United Stares
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Research Triangle Park NC 27711
EPA-600/7-79-184
August 1979
Applicability of
Coke Plant Control
Technologies to
Coal Conversion
Interagency
Energy/Environment
R&D Program Report
-------
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
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The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
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RESEARCH AND DEVELOPMENT series. Reports in this series result from the
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Development Program. These studies relate to EPA's mission to protect the public
health and welfare from adverse effects of pollutants associated with energy sys-
tems. The goal of the Program is to assure the rapid development of domestic
energy supplies in an environmentally-compatible manner by providing the nec-
essary environmental data and control technology. Investigations include analy-
ses of the transport of energy-related pollutants and their health and ecological
effects; assessments of, and development of, control technologies for energy
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tion Service, Springfield, Virginia 22161.
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EPA-600/7-79-184
August 1979
Applicability of Coke
Plant Control Technologies
to Coal Conversion
by
S.M. Hossain, P.P. Ciiione, A.B. Cherry, and
W.J. Wasylenko, Jr.
Catalytic, Inc.
1500 Market Street
Philadelphia, Pennsylvania 19102
Contract No. 68-02-2167
Task No. 10
Program Element No. EHE623A
EPA Project Officer: Robert A. McAllister
Industrial Environmental Research Laboratory
Office of Energy, Minerals, and Industry
Research Triangle Park. NC 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460
-------
ACKNOWLEDGMENTS
Catalytic, Inc. expresses grateful appreciation to the following
individuals and organizations for their contributions during this study:
William J. Rhodes,. Project Officer, EPA, IERL/RTP
Robert A. McAllister, Senior Chemical Engineer, EPA, IERL/RTP
Norman Plaks, Chief, Metallurgical Processes Branch,
Industrial Processes Div., EPA, IERL/RTP
James P. Templin, Foundry Coke Consultant
Earle F. Young, Jr., Director, Environmental Affairs,
American Iron & Steel Institute
Houdry Division of Air Products & Chemicals, Inc.
Philadelphia Coke Co., Inc.
ii
-------
ABSTRACT
Since there appear to be many similarities in the product, byproduct and
wastestream characteristics between the coke oven and coal conversion processes,
Catalytic, Inc. has been directed to conduct this study to review coke oven
processes and control technologies and to assess their applicability to the
coal conversion (synfuels) industry.
Most of the major coke oven and coal conversion processes have been
considered, with special emphasis on: Lurgi, Koppers-Totzek, SRC-I, COED,
Synthane and Byproduct coke oven processes. Detailed material balances are
given for commercial size Byproduct coke oven and SRC-1 processes. Comparisons
of the process and waste stream characteristics from the Byproduct coke oven
process with selected gasification and liquefaction processes have been made;
and recommendations regarding control technologies are suggested for air,
water and solid wastes. An extensive review of coke oven control technology
was made. State and Federal regulations concerning the disposal and treatment
of coke oven wastes are presented along with a brief assessment of health
effects attributed to the coke oven emissions.
The results of the study indicate that a number of coke oven control
technologies are applicable to coal conversion systems, especially those
dealing with desulfurization, fugitive emissions, byproduct recovery/upgrading
and wastewater treatment. Byproduct upgrading and fugitive emission control
technologies might be readily transferrable to analogous coal conversion
applications. Desulfurization and wastewater treatment technologies, however,
could not be readily transferrable to those applications where significant
differences exist in the composition, temperature and pressure of the two
categories of process/waste streams. In these cases, laboratory or pilot
plant scale tests will be required with actual coal conversion wastes to
determine the design bases and the treatability variations between the coal
conversion and the comparable coke oven streams.
iii
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CONTENTS
Page
Acknowledgments. ii
Abstract iii
Figures vii
Tables viii
1. Summary and Conclusions , . . . 1
2. Introduction 14
3. Description of Coke Oven Processes 16
Byproduct Coke Oven Process ......... 18
General Process Features 18
Coal Handling and Preparation 21
Coke Oven Operation , 21
Recovery of Tar and Ammonia Liquor. 22
Light Oil Refining 24
Desulfurization of Coke Oven Gas 24
Other Coke Oven and Related Processess 26
Beehive Process 26
Low Temperature and Recent Processes 26
4. Material Balance and Waste Characteristics of Coke Oven Processes 33
Byproduct Coke Oven Process ..... 33
Typical Product/Byproduct Quantities 33
Waste Characteristics 34
Material Balance of a Typical Byproduct Coke Oven Plant 42
Other Coke Oven Processes 58
Beehive Process 58
Low Temperature Processes 60
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CONTENTS (continued)
Page
5. Coal Gasification Processes and Their Waste Characteristics ... 61
Coal Gasification Processes 61
Acid Gas Removal and Sulfur Recovery 68
Waste Characteristics and Comparisons 71
6. Coal Liquefaction Processes and Their Waste Characteristics ... 75
Coal Liquefaction Processes 75
SRC-I Process Material Balances, ,..,.., 82
Design Basis 82
Overall Material Balance 82
Waste Characteristics and Comparisons 92
7. Coke Oven Control Technology and Its Applicability to
Coal Conversion Processes ,.,..,, 96
Desulfurization of Coke Oven Gas 96
Vacuum Carbonate Process , 99
Sulfiban Desulfurization Process 105
Iron Oxide Process 110
Stretford Sulfur Recovery Process 112
Glaus Sulfur Recovery Process 119
Wastewater Control Technology 124
Ammonia Removal and Recovery 130
Biological Oxidation 132
Carbon Adsorption 137
Oil Removal 138
Phenol Removal and Recovery 139
Solid Waste Disposal Methods 144
Light Oil Upgrading Processes 144
Litol Process . .- 146
Fugitive Emissions Control 152
Charging Emission Control 153
Pushing or Discharging Emission Control 157
Quenching Emission Control 160
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CONTENTS (continued)
Page
Improvements in Operating Procedures and Maintenance 162
Recent Control Technology Developments 163
8. The Health Effects of Coke Oven Emissions 165
Health Effects/Implications 165
Chemicals Composition of Coke Oven Emissions and
Their Health Implications , 165
Particle Size and Its Health Effects 165
Synergisms. , 172
Basis of Sampling and Measurements 172
Epidemiological Study Results. ....... 175
Summary of Study Findings 179
9. Enviromental Requirements in the Coke Oven Industry 182
Federal Regulations 182
Air Pollution Control Standards ,,.,.., 182
Water Pollution Standards 186
EPA Water Quality Criteria , 187
Solid Waste Disposal Standards 188
State Regulations , . . . 189
Air Pollution Control Standards 189
Water Pollution Control Standards . . , 193
Solid Waste Disposal Standards 193
Bibliography 194
Appendix A , 199
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FIGURES
Number Page
3-1 Yields of carbonization products from upper banner seam coal ... 17
3-2 Simplified block flow diagram of a Byproduct Coke Oven Plant ... 20
3-3 Simplified block flow diagram of the Houndry LITOL Process .... 25
4-1 Detailed block flow diagram of a byproduct coke oven plant .... 45
5-1 Hypothetical coal gasification flow diagram 64
5-2 Byproduct from Lurgi Plant 66
6-1 Hypothetical coal liquefaction flow diagram 78
6-2 Overall flow diagram: 20,000 TPD coal feed SRC-I process 85
7-1 Two stage Vacuum Carbonate system flow diagram 101
7-2 Sulfiban desulfurization process . 107
7-3 Stretford sulfur recovery process flow diagram 115
7-4 Claus sulfur recovery process, ............ 120
7-5 Coke plant wastewater treatment systems. ... 126
7-6 Phosam-W ammonia recovery process. ........ 133
7-7 Phenol removal by light oil caustic process 141
7-8 Phenol removal by high boiling solvent process 143
7-9 Typical LITOL reactions -, 147
7-10 Houndry's LITOL light oil upgrading process 148
vli
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TABLES
Number Page
1-1 Coke Oven and Coal Conversion Stream Similarities ........ 4
1-2 Comparison of Raw Gases ,,,,, 5
1-3 Comparison of Process Wastewaters
1-4 Coke Plant Control Technologies and Their
Applicability to Coal Conversion 11
3-1 Other Coke Oven and Related Processes , , ....... 27
3-2 Recent Coal Carbonization/Pyrolysis Processes ..... 30
4-1 Yields and Analyses of Products of By-Product Coke Oven Process . 35
4-2 Ammonia Liquor Blow-Down Composition 36
4-3 Final Cooler Water Slowdown Composition ........ 37
4-4 Light Oil Plant (Benzol) Process Wastewater Composition 38
4-5 Uncontrolled Air Emissions from Coke Ovens/Quenching Operations , 41
4-6 Design Basis for A 5000 TPD Byproduct Coke Oven Plant 43
4-7 Material Balance of A 5000 TPD Coke Oven Plant 49
4-8 Summary of Air Emissions - 5000 TPD Byproduct Coke Oven Plant . . 54
4-9 Summary of Process Wastewater - 5000 TPD Byproduct Coke Oven Plant 55
4-10 Characteristics of Beehive Coke Plant Wastes 59
5-1 Coal Gasification Processes Product/By-Product and
Fuel System Similarities 63
5-2 Products/Byproducts of Different Coal Gasification Processes. . . 67
5-3 Material Balance for Gas Liquor Treatment , 69
5-4 Acid Gas Removal Processes for Coal Gasification Systems 70
5-5 Process Wastewater Analysis from Synthane Gasification of
Various Coals 73
6-1 Coal Liquefaction Processes-Product/By-Product and Fuel
System Similarities 76
6-2 Operating Conditions of Three Leading Coal Liquefaction Processes 81
6-3 Design Basis for A 20,000 TPD Coal Feed SRC-I Plant 83
viif
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TABLES (continued)
Number Page
6-4 Overall Material Balance: 20,000 TPD SRC-I Plant 87
6-5 Summary of Gaseous Waste Streams (Before Treatment) 93
5-6 Summary of Liquid Waste Streams (Before Treatment) 95
7-1 Coke Oven Gas Desulfurization Processes 97
7-2 Vacuum Carbonate Requirements 103
7-3 Vacuum Carbonate Capital Costs 104
7-4 Sulfiban Operating Requirements 108
7-5 Sulfiban - Capital Costs 109
7-6 Stretford Desulfurization - Capital & Operating Costs 118
7-7 Typical Claus Plant Feed Composition for the Coke Industry .... 122
7-8 Characteristics of Byproduct Coke Plant Ammonia Liquor Wastewater. 129
7-9 Contaminant Removal Efficiency of Byproduct Coke Oven Plant
Treatment Facilities 129
7-10 Design and Operating Conditions of Some Coke Plant
Activated Sludge Systems 135
7-11 Typical Raw Light Oil Composition 145
7-12 Typical Litol Process Yields 150
7-13 Litol Process Operating Cost 151
7-14 Byproduct Coke Oven Fugitive Emissions Control 154
8-1 Partial List of Constituents of Coke Oven Emissions 166
8-2 Some Toxic Constituents of Coke Oven Emissions and
Some of Their Toxic Properties 168
8-3 Particle Size Range and Bilogical Significance of Coke
Oven Emissions 173
8-4 Summary of Exposures of Coke Oven Workers to Coke Oven Emissions . 174
8-5 Comparison of Benzo(a)pyrene Concentrations Measured at Coke
Oven Batteries and at Other Selected Sites 176
8-6 Ambient BAP and BSD Data 177
8-7 Temperature Range of Carbonizing Chambers and Excess of
Lung Cancer Reported 177
8-8 Summary of Relative Risks of Death from Cancer Among Coke
Oven Workers 178
8-9 Estimated Effects of Coke Oven Emissions on U.S. Population Under
Weibull Probability Model Where "Hit Parameter" m=l and Adjustments
for Total Population Rates Used 181
ix
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TABLES (continued)
Number Page
9-1 National Ambient Air Quality Standards .... 185
9-2 Summary of State Air Pollution Control Regulations for the
Control of H-S Emissions from Byproduct Coke Ovens 191
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SECTION 1
SUMMARY AND CONCLUSIONS
Coal was once the major source of organic chemicals (chiefly aromatics)
produced via the upgrading of coke oven byproducts. In recent years, these
chemicals have been primarily supplied by processing petroleum and petro-
chemicals. In the future, as the coal gasification and liquefaction (coal
conversion) industry grows, it is expected that increasing amounts of these
chemicals will again be generated from coal.
Since there appear to be many similarities in the product, byproduct and
was testream characteristics between the coke oven and coal conversion processes,
Catalytic, Inc. has been directed to conduct this study to review coke oven
processes and control technologies and to assess their applicability to the
coal conversion (synfuels) industry.
Most of the process information, waste stream characteristics and control
technology data for the study were obtained from published literature. Some
were generated by consultations with process vendors and coke oven plant
operators and representatives.
Coke is produced by destructive distillation (carbonization) of low
sulfur, bituminous coal in an oven or retort in the absence of air. Coal used
in coke making is usually a blend of high-volatile coal with a 10 to 50 percent
low-volatile coal; the blend should not contain over 1.5 percent sulfur or 9
percent ash. Approximately 16 percent of the bituminous coal mined in the
U.S. is converted to coke which is used principally in blast furnaces and
foundries. More than 98 percent of the total U.S. coke is produced from
byproduct coke oven systems. The Byproduct process is oriented toward the
recovery of the gases and chemicals produced during the coking cycle.
The major unit operations/processes involved in the Byproduct coke plant
are: coal handling and preparation, coking, quenching, primary cooling, tar
separation, tar extraction, ammonia removal, final cooling, light oil scrubbing,
-1-
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and sulfur removal (desulfurization). In addition, some modern coke plants
have chemical refining (upgrading) facilities for recovery of benzene, toluene
and xylene (BTX) from light oils.
The core of the process is the coke ovens, which are narrow chambers,
usually about 38 to 50 feet long, 13 to 16 feet high, tapering in width from
17 to 20 inches at one end to 15 to 16 inches at the other. The ovens hold
from 16 to 24 tons of coal, and are usually built in batteries averaging from
80 to 100 ovens. Although coke production from each oven is basically a batch
process, a coke oven plant is operated such that the battery of ovens con-
tinuously produce coke oven gas and byproduct chemicals. In the Byproduct
coke oven process, coking is accomplished at temperatures of 1,090 to 1,150°C
and atmospheric pressure for a period of 16 to 27 hours.
One ton of the low sulfur bituminous coal (approximately 30% volatile
matter, wet and on an "as received" basis) fed into a Byproduct coke oven will
yield following products and byproducts:
Quantity, Ibs.
Coke 1,430
Coke breeze 93
Tar 78
Ammonia, anhydrous 5
Light oil 20
Gas, 10,350 scf 309
Water 65_
2,000
The principal subdivisions of coal gasification processes are low-,
intermediate-, and high-temperature operations. These are further subdivided
by operating pressures. The low-temperature gasification processes tend to
show a complete product and byproduct slate, including oils, tars, and phenols.
As the gasification temperature increases, the quantity of oils, tars and
phenol decreases in preference to lighter products. The operating pressure
also affects the yields. As the pressure increases, the product slate becomes
heavier. For example, in intermediate-temperature processes, recoverable
products such as naphthas and tars increase from zero or negligible quantities
to significant quantities of heavier molecular weight chemical compounds.
-2-
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Although the Byproduct coke oven process is vastly different from the
gasification processes, many similarities appear to exist between the product
and byproduct slates of the two industries. Therefore, it was theorized that
the characteristic waste materials from the two industries may be similar.
The report shows that this is true to some extent, but wide variations in
quantities and compositional changes are evident, making comparative
generalizations difficult.
The coal liquefaction processes are significantly different from the coal
gasification processes, and, again, markedly different from the coke oven
processes. Yet, the products and byproducts of the coal liquefaction processes
show many similarities to those from Byproduct coke oven process. All lique-
faction processes produce an acid gas stream which contains sulfur and other
contaminants similar to the raw gases from the coke oven or coal gasification
processes. Consequently, H^S removal, including sulfur recovery, will be
required for all coal conversion processes. This control technology is
practiced by many coke oven plants. The aqueous waste streams of the coal
liquefaction processes contain pollutants similar to the coke oven industry,
and the accepted wastewater control technologies utilized in the coke oven
industry should be applicable.
Table 1-1 provides a comparative listing of coke oven and coal conversion
process and waste streams. Although many similar constituents are present in
the various streams, their concentrations, temperatures and pressures are
different (e.g., see Table 1-2 for raw gas compositions). These are important
variables that will control the selection of the best available control
technology for a particular stream. For example, note in Table 1-2, the ratio
of C09 to H S in the streams. For the Lurgi and Koppers-Totzek (K-T)
gasification processes, the ratio is much higher than either the coke oven or
the Solvent Refined Coal (SRC-I) liquefaction process streams. High C02/H S
ratios make sulfur removal and recovery more difficult in the gasification
processes.
A number of processes are being utilized to remove hydrogen sulfide and
recover sulfur from coke oven gas. These processes are divided into three
major categories: 1) Liquid Absorption processes (Vacuum Carbonate, Sulfiban
(amine type), Firma Carl Still); 2) Wet Oxidative processes (Stretford, Takahax,
-3-
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TABLE 1-1. COKE OVEN AND COAL CONVERSION STREAM SIMILARITIES
Coke Oven Streams
Raw gas and acid gas
Process wastewater
Coal pile run-off
Coke breeze
Oily and biosludges
Tar, naphthalene,
light oil, phenol
and ammonia
Coal Conversion
Counterparts
Raw gas and acid gas
from gasification,
and off-gas from
liquefaction
Process wastewater
Coal pile run-off
Coal fines, chars
Oily and biosludges
Tar, naphthalene
light oil, phenol
and ammonia
Major Common Pollutants
or Similarities
H2S, NH3, CO, C02, COS, HCN
and hydrocarbons
NH~, phenols, oils, sulfides
and cyanides (See Table 1-3
for details)
Suspended solids and organic
extracts
Similar byproducts
Oil, grease and tar, biomass,
refractory organics
Similar byproducts
Fugitive emissions
. Coal pile
Coal charging and
coke pushing
Coke quenching
. Byproduct recovery
and storage
. Wastewater
treatment
Fugitive emissions
Coal pile
Coal lockhopper
vent gases
Particulates
Raw gas pollutants and
participates
Ash/char quenching Same as above
Byproduct recovery Odors, NH_, H.S, hydrocarbons
and storage and particulates
Wastewater Same as above
treatment
-4-
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TABLE 1-2. COMPARISON OF RAW GASES
Components /Parameters
H2
Cl
C2
C3 to C5
CO
co2
0_
2
No
2
NH3
HCN
H2S
COS
cs2
Light Oil
Tar Oil
Tar
Phenol
H 0
TOTAL
Temp., °F
Pressure, psia
v>O M / £1 A O
w n f ~~O
LurSl<2>
22.63
6.75
0.23
-
11.65
16.16
_
0.18
0.55
0.16
0.203
0.007
-
0.14
0.11
0.10
0.05
41.07
100.00
370
450
79.6
K-T(3)
26.37
-
-
51.79
8.82
_
0.69
0.08
0.02
0.41
0.04
-
-
-
-
-
11.78
100.00
2,730
15.3
21.5
(4")
SRC-I Off Gas
31.58
36.39
7.86
5.81
0.22
3.84
_
0.43
-
-
12.68
-
-
1.19
-
-
-
_
100.00
119
24.7
0.303
Coke Oven
38.22
25.51
2.99
-
6.18
1.33
1.26
0.452
0.70
0.16
0.51
0.018
0.01
0.79
-
0.78
0.04
21.05
100.00
1,000
14.3
2.6
1. Except as noted, all values are in vol %.
2. Sub-bituminous coal, El-Paso Lurgi process design. Bibliography 59.
3. Texas lignite feed containing 1.5% sulfur, 8% moisture. Koppers-Totzek
gasifier.
4. One of the off-gas streams from the Solvent Refined Coal process. See
other off-gases in Table 6-5.
5. Bituminous coal mixture suitable for coking;
1.0% sulfur, 4% moisture.
-5-
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Giammarco Vetrocoke); and 3) The Dry Oxidative process (Iron Oxide or Dry
Box). Historically, the Dry Oxidative process using iron oxide has been used
most extensively. However, the Vacuum Carbonate process, the Stratford
process and, more recently, the Sulfiban process have moved into commercial
prominence.
The Liquid Absorption processes are called sulfur removal processes,
since they remove sulfur compounds (e.g., H^S) from the raw gas by liquid
scrubbing and generally produce a gaseous stream more concentrated in H S
(during regeneration of the solvent). The concentrated stream requires
control via a sulfur recovery system the Glaus sulfur recovery process is
primarily used in the coke oven industry. The Glaus process initially had
some problems associated with the excessive amounts of hydrogen cyanide, iron
sulfide and iron cyanide present in the above concentrated acid gas stream.
These problems have been resolved after special adjustments to the Glaus unit.
The Wet Oxidative processes, mentioned earlier, are sulfur recovery
processes in which elemental sulfur is the product. The Stretford process
does not remove COS or other organic sulfur compounds from the gas stream.
The H2S removal or sulfur recovery efficiency achievable for the processes
in the coke oven industry are: Iron-Oxide process - 99 percent (for low gas
volumes); Vacuum Carbonate process - 93 to 98 percent; Sulfiban process - 90
to 98 percent; Stretford process - 99.5+ percent; and the Glaus Sulfur Recovery
process - 95 to 96 percent.
Among the acid gas removal processes found in the coke oven industry, the
amine and carbonate type solvent processes should have application in low-
pressure gasification processes, or in treating lo7..-pressure offgases from
liquefaction processes. The two most common sulfur recovery processes in the
coke oven industry are the Glaus and Stretford processes. Both of these
processes will have wide application in the coal conversion industry. The
Claus is in service at a number of developing gasification processes, e.g.,
both the Hygas and Bigas pilot plants have Claus sulfur recovery units. The
Stretford process is also in service at a number of coal conversion processes,
e.g., Synthane pilot plant, Pittsburgh Energy Research Center, the SRC pilot
plant at Fort Lewis, Washington, and the Sasol coal conversion plant in South
Africa. Generally, the Stretford process is more economical when the acid gas
stream contains less than 15 percent H.S, whereas the Claus process is the
economic choice for levels above 15 percent.
-6-
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Consideration must be given to the interferences caused by high C09 and
othar impurities in the application of both the Glaus and Stretford processes
when used for coal conversion systems. C09 tends to neutralize the Stretford
solution and reduces the absorption rate of the H^S, thus necessitating higher
rates of solvent circulation and larger units. High C09 affects the stability
of the flame in the Glaus reactor, and also results in higher COS concentrations
in the tail gas from the Glaus unit. Additional control of the tail gas from
the Glaus unit would be required before emission to the atmosphere. Other
impurities also have undesirable effects on the Glaus unit. For example, in
the presence of ammonia, ammonium bicarbonate can form which reduces the
performance of the Glaus catalyst.
A comparison of the wastewater characteristics of the different processes
are shown in Table 1-3. Although many similar constituents are present, their
concentrations vary from process to process. The process wastewaters from
the Byproduct coke plants contain large amounts of phenol, ammonia, sulfide,
cyanide, and oil and grease. Various control technologies are being used to
remove these pollutants.
Ammonia is being removed and recovered by steam stripping at alkaline pH,
or by Phosam-W, a proprietary (U.S. Steel) process that uses scrubbing
(ammonium phosphate solution) and distillation in combination to produce an
anhydrous ammonia product. Sulfide removal from wastewater by steam stripping
is not commonly practiced in the coke oven industry.
Phenols are being removed by solvent extraction, steam stripping and/or
biological oxidation, and carbon adsorption. Biological treatment has been
successful with coke oven wastewaters in meeting existing phenol regulatory
limitation. Phenol removal efficiency of about 99.8 to 99.9 percent has been
achieved by the activated sludge system: B.O.D. removal has ranged from 85 to
95 percent.
All the above coke oven wastewater treatment and byproduct recovery
technologies should have application in coal conversion waste treatment.
Except for the low pressure and high temperature gasification processes (e.g.,
K-T process), other gasification and all coal liquefaction processes appear to
produce process wastewaters with similar pollutants and composition ranges
(See Table 1-3). Therefore, coke oven technologies should be applicable to
these processes for wastewater treatment.
-7-
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TABLE 1-3. COMPARISON OF PROCESS WASTEWATERS
PH
Suspended Solids
Phenol
C.O.D.
Thiocyanate
Cyanide
Ammonia
Chloride
Carbonate
Sulfide
Coke Plant v '
Ammonia
Liquor
mg/1
8.4
4,000
1,000
10,000
1,000
50
5,000
6,000
-
1,250
(2)
Synthane
mg/1
8.6
600
2,600
15,000
152
-.
8,100
500
6,000
1,400
U,rgl<3>
mg/1
8.9
5,000
3,500
12,500
-
-
11,200
-
10,000
-
Koppers-
Totzek SRC-I
mg/1
8.9
50
-
70
-
0.7
25
600
1,200
-
mg/1
8.0
300
4,500
15,000
-
-
5,600
-
-
4,000
1) See other wastewater compositions in Section 4.
2) Illinois No. 6 Coal feed. Bibliography 26.
3) Lurgi Sasol plant wastewater.
4) Private communication with the Koppers Co., Inc., Pittsburgh, Pa.
-8-
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Many coke oven plants recycle wastewaters containing high-cyanide con-
centration for coke quenching. Although alkaline chlorination of cyanide
containing wastewaters is successfully practiced elsewhere in steel mills, it
is not used for coke oven wastewaters because existing cyanide limitations for
the coke oven industry are met without additional treatment. Quenching of ash
and char with untreated wastewater may not be premitted for the coal conversion
industry.
Some coke oven plants use a byproduct light oil upgrading process which
has a potential application in the synfuels industry. This process, called
(10
the LITOL process, has been developed and licensed by the Houdry Division
of Air Products and Chemicals, Inc. It is a catalytic process by which coke
oven light oils are refined and dealkylated to produce high quality, even
reagent grade, benzene at essentially stoichiometric yields. The process has
been used commercially since 1964, and is in use in the U.S. and several other
countries.
The coke ovens are a major source of air pollution emissions in the steel
industry. Topside coke oven workers have a substantially higher risk of lung
cancer than the average worker, probably from carcinogenic materials associated
with the particulate fraction of the coke oven emissions. Various schemes to
control these emissions and alleviate potentially adverse health effects are
being developed.
These include: coke oven equipment design changes; improved coke oven
operating and maintenance techniques; collection of coke oven fugitive
emissions; and control of coke oven fugitive emissions. Equipment design
changes include such items as: adding another gas collection main on coke
oven battery; hydraulically operated mechanical gooseneck cleaners; magnetic
lid lifting equipment on larry car; screw feeders on all larry car discharge
hoppers; modified steam aspiration nozzles; modification of stand-pipe caps;
replacement of luted doors with knife-edge self sealing doors equipped with
spring-loaded adjustable plungers to maintain design pressure on knife edges;
and sealing of leveler door.
Improved coke oven operating and maintenance techniques include various
innovative procedures designed to minimize fugitive emissions from openings
and leaks associated with the charging, coking cycle, pushing/discharging and
underfiring/heating operations. The collection of coke oven emissions include
-9-
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various hood and duct configurations which are custom designed to withstand
high temperatures and to handle corrosive gases. Also, they must be able to
offer the maximum collection efficiency with the least interference to the
coke making operations.
The control of the fugitive emissions subsequent to collections has been
successfully applied by use of the following air pollution control devices:
high energy scrubbers, electrostatic precipitators and fabric filters. These
devices have proven capable of capturing submicron particle size fractions of
the smoke and particulate matter associated with coke oven fugitive emissions.
Also, the devices are able to handle large volumes of corrosive gases containing
condensed tar at their upper temperature limits (600 to 1,000°F). These
fugitive emission control technologies will have application in the synfuels
industry in analogous operations, e.g., in ash quenching, SRC solidification
operations, and in the collection and control of the building exhausts and
vents associated with coal conversion systems.
A summary list of the various coke oven control technologies that may
hav6 potential applications in the coal conversion industries is shown in
Table 1-4.
A majority of the control technologies listed in Table 1-4 has been
tested in coal conversion applications; however, most of these applications
have been in process development unit or pilot scale coal gasification and
liquefaction systems. A few successful uses have been with commercial first
generation coal gasification processes, e.g. the Lurgi process. Applicability
of the control technologies does not mean that the control technology can be
duplicated (similar size equipment) from the coke oven design to the coal
conversion application. In general, the composition, flow rate, temperature
and pressure of the specific coal conversion system wastes will not be identical
to the coke oven case; these differences, however, must be taken into conside-
ration during the design of the control technology. Design information or
scale up factors in comparison to coke oven application should be developed
through laboratory or pilot scale testing with actual coal conversion wastes
to determine the system design and to develop its costs.
-10-
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TABLE 1-4. COKE PLANT CONTROL TECHNOLOGIES AND THEIR
APPLICABILITY TO COAL CONVERSION
Coke Plant Control Technology
Applicability To Coal Conversion Systems
Acid Gas Treatment
Amine solvents
Carbonate solvents
(e.g. Vacuum carbonate
and Benfield)
Suitable for removal of H^S and C0_ from
low pressure raw product and off gases.
Solvent degradation may be encountered.
High C0? level may produce a Glaus feed
with too low an H?S concentration.
Suitable for selective removal of H_S and
CO,,. Processes partially remove carbonyl
sulfide and cyanides.
Sulfur Recovery
Stretford
Suitable for low H2S (less than 15%)
containing gases. Organic sulfur not
removed. High CO- levels require large
units.
Glaus
Applicable to high H2S (greater than 15%)
containing gases. Removal of high levels
of cyanide, ammonia and hydrocarbons will
be required.
Fugitive Emissions Control
Enclosed coke pushing
and quenching system
Fume recovery and
scrubbing
Improved operating
Procedures and
maintenance
Potentially suitable for ash quenching,
SRC solidification applications.
Applicable to analogous sources
Applicable to analogous sources
Byproduct Recovery/Refining
Ammonia from wastewater
(Stripping, Phosam - W)
Ammonia from raw gases
(Scrubbing, Phosam - W)
Suitable for sour waters.
Applicable to low pressure gas
purification.
-11-
-------
TABLE 1-4 (Continued)
Coke Plant Control Technology
(Byproduct Recovery/Refining
Continued)
Phenol from wastewater
(Solvent extraction)
Tar, naphthalene, 1ight
oil from raw gases
Light oil refining
(e.g. Litol process
and solvent extraction)
Applicability To Coal Conversion Systems
Suitable for process wastewater
containing 1,000 mg/1 or more phenol.
Suitable, but design must be modified
for different pressures, temperatures
and compositions.
Suitable for recovery of BTX from coal
derived naphthas.
Wastewater Treatment Technology
Biological oxidation;
carbon adsorption;
ammonia, phenol and
oil removal processes
Generally applicable: design basis must
be established for the specific waste.
-12-
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An assessment of the health effects of coke oven emissions was recently
made by EPA (Office of R&D) and a .draft report was issued in April, 1978. The
summary findings of the above report are as follows:
Exposure to coke oven emissions provides an elevated risk for cancer
of all sites and non-malignant respiratory diseases to coke oven
workers and an increased risk among lightly exposed workers (non-
oven workers in coke plant).
The general population, which includes the young, the old and the
infirm in the vicinity of a coke oven plant should be considered
more susceptible than the workers, especially for development of
chronic bronchitis, since they are generally in poorer health.
Coke oven emissions contain an array of identified carcinogens,
irritants, particulate matter, trace elements, and other chemicals.
The toxic effects observed in both humans and animals are greater
than the effects that can be attributed to any individual component.
Thus "coke oven emissions" as a whole should be considered the toxic
agents.
There is an exposure difference of about 2 orders of magnitude
estimated between lightly exposed workers and people living in the
vicinity of a coke plant. Since these lightly exposed workers show
an elevated risk for cancer and non-malignant respiratory disease,
it is reasonable to assume that levels up to one-hundreth of those
to which lightly exposed workers are subjected could cause an
increased risk to the general population.
Since the coke oven and the coal conversion system emissions have many of
the same hazardous components in high concentrations, such as H^S, CO, C0_,
hydrocarbons and polynuclear aromatics, there is a potential occupational
health hazard to coal conversion plant workers and the general population in
the vicinity of the plant. Many of the new control technologies under
development in the coke oven industry, especially those for fugitive emissions
control, should result in significant removal of these hazardous pollutants.
Whether or not additional controls will be required cannot be defined yet,
since these new technologies have not been in use for a sufficiently long
period of time.
-13-
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SECTION 2
INTRODUCTION
In the primary contract with the U.S. Environmental Protection Agency,
Catalytic, Inc. has been directed to conduct a program aimed at: assessment
of pollution control needs, determination of available control technologies,
and development of new control technologies for the products and byproducts of
coal conversion (coal gasification and liquefaction) systems. Whereas there
appeared to he gross similarities between the products, byproducts and waste-
streams from £he coal conversion and coke oven industry, and whereas the
application of coke oven controls to the coal conversion industry appeared to
be transferable, one of the assigned tasks (Task No. 10) in the project has
been to determine the potential applicability of coke oven control technologies
to the coal gasification/liquefaction industry.
The coke oven industry is long established and employs many types of air
and water pollution control equipment. This industry has been active in the
development of new environmental control technologies, especially for fugitive
emission control, desulfurization and process wastewater treatment. The
objective of the Catalytic study has been to review the coke oven control
technologies and identify those that would have application to coal conversion
process/waste streams. The approach methodology lias been to characterize
(compositions and quantities) those coke oven process and waste streams which
have counterparts in coal conversion processes, and to identify and review the
control technologies that could be applied to the coal conversion industry.
A meeting and discussions were held with representatives of the American
Iron and Steel Institute (A.I.S.I.) and the American Association of Coal and
Coke Fuel Dealers to obtain technical data.
A plant visit was made and consultations were held with representatives
of an operating coke plant for first hand observations and discussions of the
applications of processes and control technologies. To supplement discussions
-14-
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with E.P.A., A.I.S.I, and others, a comprehensive literature review was
conducted utilizing computer-based technical literature search services to
obtain published information on environmental controls and processes relating
to coke oven systems byproducts. From the approximately 250 technical articles
and text abstracts retrieved, a large number of publications were found to
have significant information pertinent to the study.
Existing and proposed State and Federal regulations concerning disposal
and treatment of waste materials were reviewed and are included in this report.
A brief assessment of health effects attributed to coke oven emissions,
based principally on information released in draft form by the EPA's Office of
Research and Development, is also part of this report.
A material balance for a typical coke plant was prepared. The balance
embraces all the major unit operations and provides approximate compositions
and quantities of the major process and waste streams. Both literature
references and engineering judgment were applied in developing this infor-
mation.
Comparisons of the waste characteristics from coke ovens with selected
coal gasification and liquefaction process wastes have been made and recom-
mendations offered regarding the control technologies for air, water and solid
wastes that could be appropriately applied to coal conversion processes,
including discussions on the conditions of applicability.
Results of an extensive review of coke oven control technology have been
reported with special emphasis on coke oven gas desulfurization and wastewater
treatment control strategies. Capital and operating cost data for these
control strategies and some major process unit operations are included,
whenever available.
-15-
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SECTION 3
DESCRIPTION OF COKE OVEN PROCESSES
Coke is made from the destructive distillation of coal in an oven or
retort in the absence of air; a process also referred to as pyrolysis or, more
frequently as carbonization. Coke is the solid carbonaceous residue remaining
after the high-temperature distillation of moisture and volatile matter from
the coal. It is used primarily in blast furnaces, in foundries and in gas
producers. Approximately 16 percent of the bituminous coal mined in the
United States is converted to coke.
The coal used in coke making is usually a blend of high-volatile coal
with 10 to 50 percent low-volatile coal. In order for the coal to form a
strong, coherent coke, expansion is restrained in the oven during the heating
process. Also, the coal should not contain more than 1.5 percent sulfur or 9
percent ash. Bituminous coal is the most suitable type because it has the
best agglomerating properties.
Besides coal types, other important variables that affect coke and
byproducts characteristics are oven temperature, residence time and oven
construction features. For example, the effect of carbonizing temperature on
the yields of coke and byproducts are shown in Figure 3-1. Although a small
amount of coke has been made in the United States by low-temperature (450 to
700 C) and medium-temperature (700 to 900 C) carbonization, most of the coke
is produced by high-temperature carbonization at 1,000 to 1,150 C.
There are two proven high-temperature processes: "Byproduct" coke oven
(recovery type) and "Beehive" (nonrecovery) processes. Approximately 98
percent of the total coke production in the United States is from Byproduct
coke plants. Therefore, the major focus of this report will be on the
Byproduct coke oven process, with only brief discussions of the Beehive and
low-temperature processes.
