AP-42
Supplement 13
SUPPLEMENT NO. 13
FOR
COMPILATION
OF AIR POLLUTANT
EMISSION FACTORS,
THIRD EDITION
(INCLUDING SUPPLEMENTS 1-7)
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air, Noise and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
August 1982
-------
AP-42
Supplement 13
SUPPLEMENT NO. 13
FOR
COMPILATION
OF AIR POLLUTANT
EMISSION FACTORS,
THIRD EDITION
(INCLUDING SUPPLEMENTS 1-7)
Region V, Ml
230 South De ftrees
Chicago, ii'. seeo«»
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air, Noise and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
August 1982
-------
This report has been reviewed by the Office of Air Quality Planning and
Standards, EPA, and approved for publication. Mention of trade names or
commercial products is not intended to constitute endorsement or
recommendation for use.
U.S. Environmental Protection
«- . < . , '
-------
INSTRUCTIONS FOR INSERTING SUPPLEMENT 73
Into AP-42
Page* lH through v replace. *ame. New Content*.
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Add pages 8.23-1 through 8.23-6. New Section.
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CONTENTS
Page
INTRODUCTION 1
1. EXTERNAL COMBUSTION SOURCES 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 Liquefied 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 Wood Stoves 1.10-1
1.11 Waste Oil Disposal 1.11-1
2. SOLID WASTE DISPOSAL 2.0-1
2.1 Refuse Incineration 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. INTERNAL COMBUSTION ENGINE SOURCES 3-1
GLOSSARY OF TERMS 3-1
3.1 Highway Vehicles 3.1-1
3.2 Off Highway Mobile Sources 3.2-1
3.3 Off Highway Stationary Sources 3.3-1
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 Petroleum 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
5.9 Nitric Acid 5.9-1
iii
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Page
5.10
5.11
5.12
5.13
5.14
5.15
5.16
5.17
5.18
5.19
5.20
5.21
5.22
5.23
5.24
FOOD
6.1
6.2
6.3
6.4
6.5
6.6
6.7
6.8
6.9
6.10
6.11
6.12
6.13
6.14
6.15
6.16
6.17
6.18
Phthalic Anhydride
Plastics
Printing Ink
Sulfuric Acid
Synthetic Fibers
Synthetic Rubber
Terephthalic Acid
Lead Alkyl
AND AGRICULTURAL INDUSTRY
Alfalfa Dehydrating
Feed And Grain Mills And Elevators ....
Starch Manufacturing
Beef Cattle Feedlots
METALLURGICAL INDUSTRY
7.1
7.2
7.3
7.4
7.5
7.6
7.7
7.8
7.9
7.10
7.11
7.12
7.13
7.14
7.15
7.16
Zinc Smelting
Secondary Copper Smelting And Alloying . .
. . . 5.10-1
. . . 5.11-1
. . . 5.12-1
. . ., 5.13-1
. . .. 5.14-1
. . . 5.15-1
. . . 5.16-1
. . . 5.17-1
. . . 5.18-1
. . . 5.19-1
. . . 5.20-1
. . . 5.21-1
. . . 5.22-1
. . . 5.23-1
. . ., 5.24-1
. . . 6.1-1
. . . 6.1-1
. . 6.2-1
. . ., 6.3-1
. . 6.4-1
. . ., 6.5-1
. . ., 6.6-1
. . . 6.7-1
. . ., 6.8-1
. . , 6.9-1
. . . 6.10-1
. . ., 6.11-1
. . . 6.12-1
. . ., 6.13-1
. . . 6.14-1
. . ., 6.15-1
. . ., 6.16-1
. . ., 6.17-1
. . . 6.18-1
. . . 7.1-1
. . . 7.1-1
. . . 7.2-1
. . . 7.3-1
. . , 7.4-1
. . . 7.5-1
. . . 7.6-1
. . . 7.7-1
. . . 7.8-1
. . . 7.9-1
. . ., 7.10-1
. . . 7.11-1
. . . 7.12-1
. . ., 7.13-1
. . . 7.14-1
. . ., 7.15-1
. . . 7.16-1
iv
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Page
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 Sand And Gravel Processing 8.19-1
8.20 Stone Quarrying And Processing 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
9. PETROLEUM INDUSTRY 9.1-1
9.1 Petroleum Refining 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 Forest Wildfires 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
APPENDIX B. Emission Factors And New Source Performance
Standards For Stationary Sources . B-l
APPENDIX C. NEDS Source Classification Codes And
