SEPA
United States Industrial Environmental Research EPA-600/7-78-184a
Environmental Protection Laboratory September 1978
Agency Research Triangle Park NC 27711
Environmental Assessment
Data Base for Coal
Liquefaction Technology:
Volume I. Systems for 14
Liquefaction Processes
Interagency
Energy/Environment
R&D Program Report
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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-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
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)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the INTERAGENCY ENERGY-ENVIRONMENT
RESEARCH AND DEVELOPMENT series. Reports in this series result from the
effort funded under the 17-agency Federal Energy/Environment Research and
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
systems; and integrated assessments of a wide range of energy-related environ-
mental issues.
REVIEW NOTICE
This report has been reviewed by the participating Federal Agencies, and approved
for publication. Approval does not signify that the contents necessarily reflect the
views and policies of the Government, nor does mention of trade names or commercial
products constitute endorsement or recommendation for use.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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ABSTRACT
This report was prepared as part of an overall environ-
mental assessment program for the technology involved in the
conversion of coal to clean liquid fuels. The program is
being directed by the Fuel Process Branch of the Environ-
mental Assessment and Control Division of the Industrial
Environmental Research Laboratory at Research Triangle Park,
North Carolina. The two volumes of this report plus the
Standards of Practice Manual for the Solvent Refined Coal
Liquefaction Process (EPA-600/7-78-091) represent the cur-
rent data base for the environmental assessment of coal
liquefaction technology.
In general, liquefaction operations begin with pre-
treatment of the feed. Feed must be reduced to the required
coal particle size, and either dried or formed into a slurry
by mixing with a process-derived slurry. Thus prepared the
feed enters the liquefaction operation where the addition of
hydrogen to carbon occurs along with a dissociation of the
components in the coal. These components are then separated
from the liquefaction products through a variety of opera-
tions. The resulting products and by-products are purified,
upgraded, and refined. By means of a modular concept, the
characteristics of process input and output streams includ-
ing wastes are displayed.
Volume I, "Systems for Fourteen Liquefaction Processes,1
provides a summary of pertinent information about prominent
coal liquefaction systems now under development. For each
system it includes a brief description, a flow diagram, and
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a list of the materials entering and leaving the system.
The processes required to produce clean liquid fuels from
coal are divided into discrete operations. Each of these
operations is then further divided into discrete modules,
with each module having a defined function, identifiable raw
materials, products, and discharge streams. A general
discussion of potential applicable control techniques is
presented along with the current status and development
plans for the fourteen coal liquefaction systems.
The main conclusion reached from the preparation of
Volume I is that these processes are not environmentally
defined in the published literature, however, there is
some indication that current development plans may help to
correct this situation. Hittman Associates, Inc., will be
investigating ways to help fill in the missing information
through contacts with others and through the development of
test plans.
Volume II, "Detailed Discussion of Synthoil, H-Coal and
Exxon Donor Solvent Processes," is an environmental charac-
terization report covering three of four selected coal
liquefaction systems. It provides documentation and evalu-
ation of existing environmentally significant data. Envi-
ronmental characterization includes an integrated multimedia
assessment of the discharges to the environment from con-
3
ceptualized 7,950 m (50 kbbl) per day systems. Estimations
are given for the raw waste streams, treatment/control
processes, treated waste stream discharges, and the effects
of these discharges on the environment.
111
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CONTENTS
Abstract ii:L
Figures vii
Tables ix
Acknowledgements x
Introduction xl
Executive Summary xii
1. Technology Characteristics 1
Introduction 1
Hydrogenation 3
Synthoil System 3
H-Coal System 8
Bergius System 15
Solvent Refined Coal System 18
CO-Steam System 27
Donor Solvent System 31
Pyrolysis and hydrocarbonization 40
Char-Oil-Energy Development (COED)
System 40
Coalcon System 50
Clean Coke System 59
TOSCOAL System 63
Occidental Research Corporation (ORC)
System 67
Extraction 72
Supercritical Gas Extraction System . . 72
Catalytic Synthesis 76
Fischer-Tropsch System 76
Methanol System 81
iv
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CONTENTS (continued)
2. System Operations and Auxiliary Processes . . 87
Introduction and summary 87
Coal pretreatment 95
Coal liquefaction 100
Separation 112
Purification and upgrading 124
Auxiliary processes 132
3. Environmental Assessment Requirements .... 162
Introduction 162
Selection of suitable air pollution
controls 163
Selection of suitable water pollution
controls 165
Selection of suitable solid waste
controls 167
4. Plans and Timing for Development 171
Introduction 171
Hydrogenation 174
Pyrolysis and hydrocarbonization .... 175
Extraction 176
Catalytic synthesis 176
References 177
Bibliography 180
Appendices: A. SI (Metric) Conversion Factors 183
B. Sieve Series 186
C. SI Series 187
v
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FIGURES
XT v Page
Number °
1 Module diagram for coal liquefaction systems . . . xiv
2 Synthoil system
3 H-Coal system -1-1
4 Bergius system -*-"
5 Solvent refined coal system ^0
6 Sizing, drying, pulverizing, and slurrying .... 22
7 Hydrogenation and mineral separation 24
8 Gas cleaning 26
9 CO-Steam system 29
10 Exxon Donor Solvent (EDS) system 32
11 Consol Synthetic Fuel (CSF) system 33
12 Arthur D. Little (ADL) system 34
13 Liqui-Coal (L-C) system 35
14 Pott-Broche (P-B) system 36
15 COED system 43
16 Stage I, COED system 45
17 Stages II, III and IV, COED system 46
18 Oil separation and hydrotreating 48
19 Coalcon system 53
20 Sizing, drying, preheating and feeding 54
21 Hydrocarbonization and product recovery 55
VI
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FIGURES (continued)
Number Page
22 Hydrogen generation 57
23 Clean Coke (CC) system 60
24 TOSCOAL system 65
25 ORC system 70
26 Supercritical Gas Extraction (SGE) system 74
27 Fischer-Tropsch (F-T) system 78
28 Methanol system 83
29 Modules in coal preparation operation 96
30 Hydrogenation module in the H-Coal process .... 101
31 Pyrolysis/hydrocarbonization module . 104
32 Extraction module 108
33 Catalytic synthesis module 110
34 Flashing and condensation module 115
35 Filtration module 116
36 Centrifugation module 117
37 Solvent de-ashing module 118
38 Vacuum distillation module 119
39 Coking module 120
40 Quenching module 121
41 Oil-water separation module 122
42 Fractionation module 126
43 Hydrotreating module 129
44 Hydrogen/synthesis gas generation 133
VII
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TABLES
Number
1 Prepared Coal Characteristics "'
2 Separation Methods for Coal Liquefaction 114
3 Gasifier Conditions 136
4 Partial List of Control Approaches for Waste
Treatment 146
5 Sources and Characteristics of Wastewater
Streams 147
6 Sources and Characteristics of Air Emissions . . . 150
7 Emissions Affected by Air Pollution Control
Equipment 151
8 Sources and Characteristics of Solid Wastes .... 153
9 Some Characteristics of Wastewater 166
10 Wastewater Control Systems 168
11 Coal Liquefaction Development Schedule 172
Vlll
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ACKNOWLEDGEMENT S
This report was prepared by the staff of Hittman Asso-
ciates, Inc., Columbia, Maryland, under the direction of Mr
J. Wayne Morris, Program Manager.
For their contributions and assistance, our appre-
ciation is extended to the following members of the Syn-
thetic Fuels Section:
Mr. John E. Robbins, Technical Information Specialist
Mr. Kevin J. Shields, Chemical Engineer
Mr. Dewey Dykstra, Senior Chemical Engineer
IX
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INTRODUCTION
Volume I of this document presents a summary of the
technology and environmental factors associated with the
production of liquid fuels from coal. It provides a broad
picture of the liquefaction program, identifies the pro-
cesses which constitute program elements and areas needing
study, and proposes a preliminary modular approach for later
work.
Information has been included for as many specific pro-
cesses as data permitted. The approach taken has been to
make the liquefaction technology coverage general rather
than to attempt detailed descriptions. Detailed descrip-
tions for selected processes have been developed in Volume
II and in the Standards of Practice Manual for Solvent
Refined Coal, EPA-600/7-78-091.
x
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EXECUTIVE SUMMARY
In its broadest sense, the coal liquefaction program
includes Federal, state, and private efforts to develop
means of producing liquid hydrocarbons from coal. Projects
are being sponsored by each of these segments. By far the
largest number of projects are funded by DOE or jointly by
DOE and private industry. These are also the most pub-
licized in terms of availability of technical, economic, and
programmatic information. For these reasons, the primary
concern of this document is with DOE supported projects,
though not to the total exclusion of other efforts.
Near-term objectives of the DOE coal liquefaction
program appear to be: to develop commercialization of poten-
tial second generation technology for producing boiler fuel,
heating oil, gasoline, and chemical feed stocks; to provide
technology needed for commercial liquefaction via first
generation technology; and to provide basic research and
development in support of third generation processes. Long-
term objectives are to achieve commercialization of second
generation technology and to demonstrate and ultimately
commercialize third generation technology.
These objectives are being met by project support in
each element of the program. The program elements include
hydroliquefaction, pyrolysis, indirect hydrogenation, and
supporting technologies. For the purposes of this summary
document the technology categories used are hydrogenation,
XI
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pyrolysis and hydrocarbonization, and extraction and cataly-
tic synthesis. There is a limited number of advanced pro-
cesses at this time. In the projects which have been
active, emphasis has been adjusted to conform with the
results of research and development studies and of changing
needs.
The hydrogenation process is the most advanced. Two
SRC pilot plants are successfully operating. A full scale
test of the combustion characteristics of solvent refined
coal (SRC-I) was conducted in the spring of 1977. The H-
Coal process, also in the hydrogenation category, is nearing
completion of the pilot plant construction stage. When
operational this facility will be the largest liquefaction
plant in the United States. The Exxon Donor Solvent (EDS)
process is planned for piloting in the near-term. A 227-
metric ton (250-ton) per day pilot plant is to be built at
Baytown, Texas, as a joint government-industry project. The
schedule plans for operation to begin in FY 80. It is
projected as a major developmental effort.
Pyrolysis and hydrocarbonization projects include the
two primary efforts of the Char-Oil-Energy-Development
(COED) and Coalcon processes. COED has progressed success-
fully through the pilot plant and work on this process has
been terminated; however, the developers are pursuing
related efforts. The Coalcon process developers faced with
the problems of escalating costs as well as technical prob-
lems, have shelved plans for construction of a pilot plant.
All processes in this category will have the disadvantage of
comparatively low thermal efficiency.
The Supercritical Gas Extraction process has not been
developed beyond the laboratory stage. Catalytic synthesis
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includes the Fischer-Tropsch process which is currently used
in South Africa to produce gasoline and chemical feedstocks.
Although significant technical differences between the
liquefaction processes do exist, many of the individual unit
and processing steps are common to several systems. To
avoid the redundancy of studying these common areas in each
system, a process modular concept is used. A process module
is a representation of a process which is used to display
input and output streams. Thus the operations in coal lique-
faction technology; coal pretreatment, liquefaction, separa-
tion and purification each consist of a series of steps such
as coal crushing, hydrogenation, filtration, and hydro-
treating which can be represented by modules. Figure 1
displays this concept. Figure 1 also shows the auxiliary
processes (such as oxygen generation and sulfur recovery)
which are associated with coal liquefaction technology al-
though they are incidental to the main functions involved in
the transformation of raw materials into end products.
XX 3.1
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HYDROGEN
(SYNTHESIS GAS)
SYN GAS
Figure 1. Module diagram for coal liquefaction systems
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SECTION 1
TECHNOLOGY CHARACTERISTICS
INTRODUCTION
Estimates of current petroleum reserves indicate a
limited remaining life for useful production of fuels. This
has generated renewed interest in technology for producing
liquid hydrocarbons from coal, with the primary objective of
producing clean liquid fuels. Coal liquefaction is not a
new technology; it dates back to the early part of the
twentieth century - the concept even earlier.
During the nineteen-twenties and thirties, extensive
research into the hydrogenation of coal was performed in
Germany. German interest in liquid fuels stemmed from the
fact that the nation had extensive coal reserves but no
domestic petroleum. The United States Department of the
Interior conducted small scale feasibility studies of the
German technology, but these efforts were abandoned when
immense quantities of oil were discovered in east Texas in
1930.
In 1944, during the latter part of the second World
War, interest in coal liquefaction in the United States was
renewed. In that year the Synthetic Fuels Act provided sixty
million dollars to fund studies through 1955. Another large
oil discovery, this time in the Middle East, reduced inter-
est in creating liquid fuels from coal.
1
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With the advent of declining petroleum reserves,
fewer new discoveries, escalation of prices, and real or
induced shortages, coal liquefaction technology has once
more assumed a major role as a potential solution to liquid
fuel problems. Currently some twenty-odd processes are in
various stages of development by industry and federal
agencies.
In general, liquefaction processes offer several advan-
tages over gasification of coal. The overall thermal effi-
ciency is usually higher and process water requirements are
reduced. Liquid fuels have a much higher energy density
than fuel gases. Liquefaction processes operate under less
severe temperature and pressure conditions than gasification
processes. These advantages may tend to favor more rapid
development and commercialization of new liquefaction than
new gasification (1).
All liquefaction processes produce liquids by yielding
a material having higher hydrogen content than coal. Hydro-
gen is present in coal at a level of about 5 percent. In
high-Btu gas it is roughly 25 percent. Fuel oils contain 9
to 11 percent hydrogen and gasoline about 14 percent.
Whether the required hydrogen increase is obtained by adding
hydrogen to the coal components, or by stripping the hydro-
gen-rich components from the coal depends upon the particu-
lar process. The method used also affects the yield of
liquid from the process.
The hydrogen increase is not completed in the initial
reaction. Upgrading by hydrotreating is required to produce
higher quality fuels. The initial crude liquid is suitable
only for utility fuel. Hydrotreating is also necessary to
reduce sulfur, nitrogen and oxygen content.
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Varying amounts of carbon remain unreacted as a char,
depending upon the process. In some systems, this char is
used to generate hydrogen by the steam carbon reaction.
Other processes produce such a high proportion of char that
it must be considered by-product fuel.
In place of hydrogen, synthesis gas may be used in
several processes. Synthesis gas is a mixture of hydrogen
and carbon monoxide in varying proportions generated by the
reaction of carbon with oxygen and steam.
For specific applications the ratio of hydrogen to
carbon monoxide can be adjusted by the CO-shift reaction,
CO
If carried to completion, actually equilibrium, essentially
pure hydrogen, except for impurities which may have been in
the feed gas mixture, results after the carbon dioxide is
removed.
A wide range of process conditions and configurations
exist within the liquefaction technology. Descriptions of
the more important processes are presented in the remainder
of this section.
HYDROGENATION
Synthoil System
Background--
While much of the past research in liquefaction was
directed towards making a substitute refinery feedstock, the
Synthoil Process is one of the few specifically aimed at
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making a low sulfur fuel oil for the electric utility indus-
try. The urgent need for such a fuel was emphasized by the
shortage of petroleum in the heating season of 1973-1974.
Many power plants are now fired with petroleum-derived fuel
instead of coal because petroleum, which burns cleaner than
coal, complies with greater ease to environmental regula-
tions. An environmentally acceptable coal-derived Synthoil,
therefore, could help release petroleum fuel oil for other
uses (1).
The intent of the Synthoil Process development was to
show that, under the right conditions, reaction of coal with
hydrogen will promote desulfurization and minimize addi-
tional hydrogenation of the products from the primary lique-
faction. 'Work on such a process was initiated by the United
States Bureau of Mines at the Pittsburgh Energy Research
Center in 1969. It has led to a process in which coal is
liquefied and desulfurized in a single step by catalytic
hydrotreatment in a highly turbulent, co-current, up-flow,
packed-bed reactor. The initial work used a reactor with an
internal diameter of 8 mm with daily feed rates of 22 kg of
coal or 54 kg of slurry.
Experimental work was carried out on various coals
including Pittsburgh, Indiana No. 5, Middle Kittanning, Ohio
No. 6, and Kentucky coal. All of these types of coal were
satisfactorily converted to low-sulfur fuel oil with no
appreciable attrition of catalyst or loss of catalyst desul-
furization activity. Other parameters investigated were
hydrogen flow rate, coal content of feed slurry, recycling
of product oil, and the effects of hydrogen sulfide on
recycled gas. A larger bench-scale unit, 28 mm internal
diameter and 4.42 m long, was operated at daily feed rates
up to 181 kg of coal and 454 kg of slurry. Reactor pressure
was varied from 14.7 to 29.4 MPa at temperatures up to 450°C.
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The lower reactor pressure corresponded to lower yields,
heating value, and hydrogen consumption. Sulfur and ash
content of the low pressure oil were higher than those of
the oil made at 29.7 MPa. Operation at the lower pressure
is desirable provided an environmentally acceptable product
can be made. A 9.1-metric ton per day process development
unit (PDU) is under construction (2).
System Description--
Figure 2 is a flowsheet of the system. Coal feed for
the Synthoil Process is prepared by drying and then grinding
to 90 percent less than 250 fim or 65 percent less than 63 jum
The ground coal is thoroughly mixed with recycled product
oil to form a paste or slurry containing about 40 percent
coal and 60 percent oil. The slurry, together with recycled
and makeup hydrogen, is preheated and then passed to the
reaction zone. The reactor is packed with one-eighth inch
pellets of a type of commercial catalyst used in desulfur-
izing petroleum derivatives. Under operating conditions
described above, hydrogen liquefies the coal and simultan-
eously removes sulfur, oxygen, and nitrogen (3).
The major portion of the coal is hydrogenated to gas
and oil which are separated by a pressure reduction. The
oil stream containing Synthoil residue, and mineral matter
is treated to separate the oil and solids. The oil is
divided into two streams, one of which is returned to feed
preparation and the other withdrawn as product. Residue and
oil are separated; the oil is sent to product storage and
the residue goes to the hydrogen production area. The
gaseous mixture from the reaction contains unused hydrogen
which can be recycled through the reactor. However, it also
contains hydrogen sulfide and ammonia. These two contami-
nants are removed by absorption in the gas purification
system. The hydrogen sulfide is sent to a sulfur recovery
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COAL
SIZING
DRYING
&
SLURRYING
MAKEUP
H2
GASIFICATION
HYDROCARBON
GASES
RECYCLED \\2
RECYCLET
OIL
SLURRY
FEED STREAM
SYNTHOIL
(HYDROGENATICN)
GAS PURIFICATION
SYSTEM
CARBONACEOUS NH3'H2S'H2°
RESIDUES
GASES
PYROLYSIS
SOLIDS
PRODUCT
OIL
PRODUCT
STREAM
GAS
SEPARATION
LIQUIDS AND
UNREACTED
SOLIDS
SOLIDS
SEPARATION
LIQUIDS
PRODUCT
OIL
Figure 2. Synthoil system (3)
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unit and the ammonia is used to produce ammonium sulfate.
Sulfuric acid also may be produced (1).
Coal and residue from the reactor are used to produce a
rich hydrogen (97.5 percent) mixture to use in the lique-
faction reaction.
Major Operations and/or Modules--
Sizing, drying and slurrying
Hydrogenation
Separation
Hydrogen production
Material Inputs--
Coal
Catalyst - Co-Mo/SiC^-A^C^
Hydrogen
Monoethanolamine
Water
Material Outputs--
Synthoil
Sulfur
Ammonium sulfate
Sulfuric acid
Ash
Carbonaceous residue
Water from coal drying
Dust from crushing
Fuel gas
Tar
Spent catalyst
Spent MEA
Waste liquids, oil and water
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Slowdown and sludge from:
Power plant
Water treatment
Cooling tower
Advantages, Disadvantages, and Efficiency--
The high superficial velocity and rapid turbulent flow
rates keep the catalyst surface free of deposits, inhibit
agglomerating tendencies, and enhance hydrogen transfer (1)..
The short residence time and high yield would indicate
possibilities for high production rates per unit volume in
commercial-size operations.
On the other hand factors related to the maintenance of
turbulent flow, good catalyst-reactant contact, and even
flow distribution may limit practical diameter size in
scale-up to commercial size. Other disadvantages are the
relatively high pressure and the dependence on centrifuga-
tion for mineral separation. High yields of fuel oil, low
sulfur (0.19 to 0.3 percent) and low-ash (one percent)
3
ranged from 0.525 to 0.700 m per metric ton of coal.
H-Coal System
Background--
The direct hydrogenation process developed by Berguis
in Germany for conversion of coal to liquid products led to
later development in the U.S. of the H-Coal process. It was
developed by Hydrocarbon Research, Incorporated (HRI) as a
further application of the H-Oil process ebullating bed
technology originally employed to convert heavy oil residues
into lighter fractions. The feed to hydrogen manufacture
is liquid rather than solid. Direct catalytic processes use
less hydrogen in converting coal to liquids than do the non-
catalytic or indirect catalytic hydrogenation processes.
8
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Early development work on the H-Coal process, beginning
in 1964, involved research with a bench-scale unit and a
process development unit, both located at HRI's Trenton
Laboratory, under contract with the Department of Interior's
Office of Coal Research. The government contract was can-
celled in 1967 due to lack of funds but private industry
continued to support the program. A conceptual process
design was prepared and an independent evaluation in 1968
confirmed the technical and economic feasibility of the
process (4).
In bench-scale and process development unit tests the
process proved to be highly flexible. Bench-scale tests
were conducted on many coals including eastern, midwestern
and western bituminous coals, western subbituminous coals,
lignite from Texas and North Dakota, and Australian brown
coal. Variables investigated include: life and activity
of catalyst type; temperature; pressure; coal feed rate; and
slurry oil composition. The process development unit tests
demonstrated sustained operational reliability (4).
Based on the data obtained from the bench-scale and
process development units, design and engineering of a 544-
metric ton per day pilot plant was initiated under the
current DOE contract on December 1973. The final design of
the pilot plant is complete and construction is underway at
Catlettsburg, Kentucky. Ashland Synthetic Fuels, Inc.,
Ashland, Kentucky, and Hydrocarbon Research, Inc., Morris-
town, New Jersey are the prime contractors. Operation is
scheduled for September 1, 1978 to June 1, 1980. The plant
is to be dismantled and disposed by the end of 1980.
Ashland Synthetic Fuels will be responsible for con-
struction and operation of the pilot plant. HRI will moni-
tor the construction and operation of the plant to ensure
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that data suitable for a commercial plant design is ob-
tained. A separate subcontractor will design the solids/
liquids separation system to be installed in the pilot
plant. Product characteristics will be determined and
operational problems identified (2).
System Description--
The H-Coal process utilizes an ebulliating bed reactor
to continuously convert coal in a direct catalytic hydro-
genation process.
The system configuration is depicted in the block flow
diagram, Figure 3. Coal is crushed, dried, and slurried
with recycled oil. Part of the coal is fed to the gasifier
to provide for increased hydrogen production. Compressed
hydrogen is added to the slurry; the mixture is preheated
and charged continuously to the bottom of the reactor at a
pressure of about 50.6 MPa. The cobalt/molybdenum catalyst
is maintained in an expanded state by internal recycling of the
reaction mixture. The temperature of the reactor, about
455°C, is controlled by adjusting the temperature of the
reactants from the preheater (4).
Figure 3 depicts the disposition of by-products in the
H-Coal system. Gas and vapor products leaving the top of
the reactor are cooled to condense the heavier components.
The gas cleanup system recovers light hydrocarbons, ammonia,
and sulfur from the gas stream. The remaining hydrogen rich
gas is recompressed and recycled to mix with the input
slurry. The liquid from the condenser is fed to an atmos-
pheric distillation unit. The liquid/solid product from the
reactor is subjected to reduced pressure and the resultant
vapors are passed to an atmospheric distillation unit that
yields light and heavy distillate products. The bottoms
product from the flash separator consists of solids and
10
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COAL
HYDROGEN
GENERATION
HYDROGEN
RECYCLED
HYDROGEN-
RICH GAS
GAS
CLEANUP AND
SULFUR RECOVERY
I
AMMONIA
LIGHT
HYDROCARBONS
SIZING
AND
DRYING
SLURRY
PREPARATION
PREHEATING
H-COAL
(HYDROGENATION)
PRODUCT
SEPARATION
RECYCLED
OIL
LIQUID
PRODUCTS
HEAVY
BOTTOMS
SULFUR
Figure 3. li-Coal system(4)
11
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heavy oil. This mixture is passed through a hydroclone to
remove the solids. Other separation methods have shown only
limited effectiveness. The heavy oil is then further pro-
cessed in a vacuum still. Gas and liquid products are
refined as necessary and the heavy distillate is recycled to
serve as the slurry medium. The solids residue can be used
for hydrogen manufacture (4).