-16-
-------
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-------
BYPRODUCT COKE OVEN PROCESS
The Byproduct process is oriented toward the recovery of the gaseous and
liquid chemicals produced during the coking cycle. The principal unit of
equipment in the manufacture of coke is the coke oven, which is a narrow
chamber, usually about 38 to 50 feet long, 13 to 16 feet high, and tapering in
width from 17 to 20 inches at one end to 15 to 16 inches at the other. A
typical oven holds from 16 to 24 tons of coal, and the ovens are usually built
and operated in batteries of 10 to 100 (typically 80 to 100) ovens. Although
coke production from each oven is basically a batch process, a coke oven plant
uses this battery of ovens for continuous production of coke oven gas and
byproduct chemicals. Some of the major high-temperature coke oven processes
with their characteristic differences are:
Process/Developer Description
Koppers (Includes Becker) Cross-regenerative
byproduct oven
Wilputte Vertical flue oven
Semet-Solvay Horizontal heating flues
Otto Vertical flue ovens
The batch coke making step and the continuous processing of the raw coke
oven gas are described in the following paragraphs.
General Process Features
Coal is charged to the ovens through ports in the top, which are then
sealed. The heat required to maintain the high temperature is supplied to the
ovens by burning some of the coke oven gas produced. Coking is largely
accomplished at temperatures of 1,090 to 1,150 C and at atmospheric pressure
for a period of about 16 to 27 hours. At the end of the coking period, the
coke is pushed from the oven by a ram and quenched with water in an area
remote from the ovens.
The gaseous mixture generated in the Byproduct coke oven is composed of
permanent gases which form the final purified coke oven gas for the market,
accompanied by condensable water vapor, tar, light oils, solid particles of
coal dust, and heavy aromatic hydrocarbons. Figure 3-1 shows the yields of
coke oven byproducts at various carbonizing temperatures for a given coal
-18-
-------
type. The raw gas also contains pollutants such as ammonia, hydrogen cyanide,
cyanogen, hydrogen sulfide, carbonyl sulfide and carbon disulfide. Since raw
gas from coal gasification processes and off-gas from coal liquefaction
processes contain chemicals and pollutants similar to those listed for the raw
Byproduct coke oven gas, it is of significant importance to this study to
place particular emphasis on the processing schemes used to remove, recover or
destroy these chemicals and pollutants.
Figure 3-2 is a process block flow diagram of a typical byproduct coke
oven plant. It shows the various processing schemes used to recover chemicals
and remove pollutants from the raw coke oven gas. The sequence of the unit
operations can be varied; however, the following process sequence for the
manufacture of coke and its major byproducts is typical:
1. Coal is transferred, crushed, and screened.
2. Coal is charged to a hot empty oven.
3. Coal is chemically transformed to coke and volatiles by pyrolysis.
4. Hot coke is pushed out of the oven, quenched, and transported for
storage and use.
5. Some condensable products (primarily tar and ammonia) are condensed
and collected in the hydraulic main and primary cooler. Tar and
excess ammonia liquor are recovered.
6. Coke oven gas is pulled through an exhauster with a suction of 15 to
20 inches of water and is discharged at a pressure of 45 to 75
inches of water.
7. The coke oven gas then passes through electrostatic precipitators
which remove most of the remaining traces of tar.
8. Ammonia is removed from the gas as ammonium sulfate, or as anhydrous
ammonia.
9. The gas is further cooled and light ends are removed by absorption
in a petroleum-based absorbent (e.g., No. 2 fuel oil, straw oil).
Some plants have the facilities to upgrade or refine the light oil
and recover benzene, toluene and xylene (BTX).
10. Hydrogen sulfide is removed from the coke oven gas using various
processes (see Section 4).
11. Clean coke oven gas is metered and sent to users.
-19-
-------
1
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Figure 3-2. Simplified block flow diagram of a byproduct coke oven plant.
-------
Detailed descriptions of the foregoing operations and processes are presented
in the following paragraphs.
Coal Handling and Preparation
The primary functions are to prepare coal by blending, crushing mixing,
and pulverizing it to the required size and to transport the prepared coal to
the ovens for coking. A typical analysis of a mixed coal charge would be as
follows:
Percent
(by wt.)
Volatile Matter 30.00
Fixed Carbon 63.65
Ash 5.50
Sulfur 0.85
100.00
As mentioned previously, a blend of high-volatile bituminous coal with 10
to 50 percent of low-volatile bituminous coal is used to obtain a composition
similar to the above analysis.
After blending, the coal is crushed until it passes through 2-inch
openings, and is then pulverized in a hammer mill so that about 80 percent
passes through a 1/8-inch screen. In the hammer mills, approximately 0.1
gallon of oil per ton of coal is added to control the bulk density of the coal
which is then ready for charging to the coke oven.
Coke Oven Operation
The coal is delivered to the ovens by means of charging cars (larry cars)
that transport a measured amount of coal from the storage bins. This coal is
introduced into the ovens through charging holes at the top. The ovens are
heated by either raw or purified coke oven gas, which burns in vertical heating
flues set in the side walls of the ovens. Air for combustion is drawn through
regenerators which cool the-flue gases to about 750 F before entering the
stack. About 40 to 45 percent of the total coke oven gas produced is used to
supply heat for the ovens.
When the coal is charged into a hot oven, the layer of coal adjacent to
the heated walls is quickly decomposed. A plastic layer is formed, and moves
-21-
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slowly toward the center of the oven as carbonization proceeds. Coal is an
extremely poor conductor of heat and the center of the charge remains at a low
temperature for several hours. The average coking rate is about 1 in/hr (1/2
in/hr from each side) and it takes about 16 hours to complete the coking
cycle. At the end of the cycle, the coke is pushed out of the oven into a
quench car. The hot coke is quenched by a water spray, and is then dumped
onto an inclined coke wharf where it dries and cools.
Recovery of Tar and Ammonia liquor
The volatile matter and gas evolved during the coking process (raw coke
oven gas) leave the ovens through standpipes (vents) and pass into a gas
collecting main. There, the temperature of the gas is reduced from a range of
approximately 800 to 1,300°F to about 175 to 200°F by spraying it with recycled
ammonia liquor. This reduction in gas temperature causes condensation of
approximately 75 percent of the tar in the gas and most of the water vapor in
the raw gas.
From the collecting main, the gas passes to the primary coolers, where it
is cooled to about 85 to 104°F by ammonia liquor spray. This cooling removes
additional tar and water vapor and, again, a small portion of the total
ammonia in the gas. The gas is next conducted to an exhauster (positive-
displacement type). Beside compressing the gas, -it also serves to remove tar
by the highspeed swirling motion imparted to the gas.
The gas passing through the exhausters still contains traces of tar fog,
which is further reduced by electrostatic precipitators (ESP). The tar drains
from the bottom of the precipitators into a settlirg pit, which also collects
the tar removed in the collecting main and primary coolers. It is then pumped
from the pit and transferred to a storage tank, where water is decanted. This
tar, containing approximately 2 to 5 percent moisture, is sold for processing
and recovery of valuable aromatic compounds such as food coloring.
The condensed water, which results from gas cooling in the collecting
ma-fn and primary coolers, appears as excess ammonia liquor and is the major
process wastewater from the Byproduct coke oven plant. This stream is also
referred to as ammonia liquor blowdown. The excess ammonia liquor is treated
before discharge for byproduct recovery and pollutant removal according to the
various schemes discussed in Section 7.
-22-
-------
The coke oven gas which has passed through the tar extractors (ESP) is
next sent to the ammonia removal unit for recovery of ammonia by one of the
following methods:
1. Indirect process. The ammonia is removed from the gas by scrubbing
with water. Scrubber blowdown is treated by an alkali solution and
steam stripping; the stripped vapor is then passed through a saturator
containing a solution of sulfuric acid to recover ammonium sulfate.
2. Direct process. Raw coke oven gas, after separation of tar, is
passed through a saturator containing a solution of sulfuric acid to
remove ammonia.
3. Semi-direct process. The ammonia in the liquor, which is produced
by direct and indirect cooling, is removed by alkali treatment and
distillation, and added to the gas stream. This stream is then
passed through an absorber (saturator) containing dilute sulfuric
acid to extract the ammonia as ammonium sulfate.
Of these three processes, the semi-direct, developed by Koppers, is most
extensively used in the U.S. (Note: A new process known as Phosam-W (U.S.
Steel) is emerging. This provides for ammonia removal by scrubbing the gas
with a lean ammonium phosphate solution and then recovering anhydrous ammonia
from the scrubbed liquid by stripping and distillation. See further discussion
of this process in Section 7.0).
After the ammonia removal unit, the gas passes through the final coolers
where direct contact water is used to cool the gas to a temperature of 70 to
90 F. A major portion of the naphthalene condenses out of the gas as a result
of this cooling and is recovered from the cooling water at the settling basin
or in flotation cells where it is skimmed off as it rises to the top. The
naphthalene is either added to the tar or is processed further to produce a
commercial product. In some facilities, it is recovered from the cooling
water by having tar circulate countercurrently to the flow of water in the
base of the final cooler.
For the recovery of light oil, which is generally the last step in the
coal chemical recovery process, there are three general methods used:
1. Refrigeration and compression involving temperatures below minus
70 C and pressures of 10 atmospheres.
-23-
-------
2. Adsorption by activated carbon followed by heating to recover organic
compounds.
3. Absorption by solvents involving washing of the gas with a petroleum
solvent, coal-tar fraction, or other absorbent, followed by steam
distillation of the enriched absorbent to recover the light oil.
Light Oil Refining
The traditional method for purifying the recovered light oil is to wash
it with sulfuric acid and caustic soda, followed by distillation to separate
benzene, toluene, xylene (BTX), and solvent naphtha cuts. The thiophene
content of benzene produced by acid washing is high (100 to 400 ppm) and
precludes utilization of this benzene in many chemical reactions, particularly
where sulfur sensitive catalysts are employed. As a result, coke oven BTX has
a less marketable demand than petroleum derived benzene, which contains less
than 1 ppm thiophene.
The Houdry LITOL process was developed to purify the light aromatic
fraction produced as a byproduct of high-purity BTX and is also capable of
dealkylating the toluene and xylene to benzene at high selectivities, whenever
desired. Nonaromatic materials (mainly paraffins, olefins, diolefins,
naphthenes, and sulfur compounds) are completely converted to lighter hydro-
carbons and to hydrogen sulfide.
Figure 3-3 shows a simplified block flow diagram for the LITOL process.
Applicability of the LITOL process to coal conversion systems is discussed in
Section 7 under Light Oil Upgrading Processes.
Desulfurization of Coke Oven Gas
The gas, after being stripped of its ammonia and light oil, is next sent
to the desulfurization unit for sulfur removal. Many processes available for
gas purification are discussed in detail in Section 7. Historically, the dry
oxidative process using iron oxide boxes has been the most extensively used
method for sulfur removal. However, the Vacuum Carbonate, the Holmes-Stretford,
and more recently, the Sulfiban process have moved into commercial prominence.
After the gas is desulfurized, it is ready for use as a clean fuel.
-24-
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NAPHTHA
(LIGHT OIL)
LIGHT HYDROCARBONS
AND
HYDROTREATMENT
REACTORS
T
I
SEPARATOR
STABILIZER TOWER
CLAY TREATER
HYDROGEN
BTX PRODUCTS
DISTILLATION
HEAVIER
AROMATICS
Figure 3-3. Simplified block flow diagram of the Houdry LITOL Process,
-------
OTHER COKE OVEN AND RELATED PROCESSES
Beehive Process
Except for the coke, this is a nonrecovery type of process. The Beehive
oven is a refractory-lined enclosure with a dome-shaped roof. The coal charge
(10 to 15 tons), deposited onto the floor of the oven through a trunnel head
in the roof, is leveled to give a uniform depth of material. Openings above a
door on the side of the oven are restricted to control the amount of air
reaching the coal. This air is required to burn the volatile products dis-
tilled from the coal and thus generate heat for further distillation. The
carbonization process begins at the top of the coal pile and works down
through it. The volatile matter being distilled burns near the top of the
oven and the combustion products leave through the opening in the roof. Upon
completion of the coking (which takes from 48 to 96 hours), the coke is
"watered out" or quenched. After quenching, the coke is "drawn," i.e., removed
either mechanically and/or by hand.
Low Temperature and Recent Processes
There are numerous types of process equipment used and byproducts generated
from the low-temperature processes. Most of these processes are commercially
prominent in Europe for the production of domestic fuels, along with gas and
chemical byproducts. Table 3-1 summarizes some old commercially developed
low-temperature carbonization processes.
The only commercially successful, low-temperature (570 C) carbonization
process ever utilized in the United States was the "Disco" process. However,
because of the availability of other cheaper fuels, the company discontinued
the process in 1963.
In the Disco process, wet fine coal from the washery goes through five
basic steps: predrying; roasting; carbonizing in the retorts; cooling the
char; and screening and loading.
The process is unique because it produces a final semicoke or lump char
directly from the fine coal in indirectly heated continuous rotating retorts.
This is done, without a briquetting step, through preliminary oxidation or
"roasting" of the coal in contact with air, thus destroying a portion of its
excessive caking characteristics. In the rotating retort, the oxidized coal,
together with recycled char, rolls up in'to balls of char without adhering to
the sides of the retort. The balls of char are screened and sold as smokeless
domestic product.
-26-
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TABLE 3-1. OTHER COKE OVEN AND RELATED PROCESSES
Process
Disco
Status
Was installed
by Disco Co.
near Pittsburgh
in the 50s.
Objective Process Description
Coke, tar Designed for certain coals.
and gas. Bituminous coal, ground to
3/8-in size, is heated in
a revolving steel retort.
The carbonizer gas is at
450-480°C.
Distribution of
Contaminants in Products
The low temperature of
operation does not remove
any contaminants. Feed
coal has 2.2% S, and coke
produced has 2.1% S.
Hayes Process
i
NS
Krupp-Lurgi
Process
Was operated by
Allis-Chambers
Moundsville, W.V.
in the 50s.
Developed in the
30s. Only large
scale plant is
in Germany.
Coke, tar Uses a rotating tube retort
and gas, with a screw conveyor. The
temperature at feed end is
595-705°C. The gas has a ,
heating value of 939 Btu/ft"
Coke, tar Oven consists of six carboni-
and gas. zation cells; entering gas is
at 620°C and exit gas at
570-580°C.
Coke contains 3.5% ash
compared to 9.85% for
coal.
The ash content of coke
is 3.8% versus 5.4% for
coal. The gas contains
6% nitrogen.
Brennstoff-Technak Process developed Coke
Cellon Jones Oven
Carmaux Oven
Otto Retort
Weber Process
Phurnacite Process
Parker Retort
for specific
coals, e.g.,
slightly caking.
Fixed-bed operation is used.
The temperatures control
contaminant removal from
the coke.
Rexco Process
Developed and
operated in
England.
Coke, tar The directly heated fixed-bed
and gas retorts are operated at 700 C.
Rexco coke has 7.2% ash
versus 4.9% for coal.
-------
TABLE 3-1. (Continued)
Process
Koppers
Status
Developed in
Germany.
Objective Process Description
Coke, tar Uses a continuous vertical
and gas retort for non-caking coals.
Temperatures of 800-1,000°C
are attained.
Distribution of
Contaminants in Products
Higher temperatures
would remove S, N and
trace metal contaminants
from the coke.
Parry Process
Developed by
U.S. Bureau of
Mines
Coke, tar Uses entrained carbonization;
and gas temperatures are 1,038 C.
Fine particle size of
Feed coal and high
operating temperatures
remove S, N and trace
elements from the coke.
-------
The byproduct gas generated during carbonization is cooled, scrubbed, and
returned to the retort furnace to .provide heat for carbonization. Low-
temperature tar is recovered and sold,, for further processing.
Recent Processes
In order to find solutions to our energy problem, several new coal
carbonization/pyrolysis processes are in the developmental stage. They produce
more liquids and gas products than the Byproduct coke oven process. Table 3-2
briefly describes these new processes. Additional characteristics of the
important processes are given in Sections 5 and 6.
There are no commercial low temperature coke oven processes available in
the U.S. today. However, low temperature carbonization of the char and filter
cake residue of some coal liquefaction processes such as the SRC-I process is
being considered for recovery of carbon values. (Note: The SRC-I process is
discussed in further detail under Section 6 of the report.)
FMC Corp. operates a demonstration plant (265 TPD) in Kemmerer, Wyoming
which produces a coke from sub-bituminous, and non-coking local Wyoming coals.
The FMC coke process is a continuous process unlike the coke oven battery
which is a cyclical batch operation. The process consists of a pyrolysis
section where coal is devolatilized in a sequential series of fluid beds
operating under controlled time, temperature and environmental conditions. It
also has a coke forming section consisting of briquetting, curing and coking.
The coke product is not exposed to the atmosphere until it appears as cooled
product being delivered to the storage silo. There are no pushing, charging,
door, topside or quenching emissions as associated with the byproduct coke
ovens. Emissions which do occur are from the coal.preparation section and the
three vessels in the fluid processing section. These emissions are incinerated
in a front end afterburner, emissions from briquetting are also controlled by
the front end afterburner after passing through cyclonic separators. Emissions
from the fluid bed primary and secondary coolers are combined and passed
through a single baghouse. .The organic emissions from the curing oven and
kiln are oxidized in a back end afterburner. Fugitive emissions from kiln air
locks, coke cooling, coke loading and associated transfer points are controlled
by a baghouse. No commercial plant has been built based on this process.
-29-
-------
TABLE 3-2. RECENT COAL CARBONIZATION/PYROLYSIS PROCESSES
Process
Status
Char Oil Energy
Development
(COED)
Developed by
FMC, Princeton*
MJ in 1962: 36
tons/day pilot
plant.
COED/COgas
process has
been selected
for
demonstration.
Objective
Maximize
liquid
production
from coal by
pyrolysis.
Process Description
Us«s multi-stage fluidized-bed
pyrolysia of coal. Catalytic
hydrotraating of the oil
yields synthetic crude
suitable as petroleum refinery
feedstock. The product gas
can be used as boiler fuel or
for gasification. Four
fluidized beds have temperatures
from 316-816°C; char 59.5%, oil
19.3%, gas 15.1%, liquor 6.1%,
based on Illinois No. 6 coal.
Distribution of
Contaminants in Products
The low temperature of
pyrolysis will concen-
trate the trace elements
and N, S compounds in the
char. The liquid product
contains S, N which are
removed by hydrotreatment.
COALCON
(Hydrocarboni-
zation)
Developed by
Union Carbide:
pilot plant in
South Charleston
Produces Sized, driad and preheated
liquid and coal is fed to a dry,
gas fluidized-bed hydrogenation
is gasified.
First state hydrogenation
would remove S, N to some
extent depending on
Clean
Coke
Developed by
U.S. Steel
1972
500 Ib/day (Process
Development Unit)
Detailed designs of PDU's
on: (1) Coal and coke
preparation, (2) Carbonization,
(3) Hydrogenation, (4) Slurry
oil preparation, and (5) Binder
preparation. Coal after
beneficiation is split into
two fractions. Portion of coal
carbonized and desulfurized to
produce metallurgical coke. The
rest of coal is slurriad with
process derived oil and
hydrogenated.
The liquid produced is
desulfurized by hydrogen
treatment. The char
contains 0.5% S versus
1.74% for coal.
-------
Process
Cogas
Status
Developed by
Cogas Develop Co.,
Princeton, 2.5 TPD
and 50 TPD pilot
plants are being
operated. COED/
Cogas has been
selected for
demonstration.
TABLE 3-2. (Continued)
Obj active Process Description
Variation of COED process;
Gasifier-Combuster operates
at 816-927°C. Med-Btu gas
is cleaned of S.
Distribution of
Contaminants in Products
The liquid is desulfurized
by hydrogen treatment.
Garrett's Coal
Pyrolysis
i
u>
Developed by
Occidental
Petroleum Corp.
3.6 TPD pilot
plant is being
tested.
Crushed coal is introduced
into the pyrolyzer in a
stream of recycle gas and is
pyrolyzed at 593°C through
contact with hot char
(649-841°C). Part of product
gas is reformed for hydrogen
to hydrotreat tar. Tfields
are: char 56.7%, tar 35%,
gas 6.5%, and 1.8% water.
Desulfurization of char
by acid treatment is
proposed. The trace
elements will concentrate
in the char.
Fractional
Carbonization
of coal.
Eddinger, R.T.,
et al.
U.S. Patent
3,574,065
Liquids
and gas
Staged pyrolysis and final
combustion is used.
Fate of trace elements
is the same as in any
carbonization study.
Pyrolyzing of
solid or
liquid fuel.
A.M. Squires;
U.S. Patent
3,597,327
8/31/71
Gas and
char
Uses a two-stage fluidized-
bed pyrolyzer. The heat is
supplied to the lower zone
by conduction from the top
zone. The lower bed
carbonizer is at 760 C and
the top one at 949°C.
Dolmite is used to remove
the sulfur.
Fuel gas and coke
products free of sulfur
are produced. The fate
of trace elements is
not mentioned.
(It is postulated that
they would end up in
the coke pellets.)
-------
Pennsylvania Control Technology, Inc. has developed a prototype non-
recovery type coking process which claims to minimize pollutant emissions.
The unit presently operating at the Alverton Fuel Co., Alverton, Pa. essentially
consists of two ovens with a single flue heating system. The hot gas from the
combustion of the coal is mixed with fuel oil and air and burned in an
incinerator situated between the ovens. The heat is recovered from the
incinerator and is used for heating the flue system. The coking cycle lasts
from 40-48 hours. The system is under 0.95 inches of water vacuum with outside
air drawn through the trunnel head (coal charge points) on top of the ovens.
The coke is removed from the ovens into an enclosed quench wharf and the gases
are exhausted and burned in the incinerator. Tests conducted on emissions
from this unit show 0.052 grains per standard cubic foot of air of particulate
matter and 252 ppm of sulfur dioxide burning 0.7 percent sulfur coal. The
test unit has been approved by the state regulatory agency, and four commercial
development units at mine-mouth locations are in the planning stage.
-32-
-------
SECTION 4
MATERIAL BALANCE AND WASTE CHARACTERISTICS OF COKE OVEN PROCESSES
BYPRODUCT COKE OVEN PROCESS
Typical Product/Byproduct Quantities
The quantity and characteristics of the coke product and chemical
byproducts vary with coal types, oven temperatures, and operating conditions.
Using the coal composition and operating conditions specified in Section 3
under "Coal Handling and Preparation," literature information shows that one
ton of coal (wet and as fed to the oven) will yield 1,935 pounds of products
and byproducts with the following typical slate:
Pounds Pounds
Coke 1,430 Ammonia, anhydrous 5
Coke Breeze 93 Light Oil (2.81 gal) 20
Tar (8.41 gal) 78 Gas (10,350 scf) 309
The remainder (65 Ib) is assumed to be composed of condensed moisture and
pollutants (e.g., particulates, phenolics) in the process wastewater and in
the fugitive air emissions. The foregoing assumption needs verification,
since literature data were not definitive regarding these losses.
The following summary of clean coke-oven gas composition is typical:
Volume %
Constituent
co2
C H
n m
CO
H2
C_ and homologs
N2
0,,
-33-
Typical
2.5
3.5
8.0
53.5
30.0
2.0
0.5
Ranges
1.3 -
3.1 -
4.5 -
46.5 -
26.7 -
1.5 -
0.2 -
2.5
4.0
9.0
57.9
34.0
9.6
0.9
-------
Table 4-1, a detailed breakdown of the feed coal into various products,
byproducts and contaminants, shows that the feed coal contains about 1.0 percent
sulfur; and the product coke contains about 0.96 percent sulfur. The balance
of the sulfur converts principally to hydrogen sulfide, carbonyl sulfide and
carbon disulfide in the raw coke-oven gas.
Waste Characteristics
Process Wastewater
The principal sources of byproduct coke plant process wastewater before
treatment are ammonia liquor blowdown, final cooler blowdown water, light oil
plant wastewater: 25 gallons, 25 gallons, and 30 gallons, respectively, per
ton of coke for the plant utilizing the best available technology (BAT).
Barometric condenser water is also a potential source when a crystallizer is
used for ammonium sulfate production.
Table 4-2 presents typical pollutant concentrations in the ammonia liquor
blowdown. The blowdown rates range from 18 to 90 gallons per ton of coal (dry
basis) depending on the type of process used to remove ammonia from the coke
oven gas. The Phosam-W and sulfuric acid scrubbing processes exhibit lower
flows; higher flows occur with the outdated water scrubbing process.
Final cooler blowdown water represents the condensate resulting from
cooling the saturated gas with direct contact cooling water. Typical pollutant
concentrations in the blowdown are shown in Table 4-3. The quantity of con-
densed water ranges between 5 to 10 gallons per ton of coal (dry) and is one
of the major sources of hydrogen cyanide in wastewater.
Table 4-4 shows representative pollutant concentrations in the light oil
plant (also called benzol plant) wastewater. The volume of water generated
from these sources ranges from 18 to 56 gallons per ton of coal (dry).
Plants with a crystallizer for ammonium sulfate production generally use
barometric condensers that create large amounts of wastewater, ranging from
175 to 300 gallons per ton of coal (dry). Pollutant concentrations repre-
sentative of barometric condenser water are:
Constituent mg/1
Ammonia 20
Phenol 40
Cyanide 40
Oil 20
-34-
-------
TABLE 4-1.
YIELDS AND ANALYSES OF PRODUCTS OF BY-PRODUCT COKE OVEN PROCESS
(SOURCE - BIBLOGRAPHY 51)
Product
Coke
Gas
Ammonia
Tar
Liquor
Light Oils
Cyanogen
Carbon disufide
Hydrogen sulfide
Percent of
coal
Constituent by weight
Ash
Carbon
Hydrogen
Sulfur
Nitrogen
Totals
CO
CO
CH
N2 4
"I
Totals
Hydrogen
Nitrogen
Totals
Carbon
Hydrogen
Oxygen
Totals
Water
Organics (phenolics)
Totals
C,H, (Equivalent)
b o
cs2
7.210
61.711
0.469
0.683
0.270
70.343
1.042
3.154
7.468
1.529
0.385
1.366
0.717
15.661
0.040
0.183
0.223
4.687
0.327
0.436
5.450
6.78
0.025
6.805
1.102
0.078
0.013
0.325
Analysis
percent of product
by weight
10.24
87.76
0.66
0.96
0.38
100.00
6.66
20.14
47.69
9.76
2.46
8.72
4.57
100.00
17.9
82.1
100.0
86.0
6.0
8.0
100.0
99.63
0.37
100.0
100.0
100.0
100.0
100.0
100.00
-35-
-------
TABLE 4-2. AMMONIA LIQUOR BLOW-DOWN COMPOSITION
(SOURCE: BIBLIOGRAPHY 7)
Constituents
Concentration Range
Total ammonia, mg/1 as N
Free ammonia (% of total)
Fixed ammonia (% of total)
Oil and grease, mg/1
Sulfide and Sulfite, mg/1 as S
Sulfate, mg/1 as SO,
Chloride, mg/1 as Cl
Cyanide as HCN, mg/1 as CN
Thiocyanate, mg/1 as CNS
Phenols, mg/1
COD, mg/1
Solids - total, mg/1
Solids - suspended, mg/1
3,000
20
40
500
500
200
2,000
20
300
500
8,000
9,000
60
80
2,000
2,000
800
6,000
100
- 1,200
3,000
- 16,000
Unknown
Unknown
-36-
-------
TABLE 4-3., FINAL COOLER WATER SLOWDOWN COMPOSITION
(SOURCE: BIBLIOGRAPHY 7)
Constitutents Concentration Range
Annnonia-N, mg/1 200 - 400
Phenols, mg/1 500 - 1,500
BOD5, mg/1 2,000 - 3,000
COD, mg/1 3,000 - 4,000
TOC, mg/1 800 - 1,400
Cyanide (CN), mg/1 100 - 300
Sulfide (H2S), mg/1 10 - 40
Thiocyanate (CNS), mg/1 200 - 1,000
Solids - total, mg/1 200 - 700
Solids - suspended, mg/1 20 - 60
Oil, mg/1 10-40
PH 7 - 9
-37-
-------
TABLE 4-4. LIGHT OIL PLANT (BENZOL) PROCESS WASTEWATER COMPOSITION
(SOURCE: BIBLIOGRAPHY 7)
Constitutents Concentration Range
Ammonia-N, mg/1 10 - 100
Phenols, mg/1 60 - 200
BOD5, mg/1 300 - 600
COD, mg/1 500 - 1,000
TOG, mg/1 200 - 600
Cyanides, mg/1 10 - 60
Solids-total, mg/1 200 - 700
Solids-suspended, mg/1 30 - 70
Oil, mg/1 10 - 200
pH 5-8
-38-
-------
In plants that remove hydrogen sulfide from the gas, fouling of the
absorber solution is another source of contaminated wastewater. The volume of
water generated from this source can range from 0.3 to 12 gallons per ton of
coal (dry) depending on the removal process employed.
Concentrations representative of the effluent wastewater from a vacuum
carbonate desulfurization process are:
Constituents Concentration
Ammonia, mg/1 50
Phenol, mg/1 5
Cyanide, mg/1 1,200
Sulfide, mg/1 30
BOD5, mg/1 1,200
COD, mg/1 1,700
TOG, mg/1 700
This effluent wastewater is usually recycled to the coke quenching station for
reuse.
Coal pile runoff, another major wastewater stream from coke oven plants,
has characteristics that depend on the type of coal stored. Typical wastewaters
from the two types of coal generally stored in the coke oven industry are:
High Volatile, Low Volatile,
Bituminous Bituminous
(38% V.M.) (17% V.M.)
pH 6-7 2.5-7
Suspended Solids 600 - 14,000 mg/1 100 - 1,000 mg/1
Avg. 10,000 mg/1 Avg. 500 mg/1
Other miscellaneous wastewaters originate from the following:
a. Pump and compressor seal water
b. Floor washdowns
c. Tank washings
d. Spills
e. Rain water runoff from process and storage areas
f. Wastewater from steaming or flushing of piping and equipment.
-39-
-------
Air Emissions
In the Byproduct coke plants, the majority of the air emissions emanate
from the coke oven (including quenching) operations and consist of two types:
fugitive losses, and stack emissions from the fuel burning operation (under-
firing) at the coke ovens. Table 4-5 gives the quantities of air emissions
from the coke ovens and quenching operations per ton of coal charged. These
emission factors were developed by the EPA based on data gathered prior to
1972. Since that time, more extensive data have been acquired by the EPA. It
is expected that additional pollutant factors (e.g., benzene soluble organics)
may be added or others modified in the table in the near future. The calcu-
lated sulfur dioxide (SO ) emissions in Table 4-5 are based on the assumption
that the coke oven gas has not been desulfurized prior to the underfiring
operation. However, many coke plants are using cleaner fuels for underfiring.
Besides the coke ovens, small amounts of fugitive emissions (containing
smoke, particulates, hydrocarbons, etc.) emanate from all other unit operations/
processes of the Byproduct Coke plants. Quantitative information on these
losses is not available from the literature.
The types of fugitive emissions found in the unit operations/processes
are as follows:
Unit Operation/Process
Coal Pile
Coal Handling and Preparation
Contaminant
Particulates
Particulates
Coke Ovens (Fugitive and Underfiring) Particulates, So , CO, H-C,
including Quench Station NO , NH» (see Table 4-5)
Particulates
Odors (NH~» organics)
Primary Cooler
Tar Separator, Exhauster and Tar
Extractor
Ammonia Removal
Fine Cooler, Naphthalene
Skimmer basin
Light Oil Recovery, Light Oil
Refining
Gas Compressor, H2S Removal and
Sulfur Recovery.
Particulates, H2SOA
and NH~
Odors
Particulates, odors
Particulates, H S, S0~
-40-
-------
TABLE 4-5. UNCONTROLLED AIR EMISSIONS FROM COKE OVENS/QUENCHING OPERATIONS
Stream
Charging
Coking Cycle
Pushing/Discharging
Quenching
Underfiring
TOTAL:
Air Emissions, Lbs.*
Participates
SO.
CO
Hydrocarbons
NO
3.1
4.02
1.27
4.2
x
0.04
Ammonia
1.5
0.1
0.6
0.9
-
0.02 0.60
0.60
0.07
-
4.0 **
2.5
1.5
0.2
-
-
0.03
0.01
-
-
-
0.02
0.06
0.10
-
-
0.18
* Based on one ton of coal input to the coke ovens.
**Coke oven gas before desulfurization is used for underfiring the ovens.
1 "Compilation of Air Pollutant Emission Factors", 3rd Edition, EPA-AP 42.
-41-
-------
Solid Wastes
Solid waste sources from the Byproduct coke oven plants are:
a) Coke breeze from coke sizing and screening, quenching operations.
About 70 to 100 pounds per ton of coal charged to the ovens are
converted to coke breeze with the following typical composition:
Range (wt. %)
Volatile Matter 4 - 6
Fixed Carbon 76 - 80
Ash 10 - 20
H20 0.5 - 5.0
Coke breeze has an economic value, and is sold or reused in many
installations.
b) Coal particulates from coal pile run-off wastewater treatment.
Recovered coal from the coal pile runoff could be returned to the
coal pile for reuse.
c) Solid wastes from process wastewater treatment (from biological
treatment system and ammonia stripping unit). Biological treatment
systems yield about 7.6 pounds of dry solids per ton of coal fed.
d) Residue in the form of tar sludge generated from tar decanting in
the tar separator. About 3.3 pounds of tar sludge per ton of coal
fed is periodically removed as a solid waste from the tar storage
tank.
Material Balance of a Typical Byproduct Coke Oven Plant
To assess the quality and quantities of products, byproducts and wastes
generated from an average coke oven plant, a 5,000 TPD (coal input) plants was
selected as a typical model. The material balance basis of the above plant is
summarized in Table 4-6. Many of the major design assumptions including yield
and analyses of different products are taken from the literature. Figure 4-1
and Table 4-7 depict the block flow diagram and overall material balance for
the 5,000 TPD coke oven plant, respectively.
Tables 4-8 and 4-9 provide a summary of the air emissions and wastewater
effluent from the 5,000 TPD model coke oven plant.
-42-
-------
TABLE 4-6. DESIGN BASIS FOR A 5000 TPD BYPRODUCT COKE OVEN PLANT
Coal Type
Coal Moisture:
Sulfur Content:
Bituminous Mixture
4.0% by wt.
1.0% by wt.
Coke Ovens Operating Conditions
Batteries:
Coke Ovens per battery:
Coal charge per oven:
Coking cycle:
Temperature:
Underfire excess air:
3
85
20 tons
17 hours
900°C
6%
3. Yields
Products, byproducts, % wt. coal (volume, scf/ton of coal)
Coke 70.343
Tar 5.45
Light Oil 1.102
Ammonia 0.223
Coke Oven Gas 15.661 (12,000)
Water (Liquor) 6.805
Other Gases 0.416
4. Raw Coke Oven Gas Composition
% wt. of coal feed:
H2
N2
co2
CO
CH4
C2H4
°2
NH3
Tar
C,.H, (equiv)
b o
cs
Phenol (organics)
1.366
0.385
1.042
3.154
7.468
1.529
0.717
0.223
5.45
6.776
1.102
0.078
0.013
0.325
0.029
-43-
-------
TABLE 4-6 (Continued)
5. Quench Water
Feed Rate: 500 gallons per ton
of coke
Evaporation Rate: 35%
6. Weak Ammonia Liquor
Recycle Rate, gal/ton of coal 1,430
7. Wash Oil Recirculation Rate in the 15°
Light Oil Recovery Unit, gal/ton of coal
8. 75% of the total naphthalene in the coke oven
raw gas is recovered from the final cooler
skimmer basin.
9. Overall Sulfur Removal 90%
Through the Vacuum Carbonate System
-44-
-------
HOT COKE OVEN GAS
f
FUGITIVE EMISSIONS
COAL HANDLING
PREPARATION
<£>
COKE OVENS
X"
COMBUSTION
''5s
&'
AIR
-*- TO PAGE 2
FLUE GAS
UNRECOVERED COKE
BREEZE a EVAPORATED WATER
<1>>
>v-
HOT COKE
1
QUENCH
STATION
^QUENCHED
" COKE
RECYCLE
QUENCH
QUENCH WATER RECOVERED COKE BREEZE
a SPENT QUENCH WATER
. RECYCLE COKE-OVEN GAS
+ FROM PAGE 4
Figure 4-1 (Pg. 1 of 4). Detailed block^flow diagram of a byproduct coke oven plant.
