AIR

EPA

United States Office of Air Quality

Environmental Protection Planning And Standards June 1998

Agency Research Triangle Park, NC 27711

EPA-454/R-98-011

LOCATING AND ESTIMATING

AIR EMISSIONS FROM

SOURCES OF BENZENE
ii

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
iii

TABLE OF CONTENTS

Section Page

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
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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

5.2.2 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
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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

5.9.1 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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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
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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
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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 the 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
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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
x

LIST OF TABLES

Table Page

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 in 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 Air 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
LIST OF TABLES, continued

Table Page

xi

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 the 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
LIST OF TABLES, continued

Table Page

xii

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
LIST OF TABLES, continued

Table Page

xiii

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 Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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 in 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
LIST OF TABLES, continued

Table Page

xiv

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
LIST OF TABLES, continued

Table Page

xv

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
xvi

LIST OF FIGURES

Figure Page

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
LIST OF FIGURES, continued

Figure Page

xvii

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 Olefin 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
LIST OF FIGURES, continued

Figure Page

xviii

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
LIST OF FIGURES, continued

Figure Page

xix

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

9-6 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
xx

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.
1-1

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
Substance EPA Publication Number

1-2

Coal and Oil Combustion Sources EPA-450/2-89-001

Cyanide Compounds EPA-454/R-93-041

Dioxins and Furans EPA-454/R-97-003

Epichlorohydrin EPA-450/4-84-007j

Ethylene Dichloride EPA-450/4-84-007d

Ethylene Oxide EPA-450/4-84-007l

Formaldehyde EPA-450/4-91-012

Lead EPA-454/R-98-006

Manganese EPA-450/4-84-007h

Medical Waste Incinerators EPA-454/R-93-053

Mercury and Mercury Compounds EPA-453/R-93-023

(under revision)

Methyl Chloroform EPA-454/R-93-045

Methyl Ethyl Ketone EPA-454/R-93-046

Methylene Chloride EPA-454/R-93-006

Municipal Waste Combustors EPA-450/2-89-006

Nickel EPA-450/4-84-007f

Perchloroethylene and EPA-450/2-89-013

Trichloroethylene

Phosgene EPA-450/4-84-007i

Polychlorinated Biphenyls (PCBs) EPA-450/4-84-007n

Polycyclic Organic Matter (POM) EPA-450/4-84-007p

Sewage Sludge Incinerators EPA-450/2-90-009

Styrene EPA-454/R-93-011

Toluene EPA-454/R-93-047

Vinylidene Chloride EPA-450/4-84-007k

Xylenes 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.
1-3

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

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). Section 313 requires owners and operators of facilities in 1

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.
1-4

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 air 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 in 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 
1-5

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
2-1

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 in 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.
2-2

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 in 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 in 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 in the document Procedures for Preparing Emission Factor

Documents. The criteria for assigning the data quality ratings are as follows: 2

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
2-3

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.
2-4

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, and 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. 
H

C

H

H H

H H

C C

C C

C

3-1

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 Table-3-1. Selected physical and chemical properties of benzene are

presented in Table 3-2 .4-7

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. 
3-2

TABLE 3-1. CHEMICAL IDENTIFICATION OF BENZENE

Chemical Name Benzene

Synonyms Benzol, phenyl hydride, coal naphtha,

phene, benxole, cyclohexatriene

Molecular formula C6 6 H

Identification numbersa

CAS Registry 71-43-2

NIOSH RTECS CY 1400000

DOT/UN/NA UN 1114; Benzene (Benzol)

DOT Designation Flammable liquid

Source: References 4 and 5.

Chemical Abstract Services (CAS); National Institute of Occupational Safety and Health (NIOSH); Registry of a

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. The most common commercial grade of benzene contains 50 to 8
3-3

TABLE 3-2. PHYSICAL AND CHEMICAL PROPERTIES OF BENZENE

Property Value

Molecular weight 0.17 lbs (78.12 g)

Melting point 41.9(F (5.5(C)

Boiling point at 1 atmosphere (760 mm Hg) 176.18(F (80.1(C)

Density, at 68(F (20(C) 0.0141 lb/ft (0.8794 g/cm ) 3 3

Physical state (ambient conditions) Liquid

Color Clear

Odor Characteristic

Viscosity (absolute) at 68(F (20(C) 0.6468 cP

Surface tension at 77(F (25(C) 0.033 g/cm (28.18 dynes/cm ) 3 3

Heat of vaporization at 176.18(F (80.100(C) 33.871 KJ/Kg·mol (8095 Kcal/Kg·mol)

Heat of combustion at constant pressure and 41.836 KJ/g (9.999 Kcal/g)

77(F (25(C) (liquid C H to liquid H O and 6 6 2

gaseous CO )2

Odor threshold 0.875 ppm

Solubility:

Water at 77(F (25(C) Very slightly soluble (0.180 g/100 mL,

1800 ppm)

Organic Solvents Soluble in alcohol, ether, acetone, carbon

tetrachloride, carbon disulfide, and acetic

acid

Vapor pressure at 77(F (25(C) 95.2 mm Hg (12.7 kPa)

Auto ignition temperature 1044(F (562(C)

Flashpoint 12(F (-11.1(C) (closed cup)

Conversion factors (Vapor weight to volume) 1 ppm = 319 mg/m at 77(F (25(C); 3

1 mg/L = 313 ppm

Source: References 4, 5, 6, and 7.
3-4

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 (NO ), or the relative degradation rate of various 2

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. Oxidation of benzene 8

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 1.1x10 inches (in) -5

(275 nanometers [nm]). 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. Other products that are predicted to form from indirect reactions 6

with benzene in the atmosphere include aldehydes, peroxides, and epoxides. Photodegradation

of NO produces atomic oxygen, which can react with atmospheric benzene to form phenols. 2

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 in the United States around 1941. It was used primarily as feedstock in

the chemical manufacturing industry. For United States industries, benzene is currently 10

produced in the United States, the Virgin Islands, and Puerto Rico by 26 companies at 
3-5

36 manufacturing facilities. The majority of benzene production facilities in the United States 11

are found in the vicinity of crude oil sources, predominantly located around the Texas and

Louisiana Gulf coast. They are also scattered throughout 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). Production was expected to increase by approximately 3 to 11

3.5 percent per year through 1994. Exports of benzene in 1993 were about 23 million gal (87

million L), around 1 percent of the total amount produced in the United States. 12

Benzene is produced domestically by five major processes. Approximately 12

45 percent of the benzene consumed in the United States is produced by the catalytic

reforming/separation process. With this process, the naphtha portion of crude oil is mixed 11

with hydrogen, heated, and sent through catalytic reactors. The effluent enters a separator 13

while the hydrogen is flashed off. The resulting liquid is fractionated and the light ends (C 13

1

to C ) are split. Catalytic reformate, from which aromatics are extracted, is the product. 4

13

Approximately 22 percent of the benzene produced in the United States is

derived from ethylene production. Pyrolysis gasoline is a by-product formed from the steam 11

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. Toluene dealkylation 11

produces benzene and methane from toluene or toluene-rich hydrocarbons through cracking

processes using heat and hydrogen. The process may be either 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 in the United States is derived from coke

oven light oil distillation at coke by-product plants. Light oil is recovered from coke oven 11
3-6

gas, usually by continuous countercurrent absorption in a high-boiling liquid from which it is

stripped by steam distillation. A light oil scrubber or spray tower removes the light oil from 9

coke oven gas. Benzene is recovered from the light oil by a number of processes, including 10

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. Figure 3-1 presents a simplified production and use 11

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 in 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. Ethylbenzene is formed by 12

reacting benzene with ethylene and propylene using a catalyst such as anhydrous aluminum

chloride or solid phosphoric acid. Styrene is the product of dehydrogenation of 8

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. Cumene is oxidized to produce phenols and acetone. Phenol is used to make resins 7 12

and resin intermediates for epoxies and polycarbonates, and caprolactam for nylon. Acetone 12

is used to make solvents and plastics. 16

Cyclohexane production accounts for 13 percent of benzene use. Cyclohexane 12

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
3-7

Figure 3-1. Production and Use Tree for Benzene

Source: References 11 and 12.
3-8

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. Aniline, in turn, is used to manufacture isocyanates for polyurethane foams, plastics, 10

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 in gasoline was increased in recent years. The 4

concentration of benzene in refined gasoline depends on many variables, such as gasoline

grade, refinery location and processes, and crude source. The various sources of benzene 6

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;
3-9

& 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 in revised emission factors. For off-road vehicles, EPA has also completed 20

a recent study to estimate emissions.
4-1

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 to 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 in Section 5.0.
4-2

TABLE 4-1. BENZENE PRODUCTION FACILITIES

Company Name Location

Annual

Capacity

million gal

(million L) Prod

Amerada Hess Corporation Hess Oil Virgin Islands Corporation, subsidiary

St. Croix, Virgin Islands 75 (284) Catalytic ref

toluene; no c

American Petrofina, Incorporated Fina Oil and Chemical Company, subsidiary

Port Arthur, Texas 33 (125)

31 (117)

Catalytic refToluene; par

Amoco Corporation Amoco Oil Company, subsidiary

Texas City, Texas 85 (322)

25 (95)12 (45)

Catalytic refPyrolysis gaXylene isom

Aristech Chemical Corporation Clairton, Pennsylvania 45 (170) Coke-oven lAshland Oil, Incorporated Ashland Chemical Company, division  Petrochemicals Division

Catlettsburg, Kentucky 55 (208)

2 (8)

Coke-oven lCatalytic ref

Atlantic Richfield Corporation Lyondell Petrochemical Company, subsidiary

Channelview, TexasHouston, Texas

90 (341)35 (132)

15 (57)

Pyrolysis gaCatalytic refToluene; no 
4-3

TABLE 4-1. CONTINUED

Company Name Location

Annual

Capacity

million gal

(million L) Prod

BP Oil Alliance, Louisiana

Lima, Ohio

18 (68)

47 (178)35 (132)80 (303)

Catalytic refTolueneCatalytic refToluene

Chevron Corporation Chevron Chemical Company, subsidiary  Aromatics and Derivatives Division

Philadelphia, PennsylvaniaPort Arthur, Texas

24 (91)21 (79)

42 (159)

24 (91)

35 (132)

Catalytic refToluene; capCatalytic refPyrolysis gaToluene; par

Citgo Petroleum Corporation Corpus Christi, Texas 55 (208)

23 (87)

Catalytic refToluene

Coastal Eagle Point Oil Co. Westville, New Jersey 15 (57) Catalytic refCoastal Refining and Marketing, Inc. Corpus Christi, Texas 50 (189)

7 (26)

Toluene; capCatalytic ref

Dow Chemical U.S.A. Freeport, Texas

Plaquemine, Louisiana

25 (95)

80 (303)120 (454)

Pyrolysis gaPyrolysis gaToluene; cap
4-4

TABLE 4-1. CONTINUED

Company Name Location

Annual

Capacity

million gal

(million L) Prod

Exxon Corporation Exxon Chemical Company, division Exxon Chemical Americas

Corpus Christi, TexasBaton Rouge, LouisianaBaytown, Texas

50 (189)30 (114)50 (189)30 (114)75 (284)

20 (76)20 (76)23 (87)

Pyrolysis gasTolueneCatalytic refoPyrolysis gasCatalytic refoPyrolysis gasXylene isomToluene

Huntsman Chemical Corporation Bayport, Texas 15 (57) Toluene; capKerr-McGee Corporation Southwestern Refining Company, Incorporated, subsidiary

Corpus Christi, Texas 17 (64) Catalytic refo

Koch Industries, Incorporated Koch Refining Company, subsidiary

Corpus Christi, Texas 25 (95)

55 (208)

10 (38)

50 (189)

Catalytic refoToluene; capXylene isomToluene

Mobil Corporation Mobil Oil Corporation Mobil Chemical Company, division Petrochemicals Division U.S. Marketing and Refining Division

Beaumont, TexasChalmette, Louisiana

90 (341)

10 (38)20 (76)

Catalytic refoPyrolysis gasCatalytic refo
4-5

TABLE 4-1. BENZENE PRODUCTION FACILITIES

Company Name Location

Annual

Capacity

million gal

(million L) Prod

Occidental Petroleum Corporation Petrochemicals Olefins and Aromatics Division

Chocolate Bayou, Texas 60 (227)

40 (151)

Pyrolysis gaToluene

Phibro Energy USA, Inc. Houston, Texas 5 (19) Catalytic refPhillips Petroleum Company Chemicals Division Olefins and Cyclics Branch

Sweeny, Texas 11 (42) Catalytic ref

Phillips Puerto Rico Core, Incorporated, subsidiary Guayama, Puerto Rico 35 (132)

48 (182)

Catalytic refToluene; cap

Shell Oil Company Shell Chemical Company, division

Deer Park, TexasWood River, Illinois

75 (284)80 (303)50 (189)

Catalytic refPyrolysis gaCatalytic ref

Sun Company, Incorporated Sun Refining and Marketing Company, Incorporated, subsidiary

Marcus Hook, PAToledo, Ohio

26 (98)11 (42)19 (72)

Catalytic refToluene; no Catalytic ref
4-6

TABLE 4-1. BENZENE PRODUCTION FACILITIES

Company Name Location

Annual

Capacity

million gal

(million L) Prod

Texaco, Incorporated Texaco Chemical Company, subsidiary

El Dorado, KansasPort Arthur, Texas

15 (57)

46 (174)

20 (76)

Catalytic refCatalytic refPyrolysis ga

The UNO-VEN Company Lemont, Illinois 12 (45)

7 (26)

Catalytic refCoke-oven l

USX Corporation Marathon Oil Company, subsidiary Marathon Petroleum Company, subsidiary

Lake Charles, LouisianaTexas City, Texas

55 (208)

7 (26)

Catalytic refToluene

TOTAL 2,350(8,896)

Source: Reference 11.