Auxiliary processes require an oxygen plant, sulfur
plant, steam and electric power generation, and water supply.
Wastewater treatment and solid waste disposal are also neces-
sary. Auxiliary processes will consume additional fuel in
the form of coal or clean products from the process.
Major Operations and/or Modules--
Sizing, drying and slurrying--The coal is crushed to
about 18 mm and stockpiled. For feed preparation, it is
dried to 4 percent moisture, and then ground to minus 250
fj.m. Crushed coal is mixed with recycled oil to form a
slurry feed for the high pressure hydrogenation module.
Hydrogenation--Coal slurry and hydrogen are passed
through a preheated furnace and then fed to the bottom of
the reactor. The liquid slurry is hydrogenated as it comes
in contact with the ebulliating bed of catalyst. The
reaction takes place at a temperature of about 455°C and
pressure of about 20.3 MPa. Fresh catalyst is added to
replace the used catalyst on a semicontinuous basis which
permits reactor operation at a constant equilibrium activ-
ity level (4).
Product separationGases and vapors are withdrawn from
the top of the reactor and passed through condensers.
Condensed oil vapors are sent to an atmospheric distillation
unit. Further cooling of gases condenses a large amount of
12
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sour water containing ammonia, hydrogen sulfide, phenols,
light oil, and suspended solids. Uncondensed gases are
passed through an acid gas removal unit where hydrogen
sulfide is removed and further processed to elemental sul-
fur. Part of the clean gas is used as plant fuel and part
is recycled to the main reactor system. Fresh hydrogen is
added to achieve the required concentration for use in the
main reactor (4).
Solids separationThe heavier portion of the product
oil leaves as a sidestream from the liquefaction reactor.
It contains particulates such as mineral matter and unreac-
ted coal which must be removed. The hot oil is flashed in a
separator and the vapors are condensed and pumped to an
atmospheric distillation unit.
Distillation--The bottoms product from the flash sep-
arator is further separated with a hydroclone, a liquid-
solid separator, and a vacuum still. The overhead is a
heavy oil refinery feedstock. The stream removed from the
bottom of the vacuum tower contains heavy liquid residue
together with some particulates. The bottoms product from
the distillation unit is recycled for slurry preparation and
the overhead stream of light liquid hydrocarbons is further
refined as necessary. Synthesis gas for use in making
hydrogen can be generated by using the slurry bottoms from
the vacuum tower as feed to a slagging type gasifier.
Supplemental coal feed may be needed (4).
Material Inputs--
Coal
e Steam
Air
Catalyst
Absorption solvent
13
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Material Outputs--
Synthetic oil
Sulfur
Ammonia
Ash
Residue
Spent catalyst
Spent solvent
Water from coal drying
Dust from coal crushing
Fuel gas
Tar
Waste liquids, oil and water
Slowdown and sludges from:
Power plant
Water treatment
Cooling tower
Advantages, Disadvantages, and Efficiency--
A consistent product quality is achieved because the
operating temperature and the catalyst level can be con-
trolled at constant values. The process can be operated to
produce either a syncrude product or a residual fuel oil as
the main product (4).
The reactor design uses a rotating shaft through the
bottom of the vessel. At 20.3 MPa operating pressure,
sealing of this shaft may present a difficult maintenance
problem. Operation of hydroclones in the mineral separation
step also may prove difficult. Factors related to an even
distribution and good mixing may limit practical diameter
size in scale-up of the reaction vessel to commercial size.
The system converts about 90 percent of the carbon con-
tained in coal to a liquid. The pilot plant design capacity
14
-------
3
of 358 m /day from 544 metric tons of coal indicates an
expected yield of 0.66 m3/metric ton of coal.
Bergius System
Background--
The Bergius process is one of the forerunners in coal
liquefaction technology. It was used by Germany to produce
aviation fuel and diesel oil during World War II. There
o
were 18 Bergius plants producing about 4.8 Mm of oil per
year. The process uses catalytic liquid phase hydrogenation
to produce liquid fuels. Though there are no commercial
Bergius plants operating currently, the process has led to
the recent developments in the United States of the H-Coal
and Synthoil processes (5).
System Description--
The major operations of the Bergius system are shown in
Figure 4. Coal from the stockpiles is dried and finely
ground. It is then mixed with process derived hydrocarbon
liquid to form a paste containing approximately 40 percent
coal. The paste is pressurized to about 68.6 MPa and
heated to a temperature of 430°C. The heated paste and the
recycled hydrogen-rich gas are then fed to a catalytic
reaction zone.
The products from the first reaction are separated into
an overhead gaseous stream, a light oil stream, and a heavy
oil stream which contains unreacted coal and mineral matter.
The overhead hydrogen-rich gas is scrubbed to remove any
particulate matter and recycled to the reactor. The light
oil stream is then catalyzed to produce materials similar to
petroleum. The heavy oil stream is treated to separate
untreated coal, catalyst, and mineral matter from the oil.
Recovered oil is recycled to the past preparation area (6).
15
-------
COAL
o
00
o
UJ
FeS,
DRYING
CATALYST
RECYCLED GAS
GRINDING
PASTING
SCRUBBING
PREHEATING
MAKEUP
Ho
BERGIUS
KHYDROGENATION).
GAS-LIQUID
SEPARATION
LIGHT OIL
DISTILLATION
SOLIDS
SEPARATION
LIGHTS
CAKE
COKING
MID-OIL
AND
GASOLINE
SOLIDS
Figure 4. Bergius system (5)
16
RECYCLED OIL
-------
Major Operations and/or Modules--
Drying, sizing and pasting
Hydrogenation
Separation
Material Inputs--
Coal
Hydrogen
Water
Catalyst
Material Outputs--
Carbonaceous residue
Light oil
Middle oil
Wastewater
Spent catalyst
Sulfur
Ammonia
Dust
Fuel gas
Tar
Waste oil
Blowdown and sludges from:
Power generation
Water treatment
Cooling towers
Advantages, Disadvantages, and Efficiency--
A major advantage of the Bergius Process is that it has
been operated commercially.
Two disadvantages are the high pressure requirements
and high hydrogen consumption.
17
-------
The catalysts were of poor quality by today's standards
and this is reflected in the low yields of 30-55 percent.
Solvent Refined Coal System
Background--
Two alternatives are being pursued for electric power
generation. One is to burn coal directly and remove par-
ticulates and S02 by scrubbing the stack gases; the other is
to refine or clean the coal by removing sulfur and ash or
mineral matter before it is fired in the utility steam
generator, thus obviating the need for stack gas cleaning.
Solvent Refined Coal (SRC) represents the second alter-
native and is receiving serious consideration. The process
was originally developed by Spencer Chemical Company for the
United States Department of the Interior, Office of Coal
Research. Gulf Oil subsequently acquired Spencer Chemical
Company; development is continuing under the Pittsburgh and
Midway Coal Mining Company, a part of Gulf Oil (2).
In 1972 an all-industry group, presently consisting of
The Electric Power Research Institute and Southern Companies
Services, initiated a pilot plant project to study the
technological feasibility of the SRC Process. Early opera-
tions were performed at fixed conditions to establish pro-
cess reliability. Later operations were conducted to study
the effect of process variables such as temperature, pres-
sure, retention time, solvent to coal ratio, and hydrogen
consumption. Operating information from this pilot plant
has been used to design and build a 45 metric ton per day
pilot plant near Tacoma, Washington. This project, funded
by DOE, is being developed by Pittsburgh and Midway Coal
Mining Company (2).
18
-------
Operation of and data from the Tacoma plant will pro-
vide opportunities for:
Further study and development of the system
Accumulation of engineering and cost data for
evaluation of commercial possibilities, and de-
sign of demonstration or commercial plants
Product evaluation and market development.
The Tacoma pilot plant has been in operation since
October, 1974. It has recently produced about 2720 metric
tons of SRC which was used for functional product testing in
a 22 MW boiler.
The SRC process concept involves non-catalytic hydro-
liquefaction. Modifications of the SRC process include SRC
II and the Gulf Catalytic Coal Liquid Process. A process
development unit (PDU) using SRC technology is being operat-
ed by the University of North Dakota at Grand Forks, North
Dakota, under DOE sponsorship. The unit is designed to
process one-half metric ton of lignite per day.
System Description--
The SRC system converts high sulfur and high ash coal
to a clean fuel product with a sulfur content of less than
one percent and an ash content of 0.2 percent or less. SRC
has a heating value of about 37.2 MJ/kg.
A block flow diagram of the SRC system is shown in
Figure 5. In the coal preparation and handling area raw
coal is unloaded, crushed, and stored in piles. The coal is
sized, pulverized, and mixed with a recycled hydrocarbon
solvent. The resulting coal/solvent slurry is mixed with a
19
-------
COAL
RECYCLED
SOLVENT
COAL PREPARATION
AND HANDLING
SRC
(HYDROGENATION)
I
SOLIDS
SEPARATION
FILTRATE
WASH
SOLVENT
RECYCLED
HYDROGEN
GAS CLEANUP
AND BY-PRODUCT
RECOVERY
SOLVENT
RECOVERY
KEY
SRC II
Figure 5. Solvent refined coal system (7)
HYDROCARBONS
AND WATER
SULFUR
MINERAL
RESIDUE
SRC PRODUCT
LIGHT
LIQUIDS
20
-------
hydrogen-rich gas and then preheated. The preheated mixture
enters the hydrogenation zone which operates* at 425° to
480°C and 6.9 to 13.8 MPa, with about a 30 minute holding
time. The coal is liquefied by reaction with hydrogen. The
liquefied product contains some undissolved material, pri-
marily mineral matter and undissolved coal. The excess
hydrogen and gases produced in the reaction are separated
from the slurry of undissolved solids and coal solution.
The gaseous stream passes through a cleanup system to take
out H^S and CC^ and is then recycled to the reaction zone.
Fresh hydrogen from the hydrogen production area is added to
this recycled gas stream. The slurry of solids and coal
solution is cooled and the solids are separated from the
coal solution, stored, and used for hydrogen generation.
The coal solution is further separated into a light oil
fraction, a wash solvent fraction, the process solvent, and
the solvent refined coal. The SRC is solidified by cooling.
The gasification system will gasify either the residue or a
mixture of residue and coal (5).
Auxiliary processes require steam electric power,
cooling water, wastewater treatment utilities, and an oxygen
plant for gasification.
Major Operations and/or Modules--
Seizing, drying, and slurry ing--A flow diagram for this
area is shown in Figure 6. As the coal is received it is
separated according to lump size. Lumps smaller than 76 by
152 mm are sent to a primary crushing step which reduces
their size to 19 mm. Large lumps are crushed to 76 by
152 mm and returned to the primary crushing step. The coal,
from the primary crushing step is stored and later trans-
ferred to the pulverizer system. This system simultaneously
grinds the coal to about 74 (j.m size and dries it to one to
three percent moisture. The pulverized dry coal is slurried
21
-------
RUN OF
MINE COAL
RECYCLED SOLVENT
RECEIVING
CRUSHING
STORAGE
DRYING
PULVERIZING
SLURRY
BLENDING
TO
PREHEATING
Figure 6. Sizing, drying, pulverizing, and slurrying
22
-------
with solvent. Fines from both primary crushing and pulver-
izing, less than 74 |a.m size, can be used to produce hydrogen
for the hydrogenation step.
Hydrogenation--A flow diagram of the coal hydrogena-
tion, mineral separation, and solvent recovery parts of the
system are shown in Figure 7. A 70 to 85 percent hydrogen
gas mixture is added to the coal/solvent slurry. These
materials are first preheated and subjected to the condi-
tions of the hydrogenation operation. Depending on the
nature of the coal and its sulfur content, the temperature
range is 425° to 495°C and the pressure range is 6.9 to
13.8 MPa. Other variables which affect this operation are the
partial pressure of hydrogen, the residence time, and the
solvent to coal ratio. These variables are interdependent,
so a change in one may cause changes in the others. This
gives flexibility to the process, permitting the output of
a heavy or light product, the lighter product having the
higher hydrogen content (5).
The hydrogenation or liquefaction operation produces a
mixture of gases, vapors, liquids and solids. This mixture
is cooled to 290°C and the vapor and gases are separated
from the liquids and solids by a series of pressure reduc-
tions. The vapors consisting of light hydrocarbons, heavy
hydrocarbons, and water are condensed and collected.
Solids separation--The mixture of coal solution and
solids are separated by filtration or centrifugation. The
solids contain mineral matter and undissolved coal. This
residue is cooled to 38°C and stored. It can be gasified to
produce the hydrogen required in the process.
Solvent recoveryLiquid material from the solid-liquid
separation is heated to 425° to 470°C at about 0.71 MPa.
23
-------
COAL
SLURRY
RECYCLED
HYDROGEN
PREHEATING
SRC
(HYDROGENATION)
GAS-LIQUID
SEPARATION
GAS STREAM
TO CLEANUP
AND BY-PRODUCT
RECOVERY
FILTF
SOLID-LIQUID
SEPARATION
IATE
\ r
' WASH
SOLVENT
SOLVENT
RECOVERY
MINERAL
RESIDUE
SRC
PRODUCT
LIGHT
LIQUIDS
Figure 7. Hydrogenation and mineral separation
24
-------
All the unused process solvent and lighter liquids are
vaporized. They are cooled, collected, and separated.
The remaining material is the molten solvent refined
coal which is cooled from 316°C to about 66°C, the tempera-
ture at which it is solid.
Gas cleaning--The block flow diagram for gas cleaning
is shown in Figure 8. In the hydrogenation operation most
of the sulfur in the coal is converted to hydrogen sulfide
and other gaseous compounds. Excess hydrogen is used in the
operation and unused hydrogen can be recycled. However, it
must first be cleaned to remove gaseous sulfur compounds. A
number of patented processes are available for this purpose.
Some remove carbon dioxide as well as hydrogen sulfide.
After the hydrogen sulfide is removed from the gas stream,
the solution used to absorb it is stripped to yield a con-
centrated hydrogen sulfide gas from which elemental sulfur
is produced.
Material Inputs--
Coal
Steam, water
Air
Start-up solvent
Absorption solvent
Material Outputs--
Solvent refined coal
Ash slag or ash
Hydrocarbon gases
Water (process, storm drainage from coal storage
and preparation)
Spent catalyst
Sulfur
25
-------
SOUR GAS
HYDROGEN-RICH
GAS
MAKE UP
HYDROGEN
ABSORPTION
ACID GAS REMOVAL
REGENERATION
SULFUR-RICH
GAS
SULFUR RECOVERY
HYDROGEN
COMPRESSION
-»- SULFUR
HYDROGEN-RICH
GAS TO COAL
SLURRY STREAM
CONDENSED
LIQUID TO
FLARE
Figure 8. Gas cleaning
26
-------
Ammonia
Coal dust
Tar
Waste liquids, oil and water
Slowdown and sludges from:
Power plant
Water treatment
Cooling towers
Advantages, Disadvantages and Efficiency--
The process requires no catalyst and lower amounts of
hydrogen than most alternative processes. The solid product
is low in sulfur and ash and has a high heating value. A
range of products, solids, heavy liquids and light liquids
is permitted by the flexibility of the SRC process. Recent
improvements in the original process provide for product
slurry recycling which causes a self-catalytic effect that
improves hydrogenation. The improved SRC-II process also
avoids the troublesome filtration step in the mineral sepa-
ration area. Yields of about 60 percent for the solid and
42 percent for the liquid product have been achieved. The
major difficulties lie in operating costs for filtration and
development of handling methods of the solid product.
CO-Steam System
Background--
In 1921 two German scientists, F. Fischer and H.
Schrader, reported the use of carbon monoxide as a reducing
agent in the solubilizing of coal. Interest in this dis-
covery was lacking at that time because of low yields of
heavy products and a greater interest in motor fuels. Since
the late 1960s the work has been extended, modified, and
improved. The process now has good commercial potential.
This later work indicated the importance of using a solvent
27
-------
with a coal which has not been subjected to aging, drying,
or oxidation. Carbon monoxide, water, and coal at 380° to
400°C yielded a benzene-soluble solid or semi-solid product.
More recent work has been conducted to substitute synthesis
gas for carbon monoxide and to make a product with suffi-
cient fluidity for use as a coal slurry vehicle (8).
The U.S. Department of the Interior, Bureau of Mines
has developed a new process, CO-Steam, that does not use
hydrogen directly. In this process coal reacts with carbon
monoxide and steam instead of hydrogen. It does not require
a catalyst to convert low rank coals, such as lignite, into
a low sulfur liquid fuel. There is usually enough water in
lignite to supply the needs of the process. The water or
steam supplies active hydrogen by reaction with the carbon
monoxide. Alkaline carbonates are naturally occurring
catalytic agents in lignite (8).
System Description--
Figure 9 is a schematic of the major CO-Steam steps.
Lignite is pulverized and mixed with some of the product
oil. This slurry is fed to the reactor which operates at a
temperature of 380° to 400°C and a pressure of 20.5 to 27.4
MPa. Synthesis gas or carbon monoxide is fed to the reactor
at high pressure. Reaction time is about one hour. Syn-
thesis gas or carbon monoxide reacts with water contained in
the lignite to produce hydrogen which then reacts with
lignite to form a liquefied coal product.
Product gas is separated from the product liquid stream
in a pressure reduction step. The liquid fuel product
stream contains unreacted solids and ash which are removed
by centrifugation. The unreacted solids residue can be
utilized to produce the synthesis gas required by the
28
-------
LIGNITE
SIZING
SLURRY
PREPARATION
SYNTHESIS
GAS
OR
CO
CO-STEAM
(HYDROGENATION)
(INDIRECT)
PRODUCT
SEPARATION
->- FUEL OIL
_^ PRODUCT
GAS
SOLIDS
RESIDUE
Figure 9. CO-Rteam system (5)
29
-------
process. The product fuel oil can also be further hydro-
genated to obtain gasoline.
Major Operations and/or Modules--
Sizing and slurrying
Hydrogenation
Solids separation
Synthesis gas manufacture
Material Inputs--
Coal
Water
Synthesis gas
Material Outputs--
Fuel oil
Unreacted solids
Product gas
Residue
Coal dust
Tar
Waste liquids, oil and water
Slowdown and sludges from:
Power plant
Water treatment
Cooling tower
Advantages, Disadvantages, and Efficiency--
The CO-Steam system does not require a catalyst, it can
use carbon monoxide or synthesis gas rather than pure hydro-
gen and it has a low water requirement because it uses the
water occurring naturally in the lignite feed.
30
-------
However, it does employ centrifugation, a troublesome
operation, for mineral separation and it may be limited to
lignite as a feed material.
The process converts about 70 percent of the carbon to
benzene-soluble fuel.
Donor Solvent System
Background--
The conversion of coal to liquid fuels by the high-
pressure Bergius process was used in Germany for 15 years or
more. It operates in the pressure range of 22.5 to 62.0 Mpa.
Disadvantages of high pressure processes are the expense of
high pressure vessels and of hydrogen compression. Processes
operating below 9.8 MPa, however, generally use either
direct catalysis (in the reactor) or indirect catalysis, via
a recycled solvent. Exxon is developing an indirect catalyst
method. In the Exxon Donor Solvent (EDS) system, Figure 10,
the donor solvent is prepared in a separate, fixed bed,
catalytic hydrogenation step (9). Other very similar sys-
tems are the Consol Synthetic Fuel System, Figure 11, Arthur
D. Little System, Figure 12, Liqui-Coal System, Figure 13,
and Pott-Broche System, Figure 14.
Research was begun in 1966 to identify the basic EDS
process. It included studies on both hydrogenated and un-
hydrogenated recycled solvents. Conditions ranged from 400°
to 425°C at pressures of 2 to 2.5 MPa, to 425° to 480°C at
9.8 to 19.6 MPa. A number of different solid-liquid separa-
tion methods were studied. Equipment was tested in an
integrated pilot plant system with a capacity of one-half
ton per day. Techniques were developed for analyzing prod-
uct and intermediate streams. Based on these studies, the
separation operation chosen was vacuum distillation and a
31
-------
COAL
SIZING
AND
DRYING
RECYCLED
DONOR
SOLVENT
PRODUCT
STORAGE
HYDROGEN
EDS
(HYDROGENATION)
SPENT
SOLVENT
SOLVENT
HYDROGENATION
SEPARATION
BOTTOMS
HYDROGEN
GENERATION
GAS (FOR FUEL
AND HYDROGEN
GENERATION)
RAW COAL
LIQUID
PRODUCT
ASH
Figure 10. Exxon Donor Solvent (EDS) system (9)
32
-------
COAL
SIZING
AND
DRYING
SLURRY
PREPARATION
CSF
(EXTRACTION)
SEPARATION
SOLIDS RESIDUE
CSF
(CARBONIZATION)
HYDROGEN
GENERATION
DONOR
SOLVENT
HYDROTREATING
LIQUID
PRODUCT
HEAVY,
LIQUID a
GAS I
TAR
SEPARATION
UNCONDENSED
GAS
GAS
CLEANUP
FUEL
GAS
SULFUR
ASH
Figure 11. Consol Synthetic Fuel (CSF) system (10)
33
-------
OXYGEN WATER
u>
COAL
I
SIZING
&
DRYING
SLURRY-
ING
COKE
CRUSHING
AMD
GRINDING
SHIFT
CONVER-
SION
H2S AND
CO
2
REMOVAL
FUEL-*
GAS
". MEDIUM-BTU GAS
H2S-RICH GAS
COKE
PRODUCT
TAIL GAS
METHAN-
ATION
SULFUR
RECOVERY
HIGH-ASH COKE
HYDROCARBON GAS
HEAT-
ING
ADL
(EXTRAC-
TION
COKING)
FRACTION^
ATION
SULFUR
*- I.B.P-450°F PRODUCT
HYDRO-
TREATING
450-750°F PRODUCT
750+°F PRODUCT
HYDROGEN (96%)
Figure 12. Arthur D. Little (ADL) system (11)
-------
COAL
AIR &
STEAM
GASIFICATION
SIZING AND
DRYING
RECYCLED GAS
SLURRY
PREPARATION
DONOR
SOLVENT
L-C
(EXTRACTION)
SEPARATION
SOLIDS
SLURRY
CHAR
GAS CLEANUP
AND
BY-PRODUCT
RECOVERY
RECYCLED
SOLVENT
HYDROTREATING
LOW-BTU GAS
SULFUR
PHENOL
LIGHT
OIL
WASTE-
WATER
NAPHTHA
AND
GAS OIL
PYROLYSIS
ASH
Figure 13. Liqui-Coal (L-C) system (12)
35
-------
COAL
HYDROGEN
1
HYDROGENATION
ATMOSPHERIC
DISTILLATION
SIZING
DRYING
DONOR
SOLVENT
VACUUM
DISTILLATION
SLURRY
BLENDING
PREHEATING
P-B
(EXTRACTION)
FILTRATION
FILTRATE
PRODUCT
GAS & LIQUID
VOLATILES
RECOVERY
CAKE
COKING
SOLIDS
(FUEL)
Figure 14. Pott-Broche (P-B) system (5)
36
-------
hydrogenated recycled solvent operation was selected for
further development.
Studies of system variables are continuing in a 0.9-
metric ton per day pilot plant. Plans for a 225-metric ton
per day pilot plant were announced in July, 1977. This work
is sponsored by DOE.
System Description--
The four major areas of the EDS system are shown in the
preceding simplified block diagram in Figure 10. Prepared
coal feed, hydrogen, and recycled solvent are inputs to the
liquefaction area. These materials react to produce raw
coal liquid, gases, and a heavy bottoms stream containing
unreacted coal and mineral matter. The recycled solvent is
separated from this mixture in the separation area. The
solvent goes to the solvent hydrogenation area where it is
regenerated catalytically. Heavy bottoms from the separation
area are used to produce additional hydrogen or fuel gas in
the hydrogen manufacturing area. Gas generated in the
liquefaction area is used as fuel or for hydrogen manufac-
ture. The raw coal liquids may be further hydrotreated,
depending on the end use. The donor solvent is prepared
from the middle fraction of the coal liquefaction product,
which is treated by selective catalytic hydrogenation. The
main function of the solvent is to provide hydrogen to free
radicals formed by thermal "cracking" of coal "molecules."
The solvent also carries the coal into the reactor, helps to
dissolve the coal particles, and improves operability as
compared to unhydrogenated solvent. Addition of hydrogen to
the liquefaction step was found to reduce solvent require-
ments (9) .
