United States
Bwironmental Protection
Agency
AIR
CXI tee of Air Quality
Planning And Standards
Research Triangle Park, NC 27711
B3A-454/R-98-011
• June 1998
EPA
LOCATING AND ESTIMATING
AIR EMISSIONS FROM
SOURCES OF BENZENE
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Disclaimer
This report has been reviewed by the Office of Air Quality Planning and Standards, U.S.
Environmental Protection Agency, and has been approved for publication. Mention of trade
names and commercial products does not constitute endorsement or recommendation of use.
EPA-454/R-98-011
u'"~*>. U.
11
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TABLE OF CONTENTS
v/'
r-,
C Section P-2ge
r1'-,
£ LIST OF TABLES x
•*»»
^ LIST OF FIGURES xvi
EXECUTIVE SUMMARY xx
1.0 PURPOSE OF DOCUMENT 1-1
2.0 OVERVIEW OF DOCUMENT CONTENTS 2-1
3.0 BACKGROUND INFORMATION 3-1
3.1 NATURE OF POLLUTANT 3-1
3.2 OVERVIEW OF PRODUCTION AND USE 3-4
3.3 OVERVIEW OF EMISSIONS 3-8
4.0 EMISSIONS FROM BENZENE PRODUCTION 4-1
4.1 CATALYTIC REFORMING/SEPARATION PROCESS 4-7
4.1.1 Process Description for Catalytic Reforming/Separation 4-7
4.1.2 Benzene Emissions from Catalytic Reforming/Separation 4-9
4.2 TOLUENE DEALKYLATION AND TOLUENE
DISPROPORTIONATION PROCESS 4-11
4.2.1 Toluene Dealkylation 4-12
4.2.2 Toluene Disproportionation 4-13
4.3 ETHYLENE PRODUCTION 4-16
4.3.1 Process Description 4-16
4.3.2 Benzene Emissions from Ethylene Plants and Benzene Recovery
from Pyrolysis Gasoline 4-32
4.4 COKE OVEN AND COKE BY-PRODUCT RECOVERY PLANTS . . . 4-36
4.4.1 Process Description 4-36
4.4.2 Benzene Emissions 4-46
111
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TABLE OF CONTENTS, continued
Section page
4.5 METHODS FOR ESTIMATING BENZENE EMISSIONS FROM
EMISSION SOURCES ; 4-61
4.5.1 Process Vent Emissions, Controls, and Regulations 4-62
4.5.2 Equipment Leak Emissions, Controls, and Regulations 4-70
4.5.3 Storage Tank Emissions, Controls, and Regulations 4-77
4.5.4 Wastewater Collection and Treatment System Emissions,
Controls, and Regulations 4-82
4.5.5 Product Loading and Transport Operations Emissions, Controls,
and Regulations 4-85
5.0 EMISSIONS FROM MAJOR USES OF BENZENE 5-1
5.1 ETHYLBENZENE AND STYRENE PRODUCTION 5-2
5.1.1 Process Description for Ethylbenzene and Styrene Production
Using Benzene Alkylation and Ethylbenzene Dehydrogenation .... 5-3
5.1.2 Process Description for Ethylbenzene Production from Mixed
Xylenes 5-9
5.1.3 Process Description for Styrene Production from Ethylbenzene
Hydroperoxidation 5-10
5.1.4 Process Description for Styrene Production by an Isothermal
Process 5-12
5.1.5 Benzene Emissions from Ethylbenzene and Styrene Production
via Alkylation and Dehydrogenation 5-14
5.1.6 Control Technology for Ethylbenzene/Styrene Processes 5-19
5.2 CYCLOHEXANE PRODUCTION 5-20
5.2.1 Process Description for Cyclohexane Production via Benzene
Hydrogenation 5-21
5.22 Benzene Emissions from Cyclohexane Production via Benzene
Hydrogenation 5-23
5.2.3 Process Description for Cyclohexane Production via Separation
of Petroleum Fractions 5-24
5.2.4 Benzene Emissions from Cyclohexane Production via Separation
of Petroleum Fractions 5-26
5.3 CUMENE PRODUCTION 5-26
5.3.1 Process Descriptions for Cumene Production by Alkylating
Benzene with Propylene 5-27
5.3.2 Benzene Emissions From Cumene Production 5-34
IV
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TABLE OF CONTENTS, continued
Section P-Sg£
5.4 PHENOL PRODUCTION 5-35
5.4.1 Phenol Production Techniques 5-39
5.4.2 Benzene Emissions from Phenol Production 5-47
5.5 NITROBENZENE PRODUCTION 5-49
5.5.1 Process Descriptions for Continuous Nitration 5-49
5.5.2 Benzene Emissions from Nitrobenzene Production ." 5-53
5.6 ANILINE PRODUCTION 5-58
5.6.1 Process Descriptions for Aniline Production for Nitrobenzene ... 5-58
5.6.2 Benzene Emissions from Aniline Production 5-61
5.7 CHLOROBENZENE PRODUCTION 5-62
5.7.1 Process Description for Chlorobenzene Production by Direct
Chlorination of Benzene 5-62
5.7.2 Benzene Emissions from Chlorobenzene Production 5-67
5.8 LINEAR ALKYLBENZENE PRODUCTION 5-70
5.8.1 Process Description for Production of LAB Using the Olefin
Process 5-70
5.8.2 Benzene Emissions from LAB Production Using the Olefin
Process 5-74
5.8.3 Process Description for Production of LAB Using the
Chlorination Process 5-74
5.8.4 Benzene Emissions from LAB Production Using the Chlorination
Process 5-78
5.9 OTHER ORGANIC CHEMICAL PRODUCTION 5-80
5 9 ! Hydroquinone 5-80
5.9.2 Benzophenone 5-81
5.9.3 Benzene Sulfonic Acid 5-81
5.9.4 Resorcinol 5-81
5.9.5 Biphenyl 5-82
5.9.6 Anthraquinone 5-82
5.10 BENZENE USE AS A SOLVENT ; 5-82
6.0 EMISSIONS FROM OTHER SOURCES 6-1
6.1 OIL AND GAS WELLHEADS 6-1
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TABLE OF CONTENTS, continued
Section Page
6.1.1 Description of Oil and Gas Wellheads 6-1
6.1.2 Benzene Emissions from Oil and Gas Wellheads 6-2
6.2 GLYCOL DEHYDRATION UNITS 6-4
6.2.1 Process Description for Glycol Dehydration Units 6-5
6.2.2 Benzene Emissions from Glycol Dehydration Units 6-8
6.2.3 Controls and Regulatory Analysis 6-13
6.3 PETROLEUM REFINERY PROCESSES 6-14
6.3.1 Description of Petroleum Refineries 6-14
6.3.2 Benzene Emissions from Petroleum Refinery Processes and
Operations 6-17
6.3.3 Controls and Regulatory Analysis 6-28
6.4 GASOLINE MARKETING 6-31
6.4.1 Benzene Emissions from Loading Marine Vessels 6-34
6.4.2 Benzene Emissions from Bulk Gasoline Plants and Bulk Gasoline
Terminals 6-37
6.4.3 Benzene Emissions from Service Stations 6-46
6.4.4 Control Technology for Marine Vessel Loading 6-49
6.4.5 Control Technology for Gasoline Transfer 6-53
6.4.6 Control Technology for Gasoline Storage 6-53
6.4.7 Control Technology for Vehicle Refueling Emissions 6-56
6.4.8 Regulatory Analysis 6-58
6.5 PUBLICLY OWNED TREATMENT WORKS 6-59
6.5.1 Process Description of POTWs 6-59
6.5.2 Benzene Emissions From POTWs 6-68
6.5.3 Control Technologies for POTWs 6-69
6.5.4 Regulatory Analysis 6-72
6.6 MUNICIPAL SOLID WASTE LANDFILLS 6-72
6.6.1 Process Description of MSW Landfills 6-73
6.6.2 Benzene Emissions from MSW Landfills 6-74
6.6.3 Control Technologies for MSW Landfills 6-80
6.6.4 Regulatory Analysis 6-81
6.7 PULP, PAPER, AND PAPERBOARD INDUSTRY 6-81
6.7.1 Process Description for Pulp, Paper, and Paperboard Making
Processes 6-82
6.7.2 Benzene Emissions from Pulp, Paper and Papermaking Processes 6-91
. vi
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TABLE OF CONTENTS, continued
Section Page
6.8 SYNTHETIC GRAPHITE MANUFACTURING 6-93
6.8.1 Process Description for Synthetic Graphite Production 6-94
6.8.2 Benzene Emissions from Synthetic Graphite Production 6-97
6.8.3 Control Technologies for Synthetic Graphite Production 6-99
6.9 CARBON BLACK MANUFACTURE 6-99
6.9.1 Process Description for Carbon Black Manufacture 6-101
6.9.2 Benzene Emissions from Carbon Black Manufacture 6-104
6.10 RAYON-BASED CARBON FIBER MANUFACTURE 6-105
6.10.1 Process Description for the Rayon-Based Carbon Fiber
Manufacturing Industry 6-106
6.10.2 Benzene Emissions from the Rayon-Based Carbon Fiber
Manufacturing Industry 6-107
6.10.3 Controls and Regulatory Analysis 6-107
6.11 ALUMINUM CASTING 6-107
6.11.1 Process Description for Aluminum Casting Facilities 6-107
6.11.2 Benzene Emissions From Aluminum Metal Casting 6-111
6.11.3 Control Technologies for Aluminum Casting Operations 6-112
6.12 ASPHALT ROOFING MANUFACTURING 6-112
6.12.1 Process Description 6-114
6.12.2 Benzene Emissions from Asphalt Roofing Manufacture 6-127
6.13 CONSUMER PRODUCTS/BUILDING SUPPLIES 6-129
7.0 EMISSIONS FROM COMBUSTION SOURCES 7-1
7.1 MEDICAL WASTE INCINERATORS 7-1
7.1.1 Process Description: Medical Waste Incinerators 7-2
7.1.2 Benzene Emissions From Medical Waste Incinerators 7-7
7.1.3 Control Technologies for Medical Waste Incinerators 7-7
7.1.4 Regulatory Analysis 7-9
7.2 SEWAGE SLUDGE INCINERATORS 7-10
7.2.1 Process Description: Sewage Sludge Incinerators 7-11
7.2.2 Benzene Emissions from Sewage Sludge Incineration 7-19
7.2.3 Control Technologies for Sewage Sludge Incinerators 7-19
7.2.4 Regulatory Analysis 7-25
vn
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TABLE OF CONTENTS, continued
Section Page
7.3 HAZARDOUS WASTE INCINERATION 7-25
7.3.1 Process Description: Incineration 7-26
7.3.2 Industrial Kilns, Boilers, and Furnaces 7-36
7.3.3 Benzene Emissions From Hazardous Waste Incineration 7-37
7.3.4 Control Technologies for Hazardous Waste Incineration 7-37
7.3.5 Regulatory Analysis 7-39
7.4 EXTERNAL COMBUSTION OF SOLID, LIQUID, AND GASEOUS
FUELS IN STATIONARY SOURCES FOR HEAT AND POWER
GENERATION 7-40
7.4.1 Utility Sector 7-40
7.4.2 Industrial/Commercial Sector 7-51
7.4.3 Residential Sector 7-59
7.5 STATIONARY INTERNAL COMBUSTION 7-67
7.5.1 Reciprocating Engines 7-67
7.5.2 Gas Turbines 7-74
7.6 SECONDARY LEAD SMELTING 7-79
7.6.1 Process Description 7-79
7.6.2 Benzene Emissions From Secondary Lead Smelters 7-91
7.6.3 Control Technologies for Secondary Lead Smelters 7-95
7.7 IRON AND STEEL FOUNDRIES 7-95
7.7.1 Process Description for Iron and Steel Foundries 7-97
7.7.2 Benzene Emissions From Iron and Steel Foundries 7-100
7.7.3 Control Technologies for Iron and Steel Foundries 7-102
7.8 PORTLAND CEMENT PRODUCTION 7-103
7.8.1 Process Description for me Portland Cement Industry 7-104
7.8.2 Benzene Emissions from the Portland Cement Industry and
Regulatory Analysis 7-107
7.9 HOT-MIX ASPHALT PRODUCTION 7-110
7.9.1 Process Description : ... 7-110
7.9.2 Benzene Emissions from the Hot-Mix Asphalt Production 7-119
7.10 OPEN BURNING OF BIOMASS, SCRAP TIRES, AND
AGRICULTURAL PLASTIC FILM 7-121
7.10.1 Biomass Burning 7-121
7.10.2 Tire Burning 7-125
7.10.3 Agricultural Plastic Film Burning 7-129
viii
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TABLE OF CONTENTS, continued
Section
8.0 BENZENE EMISSIONS FROM MOBILE SOURCES 8-1
8.1 ON-ROAD MOBILE SOURCES 8-2
8.2 OFF-ROAD MOBILE SOURCES 8-5
8.3 MARINE VESSELS 8-10
8.4 LOCOMOTIVES 8-13
8.5 AIRCRAFT 8-14
8.6 ROCKET ENGINES 8-15
9.0 SOURCE TEST PROCEDURES 9-1
9.1 EPA METHOD 0030 9-2
9.2 EPA METHODS 5040/5041 9-4
9.3 EPA METHOD 18 9-5
9.4 EPA METHOD TO-1 9-8
9.5 EPA METHOD TO-2 9-9
9.6 EPA METHOD TO-14 9-14
9.7 FEDERAL TEST PROCEDURE (FTP) 9-16
9.8 AUTO/OIL AIR QUALITY IMPROVEMENT RESEARCH
PROGRAM SPECIATION METHOD 9-18
10.0 REFERENCES 10-1
APPENDICES
Appendix A Summary of Emission Factors
Appendix B United States Petroleum Refineries: Location by State
ix
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LIST OF TABLES
Table Eag£
3-1 Chemical Identification of Benzene 3-2
3-2 Physical and Chemical Properties of Benzene 3-3
4-1 Benzene Production Facilities 4-2
4-2 Ethylene Producers - Location and Capacity 4-17
4-3 Stream Designations for Figure 4-5, Production of Ethylene from Naphtha
and/or Gas-oil Feeds 4-24
4-4 Benzene Emission Factors for a Hypothetical Ethylene Plant 4-33
4-5 Coke Oven Batteries Currently Operating hi the United States 4-38
4-6 Summary of Benzene Emission Factors for Furnace and Foundry Coke
By-product Recovery Plants 4-51
4-7 Summary of Benzene Emission Factors for Equipment Leaks at Furnace Coke
By-product Recovery Plants 4-54
4-8 Summary of Benzene Emission Factors for Equipment Leaks at Foundry Coke
By-product Recovery Plants 4-56
4-9 Techniques to Control Benzene Emissions from Equipment Leaks Required by
the Benzene NESHAP for Coke By-product Control Recovery Plants 4-61
4-10 Control Technologies that Form the Basis of Ah-Pollution Control Standards .. 4-63
4-11 Other Control Technologies that Can be Used to Meet Standards 4-64
4-12 Comparison of VOC Control Technologies 4-68
4-13 SOCMI Average Total Organic Compound Emission Factors for Equipment
Leak Emissions 4-72
4-14 Refinery Average Emission Factors 4-73
4-15 Marketing Terminal Average Emission Factors 4-74
4-16 Oil and Gas Production Operations Average Emission Factors 4-75
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LIST OF TABLES, continued
Table Page
4-17 SOCMI Screening Value Range Total Organic Compound Emission Factors for
Equipment Leak Emissions 4-76
4-18 Refinery Screening Ranges Emission Factors 4-77
4-19 Marketing Terminal Screening Ranges Emission Factors 4-78
4-20 Oil and Gas Production Operations Screening Ranges Emission Factors 4-79
4-21 Control Techniques and Efficiencies Applicable to Equipment Leak Emissions . . 4-80
5-1 U.S. Producers of Ethylbenzene and Styrene 5-4
5-2 Emission Factors for Ethylbenzene/Styrene Production via Alkylation and
Dehydrogenation 5-15
5-3 U.S. Producers of Cyclohexane 5-21
5-4 U.S. Producers of Cumene 5-27
5-5 Summary of Emission Factors for Cumene Production at One Facility Using the
Aluminum Chloride Catalyst 5-36
5-6 U.S. Producers of Phenol 5-37
5-7 Summary of Emission Factors for Phenol Production by die Peroxidation of
Cumene 5-48
5-8 U.S. Producers of Nitrobenzene 5-50
5-9 Summary of Emission Factors for Hypothetical Nitrobenzene Production Plants . 5-54
5-10 U.S. Producers of Aniline 5-59
5-11 U.S. Producers of Mono-, Di-, and Trichlorobenzene 5-63
5-12 Emission Factors for Chlorobenzene Production by Direct Chlorination of
Benzene 5-68
5-13 U.S. Producers of Linear Alkylbenzene (Detergent Alkylates) 5-71
XI
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LIST OF TABLES, continued
Table
5-14 Summary of Emission Factors for Hypothetical Linear Alkylbenzene Plant
Using the Olefin Process .................. ................... 5-75
5-15 Summary of Emission Factors for Hypothetical Linear Alkylbenzene Plant
Using the Chlorination Process ................................. 5-79
5-16 Partial List of Manufacturers in Source Categories where Benzene Is Used as a
Solvent ................................................ 5-84
5-17 U.S. Producers of Ethanol or Isopropanol .......................... 5-86
5-18 U.S. Producers of Caprolactam ................................ 5-89
5-19 Summary of Emission Factors for Benzene Use as a Solvent .............. 5-90
6-1 Benzene and Total Hydrocarbons Equipment Leak Emission Factors for Oil
Wellhead Assemblies ........................................ 6-3
6-2 Glycol Dehydration Unit Population Data ................ . .......... 6-6
6-3 Reactive Organic Compounds (ROCs) and BTEX Emission Factors for Glycol
Dehydration Units .......................................... 6-9
6-4 Glycol Dehydration Emission Program Inputs and Outputs ............... 6-12
6-5 Potential Sources of Benzene Emissions at Petroleum Refineries ........... 6-18
6-6 Concentration of Benzene in Refinery Process Unit Streams .............. 6-19
6-7 Concentration of Benzene in Refinery Products ...................... 6-20
6-8 Median Component Counts for Process Units from Small Refineries ........ 6-22
6-9 Median Component Counts for Process Units from Large Refineries ........ 6-23
6-10 Model Process Unit Characteristics for Petroleum Refinery Wastewater ...... 6-25
6-11 Wastewater Emission Factors for Petroleum Refineries ................. 6-27
6-12 Uncontrolled Volatile Organic Compound and Benzene Emission Factors for
Loading, Ballasting, and Transit Losses from Marine Vessels ............. 6-35
xn
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LIST OF TABLES, continued
Table Page
6-13 Uncontrolled Total Organic Compound Emission Factors for Petroleum Marine
Vessel Sources 6-36
6-14 Benzene Emission Factors for Gasoline Loading Racks at Bulk Terminals and
Bulk Plaints 6-38
6-15 Benzene Emission Factors for Storage Losses at a Typical Gasoline Bulk
Terminal 6-41
6-16 Gasoline Vapor and Benzene Emission Factors for a Typical Bulk Plant 6-43
6-17 Benzene Emission Factors for Storage Losses at a Typical Pipeline Breakout Station 6-44
6-18 Gasoline Vapor and Benzene Emission Factors for a Typical Service Station . . . 6-48
6-19 RVP Limits by Geographic Location 6-50
6-20 Seasonal Variation for Temperature Difference between Dispensed Fuel and
Vehicle Fuel Tank 6-52
6-21 Monthly Average Dispensed Liquid Temperature 6-52
6-22 Summary of Benzene Emission Factors for POTWs 6-70
6-23 Summary of Uncontrolled Emission Concentrations of Benzene from Landfills . . 6-77
6-24 Controlled Benzene Emission Factor for Landfills 6-81
6-25 Distribution of Kraft Pulp Mills in the United States (1993^ .. .... 6-83
6-26 List of Common Potential Emission Points within the Kraft Pulp and
Papermaking Process 6-84
6-27 Emission Factors for Synthetic Graphite Production 6-98
6-28 Locations and Annual Capacities of Carbon Black Producers hi 1994 6-100
6-29 Stream Codes for the Oil-Furnace Process Illustrated in Figure 6-10 6-103
6-30 Typical Operating Conditions for Carbon Black Manufacture (High Abrasion
Furnace) 6-105
xin
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LIST OF TABLES, continued
Table
6-31 Emission Factor for Carbon Black Manufacture 6-105
6-32 Rayon-based Carbon Fiber Manufacturers 6-106
6-33 Emission Factor for Rayon-based Carbon Manufacture 6-108
6-34 Emission Factors for Aluminum Casting 6-113
6-35 Asphalt Roofing Manufacturers 6-115
»
6-36 Emission Factor for Asphalt Roofing Manufacture 6-128
7-1 Emission Factor for Medical Waste Incineration 7-8
7-2 Summary of Emission Factors for Sewage Sludge Incineration 7-20
7-3 Summary of Emission Factors for One Sewage Sludge Incineration Facility
Utilizing a Multiple Hearth Furnace 7-21
7-4 Summary of Benzene Emission Factors for Hazardous Waste Incineration 7-38
7-5 Summary of Benzene Emission Factors for Utility Boilers 7-50
7-6 Summary of Benzene Emission Factors for Industrial and
Commercial/Institutional Boilers 7-57
7-7 Summary of Benzene Emission Factors for Residential Woodstoves 7-66
7-8 Summary of Benzene Emission Factors for Reciprocating Engines 7-73
7-9 Summary of Benzene Emission Factors for Gas Turbines 7-77
7-10 U.S. Secondary Lead Smelters 7-80
7-11 Summary of Benzene Emission Factors for Secondary Lead Smelting 7-94
7-12 Benzene Emission Factor for Iron Foundries 7-101
7-13 Summary of Portland Cement Plant Capacity Information 7-105
7-14 Summary of Emission Factors for the Portland Cement Industry 7-109
xiv
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LIST OF TABLES, continued
Table Page
7-15 Emission Factors for Hot-Mix Asphalt Manufacture 7-120
7-16 Summary of Benzene Emission Factors for Biomass Burning 7-124
7-17 Summary of Benzene Emission Factors for Biomass Burning by Fuel Type .... 7-126
7-18 Summary of Benzene Emission Factors for Open Burning of Tires 7-128
7-19 Summary of Benzene Emission Factors for Open Burning of Agricultural Plastic
Film 7-130
8-1 Benzene Emission Factors for 1990 Taking into Consideration Vehicle Aging . . . 8-4
8-2 Off-road Equipment Types and Hydrocarbon Emission Factors Included in the
NEVES 8-6
8-3 Weight Percent Factors for Benzene : . 8-11
8-4 Benzene Emission Factors for Commercial Marine Vessels 8-12
8-5 Benzene Emission Factors for Locomotives 8-13
8-6 Benzene Content in Aircraft Landing and Takeoff Emissions 8-14
8-7 Emission Factors for Rocket Engines 8-16
xv
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LIST OF FIGURES
Figure Eag£
3-1 Production and Use Tree for Benzene 3-7
4-1 Universal Oil Products Platforming (Reforming) Process 4-8
4-2 Flow Diagram of a Glycol BTX Unit Process 4-10
4-3 Process Flow Diagram of a Toluene Dealkylation Unit 4-14
4-4 Toluene Disproportionation Process Flow Diagram (Tatory Process) 4-15
4-5 Process Flow Diagram for Ethylene Production from Naphtha and/or Gas-Oil
Feeds 4-22
4-6 Production of BTX by Hydrogenation of Pyrolysis Gasoline 4-31
4-7 Coke Oven By-Product Recovery, Representative Plant 4-41
4-8 Litol Process Flow Diagram 4-45
5-1 Basic Operations that May be used in the Production of Ethylbenzene by
Benzene Alkylation with Ethylene 5-6
5-2 Basic Operations that May be used in the Production of Styrene by Ethylbenzene
Dehydrogenation 5-8
5-3 Ethylbenzene Hydroperoxidation Process Block Diagram 5-11
5-4 Isothermal Processing of Styrene 5-13
5-5 Process Flow Diagram for Cyclohexane Production using the Benzene
Hydrogenation Process 5-22
5-6 Process Flow Diagram for Cyclohexane from Petroleum Fractions 5-25
5-7 Process for the Manufacture of Cumene Using Solid Phosphoric Acid Catalyst . . 5-29
5-8 Process for the Manufacture of Cumene Using Aluminum Chloride Catalyst ... 5-31
5-9 Flow Diagram for Phenol Production from Cumene Using the Allied Process . . 5-40
5-10 Flow Diagram for Phenol Production Using the Hercules Process 5-44
xvi
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LIST OF FIGURES, continued
Figure Page
5-11 Process Flow Diagram for Manufacture of Nitrobenzene 5-51
5-12 Flow Diagram for Manufacture of Aniline 5-60
5-13 Monochlorobenzene Continuous Production Process Diagram 5-64
5-14 Dichlorobenzene and Trichlorobenzene Continuous Production Diagram 5-66
5-15 Linear Alkylbenzene Production Using the Olefln Process . 5-73
5-16 Production of Linear Alkylbenzenes Via Chlorination 5-76
6-1 Flow Diagram for Glycol Dehydration Unit 6-7
6-2 Process Flow Diagram for a Model Petroleum Refinery 6-16
6-3 The Gasoline Marketing Distribution System in the United States 6-32
6-4 Bulk Plant Vapor Balance System (Stage I) 6-54
6-5 Service Station Vapor Balance System 6-55
6-6 Process Flow Diagram for a Typical POTW 6-61
6-7 Typical Kraft Pulp-Making Process with Chemical Recovery 6-85
6-8 Typical Down-flow Bleach Tower and Washer 6-92
6-9 Process Flow Diagram for Manufacture of Synthetic Graphite 6-95
6-10 Process Flow Diagram for an Oil-furnace Carbon Black Plant 6-102
6-11 Flow Diagram of a Typical Aluminum Casting Facility 6-109
6-12 Asphalt Blowing Process Flow Diagram 6-119
6-13 Asphalt-Saturated Felt Manufacturing Process 6-122
6-14 Organic Shingle and Roll Manufacturing Process Flow Diagram 6-123
. xvu
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LIST OF FIGURES, continued
Figure Cage
7-1 Controlled-Air Incinerator 7-3
7-2 Excess-Air Incinerator 7-5
7-3 Cross Section of a Multiple Hearth Furnace 7-12
7-4 Cross Section of a Fluidized Bed Furnace 7-14
7-5 Cross Section of an Electric Infrared Furnace 7-17
7-6 Venturi/Impingement Tray Scrubber 7-23
7-7 General Orientation of Hazardous Waste Incineration Subsystems and Typical
Component Options 7-27
7-8 Typical Liquid Injection Combustion Chamber 7-30
7-9 Typical Rotary Kiln/Afterburner Combustion Chamber 7-32
7-10 Typical Fixed Hearth Combustion Chamber 7-33
7-11 Simplified Boiler Schmatic 7-42
7-12 Single Wall-fired Boiler 7-44
7-13 Cyclone Burner 7-46
7-14 Simplified Atmospheric Fluidized Bed Combustor Process Flow Diagram 7-47
7-15 Spreader Type Stoker-fired Boiler - Continuous Ash Discharge Grate 7-48
7-16 Basic Operation of Reciprocating Internal Combustion Engines 7-69
7-17 Gas Turbine Engine Configuration 7-75
7-18 Simplified Process Flow Diagram for Secondary Lead Smelting 7-81
7-19 Cross-sectional View of a Typical Stationary Reverberatory Furnace 7-84
7-20 Cross Section of a Typical Blast Furnace 7-86
xvm
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LIST OF FIGURES, continued
Figure Page
7-21 Side-View of a Typical Rotary Reverbatory Furnace 7-89
7-22 Cross-sectional View of an Electric Furnace for Processing Slag 7-92
7-23 Process Flow Diagram for a Typical Sand-Cast Iron and Steel Foundry 7-98
7-24 Emission Points in a Typical Iron Foundry and Steel Foundry 7-99
7-25 Process Diagram of Portland Cement Manufacture by Dry Process with
Preheater 7-108
7-26 General Process Flow Diagram for Batch Mix Asphalt Paving Plants 7-113
7-27 General Process Flow Diagram for Drum Mix Asphalt Paving Plants 7-116
7-28 General Process Flow Diagram for Counter Flow Drum Mix Asphalt Paving
Plants 7-117
9-1 Volatile Organic Sampling Train (VOST) 9-3
9-2 Trap Desorption/Analysis Using EPA Methods 5040/5041 9-6
9-3 Integrated Bag Sampling Train 9-7
9-4 Block Diagram of Analytical System for EPA Method TO-1 9-10
9-5 Typical Tenax® Cartridge 9-11
9-b Carbon Molecular Sieve Trap (CMS) Construction 9-12
9-7 GC/MS Analysis System for CMS Cartridges 9-13
9-8 Sampler Configuration for EPA Method TO-14 9-15
9-9 Vehicle Exhaust Gas Sampling System 9-17
xix
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EXECUTIVE SUMMARY
The 1990 Clean Air Act Amendments contain a list of 188 hazardous air
pollutants (HAPs) which the U.S. Environmental Protection Agency must study, identify
sources of, and determine if regulations are warranted. One of these HAPs, benzene, is the
subject of this document. This document describes the properties of benzene as an air
pollutant, defines its production and use patterns, identifies source categories of air emissions,
and provides benzene emission factors. The document is a part of an ongoing EPA series
designed to assist the general public at large, but primarily State/local air agencies, in
identifying sources of HAPs and developing emissions estimates.
Benzene is primarily used in the manufacture of other organic chemicals,
including ethylbenzene/styrene, cumene/phenol, cyclohexane, and nitrobenzene/aniline.
Benzene is emitted into the atmosphere from its production, its use as a chemical feedstock in
the production of other chemicals, the use of those other chemicals, and from fossil fuel and
biomass combustion. Benzene is also emitted from a wide variety of miscellaneous sources
including oil and gas wellheads, glycol dehydrators, petroleum refining, gasoline marketing,
wastewater treatment, landfills, pulp and paper mills, and from mobile sources.
In addition to identifying sources of benzene emissions, information is provided
that specifies how individual, sources of benzene may be tested to quantify air emissions.
xx
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SECTION 1.0
PURPOSE OF DOCUMENT
The U.S. Environmental Protection Agency (EPA), State, and local air pollution
control agencies are becoming increasingly aware of the presence of substances in the ambient
air that may be toxic at certain concentrations. This awareness, in turn, has led to attempts to
identify source/receptor relationships for these substances and to develop control programs to
regulate emissions. Unfortunately, limited information is available on the ambient air
concentrations of these substances or about the sources that may be discharging them to the
atmosphere.
To assist groups interested in inventorying air emissions of various potentially
toxic substances, EPA is preparing a series of locating and estimating (L&E) documents such
as this one that compiles available information on sources and emissions of these substances.
Other documents in the series are listed below:
Substance EPA Publication Number
Acrylonitrile EPA-450/4-84-007a
Arsenic (Document under revision)
Butadiene EPA-454/R-96-008
Cadmium EPA-454/R-93-040
Carbon Tetrachloride EPA-450/4-84-007b
Chlorobenzene (update) EPA-454/R-93-044
Chloroform EPA-450/4-84-007c
Chromium (supplement) EPA-450/2-89-002
Chromium EPA-450/4-84-007g
1-1
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Substance
Coal and Oil Combustion Sources
Cyanide Compounds
Dioxins and Furans
Epichlorohydrin
Ethylene Dichloride
Ethylene Oxide
Formaldehyde
Lead
Manganese
Medical Waste Incinerators
Mercury and Mercury Compounds
(under revision)
Methyl Chloroform
Methyl Ethyl Ketone
Methylene Chloride
Municipal Waste Combustors
Nickel
Perchloroethylene and
Trichloroethylene
Phosgene
Polychlorinated Biphenyls (PCBs)
Polycyclic Organic Matter (POM)
Sewage Sludge Incinerators
Styrene
Toluene
Vinylidene Chloride
Xylenes
EPA Publication Number
EPA-450/2-89-001
EPA-454/R-93-041
EPA-454/R-97-003
EPA-450/4-84-007J
EPA-450/4-84-007d
EPA-450/4-84-0071
EPA-450/4-91-012
EPA-454/R-98-006
EPA-450/4-84-007h
EPA-454/R-93-053
EPA-453/R-93-023
EPA-454/R-93-045
EPA-454/R-93-046
EPA-454/R-93-006
EPA-450/2-89-006
EPA-450/4-84-007f
EPA-450/2-89-013
EPA-450/4-84-007i
EPA-450/4-84-007n
EPA-450/4-84-007p
EPA-450/2-90-009
EPA-454/R-93-011
EPA-454/R-93-047
EPA-450/4-84-007k
EPA-454/R-93-048
This document deals specifically with benzene. Its intended audience includes
Federal, State, and local air pollution personnel and others who are interested in locating
potential emitters of benzene and estimating their air emissions.
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Because of the limited availability of data on potential sources of benzene
emissions and the variability in process configurations, control equipment, and operating
procedure among facilities, this document is best used as a primer on (1) types of sources that
may emit benzene, (2) process variations and release points that may be expected, and
(3) available emissions information on the potential for benzene releases into the air. The
'"i
reader is cautioned against using the emissions information in this document to develop an
exact assessment of emissions from any particular facility.
Emission estimates may need to be adjusted to take into consideration
participation in EPA's voluntary emission reduction program or compliance with State or local
regulations.
It is possible, in some cases, that orders-of-magnitude differences may result
between actual and estimated emissions, depending on differences in source configurations,
control equipment, and operating practices. Thus, in all situations where an accurate
assessment of benzene emissions is necessary, the source-specific information should be
obtained to confirm the existence of particular emitting operations and the types and
effectiveness of control measures, and to determine the impact of operating practices. A
source test and/or material balance calculation should be considered as better methods of
determining air emissions from a specific operation.
In addition to the information presented in this document, another potential
source of emissions data for benzene from facilities is the Toxic Chemical Release Inventory
(TRI) form required by Title III, Section 313 of the 1986 Superfund Amendments and
Reauthorization Act (SARA).1 Section 313 requires owners and operators of facilities in
certain Standard Industrial Classification Codes that manufacture, import, process, or
otherwise use toxic chemicals (as listed in Section 313) to report annually their releases of
these chemicals to all environmental media. As part of SARA 313, EPA provides public
access to the annual emissions data.
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The TRI data include general facility information, chemical information, and
emissions data. Air emissions data are reported as total facility release estimates for fugitive
emissions and point source emissions. No individual process or stack data are provided to
EPA under the program. SARA Section 313 requires sources to use available stack monitoring
data for reporting but does not require facilities to perform stack monitoring or other types of
emissions measurement. If monitoring data are unavailable, emissions are to be quantified
based on best estimates of releases to the environment.
The reader is cautioned that TRI will not likely provide facility, emissions, and
chemical release data sufficient for conducting detailed exposure modeling and risk assessment.
In many cases, the TRI data are based on annual estimates of emissions (i.e., on emission
factors, material balance calculations, and engineering judgment). The EPA recommends use
of TRI data in conjunction with the information provided in this document to locate potential
emitters of benzene and to make preliminary estimates of ah- emissions from these facilities.
For mobile sources, more data are becoming available for on-road vehicles.
Additionally, the EPA model that generates emission factors undergoes regular update. The
on-road mobile sources section in this document should therefore be viewed as an example of
how emissions can be determined and the reader should look for more detailed data for the
most accurate estimates.
Data on off-road vehicles and other stationary sources remain unavailable.
However, with EPA's increased emphasis on air toxics, more benzene data are likely to be
generated hi the future.
As standard procedure, L&E documents are sent to government, industry, and
environmental groups wherever EPA is aware of expertise. These groups are given the
opportunity to review a document, comment, and provide additional data where applicable.
Where necessary, the document is then revised to incorporate these comments. Although this
document has undergone extensive review, there may still be shortcomings. Comments
1-4
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subsequent to publication are welcome and will be addressed based on available time and
resources. In addition, any information on process descriptions, operating parameters, control
measures, and emissions information that would enable EPA to improve on the contents of this
document is welcome. All comments should be sent to:
Group Leader
Emission Factor and Inventory Group (MD-14)
Office of Air Quality Planning and Standards
U. S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
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SECTION 2.0
OVERVIEW OF DOCUMENT CONTENTS
This section briefly outlines the nature, extent, and format of the material
presented in the remaining sections of this report.
Section 3.0 provides a brief summary of the physical and chemical
characteristics of benzene and an overview of its production, uses, and emissions sources.
This background section may be useful to someone who needs to develop a general perspective
on the nature of benzene, how it is manufactured and consumed, and sources of emissions.
Section 4.0 focuses on the production of benzene and the associated air
emissions. For each major production source category described hi Section 4.0, an example
process description and a flow diagram(s) with potential emission points are given. Available
emissions estimates are used to calculate emission factors that show the potential for benzene
emissions before and after controls employed by industry. Also provided are estimates of
emissions from process vents, equipment leaks, storage tanks, and wastewater. Individual
companies that are reported in trade publications to produce benzene are named.
Section 5.0 describes major source categories that use benzene as a feedstock to
produce industrial organic chemicals. For each major production process, a description(s) of
the process is given along with a process flow diagram(s). Potential emission points are
identified on the diagrams and emission ranges are presented, where available. Individual
companies that use benzene as a feedstock are reported.
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Section 6.0 describes emission sources where benzene is emitted as the
by-product of a process (such as petroleum refineries) and post-manufacturing activities where
releases from benzene-containing products may occur (such as from gasoline distribution).
Example process descriptions and flow diagrams are provided hi addition to available emission
factors for each major industrial category described in this section.
Section 7.0 presents information on stationary combustion sources (such as
municipal waste combustors) and area combustion sources (such as open burning). Example
incinerator, furnace, or boiler diagrams are given, when appropriate. Emission factors are
also given, when available.
Section 8.0 provides a brief summary on benzene emissions from mobile
sources. This section addresses both on-road and off-road sources. Section 9.0 summarizes
available procedures for source sampling and analysis of benzene. This section provides an
overview of applicable sampling procedures and cites references for those interested in
conducting source tests. Section 10.0 presents a list of all the references cited in this
document.
Appendix A presents a summary table of the emission factors contained in this
document. This table also presents the factor quality rating and the Source Classification Code
(SCC) or Area/Mobile Source (AMS) code associated with each emission factor. Appendix B
presents a list of all the petroleum refineries in the United States.
Each emission factor listed hi Sections 4.0 through 8.0 was assigned an emission
factor rating (A, B, C, D, E, or U), based on the criteria for assigning data quality ratings and
emission factor ratings as discussed hi the document Procedures for Preparing Emission Factor
Documents? The criteria for assigning the data quality ratings are as follows:
A - Tests are performed by using an EPA reference test method, or when not
applicable, a sound methodology. Tests are reported in enough detail for
.2-2
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adequate validation, and, raw data are provided that can be used to
duplicate the emission results presented in the report.
B - Tests are performed by a generally sound methodology, but lacking
enough detail for adequate validation. Data are insufficient to completely
duplicate the emission result presented in the report.
C - Tests are based on an unproven or new methodology, or are lacking a
significant amount of background information.
D - Tests are based on generally unacceptable method, but the method may
provide an order-of-magnitude value for the source.
Once the data quality ratings for the source tests had been assigned, these
ratings along with the number of source tests available for a given emission point were
evaluated. Because of the almost impossible task of assigning a meaningful confidence limit to
industry-specific variables (e.g., sample size vs. sample population, industry and facility
variability, method of measurement), the use of a statistical confidence interval for establishing
a representative emission factor for each source category was not practical. Therefore, some
subjective quality rating was necessary. The following emission factor quality ratings were
used in the emission factor tables in this document:
A - Excellent. Emission factor is developed primarily from A- and B-rated
source test data taken from many randomly chosen facilities in the industry
population. The source category population is sufficiently specific to
minimize variability.
B - Above average. Emission factor is developed primarily from A-or
B-rated test data from a moderate number of facilities. Although no
specific bias is evident, it is not clear if the facilities tested represent a
random sample of the industry. As with the A rating, the source category
population is sufficiently specific to minimize variability.
C - Average. Emission factor is developed primarily from A-, B-, and C-rated
test data from a reasonable number of facilities. Although no specific bias
is evident, it is not clear if the facilities tested represent a random sample
of the industry. As with the A rating, the source category population is
sufficiently specific to minimize variability.
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D - Below average. Emission factor is developed primarily form A-, B-, and
C-rated test data from a small number of facilities, and there may be
reason to suspect that these facilities do not represent a random sample of
the industry. There also may be evidence of variability within the source
population.
E - Poor. Factor is developed from C- rated and D-rated test data from a very
few number of facilities, arid there may be reasons to suspect that the
facilities tested do not represent a random sample of the industry. There
also may be evidence of variability within the source category population.
U - Unrated (Only used in the L&E documents). Emission factor is developed
from source tests which have not been thoroughly evaluated, research
papers, modeling data, or other sources that may lack supporting
documentation. The data are not necessarily "poor," but there is not
enough information to rate the factors according to the rating protocol.
This document does not contain any discussion of health or other environmental
effects of benzene, nor does it include any discussion of ambient air levels.
2-4
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SECTION 3.0
BACKGROUND INFORMATION
3.1
NATURE OF POLLUTANT
Benzene is a clear, colorless, aromatic hydrocarbon that has a characteristic
sickly sweet odor. It is both volatile and flammable. Chemical identification information for
benzene is found in TabIe-3-1. Selected physical and chemical properties of benzene are
presented in Table 3-2 A7
Benzene contains 92.3 percent carbon and 7.7 percent hydrogen (by mass). The
benzene molecule is represented by a hexagon formed by six sets of carbon and hydrogen
atoms bonded together with alternating single and double bonds.
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TABLE 3-1. CHEMICAL IDENTIFICATION OF BENZENE
Chemical Name
Benzene
Synonyms
Molecular formula
Identification numbers2
CAS Registry
NIOSH RTECS
DOT/UN/NA
DOT Designation
Benzol, phenyl hydride, coal naphtha,
phene, benxole, cyclohexatriene
C6H6
71-43-2
CY 1400000
UN 1114; Benzene (Benzol)
Flammable liquid
Source: References 4 and 5.
* Chemical Abstract Services (CAS); National Institute of Occupational Safety and Health (NIOSH); Registry of
Toxic Effects of Chemical Substances (RTECS); Department of Transportation/United Nations/North American
(DOT/UN/NA).
The chemical behavior of benzene indicates that the benzene molecule is more realistically
represented as a resonance-stabilized structure:
in which the carbon-to-carbon bonds are identical. The benzene molecule is the cornerstone
for aromatic compounds, all of which contain one or more benzene rings.8
Because of its resonance properties, benzene is highly stable for an unsaturated
hydrocarbon. However, it does react with other compounds, primarily by substitution and, to
a lesser degree, by addition. Some reactions can rupture the molecule or result in other groups
cleaving to the molecule. Through all these types of reactions, many commercial chemicals
are produced from benzene.8 The most common commercial grade of benzene contains 50 to
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TABLE 3-2. PHYSICAL AND CHEMICAL PROPERTIES OF BENZENE
Property
Value
Molecular weight
Melting point
Boiling point at 1 atmosphere (760 mm Hg)
Density, at 68°F (20°C)
Physical state (ambient conditions)
Color
Odor
Viscosity (absolute) at 68°F (20°C)
Surface tension at 77 °F (25 °C)
Heat of vaporization at 176.18°F (80.100°C)
Heat of combustion at constant pressure and
77°F (25°C) (liquid C6H6 to liquid H2O and
gaseous C02)
Odor threshold
Solubility:
Waterat77°F(25°C)
Organic Solvents
Vapor pressure at 77°F (25 °C)
Auto ignition temperature
Flashpoint
Conversion factors (Vapor weight to volume)
0.171bs.(78.12g)
41.9°F(5.5°C)
176.180F(80.1°C)
0.0141 Ib/ft3 (0.8794 g/cm3)
Liquid
Clear
Characteristic
0.6468 cP
0.033 g/cm3 (28.18 dynes/cm3)
33.871 KJ/Kg-mol (8095 Kcal/Kg-mol)
41.836 KJ/g (9.999 Kcal/g)
0.875 ppm
Very slightly soluble (0.180 g/100 mL,
1800 ppm)
Soluble in alcohol, ether, acetone, carbon
tetrachloride, carbon disulfide, and acetic
acid
95.2 mm Hg (12.7 kPa)
1044°F (562°C)
12°F(-ll.rC) (closed cup)
1 ppm = 319 mg/m3 at 77°F (25°C);
1 mg/L = 313 ppm
Source: References 4, 5, 6, and 7.
3-3
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100 percent benzene, the remainder consisting of toluene, xylene, and other constituents that
distill below 248°F (120°C).4
Laboratory evaluations indicate that benzene is minimally photochemically
reactive in the atmosphere compared to the reactivity of other hydrocarbons. Reactivity can be
determined by comparing the influence that different hydrocarbons have on the oxidation rate
of nitric oxide (NO) to nitrogen dioxide (NOz), or the relative degradation rate of various
hydrocarbons when reacted with hydroxyl radicals (OH), atomic oxygen or ozone. For
example, based on the NO oxidation test, the photochemical reactivity rate of benzene was
determined to be one-tenth that of propylene and one-third that of n-hexane.9
Benzene shows long-term stability in the atmosphere.8 Oxidation of benzene
will occur only under extreme conditions involving a catalyst or elevated temperature or
pressure. Photolysis is possible only in the presence of sensitizers and is dependent on.
wavelength absorption. Benzene does not absorb wavelengths longer than l.lxlO"5 inches (in)
(275 nanometers [ran]).8
In laboratory evaluation, benzene is predicted to form phenols and ring cleavage
products when reacted with OH, and to form quinone and ring cleavage products when reacted
with aromatic hydrogen.6 Other products that are predicted to form from indirect reactions
with benzene in the atmosphere include aldehydes, peroxides, and epoxides. Photodegradation
of NO2 produces atomic oxygen, which can react with atmospheric benzene to form phenols.9
3.2 OVERVIEW OF PRODUCTION AND USE
During the eighteenth century, benzene was discovered to be a component of
oil, gas, coal tar, and coal gas. The commercial production of benzene from coal
carbonization began hi the United States around 1941. It was used primarily as feedstock hi
the chemical manufacturing industry.10 For United States industries, benzene is currently
produced in the United States, the Virgin Islands, and Puerto Rico by 26 companies at
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36 manufacturing facilities.11 The majority of benzene production facilities in the United States
are found in the vicinity of crude oil sources, predominantly located around die Texas and
Louisiana Gulf coast. They are also scattered diroughout Kentucky, Pennsylvania, Ohio,
Illinois, and New Jersey.11
Domestic benzene production in 1992 was estimated at 2,350 million gallons
(gal) (8,896 million L).11 Production was expected to increase by approximately 3 to
3.5 percent per year through 1994. Exports of benzene hi 1993 were about 23 million gal (87
million L), around 1 percent of the total amount produced hi the United States.12
Benzene is produced domestically by five major processes.12 Approximately
45 percent of the benzene consumed in the United States is produced by the catalytic
reforming/separation process.11 With this process, the naphtha portion of crude oil is mixed
with hydrogen, heated, and sent through catalytic reactors.13 The effluent enters a separator
while the hydrogen is flashed off.13 The resulting liquid is fractionated and the light ends (C,
to C4) are split. Catalytic reformate, from which aromatics are extracted, is the product.13
Approximately 22 percent of the benzene produced hi the United States is
derived from ethylene production.11 Pyrolysis gasoline is a by-product formed from the steam
cracking of natural gas concentrates, heavy naphthas, or gas oils to produce ethylene.14
Toluene dealkylation or toluene disproportionation processes account for
another 25 percent of the United States production of benzene.11 Toluene dealkylation
produces benzene and methane from toluene or toluene-rich hydrocarbons through cracking
processes using heat and hydrogen. The process may be eitiier fixed-bed catalyst or thermal.
Toluene disproportionation produces benzene and xylenes as co-products from toluene using
similar processes.15
Three percent of benzene produced hi the United States is derived from coke
oven light oil distillation at coke by-product plants.11 Light oil is recovered from coke oven
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gas, usually by continuous countercurrent absorption in a high-boiling liquid from which it is
stripped by steam distillation.9 A light oil scrubber or spray tower removes the light oil from
coke oven gas.10 Benzene is recovered from the light oil by a number of processes, including
fractionating to remove the lighter and heavier hydrocarbons, hydrogenation, and conventional
distillation.
Finally, about 2 percent of benzene produced in the United States is derived as a
coproduct from xylene isomerization.11 Figure 3-1 presents a simplified production and use
tree for benzene. Each major production process is shown, along with the percent of benzene
derived from each process. The primary uses of benzene and the percentage for each use are
also given hi the figure.
The major use of benzene is still as a feedstock for chemical production, as in
the manufacture of ethylbenzene (and styrene). In 1992, the manufacture of ethylbenzene (and
styrene) accounted for 53 percent of benzene consumption.12 Ethylbenzene is formed by
reacting benzene with ethylene and propylene using a catalyst such as anhydrous aluminum
chloride or solid phosphoric acid.8 Styrene is the product of dehydrogenation of
ethylbenzene.9
Twenty-three percent of the benzene supply is used to produce cumene.12
Cumene is produced from benzene alkylation with propylene using solid phosphoric acid as a
catalyst.7 Cumene is oxidized to produce phenols and acetone.12 Phenol is used to make resins
and resin intermediates for epoxies and polycarbonates, and caprolactam for nylon.12 Acetone
is used to make solvents and plastics.16
Cyclohexane production accounts for 13 percent of benzene use.12 Cyclohexane
is produced by reducing benzene hydrogenated vapors using a nickel catalyst at 392°F
(200°C). Almost all of Cyclohexane is used to make nylon or nylon intermediates.17
.3-6
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U)
Benzene Production Proc»i§e»
Catalytic Reforming
45%
1
Ethylene Production
22%
Toluene Dealkylatlon/Dlsproportlonstlon I
25% r
Coke Oven Light OH Distillation
3%
Xylene Isomerizatlon
2%
-Benzene-
o
\/
CeHe
ChemlcaJt Produced Using Benzene *s • Feedstock
Ethylbenzene (Styrene)
53%
Cum«n« (Phenol)
23%
Cyclohexane
13%
Nitrobenzene (Aniline)
5%
Linear Alkylbenzene*
2%
Chlorobanzene*
2%
Other Benzene Chemical* 2%
(Including Use In Gasoline Blending)
N
m
O
on
Figure 3-1. Production and Use Tree for Benzene
Source: References 11 and 12.
-------
The production of nitrobenzene, from which aniline is made, accounts for
5 percent of benzene consumption. Nitrobenzene is produced by the nitration of benzene with
a concentrated acid mixture of nitric and sulfuric acid. Nitrobenzene is reduced to form
aniline.10 Aniline, in turn, is used to manufacture isocyanates for polyurethane foams, plastics,
and dyes.18
Chlorobenzene production accounts for 2 percent of benzene use. The
halogenation of hot benzene with chlorine yields Chlorobenzene. Monochlorobenzene and
dichlorobenzene are produced by halogenation with chlorine using a molybdenum chloride
catalyst.19
The remainder of the benzene produced is consumed in the production of other
chemicals. Other benzene-derived chemicals include linear alkylbenzene, resorcinol, and
hydroquinone.
Though much of the benzene consumed in the United States is used to
manufacture chemicals, another important use is in gasoline blending. Aromatic
hydrocarbons, including benzene, are added to vehicle fuels to enhance octane value. As lead
content of fuels is reduced, the amount of aromatic hydrocarbons is increased to maintain
octane rating, such that the benzene content hi gasoline was increased in recent years.4 The
concentration of benzene hi refined gasoline depends on many variables, such as gasoline
grade, refinery location and processes, and crude source.6 The various sources of benzene
emissions associated with gasoline marketing are discussed in Section 6.0, and benzene
emissions associated with motor vehicles are discussed in Section 8.0 of this document.
3.3 OVERVIEW OF EMISSIONS
Sources of benzene emissions from its production and uses are typical of those
found at any chemical production facility:
• Process vents;
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• Equipment leaks;
• Waste streams (secondary sources);
• Transfer and storage; and
• Accidental or emergency releases.
These sources of benzene emissions are described in Sections 4.0 and 5.0 of this document.
Miscellaneous sources of benzene including oil and gas production, glycol
dehydrators, petroleum refineries, gasoline marketing, POTWs, landfills, and miscellaneous
manufacturing processes are addressed in Section 6.0. Combustion sources emitting benzene
are addressed in Section 7.0. Section 8.0 presents a discussion of benzene emissions from
mobile sources. Recent work by the EPA Office of Mobile Sources on benzene in vehicle
exhaust resulted hi revised emission factors.20 For off-road vehicles, EPA has also completed
a recent study to estimate emissions.
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SECTION 4.0
EMISSIONS FROM BENZENE PRODUCTION
This section presents information on the four major benzene production source
categories that may discharge benzene air emissions. The four major processes for producing
benzene are:
• Catalytic reforming/separation;
• Toluene dealkylation and disproportionation;
• Ethylene production; and
• Coke oven light oil distillation.
For each of these production source categories, the following information is
provided in the sections below: (1) a brief characterization of the national activity in the
United States, (2) a process description, (3) benzene emissions characteristics, and (4) control
technologies and techniques for reducing benzene emissions. In some cases, the current
Federal regulations applicable tc the source category are discussed. Table 4-1 lists U. S.
producers of benzene and the type of production process used.11
Following the discussion of the major benzene production source categories,
Section 4.5 contains a discussion of methods for estimating benzene emissions from process
vents, equipment leaks, storage tanks, wastewater, and transfer operations. These emissions
estimation methods are discussed in general terms and can be applied to the source categories
in this section as well as the source categories hi Section 5.0.
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TABLE 4-1. BENZENE PRODUCTION FACILITIES
Company Name
Location
Annual
Capacity
million gal
(million L)
Production Processes'
Amerada Hess Corporation
Hess Oil Virgin Islands Corporation, subsidiary
St. Croix, Virgin Islands 75 (284)
Catalytic reformate;
toluene; no captive use
American Petrofina, Incorporated
Fina Oil and Chemical Company, subsidiary
Port Arthur, Texas
33 (125) Catalytic reformate; partly captive
31 (117) Toluene; partly captive
Amoco Corporation
Amoco Oil Company, subsidiary
Texas City, Texas
85 (322) Catalytic reformate; partly captive
25 (95) Pyrolysis gasoline; partly captive
12 (45) Xylene isomerization
Aristech Chemical Corporation
Clairton, Pennsylvania
45 (170) Coke-oven light oil
Ashland Oil, Incorporated
Ashland Chemical Company, division
Petrochemicals Division
Catlettsburg, Kentucky 55 (208) Coke-oven light oil; captive
2 (8) Catalytic reformate; captive
Atlantic Richfield Corporation
Lyondell Petrochemical Company, subsidiary
Channelview, Texas
Houston, Texas
90 (341) Pyrolysis gasoline; captive
35 (132) Catalytic reformate; no captive use
15 (57) Toluene; no captive use
(continued)
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TABLE 4-1. CONTINUED
Company Name Location
BP Oil Alliance, Louisiana
Lima, Ohio
Chevron Corporation Philadelphia, Pennsylvania
Chevron Chemical Company, subsidiary
Aromatics and Derivatives Division Port Arthur, Texas
4*.
u>
Citgo Petroleum Corporation Corpus Christi, Texas
Coastal Eagle Point Oil Co. Westville, New Jersey
Coastal Refining and Marketing, Inc. Corpus Christi, Texas
Dow Chemical U.S.A. Freeport, Texas
Plaquemine, Louisiana
Annual
Capacity
million gal
(million L)
18 (68)
47 (178)
35 (132)
80 (303)
24 (91)
21 (79)
42(159)
24 (91)
35 (132)
55 (208)
23 (87)
15 (57)
50(189)
7(26)
25 (95)
80 (303)
120 (454)
Production Processes'
Catalytic reformate; no captive use
Toluene
Catalytic reformate; no captive use
Toluene
Catalytic reformate; captive
Toluene; captive
Catalytic reformate; partly captive
Pyrolysis gasoline; partly captive
Toluene; partly captive
Catalytic reformate; captive
Toluene
Catalytic reformate
Toluene; captive use
Catalytic reformate
Pyrolysis gasoline; captive
Pyrolysis gasoline; captive
Toluene; captive
(continued)
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TABLE 4-1. CONTINUED
Company Name
Location
Annual
Capacity
million gal
(million L)
Production Processes'
Exxon Corporation
Exxon Chemical Company, division
Exxon Chemical Americas
Corpus Christi, Texas
Baton Rouge, Louisiana
Baytown, Texas
50 (189) Pyrolysis gasoline
30(114) Toluene
50 (189) Catalytic reformate
30 (114) Pyrolysis gasoline; no captive use
75 (284) Catalytic reformate; no captive use
20 (76) Pyrolysis gasoline
20 (76) Xylene isomerization
23 (87) Toluene
Huntsman Chemical Corporation
Kerr-McGee Corporation
Southwestern Refining Company,
Incorporated, subsidiary
Bayport, Texas 15 (57)
Corpus Christi, Texas 17 (64)
Toluene; captive
Catalytic reformate; no captive use
Koch Industries, Incorporated
Koch Refining Company, subsidiary
Corpus Christi, Texas
25 (95) Catalytic reformate; captive
55 (208) Toluene; captive
10 (38) Xylene isomerization
50(189) Toluene
Mobil Corporation
Mobil Oil Corporation
Mobil Chemical Company, division
Petrochemicals Division
U.S. Marketing and Refining Division
Beaumont, Texas
Chalmette, Louisiana
90 (341) Catalytic reformate; no captive use
10 (38) Pyrolysis gasoline
20 (76) Catalytic reformate; no captive use
(continued)
-------
TABLE 4-1. BENZENE PRODUCTION FACILITIES
Company Name
Location
Annual
Capacity
million gal
(million L)
Production Processes'
Occidental Petroleum Corporation
Petrochemicals Olefins and Aromatics Div ision
Chocolate Bayou, Texas
60 (227)
40(151)
Pyrolysis gasoline
Toluene
Phibro Energy USA, Inc.
Houston, Texas
5 (19) Catalytic reformate; no captive use
Phillips Petroleum Company
Chemicals Division
Olefins and Cyclics Branch
Sweeny, Texas
11 (42) Catalytic reformate; captive
Phillips Puerto Rico Core, Incorporated, subsidiary
Guayama, Puerto Rico
35 (132) Catalytic reformate; captive
48 (182) Toluene; captive
Shell Oil Company
Shell Chemical Company, division
Deer Park, Texas
Wood River, Illinois
75 (284) Catalytic reformate; partly captive
80 (303) Pyrolysis gasoline; partly captive
50 (189) Catalytic reformate; no captive use
Sun Company, Incorporated
Sun Refining and Marketing Company,
Incorporated, subsidiary
Marcus Hook, PA
Toledo, Ohio
26 (98) Catalytic reformate; no captive use
11 (42) Toluene; no captive use
19 (72) Catalytic reformate
(continued)
-------
TABLE 4-1. BENZENE PRODUCTION FACILITIES
Company Name
Texaco, Incorporated
Texaco Chemical Company, subsidiary
The UNO-YEN Company
Location
El Dorado, Kansas
Port Arthur, Texas
Lemon t, Illinois
Annual
Capacity
million gal
(million L)
15 (57)
46 (174)
20 (76)
12 (45)
7(26)
Production Processes'
Catalytic reformate; captive
Catalytic reformate; captive
Pyrolysis gasoline; captive
Catalytic reformate
Coke-oven light oil; no captive
USX Corporation
Marathon Oil Company, subsidiary
Marathon Petroleum Company, subsidiary
Lake Charles, Louisiana 55 (208)
Texas City, Texas 7 (26)
Catalytic reformate; captive
Toluene
TOTAL
2.350(8.8%)
Source: Reference 11.
1 Captive means used for subsequent processes on site.
Note: This list is subject to change as market conditions change, facility ownership changes, or plants are closed down. The reader should verify the
existence of particular facilities by consulting current listings or the plants themselves. The level of emissions from any given facility is a function of
variables such as throughput and control measures, and should be determined through direct contacts with plant personnel. Reference SRI '93
indicates these data reflect changes made in product locations as of January 1993.
-------
4.1 CATALYTIC REFORMING/SEPARATION PROCESS
Production of benzene by reforming/separation is associated with the production
of toluene and xylene (BTX plants). Catalytic reforming is used to prepare high-octane
blending stocks for gasoline production and for producing aromatics as separate chemicals.
The reforming process, shown hi Figure 4-1,22 accounts for about 45 percent of all benzene
produced in the United States.12 In the following description of the reforming process,
potential emission points are identified; however, not all of the emission points discussed in
this section are always present at plants using this production process. Some companies have
indicated that they have closed systems; others have indicated that process vent emissions are
well-controlled by flares or scrubbers.22
4.1.1 Process Description for Catalytic Reforming/Separation
The reforming process used at BTX plants (shown in Figure 4-1) can greatly
increase the aromatic content of petroleum fractions by such reactions as dehydrogenation,
isomerization and dehydrogenation, or cyclization. The usual feedstock hi this process is a
straight-run, hydrocracked, thermally cracked, or catalytically cracked naphtha. After the
naphtha is hydrotreated to remove sulfur (Stream 1), it is mixed with recycled hydrogen
(Stream 4) and heated. This feed (Stream 2) is sent through catalytic reactors hi which the
catalyst, usually platinum or rhenium chloride, converts paraffins to aromatic compounds. The
product stream (Stream 3) t-onMSis of excess hydrogen and a reformats; rich in aromatics.
Products from the reactor (Stream 3) are fed to the separation section, which separates the
hydrogen gas from the liquid product. The hydrogen gas can be recycled to the reactor
(Stream 4). The liquid product from the separator (Stream 5) is fed to a stabilizer (not shown
in the figure).22 The stabilizer is a fractionator hi which more volatile, light hydrocarbons are
removed from the high-octane liquid product. The liquid is then sent to a debutanizer (not
shown hi the figure). Aromatics (benzene, toluene, and mixed xylenes) are then extracted
from the stabilized reformate.22
4-7
-------
Ructora
0
RiQinirator
' Citilyii to
RiOinirator
High PriHun
Sipirator
N*t Stparator
0«t
<£_
Hydrotnitid Niphthi
Chirga
Not*: Th« strain) numbira on thi flgura corrnpond to tfti dbcuiilon In thi tixt for
Hid prociu. Littir* corrnpond to potintfal louren of binzini imliiloni.
Figure 4-1. Universal Oil Products Platforming (Reforming) Process
Source: Reference 22.
-------
22
Numerous solvents are available for the extraction of aromatics from the
stabilized reformate stream. Glycols (tetraethylene glycol)-and sulfolane
(1,1-tetrahydrothiophene dioxide) are most commonly used. The processes in which these
solvents are used are similar, so only the glycol process is described here. In the glycol
process shown in Figure 4-2, aromatics are separated from the reformate in the extractor.
The raffinate (stream 2) is water-washed and stored. The dissolved aromatics extract
(Stream 1) is steam-stripped and the hydrocarbons separated from the solvent. The
hydrocarbon stream (Stream 3) is water-washed to remove remaining solvent and is then
heated and sent through clay towers to remove olefins (Stream 4). Benzene, toluene, and
xylene (Stream 5) are then separated by a series of fractionation steps.22
4.1.2 Benzene Emissions from Catalytic Reforming/Separation
The available information on benzene emissions from process vents, equipment
leaks, storage vessels, wastewater collection and treatment systems, and product loading and
transport operations associated with benzene production using the catalytic'
reforming/separation process is presented below. Where a literature review revealed no
source-specific emission factors for uncontrolled or controlled benzene emissions from these
emission points from this process, the reader is referred to Section 4.5 of this chapter, which
provides a general discussion of methods for estimating uncontrolled and controlled benzene
emissions from these emission points.
A literature search, a review of materials hi the docket (A-79-27) for some
National Emission Standards for Hazardous Air Pollutants (NESHAP) efforts on benzene, and
information provided by the benzene production industry revealed no source-specific emission
factors for benzene from catalytic reforming/separation.22 However, information provided by
the benzene production industry indicates that BTX is commonly produced hi closed systems,
and that any process vent emissions are well-controlled by flares and/or scrubbers. (See
Section 4.5 of this chapter for a discussion of control devices.)22 Furthermore, some
descriptive data were found, indicating that benzene may be emitted from the
.4-9
-------
Extractor
•ft
I—*
O
Rafflnata
Solvent
©
Feed
(reformat*)
1
(c)
\
I
E
Rich
Solvent
Light
HC
Reflux
Stripper Water
Receiver Receiver
0__D
Raftlnate
Water
Waeh
1
®E«tract
Receiver ,
I
Reel
r
V-
culation
Water
Note: The «tream numbers on the Dgur* eorreepond to the dlaeuatlon for this process.
Letters correspond to potential source* of benzene emleslons
^_ Benzene
Product
Figure 4-2. Flow Diagram of a Glycol BTX Unit Process
Xylene
Product
Toluene
Product
s
O
o:
HI
Source: Reference 22.
-------
catalytic/reforming process during catalyst regeneration or replacement, during recycling of
hydrogen gas to the reformer, and from the light gases taken from the separator. These
potential emission points are labeled as A, B, and C, respectively, in Figure 4-1.
One general estimate of the amount of benzene emitted by catalytic
reforming/separation has been reported in the literature. In this reference, it was estimated
that 1 percent of total benzene produced by catalytic reforming is emitted.23
Benzene may be emitted from separation solvent regeneration, raffinate wash
water, and raffinate in association with the separation processes following catalytic reforming.
These potential sources are shown as A, B, and C, respectively, hi Figure 4-2. However, no
specific data were found showing emission factors or estimates for benzene emissions from
these potential sources. One discussion of the Sulfolane process indicated that 99.9-percent
recovery of benzene was not unusual. Therefore, the 0.1 percent unrecovered benzene may be
a rough general estimate of the benzene emissions from separation processes.23
4.2 TOLUENE DEALKYLATION AND TOLUENE DISPROPORTIONATION
PROCESS
Benzene can also be produced from toluene by hydrodealkylation (HDA) or
disproportionation. The amount of benzene produced from toluene depends on the overall
demand and price for benzene because benzene produced by HDA costs more than benzene
produced through catalytic reforming or pyroiysis gasoline.-' At present, benzene production
directly from toluene accounts for almost 30 percent of total benzene produced.11 Growth in
demand for toluene hi gasoline (as an octane-boosting component for gasoline blending)
appears to be slowing because of increased ah- quality legislation to remove aromatics from
gasoline. (At present, gasoline blending accounts for 30 percent of the end use of toluene.) If
toluene is removed from the gasoline pool to any great extent, its value is expected to drop
because surpluses will occur. In such a scenario, increased use of toluene to produce benzene
by HDA or disproportionation would be expected.24 At present, production of benzene by the
HDA and disproportionation processes accounts for 50 percent of toluene end use.
4-11
-------
4.2.1 Toluene Dealkvlation
Process Description
Hydrodealkylation of toluene can be accomplished through thermal or catalytic
processes.25 The total dealkylation capacity is almost evenly distributed between the two
methods.10 As shown in Figure 4-3, pure toluene (92 to 99 percent) or toluene (85 to
90 percent) mixed with other heavier aromatics or paraffins from the benzene fractionation
column is heated together with hydrogen- containing gas to 1,346°F (730°C) at a specified
pressure (Stream 1) and is passed over a dealkylation catalyst in the reactor (Stream 2).
Toluene reacts with the hydrogen to yield benzene and methane. The benzene may be
separated from methane in a high-pressure separator (Stream 3) by flashing off the
methane-containing gas.25
The product is then established (Stream 4), and benzene is recovered by
distillation in the fractionalization column (Stream 5).10 Recovered benzene is sent to storage
(Stream 6). Unreacted toluene and some heavy aromatic by-products are recycled (Stream 7).
About 70 to 85 percent conversion of toluene to benzene is accomplished per pass through the
system, and the ultimate yield is 95 percent of the theoretical yield. Because there is a weight
loss of about 23 percent, the difference in toluene and benzene prices must be high enough to
justify use of the HDA process.
Benzene Emissions
The available information on benzene emissions from process vents, equipment
leaks, storage vessels, waste water collection and treatment systems, and product loading and
transport operations associated with benzene production using the toluene dealkylation process
was reviewed. No source-specific emission factors were found for benzene emissions from its
production through dealkylation of toluene. The reader is referred to Section 4.5 of this
4-12
-------
chapter, which provides a general discussion of methods for estimating uncontrolled and
controlled benzene emissions from these emission points.
Potential sources of emissions from the dealkyiation process include the
separation of benzene and methane, distillation, catalyst regeneration, and stabilization.23
These potential sources are shown as emission points A, B, C, and D respectively, in
Figure 4-3.10-15-25
4.2.2 Toluene Disproportionation
Process Description
Toluene disproportionation (or transalkylation) catalytically converts two
molecules of toluene to one molecule each of benzene and xylene.24 As shown hi Figure 4-4,
the basic process is similar to toluene hydrodealkylation, but can occur under less severe
conditions.15-26 Transalkylation operates at lower temperatures, consumes"little hydrogen, and
no loss of carbon to methane occurs as with HDA.24 Toluene material is sent to a separator for
removal of off-gases (Stream 3). The product is then established (Stream 4) and sent through
clay towers (Stream 5). Benzene, toluene, and xylene are recovered by distillation, and
unreacted toluene is recycled (Stream 6). Note that if benzene is the only product required,
then HDA is a more economical and feasible process.27
Benzene Emissions
No specific emission factors were found for benzene emissions from its
production via toluene disproportionation. Potential sources of benzene emissions from this
process are associated with the separation of benzene and xylene, catalyst regeneration, and
heavy hydrocarbons that do not break down.23 These potential sources are shown as points A,
B, and C, respectively, in Figure 4-4.
4-13
-------
Heater
Reactor
Separator
(Flash Drum)
Stabilizer
Benzene
Fractionatlon
Column
Hydrogen
Makeup
Gas
A
o
Fresh Toluene Feed
I:
T.
_ To Benzene
Benzene*" Slorafl*
Recycled Toluene and Heavier Aromatic*
Heavies
» Purge
Not*: Til* itrttm numbari on th* flgur* eorraipond to th« dlieunlon In th» text (or
this proeoo*. Letter* cotr««pond to potcntlii >ourc«> or b«nz«n* cmlMlon*.
Figure 4-3. Process Flow Diagram of a Toluene Dealkylation Unit
Source: References 10, 15, and 25.
-------
Recycle Toluene
Ut
Toluene
Xytene
Slngln
Adlabatlc
Fixed-bed Heevy
Reactor End*
C* From
Oulelde
Source II
Desired
N
"l
O
te.
ui
Note: Stream numbers correspond to the discussion In the text for this process. Letters
represent potential sources of benzene emissions.
Figure 4-4. Toluene Disproportionation Process Flow Diagram (Tatoray Process)
Source: References 15 and 26.
-------
4.3 ETHYLENE PRODUCTION
4.3.1 Process Description
Ethylene is produced through pyrolysis of natural gas concentrates or petroleum
fractions such as naphthas and atmospheric gas oils.28 Pyrolysis gasoline is a liquid by-product
formed as part of the steam-cracking process. The liquid pyrolysis gasoline is rich in benzene.
Ethylene plants of the same production capacity, but using different feedstocks (ethane/propane
versus naphthas/gas oils), will produce different amounts of pyrolysis gasoline with different
benzene concentrations. For example, an ethylene plant producing 1 billion pounds
(453.5 gigagrams [Gg]) of ethylene per year from ethane will produce about 16,097,023 Ibs
(7.3 Gg) pyrolysis gasoline with about 7,497,244 Ibs (3.4 Gg) benzene in the pyrolysis
gasoline.28 A plant producing the same amount of ethylene from atmospheric gas oils will
produce about 754,134,509 Ibs (342 Gg) of pyrolysis gasoline containing 213,450,937 Ibs
(96.8 Gg) benzene.28
Because the benzene content of pyrolysis gasoline can be high, some plants
recover motor gasoline, aromatics (BTX), or benzene from the pyrolysis gasoline. Table 4-1
lists facilities reported to recover benzene from pyrolysis gasoline. However, benzene can be
emitted from ethylene plants that produce pyrolysis gasoline but do not recover benzene.
Table 4-2 lists ethylene producers and their locations. To locate most of the potential sources
of benzene from ethylene/pyrolysis gasoline plants, information is included here on
ethylene/pyrolysis gasoline production, as well as information on recovery of benzene from
pyrolysis gasoline. But because ethylene plants using naphthas/gas oils as feedstocks produce
more pyrolysis gasoline and more often treat the gasoline prior to storage, these types of plants
are emphasized in the following discussion.
Reference 28 provides more detailed information on ethylene plants using
natural gas concentrates as feedstocks. In general, natural gas-using plants are less complex
than naphtha-using plants. The potential emissions sources of benzene at the two types of
4-16
-------
TABLE 4-2. ETHYLENE PRODUCERS - LOCATION AND CAPACITY
Producer
Location
Annual Capacity
million Ib
(million kg)
Notes'
Atlantic Richfield Company
Lyondell Petrochemical Company, subsidiary
Channelview, Texas
3,360(1,524)
Partly captive
The BF Goodrich Company
BF Goodrich Chemical Group
Calvert City, Kentucky
350 (159)
Merchant
Chemicals & Speciality Products Group
Alvin, Texas
2,384(1,081)
Mostly merchant
Chevron Corporation
Chevron Chemical Company, subsidiary
Olefins and Derivatives Division
Cedar Bayou, Texas
Port Arthur, Texas
1,450(658)
1,250(567)
Mostly captive
Mostly captive use at Orange,
Texas
Dow Chemical U.S.A.
Freeport, Texas
Plaquemine, Louisiana
2,050 (930)
2,300(1,043)
Captive
Captive
Du Pont
Du Pont Chemicals
Orange, Texas
1,050(476)
Captive
Eastman Chemical Company
Texas Eastman Company
Longview. Texas
1.400(635)
Mostly Captive
(continued)
-------
TABLE 4-2. CONTINUED
Producer
Location
Annual Capacity
million Ib
(million kg)
Notes'
Exxon Chemical Company
Exxon Chemical Americas
Baton Rouge, Louisiana
Baytown, Texas
1,775(805)
2,100(953)
Captive
Some captive use at Mont
Belvieu, Texas
Javelina Gas Processing
Corpus Christi, Texas
180 (82)
Recovered from gas by-products
of local refineries; merchant
»—*
oo
Koch Industries, Inc.
Koch Refining Company, subsidiary
Corpus Christi, Texas
24(11)
Captive
Mobil Oil Corporation
Mobil Chemical Company, division
Petrochemicals Division
Beaumont, Texas
Houston, Texas
1,100(499)
500 (227)
Mostly captive
Mostly captive
Occidental Petroleum Corporation
Petrochemicals
Olefins & Aromatics Division
Chocolate Bayou, Texas
Corpus Christi, Texas
Lake Charles, Louisiana
1,100(499)
1,700(771)
750 (340)
Mostly captive
Mostly captive
Captive
Phillips Petroleum Company
Chemicals Division
Olefins and Cyclics Branch
Sweeny, Texas
2,550(1,157)
Partly captive
(continued)
-------
TABLE 4-2. CONTINUED
Producer
Location
Annual Capacity
million Ib
(million kg)
Notes1
Quantum Chemical Corp.
USI Division
Clinton, Iowa
Deer Park, Texas
Morris, Illinois
900 (408)
1,500(680)
1,000(454)
Captive
Captive
Captive
Rexene Corporation
Odessa, Texas
500 (228)
Partly captive
i—»
VO
Shell Oil Company
Shell Chemical Company, division
Deer Park, Texas
Noroco, Louisiana
1,900(862)
2,560(1,161)
Partly merchant
Partly captive
Sun Refining and Marketing Co.
Brandenburg, Kentucky
Claymont, Delaware
NA
250(113)
Captive
Partly captive
Sweeny Olefins Limited Partnership
Sweeny, Texas
1,500(680)
Merchant
Texaco Chemical Company
Port Arthur, Texas
Port Neches, Texas
1,150(522)
350 (159)
Some captive use at Port Neches
Captive
Union Carbide Corporation
Industrial Chemicals Division
Seadrift, Texas
Taft, Louisiana
Texas City. Texas
880 (399)
1,405(637)
1.400(635)
Captive
Captive
Mostly captive
(continued)
-------
TABLE 4-2. CONTINUED
Producer
Location
Annual Capacity
million Ib
(million kg)
Notes1
Union Texas Petroleum/BASF
Corporation/GE Petrochemicals, Inc.
Chemical Company
Geismar, Louisiana
1,160(526)
Captive
Vista Chemical Company
Lake Charles, Louisiana
920 (417)
Mostly captive
K)
o
Westlake Petrochemicals Corporation
TOTAL
Sulphur, Louisiana
1,000(454)
45,798 (20,774)
Mostly captive
Source: Reference 11.
1 Captive means used for subsequent processes on site. Merchant means sold as a final product.
NA = not available
Note: This list is subject to change as market conditions change, facility ownership changes, or plants are closed down. The reader should verify the
existence of particular facilities by consulting current listings or the plants themselves. The level of benzene emissions from any given facility is a
function of variables such as throughput and control measures; and should be determined through direct contacts with plant personnel. Data represent
producers, locations, and capacities as of January 1993.
-------
plants are similar, with smaller amounts of benzene being emitted from natural gas
concentrate-using plants.
Ethylene/Pyrolysis Gasoline Production
A process flow diagram for a plant producing ethylene from naphtha and/or gas
oil is shown in Figure 4-5. Many older facilities use larger numbers of compressors (hi
parallel) than are shown in the flow diagrams hi Figure 4-5. For reference, Table 4-3 lists
stream descriptions and corresponding stream numbers hi Figure 4-5. The description of the
process is taken almost entirely from Reference 28.
Naphtha and/or gas oil (Stream 1), diluted with steam, is fed hi parallel to a
number of gas- or oil-fired tubular pyrolysis furnaces. The fuel gas and oil (Stream 2) for
these furnaces are supplied from gas and oil fractions removed from the cracked gas hi later
separation steps. Ethane and propane, which are present hi the cracked gas and are separated
in later distillation steps (Streams 35 and 38), are combined and recycled (Stream 3) through a
separate cracking furnace. The resulting cracked gas is combined with the cracked gas from
the naphtha/gas-oil furnaces (Stream 5). The flue gas from the pyrolysis furnaces is vented
(Vent A on Figure 6).
During operation, coke accumulates on the inside walls of the reactor coils, and
each furnace must be periodically taken out of service for removal of the accumulated coke.
Normally, one furnace is out of service for decoking at all tunes. Decoking is accomplished
by passing steam and air through the coil while the furnace is maintained at an elevated
temperature, effectively burning the carbon out of the coil. While a furnace is being decoked,
the exhaust is diverted (Stream 7) to an emissions control device (Vent B) whose main function
is to reduce paniculate emissions. The collected particles are removed as a slurry (Stream 8).
The cracked gas (Stream 4) leaving the pyrolysis furnaces is rapidly cooled
(quenched) to 482 to 572°F (250 to 300°C) by passing it through transfer-line exchangers,
4-21
-------
N)
kitonnKtont Prouti Emkiloni
Mlh Proem Vint
«t
EthyUno
Ethyl.no '" p">""
liom i , , ©
f$<
Drying Trap*
Controltod Em«rg«ney Vintt
•ltd Gitected S.l.ty R.lUf ViVt
I Q| Ediana/Pmpan*
pyrolyili Fura«co« | Pyroly»h Fumicoi
EBiino
®"
Oltuni*
Ol from Mofmtiy
•Him
-sj Rteycto Suim *
-— T Otntntor i
F
-^
»
r_
imtct/
Bolter Fi»l
Product Fu*l OK
©*<$
^-~^
— »•
pyralyilt
fu.!0«
eiongi
I
Mel*: Th» «tr»im Humbert en tti* llgura corraipond to tht discuiilon In tti* text for thli
proecu. Litten correspond to polintiil iourc*t of binzin* tmlttioni.
Figure 4-5. Process Flow Diagram for Ethylene Production from Naphtha and/or Gas-Oil Feeds
Source: Reference 28.
-------
Regeneration
Vent
u>
From Drying Trape
Ethyleno
Vented
from Brine
I r-^f1-!
•mporatur* I | T
B Section W ^ •. ' I
Net*: Th« stream numbora on tho flgura eorratpond to Ots discussion In the tout tor this
process. Letters correspond to potential aourcee of benzene emlasfona
RawPyrolyele
O*SOllno
Storage
Oaeollne
Traatmant
Section
OsisoHno
Hydrofl* nation
Reactor
Heater
Tree ted
Pyroh/sls
OaaoHne
Storage
Figure 4-5. Process Flow Diagram for Ethylene Production from Naphtha and/or Gas-Oil Feeds, continued
Source: Reference 28.
-------
TABLE 4-3. STREAM DESIGNATIONS FOR FIGURE 4-5, PRODUCTION OF
ETHYLENE FROM NAPHTHA AND/OR GAS-OIL FEEDS
Stream Number Stream Description
1 Naphtha or gas oil feed
2 Fuel gas and oil
3 Ethane/propane recycle stream
4 Cracked gas
5 Cracked gas
6 Recycled pyrolysis fuel oil from gasoline fractionator
7 Furnace exhaust
8 Slurry of collected furnace decoking particles
9 Quenched cracked gas
10 Surplus fuel oil
11 Light fractions
12 Overheads from gasoline fractionator
13 Condensed organic phase
14 Raw pyrolysis gasoline to intermediate storage
15 Water phase (saturated with organics) from quench tower
16 Recycled water phase from heat exchangers
17 Surplus water from quench tower
18 Wastewater blowdown from recycle steam generator
19 Overheads from quench towei
20 Water condensed during compression
21 Organic fractions condensed during compression
22 Acid gas stripped in amine stripper
23 Diethanolamine (DEA)
24 Liquid waste stream from caustic wash tower
25 Liquid waste stream from caustic wash tower
26 Process gas stream from caustic wash tower
27 Solid waste stream from drying traps
4-24 (continued)
-------
TABLE 4-3. CONTINUED
Stream Number Stream Description
28 Process gas
29 Hydrogen rich stream from demethanizer
30 Methane rich stream from demethanizer
31 Q components from de-ethanizer
32 C3 and heavier components from de-ethanizer
33 Hydrogenated acethylene from acetylene convenor
34 Overheads from ethylene fractionator
35 Ethane to recycle pyrolysis furnace
36 Overheads from depropanizer
37 Propylene (purified)
38 Propane to ethane/propane pyrolysis furnace
39 C4 and heavier components to debutanizer
40 Overheads from debutanizer
41 C5 and heavier components from debutanizer
42 Combined C5 components and gasoline stripper bottoms
fractions
43 Light ends to cracked gas compressor
44 C5 and heavier components
45 Superheated stream
46 Stream and hydrocarbons
47 Organic vapor from separator pot
48 Organic vapor from separator pot
49 Organic vapor from separator pot
4-25
-------
which end pyrolysis and simultaneously generate steam. The streams from the transfer-line
exchangers (Stream 5) are combined and further quenched by the injection of recycled
pyrolysis fuel oil from the gasoline fractionator (Stream 6).
The remaining operations shown in Figure 4-5 are required for separation of the
various product fractions formed in the cracking of gas oil and/or naphtha; for removal of acid
gases (primarily hydrogen sulfide [H2S]) and carbon dioxide (COJ and water; and for
hydrogenation of acetylene compounds to olefins or paraffins.
The quenched cracked gas (Stream 9) passes to the gasoline fractionator, where
pyrolysis fuel oil is separated. Most of the fuel oil passes through water-cooled heat
exchangers and is recycled (Stream 6) to the preceding oil-quenching operation. The surplus
fuel oil (Stream 10), equivalent to the quantity initially present in the cracked gas, passes first
to the fuel oil stripper, where light fractions are removed, and then to fuel oil storage. The
light fractions (Stream 11) removed hi the fuel oil stripper are recycled to the gasoline
fractionator. The gasoline fractionator temperatures are well above the vaporization
temperature of water, and the contained water remains as superheated steam, with the overhead
stream containing the lighter cracked-gas components.
The overhead stream from the gasoline fractionator (Stream 12) passes to the
quench tower, where the temperature is further reduced, condensing most of the water and part
of the C5 and hea\ ier compounds. The condensed organic phase (Stream 13) is stripped of the
lighter components hi the gasoline stripper and is passed to raw pyrolysis gasoline intermediate
storage (Stream 14). Most of the water phase, which is saturated with organics, is separated hi
the quench tower (Stream 15), passed through water-cooled heat exchangers (Stream 16), and
then recycled to the quench tower to provide the necessary cooling. The surplus water
(Stream 17), approximately equivalent to the quantity of steam injected with the pyrolysis
furnace feed, passes to the dilution steam generator, where it is vaporized and recycled as
steam to the pyrolysis furnaces. Blowdown from the recycle steam generator is removed as a
wastewater stream (Stream 18).
4-26
-------
On leaving the quench tower, the pyrolysis gas is compressed to about 3.5 mPa
in five stages.29 The overhead stream from the quench tower (Stream 19) passes to a
centrifugal charge-gas compressor (first three stages), where it is compressed. Water
(Stream 20) and organic fractions (Stream 21) condensed during compression and cooling are
recycled to the quench tower and gasoline stripper.
Lubricating oil (seal oil) discharged from the charge-gas compressor is stripped
of volatile organics in a separator pot before the oil is recirculated. The organic vapor is
vented to the atmosphere (Vent G). Similar separator pots separate volatile organics from
lubricating oil from both the ethylene and propylene refrigeration compressors (Streams 48 and
49).
Following compression, acid gas (H2S and CO^ is removed by absorption hi
diethanolamine (DEA) or other similar solvents hi the amine wash tower followed by a caustic
wash step. The amine stripper strips the acid gas (Stream 22) from the saturated DEA and the
DEA (Stream 23) is recycled to the amine wash tower. Very little blowdown from the DEA
cycle is required.
The waste caustic solution, blowdown from the DEA cycle, and wastewater
from the caustic wash tower are neutralized, stripped of acid gas, and removed as liquid waste
streams (Streams 24 and 25). The acid gas stripped from the DEA and caustic waste
(Stream 22) passes to an emission control device (Vent D), primarily to control H-,8 emissions.
Following acid gas removal, the remaining process gas stream (Stream 26) is
further compressed and passed through drying traps containing a desiccant, where the water
content is reduced to the low level necessary to prevent ice or hydrate formation in the low-
temperature distillation operations. The drying traps are operated on a cyclic basis, with
periodic regeneration necessary to remove accumulated water from the desiccant. The
desiccant is regenerated with heated fuel gas and the effluent gas is routed to the fuel system.
Fouling of the desiccant by polymer formation necessitates periodic desiccant replacement,
4-27
-------
which results hi the generation of a solid waste (Stream 27). However, with a normal
desiccant service life of possibly several years, this waste source is relatively minor.
With the exception of three catalytic hydrogenation operations, the reniaining
process steps involve a series of fractionations hi which the various product fractions are
successively separated.
The demethanizer separates a mixture of hydrogen and methane from the C2 and
heavier components of the process gas (Stream 28). The demethanizer overhead stream
(hydrogen and methane) is further separated into hydrogen-rich and methane-rich streams
(Streams 29 and 30) hi the low-temperature chilling section. The methane-rich stream is used
primarily for furnace fuel. Hydrogen is required hi the catalytic hydrogenation operations.
The de-ethanizer separates the C2 components (ethylene, ethane, and acetylene)
(Stream 31) from the C3 and heavier components (Stream 32). Following catalytic
hydrogenation of acetylene to ethylene by the acetylene converter (Stream'33), the ethylene-
ethane split is made by the ethylene fractionator. The overhead from the ethylene fractionator
(Stream 34) is removed as the purified ethylene product, and the ethane fraction (Stream 35) is
recycled to the ethane/propane cracking furnace. For the separation of binary mixtures with
close boiling points, such as in the ethylene-ethane fractions, open heat pumps are
thermodynamically the most attractive. Both heating and cooling duties have to be
incorporated into the cascade refrigeration system for optimum energy utilization.29
The de-ethanizer bottoms (C3 and heavier compounds) (Stream 32) pass to the
depropanizer, where a C3-C4 split is made. The depropanizer overhead stream (primarily
propylene and propane) (Stream 36) passes to a catalytic hydrogenation reactor (C3 converter),
where traces of propadiene and methyl acetylene are hydrogenated. Following hydrogenation,
the C3 fraction passes to the propylene fractionator, where propylene is removed overhead as a
purified product (Stream 37). The propane (Stream 38) is recycled to the ethane/propane
pyrolysis furnace.
4-28
-------
The C4 and heavier components (Stream 39) from the depropanizer pass to the
debutanizer, where a C4-C5 split is made. The overhead C4 stream (Stream 40) is removed as
feed to a separate butadiene process.
The stream containing C5 and heavier compounds from the debutanizer
(Stream 41) is combined with the bottoms fraction from the gasoline stripper as raw pyrolysis
gasoline. The combined stream (Stream 42) is hydrogenated in the gasoline treatment section,
Following the stripping of lights (Stream 43), which are recycled to the cracked-gas
compressor, the C5 and heavier compounds (Stream 44) are transferred to storage as treated
pyrolysis gasoline. This stream contains benzene and other aromatics formed by pyrolysis.
The three catalytic hydrogenation reactors for acetylene, C3 compounds, and
pyrolysis gasoline all require periodic regeneration of the catalyst to remove contaminants.
The catalyst is generally regenerated every four to six months. At the start of regeneration, as
superheated steam (Stream 45) is passed through a reactor, a mixture of steam and
hydrocarbons leaving the reactor (Stream 46) is passed to the quench tower. After sufficient
time has elapsed for stripping of organics (approximately 48 hours), the exhaust is directed to
an atmospheric vent (Vent F) and a steam-air mixture is passed through the catalyst to remove
residual carbon. This operation continues for an additional 24 to 48 hours. The presence of
air during this phase of the regeneration prevents the vented vapor from being returned to the
process.
Because the olefins and di-olefins present in pyrolysis gasoline are unstable in
motor gasoline and interfere with extraction of aromatics, they are hydrogenated prior to
extraction of aromatics.10 Also, as mentioned before, because the benzene content of pyrolysis
gasoline can be high, some plants recover motor gasoline, aromatics (BTX), or benzene from
the pyrolysis gasoline.
4-29
-------
Recovery of Benzene from Pyrolysis Gasoline
A process flow diagram for a plant producing benzene, toluene, and xylenes by
hydrogenation of pyrolysis gasoline is presented in Figure 4-6. Pyrolysis gasoline is fed with
make-up hydrogen into the first stage hydrogenation reactor (Stream 1), where olefins are
hydrogenated. The reaction conditions are mild (104 to 203°F [40 to 95°C] and 147 to
588 lb/in2 [10 to 40 atmospheres pressure]).10
The catalyst in the first stage reactor (nickel or palladium) requires more
frequent regeneration than most refinery catalysts because of the formation of gums. Catalyst
may be regenerated about every 4 months and coke is burned off every 9 to 12 months.10'30
From the first reactor, the hydrogenated di-olefins and olefins are sent to a
second reactor (Stream 2). Reactor effluent is then cooled and discharged into a separator
(Stream 3). Part of the gas stream from the separator is recycled back to the reactor (Stream 4)
after being scrubbed with caustic solution. The liquid phase from the separator is sent to a
coalescer (Stream 5), where water is used to trap particles of coke formed in the reactor.30
Next, the light hydrocarbons are removed from the liquid in the stabilizer (Stream 6). At this
point, the process becomes similar to the solvent extraction of reformate in the catalytic
reforming of naphtha. The stabilized liquid is extracted with a solvent, usually Sulfolane or
tetraethylene glycol (Stream 7).
The raffinate (Stream 8) contains paraffins and may be sent to a cracking
furnace to produce olefins.30 The solvent may be regenerated (Streams 9 and 10). Dissolved
aromatics (benzene, toluene, and xylene) are separated from the solvent by distillation
(Stream 11) and sent through clay towers (Stream 12). Individual components (benzene,
toluene, and xylene) are finally separated (Stream 13) and sent to storage.
The above process may vary among facilities. For example, Stream 1 may be
passed over additional catalyst, such as cobalt molybdenum, after being passed over a nickel or
4-30
-------
u>
Pyrolyili
Gasoline
Feedstock
Steam
-»- Wastewater
il
Solvent
S
a
•
in
Wastewater
Coalescer
Wastewater
w
Steam Water
Hydrotreattng
Section
0
a
a
5
W
Product
II
II
oc.
Extract
Storage
Benzene
• c
si
Toluene
Sludge
Solvent
Extraction
Section
Xylene
a
o
Not*: No data were available concerning benzene emission points. Likely emission points
Include reactor vents, compressors, and any vents on the benzene column.
Figure 4-6. Production of BTX by Hydrogenation of Pyrolysis Gasoline
Source: Reference 30.
-------
palladium catalyst. Also, the olefins produced from the raffinate stream (Stream 8) may be
added to a gasoline process or sold as a reformer stock.31
4.3.2 Benzene Emissions from Ethylene Plants and Benzene Recovery from Pyrolysis
Gasoline
Production of ethylene from naphtha/gas oil does not produce large quantities of
volatile organic compounds (VOC) or benzene emissions from process vents during normal
operations.28 Emission factors for benzene from sources at ethylene plants are shown in
Table 4-4. The chief source of benzene emissions during normal operations is the charge gas
compressor lubricating oil vent (Stream 47, Vent G in Figure 4-5). The emission factors in
Table 4-4 were developed from data supplied by ethylene manufacturers.
Most benzene emissions from ethylene plants are intermittent and occur during
plant startup and shutdown, process upsets, and emergencies (Vent E). For example, benzene
may be emitted from pressure relief devices, during intentional venting of .off-specification
materials, or during depressurizing and purging of equipment for maintenance.28 Charge gas
compressor and refrigeration compressor outages are also potential sources. Emissions from
these compressors are generally short term hi duration, but pollutants may be emitted at a high
rate.
In general, intermittent emissions and emissions from all pressure relief devices
and emergency vents are routed through the main process vent (Vent E in Figure 4-5). The
vent usually is controlled. The relief valve from the demethanizer is usually not routed to the
mam vent, but the valve is operated infrequently and emits mainly hydrogen and methane.28
Potential sources of benzene such as flue gas from the cracking furnace
(Vent A), pyrolysis furnace decoking (Vent B), acid gas removal (Vent D), and hydrogenation
catalyst regeneration (Vent F) generally are not significant sources.28 Flue gas normally
contains products of hydrogen and methane combustion. Emissions from pyrolysis furnace
decoking consist of air, steam, CO2, CO, and particles of unburned carbon.28 Emissions from
.4-32
-------
TABLE 4-4. BENZENE EMISSION FACTORS FOR A HYPOTHETICAL ETHYLENE PLANT"
u>
3-01-197-42
Ethylene Manufacturing -
Pyrolysis Furnace Decoking
3-01-197-43
Ethylene Manufacturing-Acid Gas
Removal
3-01-197-44
Ethylene Manufacturing -
Catalyst Regeneration
3-01-197-XX
Ethylene Manufacturing -
Secondary Sources
Pyrolysis Furnace Decoking
Acid Gas Removal
Catalyst Regeneration
Secondary Uncontrolled
Wastewater Treatment
No benzene emissions
No benzene emissions
No benzene emissions
0.0434 U
(0.0217)
3-01-197-49
Ethylene Manufacturing -
Equipment Leak Emissions
Equipment Leak Emissions
Detection/
Correction of leaks
Uncontrolled
See Section 4.S.2
See Section 4.S.2
-------
TABLE 4-4. BENZENE EMISSION FACTORS FOR A HYPOTHETICAL ETHYLENE PLANT"
SCC and Description Emission Source Control Device Emission Factor in Ib/ton (kg/Mg)
3-01-197-XX Intermittent Emissions'
Ethylene Manufacturing-
Intermittent Emissions Single Compressor Train Flare 0.1584-0.0316
(0.0792-0.0158)
Uncontrolled 1.584
(0.7919)
Dual Compressor Train Flare 0.0202-0.004
(0.0101-0.002)
Uncontrolled 0.2022
(0.1011)
Factor
Rating
U
U
U
U
LO
*"• ' Data are for a hypothetical plant using 50 percent naphtha/50 percent gas oil as feed and having an ethylene capacity of 1 , 199,743 Ib/yr (544.2 Gg/yr).
b Factors are expressed as Ib (kg) benzene emitted per ton (Mg) ethylene produced.
c Intermittent emissions have been reported from the activation of pressure relief devices and the depressurization and purging of equipment for maintenance
purposes.
-------
acid gas removal are H2S, S02, and C02; these emissions are generally controlled to recover
H2S as sulfur or convert H2S to SO2. As discussed earlier," catalyst regeneration is infrequent
and no significant concentrations of benzene have been reported as present in the emissions.28
Equipment leak benzene emissions at ethylene plants may originate from pumps,
valves, process sampling, and continuous process analysis. Refer to Section 4.5.2 of this
document, for information on emission estimates procedures, and available emission factors.
Regarding equipment leak component counts, totals of 377 and 719 valves for benzene vapor
and benzene liquid service respectively had been reported for ethylene plants.32 Storage of
ethylene in salt domes is not a potential source of benzene emissions because the ethylene
generally does not contain benzene.
The emission factor for benzene from storage vessels shown in Table 4-4 was
derived from AP-42 equations.33 No supporting data showing how the equations were applied
were provided by the emission factor reference.