 Captive means used for subsequent processes on site. a

Note: This list is subject to change as market conditions change, facility ownership changes, or plants are closed down. The reader should 

particular facilities by consulting current listings or the plants themselves. The level of emissions from any given facility is a function throughput and control measures, and should be determined through direct contacts with plant personnel. Reference SRI '93 indicatechanges made in product locations as of January 1993.
4-7

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 in Figure 4-1, accounts for about 45 percent of all benzene 22

produced in the United States. In the following description of the reforming process, 12

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 in 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 in which the

catalyst, usually platinum or rhenium chloride, converts paraffins to aromatic compounds. The

product stream (Stream 3) consists of excess hydrogen and a reformate 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). The stabilizer is a fractionator in which more volatile, light hydrocarbons are 22

removed from the high-octane liquid product. The liquid is then sent to a debutanizer (not

shown in the figure). Aromatics (benzene, toluene, and mixed xylenes) are then extracted 

from the stabilized reformate.22
4-8

Figure 4-1. Universal Oil Products Platforming (Reforming) Process

Source: Reference 22.
4-9

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. 22

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 in 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. However, information provided by 22

the benzene production industry indicates that BTX is commonly produced in 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.) Furthermore, some 22

descriptive data were found, indicating that benzene may be emitted from the
4-10

Figure 4-2. Flow Diagram of a Glycol BTX Unit Process

Source: Reference 22.
4-11

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, in 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 pyrolysis gasoline. At present, benzene production 24

directly from toluene accounts for almost 30 percent of total benzene produced. Growth in 11

demand for toluene in gasoline (as an octane-boosting component for gasoline blending)

appears to be slowing because of increased air 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. At present, production of benzene by the 24

HDA and disproportionation processes accounts for 50 percent of toluene end use.
4-12

4.2.1 Toluene Dealkylation

Process Description

Hydrodealkylation of toluene can be accomplished through thermal or catalytic

processes. The total dealkylation capacity is almost evenly distributed between the two 25

methods. As shown in Figure 4-3, pure toluene (92 to 99 percent) or toluene (85 to 10

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). Recovered benzene is sent to storage 10

(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, wastewater 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 
4-13

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 dealkylation 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. As shown in Figure 4-4, 24

the basic process is similar to toluene hydrodealkylation, but can occur under less severe

conditions. Transalkylation operates at lower temperatures, consumes little hydrogen, and 15,26

no loss of carbon to methane occurs as with HDA. Toluene material is sent to a separator for 24

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. These potential sources are shown as points A, 23

B, and C, respectively, in Figure 4-4.
4-14

Figure 4-3. Process Flow Diagram of a Toluene Dealkylation Unit

Source: References 10, 15, and 25.
4-15

Figure 4-4. Toluene Disproportionation Process Flow Diagram (Tatoray Process)

Source: References 15 and 26.
4-16

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. Pyrolysis gasoline is a liquid by-product 28

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 lbs

(7.3 Gg) pyrolysis gasoline with about 7,497,244 lbs (3.4 Gg) benzene in the pyrolysis

gasoline. A plant producing the same amount of ethylene from atmospheric gas oils will 28

produce about 754,134,509 lbs (342 Gg) of pyrolysis gasoline containing 213,450,937 lbs

(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
4-17

TABLE 4-2. ETHYLENE PRODUCERS - LOCATION AND CAPACITY

Producer Location

Annual Capacity

million lb

(million kg) 

Atlantic Richfield Company

Lyondell Petrochemical Company, subsidiary Channelview, Texas 3,360 (1,524) Partly capti

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 merChevron Corporation

Chevron Chemical Company, subsidiary

Olefins and Derivatives Division Cedar Bayou, Texas

Port Arthur, Texas

1,450 (658)1,250 (567)

Mostly captMostly capt

Dow Chemical U.S.A. Freeport, Texas

Plaquemine, Louisiana

2,050 (930)

2,300 (1,043)

CaptiveCaptive

Du Pont

Du Pont Chemicals Orange, Texas 1,050 (476) Captive

Eastman Chemical Company

Texas Eastman Company Longview, Texas 1,400 (635) Mostly Cap
4-18

TABLE 4-2. CONTINUED

Producer Location

Annual Capacity

million lb

(million kg) 

Exxon Chemical Company

Exxon Chemical Americas Baton Rouge, Louisiana

Baytown, Texas

1,775 (805)2,100 (953)

CaptiveSome captivBelvieu, Te

Javelina Gas Processing Corpus Christi, Texas 180 (82) Recovered 

local refiner

Koch Industries, Inc.

Koch Refining Company, subsidiary Corpus Christi, Texas 24 (11) Captive

Mobil Oil Corporation

Mobil Chemical Company, division

Petrochemicals Division

Beaumont, TexasHouston, Texas

1,100 (499)

500 (227)

Mostly captMostly capt

Occidental Petroleum Corporation

Petrochemicals

Olefins & Aromatics Division Chocolate Bayou, Texas

Corpus Christi, TexasLake Charles, Louisiana

1,100 (499)1,700 (771)

750 (340)

Mostly captMostly captCaptive

Phillips Petroleum Company

Chemicals Division

Olefins and Cyclics Branch

Sweeny, Texas 2,550 (1,157) Partly capti
4-19

TABLE 4-2. CONTINUED

Producer Location

Annual Capacity

million lb

(million kg) 

Quantum Chemical Corp.

USI Division Clinton, Iowa

Deer Park, TexasMorris, Illinois

900 (408)

1,500 (680)1,000 (454)

CaptiveCaptiveCaptive

Rexene Corporation Odessa, Texas 500 (228) Partly captiShell Oil Company

Shell Chemical Company, division Deer Park, Texas

Noroco, Louisiana

1,900 (862)

2,560 (1,161)

Partly mercPartly capti

Sun Refining and Marketing Co. Brandenburg, Kentucky

Claymont, Delaware

NA

250 (113)

CaptivePartly capti

Sweeny Olefins Limited Partnership Sweeny, Texas 1,500 (680) MerchantTexaco Chemical Company Port Arthur, Texas

Port Neches, Texas

1,150 (522)

350 (159)

Some captivCaptive

Union Carbide Corporation

Industrial Chemicals Division

Seadrift, TexasTaft, LouisianaTexas City, Texas

880 (399)

1,405 (637)1,400 (635)

CaptiveCaptiveMostly capt
4-20

TABLE 4-2. CONTINUED

Producer Location

Annual Capacity

million lb

(million kg) 

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 captWestlake Petrochemicals Corporation Sulphur, Louisiana 1,000 (454) Mostly captTOTAL 45,798 (20,774)

Source: Reference 11.

 Captive means used for subsequent processes on site. Merchant means sold as a final product. a

NA = not availableNote: This list is subject to change as market conditions change, facility ownership changes, or plants are closed down. The reader should 

particular facilities by consulting current listings or the plants themselves. The level of benzene emissions from any given facility is such as throughput and control measures; and should be determined through direct contacts with plant personnel. Data represent prcapacities as of January 1993.
4-21

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 (in 

parallel) than are shown in the flow diagrams in Figure 4-5. For reference, Table 4-3 lists

stream descriptions and corresponding stream numbers in 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 in 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 in later

separation steps. Ethane and propane, which are present in 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 times. 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 particulate 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,
4-22

Figure 4-5. Process Flow Diagram for Ethylene Production from Naphtha and/or Gas-Oil Feed

Source: Reference 28.
4-23

Figure 4-5. Process Flow Diagram for Ethylene Production from Naphtha and/or Gas-Oil Feeds, co

Source: Reference 28.
4-24 (continued)

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 tower

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
TABLE 4-3. CONTINUED

Stream Number Stream Description

4-25

28 Process gas

29 Hydrogen rich stream from demethanizer

30 Methane rich stream from demethanizer

31 C components from de-ethanizer 2

32 C and heavier components from de-ethanizer 3

33 Hydrogenated acethylene from acetylene convertor

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 C and heavier components to debutanizer 4

40 Overheads from debutanizer

41 C and heavier components from debutanizer 5

42 Combined C components and gasoline stripper bottoms 5

fractions

43 Light ends to cracked gas compressor

44 C and heavier components 5

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
4-26

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 [H S]) and carbon dioxide (CO ) and water; and for 2 2

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 in 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 C and heavier compounds. The condensed organic phase (Stream 13) is stripped of the 5

lighter components in 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 in

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). 
4-27

On leaving the quench tower, the pyrolysis gas is compressed to about 3.5 mPa

in five stages. The overhead stream from the quench tower (Stream 19) passes to a 29

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 (H S and CO ) is removed by absorption in 2 2

diethanolamine (DEA) or other similar solvents in 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 S emissions. 2

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 lowtemperature 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, 
4-28

which results in 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 remaining

process steps involve a series of fractionations in which the various product fractions are

successively separated.

The demethanizer separates a mixture of hydrogen and methane from the C and 2

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) in the low-temperature chilling section. The methane-rich stream is used

primarily for furnace fuel. Hydrogen is required in the catalytic hydrogenation operations. 

The de-ethanizer separates the C components (ethylene, ethane, and acetylene) 2

(Stream 31) from the C and heavier components (Stream 32). Following catalytic 3

hydrogenation of acetylene to ethylene by the acetylene converter (Stream 33), the ethyleneethane 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 (C and heavier compounds) (Stream 32) pass to the 3

depropanizer, where a C -C split is made. The depropanizer overhead stream (primarily 3 4

propylene and propane) (Stream 36) passes to a catalytic hydrogenation reactor (C converter), 3

where traces of propadiene and methyl acetylene are hydrogenated. Following hydrogenation,

the C fraction passes to the propylene fractionator, where propylene is removed overhead as a 3

purified product (Stream 37). The propane (Stream 38) is recycled to the ethane/propane

pyrolysis furnace.
4-29

The C and heavier components (Stream 39) from the depropanizer pass to the 4

debutanizer, where a C -C split is made. The overhead C stream (Stream 40) is removed as 4 5 4

feed to a separate butadiene process. 

The stream containing C and heavier compounds from the debutanizer 5

(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 C and heavier compounds (Stream 44) are transferred to storage as treated 5

pyrolysis gasoline. This stream contains benzene and other aromatics formed by pyrolysis. 

The three catalytic hydrogenation reactors for acetylene, C compounds, and 3

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. Also, as mentioned before, because the benzene content of pyrolysis 10

gasoline can be high, some plants recover motor gasoline, aromatics (BTX), or benzene from

the pyrolysis gasoline.
4-30

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/in [10 to 40 atmospheres pressure]). 2 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. The solvent may be regenerated (Streams 9 and 10). Dissolved 30

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
4-31

Figure 4-6. Production of BTX by Hydrogenation of Pyrolysis Gasoline

Source: Reference 30.
4-32

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. Emission factors for benzene from sources at ethylene plants are shown in 28

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. Charge gas 28

compressor and refrigeration compressor outages are also potential sources. Emissions from

these compressors are generally short term in 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

main 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. Flue gas normally 28

contains products of hydrogen and methane combustion. Emissions from pyrolysis furnace

decoking consist of air, steam, CO , CO, and particles of unburned carbon. Emissions from 2

28
4-33

TABLE 4-4. BENZENE EMISSION FACTORS FOR A HYPOTHETICAL ETHYLENE PLAN

SCC and Description Emission Source Control Device Emission Factor in lb/ton 

3-01-197-45

Ethylene Manufacturing-Compressor LubeOil Vent

Compressor Lube Oil Vents Uncontrolled 0.0006

(0.0003)

Single Compressor Train Uncontrolled 0.0004 

(0.0002)

Dual Compressor Train Uncontrolled 0.0008 

(0.0004)

3-01-197-42

Ethylene Manufacturing -Pyrolysis Furnace Decoking

Pyrolysis Furnace Decoking No benzene emissi

3-01-197-43

Ethylene Manufacturing-Acid GasRemoval

Acid Gas Removal No benzene emissi

3-01-197-44

Ethylene Manufacturing -Catalyst Regeneration

Catalyst Regeneration No benzene emissi

3-01-197-XX

Ethylene Manufacturing -Secondary Sources

SecondaryWastewater Treatment

Uncontrolled 0.0434 

(0.0217)

3-01-197-49

Ethylene Manufacturing -Equipment Leak Emissions

Equipment Leak Emissions Detection/

Correction of leaks

See Section 4.5.