-------
RECYCLE AMMONIA LIQUOR (TO SPRAYS)
/£s HOT COKE OVEN ^
S/ GAS.FROM
PAGE 1
COAL TAR <
TAR SLUDGED
8.3 TPO ~"
1
COLLECTING MAIN
a
PRIMARY COOLER
i
t
CONDENSED '
TAR
i
TAR
SEPARATOR
/ftv
1
i
LIQUOR
STORAGE
i
1
^C rvHAiiCTri) fc ELECTROSTATIC _ _v_ ^.70 RFHEATFR
*. EXHAUSTER + PRECWTATOR PAGES
<$>
ADDITIONAL TAR PARTICLES
i
WASTEWATER <^> pHpNQL ^ ^ T0 NHs STILL
w REMOVAL PAGE 3
SODIUM PHENOLATE
Figure 4-1 (Pg, 2 of 4). Detailed block flow diagram of a byproduct coke oven plant,
-------
SULFURIC
ACID
EVAPORATED WATER
EVAPORATED WATER,350 TPD
RECYCLE COOLING WATER
COOLfNG
TOWER
FROM PHENOL REMOVM,
PAGE a
FINAL
COOLER
MAKE-UP
WATER
AMMONIUM SULFATE
-25 % AMMONIA VAPOR
WATER
NAPHTHALENE
COKE OVEN GAS
TO WASH OIL SCRUBBER,
PAGE 4
LfVE STEAM
EFFLUENT DISCHARGE
NAPHTHALENE
SKIMMER BASIN
WASTEWATER SLOWDOWN
RECYCLED TO COKE
QUENCHING
, MAKE-UP WftTER
256 TPD
NAPHTHALENE (8 TAP
Figure 4-1 (Pg. 3 of 4). Detailed block flow diagram of a byproduct coke oven plant.
-------
COKE OVEN GAS FROM FINAL COOLER PAGE 3
WASH OIL
SCRUBBER
(VACUUM
CARBONATE)
I
MAKE-UP
TO COKE OVENS
PAGE 1
v |No2C03
H2S ABSORBER/i
ACTIFIER/ |
STEAM EJECTORS
CLEAN COKE OVEN
GAS
WASTEWATER RECYCLED
TO COKE QUENCHING
WASH OIL
STRIPPER
. i w CTPAM
LIVE STEAM
GAS
CONDENSERS/
SEPARATORS
LIGHT
OIL
- DECANTED WASTEWATER
WASH OIL RECYCLED TO COKE
QUENCHING
-fr-SULFUR
CLAUS I3.24TPD
PLANT
TAILGAS
Figure 4-1 (Pg. 4 of 4). Detailed block flow diagram of a byproduct coke oven plant.
-------
Coal or Coke
Tar
Light Oil
Ammonia
Water
CO
H2
CH/i
02
C2N2
CS2
H2S
Cyanides
Phenol
Napthalene
Wash Oil
Na2C03
Others
TOTAL
TABLE 4-7 MATERIAL BALANCE 01' A 5000 TI'D COKE OVEN PLANT
FLOWS, TPD
1
Coal From
Handling
4,800
200.0
2
Fugitive
Emissions
5.5
0.45
3.18
8.7
1.8
3
Hot Coke
Oven Gas
267.0
55.1
10.6
338.95
154.5
68.3
19.2
52.1
364.6
74.7
35.9
3.9
0.7
16.2
1.25
4 5
Recycled
Hot Coke Oven
Coke Gas
3517.2
16.92
61.8
27.32
7.68
19.33
145.84
29.88
14.36
0.64
0.28
0.65
Trace
Trace
6 7
Combustion Flue
Air Gas
631.07
3233.4 3241.04
614.9
55.3
985.9
5,000
0.15
19.8
Quencher!
Coke
3264.9
101.0
10
Total
Quench
2915.0
7325.0
Trace
Trace
1463.0
3517.2
324.7
4219.3
4544
3365.9
2915.0
7325.0
(continued)
-------
TABLE 4-7. (Continued)
11
12
13
14
15
16
17
18
19
20
21
Coal or Coke
Tar
tight 0:1
Amonla
Water
CO
H2
N2
O>2
CH*
02
C2N2
CS2
H2S
Cyanide*
Phenol
H2S04
Unrecovered
Coke Breeze
and Evapo-
rated Water
2.3
2,564.0
Recovered
Coke Breeze C.O.C.
and Spent Condensed to
Quench Water Tar Exhauster
2SO.O
244.13 22.87
2.8 52.3
309.65 7.95
250.0 29.729.4 82.5
154.5
68.3
19.2
52.1
364.6
74.7
35.9
3.5
0.7
16.2
C.O.C. Additional
To Electro- Tar Coal
Static Preclp. Particles Tar
2.29 22.85 258.69
52.3 2.8
7.95 0.06
82.5 5.45
154.5
68.3
19.2
52.1
364.6
74.7
35.9
3.5
0.7
16.2
Liquor Liquor Liquor
to Recycle to
Storage Liquor Phenol NH Still
309.59 307.0 2.59 2.59
29.723.9 29.473.0 250.9 250.9
Trace
Trace
40.49
89,32
0.50
0.50
0.75
40.49
89.32
40.15
88.57
0.34
0.75
0.34
Napthaleoe
Waah Oil
Others
TOTAL
2,566.3
500.0
30,415.8
955.8
935.2
23.60
267.0
30,163.3 29,908.7 254.6
253.8
(continued)
-------
22
Sodium
Phenolate
23
C.O.G.
to
Reheater
24
C.O.G.
to
NH,. Removal
TABLE 4-7. (Continued)
25 26 27
Steam to
NH
Still3
Uastewater
From
NH, Still
25% Nil
to NH§
Removal
28
to
NH. Removal
29
Makeup
to
Removal
H20
30
Ammonium
Sulfate
31
Evaporation
H20 from NH3
Removal
I
Ui
H
Coal or Coke
Tar
Light Oil
Ammonia
Water
CO
H2
N2
C02
02
C2N2
CS2
H2S
Cyanides
Phenol
H2SO/,
0.75*
0.02
52.3
7.95
82.5
154.5
68.3
19.2
52.1
364.6
74.7
35.9
3.5
0.7
16.2
0.02
52.3
7.95
82.5
154.5
68.3
19.2
52.1
364.6
74.7
35.9
3.5
0.7
16.2
0.50
Napthalene
Wash Oil
Na2C03
Other*
TOTAL 0.75 933.0
*Phenol content of sodium phenolate
0.50
933.0
42.25
0.03
285.45
2.57
7.70
10.00
254.8
0.04
9.95
0.34
29.99
42.25
285.82
10.27
39.99
254.8
40.39
40.4
(continued)
9.95
** About 50 mg/1 free cyanide and the remainder as thiocyanates.
-------
TABLE 4-7. (Continued)
32
C.O.C.
co Final
Cooler
33
Water &
Naphthalene
Final Cool
34
Naphthalene
&
Tar
35
Waatewater
Slowdown
36
Recycle
Cooling Water
to Final Cooler
37
C.O.C.
to Wash Oil
Scrubber
38
Light Oil
to
Stripping
39
Live Steam
to Light Oil
Stripper
Tallgaa
41
Recycled
Wash Oil
Coal or Coka
Tar
Light Oil
Aononla
Wacar
CO
H2
N2
C02
CH4
r-iH/i
02
C2N2
1 CS2
J-n H2S
1 Cyanldaa
Phenol
H2SOA
(HU4)2S04
Napthalana
Utah Oil
Othara
TOTAL
0.02
52.3
0.11
345.0
154.5
68.3
19.2
52.1
364.6
74.7
35.9
3.5
0.7
16.2
0.50
1187.63
0.02
4.04
11,130.
3.3
16.5
0.91
1154.9
0.02
0.98
1.0
0.11
209.
3.93
10827.0
0.09
0.45
3.22
16.1
51.32
42.30
154
68
19
52
364.6
74.7
35.9
3,5
0.7
16.2
0.05
53.96
250
5.2
250
209.65
10850.25
883.27
0.02
0.05
2602.44
2906.47
250
31.1
2602.44
2607.64
(continued)
-------
TABLE 4-7. (Continued)
42
Light Oil to
Condenser/
Separators
43
Light Oil from
Condenser/
Separators
44
Wash Oil from
Condenser/
Separators
45 46
Uastewater from C.O.G.
Condenser/ to
Separators 112S
47 48
Acid
Na2C03 Gas
49
Waste-
Water
from H2S
50
Clean
C.O.C.
51
Product
I
Ul
Coal or Coke
Tar
Light Oil
Ammonia
Water
CO
H2
N2
C02
02
C2N2
Cyanides
Phenol
H2S04
Napthal^ne
Wash Oil
N82C03
Other*
TOTAL
48.76
250.00
0.02
0.05
2.44
301.27
48.76
250
0.02
0.05
48.76
2.44
2.44
250.07
2.57
42.30
154.
68.
19,
52.
74.
35,
364.6
3.4
0.7
16.2
Trace
834.47
7.3
3.78
14.58
1.54
0.27
7.57 19.9
2.57
232.3
0.28
Trace
0.27
235.42
42.3
154.5
68.3
19.2
52.1
364.6
74.7
35.9
1.58
0.7
1.62
25.38
92.7
40.98
11.52
32.76
218.76
44.82
21.54
0.95
0.42
0.97
815.5
490.8
-------
TABLE 4-8 SUMMARY OF AIR EMISSIONS - 5000 TPD BYPRODUCT COKE OVEN PLANT
(Emissions are in tons per day.)
Ln
f
Stream
Fugitive Emissions
Flue Gas
Unrecovered
Coke Breeze and
Evaporated Water
Evaporated Water
(Cooling Tower
& Others)
Claus Tail Gas
Totals
Total Flow Partlculate
(TPD) Matter
SO,
CO
H-C
NO
19.8
4544
5.5 (Tar)
0.05 3.18 10.52 0.10
1.69 55.3
2566.3** 2.3 (Coke
Breeze)
360.0
31.103
7,521.203 7.8
0.096
1.836 3.18 65.82 0.10
NH3
0.45
0.45
614.9 3241.04 631.07
2564.0
360.0
5.32 25.508 .179*
620.22 3,266.548 3,555.07 .179
* Includes .015 and 0.096 TPD of CS~ and COS, respectively.
** Fugitive emissions from cooling tower and coke quenching with contaminated water may lead to
substantial air pollution problem. The quantity of these pollutants has not been ascertained.
-------
TABLE 4-9. SUMMARY OF PROCESS WASTEWATER - 5000 TPD BYPRODUCT COKE OVEN PLANT
(Wastewater Contaminants, tons/day)
Stream No.
20
35
45
49
Totals
Total Flow
(TPD)
254.58
209.65
250.07
232.58
946.88
Water
250.9
209.0
250.0
232.3
942.20
Phenol
0.75
0.45
0.05
Trace
1.25
Cyanides
0.34
0.09
0.02
0.28
0.73
Ammonia
2.59
0.11
-
-
2.7
-------
Solid wastes quantities generated by the model plant are the following
(water free basis): 250 tons/day coke breeze; 8.3 tons/day of tar sludges;
and 19 tons/day of bio-sludges.
Process Description
Bituminous coal containing about 30 percent volatile matter and 4 percent
water is crushed to about 1/8-inch size in a hammer mill and then fed to the
coke ovens. Three batteries of coke ovens, each battery containing 85 ovens,
are provided. Coking temperature and cycle are 900 C and 17 hours, respectivelj
At the end of the coking cycle, hot coke is quenched with water in a quench
station.
From the coal handling, preparation and coke oven operations, approximately
19.8 TPD of fugitive emissions are lost to the atmosphere. In the quenching
operation, 2.3 TPD of fine coke breeze is emitted to the atmosphere as well as
large amounts of evaporated quench water.
During coking of the coal, raw coke oven gas is evolved containing a
mixture of gases, entrained solids, various products and pollutants such as
cyanide, hydrogen sulfide and phenol.
The crude gas leaves the ovens through standpipes and passes into a gas
collecting main. There, the temperature of the gas is reduced from approxi-
mately 800 to 1,300°F to about 175 to 200°F by spraying with recycled ammonia
liquor. This reduction in gas temperature causes condensation of approximately
75 percent of the tar in the gas together with a small portion of ammonia.
The condensed ammonia appears as excess ammonia liquor, which is sent to an
ammonia stripping operation.
From the collecting main, the gas passes to the primary coolers where it
is cooled to about 85 to 104 F by ammonia liquor spray. This cooling removes
additional tar, and again, a small portion of the total ammonia in the gas.
The gas is next conducted to an exhauster (positive displacement type) which
serves not only to compress the gas but also to remove tar by the high-speed
swirling motion imparted to the gas.
The gas passing through the exhausters still contains traces of tar fog
which is further reduced by electrostatic precipitators. The tar drains from
the bottom of the precipitators into a settling pit which also collects the
tar removed from the collecting main and primary coolers. It is then pumped
-56-
-------
from the pit and transferred to a storage tank where excess water is decanted.
This tar, containing about 2 percent moisture, is sold to chemical companies
for processing and recovery of valuable aromatic compounds.
The excess ammonia liquor which results from gas cooling in the collecting
main and primary coolers is pumped from liquor storage to a phenol removal
unit. Here, phenol is extracted from the liquor through use of a solvent such
as a light oil fraction, and recovered as sodium phenolate by treatment with
caustic.
The liquor is then sent to an ammonia stripping unit, where ammonia is
removed by contact with live steam. The stripped liquor is discharged to
waste treatment (physical/chemical or biological), and the vapor stream,
containing 25 weight percent of ammonia, joins the detarred coke oven gas
stream in entering the ammonia removal unit.
In the ammonia removal unit, the combined gas stream flows through an
absorbent tower into which is sprayed a dilute sulfuric acid solution. The
sulfuric acid reacts with the ammonia to produce ammonium sulfate. The
ammonium sulfate eventually reaches a saturation point in the solution, and
begins to crystallize. The crystal slurry is pumped to a centrifuge, where a
cake is produced and dried in a rotary drum dryer to about a 0.1 weight percent
moisture content.
In some plants, a crystallizer is equipped with a barometric condenser
which uses a large quantity of water. An example of this process is the
Wilputte process.
After the ammonia removal unit, the gas passes through the final coolers
where direct contact water is used to cool the gas to a temperature of 70 to
90 F. A major portion of the naphthalene condenses out of the gas due to this
cooling. The naphthalene is recovered from the cooling water at the settling
basin where it is skimmed off as it rises to the top. It is either added to
the tar or is processed further to produce a commercial product.
The cooled coke oven gas is scrubbed with a petroleum wash oil. The gas
comes in direct contact with the wash oil in one or more scrubbing towers
containing packing and interlocking sprays. The flow of gas and wash oil is
counter-current in each tower, and counter-current over the entire multi-tower
system. The wash oil absorbs the light oil so that the benzolized wash oil
contains 2 to 3 percent light oil. From 90 to 95 percent of the light oil
content of the gas is recovered in this operation
-57-
-------
The wash oil is debenzolized by steam distillation. The carryover of
wash oil into the light oil is kept to about 5 percent and the debenzolized
wash oil contains 0.2 percent light oil. The mixture of light oil and steam
exists the top of the stripping column, is condensed, and separated. The
light oil is sent to the Houdry LITOL process for refining of benzene and
other components.
The gas, after being stripped of light oil, is next sent to the desulfur-
ization unit for sulfur removal. Many desulfurization processes are available,
however, the Vacuum Carbonate process has moved into commercial prominence.
In the Vacuum Carbonate process, the gas is contacted counter-currently
with a solution of sodium carbonate in an absorber tower to remove the hydrogen
sulfide and other impurities such as hydrogen cyanide. The foul solution from
the base of the absorber is circulated over the actifier where the hydrogen
sulfide is removed by counter-current stripping with water vapor under vacuum.
The actified solution is pumped from the base of the actifier through a cooler
to the absorber to complete the cycle. The acid gas, Stream No. 48, is sent
to ,a Claus plant for sulfur recovery.
After desulfurization, approximately 40 percent of the product gas is
returned to the coke ovens as a fuel source.
OTHER COKE OVEN PROCESSES
Beehive Process
The only product recovered from the Beehive ovens is the coke itself.
Approximately 1,200 pounds of coke per ton of coal are recovered.
Raw waste loads from the Beehive oven are a function of coking time,
water use systems, moisture and volatility of the coal, and carbonizing
temperature of the ovens. However, the raw waste is affected most by the type
of water use systems, that is, once-through or recycle. Table 4-10 summarizes
the net plant raw waste load from three selected plants. Raw waste loads are
presented only for the critical parameters which include ammonia, BOD,-,
cyanide, phenol and suspended solids.
For the Beehive coke plant, the majority of the emissions emanate from
the oven door during watering-out and drawing of the coke. The estimated
nature and quantity of these emissions based on one ton of coal input are:
-58-
-------
TABLE 4-10. CHARACTERISTICS OF BEEHIVE COKE PLANT WASTES
(Net Plant Raw Waste Load)
Characteristics Plants
I 1 1
Flow, 1/kkg 2,040 2,040 513
Ammonia, mg/1 0.33 0 0
BOD, mg/1 3.00 0 0
Cyanides, mg/1 0.002 0 0
Phenol, mg/1 0.011 0 0
Suspended Solids, mg/1 - 29 722
1^ Data obtained from Bibliography 21.
-59-
-------
Particulates - 200 Ibs
Carbon Monoxide - 1 lb
Hydrocarbons - 8 Ibs
Ammonia - 2 Ibs
Low Temperature Processes
In low temperature coke manufacturing applications, the main objective is
to obtain maximum yields of liquid products and semi-cokes containing from 8
to 20 percent volatile matter. Here again, the characteristics and yields of
the various products and byproducts depend upon the coal, the temperature and
the treatment.
One ton of coal would yield on an average the following products and
byproducts:
Pounds
Semi-coke (char) 1,440
Tar (15.8 gal) 150
Ammonia, anhydrous 5
Light oil (2.5 gal) 16
Gas (3,720 scf) 250
1,861
The balance (139 Ibs) probably consists mostly of condensed moisture,
small amounts of pollutants (e.g. particulates, phenols) in the process
wastewater and the fugitive air emissions. However, this assumption needs
verification, since the data varies among different references in the
literature.
The typical clean gas composition is as follows:
Constituent Volume %
Co2 9.0
C H 8.0
n m
CO 5.5
H2 10.0
CH, and Homologs 65.0
N2 2.5
No information on the wastewater and air emission was available from the
literature reviewed. There is no commercial or developmental low temperature
coke oven process in the United States.
-60-
-------
SECTION 5
COAL GASIFICATION PROCESSES AND THEIR WASTE CHARACTERISTICS
COAL GASIFICATION PROCESSES
In contrast to coke oven gas which is produced from distillation
(carbonization) of coal, coal gasification process gases are produced by a
combination of the following mechanisms:
Distillation of coal by heating;
Reaction of solid coal with oxygen and steam; and
Reaction of various intermediate gases.
Four principal chemical reactions occur in a gasification reactor:
Standard Enthalpy Change
@ 1,200°K
(1) C + HO * »T CO + H - 32,457 cal/g.mol
(2) CO + H20 « » C02 + H2 + 7,838 " " "
(3) C + 2H2 «, » CH4 + 21,854 " " "
(4) C + 1/2 02 *" » CO + 26,637 " " "
Reaction (3) demonstrates the formation of methane, which is favored at
low temperatures (below 1,000 F) and high pressures. High temperature and low
pressure gasification processes (e.g., K-T process) do not produce much methane
in the gasifier reactor.
Besides the above four reactions, other chemical reactions and devolatil-
ization of coal in the gasifier result in the formation of byproducts and
trace pollutants, such as:
Gases containing reduced sulfur compounts - (H_S, COS, CS?, etc.)
Gases containing nitrogen compounds - (NH_, HCN, etc.)
Hydrocarbons
Heavy metals/trace contaminants.
-61-
-------
Most of the above mentioned byproducts and pollutants are also found in
the coke oven raw gases.
Approximately 68 different gasification processes have been used
commercially in the past or are currently under development. Most of these
systems, however, were retired or did not achieve commercial status because of
the availability of less costly natural gas. Prominent gasification processes
(fourteen) of current and potential interest are shown in Table 5-1 along with
their expected products and byproducts.
Principal sub-divisions of coal gasification processes are differentiated
by low-, intermediate- and high-temperature operations. The type of reactor
bed (fixed, fluidized or entrained) is also another operating variable. The
low-temperature and fixed-bed processes tend to show a complete product and
byproduct slate similar to the coke oven process. As the temperature of
gasification increases* recoverable quantities of heavier tars begin to
diminish in preference to increasing lighter molecular weight products.
Operating pressure also affects the yields, as shown in Table 5-1. As the
pressure increases, the product slate tends towards the heavier molecular
weight substances.
A coal gasification plant consists of many unit operations/processes. A
block flow diagram of a hypothetical synthetic natural gas plant is shown in
Figure 5-1. The plant is comprised of the following major areas:
1. Coal Storage, Preparation and Feeding;
2. Gasification and Gas Cleaning;
3. Product Upgrading (Methanation);
4 Byproduct Recovery and Upgrading; and
5. Waste Treatment.
The basic steps to produce a synthetic natural gas (SNG) fuel are as
follows: First, coal is prepared to the desired size by crushing, removing
fines and drying the coal (if necessary). The coal is then either fed to the
gasifier or, if it is a caking coal and the process cannot operate with such a
coal, it is pretreated with heat to prevent the formation of coke.
The coal is then reacted with oxygen and steam in the gasifier. (Note:
If the final product gas is to be a low-Btu gas, then air can be used instead
of oxygen.) Pertinent chemical reactions and the devolatilization step mechanism
which generates the raw gases within the gasifier have been previously discussed.
-62-
-------
OJ
TABLE 5-1
COAL GASIFICATION PROCESSES PRODUCT/BY-PRODUCT AND FUEL SYSTEM SIMILARITIES
LEGEND:
P - Product/Bv-Product
present in recoverable
quantities.
Neg. - Negligible or small
amounts present.
- Stream present in traces.
N.A. - Information not
available, not com-
plete, or not reported
at this time.
1*roduct!/By-Products
High BTU Gas - SNG
Low (Intermediate)
BTU Gas
H2S - Acid Gas/Sulfur
Ammonia
Phenols
Naphthas/Benzenes
Tar Oils/Light Oils
Tars
Char/Unreacted Coal
Ash/Slag
CLASSIFICATION OF FUEL SYSTEMS
Low Temperature
Fixed Bed
Low
Pressure
Wellman - Galusha
P
P
P
P
P
N.A.
P
-
P
-
Intermediate
Pressure
'§»
3
_)
P
P
P
P
P
P
P
P
-
P
BGC/Lurgi
Slagging Gasifier
P
P
P
P
P
P
P
P
-
P
Pressurized Stirred Fixed
Bed - Morgantown
-
P
P
P
P
-
P
P
P
P
Intermediate Temperature
Fluidized Bed
Low
Pressure
k*
a>
jf
c.
P
P
P
NA
Neg.
-
-
-
P
-
Inter-
mediate
Pressure
8
en
1
=3
-
P
P
P
Neg.
N.A.
Neg.
Neg.
P :
-
High Pressure
Synthane
P
-
P
P
P
P
P
P
P
-
|
P
_
P
P
P
P
P
-
P
-
High Temperature
Entrained Bed
Low
Pressure
.*
Q)
2
O
e
8.
n.
o
X
P
P
P
Neg.
-
-
-
-
-
P
High
Pressure
S
. CD
.J.
00
P
-
P
P
-
-
-
-
-
P
Dolomite
Acceptor
Intermediate
Temperature
Intermediate
Pressure
S
I
0
<
CN
0
o
P
-
P
P
N.A.
N.A.
N.A.
N.A.
P
-
Westinghouse-Advanced
Gasifier
_
P
P
N.A,
-
-
-
-
-
P
Coal
Pyrolysis
Entratnet
Inter.
Temp.
Low
Pressure
**
' S
E
S o
II
P
P
P
P
-
-
-
-
-
P
Fluid Bed
Inter.
Temp.
Inter.
Pressure
Garretts Coal
Gasification
P
P
P
N.A.
-
-
-
P
P
-
-------
CM!
Figure 5-1. Hypothetical coal gasification flow diagram.
-------
The raw gases are next processed through the gas cleaning and purification
steps to remove tar, particulate matters and sulfur compounds.
The raw gases produced in the gasifier do not have the proper proportion
of CO and H necessary to form SNG or synthesis gas. A shift catalyst reactor
unit is introduced to produce appropriate gas mixtures. In the shift reactor,
any desired ratio of carbon monoxide and hydrogen can be achieved by varying
the amounts of steam and carbon dioxide as demonstrated by the following
reaction:
CO + H_0 "" ». H0 + C0_, A H° =9.9 Kcal/mol
2 2 2 25°C
(Note: If hydrogen is the desired final product, the carbon monoxide is all
converted to carbon dioxide and hydrogen; carbon dioxide is then scrubbed from
the gas by any of several available processes.)
If a high Btu gas (SNG) is the objective, then the required ratio of
hydrogen to carbon monoxide is 1:3. The following chemical reaction (called
methanation) is employed:
CO + 3H, * » CH, + H.O, A H° = 49.3 Kcal/mol
Z * -* 25°C
The methanation reaction is highly exothermic; consequently, heat removal
methods are the dominating feature of the different developing processes.
The Byproduct recovery and waste treatment aspects of the coal gasification
processes will vary for each specific process, since the recoverable quantities
of byproducts and the waste characteristics are dependent on gasifier operating
conditions. The feed coal characteristics also significantly affect the
quantities of products and byproducts generated from a process. Adequate
literature information is unavailable to establish the effects of coal types
on the distribution of products and byproducts for different gasification
processes. Table 5-2 shows the quantities of products and byproducts generated
by a few selected processes.
Figure 5-2 illustrates the Byproduct recovery scheme and the distribution
of the various byproducts from a Lurgi plant that will produce 288 SCFD of
synthetic pipeline quality gas. A sizable portion of the byproducts are
absorbed in, or condensed with, the organic and aqueous condensates as the
gases are quenched with water and then cooled. The heavier tars separate out
first in the gasifier waste heat boiler and are called "tarry gas liquor."
Further downstream, in the gas cooling section, the tar oils with the remaining
-65-
-------
COAL
TEAM
OXTWN
Y M00UCT
TREATMENT
BYPRODUCT
STOAAOE
TO UCTHAMATKM
VENT
TAR
TAR (ML
CONTAMINATED S\ CltUi
WATEH WATER |f _,Q
VENT
CRUDE
PHENOL
VENT
1
AQUEOUS
AMMONIA
VENT
LIQUID
tULFUR
VENT
NAPHTHA
Figure 5-2. Byproduct from Lurgi Plant,
-------
TABLE 5-2. PRODUCTS/BYPRODUCTS OF DIFFERENT COAL GASIFICATION PROCESSES
(SOURCE - Bibliography 35)
Char/Ash, Ib/hr
(Slag)
Coal, Ib/hr x 106
Feed Coal
Sulfur Content (%)
Wellman
Galusha
28.
170
177
1,153
120
219
1,768
0.
Bitum.
3.
Lurgi
4 288
(SNG)
15,600
88,800
48,600
11,300
21,400
20,000
(naphtha)
476,000
(ash)
021 1.94
9 1.07
Koppers
Totzek
524
290
23,600
Neg.
Neg.
Neg.
Neg.
24,400
(ash, slag)
0.7
3.8
Bumlnes
Stirred Bed
995
160
24,200
75,600
11,100
114,100
(ash)
0.7
W. Ky. #9
3.9
Winkler
912
280
50,400
Neg.
To Glaus
372,500
(char)
1.68
Lignite
Syn thane
250
(SNG)
11,400
43,200
4,000
13,200
7,400
(BTX, naphtha)
362,000
(char)
1.18
Pitts Seam
1.6
Hygas
260
(SNG)
55,500
1,300
11,300
39,800
139,000
(char)
1.06
111. #6
4.75
Note: "SNG" signifies Synthetic Natural Gas.
-------
tars condense out, forming the "oily gas liquor." In the acid gas removal
step, H?S and naphtha separate. Naphtha goes directly to a storage tank.
H_S-containing acid gases are further processed to recover the sulfur. Table
5-3 gives the material balance for the gas liquor treatment.
Acid Gas Removal and Sulfur Recovery
The acid gas removal unit removes sulfur compounds, carbon dioxide and
any other material which would interfere with the methanation or synthesis
step that follows. The unit processes involve chemical or physical absorption
of the acidic materials in a suitable liquid with subsequent desorption of the
acid gases at a lower pressure (in some cases higher temperature) to regenerate
the absorbent.
Among the many acid gas removal processes, the following are the most
widely considered for coal conversion systems:
Chemical Processes Physical Processes
Hot Carbonate System Rectisol CMethanol Solvent)
Amine System Selexol (Dimethoxy Tetraethylene Glycol)
Stretford Process
In the coke oven industry, only the chemical solvent type acid gas removal
processes have been commercially utilized. The physical solvent type processes
will be more applicable when the raw gas is at a higher pressure (which obviously
cannot be related to the coke oven process since it operates near atmospheric
pressure). Detailed discussions of the coke oven gas desulfurization processes
and their applicability to coal conversion systems are given in Section 7.0.
Table 5-4 shows the acid gas removal processes that have been considered in a
(39)
recent study for various gasification processes.
The Stretford process not only removes acid gases from the gaa; but, it
also recovers byproduct sulfur. Therefore, it is also considered a sulfur
recovery process. Other processes listed above, produce a concentrated acid
gas stream (rich in hydrogen sulfide concentration) which requires further
control through a sulfur recovery and tail gas unit to meet air pollution
control regulations. The two most common sulfur recovery processes are the
Glaus and Stretford. The Stretford process is economic when the acid gas
-68-
-------
STREAM NUMBER
11.1
11.2
TABLE 5-3. MATERIAL BALANCE FOR GAS LIQUOR TREATMENT
11.3 11.4 11.5 11.6 11.7 11.8
11.9
11.10
11.11
TOTAL (Ib/hr)
277,450 1,314,800 62,165
103,000 48,600 88,800
11.12
Stream Description
Phase
Component (Ib/hr)
Water
Tar
Tar Oil
Recoverable Crude Phenol
Unrecoverable Phenol & Organic
Ammonia
H-S
c82
CO'1
CH,
Monohydric Phenols
Polyhydric Phenols
Other Organics
Contained Sulfur
Naphtha
Tarry Gas
Liquor
Liquid
165, 000
79,900
14,600
210
130
300
17,200
70
40
Oily Gas
Liquor
Liquid
1,180,000
8,900
34,000
11,100
4,100
21,600
300
54,800
Expansion
Gas
Gas
2,030
315
59,700
70
50
Process
Condenaate
Liquid
103,000
__
Tar
Oil
Liquid
48,600
__
__
(73)
Contaminated
Gas
Tar Liquor
Liquid Liquid
164,000
88,800
_
3
70
60
(240)
Crude
Phenol
Liquid
__
9,100
1,600
560
Acid
Gas
Gas
8,870
280
8,570
Clean
Water
Liquid
1,190,000
240
__
24
900
3,200
Aqueous
Ammonia
Liquid
82,000
21,400
10
3,660
--
Naphtha
Liquid
__
20.000
164,133 11,260 17,720 1,194,364 107,070 20,000
-------
TABLE 5-4. ACID GAS REMOVAL PROCESSES FOR COAL GASIFICATION SYSTEMS
(SOURCE - BIBLIOGRAPHY 39)
Gasification Process
Lurgi
Synthane
Bigas
Hygas
Koppers-Totzek
U-Gas
Winkler
% H S in acid
gas feed
(on dry basis)
1.10
1.50
14.6
29.8
23.1
17.9
15.0
Preferred
Acid Gas
Process
Rectisol
Hot Carbonate
(Benfield)
Hot Carbonate
(Benfield)
Rectisol
Methyl diethanolamine
Selexol
Hot Carbonate
(Benfield)
Type of S
Guard
Zinc or
Iron Oxide
Zinc or
Iron Oxide
Zinc or
Iron Oxide
Zinc or
Iron Oxide
Not needed
Not needed
Not needed
-70-
-------
contains less than 15 percent H S, whereas the Glaus process is more economical
above a 15 percent H S inlet concentration. Both Glaus and Stretford have
been utilized in coke oven plants and should have applications in coal con-
version systems.
The sulfur content of the gas leaving the acid gas absorption system is
decreased further, usually by reaction with iron oxide or zinc oxide. This
step is necessary to protect the methanation or synthesis catalyst, which is
highly sensitive to sulfur compounds. In the coke oven plants, the iron oxide
process is frequently used to remove sulfur compounds.
Waste Characteristics and Comparisons
At present, the nature of the waste characteristics from coal gasification
and liquefaction plants have been described mostly in qualitative terms. Much
of the published quantitative information is based on pilot systems which may
not be indicative of future commercial systems. The characteristics of waste
streams that are predicted for commercial systems, therefore, are based on
engineering analysis of the coal conversion processes and related operations,
such as coke ovens and coal preparation plants.
Wastewaters
The following major wastewaters are associated with coal gasification
systems:
1. Quench and condensate waters from gasification;
2. Wastewater from the shift and methanation (or synthesis) units;
3. Coal pile runoff; and
4. Miscellaneous waters, e.g., storm water runoff, boiler blowdown, etc.
Detailed characteristics of these wastewaters for the different types of
coal gasification processes are not available. However, many studies are in
progress under DOE and EPA sponsorship to develop additional information.
Coal pile and storm water runoffs will contain relatively less pollutants than
the process wastewaters.
The compositions of the quench and condensate waste streams from the
gasification process are expected to be dependent on the coal conversion
process, the operating conditions, and the coal type. The limited experimental
-71-
-------
data available indicate that those gasification processes which produce
byproducts similar to coke ovens (e.g. tars, tar oils, naphtha) will generate
wastewaters similar to the Byproduct coke oven process. This was illustrated
by the wastewater composition shown in Table 1-3 (abstracted from Tables 4-2,
5-3 and 5-5).
High temperature and low pressure gasification processes that do not
generate much byproduct (e.g. K-T process), on the other hand, will generate
low concentrations of contaminants in the process wastewater and are not
comparable to the Byproduct coke oven process.
Coal type and composition have significant effects on the process waste-
water. This is illustrated in Table 5-5, where the effect of various coals on
Synthane wastewaters are shown. These data were obtained from a laboratory
scale operation of the Synthane process.
Approximately 60 to 80 percent of the toal organic carbon in the coke
oven and coal conversion wastewater appears to be phenolic in nature consisting
of monohydric, dihydric and polyphenols. Singer, et al. have recently reported
the breakdown of the phenolics and other organics in the coal conversion
(58)
wastewater
Gaseous Waste Streams
The following major gaseous streams are associated with coal gasification
processes:
1. Raw product gas from the gasifier;
2. Acid gases from the acid gas removal unit;
3. Cooling tower emissions;
4. Flue gases from the utility boilers; and
5. Fugitive emissions, e.g. from coal pile, compressors, storage
tanks, etc.
The characteristics of the raw product gas and the acid gases have been
discussed previously. Characteristics of the flue gases from the utility
boilers will be dependent on the type of fuel used in the boilers, e.g., raw
coal, processed clean product gas, or raw product gas.
No data is available on the fugitive emissions. Fugitive emissions
sources are: cooling towers; compressors; valves; flanges; coal pile; waste-
water and solid handling units; etc. The fugitive emissions are expected to
-72-
-------
TABLE 5-5. PROCESS WASTEWATER ANALYSIS FROM SYNTHANE GASIFICATION OF VARIOUS COALS
(All values in mg/1, except pH; Bibliography 26)
Illinois
No. 6
Coal
8.6
600
2,600
15,000
152
0.6
8,100
500
6,000
11,000
1,400
Wyoming
Sub-bit.
Coal
8.7
140
6,000
43,000
23
0.23
9,520
_
-
-
-
North
Dakota
Lignite
9.2
64
6,600
38,000
22
0.1
7,200
-
-
-
Western
Kentucky
Coal
8.9
55
3,700
19,000
200
0.5
10,000
-
-
-
-
Pittsburgh
Seam
Coal
9.3
23
1,700
19,000
188
0.6
11,000
-
-
-
-
- Data not available
-------
contain hazardous species that are in the raw product gas such as hydrogen
sulfide, carbon monoxide, and hydrogen cyanide. These pollutants are also
present in the coke oven fugitive emissions.
Solid Wastes-
The following are major solid waste sources from a coal gasification
plant:
1. Ash or slag from the gasifier;
2. Particulates from coal preparation;
3. Ash from coal burning in the Utility Boiler;
4. Wastewater treatment sludges; and
5. Spent catalyst from the methanation (or synthesis) reactor and shift
converter.
The ash or slag from the gasifier accounts for the largest quantitative
source of solid wastes, and these wastes contain the most numerous types of
contaminants including many heavy metals. Solid wastes of similar composition
are not generated in the coke oven industry.
Characteristics of the particulate matter from coal preparation and the
sludges from wastewater treatment will have some similarity between the two
industries.
