los Angeles Air Pollution Control District, Los Angeles, CA,
February 1972.
9. Emission Test No. 72-CI-8, Office of Air Quality Planning and
Standards, U.S. Environmental Protection Agency, Research Triangle
Park, NC, July 1972.
10. Emission Test No. 72-CI-7, Office of Air Quality Planning and
Standards, U.S. Environmental Protection Agency, Research Triangle
Park, NC, August 1972.
11. A. E. Vandergrift, et al., Particulate Pollutant Systems Study,
Volume I: Mass Emissions, APTD-0743, U.S. Environmental Protection
Agency, Research Triangle Park, NC, May 1971.
12. Emission Test No. 71-CI-33, Office of Air Quality Planning and
Standards, U.S. Environmental Protection Agency, Research Triangle
Park, NC, August 1972.
13. Emission Test No. 71-CI-34, Office of Air Quality Planning and
Standards, U.S. Environmental Protection Agency, Research Triangle
Park, NC, July 1972.
14. Technical Guidance for Control of Industrial Process Fugitive
Particulate Emissions, EPA-450/3-77-010, U.S. Environmental
Protection Agency, Research Triangle Park, NC, March 1977.
15. Silver Valley/Bunker Hill Smelter Environmental Investigation
(Interim Report), EPA Contract No. 68-02-1343, PEDCo-Environmental
Specialists, Inc., Cincinnati, OH, February 1975.
16. E. I. Hartt, An Evaluation of Continuous Particulate Monitors at a
Secondary Lead Smelter, M.S. Report No. O.R.-16, Environmental
Protection Service, Environment Canada.
17. J. E. Howes, et al., Evaluation of Stationary Source Particulate
Measurement Methods, Volume V: Secondary Lead Smelters, EPA Contract
No. 68-02-0609, Battelle Columbus Laboratories, Columbus, OH,
January 1979.
10/80
Metallurgical Industry
7.11-9
-------
-------
7.12 SECONDARY MAGNESIUM SMELTING
7.12.1 Process Description'
Magnesium smelting is carried out in crucible or pot-type furnaces that are charged with magnesium scrap
and fired by gas, oil, or electric heating. A flux is used to cover the surface of the molten metal because
magnesium will burn in air at the pouring temperature (approximately 1500 F or 815°C). The molten
magnesium, usually cast by pouring into molds, is annealed in ovens utilizing an atmosphere devoid of oxygen.
7.12.2 Emissions'
Emissions from magnesium smelting include particulate magnesium (MgO) from the melting, nitrogen oxides
from the fixation of atmospheric nitrogen by the furnace temperatures, and sulfur dioxide losses from annealing
oven atmospheres. Factors affecting emissions include the capacity of the furnace; the type of flux used on the
molten material: the amount of lancing used; the amount of contamination of the scrap, including oil and other
hydrocarbons; and the type and extent of control equipment used on the process. The emission factors for a pot
furnace are shown in Table 7.12-1.
Table 7.12-1. EMISSION FACTORS
FOR MAGNESIUM SMELTING
EMISSION FACTOR RATING: C
Type of furnace
Pot furnace
Uncontrolled
Controlled
Particulates3
Ib/ton
4
0.4
kg/MT
2
0.2
References 2 and 3. Emission factors
expressed as units per unit weight of
metal processed.
2/72
Metallurgical Industry
7.12-1
-------
References for Section 7.12
1. Air Pollutant Emission Factors. Final Report. Resources Research, Inc. Reston, Va. Prepared for National
Air Pollution Control Administration, Durham, N.C., under Contract Number CPA-22-69-119. April 1970.
2. Allen, G. L. et al. Control of Metallurgical and Mineral Dusts and Fumes in Los Angeles County. Department
of the Interior, Bureau of Mines. Washington, D.C. Information Circular Number 7627. April 1952.
3. Hammond, W. F. Data on Non-Ferrous Metallurgical Operations. Los Angeles County Air Pollution Control
District. November 1966.
7.12-2 EMISSION FACTORS 2/72
-------
7.13 STEEL FOUNDRIES
7.13.1 Process Description
Steel foundries produce steel castings by the melting, alloying
and molding of pig iron and steel scrap. The process flow diagram
of a typical steel foundry is presented in Figure 7.13-1. The
major processing operations of the typical steel foundry are raw
materials handling, metal melting, mold and core production, and
casting and finishing.
Raw Materials Handling - The raw material handling operations
include the receiving, unloading, storage and conveying of all raw
materials for the foundry. Some of the raw materials used by steel
foundries are pig iron, iron and steel scrap, foundry returns,
metal turnings, alloys, carbon additives, fluxes (limestone, soda
ash, fluorspar, calcium carbide), sand, sand additives, and binders.
These raw materials are received in ships, railcars, trucks, and
containers, and are transferred by trucks, loaders, and conveyors
to both open pile and enclosed storage areas. They are then
transferred by similar means from storage to the subsequent processes.
Metal Melting - Generally, the first step in the metal melting
operations is scrap preparation. Since scrap is normally purchased
in the proper size for furnace feed, preparation primarily consists
of scrap degreasing. This is very important for electric induction
furnaces, as organics on scrap can be explosive. Scrap may be
degreased with solvents, by centrifugation or by incinerator or
preheater combustion. After preparation, the scrap, metal, alloy,
and flux are weighed and charged to the furnace.
Electric arc furnaces are used almost exclusively in the steel
foundry for melting and formulating steel. Electric arc furnaces
are large refractory lined steel pots, fitted with a refractory
roof through which three graphite electrodes are inserted. The
metal charge is melted with resistive heating generated by electrical
current flowing among the electrodes and through the charge.
Electric arc furnaces are charged with raw materials by removing
the lid, through a chute opening in the lid, or through a door in
the side. The molten metal is tapped by tilting and pouring
through a hole in the side. Melting capacities range up to
10 megagrams (11 tons) per hour.
A. second, less common, furnace used in steel foundries is the
open hearth furnace, a very large shallow refractory lined vessel
which is operated in a batch manner. The open hearth furnace is
fired at alternate ends, using the heat from the waste combustion
gases to heat the incoming combustion air.
A third furnace used in the steel foundry is the induction
furnace. Induction furnaces are vertical refractory lined cylinders
4/81 Metallurgical Industry 7.13-1
-------
RAW MATERIALS
UNLOADING, STORAGE,
TRANSFER
• FLUX
• METALLICS
• CARBON SOURCES
• SAND
• BINDER
SCRAP
PREPARATION
-HYDROCARBONS
AND SMOKE
i
-FURNANCE
VENT
FURNANCE
• ELECTRIC ARC
• INDUCTION
•OTHER
i •*• FUGITIVE FUMES
AND DUST
TAPPING,
TREATING
.— --^FUGITIVE FUMES
AND DUST
MOLD POURING,
COOLING
SAND
OVEN VENT
CASTING
SHAKEOUT
-^-FUGITIVE
DUST
COOLING
.FUMES AND
FUGITIVE
DUST
CLEANING,
FINISHING
-»-FUGITIVE
DUST
SHIPPING
Figure 7.13-1. Typical flow diagram of a steel foundry.
7.13-2
HUSSION FACTORS
4/81
-------
surrounded by electrical coils energized with alternating current.
The resulting fluctuating magnetic field heats the metal. Induction
furnaces are kept closed except when charging, skimming and tapping.
The molten metal is tapped by tilting and pouring through a hole in
the side. Induction furnaces are also used with other furnaces, to
hold and superheat a charge melted and refined in the other furnaces.
A very small fraction of the secondary steel industry also uses
crucible and pneumatic converter furnaces.
The basic melting process operations are 1) furnace charging,
in which metal, scrap, alloys, carbon, and flux are added to the
furnace, 2) melting, during which the furnace remains closed,
3) backcharging, which is the addition of more metal and possibly
alloys, 4) refining, during which the carbon content is adjusted,
5) oxygen lancing, which is injecting oxygen into the molten steel
to dislodge slag and to adjust the chemistry of the metal, 6) slag
removal, and 7) tapping the molten metal into a ladle or directly
into molds.
Mold and Core Production - Cores are forms used to make the internal
voids in castings, and molds are forms used to shape the casting
exterior. Cores are made of sand with organic binders, molded into
a core and baked in an oven. Molds are made of wet sand with clay
and organic additives, dried with hot air. Increasingly, coal
setting binders are being used in both core and mold production.
Used sand from castings shakeout operations is recycled to the sand
preparation area, where it is cleaned, screened and reused.
Casting and Finishing - When the melting process is complete, the
molten metal is tapped and poured into a ladle. At this time, the
molten metal may be treated by adding alloys and/or other chemicals.
The treated metal is then poured into molds and is allowed partially
to cool under carefully controlled conditions. Molten metal may be
poured directly from the furnace to the mold.
When partially cooled, the castings are placed on a vibrating
grid, and the sand of the mold and core are shaken away from the
casting. The sand is recycled to the mold manufacturing process,
and the casting is allowed to cool further.
In the cleaning and finishing process, burrs, risers and gates
are broken or ground off to match the contour of the casting.
Afterward, the castings are usually shot blasted to remove remaining
mold sand and scale.
7.13.2 Emissions and Controls
Emissions from the raw materials handling operations are
fugitive particulates generated from receiving, unloading, storage
and conveying all raw materials for the foundry. These emissions
are controlled by enclosing the major emission points and routing
the air from the enclosures through fabric filters.
4/81 Metallurgical Industry 7.13-3
-------
Emissions from scrap preparation consist of hydrocarbons if
solvent degreasing is used, and consist of smoke, organics and
carbon monoxide if heating is used. Catalytic incinerators and
afterburners of approximately 95 percent control efficiency for
carbon monoxide and organics can be applied to these sources.
Emissions from melting furnaces are particulates, carbon
monoxide, organics, sulfur dioxide, nitrogen oxides, and small
quantities of chlorides and fluorides. The particulates, chlorides
and fluorides are generated by the flux, the carbon additives, and
dirt and scale on the scrap charge. Organics on the scrap and the
carbon additives effect CO emissions. The highest concentrations
of furnace emissions occur during charging, backcharging, alloying,
oxygen lancing, slag removal, and tapping operations, when the
furnace lids and doors are opened. Characteristically, these
emissions have escaped into the furnace building and have been
vented through roof vents. Controls for emissions during the
melting and refining operations focus on venting the furnace gases
and fumes directly to an emission collection duct and control
system. Controls for fugitive furnace emissions involve either the
use of building roof hoods or of special hoods near the furnace
doors, to collect emissions and route them to emission control
systems. Emission control systems commonly used to control partic-
ulate emissions from electric arc and induction furnaces are bag
filters, cyclones and venturi scrubbers. The capture efficiencies
of the collection systems, presented in Table 7.13-1, range from
80 to 100 percent. Usually, induction furnaces are uncontrolled.
The major pollutants from mold and core production are
particulates from sand reclaiming, sand preparation, sand mixing
with binders and additives, and mold and core forming. There are
volatile organics (VOC), CO and particulate emissions from core
baking, and VOC emissions from mold drying. Bag filters and high
energy scrubbers can be used to control particulates from mold and
core production. Afterburners and catalytic incinerators can be
used to control VOC and CO emissions.
In the casting operations, large quantities of particulates
can be generated in the steps prior to pouring. Emissions from
pouring consist of fumes, CO, VOC, and particulates from the mold
and core materials when contacted by the molten steel. As the mold
cools, emissions continue. A significant quantity of particulate
emissions is also generated during the casting shakeout operation.
The particulate emissions from the shakeout operations can be
controlled by either high efficiency cyclones or bag filters.
Emissions from pouring are usually uncontrolled.
Emissions from finishing operations consist of large particulates
from the removal of burrs, risers and gates, and during shot blasting.
Particulates from finishing operations typically are large and are
generally controlled by cyclones.
7.13-4 EMISSION FACTORS 4/81
-------
TABLE 7.13-1. EMISSION FACTORS FOR STEEL FOUNDRIES
EMISSION FACTOR RATING: A
Particulates
Nitrogen
oxides
Process
Melting
b c
Electric arc '
d e
Open hearth '
Open hearth oxygen lanced '
Electric induction
6
5
5
0
kg/Mg
.5 (2 to
.5 (1 to
(4 to 5'.
.05
Ib/ton
20)
10)
5)
13
11
10
0.
(4 to
(2 to
(8 to
1
40)
20)
11)
kg/Mg Ib/ton
0.1 0.2
0.005 0.01
_
Expressed as units per unit weight of metal processed. If the scrap metal
is very dirty or oily, or if increased oxygen lancing is employed, the
.emission factor should be chosen from the high side of the factor range.
Electrostatic precipitator, 92 - 98% control efficiency; baghouse
(fabric filter), 98 - 99% control efficiency; venturi scrubber, 94 - 98%
control efficiency.
References 2-10.
Electrostatic precipitator, 95 - 98.5% control efficiency; baghouse, 99.9%
control efficiency; venturi scrubber, 96 - 99% control efficiency.
-References 2, 11-13.
Electrostatic precipitator, 95 - 98% control efficiency; baghouse, 99% control
efficiency; venturi scrubber, 95 - 98% control efficiency.
^References 6 and 14.
Usually not controlled.
Emission factors for melting furnaces in the steel foundry are
presented in Table 7.13-1.
Although no emission factors are available for nonfurnace
emission sources in steel foundries, they are very similar to those
in iron foundries.^ Nonfurnace emission factors and particle size
distributions for iron foundry emission sources are presented in
Section 7.10, Gray Iron Foundries.
References for Section 7.13
1. Paul F. Fennelly and Peter D. Spawn, Air Pollutant Control
Techniques for Electric Arc Furnaces in the Iron and Steel
Foundry Industry, EPA-450/2-78-024, U.S. Environmental
Protection Agency, Research Triangle Park, NC, June 1978.
4/81 Metallurgical Industry
7.13-5
-------
2 . J . J . Schueneman , et al. , Air Pollution Aspects of the Iron and
Steel Industry, National Center for Air Pollution Control,
Cincinnati, OH, June 1963.
3. Foundry Air Pollution Control Manual, 2nd Ed., Foundry Air
Pollution Control Committee, Des Plaines, IL, 1967.
4. R.S. Coulter, "Smoke, Dust, Fumes Closely Controlled in Electric
Furnaces", Iron Age, 173: 107-110, January 14, 1954.
5. Air Pollution Aspects of the Iron and Steel Industry, p. 109.
6. J.M. Kane and R.V. Sloan, "Fume Control Electric Melting
Furnaces", American Foundry man, _18^: 33-34, November 1950.
7. Air Pollution Aspects of the Iron and Steel Industry, p. 109.
8. C.A. Faist, "Electric Furnace Steel", Proceedings of the
American Institute of Mining and Metallurgical Engineers,
^1160-161, 1953.
9. Air Pollution Aspects of the Iron and Steel Industry, p. 109.
10. I.H. Douglas, "Direct Fume Extraction and Collection Applied
to a Fifteen Ton Arc Furnace" , Special Report on Fume Arrestment ,
Iron and Steel Institute, 1964, pp. 144, 149.
11. Inventory of Air^ Contaminant Emissions, New York State Air
Pollution Control Board, Table XI, pp. 14-19. Date unknown.
12. A.C. Elliot and A.J. Freniere, "Metallurgical Dust Collection
in Open Hearth and Sinter Plant", Canadian Mining and Metal-
lurgical Bulletin, ^5(606) : 724-732, October 1962.
13. C.L. Hemeon, "Air Pollution Problems of the Steel Industry",
JAPCA, j^(3): 208-218, March I960.
14. D.W. Coy, Unpublished data, Resources Research, Incorporated,
Reston, VA.
7.13-6 EMISSION FACTORS 4/81
-------
7.14 SECONDARY ZINC PROCESSING
1 2
7.14.1 Process Description '
The secondary zinc industry processes obsolete and scrap
materials to recover zinc as slabs, dust and zinc oxide. Pro-
cessing involves three operations, scrap pretreatment, melting and
refining. Processes typically used in each operation are shown in
Figure 7.14-1. Molten product zinc may be used in zinc galvanizing.
Scrap Pretreatment - Pretreatment is the partial removal of metal
and other contaminants from scrap containing zinc. Sweating
separates zinc from high melting metals and contaminants by melting
the zinc in kettle, rotary, reverberatory, muffle or electric
resistance furnaces. The product zinc then is usually directly
used in melting, refining or alloying processes. The high melting
residue is periodically raked from the furnace and further processed
to recover zinc values. These residues may be processed by crushing/
screening to recover impure zinc or by sodium carbonate leaching to
produce zinc oxide.
In crushing/screening, zinc bearing residues are pulverized or
crushed to break the physical bonds between metallic zinc and
contaminants. The impure zinc is then separated in a screening or
pneumatic classification step.
In sodium carbonate leaching, the zinc bearing residues are
converted to zinc oxide, which can be reduced to zinc metal. They
are crushed and washed to leach out zinc from contaminants. The
aqueous stream is then treated with sodium carbonate, precipitating
zinc as the hydroxide or carbonate. The precipitate is then dried
and calcined to convert zinc hydroxide into crude, zinc oxide. The
ZnO product is usually refined to zinc at primary zinc smelters.
Melting - Zinc is melted at 425-590°C (800-1100°F) in kettle,
crucible, reverberatory and electric induction furnaces. Zinc to
be melted may be in the form of ingots, reject castings, flashing
or scrap. Ingots, rejects and heavy scrap are generally melted
first, to provide a molten bath to which light scrap and flashing
are added. Before pouring, a flux is added and the batch agitated
to separate the dross accumulating during the melting operation.
The flux floats the dross and conditions it so it can be skimmed
from the surface. After skimming, the melt can be poured into
molds or ladles.
Refining/Alloying - Additional processing steps may involve alloying,
distillation, distillation and oxidation, or reduction. Alloying
produces mainly zinc alloys from pretreated scrap. Often the
alloying operation is combined with sweating or melting.
Distillation retorts and furnaces are used to reclaim zinc
from alloys or to refine crude zinc. Retort distillation is the
4/81 Metallurgical Industry 7.14-1
-------
PRETHEATMENT
MELTING
REFINING/ALLOYING
r
FUEL
ALLOYING AGENT
FUEL-i | r-FLUX
H
W
to
O
a
n
H
I
DIE CAST
PRODUCTS
RESIDUES
SKIMMINGS
OTHER
MIXED
SCRAP
CLEAN
SCRAP
ZINC ALLOYS
CONTAMINATED
ZINC OXIDE,
BAGHOUSEDU5T
RESIDUES
SKIMMINGS
1
1
-»-
-^
-»-
REVERBERATORY
SWEATING
r-FUEL
ROTARY
SWEATING
r-FUEL
MUFFLE
SWEATING
r-FUEL
KETTLE (POT)
SWEATING
r- ELECTRICITY
ELECTRIC
RESISTANCE
SWEATING
-»-
-»-
i
-»-
I
i /SWEATED\
. \OR INGOT)/ '
1
T
r~
CRUSHING/
SCREENING
FL
-^
FL
FL)
FL
UX-i r— FUEL
^ r
KETTLE (POT)
MELTING
•»-
.X-j rFUEL
CRUCIBLE
MELTING
IX-j rFUEL
REVEHBERATORY
MELTING
1
j
^»-
UX__ ELECTRICITY
ELECTRIC
INDUCTION
MELTING
SODIUM
WATER-1 CARBONATE
^
SODIUM
CARBONATE
LEACHING
/ CRUDE \
^1 7INT 1 M.
V OXIDE y
TO PRIMARY
SMELTERS
-^
i
CARBO
•»-
FUE
-^f-
FUE
EL
FUE
FUE
ALLOYING
— 1 III i nut-
L-n r-WATER
RETORT
DISTILLATION
•»-
L-i r-WATER
* r j
MUFFLE
DISTILLATION
ECTR.CITY ^_WAT[
, GRAPHITE
ROD
: DISTILLATION
••-
.H
_/Z1NC 1
|~~^y INGOT ,
/ ZINC i
I DUST ,
L-i r-AIR r-WATER
' RETORT
•DISTILLATION
OXIDATION
-n
L-, _AIR r-WATER j
MUFFLE
DISTILLATION
OXIDATION
-1
( ZINC 1
^\ OXIDE j
N MONOXIDE
1 FUEL-1 f-WATEH
_
RETORT
REDUCTION
00
Figure 7.14-1. Process flow diagram of secondary zinc processing.
-------
TABLE 7.14-1.
UNCONTROLLED PARTICULATE EMISSION FACTORS
FOR SECONDARY ZINC SMELTING3
EMISSION FACTOR RATING: C
Emissions
Operation
b
Reverberatory sweating
clean metallic scrap
general metallic scrap
residual scrap
Rotary sweating
Muffle sweating
Kettle sweating
clean metallic scrap
general metallic scrap
residual scrap
Electric resistance sweating0
Crushing/ screening
Sodium carbonate leaching
crushing/ screening0
calciningd
Kettle (pot) melting
Crucible melting
Reverberatory melting
Electric induction melting
Alloying
Retort and muffle distillation
pouring
casting ,
muffle distillation
Graphite rod distillationC'e
Retort distillation/oxidation
Muffle distillation/oxidationf
Retort reduction
Galvanizing
kg/Mg
Negligible
6.5
16
5.5-12.5
5.4-16
Negligible
5.5
12.5
<5
0.5-3.8
0,5-3.8
44.5
0.05
DNA
DNA
DNA
DNA
0.2-0.4
0.1-0.2
22,5
Negligible
10-20
10-20
23.5
2.5
Ib/ton
Negligible
13
32
11-25
10.8-32
Negligible
11
25
<10
1.0-7.5
1.0-7.5
89
0.1
DNA
DNA
DNA
DNA
0.4-0.8
0.2-0.4
45
Negligible
20-40
20-40
47
5
a
crushing/screening, skimming/residues processed; for kettle (pot)
melting and retort and muffle distillation operations, metal
product. Galvanizing factor expressed in units per unit weight
,of zinc used. DNA: Data not available.
Reference 3.
.Reference 4,
References 5-7.
,Reference 1,
Reference 4. Factor units per unit weight of ZnO produced. The
product zinc oxide dust is totally carried over in the exhaust gas
from the furnace and is recovered witb 98-99X efficiency.
4/81
Metallurgical Industry
7.14-3
-------
vaporization at 980-1250°C (1800-2280°F) of elemental zinc with its
subsequent condensation as zinc dust or liquid zinc. Rapid cooling
of the vapor stream below the zinc melting point produces zinc
dust, which can be removed from the condenser and packaged. If
slab zinc is the desired product, the vapors are condensed slowly
at a higher temperature. The resultant melt is cast into ingots or
slabs. Muffle distillation furnaces produce principally zinc
ingots, and graphite rod resistance distillation produces zinc
dust.
Retort and muffle furnace distillation and oxidation processes
produce zinc oxide dust. These processes are similar to distillation
through the vaporization step. In contrast, for distillation/oxi-
dation, the condenser is omitted, and the zinc vapor is discharged
directly into an air stream leading to a refractory lined combustion
chamber. Excess air is added to complete oxidation and to cool the
product. The zinc oxide product is usually collected in a baghouse.
In retort reduction, zinc metal is produced by the reaction of
carbon monoxide and zinc oxide to yield zinc and carbon dioxide.
Carbon monoxide is supplied by the partial oxidation of the coke.
The zinc is recovered by condensation.
Zinc Galvanizing - Zinc galvanizing is the coating of clean oxide
free iron or steel with a thin layer of zinc by immersion in molten
zinc. The galvanizing occurs in a vat or in dip tanks containing
molten zinc and cover flux.
1 2
7.14.2 Emissions and Controls '
Factors for uncontrolled point source and fugitive particulate
emissions are tabulated in Tables 7.14-1 and 7.14-2 respectively.
Emissions from sweating and melting operations consist
principally of particulates, zinc fumes, other volatile metals,
flux fumes and smoke generated by the incomplete combustion of
grease, rubber and plastics in the zinc bearing feed material.
Zinc fumes are negligible at low furnace temperatures, for they
have a low vapor pressure even at 480°C (900°F). With elevated
temperatures, however, heavy fuming can result. Flux emissions are
minimized by the use of a nonfuming flux. Substantial emissions
may arise from incomplete combustion of carbonaceous material in
the zinc scrap. These contaminants are usually controlled by
afterburners. Further emissions are the products of combustion of
the furnace fuel. Since the furnace fuel is usually natural gas,
these emissions are minor. In reverberatory furnaces, the products
of fuel combustion are emitted with the other emissions. Other
furnaces emit the fuel combustion products as a separate emission
stream.
Particulates from sweating and melting are mainly hydrated
ZnCl2 and ZnO, with small amounts of carbonaceous material. Chemical
7.14-4 EMISSION FACTORS 4/81
-------
TABLE 7.14-2. FUGITIVE PARTICULATE UNCONTROLLED EMISSION
FACTORS FOR SECONDARY ZINC SMELTING
EMISSION FACTOR RATING: E
Particulate
Operation
Reverberatory sweating
Rotary sweating
Muffle sweating
Kettle (pot) sweating
Electric resistance sweating
Crushing/ screening
Sodium carbonate leaching
Kettle (pot) melting furnace
Crucible melting furnace
Reverberatory melting furnace
Electric induction melting
Alloying retort distillation
Retort and muffle distillation
Casting
Graphite rod distillation
Retort distillation/oxidation
Muffle distillation/oxidation
Retort reduction
kg/Mg
0.63
0.45
0.54
0.28
0.25
2.13
DNA
0.0025
0.0025
0.0025
0.0025
DNA
1.18
0.0075
DNA
DNA
DNA
DNA
Ib/ton
1.30
0.90
1.07
0.56
0.50
4.25
DNA
0.005
0.005
0.005
0.005
DNA
2.36
0.015
DNA
DNA
DNA
DNA
Reference 8. Expressed as units per end product, except factors
for crushing/screening and electric resistance furnaces, which are
expressed as units per unit of scrap processed. DNA: Data not
.available.
Estimate based on stack emission factor given in Reference 1,
Assuming fugitive emissions to be equal to 5% of stack emissions.
Reference 1. Average of reported emission factors.
Engineering judgement, assuming fugitive emissions from crucible
melting furnace to be equal to fugitive emissions from kettle
(pot) melting furnace.
4/81
Metallurgical Industry
7.14-5
-------
analyses of particulate emissions from kettle sweat are shown in
Table 7.14-3.
TABLE 7.14-3. COMPOSITION OF PARTICULATE EMISSIONS
FROM KETTLE SWEAT PROCESS ING a
Component Percent
ZnCl2 14.5 - 15.3
ZnO 46.9 - 50.0
NH4C1 1.1 - 1.4
A1203 1.0 - 2.7
Fe203 0.3 - 0.6
PbO 0.2
H0 (in ZnCl • 4H0) 7.7 - 8.1
Oxide of Mg, Sn, Ni, Si, Ca, Na 2.0
Carbonaceous material 10.0
Moisture (deliquescent) 5.2 - 10.2
Reference 3.
These particulates also contain Cu, Cd, Mn and Cr. Another
analysis showed the following composition: 4 percent ZnCl2, 77 percent
ZnO, 4 percent H20, 4 percent metal chlorides and 10 percent carbona-
ceous matter. These particulates vary widely in size. Particulates
from kettle sweating of residual zinc scrap had the following size
distributions :
60% 0 -
17% 11 -
23%
Particulates from kettle sweating of metallic scrap had mean particle
size distributions ranging from Dp^Q = 1.1 AI to Dp^Q = 1.6|_u Emissions
from a reverberatory sweat furnace had an approximate Dp^Q = lu.
Baghouses are most commonly used to recover particulate emissions
from sweating and melting. In one application on a muffle sweating
7.14-6 EMISSION FACTORS 4/81
-------
furnace, a cyclone and baghouse achieved particulate recovery
efficiencies in excess of 99.7 percent/* In another application on
a reverberatory sweating furnace, a baghouse removed 96.3 percent
of the particulates, reducing the dust loading from 0.513 g/Nmr to
0.02 g/Nm-^. Baghouses show similar efficiencies in removing
particulates from exhaust gases of melting furnaces.
Crushing and screening operations are also sources of dust
emissions. These particulates are composed of Zn, Al, Cu, Fe, Pb,
Cd, Sn and Cr, and they can be recovered from hooded exhausts by
baghouses.
The sodium carbonate leaching process produces particulate
emissions of ZnO dust during the calcining operation. This dust
can be recovered in baghouses, although ZnCl2 in the dust may cause
plugging problems.
Emissions from refining operations are mainly metallic fumes.
These fume and dust particles are quite small, with sizes ranging
from 0.05 - lu. Distillation/oxidation operations emit their
entire ZnO product in the exhaust gas. The ZnO has a very small
particle size (0.03 to 0.5[_0 and is recovered in baghouses with
typical collection efficiencies of 98—99 percent.^
Some emissions of zinc oxide occur during galvanizing, but
these emissions are small because of the bath flux cover and the
relatively low temperature maintained in the bath.
Data describing the particle size distribution of fugitive
emissions are unavailable. These emissions are probably similar In
size to stack emissions.
References for Section 7.14
1. William M. Coltharp, et al., Multimedia Environmental Assessment
of the Secondary Nonf ejrrous JMetal Industry, Draft Final Report,
2 vols., EPA Contract No. 68-02-1319, Radian Corporation,
Austin, TX, June 1976.
2. John A. Danielson, Air Pollution Engineering Manual, 2nd
Edition, AP-42, U.S. Environmental Protection Agency, Research
Triangle Park, NC, 1973. Out of Print.
3. W. Herring, Secondary Zinc Industry Emission Control Problem
Definition Study (Part I), APTD-0706, U.S. Environmental
Protection Agency, Research Triangle Park, NC, May 1971.
4. H. Nack, et al., Development of an Approach to Identification
of Emerging Technology and Demonstration Opportunities, EPA-650/
2-74-048, U.S. Environmental Protection Agency, Research
Triangle Park, NC, May 1974.
4/81 Metallurgical Industry 7.14-7
-------
5. G.L. Allen, et ar._, Control of Metallurgical and Mineral Dusts
and Fumes in Los Angeles County, Number 7627, U.S. Department
of the Interior, Washington, DC, April 1952.
6. Restricting Dust and Sulfur Dioxide Emissions from Lead Smelters,
translated from German, VDI Number 2285, U.S. Department of
Health, Education and Welfare, Washington, DC, September 1961.
7. W.F. Hammond, Data on Nonferrous^Metallurgical Operations, Los
Angeles County Air Pollution Control District, Los Angeles,
CA, November 1966.
8. Assessment of jFugitive Particulate Emission Factors for
Industrial Processes, EPA-450/3-78-107, U.S. Environmental
Protection Agency, Research Triangle Park, NC, September 1978.
7.14-8 EMISSION FACTORS 4/81
-------
7.15 STORAGE BATTERY PRODUCTION
7.15.1 Process Description1
Lead acid storage batteries are produced from lead alloy ingots and lead
oxide. The lead oxide may be prepared by the battery manufacturer or may be
purchased from a supplier. See Section 7.16.
Lead alloy ingots are charged to a melting pot, from which the molten
lead flows into molds that form the battery grids. Pasting machines force a
paste into the interstices of the grids, after which they are referred to as
plates. The grids are often cast in doublets and split apart (slitting)
after they have been pasted and cured. The paste is made in a batch type
process. Mixing lead oxide powder, water and sulfuric acid produces a
positive paste, and the same ingredients in slightly different proportions
plus an expander (generally a mixture of barium sulfate, carbon black and
organics) make the negative paste.
After the plates are cured, they are sent to the three process operation
of plate stacking and burning and element assembly in the battery case.
Doublet plates are cut apart and stacked in an alternating positive and
negative block formation, with insulators between them. These insulators are
of materials such as wood, treated paper, plastic or rubber. Then, in the
burning operation, leads are welded to tabs on each positive or negative
plate. An alternative to this operation is the cast-on strap process, in
which molten lead is poured around the plate tabs to form the connection, and
positive and negative terminals are then welded to each such connected
element. The completed elements are assembled in battery cases either before
(wet batteries) or after (dry batteries) the formation step.
Formation is the immersing of plates in a dilute sulfuric acid solution
and the connecting of positive plates to the positive pole of a direct
current (dc) source and the negative plates to the negative pole of the dc
source. In the wet formation process, this is done in the battery case.
After forming, the acid is dumped, fresh acid is added, and a boost charge is
applied to complete the battery. In dry formation, the individual plates may
be formed in tanks of sulfuric acid before assembly. Also, they may be
assembled first and then formed in tanks. The formed elements from either
method are then placed in the battery cases, and the batteries are shipped
dry. Figure 7.15-1 is a process flow diagram for lead acid battery
manufacture.
Defective parts are either reclaimed at the battery plant or are sent to
a secondary lead smelter (See Section 7.11). Lead reclamation facilities at
battery plants generally are small pot furnaces. Approximately 1 percent of
the lead processed at a typical lead acid battery plant is recycled through
the reclamation operation.
Lead acid storage battery plants range in production capacity from less
than 500 batteries per day to about 10,000 batteries per day. Lead acid
storage batteries are produced in many sizes, but the majority is produced
for use in automobiles and falls into a standard size range. A standard
8/82 Metallurgical Industry 7.15-1
-------
Ln
I
NJ
t
1 PARTICULATE
] MATTER
l~"
LEAD OXIDE
PRODUCTION
GRID CASTING
FURNACE
*
IP*
!"
t
1 RARTICULATE
| MATTER
LEAD PASTE
MIXING
RTICULATE
1TTER
~\
GRID
CASTING
»
! PARTICULATE
1 MATTER
r n
GRID PLATE PLATE ELEMENT fc
PASTING STACKING BURNING ASSEMBLY
GRID CASTING OPERATION
THREE PROCESS OPERATION
CO
CO
1
a
o
4
ISULFUR1C
IACID MIST
FORMATION
-
RINSING
AND DRYING
ASSEMBLY INTO
BATTERY CASE
ASSEMBLY INTO
BATTERY CASE
FRESH
ACID
H
ACID
4
JSULFURIC
J ACID MIST
FORMATION
ACID
REFILL
BOOST
CHARGE
WASH AND
PAINT
SHIPPING
-»• PROCESS STREAM
-*• ATMOSPHERIC EMISSION
STREAM
00
00
to
Figure 7.15-1. Process flow diagram for storage battery production.
-------
TABLE 7.15-1. STORAGE BATTERY PRODUCTION EMISSION FACTORS
Process
Grid casting
Paste mixing
Lead oxide mill
(baghouse outlet)
Three process operation
Lead reclaim furnace
Dry formation
Total production
Particulate
kg(lb)/103
batteries
1.42
(3.13)
1.96
(4.32)
0.05
(0.11)
42.0
(92.6)
3.03
(6.68)
14.7
(32.4)
63.2
(139)
Lead
kg(lb)/103
batteries
0.35
(0.77)
1.13
(2.49)
0.05
(0.11)
4.79
(10.6)
0.63
(1.38)
NA
6.94
(15.3)
Emission
Factor
Rating
B
B
C -
B
B
B
References 1-7. NA = not applicable. Based on standard automotive
batteries of about 11.8 kg (26 Ib) of lead, of which approximately half is
present in the lead grids and half in the lead oxide paste. Particulate
emissions include lead and its compounds, as well as other substances.
Lead emission factors are expressed as emissions of elemental lead.
Reference 5. Emissions measured for a well controlled facility (fabric
filters with an average airrcloth ratio of 3:1) were 0.025 kg (0.055 Ib)
particulate/1000 batteries and 0.024 kg (0.053 Ib) lead/1000 batteries.
Factors represent emissions from a facility with typical controls (fabric
filtration with an air:cloth ratio of about 4:1). Emissions from a
facility with typical controls are estimated to be about twice those from
a well controlled facility (Reference 1).
f*
Based on the assumption that about 1% of the lead processed at a typical
battery plant is processed by the reclaim operation.
For sulfates in aerosol form, expressed as sulfuric acid, and not account-
ing for water and other substances which might be present.
8/82
Metallurgical Industry
7.15-3
-------
battery contains about 11.8 kilograms (26 Ib) of lead, of which about half is
present in the lead grids and half in the lead oxide paste.
7.15.2 Emissions and Controls1"7
Lead oxide emissions result from the discharge of air used in the lead
oxide production process. In addition, particulate matter and lead
particulate are generated in the grid casting, paste mixing, lead reclamation,
three process operations, and other operations such as slitting and small
parts casting. These particulates are usually collected by ventilation
systems to reduce employee exposure to airborne lead. Sulfuric acid mist
emissions are generated during the formation step. Acid mist emissions are
significantly higher for dry formation processes than for wet formation
processes, because wet formation is conducted in battery cases, while dry
formation is conducted in open tanks. Table 7.15-1 presents average
uncontrolled emission factors for grid casting, paste mixing, lead reclamation,
dry formation, and three process operations, and an average controlled
emission factor for lead oxide production. The particulate emission factors
presented in the Table include lead and its compounds. The lead emission
factors represent emissions of lead in element and compound form, expressed
as elemental lead.
A fabric filter is used as part of the process equipment to collect
product from the lead oxide facility. Typical air to cloth ratios of fabric
filters used for this facility are about A to 1. It is estimated that
emissions from a facility controlled by a fabric filter with a 3 to 1 air to
cloth ratio are about 50 percent less than those from a facility with a
typical collection system.^
Fabric filters can also be used to control emissions from slitting and
three process operations. The paste mixing operation consists of two phases.
The first, in which dry ingredients are charged to the mixer, results in
major emissions of lead oxide and is usually vented to a baghouse. For the
second phase of the cycle, when moisture is present in the exhaust stream,
the paste mixer generally is vented to an impingement scrubber. Grid casting
machines are sometimes vented to an impingement scrubber. Lead reclamation
facilities generally are also vented to impingement scrubbers.
Emission reductions of 99 percent and above can be obtained where fabric
filtration is used to control slitting, paste mixing and three process
operations. Application of scrubbers to paste mixing, grid casting and lead
reclamation facilities can result in emission reductions from 85 percent to
over 90 percent.
Wet formation processes usually do not require control. Emissions of
sulfuric acid mist from dry formation processes can be reduced by over
95 percent with mist eliminators. Surface foaming agents are also used
commonly in dry formation baths to control acid mist emissions.
References for Section 7.15
1. Lead Acid Battery Manufacture - Background Information for Proposed
Standards, EPA 450/3-79-028a, U.S. Environmental Protection Agency,
Research Triangle Park, NC, November 1979.
7.15-4 EMISSION FACTORS 8/82
-------
2. Source Test EPA-74-BAT-1, U.S. Environmental Protection Agency, Research
Triangle Park, NC, March 1974.
3. Source Testing of Lead Acid Battery Manufacturing Plant - Globe-Union,
Inc., Canby, OR, EPA-76-BAT-4, U.S. Environmental Protection Agency,
Research Triangle Park, NC, 1976.
4. R.C. Fulton and G.W. Zolna, Report of Efficiency Testing Performed
April 30, 1976, on American Air Filter Roto-Clone, Spotts, Stevens and
McCoy, Inc., Wyomissing, PA, June 1, 1976.
5. Source Testing at a Lead Acid Battery Manufacturing Company - ESB, Canada,
Ltd., Mississauga, Ontario, EPA-76-3, U.S. Environmental Protection
Agency, Research Triangle Park, NC, 1976.
6. Emissions Study at a Lead Acid Battery Manufacturing Company - ESB, Inc.,
Buffalo, NY, EPA-76-BAT-2, U.S. Environmental Protection Agency,
Research Triangle Park, NC, 1976.
7. Test Report - Sulfuric Acid Emissions from ESB Battery Plant Forming Room,
Allentown, FA, EPA-77-BAT-5. U.S. Environmental Protection Agency,
Research Triangle Park, NC, 1977.
8/82
Metallurgical Industry
7.15-5
-------
-------
7.16 LEAD OXIDE AND PIGMENT
PRODUCTION
7.16.1 General
Lead oxide is used in the manufacture of lead/acid storage batteries (Section 7.15) and as a pigment in
paints. Black oxide, which is used exclusively in storage batteries, contains 60 to 80 percent litharge (PbO)
the remainder being finely divided metallic lead. l The major lead pigment is red lead (Pb3O4), which is used
principally in ferrous metal protective paints. Other lead pigments include white Lead and lead chromates.
Most lead oxides and many lead pigments are derived from lead monoxide (PbO) in the form of litharge,
which is produced by (1) partially oxidizing lead and milling it into a powder, which is then completely oxi-
dized in a reverberatory furnace; (2) oxidizing and stirring pig lead in a reverberatory furnace or rotary kiln;
(3) running molten lead into a cupelling furnace; or (4) atomizing molten lead in a flame. The product must
be cooled quickly to below 300°C (5?2T) to avoid formation of red lead.2
Black oxide is usually produced (in the same furnace in which the litharge is made) by either the ball
mill or Barton process. Cyclones and fabric filters collect the product. Red lead is produced by oxidizing
litharge in a reverberatory furnace. Basic carbonate white lead production is based on the reaction of
litharge with acetic acid or acetate ions. White leads other than carbonates are made either by chemical
or fuming processes. Chromate pigments are generally manufactured by precipitation or calcination.
7.16.2 Emissions and Controls
Automatic shaker type fabric filters, often preceded by cyclone mechanical collectors or settling cham-
bers, are the almost universal choice for collecting lead oxides and pigments. Where fabric filters are not
appropriate, scrubbers are used, resulting in higher emissions. The ball mill and Barton processes of black
oxide manufacturing recover the lead product by these two means. Collection of dust and fumes from the
production of red lead is likewise an economic necessity, since particulate emissions, although small, are-
about 90 percent lead. Data on emissions from the production of white lead pigments are not available, but
'hey have been estimated because of health and safety regulations. The emissions from dryer exhaust
. crubbers account for over 50 percent of the total lead emitted in lead chromate production.
7/79
Metallurgical Industry
7.16-1
-------
Table 7.16-1. LEAD OXIDE AND PIGMENT PRODUCTION EMISSION FACTORS0
EMISSION FACTOR RATING: B
Process
Lead oxide
production:
Barton potb
CaJcining
furnace
Pigment
production;
Red leadb
White leadb
Chrome
pigments:
Particulate
Ib/ton
produced
0.43-0.85
c
1.0d
c
c
kg/103 kg
produced
0.21-0.43
c
0.5d
C
c
Lead emission factor
Ib/ton
produced
0.44
14.0
0.9
0.55
0.13
kg/103 kg
produced
0.22
7.0
0.5
0.28
0.065
References
4,6,7
6
4,5
4,5
4,5
Reference 4, pp. 4-283 and 4-287.
^Measured at bag ho use outlet. Baghouse is considered process equipment.
cData not available.
dOnly PbO and oxygen used in red lead production, so participate emissions assumed to be about 90% lead.
Table 7.16-2. LEAD OXIDE AND PIGMENT PRODUCTION CONTROL EFFICIENCIES
Process.
Control
Percent
reduction
Lead oxide and
pigment production
Mechanical shaker fabric
filter (preceded by dry
cyclone or settling chamber)
Scrubber
99a
70-95b
"Reference 3.
Reference 4.
7.16-2
EMISSION FACTORS
7/79
-------
References for Section 7.16
1. E. J, Ritchie, Lead Oxides, Independent Battery Manufacturers Association, Inc., Largo, FL. 1974.
2. W. E. Davis, Emissions Study of Industrial Sources of Lead Air Pollutants, 1970, EPA Contract No.
68-02-0271, W. E. Davis and Associates, Leawood, KS, April 1973.
3. Background Information in Support of the Development of Performance Standards for the Lead Addi-
tive Industry, EPA Contract No. 68-02-2085, PEDCo-Environmental Specialists. Inc., Cincinnati. OH,
January 1976.
4. Control Techniques for Lead Air Emissions, EPA-450/2-77-012. U.S. Environmental Protectio!
Agency, Research Triangle Park, NC. December 1977.
5. R. P. Betz, et al., Economics of Lead Removal in Selected Industries, EPA Contract No. 68-02-0299,
Battelle Columbus Laboratories, Columbus, OH. December 1972.
6. Emission Test No. 74-PB-O-l. Office of Air Quality Planning and Standards. U.S. Environmental
Protection Agency, Research Triangle Park, NC. August 1973.
7/79 Metallurgical Industry 7.16-3
-------
-------
7.17 MISCELLANEOUS LEAD PRODUCTS
7,17.1 Type Metal Production
7.17.1.1 General — Lead type, used primarily in the letterpress segment of the printing industry, is east
from a molten lead alloy and remelted after use. Linotype and monotype processes produce a mold, while
the stereotype process produces a plate for printing. All type rnetal is an alloy consisting of 60 to 85 percent
recovered lead, with antimony, tin and a small amount of virgin metal.
7.17.1.2 Emissions and Controls — The melting pot is the major source of emissions, containing hydro-
carbons as well as lead particulates. Pouring the molten metal into the molds involves surface oxidation of
the metal, possibly producing oxidized fumes, while the trimming and finishing operations emit lead par-
ticles. It is estimated that 35 percent of the total emitted particulate is lead.1
Approximately half of the current lead type operations control lead emissions, by about 80 percent. The
other operations are uncontrolled.2 The most frequently controlled sources are the main melting pots and
dressing areas. Linotype equipment does not require controls when operated properly. Devices in current
use on monotype and stereotype lines include rotoclones. wet scrubbers, fabric filters, and electrostatic
precipitators, all which can be used in various combinations.
7.17.2 Can Soldering
7.17.2.1 Process Description — Side seams of cans are soldered on a machine consisting of a solder-
coated roll operating in a bath of molten solder, typically containing 98 percent lead. Alter soldering, excess
is wiped away by a rotating cloth buffer, which creates some dust (Table 7.17-1).3
7.17.2.2 Emissions and Controls - Hoods, exhaust ducts and mechanical cyclones (Table 7.17-2) collect
the large flakes generated at the wiping station, but some dust escapes in the form of particles 20 microns or
smaller, with a lead content of 3 to 38 percent. Maintaining a good flux cover is the most effective means
of controlling lead emissions from the solder batch. Low energy wet collectors or fabric filters can also con-
trol lead emissions from can soldering.
7.17.3 Cable Covering
7.17.3.1 Process Description - About 90 percent of the lead cable covering produced in the United States
is lead cured jacketed cables, and 10 percent is on lead sheathed cables. In preparation of the former type,
an unalloyed lead cover applied in the vulcanizing treatment during the manufacture of rubber-insulated
cable must be stripped from the cable and remelted.
Lead coverings are applied to insulated cable by hydraulic extrusion of solid lead around the cable.
Molten lead is continuously fed into an extruder or screw press, where it solidifies as it progresses. A melt-
ing kettle supplies lead to the press.
7.17.3.2 Emissions and Controls — The melting kettle is the only source of atmospheric lead emissions.
and it is generally uncontrolled.4 Average particle size is approximately 5 microns, with a lead content of
about 70 to 80 percent.3-s
Cable covering processes do not usually include particulate collection devices, although fabric filters.
rotoclone wet collectors and dry cyclone collectors can reduce lead emissions (Table 7.17-2). Lowering and
controlling the melt temperature, enclosing the melting unit and using fluxes to provide a cover on the melt
can also minimize emissions.
7/79 Metallurgical Industry 7.17-1
-------
Table 7.17-1 EMISSION FACTORS FOR MISCELLANEOUS SOURCES3
EMISSION FACTOR RATING: C
Process
Type metal
production
Can soldering
Cable covering
Metallic lead
products
Ammunition
Bearing metals
Other sources
of lead
Particulate emission factor
Metric
0.4 kg/103 kg
Pb procb
0.8 x 106
baseboxes
prod0
0.3. kg/103 kg
Pb procd
e
e
e
English
0.7 Ib/ton Pb
procb
0.9 ton/106
baseboxes
prodc
0.6 Ib/ton Pb
procd
e
e
e
Lead emission factor
Metric
0.13 kg/103
kg Pb proc
160 kg/106
baseboxes
prod'
0.25 kg/103
kg Pb proc
<0.5 kg/106
kg Pb proc
negligible
0.8 kg/103 kg
Pb proc
English
0.25 Ib/ton
Pb proc
0.18 ton/106
baseboxes
prod
0.5 Ib/ton Pb
proc
1.0 lb/103ton
Pb proc
negligible
1.5 Ib/ton Pb
proc
References
2,7
7
3,5,7
3,7
3,7
3,7
aProc = processed; prod = produced.
"Calculated on the basis of 35% of the total (Reference 1).
cReference 7, pp. 4-297 and 4-298.
^Reference 7, p. 4-301.
"Data not available.
'Basebox = 20.23 m2 (217.8 ft2), standard tin plate sheet area.
Table 7.17-2. CAN SOLDERING AND CABLE COVERING
CONTROL EFFICIENCIES
Process
Can soldering
Cable covering
Control
Mechanical cyclone
Fabric filter
Rotoclone wet collector
Dry cyclone collector
Percent
reduction
75 4-
99.9
75-85
45 +
"Reference 7
7.17-2
EMISSION FACTORS
7/7*)
-------
7.17.4 Metallic Lead Products
7.17.4.1 General — Lead is consumed and emitted in the manufacture of ammunition, bearing metals
and other lead products. Lead used in the manufacture of ammunition is melted and alloyed before it is
cast, sheared, extruded, swaged or mechanically worked. Some lead is also reacted to form lead azide, a
detonating agent. Lead is used in bearing manufacture by alloying it with copper, bronze, antimony and tin.
Other lead products include terne metal (a plating alloy), weights and ballasts, caulking lead, plumbing
supplies, roofing materials, casting metal foil, collapsible metal tubes and sheet lead. Lead is also used for
galvanizing, annealing and plating. It is usually melted and cast prior to mechanical forming operations.
7.17.4.2 Emissions and Controls — Little or no air pollution control equipment is currently used by manu-
facturers of metallic lead products.8 Emissions from bearing manufacture are negligible, even without
controls.3
References for Section 7.17
1. N. J. Kulujian, Inspection Manual for the Enforcement of New Source Performance Standards:
Portland Cement Plants, EPA Contract No. 68-02-1355, PEDCo-Environmental Specialists, Inc.,
Cincinnati, OH, January 1975.
2. Atmospheric Emissions from Lead Typesetting Operation Screening Study, EPA Contract No. 68-02-
2085, PEDCo-Environmental Specialists, Inc., Cincinnati, OH, January 1976,
3. ^ . E. Davis, Emissions Study of Industrial Sources of Lead Air Pollutants, 1970, EPA Contract No.
68-02-0271, W. E. Davis Associates. Leawood, KS, April 1973.
4. R. P. Betz, et al., Economics of Lead Removal in Selected Industries, EPA Contract No. 68-02-0611,
Battelle Columbus Laboratories, Columbus. OH, August 1973.
5. E. P. Shea, Emissions from Cable Covering Facility, EPA Contract No. 68-02-0228, Midwest Re-
search Institute, Kansas City, MO. June 1973.
6. Mineral Industry Surveys: Lead Industry in May 1976, Bureau of-Mines, U.S. Department of the
Interior, Washington, DC, August 1976.
7. Control Techniques for Lead Air Emissions, EPA-450/2-77-012, U.S. Environmental Protection
Agency. Research Triangle Park. NC. December 1977.
7/79
Metallurgical Industry
7.17-3
-------
-------
7.18 LEADBEARING ORE CRUSHING
AND GRINDING
7.18.1 Process Description
Lead and zinc ores are normally deep mined, whereas copper ores are open pit mined. Lead, zinc and
copper are usually found together (in varying percentages) in combination with sulfur and/or oxygen.
In underground mines, the ore is disintegrated by percussive drilling machines, run through a primary
crusher, and then conveyed to the surface. In open pit mines, ore and gangue are loosened and pulverized
by explosives, scooped up by mechanical equipment, and transported to the concentrator.
Standard crushers, screens, and rod and ball mills classify and reduce the ore to powders in the 65 to 325
mesh range. The finely divided particles are separated from the gangue and are concentrated in a liquid
medium by gravity and/or selective flotation, then cleaned, thickened and filtered. The concentrate is dried
prior to shipment to the smelter.
7.18.2 Emissions and Controls
Lead emissions are basically fugitive, caused by drilling, blasting, loading, conveying, screening.
unloading, crushing and grinding. The primary means of control are good mining techniques and equip-
ment maintenance. These practices include enclosing the truck loading operation, wetting or covering
truck loads and stored concentrates, paving the road from mine to concentrator, sprinkling the unloading
area,-and preventing leaks in the crushing and griding enclosures. Cyclones and fabric filters can be used
in the milling operations.
l';irll< ulate and lead omission fai'lnr- lor lead ore crushing and materials handling operal inns
are gi\cn in Table 7.18-1. Lead emissions from the mining and milling of copper ore.- arc
negligible.
7/79
Metallurgical Industry
7.18-1
-------
Table 7.18-1. EMISSION FACTORS FOR ORE CRUSHING AND
GRINDING
EMISSION FACTOR RATING: B
Type of
ore
Pbc
Zn
Cu
Pb-Zn
Cu-Pb
Cu-Zn
Cu-Pb-Zn
Participate
emission factor3
Ib/ton
processed
6.0
6.0
6.4
6.0
6.4
6.4
6.4
kg/103 kg
processed
3.0
3.0
3.2
3.0
3.2
3.2
3.2
Lead
emission factorb
Ib/ton
processed
0.3
0.012
0.012
0.12
0.12
0.012
0.12
kg/103 kg
processed
0.15
0.006
0.006
0.06
0.06
0.006
0.06
aReference 1, pp. 4-39
References 1-5
cRe-fer to Section 7.6
References for Section 7.18
1. Control Techniques for Lead Air Emissions. EPA-450/2-77-012, U. S. Environmental Protection Agency. Re-
search Triangle Park. XC. December 1977.
2. W. E. Davis. Emissions Study of Industrial Sources of Lead Air Pollutants, 1970. EPA Contract No. 68-02-0271.
W. E. Davis and Associates, Leawood. KS.. April 1973.
3. Environmental Assessment of the Domestic Primary Copper. Lead, and Zinc Industry, EPA Contract No. 68-02'
1321. PEDCO-Environmental Specialists. Inc., Cincinnati, OH, September 1976.
4. Communication with Mr. J. Patrick Ryan, Bureau of Mines. U. S. Department of the Interior. \^ ashington. DC.
September 9. 1976.
5. B. G. Wixion and J. C. Jennett. "The New Lead Belt in the Forested Ozarks of Missouri", Eniironniental
Science and Technology. 9tl3r. 1128-1133. December 1975.
r.18-2
EMISSION FACTORS
7/79
-------
8. MINERAL PRODUCTS INDUSTRY
This section involves the processing and production of various minerals. Mineral processing is characterized
by participate emissions in the form of dust. Frequently, as in the case of crushing and screening, this dust is
identical to the material being handled. Emissions also occur through handling and storing the finished product
because this material is often dry and fine. Paniculate emissions from some of the processes such as quarrying,
yard storage, and dust from transport are difficult to control. Most of the emissions from the manufacturing pro-
cesses discussed in this section, however, can be reduced by conventional paniculate control equipment such as
cyclones, scrubbers, and fabric filters. Because of the wide variety in processing equipment and final product,
emissions cover a wide range; however, average emission factors have been presented for general use.
4/81 Mineral Products Industry 8.0-1
-------
1
-------
8.1 ASPHALTIC CONCRETE PLANTS
8.1.1 General
Asphaltic concrete (asphaltic hot mix) is a paving material
which consists of a combination of graded aggregate that is dried,
heated and evenly coated with hot asphalt cement.
Asphalt hot mix is produced by mixing hot, dry aggregate with
hot liquid asphalt cement, in batch or continuous processes. Since
different applications require different aggregate size distribu-
tions, the aggregate is segregated by size and is proportioned into
the mix as required. In 1975, about 90 percent of total U.S.
production was conventional batch process, and most of the remainder
was continuous batch. The dryer drum process, another method of
hot mix asphalt production, in which wet aggregate is dried and
mixed with hot liquid asphalt cement simultaneously in a dryer,
comprised less than 3 percent of the total, but most new construc-
tion favors this design. Plants may be either permanent or portable.
Conventional Plants - Conventional plants produce finished asphaltic
concrete through either batch (Figure 8.1-1) or continuous
(Figure 8.1-2) aggregate mixing operations. Raw aggregate is
normally stockpiled near the plant, at a location where the moisture
content will stabilize to between 3 and 5 percent by weight.
As processing for either type of operation begins, the aggregate
is hauled from the storage piles and is placed in the appropriate
hoppers of the cold feed unit. The material is metered from the
hoppers onto a conveyor belt and is transported into a gas or oil
fired rotary dryer. Because a substantial portion of the heat is
transferred by radiation, dryers are equipped with flights designed
to tumble the aggregate to promote drying.
As it leaves the dryer, the hot material drops into a bucket
elevator and is transferred to a set of vibrating screens, where it
is classified into as,many as four different grades (sizes). The
classified hot materials then enter the mixing operation.