Emission Factor Listing C-l
APPENDIX D. Projected Emission Factors For Highway
Vehicles D-l
APPENDIX E. Table Of Lead Emission Factors E-l
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PUBLICATIONS IN SERIES (CONT'D)
Issuance
Supplement No. 13
Release Date
8/82
Bituminous and Subbituminous Coal Combustion
Fuel Oil Combustion
Natural Gas Combustion
Liquefied Petroleum Gas Combustion
Wood Waste Combustion In Boilers
Lignite Combustion
Stationary Large Bore Diesel and Dual Fuel Engines
8 Automobile and Light Duty Truck Surface Coating
9 Pressure Sensitive Tapes and Labels
10 Metal Coil Surface Coating
Textile Fabric Printing
Sodium Carbonate
Synthetic Rubber
Storage Battery Production
Section 8.23 Metallic Minerals Processing
Section 1.1
Section 1.3
Section
Section
Section
Section
Section
Section 4.2.2,
Section 4.2.2,
Section
Section 4,
Section 5,
Section 5
Section
1.4
1.5
.6
1.7
3.3.4
.2.2
.11
.16
.20
.15
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COMPILATION OF AIR POLLUTANT EMISSION FACTORS
INTRODUCTION
Emission factors are very useful tools for estimating air pollutant
emissions from sources. An emission factor relates the quantity of a pollutant
released to the atmosphere to an activity associated with release of that
pollutant, and it is usually expressed as weight of pollutant divided by unit
weight, volume, distance or time of that activity (e.g., kg particulate emitted
per Mg coal combusted). In most cases, these factors are simply averages of
all available data of acceptable quality, without regard to the influence of
process parameters such as temperature, reactant concentrations, etc. However,
for a few cases, such as in the estimation of volatile organic emissions from
petroleum storage tanks, empirical formulae have been developed which relate
emissions to such variables as tank diameter, liquid temperature and wind
velocity. Emission factors which are correlated with such variables tend to
yield more precise emission estimates than do factors derived from broader
statistical averages.
Because emission factors are averages obtained from data of wide range and
varying degrees of accuracy, emissions calculated from such factors for a given
facility are likely to be different from that facility's actual emissions.
Only an onsite source test can accurately determine actual emissions from a
source, under the conditions existing at the time of the test. Factors are
more appropriately used to estimate collectively the emissions of a number of
sources, such as is done in emission inventory work.
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
with air pollution control equipment in place. These factors generally are not
intended to represent best available or state of the art control technology,
rather they relate to the level of control commonly found on existing facilities,
The reliability of this information should be considered carefully in light of
rapid changes in air pollution control technology. The user should consider
the age, level of maintenance, and other aspects which may influence equipment
efficacy.
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
Table 1.3-1 of AP-42, the CO emission factor for industrial boilers burning
distillate oil is 0.63 kg CO per 103 liters of oil burned. Then,
kg CO emissions/day
= CO emission factor x 103 1 distillate oil burned/day
= 0.63 x 90
= 56.7
-------
In some instances, the factors may reflect more complex relationships
between process characteristics and emissions, as with fuel ash in coal
combustion, where emissions involve rate of combustion and ash content.