-74-
-------
SECTION 6
COAL LIQUEFACTION PROCESSES AND THEIR WASTE CHARACTERISTICS
COAL LIQUEFACTION PROCESSES
The objectives of the U.S. coal liquefaction development programs are to
develop viable processes that will produce low-sulfur and low-ash products
from coal to be used as boiler fuels, heating oils, gasoline and chemical
feedstocks. Although none of the processes currently under development has
achieved commercial status, several have reached the pilot plant stage. Table
6-1 shows the processes of current and potential interest along with their
expected products and byproducts.
Since coal has only about 5 percent hydrogen compared to 9 to 11 percent
for fuel oils and 14 percent for gasoline, converting solid coal to liquid
fuels requires increasing the hydrogen content relative to carbon (H/C) in the
coal. Coal liquefaction processes increase the H/C ratio either by adding
hydrogen to the coal or by removing part of the carbon as is done in the coal
pyrolysis processes. Pyrolysis processes that developed from coke oven
technology, however, yield small quantities of liquid products, since large
amounts of gaseous and solid char products are also produced. Table 6-1 shows
the four types of coal liquefaction processes: catalytic hydrogenation,
solvent extraction, hydrocarbonization, and pyrolysis.
In the catalytic hydrogenation and solvent extraction processes, the coal
is dissolved in process-derived solvent, and molecular hydrogen is added via a
hydrogen donor solvent. Three of the processes under these categories (SRC-I,
fl-Coal and Exxon Donor Solvent processes) have, thus far, received the most
concerted development effort. They will be discussed subsequently in detail.
Pyrolysis processes are similar to coal coking in that the coal is heated
to remove tars, gas and other volatiles leaving a coal char that is largely
carbon. Coal pyrolysis processes usually operate at low pressures (20 to 50
psia) and moderately high temperature (approximately 1,600 F).
-75-
-------
TABLE 6-1
COAL LIQUEFACTION PROCESSES-PRODUCT/BY-PRODUCT AND FUEL SYSTEM SIMILARITIES
LEGEND:
PPrnduct/ftv-Prnrtiirt nratnnt
in recoverable quantities.
Meg.- Negligible or (null amounts
present.
- Stream present in traces.
N.A. - Information not available,
not complete, or not reported
at this time.
Products/By -Products
High B.T.U. Gat - SNG, LPG, ethylene,
hydrocarbon, product gas.
Low Intermediate) BTU Gas -
Fuel Gas. Synthesis Gas
H2S Acid Gas/Sulfur
Ammonia
Phenols
Benzenes
Naphtha, Gasoline
Syncrudes
Middle Distillates, Fuel Oil
Gas Oils, Neutral Oils, Chemical Oils
Residual Fuel Oils
Tars (Tar Acids and Tar Bases)
Solvent Refined Coal
Cher/Coke/Unreacted Coal
Ash/Slag
CLASSIFICATION OF FUEL SYSTEMS
Catalytic Hydrogenation
3
P
-
P
P
Nag.
N.A.
P
P
P
P
P
-
-
P
P
S
£
j?
P
-
P
P
N.A.
N.A.
-
P
-
-
P
-
-
P
-
e
_o
sfii
N.A.
N.A.
P
P
P
P
P
P
P
P
P
-
-
N.A.
N.A.
Sefveffl Extraction
Non-Catalytic
Solvent
Hydrogenation
u
^ K
5 tr t>
P
P
P
P
-
P
-
P
-
P
-
P
P
P
Catalytic
Solvent
Hydrogenation
Ml
LU a c/S £
P
P
N.A.
N.A.
N.A.
P
-
P
P
-
-
-
-
P
HydroearbanbatiM
Intermediate
Temperature
g
a -a -p
3*1
p
p
p
p
p
p
-
p
p
-
p
-
p
-
High
Temperature
<3 CM
S*l §
££Z£
p
p
p
p
p
p
-
-
p
-
p
-
p
p
fc.-- at. »^-
Low
Temperature
Fluid Bed
Skis
lilS
SiSaS
-
P
P
N.A.
P
P
-
P
-
-
-
-
-
P
-
Intermediate
Temperature
Entrained
Bed
SI
p
p
p
N.A.
-
-
-
P
P
-
-
P
-
P
' -
-------
Hydrocarbonization is a refinement of the coal pyrolysis process. It
consists of carbonization of coal and thermal cracking of the heavy coal
liquids (tars) in a hydrogen atmosphere to produce fuel oil, distillate and
fuel gas. Hydrocarbonization operates at both a moderate pressure (500 psi)
and temperature (1000 F). The pyrolysis and hydrocarbonization processes are
the direct development of the Byproduct coke oven process. Their product/
byproduct slates are very similar. The waste characteristics are expected to
be similar also. However, insufficient data exist to verify this hypothesis.
Figure 6-1 shows the block flow diagram of a hypothetical coal liquefaction
process (hydrogenation or extraction type). The principal features of the
process are:
1. Hydrogenation reaction unit;
2. Separation unit (where gaseous products are separated from the
liquid and solid products);
3. Filtration (or solid separation) unit;
4. Acid gas treatment and sulfur recovery unit; and
5. Product fractionation and upgrading units.
The feed coal is crushed, dried, and slurried with a coal-derived solvent
(produced by the process) and fed to the liquefaction reactor in admixture
with gaseous hydrogen. Gas, liquid.and solid phases are produced in the
reactor by a series of complex chemical reactions which include decomposition
(depolymerization), hydrogenation, and rearrangement of the organic coal
structure.
The reactor effluent containing liquid products, solids and gases are
next separated for product and byproduct recovery. The separation schemes
vary for each process.
Separation of ash and unreacted coal from viscous coal liquids is a
difficult problem common to all liquefaction processes and has been the focus
of considerable development effort. Many techniques are being investigated,
including filtration, centrifugation, fractionation, and solvent separation.
In coal liquefaction processes, distinct patterns of product slates
(Table 6-1) do not readily emerge as in the coal-gasification processes.
-77-
-------
CM) Store.*,
Fttdinf ind Sytttnt Wtrtti
Convtrttr Output
Product! Md By Product!
D*o.,
Stud*
Co*l
Storift
1
Cotl
fVtpmtion
1
Slurry
Prtpartlion
9ud«t
Wrttr
(
4 (
I
I
!
__.
»j
Itlon
T
1
Alh ind Char
t
GM Production
t
' ,
Filttr Ciki
t
Fittritian
i
ConlHninited
Wirrr
4
Witir
Tri«tm«nl
Utilifition
1
_.___- Solution __^
RtoiiKirtkin
r&v
T i
Stptntlon -*!
T«Hfti
Trtilmint
i
i
PwrWicitlon t
Furl Cw
Jt t
( N»pht1>»
^~ "^ |" ~* Hydrotr««i-«nt "*
(tiphlhi
i -r x
_.,,,, ft f«"' «« . _»
-» FrKtiorwtlqn * Hydrotmnwm *
i J
j T T
jLi
Fuil Oil
Htm/ Product
s;rd
Figure 6-1. Hypothetical coal liquefaction flow diagram.
-------
However, the following observations can be made:
All liquefaction processes produce an acid gas stream which will
contain sulfur and other contaminants. In this regard, they are
similar to coal gasification processes which also produce an acid
gas stream. Consequently, H S removal and sulfur recovery will be
required for all coal processing plants.
Liquid product distribution shows a range from syncrudes to naphtha
and gas oils. However, all will contain varying amounts of sulfur,
nitrogen, and metal contaminants which will have to be removed by
subsequent upgrading treatments. Only the solvent refined coal
(SRC-I) process yields a solid fuel. In all other processes,
additional hydrogenation results in the formation of liquid products.
Almost all the processes produce a char (coke and unreacted coal
combined with ash) byproduct with some fuel value. These byproducts
will require additional processing (e.g., specially designed
combustion units) to utilize the carbon value. This will increase
the energy efficiency of the conversion process.
Phenols and/or ammonia will be present in the aqueous waste streams
in most cases and could be recovered as byproducts.
It is difficult to give quantitative yield data and waste characteristics
of coal liquefaction process since these are dependent on many variables such
as:
1. Coal type and composition;
2. Hydrogen consumption;
3. Liquefaction process and its operating conditions;
4. Hydrogen generation method;
5. Product specifications; and
6. Power generation method.
Unlike the coke oven process which uses a specific type of coal mix,
various coals can be used to produce liquid products. Yields will vary
depending on the coal composition. For example, the liquid yield is about 2.6
barrels per ton (B/T) of dry Illinois #6 coal, and about 2.3 B/T from Wyoming
(25)
coal for the Exxon Donor Solvent Process
-79-
-------
Hydrogen consumption in the process has a direct bearing on the quantity
and quality of the liquefied products. As an example, the hydrogen consumption
for the SRC-I process is about 2 weight percent of moisture-free coal; whereas,
it is approximately 4 weight percent for the H-Coal and the EDS process. Less
hydrogen consumption in the SRC-I process is the reason for its production of
mostly solid refined coal and a lesser amount of liquid products. If additional
hydrogen is consumed in the SRC system (by additional hydrogenation in the
reactor), more liquid products will be generated, as in the SRC-II process.
The liquefaction process and its operating conditions have a significant
effect on product type as illustrated in Table 6-2 for the three major processes.
Other variables such as reactor detention time, catalyst utilization, solvent
type and reactor type have an impact on product/byproduct yield. The lique-
faction reactor design for the SRC-I and Exxon Donor Solvent (EDS) process is
an upward plug flow type; whereas, the H-Coal uses an ebullated bed where a
catalyst is also added. The EDS process uses a solvent oil which has been
catalytically hydrogenated in a fixed bed reactor.
The method of hydrogen generation affects the product/byproduct slate and
the environmental aspects of the plant. Since the cost of hydrogen is a key
economic factor in coal liquefaction processes, various schemes are under
consideration to generate hydrogen from the byproducts of the coal liquefaction
(e.g., gasification of char and solid wastes, steam reforming of fuel gas).
The hydrogen generation plant is a large unit in the overall coal liquefaction
complex and its contribution to the plant waste streams would be significant.
The power generation plant is another large contributor to the general
waste streams. Methods of power generation will vary from plant to plant. In
order to decrease the complexity and number of variables, the power generation
unit and other auxiliary units such as the oxygen plant, the water treatment
unit etc. have not been considered in this report.
As the foregoing discussion shows, the potential variables are so numerous
that the material balance and quantitative yield data for a specific liquefaction
process can be presented meaningfully only when all the different variables
are considered in detail. (Also, comparison of one process with another will
not be meaningful if these variables are not fixed.) This has been done for
an example coal liquefaction plant for the SRC-I process.
-80-
-------
TABLE 6-2. OPERATING CONDITIONS OF THREE LEADING
COAL LIQUEFACTION PROCESSES
Process
H-Coal
Reactor
Pressure
(psia)
2,700-3.000
Reactor Hydrogen
Temp. Consumption
( °F) (scf/bbl product)
850 4,000-7,000
Product
Type
Syncrude or
fuel oil,
fuel gas
Exxon
Donor
Solvent
Process
1,500-2,500 700-900
5,000-6,000
Fuel oil,
naphtha,
fuel gas
SRC-1
1,000-2,400 625-850
1.5-3.0
wt% of
MF Coal
Solid boiler
fuel, naphtha,
fuel gas
-81-
-------
SRC-I PROCESS MATERIAL BALANCES
Design Basis
Based on the published information on the process conditions and operating
results from the Wilsonville and Fort Lewis SRC pilot plants, a conceptual
design for a 20,000 TPD coal feed SRC-I plant was prepared and is discussed
here. The data obtained at Wilsonville in Runs 70 through 81 and at Fort
Lewis in Runs 4 through 9, using Kentucky #9 and #14 coals and solvent of
boiling range 450 to 780 F, were used to develop the design basis. Table 6-3
summarizes the design basis.
Overall Material Balance
An overall flow diagram and material balance for the SRC-I process are
shown in Figure 6-2 and Table 6-4 respectively. The basic SRC-I process
consists of seven modules:
Coal receiving and preparation;
Slurry preparation, preheating and dissolving;
Hydrogen recovery;
Precoating and filtration;
Solvent recovery;
Product recovery and solidification; and
Hydrogen manufacture
Coal is dried, crushed, mixed with coal-derived solvent and hydrogen,
preheated, and introduced into a dissolver (liquefaction) reactor where coal
is reduced to liquid products. The resultant process stream is flashed to
remove hydrocarbon gases. Unreacted coal and ash solids are next removed from
the liquid slurry by precoat filtration. The filter cake is sent to the
hydrogen generation module where the Koppers-Totzek gasification process will
be used to generate hydrogen. The filtrate, containing SRC liquid and the
solvent, is next sent to the product recovery module where fractionation and
solidification are used to obtain the SRC solid product.
-82-
-------
TABLE 6-3. DESIGN BASIS FOR A 20,000 TPD COAL FEED SRC-I PLANT
1. Coal Type:
Unground Coal Moisture:
2. Ground Coal Analysis
A. Proximate Analysis (Dry Basis)
Volatile Matter
Fixed Carbon
Ash
High Heating Value (MF)
Moisture (wt %)
B. Ultimate Analysis (Dry Basis)
Carbon
Hydrogen
Nitrogen
Chlorine
Sulfur
Ash
Oxygen
C. Sulfur Forms
Pyritic
Sulfate
Organic
3. Operating Conditions
Coal Cone. % MF
Space rate Ibs/hr-ft , MF
Dissolver Outlet Pressure, psig
Hydrogen Purity, Mol %
Hydrogen Partial Pressure, psig
Preheater Inlet
Dissolver Outlet
4. Yields
Conversion, % MAF coal
Hydrogen Consumption, % MF Coal
Yields, % MF Coal:
CO
co
Kentucky 9-14 Colonial Mine
9.2 wt %
Wt.%
39.8
49.8
10.4
IBP-350 F
350°F - 450°F
450°F -
EP
SRC
Unconverted Carbon
Ash
HO
Sulfur in SRC, %
12,929 Btu/lb
2.0
70.4
5.1
1.4
0.1
3.4
10.4
9.2
1.5
0.2
1.7
'38.4
75.0
1650.0
87.0
1450,0
870.0
91,2
1.95
(-0.14)
0.64
1.81
1.40
0.76
0.76
0.16
0.17
2.
7.
.92
.58
2.11
61.66
7.86
10.15
4.11
0.96
-83-
-------
TABALE 6-3 (Cont'd)
5.
6.
7.
8.
9.
Organic Sulfur Removal: 57.5 wt%
N and 0 Removal: In Feed Coal
22 Wt %
N2 1.36
02 9.32
Recycle Solvent Boiling Range: 450 -
In SRC
Wt %
1.72
4.44
780°F
Filter Cake Composition (Feed to H2 Plant)
C
H
N
Cl
S
0
Ash
Physical Properties:
A. Sp. Gr. of Various Coal Slurries
Cone. % 25 25
Temp., °F 60 150
Sp. Gr. 1.083 1
B. Sp. Gr. of Process Solvent (450-780°
Wt %
46.38
3.36
0.90
0.02
6.17
4.40
38.77
.065
F)
Temp., °F 60 150
Sp. Gr. 1.025 0.980
C. Viscosity of Coal Slurries
Cone. % 25 25 25
Temp. °F 85 125 165
Vise. , CP 55 35 21
D. Properties of Liquid Products
Product Liquid, BP°F
Light Oil IBP-350
Wash Solvent 350-450
Process Solvent 450-780
SRC
API°
15.9
10.0
4.6
-22.6
Removal
22
71
38
60
1.133
200
0,972
38.5
85
177
BP°F
320
400
567
1300
38
150
1.106
250
0.955
38.5
125
70
MW
115
130
170
750
38.5
165
62
BTU/lb
19,000
18,000
17,000
15,800
-84-
-------
COAL
AIR
SEPARATION
FS-7
STEAM (46) * (MI to
M7) (51) B (56)
\ > 1
SEE NOTE 3 (TYPICAL)
__ _^ re o
vnonrcM ^^vrNT GASPS . C99> RECOVERED H2 FROM
LANT U-T) ^VENTGASES WASTE GASES
re *
t
TO .STACK
A (2)
1(4)
8AGHOUSE
(64) (65)
\ i
( , } COAL RECEIVING B ,,,
L j (48, 1
SLAG
T
(6)1
f '
16, « FS/9
, r ,r '' * >
U (IS) (17)
r-s i <281 fc "? RECOVERY
FS-3
i t
(71 Mi)
-------
SEE NOTE 3 (TYPICAL)
(36)
Fs-9
F5-8
.(29) ft (35)
FROM FIGURE 6-2
PAGE I
(13)
(19)
FROM FIGURE 6-2
PAGE I
(22)
FS-8 FS-9
(24)
«-B
4 «
PRECOAT AND
FILTRATION
FS-4
PRECOAT
(26)
T
SOLVENT RECOVERY
FS-5
|(20)
FUEL
LIGHT OIL
STORAGE
FS-5
(28)
(37)
FS-3
-» TO PLANT FUEL
WASH SOLVENT
STORAGE
FS-9
(25) a (27)
(39)
(40)
-»»FS-4
-^ SALES
-»»TO PLANT FUEL
PROCESS SOLVENT
STORAGE
FS-5
(6)
(34)
SALES
FS-8 FS-9
(42)
(41)
(44)
PRODUCT RECOVERY
a
SOLIDIFICATION
FS-6
(30) 6(31)
FS-S FS-7
(43)
SRC PRODUCT
TO SALES
NOTE: FOR NOTE 1-3 SEE PAGE I
OF THIS FIGURE.
Figure 6-2 (Pg. 2 of 2). Overall flow diagram: 20,000 TPD coal feed SRC-1 process.
-------
I
CO
VI
Stream No.
Hydrogen
CO
°
N,
Light Oil
Wash Solvent
Process Solvent
SRC
Coal
Ash/Slag
Precoat
HO/Steam
Ammonia
TABLE 6-4. OVERALL MATERIAL BALANCEj 20,000 TPD SRC-I PLANT
(All flow rates are in tons per hour)
1 2 3 4 5&126
45.
2.
7.
4.
7.
30.
3.
1.
0.
0.
0.
1306.67
776.83 45.99 730.83 0,012
92.52 5.48 87.04 0,001
7
812
99
93
29
08
63
42
23
05
01
62
10
2
0
1
1
3
2
0
0
0
0
8
25
795
504
64
83
.03
.37
.60
.61
.31
.92
.82
.59
.19
.24
.36
.06
.93
.26
.27
.00
11
27.
1.
10.
12.
3.
37.
7.
5.
0.
0.
0.
61
46
61
28
77
41
75
53
46
21
02
13
0.
0.
0.
5.
1.
1.
1.
0.
0.
16.
36.
528.
27
03
96
17
75
07
33
71
96
14
96
00
88.08
1.05 16.67
70.36
44.61
5.48 0.17
Total
957.43 52.52 834.54 70.37 44.61 1306.67 104.06 1500.04 107.28 593.35
-------
TABLE 6-4 (ContM)
Stream No.
Hydrogen
CO
co2
°2
N2
C,
1
C2
C_
3
C4
CC
i 5
» Light Oil
Wash Solvent
Process Solvent
SRC
Coal
Ash/Slag
Precoat
H20/ Steam
14
26.44
1.34
7.47
4.29
3.54
26.62
3.38
1.23
0.05
0.01
0.62
15 16 17
1,17 16.09
0.12 1.64
3.14 0.46
7.99
0,23 3.39
10.79
4.37
4.30
0,41
0.20
2.20
0.17
19
1,98
0.35
1.53
1.52
3.26
2,83
0.76
0,54
0,16
0.20
3.76
7.70
82.50
4.52
20
0,05
0.02
0.07
0.09
0,05
0,09
0.06
0.05
0,03
0.04
5.31
36.18
673.33
475.01
0.96
21 22
0.05 0.74
10.87 120.33
4.82 36.65
29.25
64.27
83.00
5.5
23
24
0.0
0.0
0.03
1.68
Ammonia
Total
74.99 34.92 21.58 0.17 111.61 1191.34 197.76 157.72
1.68
0.03
-------
TABLE 6-4 (Cont'd)
Stream No. 25 26 27 28 29 & 35 30 & 31 34 36 37
Hydrogen
CO
co2
°2
N2
Cl
C2
C3
C5
Light Oil 1,46 0,05 2.8 1.58 5.19 19.45
Wash Solvent 144.65 5.40
Process Solvent 1.3 0.05 0.06 668.28 6.9
SRC
Coal
Ash/Slag
Precoat 5.5
H20/Steatn 1.52 0.94 3.94
Ammonia
Total 147.41 5.5 5,5 2,8 29.26 710.40 6.9 3.94 19.45
2.30
0.40
2.56
6.78
3.31
4.67
1,89
1.92
0.90
1.20
1.58
0,17
0.06
0,05
0.02
0.07
0.09
0.05
0.09
0.06
0.05
0.03
0.04
5.19
35.44
668.28
-------
TABLE 6-4 (Cont'd)
Stream No.
Hydrogen
CO
co
H2S
°
39
41 & 44
42
43
46
47
48
49
110.34
51 & 56
0.008
21.93
12.94
I
?
Light Oil
Wash Solvent
Process Solvent
SRC
Coal
Ash/Slag
Precoat
H,,0/Steam
Ammonia
H0S
0.49
49.9
0.44
27.6
0.12
0.69 0.05
0.05 5.00
475.01
0,36
0.01
0.31
0.01
122.39
46.00
1.35
0.01
0.02
Total
50.83
27.6
1.22 480.06
46.00 110.34 122,39
0.33
36.26
-------
TABLE 6-4 (Cont'd)
Stream No.
Hydrogen
CO
co
53
55
0,11
0.01
286.4
59
3.29
0.01
°
0.15
4.01
0.04
Light Oil
Wash Solvent
Process Solvent
SRC
Coal
Ash/Slag
Precoat
H20/Steam
Ammonia
H2S
3.78
0.08
0.06
Total
3.92
286.52
7.50
-------
Auxiliary facilities required for the plant are the following:
Air separation plant
(to supply oxygen to the K-T gasification process);
Power and steam generation;
Cooling towers; and
Water treatment
Control/disposal modules will be required for gaseous, liquid and solid
wastes.
Waste Characteristics and Comparisons
Gaseous Wastes
The various gaseous waste stream sources are the following:
Module Stream Noa. in Figure 6-2
Solvent recovery 29 and 35
Hydrogen recovery 15
Precoating and filtration 24
Product recovery and solidification 42
Hydrogen manufacturing 51 and 56
Table 6-5 gives the flow rates and compositions of the above waste streams.
Streams 15, 29, 35, 51 and 56 have sufficient sulfur for recovery. Sulfur
recovery modules are not included in this section.
The off-gases from the SRC plant, Streams 15, 29, and 35 contain large
amounts of hydrocarbons in addition to the sour gases. Thus, a chemical type
acid gas removal process (e.g., carbonate type) which is very common in the
coke oven industry, could be used to concentrate the sour gases; and followed
by a Claus process, together would recover sulfur from the concentrated sour
gas stream.
Streams 24 and 42 containing small amounts of hydrocarbons should be
incinerated.
-92-
-------
TABLE 6-5. SUMMARY OF GASEOUS WASTE STREAMS, TONS/HR
(BEFORE TREATMENT)
Stream No.
Hydrogen
CO
co2
V
Light Oil
Wash Solvent
Process Solvent
SRC
Coal
Ash/Slag
Precoat
H-O/Steam
Ammonia
HCN
15 .24 29_ _35 42_
1.17 0.27 2,03
0.12 0.03 0.37
3.14 0.94 1.62
7.99 4.46 2.32
0.23 3.31
10.79 1.73 2.94
4.37 1.00 0.89
4.30 1.13 .79
0,41 0.41 0.49
0.20 0.33 0.87
2.20 0.12 1.46 0.12
0.03 0.07 0.10 0.69
0.06 0.05
_5.L
0.006
16.09
11.62
1.52 0.36 1-35
0.01
0.02
0.002
5.84
1.32
Total
34.92 0.03 10.07 18.71 1.22 29.10
7.16
-93-
-------
Liquid and Solid Wastes
Process wastewater originates from both the basic SRC plant and the
hydrogen generation plant. About 310 gpm of process wastewater from the SRC
plant are discharged from the following modules:
Module Stream No. in Figure 6-2
Slurry preparation, preheating and 5 and 12
dissolving
Hydrogen recovery 17
Precoating and filtration 23
Solvent recovery 36
Product recovery and solidification 41 and 44
About 150 gpm of process wastewater will be discharged from the Hydrogen
Manufacturing Plant, contributed mainly by Stream Nos. 88 and 89.
Table 66 summarizes the flow rate and compositions of all liquid waste
streams from the plant.
About 122 tons per hour of solid wastes will be discharged from the
plant, all originating from the Hydrogen Manufacturing Module (Stream No. 48).
The above solid wastes will contain about 25 percent moisture.
The SRC plant wastewater, shown in Table 6-6, is quite similar to coke
oven wastewater. It contains large quantities of phenol, ammonia, sulfide,
and therefore, could be treated in a manner similarly to the coke oven
wastewater treatment scheme. The wastewater from the hydrogen plant (mostly
from the K-T gasification process), however, is dissimilar to the coke oven
wastewater. It is a dilute stream and, therefore, no byproduct recovery type
treatment is necessary.
-94-
-------
TABLE 6-6. SUMMARY OF LIQUID WASTE STREAMS*
(BEFORE TREATMENT)
VD
Ul
Stream No.
Ammonia
Sulfide
Phenolics
BOD
Suspended
Solids
Water/Steam
COD
Extractable
Oils
SRC Plant
Process Waste
0.44
0.312
0.351
0.023
78.0
1.170
0.016
H2 Plant
Process Waste
0.008
Trace
0.004
0.008
Trace
37.8
0.076
0.004
Storm
Runoff
0.012
0,006
0.012
0.003
57.5
0.115
Cooling Tower Coal Pile
Slowdown Runoff
0.001
Trace
0.001
0.001
287.5 68.75
0.002
Boiler
Slowdown
102.5
Total
80.312
37.900
57,648
287.5
68.755
102.5
* All flow rates are in tons per hour,
-------
SECTION 7
COKE OVEN CONTROL TECHNOLOGY AND ITS APPLICABILITY TO
COAL CONVERSION PROCESSES
DESULFURIZATION OF COKE OVEN GAS
In the coking operation, unacceptable quantities of hydrogen sulfide and
organic sulfur compounds are formed along with the major byproduct constituent,
coke oven gas. According to most government regulations, coke oven gas cannot
be burned if it exceeds 15 to 50 gr/100 SCF (240 to 480 ppm by vol.) of H S.
These regulations are summarized in Chapter 9. Since raw coke oven gas contains
about 5,000 ppmv of H-S, considerable desulfurization of the gas is, therefore,
required.
Many technologies are currently employed worldwide for COG desulfurization.
Table 7-1 shows the commercially available control systems and their cited
efficiency ranges. All of them are of the chemical type processes rather than
physical absorption type processes. These technologies are divided into three
major categories: 1) Liquid Absorption Processes (e.g., Vacuum Carbonate,
Sulfiban, Fiona Carl Still, Diamox), 2) Wet Oxidative Processes (e.g.,
Stretford, Takahax, Fumaks, Giammarco Vetrocoke), and 3) Dry Oxidative Processes
(Iron Oxide Boxes).
1. Liquid Absorption Processes
Three basic steps are involved:
a. Absorption of acid gases (H S, HCN, CO-) into a recirculating
solution.
b. Stripping of acid gases from solution, and
c. Conversion of H S in acid gases to either elemental sulfur or
sulfuric acid.
Absorbing Solutions:
Vacuum Carbonate - sodium carbonate solution.
Sulfiban - alkanolamine solution.
-96-
-------
TABLE 7-1, COKE OVEN GAS DESULFURIZAHON PROCESSES
Category
Commercial Processes
Ranges of % Sulfur Removal
Dry Oxidative
Iron-oxide boxes
90-99%
Wet Oxidative
Stretford
Takahax
Rhodaks/Fumaks
Giammarco - Vetrocoke
98-99%
unknown
unknown
unknown
Liquid Absorption
Vacuum Carbonate
Sulfiban
Firma Carl/Still
Diamox
90-98%
90-98%
90-98%
97%
-------
Firma Carl Still - ammonia solution.
Diamox - ammonia solution.
2. Wet Oxidation Process
Once hydrogen sulfide is absorbed into solution, it is oxidized
directly to elemental sulfur which is removed from solution by
filtration.
Oxidizing Agents:
Stretford - anthraquinone disulfonic acid and sodium vanadate.
Takahax - naphthaquinone sulfonic acid.
Fumaks - ammonia and picric acid,
Giammarco Vetrocoke - alkaline arsenite and arsenate.
In each case, the oxidizing agent is regenerated by air oxidation.
3. Dry Oxidative Processing (Iron Oxide or Dry Box)
Hydrogen sulfide is adsorbed by a solid and either held as a sulfide
or oxidized to elemental sulfur. Excessive labor costs and space
requirements have largely eliminated the use of dry oxidative
processes for new plants. A majority of the old coke oven plants
use the Iron Oxide process for desulfurization.
The Iron Oxide/Dry Box process will have limited application in coal
conversion processes. If applied, it will be used mostly for controlling low
sulfur containing air emissions. A modified version, under laboratory scale
development through DOE and EPA sponsorships, seems capable of desulfurizing
acid gases at high temperatures. If this hot gas desulfurization process
becomes competitive with other control processes, it could have broader
applications.
Based on the desulfurization processes utilized in the coke oven industry,
it appears that the Stretford process should have broad base applications in
coal conversion systems. The Vacuum Carbonate and the Sulfiban process, two
acid gas removal processes which have been widely employed in the U.S. for
coke oven applications, should find use in the low-pressure gasification
processes, or in the control of low-pressure off-gases from liquefaction
processes. The physical solvent type acid gas removal processes, such as
Selexol and Rectisol, have not been used for coke oven gas desulfurization
because they require high-pressure feed (gas) streams. These processes,
however, should have much wider application in coal conversion systems.
-98-
-------
In the coke oven, industry, the Claus process has also been used to recover
sulfur from the rich acid gas stream produced from the Vacuum Carbonate and
the Sulfiban processes. The Claus process has required several modifications
because of the presence of hydrogen cyanide and other impurities in the acid
gas feed. Since these impurities are also present in the acid gases from coal
conversion systems, the Claus modifications that have been developed are of
special interest because the Claus process would be a feasible sulfur recovery
technology for the coal conversion systems. Discussed below are the process
and design data that were available from literature sources for the various
desulfurization processes which may be applicable to coal conversion systems.
Vacuum Carbonate Process
The Vacuum Carbonate process was first marketed by Koppers in the mid-
1950 's as an improvement over its older Seaborad process. In the Seaboard
process, regeneration of the absorbing solution was accomplished by air
stripping. Although this process was simple and economical, it had several
disadvantages. Contact with oxygen led to numerous side reactions in the
solution, resulting in the need for excessive solution replacement and in salt
disposal problems. The odors resulting from the foul air disposal also caused
problems.
To overcome these deficiencies, the Seaboard process was modified so that
the spent carbonate solution was regenerated by vacuum distillation rather
than air stripping. The use of steam distillation allowed the hydrogen sulfide
to be recovered in a concentrated form from which sulfuric acid or elemental
sulfur could be produced.
Chemical Reactions
Na2C03 + C02 + H20
» isana T wdm^u..
». ovToTirr*
_ .., , ..^ NifTJ + NnlTPO
The introduction of oxygen, either as the result of its presence in the
coke oven gas or by air leakage into the system, results in several side
reactions that produce non-regenerable salts:
2NaHS + 202 - * Na2S2°3 + ^0
NaS0 + NaCN - * NaS0 + NaCNS
-99-
-------
03 + 2NaHs + H20 - + 3Na2S203 + 4NaOH
2NaOH +
Process Description
Gas is contacted counter-currently with a 3 to 3.5 percent solution of
sodium carbonate in an absorber tower to remove the H?S and other impurities
such as HCN and CQ (See Figure 7-1). The foul solution from the base of the
absorber is circulated over the actifier, where the H2S is removed by counter-
current stripping from the base of the actifier through a cooler to the
absorber to complete the cycle. Typical acid gas from an actifier contains 65
to 75 percent H S, 10 to 15 percent C02, 6 to 9 percent HCN. Where closed
loop final coolers are used to process COG, HCN can exceed 20 percent.
Traditionally, the Vacuum Carbonate process was designed as a single
stage unit with an 80 to 90 percent hydrogen sulfide removal efficiency (93
percent maximum). However, a recent redesign of the process to a two-stage
system in both the absorber and the actifier increases the overall efficiency
of the process to 98 percent.
In this redesigned process, the raw coke oven gas is scrubbed of hydrogen
sulfide in a two-stage packed absorber by a counter-current flow of sodium
carbonate solution. The foul solution is pumped from the absorber to a two-
stage actifier (regenerator), where steam stripping is used. To minimize
steam consumption, stripping is carried out at 4.4 inches of mercury absolute
and 54 C. Separate carbonate solution loops are maintained in each stage.
However, a one-stage vapor flow is maintained in the actifier tower. The
carbonate solution that contacts the inlet raw coke oven gas (and is, thus,
richest in hydrogen sulfide) is sent to the upper stage of the actifier, while
the solution from the upper stage of the absorber is stripped in the lower, or
secondary stage, of the actifier. Solutions are circulated at a rate such as
to give ma-g-tnnnn cleaning in the second stage of the absorber. A 90 percent
hydrogen sulfide removal is claimed in the first stage, with an additional 8
to 9 percent cleaning in the second.
The stripped gases and steam pass from the actifier to the vapor condenser
under vacuum, and the bulk of the steam is condensed. The remaining vapors
then pass through a series of steam jet ejectors and intercondensers and,
-100-
-------
SWEET COKE-OVEN GAS
ABSORBER
SOUR COKE-
GAS
MAKE-UP
SOLUTION
SOUR
CONDENSATE
WASTE WATER
ABSORPTION SOLUTION SLOWDOWN
Figure 7-1. Two stage Vacuum Carbonate system flow diagram.
-------
finally, on to the sulfur recovery unit. Energy economy is achieved by a
system that recovers waste heat and converts it into stripping steam for the
actifier. Operating costs equal to those of a 93 percent removal plant are
claimed.
Waste StreamsFigure 7-1 shows that the Vacuum Carbonate process produces
two wastewater streams: 1) spent absorbing solution containing large amounts
of suspended and dissolved solids; and 2) ejector jet condensates containing
significant amounts of HCN and H_S.
The absorbing solution is degraded by the reaction of oxygen, cyanide and
perhaps ammonia in the presence of H S. Some of these side reactions were
shown earlier. Complete replacement of spent absorbing solution is necessary
after 8 to 36 months of operation (based on a few existing plant experiences).
The ejector jet condensate quantity is about 55,400 gal/day for a 60 MM
SCFD desulfurization plant (9.72 gal/ton coal charged). Since this contami-
nated stream will contain H S and HCN, it will require steam stripping.
Stripped gases can be recycled back to the coke oven gas feed to the Vacuum
Carbonate process or incinerated.
Economics and Applications
Table 7-2 shows the utility requirements for a 20 MM SCFD and a 60 MM
SCFD Vacuum Carbonate plant. Table 7-3 gives the capital equipment costs at
two different efficiencies for the plants shown in Table 7-2.
Carbonate type desulfurization processes are most applicable to gas
streams containing an appreciable amount of C02. If H_S is present, with
little C0_, then carbonate type processes are not suitable for desulfurization.
For many applications with gas streams contaiuing large amounts of C02,
the advantages of carbonate type processes over amine systems are lower utility
requirements, lower plant investment (due to elimination of major heat-exchange
equipment) and effective COS and CS^ removal.
As mentioned earlier, the Vacuum Carbonate process is similar to the
obsolete Seaboard process, but allows for sorbent regeneration unlike the
Seaboard process.
The Vacuum Carbonate process sorbent (Na2C03) is not very soluble in
water and therefore, requires large circulating liquor rates. Newer carbonate
processes use K~CO_ as the sorbent which requires lower liquor flow rates.
-102-
-------
Note: Inlet gas concentration is based on 500 grains H S/100 SCF.