Uncontrolled See Section 4.5.
4-34

TABLE 4-4. BENZENE EMISSION FACTORS FOR A HYPOTHETICAL ETHYLENE PLANT

SCC and Description Emission Source Control Device Emission Factor in lb/ton (k

3-01-197-XX

Ethylene ManufacturingIntermittent Emissions

Intermittent Emissionsc

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)

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 lb/yr (544.

a

Factors are expressed as lb (kg) benzene emitted per ton (Mg) ethylene produced. bIntermittent emissions have been reported from the activation of pressure relief devices and the depressurization and purging of equipment for m

c
4-35

acid gas removal are H S, SO , and CO ; these emissions are generally controlled to recover 2 2 2

H S as sulfur or convert H S to SO . As discussed earlier, catalyst regeneration is infrequent 2 2 2

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. Storage of 32

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. No supporting data showing how the equations were applied 33

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 greater while 34

control efficiencies for industrial waste boilers vary depending upon design and operation. 28
4-36

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. For additional discussion on storage tank emissions, see 28

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). Most by-product recovery plants recover light oil, but not all plants 26

refine it. About 3.4 to 4.8 gal (13 to 18 liters [L]) of light oil can be recovered from the coke 
4-37

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;

& Naphthalene, used primarily as an intermediate in the production of

organic chemicals; and

& Coke oven gas, a high-quality fuel similar to natural gas.38

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. The figure does not necessarily reflect any given plant, nor does it include all 37,39

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 in 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 in the original beehive ovens. 
4-38 (continued)

TABLE 4-5. COKE OVEN BATTERIES CURRENTLY OPERATING

IN THE UNITED STATES

Plant (Location)

Battery Identification

Number

ABC Coke (Tarrant, AL) A

 5

 6

Acme Steel (Chicago, IL) 1

 2

Armco, Inc. (Middletown, OH) 1

 2

 3

Armco, Inc. (Ashland, KY) 3

 4

Bethlehem Steel (Bethlehem, PA) A

 2

 3

Bethlehem Steel (Burns Harbor, IN) 1

 2

Bethlehem Steel (Lackawanna, NY) 7

 8

Citizens Gas (Indianapolis, IN) E

 H 

 1 

Empire Coke (Holt, AL) 1

 2

Erie Coke (Erie, PA) A

 B

Geneva Steel (Provo, UT) 1

 2

 3

 4

Gulf States Steel (Gadsden, AL) 2

3
TABLE 4-5. CONTINUED

Plant (Location) Battery Identification Number

4-39 (continued)

Inland Steel (East Chicago, IN) 6

 7 

 9 

10

11

Koppers (Woodward, AL) 1

2A

2B

4A

4B

5

LTV Steel (Cleveland, OH) 6

7

LTV Steel (Pittsburgh, PA) P1

P2

P3N

P3S

P4

LTV Steel (Chicago, IL) 2

LTV Steel (Warren, OH) 4

National Steel (Ecorse, MI) 5

National Steel (Granite City, IL) A

 B

New Boston Coke (Portsmouth, OH) 1

Sharon Steel (Monessen, PA) 1B

2

Shenango (Pittsburgh, PA) 1

4

Sloss Industries (Birmingham, AL) 3

4

5

Toledo Coke (Toledo, OH) C

Tonawanda Coke (Buffalo, NY) 1
TABLE 4-5. CONTINUED

Plant (Location) Battery Identification Number

4-40

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.
4-41

Figure 4-7. Coke Oven By-Product Recovery, Representative Plant

Source: Reference 37 and 39.
4-42

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 in 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. The coking time affects the 22

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.
4-43

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 particulate

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). Another 37

20 percent of the tar is “light” tar, which is cleaner and less viscous, and is condensed and

collected in the primary cooler. Smaller amounts of “tar fog” are removed from the gas by 39

collectors (electrostatic precipitators or gas scrubbers) (Stream 4). Light tar and tar fog is 37

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 
4-44

(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 in the tar bottom of the

final cooler, and (3) direct cooling with wash oil and naphthalene recovery in 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 in 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). 

As shown in Figure 4-7, light oil is primarily recovered from coke oven gas 

by continuous countercurrent absorption in a high-boiling liquid from which it is stripped by

steam distillation. Coke oven gas is introduced into a light oil scrubber (Stream 16). 10

Packed or tray towers have been used in this phase of the process, but spray towers are now

commonly used. Wash oil is introduced into the top of the tower (Stream 17) and is 10

circulated through the contacting stages of the tower at around 0.11 to .019 gal/ft (1.5 to 3

2.5 liters per cubic meter [L/m3]) of coke oven gas. At a temperature of about 86(F 39

(30(C), a light oil scrubber will remove 95 percent of the light oil from coke oven gas. The 
4-45

Figure 4-8. Litol Process Flow Diagram

Source: References 40 and 41.
4-46

benzene-containing wash oil is steam-stripped (Stream 18) to recover the light oil. Steam 39

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 following 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 C and lighter 5

fractions, and the C and heavier fractions (Stream 2). The remaining “heart cut” is sent to a 9

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

(Stream 5). 

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 H S and organics are 2

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 
4-47

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 mains, 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. The hoppers delivering the coal are 42

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 time. 

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 
4-48

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. 
4-49

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 to 6.2 x 10 lb/ft (1 to 3 parts per million -7 -7 3

[ppm] or about 3 to 10 milligrams per cubic meter [Mg/m3]). These data translated into an

estimated benzene emission factor of 1.3 lb to 5.3 lb (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 lbs/ton of coal charged

(11,000 g/Mg) uncontrolled, 0.22 lbs/ton of coal charged (110 g/Mg) controlled with 

flare. No additional emission factors for benzene and coke ovens were found in the 296

literature. However, an analysis of coke oven gas indicated a benzene content of 

1.3 x 10 to 2.2 x 10 lb/ft (21.4 to 35.8 grams per cubic meter [g/m ]). -3 -3 3 3
4-50

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. The following paragraphs describe the 37,43

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 (lb/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. Wash oil is 37

separated after it leaves the heat exchanger and recirculates 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. Vapors from 37

naphthalene separation tanks have been reported to contain benzene, benzene homologs, and

other aromatic hydrocarbons. The emission factors for naphthalene separation and 37
4-51

TABLE 4-6. SUMMARY OF BENZENE EMISSION FACTORS FOR FURNACE AND

FOUNDRY COKE BY-PRODUCT RECOVERY PLANTS

SCC and Description Emissions Sourcea Control Device

Emission Factor lb/ton (g/M

Furnace Coke Found

3-03-003-15

By-Product Coke -Gas By-Product Plant

Cooling Tower- Direct Water (A)c Uncontrolled 0.54 (270) 0.40 

- Tar bottom (B)c Uncontrolled 0.14 (70) 0.10 Light-Oil CondenserVent (C)

Uncontrolled 0.18 (89) 0.09

Gas Blanketing 3.6 x 10 (1.8) -3 1.9 x 10 

Naphthalene Separationand Processing (D)

Uncontrolled 0.22 (110) 0.16 

Activated Carbon 7.0 x 10 (0.35) -4 5.0 x 10 

Tar-Intercepting Sump(E)

Uncontrolled 0.019 (9.5) 0.009 

Tar Dewatering (F) Uncontrolled 0.042 (21) 0.020 

Gas Blanketing 8.4 x 10 (0.45) -4 4 x 10 
4-52

TABLE 4-6. CONTINUED

SCC and Description Emissions Sourcea Control Device

Emission Factor lb/ton (g/M

Furnace Coke Found

Tar Decanter (G) Uncontrolled 0.11 (54) 0.05 

Gas Blanketing 22 x 10 (1.1) -3 1.0 x 1

Tar Storage (H) Uncontrolled 0.013 (6.6) 6.2 

Gas Blanketing 7.6 x 10 (0.38) -4 3.6 x 10 

Light-Oil Sump (I) Uncontrolled 0.03 (15) 0.016 

Gas Blanketing 6 x 10 (0.3) -4 3.2 x 10 

Light-Oil Storage (J) Uncontrolled 0.012 (5.8) 6.2 x 1

Gas Blanketing 2.4 x 10 (0.12) -4 1.2 x 10 

BTX Storage (K)d Uncontrolled 0.012 (5.8) 6.2 x 1

Gas Blanketing 2.4 x 10 (0.12) -4 1.2 x 10 

Benzene Storage (L)d Uncontrolled 0.0116 (5.8) 6.2 x 1

Gas Blanketing 2.4 x 10 (0.12) -4 1.2 x 10 
4-53

TABLE 4-6. CONTINUED

SCC and Description Emissions Sourcea Control Device

Emission Factor lb/ton (g/M

Furnace Coke Found

Flushing-LiquorCirculation Tank (M)

Uncontrolled 0.026 (13) 0.019 

Gas Blanketing 5.2 x 10 (0.26) -4 3.8 x 10 

Excess-Ammonia LiquorTank (N)

Uncontrolled 2.8 x 10-3 2.0 x 

Gas Blanketing 5.6 x 10 (0.028) -5 4.0 x 10 

Wash-Oil Decanter (O) Uncontrolled 7.6 x 10 (3.8) -3 4.2 x 1

Gas Blanketing 1.5 x 10 (0.076) -4 8.2 x 10 

Wash-Oil CirculationTank (P)

Uncontrolled 7.6 x 10 (3.8) -3 4.2 x 1

Gas Blanketing 1.5 x 10 (0.076) -4 8 .2 x 10 

Source: Reference 296.

Source identification letters correspond to locations identified in Figure 4-7. a

Emission factors are expressed as g benzene emitted per Mg coke produced. bUsually only smaller plants use direct-water final cooler; all final coolers are shown as one unit in Figure 4-7. cNot all plants separate BTX or benzene. Therefore, all product storage is indicated in one box on the diagram in Figure 4-7. d
4-54

TABLE 4-7. SUMMARY OF BENZENE EMISSION FACTORS FOR EQUIPMENT LEAKS 

FURNACE COKE BY-PRODUCT RECOVERY PLANTS

SCC and Description Emissions Source Control (% efficiency)

Emission Factor 

lb/source day (kg/source day

Light Oil BTX

Recoveryc

Light Oil R

Benzene R

3-03-003-15

By-Product Coke -Gas By-ProductRecovery

Valves Uncontrolled 0.4 (0.18) 0.49 (0

Quarterly inspection (63) 0.15 (0.07) 0.18 (0Monthly inspection (72) 0.11 (0.05) 0.13 (0Use sealed bellows valves (100) -- --

Pumps Uncontrolled 4.2 (1.9) 5.1 (2

Quarterly inspection (71) 1.2 (0.55) 1.5 (0Monthly inspection (83) 0.71 (0.32) 0.86 (0Use dual mechanical seals (100) -- --

Exhausters Uncontrolled 0.62 (0.28 )c 0.62 (0

Quarterly inspection (55) 0.29 (0.13) 0.29 (0Monthly inspection (64) 0.22 (0.10) 0.22 (0Use degassing reservoir vents (100) -- --

Pressure Relief Devices Uncontrolled 6.0 (2.7) 7.5 (3

Quarterly inspection (44) 3.3 (1.5) 4.2 (1

Monthly inspection (52) 2.9 (1.3) 3.5 (1

Use rupture disk system (100) -- --

Sampling Connections Uncontrolled 0.55 (0.25) 0.68 (0

Closed-purge sampling (100) -- --
4-55

TABLE 4-7. CONTINUED

SCC and Description Emissions Source Control (% efficiency)

Emission Factor 

lb/source day (kg/source day)a,

Light Oil BTX

Recoveryc

Light Oil Rec

Benzene Ref

Open-ended Lines Uncontrolled 0.084 (0.038) 0.104 (0.0

Plug or cap (100

)

-- --

Source: Reference 37.

a 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 lb 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 pl
4-56

TABLE 4-8. SUMMARY OF BENZENE EMISSION FACTORS FOR EQUIPMENT LEAKS AT FO

COKE BY-PRODUCT RECOVERY PLANTS

SCC and Description Emissions Source Control (% efficiency)

Emission Factor 

lb/source day (kg/source da

Light Oil BTX

Recoveryc

Light Oil 

Benzene 

3-03-003-15

By-Product Coke -Gas By-ProductRecovery

Valves Uncontrolled 0.35 (0.16) 0.44 (

Quarterly inspection (63) 0.13 (0.06) 0.15 

Monthly inspection (72) 0.09 (0.04) 0.13 Use sealed bellows valves (100) -- 

Pumps Uncontrolled 3.7 (1.7) 4.6 

Quarterly inspection (71) 1.1 (0.5) 1.3 Monthly inspection (83) 0.66 (0.3) 0.88 

Use dual mechanical seals (100) -- 

Exhausters Uncontrolled 0.55 (0.25) 0.55 

Quarterly inspection (55) 0.24 (0.11) 0.24 Monthly inspection (64) 0.20 (0.09) 0.20 Use degassing reservoir vents (100) -- 