In a batch plant, the classified aggregate drops into one of
four large bins. The operator controls the aggregate size distri-
bution by opening individual bins and allowing the classified
aggregate to drop into a weigh hopper until the desired weight is
obtained. After all the material is weighed, the sized aggregates
are dropped into a mixer and mixed dry for about 30 seconds. The
asphalt, a solid at ambient temperatures, is pumped from heated
storage tanks, weighed and injected into the mixer. The hot mix is
then dropped into a truck and hauled to the job site.
In a continuous plant, the classified aggregate drops into a
set of small bins which collect and meter the classified aggregate
to the mixer. From the hot bins, the aggregate is metered through
4/81 Mineral Products Industry 8.1-1
-------
CO
W
3
hH
CC
«J
P-H
o
O
g
50
EXHAUST TO i
ATMOSPHERE I
PRIMARY DUST
COLLECTOR
COARSE
AGGREGATE
STORAGE
PILE
FINE
AGGREGATE
LOADER STORAGE
PILE
FEEDERS-
CONVEYOR/^
WEIGH. HOPPER
MIXER
HEATER ASpH/
f \ STORJ
ASPHALT
STORAGE
oo
8.1-1. Batch hot mix asphalt plant. "P" denotes participate emission points.1
-------
.p-
~~-
03
r
3
O
D-
e
9
&
an
EXHAUST TO
ATMOSPHERE
SECONDARY
COLLECTION
DRAFT FAN (LOCATION
DEPENDENT UPON
TYPE OF SECONDARY)
COARSE FINE
AGGREGATE AGGREGATE
STORAGE
TANK
^..{OPTIONAL)
FEEDERS*-
CONVEYOR
ELEVATORS-
TRUCK
8.1 2. Continuous hot-mix asphalt plant. "P" denotes paniculate emission points.1
CO
-------
a set of feeder conveyors to another bucket elevator and Into the
mixer. Asphalt is metered through the inlet end of the mixer, and
retention time is controlled by an adjustable dam at the end of the
mixer. The mix flows out of the mixer into a hopper from which
trucks are loaded.
Dryer Drum Plants - The dryer drum process simplifies the conven-
tional process by using proportioning feed controls in place of hot
aggregate storage bins, vibrating screens and the mixer.
Figure 8.1-3 is a diagram of the dryer drum process. Both
aggregate and asphalt are introduced near the flame end of the
revolving drum. A variable flow asphalt pump is linked electron-
ically to the aggregate belt scales to control mix specifications.
Dryer drum plants generally use parallel flow design for hot
burner gases and aggregate flow. Parallel flow has the advantage
of giving the mixture a longer time to coat and to collect dust in
the mix, thereby reducing particulate emissions to the atmosphere.
The amount of particulates generated within the dryer in this
process is lower than that generated within conventional dryers,
but because asphalt is heated to high temperatures for a long
period of time, organic emissions are greater.
The mix is discharged from the revolving dryer drum into surge
bins or storage silos.
22
Recycle Process for Drum Mix - Asphalt injected directly into the
dryer in the drum mix process is uniquely suited for the new, fast
developing technology of recycling asphalt pavement. Many drum mix
plants are now sold with a "recycle kit", which allows the plant to
be converted to process blends of virgin and recycled material.
In a recycling process, salvaged asphalt pavement (or base
material) that has been crushed and screened is introduced into the
dryer drum at a point somewhere downstream of the virgin aggregate
inlet. The amount of recycled pavement that can be successfully
processed has not yet been determined, but eventually, as the tech-
nology is developed, the blends may approach 100 percent recycled
material. Current blends range from about 20 percent to a maximum
of 50 percent recycled material.
The advantages of the recycling process are that blended
recycled material and virgin aggregate are generally less expensive
than 100 percent virgin aggregate, liquid asphalt requirements are
less due to residual asphalt in the recycled material, and the
recycled material requires less drying than the virgin aggregate.
The chief problem with recycling is opacity standards, because of
emissions of blue smoke (an aerosol of submicron organic droplets
volatilized from the asphalt and subsequently condensed before
exiting the stack). However, current recycle plant designs have
8.1-4 EMISSION FACTORS 4/81
-------
00
R
l-t
o
r
rt
cn
a
01
AGGREGATE STORAGE BINS
VARIABLE SPEED
CONVEYOR
BURNER AND
TURBO-COMPRESSOR
ASPHALT
STORAGE
TANK
HEATED
STORAGE
SILO
FINISHED
PRODUCTTO
TRUCKS^
8.1-3. Shearer type dryer-drum hot asphalt plant.
-------
reduced blue smoke emissions greatly by preventing direct contact
of flame and liquid asphalt as it is injected.
8.1.2 Emissions and Controls
Emission points at batch, continuous and drum dryer hot mix
asphalt plants numbered below refer to Figures 8.1-1, 2 and 3,
respectively.
Emissions from the various sources in an asphaltic concrete
plant are vented either through the dryer vent or the scavenger
vent. The dryer vent stream goes to the primary collector. The
outputs of the primary collector and the scavenger vent go to the
secondary collector, then to the stack (1) for release to the atmos-
phere. The scavenger vent carries releases from the hot aggregate
elevator (5), vibrating screens (5), hot aggregate storage bins
(5), weigh hopper and mixer (2). The dryer vent carries emissions
only from the dryer. In the dryer drum process, the screens, weigh
hopper and mixer are not in a separate tower. Dryer emissions in
conventional plants contain mineral fines and fuel combustion
products, and the mixer assembly (2) also emits materials from the
hot asphalt. In dryer drum plants, both types of emissions arise
in the drum.
Emissions from drum mix recycled asphalt plants are similar
to emissions from regular drum mix plants, except for greater vola-
tile organics due to direct flame volatilization of petroleum deriva-
tives contained in used asphalt. Control of liquid organic emissions
in the drum mix recycle process is by (1) introduction of recycled
material at the center of the drum or farther toward the discharge
end, coupled with a flight design that causes a dense curtain of
aggregate between the flame and the residual asphalt, (2) protection
of the material from the flame by a heat shield, or (3) insulation
of the recycled material from the combustion zone entirely by a
drum-within-a-drum arrangement in which virgin material is dried
and coated in the inner drum, recycled material is indirectly heated
in the annular space surrounding the inner drum, and the materials
OO
are mixed at discharge of the inner drum.
Potential fugitive particulate emission sources from asphaltic
concrete plants include unloading of aggregate to storage bins (5),
conveying aggregate by elevators (5), and aggregate screening
operations (5). Another source of particulate emissions 'is the
mixer (2), which, although it is generally vented into the secondary
collector, is open to the atmosphere when a batch is loaded onto a
truck. This is an intermittent operation, and ambient conditions
(wind, etc.) are quite variable, so these emissions are best regarded
as fugitive. The open truck (4) can also be a source of fugitive
VOC emissions, as can the asphalt storage tanks (3), which may also
emit small amounts of polycyclics.
8.1-6 EMISSION FACTORS 4/81
-------
Thus, fugitive particulate emissions from hot mix asphalt plants are
mostly dust from aggregate storage, handling and transfer. Stone dust may
range from 0.1 to more than 300 micrometers in diameter. On the average, 5
percent of cold aggregate feed is less than 74 micrometers (minus 200 mesh).
Dust that may escape before reaching primary dust collection generally is 50
to 70 percent less than 74 micrometers. Materials emitted are given in
Tables 8.1-1 and 8.1-4.
Emission factors for various materials emitted from the stack are given
in Table 8.1-1. With the exception of aldehydes, the materials listed in this
Table are also emitted from the mixer, but mixer concentrations are 5 to 100
fold smaller than stack concentrations, lasting only during the discharge of
the mixer.
TABLE 8.1-1.
EMISSION FACTORS FOR SELECTED MATERIALS FROM AN
ASPHALTIC CONCRETE PLANT STACKa
Material emitted*5
Particulate^
Sulfur oxides (as S02)d '6
Nitrogen oxides (as NOj)
Volatile organic compounds^
Carbon monoxide^
Polycyclic organic matter^
Aldehydes^
Formaldehyde
2-Methylpropanal
(i sobutyraldehyde )
1-Butanal
(n-butyraldehyde)
3-Methylbutanal
(isovaleraldehyde)
Emission factor0
g/Mg
137
146S
18
14
19
0.013
10
0.077
0.63
1.2
8.3
Ib/ton
.274
.2923
.036
.028
.038
.000026
.020
.00015
.0013
.0024
.016
Emission
Factor
Rating
B
C
D
D
D
D
D
D
D
D
D
aReference 16.
bparticulates, carbon monoxide, polycyclics, trace metals and hydrogen
sulfide were observed in the mixer emissions at concentrations that were
small relative to stack concentrations.
cExpressed as g/Mg and Ib/ton of asphaltic concrete produced.
^Mean of 400 plant survey source test results.
eReference 21. S = % sulfur in fuel. S02 may be attenuated >50% by
adsorption on alkaline aggregate.
^Based on limited test data from the single asphaltic concrete plant
described in Table 8.1-2.
4/81
Mineral Products Industry
8.1-7
-------
Reference 16 reports mixer concentrations of SOX, NOX, VOC and
ozone as less than certain values, so they may not be present at
all, while participates, carbon monoxide, polycyclics, trace metals
and hydrogen sulfide were observed at concentrations that were small
relative to stack amounts. Emissions from the mixer are thus best
treated as fugitive.
The materials listed in Table 8.1-1 are discussed below.
Factor ratings are listed for each material in the table. All emis-
sion factors are for controlled operation, based either on average
industry practice shown by survey or on actual results of testing
in a selected typical plant. The characteristics of this represen-
tative plant are given in Table 8.1-2.
TABLE 8.1-2. CHARACTERISTICS OF AN ASPHALTIC
CONCRETE PLANT SELECTED FOR SAMPLING3
Parameter
Plant Sampled
Plant type
Production rate,
Mg/hr (ton/hr)
Mixer capacity,
Mg (tons)
Primary collector
Secondary collector
Fuel
Release agent
Stack height, m (ft)
Conventional permanent
batch plant
160.3 ± 16%
(177 ± 16%)
3.6 (4.0)
Cyclone
Wet scrubber (venturl)
Oil
Fuel oil
15.85 (52)
Reference 16, Table 16.
The industrial survey showed that over 66 percent of operating
hot mix asphalt plants use fuel oil for combustion. Possible sulfur
oxide emissions from the stack were calculated assuming that all
sulfur in the fuel oil is oxidized to SOX. The amount of sulfur
oxides actually released through the stack may be attenuated by
water scrubbers or even by the aggregate itself, if limestone is
being dried. No. 2 fuel oil has an average sulfur content of
0.22 percent.
Emission factors for nitrogen oxides, nonmethane volatile
organics, carbon monoxide, polycyclic organic material and aldehydes
8.1-8
EMISSION FACTORS
4/81
-------
were determined by sampling stack gas at the representative asphalt
hot mix plant.
The choice of applicable control equipment ranges from dry
mechanical collectors to scrubbers and fabric collectors. Attempts
to apply electrostatic precipitators have met with little success.
Practically all plants use primary dust collection equipment such
as large diameter cyclones, skimmers or settling chambers. These
chambers are often used as classifiers to return collected material
to the hot aggregate elevator combine it with the dryer aggregate
load. The primary collector effluent is ducted to a secondary
collection device because of high emission levels if vented to the
atmosphere.
TABLE 8.1-3. PARTICIPATE EMISSION FACTORS FOR
CONVENTIONAL HOT MIX ASPHALTIC PLANTS3
EMISSION FACTOR RATING: B
Emission Factor
Type of Control kg/Mg Ib/ton
Uncontrolled0 'd
Precleaner^
High efficiency cyclone
Spray tower
Baffle spray tower
Multiple centrifugal scrubber
Orifice scrubber
Venturi scrubber^
Baghouse
22.5
7.5
0.85
0.20
0.15
0.035
0.02
0.02
0.01
45.0
15.0
1.7
0.4
0.3
0.07
(.007-. 138)
0.04
0.04
(.025-. 053)
0.02
(0. 07-. 036)
^References 1, 2, 5-10 and 14-16.
Expressed in terms of emissions per unit weight of asphalt
concrete produced.
Almost all plants have at least a cleaner following the
,rotary dryer.
Reference 16. These factors differ from those given in
Table 8.1-1 because they are for uncontrolled emissions and
are from an earlier survey.
eReference 15. Average emission from a properly designed,
installed, operated and maintained scrubber, based on a
-study to develop New Source Performance Standards.
References 14 and 15.
References 14 and 15. Emissions from a properly designed,
installed, operated and maintained baghouse, based on a study
to develop New Source Performance Standards.
4/81 Mineral Products Industry 8.1-9
-------
Particulate emission factors for conventional asphaltic concrete
plants are presented in Table 8.1-3. Particle size distribution
information has not been included, because the particle size distri-
bution varies with the aggregate being used, the mix being made and
the type of plant operation. Potential fugitive particulate emis-
sion factors for conventional asphaltic concrete plants are shown
in Table 8.1-4.
Particulate emission factors for dryer drum plants are presented
in Table 8.1-5. (There are no data for other pollutants released
from the dryer drum hot mix process.) Particle size distribution
has not been included, because it varies with the aggregate used,
the mix made and the type of plant operation. Emission factors for
particulates in an uncontrolled plant can vary by a factor of 10,
depending upon the percent of fine particles in the aggregate.
References for Section 8.1
1. Asphaltic Concrete Plants Atmospheric Emissions Study,
EPA Contract No. 68-02-0076, Valentine, Fisher, and Tomlinson,
Seattle, WA, November 1971.
2. Guide for Air Pollution Control of Hot Mix Asphalt Plants,
Information Series 17, National Asphalt Pavement Association,
Riverdale, MD.
3. J.A. Danielson, "Control of Asphaltic Concrete Batching Plants
in Los Angeles County", JAPCA, 10(2):29-33, 1960.
4. H.E. Friedrich, "Air Pollution Control Practices and Criteria
for Hot Mix Asphalt Paving Batch Plants", JAPCA, ±9(12) :424-8,
December 1969.
5. Air Pollution Engineering Manual, AP-40, U.S. Environmental
Protection Agency, Research Triangle Park, NC, 1973. Out of
Print.
6. G.L. Allen, et al., "Control of Metallurgical and Mineral Dust
and Fumes in Los Angeles County, California", Information
Circular 7627, U.S. Department of Interior, Washington, DC,
April 1952.
7. P.A. Kenline, Unpublished report on control of air pollutants
from chemical process industries, Robert A. Taft Engineering
Center, Cincinnati, OH, May 1959.
8. G. Sallee, Private communication on particulate pollutant study
between Midwest Research Institute and National Air Pollution
Control Administration, Durham, NC, June 1970.
8.1-10
EMISSION FACTORS
4/81
-------
TABLE 8.1-4. POTENTIAL UNCONTROLLED FUGITIVE
PARTICIPATE EMISSION FACTORS FOR CONVENTIONAL
ASPHALTIC CONCRETE PLANTS
EMISSION FACTOR RATING: E
Partlculates3
Type of Operation kg/Mg Ib/ton
Unloading coarse and fine
aggregate to storage bins^ 0.05 0.10
Cold and dried (and hot)
aggregate elevatorb 0.10 0.20
Screening hot aggregate0 0.013 0.026
^Expressed as units per unit weight of aggregate.
Reference 18. Assumed equal to similar sources.
Reference 19. Asssumed equal to similar crushed
granite processes.
TABLE 8.1-5. PARTICULATE EMISSION FACTORS
FOR DRYER DRUM HOT MIX ASPHALT PLANTS3
EMISSION FACTOR RATING: B
Type of Control
Uncontrolled
Cyclone or multlcyclone
Low energy wet scrubber
Venturi scrubber
Emission
kg/Mg
2.45
0.34
0.04
0.02
b
Factor
Ib/ton
4.9
0.67
0.07
0.04
^Reference 11.
Expressed in terms of emissions per unit weight of
asphalt concrete produced. These factors differ
from those for conventional asphaltic concrete
plants because the aggregate contacts, and is coated
with, asphalt early In the dryer drum process.
CEither stack sprays where water droplets are
injected into the exit stack, or a dynamic scrubber
that incorporates a wet fan.
4/81 Mineral Products Industry 8.1-11
-------
9. J.A. Danielson, Unpublished test data from asphalt batching
plants, Los Angeles County Air Pollution Control District,
Presented at Air Pollution Control Institute, University of
Southern California, Los Angeles, CA, November 1966.
10. M.E. Fogel et al., Comprehensive Economic Study of Air Pollution
Control Costs for Selected Industries and Selected Regions,
R-OU-455, U.S. Environmental Protection Agency, Research
Triangle Park, NC, February 1970.
11. Preliminary Evaluation of Air Pollution Aspects of the Drum
Mix Process, EPA-340/1-77-004, U.S. Environmental Protection
Agency, Research Triangle Park, NC, March 1976.
12. R.W. Beaty and B.M. Bunnell, "The Manufacture of Asphalt
Concrete Mixtures in the Dryer Drum", Presented at the Annual
Meeting of the Canadian Technical Asphalt Association, Quebec
City, Quebec, November 19-21, 1973.
13. J.S. Kinsey, An Evaluation of Control Systems and Mass Emission
Rates from Dryer Drum Hot Asphalt Plants, Colorado Air Pollution
Control Division, Denver, CO, December 1976.
14. Background Information for Proposed New Source Performance
Standards, APTD-1352A and B, U.S. Environmental Protection
Agency, Research Triangle Park, NC, June 1973.
15. Background Information for New Source Performance Standards,
EPA 450/2-74-003, U.S. Environmental Protection Agency, Research
Triangle Park, NC, February 1974.
16. Z.S. Kahn and T.W. Hughes, Source Assessment; Asphalt Paving
Hot Mix, EPA Contract No. 68-02-1874, Monsanto Research
Corporation, Dayton, OH, July 1977.
17. V.P. Puzinauskas and L.W. Corbett, Report on Emissions from
Asphalt Hot Mixes, RR-75-1A, The Asphalt Institute, College
Park, MD, May 1975.
18. Evaluation of Fugitive Dust from Mining, EPA Contract
No. 68-02-1321, Pedco Environmental Specialists, Inc., Cincinnati,
OH, June 1976.
19. J.A. Peters and P.K. Chalekode, "Assessment of Open Sources",
Presented at the Third National Conference on Energy and the
Environment, College Corner, OH, October 1, 1975.
20. Illustration of Dryer Drum Hot Mix Asphalt Plant. Pacific
Environmental Services, Inc., Santa Monica, CA, 1978.
8.1-12 EMISSION FACTORS 4/81
-------
21. Herman H. Forsten, "Applications of Fabric Filters to Asphalt
Plants", Presented at the 71st Annual Meeting of the Air Pol-
lution Control Association, Houston, TX, June 1978.
22. Emission of Volatile Organic Compounds from Drum Mix Asphalt
Plants, EPA Contract No. 68-01-2585, JACA Corporation, Fort
Washington, PA, September 1980.
4/81 Mineral Products Industry 8.1-13
-------
-------
8.2 ASPHALT ROOFING
8.2.1 General1
The asphalt roofing industry manufactures asphalt saturated felt
rolls, shingles, roll roofing with mineral granules on the surface, and
smooth roll roofing that may contain a small amount of mineral dust or
mica on the surface. Most of these products are used in roof construc-
tion, with small quantities used in walls and other building applications.
8.2.2 Process Description
The manufacturing of asphalt felt, roofing, and shingles involves
the saturating and coating of felt with heated asphalt (saturant asphalt
and/or coating asphalt) hy means of dipping and/or spraying. The process
can be divided into (1) asphalt storage, (2) asphalt blowing, (3) felt
saturation, (4) coating and (5) mineral surfacing. Glass fiber is
sometimes used in place of the paper felt, in which case the asphalt
saturation step is bypassed.
Preparation of the asphalt is an integral part of the production of
asphalt roofing. This preparation, called "blowing", involves the
oxidation of asphalt flux by bubbling air through liquid asphalt flux at
260°C (500°F) for 1 to 4.5 hours, depending on the desired characteristics
of the asphalt, such as softening point and penetration rate.2 A typical
plant will blow from four to six batches per 16 hour day, and the roofing
line will operate for 16 hours per day and 5 days per week. Blowing may
be done either in vertical tanks or in horizontal chambers. Inorganic
salts such as ferric chloride (FeCl3) may be used as catalysts to achieve
desired properties and to increase the rate of reaction in the blowing
still, thus decreasing the time required for each blow.3 Air blowing of
asphalt may be conducted at oil refineries, asphalt processing plants,
and asphalt roofing plants. Figure 8.2-1 illustrates an asphalt blowing
operation.
Figure 8.2-2 shows a typical line for the manufacture of
asphalt-saturated felt, which consists of a paper feed roll, a dry looper
section, a saturator spray section (if used), a saturator dipping section,
steam-heated drying-in drums, a wet looper, water cooled rollers, a
finish floating looper, and a roll winder.
Organic felt may weigh from 25 to 55 pounds per 480 square feet (a
common unit in the paper industry), depending upon the intended product.
The felt is unrolled from the unwind stand into the dry looper, which
maintains a constant tension on the material. From the dry looper, the
felt may pass into the spray section of the saturator (not used in all
plants), where asphalt at 205° to 250°C (400° to 480°F) is sprayed onto
one side of the felt through several nozzles. In the saturator dip
section, the saturated felt is drawn over a series of rollers, with the
bottom rollers submerged in hot asphalt at 205° to 250°C (400° to 480°F).
4/81 Mineral Products Industry 8.2-1
-------
KNOCKOUT BOX
OR CYCLONE
WATER VAPOR, OIL
AND PARTICIPATE
ASPHALT
FLUX ~r
125°-1SO°F
a.
BLOWING
STILL
CONTAINING
ASPHALT
WATER VAPOR
PARTICULATE
TO
CONTROL
DEVICE
RECOVERED OIL
WATER
AIR
FUEL
ASPHALT HEATER
AIR BLOWER
BLOWN ASPHALT
Figure 8.2.-1. Air blowing of asphalt.3
At the next step, steam heated drying-in drums and the wet looper provide
the heat and time, respectively, for the asphalt to penetrate the felt.
The saturated felt then passes through water cooled rolls and onto the
finish floating looper, and then is rolled and cut on the roll winder to
product size. Two common weights of asphalt felt are 15 and 30 pounds
per 108 square feet (108 square feet of felt covers exactly 100 square
feet of roof).
A typical process for manufacturing asphalt shingles, mineral
surfaced rolls and smooth rolls is illustrated in Figure 8.2-3. This
line is similar to the felt line, except that following the wet looper are
a coater, a granule applicator, a press section, water cooled rollers, a
finish floating looper, and either a roll winder or a shingle cutter and
stacker. After leaving the wet looper, the saturated felt passes through
the coater. Filled asphalt coating at 180° to 205°C (355° to 400°F) is
released through a valve onto the felt just as it passes into the coater.1
Filled asphalt is prepared by mixing coating asphalt at 205°C (400°F) and
8.2-2
EMISSION FACTORS
4/81
-------
VENT TO CONTROL
EQUIPMENT
BURNER
A
,-- FIRED'"
~ - HEATER
i * 4 •
VENT TO
CONTROL DEVICE
*
i r
SATURANT
STORAGE
• — 1
PUMP
PUK
8.2-2. Schematic of line for manufacturing asphalt saturated felt.1
4/81
Mineral Products Industry
8.2-3
-------
TANK
TRUCK
TANK
TRUCK
iHINCLE STACKER
8.2-3. Schematic of line for manufacturing asphalt shingles, mineral surfaced rolls and smooth
rolls.'
8.2-4
EMISSION FACTORS
4/81
-------
a mineral stabilizer (filler) in approximately equal proportions. The
filled asphalt is pumped to the coater. Sometimes the mineral stabilizer
is dried at about 120°C (250°F) in a dryer before mixing with the coating
asphalt. Heated squeeze rollers in the coater distribute the coating
evenly upon the felt surface, to form a thick base coating to which rock
granules, sand, talc, or mica can adhere. After leaving the coater, a
felt to be made into shingles or mineral surfaced rolls passes through
the granules applicator where granules are fed onto the hot, coated
surface. The granules are pressed into the coating as it passes through
squeeze rollers. Sand, talc or mica is applied to the back, or opposite,
side of the felt and is also pressed into the felt surface. Following
the application of the granules, the felt is cooled rapidly and is
transferred through the finish flowing looper to a roll winder or shingle
cutter.
8.2.3 Emissions and Controls
The atmospheric emissions from asphalt roofing manufacturing are:
1. gaseous and particulate organic compounds that include small
amounts of particulate polycyclic organic matter (PPOM),
2. emissions of small amounts of aldehydes, carbon monoxide and
sulfur dioxide, and
3. particulate emissions from mineral handling and storage.
The sources of the above pollutants are the asphalt blowing stills,
the saturator and coater, the asphalt storage tanks, and the mineral
handling and storage facilities. Emission factors from uncontrolled
blowing and saturating processes for particulate, carbon monoxide, and
volatile organic carbon as methane and nonmethane are summarized in
Table 8.2-1.
A common method to control emissions at asphalt roofing plants is
completely to enclose the saturator, wet looper and coater and then to
vent the emissions to one or more control devices (see Figures 8.2-2 and
8.2-3). Fugitive emissions from the saturator may pass through roof
vents and other openings in the building, if the saturator enclosure is
not properly installed and maintained. Control devices used in the
industry include afterburners, high velocity air filters, low voltage
electrostatic precipitators, and wet scrubbers. Blowing operations are
controlled by afterburners. Table 8.2-2 presents emission factors for
controlled blowing and saturating processes.
Particulate emissions associated with mineral handling and storage
operations are captured by enclosures, hoods or pickup pipes and are
controlled by using cyclones and/or fabric filters with removal
efficiencies of approximately 80-99 percent.
4/81 Mineral Products Industry 8.2-5
-------
TABLE 8.2-1. EMISSION FACTORS FOR ASPHALT ROOFING MANUFACTURING
WITHOUT CONTROLS3
EMISSION FACTOR RATING: PARTICULATE- A
OTHER- D
Volatile
Particulates
Operation
Asphalt blowing
c
Saturant
Coating
f
kg/Mg
3.6
13.4
Ib/ton
7
26
.2
.7
Carbon
monoxide
kg/Mg
0.14d
Ib/ton
0.27d
o
rganic
methane
kg/Mg
e
0.94
Ib/ton
e
1.88
compounds
nonme thane
kg/Mg
e
0.93
Ib/ton
e
1.
86
Shingle
saturation8 0.25
Shingle ,
saturation 1.57
0.50 0.01 0.02 0.04 0.08 0.01 0.02
3.14 0.13 0.25 0.11 0.22 0.02 0.03
.References 2 and 4.
Expressed as kg/Mg (Ib/ton) of asphalt processed.
^Saturant blow of 1.5 hours.
Reference 2. CO data for uncontrolled emissions from stills was not
obtained during latest test program.
SSpecies data not available for saturant blow. Total organics (as CH4) for
saturant blow are 0.73 kg/Mg (1.460 Ib/ton).
Coating blow of 4.5 hours.
Expressed as kg/Mg (Ib/ton) of 106.5 kg (235 Ib) shingle produced. Data
.from dip saturators.
Data from spray/dip saturator.
NOTES: -Particulate polycyclic organic matter is about 0.3 % of
particulate for blowing stills and 0.1 % of particulate for saturators.
-Aldehyde emission measurements made during coating blows:
4.6x10~5 kg/Mg (9.2xlO~5 Ib/ton).
-Aldehyde emissions data taken from one saturator only, with
afterburner the control device: 0.004 kg/Mg (0.007 Ib/ton).
-Species data not obtained for uncontrolled VOC, assumed same
percentage methane/nonmethane as in controlled emissions.
8.2-6
EMISSION FACTORS
4/81
-------
TABLE 8.2-2.
EMISSION FACTORS FOR ASPHALT ROOFING MANUFACTURING
WITH CONTROLS3
EMISSION FACTOR RATING:
PARTICULATE- A
OTHER- D
Operation
Particulates
Carbon
monoxide
Volatile
organic compounds
methane
nonmethane
kg/Mg Ib/ton kg/Mg Ib/ton kg/Mg Ib/ton kg/Mg Ib/ton
Asphalt blowing
SaturantC 0.25
Coating6 0.45
0.50 0.6 1.2 d d d d
0.89 4.4 8.8 0.05 0.10 0.05 0.09
Shingle , ,
saturation
0.03
0.06 0.45
0.898 0.08
0.15 0.01
0.02
.References 2 and 4.
Expressed as kg/Mg (Ib/ton) of asphalt processed.
,Saturant blow of 1.5 hours.
Species data not available for saturant blow. Total organics (as CH4) for
saturant blow are 0.015 kg/Mg (0.03 Ib/ton).
fCoating blow of 4.5 hours.
Expressed as kg/Mg (Ib/ton) of 106.5 kg (235 Ib) shingle produced
(averages of test data from four plants).
*CO emissions data taken from one plant only, with afterburner the
control device. Temperature of afterburner not high enough to convert
CO to C02.
NOTE: Particulate polyclic organic matter is about 0.03 % of particulate
for blowing stills and about 1.1 % of particulate for saturators.
4/81
Mineral Products Industry
8.2-7
-------
1
In this industry, closed silos are used for mineral storage, so open
storage piles are not a problem. To protect the minerals from moisture
pickup, all conveyors that are outside the buildings are enclosed.
Fugitive mineral emissions may occur at the unloading point, depending on
the type of equipment used. The discharge from the conveyor to the silos
is controlled by either a cyclone or a fabric filter.
References for Section 8.2
1. John A. Danielson, Air Pollution Engineering Manual (2d Ed.), AP-40,
U.S. Environmental Protection Agency, Research Triangle Park, NC,
May 1973. Out of print.
2. Atmospheric Emissions from Asphalt Roofing Processes, EPA Contract
No. 68-02-1321, Pedco Environmental, Cincinnati, OH, October 1974.
3. L. W. Corbett, "Manufacture of Petroleum Asphalt", Bituminous
Materials: Asphalts, Tars, and Pitches, Vol. 2, Part 1, New York,
Interscience Publishers, 1965.
4. Background Information for Proposed Standards Asphalt Roofing
Manufacturing Industry, EPA 450/3-80-021a, U.S. Enviromental
Protection Agency, Research Triangle Park, NC, June 1980.
8.2-8
EMISSION FACTORS
4/81
-------
8.3 BRICKS AND RELATED CLAY PRODUCTS
8.3.1 Process Description
The manufacture of brick and related products such as clay pipe, pottery, and some types of refractory brick
involves the mining, grinding, screening, and blending of. the raw materials, and the forming, cutting or shaping,
drying or curing, and firing of the final product.
Surface clays and shales are mined in open pits; most fine clays are found underground. After mining, the
material is crushed to remove stones and stirred before it passes onto screens that are used to segregate the
particles by size.
At the start of the forming process, clay is mixed with water, usually in a pug mill. The three principal
processes for forming brick are: stiff-mud, soft-mud, and dry-process. In the stiff-mud process, sufficient water is
added to give the clay plasticity; bricks are then formed by forcing the clay through a die and using cutter wire to
separate the bricks. All structural tile and most brick are formed by this process. The soft-mud process is usually
used when the clay contains too much water for the stiff-mud process. The clay is mixed with water until the
moisture content reaches 20 to 30 percent, and the bricks are formed in molds. In the dry-press process, clay is
mixed with a small amount of water and formed in steel molds by applying a pressure of 500 to 1500 psi. The
brick manufacturing process is shown in Figure 8.3-1.
Before firing, the wet clay units that have been formed are almost completely dried in driers that are usually
heated by waste heat from the kilns. Many types of kilns are used for firing brick; however, the most common are
the tunnel kiln and the periodic kiln. The downdraft periodic kiln is a permanent brick structure that has a
number of fireholes where fuel is fired into the furnace. The hot gases from the fuel are drawn up over the bricks,
down through them by underground flues, and out of the oven to the chimney. Although fuel efficiency is not as
high as that of a tunnel kiln because of lower heat recovery, the uniform temperature distribution through the
kiln leads to a good quality product. In most tunnel kilns, cars carrying about 1200 bricks each travel on rails
through the kiln at the rate of one 6-foot car per hour. The fire zone is located near the middle of the kiln and
remains stationary.
In all kilns, firing takes place in six steps: evaporation of free water, dehydration, oxidation, vitrification,
flashing, and cooling. Normally, gas or residual oil is used for heating, but coal may be used. Total heating time
varies with the type of product; for example, 9-inch refractory bricks usually require 50 to 100 hours of firing.
Maximum temperatures of about 2000° F (1090°C) are used in firing common brick.
8.3.2 Emissions and Controls1 •3
Particulate matter is the primary emission in the manufacture of bricks. The main source of dust is the
materials handling procedure, which includes drying, grinding, screening, and storing the raw material.
Combustion products are emitted from the fuel consumed in the curing, drying, and firing portion of the process.
Fluorides, largely in gaseous form, are also emitted from brick manufacturing operations. Sulfur dioxide may be
emitted from the bricks when temperatures reach 2500°F (1370°C) or greater; however, no data on such
emissions are available.4
4/73 Mineral Products Industry 8.3-1
-------
(P)
PULVERIZING
(P)
SCREENING
t
)
GLAZING
_
(P)
DRYING
HOT
GASES
4
FUEL
*•
t
(P)
KILN
(P)
STORAGE
AND
SHIPPING
Figure 8.3-1. Basic flow diagram of brick manufacturing process.
source of particulate emissions.
'P" denotes a major
A variety of control systems may be used to reduce both particulate and gaseous emissions. Almost any type
of particulate control system will reduce emissions from the material handling process, but good plant design and
hooding are also required to keep emissions to a minimum.
The emissions of fluorides can be reduced by operating the kiln at temperatures below 2000°F (1090°C) and
by choosing clays with low fluoride content. Satisfactory control can be achieved by scrubbing kiln gases with
water; wet cyclonic scrubbers are available that can remove fluorides with an efficiency of 95 percent, or higher.
Emission factors for brick manufacturing are presented in Table 8.3-1. Insufficient data are available to present
particle size information.
8.3-2
EMISSION FACTORS
4/73
-------
J^
w
Table 8.3-1. EMISSION FACTORS FOR BRICK MANUFACTURING WITHOUT CONTROLS3
EMISSION FACTOR RATING: C
Type of process
Raw material handling0
Dryers, grinders, etc.
Storage
Curing and firingd
Tunnel kilns
Gas-fired
Oil-fired
Coal-fired
Periodic kilns
Gas- fired
Oil-fired
Coal-fired
Participates
fb/ton
96
34
0.04
0.6
1.0A
0.11
0.9
1.6A
kg/MT
48
17
0.02
0.3
0.5A9
0.05
0.45
0.8A
Sulfur oxides
(SOJ
Ib/ton
—
—
Nege
4.0Sf
7.2S
Neg
5.9S
12. OS
kg/MT
-
—
Neg
2. OS
3.6S
Neg
2.95S
6.0S
Carbon monoxide
(CO)
Ib/ton
-
—
0.04
Neg
1.9
0.11
Neg
3.2
kg/MT
—
—
0.02
Neg
0.95
0.05
Neg
1.6
Hydrocarbons
(HC)
Ib/ton
-
—
0.02
0.1
0.6
0.04
0.1
0.9
kg/MT
—
Nitrogen oxides
{NOJ
Ib/ton
—
— ! —
0.01
0.05
0.3
0.02
0.05
0.45
0.15
1.1
0.9
0.42
1.7
1.4
kg/MT
—
—
0.08
0.55
0.45
0.21
0.85
0.70
Fluor id esb
(HF)
Ib/ton
—
_
1.0
1.0
1.0
1.0
1.0
1.0
kg/MT
-
—
0.5
0.5
0.5
0.5
0.5
0.5
s
5-
o
a,
e
o
CL
C
VI
f-i-
i-(
«<
aOne brick weighs about 6.5 pounds (2.95 kg}. Emission factors expressed as units per unit weight of brick produced,
Based on data from References 3 and 6 through 1 0.
c Based on data from sections on ceramic clays and cement manufacturing in this publication. Because of process variation, some steps may be omitted. Storage losses
apply only to that quantity of material stored.
Based on data from References 1 and 5 and emission factors for fuel combustion.
"Negligible.
S is the percent sulfur in the fuel.
^A is the percent ash in the coal.
o
-------
References for Section 8.3
1. Air Pollutant Emission Factors. Final Report. Resources Research, Inc., Reston, Virginia. Prepared for
National Air Pollution Control Administration, Durham, N.C., under Contract Number CPA-22-69-119 April
1970.
2. Technical Notes on Brick and Tile Construction. Structural Clay Products Institute. Washington, D.C.
Pamphlet Number 9. September 1961.
3. Unpublished control techniques for fluoride emissions. Environmental Protection Agency, Office of Air
Programs, Research Triangle Park, N.C.
4. Allen, M. H. Report on Air Pollution, Air Quality Act of 1967 and Methods of Controlling the Emission of
Particulate and Sulfur Oxide Air Pollutants. Structural Clay Products Institute, Washington, D. C. September
1969.
5. Norton, F. H. Refractories, 3rd Ed. New York, McGraw-Hill Book Company. 1949.
6. Semran, K. T. Emissions of Fluorides from Industrial Processes: A Review. J. Air Pol. Control Assoc.
7(2):92-l08. August 1957.
7. Kirk-Othmer. Encyclopedia of Chemical Technology, Vol. V, 2nd Ed. New York, Interscience (John Wiley
and Sons, Inc.), 1964. p. 561-567.
8. Wentzel, K. F. Fluoride Emissions in the Vicinity of Brickworks. Staub. 25(3):45-50. March 1965.
9. Allen, G. L. et al. Control of Metallurgical and Mineral Dusts and Fumes in Los Angeles County. U. S.
Department of Interior, Bureau of Mines. Washington, D.C. Information Circular Number 7627. April 1952.
10. Private communication between Resources Research, Inc. Reston, Va. and the State of New Jersey Air
Pollution Control Program, Trenton. July 20, 1969.
8.3-4 EMISSION FACTORS 4/73
-------
8.4 CALCIUM CARBIDE MANUFACTURING
8.4.1 General
Calcium carbide (CaC£) is manufactured by heating a lime and carbon
mixture to 2,000 to 2,100°C (3,632 to 3,812°F) in an electric arc furnace.
At those temperatures, the lime is reduced by carbon to calcium carbide and
carbon monoxide, according to the following reaction:
CaO + 3C
CaC2 + CO
Lime for the reaction is usually made by reducing limestone in a kiln at the
plant site. The sources of carbon for the reaction are petroleum coke,
metallurgical coke or anthracite coal. Because impurities in the furnace
charge remain in the calcium carbide product, the lime should contain no more
than 0.5 percent each of magnesium oxide, aluminum oxide and iron oxide, and
0.004 percent phosphorous. Also, the coke charge should be low in ash and
sulfur. Analyses indicate that 0.2 to 1.0 percent ash and 5 to 6 percent
sulfur are typical in petroleum coke. About 991 kilograms (2,185 Ib) of
lime, 683 kilograms (1,506 Ib) of coke, and 17 to 20 kilograms (37 to 44 Ib)
of electrode paste are required to produce one megagram (2,205 Ib) of calcium
carbide.
The process for manufacturing calcium carbide is illustrated in
Figure 8.4-1. Moisture is removed from coke in a coke dryer, while lime-
stone is converted to lime in a lime kiln. Fines from coke drying and lime
operations are removed and may be recycled. The two charge materials are
then conveyed to an electric arc furnace, the primary piece of equipment used
to produce calcium carbide. There are two basic types of electric arc
furnaces, the open furnace, in which the carbon monoxide burns to carbon
dioxide when it contacts the air above the charge, and the closed furnace, in
which the gas is collected from the furnace and either used as fuel for other
processes or flared. Electrode paste composed of coal tar pitch binder and
1/84
Figure 8.4-1. Calcium carbide manufacturing process.
Mineral Products Industry
i.4-1
-------
anthracite coal is continuously fed into a steel casing where it is baked by
heat from the electric arc furnace before introduction into the furnace. The
baked electrode exits the steel casing just Inside the furnace cover and is
consumed in the calcium carbide production process. Molten calcium carbide
is tapped continuously from the furnace into chill cars and is allowed to
cool and solidify. Then, primary crushing of the solidified calcium carbide
by jaw crushers is followed by secondary crushing and screening for size. To
prevent explosion hazards from acetylene generated by reaction of calcium
carbide with ambient moisture, crushing and screening operations may be
performed in an air swept environment before the calcium carbide has
completely cooled or may be carried out in an inert atmosphere. The calcium
carbide product is used primarily in acetylene generation and also as a
desulfurizer of iron.
8.4.2 Emissions and Controls
Emissions from calcium carbide manufacturing include particulate matter,
sulfur oxides, carbon monoxide and hydrocarbons. Particulate matter is
emitted from a variety of equipment and operations in the production of
calcium carbide, including the coke dryer, lime kiln, electric furnace, tap
fume vents, furnace room vents, primary and secondary crushers, and conveying
equipment. (Lime kiln emission factors are presented in Section 8.15.)
Particulate matter emitted from process sources such as the electric furnace
are ducted to a particulate control device, usually fabric filters and wet
scrubbers. Fugitive particulate matter from sources such as tapping opera-
tions, furnace room and conveyors is captured and sent to a particulate
control device. The composition of the particulate matter emissions varies
according to the specific equipment or operation, but the primary components
are magnesium, calcium and carbon compounds. Sulfur oxides are emitted by
the electric furnace from volatilization and oxidation of sulfur in the coke
feed and by the coke dryer and lime kiln from fuel combustion. These process
sources are not controlled specifically for sulfur oxide emissions. Carbon
monoxide is a byproduct of calcium carbide formation in the electric furnace.
Carbon monoxide emissions to the atmosphere are usually negligible. In open
furnaces, carbon monoxide is oxidized to carbon dioxide, thus eliminating
carbon monoxide emissions. In closed furnaces, a portion of the generated
carbon monoxide is burned in the flames surrounding the furnace charge holes,
and the remaining carbon monoxide is used as fuel for other processes or is
flared. The only potential source of hydrocarbon emissions from the manu-
facture of calcium carbide is the coal tar pitch binder in the furnace
electrode paste. Since the maximum volatiles content in the electrode paste
is about 18 percent, the electrode paste represents only a small potential
source of hydrocarbon emissions. In closed furnaces, actual hydrocarbon
emissions from consumption of electrode paste typically are negligible due to
high furnace operating temperature and flames surrounding the furnace charge
holes. Hydrocarbon emissions from open furnaces are also expected to be
negligible because of high furnace operating temperature and the presence of
excess oxygen above the furnace.
Table 8.4-1 gives controlled and uncontrolled emission factors for
various processes in the manufacture of calcium carbide. Controlled factors
are based on test data and permitted emissions for operations with the fabric
filters and wet scrubbers that are typically used to control particulate
emissions in calcium carbide manufacturing.
8.4-2 EMISSION FACTORS 1/84
-------
CO
.p-
TABLE 8.4-1. EMISSION FACTORS FOR CALCIUM CARBIDE MANUFACTURING PLANTS
Process
Particulate Matter
Uncontrolled Controlled1"
Electric
Q
furnace main stack
g Coke dryer
inera
M
0
o
;s Industr-
Tap fume
Furnace
Primary
Circular
Factors
P1or-*-f i
vents
room vents
and secondary crushing
charging conveyor
are in kg/Mg (Ib/ton)
r* -f n-rn ones* n-riFna-ril^j n
12 (24)
1.0 (2.0)
ND
13 (26)
ND
ND
of calcium
0
0
0
0
0
0
.39
.13
.07
.07
.57
.17
carbide
(0
(0
(0
(0
(1
(0
.78)
.26)
.14)
.14)
.14)
.34)
produced.
TiT-l t-"h GfTlO 1 1
Sulfur- Oxides Emission Factor
Rating
1.5 (3.0) B, C
1.5 (3.0) C
0 C
0 C
0 C
0 C
ND - No data.
omnnnf-e nf r* u 1 r»-inm r» a -rh n-n a 1 iimi niltn
iron, silicon compounds. Coke dryer: carbon compounds. Tap fume vents and furnace room vents:
carbon, calcium, magnesium, silicon, iron compounds. Primary and secondary crushing: calcium
carbide. Circular charging conveyor: lime, coke.
"Based on emissions data and not on assumed control efficiencies.
Uncontrolled.
a
"Rating is B for particulate matter emission factor, C for sulfur oxides. Factors applicable to
open furnaces using petroleum coke.
oo
-P-
OJ
-------
References for Section 8.4
1. "Permits to Operate: Airco Carbide, Louisville, Kentucky", Jefferson
County Air Pollution Control District, Louisville, KY, December 16,
1980.
2. "Manufacturing or Processing Operations: Airco Carbide, Louisville,
Kentucky", Jefferson County Air Pollution Control District, Louisville,
KY, September 1975.
3. Written communication from A. J. Miles, Radian Corp., Durham, NC, to
Douglas Cook, U. S. Environmental Protection Agency, Atlanta, GA,
August 20, 1981.
4. "Furnace Offgas Emissions Survey: Airco Carbide, Louisville, Kentucky",
Environmental Consultants, Inc., Clarksville, IN, March 17, 1975.
5. J. W. Frye, "Calcium Carbide Furnace Operation", Electric Furnace
Conference Proceedings, American Institute of Mechanical Engineers, New
York, December 9-11, 1970.
6. The Louisville Air Pollution Study, U. S. Department of Health and Human
Services, Robert A. Taft Center, Cincinnati, OH, 1961.
7. R. N. Shreve and J. A. Brink, Jr., Chemical Process Industries, Fourth
Edition, McGraw Hill Company, New York, 1977.
8. J. H. Stuever, "Particulate Emissions - Electric Carbide Furnace Test
Report: Midwest Carbide, Pryor, Oklahoma", Stuever and Associates,
Oklahoma City, OK, April 1978.
9. L. Thomsen, "Particulate Emissions Test Report: Midwest Carbide,
Keokuk, Iowa", Beling Consultants, Inc., Moline, IL, July 1, 1980.
10. D. M. Kirkpatrick, "Acetylene from Calcium Carbide Is an Alternate
Feedstock Route", Oil and Gas Journal, June 7, 1976.
11. L. Clarke and R. L. Davidson, Manual for Process Engineering
Calculations, Second Edition, McGraw-Hill Company, New York, 1962.
8.4-4 EMISSION FACTORS 1/84
-------
8.5 CASTABLE REFRACTORIES
8.5.1 Process Description
1-3
Castable or fused-cast refractories are manufactured by carefully blending such components as alumina,
zirconia, silica, chrome, and magnesia; melting the mixture in an electric-arc furnace at temperatures of 3200 to
4500°F (1760 to 2480°C); pouring it into molds; and slowly cooling it to the solid state. Fused refractories are
less porous and more dense than kiln-fired refractories.
8.5.2 Emissions and Controls1
Particulate emissions occur during the drying, crushing, handling, and blending of the components; during the
actual melting process; and in the molding phase. Fluorides, largely in the gaseous form, may also be emitted
during the melting operations.
The general types of particulate controls may be used on the materials handling aspects of refractory
manufacturing. Emissions from the electric-arc furnace, however, are largely condensed fumes and consist of very
fine particles. Fluoride emissions can be effectively controlled with a scrubber. Emission factors for castable
refractories manufacturing are presented in Table 8.5-1.
Table 8.5-1. PARTICULATE EMISSION FACTORS FOR CASTABLE
REFRACTORIES MANUFACTURING8
EMISSION FACTOR RATING: C
Type of process
Raw material dryerb
Raw material crushing
and processingc
Electric-arc meltingd
Curing oven6
Molding and shakeoutb
Type of control
Baghouse
Scrubber
Cyclone
Baghouse
Scrubber
-
Baghouse
Uncontrolled
Ib/ton
30
120
50
0.2
25
kg/MT
15
60
25
0.1
12.5
Controlled
Ib/ton
0.3
7
45
0.8
10
-
0.3
kg/MT
0.15
3.5
22.5
0.4
5
-
0.15
aFluoride emissions from the melt average about 1.3 pounds of HF per ton of melt (0.65 kg
HF/MT melt). Emission factors expressed as units per unit weight of feed material.
^Reference 4.
cReferences 4 and 5.
References 4 through 6.
eReference 5.
2/72
Mineral Products Industry
8.5-1
-------
References for Section 8.5
1. Air Pollutant Emission Factors. Final Report. Resources Research, Inc. Reston, Va. Prepared for National
Air Pollution Control Administration, Durham, N.C., under Contract Number CPA-22-69-1 1 9. April 1970.
2' ?6°T969R' W' 3nd K' H' Sandmeyer" APPlications of Fused-Cast Refractories. Chem. Eng. 76:106-114, June
3. Shreve, R.N. Chemical Process Industries, 3rd Ed. New York, McGraw-Hill Book Company. 1967. p. 158.
4. Unpublished data provided by a Corhart Refractory. Kentucky Department of Health, Air Pollution Control
Commission. Frankfort, Kentucky. September 1969.
5. Unpublished stack test data on refractories. Resources Research, Incorporated. Reston, Virginia. 1 969.
6. Unpublished stack test data on refractories. Resources Research, Incorporated. Reston, Virginia. 1967.
8-5-2 EMISSION FACTORS 2/72
-------
8.6 PORTLAND CEMENT MANUFACTURING
8.6.1 Process Description }"3
Portland cement manufacture accounts for about 98 percent of the cement production in the United States.
The more than 30 raw materials used to make cement may be divided into four basic components: lime
(calcareous), silica (siliceous), alumina (argillaceous), and iron (ferriferous). Approximately 3200 pounds of dry
raw materials are required to produce 1 ton of cement. Approximately 35 percent of the raw material weight is
removed as carbon dioxide and water vapor. As shown in Figure 8.6-1, the raw materials undergo separate
crushing after the quarrying operation, and, when needed for processing, are proportioned, ground, and blended
using either the wet or dry process.
In the dry process, the moisture content of the raw material is reduced to less than 1 percent either before or
during the grinding operation. The dried materials are then pulverized into a powder and fed directly into a rotary
kiln. Usually, the kiln is a long, horizontal, steel cylinder with a refractory brick lining. The kilns are slightly
inclined and rotate about the longitudinal axis. The pulverized raw materials are fed into the upper end and travel
slowly to the lower end. The kilns are fired from the lower end so that the hot gases pass upward and through the
raw material. Drying, decarbonating, and calcining are accomplished as the material travels through the heated
kiln, finally burning to incipient fusion and forming the clinker. The clinker is cooled, mixed with about 5
percent gypsum by weight, and ground to the final product fineness. The cement is then stored for later
packaging and shipment.
With the wet process, a slurry is made by adding water to the initial grinding operation. Proportioning may
take place before or after the grinding step. After the materials are mixed, the excess water is removed and final
adjustments are made to obtain a desired composition. This final homogeneous mixture is fed to the kilns as a
slurry of 30 to 40 percent moisture or as a wet filtrate of about 20 percent moisture. The burning, cooling,
addition of gypsum, and storage are carried out as in the dry process.
8.6.2 Emissions and Controls1'2-4
Particulate matter is the primary emission in the manufacture of portland cement. Emissions also include the
normal combustion products of the fuel used to supply heat for the kiln and drying operations, including oxides
of nitrogen and small amounts of oxides of sulfur.
Sources of dust at cement plants include: (1) quarrying and crushing, (2) raw material storage, (3) grinding and
blending (dry process only), (4) clinker production, (5) finish grinding, and (6) packaging. The largest source of
emissions within cement plants is the kiln operation, which may be considered to have three units: the feed
system, the fuel-firing system, and the clinker-cooling and handling system. The most desirable method of
disposing of the collected dust is injection into the burning zone of the kiln and production of clinkers from the
dust. If the alkali content of the raw materials is too high, however, some of the dust is discarded or leached
before returning to the kiln. In many instances, the maximum allowable alkali content of 0.6 percent (calculated
as sodium oxide) restricts the amount of dust that can be recycled. Additional sources of dust emissions are raw
material storage piles, conveyors, storage silos, and loading/unloading facilities.
The complications of kiln burning and the large volumes of materials handled have led to the adoption of
many control systems for dust collection. Depending upon the emission, the temperature of the effluents in the
•1/73 Mineral Products Industry 8.6-1
-------
00
QUARRYING
RAW
MATERIALS
"
PRIMARY AND
SECONDARY
CRUSHING
cn
cfl
MM
o
i
SLURRY MIXING
AND
BLENDING
-
STORAGE
KILN
CLINKER
COOLER
STORAGE
AIR
SEPARATOR
STORAGE
Figure 8.6-1. Basic flow diagram of Portland cement manufacturing process.
OJ
-------
plant in question, and the particulate emission standards in the community, the
cement industry generally uses mechanical collectors, electrical precipitators,
fabric filter (baghouse) collectors, or combinations of these devices to control
emissions.
Table 8.6-1 summarizes emission factors for cement manufacturing and also
includes in footnote d typical control efficiencies of particulate emissions.
Table 8.6-2 indicates the particle size distribution for particulate emissions
from kilns and cement plants before control systems are applied.
TABLE 8.6-1. EMISSION FACTORS FOR CEMENT MANUFACTURING
WITHOUT CONTROLS*1 >b>c>d
EMISSION FACTOR RATING: B
Pry Process Wet Process
Pollutant Dryers, Dryers,
Kilns grinders, etc. Kilns grinders, etc.
Particulate15
kg/Mg 122.0 48.0 114.0 16.0
Ib/ton 245.0 96.0 228.0 32.0
Sulfur dioxldef
Mineral source
kg/Mg
Ib/ton
Gas combustion
kg/Mg
Ib/ton
Oil combustion
kg/Mg
Ib/ton
Coal combustion
kg/Mg
Ib/ton
Nitrogen oxides
kg/Mg
Ib/ton
Lead
kg/Mg
Ib/ton
5.1
10.2
Negh
Neg
2. IS1
4.2S
3.4S
6.8S
1.3
2.6
0.06
0.12
5.1
10.2
Neg
Neg
2. IS
4.2S
3.4S
6.8S
:.3
2.6
0.02 . 0.05
0.04 0.10
-
-
-
-
-
-
-
-
-
-
0.01
0.02
aOne barrel of cement weighs 171 kg (376 pounds).
bThese emission factors include emissions from fuel combustion, which should not
be calculated separately.
References 1-2.
"Emission factors expressed in weight per unit weight of cement produced. Dash
Indicates no available data.
eTypical collection efficiencies for kilns, dryers, grinders, etc., are: multi-
cyclones, 80%; electrostatic precipitators, 95X; electrostatic precipitators with
multicyclones, 97.5%; fabric filter units, 99.8%.
*The sulfur dioxide factors presented take into account the reactions with the alk-
aline dusts when no baghouses are used. With baghouses, approximately 50% more SO2
is removed because of reactions with the alkaline particulate filter cake. Also
note that the total S02 from the kiln is determined by summing emission contribu-
tions from the mineral source and the appropriate fuel.
SThese emissions are the result of sulfur being present in the raw materials and are
thus dependent upon source of the raw materials used. The 5.1 kg/Mg (10.2 Ib/ton)
factors account for part of the available sulfur remaining behind in the product
because of its alkaline nature and affinity for S02-
Negligible.
*-S => % sulfur in fuel.
JReferences 7-8.
12/81 Mineral Products Industry 8.6-3
-------
TABLE 8.6-2. SIZE DISTRIBUTION OF DUST EMITTED
FROM UNCONTROLLED KILN OPERATIONS1>5
Particle size, Kiln dust finer than corresponding
microns particle size.%
60 93
50 90
40 84
30 74
20 58
10 38
5 23
1 3
Sulfur dioxide may be generated from the sulfur compounds in the ores as
well as from combusion of fuel. The sulfur content of both ores and fuels will
vary from plant to plant and with geographic location. The alkaline nature of
the cement, however, provides for direct absorption of S02 into the product.
The overall control inherent In the process Is approximately 57 percent or
greater of the available sulfur in ore and fuel if a baghouse that allows the
S02 to come in contact with the cement dust is used. Control, of course, will
vary according to the alkali and sulfur content of the raw materials and fuel.*'
References for Section 8.6
1. T. E. Kreichelt, D. A. Kemnitz, and S. T. Cuffe, Atmospheric Emissions
from the Manufacture of Portland Cement, U.S. DHEW, Public Health Service,
Cincinnati, OH, PHS Publication Number 999-AP-17, 1967.
2. Unpublished standards of performance for new and substantially modified
Portland cement plants, U.S. Environmental Protection Agency, Bureau of
Stationary Source Pollution Control, Research Triangle Park, NC, August
1971.