In a somewhat more complex case, suppose a sulfuric acid (112804) plant
produces 200 Mg of 100% I^SO^ per day by converting sulfur dioxide (S02) to
sulfur trioxide (S03) at 97.5% efficiency. In Table 5.17-1, the S02 emission
factors are listed according to 802 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% 862 to 863 conversion:
Emission factor, kg S02/Mg 100% H2SOi+
= 682 - [(6.82)(% S02 to S03 conversion)]
= 682 - [(6.82)(97.5)]
= 682 - 665
= 17
For production of 200 Mg of 100% I^SO^/day, S02 emissions are calculated
as kg 802 emissions/day
= 17 kg S02 emissions/Mg 100% H2S01+ x 200 Mg 100% H2SOi+/day
= 3400
To help users understand the reliability and accuracy of AP-42 emission
factors, each table (and sometimes individual factors in a table) is subjectively
assigned a rating (ranging from A through E) which reflects the quality and
the amount of data on which the factors are based. In general, factors based
on many observations are assigned higher rankings, as are factors based on
more widely accepted test procedures. 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 under a single reference measurement technique or
equivalent techniques. Conversely, a factor based on a single observation of
questionable quality or extrapolated from another factor for a similar process
would probably be labeled D or E. Several subjective schemes have been used
in the past, and continue to be used, 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. And this
indicator will largely reflect the professional judgment of an AP-42 Section's
author and reviewers of the reliability of any estimates derived with the
factor.
-------
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 General1
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 1.1-1
-------
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"1* - 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"9 - Gaseous sulfur oxides from external coal combustion
are largely sulfur dioxide (S02) and much lesser quantities of sulfur tri-
oxide (S03) 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
-------
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EMISSION FACTORS
8/82
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External Combustion Sources
1.1-5
-------
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 SQx 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 iO-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 NGX 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 Fired Boilers for 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 for Sulfur Dioxide Emissions from Stationary 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 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.
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 NOx
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
Boilers, 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, et 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, £(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, General Motors Corporation,
Parma, Ohio, Volume I, EMB-80-IBR-4, U.S. Environmental Protection
Agency, Research Triangle Park, NC, March 1980.
38. A Field 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-600/7-80-136a, May 1980.
44. ibidem-Site J, EPA-600/7-80-137a, May 1980.
1.1-10 EMISSION FACTORS 8/82
-------
45. ibldem-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: Coal-fired Industrial Combustion Equipment Field
Tests, EPA-600/2-78-Q04o, 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 Utilit3r Boilers,
EPA-600/7-80-111, U.S. Environmental Protection Agency, Washington, DC,
May 1980.
59. Industrial Boilers; Emission Test Report, DuPont 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.
1.1-12 EMISSION FACTORS 8/82
-------
1.3 FUEL OIL COMBUSTION
1 999
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.
O "7 1O 1 Q 1 / O C^ O~7
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
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1.3-2
EMISSION FACTORS
8/82
-------
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.
15 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 I
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.
1 Q_O 1
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.
1_4 8-9 13-14 23
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.
o r in on
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 oE 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.
i c i /: 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, et al., 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 NQX 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, JJ^: 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 Study 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, t)C, 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-1-257
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 OilFired
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 f\ r
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 Combus.tion 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
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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
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8/82
External Combustion Sources
1.4-3
-------
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
No nme thane
C
c
D
D
Methane
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, _14_: 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 10;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
-------
10. Unpublished data on domestic gas fired units, National Air
Pollution Control Administration, U.S. Department of Health,
Education and Welfare, Cincinnati, OH, 1970.
11. 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.
12. 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.
13. 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.
14. 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.
15. 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.
16. 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.
17. 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.
18. 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.
19. 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.
20. 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. Lira, et al., Technology Assessment Report for Industrial
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
domestic/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
-------
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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
1-3
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.
1-3
1.6.2 Firing Practices
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.
4-28
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
-------
TABLE 1.6-1. EMISSION FACTORS FOR WOOD AND BARK COMBUSTION IN BOILERS
EMISSION FACTOR RATING: B
Pollutant/Fuel Type kg/Mg Ib/ton
Particulate '
Barkc
Controlled, with flyash 7 14
reinjection
Controlled, without flyash
reinjection 4.5 9
Uncontrolled 24 47
Wood/bark mixture
Controlled, with flyash
reinjection * 3 b
Controlled, without flyash
reinjection 2.7 5.3
Uncontrolled 3.6 7.2
»'oods
Uncontrolled 4.4 8.8
Sulfur Dioxideh 0.074 0.148
(0.009-0.193) (0.019-0.386)
Nitrogen Oxides(as N02)
50,000-400,000 Ib steam/hr
<50,000 Ib steam/hr
Carbon Monoxide
Nonmethane VOC
1.4
0.34
2-24
0.8
2.8
0.68
4-47
1.7
References 2,4,9,17-18. For boilers burning gas or oil as an
auxiliary fuel, assuming all particulates result from the waste
.fuel alone.