37
-------
Major Operations and/or Modules--
Sizing and drying-Coal, bituminous or subbituminous,
is dried, ground, and screened to minus 595 fim. Prepared
feed coal is supplied to the slurry preparation system. The
coal/solvent slurry is metered continuously to the hydro-
genation systems.
Hydrogenation--The slurry feed stream is preheated
before it enters the reaction zone. Hydrogen gas is also
preheated, and fed to the reaction zone, either separately
or mixed with the slurry feed. Conditions for the lique-
faction process are: pressure 9.8 to 17.1 MPa; temperature
370° to 380°C; solvent-to-coal ratio of 1.2 to 2.6; and
residence time of 15 to 140 minutes (9) .
Separation--The material from the liquefaction process
consists of gas, raw coal liquids, and a heavy stream con-
taining unreacted coal and mineral matter. The pressure on
this material is decreased in several steps. Some gas and
water vapor are removed in the first step. This gas is sent
to the recycled gas cleanup system for recovery of hydrogen
and reuse in liquefaction (9).
In the second depressurizing step more gas is released,
containing heavier hydrocarbons, suitable for fuel gas. In
the third step the remaining liquids and solids are heated
and flashed under vacuum. This releases additional gas and
vaporizes light oil containing some gas. The bottoms mater-
ial contains the solids residue, i.e., unreacted coal,
mineral matter, and heavy tars.
Solvent hydrotreating--The light vacuum gas oil, com-
bined with other liquid hydrocarbon streams, is catalyti-
cally hydrotreated. Gaseous and liquid products from this
reaction are separated. The liquid is a mixture of
38
-------
liquefied coal product, a heavier fraction with a higher
boiling point, and a lighter fraction with a lower boiling
point. The solvent fractionation system separates the
desired liquefied coal product from the higher and lower
boiling fractions of the hydrotreated liquid product. Some
of this mid-range solvent is recycled to the slurry prepara-
tion area and the rest is sent to product storage (9).
Hydrogen manufacture--The gas streams from the first
depressurizing step and the hydrotreating area are scrubbed
with monoethanolamine to remove hydrogen sulfide and carbon
dioxide. If the hydrogen content is not high enough, high
purity makeup hydrogen is added. This stream is then com-
pressed and sent to the hydrogenation and solvent hydro-
treating areas (9).
High purity hydrogen can be made from fuel gas and
solids residue from the separation section.
Material Inputs--
Coal
Cobalt-molybdate, catalysts
Monoethanolamine
Water
Material Outputs--
Low sulfur fuel oil
Naphtha
Fuel gas
Sulfur
Residue
Ammonia
Coal dust
Tar
Spent catalyst
39
-------
Spent MEA
Waste liquids, oil and water
Slowdown and sludges from:
Power plant
Water treatment
Cooling tower
Advantages, Disadvantages, and Efficiency--
The system uses steps that entail engineering and
design technology derived from the petroleum industry. It
operates at relatively low pressure 10.2 to 17.1 MPa. It
has flexibility; varying, amounts of hydrogen can be added to
the slurry ahead of the preheater which decreases solvent
hydrogenation requirements while improving yields and physi-
cal properties of the products. It does not require mechan-
ical separation devices or catalysts that are sensitive to
solids (9).
Key areas requiring scaled-up demonstration are the 3-
phase coal liquefaction reactor and the coal slurry preheat
furnace. The overall process efficiency is 65 to 75 percent
o
and the maximum practical liquid yield is 0.47 to 0.54 m /
metric ton.
PYROLYSIS AND HYDROCARBONIZATION
Char-Oil-Energy Development (COED) System
Background--
The COED system converts coal to low sulfur synthetic
crude oil, clean fuel gas, and char. The oil product can be
used directly as fuel oil or as a feedstock for oil refin-
ing. Fuel gas is generally defined as a combustible gas
having an intermediate or low heating value of 5.6 to 22.4
40
-------
3
MJ/m . The gas can be further purified and methanated to
produce pipeline quality gas, which is the equivalent of
o
natural gas, having a heating value of 33.5 MJ/m .
Pyrolysis processes, which are essentially coking
operations, produce significant quantities of char which
must be disposed of economically. The char has good fuel
properties and for certain applications is better than the
coal from which it was made. For example, char produced
from two highly volatile, bituminous coals had heating
values equal to 90 percent of that of the coal, sulfur
content was reduced by 17 percent, hydrogen by 81 percent,
and volatile matter by 90 percent, but ash increased by 191
percent. The syncrude oil or liquid product contains small
amounts of oxygen, nitrogen, and sulfur which can be removed
by hydrotreatment. Subbituminous coals with a significant
content of volatile components produce more oil than other
coals (13).
Project COED was initiated in 1962 when the FMC Cor-
poration, under sponsorship of the Office of Coal Research,
Department of the Interior started research work to upgrade
coal to more valuable products. Following bench-scale
studies, operation of a 45-kg per hour PDU was undertaken
during 1965 to 1967. Western and midwestern coals were pro-
cessed in a multi-stage, fluidized bed, pyrolysis system
(2).
A small bench scale hydrotreating study was performed
by Atlantic Richfield Company and economic evaluations for a
conceptual commercial design were made. Promising results
from these preliminary studies led to the design, construc-
tion, and operation of a 33-metric ton per day pilot plant
at the FMC Corporation's Research and Development Center in
Princeton, New Jersey. The plant was completed in August,
41
-------
1970, and the first successful 30-day run was made in
December, 1970. The pilot plant completed a number of long-
term runs with good operating reliability. The plant
processed about 18,144 metric tons of a wide variety of
American coals including the highly caking types. Suffi-
cient engineering data was obtained for the design of a
commercial plant. All project objectives were completed and
the pilot plant was shut down in April, 1975. It has since
been dismantled.
The Seacoke process is a similar process, using a five-
stage, fluidized bed, pyrolysis system. The Seacoke pro-
ducts are syncrude, char, and fuel gas. The Seacoke process
operates at atmospheric pressure and in the temperature
range of 315° to 870°C.
System Description--
A general block flow diagram is shown in Figure 15.
The prepared coal is fed to the first stage fluid bed.
Recycled gas is used as the fluidizing medium. Vapors from
Stage 1 are sent to a gas scrubber and the char passes on to
the second fluid bed stage. The temperature of Stage II is
maintained by hot gas from Stage III. Vapors from Stage II
are sent to product recovery for separation of fuel gas and
the product tar oil. The fuel gas is further processed
through a gas cleaning system to recover elemental sulfur.
The clean gas can be used to hydrotreat the product oil. The
char from Stage II goes to the third stage.
Fluidizing gas for Stage III is the gas from Stage IV.
Char from Stage III is fed to Stage IV where it reacts with
oxygen and steam. Pressures in the pyrolysis operation
range between 145 and 172 kPa. The temperature in each stage
must be held just below the temperature at which the coal
42
-------
u>
CRUSHED
COAL
COED GAS
PYROLYSIS
GAS
GAS SCRUBBING
AMD PROCESSING
OIL RECOVERY
AND FILTRA-
TION SECTION
COED OIL
H
FIXED-BED
HYDRO-
TREATMENT
PRODUCT
GAS(ES)
._ FLUIDIZING
GAS
SYNTHETIC
CRUDE OIL
CHAR
PRODUCT
STEAM
Figure 15. COED system (2)
-------
agglomerates and plugs the bed. This value depends on the
type of coal and its composition.
The product oil from the recovery section is hydro-
treated in a fixed-bed catalytic operation to provide a low
sulfur synthetic fuel (13).
Auxiliary facilities include an oxygen plant and utili-
ties that include steam, electric power, cooling water and
wastewater treating.
Major Operations and/or Modules--
Sizing and dryingCoal is crushed and dried simulta-
neously. This operation reduces the particle size to about
1.6 mm and removes from 60 to 70 percent of the moisture in
the coal. The remaining moisture is evolved in the first
stage of pyrolysis. The milling operation takes place in a
gas swept atmosphere, under a slight vacuum, at 70°C.
Pyrolysis--A flow diagram of Stage I is shown in Figure
16. A mixture of combustion and recycled gases fluidizes
and heats the coal to about 175°C in the first pyrolysis
stage. The coal is partially devolatilized and the gases
evolved are scrubbed with recycled liquor and cooled.
A flow diagram for pyrolysis stages II, III, and IV is
shown in Figure 17. The partially devolatilized coal from
Stage I is passed to Stage II. Stages II, III, and IV are
located on successively descending levels and are coupled
closely to minimize heat losses and pressure drops. The
cascaded arrangement permits gravity flow of the char
between the stages. Superheated steam and oxygen are in-
jected at the bottom of Stage IV. Stage IV operates at 815°C
and the hot gases pass countercurrently through Stages III
44
-------
PULVERIZED COAL
STORAGE
RECYCLED
GAS
COED
STAGE I
(PYROLYSIS)
CHAR TO
STAGE II
GASES AND
VAPORS
PARTICULATE
REMOVAL
GAS SEPARATION
OIL TO
SOLID-LIQUID
SEPARATION
(FILTRATION)
Figure 16. Stage I, COED system (13)
45
-------
CHAR FROM STAGE I
STAGE II
PARTICIPATE
REMOVAL
STAGE III
STEAM
&
OXYGEN
OIL-WATER
SEPARATION
STAGE IV
CHAR COOLING
CHAR TO
STORAGE
GAS TO
ACID GAS
REMOVAL
TO
PYROLYSIS
SECTION
OIL TO
SOLID-LIQUID
SEPARATION
(FILTRATION)
WATER TO
- GAS
SEPARATION
Figure 17. Stages II, III and IV, COED system (13)
46
-------
and II, providing the fluidizing medium. Stages II and III
operate at about 430°C and 540°C respectively.
All stages are equipped with internal particulate
separations systems to remove entrained solids from the exit
gases. Most of the volatile matter contained in the coal is
evolved in the second stage. The rest of the volatile
matter evolves in the third and fourth stages. The pyrolysis
gases and oil vapors from the second stage pass through an
external particulate separation system to remove solids
which would otherwise collect in and plug subsequent pro-
cessing steps. They are next treated in an absorption system
which removes the oil vapors, treated for removal of hydro-
gen sulfide and carbon dioxide, and then used as product
gas.
Oil and water condensed from the pyrolysis gas/vapor
stream are separated into two oil fractions, one heavier and
one lighter than water, and an aqueous fraction. The two
oil fractions are dehydrated and sent to filtration. The
aqueous phase is cooled and recycled to the scrubbers. Hot
char is discharged from Stage IV to a fluidized bed cooling
step which generates high pressure steam. Recycled gas from
Stage 1 is used to fluidize the cooling char (13).
FiltrationA flow diagram of the filtration and hydro-
treating operations is shown in Figure 18. Oil from the
product recovery system may contain some char particles
which would plug the catalyst bed in the hydrotreating
operation. These particles are removed by filtration. Hot
filter cake consisting of char, oil, and filter aid is
discharged to char storage. Filtered oil goes to the hydro-
treating area.
47
-------
COMPRESSED
AIR
HYDROGEN
OIL FROM
PYROLYSIS SECTION
SOLID-LIQUID
SEPARATION
(FILTRATION)
. SOLIDS CAKE
TO STORAGE
HYDROTREATING
OIL-WATER-GAS
SEPARATION
HYDROGEN-RICH
RECYCLED GAS
GAS TO
HYDROGEN
PLANT
H2S AND
REMOVAL
PRODUCT OIL
TO STORAGE
Figure 18. Oil separation and hydrotreating (13)
48
-------
Hydrotreating--The filtered oil contains small amounts
of sulfur, nitrogen, and oxygen as impurities. To improve
its properties the oil is treated with hydrogen. This
treatment also converts the impurities into hydrogen sul-
fide, ammonia, and water which are then separated from the
product oil.
Material Inputs--
Coal
Steam
Air
Oxygen
Catalyst
Absorption solvent
Material Outputs--
Synthetic oil
Sulfur
Ammonia
Ash
Spent catalyst
Spent solvent
Low-Btu gas
Char
Filter cake
Pyrolysis gas
Wastewater
Tar
Waste oil
Advantages, Disadvantages, and Efficiency--
In the COED process, coal is heated in several stages
of fluidized beds at increasing temperatures. This enables
the process to handle caking coals without the preoxidation
or recirculation of char usually necessary to prevent
49
-------
agglomeration in the system. This feature permits the
achievement of high yields of oil with minimum sized equip-
ment. The aforementioned are the major advantages of the
COED process. An additional advantage is that the process
operates at low pressure, less than 70 kPa, which permits
the use of conventional oil processing equipment (13).
The low pressure, multistage aspects of this process
simplifies operation and maintenance. The countercurrent
flow of coal and char to the gas and vapor flow helps to
remove particulate matter, reducing the load on the scrub-
bing equipment. The process should integrate very well with
a low Btu char gasification system such as Cogas.
However, the process does not remove pyritic sulfur
from the char. This constraint would appear to limit the
process to low sulfur coals if the char product is to be
used for steam power generation without flue gas desulfuri-
zation.
Yields are about 588 kg of char, 0.175 to 0.263 m3 of
3
oil, 0.03 m of liquor, and 250 to 312 standard cubic
o
meters of 22.4 MJ/m gas per metric ton of coal. On a
weight percentage basis this is 60 for char, 19.6 for oil,
5.5 for liquor and 15.8 for gas.
Coalcon System
Background--
Union Carbide has been involved in coal conversion
studies since 1936. The extent of this work includes opera-
tion of several pilot plants and a fully integrated 454-
metric ton per day processing facility, which used a liquid
phase catalytic hydrogenation process. The plant operated
over a period of about six years in the mid 1950s. At the
50
-------
same time extensive research was carried out to convert coal
to chemical products by pyrolysis of coal in the presence of
hydrogen. The process, termed hydrocarbonization, was
evaluated in an 18-metric ton per day pilot plant operation.
A 4540-metric ton per day conceptual design was made in the
mid 1960s but the economics did not favor chemical produc-
tion via coal conversion, consequently, interest in the
program waned (14).
In the early 1970s problems with petroleum supply
caused Union Carbide to reevaluate its coal conversion
experience. It was concluded that the hydrocarbonization
route to convert coal to liquid fuels had potential applica-
tion and a joint venture known as Coalcon was formed with
Chemical Construction Corporation. In January, 1975, the
Department of the Interior, through its Office of Coal
Research, chose Coalcon to build and operate the Clean
Boiler Fuels Demonstration Plant (14).
The preliminary design phase is near completion. DOE
has reported that the economics are marginal and technical
problems with the fluid bed carbonizer are greater than
first believed. Latest reports indicate that only the
design phase will be completed at this time and that addi-
tional research and development are required on the process.
System Description--
The Coalcon system is based on hydrocarbonization of
coal. When heated in a hydrogen atmosphere, coal produces
liquid, gaseous, and solid products. These materials are
separated and treated to produce the final clean products.
The solid material or char is then gasified with oxygen to
produce a portion of the hydrogen-rich gas required for
hydrocarbonization.
51
-------
The system configuration is depicted in the overall
process block flow diagram, Figure 19. The coal is washed,
crushed, and stockpiled. The crushed coal is ground, dried,
heated, and fed to the reaction zone using hydrogen as a
carrier. Gases and vaporized liquids leaving the reaction
zone carry some char particles. The vaporized liquids are
condensed by contact with a recycled oil stream. These
condensed liquids are separated into light and heavy frac-
tions. The gas is treated to remove ammonia, hydrogen sul-
fide, and carbon dioxide. Sulfur is recovered from the
hydrogen sulfide. The gas stream is separated cryogenically
into a high purity hydrogen stream, a methanation synthesis
gas stream, and a by-product liquefied gas fraction. The
synthesis gas stream is processed to produce pipeline
quality gas. The bulk of the char is removed from the
bottom of the process (15).
Major Operations and/or Modules--
Sizing and drying--Figure 20 shows the coal preparation
and handling operation. Coal is received, unloaded, and
stockpiled. It then is crushed and ground to a particle
size in the range of 250 to 44 fim. The coal is dried to
about 1 percent moisture.
Hydrocarbonization--A flow sheet for the hydrocarboni-
zation and product recovery operations is shown in Figure
21. The prepared coal is preheated and is injected into the
reaction zone with pressurized hydrogen. In the reaction
zone the temperature is 560°C and the pressure is 3.85 MPa.
Other variables that affect the yield of products are resi-
dence time, partial pressure of hydrogen, and superficial
gas velocity. Solid particles carried out by the gas stream
are recovered and combined with the char (15).
52
-------
COAL
SIZING
AND
DRYING
COALCON
(HYDROCARBON-
IZATION)
HYDROGEN-
RICH GAS
CHAR
HYDROGEN
HYDROGEN
GENERATION
GAS-LIQUID
PRODUCT
TO METHANATION
FOR SNG
PRODUCTION
SEPARATION
GAS CLEANUP
AND BY-PRODUCT
RECOVERY
ASH
SULFUR
AMMONIA
LIGHT OIL
PRODUCT
FUEL OIL
PRODUCT
Figure 19. Coalcon system (15)
53
-------
COAL
HANDLING AND
STORAGE
SIZING
AND
DRYING
PREHEATING
FEEDING
-*- TO REACTOR
Figure 20. Sizing, drying, preheating and feeding (15)
54
-------
PREPARED
COAL
COALCON
(HYDRO-
CARBONIZATION)
PRODUCT
SEPARATION
GAS
AMMONIA
RECOVERY
ACID GAS
REMOVAL
CHAR TO
HYDROGEN GENERATION
HEAVY OIL
LIGHT OIL
WASTEWATER
AMMONIA
SULFUR
GAS TO
HYDROGEN
GENERATION
Figure 21.
Hydrocarbonization and product recovery (15)
55
-------
Product recovery--The gas and vapors are separated into
gas, light oil, heavy oil, and wastewater streams. A por-
tion of the heavy oil is recycled to the scrubbing step
which removes any solids which may have escaped with the
gas. The recycled mixture is then fractioned into a heavy
fuel stream and overheads stream. The heavy oil product is
cooled and pumped to storage. Ammonia generated in the
process is recovered as a by-product. The acid gas removal
step absorbs C0?, H2S and aromatics from the gas. The t^S is
recovered as elemental sulfur (15).
Hydrogen generation--Figure 22 shows the hydrogen
generation operation. Gas from the acid-gas removal step is
processed by cryogenic separation into: a purified hydrogen
stream, which will be recycled to the hydrocarbonization
reactor; a synthesis gas stream, which is further processed
to make substitute natural gas; and a liquefied hydrocarbon
stream (15).
Char from the hydrocarbonization step is gasified with
steam and oxygen to generate hydrogen.
Material Inputs--
Coal
Steam
Oxygen
Absorption solvent
Ammonia recovery solvent
Hydrogen
Material Outputs--
Heavy fuel oil
Light fuel oil
Ammonia
Sulfur
56
-------
GAS FROM
ACID GAS
REMOVAL
OPERATION
CRYOGENIC
PROCESS
UNIT
DE-ETHANIZER
METHANATION
HYDROGEN TO
HYDROCARBONIZATION
OPERATION
HYDROCARBON
GASES TO
LIQUEFACTION
SUBSTITUTE
NATURAL
GAS
CHAR FROM
HYDROCARBONIZATION
OXYGEN
STEAM
GASIFICATION
SHIFT AND
ACID GAS REMOVAL
SYSTEM
SULFUR
RECOVERY
ASH
HYDROGEN-RICH GAS
TO
HYDROCARBONIZATION
-*- SULFUR
Figure 22. Hydrogen generation (15)
57
-------
Substitute natural gas
Liquefied hydrocarbon gas
Ash
Spent catalyst
Waste liquids, oil, and water
Aromatic chemicals
Slowdown and sludges from:
Power plant
Water treatment
Cooling tower
Advantages, Disadvantages, and Efficiency--
The system is non-catalytic and produces two main
products, a clean liquid fuel and a high-Btu gas. Because
the process is a dry, fluidized-bed hydrocarbonization
reaction there is no formidable solids-liquids separation
step.
Two factors were investigated which might pose con-
straints to large scale operation:
(1) The lack of facilities and capabilities to fab-
ricate large, heavy wall pressure vessels, 9 mm in
diameter with 150 mm walls
(2) The operability, reliability and scale-up poten-
tial of the pressurized reactor must await opera-
tion of a demonstration plant.
The thermal efficiency of the system is 70 percent.
58
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Clean Coke Process
Background--
The United States Steel Engineers and Consultants,
Inc., a subsidiary of United States Steel Corporation is
developing a system to convert low grade, high sulfur coal
to clean metallurgical coke, chemical feedstock, and liquid
and gaseous fuels. The system, known as the Clean Coke
Process, is sponsored by DOE. The Clean Coke system pro-
duces a variety of chemical feedstocks and metallurgical
coke (2).
Laboratory and bench scale development studies on
Illinois No. 6 Seam Coal have been underway since 1969.
Various aspects including coal preparation, carbonization/
desulfurization of coal in fluidized beds, and high pressure
hydrogenation reactions have been the subjects of these
investigations. Process development units have been built
and are now operating. Two additional types of coal are
scheduled to be processed. Information obtained from the
PDUs will be used for the design of 218-metric ton per day
pilot plant (2).
System Description--
The generalized flow diagram is shown in Figure 23.
The process can be divided into carbonization and hydrogena-
tion sections. Hydrogen required is produced within the
process itself. The process design provides for operating
the plant as a closed system (16).
Run of mine coal is dried, crushed, and ground.
Approximately half of the prepared coal is conveyed to the
carbonization section and the rest to the hydrogenation
section.
59
-------
COAL
H2-
RICH
RECYCLED
GAS
CC
(CARBONIZA-
TION)
CHAR
COKING
SIZING &
DRYING
LIQUID
PROCESSING
GAS CLEANUP
AND
BY-PRODUCT
RECOVERY
CC
(HYDROGENA-
TION)
SEPARATION
MEDIUM
OIL
ASH
CHEMICAL
FEEDSTOCKS
FUEL GAS
AND
BY-PRODUCTS
METALLURGICAL
COKE
Figure 23. Clean Coke (CC) system (2)
60
-------
In the carbonization section coal is pyrolyzed in a
fluidized bed zone operating at temperatures of 705° to
760°C and pressures of 0.7 to 1.1 MPa. The fluidizing
medium is hydrogen-rich recycled gas. The products from the
carbonization section are char, a liquid stream which is
directed to the liquid processing section, and a hydrogen-
rich gas which is recycled back to the reactor. The char is
pelletized with process derived heavy oil and the pellets
are heated in the absence of oxygen to produce low sulfur
metallurgical coke and a hydrogen-rich gas. Part of the gas
is recycled to the carbonization step and the rest is sent
to gas cleanup (16).
In the hydrogenation section prepared coal is mixed
with a process derived oil to form a coal/oil slurry. The
slurry is fed to a high pressure noncatalytic hydrogenation
zone along with hydrogen from the gas cleanup section. The
hydrogenation section operates at pressures of 20 to 30 MPa.
The slurry feed is converted to a chemical-rich liquid and a
gas, rich in light paraffins. These products are separated
from the unconverted coal and mineral matter. Condensate
from the vapor goes to a processing section where light,
medium, and heavy oil are separated. Light oil is further
processed to obtain chemical feedstocks, which include
gasoline, benzene, naphthalene, and residual tars. Medium
oil is used for slurry preparation. Part of the heavy oil
is used in the pelletizing step, with the rest being fed to
the carbonization section. Uncondensed gases are sent to the
gas treatment section for separation into chemical feed-
stocks, which include ethylene and propylene, ammonia,
sulfur, and fuel gas. Recovered hydrogen is recycled to the
hydrogenation section (16).
61
-------
Major Operations and/or Modules--
Sizing and drying
Carbonization
Hydrogenation
Product separation
Material Inputs--
Coal
Water
Hydrogen
Material Outputs--
Metallurgical coke
Chemical feedstocks
Ash and unreacted coal
Waste liquids, oil and water
Tar acids
Tar bases
Oil
Organic chemicals
Gasoline
Sulfur
Fuel gas
Ammonia
Hydrogen
Slowdown and sludges from:
Power plant
Water treatment
Cooling tower
Advantages, Disadvantages, and Efficiency--
This system is unique among coal conversion schemes in
that it offers as principal products metallurgical coke and
aromatic chemicals, called petrochemicals. The capability
of producing "clean coke" from low-grade, high-sulfur coals
62
-------
will help assure the basic steel industry of the United
States an adequate supply of this essential raw material.
This will reduce and eventually eliminate the present urgent
search for coal deposits that are naturally suited to coke-
making. High yields of aromatics and olefins will help the
short supply of chemical feedstocks. The design of the
process provides for conducting all operations in closed
systems (16).