3. A Study of the Cement Industry in the State of Missouri, Resources Re-
search Inc., Reston, VA, prepared for the Air Conservation Commission of
the State of Missouri, December 1967.
4. Standards of Performance for New Stationary Sources, U.S. Environmental
Protection Agency, Federal Register 36(247,Pt II): December 23, 1971.
5. Particulate Pollutant System Study, Midwest Research Institute, Kansas
City, MO, prepared for U.S. Environmental Protection Agency, Air Pollution
Control Office, Research Triangle Park, NC, under Contract Number CPA-22-
69-104, May 1971.
6. Restriction of Emissions from Portland Cement Works, VDI Richtlinien,
Dusseldorf, Germany, February 1967.
7. Emission Tests Nos. 71-MM-02, 71-MM-03 and 71-MM-05, Office of Air Quality
Planning and Standards, Research Triangle Park, NC, March-April 1972.
8. Control Techniques for Lead Air Emissions, EPA 450/2-77-012, U. S. Environ-
mental Protection Agency, Research Triangle Park, NC, December 1972.
8.6-4 EMISSION FACTORS 12/81
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8.7 CERAMIC CLAY MANUFACTURING
8.7.1 Process Description1
The manufacture of ceramic clay involves the conditioning of the basic ores by several methods. These include
the separation and concentration of the minerals by screening, floating, wet and dry grinding, and blending of the
desired ore varieties. The basic raw materials in ceramic clay manufacture are kaolinite (A^C^'SSiOo-lrhO)
and montmorillonite [(Mg, Ca) O-A^C^-SSiC^'nt^O] clays. These clays are refined by separation and
bleaching, blended, kiln-dried, and formed into such items as whiteware, heavy clay products (brick, etc.),
various stoneware, and other products such as diatomaceous earth, which is used as a filter aid.
8.7.2 Emissions and Controls1
Emissions consist primarily of particulates, but some fluorides and acid gases are also emitted in the drying
process. The high temperatures of the firing kilns are also conducive to the fixation of atmospheric nitrogen and
the subsequent release of NO, but no published information has been found for gaseous emissions. Particulates
are also emitted from the grinding process and from storage of the ground product.
Factors affecting emissions include the amount of material processed, the type of grinding (wet or dry), the
temperature of the drying kilns, the gas velocities and flow direction in the kilns, and the amount of fluorine in
the ores.
Common control techniques include settling chambers, cyclones, wet scrubbers, electrostatic precipitators, and
bag filters. The most effective control is provided by cyclones for the coarser material, followed by wet scrubbers,
bag filters, or electrostatic precipitators for dry dust. Emission factors for ceramic clay manufacturing are
presented in Table 8.7-1.
Table 8.7-1. PARTICIPATE EMISSION FACTORS FOR CERAMIC CLAY MANUFACTURING3
EMISSION FACTOR RATING. A
Type of process
Dryingd
Grinding6
Storaged
Uncontrolled
Ib/ton
70
76
34
kg/MT
35
38
17
Cyclone6
Ib/ton
18
19
8
kg/MT
9
9.5
4
Multiple-unit
cyclone and scrubber0
Ib/ton
7
-
-
kg/MT
3.5
-
-
aEmission factors expressed as units per unit weight of input to process.
"Approximate collection efficiency: 75 percent.
cApproximate collection efficiency: 90 percent.
^References 2 through 5.
e Reference 3,
2/72
Mineral Products Industry
8.7-1
-------
References for Section 8.7-1
1. Air Pollutant Emission Factors. Final Report. Resources Research, Inc. Reston, Va. Prepared for National
Air Pollution Control Administration, Durham, N.C., under Contract Number CPA-22-69-119. April 1970.
2. Allen, G. L. et al. Control of Metallurgical and Mineral Dusts and Fumes in Los Angeles County Department
of Interior, Bureau of Mines. Washington, D.C. Information Circular Number 7627. April 1952.
3. Private Communication between Resources Research, Incorporated, Reston, Virginia, and the State of New
Jersey Air Pollution Control Program, Trenton, New Jersey. July 20,1969.
4. Henn, J. J. et al. Methods for Producing Alumina from Clay: An Evaluation of Two Lime Sinter Processes
Department of Interior, Bureau of Mines. Washington, D.C, Report of Investigations Number 7299
September 1969.
5. Peters, F. A. et al. Methods for Producing Alumina from Clay: An Evaluation of the Lime-Soda Sinter
Process. Department of Interior, Bureau of Mines. Washington, D.C. Report of Investigation Number 6927.
8.7-2
EMISSION FACTORS
2/72
-------
8.8 CLAY AND FLY-ASH SINTERING
8.8.1 Process Description1
Although the processes for sintering fly ash and clay are similar, there are some distinctions that justify a
separate discussion of each process. Fly-ash sintering plants are generally located near the source, with the fly ash
delivered to a storage silo at the plant. The dry fly ash is moistened with a water solution of lignin and
agglomerated into pellets or balls. This material goes to a traveling-grate sintering machine where direct contact
with hot combustion gases sinters the individual particles of the pellet and completely burns off the residual
carbon in the fly ash. The product is then crushed, screened, graded, and stored in yard piles.
Clay sintering involves the driving off of entrained volatile matter. It is desirable that the clay contain a
sufficient amount of volatile matter so that the resultant aggregate will not be too heavy. It is thus sometimes
necessary to mix the clay with finely pulverized coke (up to 10 percent coke by weight).2'3 In the sintering
process the clay is first mixed with pulverized coke, if necessary, and then pelletized. The clay is next sintered in
a rotating kiln or on a traveling grate. The sintered pellets are then crushed, screened, and stored, in a procedure
similar to that for fly ash pellets.
8.8.2 Emissions and Controls1
In fly-ash sintering, improper handling of the fly ash creates a dust problem. Adequate design features,
including fly-ash wetting systems and particulate collection systems on all transfer points and on crushing and
screening operations, would greatly reduce emissions. Normally, fabric filters are used to control emissions from
the storage silo, and emissions are low. The absence of this dust collection system, however, would create a major
emission problem. Moisture is added at the point of discharge from the silo to the agglomerator, and very few
emissions occur there. Normally, there are few emissions from the sintering machine, but if the grate is not
properly maintained, a dust problem is created. The consequent crushing, screening, handling, and storage of the
sintered product also create dust problems.
In clay sintering, the addition of pulverized coke presents an emission problem because the sintering of
coke-impregnated dry pellets produces more particulate emissions than the sintering of natural clay. The crushing,
screening, handling, and storage of the sintered clay pellets creates dust problems similar to those encountered in
fly-ash sintering. Emission factors for both clay and fly-ash sintering are shown in Table 8.8-1.
2/72 Mineral Products Industry 8.8-1
-------
Table 85-1. PARTICULATE EMISSION FACTORS FOR
SINTERING OPERATIONS3
EMISSION FACTOR RATING: C
Type of material
Fly ashd
Clay mixed with cokef -9
Natural clayh-'
Sintering operation13
Ib/ton
110
40
12
kg/MT
55
20
6
Crushing, screening.
and yard storageb'c
Ib/ton
e
15
12
kg/MT
e
7.5
6
aEmission factors expressed as units per unit weight of finished product.
bCy clones would reduce this emission by about 80 percent.
Scrubbers would reduce this emission by about 90 percent.
cBased on data in section on stone quarrying and processing.
dReference 1.
eIncluded in sintering losses.
90 percent clay, 10 percent pulverized coke; traveling-grate, single-pass, up-draft sintering
machine.
^References 3 through 5.
"Rotary dryer sinterer.
1 Reference 2.
References for Section 8.8
1. Air Pollutant Emission Factors. Final Report. Resources Research, Inc. Reston, Va. Prepared for National
Air Pollution Control Administration, Durham, N.C., under Contract Number CPA-22-69-119. April 1970.
2. Communication between Resources Research, Incorporated, Reston, Virginia, and a clay sintering firm.
October 2, 1969.
3. Communication between Resources Research, Incorporated, Reston, Virginia, and an anonymous Air
Pollution Control Agency. October 16, 1969.
4. Henn, J. J. et al. Methods for Producing Alumina from Clay: An Evaluation of Two Lime Sinter Processes.
Department of the Interior, Bureau of Mines. Washington, D.C. Report of Investigation Number 7299.
September 1969.
5. Peters, F. A. et al. Methods for Producing Alumina from Clay: An Evaluation of the Lime-Soda Sinter
Process. Department of the Interior, Bureau of Mines. Washington, D.C. Report of Investigation Number
6927.1967.
8.8-2
EMISSION FACTORS
2/72
-------
8.9 COAL CLEANING
1 2
8.9.1 Process Description '
Coal cleaning is a process by which impurities such as sulfur, ash
and rock are removed from coal to upgrade its value. Coal cleaning
processes are categorized as either physical cleaning or chemical clean-
ing. Physical coal cleaning processes, the mechanical separation of
coal from its contaminants using differences in density, are by far the
major processes in use today. Chemical coal cleaning processes are not
commercially practical and are therefore not included in this discussion.
The scheme used in physical coal cleaning processes varies among
coal cleaning plants but can generally be divided into four basic phases:
initial preparation, fine coal processing, coarse coal processing, and
final preparation. A sample process flow diagram for a physical coal
cleaning plant is presented in Figure 8.9-1.
In the initial preparation phase of coal cleaning, the raw coal is
unloaded, stored, conveyed, crushed, and classified by screening into
coarse and fine coal fractions. The size fractions are then conveyed to
their respective cleaning processes.
Fine coal processing and coarse coal processing use very similar
operations and equipment to separate the contaminants. The primary
differences are the severity of operating parameters. The majority of
coal cleaning processes use upward currents or pulses of a fluid such as
water to fluidize a bed of crushed coal and impurities. The lighter
coal particles rise and are removed from the top of the bed. The
heavier impurities are removed from the bottom. Coal cleaned in the wet
processes then must be dried in the final preparation processes.
Final preparation processes are used to remove moisture from coal,
thereby reducing freezing problems and weight, and raising the heating
value. The first processing step is dewatering, in which a major por-
tion of the water is removed by the use of screens, thickeners and
cyclones. The second step is normally thermal drying, achieved by any
one of three dryer types: fluidized bed, flash and multilouvered. In
the fluidized bed dryer, the coal is suspended and dried above a per-
forated plate by rising hot gases. In the flash dryer, coal is fed into
a stream of hot gases, for instantaneous drying. The dried coal and wet
gases are drawn up a drying column and into a cyclone for separation.
In the multilouvered dryer, hot gases are passed through a falling
curtain of coal. The coal is raised by flights of a specially designed
conveyor.
1 2
8.9.2 Emissions and Controls '
Emissions from the initial coal preparation phase of either wet or
dry processes consist primarily of fugitive particulates, as coal dust,
from roadways, stock piles, refuse areas, loaded railroad cars, conveyor
2/80 Mineral Products Imluslrv
-------
Storage
M
Lfi
Cf)
o
H
O
53
O
Figure 8.9-1. Typical coal cleaning plant process flow diagram.
-------
belt pouroffs, crushers, and classifiers. The major control technique
used to reduce these emissions is water wetting. Another technique
applicable to unloading, conveying, crushing, and screening operations
involves enclosing the process area and circulating air from the area
through fabric filters.
Table 8.9-1. EMISSION FACTORS FOR COAL CLEANING3
EMISSION FACTOR RATING: B
— — — -J2g er at ion
Particulates
Before Cyclone
After Cyclone
After Scrubber
so2s
After Cyclone
After Scrubber
NO ^
X
After Scrubber
k
VOC
After Scrubber
Fluidized
Ib/ton
20b
12e
£l
0.09e
0.43h
0.25
0.14
0.10
Bed Flash Multilouvered
kg/MT
iob
6e
fa
0.05e
0.22h
0.13
0.07
0.05
Ib/ton kg/MT '
16b 8b
10f 5f
f f
0.4 0.2
i
- -
-
Ib/ton kg/MT
25C 13C
8C 4C
f c
0.1 0.05
-
- -
_
Emission factors expressed as units per weight of coal dried.
References 3 and 4.
^Reference 5.
Cyclones are standard pieces of process equipment for product collection.
-References 6, 7, 8, 9 and 10.
Reference 1.
rj
References 7 and 8. The control efficiency of venturi scrubbers
on S02 emissions depends on the inlet S02 loading, ranging from 70 to
80% removal for low sulfur coals (.7% S) down to 40 to 50% removal for
high sulfur coals (3% S).
.References 7, 8 and 9.
Not available.
^Reference 8. The control efficiency of venturi scrubbers on NOX
.emissions is approximately 10 to 25%.
volatile organic compounds as Ibs of carbon/ton of coal dried.
The major emission source in the fine or coarse coal processing
phases is the air exhaust from the air separation processes. For the
dry cleaning process, this is where the coal is stratified by pulses of
air. Particulate emissions from this source are normally controlled
with cyclones followed by fabric filters. Potential emissions from wet
cleaning processes are very low.
2/80
Mineral Products Industry
-------
The major source of emissions from the final preparation phase is
the thermal dryer exhaust. This emission stream contains coal particles
entrained in the drying gases, in addition to the standard products of
coal combustion resulting from burning coal to generate the hot gases.
Factors for these emissions are presented in Table 8.9-1. The most
common technologies used to control this source are venturi scrubbers
and mist eliminators downstream from the product recovery cyclones. The
particulate control efficiency of these technologies ranges from 98 to
99.9 percent. The venturi scrubbbers also have an NO removal efficiency
of 10 to 25 percent, and an S02 removal efficiency ranging from 70 to 80
percent for low sulfur coals to 40 to 50 percent for high sulfur coals.
References for Section 8.9
1. Background Information for Establishment of National Standards of
Performance for New Sources: Coal Cleaning Industry, Environmental
Engineering, Inc., Gainesville, FL, EPA Contract No. CPA-70-142,
July 1971.
2. Air Pollutant Emissions Factors, National Air Pollution Control
Administration, Contract No. CPA-22-69-119, Resources Research
Inc., Reston, VA, April 1970.
3. Stack Test Results on Thermal Coal Dryers (Unpublished), Bureau of
Air Pollution Control, Pennsylvania Department of Health,
Harrisburg, PA.
4. "Amherst's Answer to Air Pollution Laws", Coal Mining and
Processing, 7(2)-.26-29, February 1970.
5. D. W. Jones, "Dust Collection at Moss No. 3", Mining Congress
Journal, 55(7):53-56, July 1969.
6. Elliott Northcott, "Dust Abatement at Bird Coal", Mining Congress
Journal, _53_: 26-29, November 1967.
7. Richard W. Kling, Emissions from the Island Creek Coal Company Coal
Processing Plant, York Research Corporation, Stamford, CT,
February 14, 1972.
8. Coal Preparation Plant Emission Tests, Consolidation Coal Company,
Bishop, West Virginia, EPA Contract No. 68-02-0233, Scott Research
Laboratories, Inc., Plumsteadville, PA, November 1972.
9.
10.
Coal Preparation Plant Emission Tests, Westmoreland Coal Company,
Wentz Plant, EPA Contract No. 68-02-0233, Scott Research
Laboratories, Inc., Plumsteadville, PA, April 1972.
Background Information for Standards of Performance: Coal
Preparation Plants, Volume 2: Test Data Summary,
EPA-450/2-74-021b, U. S. Environmental Protection Agency, Research
Triangle Park, NC, October 1974.
8.9-1
EMISSION FACTORS
2/80
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8.10 CONCRETE BATCHING
8.10.1 Process Description* ~3
Concrete batching involves the proportioning of sand, gravel, and cement by means of weigh hoppers and
conveyors into a mixing receiver such as a transit mix truck. The required amount of water is also discharged into
the receiver along with the dry materials. In some cases, the concrete is prepared for on-site building construction
work or for the manufacture of concrete products such as pipes and prefabricated construction parts.
8.10.2 Emissions and Controls1
Particulate emissions consist primarily of cement dust, but some sand and aggregate gravel dust emissions do
occur during batching operations. There is also a potential for dust emissions during the unloading and conveying
of concrete and aggregates at these plants and during the loading of dry-batched concrete mix. Another source of
dust emissions is the traffic of heavy equipment over unpaved or dusty surfaces in and around the concrete
batching plant.
Control techniques include the enclosure of dumping and loading areas, the enclosure of conveyors and
elevators, filters on storage bin vents, and the use of water sprays. Table 8.10-1 presents emission factors for
concrete batch plants.
Table 8.10-1. PARTICULATE EMISSION FACTORS
FOR CONCRETE BATCHING*
EMISSION FACTOR RATING: C
Concrete
hatching13
Uncontrolled
Good control
Emission
Ib/yd3 of
concrete
0.2
0.02
kg/m3 of
concrete
0.12
0.012
30ne cubic yard of concrete weighs 4000 pounds (1 m3 = 2400 kg).
The cement content varies with the type of concrete mixed, but
735 pounds of cement per yard (436 kg/m3) may be used as a typi-
cal value.
bReference 4.
2/72
Mineral Products Industry
8.10-1
-------
References for Section 8.10
1. Air Pollutant Emission Factors. Final Report. Resources Research Inc. Reston, Va. Prepared for National Air
Pollution Control Administration, Durham, N.C., under Contract Number CPA-22-69-119. April 1970.
2. Vincent, E J and J. L. McGinnity. Concrete Batching Plants. In: Air Pollution Engineering Manual.
Danielson, J. A. (ed.). U.S. DHEW, PHS, National Center for Air Pollution Control. Cincinnati Ohio PHS
Publication Number 999-AP-40. 1967. p. 334-335.
3. Communication between Resources Research, Incorporated, Reston, Virginia, and the National Ready-Mix
Concrete Association. September 1969.
4. Allen, G. L. et al. Control of Metallurgical and Mineral Dusts and Fumes in Los Angeles County Department
of the Interior, Bureau of Mines. Washington, D.C. Information Circular Number 7627. April 1952.
8-10-2 EMISSION FACTORS 2/72
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8.11 GLASS FIBER MANUFACTURING
8.11.1 General
Glass fiber manufacturing is the high temperature conversion of various
raw materials (predominantly borosilicates) into a homogeneous melt, followed
by the fabrication of this melt into glass fibers. The two basic types of
glass fiber products, textile and wool, are manufactured by similar pro-
cesses. A typical diagram of these processes is shown in Figure 8.11-1.
Glass fiber production can be segmented into three phases: raw materials
handling, glass melting and refining, and fiber forming and finishing, this
last phase being slightly different in textile and the wool glass fiber
production.
Raw Materials Handling - The primary component of glass fiber is sand,
but it also includes varying quantities of feldspar, sodium sulfate, an-
hydrous borax, boric acid, and many other materials. The bulk supplies are
received by rail car and truck, and the lesser volume supplies are received
in drums and packages. These raw materials are unloaded by a variety of
methods, including drag shovels, vacuum systems and vibrator/gravity systems.
Conveying to and from storage piles and silos is accomplished by belts,
screws and bucket elevators. From storage, the materials are weighed
according to the desired product recipe and then blended well before their
introduction into the melting unit. The weighing, mixing and charging
operations may be conducted in either batch or continuous mode.
Glass Melting And Refining - In the glass melting furnace, the raw
materials are heated to temperatures ranging from 1500° to 1700°C (2700° to
3100°F) and are transformed through a sequence of chemical reactions to
molten glass. Although there are many furnace designs, furnaces are gener-
ally large, shallow and well insulated vessels which are heated from above.
In operation, raw materials are introduced continuously on top of a bed of
molten glass, where they slowly mix and dissolve. Mixing is effected by
natural convection, gases rising from chemical reactions, and in some
operations, by air injection into the bottom of the bed.
Glass melting furnaces can be categorized, by their fuel source and
method of heat application, into four types: recuperative, regenerative,
unit, and electric melter. The recuperative, regenerative, and unit melter
furnaces can be fueled by either gas or oil. The current trend is from gas
fired to oil fired. Recuperative furnaces use a steel heat exchanger,
recovering heat from the exhaust gases by exchange with the combustion air.
Regenerative furnaces use a lattice of brickwork to recover waste heat from
exhaust gases. In the initial mode of operation, hot exhaust gases are
routed through a chamber containing a brickwork lattice, while combustion
air is heated by passage through another corresponding brickwork lattice.
About every twenty minutes, the air flow is reversed, so that the combustion
air is always being passed through hot brickwork previously heated by exhaust
gases. Electric furnaces melt glass by passing an electric current through
the melt. Electric furnaces are either hot top or cold top. The former use
gas for auxiliary heating, and the latter use only the electric current.
9/85 Mineral Products Industry 8.11-1
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Forming
Binder addition
Compression
Oven curing
Cooling
Fabrication
Packaging
Raw materials
receiving and handling
Raw materials storage
Crushing, weighing, mixing
material
handling
Melting and refining
Direct
process
Wool glass fiber
Indirect
process
Marble forming
Annealing
Marble storage, shipment
Marble melting
Textile glass fiber
Forming
Sizing, binding addition
Winding
Oven drying
Oven curing
Fabrication
Packaging
Glass
me1r i n g
and
forming
> forming
and
fini s
Figure 8.11-1.
8.11-2
Typical flow diagram of the glass fiber
production process.
EMISSION FACTORS
9/85
-------
Electric furnaces are currently used only for wool glass fiber production,
because of the electrical properties of the glass formulation. Unit melters
are used only for the "indirect" marble melting process, getting raw
materials from a continuous screw at the back of the furnace adjacent to the
exhaust air discharge. There are no provisions for heat recovery with unit
melters.
In the "indirect" melting process, molten glass passes to a forehearth,
where it is drawn off, sheared into globs, and formed into marbles by roll
forming. The marbles are then stress relieved in annealing ovens, cooled,
and conveyed to storage or to other plants for later use. In the "direct"
glass fiber process, molten glass passes from the furnace into a refining
unit, where bubbles and particles are removed by settling, and the melt is
allowed to cool to the proper viscosity for the fiber forming operation.
Wool Glass Fiber Forming And Finishing - Wool fiberglass is produced
for insulation and is formed into mats that are cut into batts. (Loose wool
is primarily a waste product formed from mat trimming, although some is a
primary product, and is only a small part of the total wool fiberglass pro-
duced. No specific emission data for loose wool production are available.)
The insulation is used primarily in the construction industry and is
produced to comply with ASTM C167-64, the "Standard Test Method for
Thickness and Density of Blanket or Batt Type Thermal Insulating Material."2
Wool fiberglass insulation production lines usually consist of the
following processes: (1) preparation of molten glass, (2) formation of
fibers into a wool fiberglass mat, (3) curing the binder coated fiberglass
mat, (4) cooling the mat, and (5) backing, cutting and packaging the insula-
tion. Fiberglass plants contain various sizes, types, and numbers of
production lines, although a typical plant has three lines. Backing (appli-
cation of a flat flexible material, usually paper, glued to the mat),
cutting and packaging operations are not significant sources of emissions to
the atmosphere.
The trimmed edge waste from the mat and the fibrous dust generated
during the cutting and packaging operations are collected by a cyclone and
are either transported to a hammer mill to be chopped into blown wool (loose
insulation) and bulk packaged or recycled to the forming section and blended
with newly forming product.
During the formation of fibers into a wool fiberglass mat (the process
known as forming in the industry), glass fibers are made from molten glass,
and a chemical binder is simultaneously sprayed on the fibers as they are
created. The binder is a thermosetting resin that holds the glass fibers
together. Although the binder composition varies with product type, typi-
cally the binder consists of a solution of phenol-formaldehyde resin, water,
urea, lignin, silane and ammonia. Coloring agents may also be added to the
binder. Two methods of creating fibers are used by the industry. In the
rotary spin process, depicted in Figure 8.11-2, centrifugal force causes
molten glass to flow through small holes in the wall of a rapidly rotating
cylinder to create fibers that are broken into pieces by an air stream.
This is the newer of the two processes and dominates the industry today.
In the flame attenuation process, molten glass flows by gravity from a
furnace through numerous small orifices to create threads that are then
9/85 Mineral Products Industry 8.11-3
-------
CO
*— I
o
n
H
o
»
t/i
\o
Co
MOLTEN
GLASS
ATTENUATION AIR
SPINNER
BUCKET
BINDER SPRAY
GLASS FIBERS
TO CURING OVEN
7
O
O O
CONVEYOR
FORMING EXHAUST IS PULLED THROUGH
THE CONVEYOR AND MAT BY FANS
Figure 8.11-2. A typical rotary spin process.
-------
attenuated (stretched to the point of breaking) by high velocity, hot air
and/or a flame. After the glass fibers are created (by either process) and
sprayed with the binder solution, they are collected by gravity on. a conveyor
belt in the form of a mat.
The conveyor carries the newly formed mat through a large oven for
curing of the thermosetting binder and then through a cooling section where
ambient air is drawn down through the mat. Figure 8.11-3 presents a
schematic drawing of the curing and cooling sections. The cooled mat remains
on the conveyor for trimming of the uneven edges. Then, if product specifi-
cations require it, a backing is applied with an adhesive to form a vapor
barrier. The mat is then cut into batts of the desired dimensions and
packaged.
Textile Glass Fiber Forming And Finishing - Molten glass from either
the direct melting furnace or the indirect marble melting furnace is tempera-
ture regulated to a precise viscosity and delivered to forming stations. At
the forming stations, the molten glass is forced through heated platinum
bushings containing numerous very small orifices. The continuous fibers
emerging from the orifices are drawn over a roller applicator which applies
a coating of water soluble sizing and/or coupling agent. The coated fibers
are gathered and wound into a spindle. The spindles of glass fibers are next
conveyed to a drying oven, where moisture is removed from the sizing and
coupling agents. The spindles are then sent to an oven to cure the coatings.
The final fabrication includes twisting, chopping, weaving and packaging of
the fiber.
8.11.2 Emissions And Controls
Emissions and controls for glass fiber manufacturing can be categorized
by the three production phases with which they are associated. Emission
factors for the glass fiber manufacturing industry are given in Tables 8.11-1
and 8.11-2.
Raw Materials Handling - The major emissions from the raw materials
handling phase are fugitive dust and raw material particles generated at each
of the material transfer points. Such a point would be where sand pours from
a conveyor belt into a storage silo. The two major control techniques are
wet or very moist handling and fabric filters. When fabric filters are used,
the transfer points are enclosed, and air from the transfer area is
continuously circulated through the fabric filters.
Glass Melting And Refining - The emissions from glass melting and
refining include volatile organic compounds from the melt, raw material
particles entrained in the furnace flue gas and, if furnaces are heated with
fossil fuels, combustion products. The variation in emission rates among
furnaces is attributable to varying operating temperature, raw material com-
position, fuels, and flue gas flow rates. Electric furnaces generally have
the lowest emission rates, because of the lack of combustion products and of
the lower temperature of the melt surface caused by bottom heating. Emission
control for furnaces is primarily fabric filtration. Fabric filters are
effective on particulates and SO and, to a lesser extent, on CO, NO and
fluorides. Efficiency on these compounds is attributable to both condensa-
tion on filterable particulates and chemical reaction with particulates
9/85 Mineral Products Industry 8.11-5
-------
00
§
CURING AIR
COOLING AIR
CURED MAT
COOLING
EXHAUST
CURING EXHAUST
TO CONTROL DEVICE
(INCLUDES FUEL
COMBUSTION GASES)
UD
CO
Figure 8.11-3. Side view of curing oven (indirect heating) and cooling section.
-------
trapped on the filters. Reported fabric filter efficiencies on regenerative
and recuperative wool furnaces are for particulates, 95+ percent; SO ,
99+ percent; CO, 30 percent; and fluoride, 91 to 99 percent. Efficiencies
on other furnaces are lower because of lower emission loading and pollutant
characteristics.
Wool Fiber Forming And Finishing - Emissions generated during the
manufacture of wool fiberglass insulation include solid particles of glass
and binder resin, droplets of binder, and components of the binder that have
vaporized. Glass particles may be entrained in the exhaust gas stream during
forming, curing or cooling operations. Test data show that approximately
99 percent of the total emissions from the production line is emitted from
the forming and curing sections. Even though cooling emissions are negli-
gible at some plants, cooling emissions at others may include fugitives from
the curing section. This commingling of emissions occurs because fugitive
emissions from the open terminal end of the curing oven may be induced into
the cooling exhaust ductwork and be discharged into the atmosphere. Solid
particles of resin may be entrained in the gas stream in either the curing
or cooling sections. Droplets of organic binder may be entrained in the gas
stream in the forming section or may be a result of condensation of gaseous
pollutants as the gas stream is cooled. Some of the liquid binder used in
the forming section is vaporized by the elevated temperatures in the forming
and curing processes. Much of the vaporized material will condense when the
gas stream cools in the ductwork or in the emission control device.
Particulate matter is the principal pollutant that has been identified
and measured at wool fiberglass insulation manufacturing facilities. It was
known that some fraction of the particulate emissions results from condensa-
tion of organic compounds used in the binder. Therefore, in evaluating
emissions and control device performance for this source, a sampling method,
EPA Reference Method 5E, was used that permitted collection and measurement
of both solid particles and condensed particulate material.3
Tests were performed during the production of R-ll building insulation,
R-19 building insulation, ductboard and heavy density insulation.4 These
products, which account for 91 percent of industry production, had densities
ranging from 9.1 to 12.3 kilograms per cubic meter (kg/m3) for R-ll, 8.2 to
9.3 kg/m3 for R-19, and 54.5 to 65.7 kg/m3 for ductboard. The heavy density
insulation had a density of 118.5 kg/m3. (The remaining 9 percent of
industry wool fiberglass production is a variety of specialty products for
which qualitative and quantitative information is not available.) The loss
on ignition (LOI) of the product is a measure of the amount of binder
present. The LOI values ranged from 3.9 to 6.5 percent, 4.5 to 4.6 percent,
and 14.7 to 17.3 percent, respectively. The LOI for heavy density is
10.6 percent. A production line may be used to manufacture more than one of
these product types because the processes involved do not differ. Although
the data base did not show sufficient differences in mass emission levels to
establish separate emission standards for each product, the uncontrolled
emission factors are sufficiently different to warrant their segregation for
AP-42.
The level of emissions control found in the wool fiberglass insulation
manufacturing industry ranges from uncontrolled to control of forming, curing
9/85 Mineral Products Industry 8.11-7
-------
00
M
K
M
W
co
o
H
O
Crt
TABLE 8.11-1. EMISSION FACTORS FOR GLASS FIBER MANUFACTURING WITHOUT CONTROLS3
EMISSION FACTOR RATING: B
Particulates
Unloading and
conveying
Storage binsc
Mixing and weighing0
Crushing and batch
charging
Glass furnace - wool
Electric
Gas-regenerative
Gas -recuperative
Gas-unit melter
Glass furnace - textile
Recuperative
Regenerative
Unit melter
Forming - wool
Flame attenuation
Forming - textile
Oven curing - wool
Flame attenuation
Oven curing and
cooling - textile
lb/ton
3.0
0.2
0.6
Meg
0.5
22
25-30
9
2
16
6
2
1
6
1.2
kg/Mg
1.5
0.1
0.3
Neg
0.25
11
13-15
4.5
1
8
3
1
0.5
3
0.6
SO
X
lb/ton
d
d
d
d
0.04
10
10
0.6
3
30
e
d
d
e
d
kg/Mg
d
d
d
d
0.02
5
5
0.3
1.5
15
e
d
d
e
d
CO NO
lb/ton
d
d
d
d
0.05
0.25
0.25
0.25
0.5
1
0.9
d
d
3.5
1.5
kg/Mg
d
d
d
d
0.025
0.13
0.13
0.13
0.25
0.5
0.15
d
d
1.8
0.75
lb/ton
d
d
d
d
0.27
5
1.7
0.3
20
20
20
d
d
2
2.6
kg/Mg
d
d
d
d
0.14
2.5
0.85
0.15
10
10
10
d
d
1
1.3
vocb
lb/ton
d
d
d
e
e
e
e
d
d
d
0.3
Neg
7
Neg
kg/Mg
d
d
d
e
e
e
e
,
d
d
0.15
Neg
3.5
Neg
Flourides
lb/ton
d
d
d
0.002
0.12
0.11
0.12
2
9
2
e
d
e
d
kg/Mg
d
d
d
0.001
0.06
0.06
0.06
i
1
e
d
e
d
^Expressed as units per unit weight of raw material processed. Neg = negligible.
^Includes primarily phenols and aldehydes, and to a lesser degree, methane.
00
-------
and cooling emissions from a line. The exhausts from these process opera-
tions may be controlled separately or in combination. Control technologies
currently used by the industry include wet ESPs, low and high pressure drop
wet scrubbers, low and high temperature thermal incinerators, high velocity
air filters, and process modifications. These added control technologies
are available to all firms in the industry, but the process modifications
used in this industry are considered confidential. Wet ESPs are considered
to be best demonstrated technology for the control of emissions from wool
fiberglass insulation manufacturing lines.4 Therefore, it is expected that
most new facilities will be controlled in this manner.
Textile Fiber Forming And Finishing - Emissions from the forming and
finishing processes include glass fiber particles, resin particles, hydro-
carbons (primarily phenols and aldehydes), and combustion products from
dryers and ovens. Emissions are usually lower in the textile fiber glass
process than in the wool fiberglass process because of lower turbulence in
the forming step, roller application of coatings, and use of much less
coating per ton of fiber produced.
TABLE 8.11-2. UNCONTROLLED EMISSION FACTORS FOR ROTARY SPIN WOOL GLASS
FIBER MANUFACTURING3
EMISSION FACTOR RATING: B
Particulate
Organic compounds
Products Front half
R-19
R-ll
Ductboard
Heavy
density
17.81
(36.21)
19.61
(39.21)
27.72
(55.42)
4.91
(9-81)
Back half
4.25
(8.52)
3.19
(6.37)
8.55
(17.08)
1.16
(2.33)
Total
22.36
(44.72)
22.79
(45.59)
36.26
(72.50)
6.07
(12.14)
Phenolics
3.21
(6.92)
6.21
(12.41)
10.66
(21.31)
0.88
(1-74)
Phenol Formaldehyde
0.96
(1.92)
0.92
(1-84)
3.84
(7.68)
0.53
(1-04)
0.75
(1-50)
1.23
(2.46)
1.80
(3.61)
0.43
(0.85)
Reference 4. Expressed in kg/Mg (Ib/ton) of finished product. Gas stream
did not pass through any added primary control device (wet ESP, venturi
scrubber, etc.).
Included in total particulate catch. These organics are collected as con-
densible particulate matter and do not necessarily represent the entire
organics present in the exhaust gas stream.
Includes phenol.
References for Section 8.11
1. J. R. Schorr, et al., Source Assessment: Pressed and Blown Glass
Manufacturing Plants, EPA-600/2-77-005, U. S. Environmental Protection
Agency, Research Triangle Park, NC, January 1977.
9/85
Mineral Products Industry
8.11-9
-------
2. Annual Book of ASTM Standards, Part 18, ASTM Standard C167-64
(Reapproved 1979), American Society for Testing and Materials,
Philadephia, Pa.
3. Standard of Performance For Wool Fiberglass Insulation Manufacturing
Plants, 50 FR 7700, February 25, 1985-
4. Wool Fiberglass Insulation Manufacturing Industry: Background
Information for Proposed Standards, U. S. Environmental Protection
Agency, Research Triangle Park, NC, EPA-450/3-83-022a, December 1983.
8.11-10 EMISSION FACTORS 9/85
-------
8.12 FRIT MANUFACTURING
8.12.1 Process Description1 >2
Frit is used in enameling iron and steel and in glazing porcelain and pottery. In a typical plant, the raw
materials consist of a combination of materials such as borax, feldspar, sodium fluoride or fluorspar, soda ash,
zinc oxide, litharge, silica, boric acid, and zircon. Frit is prepared by fusing these various minerals in a smelter,
and the molten material is then quenched with air or water. This quenching operation causes the melt to solidify
rapidly and shatter into numerous small glass particles, called frit. After a drying process, the frit is finely ground
in a ball mill where other materials are added.
8.12.2 Emissions and Controls2
Significant dust and fume emissions are created by the frit-smelting operation. These emissions consist
primarily of condensed metallic oxide fumes that have volatilized from the molten charge. They also contain
mineral dust carryover and sometimes hydrogen fluoride. Emissions can be reduced by not rotating the smelter
too rapidly (to prevent excessive dust carry-over) and by not heating the batch too rapidly or too long (to prevent
volatilizing the more fusible elements).
The two most feasible control devices for frit smelters are baghouses and venturi water scrubbers. Emission
factors for frit smelters are shown in Table 8.12-1. Collection efficiencies obtainable for venturi scrubbers are also
shown in the table.
4/73
Mineral Products Industry
8.12-1
-------
Table 8.12-1. EMISSION FACTORS FOR FRIT SMELTERS
WITHOUT CONTROLS3
EMISSION FACTOR RATING: C
Type of furnace
Rotary
Particulatesb
Ib/ton
16
kg/MT
8
Fluoridesb
Ib/ton
5
kg/MT
2.5
aReference 2. Emission factors expressed as units per unit weight of charge.
bA venturi scrubber with a 21-inch (535-mm) water-gauge pressure drop can reduce par-
ticulate emissions by 67 percent and fluorides by 94 percent.
References for Section 8.12
1. Duprey, R. L. Compilation of Air Pollutant Emission Factors. U.S. DHEW, PHS, National Center for Air
Pollution Control. Durham, N.C. PHS Publication Number 999-AP-42. 1968. p. 37-38.
2. Spinks, J. L. Frit Smelters. In: Air Pollution Engineering Manual. Danielson, J. A. (ed.), U.S. DHEW, PHS,
National Center for Air Pollution Control. Cincinnati, Ohio. PHS Publication Number 999-AP-40. 1967. p.
738-744.
8.12-2
EMISSION FACTORS
2/72
-------
8.13 GLASS MANUFACTURING
8.13.1 General !-s
Commercially produced glass can be classified as either soda-lime, lead, fused silica, borosilicate, or 96
percent silica. Soda-lirne glass, which constitutes 77 percent of total glass production, will be discussed in this
section. Soda-lime glass consists of sand, limestone, soda ash, and cullet (broken glass). The manufacture of glass
can be broken down into four phases: (1) preparation of raw material, (2) melting in a furnace, (3) forming, and
(4) finishing. Figure 8.13-1 shows an overall flow diagram for glass manufacturing.
The products of the glass manufacturing industry are flat glass, container glass, or pressed and blown glass.
The procedure for manufacturing glass is the same for all three categories except for forming and finishing. Flat
glass, which comprises 24 percent of total glass production, is formed by either the float, drawing, or rolling
process. Container glass and pressed and blown glass, which comprise 51 and 25 percent, respectively, of total
glass production, utilize either pressing, blowing, or pressing and blowing to form the desired product.
As raw materials are received, they are crushed and stored in separate elevated bins. The raw materials are
transferred through a gravity feed system to the weigher and mixer, where the material and cullet are mixed to
ensure homogeneous melting. The mixture is then transferred by conveyor to the batch storage bin where it
remains until being dropped into the furnace feeder, which supplies the raw material to the melting furnace. All
equipment used in handling and preparing the raw material is housed separately from the furnace and is usually
referred to as the batch plant. Figure 8.13-2 shows a flow diagram of a batch plant.
The furnace most commonly utilized is a continuous regenerative furnace capable of producing between 50
and 300 tons (45 and 272 metric tons) of glass per day. A furnace may have either side or end ports connecting
brick checkers to the inside of the melter. The purpose of the checkers is to conserve fuel by utilizing the heat of
the combustion products in one side of the furnace to preheat combustion air in the other side. As material enters
the melting furnace through the feeder, it floats on the top of the molten glass already in the furnace. As it melts,
it passes to the front of the melter and eventually flows through a throat connecting the melter and the refiner. In
the refiner, the molten glass is heat conditioned for delivery to the forming process. Figures 8.13-3 and 8.13-4
show side-port and end-port regenerative furnaces.
RAW
MATERIAL
i
MELTING
FURNACE
*»
f
FINISHING -i r- FINIS
n
GLASS
FORMING
CULLET
CRUSHING
•*• ANNEALING ->
HING
1
\
INSPECTION
*• AND
TESTING
RECYCLE UNDESIRABLE
GLASS
u
PACKING
STORAGE
OR
SHIPPING
12/77
8.13-1. Flow diagram for glass manufacturing.
Mineral Products Industry
8.13-1
-------
GULLET
RA* MATERIALS
RECEIVING
HOPPER
V.
SCREH
CONVEYOR
FILTER
VENTS
STORAGE BINS
MAJOR RAN MATERIALS
MINOR
INGREDIENT
STORAGE
BINS
BELT CONVEYOR
BATCH
STORAGE
BIN
GLASS-
MELTING
FURNACE
8.13-2. Flow diagram of a batch plant.1
After refining, the molten glass leaves the furnace through forehearths (except for the float process in which
molten glass goes directly to the tin bath) and goes to be shaped by either pressing, blowing, pressing and blowing,
drawing, rolling, or floating, depending upon the desired product. Pressing and blowing are preformed
mechanically using blank molds and glass cut into sections (gobs) by a set of shears. In the drawing process,
molten glass is drawn upward through rollers that guide the sheet glass. The thickness of the sheet is determined
by the speed of the draw and the configuration of the draw bar. The rolling process is similar to the drawing
process except that the glass is drawn horizontally by plain or patterned rollers and, for plate glass, requires
grinding and polishing. The float process utilizes a molten tin bath over which the glass is drawn and formed into a
finely finished surface requiring no grinding or polishing. The product undergoes finishing (decorating or
coating) and annealing (removing unwanted stress areas in the glass), and is then inspected and prepared for
shipment to market. Any damaged or undersirable glass is transferred back to the batch plant to be used as cullet.
8.13.2 Emissions and Controls1'5
Table 8.13-1 lists controlled and uncontrolled emission factors for glass manufacturing.
The main pollutant emitted by the batch plant is particulates in the form of dust. This can be controlled, with
99 to 100 percent efficiency, by enclosing all possible dust sources and using baghouses or cloth filters. Another
way to control dust emissions, also with an efficiency approaching 100 percent, is to treat the batch to reduce the
amount of fine particles present. Forms of preparation are presintering, briquetting, pelletizing, or liquid alkali
treatment.
8.13-2
EMISSION FACTORS
12/77
-------
REFINES SIDE «ALL,
CLASS SURFACE
HIDED ARCHES
8.13-3. Side-port continuous regenerative furnace.1
REFINER SIDE WALL
GLASS SURFACE IN REFINER
INDUCED DRAFT FAN
PARTING WALL
SECONOARY CHECKERS'
- RIDER ARCHES
12/77
8.13-4. End-port continuous regenerative furnace.1
MINERAL PRODUCTS INDUSTRY
8.13-3
-------
00
s
M
co
O
^
co
00
ro
TABLE 8.13-1. EMISSION FACTORS FOR GLASS MANUFACTURING3^
EMISSION FACTOR RATING: B
Process
Raw materials handling6
(all types of glass)
Metal furnace S
Container
Uncontrolled
W/low-energy scrubber"
W/venturi scrubber*
W/baghouseJ
W/electrostatic precipitator''
Flat
Uncontrolled
tf/low— energy scrubber"
W/venturi scrubber*
W/bsghouseJ
W/electrostatic precipitator''
Pressed and blown
Uncontrolled
W/low-energy scrubber"
W/venturi scrubber*
W/baghouseJ
W/electrostatlc precipitator11
Forming and finishing
Container1 •nl
Flat
Pressed and blownki1
Lead glass manufacturing,
totaln'°'P
Partlculated
kg/Mg
Neglf
0.7
(0.4-0.9)
0.4
< 0.1
Negl
Negl
1.0
(0.4-1.6)
0.5
Negl
Negl
Negl
8.7
(0.5-12.6)
4.2
0.5
0.1
O.I
Negl
Negl
Negl
-
Ib/ton
Neglf
1.4
(0.9-1.9)
0.7
0.1
Negl
Negl
2.0
(0.8-3.2)
1.0
Negl
Negl
Negl
17.4
(1.0-25.1)
8.4
0.9
0.2
0.2
Negl
Negl
Negl
-
Sulfur oxides
kg/Mg
0
1.7
(1.0-2.4)
0.9
0.1
1.7
1.7
1.5
(1.1-1.9)
0.8
0.1
1.5
1.5
2.S
(0.5-5.4)
1.3
0.1
2.8
2.8
Negl
Negl
Negl
-
Ib/ton
0
3.4
(2.0-4.8)
1.7
0.2
3.4
3.4
3.0
(2.2-3.8)
1.5
0.2
3.0
3.0
5.6
(1.1-10.9)
2.7
0.3
5.6
5.6
Negl
Negl
Negl
-
Nitrogen
kg/Mg
0
3.1
(1.6-4.5)
3.1
3.1
3.1
3.1
4.0
(2.8-5.2)
4.0
4.0
4.0
4.0
4.3
(0.4-10.0)
2.2
2.2
2.2
2.2
Negl
Negl
Negl
-
oxides
Ib/ton
0
6.2
(3.3-9.1)
6.2
6.2
6.2
6.2
8.0
(5.6-10.4)
8.0
8.0
8.0
8.0
8.5
(0.8-20.0)
8.5
8.5
8.5
8.5
Negl
Negl
Negl
-
Organ tcs
kg/Mg
0
0.1
(0-0.
0.1
0.1
0.1
0.1
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
0.2
«0.1-0.
0.2
0.2
0.2
0.2
4.4
Negl
4.5
-
Ib/ton
0
0.2
2) (0-0.4)
0.2
0.2
0.2
0.2
< 0.1
< 0.1
< 0.1
< 0.1
< 0.1
0.3
3)(0. 1-1.0)
0.3
0.3
0.3
0.3
8.7
Hegl
9.0
-
Carbon monoxide Lead
kg/Mg
0
0.1
(0-0.2)
0.1
0.1
0.1
0.1
< 0.1
< 0, 1
< 0.1
< 0.1
< 0.1
0.1
Ib/ton kg/Mg Ib/ton
0 -
0.2
(0-0.5)
0.2
0.2
0.2
0.2
< 0.1
< 0.1
< 0.1
< 0. 1
< 0.1
0.2
(0.1-0.2X0.1-0.3)
0.1
0.1
0.1
0.1
Negl
Negl
Negl
-
0.2
0.2
0.2
0.2
Negl
Negl
Negl
5 2.5
aReferences 2-3, 5. Dash indicates no available data.
^Emission factors are expressed as kg/Mg (Ib/ton) of glass produced.
°When literature references reported ranges in emission rates, these
ranges are shown in parentheses along with the average emission factor.
Single emission factors are averages of literature data for which no
ranges were reported.
^Particulates are submicron in size.
eEmission factors for raw materials handling are not separated into types
of glass produced since batch preparation is the .same for all types. Par-
tlculate emissions are negligible because almost all plants utilize some
form of control (i.e. baghouses, scrubbers, or centrifugal collectors).
fNegligible,
^Control efficiencies for the various devices are applied only to the
average emission factor.
"Approximately 52 percent efficient in reducing particulate and sulfur
oxides emissions. Effect on nitrogen oxides is unknown.
^Approximately 95% efficient in reducing particulate and sulfur oxide
emissions. Effect on nitrogen oxides is unknown.
JApproximately 99% efficient in reducing particulate emissions,
kParticulate emission factors are calculated using data for furnaces
melting soda lime and lead glasses. No data are available for boro-
silicate or opal glasses.
^Hydrocarbon emission factors for container and pressed and blown glass
are from the decorating process. Emissions can be controlled by incin-
eration, absorption, or condensation; however, efficiencies are not
known,
Tor container and pressed and blown glass, tin chloride, hydrated tin
chloride, and hydrogen chloride are also emitted during the surface
treatment process at a rate of less than 0.1 kg/Mg (0.2 Ib/ton) each.
nReferences 6 and 7.
°For specific processes within lead glass manufacturing, use the general
emission factors which apply to the specific process.
PParttculate containing 23% lead.
-------
The melting furnace contributes over 99 percent of the total emissions
from the glass plant. In the furnace, both particulates and gaseous pollutants
are emitted. Particulates result from volatilization of materials in the melt
that combine with gases to form condensates. These are either collected in the
checker-work and gas passages or escape to the atmosphere. Serious problems
arise when the checkers are not properly cleaned in that slag can form, clog-
ging the passages and eventually deteriorating the condition and efficiency
of the furnace. Nitrogen oxides form when nitrogen and oxygen react in the
high temperatures of the furnace. Sulfur oxides result from the decomposition
of the sulfates in the batch and the fuel. Proper maintenance and firing of
the furnace can control emissions and also add to the efficiency of the
furnace and reduce operational costs. Low-pressure wet centrifugal scrubbers
have been used to control particulates and sulfur oxides, but their low
efficiency (approximately 50 percent) indicates their inability to collect
particulates of subraicron size. High-energy venturi scrubbers are approx-
imately 95 percent effective in reducing particulate and sulfur oxide emis-
sions; their effect on nitrogen oxide emissions is unknown. Baghouses,
which have up to 99 percent particulate collection efficiency, have been
used on small regenerative furnaces, but due to fabric corrosion, require
careful temperature control. Electrostatic precipitators have an efficiency
of up to 99 percent in the collection of particulates.
Emissions from the forming and finishing phase depend upon the type of
glass being manufactured. For container, press, and blow machines, the major-
ity of emissions result from the gob coming into contact with the machine
lubricant. Emissions in the form of a dense white cloud, which can exceed
40 percent opacity, are generated by flash vaporization of hydrocarbon greases
and oils. Grease and oil lubricants are being replaced by silicone emulsions
and water-soluble oils, which may virtually eliminate the smoke. For flat
glass, the only contributor to air pollutant emissions is gas combustion in
the annealing lehr, which is totally enclosed except for entry and exit
openings. Since emissions are small and operational procedures are efficient,
no controls are utilized.
References for Section 8.13
1. J. A. Danielson (ed.)., Air Pollution Engineering Manual (2nd Ed.), AP-40,
U.S. Environmental Protection Agency, Research Triangle Park, NC, 1973.
Out of Print.
2. Richard B. Reznik, Source Assessment: Flat Glass Manufacturing Plants,
EPA-600/20-76-032b, U. S. Environmental "Protection Agency, Research Tri-
angle Park, NC, March 1976.
3. J. R. Schoor, D. T. Hooie, P. R. Sticksel, and Clifford Brockway, Source
Assessment: Glass Container Manufacturing Plants, EPA-600/2-76-269, U.S.
Environmental Protection Agency, Washington, DC, October 1976.
12/81
Mineral Products Industry
8.13-5
-------
I
4. A. B. Tripler, Jr. and G. R. Smithson, Jr., A Review of Air Pollution Prob-
lems and Control in the Ceramic Industries, Battelle Memorial Institute,
Columbus, OH, presented at 72nd Annual Meeting of the American Ceramic
Society, May 1970.
5. J. R. Schorr, D. T. Hooie, M. C. Brockway, P. R. Sticksel, and D. E. Niesz,
Source Assessment; Pressed and Blown Glass Manufacturing Plants, prepared
for U. S. Environmental Protection Agency, Research Triangle Park, NC,
Publication Number EPA-600/2-77-005, January 1977.
6. Control Techniques for Lead Air Emissions, EPA-450/2-77-012, U. S. Environ-
mental Protection Agency, Research Triangle Park, NC, December 1977.
7. Confidential test data, PEDCo-Environmental Specialists, Inc., Cincinnati,
OH.
8.13-6 EMISSION FACTORS 12/81
-------
8.14 GYPSUM MANUFACTURING
8.14.1 Process Description
1-2
,w, 2H2°)» a white or gray
Raw gypsum ore is processed into a variety of
Gypsum is calcium sulfate dihydrate (CaSO,
naturally occurring mineral.
products such as a Portland cement additive, soil conditioner, industrial
and huilding plasters, and gypsum wallboard. To produce plasters or
wallboard, gypsum must first be partially dehydrated or calcined to produce
calcium sulfate hemihydrate (CaSO • %H 0) , commonly called stucco.
A flow diagram for a typical gypsum process producing both crude and
finished gypsum products is shown in Figure 8.14-1. In this process, gypsum
is crushed, dried, ground and calcined. Some of the operations shown in
Figure 8.14-1 are not performed at all gypsum plants. Some plants produce
only wallboard, and many plants do not produce soil conditioner.
Gypsum ore, from quarries and/or underground mines, is crushed and
stockpiled near a plant. As needed, the stockpiled ore is further crushed
and screened to about 50 millimeters (2 inches) in diameter. If the
moisture content of the mined ore is greater than about 0.5 weight percent,
the ore must be dried in a rotary dryer or a heated roller mill. Ore dried
in a rotary dryer is conveyed to a roller mill where it is ground to
90 percent less 149 micrometers (100 mesh). The ground gypsum exits the
mill in a gas stream and is collected in a product cyclone. Ore is
sometimes dried in the roller mill by heating the gas stream, so that drying
and grinding are accomplished simultaneously and no rotary dryer is needed.
The finely ground gypsum ore is known as landplaster, which may be used as
soil conditioner.
In most plants, landplaster is fed to kettle calciners or flash
calciners, where it is heated to remove three quarters of the chemically
bound water to form stucco. Calcination occurs at approximately 120 to
150°C (250 to 300°F) , and 0.908 megagrams (Mg) (one ton) of gypsum calcines
to about 0.77 Mg (0.85 ton) of stucco.
In kettle calciners, the gypsum is indirectly heated by hot combustion
gas passed through flues in the kettle, and the stucco product is discharged
into a "hot pit" located below the kettle. Kettle calciners may be operated
in either batch or continuous modes. In flash calciners, the gypsum is
directly contacted with hot gases, and the stucco product is collected at
the bottom of the calciner. A major gypsum manufacturer holds a patent on
the design of the flash calciner.
At some gypsum plants, drying, grinding and calcining are performed in
heated impact mills. In these mills, hot gas contacts gypsum as it is
ground. The gas dries and calcines the ore and then conveys the stucco to a
product cyclone for collection. The use of heated impact mills eliminates
the need for rotary dryers, calciners and roller mills.
5/83
Mineral Products Industry
8.14-1
-------
Oo
ro
o
1-3
CO
Ul
00
I Conveying
V \Z
Stucco
storage
bins
,.,.--O ©
'
'Sold as
/prefabrl-
[cated board K
products
J BoardMne conveyor
(
i
eoaro eno
sawing
*» " ~
/
Huttl-rfeck
board drying
kiln
I
OtT
Figure 8.14-1. Overall gypsum manufacturing process flow diagram.
-------
Gypsum and stucco usually are transferred from one process to another
in screw conveyors or bucket elevators. Storage bins or silos are normally
located downstream of roller mills and calciners but may also be used
elsewhere.
In the manufacture of plasters, stucco is ground further in a tube or
ball mill and then batch mixed with retarders and stabilizers to produce
plasters with specific setting rates. The thoroughly mixed plaster is fed
continuously from intermediate storage bins to a bagging operation.
In the manufacture of wallboard, stucco from storage is first mixed
with dry additives such as perlite, starch, fiberglass or vermiculite. This
dry mix is combined with water, soap foam, accelerators and shredded paper
or pulpwood in a pin mixer at the head of a board forming line. The slurry
is then spread between two paper sheets that serve as a mold. The edges of
the paper are scored, and sometimes chamfered, to allow precise folding of
the paper to form the edges of the board. As the wet board travels the
length of a conveying line, the calcium sulfate hemihydrate combines with
the water in the slurry to form solid calcium sulfate dihydrate or gypsum,
resulting in rigid board. The board is rough cut to length, and it enters a
multideck kiln dryer where it is dried by direct contact with hot combustion
gases or by indirect steam heating. The dried board is conveyed to the
board end sawing area and is trimmed and bundled for shipment.
2
8.14.2 Emissions and Controls
Potential emission sources in gypsum manufacturing plants are shown in
Figure 8.14-1. Although several sources may emit gaseous pollutants,
particulate emissions are of greatest concern. The major sources of
particulate emissions include rotary ore dryers, grinding mills, calciners
and board end sawing operations. Particulate emission factors for these
operations are shown in Table 8.14-1. All these factors are based on output
production rates. Particle size data for ore dryers, calciners and board
end sawing operations are shown in Tables 8.14-2 and 8.14-3.
The uncontrolled emission factors presented in Table 8.14-1 represent
the process dust entering the emission control device. It is important to
note that emission control devices are frequently needed to collect the
product from some gypsum processes and, thus, are commonly thought of by the
industry as process equipment and not added control devices.
Emissions sources in gypsum plants are most often controlled with
fabric filters. These sources include:
- rotary ore dryers - board end sawing
roller mills - scoring and chamfering
- impact mills - plaster mixing and bagging
- kettle calciners - conveying systems
flash calciners - storage bins
Uncontrolled emissions from scoring and chamfering, plaster mixing and
bagging, conveying systems, and storage bins are not well quantified.