TABLE 7-2 VACUUM CARBONATE REQUIREMENTS
20 !*MSCFD 60 MMSCFD
Removal Efficiency 90% 93% 9Q%
Cooling Water, GPH 1,160 1,320 4,500
Power, KV7-hr/day 1,835 1,835 5,440
Na2C03(100%), Ib/day 177 177 530
Steam Requirements, Ib/hr
Actifier and/or Ejectors 6,240 6,315 18,740 19,180
Condensate Treatment 1,120 1,120 3,380 3,380
Total 7,360 7,435 22,120 22,560
Claus Steam Credits, Ib/hr
High Pressure (150 psig) 558 577 1,674 1,730
Low Pressure ( 30 psig) 282 292 846 875
Total 840 869 2,520 2,605
Net Process Steam Demand Ib/hr 6,520 6,566 19,550 19,955
-103-
-------
TABLE 7-3, VACUUM CARBONATE CAPITAL COSTS
(40)
Removal Efficiency
Desulfurization Installed:
Capital Cost, $MM
20 MMSCFD
90% 93%
1.38 1.43
60 MMSCFD
90% 93%
2.56 2.77
Glaus Sulfur Recovery:
Installed Capital Cost, $MM
0.53 0.53
0.73 0.73
Total Installed:
Capital Costs, $MM
1,91 1.96
3,29 3.50
NOTES: 1. Inlet gas concentration is based on 500 grains H2S/100 SCF.
2. Cost data are based on 1974 costs.
-104-
-------
Several versions of the potassium carbonate p- ^cesses are available. The hot
potassium carbonate process was previously developed by the U. S. Bureau of
Mines. The Benfield and Catacarb are very similar to the hot potassium process,
except that they employ a proprietary catalyst to increase the rate of
absorption and stripping, thus further decreasing the circulation rates of the
carbonate solution. These newer carbonate processes are being considered for
desulfurization of coal conversion gases because of their better economics.
Sulfiban Desulfurization Process
The Sulfiban process is a joint development of Bethlehem Steel and Black,
Sivalls and Bryson.
Although the Sulfibaa process was not introduced until 1972, the use of
Sulfiban absorbing solution (alkanolamines) to sweeten natural and manufactured
gases had been practiced for decades. Monoethanolamine (MEA) is preferred
over diethanolamine for the desulfurization of coke oven gas, since it lends
itself to reclamation in a sidestream reclaimer.
Chemical Reactions
The H^S, HCN, organic sulfides and a portion of the CO- are chemically
absorbed in MEA as follows:
HCN
co2
RNH3HS
When heat is applied in the regenerator stripper, the above reactions are
reversed, freeing the acid gas. However, reactions between MEA and organic
sulfides such as COS and CS~ are not reversible. Also, if oxygen is present
in the system, an irreversible side reaction will take place between the MEA,
HCN and 0? producing amine thiocyanates and thiosulfates.
Process Description
The Sulfiban process is operationally similar to the Vacuum Carbonate
process with the single exception that the actifier operates at atmospheric
pressure and about 230 F. As a r<
process steam (at least 30 psig).
pressure and about 230 F. As a result, heat must be supplied in the form of
-105-
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The sour coke oven gas is contacted counter-currently (see Figure 7-2)
with a 13 to 18 weight percent aqueous solution of MEA in an absorption
column. The resulting foul solution is regenerated with steam in an actifier.
The acid gases from the actifier typically contain 35 to 45 mole percent
hydrogen sulfide, 55 to 60 mole percent carbon dioxide, and 2 to 4 mole percent
hydrogen cyanide, together with fractional percentages of organic sulfur
compounds (primarily carbon disulfide and carbonyl sulfide).
After counter-current contact with the coke oven gas, the fouled solution
passes through a series of heat recovery exchangers on its way to the actifier.
The actifier overhead, consisting primarily of water vapor and acid gas, is
passed through a condenser and into an accumulator where separation of the
condensables occurs. The acid gas vapors pass on to the sulfur recovery
system, and the condensate is returned to the actifier as reflux.
After passing down the actifier, the MEA solution enters a steam-fired
reboiler, where additional stripping occurs (primarily of carbon dioxide), and
stripping steam for the actifier is generated. A sidestream from the reboiler
enters a reclaimer fired by higher-pressure steam, in which the MEA is vaporized
and returned to the system and the non-volatile components are removed from
the circulating solution. The bulk of the reboiler effluent passes to a surge
tank, from which it is returned to the absorber via the solution heat exchangers
and cooler.
Sulfiban pilot plant studies have demonstrated a clear capability for COG
desulfurization to EJS concentrations of 10 grains/100 scf or less. Efficiencies
range between 90 and 98 percent.
Only one liquid waste stream of consequence *s produced in the Sulfiban
plant; spent absorbing solution accumulates as a sludge in the actifier
reboiler and must be discharged periodically. Pilot plant data indicate that
about 37 gal/day of sludge containing FeS, iron ferrocyanide, thiourea, etc.
will have to be removed from a plant producing 60 MM SCFD of coke oven gas.
Sulfiban operating requirements are given in Table 7-4 for 20 MM SCFD and
60 MM SCFD plants. Cost data for the plants are presented in Table 7-5.
Applications
The Sulfiban is a basic amine process (MEA) which has been used as a
standard in the gas purification/removal industry. It has been applied in the
-106-
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CONDENSER
SWEET COKE-OVEN GAS
ABSORBER
SOUR COKE-OVEN GAS
ACID GAS
H.P STM
RECLAIMER
SLUDGE
DISCHARGE
Figure 7-2. Sulfiban desulfurization process
-------
TABLE 7-4. SULFIBAN OPERATING REQUIREMENTS ^
20 MMSCFD 60 MMSCFD
Efficiency 90% 98% 90% 98%
Cooling Water, GPM 530 1,060 1,590 3,180
Power, KW-Hr/Day 1,300 1,300 4,148 4,148
Monoethanolamine (100%), Ib/day 300 300 900 900
Steam Requirements, Ib/hr: Actifier 5,840 10,914 17,520 32,746
Claus Steam Credits, Ib/hr:
High Pressure (150 psig) 558 607 1,674 1,824
Low Pressure ( 30 psig) 282 307 846 922
TOTAL 840 914 2,520 2,746
NET PROCESS STEAM DEMAND
Ib/hr 5,000 10,000 15,000 3,000
NOTE: Basis - 500 grains H2S/100 scf at inlet.
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TABLE 7-5. SULFIBAN - CAPITAL COSTS
(40)
Efficiency
Desulfurization Installed:
Capital Cost, $MM
20 MMSCFD
90% 98%
1,27 1.42
60 MMSCFD
90%
2.5
98%
2.8
Claus Sulfur Recovery:
Installed Capital Cost, $MM
0.55 0,55
0,70 0.70
HCN Pretreatment:
Installed Capital Cost
(via catalytic decomposition), $MM 0,20 0.20
0.25 0.25
TOTAL INSTALLED CAPITAL COSTS, $MM
2,02 2,17
3.45 3.75
NOTES: 1. Basis - 500 grains lUS/lOO scf at inlet,
2. 1974 costs data.
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desulfurization of coke oven gas, refinery gas, natural gas, and in the
manufacture of synthesis gas and hydrogen (more than 100 plants have been
built world wide by Black, Sivalls and Bryson).
The Sulfiban process will have applicability in the U.S. coal conversion
processes especially for the removal of H.-S and C0» from low pressure raw
product and off-gases. Since the process removes organic sulfides by
irreversible chemical reactions, solvent make up is required by the process.
The temperature of the feed gas has to be below 100 F.
Iron Oxide Process
The Iron Oxide or Dry Box process is one of the oldest gas treating
techniques known. The process has found widespread use in some European
countries where essentially complete H.S removal is necessary and where some
manufactured and synthesis gases contain impurities which react irreversibly
with chemicals used in liquid purification processes. The process is usually
limited to treating gases of small to medium volumes and containing 1.5 volume
percent H_S or less.
Advantages of the process are essentially complete H_S removal, ease of
operation and simplicity of installation. Disadvantages are: 1) the sulfur
removed by the process cannot be recovered economically; and 2) large amounts
of labor are required during periodic bed replacement and solid wastes disposal.
For these reasons, the Iron Oxide process will have very limited application
in coal conversion processes. Example of a possible application is the
treatment of low volume sour gases produced by the byproduct upgrading plants
which are remotely located from the main sulfur removal plant of the coal
conversion process.
Chemical Reactions
(1) Reaction: 2Fe2°3 + 6H2S *" 2Fe2S3 + 6H20
(2) Regeneration: 2Fe2S3 + 302 *- 2Fe2°3 + 6S
Overall: 6H2S + 302 + 6H20 + 6S
Process Description
Dry Box purification is the removal of hydrogen sulfide from gas by
bringing the gas into contact with iron oxide in the presence of water. The
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efficiency and economy of sulfur removal are dependent upon the activity,
capacity and availability of the oxide used, the ease with which the gas can
be passed through the bed containing the oxide, and upon certain conditions of
temperature and moisture. Hydrogen sulfide removal is quite exceptional for
small gas volumes; a sweetened gas of less than 0.1 grain H.S/100 scf is
easily obtained.
The process uses wood shavings impregnated with ferric oxide in hydrated
form. The bed is gradually deactivated by formation of ferric sulfide and can
be partially regenerated by air oxidation of the ferric sulfide to ferric
oxide and sulfur. However, eventually the bed becomes plugged with sulfur and
must be replaced. If a batch-type regeneration is employed, about 4 regen-
erations are possible before the beds of iron sponge must be changed. Two or
more towers or iron oxide boxes are utilized.
In general, the sulfur is not recovered from the sponge beds. The process
removes no C0_.
There is no theoretical basis for the design procedure, but several
empirical rules can be followed:
1. The tower or box should be of such a horizontal cross-section as to
limit sulfur deposition to a maximum of 15 grains per square foot of
bed cross-sectional area per minute.
2. The operating temperature of the bed should always be below 105 F.
Otherwise, the water of crystallization in the Fe2°3 molecule will
be driven off and the activity of the material destroyed.
3. The height of the tower or box is recommended to be at least 10 feet
to produce a pressure drop sufficient for proper gas distribution
over the entire cross-sectional area of the tower.
4. Sponge mixtures containing 5 to 10 Ibs of Fe-O-a per cubic foot are
satisfactory, and it is customary to figure on 6 cubic feet of
sponge per 100 SCFD.
5. The sponge does not function properly if it contains less than 17
percent moisture, or more than 55 percent. A desirable moisture
content is between 30 and 50 percent. The function of the water in
the tower or box is to act as a differential solvent for the H_S,
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and to hold it for a sufficient time for the oxide to react with it.
A further function of the water is to furnish sufficient drops to
dissolve and remove from the tower or box the soluble salts formed
during purification.
6. The theoretical maximum for sulfur removal per cubic foot of sponge
is 5.8 pounds. This is based on 10 pounds of iron-oxide per cubic
foot of sponge mixture.
Stretford Sulfur Recovery Process
The Stretford process was originally developed to overcome some of the
shortcomings of earlier absorption/oxidation processes. The process is capable
of reducing the H S content in coke oven gas to less than 10 grains/100 scf.
Sulfur recovery between 98 and 99.percent is possible. The process does not
remove organic sulfur, and requires pretreatment for removal of large quantities
of S0_, HCN, or heavy hydrocarbons. It produces a wastewater stream containing
Stretford solution which requires treatment.
Chemical Reactions
(1) H_S absorption:
H9S + Na.CO, ^ NaHS + NaHCO,
£ *m 3 J
(2) Vanadium reduction and sulfur formation:
4NaV03 + 2NaHS + H20 +> Na^O + 2S + 4NaOH
(3) Vanadate reoxidation with anthraquinone disulfonic acid (ADA):
Na2V409 + 2NaOH H20 + 2ADA * 4NaV03 + 2ADA (reduced)
(4) ADA reoxidation:
2ADA (reduced) + 02 ^ 2ADA + 2H20
Major Side Reactions
(1) Thiosulfate formation:
2NaHS + 202 + ,Na2S203 + H20
(2) Cyanide conversion to sodium thiocyanate:
HCN + NaHS + 1/2 02 » NaCNS + H20
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(3) Sulfur dioxide conversion to sodium sulfate:
Na2S°3 + 2NaHC°3
1/2
Polysulfide Pretreatment Reactions
(1) (NH)S + HCN + ^
(2)
Process Description
The raw coke oven gas (COG) is first pretreated to remove hydrogen cyanide
in a counter-current absorber with a solution of ammonium or sodium polysulfide,
The polysulfide reacts with the hydrogen cyanide in the coke oven gas to form
thiocyanate. The spent polysulfide is regenerated by the reaction of the wash
solution with elemental sulfur (see pretreatment reactions above). Fresh
polysulfide solution is continually added to the wash solution, and a purge
stream of the spent wash solution is sent to waste treatment. The cyanide
absorber can have an efficiency of between 90 to 97 percent.
The cyanide-free COG is then scrubbed (see Figure 7-3) in an absorber by
counter-current washing with an aqueous solution of sodium carbonate,
anthraquinone disulfonic acid (ADA), citric acid, and sodium meta-vanadate.
The hydrogen sulfide initially dissolves in the wash solution and is then
rapidly oxidized by the vanadate ion to elemental sulfur. The vanadate ion is
reduced to the vanadous state, which is returned to its original form by the
ADA. The now sweetened COG passes into the distribution system.
Underneath the absorber there is a delay (reaction) tank where a liquid
residence time of 10 to 20 minutes is maintained to allow complete conversion
of the hydrosulfide to elemental sulfur.
The spent solution passes into an oxidizer, where air (up to 400 percent
excess) is bubbled through the solution to reoxidize the ADA. The rising air
bubbles also carry the suspended sulfur particles to the surface, where they
form a froth (6 to 8 percent sulfur) which is skimmed off. Underflow goes to
a surge tank and is eventually recycled to the H_S absorber. A purge stream
containing contaminated Stretford solution is withdrawn from the surge tank
and sent to waste treatment.
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SWEETENED COKf OVEN OAS
ACIO OAS IN
H2S
ABSORBER
a
REACTION
TANK
X
STRETFORD
SOLUTION-
MAKE-UP CHEMICALS
MAKE-UP WATER
EXCESS AIR
OXIDIZE*
V V. V v/
FROTH
OXIDATION
AIR
J
X
~CENTRIFUGE
FEED TANK
SLURRY FEEDp.
FILTRATE SOLUTION
WATER
PUMP TANK
CENTRIFUGE
->
I
_J
SO
yps
AUTOCLAVE
FEED TANK
[ 'AUTOCLAVE. \ W SULFUR
1 \ SEPARATOR JT SLURRY
I
COND.
SULFUR
PRODUCT
WASH
PURGE TO WASTE TREATMENT
Figure 7-3. Stratford sulfur recovery process flow diagram.
-------
Sulfur RecoveryA number of methods are available for handling the
sulfur froth. Some of the alternative sulfur recovery methods, and the final
product form, are:
1. Filtration, yielding sulfur cake;
2. Centrifugation, yielding sulfur cake;
3. Filtration or Centrifugation followed by autoclaving and separation,
yielding high purity molten sulfur; and
4. Filtration or Centrifugation followed by direct injection steam
melting and separation, yielding high purity molten sulfur.
When sulfur is to be recovered by filtration, a rotary vacuum drum filter
is generally used. The filter cake produced contains 50 to 60 percent solids.
One or more wash cycles are employed to remove solution components from the
cake. The filtrate and wash are collected and returned to the system.
Continuous centrifuges may be employed for higher throughput. Again, the
filtrate and wash are returned to the system for reuse of valuable components
in the liquor.
Sulfur cake, or sulfur cake reslurried in water, can be fed to an autoclave
melter-separator. The melter-separator is a vessel with a jacket or internal
coil that is heated by steam at about 40 psig. Sulfur melts (at the operating
conditions of 25 psig and 266 F) and is separated from the aqueous layer
containing the Stretford solution components. The molten sulfur is pumped to
storage and recovered liquor is returned to the system. It has been reported
that part of the ADA that enters the autoclave is desulfona.ted at the elevated
temperatures to 2,7-dihydroxyanthraquinone. This compound must then be
separated and purged from the system.
Direct injection sulfur melting is similar to that described above except
that steam is used directly rather than indirect coil or jacket heating.
Sulfur recovered by any of the above methods should be of a typical
purity of 99.5 percent or better.
Stretford Process Wastewater Treatment
Treatment of Polysulfide Pretreatment Purge StreamThe purge stream from
the polysulfide pretreatment contains large concentrations of thiocyanate,
polysulfide, ammonia, sulfide and elemental sulfur. Two processes have been
investigated with success on a laboratory scale for the treatment of these
wastes: (1) combustion and (2) decomposition.
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When combustion is performed in an excess of air, sodium sulfate is
formed as a combustion product; whereas with a deficiency of air, sodium
sulfide and sodium sulfite are formed. If sufficient sodium is not present in
the aqueous waste, caustic must be added to the feed stream.
The Ralph M. Parsons Co. has developed a process to decompose the poly-
sulfide process wastes by catalytic hydrogenation. The process converts the
wastes to NH_, H_S and CO which can be returned to the coke oven gas stream.
No large treatment plant has been built based on this process.
Treatment of Stretford Purge StreamThe contaminated Stretford solution
purge stream contains large amounts of pollutants similar to the polysulfide
pretreatment waste. It has been treated according to the following three
methods:
1. Combustion,
2. High temperature hydrolysis, and
3. Carbon adsorption followed by ion exchange.
The combustion disposal method is essentially the same as that described
above for the treatment of polysulfide pretreatment wastes. Although com-
bustion is effective, the other two -methods are potentially attractive since
costly reagents can be recovered and recycled to the process.
The high temperature hydrolysis process has been developed by Woodall
Duckham Limited. In this process, both the Stretford purge stream and the
polysulfide pretreatment waste can be treated to recover vanadium, sodium
carbonate, and some sodium sulfide and sulfate; and to break down all of the
thiocyanate and most of the thiosulfate in the effluent.
In the Woodall Duckham process the wastewater is first concentrated in an
evaporator. The concentrated solution is next fed to a high-temperature
hydrolyzer where the solution is evaporated to dryness and decomposed in a
reducing environment. The reducing atmosphere is produced by combustion of
fuel, e.g., coke oven gas. Gases leaving the hydrolyzer are cleaned of solids
in cyclones and then fed to the Stretford absorber. The solids recovered from
the cyclones, containing vanadium and sodium salts, are dissolved and recycled
to the Stretford plant.
A U.S. patent was issued in May, 1974 to the North Western Gas Board for
(45)
a process to recover ADA and vanadium salt from Stretford waste liquor
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The process uses carbon adsorption and ion exchange to selectively remove ADA
and vanadium salts, respectively. The materials are recovered upon regeneration
of the beds. It is not known if the process has been t-ied commercially.
In the process, the Stretford effluent, adjusted to a pH in the range of
2.5 to 3, is passed through an adsorbent bed containing activated carbon. ADA
and dihydroxyanthraquinone are adsorbed and retained in the bed. The solution
then enters an ion exchange bed where vanadium compounds are removed. In the
above mentioned pH range, an anion exchange resin of the modified polystyrene
type is reported to be suitable.
The activated carbon and the anion exchange resin may be regenerated for
reuse. This is achieved in the case of the carbon by washing the bed with hot
water, dilute sodium hydroxide or alkaline sodium dithionite. This removes
the adsorbed anthraquinone compounds from the bed. ADA is separated from the
dihydroxyanthraquinone and recycled back to the process. The dihydroxyanthra-
quinone is discarded.
Regeneration of the ion exchange resin is accomplished by passing sodium
hydroxide through the bed. Vanadate ion is eluted from the bed as sodium
vanadate and returned to the Stretford plant.
Economics and Applications
Capital and operating costs for the Stretford process are affected by
many variables. These include: inlet gas composition, operating pressure,
outlet gas purity, pretreatment and waste treatment requirements. Generalized
economic analyses, therefore, can be misleading.
Table 7-6 presents cost data for 20 MM SCFD and 60 MM SCFD coke oven gas
plants. A 5,000 TPD coal-fired low-Btu gas production facility burning
2 percent (by wt) sulfur with a gas volume of 60,000 SCFM is operated by
Combustion Engineering in Windsor, Conn., and utilizes Stretford capital
equipment estimated to cost three million dollars (1978 costs).
Major applications of the Stretford process include the desulfurization
of: refinery and petrochemical off-gases, coke oven gas, flexicoking fuel
gas, Claus tail gas, fluidized bed combustion of coal and coal gasification/
liquefaction off-gases. Currently, over 50 plants are utilizing the Stretford
process including several coal conversion plants. The process is operating in
a commercial coal conversion plant in Sasol, South Africa. Several developing
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TABLE 7-6, STRETFORD DESULFURIZATION - CAPITAL & OPERATING COSTS
(40)
ITEM
Operating Costs
Power, 1.4c/KWHR
Cool. H20, 12c/M Gal
Steam $1.50/M Ib
Chemical Makeup, $/day
(W/0 HCN or Effluent Treatment)
20 MMSCFD 60 MMSCFD 60 MMSCFD*
$64.60
43.20
53.36
$186.20
95.04
150,08
$252.00
2.16
237.60
668.28
Total Installed Capital Costs
$ MM
1.45
2.88
3.45
* Integrated system includes Woodall-Duckham wastewater effluent treatment
and no polysulfide pretreatment equipment.
NOTE: Basis - 500 grain H-S/100 SCF.
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coal conversion processes are also employing it. They are: the Synthane
pilot plant at the Pittsburgh Energy Research Center; the Combustion Engi-
neering low Btu gasification facility in Windsor, Conn.; the SRC pilot plant
at Tacoma, Washington; and the DOE-owned Cresap test facility. Several Lurgi
based commercial coal gasification plants under design conditions in the U.S.
(e.g., El Paso and WESCO plants) have utilized Stretford to remove H_S from
Claus tail gas and low-H_S containing off-gas from the Rectisol acid gas
removal process. The Stretford process is suitable for gas streams with low
H9S (less than 15 percent) concentrations.
Claus Sulfur Recovery Process
The Claus process has been used in several coke oven plants to recover
elemental sulfur from the coke oven gases. Operating experiences of three
(34)
Bethlehem Steel Corporation plants were recently published . It was found
that certain process modifications were necessary due to the effect of chemical
components present in the coke oven gas which are not typical of the Claus
plant application for petroleum derived gases. The constituents are hydrogen
cyanide, tar, naphthalene, hydrocarbons, organic sulfur, etc. Since these
components are also present in the coal conversion acid gases, Claus plant
experiences from the coke oven application could be useful.
Elemental sulfur is produced in the process by the Claus reaction between
hydrogen sulfide and sulfur dioxide which yields sulfur and water, as follows:
Cat
2H S + SO, « 3S + 2H0
£,
£-
The S07 is supplied either by burning one-third of the H^S-containing acid gas
in a slip-stream and recombining the gases, or by reacting the total acid gas
with a limited amount of air. When the acid gas feed to the Claus plant is a
lean stream, i.e., 25 to 35 vol percent H_S in the feed, the slip-stream
scheme is favored. For rich acid gas feed, the latter technique is more cost
effective. (Note: Most of the Claus plants in the coke oven industry follow
this technique.)
Figure 7-4 shows a flow diagram of a typical Claus plant in the coke oven
industry. The plant consists of:
1. A furnace section where the SO- reactants are produced by burning
the H^S-containing feed gas. Also, a substantial amount of sulfur
is formed in this section by non-catalytic reaction of hydrogen
sulfide and sulfur dioxide.
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BURNER a THERMAL REACTOR
rHOT OAS BYPASS REHEATS
TO ATM
ACID OAS
HEAT
RECOVERY UNIT
50% OF TOTAL
SULFUR PRODUCED
SULFUR STORAGE TANK
FLUE GAS
AIM
ICOALESCCR
Figure 7-4. Glaus sulfur recovery process.
-------
2. A series of catalytic reaction zones where the Glaus reaction proceeds
to a further degree of completion. This section consists of a
repetition of three basic steps: reaction, cooling and condensing
of sulfur, and reheating of gas going to the next reactor.
Typical compositions of acid gas feeds (produced by Vacuum Carbonate
systems) to the three Glaus plants operating at Bethlehem Steel coke oven
plants are shown in Table 7-7. Using these rich feed streams and a Glaus
process that contains a furnace section and three catalytic converter steps,
the Bethlehem Steel experience has demonstrated sulfur recovery efficiencies
of 95 to 96 percent.
Approximately 50 percent of the total sulfur production occurs in the
thermal section (furnace and waste heat recovery); sulfur made in the three
reactor/condenser passes is 40 percent, 8 percent and 2 percent of the total
production, respectively.
The tail gas quantity from the above process is approximately 1.77 times
the volumetric flow rate of the acid gas feed. Substantial amounts of sulfur
compounds will be present in the tail gas, e.g., 2,200 ppmv of H^S, 1,500 ppmv
of COS, 1,300 ppmv of SO and 100 ppmv of CS_. Therefore, the tail gas is
incinerated to convert more odorous and toxic sulfur compounds to S0», before
discharge to the atmosphere. Other types of tail gas control systems do not
appear to be used in the coke oven industry according to our literature review.
The organic sulfur compounds in the tail gas originate from many side
reactions in the Claus process involving carbon dioxide, hydrocarbons, carbon
monoxide, hydrogen sulfide and sulfur dioxides. Some of these reactions are
given below:
CO,, H
2
CO H
CH H
4
CS2 H
CH H
1- 1/2 S2 ~
h SO
h 2, S ^^
- cos
Si*: cos
-** cos
* r.os
fc r.s^
Increasing the CO- and hydrocarbons present in the feed gas to the Claus unit,
will increase the amount of COS and CS_ present in the tail gas. The effect
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(34)
TABLE 7-7. TYPICAL CLAUS PLANT FEED COMPOSITION FOR THE COKE INDUSTRY
Composition in Vol %
Component Plant A Plant B Plant C
Hydrogen sulfide 69.20 78.97 77.82
Carbon dioxide 8.28 15.43 9.71
Hydrogen cyanide 19.99 0.35 7.71
Carbon disulfide 0.04 0.48 0.29
Sulfur dioxide 0.02 0.08 0.09
Toluene 0.11 0.03 0.05
Benzene 0.83 0.11 0.05
Ethylene - 0.50 0.41
Methane 0.33 1.91 0.68
Oxygen - - 0.29
Nitrogen 0.17 2.04 2.81
Argon 0.28 0.04 0.09
Water 0.85 0.06
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of the above impurities is more pronounced when the Glaus feed gas is a lean
stream (less than 35 percent H S) .
Effect of Hydrogen Cyanide
The hydrogen cyanide in the acid gas feed to the Glaus unit was found to
cause severe corrosion of the burner, sulfur separator vessel and sulfur line.
Analysis of the corrosion products showed that they contained large amounts of
thiocyanates.
To eliminate the hydrogen cyanide from the acid gas feed to the Glaus
unit, Bethlehem Steel has successfully applied a catalytic oxidation reactor
(cyanide destruct reactor) . The reactor uses Glaus type catalyst at a
temperature of approximately 500 to 600 F. Cyanides are destroyed according
to the following:
HCN + H20 - »- NH3 + CO
HCN + 2HS + 1/2
The above system oxidizes 95 percent of the cyanide present in the acid
gas feeding the Glaus plant, thereby eliminating the previous corrosion problems.
Other systems that have been examined for removing hydrogen cyanide from
the acid gas feed streams are:
1. Water washing (scrubbing), Bethlehem Steel,
2. Improved Glaus combustion methods, Koppers, and
3. Catalytic hydrolysis, the North Western Gas Board, U.K.
Water washing worked but required higher capital cost than the catalytic
oxidation process. Modified Glaus combustion requires a slightly air-rich
condition during Glaus combustion, resulting in lower sulfur yields. Catalytic
hydrolysis process encountered catalyst fouling with the small amounts of tars
present in the acid gas feed.
Economics and Applications
The capital cost of a Glaus plant depends on many factors such as: the
concentration of H S in the gas; the removal efficiencies (number of converter
stages); and the concentration of impurities such as hydrocarbons, cyanides
and ammonia. Costs for coke oven applications (inlet gas concentration of 500
grains per 100 SCF) are given, for two sizes (20 MM SCFD and 60 MMSCFD) , in
Tables 7-3 and 7-5. For the larger plant, which will recover about 20 ton/day
of sulfur, the capital cost is about $730,000 (1974 costs).
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For a Glaus sulfur recovery plant needed to recover about 560 ton/day of
sulfur from a 20,000 TPD SRC-I process discussed in Section 6, it was estimated
that the capital cost would be approximately six million dollars (1976 costs).
The cost would be about fourteen million dollars with a tail gas unit (SCOT
process) which is needed to meet air pollution control standards.
The Glaus process has been used commercially for sulfur recovery from
refinery, coke oven and natural gases. Although it has not been used in any of
the existing commercial coal gasification plants, it is included in the design
of a number of proposed commercial gasification and liquefaction plants for
gas streams with high H S (more than 15 percent). The Glaus process has been
used with a number of developing gasification processes, e.g. Hygas, Bigas and
the Lurgi installation at Westfield, Scotland.
WASTEWATER CONTROL TECHNOLOGY
In Section 4, the principal sources of Byproduct coke plant wastewaters
were identified as ammonia liquor blowdown, final cooler blowdown, light oil
plant (also called benzol) wastewater and coal pile runoff. Characteristics
of these wastewaters and their counterparts in the coal conversion systems
were discussed in Section 4, 5 and 6. Since the first three process waste-
water streams come in contact with coke oven gases, they contain large amounts
of the following pollutants: phenol, ammonia, cyanide, thiocyanate, sulfides,
etc. The ammonia liquor blowdown stream has the largest concentration of
these and other pollutants.
Various treatment schemes for these streams are used in the coke oven
industry. A summary of the important control/disposal methods is given below:
Light Oil Plant and Final Cooler WastewatersAlthough these streams
contain large amounts of phenol, ammonia and cyanide, a majority of the plants
send these streams to coke quenching without any treatment. (Note: It may be
construed that similar practices would not be permitted in the coal conversion
processes in analogous situations; e.g. ash quenching with dirty process
wastewater.) A few plants treat these streams similar to the ammonia liquor
blowdown before re-use or discharge to the receiving stream.
Coal Pile RunoffA majority of the plants have some kind of control
technology to recover fine coal particles from the runoff. Since there are no
existing effluent limitations on storm water runoff from the coal pile, no
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other treatment technology is used. The EPA, however, has proposed suspended
solids concentration and pH limitations that may be effective in 1983. Should
these limitations become effective, better settling systems (e.g., with
flocculating chemical addition chambers, and clarification vessels) and pH
controlling vessels will be required.
Ammonia Liquor SlowdownMost plants keep this stream segregated from
other low strength wastewaters and treat it extensively before discharge to
the receiving stream. Phenols and ammonia are removed from the wastewater by
various means. Steam stripping of ammonia, biological oxidation and/or solvent
extraction of the phenolics and organics are very common treatment technologies.
Figure 7-5 presents currently employed treatment practices at five coke
oven plants. All the plants perform extensive treatment of the ammonia liquor
blowdown before discharge to the receiving stream. The treatment schemes,
however, vary significantly among the different plants. With the exception of
Plant E, all the plants recycle the final cooler and the benzol plant (light
oil) wastewaters to coke quenching. Plant E uses complete physical/chemical
treatment for the ammonia liquor blowdown, final cooler, and benzol plant
wastewaters; carbon adsorption is the significant unit operation in the
treatment scheme. Summary features of the treatment plants are given below:
Plant AWaste ammonia liquor, light oil wastewaters and final cooler
wastewaters are treated first in a free-leg ammonia still (fixed ammonia not
removed), and subsequently, with a proprietary solvent extraction process for
phenol removal before discharge to receiving stream.
Plant BWaste ammonia liquor, after dilution with non-contact cooling
water, is treated via the activated sludge system and clarification, followed
by discharge to the receiving stream. Final cooler and benzol plant waste-
waters are sent to coke quenching for complete evaporation.
Plant CWaste ammonia liquor is treated via solvent extraction of phenol
followed by ammonia stripping (fixed ammonia released by lime treatment)
before discharge to a municipal facility. Final cooler and light oil waste-
waters are sent to coke quenching for complete evaporation.
Plant DWaste ammonia liquor is first treated in a stripping tower for
H S removal; next, phenol is removed by solvent extraction; and, finally,
ammonia is removed by steam stripping (fixed ammonia released by lime treatment) .
-125-
-------
I *-NH3 RECOVERY
PHENOL
AMMOffA LIQUOR^
SLOWDOWN
FREE LEG
NH3 STRIPPING
SOLVENT
EXTRACTION
1 -.,..- CTFAM
PLANT A
(NON-CONTACT COOLING WATER)
PLANTS
AMMONIA UQUOR
SLOWDOWN
ACTIVATED
SLUDGE
T
nit i rrirtu UIATTD
CLARIFIER
DISCHARGE
AMMONIA LIQUOR
SLOWDOWN
PHENOL
SOLVENT
EXTRACTION
NH3
LIME TREATMENT a
NH3 STRIPPING
LIME STEAM
PLANT C
Figure 7-5 (Pg. 1 of 2). Coke plant wastewater treatment systems.
-------
VA
AMMONIA LIQUOR
SLOWDOWN
POR TO DESULFURIZER
STRIPPING
PHENOL
SOLVENT
EXTRACTION
NH3
LIME TREATMENT a
STEAM STRIPPING
LIME
STEAM
PLANT D
AMMONIA LIQUOR
SLOWDOWN
SOLVENT
EXTRACTION
ncnui-
CARBON
ADSORPTION
AMMONIA
STRIPPING
No OH
STEAM
OIL
RNAL COOLER 8
LIGHT OIL PLANT
WASTEWATER
ACID
TREATMENT
DISSOLVED
AIR FLOTATION
^
CARBON
ADSORPTION
k-
RECYCLE TO
COKE QUENCHING
SPENT PICKLE
LIQUOR
PLANT E
Figure 7-5 (Pg. 2 of 2). Coke plant wastewater treatment systems.
-------
Before discharge to the receiving stream, the treated process wastewater is
mixed with once-through, non-contact cooling water. The quantities of the
treated process wastewater and the cooling water are 60 gpm and 5,220 gpm,
respectively. (Note: Bibliography 21, from which the above information was
obtained, gave data based on the composite effluent stream. The data shown in
Table 7-8 are based on the ammonia liquor wastewater only.)
Plant EPhenol is removed from the waste ammonia liquor by solvent
extraction (which reduces the phenol loading from 1,600 mg/1 to 30 mg/1)
followed by an activated carbon system. Ammonia is next removed by steam
stripping. Final cooler and light oil plant wastewaters are treated with
spent pickle liquor (and caustic soda, if necessary, for pH adjustment)
followed by dissolved air flotation. The wastewaters are next treated in an
activated carbon system before recycling for coke quenching. Both the carbon
absorption systems are preceded by a multimedia filter.
Table 7-8 gives the wastewater characteristics of the feed going to the
different treatment plants described above. Table 7-9 gives the overall
removal efficiency of the different pollutants by the treatment schemes.
Steam stripping of wastewater 'specifically to remove hydrogen sulfide is
not generally practiced in the coke oven industry. In Figure 7-5, Plant D is
shown to have a H^S stripper. However, no removal efficiency or design
information was available in the literature.
Other variations and new control technologies are being applied in
wastewater treatment. Some of these developments are discussed below.
Ammonia can be removed economically by the Phosam-W Process, details of
which are given later in this section. Ion exchange has been tried for ammonia
removal but the cost is excessive. A new development in recovery of coke oven
byproducts from ammonia liquor blowdown and coke oven gas is the pairing of
two systems: the Firma Carl Still desulfurization process (discussed earlier)
and the Phosam-W process. Armco Steel Co. at Middle town, Ohio is constructing
this plant. This system will recover anhydrous ammonia from the ammonia
liquor blowdown and the coke oven raw gas, and recover a concentrated sour gas
containing H S, HCN and CO , which will be burned in a sulfuric acid plant to
(18)
produce acid gas and also destroy HCN . A commercial wet air oxidation
system, designed to eliminate thiocyanates and cyanides from coke oven waste
liquors, is being purchased by DOFASCO from Zimpro, Inc. The expected removal
efficiency of the system is 99.9 percent for cyanides.
-128-
-------
TABLE 7-8. CHARACTERISTICS OF BYPRODUCT COKE PLANT
AMMONIA LIQUOR
Plant Identification
Flow, gal/ton
Flow, gpm
Ammonia, mg/1
BOD5, mg/1
Cyanide, mg/1
Oil & grease, mg/1
Phenol, mg/1
Sulfide, mg/1
Suspended solids, mg/1
A
139
490
1,900
1,500
102
N/A
450
N/A
N/A
B
127
390
1,380
1,280
110
240
350
629
36
C
41
169
7,330
1,120
91
101
910
197
421
D
46
53
3,900
1,200
N/A
210
610
420
2,300
E
N/A
150
5,000
N/A
20
1,000
1,600
N/A
N/A
TABLE 7-9. CONTAMINANT REMOVAL EFFICIENCY OF BYPRODUCT
COKE OVEN PLANT TREATMENT FACILITIES
% Overall Removal Efficiency
Ammonia
Cyanide
Phenol
Oil & grease
Suspended solids
Sulfide
A
44.6
95.4
89.6
99.6
N/A
N/A
N/A
B
28.8
98.5
71.8
99.8
99.1
N/A
99.96
C
92.9
47.7
18.4
73.4
80.2
74.4
37.0
D
95.3
61.2
N/A
99.1
99.5
76.6
64.4
E
99.0
N/A
N/A
99.9
99.5
N/A
N/A
-129-
-------
Following are the major coke oven wastewater treatment processes, all of
which are applicable to coal conversion waste treatment:
1. Ammonia removal and recovery processes (steam stripping followed by
sulfuric acid treatment to form ammonium sulfate, or Phosam-W
process producing anhydrous ammonia);
2. Biological oxidation;
3. Activated carbon adsorption;
4. Oil removal processes (API gravity separators and dissolved air
flotation); and
5. Phenol removal processes (solvent extraction, biological oxidation
and activated carbon adsorption).