Pressure Relief Devices Uncontrolled 5.5 (2.5) 6.8 

Quarterly inspection (44) 3.1 (1.4) 3.7 Monthly inspection (52) 2.6 (1.2) 3.3 

Use rupture disk system (100) -- 

Sampling Connections Uncontrolled 0.51 (0.23) 0.62 

Plug or cap (100) -- 
4-57

TABLE 4-8. SUMMARY OF BENZENE EMISSION FACTORS FOR EQUIPMENT LEAKS AT FO

COKE BY-PRODUCT RECOVERY PLANTS

SCC and Description Emissions Source Control (% efficiency)

Emission Factor 

lb/source day (kg/source day

Light Oil BTX

Recoveryc

Light Oil R

Benzene R

Open-ended Lines Uncontrolled 0.077 (0.035) 0.95 (0

Closed-purge sampling (100) -- --

Source: Reference 37.

a Factors for foundry coke are drawn from Reference 43.b Factors are expressed in terms of lb (kg) of benzene emitted per source day.c Emission factors are presented for two different types of foundry coke by-product recovery plants, but are not representative of any par

"--" = Data not available.
4-58

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). With this technology, a positive (or negative) pressure 44

 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. Such systems are currently in use at some by-product recovery plants and 37

reportedly have operated without difficulty. Examples of gases that may be used as the gas

blanket include dirty or clean coke gas, nitrogen, or natural gas. The control efficiency is 37

estimated to be 98 percent. The control technique required by the benzene NESHAP for 37,44

the light oil sump is a tightly fitting, gasketed cover with an estimated 96-percent 

efficiency. The emission factors for benzene sources in the light oil plant shown in 44

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. These two 37

variables should be kept in mind when using the emission factors presented in Table 4-6. 
4-59

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. Emissions were measured at tar decanters at several locations in the United 37

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 lb 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. The actual benzene emission rate from the flushing liquor circulation tank and 296

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. No significant benzene 37

emissions have been identified from the recovery of ammonia, but benzene can be emitted 

from the intercepting sump. An emission factor of 0.019 lb/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. In steam heating, benzene could be driven off in the 39

vapors. The emission factor for tar dewatering in Table 4-6 was derived by averaging three

factors (0.082, 0.019, and 0.0258 lb benzene/ton coke [41, 9.5, and 12.9 g benzene/Mg 
4-60

coke]) based on source tests at tar dewatering tanks. Gas blanketing is the control 37

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. Two different 37

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 tarinterrupting 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 in 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. The control techniques required by the benzene NESHAP to control benzene 44

emissions from equipment leaks are presented in Table 4-9.

For the nonrecovery process, benzene emissions for coal charging are 

3.6 x 10 lb/ton of coal charged (1.8 x 10 g/Mg). Emissions from pushing and quenching -5 -2

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 lb/ton of coal charged (0.26 g/Mg). -4 296
4-61

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) a

Dual Mechanical Seals (100)

Valves Monthly Inspection (73) a

Sealed-Bellows Valves (100)

Exhausters Quarterly Inspections (55) a

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. a

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 in this chapter) as well as to facilities that use benzene 

as a feedstock to produce cyclic intermediates (discussed in Chapter 5.0).
4-62

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. The reader should keep in mind that the most appropriate recovery control device, 45

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
4-63

TABLE 4-10. CONTROL TECHNOLOGIES THAT FORM THE BASIS OF AIR

POLLUTION CONTROL STANDARDS

Type Achievable Control Level Comments

Control Levels Design Conditions to Meet

Flares  98% & Flame present at all times - & Destroys rather

monitor pilot than recovers

& Non-assisted Flares - organics

>200 Btu/scf heating value, & Smoking allowed

and 60 ft/sec (18 m/sec) for 5 min/2 hr

maximum exit velocity & Not used on

& Air and Steam Assisted corrosive streams

Flares - >300 Btu/scf

heating value, and maximum

exit velocity based on Btu

content formula

Industrial  98% & Vent stream directly into & Destroys rather

Boilers/Process flame than recovers

Heaters organics

Thermal  98%, or & 1600(F (871(C) Combustion & Destroys rather

Oxidation 20 ppm temperature than recovers

& 0.75 sec. residence organics

& For halogenated streams & May need vapor

2000(F (1093(C), 1.0 sec. holder on

and use a scrubber on outlet intermittent

& Proper mixing streams

Adsorption  95% & Adequate quantity and & Most efficient on

appropriate quality of carbon streams with low

& Gas stream receives relative humidity

appropriate conditioning (<50 percent).

(cooling, filtering) & Recovers

& Appropriate regeneration and organics

cooling of carbon beds before

breakthrough occurs

Source: Reference 45.
4-64

TABLE 4-11. OTHER CONTROL TECHNOLOGIES THAT CAN BE USED

TO MEET STANDARDS

Type Level That Affect Control Level Comments

Estimated

Control Critical Variables

Catalytic up to 98% & Dependent on & Destroys rather than

Oxidation compounds, temp. and recovers organics

catalyst bed size & Technical limitations

include particulate or

compounds that poison

catalysts

Absorption 50 to 95% & Solubility of gas stream & Appropriate absorbent

in the absorbent needed may not be

& Good contact between readily available

absorbent and gas & Disposal of spent

stream absorbent may require

special treatment

procedures, and

recovery of organic from

absorbent may be time

consuming

& Preferable on

concentrated streams

Condensation 50 to 95% & Proper design of the & Preferable on

heat exchanger concentrated streams

& Proper flow and & Recovers organics

temperature of coolant

Source: Reference 45.
4-65

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. Stream temperature, specific gravity (the degree of adsorbing liquid 46

saturation), and the organic concentration level must remain within a certain range to ensure

optimal control efficiency. Absorbers are generally not used on streams with VOC 46

concentrations below 300 ppmv. Control efficiencies vary from 50 to 95 percent. 45 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
4-66

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. Adsorbers are 46

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 CO and 2

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
4-67

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
4-68

TABLE 4-12. COMPARISON OF VOC CONTROL TECHNOLOGIES

Control

Technology

Applicable

Concentration

Range, ppm

Capacity Range,

cfm

Removal

Efficiency

Secondary

Wastes Advantages Limitations 

ThermalOxidation

100-2,000 1,000-500,000 95-99+% Combustion

products

Up to 94% energyrecovery is possible.

Halogenated compadditional control downstream. Not batch operations.

CatalyticOxidation

100-2,000 1,000-100,000 90-95% Combustion

products

Up to 70% energyrecovery is possible.

Thermal efficiency in operating condicompounds may rcontrol equipment compounds can poarsenic, phosphorparticulate matter)

Condensation >5,000 100-20,000 50-90% Condensate Product recovery can

offset annual operatingcosts.

Not recommended boiling point <100subject to scale bufouling.

CarbonAdsorption

20-5,000 100-60,000 90-98% Spent carbon;

collectedorganic

Product recovery canoffset annual operatingcosts. Can be used as aconcentrator inconjunction withanother type of controldevice. Works wellwith cyclic processes.

Not recommended relative humidity <aldehydes, and estthe carbon, decrea
4-69

TABLE 4-12. CONTINUED

Control

Technology

Applicable

Concentration

Range, ppm

Capacity Range,

cfm

Removal

Efficiency

Secondary

Wastes Advantages Limitation

Absorption 500-5,000 2,000-100,000 95-98% Wastewater;

Capturedparticulate

Product recovery canoffset annual operatingcosts.

Might require exDesign could be lack of equilibriusubject to pluggiparticulates are iformation from ainteraction can o

Biofiltration 0-1,000 <90,000 80-99% Disposal of

spent compostbeds.

Efficient for lowconcentration streams. Low operating costs.

Large amount of Microorganisms 50 to 100(F tem be killed if propand pH is not ma

Source: Reference 47.
4-70

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:

54

& Average emission factor approach;

& Screening ranges approach;

& EPA correlation approach; and

& Unit-specific correlation approach.
No. of

equipment

components

x

Weight %

benzene

in the stream

x

Component	

specific

emission factor

x No. hr/yr in

benzene service

4-71

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. This method is an improvement on using generic emissions 54

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:

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
4-72

TABLE 4-13. SOCMI AVERAGE TOTAL ORGANIC COMPOUND EMISSION

FACTORS FOR EQUIPMENT LEAK EMISSIONSa

Equipment Type Service lb/hr/source (kg/hr/source)

Emission Factorb

Valves Gas 0.01313 (0.00597)

Light liquid 0.00887 (0.00403)

Heavy liquid 0.00051 (0.00023)

Pump seals Light liquid 0.0438 (0.0199) c

Heavy liquid 0.01896 (0.00862)

Compressor seals Gas 0.502 (0.228)

Pressure relief valves Gas 0.229 (0.104)

Connectors All 0.00403 (0.00183)

Open-ended lines All 0.0037 (0.0017)

Sampling connections All 0.0330 (0.0150)

Source: Reference 54.

The emission factors presented in this table for gas valves, light liquid valves, light liquid pumps, and a

connectors are revised SOCMI average emission factors.

These factors are for total organic compound emission rates. b

The light liquid pump seal factor can be used to estimate the leak rate from agitator seals. c

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. 
4-73

TABLE 4-14. REFINERY AVERAGE EMISSION FACTORS

Equipment type Service (kg/hr/source)

Emission Factora

Valves Gas 0.0268

Light Liquid 0.0109

Heavy Liquid 0.00023

Pump seals Light Liquid 0.114 b

Heavy Liquid 0.021

Compressor seals Gas 0.636

Pressure relief valves Gas 0.16

Connectors All 0.00025

Open-ended lines All 0.0023

Sampling connections All 0.0150

Source: Reference 54.

 These factors are for non-methane organic compound emission rates. a

 The light liquid pump seal factor can be used to estimate the leak rate from agitator seals. b

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. This 56

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.
4-74

TABLE 4-15. MARKETING TERMINAL AVERAGE EMISSION FACTORS

Equipment Type Service (kg/hr/source)

Emission Factora

Valves Gas 1.3x10

Light Liquid 4.3x10

-5

-5

Pump seals Gas 6.5x10

Light Liquid 5.4x10

-5

-4

Others (compressors and Gas 1.2x10

others) Light Liquid 1.3x10 b

-4

-4

Fittings (connectors and Gas 4.2x10

flanges) Light Liquid 8.0x10 c

-5

-6

Source: Reference 54.

These factors are for total organic compound emission rates (including non-VOC such as methane and ethane). a

The "other" equipment type should be applied for any equipment type other than fittings, pumps, or valves. b

"Fittings" were not identified as flanges or non-flanged connectors; therefore, the fitting emissions were c

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. The 57

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, 1983 also apply to equipment leak emissions. These standards apply to VOC 58

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. These standards apply to the same sources 53

(equipment leak components) as indicated in Subpart J, and V of Part 61.
4-75

TABLE 4-16. OIL AND GAS PRODUCTION OPERATIONS AVERAGE 

EMISSION FACTORS (kg/hr/source)

Equipment Type Service (kg/hr/source) a

Emission Factor

b

Valves Gas 4.5x10

Heavy Oil 8.4x10

Light Oil 2.5x10

Water/Oil 9.8x10

-3

-6

-3

-5

Pump seals Gas 2.4x10

Heavy Oil NA

Light Oil 1.3x10

Water/Oil 2.4x10

-3

-2

-5

Others Gas 8.8x10 c

Heavy Oil 3.2x10

Light Oil 7.5x10

Water/Oil 1.4x10

-3

-5

-3

-2

Connectors Gas 2.0x10

Heavy Oil 7.5x10

Light Oil 2.1x10

Water/Oil 1.1x10

-4

-6

-4

-4

Flanges Gas 3.9x10

Heavy Oil 3.9x10

Light Oil 1.1x10

Water/Oil 2.9x10

-4

-7

-4

-6

Open-ended lines Gas 2.0x10

Heavy Oil 1.4x10

Light Oil 1.4x10

Water/Oil 2.5x10

-3

-4

-3

-4

Source: Reference 54.

Water/Oil emission factors apply to water streams in oil service with a water content greater than 50 percent, a

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.

These factors are for total organic compound emission rates (including non-VOC such as methane and ethane) b

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.