Secondary emissions include those associated with handling and disposal of
process wastewater. The emission factor in Table 4-4 was derived from estimates of
wastewater produced and the estimated percent of the volatile organic compounds (VOC)
emitted from the wastewater that is benzene.
No data were available concerning benzene emissions from recovering benzene
from pyrolysis gasoline. Likely sources include reactor vents, compressors, and any vents on
the benzene column (Figure 4-6).
The primary control techniques available for intermittent emissions of benzene
(pressure relief valves, emergency vents) are flaring and combustion within industrial waste
boilers. Other control methods are not as attractive because the emissions are infrequent and
of short duration. The estimated control efficiency of flares is 98 percent or greater34 while
control efficiencies for industrial waste boilers vary depending upon design and operation.28
4-35
-------
For additional discussion on flares and industrial waste boilers as control methods, see
Section 4.5.1. One ethylene producer that provided a process description stated that all
process vents are connected to flares. However, it was not possible to determine how
prevalent such systems are for ethylene production.35
Equipment leak emissions may be controlled by inspection/maintenance plans or
use of equipment such as tandem seal pumps. For additional discussion on equipment leak
emissions, see Section 4.5.2. Emissions from sampling lines can be controlled by piping
sample line purge gas to the charge gas compressor or to a combustion chamber. Streams
from process analyzers may be controlled in the same manner.28
The primary means of controlling emissions from pyrolysis gasoline or naphtha
feedstock storage is floating roof tanks. Emissions can be reduced by 85 percent when internal
floating roof devices are used.28 For additional discussion on storage tank emissions, see
Section 4.5.3.
4.4 COKE OVEN AND COKE BY-PRODUCT RECOVERY PLANTS
Most coke is produced in the U.S. using the by-product recovery process. In
1994, there was one plant that used a "nonrecovery" process. This section will focus on the
by-product recovery process because there are so few nonrecovery facilities in operation.296
4.4.1 Process Description
Although most benzene is obtained from petroleum, some is recovered through
distillation of coke oven light oil at coke by-product recovery plants. Light oil is a clear
yellow-brown oil that contains coke oven gas components with boiling points between 32 and
392°F (0 and 200°C).26 Most by-product recovery plants recover light oil, but not all plants
refine it. About 3.4 to 4.8 gal (13 to 18 liters [L]) of light oil can be recovered from the coke
4-36
-------
oven gas evolved in coke ovens producing 0.91 ton (1 megagram [Mg]) of furnace coke (3 to
4 gal/ton [10.3 to 13.7 L/Mg]). Light oil itself is 60 to 85 percent benzene.37
The coke by-product industry recovers various components of coke oven gas
including:
• Coal tar, a feedstock for producing electrode binder pitch, roofing pitch,
road tar, and numerous basic chemicals;
• Light oil, a source of benzene and other light aromatic chemicals;
• Ammonia or ammonium sulfate, for agriculture and as chemical
feedstocks;
• Sulfur, a basic chemical commodity;
• Naphdialene, used primarily as an intermediate in the production of
organic chemicals; and
38
• Coke oven gas, a high-quality fuel similar to natural gas.
Because it is contained in the coke oven gas, benzene may be emitted from
processes at by-product recovery plants that do not specifically recover or refine benzene.
Table 4-5 lists coke oven batteries with by-product recovery plants in the United States.36
Figure 4-7 shows a process flow diagram for a representative coke by-product recovery
plant.37'39 The figure does not necessarily reflect any given plant, nor does it include all
possible operations that could be found at a given facility. The number of units and the types
of processes used varies among specific plants. For example, naphthalene recovery is not
practiced at all plants, and some plants do not separate benzene from the light oil. Therefore,
it is advisable to contact a specific facility to determine which processes are used before
estimating emissions based on data hi this document.
Coal is converted to coke in coke ovens. About 99 percent of the U.S.
production of coke uses the slot oven process, also referred to as the Kopper-Becker
by-product coking process; the other 1 percent is produced hi the original beehive ovens.
4-37
-------
TABLE 4-5. COKE OVEN BATTERIES CURRENTLY OPERATING
IN THE UNITED STATES
Plant (Location)
ABC Coke (Tarrant, AL)
Acme Steel (Chicago, IL)
Armco, Inc. (Middletown, OH)
Armco, Inc. (Ashland, KY)
Bethlehem Steel (Bethlehem, PA)
Bethlehem Steel (Burns Harbor, IN)
Bethlehem Steel (Lackawanna, NY)
Citizens Gas (Indianapolis, IN)
Empire Coke (Holt, AL)
Erie Coke (Erie, PA)
Geneva Steel (Provo, UT)
Gulf States Steel (Gadsden, AL)
Battery Identification
Number
A
5
6
1
2
1
2
3
3
4
A
2
3
1
2
7
8
E
H
1
1
2
A
B
1
2
3
4
2
3
.4-38
(continued)
-------
TABLE 4-5. CONTINUED
Plant (Location)
Battery Identification
Number
Inland Steel (East Chicago, IN)
Koppers (Woodward, AL)
LTV Steel (Cleveland, OH)
LTV Steel (Pittsburgh, PA)
LTV Steel (Chicago, IL)
LTV Steel (Warren, OH)
National Steel (Ecorse, MI)
National Steel (Granite City, IL)
New Boston Coke (Portsmouth, OH)
Sharon Steel (Monessen, PA)
Shenango (Pittsburgh, PA)
Sloss Industries (Birmingham, AL)
Toledo Coke (Toledo, OH)
Tonawanda Coke (Buffalo. NY)
6
7
9
10
11
1
2A
2B
4A
4B
5
6
7
PI
P2
P3N
P3S
P4
2
4
5
A
B
1
IB
2
1
4
3
4
5
C
1
4-39
(continued)
-------
TABLE 4-5. CONTINUED
Battery Identification
Plant (Location) Number
USX (Clairton, PA) 1
2
3
7
8
9
13
14
15
19
20
B
USX (Gary, IN) 23
5
7
Wheeling-Pittsburgh (East Steubenville, WV) 1
. 2
3
8
Source: Reference 36.
NOTE: This list is subject to change as market conditions change, facility ownership changes, plants are closed,
etc. The reader should verify the existence of particular facilities by consulting current lists and/or the
plants themselves. The level of benzene emissions from any given facility is a function of variables
such as capacity, throughput and control measures, and should be determined through direct contacts
with plant personnel These operating plants and locations were current as of April 1, 1992
4-40
-------
Coke
Tar
Removal Reheater
Am in on la
Absorber
Acid Storage
(NH4)2 S04
Crystalllzer/
Drying
Final
Cooler
JT
Light-Oil
Scrubber
/O.
x^
1
Naphthalani
Separation
Cooling
Tower
Handling
Tar Product
Source: Reference 37 and 39.
Figure 4-7. Coke Oven By-Product Recovery, Representative Plant
Note: The etream number* on the figure correspond to the dlecueelon hi
the text (or thta proceea. Letters corretpond to potential aourcea
of benzene embilont.
4
o
p
-------
Each oven has 3 main parts: coking chambers, heating chambers, and regenerative
chambers. All of the chambers are lined with refractory (silica) brick. The coking chamber
has ports in the top for charging of the coal.22
Each oven is typically capable of producing batches of 10 to 55 tons (9.1 to
49.9 Mg) of coke product. A coke oven battery is a series of 20 to 100 coke ovens operated
together, with offtake flues on either end of the ovens to remove gases produced. The
individual ovens are charged and discharged at approximately equal time intervals during the
coke cycle. The resulting constant flow of evolved gas from all the ovens hi a battery helps
to maintain a balance of pressure in the flues, collecting main, and stack. Process heat
comes from the combustion of gases between the coke chambers. Approximately 40 percent
of cleaned oven gas (after the removal of its byproducts) is used to heat the coke ovens. The
rest is either used in other production processes related to steel production or sold. Coke
oven gas is the most common fuel for underfiring coke ovens.22 The coking time affects the
type of coke produced. Furnace coke results when coal is coked for about 15 to 18 hours.
Foundry coke, which is less common and is of higher quality (because it'is harder and less
readily ignited), results when coal is coked for about 25 to 30 hours.37
The coking process is actually thermal distillation of coal to separate volatile
and nonvolatile components. Pulverized coal is charged into the top of an empty, but hot,
coke oven. Peaks of coal form under the charging ports and a leveling bar smoothes them
out. After the leveling bar is withdrawn, the topside charging ports are closed and the
coking process begins.
Heat for the coke ovens is supplied by a combustion system under the coke
oven. The gases evolved during the thermal distillation are removed through the offtake
main and sent to the by-product recovery plant for further processing.
4-42
-------
After coking is completed (no volatiles remain), the coke in the chamber is
ready to be removed. Doors on both sides of the chamber are opened and a ram is inserted
into the chamber. The coke is pushed out of the oven in less than 1 minute, through the coke
guide and into a quench car. After the coke is pushed from the oven, the doors are cleaned
and repositioned. The oven is then ready to receive another charge of coal.
The quench car carrying the hot coke moves along the battery tracks to a quench
tower where approximately 270 gallons of water per ton of coke (1,130 L of water per Mg)
are sprayed onto the coke mass to cool it from about 2000 to 180°F (1100 to 80 °C) and to
prevent it from igniting. The quench car may rely on a movable hood to collect paniculate
emissions, or it may have a scrubber car attached. The car then discharges the coke onto a
wharf to drain and continue cooling. Gates on the wharf are opened to allow the coke to fall
onto a conveyor that carries it to the crushing and screening station. After sizing, coke is
sent to the blast furnace or to storage.
As shown in Figure 4-7, coke oven gas leaves the oven at about 1292°F
(700 °C) and is immediately contacted with flushing liquor (Stream 1). The flushing liquor
reduces the temperature of the gas and acts as a collecting medium for condensed tar. The
gas then passes into the suction main. About 80 percent of the tar is separated from the gas
in the mains as "heavy" tar and is flushed to the tar decanter (Stream 2).37 Another
20 percent of the tar is "light" tar, which is cleaner and less viscous, and is condensed and
collected in the primary cooler.39 Smaller amounts of "tar fog" are removed from the gas by
collectors (electrostatic precipitators or gas scrubbers) (Stream 4).37 Light tar and tar fog is
collected in the tar intercept sump (stream 6) and is routed to the tar decanter (Stream 5).
Depending on plant design, the heavy and light tar streams (Streams 2 and 5)
may be merged or separated. The tar is separated from the flushing liquor by gravity in the tar
decanter. Recovered flushing liquor is returned to the Flushing Liquor Circulation Tank
(Stream7) and re-used. Tar from the decanter is further refined in the tar dewater tank
4-43
-------
(Stream 3). Tar may be sold to coal tar refiners or it may be refined further on site. Tar and
tar products are stored on site in tanks.
Wastewater processing can recover phenol (Stream 8) and ammonia, with the
ammonia routinely being reinjected into the gas stream (Stream 9). Ammonia salts or
ammonia can be recovered by several processes. Traditionally, the ammonia-containing coke
oven gas is contacted with sulfuric acid (Stream 10), and ammonium sulfate crystals are
recovered (Stream 11). The coke oven gas from which tar and ammonia have been
recovered is sent to the final cooler (Stream 12). The final cooler is generally a spray tower,
with water serving as the cooling medium.37
Three types of final coolers and naphthalene recovery technologies are
currently used: (1) direct cooling with water and naphthalene recovery by physical
separation, (2) direct cooling with water and naphthalene recovery hi the tar bottom of the
final cooler, and (3) direct cooling with wash oil and naphthalene recovery hi the wash oil.37
Most plants use direct water final coolers and recover naphthalene by physical separation.37
In this method, naphthalene in the coke oven gas is condensed hi the cooling medium and
separated by gravity (Stream 13). After the naphthalene is separated, the water is sent to a
cooling tower (Stream 14) and recirculated to the final cooler (Stream 15). The coke oven
gas that leaves the final cooler is sent to the light oil processing segment of the plant
(Stream 16).
i
As shown in Figure 4-7, light oil is primarily recovered from coke oven gas
by continuous countercurrent absorption hi a high-boiling liquid from which it is stripped by
steam distillation.10 Coke oven gas is introduced into a light oil scrubber (Stream 16).
Packed or tray towers have been used hi this phase of the process, but spray towers are now
commonly used.10 Wash oil is introduced into the top of the tower (Stream 17) and is
circulated through the contacting stages of the tower at around 0.11 to .019 gal/ft3 (1.5 to
2.5 liters per cubic meter [L/m3]) of coke oven gas.39 At a temperature of about 86°F
(30°C), a light oil scrubber will remove 95 percent of the light oil from coke oven gas. The
.4-44
-------
Recycle
Gas Healer
J^
]
' r
•*
Hydrogen
Generation Unit
and/or Make-up
Gas Compression
a f
4i . »»• Excess CrC4
m
1
^ H2S
Cryogenic
Processing
a- ' i i
I ' ' Compressor Benzene Toluene
(A
4^. Raw
^ Coko Ovfln
<-" Light 0»
S\
^
/>
5
k.
>
»»
/•K
s^
f
i
*
J
x-
V«
"N
^^
«•
^-
/£\ /^v . °6 Product Product
i <$> ® i «i 4
O,,r|-r "If W t \ r ^"\. 1 \
KOflCtOi
-N
x
V,.
J~L
•^ ',•
Charge
r^\ s~\ r* \
X% 3- - - -
<-<^ ^_ ^/ *^ ^ Separator —— —
&
Vaporizer
Prafracoonatlon
> P 1 |l :
Lilol Reactors TT \*s \y j
iStabMzer Clay Benzene Toluene
Steam Generation T Tow T
and Other Heat
Exchange .j
Note: The stream numbers on the figure correspond to the discussion In the text for
this process. Letters correspond to potential sources of benzene emissions.
Figure 4-8. Litol Process Flow Diagram
3
O
*
Source: References 40 and 41.
-------
benzene-containing wash oil is steam-stripped (Stream 18) to recover the light oil.39 Steam
and stripped vapors are condensed and separated (Streams 19 and 20). The light oil is sent to
storage (Stream 21).37-39
To recover the benzene present in the light oil, processes such as Litol
(licensed by Houdry) or Hydeal (licensed by UOP) are used. Figure 4-8 shows a process
diagram of the Litol process. The folio whig discussion of the Litol process is drawn from
two published descriptions of the process.40-41
The light oil is prefractionated (Stream 1) to remove the C5 and lighter
fractions, and the C9 and heavier fractions (Stream 2). The remaining "heart cut" is sent to a
vaporizer, where it contacts gas with a high hydrogen content (Stream 3). The light oil and
hydrogen then flow to a pretreat reactor (Stream 4), where styrene, di-olefins, and some
sulfur compounds are hydrogenated (at about 572°F [300°C]). The partially hydrogenated
stream is heated by the charge heater to the temperature required for the main reactor
(StreamS).
The stream is then sent through a set of fixed-bed (Litol) reactors (Streams 6
and 7), where all remaining sulfur compounds are converted to H2S and organics are
dehydrogenated or dealkylated. The reactor effluent is cooled by post-reactor exchangers
(Streams 8 and 9). At the flash drum, aromatics are condensed and separated from the gas
stream (Stream 10). At the stabilizer, additional gas is removed, resulting in a hot liquid fuel
for clay treatment (Stream 11). The clay treater removes the last trace of unsaturates from
the aromatics (Stream 12). Conventional distillation yields pure benzene followed by pure
toluene (Stream 13). Benzene product may then be sent to storage (Stream 14).40-41
4.4.2 Benzene Emissions
Benzene may be emitted from many points in a coke and coke by-product
plant; emissions are not limited to the benzene recovery section of the process. The coke
4-46
-------
ovens themselves are potential sources of benzene emissions from the charging operation,
leaking coke oven doors, topside port lids and offtake systems on the topside of the battery,
collecting mams, and bypass/bleeder stacks.36
During charging, moist coal contacts the hot oven floor and walls and, as a
result, the release of volatile components begins immediately. Control of charging emissions
is more dependent on operating procedures than on equipment. Control options include
staged charging, sequential charging, and use of wet scrubbers on larry cars (the mobile
hoppers that discharge the coal).
Staged charging involves pouring coal into the coke ovens so that an exit space
for the generated gases is constantly maintained.42 The hoppers delivering the coal are
discharged such that emissions are contained in the ovens and collecting mains by steam
aspiration. Generally, a maximum of two hoppers are discharging at the same tune.
In sequential charging, the first hoppers are still discharging when subsequent
hoppers begin discharging coal. As with staged charging, the coke ovens are under
aspiration in sequential charging. The sequential charging procedure is designed to shorten
the charging time.
In the use of wet scrubbers on larry cars, the scrubber emissions are contained
by hoods or shrouds that are lowered over the charging ports.
Another potential source of benzene emissions at coke ovens is leaking doors.
The doors are sealed before the coking process begins. Some doors have a flexible metal
band or rigid knife edge as a seal. The seal is formed by condensation of escaping tars on
the door's metal edge. Other doors are sealed by hand by troweling a mixture into the
opening between the coke oven door and door frame. After the coking process is complete,
the doors are opened to push the coked coal out into special railroad cars called quench cars
for transport to the quench tower. Quenched coke is then discharged onto a "coke wharf" to
4-47
-------
allow quench water to drain and to let the coke cool. Control techniques for leaking doors
include oven door seal technology, pressure differential devices, hoods/shrouds over the
doors, and the use of more efficient operating/maintenance procedures.42
Oven door seal technology relies on the principle of producing a resistance to
the flow of gases out of the coke oven. This resistance may be produced by a metal-to-metal
seal, a resilient soft seal, or a luted seal (applying a slurry mixture of clay, coal, and other
materials). Small cracks and defects in the seal allow pollutants to escape from the coke
oven early in the cycle. The magnitude of the leak is determined by the size of the opening,
the pressure drop between the oven and the atmosphere, and the composition of the
emissions.
The effectiveness of a pressure differential control device depends on the
ability of the device to reduce or reverse the pressure differential across any defects, in the
door seal. These systems either provide a channel to permit gases that evolve at the bottom
of the oven to escape to the collecting main, or the systems provide external pressure on the
seal through the use of steam or inert gases.
Oven door emissions also can be reduced by collecting the leaking gases and
particulates and subsequently removing these pollutants from the air stream. A suction hood
above each door with a wet electrostatic precipitator for fume removal is an example of this
type of system.
Other control techniques rely on operating and maintenance procedures rather
than only hardware. Operating procedures for emission reduction could include changes in
the oven cycle times and temperatures, the amount and placement of each charge, and any
adjustments of the end-door while the oven is on line. Maintenance procedures include
routine inspection, replacement, and repair of control devices and doors.
4-48
-------
Topside leaks are those occurring from rims of charging ports and standpipe
leaks on the top of the coke oven. These leaks are primarily controlled by proper
maintenance and operating procedures that include:42
• Replacement of warped lids;
• Cleaning carbon deposits or other obstructions from the mating
surfaces of lids or their seats;
• Patching or replacing cracked standpipes;
• Sealing lids after a charge or whenever necessary with lute; and
• Sealing cracks at the base of a standpipe with lute.
Luting mixtures are generally prepared by plant personnel according to
formulas developed by each plant. The consistency (thickness) of the mixture is adjusted to
suit different applications.
There are few emission factors specifically for benzene emissions at coke
ovens. One test that examined emissions of door leaks detected benzene in the emissions.42
The coke oven doors being tested were controlled with a collecting device, which then fed
the collected emissions to a wet electrostatic precipitator. Tests at the precipitator inlet
showed benzene concentrations of 1.9 x 10'7 to 6.2 x 10'7 Ib/ft3 (1 to 3 parts per million
[ppm] or about 3 to 10 milligrams per cubic meter [Mg/m3]). These data translated into an
estimated benzene emission factoi of 1.3 Ib to 5.3 Ib (0.6 to 2.4 kilograms [kg]) benzene per
hour of operation for coke oven doors. In addition to coke oven door emissions, benzene
may also be emitted from the coke oven bypass stack at a rate of 22 Ibs/ton of coal charged
(11,000 g/Mg) uncontrolled, 0.22 Ibs/ton of coal charged (110 g/Mg) controlled with
flare.296 No additional emission factors for benzene-and coke ovens were found in the
literature. However, an analysis of coke oven gas indicated a benzene content of
1.3 x 10'3 to 2.2 x 10"3 Ib/ft3 (21.4 to 35.8 grams per cubic meter [g/m3]).
4-49
-------
Other potential sources of benzene emissions associated with the by-product
recovery plant are given in Table 4-6, along with emission factors.37-43
Equipment leaks may also contribute to benzene emissions. Emission factors
for pumps, valves, etc., at furnace coke and foundry coke by-product recovery plants are
shown in Tables 4-7 and 4-8, respectively.37-43 The following paragraphs describe the
potential sources of benzene emissions listed in Tables 4-6, 4-7, and 4-8. Emission sources
and control technologies are described in groups of related processes, beginning with the
final cooling unit.
The final cooling unit itself is not a source of benzene because coolers are
closed systems. However, the induced-draft cooling towers used in conjunction with
direct-water and tar-bottom final coolers are potential sources of benzene. Benzene can be
condensed in the direct-contact cooling water, and in the cooling tower, lighter components
(such as benzene) will be stripped from the recirculating cooling water. The emission factor
of 0.54 pound per ton (Ib/ton) (270 g/Mg) coke shown in Table 4-6 was'based on actual
measurements of benzene concentrations and volumetric gas flow rates taken from source
testing reports.37
Use of a wash oil final cooler effectively eliminates the benzene emissions
associated with direct water or tar bottom coolers because the wash oil is cooled by an
indirect heat exchanger, thereby eliminating the need for a cooling tower.37 Wash oil is
separated after it leaves the heat exchanger and recu-culates back through the circulation tank
to the final cooler.
Coke by-product recovery plants may recover naphthalene by condensing it
from the coke oven gas and separating it from the cooling water by flotation. Benzene may
be emitted from most naphthalene separation and processing operations.37 Vapors from
naphthalene separation tanks have been reported to contain benzene, benzene homologs, and
other aromatic hydrocarbons.37 The emission factors for naphthalene separation and
4-50
-------
TABLE 4-6. SUMMARY OF BENZENE EMISSION FACTORS FOR FURNACE AND
FOUNDRY COKE BY-PRODUCT RECOVERY PLANTS
Emission Factor Ib/ton (g/Mg)b
SCC and Description
3-03-003-15
By-Product Coke -
Gas By-Product Plant
Emissions Source"
Cooling Tower
- Direct Water (A)c
- Tar bottom (B)c
Light-Oil Condenser
Vent (C)
Naphthalene Separation
and Processing (D)
Tar-Intercepting Sump
(E)
Tar Dewatering (F)
Control Device
Uncontrolled
Uncontrolled
Uncontrolled
Gas Blanketing
Uncontrolled
Activated Carbon
Uncontrolled
Uncontrolled
Gas Blanketing
Furnace Coke
0.54 (270)
0.14(70)
0.18(89)
3.6 x 10 3 (1.8)
0.22(110)
7.0 x 10^ (0.35)
0.019 (9.5)
0.042 (21)
8.4 x 10^ (0.45)
Foundry Coke
0.40 (200)
0.10(51)
0.096 (48)
1. 9x10* (0.97)
0.16(80)
5.0 x lO^1 (0.25)
0.009 (4.5)
0.020(9.9)
. 4x10^(0.2)
Factor
Rating
E
E
E
E
E
E
E
E
E
(continued)
-------
TABLE 4-6. CONTINUED
SCC and Description Emissions Source' Control Device
Tar Decanter (G) Uncontrolled
Gas Blanketing
Tar Storage (H) Uncontrolled
Gas Blanketing
Light-Oil Sump (I) Uncontrolled
•£>• Gas Blanketing
en
N>
Light-Oil Storage (J) Uncontrolled
Gas Blanketing
BTX Storage (K)d Uncontrolled
Gas Blanketing
Benzene Storage (L)d Uncontrolled
Gas Blanketing
Emission Factor
Furnace Coke
0.11 (54)
22 x 10 3 (1.1)
0.013 (6.6)
7.6 x 10^ (0.38)
0.03 (15)
6 x lO^1 (0.3)
0.012(5.8)
2.4 x 10^(0.12)
0.012 (5.8)
2.4 x 10^(0.12)
0.0116(5.8)
2.4x10^(0.12)
Ib/ton (g/Mg)b
Foundry Coke
0.05 (25)
1. Ox Iff1 (0.5)
6.2 x 10 3
3.6x10^(0.18)
0.016(8.1)
3.2 x 10^(0.16)
6.2 x 10 '(3.1)
1.2x10^(0.06)
6.2 x 10 3 (3.1)
l,2x 10^(0.06)
6.2xl03(3.1)
1.2x10^(0.06)
Factor
Rating
E
E
E
E
E
E
E
E
E
E
E
E
(continued)
-------
TABLE 4-6. CONTINUED
Emission Factor Ib/ton (g/Mg)b
SCC and Description Emissions Source1
Flushing-Liquor
Circulation Tank (M)
Excess- Ammonia Liquor
Tank(N)
^ • Wash-Oil Decanter (O)
U)
Wash-Oil Circulation
Tank(P)
Control Device
Uncontrolled
Gas Blanketing
Uncontrolled
Gas Blanketing
Uncontrolled
Gas Blanketing
Uncontrolled
Gas Blanketing
Furnace Coke
0.026 (13)
5.2 x 104 (0.26)
2.8 x 103
5.6 x 10 5 (0.028)
7.6 x 103 (3.8)
1.5x10^(0.076)
7.6 x 103 (3.8)
1.5x10^(0.076)
Foundry Coke
0.019 (9.5)
3.8x10^(0.19)
2.0 x 103
4.0 x 10 5 (0.020)
4.2xl03(2.1)
8.2 x 10s (0.041)
4.2 x 10 3 (2.1)
8. 2 x 10 5 (0.041)
Factor
Rating
E
E
E
E
E
E
E
E
Source: Reference 296.
1 Source identification letters correspond to locations identified in Figure 4-7.
b Emission factors are expressed as g benzene emitted per Mg coke produced.
c Usually only smaller plants use direct-water final cooler; all final coolers are shown as one unit in Figure 4-7.
d Not all plants separate BTX or benzene. Therefore, all product storage is indicated in one box on the diagram in Figure 4-7.
-------
TABLE 4-7. SUMMARY OF BENZENE EMISSION FACTORS FOR EQUIPMENT LEAKS AT
FURNACE COKE BY-PRODUCT RECOVERY PLANTS
t-
en
Emission Factor
Ib/source day (kg/source day)''b
SCC and Description Emissions Source Control (% efficiency)
3-03-003-15 Valves Uncontrolled
By-Product Coke - , . .
Gas Bv-Product Quarterly inspection
Recovery Monthly inspection
Use sealed bellows valves
Pumps Uncontrolled
Quarterly inspection
Monthly inspection
Use dual mechanical seals
Exhausters Uncontrolled
Quarterly inspection
Monthly inspection
Use degassing reservoir vents
Pressure Relief Devices Uncontrolled
Quarterly inspection
Monthly inspection
Use rupture disk system
Sampling Connections Uncontrolled
Closed-purge sampling
(63)
(72)
(100)
(71)
(83)
(100)
(55)
(64)
(100)
(44)
(52)
(100)
(100)
Light Oil BTX
Recovery'
0.4(0.18)
0.15(0.07)
0.11(0.05)
-
4.2(1.9)
1.2(0.55)
0.71 (0.32)
--
0.62 (0.28C)
0.29(0.13)
0.22(0.10)
~
6.0 (2.7)
3.3(1.5)
2.9(1.3)
~
0.55 (0.25)
Light Oil Recovery,
Benzene Refining0
0.49 (0.22)
0.18(0.08)
0.13(0.06)
.
5.1(2.3)
1.5(0.67)
0.86 (0.39)
~
0.62 (0.28C)
0.29(0.13)
0.22(0.10)
-
7.5 (3.4)
4.2(1.9)
3.5(1.6)
~
0.68(0.31)
Factor
Rating
U
U
U
U
U
U
U
u •
U
u
u
u
u
(continued)
-------
TABLE 4-7. CONTINUED
Emission Factor
Ib/source day (kg/source day)1>b
SCC and Description Emissions Source Control (% efficiency)
Open-ended Lines Uncontrolled
Plug or cap (100)
Light Oil BTX
Recovery'
0.084 (0.038)
Light Oil Recovery,
Benzene Refining'
0.104(0.047)
Factor
Rating
U
Source: Reference 37.
f-
en
* Factors are based on the total VOC emissions from petroleum refineries and the percent of benzene in light oil and refined benzene.
b Factors are expressed as Ib emitted per source day (kg benzene emitted per source day).
c Emission factors are presented for two different types of coke by-product recovery plants, but are not representative of any particular plant.
-------
TABLE 4-8. SUMMARY OF BENZENE EMISSION FACTORS FOR EQUIPMENT LEAKS AT FOUNDRY
COKE BY-PRODUCT RECOVERY PLANTS
o\
Emission Factor
Ib/source day (kg/source day)'-b
SCC and Description Emissions Source Control (% efficiency)
3-03-003-15 Valves Uncontrolled
By-Product Coke - „
/-i n n j . Quarterly inspection
Gas By-Product J r
Recovery Monthly inspection
Use sealed bellows valves
Pumps Uncontrolled
Quarterly inspection
Monthly inspection
Use dual mechanical seals
Exhausters Uncontrolled
Quarterly inspection
Monthly inspection
Use degassing reservoir vents
Pressure Relief Devices Uncontrolled
Quarterly inspection
Monthly inspection
Use rupture disk system
Sampling Connections Uncontrolled
Plug or cap
(63)
(72)
(100)
(71)
(83)
(100)
(55)
(64)
(100)
(44)
(52)
(100)
(100)
Light Oil BTX
Recovery0
0.35(0.16)
0.13(0.06)
0.09 (0.04)
-
3.7(1.7)
1.1(0.5)
0.66 (0.3)
-
0.55 (0.25)
0.24(0.11)
0.20 (0.09)
-
5.5 (2.5)
3.1 (1.4)
2.6(1.2)
~
0.51 (0.23)
~
Light Oil Recovery,
Benzene Refining0
0.44 (0.20)
0.15(0.07)
0.13(0.06)
-
4.6(2.1)
1.3(0.6)
0.88 (0.4)
-
0.55 (0.25)
0.24(0.11) .
0.20(0.09)
~
6.8(3.1)
3.7(1.7)
3.3(1.5)
,
0.62 (0.28)
—
Factor
Rating
U
U
U
U
U
U
U
U
U
U
U
U
U
(continued)
-------
TABLE 4-8. SUMMARY OF BENZENE EMISSION FACTORS FOR EQUIPMENT LEAKS AT FOUNDRY
COKE BY-PRODUCT RECOVERY PLANTS
Emission Factor
Ib/source day (kg/source day)"ib
SCC and Description Emissions Source Control ( % efficiency)
Open-ended Lines Uncontrolled
Closed-purge sampling (100)
Light Oil BTX
Recover/
0.077 (0.035)
Light Oil Recovery,
Benzene Refining0
0.95 (0.043)
Factor
Rating
U
Source: Reference 37.
1 Factors for foundry coke are drawn from Reference 43.
b Factors are expressed in terms of Ib (kg) of benzene emitted per source day.
c Emission factors are presented for two difierent types of foundry coke by-product recovery plants, but are not representative of any particular plant.
"--" = Data not available.
-------
processing shown in Table 4-6 are based on source testing data from a flotation unit, drying
tank, and melt pit at a coke by-product recovery plant.37 '
Benzene may also be emitted from the light oil plant, which includes the
light-oil condenser vent, light oil decanter, storage tank, intercepting sumps, the wash-oil
decanter, wash-oil circulation tank(s), and BTX storage. A control technique required by the
benzene NESHAP is the use of gas blanketing with clean coke oven gas from the gas holder
(or battery underfire system).44 With this technology, a positive (or negative) pressure
blanket of clean coke oven gas is piped to the light oil plant and the enclosed sources are
connected to the blanketing line. Using a series of piping connections and flow inducing
devices (if necessary), vapor emissions from the enclosed sources are transported back into
the clean gas system (the coke-oven battery holder, the collecting main, or another point in
the by-product recovery process).
Ultimate control of the vapors is accomplished by the combustion of the coke
oven gas.37 Such systems are currently in use at some by-product recovery plants and
reportedly have operated without difficulty. Examples of gases that may be used as the gas
blanket include duty or clean coke gas, nitrogen, or natural gas.37 The control efficiency is
estimated to be 98 percent.37'44 The control technique required by the benzene NESHAP for
the light oil sump is a tightly fitting, gasketed cover with an estimated 96-percent
efficiency.44 The emission factors for benzene sources in the light oil plant shown in
Table 4-6 are based on source tests.37
Sources of benzene emissions from tar processing include the tar decanter, the
tar-intercepting sump, tar dewatering and storage, and the flushing-liquor circulation tank.
Emission factors for these sources are shown in Table 4-6.
Benzene emissions from the tar decanter are sensitive to two operating
practices: residence time in the separator and optimal heating of the decanter.37 These two
variables should be kept hi mind when using the emission factors presented hi Table 4-6.
4-58
-------
Benzene is emitted from tar decanters through vents. Coke oven gas can be mechanically
entrained with the tar and liquor that are fed into the decanter. Because tar is fed into the
decanter at a slightly higher pressure, the coke oven gas will build up in the decanter if it is
not vented.37 Emissions were measured at tar decanters at several locations in the United
States and the emission factor shown in Table 4-6 is the average of the test values.37
The water that separates from the tar in the decanter is flushing liquor, which
is used to cool the gas leaving the coke oven. Excess flushing liquor is stored in the excess
ammonia liquor tank. Benzene may be emitted from the flushing liquor circulation tank and
the excess ammonia liquor tank. The emission factor of 0.026 Ib benzene/ton (13 g
benzene/Mg) coke produced was derived from a source test of fugitive emissions from a
primary cooler condensate tank. It was assumed that the condensate tank was similar in
design and in liquids stored as the ammonia liquor and the flushing liquor circulation
tanks.296 The actual benzene emission rate from the flushing liquor circulation tank and
excess ammonia liquor tank depends on the number of tanks, the number of vents, and the
geometry of the tanks.37
The tar-intercepting sump is a type of decanter that accepts light tar and
condensate from the primary cooler. Some of this condensate may be used to make up
flushing liquor and some may be forwarded to ammonia recovery.37 No significant benzene
emissions have been identified from the recovery of ammonia, but benzene can be emitted
from the intercepting sump. An emission factor of 0.019 Ib/ton (9.5 g benzene/Mg) coke
was reported in the literature.296
Tar dewatering may be accomplished by steam heating or centrifugal
separation or a combination of the two methods. Use of centrifugal separation will probably
not be a source of benzene emissions directly, but benzene may be emitted as a fugitive
emission if storage vessels are used.39 In steam heating, benzene could be driven off in the
vapors. The emission factor for tar dewatering in Table 4-6 was derived by averaging three
factors (0.082, 0.019, and 0.0258 Ib benzene/ton coke [41, 9.5, and 12.9 g benzene/Mg
4-59
-------
coke]) based on source tests at tar dewatering tanks.37 Gas blanketing is the control
technology required by the benzene NESHAP for tar processing.
The final source of benzene emissions at coke by-product recovery plants is
leaks from equipment such as pumps, valves, exhausters, pressure relief devices, sampling
connection systems, and open-ended lines. Emission factors are shown in Tables 4-7 and 4-8
and are based on emission factors from a comprehensive survey of petroleum refineries and
the percent of benzene in the liquid associated with each type of equipment.37 Two different
sets of emission factors are presented, one set for a plant practicing light oil and BTX
recovery and one set for a plant producing refined benzene in addition to light oil. Emission
factors for exhausters were derived by multiplying the VOC emission factor for compressors
in hydrogen service and refineries by 0.235, the measured ratio of benzene to nonmethane
hydrocarbons present in the coke oven gas at the exhausters.37
To control benzene emissions from process vessels, storage tanks, and tar-
interrupting sumps as required by the benzene NESHAP, all openings must be enclosed or
sealed. All gases must be routed to a gas collection system (or similar configuration) where
the benzene hi the gas will be removed or destroyed. Alternately, the gases may be routed
through a closed vent system to a carbon absorber or vapor incinerator that is at least
98 percent efficient. See Section 4.5 for a discussion of these types of process control
devices.44 The control techniques required by the benzene NESHAP to control benzene
emissions from equipment leaks are presented in Table 4-9.
For the nonrecovery process, benzene emissions for coal charging are
3.6 x 10'5 Ib/ton of coal charged (1.8 x 10'2 g/Mg). Emissions from pushing and quenching
are expected to be similar to those from the by-product recovery process. Additional
benzene emissions occur from the combustion stack of nonrecovery batteries at the rate of
5.1 x 10"4 Ib/ton of coal charged (0.26 g/Mg).296
4-60
-------
TABLE 4-9. TECHNIQUES TO CONTROL BENZENE EMISSIONS FROM
EQUIPMENT LEAKS REQUIRED BY THE BENZENE NESHAP FOR COKE
BY-PRODUCT RECOVERY PLANTS
Emission Points Control Technique (% efficiency)
Pumps Monthly Inspection* (83)
Dual Mechanical Seals (100)
Valves Monthly Inspection* (73)
Sealed-Bellows Valves (100)
Exhausters Quarterly Inspections* (55)
Degassing Reservoir Vents (100)
Pressure-Relief Devices Rupture Disc System (100)
Sampling Connection Systems Closed-Purge Sampling (100)
Open-Ended Lines Cap or Plug (100)
Source' Reference 44.
' Inspection and maintenance programs include tightening seals, replacing manufacturing equipment, etc.
4.5 METHODS FOR ESTIMATING BENZENE EMISSIONS FROM EMISSION
SOURCES
In this section, the sources of benzene emissions from process vents, equipment
leaks, storage tanks, wastewater, and transfer operations are summarized, along with the
types of controls currently available for use in the industry. In addition, an overview of
methods for estimating uncontrolled and controlled emissions of benzene is
presented where available. Current Federal regulations applicable to these benzene emission
sources are identified. The information provided in this section is applicable to benzene
production facilities (discussed earlier hi this chapter) as well as to facilities that use benzene
as a feedstock to produce cyclic intermediates (discussed hi Chapter 5.0).
4-61
-------
4.5.1 Process Vent Emissions. Controls, and Regulations
Benzene emissions can occur from any process vent in any chemical production
operation that manufactures or uses benzene. Section 4.0 of this document contains a
discussion of chemical operations that manufacture benzene, whereas Section 5.0 contains a
discussion of chemical operations that use benzene as feedstock. Chemical operations that
emit benzene include air oxidation processes, reactor processes, and distillation operations.
In air oxidation processes, one or more chemicals are reacted with oxygen supplied as air or
air enriched with oxygen to create a product. With reactor processes, one or more chemicals
are reacted with another chemical (besides oxygen) and chemically altered to create one or
more new products. In distillation, one or more inlet feed streams is separated into two or
more outlet product streams, each product stream having component concentrations different
from those in the feed streams. During separation, the more volatile components are
concentrated in the vapor phase and the less volatile components in the liquid phase.45
Calculations for estimating emissions from any of these three processes are
specific to the type of vent stream and the type of control in place.
Two general types of methods are used for controlling benzene emissions from
process vents: recovery devices and combustion devices. Examples of each type of control
device that can be used to comply with air pollution control standards, along with its
estimated control efficiency, are summarized in Tables 4-10 and 4-11 and discussed briefly
below.45 The reader should keep hi mind that the most appropriate recovery control device,
as well as its effectiveness, is highly dependent upon flow rate, concentration, chemical and
physical properties of the vent stream, contaminants present, and stream temperature. To
achieve optimal control efficiency with recovery devices, several stream characteristics must
remain within a certain range. Combustion control devices are less dependent upon these
process and vent stream characteristics; however, combustion temperature and stream flow
must remain within a certain range to ensure complete combustion.46
4-62
-------
TABLE 4-10. CONTROL TECHNOLOGIES THAT FORM THE BASIS OF AIR
POLLUTION CONTROL STANDARDS
Type
Control Levels
Achievable
Design Conditions to Meet
Control Level
Comments
Flares
Industrial
Boilers/Process
Heaters
Thermal
Oxidation
;> 98%, or
20ppm
Adsorption
> 95%
• Flame present at all times -
monitor pilot
• Non-assisted Flares -
> 200 Btu/scf heating value,
and 60 ft/sec (18 m/sec)
maximum exit velocity
• Air and Steam Assisted
Flares - > 300 Btu/scf
heating value, and maximum
exit velocity based on Btu
content formula
• Vent stream directly into
flame
1600°F (87-rC) Combustion
temperature
0.75 sec. residence
For halogenated streams
2000°F(1093°C), 1.0 sec.
and use a scrubber on outlet
Proper mixing
Adequate quantity and
appropriate quality of carbon
Gas stream receives
appropriate conditioning
(cooling, filtering)
Appropriate regeneration and
cooling of carbon beds before
breakthrough occurs
Destroys rather
than recovers
organics
Smoking
allowed for
5 min/2 hr
Not used on
corrosive
streams
Destroys rather
than recovers
organics
Destroys rather
than recovers
organics
May need vapor
holder on
intermittent
streams
Most efficient on
streams with low
relative humidity
(< 50 percent).
Recovers
organics
Source: Reference 45.
.4-63
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TABLE 4-11. OTHER CONTROL TECHNOLOGIES THAT CAN BE USED
TO MEET STANDARDS
Type
Estimated
Control
Level
Critical Variables
That Affect Control Level
Comments
Catalytic
Oxidation
up to 98%
Absorption
50 to 95%
Condensation
50 to 95%
Dependent on
compounds, temp, and
catalyst bed size
Solubility of gas stream
in the absorbent
Good contact between
absorbent and gas
stream
Proper design of the
heat exchanger
Proper flow and
temperature of coolant
• Destroys rather than
recovers organics
• Technical limitations
include particulate or
compounds that poison
catalysts
• Appropriate absorbent
needed may not be
readily available
• Disposal of spent
absorbent may require
special treatment
procedures, and
recovery of organic from
absorbent may be time
consuming
• Preferable on
concentrated streams
• Preferable on
concentrated streams
• Recovers organics
Source: Reference 45.
4-64
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Three types of recovery devices have been identified for controlling benzene
emissions: condensation, absorption, and adsorption. With a condensation-type recovery
device, all or part of the condensible components of the vapor phase are converted to a liquid
phase. Condensation occurs as heat from the vapor phase is transferred to a cooling medium.
The most common type of condensation device is a surface condenser, where the coolant and
vapor phases are separated by a tube wall and never come in direct contact with each other.
Efficiency is dependent upon the type of vapor stream entering the condenser and the flow rate
and temperature of the cooling medium. Condenser efficiency varies from 50 to 95 percent.
Stream temperature and the organic concentration level in the stream must remain within a
certain range to ensure optimal control efficiency.46
In absorption, one or more components of a gas stream are selectively transferred
to a solvent liquid. Control devices in this category include spray towers, venturi scrubbers,
packed columns, and plate columns. Absorption efficiency is dependent upon the type of
solvent liquid used, as well as design and operating conditions. Absorption is desirable if there
is a high concentration of compound in the vent stream that can be recovered for reuse. For
example, in the manufacture of monochlorobenzene, absorbers are used to recover benzene for
reuse as a feedstock.46 Stream temperature, specific gravity (the degree of adsorbing liquid
saturation), and the organic concentration level must remain within a certain range to ensure
optimal control efficiency.46 Absorbers are generally not used on streams with VOC
concentrations below 300 ppmv.45 Control efficiencies vary from 50 to 95 percent.45
In adsorption, the process vent gas stream contains a component (adsorbate) that
is captured on a solid-phase surface (adsorbent) by either physical or chemical adsorption
mechanisms. Carbon adsorbers are the most commonly used adsorption method. With carbon
adsorption, the organic vapors are attracted to and physically held on granular activated carbon
through intermolecular (van der Waals) forces. The two adsorber designs are fixed-bed and
fluidized-bed. Fixed-bed adsorbers must be regenerated periodically to desorb the collected
organics. Fluidized-bed adsorbers are continually regenerated.46
4-65
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Adsorption efficiency can be 95 percent for a modern, well-designed system.
Removal efficiency depends upon the physical properties of the compounds in the offgas, the
gas stream characteristics, and the physical properties of the adsorbent. Stream mass flow
during regeneration, the temperature of the carbon bed, and organic concentration level in the
stream must remain within a certain range to ensure optimal control efficiency.46 Adsorbers are
not recommended for vent streams with high VOC concentrations.45
Four types of combustion devices are identified for control of benzene emissions
from process vents: flares, thermal oxidizers, boilers and process heaters, and catalytic
oxidizers. A combustion device chemically converts benzene and other organics to CO2 and
water. If combustion is not complete, the organic may remain unaltered or be converted to
another organic chemical, called a product of incomplete combustion. Combustion
temperature and stream flow must remain within a certain range to ensure complete
combustion.46
A flare is an open combustion process that destroys organic emissions with a
high-temperature oxidation flame. The oxygen required for combustion is provided by the air
around the flame. Good combustion is governed by flame temperature, residence time of the
organics in the combustion zone, and turbulent mixing of the components to complete the
oxidation reaction. There are two main types of flares: elevated and ground flares. A
combustion efficiency of at least 98 percent can be achieved with such control.46
A thermal oxidizer is usually a refractory-lined chamber containing a burner (or
set of burners) at one end. The thermal oxidation process is influenced by residence time,
mixing, and temperature. Unlike a flare, a thermal oxidizder operates continuously and is not
suited for intermittent streams. Because it operates continuously, auxiliary fuel must be used to
maintain combustion during episodes in which the organic concentration in the process vent
stream is below design conditions. Based on new technology, it has been determined that all
new thermal oxidizers are capable of achieving at least 98 percent destruction efficiency or a 20
parts per million by volume (ppmv) outlet concentration, based on operation at 870°C
(1,600°F) with a 0.75-second residence time.46
4-66
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Industrial boilers and process heaters can be designed to control organics by
combining the vent stream with the inlet fuel or by feeding the stream into the boiler or stream
through a separate burner. An industrial boiler produces steam at high temperatures. A
process heater raises the temperature of the process stream as well as the superheating steam at
temperatures usually lower than those of an industrial boiler. Greater than 99 percent control
efficiency is achievable with these combustion devices.46
By using catalysts, combustion can occur at temperatures lower than those used in
thermal incineration. A catalytic oxidizer is similar to a thermal incinerator except that it
incorporates the use of a catalyst. Combustion catalysts include platinum, platinum alloys,
copper oxide, chromium, and cobalt. Catalytic oxidizers can achieve destruction efficiencies of
98 percent or greater.46
Biofiltration is another type of VOC control. In biofiltration, process exhaust
gases are passed through soil on compost beds containing micro organisms, which convert
VOC to carbon dioxide, water, and mineral salts.47
Table 4-12 presents a comparison of the VOC control technologies (excluding
combustion) that are discussed in this section.47
Process vents emitting benzene and other VOC that are discussed in Sections 4.1
through 4.4 and in Section 5.0 are affected by one or more of the following six Federal
regulations:
1. "National Emission Standards for Organic Hazardous Air Pollutants from
the Synthetic Organic Chemical Manufacturing Industry," promulgated
April 22, 1994.48
2. "National Emission Standards for Hazardous Air Pollutants from
Petroleum Refineries," promulgated August 18, 1995,49
4-67
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TABLE 4-12. COMPARISON OF VOC CONTROL TECHNOLOGIES
Control
Technology
Thermal
Oxidation
Applicable
Concentration
Range, ppm
100-2,000
Capacity
Rangt , cfm
l.OOO-.'* 00,000
Removal
Efficiency
95-99+%
Secondary
Wastes
Combustion
products
Advantages
Up to 94% energy
recovery is possible.
Limitations and Contradictions
Halogenated compounds may require
additional control equipment
downstream. Not recommended for
batch operations.
Catalytic
Oxidation
oo
Condensation
Carbon
Adsorption
100-2,000 1,000-100,000 90-95% Combustion
products
> 5,000 100-20,000 50-90% Condensate
20-5,000 100-60,000 90-98% Spent carbon;
collected
organic
Up to 70% energy
recovery is possible.
Product recovery can
offset annual operating
costs.
Product recovery can
offset annual operating
costs. Can be used as a
concentrator in
conjunction with
another type of control
device. Works well
with cyclic processes.
Thermal efficiency suffers with swings
in operating conditions. Halogenated
compounds may require additional
control equipment downstream. Certain
compounds can poison the catalyst (lead,
arsenic, phosphorous, chlorine, sulfur,
paniculate matter).
Not recommended for materials with
boiling point < 100°F. Condensers are
subject to scale buildup which can cause
fouling.
Not recommended for streams with
relative humidity <50%. Ketones,
aldehydes, and esters clog the pores of
the carbon, decreasing system efficiency.
(continued)
-------
TABLE 4-12. CONTINUED
ON
Control
Technology
Absorption
Biofiltration
Applicable
Concentration Capacity
Range, ppm Range, cfm
500-5,000 2,000100,000
0-1,000 <<>0,000
Removal Secondary
Efficiency Wastes
95-98% Wastewater;
Captured
particulate
80-99% Disposal of
spent compost
beds.
Advantages
Product recovery can
offset annual operating
costs.
Efficient for low
concentration streams.
Low operating costs.
Limitations and Contradictions
Might require exotic scrubbing media.
Design could be difficult in the event of
lack of equilibrium data. Packing is
subject to plugging and fouling if
particulates are in the gas stream. Scale
formation from adsorbent/adsorber
interaction can occur.
Large amount of space may be required.
Microorganisms are effective only in the
50 to 100°F temperature range and may
be killed if proper bed moisture content
and pH is not maintained.
Source: Reference 47.
-------
3. "Standards of Performance for New Stationary Sources; Volatile Organic
Compound (VOC) Emissions from the Synthetic Organic Chemical
Manufacturing Industry (SOCMI) Air Oxidation," promulgated
July 1, 1994.50
4. "Standards of Performance for New Stationary Sources; Volatile Organic
Compound (VOC) Emissions from the Synthetic Organic Chemical
Manufacturing Industry (SOCMI) Distillation Operations," promulgated
July 1, 1994.51
5. "Standards of Performance for New Stationary Sources; Volatile Organic
Compound (VOC) Emissions from the Synthetic Organic Chemical
Manufacturing Industry (SOCMI) Reactor Processes," promulgated
July 1, 1994.52
6. "National Emission Standards for Benzene Emissions from Coke
By-Product Recovery Plants, promulgated October 27, 1993."53
In general, for the affected facilities subject to these six regulations, use of the recovery
devices and combustion devices discussed above is required. Tables 4-10 and 4-11 present a
summary of those controls and the required operating parameters and monitoring ranges needed
to ensure that the required control efficiency is being achieved.
4.5.2 Equipment Leak Emissions. Controls, and Regulations
Equipment leak emissions occur from process equipment components whenever
the liquid or gas streams leak from the equipment. Equipment leaks can occur from the
following components: pump seals, process valves, compressor seals and safety relief valves,
flanges, open-ended lines, and sampling connections. The following approaches for estimating
equipment leak emissions are presented in the EPA publication Protocol for Equipment Leak
Emission Estimates'?4
• Average emission factor approach;
• Screening ranges approach;
• EPA correlation approach; and
• Unit-specific correlation approach.
4-70
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The approaches differ in complexity; however, greater complexity usually yields more accurate
emissions estimates.
The simplest method, the average emission factor approach, requires that the
number of each component type be known. For each component, the benzene content of the
stream and the time the component is in service are needed. This information is then
multiplied by the EPA's average emission factors for the SOCMI shown in Table 4-13.54
Refinery average emission factors are shown in Table 4-14; marketing terminal average
emission factors are shown in Table 4-15; and oil and gas production average emission factors
are shown in Table 4-16.54 This method is an improvement on using generic emissions
developed from source test data, inventory data, and/or engineering judgement. However, this
method should only be used if no other data are available because it may result in an
overestimation or underestimation of actual equipment leak emissions. For each component,
estimated emissions are calculated as follows:
No. of
equipment
components
X
Weight %
benzene
in the stream
X
Component -
specific
emission factor
No. hr/yr in
benzene service
To obtain more accurate equipment leak emission estimates, one of the more
complex estimation approaches should be used. These approaches require that some level of
emissions measurement for the facility's equipment components be collected. These are
described briefly, and the reader is referred to the EPA protocol document for the calculation
details.
The screening ranges approach (formerly known as the leak/no leak approach) is
based on a determination of the number of leaking and non-leaking components. This
approach may be applied when screening data are available as either "greater than or equal to
10,000 ppmv" or as "less than 10,000 ppmv." Emission factors for these two ranges of
screening values are presented in Table 4-17 for SOCMI screening; Table 4-18 for refinery
screening, Table 4-19 for marketing terminal screening, and Table 4-20 for oil and gas
production screening.54
4-71
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TABLE 4-13. SOCMI AVERAGE TOTAL ORGANIC COMPOUND EMISSION
FACTORS FOR EQUIPMENT LEAK EMISSIONS"
Equipment Type
Valves
Pump seals0
Compressor seals
Pressure relief valves
Connectors
Open-ended lines
Sampling connections
Service
Gas
Light liquid
Heavy liquid
Light liquid
Heavy liquid
Gas
Gas
All
All
All
Emission Factor*
Ib/hr/source (kg/hr/source)
0.01313 (0.00597)
0.00887 (0.00403)
0.00051 (0.00023)
0.0438 (0.0199)
0.01896(0.00862)
0.502 (0.228)
0.229(0.104)
0.00403 (0.00183)
0.0037 (0.0017)
0.0330 (0.0150)
Source: Reference 54.
* The emission factors presented in this table for gas valves, light liquid valves, light liquid pumps, and
connectors are revised SOCMI average emission factors.
b These factors are for total organic compound emission rates.
c The light liquid pump seal factor can be used to estimate the leak rate from agitator seals.
The EPA correlation approach offers an additional refinement to estimating
equipment leak emissions by providing an equation to predict mass emission rate as a function
of screening value for a specific equipment type. The EPA correlation approach is preferred
when actual screening values are available. Correlation operations for SOCMI, refinery,
marketing terminals, and oil and gas production along with respective correlation curves are
provided in Reference 54.
The unit-specific correlation approach requires the facility to develop its own
correlation equations and requires more rigorous testing, bagging, and analyzing of equipment
leaks to determine mass emission rates.
Appendix A of the EPA protocol document provides example calculations for
each of the approaches described above.
4-72
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TABLE 4-14. REFINERY AVERAGE EMISSION FACTORS
Equipment type
Valves
Pump seals'"
Compressor seals
Pressure relief valves
Connectors
Open-ended lines
Sampling connections
Service
Gas
Light Liquid
Heavy Liquid
Light Liquid
Heavy Liquid
Gas
Gas
All
All
All
Emission Factor
(kg/hr/source)a
0.0268
0.0109
0.00023
0.114
0.021
0.636
0.16
0.00025
0.0023
0.0150
Source: Reference 54.
* These factors are for non-methane organic compound emission rates.
b The light liquid pump seal factor can be used to estimate the leak rate from agitator seals.
Although no specific information on controls of fugitive emissions used by the
industry was identified, equipment components in benzene service will have some controls in
place. Generally, control of fugitive emissions will require the use of sealless or double
mechanical seal pumps and an inspection and maintenance program, as well as replacement of
leaking valves and fittings. Typical controls for equipment leaks are listed in Table 4-21.55
Some leakless equipment is available, such as leakless valves and sealless pumps.55
Equipment leak emissions are regulated by the National Emission Standard for
Equipment Leaks (Fugitive Emission Sources) of Benzene promulgated in June 6, 1984.56 This
standard applies to sources that are intended to operate in benzene service, such as pumps,
compressors, pressure relief devices, sampling connection systems, open-ended valves or lines,
valves, flanges and other connectors, product accumulator vessels, and control devices or
systems required by this subpart.
4-73
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TABLE 4-15. MARKETING TERMINAL AVERAGE EMISSION FACTORS
Equipment Type
Valves
Pump seals
Others (compressors and
others)15
Fittings (connectors and
flanges)0
Service
Gas
Light Liquid
Gas
Light Liquid
Gas
Light Liquid
Gas
Light Liquid
Emission Factor
(kg/hr/source)a
l.SxlO'5
4.3x1 0'5
6.5xlO-5
5.4x10^
1.2X10-4
l.SxlO"4
4.2x1 0'5
S.OxlQ-6
Source: Reference 54.
1 These factors are for total organic compound emission rates (including non-VOC such as methane and ethane).
b The "other" equipment type should be applied for any equipment type other than fittings, pumps, or valves.
c "Fittings" were not identified as flanges or non-flanged connectors; therefore, the fitting emissions were
estimated by averaging the estimates from the connector and the flange correlation equations.
Each owner or operator subject to Subpart J shall comply with the requirement of
the National Emission Standard for Equipment Leaks promulgated in June 6, 1984.57 The
provisions of this subpart apply to the same sources mentioned above that are intended to
operate in volatile hazardous air pollutant (VHAP) service. Benzene is a VHAP.
The SOCMI New Source Performance Standards promulgated in
October 18, 198358 also apply to equipment leak emissions. These standards apply to VOC
emissions at affected facilities that commenced construction, modification, or reconstruction
after January 5, 1981.
Equipment leak emissions from Coke by-product recovery plants are regulated
by the National Emission Standard for Benzene Emissions from Coke By-Product Recovery
Plants promulgated in September 14,1989.53 These standards apply to the same sources
(equipment leak components) as indicated in Subpart J, and V of Part 61.
4-74
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TABLE 4-16. OIL AND GAS PRODUCTION OPERATIONS AVERAGE
EMISSION FACTORS (kg/hr/source)
Equipment Type
Valves
Pump seals
Others'
Connectors
Ranges
Open-ended lines
Service"
Gas
Heavy Oil
Light Oil
Water/Oil
Gas
Heavy Oil
Light Oil
Water/Oil
Gas
Heavy Oil
Light Oil
Water/Oil
Gas
Heavy Oil
Light Oil
Water/Oil
Gas
Heavy Oil
Light Oil
Water/Oil
Gas
Heavy Oil
Light Oil
Water/Oil
Emission Factor
(kg/hr/source)b
4.5xlO'3
8.4x10-*
2.5xlO'3
9.8xlO-5
2.4x1 O'3
NA
l.SxlO'2
2.4xlO-5
8.8xlO'3
3.2xlO'5
7.5xlO'3
1.4xlO'2
2.0X10-4
7.5X10'6
2-lxlO4
- l.lxHT*
3.9x10^
3.9xlO'7
1.1x10^
2.9x1 0"6
2.0xlO'3
1.4X10-4
1.4xlO'3
2.5x10^
Source: Reference 54.
1 Water/Oil emission factors apply to water streams in oil service with a water content greater than 50 percent,
from the point of origin to the point where the water content reaches 99 percent. For water streams with a water
content greater than 99 percent, the emission rate is considered negligible.
b These factors are for total organic compound emission rates (including non-VOC such as methane and ethane)
and apply to light crude, heavy crude, gas plant, gas production, and offshore facilities. "NA" indicates that not
enough data were available to develop the indicated emission factor.
c The "other" equipment type was denved from compressors, diaphrams, drains, dump arms, hatches, instruments,
meters, pressure relief valves, polished rods, relief valves, and vents. This "other" equipment type should be
applied for any equipment type other than connectors, flanges, open-ended lines, pumps, or valves.
4-75
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Ch
TABLE 4-17. SOCMI SCREENING VALUE RANGE TOTAL ORGANIC COMPOUND EMISSION FACTORS
FOR EQUIPMENT LEAK EMISSIONS"
Equipment Type
Valves
Pump seals0
Compressor seals
Pressure relief valves
Connectors
Open-ended lines
Service
Gas
Light liquid
Heavy liquid
Light liquid
Heavy liquid
Gas
Gas
All
All
z 10,000 ppmv Emission Factorb
lb/hr/source(kg/hr/source)
0.1720(0.0782)
0.1962(0.0892)
0.00051 (0.00023)
0.535 (0.243)
0.475 (0.216)
3.538(1.608)
3.720(1.691)
0.249(0.113)
0.02629(0.01195)
< 10,000 ppmv Emission Factor6
lb/hr/source(kg/hr/source)
0.000288 (0.000131)
0.000363 (0.000165)
0.00051 (0.00023)
0.00411(0.00187)
0.00462 (0.00210)
0.1967(0.0894)
0.0983 (0.0447)
0.0001782 (0.0000810)
0.00330 (0.00150)
Source: Reference 54.
• The emission factors presented in this table for gas valves, light liquid valves, light liquid pumps, and connectors are revised SOCMI ;> 10,0007 < 10,000
ppmv emission factors.
h These factors are for total organic composind emission rates.
c The light liquid pump seal factors can be applied to estimate the leak rate from agitator seals.
-------
TABLE 4-18. REFINERY SCREENING RANGES EMISSION FACTORS
Equipment Type
Valves
Pump sealsb
Compressor seals
Pressure relief valves
Connectors
Open-ended lines
Service
Gas
Light Liquid
Heavy Liquid
Light Liquid
Heavy Liquid
Gas
Gas
All
All
si 0,000 ppmv
Emission Factor
(kg/hr/source)a
0.2626
0.0852
0.00023
0.437
0.3885
1.608
1.691
0.0375
0.01195
<1 0,000 ppmv
Emission Factor
(kg/hr/source)a
0.0006
0.0017
0.00023
0.0120
0.0135
0.0894
0.0447
0.00006
0.00150
Source: Reference 54.
' These factors are for non-methane organic compound emission rates.
b The light liquid pump seal factors can be applied to estimate the leak rate from agitator seals.
The hazardous organic NESHAP (or HON) equipment leak provisions
promulgated on April 22, 1994, affect chemical production processes.59-60 The HON provisions
apply to new and existing facilities and specify a control level of 90 percent.
The petroleum refineries NESHAP equipment leak provisions promulgated on
August 18, 1995 affects petroleum refinery process units. The petroleum refinery provisions
appl_> to nevv and existing facilities.
4.5.3
Storage Tank Emissions. Controls, and Regulations
A possible source of benzene emissions from chemical production operations that
produce or use benzene are storage tanks that contain benzene. Emissions from storage tanks
include "working losses" and "breathing losses." Working losses are emissions that occur
while a tank is being filled (filling the tank with liquid forces organic vapors out of the tank).
Breathing losses are emissions that result from expansion due to temperature changes (a higher
4-77
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TABLE 4-19. MARKETING TERMINAL SCREENING RANGES
EMISSION FACTORS
Equipment Type
Valves
Pump seals
Others (compressors and
others)"
Fittings (connectors and
flanges)0
Service
Gas
Light Liquid
Light Liquid
Gas
Light Liquid
Gas
Light Liquid
*1 0,000 ppmv
Emission Factor
(kg/hr/source)a
NA
2.3X10'2
7,7xlO-2
NA
3.4xlO'2
3.4xlO'2
6.5x10°
<1 0,000 ppmv
Emission Factor
(kg/hr/source)a
l.SxlO-5
1.5xlO'5
2.4X10-4
1.2x10*
2.4xlO-5
5.9x10-*
7.2x10^
Source: Reference 54.
1 These factors are for total organic compound emission rates (including non-VOC such as methane and ethane).
"NA" indicates that not enough data were available to develop the indicated emission factors.
b The "other" equipment type should be applied for any equipment type other than fittings, pumps, or valves.
c "Fittings" were not identified as flanges or connectors; therefore, the fitting emissions were estimated by
averaging the estimates from the connector and the flange correlation equations.
ambient temperature heats the air inside the tank, causing the air to expand and forcing organic
vapors out of the tank). The calculations to estimate working and breathing loss
emissions from storage tanks are complex and require knowledge of a number of site-specific
factors about the storage tank for which emissions are being estimated. Equations for
estimating emissions of organic compounds from storage tanks are provided in the EPA
document entitled Compilation of Air Pollutant Emission Factors (AP-42), Chapter 7.33
Benzene emissions from storage tanks may be reduced with control equipment
and by work practices. Various types of control equipment may be used to reduce organic
emissions, including (1) storing the liquid in a storage tank with a floating deck (i.e., an
internal-floating-roof tank or external-floating-roof tank), (2) equipping floating decks with
additional devices to reduce emissions (e.g., applying sealing mechanisms around the perimeter
of the floating deck, welding the deck seams, installing gaskets around openings and in closure
devices on the floating deck), and (3) venting air emissions from a fixed-roof storage tank to a
control device (e.g., a closed-vent system and a carbon adsorber, condenser, or flare). Work
4-78
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TABLE 4-20. OIL AND GAS PRODUCTION OPERATIONS SCREENING RANGES
EMISSION FACTORS
Equipment Type
Valves
Pump seals
Others0
Connectors
Flanges
Open-ended lines
Service8
Gas
Heavy Oil
Light Oil
Water/Oil
Gas
Heavy Oil
Light Oil
Water/Oil
Gas
Heavy Oil
Light Oil
Water/Oil
Gas
Heavy Oil
Light Oil
Water/Oil
Gas
Heavy Oil
Light Oil
Water/Oil
Gas
Heavy Oil
Light Oil
Water/Oil
;>! 0,000 ppmv
Emission Factor
(kg/hr/source)b
9.8xlO-2
NA
8.7xlO'2
6.4xlO'2
7.4xlO-2
NA
1.0x10-'
NA
8.9x1 0-2
NA
8.3xlO'2
6.9x1 0-2
2.6x1 O'2
NA
2.6xlO-2
2.8x1 0'2
8.2xlO'2
NA
7.3xlO'2
NA
5.5xlO-2
S.OxlO-2
4.4x1 0"2
3.0xlO'2
10,000 ppmv
Emission Factor
(kg/hr/source)b
2.5xlO'5
8.4x10-*
1.9xlO-5
9.7X10-6
3.5x10"
NA
5.1x10"
2.4x1 0'5
1.2x10"
3.2xlO'5
1.1x10"
5.9x1 0-5
l.OxlO'5
7.5X10"6
9.7x1 0-6
l.OxlO'5
SJxlO-6
3.9xlO'7
2.4x10^
2.9x10-*
l.SxlO'5
7.2X10"6
1.4xlO-5
3.5x10-"
Source: Reference 54.
1 Water/Oil emission factors apply to water streams in oil service with a water content greater than 50 percent,
from the point of origin to the point where the water content reaches 99 percent. For water streams with a water
content greater than 99 percent, the emission rate is considered negligible.
b These factors are for total organic compound emission rates (including non-VOC such as methane and ethane)
and apply to light crude, heavy crude, gas plant, gas production, and off shore facilities. "NA" indicates that not
enough data were available to develop the indicated emission factor.
c The "other" equipment type was derived from compressors, diaphrams, drains, dump arms, hatches,
instruments, meters, pressure relief valves, polished rods, relief valves, and vents. This "other" equipment type
should be applied for any equipment type other than connectors, flanges, open-ended lines, pumps, or valves.
4-79
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TABLE 4-21. CONTROL TECHNIQUES AND EFFICIENCIES APPLICABLE TO
EQUIPMENT LEAK EMISSIONS
Equipment Component
(Emission Source)
Control Technique
Percent Reduction*
Pump Seals:
Packed and Mechanical
Double Mechanicalc
Compressors
Flanges
Valves:
Seal area enclosure vented
to a combustion device
Monthly LDARb
Quarterly LDAR
N/Ad
Vent degassing reservoir to
combustion device
None available
100
69
45
100
0
Gas
Liquid
Pressure Relief Devices
Gas
Sample Connections
Open-Ended Lines
Monthly LDAR
Quarterly LDAR
Monthly LDAR
Quarterly LDAR
Monthly LDAR
Quarterly LDAR
Rupture Disk
Closed-purge sampling
Caps on open ends
87
67
84
61
50
44
100
100
100
Source: Reference 55. •
1 If a negative reduction for a control technique was indicated, zero was used.
b LDAR = Leak detection and repair, at a leak definition of 10,000 ppmv.
c Assumes the seal barrier fluid is maintained at a pressure above the pump stuffing box pressure and the system
is equipped with a sensor that detects failure of the seal and/or barrier fluid system.
a N/A - Not applicable. There are no VOC emissions from this component.
4-80
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practices that reduce organic emissions include keeping manholes and other access doors
gasketed and bolted unless in use.
The control efficiencies achieved by the various types of control equipment
vary. Storage tanks with internal or external floating roofs will have varying emission control
efficiencies depending on the type of floating deck and seal mechanism used, as well as various
other factors. The control efficiency achieved by closed-vent systems and control devices also
varies, depending on the type and specific design of the control device used. For information
on the control efficiencies associated with specific control devices, refer to Tables 4-10 and
4-11. The control devices applicable to reducing process vent emissions listed in these tables
are also applicable to storage tanks.
Storage tanks containing benzene and other organic compounds are regulated by
the four following Federal rules:
1. "National Emission Standard for Benzene Emissions from Benzene
Storage Vessels;"61
2. "Standards of Performance for Volatile Organic Liquid Storage Vessels
for which Construction, Reconstruction, or Modification Commenced
after July 23, 1984;"62
3. "National Emission Standards for Organic Hazardous Air Pollutants
from the Synthetic Organic Chemical Manufacturing Industry for
Process Vents, Storage Vessels, Transfer Operations, and
. Wastewater;"63 and
4. "National Emission Standards for Hazardous Air Pollutants from
Petroleum Refineries."49
In combination, these four regulations generally require new and existing
facilities subject to the rules to store benzene in an internal-floating-roof storage tank, an
external-floating-roof storage tank, or a fixed-roof storage tank with a closed-vent system and
control device that reduces emissions by 95 percent for a new facility, or 90 percent for an
existing facility. Additionally, the four regulations include requirements for specific seal
mechanisms and gaskets to be utilized on a floating roof, as well as certain work practices.
.4-81
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4.5.4 Wastewater Collection and Treatment System Emissions. Controls, and
Regulations
A possible source of benzene emissions from chemical production operations
that use benzene are wastewater collection and treatment systems that handle wastewater
containing benzene. Benzene emissions from wastewater collection systems can originate from
various types of equipment including wastewater tanks, surface impoundments, containers,
drain systems, and oil-water separators. Emissions also originate from wastewater treatment
systems. Equations for estimating emissions of organic compounds from wastewater collection
and treatment systems are provided in the EPA document Compilation of Air Pollutant
Emission Factors (AP-42), Chapter 4.64
Two control strategies can be applied to benzene emissions from wastewater.
The first control strategy is waste minimization through process modifications, modification of
operating practices, preventive maintenance, recycling, or segregation of waste streams. The
second control strategy is to reduce the benzene content of the wastewater.through treatment
before the stream contacts ambient air. A complete strategy for reducing the benzene content
of the wastewater includes: (1) suppression of emissions from collection and treatment system
components by hard piping or enclosing the existing wastewater collection system up to the
point of treatment, (2) treatment of the wastewater to remove benzene, and (3) treatment of
residuals. Residuals include oil phases, condensates, and sludges from nondestructive
treatment units.65 This section will discuss the second control strategy of reducing benzene
emissions by suppression and treatment.
The benzene emissions from wastewater collection and treatment systems can
be controlled either by hard piping or by enclosing the transport and handling system from the
point of wastewater generation until the wastewater is treated to remove or destroy the organic
compounds. Suppression techniques can be broken down into four categories: collection
system controls, roofs, floating membranes, and air-supported structures. These techniques can
be applied to drain systems, tanks, containers, surface impoundments, and oil-water separators.
Suppression of benzene emissions merely keeps the organic compounds in the wastewater until
4-82
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they reach the next potential benzene emission source. Therefore, these techniques are not
effective unless the benzene emissions are suppressed until the wastewater reaches a treatment
device where the organic compounds are either removed or destroyed. Also, work practices,
such as leak detection and repair, must be used to maintain equipment effectiveness.65
Treatment techniques that can be used to remove or destroy benzene are steam
stripping and air stripping (removal) and biological treatment (destruction). Steam and air
stripping accomplish removal by stripping benzene out of the wastewater into a gas stream,
which must then be controlled and vented to the atmosphere. Biological treatment destroys
benzene by using microorganisms to biodegrade the benzene in the process of energy and
biomass production.
Add-on controls serve to reduce benzene emissions by destroying or extracting
benzene from gas phase vent streams before it is discharged to the atmosphere. Add-on
controls are applicable to vents associated with collection and treatment covers, such as drain
covers, fixed roofs, and air-supported structures, and with organic compound removal devices,
such as air strippers and steam strippers. Add-on controls for benzene emissions are classified
into four broad categories: adsorption, combustion, condensation, and absorption. The type of
add-on control best suited for a particular wastewater emission source depends on the size of
the source and the characteristics of the wastewater in the source.65
The control efficiencies associated with the various types of suppression,
treatment, and add-on control equipment vary. Estimating the control efficiency of emissions
suppression techniques for wastewater collection systems (e.g., water seals, covers, floating
roofs, and submerged fill pipes) is complex, and equations for estimating emissions from these
sources are not readily available. The control efficiency associated with use of a fixed-roof or
gasketed cover and a closed-vent system routed to a control device would be equivalent to the
efficiency achieved by the control device. Refer to Tables 4-10 and 4-11 for a listing of control
devices applicable to wastewater systems. Additionally, the control efficiencies associated
with steam and air strippers and biological treatment units vary, depending on the design of the
systems. Refer to the discussion below for the specific control efficiencies associated with
4-83
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steam strippers and biological treatment units that would be designed to comply with existing
Federal regulations.
Wastewater streams containing benzene are Federally regulated by the following
rules:
1. "National Emission Standard for Benzene Waste Operations;"66
2. "National Emission Standards for Organic Hazardous Air Pollutants
from the Synthetic Organic Chemical Manufacturing Industry for
Process Vents, Storage Vessels, Transfer Operations, and Wastewater"
(HON);63 and
3. "National Emission Standards for Hazardous Air Pollutants at
Petroleum Refineries."49
The rules regulate benzene emissions from wastewater collection and treatment
systems, and apply to new and existing facilities. Chemical production processes subject to the
regulations would be required to apply many of the controls specified above for both
wastewater collection and waste water treatment systems.
The rules require specific suppression equipment (e.g., roofs) and work
practices (e.g.. leak detection and repair) rather than specifying a suppression control efficiency
that must be achieved. For add-on control devices (e.g., incinerators, adsorbers) to destroy
organics vented from collection and treatment equipment, both rules require 95 percent
efficicnc}.
For treatment, the National Emission Standard for Benzene Waste Operations66
and the National Petroleum Refinery NESHAP49 do not require specific treatment equipment.
Instead, the rule requires the treatment process to achieve either removal or destruction of
benzene in the waste system by 99 percent, or removal of benzene to less than 10 parts per
million by weight (ppmw). However, the technology basis for the 99 percent efficiency
standard is steam stripping.
4-84
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The HON offers several different wastewater treatment compliance options.
These options include concentration-based limits, pollutant reduction percentages, and an
equipment standard. The equipment standard is a steam stripper with specific design criteria
that would result in a 99 percent reduction in benzene emissions. The HON also allows
facilities to comply with the treatment standard by using biological treatment units that achieve
a 95 percent reduction of total organic hazardous air pollutants in the wastewater. (Benzene is
one of the hazardous air pollutants).
4.5.5 Product Loading and Transport Operations Emissions. Controls, and
Regulations
Although pipeline transfer of raw materials and products is widely used in the
different industries, shipment by tank cars, tank trucks, ships, and barges is also common. The
product loading and transportation of chemicals and petroleum liquids represent potential
sources of evaporation losses.
Emissions from the above sources are due to loading losses, ballasting losses,
and transit losses. Refer to Section 6.3 (Gasoline Marketing) of this document for information
on emission factors and equations to estimate emissions from loading and transport operations,
as well as information on control technology.
The HON regulates organic hazardous air pollutants (HAP) emissions from
product loading and transport operations.59'63 The National Emission Standard for Benzene
Emissions from Benzene Transfer Operations also regulates benzene transfer emissions.67
4-85
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SECTION 5.0
EMISSIONS FROM MAJOR USES OF BENZENE
The largest portion of benzene produced is used in the production of
ethylbenzene/styrene. Other major chemicals for which benzene is used as a feedstock include
cyclohexane, cumene, phenol, nitrobenzene, and linear alkylbenzene. For each of these
emission sources, the following information is provided in the sections below: (1) a brief
characterization of the national activity in the United States, (2) a process description,
(3) benzene emissions characteristics, and (4) control technologies and techniques for reducing
benzene emissions. In some cases, the current Federal regulations applicable to the source
category are discussed.
Emission factors are presented, as available. The reader is advised to contact
the specific source in question to verify the nature of the process, production volume, and
control techniques used before applying any of the emission factors presented in this report.
Other minor chemicals where benzene is used as a feedstock include resorcinol,
benzophenone, hydroquinone, anthraquinone, biphenyl, and benzene sulfonic acid.68 These
chemical processes are discussed briefly in this section. Although benzene has been used in the
past as a feedstock in the production of maleic anhydride, all capacity for producing maleic
anhydride hi the United States is now n-butane based; therefore, the process for producing
maleic anhydride from benzene is not included hi this section.
5-1
-------
5.1 ETHYLBENZENE AND STYRENE PRODUCTION
Ethylbenzene is a liquid at standard conditions, with a boiling point of 277 °F
(136°C) and a vapor pressure of 1,284 Pa (0.0126 atm).69 About 50 percent of the U.S.
production of benzene is used to produce ethylbenzene. The ethylbenzene industry is closely
tied to the styrene industry because styrene is produced exclusively from ethylbenzene. There
can be approximately a 0.3 percent by weight carry-over of benzene into ethylbenzene and
styrene.9 Additionally, some benzene is reformed in the production of styrene. Ethylbenzene
production processes and uses thereby constitute a major potential source of benzene
emissions, particularly because styrene production is anticipated to experience continued
growth. Ethylbenzene demand is expected to show growth of only 2.5 to 3.5 percent per year
over the next several years.70
Ethylbenzene is used almost exclusively to produce styrene. Some ethylbenzene
is used as a solvent (often replacing xylene) and in the production of some dyes.71 Total
ethylbenzene production capacity is currently 13,874 million pounds per year (Ib/yr) (6,293
kg/yr).11 Approximately 95 percent of this capacity is based on benzene alkylation, with the
remainder based on extraction from mixed xylene streams. Most styrene is produced by two
methods: hydrogenation of ethylbenzene (89 percent) and peroxidation of ethylbenzene with
subsequent hydration (11 percent). The latter process can also co-produce propylene oxide. A
third process, converting ethylbenzene isothermally to styrene, was developed in Europe. To
date, no U.S. facilities report using this method.
Another method that co-produces both ethylbenzene and styrene has been
patented.72 In this process, toluene and light alkanes other than ethane are reacted at 1,832 to
2,192 °F (1,000 to 1,200°C) and then gradually cooled to produce an 80 percent
ethylbenzene/12 percent styrene product with a mass of about 25 percent by weight of the
toluene reactant. These products can be separated by distillation, and the ethylbenzene either
recycled, sold, or converted to styrene by another process-dehydrogenation or peroxidation.
This process is not reported to be in use at this time.
5-2
-------
Table 5-1 lists U.S. producers of ethylbenzene and styrene.11-69-73 Most facilities
produce both ethylbenzene and styrene on site, thus reducing shipping and storage. Only one
styrene production site does not have ethylbenzene production capacity. Four ethylbenzene
production sites do not have styrene production capacity. Ethylbenzene from mixed xylene
separation is generally shipped or supplemented with another ethylbenzene source for styrene
production. Only one site uses the peroxidation process to produce styrene. Table 5-1 also
gives the latest facility capacity.
5.1.1 Process Description for Ethvlbenzene and Stvrene Production Using Benzene
Alleviation and Ethvlbenzene Dehvdrogenation
Most ethylbenzene production is integrated with the dehydrogenation process to
produce styrene; therefore, these processes are described together. The primary reactions are
(1) catalytic alkylation of benzene with ethylene to produce ethylbenzene, and (2) catalytic
dehydrogenation of ethylbenzene to produce styrene.
A process flow diagram including the basic operations that may be used in the
production of ethylbenzene by benzene alkylation with ethylene is shown in Figure 5-l.14>74
The first step in the process is the drying of benzene to remove water from both
feed and recycled benzene. An emission source in this process is the vent from the benzene
drying column (Vent B).69
The dry benzene (Stream 1) is fed to the alkylation reactor along with ethylene,
aluminum chloride catalyst, and recycled polyediylbenzenes. The reactor effluent (Stream 2)
goes to a settler, where crude ethylbenzene is decanted and the heavy catalyst-complex layer is
recycled to the reactor. Any inert gases fed with the ethylene or produced in the alkylation
reactor, along with some unreacted benzene, other organics, and hydrogen chloride, are
exhausted from the reactor or from the treating section (Vent A). Reactor vent gas is generally
routed through a condenser and scrubbers in the alkylation reaction section (not shown on the
5-3
-------
TABLE 5-1. U.S. PRODUCERS OF ETHYLBENZENE AND STYRENE
Ethylbenzene
Company
Amoco Chemical Company
ARCO Chemical Company
Chevron Chemical Company
Cos-Mar, Inc.
Deltech Corporation
Dow Chemical U.S.A.
Huntsman Chemical
Corporation
Koch Refining Company
Phibro Energy USA, Inc.
Rexene Corporation
Sterling Chemicals, Inc.
Westlake Styrene Corporation
Location
Texas City, TX
Channelview, TX
Monarca, PA
St. James, LA
Carville, LA
Baton Rouge, LA
Frceport, TX
Bayport, TX
Corpus Christi, TX
Houston, TX
Odessa, TX
Texas City, TX
Lake Charles, LA
Sulphur, LA
Process
NA
NA
NA
Ac
NA
Ac
NA
65% Ac
35% Bc
NA
NA
NA
NA
Capacity
million Ib
(million kg)
908a (412)
2789a (1265)
220 (100)
1700a (771)
2200M (998)
694'-e(315)
1750" (794)
1240a (562)
100a (45)
25a(ll)
350a (159)
1750a (794)
368a (167)
Styrene
Process
Cb
Db
Cb
Cb
—
cb
cb
-„
cb
cb
cb
Capacity
million Ib
(million kg)
800" (363)
2525a(1145)
1525a (692)
19001 (862)
—
14201 (644)
1250a (567)
—
—
320a (145)
16001 (726)
353" (160)
(continued)
-------
TABLE 5-1. CONTINUED
Source: References 11, 69, and 73.
•Reference 11.
"Reference 73.
'Reference 69.
Capacity does not include an excess capacity of 500 million pounds (227 million kg) of capacity on standby.
'Plant is on standby.
NA = Not available.
A = Benzene Alkylation (ethylbenzene production) C = EB Hydrogenation (styrene production)
B = Xylene Separation (ethylbenzene production) D = EB Peroxidation and Dehydration (styrene production)
"-" = means that the plant does not make this product.
V Note: This list is subject to change as market conditions change, facility ownership changes, plants are closed, etc. The reader should verify the existence
*"" of particular facilities by consulting current lists and/or the plants themselves. The level of benzene emissions from any given facility is a function of
variables such as capacity, throughput, and control measures, and should be determined through direct contact with plant personnel. These data for
producers and locations were current as of January 1993.
-------
Aluminum Chloride Catalyst
Waste Water
Ui
O\
Storage
Recycled Benzene
from Integrated
Styrene Plant
Benzene
Drying
Column
ALKYLATION REACTION SECTION
Aluminum Spent
Chloride Caustic to
Solution to Weete
Wane Treatment Treatment
Plant Plant
TREATING SECTION
Benzene Ethylbenzene Poryothyltaenzene
Recovery Recovery Column
Column Column
ETHYLBENZENE PURIFICATION SECTION
Nate: The stream numbers on the figure correspond to the discussion In the text for
this process. Letters correspond to potential sources of benzsne emissions.
Ethylbenzene to
Oehydrogenatlon
Reaction Section
at Integrated
Styrene Plant
Ethylbenzene
Storage
Recycled Ethylbenzene
from Intagrttad Styrene Plant
Figure 5-1. Basic Operations that may be used in. the Production of Ethylbenzene by
Benzene Alkylation with Ethylbenzene
Source: References 14 and 74.
-------
figure) to recover aromatics and to remove hydrogen chloride (HC1) before the remaining inert
gases are vented.69
The crude ethylbenzene (Stream 3) from the settler is washed with water and
caustic to remove traces of chlorides and then fed to the ethylbenzene purification section. The
crude ethylbenzene contains 40 to 55 percent benzene, 10 to 20 percent polyethylbenzene
(PEB), and high-boiling point materials. The first step in purification is separation of recycled
benzene (Stream 4) from the crude ethylbenzene in the benzene recovery column. In the
second step, the product ethylbenzene (Stream 5) is separated from the heavier hydrocarbons in
the ethylbenzene recovery column. The heavier hydrocarbons are distilled in the
polyethylbenzene column to separate the polyethylbenzenes, which are recycled (Stream 7),
from the residue oil.69 Emission points in the purification section include vents from the
benzene and ethylbenzene recovery columns (Vent C and D, respectively) and the
polyethylbenzene column (Vent E).69
Fresh ethylbenzene (Stream 6) from the ethylbenzene purification section is
combined with recycled ethylbenzene (Stream 8) from the styrene purification section at the
integrated styrene plant and is stored for use as an intermediate for making styrene.69 Other
emission points from the process including storage tanks, are shown in Figure 5-1.
A process flow diagram including the basic operations that may be used in the
production of styrene by ethylbenzene dehydrogenation is shown in Figure 5-2.6974
Fresh ethylbenzene from the ethylbenzene purification section (ethylbenzene
plant) is combined with recycled ethylbenzene (Stream 1) from the styrene purification section.
The purified ethylbenzene is preheated in a heat exchanger. The resultant vapor (Stream 2) is
then mixed continuously with steam at 1,310°F (710°C) hi the dehydrogenation reactor, which
contains one of several catalysts. The reaction product (Stream 3) then exits through the heat
exchanger and is further cooled hi a condenser, where water and crude styrene vapors are
condensed.
5-7
-------
Ethylbenzene from
Elhybenzene Purification
Section at Integrated
Ethylbenzene Plant
Recycled
Ethylbenzene
Benzene To
Ethylbenzene
Plant
Hydrogen-Rich Gas
oluene
'<*>
_>
> k,
$>
Benzene Recycle
Column
4
Steam
oo
Toluene
Storage
Natural
Gat Fuel
-k> To Boiler
Ethylbenzene
Recycle
Column
Styrene
Finishing
Column
Slyrene Styrena
Day Tank Storage
Tar
Storage
^ 7
\ /
Barge
Steam
Super Heater
Dehydrogenation
Reaction Section
Process Water
Stripper
Nota: TtwMTMmiHiirtMnontMrlguraixMiMpondtomcoteaiulonlnllwtwtlortliliprouu.
L**M MUMpond la patanTW IOUICM at benzene wnbilocw.
Styrene PurHteallon
Section
Figure 5-2. Basic Operations that may be used in the Production of Styrene by
Ethylbenzene Dehydrogenation
Source: References 14 and 74.
-------
The hydrogen-rich process gas is recovered and used as a fuel (Stream 7) and
the process water is purified in a stripper and recycled to the boiler. The remaining crude
styrene liquid (Stream 6) goes to a storage tank. Benzene and toluene (Stream 8) are removed
from the crude styrene in the benzene/toluene column. They are then typically separated by
distillation. The toluene is sold and the benzene is returned to ethylbenzene production section
(Stream 10), or it may also be sold. Next, the ethylbenzene column removes ethylbenzene,
which is directly recycled (Stream 1). Tars are removed and the product styrene (Stream 9)
emerges from the styrene finishing column. In some facilities, an
ethylbenzene/benzene/toluene stream is separated from the crude styrene initially and then
processed separately.
Emission points in this process include vents from the columns for the styrene
purification section between the separator and the recovery sections. These include the
benzene toluene column (Vent A), the ethylbenzene recycle column (Vent B) and the
emergency vent in the styrene finishing column (Vent C). Other emission points from the
process including storage tanks and barge loading are shown hi Figure 5-2.
5.1.2 Process Description for Ethvlbenzene Production from Mixed Xylenes
Ethylbenzene can also be extracted from mixed xylene streams.
Proportionately, however, very little ethylbenzene is produced hi this fashion. The two major
sources of ethylbenzene containing xylenes are catalytic reformate from refineries, and
pyrolysis gasoline from ethylene production (see process description for ethylene production hi
Section 4.3). The amount of ethylbenzene available is dependent on upstream production
variables. The ethylene separation occurs downstream of the benzene production. For this
reason, the ethylbenzene produced by this process is not considered a source of benzene
emissions. Instead, benzene emissions from the entire process train are considered to be
emissions from benzene production and are included elsewhere in this document (Section 4.0).
5-9
-------
When combined with the dehydrogenation process previously described to
produce styrene (Figure 5-2), the process is similar except that the benzene recycling
(Stream 10 hi Figure 5-2) cannot be reused directly.
5.1.3 Process Description for Stvrene Production from Ethylbenzene
Hvdroneroxidation
Presently, only one U.S. facility uses the hydroperoxidation process to produce
styrene. Figure 5-3 shows a process flow diagram. The four major steps are described below.
Ethylbenzene (Stream 1) is oxidized with air to produce ethylene hydroperoxide
(Stream 2) and small amounts of a-methyl-benzyl alcohol and acetophenone. The exit gas
(principally nitrogen) is cooled and scrubbed to recover aromatics before venting. Unreacted
ethylbenzene and low-boiling contaminants are removed in an evaporator. Ethylbenzene is
then sent to the recovery section to be treated before reuse.
Ethylbenzene hydroperoxide (Stream 3) is combined with propylene over a
catalyst mixture and high pressures to produce propylene oxide and acetophenone. Pressure is
then reduced and residual propylene and other low-boiling compounds (Stream 4) are separated
by distillation. The vent stream containing propane and some propylene can be used as a fuel.
Propylene is recycled to the epoxidation reactor. The crude epoxidate (Stream 5) is treated to
remove acidic impurities and residual catalyst material and the resultant epoxidate stream is
distilled to separate the propylene oxide product for storage.
Residual water and propylene are recycled to the process train and liquid
distillate is recovered as a fuel. The organic layer is routed (Stream 6) to the ethylbenzene and
a-methyl-benzyl alcohol recovery section. Distillation removes any remaining ethylbenzene.
Organic waste streams are separated from the a-methyl-benzyl alcohol and acetophenone
organic waste liquids are used as fuel.
5-10
-------
Mr
Hydropor-
OxIdaUon
Reactor
Ethylbenzena
Evaporation
EB
Ethylbanzeno
Ethylbanzana
Hydroperoxlde
MBA
Dehydration
Cruda
SM
S tyrant
Raflnlng
CD)
i >
Ethylbanzene,
Mathyl-Banzyl
Alcohol
Racevary Sactton
MBA
Styrone
Catalyst
Waste
Aeetophenone
Dahydroganatlon
i
Propylan
•
\
•• s
EpexIdaUen
Raactor
.
Propylana
Dlallllatlon
Pro pan a
Racyclad Prepylana
" ~ ^
Cauttlc and
Watar Wath
i
Racyclad Waah Watar
Propylana
Oxlda
OUUNatlon
Liquid "
Fuala
Propylana Oxlda
— — a»-
/EB > Ethylbanzana \
I MBA - Uathyl-Banzyl Alcohol
\6M - Styrana Monomar J
Nata: The ttraam number* en the figure correspond te ttta dlicutalon In the text (or
thla proceae. Letter* correspond to potentlel eourcti of btnzene emliilon*.
Figure 5-3. Ethylbenzene Hydroperoxidation Process Block Diagram
Vapor
Fiiala
5
s
Source: Reference 74.
-------
The mixed stream of a-methyl-benzyl alcohol and acetophenone (Stream 7) is
then dehydrated over a solid catalyst to produce styrene. Residual catalyst solids and
high-boiling impurities are separated and collected for disposal. The crude styrene goes to a
series of distillation columns, where the pure styrene monomer product is recovered. The
residual organic stream contains crude acetophenone, catalyst residue, and various impurities.
This mixture is treated under pressure with hydrogen gas to convert the acetophenone to
a-methyl-benzyl alcohol. Catalyst waste is separated from the a-methyl-benzyl alcohol, which
is returned to the recovery section for processing and reuse. Hydrogen and organic vapors are
recovered for use as fuel.
5.1.4 Process Description for Styrene Production by an Isothermal Process
Ethylbenzene may also be converted to styrene by an isothermal process
(Figure 5-4). Liquid ethylbenzene is vaporized by condensing steam in a heat exchanger
(Stream 1). Process steam (Stream 2) is then introduced into the ethylbenzene stream and the
feed mixture is superheated (Stream 3) before it enters the molten-salt reactor (Stream 4)
(see Figure 5-4).75
In the reactor, the ethylbenzene/steam mixture passes through the tubes, where
it comes into contact with the catalyst and is dehydrogenated. Heat for the dehydrogenation
reaction is supplied by molten salt (preferably a mixture of sodium carbonate, lithium
carbonate, and potassium carbonate) surrounding the tubes (Stream 5). The reactor is
maintained at a uniform wall temperature by circulating the molten-salt mixture through the
heat exchanger of a fired heater (Stream 6).75
The reaction products are cooled and condensed in a separator (Stream 7). The
liquid phase is a mixture of organic products: styrene, unreacted ethylbenzene, and small
quantities of benzene, toluene, and high-boiling compounds. Styrene (Stream 8) is separated
from the other liquid constituents, which then are recovered and recycled.75
5-12
-------
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The gas phase from the condensation step in the separator consists mainly of
hydrogen, with small quantities of CO2, CO, and methane.- After these gases are compressed,
they are cooled. Condensible products from this final cooling stage are then recovered and
recycled to the separator. When hydrogen-rich offgas is used as fuel for the heater of the
molten-salt reactor, the fuel requirement for this stage of the process is zero.75
5.1.5 Benzene Emissions from Ethvlbenzene and Stvrene Production via Alleviation
and Dehvdrogenation
Emission Estimates from Ethylbenzene Production and Dehydrogenation to
Styrene
Emission factors have been developed based on an uncontrolled 300-million-
kg/yr capacity integrated ethylbenzene/styrene production plant. Major process emission
sources are the alkylation reactor area vents (Vent A in Figure 5-1), atmospheric and pressure
column vents (Vents B, C, and D in Figure 5-1), vacuum column vents (Vent B in Figure 5-2),
and the hydrogen separation vent (Stream 7 in Figure 5-2). Emission factors from these
sources are given in Table 5-2.69>74 The first four process vent streams in Table 5-2 are low-
flow, high-concentration streams. The hydrogen separation stream (Stream 7 in Figure 5-2) is
high-flow, low-concentration. Other emission sources listed in Table 5-2 include storage
losses and shipment losses (Vent G). Fugitive emissions from valves and other equipment
leaks are not indicated in Figure 5-1 or 5-2.
Reactor area vents remove various inerts plus entrained aromatics (benzene).
Inerts include nitrogen or methane used in pressure control, unreacted ethylene, reaction
byproducts, and ethylene feed impurities. In typical plants using liquid-phase aluminum
chloride catalyst with high-purity ethylene, vent streams are usually cooled and scrubbed to
recover aromatics. In plants using the newer solid support catalysts of the UOP or
Mobil/Badger process, reactor vent flow rates are very high because of the low-purity ethylene
feed. Process economics requires that these vent gases be burned as fuel.
.5-14
-------
TABLE 5-2. EMISSION FACTORS FOR ETHYLBRNZENE/STYRENE PRODUCTION VIA
ALKYLATION AND DEHYDROGENATION
SCC and Description Emission Source Control Device
3-01-169-02 Alky lation Reactor Vent Process Heater
Ethylbenzene Manufacturing -
Alkylation Reactor Vent Uncontrolled
3-01-169-03 Atmospheric/Pressure Flare
Ethylbenzene Manufacturing - Column Ventsd
Benzene Drying Column , , „ .
3 6 Uncontrolled
3-01-169-04
Ethylbenzene Manufacturing -
Benzene Recovery Column
3-01-169-05
Ethylbenzene Manufacturing -
Ethylbenzene Recovery Column
3-01-169-06 Other Vacuum Vents' Flare
Ethylbenzene Manufacturing -
Polyethylbenzene Recovery , . „ .
„ , Uncontrolled
Column
3-01-206-02
Styrene Manufacturing -
Benzene Recycle Column
Emission Factor in
Ib/ton (kg/Mg)a
0.0006 (0.0003)
0.6" (0.3)
0.024" - 0.96d
(0.012 - 0.48)
2.4" (1.2)
0.0010" - 0.004"
(0.005 - 0.002)
0.10" (0.05)
Factor Rating
U
U
U
U
U
U
3-01-206-03
Styrene Manufacturing - Styrene
Purification Vents
3-01-206-XX Benzene-Toluene Vacuum Flare
Styrene Manufacturing -Benzene Vent
- Toluene Vacuum Vent , , „ .