May include condensible hydrocarbons consisting of pitches and
tars, mostly from the back half catch of EPA Method 5. Tests
reported in Reference 20 indicate that condensible hydrocarbons
account for about 4% of total particulate by weight.
.Based on moisture content of about 50%.
After the control equipment, assuming an average collection efficiency
of 80%. Data from References 4, 7 and 8 indicate that 50% flyash
reinjection increases the dust load at the boiler outlet (before
control) by 1.2 to 1.5 times, while 100% flyash reinjection increases
the load 1.5 to 2 times the load without reinjection.
Based on large dutch ovens and spreader stokers (averaging 23,430 kg
fsteam/hr) with steam pressures from 10.5 - 42 kg/cm2.
Based on small dutch ovens and spreader stokers (usually operating
less than 9075 kg/hr of steam), with steam pressures from 2.8 - 17.6
kg/cm2. Careful air adjustments and improved fuel separation and
firing were used on some of these boilers, but the effects cannot
be isolated.
References 12-13,19,27. Wood waste includes cuttings, shavings,
sawdust and chips, but not bark. Moisture content ranges from
20 to 50% by weight. Based on 28 small boilers (less than 3,300 kg
steam/hr) located in the States of 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 4,987 kcal/kg (9,000 Btu/lb)
is assumed. The factors are based on the dry weight of fuel.
'"'References 7,24-26. It should be noted that several factors can
influence emission rates, including combustion zone, temperatures,
excess air, boiler operating conditions, fuel moisture and fuel
.nitrogen content.
^Reference 30.
Reference 20. Nonmethane VOC reportedly consists of compounds
with a high vapor pressure such as alpha pinene. Emission factors
for methane are not available.
8/82
External Combustion Sources 1.6-3
-------
a tenfold increase in the dust loadings of some systems, althoug,h
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 Waste Fuels", Mechanical
Engineering, jjlj 115-120, February 1939.
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 Factors, 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. D.C. Junge and K. Kwan, "An Investigation of the Chemically
Reactive Constituents of Atmospheric Emissions from HogFuel
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 Oxide Emissions from a Pilot Plant
Spreader Stoker Bark Fired Boiler, Department of Civil
Engineering, University of Washington, Seattle, WA,
December 1979.
26. A. Nunn, NOy 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 Wide Bodied
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 niidwestern 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
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EMISSION FACTORS
8/82
-------
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 S02 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 particulates, 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. 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.
12. Source test data on lignite fired cyclone boilers, North Dakota
State Department of Health, Bismarck, ND, March 1982.
8/82 External Combustion Sources 1.7-5
-------
3.3.4 STATIONARY LARGE BORE DIESEL AND DUAL FUEL ENGINES
3.3.4.1 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.
3.3.4.2 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 Internal Combustion Engine Sources 3.3.4-1
-------
TABLE 3.3.4-1. EMISSION FACTORS FOR STATIONARY LARGE BORE
DIESEL AND DUAL FUEL ENGINES3
EMISSION FACTOR RATING: C
Engine Nitrogen Carbon VOC Sulfur
Type Oxides^ Monoxide Methane Nonroethane Dioxide
Diesel
lb/103 hph 24 6.4 0.07 0.63 7
g/hph 11 2.9 0.03 0.29 3.2
g/kWh 15 3.9 0.04 0.04 4.3
lb/103 gal6 500 130 1 13 150
g/le 60 16 0.2 1.6 18
Dual Fuel
lb/103 hph
g/hph
g/kWh
18
8
11
5.9
2.7
3.6
4.7
2.1
2.9
1.5
0.7
0.9
0.70
0.32
0.43
a
Representative uncontrolled levels for each fuel determined by weighting
data from several manufacturers. Weighting based on % of total horsepower
sold by each manufacturer during a five year period.