Details of these processes and their operating experiences from coke oven
applications are given below:
Ammonia Removal and Recovery
Ammonia removal and recovery from the coke oven wastewaters is very
common as already shown in Figure 7-5. Steam stripping of ammonia from the
wastewater and absorption of the resulting ammonia vapor in the coke oven gas
saturator with sulfuric acid to yield ammonium sulfate as a byproduct is the
most common treatment. An alternate ammonia recovery process is the Phosam-W,
whereby an anhydrous ammonia byproduct is recovered from the wastewater. A
few plants strip ammonia from the wastewater and incinerate the resulting
vapors.
Ammonia Stripping
The ammonia concentration of the flushing liquor (ammonia liquor blowdown)
varies between 3,000 to 9,000 mg/1, a concentration range generally found for
the coal conversion process wastes also. At least half of the ammonia in the
above coke oven wastewater is in the fixed form, mostly as ammonium chlorides
and some as ammonium sulfides, cyanide and thiocyanate, etc. When the ammonia
liquor blowdown is steam stripped without pH adjustment, only the free ammonia
will be removed as is the case of the "free leg" stripping process. For
greater ammonia removal, the fixed ammonium is liberated by treating with an
alkali before steam stripping. Most of the plants use lime for pH adjustment
and freeing ammonia. A pH of at least 11.0 is required to liberate all fixed
ammonia. Lime consumption is substantial, being in the order of 1.0 pounds
per ten gallons of wastewater.
-130-
-------
Caustic can be used in place of lime for pH adjustment with attendant
higher operating cost. Plant E in Figure 7-5 was found to use caustic and
claimed the following advantages:
Stripping steam requirements were reduced by about 50 percent
over a lime still at the same ammonia removal efficiency,
. Accurate pH control was obtained, and
The disadvantage of a lime sludge disposal problem was
eliminated.
Lime treatment followed by steam stripping, however, is the principal
control technology for ammonia in the coke oven industry.
The ammonia stripping tower consists of a distillation column containing
mostly stripping trays, one or two rectifying trays and a partial condenser
(also called dephlegmator). The overhead vapor product generally contains
about 25 percent ammonia, which is sent to an existing coke oven saturator
where an ammonium sulfate byproduct is produced. The tower bottoms contain
around 50 to 100 mg/1 of ammonia when the pH of the feed to the tower is
maintained around 11.0 and adequate steam is used for stripping. The steam
requirement is between 0.1 to 0.2 Ib per pound of feed to the tower.
Several types of distillation columns are in use. The older plants use
bubble cap distillation columns, each containing a "free leg" section and a
"fixed leg" section. The liquid entering the fixed leg section is treated
with lime to free the fixed ammonia. Newer plants use various modifications
of the above column or completely new types of distillation trays.
Applications
Steam stripping will be used to remove hydrogen sulfide and ammonia from
coal conversion wastewaters whenever the levels of H2S and NH» are high
(approximately 1,000 ppm or greater). Steam stripping with ammonium sulfate
recovery has been used in a commercial coal conversion complex in Sasol, South
Africa. All of the commercial coal gasification and liquefaction processes
under design consideration in the U.S. show steam stripping of sour process
wastewaters for ammonia and hydrogen sulfide removal.
Phosam-W Ammonia Removal and Recovery
The U.S. Steel Phosam-W process has been in use in a dozen or more
installations around the world to recover ammonia from coke oven plants. The
-131-
-------
process has been used to recover ammonia from both the coke oven gas and the
ammonia liquor wastewater stream. To recover ammonia from coke oven gas a
scrubber (an absorber) is used to remove ammonia and form an ammonium phosphate
solution, which is then steam stripped to regenerate it for re-use. The
stripper overhead vapor is next fractionated in a distillation colucn to yield
anhydrous ammonium product.
To remove and recover ammonia from the ammonia liquor blowdown, the
wastewater is first steam stripped in a sour water stripper (see Figure 7-6).
The rest of the system remains the same. The stripper overhead vapor is sent
to a scrubber where ammonium phosphate solution is used to absorb ammonia.
The rich solution is thermally regenerated to yield fresh solution for recycle
to the absorber and a vapor containing ammonia and steam. The vapor stream is
next fractionated to yield anhydrous (99.9% pure) ammonia.
The treated wastewater from the Phosam-W process will contain about 50
ppm of ammonia provided the fixed ammonia in the wastewater feed is liberated
by pH adjustment to around 11.0.
The difference between the Phosam-W and the conventional steam stripping
followed by sulfuric acid absorption'is that the former produces anhydrous
ammonia and the latter ammonium sulfate as the recovered byproduct. Byproduct
utilization and market conditions will dictate which of the two processes is
the preferred one for a particular situation. Anhydrous ammonia product has
the advantage of easy marketability and higher product value. Primarily for
this reason, the Phosam-W process has been recommended for application to coal
conversion wastewaters in two recent studies
Biological Oxidation
Oxidation of dissolved and colloidal organic matter in wastewater by
bacteria and other microoganisms to carbon dioxide and settleable organic
sludge (consisting primarily of dead and live microorganisms) is a net result
of biological oxidation systems. Various biological treatment systems have
been tested in the pilot plant scale level with the coke oven ammonia liquor
wastewater, e.g., activated sludge, aerated lagoon, trickling filter and
rotating biological contactor. The activated sludge process has given the
best results, and full scale treatment plants in the coke oven industry are
generally of this type.
-132-
-------
SOUR GAS<4
HtPCUTANK-7
"" ~~L
FEED
STRIPPER
FRACTIONATOR FEED TANK
VCAUSTIC
^ TANK
Figure 7-6. Phosam-W ammonia recovery process.
-------
In the activated sludge process, new wastewater after being equalized
(and neutralized, if necessary) is fed to an aeration or reaction tank where
sufficient detention time is provided for the oxidation removal of the dissolved
and colloidal organics. If the wastewater is nutrient deficient, nitrogen and
phosphorus are added to the reaction tank in a minimum ratio of 100:5:1 of
BOD:N:P. Also, the wastewater feed is admixed in the reaction tank with
active, microbial solids collected from the secondary settling (clarifier)
tank that follows the reaction tank. By controlling the recycle rate and
concentration, a proper food to biological mass ratio in the reaction tank can
be maintained. In an activated sludge system the important design parameters
are: detention time in the reaction tank, MLSS concentration, clarifier
overflow rate and sludge wasting rate.
An activated sludge system has been operating successfully with the
ammonia liquor wastewater at Bethlehem Steel Coke Plant, Bethlehem, FA since
1962. Since then, other activated sludge systems have been constructed and
operated with coke plant wastewaters. Table 7-10 shows the typical design
parameters and operating data obtained from some actual activated sludge
systems.
The Bethlehem coke plant studied the effects of various factors on phenol
(37)
oxidation by the activated sludge process . Phenol loadings, ammonium ion
concentrations, tar concentrations and temperatures were important variables.
Although phenol loadings of 30 lb/day/100 cu ft could be successfully bio-
oxidized, the system was difficult to operate due to excessive foaming. At
phenol loading rates below about 12 lb/day/100 cu ft and at a phenol-to-sludge
ratio 0.7 Ib/lb MLSS, the activated sludge system has been operating well.
Phenol removals of 99.8 to 99.9 percent are being achieved. BOD removal
efficiency, however, has ranged from 85 to 95 percent. A portion of the
wastewater organics, therefore, is not readily biodegradable.
The concentration of ammonia in the reaction tank has a significant
effect on the phenol oxidation rate. Although ammonia is a nutrient source of
nitrogen for the bacteria, ammonia in concentrations exceeding the range of
1,800 to 2,000 mg/1 has shown a severe inhibitory effect on microbial growth.
Since the coal conversion wastewaters, including the coke oven ammonia liquor,
contain much higher levels of ammonia than the above range, ammonia removal
pretreatment will have to be incorporated before the biological system.
-134-
-------
TABLE 7-10. DESIGN AND OPERATING CONDITIONS OF SOME COKE PLANT ACTIVATED SLUDGE SYSTEMS
CD
(2)
(3)
(4)
1
h->
co
Ln
1
Wastewater Parameters
Influent phenol, mg/1
Effluent phenol, mg/1
BOD removal, %
Operating Conditions
NHg concentration in
aeration tank, mg/1
PH
Temperature °F
F/M, Ibs phenol
per Ib MLSS per day
MLSS, mg/1
Aeration time, hrs
1,400
0.1
85 - 95
2,000
6 - 8
80 - 100
0.7
3,300 - 4,700
56
250 - 475
0.1 - 0.3
H/A
N/A
7 - 8
>70
0,2 - 0.25
2,500 - 3,500
24
260 - 400
0.8 - 3.6
N/A
<1,200
N/A
N/A
N/A
N/A
37
3,000
0.1
N/A
N/A
N/A
N/A
N/A
2,500 - 3,00
114
(1) Data from Bibliography 37.
(2) Data from Bibliography 9.
(3) Data from Bibliography 9.
(4) Data from Bibliography 37.
-------
Dissolved tars present in the hot ammonia liquor adversely affect phenol
removal by bio-oxidation. This is probably due to occlusion of the microbial
cells by precipitated tars. Storing ammonia liquor at ambient temperature to
decrease the solubility of the tars or lime treatment of the hot liquor
followed by clarification prior to biological treatment was found to be a
satisfactory control technology that solved the problem.
Temperature at the biological reaction tank has a significant effect on
phenol oxidation. The optimum temperature is around 95°F. Adequate phenol
removal efficiency is obtained at a temperature range between 70 to 100 F
range: 99.8 percent in the temperature range of 80 to 95°F and 99.6 percent
at 70°F or 100°F.
The Bethlehem Steel Coke Plant wastewater, which has a pH range of 8.3 to
8.8, is directly fed to the activated sludge system without pH adjustment.
Dilution of the wastewater is done, however, with cooling water in order to
reduce the ammonia and dissolved solids concentrations at the biological
reaction tank.
Foaming in the aeration tank is an operating problem. It is controlled
by antifoam agents along with water -sprays. The reasons for foaming are not
fully understood. Coal mixes, coking practices and phenol loadings have
effects. Increased phenol loadings increase foaming.
Thiocyanates and cyanides generally cause problems in a biological treat-
ment process. However, although they are present in the coke oven ammonia
liquor, the activated sludge process has performed smoothly. This is probably
because of acclimation enhanced by the presence of phenol. In fact, the
Bethlehem system has been able to degrade about 70 percent of the thiocyanates
by oxidation. Cyanide oxidation efficiencies, however, have been erratic.
During periods of good thiocyanate oxidation, cyanide reduction through
(equalization) storage and bio-oxidation was around 70 percent. Other times,
efficiencies have been poor. For consistent cyanide removal to a low level,
alkaline chlorination of the bio-effluent would be necessary.
Since coal conversion wastewaters are similar to coke oven ammonia liquors,
biological oxidation systems should be applicable to this treatment for the
removal of phenols and other dissolved organics. Coal conversion wastewaters,
especially from low-temperature gasification and liquefaction processes, will
contain various types of phenolics, some of which have low biodegradability.
-136-
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The activated sludge process applied to these waste streams will probably
require additional detention time and more severe treatment than the coke oven
wastewaters. The pilot scale bio-test works at the Wilsonville and the Fort
Lewis, Washington, facilities showed this to be true. The waste treatment
experience at the above two facilities and the trickling filter plant operation
experience at the Sasol Plant complex indicate that biological treatment of
the coal conversion wastewater is practical. Prior removal of ammonia,
sulfide, and phenolics are, however, suggested pretreatment requirements.
Actual pilot tests with real waste streams from the particular coal conversion
system will be necessary to arrive at optimum design conditions and to ensure
reliable treatment plant operation.
Carbon Adsorption
Activated carbon treatment of coke plant wastewaters has been successful
in removing phenol, color, COD and BOD in both pilot plant and full scale
wastewater treatment systems. The first full-scale system went on stream in
1976 at the Cleveland District Coke Plant, a Republic Steel Corporation facility.
Figure 7-5, Plant E, shows the block flow diagram of the above treatment
facility. The ammonia liquor blowdown, containing about 1,600 mg/1 of phenol,
is first dephenolized to a level of 30 mg/1 by solvent extraction before
carbon adsorption is utilized. Other low strength wastewaters containing
around 40 mg/1 of phenol are treated with activated carbon after oil and
suspended solids removal.
Phenol concentration in the effluent can be reduced to as low as 0.01
mg/1 by carbon adsorption. The above plant, however, is operated to meet
around 1 mg/1 phenol level. Excellent color removal is attained, which is not
the case with biological treatment of the coke plant wastewater. Negligible
cyanide and ammonia removal are obtained, however, from carbon treatment.
Carbon usage at the Cleveland District Coke Plant is about 5.3 pounds per
(44)
1,000 gallons of wastewater. Other design conditions were not given .
However, in a pilot study to determine the design conditions of a carbon
adsorption system for the coke plant wastewaters, it was determined that
wastewater contact time of about 60 minutes was necessary; and the wave front
length was about 5 ft at the test conditions
-137-
-------
Advantages of carbon adsorption are many. It is a physical process which
is not affected by toxic pollutants; and it can handle fluctuations in waste
loads. Influent wastewater varying from 2 to 30 C did not show much effect on
removal efficiency. However, carbon is expensive. Regeneration requires a
lot of energy. At the Cleveland District Plant, it is felt that the physical-
chemical treatment (Plant E in Figure 7-5) of the coke plant wastewater is
competitive with the physical-biological treatment systems.
Carbon adsorption probably will have applicability in coal conversion
wastewater treatment, especially for final polishing treatment and pretreatment
of wastestreams that contain toxic and refractory substances. Due to the
differences in the characteristics of the coal conversion and coke oven waste-
waters, the performance and design conditions might be different. Laboratory
tests with actual coal conversion wastewater will be necessary (adsorption
isotherm and column runs) before full-scale plant design.
Some coal conversion systems generate char as a byproduct, which is
utilized in a gasifier, e.g. COED process. If it could be possible to utilize
the byproduct char as an activated carbon, then carbon treatment of the waste-
water for that system will become very economical, since regeneration will
not be necessary. The spent carbon would be combusted/gasified in the usual
manner. Whether or not char will behave as an activated carbon is to be
determined on a case-by-case basis. The coke or fine coals generated in the
coke oven process, however, has not been successfully used to remove phenol
and dissolved organics from the coke oven wastewaters .
Oil Removal
In the coke oven wastewater treatment both API separators and dissolved
air flotation (DAF) systems are used to remove oils. API separators are used
to remove oils from storm water runoffs and from process wastewaters generated
in the light oil recovery and refining section of the Byproduct coke oven
plant. Dissolved air flotation is used to remove emulsified oils (an example
is shown in Figure 7-5, Plant E).
API gravity separators and DAF systems will be the primary treatment of
oily wastewaters in coal conversion plants. Such wastewaters include process
wastewaters and storm water runoffs from the coal conversion complex. All
-138-
-------
developing coal conversion plants in the U.S. use these types of treatment for
oily-waste waters. The wastewater treatment systems at the South African and
Yugoslavian Lurgi plant complexes also use them.
Phenol Removal and Recovery
Phenols are being removed from coke oven weak ammonia liquor by solvent
extraction, steam stripping and/or biological oxidation. Steam stripping for
phenol removal is not a common treatment application. Phenol forms a minimum
boiling point azeotrope with water at 9.2 percent (by wt.) phenol, and there-
fore, stripping requires large amounts of steam, and proves to be uneconomical.
Biological oxidation removal efficiencies of phenol, as discussed earlier, are
high (99.8 to 99.9%), but requires proper plant design and operation.
Fluctuations in influent phenol composition can create upset conditions in the
biological system. Solvent extraction, however, can more reliably handle feed
fluctuations and recover byproduct phenol from the waste stream. Solvent
extraction becomes most economical with highly contaminated streams and with
biological oxidation for dilute streams. Solvent extraction becomes competitive
with biological oxidation at phenol concentrations of about 1,000 mg/1 (waste
flow rates above 50 gpm).
The earliest large-scale use of solvent extraction for phenol recovery
from coke oven wastewater was done in Germany. Benzene or light oil solvent
was used in some processes to extract phenolics. Regeneration of the benzene
(or light oil) was accomplished with caustic extraction. The process thus
recovered phenolics as sodium phenolate. Another process used tricresyl
phosphate as a solvent for phenol extraction. Both these processes are dis-
cussed in detail in the following sections.
Newer proprietary processes are presently available for phenol extraction
which claim to be more economical. These processes use volatile solvents
which are easier to recover during regeneration steps. The Phenosolvan process
is one which has been used commercially to recover phenol from Lurgi process
gas liquor in South Africa and Yugoslavia (see Figure 5-2). This process uses
isopropyl ether as the solvent. Details of the Phenosolvan process are dis-
cussed elsewhere , and therefore, will not be covered here. The Phenosolvan
process is likely to be used in several of the presently planned coal gasifi-
cation projects in the U.S.
-139-
-------
Jones and Laughlin Steel Corp. has developed a proprietary solvent
extraction process which has been used in several coke plants in the U.S. The
process can recover 99+ percent pure phenol and generate an effluent containing
about 1 ppm of phenol. It uses a Karr reciprocating plate extractor for
phenol extraction (the type of solvent used is proprietary information), a
solvent stripper and a distillation column to produce pure phenol.
To illustrate the types of equipment involved in solvent extraction the
light oil (benzene) - caustic process and the tricresyl phosphate process, the
two earliest processes still in use, are discussed in detail in the following
sections.
Light Oil - Caustic Process
The phenolized ammonia liquor is pumped into the distributor header
located near the top of the ammonia liquor scrubber (see Figure 7-7). The
liquor passes downward through the scrubber and comes in contact with a
counter-current flow of light oil. The light oil, having a lower specific
gravity than the liquor, rises to the top of the column as it extracts the
phenol from the liquor. The ammonia liquor falls to the bass of the column
and is pumped away for further treatment.
The phenolized light oil flows out the top of the ammonia liquor scrubber
to the caustic washer in the caustic treatment tower.
The caustic treatment tower is divided into three compartments. The
bottom chamber is the light oil circulation tank which is the pumping chamber
for the dephenolized light oil. The upper two sections are the caustic washing
compartments, packed with ceramic tile. In these compartments, the phenolized
light oil passes through the caustic to remove the phenols by chemical reaction
between the caustic and the phenols, as follows:
C,HCOH + NaOH * C.,HcONa + H_0
o j bo 2.
phenol sodium hydroxide sodium phenolate water
The phenolized light oil passes from the ammonia liquor scrubber to the
distributor header on the No. 1 washer to a distributor header on the No. 2
washer to the overflow line, where the light oil, now dephenolized, is returned
to the circulation tank.
After about a week, the caustic in the No. 1 washer is saturated with
phenols. At this point, the recovery operation is shut down so that the spent
caustic can be replaced by fresh solution.
-140-
-------
CAUSTIC CHARGE
DEPHENOLIZED
AMMONIA LIQUOR
WASHER N* 2
DEPHENOLIZED LIGHT OIL
PHENOLIZED LIGHT OIL
AMMONIA LIQUOR
SCRUBBER
PHENOLIZED AMMONIA LIQUOR
LIGHT OIL CAUSTIC
WASHER
MAKE-UP
LIGHT OIL
-WASHER N* I
ALIGHT OIL
CIRCULATION
TANK
TO CARBOLATE
"CONCENTRATOR
FROM CAUSTIC
SODA STORAGE
Figure 7-7. Phenol removal by light oil caustic process,
-------
The sodium phenolate in the No. 1 washer is drained into the carbolate
concentrator. Then the partially phenolized caustic in the No. 2 washer is
drained to the No. 1 washer, leaving the No. 2 washer empty to receive a fresh
supply of caustic soda solution.
The sodium phenolate in the concentrator is boiled to remove entrained
solvent and moisture. It is then neutralized with carbon dioxide to liberate
crude phenols and phenol homo logs.
The phenol removal efficiency of this process can be expected to be at 98
to 99 percent.
High-Boiling Solvent Process
Extraction with a high-boiling solvent allows for direct phenol recovery
by distillation or possibly by a simple flash operation. A solvent such as
tricresyl phosphate has been used in this type of process. This solvent has a
distribution coefficient for phenol about 8 times larger than that for benzene,
and is virtually Immiscible with water (solubility < 15 ppm). Distillation
can be used to separate the phenolics from the tricresyl phosphate, and since
the latter has a very high boiling point (265°C @ 10 mm Hg), vacuum distillation
should be a simple flash operation where the spent solvent is heated in a
series of interchangers and exchangers, and flashed across a control valve
into a tank where the phenols are vaporized and removed from the solvent (see
Figure 7-8).
The result of the distillation or flash operation is the recovery of a
very pure phenol product. One problem with this process is that less volatile
phenolics and other organics tend to build up in the recirculated solvent,
causing problems of increased viscosity and decrersed phenol capacity. Two
solutions are possible: either the process can be shut down and loaded with
fresh solvent, when necessary, or a continuous purge stream can be removed
from the system to maintain a steady concentrate of heavier phenolics and
organics in the solvent. Disposal of the spent solvent becomes a problem.
When these disposal costs are taken into account, this process becomes less
attractive for a large size plant.
The phenol removal efficiency of this process can be expected to be at 95
to 99 percent, depending upon the design of the system.
-142-
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ORGANIC SOLVENT
SEPARATOR
RECOVERED
EXTRACTION
SPENT
SOlWNT
HEATER
SOLVENT
STORAGE TANK
»-S£AL TANK
PHENOLIZED
DEPHENOLIZED
AMMONIA LIQUOR
AMMONIA LIQUOR
ORGANIC
SPENT SOLVENT
PUMP
SOLVENT
FEED PUMP
EFFLUENT
TRANSFER
PUMP
RECOVERED
SOLVENT
PUMP
ORGANIC
REMOVAL
PUMP
Figure 7-8. Phenol removal by high boiling solvent process
-------
SOLID WASTE DISPOSAL METHODS
Most of the sump breeze (coke) collected from quench water circuits is
sold (primarily, larger size fractions), recycled to the coal pile, or used in
the sinter mix in steel mills.
Tar sludge obtained from the tar storage tank is usually disposed of by
landfill. Incineration is an alternate method of disposal.
Coke oven plants utilizing biological systems to treat wastewater generate
an excess biomass residue which is usually landfilled.
The coke oven gas desulfurization processes convert the sulfur in the
off-gases to commercial elemental sulfur, sulfate, or sulfuric acid, instead
of producing residues.
LIGHT OIL UPGRADING PROCESSES
Light oils and coal tars are two of the coke oven byproducts which are
further refined to produce upgraded usable products. Coal tar processing is
generally done outside the coke oven industry by chemical companies, and
therefore, will not be covered in this report, since it is beyond the scope of
this study. However, light oil refining is extensively done by the coke oven
industry; consequently, it will be discussed in subsequent paragraphs.
Coke oven light oil is rich in benzene, toluene, and xylene (BTX).
However, these aromatics are contaminated by various compounds such as paraffins,
naphthenes, olefins and sulfur pollutants (see Table 7-11 for a typical light
oil composition). These contaminants can be reduced by the following processes:
1. Acid treatment followed by caustic soda wash and distillation;
2. Hydrogenation followed by extraction and distillation; and
3. Hydrodealklation by the LITOL process.
Acid treatment is the traditional method for purifying light oil. The
yields of BTX products from this process are lower and the sulfur content of
benzene produced by acid washing is higher (100 to 400 ppm of thiophene)
compared to the Litol process.
The multiple steps in the extraction process will produce high quality
aromatics from the light oil. It appears, however, that the capital and
operating costs of this process will be higher than the LITOL process. No
commercial plant has been built to upgrade coke oven light oil using this
process.
-144-
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TABLE 7-11. TYPICAL RAW LIGHT OIL COMPOSITION
Component Wt %
Cyclopentadiene 0.35
CC-C, Non-aromatics 0.06
_> o
Benzene 73.46
Thiophene 0.44
C-.-Co Non-aromatics 0.02
/ o
Toluene 14.82
Xylenes & Ethylbenzene 3.03
Styrene 1.55
Carbon Bisulfide 0.45
Propylbenzene 0.05
Mesitylene 0.14
Pseudocumene 0.25
Dicyclopentadiene 0.33
Diethylbenzene 0.05
Coumarone 0.31
Indene & Durene 1.98
Naphthalene 1.83
Dimethylnaphthalene 0.43
Other Methylnaphthalenes and Higher 0.45
Homologs of Benzene
100.00
-145-
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The LITOL process, which was developed by the Houdry Division of Air
Products and Chemicals, Inc., has been employed commercially since 1964 to
produce high quality (even reagent grade) benzene from coke oven light oils.
Seven commercial plants have been build worldwide utilizing the LITOL process.
It is anticipated that LITOL will be applied widely for upgrading csal
gasification and liquefaction derived light oils (naphthas) in the future.
LITOL Process
The Houdry LITOL process is a catalytic process with two principal
reaction zones: a hydrogenation section, and a hydrocracking/dealkylation/
desulfurization section. Various chemical reactions occur within the LITOL
reactors. Figure 7-9 shows some of the major ones. Hydrodealkylation
reactions dominate, explaining why the Litol process produces mostly high-
quality benzene with very little CQ aromatics.
o
Figure 7-10 depicts the flow diagram for the LITOL process. The crude
light oil is pumped to unit pressure (700 to 900 psig), heated to 1,050 to
1,150 F, and vaporized by contact with a hot hydrogen stream. The vaporized
charge is taken overhead while a small amount of tar (styrene polymer) is
withdrawn as bottoms product. The overhead vapors flow through a pretreat
reactor for saturation of the remaining styrenes and through a fired heater to
bring the light oil hydrogen stream up to reaction temperature. The preheated
feed flows through the reactors (which contain a chromia-alumina catalyst),
exchanges heat with the feed streams, and is flashed in a high-pressure flash
drum.
The non-aromatic materials - mainly paraffins, olefins, diolefins,
naphthenes, and sulfur compounds - are completely converted to lighter hydro-
carbons and to hydrogen sulfide. Substitute aromatics are partially
hydrodealkylated to produce additional benzene.
The vapors from the flash drum (after the reactors) divide, a portion
being vented to fuel while the rest are recycled to generate hydrogen. The
flashed liquid flows to a stabilizer tower for removal of light ends, through
a clay treater for removal of trace olefins and then to product fractionation.
-146-
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HYDRO-CRACKING
1. CH3-CH(CH3)-CH2-CH(CH3)-CH3 + H
2,4- Dimethyl Pentane
2.
Cyclohexane
C6H12
Cyclohexane
3H,
2H,
C3H8
Propane
3C2H6
Ethane
2C3H8
Propane
C4H10
Butane
HYDRODE ALKYLATION
1. C-.H + H,
7 8
Toluene
2' C8H10
Ethylbenzene
Me thane
E thane
Benzene
C6H6
Benzene
HYDRODESULFURIZATION
1. C4H4S +
Thiophene
2. CS2
Carbon Bisulfide
4H
4H2
C4H10
Butane
H2S
Methane
HYDROGENATION
1.
C8H8
S tyrene
Ethylbenzene
DEHYDROGENATION
Cyclohexane
C6H6
Benzene
3H,
Figure 7-9. Typical LITOL reactions.
-------
OPTIONAL
MAKE-UP HYDROGEN
FUEL GAS
CRUDE
GENERATION a
PURIFICATION
LIGHT OIL
VAPORIZER
POLYMER
HOUORY
LITOL
REACTORS
BENZENE
TOLUENE
FLASH
DRUM
mo
"
CQ FRACTION
te.
u
o
>
_i
u
2g
N O
!«
I*J<
ZZ
UJQ
CE
O
u
K.
00
U
C9* BOTTOMS
Figure 7-10. Houdry's CITOL light oil upgrading process.
-------
Benzene product is separated from heavier aromatics by conventional
distillation. The benzene tower bottoms, consisting primarily of toluene, can
be recycled to the process for further conversion or can ba further distilled
to produce a toluene product with recycle of the bottoms from that tower. An
additional tower can be used to separate C0 aromatics from a heavier Cn
o y~t"
fraction.
The process is a consumer of hydrogen which can be generated readily in a
steam methane reformer using the methane-rich recycle gas stream (flash drum
vapor) as the feed stream. No outside source of gas is needed to maintain the
required hydrogen balance. Hydrogen consumption is about 0.47 moles per mole
of benzene product.
Typical yields from the LITOL process are shown in Table 7-12 for two
cases: toluene recycle, and no toluene recycle. When higher benzene yield is
desired, toluene can be recycled to the LITOL reactor for conversion to benzene
by hydrodealkylation reaction (See Figure 7-7).
The installed capital cost of a LITOL facility to. process 70,000 metric
tons per year of coke oven light oil will be about $8.1 million dollars (1978
costs) approximately distributed as follows:
Unit Installed Capital Cost
Feed Pretreatment $ 800,000
Main LITOL $4,800,000
Cryogenic $1,300,000
Hydrogen Generation $1,200,000
$8,100,000
The operating costs of the plant are summarized in Table 7-13 which shows
that the total cost per ton of benzene product is $153.34. Since the selling
price of benzene is about $180.00 per metric ton, there is an economic incentive
to refine the crude light oil. An additional benefit of the process is the
removal of sulfur and nitrogen pollutants from the crude light oils which would
contribute to our pollution problems, if not removed by upgrading. In the
LITOL process, sulfur and nitrogen are converted to hydrogen sulfide and
ammonia, which are subsequently removed by the purification steps associated
with the hydrogen plant.
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TABLE 7-12. TYPICAL LITOL PROCESS YIELDS
(Basis: 100 Ton of Raw Light Oil Feed)
No Toluene Recycle Toluene Recycle
Reactor Feed^ Products Reactor Feed^ Products
Hydrogen 0.95 0.10 1.13 0.13
Hydrogen Sulfide 0.41 0.41
C1~C5 Hydrocarbons 0.53 6.80 0.59 8.13
C6 Non-Aroma tics 0.59 0.02 0.59 0.02
Cy Non-Aromatics 0.21 0.21
Benzene 74.09 86.66 74.09 92.88
Toluene 19.22 7.36 19.22 0.02
Cg Non-Aromatics 0.09 0.09
Xylene 3.12 3.12
Ethylbenzene 0.22 0.22
Styrene 0.62 0.62
C9+ 0.70 0.01 0.70 0.01
Thiophene 1.02 1.Q2
101.36 101.36 101.60 101.60
(1) Includes makeup hydrogen (95 mol% H~ and 5 mol% C, composition)
-150-
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TABLE 7-13. LITOL PROCESS OPERATING COST
(Basis: 70,000 Metric Tons/yr of Light Oil Feed)
Item
Feedstock
Utilities
Fuel
Power
Steam
Cooling Water
Chemicals & Catalyst
Sub-total
Units
$105/M.T.
$8...00/MMKcal
2.0C/KWH
$7.00/M.T.
0.8C/M3
U.S. $/Metric ton of Benzene
142.27
11.27
1.67
1.05
0.31
0.55
157.12
Fixed Cost
Operating Labor
Operating Overhead
Maintenance
Supplies (including
Insurance & Taxes
Depreciation
Sub-total
$7.00/hr-4 men/shift
150% of Operating Labor
4% of Investment
1% of Investment
15 years-Straight line
4.75
7.13
6.27
0.50
1.57
10.45
30.67
Credit
Fuel Gas
Fuel Oil
Toluene
TOTAL
Sub-total
$8.00/MMKcal
$75/M.T.
$150/M.T.
5.46
16.21
12.78
34.45
153.34
NOTE: LITOL unit feed is 59,750 MTPY after prefractionation.
51,650 MTPY of benzene and 4,400 MTPY of toluene.
Yields
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The LITOL process is expected to have wide application in upgrading coal
conversion system light oils. It has been considered for upgrading the light
oils (naphthas) that will be produced from the proposed El Paso Lurgi process
Although the BTX concentrations of the naphtha from the referenced plant will
be only 46.8 wt. percent as compared to about 85 percent for the coke oven
light oil, upgrading of the naphtha is still considered to be economic.
The reason the BTX concentration in the naphtha from the El Paso Lurgi
plant will be about 46.8 percent is that a sub-bituminous type coal will be
used in the process. If, instead, a bituminous coal similar to the coal fed
to the coke ovens, is used in the Lurgi process, the BTX concentrations in the
Lurgi naphtha will also be about 85 percent. This dependence of BTX concen-
tration on coal type in the light oil has been proven by the Lurgi gassifi-
cation data.
At design conditions, 20,000 Ibs/hr of naphtha byproduct will be produced
from the El Paso Lurgi plant. Processing of this naphtha through the LITOL
system will yield the following products:
Quantities, Ibs/hr
Benzene - 8,732
C + - 1,000
c5- - 1,000 .
The process will require 3,827 Ibs/hr of make-up hydrogen. Waste streams
from the above LITOL system will contain the following:
A small stream of sour gas, 827 Ibs/hr, which will contain about
5 percent H S and 4 percent NH_.
A small amount of process wastewater, 291 Ibs/hr, which will require
treatment for ammonia, sulfides and oil removal.
FUGITIVE EMISSIONS CONTROL
Air pollution control technology (existing and proposed) for the collection
and removal of particulate matter and gaseous emissions in the Byproduct coke
oven industry is discussed in subsequent sections. Since much of the air
pollution control technology has been or is being developed around the coke
oven batteries and coke quench systems, the major thrust of industry and
manufacturers has been to focus on these areas of the plant for the control
of the more obvious visible particulate matter, and gaseous emissions.
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The coke ovens are a major source of air pollution emissions in the steel
industry . Topside coke oven workers have a substantially higher risk of
having cancer than the average worker (see Section 8 for details), probably
from carcinogenic materials associated with the particulate fraction of the
coke oven emissions. Various schemes to control the fugitive emissions and
alleviate potentially adverse health effects are being developed. The Air
Pollution Control Association and the EPA co-sponsored a conference on "Control
of Air Emissions from Coke Plants" which was held in Pittsburgh, PA in April
1979. In this conference, various fugitive emission control technologies were
discussed which are reflected below.
Coal charging emissions can be controlled by: staged charging with coke
oven raw gas evacuation to the gas collecting main; larry cars with gas
capturing equipment (e.g. hoods and ducts) and wet scrubbers; and pipeline
charging (closed charging). Coking cycle emissions can be minimized by improved
door sealing, but better control is obtained with sheds ducted to air pollution
control devices (e.g scrubbers) whose main purpose is to control pushing (coke
discharging) operation emissions. Other systems being developed for pushing
emission control are various mobile and fixed duct collection systems
integrated with control devices (e.g. scrubbers, fabric filters, electrostatic
precipitators). Coke quenching emissions can be controlled by the use of a
hooded quench system, or they can be significantly reduced by the use of dry
quenching methods. A summary of the various coke oven control technologies
for fugitive emissions are shown in Table 7-14. Many of these control methods
will have applications in the synfuels industry in analogous situations.
Charging Emission Control
Coal is charged into the coking chamber through charging holes provided
in the roof of the oven. The oven retort or coking chamber and the heating
system are designed to process a coal charge of definite volume with a level
upper surface approximately one foot below the oven roof. The coal is charged
from a device called a larry car situated on tracks supported by the battery
top. The charging of coal into coke ovens results in a fugitive emission
consisting of coal dust, tars and gases from the changing hole. Several types
of control technologies are available to contain emissions during oven charging.