Uncontrolled
0.06" - 2.4"
(0.03- 1.2)
6.0" (3.0)
U
U
(continued)
-------
TABLE 5-2. CONTINUED
SCC and Description
3-01-206-XX
Styrene Manufacturing -
Hydrogen Separation Vent
Emission Source Control Device
Hydrogen Separation Vent Flare
Uncontrolled
Emission Factor in
Ib/ton (kg/Mg)a
0.00006" - 0.0024"
(0.00003-0.0012)
0.006" (0.003)
Factor Rating
U
U
3-01-169-80/3-01-206-80
Ethylbenzene/Styrene
Manufacturing - Equipment
Leaks
Equipment Leaks
Detection and Correction
Uncontrolled
See Section 4.5.2
4-07-196-XX/4-07-196-13
Ethylbenzene/Styrene
Manufacturing -
Storage and Handling
Storage and Handling
Floating Roof, Vented to
Flare, Refrigerated Vent
Condenser, and
Uncontrolled
See Section 4.5.3
O\
' Emission factors are for a model plant with capacity 661 million Ibs (300 million kg) per year. Actual emission factors may vary with throughput and
control measures and should be determined through direct contacts with plant personnel. Factors are expressed as Ib (kg) benzene emitted per ton (Mg)
ethylbenzene/styrene produced.69
" Reference 74.
c Includes the following vents: benzene drying column, benzene recovery column, and ethylbenzene recovery column.
" Reference 69.
e Includes the following vents: polyethylbenzcne recovery column at ethylbenzene plants; and benzene recycle column and styrene purification vents at
styrene plants.
-------
Atmospheric and column vents remove non-combustibles in the column feeds,
light aliphatic hydrocarbons, and any entrained aromatics. The benzene drying column also
removes impurities in the benzene feed. Most emissions occur in the first column of the
distillation tram (benzene recovery column in Figure 5-1).
Vacuum column vents remove air that leaks into the column, light hydrocarbons
and hydrogen formed in dehydrogenation, non-combustibles in the column feed, and entrained
aromatics. Most emissions occur on the benzene/toluene column (vent A in Figure 5-2).
Uncontrolled distillation vents emit 4.2xlO'3 Ib hydrocarbons/lb styrene (4.2xlO~3 kg
hydrocarbons/kg styrene) in one plant where the hydrocarbons are benzene and toluene.
Another condenser controlled vent emits 0.4xlO'3 Ib benzene/lb styrene (0.4xlO'3 kg
benzene/kg styrene).9
Following dehydrogenation, a hydrogen-rich gas (Stream 4 in Figure 5-2)
containing methane, ethane, ethylene, CO2, CO, and aromatics is normally cooled and
compressed to recover aromatics. The stream should be vented to the atmosphere (Vent E in
Figure 5-2) only during startup, shutdown, and recovery section compressor outages. Some
plants may also vent this stream to a flare. Flares are an efficient (99 percent) emission control
only when flare diameter and gas flow are closely matched for optimum turbulence and
mixing. Emissions can be better controlled when the stream is routed to a manifold and
burned with other fuels.
Stripper vents have been reported to emit 0.032 Ib ethylbenzene/lb styrene (32 g
ethylbenzene/kg styrene).9 This corresponds to 9.6x10^ Ib benzene/lb styrene (9.6xlO'3 g
benzene/kg styrene). Benzene hi shipping and storage (Vent F in Figure 5-1) must also be
considered as a source if benzene is not produced on site (in which case these emissions would
be considered part of the benzene production process).
5-17
-------
Benzene Emissions from Styrene Production Using Ethylbenzene
Hydroperoxidation
Only one U.S. facility currently reports using this method. Emission estimates
presented in this section are based on a capacity of 1200 million Ib styrene/yr (544 million kg
styrene/yr).
' "V
The three main process emission sources are the ethylbenzene oxidation reactor
vent (A in Figure 5-3), the propylene recycle purge vent (B), and the vacuum column vents (C)
and (D). Propane vapor (B) is considered a fuel if it is not vented to the atmosphere. Of these
sources, only the vacuum vents are large benzene emitters. These emissions result from
benzene impurities in the ethylbenzene feed, which may result in minor side reactions in the
process train.
The ethylbenzene oxidation reactor vent (A) releases CO, light organics,
entrained aromatics with nitrogen, oxygen, and CO2. The vent gas is scrubbed with oil and
water for a 99 percent removal efficiency for organics. The resulting vent stream contains
approximately 35 ppm benzene (0.11 mg benzene/1) or 15.9 Ib benzene/hr (7.2 kilograms
benzene per hour [kg/hr]).74
The propylene recycle vent (B) releases propane, propylene, ethane, and other
impurities. No flow volume data are available but, based on a similar procedure in high-grade
propylene production, this stream is a high-Btu gas and would be used as a fuel. No
significant benzene emissions are expected.74
The ethylbenzene hydroperoxidation process contains numerous vacuum
columns and evaporators. Vents on these operations (C-l to C-3) release inerts and light
organics dissolved in the column feeds, nitrogen used for process pressure control, and
entrained aromatics. A combined vent flow is reported to be 264,200 gal/hr (l.OxlO61/hr)
containing about 60 Ibs benzene/hr (27 kg benzene/hr).74
5-18
-------
The dehydrogenation vent (D in Figure 5-3) may be an emergency pressure vent
similar to the separation vent (C hi Figure 5-2). No specific information is available on
storage, transport, or fugitive emissions for this process.
5.1.6 Control Technology for Ethvlbenzene/Stvrene Processes
Control methods for the two ethylbenzene/styrene processes hi use hi the United
States include condensation, adsorption, flaring, and combustion hi boilers or other process
heaters. Controls for fugitive emissions from storage tanks, equipment leaks, and others
include the use of floating-roof tanks and leak detection/correction programs. No information
is available on control methods specific to the two processes mentioned hi this report but not hi
use in the United States.
Condensers may be used to control benzene emissions associated with
ethylbenzene/styrene production. The control efficiency of a condenser is determined by the
temperature and pressure at which the condenser operates and by the concentration and vapor
pressure of the organics in die vent stream. At typical pressures of 1 to 3 atmospheres and coil
temperatures of 36 to 41 °F (2 to 5°C), condensers can achieve 80 to 90 percent benzene
reduction when used on vent streams at 70 to 100 percent saturation hi benzene at 104 to
122 °F (40 to 50°C).74 Higher efficiencies become prohibitively expensive.
Condensers have limited use hi handling high-volume streams, short duration
emergency releases, or cyclic releases such as from the hydrogen separation vent.
Furthermore, condensers are inefficient at low saturations such as with the alkylation reactor
vents and die column vents of Figure 5-1.
In an ethylbenzene/styrene plant, a packed tower can be used to remove
benzene. PEB and various ethylbenzene produced during benzene alkylation are good
absorbers of benzene and are normally recycled. This system is unsuitable, however, for
handling high-volume or intermittent releases of gases beyond the tower design capabilities.
5-19
-------
Absorption systems can maintain 80 to 99 percent benzene removal efficiencies for both
saturated and unsaturated benzene streams, depending on the tower design and operating
variables.
Flare systems can control some streams for which condensation or absorption is
not suitable. Flares can efficiently handle highly saturated streams such as from the alkylation
,vents. They can also control upset releases and other irregular releases, although efficiency
can be variable. The major difficulty here occurs hi manifolding. High-nitrogen or other low-
or non-combustible gases may also be problematic. Consequently, there are no conclusive data
on flare efficiency. Limited data show benzene destruction efficiencies ranging from 60 to
99 percent. A properly designed flare system must account for a range of flow and gas
composition as well as the potential for explosion.
Use of vent gases as a fuel combined with regular process fuel is advantageous
because vent flow variations can be better accounted for. Also, better gas/air mixing occurs
along the entire flare front. As with flares, however, manifolding to ensure optimal
combustion characteristics is the major technical problem. Process pressure variations and the
possibility of emergency releases are complicating factors.
5.2 CYCLOHEXANE PRODUCTION
About 15 percent of the U.S. supply of benzene is used to produce
cyclohexane.10 Table 5-3 lists the location and current capacity for U.S. cyclohexane
producers.11 Two basic methods are used to produce cyclohexane: hydrogenation of benzene
and petroleum liquid separation. Most of the cyclohexane produced domestically is produced
through hydrogenation of benzene. The following discussions of diese two processes are taken
from Reference 76.
.5-20
-------
TABLE 5-3. U.S. PRODUCERS OF CYCLOHEXANE
Company
Chevron Chemical Company
Phillips Petroleum Company
Specialty Chemicals Branch
Olefins and Cyclics Branch
Phillips Puerto Rico Core, Inc.
Texaco Chemical Company
CITGO Petroleum Corporation
TOTAL
Location
Port Arthur, TX
Borger, TX
Sweeny, TX
Guayama, PR
Port Arthur, TX
Corpus Christi, TX
Annual Capacity
millions of gal (1)
38 (144)
35 (132)
90(341)
100 (379)
75 (284)
30(114)
368 (1,393)
Source: Reference 11.
Note: This list is subject to change as market conditions change, facility ownership changes, plants are closed,
etc. The reader should verify the existence of particular facilities by consulting current lists and/or the
plants themselves. The level of benzene emissions from any given facility is a function of variables such
as capacity, throughput and control measures, and should be determined through direct contacts with plant
personnel. These plant locations and capacities were current as of January 1, 1993.
5.2.1 Process Description for Cvclohexane Production via Benzene Hvdrogenation
Figure 5-5 shows a model flow diagram for the manufacture of cyclohexane by
benzene hydrogenation.76 High-purity benzene (Stream 1) is fed to the catalytic reactors in
parallel and hydrogen (Stream 2) is fed into the reactors in series. Part of the cyclohexane
separated in the flash separator is recycled (Stream 3) and fed to the reactors in series.
Recycling helps to control the reactor temperature, because the reaction is highly exothermic.
The temperature is also controlled by generating steam, which is used elsewhere in the
petrochemical complex. Both platinum and nickel catalysts are used presently to produce
cyclohexane.
5-21
-------
•-Byproducts ,
•1 Oat System
<•>
Hydrogen
Purification
Recycle Hydrogen
'
; Aqueous Stream from
(Cj ; Plants Uilng W«t*r Wash
LlqukU-ByproducUo
Petrochemical Complex
Oases-Byproduct*
to Fuel Oes
System
H»t»: Th« ilrMm numbwi on tti* flgura corrtipond to tti« dlieuuton In the In) far
ttito proctii. Ltltora comipond to ponntltl toutcci of btnzin* >m Itiloni.
O • •••-Byproduct*
to Fuel OM
Systems
i
SllbWz.r
Figure 5-5. Process Flow Diagram for Cyclohexane Production Using the Benzene
Hydrogenation Process
Source: Reference 76.
-------
After leaving the flash separator, the cyclohexane (Stream 4) is sent to a
distillation column (stabilizer) for removal of methane, ethane, other light hydrocarbons, and
soluble hydrogen gas from the cyclohexane product. These impurities (Stream 6) are routed to
the fuel-gas storage system for the facility and used as fuel in process heaters. Cyclohexane
(Stream 5) purified in the stabilizer may be greater than 99.9 percent pure. The residual
benzene content is typically less than 0.0042 Ib/gal (500 mg/1). This pure product is stored in
large tanks prior to shipment.
Gas from the flash separator, largely hydrogen, is not pure enough for direct
reuse. Therefore, the stream (8) is purified before being recycled to (Stream 2) the reactor.
Typical processes used for hydrogen purification are absorption and stripping of the hydrogen
gas and cryogenic separation. Some plants use a combination of the two processes. Organic
liquids (Stream 10) that are separated from the hydrogen in the hydrogen purification unit are
sent to other petroleum processing units in the petrochemical complex. The separated gases
^Stream 9) are used as fuel gas.
Depending on the type of hydrogen purification used, inert impurities present in
the gas from the flash separator can be purged from the system before the gas enters the
hydrogen purification equipment. This stream (7) is sent to the fuel gas system.
5.2.2 Benzene Emissions from Cyclohexane Production via Benzene Hydrogenation
There are no process emissions during normal operation.76 During shutdowns,
individual equipment vents are opened as required during final depressurization of equipment.
Except for the feed streams, the concentration of benzene hi the process equipment is low;
therefore, few or no benzene emissions would be expected during a shutdown.76
Equipment leak emissions from process pumps, valves, and compressors may
contain benzene or other hydrocarbons. Storage of benzene (Vent A hi Figure 5-5) may also
contribute to benzene emissions.
5-23
-------
Other potential sources of emissions are catalyst handling (B) and absorber
wastewater (C) (when an aqueous solution is used to purify the recycled hydrogen). Caution is
taken to remove the organic compounds from the spent catalyst before it is replaced. The
spent catalyst is sold for metal recovery.76
5.2.3 Process Description for Cvclohexane Production via Separation of Petroleum
Fractions
Cyclohexane may also be produced by separation of select petroleum fractions.
The process used to recover cyclohexane hi this manner is shown hi Figure 5-6.76 A petroleum
fraction rich in cyclohexane (Stream 1) is fed to a distillation column, in which benzene and
methylcyclopentane are removed (Stream 2) and routed to a hydrogenation unit. The bottoms
(Stream 3) from the column containing cyclohexane and other hydrocarbons are combined with
another petroleum stream (4) and sent to a catalytic reformer, where the cyclohexane is
converted to benzene. The hydrogen generated in this step may be used in the hydrogenation
step or used elsewhere in the petrochemical complex.
The benzene-rich stream (5) leaving the catalytic reformer is sent to a distillation
column, where compounds that have vapor pressure higher than benzene (pentanes, etc.) are
removed (Stream 6) and used as byproducts. The benzene-rich stream (7) that is left is sent to
another distillation column, where the benzene and methylcyclopentane (Stream 8) are
removed. The remaining hydrocarbons (largely dimethylpentanes) are used elsewhere in the
petrochemical complex as byproducts (Stream 9).
Stream 8 (benzene and methylcyclopentane) is combined with Stream 2 and sent
to a hydrogenation unit (Stream 10). Hydrogen is fed to this unit and the benzene is converted
to cyclohexane. Isomers of cyclohexane, such as methylcyclopentane, are converted to
cyclohexane hi an isomerization unit (Stream 11) and the effluent from this equipment
(Stream 12) is separated in a final distillation step. Pure cyclohexane (Stream 14) is separated
from isomers of cyclohexane (Stream 13) and compounds with lower vapor pressures
(Stream 15).
5-24
-------
Hydrogen
Natural C
B
Hydrocarbon
€
2
to
Hydrogenation
Unit
Isomerization
Unit
Hexanes
Methylcyclopentane
5
a
c
g
2
Methylcyclopentane and Benzene
^L
r Cyclohexane
S
e
u.
Heavies
Natural Cyclohexane
Catalytic
Reformer
Gasoline
o
a
c
.9
t>
2
Pentanea and
Lighter
s
$>
Dlmethylpantanes
Not*: The stream numbers on the figure correspond to the discussion in the text for
this process. Letters correspond to potential sources of benzene emissions.
$
m
o
Figure 5-6. Process Flow Diagram for Cyclohexane from Petroleum Fractions
Source: Reference 76.
-------
5.2.4 Benzene Emissions from Cyclohexane Production via Separation of Petroleum
Fractions
There are no process emissions during normal operation.76 During emergency
shutdowns, individual equipment vents are opened as required.
Equipment leaks can be sources of benzene, cyclohexane, methane, or other
petroleum compound emissions. Leaks from heat exchangers into cooling water or steam
production can be a potential fugitive loss. Equipment leak losses have special significance
because of the high diffusivity of hydrogen at elevated temperatures and pressures and the
extremely flammable nature of the liquid and gas processing streams.77 No specific emission
factors or component counts (valves, flanges, etc.) were found for benzene associated with
equipment leak emissions at these plants.
A potential source of benzene emissions is catalyst handling. Special efforts are
made to remove the organic compounds from the spent catalyst before it is replaced. The
spent catalyst is sold for metal recovery.76 No emission factors were found for benzene as
related to catalyst handling.
5.3 CUMENE PRODUCTION
In the United States, all commercial cumene is produced by the reaction of
benzene with propylene. Typically, the catalyst is phosphoric acid, but sulfuric acid or
aluminum chloride may be used. Additionally, various new processes based on solid zeolite
catalysts were introduced during 1993; however, information about these new processes is
limited, and they are not discussed hi this section. The location and capacities of U.S.
producers of cumene are provided hi Table 5-4.11<78
.5-26
-------
TABLE 5-4. U.S. PRODUCERS OF CUMENE
Plant
Ashland Chemical Company
BTL Specialty Resins Corporation
Chevron Chemical Company
Citgo Petroleum Corp.
(Champlin)
Coastal Refining
Georgia Gulf Corporation
Koch Refining Company
Shell Chemical Company
Texaco Chemical Company
Location
Catlettsburg, KY
Blue Island, EL
Philadelphia, PA
Port Arthur, TX
Corpus Christi, TX
Westville, NJ
Pasadena, TX
Corpus Christi, TX
Deer Park, TX
El Dorado, KS
Annual
Capacity
million Ib
(million. kg)
550 (249)
120 (54)
450 (204)
450 (204)
825 (374)
150 (68)
1,420 (644)
750 (340)
900(408)
135 (61)
Notes
Cumene is sold
Captive for phenol and
acetone
Cumene is sold
Cumene is sold
--
Cumene is sold
Some cumene transferred to
company's phenol/acetone
plant
Cumene is sold
Captive for phenol/acetone
Captive for phenol/acetone
Source: References 11 and 78.
Note: This list is subject to change as market conditions change, facility ownership changes, plants are closed,
etc. The reader should verify the existence of particular facilities by consulting current list and/or the
plants themselves. The level of benzene emissions from any given facility is a function of variables
such as capacity, throughput, and control measures, and should be determined through direct contacts
with plant personnel. These locations, producers, and capacities were current as of November 1993.
5.3.1
Process Descriptions for Cumene Production by Alkylating Benzene with
Propvlene
Cumene is present in crude oils and refinery streams. However, all commercial
cumene is produced by the reaction of benzene and propylene.
Benzene and propylene are reacted at elevated temperatures and pressures in the
presence of an acidic catalyst. A simplified equation for this reaction is as follows:
5-27
-------
C6H6 + CI^CHCHj [catalyst] (CH3)2CHC6H5
(benzene) (propylene) - (cumene)
The exothermic reaction is typically conducted using solid phosphoric acid as a
catalyst, but the reaction may also be conducted using aluminum chloride or sulfuric acid as
the catalyst. The aluminum chloride and sulfuric acid processes are similar; therefore, the
sulfuric acid process is not described here.79
Solid Phosphoric Acid Catalyst Process
Figure 5-7 is a typical flow diagram for the manufacture of cumene by the
process using phosphoric acid as the catalyst support.80 Solid phosphoric acid is the most
favored catalyst system for manufacturing cumene and is a selective alkylation catalyst that
promotes the alkylation of benzene with propylene in a vapor-phase system.79
Because the catalyst is selective, propylene feedstock for this process does not
have to be thoroughly refined before use. Crude propylene streams (Stream 1) from refinery
crackers that are fractionated to about 70 percent propylene can be used without further
purification. The benzene (Stream 2) used in this process does not have to be dried before use
because the catalyst system requires small amounts of water vapor hi the reactor stream to
activate the catalyst.79
Propylene and benzene (Streams 1 and 2) are combined hi a feed drum and then
fed (Stream 3) to a reactor containing the phosphoric acid catalyst. The feed ratio is normally
at least four moles of benzene per mole of propylene. An excess of benzene is maintained in
order to inhibit side reactions. The propylene is completely consumed. From the reactor, the
byproducts, unreacted material, and product are separated by distillation. The reaction
products (Stream 4) are sent to a depropanizers where residual hydrocarbons (mostly propane)
are removed. The propane (Stream 5) is sent through a condenser, after which some of the
5-28
-------
Y_^
Fr»»h Propyl«n«
Fr*th Banz«n*
O
Propan*
o
Condomor
Y <£>
Heavy
Aromatic*
n
Condomor
5
2
Hot*: TlM «tr»«m number* on tho flgur* eorr«»pond to th« dl*cu«*lon In the text lor
Into prooou L*tt*re eormpond to po*ntl«l courcM of banzina amliilon*.
Figure 5-7. Process for the Manufacture of Cumene Using Solid Phosphoric Acid
Catalyst
Source: Reference 80.
-------
recovered propane is recycled to the reactor (Stream 6) for cooling. The remainder (Stream 7)
can be returned to a refinery for use as feedstock or fuel gas.79
Unpurified product from the depropanizer (Stream 8) is sent to the benzene
distillation column, where unreacted benzene is recovered overhead (Stream 9), sent through a
condenser, and recycled to the feed drum (Stream 10). From the bottom of the benzene
column (Stream 11), the crude product is sent to the cumene distillation column, where the
high-purity cumene is separated from heavy aromatics and then condensed (Stream 12) and
stored (Stream 13). The bottoms (compounds of relatively lower volatility) from cumene
distillation (Stream 14) contain primarily diisopropylbenzene and are sent to a refinery or used
as fuel gas.79
The cumene distillation column is normally operated slightly above atmospheric
pressure and is padded with methane (or nitrogen) to protect the cumene from contact with the
air. As the pressure fluctuates, a pressure-control valve relieves excess pressure on this system
by bleeding off a mixture of methane (or nitrogen) and cumene vapor (Vent A).79
Aluminum Chloride Catalyst Process
The production of cumene using an aluminum chloride catalyst is similar to that
using a solid phosphoric acid catalyst. The aluminum chloride method requires additional
equipment tc dry recycled streams and to neutralize reaction products. Figure 5-8 shows a
typical process diagram for cumene manufacture using aluminum chloride as the alkylation
catalyst. Aluminum chloride is a much more active and much less selective alkylation catalyst
than solid phosphoric acid.79
The aluminum chloride used as a catalyst in this process is received and handled
as a dry powder. To prevent undesirable side reactions, the propylene used with this catalyst
system must be of chemical grade (95 percent pure) and must contain no more than minute
amounts of other olefins such as ethylene and butylene. This propylene feedstock must also be
5-30
-------
U)
©
Nate:
Th» (Imam numlwn on th« llgura coirmpond to Bit dl»cu««lon In th« tent lor
thk) proctu. Lttton conitpond to potential aourcei of btnzene amlaalona.
Figure 5-8. Process for the Manufacture of Cumene Using Aluminum Chloride
Catalyst
Source: Reference 80.
-------
dried and treated (Stream 1) to remove any residual organic sulfur compounds. The benzene
used in this process must be azeotropically dried (Stream 2) to remove dissolved water. The
azeotrope drying distillation generates a vent gas (Vent A) that is rich in benzene.79
Benzene and propylene (Streams 3 and 4) are fed to a catalyst mix tank, where
the aluminum chloride powder (Stream 5) is added. This mixture is treated with HCI gas
(Stream 6) to activate the catalyst. The catalyst preparation operation generates a vent gas
consisting of inert gases and HCI gas saturated with vapors of benzene and diisopropylbenzene.
A scrubber is typically used to absorb the HCI gas and the residual vapors are then vented
(Vent B). The resulting catalyst suspension (Stream 7) and additional dried benzene (Stream 8)
are fed to the alkylation reactor as liquids, and additional dried propylene (Stream 9) is
introduced into the bottom of the reactor. The feed ratio to the alkylation reactor is maintained
at or above four moles of benzene per mole of propylene to inhibit side reactions.79
The crude reaction mixture from the alkylation reactor (Stream 10) is sent to a
degassing vessel, where hydrocarbons such as propane are released from solution (Stream 11).
This vapor stream is scrubbed with a weak caustic solution and then fed (Stream 12) to the
diisopropylbenzene (DIPB) scrubber, where the hydrocarbon vapor is recontacted with DIPB
to extract residual unreacted propylene. The stream containing the propylene (Stream 13) is
sent to the catalyst mix tank.79
The degassed product (Stream 14) is sent to the acid wash tank, where it is
contacted with a weak acid solution that breaks down the catalyst complex and dissolves the
aluminum chloride hi the water layer. The crude product from the acid wash tank is sent to a
decanter tank, where the water is removed. The product is then sent to a caustic wash tank,
where any residual acid in the product is extracted and neutralized. The product is decanted
again to remove water and then enters a water wash tank, where it is mixed with fresh process
water. This process water extracts and removes any residual salt or other water soluble
material from the product. The product from the water wash tank is sent to a third decanter
tank, where the crude product and water settle and separate.79
.5-32
-------
The entire wash-decanter system is tied together by one common vent-pad line
that furnishes nitrogen for blanketing this series of tanks. A pressure control valve on the end
of the vent-pad manifold periodically releases vent gas (Vent C) as levels rise and fall in the
various tanks of the wash-decanter system. The vent gas is saturated with water vapor and
hydrocarbon vapor (principally benzene) as contained VOC.79
The washed and decanted product (Stream 15) is stored in a washed-product
receiver tank. The crude product from the washed-product tank (Stream 16) is sent to a
recovery column, where the excess benzene is stripped out. The recovered benzene
(Stream 17) is returned to the benzene feed tank. The vent line associated witii the benzene
recovery column and with the benzene receiver tank releases some vent gas (Vent D). This
vapor is principally inert gas saturated with benzene vapor as contained VOC.79
The crude cumene (Stream 18) is sent to the cumene distillation column for
distillation of the cumene product. The cumene product (Stream 19) is then stored for sale or
in-plant use. The cumene distillation column and die associated cumene receiver tank are
operated above atmospheric pressure and are blanketed with nitrogen (or methane) to protect
the cumene from reacting with oxygen hi the air and forming cumene hydroperoxide. The vent
line associated with the cumene distillation column and with die cumene receiver tank releases
some vent gas (Vent E). This vent gas is nitrogen (or methane) saturated with cumene vapor
as the contained VOC.79
The bottoms from the cumene distillation column contain a small amount of
cumene, along with mixed isomers of diisopropylbenzene and a small amount of higher-boiling
alkylbenzenes and miscellaneous tars. The bottoms stream (Stream 20) is sent to a DIPB
stripping column, where DIPB is recovered and uien stored (Stream 21). This stripping
column is normally operated under vacuum because of the high-boiling points of the DIPB
isomers. The vacuum system on the stripping column draws a vent stream from the column
condenser, and diis vent stream is air (or inert gas) saturated with cumene and DIPB vapors as
5-33
-------
the contained VOC. Depending on the design and operation of the vacuum system for the
column, part or all of the vent gas could be discharged to the atmosphere (Vent F).79
The bottoms from the DIPB stripper (Stream 22) are stored in a receiver tank
and then sent to waste disposal for use as a fuel. The recycle DIPB (Stream 23) is sent to the
DIPB scrubber, where it is used to absorb residual propylene from the propane waste gas
stream. This recycle DIPB eventually returns to the alkylatton reactor, where it is
transalkylated with excess benzene to generate additional cumene.79
5.3.2 Benzene Emissions From Cumene Production
Information related to benzene emissions from process vents, equipment leaks,
storage vessels, wastewater collection and treatment systems, and product loading and
transport operations associated with cumene production is presented below. Where a literature
review has revealed no source-specific emission factors for uncontrolled or controlled benzene
emissions from these emission points, the reader is referred to Section 5.10 of this chapter,
which provides a general discussion of methods for estimating uncontrolled and controlled
benzene emissions from these emission points.
Benzene Emissions from the Solid Phosphoric Acid Catalyst Process
In the solid phosphoric acid process, potential process vent emissions of benzene
may be associated with the cumene column vent (Vent A in Figure 5-7). Using methane to
pressurize the system, the process operates at a pressure slightly higher than atmospheric
pressure to make sure that no air contacts the product.80 The methane is eventually vented to
the atmosphere, carry ing with it other hydrocarbon vapors.80
No specific emission factors were found for benzene emissions from the cumene
column. One factor for total VOC emissions indicated that 0.015 Ib (0.03 kg) of total VOC
are emitted per ton (Mg) of cumene produced, and that benzene constituted a "trace amount"
5-34
-------
of the hydrocarbons hi the stream.80 One cumene producer has indicated that it uses a closed
system (all process vents are served by a plant flare system). Thus, it is possible that there are
no process vent emissions occurring directly from the production of cumene, although there
may be emissions from the flares.79
Benzene Emissions from the Aluminum Chloride Catalyst Process
Process vent emissions of benzene from the production of cumene using an
aluminum chloride catalyst are associated with the benzene drying column (Vent A in
Figure 5-8), the scrubber or the catalyst mix tank (Vent B), the wash-decanter system
(Vent C), the benzene recovery column (Vent D), the cumene distillation system (Vent E), and
the DIPB stripping system (Vent F).80 No specific emission factors were located for benzene
emissions from these sources. However, as presented hi Table 5-5, one reference provided
total VOC emission factors and estimates of benzene percent composition of the emissions.3-80
The percent (weight) of benzene may be used along with a cumene production volume to
calculate an estimate of benzene emissions from these sources. The control technique most
applicable to these sources is flaring, with an estimated efficiency of at least 98 percent (see
Section 4.5.1 of this chapter for further discussion of this control device).
5.4 PHENOL PRODUCTION
Most U.S. phenol (97 percent) is produced by the peroxidation of cumene, a
process hi which cumene hydroperoxide (CHP) is cleaved to yield acetone and phenol, as well
as recoverable by-products a-methylstyrene (AMS) and acetophenone. Phenol is also
produced by toluene oxidation and distillation from petroleum operations.81'82 Table 5-6 shows
the locations, capabilities, and production methods of the phenol producers in the United
States.11'81-83 Because benzene may be present hi the feedstock, it may be emitted during
production of phenol.
5-35
-------
TABLE 5-5. SUMMARY OF EMISSION FACTORS FOR CUMENE PRODUCTION
AT ONI FACILITY USING THE ALUMINUM CHLORIDE CATALYST
SCC and Description Emission Source
3-01-156-02 Process Vent
Cumene Manufacturing -
Benzene Drying Column
3-01-1 56-03 Process Vent
Cumene Manufacturing -
Catalyst Mix Tank Scrubber
Vent
3-01-156-04 Process Vent
Cumene Manufacturing -
Wash-Decant System Vent
3-01-156-05 Process Vent
Cumene Manufacturing -
Benzene Recovery Column
Control Device
Uncontrolled
Flare
Uncontrolled
Flare
Uncontrolled
Flare
Uncontrolled
Flare
Emission Factor in
Ib/ton (kg/Mg)a-b
4.00 x 10 2
(2.00 x 10-2)
2.00 x 10 3
(l.OOxlO3)
3.18x 10-'
(1.59x 10 -')
1.59x 10'2
(7.95 x 103)
1.57x ID'2
(7.85 x lO'3)
7.84 x 10"4
(3.92 x lO'4)
3.40 x 10-2
(1.70xlO-2)
1.70xlO-3
(8.50 x 10-4)
Factor Rating
U
U
U
U
U
U
U
U
Source: References 3 and 80.
' Factors are expressed as Ib (kg) benzene emitted per ton (Mg) cumene produced.
b Derived by multiplying the total VOC emission factor by percent of benzene in the stream.
-------
TABLE 5-6. U.S PRODUCERS OF PHENOL
Facility
Location
Annual Capacity
million Ib
(million kg)
Process and Raw Material
Lft
Allied-Signal, Inc.
Engineering Materials Sector
Aristech Chemical Corporation
BTL Specialty Resins Corporation
Dakota Gasification Company
Dow Chemical U.S.A.
General Electric Company
GE Plastics
Georgia Gulf Corporation
Kalama Chemical, Inc.
Merichem Company
PMC, Inc.
Shell Chemical Company
Shell Chemical Company,
Division
Stimson Lumber Company
Northwest Petrochemical
Corporation, Division
Philadelphia, PA
Haverhill, OH
Blue Island, IL
Beulah, ND
Oyster Creek, TX
Mount Vernon, IN
Pasadena, TX
Plaquemine, LA
Kalama, WA
Houston, TX
Santa Fe Springs, CA
Deer Park, TX
Anacortes, WA
810 (367)
630 (286)
90 (41)
50 (23)
550 (249)
640 (290)
160 (73)
440 (200)
70 (32)
35 (16)
8 (3.6)
600 (272)
<5(<2.3)
Cumene peroxidation
Cumene peroxidation
Cumene peroxidation
Petroleum and coal tar
Cumene peroxidation
Cumene peroxidation
Cumene peroxidation
Cumene peroxidation
Toluene oxidation
Petroleum and coal tar
Petroleum and coal tar
Cumene peroxidation
Petroleum
(continued)
-------
TABLE 5-6. CONTINUED
Facility
Location
Annual Capacity
million Ib
(million kg)
Process and Raw Material
Texaco,Inc.
Texaco Chemical Company,
Subsidiary
TOTAL
El Dorado, KS
95 (43)
<3,398 (< 1,541)
Cumene peroxidation
oo
Source: References 11, 81, and 83.
Note: This list is subject to change as market conditions change, facility ownership changes, plants are closed, etc. The reader should verify the existence
of particular facilities by consulting current lists and/or the plants themselves. The level of benzene emissions from any given facility is a function of
variables such as capacity, throughput, and control measures, and should be determined through direct contacts with plant personnel. These data on
producers and locations were current as of November 1993.
-------
In the process involving peroxidation of cumene, acetone and phenol are
produced by the peroxidation of cumene followed by cleavage of the resulting CHP. The two
basic reactions for this process are as follows:80
C6H5CH(CH3)2 + 02 - C6H5COOH(CH3)2
(cumene) (air) (cumene hydroperoxide)
[HjSOJ
C6H5COOH(CH3)2 _ CH3COCH3 + C6H5OH
(cumene hydroperoxide) ^ac^ (acetone) (phenol)
5.4.1 Phenol Production Techniques
There are two technologies for producing phenol by the peroxidation of
cumene--one licensed by Allied Chemical and the other licensed by Hercules. The major
differences between the Allied and Hercules processes involve the operating conditions of the
peroxidation reaction and the method of neutralization of the acid in the cleavage product.
These differences affect plant design primarily in the peroxidation and cleavage-product
neutralization steps, in the location of process emission points, and in die potential quantity of
process emissions. These two process types are discussed below.80
In addition to the two cumene peroxidation processes, phenol is produced by the
oxidation of toluene. This process is described below; however, the description is brief
because of limited available information on the process.
Allied Process
Figure 5-9 shows a typical flow diagram for the manufacture of phenol by die
Allied process.79 Cumene (Stream 1), manufactured on site or shipped to the site, and recycle
cumene (Stream 2) are combined (Stream 3) and fed with air (Stream 4) to the multiple-reactor
system, where cumene is oxidized to form CHP. Substantial quantities of cumene (Stream 5)
are carried out of the reactors widi the spent air to a refrigerated vent system, where part of the
5-39
-------
•n* • x\ ..—-
- —.
Sr
•condt
Crud«
lectori
Utffittl
Crud.
Aoton*
T«nk>
I
•ry
•
— J
4
Recycle
Cumin*
Storagt
0
Further
^. AMS
Refining
Crude
AMS
DletllaHon
Crude
AMS Phenol
Rennbig Tenk
Phenol
Topping
Phenol
Product
Phenol
ReeMu*
Stripping
Phenol
ReaMue
Uaed
tor Fuel
I
•V
Note: The atreem numbort on the figure oorraapond to the dleeueelon In me tt«t for
tileprooeaa. Lettere oorreepond to potential n>urc«« of b«ni«n« emlulone
Lkiee hi bold Indicate Vie now of Bio product etr>am.
Figure 5-9. Flow Diagram for Phenol Production from Cumene Using the Allied Process
Source: Reference 79.
-------
cumene is recovered and recycled.80 Uncondensed vapors, including organic compounds, are
vented (Vent A).
The reaction product (Stream 6), containing primarily cumene and CHP, is
vacuum flashed first in the pre-flash distillation column and then (Stream 8) in the flash
distillation column to remove most of the cumene, which is recycled (Streams 7 and 9).
Uncondensed vapors, including organic compounds, are vented (Vents B and C). The
concentrated CHP (Stream 10) flows through the CHP concentrate tank to the cleavage reactor,
where the CHP is cleaved to acetone and phenol by the addition of SO2 (Stream 11). The
cleavage product (Stream 12) is neutralized in ion-exchange columns and fed through the
crude-product surge tank (Stream 13) to a multi-column distillation system.80'84-85
In the primary crude acetone distillation column, acetone and lower-boiling
impurities such as acetaldehyde and formaldehyde are distilled overhead. This product
(Stream 14) is condensed and flows through the crude acetone surge tank to the acetone
refining column, where the acetone is distilled overhead. Acetone product is condensed
(Stream 15) and sent to storage. Uncondensed vapors, including organic compounds, are
vented from the condensers after both the primary crude acetone and acetone refining columns
(Vents D and E).80-84
The compounds of relatively lower volatility (bottoms) from the primary crude
acetone column (Siream 16) are distilled in the cumene recovery column to remove residual
cumene. The overheads from the cumene recovery column are sent through a condenser
(Stream 17) and into a secondary crude acetone distillation column to further remove acetone
from the residual cumene. The residual cumene (i.e., the bottoms from the secondary crude
acetone column) is stored for recycling.80 The Uncondensed vapors from the condensers,
following both the cumene recovery column and secondary crude acetone column are vented
(Vents F and G). The condensed overheads from the secondary crude acetone column
(Stream 18) are fed through a crude acetone surge tank back to the acetone refining column.
5-41
-------
Some facilities using this process may not incorporate the secondary crude
acetone distillation column, which is utilized both to further recover acetone product and to
reduce organic emissions from the storage tanks containing the recycle cumene. Some
processes store the condensed product from the overhead of the cumene recovery column as
the recycle cumene (Stream 17).
The bottoms from the cumene recovery column (Stream 19) contain primarily
phenol, AMS, acetophenone, and other organics with higher boiling points than phenol. This
stream is fed to the crude AMS distillation column. The crude AMS distillation column
overhead stream (Stream 20) is condensed and sent to the AMS refining column. Uncondensed
vapors from the condenser after the crude AMS distillation column are vented (Vent H). The
stream entering the AMS refining column undergoes distillation to refine out AMS. The
refined overhead stream is condensed (Stream 21) and sent to additional columns (not shown)
for further refining.
The uncondensed vapors from the condenser following the AMS refining
column are vented (Vent I). The bottoms from the AMS refining column (Stream 22) are
stored in a crude phenol tank. The phenol in this storage tank is either sold as crude product
or is fed to the phenol refining column for further refining. Crude phenol from the bottom of
the crude AMS column (Stream 23) flows to the phenol refining column, where phenol is
distilled overhead, condensed, (Stream 24), and fed to phenol product storage tanks. The
uncondensed vapors from the condenser following the phenol refining column are vented
(VentJ).80-84-85
The bottoms from the phenol refining column (Stream 25) are further processed
to recover phenol. The bottoms are sent to a phenol topping column, from which the overhead
stream is condensed (Stream 26) and fed to phenol product storage. Uncondensed vapors from
the condenser after the phenol topping column are vented (Vent K). The bottoms from the
phenol topping column (Stream 27) are fed to a phenol residue stripping column, which
removes phenol residue hi the bottoms (Stream 29). The phenol residue may be used as fuel
5-42
-------
for on-site industrial boilers. The overheads from the phenol residue stripping column are
condensed (Stream 28) and fed back to the phenol topping column to further recover phenol
product. The uncondensed vapors from the condenser following the phenol residue stripping
column are vented (Vent L).84-85
The phenolic wastewater generated by the Allied process (e.g., generated by
recovery devices, such as condensers and scrubbers) is fed through distillation columns to
further recover acetone and phenol products. This batch distillation cycle, which is not a
continuous process, is not shown hi Figure 5-9. Phenolic wastewater is fed through a
dephenolizer (i.e., a steam stripping process) and one or two batch distillation columns. The
recovered product is crude phenol or acetol phenol.84"86
Hercules Process
Figure 5-10 shows a typical flow diagram for the manufacture of acetone and
phenol by the Hercules process.79 Cumene from storage (Stream 1) and recycle cumene
(Streams 2 and 9) are combined (Stream 3) and then fed with air (Stream 4) to the multiple-
reactor system. Additionally, an aqueous sodium carbonate solution (Stream 5) is fed to the
reactor system to promote the peroxidation reaction. In the reactor system, cumene is
peroxidized to cumene hydroperoxide. Unreacted cumene is carried out of the reactors with
the spent air (Stream 6) to a refrigerated vent system, where part of the cumene is recovered
and recycled (Stream 2). Uncondensed vapors are vented (Vent A).!
80
The oxidation reaction product (Stream 7) flows into a separator to remove
spent carbonate solution and then is washed with water to remove remaining carbonate and
other soluble components. The air stream removed is sent to a condenser from which
uncondensed vapors are vented (Vent B). The washed product (Stream 8) is fed to a
distillation column operated under vacuum, where the cumene hydroperoxide is separated from
the cumene. The overheads from the CHP concentrator are condensed and the recovered
5-43
-------
Ul
Cumen*
AQ
n
N.2C03
S«p«r«lor/W»«h«r
CHP
Concentrator
Action*
H2604
Cum*n«/CHP
Tank
Dllut*
[k
LT
Cruda
Rtcyeto from
Phenol
Crude Acetone
Tank
To Light-
End!
Column -
Cleavage Cleavage Product Product
B^aptnr H«*-T1
Raactor
Nautralizir
•To Haavy-
Tank
Crude Phenol/ End* Column
Acetone Column
Net*: Th* itttim numb>r* on In* tguit cotrtipond to Vi* dUeuiilon In th« l««l lor
M* proewt. L*tt*ra urmpond to patontiil IDUICII of b«ni«n« tmltiloni.
Un» to »eld Indlcili »• low ol Bi. product >tr»m.
Figure 5-10. Flow Diagram for Phenol Production Using the Hercules Process
Source: Reference 79.
-------
Action* Product to
Slortgt/Lotdlng
Light-Ends
Column
Anton* Finishing
Column
ToAMS
DliUHttlon
From Cmdt
Phtnol/Acttont
Column
Phonol Product to
SloriB*/Lo«Ulne
Htivy-Endi
Column
T*rs
Ttnks
Phenol
Topping
Column
Phenol
Dohydratkig
Column
Phinol
Finishing
Column
Th« sknm numkcrs on Iht Igura con-upend to Iho dtacuitlon In tht toil me
tfilt prtetts. Lttttfs eorrtspond to potonflsl sourcoo of btnzono omloolono.
Llnoo kl bold tndkolo ttit (low ol tht product otrttm
Figure 5-10. (Continued)
-------
cumene (Stream 9) is recycled. The uncondensed vapors from the condenser are vented
(Vent C).
The concentrated CHP (Stream 10) is transferred through a surge tank to the
cleavage reactor (Stream 11). Sulfuric acid, diluted to 5 to 10 percent with acetone
(Stream 12), is added to catalyze the decomposition of CHP to acetone and phenol.80
Uncondensed vapors captured from the cleavage reactor are vented (Vent D). Excess acid in
the cleaved mixture (Stream 13) is neutralized with sodium hydroxide solution (Stream 14).
The neutralized product (Stream 15) flows through the crude-product surge tank to a
multi-column distillation train to produce product-grade acetone, phenol, and AMS.80
The crude product is separated in the first distillation column into a crude
acetone fraction (Stream 16) and a crude phenol stream (Stream 17). The crude acetone
(Stream 16) is combined with recycled hydrocarbons from the phenol topping column
(Stream 18) and fed through a surge tank to the light-ends column (Stream 19) to strip
low-boiling hydrocarbon impurities, such as acetaldehyde and formaldehyde, which are vented
to the atmosphere (Vent E).
The bottoms stream from die light-ends column (Stream 20) is fed to the acetone
finishing column, where the acetone is distilled overhead, condensed (Stream 21), and sent to
day tanks and subsequently to acetone product storage and loading. Uncondensed vapors are
vented (Vent F). The bottoms stream (Stream 22) is processed to produce AMS (not shown).80
The crude phenol stream (Stream 17) and the bottoms from the phenol finishing
column (Stream 23) are fed to the heavy-ends column and distilled under vacuum to separate
tars (Stream 24) from the impure phenol stream (Stream 25).80 Uncondensed vapors from the
condenser following the heavy-ends column are vented (Vent G).
The impure phenol is fed to the phenol topping column to remove hydrocarbons
such as cumene and AMS. The overhead stream from the phenol topping column (Stream 18)
5-46
-------
may be condensed and recycled to the light-ends column of the acetone process for removal of
residual acetone, cumene, and AMS. The uncondensed vapors from the condenser following
the phenol topping column are vented (Vent H). The phenolic stream (Stream 26) is then fed
to a dehydrating column, where water is removed overhead as a phenol/water azeotrope.
«•
Uncondensed vapors are vented (Vent I).80
The dried phenol stream (Stream 27) is distilled under vacuum in the phenol
finishing column to separate product-quality phenol (Stream 28) from higher boiling
components (Stream 23), which are recycled to the heavy ends column. Uncondensed vapors
from the condenser after the phenol finishing column are vented (Vent J). The product-quality
phenol is stored in tanks for subsequent loading.80
Toluene Oxidation Process
In this process, toluene is oxidized by air to benzoic acid. Following
separation, the benzoic acid is catalytically converted to phenol.
5.4.2 Benzene Emissions from Phenol Production
Information related to benzene emissions from process vents, equipment leaks,
storage vessels, wastewater collection and treatment systems, and product loading and
transport operations associated with phenol production is presented below. Where a literature
review revealed no source-specific emission factors for uncontrolled or controlled benzene
emissions from these emission points, the reader is referred to Section 5.10 of this chapter,
which provides a general discussion of methods for estimating uncontrolled and controlled
benzene emissions from these types of emission points.
"Spent ah-" from the oxidizer reactor (Vent A, Figure 5-9) is the largest source
of benzene emissions at phenol production plants utilizing the Allied process.87 Table 5-7
provides uncontrolled and controlled (i.e., thermal oxidizer) emission factors from the oxidizer
5-47
-------
TABLE 5-7. SUMMARY OF EMISSION FACTORS FOR PHENOL PRODUCTION
BY Till- PEROXIDATION OF CUMENE
SCC and Description Emission Source
3-01-202-02 Process Vent
Phenol Manufacturing -
Cumene Oxidation
3-0 1 -202-02 Process Vent
Phenol Manufacturing -
Cumene Oxidation
Control Device
Uncontrolled6
Thermal Oxidizer
Emission Factor in
Ib/ton (kg/Mg)a Factor Rating
4.00 x 10 3 U
(2.00 x 103)
1.16X10'4 D
(5.82 x 10'5)
Reference
3
88,89
' Factors are expressed in Ib (kg) benzene emitted for ton (Mg) cumene produced.
b Measured at post oxidizer condenser vent.
00
-------
reactor vent from the phenol production process based on the peroxidation of cumene.88-89
Charcoal adsorption is the most commonly used method to' control emissions from the oxidizer
reactor vent; however, condensation, absorption, and thermal oxidation have also been used.90
Recovery devices (i.e., one or more condensers and/or absorbers) are the most commonly used
methods to recover product and control emissions from the cleavage (Vent D, Figure 5-9) and
product purification distillation columns; however, adsorption and incineration have also been
used for emissions reduction.81-90
5.5 NITROBENZENE PRODUCTION
Benzene is a major feedstock in commercial processes used to produce
nitrobenzene. Approximately 5 percent of benzene production in the United States is used in
the production of nitrobenzene.12 In these processes, benzene is directly nitrated with a
mixture of nitric acid, sulfuric acid, and water.
As of February 1991, five companies were producing nitrobenzene in the United
States.91 Their names and plant locations are shown in Table 5-8.u In addition to these plants,
plans are underway for Miles and First Chemical to start up a possible 250-million-pound
(113.4-Gg) aniline plant, along with feedstock nitrobenzene, at Baytown, Texas.92
A discussion of the nitrobenzene production process, potential sources of
benzene emissions, and control techniques is presented in this section. Unless otherwise
referenced, the information that follows has been taken directly from Reference 93.
5.5.1 Process Descriptions for Continuous Nitration
Nitrobenzene is produced by a highly exothermic reaction in which benzene is
reacted with nitric acid in the presence of sulfuric acid. Most commercial plants use a continuous
5-49
-------
TABLE 5-8. PRODUCERS OF NITROBENZENE
Capacity in
million Ib/yr
Company Location ; (million kg/yr)
Rubicon, Inc. Geismar, LA 550 (250)
First Chemical Corporation Pascagoula, MS 536 (244)
E.I. duPont de Nemours and Beaumont, TX 350 (160)
Company, Inc.
BASF Corporation Geisman, LA 250(110)
(Polymers Division
Urethanes)
Miles, Inc. (Polymers New Martinsville, WV 100 (45)
Division Polyurethane)
TOTAL 1,786(809)
Source: Reference 11.
Note: This list is subject to change as market conditions change, facility ownership changes, plants are closed, etc.
The reader should verify the existence of particular facilities by consulting current lists and/or the plants
themselves. The level of benzene emissions from any given facility is a function of variables such as
capacity, throughput, and control measures, and should be determined through direct contacts with plant
personnel. These data on producers and location were current as of January 1993.
nitration process, where benzene and the acids are mixed in a series of continuous stirred-
tank reactors.94 A flow diagram of the basic continuous process is shown in Figure 5-11.93
As shown in the figure, nitric acid (Stream 1) and sulfuric acid (Stream 2) are mixed before
flowing into the reactor. Benzene extract (Stream 6), two recovered and recycled benzene
streams (Streams 7 and 8), and as much additional benzene (Stream 9) as is required are combined
to make up the benzene charge to the reactor.
For the process depicted here, nitration occurs at 131°F (55 °C) under
atmospheric pressure. Cooling coils are used to remove the heat generated by the reaction.
. 5-50
-------
Recycle Benzene
Benzene
Storage
Recycle Benzene
B>
v/
Crude Nitrobenzene
Extractor
Nitrobenzene
Stripper
Nitrobenzene
Storage
To H2SO4 Concentration
for Recycle or Sale*
Note: The itream numbers on the figure correipond to the discussion In the
taxi for this procen. Letteri correspond to potential tourcei of
benzant emissions.
§
Figure 5-11. Process Flow Diagram for Manufacture of Nitrobenzene
-------
Following nitration, the crude reaction mixture (Stream 3) flows to the decanter,
where the organic phase of crude nitrobenzene is separated from the aqueous waste acid. The
crude nitrobenzene (Stream 12) subsequently flows to the washer and neutralizer, where
mineral (inorganic) and organic acids are removed. The washer and neutralizer effluent are
discharged to wastewater treatment. The organic layer (Stream 13) is fed to the nitrobenzene
stripper, where water and most of the benzene and other low-boiling-point components are
carried overhead. The organic phase carried overhead is primarily benzene and is recycled
(Stream 7) to the reactor. The aqueous phase (carried overhead) is sent to the washer.
Stripped nitrobenzene (Stream 14) is cooled and then transferred to nitrobenzene storage.
The treatment, recycling, or discharge of process streams is also shown in the
flow diagram. Aqueous waste acid (Stream 4) from the decanter flows to the extractor, where
it is denitrated. There, the acid is treated with fresh benzene from storage (Stream 5) to
extract most of the dissolved nitrobenzene and nitric acid. The benzene extract (Stream 6)
flows back to the nitrating reactor, whereas the denitrated acid is stored in the waste acid tank.
Benzene is commonly recovered from the waste acid by distillation in the acid
stripper. The benzene recovered is recycled (Stream 8), and water carried overhead with the
benzene is forwarded (Stream 11) to the washer. The stripped acid (Stream 10) is usually
reconcentrated on site but may be sold.93
Typically, many of the process steps are padded with nitrogen gas to reduce the
chances of fire or explosion. This nitrogen padding gas and other inert gases are purged from
vents associated with the reactor and separator (Vent A in Figure 5-11), the condenser on the
acid stripper (Vent B), the washer and neutralizer (Vent C), and the condenser on the
nitrobenzene stripper (Vent D).
5-52
-------
5.5.2 Benzene Emissions from Nitrobenzene Production
Benzene emissions may occur at numerous points during the manufacture of
nitrobenzene. These emissions may be divided into four types: process emissions, storage
emissions, equipment leak emissions, and secondary emissions.
Process emissions occur at the following four gas-purge vents: the reactor and
separator vent (A), the acid stripper vent (B), the washer and neutralizer vent (C), and the
nitrobenzene stripper vent (D). The bulk of benzene emissions occur from the reactor and
separator vent. This vent releases about three times the level of benzene released from
Vents B and D (Figure 5-11), and about 120 times that released from Vent C. For all of these
vents, the majority of VOC emissions is in the form of benzene. Benzene accounts for 99,
100, 76, and 99 percent of total VOC emissions from Vents A, B, C, and D, respectively.
Table 5-9 shows estimated emission factors for benzene from these sources.93
Other emissions include storage, equipment leak, and secondary emissions.
Storage emissions (G) occur from tanks storing benzene, waste acid, and nitrobenzene.
Equipment leak emissions of benzene can occur when leaks develop in valves, pump seals, and
other equipment. Leaks can also occur from corrosion by the sulfuric and nitric acids and can
hinder control of fugitive emissions.
Secondary emissions can result from the handling and disposal of process waste
liquid. Three potential sources of secondary benzene emissions (J) are the wastewater from the
nitrobenzene washer, waste caustic from the nitrobenzene neutralizer, and waste acid from the
acid stripper. Where waste acid is not stripped before its sale or reconcentration, secondary
emissions will be significantly affected (increased) unless the reconcentration process is
adequately controlled.
Table 5-9 gives benzene emission factors before and after the application of
possible controls for two hypothetical plants using the continuous nitration process. The two
5-53
-------
TABLE 5-9. SUMMARY OF HMISSION FACTORS FOR HYPOTHETICAL NITROBENZENE
PRODUCTION PLANTS
SCC and Description
3-01-195-01
Nitrobenzene - General
3-01-195-01
Nitrobenzene - General
3-01-195-01
Nitrobenzene - General
3-01-195-01
Nitrobenzene - General
3-01-195-03
Nitrobenzene -
Acid Stripper Vent
3-01-195-04
Nitrobenzene -
Washer/Neutralizer Vent
Emissions Source"
Small Benzene Storage0
(Point G)
Benzene Storage0
(Point-G)
Secondary
(Point J)
Total
Waste-Acid Stripper
(Point B)
Wash and Neutralization
(Point C)
Control Device
Uncontrolled
Uncontrolled
Internal Floating
Roof
Uncontrolled
Uncontrolled
Vent Adsorber
Thermal Oxidizer
Uncontrolled
Uncontrolled
Vent Adsorber
Emission Factor
in Ib/ton (g/kg)b
0.156(0.078)d
0.154(0.077)e
0.566 (0.283)d
0.562 (0.281)e
0.085 (0.0425)d-e
0.20(0.10)d-e
4.9 (2.45)d
4.4(2.19)e
0.78 (0.39)d
0.64 (0.32)e
0.44 (0.22)d
0.52 (0.26)e
0.034 (0.170)de
0.0162 (0.0081)d-e
0.155(0.0776)d-e
Factor
Rating
U
U
U
U
U
U
U
U
U
U
U
U
U
U
U
(continued)
-------
TABLE 5-9. CONTINUED
SCC and Description
3-01-195-05
Nitrobenzene -
Nitrobenzene Stripper Vent
3-01-195-06
Nitrobenzene - Waste Acid
Storage
3-01-195-80
Nitrobenzene - Equipment
Leak Emissions
Emissions Source3
Nitrobenzene Stripper
(Point D)
Waste Acid Storage
(Point G)
Process Pumps and Valvesf
Control Device
Uncontrolled
Thermal Oxidizer
Uncontrolled
Uncontrolled
LD&R plus
mechanical seals
Emission Factor
in Ib/ton (g/kg)b
0.34(0.170)d-e
0.0288 (0.0144)d-e
0.102(0.051)d'e
0.96 (0.048)d-e
1.26(0.63)d
0.76 (0.38)e
0.33(0.165)"
0.198(0.099)e
Factor
Rating
U
U
U
U
U
U
U
U
Source: Reference 93.
* Emission points refer to Figure 5-11.
b Factors are expressed as Ib (g) benzene emitted per ton (kg) nitrobenzene produced.
Storage emission factors are based on these tank parameters:
For 198 million Ib/vr (90.000 Mg/vr) Model Plant
Tank Size ft3 (m3) Turnovers/Year Bulk Liquid Temperature °F (°O
Benzene (large tank)
Benzene (small tank)
Benzene (large tank)
Benzene (small tank)
100,292 (2,840) 24 68 (20)
10,029 (284) 236 68 (20)
For 331 million Ib/vr (150.000 Mg/vr) Model Plant
Tank Size ft3 (m3) Turnovers/Year Bulk Liquid Temperature "F (°C)
160,035 (4,730) 24 68 (20)
16,704 (473) 236 68 (20)
(continued)
-------
Ut
Ul
o\
TABLE 5-9. CONTINUED
Emission factor for a hypothetical 198 million Ib/yr (90,000 Mg/yr) capacity plant.
Emission factor for a hypothetical 331 million Ib/yr (150,000 Mg/yr) capacity plant.
Process pumps and valves are potential sources of fugitive emissions. Each model plant is estimated to have 42 pumps (including 17 spares), 500 process
valves, and 20 pressure-relief valves based on data from an existing facility. All pumps have mechanical seals. Twenty-five percent of these pumps and
valves are being used in benzene service The fugitive emissions included in this table are based on the factors given in Section 4.5.2.
-------
plants differ in capacity; one produces 198 million Ib/yr (90,000 Mg/yr) and the other
331 million Ib/yr (150,000 Mg/yr) of nitrobenzene. Both plants use a vent absorber or thermal
oxidizer to control process emissions in conjunction with waste-acid storage and small benzene
storage emissions.
The values presented for the main benzene storage emissions were calculated by
assuming that a contact-type internal floating roof with secondary seals will reduce fixed-roof
tank emissions by 85 percent. The values presented for controlled equipment leak emissions
are based on the assumption that leaks from valves and pumps, resulting in concentrations
greater than 10,000 ppm on a volume basis, are detected, and that appropriate measures are
taken to correct the leaks.
Secondary emissions and nitrobenzene storage emissions are assumed to be
uncontrolled. Uncontrolled emission factors are based on the assumptions given in the
footnotes to Table 5-9. The total controlled emission factors for these hypothetical plants
range from 0.44 to 0.78 Ib/ton (0.22 to 0.39 kg/Mg). Actual emissions from nitrobenzene
plants would be expected to vary, depending on process variations, operating conditions, and
control methods.93
A variety of control devices may be used to reduce emissions during
nitrobenzene production, but insufficient information is available to determine which devices
nitrobenzene producers are using currently. Process emissions may be reduced by
vent absorbers, water scrubbers, condensers, incinerators, and/or thermal oxidizers.
Storage emissions from the waste-acid storage tank and the small benzene
storage tank can be readily controlled in conjunction with the process emissions. (A small
storage tank contains approximately one day's supply of benzene; the larger tank is the main
benzene storage tank.) In contrast, emissions from the main benzene storage tanks are
controlled by using floating-roof storage tanks.
5-57
-------
Equipment leak emissions are generally controlled by leak detection and repair,
whereas secondary emissions are generally uncontrolled.
5.6 ANILINE PRODUCTION
Almost 97 percent of the nitrobenzene produced in the United States is
converted to aniline.91 Because of its presence as an impurity in nitrobenzene, benzene may be
emitted during aniline production. Therefore, a brief discussion of the production of aniline
from nitrobenzene and its associated benzene emissions is included in this document.
Table 5-10 lists the U.S. producers of aniline and the production method.11 The
main derivative of aniline (75 percent) is p.p.-methylene diphenyl diisocyanate (MDI). The
growth outlook for aniline is expected to remain strong because of its continued use hi housing
and automobile parts.95
5.6.1 Process Descriptions for Aniline Production for Nitrobenzene
A process flow diagram of the most widely used process for manufacturing of
aniline—by hydrogen reduction of nitrobenzene—is shown in Figure 5-12.96 As shown hi the
figure, nitrobenzene (Stream 1) is vaporized and fed with excess hydrogen (Stream 2) to a
fluidized-bed reactor. The product gases (Stream 3) are passed through a condenser. The
condensed materials are decanted (Stream 4), and non-condensible materials are recycled to the
reactor (Stream 5). In the decanter, one phase (Stream 6) is crude aniline and the other is an
aqueous phase (Stream 7).
The crude aniline phase is routed to a dehydration column that operates under
vacuum. Aniline is recovered from the aqueous phase by stripping or extraction with
nitrobenzene. Overheads from the dehydration column (Stream 8) are condensed and recycled
to the decanter. The bottoms from the dehydration column (Stream 9), which contain aniline,
5-58
-------
TABLE 5-10. U.S. PRODUCERS OF ANILINE
Facility
Location
Annual Capacity in
million gal/yr
(million kg/yr)
Process and Remarks
L/1
vo
Aristech Chemical Corporation
E.I. duPont de Nemours and
Company, Inc.
duPont Chemicals
First Chemical Corporation
ICI American Holdings, Inc. and
Uniroyal, Inc. Affiliate
Rubicon, Inc.
Miles, Inc.
Polymers Polyurethane
Division
BASF Corporation
Polymers Division Urethanes
TOTAL
Haverhill, OH
Beaumont, TX
Pascagoula, MS
Geismar, LA
New Martinsville, WV
Geismar, LA
200(90)
260(120)
275(130)
400(180)
40 (20)
190(90)
1.365 (630)
Ammonolysis of phenol (Halcon
process)
Hydrogen reduction of nitrobenzene
Hydrogen reduction of nitrobenzene
Hydrogen reduction of nitrobenzene
Nitrobenzene (acid-iron reduction
process)
Source: Reference 11.
Note: This list is subject to change as market conditions change, facility ownership changes, plants are closed, etc. The reader should verify the existence
of particular facilities by consulting current lists and/or the plants themselves. The level of benzene emissions from any given facility is a function
of variables such as capacity, throughput, and control measures, and should be determined through direct contacts with plant personnel. These data
on producers and locations were current as of January 1, 1993.
-------
Hydrogen--
Nitrobenzene
Compressor
r®
Catalyst
Handling
Nitrobenzene
Vaporizer
Reactor
Decanter
Dehydration
Column
Aniline
Tars
Purification
Column
Note: The stream numbers on the figure correspond to the discussion in the text for this
process. Letters correspond to potential sources of benzene emissions.
Figure 5-12. Flow Diagram for Manufacture of Aniline
o
<0
o
o
Source: Reference 96.
-------
are sent to the purification column. Overheads (Stream 10) from the purification column
contain the aniline product, while the bottoms (Stream 11) contain tars.
Fourteen percent of current aniline production (produced by Miles, Inc.)
involves an acid-iron reduction process where iron oxide is created as a co-product.
Nitrobenzene is reacted with iron and dilute hydrochloric acid at reflux. When the reaction is
complete, the aniline-water mixture is separated from the iron-hydroxide sludge and the
heavier aniline layer is removed and vacuum distilled to yield purified aniline.18
5.6.2 Benzene Emissions from Aniline Production
Process emissions of benzene typically originate from the purging of non-
condensibles during recycle to the reactor and purging of inert gases from separation and
purification equipment (Vent A in Figure 5-12).9
Only one emission factor was found for benzene emissions from aniline
production. For process vents (Vent A), an uncontrolled emission factor of 0.0114 Ib
benzene/ton aniline produced (0.0057 kg/Mg) was reported in the literature.96 The SCC code
for this emission point is 3-01-034-03: Aniline-Reactor Recycle Process Vent. No details of
the emission factor derivation were provided, other than it was based on data provided by an
aniline producer, so it was assigned a U rating.
Control techniques available for emissions associated with the purging of
equipment vents include water scrubbing and thermal oxidation.96 No data were found to
indicate the efficiencies of these control devices for benzene emissions. The reader is urged to
contact specific production facilities before applying the emission factor given in this report to
determine exact process conditions and control techniques.
5-61
-------
5.7 CHLOROBENZENE PRODUCTION
The most important chlorobenzenes for industrial applications are
monochlorobenzene (MCB), dichlorobenzene (DCB), and trichlorobenzene (TCB). Therefore,
this section focuses on benzene emissions associated with production of these three types of
chlorobenzenes. Table 5-11 lists the U.S. producers of MCB, DCB, and TCB. The producing
companies' capabilities are flexible, such that different chlorobenzenes may be isolated,
depending on market demand. DCBs and TCBs are produced in connection with MCB. The
relative amounts of the products can be varied by process control.97
5.7.1 Process Description for Chlorobenzene Production by Direct Chlorination of
Benzene
The most widely used process for the manufacture of chlorobenzenes is direct
chlorination of benzene hi the presence of ferric chloride catalyst to produce MCB and DCB.
HC1 is a by-product. The two major isomers of DCB are ortho and para. As chlorination
continues, tri-, tetra-, penta-, and, finally, hexachlorobenzenes are formed. However, TCB is
the only one of the more highly chlorinated products found in significant amounts.
Basic operations that may be used in die continuous production of MCB are
shown in Figure 5-13.19 The process begins with a series of small, externally cooled cast iron
or steel vessels containing the catalyst (which may consist of Hashing rings of iron or iron
wire). Chlorine is supplied into each vessel through suitably positioned inlets to maintain a
large benzene-to-chlorine reaction at all points along the reaction stream. The temperature is
held between 68 to 104°F (20 to 40°C) to minimize the production of DCBs, which form at
higher temperatures. Dry benzene (Stream 1) and dried recycled benzene (Stream 2) are
introduced into the reactor, which produces an overhead gas (Stream 3).
The gas stream (containing HC1, unreacted chlorine, inert gases from the
chlorine feed, benzene, and other VOC) is sent to an organic absorber, where benzene and
.5-62
-------
TABLE 5-11. U.S. PRODUCERS OF MONO-, DI-, AND TRICHLOROBENZENE
Company
Location
Product
Annual Capacity
million Ib
(million kg)
u>
Monsanto Company
Chemical Group
PPG Industries, Inc.
Chemical Group
Standar Chlorine
Chemical Company, Inc.
Sauget, IL
Natrium, WV
Delaware City, DE
Southland Corporation
Chemical Division
Great Meadows, NJ
Monochlorobenzene
o-Dichlorobenzene
p-Dichlorobenzene
Monochlorobenzene
o-Dichlorobenzene
p-Dichlorobenzene
Monochlorobenzene
o-Dichlorobenzene
p-Dichlorobenzene
1,2,3-Trichlorobenzene
1,2,4-Trichlorobenzene
1,3,5-Trichlorobenzene
176 (80)
11(5)
22 (10)
45 (20)
20(9)
30 (14)
150 (68)
50 (23)
75 (34)
NA
NA
NA
Source: Reference 11.
NA = Not available
Note: This is a list of major facilities producing mono-, di-, and trichlorobenzene. The list is subject to change as market conditions change, facility
ownership changes, or plants are closed down. The reader should verify the existence of particular facilities by consulting current lists or the
plants themselves. The level of emissions from any given facility is a function of variables such as throughput and control measures, and should
be determined through direct contacts with plant personnel. The data on producers and locations were current as of January 1993.
-------
Til-Go Treatment
Ui
ON
Banzane
Receiving
(TD—
WetBanzan*
Slung*
OL ..
Benzene
Banzane
Reoovaiy
MCB
DIstlBaSon
Isomar
FricSonitkwi
(Se«Flgura5-14)
Sodium
, Hydroxide
SoluUon
Heavy-Ends
Processing
Neutralization
Recovery.
Drying
(0^J<».
©
FugWw
Emissions
Overs!
Plant
Figure 5-13. Monochlorobenzene Continuous Production Process Diagram
Source: Reference 19.
-------
other VOC are removed. The bottoms from the organic absorber (Stream 6) flow to the HC1
stripper for recovery of HC1. The overhead gas (Stream 5) is sent to HC1 absorption.
By-product HC1 is then removed hi the HC1 absorber, where it is saturated by washing with a
refrigerated solvent (e.g., o-DCB) or low vapor pressure oil, and then recovered in wash
towers as commercially usable hydrochloric acid.98
Crude reaction liquid product (Stream 4) enters the crude chlorobenzene
distillation column, which produces overheads (Stream 7) that contains most of the
chlorobenzenes, unreacted benzene, and some HC1, and a bottom stream from which catalyst
and other byproducts are separated (Stream 8) and processed for reuse. The overheads
(Stream 7) pass through an HC1 stripper and into a benzene recovery column (Stream 9). Part
of the subsequent benzene-free stream (Stream 10) is returned to the organic absorber; the
remainder (Stream 11) enters the MCB distillation column. The overhead MCB distillation
product (Stream 12) is then stored and the bottom stream containing DCB and TCB isomers is
processed.98
Figure 5-14 presents basic operations that may be used to produce o- and p-DCB
and TCB. In a continuation of the production of MCB, o- and p-DCB can be separated by
fractional distillation. Isomer fractionation yields p-DCB (with traces of o-DCB and m-DCB),
which enters the overhead (Stream 1); the o-DCB enters the bottoms (Stream 2). The o-DCB
bottoms (Stream 2) undergoes fractional distillation and produces an o-DCB overhead
(Stream 3), which is sent to storage, and bottoms (Stream 4), which is further processed to
yield TCBs.98
The crude p-DCB with other trace isomers (Stream 5) is purified by batch
crystallization. Part of the purified p-DCB (Stream 6) is sent to liquid storage. The remainder
(Stream 7) undergoes freezing, crushing, screening, and packing of p-DCB crystals. The
mother liquor from crystallization (Stream 8) is sent to DCB solvent-grade fractionalization,
where it is separated into solvent grade o-DCB (Stream 9) and p-DCB (Stream 10) and
stored.98
5-65
-------
in
(From
Figure 5-13)
MCB
Fractional
Distillation
Distfetion
Figure 5-14. Dichlorobenzene and Trichlorobenzene Continuous Production Diagram
Source: Reference 19.
-------
The isolation of m-DCB from mixed DCB streams is not economical, because it
usually occurs at a level of 1 percent or less. Metadichlorobenzene is sold with other isomers
as mixed chlorobenzenes.98
*s
Other processes that are most often used in the production of MCB are the batch
and Rashing methods.98 Other TCB production processes are the reaction of a, P, or
y-benzene hexachloride with alcoholic potash, the dehalogenation of a-benzene hexachloride
with pyridine, and the reaction of a-benzene hexachloride with calcium hydroxide to form
primarily 1,2,4-TCB.19
5.7.2 Benzene Emissions from Chlorobenzene Production
The primary source of benzene emissions during MCB production is the tail gas
treatment vent of the tail gas scrubber (Vent A in Figure 5-13). Usually, this vent does not
have a control device.19 Other potential sources of benzene emissions are atmospheric
distillation vents from the benzene drying column, heavy-ends processing,-the benzene
recovery column, and MCB distillation (Vents B, C, D, E in Figure 5-13, respectively),
equipment leak emissions, emissions from benzene storage, and secondary emissions from
wastewater.19
Table 5-12 presents estimated controlled and uncontrolled emission factors for
benzene emissions from the tail gas treatment vent, atmospheric distillation vents, equipment
leak emissions, and benzene storage.19 The point source factors are based on emissions
reported to EPA in response to information requests and trip reports.19 For information on
emission factors for estimating equipment leak and storage tank emissions refer to
Sections 4.5.2 and 4.5.3 respectively of this document. As noted in Table 5-12, carbon
adsorption is an appropriate control technology for control of emissions from tail gas treatment
and distillation column vents. The control technique applicable to process equipment leak
emissions is an inspection/maintenance program for pumps, valves, and flanges. Internal
floating roof tanks may be used to control benzene emissions resulting from benzene storage.19
5-67
-------
TABLE 5-12. EMISSION FACTORS FOR CHLOROBENZENE PRODUCTION BY DIRECT
CHLORINATION OF BENZENE
SCC and Description
3-01-301-01
Chlorobenzene
Manufacturing -
Tail-gas Scrubber
3-01-301-02
Chlorobenzene
Manufacturing -
Benzene Dry Distillation
^ 3-01-301-04
d^ Chlorobenzene
00 Manufacturing -
Emissions Source
Tail-gas Scrubber
Treatment
Atmospheric Distillation
Vents'
Contol Device
Carbon Adsorption
Uncontrolled
Carbon Adsorption
Uncontrolled
Emission Factor in Ib/ton
(kg/Mg)''b
0.0134 (0.0067)
1.04(0.52)
0.0084 (0.0042)
0.64 (0.32)
Factor Rating
U
U
U
U
Heavy Ends Processing
3-01-301-05
Chlorobenzene
Manufacturing -
Monochlorobenzene
Distillation
3-01-301-03
Chlorobenzene
Manufacturing -
Benzene Recovery
3-01-3-1080
Chlorobenzene
Manufacturing -
Equipment Leaks
Atmospheric Distillation
Vent - Benzene Recovery
Equipment Leaks
Carbon Adsorption
Uncontrolled
Detection and Repair of
Major Leaks
Uncontrolled
0.00104 (0.00052)
0.08 (0.04)
See Section 4. 5. 2
See Section 452
U
U
(continued)
-------
TABLE 5-12. CONTINUED
Emission Factor in Ib/ton
SCC and Description Emissions Source Contol Device (kg/Mg)'-" Factor Rating
4-07-196-01 Benzene Storage Vessel Internal Floating Roof See Section 4.5.3
Organic Chemical
Storage - Benzene ., ... _ _, . . , „
_. e Uncontrolled See Section 4.5.3
Storage
Source: Reference 19.
" Emission factors are expressed as Ib (kg) benzene emitted per ton (Mg) chlorobenzene product produced.
b These emission factors are based on a hypothetical plant producing 74,956 tons (68 Gg) monochlorobenzene, 13,669 tons (12.4 Gg) o-dichlorobenzene, and
17,196 tons (15.6 Gg) p-dichlorobenzene. The reader is urged to contact a specific plant as to process, products made, and control techniques used before
applying these emission factors.
c Includes the following vents: benzene dry distillation, heavy ends processing, and monochlorobenzene distillation.
a,
-------
5.8 LINEAR ALKYLBENZENE PRODUCTION
Approximately 2 percent of the benzene produced in the United States is used in
the production of linear alkylbenzene (LAB). LAB (or linear alky late) improves the surfactant
performance of detergents. The primary end use for LAB is in the production of linear
alkylbenzene sulfonates (LAS). Because of their water-soluble properties, LAS are used
extensively in powdered home laundry products (over 50 percent of LAS produced) and in
heavy-duty liquid products."
Alkyl benzene sulfonates with highly branched C12 side chains possess excellent
detergent properties, and they have also been used in the past in formulating detergents.
However, in recent years, LAS have essentially replaced all branched alkylbenzene sulfonates
in detergent formulations in the United States because of environmental considerations. LAB
is extensively degraded (> 90 percent) by microorganisms in sewage plants after a relatively
short period of time. In comparison, the highly branched alkyl benzene sulfonates have a
much lower biological degradability.100 Dodecylbenzene and tridecylbenzene are the two most
common LABs. The locations of the LAB producers in the United States are shown in
Table 5-13.1U01
In the United States, LAB is produced using two different processes. Vista's
Baltimore plant uses a monochloroparaffin LAB production process. Vista's Lake Charles
plant and Monsanto's Alvin plant use an olefin process, wherein hydrogen fluoride serves as a
catalyst. Approximately 64 percent of LAB is produced by the olefin process. The paraffin
chlorination process accounts for about 36 percent of LAB production. Both processes are
described in the following sections.
5.8.1 Process Description for Production of LAB Using the Olefin Process
Production of LAB using the olefin process consists of two steps: a
dehydrogenation reaction and an alkylation reaction. The C10 to C14 linear paraffins are
5-70
-------
TABLE 5-13. U.S. PRODUCERS OF LINEAR ALKYLBENZENE (DETERGENT ALKYLATES)
Company
Location
Annual Capacity
million Ib/yr
(million kg/yr)
Process
Linear Alkylbenzene
(Dodecyclbenzene and tridecyclbenzene)
Monsanto Company Chemical Alvin, TX
Group
Vista Chemical Company Baltimore, MD
Lake Charles, LA
Linear Alkylbenzene
(except dodecyl and tridecyl)
Phillips 66 Company
NA
330 (150)
300 (140)
210 (95)
NA
Internal olefms-HFl;
merchant
Monochloroparaffin,
merchant and captive
Internal olefins—HF1;
merchant and captive
TOTAL
840 (385)
Source: References 11 and 101.
NA = Not available
Note: This is a list of major facility that produce linear alkylbenzene. This list is subject to change as market conditions change, facility ownership
changes, or plants are closed down The reader should verify the existence of particular facilities by consulting current listings or the plants
themselves. The level of emissions from any given facility is a function of variables, such as throughput and control measures, and should be
determined through direct contacts with plant personnel. These data for producers and locations were current as of January 1993.
-------
dehydrogenated to n-olefins, which are reacted with benzene under the influence of a solid,
heterogenous catalyst (such as hydrogen fluoride [HF1]) to form LAB. The discussion of LAB
production using the olefin process is taken from references 102 and 103.
First, n-paraffins are transferred from bulk storage to the linear paraffin feed
tank in Stream 1 (Figure 5-15. )103 The paraffins are heated to the point of vaporization
(Stream 2) and passed through a catalyst bed hi the Pacol reactor (Stream 3), where the feed is
dehydrogenated to form die corresponding linear olefins by the following reaction:
R, - CH2 - CH2 - R2 — > R, CH = CH - R2 + H2
The resulting olefins contain from 10 to 30 percent a-olefms, and a mixture of internal olefins,
unreacted paraffins, some diolefins, and lower-molecular-weight "cracked materials." The gas
mixture is quickly quenched with a cold liquid stream as it exits to process thermally-promoted
side reactions (Stream 4). The hydrogen-rich offgases (e.g., hydrogen, methane, ethane, etc.)
are then separated from the olefin liquid phases (Stream 5). The gas is used as process fuel
(Stream 6) or vented to a flare stack.
Di-olefins in the Pacol separator liquid are selectively converted back to
mono-olefins in the Define reactor (Stream 7). The effluent from the reactor is routed to a
stripper (Stream 8), where light ends are removed (Stream 9). The olefinTparaffin mixture
(Stream 10) is then alkylated with benzene (Stream 11) in the fixed-bed reactor to be blended
with a HF1 catalyst. The blend is held at reaction conditions long enough for die alkylation
reaction to go to completion as follows:
= CHR2 + C6H6 — > RjCHj - CHR2
Product from the reactor flows to the benzene stripping column (Stream 12) for separation and
recycle of unreacted benzene to the fixed-bed reactor (Stream 13). The liquid HF1 is also
separated and recycled to the alkylation vessel to be mixed with fresh HF1.
5-72
-------
Fresh B*nzene
U)
u>
h-O
n-Parafflni
Bulk Storage
LAB
Heavy
Alkylale
o.
t
8
Figure 5-15. Linear Alkybenzene Production Using the Olefin Process
Source: Reference 103.
-------
Following benzene stripping, a lime water solution is then fed into the HF1
scrubber column (Stream 14) to neutralize the HF1. The solution is filtered (Stream 15); the
wastewater is routed to the treatment facility and the solids are transferred to a landfill.
Unreacted paraffins are separated in the paraffin stripping column (Stream 16) and recycled to
the Pacol reactor (Stream 17). The last distillation column purifies the main LAB (Stream 18).
Heavy alky late byproducts are stored (Stream 19) and the pure LAB is transferred to storage
tanks (Stream 20) awaiting sale.
5.8.2 Benzene Emissions from LAB Production Using the Olefin Process
Benzene emissions from the LAB olefin process are shown in Table 5-14.102
The two major sources of emissions are the benzene azeotropic column (Vent A) and the HF1
scrubber column controlling emissions from the benzene stripping column (Vent B). Some
benzene can be emitted through the HF1 scrubber column. Inert gases and air venting from the
unit, temperature, and purge rate of the scrubber can influence the amount of volatiles emitted.
These gases are usually sent to a flare. The control for both of these emissions is use as fuel.
Benzene emissions can also occur from benzene storage tanks and equipment leaks. Refer to
Section 4.5 for a discussion of benzene emissions from these sources.
5.8.3 Process Description for Production of LAB Using the Chlorination Process
The LAB chlorination process consists of two sequential reactions. In the first
step, n-paraffins are chlorinated to monochlorinated n-paraffins. In the second reaction,
benzene and crude secondary alkyl chlorides (chloroparaffins) are blended with an aluminum
chloride catalyst to form crude LAB. The following discussion of LAB production using the
chlorination process is taken from references 100 and 102.
As shown in Figure 5-16, n-paraffins (alkanes) (Stream 1) are reacted with
liquid chlorine (Stream 2) in a series of UV-catalyzed chlorination reactors.100 The n-paraffins
5-74
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TABLE 5-14- SUMMARY OF EMISSION FACTORS FOR HYPOTHETICAL LINEAR ALKYLBENZENE PLANT
USING THE OLEFIN PROCESS
SCC and Description
3-01-211-02
Linear Alkylbenzene -
Benzene Drying
3-01-211-03
Linear Alkylbenzene HF1
Scrubber Vent
Emissions Source
Benzene Azeotropic
Column Vent
(Point A)c
Hydrogen Fluoride
Scrubber Column Vent
(Point B)c
Control Device
Uncontrolled
Used as fuel
Uncontrolled
Used as fuel
Flare
Emission Factor
Ih/ton (g/Mg)a-b
7.4 x lO'3 (3.7)
1. 5 xlO'6 (7.4x10^)
0.022(11)
4.4 x 10-6 (2.2 x 10 3)
2.2 x 10 3 (1.1)
Factor
Rating
U
u
U
u
u
Source: Reference 102.
-Ij
*•" * Emission factor estimates based on a 198 million Ib/yr (90,000 Mg/yr) hypothetical plant.
b Emission factors refer to Ib (g) benzene emitted per ton (Mg) LAB produced by the olefin process.
c Letters refer to vents designated in Figure 5-15.
Note: Any given LAB olefin producing plant may vary in configuration and level of control from this hypothetical facility. The reader is encouraged to
contact plant personnel to confirm the existence of emitting operations and control technology at a particular facility prior to estimating emissions
therefrom.
-------
A
n-Pir*ffint
Chlorint
HCI
A
A
HCI
A
B«nz«ne
\J
HCI to
Storage
©
Paraffin
(racycl(d)
Alkylbanzan*
(pur*)
ct
UV Catalyzad
Chlorination
Raacton
Dechlorlnitlon
Benzine
Azeotropic
Column
Alkylation
6apar«tor
Binzan*
Stripping
Column
Figure 5-16. Production of Linear Alkybenzenes via Chlorination
Source: Reference 100.
-------
are converted at 212°F (100°C) to a mixture of about 35 percent chlorinated paraffins, and the
remainder to paraffins and HC1 as shown hi the following reaction:
R, - CH2 - R2 + Cl — > R - CH - R2 + HC1 + heat
I
Cl
Following this reaction, dehydrochlorination (elimination of HC1) of the monochloroalkanes
takes place at 392 to 752°F (200 to 300°C) over an iron catalyst to form olefins (linear alkenes
with internal double bonds) (Stream 3). It is necessary to remove all chlorinated paraffins
(such as dichloroalkenes) from the process stream because they form other products besides
LAB. Therefore, the remaining chlorinated paraffins are dehydrochlorinated to give tar-like
products that are easily separated and recycled back to the reactor (Stream 4). HC1 is also
removed from the mixture (Stream 5), leaving a mixture of only olefins and paraffins for the
alkylation reaction.100
This olefin-paraffm mixture (Stream 6) is combined with benzene from storage
that has been dried in a benzene azeotropic column (Stream 7). These two streams are
combined in an alkylation reactor with an aluminum chloride catalyst at 122°F (50°C)
(Stream 8). The subsequent reaction produces LAB, illustrated below:
R! - CH - R2 + C6H6 — > Rj - CH - R2 + HC1 + heat, possible olefins,
| short-chained paraffins, etc.
Cl
At this point, HC1 gas and some fugitive volatile organics given off during the
reaction are treated with adsorbers and excess HC1 is routed to storage (Vent B). Next, the
LAB (Stream 9) is routed to a separator where hydrolysis is performed in the presence of HF1
at 50°F (10°C) to separate crude LAB and the organics (benzene, tar, etc.) (Stream 10) from
the catalyst sludge (Stream 11). Benzene is recovered in the benzene stripping column and
recycled back to the reactor (Stream 12).
5-77
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The resulting paraffin-alkylate mixture (Stream 13) is sent through rectification
and purification (which includes washing and decanting) to yield pure alkylbenzene and
paraffin, which can be recycled as feedstock.100
5.8.4 Benzene Emissions from LAB Production Using the Chlorination Process
Benzene emissions using the LAB chlorination process are shown hi Table 5-14.
The four major points of benzene emissions are listed below. Emission factors for these points
also are presented hi Table 5-15.102
One emission point is the benzene azeotropic column vent, which serves to dry
the benzene before it enters the alkylation reactor. Some benzene emissions can escape from
the vent in the column (Vent A). The quantity of escaping emissions is dependent on the
dryness of the benzene and the design of the column condenser.
A second emission point is the hydrochloric acid adsorber vent. Following the
alkylation reaction, the HC1 gas and fugitive volatile organics are treated by absorbers. Most
of the product goes to hydrochloric acid storage, but some is vented off (Vent B). The amount
of benzene emissions given off here is dependent on the fluid temperature hi the absorber and
the vapor pressure of the mixed absorber fluid.
The third type of emission point is the atmospheric wash decanter vents. In the
final purification/rectification stage, the crude LAB is washed with alkaline water to neutralize
it. Benzene emissions can escape from these atmospheric washer vents (Vent C).
Finally, hi the benzene stripping column, benzene is recovered and returned to
the benzene feed tank. Residual inert gases and benzene emissions can occur at this point
(Vent D). The amount of benzene in the stream depends on the quantity of inert gases and the
temperature and design of the reflux condenser used.
5-78
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TABLE 5-15. SUMMARY OF EMISSION FACTORS FOR HYPOTHETICAL LINEAR ALKYLBENZENE'PLANT
USING THE CHLORINATION PROCESS
VO
SCC and Description
3-01-211-02
Linear Alkylbenzene-Benzene
Drying
3-01-211-23
Linear Alkylbenzene - HC1
Adsorber Vent
3-01-211-24
Linear Alkylbenzene -
Atmospheric Wash/Decanter
Vent
3-01-211-25
Linear Alkylbenzene -
Benzene Strip Column
Emissions Source
Benzene Azeotropic
Column Vent
(Point A)c
Hydrochloric Acid
Adsorber Vent
(Point B)c
Atmospheric
Wash/Decanter Vent
(Point C)c
Benzene Stripping Column
Vent
(Point D)c
Control Device
Uncontrolled
Used as fuel
Uncontrolled
Used as fuel
Uncontrolled
Used as a fuel
Uncontrolled
Used as a fuel
Emission Factor in
Ib/ton (g/Mg)a Factor Rating
7.4 x lO'3 (3.7)
1.5xl06(7.4xl04)
0.5 (250)
1 x 104 (0.05)
0.0246 (12.3)
5 x 10"* (2.5 x 10'3)
7.4 x 10'3 (3.7)
1.48xlO-6(7.4xl04) .
U
U
U
U
U
U
U
U
Source: Reference 102.
1 Emission factor estimates based on a 198 million Ib/yr (90,000 Mg/yr) hypothetical plant.
b Emission factors refer to Ib (g) benzene emitted per ton (Mg) LAB produced by the chlorination process.
c Letters refer to vents designated in Figure 5-16.
Note: Any given LAB olefin producing plant may vary in configuration and level of control from this hypothetical facility. The reader is encouraged to
contact plant personnel to confirm the existence of emitting operations and control technology at a particular facility prior to estimating emissions
therefrom.
-------
The most frequently applied control option for all of these sources is to use the
emissions for fuel.
5.9 OTHER ORGANIC CHEMICAL PRODUCTION
Several additional organic chemicals that are produced using benzene as a
feedstock are believed to have benzene emissions. These chemicals include hydroquinone,
benzophenone, benzene sulfonic acid, resorcinol, biphenyl, and anthraquinone.68 A brief
summary of the producers, end uses, and manufacturing processes for these chemicals is given
below. No emissions data were available for these processes.
5.9.1 Hydroquinone
The primary end use of hydroquinone is in developing black-and-white
photographic film (46 percent). A secondary end use is as a raw material for rubber
antioxidants (31 percent).104
A technical grade of hydroquinone is manufactured using benzene and propylene
as raw materials by Goodyear Tire and Rubber Company in Bayport, TX, 11 million Ib/yr
(5 million kg/yr) and by the Eastman Chemical Company, Tennessee Eastman Division, in
Kingsport, Tennessee, 26 million Ib/yr (12 million kg/yr).1U01
In this process, benzene and recycled cumene are alkylated with propylene in
the liquid phase over a fixed-bed silica-alumina catalyst to form a mixture of
diisopropylbenzene isomers. The meta isomer is transalkylated with benzene over a fixed bed
silica-alumina catalyst to produce cumene for recycle. The para isomer is hydroperoxidized hi
the liquid phase, using gaseous oxygen, to a mixture of diisopropylbenzene hydroperoxide
isomers. The mono isomer is recycled to the hydroperoxidation reactor. The
diisopropylbenzene hydroperoxide is cleaved in the liquid phase with sulfuric acid to
hydroquinone and acetone. Acetone is produced as a co-product.104
5-80
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5.9.2 Benzophenone
Benzophenone (diphenylketone) is used as an intermediate in organic synthesis,
aHd as an odor fixative. Derivatives are used as ultraviolet (UV) absorbers, such as in the UV
curing of inks and coatings.105 Benzophenone is also used as flavoring, soap fragrance, in
Pharmaceuticals, and as a polymerization inhibitor for styrene. Nickstadt-Moeller, Inc., in
Ridgefield, New Jersey, and PMC, Inc., PMC Specialties Group Division in Chicago, Illinois,
produce a technical grade of benzophenone.11 Benzophenone is also produced by Upjohn
Company, Fine Chemicals.101 Benzophenone is produced by acylation of benzene and benzyl
chloride.68
5.9.3 Benzene Sulfonic Acid
Benzene sulfonic acid is used as a catalyst for furan and phenolic resins and as a
chemical intermediate in various organic syntheses including the manufacture of phenol and
resorcinol.105'106 Benzene sulfonic acid is manufactured by sulfonation-reactmg benzene with
fuming sulfuric acid.106 Burroughs Wellcome in Greenville, North Carolina; CL Industries,
Inc., in Georgetown, Illinois; and Sloss Industries Corporation in Birmingham, Alabama,
produce benzene sulfonic acid.11
5.9.4 Resorcinol
Resorcinol is produced by INDSPEC Chemical Corporation in Petrolia,
Pennsylvania.11 Resorcinol is produced by fusing benzene-m-disulfonic acid with sodium
hydroxide. Resorcinol is used hi manufacturing resorcinol-formaldehyde resins, dyes, and
Pharmaceuticals. It is also used as a cross-linking agent for neoprene, as a rubber tackifier, in
adhesives for wood veneers and runner-to-textiles composites, and hi the manufacture of
styphnic acid and cosmetics.106
5-81
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5.9.5 Biphenvl
Biphenyl (diphenyl or phenylbenzene) is produced by Chemol Co. in
Greensboro, North Carolina; Koch Refining Co. in Corpus Christi, Texas; Monsanto Co. hi
Anniston, Alabama; Sybron Chemical Inc., hi Wellford, South Carolina; and Chevron
Chemical Co. of Chevron Corp.11-101 One method for producing biphenyl is by
dehydrogenation-slowly passing benzene through a red-hot iron tube.106
Biphenyl is used in organic synthesis, as a heat-transfer agent, as a fungistat in
packaging citrus fruit, in plant disease control, in the manufacture of benzidine, and as a
dyeing assistant for polyesters.106 In 1991, 8,976 tons (8,143 Mg) of biphenyl were sold.1
101
5.9.6 Anthraquinone
Anthraquinone is manufactured by heating phthalic anhydride and benzene in the
presence of aluminum chloride and dehydrating the product. Anthraquinone is used as an
intermediate for dyes and organics, as an organic inhibitor, and as a bird repellent for seeds.
5.10 BENZENE USE AS A SOLVENT
Benzene has been used historically as an industrial solvent. Because benzene is
readily soluble in a variety of chemicals (including alcohol, ether, and acetone), it has
commonly been used as an agent to dissolve other substances. As an industrial solvent,
benzene application has included use as an azeotropic agent, distilling agent, reaction solvent,
extracting solvent, and recrystallizing agent. However, benzene use as an industrial solvent
has been steadily declining over the last few years because of its adverse health effects and
increased regulation. The Occupational Safety and Health Administration has cited health risk
to workers from exposure to benzene, and EPA has classified benzene as a Group A chemical,
a known human carcinogen.107
5-82
-------
Source categories that currently use benzene as a solvent include pharmaceutical
manufacturing; general organic synthesis; alcohol manufacturing; caprolactam production, and
plastics, resins, and synthetic rubber manufacturing. Benzene is also used in small quantities
(generally less than 0.1 percent) hi solvents used in the rubber tire manufacturing industry;
however, the amount of emissions generated is variable depending on the amount of solvent
used.108
Facilities in the above-listed source categories indicate that they plan to
eliminate benzene solvent use in the next few years.107 Facilities have been experimenting with
substitutes, such as toluene, cyclohexane, and monochlorobenzene. However, those facilities
that continue to use benzene indicate that they have been unable to identify a solvent substitute
as effective as benzene.109
Several facilities in the source categories listed above reported benzene
emissions in the 1992 TRI. These facilities and their locations are included in Table 5-16.
Emissions of benzene from solvent used in the manufacture and use of
pesticides, use of printing inks, application of surface coatings, and manufacture of paints are
believed to be on the decline or discontinued.107'110 However, several facilities in these source
categories reported benzene emissions in the 1992 TRI.111 These facilities and their locations
are also included in Table 5-16.ni
Benzene continues to be used in alcohol manufacture as a denaturant for ethyl
alcohol. It is also used as an azeotropic agent for dehydration of 95 percent ethanol and
91 percent isoproponal.109 Companies currently producing these alcohols are presented in
Table 5-17.lun
Benzene is also used as a solvent to extract crude caprolactam.112 The three
major caprolactam facilities currently operating in the United States are listed in
5-83
-------
TABLE 5-16. PARTIAL LIST OF MANUFACTURERS IN SOURCE CATEGORIES
WHERE BENZENE IS USED AS A SOLVENT
Solvent Use Source Category
Location
Plastics Materials and Resins
Amoco Chemical Co.
Arizona Chemical Co.
Chemfax Inc.
Exxon Chemical Americas Baton
Rouge Resin Finishing
Formosa Plastics Corp.
Lawter Intl. Inc.
Southern Resin Division
Neville Chemical Co.
Quantum Chemical Corp. La Porte
Quantum Chemical Corp.
USI Division
Rexene Corp. Polypropylene Plant
Union Carbide Chemicals & Plastics
Co. Texas City Plant
Moundville, AL
Gulfport, MS
Gulfport, MS
Baton Rouge, LA
Point Comfort, TX
Moundville, AL
Pittsburgh, PA
La Porte, TX
Clinton, IA
Odessa, TX
Texas City, TX
Pharmaceutical Manufacturing
Warner-Lambert Co.
Parke Davis Division
Pesticides and Agricultural Chemicals
Rhone-Poulenc Ag Co.
Agribusiness Maketers, Inc.
Commercial Printing (Gravure)
Piedmont Converting, Inc.
Holland, MI
Institute, WV
Baton Rouge, LA
Lexington, NC
(continued)
5-84
-------
TABLE 5-16. CONTINUED
Solvent Use Source Category
Location
'Paints and Allied Products
BASF Corporation Inks & Coating
Division
St. Louis Paint Manufacturing Co.,
Inc.
Greenville, OH
St. Louis, MS
Synthetic Rubber
DuPont Pontchartrain Works
DuPont Beaumont Plant
La Place, LA
Beaumont, TX
Source: Reference 111.
5-85
-------
TABLE 5-17. U.S. PRODUCERS OF ETHANOL OR ISOPROPANOL
Facility
Location
Annual Capacity
million gal
(million L)
Ethanol
Archer Daniels Midland Company
ADM Corn Processing Division
Cedar Rapids, IA
Clinton, IA
Decatur, IL
Peoria, IL
700 (2,650)
Biocom USA Ltd.
Cargill, Incorporated
Domestic Corn Milling Division
Chief Ethanol Fuels Inc.
Eastman Chemical Company
Texas Eastman Division
Georgia-Pacific Corporation
Chemical Division
Giant Refining Co.
Grain Processing Corporation
High Plains Corp.
Hubinger-Roquette Americas, Inc.
Midwest Grain Products, Inc.
Minnesota Corn Processors
New Energy Company of Indiana
Pekin Energy Company
Quantum Chemical Corp.
USI Division
South Point Ethanol
A. E. Staley Manufacturing Company
Sweetner Business Group
Ethanol Division
Walhalla, ND
Jennings, LA
Eddyville, IA
Hastings, NB
Longview, TX
Bellingham, WA
Portales, NM
Muscatine, IA
Colwich, KS
Keokuk, IA
Atchison, KS
Pekin, IL
Columbus, NB
Marshall, MN
South Bend, IN
Pekin, IL
Tuscola, IL
South Point, OH
Loudon, TN
11(42)
40(151)
30(113)
14 (53)
25 (95)
12 (45)
10 (38)
60 (227)
15 (57)
11(42)
22 (83)
19 (72)
NA
28 (106)
70 (265)
80 (303)
68 (257)
60 (227)
60 (227)
(continued)
5-86
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TABLE 5-17. CONTINUED
Facility
Location
Annual Capacity
million gal
(million L)
Ethanol (continued)
Union Carbide Corporation
Solvents and Coatings Materials Division
Texas City, TX
123 (466)
TOTAL
1,458 (5,519)
Isopropanol
Exxon Chemical Company
Exxon Chemical Americas
Lyondell Petrochemical Company
Shell Chemical Company
Union Carbide Corporation
Solvents and Coatings Materials Division
Baton Rouge, LA
Channelview, TX
Deer Park, TX
Texas City, TX
650 (2,460)
65 (246)
600 (2,271)
530 (2,006)
TOTAL
1,845 (6.984)
Source: References 11 and 111.