The "other" equipment type was derived from compressors, diaphrams, drains, dump arms, hatches, instruments, c

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.
4-76

TABLE 4-17. SOCMI SCREENING VALUE RANGE TOTAL ORGANIC COMPOUND EMISSION 

FOR EQUIPMENT LEAK EMISSIONSa

Equipment Type Service

10,000 ppmv Emission Factorb <10,000 ppmv 

lb/hr/source(kg/hr/source) lb/hr/source

Valves Gas

Light liquid

Heavy liquid

0.1720 (0.0782)0.1962 (0.0892)

0.00051 (0.00023)

0.000288 0.000363 

0.00051 

Pump sealsc Light liquid

Heavy liquid

0.535 (0.243)0.475 (0.216)

0.00411 0.00462 

Compressor seals Gas 3.538 (1.608) 0.1967 

Pressure relief valves Gas 3.720 (1.691) 0.0983 

Connectors All 0.249 (0.113) 0.0001782 

Open-ended lines All 0.02629 (0.01195) 0.00330 

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

a

ppmv emission factors.These factors are for total organic compound emission rates. bThe light liquid pump seal factors can be applied to estimate the leak rate from agitator seals. c
4-77

TABLE 4-18. REFINERY SCREENING RANGES EMISSION FACTORS

Equipment Type Service (kg/hr/source) (kg/hr/source)

10,000 ppmv <10,000 ppmv

Emission Factor Emission Factor a a

Valves Gas 0.2626 0.0006

Light Liquid 0.0852 0.0017

Heavy Liquid 0.00023 0.00023

Pump seals Light Liquid 0.437 0.0120 b

Heavy Liquid 0.3885 0.0135

Compressor seals Gas 1.608 0.0894

Pressure relief valves Gas 1.691 0.0447

Connectors All 0.0375 0.00006

Open-ended lines All 0.01195 0.00150

Source: Reference 54.

 These factors are for non-methane organic compound emission rates. a

 The light liquid pump seal factors can be applied to estimate the leak rate from agitator seals. b

The hazardous organic NESHAP (or HON) equipment leak provisions

promulgated on April 22, 1994, affect chemical production processes. The HON provisions 59,60

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

apply to new 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 
4-78

TABLE 4-19. MARKETING TERMINAL SCREENING RANGES

EMISSION FACTORS

Equipment Type Service (kg/hr/source) (kg/hr/source)

10,000 ppmv <10,000 ppmv

Emission Factor Emission Factor a a

Valves Gas NA 1.3x10

Light Liquid 2.3x10 1.5x10 -2

-5

-5

Pump seals Light Liquid 7.7x10 2.4x10 -2 -4

Others (compressors and Gas NA 1.2x10

others) Light Liquid 3.4x10 2.4x10 b -2

-4

-5

Fittings (connectors and Gas 3.4x10 5.9x10

flanges) Light Liquid 6.5x10 7.2x10 c

-2

-3

-6

-6

Source: Reference 54.

These factors are for total organic compound emission rates (including non-VOC such as methane and ethane). a

"NA" indicates that not enough data were available to develop the indicated emission factors.

The "other" equipment type should be applied for any equipment type other than fittings, pumps, or valves. b

"Fittings" were not identified as flanges or connectors; therefore, the fitting emissions were estimated by c

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 
4-79

TABLE 4-20. OIL AND GAS PRODUCTION OPERATIONS SCREENING RANGES

 EMISSION FACTORS

Equipment Type Service (kg/hr/source) (kg/hr/source) a

10,000 ppmv 10,000 ppmv

Emission Factor Emission Factor

b b

Valves Gas 9.8x10 2.5x10

Heavy Oil NA 8.4x10

Light Oil 8.7x10 1.9x10

Water/Oil 6.4x10 9.7x10

-2

-2

-2

-5

-6

-5

-6

Pump seals Gas 7.4x10 3.5x10

Heavy Oil NA NA

Light Oil 1.0x10 5.1x10

Water/Oil NA 2.4x10

-2

-1

-4

-4

-5

Others Gas 8.9x10 1.2x10 c

Heavy Oil NA 3.2x10

Light Oil 8.3x10 1.1x10

Water/Oil 6.9x10 5.9x10

-2

-2

-2

-4

-5

-4

-5

Connectors Gas 2.6x10 1.0x10

Heavy Oil NA 7.5x10

Light Oil 2.6x10 9.7x10

Water/Oil 2.8x10 1.0x10

-2

-2

-2

-5

-6

-6

-5

Flanges Gas 8.2x10 5.7x10

Heavy Oil NA 3.9x10

Light Oil 7.3x10 2.4x10

Water/Oil NA 2.9x10

-2

-2

-6

-7

-6

-6

Open-ended lines Gas 5.5x10 1.5x10

Heavy Oil 3.0x10 7.2x10

Light Oil 4.4x10 1.4x10

Water/Oil 3.0x10 3.5x10

-2

-2

-2

-2

-5

-6

-5

-6

Source: Reference 54.

Water/Oil emission factors apply to water streams in oil service with a water content greater than 50 percent, a

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.

These factors are for total organic compound emission rates (including non-VOC such as methane and ethane) b

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.

The "other" equipment type was derived from compressors, diaphrams, drains, dump arms, hatches, c

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.
4-80

TABLE 4-21. CONTROL TECHNIQUES AND EFFICIENCIES APPLICABLE TO

EQUIPMENT LEAK EMISSIONS

Equipment Component

(Emission Source) Control Technique Percent Reductiona

Pump Seals:

Packed and Mechanical Seal area enclosure vented 100

 to a combustion device

Monthly LDAR 69 b

Quarterly LDAR 45

Double Mechanical N/A -- c d

Compressors Vent degassing reservoir to 100

 combustion device

Flanges None available 0

Valves:

Gas Monthly LDAR 87

Quarterly LDAR 67

Liquid Monthly LDAR 84

Quarterly LDAR 61

Pressure Relief Devices

Gas Monthly LDAR 50

Quarterly LDAR 44

Rupture Disk 100

Sample Connections Closed-purge sampling 100

Open-Ended Lines Caps on open ends 100

Source: Reference 55.

If a negative reduction for a control technique was indicated, zero was used. a

LDAR = Leak detection and repair, at a leak definition of 10,000 ppmv. b

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.

N/A - Not applicable. There are no VOC emissions from this component. d
4-81

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;” and 63

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.
4-82

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. This section will discuss the second control strategy of reducing benzene 65

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
4-83

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
4-84

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); and 63

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

efficiency.

For treatment, the National Emission Standard for Benzene Waste Operations66

and the National Petroleum Refinery NESHAP do not require specific treatment equipment. 49

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.
4-85

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. The National Emission Standard for Benzene 59,63

Emissions from Benzene Transfer Operations also regulates benzene transfer emissions.67
5-1

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. These 68

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 in the United States is now n-butane based; therefore, the process for producing

maleic anhydride from benzene is not included in this section. 
5-2

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). About 50 percent of the U.S. 69

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. Additionally, some benzene is reformed in the production of styrene. Ethylbenzene 9

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. Total 71

ethylbenzene production capacity is currently 13,874 million pounds per year (lb/yr) (6,293

kg/yr). Approximately 95 percent of this capacity is based on benzene alkylation, with the 11

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. In this process, toluene and light alkanes other than ethane are reacted at 1,832 to 72

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. 
5-3

Table 5-1 lists U.S. producers of ethylbenzene and styrene. Most facilities 11,69,73

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 Ethylbenzene and Styrene Production Using Benzene

Alkylation and Ethylbenzene Dehydrogenation

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 5-1.14,74

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 polyethylbenzenes. 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
5-4

TABLE 5-1. U.S. PRODUCERS OF ETHYLBENZENE AND STYRENE

Company Location

Ethylbenzene 

Process

Capacity

million lb

(million kg) Process

Amoco Chemical Company Texas City, TX NA 908 (412) a Cb 

ARCO Chemical Company Channelview, TX

Monarca, PA

NA 2789 (1265) a

220 (100)

Db---

Chevron Chemical Company St. James, LA NA 1700 (771) a Cb Cos-Mar, Inc. Carville, LA Ac 2200 (998) a,d Cb Deltech Corporation Baton Rouge, LA NA 694 (315) a,e --- Dow Chemical U.S.A. Freeport, TX Ac 1750 (794) a Cb Huntsman Chemical Corporation Bayport, TX NA 1240 (562) a Cb Koch Refining Company Corpus Christi, TX 65% Ac

35% Bc

100 (45) a --- 

Phibro Energy USA, Inc. Houston, TX NA 25 (11) a --- Rexene Corporation Odessa, TX NA 350 (159) a Cb Sterling Chemicals, Inc. Texas City, TX NA 1750 (794) a Cb Westlake Styrene Corporation Lake Charles, LA

Sulphur, LA

NA 

---

368 (167) a

---

---

Cb
5-5

TABLE 5-1. CONTINUED

Source: References 11, 69, and 73.

Reference 11. a

Reference 73. b

Reference 69. c

Capacity does not include an excess capacity of 500 million pounds (227 million kg) of capacity on standby. d

Plant is on standby. e

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.Note: This list is subject to change as market conditions change, facility ownership changes, plants are closed, etc. The reader should ver

of particular facilities by consulting current lists and/or the plants themselves. The level of benzene emissions from any given facilivariables such as capacity, throughput, and control measures, and should be determined through direct contact with plant personnelproducers and locations were current as of January 1993.
5-6

Figure 5-1. Basic Operations that may be used in the Production of Ethylbenzene by

Benzene Alkylation with Ethylbenzene

Source: References 14 and 74.
5-7

figure) to recover aromatics and to remove hydrogen chloride (HCl) 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. Emission points in the purification section include vents from the benzene 69

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. Other 69

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 5-2.69,74

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) in the dehydrogenation reactor, which

contains one of several catalysts. The reaction product (Stream 3) then exits through the heat

exchanger and is further cooled in a condenser, where water and crude styrene vapors are

condensed. 
5-8

Figure 5-2. Basic Operations that may be used in the Production of Styrene by

Ethylbenzene Dehydrogenation

Source: References 14 and 74.
5-9

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 in Figure 5-2.

5.1.2 Process Description for Ethylbenzene Production from Mixed Xylenes

Ethylbenzene can also be extracted from mixed xylene streams. 

Proportionately, however, very little ethylbenzene is produced in 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 in

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). 
5-10

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

in Figure 5-2) cannot be reused directly. 

5.1.3 Process Description for Styrene Production from Ethylbenzene

Hydroperoxidation

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 -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

-methyl-benzyl alcohol recovery section. Distillation removes any remaining ethylbenzene. 

Organic waste streams are separated from the -methyl-benzyl alcohol and acetophenone

organic waste liquids are used as fuel. 
5-11

Figure 5-3. Ethylbenzene Hydroperoxidation Process Block Diagram

Source: Reference 74.
5-12

The mixed stream of -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

-methyl-benzyl alcohol. Catalyst waste is separated from the -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
5-13

Figure 5-4. Isothermal Processing of Styrene

Source: Reference 75.
5-14

The gas phase from the condensation step in the separator consists mainly of

hydrogen, with small quantities of CO , CO, and methane. After these gases are compressed, 2

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 Ethylbenzene and Styrene Production via Alkylation

and Dehydrogenation

Emission Estimates from Ethylbenzene Production and Dehydrogenation to

Styrene

Emission factors have been developed based on an uncontrolled 300-millionkg/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. The first four process vent streams in Table 5-2 are low- 69,74

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. 
5-15

TABLE 5-2. EMISSION FACTORS FOR ETHYLBENZENE/STYRENE PRODUCTION V

ALKYLATION AND DEHYDROGENATION

SCC and Description Emission Source Control Device

Emission Factor in 

lb/ton (kg/Mg)a F

3-01-169-02

Ethylbenzene Manufacturing -Alkylation Reactor Vent

Alkylation Reactor Vent Process Heater 0.0006 (0.0003) 

Uncontrolled 0.6 (0.3) b 

3-01-169-03

Ethylbenzene Manufacturing -Benzene Drying Column

Atmospheric/PressureColumn Ventsd

Flare 0.024 - 0.96 b d

(0.012 - 0.48)

Uncontrolled 2.4 (1.2) b 

3-01-169-04

Ethylbenzene Manufacturing -Benzene Recovery Column

3-01-169-05

Ethylbenzene Manufacturing -Ethylbenzene Recovery Column

3-01-169-06

Ethylbenzene Manufacturing -Polyethylbenzene RecoveryColumn

Other Vacuum Ventse Flare 0.0010 - 0.004 b d

(0.005 - 0.002) 

Uncontrolled 0.10 (0.05) b 

3-01-206-02

Styrene Manufacturing - BenzeneRecycle Column

3-01-206-03

Styrene Manufacturing - StyrenePurification Vents

3-01-206-XX

Styrene Manufacturing -Benzene- Toluene Vacuum Vent

Benzene-Toluene VacuumVent

Flare 0.06 - 2.4 b d

(0.03 - 1.2) 

Uncontrolled 6.0 (3.0) b 
5-16

TABLE 5-2. CONTINUED

SCC and Description Emission Source Control Device

Emission Factor in 

lb/ton (kg/Mg)a F

3-01-206-XX

Styrene Manufacturing -Hydrogen Separation Vent

Hydrogen Separation Vent Flare 0.00006 - 0.0024 b d

(0.00003 -0.0012) 

Uncontrolled 0.006 (0.003) d 

3-01-169-80/3-01-206-80 Equipment Leaks Detection and Correction See Section 4.5.2

Ethylbenzene/StyreneManufacturing - EquipmentLeaks

Uncontrolled

4-07-196-XX/4-07-196-13

Ethylbenzene/StyreneManufacturing - Storage and Handling

Storage and Handling Floating Roof, Vented to

Flare, Refrigerated VentCondenser, andUncontrolled

See Section 4.5.3

Emission factors are for a model plant with capacity 661 million lbs (300 million kg) per year. Actual emission factors may vary with thro

a

control measures and should be determined through direct contacts with plant personnel. Factors are expressed as lb (kg) benzene emitted ethylbenzene/styrene produced.69Reference 74. bIncludes the following vents: benzene drying column, benzene recovery column, and ethylbenzene recovery column. cReference 69. dIncludes the following vents: polyethylbenzene recovery column at ethylbenzene plants; and benzene recycle column and styrene purificat

e

styrene plants.
5-17

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 train

(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 4.2x10 lb hydrocarbons/lb styrene (4.2x10 kg -3 -3

hydrocarbons/kg styrene) in one plant where the hydrocarbons are benzene and toluene. 