During startup of the PDU some difficulties were ex-
perienced in operation of the carbonization step. Char
produced by carbonization is converted to coke, thus elimin-
ating the problem of char use and disposal. No mechanical
separation equipment is used to separate the solids from the
liquid product. Hydrogenation is non-catalytic and no
external hydrogen is required. However, the hydrogenator
operates at a very high pressure. A plant designed to
process 5.9 million metric tons per year of coal would
produce 2.0 million metric tons of coke pellets, 1.04 Tg of
o
chemicals, 30 km of liquid fuels and about 6.33 PJ of fuel
gas.
TOSCOAL System
Background--
The Oil Shale Corporation (TOSCO), in cooperation with
other private industries, has developed a process for re-
torting oil shale, known as the TOSCO II process. A semi-
works facility was constructed at Grand Valley, Colorado to
test the feasibility of the system. The capacity of this
plant is 907 metric tons per day.
The technology of oil shale retorting has been applied
to the low temperature carbonization of coal. A pilot plant
for processing 22.5 metric tons per day of subbituminous
63
-------
coal has been operated at the Rocky Flats Research Center
near Golden, Colorado.
Subbituminous coal has been processed, yielding a low
sulfur char product of half the weight of coal with higher
heating value than coal and low sulfur liquid fuel (17) .
System Description--
The general flow diagram is shown in Figure 24. Run of
mine coal received in the coal preparation and handling is
unloaded, crushed, and stored in piles. The coal is then
ground, dried, and preheated. The coal is partially devola-
tilized and fines carried over are removed from the vapors
in a gas-solid separation system. The vapor is passed to a
scrubbing system and the preheated coal is sent to a pyroly-
sis reactor. Here the coal is heated to carbonization
temperatures of 425° to 535°C by contact with hot ceramic
balls.
The char product leaves the pyrolysis zone and is sub-
sequently cooled and sent to storage. Cool ceramic balls
are returned to a ball heating system. Pyrolysis vapor is
cooled to condense oil and water and to separate gaseous
products. Oil and water are separated. The oil is dis-
tilled to yield gas oil, naphtha, and residuum. Uncondensed
gas is used as fuel for heating the balls (17) .
Major Operations and/or Modules--
Sizing and drying
Pyrolysis
Product separation
Gas purification
64
-------
COAL
GAS
SIZING
AND
DRYING
PREHEATING
COAL
PURIFICATION
SEPARATION
L
LIQUID
PRODUCTS
TOSCOAL
(PYROLYSIS)
CHAR
HOT
BALLS
BALL
HEATING
CHAR
COOLING
CHAR
HOT FLUE GAS
AIR
& FUEL
Figure 24. TOSCOAL system (18)
65
-------
Material Inputs--
Coal
Air
Water
Material Outputs--
Char
Fuel oil
Fuel gas
Wastewater
Flue gas
Naphtha
Gas oil
Coal dust
Ash
H2S
C02
Slowdown and sludges from:
Power plant
Water treatment
Cooling tower
Advantages, Disadvantages, and Efficiency--
The use of an indirect heat source permits the produc-
tion of gas having a high heating value. The char appears
to have good possibilities for use as boiler fuel, for gasi-
fication and for making Formcoke. The process operates with
a high throughput of solid per unit volume of retort., good
heat transfer and moderate mixing. Pollution control is
much better than for conventional coke ovens used in high
temperature carbonization. The process is technically
straightforward and has been proven operable on a large
pilot scale. Hydrogen generation is not required and the
system uses the generated flue gases for preheating the dry
coal (17).
66
-------
The product char is very dusty, highly pyrophoric, and
not suited to conventional materials handling (17). The
process has difficulty with caking coals unless they have
been pretreated with steam and air before retorting. The
system apparently possesses some mechanical complexities,
which could contribute to high equipment and maintenance
costs. Hauling and transfer of hot ceramic balls, which
provide heat for pyrolysis, causes a major problem.
The yield is 0.05 to 0.09 m3 of oil, 50 cubic meters of
gas (heating value, 18.6 to 24.2 MJ/m3) and 500 kg of char.
This product mix compares least favorably with other pyroly-
tic processes in regard to the amount of liquids produced.
Occidental Research Corporation (ORC) System
Background--
Garrett Research and Development initiated a coal
research program in 1969 to explore the feasibility of
converting coal to liquid fuels. Garrett is a wholly-owned
subsidiary of the Occidental Petroleum Corporation. Because
of involvement in the petroleum industry, and the fact that
conversion of coal to liquid fuel then appeared more eco-
nomical than its conversion to gas, emphasis was placed on a
study of coal liquefaction processes. Coal pyrolysis was
selected from the alternatives because pyrolysis offered the
simplicity and relatively low cost needed for rapid commer-
cialization.
The initial laboratory scale results were quite en-
couraging and in 1971, a 3.6-metric ton per day pilot
facility was constructed at LaVerne, California. Although
built for the study of coal pyrolysis, during the first two
years it processed solid waste materials only.
67
-------
During this period, a variety of solid waste feedstocks
were converted to liquid fuel oil. The pilot facility began
processing coal in 1974. The operation has been relatively
free of problems largely due to operating expertise devel-
oped during the solid waste program. Caking and noncaking
coals have been successfully tested. Based on these results,
a 227-metric ton per day municipal waste processing plant is
being constructed in San Diego County.
The ORC Process is a solid phase hydrocarbonization
process in which pulverized coal is almost completely con-
verted to liquid and gaseous products in less than one
minute. At 14.3 MPa and 500°C the yield is up to 30 percent
distillable liquid, 40 percent tar, and the balance gas.
The reaction is faster if a solution of ammonium molybdate
is spread on the coal. Tests using a 15 percent stannous
chloride catalyst indicate conversion in a few seconds to 55
percent liquid, 40 percent gas, and 5 percent tar. Coal
feed size is about 74 fj.m. The fast reaction time should
permit savings in capital costs for reactors (19) .
A 227-metric ton per day pilot plant is being designed
by ORC and the Commonwealth of Kentucky (20) . Research and
development on solid phase hydrocarbonization under a DOE
contract is underway by Rocketdyne Division of Rockwell
International at Canoga Park, California.
System Description--
ORC's coal pyrolysis system is being developed with the
aim of maximum liquid yield. The process involves very
rapid heating and devolatilization of pulverized coal in the
absence of air, a short residence time in an entrained flow
reactor, and a quick quench which prevents degradation of
the liquid and gaseous products. Product distribution is
strongly influenced by pyrolysis temperature, with lower
68
-------
temperatures favoring liquid formation. The pyrolysis
products can be further refined and purified to obtain
synthetic crude oil, char which is suitable for combustion
in an electric utility boiler, pipeline gas, and elemental
sulfur (19).
A general flow diagram is shown in Figure 25. Coal is
first dried and pulverized as it would be for a utility
boiler. The coal is then conveyed pneumatically with re-
cycled product gas to the pyrolysis reactor. The reactor is
an entrained flow vessel where recycled char is mixed with
coal. Heated char provides the energy input for pyrolysis.
The coal is heated to its decomposition temperature within
one-tenth second at a reactor temperature of about 595°C.
Volatile products are separated from char by cyclones and
are rapidly quenched to avoid secondary decomposition. Part
of the char is transported to a char heater where the tem-
perature of the char is raised to about 650° to 870°C by
adding a controlled amount of air at the bottom of the
heater. The heater is also an entrained flow vessel and the
short residence time inhibits formation of carbon monoxide,
improving process thermal efficiency. Combustion gas from
the heater passes through cyclones where unreacted char is
separated and returned to the pyrolysis reactor (19).
The gases from the reactor are cooled and scrubbed to
collect product tar. A portion of the gas stream is used to
transport pulverized coal and heated char to the pyrolysis
reactor. The rest is treated to remove acid gas and recover
sulfur. The product gas can be upgraded to produce pipeline
quality gas or it can be used as a hydrogen source for
hydrotreating the tar product to a synthetic crude oil or a
low sulfur fuel oil. Hydrotreating is carried out under
pressure.
69
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COAL
HEATED
CHAR
AIR
CHAR
HEATING
AND
SEPARATION
SIZING
AND
DRYING
ORC
(PY'ROLYSIS)
PRODUCT
SEPARATION
TAR
HYDROTREATING
FLUE GAS
GAS PROCESS-
ING AND
SULFUR
RECOVERY
PIPELINE
+- GAS
SULFUR
SYNTHETIC
CRUDE
Figure 25. ORC system (19)
70
-------
Remaining char, not passed to the char heater, can be
used as a solid boiler fuel. The char is already dried and
pulverized which offers an advantage over raw coal. Boiler
modifications will be necessary due to the sulfur content of
the char.
Major Operations and/or Modules--
Sizing and drying
Pyrolysis
Product separation
Hydrotreating
Gas processing and sulfur recovery
Material Inputs--
Coal
Air
Material Outputs--
Synthetic crude oil
Char
Sulfur
Pipeline gas
Flue gas
Tar
Tar acids
Waste liquids, oil and water
Coal dust
Ammonia
Slowdown and sludges from:
Power plant
Water treatment
Cooling tower
71
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Advantages, Disadvantages, and Efficiency--
Tests to date indicate process conditions should allow
the design of a small reactor because of the short residence
time.
With high sulfur feed coals the char produced will
contain too much sulfur to permit direct firing in utility
boilers. Yields are about 59 percent char (27.9 MJ/kg) 33
3
percent oil and 6.6 percent gas of 26.1 MJ/m .
EXTRACTION
Supercritical Gas Extraction System
Background--
Two major problems facing advancement of coal lique-
faction to commercialization are the operability of solid-
liquid separation equipment and the high hydrogen consump-
tion. The Supercritical Gas Extraction Process (SGE), now
under development by the National Coal Board in England
seems to have solved these problems. Catalytic, Inc., a
subsidiary of Air Products and Chemicals, Inc. is evaluating
the technical feasibility of this process for United States
coals (21).
The solvent power of a gas or vapor increases with
density; for a given gas at a given pressure the greatest
density is obtained at its critical temperature. With
proper conditions the level of supercritical extraction can
be high, and increases of up to 10,000 fold in volatility of
slightly volatile substances have been experienced. There-
fore, if a gas or vapor is chosen having a critical tem-
perature slightly below the temperature at which the extrac-
tion is to be carried out, it is possible to extract
72
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substances of low volatility at temperatures well below
their normal boiling points. This principle has been used
to extract liquids that are formed when coal is heated. The
extractant gas can be recovered by reducing the pressure of
the extracted liquid vapors and thereby separating them in
solid form (21).
System Description--
A block diagram of the Supercritical Gas Extraction
system is shown in Figure 26. Coal received from the mine
is crushed, dried and pulverized to 74 |j.m size. The pul-
verized coal is fed to the extractor where it is mixed with
recovered and makeup toluene and heated to about 395°C at
9.8 MPa pressure. Overhead vapors consisting of toluene,
extract, water vapor, and hydrocarbon gases are cooled to
condense solvent and extract. Uncondensed hydrocarbons are
used as fuel gases. The condensed liquid product is flashed
to separate solvent toluene and water vapor as overhead,
from extract liquid product as bottoms. Toluene is sep-
arated from water and recycled to the extractor. Water is
treated in the wastewater treatment unit. The residue in
the reactor is removed mechanically, depressurized, and
steam stripped to recover entrained toluene. The char can
be used as fuel. The liquid extract product is fractionated
to remove any remaining entrained toluene. The extract
product which is rich in hydrogen and has low molecular
weight can be readily converted to hydrocarbon oils and
chemicals (21).
Major Operations and/or Modules--
The process includes the following major operations:
Sizing and drying
Supercritical extraction
73
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COAL >
r\ i/*r? *
SIZING AND
DRYING
i
SGE
(EXTRACTION)
-
} »
SOLVENT
SEPARATIONS
FUEL GAS
^ EXTRACT
PRODUCT
Figure 26. Supercritical Gas Extraction (SGE) system (21)
74
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Solvent and extract recovery
Auxiliary facilities
Material Inputs--
Coal
Toluene
Material Outputs--
Extract product
Char
Fuel gases
Wastewater
Flue gases
Sulfur
Ammonia
Tar
Tar acids
Blowdown and sludges from:
Power plant
Water treatment
Cooling tower
Advantages, Disadvantages, and Efficiency--
No high pressure gas supply is required. The coal
extracts contain more hydrogen and are of lower molecular
weight than the products of other processes, thus facili-
tating their conversion to hydrocarbon oils and chemicals.
The char or residue is a non-caking porous product having a
significant volatile material content making it ideal for
gasification. Products separate readily from the extractant
since only solid and vapor phases are involved during
extraction. Filtration of a high viscosity fluid is avoided
(21).
75
-------
The process produces more char than other liquefaction
schemes. This would require that a commercial plant would
need either a market for the char or facilities to convert
it to gaseous fuels. Using toluene, up to one third of the
coal feed has been extracted (21).
CATALYTIC SYNTHESIS
Fischer-Tropsch System
Background--
Interest in the synthesis of liquid hydrocarbons dates
back to 1913, when patent applications described the reac-
tion of hydrogen with carbon monoxide at high temperature
and pressure and the hydrogenation of coal under pressure.
In 1927 the hydrogenation of coal was undertaken on an
industrial scale by I.G. Farben as a result of the devel-
opment of catalysts with adequate activity and sulfur resis-
tance. In 1922 Franz Fischer engaged in studies of the
hydrogenation of carbon monoxide at low pressures with iron
or cobalt catalysts activated by oxides of chromium, zinc,
copper, and alkali metals. In 1925 at the Max Planck
Institute, Franz Fischer and Hans Tropsch synthesized liquid
hydrocarbons for the first time. Technical development of
this synthesis was continued at Ruhrchemie beginning in
1934. The purpose, to produce motor fuel, was realized with
an output of 675,000-metric tons per year from nine plants
in Germany. An equal number of plants were built in other
countries, many of which, however, were destroyed during
World War II. Changes in the energy market and increasing
coal prices discouraged the synthesis of motor fuels from
coal. Conversion plants also required much maintenance,
another detracting feature. With the decreasing interest in
synthesized fuels, no new plants in Europe were started; in
76
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1962 the last European plant, in Bergkamen, Germany, closed.
However, in the Union of South Africa the situation was more
conducive to coal based Fischer-Tropsch Synthesis. A Fischer-
Tropsch plant was constructed near Johannesburg and began
operation in 1955 (22). A second plant is now under con-
struction in the Transvaal Region (23).
System Description--
Synthesis gas is produced by burning coal in pressure
gasifiers in the presence of steam and oxygen, Figure 27.
Other products, such as ammonia, phenols, carbon dioxide,
hydrogen sulfide, naphtha, water, cyanides, various tar and
oil components as well as numerous other impurities in minor
amounts emerge from the gasifiers simultaneously with the
desired constituents, hydrogen and carbon monoxide. The
crude synthesis gas is fed to gas-purification units where
the unwanted components are removed. The cleaned gas mix-
ture is the raw material of feedstock for further processing
by Fischer-Tropsch synthesis into liquid fuels and for the
production of ammonia. The Fischer-Tropsch reaction uses a
powdered iron catalyst which is recycled as an entrained
bed. Feed gas with a H_:CO ratio of 3.5:1 is passed through
the catalyst bed where temperatures are in the range of 320°
to 340°C and the pressure is 2.2 MPa.
Major Operations and/or Modules--
Sizing--The coal is crushed, ground, and wet screened.
The minimum size feed that can be used is about 6 mm.
Fines, about 25 percent, are used for steam generation.
Gasification and gas purification--The raw gaseous
mixture formed by the reaction of coal with steam and oxygen
is cooled and oil and tar are separated. The raw gas is
further purified by scrubbing with methanol. The Fischer-
Tropsch catalyst is very sensitive to sulfur, so the gas
77
-------
COAL
SIZING
STEAM
OXYGEN
GASIFICATION
GAS
PURIFICATION
& SULFUR
RECOVERY
FISCHER-
TROPSCH
SYNTHESIS
PRODUCT
SEPARATION
-»~ SULFUR
HYDROCARBON
PRODUCTS
_^ PRODUCT
SNG
Figure 27. Fischer-Tropsch (F-T) system (5)
78
-------
must be treated to remove all sulfur. The hydrogen to
carbon monoxide ratio is adjusted by the CO shift reaction.
Synthesis--Fresh synthesis gas combined with recycled
gas is fed to the reaction zone where it mixes with catalyst,
A mixture of gases, vapors, and liquids is formed. These
products must be separated from the catalyst, which must
remain in the zone.
Product separationGas and vapors separate from the
heaviest hydrocarbons in the reaction zone. Cooling causes
vapors to condense from the product gas stream. These
liquids are sent to the refinery for separation into the
output products listed in Material Outputs. Part of the gas
is used for recycling.
The product of the Fischer-Tropsch system is not a
synthetic crude oil. It is a mixture of relatively simple
hydrocarbons in a semi-refined state and is completely free
of sulfur and nitrogen compounds (23).
Material Inputs--
Coal
Steam
Oxygen
Catalyst
Methanol
Material Outputs--
Fuel gas
Propane/propylene
Butane/butylene
Gasoline
Methylethyl ketone
Light furnace oil
79
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Waxy oil
Methanol
Ethanol
Propanol
Butanol
Pentanol
Acetone
Naphtha
Waste acids
Benzol
Toluol
Diesel oil
Tar
Creosote
Ammonium sulfate
Sulfur
Spent catalyst
Wastewater
Waste oil
Waste liquids, oil and water
Slowdown and sludges from:
Power generation
Water treatment
Cooling tower
Gas reforming
Ash and ash-conveying water
Advantages, Disadvantages, and Efficiency--
The process avoids the handling and treatment of high
viscosity mixtures of tarry materials and mineral matter.
It can produce a wide variety of products and is currently
in commercial operation. The primary gasification step can
be accomplished in commercially available gasifiers or in
any of the various reactor configurations being investigated
for low, medium and high-Btu gasification processes. It can
80
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use a wide variety of fossil fuel feeds, anything that can
be converted to synthesis gas.
Since the conversion is a 2-step process more opera-
tions are required than in other processes. Heat removal
from the synthesis step is a major problem. Plants now
operating use a large number of small gasifiers. In addi-
tion the plants are difficult to operate, requiring much
maintenance. The process yield is equivalent to about
3
0.54 m per metric ton of coal. Conversion of the CO and HZ
entering the synthesis step is 85 percent.
Methanol System
Background--
Methanol was first produced commercially from wood.
Natural gas, reformed to synthesis gas, is currently pre-
ferred for methanol production in countries where it is
available as a cheap feedstock. Prior to the discovery of
natural gas, solid fuels had been the major source of synthesis
gas for methanol production. In Europe, Asia, and South
Africa where natural gas was not available, coal became the
primary source for synthesis gas. In countries where econ-
omics still favor this route, methanol is produced from
coal.
In the United States natural gas is no longer readily
available, hence alternate sources for synthesis gas are
being evaluated. Abundant coal reserves in the United
States may play an important role in synthesis gas produc-
tion.
Some of the first generation systems that have been
used to convert coal to synthesis gas are Koppers-Totzek,
Lurgi and Winkler. The three systems employ different
81
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features and operating conditions, and each produces a
gaseous product of different composition. A number of
second generation processes are under development (24).
System Description--
Production of methanol from coal is a two stage pro-
cess. In the first stage, coal is gasified to produce raw
synthesis gas. The raw synthesis gas must be "cleaned"
before it can be used for methanol synthesis. All extran-
eous compounds, other than H2 and CO, must be removed.
There is generally more CO than H2 present in the raw gas;
the ratio of H?:CO must be adjusted to at least 2:1.
The methanol synthesis reaction is favored by high
pressure, therefore synthesis gas from first generation
gasification processes must be compressed. Other disad-
vantages of some first generation systems are the restric-
tion to the use of non-caking coals and to particle sizes
greater than 6 mm.
The second generation gasification systems produce
better quality synthesis gas and require less treatment
prior to methanol synthesis. They also operate at high
pressures, eliminating the need for compression.
A block flow diagram of the system is shown in Figure
28. Raw coal from storage is crushed to a specific size and
dried to a moisture content, depending on the type of gasi-
fication system. The coal is then preheated, if necessary,
and conveyed to the gasification reactor. Steam and oxygen
are injected and the coal is converted to a mixture of
gases, liquids, and tars. The hot gases leave the reaction
zone. A heat recovery system generates high pressure steam
and heats boiler feedwater. Part of the steam is used in
the process and the rest provides energy for product gas
82
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COAL
SIZING AND
DRYING
PREHEATING
GASIFICATION
SHIFT
CONVERSION
ACID GAS
REMOVAL
METHANOL
(SYNTHESIS)
ASH
SULFUR
RECOVERY
SULFUR
METHANOL
PURIFICATION
Figure 28. Methanol system (24)
83
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compression. Particulates carried out with the gas are
removed by a separation system. Gas from the Lurgi gasi-
fication system requires processing to remove tars, heavy
oils, and phenols. Gas from the Koppers-Totzek and Winkler
gasification systems must be compressed before the ratio of
hydrogen to carbon monoxide is adjusted to 2:1 by the CO
shift reaction. The shifted gas is treated in an acid gas
removal system to remove C02 and H2S. C02 is rejected to
the atmosphere and tUS is further treated to recover ele-
mental sulfur.
The purified gas goes to the methanol synthesis zone.
The Lurgi process requires compression at this .step. Operat-
ing conditions for methanol synthesis vary from 0.5 to 30.8
MPa and 260° to 426°C, depending on catalyst and conversion
per pass desired. Higher temperatures and pressures in-
crease the side reactions and produce lighter materials,
such as ethers, and heavier alcohols in the crude methanol
stream. The crude methanol from the synthesis reaction is
condensed and purified by distillation. Unconverted gas is
returned to the reaction zone. High, medium, and low pres-
sure processes are available for methanol synthesis (24).
Additional auxiliary processes required include steam
and power generation, water treatment and cooling, and air
separation.
Major Operations and/or Modules--
Sizing and drying
Synthesis gas generation
Synthesis gas treatment
Methanol synthesis and purification
84
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Material Inputs--
Coal
Water
Air
Oxygen
Catalyst
Material Outputs--
Methanol
Ash
Coal sludge
Wastewater
Sulfur
Tars
Heavy oils
Tar acids
Spent catalyst
Coal dust
Ammonia
Slowdown and sludge from:
Power plant
Water treatment
Cooling tower
Advantages, Disadvantages, and Efficiency--
No new basic technology beyond coal gasification is
needed to produce methanol from coal. The synthesis feed
gas can be produced by many steam-carbon-oxygen coal gasi-
fication schemes. The new low pressure process for methanol
synthesis uses copper base catalysts, is cheaper and in most
cases it is used instead of the older classical high pres-
sure process which used zinc and chromium oxide catalysts.
The older methanol synthesis catalysts are readily posi-
tioned by sulfur compounds.
85
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A material balance for a 4540-metric ton per day
methanol facility shows hourly flow rates of 408 metric tons
of process coal feed for 189 metric tons of methanol produced,
or 2.15 units of coal per unit of methanol.
86
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SECTION 2
SYSTEM OPERATIONS AND AUXILIARY PROCESSES
INTRODUCTION AND SUMMARY
Significant technical differences exist among the
liquefaction processes. Many individual unit and processing
steps are common to two or more systems, however. Further-
more, at the present stage of development, most published
system designs are conceptual only; significant differences
between the current design and future commercial plants are
certain to arise.
To avoid the redundancy of studying each unit operation
in each system, the unit operations have been grouped within
functional modules. Each module performs a specific func-
tion, for example: hydrogenation, gas cleanup, coal prepara-
tion and hydrotreating.
These modules are composed of one or more individual
unit operations or specific processes. Individual compon-
ents of the module may vary slightly for different proc-
esses. However, because of the functional orientation, the
streams entering and leaving a module will be essentially
the same.
The major objectives of this section are the identifi-
cation of waste streams originating in each module and of
the technologies needed to control them. For this purpose,
87
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the modules have been defined and are individually discussed
in this introduction. It has been noted where the module
may serve the same function but with different exit streams.
For the purposes of this section, process streams are de-
fined as any stream entering a module and any stream leaving
a module having as its destination another module (also
called an output stream). Waste streams are defined as
those streams leaving a module having as destinations either
a control system or the environment.
These definitions are still undergoing some revision;
therefore, future reports may present some modifications to
those used here.