' Emissions listed are those reported in the 1992 TRI.
NA = Not available
= no emissions reported
5-87
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Table 5-18.lun Of the three facilities, DSM and BASF use benzene as a solvent, and Allied Signal
produces benzene as a co-product.113
Benzene is also used as a solvent in the blending and shipping of aluminum alkyls.
113
Emission points identified for solvent benzene are process vents, dryer vents, and
building ventilation systems.107 As shown in Table 5-19, only one emission factor was identified for
any of the solvent use categories.114 The emission factor presented is for the vacuum dryer vent
controlled with a venturi scrubber in pharmaceutical manufacturing.
-------
1 ABLE 5-18. U.S. PRODUCERS OF CAPROLACTAM
Ui
i
oo
Facility
Chemicals Division
Fiber Raw Materials
DSM Chemicals
North America, Inc.
Location
August, GA
Annual Capacity
million Ib
(million kg)
TOTAL
360(163)
1,440(653)
Raw Material
Allied-Signal, Inc.
Engineered Materials Sector
BASF Corporation
Hope well, VA
Freeport, TX
660 (299)
420 (191)
Phenol
Cyclohexane
Cyclohexane
Source: References 11 and 111.
' Emissions listed are those reported in the 1992 TRI.
"--" = no emissions reported.
-------
TABLE 5-19. SUMMARY OP EMISSION FACTORS EOR BENZENE USE AS A SOLVENT
SCC and Description
3-01-060-01
Pharmaceuticals -
General Process -
Vacuum Dryers
Emissions Source Control Device
Vacuum Dryer Vent Venturi Scrubber
(99.10% efficiency)
Emission Factor"
Ib/ 1,000 gal
(g/L)
2.1 (0.25)
Factor
Rating
B
Source: Reference 114.
* Factor is expressed as Ib (kg) benzene emitted per 1,000 gal (L) pharmaceutical product produced.
-------
SECTION 6.0
EMISSIONS FROM OTHER SOURCES
The following activities and manufacturing processes (other than benzene
production or use of benzene as a feedstock) were identified as additional sources of benzene
emissions: oil and gas wellheads, petroleum refineries, glycol dehydrators, gasoline
marketing, publicly owned treatment works (POTWs), landfills, pulp and paper
manufacturing, synthetic graphite manufacturing, carbon black manufacturing, rayon-based
carbon manufacturing, aluminum casting, asphalt roofing manufacturing, and use of consumer
products and building supplies.
For each of these categories, the following information is provided in the
sections below: (1) a description of the activity or process, (2) a brief characterization of the
national activity in the United States, (3) benzene emissions characteristics, and (4) control
technologies and techniques for reducing benzene emissions. In some cases, the current
Federal regulations applicable to the source category are discussed.
6.1 OIL AND GAS WELLHEADS
6.1.1 Description of Oil and Gas Wellheads
Oil and gas production (through wellheads) delivers a stream of oil and gas
mixture and leads to equipment leak emissions. Emissions from the oil and gas wellheads,
6-1
-------
including benzene, are primarily the result of equipment leaks from various components at the
wellheads (valves, flanges, connections, and open-ended lines). Component configurations for
wellheads can vary significantly.
Oil and gas well population data are tracked by State and Federal agencies,
private oil and gas consulting firms, and oil and gas trade associations. In 1989 a total of
262,483 gas wells and 310,046 oil wells were reported in the United States.115-116
Reference 117 presents a comprehensive review of information sources for oil and gas well
count data. The activity factor data are presented at four levels of resolution: (1) number of
wells by county, (2) number of wells by State, (3) number of fields by county, and (4) number
of fields by State.
6.1.2 Benzene Emissions from Oil and Gas Wellheads
Emissions from oil and gas wellheads can be estimated using the average
emission factor approach as indicated in the EPA Protocol for Equipment Leak Emission
Estimates.54 This approach allows the use of average emission factors hi combination with
wellheads-specific data. These data include: (1) number of each type of components (valves,
flanges, etc.), (2) the service type of each component (gas, condensate, mixture, etc.), (3) the
benzene concentration of the stream, and (4) the number of wells.
A main source of data for equipment leak hydrocarbon emission factors for oil
and gas field operations is an API study118 developed in 1980.
Average gas wellhead component count has been reported as consisting of
11 valves, 50 screwed connections, 1 flange, and 2 open-ended lines.119 No information was
found concerning average component counts for oil wellheads.
Benzene and total hydrocarbons equipment leak emission factors from oil
wellheads are presented in Table 6-1.120 These emission factors were developed from
6-2
-------
TABLE 6-1. BENZENE AND TOTAL HYDROCARBONS EQUIPMENT LEAK EMISSION FACTORS
FOR OIL WELLHEAD ASSEMBLIES2
Emission
SCC Number Description Emission Source levelb
3-10-001-01 Oil wellheads0 Equipment leaks 1
2
3
o\
4
5
Emission
Total Hydrocarbons
Ib/hr/wellhead
(kg/hr/wellhead)
3.67 x 10 2
(1.65xl02)
6.53 x 10 3
(2.97 x 103)
9.74 x 104
(4.43 x 104)
3.48 x 104
(1.58xl04)
1.06x10"
(4.82 x 10 5)
Factor
Benzene
Ib/hr/wellhead
(kg/hr/wellhead)
1.27xlO'7
(5.77 x 10 8)
3.9xlO'8
(1.77xlO-8)
6.25 x lO'9
(2.84 x 10'9)
NA
NA
Emission
Factor
Rating
D
D
D
D
D
Source: Reference 120.
' Over 450 accessible production wellhead assemblies were screened, and a total of 28 wellhead assemblies were selected for bagging. The oil production
facilities included in this study are located in California.
b The concentration ranges applicable to the 5 emission levels developed were as follows: level 1— > 10,000 ppm at two or more screening points or causing
instrument flameout; level 2-3,000 to 10,000 ppm; level 3--500 to 3,000 ppm; level 4--50 to 500 ppm; level 5-0 to 50 ppm.
c Field wellhead only. Does not include other field equipment (such as dehydrators, separators, inline heaters, treaters, etc.).
NA = Not available.
-------
screening and bagging data obtained in oil production facilities located in California.120 Over
450 accessible production wellhead assemblies were screened, and a total of 28 wellhead
assemblies were selected for bagging. For information about screening and bagging
procedures refer to Reference 54.
The composition of gas streams varies among production sites. Therefore,
when developing benzene emission estimates, the total hydrocarbons emission factors should
be modified by specific benzene weight percent, if available.
Benzene constituted from less than 0.1 up to 2.3 percent weight of total
non-methane hydrocarbons (TNMHC) for water flood wellhead samples from old crude oil
production sites in Oklahoma. Also, benzene constituted approximately 0.1 percent weight of
TNMHC for gas driven wellhead samples.121 The VOC composition in the gas stream from
old production sites is different than that from a new field. Also, the gas-to-oil ratio for old
production sites may be relatively low.121 The above type of situations should be analyzed
before using available emission factors.
6.2 GLYCOL DEHYDRATION UNITS
Glycol dehydrators used in the petroleum and natural gas industries have only
recently been discovered to be an important source of volatile organic compound (VOC)
emissions, including benzene, toluene, ethylbenzene, and xylene (BTEX). Natural gas is
typically dehydrated hi glycol dehydration units. The removal of water from natural gas may
take place in field production, treatment facilities, and in gas processing plants. Glycol
dehydration units hi field production service have smaller gas throughputs compared with units
in gas processing service. It has been estimated that between 30,000 and 40,000 glycol
dehydrating units are hi operation in the United States.122 In a survey conducted by the
Louisiana Department of Environmental Quality, triethylene glycol (TEG) dehydration units
accounted for approximately 95 percent of the total hi the United States, with ethylene glycol
(EG) and diethylene glycol (DEC) dehydration units accounting for approximately 5 percent.123
6-4
-------
Data on the population and characteristics of glycol dehydration units
nationwide is limited. Demographic data has been collected by Louisiana Department of
Environmental Quality, Texas Mid-Continent Oil and Gas Association and Gas Processors
Association, Air Quality Service of the Oklahoma Department of Health (assisted by the
Oklahoma Mid-Continent Oil and Gas Association), and Air Quality Division of the Wyoming
Department of Environmental Quality.124 Table 6-2 presents population data and
characteristics of glycol dehydration units currently available.124
6.2.1 Process Description for Glvcol Dehydration Units
The two basic unit operations occurring in a glycol dehydration unit are
absorption and distillation. Figure 6-1 presents a general flow diagram for a glycol
dehydration unit.125 The "wet" natural gas (Stream 1) enters the glycol dehydrator through an
inlet separator that removes produced water and liquid hydrocarbons. The gas flows into the
bottom of an absorber (Stream 2), where it comes in contact with the "lean" glycol (usually
triethylene glycol [TEG]). The water and some hydrocarbons in the gas are absorbed by the
glycol. The "dry" gas passes overhead from the absorber through a gas/glycol exchanger
(Stream 3), where it cools the incoming lean glycol. The gas may enter a knock-out drum
(Stream 4), where any residual glycol is removed. From there, the dry natural gas goes
downstream for further processing or enters the pipeline.
After absorbing water from the gas in the absorber, the "rich" glycol (Stream 5)
is preheated, usually in the still, and the pressure of the glycol is dropped before it enters a
three-phase separator (Stream 6). The reduction in pressure produces a flash gas stream from
the three-phase separator. Upon exiting the separator (Stream 7), the glycol is filtered to
remove particles. This particular configuration of preheat, flash, and filter steps may vary
from unit to unit. The rich glycol (Stream 8) then passes through a glycol/glycol exchanger
for further preheating before it enters the reboiler still.
6-5
-------
TABLE 6-2. GLYCOL DEHYDRATION UNIT POPULATION DATA
ON
Survey
Texas Mid-Continent Oil and Gas
Association (TMOGA) and Gas
Processors Association (GPA)
Survey*
Louisiana Department of
Environmental Quality (LDEQ)
Surveyb
Oklahoma Mid-Continent Oil and Gas
Association (OKMOGA) Survey0
Wyoming Department of
Environmental Survey*1
Service
Production
Gas Processing
Pipeline
Total
Ethylene Glycol
Triethylene Glycol
Total
Total
Total
Total
618
206
192
1016
12
191
203
1,333
1,221
No. of Units
Capacity
s 10 MMscfd
556
103
144
803
0
96
96
NR
1,185
Capacity
> 10 MMscfd
62
103
48
213
12
95
107
NR
36
Source: Reference 124.
* The survey only covers some companies; therefore it should not be considered a complete listing of units in Texas.
k The survey was only directed to units > 5 MMscfd; therefore it should not be considered a complete listing of units in Louisiana.
c The survey only covers dehydrator units for eight companies; therefore it should not be considered a complete listing of units in Oklahoma.
d The survey covered 50 companies owning and/or operating glycol units in Wyoming.
NR = Not reported.
-------
Dry Natural Gas
Knock-Out
Drum
Still Vent
Gatet
Vent, Fuel or
Stripping Gat
Natural Gas
Surge
Tank
Glycol/Glycol
Exchanger
o
o
Paniculate Filter
Figure 6-1. Flow Diagram for Glycol Dehydration Unit
Source: Reference 125.
-------
Then, the rich glycol enters the reboiler still (Stream 9) (operating at
atmospheric pressure), where the water and hydrocarbons are distilled (stripped) from the
glycol making it lean. The lean glycol is pumped back to absorber pressure and sent to the
gas/glycol exchanger (Stream 10) before entering the absorber to complete the loop.
6.2.2 Benzene Emissions from Glycol Dehydration Units
The primary source of VOC emissions, including BTEX, from glycol
dehydration units is the reboiler still vent stack (Vent A).
Because the boiling points of BTEX range from 176°F to 284°F (80 to 140°C),
they are not lost to any large extent in the flash tank but are separated from the glycol in the
still. These separations hi the still result in VOC emissions that contain significant quantities
of BTEX.126
Secondary sources of emissions from glycol dehydration units are the phase
separator vent (Vent B) and the reboiler burner exhaust stack (Vent C).
Most glycol units have a phase separator between the absorber and the still to
remove dissolved gases from the warm rich glycol and reduce VOC emissions from the still.
The gas produced from the phase separator can provide the fuel and/or stripping gas required
for the reboiler.
A large number of small glycol dehydration units use a gas-fired burner as the
heat source for the reboiler. The emissions from the burner exhaust stack are considered
minimal and are typical of natural gas combustion sources.
Reboiler still vent data have been collected by the Louisiana Department of
Environmental Quality,123 and the Ventura County (California) Air Pollution Control
District.127 Table 6-3 presents emission factors for both triethylene glycol (TEG) units and
6-8
-------
o\
TABLE 6-3. REACTIVE ORGANIC COMPOUNDS (ROCs)a AND BTEX EMISSION FACTORS FOR
GLYCOL DEHYDRATION UNITS
SCC Number
3-10-003-01
3-10-003-XX
SCC and
Description Emissions Source
Glycol Reboiler Still Vent
dehydration
units
TEG units
Glycol Reboiler Still Vent
dehydration
units
EG units
Control
Device
None
None
None
None
None
None
Emission Factor
34xl02 Ib/yr of ROC/MMscfdb
(54.46xl03 kg/yr of ROC/MMscmd)
18.6xl02 Ib/yr of BTEX/MMscfdb
(29.79xl03 kg/yr of BTEX/MMscmd)
32.4X102 Ib/yr of ROC/MMscfdc
(51 .90xl03 kg/yr of ROC/MMscmd)
54.0x10' Ib/yr of ROC/MMscfd"
(8.65xl03 kg/yr of ROC/MMscmd)
24x10' Ib/yr of BTEX/MMscfdb
(3.84xl03 kg/yr of BTEX/MMscmd)
74.0x10' Ib/yr of ROC/MMscfdc
(1 1 .85xl03 kg/yr of ROC/MMscmd)
Emission
Factor •
Rating
U
U
U
U
U
U
" ROC are defined as total non-methane and ethane hydrocarbons.
b Louisiana DEQ emission factor from glycol dehydration unit survey.
c Ventura County (California) Air Pollution Control District emission factor from one source test.
MMscfd = Million standard cubic feet per day.
MMscmd = Million standard cubic meter per day.
-------
ethylene glycol (EG) units based on the natural gas throughput of the gas treated. The
emission factors developed from the LDEQ study were based on responses from 41 companies
and 208 glycol dehydration units. The Ventura County, California, factors include testing
results at two locations (one for TEG and one for EG). The amount of produced gas treated is
thought to be the most important because it largely determines the size of the glycol system.127
However, the data base does not show a strong correlation because other variables with
countervailing influences were not constant.127 VOC and BTEX emissions from glycol units
vary depending upon the inlet feed composition (gas composition and water content) as well as
the configuration, size, and operating conditions of the glycol unit (i.e., glycol type, pump
type and circulation rate, gas and contactor temperatures, reboiler fire-cycles, and inlet
scrubber flash tank efficiencies).129
The speciation of Total BTEX for TEG units reported by the LDEQ hi then-
study indicated the following composition (% weight): benzene (35); toluene (36);
ethylbenzene (5), and xylene (24). For EG units, the following compositions were reported:
benzene (48); toluene (30); ethylbenzene (4); and xylene (17). Note that the BTEX
composition of natural gas may vary according to geographic areas. Limited information/data
on the BTEX composition is available.
Four methods for estimating emissions have been reported for glycol
dehydration units: (1) rich/lean glycol mass balance, (2) inlet/outlet gas mass balance,
(3) unconventional stack measurements (total-capture condensation, and partial stack
condensation/flow measurement), and (4) direct stack measurements (conventional stack
measurements, and novel stack composition/flow measurement).129
Sampling of the rich/lean glycol then estimating emissions using mass balance
has been the selected method for measuring emissions to date. The Louisiana Department of
Environmental Quality requested emission estimates using reboiler mass balances on the
rich/lean glycol samples.
6-10
-------
Based upon a set of studies conducted by Oryx Energy Co as part of a task force
for the Oklahoma-Kansas Midcontinent Oil & Gas Association, rich/lean glycol mass balance
is a highly convenient, cost effective method for estimating ah- emissions from glycol
dehydration units.129 The following conclusions were addressed hi reference 129 regarding this
method: (a) good estimates of BTEX can be obtained from rich/lean glycol mass balance,
(b) the rich/lean glycol mass balance BTEX estimates are in excellent agreement with total
capture condensation method, and (c) rich/lean glycol mass balance is a more reproducible
method for emission estimations than nonconventional stack methods. Note that conventional
stack methods cannot be used on the stacks of glycol dehydration units because they are too
narrow hi diameter and have low flow rates.
An industry working group consisting of representatives from the American
Petroleum Institute, Gas Processors Association, Texas-Midcontinent Oil & Gas Association,
Louisiana Mid-Continent Oil and Gas Association, and GRI is conducting field evaluation
experiments 10 determine appropriate and accurate sampling and analytical methods to calculate
glycol dehydration unit emissions.125 GRI has developed a computer tool, entitled
GRI-GLYCalc, for estimating emissions from glycol dehydrators. The U.S. EPA has
performed their own field study of GRI-GLYCalc and has recommended that it be included hi
EPA guidance for State/local agency use for development of emission inventories.130
Atmospheric rich/lean glycol sampling is being evaluated as a screening
technique in the above working group program. The goal is to compare these results to the
stack and other rich/lean results and determine if a correction factor can be applied to this
approach.125
A second screening technique under study is natural gas sampling and analysis
combined with the software program GRI-GLYCalc® to predict emissions. Table 6-4 shows
the inputs required of the user and also shows the outputs returned by GRI-GLYCalc®.132
6-11
-------
TABLE 6-4. GLYCOL DEHYDRATION EMISSION PROGRAM
INPUTS AND OUTPUTS
Inputs
Units
Gas Flow Rate
Gas Composition
Gas Pressure
Gas Temperature
Dry Gas Water Content"
Number of Equilibrium Stages8
Lean Glycol Circulation
Lean Glycol Composition
Flash Temperature0
Flash Pressure0
Gas-Driven Pump Volume Ratio'
MMscfd
Volume percent for CrC6 hydrocarbons and
BTEX compounds
psig
Ibs/MMscf
Dimensionless
gpm
Weight % H2O
°F
psig
acfrn gas/gpm glycol
Outputs
Units
BTEX Mass Emissions
Other VOC Emissions
Flash Gas Composition
Dry Gas Water Content"
Number of Equilibrium Stages6
Ibs/hr or Ib-moles/hr, Ibs/day, tpy, vol%
Ibs/hr or Ib-moles/hr, Ibs/day, tpy, vol%
Ibs/hr or Ib-moles/hr, Ibs/day, tpy, vol%
Ibs/MMscf
Dimensionless
Source: Reference 132.
' Specify one of these inputs.
b Dry Gas Water Content is an output if the Number of Equilibrium Stages is specified and vice versa.
c Optional
6-12
-------
6.2.3 Controls and Regulatory Analysis
Controls applicable to glycol dehydrator reboiler still vents include hydrocarbon
skimmers, condensation, flaring, and incineration. Hydrocarbon skimmers use a three-phase
separator to recover gas and hydrocarbons from the liquid glycol prior to its injection into the
reboiler. Condensation recovers hydrocarbons from the still vent emissions, whereas flaring
and incineration destroy the hydrocarbons present in the still vent emissions.
For glycol dehydrators it has been determined by the Air Quality Service,
Oklahoma State Department of Health that the Best Available Control Technology (BACT)
could include one or more of the following: (1) substitution of glycol, (2) definition of specific
operational parameters, such as the glycol circulation rate, reduction of contactor tower
temperature, or increasing temperature in the three-phase separator, (3) flaring/incineration,
(4) product/vapor recovery, (5) pressurized tanks, (6) carbon adsorption, or (7) change of
desiccant system.125
The Air Quality Division, Wyoming Department of Environmental Quality has
stated that facilities will more than likely be required to control emissions from glycol
dehydration units. The Division has determined and will accept the use of condensers in
conjunction with a vapor recovery system, incinerator, or a flare as representing BACT.133
Most gas processors have begun to modify existing glycol reboiler equipment to
reduce or eliminate VOC emissions. Some strategies and experiences from one natural gas
company are presented in Reference 124. For other control technologies refer to
Reference 134.
Glycol dehydration units are subject to the NSPS for VOC emissions from
equipment leaks for onshore natural gas processing plants promulgated in June 1985.135 The
NSPS provides requirements for repair schedules, recordkeeping, and reporting of equipment
leaks.
6-13
-------
The Clean Air Act Amendments (CAAA) of 1990 resulted in regulation of
glycol dehydration units. Title HI of the CAAA regulates the emissions of 188 hazardous air
pollutants (HAPs) from major sources and area sources. Title in has potentially wide-ranging
effects for glycol units. The BTEX compounds are included in the list of 188 HAPs and may
be emitted at levels that would cause many glycol units to be defined as major sources and
subject to Maximum Achievable Control Technology (MACT).125
Currently, the MACT standard for the oil and natural gas production source
category, which includes glycol dehydration units, is being developed under authority of
Section 112(d) of the 1990 CAAA and is scheduled for promulgation in May, 1999.
In addition to the federal regulations, many states have regulations affecting
glycol dehydration units. The State of Louisiana has already regulated still vents on large
glycol units, and its air toxics rule may affect many small units. Texas, Oklahoma, Wyoming,
and California are considering regulation of BTEX and other VOC emissions from dehydration
units.125
6.3 PETROLEUM REFINERY PROCESSES
6.3.1 Description of Petroleum Refineries
Crude oil contains small amounts of naturally occurring benzene. One estimate
indicates that crude oil consists of 0.15 percent benzene by volume.136 Therefore, some
processes and operations at petroleum refineries may emit benzene independent of specific
benzene recovery processes. Appendix B (Table B-l) lists the locations of petroleum refineries
in the U.S. As of January 1995, there were 173 operational petroleum refineries in the United
States, with a total crude capacity of 15.14 million barrels per calendar day.137-138 The majority
of refinery capacity is located in Texas, Louisiana, and California. Significant refinery
capacities are also found in the Chicago, Philadelphia, and Puget Sound areas. A flow diagram
6-14
-------
of processes likely to be found at a model refinery is shown in Figure 6-2. The arrangement
of these processes varies among refineries, and few, if any', employ all of these processes.
*
Processes at petroleum refineries can be grouped into five types: (1) separation
processes, (2) conversion processes, (3) treating processes, (4) auxiliary processes and
operation, and (5) feedstock/product storage and handling. These are discussed briefly below.
The first phase in petroleum refining operations is the separation of crude oil
into its major constituents using four separation processes: (1) desalting, (2) atmospheric
distillation, (3) vacuum distillation, and (4) light ends recovery.
To meet the demands for high-octane gasoline, jet fuel, and diesel fuel,
components such as residual oils, fuel oils, and light ends are converted to gasolines and other
light fractions using one or more of the following conversion processes: (1) catalytic cracking
(fluidized-bed and moving-bed), (2) thermal processes (coking, and visbreaking),
(3) alkylation, (4) polymerization, (5) isomerization, and (6) reforming.
Petroleum treating processes stabilize and upgrade petroleum products by
separating them from less desirable products. Among the treating processes are
(1) hydrotreating, (2) chemical sweetening, (3) deasphalting, and (4) asphalt blowing.
Auxiliary processes and operations include process heaters, compressor engines,
sulfur recovery units, blowdown systems, flares, cooling towers, and waste water treatment
facilities.
Finally, all refineries have a feedstock/product storage area (commonly called a
"tank farm") with storage tanks whose capacities range from less than 1,000 barrels to more
than 500,000 barrels. Also, feedstock/product handling operations (transfer operations) consist
of the loading and unloading of transport vehicles (including trucks, rail cars, and marine
vessels).
6-15
-------
Fual Oat and LPO
O\
t—*
O\
(A)
Cfuda
Oil
LPQ and
Qat
Naphtha
Naphtha
1
Middle Dfctltates
©.
Catalytic
Reforming
Heavy Aim. Oaa
Catalytic
Cracking
Tal Qat
Traatlng
Sulfur ^
BTX
r
Aromatic*
Extraction
Ratormate
Hydro-
Irattlng
Oaiolna
Cycle On OHs
To
Hydrolraateri
H*
1
CLXJv H
* If
1
ydro-
latlng
Alkylatlon
Aftyhla
OatoHna. Naphtha, MIddIa DlatHatas
Qatollna
SolvtnU
Aviation Fuaat
Dtoaals
Haatlng Qua
. ^^
Aromatlcs
Patrochamlcil
Faadttock*
Atphalta
Induitrlal Fuala
Itaflnary Fual Ol
Cokl
Note Ltttart correspond to potential source* of benzene emissions, listed In Table 8-5.
Wastawatar Treatment
J®
-(U)
Figure 6-2. Process Flow Diagram for a Model Petroleum Refinery
Source: Reference 139.
-------
For a complete description of the various processes and operations at petroleum
refineries refer to References 139, 140, and 141.
6.3.2 Benzene Emissions from Petroleum Refinery Processes and Operations
Benzene emissions, as well as Hazardous Air Pollutant (HAPs) emissions from
petroleum refineries can be grouped into five main categories: (1) process vents, (2) storage
tanks, (3) equipment leaks, (4) transfer operations, and (5) wastewater collection and
treatment. Table 6-5 presents a list of specific processes and operations which are potential
sources of benzene emissions at petroleum refineries emitted from one or more of the above
no
categories.
Also, process heaters and boilers located at the different process units across a
refinery emit flue gases containing benzene, and other HAPs. The HAPs emitted result either
from incomplete combustion of fuel gas or from the combustion products.
According to the Information Collection Request (ICR) and Section 114 survey
submitted to EPA by U.S. refiners as part of the Petroleum Refinery NESHAP study, benzene
emissions from process vents were reported for the following process units within a refinery:
(1) thermal cracking (coking), (2) Methyl Ethyl Ketone (MEK) dewaxing, and
(3) miscellaneous vents at crude distillation units, catalytic reforming units,
hydrotreating/hydrorefining, asphalt plants, vacuum distillation towers, and full-range
distillation units (light ends, naphtha, solvent, etc.). Also, benzene emissions were reported
from blowdown and flue gas system vents.
The Section 114 and ICR questionnaire responses also provided estimates of
benzene concentrations in refinery processes, and in petroleum refinery products. Table 6-6
summarizes concentrations of benzene for gas, light liquid, and heavy liquid streams at some
refinery process units.142 Table 6-7 summarizes concentrations of benzene in common refinery
products.143'144
6-17
-------
TABLE 6-5. POTENTIAL SOURCES OF BENZENE EMISSIONS AT
PETROLEUM REFINERIES
A Crude Storage
B Desalting
C Atmospheric distillation (crude unit)
D Vacuum distillation
E Naphtha hydrodesulfurization
F Catalytic reforming
G Light hydrocarbon storage and blending
H Kerosene hydrodesulfurization
I Gas oil hydrodesulfurization
J Fluid bed catalytic cracking
K Moving bed catalytic cracking
L Catalytic hydrocracking
M Middle distillate storage and blending
N Lube oil hydrodesulfurization
O Deasphalting
P Residual oil hydrodesulfurization
Q Visbreaking
R Coking
S Lube oil processing
T Asphalt blowing
U Heavy hydrocarbon storage and blending
V Wastewater collection and treatment units
Source: Reference 139.
6-18
-------
TABLE 6-6. CONCENTRATION OF BENZENE IN REFINERY PROCESS UNIT
STREAMS (WEIGHT PERCENT)
Stream Type
Process Unit
Crude
Alkylation (sulfuric acid)
Catalytic Reforming
Hydrocracking
Hydrotreating/hydrorefining
Catalytic Cracking
Thermal Cracking (visbreaking)
Thermal Cracking (coking)
Product Blending
Full-Range Distillation
Vacuum Distillation
Isomerization
Polymerization
MEK Dewaxing
Other Lube Oil Processing
Gas
1.3
0.1
2.93
0.78
1.34
0.39
0.77
0.24
1.20
0.83
0.72
2.49
0.10
0.36
1.20
Light Liquid
1.21
0.23
2.87
1.09
1.38
0.71
1.45
0.85
1.43
1.33
0.15 .
2.49
0.10
NR
1.20
Heavy Liquid
0.67
0.23
1.67
0.10
0.37
0.20
1.45
0.18
2.15
1.08
0.22
0.62
0.10
NR
0.10
Source: Reference 142.
NR means not reported
6-19
-------
TABLE 6-7. CONCENTRATION OF BENZENE IN REFINERY PRODUCTS
Material Weight Percent in Liquid
Asphalt . 0.03
Aviation Gasoline 0-51
Alkylale 0.12
Crude Oil 0.45.
Diesel/Distillate 0.008
Gasoline (all blends) 0.90
Heavy Gas Oil 0.0002
Jet Fuel 1.05
Jet Kerosene 0.004
Naphtha 1.24
Reformates 4.61
Residual Fuel Oil 0.001
Recovered Oil 0.95
Source: References 143, 144 and 158.
6-20
-------
Storage tanks at petroleum refineries containing petroleum liquids are potential
sources for benzene emissions. VOC emissions from storage tanks, including fixed-roof,
external floating-roof, and internal floating-roof types, can be estimated using Compilation of
Air Pollutant Emission Factors (AP-42), Chapter 733 and the TANKS model. Emissions of
benzene from storage vessels may be estimated by applying the benzene concentrations in
Table 6-7 to the equations in AP-42 which are also used in TANKS.
Equipment leak emissions from refineries occur from process equipment
components such as valves, pump seals, compressor seals, pressure relief valves, connectors,
open-ended lines, and sampling connections. Non-methane VOC emissions are calculated
using emission factors (in Ib/hr/component) and emission equations developed by the EPA in
the Protocol for Equipment Leak Emission Estimates.54 The number of components at a
refinery are specific to a refinery. However, model equipment counts were developed for the
petroleum refinery NESHAP for refineries with crude charge capacities less than
50,000 barrels/stream day (bbl/sd) and greater than or equal to 50,000 bbl/sd. These counts
are presented in Tables 6-8 and 6-9.142 Benzene emissions from equipment leaks may be
estimated by multiplying the equipment counts, the equipment leak factor, and the benzene
concentration in the process from Table 6-6. It is generally assumed that the speciation of
compounds inside a process line are equal to the compounds leaking.
The Western States Petroleum Association (WSPA) and the American Petroleum
Institute (API) commissioned the development of a 1993 refinery equipment leak study145 to
develop new emission factors and correlation equations.139 The data from the 1993 study has
been combined with data from a 1993 marketing terminal equipment leak study.146
For information on emission factors and equations for loading and transport
operations, refer to Section 6.4 (Gasoline Marketing) of this document.
6-21
-------
TABLE 6-8. MEDIAN COMPONENT COUNTS FOR PROCESS UNITS FROM SMALL REFINERIES"
Process Unit
Crude Distillation
Alkylation (sulfuric acid)
Alkylation (HP)
Catalytic Reforming
Hydrocracking
Hydrotreating/hydrorefining
Catalytic Cracking
Thermal Cracking
(visbreaking)
9s Thermal Cracking (coking)
1° Hydrogen Plant
Asphalt Plant
Product Blending
Sulfur Plant
Vacuum Distillation
Full-Range Distillation
Isomerization
Polymerization
MEK Dewaxing
Other Lube Oil Processes
Gas
75
278
102
138
300
100
186
206
148
168
120
67
58
54
157
270
224
145
153
Valves
Light
Liquid
251
582
402
234
375
208
375
197
174
41
334
205
96
26
313
352
563
1208
242
Pumps
Heavy
Liquid
2K)
34
62
293
3M
218
450
0
277
0
250
202
127
84
118
M
15
2(K)
201
Light
Liquid
8
18
13
8
12
5
13
7
9
3
5
6
6
6
7
9
12
35
7
Heavy
Liquid
8
10
3
5
9
5
14
0
8
0
8
11
6
6
4
2
0
39
5
Compressors
2
1
2
3
2
2
2
0
2
2
2
1
3
2
2
2
1
3
2
Pressure Relief Valves
Gas
6
12
12
5
9
5
8
4
7
4
5
10
3
2
5
7
10
10
5
Light
Liquid
6
15
13
3
4
3
8
0
16
2
10
6
88
5
4
10
5
14
5
Heavy
' Liquid
5
4
0
3
4
5
7
0
13
0
9
22
15
2
6
1
3
4
5
Gas
164
705
300
345
1038
290
490
515
260
304
187
230
165
105
171
432
150
452
167
Flanges
Light
Liquid
555
1296
1200
566
892
456
943
405
322
78
476
398
240
121
481
971
450
1486
307
Heavy
Liquid
454
785
468
732
623
538
938
0
459
0
900
341
345
230
210
243
27
2645
249
Open-
ended
Lines
39
20
26
27
25
20
8
0
13
8
16
33
50
16
20
7
5
19
60
Sampling
Connections
10
16
8
6
10
6
8
4
8
4
6
14
3 •
4
6
8
7
17
6
Source: Reference 142.
* Refineries with crude charge capacities less than 50,000 bbl/sd.
-------
TABLE 6-9. MEDIAN COMPONENT COUNTS FOR PROCESS UNITS FROM LARGE REFINERIES'
Process Unit
Crude Distillation
Alkylation (sulfuric acid)
Alkylation (HF)
Catalytic Reforming
Hydrocracking
Hydrotreating/hydrorefining
Catalytic Cracking
Thermal Cracking
(visbreaking)
9s Thermal Cracking (coking)
NJ
00 Hydrogen Plant
Asphalt Plant
Product Blending
Sulfur Plant
Vacuum Distillation
Full-Range Distillation
Isomerization
Polymerization
MEK Dewaxing
Other Lube Oil Processes
Gas
204
192
104
310
290
224
277
no
190
301
76
75
100
229
160
164
129
419
109
Valves
Light
Liquid
440
597
624
383
651
253
282
246
309
58
43
419
125
108
561
300
351
1075
188
Pumps
He ivy
Liquid
49R
0
12R
84
308
200
445
130
250
0
0
186
110
447
7^
7K
82
130
375
Light
Liquid
15
21
13
12
22
7
12
7
12
7
4
10
8
2
14
9
6
29
5
Heavy
Liquid
14
0
8
2
12
6
12
6
11
360
0
10
3
12
2
5
2
10
16
Compressors
2
2
1
3
2
2
2
1
1
3
0
2
1
1
2
2
0
4
3
Pressure Relief Valves
Gas
7
13
9
8
10
9
11
6
8
4
3
9
4
5
7
15
7
33
8
Light
Liquid
5
4
11
11
12
4
9
3
5
139
7
16
4
1
8
5
12
6
6
.Heavy
Liquid
12
0
1
0
0
8
13
15
10
0
0
6
4
4
2
2
28
18
20
Gas
549
491
330
653
418
439
593
277
627
162
90
227
280
473
562
300
404
1676
180
Flanges
Light
Liquid
982
1328
1300
842
1361
581
747
563
748
148
90
664
460
136
1386
540
575
3870
187
Heavy
Liquid
1046
600
180
132
507
481
890
468
791
0
0
473
179
1072
288
265
170
468
1260
Open-
ended
Lines
75
35
40
48
329
49
59
30
100
59
24
24
22
0
54
36
17
0
18
Sampling
Connections
9
6
14
9
28
8
15
7
10
21
24
8
7
7
6
7
9
7
9
Source: Reference 142.
• Refineries with crude charge capacities greater than 50,000 bbl/sd.
-------
Air emissions from petroleum refinery wastewater collection and treatment are
one of the largest sources of VOC emissions at a refinery and are dependent on variables
including wastewater throughput, type of pollutants, pollutant concentrations, and the amount
of contact wastewater has with the air.
Table 6-10 presents model process unit characteristics for petroleum refinery
wastewater.147 The table includes average flow factors, average volatile HAP concentrations,
and average benzene concentrations by process unit type to estimate uncontrolled emissions
from petroleum refinery wastewater streams. Flow factors were derived from Section 114
questionnaire responses compiled for the Refinery NESHAP study. Volatile HAP and
benzene concentrations were derived from Section 114 questionnaire responses, 90-day
Benzene Waste Operations NESHAP (BWON) reports, and equilibrium calculations.
Uncontrolled wastewater emissions for petroleum refinery process units can be
estimated multiplying the average flow factor, the volatile HAP concentrations, and the
fraction emitted presented in Table 6-10, for each specific refinery process unit capacity.
Wastewater emission factors for oil/water separators, air flotation systems, and
sludge dewatering units are presented in Table 6-11.148"151
Another option for estimating emissions of organic compounds from wastewater
treatment systems is to use the air emission model presented in the EPA document Compilation
of Air Pollutant Emission Factors (AP-42), hi Section 4.3, entitled "Wastewater Collection,
Treatment, and Storage. "M This emission model (referred to as SIMS hi AP-42 and now
superceded by Water 8) is based on mass transfer correlations and can predict the emissions of
individual organic species from a wastewater treatment system.
6-24
-------
TABLE 6-10. MODEL PROCESS UNIT CHARACTERISTICS
FOR PFTROLEUM REFINFRY WASTE WATER
Process Unit
Crude distillation
Alkylation unit
Catalytic reforming
Hydrocracking unit
Hydrotreating/
hydrorefming
o\ Catalytic cracking
N>
Thermal cracking/
coking
Thermal cracking/
visbreaking
Hydrogen plant
Asphalt plant
Product blending
Sulfur plant
Vacuum distillation
Full range distillation
Isomerization
Average How factoi
(gal/bbl)c
2.9
6.0
1.5
2.6
2.6
2.4
5.9
7.1
80g
8.6
2.9
9.7h
3.0
4.5
1.5
Average Ben/.ene
h Concentration3
r
Value (ppmw)d
21
3
106
14
6.3
13
40
40
62
40
24
0.8
12
12
33
Origin6
114
Eq.
Eq.
114
114
114
Eq.
Eq.
90-day
Eq,
114
90-day
90-day
114
Eq.
Average Volatile HAP
Concentration"
Value (ppmw)d
140
6.9
238
72
32
165
75
75
278
75
1,810
3.4
53
65
117
Origine
114
Eq-
Eq-
114
114
114
Eq-
Eq.
Ratio
Eq-
114
Ratio
Ratio
114
Eq.
Fraction
Emitted'
0.85
0.85
0.85
0.85
0.85
0.85
0.85
0.85
0.85
0.85
0.85
0.85
0.85
0.85
0.85
(continued)
-------
TABLE 6-10. CONTINUED
Average flow factor
Process Unit (gal/hbl)c
Polymerization
MEK dewaxing units
Lube oil/specialty
processing unit
Tank drawdown
3.5
0.011
2.5
0.02
Average Benzene
h Concentration3
Value (ppmw)d
0.01
0.1
40
188
Origin6
90-day
90-day
Eq.
90-day
Average Volatile HAP
Concentration"
Value (ppmw)d
0.04
27
75
840
Origin6
Ratio
114
Eq.
Ratio
Fraction
Emittedf
0.85
0.49
0.85
0.85
Source: Reference 147.
1 Average concentration in the wastewater.
b All flow factors were derived from Section 114 questionnaire responses.
c gal/bbl = gallons of wastewater per barrel of capacity at a given process unit.
d ppmw = parts per million by weight.
e 114 = Section 114 questionnaire response; 90-day = 90-day BWON report; Eq. = Equilibrium calculation; and Ratio = HAP-to-benzene ratio (4.48).
1 These factors are given in units of pounds of HAP emitted/pound of HAP mass loading.
' Tliis flow factor is given in units of gallons/million cubic feet of gas production.
b This flow factor is given in units of gallons/ton of sulfur.
-------
TABLE 6-11. WASTEWATER EMISSION FACTORS FOR PETROLEUM REFINERIES
o\
SCC Number
3-06-005-08
3-06-005-XX
3-06-005-XX
Description
Oil/Water
Separators
Air Flotation
Systems
Sludge
dewatering units
Control
Emissions Source Device Emission Factor
Oil/water separator Uncontrolled 1 . 3 Ib of Benzene/106 gal of feed water
(0. 16 kg of Benzene/106 1 of feed water)
923 Ib of TOC/106 gal of feed water
(1 1 1 kg of TOC/106 1 of feed water)
Air flotation systems' Uncontrolled 4 Ib of Benzene/106 gal of feed water
(0.48 kg of Benzene/106 1 of feed water)
30 Ib of TOC/106 gal of feed water
(3.60 kg of TOC/106 1 of feed water)
Sludge dewatering Uncontrolled 660 Ib of TOC/106 Ib sludge
unit" (660 kg of TOC/10* kg sludge)
Factor
Rating
E
C
E
B
C
Reference
148
149
150
149
151
' Includes dissolved air flotation (DAF) or induced air flotation (IAF) systems.
b Based on a 2.2 meter belt filter press dewatering oil/water separator bottoms, DAF float, and biological sludges at an average temperature of 125°F. '"
-------
6.3.3 Controls and Regulatory Analysis
This section presents information on controls for process vents at petroleum
refineries, and identifies other sections in this document that .may be consulted to obtain
information on control technology for storage tanks, and equipment leaks. Applicable Federal
regulations to process vents, storage tanks, equipment leaks, transfer operations, and
wastewater emissions are briefly described.
According to the EPA ICR and Section 114 surveys, the most reported types of
control for catalyst regeneration process vents at fluid catalytic cracking units were
electrostatic precipitators, carbon monoxide (CO) boilers, cyclones, and scrubbers. Some
refineries have reported controlling their emissions with scrubbers at catalytic reformer
regeneration vents.
For miscellaneous process vents, including miscellaneous equipment in various
process units throughout the refinery, the most reported controls were flares, incinerators,
and/or boilers. Other controls for miscellaneous process vents reported by refineries include
scrubbers, electrostatic precipitators, fabric filters, and cyclones.
The process vent provisions included in the Petroleum Refinery NESHAP
promulgated on September 18, 1995 affect organic HAP emissions from miscellaneous process
vents throughout a refinery.49 These vents include but are not limited to vent streams from
caustic wash accumulators, distillation condensers/accumulators, flash/knock-out drums,
reactor vessels, scrubber overheads, stripper overheads, vacuum (steam) ejectors, wash tower
overheads, water wash accumulators, and blowdown condensers/accumulators.
For information about controls for storage tanks refer to Section 4.5.3 - Storage
Tank Emissions, Controls, and Regulations.
6-28
-------
Storage tanks containing petroleum liquids and benzene are regulated by the
following Federal rules:
1. "National Emission Standard for Benzene Emissions from Benzene
Vessels;"61
2. "Standards of Performance for Volatile Organic Liquid Storage Vessels
(Including Petroleum Liquid Storage Vessels) for which Construction,
Reconstruction, or Modification Commenced after July 23, 1984;"62 and
3. "National Emission Standards for Hazardous Air Pollutants: Petroleum
Refineries."49
The Petroleum Refinery NESHAP requires that liquids containing greater than
4 weight percent HAPs at existing storage vessels, and greater than 2 weight percent HAPs at
new storage vessels be controlled.
There are two primary control techniques for reducing equipment leak
emissions: (1) modification or replacement of existing equipment, and (2).implementation of a
Leak Detection and Repair (LDAR) program.
Equipment leak emissions are regulated by the New Source Performance
Standards (NSPS) for Equipment Leaks of VOC hi Petroleum Refineries promulgated in
May 30, 1984.152 These standards apply to VOC emissions at affected facilities that
commenced construction, modification, or reconstruction after January 4, 1983.
The standards regulate compressors, valves, pumps, pressure relief devices,
sampling connection systems, open-ended valves or lines, and flanges or other connectors hi
VOC service.
The Benzene Equipment Leaks National Emission Standard for Hazardous Air
Pollutants (NESHAP)56 and the Equipment Leaks NESHAP57 for fugitive emission sources
regulate equipment leak emissions from pumps, compressors, pressure relief devices, sampling
connecting systems, open-ended valves or lines, valves, flanges and other connectors, product
6-29
-------
accumulator vessels, and specific control devices or systems at petroleum refineries. These
NESHAPs were both promulgated in June 6, 1984.
Equipment leak provisions included in the Petroleum Refinery NESHAP require
equipment leak emissions to be controlled using the control requirements of the petroleum
refinery equipment leaks NSPS or the hazardous organic NESHAP.
Any process unit that has no equipment in benzene service is exempt from the
equipment leak requirements of the benzene waste NESHAP. "In benzene service" means that
a piece of equipment either contains or contacts a fluid (liquid or gas) that is at least 10 percent
benzene by weight (as determined according to respective provisions). Any process unit that
has no equipment in organic HAP service is exempt from the equipment leak requirements of
the petroleum refinery NESHAP. "In organic HAP service" means that a piece of equipment
contains or contacts a fluid that is at least 5 percent benzene by weight.
Refer to Section 6.4 (Gasoline Marketing) of this L&E document for
information on control technologies and regulations for loading and transport operations.
For information about controls for wastewater collection and treatment systems,
refer to Section 4.5.4 - Wastewater Collection and Treatment System Emissions, Controls, and
Regulation.
Petroleum refinery wastewater streams containing benzene are regulated by the
following Federal rules:
1. "National Emission Standard for Benzene Waste Operations;"66
2. "New Source Performance Standard for Volatile Organic Compound
Emissions from Petroleum Refinery Wastewater Systems;"153 and
3. "National Emission Standards for Hazardous Air Pollutants: Petroleum
Refineries."49
6-30
-------
The wastewater provisions in the Petroleum Refinery NESHAP are the same as
the Benzene Waste Operations NESHAP.
6-4 GASOLINE MARKETING
Gasoline storage and distribution activities represent potential sources of
benzene emissions. The benzene content of gasoline ranges from less than 1 to almost
5 percent by liquid volume, but typical liquid concentrations are currently around 0.9 percent
by weight.158 Under Title II of the Clean Air Act as amended in 1990, the benzene content of
reformulated gasoline (RFG) will be limited to 1 percent volume maximum (or 0.95 percent
volume period average) with a 1.3 percent volume absolute maximum. In California, the
"Phase 2 Reformulated Gasoline," which will be required starting March 1998, also has a
1 percent volume benzene limit (or 0.8 percent volume average) with an absolute maximum of
1.2 percent volume.20 For this reason, it is expected that the overall average of benzene
content in gasoline will decrease over the next few years. Total hydrocarbon emissions from
storage tanks, material transfer, and vehicle fueling do include emissions of benzene. This
section describes sources of benzene emissions from gasoline transportation and marketing
operations. Because the sources of these emissions are so widespread, individual locations are
not identified in this section. Instead, emission factors are presented, along with a general
discussion of the sources of these emissions.
The flow of the gasoline marketing system in the United States is presented in
Figure 6-3."3 The gasoline distribution network includes storage tanks, tanker ships and
barges, tank trucks and railcars, pipelines, bulk terminals, bulk plants, and service stations.
From refineries, gasoline is delivered to bulk terminals by way of pipelines, tanker ships, or
barges. Bulk terminals may also receive petroleum products from other terminals. From bulk
terminals, petroleum products (including gasoline) are distributed by tank trucks to bulk plants.
Both bulk terminals and bulk plants deliver gasoline to private, commercial, and retail
customers. Daily product at a terminal averages about 250,000 gallons (950,000 liters), hi
contrast to about 5,000 gallons (19,000 liters) for an average size bulk plant.154
6-31
-------
Ship, Rail, Barge
Service Stations
Refinery Storage
I
Bulk Terminals
Tank Trucks
Automobiles, Trucks
Pipeline
Bulk Plants
Trucks
Commercial,
Rural Users
Figure 6-3. The Gasoline Marketing Distribution System in the United States
Source: Reference 153.
6-32
-------
Service stations receive gasoline by tank truck from terminals or bulk plants or
directly from refineries, and usually store the gasoline in underground storage tanks. Gasoline
service stations are establishments primarily selling gasoline and automotive lubricants.
Gasoline is by far the largest volume of petroleum product marketed in the
United States, with a nationwide consumption of 115 billion gallons (434 billion liters) in
1993.155 There are presently an estimated 1,300 bulk terminals storing gasoline in the
United States.156 About half of these terminals receive products from refineries by pipeline
(pipeline breakout stations), and half receive products by ship or barge delivery (bulk gas-line
terminals). Most of the terminals (66 percent) are located along the east coast and in the
Midwest. The remainder are dispersed throughout the country, with locations largely
determined by population patterns.
The benzene emission factors presented in the following discussions were
derived by multiplying AP-42 VOC emission factors for transportation and marketing157 times
the fraction of benzene in the vapors emitted. The average weight fraction of benzene hi
gasoline vapors (0.009) was taken from Reference 157. When developing emission estimates,
the gasoline vapor emission factors should be modified by specific benzene weight fraction in
the vapor, if available. Also a distinction should be made between winter and summer blends
of gasoline (a difference in the Reid vapor pressure of the gasoline, which varies from an
average of 12.8 psi in the winter to an average of 9.3 in non-winter seasons) to account for the
different benzene fractions present in both.158
The transport of gasoline with marine vessels, distribution at bulk plants, and
distribution at service stations, then* associated benzene emissions, and their controls are
discussed below.
6-33
-------
6.4.1 Benzene Emissions from Loading Marine Vessels
Benzene can be emitted while crude oil and refinery products (gasoline,
distillate oil, etc.) are loaded and transported by marine tankers and barges. Loading losses
are the primary source of evaporative emissions from marine vessel operations.159 These
emissions occur as vapors in "empty" cargo tanks are expelled into the atmosphere as liquid is
added to the cargo tank. The vapors may be composed of residual material left in the "empty"
cargo tank and/or the material being added to the tank. Therefore, the exact composition of
the vapors emitted during the loading process may be difficult to predict.
Benzene emissions from tanker ballasting also occur as a result of vapor
displacement.. Ballasting emissions occur as the ballast water enters the cargo tanks and
displace vapors remaining in the tank from the previous cargo. In addition to loading and
ballasting losses, transit losses occur while the cargo is in transit.157-160
Volatile organic compound (VOC) emission factors for petroleum liquids for
marine vessel loading are provided in the EPA document Compilation of Air Pollutant
Emission Factors (AP-42), Chapter 5157 and the EPA document VOC/HAP Emissions from
Marine Vessel Loading Operations - Technical Support Document for Proposed Standards™
Uncontrolled VOC and benzene emission factors for loading gasoline in marine
vessels are presented in Table 6-12. This table also presents emission factors for tanker
ballasting losses and transit losses from gasoline marine vessels.
Table 6-13 presents total organic compound emission factors for marine vessels
including loading operations, and transit for crude oil, distillate oil, and other fuels. Emissions
of benzene associated with loading distillate fuel and other fuels are very low, due primarily to
their low VOC emission factor and benzene content. When developing benzene emission
estimates, the total organic compound emission factors presented in Table 6-13 should be
multiplied by specific benzene weight fraction in the fuel vapor, if available.
6-34
-------
OJ
Lfl
TABLE 6-12. UNCONTROLLED VOLATILE ORGANIC COMPOUND AND BENZENE EMISSION FACTORS FOR
LOADING, BALLASTING, AND TRANSIT LOSSES FROM MARINE VESSELS
SCC Number
4-06-002-36/
4-06-002-37
4-06-002-034/
4-06-002-035
4-06-002-36
4-06-002-31/
4-06-002-32/
4-06-002-36
4-06-002-00/
4-06-002-40
4-06-002-38
4-06-002-33
4-06-002-39
4-06-002-42
Emission Source
Ship/Ocean Barge0 Loading Operations - Uncleaned,
volatile previous cargo
Ship/Ocean Barge0 Loading Operations - Ballasted;
volatile previous cargo
Ship/Ocean Bargec Loading Operations - Cleaned;
volatile previous cargo
Ship/Ocean Barge0 Loading Operations - Any
condition; nonvolatile previous cargo
Ship/Ocean Barge0 Loading Operations - Typical
situation, any cargo
Barge0 Loading Operations - Uncleaned; volatile
previous cargo
Barge0 Loading Operations - Gas-free, any cargo
Tanker Ballasting
Transit
VOC Emission Factor1
lb/10(K) gal Transferred
(mg/liter Transferred)
2.6(315)
1.7(205)
1.5(180)
0.7 (85)
1.8(215)
3.9 (465)
2.0 (245)
0.8 (100)
2.7 (320)"
Benzene Emission Factor6
lb/ 101)0 gal Transferred
(mg/liter Transferred)
0.023 (2.8)
0.015(1.8)
0.014(1.6)
0.006 (0.77)
0.016(1.9)
0.035 (4.2)
0.018 (2.2)
0.007 (0.9)
0.024 (2.8)d
Emission
Factor Rating
D
D
D
D
D
D
D
D
D
Source: References 157 and 159.
• Factors are for nonmethane-nonethane VOC emissions.
b Based on the average weight percent of benzene/VOC ratio of 0.009.IM
c Ocean barge is a vessel with compartment depth of 40 feet; barge is a vessel with compartment depth of 10-12 feet.
" Units for this factor are lb/week-1000 gal (mg/week-liter) transported.
-------
o\
UJ
ON
TABLE 6-13. UNCONTROLLED TOTAL ORGANIC COMPOUND EMISSION FACTORS
FOR PETROLEUM MARINE VESSEL SOURCES3
Emission source
Loading operations
Ships/ocean barge
Barge
Transit0
Crude Oil"
lb/103 gal (mg/f>
0.61
(73)
1.0
(120)
1.3
(150)
Jet Naphtha"
lb/103 gal (mg/0
0.50
(60)
1.2
(150)
0.7
(84)
Jet Kerosene
lb/103 gal (mg/f)
0.005
(0.63)
0.013
(1.60)
0.005
(0.60)
Distillate Oil No. 2
lb/10' gal (mg/f)
0.005
(0.55)
0.012
(1.40)
0.005
(0.54)
Residual Oil No. 6
lb/103 gal (mg/f)
0.00004
(0.004)
0.00009
(0.011)
3xlO'J
(0.003)
Emission Factor
Rating
D
D
E
Source: Reference 157.
1 Emission factors are calculated for a dispensed product temperature of 60° F.
b Nonmethane-nonethane VOC emission factors for a typical crude oil are 15 percent lower than the total organic factors shown. The example crude oil has a
Reid Vapor Pressure of 5 psia.
' Units are mg/week-J transferred or lb/week 10 3gal transferred.
-------
6.4.2 Ren7.ene Emissions from Bulk Gasoline Plants and Bulk Gasoline Terminals
* Each operation in which gasoline is transferred or stored is a potential source of
benzene emissions. At bulk terminals and bulk plants, loading, unloading, and storing
gasoline are sources of benzene emissions.
4.
Emissions from Gasoline Loading and Unloading
The gasoline that is stored in above ground tanks at bulk terminals and bulk
plants is pumped through loading racks that measure the amount of product. The loading racks
consist of pumps, meters, and piping to transfer the gasoline or other liquid petroleum
products. Loading of gasoline into tank trucks can be accomplished by one of three methods:
splash, top submerged, or bottom loading. Bulk plants and terminals use the same three
methods for loading gasoline into tank trucks. In splash loading, gasoline is introduced into
the tank truck directly through a hatch located on the top of the truck.160 Top submerged
loading is done by attaching a downspout to the fill pipe so that gasoline is added to the tank
truck near the bottom of the tank. Bottom loading is the loading of product into the truck tank
from the bottom. Emissions occur when the product being loaded displaces vapors in the tank
being filled. Top submerged loading and bottom loading reduce the amount of material
(including benzene) that is emitted by generating fewer additional vapors during the loading
process.160 A majority of facilities loading tank trucks use bottom loading.
Table 6-14 lists emission factors for gasoline vapor and benzene from gasoline
loading racks at bulk terminals and bulk plants.160 The gasoline vapor emission factors were
taken from Reference 157. The benzene factors were obtained by multiplying the gasoline
vapor factor by the average benzene content of the vapor (0.009 percent).158
6-37
-------
TABLE 6-14. BBNZENE EMISSION FACTORS FOR GASOLINE LOADING RACKS
AT BULK TERMINALS AND BULK PLANTS
SCC Number
Loading Method
Gasoline Vapor Emission
Factor" Benzene Emission Factor1" Emission
lb/1000 gal (mg/liter) lb/1000 gal (mg/liter) Factor Rating
4-04-002-50
4-04-002-50
4-04-002-50
Splash loading - normal service
Submerged loading0 - normal service
Balance service*1
11.9(1430)
4.9 (590)
0.3 (40)
0.11 (12.9)
0.044 (5.3)
0.004 (0.36)
D
D
D
Source: Reference 160.
1 Gasoline factors represent emissions of nonmethane-nonethane VOC. Factors are expressed as mg gasoline vapor per liter gasoline transferred.
^ " Based on an average benzene/VOC ratio of 0.009. l57
to c Submerged loading is either top or bottom submerged.
00 d Splash and submerged loading. Calculated using a Stage I control efficiency of 95 percent.
156
-------
Emissions from Storage Tanks
Storage emissions of benzene at bulk terminals and bulk plants depend on the
type of storage tank used. A typical bulk terminal may have four or five above ground storage
tanks with capacities ranging from 400,000 to 4 million gallons (1,500 to 15,000 m3).160 Most
tanks in gasoline service are of an external floating roof design. Fixed-roof tanks, still used in
some areas to store gasoline, use pressure-vacuum vents to operate at a slight internal pressure
or vacuum and control breathing losses. Some tanks may use vapor balancing or processing
equipment to control working losses.
The major types of emissions from fixed-roof tanks are breathing and working
losses. Breathing loss is the expulsion of vapor from a tank vapor space that has expanded or
contracted because of daily changes hi temperature and barometric pressure. The emissions
occur in the absence of any liquid level change in the tank. Combined filling and emptying
losses are called "working losses." Emptying losses occur when the air that is drawn into the
tank during liquid removal saturates with hydrocarbon vapor and is expelled when the tank is
filled.
A typical external floating-roof tank consists of a cylindrical steel shell equipped
with a deck or roof that floats on the surface of the stored liquid, rising and falling with the
liquid level. The liquid surface is completely covered by the floating roof except in the small
annular space between the roof and the shell. A seal attached to the roof touches the tank wall
(except for small gaps hi some cases) and covers the remaining area. The seal slides against
the tank wall as the roof is raised or lowered. The floating roof and the seal system serve to
reduce the evaporative loss of the stored liquid.
An internal floating-roof tank has both a permanently affixed roof and a roof
that floats inside the tank on the liquid surface (contact roof), or is supported on pontoons
several inches above the liquid surface (noncontact roof). The internal floating-roof rises and
falls with the liquid level, and helps to restrict the evaporation of organic liquids.
6-39
-------
The four classes of losses that floating roof tanks experience include withdrawal
loss, rim seal loss, deck fitting loss, and deck seam loss. Withdrawal losses are caused by the
stored liquid clinging to the side of the tank following the lowering of the roof as liquid is
withdrawn. Rim seal losses are caused by leaks at the seal between the roof and the sides of
the tank. Deck fitting losses are caused by leaks around support columns and deck fittings
within internal floating roof tanks. Deck seam losses are caused by leaks at the seams where
panels of a bolted internal floating roof are joined.
Table 6-15 shows emission factors during both non-winter and winter for
storage tanks at a typical bulk terminal.158 The emission factors were derived from AP-42
equations and a weight fraction of benzene in the vapor of 0.009.!58 Table 6-16 shows
uncontrolled emission factors for gasoline vapor and benzene for a typical bulk plant.160
Table 6-17 shows emission factors during both non-winter and winter months for storage tanks
at pipeline breakout stations.158 The emission factor equations in AP-42 are based on the same
equations contained in the EPA's computer-based program "TANKS." Since TANKS is
regularly updated, the reader should refer to the latest version of the TANKS program
(version 3.1 at the time this document was finalized) to calculate the latest emission factors for
fixed- and floating-roof storage tanks. The factors in Tables 6-15 and 6-17 were calculated
with equations from an earlier version of TANKS and do not represent the latest information
available. They are presented to show the type of emission factors that can be developed from
the TANKS program.
Emissions from Gasoline Tank Trucks
Gasoline tank trucks have been demonstrated to be major sources of vapor
leakage. Some vapors may leak uncontrolled to the atmosphere from dome cover assemblies,
pressure-vacuum (P-V) vents, and vapor collection piping and vents. Other sources of vapor
leakage on tank trucks that occur less frequently include tank shell flaws, liquid and vapor
transfer hoses, improperly installed or loosened overfill protection sensors, and vapor
couplers. This leakage has been estimated to be as high as 100 percent of die vapors which
6-40
-------
TABLE 6-15. BENZENE EMISSION FACTORS FOR STORAGE LOSSES AT A
TYPICAL GASOLINE BULK TERMINAL
Gasoline Vapor
VOC Emission Factor1-"
ton/yr/Tank (Mg/yr/Tank)
SCC Number
4-04-001-07/
4-04-001-08
4-04-001-04/
4-04-001-05
4-04-001-XX
4-04-001-3 1/
4-04-001-32
4-04-001-41/
4-04-001-42
4-04-001-XX
4-04-001-XX
4-04-001-XX
4-04-001-XX
4.Q4-001-XX
Storage Method
Fixed Roof1 - Working Losses
(Uncontrolled)
Fixed Roof - Breathing Losses
(Uncontrolled)
External Floating Roof - Working
Losses
External Floating Roof - Standing
Storage Losses - Primary Metallic Shoe
Seal and Uncontrolled Fittings
External Floating Roof - Standing
Storage Losses - Secondary Metallic
Shoe Seal and Uncontrolled Fittings
External Floating Roof - Primary and
Secondary Metallic Shoe Seals and
Uncontrolled Fittings
Internal Floating Roof -
Vapor-mounted Rim Seal Losses
Internal Floating Roof -
Liquid-Mounted Seal Losses
Internal Floating Roof - Vapor
Primary and Secondary Seal
Internal Floating Roof -
Uncontrolled Fitting Losses'1
Non-Winter
35.6(32.3)
9.42 (8.55)
~f(--')
12.6(11.4)
5.9(5.38)
3.85 (3.49)
1.12(1.02)
0.51 (0.46)
0.42 (0.38)
1.11(1.01)
Winter
46.4(42.1)
13.2 (12.0)
--'(»')
17.61 (15.98)
8.31 (7.54)
5.38 (4.88)
1.59(1.44)
0.71 (0.64)
0.60(0.54)
1.56(1.42)
Benzene Emission Factor0
ton/yr/Tank (Mg/yr/Tank)
Non-Winter
0.320 (0.291)
0.085 (0.077)
--'(--')
0.113(0.103)
0.035 (0.031)
0.053 (0.048)
0.0101 (0.0092)
0.0046(0.0041)
0.0038 (0.0034)
0.0100 (0.0091)
Winter
0.418 (0.379)
0.119(0.108)
~f(~')
0.158(0.144)
0.075 (0.068)
0.048(0.044)
0.0143
(0.0130)
0.0063
(0.0058)
0.0054
(0.0049)
0.0141
(0.0128)
Emission
Factor
Rating
E
E
E
E
E
E
E
E
E
E
(continued)
-------
TABLE 6-15. CONTINUED
£
to
SCC Number
4-04-001-XX
4-04-001-XX
4-04-001-XX
Gasoline Vapor
VOC Emission Factor" b
ton/yr/Tank (Mg/yr/Tank)
Storage Method Non-Winter Winter
Internal Floating Roof - Controlled 0. 76 (0. 69) 1 .07 (0. 97)
Fitting Losses1
Internal Floating Roof - Deck Seam 0.57 (0.52) 0.80 (0.73)
Losses
Internal Floating Roof - Working -J (~k) — ' (--k)
Losses
Benzene Emission Factor*
ton/yr/Tank (Mg/yr/Tank)
Non-Winter Winter
0.0068 (0.0062) 0.0096
(0.0087)
0.0052 (0.0047) 0.0072
(0.0066)
-J(»k) -J(-k)
Emission
Factor
Rating
E
E
E
Source: Reference 158.
1 Emission factors calculated with equations from Chapter 4.3 of AP-42 (TANKS program version 1.0), using a non-winter RVP of 9:3 psia, a winter RVP
of 12.8 psia, and a temperature of 60°F. The reader should be aware that the TANKS program is regularly updated and that the latest version of the
program should be used to calculate emission factors. At the time this document was printed, version 3.1 of the TANKS program was available.
b Terminal with 250,000 gallons/day (950,000 liters/day) with four storage tanks for gasoline.
c Based on gasoline emission factor and an average benzene/VOC ratio of 0.009.
d Typical fixed-roof tank or internal floating roof tank based upon capacity of 2,680 m \\6J50 bbls), a diameter of 50 feet (15.2 meters), and a height of
48 feet (14.6 meters).
' Typical floating-roof tank based upon capacity of 36,000 bbls (5,760 m J, a diameter of 78 feet (24.4 meters), and a height of 40 feet (12.5 meters).
f Gasoline vapor emission factor = (5.1x10 "Q) ton/yr, where Q is the throughput through the tanks in barrels.
Benzene emission factor = (4.6 x 1010 Q) ton/yr.
* Gasoline vapor emission factor = (4.6 x 10 ^Q) Mg/yr, where Q is the throughput through the tanks in barrels.
Benzene emission factor = (4.1 x 1010 Q) Mg/yr.
h Calculated assuming the "typical" level of control in the "TANKS" program.
1 Calculated assuming the "controlled" level of control in the "TANKS" program.
1 Gasoline vapor emission factor = (8.1 x 10 "\J) ton/yr, where Q is the throughput through the tanks in barrels.
Benzene emission factor = (7.3 x 1010 Q) ton/yr.
k Gasoline vapor emission factor = (7.3 x 10 ^Q) Mg/yr, where Q is the throughput through the tank in barrels.
Benzene emission factor = (6.6 x 1010 Q) Mg/yr.
"-" means no data available.
-------
TABLE 6-16. GASOLINE VAPOR AND BENZENE EMISSION FACTORS FOR A TYPICAL BULK PLANT
t
Ui
SCC Number Emission Source
4-04-002-01 Storage Tanks - Fixed Roof -
Breathing Loss
4-04-002-04 Storage Tanks - Fi xed Roof -
Working Loss:
Filling
Emptying
4-04-002-50 Gasoline Loading Racks:
Splash Loading
(normal service)
Submerged Loading
(normal service)
Splash and Submerged Loading
(balance service)0
Gasoline Vapor
Emission Factor*
lb/1000 gal (mg/liter)
5.0 (600)
9.6(1150)
3.8 (460)
11.9(1430)
4.9 (590)
0.3 (40)
Benzene
Emission Factorb
lb/1000 gal (mg/liter)
0.5 (5.4)
0.086 (10.3)
0.034(4.1)
0. 107 (12.9)
0.044 (5.3)
0.002 (0.4)
Emission
Factor Rating
E
E
E
E
E
E
Source: Reference 160.
' Typical bulk plant with gasoline throughput of 19,000 liters/day (5,000 gallons/day).
" Based on gasoline emission factor and an average benzene/VOC ratio of 0.009.
c Calculated using a Stage I control efficiency of 95 percent.
-------
TABLE 6-17. BENZENE EMISSION FACTORS FOR STORAGE LOSSES AT A
TYPICAL PIPELINE BREAKOUT STATION"-"
Gasoline Vapor VOC Emission Factor" b
ton/yr/Tank (Mg/yr/Tank)
SCC Number
4-04-OOX-XX
4-04-OOX-XX
4-04-OOX-XX
4-04-OOX-XX
4-04-OOX-XX
4-04-OOX-XX
4-04-OOX-XX
4-04-OOX-XX
4-04-OOX-XX
4-04-OOX-XX
4-04-OOX-XX
Storage Method .
Fixed Roof Uncontrolled -
Breathing Losses
Fixed Roof Uncontrolled - Working
Losses
Internal Floating Roof - Vapor-
mounted rim seal losses
Internal Floating Roof - Liquid-
mounted rim seal losses
Internal Floating Roof - Vapor
primary and secondary seal
Internal Floating Roof -
Uncontrolled fitting losses'
Internal Floating Roof - Controlled
fitting losses'1
Internal Floating Roof - Deck seam
losses
Internal Floating Roof - Working
losses primary and secondary seal
External Floating Roof - Standing
Storage losses - Primary seal
External Floating Roof - Standing
Storage losses - Secondary seal
Non- Winter
36.9 (33.5)
477.5 (433.3)
2.26 (2.05)
1.01 (0.92)
0.84 (0.76)
2.60 (2.36)
1.77(1.61)
2.29 (2.08)
-•(-^ .
15.43 (14.00)
6.91 (6.27)
Winter
52.0 (47.2)
621.5(564.0)
3.16(2.87)
1.42(1.29)
1.18(1.07)
3.65 (3.31)
2.48 (2.25)
3.20 (2.90)
-•(.-i
21.61(19.61)
9.69 (8.79)
Benzene Emission Factor1
ton/yr/Tank (Mg/yr/Tank)
Non- Winter
0.332 (0.302)
4.297 (3.9)
0.020 (0.018)
0.009 (0.008)
0.008 (0.007)
0.023 (0.021)
0.016 (0.014)
0.021 (0.019)
-•M
0.139(0.126)
0.062 (0.056)
Winter
0.468 (0.425)
5.6(5.1)
0.028 (0.026)
0.013 (0.012)
0.011(0.010)
0.033 (0.030)
0.022 (0.020)
0.029 (0.026)
•••(-',
0.194(0.176)
0.087 (0.079)
Emission
Factor
Rating
E
E
E
E
E
E
E
E
E
E
E
(continued)
-------
TABLE 6-17. CONTINUED
Gasoline Vapor VOC Emission Factor" b
ton/yr/Tank (Mg/yr/Tank)
SCC Number
4-04-OOX-XX
Storage Method
External Floating Roof - Standing
Non-Winter
5.10(4.63)
Winter
7.03 (6.38)
Benzene Emission Factor0
ton/yr/Tank (Mg/yr/Tank)
Non-Winter
0.046 (0.042)
Winter
0.063 (0.057)
Emission
Factor
Rating
E
4-04-OOX-XX
Storage losses - Primary and
secondary fittings
External Floating Roof- Standing
Storage losses - Working losses
£
Source: Reference 158.
1 Emission factors calculated with equations from Chapter 4.3 of AP-42 (TANKS program version 1.0), using a non-winter RVP of 9.3 psia, a winter RVP
of 12.8 psia, and a temperature of 60°F. The reader should be aware that the TANKS program is regularly updated and that the latest version of the
program should be used to calculate emission factors. At the time this document was printed, version 3.1 of the TANKS program was available.
" Assumes storage vessels at pipeline breakout stations have a capacity of 50,000 bbl (8,000 m ?, a diameter of 100 feet (30 meters), and a height of 40 feet
(12 meters).
c Calculated assuming the "typical" level of control in the "TANKS" program.
6 Calculated assuming the "Controlled" level of control in the "TANKS" program.
' Gasoline vapor emission factor = (5.1 x 10 ^Q) ton/yr, where Q is the throughput through the tanks in barrels.
Benzene emission factor = (4.6 x 1010 Q) ton/yr.
' Gasoline vapor emission factor = (4.6 x 10 ^Q) Mg/yr, where Q is the throughput through the tanks in barrels.
Benzene emission factor = (4.1 x 10'° Q) Mg/yr.
1 Gasoline vapor emission factor = (8.1 x 10 \J) ton/yr, where Q is the throughput through the tanks in barrels.
Benzene emission factor = (7.3 x 1010 Q) ton/yr.
h Gasoline vapor emission factor = (7.3 x 10 ~^Q) Mg/yr, where Q is the throughput through the tank in barrels.
Benzene emission factor = (6.6 x 10 m Q) Mg/yr.
"-" means data not available.
-------
should have been captured and to average 30 percent. Because terminal controls are usually
found in areas where trucks are required to collect vapors after delivery of product to bulk
plants or service stations (balance service), the gasoline vapor emission factor associated with
uncontrolled truck leakage was assumed to be 30 percent of the uncontrolled balance service
truck loading factor (980 mg/liter x 0.30 = 294 mg/liter).160 Thus the emission factor for
benzene emissions from uncontrolled truck leakage is 2.6 mg/liter, based on a benzene/vapor
ratio of 0.009.
6.4.3 Benzene Emissions from Service Stations
The discussion on service station operations is divided into two areas: the
filling of the underground storage tank (Stage I) and automobile refueling (Stage II). Although
terminals and bulk plants also have two distinct operations (tank filling and truck loading), the
filling of the underground tank at the service station ends the wholesale gasoline marketing
chain. The automobile refueling operations interact directly with the public so that control of
these operations can be performed by putting control equipment on either the service station or
the automobile.
Stage I Emissions at Service Stations
Normally, gasoline is delivered to service stations hi large tank trucks from bulk
terminals or smaller account trucks from bulk plants. Emissions are generated when
hydrocarbon vapors in the underground storage tank are displaced to the atmosphere by the
gasoline being loaded into the tank. As with other loading losses, the quantity of the service
station tank loading loss depends on several variables, including the quantity of liquid
transferred, size and length of the fill pipe, the method of filling, the tank configuration and
gasoline temperature, vapor pressure, and composition. A second source of emissions from
service station tankage is underground tank breathing. Breathing losses tend to be minimal for
underground storage tanks due to nearly constant ground temperatures and are primarily the
result of barometric pressure changes.
6-46
-------
Stage n Emissions of Service Stations
In addition to service station tank loading losses, vehicle refueling operations
are considered to be a major source of emissions. Vehicle refueling emissions are attributable
to vapor displaced from the automobile tank by dispensed gasoline and to spillage. The major
factors affecting the quantity of emissions are dispensed fuel temperature, differential
temperature between the vehicle's tank temperature and the dispensed fuel temperature, and
fuel Reid vapor pressure (RVP).161-162 Several other factors that may have an effect upon
refueling emissions are: fill rate, amount of residual fuel in the tank, total amount of fill,
position of nozzle in the fill-neck, and ambient temperature. However, the magnitude of these
effects is much less than that for any of the major factors mentioned above.161
Spillage loss is made up of configurations from prefill and postfill nozzle drip
and from spit-back and overflow from the vehicle's fuel tank filler pipe during filling.
Table 6-18 lisis the uncontrolled emission factors for a typical gasoline service station.160-163
This table incudes an emission factor for displacement losses from vehicle refueling.
However, the following approach is more accurate to estimate vehicle refueling emissions.
Emissions can be calculated using MOBILE 5a, EPA's mobile source emission
factor computer model. MOBILE 5a uses the following equation:163
Er = 264.2 [(-5.909) - 0.0949 (AT) + 0.0884 (TD) + 0.485 (RVP)]
where:
Er = Emission rate, mg VOC/{ of liquid loaded
RVP = Reid vapor pressure, psia (see Table 6-19)163
AT = Difference between the temperature of the fuel in the automobile
tank and the temperature of the dispensed fuel, °F (see
Table 6-20)161
TD = Dispensed fuel temperature, °F (see Table 6-21)164
Using this emission factor equation, vehicle refueling emission factors can be derived for
specific geographic locations and for different seasons of the year.
6-47
-------
TABLE 6-18. GASOLINE VAPOR AND BENZENE EMISSION FACTORS FOR
A TYPICAL SERVICE STATION
SCC Number
Emission Source
Gasoline Vapor
Emission Factor3
lb/1000 gal (mg/liter)
Benzene
Emission Factor11
lb/1000 gal (mg/liter)
Emission Factor
Rating
4-06-003-01
4-06-003-02
4-06-003-06
£ 4-06-003-07
4-06-004-01
4-06-004-02
Underground Storage Tanks - Tank
Filling Losses - Splash Fill
Underground Storage Tanks - Tank
Filling Losses - Submerged Fill
Underground Storage Tanks - Tank
Filling Losses - Balanced Submerged
Filling0
Underground Storage Tanks -
Breathing Losses
Vehicle Refueling*1 - Displacement
Losses
- Uncontrolled
- Controlled
Vehicle Refueling*1 - Spillage
11.5(1,380)
7.3 (880)
0.3 (40)
1.0(120)
11.0(1,320)
1.1 (132)
0.7 (84)
0.104(12.4)
0.066 (7.9)
0.003 (0.4)
0.009(1.1)
0.099(11.9)
0.0099(1.2)
0.0063 (0.76)
E
E
E
E
E
E
E
Source: References 160 and 163.
1 Typical service station has a gasoline throughput of 190,000 liters/month (50,000 gallons/month).
b Based on gasoline emission factor and an average benzene/VOC ratio of 0.009.
c Calculated using a Stage I control efficiency of 95 percent.
d Vehicle refueling emission factors can also be derived for specific geographic locations and for different seasons of the year using the MOBILE 5a, EPA's
mobile source emission factor computer model.161
-------
In the absence of specific data, Tables 6-19, 6-20, and 6-21 may be used to
estimate refueling emissions. Tables 6-19, 6-20, and 6-21 list gasoline RVPs, AT, and TD
values respectively for the United States as divided into six regions:
Region 1: Connecticut, Delaware, Illinois, Indiana, Kentucky, Maine,
Maryland, Massachusetts, Michigan, New Hampshire,
New Jersey, New York, Ohio, Pennsylvania, Rhode Island,
Virginia, West Virginia, and Wisconsin.
Region 2: Alabama, Arkansas, Florida, Georgia, Louisiana, Mississippi,
North Carolina, South Carolina, and Tennessee.
Region 3: Arizona, New Mexico, Oklahoma, and Texas.
Region 4: Colorado, Iowa, Kansas, Minnesota, Missouri, Montana,
Nebraska, North Dakota, South Dakota, and Wyoming.
Region 5: California, Nevada, and Utah.
Region 6: Idaho. Oreeon. and Washineton.
6.4.4 Control Technology for Marine Vessel Loading
Marine vapor control systems can be divided into two categories: vapor
recover}' systems and vapor destruction systems. There are a wide variety of vapor recovery
systems that can be used with vapor collection systems. Most of the vapor recovery systems
installed to date include refrigeration, carbon adsorption/absorption, or lean oil absorption.
Three major types of vapor destruction or combustion systems that can operate over the wide
flow rate and heat content ranges of marine applications are: open flame flares, enclosed flame
flares, and thermal incinerators.165
- When selecting a vapor control system for a terminal, the decision on
recovering the commodity depends on the nature of the VOC stream (expected variability in
flow rate and hydrocarbon content), and locational factors, such as availability of utilities and
distance from the tankship or barge to the vapor control system. The primary reason for
selecting incineration is that many marine terminals load more than one commodity.159-164
6-49
-------
TABLE 6-19. RVP LIMITS BY GEOGRAPHIC LOCATION
State
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
District of Columbia
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Weighted average
Summer Winter
(Apr.-Sep.) (Oct.-Mar.)
8.6
13.9
8.4
8.5
8.6
8.6
9.7
9.7
8.8
8.7
8.6
11.5
9.5
9.7
9.7
9.6
8.6
9.6
8.6
9.6
9.0
9.7
9.7
9.7
8.6
8.7
9.5
12.8
15.0
11.6
13.5
12.6
13.1
14.5
14.3
14.1
12.9
12.8
11.5.
13.2
14.2
14.3
14.2
13.1
14.0
12.8
14.5
14.3
14.5
14.5
14.3
12.8
13.8
14.3
Annual
10.6
14.3
10.0
10.7
10.6
10.7
12.0
11.9
11.4
10.7
10.7
11.5
11.3
12.0
11.9
11.8
10.8
11.7
10.6
11.9
11.6
12.0
12.0
11.8
10.7
11.1
11.7
(continued)
6-50
-------
TABLE 6-19. CONTINUED
State
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Wyoming
Nationwide Annual Average
Nonattainment Annual Average
Weighted average
Summer
(Apr.-Sep.)
9.5
8.5
9.7
9.7
8.5
9.7
8.8
9.7
9.7
8.6
9.0
9.7
9.7
9.0
9.5
8.8
8.5
8.7
9.6
8.8
9.7
9.7
9.7
9.5
9.4
9.2
Winter
(Oct.-Mar.)
13.5
12.5
14.5
14.4
12.4
14.5
13.6
14.2
14.3
12.9
13.9
14.5
14.5
13.3
13.5
13.6
12.5
13.3
14.5
14.0
14.3
14.3
14.3
13.6
Annual
11.4
10.4
12.0
12.1
10.3
12.0
11.1
11.7
11.9
10.7
11.2
12.0
12.1
11.0
11.3
11.1
10.4
10.9
12.0
11.3
11.9
11.9
11.9
11.5
11.4
11 3
Source: Reference 163.
6-51
-------
TABLE 6-20. SEASONAL VARIATION FOR TEMPERATURE DIFFERENCE
BETWEEN DISPENSED FUEL AND VEHICLE FUEL TANK3
Temperature difference (°F)
National average
Region 1
Region 2
Region 3
Region 4
Region 5
Average
annual
4.4
5.7
4.0
3.7
5.5
0.1
Summer
(Apr.-Sep.)
8.8
10.7
6.8
7.6
11.7
3.9
Winter
(Oct.-Mar.)
-0.8
-0.3
0.9
-0.4
-2.4
-4.4
5-Month
Ozone Season
(May-Sep.)
9.4
11.5
7.5
7.1
12.1
5.1
2-Month
Ozone Season
(July-Aug.)
9.9
12.5
8.2
7.0
13.3
3.2
Source: Reference 161.
a Region 6 was omitted, as well as Alaska and Hawaii.
TABLE 6-21. MONTHLY AVERAGE DISPENSED LIQUID TEMPERATURE (TD)
National average
Region 1
Region 2
Region 3
Region 4
Region 5
Region 6
Summer
(Apr.-Sep.)
74
70
85
79
74
79
64
Weighted average
Winter
(Oct.-Mar.)
58
51
76
62
56
63
50
(Annual)
66
61
81
70
65
72
57
Source: Reference 164.
6-52
-------
160
For additional information on emission controls at marine terminals refer to
References 159 and 165.
6.4.5 Control Technology for Gasoline Transfer
' At many bulk terminals and bulk plants, benzene emissions from gasoline
transfer are controlled by CTG, NSPS, and new MACT programs. Control technologies
include the use of a vapor processing system in conjunction with a vapor collection system.'
Vapor balancing systems, consisting of a pipeline between the vapor spaces of the truck and
the storage tanks, are closed systems. These systems allow the transfer of displaced vapor into
the transfer truck as gasoline is put into the storage tank.160
Also, these systems collect and recover gasoline vapors from empty, returning
tank trucks as they are filled with gasoline from storage tanks. The control efficiency of the
balance system ranges from 93 to 100 percent.15 Figure 6-4 shows a Stage I control vapor
balance system at a bulk plant.160
At service stations, vapor balance systems contain the gasoline vapors within the
station's underground storage tanks for transfer to empty gasoline tank trucks returning to the
bulk terminal or bulk plant. Figure 6-5 shows a diagram of a service station vapor balance
system.160 For more information on Stage II controls refer to Section 6.4.7.
6.4.6 Control Technology for Gasoline Storage
The control technologies for benzene emissions from gasoline storage involve
upgrading the type of storage tank used or adding a vapor control system. For fixed-roof
tanks, emissions are most readily controlled by installation of internal floating roofs. An
internal floating roof reduces the area of exposed liquid surface on the tank and, therefore,
6-53
-------
Balance to Transport
Balance to Storage
Gasoline Line
Gasoline Line
Transport Truck Unloading
Figure 6-4. Bulk Plant Vapor Balance System (Stage I)
Source: Reference 160.
Account Truck Loading
-------
Stage I Controls
Stage II Controls
ON
Tank Truck
Vapor Return Line
r i i
Submerged Fill Pipe
Vent of Underground Tank
Gasoline Pump
Nozzle
Gasoline
Delivery Line
a—•
a]/
Vehicle
Vapor Return Line
Underground Tank
Figure 6-5. Service Station Vapor Balance System
Source: Reference 160.
-------
decreases evaporative loss. Installing an internal floating roof in a fixed-roof tank can reduce
total emissions by 68.5 to 97.8 percent.160
For external floating-roof tanks, no control measures have been identified for
controlling withdrawal losses and emissions.160 These emissions are functions of the turnover
rate of the tank and the characteristics of the tank shell. Rim seal losses in external floating
roof tanks depend on the type of seal. Liquid-mounted seals are more effective than
vapor-mounted seals in reducing rim seal losses. Metallic shoe seals are more effective than
vapor-mounted seals but less effective than liquid-mounted seals.160
For additional information on control technology for storage tanks refer to the
EPA documents Compilation of Air Pollutant Emission Factors (AP-42), Chapter 733 and
Reference 158.
6.4.7 Control Technology for Vehicle Refueling Emissions
Vehicle refueling emissions are attributable to vapor displaced from the
automobile tank by dispensed gasoline and to spillage.
The two basic refueling vapor control alternatives are: control systems on
service station equipment (Stage II controls), and control systems on vehicles (onboard
controls). Onboard controls are basically limited to the carbon canister.
There are currently three types of Stage n systems in limited use in the United
States: the vapor balance, the hybrid, and the vacuum assist systems. In the vapor balance
system, gasoline vapor in the automobile fuel tank is displaced by the incoming liquid gasoline
and is prevented from escaping to the atmosphere at the fillneck/nozzle interface by a flexible
rubber "boot." This boot is fitted over the standard nozzle and is attached to a hose similar to
the liquid hose. The hose is connected to piping which vents to the underground tank. An
exchange is made (vapor for liquid) as the liquid displaces vapor to the underground storage
6-56
-------
tank. The underground storage tank assists this transaction by drawing in a volume of vapor
equal to the volume of liquid removed.160
The vacuum assist system differs from the balance system in that a "blower" (a
vacuum pump) is used to provide an extra pull at the nozzle/fillneck interface. Assist systems
can recover vapors effectively without a tight seal at the nozzle/fillpipe interface because only a
close fit is necessary. A slight vacuum is maintained at the nozzle/fillneck interface allowing
air to be drawn into the system and not allowing the vapors to escape. Because of this assist,
the interface "boot" need not be as tight fitting as with balance systems. Further, the vast
majority of assist nozzles do not require interlock mechanisms. Assist systems generally have
vapor passage valves located in the vapor passage somewhere other than in the nozzles,
resulting in a nozzle which is less bulky and cumbersome than nozzles employed by vapor
balance systems.160
There are four assist systems that are currently available and certified by the
California Air Resources Board (CARB): the Hasstech, the Healy, the Hut, and the Amoco
Bellowless Nozzle System.163
The hybrid system borrows from the concepts of both the balance and vacuum
assist systems. It is designed to enhance vapor recovery at the nozzle/fillneck interface by
vacuum, while keeping the vacuum low enough so that a minimum level of excess vapor/air is
returned to the underground storage tank.
With the hybrid system, a small amount of the liquid gasoline (less than
10 percent) pumped from the storage tank is routed (before metering) to a restricting nozzle
called an aspirator. As the gasoline goes through this restricting nozzle, a small vacuum is
generated. This vacuum is used to draw vapors into the rubber boot at the interface. Because
the vacuum is so small, very little excess air, if any, is drawn into the boot, hose and
underground storage tank, and thus there is no need for a secondary processor, such as the
vacuum assist's incinerator.153
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Results of the California Air Resources Board certification testing program on
Stage II vapor recovery systems indicate that all of the Stage n vapor recovery systems
discussed above are capable of achieving an emission reduction of 95 percent.160 However,
efficiencies vary depending upon inspection frequency, maintenance, and number of stations
exempted. Reference 163 discusses efficiency in more detail.
Onboard vapor control systems consist of carbon canisters installed on the
vehicle to control refueling emissions. The carbon canister system adsorbs, on activated
carbon, the vapors which are displaced from the vehicle fuel tank by the incoming gasoline.
Such a system first absorbs the emissions released during refueling and subsequently purges
these vapors from the carbon to the engine carburetor when it is operating. This system is
essentially an expansion of the present evaporative emissions control system used in all new
cars to minimize breathing losses from the fuel tank and to control carburetor evaporative
emissions. However, unlike the present system, a refueling vapor recovery system will require
a tight seal at the nozzle/fiilneck interface during refueling operations to ensure vapors flow
into the carbon canister and are not lost to the atmosphere. An efficiency of 98 percent has
been reported for control of automobile refueling losses using onboard control systems.160
For additional information on control of vehicle refueling emissions at gasoline
dispensing facilities refer to Reference 163.
6.4.8 Regulatory Analysis
Gasoline loading emissions at bulk gasoline terminals are regulated by the New
Source Performance Standards promulgated on August 18, 1983.166 These standards apply to
VOC emissions at affected facilities that commenced construction or modification after
December 17, 1980. The standards regulate bulk gasoline terminals with a throughput greater
than 75,700 liters per day.
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Also, the NESHAP for gasoline distribution that was promulgated on
December 14, 1994, regulates organic hazardous air pollutant (HAP) emissions (including
benzene) from gasoline loading and transport operations. The NESHAP covers HAP
emissions from storage vessels, piping and handling, and loading at bulk gasoline terminals,
and storage vessels at piping systems that handle the gasoline at pipeline breakout stations.167
6.5 PUBLICLY OWNED TREATMENT WORKS
Publicly owned treatment works (POTWs) treat wastewater from residential,
institutional, commercial, and industrial facilities. In general, benzene emissions from POTWs
originate from the benzene content of industrial wastewater that is introduced into POTWs, and
benzene may be emitted by volatilization at the liquid surface of the wastewater.
Industrial wastewater sent to POTWs from industrial facilities may be pre-
ireated or untreated, depending on State and Federal industrial wastewater quality standards.
The following discussion describes the various treatment process units at POTWs from which
benzene may be emitted.
6.5.1 Process Description of POTWs
A POTW treats wastewater using physical, chemical, and biological treatment
processes. Most POTWs are required by Federal and State laws to treat wastewater using
"primary" treatment methods to remove coarse and suspended solids and "secondary"
treatment methods to remove biodegradable organics, pathogens, and additional solids.
Additionally, some POTWs are required to use "tertiary" treatment methods to remove
refractory organics, nutrients (e.g., phosphorus and nitrogen), dissolved inorganic salts, and
heavy metals, among other contaminants. As the wastewater is treated, all of the collected
solids and sludge undergo additional processing at the POTW to reduce sludge volume,
organic content, and bacterial activity prior to disposal.
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The following discussion describes the various process units included in a
typical POTW facility (shown in Figure 6-6), that uses primary and secondary wastewater
treatment methods.168 As discussed hi Section 6.6.2, a testing program for organic emissions
from POTWs documented that benzene is emitted from most of these process units.
Comminutors
Comminutors (or shredders) are devices that are used to grind or cut waste
solids to about one-quarter-inch (6 mm) particles. In one common type of comminutor, the
untreated wastewater enters a slotted cylinder within which another similar cylinder with
sharp-edged slots rotates rapidly. As the solids are reduced hi size, they pass through the slots
of the cylinders and move on with the liquid to the treatment plant. Comminution eliminates
the need to use screens, which collect large solid waste material that must be disposed of
separately from the sludge.169
Aerated Grit Chambers
Grit chambers are used at many POTWs to remove dense solids (both inorganic
and organic) present in wastewater (e.g., sand, gravel, glass, coffee grounds). Aerated grit
chambers work by imparting a helical flow pattern to the sewage by aerating one side of the
chamber. The aeration allows the dense grit to settle while keeping less dense organic material
in suspension. Benzene emissions arise from aeration of the wastewater in the grit chamber.168
Primary Sedimentation Tanks
The main function of primary sedimentation tanks is to remove suspended
material that settles readily from raw sewage. This material includes slower-settling organic
matter as well as fast-settling grit if the POTW does not have grit removal upstream.
Additionally, the system removes floatable solids, which are composed mostly of fats and
grease. The wastewater enters the tank at one end, flows through the tank and under a surface
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Waste-
water
Comminutor
Aerated
Chamber
Primary
Tank
Aerobic
Treatment
Secondary
Clarifier
Tertiary
Filter*
Chlorine
Tank
Dechlorination
ON
ON
Wastewater
Sludge
Digester Gas
Sludge
Thickener
i
Anaerobic
Digester
Discharge
for
Treated
Wastewater
Dewaterlng
a.
-p
Figure 6-6. Process Flow Diagram for a Typical POTW
Source: Reference 168.
-------
baffle located near the tank's downstream edge, over a weir, and into an effluent channel.
Sludge collects on the bottom of the tank. A system of scrapers collects the sludge from the
bottom of the tank and pumps it to gravity sludge thickeners for further treatment. The surface
baffle skims the surface of the water and collects the floatables for removal and treatment in
anaerobic digesters.
Small amounts of benzene are released by volatilization from the quiescent
section of the tank prior to the weir. Most of the benzene emissions from the primary
sedimentation tank result from the turbulence that the water undergoes dropping over the weir
into the outlet conveyance channel. The height of the water drop from the weir is a measure of
the energy dissipated and may relate to the release of benzene emissions.168
Aerobic Biological Treatments
Aerobic biological treatment involves the use of microorganisms to metabolize
dissolved and colloidal organic matter in the wastewater in an aerobic environment. Two types
of processes are used: suspended-growth and attached-growth. The most common
suspended-growth process used in POTWs is the activated sludge process; the most common
attached-growth process is the trickling filter. These two types of processes are described
below.169
Activated Sludge Process—In the activated sludge process, a high concentration
of microorganisms that have settled in the secondary clarifiers (called activated sludge) is
added to settled wastewater that enters an aerobic tank. The mixture enters an aeration tank,
where the organisms and wastewater undergo further mixing with a large quantity of air or
oxygen to maintain an aerobic environment. There are three common types of aeration tanks:
diffused air, mechanically mixed air, and pure oxygen (which can be diffused or mechanically
mixed). Diffused air systems aerate the water by bubbling air from the atmosphere through the
water from the bottom of the tank. Mechanically mixed air systems use mechanical surface
mixers that float on the water surface.
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In pure oxygen systems (which are more likely to be covered systems), pure
oxygen is fed to either submerged diffusers or to the head space over a tank employing
mechanical aerators. In diffused air or oxygen systems, the air or oxygen bubbles can strip
VOC from the liquid phase depending on the concentrations and partial pressures of the
specific substances. In mechanically mixed systems, the area where the wastewater/activated
sludge mixture is agitated is a potential source of VOC (benzene) emissions.168-169
Trickling Filter-The trickling filter is an aerobic attached-growth treatment
process that uses microorganisms growing on a solid media to metabolize organic compounds
hi the wastewater. Trickling filter media beds are typically 40 to 100 ft hi diameter and 15 to
40 ft deep. Influent wastewater from the primary sedimentation tank is sprayed on top of the
media bed. The wastewater is biologically treated as it trickles downward through the media.
Effluent from the process is collected by the underdrain system and sent to a secondary
clarifier. Ambient ah- is blown upward through the media to provide oxygen to sustain
microbial growth. The exhaust air from the process may contain benzene that was stripped
from the wastewater during treatment.168
Secondary Clarification
Secondary clarification is a gravity sedimentation process used in wastewater
treatment to separate out the activated sludge solids from the effluent from the upstream
biotreatment process. Effluent from the biological treatment process is introduced into the
clarifier through submerged diffusers. As the wastewater flows through the clarifier tank from
inlet to outlet weirs, die solids settle to the bottom of the tank while the floatables and scum are
skimmed off the top. The tank bottom is sloped slightly to the discharge end of the tank to two
hoppers, where sludge is collected by a chain and flight conveyor system and returned to the
biological treatment system or to the waste sludge handling system. The quiescent section of
the tank may release benzene by volatilization from the water surface. However, most of the
benzene emissions from the secondary clarifier result from the turbulence that the water
undergoes dropping over the weir into the outlet conveyance channel. In some cases, the weir
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is notched, such that the water flows through the notches, falling only a few inches onto a
support structure. In this latter case, there is much less turbulence in the water, and it is
expected that there would be fewer emissions of VOC than in the case where the water
free-falls directly into the collection channel.168
Tertiary Filters
Tertiary filters remove unsettled particles from the wastewater by using enclosed
(pressure) filters or open (gravity) filters. The filtering medium typically consists of sand and
anthracite coal, and may consist of one or two grain sizes. To collect activated sludge effluent,
the filters typically remove particles in the size ranges of 3 to 5 fj.m and 80 to 90 /zm. Alum or
polymer is often added prior to filtration to form a floe and thus increase particulate removal.
Cleaning of tertiary filters (called backwashing) typically occurs by forcing
water back through the filter. The backwash water is typically recirculated upstream in the
plant. Except for the brief periods during backwash, gravity tertiary filters have quiescent
surfaces, and little VOC release would be expected. Pressure filters are totally enclosed, and
no air emissions occur during filtration from these units.168
Chlorine Contact Tanks
For the purposes of disinfection, chlorine in the form of chlorine gas or calcium
or sodium hypochlorite is fed into the wastewater just prior to the chlorine contact tank. The
chlorine contact tank is designed to allow the mixture of chlorine and wastewater to remain in
contact long enough to adequately kill the target organisms (15 minutes to 2 hours). The
typical flow pattern is a serpentine pattern, consisting of ulterior baffle walls within a
rectangular tank. Although water surfaces are generally quiescent, most chlorine contact tanks
have weirs at the end of the tank to control water levels in the tank. Depending on the depth of
fall and flow rate, the turbulence at the weir overflow may result in benzene emissions.168
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Dechlorination Chambers
Typically, a dechlorination chamber is located adjacent to the chlorine contact
tank to remove chlorine residual in the disinfected wastewater. Chlorinated effluent from the
chlorine contact tank flows into the dechlorination chamber through a gate valve. In the
dechlorination chamber, an SO2 solution or sodium bisulfate is introduced into the wastewater
through submerged diffusers. The wastewater is hydraulicaily mixed as the SO2 is added. The
dechlorinated water is discharged from the facility.168
Sludge Thickeners
Sludge thickeners collect primary sludge (from the primary sedimentation tank)
and waste-activated sludge (from the secondary clarifier) to reduce the volume of the sludge
prior to treatment in an anaerobic digester. The two most common types of thickening
processes are gravity sludge thickeners and dissolved air floatation thickeners. These two
types of thickeners are described below.168 Additionally, centrifuges are used to thicken sludge
both prior to and after aerobic digestion. (Centrifuges are discussed below under dewatering
techniques.)