5/83 Mineral Products Industry 8.14-3
-------
TABLE 8.14-1. PARTICULATE EMISSION FACTORS FOR GYPSUM PROCESSING'
EMISSION FACTOR RATING: B
With
fabric
Process Uncontrolled filter0
kg/Mg Ib/ton kg/Mg Ib/ton
Crushers, screens,
stockpiles, roads d d - -
Rotary ore dryerse'f'S 0.0042(FFF)1-7? 0.16(FFF)1-77 0.02h 0.04h
Roller mills1 l.S^ 2.6j 0.06 0.12
, Impact mills5'1 50e>J 100g>j 0.01 0.02
Flash calcinerse'm 19 37 0.02 0.04
Continuous kettle
calciners11 21P 41P 0.003P 0.006P
With
electrostatic
precipitator
kg/Mg Ib/ton
NA
0.05k 0.09k
NA
NA
0.05-5 0.09^
kg/n
lb/100 ft
kg/106 m2 lb/106 ft2
Board end sawing''
2.4 m (8 ft) boards
3.7 m (12 ft) boards
0.04
0.03
0.8
0.5
36
36
7.5
7.5
aBased on process output production rate. Rating applies to all factors except where otherwise noted.
Dash ~ not applicable. NA = not available.
Factors represent any dust entering the emission control device.
References 3-6, 8-11. Factors for sources controlled with fabric filters are based on pulse Jet fabric
filters with actual air/cloth ratios ranging from Z.3:l - 7.0:1, mechanical shaker fabric filters with
ratios from 1.5:1 - 4.6:1, and a reverse flow fabric filter with a ratio of 2.3:1.
Factors for these operations are in Sections 8.19 and 11.2.
elncludes particulate matter from fuel combustion.
References 3-4, 8, 11-12. Equation is for emission rate upstream of any process cyclones and is
applicable only to concurrent rotary ore dryers with flowrates of 7.5 m /s (16,000 acfm) or less.
FFF in the uncontrolled emission factor equation is "flow feed factor", the ratio of gas mass
rate per unit dryer cross sectional area to the dry mass feed rate, in the following units:
2 2
kg/hr - m of gas flow Ib/hr - ft of gas flow
Mg/hr dry feedor ton/hr dry feed
Measured uncontrolled emission factors for 4.2 and 5.7 m IB (9000 and 12,000 acfm) range from 5 -
60 kg/Mg (10 - 120 Ib/ton).
8EMISSION FACTOR RATING: C.
Applicable to rotary dryers with and without process cyclones upstream of the fabric filter.
References 11-14. Factors apply to both heated and unheated roller mills.
Factors represent emissions downstream of the product cyclone.
Factor is for combined emissions from roller mills and kettle calciners, based on the sum of the roller
mill and kettle calciner output production rates.
References 9,15. As used here, an impact mill is a process unit with process cyclones and is
used to dry, grind and calcine gypsum simultaneously.
References 3, 6, 10. A flash calciner is a process unit used to calcine gypsum through direct contact
with hot gas. No grinding is performed in this unit.
"References 4-5, 11, 13-14.
"Based on emissions from both the kettle and the hot pit. Not applicable to batch kettle calciners.
References 4-5, 16. Eased on 13 mm (h in.) board thickness and 1.2 m (4 ft)
board width. For other board thicknesses, multiply the appropriate emission factor by 0.079 times
board thickness in millimeters, or by 2 times board thickness in inches.
8.14-4
EMISSION FACTORS
5/83
-------
TABLE 8.14-2. UNCONTROLLED PARTICLE SIZE DATA
FOR GYPSUM PROCESSING
Process
Weight Percent
10 ym 2 ym
Rotary ore dryer
with cyclones
without cyclones
45
b
,b
Continuous kettle calciners
Flash calciners
63'
38
17'
10L
.Reference 4.
Aerodynamic diameter, Andersen analysis.
.Reference 3.
References 4-5.
^Equivalent diameter, Bahco and Sedigraph analyses.
References3, 6.
TABLE 8.14-3. PARTICLE SIZE DATA FOR GYPSUM PROCESSING
OPERATIONS CONTROLLED WITH FABRIC FILTERS
a
Process
Rotary ore dryer.
with cyclones
without cyclones
Flash calciners
Board end sawing
Weight Percent
10 ym 2 ym
c 9
26 9
84 52
76 49
, Aerodynamic diameters, Andersen analysis.
Reference 4.
Q
,Not available
Reference 3.
fReferences 3, 6.
References 4-5.
5/83
Mineral Products Industry
8.14-5
-------
Emissions from some gypsum sources are also controlled with
electrostatic precipitators (ESP). These sources include rotary ore dryers,
roller mills, kettle calciners and conveying systems. Although rotary ore
dryers may be controlled separately, emissions from roller mills and
conveying systems are usually controlled jointly with kettle calciner
emissions. Moisture in the kettle calciner exit gas improves the ESP
performance by lowering the resistivity of the dust.
Other sources of particulate emissions in gypsum plants are primary and
secondary crushers, screens, stockpiles and roads. If quarrying is part of
the mining operation, particulate emissions may also result from drilling
and blasting. Emission factors for some of these sources are presented in
Sections 8.19 and 11.2.
Gaseous emissions from gypsum processes result from fuel combustion and
may include nitrogen oxides, carbon monoxide and sulfur oxides. Processes
using fuel include rotary ore dryers, heated roller mills, impact mills,
calciners and board drying kilns. Although some plants use residual fuel
oil, the majority of the industry uses clean fuels such as natural gas or
distillate fuel oil. Emissions from fuel combustion may be estimated
using emission factors presented in Sections 1.3 and 1.4.
References for Section 8.14
1. Kirk-Othmer Encyclopedia of Chemical Technology, Volume 4, John Wiley &
Sons, Inc., New York, 1978.
2. Gypsum Industry - Background Information for Proposed Standards
(Draft), U. S. Environmental Protection Agency, Research Triangle Park,
NC, April 1981.
3. Source Emissions Test Report, Gold Bond Building Products, EMB-80-
GYP-1, U. S. Environmental Protection Agency, Research Triangle Park,
NC, November 1980.
4. Source Emissions Test Report, United States Gypsum Company, EMB-80-
GYP-2, U. S. Environmental Protection Agency, Research Triangle Park,
NC, November 1980.
5. Source Emission Tests, United States Gypsum Company Wallboard Plant,
EMB-80-GYP-6, U. S. Environmental Protection Agency, Research Triangle
Park, NC, January 1981.
6. Source Emission Tests, Gold Bond Building Products, EMB-80-GYP-5, U. S.
Environmental Protection Agency, Research Triangle Park, NC,
December 1980.
7. S. Oglesby and G. B. Nichols, A Manual of Electrostatic Precipitation
Technology, Part II: Application Areas, APTD-0611, U. S. Environmental
Protection Agency, Cincinnati, OH, August 25, 1970.
8. Official Air Pollution Emission Tests Conducted on the Rock Dryer
and #3 Calcidyne Unit, Gold Bond Building Products, Report No. 5767,
Rosnagel and Associates, Medford, NJ, August 3, 1979.
8.14-6 EMISSION FACTORS 5/83
-------
9. Particulate Analysis of Calcinator Exhaust at Western Gypsum Company,
Kramer, Callahan and Associates, Rosario, NM, April 1979. Unpublished.
10. Official Air Pollution Tests Conducted on the #1 Calcidyner Baghouse
Exhaust at the National Gypsum Company, Report No. 2966, Rossnagel and
Associates, Atlanta, GA, April 10, 1978.
.11. Report to United States Gypsum Company on Particulate Emission
Compliance Testing, Environmental Instrument Systems, Inc., South
Bend, IN, November 1975. Unpublished.
12. Particulate Emission Sampling and Analysis, United States Gypsum
Company, Environmental Instrument Systems, Inc., South Bend, IN,
July 1973. Unpublished.
13. Written communication from Wyoming Air Quality Division, Cheyenne, WY,
to Michael Palazzolo, Radian Corporation, Durham, NC, 1980.
14. Written communication from V. J. Tretter, Georgia-Pacific Corporation,
Atlanta, GA, to M. E. Kelly, Radian Corporation, Durham, NC,
November 14, 1979.
15. Telephone communication between Michael Palazzclo, Radian Corporation,
Durham, NC, and D. Louis, C. E. Raymond Company, Chicago, IL, April 23,
1981.
16. Written communication from Michael Palazzolo, Radian Corporation,
Durham, NC, to B. L. Jackson, Weston Consultants, West Chester, PA,
June 19,
1980.
17. Telephone communication between P. J. Murin, Radian Corporation,
Durham, NC, and J. W. Pressler, U. S. Department of the Interior,
Bureau of Mines, Washington, DC, November 6, 1979.
5/83 Mineral Products Industry 8.14-7
-------
-------
8.15 LIME MANUFACTURING
8.15.1 General1'4
Lime is the high-temperature product of the calcination of limestone. There are two kinds of lime:
high-calcium lime (CaO) and dolomitic lime (CaO • MgO). Lime is manufactured in various kinds of
kilns by one of the following reactions:
CaCOs + heat —» CO2 + CaO (high calcium lime)
CaCCh . MgCO3 + heat —> COz + CaO . MgO (dolomitic lime)
In some lime plants, the resulting lime is reacted (slaked) with water to form hydrated lime.
The basic processes in the production of lime are (1) quarrying the raw limestone, (2) preparing the
limestone for the kilns by crushing and sizing, (3) calcining the limestone, (4) processing the quicklime
further by hydrating, and (5) miscellaneous transfer, storage, and handling operations. A generalized
material flow diagram for a lime manufacturing plant is given in Figure 8.15-1. Note that some of the
operations shown may not be performed in all plants.
The heart of a lime plant is the kiln. The most prevalent type of kiln is the rotary kiln, accounting
for about 90 percent of all lime production in the United States. This kiln is a long, cylindrical, slightly
inclined, refractory-lined furnace through which the limestone and hot combustion gases pass count-
ercurrently. Coal, oil, and natural gas may all be fired in rotary kilns. Product coolers and kiln-feed
preheaters of various types are commonly employed to recover heat from the hot lime product and
and hot exhaust gases, respectively.
The next most prevalent type of kiln in the United States is the vertical, or shaft, kiln. This kiln can
be described as an upright heavy steel cylinder lined with refractory material. The limestone is
charged at the top and calcined as it descends slowly to the bottom of the kiln where it is discharged. A
primary advantage of vertical kilns over rotary kilns is the higher average fuel efficiency. The primary
disadvantages of vertical kilns are their relatively low production rates and the fact that coal cannot
be used without degrading the quality of the lime produced. Although still prevalent in Europe, there
have been few recent vertical kiln installations in the United States because of the high production
requirements of domestic manufacturers.
Other, much less common, kiln types include rotary hearth and fluidized-bed kilns. The rotary
hearth kiln, or "calcimatic" kiln, is a circular-shaped kiln with a slowly revolving donut-shaped hearth.
In fluidized-bed kilns, finely divided limestone is brought into direct contact with hot combustion
air in a turbulent zone, usually above a perforated grate. Dust collection equipment must be installed
on fluidized-bed kilns for process economics because of the high lime carryover into the exhaust gases.
Both kiln types can achieve high production rates, but neitner can operate with coal.
About 10 percent of all lime produced is converted to hydrated (slaked) lime. There are two kinds
of hydrators: atmospheric and pressure. Atmospheric hydrators, the most prevalent kind, are used to
produce high calcium and normal dolomitic hydrates. Pressure hydrators, on the other hand, are only
employed when a completely hydrated dolomitic lime is needed. Atmospheric hydrators operate
continuously, whereas pressure hydrators operate in a batch mode. Generally, water sprays or wet
scrubbers are employed as an integral part of the hydrating process to prevent product losses. Follow-
ing hydration, the resulting product may be milled and conveyed to air separators for further drying
and for removal of the coarse fractions.
4/77 Mineral Products Industry 8.15-1
-------
LIMESTONE
QUARRY/MINE
PRIMARY
CRUSHER
SECONDARY
CRUSHER
SCREENS AND
CLASSIFIERS
CONTROL
DEVICE
CONTROL
DEVICE
WATER'
FUEL-
HYDRATOR
HYDRATED
LIME
STONE
PREHEATER
LIMESTONE
KILN
LIME
PRODUCT
COOLER
LIME
n
KIL
EXHA
KILN
EXHAUST
•AIR
WATER/DUST SLURRY
WATER SPRAY/
WET SCRUBBER
STORAGE/
SHIPMENT
8.15-2
MILL/AIR
SEPARATOR
STORAGE/
SHIPMENT
STONE
EMITTING POINTS
AIR/EXHAUST
Figure 8.15-1. Generalized lime manufacturing plant.
EMISSION FACTORS
4/77
-------
In the United States, the major use of lime is in chemical and metallurgical applications. Two of the
largest uses in these areas are as steel flux and in alkali production. Other lesser uses include con-
struction, refractory, and agricultural applications.
8.15.2 Emissions and Controls3-5
Potential air pollutant emitting points in lime manufacturing plants are shown in Figure 8.15-1.
Particulate is the only pollutant of concern from most of the operations; however, gaseous pollutants
are also emitted from kilns.
The largest source or paniculate is the kiln. Of the various kiln types in use, fluidized-bed kilns
have the highest uncontrolled paniculate emissions. This is due primarily to the very small feed size
combined with the high air flow through these kilns. Fluidized-bed kilns are well controlled for
maximum product recovery. The rotary kiln is second to the fluidized-bed kiln in uncontrolled
particulate emissions. This is attributed to the small feed size and relatively high air velocities and
dust entrainment caused by the rotating chamber. The rotary hearth, or "calcimatic" kiln ranks third
in dust production, primarily because of the larger feed size combined with the fact that the limestone
remains in a stationary position relative to the hearth during calcination. The vertical kiln has the
lowest uncontrolled dust emissions due to the large lump-size feed and the relatively slow air velocities
and slow movement of material through the kiln.
Some sort of particulate control is generally employed on most kilns. Rudimentary fallout chamb-
ers and cyclone separators are commonly used for control of the larger particles; fabric and gravel bed
filters, wet (commonly venturi) scubbers, and electrostatic precipitators are employed for secondary
control. Table 8.15-1 yields approximate efficiencies of each type of control on the various types of
kilns.
Nitrogen oxides, carbon monoxide, and sulfur oxides are all produced in kilns, although the latter
are the only gaseous pollutant emitted in significant quantities. Not all of the sulfur in the kiln fuel is
emitted as sulfur oxides because some fraction reacts with the materials in the kiln. Some sulfur oxide
reduction is also effected by the various equipment used for secondary particulate control. Estimates
of the quantities of sulfur oxides emitted from kilns, both before and after controls, are presented in
Table 8.15-1.
Hydrator emissions are low because water sprays or wet scrubbers are usually installed for econom
ic reasons to prevent product loss in the exhaust gases. Emissions from pressure hydrators may be
higher than from the more common atmospheric hydrators because the exhaust gases are released
intermit lent l\ . niukiii'.: coi iol mort1 difficult.
Product coolers are emission sources only when some of their exhaust gases are not recycled
through the kiln for use as combustion air. The trend is away from the venting of product cooler ex-
haust, however, to maximize fuel use efficiencies. Cyclones, baghouses, and wet scrubbers have been
employed on coolers for particulate control.
Other particulate sources in lime plants include primary and secondary crushers, mills, screens,
mechanical and pneumatic transfer operations, storage piles, and unpaved roads. If quarrying is a part
of the lime plant operation, particulate may also result from drilling and blasting. Emission factors
for some of these operations are presented in Sections 8.20 and 11.2.
Emission factors for lime manufacturing are presented in Table 8.15-1.
4/77 Mineral Products Industry 8.15-3
-------
Table 8.15-1. EMISSION FACTORS FOR LIME MANUFACTURING
EMISSION FACTOR RATING: B
Source
Crushers, screens,
conveyors, storage
piles, unpaved roads
Rotary kilns
Uncontrolled0
After settling chamber
or large diameter
cyclone
After multiple cyclones
After secondary dust
collection^
Vertical kilns
Uncontrolled
Calcimatic kilns'
Uncontrolled
After multiple cyclones
After secondary dust
collection]
Fluidized-bed kilns
Product coolers
Uncontrolled
Hydrators
Emissions8
Paniculate
Ib/ton
b
340
200
85e
1
8
50
6
NA
NAk
401
0.1m
kg/MT
b
170
100
43e
0.5
4
25
3
NA
NAk
201
0.05m
Sulfur dioxide
Ib/ton
Neg.
d
d
d
9
NAh
NA
NA
NA
NA
Neg.
Neg.
1
kg/MT
Neg.
d
d
d
9
NAh
NA
NA
NA
NA
Neg.
Neg.
Nitrogen oxides
Ib/ton
Neg.
3
3
3
3
NA
0.2
0.2
0.2
NA
Neg.
Neg.
kg/MT
Neg.
1.5
1.5
1.5
1.5
NA
0.1
0.1
0.1
NA
Neg.
Neg.
Carbon monoxide
Ib/ton
Neg.
2
2
2
2
NA
NA
NA
NA
NA
Neg.
Neg.
kg/MT
Neg.
1
1
1
1
NA
NA
NA
NA
NA
Neg.
Neg.
aAII emission factors for kilns and coolers are per unit of lime produced. Divide by two to obtain factors per unit of limestone feed to the kiln-
Factors for hydrators are per unit of h yd rated lime produced. Multiply by 1.25 to obtain factors per unit of lime feed to the hydrator. All
emissions data are based on References 4 through 6.
bEmission factors for these operations are presented in Sections 8.20 and 11.2.
GNo particulate control except for settling that may occur in the stack breeching and chimney base.
^When low-sulfur (less than 1 percent, by weight) fuels are used, only about 10 percent of the fuel sulfur is emitted as SO2- When high-
sulfur fuels are used, approximately 50 percent of the fuel sulfur is emitted as SOj.
eThis factor should be used when coal is fired in the kiln. Limited data suggest that when only natural gas or oil is fired, particulate
emissions after multiple cyclones may be as low as 20 to 30 Ib/ton (10 to 15 kg/MT),
'Fabric or gravel bed filters, electrostatic precipitators, or wet (most commonly verituri) scrubbers. Particulate concentrations as low as
0.2 Ib/ton (0.1 kg/MT) have been achieved using these devices.
9When scrubbers are used, less than 5 percent of the fuel sulfur will be emitted as SO2, even with high-sulfur coal. When other secondary
collection devices are used, about 20 percent of the fuel sulfur will be emitted as SC>2 with high-sulfur fuels and less than 10 percent
with low-sulfur fuels.
"Not available.
'Calcirnatic kilns generally employ stone preheaters. All factors represent emissions after the kiln exhaust passes through a preheater.
^Fabric filters and venturi scrubbers have been employed on calcimatic kilns. No data are available on particulate emissions after
secondary control.
^Fluidized-bed kilns must employ sophisticated dust collection equipment for process economics; hence, particulate emissions will
depend on the efficiency of the control equipment installed.
'Some or all of the cooler exhaust is typically used in the kiln as combustion air. Emissions will result only from that fraction that
is not recycled to the kiln.
mThis is a typical particulate loading for atmospheric hydrators following water sprays or wet scrubbers. Limited data suggest
particulate emissions from pressure hydrators may be approximately 2 Ib/ton (1 kg/MT) of hydrate produced, after wet collectors.
8.15-4
EMISSION FACTORS
4/77
-------
References for Section 8.15
1. Lewis, C. J. and B.B. Crocker. The Lime Industry's Problem of Airborne Dust. J. Air Pol. Control
Asso. Vol. 19, No. 1. January 1969.
2. Kirk-Othmer Encyclopedia of Chemical Technology. 2nd Ed. Vol 12. New York, John Wiley and
Sons. 1967. p. 414-459.
3. Screening Study for Emissions Characterization From Lime Manufacture. Vulcan-Cincinnati.
Cincinnati, Ohio. Prepared for U.S. Environmental Protection Agency, Research Triangle Park,
N.C. Under Contract No. 68-02-0299. August 1974.
4. Evans, L.B. et al. An Investigation of the Best Systems of Emission Reduction For Rotary Kilns
and Lime Hydrators in the Lime Industry. Standards Support and Environmental Impact
Statement. Office of Air Quality Planning and Standards. U.S. Environmental Protection
Agency. Research Triangle Park, N.C. February 1976.
5, Source Test Data on Lime Plants from Office of Air Quality Planning and Standards. U.S.
Environmental Protection Agency. Research Triangle Park, N.C. 1976.
6. Air Pollutant Emission Factors. TRW Systems Group. Reston, Virginia. Prepared for the
National Air Pollution Control Administration, U.S. Department of Health, Education, and
Welfare. Washington, D.C. under Contract No. CPA 22-69-119. April 1970. P. 2-2 through 2-19.
4/77 Mineral Products Industry 8.15-5
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8.16 MINERAL WOOL MANUFACTURING
8.16.1 Process Description' •2
The product mineral wool used to be divided into three categories: slag wool, rock wool, and glass wool-
Today, however, straight slag wool and rock wool as such are no longer manufactured. A combination of slag and
rock constitutes the charge material that now yields a product classified as a mineral wool, used mainly for
thermal and acoustical insulation.
Mineral wool is made primarily in cupola furnaces charged with blast-furnace slag, silica rock, and coke. The
charge is heated to a molten state at about 3000°F (1650°C) and then fed to a blow chamber, where steam
atomizes the molten rock into globules that develop long fibrous tails as they are drawn to the other end of the
chamber. The wool blanket formed is next conveyed to an oven to cure the binding agent and then to a cooler.
8.16.2 Emissions and Controls
The major source of emissions is the cupola or furnace stack. Its discharge consists primarily of condensed
fumes that have volatilized from the molten charge and gases such as sulfur oxides and fluorides. Minor sources of
particulate emissions include the blowcharnber, curing oven, and cooler. Emission factors for various stages of
mineral wool processing are shown in Table 8.16-1. The effect of control devices on emissions is shown in
footnotes to the table.
2/72 Mineral Products Industry 8.16-1
-------
Table 8.16-1. EMISSION FACTORS FOR MINERAL WOOL PROCESSING
WITHOUT CONTROLS3
EMISSION FACTOR RATING: C
Type of process
Cupola
Reverberatory furnace
Blow chamber0
Curing ovend
Cooler
Particulates
Ib/ton
22
5
17
4
2
kg/MT
11
2.5
8.5
2
1
Sulfur oxides
Ib/ton
0.02
Negb
Neg
Neg
Neg
kg/MT
0.01
Neg
Neg
Neg
Neg
^Reference 2. Emission factors expressed as units per unit weight of charge
"Negligible.
°A centrifugal water scrubber can reduce paniculate emissions by 60 percent.
A direct-flame afterburner can reduce paniculate emissions by 50 percent.
References for Section 8.16
1.
Duprey, R. L. Compilation of Air Pollutant Emission Factors. U.S. DHEW, PHS, National Center for Air
Pollution Control. Durham, N. C. PHS Publication Number 999-AP-42. 1968. p. 39-40.
2.
Spinks, J. L. Mineral Wool Furnaces. In: Air Pollution Engineering Manual. Danielson, J. A. (ed) US
DHEW, PHS, National Center for Air Pollution Control. Cincinnati, Ohio. PHS Publication Number
999-AP-40. 1967. p. 343-347.
8.16-2
EMISSION FACTORS
2/72
-------
8.17 PERLITE MANUFACTURING
8.17.1 Process Description1 >2
Perlite is a glassy volcanic rock consisting of oxides of silicon and aluminum combined as a natural glass by
water of hydration. By a process called exfoliation, the material is rapidly heated to release water of hydration
and thus to expand the spherules into low-density particles used primarily as aggregate in plaster and concrete. A
plant for the expansion of perlite consists of ore unloading and storage facilities, a furnace-feeding device, an
expanding furnace, provisions for gas and product cooling, and product-classifying and product-collecting
equipment. Vertical furnaces, horizontal stationary furnaces, and horizontal rotary furnaces are used for the
exfoliation of perlite, although the vertical types are the most numerous. Cyclone separators are used to collect
the product.
8.17.2 Emissions and Controls2
A fine dust is emitted from the outlet of the last product collector in a perlite expansion plant. The fineness of
the dust varies from one plant to another, depending upon the desired product. In order to achieve complete
control of these particulate emissions, a baghouse is needed. Simple cyclones and small multiple cyclones are not
adequate for collecting the fine dust from perlite furnaces. Table 8.17-1 summarizes the emissions from perlite
manufacturing.
Table 8.17 1. PARTICULATE EMISSION FACTORS
FOR PERLITE EXPANSION FURNACES
WITHOUT CONTROLS3
EMISSION FACTOR RATING: C
Type of furnace
Vertical
Emissions6
Ib/ton
21
kg/MT
10.5
aReference 3. Emission factors expressed as units per unit weight of
charge.
^Primary cyclones will collect 80 percent of the particulates above
20 micrometers, and baghouses will collect 96 percent of the particles
above 20 micrometers.2
2/72
Mineral Products Industry
8.17-1
-------
References for Section 8.17
1. Duprey, R. L. Compilation of Air Pollutant Emission Factors. U.S. DHEW, PHS, National Center for Air
Pollution Control. Durham, N.C. PHS Publication Number 999-AP-42. 1968. p. 39.
2. Vincent, E. J. Perlite-Expanding Furnaces. In: Air Pollution Engineering Manual. Danielson, J. A. (ed.). U.S.
DHEW, PHS, National Center for Air Pollution Control. Cincinnati, Ohio. PHS Publication Number
999-AP-40. 1967. p. 350-352.
3. Unpublished data on perlite expansion furnace. National Center for Air Pollution Control. Cincinnati Ohio
July 1967.
8.17-2 EMISSION FACTORS 2/72
-------
8.18 PHOSPHATE ROCK PROCESSING
8.18.1 General
The processing of phosphate rock for use in fertilizer manufacture
consists of beneficiation, drying or calcining, and grinding stages.
Since the primary use of phosphate rock is in the manufacture of phos-
phatic fertilizer, only those phosphate rock processing operations
associated with fertilizer manufacture are discussed here. A flow
diagram of these operations is shown in Figure 8.18-1.
Phosphate rock from the mines is first sent to heneficiation units
to remove impurities. Steps used in heneficiation depend on the type of
rock. A typical beneficiation unit for processing phosphate rock mined
in Florida (about 78 percent of United States plant capacity in 1978)
begins with wet screening to separate pebble rock (smaller than 1/4 inch
and larger than 14 mesh) from the balance of the rock. The pebble rock
is sent to the rock dryer, and the fraction smaller than 14 mesh is
slurried and treated by two-stage flotation. The flotation process uses
hydrophilic or hydrophobia chemical reagents with aeration to separate
suspended particles. Phosphate rock mined in North Carolina (about 8
percent of United States capacity in 1978) does not contain pebble rock.
In processing this type of phosphate, the fraction larger than 1/4 inch
is sent to a hammer mill and then recycled to the screens, and the
fraction less than 14 mesh is treated by two-stage floation, like
Florida rock. The sequence of beneficiation steps at plants processing
Western hard phosphate rock (about 10 percent of United States capacity
in 1978) typically includes crushing, classification and filtration.
The size reduction is carried out in several steps, the last of which is
a slurry grinding process using a wet rod mill to reduce the rock to
particles about the size of beach sand. The slurry is then classified
by size in hydroclones to separate tailings (clay and particles smaller
than about 100 mesh), and the rock is then filtered from the slurry.
Beneficiated rock is commonly stored in open wet piles. It is reclaimed
from these piles by one of several methods (including skip loaders,
underground conveyor belts, and aboveground reclaim trolleys) and is
then conveyed to the next processing step.
The wet beneficiated phosphate rock is then dried or calcined,
depending on its organic content. Florida rock is relatively free of
organics and is dried in direct fired dryers at about 250°F (120°C),
where the moisture content of the rock falls from 10-15 percent to 1-3
percent. Both rotary and fluidized bed dryers are used, but rotary
dryers are more common. Most dryers are fired with natural gas or fuel
oil (No. 2 or No. 6), with many equipped to burn more than one type of
fuel. Unlike Florida rock, phosphate rock mined from other reserves
contains organics and must be heated to 1400° - 1600°F (760°C - 870°C)
to remove them. Fluidized bed calciners are most commonly used for this
purpose, but rotary calciners are also used. After drying, the rock is
usually conveyed to storage silos on weather protected conveyors and,
from there, to grinding mills.
2/80 Mineral Protliic-ltf IntliiKlrv 8.18-1
-------
Table 8.18-1. UNCONTROLLED PARTICULATE EMISSION FACTORS
FOR PHOSPHATE ROCK PROCESSINGa
EMISSION FACTOR RATING: B
Type of Source
Drying
Calcining
Grinding
Transfer and storage
Open storage piles
Ib/ton
5.7
(1.4 - 14.0)
15.4
(3.8 - 38.0)
1.5
(0.4 - 4.0)
2
40
Emissions
kg/MT
2.9
(0.7 - 7.0)
7.7
(1.9 - 19.0)
0.8
(0.2 - 2.0)
1
20
Emission factors expressed as units per unit weight of processed
, phosphate rock. Ranges in parentheses.
Reference 1.
Q
Reference 3.
Reference 4.
Dried or calcined rock is ground in roll or ball mills to a fine
powder, typically specified as 60 percent by weight passing a 200 mesh
sieve. Rock is fed into the mill by a rotary valve, and ground rock is
swept from the mill by a circulating air stream. Product size classi-
fication is provided by "revolving whizzers" and by an air classifier.
Oversize particles are recycled to the mill, and product size particles
are separated from the carrying air stream by a cyclone.
8.18.2 Emissions and Controls
The major emission sources for phosphate rock processing are
dryers, calciners and grinders. These sources emit particulates in the
form of fine rock dust. Emission factors for these sources are pre-
sented in Table 8.18-1. Beneficiation has no significant emission
potential, since the operations involve slurries of rock and water.
Emissions from dryers depend on several factors, including fuel
types, air flow rates, product moisture content, speed of rotation, and
the type of rock. The pebble portion of Florida rock receives much less
washing than the concentrate rock from the floation processes. It has a
higher clay content and generates more emissions when dried. No signi-
ficant differences have been noted in gas volume or emissions from fluid
bed or rotary dryers. A typical dryer processing 250 tons per hour (230
metric tons per hour) of rock will discharge between 70,000 and 100,000
dscfm (31 - 45 dry nm3/sec) of gas, with a particulate loading of 0.5 to
8.18-2
EMISSION FACTORS
2/80
-------
to
\
cc
o
To Control
To Control
=- Rock
"5 from
c Mine
hate
• *
i
Beneficiation
tqui
i
jment
i
Drying
or
Calcining
A t
i
Eiqui.
1
[j me 11 L
i
Grinding
Ground
Rock
Transfer
To
Fertilizer
Manufacturing
Fuel
Air
Figure 8.18-1. Typical flowsheet for processing phosphate rock.
-------
5 grams/dscf (1.2 - 12 grams/dry nm3). A particle size distribution of
the uncontrolled dust emissions is given In Table 8.18-2.
Scrubbers are most commonly used to control emissions from phosphate
rock dryers, but electrostatic precipitators are also used. Fabric
filters are not currently being used to control emissions from dryers.
Venturi scrubbers with a relatively low pressure loss (12 inches of
water, or 3000 Pa) may remove 80 to 99 percent of particulates 1 to 10
micrometers in diameter, and 10 to 80 percent of particulates less than
1 micrometer. High pressure drop scrubbers (30 inches of water, or 7500
Pa) may have collection efficiencies of 96 to 99.9 percent for 1-10
micrometer particulates and 80 to 86 percent for particles less than 1
micrometer. Electrostatic precipitators may remove 90 to 99 percent of
all particulates. Another control technique for phosphate rock dryers
is use of the wet grinding process, in which the drying step is
eliminated.
A typical 50 ton per hour (45 Ml/hour) calciner will discharge
about 30,000 to 60,000 dscfm (13 - 27 dry nm3/sec) of exhaust gas, with
a particulate loading of 0.5 to 5 g/dscf (1.2 - 12 g/dry nm3). As
shown in Table 8.18-2, the size distribution of the uncontrolled calciner
emissions is very similar to that of the dryer emissions. As with
dryers, scrubbers are the most common control devices used for calciners.
At least one operating calciner is equipped with a precipitator. Fabric
filters could also be applied.
Oil fired dryers and calciners have a potential to emit sulfur
oxides when high sulfur residual fuel oils are burned. However, phos-
phate rock typically contains about 55 percent CaO, which reacts with
the SOX to form calcium sulfites and sulfates and thus reduces SOX
emissions.
Low levels of gaseous fluoride emissions (0.002 Ib/ton or 0.001
kg/MT) of rock processed from calciners have been reported, although
other reports indicate that the calcination temperature is too low to
drive off gaseous fluorides. Fluoride emissions from dryers are
negligible.
A typical grinder of 50 tons per hour (45 MT/hr) capacity will
discharge about 3500 to 5500 dscfm (1.6 - 2.5 dry nm3/sec) of air
containing 0.5 to 5.0 gr/dscf (1.2 - 12 g/dry nm3) of particulates. The
air discharged is "tramp air" which infiltrates the circulating streams.
To avoid fugitive emissions of rock dust, these streams are operated at
negative pressure. Fabric filters, and sometimes scrubbers, are used to
control grinder emissions. Substituting wet grinding for conventional
grinding would reduce the potential for particulate emissions.
Emissions from material handling systems are difficult to quantify,
since several different systems are employed to convey rock. Moreover,
a large part of the emission potential for these operations is fugitives.
Conveyor belts moving dried rock are usually covered and sometimes
8.18-1 EMISSION FACTORS 2/80
-------
enclosed. Transfer points are sometimes hooded and evacuated. Bucket
elevators are usually enclosed and evacuated to a control device, and
ground rock is generally conveyed in totally enclosed systems with well
defined and easily controlled discharge points. Dry rock is normally
stored in enclosed bins or silos which are vented to the atmosphere,
with fabric filters frequently used to control emissions.
Table 8.18-2. PARTICLE SIZE DISTRIBUTION OF EMISSIONS
FROM PHOSPHATE ROCK DRYERS AND CALCINERSa
Diameter (ym)
10.0
5.0
2.0
1.0
0.8
0.5
Percent Less
Dryers
82
60
27
11
7
3
Than Size
Calciners
96
81
52
26
10
5
ileference 1.
References for Section 8.18
1. Background Information: Proposed Standards for Phosphate Rock
Plants (Draft), EPA-450/3-79-017, U. S. Environmental Protection
Agency, Research Triangle Park, NC, September 1979.
2. "Sources of Air Pollution and Their Control", Air Pollution,
Volume III, 2nd Ed., Arthur Stern, ed., New York, Academic Press,
1968, pp. 221-222.
3. Unpublished data from phosphate rock preparation plants in Florida,
Midwest Research Institute, Kansas City, MO, June 1970.
4. Control Techniques for Fluoride Emissions, Internal document,
Office of Air Quality Planning and Standards, U. S. Environmental
Protection Agency, Research Triangle Park, NC, pp. 4-34, 4-36 and
4-46.
2/80
Mineral Pro
-------
-------
8.19 CONSTRUCTION AGGREGATE PROCESSING
General-'-"^
The construction aggregate industry covers a range of subclassifications
of the nonmetallic minerals industry (see Section 8.23, Metallic Minerals
Processing, for information on that similar activity). Many operations and
processes are common to both groups, including mineral extraction from the
earth, loading, unloading, conveying, crushing, screening, and loadout. Other
operations are restricted to specific subcategories. These include wet and dry
fine milling or grinding, air classification, drying, calcining, mixing, and
bagging. The latter group of operations is not generally associated with the
construction aggregate industry but can be conducted on the same raw materials
used to produce aggregate. Two examples are processing of limestone and sand-
stone. Both substances can be used as construction materials and may be pro-
cessed further for other uses at the same location. Limestone is a common
source of construction aggregate, but it can be further milled and classified
to produce agricultural limestone. Sandstone can be processed into construction
sand and also can be wet and/or dry milled, dried, and air classified into
industrial sand.
The construction aggregate industry can be categorized by source, mineral
type or form, wet versus dry, washed or unwashed, and end uses, to name but a
few. The industry is divided in this document into Section 8.19.1, Sand And
Gravel Processing, and Section 8.19.2, Crushed Stone Processing. Sections on
other categories of the Industry will be published when data on these processes
become available.
Uncontrolled construction aggregate processing can produce nuisance pro-
blems and can have an effect upon attainment of ambient particulate standards.
However, the generally large particles produced often can be controlled readily.
Some of the Individual operations such as wet crushing and grinding, washing,
screening, and dredging take place with "high" moisture (more than about 1.5 to
4.0 weight percent). Such wet processes do not generate appreciable particulate
emissions.
References for Section 8.19
1. Air Pollution Control Techniques for Nonmetallic Minerals Industry,
EPA-450/3-82-014, U. S. Environmental Protection Agency, Research
Triangle Park, NC, August 1982.
2. Review Emissions Data Base And Develop Emission Factors For The
Construction Aggregate Industry, Engineering-Science, Inc., Arcadia,
CA, September 1984.
9/85
Mineral Products Industry
8.19-1
-------
1
-------
8.19.1 SAND AND GRAVEL PROCESSING
8.19.1.1 Process Description1"3
Deposits of sand and gravel, the consolidated granular materials result-
ing from the natural disintegration of rock or stone, are generally found in
near-surface alluvial deposits and in subterranean and subaqueous beds. Sand
and gravel are products of the weathering of rocks and unconsolidated or poorly
consolidated materials and consist of siliceous and calcareous components.
Such deposits are common throughout the country.
Depending upon the location of the deposit, the materials are excavated
with power shovels, draglines, front end loaders, suction dredge pumps or other
apparatus. In rare situations, light charge blasting is done to loosen the
deposit. The materials are transported to the processing plant by suction
pump, earth mover, barge, truck or other means. The processing of sand and
gravel for a specific market involves the use of different combinations of
washers, screens and classifiers to segregate particle sizes; crushers to
reduce oversize material; and storage and loading facilities. Crushing oper-
ations, when used, are designed to reduce production of fines, which often
must be removed by washing. Therefore, crusher characteristics, size reduction
ratios and throughput, among other factors, are selected to obtain the desired
product size distribution.
In many sand and gravel plants, a substantial portion of the initial feed
bypasses any crushing operations. Some plants do no crushing at all. After
initial screening, material is conveyed to a portion of the plant called the
wet processing section, where wet screening and silt removal are conducted to
produce washed sand and gravel. Negligible air emissions are expected from the
wet portions of a sand and gravel plant.
Industrial sand processing is similar to that of construction sand, insofar
as the initial stages of crushing and screening are concerned. Industrial sand
has a high (90 to 99 percent) quartz or silica content and is frequently obtained
from quartz rich deposits of sand or sandstone. At some plants, after initial
crushing and screening, a portion of the sand may be diverted to construction
sand use. Industrial sand processes not associated with construction sand
include wet milling, scrubbing, desliming, flotation, drying, air classifica-
tion and cracking of sand grains to form very fine sand products.
8.19.1.2 Emissions and Controls*
Dust emissions can occur from many operations at sand and gravel proces-
sing plants, such as conveying, screening, crushing, and storing operations.
Generally, these materials are wet or moist when handled, and process emissions
are often negligible. A substantial portion of these emissions may consist of
heavy particles that settle out within the plant. Emission factors (for process
or fugitive dust sources) from sand and gravel processing plants are shown in
Table 8.19.1-1. (If processing is dry, expected emissions could be similar to
those given in Section 8.19.2, Crushed Stone Processing).
Emission factors for crushing wet materials can be applied directly or
on a dry basis, with a control efficiency credit being given for use of wet
8.19.1-1
EMISSION FACTORS
9/85
-------
materials (defined as 1.5 to 4.0 percent moisture content or greater) or wet
suppression. The latter approach is more consistent with current practice.
The single valued fugitive dust emission factors given in Table 8.19.1-1
may be used for an approximation when no other information exists. Empirically
derived emission factor equations presented in Section 11.2 of this document
are preferred and should be used when possible. Each of those equations has
been developed for a single source operation or dust generating mechanism which
crosses industry lines, such as vehicle traffic on unpaved roads. The predic-
tive equation explains much of the observed variance in measured emission
factors by relating emissions to the differing source variables. These vari-
ables may be grouped as (1) measures of source activity or expended energy
(e. g., feed rate, or speed and weight of a vehicle traveling on an unpaved
road), (2) properties of the material being disturbed (e. g., moisture content,
or content of suspendable fines in the material) and (3) climate (e. g., number
of precipitation free days per year, when emissions tend to a maximum).
Because predictive equations allow for emission factor adjustment to
specific conditions, they should be used instead of the factors given in Table
8.19.1-1 whenever emission estimates are needed for sources in a specific sand
and gravel processing facility. However, the generally higher quality ratings
assigned to these equations are applicable only if (1) reliable values of cor-
rection parameters have been determined for the specific sources of interest,
and (2) the correction parameter values lie within the ranges found in develop-
ing the equations. Section 11.2 lists measured properties of aggregate materials
used in operations similar to the sand and gravel industry, and these properties
can be used to approximate correction parameter values for use in the predictive
emission factor equations, in the event that site specific values are not avail-
able. Use of mean correction parameter values from Chapter 11 reduces the
quality ratings of the emission factor equations by at least one level.
Since emissions from sand and gravel operations usually are in the form
of fugitive dust, control techniques applicable to fugitive dust sources are
appropriate. Some successful control techniques used for haul roads are
application of dust suppressants, paving, route modifications, soil stabiliza-
tion, etc.; for conveyors, covering and wet suppression; for storage piles, wet
dust suppression, windbreaks, enclosure and soil stablizers; and for conveyor
and batch transfer points (loading and unloading, etc.), wet suppression and
various methods to reduce freefall distances (e. g., telescopic chutes, stone
ladders, and hinged boom stacker conveyors); for screening and other size
classification, covering and wet suppression.
Wet suppression techniques include application of water, chemicals and/or
foam, usually at crusher or conveyor feed and/or discharge points. Such spray
systems at transfer points and on material handling operations have been esti-
mated to reduce emissions 70 to 95 percent.' Spray systems can also reduce
loading and wind erosion emissions from storage piles of various materials 80
to 90 percent.^ Control efficiencies depend upon local climatic conditions,
source properties and duration of control effectiveness. Wet suppression has
a carryover effect downstream of the point of application of water or other
wetting agents, as long as the surface moisture content is high enough to cause
the fines to adhere to the larger rock particles.
9/85 Mineral Products Industry 8.19.1-2
-------
TABLE 8.19.1-1. UNCONTROLLED PARTICIPATE EMISSION FACTORS
FOR SAND AND GRAVEL PROCESSING PLANTS3
Uncontrolled Operation
Process Sources0
Primary or secondary
crushing (wet)
Open Dust Sources0
Screening"
Flat screens
(dry product)
Contlnous dropc
Transfer station
Pile formation - stacker
Batch dropc
Bulk loading
Active storage pilesB
Active day
Inactive day (wind
erosion only)
Unpaved haul roads
Wet materials
Emissions by Particle Size Range (aerodynamic diameter)1'
Total
Particulate
NA
NA
0.014 (0.029)
NA
0.12 (0.024)
NA
NA
i
TSP
(< 30 um)
0.009 (0.018)
0.08 (0.16)
NA
0.065 (0.13)
0.028 (0.056)f
14.8 (13.2)
3.9 (3.5)
i
PM10
(<_ 10 pm)
NA
0.06 (0.12)
NA
0.03 (0.06)e
0.0012 (0.0024)f
7.1 (6.3)e
1.9 (1.7)e
i
Units
kg/Mg (Ib/ton)
kg/Mg (Ib/ton)
kg/Mg (Ib/ton)
kg/Mg (Ib/ton)
kg/Mg (Ib/ton)
kg/hectare/day11
(Ib/acre/day)
kg/hectare/day11
(Ib/acre/day)
Emission
Factor
Rating
D
C
E
£
E
D
D
D
aNA = not available. TSP - total suspended particulate. Predictive emission factor equations, which generally
provide more accurate estimates of emissions under specific conditions, are presented in Chapter 11. Factors
for open dust sources are not necessarily representative of the entire industry or of a "typical" sltutation.
"Total particulate is airborne particles of all sizes in the source plume. TSP is what is measured by a standard
high volume sampler (see Section 11.2).
cReferences 5-9.
"^References 4-5. For completely wet operations, emissions are likely to be negligible.
Extrapolation of data, using k factors for appropriate operation from Chapter 11.
^For physical, not aerodynamic, diameter.
SRefereuce 6. Includes the following distinct source operations In the storage cycle: (1) loading of aggregate
onto storage piles (batch or continuous drop operations), (2) equipment traffic in storage areas, (3) wind
erosion of pile (batch or continuous drop operations). Assumes 8 to 12 hours of activity/24 hours.
^Kg/hectare (lb/acre) of storage/day (Includes areas among piles).
^See Section 11.2 for empirical equations.
References for Section 8.19.1
1• Air Pollution Control Techniques For Nonmetallic Minerals Industry,
EPA-450/3-82-014, U. S. Environmental Protection Agency, Research
Triangle Park, NC, August 1982.
2. S. Walker, "Production of Sand and Gravel", Circular Number 57, National
Sand and Gravel Association, Washington, DC, 1954.
3. Development Document For Effluent Limitations Guidelines And Standards -
Mineral Mining And Processing Industry, EPA-440/l-76-059b. U. S. Environ-
raental Protection Agency, Washington, DC, July 1979.
9/85
EMISSION FACTORS
8.19.1-3
-------
4- Review Emissions Data Base And Develop Emission Factors For The Construc-
tion Aggregate Industry, Engineering-Science, Inc., Arcadia, CA, September
1984.
5. "Crushed Rock Screening Source Test Reports on Tests Performed at Conrock
Corp., Irwindale and Sun Valley, CA Plants", Engineering-Science, Inc.,
Arcadia, CA, August 1984.
6. C. Cowherd, Jr., et al., Development Of Emission Factors For Fugitive Dust
Sources, EPA-450/3-74-037, U. S. Environmental Protection Agency, Research
Triangle Park, NC, June 1974.
7. R. Bohn, et al., Fugitive Emissions^ From Integrated Iron And Steel Plants,
EPA-600/2-78-050, U. S. Environmental Protection Agency, Washington, DC,
March 1978.
8. G. A. Jutze and K. Axetell, Investigation Of Fugitive Dust, Volume I:
Sources, Emissions and Control, EPA-450/3-74-036a, U. S. Environmental
Protection Agency, Research Triangle Park, NC, June 1974.
9. Fugitive Dust Assessment At Rock And Sand Facilities In The South Coast
Air _Basin, Southern California Rock Products Association and Southern
California Ready Mix Concrete Association, P.E.S., Santa Monica, CA,
November 1979.
8.19.1-4 Mineral Products Industry 9/85
-------
8.19.2 CRUSHED STONE PROCESSING
8.19.2.1 Process Description1
Major rock types processed by the rock and crushed stone industry include
limestone, dolomite, granite, traprock, sandstone, quartz and quartzite. Minor
types include calcareous marl, marble, shell and slate. Industry classifica-
tions vary considerably and, in many cases, do not reflect actual geological
definitions.
Rock and crushed stone products generally are loosened by drilling and
blasting, then are loaded by power shovel or front end loader and transported
by heavy earth moving equipment. Techniques used for extraction vary with the
nature and location of the deposit. Further processing may include crushing,
screening, size classification, material handling, and storage operations. All
of these processes can be significant sources of dust emissions if uncontrolled.
Some processing operations also include washing, depending on rock type and
desired product.
Quarried stone normally is delivered to the processing plant by truck and
is dumped into a hoppered feeder, usually a vibrating grizzly type, or onto
screens, as illustrated in Figure 8.19.2-1. These screens separate or scalp
large boulders from finer rocks that do not require primary crushing, thus
reducing the load to the primary crusher. Jaw, or gyratory, crushers are
usually used for initial reduction. The crusher product, normally 7.5 to 30
centimeters (3 to 12 inches) in diameter, and the grizzly throughs (undersize
material) are discharged onto a belt conveyor and usually are transported either
to secondary screens and crushers or to a surge pile for temporary storage.
Further screening generally separates the process flow into either two
or three fractions (oversize, undersize and throughs) ahead of the secondary
crusher. The oversize is discharged to the secondary crusher for further
reduction, and the undersize usually bypasses the secondary crusher. The
throughs sometimes are separated, because they contain unwanted fines, and are
stockpiled as crusher run material. Gyratory crushers or cone crushers are
commonly used for secondary crushing, although impact crushers are sometimes
found.
The product of the secondary crushing stage, usually 2.5 centimeters (1
inch) diameter or less, is transported to secondary screens for further sizing.
Oversize material is sent back for recrushing. Depending on rock type and
desired product, tertiary crushing or grinding may be necessary, usually using
cone crushers or hammermills. (Rod mills, ball mills and hammer mills normally
are used in milling operations, which are not considered a part of the construc-
tion aggregate industry.) The product from tertiary crushing may be conveyed
to a classifier, such as a dry vibrating screen system, or to an air separator.
Any oversize is returned to the tertiary crusher for further reduction. At this
point, end products of the desired grade are conveyed or trucked directly to
finished product bins or to open area stockpiles.
9/85 Mineral Products Industry 8.19.2-1
-------
1
FIGURE 8.19.2-1. TYPICAL STONE PROCESSING PLANT
8.19.2-2
EMISSION FACTORS
9/85
-------
In certain cases, stone washing is required to meet particular end product
specifications or demands, as with concrete aggregate processing. Crushed and
broken stone normally are not milled but are screened and shipped to the consumer
after secondary or tertiary crushing.
8.19.2.2 Emissions and Controls1"^
Dust emissions occur from many operations in stone quarrying and pro-
cessing. A substantial portion of these emissions consists of heavy particles
that may settle out within the plant. As in other operations, crushed stone
emission sources may be categorized as either process sources or fugitive dust
sources. Process sources include those for which emissions are amenable to
capture and subsequent control. Fugitive dust sources generally involve the
reentrainment of settled dust by wind or machine movement. Factors affecting
emissions from either source category include the type, quantity and surface
moisture content of the stone processed; the type of equipment and operating
practices employed; and topographical and climatic factors.
Of geographic and seasonal factors, the primary variables affecting uncon-
trolled particulate emissions are wind and material moisture content. Wind
parameters vary with geographical location, season and weather. It can be
expected that the level of emissions from unenclosed sources (principally fugi-
tive dust sources) will be greater during periods of high winds. The material
moisture content also varies with geographic location, season and weather.
Therefore, the levels of uncontrolled emissions from both process emission
sources and fugitive dust sources generally will be greater in arid regions
of the country than in temperate ones, and greater during the summer months
because of a higher evaporation rate.
The moisture content of the material processed can have a substantial
effect on uncontrolled emissions. This is especially evident during mining,
initial material handling, and initial plant process operations such as primary
crushing. Surface wetness causes fine particles to agglomerate on, or to adhere
to, the faces of larger stones, with a resulting dust suppression effect. How-
ever, as new fine particles are created by crushing and attrition, and as the
moisture content is reduced by evaporation, this suppressive effect diminishes
and may disappear. Depending on the geographic and climatic conditions, the
moisture content of mined rock may range from nearly zero to several percent.
Since moisture content is usually expressed on a basis of overall weight per-
cent, the actual moisture amount per unit area will vary with the size of the
rock being handled. On a constant mass fraction basis, the per unit area mois-
ture content varies inversely with the diameter of the rock. Therefore, the
suppressive effect of the moisture depends on both the absolute mass water con-
tent and the size of the rock product. Typically, a wet material will contain
1.5 to 4 percent water or more.
There are a large number of material, equipment and operating factors
which can influence emissions from crushing. These include: (1) rock type,
(2) feed size and distribution, (3) moisture content, (4) throughput rate, (5)
crusher type, (6) size reduction ratio, and (7) fines content. Insufficient
data are available to present a matrix of rock crushing emission factors
detailing the above classifications and variables. Data available from which
to prepare emission factors also vary considerably, for both extractive testing
and plume profiling. Emission factors from extractive testing are generally
9/85 Mineral Products Industry 8.19.2-3
-------
higher than those based upon
degree of reliability. Some
emissions than from secondary
rates and visual observations
factor, on a throughput basis
factors for either primary or
base. An emission factor for
extremely limited data. All
highly variable data base.
plume profiling tests, but they have a greater
test data for primary crushing indicate higher
crushing, although factors affecting emission
suggest that the secondary crushing emission
should be higher. Table 8.19.2-1 shows single
secondary crushing reflecting a combined data
tertiary crushing is given, but it is based on
factors are rated low because of the limited and
TABLE 8.19.2-1.
UNCONTROLLED PARTICIPATE EMISSION FACTORS
FOR CRUSHING OPERATIONSa
Type of Crushingb
Primary or secondary
Dry material
Wet material0
Tertiary, dry material^
Particulate Matter
< 30 pm
kg/Mg (Ib/ton)
0.14 (0.28)
0.009 (0.018)
0.93 (1.85)
< 10 urn
kg/Mg (Ib/ton)
0.0085 (0.017)
-
-
Emission
Factor
Rating
D
D
E
aBased on actual feed rate of raw material entering the particular operation.
Emissions will vary by rock type, but data available are insufficient to
characterize these phenomena. Dash = no data.
^References 4-5. Factors are uncontrolled. Typical control efficiencies:
cyclone, 70 - 80%; fabric filter, 99%; wet spray systems, 70 - 90%.
^References 5-6. Refers to crushing of rock either naturally wet or after
moistened to 1.5 to 4 weight % by use of wet suppression techniques.
dRange of values used to calculate emission factor was 0.0008 - 1.38 kg/Mg.
There are no screening emission factors presented in this Section. How-
ever, the screening emission factors given in Section 8.19.1, Sand and Gravel
Processing, should be similar to those expected from screening crushed rock.
Milling of fines is also not included in this Section as this operation is
normally associated with non construction aggregate end uses and will be covered
elsewhere in the future when information is adequate.
Open dust source (fugitive dust) emission factors for stone quarrying and
processing are presented in Table 8.19.2-2. These factors have been determined
through tests at various quarries and processing plants.6~7 -phe single valued
open dust emission factors given in Table 8.19.2-2 may be used when no other
information exists. Empirically derived emission factor equations presented
in Section 11.2 of this document are preferred and should be used when possible.
Because these predictive equations allow the adjustment of emission factors for
8.19.2-4
EMISSION FACTORS
9/85
-------
-------
specific source conditions, these equations should be used instead of those in
Table 8.19.2-2, whenever emission estimates applicable to specific stone quarry-
ing and processing facility sources are needed. Chapter 11.2 provides measured
properties of crushed limestone, as required for use in the predictive emission
factor equations.
References for Section 8.19.2
1. Air Pollution Control Techniques for Nonmetallic Minerals Industry,
EPA-450/3-82-014, U. S. Environmental Protection Agency, Research
Triangle Park, NC, August 1982.
2. P. K. Chalekode, et al., Emissions from the Crushed Granite Industry;
State of the Art, EPA-600/2-78-021, U. S. Environmental Protection
Agency, Washington, DC, February 1978.
3. T. R. Blackwood, et al., Source Assessment; Crushed Stone, EPA-600/2-78-
004L, U. S. Environmental Protection Agency, Washington, DC, May 1978.
4. F. Record and W. T. Harnett, Farticulate Emission Factors for the
Construction Aggregate Industry, Draft Report, GCA-TR-CH-83-02, EPA
Contract No. 68-02-3510, GCA Corporation, Chapel Hill, NC, February 1983.
5. Review Emission Data Base and Develop Emission Factors for the Con-
struction Aggregate Industry, Engineering-Science, Inc., Arcadia, CA,
September 1984.
6. C. Cowherd, Jr., et al., Development of Emission Factors for Fugitive Dust
Sources, EPA-450/3-74-037, U. S. Environmental Protection Agency, Research
Triangle Park, NC, June 1974.
7. R. Bohn, et al., Fugitive Emissions from Integrated Iron and Steel Plants,
EPA-600/2-78-050, U. S. Environmental Protection Agency, Washington, DC,
March 1978.
8.19.2-6
EMISSION FACTORS
9/85
-------
SECTION 8.20
This Section is reserved for future use.
9/85 Mineral Products Industry 8.20-1
-------
-------
8.21 COAL CONVERSION
In addition to its direct use for combustion, coal can be converted
to organic gases and liquids, thus allowing the continued use of conven-
tial oil and gas fired processes when oil and gas supplies are not
available. Currently, there is little commercial coal conversion in the
United States. Consequently, it is very difficult to determine which of
the many conversion processes will be commercialized in the future. The
following sections provide general process descriptions and general
emission discussions for high-, medium- and low-Btu gasification (gasi-
faction) processes and for catalytic and solvent extraction liquefaction
processes.