Systems Operations
Coal Pretreatment--
For purposes of this document, coal cleaning is assumed
to have been done prior to receipt on site. Within the coal
pretreatment operation there are modules to size, crush,
grind, pulverize, and dry the coal and to prepare and pre-
heat the slurry. Output streams include prepared coal,
heated coal/oil slurry, particulates from mechanical opera-
tions, and stack gas from drying. Although no coal cleaning
is performed, there may be a refuse stream. Specific pro-
cesses in which slurrying and preheating is involved will
have an additional stack gas stream as well as potential
venting of gases.
Coal Liquefaction--
Hydrogenation--In these modules hydrogen is added to
the "coal molecule." Portions of the coal which can be
converted to soluble compounds dissolve leaving an insoluble
carbon residue and mineral matter in suspension. Variations
of the hydrogenation module include catalytic, non-catalytic,
88
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and donor solvent methods. Since these are usually carried
out at high pressure, a pressure reducing step may be
included. The crude liquid/solids leaving the reactor may
be cooled using waste heat boilers or heat exchangers.
There are only two output streams leaving the modules.
These are the crude coal liquid and, in some systems, a gas
stream. Occasional venting may occur, and periodic replace-
ment of the catalyst will be necessary for catalytic proc-
esses .
Fy_roly_s_is--High temperature gases are used to strip
volatiles from and/or chemically add hydrogen to coal in
this module. Pyrolysis uses steam and oxygen to react with
the coal.
Vapor leaving the pyrolysis reactor is cooled by quench-
ing with either water or oil. Non-condensibles are used
elsewhere in the system. Waste heat recovery may precede
the quench. The condensed liquid may contain an aqueous
phase as well as particulates, and a separation step may be
included. Output streams include the crude quenched liquid,
non-condensible gas, char, water used to cool the char and
excess quench water.
Hydrocarbonization--High temperature gases are used to
strip volatiles from and/or chemically add hydrogen to the
coal. Hydrocarbonization uses hydrogen to react with the
coal.
Vapor leaving the hydrocarbonization reactor is cooled
by quenching with either water or oil. Non-condensibles are
used elsewhere in the system. Waste heat recovery may pre-
cede the quench. The condensed liquid may contain an
aqueous phase as well as particulates, and a separation step
may be included. Output streams include the crude quenched
89
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liquid, non-condensible gas, char, water used to cool the
char and excess quench water.
Extraction--Under conditions which cause increased
volatility, this module extracts fuel components of low
volatility at temperatures below their normal boiling
points, permitting their separation from mineral matter and
other contaminants.
Catalytic synthesis--This module catalytically converts
synthesis gas into liquid hydrocarbons or methanol. Func-
tions are heating and pressurizing the feedstock, catalytic
conversion, and cooling the raw product. A sulfur guard
reactor may be used to protect the catalyst. Output streams
are liquid hydrocarbons, hydrocarbon gases, water, spent
catalyst, spent sulfur guard absorbent, and stack gas.
Separation--
Solids, liquids and gases are separated in numerous
different steps. In coal liquefaction systems, situations
arise involving two, three, and four phases. The phase
separations are gas/solid, gas/liquid, liquid/solid, liquid/
liquid, gas/liquid/solid, and gas/liquid/liquid/solid.
Modules include flashing and condensation, filtering,
centrifuging, de-ashing, decanting, vacuum distillation,
coking, and quenching. Output streams generally will be
oils, carbon-containing residues, fuel gases, water, ash or
slag, and tars or other heavy residuals.
Purification and Upgrading--
Fractionation--The fractionation module separates crude
feedstock into product and by-product components. Primary
steps used may be distillation, vacuum flashing, and strip-
ping. In addition, heat must be supplied, depressurization
90
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may be necessary, and cooling is required. Output streams
include products and by-products, recycled process solvent,
fuel gases, solvents, water, liquid hydrocarbons, and solid
or semisolid residues.
Hydrotreating--The purposes of hydrotreating are to
remove sulfur, nitrogen, and oxygen compounds by conversion
into hydrogen sulfide, ammonia, and water, and to further
hydrogenate the crude oil. Hydrotreating, in this case an
exothermic reaction, is a high pressure and high temperature
process. Heat is supplied by plant fuel gas to preheat the
crude. The reactor product is depressurized and cooled. An
oil and an aqueous phase are formed. The oil is stripped to
remove hydrogen sulfide and ammonia. Output streams include
a sour gas stream from depressurization, the sour stripping
stream, purified oil, stack gas, sour water, intermittent
vents, and periodic catalyst disposal or regeneration.
Auxiliary Processes
Hydrogen/Synthesis Gas Generation--
Gasification, particulate removal, CO-shift, and gas
cleanup are the major steps. In addition, there are quench-
ing, cooling, and drying steps. Waste heat recovery is
included (25). Output streams are synthesis gas; ash, slag,
or char; water; particulates; carbon dioxide; hydrogen sul-
fide; and spent catalyst,
Oxygen Generation--
Requirements for oxygen are met by this process.
Cryogenic separation of air is assumed. Electric or steam
driven compressors provide the motive force and cooling
water is required. Oxygen is the only process stream.
Nitrogen, argon, and carbon dioxide are output streams,
which may be recovered as by-products or be wastes..
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Acid Gas Pv.emoval--
This process separates hydrogen sulfide from hydrocar-
bon gas streams. In some instances, carbon dioxide may also
be separated. Steps in the primary section consist of one
or more gas/liquid or gas/solid contacts, appropriate tem-
perature and pressure adjustment, and demisting when neces-
sary. Supporting steps are absorbent regeneration and makeup
Product gas, free of acidic constituents, is the main output
stream. Other output streams are regenerator off gas, hydro-
gen sulfide, carbon dioxide and spent solid absorbent or
solution.
Water Supply--
The function of this module is conditioning and puri-
fication of raw water for use as cooling water, boiler feed
water, process and motive steam, and process water. Steps
include standard chemical and physical water treatment
techniques. Flocculation, pH control, deaeration, screen-
ing, filtering, and ion exchange are some potential meth-
ods. Output streams are water of varying degrees of purity,
sludges, brines, and spent regenerant solutions.
Water Cooling--
This module includes cooling and conditioning of the
plant cooling water. Evaporative cooling is assumed for
heat removal. Chemical additives maintain cooling water
quality. The output streams are cold water, cooling tower
blowdown, evaporation, and drift.
Product Storage--
This module includes storage and shipment facilities.
Only transfer operations are carried out. Process streams
are the product and by-product materials. Intermittent and
fugitive losses of vapors, liquids, and particulate may
occur during loading and storage periods.
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Sulfur Recovery--
The function of this module is the treatment of gaseous
streams in which the concentrations of sulfur compounds are
too high for discharge tc the atmosphere. Such compounds
are converted to elemental sulfur. Other output streams are
carbon oxides, hydrocarbons, and sulfides. Examples of
generic systems are the Glaus and Stretford systems.
Wastewater Treatment--
This module separates pollutant materials from waste-
water streams by physical, chemical and biological methods.
Water quality is improved to the extent that the stream can
either be reused or discharged to the environment.
Gaseous Waste Treatment--
This module separates and/or removes gaseous and vapor-
ous components from waste streams. Such components may be
either pollutants or by-products. Physical and chemical
methods are employed. Components include compounds contain-
ing nitrogen, sulfur or carbon, organics, and ammonia.
Solid Waste Treatment--
This module provides for control of solids other than
those which are airborne. Input streams are the solid waste
materials from all modules. Major output streams will be
ash, sludge and vacuum flash bottoms.
Particulate Recovery--
This module physically captures coal, ash, and other
airborne solids some of which may be recycled or processed
into by-products. Other output streams will be the cleaned
gaseous components from which the particulate is removed.
93
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Miscellaneous By-Product Recovery--
In addition to sulfur the range of by-products from
coal liquefaction goes from syncrudes to naphtha and gas
oils. These by-products with the exception of sulfur are
amenable to petroleum refinery practices for their recovery.
In addition phenol and/or ammonia will be present in the
aqueous waste streams in recoverable amounts. Ammonia may
be removed by air stripping, ion-exchange, and break-point
chlorination. Phenols can be recovered by solvent extrac-
tion. Char, fuel oil, and fuel gases are other recoverable
by-products. Hydrocarbon removal from liquid waste streams
is best accomplished by steam stripping.
Steam and Power Generation--
This module produces process steam for heat and chemi-
cal reaction, steam for power generation, and steam for
driving compressors, pumps, and other equipment. Steps are
combustion of fuel, steam generation, and power generation.
In most cases fuel will be plant fuel gas, but may be oil,
char, or coal. Output streams are steam, electric power,
stack gas, and boiler blowdown. If char or coal is burned,
an additional stream will be ash.
Transient Waste Treatment--
Most discharges are anticipated but some are not. Such
discharges are the result of accidents, leaks, and spills.
This module provides the containment, treatment and disposal
of these fugitive streams.
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COAL PRETREATMENT
Crushing and Grinding
The coal as received may range in size from dust to
large lumps. It is first crushed in a primary size-reduc-
tion step and then ground to a uniform small size, see
Figure 29.
Pulverizing and Sizing
Coal ground to a small uniform size is pulverized in
the final reduction step to reduce the bulk of the coal to
the particle size range required for the process (see Table
1). A final sizing step consists of screening out the
oversize particles which are recycled through the pulverizing
steps.
Drying
The coal usually has a free moisture content which is
too high for most processes (see Table 1). Hot combustion
gases are used to dry the coal.
Slurrying and Preheating
The dried, sized coal may be used in this form as feed
to the liquefaction operation or it may be mixed with
recycled solvent to form a slurry which is then heated and
used as the feed.
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CRUSHING &
GRINDING
PULVERIZING
& SIZING
DRYING
SLURRYING «
PREHEATING
-K7
1. CLEAN COAL
2. HOT GASES (FUEL GAS, N?)
3. FLUE GAS
4. COAL (TO GASIFIER OR
PYROLYSIS REACTOR SYSTEM)
5. RECYCLED OIL
6. HYDROGEN OR
SYNTHESIS GAS
7. SLURRY TO REACTOR SYSTEM
8. VAPOR LEAKAGE
9. TRANSIENT SPILLS
-K9
Figure 29. Modules in coal preparation operation
96
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TABLE 1. PREPARED COAL CHARACTERISTICS
Process
Hydrogenation
Synthoil
H-Coal
Bergius
SRC
CO-Steam
Exxon Donor
Solvent
CSF
ADL
Liqui-Coal
Pyrolysis/
Hydrocarboni-
zation
COED
COALCON
Clean Coke
TOSCOAL
ORC
Extraction
Super Critical
Gas Extraction
Catalytic
Synthesis
Fischer-
Tropsch
Methanol
Particle Moisture,
size, ^j.m percent
60iS<149 <3.0
<420 0
<250 1.5
<3200 <3
<149 20 to 30
< 595
<1410 1
fln?
-------
Process Application
Crushing and grinding apply to all processes. As to
pulverizing, the coal feed size requirements vary somewhat.
In general the hydrogenation processes, both catalytic and
non-catalytic, and the hydrocarbonization/pyrolysis proces-
ses use a larger particle size than the donor solvent pro-
cesses. In processes where the coal is gasified for syn-
thesis gas generation, such as Fischer-Tropsch and Methanol
Synthesis, the coal feed size requirement will be determined
by the gasification system used. Sizing applies to all
processes and a drying stage is essential for almost all
processes. The extent of drying depends on the process but
generally the coal feeds are limited to less than two per-
cent moisture. The COED process will accept a moisture con-
tent of up to six percent and CO-Steam up to 30 percent.
Feed to the liquefaction operation is either dry coal
or a coal/oil slurry. Pyrolysis processes and those based
on synthesis gas generation with few exceptions, use a dry
feed system.
Materials Entering
The primary raw material is coal. Heated air, fuel
gas, recycled solvent, nitrogen, hydrogen or synthesis gas,
are also input streams. Rain, snow and other precipitation
will be inadvertent inputs. Water used for washdown of
equipment may be an additional input.
Conditions
Crushing, grinding and sizing are accomplished at
ambient temperature and pressure. Pulverizing is accom-
plished at ambient conditions or at slightly elevated
98
-------
temperatures in a hot air stream to provide additional dry-
ing by taking advantage of the increased surface area.
Mechanical dewatering for reduction of surface moisture is
accomplished at ambient conditions. In thermal drying the
dry product must be kept below its critical ignition tem-
perature of 54° to 66°C to prevent spontaneous combustion.
Otherwise an inert atmosphere must be used. Conditions for
slurry formation are approximately 340°C and up to 446 kPa.
Equipment
Crushers
Conveyors
Breakers
Screens
Grates
Grizzlies
Baghouses
Precipitators
Feeders
Elevators
Bins
Dust collectors
Chutes
Vibrators
Dryers
Sump pumps
Blowers
Wet scrubbers
Dry pulverizers
Pulverizer dust collectors
Coal dust scrubbers
Dehumidifier heat exchangers
Feeder to pulverizer chutes
Inert gas blowers
Slurry blend tanks
Slurry blend tank mixers
Slurry pumps
Circulating pumps
Dry pulverizer gas preheaters Sump pumps
Slurry heat exchangers
Output Streams
Outputs are dried, sized coal, slurry, fugitive coal
dust, contaminated water, flue gas containing particulates,
sulfur oxides, nitrogen oxides, carbon monoxide, hydrocar-
bons, aldehydes, ammonia, and hydrogen sulfide. Other
potential environmental effects are noise and spontaneous
ignition.
99
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COAL LIQUEFACTION
Hydrogenation Modules
At high temperatures and pressures, coal reacts with
hydrogen, yielding a mixture of liquid and gaseous com-
pounds. The hydrogen content in coal is generally around 5
percent by weight while the carbon content is approximately
75 percent. If the hydrogen to carbon ratio is increased
from 1:15 to approximately 1:9, the coal will be liquefied.
Some processes such as H-Coal, Bergius, Synthoil, and Donor
Solvent use catalysts, while others, including SRC and CO-
Steam, use more extreme operating conditions or different
reactants without an added catalyst. Products from pro-
cesses generally include gases, and light and heavy oils.
Most of these products require separation, filtration,
condensation, or purification.
An example is the H-Coal process, Figure 30, in which
the coal slurry is combined with makeup and recycled hydro-
gen. The mixture passes through a preheater and into the
ebulliating bed catalytic reactor where hydrogenation
occurs. Unreacted carbon, less than 5 percent, is removed
from the reactor with some product oil. A portion of this
slurry is returned to the reactor. After sulfur removal, a
portion of the gas withdrawn from the top of the reactor is
recycled to the reactor inlet. The remainder of the gas is
used either as product gas or to supply fuel to the coal
dryer, reactor preheater, and tail gas incineration on the
Glaus plant. After settling out large catalyst particles
from the product oil, the bottom oil, with unreacted coal
particles and ash, is separated by vacuum distillation and
sent to the hydrogen manufacturing unit. Waste heat from
the hydrogenation process is used to preheat fuel streams or
to generate steam.
100
-------
d>
©
HYDROGENATION
MODULE
©
1. COAL/OIL SLURRY
2. HYDROGEN
3. PRODUCT GAS
4. SPENT CATALYST (IF APPLICABLE)
5. REACTION PRODUCTS
6. VAPOR LEAKAGE
7. TRANSIENT SPILLS
Figure 30. Hydrogenation module in the H-Coal process
101
-------
Process Application--
Catalytic
Synthoil
H-Coal
Bergius
Non-catalytic
SRC
CO-Steam
Donor Solvent
EDS
Materials Entering--
Process
Synthoil
H-Coal
Bergius
SRC
CO-Steam
Input materials
Coal/oil slurry, hydrogen
Coal/oil slurry, hydrogen
Coal/oil slurry, hydrogen
Coal/solvent slurry, hydrogen
Lignite/oil slurry, syngas or CO
Donor Solvent Coal/solvent slurry, hydrogen
Added
catalysts
Co/Mo/SK>2-
A12°3
Co/Mo
Iron oxide
None
None
Not specified
Conditions--
Process
Synthoil
H-Coal
Bergius
SRC
CO-Steam
Donor Solvent
Pressure,
MPa
14-27
20
23-60
7-14
21-27
10-18
Temperature C
450
455
480
425-480
380-400
370-380
Residence time Phase
Not specified Liquid-solid-gas
Not specified Liquid-solid-gas
Not specified Liquid-solid-gas
1-2 hours Liquid-solid-gas
1 hour
15-240
minutes
Liquid-solid-gas
Liquid-solid
102
-------
Equipment--
The major process unit in each of the hydrogenation
processes is:
Synthoil - fixed bed catalytic reactor
H-Coal - ebulliating bed reactor
Bergius - catalytic reactor
SRC - dissolver, noncatalytic reactor
CO-Steam - noncatalytic reactor
Exxon Donor Solvent - ebulliating bed reactor
Output Streams--
Process Streams
Reaction products
Recycled oil
Waste Streams
Vapor leakage
Transient spills
Spent catalyst
Pyrolysis/Hycrocarbonization Module
This module .is shown in Figure 31. When pyrolysis
occurs, the large heterogenous coal molecule is broken down
into a series of aliphatic and aromatic chemical compounds.
This involves the formation and reassociation of free radi-
cals and hydrogen units. It leaves a skeleton structure
which is mainly carbon or coke. Hydrocarbonization is
103
-------
©-
PYROLYSIS/
HYDROCARBONIZATION
MODULE
©
© ©
1. COAL
2. CHAR
3. REDUCING GASES
(HYDROGEN, SYNTHESIS GAS,
ETC.)
4.
5.
STEAM
OXYGEN
6. RAW PYROLYTIC VAPORS AND GASES
7. CHAR AND ASH
8. VAPOR LEAKAGE
9. TRANSIENT SPILLS
Figure 31. Pyrolysis/hydrocarbonization module
104
-------
similar to pyrolysis except that much more hydrogen is
present causing the occurrence of more combinations of the
free radicals with hydrogen than their reassociation with
each other. This produces a larger proportion of liquid and
gaseous hydrocarbons and less char.
Process Application--
Pyrolysis
COED
Seacoke
TOSCOAL
Garrett (ORC)
Hydrocarbonization
Coalcon
Clean Coke
Materials Entering--
Coal
Char
Reducing gases
Hydrogen-rich gas
Water
Heating medium
Steam
Oxygen
Synthesis gas
Hydrogen
Conditions--
Ranges for temperature and pressure are:
Temperature: 175° to 815°C
Pressure: 145 to 982 kPa
105
-------
Equipment--
Multiple-stage, fluidized-bed reactor
Single-stage, fluidized-bed reactor
Entrained flow reactor
Quench tower
Heat exchanger
Cyclone
Decanter
Filter
Output Strearns--
Process Streams
Char
Raw crude oils
Coke
Hydrocarbon vapors
Pyrolysis gases
Waste Streams
Ash
Particulates
Tar and tar acids
Aqueous condensates
NH3
Flue gas
Coal fines
Cooling water
Quench water
Extraction Module
Gas extraction is a scientific principle which has
been applied to coal conversion. It involves the extraction
of liquid products formed when coal is heated. The tech-
nique permits the extraction of these low volatility liquids
106
-------
at temperatures well below their boiling points. The sol-
vent capacity of a gas increases with its density. For any
gas at a given pressure, its density will be greatest at its
critical temperature. The extraction gas is therefore
chosen so that its critical temperature is slightly below
the temperature to which the extraction is to be carried
out. Under these conditions the level of "supercritical"
extraction can be high, and the volatility of a slightly
volatile substance may be increased up to 10,000 fold.
Using this technique, extractions of about one-third of the
coal feed have been made. The remainder is recovered pri-
marily as a solid char residue (see Figure 32).
Process Application--
The only process to which this module applies is the
Supercritical Gas Extraction Process.
Materials Entering--
Dry pulverized coal
Toluene vapors
Steam and water
Conditions--
Supercritical gas extraction, when using toluene as
the extractant, is carried out under conditions of 400°C
and 10 MPa.
Equipment--
Feed lock hopper
Extraction
Residue-discharge lock hopper
Quench tank
Heat exchanger
Degasser
107
-------
o-
EXTRACTION
MODULE
© ©
1. COAL
2. TOLUENE VAPOR
3. CRUDE EXTRACT,
TOLUENE, AND GASES
4. CHAR
5. VAPOR LEAKAGE
6. TRANSIENT SPILLS
Figure 32. Extraction module
108
-------
Output Streams--
Process Streams
Fuel gas
Crude extract
Toluene and toluene vapors
Char
Coal dust
Waste Streams
Wastewater (from char quenching)
Catalytic Synthesis Module
Catalytic synthesis processes yield liquid hydrocarbon
products by catalytically reacting hydrogen and carbon mon-
oxide. Synthesis gas, produced from coal, cleaned, and then
shifted to the appropriate H» to CO ratio, is used as feed
to the reactor. Either hydrocarbon mixtures or methanol can
be synthesized by proper choice of the process and catalyst.
The catalysts are generally pyrophoric and sensitive to
sulfur. Because of the sulfur sensitivity, synthesis gas
feed must be sulfur free.
Typically, as seen in Figure 33, the gas mixture upon
entering this module will be adjusted to the appropriate
pressure and temperature. The hydrogen to carbon monoxide
ratio also will have been adjusted prior to entering the
catalytic synthesis module. A sulfur guard reactor, which
contains a sulfur scavenger such as zinc oxide, will precede
the catalytic reactor. In the catalytic reactor, hydrogen
and carbon monoxide will react to form hydrocarbons and/or
methanol. The catalysts used are either iron or copper
based with appropriate promoters.
109
-------
CATALYTIC
SYNTHESIS
MODULE
1. SYNTHESIS GAS
2. FRESH CATALYST
3. LIQUID PRODUCTS
4. SPENT CATALYST
5. WASTES
6. VAPOR LEAKAGE
7. TRANSIENT SPILLS
Figure 33. Catalytic synthesis module,
110
-------
Following catalytic synthesis, condensation of the exit
stream leaves liquid and vapor phases. These are separated
and the vapor may be recycled or used as fuel. The liquid
is depressurized, yielding a second vapor stream, which also
may be recycled or used as fuel.
The remaining liquid is a mixture of the various by-
products of catalytic synthesis. The Fischer-Tropsch
synthesis produces numerous hydrocarbon fractions, which,
upon distillation yield fuel gases and oils, waxes, lubri-
cants, solvents, and other organics, mostly paraffins.
Methanol synthesis, in addition to producing methanol,
yields some light hydrocarbons, heavier alcohols, and water.
These latter products are separated by distillation.
Process Application--
Fischer-Tropsch Synthesis (Arge, Synthol)
Methanol Synthesis
Materials Entering--
Synthesis gas (hydrogen to carbon monoxide ratio
adjusted to appropriate values for specific prod-
uct desired)
Copper or iron based catalyst
Conditions--
Temperature: 210 to 300°C
Pressure: 2 to 5 MPa
Equipment--
Compressor
Heat exchanger
Sulfur guard reactor
Catalytic reactor
Condenser
111
-------
Phase separator
Flash-expansion vessel
Distillation column
Output Strearns--
Process Streams
Synthesis gas
Hydrocarbon noncondensibles, fuel, and
recycled gas
Hydrocarbon liquid fuels, oils and waxes
Alcohols
Waste Streams
Water from distillation - may contain hydro-
carbons and alcohols (fuel oil) as con-
taminants
Spent copper or iron catalyst
Zinc sulfide
SEPARATION
Once coal has been liquefied in the reactor, the rest
of the system consists of separations and purification of
reactor products. All coal liquefaction systems require
separation of one phase from another and separation of
single phase products, which may include one or more of the
following separations.
gas/liquid
gas/solid
liquid/solid
liquid/liquid
gas/liquid/solid
gas/liquid/liquid/solid.
112
-------
The separation methods used in coal liquefaction technology
are shown in Table 2.
The mixture of solids, liquids, and gases leaving the
reactor is processed through various separation modules
which can be grouped as: flashing and condensation; fil-
tration; centrifugation; solvent de-ashing; vacuum distil-
lation; coking; quenching and oil-water separation. They
are shown in Figures 34 through 41.
Vapors produced in the reactor exit either as a separ-
ate overhead stream or as a combined gas/liquid/solid
stream depending on reactor configuration and process oper-
ating conditions. In systems based on pyrolysis and hydro-
carbonization the reactor products are a gaseous stream and
solid char product. Vapors leaving the reactor as a separ-
ate stream are cooled to separate light hydrocarbons from
uncondensable gases. Vapors are generally cooled by quench-
ing with either water or oil.
All liquefaction systems, except those based on syn-
thesis gas, require separation of solids entrained in the
liquid product. The solids consist of unreacted coal and
mineral matter or char. Mechanical separation can be per-
formed by filters, centrifuges and hydroclones. Solvent
separation and products separation, mainly fractionation,
are discussed later under Fractionation.