Gravity Sludge Thickener—In this process, sludge is thickened by allowing
heavier sludge particles to settle. Sludge is pumped into the center of a circular tank from
below. Heavier solid particles sink to the bottom of the tank, are removed as thickened
sludge, and are sent to digesters. Lighter sludge particles (e.g., greases) float to the surface of
the tank and are removed into a scum trough, where they are directed to a scum conditioner.
As sludge is added to the tank, the sludge flows outward radially, and liquid effluent from the
process flows outward over weirs and into the effluent trough located on the periphery of the
tank. Typically, this liquid returns to the aeration tanks in the activated sludge process for
further treatment.168
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Dissolved Air Flotation Thickener—This process is used to float sludge by
forcing the sludge to rise to the water surface. Sludge is pumped into a circular tank with
central feed or into a rectangular tank with end feed. As the sludge enters the tank,
microbubbles are introduced into the sludge by pressurizing in a retention tank a portion of the
effluent liquid from the tank. Pressurization of the liquid causes the air to be dissolved in the
liquid phase. After pressurization, the recirculated effluent is mixed with the sludge feed.
When the pressurized liquid is released to atmospheric pressure, the dissolved air is released
into the solution in the form of microbubbles. As the sludge and pressurized liquid mix, the
sludge and air mixture rises to the surface in the form of a sludge blanket. Sludge thickening
occurs as a result of the sludge blanket and by drainage of entrained water from the sludge
blanket. Surface skimmers are used to remove the sludge blanket from the water surface for
further treatment in an anaerobic digester.
Anaerobic Digestion
Anaerobic digestion is a biological process conducted in the absence of free
oxygen in which anaerobic and facultative bacteria metabolize organic solids in sludge,
releasing methane and CO2 as a by-product. Anaerobic digesters are most commonly
cylindrical, with a diameter of 20 to 125 ft and a depth of 20 to 40 ft. In most digesters, to
promote adequate contact between the anaerobic biota and organic matter, the sludge is mixed
by either internal gas recirculation or by digested sludge recirculation. Additionally, the
sludge is kept heated to about 95°F (35°C) by either direct steam injection into the sludge or
by recirculating sludge through an external heat exchanging device. With mixing and heating,
sludge undergoes digestion for about 15 to 25 days.168-169
Most digesters are closed containers under a slight pressure. Under normal
operation, there should be no direct emissions of benzene to the atmosphere. The digester gas
produced is typically collected and routed to internal combustion engines to produce steam or
generate electricity. (Refer to Section 7.5 for information about benzene emissions from an
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internal combustion engine fueled with POTW digester gas.) If the digester is not covered or
the digester gases are not collected, then benzene may be emitted directly from the digester.168
Dewatering Techniques
Sludge dewatering operations involve removal of water from sludges by gravity,
compression, and evaporation processes. Common methods of dewatering are using a belt
filter press, a sludge centrifuge, and sludge drying beds.
Belt Filter Press-^Dieested sludge is mixed with flocculating cationic polymers
which aid in the separation of the solids from the water. The flocculated sludge is initially
spread out horizontally over a moving filter belt that passes under plows that turn the
sludge/polymer solution, aiding in the dewatering process. After gravity thickening on the
belt, the partially dewatered sludge is conveyed to and falls into a vertical compression zone,
where water is squeezed out of the sludge between two filter belts moving concurrently
through a series of rollers. The filtrate from dewatering is collected and returned to the head
of the treatment plant for processing. Sludge particles enmeshed in the polyester belt fabric are
continuously washed off by a highly pressurized spray. The dried sludge ("cake") product is
collected and carried to silos for storage.
Benzene emissions from the belt filter press process may be released from die
following locations: (1) the gravity section, where liquid sludge is discharged and tilled by
plows, (2) the filtrate pans, where filtrate cascades down from the belts to the filtrate collection
channel below, (3) the compression zone, where the sludge is squeezed between the two belts,
and (4) the drainage sump into which the filtrate and wash water are discharged.168
Sludge Centrifuge-Digested or pre-digested sludge mixed with flocculating
cationic polymers is introduced into a spuming cylinder with a conical end bowl that rotates at
sufficient velocity to force the solids to the sides of the drum. Inside the bowl, a concentric
screw conveyor with helical flights turns at a slightly different speed than the rotating drum,
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forcing the dewatered solids to a discharge at one end of the centrifuge, while the liquid flows
over to a weir into a discharge at the other end. The dewatered sludge is collected and
stored.168 Benzene emissions may be emitted from the point where the separated liquid flows
over the weir and is discharged from the centrifuge.
Sludge Drying Bed—A certain volume of sludge is piped into shallow beds,
where the sludge is allowed to dry by gravity settling, evaporation, and percolation. Some
drying beds are equipped with a system for decanting the liquid from the drying bed or
draining the liquid through a sand bed to a collection pipe. Due to factors such as rainfall,
ambient temperature, wind speed, relative humidity, amount of sun, and the character of the
sludge, the drying time varies from 30 to 60 days.168 These same factors will likely affect the
level of benzene emissions from the sludge drying beds.
6.5.2 Benzene Emissions From PQTWs
Under a program called the Pooled Emission Estimation Program (PEEP), 21
POTW facilities in California were tested for emissions of benzene (among other VOC) from
18 types of process units commonly included in POTW wastewater treatment processes. With
the exception of one type of process unit (comminutor controlled with wet scrubber), the
emissions test data yielded uncontrolled benzene emission factors. On average, three facilities
were tested for each type of process unit. The types of process units that were tested are
discussed above in section 6.6.1, and include aerated processes (aerated grit chambers, three
types of activated sludge units, trickling filters, and dissolved air floatation thickeners), gas
handling processes (anaerobic digesters and digester gas combustion devices), quiescent basins
(primary sedimentation tanks, secondary clarifiers, tertiary filters, chlorine contact tanks,
dechlorination, and gravity thickeners), sludge facilities (belt filter press, sludge centrifuges,
and sludge drying beds), and other processes (comminutors).
Based on the data collected by PEEP, emission factors could be developed for
most of the above process steps in the form of pounds of benzene emitted per million gallons
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of wastewater treated at a POTW. One type of process unit tested (mechanically-mixed
activated sludge) did not yield air emissions of benzene above the detection limit in the tests
performed; however, benzene was detected in the wastewater treated by the tested units.
Additionally, a benzene emission factor for the dechlorination process unit could only be
calculated in the form of pounds of benzene emitted per pound of benzene in the wastewater
influent to the dechlorination chamber. Refer to Table 6-22 for a listing of the emission
factors.3-168
With one exception, all of the emission factors presented in Table 6-21 represent
uncontrolled emissions of benzene. However, many facilities employ measures for odor
control that may also reduce benzene emissions to the atmosphere (see discussion in
Section 6.6.3). Most of the facilities tested under PEEP did employ odor control methods;
however, benzene emissions after control were not measured.
6.5.3 Control Technologies for POTWs
In general, the only types of control devices and techniques found at POTWs are
the scrubbers and covers used to improve the odor of the air released from the process units.
Using the information provided by PEEP, it could be determined which process units
commonly employ covers and scrubbers.
In many cases, aerated grit chambers are covered and vented to a scrubber.
Primary sedimentation tanks are sometimes covered and vented to a scrubber; however, many
of these units are uncovered. Activated sludge units may sometimes be completely covered
and vented to a scrubber or partially covered and vented to the atmosphere. This practice is
more common if a pure oxygen system is employed. Trickling filter units are sometimes
covered and vented to a scrubber. Secondary clarifiers may be uncovered or partially covered
over the weir discharge area with no vents. Tertiary filters are commonly uncovered.
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TABLE 6-22. SUMMARY OF BENZENE EMISSION FACTORS FOR POTWs
SCC Number
Emission Source
Control Device
Emission Factor
Ib/million gal
(kg/million liters)'
Emission Factor
Rating
5-01-007-07 Comminutor
5-01-007-15 Aerated grit chamber
5-01-007-20 Primary sedimentation tank
5-01-007-31 Diffused air activated sludge
5-01-007-33 Pure oxygen activated sludge
5-01-007-34 Trickling filter
5-01-007-40 Secondary clarifier
5-01-007-50 Tertiary filter
5 -01 -007-60 Chlorine contact tank
5 -01 -007-61 Dechlorination
5-01-007-71 Gravity sludge thickener
Wet scrubber
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
6.50x 10 -1
(7.79 x 10 •')
3.56x10'
(4.27 x 10')
5.50 x 104
(6.59 x 105)
6.67 x 104
(7.99 x 105)
3.80 x 106
(4.55 x 107)
1.60 x 103
(1.92xl04)
1.40xl04
(1.68xl05)
4.00 x 106
(4.79 x 107)
1.39xl04
(1.67xl05)
7.50 x 10'1 Ib/lb
(7.50 x 10-' kg/kg)b
2.09 x 104
(2.50 x 10s)
E
C
C
B
B
C
C
B
E
B
B
(continued)
-------
TABLE 6-22. CONTINUED
SCC Number
5-01-007-72
5-01-007-81
5-01-007-91
5-01-007-92
5-01-007-93
Source: References
Emission Source
Dissolved air floatation
thickener
Anaerobic digester
Belt filter press
Sludge centrifuge
Sludge drying bed
3 and 168.
Control Device
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Emission Factor
Ib/million gal
(kg/million liters)"
3.00 x 10 3
(3.59 x 10^)
3.08 x 10'1
(3.69 x lO'2)
5.00 x 102
(5.99 x 10'3)
2.05 x 103
(2.46 x 10-4)
2.80 x 10 3
(3.36 x 10^)
Emission Factor
Rating
B
B
B
B
B
' Factors are expressed as Ib (kg) of benzene emitted per million gal (million liters) of wastewater treated.
b Factor is expressed as Ib (kg) of benzene emitted per Ib (kg) of benzene in the wastewater influent to the process unit (emission source).
-------
Chlorine contact tanks are either uncovered or partially covered. Dechlorination
units are often enclosed in a building that vents to a scrubber. Thickeners are commonly
covered and sometimes vented to a scrubber. Anaerobic digesters are commonly closed under
a slight pressure, and the gas is sent to an internal combustion engine or boiler to produce
steam or electricity; however, some digesters may vent to the atmosphere. Belt filter presses
are commonly enclosed in a building that vents to a scrubber. Sludge centrifuges are
commonly enclosed and vented to a scrubber. Drying beds are most commonly uncovered.168
6.5.4 Regulatory Analysis
At the present, there are no Federal regulations diat apply directly to benzene air
emissions from POTWs. However, two regulations indirectly apply: the HON and the
Benzene Waste Operations NESHAP. Both of these apply directly to specific types of
industrial facilities that may generate wastewater containing benzene. Both regulations
stipulate that these facilities may comply with the treatment requirements by sending their
wastewater to an off-site treatment plant. However, the off-site plant must remove or destroy
the benzene in the wastewater to the level specified in the regulations. Further information on
the regulation can be found hi Section 4.5.4 of this document.
6.6 MUNICIPAL SOLID WASTE LANDFILLS
A municipal solid waste (MSW) landfill unit is a discrete area of land or an
excavation that receives household waste, but is not a land application unit (i.e. for receiving
sewage sludge), surface impoundment, injection well, or waste pile. An MSW landfill unit
may also receive other types of wastes, such as commercial solid waste, nonhazardous sludge,
and industrial solid waste. Benzene emissions from MSW landfills are expected to originate
from the non-household sources of MSW. The types of waste potentially accepted by MSW
landfills include:
MSW;
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• Household hazardous waste;
• Municipal sludge;
• Municipal waste combustion ash;
• Infectious waste;
• Waste tires;
• Industrial non-hazardous waste;
• Conditionally exempt small quantity generator hazardous waste;
• Construction and demolition waste;
Agricultural wastes;
• Oil and gas wastes; and
• Mining wastes.
MSW management in the United States is dominated by disposal in landfills.
Approximately 67 percent of solid waste is landfllled, 16 percent is incinerated, and 17 percent
is recycled or composted. There were an estimated 5,345 active MSW landfills in the United
States in 1992. In 1990, active landfills were receiving an estimated 130 million tons
(118 million Mg) of waste annually., with 55 to 60 percent reported as household waste and
35 to 45 percent reported as commercial waste.170
6.6.1 Process Description of MSW Landfills170
There are three major designs for municipal landfills: the area method, the
trench method, and the ramp method. They all utilize a three-step process, which includes
spreading the waste, compacting the waste, and covering the waste with soil. The area fill
method involves placing waste on the ground surface or landfill liner, spreading it in layers,
and compacting it with heavy equipment. A daily soil cover is spread over the compacted
waste. The trench method entails excavating trenches designed to receive a day's worth of
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waste. The soil from the excavation is often used for cover material and wind breaks. The
ramp method is typically employed on sloping land, where waste is spread and compacted in a
manner similar to the area method; however, the cover material obtained is generally from the
front of the working face of the filling operation. The trench and ramp methods are not
commonly used, and are not the preferred methods when liners and leachate collection systems
are utilized or required by law.
Modern landfill design often incorporates liners constructed of soil
(e.g., recompacted clay) or synthetics (e.g., high density polyethylene) or both to provide an
impermeable barrier to leachate (i.e., water that has passed through the landfill) and gas
migration from the landfill.
6.6.2 Benzene Emissions from MSW Landfills
The rate of benzene emissions from a landfill is governed by gas production and
transport mechanisms. Production mechanisms involve the production of the emission
constituent in its vapor phase through vaporization, biological decomposition, or chemical
reaction. Transport mechanisms involve the transportation of benzene in its vapor phase to the
surface of the landfill, through the air boundary layer above the landfill, and into the
atmosphere. The three major transport mechanisms that enable transport of benzene in its
vapor phase are diffusion, convection, and displacement.170
no
Uncontrolled Benzene Emissions
Uncontrolled benzene emissions from a landfill may be estimated by utilizing
the series of equations provided below. The three equations estimate the following three
variables: (1) the uncontrolled methane generation rate, (2) the uncontrolled benzene emission
rate (calculated based on the uncontrolled methane generation rate), and (3) the uncontrolled
benzene mass emission rate (calculated based on the uncontrolled benzene emission rate). As
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indicated, the second equation utilizes the product of the first equation, and the third equation
utilizes the product of the second equation.
< The uncontrolled CH4 volumetric generation rate may be estimated for
individual landfills by using a theoretical first-order kinetic model of CH4 production
developed by EPA. This model is known as the Landfill Air Emissions Estimation model, and
it can be accessed from the EPA's Control Technology Center bulletin board. The Landfill
Air Emissions Estimation model equation is as follows:
QCH4 = L0 R (e'te - e*)
where:
<;cH4 - Methane volumetric generation rate at time t, m3/yr
L0 = Methane generation potential, m3 CH4/Mg refuse
R = Average annual acceptance rate of degradable refuse during
active life, Mg/yr
e = Base log, unitless
k = Methane generation rate constant, yr1
c = Time since landfill closure, yrs (c = 0 for active landfills)
t = Tune since the initial refuse placement, yrs
Site-specific landfill information is generally available for variables R, c, and t.
When refuse acceptance rate information is scant or unknown, R can be determined by
dividing the refuse in place by the age of die landfill. Also, nondegradable refuse should be
subtracted from the mass of acceptance rate to prevent overestimation of CH4 generation. The
average annual acceptance rate should only be estimated by this method when mere is
inadequate information on the actual average acceptance rate.
Values for variables L0 and k must be estimated. Estimation of the potential
CH4 generation capacity of refuse (Lo) is generally treated as a function of the moisture and
organic content of the refuse. Estimation of the CH4 generation constant (k) is a function of a
variety of factors, including moisture, pH, temperature, and other environmental factors, and
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landfill operating conditions. Specific CH4 generation constants can be computed by use of
EPA Method 2E.
The Landfill Air Emission Estimation model uses the proposed regulatory (see
Section 6.6.4) default values for L0 and k. However, the defaults were developed for
regulatory compliance purposes. As a result, the model contains conservative L0 and k default
values in order to protect human health, to encompass a wide range of landfills, and to
encourage the use of site-specific data. Therefore, different L0 and k values may be
appropriate in estimating landfill emissions for particular landfills and for use in an emissions
inventory.
A higher k value of 0.05/yr is appropriate for areas with normal or above
normal precipitation. An average k value is 0.04/yr. For landfills with drier waste, a k value
of 0.02/yr is more appropriate. An L0 value of 125 m3/Mg (4,005 ftVton) refuse is appropriate
for most landfills. It should be emphasized that in order to comply with the proposed
regulation (see Section 6.6.4), the model defaults for k and L0 must be applied as specified in
the final rule.
Based on the CH4 volumetric generation rate calculated above, the benzene
volumetric emission rate from a landfill can be estimated by the following equation:
QBZ = 2 QCH4 * CBZ/(lxl06)
where:
QBZ = Benzene volumetric emission rate, m3/yr
QcH4 = CH4 volumetric generation rate, m3/yr (from the Landfill Air
Emission Estimation model)
CBZ = Benzene concentration in landfill gas, ppmv
2 = Multiplication factor (assumes that approximately 50 percent of
landfill gas is CH4)
Uncontrolled emission concentrations of benzene based on a landfill site's
history of co-disposal with hazardous wastes are presented in Table 6-23.3>17° An analysis of
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TABLE 6-23. SUMMARY OF UNCONTROLLED EMISSION CONCENTRATIONS OF
BENZENE FROM LANDFILLS
SCC Number
5-02-006-02
Emission Source
Landfill dump
Type of Waste Disposed
MSW co-disposed with hazardous
Emission Concentration
(ppmv)
24.99
Emission
Factor Rating
D
waste
MSW, unknown history of
co-disposal with hazardous waste
MSW only
2.25
0.37
B
D
Source: References 3 and 170.
-------
benzene emissions data based on the co-disposal history of the individual landfills from which
the concentration data were derived indicates that benzene emissions do vary with the amount
of hazardous waste co-disposed. These benzene concentrations have already been corrected for
air infiltration and can be used, when site-specific data are not available, as input parameters
(for the variable CBZ) in the above equation for estimating benzene volumetric emission rates
from landfills.
Then, based on the benzene volumetric emission rate calculated using the above
equation, the uncontrolled mass emission rate of benzene from a landfill can be estimated by
the following equation:
T n 78.113
I = QR7 *
(8.205x10-5 m3-atm/mol-°K) (1000 g) (273 + T)
where:
IBZ = Uncontrolled benzene mass emission rate, kg/yr
QBZ = Benzene volumetric emission rate, m3/yr
T = Temperature of landfill gas, °C
78.113 = Molecular weight of benzene
This equation assumes that the operating pressure of the system is approximately
1 atmosphere. If the temperature of the landfill gas is not known, a temperature of 25 °C is
recommended.
Controlled Benzene Emissions
As discussed in more detail in Section 6.6.3, emissions from landfills are
typically controlled by installing a gas collection system and destroying the collected gas
through the use of internal combustion engines, flares, or turbines. The control system for
landfills consists of two stages, and estimating controlled benzene emissions involves the
following two steps: (1) estimating the amount of benzene that is not collected by the gas
collection system, and (2) estimating the amount of collected benzene that is not destroyed by
the control device.
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The amount of benzene that is not collected by the gas collection system may be
calculated with the following equation:
TT/_ ( , Collection Efficiency}
UCBZ -\l
100 J
where:
UCBZ = Uncollected benzene mass emission rate, kg/yr
Collection Efficiency = Collection efficiency of the gas collection
system, %
IBZ = Uncontrolled benzene mass emission rate, kg/yr
If the site-specific collection efficiency cannot be determined, one may assume that a gas
collection system collects 75 percent of the benzene emitted by a landfill. Reported collection
efficiencies typically range from 60 to 85 percent, with the average of 75 percent being most
commonly used for estimation of UCBZ.
The amount of benzene that is not destroyed by the control device may be
calculated with the following equation:
( Destruction Efficiency} n TTr, ,
NDR7 = 1 - -=- * (IR7 - UCB7)
BZ I I BZ BZ'
where:
NDB2 = Non-destroyed benzene mass emission rate, kg/yr
Destruction Efficiency = Destruction efficiency of the control device, %
IBZ = Uncontrolled benzene mass emission rate, kg/yr
UCBZ = Uncollected benzene mass emissions rate, kg/yr
If the site-specific destruction efficiency of a control device cannot be determined, one may
assume the destruction efficiencies provided here. Flares have been documented to destroy
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89.5 percent of the benzene routed to the flare. Internal combustion engines have been
documented to destroy 83.8 percent of the benzene routed to the internal combustion engine.
After promulgation of standards proposed in 1991 (see Section 6.6.4), however, all control
devices utilized at both new and existing landfills may be required to reduce the
non-methanogenic organic compounds (NMOCs) in the collected gas by 98 weight percent.
Alternatively, if the control device utilized is a flare and the heat content of the
landfill gas is known, the emission factor provided in Table 6-24 may be used to calculate
non-destroyed benzene emissions.3 Additionally, if the control device is an industrial boiler,
refer to Section 7.4 for information regarding controlling benzene emissions from an industrial
boiler treating landfill gas.
After UCBZ and NDBZ have been calculated, these two variables may be added
together to calculate the total benzene mass emission rate after the control system.
6.6.3 Control Technologies for MSW Landfills170
Landfill gas collection systems are either active or passive systems. Active
collection systems provide a pressure gradient in order to extract landfill gas by use of
mechanical blowers or compressors. Passive systems allow the natural pressure gradient
created by the increase in landfill pressure from landfill gas generation to.mobilize the gas for
collection.
Landfill gas control and treatment options include (1) combustion of the landfill
gas, and (2) purification of the landfill gas. Combustion techniques include techniques that do
not recover energy (e.g., flares and thermal incinerators) and techniques that recover energy
and generate electricity from the combustion of the landfill gas (e.g., gas turbines and internal
combustion engines). Boilers can also be employed to recover energy from landfill gas hi the
form of steam. Flares involve an open combustion process that requires oxygen for
combustion; the flares can be open or enclosed. Thermal incinerators heat an organic chemical
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TABLE 6-24. CONTROLLED BENZENE EMISSION FACTOR FOR LANDFILLS
Control Emission Factor Emission
SCC Number Emission Source Device Ib/MMBtu (g/kJ)a Factor Rating
5-02-006-01 Landfill Dump Flare T.lOxlQ-6 (3.05xlQ-9)b D
Source: Reference 3.
1 Emission factor is in Ib (g) of benzene emitted per MMBtu (U) of heat input to the flare.
b Based on two tests conducted at two landfill sites.
to a high enough temperature in the presence of sufficient oxygen to oxidize the chemical to
CO2 and water. Purification techniques can also be used to process raw landfill gas to pipeline
quality natural gas by using adsorption, absorption, and membranes.
6.6.4 Regulatory Analysis170
Proposed NSPS and emission guidelines for air emissions from MSW landfills
for certain new and existing landfills were published in the Federal Register on May 30, 1991,
and promulgated March 12, 1996. The regulation requires that Best Demonstrated Technology
be used to reduce MSW landfill emissions from affected new and existing MSW landfills with
a design capacity greater than 2.8 million tons (2.5 million Mg by mass or 2.5 million cubic
meters by volume) of MSW and emitting greater than or equal to 55 tons/yr (50 Mg/yr) of
NMOCs. The MSW landfills that would be affected by the proposed NSPS would be each new
MSW landfill and each existing MSW landfill that has accepted waste since May 30, 1991, or
that has capacity available for future use. Control systems would require (1) a well-designed
and well-operated gas collection system, and (2) a control device capable of reducing NMOCs
in the collected gas by 98 weight percent.
6.7 PULP, PAPER, AND PAPERBOARD INDUSTRY
In the pulp, paper, and paperboard industry, wood pulp is chemically treated by
dissolving the lignin that binds the cellulose together and then extracting the cellulose to make
paper and paperboard. Four types of chemical wood pulping processes are practiced hi the
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United States. Kraft pulping is the most prevalent type of process, accounting for about
85 percent of pulp production. Three other pulping processes, semi-chemical, soda-mill, and
acid sulfite, account for 4, 5, and 6 percent of domestic pulp production, respectively.
Because kraft pulping is the most common type of pulping and the other processes are
relatively similar to it, kraft pulping will be the focus of this section. More information on the
other three pulping processes can be found in References 171 and 172.
The distribution of kraft pulp mills in the United States in 1993 is shown in
Table 6-25.171 Kraft pulp mills are located primarily in the southeast, whose forests provide
over 60 percent of U.S. pulp wood.
The U.S. EPA is developing benzene emission factors for pulp and papermaking
processes in conjunction with MACT standards that are under development. Please refer to the
CHIEF bulletin board for benzene emission factors that will be forthcoming from the MACT
development process. More information on the MACT effort is given in Section 6.7.2.
6.7.1 Process Description for Pulp. Paper, and Paperboard Making Processes
The key unit operations in the kraft pulp and papermaking process include:
(1) cooking and evaporation, (2) pressure knotting and screening, (3) brown stock washing,
(4) decker washing and screening, (5) oxygen delignification, (6) pulp storage, (7) chemical
recovery and causticizing, (8) co-product recovery, (9) bleaching, and (10) paper making.
Common potential emission points found in the pulp and papermaking process are listed in
Table 6-26.m Each of the key steps, along with their associated emission points, are
illustrated in the diagram of a typical Kraft pulping and recovery process (Figure 6-7) and
these are discussed below hi more detail.171 Bleaching, which is frequently used as a final step,
and papermaking are discussed at the end of this section.
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TABLE 6-25. DISTRIBUTION OF KRAFT PULP MILLS IN THE
UNITED STATES (1993)
State
Alabama
Arizona
Arkansas
California
Florida
Georgia
Idaho
Kentucky
Louisiana
Maine
Maryland
Michigan
Minnesota
Mississippi
Montana
New Hampshire
North Carolina
Ohio
Oklahoma
Oregon
Pennsylvania
South Carolina
Tennessee
Texas
Virginia
Washington
Wisconsin
Total
Kraft Pulp Mills
16
1
7
4
8
12
1
2
10
7
1
3
2
6
1
1
5
1
1
7
3
6
2
6
4
7
4
126
Source: Reference 171.
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TABLE 6-26. LIST OF COMMON POTENTIAL EMISSION POINTS WITHIN THE
KRAFT PULP AND PAPERMAKING PROCESS
Digester relief vents Washer filtrate tanks
Turpentine recovery system vents Decker
Digester blow gas vents Screen
Noncondensible gas system vents Weak black liquor storage tank
Evaporator noncondensible gas vent Recovery furnace stack
Evaporator hotwell gas vent Slaker/causticizer vents
Knotter Lime kiln stack
Brownstock or pulp washer Bleach plant vents
Washer foam tanks Papermachine vents
Source: Reference 173.
Cooking and Evaporation
The pulping or cooking process begins with the digester, which is a pressure
vessel that is used to chemically treat chips and other cellulosic fibrous materials (such as
straw, bagasse, rags, etc.) under elevated temperature and pressure to separate fibers from
each other. This digestion process frequently takes place in an aqueous chemical solution
(frequently a white liquor solution of sodium hydroxide and sodium sulfide). The digestion
process may be batch or continuous. After cooking the liquor containing the cooking
chemicals and lignin is separated from the pulp and sent to a series of evaporators for
concentration.
The entire digester and black liquor evaporator system includes (a) the outlet to
the incinerator for the low-volume-high-concentration (LVHC) gases that are commonly
collected and routed to such an incineration device, (b) chip bin exhaust vents, and (c) other
miscellaneous digester and evaporator system emission points. These systems were combined
since all kraft mills collect and incinerate digester relief gases (Vent C), digester blow tank and
accumulator gases (Vent A [continuous] and Vent B [batch process]), and evaporator
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00
ToWMtewater V^/i
Treatment Plant
or Condensate . • '
Stripper
©
Wood Chip*
7^
1
V
Cooking Liquor
©
Digester
System
Condentate Stripper (Not Shown)
May Strip Condensats or
Wattewater from Emi&ftlon
Points O, P. and/or Q
1
1
Oxygen
Dellgntftcatton
Blow Tank
To Storage
or Bleaching
ToWastewater
Treatment Plan
Condensal
0©
Crude Tall OH
To Tad
OH Storage
Note: Tha atraam numbers on the figure correspond to the discussion In the text (or
thte proceea. Lettera correspond to potential eourcee of benzene •minions.
Figure 6-7. Typical Kraft Pulp-making Process with Chemical Recovery
Source: Reference 171,
-------
condenser vents (Vent J). The gases at these emission points are assumed to be routed to the
combustion device and the benzene reduced by 98 percent.171
Deknotting and Prewash Screening
The pulp from the blow tank enters a knotter where knots (pieces of undigested
wood) are removed prior to pulp washing in order to produce a higher-quality chemical pulp
(Emission Point D).171 The pressure knotter and pre-washer screening system includes all the
equipment following the digester system (i.e., post blow tank) and preceding the first stage of
brown stock washing. There are two types of knotters typically used hi the industry, open and
pressurized. The air flow across the two types varies. Open knotters have a greater flow and,
therefore, are expected to have higher emissions than pressurized knotters. Knotter systems
typically include equipment such as knot drainer hoods, knot tanks, knot elevators, and
screened stock chests. Not every piece of equipment is necessarily vented to the atmosphere
(Emission Point D). The emission factor presented is based on the assumption of a pressurized
knotter and pre-washing screening system.
Brown Stock Wash
Pulp that has been through the blow tank and knotter is then washed with water
in the brownstock washing process. The purpose of washing is to remove.black liquor from
the pulp so as to recover the cooking chemicals sodium and sulfur and to avoid contamination
during subsequent processing steps. The brown stock washing system includes all the brown
stock washers, associated filtrate tanks, vacuum pump exhausts, and any interstage storage
chests that follow pre-washer screening. In washing, water (fresh or recycled) is used to rinse
die pulp and recover the black liquor. There are two basic types of brown stock washing
systems, the rotary vacuum drum system and the more advanced pressure or diffusion washers.
Emissions from the washing process occur as compounds entrained hi the pulp and black liquor
slurry volatilize (Emission Point E).
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The diluted or "weak" black liquor is recovered in a washer filtrate tank and
sent to the evaporator area. A washer foam tank is typically used to capture the foam
separated hi the filtrate tank. Foam is formed when soap, which is dissolved by the caustic
cooking liquors, goes through the washing process. In general, defoaming is completed in the
foam tank using centrifugal or mechanical force to break up the foamed mass. This force
allows air trapped hi the foam mass to vent to the atmosphere from the washer foam tank
(Emission Point F). The defoamed weak black liquor is routed to a weak black liquor storage
tank (Emission Point N) before it is typically piped to the evaporator area.171
Screening and Decking
Screening is performed to remove oversized particles from the pulp slurry after
washing the pulp and prior to the papermaking process. The decker is a washing and
thickening unit that follows brown stock washing and precedes oxygen delignification (if
present), bleaching (if present), or the paper machines. The decker unit is assumed to consist
of a drum and a filtrate tank, both of which are assumed to be vented to the atmosphere. The
emissions from each part of this decker unit (i.e., both the washer and the filtrate tank) fall
within the range of emissions reported for individually tested decker washers and decker
filtrate tanks and is therefore assumed to be representative.
Decker vents may be either hooded (an open space above the decker with a hood
covering the unit) or well-enclosed (tightly fitted hood around the unit, no open space except
through the hood). Hooded deckers are likely to have a much greater air flow across the
decker, and therefore are expected to have greater emissions (Emission Point G).
Oxygen Delignification
Following the screening and/or decking, delignification of pulp with oxygen
(called oxygen delignification) prior to bleaching is sometimes used. By removing more of the
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lignin from the pulp, this pretreatment step helps to reduce the amount of chemicals used by
the bleach plant.
The oxygen delignification (OD) system begins with the oxygen reactor and
associated blow tank (Emission Point H). This system includes a series of two washers and/or
presses following the oxygen reactor blow tank, each with a filtrate tank. An interstage
storage chest located between the first and second washers and/or presses is also a common
configuration.
Pulp Storage Tank
Pulp storage tanks refers to the large bulk storage tanks following OD (if
present) or brown stock washers that store the pulp that is to be routed to die bleach plant or to
the paper machines. One pulp storage tank is assumed to be present for each pulping line.
Chemical Recovery and Causticizing
The chemical recovery and causticizing area of the mill is where strong black
liquor recovered from the evaporators and concentrators is converted into white liquor for
reuse in the digesters. This system includes all the equipment associated with chemical
recovery, beginning with the recovery furnace, the smelt dissolving tanks and ending with the
white liquor clarifier.
The chemical recovery and causticizing area is an example of a mill system
where the number of pieces of equipment tested was driving the emissions. In other words, if
one mill tested all the components of the recovery loop, that mill would show higher emissions
for the causticizing area system. The causticizing area system can be broken down into the
following subsystems:
.6-i
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Recovery furnace. Strong black liquor from the multiple effect evaporators is
concentrated from 50 to about 70 percent solids either in a concentrator or in a direct contact
evaporator before being fired in a recovery furnace. The organics in the liquor provide the
energy required to both make steam and to capture the inorganic chemicals as smelt at the
bottom of the furnace.
Smelt dissolving tank. Smelt from the recovery furnace is fed into the tank
where it is dissolved by weak wash. Smelt dissolving tanks are typically equipped with a
venturi scrubber for particulate control. Weak wash from the lime mud washer is often used
as the make-up solution in the scrubber, with spent scrubbing solution flowing into the
dissolving tank.
Green liquor clarifier. Effluent from the smelt dissolving tank (green liquor)
enters a clarifier. Dregs are drained off the bottom of the clarifier, and the clarified green
liquor passes on to a slaker.
Slaker and causticizers. Green liquor from the green liquor clarifier is
convened into white liquor by adding lime in the slaker and causticizers. Emissions from the
causticizers and the slaker are typically routed to a common venturi scrubber with green liquor
or fresh mill water as the scrubbing medium.
White liquor clarifier. White liquor is clarified and the clarified white liquor is
sent to storage. The bottoms from the white liquor clarifier (lime mud) are sent to a mud
washer.
Lime mud washer system. Lime mud from the white liquor clarifier is washed
here with fresh mill water. The wash water effluent from the mud washer is termed weak
wash which is used in the smelt dissolving tank. The lime mud washer system includes the
actual washer plus all associated equipment such as dilution tanks, pressure filters, and mix
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tanks. If condensates are used as the wash water, the emissions could be much higher,
depending on the quality of the condensates.
Lime kiln. The lime kiln accepts washed lime mud and calcines it to produce
lime. This lime hi turn is fed to the slaker, and the cycle is repeated. The lime kiln is
typically equipped with a venturi scrubber using fresh mill water as the scrubbing medium for
paniculate emission control. Alternatively, particulates may be controlled by an electrostatic
precipitator (ESP).
Co-product Recovery
Turpentine and soap (tall oil) are two saleable coproducts that may be
byproducts of the pulping process. Turpentine is recovered from digester relief gases when
resinous softwoods such as pines are pulped. In general, the digester relief gases are vented to
a condenser to reduce the gas moisture content and to a cyclone separator to remove any small
wood chips or fines. Emissions are generated as turpentine and water and are separated in a
decanter. These emissions are released through the turpentine recovery system vent. Tall oils
are recovered hi a reactor, but emissions are expected to be low because the weak black liquor
has already been stripped of volatiles in the evaporation process (Vent M).171
Bleaching
Bleaching is the process of further delignifying and whitening pulp by
chemically treating it to alter the coloring matter and to impart a higher brightness.
To enhance the physical and optical qualities (whiteness and brightness) of the
pulp, one of two types of chemical bleaching is used. The first type of bleaching, called
brightening, uses selective chemicals (such as hydrogen peroxide) that destroy
chromatographic groups but do not materially attack the lignin. Brightening produces a
product with a temporary brightness (such as newspaper). In the second type (true bleaching),
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oxidizing chemicals (such as chlorine, chlorine dioxide, and sodium hypochlorite) are used to
remove residual lignin, resulting in a high-quality, stable paper pulp.171
The most common bleaching and brightening-agents are chlorine, chlorine
dioxide, hydrogen peroxide, oxygen, caustic (sodium hydroxide) and sodium hypochlorite.
Typically, the pulp is treated with each chemical in a separate stage. One example stage which
illustrates the use of one bleaching agent is shown in Figure 6-8.m Each stage includes a
tower where the bleaching occurs (Vent A). The washer (Vent B) removes the bleaching
chemicals and dissolved lignins from the pulp prior to entering the next stage. The seal tank
(Vent C) collects the washer effluent to be used as wash water in other stages or to be sewered
(VentD).171
Paper Machine
Paper machine emissions include all the emissions from the various pieces of
equipment following pulp storage and/or bleaching that are used to turn the pulp into a finished
paper product. The data show that the factor driving emissions from paper machines is paper
type (i.e., unbleached versus bleached).
Wastewater/Condensate Treatment
In addition to process vents, emissions also occur from the treatment of
wastewater or condensates generated during the making of pulp and paper (Emission
Point O).171
6,7.2 Benzene Emissions from Pulp. Paper and Papermaking Processes
EPA published MACT standards for the pulp, paperboard, and papermaking
industry on April 15, 1998.173 While the supporting documentation for these standards does
not specifically call out benzene as a major pollutant from pulp and paper mills, it
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Bleaching
Chemicals
Vent to Scrubber
or Atmosphere
Gb
Bleach Tower Plant
Pulp/Chemical Slurry
Recycled from
Next Wash Stage
Vent to Scrubber
or Atmosphere
©
Pulp and
Spent Chemicals
Vent to Scrubber
' (5)
Seal Tank
Recycle to Previous Wash Stage
or Sewer
Figure 6-8. Typical Down-flow Bleach Tower and Washer
Source: Reference 171.
6-92
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does mention benzene as being emitted from this source and as a pollutant that would be
affected by VOC reductions achieved by compliance with the standards.
Emission points may include the digester relief vents, digester blow gas vents,
brownstock or pulp washer, screen, as well as bleaching and brightening. Once washing has
occurred, it is expected that benzene would be found in the wastewater, which is recycled for
use throughout the process. Such uses of this recycled water include as a solvent for digesting
chemicals, as the pulp digesting medium, as pulp waste water, and as a diluent for screening,
cleaning, and subsequent pulp processing. Benzene emissions would then be expected from
each step hi the pulping process where this recycled wastewater is used. Note that the extent
of benzene emissions (as with any HAP) during the pulping process is a function of the level of
pulp production, type of digestion (batch or continuous), and the type of wood pulped.
6.8 SYNTHETIC GRAPHITE MANUFACTURING
Synthetic graphite is a composite of coke aggregate (filler particles), petroleum
pitch (binder carbon), and pores (generally with a porosity of 20 to 30 percent). Syndietic
graphite is a highly refractory material that has been thermally stabilized to as high as 5,400°F
(3,000°C). Graphite is a valuable structural material because it has high resistance to thermal
shock, does not melt, and possesses structural strength at temperatures well above the melting
point of most metals and alloys. Applications for synthetic graphite include the following
industries: aerospace (e.g., nose cones, motor cases, and thermal insulation), chemical (e.g.,
heat exchangers and centrifugal pumps and electrolytic anodes for die production of chlorine
and aluminum), electrical (e.g., telephone equipment products, electrodes hi fuel cells and
batteries, and contacts for circuit breakers and relays), metallurgical (e.g., electric furnace
electrodes for the production of iron and steel, furnace linings, ingot molds, and extrusion
dies), nuclear (e.g., moderators, thermal columns, and fuel elements), and miscellaneous
(e.g., motion picture projector carbons).174
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The number of facilities manufacturing synthetic graphite in the United States
was not identified.
6.8.1 Process Description for Synthetic Graphite Production
Synthetic graphite is produced from calcined petroleum coke and coal tar pitch
through a series of processes including crushing, sizing, mixing, cooling, extruding, baking,
pitch impregnation, rebaking, and graphitization. Throughout the process of thermal
conversion of organic materials to graphite, the natural chemical driving forces cause the
growth of larger and larger fused-ring aromatic systems, and ultimately result hi the formation
of the stable hexagonal carbon network of graphite. A process flow diagram of the synthetic
graphite manufacturing process is provided in Figure 6-9.174'175
Calcined petroleum coke (i.e., raw coke that has been heated to temperatures
above 2,200°F (1,200°C) to remove volatiles and shrink the coke to produce a strong, dense
particle) is crushed and screened to obtain uniform-sized fractions for the formulation of dry
ingredient. Coal tar pitch is stored in heated storage tanks and is pumped to the mixing
process, as needed, as the liquid ingredient. The dry ingredient is weighed and loaded, along
with a metered amount of coal tar pitch, into a heated mixing cylinder (heated to at least 320°F
[160°C]), where they are mixed until they form a homogeneous mixture. During the mixing
process, vapors (Vent A in Figure 6-9) are ducted to a stack where they are discharged to the
atmosphere.174-175
The heated mixture is sent to a cooling cylinder which rotates, cooling the
mixture with the aid of cooling fans to a temperature slightly above the softening point of the
binder pitch. Vapors from the cooling process (Vent B in Figure 6-9) are often vented to a PM
control device before being vented to the atmosphere.174-175
The cooled mixture is charged to a hydraulic press, then pressed through a die
to give the mixture the desired shape and size. The extruded mixture is referred to as "green
.6-94
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'
©
Mixing
Cylinder
Hot
Mix
Mixing
(Bl
i
Cooling |
Cylinder
Cooling
Cool\
Mix J~"
Hydraulic
Pratt
Extruding
Initial
Baking
ON
SO
Pitch
Working
Tank
Pra-
haalar
Autoclave
Pitch Impregnation
Rebaking
Nota: Tha atraam numbera on lha figure corratpond to tha ditcuttion In the taxi (or
thlt procatt. Lanert corratpond to potantial tourcaa of banzana'amiiilona.
Oraphltlzatlon
a.
i-
or
Figure 6-9. Process Flow Diagram for Manufacture of Synthetic Graphite
Source: Reference 174.
-------
stock." The green stock is placed in cooling ponds, where it is further cooled and awaits
shipping to the baking process.175
In general, for producing graphite with high-performance applications, the
baking process consists of three stages: initial baking, pitch impregnation, and rebaking. In
producing graphite for some lower-performance applications, the pitch impregnation step is
excluded. This baking process chemically changes the binder pitch within the green stock by
forming a permanent carbon bond between the coke particles. By using a slow heating rate,
the baking process removes most of the shrinkage hi the product associated with pyrolysis of
the pitch binder. This procedure avoids cracking during subsequent graphitization where very
fast firing rates are used. The impregnation step deposits additional coke hi the open pores of
the baked stock, thereby improving the properties of the subsequent graphite product. The
product (later referred to as "rebaked stock") is a solid, rigid body that is much harder and
stronger than the green stock.174'175
Initial baking is achieved by placing the green stock into a furnace cell (if a
recirculating furnace is used) or a can (if a sagger or pit furnace is used) and surrounding the
stock with a suitable pack media to support the stock. During the baking process, the furnace
temperature is increased incrementally (e.g., starting at 350 to 400°F [175 to 200°C] and
ending at 400 to 570°F (200 to 300 °C]). The furnace temperature varies according to the
stock. During the initial baking process, fumes (Vent C in Figure 6-9) are often vented to an
afterburner prior to discharge to the atmosphere.175
Baked stock is pre-heated hi a pre-heater to a desired temperature prior to
impregnation with pitch. Fumes from the pre-heater (Vent D hi Figure 6-9) are often vented to
an afterburner before release to the atmosphere. The pre-heated, baked stock is loaded into
autoclaves where a vacuum is pulled. Heated petroleum pitch (or coal tar) is pumped from
storage to the autoclave. Vapors from the storage tank for the heated pitch (Vent D hi
Figure 6-9) are often vented to an afterburner prior to their release to the atmosphere. The
baked stock is impregnated with pitch under increased temperature and pressure. The pitch
6-96
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impregnated stock is then stored prior to the rebaking process. Many high-performance
applications of graphite (e.g., nuclear and aerospace applications) require that the baked stock
be*multiply pitch-treated to achieve the greatest possible assurance of high performance.174-175
Rebaking is similar to initial baking. The same types of furnaces are used for
both baking and rebaking. The pitch impregnated stock is heated to higher temperatures than
the green stock (e.g., from 210°F [100°C] to 900 to 1,800°F [500 to 1,000°C]). During the
rebake process, fumes (Vent E in Figure 6-9) are often vented to an afterburner. Off-gases
from the afterburner are vented to the atmosphere.174-175
The last step in the manufacturing process is graphitization. In this step,
electricity is used to create temperatures, by resistance, high enough to cause physical and
chemical changes in the rebaked stock (the carbon atoms in the petroleum coke and pitch orient
into the graphite lattice configuration). As a result of this step, the hard-baked stock becomes
softer and machinable, the stock becomes an electrical conductor, and impurities vaporize.174'175
In the graphitization step, rebaked stock is placed hi a furnace, either
perpendicular or parallel to the direction of the current flow, depending on the type of furnace
used. Electricity is used to create temperatures in the stock exceeding 4,350°F (2,400°C), and
preferably 5,070 to 5,450°F (2,800 to 3,000°C). After graphitization, the stock (i.e.,
synthetic graphite) is stored for on-site use or shipment. Fumes from the furnace are vented to
the atmosphere (Vent F in'Figure 6-9).174-175
6.8.2 Benzene EmissionsJrom Synthetic Graphite Production175
*.
There is limited information currently available about benzene emissions from
synthetic graphite production plants. Emission factors for die mixing and cooling cylinders
(Vents A and B in Figure 6-9) are provided hi Table 6-27.175 Additionally, one emission test
report indicated that benzene is emitted from the initial baking, rebaking, and
6-97
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o\
vb
oo
TABLE 6-27. EMISSION FACTORS FOR SYNTHETIC GRAPHITE PRODUCTION
SCC Number
3-XX-XXX-XX
3-XX-XXX-XX
Description
Synthetic Graphite
Synthetic Graphite
Emissions Source
Mixing Cylinder (Vent A)
Cooling Cylinder (Vent B)
Control Device
Uncontrolled
Uncontrolled
Emission Factor
Ib/lb (g/kg)'
2.82x10^ (1.41x10*)
3.70XKT1 (1.8x10*)
Emission Factor
Rating
D
D
Source: Reference 175.
* Emission factor is Ib (g) of benzene emitted per Ib (kg) of synthetic graphite produced.
-------
pitch-impregnation processes (Vents C through E in Figure 6-9); however, emission factors
could not be developed.175
6.8.3 Control Technologies for Synthetic Graphite Production173
As discussed in Section 6.9.1, afterburners may be used to control emissions of
unburned hydrocarbons from the initial baking and rebaking furnace (Vents C and E in
Figure 6-9), as well as the preheater and heated storage tank used for the pitch impregnation
process (Vent D in Figure 6-9). Data regarding the use of afterburners in this application were
not available; however, it is likely that the afterburners would reduce benzene emissions.
Additionally, an ESP may be used to control paniculate emissions from the cooling cylinder;
however, it is unlikely that an ESP would reduce benzene emissions.
6.9 CARBON BLACK MANUFACTURE
The chemical carbon black consists of finely divided carbon produced by the
thermal decomposition of hydrocarbons hi the vapor phase, unlike coke that is produced by the
pyrolysis of solids. Carbon black is a major industrial chemical used primarily as a reinforcing
agent in rubber compounds, which accounts for over 90 percent of its use. It is used primarily
in tires (both original equipment and replacement), which accounts for over 70 percent of its
use.176 Other tire-related applications include inner tubes and retreads. Other uses include
automotive hoses and belts, wire and cable, roofing, pigment in inks and coatings and as a
plastic stabilizer.176 As of January 1994, there were 24 carbon black manufacturing facilities in
the United States. Over 75 percent of all carbon black production occurs in the States of Texas
and Louisiana (36 and 40 percent, respectively). The location of all facilities and then-
estimated annual production capacities in 1993 are provided in Table 6-28.177 The manufacture
of carbon black is of potential concern for benzene emissions because the predominantly used
production process involves the combustion of natural gas and the high-temperature pyrolysis
of aromatic liquid hydrocarbons.
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TABLE 6-28. LOCATIONS AND ANNUAL CAPACITIES OF CARBON BLACK
PRODUCERS IN 1994
Company
Cabot Corporation
Chevron Corporation
Columbian Chemicals Company
Degussa Corporation
Ebonex Corporation
General Carbon Company
Hoover Color Corporation
J.M. Huber Corporation
Sid Richardson Carbon and Gasoline
Company
Waco Corporation
TOTAL
Facility Location
Franklin, LA
Pampa,TX
Villa Platte, LA
Waverly, WV
Cedar Bayou, TX
El Dorado, AR
Moundsville, WV
North Bend, LA
Ulysses, KS
Arkansas Pass, TX
Belpre, OHa
New Iberia, LA
Melvindale, MI
Los Angeles, CA
Hiwassee, VA
Baytown, TX
Borger, TX
Orange, TX
Addis, LA
Big Springs, TX
Borger, TX
Phoenix City, AL
Ponca City, OK
Sunray, TX
Annual Capacity,
millions of pounds
(millions of kg)
260(118)
60 (27)
280(127)
180 (82)
20(9)
120 (54)
170 (77)
220(100)
85 (39)
180(82)
130 (59)
200(91)
8 (3.6)
1 (0.45)
1 (0.45)
225 (102)
175 (79)
135(61)
145 (66)
115(52)
275 (125)
60 (27)
255(116)
120(54)
3,420(1,551)
Source: Reference 177.
* Emissions of 81,000 Ib/yr (36,741 kg/yr) of benzene reported for 1992.111
Note: This listing is subject to change as market conditions change, facility ownership changes, plants are closed
down, etc. The reader should verify the existence of particular facilities by consulting current listings
and/or the plants themselves. The level of benzene emissions from any given facility is a function of
variables such as capacity, throughput, and control measures, and should be determined through direct
contacts with plant personnel.
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6.9.1 Process Description for Carbon Black Manufacture
Approximately 90 percent of all carbon black produced in the United States is
manufactured by the oil-furnace process, a schematic of which is given in Figure 6-10. The
process streams identified in Figure 6-10 are defined in Table 6-29.178-179 Generally, all
oil-furnace carbon black plants are similar in overall structure and operation. The most
pronounced differences in plants are primarily associated with the details of decomposition
furnace design and raw product processing.178
In the oil-furnace process, carbon black is produced by the pyrolysis of an
atomized liquid hydrocarbon feedstock hi a refractory-lined steel furnace. Processing
temperatures in the steel furnace range from 2,408 to 2,804°F (1,320 to 1,540°C). The heat
needed to accomplish the desired hydrocarbon decomposition reaction is supplied by the
combustion of natural gas.178
Feed materials used in the oil-furnace process consist of petroleum oil, natural
gas, and air. Also, small quantities of alkali metal salts may be added to the oil feed to control
the degree of structure of the carbon black.179 The ideal raw material for the production of
modern, high structure carbon blacks is an oil which is highly aromatic; low in sulfur,
asphaltenes and high molecular weight resins; and substantially free-of suspended ash, carbon,
and water. To provide maximum efficiency, the furnace and burner are designed to separate,
insofar as possible, die heat generating reaction from the carbon forming reaction. Thus, the
natural gas feed (Stream 2 in Figure 6-10) is burned to completion with preheated air
(Stream 3) to produce a temperature of 2,408 to 2,804°F (1,320 to 1,540°C). The reactor is
designed so that this zone of complete combustion attains a swirling motion, and the oil feed
(Stream 1), preheated to 392 to 698°F (200 to 370°C), is sprayed into the center of the zone.
Preheating is accomplished by heat exchange with die reactor effluent and/or by means of a
gas-fired heater. The oil is cracked to carbon and hydrogen with side reactions producing
carbon oxides, water, methane, acetylene and other hydrocarbon products. The heat
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o
to
ATMOSPHERIC EMISSIONS
>•»• OH. STORAGE TANK
VENT GAS
KROCESS VENT GAS
•«»> INCINERATOR STACK 6AS
.FUGITIVE EMISSIONS
PNEUMATIC SYSTEM
VENT GAS
DRYER VENT OAS
VACUUM CLEAN UP
SYSTEM VENT GAS
TO STORAGE OPTIONAL STREAM
K.
I
S3
Figure 6-10. Process Diagram for an Oil-Furnace Carbon Black Plant
Source: Reference 179.
-------
TABLE 6-29. STREAM CODES FOR THE OIL-FURNACE PROCESS
ILLUSTRATED IN FIGURE 6-10
Stream
Identification
Stream
Identification
1 Oil feed
2 Natural gas feed
3 Air to reactor
4 Quench water
5 Reactor effluent
6 Gas to oil preheater
7 Water to quench tower
8 Quench tower effluent
9 Bag filter effluent
10 Vent gas purge for dryer fuel
11 Main process vent gas
12 Vent gas to incinerator
13 Incinerator stack gas
14 Recovered carbon black
15 Carbon black to micropulverizer
16 Pneumatic conveyor system
17 Cyclone vent gas recycle
18 Cyclone vent gas
19 Pneumatic system vent gas
20 Carbon black from bag filter
21 Carbon black from cyclone
22 Surge bin vent
23 Carbon black to pelletizer
24 Water to pelletizer
25 Pelletizer effluent
26 Dryer direct heat source vent
27 Dryer bag filter vent
28 Carbon black from dryer bag filter
29 Dryer indirect heat source vent
30 Hot gases to dryer
31 Dried carbon black
32 Screened carbon black
33 Carbon black recycle
34 Storage bin vent gas
35 Bagging system vent gas
36 Vacuum cleanup system vent gas
37 Dryer vent gas
38 Fugitive emissions
39 Oil storage tank vent gas
Source: Reference 178.
6-103
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transfer from the hot combustion gases to the atomized oil is enhanced by highly turbulent flow
hi the reactor.179
The reactor converts 35 to 65 percent of the feedstock carbon content to carbon
black, depending on the feed composition and the grade of black being produced. The yields
are lower for the smaller particle size grades of black. Variables that can be adjusted to
produce a given grade of black include operating temperature, fuel concentration, space
velocity in the reaction zone, and reactor geometry (which influences the degree of turbulence
in the reactor). A typical set of reactor operating conditions for high abrasion furnace carbon
black is given hi Table 6-30.179
The hot combustion gases and suspended carbon black are cooled to about
1004°F (540°C) by a direct water spray hi the quench area, which is located near the reactor
outlet. The reactor effluent (Stream 5 in Figure 6-10) is further cooled by heat exchange hi the
air and oil preheaters. It is then sent to a quench tower where direct water sprays finally
reduce the stream temperature to 446°F (230°C).
Carbon black is recovered from the reactor effluent stream by means of a bag
filter unit. The raw carbon black collected in the bag filter unit must be further processed to
become a marketable product. After passing through the pulverizer, the black has a bulk
density of 1.50 to 3.68 Ib/ft3 (24 to 59 kg/m3), and it is too fluffy and dusty to be transported.
It is therefore converted into pellets or beads with a bulk density of 6.06 to 10.68 Ib/ft3 (97 to
171 kg/m3). In this form, it is dust-free and sufficiently compacted for shipment.
6.9.2 Benzene Emissions from Carbon Black Manufacture
Although no emission factors are readily available for benzene from carbon
black manufacture, one carbon black manufacturer with annual capacity of 130 million pounds
(59 million kg) using the oil-furnace process reported benzene emissions of 81,000 Ib/yr
(36,741 kg/yr) for 1992, which translates to 6.23X10"4 Ib (2.83X10"4 kg) benzene per Ib (kg)
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TABLE 6-30. TYPICAL OPERATING CONDITIONS FOR CARBON BLACK
MANUFACTURE (HIGH ABRASION FURNACE)
Parameter Value
Rate of oil feed 27 ft3/hr (0.76 nrVhr)
Preheat temperature of oil 550°F (288°C)
Rate of ak feed 234,944 tf/hr (6,653 m3/hr)
Rate of natural gas feed 22,001 tf/hr (623 m3/hr)
Furnace temperature hi reaction zone 2,552°F (1,400°C)
Rate of carbon black production 860 Ib/hr (390 kg/hr)
Yield of black (based on carbon hi oil feed) 60 percent
Source: Reference 179.
carbon black produced. No regulations applicable to carbon black manufacture were identified
that would affect benzene emissions. The emission factor is given in Table 6-31.111
TABLE 6-31. EMISSION FACTOR FOR CARBON BLACK MANUFACTURE
Emission Factor Emission
SCC Number Description (Ib benzene/lb carbon black) Factor Rating
Oil Furnace Process 6.23XJO"4
Source: Reference 111.
6.10 RAYON-BASED CARBON FIBER MANUFACTURE
Rayon-based carbon fibers are used primarily in cloth for aerospace
applications, including phenolic unpregnated heat shields and hi carbon-carbon composites for
missile parts and aircraft brakes.180 Due to then: high carbon content, these fibers remain
stable at very high temperatures.
A list of U.S. producers of rayon-based carbon fibers is given hi Table 6-32.177
. 6-105
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TABLE 6-32. RAYON-BASED CARBON FIBER MANUFACTURERS
Manufacturer Location
Amoco Performance Products, Inc. Greenville, SC
BP Chemicals (Hitco) Inc. Gardena, CA
Fibers and Materials Division
Polycarbon, Inc. Valencia, CA
Source: Reference 177.
6.10.1 Process Description for the Rayon-Based Carbon Fiber Manufacturing Industry
There are three steps hi the production process of rayon-based carbon cloth:
• Preparation and heat treating;
• Carbonization; and
• High heat treatment (optional).180
In die preparation and heat treating step, die rayon-based clodi is heated at 390 to 660°F (200
to 350°C). Water is driven off (50 to 60 percent weight loss) during this step to form a char
with thermal stability. In the carbonization step, the cloth is heated to 1,800 to 3,600°F
(1,000 to 2,000°C), where additional weight is lost and the beginnings of a carbon layer
structure is formed. To produce a high strength rayon-based fiber, a third step is needed.
The cloth is stretched and heat treated at temperatures near 5,400°F (3,000°C).180
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6.10.2 Benzene Emissions from the Ravon-Based Carbon Fiber Manufacturing Industry
Benzene emissions occur from the exhaust stack of the carbon fabric dryer,
which is used in carbonization of the heat treated rayon.180 An emission factor for this source
is given in Table 6-33.181
6.10.3 Controls and Regulatory Analysis
No controls or regulations were identified for the rayon-based carbon fiber
manufacturing industry.
6.11 ALUMINUM CASTING
The aluminum casting industry produces aluminum products, such as aluminum
parts for marine outboard motors, from cast molds. Sections 6.11.1 through 6.12.3 describe
the aluminum casting process, benzene emissions resulting from this process, and air emission
control devices utilized in the process to reduce benzene emissions.
The number of aluminum casting facilities in the United States was not
identified.
6.11.1 Process Description for Aluminum Casting Facilities
A common method for making the mold for aluminum motor parts is to utilize
polystyrene foam patterns or "positives" of the desired metal part. The basic principle of the
casting operation involves the replacement of the polystyrene pattern held within a sand mold
with molten metal to form the metal casting. Figure 6-11 presents a simplified flow diagram
for a typical aluminum casting facility utilizing polystyrene patterns.
6-107
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TABLE 6-33. EMISSION FACTOR FOR RAYON-BASED CARBON MANUFACTURE
Emission Factor Emission Factor
SCC Number Description Emissions Source Control Device Ib/lb (g/kg)a Rating
3-64-920-000 Rayon-based Caibon Carbon Fabric Uncontrolled 7.17x107 (7.17X1Q-4) B
Fibers Dryer
Source: Reference 181.
* Emission factor is Ib (g) of benzene emitted per Ib (kg) of rayon-based carbon produced.
-------
©
Casting
S'lakeout
Sand
©
Sand
Screening
••p
Note: The stream numbers on the figure correspond to the discussion In the text for this
process. Letters correspond to potential sources of benzene emissions.
O
o
Figure 6-11. Flow Diagram of a Typical Aluminum Casting Facility
-------
The aluminum casting process essentially consists of four stages: (1) mold
assembly, (2) casting (i.e., mold pouring, mold cooling, and cast extraction), (3) cast cleaning
and finishing (i.e., casting shakeout, cast cooling, and cast cleaning and finishing), and
(4) sand handling (i.e., sand screening and cleaning). A polystyrene foam pattern is first
coated with a thin layer of ceramic material for stability. The polystyrene foam pattern is
placed within a metal flask. Sand is poured into the flask, surrounding and covering the
pattern. The sand is compacted around the polystyrene pattern to form the mold. Low levels
of benzene may be emitted from the sand fill operation, depending on the residue of organic
matter remaining on the sand recycled from the casting shakeout process step. These
emissions may be collected in a fume hood and vented to the atmosphere (Vent A hi
Figure 6-11).
The metal flask is moved to the pouring station where molten aluminum is
poured into the mold. The foam vaporizes as it is displaced by the molten aluminum, which
fiiii ihc cavity left withhi the :>anu mold. A majority of the foam vapors migrate into the sand
and remain trapped in the sand until the casting shakeout process. Some of the vapors are
released during the mold pouring event. These vapors are collected in a fume hood and vented
to the atmosphere (Vent B in Figure 6-11).
The poured molds are conveyed within the flasks along a cooling conveyor,
allowing the aluminum casting to harden. The cooling process may result in benzene
emissions (as depicted as Vent C in Figure 6-11).
When the casting has formed and cooled sufficiently, the cast is extracted from
the metal flask. Benzene may be emitted from this process step. The emissions are captured
and vented to the atmosphere (Vent D hi Figure 6-11).
The casting and flask are moved to the casting shake-out area, where sand used
in forming the mold is dumped from the flask and removed from the casting by utilizing
vibration to loosen the compacted sand. The collected sand (including pieces of molding) are
6-110
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shaken, breaking up the sand mold. The majority of benzene emissions occur during this step.
Vapors released by breaking the sand molds are captured and either treated with a catalytic
incinerator or released to the atmosphere (Vent E in Figure 6-11).
The shaken sand is sent through a screen, then transported to a cleaning process
for removal of remaining residue, such as a fluidized bed. Benzene emissions may be emitted
during these process steps (depicted as Vents F and G in Figure 6-11). The cleaned sand is
then transported to storage for reuse in the process.
Meanwhile, the casting, which has just undergone shakeout, is sent through a
series of cooling, cleaning, and finishing steps to produce a final product. Benzene may be
emitted from these process steps. The final products are stored to await shipping off-site.
6.11.2 Benzene Emissions From Aluminum Metal Casting
Benzene emissions from aluminum metal casting are produced by the
vaporization of the polystyrene foam patterns used to form the molds, resulting from contact of
the foam with molten aluminum. As described in Section 6.11.1, the polystyrene foam vapors
migrate into the sand inside the mold, becoming trapped in the sand mold. As a result, most
benzene emissions from the process are associated with sand handling activities, such as
casting shake-out and sand screening. However, additional benzene is emitted from the casting
steps, including mold pouring, mold cooling, and cast extraction.
Two test reports from two aluminum casting facilities were used to develop
benzene emission factors.182'183 Both facilities utilized polystyrene foam patterns in their
casting operations. One facility was equipped with a catalytic incinerator on its casting
shakeout operation and a fabric filter on its sand cleaning operation (utilizing a fluidized bed
for sand cleaning).183 The other facility was equipped with fabric filters on its mold assembly
operation (i.e., filling the flask with sand), cast extraction, casting shakeout, and sand
screening operations.182
6-111
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General facility benzene emissions were measured at the two facilities. For one
facility, general facility emissions consisted of emissions from the mold assembly, cast
extraction, casting shakeout, sand screening, and sand storage operations, all of which were
controlled by fabric filters.182 For the other facility, general-facility emissions consisted of
emissions from the mold assembly, mold pouring, cast extraction, casting shakeout, and sand
cleaning operations, and only the cleaning operation was controlled with a fabric filter.183
Additionally, benzene emissions from the casting shakeout operation were measured both
before and after the catalytic incinerator, yielding a benzene control efficiency of 89 percent.183
The emission factors associated with these emission data are shown in Table 6-34.l81
6.11.3 Control Technologies for Aluminum Casting Operations
Fabric filters are most commonly utilized for controlling emissions from
aluminum casting operations; however, these control devices are not utilized for controlling
benzene emissions, hm are rather used to control fugitive dust emissions from sand handling
The only control device identified for controlling benzene emissions is a catalytic incinerator.
As specified in Section 6.12.2, it has been demonstrated that catalytic incinerators achieve
89 percent reduction in benzene emissions.
No regulations were identified that control emissions of benzene from aluminum
casting operations. However, a MACT standard for control of HAPs from secondary
aluminum facilities is currently underway.
6.12 ASPHALT ROOFING MANUFACTURING
The asphaltic material that is obtained toward the end of the process of
fractional distillation of crude oil is mainly used as asphalt paving concrete (discussed in
Section 7.9) and for asphalt roofing. The asphalt roofing manufacturing process and the
emissions associated with its manufacture are described hi this section.
6-112
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TABLR 6-34. EMISSION FACTORS FOR ALUMINUM CASTING
SCC Number
3-04-001-99
3-04-001-14
Description
Secondary Metals-
Secondary Aluminum- Not
Classified
Secondary Metals-
Secondary Aluminum-
Pnnrinp/f!astinp
Emissions
General Facility
(Vents A, D, E,
General Facility
(Vents A, B, D,
Source
F, and H)
E, and G)
Casting Shakeout Operation
Control Device
Uncontrolled
Uncontrolled
( atalytic Incinerator
Uncontrolled
Emission Factor
Ib/ton (kg/Mg)'
7.08x10 2 (3.54x10 2)
7.47xl02 (3.73xl02)
6.09x10° (3.45x10°)
5.48x10° (2.74xl02)
Emission Factor
D
D
D
D
Rating
Source: Reference 181.
* Emission factor is Ib (kg) of benzene emitted per ton (Mg) of molten aluminum poured.
u>
-------
In 1992, there were 98 asphalt roofing manufacturing plants operating in the
United States. A list of all current facilities, as identified by the Asphalt Roofing
Manufacturers Association, is provided hi Table 6-35.m Total national production hi 1993 of
asphalt roofing materials (saturated felts) was estimated at 557,487 tons (505,749 Mg).184
States containing a relatively significant number of roofing plants include California (14),
Texas (14), Ohio (6), and Alabama (5). These four states contain approximately 40 percent of
the total number of roofing facilities. The majority of all plants nationwide are located in
urban as opposed to rural areas.
6.12.1 Process Description
The production of asphalt roofing materials is common owing to the widespread
usage of these materials in the United States. The asphalt roofing industry manufactures
asphalt-Saturated felt rolls, shingles, roll roofing with mineral granules on the surface, and
smooth roll roofing, which may contain a small amount of mineral dust or mica on the surface.
Most of these products are used in roof construction, but small quantities are used in walls and
other building applications.185
The asphaltic material derived from crude oil and used to make asphalt roofing
products is also called asphalt flux. The handling and storing of asphalt flux is a potential
source of benzene emissions. Asphalt is normally delivered to an asphalt roofing plant in bulk
by pipeline, tanker truck, or railcar. Bulk asphalt delivered hi liquid form may range in
temperature from 200 to 400° F (93 to 204 °C), depending on the type of asphalt and local
practice.186-188
With bulk liquid asphalt, the most common method of unloading is to couple a
flexible pipe to the tanker and pump the asphalt directly into the appropriate storage tanks.
The tanker cover is partially open during the transfer. Because this is a closed system, the
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TABLE 6-35. ASPHALT ROOFING MANUFACTURERS
Company
Roofine Plant Location
Allied-Signal Incorporated
Bird Incorported
The Celotex Corporation
Certainteed Corporation
Elk Corportion of America
Fields Corporation
GAP Building Materials, Inc.
Gate Roofing Manufacturing, Inc.
Georgia-Pacific Corporation
Detroit, MI
Fairfiel'd, AL
Ironton, OH
Norwood, MA
Camden, AR
Fremont, CA
Birmingham, AL
Goldsboro, NC
Houston, TX
Lockland, OH
Perth Amboy, NJ
San Antonio, TX
Los Angeles, CA
Memphis, TN
Shakopee, MN
Oxford, NC
Milan, OH
Ennis, TX
Tuscaloosa, AL
Kent, WA
Tacoma, WA
Baltimore, MD
Dallas, TX
Erie, PA
Fontana, CA
Millis, MA
Minneapolis, MN
Mobile, AL
Mount Vernon, IN
Savannah, GA
Tampa, FL
Green Cove Springs, FL
Ardmore, OK
Daingerfield, TX
Franklin, OH
Hampton, GA
Quakertown, PA
(continued)
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TABLE 6-35. CONTINUED
Company
Roofing Plant Location
Globe Building Materials
GS Roofing Products Company, Inc.
Herbert Malarkey Roofing Company
IKO Chicago Incorporated
IKO Production Incorporated
Kopners Industries. Incorporated
Leatherback Industries
Lunday-Thagard Company
Manville Sales Corporation
Neste Oil Services
Whiting, IN
St. Paul, MN
Chester, WV
Charleston, SC
Ennis, TX
Little Rock, AR
Martinez, CA
Peachtree City, GA
Portland, OR
Shreveport, LA
Wilmington, CA
Portland, OR
Chicago, IL
Franklin, OH
Wilmington, DE
Birmingham. AL
Chicago, IL
Follensbee, WV
Houston, TX
Alburquerque, NM
Hollister, CA
South Gate, CA
Fort Worth, TX
Pittsburg, CA
Savannah, GA
Waukegan, IL
Belton, TX
Calexico, CA
Fresno, CA
Houston, TX
Long Beach, CA
Pittsburg, CA
Salt Lake City, UT
San Diego. CA
(continued)
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TABLE 6-35. CONTINUED
Comcanv
Roofing Plant Location
Owens-Corning Fiberglas Corporation
PABCO Roofing Products
TAMKO Asphalt Products, Incorporated
TARCO, Incorporated
U.S. Intec, Incorporated
Atlanta, GA
Brookville, IN
Compton, CA
Denver, CO
Detroit, MI
Houston, TX
Irving, TX
Jacksonville, FL
Jessup, MD
Kearny, NJ
Medina, OH
Memphis, TN
Minneapolis, MN
Morehead City, NC
Oklahoma City, OK
Portland, OR
Richmond, CA
Tacoma, WA
Dallas, TX
Frederick, MD
Joplin, MO
Phillipsburg, KS
Tuscaloosa, AL
North Little Rock, AR
Belton, TX
Corvallis, OR
Monroe, GA
Source: Reference 184
.6-117
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only potential sources of emissions are the tanker and the storage tanks. The magnitude of the
emissions from the tanker is at least partially dependent on how far the cover is opened.
Another unloading procedure, of which there are numerous variations, is to
pump the hot asphalt into a large open runnel that is connected to a surge tank. From the surge
tanks, the asphalt is pumped directly into storage tanks. Emission sources under the surge tank
configuration are the tanker, the interface between the tanker and the surge tank, the surge
tank, and the storage tanks. The quantity of emissions depends on the asphalt's temperature
and characteristics.
After delivery, asphalt flux is usually stored at 124 to 174°F (51 to 79°C),
although storage temperatures of up to 450°F (232°C) have been noted. The lower
temperatures are usually maintained with steam coils in the tanks. Oil- or gas-fired preheaters
are used to maintain the asphalt flux at temperatures above 200°F (93°C).18M88
Asphalt is transferred within a roofing plant by closed pipeline. Barring leaks,
the only potential emissions sources are at the end-points of the pipes. These end-points are
the storage tanks, the asphalt heaters (if not the closed tube type), and the air-blowing stills.
Asphalt flux is used to make two roofing grades of asphalt: saturant and
coating. Saturant and coating asphalts are primarily distinguished by the differences in their
softening points. The softening point of saturant asphalts is between 104 to 165°F (40 and
74°C); coating asphalts soften at about 230°F (110°C). These softening points are achieved
by "blowing" hot asphalt flux, that is, by blowing air through tanks of hot asphalt flux.
The configuration of a typical air-blowing operation is shown hi Figure 6-12.185
This operation consists primarily of a blowing still, which is a tank with a sparger fitted near
its base. The purpose of the sparger is to increase contact between the blowing air and the
asphalt. Air is forced through holes in the sparger into a tank of hot (400 to 470 °F [204 to
243 °C]) asphalt flux. The air rises through the asphalt and initiates an exothermic oxidation
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\
ASPHALT
FLUX
\
T
I ASPHALT HEATER
VENT TO
CONTROL OR A
ATMOSPHERE
VENT TO
ATMOSPHERE
HEATER
ASPHALT FLUX
STORAGE TANK
KNOCKOUTBOX
OR CYCLONE
AIR, WATER VAPOR, OIL,
VOC's. AND PM
BLOWING
STILL
CONTAINING
ASPHALT
r~~
A A A
AIR, WTER VAPOR
,
VOC's, AND PM
RECOVERED OIL
AIR BLOWER
->. BLOWN ASPHALT
Figure 6-12. Asphalt Blowing Process Flow Diagram
Source: Reference 185.
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reaction. Oxidizing the asphalt has the effect of raising its softening temperature, reducing
penetration, and modifying other characteristics. Inorganic salts such as ferric chloride (FeCl3)
may be used as catalysts added to the asphalt flux during air blowing to better facilitate these
transformations.185
The tune required for air blowing of asphalt depends on a number of factors
including die characteristics of the asphalt flux, the characteristics desired for the finished
product, the reaction temperature, the type of still used, the air injection rate, and die
efficiency with which the air entering the still is dispersed throughout the asphalt. Blowing
times may vary in duration from 30 minutes to 12 hours, with typical times from 1 to
4.5 hours.185-186
Asphalt blowing is a highly temperature-dependent process because the rate of
oxidation increases rapidly with increases in temperature. Asphalt is preheated to 400 to
471TF (2U4 to 243 "C) before blowing is initiated to ensure that the oxidation process will start
an acceptable rate. Conversion does take place at lower temperatures but is much slower.
Because of the exothermic nature of the reaction, the asphalt temperature rises as blowing
proceeds. This, in turn, further increases the reaction rate. Asphalt temperature is normally
kept at about 500°F (260 °C) during blowing by spraying water onto the surface of the asphalt,
although external cooling may also be used to remove the heat of reaction. The allowable
upper limit to the reaction temperature is dictated by safety considerations, with the maximum
temperature of the asphalt usually kept at least 50°F (28 °C) below the flash point of the asphalt
being blown.186
The design and location of the sparger in the blowing still governs how much of
the asphalt surface area is physically contacted by the injected air, and the vertical height of the
still determines die tune span of this contact. Vertical stills, because of their greater head
(asphalt height), require less air flow for the same amount of asphalt-air contact. Both vertical
and horizontal stills are used for asphalt blowing, but in new construction, the vertical type is
preferred by the industry because of the increased asphalt-air contact and consequent reduction
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in blowing times.186 Also, asphalt losses from vertical stills are reported to be less than those
from horizontal stills. All recent blowing still installations- have been of the vertical type.
Asphalt blowing can be either a batch process or a continuous operation;
however, the majority of facilities use a batch process. Asphalt flux is sometimes blown by
the oil refiner or asphalt processor to meet the roofing manufacturer's specifications. Many
roofing manufacturers, however, purchase the flux and carry out their own blowing.
Blown asphalt (saturant and coating asphalt) is used to produce asphalt felt and
coated asphalt roofing and siding products in the processes depicted in Figures 6-13 and
6-14.185 The processes are identical up to the point where the material is to be coated. A roll
of felt is installed on the felt reel and unwound onto a dry floating looper. The dry floating
looper provides a reservoir of felt material to match the intermittent operation of the felt rqller
to the continuous operation of the line. Felt is unwound from the roll at a faster rate than is
requncu u_y LUC line, vvuii die excess being stoieu iii die ui^ loopci. The flow of fell to die line
and the tension on the material is kept constant by raising the top set of rollers and increasing
looper capacity. The opposite action occurs when a new roll is being put on the felt reel and
spliced in, and the felt supply ceases temporarily. There are no benzene emissions generated
in this processing step.186
Following the dry looper, the felt enters the saturator, where moisture is driven
out and the felt fibers and intervening spaces are filled with saturant asphalt. (If a fiberglass
mat web is used instead of felt, the saturation step and the subsequent drying-in process are
bypassed.) The saturator also contains a looper arrangement, which is almost totally
submerged in a tank of asphalt maintained at a temperature of 450 to 500 °F (232 to 260 °C).
The absorbed asphalt increases the sheet or web weight by about 150 percent. At some plants,
the felt is sprayed on one side with asphalt to drive out the moisture prior to dipping. This
approach reportedly results in higher benzene emissions than does use of the dip process
alone.186 The saturator is a significant benzene emissions source within the asphalt roofing
process.
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VENT TO CONTROL
EQUIPMENT
SATURATOR ENCLOSURE-i
FLOATING LOOPER
.PAPER FELT
FEED ROLL
VENT TO CONTROL EQUIPMENT
OR ATMOSPHERE
BURNER
SATURATOR DIP
SECTION GATES
ROLL WINDER
FOR ASPHALT
FELT
Figure 6-13. Asphalt-Saturated Felt Manufacturing Process
Source: Reference 185.
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TO CONTROL
EQUIPMENT
RAIL
CAR TANK
TRUCK
GRANULES AND SAND
STORAGE
I\\\\\V\\\\\\\\
"\ 4 ROER
W^4-- HEATER
VENTTO SCREW liiiiiiiiiiiiii
CONTROL CONVEYOR
EQUIPMENT
©XoN.
Pi
SEAL DOWN
APPLICATOR L>T| USE TANK
Figure 6-14. Organic Shingle and Roll Manufacturing Process Flow Diagram
Source: Reference 185.
.6-123
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The saturated felt then passes through drying-in drums and onto the wet looper,
sometimes called the hot looper. The drying-in drums press surface saturant into the felt.
Depending on the required final product, additional saturant may also be added at this point.
The amount of absorption depends on the viscosity of the asphalt and the length of time the
asphalt remains fluid. The wet looper increases absorption by providing time for the saturant
asphalt to penetrate the felt. The wet looper operation has been shown to be a significant
source of organic paniculate emissions within the asphalt roofing process; however, the
portion that is benzene has not been defined.186-187
If saturated felt is being produced, the sheet passes directly to the cool-down
section. For surfaced roofing products, however, the saturated felt is carried to the coater
station, where a stabilized asphalt coating is applied to both the top and bottom surfaces.
Stabilized coating contains a mineral stabilizer and a harder, more viscous coating asphalt that
has a higher souening point, than saturani asphalt. The coating asphalt and mineral stabilizer
are mixed in approximately equal proportions. The mineral stabilizer may consist of finely
divided lime, silica, slate dust, dolomite, or other mineral materials.
The weight of the finished product is controlled by the amount of coating used.
The coater rollers can be moved closer together to reduce the amount of coating applied to the
felt, or separated to increase it. Many modern plants are equipped with automatic scales that
weigh the sheets in the process of manufacture and warn the coater operator when the product
is running under or over specifications. The coater is a significant emissions source within the
roofing production process. It releases asphalt fumes containing organics, some of which may
be benzene compounds.186'187
The function of the coater-mixer is to mix coating asphalt and a mineral
stabilizer in approximately equal proportions. The stabilized asphalt is then piped to the
coating pan. The asphalt is piped in at about 450 to 500°F (232 to 260°C), and the mineral
stabilizer is delivered by screw conveyor. There is often a preheater immediately ahead of the
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coater-mixer to dry and preheat the material before it is fed into the coater-mixer. This
eliminates moisture problems and also helps to maintain the temperature above 320°F (160°C)
in the coater-mixer. The coater-mixer is usually covered or enclosed, with an exhaust pipe for
the air displaced by (or carried with) the incoming materials: The coater-mixer is viewed as a
potential source of benzene emissions, but not a significant one.186-187
The next step hi the production of coated roofing products is the application of
mineral surfacing. The surfacing section of the roofing line usually consists of a
multi-compartmented granule hopper, two parting agent hoppers, and two large press rollers.
The hoppers are fed through flexible hoses from one or more machine bins above the line.
These machine bins provide temporary storage and are sometimes called surge bins. The
granule hopper drops colored granules from its various compartments onto the top surface of
the moving sheet of coated felt hi the sequence necessary to produce the desired color pattern
on the roofing. This step is not required for smooth-surfaced products.186
Parting agents such as talc and sand (or some combination thereof) are applied
to the top and back surfaces of the coated sheet from parting agent hoppers. These hoppers are
usually of an open-top, slot-type design, slightly longer than the coated sheet is wide, with a
screw arrangement for distributing the parting agent uniformly throughout its length. The first
hopper is positioned between the granule hopper and the first large press roller, and 8 to
12 inches (0.2 to 0.3 m) above the sheet. It drops a generous amount of parting agent onto the
top surface of the coated sheet and slightly over each edge. Collectors are often placed at the
edges of the sheet to pick up this overspray, which is then recycled to the parting agent
machine bin by open screw conveyor and bucket elevator. The second parting agent hopper is
located between the rollers and dusts the back side of the coated sheet. Because of the steep
angle of the sheet at this point, the average fall distance from the hopper to the sheet is usually
somewhat greater than on the top side, and more of die material falls off the sheet.186
In a second technique used to apply backing agent to the back side of a coated
sheet, a hinged trough holds the backing material against the coated sheet and only material
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that will adhere to the sheet is picked up. When the roofing line is not operating, the trough is
tipped back so that no parting agent will escape past its lower lip.
Immediately after application of the surfacing material, the sheet passes through
the cool-down section. Here the sheet is cooled rapidly by passing it around water-cooled
rollers in an abbreviated looper arrangement. Usually, water is also sprayed on the surfaces of
the sheet to speed the cooling process. The cool-down section is not a source of benzene
emissions.
Following cooling, self-sealing coated sheets usually have an asphalt seal-down
strip applied. The strip is applied by a roller, which is partially submerged in a pan of hot
sealant asphalt. The pan is typically covered to minimize fugitive emissions. No seal-down
strip is applied to standard shingle or roll-goods products. Some products are also texturized
at this point by passing the sheet over an embossing roll that imparts a pattern to the surface of
The cooling process for both asphalt felt and coated sheets is completed in the
next processing station, known as the finish looper. In the finish looper, sheets are allowed to
cool and dry gradually. Secondly, the finish looper provides line storage to match the
continuous operation of the line to the intermittent operation of the roll winder. It also allows
time for quick repairs or adjustments to die shingle cutter and stacker during continuous line
operation or, conversely, allows cutting and packaging to continue when the line is down for
repair. Usually, this part of the process is enclosed to keep the final cooling process from
progressing too rapidly. Sometimes, in cold weather, heated air is also used to retard cooling.
The finish looper is not viewed as a source of benzene emissions.186
Following finishing, asphalt felt to be used in roll goods is wound on a mandrel,
cut to the proper length, and packaged. When shingles are being made, die material from the
finish looper is fed into the shingle-cutting machine. After the shingles have been cut, they are
6-126
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moved by roller conveyor to manual or automatic packaging equipment. They are then stacked
on pallets and transferred by forklift to storage areas or waiting trucks.186
6.12.2 Benzene Emissions from Asphalt Roofing Manufacture
The primary benzene emission sources associated with asphalt roofing are the
asphalt air-blowing stills (and associated oil knockout boxes) and the felt saturators.186 An
emission factor for benzene emissions from the blowing stills or saturators is given in
Table 6-36.189 Additional potential benzene emission sources may include the wet looper, the
coater-mixer, the felt coaler, the seal-down stripper, and air-blown asphalt storage tanks.
Minor fugitive emissions are also possible from asphalt flux and blown asphalt handling and
transfer operations.18^188-190
Process selection and control of process parameters have been promoted to
minimize uncontrolled emissions, including benzene, from asphalt air-blowing stills, asphalt
saturators, wet loopers, and coaters. Process controls include the use of:184
• Dip saturators, rather than spray or spray-dip saturators;
Vertical stills, rather than horizontal stills;
• Asphalts that inherently produce low emissions;
• Higher-flash-point asphalts;
• Reduced temperatures in the asphalt saturant pan;
• Reduced asphalt storage temperatures; and
• Lower asphalt-blowing temperatures.
Dip saturators have been installed for most new asphalt roofing line installations
in recent years, and this trend is expected to continue. Recent asphalt blowing still
installations have been almost exclusively of the vertical type because of its higher efficiency
and lower emissions. Vertical stills occupy less space and require no heating during oxidizing
6-127
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TABLE 6-36. EMISSION FACTOR FOR ASPHALT ROOFING MANUFACTURE
SCC Emission Factor Emission Factor
Number Description Emissions Sourc e Control Device Ib/ton (kg/Mg)a Rating
3-05-001-01 Petroleum Industry - Asphalt Blowing Stills or Uncontrolled 52 (26) E
Roofing - Asphalt Blowing - Saturators
Saturant
Source: Reference 189.
1 Emission factor is in Ib (kg) of benzene emitted per ton (Mg) of asphalt roofing produced.
to
oo
-------
(if the temperature of the incoming flux is above 400°F [204°C]). Vertical stills are expected
to be used in new installations equipped with stills and in most retrofit situations.186
Asphalt fluxes with lower flash points and softening points tend to have higher
emissions of organics because these fluxes generally have been less severely cracked and
contain more low-boiling fractions. Many of these light ends can be emitted during blowing.
Limiting the minimum softening and flash points of asphalt flux should reduce the amount of
benzene-containing fumes generated during blowing because less blowing is required to
produce a saturant or coating asphalt. Saturant and coating asphalts with high softening points
should reduce benzene emissions from felt saturation and coating operations. However,
producing the higher softening point asphalt flux requires more blowing, which increases
uncontrolled emissions from the blowing operation.186
Although these process-oriented emissions control measures are useful,
emissions capture equipment anu aaa-on emissions control equipment are also necessary in
asphalt roofing material production facilities. The capture of potential benzene emissions from
asphalt blowing stills, asphalt storage tanks, asphalt tank truck unloading, and the coater-mixer
can and is being achieved in the industry by the use of enclosure systems around the
emissions-producing operations. The enclosures are maintained under negative pressure, and
the contained emissions are ducted to control devices.186 Potential emissions from the
saturator, wet looper, and coater are generally collected by a single enclosure by a canopy type
hood or an enclosure/hood combination.
No regulations were identified to control benzene emissions from hot-mix
asphalt plants.
6.13 CONSUMER PRODUCTS/BUILDING SUPPLIES
This section covers benzene emissions from the application and use of consumer
products rather than from the manufacture of such products. Because the types of consumer
6-129
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products to which benzene emissions are attributed are so extensive, no list of manufacturers is
presented here.
Benzene emissions from the use of consumer products and building supplies
have been reported in the literature. One indoor air quality data base for organic compounds,
shows that indoor benzene levels have been measured in residences, commercial buildings,
hospitals, schools, and office buildings. Substantiated sources of these benzene emissions were
attributed to tobacco smoke, adhesives (including epoxy resins and latex caulks), spot cleaners,
paint removers, particle board, foam insulation, inks, photo film, auto exhaust, and wood
stain.191-192 Although benzene emissions were detected from these consumer sources, no
specific benzene emission factors were identified. In addition to these consumer sources,
detergents have been identified as another possible source of benzene emissions.191
In another report, aromatic hydrocarbons (most likely including benzene) were
listed as a constituent in certain automotive detailing and cleaning products, including
body-cleaning compounds and engine cleaners/degreasers/parts cleaners. 'However, no
specific emission levels were given.192
Naphtha (CAS number 8030-30-6) is a mixture of a small percentage of
benzene, toluene, xylene, and higher homologs derived from coal tar by fractional distillation.
Among its applications, naphtha is used as thinner in paints and varnishes and as a solvent in
rubber cement.106 Because naphtha contains a small percentage of benzene, some benzene
emissions would be expected from these products. However, no qualifiable benzene emissions
from naphtha-containing products were identified.
The main control for reducing benzene emissions from consumer products is
reformulation, such as substituting water or lower-VOC-emitting alternatives.192
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The federal government and several states are currently working on regulations
for the benzene (or VOC) content of consumer products. Consumer products is a very diverse
category and the products are used in a variety of applications.193
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SECTION 7.0
EMISSIONS FROM COMBUSTION SOURCES
The following stationary point and area combustion source categories have been
identified as sources of benzene emissions: medical waste incinerators (MWIs), sewage sludge
incinerators (SSIs), hazardous waste incinerators, external combustion sources (e.g., utility
boilers, industrial boilers, and residential stoves and furnaces), internal combustion sources,
secondary lead smelters, iron and steel foundries, portland cement kilns, hot-mix asphalt
plants, and open burning (of biomass, tires, and agricultural plastic). For each combustion
auuicc uau,£uij , Luc IGiluVt iii£ iliiGnZuuiOH IS pIO'v iuCd ITi tuC SCCtlOIlS uCiOWl (j._/ a uUCi
characterization of the U.S. population, (2) the process description, (3) benzene emissions
characteristics, and (4) control technologies and techniques for reducing benzene emissions. In
some cases, the current Federal regulations applicable to the source category are discussed.
7.1 MEDICAL WASTE INCINERATORS
MWIs burn wastes produced by hospitals, veterinary facilities, crematories, and
medical research facilities. These wastes include both infectious ("red bag" and pathological)
medical wastes and non-infectious, general housekeeping wastes. The primary purposes of
MWIs are to (1) render the waste innocuous, (2) reduce the volume and mass of the waste, and
(3) provide waste-to-energy conversion. The total number and capacity of MWIs in the United
States is unknown; however, it is estimated that 90 percent of the 6,872 hospitals (where the
majority of MWIs are located) in the nation have some type of on-site incinerator, if only a
small unit for incinerating special or pathological waste.194 The document entitled Locating
and Estimating Air Toxic Emissions From Sources of Medical Waste Incinerators, contains a
7-1
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more detailed characterization of the MWI industry, including a partial list of the U.S. MWI
population.
Three main types of incinerators are used for medical waste incineration:
controlled-air, excess-air, and rotary kiln. Of the incinerators identified, the majority
(> 95 percent) are controlled-air units. A small percentage (< 2 percent) are excess-air. Less
than 1 percent were identified as rotary kiln. The rotary kiln units tend to be larger, and
typically are equipped with air pollution control devices. Approximately 2 percent of the total
population identified were found to be equipped widi air pollution control devices.195
7.1.1 Process Description: Medical Waste Incinerators195
Controlled-Air Incinerators
Coniroiied-air incineration is ihe most widely used MWI technology and it now
dominates the market for new systems at hospitals and similar medical facilities. This
technology is also known as starved-air incineration, two-stage incineration, and modular
combustion. Figure 7-1 presents a schematic diagram of a typical controlled-air unit.195
Combustion of waste in controlled-air incinerators occurs in two stages. In the
first stage, waste is fed into the primary, or lower, combustion chamber, which is operated
with less than the stoichiometric amount of air required for combustion. Combustion air enters
the primary chamber from beneath the incinerator hearth (below the burning bed of waste).
This air is called primary or underfire air. In the primary (starved-air) chamber, the low air-
to-fuel ratio dries and facilitates volatilization of the waste, and most of the residual carbon in
the ash burns. At these conditions, combustion gas temperatures are relatively low (1,400 to
l,800°F[760to980°C]).
In the second stage, excess air is added to the volatile gases formed in the
primary chamber to complete combustion. Secondary chamber temperatures are higher than
7-2
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Carbon Dioxide,
— Water Vapor
and Excess
Oxygen and Nitrogen
to Atmosphere
Air
Main Burner for
Minimum Combustion
Temperature
Air
Volatile Content
is Burned in
Upper Chamber
Excess Air
Condition
Starved-Air
Condition in
Lower Chamber
Controlled
Underfire Air
for Suming
Down Waste
Figure 7-1. Controlled-Air Incinerator
Source: Reference 195.
. 7-3
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primary chamber temperatures-typically 1,800 to 2,000°F (980 to 1,095°C). Depending on
the heating value and moisture content of the waste, additional heat may be needed. This can
be provided by auxiliary burners located at the entrance to the secondary (upper) chamber to
maintain desired temperatures.
Waste feed capacities for controlled-air incinerators range from about 75 to
6,500 Ib/hour (0.6 to 50 kg/min) (at an assumed fuel heating value of 8,500 Btu/lb
[19,700 kJ/kg]). Waste feed and ash removal can be manual or automatic, depending on the
unit size and options purchased. Throughput capacities for lower heating value wastes may be
higher because feed capacities are limited by primary chamber heat release rates. Heat release
rates for controlled-air incinerators typically range from 15,000 to 25,000 Btu/hr-ft3
(430,000 to 710,000 kJ/hr-m3).
Because of the low air addition rates in the primary chamber and corresponding
io\v flue gdi velocities (and turbulence), the amount of solids entrained in the gases leaving the
primary chamber is low. Therefore, the majority of controlled-air incinerators do not have
add-on gas cleaning devices.
Excess-Air Incinerators
Excess-air incinerators are typically small modular units. They are also referred
to as batch incinerators, multiple-chamber incinerators, and "retort" incinerators. Excess-air
incinerators are typically a compact cube with a series of internal chambers and baffles.
Although they can be operated continuously, they are usually operated in a batch mode.
Figure 7-2 presents a schematic for an excess-air unit.195 Typically, waste is
manually fed into the combustion chamber. The charging door is then closed and an
afterburner is ignited to bring the secondary chamber to a target temperature (typically 1,600
to 1,800°F [870 to 980°C]). When the target temperature is reached, the primary chamber
burner ignites. The waste is dried, ignited, and combusted by heat provided by the primary
7-4
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Flame Port
Stack
Charging
Door
Igniti
Chamber
Hearth
Secondary
Air Ports
Secondary
X Burner Port
Mixing
Chamber
First
Underneath Port
Secondary
Combustion
Chamber
\
Mixing
Chamber Flame Port
Side View
Cleanout
Doors
Charging Door
Hearth
Primary
Burner Port
Secondary
Underneath Port
Figure 7-2. Excess-Air Incinerator
o
CO
o
-------
chamber burner, as well as by radiant heat from the chamber walls. Moisture and volatile
components in the waste are vaporized and pass (along with combustion gases) out of the
primary chamber and through a flame port that connects the primary chamber to the secondary
or mixing chamber.
Secondary air is added through the flame port and is mixed with the volatile
components in the secondary chamber. Burners are also installed in the secondary chamber to
maintain adequate temperatures for combustion of volatile gases. Gases exiting the secondary
chamber are directed to the incinerator stack or to a control device. When the waste is
consumed, the primary burner shuts off. Typically, the afterburner shuts off after a set time.
After the chamber cools, ash is manually removed from the primary chamber floor and a new
charge of waste can be added.
Incinerators designed to burn general hospital waste operate at excess air levels
of up TO 300 percent If'only pathological wastes are combusted, excess air level* nea^
100 percent are more common. The lower excess air helps maintain higher chamber
temperature when burning high-moisture waste. Waste feed capacities for excess-air
incinerators are usually 500 Ib/hr (3.8 kg/min) or less.
Rotary Kiln Incinerators
Rotary kiln incinerators, like the other types, are designed with a primary
chamber where the waste is heated and volatilized and a secondary chamber where combustion
of the volatile fraction is completed. The primary chamber consists of a slightly inclined,
rotating kiln in which waste materials migrate from the feed end to the ash discharge end. The
waste throughput rate is controlled by adjusting the rate of kiln rotation and the angle of
inclination. Combustion air enters the primary chamber through a port. An auxiliary burner
is generally used to start combustion and maintain desired combustion temperatures. Both the
primary and secondary chambers are usually lined with acid-resistant refractory brick. Refer
to Figure 7-9 of this chapter for a schematic diagram of a typical rotary kiln incinerator. In
7-6
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Figure 7-9, the piece of equipment referred to as the "afterburner" is the equivalent of the
"secondary chamber" referred to in this section.
Volatiles and combustion gases pass from the primary chamber to the secondary
chamber. The secondary chamber operates at excess air. Combustion of the volatiles is
completed in the secondary chamber. Because of the turbulent motion of the waste in the
primary chamber, solids burnout rates and paniculate entrainment hi the flue gas are higher for
rotary kiln incinerators than for other incinerator designs. As a result, rotary kiln incinerators
generally have add-on gas cleaning devices.
7.1.2 Benzene Emissions From Medical Waste Incinerators
There is limited information currently available on benzene emissions from
MWIs. One emission factor for benzene emissions is provided in Table 7-1.196 This factor
rcpicbeuii uciu.cue cim;»aiuiu> uuiiug toiuLu^iiuii of uolL general hospital wastes and
pathological wastes.
7.1.3 Control Technologies for Medical Waste Incinerators
Most control of air emissions of organic compounds is achieved by promoting
complete combustion by following good combustion practice (GCP). In general, the
conditions of GCP are as follows:194
• Uniform wastefeed;
• Adequate supply and good air distribution in the incinerator;
Sufficiently high incinerator gas temperatures (> 1,500°F [>815°CJ);
• Good mixing of combustion gas and air in all zones;
• Minimization of PM entrainment into the flue gas leaving the incinerator;
and
7-7
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TABLE 7-1. EMISSION FACTOR FOR MEDICAL WASTE INCINERATION
Emission Factor
SCC Emissions Source Control Device Ib/ton (kg/Mg)' Factor Rating
5-02-005-05 Incinerator Uncontrolled 4.92 x 10'3 D
(2.46 x IP'3)
Source: Reference 196.