1-2
8.21.1 Process Description
8.21.1.1 Gasification - One means of converting coal to an alternate
form of energy is gasification. In this process, coal is combined with
oxygen and steam to produce a combustible gas, waste gases, char and
ash. The more than 70 coal gasification systems currently available or
being developed (1979) can be classified by the heating value of the gas
produced and by the type of gasification reactor used. High-Btu gasi-
fication systems produce a gas with a heating value greater than 900
Btu/scf (33,000 J/m3). Medium-Btu gasifiers produce a gas having a
heating value between 250 - 500 Btu/scf (9,000 - 19,000 J/m3). Low-Btu
gasifiers produce a gas having a heating value of less than 250 Btu/scf
(9,000 J/m3).
The majority of the gasification systems consist of four operations:
coal pretreatment, coal gasification, raw gas cleaning and gas beneficia-
tion. Each of these operations consists of several steps. Figure
8.21-1 is a flow diagram for an example coal gasification facility.
Generally, any coal can be gasified if properly pretreated. High
moisture coals may require drying. Some caking coals may require
partial oxidation to simplify gasifier operation. Other pretreatment
operations include crushing, sizing, and briqueting of fines for feed to
fixed bed gasifiers. The coal feed is pulverized for fluid or entrained
bed gasifiers.
After pretreatment, the coal enters the gasification reactor, where
it reacts with oxygen and steam to produce a combustible gas. Air is
used as the oxygen source for making low-Btu gas, and pure oxygen is
used for making medium- and high-Btu gas (inert nitrogen in the air
dilutes the heating value of the product). Gasification reactors are
classified by type of reaction bed (fixed, entrained or fluidized), the
operating pressure (pressurized or atmospheric), the method of ash
removal (as molten slag or dry ash), and the number of stages in the
gasifier (one or two). Within each class, gasifiers have similar
emissions.
Mineral Pnxlucls Irnlusirv 8.21-1
-------
1
The raw gas from the gasifier contains varying concentrations of
carbon monoxide, carbon dioxide, hydrogen, methane, other organics,
hydrogen sulfide, miscellaneous acid gases, nitrogen (if air was used as
the oxygen source), particulates and water. Four gas purification proc-
esses may be required to prepare the gas for combustion or further
benef iciation: particulate removal, tar and oil removal, gas quenching
and cooling, and acid gas removal. The primary function of the partic-
ulate removal process is the removal of coal dust, ash and tar aerosols
in the raw product gas. During tar and oil removal and gas quenching
and cooling, tars and oils are condensed, and other impurities such as
ammonia are scrubbed from raw product gas using either aqueous or
organic scrubbing liquors. Acid gases such as H2S, COS, CS2 , mercap-
tans, and C(>2 can be removed from gas by an acid gas removal process.
Acid gas removal processes generally absorb the acid gases in a solvent,
from which they are subsequently stripped, forming a nearly pure acid
gas waste stream with some hydrocarbon carryover. At this point, the
raw gas is classified as either a low-Btu or medlum-Btu gas.
To produce high-Btu gas, the heating value of the mediutn-Btu gas is
raised by shift conversion and methanation. In the shift conversion
process, H20 and a portion of the CO are catalytically reacted to form
C02 and H2. After passing through an absorber for C02 removal, the
remaining CO and H2 in the product gas are reacted in a methanation
reactor to yield Ctfy and
There are also many auxiliary processes accompanying a coal gasi-
fication facility, which provide various support functions. Among the
typical auxiliary processes are oxygen plant, power and steam plant,
sulfur recovery unit, water treatment plant, and cooling towers.
8.21.1.2 Liquefaction - Liquefaction is a conversion process designed
to produce synthetic organic liquids from coal. This conversion is
achieved by reducing the level of impurities and increasing the hydrogen
to carbon ratio of coal to the point that is becomes fluid. Currently,
there are over 20 coal liquefaction processes in various stages of
development by both industry and Federal agencies (1979) . These
processes can be grouped into four basic liquefaction techniques:
- Indirect liquefaction
- Pyrolysis
- Solvent extraction
- Catalytic liquefaction
Indirect liquefaction involves the gasification of coal followed by the
catalytic conversion of the product gas to a liquid. Pyrolysis lique-
faction involves heating coal to very high temperatures, thereby crack-
ing the coal into liquid and gaseous products. Solvent extraction uses
a solvent generated within the process to dissolve the coal and to
transfer externally produced hydrogen to the coal molecules. Catalytic
liquefaction resembles solvent extraction, except that hydrogen is added
to the coal with the aid of a catalyst.
8.21-2 EMISSION FACTORS 2/80
-------
Steam
Oxygen or
Air
Coal Preparation
Drying
Crushing
Partial Oxidation
Briqueting
-*Coal Hopper Gas
product gas
High-Btu
Product Gas
Coal
preparation
Tar
•Tail Gas
Sulfur
Gasification
Raw gas
cleaning
Gas
beneficiation
Figure 8.21-1. Flow diagram of typical coal gasification plant.
2/80
Mineral Products liuluslr\
K.2 1 -3
-------
Figure 8.21-2 presents the flow diagram of a typical solvent extrac-
tion or catalytic liquefaction plant. These coal liquefaction processes
consist of four basic operations: coal pretreatment, dissolution and
liquefaction, product separation and purification, and residue
gasification.
Coal pretreatment generally consists of coal pulverizing and
drying. The dissolution of coal is best effected if the coal is dry and
finely ground. The heater used to dry coal is typically coal fired, but
it may also combust low-BTU value product streams or may use waste heat
from other sources.
The dissolution and liquefaction operations are conducted in a
series of pressure vessels. In these processes, the coal is mixed with
hydrogen and recycled solvent, heated to high temperatures, dissolved
and hydrogenated. The order in which these operations occur varies
among the liquefaction processes and, in the case of catalytic liquefac-
tion, involves contact with a catalyst. Pressures in these processes
range up to 2000 psig (14,000 Pa), and temperatures range up to 900°F
(480°C). During the dissolution and liquefaction process, the coal is
hydrogenated to liquids and some gases, and the oxygen and sulfur in the
coal are hydrogenated to H20 and H2S.
After hydrogenation, the liquefaction products are separated,
through a series of flash separators, condensers, and distillation
units, into a gaseous stream, various product liquids, recycle solvent,
and mineral residue. The gases from the separation process are separ-
ated further by absorption into a product gas stream and a waste acid
gas stream. The recycle solvent is returned to the dissolution/lique-
faction process, and the mineral residue of char, undissolved coal and
ash is used in a conventional gasification plant to produce hydrogen.
The residue gasification plant closely resembles a convential high-
Btu coal gasifaction plant. The residue is gasified in the presence of
oxygen and steam to produce CO, H2, f^O, other waste gases, and partic-
ulates. After treatment for removal of the waste gases and particulates,
the CO and H20 go into a shift reactor to produce C02 and additional H2.
The H2 enriched product gas from the residue gasifier is used subsequently
in the hydrogenation of the coal.
There are also many auxiliary processes accompanying a coal lique-
faction facility which provide various support functions. Among the
typical auxiliary processes are oxygen plant, power and steam plant,
sulfur recovery unit, water treatment plant, cooling towers, and sour
water strippers.
1-3
8.21.2 Emissions and Controls
Although characterization data are availabe for some of the many
developing coal conversion processes, describing these data in detail
would require a more extensive discussion than possible here. So, this
8.21-4 EMISSION FACTORS 2/80
-------
to
09
-O
Product
liquids
Hydrogen
Gasification
Shift conversion
Acid gas removal
Dehydration
Mineral residue
"">• Condensates
*• Ash
" Waste gases
Figure 8.21-2. Flow diagram for an example coal liquefaction facility.
co
to
-------
CO
to
1-3
Table 8.21-1. SUMMARY OF EMISSIONS FROM COAL GASIFICATION PLANTS
Operation/Emission Source/Stream Characterization of Emission Summary of Emission Control Choices
Coal Pretreatment
Storage, handling and crushing/
sizing - Dust emissions
W
M
Vl
VI
O
2
^
W
a
Drying, partial oxidation
and briqueting - Vent gases
Coal Gasification
Feeding - Vent gases
Emissions from coal storage,
handling and crushing/sizing
mainly consist of coal dust.
These emissions vary from
site to site, depending on
wind velocities, coal and
pile size, and water
content.
These emissions comprise
coal dust and combustion
gases along with a variety
of organic compounds devola-
tilized from the coal.
Organic species have not
been determined.
These gases contain all the
hazardous species found in
the raw product gas exiting
the gasifier, including H2S,
COS, CS2, S02, CO, NH3, CH4,
HCN, tars and oils, parti-
culates, and trace organics
and inorganics. The size
and composition of this
stream depend on the type
of gasifier, e.g., fluidized
Water sprays and polymer coatings
are used to control dust emissions
from coal storage piles. Water
sprays and enclosed equipment are
vented to a baghouse to reduce or
capture particulates from coal
handling. Emissions from crushing/
sizing are also usually vented to a
baghouse or other particulate
control device.
In addition to particulate control
devices, afterburners may be needed
to destroy organic species.
This stream could represent a sign
ificant environmental problem.
Control could include scrubbing or
incineration (to capture or destroy
the most hazardous species), or
venting to the raw product gas or
gasifier inlet air. The desired
control depends on the type and size
of gasification facility. Screw
fed conveyors can be used instead of
lock hoppers.
-------
OS
o
Table 8.21-1 (cont.). SUMMARY OF EMISSIONS FROM COAL GASIFICATION PLANTS1"3
Operation/Emission Source/Stream Characterization of Emission Summary of Emission Control Choices
bed gasifiers emit substant-
ially fewer tars and oils
than fixed bed gasifiers.
Ash removal - Vent gases
Startup - Vent gases
Fugitives
co
Emissions from ash removal
and disposal depend on the
type of gasifier. Ash dust
will be released from all
gasifiers that are not
slagging or agglomerating
ash units. If contaminated
water is used for ash quench-
ing, volatile organic and
inorganic species may be
released from the quench
liquor.
This vent gas initially
resembles a coal combustion
gas in composition. As the
operating temperature of
the gas increases, the
startup gas begins to
resemble the raw product
gas.
These emissions have not
been characterized, but they
comprise hazardous species
found in the raw product gas
such as H2S, COS, CS2, CO,
HCN, CH^ and others.
These emissions have not been
sufficiently characterized to recom-
mend necessary controls. Particulate
or organic emission controls could be
needed. Clean water may be used for
quenching to avoid the potential
emission of hazardous volatile organic
and inorganic species.
A flare can incinerate the combustible
constituents in the startup gas, but
heavy tars and coal particulates will
affect the performance of the flare.
Potential problems with tars and
particulates can be avoided by using
charcoal or coke as the startup fuel.
Control methods mainly involve good
maintenance and operating practices.
-------
CO
to
I
CO
Table 8.21-1 (cont.).
Operation/Emission Source/Stream
Raw Gas Cleaning/Beneficiation
Fugitives
w
Acid Gas Removal - Tail gases
to
\
CO
o
Auxiliary Operations
Sulfur recovery
Power and steam generation
SUMMARY OF EMISSIONS FROM COAL GASIFICATION PLANTS1"3
Characterization of Emission Summary of Emission Control Choices
These emissions have not
been characterized, but they
comprise hazardous species
found in the various gas
streams. Other emissions
result from leaks from pump
seals, valves, flanges and by-
product storage tanks.
Control methods mainly involve good
maintenance and operating practices.
The composition of this
stream highly depends on the
kind of acid gas removal
employed. Processes
featuring the direct removal
and conversion of sulfur
species in a single step
(e.g., the Stretford process)
produce tail gases contain-
ing small amounts of NHs
and other species. Pro-
cesses absorbing and
subsequently desorbing a
concentrated acid gas
stream require a sulfur
recovery process to avoid
the emission of highly toxic
gases having quantities of H2S
See Section 5.18
See Section 1.1
Some tail gas streams (from the
Stretford process, for example) are
probably not very hazardous. These
streams have not been characterized,
nor have control technology needs
been demonstrated. Tail gases from
other processes always require the
removal of sulfur species. Trace
constituents such as organics, trace
elements and cyanides affect the
performance of the auxiliary sulfur
removal processes.
-------
to
\
CO
o
1-3
Table 8.21-1 (cont.). SUMMARY OF EMISSIONS FROM COAL GASIFICATION PLANTS
Operation/Emission Source/Stream Characterization of Emission Summary of Emission Control Choices
Wastewater Treatment -
Expansion gases
Cooling Towers - Exhaust gas
•1
"3
These streams comprise
volatile organic and in-
organic species that desorb
from quenching/cooling
liquor. The streams potent-
ially include all the
hazardous species found in
the product gas.
Emissions from cooling
towers are usually minor.
However, if contaminated
water is used as cooling
water makeup, volatile
organic and inorganic
species from the con-
taminated water could be
released.
These streams could pose significant
environmental problems. Potential
controls are generally similar to
those needed to treat coal feeding
vent gases.
The potential emission of hazardous
volatile organic and inorganic species
may be avoided by using clean water
for cooling.
CO
Is
-------
Section will cover emissions and controls for coal conversion processes
on a qualitative level only.
8.21.2.1 Gasification - All of the major operations associated with
low-, medium- and high-Btu gasification technology (coal pretreatment,
gasification, raw gas cleaning, and gas beneficiation) can produce
potentially hazardous air emissions. Auxiliary operations, such as
sulfur recovery and combustion of fuel for electricity and steam genera-
tion, could account for a major portion of the emissions from a gasifica-
tion plant. Discharges to the air from both major and auxiliary operations
are summarized and discussed in Table 8.21-1.
Dust emissions from coal storage, handling and crushing/sizing can
be controlled with available techniques. Controlling air emissions from
coal drying, briqueting and partial oxidation processes is more difficult
because of the volatile organics and possible trace metals liberated as
the coal is heated.
The coal gasification process itself appears to be the most serious
potential source of air emissions. The feeding of coal and the with-
drawal of ash release emissions of coal or ash dust and organic and
inorganic gases that are potentially toxic and carcinogenic. Because of
their reduced production of tars and condensable organics, slagging
gasifiers pose less severe emission problems at the coal inlet and ash
outlet.
Gasifiers and associated equipment also will be sources of potenti-
ally hazardous fugitive leaks. These leaks may be more severe from
pressurized gasifiers and/or gasifiers operating at high temperatures.
Raw gas cleaning and gas beneficiation operations appear to be
smaller sources of potential air emissions. Fugitive emissions have not
been characterized but are potentially large. Emissions from the acid
gas removal process depend on the kind of removal process employed at a
plant. Processes used for acid gas removal may remove both sulfur
compounds and carbon dioxide or may be operated selectively to remove
only the sulfur compounds. Typically, the acid gases are stripped from
the solvent and processed in a sulfur plant. Some processes, however,
directly convert the absorbed hydrogen sulfide to elemental sulfur.
Emissions from these direct conversion processes (e.g., the Stretford
process) have not been characterized but are probably minor, consisting
of C02, air, moisture and small amounts of
Emission controls for two auxiliary processes (power and steam
generation and sulfur recovery) are discussed elsewhere in this document
(Sections 1.1 and 5.18, respectively). Gases stripped or desorbed from
process wastewaters are potentially hazardous, since they contain many
of the components found in the product gas. These include sulfur and,
nitrogen species, organics, and other species that are toxic and potenti
ally carcinogenic. Possible controls for these gases include incinera-
tion, byproduct recovery, or venting to the raw product gas or inlet
8.21-10 EMISSION FACTORS 2/80
-------
to
\
CO
o
Table 8.21-2. SUMMARY OF EMISSIONS FROM COAL LIQUEFACTION FACILITY1
Operation/Emission Source/Stream Characterization of Emission Summary of Emission Control Choices
Coal Preparation
Storage, handling and
crushing/sizing
Drying
Emissions primarily consist
of fugitive coal dust gen-
erated at transfer points
and points exposed to wind
erosion. A potentially
significant source.
Emissions include coal dust,
combustion products from
heater, and organics
volatilized from the coal.
A potentially significant
particulate source.
Water sprays and polymer coatings are
used to control dust from storage sites.
Water sprays and enclosures vented to
baghouses are effective on crushing
and sizing operations.
Scrubbers, electrostatic precipitators,
and baghouses are effective coal dust
controls. Low drying temperatures
reduce organics formation.
Coal Dissolution and
Liquefaction
Process heater (fired with
low grade fuel gas)
Emissions consist of combus-
tion products (particulates,
CO, S02, NOx and HC) .
Fuel desulfurization for S02 control
and combustion modifications for
reduced CO, HC and
Slurry mix tank
Product Separation and
Liquefaction - Sulfur recovery
plant
Evolution of dissolved gases
from recycle solvent (HC,
acid gases, organics) due to
low pressure (atmospheric)
of tank. Some pollutants are
toxic even in small quantities.
Controls might include scrubbing,
incineration or venting to heater
combustion air supply.
Tail gases containing acids
(H2S, S02, COS, CS2 NH3 and
particulate sulfur).
Venting to tail gas treatment plant,
or operating sulfur recovery plant at
higher efficiency.
-------
Table 8.21-2 (cont.). SUMMARY OF EMISSIONS FROM COAL LIQUEFACTION FACILITY
Operation /Emission Source/Stream Characterization of Emission Summary of Emission Control Choices
Residue Gasification See 8.21.2.1, in text.
Auxiliary Processes
Power and steam generation
Wastewater system
Cooling towers
x
^
<•»,
^j
X
55
Fugitives
See Section 1.1.
Volatile organics, acid
gases, ammonia and cyanides,
which evolve from various
waste water collection and
treating systems.
Any chemical in the facility
can leak to cooling water
system from leaking heat
exchangers and can be
stripped to the atmosphere in
the cooling tower.
All organic and gaseous com-
pounds in plant can leak
from valves, flanges, seals
and sample ports. This may
be the largest source of
hazardous organics.
Enclosure of the waste water system
and venting gases from system to
scrubbers or incinerators.
Good heat exchanger maintenance and
surveillance of cooling water quality.
Good housekeeping, frequent main-
tenance and selection of durable
components are major control
techniques.
-------
air. Cooling towers are usually minor emission sources, unless the
cooling water is contaminated.
8.21.2.2 Liquefaction - The potential exists for generation of signifi-
cant levels of atmospheric pollutants from every major operation in a
coal liquefaction facility. These pollutants include coal dust, combust-
ion products, fugitive organics and fugitive gases. The fugitive
organics and gases could include carcinogenic polynuclear organics and
toxic gases such as metal carbonyls, hydrogen sulfides, ammonia, sulfu-
rous gases, and cyanides. Many studies are currently underway to charac-
terize these emissions and to establish effective control methods.
Table 8.21-2 presents information now available on liquefaction emissions.
Emissions from coal preparation include coal dust from the many
handling operations and combustion products from the drying operation.
The most significant pollutant from these operations is the coal dust
from crushing, screening and drying activities. Wetting down the surface
of the coal, enclosing the operations, and venting effluents to a
scrubber or fabric filter are effective means of particulate control.
A major source of emissions from the coal dissolution and lique-
faction operation is the atmospheric vent on the slurry mix tank. The
slurry mix tank is used for mixing feed coal and recycle solvent. Gases
dissolved in the recycle solvent stream under pressure will flash from
the solvent as it enters the unpressurized slurry mix tank. These gases
can contain hazardous volatile organics and acid gases. Control tech-
niques proposed for this source include scrubbing, incineration or
venting to the combustion air supply for either a power plant or a
process heater.
Emissions from process heaters fired with waste process gas or
waste liquids will consist of standard combustion products. Industrial
combustion emission sources and available controls are discussed in
Section 1.1.
The major emission source in the product separation and purifi-
cation operations is the sulfur recovery plant tail gas. This can
contain significant levels of acid or sulfurous gases. Emission factors
and control techniques for sulfur recovery tail gases are discussed in
Section 5.18.
Emissions from the residue gasifier used to supply hydrogen to the
system are very similar to those for coal gasifiers previously discussed
in this Section.
Emissions from auxiliary processes include combustion products from
onsite steam/electric power plant and volatile emissions from the
wastewater system, cooling towers and fugitive emission sources.
Volatile emissions from cooling towers, wastewater systems and fugitive
emission sources possibly can include every chemical compound present in
the plant. These sources will be the most significant and most difficult
2/80 Mineral PrmhirlK IncliiNlrv 8.21-13
-------
to control in a coal liquefaction facility. Compounds which can be
present include hazardous organics, metal carbonyls, trace elements such
as mercury, and toxic gases such as CO, H2S, HCN, NH3, COS and CS2.
Emission controls for wastewater systems involve minimizing the
contamination of water with hazardous compounds, enclosing the waste
water systems, and venting the wastewater systems to a scrubbing or
incineration system. Cooling tower controls focus on good heat exchanger
maintenance, to prevent chemical leaks into the system, and on surveil-
lance of cooling water quality. Fugitive emissions from various valves,
seals, flanges and sampling ports are individually small but collec-
tively very significant. Diligent housekeeping and frequent maintenance,
combined with a monitoring program, are the best controls for fugitive
sources. The selection of durable low leakage components, such as
double mechanical seals, is also effective.
References for Section 8.21
1. C. E. Burklin and W. J. Moltz, Energy Resource Development System,
EPA Contract No. 68-01-1916, Radian Corporation and The University
of Oklahoma, Austin, TX, September 1978.
2. E. C. Cavanaugh, et al., Environmental Assessment Data Base for
Low/Medium-BTU Gasification Technology, Volume 1,
EPA-600/7-77-125a, U. S. Environmental Protection Agency, Research
Triangle Park, NC, November 1977.
3. P. W. Spaite and G. C. Page, Technology Overview: Low- and Medium-
BTU Coal Gasification Systems, EPA-600/7-78-061, U.S. Environmental
Protection Agency, Research Triangle Park, NC, March 1978.
8.21-14 EMISSION FACTORS 2/80
-------
8.22 TACONITE ORE PROCESSING
8.22.1 General1'2
More than two thirds of the iron ore produced in the United States for
making iron consists of taconite concentrate pellets. Taconite is a low
grade iron ore, largely from deposits in Minnesota and Michigan, but from
other areas as well. Processing of taconite consists of crushing and
grinding the ore to liberate ironbearing particles, concentrating the ore
by separating the particles from the waste material (gangue), and pelletiz-
ing the iron ore concentrate. A simplified flow diagram of these process-
ing steps is shown in Figure 8.22-1.
Liberation - The first step in processing crude taconite ore is crushing
and grinding. The ore must be ground to a particle size sufficiently close
to the grain size of the ironbearing mineral, to allow for a high degree of
mineral liberation. Most of the taconite used today requires very fine
grinding. The grinding is normally performed in three or four stages of
dry crushing, followed by wet grinding in rod mills and ball mills. Gy-
ratory crushers are generally used for primary crushing, and cone crushers
are used for secondary and tertiary fine crushing. Intermediate vibrating
screens remove undersize material from the feed to the next crusher and al-
low for closed circuit operation of the fine crushers. The rod and ball
mills are also in closed circuit with classification systems such as cy-
clones. An alternative is to feed some coarse ores directly to wet or dry
semiautogenous or autogenous grinding mills, then to pebble or ball mills.
Ideally, the liberated particles of iron minerals and barren gangue should
be removed from the grinding circuits as soon as they are formed, with
larger particles returned for further grinding.
Concentration - As the iron ore minerals are liberated by the crushing
steps, the ironbearing particles must be concentrated. Since only about 33
percent of the crude taconite becomes a shippable product for iron making,
a large amount of gangue is generated. Magnetic separation and flotation
are most commonly used for concentration of the taconite ore.
Crude ores in which most of the recoverable iron is magnetite (or, in
rare cases, maghemite) are normally concentrated by magnetic separation.
The crude ore may contain 30 to 35 percent total iron by assay, but theo-
retically only about 75 percent of this is recoverable magnetite. The re-
maining iron becomes part of the gangue.
Nonmagnetic taconite ores are concentrated by froth flotation or by a
combination of selective flocculation and flotation. The method is deter-
mined by the differences in surface activity between the iron and gangue
particles. Sharp separation is often difficult.
Various combinations of magnetic separation and flotation may be used
to concentrate ores containing various iron minerals (magnetite and hema-
tite, or maghemite) or wide ranges of mineral grain sizes. Flotation is
also often used as a final polishing operation on magnetic concentrates.
5/83 Mineral Products Industry 8.22-1
-------
Oversize ore
CO
rO
ho
tn
tn
H
§
H
O
oo
Raw
Taconite
t
Primary
(Coarse)
Crusher
>
i
Secondary
(Fine)
Crusher
t
Screen
i
I
Tertiary
(Fine)
Cruaher
t
Screen
Crushed
Primary
(Rod)
Hill
-
Classifier
Overstze ore
Tail
and screened ore
Magnetic
Separator
incs i
Secondary
(Ball)
Hill
Oversize
ore
Classifier
1
(Additional stages of grinding and
magnetic separation may bt;
enip loyed)
Hydro-
separator
Magnetic
Separator
Tailings
Ore
Concentrate
Fuel
Figure 8.22-1, Taconite ore processing plant. (Process emissions are indicated by (.}
t
-------
Pelletization - Iron ore concentrates must be coarser than about No. 10
mesh to be acceptable as blast furnace feed without further treatment. The
finer concentrates are agglomerated into small "green" pellets. This is
normally accomplished by tumbling moistened concentrate with a balling drum
or balling disc. A binder additive, usually powdered bentonite, may be
added to the concentrate to improve ball formation and the physical quali-
ties of the "green" balls. The bentonite is lightly mixed with the care-
fully moistened feed at 4.5 to 9 kilograms per megagram (10 to 20 Ib/ton).
The pellets are hardened by a procedure called induration, the drying
and heating of the green balls in an oxidizing atmosphere at incipient fu-
sion temperature [1290 to 1400°C (2350 to 2550°F), depending on the compo-
sition of the balls] for several minutes and then cooling. Four general
types of indurating apparatus are currently used. These are the vertical
shaft furnace, the straight grate, the circular grate and grate/kiln. Most
of the large plants and new plants use the grate/kiln. Natural gas is most
commonly used for pellet induration now, but probably not in the future.
Heavy oil is being used at a few plants, and coal may be used at future
plants.
In the vertical shaft furnace, the wet green balls are distributed
evenly over the top of the slowly descending bed of pellets. A rising
stream of gas of controlled temperature and composition flows counter to
the descending bed of pellets. Auxiliary fuel combustion chambers supply
hot gases midway between the top and bottom of the furnace. In the
straight grate apparatus, a continuous bed of agglomerated green pellets is
carried through various up and down flows of gases at different tempera-
tures. The grate/kiln apparatus consists of a continuous traveling grate
followed by a rotary kiln. Pellets indurated by the straight grate appara-
tus are cooled on an extension of the grate or in a separate cooler. The
grate/kiln product must be cooled in a separate cooler, usually an annular
cooler with countercurrent airflow.
8.22.2 Emissions and Controls
1-3
Emission sources in taconite ore processing plants are indicated in
Figure 8.22-1. Particulate emissions also arise from ore mining opera-
tions. Uncontrolled emission factors for the major processing sources are
presented in Table 8.22-1, and control efficiencies in Table 8.22-2.
The taconite ore is handled dry through the crushing stages. All
crushers, size classification screens and conveyor transfer points are ma-
jor points of particulate emissions. Crushed ore is normally ground in wet
rod and ball mills. A few plants, however, use dry autogenous or semi-
autogenous grinding and have higher emissions than do conventional plants.
The ore remains wet through the rest of the beneficiation process, so par-
ticulate emissions after crushing are generally insignificant.
The first source of emissions in the pelletizing process is the trans-
fer and blending of bentonite. There are no other significant emissions in
the balling section, since the iron ore concentrate is normally too wet to
cause appreciable dusting. Additional emission points in the pelletizing
process include the main waste gas stream from the indurating furnace,
5/83
Mineral Products Industry
8.22-3
-------
TABLE 8.22-1. UNCONTROLLED PARTICULATE EMISSION
FACTORS FOR TACONITE ORE
PROCESSING3
EMISSION FACTOR RATING: D
Source
Fine crushing
Waste gas
Pellet handling
Grate discharge
Grate feed
Bentonite blending
Coarse crushing
Ore transfer
Bentonite transfer
kg/Mg
39.9
14.6
1.7
0.66
0.32
0.11
0.10
0.05
0.02
Emissions
Ib/ton
79.8
29.2
3.4
1.32
0.64
0.22
0.20
0.10
0.04
•a
, Reference 1. Median
values.
produced.
pellet handling, furnace transfer points (grate feed and discharge), and
for plants using the grate/kiln furnace, annular coolers. In addition,
tailings basins and unpaved roadways can be sources of fugitive emissions.
Fuel used to fire the indurating furnace generates low levels of sul-
fur dioxide emissions. For a natural gas fired furnace, these emissions
are about 0.03 kilograms of SOg per megagrara of pellets produced (0.06 lb/
ton). Higher S02 emissions (about 0.6 to 0.7 kg/Mg, or 0.12 to 0.14 lb/
ton) would result from an oil or coal fired furnace.
Particulate emissions from taconite ore processing plants are con-
trolled by a variety of devices, including cyclones, multiclones, roto-
clones, scrubbers, baghouses and electrostatic precipitators. Water sprays
are also used to suppress dusting. Annular coolers are generally left un-
controlled, because their mass loadings of particulates are small, typi-
cally less than 0.11 grams per cubic meter (0.05 g/scf).
The largest source of particulate emissions in taconite ore mines is
traffic on unpaved haul roads.3 Table 8.22-3 presents size specific emis-
sion factors for this source determined through source testing at one taco-
nite mine. Other significant particulate emission sources at taconite
mines are wind erosion and blasting.3
As an alternative to the single valued emission factors for open dust
sources given in Tables 8.22-1 and 8.22-3, empirically derived emission
8.22-4 Mineral Products Industry 5/83
-------
Ln
oo
UJ
TABLE 8.22-2.
CONTROL EFFICIENCIES FOR COMBINATIONS OF
CONTROL DEVICES AND SOURCES3
H-
p
Tf
t-i
o
CL
n
P
CL
e
tn
n-
Control
Scrubber
Cyclone
Hulticlone
Rotoclone
Bag collector
Coarse
crushing
95(10)f
99(2)m
85(l)f
92(2)f
88(2)f
91.6(4)f
99(2)m
99.9(2)m
Ore
transfer
99.5(18)f
99(5)f
99(l)m
95(2)e
98(l)f
Fine
crushing
99.5(5)f
99.6(6)f
97(10)m
97(19)e
99.7(7)f
98.3(4)f
Bentonite Bentonite
transfer blending
98(l)f 98.7(l)f
99.3(l)f
99(8)e 99(2)E
99.7(l)f
Grate Grate Waste
feed discharge gas
98.7(2)f 99.3(2)f 98,5(l)e
98(l)m 99(5)e 89(l)e
99(5)e 98(l)e
95-98(56)f
95-98 (2) f
Pellet
handling
99.3(2)f
99,7(l)f
99(2)f
97,5(!)e
98(l)e
Electrostatic
precipitator
Dry mechanical
collector
Centrifugal
collector
99.9(2)e
B5(l}f
98.8(l)e
85(l)f
88(l)f 88(l)f
98(l)e 99.4(l)e
99.4(l)e
CO
ho
ho
i
Reference I. Control efficiencies are expressed as percent reduction. Numbers in parentheses are the number of
indicated combinations with the stated efficiency. The letters m, f, e denote whether the stated efficiencies
were based upon manufacturer's rating (m), field testing (f), or estimations (e). Blanks indicate that no
such combinations of source and control technology are known to exist, or that no data on the efficiency of
the combination are available.
-------
TABLE 8.22-3. UNCONTROLLED PARTICIPATE EMISSION FACTORS FOR
HEAVY DUTY VEHICLE TRAFFIC ON HAUL ROADS AT
TACONITE MINES3
material
Crushed rock
and gla-
cial till
Crushed
taconite
and waste
Emission factor by aerodynamic diameter
< 30
3.
11.
2.
9.
pm
1
0
6
3
< 15
2.
7.
1.
6.
|Jm
2
9
9
6
< 10 |Jm
1.7
6.2
1.5
5.2
< 5 (Jin < 2
1.1 0
3.9 2
0.90 0
3.2 1
.5 urn
.62
.2
.54
.9
ITm" -he
kg/VKT
Ib/VMT
kg/WT
Ib/VMT
Emission
Rating
C
C
D
D
Reference 3. Predictive emission factor equations, which generally pro-
vide more accurate estimates of emissions, are presented in Chapter 11.
VKT = Vehicle kilometers traveled. VMT = Vehicle miles traveled.
factor equations are presented in Chapter 11 of this document. Each equa-
tion was developed for a source operation defined on the basis of a single
dust generating mechanism which crosses industry lines, such as vehicle
traffic on unpaved roads. The predictive equation explains much of the ob-
served variance in measured emission factors by relating emissions to pa-
rameters which characterize source conditions. These parameters may be
grouped into three categories: 1) measures of source activity or energy
expended (e.g., the speed and weight of a vehicle traveling on an unpaved
road), 2) properties of the material being disturbed (e.g., the content of
suspendable fines in the surface material on an unpaved road), 3) climatic
parameters (e.g., number of precipitation free days per year, when emis-
sions tend to a maximum).
Because the predictive equations allow for emission factor adjustment
to specific source conditions, the equations should be used in place of
the single valued factors for open dust sources, in Tables 8.22-1 and
8.22-3, if emission estimates for sources in a specific taconite ore mine
or processing facility are needed. However, the generally higher quality
ratings assigned to the equations are applicable only if 1) reliable values
of correction parameters have been determined for the specific sources of
interest and 2) the correction parameter values lie within the ranges
tested in developing the equations. Chapter 11 lists measured properties
of aggregate process materials and road surface materials found in taconite
mining and processing facilities, which can be used to estimate correction
parameter values for the predictive emission factor equations, in the event
that site specific values are not available. Use of mean correction param-
eter values from Chapter 11 reduces the quality ratings of the emission
factor equations by one level.
8.22-6
EMISSION FACTORS
5/83
-------
References for Section 8.22
1. J. P. Pilney and G. V. Jorgensen, Emissions from Iron Ore Mining, Ben-
ficiation and Pelletization, Volume 1, EPA Contract No. 68-02-2113,
Midwest Research Institute, Minnetonka, MN, June 1978-
2. A. K. Reed, Standard Support and Environmental Impact Statement for
the Iron Ore Beneficiation Industry (Draft), EPA Contract No. 68-02-
1323, Battelle Columbus Laboratories, Columbus, OH, December 1976.
3. T. A. Cuscino, et al., Taconite Mining Fugitive Emissions Study,
Minnesota Pollution Control Agency, Roseville, MN, June 1979-
5/83
Mineral Products Industry
8.22-7
-------
-------
8.23 METALLIC MINERALS PROCESSING
8.23.1 Process Description1-6
Metallic mineral processing typically involves the mining of ore,
either from open pit or underground mines; the crushing and grinding of ore;
the separation of valuable minerals from matrix rock through various concen-
tration steps; and at some operations, the drying, calcining or pelletizing
of concentrates to ease further handling and refining. Figure 8.23-1 is a
general flow diagram for metallic mineral processing. Very few metallic
mineral processing facilities will contain all of the operations depicted in
this Figure, but all facilities will use at least some of these operations
in the process of separating valued minerals from the matrix rock.
The number of crushing steps necessary to reduce ore to the proper size
will vary with the type of ore. Hard ores, including some copper, gold, iron
and molybdenum ores, may require as much as a tertiary crushing. Softer
ores, such as some uranium, bauxite and titanium/zirconium ores, require
little or no crushing. Final comminution of both hard and soft ores is often
accomplished by grinding operations using media such as balls or rods of var-
ious materials. Grinding is most often performed with an ore/water slurry,
which reduces particulate emissions to negligible levels. When dry grinding
processes are used, particulate emissions can be considerable.
After final size reduction, the beneficiation of the ore increases the
concentration of valuable minerals by separating them from the matrix rock.
A variety of physical and chemical processes is used to concentrate the
mineral. Most often, physical or chemical separation is performed in an
aqueous environment which eliminates particulate emissions, although some
ferrous and titaniferous minerals are separated by magnetic or electrostatic
methods in a dry environment.
The concentrated mineral products may be dried to remove surface
moisture. Drying is most frequently done in natural gas fired rotary
dryers. Calcining or pelletizing of some products, such as alumina or iron
concentrates, are also performed. Emissions from calcining and pelletizing
operations are not covered in this Section.
8.23.2 Process Emissions7-9
Particulate emissions result from metallic mineral plant operations
such as crushing and dry grinding of ore; drying of concentrates; storing
and reclaiming of ores and concentrate's from storage bins; transfer of
materials; and loading of final products for shipment. Particulate emission
factors are provided in Table 8.23-1 for various metallic mineral process
operations, including primary, secondary and tertiary crushing; dry grinding;
drying; and material handling and transfer. Fugitive emissions are also
possible from roads and open stockpiles, factors for which are in Section
11.2.
8/82
Mineral Products Industry
1.23-1
-------
Storage
Bin(s)
I—Ore From Mines
Primary
Crushers
Storage
Bin(s)
Secondary
Crushers
Tertiary
Crushers
Grinders
Product
Loadout
Dryers
Beneficiation
T
Tailings
Figure 8.23-1. A metallic mineral processing plant.
The emission factors in Table 8.23-1 are for the process operations as
a whole. At most metallic mineral processing plants, each process operation
will require several types of equipment. A single crushing operation likely
will include a hopper or ore dump, screen(s), crusher, surge bin, apron
feeder, and conveyor belt transfer points. Emissions from these various
pieces of equipment are often ducted to a single control device. The emis-
sion factors provided in Table 8.23-1 for primary, secondary and tertiary
crushing operations are for process units that are typical arrangements of
the above equipment.
Emission factors are provided in Table 8,23-1 for two types of dry
grinding operations, those grinding operations that involve air conveying
and/or air classification of material and those that involve screening of
material without air conveying. Grinding operations that involve air
conveying and air classification usually require dry cyclones for efficient
product recovery. The factors in Table 8.23-1 are for emissions after
product recovery cyclones. Grinders in closed circuit with screens usually
do not require cyclones. Emission factors are not provided for wet grinders,
because the high moisture content in these operations can reduce emissions
to negligible levels.
8.23-2
EMISSION FACTORS
8/82
-------
The emission factors for dryers in Table 8.23-1 include transfer points
integral with the drying operation. A separate emission factor is provided
for dryers at titanium/zirconium plants that use dry cyclones for product
recovery and for emission control. Titanium/zirconium sand type ores do not
require crushing or grinding, and the ore is washed to remove humic and clay
material before concentration and drying operations.
At some metallic mineral processing plants, material is stored in
enclosed bins between process operations. The emission factors provided in
Table 8.23-1 for the handling and transfer of material should be applied to
the loading of material into storage bins and the transferring of material
from the bin. The emission factor will usually be applied twice to a storage
operation, once for the loading operation and once for the reclaiming oper-
ation. If material is stored at multiple points in the plant, the emission
factor should be applied to each operation and should apply to the material
being stored at each bin. The material handling and transfer factors do not
apply to small hoppers, surge bins or transfer points that are integral with
crushing, drying or grinding operations.
At some large metallic mineral processing plants, extensive material
transfer operations, with numerous conveyor belt transfer points, may be
required. The emission factors for material handling and transfer should be
applied to each transfer point that is not an integral part of another
process unit. These emission factors should be applied to each such conveyor
transfer point and should be based on the amount of material transferred
through that point.
The emission factors for material handling can also be applied to final
product loading for shipment. Again, these factors should be applied to
each transfer point, ore dump or other point where material is allowed to
fall freely.
Test data collected in the mineral processing industries indicate that
the moisture content of ore can have a significant effect on emissions from
several process operations. High moisture generally reduces the uncon-
trolled emission rates, and separate emission rates are provided for primary
crushers, secondary crushers, tertiary crushers, and material handling and
transfer operations that process high moisture ore. Drying and dry grinding
operations are assumed to produce or to involve only low moisture material.
For most metallic minerals covered in this Section, high moisture ore
is defined as ore whose moisture content, as measured at the primary crusher
inlet or at the mine, is 4 weight percent or greater. Ore defined as high
moisture at the primary crusher is presumed to be high moisture ore at any
subsequent operation for which high moisture factors are provided, unless a
drying operation precedes the operation under consideration. Ore is defined
as low moisture when a dryer precedes the operation under consideration or
when the ore moisture at the mine or primary crusher is less than 4 weight
percent.
Separate factors are provided for bauxite handling operations, in that
some types of bauxite with a moisture content as high as 15 to 18 weight
percent can still produce relatively high emissions during material handling
8/82 Mineral Products Industry 8.23-3
-------
oo
•
K>
-P-
TABLE 8.23-1. UNCONTROLLED PARTICULATE EMISSION FACTORS FOR METALLIC MINERAL PROCESSES3
H
S
I
H
O
Process
Crushing
Primary
Secondary
Tertiary
Wet grinding
Dry grinding
With air conveying and/or air
classification
Without air conveying or air
classification
Drying
All minerals but titanium/
zirconium sands
Titanium/ zirconium with
cyclones
Material handling and transfer
All minerals but bauxite
Bauxite/alumina
Low
Emissions
kg/Mg (Ib/ton)
0.2 (0.5)
0.6 (1.2)
1.4 (2.7)
Negligible
14.4 (28.8)
1.2 (2.4)
9.8 (19.7)
0.3 (0.5)
0.06 (0.12)
0.6 (1.1)
moisture ore
Particulate emissions
< 10 ym
kR/Mg (Ib/ton)
0.02 (0.05)
NA
0.08 (0.16)
-
13.0 (26.0)
0.16 (0.31)
5.9 (12.0)
HA
0.03 (0.06)
NA
High
Emissions
kg/Mg (Ib/ton)
0.01 (0.02)
0.03 (0.05)
0.03 (0.06)
Negligible
d
d
e
e
0.005 (0.01)
NA
moisture ore
Particulate emissions
< 10 urn
kg/Mg (Ib/ton)
0.004 (0.009)
0.012 (0.02)
0.001 (0.02)
-
d
d
e
e
0.002 (0.006)
NA
Emission
Factor
Rating
C
D
E
C
D
C
C
C
C
00
00
N>
^References 9-12. Controlled particulate emission factors are discussed in Section 8.23.3. NA = not available.
Defined in Section 8.23.2.
.Based on weight of material entering primary crusher.
Based on weight of material entering grinder. Factors are the same for both high moisture and low moisture ores, because material is
usually dried before entering grinder.
eBased on weight of material exiting dryer. Factors are the same for both high moisture and low moisture ores. SOx emissions are fuel
dependent (see Chapter 1). NOx emissions depend on burner design, combustion temperature, etc. (see Chapter 1).
Based on weight of material transferred. Applies to each loading or unloading operation and to each conveyor belt transfer point.
^Bauxite with moisture content as high as 15 - 18% can exhibit the emission characteristics of low moisture ore. Use low moisture
factor for bauxite unless material exhibits obvious sticky, nonduating characteristics.
-------
procedures. These emissions could be eliminated by adding sufficient mois-
ture to the ore, but bauxite then becomes so sticky that it is difficult to
handle. Thus, there is some advantage to keeping bauxite in a relatively
dusty state, and the low moisture emission factors given represent condi-
tions fairly typical of the industry.
Particulate matter size distribution data for some process operations
have been obtained for control device inlet streams. Since these inlet
streams contain particulate matter from several activities, a variability
has been anticipated in the calculated size specific emission factors for
particulates.
Emission factors for particulate matter equal to or less than lOym
aerodynamic diameter, from a limited number of tests performed to charac-
terize the processes, are presented in Table 8.23-1.
In some plants, particulate emissions from multiple pieces of equipment
and operations are collected and ducted to a control device. Therefore,
examination of reference documents is recommended before application of the
factors to specific plants.
Emission factors for particulate matter equal to or less than lOym from
high moisture primary crushing operations and material handling and transfer
operations were based on test results usually in the 30 to 40 weight percent
range. However, high values were obtained for high moisture ore at both the
primary crushing and the material handling and transfer operations, and
these were included in the average values in the Table. A similarly wide
range occurred in the low moisture drying operation.
Several other factors are generally assumed to affect the level of
emissions from a particular process operation. These include ore character-
istics such as hardness, crystal and grain structure, and friability.
Equipment design characteristics, such as crusher type, could also affect
the emissions level. At this time, data are not sufficient to quantify each
of these variables.
8.23.3 Controlled Emissions7-9
Emissions from metallic mineral processing plants are usually controlled
with wet scrubbers or baghouses. For moderate to heavy uncontrolled emis-
sion rates from typical dry ore operations, dryers and dry grinders, a wet
scrubber with pressure drop of 1.5 to 2.5 kilopascals (6 to 10 inches of
water) will reduce emissions by approximately 95 percent. With very low
uncontrolled emission rates typical of high moisture conditions, the
percentage reduction will be lower (approximately 70 percent).
Over a wide range of inlet mass loadings, a well designed and main-
tained baghouse will reduce emissions to a relatively constant outlet
concentration. Such baghouses tested in the mineral processing industry
consistently reduce emissions to less than 0.05 grams per dry standard cubic
meter (0.02 grains per dry standard cubic foot), with an average concentra-
tion of 0.015 g/dscm (0.006 gr/dscf). Under conditions of moderate to high
uncontrolled emission rates of typical dry ore facilities, this level of
8/82 Mineral Products Industry 8.23-5
-------
controlled emissions represents greater than 99 percent removal of partic-
ulate emissions. Because baghouses reduce emissions to a relatively constant
outlet concentration, percentage emission reductions would be less for
baghouses on facilities with a low level of uncontrolled emissions.
References for Section 8.23
1. D. Kram, "Modern Mineral Processing: Drying, Calcining and Agglo-
meration", Engineering and Mining Jcmrnal. 181(6);134-151, June 1980.
2. A. Lynch, Mineral Crushing and Grinding Circuits, Elsevier Scientific
Publishing Company, New York, 1977.
3. "Modern Mineral Processing: Grinding", Engineering and Mining Journal,
181(161):106-113, June 1980.
4. L. Mollick, "Modern Mineral Processing: Crushing", Engineering and
Mining Journal. 181(6):96-103. June 1980.
5. R. H. Perry, et al., Chemical Engineer's Handbook, 4th Ed, McGraw-Hill,
New York, 1963.
6. R. Richards and C. Locke, Textbook of Ore^jDressing, McGraw-Hill, New
York, 1940.
7. "Modern Mineral Processing: Air and Water Pollution Controls",
Engineering and Mining Journal, 181(6)-.156-171, June 1980.
8. W. E. Horst and R. C, Enochs, "Modern Mineral Processing: Instru-
mentation and Process Control", Engineering and Mining Journal.
181(6):70-92, June 1980.
9. Metallic Mineral Processing Plants - Background Information for Proposed
Standards (Draft). EPA Contract No. 68-02-3063, TRW, Research Triangle
Park, NC, 1981.
10. Telephone communication between E. C. Monnig, TRW Environmental
Division, and R. Beale, Associated Minerals, Inc., May 17, 1982.
11. Written communication from W. R. Chalker, DuPont, Inc., to S. T. Cuffe,
U. S. Environmental Protection Agency, Research Triangle Park, NC,
December 21, 1981.
12. Written communication from P. H. Fournet, Kaiser Aluminum and Chemical
Corporation, to S. T. Cuffe, U. S. Environmental Protection Agency,
Research Triangle Park, NC, March 5, 1982.
8.23-6 EMISSION FACTORS 8/82
-------
8.24 WESTERN SURFACE COAL MINING
8.24.1 General1
There are 12 major coal fields in the western states (excluding the
Pacific Coast and Alaskan fields), as shown in Figure 8.24-1. Together,
they account for more than 64 percent of the surface rainable coal reserves
COAL TYPE
LIGNITE
SUBBITUMINOUSE3
BITUMINOUS
1
2
3
4
5
6
7
8
9
10
11
12
Coal-field
Fort Union
Powder River
North Central
Bighorn Basin
Wind River
Hams Fork
Uinta
Southwestern Utah
San Juan River
Raton Mesa
Denver
Green River
Strippable reserves
(1Q6 tons)
23,529
56,727
All underground
All underground
3
1,000
308
224
2,318
All underground
All underground
2,120
5/83
Figure 8.24-1. Coal fields of the western U.S.3
Mineral Products Industry
8.24-1
-------
in the United States.2 The 12 coal fields have varying characteristics
which may influence fugitive dust emission rates from mining operations,
including overburden and coal seam thicknesses and structure, mining equip-
ment, operating procedures, terrain, vegetation, precipitation and surface
moisture, wind speeds and temperatures. The operations at a typical west-
ern surface mine are shown in Figure 8.24-2. All operations that involve
movement of soil, coal, or equipment, or exposure of erodible surfaces,
generate some amount of fugitive dust.
The initial operation is removal of topsoil and subsoil with large
scrapers. The topsoil is carried by the scrapers to cover a previously
mined and regraded area as part of the reclamation process or is placed in
temporary stockpiles. The exposed overburden, the earth which is between
the topsoil and the coal seam, is leveled, drilled and blasted. Then the
overburden material is removed down to the coal seam, usually by a dragline
or a shovel and truck operation. It is placed in the adjacent mined cut,
forming a spoils pile. The uncovered coal seam is then drilled and
blasted. A shovel or front end loader loads the broken coal into haul
trucks, and it is taken out of the pit along graded haul roads to the tip-
ple, or truck dump. Raw coal sometimes may be dumped onto a temporary
storage pile and later rehandled by a front end loader or bulldozer.
At the tipple, the coal is dumped into a hopper that feeds the primary
crusher, then is conveyed through additional coal preparation equipment
such as secondary crushers and screens to the storage area. If the mine
has open storage piles, the crushed coal passes through a coal stacker onto
the pile. The piles, usually worked by bulldozers, are subject to wind
erosion. From the storage area, the coal is conveyed to a train loading
facility and is put into rail cars. At a captive mine, coal will go from
the storage pile to the power plant.
During mine reclamation, which proceeds continuously throughout the
life of the mine, overburden spoils piles are smoothed and contoured by
bulldozers. Topsoil is placed on the graded spoils, and the land is pre-
pared for revegetation by furrowing, mulching, etc. From the time an area
is disturbed until the new vegetation emerges, all disturbed areas are sub-
ject to wind erosion.
8.24.2 Emissions
Predictive emission factor equations for open dust sources at western
surface coal mines are presented in Tables 8-24-1 and 8.24-2. Each equa-
tion is for a single dust generating activity, such as vehicle traffic on
unpaved roads. The predictive equation explains much of the observed vari-
ance in emission factors by relating emissions to three sets of source pa-
rameters: l) measures of source activity or energy expended (e.g., speed
and weight of a vehicle traveling on an unpaved road); 2) properties of the
material being disturbed (e.g., suspendable fines in the surface material
of an unpaved road); and 3) climate (in this case, mean wind speed).
The equations may be used to estimate particulate emissions generated
per unit of source extent (e.g., vehicle distance traveled or mass of mate-
rial transferred).
8.24-2 EMISSION FACTORS 5/83
-------
Ln
00
H-
i-ti
hj
o
EL
n
C»
To Preparation and
Shipping Facilities
haul toad
Figure 8.24-2. Operations at typical western surface coal mines.
-------
oo
•
to
*-
TABLE 8.24-1.
en
M
i
H
a
5»
cn
EMISSION FACTOR EQUATIONS FOR UNCONTROLLED OPEN DUST SOURCES AT
WESTERN SURFACE COAL MINES (METRIC UNITS)3
Operation Material
Blasting Coal or
overburden
Truck loading Coal
Bulldozing Coal
Overburden
Dragline Overburden
Scrapers
(travel mode)
Grading
Vehicle traffic
(light/medium duty)
Haul trucks
Active storage pile Coal
(wind erosion and
maintenance)
Emissions by particle size range (aerodynamic diameter) '
TSP (< ~ 30 urn) < 15 pm < 2.5 Mn/TSPd
344 (A)0'8 811 (A)0'6
I fl 1 Q t ^ 1 1 U.UJU
(D)1'8 (M)1'* (D)1'5 (Hr'J
0.580 0.0596
35.6 (6)1'2 8.44 (s)1'5
.1 , , V.Vii
(„)»••* tH)!.1
2.6 (s)1'2 0.45 (s)1'5 Q j „
11 t i U.1UJ
(H)llJ (H)1'*
0.0046 (d)1'1 0.0029 (d)0'7
n i n t v.vii
(rt)°-J (H)°-J
9.6 x 10"6 {s)1-3 (W)2'4 2.2 x 10"6 (s)1'4 (W)2'5 0.026
0.0034 (S)2'5 0.0056 {S)2-0 0.031
-^ -^ °-040
0.0019 (w)3'* (L)0'2 0.0014 (w)3'5 0.017
l.B u MA NA
Emission
Units Factor
Rating
kg/blast
kg/Mg
hg/ht
kg/m3
kg/VKT
hg/VKT
kg/VKT
kg/VKT
kg
(hectare) (hr)
8
B
B
B
B
A
B
B
A
ce
All equations are from Reference 1, except for coal storage pile equation from Reference 4. TSP = total suspended particulate. VHT =
vehicle miles traveled. VKT = vehicle kilometers traveled. NA = not available.
TSP denotes what is measured by a standard high volume sampler (see Section 11.2).
Symbols for equations:
A = area blasted
H = material moisture content (%)
D = hole depth (m)
s = material silt content (%)
u = wind speed (m/sec)
d = drop height (m)
W = mean vehicle weight (Hg)
S = mean vehicle speed (kph)
w = mean number of wheels
L = road surface silt loading (g/m2)
CO
OJ
Multiply the TSP predictive equation by this fraction to determine emissions in the < 2.5 Mm size range.
Rating applicable to Mine Types I, II and IV (see Tables 8.24-5 and 8.24-6).
-------
00
OO
to
TABLE 8.24-2. EMISSION FACTOR EQUATIONS FOR UNCONTROLLED OPEN DUST SOURCES AT
WESTERN SURFACE COAL MINES (ENGLISH UNITS)a
Emimicns H rirHrlp *i" ranje (aerodynamic diameter) '
3
H-
n>
to
t-1
o
n
en
HH
P
M
ft
M
Operation Material
TSP (< ~ 30 \m)
. . 961 (A)0'6
Blasting Coal 01 j 8 , 9
overburden (D) ' 01)
. , .. . . 1-16
Truck loading Coal j z
78.4 (s)1'2
Bulldozing Coal j j
(M)
5.7 Cs)1'2
(H)1'3
n , . 0.0021 (d)1'1
Dragline Overburden jj j
Scrapers 2.7 x Ifl'5 (s)1'3 (W)2'4
(travel mode)
Grading 0.040 (S)2'5
„ u- , ff 5'79
Vehicle traffic ^ 0
(light/medium duty) (M)
Haul trucks 0.0067 (w) * (t)
Active storage pile Coal 1.6 u
(wind erosion and
maintenance)
< 15 Mm < 2-5 Mm/TSp"
2,550 (A)0'6
(D)1'5 (H)2'3
0.159 no1Q
(H)0'9
18.6 (s)1'5 n n,,
CM)1'4
1.0 (s) ' n 10s
CM)1'4
0.0021 (d)0'7 0 f,n
(H)0'3
6,2 x Uf6 (s)1'4 (W)2'5 0.026
0.051
-------
The equations were developed through field sampling various western surface
mine types and are thus applicable to any of the surface coal mines located
in the western United States.
In Tables 8.24-1 and 8.24-2, the assigned quality ratings apply within
the ranges of source conditions that were tested in developing the equa-
tions, given in Table 8.24-3- However, the equations are derated one let-
ter value (e.g., A to B) if applied to eastern surface coal mines.
TABLE 8.24-3.
TYPICAL VALUES FOR CORRECTION FACTORS APPLICABLE TO THE
PREDICTIVE EMISSION FACTOR EQUATIONS3
Source
Blasting
Coal loading
Bulldozers
Coal
Overburden
Dragline
Scraper
Grader
Light/medium
duty vehicles
Haul truck
Correction Number
factor of test
samples
Moisture
Depth
Area
Moisture
Moisture
Silt
Moisture
Silt
Drop distance
Moisture
Silt
Weight
Speed
Moisture
Wheels
Silt loading
5
18
18
7
3
3
8
8
19
7
10
15
7
7
29
26
Range
7.2
6
20
90
1,000
6.6
4-0
6.0
2.2
3.8
1.5
5
0.2
7.2
33
36
8.0
5.0
0.9
6.1
3.8
34
- 38
- 41
- 135
- 9,000
- 100,000
- 38
- 22.0
- 11.3
- 16.8
-15.1
- 30
- 100
- 16.3
-25.2
- 64
- 70
-19.0
- 11.8
- 1.7
- 10.0
- 254
- 2,270
Geometric
mean Units
17.2
7.9
25.9
1,800
19,000
17.8
10.4
8.6
7.9
6.9
8.6
28.1
3.2
16.4
48.8
53.8
11.4
7.1
1.2
8.1
40.8
364
%
m
ft
m2
ft2
%
%
%
I
I
m
ft
%
%
Mg
tons
kph
mph
°/
h
number
g/m2
Ib/acre
Reference 1.