Process Application
Separation applies to all coal liquefaction processes.
113
-------
TABLE 2. SEPARATION METHODS FOR COAL LIQUEFACTION
Name
Feed
Separating agent
Products
Principle of separation
Equilibration
separation methods
1. Flash expansion Liquid (slurry)
2. Vacuum/flash
distillation
3. Stripping
4. Solvent de-ash-
ing
5. Condensation
Mechanical
separation methods
1. Filtration
2. Centrifuge
(filtration
type)
3. Cyclone
Liquid (slurry)
and/or vapor
Liquid (slurry)
Liquid + solid
Liquid and/or
vapor
Liquid + solid
Pressure reduction Liquid + vapor Difference in volatilities
(vapor pressure)
Heat
Noncondensate gas
Solvent
Cooling
Liquid + vapor Difference in volatilities
Liquid + vapor
Liquid + vapor
Difference in volatilities
Precipitation by increasing
particle size
Liquid + vapor Difference in volatilities
Pressure reduction
(energy), filter
medium
Liquid + solid
Liquid + solid Centrifugal force Liquid + solid
Size of solid greater than
pore size of filter, medium
Size of solid greater than
pore size of filter, medium
Gas + solid or Flow inertia
liquid
Gas + solid or Density difference
liquid
-------
©
FLASHING
AND
CONDENSATION
MODULE
-K 5
1. RAW COAL LIQUEFACTION PRODUCTS(S)
GASES AND SOLIDS
2. UNCONDENSED GASES TO ACID GAS REMOVAL
3. RAW COAL LIQUEFACTION PRODUCT(S)
AND SOLIDS
4. VAPOR LEAKAGE
5. TRANSIENT SPILLS
Figure 34. Flashing and condensation module
115
-------
©
©-
FILTRATION
MODULE
1. RAW COAL LIQUEFACTION PRODUCT(S)
2. SOLIDS-FREE LIQUID PRODUCT(S)
3. SOLIDS RESIDUE
4. VAPOR LEAKAGE
5. TRANSIENT SPILLS
Figure 35. Filtration module
116
-------
d>
CENTRIFUGATION
MODULE
2
*
,-^,
3
1. RAW COAL LIQUEFACTION PRODUCT(S)
2. SOLIDS-FREE LIQUID PRODUCT(S)
3. SOLIDS RESIDUE
4. VAPOR LEAKAGE
5. TRANSIENT SPILLS
Figure 36. Centrifugation module
117
-------
©
SOLVENT
DE-ASHING
MODULE
-K 2
'-
»^N
3
***
--s
5
1. RAW COAL LIQUEFACTION PRODUCT(S)
2. SOLIDS-FREE LIQUID PRODUCT(S)
3. SOLIDS RESIDUE
4. VAPOR LEAKAGE
5. TRANSIENT SPILLS
Figure 37. Solvent de-ashing module
118
-------
©
d>
VACUUM
DISTILLATION
MODULE
2
T
5
1. RAW COAL LIQUEFACTION PRODUCT(S)
2. SOLIDS-FREE LIQUID PRODUCT(S)
3. SOLIDS RESIDUE
4. VAPOR LEAKAGE
5. TRANSIENT SPILLS
Figure 38. Vacuum distillation module
119
-------
d>
COKING
MODULE
*( 2
©
1. RAW COAL LIQUEFACTION PRODUCT(S)
2. SOLIDS-FREE LIQUID PRODUCT(S)
3. SOLIDS RESIDUE
4. VAPOR LEAKAGE
5. TRANSIENT SPILLS
Figure 39. Coking module
120
-------
QUENCHING
MODULE
3
"^_>
,---
5
1. RAW HOT GASES
2. UNCONDENSED GASES TO ACID GAS
REMOVAL
3. LIQUEFIED PRODUCT(S) AND
WASTEWATER
4. VAPOR LEAKAGE
5. TRANSIENT SPILLS
Figure 40. Quenching module
121
-------
©
0>
OIL-WATER
SEPARATION
MODULE
-K 2
v_^
X->
3
^*
f^-^,
5
1. LIQUEFIED PRODUCT(S)
AND WASTEWATER
2. PRODUCTS
3. WASTEWATER
4. VAPOR LEAKAGE
5. TRANSIENT SPILLS
Figure 41. Oil-water separation module
122
-------
Materials Entering
Unreacted coal
Char
Mineral materials
Hydrocarbons
Solvents
Water
Ammonia
Hydrogen sulfide
Hydrogen
Conditions
Temperatures range from ambient to reactor exit tem-
perature. Pressures range from ambient to reactor exit
pressure.
Equipment
Hydroclones
Filters
Centrifuges
Condensers
Venturi scrubbers
Decanters
Vacuum/flash separators
Flash expansion vessels
Vapor strippers
Output Streams
Process Streams--
Hydrocarbons
Solvents
123
-------
Char
Hydrogen
Waste Streams--
Carbon residues
Water containing ammonia, hydrogen sulfide, cyanide,
tars, oils, particulates, ash and char
Tars, heavy ends
Phenols
Vapors containing hydrocarbons, sulfides, sulfur
dioxide, ammonia and particulates
PURIFICATION AND UPGRADING
Fractionation Module
Fractionation serves the dual purpose of recovering
solvent and refining raw oil into fractions of specified
boiling point ranges. The types of processes include pre-
fractionation, atmospheric distillation, and vacuum frac-
tionation. Prefractionation is a distillation process which
separates light gases (C, through C,) from the raw oil.
Lower temperature and higher pressure conditions are used
than for atmospheric distillation. Feed to the prefrac-
tionation column consists of raw oil and light hydrocarbons,
Some water can also be carried over with the light hydro-
carbons .
After prefractionation, atmospheric distillation can
be used to separate the oil stream into:
Light overhead products (C^ and lighter)
124
-------
Naphtha or gasoline, middle oil having a boiling
range of 38° to 205°C
Heavy oil having a boiling range of 205° to 297°C
Residual or reduced crude oil.
Residual oil can be further fractionated in vacuum stills to
recover additiona
residue is pitch.
recover additional heavy gas oil, C _ to C^-. The bottoms
The light overhead product stream is cooled and the
uncondensed gases are fed to the gas cleanup module.
Condensed oil and water are separated in an oil/water sep-
arator. Middle oil can be boiled off as sidestream dis-
tillate cuts of kerosene, heating oil, and gas oil in a
single tower or in a series of topping towers, each tower
yielding a successively heavier product. Process solvent is
distilled off at a temperature of about 260°C. In some
processes the recycled solvent may be part of the product
oil. The block diagram for the module is shown in Figure
42.
Process Application--
Bergius
SRC
Coalcon
Clean Coke
Exxon Donor Solvent
Consol Synthetic Fuel
Arthur D. Little
Liqui-Coal
Methanol Synthesis
Supercritical Gas Extraction
125
-------
0 0
FRACTIONATION
MODULE
-K 2
-K 5
1. RAW LIQUID PRODUCT, SOLVENT,
WATER & LIGHT HYDROCARBONS
2. REFINED LIQUID PRODUCTS
3. WASTEWATER
4. UNCONDENSED GASES
5. BOTTOMS-PITCH, TAR, CARBON
AND MINERAL MATTER
6. VAPOR LEAKAGE
7. TRANSIENT SPILLS
Figure 42. Fractionation module
126
-------
Materials Entering--
Process solvent
Synthetic crude oil
Process water
Light hydrocarbons
Conditions--
Temperature ranges for different fractions of hydrocar-
bonization product liquid are:
Fraction Temperature range °C
Light hydrocarbon gases 45 to 75
Benzene/toluene/xylene 75 to 130
Light oil 130 to .260
Middle oil 260 to 340
Heavy oil 340 at 1.33 Pa
Pitch 340 at 1.33 Pa
Equipment--
Fractionation column
Oil/water decanter
Output Strearns--
Process Streams
Benzene/toluene/xylene
Light hydrocarbons
Light oil
Middle oil
Heavy oil
Process solvent
Waste Streams
Water containing phenols and dissolved organic
matter
127
-------
Pitch containing unreacted carbon, mineral
matter, tars and oils
Uncondensed gases (^S, CC^)
Hydrotreating Module
Hydrotreating is the treatment of liquid hydrocarbons
(HC) with hydrogen under high temperature and pressure for
purposes of purification and upgrading. This process con-
verts the sulfur, nitrogen, and oxygen compounds contamin-
ating the hydrocarbons to hydrogen sulfide, ammonia, and
water. The hydrogen content of the hydrocarbons is in-
creased through saturation reactions.
In a typical design, Figure 43, filtered oil and
hydrogen are pumped, along with some recycled oil, through a
gas-fired preheater into an initial catalyst guard reactor.
The purpose of the guard reactor is to permit deposition of
coke on low surface to volume packing, preventing plugging
of the main hydrotreating reactor. From the guard reactor
the gas-oil mixture is fed into a three section downflow
hydrotreating reactor.
The hydrotreated product is cooled in a heat exchanger
and fed into a high pressure flash drum where oil/water/gas
separation occurs. Approximately 60 percent of the gas is
recycled to the hydrotreaters. The remainder is sent to the
hydrogen plant.
About half the separated oil is recycled to the hydro-
treaters. The remainder is depressurized into a receiving
tank, where water is separated from the product oil, and the
oil is pumped into a stripping tower where clean product gas
is used to strip the hydrogen sulfide and ammonia. The gas
128
-------
HYDROTREATING
MODULE
-©
-0
1. LIQUID PRODUCTS
2. HYDROGEN
3. FUEL
4. CATALYST
5. PRODUCT OIL
6. BY-PRODUCT GAS
7. WASTEWATER
8. .SPENT CATALYST
9. COKE
10. FLUE GAS
11. VAPOR LEAKAGE
12. TRANSIENT SPILLS
Figure 43. Hydrotreating module
129
-------
product from the stripper is sent to gas cleanup. The
stripped oil is then ready for further processing.
In addition to hydrotreating the product oil in the
Exxon Donor Solvent Process, a fixed bed catalytic hydro-
treating reactor is used to regenerate the spent solvent
from the liquefaction process.
Process Application--
Hydrotreating can be used with all liquefaction pro-
cesses to upgrade the oil to gasoline and to reduce sulfur
content. However, it is an essential part of COED, ORC,
and Exxon Donor Solvent processes.
Materials Entering--
COED - Filtered product oil, hydrogen makeup
from hydrogen plant, stripping product gas,
cobalt/molybdenum or nickel/tungsten sulfide
catalyst
ORC - Tar product, hydrogen from product gas,
catalysts
Donor Solvent - Spent solvent from liquefaction
separation, hydrogen from hydrogen manufacturing,
cobalt molybdate catalyst.
Conditions--
Process Pressure Temperature Phase
COED 13.8 to 20.6 MPa 400° to 427°C Liquid-gas<
solid
ORC "Under pressure" Not specified Liquid-gas
Exxon Not specified Not specified Liquid-gas
Donor
Solvent
130
-------
Equipment--
Typical hydrotreating
process
Preheater
Catalyst guard reactor
Three section downflow
catalytic reactor
Stripping column
Output Streams--
Process Streams
Syncrude
Naphthalene
Bleed gas
Contaminated gas
Coke
Waste Streams
Donor Solvent
Fixed bed catalyst
Liquid gas separator
Preheater
Stripping column
Normal Operating Conditions
Wastewater: containing NH~, ^S, tars,
phenols, BTX, organic sulfur compounds and
traces of hydrocarbons such as naphthalene,
dihydroxpyrene, dibenzofuran and acenaphthene/
biphenyl.
Preheater flue gas: containing nitric
oxides, and carbon monoxide.
Periodic Discharges
Gas with NH», H2S and spent catalyst (heavy
metals, metal carbonyls, and sulfides, during
catalyst removal.
Gas with particulates, NH3, H2S during catalyst
replacement.
131
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AUXILIARY PROCESSES
This category covers those processes associated with
coal liquefaction but used for purposes incidental to the
main functions involved in the conversion of coal to liquid
products. It includes utilities supply and environmental
control.
Hydrogen/Synthesis Gas Generation
The need for hydrogen generation in coal liquefaction
arises from the fact that the ratio of hydrogen to carbon
in coal, which is about 1:(15-20), has to be raised to
about 1:(6-10) to obtain liquid fuels. Generally speaking,
3
400 to 600 m hydrogen is required to process one metric
ton of coal to liquid fuels. Hydrogen is used in liquefac-
tion processes in the following modules:
Hydrogenation
Hydrocarbonization
Hydrotreating
Hydrogen is generated from the gasification of coal,
carbon residues, and/or char, and is recovered from gases
generated during liquefaction. Hydrogen generation and its
end uses are shown in Figure 44.
Coal is gasified with steam and air. Vapors from the
gasifier are purified to remove acid gases. The remaining
gas, mainly a mixture of CO and H9, is used as a recycled
hydrogen-rich stream to any of the three hydrogen-using
modules mentioned. For further details on the hydrogen/
syngas generation operation, Reference 25 should be
consulted.
132
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COAL
GASIFICATION
CHAR
GASIFICATION
LIQUEFACTION
GAS
PURIFICATION
AND
CO-SHIFT
CONVERSION
-K10)
1. COAL
2. AIR OR OXYGEN
3. STEAM
4. OXYGEN
5. STEAM
6. COAL SLURRY
7. CHAR
8. CHAR
9. REACTION GASES
10. HYDROGEN RICH-GAS TO
HYDROGENATION, HYDROTREATING,
HYDROCARBONIZATION OR
CATALYTIC SYNTHESIS
Figure 44. Hydrogen/synthesis gas generation
133
-------
Gases discharged from some modules, such as hydro-
genation, separation, and hydrotreating, have a significant
hydrogen content. All such streams are fed to the acid gas
removal module for purification, and the recovered hydrogen-
rich stream is recycled for further use.
Process Application--
All hydrogenation and donor solvent processes require
an external source of hydrogen. Part of the prepared coal
and char will be gasified to produce a gaseous mixture
containing hydrogen, carbon monoxide, methane, carbon dio-
xide, hydrogen, sulfide, and small amounts of other impuri-
ties. Particulates if present in the mixture are removed.
The gaseous mixture is then quenched and shifted to produce
synthesis gas.
Processes based on pyrolysis and hydrocarbonization
produce large quantities of char which can be used to
produce synthesis gas, as described above. Additional coal
may or may not be necessary to meet hydrogen requirements
for these processes.
Hydrogen-rich gases recovered from the acid gas removal
module provide part of the hydrogen required in all but
the supercritical gas extraction process. This process uses
hydrogen, however, to hydrorefine the products.
Materials Entering--
Char
Air
Oxygen
. Acid gases
Coal
134
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Equipment--
The type of equipment used for hydrogen generation will
depend on many factors. Hydrogenation and donor solvent
processes produce solid residues which contain unreacted
carbon. However, the amount of residue produced generally
will not be sufficient to generate the amount of hydrogen
consumed by the process. Additional coal will be required.
The solid residue cake must be dried, sized and then mixed
with coal to make the feed acceptable for first generation
gasifiers, such as Lurgi and Winkler. Second generation
gasifiers, such as BI-GAS and Texaco gasifiers, are being
developed which could possibly accept solid residue feed
directly.
All pyrolysis processes produce large amounts of char,
a by-product which is utilized to generate hydrogen. Char
has to be sized for use in the first generation Koppers-
Totzek process. The COGAS fluidized bed gasifier is being
developed to gasify char produced in a pyrolysis process.
The following is a list of major equipment required for
hydrogen generation.
Gasifier
Shift converter
Acid gas absorber
Regenerator.
Conditions--
Gasifier operating conditions are shown in Table 3.
The CO-shift converter operates at a temperature of 340° to
370°C and a pressure of 1.0 to 9.8 MPa in the presence of
iron-chromium oxide catalysts.
135
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TABLE 3. GASIFIER CONDITIONS
Gasifier type Pressure, MPa
Lurgi 2.4 - 3.1
Winkler 0.1 - 0.3
Koppers-Totzek 0.1
BI-GAS 9.8
Texaco 2 . 7
COGAS 0.1 - 0.3
Temperature, °C
620
815
925
1095
870
- 760
- 1010
1815
- 1480
- 1370
_ 925
Output Streams--
Process Streams
H?-rich gas (synthesis gas)
Waste Streams
Flue gases containing CO,., and trace amounts
of sulfur compounds in hydrocarbons
Wastewater containing phenols, ammonia, tar
and oils
Purge from acid gas removal
Ash.
Oxygen Generation
Air is compressed, cooled and liquefied. The lique-
fied air is then fractionated. Each component is allowed
to boil off or vaporize separately and in this manner oxy-
gen is separated from nitrogen, carbon dioxide, argon and
the minor component gases.
Process Application--
Systems to which oxygen generation applies include all
of the liquid phase hydrogenation systems except CO-Steam,
136
-------
the Donor Solvent, COED, Coalcon, Fischer-Tropsch and
Methanol Synthesis.
Input Streams--
The input requirements are air, steam, cooling water
and electric power. Activated carbon and silica gel are
also used. Air consists of an invariable mixture of gases,
in percent by volume: nitrogen - 78, oxygen - 21, argon -
0.94, hydrogen - 0.01; and small amounts of neon, helium,
krypton and xenon. It also contains varying amounts of
carbon dioxide (0.03 to 0.07), water vapor (0.01 to 0.02)
and hydrocarbon gases such as acetylene and methane, as well
as local pollutants.
Conditions--
The pressures of the various cycles range from 0.4 to
214 IDPa. The temperatures go down to -190°C.
Equipment--
Filters
Compressors
Heat exchangers
Activated carbon filters
Silica-gel dryers
a Turboexpanders
High-speed turbines
Electric generators
Double fractionating columns
Condenser-reboilers
Glass cloth filters
Sub-coolers
137
-------
Output Strearns--
Oxygen of course, is an intermediate product of this
module. By-products are nitrogen, neon, helium, argon,
krypton, and xenon.
Acid Gas Removal
Most acid gas removal procedures usually involve chem-
ical or physical absorption of the C^ and ^S in a liquid,
and then regeneration of the absorbent by desorption of the
acid gas at a lower pressure or higher temperature. There
are a number of specific processes that are applicable for
liquefaction processes. A brief discussion of several of
the more common specific processes are discussed below.
Hot Carbonate Process--
Acid gases are absorbed in a solution of potassium
carbonate. The solution is regenerated by desorption in a
tower at reduced pressure with steam stripping. By modify-
ing the design, two acid gas streams can be obtained, one
high in sulfur content which can be used for a feed into a
Glaus plant, and one high in carbon dioxide. Hydrogen
sulfide can be removed from the latter by incineration.
Cold Methanol Process--
All types of sulfur compounds as well as combustibles
can be removed by this proprietary process, known as
Rectisol. The acid gases are absorbed in methanol at re-
duced temperatures. One type of Rectisol unit incinerates
the acid gas following sulfur removal. In some cases the
P\.ectisol process uses nitrogen as stripping gas and can also
be used to remove water from the product gas.
138
-------
Amine Process--
A process which uses an amine system produces a suf-
ficiently high concentration of H2S in the sour gas stream
for a Glaus plant to accept. Although several hundred parts
per million of sulfur compounds and most of the C0? remain,
the gas is acceptable for product gas.
Dimethoxytetraethylene Glycol Process--
This process, also known as Selexol, prepares a rich
enough H^S stream to be used in a sulfur recovery plant,
such as Glaus. Acid gases are absorbed with dimethoxy-
tetraethylene glycol. The solvent is regenerated by physi-
cal desorption.
Process Application--
All coal liquefaction processes require acid gas
removal units for purposes of sulfur and carbon dioxide
control.
Materials Entering--
Sour gas streams rich in H2S and C02 from product
recovery, gasification, etc. are sent to the acid gas re-
moval unit where they are absorbed by a variety of reac-
tants, dependent on the particular gas removal process.
Conditions--
Pressure: 1.5 to 13.8 MPa, depending on process.
Feed Gas Temperature: 0° to 43°C, depending on process
Equipment--
Absorber
Regenerator (stripper, flash drums, etc.)
Condensers
139
-------
Output Streams-
Process
Hot carbonate
(the Amine
and Selexol
processes
have similar
streams)
Process Streams
Product gas
Cold Methanol
Product gas
Waste Streamy
Process condensate contain-
ing phenol, cyanide,
ammonia, and sulfides
C02 stream containing H2,
CO, HC, etc. and sulfur com-
pounds
Process condensate contain-
ing phenol, cyanide,
ammonia, and sulfides
Lean H2S flash gas contain-
ing C02, hydrocarbons and
Rich H2S flash gas contain-
ing methanol, C02, H2S, and
hydrocarbons
Expansion gas and C02
CO hydrocarbons and Ho
Water Supply
The function of this module is to improve the quality
of both raw water and any recycled water to meet the require-
ments of the coal liquefaction system. Standard water con-
ditioning methods are used.
Process Application--
This module applies to all coal liquefaction systems.
Input Streams--
Raw water
Slightly contaminated wastewater
140
-------
Treated wastewater
Treatment chemicals
Conditions--
Ambient conditions are satisfactory for most of the
operations in this module.
Equipment--
Filters
Tanks
Pump s
Chemical feeders
e Electrodialysis
Clarifiers
Mixers
Ion exchangers
Reverse osmosis
Deaerators
Output Strearns--
Treated water
Sludges
Brines
Spent regenerant solutions
Water Cooling
The function of this module is to provide for heat
release, using evaporation via cooling towers and ponds
and/or air cooling.
Process Application--
This module applies to all coal liquefaction systems
141
-------
Input Streams--
The major input is heated water from non-contact heat
transfer applications in other process and auxiliary modules,
Other inputs to this module are chemical additives used to
maintain cooling water quality by preventing corrosion and
algal growth.
Conditions--
Temperatures may range from near 0° to 100°C and
atmospheric pressure.
Equipment--
Cooling towers, wet or dry
Spray ponds
Pumps
Filters
Output Streams--
Water
Slowdown
Evaporation
Spray and windage loss
Product Storage
This module provides for storage, handling and loading
of products and by-products.
Process Application--
All coal liquefaction systems use this module.
Input Streams--
Liquefied coal
Sulfur
142
-------
Naphtha
Light oil
Heavy oil
Tar
Still bottoms
Phenol
Conditions--
Ambient conditions of temperature and pressure obtain
in this module except when certain products may be too vis-
cous to flow at ambient temperature.
Equipment--
Tanks
Bins
Silos
Pump s
Heaters
Output Strearns--
All of the input streams also appear as output streams.
Waste streams include spills of product and by-product
materials, fugitive vapor losses, tank cleaning wastes and
area drainage.
Sulfur Recovery
The purpose of this module is to trap or recover the
sulfur which is separated from the liquefaction products by
previous operations, and to prevent the release of sulfur
compounds to the atmosphere. The Glaus Sulfur Recovery
Process with a Stretford Section has become a widely used
method for converting hydrogen sulfide gases to elemental
sulfur.
143
-------
Process Application--
This module applies to all coal liquefaction systems.
Input Streams--
The major input stream is an acid gas mixture contain-
ing mainly H?S with some C02 and lesser amounts of hydro-
carbons, NH~ and water.
Conditions--
The theoretical flame temperature is about 1370°C. The
reaction furnace effluent is about 1295°C.
Equipment--
Furnaces
Blowers
Waste heat boilers
Catalytic converters
Coalescers
Stack/incinerator
Condensers
Heaters
Pumps
Pits
Knockout drums
Output Streams--
Sulfur
Wastewater
Exhaust or vent gas containing mainly nitrogen
and carbon dioxide with some water vapor, a
fractional percent of CO, less than 250 ppm of
COS, and lesser amounts of hydrocarbons
Spent catalyst (cobalt-molybdate)
144
-------
Wastewater Treatment
The complexity of wastewater streams from coal lique-
faction systems requires a broad variety of treatments for
control of the potential environmentally significant mater-
ials borne by such streams. These requirements include most
of the known wastewater treatment systems and new ones yet
to be devised. Table 4 lists some of the standard systems
under Liquids Treatment.
Almost all modules discharge a wastewater stream. The
volume and characteristics of wastewater from each module
are process specific but constituents of wastewater are
similar for all processes utilizing a specific module. Some
wastewater streams may be treated and reused.
Process Application--
This module applies to all coal liquefaction systems.