1 Emission factor is in Ib (kg) of benzene emitted per ton (Mg) of medical waste incinerated.
oo
-------
• Temperature control of the gas entering the air pollution control device
to 450°F (230°C) or less.
Failure to achieve complete combustion of organic materials evolved from the
waste can result in emissions of a variety of organic compounds. The products of incomplete
combustion (PICs) range from low-molecular-weight hydrocarbons (e.g., methane, ethane, or
benzene) to high-molecular-weight organic compounds (e.g., dioxins/furans). In general,
adequate oxygen, temperature, residence tune, and turbulence will minimize emissions of most
organics.
Control of organics may be partially achieved by using acid gas and PM control
devices. To date, most MWIs have operated without add-on air pollution control devices. A
small percentage (approximately 2 percent) of MWIs do use ah- pollution control devices, most
frequently wet scrubbers and fabric filters. Fabric filters provide mainly PM control. Other
PM control technologies include venruri scrubbers and electrostatic precipitators (ESPs). In
addition to wet scrubbing, dry sorbent injection and spray dryer absorbers have also been used
for acid gas (i.e., hydrogen chloride [HC1] and sulfur dioxide [SOJ) control. Because it is not
documented that acid gas/PM control devices provide reduction in benzene emissions from
MWTs, further discussion of these types of control devices is not provided in this section.
Locating and Estimating Air Toxic Emissions From Sources of Medical Waste Incinerators,194
contains a more detailed description of the acid gas/PM air pollution control devices utilized
for MWIs, including schematic diagrams.
7.1.4 Regulatory Analysis
Air emissions from MWIs are not currently regulated by Federal standards.
However, Section 129 of the CAA requires that standards be established for new and existing
MWIs. Standards for MWIs were proposed under Section 129 of the CAA on
February 27, 1995 (38 FR 10654). Section 129 requires that the standards include emission
limits for HC1, SO2, and CO, among other pollutants. Section 129 also specifies that the
standards may require monitoring of surrogate parameters (e.g., flue gas temperature). Thus,
. 7-9
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the standards may require GCP, which would likely result in benzene emissions reduction.
Additionally, the standards may require acid gas/PM control device requirements, which may
result in some benzene emissions reduction.
7.2 SEWAGE SLUDGE INCINERATORS
There are approximately 170 sewage sludge incineration (SSI) plants operating
in the United States. The three main types of SSIs are: multiple-hearth furnaces (MHF),
fluidized-bed combustors (FBC), and electric infrared incinerators. Some sludge is co-fired
with municipal solid waste in combustors, based on refuse combustion technology. Refuse
co-fired with sludge in combustors based on sludge incinerating technology is limited to MHFs
only.197
Over 80 percent of the identified operating sludge incinerators are of the
multiple-hearth design. About 15 percent are FBCs and 3 percent are electric infrared
incinerators. The remaining combustors co-fire refuse with sludge. Most sludge incinerators
are located in the Eastern United States, although there are a significant number on the West
Coast. New York has the largest number of facilities, with 33. Pennsylvania and Michigan
have the next largest number of facilities, with 21 and 19 sites, respectively.197'198 Locating
and Estimating Air Toxics Emissions for Sewage Sludge Incinerators contains a diagram
showing the geographic distribution of the existing population.198
The three main types of sewage sludge incinerators are described hi the
following sections. Single hearth cyclone, rotary kiln, wet air oxidation, and co-incineration
are also briefly discussed.
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7.2.1 Process Description: Sewage Sludge Incinerators197'198
Multiple-Hearth Furnaces
A cross-sectional diagram of a typical MHF is shown in Figure 7-3.198 The
basic MHF is a vertically oriented cylinder. The outer shell is constructed of steel, lined with
refractory, and surrounds a series of horizontal refractory hearths. A hollow cast-iron rotating
shaft runs through the center of the hearths. Cooling air is introduced into the shaft, which
extend above the hearths. Attached to the central shaft are the rabble arms, which extend
above the hearths. Each rabble arm is equipped with a number of teeth approximately 6 inches
in length and spaced about 10 inches apart. The teeth are shaped to rake the sludge in a spiral
motion, alternating in direction from the outside in to the inside out, between hearths. Burners
are located in the sidewalls of the hearths to provide auxiliary heat.
In riiGs; MIIIX partially dewatered sludge is fed onto the perimeter of the top
hearth. The rabble arms move the sludge through the incinerator by raking the sludge toward
the center shaft, where it drops through holes located at the center of the hearth. In the next
hearth, the sludge is raked hi the opposite direction. This process is repeated in all of the
subsequent hearths. The effect of the rabble motion is to break up solid material to allow
better surface contact with heat and oxygen. A sludge depth of about 1 inch is maintained in
each hearth at the design sludge flow rate.
Scum may also be fed to one or more hearths of the incinerator. Scum is the
material that floats on wastewater. It is generally composed of vegetable and mineral oils,
grease, hair, waxes, fats, and other materials that will float. Scum may be removed from
many treatment units, including pre-aeration tanks, skimming tanks, and sedimentation tanks.
Quantities of scum are generally small compared to those of other wastewater solids.
Ambient air is first ducted through the central shaft and its associated rabble
arms. A portion or all of this air is then taken from the top of the shaft and recirculated into
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COOLING AIR
DISCHARGE
LZ^xDAMPER
SLUDGE -i
tr^MA
1 /ci=ni
AUXILIARY
AIR PORTS
RABBLE ARM
2 OR 4 PER
HEARTH
BURNERS
SUPPLEMENTAL
FUEL
COMBUSTION AIR
SHAFT COOLING
AIR RETURN
SOLIDS FLOW
DROP HOLES
o.
g
n
Figure 7-3. Cross Section of a Multiple Hearth Furnace
Source: Reference 198.
7-12
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the lower-most hearth as preheated combustion air. Shaft cooling air that is not circulated back
into the furnace is ducted into the stack downstream of the air pollution control devices. The
combustion air flows upward through the drop holes hi the hearths, countercurrent to the flow
of the sludge, before being exhausted from the top hearth. Air enters the bottom to cool the
ash. Provisions are usually made to inject ambient air directly into the middle hearths as well.
Overall, an MHF can be divided into three zones. The upper hearth comprises
the drying zone, where most of the moisture in the sludge is evaporated. The temperature hi
the drying zone is typically between 800 and 1,400°F (425 and 760°C). Sludge combustion
occurs in the middle hearth (second zone) as the temperature is increased to 1,100 to 1,700°F
(600 to 930 °C). The combustion zone can be further subdivided into the upper-middle hearth,
where the volatile gases and solids are burned, and the lower-middle hearth, where most of the
fixed carbon is combusted. The third zone, made up of the lower-most hearth, is the cooling
zone. In this zone, the ash is cooled as its heat is transferred to the incoming combustion air.
Under normal operating conditions, 50 to 100 percent excess air must be added
to an MHF in order to ensure complete combustion of the sludge. Besides enhancing contact
between fuel and oxygen hi the furnace, these relatively high rates of excess air are necessary
to compensate for normal variations in both the organic characteristics of the sludge feed and
the rate at which it enters the incinerator. When the supply of excess air is inadequate, only
partial oxidation of the carbon will occur, with a resultant increase in emissions of CO, soot,
and hydrocarbons. Too much excess air, on the other hand, can cause increased entrainment
of paniculate and unnecessarily high auxiliary fuel consumption.
Fluidized-Bed Combustors
Figure 7-4 shows a cross-sectional diagram of an FBC.198 FBCs consist of a
vertically oriented outer shell constructed of steel and lined with refractory. Tuyeres (nozzles
designed to deliver blasts of air) are located at the base of the furnace within a refractory-lined
grid. A bed of sand, approximately 2.5 feet (0.75 meters) thick, rests upon the grid. Two
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Exhaust and Ash
Thermocouple
Sludge
Inlet
Pressure Tap
Sight
Glass
Burner
Tuyeres
Fuel Gun
Pressure Tap
Fluidizing
Air Inlet
TT — '
M
Keiraaory
Arch
J
_, Windbox P
^1
Startup
Preheat
Burner
for Hot
Windbox
Figure 7-4. Cross Section of a Fluidized Bed Furnace
Source: Reference 198.
7-14
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general configurations can be distinguished on the basis of how the fluidizing air is injected
into the furnace. In the "hot windbox" design, the combustion air is first preheated by passing
through a heat exchanger, where heat is recovered from the hot flue gases. Alternatively,
ambient air can be injected directly into the furnace from a cold windbox.
Partially dewatered sludge is fed into the lower portion of the furnace. Air
injected through the tuyeres at a pressure of 3 to 5 pounds per square inch gauge (20 to
35 kilopascals), simultaneously fluidizes the bed of hot sand and the incoming sludge.
Temperatures of 1,400 to 1,700°F (750 to 925°C) are maintained in the bed. As the sludge
burns, fine ash particles are carried out the top of the furnace. Some sand is also removed hi
the air stream and must be replaced at regular intervals.
Combustion of the sludge occurs in two zones. Within the sand bed itself (the
first zone), evaporation of the water and pyrolysis of the organic materials occur nearly
simultaneously as tne temperature 01 tne sludge is rapidly raised. In the freeboard area (ihe
second zone), the remaining free carbon and combustible gases are burned. The second zone
functions essentially as an afterburner.
Fluidization achieves nearly ideal mixing between the sludge and the combustion
air, and the turbulence facilitates the transfer of heat from the hot sand to the sludge. The
most noticeable impact of the better burning atmosphere provided by an FBC is seen hi the
limited amount of excess air required for complete combustion of the sludge. Typically, FBCs
can achieve complete combustion with 20 to 50 percent excess ah", about half the excess air
required by MHFs. As a consequence, FBCs generally have lower fuel requirements
compared to MHFs.
Electric Infrared Incinerators
Electric infrared incinerators consist of a horizontally oriented, insulated
furnace. A woven wire belt conveyor extends the length of the furnace and infrared heating
7-15
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elements are located in the roof above the conveyor belt. Combustion air is preheated by the
flue gases and is injected into the discharge end of the furnace. Electric infrared incinerators
consist of a number of prefabricated modules that can be linked together to provide the
necessary furnace length. A cross-section of an electric furnace is shown hi Figure 7-5.198
The dewatered sludge cake is conveyed into one end of the incinerator. An
internal roller mechanism levels the sludge into a continuous layer approximately 1 inch thick
across the width of the belt. The sludge is sequentially dried and then burned as it moves
beneath the infrared heating elements. Ash is discharged into a hopper at the opposite end of
the furnace. The preheated combustion air enters the furnace above the ash hopper and is
further heated by the outgoing ash. The direction of air flow is countercurrent to the
movement of the sludge along the conveyor. Exhaust gases leave the furnace at the feed end.
Excess air rates vary from 20 to 70 percent.
Other Technologies
A number of other technologies have been used for incineration of sewage
sludge, including cyclonic reactors, rotary kilns, and wet oxidation reactors. These processes
are not in widespread use in the United States and are discussed only briefly.
The cyclonic reactor is designed for small-capacity applications and consists of a
vertical cylindrical chamber that is lined with refractory. Preheated combustion air is
introduced into the chamber tangentially at high velocities. The sludge is sprayed radially
toward the hot refractory walls. Combustion is rapid, such that the residence tune of the
sludge in the chamber is on the order of 10 seconds. The ash is removed with the flue gases.
Rotary kilns are also generally used for small capacity applications. The kiln is
inclined slightly from the horizontal plane, with the upper end receiving both the sludge feed
and the combustion air. A burner is located at the lower end of the kiln. The circumference of
7-16
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BELT
DRIVE-
ROLLER
- LEVELER
GAS
EXHAUST
RADIANT
INFRARED
HEATING
ELEMENTS
WOVEN WIRE
CONTINUOUS IELT
COOLING
AIR
RABBLING I
DEVICE 1
COOLING
AIR
00000 00000000000
QUO
o o o o o
o u o
o o o
COMBUSTION
AIR
Figure 7-5. Cross Section of an Electric Infrared Furnace
Source: Reference 198.
-------
the kiln rotates at a speed of about 6 inches per second. Ash is deposited into a hopper located
below the burner.
The wet oxidation process is not strictly one of incineration; it instead utilizes
oxidation at elevated temperature and pressure in the presence of water (flameless combustion).
Thickened sludge, at about 6-percent solids, is first ground and mixed with a stoichiometric
amount of compressed air. The sludge/air mixture is then circulated through a series of heat
exchangers before entering a pressurized reactor. The temperature of the reactor is held
between 350 and 600°F (175 and 315°C). The pressure is normally 1,000 to 1,800 pounds
per square inch grade (7,000 to 12,500 kilopascals). Steam is usually used for auxiliary heat.
The water and resulting ash are circulated out the reactor and are separated in a tank or lagoon.
The liquid phase is recycled to the treatment plant. Off-gases must be treated to eliminate
odors.
Co-Incineration and Co-Firing
Wastewater treatment plant sludge generally has a high water content and, hi
some cases, fairly high levels of inert materials. As a result, the net fuel value of sludge is
often low. If sludge is combined with other combustible materials in a co-incineration scheme,
a furnace feed can be created that has both a low water concentration and a heat value high
enough to sustain combustion with little or no supplemental fuel. Virtually any material that
can be burned can be combined with sludge in a co-incineration process. Common materials
for co-incineration are coal, municipal solid waste (MSW), wood waste, and agricultural
waste.
There are two basic approaches to combusting sludge with MSW: (1) use of
MSW combustion technology by adding dewatered or dried sludge to the MSW combustion
unit, and (2) use of sludge combustion technology by adding processed MSW as a
supplemental fuel to the sludge furnace. With the latter, MSW is processed by removing
noncombustibles, shredding, air classifying, and screening. Waste that is more finely
7-18
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processed is less likely to cause problems such as severe erosion of the hearths, poor
temperature control, and refractory failures.
7,2.2 Benzene Emissions from Sewage Sludge Incineration
Emission factors associated with MHFs and FBCs are provided in Table 7-2.197
This table provides a comparison of benzene emissions based on no control and control with
various PM control devices and an afterburner. However, these emission factors do not reflect
the effect of increased operating temperature on reducing benzene emissions. As discussed in
Section 7.2.3, increasing the combustion temperature facilitates more complete combustion of
organics, resulting in lower benzene emissions. It was not possible in this study to compare
the combustor operating conditions of all SSIs for which emissions test data were available to
develop the emission factors in Table 7-2.197 As a result, it was not possible to reflect the
effect of combustion temperature on benzene emissions. The emission factors for MHFs
presented in laoie 1-2. are based on test data of combusiors operated at a variety of combustion
temperatures in the primary combustion hearths (1,100 to 1,700°F [600 to" 930°C]).
Using emissions test data for one sewage sludge combustion facility, it was
possible to demonstrate the benzene emission reduction achieved with the practice of increasing
operating temperature versus utilizing an afterburner or a scrubber. This comparison is
provided in Table 7-3.'" The emissions test data for the one facility used to develop the
emission factors presented in Table 7-3 are also averaged into the emission factors presented in
Table 7-2.
7.2.3 Control Technologies for Sewage Sludge Incinerators197-198
Control of benzene emissions from SSIs is achieved primarily by promoting
complete combustion by following GCP. The general conditions of GCP are summarized in
Section 7.1.3. As with MWIs, failure to achieve complete combustion of organic materials
evolved from the waste can result in emissions of a variety of organic compounds, including
7-19
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TABLE 7-2. SUMMARY OF EMISSION FACTORS FOR SEWAGE SLUDGE INCINERATION
SCC Emission Source Control Device
5-01-005-15 MHF Uncontrolled
Cyclone/venruri
scrubbers
Venturi scrubber
Venruri/impingement
scmbbers
Venruri/impingement
scrubbers and
afterburner
5-01-005-16 FBC Venruri/impingement
scrubbers
Emission Factor
Ib/ton (g/Mg)'
1.2x 10 2
(5.8)
7.0 x 10"1
(3.5 x 10 ')
2.8 x 102
d-4)
1.3xlO'2
(6.3)
3.4 x 10 4
(1.7x 10-')
4.0 x 104
(2.0 x 10 ')
Factor Rating
D
E
E
D
E
E
Source: Reference 197.
* Emission factors are in Ib (g) of benzene emitted per ton (Mg) of dry sludge feed.
MHF = multiple hearth furnace.
FBC = fluidized bed combustor.
-------
TABLE 7-3. SUMMARY OF EMISSION FACTORS FOR ONE SEWAGE SLUDGE INCINERATION
FACILITY UTILIZING A MULTIPLE HEARTH FURNACE
Emission
SCC Source Control Device/Method
5-01-005-15 Incinerator Uncontrolled"
Venturi/Impingement Scrubbers'"
Elevated Operating Temperature0
Elevated Operating Temperature/ Afterburner0
Elevated Operating Temperature/
Afterburner/ Venturi and Impingement
Scrubbers0
Emission
Factor
Ib/ton (g/Mg)a
1.73x10-'
(8.61)
1.34xlO'2
(6.66)
2.65 x 10'3
(1.32)
1.41 x 10 3
(7.02 x 10 -')
3.35 x 10-4
(1.67x10-')
Efficiency
Percent
—
23
85
92
98
Factor
Rating
D
D
D
D
D
Source: Reference 199.
1 Emission factors are in Ib (g) of benzene emitted per ton (Mg) of dry sludge feed.
b Furnace operated at "normal" operating temperature of, on average, 1350°F (730°C).
c Furnace operated at a higher than "normal" operating temperature of, on average, 1600°F (870°C).
-------
benzene, and adequate oxygen, temperature, residence time, and turbulence will generally
minimize emissions of most organics.
Many SSIs have greater variability in their organic emissions than do other
waste incinerators because, on average, sewage sludge has a high moisture content and the
moisture content can vary widely during operation.200
Additional reductions in benzene emissions may be achieved by utilizing PM
control devices; however, it is not always the case that a PM control device will reduce
benzene emissions. In some cases, the incinerator operating conditions (e.g., combustion
temperature and temperature at the air pollution control device) may affect the performance of
scrubbers.199 The types of existing SSI PM controls range from low-pressure-drop spray
towers and wet cyclones to higher-pressure-drop venturi scrubbers and venturi/impingement
tray scrubber combinations. A few ESPs and baghouses are employed, primarily where sludge
is co-fired with MSW.
The most widely used PM control device applied to an MHF is the impingement
tray scrubber. Older units use the tray scrubber alone and combination venturi/impingement
tray scrubbers are widely applied to newer MHFs and some FBCs. Most electric incinerators
and some FBCs use venturi scrubbers only. As indicated in Table 7-3, venturi/impingement
tray scrubbers have been demonstrated to reduce benzene emissions from SSIs.
A schematic diagram of a typical combination venturi/impingement tray
scrubber is presented in Figure 7-6.198 Hot gas exits the incinerator and enters the precooling
or quench section of the scrubber. Spray nozzles in the quench section cool the incoming gas,
and the quenched gas then enters the venturi section of the control device.
Venturi water is usually pumped into an inlet weir above the quencher. The
venturi water enters the scrubber above the throat, completely flooding the throat. Turbulence
created by high gas velocity in the converging throat section deflects some of the water
7-22
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Ga* Exit to Induced Draft
Fan and Stack
Water
Incinerator Exhaust
Weir Box
Quencher
Section
Hooded Elbow
Flooded Perforated
Imping&meni Trayi
Mist
Eliminator
Water Irom
Treatment Overflow
Impingement Tray
Scrubber
Figure 7-6. Venturi/Impingement Tray Scrabber
Source: Reference 198.
7-23
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traveling down the throat into the gas stream. PM carried along with the gas stream impacts
on these water particles and on the water wall. As the scrubber water and flue gas leave the
venturi section, they pass into the flooded elbow, where the stream velocity decreases,
allowing the water and gas to separate. By restricting the throat area within the venturi, the
linear gas velocity is increased and the pressure drop is subsequently increased, increasing PM
removal efficiency.
At the base of the flooded elbow, the gas stream passes through a connecting
duct to the base of the impingement tray tower. Gas velocity is further reduced upon entry to
the tower as the gas stream passes upward through the perforated impingement trays. Water
usually enters the trays from inlet ports on opposite sides and flows across the tray. As gas
passes through each perforation in the tray, it creates a jet that bubbles up the water and further
entrains solid particles. At the top of the tower is a mist eliminator to reduce the carryover of
water droplets in the stack effluent gas. The impingement section can contain from one to four
trays.
In the case of MHFs, afterburners may be utilized to achieve additional
reduction of organic emissions, including benzene. MHFs produce more benzene emissions
because they are designed with countercurrent air flow. Because sludge is usually fed into the
top of the furnace, hot air and wet sludge feed are contacted at the top of the furnace, such that
any compounds distilled from the solids are immediately vented from the furnace at
temperatures too low to completely destroy them.
Utilization of an afterburner provides a second opportunity for these unburned
hydrocarbons to be fully combusted, m afterburning, furnace exhaust gases are ducted to a
chamber, where they are mixed with supplemental fuel and ah- and completely combusted.
Additionally, some incinerators have the flexibility to allow sludge to be fed to a lower hearth,
thus allowing the upper hearth(s) to function essentially as an afterburner.
7-24
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7.2.4 Regulatory Analysis
Prior to 1993, organic emissions from SSIs were not regulated. On
February 19, 1993, Part 503 was added to Subchapter O in Chapter I of Title 40 of the CFR,
establishing standards for use or disposal of sewage sludge. Subpart E of Part 503 regulates
emissions of total hydrocarbons (THC) from the incineration of SSIs and applies to all SSIs.
The THC limit of 100 ppm (measured as a monthly average) is a surrogate for all organic
compounds, including benzene. In establishing a standard for organic emissions, EPA had
considered establishing a standard for 14 individual organic compounds, including benzene;
however, it was concluded that the individual organic pollutants were not significant enough a
factor in sewage sludge to warrant requiring individual pollutant limits. Furthermore, based
on a long-term demonstration of heated flame ionization detection systems monitoring organic
emissions from SSIs, it was concluded that there is an excellent correlation between THC
emission levels and organic pollutant emission levels.
The THC limit established in Part 503 is an operational standard that would, in
general, not require the addition of control devices to existing incinerators, but would require
incinerators to adopt good operating practices on a continuous basis. It is expected that FBCs
and MHFs will have no difficulty meeting the standard.200 To ensure the adoption of GCP, the
standard requires continuous THC monitoring using a flame ionization detection system,
continuous monitoring of the moisture content in the exit gas, and continuous monitoring of
combustion temperature.
7.3 HAZARDOUS WASTE INCINERATION
Hazardous waste is produced in the form of liquids (e.g., waste oils,
halogenated and nonhalogenated solvents, other organic liquids, and pesticides/ herbicides)
and sludges and solids (e.g., halogenated and nonhalogenated sludges and solids, dye and paint
sludges, resins, and latex). Based on a 1986 study, total annual hazardous waste generation in
the United States was approximately 292 million tons (265 million metric tons).201 Only a
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small fraction of the waste (< 1 percent) was incinerated. The major types of hazardous waste
streams incinerated were spent nonhalogenated solvents and corrosive and reactive wastes
contaminated with organics. Together, these accounted for 44 percent of the waste
incinerated. Other prominent wastes included hydrocyanic acid, acrylonitrile bottoms, and
nonlisted ignitable wastes.
Hazardous waste can be thermally destroyed through burning under oxidative
conditions in incineration systems designed specifically for this purpose and in various types of
industrial kilns, boilers, and furnaces. The primary purpose of a hazardous waste incinerator
is the destruction of the waste; some systems include energy recovery devices. An estimated
1.9 million tons (1.7 million Mg) of hazardous waste were disposed of in incinerators in
1981.201 The primary purpose of industrial kilns, boilers, or furnaces is to produce a
commercially viable product such as cement, lime, or steam. An estimated 230 million gallons
of waste fuel and waste oil were treated at industrial kilns, boilers, and furnaces in 1983.201 In
1961, ii wai csiiiuau-J ilia: industrial kilns, boiler:, and furnaces disposed of more than twice
the amount of waste that was disposed of via incinerators.201
7.3.1 Process Description: Incineration
Incineration is a process that employs thermal decomposition via thermal
oxidation at high temperatures (usually 1,650°F [900 °C] or greater) to destroy the organic
fraction of the waste and reduce volume. A study conducted in 1986 identified 221 hazardous
waste incinerators operating under the Resource Conservation and Recovery Act (RCRA)
system in the United States. (See Section 7.3.5 for a discussion of this and other regulations
applicable to hazardous waste incineration.) These incinerators are located at 189 separate
facilities, 171 of which are located at the site of waste generation.201
A diagram of the typical process component options in a hazardous waste
incineration facility is provided in Figure 7-7.201 The diagram shows that the major subsystems
that may be incorporated into the hazardous waste incineration system are (1) waste
7-26
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Waste Preparation
_L
Blending
Screening
Shredding
Heating
1
I
Waste
Preparation
Atomization
Ram
Gravity -
Auger
Lance
Waste
Feeding
IWS = Ionizing Wet Scrubber
ESP = Electrostatic Predpitator
POTW = Publically Owned
Treatment Works
Combustion
I
Liquid Injection Quench
Rotary Kiln Heat
Fixed Hearth Recover/
Fluidized Bed
Combustion
Chambers)
. L
Ash
Disposal
Combustion
> Gas
Conditioning
Dewatering
Chemical
Stabilization 1
Secure Landfill
Air Pollution Control
i
\
\
t.
-
\/enturi
I/Vet ESP*
WS*
Fabric Filter
Particulate
Removal
i
'
Residue
Treatment
1
Backed Tower
Spray Tower
Tray Tower
WS
Wet ESP .
Add Demlster
Gas > and
Remova stack
-•
(
Return to
Process
Neutralization
Chemical Treatment
Residue
and Ash
Handling
POTW*
Figure 7-7. General Orientation of Hazardous Waste Incineration Subsystems and Typical Component Options
Source: Reference 201.
-------
preparation and feeding, (2) combustion chamber(s), (3) air pollution control, and (4)
residue/ash handling. These subsystems are discussed in this section, except that air pollution
control devices are discussed in Section 7.3.4 of this section.
Additionally, energy-recovery equipment may be installed as part of the
hazardous waste incineration system, provided that the incinerator is large enough to make
energy recovery economically productive (i.e., bigger than about 7 million Btu/hour
[7.4 million kJ/hour]) and that corrosive constituents (e.g., HC1) and adhesive particulates are
not present at levels that would damage the equipment.202
Additionally, a few other technologies have been used for incineration of
hazardous waste, including ocean incineration vessels and mobile incinerators. These
processes are not in widespread use hi the United States and are discussed only briefly.
Waste Preparation and Peeding:G:
The feed method is determined by the physical form of the hazardous waste.
Waste liquids are blended and then pumped into the combustion chamber through nozzles or
via atomizing burners. Liquid wastes containing suspended particles may need to be screened
to avoid clogging of small nozzle or atomizer openings. Liquid wastes may also be blended in
order to control the heat content of the liquid to achieve sustained combustion (typically to
8,000 Btu/lb [18,603 kJ/kg]) and to control the chlorine (Cl:) content of the waste fed to the
incinerator (typically to 30 percent or less) to limit the potential for formation of
hazardous-free C12 gas hi the combustion gas.
Waste sludges are typically fed to the combustion chamber using progressive
cavity pumps and water-cooled lances. Bulk solid wastes may be shredded to control particle
size and may be fed to the combustion chamber via rams, gravity feed, air lock feeders,
vibratory or screw feeders, or belt feeders.
7-28
-------
Combustion Chambers201-202
The following five types of combustion chambers are available and operating
today:202 ' .
* Liquid injection;
• Rotary kiln;
• Fixed-hearth;
• Fluidized-bed; and
• Fume.
These five types of combustion chambers are discussed below.
Liquid injection--Liquid injection combustion chambers are applicable almost
exclusively for pumpable liquid waste, including some low-viscosity sludges and slurries. The
typical capacity of liquid injection units is about 8 to 28 million Btu/hour (8.4 to 29.5 million
kJ/hr). Figure 7-8 presents a typical schematic diagram of a liquid-injection unit.201
Liquid injection units are usually simple, refractory-lined cylinders (either
horizontally or vertically aligned) equipped with one or more waste burners. Vertically
aligned units are preferred when wastes are high in organic salts and fusable ash content;
horizontal units may be used with low-ash waste. Liquid wastes are injected through the
burner(s), atomized to fine droplets, and burned in suspension. Burners and separate waste
injection nozzles may be oriented for axial, radial, or tangential firing. Good atomization,
using gas-fluid nozzles with high-pressure air or steam or with mechanical (hydraulic) means,
is necessary to achieve high liquid waste destruction efficiency.
Rotary Kiln—Rotary kiln incinerators are applicable to the destruction of solid
wastes, slurries, containerized waste, and liquids. Because of their versatility, they are most
7-29
-------
u>
o
Aqueous
Waste
Steam
Auxiliary
Fuel
Liquid
Waste
Atomizing
Steam or
Air
Air
120-250%
Excess Air \
Discharge
to Quench or
Waste Heat Recovery
x- ~Refractory Wall
///////v ///////
rk
Primary
Combustion
Air
:600 9= - 300CP F
T
///
0.3 - 2.0 Seconds
Mean Combustion
Gas Residence Time
1500^-220* F
Figure 7-8. Typical Liquid Injection Combustion Chamber
g.
Source: Reference 201.
-------
frequently used by commercial off-site incineration facilities. The typical capacity of these
units is about 10 to 60 million Btu/hour. Figure 7-9 presents a typical schematic diagram of a
rotary kiln unit.201
Rotary kiln incinerators generally consist of two combustion chambers: a
rotating kiln and an afterburner. The rotary kiln is a cylindrical refractory-lined shell that is
mounted on a slight incline. The incline facilitates ash and slag removal. Rotation of the shell
provides transportation of the waste through the kiln and enhances mixing of the waste with
combustion air. The rotational speed of the kiln is used to control waste residence time and
mixing. The primary function of the kiln is to convert solid wastes to gases, which occurs
through a series of volatilization, destructive distillation, and partial combustion reactions.
An afterburner is connected directly to the discharge end of the kiln. The
afterburner is used to ensure complete combustion of flue gases before their treatment, for air
r^oii'Tto-*- A fe>T-t-;-i-^.. "ornHnct'or; ^h&rr^cr rn2v ^? added if needed. The afterburner itself
j,^..— .— .*_. .- *--w.~~^ w ^-.li^ **- V~~ -* - ^-~~* ^J ~ <- . ~
may be horizontally or vertically aligned, and functions much on the same principles as the
liquid injection unit described above. Both the afterburner and the kiln are usually equipped
with an auxiliary fuel-firing system to control the operating temperature.
Fixed-Hearth—Fixed-hearth incinerators, also called controlled-air, starved-air,
or pyrolytic incinerators, are the third major technology used for hazardous waste incineration.
This type of incinerator may be used for the destruction of solid, sludge, and liquid wastes.
Fixed-hearth units tend to be of smaller capacity (typically 5 million Btu/hr [5.3 million kJ/hr])
than liquid injection or rotary kiln incinerators because of physical limitations in ram-feeding
and transporting large amounts of waste materials through the combustion chamber. Lower
relative capital costs and reduced paniculate control requirements make fixed-hearth units more
attractive than rotary kilns for smaller on-site installations. Figure 7-10 presents a typical
schematic diagram of a fixed-hearth unit.201
7-31
-------
U)
N)
CombtMdon
AJr
W»«l« Liquids
Auxiliary Fuel
Wasta •olldi
Contslncra or
Sludges
Kiln
8hroud
Discharge la
Qusnchor
Hwrt Recovery
\
-X-
^-^
—
120-2OOH
ExcsssAIr
1.0-3.0 Seconds
50-230%
Excas* Air
Rotary Kiln
Figure 7-9 Typical Rotary Kiln/Afterburner Combustion Chamber
Source: Reference 201.
-------
-1
UJ
u>
Auxiliary Fuel
Feed
Ram
Discharge to
Quench or
Haat Rncovery
0.25-2.5 Seconds
Mean Residence Time
Secondary
Chamber
1400"F-2000"F
Ash Discharge
Ram Ash Discharge
Figure 7-10. Typical Fixed-Hearth Combustion Chamber
Steam
Auxliary Fuel or
Liquid Waste
Refractory
Era_n_tti.d«4
Source: Reference 201.
-------
Fixed-hearth units consist of a two-stage combustion process similar to that of
rotary kilns. Waste is ram-fed into the primary chamber and burned at about 50 to 80 percent
of stoichiometric air requirements. This starved-air condition causes most of the volatile
fraction to be destroyed pyrolitically. The resultant smoke and pyrolytic products pass to the
secondary chamber, where additional air and, hi some cases, supplemental fuel, are injected to
complete the combustion.
Fluidized-Bed-FBCs have only more recently been applied to hazardous waste
incineration. FBCs may be applied to solids, liquids, and gases; however, this type of
incinerator is most effective for processing heavy sludges and slurries. Solids generally
require prescreening or crushing to a size less than 2 inches in diameter. The typical capacity
of this type of incinerator is 45 million Btu/hr (47.5 million U/hr). See Figure 7-4 of this
chapter for a typical schematic diagram of an FBC chamber.
FBC chambers consist of a single refractory-lined combustion vessel partially
filled with inert granular material (e.g., particles of sand, alumina, and sodium carbonate).
Combustion air is supplied through a distributor plate at the base of the combustor at a rate
sufficient to fluidize (bubbling bed) or entrain (circulating bed) the bed material. The bed is
preheated to startup temperatures by a burner. The bed material is kept at temperatures
ranging from 840 to 1,560°F (450 to 850°C). Wastes are injected into the combustion
chamber pneumatically, mechanically, or by gravity. Solid wastes are fed into the combustion
chamber through an opening above the fluidized bed (similar to the opening for sand feed,
represented in Figure 7-4). Liquid wastes are fed into the bottom of the fluidized bed
(represented in Figure 7-4 as the opening designated for sludge feed). As the waste is fed to
the combustion chamber, heat is transferred from the bed material to the wastes. Upon
combustion, the waste returns heat to the bed. The high temperature of the bed also allows for
combustion of waste gases above the bed.
jFurne-Fume incinerators are used exclusively to destroy gaseous or fume
wastes. The combustion chamber is comparable to that of a liquid-injection incinerator
7-34
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(Figure 7-8) in that it usually has a single chamber, is vertically or horizontally aligned, and
uses nozzles to inject the waste into the chamber for combustion. Waste gases are injected by
pressure or atomization through the burner nozzles. Wastes may be combusted solely by
thermal or catalytic oxidation. If no catalyst is used, the combustion chamber temperature is
maintained at 1,200 to 1,800°F (650 to 980°C). If a catalyst is used (e.g., alumina coated
with noble metals, such as platinum or palladium, and other metals, such as copper chromate
or manganese), the temperature may be maintained at lower temperatures of 500 to 900°F
(260 to 480°C).
Residue and Ash Handling201
Residue and ash consist of the inorganic components of the hazardous waste that
are not destroyed by incineration. Bottom ash is created in the combustion chamber and
residue collects in the air pollution control devices. After discharge from the combustion
ehdinbci, uo'uoiu 'n is common!) an-cooled or quenched v»ith waiei. The asL is then
accumulated on site in storage lagoons or in drums prior to disposal to a permitted hazardous
waste land disposal facility. The ash may also be dewatered or chemically fixated/stabilized
prior to disposal.
Air pollution control residues are typically aqueous streams containing PM,
absorbed acid gases, and small amounts of organic material. These streams are collected in
sumps or recirculation tanks, where the acids are neutralized with caustic and returned to the
process. When the total dissolved solids in the aqueous stream exceeds 3 percent, a portion of
the wastes is discharged for treatment and disposal.
Ocean Incinerators
Ocean incineration involves the thermal destruction of liquid hazardous wastes
at sea hi specially designed tanker vessels outfitted with high-temperature incinerators. Ocean
incinerators are identical to land-based liquid injection incinerators, except that current ocean
7-35
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incinerators are not equipped with air pollution control systems. Largely due to public concern
over potential environmental effects, ocean incineration of hazardous waste has not been used
on a routine basis in the United States.201
Mobile Incinerators
Mobile incinerators have been developed for on-site cleanup at uncontrolled
hazardous waste sites. Most of these systems are scaled-down, trailer-mounted versions of a
conventional rotary kiln or an FBC, with thermal capacities ranging from 10 to 20 million
Btu/hr (10.5 to 21.1 million kJ/hr). The performance of these mobile systems has been shown
to be comparable to equivalent stationary facilities. Because of their high cost, these types of
systems are considered to be cost-effective only at waste sites where laxge amounts of
contaminated material (e.g., soil) would need to be transported off site.201
7.5.2 Indusiiial Kiinh. Boilers, and Furnaces
Industrial kilns, boilers, and furnaces burn hazardous wastes as fuel to produce
commercially viable products such as cement, lime, iron, asphalt, or steam. These industrial
sources require large inputs of fuel to produce the desired product. Hazardous waste, which is
considered an economical alternative to fossil fuels for energy and heat, is utilized as a
supplemental fuel. In the process of producing energy and heat, the hazardous wastes are
subjected to high temperature for a sufficient time to destroy the hazardous content and the
bulk of the waste.
Based on a study conducted in 1984, there were over 1,300 facilities using
hazardous waste-derived fuels (HWDF) in 1983, accounting for a total of 230 million gallons
(871 million liters) of waste fuel and waste oil per year. Although the majority (69 percent) of
HWDF is burned by only about 2 percent of the 1,300 facilities (i.e., medium- to large-size
industrial boilers, cement and aggregate kilns, and iron-making furnaces), other industries
burning significant quantities of HWDF included the paper (SIC 26), petroleum (SIC 29),
7-36
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primary metals (SIC 33), and stone, clay, glass, and concrete (SIC 32) industries.201 Industrial
boilers and furnaces, iron foundries, and cement kilns are described in more detail in
Sections 7.4, 7.7, and 7.8, respectively, of this document.
7.3.3 Benzene Emissions From Hazardous Waste Incineration
There are limited data documenting benzene emissions from hazardous waste
incinerators. However, as discussed below, benzene is one of the most frequently identified
products of incomplete combustion (PICs) in air emissions from hazardous waste
incinerators.203 Two emission factors for benzene emissions are provided in Table 7-4.
7.3.4 Control Technologies for Hazardous Waste Incineration
Most organics control is achieved by promoting complete combustion by
follc'.ving GCP. The genera! conditions of GCP are summarized in Section 7.1.3. Again,
failure to achieve complete combustion of organic materials evolved from the waste can result
in emissions of a variety of organic compounds. Benzene is one of die most frequently
identified PICs in air emissions from hazardous waste incinerators.203
In addition to adequate oxygen, temperature, residence time, and turbulence,
control of organics may be partially achieved by using acid gas and PM control devices;
however, this has not been documented. The most frequently used control devices for acid gas
and PM control are wet scrubbers and fabric filters. Fabric filters provide mainly PM control.
Other PM control technologies include venturi scrubbers and ESPs. In addition to wet
scrubbing, dry sorbent injection and spray dryer absorbers have also been used for acid gas
(HC1 and SO2) control.
7-37
-------
TABLE 7-4. SUMMARY OF BENZENE EMISSION FACTORS
FOR HAZARDOUS WASTE INCINERATION
sec
5-03-005-01
5-03-005-01
Emission Source
Liquid injection incinerator
Liquid injection incinerator
Control Device
Uncontrolled
Various control devices0
Emission Factor
Ib/ton (kg/Mg)a
.66 x 10
(2.33 x lO'5)
.23 x 10
(6.16xlO-")d
Factor
Rating
oo
Source: Reference 3.
1 Factors are in Ib (kg) of benzene emitted per ton (Mg) of waste incinerated.
b The liquid injection incinerator has a built-in afterburner chamber.
c The incinerators tested had the following control devices: venturi, packed, and ionized scrubbers; carbon bed filters; and HEPA filters.
d The emission factor represents the average of the emission factors for the liquid injection incinerators tested with the various control devices specified in
footnote c.
-------
7.3.5 Regulatory Analysis
Organic emissions from hazardous waste incinerators are regulated under
40 CFR 246, Subpart O, promulgated on June 24, 1982.204 The standards require that in order
for a hazardous waste incineration facility to receive a RCRA permit, it must attain a 99.99
percent destruction and removal efficiency (DRE) for each principal organic hazardous
constituent (POHC) in the waste feed. Each facility must determine which one or more
organic compounds, from a list of approximately 400 organic and inorganic hazardous
chemicals (including benzene) in Appendix Vm of 40 CFR 261,^ are POHCs, based on
which are the most difficult to incinerate, considering their concentration or mass in the waste
feed. Each facility must then conduct trial burns to determine the specific operating conditions
under which 99.99 percent DRE is achieved for each POHC.
In order to ensure 99.99 percent DRE, operating limits are established in a
ptmiii foi each ii-icii^iaio: foi ihe following conditions: (1) CO level in the stack exhaust gas,
(2) waste feed rate, (3) combustion temperature, (4) an appropriate indicator of combustion gas
velocity, (5) allowable variations in incinerator system design or operating procedures, and
(6) other operating requirements considered necessary to ensure 99.99 percent DRE for the
POHCs.
Additionally, Subpart 0 of 40 CFR 246 requires that hazardous waste
incineration facilities achieve 99-percent emissions reduction of HC1 (if HC1 emissions are
greater than 1.8 kg/hr [4.0 lb/hr]) and a limit of 180 milligrams per dry standard cubic meter
(0.0787 grains per dry standard cublic foot) for PM emissions. These emission limits would
require facilities to apply acid gas/PM control devices. As mentioned hi Section 7.3.4, acid
gas/PM control devices may result in partial control of emissions of organic compounds.
7-39
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7.4 EXTERNAL COMBUSTION OF SOLID, LIQUID, AND GASEOUS FUELS
IN STATIONARY SOURCES FOR HEAT AND POWER GENERATION
The combustion of solid, liquid, and gaseous fuels such as natural gas, oil, coal,
and wood waste has been shown to be a minor source of benzene emissions. This section
addresses benzene emissions from the external combustion of these types of fuels by stationary
sources that generate heat or power in the utility, industrial/commercial, and residential
sectors.
7.4.1 Utility Sector206
Fossil fuel-fired utility boilers comprise about 72 percent (or 1,696,000 million
Btu/hr [497,000 megawatts (MW)]) of die generating capacity of U.S. electric power plants.
The primary fossil fuels burned in electric utility boilers are coal, natural gas, and oil. Of
these fuels coal is the most widely used, accounting for 60 percent of the U.S. fossil fuel
generating capacity. Natural gas represents about 25 percent and oil represents 15 percent of
the U.S. fossil fuel generating capacity.
Most of the coal-firing capability is east of the Mississippi River, with die
significant remainder being in die Rocky Mountain region. Natural gas is used primarily in the
South Central States and California. Oil is predominantly used in Florida and the Northeast.
Fuel economics and environmental regulations affect regional use patterns. For example, coal
is not used in California because of stringent air quality limitations. Information on precise
utility plant locations can be obtained by contacting utility trade associations such as die
Electric Power Research Institute in Palo Alto, California (415-855-2000); the Edison Electric
Institute in Washington, D.C. (202-828-7400); or die U.S. Department of Energy (DOE) in
Washington, D.C. Publications by EPA/DOE on the utility industry are also useful hi
determining specific facility locations, sizes, and fuel use.
7-40
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Process Description of Utility Boilers
A utility boiler consists of several major subassemblies, as shown in
Figure 7-II.206 These subassemblies include the fuel preparation system, the air supply
system, burners, the furnace, and the convective heat transfer system. The fuel preparation
system, air supply, and burners are primarily involved hi converting fuel into thermal energy
in the form of hot combustion gases. The last two subassemblies are involved in the transfer
of the thermal energy in the combustion gases to the superheated steam required to operate the
steam turbine and produce electricity.206
Three key thermal processes occur hi the furnace and convective sections of the
boiler. First, thermal energy is released during controlled mixing and combustion of fuel and
oxygen in the burners and furnace. Second, a portion of the thermal energy formed by
combustion is adsorbed as radiant energy by the furnace walls. The furnace walls are formed
bv nul^10 c!oce1v cna^H tube? filled with high-pressure water that carrv water from the
'^'i''~-'i »— i *
bottom of the furnace to absorb radiant heat energy to the steam drum located at the top of the
boiler. Third, the gases enter the convective pass of the boiler, and the balance of the energy
retained by the high-temperature gases is adsorbed as convective energy by the convective heat
transfer system (superheater, reheater, economizer, and air preheater).206
A number of different furnace configurations are used in utility boilers,
including tangentially fired, wall-fired, cyclone-fired, stoker-fired, and FBC boilers. Some of
these furnace configurations are designed primarily for coal combustion; others are designed
for coal, oil, or natural gas combustion. The types of furnaces most commonly used for firing
oil and natural gas are the tangentially fired and wall-fired boiler designs.207 One of the
primary differences between furnaces designed to burn coal versus oil or gas is the furnace
size. Coal requires the largest furnace, followed by oil, then gas.206
The average size of boilers used hi the utility sector varies primarily according
to boiler type. Cyclone-fired boilers are generally the largest, averaging about 850 to
7-41
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Superheater* and Reheaters
Flue Gas
Fuel
Figure 7-11. Simplified Boiler Schematic
Source: Reference 206.
\
7-42
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1,300 million Btu/hr (250 to 380 MW) generating capacity. Tangentially fired and wall-fired
boiler designs firing coal average about 410 to 1,470 million Btu/hr (120 to 430 MW); these
designs firing oil and natural gas average about 340 to 920 million Btu/hr (100 to 270 MW).
Stoker-fired boilers average about 34 to 58 million Btu/hr (10 to 17 MW).207 Additionally,
unit sizes of FBC boilers range from 85 to 1,360 million Btu/hr (25 to 400 MW), with the
largest FBC boilers typically closer to 680 million Btu/hr (200 MW).206
Tangentially Fired Boiler-The tangentially-fired boiler is based on the concept
of a single flame zone within the furnace. The fuel-to-air mixture in a tangentially fired boiler
projects from the four corners of the furnace along a line tangential to an imaginary cylinder
located along the furnace centerline. When coal is used as the fuel, 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), entrained in primary air, and fired in suspension.208 As fuel and air
are fed to the burners, a rotating "fireball" is formed to control the furnace exit gas
ik.iiipv.iai.LiiC aiivi pivjvivlv, StCaiii iCnipCIatuiC CGIiUGi Ciiiliiig \aIialiGIlS ill iGad. 1116 illCGaii Ill
be moved up and down by tilting the fuel-air nozzle assembly. Tangentially fired boilers
commonly burn coal (pulverized). However, oil or gas may also be burned.206
Wall-Fired Boiler-Wall-fired boilers are characterized by multiple individual
burners located on a single wall or on opposing walls of the furnace. Refer to Figure 7-12 for
a diagram of a single wall-fired boiler.206 As with tangentially fired boilers, when coal is used
as the fuel, the coal is pulverized, entrained in primary air, and fired in suspension. In
contrast to tangentially fired boilers, which produce a single flame envelope or fireball, each of
the burners in a wall-fired boiler has a relatively distinct flame zone. Depending on the design
and location of the burners, wall-fired boilers consist of various designs, including single-wall,
opposed-wall, cell, vertical, arch, and turbo. Wall-fired boilers may burn (pulverized) coal,
oil, or natural gas.206
7-43
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Burner B
Burner A
AirA-
AirB-
AirC-
AirD-
FuelA
FuelB
FueIC
FuelD
Burner D
Burner C
g
Figure 7-12. Single Wall-fired Boiler
Source: Reference 206.
7-44
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Cvclone-Fired Boiler-As shown in Figure 7-13, in cyclone-fired boilers, fuel
and air are burned in horizontal, cylindrical chambers, producing a spinning, high-temperature
flame. When coal is used, the coal is crushed to a 4-mesh size and admitted with the primary
air in a tangential fashion. The finer coal particles are burned hi suspension and the coarser
particles are thrown to the walls by centrifugal force.207 Cyclone-fired boilers are almost
exclusively coal-fired and burn crushed rather than pulverized coal. However, some units are
also able to fire oil and natural gas.206
Fluidized-Bed Combustion Boiler--Fluidized-bed combustion is a newer boiler
technology that is not as widely used as the other, conventional boiler types. In a typical FBC
boiler, crushed coal in combination with inert material (sand, silica, alumina, or ash) and/or
sorbent (limestone) are maintained in a highly turbulent suspended state by the upward flow of
primary air from the windbox located directly below the combustion floor. This fluidized state
provides a large amount of surface contact between the air and solid particles, which promotes
uniform and efficient comuus>iiuii ai iowei furnace lemperatures-between 1,575 and 1,650°F
(860 and 900°C) compared to 2,500 and 2,800°F (1,370 and 1,540°C) for conventional coal-
fired boilers. Fluidized bed combustion boilers have been developed to operate at both
atmospheric and pressurized conditions. Refer to Figure 7-14 for a simplified diagram of an
atmospheric FBC.206
Stoker-Fired Boiler-Rather than firing coal in suspension, mechanical stokers
can be used to burn coal in fuel beds. All mechanical stokers are designed to feed coal onto a
grate within the furnace. The most common stoker type of boiler used in the utility industry is
the spreader-type stoker (refer to Figure 7-15 for a diagram of a spreader type stoker
fired-boiler).206 Other stoker types are overfeed and underfeed stokers.
In spreader stokers, a flipping mechanism throws crushed coal into the furnace
and onto a moving fuel bed (grate). Combustion occurs partly in suspension and partly on the
grate.208 In overfeed stokers, crushed coal is fed onto a traveling or vibrating grate from an
adjustable gate above and burns on the fuel bed as it progresses through the furnace.
7-45
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SECONDARY
AIR INLET
COAL PIPE -
CRUSHED COAL
(1/4' Screen
Plus Primary Air)
TERTIARY
AIR INLET
SCROLL
BURNER
SLAG SPOUT CYCLONE
OPENING BARREL
a.
E
Q
2
IB
Figure 7-13. Cyclone Burner
Source: Reference 206.
7-46
-------
RIM Gas
Convection
Pass
Coal Limestone
I:
Freeboard «
Splash
Zone
Bed
Transport Air
Fluidizing Air
Forced Draft Air
Recycle
Cyclone
Distributor
Plate
Plenum
Compressor
Waste
Waste
1.
Figure 7-14. Simplified Atmospheric Fluidized Bed Combustor Process Flow Diagram
Source: Reference 206.
7-47
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-J
-U
oo
Tangential Overfire Air
Distributors
Drive Shaft
Grates
Return Rails
Tangential Overfire Air
Drag Seals
Carbon-Recovery Nozzles
Back-Stop Assembly
Take-Up
Sittings Hopper
Figure 7-15. Spreader Type Stoker-fired Boiler - Continuous Ash Discharge Grate
Source: Reference 206.
-------
Conversely, in underfeed stokers, crushed coal is forced upward onto the fuel bed from below
by mechanical rams or screw conveyors.206'208
Benzene Emissions from Utility Boilers
Benzene emissions from utility boilers may depend on various factors, including
(1) type of fossil fuel burned, (2) type of boiler used, (3) operating conditions of the boiler,
and (4) pollution control device(s) used. As described below, conditions that favor more
complete combustion of the fuel generally result in lower organic emissions. Emission factors
for benzene emissions from utility boilers are presented in Table 7-5.
Table 7-5 presents three benzene emission factors for two types of coal-fired
boilers utilizing three types of PM/SO2/NOX air pollution control systems. The data show only
slightly higher benzene emissions from a tangentially fired boiler than a cyclone-fired boiler
£;..;„„ ^^oi -i-"^ C-VIOM' tfiot tv>p*-» !c -po ci'TTi'f!r*?Tit d'^?ror!ro 'n b?nz'arip emi^'ior15 from the
different air pollution control device configurations represented.209
Table 7-5 also presents two emission factors for two types of natural gas-fired
boilers utilizing flue gas recirculation.3-209'210 The data show only slightly higher emissions for
the opposed-wall boiler than for the tangentially fired boiler. Additionally, the emission tests
from which the emission factors were generated demonstrated that changes in unit load and
excess air level did not significantly impact benzene emissions from either boiler type.210
Control Technologies for Utility Boilers
Utility boilers are highly efficient and generally the best controlled of all
combustion sources. Baghouses, ESPs, wet scrubbers, and multicyclones have been applied
for PM control in the utility sector. A combination of a wet scrubber and ESP are often used
to control bom SO2 and PM emissions.
7-49
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TABLE 7-5. SUMMARY OF BENZENE EMISSION FACTORS FOR UTILITY BOILERS
Ul
o
sec
1-01-002-03
1-01-002-03
1-01-003-02
1-01-006-01
1-01-006-04
1-01-009-01
Emission
Source
Cyclone boiler
Cyclone boiler
Tangentially-
fired boiler
Opposed-wall
boiler'
Tangentially-
fired boiler6
Boiler
Fuel Type
Coal
Coal .
Lignitec
Natural gas
Natural gas
Barkf
Control Device
Baghouse/SCR/
sulfuric acid
condenserb
Electrostatic
precipitator
Electrostatic
precipitator/
scrubber*1
Flue gas
recirculation
Flue gas
recirculation
Uncontrolled
Emission Factor
Ib/MMBtu 0*g/J)a
5.58 x 10-6
(2.40 x 10 6)
7.90 x 106
(3.40 x 10'6)
3.95 x 10 5
(l.VOxlO-5)
1.40xlO'6
(6.02 x ID'7)
4.00 x 10-7
(1.72 x 10'7)
3.60 x 10 3 Ib/ton
(l.SOx 10'3kg/Mg)«
Factor
Rating
D
D
D
D
D
E
Reference
209
209
209
210
210
3
* Factors are in Ib (/zg) of benzene emitted per MMBtu (J).
b There is an SO2 reactor prior to the condenser.
c The lignite is pulverized and dried.
d The scrubber is a spray tower using an alkali slurry.
' The furnace has overfire air ports and off-stoichiometric firing.
' The bark had a moisture of 50 percent.
1 Pound (kg) of benzene emitted per ton (Mg) of bark fired.
SCR = selective catalytic reduction.
-------
The above control technologies are not intended to reduce benzene emissions
from utility boilers. In general, emissions of organic pollutants, including benzene, are
reduced by operating the furnace hi such as way as to promote complete combustion of the
fossil fuel(s) combusted hi the furnace. Therefore, any combustion modification that increases
the combustion efficiency will most likely reduce benzene emissions. The following conditions
can increase combustion efficiency:211
• Adequate supply of oxygen;
• Good air/fuel mixing;
• Sufficiently high combustion temperature;
• Short combustion gas residence time; and
• Uniform fuel load (i.e., consistent combustion intensity).
7.4.2 Industrial/Commercial Sector
Industrial boilers are widely used in manufacturing, processing, mining, and
refining primarily to generate process steam, electricity, or space heat at the facility.
However, the industrial generation of electricity is limited, with only 10 to 15 percent of
industrial boiler coal consumption and 5 to 10 percent of industrial boiler gas and oil
consumption used for electricity generation.212 The use of industrial boilers is concentrated hi
four major industries: pulp and paper, primary metals, chemicals, and minerals. These
industries account for 82 percent of the total firing capacity.213 Commercial boilers are used by
commercial establishments, medical institutions, and educational institutions to provide space
heating.
In collecting survey data to support its Industrial Combustion Coordinated
Rulemaking (ICCR), the EPA compiled information on a total of 69,494 combustion boiler
units in the industrial and commercial sectors.213 While this number likely underestimates the
total population of boilers in the industrial and commercial sectors (due to unreceived survey
.7-51
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responses and lack of information on very small units) it provides an indication of the large
number of sources included in this category.
Of the units included in the ICCR survey database, approximately 70 percent
were classified hi the natural gas fuel subcategory, 23 percent hi the oil (distillate and residual)
subcategory, and 6 percent hi the coal burning subcategory. These fuel subcategory
assignments are based on the units burning only greater than 90 percent of .the specified fuel
for that subcategory. All other units (accounting for the other 1 percent of assignments) are
assigned to a subcategory of "other fossil fuel."213
Other fuels burned in industrial boilers are wood wastes, liquified petroleum
gas, asphalt, and kerosene. Of these fuels, wood waste is the only non-fossil fuel discussed
here because benzene emissions were not characterized for combustion of the other fuels. The
burning of wood waste in boilers is confined to those industries where it is available as a
byproduct, it is burned both to obtain neat energy and to alleviate possible solid waste disposal
problems. Generally, bark is the major type of waste burned in pulp mills. In the lumber,
furniture, and plywood industries, either a mixture of wood and bark waste or wood waste
alone is most frequently burned. As of 1980, there were approximately 1,600 wood-fired
boilers operating in the United States, with a total capacity of over 102,381 million Bru/hour
(30,000 MW).214
Industrial and commercial coal combustion sources are located throughout the
United States, but tend to follow industry and population trends. Most of the coal-fired
industrial boiler sources are located hi the Midwest, Appalachian, and Southeast regions.
Industrial wood-fired boilers tend to be located almost exclusively at pulp and paper, lumber
products, and furniture industry facilities. These industries are concentrated in the Southeast,
Gulf Coast, Appalachian, and Pacific Northwest regions. The Pacific Northwest contains
many of the boilers firing salt-laden wood bark.
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Trade associations such as the American Boiler Manufacturers Association in
Arlington, Virginia, (703-522-7350) and the Council of Industrial Boiler Owners in Fairfax
Station, Virginia, (703-250-9042) can provide information on industrial boiler locations and
trends.215
Process Description of Industrial/Commercial Boilers
Some of the same types of boilers used by the utility sector are also used by the
industrial/commercial sector; however, the average boiler size used by the
industrial/commercial sector is substantially smaller. Additionally, a few types of boiler
designs are used only by the industrial sector. For a general description of the major
subassemblies of boilers and their key thermal processes, refer to the discussion of utility
boilers in Section 7.4.1 and Figure 7-11. The following two sections describe
industrial/commercial boilers that fire fossil fuels and wood waste.
Fossil Fuel Combustion-All of the boilers used by the utility industry
(described hi Section 7.4.1) are "water-tube" boilers, which means that the water being heated
flows through tubes and the hot gases circulate outside the tubes. Water-tube boilers represent
the majority (57 percent) of industrial and commercial boiler capacity (70 percent of indust-ial
boiler capacity).212 Water-tube boilers are used in a variety of applications, ranging from
supplying large amounts of process steam to providing space heat for industrial and
commercial facilities. These boilers have capacities ranging from 10 to 1,500 million Btu/hr
(3 to 440 MW), averaging about 410 million Btu/hr (120 MW). The most common types of
water-tube boilers used hi the industrial/ commercial sector are wall-fired and stoker-fired
boilers. Tangentially fired and FBC boilers are less commonly used. Refer to Section 7.4.1
for descriptions of these boiler designs.213
The industrial/commercial sector also uses boilers with two other types of heat
transfer methods: fire-tube and cast iron boilers. Because then: benzene emissions have not
been characterized, these types of boilers are only briefly described below.
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In fire-tube boilers, the hot gas flows through the tubes and the water being
heated circulates outside of the tubes. Fire-tube boilers are not available with capacities as
large as those of water-tube boilers, but they are also used to produce process steam and space
heat. Most fire-tube boilers have a capacity between 1.4 and 24.9 million Btu/hour
(0.4 and?.3 MW thermal). Most installed firetube boilers bum oil or gas.213
In cast iron boilers, the hot gas is also contained inside the tubes, which are
surrounded by the water being heated, but the units are constructed of cast iron instead of
steel. Cast iron boilers are limited in size and are used only to supply space heat. Cast iron
boilers range in size from less than 0.3 to 9.9 million Btu/hour (0.1 to 2.9 MW thermal).213
Wood Combustion—The burning of wood waste in boilers is mostly confined to
diose industries where it is available as a byproduct. It is burned both to obtain heat energy
and to alleviate solid waste disposal problems. Wood waste may include large pieces such as
slabs, logs, ana DarK strips, as well as cuttings, shavings, pellets, and sawdust.:!!
Various boiler firing configurations are used in 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 very high moisture. Fuel is fed
into the oven through apertures in a firebox and is fired hi a cone-shaped pile on a flat grate.
The burning is done in two stages: (1) drying and gasification, and (2) 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.214
In another type of boiler, the fuel-cell oven, fuel is dropped onto suspended
fixed grates and fired in a pile. The fuel cell uses combustion air preheating and positioning of
secondary and tertiary air injection ports to improve boiler efficiency.214
In many large operations, more conventional boilers have been modified to burn
wood waste. The units may include spreader stokers with traveling grates or vibrating grate
7-54
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stokers, as well as tangentially fired or cyclone-fired boilers (see Section 7.4.1 for descriptions
of these types of boilers). The most widely used of these configurations is the spreader stoker,
which can burn dry or wet wood. Fuel is dropped in front of an air jet that casts the fuel out
over a moving grate. The burning is done in three stages: (1) drying, (2) distillation and
burning of volatile matter, and (3) burning of fixed carbon. Natural gas or oil is often fired as
auxiliary fuel. This is done to imintain constant steam when the wood supply fluctuates or to
provide more steam than can be generated from die wood supply alone.214
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 percent by weight). It is fired in a flaming horizontal torch, usually with natural gas as
an ignition aid or supplementary fuel.214
A recent development in wood firing is the FBC boiler. Refer to Section 7.4.1
for a description of this boiler type. Because of the large thermal mass represented by the hot
inert bed particles, FBCs can handle fuels with high moisture content (up to 70 percent, total
basis). Fluidized beds can also handle duty fuels (up to 30 percent inert material). Wood
material is pyrolyzed more quickly in a fiuidized bed than on a grate because of its immediate
contact with hot bed material. Combustion is rapid and results in nearly complete combustion
of organic matter, minimizing emissions of unburned organic compounds.214
Benzene Emissions from Industrial/Commercial Boilers
Benzene emissions from industrial/commercial boilers may depend on various
factors, including (1) type of fuel burned, (2) type of boiler used, (3) operating conditions of
the boiler, and (4) pollution control device(s) used. Conditions that favor more complete
combustion of die fuel generally result in lower organic emissions. Additionally, the organic
emissions potential of wood combustion is generally thought to be greater than that of fossil
fuel combustion because wood waste has a lower heating value, which may decrease
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combustion efficiency. Emission factors for benzene emissions from industrial and
commercial/institutional boilers are presented in Table 7-6.3-216-220
Table 7-6 presents emission factors primarily for wood waste combustion.
Additionally a few emission factors are presented for fossil fuel (residual oil and coke/coal)
and process gas (landfill gas and POTW digester gas) combustion. Most of the emission
factors represent emissions from a non-specified type of boiler. Only two boiler types are
specified (FBC and spreader-stoker). Additionally, the benzene emission factors presented are
emissions following various types of PM and SO2 emission control systems.
In most cases, Table 7-6 specifies the type of wood waste associated widi the
emission factors for wood combustion boilers. The composition of wood waste may have an
impact on benzene emissions. The composition of wood waste depends largely on the industry
from which it originates. Pulping operations, for example, produce great quantities of bark
that may contain more than 70 percent by weight moisture, along with sand and other
noncombustibles. Because of this, bark boilers in pulp mills may emit considerable amounts of
organic compounds to the atmosphere unless they are well controlled. On the other hand,
some operations, such as furniture manufacturing, produce a clean, dry wood waste, 5 to
50 percent by weight moisture, with relatively low organic emissions when properly burned.
Still other operations, such as sawmills, burn a varying mixture of bark and wood waste that
results in paniculate emissions somewhere between those of pulp mills and furniture
manufacturing. Additionally, when fossil fuels are co-fired with wood waste, the combustion
efficiency is typically unproved; uierefore, organic emissions may decrease.215
The type of boiler, as well as its operation, affect combustion efficiency and
emissions. Wood-fired boilers require a sufficiently large refractory surface to ensure proper
drying of high-moisture-content wood waste prior to combustion. Adequately dried fuel is
necessary to avoid a decrease hi combustion temperatures, which may increase organic
emissions because of incomplete combustion.215
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TABLE 7-6. SUMMARY OF BENZENE EMISSION FACTORS FOR INDUSTRIAL
AND COMMERCIAL/INSTITUTIONAL BOILERS
sec
1-02-004-01
1-02-007-99
1-02-008-04
1-02-009-01
1-02-009-03
1-02-009-03
1-02-009-03
1-02-009-03
1-02-009-05
1-02-009-06
Emission
Source
Boiler
Boiler
Boiler
Boiler
Boiler
Boiler
Boiler
FBC Boiler
Boiler
Spreader-stoker
boiler
Fuel Type
No. 6 fuel oil
Landfill gas
Coke and coal
Bark"
Wood"
Woodc
Wood6
Woodf
Wood and bark"
Wood1
Control Device
Uncontrolled
Uncontrolled
Baghouse
ESP
Wet Scrubber
Multiple
cycloned/ESP
Multiple
cycle ned
Multiple
cyclonea/ESP
Multiple
cycloned/wet
scrubber
Multiple
cyclone*
Emission Factor
Ib/MMBtu fag/])1
9.38 x 10 5
(4.04x 10'5)
3.78x10-"
(1.63xl04)
2.68 x 10 5
(l.lSxlO'5)
6.90 x 10-4
(2.97 x 10^)
4.20 x 103
(l.Slx 10 3)
5.12x10^
(2.20 x 10'4)
1.04X10'3
(4.46 x 10-4)
2.70 x 105g
(1.16xlO-5)
l.OlxlO'3
(4.35 x 10^)
2.43 x 10-4
(l.OSxlO-4*
Factor
Rating
D
D
D
E
E
E
E
E
E
D
Reference
216
3
217
3
3
3
3
3
3
218
(continued)
-------
TABLE 7-6. CONTINUED
-------
Control Technologies for Industrial/Commercial Boilers
Control techniques for reducing benzene emissions from industrial and
commercial boilers are similar to those used for utility boilers. Refer to Section 7.4.1 for a
discussion of control techniques also applicable to commercial and industrial boilers.
In Section 7.4.1, various operating conditions are listed that contribute to the
combustion efficiency of a boiler (e.g., oxygen supply, good air/fuel mixing, and
temperature). It has been demonstrated for a spreader-stoker boiler firing wood that benzene
emissions are an order of magnitude lower under good firing conditions than under poor firing
conditions (when the boiler was in an unsteady or upset condition). It has also been shown that
the ratio of overfire to underfire air plays an important role in benzene emissions. Based on
recent test results, the speculation is that if the balance of combustion air heavily favors
underfire air, there is insufficient combustion air in the upper furnace to complete the
combustion of FICj> (iiit-iuJiiig benzene). Conversely, wilL excess overfke aii, Ike fiamc-
quenching effect of too much combustion air in the upper furnace appears to suppress the
combustion of PICs at that stage of the combustion process.218
7.4.3 Residential Sector
The residential sector includes furnaces and boilers burning coal, oil, and
natural gas. stoves and fireplaces burning wood, and kerosene heaters. All of these units are
designed to heat individual homes. Locations of residential combustion sources are tied
directly to population trends. Coal consumption for residential combustion purposes occurs
mainly in the Northeast, Appalachian, and Midwest regions. Residential oil consumption is
greatest in the Northeast and Mid-Atlantic regions. Wood-fired residential units are generally
concentrated hi heavily forested areas of the United States, which reflects fuel selection based
on availability and price.215
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Process Description for Residential Furnaces, Boilers, Stoves, and Fireplaces
The following sections describe the types of residential furnaces, boilers, stoves,
and fireplaces that fire wood, coal, oil, natural gas, kerosene.
Wood Combustion-Residential wood combustion generally occurs in either a
wood-fired stove or fireplace unit located inside the house. The following discussion describes
the specific characterization of woodstoves, followed by a discussion on fireplaces.
Woodstoves are commonly used in residences as space heaters. They are used
both as the primary source of residential heat and to supplement conventional heating systems.
Wood stoves have varying designs based on the use or non-use of baffles and catalysts, the
extent of combustion chamber sealing, and differences hi ah- intake and exhaust systems.
The EPA has identified five different categories of wood-burning stoves based
on differences in both the magnitude and the composition of the emissions':221
• Conventional woodstoves;
• Noncatalytic woodstoves;
• Catalytic woodstoves;
• Pellet stoves; and
• Masonry heaters.
Within these categories, there are many variations hi device design and operation.
The conventional stove category comprises all stoves that do not have catalytic
combustors and are not included in the other noncatalytic categories (i.e., noncatalytic and
pellet). Conventional stoves do not have any emissions reduction technology or design
features and, in most cases, were manufactured before July 1, 1986. Stoves of many different
7-60
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airflow designs may be included in this category, such as updraft, downdraft, crossdraft and
S-flow.221
Noncatalytic woodstoves are those units that do not employ catalysts but do have
emissions-reducing technology or features. Typical noncatalytic design includes baffles and
secondary combustion chambers.221
Catalytic stoves are equipped with a ceramic or metal honeycomb device, called
a combustor or converter, that is coated with a noble metal such as platinum or palladium.
The catalyst material reduces the .ignition temperature of the unburned VOC and CO in the
exhaust gases, thus augmenting their ignition and combustion at normal stove operating
temperatures. As these components burn, the temperature inside the catalyst increases to a
point at which the ignition of the gases is essentially self-sustaining.221
Peiiei btuveb aic ihose fueled wilL pelicii uf sawdusi, wood products, and other
biomass materials pressed into manageable shapes and sizes. These stoves have active air flow
systems and unique grate design to accommodate this type of fuel. Some pellet stove models
are subject to the 1988 NSPS; others are exempt because of their high air-to-fuel ratio (greater
than 35-to-l).221
Masonry heaters are large, enclosed chambers made of masonry products or a
combination of masonry products and ceramic materials. These devices are exempt from the
1988 NSPS because of their weight (greater than 800 kg). Masonry heaters are gaming
popularity as a cleaner-burning and heat-efficient form of primary and supplemental heat,
relative to some other types of wood heaters. In a masonry heater, a complete charge of wood
is burned in a relatively short period of tune. The use of masonry materials promotes heat
transfer. Thus, radiant heat from the heater warms the surrounding area for many hours after
die fire has burned out.221
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Fireplaces are used primarily for aesthetic effects and secondarily as a
supplemental heating source in houses and other dwellings. Wood is the most common fuel for
fireplaces, but coal and densified wood "logs" may also be burned.222 The user intermittently
adds fuel to the fire by hand.
Fireplaces can be divided into two broad categories: (1) masonry (generally
brick and/or stone, assembled on site, and integral to a structure) and (2) prefabricated (usually
metal, installed on site as a package with appropriate duct work). Masonry fireplaces typically
have large, fixed openings to the fire bed and dampers above the combustion area hi the
chimney to limit room air and heat losses when the fireplace is not being used. Some masonry
fireplaces are designed or retrofitted with doors and louvers to reduce the intake of combustion
air during use.222
Prefabricated fireplaces are commonly equipped with louvers and glass doors to
reduce the intake of combustion air, and some are surrounded by ducts through which
floor-level air is drawn by natural convection, heated, and returned to the room. Many
varieties of prefabricated fireplaces are now on the market. One general class is the
freestanding fireplace, the most common of which consists of an inverted sheet metal funnel
and stovepipe directly above the fire bed. Another class is the "zero clearance" fireplace, an
iron or heavy-gauge steel firebox lined inside with firebrick and surrounded by multiple steel
walls with spaces for air circulation. Some zero clearance fireplaces can be inserted into
existing masonry fireplace openings, and thus are sometimes called "inserts." Some of these
units are equipped with close-fitting doors and have operating and combustion characteristics
similar to those of woodstoves.222
Masonry fireplaces usually heat a room by radiation, with a significant fraction
of the combustion heat lost in the exhaust gases and through fireplace walls. Moreover, some
of the radiant heat entering the room goes toward warming the air that is pulled into the
residence to make up for that drawn up the chimney. The net effect is that masonry fireplaces
are usually inefficient heating devices. Indeed, in cases where combustion is poor, where the
7-62
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outside air is cold, or where the fire is allowed to smolder (thus drawing air into a residence
without producing appreciable radiant heat energy), a net heat loss may occur in a residence
using a fireplace.
Fireplace heating efficiency may be improved by a number of measures that
either reduce the excess air rate or transfer back into the residence some of the heat that would
normally be lost in the exhaust gases or through fireplace walls. As noted above, such
measures are commonly incorporated into prefabricated units. As a result, the energy
efficiencies of prefabricated fireplaces are slightly higher than those of masonry fireplaces.222
Coal Combustion-Coal is not a widely used source of fuel for residential
heating purposes in the United States. Only 0.3 percent of the total coal consumption in 1990
was for residential use.223 However, combustion units burning coal may be sources of benzene
emissions and may be important local sources in areas that have a large number of residential
houses that relv on thi<; fup' for heating
There are a wide variety of coal-burning devices in use, including boilers,
furnaces, coal-burning stoves, and wood-burning stoves that burn coal. These units may be
hand fed or automatic feed. Boilers and warm-air furnaces are usually stoker-fed and are
automatically controlled by a thermostat. The stove units are less sophisticated, generally hand
fed, and less energy-efficient than boilers and furnaces. Coal-fired heating units are operated
at low temperatures and do not efficiently combust fuel.215 Therefore, the potential for
emissions of benzene exists.
Distillate Oil Combustion— The most frequently used home heating oil in the
United States is No. 2 fuel oil, otherwise referred to as distillate oil. Distillate oil is the
second most important home heating fuel behind natural gas.224 The use of distillate oil-fired
heating units is concentrated hi the Northeast portion of the United States. Connecticut,
Maine, Massachusetts, New Hampshire, Rhode Island, Vermont, Delaware, District of
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Columbia, Maryland, New Jersey, New York, and Pennsylvania accounted for approximately
72 percent of the residential share of distillate oil sales.223
Residential oil-fired heating units exist in a number of design and operating
variations related to burner and combustion chamber design, excess air, heating medium, etc.
Residential systems typically operate only in an "on" or "off* mode, with a constant fuel firing
rate, as opposed to commercial and industrial applications, where load modulation is used.226
In distillate oil-fired heating units, pressure or vaporization is used to atomize fuel oil in an
effort to produce finer droplets for combustion. Finer droplets generally mean more complete
combustion and less organic emissions.
When properly tuned, residential oil furnaces are relatively clean burning,
especially as compared to woodstoves.224 However, another study has shown that in practice
not all of the fuel oil is burned and tiny droplets escape the flame and are carried out in the
exhaust.227 This study also concluded that most of the organic emissions from an oil furnace
are due to the unburned oil (as opposed to soot from the combustion process), especially in the
more modern burners that use a retention head burner, where over 90 percent of the carbon in
the emissions was from unburned fuel.227
Natural Gas Combustion—Natural gas is the fuel most widely used for home
heating purposes, with more than half of all the homes being heated through natural gas
combustion. Gas-fired residential heating systems are generally less complex and easier to
maintain than oil-burning units because the fuel burns more cleanly and no atomization is
required. Most residential gas burners are typically of the same basic design. They use
natural aspiration, where the primary air is mixed with the gas as it passes through the
distribution pipes. Secondary air enters the furnace around the burners. Rue gases then pass
through a heat exchanger and a stack. As with oil-fired systems, there are usually no pollution
control equipment installed on gas systems, and excess air, residence time, flame retention
devices, and maintenance are the key factors hi the control of emissions from these units.
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Kerosene Combustion-The sale and use of kerosene space heaters increased
dramatically during the 1980s and they continue to be sold and used throughout the United
States as supplementary and, in some cases, as primary home heating sources.228 These units
are usually unvented and release emissions inside the home. There are two basic types of
kerosene space heaters: convective and radiant.
Emission Factors for Residential Furnaces, Boilers, Stoves, and Fireplaces
The combustion of fossil fuels or wood in residential units is a relatively slow
and low-temperature process. Studies do not indicate the cause(s) for benzene formation in the
residential sector; however, the mechanism may be similar to that in industrial boilers and
utility boilers. Benzene may be formed through incomplete combustion. Because combustion
in the residential sector tends to be less efficient than in other sectors, the potential to form
benzene may be greater.
Table 7-7 presents emission factors for uncontrolled benzene emissions from
both catalytic and non-catalytic woodstoves.3 Benzene emission factors for other types of
residential wood combustion sources are not presented because of limited data.
In general, emissions of benzene can vary widely depending on how the units
are operated and the how emissions are measured. The following factors may affect benzene
emissions measured from residential wood combustion sources:
• Unit design and degree of excess air;
• Wood type, moisture content, and other wood characteristics;
• Burn rate and stage of burn; and
• Firebox and chimney temperatures.
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TABLE 7-7. SUMMARY OF BENZENE EMISSION FACTORS FOR RESIDENTIAL WOODSTOVES
AMS Code
21-04-008-030
21-04-008-051
Emission Source
Catalytic Woodstove
Non-Catalytic Woodstove
Fuel Type
Wood
Wood
Control Device
Uncontrolled
Uncontrolled
Emission Factor
Ib/ton (kg/Mg)1
1.46
(7.30 x 10 ')
1.94
(9.70 x 10'1)
Factor
Rating
E
E
Source: Reference 3.
1 Factors are in Ib (kg) of benzene emitted per ion (Mg) of wood fired.
AMS = area and mobile sources.
ON
ON
-------
Control Techniques for Residential Furnaces, Boilers, Stoves, and Fireplaces
Residential combustion sources are generally not equipped with PM or gaseous
pollutant control devices. In coal- and wood-fired sources, stove design and operating practice
changes have been made to lower PM, hydrocarbon, and CO emissions. Changes include
modified combustion air flow control, better thermal control and heat storage, and the use of
combustion catalysts. Such changes may lead to reduced benzene emissions.
Woodstove emissions reduction features include baffles, secondary combustion
chambers, and catalytic combustors. Catalytic combustors or converters are similar to diose
used in automobiles. Woodstove control devices may lose efficiency over time. Control
degradation for an}' stoves, including noncatalytic woodstoves, may occur as a result of
deteriorated seals and gaskets, misaligned baffles and bypass mechanisms, broken refractories,
or other damaged functional components.221 In addition, combustion efficiencies may be
affwwLwJ uj diffu-eii^ in trie sealing of the chamber and control of the intake and exhaust
systems.215
7.5 STATIONARY INTERNAL COMBUSTION
Stationary internal combustion (1C) sources are grouped into two categories:
reciprocating engines and gas turbines. Stationary 1C engines and turbines are principally used
for electricity generation and industrial applications such as natural gas processing, and oil and
gas exploration, production and transmission.229
7.5.1 Reciprocating Engines
Process Description for Reciprocating Engines
Reciprocating engines may be classified into two types: spark and compression
ignition (diesel). However, all reciprocating 1C engines operate by the same basic process
7-67
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depicted in Figure 7-16.230 A combustible mixture is first compressed in a small volume
between the head of a piston and its surrounding cylinder. The mixture is then ignited and the
resulting high-pressure products of combustion push the piston through the cylinder. This
movement is converted from linear to rotary motion by a crankshaft. The piston returns,
pushing out exhaust gases, and the cycle is repeated.231
All diesel-fueled engines are compression-ignited and all gasoline and natural
gas fueled engines are spark-ignited; however, natural gas can be used in a compression
ignition engine, as discussed below. The two types of reciprocating 1C engines, spark ignition
and compression ignition, are discussed below, according to the following types of fuel:
distillate oil (diesel), gasoline, and natural gas.
Distillate Oil (Diesel)—In compression ignition engines, more commonly known
as diesel engines, combustion air is first compression-heated in the cylinder, and fuel is then
injected into the hot air. Ignition is spontaneous because the air is above the auto-ignition
temperature of the fuel. All distillate oil reciprocating engines are compression-ignited.
Diesel engines usually operate at a higher compression ratio (ratio of cylinder
volume when the piston is at the bottom of its stroke to the volume when it is at the top) than
spark-ignited engines because fuel is not present during compression; hence, there is no danger
of premature auto-ignition. Because engine thermal efficiency rises with increasing pressure
ratio (and pressure ratio varies directly with compression ratio), diesel engines are more
efficient than spark-ignited engines. This increased efficiency is gained at the expense of
poorer response to load changes and a heavier structure to withstand the higher pressures.232
The primary domestic use of large stationary diesel engines (greater than 600 hp
[447 kW]) 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 pumping, and hoisting
equipment, and may also operate pumps or auxiliary power generators. Another frequent
application of large stationary diesel engines is electricity generation for both base and standby
7-68
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Intake
Compression
Power
Exhausl
Figure 7-16. Basic Operation of Reciprocating Internal Combustion Engines
Source: Reference 230.
-------
service. Smaller uses of large diesel engines include irrigation, hoisting, and nuclear power
plant emergency cooling water pump operation. The category of smaller diesel engines (up to
600 hp [447 kW]) covers a wide variety of industrial applications such as aerial lifts, fork lifts,
mobile refrigeration units, generators, pumps, industrial sweepers/scrubbers, material handling
equipment (such as conveyors), and portable well-drilling equipment. The rated power of
these engines can be up to 250 hp (186 kW), and substantial differences in engine duty cycles
exist.232
Gasoline-Spark ignition initiates combustion by the spark of an electrical
discharge. Usually, fuel is mixed with the air in a carburetor, but occasionally fuel is injected
into the compressed air in the cylinder. All gasoline reciprocating engines are spark-ignited.
Gasoline engines up to 600 hp (447 kW) can be used interchangeably with diesel 1C engines in
the same industrial applications described previously. As with diesel engines, substantial
differences in gasoline engine duty cycles exist.231
Natural Gas-Most reciprocating 1C engines that use natural gas are of the
spark-ignited type. As with gasoline engines, the gas is first mixed widi the combustion air at
an intake valve, but occasionally the fuel is injected into the compressed air in the cylinder.
Natural gas can be used in a compression ignition engine, but only if a small amount of diesel
fuel is injected into the compressed air/gas mixture to initiate combustion; hence the name
dual-fuel engine. 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. Large dual-fuel engines have been used almost exclusively for prime
electric power generation.231
Natural gas-fired stationary 1C engines are also used in the natural gas industry,
primarily to power compressors used for pipeline transportation, field gathering (collecting gas
from wells), underground storage, and gas processing plant applications (i.e., prime movers).
Pipeline engines are concentrated in die major gas-producing states (such as those along the
Gulf Coast) and along the major gas pipelines.233
7-70
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Reciprocating 1C engines used in the natural gas industry are separated into
three design classes: two-stroke lean burn, four-stroke lean burn, and four-stroke rich burn.
Each of these have design differences that affect both baseline emissions as well as the
potential for emissions control. Two-stroke engines complete the power cycle in a single
engine revolution compared to two revolutions for four-stroke engines. With the two-stroke
engine, the fuel/air charge is injected with the piston near the bottom of the power stroke. The
valves are all covered or closed and the piston moves to the top of the cylinder compressing the
charge. Following ignition and combustion, the power stroke starts with the downward
movement of the piston. Exhaust ports or valves are then uncovered to remove the combustion
products, and a new fuel/air charge is ingested. Two-stroke engines may be turbocharged
using an exhaust-powered turbine to pressurize the charge for injection into the cylinder.
Non-turbocharged engines may be either blower-scavenged or piston-scavenged to improve
removal of combustion products.233
Four-stroke engines use a separate engine revolution for the intake/compression
stroke and the power/exhaust stroke. These engines may be either naturally aspirated, using
the suction from the piston to entrain the air charge, or turbocharged, using a turbine to
pressurize the charge. Turbocharged units produce a higher power output for a given engine
displacement, whereas naturally aspirated units have lower initial cost and maintenance.
Rich-burn engines operate near the fuel/air stoichiometric limit, with exhaust excess oxygen
levels less than 4 percent. Lean-burn engines may operate up to the lean flame extinction
limit, with exhaust oxygen levels of 12 percent or greater.233
Pipeline population statistics show a nearly equal installed capacity of
reciprocating 1C engines and turbines. Gas turbines emit considerably smaller amounts of
pollutants than do reciprocating engines; however, reciprocating engines are generally more
efficient in their use of fuel. For reciprocating engines, two-stroke designs contribute
approximately two-thirds of installed capacity in this industry.233
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Benzene Emissions From Reciprocating 1C Engines
Most of the pollutants from 1C engines are emitted through the exhaust.
However, some hydrocarbons escape from the crankcase as .a result of blowby (gases that are
vented from the oil pan after they have escaped from the cylinder past the piston rings) and
from the fuel tank and carburetor because of evaporation. Nearly all of the hydrocarbons from
diesel engines enter the atmosphere from the exhaust. Crankcase blowby is minor because
hydrocarbons are not present during compression of the charge. Evaporative losses are
insignificant in diesel engines because of the low volatility of diesel fuels. In general,
evaporative losses are also negligible in engines using gaseous fuels because these engines
receive their fuel continuously from a pipe rather than via a fuel storage tank and fuel pump.
Emission factors for uncontrolled benzene emissions from the following
reciprocating engine types and fuel combinations are provided in Table 7-8:
(1) reciprocating/distillate oil and publically owned treatment works (POTW) digester gas,
(2) cogeneration/distillate oil, (3) 2-cycle lean burn/natural gas, (4) large bore engine/distillate
oil, and (5) large bore engine/distillate oil and gas (dual fuel). Additionally, an emission factor
for benzene emissions after a non-selective catalytic reduction control device is provided for a
natural gas-fired, 4-cycle, lean-burn reciprocating engine.3'231'233
Control Technologies for Reciprocating Engines
Control measures for large stationary diesel engines to date have been directed
mainly at limiting NOX emissions, the primary pollutant from this group of 1C engines. All of
these controls are engine control techniques except for the selective catalytic reduction (SCR)
technique, which is a post-combustion control. As such, all of these controls usually affect the
emissions profile for other pollutants as well, and not always positively. The effectiveness of
controls on a particular engine will depend on the specific design of each engine, and the
effectiveness of each technique can vary considerably.
7-72
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TABLE 7-8. SUMMARY OF BENZENE EMISSION FACTORS FOR RECIPROCATING ENGINES
SCC Emission Source
2-02-001-02 Reciprocating distillate
oil-fueled engine
2-02-001-04 Cogeneration distillate
oil-fueled engine
2-02-002-02 2-cycle lean burn natural
gas-fueled engine
4-cycle lean burn natural
Jo gas-fueled engine
OJ V
2-02-004-01 Large bore diesel-fueled
engine
2-02-004-02 Large bore oil- and
natural gas-fueled engine
(dual fuel)
2-03-007-02 Reciprocating POTW
digester gas-fueled
engine
Control Device(s)
Uncontrolled
Uncontrolled
Uncontrolled
NSCR
Uncontrolled
Uncontrolled
Uncontrolled
Emission Factor
Ib/MMBtu (ng/J)a
9.33 x 10-4
(4.01 x 10'1)
5.36 x 10^
(2.30 x 10 •')
2.20 x lO'3
(9.46 x 10 -1)
7.1 x 10^
(3.05 x 10 ')
7.76 x lO"4
(3.34 x 10 ')
4.45 x 103
(1.91)
6.90 x 104
(2.97 x 10 ')
Emission
Factor
Rating
E
D
E
E
E
E
C
Reference
3, 232
3
3,233
233
3,231
3
3
* Factors are in Ib (ng) of benzene emitted per MMBtu (]).
NSCR = nonselective catalytic reduction.
POTW = publically owned treatment works.
-------
Other NOX control techniques include internal/external exhaust gas recirculation
(EGR), combustion chamber modification, manifold air cooling, and turbocharging. Various
other emissions reduction technologies may be applicable to the smaller diesel and gasoline
engines. These technologies are categorized into fuel modifications, engine modifications, and
exhaust treatments.
7.5.2 Gas Turbines
Stationary gas turbines are applied in electric power generators, hi gas pipeline
pump and compressor drives, and hi various process industries. Gas turbines (greater than
3 MW(e)] are used in electrical generation for continuous, peaking, or standby power.79 In
1990, the actual gas-fired combustion turbine generating capacity for electric utilities was
8,524 MW. 234 The current average size of electricity generation gas turbines is approximately
31 MW. Turbines are also used hi industrial applications, but information was not available to
estimate their installed capacity.
The same fuels used hi reciprocating engines are combusted to drive gas
turbines. The primary fuels used are natural gas and distillate (No. 2) fuel oil, although
residual fuel oil is used in a few applications.235 The liquid fuel used must be similar in
volatility to diesel fuel to produce droplets that penetrate sufficiently far into the combustion
chamber to ensure efficient combustion even when a pressure atomizer is used.230
Process Description for Gas Turbines
Gas turbines are so named not because they are gas-fired, but because
combustion exhaust gas drives the turbine. Unlike reciprocating engines, gas turbines operate
hi steady flow. As shown hi Figure 7-17, a basic gas turbine consists of a compressor, a
combustor, and a turbine.230 Combustion air enters the turbine through a centrifugal
7-74
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Combustion
chamber
Compressor
Fuel
Air
Turbine
Net work
4
F
Products
Figure 7-17. Gas Turbine Engine Configuration
Source: Reference 230.
-------
compressor, where the pressure is raised to 5 to 30 atmospheres, depending on load and the
design of the engine. Part of the air is then introduced into the primary combustion zone, into
which fuel is sprayed. The fuel burns hi an intense flame. Gas volume increases with
combustion, so as the gases pass at high velocity through the turbine, they generate more work
than is required to drive the compressor. This additional work is delivered by the turbine to a
shaft to drive an electric power generator or other machinery.230
Gas turbines may be classified into three general types: simple-open-cycle,
regenerative-open-cycle, and combined-cycle. In the simple-open-cycle, the hot gas discharged
from the turbine is exhausted to the atmosphere. In the regenerative-open-cycle, the gas
discharged from the turbine is passed through a heat exchanger to preheat the combustion air.
Preheating the air increases the efficiency of the turbine. In the combined-cycle, the gas
discharged from the turbine is used as auxiliary heat for a steam cycle. Regenerative-type gas
turbines constitute only a very small fraction of the total gas turbine population. Identical gas
turbines used in the combined-cycle and in the simple-cycle tend to exhibit the same emissions
profiles. Therefore, usually only emissions from simple-cycles are evaluated.229
Benzene Emissions From Gas Turbines
Table 7-9 presents emission factors for controlled benzene emissions from two
gas turbines utilized for electricity generation.3
Control Technologies for Gas Turbines
As with reciprocating engines, NOX is the primary pollutant from gas turbines
that controls have been directed at, and techniques for its control still have ramifications for
the emissions profiles of other pollutants such as hydrocarbons (including benzene).
7-76
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TABLE 7-9. SUMMARY OF BENZENH EMISSION FACTORS FOR GAS TURBINES
sec
2-01-001-01
2-01-002-01
Emission Source
Gas turbine fueled with
distillate oil
Gas turbine fueled with
natural gas
Contiol Device
Afterburnei
Catalytic reduction
Emission Factor
Ib/MMBtu (ng/J)a
9. 13 x 10s
(3.92 x 102)
UOxlO4
(4.73 x lO'2)
Emission
Factor
Rating
D
E
Reference
3
3
' Factors are in Ib (ng) of benzene emitted per MMBtu (J).
-------
Water/steam injection is the most prevalent NO, control for
cogeneration/combined-cycle gas turbines. Water or steam is injected with air and fuel into the
turbine combustor in order to lower the peak temperatures, which in turn decreases the NOX
produced. The lower average temperature within the combustor may produce higher levels of
CO and hydrocarbons as a result of incomplete combustion.235
As described in the previous section, SCR is a post-combustion control that
selectively reduces NOX by reaction of ammonia and NO on a catalytic surface to form N2 and
H2O. Although SCR systems can be used alone, all existing applications of SCR have been
used in conjunction with water/steam injection controls. For optimum SCR operation, the flue
gas must be within a temperature range of 600 to 800 °F (315 to 427 °C), with the precise
limits dependent on the catalyst. Some SCR systems also utilize a CO catalyst to give
simultaneous catalytic CO/NOX control.235
Advanced combustor designs are currently being phased into production
turbines. These dry techniques decrease turbine emissions by modifying the combustion
mixing, air staging, and flame stabilization to allow operation at a much leaner air/fuel ratio
relative to normal operation. Operating at leaner conditions will lower peak temperatures
within the primary flame zone of the combustor. The lower temperatures may also increase
CO and hydrocarbon emissions.235
With the advancement of NOX control technologies for gas turbines, the
emission factors for the installed gas turbine population are quite different than for
uncontrolled turbines. However, uncontrolled turbine emissions have not changed
significantly. A careful review of specific turbine details should be performed before applying
uncontrolled emission factors. Today, most gas turbines are controlled to meet local, State,
and Federal regulations.235
7-78
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7.6 SECONDARY LEAD SMELTING
In 1990, primary and secondary smelters in the United States produced
1,380,000 tons (1,255,000 Mg) of lead. Secondary lead smelters produced 946,000 tons
(860,000 Mg) or about 69 percent of the total refined lead produced in 1990; primary smelters
produced 434,000 tons (395,000 Mg). Table 7-10 lists U.S. secondary lead smelters according
to their annual lead production capacity.236
7.6.1 Process Description
The secondary lead smelting industry produces elemental lead and lead alloys by
reclaiming lead, mainly from scrap automobile batteries. Blast, reverberatory, rotary, and
electric furnaces are used for smelting scrap lead and producing secondary lead. Smelting is
the reduction of lead compounds to elemental lead hi a high-temperature furnace. It requires
higher temperatures (2,200 to 2,300°F [1,200 to 1,260°C]) than those required for melting
elemental lead (621 °F [327°C]). Secondary lead may be refined to produce soft lead (which is
nearly pure lead) or alloyed to produce hard lead alloys. Most of the lead produced by
secondary lead smelters is hard lead, which is used hi the production of lead-acid batteries.236
Lead-acid batteries represent about 90 percent of the raw materials at a typical
secondary lead smelter, although this percentage may vary from one plant to the next. These
batteries contain approximately 18 Ib (8.2 kg) of lead per battery consisting of 40 percent lead
alloys and 60 percent lead oxide. Other types of lead-bearing raw materials recycled by
secondary lead smelters include drosses (lead-containing byproducts of lead refining), which
may be purchased from companies that perform lead alloying or refining but not smelting;
battery plant scrap, such as defective grids or paste; and scrap lead, such as old pipes or roof
flashing. Other scrap lead sources include cable sheathing, solder, and babbitt metal.236
As illustrated in Figure 7-18, the normal sequence of operations in a secondary
lead smelter is scrap receiving, charge preparation, furnace smelting, and lead refining and
7-79
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TABLE 7-10. U.S. SECONDARY LEAD SMELTERS
Smelter
Location
Small-Capacitv: less than 22,000 tons (20,000 Mg)
Delatte Metals
General Smelting and Refining Company
Master Metals, Inc.
Metals Control of Kansas
Metals Control of Oklahoma
Medium-Capacity: 22,000 to 82,000 tons (20,000 to 75,000 Mg)
Doe Run Company
East Perm Manufacturing Company
Exide Corporation
Exide Corporation
GNB, Inc.
GNB, Inc.
Gulf Coast Recycling. Inc
Refined Metals Corporation
Refined Metals Corporation
RSR Corporation
RSR Corporation
Schuylkill Metals Corporation
Tejas Resources, Inc.
Large-Capacitv: greater than 82,000 tons (75,000 Mg)
Gopher Smelting and Refining, Inc.
GNB, Inc.
RSR Corporation
Sanders Lead Company
Schuylkill Metals Corporation
Ponchatoula, LA
College Grove, TN
Cleveland, OH
Hillsboro, KS
Muskosee, OK
Boss, MO
Lyon Station, PA
Muncie, IN
Reading, PA
Columbus, GA
Frisco, TX
Tampa. FL
Beech Grove, IN
Memphis, TN
City of Industry, CA
Middletown, NY
Forest City, MO
Terrell, TX
Eagan, MN
Vernon, CA
Indianapolis, IN
Troy, AL
Baton Rouge, LA
Source: Reference 236.
7-80
-------
Batteriet Arrive
by Track
Polypropylene)
Plastic tO "*
Recycling *•
*
Add to
Water Treatment
orRecyctng
Other Lead-
Bearing Materials *"
and Scrap
T
Battary
Breaking
f
OridUetal,
Hard Rubber.
Separator*
T
Material!
Storage
OPTIONAL
I
I
I
1 t
1
1 Paete
| OetulrurtzaUon
|
|
Disposal
Finished
Product
Figure 7-18. Simplified Process Flow Diagram for Secondary Lead Smelting
Source: Reference 236
7-81
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alloying.236 In the majority of plants, scrap batteries are first sawed or broken open to remove
the lead alloy plates and lead oxide paste material. The removal of battery covers is typically
accomplished using an automatic battery feed conveyor system and a slow-speed saw.
Hammermills or other crushing/shredding devices are then used to break open the battery
cases. Float/sink separation systems are typically used to separate plastic battery parts, lead
terminals, lead oxide paste, and rubber parts. The majority of lead smelters recover the
crushed plastic materials for recycling. Rubber casings are usually landtllled.
Paste desulfurization, an optional lead recovery step used by secondary lead
smelters, requires the separation .of lead sulfate and lead oxide paste from the lead grid metal,
polypropylene plastic cases, separators, and hard rubber battery cases. Paste desulfurization
involves the chemical removal of sulfur from the lead battery paste. The process improves
furnace efficiency by reducing the need for fluxing agents to reduce lead-sulfur compounds to
lead metal. The process also reduces S02 furnace emissions. However, SO2 emissions
reduction is usual!}' a less important consideration because many plants that perform paste
desulfurization are also equipped with SO2 scrubbers. About half of all smelters perform paste
desulfurization.
After removing the lead components from the charge batteries, the lead scrap is
combined with other charge materials such as refining drosses, flue dust, furnace slag, coke,
limestone, sand, and scrap iron and fed to either a reverberatory, blast, rotary or electric
smelting furnace. Smelting furnaces are used to produce crude lead bullion, which is refined
and/or alloyed into final lead products.