In using the equations to estimate emissions from sources in a spe-
cific western surface coal mine, it is necessary that reliable values for
correction parameters be determined for the specific sources of interest,
if the assigned quality ratings of the equations are to apply. For exam-
ple, actual silt content of coal or overburden measured at a facility
8.24-6
EMISSION FACTORS
5/83
-------
should be used instead of estimated values. In the event that site spe-
cific values for correction parameters cannot be obtained, the appropriate
geometric mean values from Table 8.24-3 may be used, but the assigned qual-
ity rating of each emission factor equation is reduced by one level (e.g.,,
A to B).
Emission factors for open dust sources not covered in Table 8.24-3 are
in Table 8.24-4. These factors were determined through source testing at
various western coal mines.
The factors in Table 8.24-4 for mine locations I through V were devel-
oped for specific geographical areas. Tables 8.24-5 and 8.24-6 present
characteristics of each of these mines (areas). A "mine specific" emission
factor should be used only if the characteristics of the mine for which an
emissions estimate is needed are very similar to those of the mine for
which the emission factor was developed. The other (nonspecific) emission
factors were developed at a variety of mine types and thus are applicable
to any western surface coal mine.
As an alternative to the single valued emission factors given in Table
8.24-4 for train or truck loading and for truck or scraper unloading, two
empirically derived emission factor equations are presented in Section
11.2.3 of this document. Each equation was developed for a source opera-
tion (i.e., batch drop and continuous drop, respectively), comprising a
single dust generating mechanism which crosses industry lines.
Because the predictive equations allow emission factor adjustment to
specific source conditions, the equations should be used in place of the
factors in Table 8.24-4 for the sources identified above, if emission esti-
mates for a specific western surface coal mine are needed. However, the
generally higher quality ratings assigned to the equations are applicable
only if 1) reliable values of correction parameters have been determined
for the specific sources of interest and 2) the correction parameter values
lie within the ranges tested in developing the equations. Table 8.24-3
lists measured properties of aggregate materials which can be used to esti-
mate correction parameter values for the predictive emission factor equa-
tions in Chapter 11, in the event that site specific values are not avail-
able. Use of mean correction parameter values from Table 8.24-3 reduces
the quality ratings of the emission factor equations in Chapter 11 by one
level.
5/83 Mineral Products Industry 8.24-7
-------
TABLE 8.24-4- UNCONTROLLED PARTICULATE EMISSION FACTORS FOR
OPEN DUST SOURCES AT WESTERN SURFACE COAL MINES
Source
Drilling
Topsoil removal by
scraper
Overburden
replacement
Truck loading by
power shovel
(batch drop)
Train loading (batch
or continuous drop)c
Bottom dump truck
unloading
(batch drop)
End dump truck
unloading
(batch drop)
Scraper unloading
(batch drop)c
Wind erosion of
exposed areas
Material Mine
location8
Overburden Any
Coal V
Topsoil Any
IV
Overburden Any
Overburden V
Coal Any
III
Overburden V
Coal IV
III
II
I
Any
Coal V
Topsoil IV
Seeded land, Any
stripped over-
burden, graded
overburden
TSP
emission
factor
1.3
0.59
0.22
0,10
0.058
0.029
0.44
0.22
0.012
0.0060
0.037
0.018
0.028
0.014
0.0002
0.0001
0.002
0.001
0.027
0.014
0.005
0.002
0.020
0.010
0.014
0.0070
0.066
0.033
0.007
0.004
0.04
0.02
0.38
Ooc
. OJ
Emission
Units Factor
Rating
Ib/hole
kg/hole
Ib/hole
kg/hole
Ib/T
kg/Mg
Ib/T
kg/Mg
Ib/T
kg/Mg
Ib/T
kg/Mg
Ib/T
kg/Mg
Ib/T
kg/Mg
Ib/T
kg/T
Ib/T
kg/Mg
Ib/T
kg/Mg
Ib/T
kg/Mg
Ib/T
kg/Mg
Ib/T
kg/Mg
Ib/T
kg/Mg
Ib/T
kg/Mg
I -
(acre)(yr)
Mg
(hectare) (yr)
B
B
E
E
E
E
D
D
C
C
C
C
D
D
D
D
E
E
E
E
E
E
E
E
D
D
D
D
E
E
C
C
C
Roman numerals I through V refer to specific mine locations for which the
corresponding emission factors were developed (Reference 4). Tables £.24-4
and 8.24-5 present characteristics of each of these mines. See text for
correct use of these "mine specific" emission factors. The other factors
(from Reference 5 except for overburden drilling from Reference 1) can be
applied to any western surface coal mine.
Total suspended particulate (TSF) denotes what is measured by a standard high
volume sampler (see Section 11.2).
Predictive emission factor equations, which generally provide more accurate
estimates of emissions, are presented in Chapter 11.
8.24-8
EMISSION FACTORS
5/83
-------
TABLE 8.24-5.
J3
GENERAL CHARACTERISTICS OF SURFACE COAL MINES REFERRED TO IN TABLE 8.24-4
CO
U)
Mine
I
3
H-
5 ii
1-1
I—1
i-i
0
o
ft
en
n
D
&
en
rt
(-1
IV
v
Type of
Location coal
mined
N W. Subbitum.
Colorado
S.W. Subbitum.
Wyoming
S E. Subbitum.
Montana
Central Lignite
North Dakota
N E Suhbitum.
Wyoming
Terrain
Moderately
steep
Semirugged
Gently roll-
ing to
semi rugged
Gently roll-
ing
Flat to
gently
rolling
Vegetative
cover
Moderate ,
sagebrush
Sparse,
sagebrush
Sparse ,
moderate,
prairie
grassland
Moderate,
prairie
grassland
Sparse,
sagebrush
• ~
Surface soil
type and Mean wind Mean annual
prodibilitv speed precipitation
index m/s mph cm m.
Clayey, 2.3 5.1 38 15
loamy (71)
Arid soil with 6.0 13.4 36 14
clay and
alkali or
carbonate
accumulation
(86)
Shallow clay 4.8 10.7 28 - 41 11 - 16
loamy deposits
on bedrock
(47)
Loamy, loamy 5.0 11.2 43 17
to sandy
(71)
Loamy, sandy, 6.0 13.4 36 14
clayey, and
clay loamy
(102)
Reference 4,
-------
00
to
-p-
I
TABLE 8.24-6.
OPERATING CHARACTERISTICS OF THE COAL MINES
REFERRED TO IN TABLE 8.24-4a
Cfi
CO
H
O
2!
n
H
O
Parameter
Production rate
Coal transport
Stratigraphic
data
Coal analysis
data
Surface
disposition
Storage
Blasting
, Reference 4.
Estimate.
Required information
Coal mined
Avg, unit train frequency
Overburden thickness
Overburden density
Coal seam thicknesses
Parting thicknesses
Spoils bulking factor
Active pit depth
Moisture
Ash
Sulfur
Heat content
Total disturbed land
Active pit
Spoils
Reclaimed
Barren land
Associated disturbances
Capacity
Frequency, coal
Frequency, overburden
Area blasted, coal
Area blasted, overburden
NA = not applicable. Dash = not
Units
106 T/yr
per day
ft
lb/yd3
ft
ft
%
ft
X
X, wet
X, wet
fltu/lb
acre
acre
acre
acre
acre
acre
ton
per week
per week
ft2
£t2
available.
I
1.13
NA
21
4000
9,35
50
22
52
10
8
0.46
11000
168
34
57
100
-
12
NA
4
3
16000
20000
II
5.0
NA
80
3705
15,9
15
24
100
18
10
0.59
9632
1030
202
326
221
30
186
NA
4
0.5
40000
"~
Mine
III
9.5
2
90
3000
27
NA
25
114
24
8
0.75
8628
2112
87
144
950
455
476
-
3
3
-
"*
IV
3.8
NA
65
-
2,4,8
32,16
20
80
38
7
0.65
8500
1975
-
-
-
-
-
NA
7
NA
30000
NA
V
12. Ob
2
35
-
70
NA
-
105
30
6
0.48
8020
217
71
100
100
-
46
48000
7b
7b
-
~
CO
to
-------
References for Section 8.24
1. K. Axetell and C. Cowherd, Improved Emission Factors for Fugitive Dust
from Western Surface Coal Mining Sources, 2 Volumes, EPA Contract No.
68-03-2924, U. S. Environmental Protection Agency, Cincinnati, OH,
July 1981.
2. Reserve Base of U. S. Coals by Sulfur Content: Part 2, The Western
States, IC8693, Bureau of Mines, U. S. Department of the Interior,
Washington, DC, 1975.
3. Bituminous Coal and Lignite Production and Mine Operations - 1978,
DOE/EIA-0118(78), U. S. Department of Energy, Washington, DC, June
1980.
4. K. Axetell, Survey of Fugitive Dust from Coal Mines, EPA-908/1-78-003,
U. S. Environmental Protection Agency, Denver, CO, February 1978.
5. D. L. Shearer, et al. , Coal Mining Emission Factor Development and
Modeling Study, Amax Coal Company, Carter Mining Company, Sunoco
Energy Development Company, Mobil Oil Corporation, and Atlantic
Richfield Company, Denver, CO, July 1981.
5/83 Mineral Products Industry 8.24-11
-------
-------
PETROLEUM INDUSTRY
9.1 PETROLEUM REFINING1
9.1.1 General Description
The petroleum refining industry converts crude oil into more than 2500 refined products, including liquefied
petroleum gas, gasoline, kerosene, aviation fuel, diesel fuel, fuel oils, lubricating oils, and feedstocks for the
petrochemical industry. Petroleum refinery activities start with receipt of crude for storage at the refinery,
include all petroleum handling and refining operations, and terminate with storage preparatory to shipping the
refined products from the refinery.
The petroleum refining industry employs a wide variety of processes. A refinery's processing flow
scheme is largely determined by the composition of the crude oil feedstock and the chosen slate of petroleum
products. The example refinery flow scheme presented in Figure 9.1-1 shows the general processing arrangement
used by refineries in the United States for major refinery processes. The arrangement of these processes will vary
among refineries, and few, if any, employ all of these processes. Petroleum refining processes having direct
emission sources are presented in bold-line boxes on the figure.
Listed below are five categories of general refinery processes and associated operations:
1. Separation processes
a. atmospheric distillation
b. vacuum distillation
c. light ends recovery (gas processing)
2. Petroleum conversion processes
a. cracking (thermal and catalytic)
b. reforming
c. alkylation
d. polymerization
e. isomerization
f. coking
g. visbreaking
3. Petroleum treating processes
a. hydrodesulfurization
b. hydrotreating
c. chemical sweetening
d. acid gas removal
e. deasphalting
4. Feedstock and product handling
a. storage
b. blending
c. loading
d. unloading
5. Auxiliary facilities
a. boilers
b. wastewater treatment
c. hydrogen production
12/77 9.1-1
-------
INS
s
n
3
TOPPED CRUOC
EH I1 UH OOE H I
HOCJCTION
VACUUM OIL
RESIDUAL OIL
n
»?
II
IS TILL ATE |
I
Jt
JPHAL
II
<
id":
s
s
I
%
I
VISBHEAK NG
A
f
5
S
H
I
I COKING
krrr
I-!
ASPhWIT | j= S
, S1OWIHG
TO HErW* HYDFfOCAnBON
STORAQE A BLENDING
TO MDDLE DISTTLtATE
STORAGE 1 eLENDMG
TO GASOUNE A PETROCHEMICAL
STORAGE A BLENOIHG
9.1-1. Schematic of an example integrated petroleum refinery.
-------
d. sulfur recovery plant
e. cooling towers
f. blowdown system
g. compressor engines
These refinery processes are defined in the following section and their emission characteristics and applicable
emission control technology are discussed.
9.1.1.1. Separation Processes — The first phase in petroleum refining operations is the separation of crude oil into
its major constituents using three petroleum separation processes: atmospheric distillation, vacuum distillation,
and light ends recovery (gas processing). Crude oil consists of a mixture of hydrocarbon compounds including
paraffinic, naphthenic, and aromatic hydrocarbons plus small amounts of impurities including sulfur, nitrogen,
oxygen, and metals. Refinery separation processes separate these crude oil constituents into common-boiling-
point fractions.
9.1.1.2. Conversion Processes—To meet the demands for high-octane gasoline, jet fuel, and diesel fuel,
components such as residual oils, fuel oils, and light ends are converted to gasolines and other light fractions.
Cracking, coking, and visbreaking processes are used to break large petroleum molecules into smaller petroleum
molecules. Polymerization and alkylation processes are used to combine small petroleum molecules into larger
ones. Isomerization and reforming processes are applied to rearrange the structure of petroleum molecules to
produce higher-value molecules of a similar molecular size.
9.1.1.3. Treating Processes—Petroleum treating processes stabilize and upgrade petroleum products by
separating them from less desirable products and by removing objectionable elements. Undesirable elements
such as sulfur, nitrogen, and oxygen are removed by hydrodesulfurization,hydrotreating,chemicalsweetening
and acid gas removal. Treating processes employed primarily for the separation of petroleum products include
such processes as deasphalting. Desalting is used to remove salt, minerals, grit, and water from crude oil feed
stocks prior to refining. Asphalt blowing is used for polymerizing and stabilizing asphalt to improve its weathering
characteristics.
9.1.1.4. Feedstock and Product Handling—The refinery feedstock and product handling operations consist of
unloading, storage, blending, and loading activities.
9.1.1.5. Auxiliary Facilities—A wide assortment of processes and equipment not directly involved in the refining
of crude oil are used in functions vital to the operation of the refinery. Examples are boilers, wastewater treatment
facilities, hydrogen plants, cooling towers, and sulfur recovery units. Products from auxiliary facilities (clean
water, steam, and process heat) are required by most refinery process units throughout the refinery.
9.1.2 Process Emission Sources and Control Technology
This section presents descriptions of those refining processes that are significant air pollutant contributors.
Process flow schemes, emission characteristics, and emission control technology are discussed for each process.
Table 9.1-1 lists the emission factors for direct-process emissions in petroleum refineries. The following process
emission sources are discussed in this section on petroleum refining emissions:
1. Vacuum distillation.
2. Catalytic cracking.
3. Thermal cracking processes.
4. Utility boilers.
5. Heaters.
12/77 Petroleum Industry 9.1-3
-------
6. Compressor engines.
7. Slowdown systems.
8. Sulfur recovery.
9.1.2.1. Vacuum Distillation—Topped crude withdrawn from the bottom of the atmospheric distillation column
is composed of high-boiling-point hydrocarbons. When distilled at atmospheric pressures, the crude oil
decomposes and polymerizes to foul equipment. To separate topped crude into components, it must be distilled in a
vacuum column at a very low pressure and in a steam atmosphere.
In the vacuum distillation unit, topped crude is heated with a process heater to temperatures ranging from
700 to 800° F (370 to 425° C). The heated topped crude is flashed into a multi-tray vacuum distillation column
operating at vacuums ranging from 0.5 to 2 psia (350 to 1400 kg/m2). In the vacuum column, the topped crude is
separated into common-boiling-point fractions by vaporization and condensation. Stripping steam is normally
injected into the bottom of the vacuum distillation column to assist in the separation by lowering the effective
partial pressures of the components. Standard petroleum fractions withdrawn from the vacuum distillation
column include lube distillates, vacuum oil, asphalt stocks, and residual oils. The vacuum in the vacuum
distillation column is normally maintained by the use of steam ejectors but may be maintained by the use of
vacuum pumps.
The major sources of atmospheric emissions from the vacuum distillation column are associated with the
steam ejectors or vacuum pumps. A major portion of the vapors withdrawn from the column by the ejectors or
pumps are recovered in condensers. Historically, the noncondensable portion of the vapors has been vented to the
atmosphere from the condensers. There are approximately 50 pounds (23 kg) of noncondensable hydrocarbons
per 1000 barrels of topped crude processed in the vacuum distillation column.2'12,13 A second source of
atmospheric emissions from vacuum distillation columns is combustion products from the process heater.
Process heater requirements for the vacuum distillation column are approximately 37,000 Btu per barrel (245
Joules/cm3) of topped crude processed in the vacuum column. Process heater emissions and their control are
discussed later in this section. Fugitive hydrocarbon emissions from leaking seals and fittings are also associated
with the vacuum distillation unit, but these are minimized by the low operating pressures and low vapor pressures
in the unit. Fugitive emission sources are also discussed later in this section.
Control technology applicable to the noncondensable emissions vented from the vacuum ejectors or pumps
include venting into blowdown systems or fuel gas systems, and incineration in furnaces or waste heat
boilers.2'12'13 These control techniques are generally greater than 99 percent efficient in the control of
hydrocarbon emissions, but they also contribute to the emission of combustion products.
9.1.2.2. Catalytic Cracking—Catalytic cracking, using heat, pressure, and catalysts, converts heavy oils into
lighter products with product distributions favoring the more valuable gasoline and distillate blending
components. Feedstocks are usually gas oils from atmospheric distillation, vacuum distillation, coking, and
deasphalting processes, These feedstocks typically have a boiling range of 650 to 1000° F (340 to 540° C). All of the
catalytic cracking processes in use today can be classified as either fluidized-bed or moving-bed units.
Fluidized-bed Catalytic Cracking (FCC) — The FCC process uses a catalyst in the form of very fine particles
that act as a fluid when aerated with a vapor. Fresh feed is preheated in a process heater and introduced into the
bottom of a vertical transfer line or riser with hot regenerated catalyst. The hot catalyst vaporizes the feed
bringing both to the desired reaction temperature,880 to 980° F (470 to 525° C) .The high activity of modern
catalysts causes most of the cracking reactions to take place in the riser as the catalyst and oil mixture flows
upward into the reactor. The hydrocarbon vapors are separated from the catalyst particles by cyclones in the
reactor. The reaction products are sent to a fractionator for separation.
9.1-4 EMISSION FACTORS 12/77
-------
The spent catalyst falls to the bottom of the reactor and is steam stripped as it exists the reactor bottom to
remove absorbed hydrocarbons. The spent catalyst is then conveyed to a regenerator. In the regenerator, coke
deposited on the catalyst as a result of the cracking reactions is burned off in a controlled combustion process with
preheated air. Regenerator temperature is usually 1100. to 1250° F (590 to 675° C). The catalyst is then recycled to
be mixed with fresh hydrocarbon feed.
Moving-bed Catalytic Cracking (TCC)— In the TCC process, catalyst beads (~0.5cm) flow by gravity into the
top of the reactor where they contact a mixed-phase hydrocarbon feed. Cracking reactions take place as the
catalyst and hydrocarbons move concurrently downward through the reactor to a zone where the catalyst is
separated from the vapors. The gaseous reaction products flow out of the reactor to the fractionation section of
the unit. The catalyst is steam stripped to remove any adsorbed hydrocarbons. It then falls into the regenerator
where coke is burned from the catalyst with air. The regenerated catalyst is separated from the flue gases and
recycled to be mixed with fresh hydrocarbon feed. The operating temperatures of the reactor and regenerator in
the TCC process are comparable to those in the FCC process.
Air emissions from catalytic cracking processes are (1) combustion products from process heaters and (2)
flue gas from catalyst regeneration. Emissions from process heaters are discussed later in this section. Emissions
from the catalyst regenerator include hydrocarbons, oxides of sulfur, ammonia, aldehydes, oxides of nitrogen,
cyanides, carbon monoxide, and particulates (Table 9.1-1). The particulate emissions from FCC units are much
greater than those from TCC units because of the higher catalyst circulation rates used.2'3'5
FCC particulate emissions are controlled by cyclones and/or electrostatic precipitators. Particulate control
efficiencies are as high as 80 to 85 percent.3'5 Carbon monoxide wasteheat boilers reduce the carbon monoxide
and hydrocarbon emissions from FCC units to negligible levels.3 TCC catalyst regeneration produces similar
pollutants to FCC units but in much smaller quantities (Table 9.1-1). The particulate emissions from a TCC unit
are normally controlled by high-efficiency cyclones. Carbon monoxide and hydrocarbon emissions from a TCC
unit are incinerated to negligible levels by passing the flue gases through a process heater fire-box or smoke plume
burner. In some installations, sulfur oxides are removed by passing the regenerator flue gases through a water or
caustic scrubber.2'3'5
9.1.2,3 Thermal Cracking — Thermal cracking processes include visbreaking and coking, which break heavy oil
molecules by exposing them to high temperatures.
Visbreaking — Topped crude or vacuum residuals are heated and thermally cracked (850 to 900° F, 50 to 250
psig) (455 to 480° C, 3.5 to 17.6 kg/cm2) in the visbreaker furnace to reduce the viscosity or pour point of the
charge. The cracked products are quenched with gas oil and flashed into a fractionator. The vapor overhead from
the fractionator is separated into light distillate products. A heavy distillate recovered from the fractionator
liquid can be used as a fuel oil blending component or used as catalytic cracking feed.
Coking — Coking is a thermal cracking process used to convert low value residual fuel oil to higher value gas
oil and petroleum coke. Vacuum residuals and thermal tars are cracked in the coking process at high temperature
and low pressure. Products are petroleum coke, gas oils, and lighter petroleum stocks. Delayed coking is the most
widely used process today, but fluid coking is expected to become an important process in the future.
In the delayed coking process, heated charge stock is fed into the bottom section of a fractionator where light
ends are stripped from the feed. The stripped feed is then combined with recycle products from the coke drum and
rapidly heated in the coking heater to a temperature of 900 to 1100° F (480 to 590° C). Steam injection is used to
control the residence time in the heater. The vapor-liquid feed leaves the heater, passing to a coke drum where,
with controlled residence time, pressure (25 to 30 psig) (1.8 to 2.1 kg/cm2), and temperature (750° F) (400° C), it
is cracked to form coke and vapors. Vapors from the drum return to the fractionator where the thermal cracking
products are recovered.
12/77 Petroleum Industry 9.1-5
-------
Table 9.1-1. EMISSION FACTORS FOR PETROLEUM REFINERIES
W
t/3
I— I
i
i
Process
Boilers and process heaters,
Particulates
Sulfur
oxides
(as S02)
Carbon
monoxide
Total
hydro-
carbons a
Nitrogen
oxides
(as NO 2 )
Aldehydes
Ammonia
Emission
factor
rating
Fuel Oil See Sect on 1.3 - Fuel Oil Combustion
Natural Gas See Section 1.4 - Natural Gas Combustion
Fluid catalytic cracking units b
Uncontrolled
lb/103bbl fresh feed
kg/101 liters fresh feed
Electrostatic precipitator
and CO boiler
Iti/l^bbl fresh fed
kg/103 liters Irestl feed
Moving-bed catalytic
cracking units8
tb/103 bbl fresh feed
kg/103 liters fresh feed
Fluid coking units h
Uncontrolled
lb/103 bbl fresh feed
kg/103 liters fresh feed
Electrostatic precipitator
and CO boiler
lb/103 bbl fresh feed
kg/105 liters fresh feed
Delayed coking units
Compressor engines ^
Reciprocating engines
lb/103 ft3 gas burned
kg/103 m3 gas burned
Gas turbines
lb/10s ft3 gas burned
kg/1 03 m3 gas burned
242
(93 to 340) °
0.695
(0.267 to 0.976)
45«
(7 to 150)
0.128
(0.020 to 0.428)
17
0.049
523
1.50
6.85
0.0196
MA
Neg
Neg
Neg
Neg
499
(100 to 525)
1.413
(0.286 to 1.505)
493
(100 to 525)
1.413
(0.28610 1.505)
60
0.171
NAi
NA
NA
NA
NA
2s*
32s
2s
32s
13,700
39.2
Nege
Neg
3,800
10.8
NA
NA
Neg
Neg
NA
0.43
7.02
0.12
1.94
220
0.630
Neg
Neg
87
0.250
NA
NA
Neg
Neg
NA
1.4
21.8
0.02
0.28
71.0
(37.1 to 145.0)
0.204
(0.107 to 0.416)
71.0*
(37.1 to 145.0)
0.204
(0.107(00.416)
5
0.014
NA
NA
NA
NA
NA
3.4
55.4
0.3
4.7
19
0.054
Neg
Neg
12
0.034
NA
NA
Neg
Neg
NA
0.1
1.61
NA
NA
54
0.155
Neg
Neg
6
0.017
NA
NA
Neg
Neg
NA
0.2
3.2
NA
NA
B
B
B
B
B
B
C
C
C
C
B
B
B
B
-------
Table 9.1-1. (Continued) EMISSION FACTORS FOR PETROLEUM REFINERIES
n
I
tt*
B
HH
C
Process
Blowdawn systems'
Uncontrolled
lb/10J bbl refinery
feed
kg/103 liters refinery feed
Vapor recovery system
and flaring
lb/1O> bbl refinery feed
kg/103 liters refinery feed
Vacuum distill ationm
column condensers
Uncontrolled
lb/105 bbl refinery feed
kg/101 liters refinery feed
lb/103 bbl vacuum feed
kg/10-1 liters vacuum feed
Controlled
Claus plant and tall gas treatment
Participates
Neg
Neg
Neg
Neg
Neg
Neg
Neg
Neg
Meg
Sulfur
oxides
(as S02 )
Neg
Neg
26.9
0.077
Neg
Neg
NeB
Neg
Neg
See section 5.18
Carbon
monoxide
Neg •
Neg
4.3
0.012
Neg
Neg
Neg
Neg
Neg
Total
hydro-
carbons
5BO
1.662
o.a
0.002
18
0.052
50 (0-130)
0.144
Neg
Nitrogen
oxides
(as N02 )
Neg
Neg
18.9
0.054
Neg
Neg
Neg
Neg
Neg
Aldehydes
Neg
Neg
Neg
Neg
Neg
Neg
Neg
Neg
Neg
Ammonia
Neg
Neg
Neg
Neg
Neg
Neg
Neg
Neg
Neg
Emission
factor
rating
C
C
C
C
C
C
C
C
C
Overall, less Ihan 1 percent by weight of the total hydrocarbon emissions are methane.
References 2 through 8.
0 Numbers in parenthesis indicate range of values observed.
d Under the New Source Performance Standards, controlled FCC regenerators will have participate emissions lower Ihan 19 lb/10> bbl fresh feed.
e Negligible emission.
May be higher due to the combustion of ammonia.
9 Reference 2.
h Reference 5.
| NA, Not Available.
^ References 9, 10.
s = Refinery gas sulfur content (lb/1000 ft3): Factors based on 100 percent combustion of sulfur to SO2-
References 2, 11.
m References 2, 12, 13.
-------
In the fluid coking process, typified by Flexicoking, residual oil feeds are injected into the reactor where they
are thermally cracked, yielding coke and a wide range of vapor products. Vapors leave the reactor and are
quenched in a scrubber where entrained coke fines are removed. The vapors are then fractionated. Coke from the
reactor enters a heater and is devolatilized. The volatiles from the heater are treated for fines and sulfur removal
to yield a particulate free, low-sulfur fuel gas. The devolatilized coke is circulated from the heater to a gasifier
where 95 percent of the reactor coke is gasified at high temperature with steam and air or oxygen. The gaseous
products and coke from the gasifier are returned to the heater to supply heat for the devolatilization. These gases
exit the heater with the heater volatiles through the same fines and sulfur removal processes.
From available literature, it is unclear what emissions are released and where they are released. Air
emissions from thermal cracking processes include coke dust from decoking operations, combustion gases from
the visbreaking and coking process heaters, and fugitive emissions. Emissions from the process heaters are
discussed later in this section. Fugitive emissions from miscellaneous leaks are significant because of the high
temperatures involved, and are dependent upon equipment type and configuration, operating conditions, and
general maintenance practices. Fugitive emissions are also discussed later in this section. Particulate emissions
from delayed coking operations are potentially very significant. These emissions are associated with removing the
coke from the coke drum and subsequent handling and storage operations. Hydrocarbon emissions are also
associated with cooling and venting the coke drum prior to coke removal. However, comprehensive data for
delayed coking emissions have not been included in available literature. 4'5
Particulate emission control is accomplished in the decoking operation by wetting down the coke.5
Generally, there is no control of hydrocarbon emissions from delayed coking. However, some facilities are now
collecting coke drum emissions in an enclosed system and routing them to a refinery flare.4'5
9.1.2.4 Utilities Plant — The utilities plant supplies the steam necessary for the refinery. Although the steam can
be used to produce electricity by throttling through a turbine, it is primarily used for heating and separating
hydrocarbon streams. When used for heating, the steam usually heats the petroleum indirectly in heat
exchangers and returns to the boiler. In direct contact operations, the steam can serve as a stripping medium or a
process fluid. Steam may also be used in vacuum ejectors to produce a vacuum. Emissions from boilers and
applicable emission control technology are discussed in much greater detail in Chapter 1.0.
9.1.2.5 Sulfur Recovery Plant — Sulfur recovery plants are used in petroleum refineries to convert hydrogen
sulfide (H2S) separated from refinery gas streams into the more disposable by-product, elemental sulfur.
Emissions from sulfur recovery plants and their control are discussed in Section 5.18.
9.1.2.6 Blowdown System — The blowdown system provides for the safe disposal of hydrocarbons (vapor and
liquid) discharged from pressure relief devices.
Most refining processing units and equipment subject to planned or unplanned hydrocarbon discharges are
manifolded into a collection unit, called the blowdown system. By using a series of flash drums and condensers
arranged in decreasing pressure, the blowdown is separated into vapor and liquid cuts. The separated liquid is
recycled into the refinery. The gaseous cuts can either be smokelessly flared or recycled.
Uncontrolled blowdown emissions primarily consist of hydrocarbons, but can also include any of the other
criteria pollutants. The emission rate in a blowdown system is a function of the amount of equipment manifolded
into the system, the frequency of equipment discharges, and the blowdown system controls.
Emissions from the blowdown system can be effectively controlled by combustion of the noncondensables in
a flare. To obtain complete combustion or smokeless burning (as required by most states), steam is injected in the
combustion zone of the flare to provide turbulence and to inspirate air. Steam injection also reduces emissions of
nitrogen oxides by lowering the flame temperature. Controlled emissions are listed in Table 9.1-1.2'11
9.1-8 EMISSION FACTORS 12/77
-------
9.1.2.7 Process Heaters - Process heaters (furnaces) are used
extensively in refineries to supply the heat necessary to raise the
temperature of feed materials to reaction or distillation level. They
are designed to raise petroleum fluid temperatures to a maximum of about
950°F (510°C). The fuel burned may be refinery gas, natural gas, residual
fuel oils, or combinations, depending on economics, operating conditions
and emission requirements. Process heaters may also use carbon monoxide-
rich regenerator flue gas as fuel.
All the criteria pollutants are emitted from process heaters. The
quantity of these emissions is a function of the type of fuel burned,
the nature of the contaminants in the fuel, and the heat duty of the
furnace. Sulfur oxide can be controlled by fuel desulfurization or flue
gas treatment. Carbon monoxide and hydrocarbons can be limited by more
combustion efficiency. Currently, four general techniques or modifi-
cations for the control of nitrogen oxides are being investigated:
combustion modification, fuel modification, furnace design and flue gas
treatment. Several of these techniques are presently being applied to
large utility boilers, but their applicability to process heaters has
not been established.2!1L|
9.1.2.8 Compressor Engines - Many older refineries run high pressure
compressors with reciprocating and gas turbine engines fired with natural
gas. Natural gas has usually been a cheap, abundant source of energy.
Examples of refining units operating at high pressure include hydro-
desulfurization, isomerization, reforming and hydrocracking. Internal
combustion engines are less reliable and harder to maintain than steam
engines or electric motors. For this reason, and because of increasing
natural gas costs, very few such units have been installed in the last
few years.
The major source of emissions from compressor engines is combustion
products in the exhaust gas. These emissions include carbon monoxide,
hydrocarbons, nitrogen oxides, aldehydes and ammonia. Sulfur oxides may
also be present, depending on the sulfur content of the natural gas.
All these emissions are significantly higher in exhaust of reciprocating
engines than from turbine engines.
The major emission control technique applied to compressor engines
is carburetion adjustment similar to that applied on automobiles.
Catalyst systems similar to those applied to automobiles may also be
effective in reducing emissions, but their use has not been reported.
9.1.2.9 Sweetening - Sweetening of distillates is accomplished by the
conversion of mercaptans to alkyl disulfides in the presence of a
catalyst. Conversion may be followed by an extraction step for the
removal of the alkyl disulfides. In the conversion process, sulfur is
added to the sour distillate with a small amount of caustic and air.
The mixture is then passed upward through a fixed bed catalyst counter
to a flow of caustic entering at the top of the vessel. In the conversion
and extraction process, the sour distillate is washed with caustic and
then is contacted in the extractor with a solution of catalyst and
10/80
Petroleum Industry
9.1-9
-------
Table 9.1-2. FUGITIVE EMISSION FACTORS FOR PETROLEUM REFINERIESa
Emission Process Etniss on
Emission Factors
Source Stream facto Uncontrolled
Type Unit Emissions1^
Pipeline valves'1 II Ib/hr-s urce 0.059
kg/ day- ource 0.64
III " 0,024
0.26
IV " 0.0005
0.005
V " 0.018
" 0.20
Open ended valves 'e I " 0.005
0.05
Plflnooa T " f\ nnrtSfi
(0
(0
(0
(0
(0
co
(0
(0
030 -
32 -
017 -
18 -
0002-
002 -
007 -
OS -
(0.0016-
(0
rn
017 -
nnm_
Emission
Controlled Applicable Control Technology Factor
Emissions Rarlna
0.110)
1
0
0
0
0
0
0
0
19)
036)
39)
0015)
016)
045)
49}
016)
0.17)
n
nmt: \
NA Monitoring and maintenance programs A
NA A
NA A
NA A
NA Installation of cap or plug on open end A
of valve/line
Monitoring and maintenance programs
Pump seals
Compressor seals
Process drains
Pressure vessel
relief valves
(gas service)
Cooling towers
d,f
Oil/water separators -
0.25
2.7
0.046
0.50
1.4
15
0.11
1.2
lb/106 gal cooling
water
kg/106 liters cooling
water
lb/103 bbl refinery
feedg
kg/103 liters
refinery feed
lb/103 gal wasteuater
kg/103 liter waste
water
lb/103 bbl refinery
feed
kg/103 liters refinery
feed
(0.16 - 0.37)
(1.7 - 4.0)
(0.019 - 0.11)
(0.21 - 1.2)
(0.66 - 2.9)
(7.1 - 31)
(0.05 - 0.23)
(0.5 - 2.5)
0.070 (0.023 - 0.20)
0.76 (0.25 - 2.2)
0.36 (0.10 - 1.3)
3.9 (1.1 - 14)
0.7
10
0.03
5
0.6
200
0.6
Mechanical seals, dual seals, purged
seals, monitoring and maintenance
programs, controlled degassing vent
Mechanical seals, dual seals, purged
seals, monitoring and maintenance
programs, controlled degassing vents
Traps and covers
Negligible Rupture disks upstream of relief
valves and/or venting to a flare
0.083
1.2
0.004
0.2
0.024
10
0.03
Minimization of hydrocarbon leaks
Into cooling water system. Monitoring
of cooling water for hydrocarbons
Covered separators and/or vapor recovery
Systems
Storage
Loading
Sec Section 4.3
See Section 4.4
Data from References 2, 4, 12 and 13 except as noted. Overall, less than U, by weight of the total VOC emissions are methane.
feNA = Not Available.
The volatility and hydrogen content of the process streams have a substantial effect on the emission rate of some fugitive emission sources.
The stream identification numerals and group names and descriptions are:
Stream
Identification
Numeral
I
II
III
Stream
Name
All streams
Gas streams
Light liquid and
gas/liquid streams
Stream Group Description
All streams
Hydrocarbon gaa/vapor at process
vo lume )
Liquid or gas/liquid stream with
kerosene (? 0.1 psia @ IQQ'F or
present at > 20% by volume
conditions (containing less
than 50% hydrogen,
by
a vapor pressure greater than that of
689 Pa @ 38DC), based on the most volatile class
Heavy liquid streams
Hydrogen streams
Liquid stream with a vapor pressure equal to or less than that of kerosene (^0.1
psia @ 1QO°F Or 689 Pa @ 38*0, based on the most volatile class present at > 20'^
by volume
Gas streams containing more than 50% hydrogen by volume
Numbers In parentheses are the upper and lower bounds of the 95% confidence interval for the emission factor.
Data from Reference 17.
fl'he downstream side of these valves is open to the atmosphere. Emissions are through the valve seat of the closed valve.
Emission factor for relief valves in gas service is for leakage, not for emissions caused by vessel pressure relief.
^Refinery rate is defined as the crude oil feed rate to the atmospheric distillation column-
9.1-10
EMISSION FACTORS
10/80
-------
caustic. The extracted distillate is then contacted with air to convert
mercaptans to disulfides. After oxidation, the distillate is settled,
inhibitors are added, and the distillate is sent to storage. Regeneration
is accomplished by mixing caustic from the bottom of the extractor with
air arid then separating the disulfides and excess air.
The major emission problem is hydrocarbons from contact between
the distillate product and air in the "air blowing" step. These emissions
are related to equipment type and configuration, as well as to operating
conditions and maintenance practices.4
9.1.2.10 Asphalt Blowing - The asphalt blowing process polymerizes
asphaltic residual oils by oxidation, increasing their melting temper-
ature and hardness to achieve an increased resistance to weathering.
The oils, containing a large quantity of polycyclic aromatic compounds
(asphaltic oils), are oxidized by blowing heated air through a heated
batch mixture or, in continuous process, by passing hot air counter-
current to the oil flow. The reaction is exothermic, and quench steam
is sometimes needed for temperature control. In some cases, ferric
chloride or phosphorus pentoxide is used as a catalyst to increase the
reaction rate and to impart special characteristics to the asphalt.
Air emissions from asphalt blowing are primarily hydrocarbon vapors
vented with the blowing air. The quantities of emissions are small
because of the prior removal of volatile hydrocarbons in the distilla-
tion units, but the emissions may contain hazardous polynuclear organics.
Emission are 60 pounds per ton of asphalt.13 Emissions from asphalt
blowing can be controlled to negligible levels by vapor scrubbing,
incineration, or both1**13
9.1.3 Fugitive Emissions and Controls
Fugitive emission sources are generally defined as volatile organic
compound (VOC) emission sources not associated with a specific process
but scattered throughout the refinery. Fugitive emission sources
include valves of all types, flanges, pump and compressor seals, process
drains, cooling towers, and oil/water separators. Fugitive VOC emissions
are attributable to the evaporation of leaked or spilled petroleum
liquids and gases. Normally, control of fugitive emissions involves
minimizing leaks and spills through equipment changes, procedure changes,
and improved monitoring, housekeeping and maintenance practices.
Controlled and uncontrolled fugitive emission factors for the following
sources are listed in Table 9.1-2.
0 valves (pipeline, open ended, vessel relief)
0 flanges
0 seals (pump, compressor)
0 process drains
0 oil/water separators (wastewater treatment)
0 storage
0 transfer operations
0 cooling towers
10/80 Petroleum Industry 9.1-11
-------
9.1.3.1 Valves, Flanges, Sen IK tind Drnlns - Kor these source's, a very
high correlation has been found between mass emission raLes and the type
of stream service in which the sources are employed. Except for com-
pressed gases, streams are classified into one of three stream groups,
(1) gas/vapor streams, (2) light liquid/two phase streams, and (3)
kerosene and heavier liquid streams. Gases passing through compressors
are classified as either hydrogen or hydrocarbon service. It is found that
sources in gas/vapor stream service have higher emission rates than
those in heavier stream service. This trend is especially pronounced
for valves and pump seals. The size of sources like valves, flanges,
pump seals, compressor seals, relief valves and process drains does not
affect the leak rates.17 The emission factors are independent of process
unit or refinery throughput.
Emission factors are given for compressor seals in each of the two
gas service classifications. Valves, because of their number and relatively
high emission factor, are the major emission source among the source
types. This conclusion is base.d on an analysis of a hypothetical refinery
coupled with the emission rates. The total quantity of fugitive VOC
emissions in a typical oil refinery with a capacity of 330,000 barrels
(52,500 m3) per day is estimated as 45,000 pounds (20.4 MT) per day.
See Table 9.1-3.
9.1.3.2 Storage - All refineries have a feedstock and product storage
area, termed a "tank farm", which provides surge storage capacity to
assure smooth, uninterrupted refinery operations. Individual storage
tank capacities range from less than 1000 barrels to more than 500,000
barrels (160 - 79,500 m3). Storage tank designs, emissions and emission
control technologies are discussed in detail in Section 4.3.
9.1.3.3 Transfer Operations - Although most refinery feedstocks and
products are transported by pipeline, some are transported by trucks,
rail cars and marine vessels. They are transferred to and from these
transport vehicles in the refinery tank farm area by specialized pumps
and piping systems. The emissions from transfer operations and appli-
cable emission control technology are discussed in much greater detail
in Section 4.4.
9.1.3.4 Wastewater Treatment Plant - All refineries employ some form of
wastewater treatment so water effluents can safely be returned to the
environment or reused in the refinery. The design of wastewater treat-
ment plants is complicated by the diversity of refinery pollutants,
including oil, phenols, sulfides, dissolved solids, and toxic chemicals.
Although the wastewater treatment processes employed by refineries vary
greatly, they generally include neutralizers, oil/water separators,
settling chambers, clarifiers, dissolved air flotation systems, coagu-
lators, aerated lagoons, and activated sludge ponds. Refinery water
effluents are collected from various processing units and are conveyed
through sewers and ditches to the wastewater treatment plant. Most of
the wastewater treatment occurs in open ponds and tanks.
9.1-12
EMISSION FACTORS
10/80
-------
The main components of atmospheric emissions from wastewater treat-
ment plants are fugitive VOC and dissolved gases that evaporate from the
surfaces of wastewater residing in open process drains, wastewater
separators, and wastewater ponds (Table 9.1-2). Treatment processes
that involve extensive contact of wastewater and air, such as aeration
ponds and dissolved air flotation, have an even greater potential for
atmospheric emissions.
The control of wastewater treatment plant emissions involves cov-
ering wastewater systems where emission generation is greatest (such as
covering American Petroleum Institute separators and settling basins)
and removing dissolved gases from wastewater streams with sour water
strippers and phenol recovery units prior to their contact with the
atmosphere. These control techniques potentially can achieve greater
than 90 percent reduction of wastewater system emissions.13
TABLE 9.1-3. FUGITIVE VOC EMISSIONS FROM AN OIL REFINERY
17
VOC Emissions
Source
Valves
Flanges
Pump Seals
Compressors
Relief Valves
Drains
Cooling Towers
Oil/Water Separators
(uncovered)
TOTAL
Number
11,500
46,500
350
70
100
650
—
-
Ib/day
6,800
600
1,300
1,100
500
1,000
1,600
32,100
45,000
kg /day
3,084
272
590
499
227
454
726
14,558
20,408
Emissions from the cooling towers and oil/water separators are based on
limited data. EPA is currently involved in further research to provide
better data on wastewater system fugitive emissions.
9.1.3.5 Cooling Towers - Cooling towers are used extensively in refinery
cooling water systems to transfer waste heat from the cooling water to
the atmosphere. The only refineries not employing cooling towers are
those with once-through cooling. The increasing scarcity of large water
supplies required for once-through cooling is contributing to the disappear-
ance of that form of refinery cooling. In the cooling tower, warm
cooling water returning from refinery processes is contacted with air by
cascading through packing. Cooling water circulation rates for refineries
commonly range from 0.3 to 3.0 gallons (1.1 - 11.0 liters) per minute
per barrel per day of refinery capacity.2*16
Atmospheric emissions from the cooling tower consist of fugitive
VOC and gases stripped from the cooling water as the air and water come
into contact. These contaminants enter the cooling water system from
10/80
Petroleum Industry
9.1-13
-------
leaking heat exchangers and condensers. Although the predominant conta-
minant in cooling water is VOC, dissolved gases such as hydrogen sulfide
and ammonia may also be found (Table 9.1-2) .^^s 17
Control of cooling tower emissions is accomplished by reducing
contamination of cooling water through the proper maintenance of heat
exchangers and condensers. The effectiveness of cooling tower controls
is highly variable, depending on refinery configuration and existing
maintenance practices.
References for Section 9.1
1. C. E. Burklin, et al . , Revision of Emission Factors for Petroleum
Refining, EPA-450/3-77-030, U.S. Environmental Protection Agency,
Research Triangle Park, NC, October 1977.
2. Atmospheric Emissions from Petroleum Refineries; A Guide for Measure-
ment^ and Control , PHS No. 763, Public Health Service, U.S. Depart-
ment of Health, Education and Welfare, Washington, DC, 1960.
3. Background Infjajmajbjto^^^ ^Standards: Asphalt
Concrete Plants, Pe/trol^eum^ Refineries^ S^torajge Vessels, Secondary
Lead Smelters L^nd Refineries, Brass or Bronze Ingot Production Plants,
Iron and Steel Plants, Sewage ^Treatment Plants, APTD-1352a, U.S.
Environmental Protection Agency, Research Triangle Park, NC, 1973.
4. John A. Danielson (ed.), Air Pollution Engineering Manual (2nd Ed.),
AP-40, U.S. Environmental Protection Agency, Research Triangle
Park, NC, 1973. Out of Print.
5. Ben G. Jones, "Refinery Improves Particulate Control", Oil and Gas
Journal, 69(26) ; 60-62, June 28, 1971.
6. "Impurities in Petroleum", Petreco Manual, Petrolite Corp., Long
Beach, CA, 1958.
7. Control Techniques for Sulfur Oxide in Air Pollutants, AP-52, U.S.
Environmental Protection Agency, Research Triangle Park, NC,
January 1969.
8. H. N. Olson and K. E. Hutchinson, "How Feasible Are Giant, One-
train Refineries?", Oil and Gas Journal, K)_(l): 39-43, January 3,
1972.
9. C. M. Urban and K. J. Springer, jatudy of Exhaust Emissions from
Natural Gas Pipeline Compressor Engines, American Gas Association,
Arlington, VA, February 1975.
10. H. E. Dietzmann and K. J. Springer, Exhaust Emissions from Piston
and Gas Turbine Engines Used in Natural Gas Transmission, American
Gas Association, Arlington, VA, January 1974.
9.1-14 EMISSION FACTORS 10/80
-------
11. M. G. Klett and J. B. Galeski, Flare Systems Study, EPA-600/2-76-
079, U.S. Environmental Protection Agency, Research Triangle Park,
NC, March 1976.
12. Evaporation Loss in the Petroleum Industry, Causes and Control,
API Bulletin 2513, American Petroleum Institute, Washington, DC,
1959.
13. Hydrocarbon Emissions from Refineries, API Publication No. 928,
American Petroleum Institute, Washington, DC, 1973.
14. R. A. Brown, et al., Systems Analysis Requirements for Nitrogen
Oxide Control of Stationary Sources, EPA-650/2-74-091, U.S.
Environmental Protection Agency, Research Triangle Park, NC, 1974.
15. R. P. Hangebrauck, et^ al^., Sources of Polynuclear Hydrocarbons in
the Atmosphere, 999-AP-33, Public Health Service, U.S. Department
of Health, Education and Welfare, Washington, DC, 1967.
16. W. S. Crumlish, "Review of Thermal Pollution Problems, Standards,
and Controls at the State Government Level", Presented at the
Cooling Tower Institute Symposium, New Orleans, LA, January 30, 1966.
17. Assessment of Atmospheric Emissions from Petroleum Refining,
EPA-600/2-80-075a through -075d, U.S. Environmental Protection
Agency, Research Triangle Park, NC, 1980.
10/80 Petroleum Industry 9.1-15
-------
-------
9.2 NATURAL GAS PROCESSING
9.2.1 General1
Natural gas from high-pressure wells is usually passed through field separators to remove hydrocarbon
condensate and water at the well. Natural gasoline, butane, and propane are usually present in the gas, and gas
processing plants are required for the recovery of these liquefiable constituents (see Figure 9.2-1), Natural gas is
considered "sour" if hydrogen sulfide is present in amounts greater than 0.25 grain per 100 standard cubic feet.
The hydrogen sulfide (H2S) must be removed (called "sweetening" the gas) before the gas can be utilized. If H2S
is present, the gas is usually sweetened by absorption of the H2S in an amine solution. Amine processes are used
for over 95 percent of all gas sweetening in the United States. Processes such as carbonate processes, solid bed
absorbents, and physical absorption methods are employed in the other sweetening plants. Emissions data for
sweetening processes other than amine types are very meager.
The major emission sources in the natural gas processing industry are compressor engines and acid gas wastes
from gas sweetening plants. Compressor engine emissions are discussed in section 3.3.2; therefore, only gas
sweetening plant emissions are discussed here.
9.2.2 Process Description2'3
Many chemical processes are available for sweetening natural gas. However, at present, the most widely used
method for H2S removal or gas sweetening is the amine type process (also known as the Girdler process) in which
various amine solutions are utilized for absorbing H2S. The process is summarized in reaction 1 and illustrated in
Figure 9.2-2.
2RNH2 + H2S «-(RNH3)2S (1)
where: R = mono, di, or tri-ethanol
N = nitrogen
H = hydrogen
S = sulfur
The recovered hydrogen sulfide gas stream may be (1) vented, (2) flared in waste gas flares or modern
smokeless flares, (3) incinerated, or (4) utilized for the production of elemental sulfur or other commercial
products. If the recovered H2S gas stream is not to be utilized as a feedstock for commercial applications, the gas
is usually passed to a tail gas incinerator in which the H2S is oxidized to sulfur dioxide and then passed to the
atmosphere via a stack. For more details, the reader should consult Reference 8.
9.2.3 Emissions4'5
Emissions will only result from gas sweetening plants if the acid waste gas from the amine process is flared or
incinerated. Most often, the acid waste gas is used as a feedstock in nearby sulfur recovery or sulfuric acid plants.
When flaring or incineration is practiced, the major pollutant of concern is sulfur dioxide. Most plants employ
elevated smokeless flares or tail gas incinerators to ensure complete combustion of all waste gas constituents,
including virtually 100 percent conversion of H2S to SO2. Little particulate, smoke, or hydrocarbons result from
these devices, and because gas temperatures do not usually exceed 1200°F (650°C), significant quantities of
nitrogen oxides are not formed. Emission factors for gas sweetening plants with smokeless flares or incinerators
are presented in Table 9.2-1.
4/76 Petroleum Industry 9.2-1
-------
FLARE (ONLY DURING WELL TESTING
AND COMPLETION)
cn
I
9
o
GAS,
OIL, AND
WATER
EMERGENCY FLARE OR VENT
SEPARATORS
AND
DEHYDRATORS
REINJECTION
IF SWEET
HYDROCARBON
CONDENSATES
WATER
SOUR GAS FEEDSTOCK TO CHEMICAL PLANTS
EMERGENCY FLARE
REINJECTION
FLARE OR
INCINERATOR
FLARE OR
INCINERATOR
SOUR
GAS
GAS SWEETENING PLANT
SWEET
GAS
SWEET
GAS
ACID GAS
C02-H2S
SULFUR RECOV-
ERY PLANT
EMERGENCY FLARE OR VENT
GAS PROCESSING
PLANT
-^•PIPELINE
ELEMENTAL
SULFUR
NATURAL GAS
-------
Table 9.2-1. EMISSION FACTORS FOR GAS SWEETENING PLANTS3
EMISSION FACTOR RATING: SULFUR OXIDES: A
ALL OTHER FACTORS: C
Process"
Amine
lb/106 ft3 gas processed
kg/103 m3 gas processed
Particulates
Neg.
Neg.
Sulfur oxides0
(S02)
16853d
26.98 Sd
Carbon
monoxide
Neg.
Neg.
Hydrocarbons
Neg.
Neg.
Nitrogen
oxides
Neg,
Neg.
aEmission factors are presented in this section only for smokeless flares and tail gas incinerators on the amine gas sweetening
process. Too little emissions information exists to characterize emissions from older, less efficient waste gas flares on the
amine process or from other, less common gas sweetening processes. Emission factors for various internal combustion engines
utilized in a gas processing plant are given in section 3.3.2. Emission factors for sulfuric acid plants and sulfur recovery plants
are given in sections 5.17 and 5.18, respectively.
'-'These factors represent emissions after smokeless flares (with fuel gas and steam injection) or tail gas incinerators and are based
on References 2 and 4 through 7.
°These factors are based on the assumptions that virtually 100 percent of all h^S in the acid gas waste is converted to SO2 during
flaring or incineration and that the sweetening process removes essentially 100 percent of the H^ present in the feedstock.
S is the H^S content, on a mole percent basis, in the sour gas entering the gas sweetening plant. For example, if the H^S content
is 2 percent, the emission factor would be 1685 times 2, or 3370 Ib SO2 per million cubic feet of sour gas processed. If the
HoS mole percent is unknown, average values from Table 9.2-2 may be substituted.
Note: If H^S contents are reported in grains per 100 scf or ppm, use the following factors to convert to mole percent:
0.01 mol % H2S = 6.26 gr H^/IOO scf at 60°F and 29.92 in. Hg
1 gr/100 scf = 16 ppm (by volume)
To convert to or from metric units, use the following factor:
0.044 gr/100 scf - 1 mg/^m3
ACID GAS
PURIFIED
GAS
*• STEAM
REBOILER
4/76
HEAT EXCHANGER
Figure 9.2-2. Flow diagram of the amine process for gas sweetening.
Petroleum Industry
9.2-3
-------
Table 9.2-2. AVERAGE HYDROGEN SULFIDE CONCENTRATIONS
IN NATURAL GAS BY AIR QUALITY CONTROL REGION3
State
Alabama
Arizona
Arkansas
California
Colorado
Florida
Kansas
Louisiana
Michigan
Mississippi
Montana
New Mexico
North Dakota
Oklahoma
AQCR name
Mobile-Pensacola-Panama City -
Southern Mississippi (Fla., Miss.)
Four Corners (Colo., N.M., Utah)
Monroe-El Dorado (La.)
Shreveport-Texarkana-Tyler
(La., Okla., Texas)
Metropolitan Los Angeles
San Joaquin Valley
South Central Coast
Southeast Desert
Four Corners (Ariz., N.M., Utah)
Metropolitan Denver
Pawnee
San Isabel
Yampa
Mobile-Pensacola-Panama City -
Southern Mississippi (Ala., Miss.)
Northwest Kansas
Southwest Kansas
Monroe-El Dorado (Ariz.)
Shreveport-Texarkana-Tyler
(Ariz., Okla., Texas)
Upper Michigan
Mississippi Delta
Mobile-Pensacola-Panama City -
Southern Mississippi (Ala., Fla.)
Great Falls
Miles City
Four Corners (Ariz., Colo., Utah)
Pecos-Permian Basin
North Dakota
Northwestern Oklahoma
Shreveport-Texarkana-Tyler
(Ariz., La., Texas)
Southeastern Oklahoma
AQCR
number
5
14
19
22
24
31
32
33
14
36
37
38
40
5
97
100
19
22
126
134
5
141
143
14
155
172
187
22
188
Average
H2S, mol %
3.30
0.71
0.15
0.55
2.09
0.89
3.66
1.0
0.71
0.1
0.49
0.3
0.31
3.30
0.005
0.02
0.15
0.55
0.5
0.68
3.30
3.93
0.4
0.71
0.83
1.74b
1.1
0.55
0.3
9.2-4
EMISSION FACTORS
4/76
-------
Table 9.2-2 (continued). AVERAGE HYDROGEN SULFIDE CONCENTRATIONS
IN NATURAL GAS BY AIR QUALITY CONTROL REGION3
State
Texas
Utah
Wyoming
AQCR name
Abilene-Wichita Falls
Amarillo-Lubbock
Austin-Waco
Corpus Christi-Victoria
Metropolitan Dallas-Fort Worth
Metropolitan San Antonio
Midland-Odessa-San Angelo
Shreveport-Texarkana-Tyler
(Ariz., La., Okla.)
Four Corners (Ariz., Colo., N.M.)
Casper
Wyoming (except Park, Bighorn
and Washakie Counties)
AQCR
number
210
211
212
214
215
217
218
22
14
241
243
Average
H2S, mol %
0.055
0.26
0.57
0.59
2.54
1.41
0.63
0.55
0.71
1.262
2.34
aReference 9.
"Sour gas only reported for Burke, Williams, and McKenzie Counties.
cPark, Bighorn, and Washakie Counties report gas with an average 23 mol % HjS content.