Another condenser controlled vent emits 0.4x10 lb benzene/lb styrene (0.4x10 kg -3 -3

benzene/kg styrene). 9

Following dehydrogenation, a hydrogen-rich gas (Stream 4 in Figure 5-2)

containing methane, ethane, ethylene, CO , CO, and aromatics is normally cooled and compressed 2

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 lb ethylbenzene/lb styrene (32 g

ethylbenzene/kg styrene). This corresponds to 9.6x10 lb benzene/lb styrene (9.6x10 g 9 -6 -3

benzene/kg styrene). Benzene in 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). 
5-18

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 lb styrene/yr (544 million kg

styrene/yr). 

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 CO . The vent gas is scrubbed with oil and 2

water for a 99 percent removal efficiency for organics. The resulting vent stream contains

approximately 35 ppm benzene (0.11 mg benzene/l) or 15.9 lb 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-1 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 (1.0x10 l/hr) 6

containing about 60 lbs benzene/hr (27 kg benzene/hr).74
5-19

The dehydrogenation vent (D in Figure 5-3) may be an emergency pressure vent

similar to the separation vent (C in Figure 5-2). No specific information is available on

storage, transport, or fugitive emissions for this process. 

5.1.6 Control Technology for Ethylbenzene/Styrene Processes

Control methods for the two ethylbenzene/styrene processes in use in the United

States include condensation, adsorption, flaring, and combustion in 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 in this report but not in

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 the 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 in benzene at 104 to

122 (F (40 to 50(C). Higher efficiencies become prohibitively expensive. 74

Condensers have limited use in 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 the 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. 
5-20

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 in manifolding. High-nitrogen or other low- or noncombustible 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. Table 5-3 lists the location and current capacity for U.S. cyclohexane 10

producers. Two basic methods are used to produce cyclohexane: hydrogenation of benzene 11

and petroleum liquid separation. Most of the cyclohexane produced domestically is produced

through hydrogenation of benzene. The following discussions of these two processes are taken

from Reference 76. 
5-21

TABLE 5-3. U.S. PRODUCERS OF CYCLOHEXANE

Company Location millions of gal (l)

Annual Capacity

Chevron Chemical Company Port Arthur, TX 38 (144)

Phillips Petroleum Company

Specialty Chemicals Branch Borger, TX 35 (132)

Olefins and Cyclics Branch Sweeny, TX 90 (341)

Phillips Puerto Rico Core, Inc. Guayama, PR 100 (379)

Texaco Chemical Company Port Arthur, TX 75 (284)

CITGO Petroleum Corporation Corpus Christi, TX 30 (114)

TOTAL 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 Cyclohexane Production via Benzene Hydrogenation

Figure 5-5 shows a model flow diagram for the manufacture of cyclohexane by

benzene hydrogenation. High-purity benzene (Stream 1) is fed to the catalytic reactors in 76

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. 
5-22

Figure 5-5. Process Flow Diagram for Cyclohexane Production Using the Benzene

Hydrogenation Process

Source: Reference 76.
5-23

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 fuelgas 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 lb/gal (500 mg/l). 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. During shutdowns, 76

individual equipment vents are opened as required during final depressurization of equipment. 

Except for the feed streams, the concentration of benzene in 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 in Figure 5-5) may also

contribute to benzene emissions. 
5-24

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 Cyclohexane Production via Separation of Petroleum

Fractions

Cyclohexane may also be produced by separation of select petroleum fractions. 

The process used to recover cyclohexane in this manner is shown in Figure 5-6. A petroleum 76

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 in 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). 
5-25

Figure 5-6. Process Flow Diagram for Cyclohexane from Petroleum Fractions

Source: Reference 76.
5-26

5.2.4 Benzene Emissions from Cyclohexane Production via Separation of Petroleum

Fractions

There are no process emissions during normal operation. During emergency 76

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. No specific emission 77

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. No emission factors were found for benzene as 76

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 in this section. The location and capacities of U.S.

producers of cumene are provided in Table 5-4.11,78
5-27

TABLE 5-4. U.S. PRODUCERS OF CUMENE

Plant Location (million kg) Notes

Annual

Capacity

million lb

Ashland Chemical Company Catlettsburg, KY 550 (249) Cumene is sold

BTL Specialty Resins Corporation Blue Island, IL 120 (54) Captive for phenol and

acetone

Chevron Chemical Company Philadelphia, PA 450 (204) Cumene is sold

Port Arthur, TX 450 (204) Cumene is sold

Citgo Petroleum Corp. Corpus Christi, TX 825 (374) --

(Champlin)

Coastal Refining Westville, NJ 150 (68) Cumene is sold

Georgia Gulf Corporation Pasadena, TX 1,420 (644) Some cumene transferred to

company's phenol/acetone

plant

Koch Refining Company Corpus Christi, TX 750 (340) Cumene is sold

Shell Chemical Company Deer Park, TX 900 (408) Captive for phenol/acetone

Texaco Chemical Company El Dorado, KS 135 (61) 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

Propylene

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:
C6H6

(benzene)



CH2CHCH3

(propylene)

[catalyst]



(CH3)2CHC6H5

(cumene)

5-28

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. Solid phosphoric acid is the most favored 80

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 in the reactor stream to

activate the catalyst.79

Propylene and benzene (Streams 1 and 2) are combined in 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 
5-29

Figure 5-7. Process for the Manufacture of Cumene Using Solid Phosphoric Acid

Catalyst

Source: Reference 80.
5-30

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 to 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 
5-31

Figure 5-8. Process for the Manufacture of Cumene Using Aluminum Chloride

Catalyst

Source: Reference 80.
5-32

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 HCl gas

(Stream 6) to activate the catalyst. The catalyst preparation operation generates a vent gas

consisting of inert gases and HCl gas saturated with vapors of benzene and diisopropylbenzene. 

A scrubber is typically used to absorb the HCl 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 in 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
5-33

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 with 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 the associated cumene receiver tank are

operated above atmospheric pressure and are blanketed with nitrogen (or methane) to protect

the cumene from reacting with oxygen in the air and forming cumene hydroperoxide. The vent

line associated with the cumene distillation column and with the 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 then 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 this

vent stream is air (or inert gas) saturated with cumene and DIPB vapors as 
5-34

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 alkylation 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. The methane is eventually vented to 80

the atmosphere, carrying 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 lb (0.03 kg) of total VOC

are emitted per ton (Mg) of cumene produced, and that benzene constituted a “trace amount” 
5-35

of the hydrocarbons in the stream. One cumene producer has indicated that it uses a closed 80

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). No specific emission factors were located for benzene emissions from these 80

sources. However, as presented in Table 5-5, one reference provided total VOC emission factors

and estimates of benzene percent composition of the emissions. The percent (weight) of 3,80

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 in which cumene hydroperoxide (CHP) is cleaved to yield acetone and phenol, as well

as recoverable by-products -methylstyrene (AMS) and acetophenone. Phenol is also

produced by toluene oxidation and distillation from petroleum operations. Table 5-6 shows 81,82

the locations, capabilities, and production methods of the phenol producers in the United

States. Because benzene may be present in the feedstock, it may be emitted during 11,81,83

production of phenol.
5-36

TABLE 5-5. SUMMARY OF EMISSION FACTORS FOR CUMENE PRODUCTION 

AT ONE FACILITY USING THE ALUMINUM CHLORIDE CATALYST

SCC and Description Emission Source Control Device

Emission Factor in

lb/ton (kg/Mg)a,b 

3-01-156-02

Cumene Manufacturing -Benzene Drying Column

Process Vent Uncontrolled

Flare

4.00 x 10-2

(2.00 x 10 ) -2

2.00 x 10-3

(1.00 x 10 ) -3

3-01-156-03

Cumene Manufacturing -Catalyst Mix Tank ScrubberVent

Process Vent Uncontrolled

Flare

3.18 x 10 -1

(1.59 x 10 ) -1

1.59 x 10 -2

(7.95 x 10 ) -3

3-01-156-04

Cumene Manufacturing -Wash-Decant System Vent

Process Vent Uncontrolled

Flare

1.57 x 10 -2

(7.85 x 10 ) -3

7.84 x 10 -4

(3.92 x 10 ) -4

3-01-156-05

Cumene Manufacturing - Benzene Recovery Column

Process Vent Uncontrolled

Flare

3.40 x 10 -2

(1.70 x 10 ) -2

1.70 x 10 -3

(8.50 x 10 ) -4

Source: References 3 and 80.

 Factors are expressed as lb (kg) benzene emitted per ton (Mg) cumene produced. a

 Derived by multiplying the total VOC emission factor by percent of benzene in the stream. b
5-37

TABLE 5-6. U.S PRODUCERS OF PHENOL

Facility Location

Annual Capacity

million lb

(million kg) Process a

Allied-Signal, Inc. Engineering Materials Sector

Philadelphia, PA 810 (367) Cumene per

Aristech Chemical Corporation Haverhill, OH 630 (286) Cumene perBTL Specialty Resins Corporation Blue Island, IL 90 (41) Cumene perDakota Gasification Company Beulah, ND 50 (23) Petroleum aDow Chemical U.S.A. Oyster Creek, TX 550 (249) Cumene perGeneral Electric Company GE Plastics

Mount Vernon, IN 640 (290) Cumene per

Georgia Gulf Corporation Pasadena, TX

Plaquemine, LA

160 (73)

440 (200)

Cumene perCumene per

Kalama Chemical, Inc. Kalama, WA 70 (32) Toluene oxid

Merichem Company Houston, TX 35 (16) Petroleum a

PMC, Inc. Santa Fe Springs, CA 8 (3.6) Petroleum a

Shell Chemical Company Shell Chemical Company, Division

Deer Park, TX 600 (272) Cumene per

Stimson Lumber Company Northwest Petrochemical Corporation, Division

Anacortes, WA <5 (<2.3) Petroleum

(c
5-38

TABLE 5-6. CONTINUED

Facility Location

Annual Capacity

million lb

(million kg) Process an

Texaco, Inc. Texaco Chemical Company, Subsidiary

El Dorado, KS 95 (43) Cumene pero

TOTAL <3,398 (<1,541)

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 verif

particular facilities by consulting current lists and/or the plants themselves. The level of benzene emissions from any given facility is such as capacity, throughput, and control measures, and should be determined through direct contacts with plant personnel. These dalocations were current as of November 1993.
C6H5CH(CH3)2

(cumene)

 O2

(air)

 C6H5COOH(CH3)2

(cumene hydroperoxide)

C6H5COOH(CH3)2

(cumene hydroperoxide)

[H2SO4]



(acid)

CH3COCH3

(acetone)

 C6H5OH

(phenol)

5-39

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

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 the 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 the

Allied process. Cumene (Stream 1), manufactured on site or shipped to the site, and recycle 79

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 with the spent air to a refrigerated vent system, where part of the 
5-40

Figure 5-9. Flow Diagram for Phenol Production from Cumene Using the Allied Process

Source: Reference 79.
5-41

cumene is recovered and recycled. Uncondensed vapors, including organic compounds, are 80

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 SO (Stream 11). The cleavage product (Stream 12) is 2

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 (Stream 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. The uncondensed vapors from the condensers, 80

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. 
5-42

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 (Vent J).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 in the bottoms (Stream 29). The phenol residue may be used as fuel 
5-43

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 in 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. Cumene from storage (Stream 1) and recycle cumene 79

(Streams 2 and 9) are combined (Stream 3) and then fed with air (Stream 4) to the multiplereactor 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 
5-44

Figure 5-10. Flow Diagram for Phenol Production Using the Hercules Process

Source: Reference 79.
5-45

Figure 5-10. (Continued)
5-46

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 the 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). Uncondensed vapors from the 80

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) 
5-47

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 air” from the oxidizer reactor (Vent A, Figure 5-9) is the largest source

of benzene emissions at phenol production plants utilizing the Allied process. Table 5-7 87

provides uncontrolled and controlled (i.e., thermal oxidizer) emission factors from the oxidizer 
5-48

TABLE 5-7. SUMMARY OF EMISSION FACTORS FOR PHENOL PRODUCTION

BY THE PEROXIDATION OF CUMENE

SCC and Description Emission Source Control Device

Emission Factor in

lb/ton (kg/Mg)a Factor Rating 

3-01-202-02

Phenol Manufacturing -Cumene Oxidation

Process Vent Uncontrolledb 4.00 x 10 -3

(2.00 x 10 ) -3

U 

3-01-202-02

Phenol Manufacturing -Cumene Oxidation

Process Vent Thermal Oxidizer 1.16 x 10 -4

(5.82 x 10 ) -5

D 

 Factors are expressed in lb (kg) benzene emitted for ton (Mg) cumene produced. a

 Measured at post oxidizer condenser vent. b
5-49

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. In these processes, benzene is directly nitrated with a 12

mixture of nitric acid, sulfuric acid, and water.