Measured as N02. Factors are for engines operated at rated load and speed.
Nonmethane VOC accounts for 90% of total VOC from diesel engines but only
25% of total VOC emissions from dual fuel engines. Individual chemical
species within the nonmethane fraction are not identified. Molecular
weight of nonmethane gas stream is assumed to be that of methane.
Base on assumed sulfur content of 1% by weight for diesel fuel and 0.46
g/sc (0.20 gr/scf) for pipeline quality natural gas. Dual fuel S02 emis-
sions based on 5% oil/85% gas mix. Emissions should be adjusted for other
fuel ratios.
g
These factors calculated from the above factors assuming a heating value
of 40 MJ/L (145,000 Btu/gal) for oil, 41 MJ/scm (1100 Btu/scf) for natural
gas, and an average fuel consumption of 9.9 MJ/kWh (7000 Btu/hph).
Reference for Section 3.3.4
1. Standards Support and Environmental Impact Statement Volume I -
Stationary Internal. Combustion Engines, EPA-450/2-78-125a, U. S.
Environmental Protection Agency, Research Triangle Park, NC, July 1979.
3.3.4-2 EMISSION FACTORS 8/82
-------
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 REFINISHING3
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) 21.4 (4.6) 0.84 (1.9)
g/day (Ib/day) 5.8 (0.013) 2.7 (0.006)
Per employee
Mg/yr (ton/yr) - 2.3 (2.6)
kg/day (Ib/day) - 7.4 (16.3)
n
, 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
-------
Typical ranges of control efficiencies are given in
Table 4.2.2.1-3. Emission controls normally fall under one of
three categories - modifications in paint formula, process changes,
or addon controls. These are discussed further in the specific
subsections which follow.
C_ Q
4.2.2.2 Coil and Can Coating
Process Description - Coil coating is the coating of any flat metal
sheet or strip that comes in rolls or coils. Cans are made from
two or three flat pieces of metal, so can coating is included
within this broad category, as are the coating of screens, fencing,
metal doors, aluminum siding and a variety of other products.
Figure 4.2.2.2-1 shows a typical coil coating line, and
Figure 4.2.2.2-2 depicts a three piece can sheet printing operation.
There are both "toll" and "captive" coil coating operations.
The former fill orders to customer specifications, and the latter
coat the metal for products fabricated within one facility. Some
coil coating operations do both toll and captive work.
NOTE: With Supplement 13, Metal Coil Surface
Coating has been updated and expanded into a
separate Section.
Please see pages 4.2.2.10-1 through 6.
8/82
Oven temperatures range from 40 to 380°C (100 to 1000°F),
depending on the type and desired thickness of the coating and on
the type of metal being coated. A topcoat may be applied and cured
in a similar manner.
In can coating, as with coil coating, there are both toll and
captive manufacturers. Some plants coat metal sheets, some make
three piece cans, some fabricate and coat two piece cans, and some
fabricate can ends. Others perform combinations of these processes.
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.
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
4/81 Evaporation Loss Sources 4.2.2-5
-------
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MISSION FACTORS
4/81
-------
1-1+
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
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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 flashoff 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 OPERATIONS3
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
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) of VOC
per vehicle per hour
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)
732
(1611)
10
(22)
243
(534)
87
(192)
NA
NA
673
(1480)
719
(1581)
267
(588)
All nonme thane 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.
Cl T
c2
Where: E
C2
S
Example:
SceT
emission factor for VOC, mass per vehicle (Ib/vehicle)
(exclusive of any addon control devices)
area coated per vehicle (ft2/vehicle)
« conversion factor: 1 ft/12,000 mil
thickness of the dry coating film (mil)
= VOC (organic solvent) content of coating as applied, less water
(Ib VOC/ gal coating, less water)
* conversion factor: 7.48 gallons/ft3
= solids in coating as applied, volume fraction (gal solids/gal
coating)
transfer efficiency fraction (fraction of total coating solids
used which remains on coated parts)
The VOC emissions per automobile from a cathodic electrodeposited
prime coat.
E mass of VOC
v
(850 ft2)(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.