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TABLE 7-14. BYPRODUCT COKE OVEN FUGITIVE EMISSIONS CONTROL
Operation/Emission
Source
Charging
Pushing/
Discharging
Ul
-e-
Quenching
Coking
Pollutants
Participates, SO ,
hydrocarbons, CO, NO
& ammonia
Parciculates, hydro-
carbons, ammonia & CO
Coke breeze,
participates, organics
Participates, hydro-
carbons, CO, ammonia
& NO
Control Technology
Staged/charging (with evacuation of oven
gas to collecting main)
Larry-mounted scrubbers
Fixed duct secondary collectors with gas
cleaning systems (e.g., bag house)
Closed charging systems (tested in PDU
scale only)
Bench-mounted self contained hoods
with gas cleaning systems
Coke car - mounted hoods
Fixed duct hoods with gaa cleaning systems
Spray systems
Coke-side enclosures (sheda) with gas
cleaning systems
Quench tower (containing internal baffles)
Dry quenching
Closed quenching
Mechanical/Magnetic lid lifters
Electrical eye synchronization
Oven and door maintenance
Oven/battery sheds
Relative
Control Efficiency*
High
High
High
High
High
High
High
Med.
Med.
Med.
High
High
Unknown
Unknown
Low
High
Coal Conversion
Applicability
Not applicable
Scrubbers applicable
Gas cleaning system applicable
Possibly applicable
Possibly applicable
Gas cleaning system applicable
Gas cleaning system applicable
Applicable
Applicable
Possibly applicable
Possibly applicable
Applicable
Possibly applicable
Possibly applicable
Applicable
Applicable
*High - 90+ %
Medium - 60-80%
Low - 60% or less
-------
Staged Charging
A slight negative pressure is maintained on the ovens to draw gases from
the space above the charged coal into a raw gas collecting main. This practice
is call "charging on the main." This negative pressure is provided by a
steam jet aspiration system. While the aspirator performs its task, air is
drawn into the oven through the charging holes and leveler door. Since air is
undesirable when introduced to the gas recovery equipment, the time required
for charging is kept to a minimum.
Staged charging also known as "smokeless charging", besides utilizing a
steam jet aspirator, incorporates other novel control approaches. The larry
car is sealed, air conditioned, and capable of mechanically (magnetic lifter)
opening the lids. The coal-containing hopper is lowered over the open oven
port as in other systems, but when charging is complete a plug of coal is left
in the hopper before the lid is replaced. The charging is done sequentially,
filling one side of the oven first then working across to the other side. The
advantage of this procedure is the elimination of the sudden burst of emissions
from the simultaneous charging of all oven ports. The Clairton Works of
United States Steel (U.S.S) was one of the first plants to achieve effective
stage charging through personnel training, observation and monitoring. During
the period between 1973 and 1977, U.S.S was able to reduce the charging time
from 50 seconds down to 6 seconds for equivalent opacity (visible emissions)
greater than or equal to 20 percent. This represented an overall reduction of
almost 90 percent of the fugitive emissions attributed to charging coke ovens.
In 1973, C.F. & I Steel Co, Pueblo, Colorado initiated sequential (staged)
charge techniques which achieved a reduction in visible emissions (greater
than 40% equivalent opacity) from 85 seconds per charge to 27 seconds per
charge. Additional techniques they employed, such as modification of steam
aspiration nozzles and installation and maintenance of hydraulically operated
mechanical gooseneck cleaners, have currently reduced the opacity of charging
emissions down to 5.8 seconds per charge. This application also represents a
greater than 90 percent reduction in visible emissions during the charging
operation of a coke oven.
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Since staged charging consists of special mechanisms and procedures of
coal feeding to the ovens, these techniques do not appear to be applicable to
coal conversion systems. Each coal conversion system has its own coal feed/
condition which is unique to the given system.
Gas Scrubbers
Gas scrubbers on larry cars were first introduced in Germany and brought
to the U.S. in the late 1960's when tall ovens became popular. In principle,
all scrubber cars operate in the same manner. The coal is discharged from the
larry car into the oven through a spout and the evolved gases are collected in
an annular space around the spout, ignited and cleaned before being discharged
to the atmosphere. Wet scrubbers, installed on the larry car, demonstrated a
control efficiency for charging emissions by greater than 95 percent for
particulates.
The scrubber system associated with this control technology should be
applicable to coal conversion systems. However, the capturing devices (e.g.,
larry car with concentric feed spout and exhaust system), are not applicable.
Fixed-Duct Secondary Collectors
More recently, the Japanese have installed a fixed-duct, secondary col-
lector and gas cleaning system which are utilized in conjunction with larry
car wet scrubbers. Connection ports to a stationary main are provided at each
oven to direct the larry car scrubber exhaust to a fixed scrubber and fan for
secondary emission control and exhaust to the atmosphere.
Closed-Charging Systems
The closed-charging system, also known as "pipeline charging," reduces
most of the emissions during charging by employing a completely enclosed
charging operation. The coal is first crushed, then it is preheated to 500 F
to remove all of the moisture. The dried coal is then stored in a charging
bin which is pressurized prior to charging. Afterwards, the coal is introduced
into a pipeline which follows the length of a coke oven battery with pipes
connecting to each oven along the run on the battery. The pressure in the bin
is sufficient to start the coal in motion and its movement is continued by a
series of strategically located jets that supply steam at supersonic velocities.
These jets permit both upward and forward motion of coal through the pipe. As
the coal loses momentum and starts to fall to the bottom of the pipe, another
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set of steam jets is activated and prevents the disentraintnent of the coal.
The coal is then directed in the oven which is prepared for charging. Coal
can be charged at a rate of 2.5 tons per minute. Since it is partially
fluidized, it tends to spread itself evenly throughout the oven obviating the
need for a leveling bar. The theoretical control efficiency for this prototype
system approaches 100 percent. However, in practice it has been found that
emissions evolve from the charging hole lids and the coke oven doors due to
the high pressure in the ovens. Closed-charging systems, similar to the type
described above, are being used or developed for some coal conversion systems.
Pushing or Discharging Emission Control
After the coal has been coked, it must be pushed from the oven and
transported to a quenching station. The pusher is a combination of three
machines: a pusher, a leveler and a door extractor. It is designed to operate
on an independent track which runs parallel to and independent of the battery.
The coke receiving quench car operates on tracks at grade; also, independent
of the battery and in the opposite side of the coke oven from the pusher
machine. All pushing or discharging emission control systems operate in
conjunction with the quench car.
The performance of the pushing/discharging emission control system is
extremely sensitive to the condition of the coke when it is pushed. If two
important coking cycle variables, oven residence time and homogeneous oven
temperature, are not carefully maintained throughout the cycle "green coke"
may form. If the coke is pushed in this undesirable condition, no presently
developed pushing control system can effectively capture and control the
excessive emissions associated with it. The various system control efficiencies,
where given, do not presume green coke pushes.
The pushing of the incandescent coke from the oven into the quench car
results in emission of hot coke particles and tars, as well as gases as it
leaves the oven and is dumped into the quench car. Various systems being
developed for pushing emission controls are discussed below.
Bench-Mounted Self-Contained Hoods
Bench-mounted, self-contained hood systems include designs incorporating
mobile hoods, ducts, scrubbers or other high-efficiency control devices, and
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fans that are mounted on a separate vehicle which traverses the length of the
battery on the bench with the coke guide. Utilization of this approach has
been confined to West Germany. A mobile version of this gas cleaning system
could have application for the coal conversion systems.
Coke Quench Car-Mounted Hoods
Coke quench car-mounted hood systems include a family of designs employing
hoods, ductwork, scrubbers, and fans which are mounted on and travel with, the
coke quench car.
Many recent commercial designs of this type of control system have been
developed jointly by industry and the EPA. Five different systems are operating
or are proposed to go into operation include: Koppers for its own Erie, PA
plant and for Bethlehem Steel's coke plants in Johnstown, PA; U.S.S for its
Gary Works No. 2 Battery; Dravo for Armco Steel's new battery at Middletown,
Ohio; Granite City Steel, Div. of National Steel Corp., and McKee Otto for the
Granite City plant; and Chemico Air Pollution Control Co., Div. of Envirotech
Corp. for Jones and Laughlin Steel Co.'s Pittsburgh Works. Also, National
Steel Corp., for its Brown's Island coke plant, has been operating a closed
quench car system for several years. National has started up its system on a
coke battery at Armco Steel in Hamilton, Ohio and recently installed a system
at the C.F.&I coke plant in Pueblo, Colorado.
The principal features of these designs include a modified door machine
with coke guide housing attached, a mechanism to permit the discharge of hot
coke, a control car containing gas cleaning equipment, and the operator's cab
and quench car with fixed hood. The gas cleaning systems will be applicable
to coal conversion systems but the other special design features may not be
suitable for coal conversion applications.
Fixed-Duct Hoods
Fixed-duct hood systems provide a stationary duct, fan, and scrubbing
system with duct ports for connecting to a mobile hood arrangement over the
pushing operation.
A system of this type commenced operation at the Minister Stein coke
plant in Germany in early 1975. The system was designed and constructed by
Hartung, Kuhn and Co. and formed the basis of the design of the Allied
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Chemical Co. Ashland, Kentucky plant system. This system was furnished by
Dravo-Still, in conjunction with Hartung, Kuhn and Co. The Allied Ashland
system began operation in the United States in December, 1978.
The Dravo-Still system is a combined mobile and land-based system. The
mobile section is made up of two parts. The first part consists of a main
quench car hood, a tripper car, a regenerator heat exchanger, a short section
of main hood ductwork and a short section of auxiliary ductwork which connects
to the coke guide hood ductwork. The second part is the hood and ductwork
located on the door machine above and along the sides of the coke guide. The
duct from this part is connected to the primary ductwork by a telescoping duct
section mounted in the door machine. The main feature of this system consists
of the gas transition (tripper) car which travel along the top of a stationary
duct placed along side the quench track. The duct possesses a continuous
opening along the top which is internally braced and covered with grating to
provide support for the belt which seals the opening. The tripper car lifts
the belt over the duct inlet section between the tripper rolls and covers the
duct opening to convey the gases from the mobile hooding into the stationary
duct.
When the system is in operation, emissions are collected simultaneously
above the coke guide and quench car and are carried through the stationary
duct to the particulate collection equipment, which may be a scrubber, fabric
filter or wet electrostatic precipitator. Although no test data are available,
preliminary tests have shown favorable results. A similar system is operating
successfully at Dominion Foundries & Steel Ltd. (DOFASCO), Hamilton, Ontario
in Canada. Three additional systems are under construction which will utilize
a fabric filter particulate collection device. These type systems, also known
as "smokeless pushing" have been estimated to achieve 95 percent collection
efficiency. The gas cleaning system associated with this control technology
will be applicable to the coal conversion systems. However the fixed-duct and
mobile hood arrangement will probably not be suitable.
Spray Systems
Water spray or fogging systems can be employed to minimize pushing
emissions. Such sprays can be located at the coke guide or the coke quench
car. Where sprays alone can be partially effective, they are more often used
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to enhance the effectiveness of hood and scrubber systems. Electrical safety,
ice formation, and water removal are necessary concerns with this type of
system. Spray systems will have applications in coal conversion systems in
many operations, e.g., dust control from coal storage piles.
Coke-Side Enclosures
Coke-side enclosures or sheds entail nearly complete enclosure of the
coke side of the battery instead of local hooding. Numerous design advantages
are cited, which are simplicity of design and operation, ease of retrofitting
to existing batteries, and the ability to collect emissions from leaking
doors. Since the shed encloses the coke side portion of the battery, some of
the coke oven operators working in this area might be exposed to higher
emissions. These emissions could subject the workers to additional health
hazards .
Enclosures, sheds and hood systems should have applications in coal con-
version systems for fugitive emissions control.
Quenching EfrHssion Control
Quenching (wet) in most modern plants is accomplished by receiving the
charge of hot coke from the ovens in the quenching car, which is conducted to
the quenching station or tower by a locomotive, where the coke is quenched by
water.
Quench Tower With Internal Baffles
The most common methods of reducing p articulates and gaseous emissions
which rise with the steam evolved from quenching are to trap the pollutants as
they ascend through the quench tower, or to reduce the amount of steam generated.
Both of these goals are achievable to a limited extent through use of internal
baffles, also called "mist suppressors". They are simply different arrangements
of wooden slats which are inclined and perpendicular to the path of the rising
steam in the tower. As the steam passes through the wooden configurations,
particulates tend to become trapped on the wood. Also, some of the steam
recondenses on contact with the cooler surface of the baffle.
Recently, the Dominion Foundries & Steel Ltd. at Hamilton, Ontario had
tests conducted on their quench tower. The results of the testa which varied
quench tower, quench water and mist eliminator conditions .gave an average of
0.245 pound of p articulate matter per ton of coal charged. Also it was
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determined that, upon using recycle water for quenching, the emission rate was
0.21 pound per ton of coal charged; and using once-through bay water the
average was 0.234 pounds per ton of coal charged. Also, it was found that
increasing the baffle angle from 20 to 40 to 30 to 60 had the greatest
effect on increasing the collection efficiency. The overall control efficiency
was found to be 60 percent for particles greater than 100 microns. Test
efficiencies have been reported by others as high as 80 percent.
Also, in tests conducted at the Lorain Works plant of U.S.S aside from
particulate matter, organic compounds were also detected. It was found that
10 to 100 pounds per quench of organics, with the bulk identified as aromatics,
were being emitted to the atmosphere. These organics are associated with the
oil used for controlling the bulk density of the coal charged to the ovens.
Dry Quenching
Dry quenching involves the use of an essentially inert gas as the heat
transfer medium. Heat transfer from the coke to the inert gases is accomplished
by direct contact of the gases with the coke. The gases are then conducted
through a dust collector to a waste-heat boiler or other type of heat exchanger
device.
Plants employing this technique have been operating since 1917, mostly
located at town gas plants with the largest handling 1500 TPD. The only
existing plant is in Homecourt, France, which cools about 1500 TPD of blast
furnace coke. The USSR has developed their own dry quench technology which it
has applied to 50 large, new blast furnace coke making facilities, and requires
all new and retrofit facilities.
Basically, the system operates in the following manner: incandescent
coke is carried to the dry-quenching station in a transfer car, which is
raised to the top of the dry-quenching bunker. The hot coke is dumped into
the bunker, after which the charging hole then closes and the empty car is
returned to the track for another load. As the coke descends the bunker
cooling chamber, it is cooled by a counter-current flow of circulating gas.
Quench time in the chamber ranges between 2 and 4 hours. At the completion of
this cooling cycle, the coke, which has cooled to between 400 and 500 F, is
discharged from the bunker through a measuring chamber and double gate
arrangement. Except for the periodic introduction of hot coke and a small
quantity of air, dry quenching is a closed cycle operation.
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Two such systems are presently being marketed by American-Biro Company
and Patent Management, Inc. Also, Japanese companies have signed licensing
agreements with the USSR and are interested in the potential U.S. market. The
Japanese have introduced some modifications to the basic USSR system to achieve
greater reliability and improved control efficiency.
Closed Quenching
There are several types of closed quenching operations which can signifi-
cantly reduce quenching emissions. One method of approach is to feed hot coke
at a controlled rate onto a moving, stainless steel, linear grating in an
enclosed operation. As the coke moves along the grating, water is sprayed on
it, eventually cooling the coke below combustion temperatures. At the end of
the grating, it is then dumped into another container beneath the roof of a
kiln. The steam generated is passed through a series of internal baffles
which removes most of the particulates. Another advantage of this system,
besides controlling emissions, is that a higher quality coke is obtained from
the uniform swift cooling.
Closed quenching will be applicable to analogous operations in coal
conversion systems, since most of these systems are normally closed and
pressurized systems.
Improvements in Operating Procedures and Maintenance
Relatively minor improvements in operating procedures and more subtle
approaches to maintenance requirements can significantly reduce emissions from
coke oven leaks and openings. These procedures an equipment associated with
them would be of use in the coal conversion industry.
Magnetic Lid Lifters
Until recently many coke plants removed and replaced charging hole lids
on top of the coke ovens during charging manually. This method is being
replaced by automatic magnetic type lid lifters being installed on the larry
cars.
Electric Eye Synchronization
Electric eyes are being installed on many coke ovens to verify the
positioning of the larry car directly over the oven port prior to charging.
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Also, they are being used to verify that the door extractor and pushing ram
are correctly positioned. They can also be used to properly realign the doors
after the push.
Oven and Door Maintenance
During the coking cycle, excessive emissions may result from poor oven
maintenance and from improperly maintained or designed oven doors. Emissions
can be significantly reduced by routine scheduling of repair and/or replacement
of parts.
An obvious location where significant emissions might occur is the coke
oven door. In the past, luted doors were used which required almost continuous
luting by workers to prevent emissions. Today, most oven doors are the self-
sealing knife edge type. These doors when fitted with appropriate jambs,
seals and backstays have demonstrated to be very effective in controlling
emissions due to door leakage.
U.S.S has found that through good maintenance and operating procedures,
they have achieved 98 percent compliance with a 10 percent door leakage regu-
latory requirement.
Another significant source of emissions is from the ovens themselves.
These emissions tend to increase as the oven battery ages. The Jones and
Laughlin Steel Corp. at its Pittsburgh Works found that by silica dusting and
patching of its ovens, they were able to achieve a reduction in their coke
oven stack emissions of 68 to 87 percent of greater than 20 percent opacity
for a period of 6 to 18 minutes per hour.
Recent Control Technology Developments
The Steel Company of Canada (Stelco), Hilton Works in Hamilton, Ontario
is operating a fugitive emission control system which employs a shed over the
entire coke battery. The shed is capable of capturing 600,000 ACFM of air
which is then exhausted to 9 wet-walled electrostatic precipitators. The major
drawbacks associated with this type of control system is that the hood exhaust
runs constantly and that it tends to corral emissions from the general oven
leaks and openings which could adversely affect the battery operators' health.
The capital equipment cost for this system is estimated at $7.2 million.
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Philadelphia Coke Co., Inc., after consideration of the three basic
designs: fixed-duct hood system, coke car-mounted hood system and coke-side
enclosures (general descriptions of which were given earlier) favors the
fixed-duct hood system for fugitive emission control . This system is
favored because of the operational and noise problems associated with the coke
car-mounted system and the exposure of employees to heavy dust concentrations
which would occur within the coke-side enclosure.
Based on blast furnace plants, the estimated cost of the system is in the
4 to 5 million dollar range. Since Philadelphia Coke is a foundry coke plant,
which does not experience the dirty pushes (green coke) and high sulfur
concentrations in the gas, it is expected the system for foundry coke plants
could be installed for about one-half of the above stated costs.
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SECTION 8
THE HEALTH EFFECTS OF COKE OVEN EMISSIONS
HEALTH EFFECTS/IMPLICATIONS
To briefly assess the health effects attributed to coke oven emissions, a
literature review primarily of recent information released in draft forms by
the U.S. EPA - Office of Research and Development was utilized.
The purpose of the review was to provide basic information regarding the
potential health effects on coke oven workers and on the general population
who are exposed to coke oven emissions.
Chemical Composition of Coke Oven Emissions and their Health Implications
Coke oven emissions consist of all of the constituents of bituminous coal
which are released into the atmosphere during the process of coal carbonization.
Table 8-1 shows a partial list of the constituents of the coke oven emissions.
A number of these constituents are suspected to be human carcinogens.
The toxicity of coke oven emissions may also be associated with respiratory
irritation, cocarcinogenesis, tumor promotion and other toxic effects. Table
8-2 summarizes some noncarcinogenic toxic effects.
Particle Size and^ Its Jtealth Effects
In addition to chemical composition, the form in which the various
constituents are released into the atmosphere (e.g., aerosols, gases), and the
size and density of the particulate matter with which they are associated
determine their effects on human health. Most of the particles emitted are in
the respirable range, which means that they can penetrate into the lungs
beyond the normal respiratory defense mechanisms. Particles ranging from 0.1
to 2 microns in diameter are the optimum size for such penetration, and there-
fore, are the most biologically significant. After entering the respiratory
tract, they are largely retained in the trachea, bronchi, and alevoli.
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TABLE 8-1. PARTIAL LIST OF CONSTITUENTS OF COKE OVEN EMISSIONS
(SOURCE: BIBLIOGRAPHY 62)
Anthanthrene
Anthracene
Benzindene
Benz (a) anthracene" ,
Benzo (b) fluoranthene
Benzo (ghi) fluoranthene"
Benzo (j) fluoranthene
Benzo (k) fluoranthene
Benzofluorene
Benzo (a) fluorene
Benzo (b) fluorene
Benzo (c) fluorene
Benzophenanthrene
Benzo (ghi) perylene
Benzo (a) pyreneb
Benzo (e) pyrene^3
Benzoquinoline
Chrysene
Coronene
Dibenz (ah) anthracene1'
Dibenzo (ah) pyrene'5
Dihydro anthracene
Dihydrobenzo (a) fluorene
Dlhydrobenzo (b) fluorene
Dlhydrobenzo (c) fluorene
Dihydrobenz (a) anthracene
Dihydrochrysene
D ihydrofluoranthene
Dlhydrofluorene
Dlhydromethylbenz (a)
anthracene
D ihydrome thlybe nzo
(k and b) fluoranthenes
DIhydromethylbenzo
(a and e) pyrenes
Dihydromethylchrysene
fluoranthene
D ihydrome thy Itr iphenylene
D ihydrophenanthrene
D ihydropyrene
Dihydrotr iphenylene
Dimethylbenzo (b) fluoranthene
Dime thylbenzo (k)
Dimethylbenzo (a) pyrene
Dime thyIchrysene
D imethyItriphenylene
E thylanthracene
E thylphenanthrene
Fluoranthene
Fluorene
Indeno (1,2,3-cd) pyrene
Me thylanthracene
Methylbenz (a) anthracene
Me thylbenzo (a) pyrene
Me thylbenzo (ghi) perylene
Me thyIchrysene
Me thyIfluoranthene
Me thyIflucrene
Me thylphenanthrene
Ma-thylpyrene
Me thy Itr iphenylene
Octahydroanthracene
Octahydrofluoranthene
0 ctahydrophenan threne
Octahydropyrene
Perylene
Phenanthrene
o-Phenylenepyrene
Pyrene
Triphenylene
POLYNUCLEAR AZA-HETEROCYLIC
COMPOUNDS3
Acridine
Benz (c) acridine
TRACE ELEMENTS1
Arsenic
Beryllium
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TABIE 8-1. (continued)
Dibenz (a,h) acridine
Dibenz (a,j) acridine
AROMATIC AMINESb
a-Naphthylamine
3 -Naphthy lamine
OTHER AROMATIC COMPOUNDS
Benzene
Phenol0
Toluened
Xylened
Cadmitim
Chromium
Cobalt
Iron
Lead
Nickel
Selenium
OTHER GASES
Ammonia0
Carbon disul£idec
Carbon monoxide0
Hydrogen cyanidec
Hydrogen sulfide
Methane0
Nitric oxided
Sulfur dioxide0
a Lao et al (1975), except as noted,
b
Kornreich (1976).
C Smith (1971) .
d
White (1975).
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TABLE 8-2, SOME TOXIC CONSTITUENTS OF COKE OVEN EMISSIONS AND SOME OF THEIR TOXIC PROPERTIES
(SOURCE - BIBLIOGRAPHY 62)
Constituent
ON
r
Acridine
Anthracene
Arsenic
Benzene
Suggested Threshold
Limit Value (TLV)
Potential Health Effect
Acetone
Ammonia
1,000 ppm
2,400 mg/m3
25 ppm
18 mg/m3
At 300 ppm
500 ppm
1,000 ppm
1 ppm
20 ppm
Slight irritation
Still tolerated
Chronic irritation of
respiratory tract, dizziness
Odor detectable
Discomfort in uninured workers,
0.25 mg/m3
1.0 ppm/3,0 mg/m'
complaints
100 ppm Irritation of respiratory
tract and conjuctivae
Powerful irritant:
Photosensitizer
Causes dermatitis
eyes
Irritant: eyes, skin,
respiratory tract
Photosensitizer
Contact dermatitis and
sensitization
Conjunctivitis
Ulceration and perforation
of nasal septum
Narcotic effects
Severe exposures cause bone marrow
and blood changes
Myelotoxic
25 ppm Exposure for 12 years; very little
intoxication reported
Blood changes reported
Deaths reported
60 ppm
100-200 ppm
-------
TABLE 8-2 (continued)
Constituent
Beryllium
Cadmium dust
Chromium
Cobalt
Formaldehyde
Hydrogen
Cyanide
Suggested Threshold
Limit Value (TLV)
0.002 mg/m3
0.05 mg/m3
0.5 mg/m
0.01 mg/m3
2 ppm
10 ppm
Potential Health Effect
Dermatitis, tracheobronchitis
100 yg-../m3 pneumonitis
Distinctive, nonhypertropic emphy-
sema, with or without damage to
renal tubes; anemia, eosinophilia,
anosmia, chronic rhinitus, yellow
ring on teeth, bone changes
2-15 mg/rn^ Anosmia, proteinuria (low molecular
weight) pulmonary emphysema, yellow
ring on teeth, eosinphilia, anemia
Dermatitis (salt)
Pulmonary involvement,chronic inter-
stitial pneumonitis
1-2 mg/m^ Serious and occasionally fatal
results, hypersensitivity, allergic
dermatitis
1-2 ppm
6 ppm
20-40 ppm
Irritant: eyes, respiratory tract,
skin
Itching eyes, dry and sore throat,
disturbed sleep, unusual thirst on
awakening
Eye irritation
Slight intoxication, variety of
neurological symptoms
-------
TABLE ft-2 (continued)
Constituent
Suggested Threshold
Limit Value (TLV)
Potential Health Effect
Hydrogen
sulflde
10 ppm
(15 mg/m3)
500-1,000 ppm
50-500 ppm
250-600 ppm
5-100 ppm
Lead
0.15 mg/m3
Nickel
Pyridine
1 mg/m3
5 ppm
Acts primarily as systematic
poison causing unconsciousness
and death through respiratory
paralysis.
Acts primarily as a respiratory
irritant.
Prolonged exposure may lead to
pulmonary edema and bronchial
pneumonia.
Associated with eye irritation.
Nerve function disorders, inabi-
lity to sleep, fatigue,
constipation;
Long-term exposure: anemia, colic,
neuritis, headaches, loss of appe-
tite, weakness, double vision:
Organic lead: mental disturbances,
inability to sleep, general an-
xiety, delerium - acute.
Increase in incidence of nasal,
sinus, and lung cancer in workers
in nickel refineries
0.83-2.46 ml Was toxic in human therapy with one
death from liver and kidney damage.
Central nervous system affected.
Stimulates bone marrow to production
of blood platelets .
Vapor - irritating to mucous surfaces,
15-330 ppm Nausea, headache, insomnia and ner-
vousness, low back or abdominal
discomfort.
-------
TABLE 8-2 (continued)
Constituent
Suggested Threshold
Limit Value (TLV)
Selenium
Sulfur dioxide
i
M
-J
Toluene
Xylene
0.2 mg/m3
0.007-0.05 mg/m3
0.2-0.4 mg/m3
5 ppm
13 mg/m
100 ppm
375 mg/m3
0.1 mg/m3
Intense irritation of eyes, nose,
and throat, headache. Severe
exposure: bronchial spasma, asphy-
xiation, chills, fever, bronchitis.
Headache, traecheobronchitis,
conjunctivitis.
Garlic odor of breath, skin rashes,
indigestion, metallic taste.
Irritation of the mucous membranes,
coughing, eye irritation, increased
pulmonary flow resistance; adverse
symptoms appear at levels between
5 and 10 ppm.
100-1,100 ppm Enlargement of liver, macrocytosis,
moderate decrease in erythrocyte
count and absolute lymphocystosis.
Headache, nausea, lassitude.
Impairment of coordination, momen-
tary loss of memory, anorexia.
500-1,500 ppm Palpitation, extreme weakness,
pronounced loss of coordination
and impairment of reaction time;
red cell decrease in 2 cases,
aplastic anemia (possible benzene
impurity);
200 ppm Slight but definite changes in mus-
cular coordination; 7 hours exposure
to 200 ppm cause prolongation of
reaction time, decreases in pulse
and systolic blood pressure.
Acute oral and skin irritation, sensi-
tization, gastrointestinal irritant.
200 ppm
200-500 ppm
-------
Particles larger than 2.0 microns are trapped by the mucous membranes and do
not enter the lungs. Particles smaller than 0.1 micron are retained in the
tracheobronchial tree but elution does not occur. Particles smaller than 0.04
micron do not come out of suspension in the inhaled air and are exhaled. The
trapped particles in the mucus that are not exhaled and that also do not enter
the lung are either swallowed or spit out. Table 8-3 gives the range of
particle sizes found in coke oven emissions.
jfenergjlsms
Some researchers have shown the importance of synergism of pollutants in
air, two of the most common being sulfur dioxide (SO.) and benzo-a-pyrene
(BAP). It has been postulated that SO- synergism shows ciliary action, and
therefore increases BAP retention and/or causes chronic injury; following
injury, the resultant regenerating cells may be more susceptible to the BAP.
These effects have also been demonstrated between carcinogenic chemicals (e.g.
BAP) and particulate matter (e.g., iron oxide, carbon).
The indication in laboratory experiments that different components of
coke oven emissions interact synergistically lends support to the view that
the toxic potential of the complex mixture coke oven emissions cannot be
related to the potential of a single compound.
BASIS OF SAMPLING AND MEASUREMENTS
Because of the effort and complexity that would be required in charac-
terizing all of the constituents of coke oven emissions, various surrogate
measures have been used in the past. These usually are of three types:
Total Suspended Particulates (TSP)
Benzene Soluble Organics (BSO)
Benzo (A) Pyrene (BAP)
TSP is generally considered not to be a specific enough measure for
assessing total occupational health effects. Previous occupational and
general atmospheric studies provide some justification for using a surrogate
measure rather than trying to identify and control each of the polynuclear
aromatic (PNA) compounds emitted by coke ovens.
Table 8-4 summarizes the exposures of coke oven workers to coke oven
emissions (benzene soluble fraction of total particulates).
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TABLE 8-3. PARTICLE SIZE RANGE AND BIOLOGICAL
SIGNIFICANCE OF COKE OVEN EMISSIONS
(SOURCE - BIBLIOGRAPHY 62)
Sizea
Site
Process
Reference
Biological
significance
0.1-iym (tarry Retort house
droplets)
1 ym and up (dust) Retort housa
l.Syro Topside coke oven
l.Syni Topside coke oven
2.9yro Topside coke oven
iym-1.27 mm Coke plant
5ym.-1.27 mm Coke plant
General atmosphere
(shift change)
During coking
Charging
Quenching
Lawther (1964)
Lawther (1964)
White, L.D. et alb
White, L.D. et alb
White, L.D. et alb
Fullerton, R.W. (1967)
Masek, V. (1970, 1970a)
Particles in the
0.1-2.0 y range
are respirable
and largely re-
tained in the
trachea, bronchi,
and alveoli.
Particles > 2.Oy
are trapped in the
mucous membranes.
Particles -CO.ly
are retained but
elution does not
take place. Par-
ticles <0.04y are
exhaled (Falk and
Kotin, 1961).
a For respirable particles, the rate of elution of PAH increases with the size of the particle to which the
PAH is absorbed.
No date.
-------
TABLE 8-4. SUMMARY OF EXPOSURES OF COKE OVEN WORKERS TO COKE OVEN EMISSIONS
(BENZENE SOLUBLE FRACTION OF TOTAL PARTICULATES)
[SOURCE - BIBLIOGRAPHY 32]
A Summary of Separate Air Sampling Studies by AISI Member
Companies and Pennsylvania Department of Environmental Resources.
Operator
(source No. of Range* Average**
of info.) Samples (mg/m3) (mg/m3)
Larry car operator
AISI 106 0.78 - 6.4 2.2
PA 39 0.28 - 8.8 3.1
Lidman
AISI 140 1.0 - 5.6 2.6
PA 61 0.42 - 18. 3.2
Door Machine Operator
AISI 85 0.31 - 5.1 1.2
PA 25 0.04 - 6.5 2.1
Door Cleaner/Luterman
AISI 172 0.31 - 3.2 1.1
Patcher
AISI 10 0.71 - 1.3 0.99
Eeater
AISI 60 0.12 - 2.4 0.57
PA 39 N.D. - 3.0 1.1
Quench Car Operator
AISI 70 0.05 - 1.2 0.44
PA 23 N.D. - 7.0 0.94
Pusher Operator
AISI 78 0.15 - 0.82 0.40
PA 23 N.D. - 0.93 0.39
* AISI DATA is a range of the mean coke oven emission concentration
reported for each job description by each coke plant studied.
** AISI DATA is the average of mean concentration for each coke plant
studied.
N.D. - None Detected.
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Table 8-5 shows a comparison of BAP concentrations measured at coke oven
batteries and at other selected sites.
The National Air Sampling Network (NASN) routinely monitors suspended
particulate levels in urban and non-urban areas. BAP and BSO are monitored
for 40 locations that include cities with and without coke ovens and rural
3
areas (See Table 8-6). The BAP concentrations are generally 0.1 ng/M for
rural locations. Most urban locations without coke ovens have average
3 3
concentrations of less than 1 ng/M (the average is 0.38 ng/M ); however,
areas with coke ovens generally have average concentrations in excess of
3 3
1 ng/M (the average is 1.21 ng/M ).
EPIDEMIOLOGICAL STUDY RESULTS
Epidemiological evidence of greater increases in disease rates among
workers exposed to the higher-temperature processes suggests that the higher
the temperature of carbonization, the higher the proportion of toxic compounds
released. Table 8-7 shows the excess of reported lung cancer among workers
for various carbonizing chamber temperature ranges.
Epidemiological studies in different countries have demonstrated that
workers exposed to the products of combustion and distillation of bituminous
coal experience an increased incidence of cancer of several sites (lung,
pancreas, kidney, bladder, skin). Table 8-8 is a summary of relative risks of
death from cancer among coke oven workers.
There are no epidemiological studies of the cancer exposure of populations
living near coke ovens or gas works. As a basis for estimating the magnitude
of the excess cancer risk, the summary was extrapolated from cancer mortality
data on coke oven workers and other workers in the steel industry.
Because the extensive epidemiological evidence describes adverse health
effects experienced by an industrial work force exposed to "coke oven emissions"
(i.e., the total, complex mixture, often characterized as the benzene-soluble
fraction of total particulate matter), the effects of the constituents such as
BAP and BSO acting separately or in various combinations need not be delineated
for human experience. It is, therefore, essential that the assessment of
health effects be applied to "coke oven emissions" as an entity and not to any
particular component.
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TABLE 8-5. COMPARISON OF BENZO (a) PYRENE CONCENTRATIONS MEASURED AT COKE
OVEN BATTERIES AND AT OTHER SELECTED SITES
(BIBLIOGRAPHY 62)
Concentration, (yg/m )
Country
Soviet Union
Soviet Union
Japan
Norway
Czechoslovakia
Czechoslovakia
Czechoslovakia
Czechoslovakia
England
USA
USA
USA
USA
USA
USA
USA
Switzerland
USSR
England
England
USA
USA
Year
1962
1968
1968
1959
1966
1967
1968
1974
1965
1974
1960
1974
1974
1968
1961
1961
1961
1966
1965
1965
1959
1966
Top- Side
1.27
0.05
2
1.1
3.6
10.7
0.1
3
1.2
8.3
0
0.18
95
6.1
14
640
13.7
(0.02)
2,330
(0.022)
(0.0185)
27.4
7.38
7.3
94.8
32.2
12.7
13.1
216
15.9
51
225.9
36.3
78
22
(3.84)'
(6.5)
(9.55)
(5.78)
Side
0.08 - 0.27 (0.17)
1.5 - 3.14
0.6 - 3.4
0.3 - 1.98 (1.0)
Contrast
Cigarette smoke
Auto exhaust
Roof tarring
Roof tarring
Aluminum Plant
Urban - London
Maximum found in
fumes emitted from
coke ovens
Birmingham
Birmingham
Mean.
Source: White, et al.
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TABLE 8-6. AMBIENT BAP AND BSO DATA
(SOURCE - BIBLIOGRAPHY 64)
Pollutant
BAP (ng/m3)
1975 Data
BSO (yg/ta )
1971-72 data
Statistic
Average
Sample Size
Range
Average
Sample size
Range
Cities
with
Coke
Ovens
1.21
21.00
0.3 - 4.7
4.21
25.00
2.1 - 7.3
Cities
without
Coke
Ovens
0.38
13.00
0.03 - 0.9
3.75
12.00
1.9 - 5.6
Rural Areas
3.00
<0.10
0.95
2.00
0.8 - 1.1
TABLE 8-7.
Carbonizing
Chamber
Vertical retorts
Horizontal retorts
Coke ovens
Japanese gas generators
TEMPERATURE RANGE OF CARBONIZING CHAMBERS
AND EXCESS OF LUNG CANCER REPORTED.