Some plants still use older, less efficient waste gas flares. Because these flares usually burn at temperatures
lower than necessary for complete combustion, some emissions of hydrocarbons and particulates as well as higher
quantities of t^S can occur. No data are available to estimate the magnitude of these emissions from waste gas
flares.
Emissions from sweetening plants with adjacent commercial plants, such as sulfuric acid plants or sulfur
recovery plants, are presented in sections 5.17 and 5.18, respectively. Emission factors for internal combustion
engines used in gas processing plants are given in section 3.3.2.
Background material for this section was prepared for EPA by Ecology Audits, Inc.^
References for Section 9.2
1. Katz, D.L., D. Cornell, R. Kobayashi, F.H. Poettmann, J.A. Vary, J.R. Elenbaas, and C.F. Weinaug.
Handbook of Natural Gas Engineering. New York, McGraw-Hill Book Company. 1959. 802 p.
2. Maddox, R.R. Gas and Liquid Sweetening. 2nd Ed. Campbell Petroleum Series, Norman, Oklahoma. 1974.
298 p.
3. Encyclopedia of Chemical Technology. Vol. 7. Kirk, R.E. and D.F. Othmer (eds.). New York, Interscience
Encyclopedia, Inc. 1951.
4. Sulfur Compound Emissions of the Petroleum Production Industry. M.W. Kellogg Co., Houston, Texas.
Prepared for Environmental Protection Agency, Research Triangle Park, N.C. under Contract No. 68-02-1308.
Publication No. EPA-650/2-75-030. December 1974.
5. Unpublished stack test data for gas sweetening plants. Ecology Audits, Inc., Dallas, Texas. 1974.
4/76
Petroleum Industry
9.2-5
-------
6. Control Techniques for Hydrocarbon and Organic Solvent Emissions from Stationary Sources, U.S. DHEW,
PHS, EHS, National Air Pollution Control Administration, Washington, D.C. Publication No. AP-68 March
1970. p. 3-1 and 4-5.
7. Control Techniques for Nitrogen Oxides from Stationary Sources. U.S. DHEW, PHS, EHS, National Air
Pollution Control Administration, Washington, D.C. Publication No. AP-67. March 1970. p. 7-25 to 7-32.
8. Mullins, B.J. et al. Atmospheric Emissions Survey of the Sour Gas Processing Industry. Ecology Audits, Inc.,
Dallas, Texas. Prepared for Environmental Protection Agency, Research Triangle Park, N.C. under Contract
No. 68-02-1865. Publication No. EPA-450/3-75-076. October 1975.
9. Federal Air Quality Control Regions. Environmental Protection Agency, Research Triangle Park NC
Publication No. AP-102. January 1972.
4/76 EMISSION FACTORS 9.2-6
-------
10. WOOD PRODUCTS INDUSTRY
Wood processing involves the conversion of raw wood to either pulp, pulpboard, or one of several types of
wallboard including plywood, particleboard, or hardboard. This section presents emissions data for chemical
wood pulping, for pulpboard and plywood manufacturing, and for woodworking operations. The burning of wood
waste in boilers and conical burners is not included as it is discussed in Chapters 1 and 2 of this publication.
10.1 CHEMICAL WOOD PULPING
10.1.1 General i
Chemical wood pulping involves the extraction of cellulose from wood by dissolving the lignin that binds the
cellulose fibers together. The principal processes used in chemical pulping are the kraft, sulfite, neutral sulfite
semichemical (NSSC), dissolving, and soda; the first three of these display the greatest potential for causing air
pollution. The kraft process accounts for about 65 percent of all pulp produced in the United States; the sulfite
and NSSC processes, together, account for less than 20 percent of the total. The choice of pulping process is de-
termined by the product being made, by the type of wood species available, and by economic considerations.
10.1.2 Kraft Pulping
10.1.2.1 Process Description!>2—The kraft process (see Figure 10.1.24) involves the cooking of wood chips
under pressure in the presence of a cooking liquor in either a batch or a continuous digester. The cooking liquor,
or "white liquor," consisting of an aqueous solution of sodium sulfide and sodium hydroxide, dissolves the lignin
that binds the cellulose fibers together.
When cooking is completed, the contents of the digester are forced into the blow tank. Here the major portion
of the spent cooking liquor, which contains the dissolved lignin, is drained, and the pulp enters the initial stage of
washing. From the blow tank the pulp passes through the knotter where unreacted chunks of wood are removed.
The pulp is then washed and, in some mills, bleached before being pressed and dried into the finished product.
It is economically necessary to recover both the inorganic cooking chemicals and the heat content of the spent
"black liquor," which is separated from the cooked pulp. Recovery is accomplished by first concentrating the
liquor to a level that will support combustion and then feeding it to a furnace where burning and chemical recovery
take place.
Initial concentration of the weak black liquor, which contains about 15 percent solids, occurs in the multiple-
effect evaporator. Here process steam is passed countercurrent to the liquor in a series of evaporator tubes that
increase the solids content to 40 to 55 percent. Further concentration is then effected in the direct contact
evaporator. This is generally a scrubbing device (a cyclonic or venturi scrubber or a cascade evaporator) in which
hot combustion gases from the recovery furnace mix with the incoming black liquor to raise its solids content to
55 to 70 percent.
The black liquor concentrate is then sprayed into the recovery furnace where the organic content supports
combustion. The inorganic compounds fall to the bottom of the furnace and are discharged to the smelt dissolving
tank to form a solution called "green liquor." The green liquor is then conveyed to a causticizer where slaked
lime (calcium hydroxide) is added to convert the solution back to white liquor, which can be reused in subsequent
cooks. Residual lime sludge from the causticizer can be recycled after being dewatered and calcined in the hot
lime kiln.
Many mills need more steam for process heating, for driving equipment, for providing electric power, etc., than
can be provided by the recovery furnace alone. Thus, conventional industrial boilers that burn coal, oil, natural
gas, and in some cases, bark and wood waste are commonly employed.
4/76 Wood Products Industry 10.1-1
-------
CHIPS
RELIEF
CH3SH, CH3SCH3, H2S
NONCONDENSABLES
i
*•*
en
en
s
*3
en
CH3SH.CH3SCH3, H2S
NONCONDENSABLES
HzS, CH3SH,CH3SCH3,
AND HIGHER COMPOUNDS
J^
ON
TURPENTINE
CONTAMINATED WATER
CONTAMINATED
-*• WATER
STEAM, CONTAMINATED WATER,
H2S, AND
PULP 13% SOLIDS
SPENT AIR, CH3SCHs,-*-
AND CHsSSCHs
OXIDATION
TOWER
ON
R
1
'
TJ
O
BLACK LIQUOR
50% SOLIDS
DIRECT CONTACT
EVAPORATOR
^BLACK
LIQUOR 70% SOLIfJS
CaO NaZS04
'WATER
RECOVERY
FURNACE
OXIDIZING
ZONE
REDUCTION
1
iULt-UK
* +
GREEN
LIQUOR
Na2S + NazCC
AIR
Figure 10.1.2-1. Typical kraft sulfate pulping and recovery process.
-------
10.1.2.2. Emission and Controls^-Particulate emissions from the kraft process occur primarily from the re-
covery furnace, the lime kiln, and the smelt dissolving tank. These emissions consist mainly of sodium salts but
include some calcium salts from the lime kiln. They are caused primarily by the carryover of solids plus the sub-
limation and condensation of the inorganic chemicals.
Paniculate control is provided on recovery furnaces in a variety of ways. In mills where either a cyclonic
scrubber or cascade evaporator serves as the direct contact evaporator, further control is necessary as these devices
are generally only 20 to 50 percent efficient for particulates. Most often in these cases, an electrostatic precipitator
is employed after the direct contact evaporator to provide an overall particulate control efficiency of 85 to > 99
percent. In a few mills, however, a venturi scrubber is utilized as the direct contact evaporator and simultaneously
provides 80 to 90 percent particulate control. In either case auxiliary scrubbers may be included after the
precipitator or the venturi scrubber to provide additional control of particulates.
Particulate control on lime kilns is generally accomplished by scrubbers. Smelt dissolving tanks are commonly
controlled by mesh pads but employ scrubbers when further control is needed.
The characteristic odor of the kraft mill is caused in large part by the emission of hydrogen sulfide. The major
source is the direct contact evaporator in which the sodium sulfide in the black liquor reacts with the carbon
dioxide in the furnace exhaust. The lime kiln can also be a potential source as a similar reaction occurs involving
residual sodium sulfide in the lime mud. Lesser amounts of hydrogen sulfide are emitted with the noncondensible
off-gasses from the digesters and multiple-effect evaporators.
The kraft-process odor also results from an assortment of organic sulfur compounds, all of which have extremely
low odor thresholds. Methyl mercaptan and dimethyl sulfide are formed in reactions with the wood component
lignin. Dimethyl disulfide is formed through the oxidation of mercaptan groups derived from the lignin. These
compounds are emitted from many points within a mill; however, the main sources are the digester/blow tank
systems and the direct contact evaporator.
Although odor control devices, per se, are not generally employed in kraft mills, control of reduced sulfur
compounds can be accomplished by process modifications and by optimizing operating conditions. For example,
black liquor oxidation systems, which oxidize sulfides into less reactive thiosulfates, can considerably reduce
odorous sulfur emissions from the direct contact evaporator, although the vent gases from such systems become
minor odor sources themselves. Noncondensible odorous gases vented from the digester/blow tank system and
multiple-effect evaporators can be destroyed by thermal oxidation, usually by passing them through the lime
kiln. Optimum operation of the recovery furnace, by avoiding overloading and by maintaining sufficient oxygen
residual and turbulence, significantly reduces emissions of reduced sulfur compounds from this source. In addi-
tion, the use of fresh water instead of contaminated condensates in the scrubbers and pulp washers further reduces
odorous emissions. The effect of any of these modifications on a given mill's emissions will vary considerably.
Several new mills have incorporated recovery systems that eliminate the conventional direct contact evaporators.
In one system, preheated combustion air rather than flue gas provides direct contact evaporation. In the other,
the multiple-effect evaporator system is extended to replace the direct contact evaporator altogether. In both of
these systems, reduced sulfur emissions from the recovery furnace/direct contact evaporator reportedly can be
reduced by more than 95 percent from conventional uncontrolled systems.
Sulfur dioxide emissions result mainly from oxidation of reduced sulfur compounds in the recovery furnace.
It is reported that the direct contact evaporator absorbs 50 to 80 percent of these emissions; further scrubbing, if
employed, can reduce them another 10 to 20 percent.
Potential sources of carbon monoxide emissions from the kraft process include the recovery furnace and lime
kilns. The major cause of carbon monoxide emissions is furnace operation well above rated capacity, making it
impossible to maintain oxidi/.ing condilions.
4/77 Wood Products Industry 10.1-3
-------
Some nitrogen oxides are also emitted from the recovery furnace and lime kilns although the
amounts are relatively small. Indications are that nitrogen oxides emissions from each of these sources
-are on the order of 1 pound per air-dried ton (0.5 kg/air-dried MT) of pulp produced.5 6
A major source of emissions in a kraft mill is the boiler for generating auxiliary steam and power.
The fuels used are coal, oil, natural gas, or bark/wood waste. Emission factors for boilers are presented
in Chapter 1.
Table 10.1.2-1 presents emission factors for a conventional kraft mill. The most widely used
particulate controls devices are shown along with the odor reductions resulting from black liquor
oxidation and incim , .ition of noncondensible off-gases.
10.1.3 Acid Sulfite Pulping
10.1.3.1 Process Description14 - The production of acid sulfite pulp proceeds similarly to kraft pulp-
ing except that different chemicals are used in the cooking liquor. In place of the caustic solution used
to dissolve the lignin in the wood, sulfurous acid is employed. To buffer the cooking solution, a bisul-
fite of sodium, magnesium, calcium, or ammonium is used. A simplified flow diagram of a magnesium-
base process is shown in Figure 10.1.3-1.
Digestion is carried out under high pressure and high temperature in either batch-mode or con^
tinuous digesters in the presence of a sulfurous acid-bisulfite cooking liquor. When cooking is com-
. leted, the digester is either discharged at high pressure into a blow pit or its contents are pumped out
at a lower pressure into a dump tank. The spent sulfite liquor (also called red liquor) then drains
through the bottom of the tank and is either treated and disposed, incinerated, or sent to a plant for
recovery of heat and chemicals. The pulp is then washed and processed through screens and centri-
fuges for removal of knots, bundles of fibers, and other materials. It subsequently may be bleached,
pressed, and dried in paper-making operations.
Because of the variety of bases employed in the cooking liquor, numerous schemes_f or heat_and/or
chemical recovery have evolved. In calcium-base systems, which are used mostly in older mills, chemi-
cal recovery is not practical, and the spent liquor is usually discarded or incinerated. In ammonium-
base operations, heat can be recovered from the spent liquor through combustion, but the ammonium
base is consumed in the process. In sodium- or magnesium-base operations heat, sulfur, and base
recovery are all feasible.
If recovery is practiced, the spent weak red liquor (which contains more than half of the raw
materials as dissolved organic solids) is concentrated in a multiple-effect evaporator and direct contact
evaporator to 55 to 60 percent solids. Strong liquor is sprayed into a furnace and burned, producing
steam for the digesters, evaporators, etc., and to meet the mills power requirements.
When magnesium base liquor is burned, a flue gas is produced from which magnesium oxide is
recovered in a multiple cyclone as fine white powder. The magnesium oxide is then water-slaked and
used as circulating liquor in a series of venturi scrubbers which are designed to absorb sulfur dioxide
from the flue gas and form a bisulfite solution for use in the cook cycle. When sodium-base liquor is
burned, the inorganic compounds are recovered as a molten smelt containing sodium sulfide and
sodium carbonate. This smelt may be processed further and used to absorb sulfur dioxide from the
flue gas and sulfur burner. In some sodium-base mills, however, the smelt may be sold to a nearby kraft
mill as raw material for producing green liquor.
10.1-4 EMISSION FACTORS 4, < '
-------
Table 10.1.2-1. EMISSION FACTORS FOR SULFATE PULPING3
(unit weights of air dried unbleached pulp)
EMISSION FACTOR RATING: A
Source
Digester relief and
blow tank
Brown stock washers
Multiple effect
evaporators
Recovery boiler and
direct contact
evaporator
Smelt dissolving
tank
Lime kilns
Turpentine
condenser
Miscellaneous
sources'
Type
control
Untreated 9
Untreated
Untreated g
Untreated h
Venturi
scrubbed
Electrostatic
precipitator
Auxiliary
scrubber
Untreated
Mesh pad
Untreated
Scrubber
Untreated
Untreated
P articulate^
Ib/ton
—
.
—
150
47
8
3-1^
5
1
45
3
—
..
kg/MT
—
—
75 ,
23.5
4
i
1.5-7.5*
2.5
0.5
22.5
1.5
—
Sulfur
dioxide (SC>2)C
Ib/ton
—
0.01
0.01
5
5
5
3
0.1
0.1
0.3
0.2
—
kg/MT
—
0.005
0.005
2.5
2.5
2.5
1.5
0.05
0.05
0.15
0.1
—
Carbon
monoxided
Ib/ton
—
—
—
2-60
2- 60
2 - 60
2 -60
—
—
10
10
—
kg/MT
—
—
—
1 -30
1 - 30
1 -30
1 - 30
—
—
5
5
—
Hydrogen
sutfidefS*}6.
Ib/ton
0.1
0.02
0.1
12i
12'
12i
12"
0.04
0.04
0.5
0.5
0.01
kg/MT
0.05
0.01
0.05
6!
6'
61
6'
0.02
0.02
0.25
0.25
0.005
RSH, RSR,
RSSR(S-)e'f
Ib/ton
1.5
0.2
0.4
1'
11
1'
V
0.4
0.4
0.25
0.25
0.5
0.5
kg/MT
0.75
0.1
0.2
0.5!
0.5'
0.51
0.51
0.2
0.2
0.125
0.125
0.25
0.25
ft
01
h-1
I
en
ft
O
i->
Cn
f,
For more detailed data on specific types of mills, consult Reference 1.
References 1, 7, 8,
References 1, 7, 9, 10.
References 6, 11. Use higher value for overloaded furnaces.
References 1, 4, 7-10, 12, 13. These reduced sulfur compounds are usually expressed as sulfur.
RSH-me thy I me reap tan; RSR-di methyl sulfide; RSSR-dimethyl disulfide.
9lf the noncondensible gases from these sources are vented to the lime kiln, recovery furnace, or equivalent, the reduced sulfur compounds
are destroyed..
"These factors apply when either a cyclonic scrubber or cascade evaporator is used for direct contact evaporation with no further controls.
'These reduced sulfur compounds {TRSj are typically reduced by 50 percent when black liquor oxidation is employed but can be cut by 90 to
99 percent when oxidation is complete and the recovery furnace is operated optimally.
JThese factors apply when a venturi scrubber is used for direct contact evaporation with no further controls.
"Use 15(7.5) when the auxiliary scrubber follows a venturi scrubber and 3(1.5) when employed after an electrostatic precipitator.
'Includes k no tier vents, brownstock seal tanks, etc. • When black liquor oxidation is included, a factor of 0.6(0.3) should be used.
-------
RECOVERY FURNACE/
ABSORPTION STREAM
EXHAUST
DIRECT-CONTACT
M
3
HH
C/3
CB
hH
o
H
O
MECHANICAL
DUST
COLLECTOR
RECOVERY V
RATO
S
b
R
EXHAUST
\
MgO \_
\ [ (>•
n
^l
i
STEAM FOR
PROCESS AND POWER
, RECOVERY FURNACE
oo
oo
LIQUOR
HEATER
MAKEUP
STRONG RED LIQUOR
MULTIPLE-EFFECT
EVAPORATORS
WEAK
RED
LIQUOR
STORAGE
WEAK RED LIQUOR
Figure 10.1.3-1. Simplified process flow diagram of magnesium-base process employing
chemical and heat recovery.
-------
If recovery is not practiced, an acid plant of sufficient capacity to fulfill the mill's total sulfite
requirement is necessary. Normally, sulfur is burned in a rotary or spray burner. The gas produced is
then cooled by heat exchangers plus a water spray and then absorbed in a variety of different scrubbers
containing either limestone or a solution of the base chemical. Where recovery is practiced, fortifica-
tion is accomplished similarly, although a much smaller amount of .sulfur dioxide must be produced
to make up for that lost in the process.
10.1.3.2 Emissions and Controls14 - Sulfur dioxide is generally considered the major pollutant of
concern from sulfite pulp mills. The characteristic "kraft" odor is not emitted because volatile re-
'duced sulfur compounds are not products of the lignin-bisulfite reaction.
: One of the major SOj,sources is the digester and blow pit or dump tank system. Sulfur dioxide is
present in the intermittent digester relief_gases as well as in the gases given off at the end of the cook
when the digester contents are discharged into the blow pit or dump tank. The quantity of sulfur oxide
evolved and emitted to the atmosphere in these gas streams depends on the pH of the cooking liquor,
the pressure at which the digester contents are discharged, and the effectiveness of the absorption
Systems employed for SOj recovery. Scrubbers can be installed that reduce SO? from this source by as
much as 99 percent.
Another source of sulfur dioxide emissions is the recovery system. Since magnesium-, sodium-, and
ammonium-base recovery systems all utilize absorption systems to recover SO2 generated in the re-
covery furnace, acid fortification towers, multiple-effect evaporators, etc., the magnitude of SOa
emissions depends on the desired .efficiency of these systems. Generally, such absorption systems
provide better than 95 percent sulfur recovery to minimize sulfur makeup needs.
The various pulp washing, screening, and cleaning operations are also potential sources of SO?,
These operations are numerous and may account for a significant fraction of a mill's SO2 emissions if
not controlled.
The only significant particulate source in the pulping and recovery process is the absorption system
handling the recovery furnace exhaust. Less particulate is generated in ammonium-base systems than
magnesium- or sodium-base systems as the combustion productions are mostly nitrogen, water vapor,
and sulfur dioxide.
Other major sources of emissions in a sulfite pulp mill include the auxiliary power boilers. Emis-
sion factors for these boilers are presented in Chapter 1.
Emission factors for the various sulfite pulping operations are shown in Table 10.1.3-1.
10.1.4 Neutral Sulfite Semichemical (NSSC) Pulping
10.1.4.1 Process Description'^ Vs>16 - In this process, the wood chips are cooked in a neutral solution of
sodium sulfite and sodium bicarbonate. The sulfite ion reacts with the lignin in the wood, and the
sodium bicarbonate acts as a buffer to maintain a neutral solution. The major difference between this
process (as well as all semichemical techniques) and the kraft and acid sulfite processes is that only a
portion of the lignin is removed during the cook, after which the pulp is further reduced by mechani-
cal disintegration. Because of this, yields as high as 60 to 80 percent can be achieved as opposed to 50 to
55 percent for other chemical processes.
4/77 Wood Products Industry 10.1-7
-------
Table 10.1.3-1. EMISSION FACTORS FOR SULFITE PULPING3
Source
Digester/blow pit or
dump tankc
Recovery system'
Base
All
MgO
MgO
MgO
MgO
IMH3
NH3
Na
Ca
MgO
IMH3
Acid plantS
Other sources'
Na
NH3
Na
Ca
All
Co'ntrol
None
Process change6
Scrubber
Process change
and scrubber
All exhaust
vented through
recovery system
Process change
Process change
and scrubber
Process change
and scrubber
Unknown
Multiclone and
venturi
scrubbers
Ammonia
absorption and
mist eliminator
Sodium carbonate
scrubber
Scrubber
Unknown"
Jenssen
scrubber
None
Emission factor^
Part
Ib/ADUT
Negd
Meg
Neg
Neg
Neg
Neg
Neg
Neg
Neg
2
0.7
4
Neg
Neg
Neg
Neg
culate
kg/ADUMT
Neg
Neg
Neg
Neg
Neg
Neg
Neg
Neg
Neg
1
0.35
2
Neg
Neg
Neg
Neg
Sulfur Dioxide
Ib/ADUT
10-70
2-6
1
0.2
0
25
0.4
2
67
9
7
2
0.3
0.2
8
12
kg/ADUMT
5-35
1-3
0.5
0.1
0
12.5
0.2
1
33.5
4.5
3.5
1
0.2
0.1
4
6
Emission
factor
rating
C
c
B
B
A
D
B
C
C
A
B
C
C
D
C
D
aAII emission factors represent long-term average emissions.
^Factors expressed in terms of Ib (kg) of pollutant per air dried unbleached ton (MT) of pulp. All factors are based on data
in Reference 14.
cThese factors represent emissions that occur after the cook is completed and when the digester contents are discharged in-
to the blow pit or dump tank. Some relief gases are vented from the digester during the cook cycle, but these are usually
transferred to pressure accumulators, and the S02 therein is reabsorbed for use in the cooking liquor. These factors repre-
sent long-term average emissions; in some mills, the actual emissions will be intermittent and for short time periods.
'•'Negligible emissions.
6Process changes may include such measures as raising the pH of the cooking liquor, thereby lowering the free S02, reliev-
ing the pressure in the digester before the contents are discharged, and pumping out the digester contents instead of blow-
ing them out.
f The recovery system at most mills is a closed system that includes the recovery furnace, direct contact evaporator, multi-
ple-effect evaporator, acid fortification tower, and SC>2 absorption scrubbers. Generally, there will only be one emission
point for the entire recovery system. These factors are long-term averages and include the high SC>2 emissions during the
periodic purging of the recovery system.
9 Acid plants are necessary in mills that have no or insufficient recovery systems.
"Control is practiced, but type of control is unknown.
1 Includes miscellaneous pulping operations such as knotters, washers, screens, etc.
10.1-8
EMISSION FACTORS
4/77
-------
The NSSC process varies from mill to mill. Some mills dispose of their spent liquor, some mills recover the
cooking chemicals, and some, which are operated in conjunction with kraft mills, mix their spent liquor with the
kraft liquor as a source of makeup chemicals. When recovery is practiced, the steps involved parallel those of the
sulfite process.
10.1.4.2 Emissions and Controls1- -1!i-16-Pa-rticulate emissions are a potential problem only when recovery
systems are employed. Mills that do practice recovery, but are not operated in conjunction with kraft operations
often utilize fluidized bed reactors to burn their spent liquor. Because the flue gas contains sodium sulfate and
sodium carbonate dust, efficient particulate collection may be included to facilitate chemical recovery.
A potential gaseous pollutant is sulfur dioxide. The absorbing towers, digester/blow tank system, and recovery
furnace are the main sources of this pollutant with the amounts emitted dependent upon the capability of the
scrubbing devices installed for control and recovery.
Hydrogen sulfide can also be emitted from NSSC mills using kraft-type recovery furnaces. The main potential
source is the absorbing tower where a significant quantity of hydrogen sulfide is liberated as the cooking liquor is
made. Other possible sources include the recovery furnace, depending on the operating conditions maintained, as
well as the digester/blow tank system in mills where some green liquor is used in the cooking process. Where green
liquor is used, it is also possible that significant quantities of mercaptans will be produced. Hydrogen sulfide
emissions can be eliminated if burned to sulfur dioxide prior to entering the absorbing systems.
Because the NSSC process differs greatly from mill to mill, and because of the scarcity of adequate data, no
emission factors are presented.
References for Section 10.1
1. Hendrickson, E. R. et al. Control of Atmospheric Emissions in the Wood Pulping Industry. Vol. I. U.S.
Department of Health, Education and Welfare, PHS, National Air Pollution Control Administration, Wash-
ington, D.C. Final report under Contract No. CPA 22-69-18. March 15, 1970.
2. Britt, K. W. Handbook of Pulp and Paper Technology. New York, Reinhold Publishing Corporation, 1964.
p. 166-200.
3. Hendrickson, E. R. et al. Control of Atmospheric Emissions in the Wood Pulping Industry. Vol. HI. U.S.
Department of Health, Education, and Welfare, PHS, National Air Pollution Control Administration, Wash-
ington, D.C. Final report under Contract No. CPA 22-69-18. March 15, 1970.
4. Walther, J. E. and H. R. Amberg. Odor Control in the Kraft Pulp Industry. Chem. Eng. Progress. 66:73-
80, March 1970.
5. Galeano, S. F. and K. M. Leopold. A Survey of Emissions of Nitrogen Oxides in the Pulp Mill. TAPPI.
56(3):74-76, March 1973.
6. Source test data from the Office of Air Quality Planning and Standards, U.S. Environmental Protection
Agency, Research Triangle Park, N.C. 1972.
7. Atmospheric Emissions from the Pulp and Paper Manufacturing Industry. U.S. Environmental Protection
Agency, Research Triangle Park, N.C. Publication No. EPA450/1-73-002. September 1973.
4/77 Wood Products Industry 10.1-9
-------
8. Blosser, R. 0. and H. B. Cooper. Particulate Matter Reduction Trends in the Kraft Industry. NCASI paper,
Corvallis, Oregon.
9. Padfield, D. H. Control of Odor from Recovery Units by Direct-Contact Evaporative Scrubbers with
Oxidized Black-Liquor. TAPPI. 56:83-86, January 1973.
10. Walther, J. E. and H. R. Amberg. Emission Control at the Kraft Recovery Furnaces. TAPPI. 55(3): 1185-
1188, August 1972.
11. Control Techniques for Carbon Monoxide Emissions from Stationary Sources. UJS. Department of Health
Education and Welfare, PHS, National Air Pollution Control Administration, Washington, D.C. Publication
No. AP-65. March 1970. p. 4-24 and 4-25.
12. Blosser, R. 0. et al. An Inventory of Miscellaneous Sources of Reduced Sulfur Emissions from the Kraft
Pulping Process. (Presented at the 63rd APCA Meeting. St. Louis. June 14-18, 1970.)
13. Factors Affecting Emission of Odorous Reduced Sulfur Compounds from Miscellaneous Kraft Process
Sources. NCASI Technical Bulletin No. 60. March 1972.
14. Background Document: Acid Sulfite Pulping. Prepared by Environmental Science and Engineering, Inc.,
Gainesville, Fla., for Environmental Protection Agency under Contract No. 68-02-1402, Task Order No. 14.
Document No. EPA-450/3-77-005. Research Triangle Park, N.C. January 1977.
15. Benjamin, M. et al. A General Description of Commercial Wood Pulping and Bleaching Processes. J. Air
Pollution Control Assoc. 19(3): 155-161, March 1969.
16. Galeano, S. F. and B. M. Dillard. Process Modifications for Air Pollution Control in Neutral Sulfite Semi-
Chemical Mills. J. Air Pollution Control Assoc. 22(3): 195-199, March 1972.
10.1-10 EMISSION FACTORS 4/77
-------
10.2 PULPBOARD
10.2.1 General"
Pulpboaul manufacturing involves the fabrication of fibrous boards from a pulp slurry. This includes two dis-
tinct types of product, papcrboard and fibcrhoard. Paperboard is a general term lluit describes a sheet 0.012 inch
(0.30 mm) or more in thickness made of fibrous material on a paper-forming machine.2 l-'iberboard. ulso referred
to as particle board, is thicker than papcrboard and is made somewhat differently.
There arc two distinct phases in the conversion of wood to pulpboard: (I) the manufacture of pulp from raw
wood and (2) the manufacture of pulpboard from the pulp. This section deals only with the latter as the former
is covered under the section on the wood pulping industry.
10.2.2 Process Description'
In the in , mfacturc of papcrboard, the slock is sent through screens into the head box, from which it Hows
onto a mo*. • s, screen. Approximately 15 percent of the water is removed by suction boxes located under the
screen. Vmiher 50 to 60 percent of the moisture content is removed in the drying section. The dried board
then entcis the calendar stack, which imparts the Final surface to Ihc product.
In the manufacture of fibcrboard, the slurry that remains after pulping is washed and sent to the stock chests
where sizing is added. The refined fiber from the stock chests is fed to the head box of the board machine. The
stock is next fed onto the forming screens and sent to dryers, after which the dry product is finally cut and
fabricated.
10.2.3 Emissions1
Emissions from the papcrboard machine consist mainly of water vapor: little or no paniculate matter is emit-
ted from the dryers.3-5 Parliculatcs are emitted, however, from the fibcrboard drying operation. Additional
particulatc emissions occur from the cutting and sanding operations. Emission factors for these operations are
given in section 10.4. Emission factors for pulpboard manufacturing are shown in Table 10.2-1.
Table 10.2-1. PARTICULATE EMISSION FACTORS FOR
PULPBOARD MANUFACTURING3
EMISSION FACTOR RATING: E
Type of product
Paperboard
Fiberboardb
Emissions
Ib/ton
Neg
0.6
kg/MT
Neg
0.3
aEmission factors expressed as units per unit weight of finished product.
^Reference 1.
References for Section 10.2
1. Air Pollutant Emission Factors. Resources Research. Inc., Rcston, Virginia. Prepared for National Air
Pollution Control Administration, Washington, D.C. under Contract No. CPA-22-M-1 14. April 11'70.
2. The Dictionary of Paper. New York, American Paper and Pulp Association, 1CHO.
4/76 Wood Products Industry 10.2-1
-------
3. Hough, C. W. and L. J. Gross. Air Emission Control in a Modern Pulp ;ind l';iper Mill. Aniei. Paper Industry.
31:36, February 1%9.
4. Pollution Control Progress. J, Air Pollution Conlrol Assoc, /7:4IO, June 1967.
5. Private communication between I. (Jcllnum und the National Couiicil ol' the Paper Industry lor Clean Air
and Stream Improvement, New York, October 28, 1969.
10.2-2 EMISSION FACTORS 4/76
-------
10.3 PLYWOOD VENEER AND LAYOUT OPERATIONS
10.3.1 General1"3
Plywood is a building material consisting of veneers (thin wood
layers or plies) bonded with an adhesive. The outer layers (faces)
surround a core which is usually lumber, veneer or particle board.
Plywood uses are many, including wall siding, sheathing, roof decking,
concrete formboards, floors, and containers. Most plywood is made from
Douglas Fir or other softwoods, and the majority of plants are in the
Pacific Northwest. Hardwood veneers make up only a very small portion
of total production.
In the manufacture of plywood, logs are sawed to the desired
length, debarked and peeled into veneers of uniform thickness. Veneer
thicknesses of less than one half inch or one centimeter are common.
These veneers are then transported to veneer dryers with one or more
decks, to reduce their moisture content. Dryer temperatures are held
between about 300 and 400°F (150 - 200°C). After drying, the plies go
through the veneer layout operation, where the veneers are sorted,
patched and assembled in perpendicular layers, and a thermosetting resin
adhesive applied. The veneer assembly is then transferred to a hot
press where, under pressure and steam heat, the product is formed.
Subsequently, all that remains is trimming, face sanding, and possibly
some finishing treatment to enhance the usefulness of the product.
Plywood veneer and layout operations are shown in Figure 10.3-1.
10.3.2 Emissions and Controls
2-8
Emissions from the manufacture of plywood include particulate
matter and organic compounds. The main source of emissions is the
veneer dryer, with other sources producing negligible amounts of organic
compound emissions or fugitive emissions. The log steaming and veneer
drying operations produce combustion products, and these emissions
depend entirely on the type of fuel and equipment used.
Uncontrolled fugitive particulate matter, in the form of sawdust
and other small wood particles, comes primarily from the plywood cutting
and sanding operations. To be considered additional sources of fugitive
particulate emissions are log debarking, log sawing and sawdust handling.
The dust that escapes into the air from sanding, sawing and other wood-
working operations may be controlled by collection in an exhaust system
and transport through duct work to a sized cyclone. Section 10.4
discusses emissions from such woodworking waste collection operations.
Estimates of uncontrolled particulate emission factors for log debarking
and sawing, sawdust pile handling, and plywood sanding and cutting are
given in Table 10.3-1. From the veneer dryer, and at stack temperatures,
the only particulate emissions are small amounts of wood fiber particles
in concentrations of less than 0.002 grams per dry standard cubic foot.
2/80
Wood Products Iiidiislr\
1 0.3-1
-------
fugitive
particulate
LOG
STORAGE
LOG
DEBARKING
AND
SAWING
LOG
STEAMING
fugitive
particulate
organic
compounds
•
•
VENEER
J
k
VENEER
VENEER
LAYOUT
AND
JLUE SPREADING
organic
compounds
fugitive
particulate
fugitive
particulate
i
PLYfc
PRESS
i
rooD
ING
•
PLYWOOD
CUTTING
*
PLYWOOD
SANDING
Figure 10.3-1. Plywood veneer and layout operations.
4,5
EMISSION FACTORS
2/80
-------
Table 10.3-1. UNCONTROLLED FUGITIVE PARTICIPATE EMISSION
FACTORS FOR PLYWOOD VENEER AND LAYOUT OPERATONS
EMISSION FACTOR RATING: E
Source
rj
Log debarking
Log sawing
Sawdust handling
Q
Veneer lathing
Particulates
0.024 Ib/ton
0.350 Ib/ton
1.0 Ib/ton
NA
0.012 kg/MT
0.175 kg/MT
0.5 kg/MT
NA
Plywood cutting and
sanding
0.1 Ib/ft"
0.05 kg/m
Reference 7. Emission factors are expressed as units per unit weight
of logs processed.
Reference 7. Emission factors are expressed as units per unit weight
of sawdust handled, including sawdust pile loading, unloading and
storage.
c
Estimates not available.
Reference 5. Emission factors are expressed as units per surface area
of plywood produced. These factors are expressed as representative
values for estimated values ranging from 0.066 to 0.132 lb/ft2
(0.322 to 0.644 kg/m2).
The major pollutants emitted from veneer dryers are organic compounds.
The quantity and type of organics emitted vary, depending on the wood
species and on the dryer type and its method of operation. There are.
two discernable fractions which are released, condensibles and volatiles.
The condensible organic compounds consist largely of wood resins, resin
acids and wood sugars, which cool outside the stack to temperatures
below 70°F (21°C) and combine with water vapor to form a blue haze, a
water plume or both. This blue haze may be eliminated by condensing the
organic vapors in a finned tube matrix heat exhanger condenser. The
other fraction, volatile organic compounds, is comprised of terpenes and
natural gas components (such as unburned methane), the latter occurring
only when gas fired dryers are used. The amounts of organic compounds
released because of adhesive use during the plywood pressing operation
are negligible. Uncontrolled organic process emission factors are given
in Table 10.3-2.
2/80
Wood Produces Industn
-------
Table 10.3-2. UNCONTROLLED ORGANIC COMPOUND PROCESS EMISSION
FACTORS FOR PLYWOOD VENEER DRYERS3
EMISSION FACTOR RATING: B
Volatile
Organic Compounds
Species
Douglas Fir
sapwood
steam fired
gas fired
heartwood
Larch
Southern pine
Otherb
4 9
lb/10 ft
0.45
7.53
1.30
0.19
2.94
0.03-3.00
4 2
kg/10 m
2.3
38.6
6.7
1.0
15.1
0.15-15.4
Condensible
Organic Compounds
4 9
lb/10 ft
4.64
2.37
3.18
4.14
3.70
0.5-8.00
li. 7
kg/10 m
23.8
12.1
16.3
21.2
18.9
2.56-41
.0
a
per 10,000 square feet of 3/8 inch thick veneer dried, and kilograms
of pollutant per 10,000 square meters of 1 centimeter thick veneer
dried. All dryers are steam fired unless otherwise specified.
These ranges of factors represent results from one source test for
each of the following species (in order from least to greatest
emissions): Western Fir, Hemlock, Spruce, Western Pine and
Ponderosa Pine.
References for Section 10.3
1. C.B. Hemming, "Plywood", Kirk-Othmer Encyclopedia of Chemical
Technology, Second Edition, Volume 15, John Wiley & Sons, Inc., New
York, NY, 1968, pp. 896-907.
2. F. L. Monroe, et al., Investigation of Emissions from Plywood
Veneer Dryers, Washington State University, Pullman, WA, February
1972.
3. Theodore Baumeister, ed., "Plywood", Standard^ Handbook for
Mechanical Engineers, Seventh Edition, McGraw-Hill, New York, NY,
1967, pp. 6-162 - 6-169.
4. Allen Mick and Dean McCargar, Air Pollution Problems in Plywood,
Particleboard, and Hardboard Mills in the Mid-Willamette Valley,
Mid-Willamette Valley Air Pollution Authority, Salem, OR,
March 24, 1969.
10.3-4
EMISSION FACTORS
2/80
-------
5. Controlled and Uncontrolled Emission Rates and Applicable
Limitations for Eighty Processes, Second Printing,
EPA-340/1-78-004, U.S. Environmental Protection Agency, Research
Triangle Park, NC, April 1978, pp. X-l - X-6.
6. John A. Danielson, ed., Air Pollution Engineering Manual,
AP-40, Second Edition, U.S. Environmental Protection Agency,
Research Triangle Park, NC, May 1973, pp. 372-374.
7. Assessment of Fugitive Particulate Emission Factors for
Industrial Processes, EPA-450/3-78-107, U.S. Environmental
Protection Agency, Research Triangle Park, NC, September 1978.
8. C. Ted Van Decar, "Plywood Veneer Dryer Control Device",
Journal of the Air FoHution Control Association, 22:968,
December 1972.
2/80 Wood ProdiK-ls Imlnslrv 10.3-5
-------
-------
10.4 WOODWORKING WASTE COLLECTION OPERATIONS
10.4.1 General1'5
Woodworking, as defined in this section, includes any operation that involves the generation of small wood
waste particles (shavings, sanderdust, sawdust, etc.) by any kind of mechanical manipulation of wood, bark, or
wood byproducts. Common woodworking operations include sawing, planing, chipping, shaping, moulding,
hogging, lathing, and sanding. Woodworking operations are found in numerous industries, such as sawmills,
plywood, particleboard, and hardboard plants, and furniture manufacturing plants.
Most plants engaged in woodworking employ pneumatic transfer systems to remove the generated wood waste
from the immediate proximity of each woodworking operation. These systems are necessary as a housekeeping
measure to eliminate the vast quantity of waste material that would otherwise accumulate. They are also a
convenient means of transporting the waste material to common collection points for ultimate disposal. Large
diameter cyclones have historically been the primary means of separating the waste material from the airstreams
in the pneumatic transfer systems, although baghouses have recently been installed in some plants for this
purpose.
The waste material collected in the cyclones or baghouses may be burned in wood waste boilers, utilized in the
manufacture of other products (such as pulp or particleboard), or incinerated in conical (teepee/wigwam)
burners. The latter practice is declining with the advent of more stringent air pollution control regulations and
because of the economic attractiveness of utilizing wood waste as a resource.
10.4.2 Emissions1-6
The only pollutant of concern in woodworking waste collection operations is particulate matter. The major
emission points are the cyclones utilized in the pneumatic transfer systems. The quantity of particulate emis-
sions from a given cyclone will depend on the dimensions of the cyclone, the velocity of the airstream, and the
nature of the operation generating the waste. Typical large diameter cyclones found in the industry will only
effectively collect particles greater than 40 micrometers in diameter. Baghouses, when employed, collect essen-
tially all of the waste material in the airstream. The wastes from numerous pieces of equipment often feed into
the same cyclone, and it is common for the material collected in one or several cyclones to be conveyed to
another cyclone. It is also possible for portions of the waste generated by a single operation to be directed to
different cyclones.
Because of this complexity, it is useful when evaluating emissions from a given facility to consider the waste
handling cyclones as air pollution sources instead of the various woodworking operations that actually generate
the particulate matter. Emission factors for typical large diameter cyclones utilized for waste collection in
woodworking operations are given in Table 10.4-1.
Emission factors for wood waste boilers, conical burners, and various drying operations—often found in
facilities employing woodworking operations—are given in Sections 1,6, 2.3, 10.2, and 10.3.
2/80
Wood Products Industry
10.4-1
-------
Table 10.4.1. PARTICULATE EMISSION FACTORS FOR LARGE DIAMETER
CYCLONES IN WOODWORKING WASTE COLLECTION SYSTEMS8
EMISSION FACTOR RATING: D
Types of waste handled
Sanderdustd
Other6
Particulate emissions13-0
gr/scf
0.055
(0.005-0.16)
0.03
(0.001-0.16)
g/Nm3
0.126
(0.0114-0.37)
0.07
(0.002-0.37)
Ib/hr
5
(0.2-30.0)
2
(0.03-24.0)
kg/hr
2.3
(0.09-13.6)
0.91
(0.014-10.9)
aTypical waste collection cyclones range from 4 to 16 feet (1.2 to 4.9 meters) in diameter
and employ airflows ranging from 2,000 to 26,000 standard cubic feet (57 to 740 normal
cubic meters) per minute. Note: if baghouses are used for waste collection, paniculate
emissions will be negligible.
DReferences 1 through 3.
cObserved value ranges are in parentheses.
These factors should be used whenever waste from sanding operations is fed directly into
the cyclone in question.
eThese factors should be used for cyclones handling waste from all operations other than
sanding. This includes cyclones that handle waste (including sanderdust) already collected
by another cyclone.
References for Section 10.4
1. Source test data supplied by Robert Harris, Oregon Department of Environmental Quality, Portland, OR,
September 1975.
2. J.W. Walton, et al., "Air Pollution in the Woodworking Industry", Presented at the 68th Annual Meeting of
the Air Pollution Control Association, Boston, MA, June 1975.
3. J.D. Patton and J.W. Walton, "Applying the High Volume Stack Sampler To Measure Emissions from Cotton
Gins, Woodworking Operations, and Feed and Grain Mills", Presented at 3rd Annual Industrial Air Pollution
Control Conference, Knoxville, TN, March 29-30,1973.
4. C.F. Sexton, "Control of Atmospheric Emissions from the Manufacturing of Furniture", Presented at 2nd
Annual Industrial Air Pollution Control Conference, Knoxville, TN, April 20-21, 1972.
5. A. Mick and D. McCargar, "Air Pollution Problems in Plywood, Particleboard, and Hardboard Mills in the
Mid-Willamette Valley", Mid-Williamette Valley Air Pollution Authority, Salem, OR, March 24,1969.
6. Information supplied by the North Carolina Department of Natural and Economic Resources, Raleigh, NC,
December 1975.
10.1-2
EMISSION FACTORS
2/80
-------
10.4.3 Fugitive Emission Factors
Since most woodworking operations control emissions out of necessity, fugitive emissions are seldom a
problem. However, the wood waste storage bins are a common source of fugitive emissions. Table 10.4-2
shows these emission sources and their corresponding emission factors.
Information concerning size characteristics is very limited. Data collected in a western red cedar furni-
ture factory equipped with exhaust ventilation on most woodworking equipment showed most suspended
particles in the working environment to be less than 2 /xm in diameter.7
Table 10.4-2. POTENTIAL UNCONTROLLED
FUGITIVE PARTICULATE EMISSION FACTORS
FOR WOODWORKING OPERATIONS
EMISSION FACTOR RATING: C
Type of operation
Wood waste storage bin ventb
Wood waste storage bin loadoutb
Participates3
Ib/ton
1.0
2.0
kg/MT
0.5
1.0
aFactors expressed as units per unit weight of wood waste handled.
Engineering judgment based on plant visits.
Additional Reference for Section 10.4
7. Lester V, Cralley, etal., Industrial Enivronmental Health, the Worker and the Community, Academic
Press, New York and London, 1972.
7/79
Wood Processing
10.4-3
-------
-------
MISCELLANEOUS SOURCES
This chapter contains emission factor information on those source categories that differ substantially from—and
hence cannot be grouped with-the other "stationary" sources discussed in this publication. These "miscellaneous"
emitters (both natural and man-made) are almost exclusively "area sources", that is, their pollutant generating
process(es) are dispersed over large land areas (for example, hundreds of acres, as in the case of forest wildfires), as
opposed to sources emitting from one or more stacks with a total emitting area of only several square feet. Another
characteristic these sources have in common is the nonapplicability, in most cases, of conventional control
methods, such as wet/dry equipment, fuel switching, process changes, etc. Instead, control of these emissions,
where possible at all, may include such techniques as modification of agricultural burning practices, paving with
asphalt or concrete, or stabilization of dirt roads. Finally, miscellaneous sources generally emit pollutants
intermittently, when compared with most stationary point sources. For example, a forest fire may emit large
quantities of particulates and carbon monoxide for several hours or even days, but when measured against the
emissions of a continuous emitter (such as a sulfuric acid plant) over a long period of time (1 year, for example), its
emissions may seem relatively minor. Effects on air quality may also be of relatively short-term duration.
11.1 FOREST WILDFIRES
11.1.1 General1
A forest "wildfire" is a large-scale natural combustion process that consumes various ages, sizes, and types of
botanical specimens growing outdoors in a defined geographical area. Consequently, wildfires are potential sources
of large amounts of air pollutants that should be considered when trying to relate emissions to air quality.
The size and intensity (or even the occurrence) of a wildfire is directly dependent on such variables as the local
meteorological conditions, the species of trees and their moisture content, and the weight of consumable fuel per
acre (fuel loading). Once a fire begins, the dry combustible material (usually small undergrowth and forest floor
litter) is consumed first, and if the energy release is large and of sufficient duration, the drying of green, live
material occurs with subsequent burning of this material as well as the larger dry material. Under proper
environmental and fuel conditions, this process may initiate a chain reaction that results in a widespread
conflagration.
The complete combustion of a forest fuel will require a heat flux (temperature gradient), an adequate oxygen
supply, and sufficient burning time. The size and quantity of forest fuels, the meteorological conditions, and the
topographic features interact to modify and change the burning behavior as the fire spreads; thus, the wildfire will
attain different degrees of combustion during its lifetime.
The importance of both fuel type and fuel loading on the fire process cannot be overemphasized. To meet the
pressing need for this kind of information, the U.S. Forest Service is developing a country-wide fuel identification
system (model) that will provide estimates of fuel loading by tree-size class, in tons per acre. Further, the
environmental parameters of wind, slope, and expected moisture changes have been superimposed on this fuel
model and incorporated into a National Fire Danger Rating System (NFDR). This system considers five classes of
fuel (three dead and two living), the components of which are selected on the basis of combustibility, response to
moisture (for the dead fuels), and whether the living fuels are herbaceous (plants) or ligneous (trees).
Most fuel loading figures are based on values for "available fuel" (combustible material that will be consumed in
a wildfire under specific weather conditions). Available fuel values must not be confused with corresponding values
for either "total fuel" (all the combustible material that would burn under the most severe weather and burning
11.1-1
-------
conditions) or "potential fuel" (the larger woody material that remains even after an extremely high intensity
wildfire). It must be emphasized, however, that the various methods of fuel identification are of value only when
they are related to the existing fuel quantity, the quantity consumed by the fire, and the geographic area and
conditions under which the fire occurs.
For the sake of conformity (and convenience), estimated fuel loadings were obtained for the vegetation in the
National Forest Regions and the wildlife areas established by the U.S. Forest Service, and are presented in Table
11.1-1. Figure 11.1-1 illustrates these areas and regions.
Table 11.1-1. SUMMARY OF ESTIMATED FUEL
CONSUMED BY FOREST
Area and
Region13
Rocky Mountain group
Region 1 :
Region 2:
Region 3:
Region 4:
Northern
Rocky Mountain
Southwestern
Intermountain
Pacific group
Region 5:
Region 6:
Region 10:
California
Pacific Northwest
Alaska
Coastal
Interior
Southern group
Region 8:
Southern
Eastern group
North Central group
Region 9:
Conifers
Hardwoods
Estimated average fuel loading
MT/hectare
83
135
67
22
40
43
40
135
36
135
25
20
20
25
25
22
27
ton/acre
37
60
30
10
8
19
18
60
16
60
11
9
9
11
11
10
12
Reference 1.
See Figure 11.1-1 for regional boundaries.
11.1.2 Emissions and Controlsl
It has been hypothesized (but not proven) that the nature and amounts of air pollutant emissions are directly
related to the intensity and direction (relative to the wind) of the wildfire, and indirectly related to the rate at
which the fire spreads. The factors that affect the rate of spread are (1) weather (wind velocity, ambient
temperature, and relative humidity), (2) fuels (fuel type, fuel bed array, moisture content, and fuel size), and (3)
topography (slope and profile). However, logistical problems (such as size of the burning area) and difficulties in
safely situating personnel and equipment close to the fire have prevented the collection of any reliable
experimental emission data on actual wildfires, so that it is presently impossible to verify or disprove the
above-stated hypothesis. Therefore, until such measurements are made, the only available information is that
11.1-2
EMISSION FACTORS
1/75
-------
-------
Table 11.1-2. SUMMARY OF EMISSIONS AND EMISSION FACTORS FOR FOREST WILDFIRES3
EMISSION FACTOR RATING: D
Geographic areat*
Rocky Mountain
group
Northern,
Region 1
Rocky Mountain,
Region 2
Southwestern,
Region 3
Intermountain,
Region 4
Pacific group
California,
Region 5
Alaska,
Region 10
Pacific N.W.
Region 6
Southern group
Southern,
Region 8
North Central group
Eastern, Region 9
(Both groups are
in Region 9)
Eastern group
(With Region 9)
Total United States
Area
smnfi innnrj
co n sum G u
by
wildfire.
hectares
313,397
142,276
65,882
83,765
21,475
469,906
18,997
423,530
27,380
806,289
806,289
94,191
141,238
47,046
1,730,830
Wilrlf iro
Uvllul lie
fuel
consumption.
MT/hectare
83
135
67
22
40
43
40
36
135
20
20
25
25
25
38
Emission factors, kg/hectare
Partic-
ulate
706
1,144
572
191
153
362
343
305
1,144
172
172
210
210
210
324
Carbon
monoxide
5,810
9,420
4,710
1,570
1,260
2,980
2,830
2,510
9,420
1,410
1,410
1,730
1,730
1,730
2,670
Hydro-
carbons
996
1,620
808
269
215
512
485
,
431
1,620
242
242
296
296
296
458
Nitrogen
oxides
166
269
135
45
36
85
81
72
269
40
40
49
49
49
76
Emissions, MT
Partic-
ulate
220,907
162,628
37,654
15,957
3,273
170,090
6,514
129,098
31,296
138,244
138,244
19,739
29,598
9,859
560,552
Carbon
monoxide
1,819,237
1,339,283
310,086
131,417
26,953
1 ,400,738
53,645
1,063,154
257,738
1,138,484
1,138,484
162,555
243,746
81,191
4,616,317
Hydro-
carbons
311,869
229,592
53,157
22,533
4,620
240,126
9,196
182,255
44,183
195,168
195,168
27,867
41,785
13,918
791,369
Nitrogen
oxides
51,978
38,265
8,860
3,735
770
40,021
1,533
30,376
7,363
32,528
32,528
4,644
6,964
2,320
131,895
w
w
O
I
t/3
Areas consumed by wildfire and emissions are for 1971.
^4 Geographic areas are defined in Figure 11.1-1.
cHvdrocarbons expressed as methane.
-------
= 2 kg/MT (4 Ib/ton) for nitrogen oxides (NOX)
= Negligible for sulfur oxides (SOX)
L = Fuel loading consumed (mass of forest fuel/unit land area burned)
A = Land area burned
Ej = Total emissions of pollutant "i" (mass of pollutant)
For example, suppose that it is necessary to estimate the total particulate emissions from a 10,000 hectare
wildfire in the Southern area (Region 8). From Table 11.1-1 it is seen that the average fuel loading is 20
MT/hectare (9 ton/acre). Further, the pollutant yield for particulates is 8.5 kg/MT (17 Ib/ton). Therefore, the
emissions are:
E = (8.5 kg/MT of fuel) (20 MT of fuel/hectare) (10,000 hectares)
E = 1,700,000 kg = 1,700 MT
The most effective method for controlling wildfire emissions is, of course, to prevent the occurrence of forest
fires using various means at the forester's disposal. A frequently used technique for reducing wildfire occurrence is
"prescribed" or "hazard reduction" burning. This type of managed burn involves combustion of litter and
underbrush in order to prevent fuel buildup on the forest floor and thus reduce the danger of a wildfire. Although
some air pollution is generated by this preventative burning, the net amount is believed to be a relatively smaller
quantity than that produced under a wildfire situation.
Reference for Section 11.1
1. Development of Emission Factors for Estimating Atmospheric Emissions from Forest Fires. Final Report. IIT
Research Institute, Chicago, 111. Prepared for Office of Air Quality Planning and Standards, Environmental
Protection Agency, Research Triangle Park, N.C., under Contract No. 68-02-0641, October 1973. (Publication
No. EPA-450/3-73-009).
1/75 Internal Combustion Engine Sources } ] i_5
-------
-------
11.2 FUGITIVE DUST SOURCES
Significant atmospheric dust arises from the mechanical disturbance of
granular material exposed to the air. Dust generated from these open
sources is termed "fugitive" because it is not discharged to the atmosphere
in a confined flow stream. Common sources of fugitive dust include unpaved
roads, agricultural tilling operations, aggregate storage piles, and heavy
construction operations.
For the above categories of fugitive dust sources, the dust generation
process is caused by two basic physical phenomena:
1. Pulverization and abrasion of surface materials by application of
mechanical force through implements (wheels, blades, etc.).
2. Entrainment of dust particles by the action of turbulent air cur-
rents, such as wind erosion of an exposed surface by wind speeds over 19
kilometers per hour (12 miles/hr).
The air pollution impact of a fugitive dust source depends on the
quantity and drift potential of the dust particles injected into the atmo-
sphere. In addition to large dust particles that settle out near the
source (often creating a local nuisance problem), considerable amounts of
fine particles are also emitted and dispersed over much greater distances
from the source.
The potential drift distance of particles is governed by the initial
injection height \of the particle, the particle's terminal settling veloc-
ity, and the degree of atmospheric turbulence. Theoretical drift dis-
tances, as a function of particle diameter and mean wind speed, have been
computed for fugitive dust emissions.1 These results indicate that, for a
typical mean wind speed of 16 kilometers per hour (10 miles/hr), particles
larger than about 100 micrometers are likely to settle out within 6 to 9
meters (20 to 30 ft) from the edge of the road. Particles that are 30 to
100 micrometers in diameter are likely to undergo impeded settling. These
particles, depending upon the extent of atmospheric turbulence, are likely
to settle within a few hundred feet from the road. Smaller particles, par-
ticularly those less than 10 to 15 micrometers in diameter, have much
slower gravitational settling velocities and are much more likely to have
their settling rate retarded by atmospheric turbulence. Thus, based on the
presently available data, it appears appropriate to report only those par-
ticles smaller than 30 micrometers. Future updates to this document are
expected to define appropriate factors for other particle sizes.
Several of the emission factors presented in this Section are ex-
pressed in terms of total suspended particulate (TSP). TSP denotes what
is measured by a standard high volume sampler. Recent wind tunnel studies
have shown that the particle mass capture efficiency curve for the high
volume sampler is very broad, extending from 100 percent capture of parti-
cles smaller than 10 micrometers to a few percent capture of particles as
large as 100 micrometers. Also, the capture efficiency curve varies with
5/83
Miscellaneous Sources
11.2-1
-------
wind speed and wind direction, relative to roof ridge orientation. Thus,
high volume samplers do not provide definitive particle size information
for emission factors. However, an effective cutpoint of 30 micrometers
aerodynamic diameter is frequently assigned to the standard high volume
sampler.