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 4.2.2.8-1. 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
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4.2.2.8-7
-------
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 Surface 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/m2,
or 0.011 lb/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 lb/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
-------
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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.
1 r -| 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
Nonmethane VOC'
Emission Points
Drying Oven Exhaust
Fugitives0
Product Retention
Control Device6
Total Emissions
Uncontrolled
kg/kg
(Ib/lb)
0.30-0.95
0.01-0.15
0.01-0.05
1.0
85Z Control
kg/kg
(Ib/lb)
0.01-0.095
0.01-0.05
0.045
0.15
90% Control
kg/kg
(Ib/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.
References 1, 6-7, 9. Dryer exhaust emissions depend on coating line
operating speed, frequency of line downtime, coating composition and
oven design.
l)etermined 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 63. Solvent in the product eventually evaporates into
the atmosphere.
References 1, 10, 17-18. 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 35%
control, capture efficiency is 90% with a 95% efficient control device.
For 90% 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 and 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.
4.2.2.9-8 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-'-"^ _ 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
-------
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4.2.2.10-2
EMISSION FACTORS
8/82
-------
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 COATINGa
EMISSION FACTOR RATING: C
Coatings
Solventborne
uncontrolled
controlled
Waterborne
kg/hr (Ib/hr)
Average
303
(669)
30
( 67)
50
(111)
Normal
50 -
(110 -
5 -
(11 -
3 -
(7 -
range
1,798
3,964)
180
396)
337
743)
kg/m2 (lb/ft2)
Average
0.060
(0.012)
0.0060
(0.0012)
0.0108
(0.0021)
Normal
0.027
(0.006
0.0027
(0.0006
0.0011
(0.0003
range
- 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)
E =
0.623 ATVD
where
E = mass of VOC emissions per hour (Ib/hr)
A = Area of metal coated per hour (ft2)
= 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)
M
where
M = mass of VOC emissions per unit area coated.
bComputed 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
density
(Ib/gal)
7.36
7.36
7.36
Waterborne coatings
Small 200 1.67
Medium 300 3
Large 500 4
0.0018
0.0018
0.0018
0.02
0.10
0.15
0.50 7.36
0.40 7.36
0.20 7.36
aObtained from Reference 3.
"Average value assumed for emission factor calculations. Actual values should
be used to estimate emissions from individual sources.
°A11 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. gontrol 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 comriunication 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
-------
4.9.2 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 3-4
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 path 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
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EMISSION FACTORS
4/81
-------
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-450/3-80-03la, 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: Graphic
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 Containing Volatile 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
-------
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EMISSION FACTORS
4/81
-------
4.11 TEXTILE FABRIC PRINTING
1-2
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
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8/82
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Evaporation Loss Sources
4.11-3
-------
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
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 (%)
a.
References 2,4.
0.778 - 0.805
0.83 - 0.95 cP
41 - 45° C
43 - 62° C
32 - 45
(105 - 113° F)
(110 - 144° F)
157 - 166° C (315 - 330° F)
168 - 178° C (334 - 348° F)
199 - 201° C (390 - 394° F)
Total saturates
Total aromatics
GS and higher
81.5
7.7
7.5
- 92.3
-18.5
- 18.5
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 4.11-1 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 development1, 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
-------
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4.11-6
EMISSION FACTORS
8/82
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Evaporation Loss Sources
4.11-7
-------
(a function of pattern coverage and fabric weight), arid 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)/1,000 kg
(Ib) fabric 0 - 348C I42d 0 - 945° 23d 51 - 191C 79e
Mg(ton)/yr/print
line0
130°
(139)
29C
(31)
29C
(31)
aTransfer printing, carpet printing, and printing of vinyl
coated cloth are specifically excluded from this
compilation.
bplat 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 DG-1P, 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-C1(77)-1, Bureau of the Census, U.S.
Department of Commerce, Washington, DC, August 1978.
4.11-10 EMISSION FACTORS
-------
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 (Na2C03 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
Q / Q O
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, arid 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 (802) arise from calciners fired
with coal, but reaction of the evolved S(>2 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
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TABLE 5.16-1.