(SOURCE - BIBLIOGRAPHY 62)
Temperature
Range, C
400 - 500
900 - 1,100
1,200 - 1,400
> 1,500
Reported Excess of Lung
Cancer among Workers (%)
27 (Doll, 1965)
83 (Doll, 1965)
255 (Lloyd, 1971)
800 (Lloyd, 1971)
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TABLE 8-8. SUMMARY OF RELATIVE RISKS OF DEATH FROM CANCER AMONG COKE OVEN WORKERS8
(SOURCE - BIBLIOGRAPHY 62)
Length of employment
(1953-1970), yr
1
H
00
1
Work area
Total coke oven
Coke oven
Oven topside full-time
Oven topside full-time
Oven aide only
Non-oven
Mo one coke plant area
Distribution
of workers
5+ 10+ 15+
1860 1194 790
993 574 325
150 72 29
290 245 159
553 257 137
836 578 392
31 42 73
Deaths and BR's of death from Deaths and RR's of death
malignant neoplasms respiratory cancer
5+
Obs. RR
166 1.47b
101 1.66b
35 3.70b
26 l.59b
40 1.17
65 1.28
0 d
Deaths and RR's
cancer of digestive
10+ 15+ 5+ lOf
Obs,
136
85
22
31
32
48
3
RR Obs. RR Obs. RR Obs. RR
1.50b 108 1.62b
1.95b 63 2.40b 54 3.02b 44 3.42b
5.12b 12 7.63b 25 9.19b 16 11.79b
1.85b 32 2.73b 12 2.29b 16 3.07b
1.46 19 1.51 17 1.79° 12 1.99b
1.10 39 1.13
d 6 1.34
from
15+
Obs. RR
33 4.l4b
8 15.72b
18 4.72b
7 2.00
of death from
system
among non-
oven workers
5+ 10+
All malignant neoplasms
Large intestine
Pancreas
Other
Obs
of digestive system 28
11
8
9
. RR Obs.
1.58° 23
2.31C 10
3.67b 7
0.83 6
RR
1.53
2.52b
3.75b
0.65
15+
Obs. RR
19,, 1.53
8 2.37°
6 4.29b
5 0.65
^Adapted from Redmond (1976).
bp'0.01, p < o.Ol
X0'05- P < 0.05
less than 5 deaths.
-------
Several mortality studies have shown that workers at coke plants are at
an increased risk for dying of chronic bronchitis. Unlike the risks from
respiratory malignancy, the risk appears to be about the same for coke oven
workers and for non-oven workers employed at the plant. It indicates that the
risk of the plant workers is greater than two-fold relative to the rate of
mortality from chronic bronchitis in the steelworker population. Table 8-9
shows the estimated effects of coke oven emissions on U.S. population. An
affected radius of 15 kilometers (approximately 9 miles) from a coke plant is
considered as the maximum potential exposure population. The estimate indi-
cates that for the highest 100,000 people exposed there is a 0.2 to 0.6 percent
excess chance of dying of lung cancer. For the remaining 15 million people,
the excess is about 0.1 percent. The total number of excess lung cancer
deaths is about 150 cases per year. These estimates should be regarded as
crude and probably conservative; i.e., on the high side.
Without any significant coke oven exposure, the lifetime probability of
dying of lung cancer is 3.29 percent.
SUMMARY OF STUDY FINDINGS
Exposure to coke oven emissions provides an elevated risk for cancer
of all sites and non-malignant respiratory diseases to coke oven
workers and an increased risk among lightly exposed workers (non-
oven workers in coke plant).
The general population, which includes the young, the old and the
infirm in the vicinity of a coke oven plant should be considered
more susceptible than the workers, especially for development of
chronic bronchitis, since they are generally in poorer health.
Coke oven emissions contain an array of identified carcinogens,
irritants, particulate matter, trace elements, and other chemicals.
The toxic effects observed in both humans and animals are greater
than the effects that can be attributed to any individual component.
Thus "coke oven emissions" as a whole should be considered the toxic
agents.
There is an exposure difference of about 2 orders of magnitude
estimated between lightly exposed workers and people living in the
vicinity of a coke plant. Since these lightly exposed workers show
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an elevated risk for cancer and non-malignant respiratory disease,
it is reasonable to assume that levels up to one-hundreth of those
to which lightly exposed workers are subjected could cause an
increased risk to the general population.
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TABLE 8-9. ESTIMATED EFFECTS OF COKE OVEN EMISSIONS ON U.S. POPULATION
UNDER WEIBULL PROBABILITY MODEL WHERE "HIT PARAMETER11 m = 1
AND ADJUSTMENTS FOR TOTAL POPULATION RATES USED
(SOURCE: BIBLIOGRAPHY 1)
Given Coke Oven
No. of
Lung Cancer
1
M
00
M
1
X =
Exposure to_
BSO in yg/m
in Air
Background** 3 . 75
4.50
5.50
6.50
7.50
8.50
10.90
Number of
People in
Exposure
Group
-
13,900,000
1,034,000
54,000
7,780
2,420
1,800
Lifetime
Probability of
Lung Cancer
.03286
.03360
.03435
.03519
.03604
.03669
.03890
Increase in
Lung Cancer
Due to Coke
Oven Emissions
-
6.37 x 10"A
1.49 x 10~3
2.33 x 10~3
3,18 x 10"3
4.02 x 10~3
6.04 x 10~3
Emissions Caused
Lung Cancer
Average Yrs. of
Lifespan Lost
-
12.34
12.36
12.39
12.41
12.43
12.44
Deaths/Yr.
Due to
Coke Oven
Emissions
-
125.0
22.0
1.8
.4
.1
.2
Total=149.5/Yr,
-------
SECTION 9
ENVIRONMENTAL REQUIREMENTS IN THE COKE OVEN INDUSTRY
The section discusses existing and proposed Federal and State lavs, rules
and regulations pertaining to environmental control in the coke oven industry.
It is not intended to represent all applicable regulatory requirements,
particularly with respect to water quality standards, due to their variations
from state to state.
FEDERAL REGULATIONS
Air Pollution Control Standards
1. Prevention of Significant Air Quality Deterioration (PSD) program
was incorporated in the Federal Clean Air Act Amendments of 1977 (PL
95-95, August 7, 1977) under Part C, Subpart I.
This regulatory program requires that every major new and major
modification of industrial sources of air pollution must obtain a
PSD permit in order to construct the source or facility. A major
source is any source in one of 28 established categories that has
the potential (before controls) to emit 100 tons per year (approxi-
mately 25 Ibs/hr) or more of any pollutant regulated by the Clean
Air Act.
Included in the 28 major source categories are: coke oven batteries,
fuel conversion plants and sulfur recovery plants, which are pertinent
to this study report. The regulated pollutants presently include:
particulate matter, SO-, NO , CO, hydrocarbons, photo-chemical
fc 2£
oxidants, total flourides, sulfuric acid mist, asbestos, beryllium,
mercury, vinyl chloride, benzene and lead.
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The requirements for obtaining a PSD permit are:
A. Air Quality Assessment
A permit application must be accompanied by an air quality
assessment that satisfactorily demonstrates that no increment
or NAAQS will be contravened. This assessment must be based on
approved air pollutant dispersion modeling techniques and, in
the case of the NAAQS, must be supported by as much as one
year's worth of monitoring data.
B. Best Available Control Technology (BACT)
BACT is the best achievable control technology when economic,
energy and other costs are considered on a case-by-case basis.
BACT can range from the stringency of Lowest Achievable Emission
Rate (LAER) down to the New Source Performance Standards (NSPS)
as the highest acceptable emission rate.
If any control technology less than the best achievable is
selected, then that selection must be justified by a comparison
between the economic and energy cost saved and the additional
environmental cost accrued.
BACT is required for all pollutants for which the new source or
modification is considered major.
C. Impact Analysis and Public Participation
Addressed in the permit application must be the impact on:
vegetation with commercial or recreational value, soils and
visibility. Also the impact in the environment of secondary or
induced growth must also be evaluated.
The public must be afforded an opportunity for comment and
hearing on the permit application; and in the preliminary
determination to approve the application prior to issuing a
construction permit.
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D. New Sources in Non-attainment Areas
All major new sources or major modifications proposed for
location in areas where levels of any pollutant (for which they
are considered major emitters) are currently exceeding a NAAQS
must meet the following four conditions in order to secure a
state Stationary Source Review (SSR) permit (a precondition to
receiving a PSD permit).
1. LAER is required.
2. All other sources owned by the same owner in the same
state must be in compliance with the SIP or on an approved
compliance schedule.
3. Off-setting reductions in emissions from existing sources
must be provided.
4. There must be a net improvement in air quality resulting
from the off-sets.
Standards of Performance for New Stationary Sources have not been
written for the coke oven industry. Instead, the EPA* has been
considering emission standards for various coke making operations
under the National Emission Standards for Hazardous Air Pollutants
(NESHAPS 40 CFR 61). The purpose of promulgating regulations under
this category is to provide an umbrella coverage of new and existing
coke plants while acknowledging the carcinogenic properties of the
contaminants. It is anticipated that the EPA will propose an initial
regulation to control the top side charging of coke ovens by visible
emission limitations. Also, it is expected that specific emission
standards will be set for benzene and heavier polycyclic aromatic
hydrocarbons which will be applicable to the coke oven industry.
National Primary and Secondary Ambient Air Quality Standards (40 CFR
50). Table 9-1 provides ambient air quality standards for six major
air contaminants. These standards serve as guidelines to the states
^Private communications with EPA, Standards Group, R.T.P., North Carolina.
Also, the Precip Newsletter - March 20, 1978, No. 26, page 4.
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TABLE 9-1,
Pollutant
NATIONAL AMBIENT AIR QUALITY STANDARDS
(SOURCE - BIBLIOGRAPHY 19)
Averaging
Time
Primary
Standards
Secondary
Standards
Particulate matter*
Sulfur dioxide
Carbon monoxide
Photochemical**
oxidants
Hydrocarbons+
(nonmethane)
Nitrogen dioxide
Lead
Annual (geometric mean)
24 - hour
Annual (Arithmetic
mean)
24 - hour
3 - hour
8 - hour
1 - hour '
1 - hour
3 - hour
(6 to 9 a.m.)
Annual (Arithmetic
mean)
3 - month average
75 yg/in
260 yg/m
80 yg/m3
(0.03 ppm)
365 yg/m3
(0.14 ppm)
10 mg/m
(9 ppm)
3
40 mg/m
(35 ppm)
235 yg/m3
(0.12 ppm)
3
160 yg/m
(0.24 ppm)
100 yg/m
(0.05 ppm)
1.5 yg/m3
60 yg/m"
150 yg/m3
1,300 yg/ni
(0.5 ppm)
Same as primary
Same as primary
Same as primary
Same as primary
Same as primary
* The secondary annual standard (60 yg/m ) is a guide to be used in assess-
ing implementation plans to achieve the 24 - hour secondary standard.
** Expressed as ozone by the Federal Reference Method.
4- This NAAQS is for use as a guide in revising implementation plans to
achieve oxidant standards.
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for meeting air quality goals by incorporating them in their State
Implementation Flans. National standards apply when state standards
of equivalent or more stringent levels have not been adopted.
Water Pollution Standards
3.
Refuse Act of 1899 C33 USC 407); NPDES permit.
This act makes unlawful the discharge of refuse into navigable
waters or tributaries of navigable waters; or the deposit of refuse
on the banks of navigable waters where it may be washed into those
waters. Discharges may, however, be permitted under the National
Pollution Discharge Elimination System (NPDES) pursuant to the
Federal Water Pollution Control Act Amendments of 1972 (33 USC, 1251
et. seg.).
Toxic Pollutant Effluent Standards (40 CFR 129).
The pollutants presently regulated by these standards are not related
to the coke oven industry effluent compounds. It is expected that
pollutants characteristic of the effluents from the coke oven industry
such as particulate polyeyelie aromatic hydrocarbons, benzene, metals
and heavy metals will be proposed and regulated in the near future.
Effluent Guidelines and Standards (40 CFR 420) Subpart A; Byproduct
Coke Subcategory.
Basis
BATEA1, NSPS1
(Expressed as
kg/kkg)
Product
Effluent
Characteristic
2
Cyanide A
Phenol
Ammonia
Sulfide
Oil and grease
TSS
pH
Maximum for
Any One Day
.0003
.0006
.0126
.0003
.0126
.0312
Within the
range from
6.0 - 9.0
Avg. of Daily
Values For 30
Consecutive Days
Shall Not Exceed
.0001
.0002
.0042
.0001
.0042
.0104
1. Limitations specified may be exceeded up to 25 percent by those facilities
equipped with gas desulfurization units and up to 70 percent for those
utilizing the indirect ammonia recovery process.
2. "Cyanide A" means those cyanides amenable to chlorination.
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EPA Water Quality Criteria
States are required to adopt water quality standards and a plan for
enforcement and implementation consistent with the goals of the Federal Water
Pollution Control Act Amendments of 1972 (40 CFR, Part 120).
Recognized versions of water quality criteria include criteria developed
by the Department of Interior in 1968, criteria published by the National
Academy of Sciences in 1972, and EPA1s 1976 Quality Criteria for Water.
States may use any one of these criteria documents as guidelines in setting
discharge standards.
It should be understood that water quality criteria do not have direct
regulatory use, but are used for judgment of certain standards associated with
water quality programs.
Criteria pertinent to the coke oven industry taken from the proposed EPA
1976 Quality Criteria for Water are presented below:
Parameter
Ammonia
Cyanide
PH
Phenol
Solids & Turbidity
Criterion
0.02 gm/1 (as un-ionized ammonia) for freshwater
aquatic life.
5.0 yg/1 for fresh and salt water aquatic life and
wildlife.
5-9 for domestic water supplies (Welfare)
6.5 - 9.0 for freshwater aquatic life
6.5 - 8.5* for saltwater aquatic life
*but not more than 0.2 units beyond the normally
occurring range.
1 yg/1 for domestic water supply (Welfare), and
to protect against tainting of fish flesh.
For freshwater fish and other aquatic life settleable
and suspended solids should not reduce the depth of
the compensation point for photosyrtthetic activity
by more than 10 percent from the seasonally
established norm for aquatic life.
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Parameter
Oil & Grease
Sulfide
Hydrogen Sulfide:
Criteria
Virtually free from oil and grease, particularly from the
tastes and odors that emanate from petroleum products, for
domestic water supplies.
The following apply for Aquatic Life;
(1) Levels of individual petrochemicals in the water
column should not exceed 0.01 ppm of the lowest
continuous flow 96-hr. LC,-n to several important
marine species, each having a demonstrated high
susceptibility to oils and petrochemicals;
(2) Levels of oils or petrochemicals in the sediment
which cause deleterious effects to the biota should
not be allowed;
(3) Surface waters shall be virtually free from floating
non-petroleum oils of vegetable or animal origin, as
well as petroleum derived oils.
2 g/1 undissociated H_S for fish and other aquatic life
in fresh and marine water.
Solid Waste Disposal Standards
The Resource Conservation and Recovery Act of 1976 stipulated that within
18 months regulations would be developed by the EPA to handle and dispose of
hazardous waste materials. Since many of the particulates that are captured
from the coke ovens are, or could be, classified as hazardous compounds, they
would fall under the requirements of this law and the proposed regulations.
It is expected that the regulations will require safe handling, labeling and
identification of the hazardous materials, proper containerizing, safe and
effective transport, and disposal.
(NOTE: Recent conversations with the EPA indicate that the 18 months
deadline are expected to be extended an additional 6-12 months.)
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STATE REGULATIONS
Air Pollution Control Standards
An analysis was made of five (5) states which specifically regulate coke
oven plants and their air emissions. These states collectively encompass more
than 37 percent of the total coke production and have more than 41 percent of
the total number of coke plants in the United States.
Basically, the states all regulate the fugitive smoke and particulate
matter emissions that emanate from the coke oven batteries and the quench
towers. The following are the types of operations and maintenance procedures
regulated:
1. Unloading and Transferring of Coal and Coke - These operations are
required to implement unspecified but reasonable control measures to
prevent emissions.
2. Charging Operations -
a) Open Charging - Visible emissions are limited to no more than
15 seconds during any coke oven charging operation. The opacity
of the emissions is limited to less than or equal to 30 percent.
b) Closed Charging - Visible emissions are limited to one charge
out of any ten consecutive charges.
3. Pushing Operations -
a) Visible emissions are limited to less than, or equal to, 20
percent opacity for up to one minute per push. New coke plants
shall be equipped with enclosed pushing devices equipped with
particulate collection systems.
4. Topside emissions -
a) Leaks shall be wet-sealed or the oven shall not be recharged
until repairs are made.
b) At no time shall there be leaks in more than 5 percent of the
off-take piping and no more than 2 percent from the charging
hold lids on any one battery, excluding visible emissions from
open standpipe caps.
5. Coke Oven Door Emissions -
a) Visible emissions are restricted to 15 percent of the doors on
any battery at any time.
-189-
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b) Self sealing doors must be repaired prior to subsequent charge
if they fail to seal.
c) Luted doors that fail to seal after charging must be reluted
promptly.
d) Operators must have facilities to maintain and repair coke doors
with maintenance inventory of one door per 12 ovens operated.
6. Oven Maintenance -
a) Ovens shall be maintained in good condition.
b) Oven cracks are to be sealed as doon as practicable following
detection.
c) Records are to he retained on maintenance of doors, burners and
interiors.
7. Combustion Stacks -
a) Visible emissions are limited to less than or equal to, 20
percent opacity except for 3 minutes in any consecutive 60
minutes
8. Quenching -
a) Quench towers must have baffles installed.
b) Water introduced to the quench station must have a quality
approved by the control agency.
New Byproduct coke oven batteries must be equipped with control equipment
such as, but not limited to, hood(s) and/or gas mover(s) capable of capturing,
containing and collecting gases and particulate matter resulting from distil-
lation, charging, pushing and quenching of coke from an oven battery. Such
equipment shall employ the best practicalbe control technology currently
available.
New Beehive coke ovens are either prohibited from construction and
operation or, if permitted to be constructed, must have all gas and particulate
matter emissions directed through an acceptable air pollution control device.
Table 9-2, "Summary of State Air Pollution Control Regulations for the
Control of H S Emissions from Byproduct Coke Ovens," gives the limitations
from five states which regulate the emission of sulfur compounds (measured as
H?S) from coke oven gas. The majority of these states require that the coke
oven gas be desulfurized down to 50 grains per one hundred dry standard cubic
-190-
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TABLE 9-2. SUMMARY OF STATE AIR POLLUTION CONTROL REGULATIONS FOR THE
CONTROL OF 1LS EMISSIONS FROM BYPRODUCT COKE OVENS
State
Alabama
Regulations
Chap. 5 - Control of
sulfur oxides, 5.5 Process
Industries - General
H S/SO Limitations
£ X
1. Cannot construct or operate
unless source meets
applicable New Source
Performance Standards (NSPS)
and utilize hest practicable
control technology currently
available. (BPCTCA)
2, Cannot exceed primary &
secondary National Ambient
Air Quality Standards (NAAQS)
for SO
Illinois
Rule 204 (f) Sulfur
standards and limita-
tions for process
emissions sources
(1) Sulfur Dioxide
and Limitations
(A) Sulfur dioxide emissions
from process sources cannot
exceed 2,000 ppmv.
New York New York contaminant
emissions from Ferrous
Jobbing Foundries and
Byproduct coke oven
batteries, Part 214,
Byproduct coke oven
batteries, Sections 214.4
Sulfur Compound Emissions
Sources are not permitted to
burn or flare process gas
containing more than 50 grains
of sulfur compounds (measured
as H2S) per 100 standard
cubic feet of gas.
P ennsyIvania
Chapter 123, 123,2
Byproduct coke oven gas
a) Coke oven gas must be burned
prior to emission to atmosphere.
b) Burning or flaring is prohibited
if Byproduct gas contains more
than 50 grains of sulfur
compounds per 100 dry standard
cubic feet of gas (expressed as
equivalent hydrogen sulfide).
-191-
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TABLE 9-2 (Continued)
State Regulations H S/SO Limitations
Virginia Emission standards for Hydrogen Sulfide may not be
coke ovens and charcoal emitted from any process stream
kilns (Rule EX-4) Part IV which contains H_S in concen-
4.91 other Byproduct coke trations greater than 15 grains
ovens, emission standards per 100 cubic feet of gas without
for gaseous pollutants burning or removing H S in excess
(Rule EX-5) of this concentration. This
Cc) Hydrogen Sulfide limitation is acceptable provided
that the final SO emission
x
limitations are not violated.
-192-
-------
feet of gas before burning or flaring. The most stringent limitation, 15
grains per 100 cubic feet of gas, was promulgated by the State of Virginia.
The purpose of this regulation is to achieve acceptable ambient air levels of
sulfur oxide emissions.
Water Pollution Control Standards
Water Quality Criteria
The states' water quality criteria/standards usually consist of water use
classifications, water use descriptions and specific standards, as well as
general water quality criteria. The specific water quality standards which
are applicable to a given area depend on the water use classification that may
be assigned to an area.
A review was made of the five major coke producing states to examine
specific water quality criteria applicable to coke oven emissions. Based on
published state regulations and The Bureau of National Affairs (SNA) publi-
cations on state water laws at the time of this writing (current to 1976),
only Pennsylvania and West Virginia had published promulgated criteria.
Solid Waste Disposal Standards
Hazardous Waste Handling and Disposal
The EPA is delegating the enforcement authority under the "Resource
Conservation and Recovery Act of 1976" to the states. Although the specific
regulations for the handling, transport and disposal have not been promulgated
by the EPA, some states such as Pennsylvania have already implemented their
own hazardous materials transporting and disposal regulations.
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1. Albert, R.E. Carcinogens Assessment Group's Preliminary Report
on Population Risk to Ambient Coke Oven Exposures. External Review
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2. American Iron & Steel Institute. Comments of A.I.S.I. on Cyrus W.
Rice Draft Document for Effluent Limitations Guidelines and New
Source Performance Standards (Iron and Steel Industry), July 1973.
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at Hearing by A.I.S.I.-OSHA Docket No. H-059 on Proposed Standard
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5. American Iron & Steel Institute. Comments of A.I.S.I. on EPA's
Proposed Effluent Limitations Guidelines and Standards (Iron and
Steel Paint Source Category), April 5, 1974. 108 pp.
6. American Petroleum Institute. API Manual on Disposal of Refinery
Wastes. Washington, D.C. 1969.
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Federal Water Pollution Control Act Amendments of 1972 for the
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8. Balla, P.A. and Wieland, G.E. Performance of Gas-Cleaning System on
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Nitrogen Compounds from Coke Plant Wastes. EPA-R2-73-167, U.S.
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Washington, D.C., April 1973.
10. Barnes, Thomas M., Lownie, Harold W. Jr., and Varga, John, Jr.
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11. Bertrand, R.R. and Magee, E.M. Trip Report for Commercial
Gasification Plants. U.S. Environmental Protection Agency, Office
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-194-
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13. Bonham, J. W. and Atkins, W.T. Process Comparison Effluent Treatment
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15. Cannon, J.S. Environmental Steel Pollution in the Iron and Steel
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16. Christensen, K.G, and Stupin, W.J. Acid Gas Removal in Coal
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20. Cooper, F. et al. Emission Testing and Evaluation of Ford/Koppers
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Plant Operation on Coke Oven Acid Gases. Air Pollution Control
Association J. 25(4): 375-378, 1975.
35. Hossain, S.M. et al. Control Technology Development for Products/
By-Products of Coal Conversion Systems. EPA-600/7-78-063,
U.S. Environmental Protection Agency, Office of Research and
Development, Washington, D.C., April 1978.
36. Jablin, R. and Chanko, G.P. A New Process for Total Treatment of Coke
Plant Waste Liquor. A.I.C.H.E. Symposium Series 70(136):713-722, 1973.
37. Kostenbader, P.O. and Flecksteiner, J.W. Biological Oxication of Coke
Plant Waste Ammonia Liquor. Water Pollution Control Federation J.,
41(2) Feb. 1969.
38. Lowry, H.H., ed. Chemistry of Coal Utilization. Supplementary Volume.
John Wiley & Sons Inc., New York-London, 1963. 1142 pp.
39. Magee, E.M. Evaluation of Pollution Control in Fossil Fuel Conversion
Processes. EPA-600/2-76-101. U.S. Environmental Protection Agency,
Research Triangle Park, N.C. April 1976.
40. Massey, M.J. and Dunlap, R.N. Economics and Alternatives for Sulfur
Removal from Coke Oven Gas. Air Pollution Control Association J.
25(10): 1019-1027, 1975.
-196-
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41. Mazumdar, S. et al. An Epidemiological Study of Exposure to Coke Tar
Pitch Volatiles among Coke Oven Workers. Air Pollution Control
Association J. 25(4): 382-389, 1975.
42. McGannon, H. E., ed. The Making, Shaping and Treating of Steel.
United States Steel Corporation, Ninth Edition, 1971. 1420 pp.
43. Mezey, E.J. et al. Fuel Contaminants Volume 2. Removal Technology
Evaluation. EPA-600/2-76-177b, U.S. Environmental Protection Agency,
Office of Research and Development, Washington, B.C., September 1976.
298 pp.
44. Naso, A.C. and John, E.T. Physical-Chemical Treatment of Cleveland
District Coke Plant Wastewaters. American Iron & Steel Institute
85th General Meeting, Waldorf-Astoria Hotel, New York, N.Y.
May 25, 1977. 8 pp.
45. Nicklin, T. Recovery of ADA and Vanadium Salts from Stretford Waste
Liquor. U.S. Patent No. 3,810, 833 Northwestern Gas Board, May 14, 1974.
46, Nonhebel, G., ed. Gas Purification Processes. George Newnes Limited,
London, 1964,
47. O'Connor, R. B. Improving the Environmental Health of Coke Oven Workers.
American Iron & Steel Institute 78th General Meeting, New York, N.Y.,
May 27, 1970. 6 pp.
48. Parsons, W.A. and Nolde, W. Applicability of Coke Plant Water Treatment
Technology to Coal Gasification. EPA-600/7-7B-063, U.S. Environmental
Protection Agency, Washington, D.C. April 1978. 15 pp.
49. Pasztor, L. and Floyd, S.B., Jr. Managing and Disposing of Residues from
Environmental Control Facilities in the Steel Industry. U.S. Environmen-
tal Protection Agency Office of Research & Development, June 1976. 177 pp.
50. Pearson, E.F. Research Study of Coal Preparation Plant and By-Product
Coke Plant Effluents. EPA-660/2-74-050, U.S. Environmental Protection
Agency, Office of Research and Development, Washington, D.C., April 1974
287 pp.
51. Radian Corp. Industrial Process Profiles for Environmental Use: Chapter
24. The Iron and Steel Industry. PB-266 226. U.S. Environmental
Protection Agency, Research Triangle Park, N.C., Feb. 1977.
52. Rudolph, H. and Sawyer, S. Engineering Criteria for the Envirotech/
Chemico Hooded Quench Car System. Annual Meeting of the Association of
Iron and Steel Engineers, Pittsburgh, Pa. Sept. 27-29, 1976. 30 pp.
53. Schueneman, J. J. et al. Air Pollution Aspects of the Iron and Steel
Industry. U.S. Dept. of Health, Education and Welfare, Public Health
Service Publication No. 499-AP-l, Cincinnati, Ohio, June 1963. 118 pp.
54. Seil, G.E. Dry Box Purification of Gas. American Gas Association, 1943.
55. Serrurier, R. Prospects for Marketing Coal Gasification By-Products.
Hydrocarbon Processing J., September 1978.
56. Sheldrake, C. William and Homberg, Otto A. "Coke Oven Gas Desulfuriza-
tion - State of the Art." American Iron & Steel Institute, 85th General
Meeting. Waldorf Astoria Hotel, New York, N.Y. May 25, 1977. 24 pp.
-197-
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57. Shreve, R.N. Chemical Process Industries. 3rd Edition. McGraw-Hill,
Inc., New York, N.Y. 1967. 905 pp.
58. Singer, P.C. et al. Composition and Biodegradability of Organics in
Coal Conversion Waste Waters. EPA-600/7-78-063. U.S. Environmental
Protection Agency, Washington, D.C., April 1978.
59. Sinor, J.E., et. Evaluation of Background Data Relating to New
Source Performance Standards for Lurgi Gasification. EPA-600/7-77-057,
U.S. Environmental Protection Agency, Research Triangle Park, N.C.
June, 1977
60. Smith, H.I. and Werner, G.J. Coal Conversion Technology, A Review.
Millmerran Coal Pty. Ltd., Brisbane, Australia, May 1975.
61. Smith, W.M. Evaluation of Coke Oven Emissions. American Iron & Steel
Institute. 78th General Meeting, New York, N.Y. May 27, 1970. 17 pp.
62. Stellman, J.M. An Assessment of the Health Effects of Coke Oven
Emissions. External Review Draft, U.S. Environmental Protection Agency,
Office of Research and Development, Washington, D.C., April 1978. 145 pp.
63. Strup, P.E. et al. Sampling and Analysis of Coke Oven-Door Emissions.
U.S. Environmental Protection Agency, PB 276-485/AS. October 30, 1977.
182 pp.
64. Suta, B.E. Human Population Exposures to Coke-Ovens Atmospheric Emissions,
U.S. Environmental Protection Agency, Contract 68-01-4314, November 1977.
107 pp.
65. The APC Monitor. Report to the Air Pollution Control Board for the Month
of October 1978. Air Management Services, Phila. Dept, of Public Health,
Philadelphia, Pa. 23 pp.
66. Traubert, R.M. Weirton Steel Division - Brown's Island Coke Plant, Iron
and Steel Engineer, January 1977. 4 pp.
67. T.R.W. Systems & Engrg. Carcinogens Relating to Coal Conversion
Processes. E.R.D.A. Document No. FE-2217-1. June 1976. 129 pp.
68. Voelker, F.C. Jr. A Contemporary Survey of Coke-Oven Air Emissions
Abatement. Iron and Steel Engineer, February 1975. 8 pp.
69. Wilson, P.J. and Wells, J.R. Coal, Coke and Coal Chemicals. McGraw-Hill
Book Company, Inc., New York, N.Y., 1950.
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APPENDIX A. SI (METRIC) CONVERSION FACTORS
To Convert From
ft/s"
To
Acceleration
,2 , , 2.
meter per second (m/s )
Multiply By
3.048-000 E-01
Acre (U.S. survey)
ft2
in2
yd2
12
Area
2 2
meter (m )
2 2
meter (m )
2 2
meter (m )
2 2
meter (m )
4.046 873 E+03
9.290 304 E-02
6.451 600 E-04
8.361 274 E-01
British thermal unit
(mean)
Calorie (kilogram, mean)
Kilocalorie (mean)
Energy (Includes Work)
joule (J)
joule (J)
joule (J)
1.055 87 E+03
4.190 02 E+03
4.190 02 E+03
foot
inch
yard
Length
meter (m)
meter (m)
meter (m)
3.048 000 E-01
2.540 000 E-02
9.144 000 E-01
grain
grain
pound (Ib avoirdupois)
ton (metric)
ton (short, 2000 Ib)
Mass
kilogram (kg)
kilogram (kg)
kilogram (kg)
kilogram (kg)
kilogram (kg)
6.479 891 E-05
1.000 000 E-03
4.535 924 E-01
1.000 000 E+03
9.071 847 E+02
Ib/ft'
Mass Per Unit Area
2 2
kilogram per meter (kg/m )
4.882 428 E+00
-199-
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To Convert From
APPENDIX A (Continued)
To
Multiply By
degree Celsius
degree Fahrenheit
degree Fahrenheit
degree Rankine
Kelvin
ft/h
ft/min
ft/8
in/s
centipoise
centistokes
poise
stokes
acre-foot (U.S.
survey)
barrel (oil, 42 gal)
ft3
gallon (U.S. liquid)
liter*
Volume
ft^/min
fWs
gal (U.S. liquid/day)
gal (U.S. liquid/min)
Temperature
Kelvin (K)
degree Celsius
Kelvin (K)
Kelvin (K)
degree Celsius
Velocity (Includes Speed)
meter per second (m/s)
meter per second (m/s)
meter per second (m/s)
meter per second (m/s)
Viscosity
pascal second (Pa.s)_
meter per second (m /s)
pascal second (Pa.s)2
meter per second (m /s)
Volume (Includes Capacity)
3 3
meter (m )
3 3
meter (m )
meter- (m )
meter (m )
3 3
meter (m )
Per Unit Time (Includes Flow)
3 3
meter_ per second (m,/s)
meter- per second (m_/s)
meter, per second (m»/s)
meter per second (m /s)
tv = t + 273.15
K °C
t = (t - 32)/1.8
°C °F
t.. - (t + 459.67)/1.8
K °F
t = t /I. 8
K °R
t = tv - 273.15
°c K
8.466 667 E-05
5.080 000 E-03
3.048 000 E-01
2.540 000 E-02
1.000 000 E-03
1.000 000 E-06
1.000 000 E-01
1.000 000 E-04
1.233 489 E+03
1.589 873 E-01
2.831 685 E-02
3.785 412 E-03
1.000 000 E-03
4.719 474 E-04
2.831 685 E-02
4.381 264 E-03
6.309 020 E-05
*In 1964 the General Conference on Weights and Measures adopted the name
liter as a special name for the cubic decimeter. Prior to this decision
the litre? differed slightly (previous value, 1.000028 dm ) and in expression
of precision volume measurement this fact must be kept in mind.
-200-
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APPENDIX A (Continued)
To Convert From
Ib/ft
Ib/in
To
Mass Per Unit Length
Kilogram per meter (kg/m)
Kilogram per meter (kg/m)
Multiply By
1.488 164 E+00
1.785 797 E+01
Ib/h
Ib/min
ton (short)/h
Mass Per Unit Time (Includes Flow)
Kilogram per second
(kg/s)
Kilogram per second
(kg/s)
Kilogram per second
(kg/s)
1.259 979 E-04
7.559 873 E-03
2.519 958 E-01
lb/ft:
Mass J?er Unit Volume (Includes Density & Mass Capacity)
3
Ib/gal (U.S. liquid)
Ib/yd3
Kilogram per meter"
(kg/m3)
e
Kilogram per meter"
(kg/m3)
/
Kilogram per meter"
(kg/m3)
1.601 846 E+01
1.198 264 E+02
5.932 764 E-01
Power
Btu (Thermochemical)/h Watt (w)
Btu (thermochemical)/h Watt (W)
cal (thermochemical)/min Watt (w)
cal (thermochemical)/s Watt (W)
2.930 711 E-01
2.928 751 E-01
6.973 333 E-02
4.184 000 E+00
Pressure or Stress (Force Per Unit Area)
atmosphere (standard) pascal (Pa)
pascal (Pa)
foot of water (39.2 F)
lbf/ft2
lbf/in2 (psi)
pascal (Pa)
pascal (Pa)
1.013 250 E+05
2.988 98 E+03
4.788 026 E+01
6.894 757 E+03
-201-
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/7-79-184
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Applicability of Coke Plant Control Technologies to
Coal Conversion
5. REPORT DATE
August 1979
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
S.M.Hossain, P. F.Cilione, A. B.Cherry, and
W.J.Wasvlenko. Jr.
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Catalytic, Inc.
1500 Market Street
Philadelphia, Pennsylvania 19102
10. PROGRAM ELEMENT NO.
EHE623A
11. CONTRACT/GRANT NO.
68-02-2167, Task 10
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Task Final; 8/77 - 3/79
14. SPONSORING AGENCY CODE
EPA/600/13
is.SUPPLEMENTARY NOTES fERL-RTP project officer is Robert A. McAllister, Mail Drop 61,
919/541-2134.
16. ABSTRACT
repOr^ gjyes results of comparisons of process and waste stream
characteristics from the Byproduct coke oven process with selected gasification and
liquefaction processes. It includes recommendations regarding control technologies
for air, water, and solid wastes. Coke oven control technology was reviewed exten-
sively. State and Federal regulations for the disposal and treatment of coke oven
wastes are presented, along with a brief assessment of health effects attributed to
coke oven emissions. Study results indicate that a number of coke oven control tech-
nologies are applicable to coal conversion systems , especially those dealing with
desulfurization, fugitive emissions, byproduct recovery /upgrading, and wastewater
treatment. Byproduct upgrading and fugitive emission control technologies may be
readily transferrable to analogous coal conversion applications. Desulfurization and
wastewater treatment technologies , however , cannot be transferred readily to appli-
cations where significant differences exist in the composition, temperature, and
pressure of the two categories of process/waste streams. In these cases, laboratory
or pilot plant scale tests will be required with actual coal conversion wastes to deter-
mine the design bases and the treatability variations between coal conversion and
comparable coke oven streams .
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Pollution
Coking
Coal
Liquefaction
Coal Gasification
Environmental Biology
Desulfurization
Leakage
Waste Water
Water Treatment
Pollution Control
Stationary Sources
Coal Conversion
Byproduct Coke Oven
Process
Health Effects
Fugitive Emissions
13B
13H
21D
07D
07A
8. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
212
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
202
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