Refining, the final step in secondary lead production, consists of removing
impurities and adding alloying metals to the molten lead obtained from the smelting furnaces to
meet a customer's specifications. Refining kettles are used for the purifying and alloying of
molten lead.
7-82
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Blast and reverberatory furnaces are currently the most common types of
smelting furnaces in the industry, although some new plants are using rotary furnaces. There
are currently about 15 reverberatory furnaces, 24 blast furnaces, 5 rotary furnaces, and
1 electric furnace in the secondary lead industry.236 The following discussion provides process
descriptions of these four types of secondary lead smelters.
Reverberatory Furnaces
A reverberatory furnace (Figure 7-19) is a rectangular refractory-lined
furnace.236 Reverberatory furnaces are operated on a continuous basis. Natural gas- or fuel
oil-fired jets located at one end or at the sides of the furnace are used to heat the furnace and
charge material to an operating temperature of about 2,000°F (1,100°C). Oxygen enrichment
may be used to decrease the combustion air requirements. Reverberatory furnaces are
maintained at negative pressure by an induced draft fan.
Reverberatory furnace charge materials include battery grids and paste, battery
plant scrap, rerun reverberatory furnace slag, flue dust, drosses, iron, silica, and coke. A
typical charge over one hour may include 9.3 tons (8.4 Mg) of grids and paste to produce
6.2 tons (5.6 Mg) of lead.236
Charge materials are often fed to a natural gas- or oil-fired rotary drying kiln,
which dries the material before it reaches the furnace. The temperature of the drying kiln is
about 400 °F (200 °C), and the drying kiln exhaust is drawn directly into the reverberatory
furnace or ventilated to a control device. From the rotary drying kiln, the feed is either
dropped into the top of the furnace tiirough a charging chute, or fed into the furnace at fixed
intervals with a hydraulic ram. In furnaces that use a feed chute, a hydraulic ram is often used
as a stoker to move the material down the furnace.
Reverberatory furnaces are used to produce a soft (nearly pure) lead product and
a lead-bearing slag. This is done by controlling the reducing conditions in die furnace so that
7-83
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Chargn Chut*
00
Wim#tti9*&W7ytt&wv*n3!
te:.-\-.'-'--•::.»:•££
•••• -^-^T-rnTTT
L«*d Well end Tap
Hydr»u«o Chsrg* Ram
Figure 7-19. Cross-sectional View of a Typical Stationary Reverberatory Furnace
Source: Reference 236.
-------
lead components are reduced to metallic lead bullion and the alloying elements (antimony, tin,
arsenic) in the battery grids, posts, straps, and connectors are oxidized and removed hi the
slag. The reduction of PbSO4 and PbO is promoted by the carbon-containing coke added to the
charge material:
PbSO4 + C - Pb + CO2 + SO2
2PbO + C - 2Pb + CO2
The PbSO4 and PbO also react with the alloying elements to form lead bullion
and oxides of the alloying elements, which are removed in the slag.
The molten lead collects in a pool at the lowest part of the hearth. Slag collects
in a layer on top of this pool and retards further oxidation of the lead. The slag is made up of
molten fluxing agents such as iron, silica, and lime, and typically has significant quantities of
lead. Slag is usually tapped continuously and lead is tapped intermittently. The slag is tapped
into a crucible. The slag tap and crucible are hooded and vented to a control device.
Reverberatory furnace slag usually has a high lead content (as much as 70 percent by weight)
and is used as feed material in a blast or electric furnace to recover the lead content.
Reverberatory furnace slag may also be rerun through the reverberatory furnace during special
slag campaigns before being sent to a blast or electric furnace. Lead may be tapped into a
crucible or directly into a holding kettle. The lead tap is usually hooded and vented to a
control device.236
Blast Furnaces
A blast furnace (Figure 7-20) is a vertical furnace that consists of a crucible with
a vertical cylinder affixed to the top. The crucible is refractory-lined and the vertical cylinder
consists of a steel water jacket. Oxygen-enriched combustion air is introduced into the furnace
through tuyeres located around the base of the cylinder.
7-85
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Charge Hopper
Exhaust Offtake to Afterburner
Charge
Cool Water
Working Height
of Charge
2.4 to 3.0 m
Lead Spout
Diameter at Tuyeres
— 68 to 120 cm —
Hot Water
Cool Water
Lead Layer 2
i
(3
BE
UJ
Figure 7-20. Cross Section of a Typical Blast Furnace
7-86
-------
Charge materials are pre-weighed to ensure the proper mixture and then
introduced into the top of the cylinder using a skip hoist, a conveyor, or a front-end loader.
The charge fills nearly the entire cylinder. Charge material is added periodically to keep the
level of the charge at a consistent working height while lead and slag are tapped from the
crucible. Coke is added to the charge as the primary fuel, although natural gas jets may be
used to start the combustion process. Combustion is self-sustaining as long as there is
sufficient coke in the charge material. Combustion occurs in the layer of the charge nearest the
tuyeres.
At plants that operate only blast furnaces, the lead-bearing charge materials may
include broken battery components, drosses from the refining kettles, agglomerated flue dust,
and lead-bearing slag. A typical charge over one hour may include 4.8 tons (4.4 Mg) of grids
and paste, 0.3 tons (0.3 Mg) of coke, 0.1 tons (0.1 Mg) of calcium carbonate, 0.07 tons
(0.06 Mg) of silica, 0.5 tons (0.4 Mg) of cast iron, and 0.2 tons (0.2 Mg) of rerun blast
furnace slag, to produce 3.7 tons (3.3 Mg) of lead. At plants that also have a reverberatory
furnace, the charge materials will also include lead-bearing reverberatory furnace slag.236
Blast furnaces are designed and operated to produce a hard (high alloy content)
lead product by achieving more reducing furnace conditions than those typically found in a
reverberatory furnace. Fluxing agents include iron, soda ash, limestone, and silica (sand).
The oxidation of the iron, limestone, and silica promotes the reduction of lead compounds and
prevents oxidation of the lead and other metals. The soda ash enhances the reaction of PbS04
and PbO with carbon from the coke to reduce these compounds to lead metal.
Lead tapped from a blast furnace has a higher content of alloying metals (up to
25 percent) than lead produced by a reverberatory furnace. In addition, much less of the lead
and alloying metals are oxidized and removed in the slag, so the slag has a low metal content
(e.g., 1 to 3 percent) and frequently qualifies as a nonhazardous solid waste.
7-87
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Because air is introduced into the blast furnace at the tuyeres, blast furnaces are
operated at positive pressure. The operating temperature at the combustion layer of the charge
is between 2,200 and 2,600°F (1,200 and 1,400°C), but the temperature of the gases exiting
the top of the charge material is only between 750 and 950 °F (400 and 500° C).
Molten lead collects hi the crucible beneath a layer of molten slag. As in a
reverberatory furnace, the slag inhibits the further oxidation of the molten metal. Lead is
tapped continuously and slag is tapped intermittently, slightly before it reaches the level of the
tuyeres. If the tuyeres become blocked with slag, they are manually or automatically
"punched" to clear the slag. A sight glass on the tuyeres allows the furnace operator to
monitor the slag level and ensure that they are clear of slag. At most facilities, the slag tap is
temporarily sealed with a clay plug, which is driven out to begin the flow of slag from the tap
into a crucible. The slag tap and crucible are enclosed hi a hood, which is vented to a control
device.
A weir dam and siphon in the furnace are used to remove the lead from beneath
the slag layer. Lead is tapped from a blast furnace into either a crucible or directly to a
refining kettle designated as a holding kettle. The lead in the holding kettle is kept molten
before being pumped to a refining kettle for refining and alloying. The lead tap on a blast
furnace is hooded and vented to a control device.
Rotary Furnaces
As noted above, rotary furnaces (sometimes referred to as rotary reverberatory
furnaces) (Figure 7-21) are used at only a few recently constructed secondary lead smelters hi
the United States.236 Rotary furnaces have two advantages over other furnace types: it is
easier to adjust the relative amount of fluxing agents because the furnaces are operated on a
batch rather than a continuous basis, and they achieve better mixing of the charge materials
than do blast or reverberatory furnaces.
7-8
-------
Hygiene Hood
Rotary Furnace Shell
Drive Tram
o
£
Figure 7-21. Side-view of a Typical Rotary Reverbertory Furnace
Source: Reference 236.
7-89
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A rotary furnace consists of a refractory-lined steel drum mounted on rollers.
Variable-speed motors are used to rotate the drum. An oxygen-enriched natural gas or fuel oil
jet at one end of the furnace heats the charge material and the refractory lining of the drum.
The connection to the flue is located at the same end as the jet. A sliding door at the end of the
furnace opposite from the jet allows charging of material to the furnace. Charge materials are
typically placed in the furnace using a retractable conveyor or charge bucket, although other
methods are possible.
Lead-bearing raw materials charged to rotary furnaces include broken battery
components, flue dust, and drosses. Rotary furnaces can use the same lead-bearing raw
materials as reverberatory furnaces, but they produce slag that is relatively free of lead, less
than 2 percent. As a result, a blast furnace is not needed for recovering lead from the slag,
which can be disposed of as a nonhazardous waste.
Fluxing agents for rotary furnaces may include iron, silica, soda ash, limestone,
and coke. The fluxing agents are added to promote the conversion of lead compounds to lead
metal. Coke is used as a reducing agent rather than as a primary fuel. A typical charge may
consist of 12 tons (11 Mg) of wet battery scrap, 0.8 tons (0.7 Mg) of soda ash, 0.6 tons
(0.5 Mg) of coke, and 0.6 tons (0.5 Mg) of iron. This charge will yield approximately 9 tons
(8 Mg) of lead product.236
The lead produced by rotary furnaces is a semi-soft lead with an antimony
content somewhere between that of lead from reverberatory and blast furnaces. Lead and slag
are tapped from the furnace at the conclusion of the smelting cycle. Each batch takes 5 to
12 hours to process, depending on the size of the furnace. Like reverberatory furnaces, rotary
furnaces are operated at a slight negative pressure.
7-90
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Electric Furnaces
An electric furnace consists of a large, steel, kettle-shaped container that is
refractory-lined (Figure 7-22).M6 A cathode extends downward into the container and an anode
is located in the bottom of the container. Second-run reverberatory furnace slag is charged
into the top of the furnace. Lead and slag are tapped from the bottom and side of the furnace,
respectively. A fume hood covering the top of the furnace is vented to a control device.
In an electric furnace, electric current flows from the cathode to the anode
through the scrap charge. The electrical resistance of the charge causes the charge to heat up
and become molten. There is no combustion process involved in an electric furnace.
There is only one electric furnace in operation in the U.S. secondary lead
industry. It is used to process second-run reverberatory furnace slag, and it fulfills the same
role as a blast furnace used in conjunction with a reverberatory furnace. However, the electric
furnace has two advantages over a blast furnace. First, because there are no combustion gases,
ventilation requirements are much lower than for blast or reverberatory furnaces, and the
potential for formation of organics is greatly reduced. Second, the electric furnace is
extremely reducing, and produces a glass-like, nearly lead-free slag that is nonhazardous.
7.6.2 Benzene Emissions From Secondary Lead Smelters
Process emissions (i.e., those emitted from the smelting furnace's main exhaust)
contain metals, organics (including benzene), HC1, and C12. Process emissions also contain
other pollutants, including PM, VOC, CO, and SO2.
Blast furnaces are substantially greater sources of benzene emissions than
reverberatory or rotary furnaces. Low exhaust temperatures from the charge column (about
800°F [430°C]) result in the formation of PICs from the organic material in the feed material.
7-91
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Flue
Bath Level
Lead Tap
Slag Tap
Electrode
Figure 7-22. Cross-sectional View of an Electric Furnace for Processing Slag
Source: Reference 236.
-------
Uncontrolled THC emissions (which correlate closely with organic pollutant emissions) from a
typical 55,000-tons/yr (50,000 Mg/yr) blast furnace are about 309 tons/yr (280 Mg/yr).236
Controlled blast furnace benzene emissions are dependent on the add-on controls
that are used, which may be anywhere from 80 to 99 percent effective at reducing THC
emissions. Rotary and reverberatory furnaces have much higher exhaust temperatures than
blast furnaces, about 1,800 to 2,200°F (980 to 1,200°C), and much lower THG emissions
because of more complete combustion. Total hydrocarbon emissions from a typical rotary
furnace (16,500 tons/yr [15,000 Mg/yr] capacity) are about 38 tons/yr (34 Mg/yr). The
majority of these emissions occur during furnace charging, when the furnace's burner is cut
back and the temperature is reduced. Emissions drop off sharply when charging is completed
and the furnace is brought to normal operating temperature.236 Benzene emissions from
reverberatory furnaces are even lower than those from rotary furnaces because reverberatory
furnaces are operated continuously rather than on a batch basis.
Three test reports from three secondary lead smelters were used to develop
benzene emission factors.237"240 All testing was conducted in support of the EPA's Secondary
Lead National Emission Standards for Hazardous Ah" Pollutants (NESHAP) program. The
three facilities tested represent the following process configurations: a rotary smelting furnace
equipped with a baghouse and SO2 scrubber; a blast furnace equipped with an afterburner,
baghouse, and S02 scrubber; and a reverberatory and blast furnace with exhaust from each
furnace combined prior to a single afterburner, baghouse, and SO, scrubber.
Uncontrolled VOC emissions were measured at all three facilities using
VOST.241 Nineteen VOC, including benzene, were detected by the VOST. Benzene emissions
were measured at the blast furnace outlet (before the afterburner) at two facilities, and at the
rotary furnace outlet at one facility. Total hydrocarbon emissions were measured at both the
blast furnace and rotary furnace outlets and at the afterburner outlets following the blast
furnaces. Emission factors for benzene are shown hi Table 7-11.237'240 Although benzene
emissions were not measured after the control device, controlled emission factors were
7-93
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TABLE 7-11. SUMMARY OF BENZENE EMISSION FACTORS FOR SECONDARY LEAD SMELTING
sec
3-04-004-03
3-04-004-04
Emission Source Control Device
Blast furnace Uncontrolled
Afterburner
Rotary Furnace0 Uncontrolled
Emission Factor
Ib/ton (kg/Mg)1
4.08 x 10 '
(2.04 x 10 ')
2.47xl02h
(1.23xl02)
1.66x10'
(8.30 x 10 2)
Emission
Factor Rating
D
D
D
Reference
237, 238, 240
237, 238, 240
239
1 Emission factors are in Ib (kg) of benzene emitted per ton (Mg) of lead smelted.
b Average emission factor from two facility test reports.
71 c Batch-operated furnace with two charging episodes per batch and an average of 18 hours per batch (during the emissions test).
-------
estimated using the THC control efficiency for the given process configuration. These
estimates assume that the control efficiency for benzene was equal to the control efficiency for
THC.
7.6.3 Control Technologies for Secondary Lead Smelters
Controls used to reduce organic emissions from smelting furnaces in the
secondary lead smelting industry include afterburners on blast furnaces and combined blast and
reverberatory exhausts. Reverberatory and rotary furnaces have minimal benzene emissions
because of high exhaust temperatures and turbulence, which promote complete combustion of
organics. No controls for THC are necessary for these process configurations.236
Benzene emissions from blast furnaces are dependent on the type of add-on
control used. An afterburner operated at 1,300°F (700°C) achieves about 84 percent
destruction efficiency of THC.:3f Facilities with blast and reverberatory furnaces usually
combine the exhaust streams and vent the combined stream to an afterburner. The higher
operating temperature of the reverberatory furnace reduces the fuel needs of the afterburner so
that the afterburner is essentially "idling." Any temperature increase measured across the
afterburner is due to the heating value of organic compounds in the blast furnace exhaust. A
combined reverberatory and blast furnace exhaust stream ducted to an afterburner with an exit
temperature of 1,700°F (930°C) can achieve 99-percent destruction efficiency for THC.236
Additional controls used by secondary lead smelters include baghouses for
paniculate and metal control, hooding and ventilation to a baghouse for process fugitives, and
scrubbers for HC1 and SO2 control.236
7.7 IRON AND STEEL FOUNDRIES
Iron and steel foundries can be defined as those that produce gray, white,
ductile, or malleable iron and steel castings. Cast iron and steels are both solid solutions of
7-95
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iron, carbon, and various alloying materials. Although there are many types of each, the iron
and steel families can be distinguished by their carbon content. Cast irons typically contain
2 percent carbon or greater; cast steels usually contain less than 2 percent carbon.242
Iron castings are used hi almost all types of equipment, including motor
vehicles, farm machinery, construction machinery, petroleum industry equipment, electrical
motors, and iron and steel industry equipment. Steel castings are classified on the basis of
their composition and heat treatment, which determine then- end use. Steel casting
classifications include carbon, low-alloy, general-purpose-structural, heat-resistant,
corrosion-resistant, and wear-resistant. They are used in motor vehicles, railroad equipment,
construction machinery, aircraft, agricultural equipment, ore refining machinery, and chemical
manufacturing equipment.242
Based on a survey conducted by EPA hi support of the iron and steel foundry
MACT standard development, there were 756 iron and steel foundries in the United States in
1992 243 Foundry locations can be correlated with areas of heavy industry 'and manufacturing
and, in general, widi the iron and steel production industry (Ohio, Pennsylvania, and Indiana).
Additional information on iron and steel foundries and their locations may be
obtained from the following trade associations:
• American Foundrymen's Society, Des Plaines, Illinois;
• National Foundry Association, Des Plaines, Illinois;
• Ductile Iron Society, Mountainside, New Jersey;
• Iron Casting Society, Warrendale, Pennsylvania; and
• Steel Founders' Society of America, Des Plaines, Illinois.
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7.7.1 Process Description for Iron and Steel Foundries
The following four basic operations are performed in all iron and steel
foundries:
• Storage and handling of raw materials;
• Melting of die raw materials;
• Transfer of the hot molten metal into molds; and
• Preparation of the molds to hold the molten metal.
Other processes present in most, but not all, foundries include:
• Sand preparation and handling;
• Mold cooling and shakeout;
Casting cleaning, heat treating, and finishing;
• Coremaking; and
• Pattern making.
A generic process flow diagram for iron and steel foundries is given in Figure 7-23.242
Figure 7-24 depicts the emission points in a typical iron foundry.244
Iron and steel castings are produced in a foundry by injecting or pouring molten
metal into cavities of a mold made of sand, metal, or ceramic material. Input metal is melted
by the use of a cupola, an electric arc furnace, or an induction furnace. About 70 percent of
all iron castings are produced using cupolas, with lesser amounts produced in electric arc and
induction furnaces. However, the use of electric arc furnaces in iron foundries is increasing.
Steel foundries rely almost exclusively on electric arc or induction furnaces for melting
purposes. With either type of foundry, when the poured metal has solidified, the molds are
separated and the castings removed from the mold flasks on a casting shakeout unit. Abrasive
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New
Sand
Additives
Sand
Preparation
Molding
New
Sand
Chemical Resins,
Binders & Catalysts
Sand
Preparation
Core
Making
vo
oo
Hot Metal
Transfer,
Slagging and
Treatment
Mold
Pouring
and
Cooling
Melting
and
Alloying
Scrap Metal
and Ingot
(Also Fuel
and Flux)
Return Sand
Transfer,
Processing and
Storage
Shakeout
Charge
Preparation
Cleaning
and
Finishing
Finished Casting
(Product)
Figure 7-23. Process Flow Diagram for a Typical Sand-Cast Iron and Steel Foundry
Source: Reference 242.
-------
Fugitive
Particulates
1
rM
Fugitive
Dust
A
f
5and I Fumes and ^
Raw Materials,
Unloading, Storage,
Transfer
• Flux
• Metals
_ Carbon Sources
*Sand
•Binder
i
T
Scrap
Preparation
Duration | pygujyg rjust ™
i 1 '
Fugitive
y — -w- Dust
i Moid I
; Making
i
i
j
1
Furnace
• Cupola
« Electric Arc
_ Induction
•other
T
Tapping,
Treating
1
Mold Pouring,
Cooling
^ Hydrocarbons,
~r Co, and Smoke -
T
ML
w Furnace • S
^ Vent 0 B
i
i
Fugitive
^. Fumes and Core
Dust
Fugitive
fe- Fumes and
Dust
^ Core
Fugitive
" A
i
i
ring |
>and i
inder !
i
Fugitive
Dust
i
I
T !
Making
Oven
Vent
T
Baking
Sand
Casting
Shakeout
Cooling
Cleaning, Finishing
I
Fugitive
Dust
Fumes and
Fugitive
Dust
Fugitive
Dust
Shipping
Figure 7-24. Emission Points in a Typical Iron and Steel Foundry
Source: Reference 244.
7-99
5
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(shotblasting) cleaning, grinding, and heat treating are performed as necessary. The castings
are then inspected and shipped to another industry for machining and/or assembly into a final
product.242
In a typical foundry operation, charges to the melting unit are sorted by size and
density and cleaned (as required) prior to being put in the melter. Charges consist of scrap
metal, ingot, carbon (coke), and flux. Prepared charge materials are placed in crane buckets,
weighed, and transferred into the melting furnace or cupola. The charge in a furnace or cupola
is heated until it reaches a certain temperature and the desired chemistry of the melt has been
attained. After the desired product is obtained, the molten metal is either poured out of the
furnace into various sized teeming ladles and then into the molds or it is transferred to holding
furnaces for later use.
7.7.2 Benzene Emissions From Iron and Steel Foundries
Organic compounds are emitted from various process steps in an iron and steel
foundry, including scrap preparation, the furnace, tapping and treating, mold pouring and
cooling, casting shakeout, sand cooling, and mold and core production. Benzene may be
included among other organic compounds emitted from these process steps. Sources of
organic emissions during these process steps include solvent degreasers used during scrap iron
charge, coke, and organic binders and organic polymer networks that hold molds and cores
together to form the castings.
Data from one testing program at a single gray iron foundry were averaged to
develop a benzene emission factor (Table 7-12). The emission sources tested were sand cooler
and belts, casting shakeouts and mixers, and pouring and cooling. Vapors from the sand
cooler and belts and casting shakeouts and mixers were collected in hoods and ducted to a
baghouse. Sampling for benzene was performed hi accordance with EPA Method 18. All
sampling was performed at the stack, after the control devices. Benzene emissions from the
three emission sources were detected; however, because of limited process data availability, a
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TABLE 7-12. BENZENE EMISSION FACTOR FOR IRON FOUNDRIES
SCC
Emission Source
( 'ontrol Device(s)
Emission Factor
Ib/ton (kg/Mg)
Emission Factor
Rating
3-04-003-98
Sand cooling and belts
Bagliouse
6.99 x 104
(3.50 x 10^)'
D
Source: References 245 and 246.
* Factor is in Ib (kg) of benzene emitted per ton (Mg) of sand cooled.
I
t—'
o
-------
benzene emission factor could only be calculated for the sand cooler and belts, as reflected in
Table 7-12.245'246
Benzene from sand coolers and belts and casting shakeouts and mixers may be
emitted as a result of the heating during mold pouring of the organic binders used to form the
casting. During mold pouring, the binder materials in the mold are exposed to temperatures
near 2,550°F (1,400°C). At these temperatures, pyrolysis of the chemical binder may release
organic chemicals, which become trapped in the sand inside the casting. During shakeout and
sand cooling, the sand is exposed to the atmosphere and these organic chemicals may be
released.
7.7.3 Control Technologies for Iron and Steel Foundries244
Scrap preparation with heat or solvent degreasers will emit organic compounds.
Caial>iio iiiwincraiGrs and afterburners can control about 95 percent of organic emissions.
Emissions released from melting furnaces include organic compounds. The
highest concentrations of furnace emissions occur when furnace doors are open during
charging, backcharging, alloying, slag removal, and tapping operations. These emissions can
escape into the furnace building or can be collected and vented through roof openings.
Emission controls for melting and refining operations involve venting furnace gases and fumes
directly to a control device. Canopy hoods or special hoods near furnace doors and tapping
points capture emissions and route them to emission control systems.
A cupola furnace typically has an afterburner, which achieves up to 95 percent
efficiency. The afterburner is located in the furnace stack to oxidize CO and burn organic
fumes, tars, and oils. Reducing these contaminants protects the paniculate control device from
possible plugging and explosion. Toxic emissions from cupolas include both organic and
inorganic materials. Cupolas produce the most toxic emissions compared to other melting
equipment. During melting in an electric arc furnace, hydrocarbons are emitted from
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vaporization and incomplete combustion of any oil remaining on the scrap iron charge.
Electric induction furnaces emit negligible amounts of hydrocarbon emissions, and are
typically uncontrolled except during charging and pouring operations.
Organic emissions are generated during the refining of molten iron before
pouring and from the mold and core materials during pouring. Toxic emissions of halogenated
and aromatic hydrocarbons are released in the refining process. Emissions from pouring
normally are captured by a collection system and vented, either controlled or uncontrolled, to
the atmosphere. Emissions continue as the molds cool.
Organics are emitted in mold and core production operations from core baking
and mold drying. Afterburners and catalytic incinerators can be used to control organics
emissions.
In ad^'t^n to organic binders, molds and cores may be held together in the
desired shape by means of a cross-linked organic polymer network. This network of polymers
undergoes thermal decomposition when exposed to the very high temperatures of casting,
typically 2,550°F (1,400°C). At these temperatures it is likely that pyrolysis of the chemical
binder will produce a complex of free radicals that will recombine to form a wide range of
chemical compounds having widely differing concentrations.
There are many different types of resins currently in use, with diverse and toxic
compositions. No data are available for determining the toxic compounds in a particular resin
that are emitted to the atmosphere and to what extent these emissions occur.
7 . 8 PORTLAND CEMENT PRODUCTION
Most of the hydraulic cement produced in the United States is Portland
cement~a cementitious, crystalline compound composed of metallic oxides. The end-product
cement, in its fused state, is referred to as "clinker." Raw materials used in the process can be
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calcium carbonate- and aluminum-containing limestone, iron, silicon oxides, shale, clay, and
sand.247 As of December 1990, there were 112 Portland cement plants in the United States
operating 213 kilns with a total annual clinker capacity of 80 million tons (73.7 million Mg).
The kiln population included 80 wet process kilns and 133 dry process kilns.247 U.S. Portland
cement plants are listed in Table 7-13 .
7.8.1 Process Description for the Portland Cement Industry
In Portland cement production, most raw materials typically are quarried on site
and transferred by conveyor to crushers and raw mills. After the raw materials are reduced to
the desired particle size, they are blended and fed to a large rotary kiln. The feed enters the
kiln at the elevated end. and the burner is located at the opposite end. The raw materials are
then changed into cementitious oxides of metal by a countercurrent heat exchange process.
The materials are continuously and slowly moved to the low end by the rotation of the kiln
v.hile being heated to high temperatures (2,<700°F [1,482°C]) by direct firing (Stream 3 in
Figure 7-25). In this stage, chemical reactions occur, and a rock-like substance called
"clinker" is formed. This clinker is then cooled, crushed, and blended with gypsum to
produce Portland cement.247 The cement is then either bagged or bulk-loaded and transported
out.:48
Cement may be made via a wet or a dry process. Many older kilns use the wet
process. In the past, wet grinding and mixing technologies provided more uniform and
consistent material mixing, resulting in a higher quality clinker. Dry process technologies
have unproved, however, to the point that all of the new kilns since 1975 use the dry
process.249 In the wet process, water is added to the mill while die raw materials are being
ground. The resulting slurry is fed to the kiln. In the dry process, raw materials are also
ground finely in a mill, but no water is added and die feed enters die kiln hi a dry state.
More fuel is required for die wet process dian the dry process to evaporate die
water from the feed. However, for either the wet or dry process, Portland cement production
is fuel-intensive. The fuel burned hi the kiln may be natural gas, oil, or coal. Many cement
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TABLE 7-13. SUMMARY OF PORTLAND CEMENT
PLANT CAPACITY INFORMATION
Location
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Maine
Maryland
Michigan
Mississippi
Missouri
Montana
Nebraska
Nevada
New Mexico
New York
Ohio
Number of Plants
(kilns)
5(6)
1(0)'
2(7)
2(5)
12 (20)
3(5)
6(8)
2(4)
KD
1(2)
4(8)
4(8)
4(7)
4(11)
KD
1(1)
3(7)
5(9)
KD
5(7)
2(2)
1(2)
1(2)
1(2)
4(5)
4(5)
Capacity
103 tons/yr (103 Mg/yr)
4,260 (3,873)
0(0)
1,770(1,609)
1,314(1,195)
10,392 (9,447)
1,804 (1,640)
3,363 (3,057)
1,378(1,253)
263 (239)
210(191)
2,585 (2,350)
2,830 (2,573)
2,806 (2,551)
1,888(1,716)
724 (658-)
455 (414)
1,860(1,691)
4,898 (4,453)
504 (458)
4,677 (4,252)
592 (538)
961 (874)
415 (377)
494 (449)
3,097 (2,815)
1,703(1,548)
7-105
(continued)
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TABLE 7-13. CONTINUED
Location
Oklahoma
Oregon
Pennsylvania
South Carolina
South Dakota
Tennessee
Texas
Utah
Virginia
Washington
West Virginia
Wyoming
Source, keierence 2*1.
' Grinding plant only.
Number of Plants
(kilns)
3(7)
KD
11 (24)
3(7)
1(3)
2(3)
12 (20)
2(3)
1(5)
KD
1(3)
KD
Capacity
103 tons/yr (103 Mg/yr)
1,887 (1,715)
480 (436)
6,643 (6,039)
2,579 (2,345)
766 (696)
1,050 (955)
8,587 (7,806)
928 (844)
1,117(1,015)
473 (430)
822(747) '
461 (419)
7-106
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plants burn coal, but supplemental fuels such as waste solvents, chipped rubber, shredded
municipal garbage, and coke have been used in recent years.247 A major trend in the industry
is the increased use of waste fuels. In 1989, 33 plants in the United States and Canada
reported using waste fuels; the number increased to 55 plants in 1990.247
The increased use of hazardous waste-derived fuels (HWDFs) for the kilns is .
attributed to lower cost and increased availability. As waste generators reduce or eliminate
solvents from their waste steams, the streams contain more sludge and solids. As a result, two
new hazardous waste fueling methods have emerged at cement kilns. The first method pumps
solids (either slurried with liquids or dried and ground) into the hot end of the kiln. The
second method (patented by cement kiln processor and fuel blender Cadence, Inc.) introduces
containers of solid waste into the calcining zone of the kiln.250
The kiln system for the manufacture of Portland cement by dry process with
preheater is shown in Figure 7-25. The raw material enters a four-stage suspension preheater.
where hot gases from the kiln heat the raw feed and provide about 40-percent calcination
(Stream 1) before the feed enters the kiln. Some installations include a precalcining furnace
(Stream 2), which provides about 85 percent calcination before the feed enters the kiln.247
7.8.2 Benzene Emissions from the Portland Cement Industry and Regulatory Analysis
The raw materials used by some facilities may contain organic compounds,
which become a source of benzene emissions during the heating step. However, fuel
combustion to heat the kiln is believed to be the greater source of benzene emissions. As
shown in Table 7-14, benzene is emitted when either fossil fuels or HWDFs are combusted in
the kiln.247-249-251
Facilities that burn HWDF are subject to the Boilers and Industrial Furnaces
(BIF) rule promulgated February 21, 1991, under the Resource Conservation and Recovery
Act (RCRA). The BIF rule requires that a facility that burns hazardous waste demonstrate a
7-107
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o
oo
To
Grinding
MM
Clinker Storaf •
Figure 7-25. Process Diagram of Portland Cement Manufacture by Dry Process With Preheater
Source: Reference 247.
-------
TABLE 7-14. SUMMARY OF EMISSION FACTORS HQR THE PORTLAND CEMENT INDUSTRY
SCC and Description
3-05-007-06
Cement Manufacturing -
Wet Process - Kilns
3-05-006-06
Cement Manufacturing -
Emissions Source Control Device
Kiln-Burning Hazardous EP
Waste Exclusively, or with
Coal or Coke
Kiln-Burning Hazardous EP
Waste and Natural Gas as
Fuel
Kiln-Burning Hazardous EP
Waste and Coal at High
Combustion Temperature
Kiln-Burning Coal in FF
Precalciner Process
Emission Factor
Ib/ton (kg/Mg)'
3.7 x 1(V3
(l.SxlO'3)
7.5 x ID'3
(3.7 x 103)
3.9 x 106
(1.9x10-*)
1.6xl02
(8 x 10 3)
Factor
Rating
B
D
D
E
Reference
247, 251
251
251
249
Dry Process
Kiln—Burning Coal and
20 percent TDF"
FF
0.17g/MMBtu
249
' Expressed as Ib (kg) of benzene emitted per Mg (ton) of clinker produced.
b Facility burns 65 tons (59 Mg) TDF per day (6,000 tires); MMBtu/ton of clinker produced not reported for this facility.
EP = Electrostatic Precipitator.
FF = Fabric Filter.
TDF = Tire-derived fuel.
-------
99.99 percent destruction efficiency for principal organic hazardous constituents in the waste
stream. To guard against products of incomplete combustion, the BIF rule limits CO levels in
the kiln and or total hydrocarbon levels in stack gases.250'251 In addition, a NESHAP for
control of HAPs from Portland Cement Kilns is under development.
Table 7-14 presents a summary of benzene emission factors for wet process
cement kilns controlled with electrostatic precipitators burning HWDF in conjunction with
other fuels.
7.9 HOT-MIX ASPHALT PRODUCTION
In 1994, there were approximately 3,600 asphalt hot-mix plants.252
Approximately 40 percent of companies that operate hot-mix plants operate a single plant.
Because plants must be located near the job site, plants are concentrated hi areas where the
highway and road network is concentrated.^ Additional information on the locations of
individual hot-mix asphalt facilities can be obtained by contacting the National Asphalt
Pavement Association in College Park, Maryland.
7.9.1 Process Description
There are three types of hot-mix asphalt plants operating in the United States:
batch-mix, continuous-mix, and dram-mix. At batch-mix and continuous-mix plants, the
aggregate drying process is performed separately from the mixing of aggregate with asphalt
cement. Drum-mix plants combine these two processes. Production capacities for all three
types of plants range from 40 to 600 tons (36 to 544 Mg) of hot mix per hour. Almost all
plants hi use are of either the batch-mix or the drum-mix types. Less than half a percent of
operating hot-mix asphalt plants are of the continuous-mix variety.79 Over 80 percent of all
hot-mix asphalt production plants are mobile.245
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In the production of hot-mix asphalt (also referred to as asphalt concrete),
aggregate is heated to eliminate moisture and then mixed with hot asphalt cement. The
resulting hot mixture is pliable and able to be compacted and smoothed. When the hot-mix
asphalt cools and hardens, it provides a waterproof and durable pavement for roads,
driveways, parking lots, and runways.
Aggregate, the basic raw material of hot-mix asphalt, consists of any hard, inert
mineral material, usually gravel, sand, and mineral filler. Aggregate typically comprises
between 90 and 95 percent by weight of the asphalt mixture. Because aggregate provides most
of the load-bearing properties of a pavement, the performance of the pavement depends on
selection of the proper aggregate.
Asphalt cement is used as the binding agent for aggregate. It prevents
moisture from penetrating the aggregate, and it acts as a cushioning agent. Typically, asphalt
cement constitutes 4 to * p?rr?rt *»y weight of a hot-mix asphalt mixture.253
As with the asphalt flux used to produce asphalt roofing products, asphalt
cement is obtained from the distillation of crude oil. It is classified into grades under one of
several classification schemes. The most commonly used scheme classifies asphalt cement
based on its viscosity at 140°F (60 °C). The more viscous the asphalt cement, the higher its
numerical rating. An asphalt cement of grade AC-40 is considered a hard asphalt (i.e., a
viscosity of 4,000 grams per centimeter per second [g/cm-s or poises]), whereas an asphalt
cement of grade AC-2.5 is considered a soft asphalt (i.e., a viscosity of 250 g/cm-s [poises]).
Several western States use a second classification scheme that measures viscosity
of the asphalt cement after a standard simulated aging period. This simulated aging period
consists of exposure to a temperature of 325°F (163°C) for 5 hours. Viscosity is measured at
140°F (60°C), with grades ranging from AR-1000 for a soft asphalt cement (1000 g/cm-s
[poises]) to AR-16000 for a hard asphalt cement (16,000 g/cm-s [poises]).
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A third classification scheme is based on the penetration allowed by the asphalt
cement. Grade designation 40 to 50 means that a needle with a weight attached will penetrate
the asphalt cement between 40 and 50 tenths of a millimeter under standard test conditions.
The hard asphalt cements have penetration ratings of 40 to 50, whereas the soft grades have
penetration ratings of 200 to 300.253
The asphalt cement grade selected for different hot-mix asphalts depends on the
type of pavement, climate, and type and amount of traffic expected. Generally, asphalt
pavement bearing heavy traffic in warm climates would require a harder asphalt cement than
pavement subject to either light traffic or cold climate conditions.
Another material that is used to a greater extent in the production of new or
virgin hot-mix asphalt is recycled asphalt pavement (RAP), which is pavement material that
has been removed from existing roadways. This RAP material is now used by virtually all
corr.panie: in their hot-mix asphalt mixtures. The Surface Transportation Assistance Act of
1982 encourages recycling by providing a 5-percent increase in Federal funds to State agencies
that recycle asphalt pavement. Rarely does the RAP comprise more than 60 percent by weight
of the new asphalt mixture. Twenty-five percent RAP is typical in batch plants, whereas 40 to
50 percent RAP mixtures are typical in drum-mix plants.253
Rejuvenating agents are sometimes added to hot-mix asphalts where they are
blended with RAP, which brings the weathered and aged asphalt cement in the recycled
mixture up to the specifications of a new asphalt mixture. Usually, a soft asphalt cement, a
specially prepared high-viscosity oil, or a hard asphalt cement blended with a low-viscosity oil
are used as rejuvenating agents. The amount of rejuvenating agent added depends on the
properties of the RAP and on the specifications for the hot-mix asphalt product.
The primary processes of a typical batch-mix hot-mix asphalt facility are
illustrated in Figure 7-26.232 Aggregate of various sizes is stockpiled at the plant for easy
access. The moisture content of the stockpiled aggregate usually ranges from 3 to 5 percent.
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EXHAUST TO
ATMOSPHERE
LOADER
(9CC 3-05 00].V
SECONDARY FINES
RE TURN LINE
COURSE AGCREOATE
STORAGE PU
ft c©
7COLD AGGREGATE BNS
FEEDERS «SCCK*«°»"»
ASPMAIT CEMEM' STORAGE HEATER
(SCC 3««n CM. -07. OB. -001
IECENO
Eirtsslon Pobttt
I PreMM FugMra EmlMtoni
lOpwiOudEmlMbM
Figure 7-26. General Process Flow Diagram lor Batch Mix Asphalt Paving Plants
Source: Reference 252.
-------
The moisture content of recycled hot-mix asphalt typically ranges from 2 to 3 percent. The
different sizes of aggregate are typically transported by front-end loader to separate cold feed
bins and metered onto a feeder conveyor belt through gates at the bottom of the bins. The
aggregate is screened before it is fed to the dryer to keep oversize material out of the mix.
The screened aggregate is then fed to a rotating dryer with a burner at its lower
(discharge) end that is fired with fuel oil, natural gas, or propane. The dryer removes moisture
from the aggregate and heats the aggregate to the proper mix temperature. Inside the dryer are
longitudinal flights (metal slats) that lift and tumble the aggregate, causing a curtain of material
to be exposed to the heated gas stream. This curtain of material provides greater heat transfer
to the aggregate than would occur if the aggregate tumbled along the bottom of the drum
towards the discharge end. Aggregate temperature at the discharge end of the dryer is about
300 °F (149°C). The amount of aggregate that a dryer can heat depends on the size of the
drum, the size of the burner, and the moisture content of the aggregate. As the amount of
moisture to be removed from the aggregate increases, the effective production capacity of the
dryer decreases
Vibrating screens segregate the heated aggregate into bins according to size. A
weigh hopper meters the desired amount of the various sizes of aggregate into a pugmill mixer.
The pugmill typically mixes the aggregate for approximately 15 seconds before hot asphalt
cement from a heated tank is sprayed into the pugmill. The pugmill thoroughly mixes the
aggregate and hot asphalt cement for 25 to 60 seconds. The finished hot-mix asphalt is either
directly loaded into trucks or held in insulated and/or heated storage silos. Depending on the
production specifications, the temperature of the hot-mix asphalt product mix can range from
225 to 350°F (107 to 177°C) at the end of the production process.
When a hot mix containing RAP is produced, the aggregate is superheated
(compared to totally virgin hot-mix asphalt production) to about 600°F (315°C) to ensure
sufficient heat transfer to the RAP when it is mixed with the virgin materials. The RAP
7-114
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material may be added either to the pugmill mixer or at the discharge end of the dryer. Rarely
is more than 30 percent RAP used in batch plants for the production of hot-mix asphalt.
Continuous-mix plants are very similar in configuration to batch plants.
Continuous-mix plants have smaller hot bins (for holding the heated aggregate) than do batch
plants. Little surge capacity is required of these bins because the aggregate is continuously
metered and transported to the mixer inlet by a conveyor belt. Asphalt cement is continuously
added to the aggregate at the inlet of the mixer. The aggregate and asphalt cement are mixed
by the action of rotating paddles as they are conveyed through the mixer. An adjustable dam at
the outlet end of the mixer regulates the mixing tune and also provides some surge capacity.
The finished mix is transported by a conveyor belt to either a storage silo or surge bin.233
Drum-mix plants dry the aggregate and mix it with the asphalt cement in the
same drum, eliminating the need for the extra conveyor belt, hot bins and screens, weigh
ucppci, ana pugHiili of batch-mix plants. The drum of a drum-mix plant is much like the dryer
of a batch plant, but it typically has more flights than do batch dryers to increase veiling of the
aggregate and to improve overall heat transfer. The burner in a drum-mix plant emits a much
bushier flame than does the burner in a batch plant. The bushier flame is designed to provide
earlier and greater exposure of the virgin aggregate to the heat of the flame. This design also
protects the asphalt cement, which is injected away from the direct heat of the flame.253
Initially, drum-mix plants were designed to be parallel flow as depicted in
Figure 7-27.252 Recently, the counterflow drum-mix plant design shown in Figure 7-28 has
become popular.79 The parallel flow drum-mix process is a continuous mixing type process
using proportioning cold-feed controls for the process materials. Aggregate, which has been
proportioned by gradations, is introduced to the drum at the burner end. As the drum rotates,
the aggregate as well as the combustion products move toward the other end of the drum in
parallel. Liquid asphalt cement flow is controlled by a variable flow pump that is
electronically linked to the virgin aggregate and RAP weigh scales. The asphalt cement is
7-115
-------
a
!
fc
i
-------
PRIMARY
COLLECTOR
LOADER
(SCC 34)5-0024)4)
EXHAUST TO
ATMOSPHERE
-EXHAUST ',
•I FAN
RAP BIN & CONVEYOR
SECONDARY
COLLECTOR
FINE AGGREGATE
STORAGE PILE
(SCC 34)5402-03)
COURSE AGGREGATE
STORAGE PILE
(SCC3-OS-002-03)
|\ SECONDARY FINES
RETURN LINE
CONVEYOR . \ \
CONVEYOR SCALPING / COLD AGGREGATE BINS
SCREEN FEEDERS (SCC 34*402-04)
COUNTER FLOW
DRUM MIXER
(SCC 34)50024)5)
/"* Emtetl»n Point*
ASPHALT CEMENT
STORAGE
HEATER
(SCC 34B-002-06.4)7. -08.09)
(0) Dueled Entatons
I Process Fugttv* Emlsiions
I Open Dust Emissions
Figure 7-28. General Process Flow Diagram for Counter Flow Drum Mix Asphalt Paving Plants
Source: Reference 252.
-------
introduced in the mixing zone midway down the drum in a lower temperature zone, along with
any RAP and PM from the collectors. The mixture is discharged at the end of the drum and
conveyed to a surge bin or storage silos. The exhaust gases also exit the end of the drum and
pass on to the collection system.79
In the counterflow drum-mix type plant, the material flow in the drum is
opposite or counterflow to the direction of exhaust gases. In addition, the liquid asphalt
cement mixing zone is located behind the burner flame zone so as to keep the materials from
direct contact with hot exhaust gases. Liquid asphalt cement flow is still controlled by a
variable flow pump and is injected into the mixing zone along with any RAP and PM from
primary and secondary collectors.79
Parallel-flow drum mixers have an advantage in that mixing in the discharge end
of the drum captures a substantial portion of the aggregate dust, thereby lowering the load on
the downstream collection equipment. For this reason, most parallel flow drum mixers are
followed only by primary collection equipment (usually a baghouse or verituri scrubber).
However, because the mixing of aggregate and liquid asphalt cement occurs in the hot
combustion product flow, organic emissions (gaseous and liquid aerosol) from parallel-flow
drum mixers may be greater than in other processes.79
On the other hand, because the liquid asphalt cement, virgin aggregate, and
RAP are mixed in a zone removed from the exhaust gas stream, counterflow drum-mix plants
will likely have organic emissions (gaseous and liquid aerosol) that are lower than those from
parallel-flow drum-mix plants. A counterflow drum-mix plant can normally process RAP at
ratios up to 50 percent with little or no observed effect on emissions. Today's counterflow
drum-mix plants are designed for unproved thermal efficiencies.79
Of the 3,600 active hot-mix asphalt plants in the United States, approximately
2,300 are batch-mix plants, 1,000 are parallel-flow drum-mix plants, and 300 are counterflow
drum-mix plants. About 85 percent of plants being built today are of the counterflow
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drum-mix design; batch-mix plants and parallel-flow drum-mix plants account for 10 and
5 percent, respectively.79
One major advantage of both types of drum-mix plants is that they can produce
material containing higher percentages of RAP than batch-mix plants can produce. The use of
RAP significantly reduces the amount of new (virgin) rock and asphalt cement needed to
produce hot-mix asphalt. With the greater veiling of aggregate, drum-mix plants are more
efficient than batch-mix plants at transferring heat and achieving proper mixing of recycled
asphalt and virgin materials.253
7.9.2 Benzene Emissions from the Hot-Mix Asphalt Production
Emissions of benzene from hot-mix asphalt plants occur from the aggregate
rotary dryers and the asphalt heaters (due to fuel combustion). In Figure 7-26, the emission
point for the rotary dryer is indicated by SCC 3-05-002-01, and the emission point for the
heater is indicated by SCC 3-05-002-06, -07, -08, and -09. Note that most of the emission
points in Figures 7-26 and 7-27 are sources of paniculate matter. Most plants employ some
form of mechanical collection, typically cyclones, to collect aggregate particle emissions from
the rotary dryers. However, these cyclones would have a minimal collection efficiency for
benzene.
Other types of controls installed at asphalt hot-mix plants, primarily to control
PM emissions, include wet scrubbers or baghouses.253 These controls are expected to have
some effect on reducing benzene emissions; however, the control efficiencies are not known.
Table 7-15 presents four emission factors for the rotary dryer at a hot-mix
asphalt plant.3-254-263 The factors range from 1.41x10^ Ib/ton (7.04xlO'5 kg/Mg) to
1.95xlO'5 Ib/ton (9.75X10"6 kg/Mg) and differ in the type of fuel burned to heat the dryer
(LPG, oil, natural gas, or diesel) and the type of control device used (cyclone, baghouse, wet
scrubber, or uncontrolled). Table 7-15 also presents one emission factor for an
7-119
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TABLE 7-15. EMISSION FACTORS FOR HOT-MIX ASPHALT MANUFACTURE
SCC and Description
3-05-002-01
Petroleum Industry-
Asphalt Concrete-
Rotary Dryer
3-05-002-08
Petroleum Industry-
Asphalt Concrete-
Asphalt heater-Distillate oil
Emissions Source
Rotary Dryer, LPG-fired
Rotary Dryer, oil-fired
Rotary Dryer, natural gas-
or oil-fired
Rotary Dryer, natural gas-
or diesel-fired
Asphalt Heater, diesel-
fired
Control De ice
Uncontrolled
Multiple cyclone
Baghouse with single
cyclone, knock-out box,
or multiple cycl< >ne
Wet scrubber
Uncontrolled
Emission Factor
Ib/ton (kg/Mg)1
5.35x10^
(2.68x10^)
7.70xl05
(3.85xl05)
2.08x10^
(1.04x10^)
1. 95x10 5
(9.75x10*)
1.50x10^
(7.50xlO's)
Factor
Rating
C
C
B
C
D
Reference
254-256
3,257
258-261
262, 263
254
Emission factors are in Ib (kg) of benzene emitted per ton (Mg) of hot-mix asphalt produced.
-------
uncontrolled asphalt heater fired with diesel fuel. The source tests from which these emission
factors were derived all use CARS Method 401 for sampling.
No regulations were identified that require control of benzene emissions at hot
mix asphalt plants.
7.10 OPEN BURNING OF BIOMASS, SCRAP TIRES, AND AGRICULTURAL
PLASTIC FILM
Open burning involves the burning of various materials hi open drums or
baskets, in fields or yards, and hi large open drums or pits. Materials commonly disposed of
in this manner include municipal waste, auto body components, landscape refuse, agricultural
field refuse, wood refuse, bulky industrial refuse, and leaves. This section describes the open
burning of biomass, scrap tires, and agricultural plastic film, and then- associated benzene
emissions
7.10.1 Biomass Burning
Fires are known to produce respirable PM and toxic substances. Concern has
even been voiced regarding the effect of emissions from biomass burning on climate change.264
Burning wood, leaves, and vegetation can be a source of benzene emissions. In this document,
the burning of any wood, leaves, and vegetation is categorized as biomass burning, and
includes yard waste burning, land clearing/burning and slash burning, and forest
fires/prescribed burning.265
Part of the complexity of fires as a source of emissions results from the complex
chemical composition of the fuel source. Different woods and vegetation are composed of
varying amounts of cellulose, lignin, and extractives such as tannins, and other polyphenolics,
oils, fats, resins, waxes, and starches.266 General fuel type categories hi die National Fire-
Danger Rating (NFDR) System include grasses, brush, timber, and slash (residue that remains
on a site after timber harvesting).266 The flammability of these fuel types depends upon plant
7-121
-------
species, moisture content, whether the plant is alive or dead at the time of burning, weather,
and seasonal variations.
Pollutants from the combustion of biomass include CO, NOX, sulfur oxides
(SO.,), oxidants, polycyclic organic matter (POM), hydrocarbons, and PM. The large number
of combustion products is due, in part, to the diversity of combustion processes occurring
simultaneously within a fire-flaming, smoldering, and glowing combustion. These processes
are distinct combustion processes that involve different chemical reactions that affect when and
what pollutants will be emitted during burning.266
Emission factor models (based on field and laboratory data) have been
developed by the U.S. Forest Service. These models incorporate variables such as fuel type
and combustion types (flaming or smoldering). Because ratios of toxic ah- substances are
correlated with the release of other primary PICs (such as CO), the models correlate benzene
with CO emissions.:*f These emission factor models \vcre used to develop emission factors for
the biomass burning sub-categories described hi the following sections.265'
Because of the potential variety in the fuel source and die limited availability of
emission factors to match all possible fuel sources, emissions estimates may not necessarily
represent the combustion practices occurring at every location hi the United States. Therefore,
localized practices of such parameters as type of wood being burned and control strategies
should be carefully compared.265
Yard Waste Burning
Yard waste burning is the open burning of such materials as landscape refuse,
wood refuse, and leaves in urban, suburban, and residential areas.265 Yard waste is often
burned in open drums, piles, or baskets located in yards or fields. Ground-level open burning
emissions are affected by many variables, including wind, ambient temperature, composition
and moisture content of die material burned, and compactness of the pile. It should be noted
7-122
-------
that this type of outdoor burning has been banned in certain areas of the United States, thereby
reducing emissions from this subcategory.265i26? An emission factor for yard waste is shown in
Table 7-16.265-266
Land Clearing and Slash Burning
This subcategory includes the burning of organic refuse (field crops, wood, and
leaves) in fields (agricultural burning) and wooded areas (slash burning) in order to clear the
land. Burning as part of commercial land clearing often requires a permit.265 Emissions from
organic agricultural refuse burning are dependent primarily on the moisture content of the
refuse and, in the case of field crops, on whether the refuse is burned in a headfire or a
backfire.267 Other variables, such as fuel loading (how much refuse material is burned per unit
of land area) and how the refuse is arranged (piles, rows, or spread out), are also important in
certain instances.267 Emission factors for land clearing/burning and slash burning are shown in
Table 7-l* 265>266
Forest Fires/Prescribed Burning
A forest fire (or wildfire) is a large-scale natural combustion process that
consumes various ages, sizes, and types of outdoor vegetation.268 The size, intensity, and even
occurrence of a forest fire depend on such variables as meteorological conditions, the species
and moisture content of vegetation involved, and the weight of consumable fuel per acre (fuel
loading).268
Prescribed or broadcast burning is the intentional burning of forest acres as part
of forest management practices to achieve specific wildland management objectives.
Controlled burning can be used to reduce fire hazard, encourage wildlife habitat, control
insects, and enhance the vigor of the ecosystem.266 Prescribed burning occurs thousands of
times annually in the United States, and individual fires vary in size from a fraction of an acre
7-123
-------
TABLE 7-16. SUMMARY OI BENZENE EMISSION FACTORS FOR BIOMASS BURNING
to
AMS Code
26-10-030-000
28-01-500-000
28-10-005-000
Emission Source
Yard Waste Burning
Land Clearing/Burning
Slash (Pile) Burning
Control Device
Uncontrolled
Uncontrolled
Uncontrolled
Emission Factor
Ib/ton (kg/Mg)a
1.10
(5.51x10-')
9.06x10'
(4.53x10'')
9.06x10'
(4.53x10')
Emission Factor
U
U
U
Rating
Source: References 265 and 266.
' Factors are in Ib (kg) of benzene emitted per ton (Mg) of biomass burned.
AMS = Area and mobile source.
-------
to several thousand acres. Prescribed fire use is often seasonal, which can greatly affect the
quantity of emissions produced.266
HAP emission factors for forest fires and prescribed burning were developed
using the same basic approach for yard waste and land clearing burning, with an additional
step to further classify fuel types into woody fuels (branches, logs, stumps, and limbs), live
vegetation, and duff (layers of partially decomposed organic matter).265 In addition to the fuel
type, the methodology was altered to account for different phases of burning, namely, flaming
and smoldering.265 The resulting emission factors are shown in Table 7-17.
7.10.2 Tire Burning
Approximately 240 million vehicle tires are discarded annually.269 Although
viable methods for recycling exist, less than 25 percent of discarded tires are recycled; the
remaining 175 million are discarded in landfills, stockpiles, or illegal dumps.:6r Although it is
illegal in many states to dispose of tires using open burning, fires often occur at tire stockpiles
and through illegal burning activities.267 These fires generate a huge amount of heat and are
difficult to extinguish (some tire fires continue for months).
Table 7-18 contains benzene emission factors for chunk tires and shredded
tires.267 When estimating emissions from an accidental tire fire, it should be kept hi mind that
emissions from burning tires are generally dependent on the burn rate of the tire. A greater
potential for emissions exists at lower burn rates, such as when a tire is smoldering rather than
burning out of control.267 The fact that the shredded tires have a lower burn rate indicates that
the gaps between tire materials provide the major avenue of oxygen transport. Oxygen
transport appears to be a major, if not the controlling mechanism for sustaining the combustion
process.
7-125
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TABLE 7-17. SUMMARY OF BENZENE EMISSION FACTORS FOR BIOMASS BURNING BY FUEL TYPE
-j
AMS Code Emission Source Fuel Type
28-10-001-000 Forest Fires Firewood
Small wood
Large wood
(flaming)
Large wood
(smoldering)
Live
vegetation
Duff (flaming)
28-10-015-000 Prescribed Burning Fire wood
(Broadcast)
Small wood
Large wood
(flaming)
Large wood
(smoldering)
Live
vegetation
Control Device
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Emission Factor
Ib/ton (kg/Mg)a
6.6x10'
(3.3x10-')
6.6x10'
(3.3 x 10 ')
6.6 x 10 '
(3.3x10-')
2.52
(1.26)
1.48
(7.4 x 10-')
2.52
(1.26)
6.6x10'
(3.3 x 10-')
6.6x10'
(3.3 x 10-')
6.6x10' .
(3.3 x 10-')
2.52
(1.26)
1.48
(7.4 x 10'')
Emission Factor
Rating
U
U
U
U
U
U
U
U
U
U
(continued)
-------
TABLE? 17. CONTINUED
AMS Code Emission Source Fuel Type
Duff (flaming)
Duff
(smoldering)
Control Device
I ncontrolled
Uncontrolled
Emission Factor
Ib/ton (kg/Mg)a
6.6 x 10 '
(3.3 x 10 ')
2.52
(1.26)
Emission Factor
Rating
U
u
Source: References 265 and 266.
' Factors are in Ib (kg) of benzene emitted per ton (Mg) of biomass burned.
AMS = Area and mobile source.
-------
TABLE 7-18. SUMMARY OF BENZENE EMISSION FACTORS FOR OPEN BURNING OF TIRES
SCC Emission Source
5-03-002-03 Chunk Tires
Shredded Tires
Control Device
Uncontrol'ed
Uncontrolled
Emission Factor Ib/ton
(kg/Mg)a
3.05b-c
(1.53)
3.86b-c
(1-93)
Emission Factor Rating
C
C
Source: Reference 267.
1 Factors are in Ib (kg) of benzene emitted per ton (Mg) of tires burned.
b Values are weighted averages because of different burn rates.
c The data used to develop the emission factor are averaged over six sets of VOST tubes per day taken over two days.
N>
oo
-------
7.10.3 Agricultural Plastic Film Burning
Agricultural plastic film is plastic film that has been used for ground moisture
and weed control. The open burning of large quantities of plastic film commonly coincides
with the burning of field crops. The plastic film may also be gathered into large piles and
burned, with or without forced air (an air curtain).267
Emissions from burning agricultural plastic film are dependent on whether the
film is new or has been exposed to vegetation and possibly pesticides. Table 7-19 presents
emission factors for benzene emissions from burning new and used plastic film in piles with
and without forced air (i.e., air is forced through the pile to simulate an air curtain).267
7-129
-------
TABLE 7-19. SUMMARY OF BENZENE EMISSION FACTORS FOR OPEN BURNING
OF AGRICULTURAL PLASTIC FILM
u>
o
SCC Emission Source Control Device
5-03-002-02 Unused Plastic Uncontrolled1"
Forced Air0
Used Plastic Uncontrolled6
Forced Airc
Emission Factor Ib/ton
(kg/Mg)'
9.55 x 10-
(4.77 x 10 -s)
5.75 x 10-
(2.87 x 10"*)
2.47 x 10 "
(1.23x10")
4.88 x 10-
(2.44 x 10 s)
Emission Factor Rating
C
C
C
C
Source: Reference 267.
' Factors are in Ib (kg) of benzene emitted per ton (Mg) of agricultural plastic film burned.
b Emission factors are for agricultural plastic film gathered in a pile and burned.
c Emission factors for agricultural plastic film burned in a pile with a forced air air current.
-------
SECTION 8.0
BENZENE EMISSIONS FROM MOBILE SOURCES
This section quantifies benzene as one component of mobile source hydrocarbon
emissions. These emissions occur from mobile sources as evaporative emissions from
carburetors, fuel tanks, and crankcases, and as a result of combustion.
Benzene is not added to vehicle fuels such as gasoline or diesel, but is formed
during their manufacture, either through catalytic reforming or steam cracking. Most vehicle
fuei is processed using cataiyuc reforming. In catalytic reforming, benzene is produced during
the reaction that increases the octane rating of the naphtha fraction of the crude oil used as
feedstock. Gasoline produced using this process is approximately 0.90 percent benzene (by
weight).158 (See Section 4.1 for an expanded discussion of catalytic reforming.)
The other vehicle fuel manufacturing process, the use of steam cracking of
naphtha feedstock to obtain ethylene, yields gasoline with a higher benzene content-20 to
50 percent. This fuel is blended with other fuels, before it is sold, in order to comply with the
limited maximum concentration of 1.3 percent (by volume). However, steam cracking is
considered a minor source of vehicle fuel. (Refer to Section 4.3 for an expanded discussion of
pyrolysis gasoline and ethylene plants.)
Diesel fuel, on the other hand, is produced by hydrocracking of the gas oil
fraction of crude, and contains relatively insignificant amounts of benzene.
8-1
-------
Benzene is emitted in vehicle exhaust as unburned fuel and as a product of
combustion. Higher-molecular-weight aromatics in the fuel, such as ethylbenzene and toluene,
can be converted to benzene as products of combustion, accounting for approximately 70 to
80 percent of the benzene in vehicle exhaust.
The fraction of benzene in the exhaust varies depending on vehicle type, fuel
type, and control technology, but is generally between 3 to 5 percent by weight of the exhaust.
The fraction of benzene in the evaporative emissions also depends on control technology and
fuel composition, and is generally 1 percent of a vehicle's evaporative emissions.
8.1 ON-ROAD MOBILE SOURCES
Results of recent work by the Office of Mobile Sources (QMS) on toxic
emissions from on-road motor vehicles are presented in the 1993 report Motor Vehicle-Related
Air Toxics Study (MVAli>).:" Inis repon was prepared in response to Section 202(1)(1) of the
1990 amended CAA, which directs EPA to complete a study of the need for, and feasibility of,
controlling emissions of toxic air pollutants that are unregulated under the Act and are
associated with motor vehicles and motor vehicle fuels. The report presents composite
emission factors for several toxic air pollutants, including benzene.
The emission factors presented hi the MVATS were developed using currently
available emissions data in a modified version of the OMS's MOBILE4.1 emissions model
(designated MOBTOX) to estimate toxic emissions as a fraction of total organic gas (TOG)
emissions. TOG includes all hydrocarbons as well as aldehydes, alcohols, and other
oxygenated compounds. All exhaust mass fractions were calculated on a vehicle-by-vehicle
basis for six vehicle types: light-duty gasoline vehicles, light-duty gasoline trucks, heavy-duty
gasoline trucks, light-duty diesel vehicles, light-duty diesel trucks, and heavy-duty diesel
trucks.
8-2
-------
QMS assumed that light-duty gas and diesel trucks have the same mass fractions
as light-duty gas and diesel vehicles, respectively. In developing mass fractions for light-duty
gas vehicles and trucks, four different catalytic controls and two different fuel systems
(carbureted or fuel injection) were considered. Mass fractions for heavy-duty gas vehicles
were developed for carbureted fuel systems with either no emission controls or a three-way
catalyst. These mass fractions were applied to TOG emission factors developed to calculate in-
use benzene emission factors. These in-use factors take into consideration evaporative and
exhaust emissions as well as the effects of vehicle age.
A number of important assumptions were made in the development of these
on-road benzene emission factors, namely:
1. The increase in emissions due to vehicle deterioration with increased
mileage is proportional to the increase in TOG;
2 Toxics fractions remain constant with ambient temperature changes: and
3. The fractions are adequate to use for the excess hydrocarbons that come
from malfunction and tampering/misfueling.
It should be noted that, in specific situations, EPA mobile methods may over or underestimate
actual emissions.
The benzene emission factors by vehicle class in grams of benzene emitted per
mile driven are shown in Table 8-1.270 The OMS also performed multiple runs of the
MOBTOX program to derive a pollutant-specific, composite emission factor that represented
all vehicle classes, based on the percent of total vehicle miles traveled (VMT) attributable to
each vehicle class.20
For traditional gasoline, benzene is typically responsible for 70 to 75 percent of
the aggregated toxic emissions. Most of this is associated with engine combustion exhaust.
8-3
-------
TABLE 8-1. BENZENE EMISSION FACTORS FOR 1990
TAKING INTO CONSIDERATION VEHICLE AGING (g/mi)
LDGV LDGT1 I.DGT2
Exhaust
Areas with no 0.088 0.128 0.191
I/M
Areas with basic 0.068 0.128 0.191
I/M
Evaporative 0.011 0.014 0.011
Refueling Loss 0.002 0.003 0.003
Running Loss 0.005 0.005 0.008
Resting Loss 0.001 0.001 0.001
LDGV = Light-Duty Gasoline Vehicle
LDGT
0.144
0.144
0.013
0.003
0.006
0.001
HDGV LDDV LDDT HDDV . MC
0.365 0.017 0.024 0.035 0.111
0.365 0.017 0.024 0.035 0.111
0.041 - - - 0.037
0.005 -- -- - 0.002
0.013 -- -- -- 0.005
0.001 -- -- - 0.004
Weighted
VMT Mix
0.108
0.095
0.012
0.002
0.005
0.001
•
LDGT1 = Light-Duty Gasoline Truck [pick-ups and vans with gross vehicle weight
of0to6001b(0to272kg)]
LDGT2 = Light-Duty Gasoline Truck [pick-ups and vans with gross vehicle weight
of 601 to 8500 Ib (273 to 3,856 kg)]
LDGT = Light-Duty Gasoline Truck (combined category
HDGV = Heavy-Duty Gasoline Vehicle
LDDV = Light-Duty Diesel Vehicle
LDDT = Light-Duty Diesel Truck
HDDV = Heavy-Duty Diesel Vehicle
MC = Motorcycle
= Not applicable
of LDGT 1 and
LDGT2)
-------
Oxygenated fuels emit less benzene than traditional gasoline mixes but more
than diesel fuel. With the introduction of alternative fuels such as methanol blends,
compressed natural gas (CNG), and liquified petroleum gas (LPG), formaldehyde is the
dominant toxic emission, accounting for 80 to 90 percent of-aggregated toxic emissions.272
Reductions in benzene emissions associated with the use of methanol fuels is dependent upon
the methanol content of the fuel. For instance, benzene emissions for M10 (10 percent
methanol and 90 percent unleaded gasoline) are reduced by 20 percent compared with
traditional fuel, and for M85 (85 percent methanol and 15 percent unleaded gasoline) the
reduction is 84 percent (SAE1992). M100 (100 percent methanol), ethanol, LPG, and CNG
emit minimal amounts of benzene.273 Furthermore, because both LPG and CNG require closed
delivery systems, evaporative emissions are assumed to be zero.
8.2 OFF-ROAD MOBILE SOURCES
hor oil-road mobile sources, EPA prepared the 1991 report Nonroad Engine
Vehicle Emission Study (NEVES),274 which presents emission factors for 79 equipment types,
ranging from small equipment such as lawn mowers and chain saws to large agricultural,
industrial, and construction machinery (see Table 8-2). The equipment types were evaluated
based on three engine designs: two-stroke gasoline, four-stroke gasoline, and diesel. Sources
for the data include earlier EPA studies and testing and new information on tailpipe exhaust
and crankcase emissions supplied by the engine manufacturers. For test data on new engines,
OMS made adjustments to better represent in-use equipment emissions taking into
consideration evaporative emissions and increases in emissions due to engine deterioration
associated with increased equipment age; therefore, new engine data underestimate in-use
emissions.274
Although these emission factors were intended for calculating criteria pollutant
(VOC, NO2, CO) emissions for SIP emissions inventories, OMS derived emission factors for
several HAPs, including benzene, so that national air toxics emissions could be estimated. To
estimate benzene emissions, OMS expressed benzene emissions as a weight percent of exhaust
8-5
-------
TABLE 8-2. OFF-ROAD EQUIPMENT TYPES AND HYDROCARBON EMISSION
FACTORS INCLUDED IN THE NEVES (g/hp-hr)
(FACTOR QUALITY RATING E)
Equipment Type, Area and Mobile
Source Code
(2-stroke gas/4-stroke gas/diesel)
Lawn and Garden, 22-60/65/70-004-
025 Trimmers/Edgers/Brush Cutters
010 Lawn Mower:
030 Leaf Blowers/Vacuums
040 Rear-Engine Riding Mowers .
045 Front Mowers
020 Chain Saws <4hp
050 Shredders < 5 hp
015 Tillers <5hp
055 Lawn and Garden Tractors
- - - T-t • T (-__ . ,
035 Snow Blowers
065 Chippers/Stump Grinders
070 Commercial Turf Equipment
075 Other Lawn and Garden
Equipment
Airport Service. 22-60/65/70-008-
005 Aircraft Support Equipment
010 Terminal Tractors
Recreational, 22-60/65/70-001-
030 All-Terrain Vehicles (ATVs)
040 Minibikes
010 Off- Road Motorcycles
050 Golf Carts
020 Snowmobiles
060 Specialty Vehicles Carts
2-Stroke Gasoline
Engines
Crank
Exhaust Case
471.58'
436 80"
452.11'
„
-
625.80"
436.80"
436.80"
„
--
436.80"
--
436.80"
436.80"
„
4.50M 0.99"'d
1260.00"
-
1260.00"
1260.00"
228.90"
1260.00"
4-Stroke Gasoline
Engines
Exhaust
50.78'
79 17"
40.74"
19.53"
19.53"
-
79.17"
79.17"
19.74"
79 !7"
79.17"
56.55"
19.74"
79.17"
10.02"
10.02"
210.00"
210.00"
150.00"-'
210.00"
-
210.00"
Crank
Case
7.98'
12.44"
6.4V
3.07"
3.07'
-
12.44"
12.44"
3.10"
12.44"
12.44'
12.446
3.10"
12.44"
2.20"-
2.20"
33. Off*
33. 00"
33.00b-<
33.00"
—
33.00"
Diesel Engines
Crank
Exhaust Case
_
„
-
1.20 0.02
~
„
-
„
1.20. 0.02
1 20 00?
-
1.20 0.02
-
1.20 0.02
i.sr o.o3c
1.57C 0.03C
-
„
-
-
„
1.20* 0.02e
8-6
(continued)
-------
TABLE 8-2. CONTINUED
2-Stroke Gasoline
Engines
Equipment Type, Area and Mobile
Source Code Crank
(2-stroke gas/4-stroke gas/diesel) Exhaust Case
Recreational Marine Vessels,
22-82-005/010/020-
005 Vessels w/Inboard Engines 873.67"-'
010 Vessels w/Outboard Engines 873. 67"-'
015 Vessels w/Stenidii\c Engines 873.67bf
020 Sailboat Auxiliary Inboard - -
Engines
025 Sailboat Auxiliary Outboard 873.67"-'
Engines
Light Commercial, less than 50 HP,
22-60/65/70-006-
005 Generator Sets 436. 801
OiO Pumps S.991 i.4i" •
015 Air Compressors
020 Gas Compressors 6.42"-" 1.41"-"
025 Welders
030 Pressure Washers
Industrial, 22-60/65/70-003-
010 Aenai Lifts 4.50" 1.49hd
102Forklifts 4.50"-" 1.49"-"
030 Sweepers/Scrubbers 4.50M 1.49M
040 Other General Industrial 312.00"
Equipment
050 Other Material Handling
Equipment
Construction, 22-60/65/70-002-
003 Asphalt Pavers - -
006 Tampers/Rammers 436.80*
009 Plate Compactors 436. 801
012 Concrete Pavers
4-Stroke Gasoline
Engines
Exhaust
108.69*-'
131. 57*'
10S.69bf
108.69"-'
131.57*-'
19.95*
19.95r
19.95'
-
19.95*
19.951
10.02b
10.02"
10.02"
10.02"
10.02"
9.74"
13.63*
13.63*
—
Crank
Case
-
28.94"''
--
-
28.94"-'
3.14*
3.14!
3.14*.
-
3.14*
3.14*
2.20b
2.20"
2.20b
2.20"
2.20"
2.14"
2.14*
2.14*
—
Diesel Engines
Exhaust
24.39'
24.39'
24.39f
122.45'
122.45'
1.20
1.20
1.20
~
1.20
1.20
1.57r
1.57°
1.57C
1.57°
1.5T
0.60
0.00
0.80
1.10
Crank
Case
-
0.49'
--
-
2.45'
0.02
0.02
0.02
-
0.02
0.02
0.03C
0.03°
0.03C
0.03C
0.03C
0.01
0.00
0.02
0.02
8-7
(continued)
-------
TABLE 8-2. CONTINUED
2-Stroke Gasoline
_ _ _ .,,,., Engines
Source Code Crank
(2-stroke gas/4-stroke gas/diesel) Exhaust Case
Construction, 22-60/65/70-002- (con't)
015 Rollers
018 Scrapers - -
021 Paving Equipment 436.80"
024 Surfacing Equipment - —
027 Signal Boards - -
030 Trenchers - -
033 Bore/Drill Rigs 436.80"
036 Excavators
039 Concrete/Industrial Saws
042 Cement and Mortar Mixers
045 Cranes
048 Graders
051 Off-Highway Trucks
054 Crushing/Proc. Equipment
057 Rough Terrain Forklifts
060 Rubber Tire Loaders
063 Rubber Tire Dozers
066 Tractors/Loaders/Backhoes
069 Crawler Tractors
072 Skid Steer Loaders
075 Off-Highway Tractors
078 Dumpers/Tenders
081 Other Construction Equipment
Agricultural, 22-60/65/70-005-
010 2- Wheel Tractors
015 Agricultural Tractors -- -
030 Agricultural Mowers ~ —
020 Combines
035 Soravers
4-Stroke Gasoline
Engines
Exhaust
19.43'
—
13.63'
13.63'
13.63'
9.74"
9.74"
9.74"
13.63'
13.63'
9.74b
~
-
9.74b
9.74"
8.34b
-
9.74b
—
9.74b
~
13.63'
9.74b
11.53'
8.24b
15.06'
10.77"
10.77"
Crank
Case
3.05'
—"
2.14'
2.14'
2.14'
2.14b
2.14"
2.14"
2.14'
2.14'
2.14"
--
--
2.14"
2.14"
1.83"
--
2.14"
...
2.14"
...
2.14'
2.14"
1.81'
1.81"
2.371
2.37"
2.37b
Diesel Engines
Exhaust
0.80
0.70=
1.01
0.00
1.20
1.54C
1.41C
0.70<
1.41C
1.01
1.26C
1.54C
0.84C
1.41C
1.68C
0.84C
0.84C
1.40°
1.26C
2.10C
2.46C
0.84C
1.41C
~
2.23C
-
1.26C
2.23
Crank
Case
0.02
0.01C
0.02
0.00
0.02
0.03C
0.03°
0.01C
0.03C
0.02
0.03C
0.03C
0.02C
0.03C
0.03C
0.02C
0.02C
0.03C
0.03C
0.04C
0.05C
0.02C
0.03C
—
0.04C
—
0.03C
0.04
8-8
(continued)
-------
TABLE 8-2. CONTINUED
2-Stroke Gasoline
Engines
Equipment Type, Area and Mobile
Source Code Crank
(2-stroke gas/4-stroke gas/diesel) Exhaust Case
Agricultural, 22-60/65/70-005- (con't)
025 Balers
040 Tillers >5hp - -
045 Swathers -
050 Hydro Power Units
055 Other Agricultural Equipment
4-Stroke Gasoline
Engines
Crank
Exhaust Case
_ _
79. IT1 12.44"
10.77" 2.37"
15.08* 2.37"
10.77" 2.37"
Diesel
Engines
Crank
Exhaust Case
2.23
1.20
0.90
2.23
1.82
0.04
0.02
0.02
0.04
0.04
Logging, 22-60/65/70-007-
005 Chain Saws > 4 hp
010 Shredders >5hp
015 Skidders
020 Fellers/Bunchers
319.201
19.531 3.07'
0.84C
0.84C
0.02C
0.02C
a Adjusted for in-use effects using small utility engine data.
b Adjusted for in-use effects using heavy-duty engine data.
c Exhaust HC adjusted for transient speed and/or transient load operation.
d Emission factors for 4-stroke propane-fueled equipment.
eg/hr.
' g/gallon.
"--" = Not applicable
8-9
-------
hydrocarbons plus crank case hydrocarbons. In OMS's analysis, it was assumed that the
weight percent of benzene for all off-road sources was 3 percent of exhaust hydrocarbons.275
A range of OMS-recommended weight percent benzene factors for general categories of
off-road equipment are presented in Table 8-3.274 Note that development of equipment-specific
emission factors is underway, and when available, those emission factors should be considered
instead. To obtain benzene emission estimates from equipment in these general categories of
off-road equipment, the benzene weight percent factors noted hi Table 8-3 can be applied to
hydrocarbon estimates from the different NEVES equipment types.
The NEVES equipment emission factors can be used directly to estimate
emissions from specific equipment types if local activity data is available. If general nonroad
emission estimates are required, States may choose one of the 33 nonartainment areas, studied
in the NEVES report, that is similar in terms of climate and economic activity; the NEVES
nonattainment area can be adjusted to estimate emissions in another state by applying a
population ratio ot the two areas to the NEVES estimate. The NEVES report also has
estimates for individual counties of the 33 nonattainment areas such that States or local
governments may also produce regional or county inventories by adjusting the NEVES county
estimates relative to the population of the different counties. Counties can be chosen from
several of the 33 NEVES nonattainment areas if appropriate. For further details on how to
calculate emissions from specific equipment types refer to NEVES, for details on calculating
emissions of nonroad sources in general see Reference 271.
8.3 MARINE VESSELS
For commercial marine vessels, the NEVES report includes VOC emissions for
six nonattainment areas taken from a 1991 EPA study Commercial Marine Vessel Contribution
to Emission Inventories.116 This study provided hydrocarbon emission factors for ocean-going
commercial vessels and harbor and fishing vessels. The emission factors are shown in
Table 8-4.
8-10
-------
TABLE 8-3. WEIGHT PERCENT FACTORS FOR BENZENE
Benzene % by
_ As Tested Use _ Recommended Off-Road Category Weight of FID HC"
Diesel Forklift Engine Large Utility Equipment 2.4-3.0
Direct Injection Diesel Large Utility Equipment (Cyclic) 3.1-6.5
Automobile Construction Equipment
Indirect Injection Diesel Large Utility Equipment (Cyclic) 1.5-2.1
Automobile Marine, Agricultural Large Utility
Construction Equipment
Leaded Gasoline Automobiles Large Utility Equipment (Cyclic) 3.0-3.4
Marine, Agricultural, Large Utility
Leaded Gasoline Automobiles Large Utility Equipment (Cyclic) 1.1-1.3
(12% Misfire) Marine, Agricultural, Large Utility
1973 Highway Traffic 3.0
Source: Reference 274.
HC — H>aiuv
-------
TABLE 8-4. BENZENE EMISSION FACTORS FOR COMMERCIAL MARINE
VESSELS
Operating Plant Benzene Emission Factor
(operating mode/rated output) (lb/1000 gal fuel)8
Ocean-Going Commercial
Motor Propulsion
All underway modes 0.25
Auxiliary Diesel Generators
500 KW (50% load) 0.87
Harbor and Fishing
Diesel Engines
<500hp
Full 0.22
Cruise 0.54
Slow 0.60
500-1000 hp
Full 0.25
Cruise 0.18
Slow 0.18
1000-1500 hp
Full 0.25
Cruise 0.25
Slow 0.25
1500-2000 hp
Full 0.18
Cruise 0.25
Slow 0.25
2000+ hp
Full 0.23
Cruise 0.18
Slow 0.24
Gasoline Engines - all hp
ratings
Exhaust (g/bhp-hr) 0.35
Evaporative (g/hr) 0.64
* Benzene exhaust emission factors were estimated by multiplying HC emission factors by benzene TOG
fractions. Benzene exhaust emission fractions of HC for all marine diesel engines were assumed to be the same
as the TOG emission fraction for heavy-duty diesel vehicles — 0.0106. The benzene exhaust emission fraction
for marine gasoline engines was assumed to be the same as the exhaust TOG emission fraction for heavy duty
gasoline vehicles ~ 0.0527. The benzene evaporative emission fraction was also assumed to be the same as the
evaporative emission HC fraction for heavy duty gasoline vehicles — 0.0104.
8-12
-------
factors are also provided for gasoline engines in this category. These emission factors are not
broken down by horsepower rating, and are expressed in grams per brake horsepower hour
rather than pounds per thousand gallons of fuel consumed.
8.4 LOCOMOTIVES
As noted in the U.S. EPA's Procedures for Emission Inventory Preparation,
Volume IV: Mobile Sources,271 locomotive activity can be defined as either line haul or yard
activities. Line haul locomotives, which perform line haul operation, generally travel between
distant locations, such as from one city to another. Yard locomotives, which perform yard
operations, are primarily responsible for moving railcars within a particular railway yard.
The OMS has included locomotive emissions hi its Motor Vehicle-Related Air
Toxic Study.20 The emission factors used for locomotives in this report are derived from the
heavy-duty diesel on-road vehicles as there are no emission factors specifically for
locomotives. To derive toxic emission factors for heavy diesel on-road vehicles, hydrocarbon
emission factors were speciated. The emission factors provided in this study (shown in
Table 8-5) are based on g/mile traveled.20
TABLE 8-5. BENZENE EMISSION FACTORS FOR LOCOMOTIVES
Source Toxic Emission Fraction Emission Factor (Ib/gal)
Line Haul Locomotive 0.0106a 0.00022
Yard Locomotive 0.0106a 0.00054
Source: Reference 20.
* These fractions are found in Appendix B6 of EPA, 1993, and represent toxic emission fractions for heavy-duty
diesel vehicles. Toxic fractions for locomotives are assumed to be the same, since no fractions specific for
locomotives are available. It should be noted that these fractions are based on g/mile emissions data, whereas
emission factors for locomotives are estimated in Ib/gal. The toxic emission fractions were multiplied by the
HC emission factors to obtain the toxic emission factors.
8-13
-------
8.5 AIRCRAFT
There are two main types of aircraft engines in use: turbojet and piston. A
kerosene-like jet fuel is used in the jet engines, whereas aviation gasoline with a lower vapor
pressure than automotive gasoline is used for piston engines. The aircraft fleet in the United
States numbers about 198,000, including civilian and military aircraft.277 Most of the fleet is
of the single- and twin-engine piston type and is used for general aviation. However, most of
the fuel is consumed by commercial jets and military aircraft; thus, these types of aircraft
contribute more to combustion emissions than does general aviation. Most commercial jets
have two, three, or four engines. Military aircraft range from single or dual jet engines, as in
fighters, to multi-engine transport aircraft with turbojet or turboprop engines.278
Despite the great diversity of aircraft types and engines, there are considerable
data available to aid in calculating aircraft- and engine-specific hydrocarbon emissions, such as
the database maintained by 'he Federal Aviation Administration (FAA) Office of Environment
and Energy, FAA Aircraft Engine Emissions Database (FAEED). These'hydrocarbon
emission factors may be used with weight percent factors of benzene in hydrocarbon emissions
to estimate benzene emissions from this source. Benzene weight percent factors in aircraft
hydrocarbon emissions are reported in an EPA memorandum 28° concerning toxic emission
fractions for aircraft, and are presented in Table 8-6.
TABLE 8-6. BENZENE CONTENT IN AIRCRAFT LANDING AND TAKEOFF
EMISSIONS
Description
Military Aircraft
Commercial Aircraft
Air Taxi Aircraft
General Aviation
Weight Percent
AMS Code Benzene
22-75-001-000
22-75-020-000
22-75-060-000
22-75-050-000
2.02
1.94
3.44
3.91
Factor Quality
B
B
C
C
Source: Reference 279 and 280.
8-14
-------
Current guidance from EPA for estimating hydrocarbon emissions from aircraft
appears in Procedures for Emission Inventory Preparation; Volume IV: Mobile Sources.271
The landing/takeoff (LTO) cycle is the basis for calculating aircraft emissions. The operating
modes in an LTO cycle are (1) approach, (2) taxi/idle in, (3) taxi/idle out, (4) takeoff, and
(5) climbout. Emission rates by engine type and operating mode are given in the FAEED. To
use this procedure, the aircraft fleet must be characterized and the duration of each operating
mode determined. From this information, hydrocarbon emissions can be calculated for one
LTO for each aircraft type in the fleet. To determine total hydrocarbon emissions from the
fleet, the emissions from a single LTO for the aircraft type would be multiplied by the number
of LTOs for each aircraft type.
The emission estimation method noted above is the preferred approach as it
takes into consideration differences between new and old aircraft. If detailed aircraft
information is unavailable, hydrocarbon emission indices for representative fleet mixes are
provided in the emissions inventory guidance document Procedures for Emissions Inventory
Preparation; Volume IV: Mobile Sources.271 The hydrocarbon emission indices are
0.394 pounds per LTO (0.179 kg per LTO) for general aviation and 1.234 pounds per LTO
(0.560 kg per LTO) for air taxis.
The benzene fraction of the hydrocarbon total (in terms of total organic gas) can
be estimated by using the percent weight factors from Table 8-6. Because air taxis have larger
engines and more of the fleet is equipped with turboprop and turbojet engines than is the
general aviation fleet, the percent weight factor is somewhat different from the general aviation
emission factor.
8.6 ROCKET ENGINES
Benzene has also been detected from rocket engines tested or used for space
travel. Two types of rocket engines are currently in use: sustainer rocket engines, which
provide the main continual propulsion, and booster rocket engines, which provide additional
8-15
-------
force at critical stages of the lift off, such as during the separation of sections of the rocket
fuselage.
Source testing of booster rocket engines using RP-1 (kerosene) and liquid
oxygen have been completed at an engine test site. Tests for benzene were taken for eight test
runs sampling at four locations within the plume envelope below the test stand. Results from
these tests yielded a range of benzene emission factors-0.31 to 0,561 Ib/ton (0.155 to
0.280 kg/Mg) of fuel combusted-providing an average emission factor of 0.431 Ib/ton
(0.215 kg/Mg) of fuel combusted, as presented in Table 8-7.282 It should be noted that booster
fuel consumption is approximately five times that of sustainer rocket engines.
TABLE 8-7. EMISSION FACTORS FOR ROCKET ENGINES
Emission Factor
AMS Code Emissions Source Ib/ton (kg/Mg) Factor Rating
28-10-040-000 Booster rocket engines using 0.431 (0.215)a C
RP-1 (kerosene) and liquid
oxygen as fuel
Source: Reference 282.
2 Emission factors are in Ib (kg) of benzene emitted per ton (Mg) of fuel combusted.
8-16
-------
SECTION 9.0
SOURCE TEST PROCEDURES
Benzene emissions from ambient air, mobile sources, and stationary sources can
be measured utilizing the following test methods:283
EPA Method 0030: Volatile Organic Sampling Train (VOST) with EPA
Method 5040/5041: Analysis of Sorbent Cartridges from VOST;
• EPA Method 18: Measurement of Gaseous Organic Compound
Emissions by Gas Chromatography;
• EPA method TO-1: Determination of Volatile Organic Compounds in
Ambient Air Using Tenax® Adsorption and Gas Chromatography/Mass
Spectrometry (GC/MS);
• EPA method TO-2: Determination of Volatile Organic Compounds in
Ambient Air by Carbon Molecular Sieve Adsorption and Gas
Chromatography/Mass Spectrometry;
EPA Method TO-14: Determination of Volatile Organic Compounds
(VOCs) in Ambient Air Using SUMMA® Passivated Canister Sampling
and Gas Chromatographic (GC) Analysis;
• EPA Exhaust Gas Sampling System, Federal Test Procedure (FTP); and
• Auto/Oil Ah* Quality Improvement Research (AQIRP) Speciation
Methodology.
If applied to stack sampling, the ambient air monitoring methods may require
adaptation or modification. To ensure that results will be quantitative, appropriate precautions
must be taken to prevent exceeding the capacity of the methodology. Ambient methods that
9-1
-------
require the use of sorbents are susceptible to sorbent saturation if high concentration levels
exist. If this happens, breakthrough will occur and quantitative analysis will not be possible.
9.1 EPA METHOD 0030284
The VOST from SW-846 (third edition) is designed to collect VOCs from the
stack gas effluents of hazardous waste incinerators, but it may be used for a variety of
stationary sources. The VOST method was designed to collect volatile organics with boiling
points in the range of 30°C to 100°C. Many compounds with boiling points above 100°C may
also be effectively collected using this method. Because benzene's boiling point is about
80.1 °C, benzene concentrations can be measured using this method. Method 0030 is
applicable to benzene concentrations of 10 to 100 or 200 parts per billion by volume (ppbv). If
the sample is somewhat above 100 ppbv, saturation of the instrument will occur. In those
cases, another method, such as Method 18, should be used. Method 0030 is often used in
conjunction witn analytical Method 5040/5041.
Figure 9-1 presents a schematic of the principal components of the VOST.241 In
most cases, 20 L of effluent stack gas are sampled at an approximate flow rate of 1 L/min,
using a glass-lined heated probe. The gas stream is cooled to 20°C by passage through a
water-cooled condenser and the volatile organics are collected on a pair of sorbent resin traps.
Liquid condensate is collected hi the impinger located between the two resin traps. The first
resin trap (front trap) contains about 1.6 g Tenax® and the second trap (back trap) contains
about 1 g each of Tenax® and petroleum-based charcoal (SKC lot 104 or equivalent), 3:1 by
volume.
The Tenax® cartridges are then thermally desorbed and analyzed by
purge-and-trap GC/MS along with the condensate catch as specified hi EPA
Methods 5040/5041. Analysis should be conducted within 14 days of sample collection.
9-2
-------
vo
MMtod Probe
STACK
(ortMtiyttem)
lsolB«orValv»s
Carbon FlHw
let watir
Exhaust
SllcaG*!
Condensate
Trap Implnger
Figure 9-1. Volatile Organic Sampling Train (VOST)
Source: Reference 241.
-------
The sensitivity of Method 0030 depends on the level of interferences in the
sample and the presence of detectable levels of benzene in the blanks. Interferences arise
primarily from background contamination of sorbent traps prior to or after use in sample
collection. Many interferences are due to exposure to significant concentrations of benzene in
the ambient air at the stationary source site and exposure of the sorbent materials to solvent
vapors prior to assembly.
To alleviate these problems, the level of the lab blank should be determined in
advance. Calculations should be made based on feed concentration to determine if blank level
will be a significant problem. Benzene should not be chosen as a target compound at very low
feed levels because it is likely there will be significant blank problems.283
One of the disadvantages of the VOST method is that because the entire sample
is analyzed, duplicate analyses cannot be performed. On the other hand, when the entire
sample is analyzed, the sensitivity is increased. Another advantage is that breakthrough
volume is not greatly affected by humidity.
9.2 EPA METHODS 5040/5041283-284
The contents of the sorbent cartridges (collected using EPA Method 0030) are
spiked with an internal standard and thermally desorbed for 10 minutes at 80°C with
organic-free nitrogen or helium gas (at a flow rate of 40 mL/min), bubbled through 5 mL of
organic-free water, and trapped on an analytical adsorbent trap. After the 10-minute
desorption, the analytical adsorbent trap is rapidly heated to 180°C, with the carrier gas flow
reversed so that the effluent flow from the analytical trap is directed into the GC/MS. The
volatile organics are separated by temperature-programmed gas chromatography and detected
by low-resolution mass spectrometry. The concentrations of the volatile compounds are
calculated using the internal standard technique. EPA Methods 5030 and 8420 may be
referenced for specific requirements for the thermal desorption unit, purge-and-trap unit, and
GC/MS system.
9-4
-------
A diagram of the analytical system is presented in Figure 9-2. The Tenax*
cartridges should be analyzed within 14 days of collection. The detection limits for
low-resolution MS using this method are usually about 10 to 20 ng or 1 ng/L (3 ppbv).
The primary difference between EPA Methods 5040 and 5041 is the fact that
Method 5041 utilizes the wide-bore capillary column (such as 30 m DB-624), whereas
Method 5040 calls for a stainless steel or glass-packed column (1.8 x 0.25 cm I.D., 1 percent
SP-1000 on 60/80 mesh Carbopack B).
285
9.3 EPA METHOD 18
EPA Method 18 is the preferred method for measuring higher levels of benzene
from a source (approximately 1 part per million by volume [ppmv] to the saturation point of
benzene in air). In Method 18, a sample of the exhaust gas to be analyzed is drawn into a
stainless steel or glass sampling bulb or a Tedlar® or aluminized Mylar® bag as shown in
Figure 9-3.285 The Tedlar® bag has been used for some time in the sampling and analysis of
source emissions for pollutants. The cost of the Tedlar® bag is relatively low, and analysis by
gas chromatography is easier than with a stainless steel cylinder sampler because pressurization
is not required to extract the air sample in the gas chromatographic analysis process.286 The
bag is placed inside a rigid, leak-proof container and evacuated. The bag is then connected by
a Teflon® sampling line to a sampling probe (stainless steel, Pyrex® glass, or Teflon®) at the
center of the stack. The sample is drawn into the bag by pumping air out of the rigid
container.
The sample is then analyzed by gas chromatography coupled with flame
ionization detection. Based on field and laboratory validation studies, the recommended tune
limit for analysis is within 30 days of sample collection.287 One recommended column is the
8-ft x 1/8 in. O.D. stainless steel column packed with 1 percent SP-1000 in
60/80 carbopack B. However, the GC operator should select the column and GC conditions
9-5
-------
Row During
Dssoii 'ion
Flow (a
GC/MS
FlowO'irlng
Adsorp Ion
H« or N2
/
!1
' \
' '}
' \
.. i
u:
—
lermal
asorptlon
1 ^
[1 '
-
Frit
V
o
~
hamber '
X--D
' Y -T"!
•, Analytical Trap A 1-1
> with Heating Cod
(0.3cmd!«m«tar 1
CJ
v ,
by 25 cm long) '
Vant
H20
Pll'B* ( 1 ) 3%OV-l(1cn,)
Column
I 2 I Tenax (7.7 em)
(
( 3 ' Sinca Gal (7.7 cm)
..
' 4 > Charcoal (7.7 cm)
Haalad
Line
Figure 9-2. Tiap Desorption/Analysis Using EPA Methods 5040/5041
-------
Vent
Filter
(glass wool)
Reverse
(3") Type
Pilot Tube
Stack Wall
Probe
Pitot
Manometer
Male Quick
Connectors
Flowmeter
Vacuum Line
Needle
Valve
Pump
Charcoal
Tube
Rigid Leakproof Container
Figure 9-3. Integrated Hag Sampling Train
0.
ac.
u>
a>
o
o
Source: Reference 285.
-------
that provide good resolution and minimum analysis time for benzene. Zero helium or nitrogen
should be used as the carrier gas at a flow rate that optimizes the resolution.
The peak areas corresponding to the retention times of benzene are measured
and compared to peak areas for a set of standard gas mixtures to determine the benzene
concentrations. The detection limit of this method ranges from about 1 ppm to an upper limit
governed by the FID saturation or column overloading. However, the upper limit can be
extended by diluting the stack gases with an inert gas or by using smaller gas sampling loops.
The EPA's Atmospheric Research and Exposure Assessment Laboratory has
produced a modified version of Method 18 for stationary source sampling.286-288 One
difference from the original method is in the sampling rate, which is reduced to allow
collection of more manageable gas volumes. By reducing the gas volumes, smaller Tedlar*
bags can be used instead of the traditional 25-L or larger bags, which are not very practical in
the field, especially ',vhen a large number of samples is required.286 A second difference is the
introduction of a filtering medium to remove entrained liquids, which improves benzene
quantitation precision.
The advantage of EPA Method 18 is that it is rapid and relatively inexpensive.
However, it does require a fully equipped chrornatography lab and a skilled analyst.
9.4 EPA METHOD TO-1 (COMPENDIUM)
Ambient air concentrations of benzene can be measured using EPA
Method TO-1 from Compendium of Methods for the Determination of Toxic Organic
Compounds in Ambient Air.289 This method is used to collect and determine nonpolar, volatile
organics (aromatic hydrocarbons, chlorinated hydrocarbons) that can be captured on Tenax®
and determined by thermal desorption techniques. The compounds determined by this method
have boiling points hi the range of 80 to 200°C.
9-8
-------
Method TO-1 can measure benzene concentrations from about 3 to 150 ppbv.
The advantages and disadvantages are about the same as for the VOST method, and costs are
comparable.
Figure 9-4 presents a block diagram of the TO-1 system. Figure 9-5 presents a
diagram of a typical Tenax® cartridge.289 Ambient air is drawn through the cartridge, which
contains approximately 1 to 2 grams of Tenax*. The benzene is trapped on the Tenax*
cartridge, which is then capped and sent to the laboratory for analysis utilizing GC/MS
according to the procedures specified in EPA Method 5040.
The exact run tune, flow rate, and volume sampled varies from source to source
depending on .the expected concentrations and the required detection limit. Typically, 10 to
20 L of ambient air are sampled. Estimated breakthrough volume of Tenax* (for benzene) is
19 L/g at 38°C. Analysis should be conducted within 14 days of collection. A capillary
column (fused silica Sb-30 or OV-1) having an internal diameter of 0.3 mm and a length of
50 m is recommended. The MS identifies and quantifies the compounds by mass
fragmentation or ion characteristic patterns. Compound identification is normally
accomplished using a library search routine on the basis of GC retention tune and mass
spectral characteristics.
9.5 EPA METHOD TO-2283-289
Method TO-2 is used to collect and determine highly volatile, non-polar
organics (vinyl chloride, vinylidene chloride, benzene, toluene) that can be captured on a
carbon molecular sieve (CMS) trap and determined by thermal desorption techniques. The
compounds to be determined by this technique have boiling points in the range of 15 to 120°C.
Method TO-2 has the same advantages and disadvantages as the VOST method.