UNCONTROLLED EMISSION FACTORS FOR NATURAL PROCESS
SODIUM CARBONATE PLANTS3
EMISSION FACTOR RATING: B
Source
Particulate emissions
Gas fired calciner .
Coal fired calciner
Rotary steam tube dryer
Fluid bed steam tube dryer ,
Rotary steam heater predryer
Rotary gas fired bleacher
kg/Mg
184.0
195.0
33.0
73.0
1.0
155.0
Ib/ton
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
feed.
"Factor is in kg/Mg (Ib/ton) of dry product from dryer.
a Factor is in kg/Mg (Ib/ton) of dry NaHC03 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) PLANT3
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. Sodium 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
-------
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
-------
uncontrolled emission factor for SC>2 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 862 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 SO2 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
o
.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
-------
99.92
10,000
SULFUR CONVERSION, % feedstock sulfur
99.7 99.0
1.5
2.5 3
40 50 60 70 80 90100
4 5 6 7 8 9 10 15 20 25 30
SOzEMISSlONS, Ib/ton of 100% H2S04 produced
Figure 5.17-3. Sulfuric acid plant feedstock sulfur conversion versus volumetric and
mass SC>2 emissions at various inlet SC>2 concentrations by volume.
5.17-6
EMISSION FACTORS
4/81
-------
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 (HjSO^ 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
-------
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EMISSION FACTORS
8/82
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Chemical Process Industry
5.20-3
-------
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
Q
Monomer recovery, uncontrolled 2.6
Absorber vent , 0.26
Blend/coagulation tank, uncontrolled 0.42
Dryers6 2.51
5.2
0.52
0.84
5.02
Emulsion Latex
Monomer removal f
Condenser vent
Blend tanks
Uncontrolled
8.45
0.1
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
-------
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 ingocs 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
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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 4 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.1
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.
8/82 Metallurgical Industry 7.15-3
-------
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
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 air:cloth 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).
cBased 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.
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, PA, EPA-77-BAT-5. U.S. Environmental Protection Agency,
Research Triangle Park, NC, 1977.
8/82 Metallurgical Industry 7.15-5
-------
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 concentrates 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 8.23-1
-------
Ore From Mines
Primary
Crushers
Storage
Bin(s)
Storage
Bin(s)
Secondary
Crushers
Grinders
Product
Loadout
Dryers
Beneficiation
T
Figure 8.23-1.
Tailings
A metallic mineral processing plant.
3.23-1 are for the process operations as
Ss
the above equipment.
product recovery cyclones. Gnnders
ided for wet grinders,
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
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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 lOum
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 Journal, 1.81(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, ^81(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 Dressing, McGraw-Hill, New
York, 1940.
7. "Modern Mineral Processing: Air and Water Pollution Controls",
Engineering and Mining Journal, 181(6);156-171, June 1.980.
8. W. E. Horst and R. C. Enochs, "Modern Mineral Processing: Instru-
mentation and Process Control", Engineering and Mining Journal,
18H6):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
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
AP-42, Supplement 13
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Supplement 13 for Compilation of Air Pollutant
Emission Factors, AP-42
5. REPORT DATE
1982
Augus t
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Monitoring and Data Analysis Division
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
U.S. Environmental Protection Agency
Office of Air, Noise and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. 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
In this Supplement for AP-42, new or revised emissions data are presented for
Bituminous and Subbituminous Coal Combustion; Fuel Oil Combustion; Natural Gas
Combustion; Liquefied Petroleum Gas Combustion; Wood Waste Combustion In Boilers;
Lignite Combustion; Stationary Large Bore Diesel and Dual Fuel Engines;
Automobile and Light Duty Truck Surface Coating; Pressure Sensitive Tapes and
Labels; Metal Coil Surface Coating; Textile Fabric Printing; Sodium Carbonate;
Emulsion Styrene-Butadiene Copolymers; Storage Battery Production; and Metallic
Minerals Processing.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Fuel Combustion
Emissions
Emission Factors
Stationary Sources
18. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (This Report)
21. NO. OF PAGES
128
20. SECURITY CLASS (This page)
22. PRICE
J
EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION is OBSOLETE
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