Input Streams--
Sources and characteristics of some of the input
streams to this module are shown in Table 5. Some waste
streams will be treated through only part of the whole
treatment system depending on the origin of the stream and
its characteristics. Wastewater from the coal preparation
module is sent to a separate retention pond to permit the
settling of suspended solids. Oily waste streams contain-
ing high amounts of phenols and ammonia are treated for
recovery. Ammonia is recovered by stripping. After the
oil is separated, phenols are recovered by solvent extrac-
tion. A probable sequence of steps and control operations
to clean up sour water is as follows:
145
-------
TABLE 4. PARTIAL LIST OF CONTROL APPROACHES FOR
WASTE TREATMENT (26)
Gas treatment
Mechanical collection
Electrostatic precipitators
Filters (fabric, granular, etc.)
Liquid scrubbers/contactors
Condensers
Solid sorbents (mol sieves,
activated carbon)
Incineration (direct and
catalytic)
Chemical reaction
Liquids treatment
Settling, sedimentation
Precipitation, flocculation
Flotation
Centrifugation and filtration
Evaporation and concentration
Distillation, flashing
Liquid-liquid extraction
Gas-liquid stripping
pH adjustment
Biological processes
Oxidation processes
Activated carbon and other
absorbents
Ion exchange systems
Cooling towers and ponds
Chemical reaction and
separation
Water intake structures
Solids treatment
Fixation
Recovery/utilization
Processing/combustion
Chemical reaction and
separation
Oxidation/digestion
Physical separation (specific
gravity, magnetic, etc.)
4. Final disposal
Pond lining
Deep well injection
Burial and landfill
Sealed - contained storage
Dilution (water)
Dispersion (air, land)
5. Process modifications
Feedstock changes
Stream recycling
Process design improvements
6. Combustion modification
Furnace modifications
Optimum burner/furnace design
Alternate fuels/processes
Fuel additives
7. Fuel cleaning
Physical separation
Chemical refining
Carbonization/pyrolysis
Treatment of liquid fuels
Fuel gas treatment
8. Fugitive emissions control
Surface coatings/covers
Vegetation
Miscellaneous methods of control
Leak prevention
Vapor recovery systems
Ballast water treatment
9. Accidental release technology
Spill prevention in storage
Spill prevention in transporta-
tion
Spill prevention in oil & gas
production
Flares
Spill cleanup techniques
146
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TABLE 5. SOURCES AND CHARACTERISTICS OF WASTEWATER STREAMS
Module or process
Coal pretreatment
opL'ra t ton :
SizLng, drying, pul-
verizing, and slurrying
Coal liquef act ion
operat ion:
Hydrogenation
Py ro lysis /hydrocarbon i-
zation
Extraction
Catalytic synthesis
Separation operation: '
Flashing & condensing
Filtration
Cent rif ugation
Solvent de-ashing
Vacuum distillation
Coking
Quenching
Oil-water separation
Purification /upgrading
operation :
FracCionatlon
Hydrotreating
Auxiliary processes:
Hydrogen /syngas
gener.Tt ion
Oxygen genera t ion
Acid gas removal
Water supply
Wa ter cooling
Sulfur recovery
So lid waste treatment
Miscellaneous by-product
recovery
Steam and power genera-
tion
Transient waste
t reatment
Source
Coal storage piles, sizing
and drying
Cooling and quenching
Cooling and quenching
Char quenching
Condensing
Condensat ion
Condensation
Condensat ion
Condensation
Condensation
Condensa tion
Quench
Quench
Condensing
Condensing
Cooling and quenching
CO-shift
Adsorption and rugen era tion
Trea tment
Towers , ponds
Leaks , washdown
Washdown
All steps
Scrubbers
Leach ing
Scrubbers
Separat ion
Fuel combust ion
Spills, leaks , wjshdown
Waetewater stream
Water, runoff and
washdown
Foul water
Foul water
Foul water
Condensate
Process condensate
Process condensate
Process condensate
Process condensate
Process condensate
Foul water
Foul water
Condensate
Condensa te
Foul water
Water
Cooling water
Purge flows
Sludges
Slowdown , sludges
Wash water
Wash water
Sludges
Scrub water
Leachate
Scrub water
Foul water
Blowdown , ash-wa ter
Wash wa ter
Constituents
Suspended particles , dissolved
solids
Phenols, tars , ammonia, thio-
cynates , sulfides and chlorides
Phenols , tars , ammonia, thio-
cynates, sulfides and chlorides
Phenols , tars , ammonia, thio-
cynates , sulfides and chlorides
Phenols, ammonia, sulfides
Oils, HC, phenols, NH & sulfides
Oils, HC, phenols, NH & sulfides
Oils, HC, phenols, NH3 & sulfides
Oils, HC, phenols, NH & sulfides
Oils, HC, phenols, NH & sulfides
Oils, HC, phenols, NH & sulfides
Oils, HC, phenols, NH & sulfides
Oils, HC, phenols, NH & sulfides
Light hydrocarbons , dissolved salts
Phenols , ammonia, sulfides
Phenols, tars, ammonia, thio-
cyanates, sulfides and chlorides
Phenols, tars, ammonia, thio-
cyanates , sulfides and chlorides
Dissolved solids, suspended solids
Dissolved sulfides in gas removal
solvent
DS, SS, HC
DS, SS
HC
Sulfur
DS, SS, HC
DS, SS, HC
DS, HC
Coal, ash
Oils, HC, phenols, NH3 t, sulfides
OS, SS, ash
DS, SS, HC, ash, coal
147
-------
Removal of H2S, NH3, C02> and light gases:
Stripper
Initial oil and solids removal:
API separators
Baffle plate separators
Further oil and solids removal:
Clarifiers
Dissolved air flotation
Filters
Organic waste removal:
Activated sludge
Aerated lagoons
Oxidation ponds
Trickling filters
Activated carbon
Combination.
Conditions--
Most of the treatments are applied at ambient condi-
tions of temperature and pressure. Others like oxidation,
extraction and stripping involve higher temperatures and
some may involve reduced pressures.
Equipment--
Reference is made to Table 4 which suggests the types
of equipment used in this module. Additional details are
being compiled in a document, The Multimedia Environmental
Control Engineering Handbook.
Output Streams--
Treated water
Sludges
148
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Oils
Tars
Organics
Gaseous Waste Treatment
This module provides for treatment of vent gases and
exhausts from all other modules. Some of the methods used
are: oxidation, absorption, adsorption, and precipitation.
Table 4 lists additional methods.
Process Application--
This module is applicable to all coal liquefaction
systems.
Input Streams--
Inputs to this module will consist of mixtures of
gases containing:
Flue gas
Hydrocarbon vapors
Oxides of sulfur, carbon and nitrogen
Sulfides
Ammonia
Particulates
Ash
Trace elements and compounds
Table 6 lists some of the sources of these emissions. Table
7 indicates the capabilities of particular control equip-
ment .
149
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TABLE 6. SOURCES AND CHARACTERISTICS OF AIR EMISSIONS
Module
Coal pretreatment operation: -
Sizing, drying, pul-
verizing and slurry-
ing
Coal liquefaction operation:
Hydrogenation
Pyrolysis and hydro-
carbonization
Extraction
Catalytic synthesis
Flashing o condensing
Filtration
Centrif ugation
Solvent de-ashing
Vacuum distillation
Coking
Quenching
Oil-water separation
Purlficat ion/upgrad ing
operation :
Fract ionation
Hydrotrcating
Auxiliary processes :
Hydrogen /syngas
generat ion
Oxygen KL'rieration
Acid gas removal
Water cool ing
Sulfur recovery
Pn rt icu 1 ,1 tu recovery
Miscellaneous by-product
recoverv
Stream and power gene rat ion
Transient waste t reatment
Source
Vents and exhausts
Preheater flue gas
Preheater flue gas
Vapor leaks
Heater flue gas
Flash drum vapors
Evaporation £- gas
1 iberation
Evaporation & gas
1 iberation
Evaporation & gas
1 iberation
Evaporation & gas
liberation
Evaporation & gas
liberation
Evapora tlon & gas
liberation
Evaporation & gas
liberation
Un condensed gases from
condenser
Preheater flue gas
catalyst removal and
replacement
Ac id gas CO 2 steam
driers flue gas
Air separation
CO gas stream
Tower drift
Evaporation and leaks
Ta 11 gas vent
Separa t ions
Separa t ion , combustion
Land fills, handling
Separa tions
Evaporation & gas
liberation
Fuel combustion products
Spills, leaks, fugitive-
emissions, etc .
Emissions
Particulatea , hydrocarbon vapors
CO, NO , hydrocarbons
CO, NO , hydrocarbons
X
CO, NO , HC
X
CO, NO , hydrocarbons
X
Hydrocarbons, sulf ides, sulfur
dioxide, ammonia , particulates
HC, H2S, SO,,, NH3
HC, H2S, S02> NH3
HC, H2S, S02, NH3
HC, H25, S02, NH
HC, H S, SO , NH
HC, H2S, S02, NH3
HC, H2S, S02, NH3
CO, NOK, H2S, NH3, hydrocarbons,
particulates
CO 2 , CO, hydrocarbons , sulf ides ,
CO, NO , H S, NH
Nitrogen
CO 2 , H2S , CO, hydrocarbons ,
sulfides
Spray, biocides anticorrosives
Hydrocarbon vapors
so2, cos
Hydrocarbon vapors , NH
SOX, NOX, COS , CO, hydrocarbon
vapors
Hydrocarbon vapors, particulates,
Coal and ash particulates
HC, H2S, SO NH
Flyash, NO , SO , flue gas
All of the above
150
-------
TABLE 7. EMISSIONS AFFECTED BY AIR POLLUTION
CONTROL EQUIPMENT
CONTROL EQUIPMENT
EMISSIONS
ertial separators
ostatic precipitator
C ri
H 4-1
O
£>-, CU
5-1 i-l
0 K
Iters
rubbers (water)
H O
MH co
txD 4-1
CO 0)
pq rs
rubbers
o
CO
CN
O
10
co
T-H
O
5-1
4-1
O
O
X
O
co
co
5_i
cO
! 1
[ZH
g tower demisters
pj
H
i-l
O
O
CJ
recovery equipment
j_i
0
MH
rH
Jj
CO
Particulates
NO
X
H2S
NH3
Hydrocarbons
CO
Biocides
Anticorrosive additives
SO
X
X X
* *
Vc Vc
i'\ "ft
* *
* *
* *
* *
* *
X X
* Y
-' V
" 1
* Y
Vc- Y
* Y
* *
y- /v
* Y
Y
*
Y
Y
Y
*
*
*
X
*
X
Y
Vc
Y
5'C
*
*
*
*
*
*
V
X
X
Y
*
*
X
*
Vc
*
*
*
X
X
*
Vc
*
X
*
*
*
*
*
*
X = Primary pollutant controlled
Y = Other pollutants controlled
* = Does not reduce emission
151
-------
Conditions--
Temperature conditions cover the range from ambient to
flame temperatures. Pressure conditions are generally am-
bient or slightly negative.
Equipment--
Table 4 suggests the type of equipment used in this
module. Additional details are being compiled in the docu-
ment , The Multimedia Environmental Control Engineering
Handbook.
Output Streams--
* Wastewater
Sludges
Air and other gaseous mixtures having reduced
concentrations of the input materials
Solid wastes
Solid Waste Treatment
All modules discharge some solid waste, see Table 8.
Methods used for solids treatment are included in Table 4.
Process Application--
Solid waste control applies to all coal liquefaction
systems.
Input Streams--
Coal, particulates
Ash
Slag
Char
Filter cake
Still bottoms
152
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TABLE 8. SOURCES AND CHARACTERISTICS OF SOLID WASTES
Module or process
Coal pretreatment
operat ion :
Sizing, drying, pul-
verizing, and slurrying
Coal liquefaction
operat ion :
Hydrogenation
Pyrolysis/hydrocarboni-
zat ion
ExCrace ion
Catalytic synthesis
Separation operation ;
Flash ing & condensing
Filtra tion
Centrifugation
Solvent de-ashing
Vacuum distillation
Quenching
Oi1-uater separation
Solid waste
Storage piles, sizing and pulverizing Particulate coal
Reaction, wastes and catalyst disposal
Reaction wastes
Reaction wastes
Reaction wastes and catalyst disposal
Raw liquefaction mixture
Rdw liquefaction mixture
Raw 1 iquefact ion mixture
Raw liquefaction mixture
R,iw liquefaction mixture
Raw liquefaction mixture
Raw liquefaction mixture
Raw liquefaction mixture
Particulate coal, ash, slag, mineral matter,
char
Particulate coal, ash, slag, mineral matter,
char
Ash, slag, mineral matter
Particulate coal, spent catalyst, ash, slag,
mineral matter, char, spent absorbent
Particulate coal, ash, slag, mineral matter,
char
Particulate coal, ash, slag, mineral matter,
char
Particulate
char
Particulate
char
Particulate
char
Particulate
char
Particulate
char
Particulate
coal,
coal,
coal ,
coal ,
coal ,
coal ,
ash,
ash,
ash ,
ash,
ash,
ash,
slag,
slag,
slag,
slag,
slag,
slag,
mineral matter,
mineral matter,
mineral matter,
mineral matter,
mineral matter ,
mineral matter,
Purification/upgrading
opera t ion_:
Frac t innat ion
Hydrotreat ing
Auxiliary prucesses:
Hydrogen/syngas
tenerat ion
Ac id yas removal
Water supplv
Water cool in^
Product stor.ige
Sulfur recovery
Wastewater treatment
Caseous waste t reatmen t
Solid wastu treatment
P.t r t iculatc recovery
Mis< ellaneour, by-product
recovery
S team and power
m'nerat ion
Trnns ient w.iste
t reot merit
Vjcuum tower bot toms
Catalyst disposal
Fted preparation, gasification, sh i ft
Absorbent disposal
Treatment
Trea tment
Tank bot toms
Catalyst
Solids collection
Sol ids col leet ion
Solids collection
Sol ids collection
Solids collee t ion
Co.nl prepara t ion , ash disposal, blow
Spills, leaks
Particulate coal, ash, slag, mineral matter,
char
Spent catalyst
Particulate coal, spent catalyst, ash, slag,
mineral matter, char
Spent absorbent
Slowdown, sludges, spent regenerants
Blowdown, sludges, spent regenerants
HC residues
Sulfur
Spent absorbent, blowdown, sludges, spent
regenerant
Particulate coal, spent catalyst, ash, slag,
mineral matter, char, spent absorbent, blow-
down , sludges, spent regenerants
Particulate coal, spent catalyst, ash, slag,
mineral matter, char, spent absorbent, blow-
down , sludges, spent regenerants, sulfur
Particulate coal, ash, slag, mineral matter,
char, blowdown sludges, spent regenerants
HC residues
Particulate coal, ash , slag, mineral matter,
blowdown, sludges, spent regenerants
Particulate coal, spent catalyst, ash, slag,
mineral matter, char, spent absorbent, blow-
down , sludges, spent regenerants, sulfur
153
-------
Trace elements
Spent catalyst
Spent absorbents
Sludges from water treatment and flue gas desul-
furization
Conditions--
Treatment methods, see Table 4, determine the condi-
tions under which activities in this module will occur.
Equipment--
Kilns
Roasters
Incinerators
Digesters
Classifiers
Additional types of equipment are suggested by Table 4.
Output Streams--
Wastewater
Stabilized solids
Waste gases
Reclaimed coal
Reclaimed char
Regenerated catalyst
Regenerated absorbents
Recovered by-products
Particulate Recovery
The function of this module is the collection of coal
and ash particulates to prevent their release to the atmos
phere, and to recover carbon values.
154
-------
Process Application--
This module applies to all coal liquefaction systems.
Input Strearns--
Vents and discharges from coal sizing, drying, pulver-
izing, and from coal feeding steps provide the largest in-
put. Water may be an input.
Conditions--
Ambient conditions of temperature at slight negative
pressures usually obtain.
Equipment--
Baghouses
Filters
Electrostatic precipitators
Blowers
Scrubbers
Pump s
Decanters
Output Streams--
Coal
Ash
Vent gas
Air
Wastewater
Miscellaneous By-product Recovery
This auxiliary provides for the treatment of waste
streams for the removal and collection of recoverable by-
products. Some of the methods used are: refinery tech-
niques, air stripping, steam stripping, ion-exchange,
155
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break-point chlorination, hydrotreating and solvent extrac-
tion.
Process Application--
By-product recovery is applicable to all coal liquefaC'
tion systems.
Input Streams--
Feed streams to by-product recovery will consist of
mixtures containing materials from the following list:
Ammonia
Phenols
Benzenes
Naphtha
Gasoline
High-, low-, and intermediate Btu gas
Hydrocarbons
Ethylene
Char, coke
Ash/slag
Tars (tar acids and tar bases)
Water
Conditions--
It is apparent from the list of by-products and the
methods used for their recovery that a wide range of tem-
perature and pressure conditions will be involved.
Equipment--
Table 4 suggests the type of equipment that might be
required for by-product recovery. Additional details are
being compiled in a document, The Multimedia Environmental
Control Engineering Handbook.
156
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Output Strearns--
Wastewater
Sludges
Non-condensible gases
Ammonia
Phenols
Benzenes
Gasoline
Hydrocarbons
High-, low- and intermediate Btu gas
Char, coke
Ash/slag
Tar (tar acids and bases)
Naphtha
Ethylene
Steam and Electric Power Generation
In this module the chemical energy of some form of
fossil fuel, probably coal, is transformed into steam and
electric energy to meet the requirements of all other
modules in the plant. Present day methods of utilizing the
energy of fossil fuel are based on a combustion process,
followed by steam generation to convert the heat first into
mechanical energy and then to convert the mechanical energy
into electrical energy.
Process Application--
This module applies to all coal liquefaction systems.
Input Strearns--
Coal, fuel oil, and natural gas can all be used as
fuels, however, coal will probably be used. The other main
157
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input stream is water. Additional inputs are treatment
chemicals for raw water and for waste treatment.
Conditions--
Conditions will depend on the characteristics of the
steam and electric power requirements of the coal liquefac-
tion systems.
Equipment--
Boilers
Turbine generators
Condensers
Pumps
Scrubbers
Dearators
Precipitators
Ash handling systems
Output Streams--
Boiler blowdown
Fly ash
Bottom ash
Ash sluice water
Floor drains
Flue gas
Contaminated floor and yard drains
Intake screen backwash
Cleaning wastes
Transient Waste Treatment
Waste streams produced during normal process operation
are expected and provisions are made for their continuous
disposition. Consideration must be given to waste streams
158
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generated as a result of intermittent occurrences. Such
releases have been termed transient pollutants. These
releases may be unplanned or accidental; they can be caused
by leaks, spills, upsets, startups, shutdowns, power fail-
ures, process equipment failures, slugging, surging, and
overloading. They may also be caused by or occur during
maintenance operations. Because of their nature, such
releases are difficult to sample, analyze, and classify.
However, if some thought is given to possible situations, it
is more likely that the impact of fugitive emissions can be
minimized. In many cases, the best disposition of the
unwanted stream is to return it to the process.
Spills and leaks will occur and provisions for cleanup
and containment should be made. Pumps and valves are known
sources of leaks. Solids handling equipment also can cause
problems. Belt conveyors or bucket elevators can break or
jam causing spills or fires. In such cases, it may be
necessary to dump materials and make repairs to resume
normal operations. Vacuum cleanup trucks could reclaim
these spilled solids for reuse. Water flushing can wash
residual solids and flush oil spills to an "oily water"
sewer system for recovery.
During startup, shutdown, or a plant upset, off speci-
fication products may be made. Rather than dispose these
materials through the waste treatment facilities, it will
probably be much more desirable to store them and rework
them into the proper specifications. This procedure,
however, will require adequate storage. Enclosed storage
will be needed for many of the liquids removed at shutdown.
Vapors, particularly odors, may be released. Water layers
from separations will contain various sulfur, nitrogen, and
oxygen compounds that should not be allowed to escape to the
atmosphere. These liquids can be stored until a subsequent
159
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startup and used for recharge or they can be worked off
through the wastewater treating systems.
Before maintenance is performed the equipment or
system will have to be purged to remove toxic and combus-
tible gases. Purged gases should be sent to an incinerator
or furnace. This procedure also applies to shutdowns.
Certain catalysts or carbonaceous materials may be pyro-
phoric at high temperatures. Inert gas purge and cooling
will be required to prevent fire.
In the case of plugging it may be necessary to flush
the system with a light oil or with water. Provision must
be made to collect and store the cleaning stream until it
can be either recycled or treated for disposal. Slugs of
liquids resulting from upsets or surges may be sent to the
flare. Serious fires or explosions could be caused if
separators are not sized to prevent entrainment.
Inspection, monitoring, and maintenance programs are
essential to controlling transient pollutants.
Process Application--
This module applies to all liquefaction systems.
Input Streams--
Material inputs to this module include those listed
above for all other modules.
Conditions--
Conditions for transient pollutant control are deter-
mined by the pollutant and the treatment to which it is
subjected. Conditions will correspond to those of the above
control modules or to a process or operation in the case of
materials returned to processing.
160
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Equipment--
Equipment needs for this module correspond to those
identified for each module and, in addition, fire fighting
and specialized materials handling equipment such as vacuum
cleanup systems.
Output Strearns--
Outputs will correspond also to those of the control
module in which the transient pollutant is treated.
161
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SECTION 3
ENVIRONMENTAL ASSESSMENT REQUIREMENTS
INTRODUCTION
The purpose of this section is to assess the known
information and to determine criteria for selecting proper
control technologies to limit pollutant discharges. Table 4,
Section 2, provides a listing of most of the available
approaches to control technologies.
Initially the types of pollutants probably present in
waste streams were determined. This was based on available
documentation on liquefaction emissions and consideration of
discharges from related industries such as coal-fired power
plants and petroleum refineries.
Next, the pollution controls were evaluated to deter-
mine each type's capabilities and limitations. Among fac-
tors considered were:
The type of pollutants controlled by the specific
technology
Physical properties of the pollutants that might
affect selection of controls
Chemical properties of the pollutants that might
affect selection of controls
162
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Efficiency of controls
Contaminants in the waste stream that could limit
or prevent use of a specific type of control
The local environment including climate, water
availability, and soil characteristics.
When possible, controls were matched with anticipated
effluents. Specific determinants of the best suited techno-
logy were noted. The following discussion on air, water,
and solid waste controls is based upon this procedure. Fur-
ther, more detailed studies are being conducted. This is
a repetitive process due to changing waste stream and con-
trol technology characterization.
SELECTION OF SUITABLE AIR POLLUTION CONTROLS
It is well recognized that no uniform gas cleaning
method exists that will satisfy all problems and conditions.
In the selection of proper control technologies, both phy-
sical and chemical properties must be considered. The
degree of efficiency of different control options also must
be a basis for selection.
For example, in particulate control, coarse dust par-
ticles are separated by dry inertial separators whereas fine
dusts require the use of fabric filters, scrubbers, or
electrostatic precipitators. To meet a specific level of
emission, highly efficient removal systems such as precipi-
tators are required for controlling streams with large
amounts of fine particulates. Cyclones might be applicable
for removal of less concentrated coarse particles. Par-
ticulate properties which are basic to the performance and
163
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selection of gas cleaning equipment are particle size
distribution, structure, density, composition, electrical
conductivity and agglomeration tendencies. Also, gas prop-
erties such as temperature, moisture content, total gas
flow; and chemical composition must be considered. For
example, particulate removal efficiency for precipitators
increases as sulfur content in the waste stream exceeds two
percent. Fine particulates will probably need a better
control than now exists.
Sulfur dioxide controls are not now necessary with
coal-fired boilers smaller than 264 GJ/hr. This, however,
should be evaluated.
The use of flares to control hydrocarbon emissions is
primarily dependent on the availability of sufficient waste
gases to maintain combustion.
Sulfur-recovery process selection is limited by the
composition of the acid-gas feed stream. When the Stretford
process is operated on fuel gas, the concentration of sodium
thiosulfate builds up in the circulating solution and must
be purged. Other contaminants to the solution include HCN,
SC^, ammonia, and heavy hydrocarbons. Stretford cannot be
used alone if significant amounts of organic sulfur are
present. Most mercapatans, carbonyl sulfides, and carbon
dioxide pass through the absorber into the exit gas. To
maintain Glaus process efficiency, on the other hand, re-
quires a minimum concentration of approximately ten to
fifteen volume percent of PUS. High levels of C0? water
vapor and hydrocarbons in the acid gas feed also reduce the
efficiency.
164
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Availability of water also can determine which control
should be selected. In arid regions, dry methods of con-
trolling emissions must be considered.
Detailed analyses of waste stream composition and
concentration combined with aforementioned properties of air
pollution controls are needed to provide adequate data to
select the proper control system.
SELECTION OF SUITABLE WATER POLLUTION CONTROLS
All process wastewater streams mentioned in Section 2
have different characteristics. The selection of the best
control technology will depend on the information available
for each stream.