Figure 9-6 presents a diagram of a CMS trap construction and Figure 9-7 shows
the GC/MS system used in analyzing the CMS cartridges.289 Air is drawn through a cartridge
9-9
-------
Purge Gas
Thermal
Desorption
Chamber
Liquid
Nitrogen
Coolant
6-Port High-Temperature Valve
Capillary
Gas
Chroma-
tograph
Mass
Spectrometer
Data
System
Vent
Freeze Out Loop
AC-OM4
Figure 9-4. Block Diagram of Analytical System for EPA Method TO-1
Source: Reference 289.
-------
•Tenax
-1.5 Grams (6 cm Bed Depth)
Glass Wool Plugs
(0.5 cm Long)
Glass Cartridge
(13.5 mm OD x
100 mm Long)
(a) Glass Cartridge
1/2'to
1/8'
Reducing
Union
1/2"
Swagdok
Fitting
Glass Wool
Plugs
(0.5 cm Long)
Tenax
-1.5 Grams (7 cm Bed Depth)
1/8' End Cap
Metal Cartridge
(12.7mmODx
100 mm Long)
u
3
ffl,
o
K
111
(b) Metal Cartridge
Figure 9-5. Typical Tenax* Cartridge
Source: Reference 289.
9-11
-------
Heater
Wire
Teflon
Tape
Zetex
Insulation
r
/ /
T^T-
-q-
T7
Fiberglass
Tape
1/4" Nut
1/4"-1/8"
Reducing
Union
End
Cap
Stainless
Steel Tube
1/4" O.D. x 3" Long
Thermocouple
Thermocouple
Connector
Heater
Connector
Figure 9-6. Carbon Molecular Sieve Trap (CMS) Construction
Source: Reference 289.
9-12
-------
CMS Cartridges
Helium Tank
and Regulator
Flow
Controller
Liquid
Nitrogen
Fused Silica
Capillary
Column
Heated 6-Port
Injection Valve
Cryogenic Loop
Mass
Spectrometer
Ion Source
Data
Acquisition
System
Figure 9-7. GC/MS Analysis System for CMS Cartridges
Source: Reference 289.
9-13
-------
containing 0.4 g of a CMS adsorbent. The cartridge is analyzed in the laboratory by flushing
with dry air to remove adsorbed moisture and purging the sample with helium while heating
the cartridge to 350 to 400°C. The desorbed organics are collected in a cryogenic trap and
flash-evaporated into a GC followed by an MS. Only capillary GC techniques should be used.
The GC temperature is increased through a temperature program and the compounds are eluted
from the column on the basis of boiling points. The MS identifies and quantifies the
compounds by mass fragmentation patterns. Compound identification is nprmally
accomplished using a library search routine on the basis of GC retention tune and mass
spectral characteristics. The most common interferences are structural isomers.
9.6 EPA METHOD TO-14283-289
Ambient air concentrations of benzene can also be measured using EPA
Method TO-14 from Compendium of Methods for the Determination of Toxic Organic
Compounds in Ambient Air 2V) This method is based on collection of a whole-air sample in
SUMMA® passivated stainless steel canisters and is used to determine semivolatile and volatile
organic compounds.
This method is applicable to specific semivolatiles and VOCs that have been
tested and determined to be stable when stored in pressurized and subatmospheric pressure
canisters. Benzene has been successfully measured in the parts-per-billion- by-volume level
using this method.
Figure 9-8 presents a diagram of the canister sampling system.289 Air is drawn
through a sampling tram into a pre-evacuated sample SUMMA* canister. The canister is
attached to the analytical system. Water vapor is reduced in the gas stream by a Nafion dryer
and VOCs are concentrated by collection into a cryogenically cooled trap. The cryogen is
removed and the temperature of the sample raised to volatilize the sample into a
high-resolution GC column. The GC temperature is increased through a temperature program
and the compounds are eluted from the column on the basis of boiling points into a detector.
9-14
-------
To AC
Inlet
-1.6 Meters
(-sn)
Ground
Level
Vent
rm
Insulated Enclosure
Inlet
Manifold
Electronic
Timer
0
Metal Bellows i, ,,
Type Pump v'v.
forPrasaurtcad I I
Sampling '• '
Filter
:€1
Mass Flow Matar
Auxiliary
Vacuum
Pump
Thermostat
Fan
j Magnelateh
I I Valve
Mass Row
Control Unit
OQ
Heater
Vacuum/Pressure
Gauge
Valve
^
Valve
Canister
Figure 9-8. Sampler Configuration for EPA Method TO-14
Source: Reference 289.
9-15
-------
The choice of detector depends on the specificity and sensitivity required by the
analysis. Non-specific detectors suggested for benzene analysis include flame ionization
detectors (FED) with detection limits of about 4 ppbv and photoionization detectors (FDD),
which are about 25 times more sensitive than FID. Specific detectors include an MS operating
in the selected ion mode or the SCAN mode, or an ion trap detector. Identification errors can
be reduced by employing simultaneous detection by different detectors. The recommended
column for Method TO-14 is an HP OV-1 capillary type with 0.32 mm I.D. and a 0.88 fim
cross-linked methyl silicone coating or equivalent. Samples should be analyzed widiin 14 days
of collection. One of the advantages of Method TO-14 is that multiple analyses can be
performed on one sample.
9.7 . FEDERAL TEST PROCEDURE (FTP)
The most widely used test procedure for sampling emissions from vehicle
cxiiausi ia the FTP, v»LkL «>as developed in 1974.29°-292 The FTP uses the Urban
Dynamometer Driving Schedule (UDDS), which is 1,372 seconds in duration. An automobile
is placed on a chassis dynamometer, where it is run according to the following schedule:
505 seconds of a cold start; 867 seconds of hot transient; and 505 seconds of a hot start. (The
definitions of the above terms can be found in the FTP description hi die 40 CFR, Part 86).290
The vehicle exhaust is collected hi Tedlar® bags during the three testing stages.
The most widely used method for transporting vehicle exhaust from die vehicle
to the bags is a dilution tube sampling arrangement identical to the system used for measuring
criteria pollutants from mobile sources.290-293 Dilution techniques are used for sampling auto
exhaust because, in theory, dilution helps simulate the conditions under which exhaust gases
condense and react in the atmosphere. Figure 9-9 shows a diagram of a vehicle exhaust
sampling system.290-294 Vehicle exhausts are introduced at an orifice where the gases are
collected and mixed with a supply of filtered dilution air. The diluted exhaust stream flows at
a measured velocity through the dilution tube and is sampled isokinetically.
9-16
-------
Ambient Air Inlet
To
Dilution Air
Sample Bag
To
Exhaust Sample
Bag
Vehicle
Exhaust
Inlet
Flow Control Valve
Paniculate Fitter
To Methanol Sample Collection
To Formaldehyde Sample Collection
Positive Displacement Pump
Manometer
Revolution
A Counter
Pickup
Discharge
a.
oc
3
o
Figure 9-9. Vehicle Exhaust Gas Sampling System
Source: Reference 290.
-------
The major advantage to using a dilution tube approach is that exhaust gases are
allowed to react and condense onto particle surfaces prior to sample collection, providing a
truer composition of exhaust emissions as they occur in the atmosphere. Another advantage is
that the dilution tube configuration allows simultaneous monitoring of hydrocarbons, CO, CO2,
and NOX. Back-up sampling techniques, such as filtration/adsorption, are generally
recommended for collection of both paniculate- and gas-phase emissions.292
9.8 AUTO/OIL AIR QUALITY IMPROVEMENT RESEARCH PROGRAM
SPECIATION METHOD
Although there is no EPA-recommended analytical method for measuring
benzene from vehicle exhaust, the AQIRP method for the speciation of hydrocarbons and
oxygenates is widely used.292'295 Initially, the AQIRP method included three separate analytical
approaches for analyzing different hydrocarbons, but Method 3, the method designated for
benzene, \vas dropped from use because of wandering retention times Method 2 can be used
to measure benzene from auto exhaust but some interferences, which will.be discussed later,
may occur.
This analytical method calls for analyzing the bag samples collected by the FTP
method by injecting them into a dual-column GC with an FID. A recommended pre-column is
a 2 m x 0.32 mm I.D. deactivated fused silica (J&W Scientific Co.) connected to an analytical
column that is 60 m DB-1, 0.32 mm I.D., 1 ^im film thickness.295 The detection limit for
benzene with this method is 0.005 ppmC.
The peak areas corresponding to the retention times of benzene are measured
and compared to peak areas for a set of standard gas mixtures to determine the benzene
concentrations. However, there is a problem with benzene co-eluting with
1-methylcyclopentene. Therefore, the analyst should be aware of this potential interference.
9-18
-------
The amount of benzene in a sample is obtained from the calibration curve in
units of micrograms per sample. Collected samples are sufficiently stable to permit 6 days of
ambient sample storage before analysis. If samples are refrigerated, they are stable for
18 days.
9-19
-------
SECTION 10.0
REFERENCES
1. Toxic Chemical Release Reporting: Community Right-To-Know. 52 FR 21152.
June 4, 1987.
2. U.S. EPA. Procedures for Preparing Emission Factor Documents. Research Triangle
Park, North Carolina: U.S. Environmental Protection Agency, Office of Air Quality
Planning and Standards, 1997.
3. Factor Information Retrieval System Version 2.62 (FIRE 2.62). Research Triangle
Park, North Carolina: U.S. Environmental Protection Agency, March 1994.
4. Sung, M. Handbook of Toxic and Hazardous Chemicals and Carcinogens. Park
Ridge, New Jersey: Noyes Data Company, 1989.
5. R.J. Lewis, Sr. ed. Hazardous Chemicals Desk Reference, 2nd ed. New York,
New York: Von Nostrand Reinhold, 1991. pp. 115 to 117.
6. U.S. EPA. Atmospheric Reaction Products of Organic Compounds.
EPA-560/12-79-001. Washington, D.C.: U.S. Environmental Protection Agency,
1979
7. Handbook of Chemistry and Physics. Weast, R.C., ed. Boca Raton, Florida: CRC
Press, Inc., 1980.
8. Brewster, R.Q. and W.E. McEwen. Organic Chemistry, 3rd ed. Englewood Cliffs,
New Jersey: Prentice Hall, Inc., 1963.
9. U.S. EPA. Atmospheric Benzene Emissions. EPA-450/3-77-029. Research Triangle
Park, North Carolina: U.S. Environmental Protection Agency, 1977. pp. 4-19 to
4-25.
10. Purcell, W.P. Benzene. In: Kirk Other Encyclopedia of Chemical Technology.
Vol. 3. New York, New York: John Wiley and Sons, 1978.
10-1
-------
11. SRI International. 1993 Directory of Chemical Producers. Menlo Park, California:
SRI International, 1993.
12. Benzene. Chemical Products Synopsis. Asbury Park, New Jersey: Mannsville
Chemical Products Corporation, July 1993.
13. U.S. EPA. The Environmental Catalog of Industrial Processes. Vol. I- Oil/Gas
Production, Petroleum Refining, Carbon Black and Basic Petrochemicals.
EPA-600/2-76-051a. Research Triangle Park, North Carolina: U.S. Environmental
Protection Agency, 1976.
14. U.S. EPA. Ethylene: Reports. In: Organic Chemical Manufacturing. Vol. 9:
Selected Processes. EPA-450/3-80-028d. Research Triangle Park, North Carolina:
U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards,
1978.
15. Dossett, A.P. Dealkylation of Toluene and Xylene. In: Toluene, the Xylenes and
Their Industrial Derivatives, Hancock, E.G., ed. New York, New York: Elsevier
Scientific Publishing Company, 1982. pp. 157-171.
16. Acetone. Chemical Products Synopsis. Asbury Park, New Jersey: Mannsville
Chemical Product Corporation, March 1995.
17. Cyclohexane. Chemical Products Synopsis. Asbury Park, New Jersey: Mannsville
Chemical Products Corporation, April 1993.
18. Aniline. Chemical Products Synopsis. Asbury Park, New Jersey: Mannsville
Chemical Products Corporation, December 1992.
19. Dylewski. S.W. Chlorobenzenes: Report 3. In: Organic Chemical Manufacturing,
Vol.6: Selected Processes. EPA-45Q/3-80-028a. Research Triangle Park, North
Carolina: U.S. Environmental Protection Agency, Office of Air Quality Planning and
Standards, 1980.
20. U.S. EPA. Motor Vehicle-Related Air Toxic Study. EPA-420/R-93-005. Ann Arbor,
Michigan: U.S. Environmental Protection Agency, Office of Mobile Sources,
April 1993.
21. U.S. Department of Transportation. Highway Statistics 1992. Washington, D.C.:
U.S. Department of Transportation, 1993.
22. U.S. EPA. Compilation of Air Pollutant Emission Factors, 5th ed. (AP-42), Vol. I:
Stationary Point and Area Sources, Supplement A, Section 6.18: "Benzene, Toluene,
and Xylenes," 1995. Not yet published.
10-2
-------
23. U.S. EPA. Materials Balance for Benzene Level II. EPA-560/13-80-009.
Washington, D.C.: U.S. Environmental Protection Agency, 1980. pp. 2-6 to 2-34.
24. Toluene. Chemical Products Synopsis. Asbury Park, New Jersey: Mannsville
Chemical Products Corporation, October 1992.
25. U.S. EPA. Evaluation of Benzene-Related Petroleum Process Operations.
EPA-450/3-79-022. Research Triangle Park, North Carolina: U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards, 1978.
26. Otani, S. Benzene, Xylene Bonanza from Less-Price Aromatics. Chemical
Entering. 77(16): 118-120, 1970.
27. U.S. EPA. Locating and Estimating Sources of Toluene Emissions.
EPA-454/R-93-047. Research Triangle Park, North Carolina: U.S. Environmental
Protection Agency, Office of Ah- Quality Planning and Standards, 1993.
28. Standifer, R.L. Ethylene: Reports. In: Organic Chemical Manufacturing. Vol.9:
Selected Processes. EPA-450/3-80-028d. Research Triangle Park, North Carolina:
U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards,
1981.
29. Kniel, L., et al. Ethylene. In: Kirk-Othmer Encyclopedia of Chemical Technology.
Vol. 9. New York, New York: John Wiley and Sons, 1980. pp. 393-431.
30. Sirtig, M. Aromatic Hydrocarbon Manufacture and Technology. Park Ridge, New
Jersey: Noyes Data Company, 1976.
31. U.S. EPA. Compilation of Air Pollutant Emission Factors, 5th ed. (AP-42), Vol. I:
Stationary Point and Area Sources, Section 5.3: "Natural Gas Processing," Research
Triangle Park, North Carolina: U.S. Environmental Protection Agency, Office of Air
Quality Planning and Standards, January 1995.
32. Davis, B.C. "Implementation Options for MACT Standards for Emissions from
Leaking Equipment." Presented at the 84th Annual Meeting and Exhibition of the Air
and Waste Management Association. Vancouver, British Columbia: June 16-21, 1991.
33. AP-42, 5th ed., op. tit., reference 31. Section 7.1: "Organic Liquid Storage Tanks,"
1995.
34. U.S. EPA. Evaluation of the Efficiency of Industrial Flares: Flare Head Design and
Gas Composition. EPA-600/2-85-106. Research Triangle Park, North Carolina:
U.S. Environmental Protection Agency, 1985.
10-3
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35. U.S. EPA. Background Memorandum for Section 5.35 ofAP-42, Review of
Information on Ethylene Production. Research Triangle Park, North Carolina:
U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards,
September 1993.
36. National Emission Standards for Hazardous Air Pollatants for Source Categories; Coke
Oven Batteries. Proposed rule, 57 FR 57534, December 4, 1992.
37. U.S. EPA. Benzene Emissions from Coke By-Product Recovery Plants—Background
Information for Proposed Standards. EPA-450/3-83-016a. Research Triangle Park,
North Carolina: U.S. Environmental Protection Agency, Office of Air Quality
Planning and Standards, 1984.
38. McCollum, H.R., J.W. Botkin, M.E. Hohman, and G.P. Huber. "Coke Plant Benzene
By-Products NESHAP Operating Experience." Presented at the 87th Annual Meeting
and Exhibition of the Air and Waste Management Association. Cincinnati, Ohio:
June 1994.
39. U.S. EPA. Environmental Assessment of Coke By-Product Recovery Plants.
EPA-600/2-79-016. Research Triangle Park, North Carolina: U.S. Environmental
Protection Agency, 1979.
40. Dufallo, J.M., D.C. Spence, and W.A. Schwartz. "Modified Litol Process for
Benzene Production." Chemical Engineering Progress. 77(l):56-62, 1981.
41. Milton, H.E. By Carbonization. In: Toluene, the Xylenes and Their Industrial
Derivatives. Hancock, E.G., ed. New York, New York: Elsevier Scientific
Publishing Co., 1982.
42. U.S. EPA. Coke Oven Emissions from Wet-Coal Charged By-Product Coke Oven
Batteries-Background Information for Proposed Standards. Draft EIS.
EPA-450/3-85-028a. Research Triangle Park, North Carolina: U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards, April 1987.
43. Coy, D. (Research Triangle Institute). Letter to G. Lacy (U.S. Environmental
Protection Agency) concerning Benzene Emissions from Foundry Coke Plants. Docket
No. A-79-16, Item IV-B-7. March 11, 1985.
44. National Emissions Standards for Hazardous Air Pollutants; Benzene Emissions from
Maleic Anhydride Plants, Ethylbenzene/Styrene Plants, Benzene Storage Vessels,
Benzene Equipment Leaks, and Coke By-Product Recovery Plants; Final Rule.
54 FR 38044-38082, September 14, 1989.
10-4
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45. U.S. EPA. Control Techniques for Volatile Organic Compound Emissions from
Stationary Sources. EPA-453/R-92-018. Research Triangle Park, North Carolina:
U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards,
December 1992.
46. U.S. EPA. Reactor Processes in the Synthetic Organic Chemical Manufacturing
Industry—Background Information for Proposed Standards. EPA-450/3-90-016a.
Research Triangle Park, North Carolina: U.S. Environmental Protection Agency,
Office of Ah" Quality Planning and Standards, June 1990.
47. Schwartz, R.J., and C.J. Pereira (W.R. Grace & Co.). "Summary of Options for the
Control of Volatile Organic Compounds from the Chemical Process Industry."
Presented at the 87th Annual Meeting and Exhibition of the Air and Water Management
Association. Cincinnati, Ohio: June 19-24, 1994.
48. National Emission Standards for Hazardous Air Pollutants for Source Categories; Air
Pollutants for Source Categories; Organic Hazardous Air Pollutants from the Synthetic
Organic Chemical Manufacturing Industry, Final rule. 59 FR 19402, April 22, 1994.
49. U.S. Code of Federal Regulations. Title 40, Protection of the Environment,
Part 63-National Emission Standards for Hazardous Ah- Pollutants for Source
C2tegories, Subpart CC-National Emission Standards for Hazardous Air Pollutants-
Petroleum Refineries. Final Rule. 60 FR 43244. Washington, D.C.: Government
Printing Office, August 18, 1995.
50. U.S. Code of Federal Regulations. Title 40, Protection of the Environment,
Part 60--Standards of Performance for New Stationary Sources, Subpart Ill-Standards
of Performance from Volatile Organic Compound (VOC) Emissions from the Synthetic
Organic Chemical Manufacturing Industry (SOCMI) Air Oxidation Unit Process.
Washington, D.C.: Government Printing Office, July 1, 1994.
51. U.S. Code of Federal Regulations. Title 40, Protection of the Environment,
Part 60-Standards of Performance for New Stationary Sources,
Subpart NNN—Standards of Performance for Volatile Organic Compound (VOC)
Emissions from Synthetic Organic Chemical Manufacturing (SOCMI) Distillation
Operations. Washington, D.C.: Government Printing Office, July 1, 1994.
52. U.S. Code of Federal Regulations. Title 40, Protection of the Environment,
Part 60—Standards of Performance for New Stationary Sources,
Subpart RRR-Standards of Performance for Volatile Organic Compound Emissions
from Synthetic Organic Chemical Manufacturing (SOCMI) Reactor Processes.
Washington, D.C.: Government Printing Office, July 1, 1994.
10-5
-------
53. U.S. Code of Federal Regulations. Title 40, Protection of the Environment,
Part 61--National Emission Standards for Hazardous Air Pollutants,
Subpart L-National Emission Standard for Benzene Emissions from Coke By-Product
Recovery Plants. Washington, D.C.: Government Printing Office, July 1, 1994.
54. U.S. EPA. Protocol for Equipment Leak Emission Estimates. EPA-453/R-95-017.
Research Triangle Park, North Carolina: U.S. Environmental Protection Agency,
Office of Air Quality Planning and Standards, November 1995.
55. U.S. EPA. Fugitive Emission Sources of Organic Compounds—Additional Information
on Emissions, Emission Reduction, and Costs. EPA-450/3-82-010. Research Triangle
Park. North Carolina: U.S. Environmental Protection Agency, 1982.
56. U.S. Code of Federal Regulations. Title 40, Protection of the Environment,
Part 61-National Emission Standards for Hazardous Air Pollutants, Subpart J—National
Emission Standard for Equipment Leaks (Fugitive Emission Sources) of Benzene.
Washington, D.C.: Government Printing Office, July 1, 1994.
57. U.S. Code of Federal Regulations. Title 40, Protection of the Environment,
Part 61-National Emission Standards for Hazardous Air Pollutants,
Subpart V~National Emission Standard for Equipment Leaks (Fugitive Emission
Sources). Washington, D.C.: Government Printing Office, July 1, 1994.
58. U.S. Code of Federal Regulations. Title 40, Protection of the Environment,
Part 60-Standards of Performance for New Stationary Sources, Subpart W-Standards
of Performance for Equipment Leaks of VOC in the Synthetic Organic Chemical
Manufacturing Industry. Washington, D.C.: Government Printing Office,
July 1, 1994.
59. U.S. Code of Federal Regulations. Title 40, Protection of the Environment,
Part 63~National Emission Standards for Hazardous Air Pollutants for Source
Categories, Subpart F~National Emission Standards for Organic Hazardous Air
Pollutants from the Synthetic Organic Chemical Manufacturing Industry and Equipment
Leaks from Seven Other Processes. Washington, D.C.: Government Printing Office,
July 1, 1994.
60. U.S. Code of Federal Regulations. Title 40, Protection of the Environment,
Part 63~National Emission Standards for Hazardous Air Pollutants for Source
Categories, Subpart H—National Emission Standards for Organic Hazardous Air
Pollutants from Synthetic Organic Chemical Manufacturing Equipment Leaks.
Washington, D.C.: Government Printing Office, July 1, 1994.
10-6
-------
61. U.S. Code of Federal Regulations. Title 40, Protection of the Environment,
Part 61-National Emission Standards for Hazardous Air Pollutants,
Subpart Y-National Emission Standards for Benzene Emissions from Benzene Storage
Vessels. Washington, D.C.: Government Printing Office, July 1, 1994.
62. U.S. Code of Federal Regulations. Title 40, Protection of the Environment,
Part 60~Standards of Performance for New Stationary Sources, Subpart Kb~Standards
of Performance for Volatile Organic Liquid Storage Vessels (Including Petroleum
Liquid Storage Vessels) for which Construction, Reconstruction or Modification
Commenced after July 23, 1984. Washington, D.C.: Government Printing Office,
July 1, 1994.
63. U.S. Code of Federal Regulations. Title 40, Protection of the Environment,
Part 63~National Emission Standards for Hazardous Air Pollutants for Source
Categories, Subpart G-National Emission Standards for Organic Hazardous Air
Pollutants from the Synthetic Organic Chemical Manufacturing Industry for Process
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222. AP-42, 5th ed., op. dr., reference 31. Section 1.9: "Residential Fireplaces,"1995.
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266. Peterson, J. and Ward, D. An Inventory of Paniculate Matter and Air Toxic Emissions
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270. Cook, R. (Office of Mobile Sources, U.S. Environmental Protection Agency, Ann
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272. Rieger, P. and W. McMahon. Speciation and Reactivity Determination of Exhaust
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10-25
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277. FAA 1990 Census of U.S. Civil Aircraft.
278. U.S. Department of Energy. Petroleum Supply Annual 1993. Washington, D.C.:
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280. Memorandum from Rick Cook, U.S. Environmental Protection Agency, Office of
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Protection Agency, Inventory Guidance and Evaluation Section, September 1991.
284. U.S. EPA. Test Methods for Evaluating Solid Waste, 3rd ed., Report No. SW-846.
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285. U.S. Code of Federal Regulations. Title 40, Protection of the Environment,
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10-26
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288. Entropy Environmentalists, Inc. Sampling and Analysis of Butadiene at a Synthetic
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290. U.S. Code of Federal Regulations, Title 40, Protection of the Environment, Part 86,
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292. Blackley, C. (Radian Corporation) and P. Gabele (U.S. Environmental Protection
Agency). Teleconference concerning mobile sources testing, May 10, 1994.
293. U.S. EPA. Butadiene Measurement Technology. EPA 460/3-88-005. Ann Arbor,
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Pollution Control, 1988. pp. 1-23, Al-15, Bl-5, Cl-3.
294. Lee, F.S., and D. Schuetzle. Sampling, Extraction, and Analysis of Polycyclic
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295. Siegl, W.D., et al. "Improved Emissions Speciation Methodology for Phase II of the
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296. AP-42, op. cit., reference 31. Draft Section 12.2: "Coke Production,"
January 1, 1995.
10-27
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APPENDIX A
SUMMARY OF EMISSION FACTORS
-------
TABLE A 1. SUMMARY Ol: EMISSION FACTORS
SCC/A MS
Code
Description
Emission Source
Control Device
Emission Factor
3-01-197-45 Ethylene Manufacturing -
Compressor Lube Oil Vent3
3-01-197-42 Ethylene Manufacturing
Pyrolysis Furnace Decoking*
3-01-197-43 Ethylene Manufacturing -
Acid Gas Removal"
3-01-197-44 Ethylene Manufacturing -
Catalyst Regeneration'
3-01-820-09 Ethylene Manufacturing-
Secondary Sources'
3-01-197-49 Ethylene Manufacturing -
Equipment Leak Emissions'
3-01-197-99 Ethylene Manufacturing -
Intermittent Emissions'
Compressor Lube Oil Vents Uncontrolled
Single Compressor Train Uncontrolled
Dual Compressor Tram Uncontrolled
Pyrolysis Furnace Deeoking
Acid Gas Removal
Catalyst Regeneration
Secondary Wastewater Uncontrolled
Treatment
Equipment Leak Emissions Detection/Correction of
leaks
Uncontrolled
Intermittent Emissions'1
Single Compressor Train Flare
Dual Compressor Train
Uncontrolled
Flare
Uncontrolled
Factor Rating
0.0006 Ib/ton (0.0003 kg/Mg) U
0.0004 Ib/ton (0.0002 kg/Mg) U
0.0008 Ib/ton (0.0004 kg/Mg) U
Mo benzene emissions
Mo benzene emissions
Mo benzene emissions
0.0434 Ib/ton (0.0217 kg/Mg) U
See Section 4.5.2
See Section 4.5.2
0.1584-0.0316 Ib/ton U
(0.0792-0.0158 kg/Mg)
1.584 Ib/ton (0.7919 kg/Mg) U
0.0202 0.004 Ib/ton (0.0101-0.002 U
kg/Mg)
0.2022 Ib/ton (0.1011 kg/Mg) U
(continued)
-------
TABLE A-1. CONTINUED
SCC/AMS
Code Description Emission Source
3-03-003-15 By-Produci Coke - Cooling Tower
Gas By-Product Plant
(Furnace Coke) oirctl Water
Tar Bottom
1 ight-Oil Condenser Vent
Naphthalene Separation and
Processing
Tar-Intercepting Sump
Tar Dewatering
Tar Decanter
Tar Storage
Light-Oil Sump
! .ight-Oil Storage
Control Device
Uncontrolled
Uncontrolled
Uncontrolled
Gas Blanketing
Uncontrolled
Activated Carbon
Uncontrolled
Uncontrolled
Gas Blanketing
Uncontrolled
Gas Blanketing
Uncontrolled
Gas Blanketing
Uncontrolled
Source Enclosure
Uncontrolled
Gas Blanketing
Emission Factor
0 54 Ib/ton (270 g/Mg)
<>.141b/ton(70g/Mg)
o. 18 Ib/ton (89 g/Mg)
3.6 x 10 Mb/ton (1.8 g/Mg)
022 Ib/ton (110 g/Mg)
7.0 x lO^lb/ton (0.35g/Mg)
0 019 Ib/ton (9.5 g/Mg)
0 042 Ib/ton (21 g/Mg)
8.4 x 10^ Ib/ton (0.45 g/Mg)
0.1 lib/ton (54 g/Mg)
22 x 10 3 Ib/ton (1.1 g/Mg)
0.013 Ib/ton (6.6 g/Mg)
7.6 K \Q* Ib/ton (0.38 g/Mg)
0.03 Ib/ton (15 g/Mg)
6 x 10* Ib/ton (0.3 g/Mg)
0 012 Ib/ton (5.8 g/Mg)
2.4 x 10^ Ib/ton (0.1 2 g/Me)
Factor Rating
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
(continued)
-------
TABLE A-l. C ONTINUED
>
SCC/AMS
Code Description Emission Source
3-03-003-15 By-Product Coke-Gas BTX Storage
By- Product Plant
(Furance Coke)
(continued)
Benzene Storage
Flushing-Liquor Circulation
Tank
Excess- Ammonia Liquor
Tank
Wash-Oil Decanter
Wash-Oil Circulation Tank
3-03-003-15 By-Product Coke-Gas Cooling Tower
By-Product Plant
(Foundry Coke) -Direct Water
-Tar Bottom
Light-Oil Condenser Vent
Control Device
Uncontrolled
Gas Blanketing
Uncontrolled
Nitrogen or Natural Gas
Blanketing
Uncontrolled
Gas Blanketing
Uncontrolled
Gas Blanketing
Uncontrolled
Gas Blanketing
Uncontrolled
Gas Blanketing
Uncontrolled
Uncontrolled
Uncontrolled
Gas Blanketing
Emission Factor Factor Rating
0.0121b/ton(5.8g/Mg)
2. 1 x 10^ Ib/ton (0. 12 g/Mg)
().01161b/ton(5.8g/Mg)
2. 1x10^ Ib/ton (0.12 g/Mg)
0.026 Ib/ton (13 g/Mg)
5. 1 x KT1 Ib/ton (0.26 g/Mg)
0.018 Ib/ton (9 g/Mg)
5.6 x 10^ Ib/ton (0.028 g/Mg)
76x 10-' Ib/ton (3.8 g/Mg)
L.'Sx 10-4 Ib/ton (0.076 g/Mg)
7 6x 10'3 Ib/ton (3. 8 g/Mg)
1 .5 x 10^ Ib/ton (0.076 g/Mg)
0.40 Ib/ton (200 g/Mg)
0.10 Ib/ton (51 g/Mg)
0.096 Ib/ton (48 g/Mg)
1.9x 10 Mb/ton (0.97 g/Mg)
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
(continued)
-------
TABLE A-1. CONTINUED
SCC/AMS
Code Description Emission Source
3-03-003-15 By-Product Coke-Gas By- Naphthalene Separation and
Product Plant (Foundry Coke) Processing
(continued)
Tar Intercepting Sump
Tar Dewatering
Tar Decanter
Tar Storage
Light-Oil Sump
Light-Oil Storage
BTX Storage
Benzene Storage
Flushing-Liquor Circulation
Tank
Control Device
Uncontrolled
Activated Carbon
Uncontrolled
Uncontrolled
Gas Blanketing
Uncontrolled
Gas Blanketing
Uncontrolled
Gas Blanketing
Uncontrolled
Gas Blanketing
Uncontrolled
Gas Blanketing
Uncontrolled
Gas Blanketing
Uncontrolled
Nitrogen or Natural Gas
Blanketing
Uncontrolled
Gas Blanketing
Emission Factor Factor Rating
0.161b/ton(80g/Mg)
5.<}\ lO^lb/ton (0.25 g/Mg)
<>.0091b/ton(4.5g/Mg)
0.20 Ib/ton (9.9 g/Mg)
4 x 10* Ib/ton (0.2 g/Mg)
0.05 Ib/ton (25 g/Mg)
1 0 x. 10 J Ib/ton (0.5 g/Mg)
62\ 10 Mb/ton (3.1 g/Mg)
3.6 x 10^ Ib/ton (0. 18 g/Mg)
0.016 Ib/ton (8.1 g/Mg)
3.2 x 10^ Ib/ton (0.1 6 g/Mg)
62x 10 J Ib/ton (3.1 g/Mg)
I.:1, x KT1 Ib/ton (0.06 g/Mg)
6. 2 x 10'3 Ib/ton (3.1 g/Mg)
1.2 x 10^ Ib/ton (0.06 g/Mg)
6 2x 10 Mb/ton (3.1 g/Mg)
1 2 x 10^ Ib/to (0.06 g/Mg)
').019 Ib/ton (9.5 g/Mg)
3.8x 104 Ib/ton (0. 1 9 g/Mg)
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
(continued)
-------
TABLE A-1. CONTINUED
SCC/AMS
Code
3-03-003-15
3-03-003-15
Description
By-Product Coke -
Gas By-Product Plant
(Foundry Coke)
(continued)
By-Product Coke -
Furnace Coke By-Product
Recovery (Light Oil BTX
Recovery)
Emission Source
Control Device
Excess-Ammonia Liquor
Tank
Uncontrolled
Gas Blanketing
Wash-Oil Decanter Uncontrolled
Gas Blanketing
Wash-Oil Circulation Tank Uncontrolled
Gas Blanketing
Valves Uncontrolled
Quarterly Inspection
Monthly Inspection
Use Sealed Bellows
Valves
Emission Factor
2.Ox lO'Mb/ton (1.0 g/Mg)
4.0 x 105 Ib/ton (0.020 g/Mg)
4.2 x 10Mb/ton(2.1 g/Mg)
8.2 x 105lb/ton (0.041 g/Mg)
4.2xl03lb/ton(2.1 g/Mg)
8.2 x 10 5lb/ton (0.041 g/Mg)
0.4 Ib/day (0.18 kg/day)
0.15 Ib/day (0.07 kg/day)
0 11 Ib/day (0.05 kg/day)
Factor Rating
E
E
E
E
U
U
U
Pumps
Uncontrolled
Quarterly Inspection
Monthly Inspection
Use of Dual Mechanical
Seals
4. 2 Ib/day (1.9 kg/day)
1 .2 Ib/day (0.55 kg/day)
0 71 Ib/day (0.32 kg/day)
U
U
U
(continued)
-------
TABLE A-l. CONTINUED
SCC/AMS
Code
3-03-003-15
Description
By-Product Coke -
Furnace Coke By-Product
Recovery (Light Oil BTX
Recovery)
(continued)
Emission Source Control Device
Exhausters Uncontrolled
Quarterly Inspection
Monthly Inspection
Use of Degassing
Reservoir Vents
Pressure Relief Devices Uncontrolled
Quarterly Inspection
Monthly Inspection
Emission Factor
0.62 Ib/day (0.28 kg/day)
0.29 Ib/day (0.13 kg/day)
0 22 Ib/day (0.10 kg/day)
—
6.0 Ib/day (2.7 kg/day)
3.3 Ib/day (1.5 kg/day)
2. 9 Ib/day (1.3 kg/day)
Factor Rating
U
U
U
U
U
U
>
Sampling Connections
Open-ended Lines
Use of Rupture Disk
System
Uncontrolled
Closed-purge Sampling
Uncontrolled
Plug or Cap
0 55 Ib/day (0.25 kg/day)
0.084 Ib/day (0.038 kg/day)
U
U
3-03-003-15
By-Product Coke - Valves
Furnace Coke Gas By-Product
Recovery
(Light Oil Recovery, Benzene
Refining)
Uncontrolled
Quarterly Inspection
Monthly Inspection
Use of Sealed Bellows
Valves
0.49 Ib/day (0.22 kg/day)
0 18 Ib/day (0.08 kg/day)
0 13 Ib/day (0.06 kg/day)
—
U
U
U
(continued)
-------
TABLK A-1. CONTINUHD
SCC/AMS
Code Description Emission Source Control Device
3-03-003-15 By-Product Coke - Pumps Uncontrolled
Furnace Coke By-Product
Recovery Quarterly Inspection
(Light Oil Recovery, Benzene
Refining) (continued) Monthly Inspection
Use of Dual Mechanical
Seals
Exhausters Uncontrolled
Quarterly Inspection
Monthly Inspection
Use of Degassing
Reservoir Vents
Pressure Relief Devices Uncontrolled
Quarterly Inspection
Monthly Inspection
Use of Rupture Disk
System
Sampling Connections Uncontrolled
Closed-purge Sampling
Open ended Lines Uncontrolled
Plug or Cap
Emission Factor
5.1 Ib/day (2.3 kg/day)
1. 5 Ib/day (0.67 kg/day)
0. 86 Ib/day (0.39 kg/day)
-
0 62 Ib/day (0.28 kg/day)
029 Ib/day (0.1 3 kg/day)
0.22 Ib/day (0.10 kg/day)
—
7.5 Ib/day (3.4 kg/day)
4.2 Ib/day (1.9 kg/day)
3.5 Ib/day (1.6 kg/day) .
• —
0.68 Ib/day (0.31 kg/day)
--
0. 104 Ib/day (0.047 kg/day)
Factor Rating
U
U
U
U
U
U
U
U
U
U
U
(continued)
-------
TABLH A 1. CONTINUED
>
oo
SCC/AMS
Code Description Hmission Source Control Device
3-03-003-15 By- Product Coke - Valves Uncontrolled
Foundry By-Product Recovery
(Light Oil BTX Recovery) Quarterly Inspection
Monthly Inspection
Use of Sealed Bellows
Valves
Pumps Uncontrolled
Quarterly Inspection
Monthly Inspection
Use of Dual Mechanical
Seals
Exhausters Uncontrolled
Quarterly Inspection
Monthly Inspection
Use of Degassing
Reservoir Vents
Pressure Relief Devices Uncontrolled
Quarterly Inspection
Monthly Inspection
Use of Rupture Disk
System
Sampling Connections Uncontrolled
Plug or Cap
Emission Factor
0.^5 Ib/day (0.16 kg/day)
0. ! 3 Ib/day (0.06 kg/day)
0.09 Ib/day (0.04 kg/day)
—
3 7 Ib/day (1.7 kg/day)
1 . 1 Ib/day (0.5 kg/day)
066 Ib/day (0.3 kg/day)
—
0.55 Ib/day (0.25 kg/day)
0.24 Ib/day (0.11 kg/day)
0.20 Ib/day (0.09 kg/day)
~
5. 5 Ib/day (2.5 kg/day)
3 1 Ib/day (1.4 kg/day)
2. 6 Ib/day (1.2 kg/day)
—
0.51 Ib/day (0.23 kg/day)
Factor Rating
U
U
U
U
U
U
U
U
. U
U
U
U
U
(continued)
-------
TABLE A-l. CONTINUED
SCC/AMS
Code Description Emission Source Control Device
3-03-003-15 By-Product Coke - Foundry Open ended Lines Uncontrolled
By-Product Recovery (Light Oil
BTX Recovery)
(continued)
Closed-purge Sampling
3-03-003-15 By-Product Coke - Valves Uncontrolled
Foundry By-Product Recovery
(Light Oil Recovery Benzene
Refining)
Quarterly Inspection
Monthly Inspection
Valves Use of Sealed Bellows
Valves
Pumps Uncontrolled
Quarterly Inspection
Monthly Inspection
Use of Dual Mechanical
Seals
Exhausters Uncontrolled
Quarterly Inspection
Monthly Inspection
Use of Degassing
Reservoir Vents
Emission Factor
0.077 lb/day (0.035 kg/day)
-
0 44 lb/day (0.20 kg/day)
0 15 lb/day (0.07 kg/day)
0 13 lb/day (0.06 kg/day)
~
4.6 lb/day (2.1 kg/day)
1.3 lb/day (0.6 kg/day)
P. 88 lb/day (0.4 kg/day)'
~
0 55 lb/day (0.25 kg/day)
024 lb/day (0.11 kg/day)
0 20 lb/day (0.09 kg/day)
-
Factor Rating
U
U
U
U
U
U
U
U
U
U
(continued)
-------
TABLE A-1. CONTINUED
I
H-*
o
SCC/AMS
Code
3-03-003-15
3-01-169-02
3-01-169-03
3-01-169-06
3-01-206-02
3-01-206-03
Description
By-Product Coke -
Foundry By-Product Recovery
(Light Oil Recovery Benzene
Refining)
(continued)
Ethylbenzene Manufacturing -
Alkylation Reactor Ventc
Ethylbenzene Manufacturing -
Benzene Drying Column'
Ethylbenzene Manufacturing -
Polyethylbenzene Recovery
Column0
Styrene Manufacturing -
Styrene Purification Vents1
Styrene Manufacturing -
Hydrogen Separation Ventc
Emission Source Control Device
Pressure Relief Devices Uncontrolled
Quarterly Inspection
Monthly Inspection
Use of Rupture Disk
System
Sampling Connections Uncontrolled
Plug or Cap
Open ended Lines Uncontrolled
Close-purge Sampling
Alkylation Reactor Vent Process Heater
Uncontrolled
Atmospheric/Pressure Flare
Column Ventsd
Uncontrolled
Other Vacuum Vents1 Flare
Uncontrolled
Benzene-Toluene Vacuum Flare
Veni
Uncontrolled
Hydrogen Separation Vent Flare
Uncontrolled
Emission Factor Factor Rating
6.81b/day(3.1 kg/day)
}. 7 lb/day( 1.7 kg/day)
.1. 3 lb/day( 1.5 kg/day)
—
0 62 Ib/day (0.28 kg/day)
-
0. 95 Ib/day (0.043 kg/day)
--
0.0006 Ib/ton (0.0003 kg/Mg)
0.6 Ib/ton (0.3 kg/Mg)
0.024 - 0.96 Ib/ton
(0.012 - 0.48 kg/Mg)
2.4 Ib/ton (1.2 kg/Mg)
0.0010 - 0.004 Ib/ton
(0.005 -0.002 kg/Mg)
0 10 Ib/ton (0.05 kg/Mg)
0.06 - 2.4 Ib/ton
(0.03 -1.2 kg/Mg)
6.0 Ib/tpn (3.0 kg/Mg)
0.00006 -0.0024 Ib/ton
(0.00003 -0.0012 kg/Mg)
0.006 Ib/ton (0.003 kg/ME)
U
U
U
U
U
U
U
U
U
U
U
U
U
U
U
(continued)
-------
TABLE A-1. CONTINUED
SCC/AMS
Code
3-01-169-80/
3-01-206-80
4-07-196-02/
4-07-196-13
3-01-156-02
3-01-156-03
3-01-156-04
3-01-156-05
3-01-202-02
3-01-202-02
Description F.mission Source
Ethylbenzene/Styrene Equi])ment Leaks
Manufacturing - Equipment
Leaks'
Ethylbenzene/Styrene Storage and Handling
Manufacturing -
Storage and Handling1
Cumene Manufacturing - Process Vent
Benzene Drying Column
Cumene Manufacturing - Process Vent
Catalyst Mix Tank Scrubber
Vent
Cumene Manufacturing - Process Vent
Wash- Decant System Vent
Cumene Manufacturing - Process Vent
Benzene Recovery Column
Phenol Manufacturing - Cumene Process Vent
Oxidation
Phenol Manufacturing - Cumene Process Vent
Oxidation
Control Device
Detection and
Correction
Uncontrolled
Floating Roof, Vented
to Flare, Refrigerated
Vent Condenser , and
Uncontrolled
Flare
Uncontrolled
Flare
Uncontrolled
Flare
Uncontrolled
Flare
Uncontrolled
Uncontrolled'
Thermal Oxidizer
Emission Factor
See Section 4.5.2
See Section 4. 5. 3
2.00 x 10-J Ib/ton
(l.OOx 10'3 kg/Mg)
4.00 x 10-2 Ib/ton
(2.00 x 10 2 kg/Mg)
1.59 xlO'2 Ib/ton
(7.95 x 10-J kg/Mg)
3.18x 10 'Ib/ton
(1.59x 10-' kg/Mg)
7. 84 xlO4 Ib/ton
(3.92 x 10^ kg/Mg)
1. 57 xia2 Ib/ton
(7.85 xlO'3 kg/Mg)
1. 70 xlO3 Ib/ton
(8.50x 10^ kg/Mg)
3.40 x 10"2 Ib/ton
(1.70x 10'2 kg/Mg)
4.00 x 10-3 Ib/ton
(2.00 x 103 kg/Mg)
1. 16 xlO"4 Ib/ton
(5.82xlO-5ke/ME)
Factor Rating
U
U
U
U
U
U
U
U
U
D
(continued)
-------
TABLE A-1. CONTINUED
SCC/AMS
Code Description Emission Source
3-01-195-01 Nitrobenzene - General Small Benzene Storage
(Point G)
Ben/ene Storage (Point G)
Secondary (Point J)
Total Plant
i
to
3-01-195-03 Nitrobenzene - Acid Stripper Waste-Acid Stripper (Point
Vent B)
3-01-195-04 Nitrobenzene- Wash and Neutralization
Washer/Neutralizer Vent (Point C)
3-01-195-05 Nitrobenzene - Nitrobenzene Nitrobenzene Stripper
Stripper Vent (Point D)
3-01-195-06 Nitrobenzene - Waste Acid Wash Acid Storage
Storage (Point G)
Control Device
Uncontrolled
Uncontrolled
Internal Floating Roof
Uncontrolled
Uncontrolled
Vent Adsorber
Thermal Oxidizer
Uncontrolled
Uncontrolled
Vent Adsorber
Uncontrolled
Thermal Oxidizer
Uncontrolled
Emission Factor
(' 156 Ib/ton (0.078 g/kg)
0 154 Ib/ton (0.077 g/kg)
(' 566 Ib/ton (0.283 g/kg)
(|.562 Ib/ton (0.281 g/kg)
0 085 Ib/ton (0.0425 g/kg)
0.20 Ib/ton (0.10 g/kg)
4.9 Ib/ton (2.45 g/kg)
4,4 Ib/ton (2. 19 g/kg)
0.78 Ib/ton (0.39 g/kg)
0.64 Ib/ton (0.32 g/kg)
0.44 Ib/ton (0.22 g/kg)
0.52 IbAon (0.26 g/kg) '
0.034 Ib/ton (0.1 70 g/kg)
0.01 62 Ib/ton (0.0081 g/kg)
0 155 Ib/ton (0.0776 g/kg)
0.34 Ib/ton (0.1 70 g/kg)
0.0288 Ib/ton (0.0144 g/kg)
0.102 Ib/ton (0.051 g/kg)
0.96 Ib/ton (0.048 E/ke)
Factor Rating
U
U
U
U
U
U
U
U
U
U
U
U
U
U
U
U
U
U
U
(continued)
-------
TABLE A-1. CONTINUED
u>
SCC/AMS
Code
3-01-195-80
3-01-301-01
3-01-301-02
Description
Nitrobenzene - Fugitive
Emissions
Chlorobenzene Manufacturing -
Tail-Gas Scrubber"
Chlorobenzene Manufacturing -
Benzene Dry Distillation11
Emission Source Control Device
Process Pumps and Valves8 Uncontrolled
LD&R Plus Mechanical
Seals
Tail -(las Scrubber Carbon Adsorption
Treatment
Uncontrolled
Atmospheric Distillation Carbon Adsorption
Vents' ,, „ .
Uncontrolled
Emission Factor Factor Rating
1.26 Ib/ton (0.63 g/kg)
0.76 Ib/ton (0.38 g/kg)
0.33 Ib/ton (0.165 g/kg)
0 198 Ib/ton (0.099 g/kg)
0.0134 Ib/ton (0.0067 kg/Mg)
1 .04 Ib/ton (0.52 kg/Mg)
0.0084 Ib/ton (0.0042 kg/Mg)
0.64 Ib/ton (0.32 kg/Mg)
U
U
U
U
U
U
U
U
3-01-301-04
3-01-301-05
3-01-301-03
3-01-301-80
4-07-196-01
Chlorobenzene Manufacturing -
Heavy Ends Processing11
Chlorobenzene Manufacturing -
Monochlorobenzene Distillation11
Chlorobenzene Manufacturing - Atmospheric Distillation
Benzene Recovery11 Vent - Benzene Recovery
Chlorobenzene Manufacturing - Equipment Leaks
Equipment Leaks'1
Chlorobenzene Manufacturing
Benzene Storage11
Ben/ene Storage Vessel
Carbon Adsorption
Uncontrolled
Detection and Repair of
Major Leaks
Uncontrolled
Internal Floating Roof
Uncontrolled
0.00104 Ib/ton (0.00052 kg/Mg)
0.08 Ib/ton (0.04 kg/Mg)
See Section 4.5.2
See Section 4.5.2
See Section 4.5.3
See Section 4.5.3
U
U
3-01-211-02
Linear Alkylbenzene -
Benzene Drying*
Benzene Azeotropic
Column Vent
(Point A)
Uncontrolled
Used as Fuel
7.4 x Iff3 Ib/ton (3.7 g/Mg)
1.5x10-* Ib/ton
(7.4 x Iff* E/ME)
U
U
(continued)
-------
TABLE A-1. CONTINUED
SCC/AMS
Code
3-01-21103
3-01-211-02
3-01-211-23
3-01-211-24
3-01-211-25
3-01-060-01
3-10-001-01
Description
Linear Alkylbenzene HF1
Scrubber Vent'
Linear Alkylbenzene -
Benzene Drying11
Linear Alkylbenzene - HC1
Adsorber Ventk
Linear Alkylbenzene -
Atmospheric Wash/Decanter
Vent"
Linear Alkylbenzene -
Benzene Strip Columnk
Pharmaceuticals - General
Process - Vacuum Dryers
Oil and Gas Production - Oil
Wellheads
Emission Source
Hydrogen Fluoride
Scrubber Column Vent
(Point B)
Benzene Azeotropic
Column Vent
(Point A)
Hydrochloric Acid Adsorber
Vent
(Point B)
Atmospheric Wash/Decanter
Vent (Point C)
Benzene Stripping Column
Vent
(Point D)
Vacuum Dryer Vent
Equipment Leaks
Control Device
Uncontrolled
Used as Fuel
Flare
Uncontrolled
Used as Fuel
Uncontrolled
Used as Fuel
Uncontrolled
Used as Fuel
Uncontrolled
Used as Fuel
Venturi Scrubber
Uncontrolled
Uncontrolled
Uncontrolled
Emission Factor
0.022 Ib/ton (11 g/Mg)
4.4 x 10* Ib/ton
(2.2 x 103 g/Mg)
2.2 x 10 3 Ib/ton (1.1 g/Mg)
7.4 x 103 Ib/ton (3.7 g/Mg)
1.5x 10* Ib/ton
(7.4 x 10"4 g/Mg)
0.5 Ib/ton (250 g/Mg)
1 x 10* Ib/ton (0.05 g/Mg)
0.0246 Ib/ton (12.3 g/Mg)
5 x 10* Ib/ton
(2.5 x lO'3 g/Mg)
7.4 x 103 Ib/ton (3.7 g/Mg)
1.48x10* Ib/ton
(7.4 x 10^ g/Mg)
2.1 lb/ 1,000 gal (0. 25 g/L)
1. 27 xlO'7 Ib/hr
(5.77 x 10-' kg/hr)
3.9 x 10* Ib/hr
(1.77 xlO-1 kg/hr)
6.25 x 109 Ib/hr
(2.84xlO'ke/hr)
Factor Rating
U
U
U
U
U
U
U
U
U
. U
U
B
D
D
D
(continued)
-------
TABLE A-l. CONTINUED
SCC/AMS
Code
Description
Emission Source
Control Device
Emission Factor
3-10-003-01 Glycol Dehydration Units - TEG Reboiler Still Vent
Units
3-10-003-04 Glycol Dehydration Units - EG Reboiler Still Vent
Units
Factor Rating
3-06-005-08 Oil/Water Separators
3-06-005-20 Air Flotation Systems
Oil/Water Separator
Air Rotation Systems'
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
0 93 tpy of BTEX/MMscfd
(29.79 x 103 kg/yr of
BTEX/MMscmd)
0 12 tpy of BTEX/MMscfd
(3.84x 103 kg/yr of
BTEX/MMscmd)
1.3 Ib of Benzene/106 gal of feed
water
(0.1 f> kg of Benzene/10* 1 of feed
water)
4 Ib of Benzene/10* gal
of feed water
(0.48 kg of Benzene/10* 1
of feed water)
U
U
5-01-007-07
5-01-007-15
5-01-007-20
5-01-007-31
5-01-007-33
5-01-007-34
5-01-007-40
Solid Waste Disposal
Treatment
Solid Waste Disposal
Treatment
Solid Waste Disposal
Treatment
Solid Waste Disposal
Treatment
Solid Waste Disposal
Treatment
Solid Waste Disposal
Treatment
Solid Waste Disposal
Treatment
- Sewage
- Sewage
- Sewage
- Sewage
- Sewage
- Sewage
- Sewage
Comminutor
Aerated Grit Chamber
Primary Sedimentation Tank
Diffused Air Activated
Sludge
Pure Oxygen Activated
Sludge
Trickling Filter
Secondary Clarifier
Wet scrubber
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
6.50x 10 Mb/million gal
(7 79 x 10^ kg/million liters)
3.56x10 Mb/million gal
(4 27 x 10^ kg/million liters)
5. 50x10^ Ib/million gal
(6 59 x 10s kg/million liters)
6. 67 xlO4 Ib/million gal
(7 99 x 10 5 kg/million liters)
3.80x 10* Ib/million gal
(4.55 x 10 7 kg/million liters)
1.60x ia3 Ib/million gal
(1.92x 104 kg/million liters)
1 .40 x IQf4 Ib/million gal
(1 .68 x 10 5 ke/million liters)
E
C
C
B
B
C
C
(continued)
-------
TABLE A-1. CONTINUED
SCC/AMS
Code
5-01-007-50
5-01-007-60
5-01-007-61
5-01-007-71
5-01-007-72
5-01-007-81
5-01-007-91
5-01-007-92
5-01-007-93
5-02-006-01
3-04-008-53
3-04-008-50
3-01-005-04
3-01-025-01
Description
Solid Waste Disposal -
Treatment
Solid Waste Disposal -
Treatment
Solid Waste Disposal -
Treatment
Solid Waste Disposal -
Treatment
Solid Waste Disposal -
Treatment
Solid Waste Disposal -
Treatment
Solid Waste Disposal -
Treatment
Solid Waste Disposal -
Treatment
Solid Waste Disposal -
Treatment
Solid Waste Disposal -
Dump
Synthetic Graphite
Synthetic Graphite
Carbon Black
Sewage
Sewage
Sewage
Sewage
Sewage
Sewage
Sewage
Sewage
Sewage
Landfill
Rayon-based Carbon Fibers
Emission Source
Tertiary Filter
Chlorine Contact Tank
Dechlorination
Gravity Sludge Thickener
Dissolved Air Floatation
Thickener
Anaerobic Digester
Belt Filter Press
Sludge Centrifuge
Sludge Drying Bed
Waste Gas Flares
Mixing Cylinder (Vent A)
Cooling Cylinder (Vent B)
Oil Furnace Process
Carbon Fabric Dryer
Control Device
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Emission Factor
4.00x 10"* Ib/million gal
(4.79 x 10 7 kg/million liters)
1.39x 104 Ib/million gal
(1.67 x 10s kg/million liters)
7. 50 x 10 'Ib/million gal
(7.50 x 10 ' kg/million liters)
2.09 x 104 Ib/million gal
(2 50 x 10' kg/million liters)
3.00x 10'3 Ib/million gal
(3 59 x 104 kg/million liters)
3.08 x 10 ' Ib/million gal
(3 69 x 102 kg/million liters)
,
-------
TABLE A-l. CONTINUED
I
>—»
-J
SCC/AMS
Code
3-04-001-99
3-04-001-14
3-05-001-01
5-02-005-05
5-01-005-15
5-01-005-16
Description
Secondary Metals - Secondary
Aluminum - Not Classified
Secondary Metals - Secondary
Aluminum - Pouring/Casting
Petroleum Industry - Asphalt
Roofing -Asphalt Blowing -
Sarurant
Solid Waste Disposal -
Pathological Incinerator
Solid Waste Disposal - Sludge
Incinerator
Solid Waste Disposal -
Fluidized Bed Incinerator
Emission Source
General Facility
(Vents A, D, E, F, and H)
General Facility
(Vents A, B, D, E, and G)
Casting Shakeout Operation
Blowing Stills or Saturators
Incinerator
Multiple Hearth Furnace
Fluidized Bed Incinerator
Control Device
Uncontrolled
Uncontrolled
Catalytic Incinerator
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Cyclone/Venturi
Scrubbers
Venturi Scrubber
Venturi/Impingement
Scrubbers
Venturi/Impingement
Scrubbers and
Afterburner
Venturi/Impingement
Scrubbers
Emission Factor
7.08 x 102 Ib/ton
(3.54x 10'2 kg/Mg)
7.47 x 102 Ib/ton
(3.73 xlO'2 kg/Mg)
6.09 x 10° Ib/ton
(3.45 x 10'3 kg/Mg)
5. 48x10 Mb/ton
(2.74 x 102 kg/Mg)
52 Ib/ton (26 kg/Mg)
4.92 x 10'3 Ib/ton
(2.46 x 103 kg/Mg)
1.2xlO-2lb/ton(5.8g/Mg)
7.0 x 10^ Ib/ton
(3.5 x lO'1 g/Mg) '
2.8 x lO'2 Ib/ton (1.4 g/Mg)
1.3x10 Mb/ton (6. 3 g/Mg)
3.4 x 10^ Ib/ton
(1.7x10-' g/Mg)
4.0 x lO^1 Ib/ton
(2.0 x 10 ' R/Me)
Factor Rating
D
D
D
D
E
D
D
E
E
D
E
E
(continued)
-------
TABLE A-1. CONTINUED
SCC/AMS
Code Description
5-01-005-15 Solid Waste Disposal -
Multiple Hearth Incinerator
Emission Source Control Device
Mulnple Hearth Incinerator Uncontrolled
Venturi/Impingement
Scrubbers
Elevated Operating
Temperature
Elevated Operating
Emission Factor
1.7 lx 10 Mb/ton .(8. 61 g/Mg)
1.3 tx 10 2 Ib/ton (6. 66 g/Mg)
2.65 x 10 Mb/ton (1.32 g/Mg)
1.41x10-' Ib/ton
Factor Rating
D
D
D
D
oo
Temperature/
Afterburner
Elevated Operating
Temperature/
Afterburner/Venturi
and Impingement
Scrubbers
(7.02 x lO'1 g/Mg)
3.35 x 10* Ib/ton
(1.67x10'g/Mg)
D
5-03-005-01
1-01-002-03
1-01-003-02
1-01-006-01
Solid Waste Disposal -
Hazardous Waste Incinerator
External Combustion Boiler -
Electric Generation
External Combustion Boiler -
Electric Generation
External Combustion Boiler -
Electric Generation
Liquid Injection Incinerator
Liquid Injection Incinerator
Cyclone Boiler - Coal
Tangentially - Fired Boiler -
Lignite
Opposed-wall Boiler -
Natural Gas
Uncontrolled1"
Various Control
Devices"
Baghouse/SCR/
Sulfuric Acid
Condenser
Electrostatic
Precipitator
Electrostatic
Precipitator/Scrubber
Flue Gas Recirculation
4.66 x 10s Ib/ton
(2.33 x 10s kg/Mg)
1. 23 x 10 Mb/ton .
(6.16x JO"4 kg/Mg)
5.58 x 10* Ib/MMBtu
(2.40 x 10* /*g/J)
7.90 x 10* Ib/MMBtu
(3.40 x 10* /tg/J)
3.95 x 10 5 Ib/MMBtu
( 1. 70 x 10s /tg/J)
1.40x10* Ib/MMBtu
(6.02 x 107 wE/J)
U
U
D
D
D
D
(continued)
-------
TABLE A-1. CONTINUED
SCC7AMS
Code
1-01-006-04
1-01-009-01
1-02-004-01
1-02-007-99
1-02-008-04
1-02-009-01
1-02-009-03
1-02-009-05
1-02-009-06
Description
External Combustion Boiler -
Electric Generation
External Combustion Boiler -
Electric Generation
External Combustion Boiler -
Industrial
External Combustion Boiler -
Industrial
External Combustion Boiler -
Industrial
External Combustion Boiler -
Industrial
External Combustion Boiler -
Industrial
External Combustion Boiler -
Industrial
External Combustion Boiler -
Industrial
Emission Source
Tangentially - Fired Boiler -
Natural Gas
Holler Bark Fuel
Holler - No. 6 Fuel Oil
Holler - Landfill Gas Fuel
Holler Coke and Coal Fuel
Holler - Bark Fuel
Holler - Wood Fuel
FBC Boiler - Wood Fuel
Boiler - Wood and Bark
Spreader-stoker Boiler -
Wood Fuel
Control Device
Rue Gas Recirculation
Uncontrolled
Uncontrolled
Uncontrolled
Baghouse
ESP
Wet Scrubber
Multiple Cyclone/ESP
Multiple Cyclone
Multiple Cyclone/ESP
Multiple Cyclone/Wet
Scrubber
Multiple Cyclone
Mechanical Dust
Collector
Emission Factor
4 00 x 107 Ib/MMBtu
(1.72xlO-7fig/J)
3. 60x10 Mb/ton
(1.80xl03kg/Mg)
9 38 x 105 Ib/MMBtu
(4.04 x 10-5 ftg/J)
378 x 1C4 Ib/MMBtu
0.63x10^/1)
2 68 x 10s Ib/MMBtu
(1.15xl05/ig/J)
6 90 x HT1 Ib/MMBtu
(2.97 x 104 /ig/J)
420 x 10'3 Ib/MMBtu
(1.81xia3/ig/J)
5 12 x 10^ Ib/MMBtu
(2.20 x 104 /tg/J)
1 04 x WT3 Ib/MMBtu
(4.46 x 10^ /tg/J)
2 70 x 10's Ib/MMBtu
(1.16xlOVg/J)
1.01 x 10 3 Ib/MMBtu
(4.35 x lO^1 /ig/J)
2 43 x 10^ Ib/MMBtu
(l.OSxlO^Vg/.J)
1.67x10^ Ib/MMBtu
(7.18xl05«E/J)
Factor Rating
D
E
D
D
D
E
E
. E
E
E
E
D
D
(continued)
-------
TABLE A-1. CONTINUED
N)
O
SCC/AMS
Code
1-02-012-01
1-03-007-01
21-04-008-030
21-04-008-051
2-02-001-02
2-02-001-04
2-02-002-02
2-02-004-01
2-02-004-02
2-03-007-02
2-01-001-01
Description
External Combustion Boiler -
Industrial
External Combustion Boiler -
Commercial/ Institutional
Stationary Source Combustion -
Residential
Stationary Source Combustion -
Residential
Internal Combustion Engine -
Industrial
Internal Combustion Engine -
Industrial/Reciprocating
Cogeneration
Internal Combustion Engine -
Industrial/Reciprocating
Internal Combustion Engine -
Industrial
Internal Combustion Engine -
Industrial
Internal Combustion Engine -
Commercial/Institutional
Internal Combustion Engine -
Electric Generation
Emission Source
Boiler - Almond Shells and
Wood
Boiler - POTW Digester
(!as
( 'atalytic Woodstove
Non-Catalytic Woodstove
Reciprocating Distillate
Oil-fueled Engine
Cogeneration Distillate
Oil-fueled Engine
2-cycle Lean Burn Natural
Gas-fueled Engine
4-cycle Lean Burn Natural
Gas- fueled Engine
Large Bore Diesel-fueled
Engine
Large Bore Oil- and Natural
Gas- fueled Engine (Dual
Fuel)
Reciprocating POTW
Digester Gas-fueled Engine
Gas Turbine Fueled with
Distillate Oil
Control Device
Baghouse
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
NSCR
Uncontrolled
Uncontrolled
Uncontrolled
Afterburner
Emission Factor Factor Rating
5.29 x 10-J Ib/MMBtu
(2.28 x 10-J /tg/J)
3.50x 10 3 Ib/MMBtu
(1.50xl03/tg/J)
1.46 Ib/ton (7.30 x 10 ' kg/Mg)
1.941b/ton(9.70xlO'kg/Mg)
9.33 x 10* Ib/MMBtu
(4.01 x 10-' ng/J)
5. 36x10^ Ib/MMBtu
(2.30 x 10"' ng/J)
2. 20 xlO'3 Ib/MMBtu
(9.46 x lO'1 ng/J)
7.1x 10^ Ib/MMBtu
(3.05x10 'ng/J) .
7.76 x 10* Ib/MMBtu
(3.34 x ID'1 ng/J)
4.45 x 103 Ib/MMBtu
(1.91 ng/J)
6.90xl04 Ib/MMBtu
(2.97 x 10 ' ng/J)
9. 13 x 10s Ib/MMBtu
(3.92 x 102 ng/J)
D
C
E
E
E
D
E
E
E
E
C
D
(continued)
-------
TABLE A 1. CONTINUED
SCC/AMS
Code
Description
Emission Source-
Control Device
2-01-002-01 Internal Combustion Engine
Electric Generation
3-04-004-03 Secondary Metals -
Secondary Lead Production
3-04-004-04 Secondary Metals -
Secondary Lead Production
3-04-003-98 Secondary Metals - Gray Iron
Foundries
3-05-007-06 Cement Manufacturing - Wet
Process - Kilns
Gas Turbine Fueled with
Natural Oil
Blast Furnace (Cupola)
Catalytic Reduction
Uncontrolled
Afterburner
Rotary Sweating Furnace Uncontrolled
Sand Cooling and Belts Baghouse
Kiln-Burning Hazardous ESP
Waste Exclusively, or with
Coal or Coke
Kiln-Burning Hazardous ESP
Waste and Natural Gas as
Fuel
Kiln-Burning Hazardous ESP
Waste and Coal at High
Combustion Temperature
Emission Factor
l.lOx lO^lb/MMBtu
(4.73 x 102 ng/J)
4.08 x 10' Ib/ton
(2.04 x 10' kg/Mg)
2.47 x 102 Ib/ton
(1.23 x 102 kg/Mg)
1.66x10'Ib/ton
(8.30 x 102 kg/Mg)
6.99 x 10^ Ib/ton
(3.50 x 10-4 kg/Mg)
3.7 x 10-J Ib/ton
(1.8xl03kg/Mg)
7.5 x 10' Ib/ton
(3.7 x 10J kg/Mg)
3.9x10* Ib/ton
(1.9x10* kg/Mg)
Factor Rating
E
D
D
D
D
B
D
D
3-05-006-06
Cement Manufacturing - Dry
Process
Kiln-Burning Coal in
Precalciner Process
Kiln-Burning Coal and
20 Percent TDF
FF
FF
1.6x10 Mb/ton
(8 x 10-} kg/Mg)
0.17.g/MMBtu
E
E
(continued)
-------
TABLE A 1. CONTINUED
to
to
SCC/AMS
Code
3-05-002-01
3-05-002-08
26-10-030-00
28-01-500-000
28-10-005-000
28-10-001-000
Description
Petroleum Industry - Asphalt
Concrete - Rotary Dryer
Petroleum Industry - Asphalt
Concrete - Asphalt heater -
Distillate oil
Waste Disposal - On-Site
Incineration - Residential
Agricultural Production - Field
Burning
Other Combustion -
Managed Slash Burning
Other Combustion - Forest
Wildfires
Emission Source
Rotary Dryer, LPG-fircd
Rotary Dryer, Oil-fired
Rotary Dryer, Natural Gas-
nr Oil-fired
Rotary Dryer, Natural Gas-
or Diesel-fired
Asphalt Heater, Diesel-fired
Yard Waste Burning
Land Clearing/Burning
Slash (Pile) Burning
Forest Fires - Fire Wood
Forest Fires - Small Wood
Forest Fires - Large Wood
( Flaming)
Forest Fires - Large Wood
(Smoldering)
Control Device
Uncontrolled
Multiple Cyclone
Baghouse with Single
Cyclone, Knock-out
Box, or Multiple
Cyclone
Wet scrubber
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Emission Factor
5.35 x 10* Ib/ton
(2.68 x 10^ kg/Mg)
7.7 x 10s Ib/ton
(3.85x 10s kg/Mg)
2.08 x 10^ Ib/ton
(1.04x 104 kg/Mg)
1. 95 x 10 5 Ib/ton
(9.75 x 10* kg/Mg)
1. 50 xlO* Ib/ton
(7.5 x la5 kg/Mg)
1.10 Ib/ton
(5.51 x 10' kg/Mg)
9.06 x 10 ' Ib/ton
(4.53 x 10 ' kg/Mg)
9.06 x 10 ' Ib/ton
(4.53 x 10'1 kg/Mg)
6.6 x 10 ' Ib/ton
(3.3 x 10-' kg/Mg)
6.6 x 10 ' Ib/ton
(3.3 x 10 ' kg/Mg)
6. 6x10 'Ib/ton
(3.3 x 10 ' kg/Mg)
2. 52 Ib/ton (1.26 kg/Mg)
Factor Rating
C
C
B
C
D
U
• u
U
U
U
U
u
(continued)
-------
TABLE A-1. CONTINUED
SCC/ A MS
Code Description Emission Source Control Device
28-10-001-000 Other Combustion - Foresl I oresi Fires - Live Uncontrolled
Wildfires (continued) Vegetation
Foresl Fires - Duff Uncontrolled
(Flaming)
28-10-015-000 Other Combustion - Managed Prescribed Burning Uncontrolled
Prescribed Burning (Broadcast) - Fire Wood
Prescribed Burning Uncontrolled
(Broadcast) - Small Wood
Prescribed Burning Uncontrolled
(Broadcast) - Large Wood
Emission Factor Factor Rating
1.481b/ton(7.4x 10 'kg/Mg)
2 52 Ib/ton (1.26 kg/Mg)
6.6 x 10 ' Ib/ton
(3.3 x 10 ' kg/Mg)
6.6 x 10 ' Ib/ton
(3.3 x 10 ' kg/Mg)
6.6 x 10 ' Ib/ton
(3.3 x 10 ' kg/Mg)
U
U
U
U
U
5-03-002-03 Solid Waste Disposal, Open
Burning - Autobody Components
(Flaming)
Prescribed Burning
(Broadcast) - Large Wood
(Smoldering)
Prescribed Burning
(Broadcast) - Live
Vegetation
Prescribed Burning
(Broadcast) - Duff
(Flaming)
Prescribed Burning
(Broadcast) - Duff
(Smoldering)
Chunk Tires
Shredded Tires
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
2.52 Ib/ton (1.26 kg/Mg)
1.48 Ib/ton (7.4 x 10'kg/Mg)
6.6 x 10' Ib/ton
(3.3 x 10' kg/Mg)
2.52 Ib/ton (1.26 kg/Mg)
3.05 Ib/ton (1.53 kg/Mg)
3.86 Ib/ton (1.93 kg/Me)
U
U
U
U
C
C
(continued)
-------
TABLE A-1. CONTINUED
>
to
SCC/AMS
Code
5-03-002-02
4-06-002-36
4-06-002-37
4-06-002-34
4-06-002-035
4-06-002-36
4-06-002-31
4-06-002-31
Description
Solid Waste Disposal, Open
Burning - Refuge
Transportation of Petroleum
Products - Marine Vessels
Transportation of Petroleum
Products - Marine Vessels
Transportation of Petroleum
Products - Marine Vessels
Transportation of Petroleum
Products - Marine Vessels
Transportation of Petroleum
Products - Marine Vessels
Transportation of Petroleum
Products - Marine Vessels
Transportation of Petroleum
Products - Marine Vessels
Emission Source-
Unused Plastic Burning
Used Plastic Burning
Gasoline: Ship Loading -
Uncleaned Tanks
Gasoline: Ocean Barges
Loading - Uncleaned Tanks
Gasoline: Ship Loading -
Ballasted Tank
Gasoline: Ocean Barges
Loading - Ballasted Tank
Gasoline: Ship Loading -
Cleaned Tanks
Gasoline: Ocean Barges
Loading - Cleaned Tanks
Gasoline: Ship Loading -
Cleaned and Vapor- Free
Tanks
Control Device
Uncontrolled
Forced Air
Uncontrolled
Forced Air
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Emission Factor Factor Rating
9.55x 10 Mb/ton
(4.77 x 10s kg/Mg)
5.75 x 105 Ib/ton
(2.87 x lO'5 kg/Mg)
2.47 x lO'5 Ib/ton
(1.23xlO-5 kg/Mg)
4.88 x 10s Ib/ton
(2.44 x 10s kg/Mg)
0.023 lb/1000 gal (2.8 mg/liter)
0.023 lb/1000 gal (2.8 mg/liter)
0.015 lb/1000 gal (1.8 mg/liter)
0.015 lb/1000 gal (1.8 mg/liter)
0.014 lb/1000 gal (1.6 mg/liter)
0.014 lb/1000 gal (1.6 mg/liter)
0.006 lb/1000 gal (0.77 mg/liter)
C
C
C
C
D
D
D
D
D
D
D
4-06-002-32 Transportation of Petroleum
Products - Marine Vessels
Gasoline: Ocean Barges
Loading - Cleaned and
Vapor-Free Tanks
Uncontrolled
0.006 lb/1000 gal (0.77 mg/liter)
D
(continued)
-------
TABLH A 1. CONTINUED
>
N)
SCC/AMS
Code
Description
Hmission Source
Control Device
Emission Factor
4-06-002-43 Transportation of Petroleum
Products - Marine Vessels
4-06-002-43 Transportation of Petroleum
Products - Marine Vessels
4-06-002-40 Transportation of Petroleum
Products - Marine Vessels
4-06-002-38 Transportation of Petroleum
Products - Marine Vessels
4-06-002-33 Transportation of Petroleum
Products - Marine Vessels
4-06-002-39 Transportation of Petroleum
Products - Marine Vessels
4-06-002-42 Transportation of Petroleum
Products - Marine Vessels
4-04-002-01 Storage Tanks - Fixed Roof -
Breathing Loss
4-04-002-04 Storage Tanks - Fixed Roof -
Working Loss
Filling
Emptying
Gasoline: Ship/Ocean
Barges leading- Any
Condition-Nonvolatile
Previous Cargo
Gasoline: Ship Loading-
Typical Condition - Any
Cargo
Gasoline: Ocean Barge
Loading- Typical Condition
- Any Cargo
Gasoline: Barge Loading -
Uncleaned Tanks
Gasoline: Barge Loading -
Cleaned and Vapor-Free
Tanks
Gasoline: Tanker Ship
Loading - Ballasted
Condition
Gasoline: Transit Loss
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Factor Rating
Uncontrolled
Uncontrolled
0.006 lb/1000 gal (0.77 mg/liter) D
0.016 lb/1000 gal (1.9 mg/liter) D
0.016 lb/1000 gal (1.9 mg/liter) D
0.035 lb/1000 gal (4.2 mg/liter) D
0.018 lb/1000 gal (2.2 mg/liter) D
0.007 lb/1000 gal (0.9 mg/liter) . D
0 024 lb/week-1000 gal D
(2.8 mg/week-liter)
0.5 lb/1000 gal. (5.4 mg/liter) E
E
0.086 lb/1000 gal (10.3 mg/liter) E
0.034 lb/1000 gal (4.1 mg/liter) E_
(continued)
-------
TABUi A 1. CONTINUED
SCC/AMS
Code Description
4-04-002-50 Bulk Terminals/Plants - Loading
Racks
4-06-003-01 Petroleum Products Marketing -
Underground Storage Tanks
4-06-003-02 Petroleum Products Marketing -
Underground Storage Tanks
4-06-003-06 Petroleum Products Marketing -
i Underground Storage Tanks
4-06-003-07 Petroleum Products Marketing -
Underground Storage Tanks
4-06-004-01 Petroleum Products Marketing -
Vehicle Refueling
4-06-004-02 Petroleum Products Marketing -
Vehicle Refueling
3-06-010-01 Sludge dewatering units
4-06-002-XX Ocean Going Commercial
(•mission Source
Splash Loading- Normal
Service
Submerged Loading- Normal
Service
Balance Service Loading
Filling Losses - Splash Fill
Filling Losses - Submerged
Fill
Filling Losses - Balanced
Submerged Fill
Underground Tank
Breathing Losses
Displacement Losses
Controlled
Uncontrolled
Spillage
Sludge dewatering unitp
Motor Propulsion - All
Underway Modes
Auxilary Diesel Generators
500 KW (50% load)
Control Device
Uncontrolled
Uncontrolled
Vapor Balancing
Uncontrolled
Uncontrolled
Vapor Balancing
Uncontrolled
Stage II
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Emission Factor Factor Rating
0.11 lb/1000 gal (12.9 mg/liter)
0.04-! lb/1000 gal (5.3 mg/liter)
0.002 lb/1000 gal
(0.4 mg/liter)
0.104 lb/1000 gal (12.4 mg/liter)
0.066 lb/1000 gal (7.9 mg/liter)
0.003 lb/1000 gal
(0.40 mg/liter)
0.009 lb/1000 gal (1 . 1 mg/liter)
0.0099 lb/1000 gal (1.2 mg/liter)
0,099 lb/1000 gal (11, 9 nig/liter)
0.0063 ib/1000 gal (0.76 mg/liter)
660 Ib of TOC/10* Ib sludge (660
kg of TOC/106 kg sludge)
0.25 lb/1000 gal fuel
0.87 lb/1000 gal fuel
E
E
E
E
E
E
E
E
E
E
C
E
E
(continued)
-------
TABLE A-1. CONTINUED
SCC/AMS
Code Description
4-06-002-XX Commercial Marine Vessels-
Harbor and Fishing
A22-85-002-005 Line Haul Locomotive
A22-85-002-010 Yard Locomotive
Emission Source
Diesel Engines
< 500 hp
Full
Cruise
Slow
500-1 000 hp
Full
Cruise
Slow
1000-1500 hp
Full
Cruise
Slow
1 500-2000 hp
Full
Cruise
Slow
2000 + hp
Full
Cruise
Slow
Gasoline Engines - all hp
ratings
Exhaust (g/bhp-hr)
Evaporative (g/hr)
Control Device
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Uncontrolled
Emission Factor
0.22 lb/1000 gal fuel
0.54 lb/1000 gal fuel
0.60 lb/1000 gal fuel
0.25 lb/1000 gal fuel
0.18 lb/1000 gal fuel
0.1 8 lb/1000 gal fuel
0.25 lb/1000 gal fuel
0.25 lb/1000 gal fuel
0.25 lb/1000 gal fuel
0.1 8 lb/1000 gal fuel
0.25 lb/1000 gal fuel
0.25 lb/1000 gal fuel
0.23 lb/1000 gal fuel
0.18 lb/1000 gal fuel
0.24 lb/1000 gal fuel
0.35 lb/1000 gal fuel
0.64 lb/1000 gal fuel
0.00022 Ib/gal
0.00054 Ib/gal
Factor Rating
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
E
U
U '
(continued)
-------
TABLE A-1. CONTINUED
SCC/AMS
Code
28-10-040-000
Description
Rocket Engines
Emission Source
Boosler rocket engines using
Control Device
Uncontrolled
Emission Factor
0.131 Ib/ton (0.215 kg/Mg)
Factor Rating
C
RP-1 (kerosene) and liquid
oxygen as fuel
a Data are for a hypothetical plant using 50 percent naphtha/50 percent gas oil as feed and having an ethylene capacity of 1,199,743 Ib/yr (544.2 Gg/yr).
" Intermittent emissions have been reported from the at tivation of pressure relief devices and the depressurization and purging of equipment for maintenance
purposes.
c Emission factors are for a model plant with capacity 661 million Ibs (300 million kp) per year. Actual emission factors may vary with throughput and control
measures and should be determined through direct contacts with plant personnel. Factors are expressed as Ib (kg) ben/.ene emitted per ton (Mg)
ethylbenzene/styrene produced.1
d Includes the following vents: benzene drying column, ben/ene recovery column, and ethylbenzene recovery column
* Includes the following vents: polyethylbenzene recovery column at ethylbenzene plants; and benzene recycle column and styrene purification vents at styrene plants.
f Measured at post oxidizer condenser vent.
> * Process pumps and valves are potential sources of fugitive emissions. Each model plant is estimated to have 42 pumps (including 17 spares), 500 process valves,
K> and 20 pressure-relief valves based on data from an existing facility. All pumps have mechanical seals. Twenty-five percent of these pumps and valves are being
00 used in benzene service. The fugitive emissions included in this table are based on ihe factors given in Section 4.5.2.
h These emission factors are based on a hypothetical plant producing 74,956 tons (68 Gg) monochlorobenzene, 13,669 tons (12.4 Gg) o-dichlorobenzene, and 17,196
tons (15.6 Gg) p-dichlorobenzene. The reader is urged to contact a specific plant as to process, products made, and control techniques used before applying these
emission factors.
' Includes the following vents: benzene dry distillation, heavy ends processing, and monochlorobenzene distillation.
j Emission factor estimates based on a 198 million Ib/yr (90,000 Mg/yr) hypothetical plant using the Olefin Process.
k Emission factor estimates based on a 198 million Ib/yr (90,000 Mg/yr) hypothetical plant using the Chlorination Process.
1 Includes dissolved air flotation (DAF) or induced air flotation (1AF) systems.
m The liquid injection incinerator has a built-in afterburner chamber.
" The incinerators tested had the following control devices: venturi, packed, and. ionized scrubbers; carbon bed filters; and HEPA filters.
0 Emission factor is based on the detection limit because no benzene was detected above the detector limit.
p Based on a 2.2 meter belt filter press dewatering oil/water separator bottoms, DAF float, and biological sludges at an average temperature of 125°F.2
"--" = Data not available.
(continued)
-------
TABLEA-1. CONTINUED
REFERENCES
1. Key, J.A., and F.D. Hobbs. Ethylbenzene/Styrene: Pepott 5 In: Organic Chemit il Manufacturing. Vol.6: Selected Processes. EPA-450/3-3-80-028a.
Research Triangle Park, North Carolina: U.S. Environmental Protection Agency, O lice of Air Quality Planning and S'andards, 1980.
2. Research Triangle Institute. Summary Report TSDFD<'watering Organic Air Emissw'i Factors. Research Triangle Part , North Carolina: U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards, May 1991.
to
vo
(continued)
-------
APPENDIX B
UNITED STATES PETROLEUM REFINERIES: LOCATION BY STATE
-------
TABLE B-l. UNITED STATES PETROLEUM REFINERIES: LOCATION BY STATE
State
ALABAMA
ALABAMA
ALABAMA
ALABAMA
ALASKA
ALASKA
.ALASKA
ALASKA
ALASKA
ARIZONA
ARIZONA
ARKANSAS
ARKANSAS
ARKANSAS
CALIFORNIA
CALIFORNIA
CALIFORNIA
CALIFORNIA
CALIFORNIA
CALIFORNIA
CALIFORNIA
CALIFORNIA
CALIFORNIA
CALIFORNIA
CALIFORNIA
CALIFORNIA
CALIFORNIA
CALIFORNIA
CALIFORNIA
CALIFORNIA
CALIFORNIA
CALIFORNIA
CALIFORNIA
CALIFORNIA
CALIFORNIA
CALIFORNIA
Company
Coastal Mobil Refining Co.
Gamxx Energy, Inc.
Hunt Refining Co.
Louisiana Land & Exploration Co.
ARCO
ARCO
Mapco Alaska Petroleum
Petro Star Inc.
Tesoro Petroleum Corp.
Intermountain Refining CI
Sunbelt Refining Co.
Berry Petroleum Co.
Cross Oil & Refining Co. Inc.
Lion Oil Co.
Anchor Refining CI
Atlantic Richfield Co.
Chemoil Refining Corp.
Chevron USA Inc.
Chevron USA Inc.
Conoco Inc.
Edgington Oil CI
Exxon Co.
Fletcher Oil & Refining Co.
Golden West Refining Co.
Huntway Refining Co.
Huntway Refining Co.
Kern Oil & Refining Co.
Lunday-Thagard Co.
Mobil Oil Corp.
Pacific Refining Co.
Paramount Petroleum Corp.
Powerine Oil Co.
San Joaquin Refining CI
Shell Oil Co.
Shell Oil Co.
Sunland Refining Corp.
Location .
Mobile Bay
Theodore
Tuscaloosa
Sar aland
Kuparuk
Prudhoe Bav
North Pole
North Pole
Kenai
Fredonia
Randolph
Stevens
Smackover
El Dorado
McKittrick
Carson
Signal Hill
El Segundo
Richmond
Santa Maria
Long Beach
Benicia
Carson
Santa Fe Springs
Benicia
Wilmington
Bakersfield
South Gate
Torrance
Hercules
Paramount
Santa Fe Springs
Bakersfield
Martinez
Wilmington (Carson)
Bakersfield
B-l
-------
TABLE B-l. UNITED STATE PETROLEUM REFINERIES: LOCATION BY STATE
(CONTINUED)
State
CALIFORNIA
CALIFORNIA
CALIFORNIA
CALIFORNIA
CALIFORNIA
CALIFORNIA
CALIFORNIA
CALIFORNIA
COLORADO
COLORADO
COLORADO
DELAWARE
GEORGIA
GEORGIA
HAWAII
HAWAH
ILLINOIS
ILLINOIS
ILLINOIS
ILLINOIS
ILLINOIS
ILLINOIS
ILLINOIS
INDIANA
INDIANA
INDIANA
INDIANA
KANSAS
KANSAS
KANSAS
KANSAS
KANSAS
KANSAS
KANSAS
Company
Ten By, Inc.
Texaco Refining & Marketing Inc.
Texaco Refining & Marketing Inc.
Tosco Corp.
Ultramar
Unocal Corp.
Unocai Corp.
Witco Chemical Corp, Golden Bear Div.
Colorado Refining Co.
Conoco Inc.
Landmark Petroleum Inc.
Star Enterprise
Amoco Oil Co.
Young Refining Corp.
Chevron USA Inc.
Hawaiian Independent Refinery Inc.
Clark Oil & Refining Corp.
Clark Oil & Refining Corp.
Indian Refining Co.
Marathon Oil Co.
Mobil Oil Corp.
Shell Oil Co.
The UNO-YEN Co.
Amoco Oil Co.
Countrymark Cooperative, Inc.
Laketon Refining Corp.
Marathon Oil Co.
Coastal Refining and Marketing Inc.
Coastal Refining & Marketing Inc.
Coastal Refining & Marketing Inc.
Farmland Industries Inc.
Farmland Industries Inc.
National Cooperative Refinery Association
Texaco Refining & Marketing Inc.
Location
Oxnard
Bakersfield
Wilmington
Martinez
Wilmington
Los Angeles
San Francisco
(includes Santa Maria)
Oildale
Commerce City
Denver
Fruita
Delaware City
Savannah
Douslasville
Barber's Point
Ewa Beach
Blue Island
Hartford
Lawrenceville
Robinson
Joliet
Wood River
Lemont
Whiting
Mt. Vernon
Laketon
Indianapolis
Augusta
El Dorado
Wichita
Coffeyville
Phillipsburg
McPherson
El Dorado
B-2
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TABLE B-1. UNITED STATE PETROLEUM REFINERIES: LOCATION BY STATE
(CONTINUED)
State
KANSAS
KENTUCKY
KENTUCKY
LOUISIANA
LOUISIANA
LOUISIANA
LOUISIANA
LOUISIANA
LOUISIANA
LOUISIANA
LOUISIANA
LOUISIANA
LOUISIANA
LOUISIANA
LOUISIANA
LOUISIANA
LOUISIANA
LOUISIANA
LOUISIANA
LOUISIANA
LOUISIANA
LOUISIANA
MICHIGAN
MICHIGAN
MICHIGAN
MICHIGAN
MINNESOTA
MINNESOTA
MISSISSIPPI
MISSISSIPPI
MISSISSIPPI
MISSISSIPPI
MISSISSIPPI
MONTANA
MONTANA
Company
Total Petroleum Inc.
Ashland Petroleum Co.
Somerset Refinery Inc.
American International Refining, Inc.
Atlas Processing Co. Div. of Pennzoil
BP Oil Co.
Calcasieu Refining Co.
Calumet Lubricants Co.
Canal Refining Co.
CAS Refining, Inc.
Citgo Petroleum Corp.
Conoco Inc.
Exxon Co.
Kerr McGee Refining Corp.
Marathon Oil Co.
Mobil Oil Corp.
Murphy Oil USA Inc.
Phibro Refining Inc.
Phibro Refining Inc.
Placid Refining Co.
Shell Oil Co.
Star Enterprise
Crystal Refining Co.
Lakeside Refining Co.
Marathon Oil Co.
Total Petroleum Inc.
Ashland Petroleum Co.
Koch Refining Co.
Amerada-Hess Corp.
Chevron USA Inc.
Ergon Refining Inc.
Southland Oil Co.
Southland Oil Co.
Cenex
Conoco Inc.
Location
Arkansas City
Catlettsburg
Somerset
Lake Charles
Shreveport
Belle Chasse
Lake Charles
Princeton
Church Point
Mermentau
Lake Charles
Lake Charles
Baton Rouge
Cotton Valley
Garvville
Chalmette
Meraux
Krotz Springs
St. Rose
Port Allen
Norco
Convent
Carson City
Kalamazoo
Detroit
Alma
St. Paul Park
Rosemount
Purvis
Pascagoula
Vicksburg
Lumberton
Sandersville
Laurel
Billings
B-3
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TABLE B-l. UNITED STATE PETROLEUM REFINERIES: LOCATION BY STATE
(CONTINUED)
State
MONTANA
MONTANA
NEVADA
NEW JERSEY
NEW JERSEY
NEW JERSEY
Company
Exxon Co.
Montana Refining Co.
Petro Source Refining Partners
Amerada-Hess Corp.
Chevron USA Inc.
Coastal Eagle Point Oil Co.
NEW JERSEY Exxon Co.
NEW JERSEY
NEW JERSEY
NEW MEXICO
NEW MEXICO
Mobil Oil Corp.
Seaview Petroleum Co. LP
Bloomfield Refining Co.
Giant Industries Inc.
NEW MEXICO Navajo Refining Co.
NEW MEXICO
Triftway Marketing Corp.
NEW YORK Cibro Petroleum Products Co.
NORTH DAKOTA Amoco Oil Co.
OHIO Ashland Petroleum Co.
OHIO ' BPOilCo.
OHIO BPOilCo.
OHIO Sun Refining & Marketing Co.
OKLAHOMA Barrett Refining Corp.
Location
Billings
Great Falls
Tonopah
Port Reading
Perth Amboy
Westville
Linden
Paulsboro
Thorofare
Bloomfield
Gallup
Artesia
Farmington
Albany
Mandan
Canton
Lima
Toledo
Toledo
Thomas
OKLAHOMA Conoco Inc. Ponca City
OKLAHOMA . Cyril Petrochemical Corp. Cyril
OKLAHOMA Kerr-McGee Refining Corp.
OKLAHOMA ! Sinclair Oil Corp.
OKLAHOMA Sun Refining & Marketing Co.
OKLAHOMA Total Petroleum Inc.
OREGON
PENNSYLVANIA
PENNSYLVANIA
PENNSYLVANIA
PENNSYLVANIA
PENNSYLVANIA
PENNSYLVANIA
PENNSYLVANIA
TENNESSEE
Chevron USA Inc.
BP Oil Co.
Chevron USA Inc.
Pennzoil Products Co.
Sun Refining & Marketing Co.
Sun Refining & Marketing Co.
United Refining Co.
Witco Chemical Co., Kendall-Amalie Div.
Mapco Petroleum Inc.
Wynnewood
Tulsa
Tulsa
Ardmore
Portland
Marcus Hook
Philadelphia
Rouseville
Marcus Hook
Philadelphia
Warren
Bradford
Memphis
B-4
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TABLE B-l. UNITED STATE PETROLEUM REFINERIES: LOCATION BY STATE
(CONTINUED)
State
TEXAS
TEXAS
TEXAS
TEXAS
TEXAS
TEXAS
Company Location
Amoco Oil Co.
Chevron USA Inc.
Chevron USA Inc.
Citgo
Coastal Refining & Marketing Inc.
Crown Central Petroleum Corp.
Texas City
El Paso
Port Arthur
Corpus Christi
Corpus Christi
Houston
TEXAS i Diamond Shamrock Corp. Sunray
TEXAS
TEXAS
TEXAS
Diamond Shamrock Corp.
El Paso Refining CL
Exxon Co. USA
TEXAS ' Fina Oil & Chemical Co.
TEXAS Fina Oil & Chemical Co.
TEXAS Howell Hydrocarbons Inc.
TEXAS Koch Refining Co.
TEX\5 '' LaGloria Oil & Gas Co
TEXAS i Leal Petroleum Corp.
Three Rivers
El Paso
Baytown
Big Spring
Port Arthur
San Antonio
Corpus Christi
Tvler
Nixon
TEXAS Liquid Energy Corp. : Bridgeport
TEXAS Lyondell Petrochemical Co. Houston
TEXAS Marathon Oil Co. Texas City
TEXAS Mobil Oil Corp. Beaumont
TEXAS Phibro Refining Inc Houston
TEXAS Phibro Refining Inc. Texas City
TEXAS j Phillips 66 Co. Borger
TEXAS i Phillips 66 Co. Sweeny
TEXAS Pride Refining Inc.
TEXAS Shell Oil Co.
TEXAS
TEXAS
TEXAS
TEXAS
TEXAS
UTAH
UTAH
Shell Oil Co.
Southwestern Refining Co., Inc.
Star Enterprise
Trifinery
Valero Refining Co.
Amoco Oil Co.
Big West Oil Co.
UTAH Chevron USA
UTAH Crysen Refining Inc.
Abilene
Deer Park
Odessa
Corpus Christi
Port Arthur
Corpus Christi
Corpus Christi
Salt Lake City
Salt Lake City
Salt Lake Citv
Woods Cross
B-5
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TABLE B-l. UNITED STATE PETROLEUM REFINERIES: LOCATION BY STATE
(CONTINUED)
State
UTAH
UTAH
VIRGINIA
WASHINGTON
WASHINGTON
WASHINGTON
WASHINGTON
WASHINGTON
WASHINGTON
WASHINGTON
WEST VIRGINIA
WEST VIRGINIA
WISCONSIN
WYOMING
' WYOMING
WYOMING
WYOMING
Company
Pennzoil Products Co.
Phillips 66 Co.
Amoco Oil Co.
Atlantic Richfield Co.
BP Oil Co.
Location
Roosevelt
Woods Cross
Yorktown
Femdale
Ferndale
Chevron USA Inc. Seattle
Sneii Oil Co. Anacortes
Sound Refining Inc. Tacoma
Texaco Refining & Marketing Inc. Anacortes
U.S. Oil & Refining Co.
Tacoma
Phoenix Refining Co. St. Mary's
Quaker State Oil Refining Corp.
Murphy Oil USA Inc.
Frontier Oil & Refining Co.
IJttle America Refining Co
Sinclair Oil Corp.
Wyoming Refining Co.
Newell
Superior
Cheyenne
Casper
Sinclair
Newcastle
Source: 1/1/92 issue of Oil and Gas Journal
B-6
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TECHNICAL REPORT DATA
(PLEASE READ INSTRUCTIONS ON THE REVERSE BEFORE COMPLETING)
1. REPORT NO.
EPA-454/R-98-011
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
LOCATING AND ESTIMATING AIR EMISSION FROM SOURCES OF
BENZENE
6. REPORT DATE
6/1/98
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
EASTERN RESEARCH GROUP, INC
P O BOX 2010
MORRISVILLE, NC 27560
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-D7-0068
12. SPONSORING AGENCY NAME AND ADDRESS
U. S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF AIR QUALITY PLANNING AND STANDARDS (MD-14)
RESEARCH TRIANGLE PARK, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
FINAL
14. SPONSORING AGENCY CODE
13. SUPPLEMENTARY NOTES
EPA WORK ASSINGMENT MANAGER: DENNIS BEAUREGARD (919) 541-5512
16. ABSTRACT
TO ASSIST GROUPS INTERESTED IN INVENTORYING AIR EMISSIONS OF VARIOUS POTENTIALLY TOXIC
SUBSTANCES, THE U.S. ENVIRONMENTAL PROTECTION AGENCY IS PREPARING A SERIES OF
DOCUMENTS, SUCH AS THIS, TO COMPILE AVAILABLE INFORMATION ON SOURCES AND EMISSIONS OF
THESE SUBSTANCES. THIS DOCUMENT DEALS SPECIFICALLY WITH BENZENE. ITS INTENDED AUDIENCE
INCLUDES, FEDERAL, STATE, AND LOCAL AIR POLLUTION PERSONNEL AND OTHERS INTERESTED IN
LOCATING POTENTIAL EMITTERS OF BENZENE AND IN MAKING GROSS ESTIMATES OF AIR EMISSIONS
THEREFROM.
THIS DOCUMENT PRESENTS INFORMATION ON (1) THE TYPES OF SOURCES THAT MAY EMIT BENZENE; (2)
PROCESS VARIATIONS AND RELEASE POINTS FOR THESE SOURCES; AND (3) AVAILABLE EMISSIONS
INFORMATION INDICATING THE POTENTIAL FOR BENZENE RELEASES INTO THE AIR FROM EACH
OPERATION.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
BENZENE
AIR EMISSION SOURCES
TOXIC SUBSTANCES
EMISSION ESTIMATION
b. IDENTIFIERS/OPEN ENDED TERMS e. COSATI FIELD/GROUP
18. DISTRIBUTION STATEMENT
UNLIMITED
UNCLASSIFIED
21. NO. OF PAGES
UNCLASSIFIED
22. PRICE
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