Control techniques for fugitive dust sources generally involve water-
ing, chemical stabilization, or reduction of surface wind speed with wind-
breaks or source enclosures. Watering, the most common and generally least
expensive method, provides only temporary dust control. The use of chemi-
cals to treat exposed surfaces provides longer dust suppression but may be
costly, have adverse effects on plant and animal life, or contaminate the
treated material. Windbreaks and source enclosures are often impractical
because of the size of fugitive dust sources.
11.2-2 EMISSION FACTORS b/83
-------
11.2.1 UNPAVED ROADS
11.2.1.1 General
Dust plumes trailing behind vehicles traveling on unpaved roads are a
familiar sight in rural areas of the United States. When a vehicle travels an
unpaved road, the force of the wheels on the road surface causes pulverization
of surface material. Particles are lifted and dropped from the rolling wheels,
and the road surface is exposed to strong air currents in turbulent shear with
the surface. The turbulent wake behind the vehicle continues to act on the
road surface after the vehicle has passed.
11.2.1.2 Emissions And Correction Parameters
The quantity of dust emissions from a given segment of unpaved road varies
linearly with the volume of traffic. Also, field investigations have shown
that emissions depend on correction parameters (average vehicle speed, average
vehicle weight, average number of wheels per vehicle, road surface texture and
road surface moisture) that characterize the condition of a particular road and
the associated vehicle traffic.^"^
Dust emissions from unpaved roads have been found to vary in direct
proportion to the fraction of silt (particles smaller than 75 micrometers in
diameter) in the road surface materials.1 The silt fraction is determined by
measuring the proportion of loose dry surface dust that passes a 200 mesh
screen, using the ASTM-C-136 method. Table 11.2.1-1 summarizes measured silt
values for industrial and rural unpaved roads.
The silt content of a rural dirt road will vary with location, and it
should be measured. As a conservative approximation, the silt content of the
parent soil in the area can be used. However, tests show that road silt con-
tent is normally lower than in the surrounding parent soil, because the fines
are continually removed by the vehicle traffic, leaving a higher percentage
of coarse particles.
Unpaved roads have a hard nonporous surface that usually dries quickly
after a rainfall. The temporary reduction in emissions because of precipita-
tion may be accounted for by not considering emissions on "wet" days (more than
0.254 millimeters [0.01 inches] of precipitation).
The following empirical expression may be used to estimate the quantity of
size specific particulate emissions from an unpaved road, per vehicle kilometer
traveled (VKT) or vehicle mile traveled (VMT), witli a ratii.as o^ A:
9/85
Miscellaneous Sources
11.2.1-1
-------
TABLE 11.2.1-1. TYPICAL SILT CONTENT VALUES OF SURFACE MATERIALS
ON INDUSTRIAL AND RURAL UNPAVED ROADSa
CO
VI
H
O
25
H
O
!»
cn
Industry
Copper smelting
Iron and steel production
Sand and gravel processing
Stone quarrying and processing
Taconite mining and processing
Western surface coal raining
Rural roads
Road Use Or
Surface Material
Plant road
Plant road
Plant road
Plant road
Haul road
Service road
Access road
Haul road
Scraper road
Haul road
(freshly
graded)
Gravel
Dirt
Crushed limestone
Plant
Sites
1
9
1
1
1
1
2
3
3
2
1
2
2
Test
Samples
3
20
3
5
12
8
2
21
10
5
1
5
8
Silt (%, w/w)
Range
[15.9 - 19.1]
4.0 - 16.0
[4.1 - 6.0]
[10.5 - 15.6]
[ 3.7 - 9.7]
[ 2.4 - 7.1]
4.9 - 5.3
2.8 - 18
7.2 - 25
18 - 29
NA
5.8-68
7.7 - 13
Mean
[17.0]
8.0
[4.8]
[14.1]
[5.8]
[4.3]
5.1
8.4
17
24
[5.0]
28.5
9.6
00
Ul
References 4-11.Brackets indicate silt values based on samples from only one plant site.
NA = Not available.
-------
where: E = emission factor
k = particle size multiplier (dimensionless)
s = silt content of road surface material (%)
S = mean vehicle speed, km/hr (mph)
W = mean vehicle weight, Mg (ton)
w = mean number of wheels
p = number of days with at least 0.254 mm
(0.01 in.) of precipitation per year
The particle size multiplier, k, in Equation 1 varies with aerodynamic particle
size range as follows:
Aerodynamic Particle Size Multiplier For Equation 1
<30 ym
0.80
£15 ym
0.50
<10 ym
0.36
<5 ym
0.20
<2.5 ym
0.095
The number of wet days per year, p, for the geographical area of Interest
should be determined from local climatic data. Figure 11.2.1-1 gives the geo-
graphical distribution of the mean annual number of wet days per year in the
United States.
Equation 1 retains the assigned quality rating if applied within the ranges
of source conditions that were tested in developing the equation, as follows:
RANGES OF SOURCE CONDITIONS FOR EQUATION 1
Equation
1
Road silt
content
(%, w/w)
4.3 - 20
Mean vehicle weight
Mg
2.7 - 142
ton
3 - 157
Mean vehicle speed
km/hr
21 - 64
mph
13 - 40
Mean no.
of wheels
4-13
Also, to retain the quality rating of the equation applied to a specific unpaved
road, it is necessary that reliable correction parameter values for the specific
road in question be determined. The field and laboratory procedures for deter-
mining road surface silt content are given in Reference 4. In the event that
site specific values for correction parameters cannot be obtained, the appro-
priate mean values from Table 11.2.1-1 may be used, but the quality rating of
the equation is reduced to B.
Equation 1 was developed for calculation of annual average emissions, and
thus, is to be multiplied by annual vehicle distance traveled (VDT). Annual
average values for each of the correction parameters are to be substituted into
9/85
Miscellaneous Sources
11.2.1-3
-------
180
to
*
h-'
I
w
s
H
Cft
tn
H
o
2!
H
O
cn
0 S0100 200 300 400 SOO
120
MILES
00
Ul
Figure 11.2.1-1. Mean number of days with 0.01 inch or more of precipitation in United States.
-------
the equation. Worst case emissions, corresponding to dry road conditions,
may be calculated by setting p = 0 in the equation (which is equivalent to
dropping the last term from the equation). A separate set of nonclimatic
correction parameters and a higher than normal VDT value may also be justified
for the worst case averaging period (usually 24 hours). Similarly, to calc-
ulate emissions for a 91 day season of the year using Equation 1, replace the
term (365-p)/365 with the term (9l-p)/9l, and set p equal to the number of wet
days in the 91 day period. Also, use appropriate seasonal values for the
nonclimatic correction parameters and for VDT.
11.2.1.3 Control Methods
Common control techniques for unpaved roads are paving, surface treating
with penetration chemicals, working into the roadbed of chemical stabiliza-
tion chemicals, watering, and traffic control regulations. Chemical stabilizers
work either by binding the surface material or by enhancing moisture retention.
Paving, as a control technique, is often not economically practical. Surface
chemical treatment and watering can be accomplished with moderate to low costs,
but frequent retreatments are required. Traffic controls, such as speed limits
and traffic volume restrictions, provide moderate emission reductions but may
be difficult to enforce. The control efficiency obtained by speed reduction
can be calculated using the predictive emission factor equation given above.
The control efficiencies achievable by paving can be estimated by com-
paring emission factors for unpaved and paved road conditions, relative to
airborne particle size range of interest. The predictive emission factor
equation for paved roads, given in Section 11.2.6, requires estimation of the
silt loading on the traveled portion of the paved surface, which in turn depends
on whether the pavement is periodically cleaned. Unless curbing is to be
installed, the effects of vehicle excursion onto shoulders (berms) also must be
taken into account in estimating control efficiency.
The control efficiencies afforded by the periodic use of road stabili-
zation chemicals are much more difficult to estimate. The application para-
meters which determine control efficiency include dilution ratio, application
intensity (mass of diluted chemical per road area) and application frequency.
Between applications, the control efficiency is usually found to decay at a
rate which is proportional to the traffic count. Therefore, for a specific
chemical application program, the average efficiency is inversely proportional
to the average daily traffic count. Other factors that affect the performance
of chemical stabilizers include vehicle characteristics (e. g., average weight)
and road characteristics (e. g., bearing strength).
Water acts as a road dust suppressant by forming cohesive moisture films
among the discrete grains of road surface material. The average moisture level
in the road surface material depends on the moisture added by watering and
natural precipitation and on the moisture removed by evaporation. The natural
evaporative forces, which vary with geographic location, are enhanced by the
movement of traffic over the road surface. Watering, because of the frequency
of treatments required, is generally not feasible for public roads and is used
effectively only where water and watering equipment are available and where
roads are confined to a single site, such as a construction location.
9/85 Miscellaneous Sources 11.2.1-5
-------
References for Section 11.2.1
1. C. Cowherd, Jr., ej: al., Development of Emission Factors for Fugitive
Dust Sources, EPA-450/3-74-037, U. S. Environmental Protection Agency,
Research Triangle Park, NC, June 1974.
2. R. J. Dyck and J. J. Stukel, "Fugitive Dust Emissions from Trucks on
Unpaved Roads", Environmental Science and Technology, 10(10) -.1046-1048,
October 1976.
3. R. 0. McCaldin and K. J. Heidel, "Particulate Emissions from Vehicle
Travel over Unpaved Roads", Presented at the 71st Annual Meeting of the
Air Pollution Control Association, Houston, TX, June 1978.
4. C. Cowherd, Jr., etal.^ Iron and Steel Plant Open Dust Source Fugitive
Emission Evaluation, EPA-600/2-79-103, U. S. Environmental Protection
Agency, Research Triangle Park, NC, May 1979.
5. R. Bohn, et al., Fugitive Emissions from Integrated Iron and Steel Plants,
EPA-600/2-78-050, U. S. Environmental Protection Agency, Research Triangle
Park, NC, March 1978.
6. R. Bohn, Evaluation of Open Dust Sources in the Vicinity of Buffalo, New
Yprk, U. S. Environmental Protection Agency, New York, NY, March 1979.
7. C. Cowherd, Jr., and T. Cuscino, Jr., Fugitive Emissions Evaluation,
Equitable Environmental Health, Inc., Elmhurst, IL, February 1977.
8. T. Cuscino, Jr., et al., Taconite Mining Fugitive Emissions Study,
Minnesota Pollution Control Agency, Roseville, MN, June 1979.
9. K. Axetell and C. Cowherd, Jr., Improved Emission Factors for Fugitive
Dust from Western Surface Coal Mining Sources, 2 Volumes, EPA Contract
No. 68-03-2924, PEDCo Environmental, Inc., Kansas City, MO, July 1981.
10. T. Cuscino, Jr., et al., Iron and Steel Plant Open Source Fugitive
Emission Control Evaluation, EPA-600/2-83-110, U. S. Environmental Pro-
tection Agency, Research Triangle Park, NC, October 1983.
11. J. Patrick Reider, Size Specific Emission Factors for Uncontrolled Indus-
trial and Rural Roads, EPA Contract No. 68-02-3158, Midwest Research
Institute, Kansas City, MO, September 1983.
12. C. Cowherd, Jr., and P. Englehart, .Size Specific Particulate Emission
Factors for Industrial and Rural Roads, EPA-600/7-85-038, U. S. Environ-
mental Protection Agency, Research Triangle Park, NC, September 1985.
13. Climatic Atlas of _the United States, U. S. Department of Commerce,
Washington, DC, June 1968.
11.2.1-6 EMISSION FACTORS 9/85
-------
11.2.2 AGRICULTURAL TILLING
11.2.2.1 General
The two universal objectives of agricultural tilling are the creation
of the desired soil structure to be used as the crop seedbed and the eradi-
cation of weeds. Plowing, the most common method of tillage, consists of
some form of cutting loose, granulating and inverting the soil, and turning
under the organic litter. Implements that loosen the soil and cut off the
weeds but leave the surface trash in place have recently become more popu-
lar for tilling in dryland farming areas.
During a tilling operation, dust particles from the loosening and pul-
verization of the soil are injected into the atmosphere as the soil is
dropped to the surface. Dust emissions are greatest during periods of dry
soil and during final seedbed preparation.
11.2.2.2 Emissions and Correction Parameters
The quantity of dust from agricultural tilling is proportional to the
area of land tilled. Also, emissions depend on surface soil texture and
surface soil moisture content, conditions of a particular field being
tilled.
Dust emissions from agricultural tilling have been found to vary di-
rectly with the silt content (defined as particles < 75 micrometers in di-
ameter) of the surface soil depth (0 to 10 cm [0 to 4 in.]). The soil silt
content is determined by measuring the proportion of dry soil that passes a
200 mesh screen, using ASTM-C-136 method. Note that this definition of
silt differs from that customarily used by soil scientists, for whom silt
is particles from 2 to 50 micrometers in diameter.
Field measurements2 indicate that dust emissions from agricultural
tilling are not significantly related to surface soil moisture, although
limited earlier data had suggested such a dependence.1 This is now be-
lieved to reflect the fact that most tilling is performed under dry soil
conditions, as were the majority of the field tests.1"2
Available test data indicate no substantial dependence of emissions on
the type of tillage implement, if operating at a typical speed (for exam-
ple, 8 to 10 km/hr [5 to 6 mph]).1"2
11.2.2.3 Predictive Emission Factor Equation
The quantity of dust emissions from agricultural tilling, per acre of
land tilled, may be estimated with a rating of A or B (see below) using the
following empirical expression2:
E = k(5.38)(s)0'6 (kg/hectare) (1)
E - k(4.80)(s)°-6 (Ib/acre)
5/83 Miscellaneous Sources 11.2.2-1
-------
where: E = emission factor
k = particle size multipler (dimensionless)
s = silt content of surface soil (%)
The particle size multiplier (k) in the equation varies with aerodynamic
particle size range as follows:
Aerodynamic Particle Size Multiplier for Equation 1
Total
particulate
1.0
< 30 [im
0.33
< 15 |Jm
0.25
< 10 (Jm
0.21
< 5 Mm
0.15
< 2.5 pm
0.10
Equation 1 is rated A if used to estimate total particulate emissions,
and B if used for a specific particle size range. The equation retains its
assigned quality rating if applied within the range of surface soil silt
content (1.7 to 88 percent) that was tested in developing the equation.
Also, to retain the quality rating of Equation 1 applied to a specific ag-
ricultural field, it is necessary to obtain, a reliable silt value(s) for
that field. The sampling and analysis procedures for determining agricul-
tural silt content are given in Reference 2. In the event that a site spe-
cific value for silt content cannot be obtained, the mean value of 18 per-
cent may be used, but the quality rating of the equation is reduced by one
level.
11.2.2.4 Control Methods3
In general, control methods are not applied to reduce emissions from
agricultural tilling. Irrigation of fields before plowing will reduce
emissions, but in many cases, this practice would make the soil unworkable
and would adversely affect the plowed soil's characteristics. Control
methods for agricultural activities are aimed primarily at reduction of
emissions from wind erosion through such practices as continuous cropping,
stubble mulching, strip cropping, applying limited irrigation to fallow
fields, building windbreaks, and using chemical stabilizers. No data are
available to indicate the effects of these or other control methods on
agricultural tilling, but as a practical matter, it may be assumed that
emission reductions are not significant.
References for Section 11.2.2
1. C. Cowherd, Jr., et al., Development of Emission Factors for Fugitive
Dust Sources, EPA-450/3-74-037, tl. S. Environmental Protection Agency,
Research Triangle Park, NC, June 1974.
2. T. A. Cuscino, Jr., et al. , The Role of Agricultural Practices in
Fugitive Dust Emissions, California Air Resources Board, Sacramento,
CA, June 1981.
3. G. A Jutze, et al., Investigation of Fugitive Dust - Sources Emissions
And Control, EPA-450/3-74-036a, U. S. Environmental Protection Agency,
Research Triangle Park, NC, June 1974.
11.2.2-2 EMISSION FACTORS 5/83
-------
11.2.3 AGGREGATE HANDLING AND STORAGE PILES
11.2.3.1 General
Inherent in operations that use minerals in aggregate form is the
maintenance of outdoor storage piles. Storage piles are usually left un-
covered, partially because of the need for frequent material transfer into
or out of storage.
Dust emissions occur at several points in the storage cycle, during
material loading onto the pile, during disturbances by strong wind cur-
rents, and during loadout from the pile. The movement of trucks and load-
ing equipment in the storage pile area is also a substantial source of
dust.
11.2.3.2 Emissions and Correction Parameters
The quantity of dust emissions from aggregate storage operations var-
ies with the volume of aggregate passing through the storage cycle. Also,
emissions depend on three correction parameters that characterize the con-
dition of a particular storage pile: age of the pile, moisture content and
proportion of aggregate fines.
When freshly processed aggregate is loaded onto a storage pile, its
potential for dust emissions is at a maximum. Fines are easily disaggre-
gated and released to the atmosphere upon exposure to air currents from ag-
gregate transfer itself or high winds. As the aggregate weathers, how-
ever, potential for dust emissions is greatly reduced. Moisture causes ag-
gregation and cementation of fines to the surfaces of larger particles.
Any significant rainfall soaks the interior of the pile, and the drying
process is very slow.
Field investigations have shown that emissions from aggregate storage
operations vary in direct proportion to the percentage of silt (particles
< 75 fjm in diameter) in the aggregate material.1 3 The silt content is de-
termined by measuring the proportion of dry aggregate material that passes
through a 200 mesh screen, using ASTM-C-136 method. Table 11.2.3-1 summa-
rizes measured silt and moisture values for industrial aggregate materials.
11.2.3.3 Predictive Emission Factor Equations
Total dust emissions from aggregate storage piles are contributions of
several distinct source activities within the storage cycle:
1. Loading of aggregate onto storage piles (batch or continuous drop
operations).
2. Equipment traffic in storage area.
3. Wind erosion of pile surfaces and ground areas around piles.
4. Loadout of aggregate for shipment or for return to the process
stream (batch or continuous drop operations).
5/83
Miscellaneous Sources
11.2,3-1
-------
U)
N>
TABLE 11.2.3-1.
O
a
H
O
TYPICAL SILT AND MOISTURE CONTENT VALUES
OF MATERIALS AT VARIOUS INDUSTRIES
silt (%)
Industry
Iron and steel
production
Stone quarrying ,
and processing
Taconite raining
and processing
Western surface
. . . d
coal mining
Material No. of test
samples Range
Pellet ore
Lump ore
Coal
Slag
Fine dust
Coke breeze
Blended ore
Sinter
Limestone
Crushed limestone
Pellets
Tailings
Coal
Overburden
Exposed ground
10
9
7
3
2
1
1
1
1
2
9
2
15
15
3
1.4
2.8
2
3
14
1.3
2.2
3.4
3.8
5.1
- 13
- 19
- 7.7
- 7.3
- 23
- 1.9
- 5.4
HA
- 16
- 15
- 21
Moisture (%)
No. of test
Mean samples
4.9
9.5
5
5.3
18.0
5.4
15.0
0.7
0.4
1.6
3.4
11.0
6.2
7.5
15.0
8
6
6
3
0
1
1
0
0
2
7
1
7
0
3
Range Mean
0.64 - 3.5 2.1
1.6 - 8.1 5.4
2.8 - 11 4.8
0.25 - 2.2 0.92
NA HA
6.4
6.6
HA NA
HA NA
0.3 - 1. 1 0.7
0.05-2.3 0.96
0.35
2.8 - 20 6.9
NA HA
0.8 - 6.4 3.4
jj References 2-5.
Reference 1.
. Reference 6.
Reference 7.
HA = not applicable.
l_n
GO
-------
Adding aggregate material to a storage pile or removing it usually in-
volves dropping the material onto a receiving surface. Truck dumping on
the pile or loading out from the pile to a truck with a front end loader
are examples of batch drop-operations. Adding material to the pile by a
conveyor stacker is an example of a continuous drop operation.
The quantity of particulate emissions generated by a batch drop opera-
tion, per ton of material transferred, may be estimated, with a rating of
C, using the following empirical expression2:
E = k(0.00090)
E = k(0.0018)
where: E = emission factor
/s\ / U \ / H \
(5) \2.2) (
/M\2 / Y \
\2/ \4.67
/1\ /U\ /H\
\57 15/1 \5/
2 0 3^
/M\Z /Y\U'^
\2l V67
1.57
0.33
(1
(kg/Mg)
CD
(Ib/ton)
k - particle size multipler (dimensionless)
s = material silt content (%)
U — mean wind speed, m/s (mph)
H = drop height, m (ft)
M = material moisture content (%)
Y = dumping device capacity, m3 (yd3)
The particle size multipler (k) for Equation 1 varies with aerodynamic par-
ticle size, shown in Table 11.2.3-2.
TABLE 11.2.3-2.
AERODYNAMIC PARTICLE SIZE
MULTIPLIER (k) FOR
EQUATIONS 1 AND 2
Equation < 30 < 15 < 10 < 5 < 2.5
|jm (Jm [M pm |jm
Batch drop 0.73 0.48 0.36 0.23 0.13
Continuous
drop
0.77 0.49 0.37 0.21 0.11
The quantity of particulate emissions generated by a continuous drop
operation, per ton of material transferred, may be estimated, with a rating
of C, using the following empirical expression3:
5/83
Miscellaneous Sources
11.2.3-3
-------
(i) (JL) (JL)
E = k(0.00090) V5/ V2-2/ V3-0/ (kg/Mg) (2)
'I) (?) (i?)
E = k(0.0018) ' ' ^( (Ib/ton)
where: E = emission factor
k = particle size multiplier (dimensionless)
s = material silt content (%)
U - mean wind speed, m/s (mph)
H - drop height, m (ft)
M = material moisture content (%)
The particle size multiplier (k) for Equation 2 varies with aerodynamic
particle size, as shown in Table 11.2.3-2.
Equations 1 and 2 retain the assigned quality rating if applied within
the ranges of source conditions that were tested in developing the equa-
tions, as given in Table 11.2.3-3. Also, to retain the quality ratings of
Equations 1 or 2 applied to a specific facility, it is necessary that reli-
able correction parameters be determined for the specific sources of inter-
est. The field and laboratory procedures for aggregate sampling are given
in Reference 3. In the event that site specific values for correction pa-
rameters cannot be obtained, the appropriate mean values from Table
11.2.3-1 may be used, but in that case, the quality ratings of the equa-
tions are reduced by one level.
TABLE 11.2.3-3. RANGES OF SOURCE CONDITIONS FOR
EQUATIONS 1 AND 2a
Silt Moisture
Equation content content Dumping capacity Drop height.
m3 yd3 m ft
Batch drop 1.3-7.3 0.25-0.70 2.10-7.6 2.75-10 NA NA
Continuous
drop
1.4 - 19
0.64 - 4.8 NA
NA 1.5 - 12 4.8 - 39
a
NA = not applicable.
For emissions from equipment traffic (trucks, front end loaders, doz-
ers, etc.) traveling between or on piles, it is recommended that the equa-
tions for vehicle traffic on unpaved surfaces be used (see Section 11.2.1).
For vehicle travel between storage piles, the silt value(s) for the areas
11.2.3-4 EMISSION FACTORS 5/83
-------
among the piles (which may differ from the silt values for the stored mate-
rials) should be used.
For emissions from wind erosion of active storage piles, the following
total suspended particulate (TSP) emission factor equation is recommended:
(if) 0*/
-------
longer retention of the moisture film. Continuous chemical treatment of
material loaded onto piles, coupled with watering or treatment of roadways,
can reduce total particulate emissions from aggregate storage operations by
up to 90 percent.
References for Section 11.2.3
1. C. Cowherd, Jr., et al., Development of Emission Factors for Fugitive
Dust Sources, EPA-450/3-74-037, U. S. Environmental Protection Agency,
Research Triangle Park, NC, June 1974.
2. R. Bohn, et al. , Fugitive Emissions from Integrated Iron and Steel
Plants, EPA-600/2-78-050, U. S. Environmental Protection Agency,
Research Triangle Park, NC, March 1978.
3. C. Cowherd, Jr., et al., Iron and Steel Plant Open Dust Source Fugi-
tive Emission Evaluation, EPA-600/2-79-103, U. S. Environmental Pro-
tection Agency, Research Triangle Park, NC, May 1979.
4. R. Bohn, Evaluation of Open Dust Sources in the Vicinity of Buffalo,
New York, U. S. Environmental Protection Agency, New York, NY, March
1979.
5. C. Cowherd, Jr., and T. Cuscino, Jr., Fugitive Emissions Evaluation,
Equitable Environmental Health, Inc., Elmhurst, IL, February 1977.
6. T. Cuscino, et al., Taconite Mining Fugitive Emissions Study,
Minnesota Pollution Control Agency, Roseville, MN, June 1979.
7. K. Axetell and C. Cowherd, Jr., Improved Emission Factors for Fugitive
Dust from Western Surface Coal Mining Sources, 2 Volumes, EPA Contract
No. 68-03-2924, PEDCo Environmental, Inc., Kansas City, MO, July 1981.
8. G. A. Jutze, et al. , Investigation of Fugitive Dust Sources Emissions
and Control, EPA-450/3-74-036a, U. S. Environmental Protection Agency,
Research Triangle Park, NC, June 1974.
11.2.3-6 EMISSION FACTORS 5/83
-------
11.2.4 Heavy Construction Operations
11.2.4.1 General — Heavy construction is a source of dust emissions that may have substantial temporary impact
on local air quality. Building and road construction are the prevalent construction categories with the highest
emissions potential. Emissions during the construction of a building or road are associated with land clearing,
blasting, ground excavation, cut and fill operations, and the construction of the particular facility itself. Dust
emissions vary substantially from day to day depending on the level of activity, the specific operations, and the
prevailing weather. A large portion of the emissions result from equipment traffic over temporary roads at the
construction site.
11.2.4.2 Emissions and Correction Parameters — The quantity of dust emissions from construction operations
are proportional to the area of land being worked and the level of construction activity. Also, by analogy to the
parameter dependence observed for other similar fugitive dust sources,1 it is probable that emissions from heavy
construction operations are directly proportional to the silt content of the soil (that is, particles smaller than 75
jum in diameter) and inversely proportional to the square of the soil moisture, as represented by Thornthwaite's
precipitation-evaporation (PE) index.2
11.2.4.3 Emission Factor — Based on field measurements of suspended dust emissions from apartment and
shopping center construction projects, an approximate emission factor for construction operations is:
1.2 tons per acre of construction per month of activity
This value applies to construction operations with: (1) medium activity level, (2) moderate silt content (^30
percent), and (3) semiarid climate (PE ^50; see Figure 11.2-2). Test data are not sufficient to derive the specific
dependence of dust emissions on correction parameters.
The above emission factor applies to particles less than about 30 /urn in diameter, which is the effective cut-off
size for the capture of construction dust by a standard high-volume filtration sampler1, based on a particle
density of 2.0-2.5 g/cm3 .
11.2.4.4 Control Methods — Watering is most often selected as a control method because water and necessary
equipment are usually available at construction sites. The effectiveness of watering for control depends greatly on
the frequency of application. An effective watering program (that is, twice daily watering with complete
coverage) is estimated to reduce dust emissions by up to 50 percent.3 Chemical stabilization is not effective in
reducing the large portion of construction emissions caused by equipment traffic or active excavation and cut and
fill operations. Chemical stabilizers are useful primarily for application on completed cuts and fills at the
construction site. Wind erosion emissions from inactive portions of the construction site can be reduced by about
80 percent in this manner, but this represents a fairly minor reduction in total emissions compared with emissions
occurring during a period of high activity.
References for Section 11.2.4
1. Cowherd, C., Jr., K. Axetell, Jr., C. M. Guenther, and G. A. Jutze. Development of Emissions Factors for
Fugitive Dust Sources. Midwest Research Institute, Kansas City, Mo. Prepared for Environmental Protection
Agency, Research Triangle Park, N.C. under Contract No. 68-02-0619. Publication No. EPA-450/3-74-037.
June 1974.
2. Thornthwaite, C. W. Climates of North America According to a New Classification. Geograph. Rev. 21:
633-655, 1931.
3. Jutze, G. A., K. Axetell, Jr., and W. Parker. Investigation of Fugitive Dust-Sources Emissions and Control,
PEDCo Environmental Specialists, Inc., Cincinnati, Ohio. Prepared for Environmental Protection Agency,
Research Triangle Park, N.C. under Contract No. 68-02-0044. Publication No. EPA-450/3-74-036a. June 1974.
12/75 Miscellaneous Sources 11.2.4-1
-------
-------
11.2.5 PAVED URBAN ROADS
11.2.5.1 General
Various field studies have indicated that dust emissions from paved street
are a major component of the material collected by high volume samplers. Reen-
trained traffic dust has been found to consist primarily of mineral matter
similar to common sand and soil, mostly tracked or deposited onto the roadway
by vehicle traffic itself. Other particulate matter is emitted directly by the
vehicles from, for example, engine exhaust, wear of bearings and brake linings,
and abrasion of tires against the road surface. Some of these direct emissions
may settle to the street surface, subsequently to be reentrained. Appreciable
emissions from paved streets are added by wind erosion when the wind velocity
exceeds a threshold value of about 20 kilometers per hour (13 miles per hour).
Figure 11.2.5-1 illustrates particulate transfer processes occurring on urban
streets.
11.2.5.2 Emission Factors And Correction Parameters
Dust emission rates may vary according to a number of factors. The most
important are thought to be traffic volume and the quantity and particle size
of loose surface material on the street. On a normal paved street, an equili-
brium is reached whereby the accumulated street deposits are maintained at a
relatively constant level. On average, vehicle carryout from unpaved areas
may be the largest single source of street deposit. Accidental spills, street
cleaning and rainfall are activities that disrupt the street loading equili-
brium, usually for a relatively short duration.
The lead content of fuels also becomes a part of reentrained dust from
vehicle traffic. Studies have found that, for the 1975-76 sampling period,
the lead emission factor for this source was approximately 0.03 grams per
vehicle mile traveled (VMT). With the reduction of lead in gasoline and the
use of catalyst equipped vehicles, the lead factor for reentrained dust was
expected to drop below 0.01 grams per mile by I960.3
The quantity of dust emissions of vehicle traffic on a paved roadway may
be estimated using the following empirical expression4 :
e = k i^\ P (g/VKT)
e = k feA P (Ib/VMT)
where: e = particulate emission factor, g/VKT (Ib/VMT)
L = total road surface dust loading, g/m2(grains/ft2)
s = surface silt content, fraction of particles
_< 75 pm diameter (American Association of
State Highway Officials)
k = base emission factor, g/VKT (Ib/VMT)
p = exponent (dimensionless)
9/85 Miscellaneous Sources 11.2.5-1
-------
to
Ul
tv)
O
21
DEPOSITION
T) PAVEMENT WEAR AMD DECOMPOSITION
VEHICLE-RELATED DEPOSITION
DUSTFALL
4) LITTER
D MUDANDDIRTCARRYOUT
6) EROSION FROM ADJACENT AREAS
7) SPILLS
D BIOLOGICAL DEBRIS
ICE CONTROL COMPOUNDS
00
Ul
REMOVAL
REENTRAINMENT
WIND EROSION
DISPLACEMENT
RAINFALL RUNOFF TO CATCH BASIN
STREET SWEEPING
11.2.5-L Deposition and removal processes.
-------
The total loading (excluding litter) is measured by sweeping and vacuuming
lateral strips of known area from each active travel lane. The silt fraction
is determined by measuring the proportion of loose dry road dust that passes a
200 mesh screen, using the ASTM-C-136 method. Silt loading is the product of
total loading and silt content.
The base emission factor coefficients, k, and exponents, p, in the equation
for each size fraction are listed in Table 11.2.5-1. Total suspended particulate
(TSP) denotes that particle size fraction of airborne particulate matter that
would be collected by a standard high volume sampler.
TABLE 11.2.5-1. PAVED URBAN ROAD EMISSION FACTOR EQUATION PARAMETERS3
Particle Size Fraction*5
TSP
;< 15 pm
< 10 ym
< 2 . 5 ym
k
g/VKT (Ib/VMT)
5.87 (0.0208)
2.54 (0.0090)
2.28 (0.0081)
1.02 (0.0036)
P
0.9
0.8
0.8
0.6
aReference 4. See page 11.2.5-1 for equation. TSP = total suspended
particulate.
Aerodynamic diameter.
Microscopic analysis indicates the origin of material collected on high
volume filters to be about 40 weight percent combustion products and 59 per-
cent mineral matter, with traces of biological matter and rubber tire particles.
The small particulate is mainly combustion products, while most of the large
material is of mineral origin.
11.2.5.3 Emissions Inventory Applications^
For most emissions inventory applications involving urban paved roads,
actual measurements of silt loading will probably not be made. Therefore, to
facilitate the use of the previously described equation, it is necessary to
characterize silt loadings according to parameters readily available to per-
sons developing the inventories. It is convenient to characterize variations
in silt loading with a roadway classification system, and this is presented
in Table 11.2.5-2. This system generally corresponds to the classification
systems used by transportation agencies, and thus the data necessary for an
emissions inventory - number of road kilometers per road category and traffic
counts - should be easy to obtain. In some situations, it may be necessary to
combine this silt loading information with sound engineering judgment in order
to approximate the loadings for roadway types not specifically included in
Table 11.2.5-2.
9/85
Miscellaneous Sources
11.2.5-3
-------
TABLE 11.2.5-2. PAVED URBAN ROADWAY CLASSIFICATION3
Roadway Category
Freeways/ expressways
Major streets/highways
Collector streets
Local streets
Average Daily Traffic
(Vehicles)
> 50,000
> 10,000
500 - 10,000
< 500
Lanes
>_ 4
>_ 4
2b
2c
aReference 4.
kRoad width >_ 32 ft.
GRoad width < 32 ft.
A data base of 44 samples analyzed according to consistent procedures may
be used to characterize the silt loadings for each roadway category.4 These
samples, obtained during recent field sampling programs, represent a broad range
of urban land use and roadway conditions. Geometric means for this data set are
given by sampling location and roadway category in Table 11.2.5-3.
TABLE 11.2.5-3. SUMMARY OF SILT LOADINGS (sL) FOR PAVED URBAN ROADWAYS3
City
Baltimore
Buffalo
Granite City (IL)
Kansas City
St. Louis
All
Roadway Category
Local Collector Major Streets/
Streets Streets Highways
Xg (g/m2) n Xg (g/m2) n Xg (g/m2) n
1.42 2 0.72 4 0.39 3
1.41 5 0.29 2 0.24 4
- - - - 0.82 3
2.11 4 0.41 13
- - - - 0.16 3
1.41 7 0.92 10 0.36 26
Freeways/
Expressways
Xg (g/m2) n
-
-
-
-
0.022 1
0.022 1
aReference 4. Xg = geometric mean based on corresponding n sample size.
Dash = not available. To convert g/m2to grains/ft2 multiply g/m2 by 1.4337.
11.2.5-4
EMISSION FACTORS
9/85
-------
These sampling locations can be considered representative of most large
urban areas in the United States, with the possible exception of those in the
Southwest. Except for the collector roadway category, the mean silt loadings
do not vary greatly from city to city, though the St. Louis mean for major
roads is somewhat lower than those of the other four cities. The substantial
variation within the collector roadway category is probably attributable to the
effects of land use around the specific sampling locations. It should also be
noted that an examination of data collected at three cities in Montana during
early spring indicates that winter road sanding may produce loadings five to
six times higher than the means of the loadings given in Table 11.2.5-3 for the
respective road categories.5
Table 11.2.5-4 presents the emission factors by roadway category and par-
ticle size. These were obtained by inserting the above mean silt loadings into
the equation on page 11.2.5-1. These emission factors can be used directly for
many emission inventory purposes. It is important to note that the paved road
emission factors for TSP agree quite well with those developed from previous
testing of roadway sites in the major street and highway category, yielding
mean TSP emission factors of 4.3 grams/VKT (Reference 6) and 2.6 grams/VKT
(Reference 7).
TABLE 11.2.5-4. RECOMMENDED PARTICULATE EMISSION FACTORS FOR SPECIFIC
ROADWAY CATEGORIES AND PARTICLE SIZE FRACTIONS
Emission Factor
Roadway
Category
TSP
15
< 10 pm
< 2.5 ym
g/VKT (Ib/VMT) g/VKT (Ib/VMT) g/VKT (Ib/VMT) g/VKT (Ib/VMT)
Local streets 15 (0.053)
10 (0.035)
Collector
streets
Major streets/
highways 4.4 (0.016)
Freeways/
expressways 0.35 (0.0012)
5.8 (0.021) 5.2 (0.018) 1.9 (0.0067)
4.1 (0.015) 3.7 (0.013) 1.5 (0.0053)
2.0 (0.0071) 1.8 (0.0064) 0.84 (0.0030)
0.21 (0.00074) 0.19 (0.00067) 0.16 (0.00057)
References for Section 11.2.5
1. D. R. Dunbar, Resuspension of Particulate Matter, EPA-450/2-76-031, U. S.
Environmental Protection Agency, Research Triangle Park, NC, March 1976.
2. M. P. Abel, "The Impact of Refloatation on Chicago's Total Suspended
Particulate Levels", Purdue University, Purdue, IN, August 1974.
3. C. M. Maxwell and D. W. Nelson, A Lead Emission Factor JrorReentrained
Dust from a Paved Roadway, EPA-450/3-78-021, U. S. Environmental Pro-
tection Agency, Research Triangle Park, NC, April 1978.
9/85
Miscelleanous Sources
11.2.5-5
-------
4. Chatten Cowherd, Jr. and Phillip J. Englehart, Paved Road Particulate
Emissions^ EPA-600/7-84-077, U. S. Environmental Protection Agency, Wash-
ington, DC, July 1984.
5. R. Bohn, Update and Improvement of the Emission Inventory for MAPS Study
Areas, State of Montana, Helena, MT, August 1979.
6. C. Cowherd, Jr., et al . , Quantification of Dust Entrainment from Paved
Roadways, EPA-450/3-77-027 , U. S. Environmental Protection Agency,
Research Triangle Park, NC, July 1977.
7. K. Axetell and J. Zell, Control of Reentrained Dust from Payed ^
EPA-907/9-77-077, U. S. Environmental Protection Agency, Kansas City,
MO, August 1977.
11.2.5-6 EMISSION FACTORS 9/85
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11.2.6 INDUSTRIAL PAVED ROADS
11.2.6.1 General
Various field studies have indicated that dust emissions from industrial
paved roads are a major component of atmospheric particulate matter in the
vicinity of industrial operations. Industrial traffic dust has been found to
consist primarily of mineral matter, mostly tracked or deposited onto the
roadway by vehicle traffic itself when vehicles enter from an unpaved area or
travel on the shoulder of the road, or when material is spilled onto the paved
surface from haul truck traffic.
11.2.6.2 Emissions And Correction Parameters
The quantity of dust emissions from a given segment of paved road varies
linearly with the volume of traffic. In addition, field investigations have
shown that emissions depend on correction parameters (road surface silt content,
surface dust loading and average vehicle weight) of a particular road and
associated vehicle
Dust emissions from industrial paved roads have been found to vary in
direct proportion to the fraction of silt (particles <75 \im in diameter) in
the road surface material.1~2 The silt fraction is determined by measuring the
proportion of loose dry surface dust that passes a 200 mesh screen, using the
ASTM-C-136 method. In addition, it has also been found that emissions vary in
direct proportion to the surface dust loading.1~2 The road surface dust loading
is that loose material which can be collected by broom sweeping and vacuuming of
the traveled portion of the paved road. Table 11.2.6-1 summarizes measured silt
and loading values for industrial paved roads.
11.2.6.3 Predictive Emission Factor Equations
The quantity of total suspended particulate emissions generated by vehicle
traffic on dry industrial paved roads, per vehicle kilometer traveled (VKT) or
vehicle mile traveled (VMT) may be estimated, with a rating of B or D (see below),
using the following empirical expression^:
E = 0.022 I 1\ /_!
0.077
nlUji
(kg/VKT)
(Ib/VMT)
CD
where:
E = emission factor
I = industrial augmentation factor (dimensionless) (see below)
n = number of traffic lanes
s = surface material silt content (%)
L = surface dust loading, kg/km (Ib/mile) (see below)
W = average vehicle weight, Mg (ton)
9/85
Miscellaneous Sources
11.2.6-1
-------
TABLE 11.2.6-1. TYPICAL SILT CONTENT AND LOADING VALUES FOR PAVED ROADS
AT INDUSTRIAL FACILITIES3
No. of
Industry Plant Sltea
Copper melting 1
Iron and eteel
product ion 6
Asphalt batching 1
Concrete hatching 1
Sand and gravel
processing t
No. of
No. of Silt (X, w/w) Travel Total loading
Samples Range Mean Lanes Range
3 [15.4-Z1.7J [19.0] 2 [12.9-19.5]
[45.8-69.2]
2 0.006-4.77
20 1.1-35.7 12.5 2 0.020-16.9
4 [2.6-4.6] [3.6] 1 [12.1-18.0]
[43.0-64.0]
3 [5.2-6.0] [5.5] 2 [1.4-1.8]
[5.0-6.4]
3 [6.4-7.9] [7.1] 1 [2.8-5.5]
[9.9-19.4]
Mean
[15.9]
[55.4]
0.495
1.75
[15.7]
[55.7]
[1.7]
[5.9]
[3.8]
[13.3]
Silt loading
(8/« )
Unite * Range
kg/km [188-400]
Ib/nl
kg/km <1.0-2.3
Ib/nl
kg/km [76-193]
Ib/mi
kg/km [11-12]
Ib/ml
kg/to. [53-95]
Ib/nl
Mean
[292]
7
[138]
[12]
[70]
The industrial road augmentation factor (I) in the Equation 1 takes into
account higher emissions from industrial roads than from urban roads. 1-7.0
for an industrial roadway which traffic enters from unpaved areas. 1-3.5 for
an industrial roadway with unpaved shoulders where 20 percent of the vehicles
are forced to travel temporarily with one set of wheels on the shoulder. I = 1.0
for cases in which traffic does not travel on unpaved areas. A value between 1.0
and 7.0 which best represents conditions for paved roads at a certain industrial
facility should be used for I in the equation.
The equation retains the quality rating of B if applied to vehicles
traveling entirely on paved surfaces (I » 1.0) and if applied within the range
of source conditions that were tested in developing the equation as follows:
Silt
content
(%)
5.1 - 92
Surface loading
kg/km
42.0 - 2,000
Ib/mile
149 - 7,100
No. of
lanes
2-4
Vehicle weight
Mg tons
2.7 - 12 3-13
If I is >1.0, the rating of the equation drops to D because of the subjectivity
in the guidelines for estimating I.
The quantity of fine particle emissions generated by traffic consisting
predominately of medium and heavy duty vehicles on dry industrial paved roads,
per vehicle unit of travel, may be estimated, with a rating of A, using the
11.2.6-2
EMISSION FACTORS
9/85
-------
E = k
E =
-)
0.3
sL
(kg/VKT)
(Ib/VMT)
(2)
where: E = emission factor
sL = road surface silt loading, g/m2 (oz/yd2)
The particle size multiplier (k) above varies with aerodynamic size range
as follows:
Aerodynamic Particle Size
Multiplier (k) For Equation 2
(Dimensionless)
ym
ym
<2.5
0.28
0.22
0.081
To determine particulate emissions for a specific particle size range, use the
appropriate value of k above.
The equation retains the quality rating of A, if applied within the range
of source conditions that were tested in developing the equation as follows:
silt loading, 2 - 240 g/m2 (0.06 - 7.1 oz/yd2)
mean vehicle weight, 6 - 42 Mg (7 - 46 tons)
The following single valued emission factors** may be used in lieu of
Equation 2 to estimate fine particle emissions generated by light duty vehicles
on dry, heavily loaded industrial roads, with a rating of C:
Emission Factors For Light Duty
Vehicles On Heavily Loaded Roads
<15 ym
<10 ym
0.12 kg/VKT
(0.41 Ib/VMT)
0.093 kg/VKT
(0.33 Ib/VMT)
These emission factors retain the assigned quality rating, if applied within
the range of source conditions that were tested in developing the factors, as
follows:
silt loading, 15 - 400 g/m2 (0.44 - 12 oz/yd2)
mean vehicle weight, £4 Mg (^4 tons)
Also, to retain the quality ratings of Equations 1 and 2 when applied to a
specific industrial paved road, it is necessary that reliable correction para-
meter values for the specific road in question be determined. The field and
9/85
Miscellaneous Sources
11.2.6-3
-------
laboratory procedures for determining surface material silt content and surface
dust loading are given in Reference 2. In the event that site specific values
for correction parameters cannot be obtained, the appropriate mean values from
Table 11.2.6-1 may be used, but the quality ratings of the equations should be
reduced by one level.
11.2.6.4 Control Methods
Common control techniques for industrial paved roads are broom sweeping,
vacuum sweeping and water flushing, used alone or in combination. All of
these techniques work by reducing the silt loading on the traveled portions of
the road. As indicated by a comparison of Equations 1 and 2, fine particle
emissions are less sensitive than total suspended particulate emissions to the
value of silt loading. Consistent with this, control techniques are generally
less effective for the finer particle sizes.* The exception is water flushing,
which appears preferentially to remove (or agglomerate) fine particles from the
paved road surface. Broom sweeping is generally regarded as the least effec-
tive of the common control techniques, because the mechanical sweeping process
is inefficient in removing silt from the road surface.
To achieve control efficiencies on the order of 50 percent on a paved road
with moderate traffic ( 500 vehicles per day) requires cleaning of the surface
at least twice per week.^ This is because of the characteristically rapid
buildup of road surface material from spillage and the tracking and deposition
of material from adjacent unpaved surfaces, including the shoulders (berms) of
the paved road. Because Industrial paved roads usually do not have curbs, it
is important that the width of the paved road surface be sufficient for vehicles
to pass without excursion onto unpaved shoulders. Equation 1 indicates that
elimination of vehicle travel on unpaved or untreated shoulders would effect a
major reduction in particulate emissions. An even greater effect, by a factor
of 7, would result from preventing travel from unpaved roads or parking lots
onto the paved road of interest.
References for Section 11.2.6
1. R. Bohn, et al., Fugitive Emissions from Integrated Iron and Steel Plants,
EPA-600/2-78-050, U. S. Environmental Protection Agency, Research Triangle
Park, NC, March 1978.
2. C. Cowherd, Jr., et al., Iron and Steel Plant Open Dust Source Fugitive
Emission Evaluation, EPA-600/2-79-103, U. S. Environmental Protection
Agency, Research Triangle Park, NC, May 1979.
3, R. Bohn, Evaluation of Open Dust Sources in the Vicinity of Buffalo,
New York, U. S. Environmental Protection Agency, New York, NY, March 1979.
4. T. Cuscino, Jr., et al., Ironjind Steel Plant Open Source Fugitive Emis-
sion Control EvaluatJLon, EPA-600/2-83-110, U. S. Environmental Protection
Agency, Research Triangle Park, NC, October 1983.
5. J. Patrick Reider, Size Specific Particulate Emission Factors for Uncon-
trolled Industrial and Rural Roads, EPA Contract No. 68-02-3158, Midwest
Research Institute, Kansas City, MO, September 1983.
11.2.6-4 EMISSION FACTORS 9/85
-------
6. C. Cowherd, Jr. and P. Englehart, Size Specific Particulate Emission
Factors For Industrial And Rural Roads, EPA-600/7-85-051, U. S. Environ-
mental Protection Agency, Washington, DC, September 1985.
9/85 Miscellaneous Sources 11.2.6-5
-------
-------
11.3 EXPLOSIVES DETONATION
11.3.1 General 1~5
This section deals mainly with pollutants resulting from the
detonation of industrial explosives and firing of small arms. Military
applications are excluded from this discussion. Emissions associated
with the manufacture of explosives are treated in Section 5.6,
Explosives.
An explosive is a chemical material that is capable of extremely
rapid combustion resulting in an explosion or detonation. Since an
adequate supply of oxygen cannot be drawn from the air, a source of
oxygen must be incorporated into the explosive mixture. Some explo-
sives, such as trinitrotoluene (TNT), are single chemical species, but
most explosives are mixtures of several ingredients. "Low explosive"
and "high explosive" classifications are based on the velocity of
explosion, which is directly related to the type of work the explosive
can perform. There appears to be no direct relationship between the
velocity of explosions and the end products of explosive reactions.
These end products are determined primarily by the oxygen balance of the
explosive. As in other combustion reactions, a deficiency of oxygen
favors the formation of carbon monoxide and unburned organic compounds
and produces little, if any, nitrogen oxides. An excess of oxygen
causes more nitrogen oxides and less carbon monoxide and other unburned
organics. For ammonium nitrate and fuel oil mixtures (ANFO), a fuel oil
content of more than 5.5 percent creates a deficiency of oxygen.
There are hundreds of different explosives, with no universally
accepted system for classifying them. The classification used in Table
11.3-1 is based on the chemical composition of the explosives, without
regard to other to other properties, such as rate of detonation, which
relate to the applications of explosives but not to their specific end
products. Most explosives are used in two-, three-, or four-step trains
that are shown schematically in Figure 11.3-1. The simple removal of a
tree stump might be done with a two-step train made up of an electric
blasting cap and a stick of dynamite. The detonation wave from the
blasting cap would cause detonation of the dynamite. To make a large
hole in the earth, an inexpensive explosive such as ammonium nitrate and
fuel oil (ANFO) might be used. In this case, the detonation wave from
the blasting cap is not powerful enough to cause detonation, so a
booster must be used in a three- or four-step train. Emissions from the
blasting caps and safety fuses used in these trains are usually small
compared to those from the main charge, because the emissions are
roughly proportional to the weight of explosive used, and the main
charge makes up most of the total weight. No factors are given for
computing emissions from blasting caps or fuses, because these have not
been measured, and because the uncertainties are so great in estimating
emissions from the main and booster charges that a precise estimate of
all emissions is not practical.
2/80 Miscellaneous Source's 11.3-1
-------
Z. DVNAMITE
1. ELECTRIC
BLASTING CAP
PRIMARY
HIGH EXPLOSIVE
SECONDARY HIGH EXPLOSIVE
a. Two-step explosive train
3. DYNAMITE
1. SAFETY FUSE
LOW EXPLOSIVE PRIMARY
(BLACK POWDER) HIGH
EXPLOSIVE
SECONDARY HIGH EXPLOSIVE
b. Three-step explosive train
f
1 SAFETY *- NONELECTRIC
FUSE BLASTING CAP
I l"i
LOW
EXP
PRIMAA
.OSIVE HIGH E
Y
c. Four-step explosive train
Figure 11.3-1. Two-, three-, and four-step explosive trains.
I 1.3-2
EMISSION FACTORS
2/80
-------
Table 11.3-1. EMISSION FACTORS FOR DETONATION OF EXPLOSIVES
(EMISSION FACTOR RATING: D)
Explosive
Black powder2
Smokeless
Powder2
Dynamite,
Straight2
Dynamite.
Anpwnia2
Dynamite,
Gelatin2
ANFO"'5
TNT2
RDX3
PETN2
Composition
75/15/10; potassium (sodium)
nitrate/charcoal /sulfur
nitrocellulose (sometimes
with other materials)
20-60% nitroglycerine/
sodium nitrate/wood pulp/
calcium carbonate
20-601 nitroglycerine/
ammonium nitrate/sodium
n i trate/wood pulp
20-1001 nitroglycerine
amnonium nitrate with
5.8-3% fuel oil
trinitrotoluene
-------
11.3.3 Emissions and Controls '
Carbon monoxide is the pollutant produced in greatest quantity from
explosives detonation. TNT, an oxygen deficient explosive, produces
more CO than most dynamites, which are oxygen balanced. But all explo-
sives produce measurable amounts of CO. Particulates are produced as
well, but such large quantities of particulate are generated in the
shattering of the rock and earth by the explosive that the quantity of
particulates from the explosive charge cannot be distinguished. Nitrogen
oxides (both NO and N02) are formed, but only limited data are available
on these emissions. Oxygen deficient explosives are said to produce
little or no nitrogen oxides, but there is only a small body of data to
confirm this. Unburned hydrocarbons also result from explosions, but in
most instances, methane is the only species that has been reported.
Hydrogen sulfide, hydrogen cyanide and ammonia all have been
reported as products of explosives use. Lead is emitted from the firing
of small arms ammunition with lead projectiles and/or lead primers, but
the explosive charge does not contribute to the lead emissions.
The emissions from explosives detonation are influenced by many
factors such as explosive composition, product expansion, method of
priming, length of charge, and confinement. These factors are difficult
to measure and control in the field and are almost impossible to duplicate
in a laboratory test facility. With the exception of a few studies in
underground mines, most studies have been performed in laboratory test
chambers that differ substantially from the actual environment. Any
estimates of emissions from explosives use must be regarded as approxi-
mations that cannot be made more precise, because explosives are not
used in a precise, reproducible manner.
To a certain extent, emissions can be altered by changing the
composition of the explosive mixture. This has been practiced for many
years to safeguard miners who must use explosives. The U. S. Bureau of
Mines has a continuing program to study the products from explosives and
to identify explosives that can be used safely underground. Lead
emissions from small arms use can be controlled by using jacketed soft
point projectiles and special leadfree primers.
Emission factors are given in Table 11.3-1.
References for Section 11.3
1. C. R. Newhouser, Introduction to Explosives, National Bomb Data
Center, International Association of Chiefs of Police, Gaithersburg,
MD (undated).
2. Roy V. Carter, "Emissions from the Open Burning or Detonation of
Explosives", Presented at the 71st Annual Meeting of the Air
Pollution Control Association, Houston, TX, June 1978.
1 I .3-1
EMISSION FACTORS
2/80
-------
r
3. Melvin A. Cook, The Science of^jH-gh Explosives, Reinhold Publishing
Corporation, New York, 1958.
4. R. F. Chaiken, et^al., Tp_xic__Fumes from Explosives; Ammonium
Nitrate Fuel Oil Mixtures, Bureau of Mines Report of Investigations
7867, U. S. Department of Interior, Washington, DC, 1974.
5. Sheridan J. Rogers, Analysis of Noncoal Mine Atmospheres: Toxic
Fumes from Explosives, Bureau of Mines, U. S. Department of Interior,
Washington, DC, May 1976.
6. A. A. Juhasz, "A Reduction of Airborne Lead in Indoor Firing
Ranges by Using Modified Ammunition", Special Publication 480-26,
Bureau of Standards, U. S. Department of Commerce, Washington, DC,
November 1977.
2/80 Miscellaneous Sources 11.3-5
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-------
TECHNICAL REPORT DATA
/Please read Instructions en th* reverse before complttinp)
la. RECIPIENT'S ACCESSION No7
AP-42 Fourth Edition, Volume I
4 TITLE AND SUBTITLE
COMPILATION OF AIR POLLUTANT EMISSION FACTORS,
VOLUME I: STATIONARY POINT AND AREA SOURCES
5 REPpRT DATE
September 1985
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
9 PERFORMING ORGANIZATION NAME AND ADDRESS
Source Analysis Section, MDAD (MD 14)
Office Of Air Quality Planning And Standards
U. S. Environmental Protection Agency
Research Triangle Park, NC 27711
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
. SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF REPORT AND PERIOD COVERED
14, SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
EPA Editor: Whitmel M. Joyner
16. ABSTRACT
Emission data obtained from source tests, material balance studies,
engineering estimates, etc., have been compiled for use by individuals and groups
responsible for conducting air pollution emission inventories. Emission factors
given in this document cover most of the common stationary and area source emission
categories: fuel combustion; combustion of solid wastes; evaporation of fuels,
solvents and other volatile substances; various industrial processes; and
miscellaneous sources. When no specific source test data are available, these
factors can be used to estimate the quantities of pollutants being released from a
source or source -g-r-onp_.
Volume II of "this document provides emission factors for mobile sources, both
on and off highway types. This information is available from EPA's Office Of Mobile
Sources, 2565 Plymouth Road, Ann Arbor, MI 48105.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
Emissions
Emission Factors
Stationary Sources
Area Sources
Fuel Combustion
Emission Inventories
b.IDENTIFIERS/OPEN ENDED TERMS
18. DISTRIBUTION STATEMENT
COSATi l-'ield/Croup
119. SECURITY CLASS rr;i!t i-leporu i21, NO. OF PAGeS
' ! 888
EPA Ro.-rn 3220 -T-.,-Rcv. 4_/'7J P P.' E v ; c us nr.-i
OB?C;LETI-
•ft U.a GOVERNMENT P«NmNGOFFCE: 1861-281-724,28459
-------
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