As of February 1991, five companies were producing nitrobenzene in the United

States. Their names and plant locations are shown in Table 5-8. In addition to these plants, 91 11

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 
5-50

TABLE 5-8. PRODUCERS OF NITROBENZENE

Company Location (million kg/yr)

Capacity in

million lb/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 (Polymers Geisman, LA 250 (110)

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 stirredtank reactors. A flow diagram of the basic continuous process is shown in Figure 5-11. 94 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.
5-51

Figure 5-11. Process Flow Diagram for Manufacture of Nitrobenzene
5-52

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). 
5-53

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 
5-54

TABLE 5-9. SUMMARY OF EMISSION FACTORS FOR HYPOTHETICAL NITROBENZE

PRODUCTION PLANTS

SCC and Description Emissions Sourcea Control Device

Emission Fac

in lb/ton (g/k

3-01-195-01

Nitrobenzene - General

Small Benzene Storagec

(Point G)

Uncontrolled 0.156 (0.078

0.154 (0.077

3-01-195-01

Nitrobenzene - General

Benzene Storagec

(Point G)

Uncontrolled 0.566 (0.283

0.562 (0.281

Internal Floating

Roof

0.085 (0.0425

3-01-195-01

Nitrobenzene - General

Secondary

(Point J)

Uncontrolled 0.20 (0.10)d

3-01-195-01

Nitrobenzene - General

Total Uncontrolled 4.9 (2.45)d 

4.4 (2.19)e 

Vent Adsorber 0.78 (0.39)

0.64 (0.32)

Thermal Oxidizer 0.44 (0.22)

0.52 (0.26)

3-01-195-03

Nitrobenzene - Acid Stripper Vent

Waste-Acid Stripper

(Point B)

Uncontrolled 0.034 (0.170

3-01-195-04

Nitrobenzene -Washer/Neutralizer Vent

Wash and Neutralization

(Point C)

Uncontrolled 0.0162 (0.008

Vent Adsorber 0.155 (0.0776
5-55

TABLE 5-9. CONTINUED

SCC and Description Emissions Sourcea Control Device

Emission Fact

in lb/ton (g/kg

3-01-195-05

Nitrobenzene - Nitrobenzene Stripper Vent

Nitrobenzene Stripper

(Point D)

Uncontrolled 0.34 (0.170)d

Thermal Oxidizer 0.0288 (0.0144

3-01-195-06

Nitrobenzene - Waste AcidStorage

Waste Acid Storage

(Point G)

Uncontrolled 0.102 (0.051)

0.96 (0.048)d

3-01-195-80

Nitrobenzene - EquipmentLeak Emissions

Process Pumps and Valvesf Uncontrolled 1.26 (0.63)d 

0.76 (0.38)e 

LD&R plus

mechanical seals

0.33 (0.165)

0.198 (0.099

Source: Reference 93.

Emission points refer to Figure 5-11. a

Factors are expressed as lb (g) benzene emitted per ton (kg) nitrobenzene produced. bStorage emission factors are based on these tank parameters: c

For 198 million lb/yr (90,000 Mg/yr) Model Plant

Tank Size ft (m ) 3 3 Turnovers/Year Bulk Liquid Temperature (F ((C)

Benzene (large tank) 100,292 (2,840) 24 68 (20)

Benzene (small tank) 10,029 (284) 236 68 (20)

For 331 million lb/yr (150,000 Mg/yr) Model Plant

Tank Size ft (m ) 3 3 Turnovers/Year Bulk Liquid Temperature (F ((C)

Benzene (large tank) 160,035 (4,730) 24 68 (20)

Benzene (small tank) 16,704 (473) 236 68 (20)
5-56

TABLE 5-9. CONTINUED

Emission factor for a hypothetical 198 million lb/yr (90,000 Mg/yr) capacity plant. dEmission factor for a hypothetical 331 million lb/yr (150,000 Mg/yr) capacity plant. eProcess pumps and valves are potential sources of fugitive emissions. Each model plant is estimated to have 42 pumps (including 17 spa

f

and 20 pressure-relief valves based on data from an existing facility. All pumps have mechanical seals. Twenty-five percent of these pumused in benzene service. The fugitive emissions included in this table are based on the factors given in Section 4.5.2.
5-57

plants differ in capacity; one produces 198 million lb/yr (90,000 Mg/yr) and the other

331 million lb/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 lb/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. 
5-58

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. Because of its presence as an impurity in nitrobenzene, benzene may be 91

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. The 11

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 in 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. As shown in the 96

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, 
5-59

TABLE 5-10. U.S. PRODUCERS OF ANILINE

Facility Location

Annual Capacity in

million gal/yr 

(million kg/yr) Proce

Aristech Chemical Corporation Haverhill, OH 200 (90) Ammonolysis 

process)

E.I. duPont de Nemours andCompany, Inc.

duPont Chemicals Beaumont, TX 260 (120) Hydrogen red

First Chemical Corporation Pascagoula, MS 275 (130) Hydrogen red

ICI American Holdings, Inc. andUniroyal, Inc. Affiliate

Rubicon, Inc. Geismar, LA 400 (180) Hydrogen red

Miles, Inc.

Polymers Polyurethane Division New Martinsville, WV 40 (20) Nitrobenzene 

process)

BASF Corporation 

Polymers Division Urethanes

Geismar, LA 190 (90)

TOTAL 1,365 (630)

Source: Reference 11.Note: This list is subject to change as market conditions change, facility ownership changes, plants are closed, etc. The reader should ver

of particular facilities by consulting current lists and/or the plants themselves. The level of benzene emissions from any given facilof variables such as capacity, throughput, and control measures, and should be determined through direct contacts with plant persoon producers and locations were current as of January 1, 1993.
5-60

Figure 5-12. Flow Diagram for Manufacture of Aniline

Source: Reference 96. 
5-61

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 noncondensibles 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 lb

benzene/ton aniline produced (0.0057 kg/Mg) was reported in the literature. The SCC code 96

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. No data were found to indicate 96

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. 
5-62

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 in the presence of ferric chloride catalyst to produce MCB and DCB. 

HCl 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 the continuous production of MCB are

shown in Figure 5-13. The process begins with a series of small, externally cooled cast iron 19

or steel vessels containing the catalyst (which may consist of Rashing 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 HCl, unreacted chlorine, inert gases from the

chlorine feed, benzene, and other VOC) is sent to an organic absorber, where benzene and 
5-63

TABLE 5-11. U.S. PRODUCERS OF MONO-, DI-, AND TRICHLOROBENZENE

Company Location Product

An

(

Monsanto CompanyChemical Group

Sauget, IL Monochlorobenzene

o-Dichlorobenzenep-Dichlorobenzene

PPG Industries, Inc.Chemical Group

Natrium, WV Monochlorobenzene

o-Dichlorobenzenep-Dichlorobenzene

Standar ChlorineChemical Company, Inc.

Delaware City, DE Monochlorobenzene

o-Dichlorobenzenep-Dichlorobenzene1,2,3-Trichlorobenzene1,2,4-Trichlorobenzene

Southland CorporationChemical Division

Great Meadows, NJ 1,3,5-Trichlorobenzene 

Source: Reference 11.NA = Not availableNote: This is a list of major facilities producing mono-, di-, and trichlorobenzene. The list is subject to change as market conditions ch

changes, or plants are closed down. The reader should verify the existence of particular facilities by consulting current lists or thlevel of emissions from any given facility is a function of variables such as throughput and control measures, and should be detercontacts with plant personnel. The data on producers and locations were current as of January 1993.
5-64

Figure 5-13. Monochlorobenzene Continuous Production Process Diagram

Source: Reference 19.
5-65

other VOC are removed. The bottoms from the organic absorber (Stream 6) flow to the HCl

stripper for recovery of HCl. The overhead gas (Stream 5) is sent to HCl absorption. 

By-product HCl is then removed in the HCl 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 HCl, 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 HCl 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
5-66

Figure 5-14. Dichlorobenzene and Trichlorobenzene Continuous Production Diagram

Source: Reference 19.
5-67

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

Other processes that are most often used in the production of MCB are the batch

and Rashing methods. Other TCB production processes are the reaction of , , or 98

-benzene hexachloride with alcoholic potash, the dehalogenation of -benzene hexachloride with

pyridine, and the reaction of -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. Other potential sources of benzene emissions are atmospheric distillation vents 19

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. The point source factors are based on emissions reported to 19

EPA in response to information requests and trip reports. For information on emission factors 19

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
5-68

TABLE 5-12. EMISSION FACTORS FOR CHLOROBENZENE PRODUCTION BY DIREC

CHLORINATION OF BENZENE

SCC and Description Emissions Source Contol Device

Emission Factor in lb/ton

(kg/Mg)a,b 

3-01-301-01

ChlorobenzeneManufacturing - Tail-gas Scrubber

Tail-gas ScrubberTreatment

Carbon Adsorption 0.0134 (0.0067) Uncontrolled 1.04 (0.52) 

3-01-301-02

ChlorobenzeneManufacturing -Benzene Dry Distillation

Atmospheric DistillationVentsc

Carbon Adsorption 0.0084 (0.0042) Uncontrolled 0.64 (0.32) 

3-01-301-04

ChlorobenzeneManufacturing -Heavy Ends Processing

3-01-301-05

ChlorobenzeneManufacturing -MonochlorobenzeneDistillation

3-01-301-03

ChlorobenzeneManufacturing -Benzene Recovery

Atmospheric DistillationVent - Benzene Recovery

Carbon Adsorption 0.00104 (0.00052) Uncontrolled 0.08 (0.04) 

3-01-3-1080

ChlorobenzeneManufacturing -Equipment Leaks

Equipment Leaks Detection and Repair of

Major Leaks

See Section 4.5.2

Uncontrolled See Section 4.5.2
5-69

TABLE 5-12. CONTINUED

SCC and Description Emissions Source Contol Device

Emission Factor in lb/ton

(kg/Mg)a,b 

4-07-196-01

Organic ChemicalStorage - BenzeneStorage

Benzene Storage Vessel Internal Floating Roof See Section 4.5.3

Uncontrolled See Section 4.5.3

Source: Reference 19.