The compounds of interest can be divided into classes
such as dissolved gases, organics, trace elements, phenols,
and sulfur and nitrogen compounds. Knowledge concerning
characteristics such as BOD, COD, TOG, suspended solids, pH,
and oil and grease is also essential. Table 9 shows some of
the individual compounds of each class that may be present.
It may be that two or more wastewater streams can be
treated by a common method. The variation in characteristics
of wastewater streams and capability of control systems to
handle such variations can be evaluated by changes in the
feedstock and operating variables. The concentration levels
of recoverable compounds such as ammonia and phenols will
determine the feasibility of recovery. Combination physical/
chemical methods may remove some materials such as phenols.
The performance of biological oxidation systems in the
presence of toxic metals is not fully known and requires
evaluation.
165
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TABLE 9. SOltE CHARACTERISTICS OF WASTEWATER
Component
Class
Item or property of interest
Dissolved gases
Organic liquids
and solids
Trace elements
Ions
Gross
characteristics
Inorganic
Organic
Sulfurous
Polynuclear
aromatic compounds
Nitrogen compounds
Phenols
Sulfur compounds
09,.NH,, CO, SO , HC1, HCN, HF, H9S , CS9
^ J X £- /-
CH/ , C^Hx-, C^H/ , CHrjSH, C^H^SH
COS, CS2, CH3SH, C2H5SH
Pyrenes, fluorenes, benzopyrenes,
phenanthrenes , f luoranthene.s , chrysenes
Pyridine, quinoline, indole, carbazole,
acridine
Phenol, cresols, xylenols, naphthols
Hercaptans, thiophenol, thiocresol,
benzothiophenes
Ba, Be, Ca, Cr, Cu, Mn, Mo, Ni, Sr, V,
Zn, As, B, Cd, F, Hg, Pb, Sb, Se, Sn
S=,J04=, N03~, F~, Cl~, Br~, CN~, P04~,
C03=, HC03"," SCN"
BOD, COD, TOG,, suspended solids, oil and
grease, specific conductance
-------
Wastewater treatment will generate sludges requiring
proper disposal. Sludge characteristics depend on the type
of wastewater and will determine the treatment method
applied. It is important to identify hazardous materials
that may be leached by groundwater. The volume and type of
sludge will determine the disposal method that can be used.
Sludge with high water content may require pretreatment such
as dewatering if it is to be treated as a solid waste. The
presence of toxic materials must be assessed and positive
indications will make it necessary to find control means for
preventing their entry into the environment.
The complete wastewater control system will be a com-
bination of physical, chemical, and biological treatment
processes. The combination sequence of the individual treat-
ment processes will affect the degree of contaminant re-
moval. Table 10 shows the important characteristics of
wastewaters that could influence the choice of wastewater
treatment and control systems.
SELECTION OF SUITABLE SOLID WASTE CONTROLS
The bulk solid waste to be landfilled includes various
constituent materials. Ash consists of a variety of metal-
lic oxides and trace element compounds. Coal and char
particles contain organic and mineral materials. Elemental
sulfur may be generated as solid waste from hydrogen sulfide
control technologies. Limestone sludges, primarily calcium
sulfite and calcium sulfate also may be generated. Zinc
sulfide, the primary constituent of spent sulfur guard
reactor absorbents, also may be present as will spent catalyst
from applicable processes. Wastewater treatment sludges,
a mixture of coal tar residues, sand, coal fines, and treat-
ment by-products may also contain untreated quantities of
167
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TABLE 10. WASTEWATER CONTROL SYSTEMS
Important wastewater
characteristics
Control method
Flow variability
Extreme pH values
Extreme pH values
Nutrient deficiency
Settleable suspended solids
Oils, tars, suspended solids,
and other flotative matter
Organic content
Organic content
Organic content
Organic content
Dissolved solids, colloids,
metals or precipitable organics,
and emulsified oils
Oils, colloids, tar, and chemi-
cally coalesced materials
Trace amounts of organics and
color, taste, and odor produc-
ing compounds
Dissolved gases, variable or-
ganics and materials that can
be chemically converted to
gases
Equalization
Neutralization
Temperature adjustment
Nutrient additions
Sedimentation
Dissolved air-flotation
Activated sludge
Aerated lagoon
Oxidation pond
Trickling filter
Chemical mixing flocculation
and clarification
Dissolved air-flotation with
chemicals
Activated carbon absorption
Stripping
168
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phenols, ammonia, cyanides, and other potentially dangerous
materials.
Limited knowledge of solid waste component materials
restricts the depth to which this subject may be analyzed.
Chemical analysis will identify the specific composition of
solid waste materials and determine their concentration. It
may be necessary to determine the environmental impacts of
some materials. In effect, all leachable materials present
in concentrations exceeding environmentally acceptable
standards should be identified.
Solid waste disposal methods should be designed to
permit minimum environmental degradation. Little is known
about the fate of landfilled trace elements, spent catalysts,
or spent absorbents. Landfilling and minefilling
techniques will have to become more sophisticated to prevent
contamination of the surrounding area. Hazardous leachable
materials present in solid waste should be identified and
studied to determine ways to minimize detrimental envi-
ronmental effects.
One related problem, a result of groundwater leaching,
is the reentry to the environment of undesirable ash con-
stituents. A possible solution is to preclude leaching by
using impervious liners to prevent groundwater percolation.
Chemical stabilization to render leachable constituents
insoluble or inert may be a necessary control method in some
instances. A combination of physical and chemical control
methods may be the required technique.
Subsidence, the gradual settling of landfill materials,
is another problem. In some cases, waste compaction
reduces subsidence effects, allows more waste disposal per
unit volume of storage space, and reduces the permeability
169
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of landfilled wastes. This method, which reduces leaching
problems, is currently under consideration as a means of
improving solid waste disposal techniques. More information
is needed regarding the subsidence and compaction properties
of the bulk solid wastes generated by liquefaction proces-
ses .
Although no secondary wastes are anticipated after
landfilling, light hydrocarbon gases may be generated due to
reaction of organic materials present. Furthermore, com-
bustible materials may generate gases as well as cause
underground fires. Unsuspected or undetected materials may
undergo groundwater leaching. Periodic sampling and analy-
sis of landfill materials and the surrounding area may be
required to determine if secondary wastes are generated. It
may be necessary to develop control technology modifications
which will prevent the generation of such wastes.
170
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SECTION 4
PLANS AND TIMING FOR DEVELOPMENT
INTRODUCTION
Fourteen processes have been described in this summary.
They represent all four technology categories. All stages
of development, from laboratory studies to demonstration
projects, are similarly represented. Decisions necessary in
the course of program execution will influence the rate and
final extent of development of each process.
Most of the processes discussed in this document are
funded by DOE. In some cases DOE jointly funds an effort
either with another agency or with private industry. Several
projects, however, are not currently recipients of federal
support. In these cases projections of future program/
project plans are not available. Current schedules for
construction and operation are shown in Table 11.
Two solvent refined coal pilot plants are the only
liquefaction plants in operation as of June 1978. An H-Coal
pilot plant, now under construction, will not be operational
before the third quarter of FY 79.
Brief discussions of the status of each process under
development follow.
171
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TABLE 11. COAL LIQUEFACTION DEVELOPMENT SCHEDULE (2,16,27)
Operation
Scale
Time frame
FY78 I FY79 I FY80
Coal pretreatment
Crushing & grinding
Pulverizing & sizing
Drying
Slurrying & preheat-
ing
Coal liquefaction
Hydrogenation
Synthoil
H-Coal
Bergius
SRC
CO-Steam
EDS
Pyrolysis/hydro-
carbonization
COED
Coalcon
Clean coke
TOSCOAL
ORC
Extraction
SGE
Catalytic synthesis
Fischer-Tropsch
Methanol
Separation
Flashing & conden-
sation
Filtration
Centrifugation
Solvent de-ashing
Vacuum distillation
Coking
Quenching
Oil-water separation
Purification & upgrad-
ing
Fractionation
Hydrotreating
Hydrogen/synthesis
gas generation
PP
PP
PP
PP
PDU
PDU, PP
PDU
PP, DP
PDU
PDU, PP
PP - completed
DP
PDU
PDU, PP
PP
CP
CP, DP, CP
PP
PP
PP
PP
PP
PDU
PP
PP
PP
PDU, PP
VoV
(continued)
172
* *
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TABLE 11 (continued)
Time frame
Operation
Auxiliary processes
Oxygen generation
Acid gas removal
Water supply
Water cooling
Product storage
Sulfur recovery
Wastewater treat-
ment
Gas waste treatment
Solid waste treat-
ment
Particulate recovery
Miscellaneous by-
product recovery
Steam & power genera-
tion
Transient waste
treatment
Scale
Vr
PP
PP
PP
PP
PP
PP
PP
PP
PP
PP
PP
PP
FY78
FY79
FY80
= construction
= operation
= re-evaluation
* has not been announced.
**Status and population of low/intermediate Btu gasification
systems are available in Reference 25, p. 21 and Appendix
C-l.
PP = pilot plant; PDU = process development unit;
CP = commercial plant; DP = demonstration plant
173
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HYDROGENATION
Synthoil
Continued development of the Synthoil process is cur-
rently suspended. A process development unit was constructed
but no firm plans for its use have been announced.
H-Coal
A process development unit is in operation. Construc-
tion of a pilot plant is underway. Operation is planned to
begin in FY 80.
Bergius Process
This is the DOE "disposable catalyst" process. Con-
struction of a process development unit is in progress and
initial operation is planned for late 1977. No pilot plant
plans exist.
Solvent R.efined Coal
Two pilot plants are operating. The 5.4-metric ton
per day plant at Wilsonville, Alabama will operate through
FY77. A decision is to be made as to whether or not to
continue operation.
Operation of the 45.4-metric ton per day Fort Lewis,
Washington facility is planned to extend into FY81.
In addition, an 1814-metric ton per day demonstration
plant is being considered by the Kentucky Center for Energy
Research but no schedule is available.
174
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CO-Steam
Construction of a 4.5-kg per hour continuous unit was
completed in FY78. It is now being tested.
Donor Solvent
Operation of the Exxon Donor Solvent process develop-
ment unit is planned through FY82. Current scheduling calls
for pilot plant construction to be completed early in FY80
with operation from FY80 through FY82.
PYROLYSIS AND HYDROCARBONIZATION
COED
The COED project has been completed through the pilot
plant stage. The pilot plant has been dismantled. No
further work is projected for this process.
Coalcon
Although originally planned for near term construction,
DOE is considering suspension of the project due to marginal
economics and technical problems with fluidized-bed carbon-
izers. Additional work is proceeding to eliminate scale-up
problems involved in fluidized bed and the decision on the
fate of this project has not been announced.
Clean Coke
Operation of a process development unit during FY78 is
planned. There are no current plans for pilot facilities.
175
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TOSCOAL
This process is not currently funded by DOE. A facil-
ity has been tested using coal in past studies but no infor-
mation on future plans is available.
Garrett (ORC)
Operation of a small PDU is currently funded by DOE.
EXTRACTION
Supercritical Gas Extraction
This process is at such an early stage of development
that no plans beyond inception have been announced.
CATALYTIC SYNTHESIS
Fischer-Tropsch
A commercial plant has been operated in South Africa
since 1955 and a second commercial plant is under construc-
tion there. No concrete plans have been made yet for pro-
cess development or pilot studies in this country.
Methanol
DOE studies of methanol are directed to its use as a
feedstock for catalytic conversion to gasoline.
Synthesis of methanol from synthesis gas is being
planned as a commercial venture.
176
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University of Pittsburgh, August 1976.
Magee, E.M. "Evaluation of Pollution Control in Fossil Fuel
Conversion Processes: Final Report." EPA-600/3-76-
101, Research Triangle Park, North Carolina: U.S.
Environmental Protection Agency, April 1976.
Morgan, W.D. "Coalcon's Demonstration Plant for Clean
Fuels." Chemical Engineering Progress, Vol. 12, No. 8
(August 1976).
180
-------
Process Evaluation Group, U.S. Bureau of Mines. "Economic
Analysis of SYNTHOIL Plant Producing 50,000 Barrels Per
Day of Liquid Fuels from 2 Coal Seams: Wyodak and
Western Kentucky." ERDA 76-35, Washington, D.C.:
ERDA-Fossil Energy, November 1975.
Rogoshewski, P.J. et al. Standards of Practice Manual for
the Solvent Refined Coal Liquefaction Process, EPA 600/
7-78-091.Prepared for U.S. Environmental Protection
Agency, by Hittman Associates: Columbia, Md., June
1978.
Sass, A. "The Garrett Research and Development Company
Process for the Conversion of Coal into Liquid Fuels."
Presented at 65th Annual Meeting, American Institute of
Chemical Engineers, New York, November 29, 1972.
Stotler, H.H. "H-Coal Pilot Plant Program." Paper pre-
sented at 67th Annual Meeting of AIChE, Washington, DC,
December 1-5, 1974.
Yavorsky, et al. "Converting Coal into Nonpolluting Fuel
Oil." Chemical Engineering Progress, Vol. 69, No. 3
(March 1973) pp. 51-52.
181
-------
APPENDICES
A. SI (METRIC) CONVERSION FACTORS
B. SIEVE SERIES
C. SI SERIES
182
-------
APPENDIX A. SI (METRIC) CONVERSION FACTORS (28)
To Convert From
To
Multiply By
ft/s'
Acceleration
2 2
metre per second (m/s )
3.048-000 E-01
Acre (U.S. survey)
12
ft
yd
Area
2
-7
metre!; (m0)
metre2 (n^)
metre- (m_)
metre (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
metre (m)
metre (m)
metre (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/fV
Mass Per Unit Area
2 2
kilogram per metre (kg/m )
4.882 428 E+00
183
-------
APPENDIX A (continued)
To Convert From
To
Multiply By
degree Celsius
degree Fahrenheit
degree Fahrenheit
degree Rankine
Kelvin
Temperature
Kelvin (K)
degree Celsius
Kelvin (K)
Kelvin (K)
degree Celsius
K
He
= t0 + 273.15
Loc
= <*'F- 32)/1-8
= (t + 459.67)/1.8
v °F
' V1'8
-t- 273.15
ft/h
ft/min
ft/s
in/s
Velocity (Includes Speed)
metre per second (m/s)
metre per second (m/s)
metre per second (m/s)
metre per second (m/s)
8.466 667 E-05
5.080 000 E-03
3.048 000 E-01
2.540 000 E-02
centipoise
centistokes
poise
stokes
Viscosity
pascal second (Pa-s)
metre^ per second (irn/s)
pascal second (Pa-s)
metre per second (m^/s)
1.000 000 E-03
1.000 000 E-06
1.000 000 E-01
1.000 000 E-04
acre-foot (U.S.
survey)
barrel (oil, 42 gal)
ft3
gallon (U.S. liquid)
litre*
Volume (Includes Capacity)
metre (m )
metre (m )
metre (m3)
metre (m )
metre (m )
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
Volume Per Unit Time (Includes Flow)
ft /rain
ft3/
gal
gal
s
(U.
(U.
S.
S.
liquid/day)
liquid/min)
metre per
metre per
metre per
metre per
second (m/s)
second (m /s)
second (m/s)
second (m /s)
4.
2.
4.
6.
719
831
381
309
474
685
264
020
E-04
E-02
E-03
E-05
_i_i.». -u - v i - .* v - ~__ _ ^.... .,,_ j-j,. t,_ L_, cinQ JMG3. SU.1T SS SQOptGQ ttlG T13.II1G
litre as a special name for the cubic decimetre. Prior to this decision
the litre differed slightly (previous value, 1.000028 dm3) and in expres-
sion of precision volume measurement this fact must be kept in mind.
184
-------
APPENDIX A (continued)
To Convert From
lb/ft
lb/in
To
Mass Per Unit Length
kilogram per metre (kg/m)
kilogram per metre (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/ff
Mass Per Unit Volume (Includes Density & Mass Capacity)
3
Ib/gal (U.S. liquid)
lb/yd3
kilogram per metre"
(kg/m3)
kilogram per metre
(kg/m3)
kilogram per metre
(kg/m3)
1.601 846 E+01
1.198 264 E+02
5.932 764 E-01
Power
Btu (thermochemical)/h
Btu (thermochemical)/h
cal (thermochemical)/min
cal (thermochemical)/s
watt (W)
watt (W)
watt (W)
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)
foot of water (39.2 F)
lbf/ft|
Ibf/in (psi)
pascal (Pa)
pascal (Pa)
pascal (Pa)
pascal (Pa)
1.013 250 E+05
2.988 98 E+03
4.788 026 E+01
6.894 757 E+03
185
-------
APPENDIX B, SIEVE SERIES (29)
Sieve designation
Standard
107.
101.
90.
76.
64.
53.
50.
45.
38.
32.
26.
25.
22.
19.
16.
13.
12.
11.
9.
8.
6.
6.
5.
4.
4.
3.
2.
2.
2.
1.
1.
1.
1.
841
707
595
500
420
354
297
250
210
177
149
125
105
88
74
63
53
44
37
6 mm.
6 mm.
5 mm.
1 mm.
0 mm.
8 mm.
8 mm.
3 mm .
1 mm .
0 mm.
9 mm.
4 mm.
6 mm. *
0 mm.
0 mm. *
5 mm .
7 mm.
2 mm.*
51 mm.
00 mm.*
73 mm.
35 mm.
66 mm.*
76 mm.
00 mm.*
36 mm.
83 mm. *
38 mm.
00 mm.*
68 mm.
41 mm . *
19 mm.
,00 mm.*
micron
micron*
micron
micron*
micron
micron*
micron
micron*
micron
micron*
micron
micron*
micron
micron*
micron
micron*
micron
micron*
micron
Alternate
4.24 in.
4 in.**
3-l/2in.
3 in.
2-1/2 in.
2.12 in .
2 in.**
1-3/4 in.
1-1/2 in.
1-1/4 in.
1.06 in.
1 in.**
7/8 in.
3/4 in.
5/8 in.
0.530 in.
1/2 in.**
7/16 in.
3/8 in.
5/16 in.
0.265 in.
1/4 in.**
No. 3-1/2
No. 4
No. 5
No. 6
No. 7
No. 8
No. 10
No. 12
No. 14
No. 16
No. 18
No. 20
No. 25
No. 30
No. 35
No. 40
No. 45
No. 50
No. 60-
No.' 70
No. 80
No. 100
No. 120
No. 140
No. 170
No. 200
No. 230
No. 270
No. 325
No. 400
Sieve opening
in.
(approx.
equiva-
mm.
107.
101.
90.
76.
64.
53.
50.
45.
38.
32.
26.
25.
22.
19.
16.
13.
12.
11.
9.
8.
6.
6.
5.
4.
4.
3.
2.
2.
2.
1.
1.
1.
1.
0.
,
6
6
5
1
0
8
8
3
1
0
9
4
6
0
0
5
7
2
51
00
73
35
66
76
00
36
83
38
00
68
41
19
00
841
707
595
500
.420
.354
.297
.250
.210
.177
.149
.125
.105
.088
.074
.063
.053
.C'.4
.037
lents)
4.24
4.00
3.50
3.00
2.50
2.12
2.00
1.75
1.50
1.25
1.06
1.00
0.875
.750
.625
.530
.500
.438
.375
.312
.265
.250
.223
.187
.157
.132
.111
.0937
.0787
.0661
.0555
.0469
.0394
.0331
.0278
.0234
.0197
.0165
.0139
.0117
.0098
.0083
.0070
.0059
.0049
.0041
.0035
.0029
.0025
.0021
.0017
.0015
Nominal
wire diam.
in.
(approx.
equiva-
mm.
6.
6.
6.
5.
5.
5.
5.
4.
4.
4.
3.
3.
3.
3.
3.
2.
2.
2.
2.
' 2.
1.
1.
1.
1.
1.
1.
1.
1.
0.
40
30
08
80
50
15
05
85
59
23
90
80
50
30
00
75
67
45
27
07
87
82
68
54
37
23
10
00
900
810
725
650
580
510
450
390
340
.290
.247
.215
.180
.152
.131
.110
.091
.076
.064
.053
.044
.037
.030
.025
lents
0.2520
.2480
.2394
.2283
.2165
.2028
.1988
.1909
. 1807
.1665
.1535
.1496
.1378
.1299
.1181
.1083
.1051
.0965
.0894
.0815
.0736
.0717
.0661
.0606
.0539
.0484
.0430
.0394
.0354
.0319
.0285
.0256
.0228
.0201
.0177
.0154
.0134
.0114
.0097
.0085
.0071
.0060
.0052
.0043
..0036
.0030
.0025
.0021
.0017
.0015
.0012
.0010
Tyler
equivalent
designation
1.050 in.
0.883 in.
.742 in.
.624 in.
.525 in.
.441 in.
.371 in.
2-1/2 mesh
3 mesh
3-1/2 mesh
4 mesh
5 mesh
6 mesh
7 mesh
8 mesh
9 mesh
10 mesh
12 mesh'
14 mesh
16 mesh
20 mesh
24 mesh
28 mesh
32 mesh
35 mesh
42 mesh
48 mesh
60 mesh
65 mesh
80 mesh
100 mesh
115 mesh
150 mesh
170 mesh
200 mesh
250 mesh
270 mesh
325 mesh
400 mesh
recommended that wherever possible these sieves be included in all sieve analysis data or
re-ports intended for international publication.
**These sieves are not in the Eourth-root-of-2 series, but they have been included because
they are in common us^ee.
186
-------
APPENDIX C. SI SERIES (28)
Multiplication factor
1 000 000 000 000 000 000 = 10
1 000 000 000 000 000 = 10
1 000 000 000 000 = 10
1 000 000 000 = 10
1 000 000 =
1 000 =
100 =
10 = 10
0.1 = 10
0.01 = 10
0.001 = 10
0.000 001 = 10
0.000 000 001 = 10
0.000 000 000 001 = 10
0.000 000 000 000 001 = 10
0.000 000 000 000 000 001 = 10
18
15
12
9
6
3
^j
i
2
1
-1
-2
_3
^t
-6
-9
-12
-15
-18
Prefix
a
exa
Q
peta
tera
giga
mega
kilo
hecto
A 1 b
deka
b
deci
-b
centi
milli
micro
nano
pico
fern to
atto
Symbi
E
P
T
G
M
k
h
da
d
c
m
^
n
P
f
a
aAdopted by the CGPM in 1975.
^To be avoided where possible. See 3.2.2.
187
-------
TECHNICAL REPORT DATA
(Please read Insiructions on the reverse before completing)
1. REPORT NO.
EPA-600/7-78-184a
2.
3. RECIPIENT'S ACCESSION'NO.
TITLE AND SUBTITLE Environmental Assessment Data Base
for Coal Liquefaction TechnologyfVolume I. Systems
for 14 Liquefaction Processes
5. REPORT DATE
September 1978
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Craig S. Koralek and Subhash S. Patel
8. PERFORMING ORGANIZATION REPOR1
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Hittman Associates, Inc.
9190 Red Branch Road
Columbia, Maryland 21045
10. PROGRAM ELEMENT NO.
EHE623A
11. CONTRACT/GRANT NO.
68-02-2162
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
PERIOD COVERED
14. SPONSORING AGENCY CODE
EPA/60.0/13
15. SUPPLEMENTARY NOTESJERL-RTP project officer is William J. Rhodes, Mail Drop 61, 919/
541-2851.
s. ABSTRACT
two-volume report , prepared as part of an overall environmental asses-
sment (EA) program for the technology involved in the conversion of coal to clean
liquid fuels, and the Standards of Practice Manual for the Solvent Refined Coal Lique-
faction Process (EPA-600/7-78-091) represent the current database for the EA of
coal liquefaction technology. This volume summarizes pertinent information about 14
prominent coal liquefaction systems now being developed. For each system , it inclu-
des a brief description, a flow diagram, and a list of materials entering and leaving
the system. Potential applicable control techniques are described generally, along
with the current status and development plans for the 14 systems. The main conclusion
from this volume is that these processes are not environmentally defined in the pub-
lished literature; however, there is some indication that current development plans
may help to correct this situation. Volume II is an environmental characterization
of three of four selected coal liquefaction systems: Synthoil, H-Coal, and Exxon
Donor Solvent.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDEDTERMS
COS AT I Field/Group
Pollution
Coal Preparation
Liquefaction
Assessments
Pollution Control
Stationary Sources
Coal Liquefaction
Environmental Assess-
ment
13B
081
07D
14B
13. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (This Report)
Unclassified
20. SECURITY CLASS (This page)
Unclassified
21. NO. OF PAGES
202
22. PRICE
EPA Form 2220-1 (9-73)
188
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