Emission factors are expressed as lb (kg) benzene emitted per ton (Mg) chlorobenzene product produced. a

These emission factors are based on a hypothetical plant producing 74,956 tons (68 Gg) monochlorobenzene, 13,669 tons (12.4 Gg) o-dichlo

b

17,196 tons (15.6 Gg) p-dichlorobenzene. The reader is urged to contact a specific plant as to process, products made, and control techniquethese emission factors.Includes the following vents: benzene dry distillation, heavy ends processing, and monochlorobenzene distillation. c
5-70

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 alkylate) 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 heavyduty liquid products. 99

Alkyl benzene sulfonates with highly branched C side chains possess excellent 12

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. Dodecylbenzene and tridecylbenzene are the two most 100

common LABs. The locations of the LAB producers in the United States are shown in

Table 5-13.11,101

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 C to C linear paraffins are 10 14
5-71

TABLE 5-13. U.S. PRODUCERS OF LINEAR ALKYLBENZENE (DETERGENT ALKYLAT

Company Location

Annual Capacity

million lb/yr

(million kg/yr) 

Linear Alkylbenzene 

(Dodecyclbenzene and tridecyclbenzene)

Monsanto Company ChemicalGroup

Alvin, TX 330 (150) Internal o

merchant

Vista Chemical Company Baltimore, MD 300 (140) Monochlo

merchant 

Lake Charles, LA 210 (95) Internal o

merchant 

Linear Alkylbenzene 

(except dodecyl and tridecyl)

Phillips 66 Company NA NA ---

TOTAL 840 (385)

Source: References 11 and 101.NA = Not availableNote: This is a list of major facility that produce linear alkylbenzene. This list is subject to change as market conditions change, facility ow

changes, or plants are closed down. The reader should verify the existence of particular facilities by consulting current listings or thlevel of emissions from any given facility is a function of variables, such as throughput and control measures, and should be determicontacts with plant personnel. These data for producers and locations were current as of January 1993.
5-72

dehydrogenated to n-olefins, which are reacted with benzene under the influence of a solid,

heterogenous catalyst (such as hydrogen fluoride [HFl]) 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.) The paraffins are heated to the point of vaporization 103

(Stream 2) and passed through a catalyst bed in the Pacol reactor (Stream 3), where the feed is

dehydrogenated to form the corresponding linear olefins by the following reaction: 

R - CH - CH - R ---> R CH = CH - R + H 1 2 2 2 1 2 2

The resulting olefins contain from 10 to 30 percent -olefins, 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 olefin-paraffin mixture

(Stream 10) is then alkylated with benzene (Stream 11) in the fixed-bed reactor to be blended

with a HFl catalyst. The blend is held at reaction conditions long enough for the alkylation

reaction to go to completion as follows: 

R CH = CHR + C H ---> R CH - CHR 1 2 6 6 1 2 2

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 HFl is also

separated and recycled to the alkylation vessel to be mixed with fresh HFl.
5-73

Figure 5-15. Linear Alkybenzene Production Using the Olefin Pr

Source: Reference 103.
5-74

Following benzene stripping, a lime water solution is then fed into the HFl

scrubber column (Stream 14) to neutralize the HFl. 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 alkylate 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 HFl

scrubber column controlling emissions from the benzene stripping column (Vent B). Some

benzene can be emitted through the HFl 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. The n-paraffins 100
5-75

TABLE 5-14. SUMMARY OF EMISSION FACTORS FOR HYPOTHETICAL LINEAR ALKYLBENZ

USING THE OLEFIN PROCESS

SCC and Description Emissions Source Control Device

Emission Facto

lb/ton (g/Mg)a,b

3-01-211-02

Linear Alkylbenzene -Benzene Drying

Benzene Azeotropic

Column Vent

(Point A)c

Uncontrolled 7.4 x 10 (3.7) -3 

Used as fuel 1.5 x 10 (7.4 x 1

-6 

3-01-211-03

Linear Alkylbenzene HFlScrubber Vent

Hydrogen Fluoride

Scrubber Column Vent

(Point B)c

Uncontrolled 0.022 (11) 

Used as fuel 4.4 x 10 (2.2 x 1

-6 

Flare 2.2 x 10 (1.1) -3 

Source: Reference 102.

Emission factor estimates based on a 198 million lb/yr (90,000 Mg/yr) hypothetical plant. a

Emission factors refer to lb (g) benzene emitted per ton (Mg) LAB produced by the olefin process. bLetters refer to vents designated in Figure 5-15. c

Note: Any given LAB olefin producing plant may vary in configuration and level of control from this hypothetical facility. The reader is e

plant personnel to confirm the existence of emitting operations and control technology at a particular facility prior to estimating emi
5-76

Figure 5-16. Production of Linear Alkybenzenes via Chlorina

Source: Reference 100.
5-77

are converted at 212(F (100(C) to a mixture of about 35 percent chlorinated paraffins, and the

remainder to paraffins and HCl as shown in the following reaction: 

R - CH - R + Cl ---> R - CH - R + HCl + heat 1 2 2 2

|

Cl

Following this reaction, dehydrochlorination (elimination of HCl) 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). HCl is also removed from

the mixture (Stream 5), leaving a mixture of only olefins and paraffins for the alkylation

reaction. 100

This olefin-paraffin 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 - R + C H ---> R - CH - R + HCl + heat, possible olefins, 1 2 6 6 1 2

 | short-chained paraffins, etc.

 Cl

At this point, HCl gas and some fugitive volatile organics given off during the

reaction are treated with adsorbers and excess HCl is routed to storage (Vent B). Next, the

LAB (Stream 9) is routed to a separator where hydrolysis is performed in the presence of HFl

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). 
5-78

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 in Table 5-14. 

The four major points of benzene emissions are listed below. Emission factors for these points

also are presented in 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 HCl 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 in 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, in 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.
5-79

TABLE 5-15. SUMMARY OF EMISSION FACTORS FOR HYPOTHETICAL LINEAR ALKYLBENZ

USING THE CHLORINATION PROCESS 

SCC and Description Emissions Source Control Device

Emission Factor in

lb/ton (g/Mg)a 

3-01-211-02

Linear Alkylbenzene-BenzeneDrying

Benzene Azeotropic

Column Vent

(Point A)c

Uncontrolled 7.4 x 10 (3.7) -3 

Used as fuel 1.5 x 10 (7.4 x 10 

-6 -

3-01-211-23

Linear Alkylbenzene - HClAdsorber Vent

Hydrochloric Acid

Adsorber Vent

(Point B)c

Uncontrolled 0.5 (250) 

Used as fuel 1 x 10 (0.05) -4 

3-01-211-24

Linear Alkylbenzene -Atmospheric Wash/DecanterVent

Atmospheric

Wash/Decanter Vent

(Point C)c

Uncontrolled 0.0246 (12.3) 

Used as a fuel 5 x 10 (2.5 x 10 

-6 -3 

3-01-211-25

Linear Alkylbenzene -Benzene Strip Column

Benzene Stripping Column

Vent

(Point D)c

Uncontrolled 7.4 x 10 (3.7) -3 

Used as a fuel 1.48 x 10 (7.4 x 10 

-6 

Source: Reference 102.

Emission factor estimates based on a 198 million lb/yr (90,000 Mg/yr) hypothetical plant. a

Emission factors refer to lb (g) benzene emitted per ton (Mg) LAB produced by the chlorination process. bLetters refer to vents designated in Figure 5-16. c

Note: Any given LAB olefin producing plant may vary in configuration and level of control from this hypothetical facility. The reader is e

plant personnel to confirm the existence of emitting operations and control technology at a particular facility prior to estimating em
5-80

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. A brief summary 68

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 lb/yr

(5 million kg/yr) and by the Eastman Chemical Company, Tennessee Eastman Division, in

Kingsport, Tennessee, 26 million lb/yr (12 million kg/yr). 11,101

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 in 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
5-81

5.9.2 Benzophenone

Benzophenone (diphenylketone) is used as an intermediate in organic synthesis,

and as an odor fixative. Derivatives are used as ultraviolet (UV) absorbers, such as in the UV

curing of inks and coatings. Benzophenone is also used as flavoring, soap fragrance, in 105

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. Benzophenone is also produced by Upjohn 11

Company, Fine Chemicals. Benzophenone is produced by acylation of benzene and benzyl 101

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. Benzene sulfonic acid is manufactured by sulfonation--reacting benzene with 105,106

fuming sulfuric acid. Burroughs Wellcome in Greenville, North Carolina; CL Industries, Inc., in 106

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. Resorcinol is produced by fusing benzene-m-disulfonic acid with sodium 11

hydroxide. Resorcinol is used in 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 in the manufacture of styphnic

acid and cosmetics.106
5-82

5.9.5 Biphenyl

Biphenyl (diphenyl or phenylbenzene) is produced by Chemol Co. in

Greensboro, North Carolina; Koch Refining Co. in Corpus Christi, Texas; Monsanto Co. in

Anniston, Alabama; Sybron Chemical Inc., in Wellford, South Carolina; and Chevron

Chemical Co. of Chevron Corp. One method for producing biphenyl is by 11,101

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. In 1991, 8,976 tons (8,143 Mg) of biphenyl were sold. 106 101

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
5-83

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) in 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. Facilities have been experimenting with 107

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. However, several facilities in these source 107,110

categories reported benzene emissions in the 1992 TRI. These facilities and their locations 111

are also included in Table 5-16.111

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. Companies currently producing these alcohols are presented in 109

Table 5-17. 11,111

Benzene is also used as a solvent to extract crude caprolactam. The three 112

major caprolactam facilities currently operating in the United States are listed in 
5-84

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. Moundville, AL

Arizona Chemical Co. Gulfport, MS

Chemfax Inc. Gulfport, MS

Exxon Chemical Americas Baton Baton Rouge, LA

 Rouge Resin Finishing

Formosa Plastics Corp. Point Comfort, TX

Lawter Intl. Inc. Moundville, AL

 Southern Resin Division

Neville Chemical Co. Pittsburgh, PA

Quantum Chemical Corp. La Porte La Porte, TX

Quantum Chemical Corp. Clinton, IA

 USI Division

Rexene Corp. Polypropylene Plant Odessa, TX

Union Carbide Chemicals & Plastics Texas City, TX

 Co. Texas City Plant

Pharmaceutical Manufacturing

Warner-Lambert Co.

 Parke Davis Division Holland, MI

Pesticides and Agricultural Chemicals

Rhone-Poulenc Ag Co. Institute, WV

Agribusiness Maketers, Inc. Baton Rouge, LA

Commercial Printing (Gravure)

Piedmont Converting, Inc. Lexington, NC

(continued)
5-85

TABLE 5-16. CONTINUED

Solvent Use Source Category Location

Paints and Allied Products

BASF Corporation Inks & Coating Greenville, OH

 Division

St. Louis Paint Manufacturing Co., St. Louis, MS

 Inc.

Synthetic Rubber

DuPont Pontchartrain Works La Place, LA

DuPont Beaumont Plant Beaumont, TX

Source: Reference 111.
5-86

TABLE 5-17. U.S. PRODUCERS OF ETHANOL OR ISOPROPANOL

Facility Location (million L)

Annual Capacity

million gal

Ethanol

Archer Daniels Midland Company Cedar Rapids, IA 700 (2,650)

 ADM Corn Processing Division Clinton, IA

Decatur, IL

Peoria, IL

Walhalla, ND 11 (42)

Biocom USA Ltd. Jennings, LA 40 (151)

Cargill, Incorporated Eddyville, IA 30 (113)

 Domestic Corn Milling Division

Chief Ethanol Fuels Inc. Hastings, NB 14 (53)

Eastman Chemical Company Longview, TX 25 (95)

 Texas Eastman Division

Georgia-Pacific Corporation Bellingham, WA 12 (45)

 Chemical Division

Giant Refining Co. Portales, NM 10 (38)

Grain Processing Corporation Muscatine, IA 60 (227)

High Plains Corp. Colwich, KS 15 (57)

Hubinger-Roquette Americas, Inc. Keokuk, IA 11 (42)

Midwest Grain Products, Inc. Atchison, KS 22 (83)

Pekin, IL 19 (72)

Minnesota Corn Processors Columbus, NB NA

Marshall, MN 28 (106)

New Energy Company of Indiana South Bend, IN 70 (265)

Pekin Energy Company Pekin, IL 80 (303)

Quantum Chemical Corp. Tuscola, IL 68 (257)

 USI Division

South Point Ethanol South Point, OH 60 (227)

A. E. Staley Manufacturing Company Loudon, TN 60 (227)

 Sweetner Business Group

 Ethanol Division

(continued)
TABLE 5-17. CONTINUED

Facility Location (million L)

Annual Capacity

million gal

5-87

Ethanol (continued)

Union Carbide Corporation Texas City, TX 123 (466)

 Solvents and Coatings Materials Division

TOTAL 1,458 (5,519)

Isopropanol

Exxon Chemical Company Baton Rouge, LA 650 (2,460)

 Exxon Chemical Americas

Lyondell Petrochemical Company Channelview, TX 65 (246)

 Shell Chemical Company Deer Park, TX 600 (2,271)

Union Carbide Corporation Texas City, TX 530 (2,006)

 Solvents and Coatings Materials Division

TOTAL 1,845 (6,984)

Source: References 11 and 111.

 Emissions listed are those reported in the 1992 TRI. a

NA = Not available

-- = no emissions reported
5-88

Table 5-18. Of the three facilities, DSM and BASF use benzene as a solvent, and Allied 11,111

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. As shown in Table 5-19, only one emission factor was identified 107

for any of the solvent use categories. The emission factor presented is for the vacuum dryer 114

vent controlled with a venturi scrubber in pharmaceutical manufacturing. 
5-89

TABLE 5-18. U.S. PRODUCERS OF CAPROLACTAM

Facility Location

Annual Capacity

million lb

(million kg) 

Allied-Signal, Inc.

Engineered Materials Sector

Hopewell, VA 660 (299) 

BASF Corporation

Chemicals Division Fiber Raw Materials

Freeport, TX 420 (191) 

DSM Chemicals 

North America, Inc.

August, GA 360 (163) 

TOTAL 1,440 (653)

Source: References 11 and 111.

 Emissions listed are those reported in the 1992 TRI. a

“--” = no emissions reported.
5-90

TABLE 5-19. SUMMARY OF EMISSION FACTORS FOR BENZENE USE AS A SOLVEN

SCC and Description Emissions Source Control Device

Emission Facto

lb/1,000 gal

(g/L)

3-01-060-01

Pharmaceuticals -General Process -Vacuum Dryers

Vacuum Dryer Vent Venturi Scrubber

(99.10% efficiency)

2.1 (0.25) 

Source: Reference 114.

Factor is expressed as lb (kg) benzene emitted per 1,000 gal (L) pharmaceutical product produced. a