EPA-650/2-74-009-k
September 1975
Environmental Protection Technology Series
EVALUATION OF POLLUTION CONTROL
IN FOSSIL FUEL CONVERSION
PROCESSES
COAL TREATMENT: SECTION 1. MEYERS PROCESS
U.S. Environmental Protection Agency
Office of Research and Development
Washington, D.C.2046D
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EPA-650/2-74-
EYALUATION OF POLLUTION CONTROL
IN FOSSIL FUEL CONVERSION
PROCESSES
COAL TREATMENT: SECTION 1. MEYERS PROCESS
by
E.M. Magee
Exxon Research and Engineering Company
P.O. Box 8
Linden , New Jersey 07036
Contract No. 68-02-0629
ROAP No. 21ADD-023
Program Element No. 1AB013
EPA Project Officer: William J. Rhodes
Industrial Environmental Research Laboratory
Office of Energy , Minerals, and Industry
Research Triangle Park, North Carolina 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, D. C. 20460
September 1975
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EPA REVIEW NOTICE
This report has been reviewed by the U.S. Environmental Protection
Agency and approved for publication. Approval does not signify that
the contents necessarily reflect the views and policies of the Environ-
mental Protection Agency, nor does mention of trade names or commer-
cial products constitute endorsement or recommendation for use
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environ-
mental Protection Agency, have been grouped into s'eries. These broad
categories were established to facilitate- further development and applica-
tion of environmental technology. Elimination of traditional grouping was
consciously planned to foster technology transfer and maximum interface
in related fields. These 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
9. MISCELLANEOUS
This report has been assigned to the ENVIRONMENTAL PROTECTION
TECHNOLOGY series. This series describes research performed to
develop and demonstrate instrumentation, equipment and methodology
to repair or prevent environmental degradation from point and non-
point sources of pollution. This work provides the new or improved
technology required for the control and treatment of pollution sources
to meet environmental quality standards.
This document is available to the public for sale through the National
iechmcal Information Service, Springfield, Virginia 22161.
Publication No. EPA-650/2-74-009-k
11
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TABLE OF CONTENTS
1. SUMMARY 1
2. INTRODUCTION . 2
3. PROCESS DESCRIPTION 4
3.1 Reaction Section 4
3.2 Sulfur Removal Section 8
3.3 Product Drying Section 8
3.4 Sulfur Recovery Section 8
3.5 Iron Sulfate Recovery Section 8
4. MODIFIED PROCESS DESIGN INCLUDING UTILITIES AND EFFLUENTS. . . 9
4.1 Major Design Modifications 9
4.2 Effluents to Air 9
4.2.1 Coal Storage and Preparation 9
4.2.2 Reaction Section 9
4.2.3 Sulfur Removal Section 16
4.2.4 Product Drying Section 16
4.2.5 Iron Sulfate Recovery Section 16
4.2.6 Sulfur Recovery Section 16
4.2.7 Auxiliary Facilities 17
4.2.8 Minor Vents 18
4.3 Liquid and Solid Effluents 18
4.3.1 Coal Storage and Preparation 18
4.3.2 Reaction and Sulfur Removal Sections 18
4.3.3 Product Drying Section 18
4.3.4 Iron Sulfate Recovery Section 19
4.3.5 Sulfur Recovery Section 19
4.3.6 Auxiliary Facilities 19
5. THERMAL EFFICIENCY 20
6. SULFUR BALANCE 22
7. TRACE ELEMENTS 24
8. PROCESS ALTERNATIVES AND IMPROVEMENTS 28
9. PROCESS DETAILS 33
10. TECHNOLOGY NEEDS 36
11. QUALIFICATIONS 38
12. BIBLIOGRAPHY . 39
iii
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LIST OF TABLES
No. Page
1 Stream Identification, Original Design 6
2 Stream Identification for Modificed Process 11
3 Feed Coal Analysis (Dry Basis) 15
4 Thermal Efficiency 21
5 Sulfur Balance 23
6 Minor and Trace Elements In Coal Feed (Lower Kittanning)
and Product Coal (from EPA) 25
7 Trace Element Analysis Fox Mine Lower Kittanning Seam,
Clarion County, Pennsylvania (From Ref. 9) 27
8 Material Balance for Removal of Dissolved Solids
and Iron From Meyers Process. „ 30
9 Process Alternatives and Improvements ... 32
10 Power and Steam Balance 34
11 Water Balance 35
iv
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LIST OF FIGURES
1 Original Basic Design of Meyers Process ......... 5
2 Flow Diagram - Modified Meyers' Process ......... 10
3 Flow Plan for Removal of Dissolved Solids
and Iron from Meyers Process
28
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TABLE OF CONVERSION UNITS
To Convert From
Btu
Btu/pound
Cubic feet/day
• Feet
Gallons/minute
Inches
Pounds
Pounds/Btu
Pounds/hour
Pounds/square inch
Tons
Tons/day
To
Calories, kg
Calories, kg/kilogram
Cubic meters/day
Meters
Cubic meters/minute
Centimeters
Kilograms
Kilograms/calorie8kg
Kilograms/hour
Kilograms/square centimeter
Metric tons
Metric tons/day
Multiply By
0.25198
0.55552
0.028317
0,313480
0.0037854
»
2.5400
0.45359
1.8001
0-45359
0.070307
0.90719
0.90719
vi
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1. SUMMARY
The Meyers process being developed by TRW, Inc. has been reviewed
from the standpoint of its potential for affecting the environment. The
quantities of solid, liquid and gaseous effluents have been estimated,
where possible, as well as the thermal efficiency of the process. For the
purpose of reduced environmental impact, a number of possible process modifi-
cations or alternatives, which could facilitate pollution control or increase
thermal efficiency, have been proposed; and new technology needs have been
pointed out.
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2. INTRODUCTION
Along with improved control of air and water pollution, the
country is faced with urgent needs for energy sources. To improve the
energy situation, intensive efforts are under way to upgrade coal the
most plentiful domestic fuel, to liquid and gaseous fuels which give
less pollution. Other processes are intended to convert liquid fuels to
gas. A few of the coal gasification processes are already commercially
proven, and several others are being developed in large pilot plants. These
programs are extensive and will cost millions of dollars, but this is
warranted by the projected high cost for commercial gasification plants
and the wide application expected in order to meet national needs. Coal
conversion is faced with potential pollution problems that are common to
coal-burning electric utility power plants in addition to pollution pro-
blems peculiar to the conversion process. It is thus important to examine
alternative conversion processes from the standpoint of pollution and
thermal efficiencies and these should be compared with direct coal utili-
zation when applicable. This type of examination is needed well before
plans are initiated for commercial applications. Therefore, the Environ-
mental Protection Agency arranged for such a study to be made by Exxon*
Research and Engineering Company under contract EPA-68-02-0629, using all
available non°proprietary information.
The present study under the contract involves preliminary design
work to assume that conversion processes are free from pollution where pol-
lution abatement techniques are available, to determine the overall efficiency
of the processes and to point out areas where present technology and infor-
mation are not available to assure that the processes are non-polluting.
All significant input streams to the processes must be defined
as well as all effluents and their compositions. This requires complete'
mass and energy balances to define all gas, liquid, and solid streams.
With this information, facilities for control of pollution can be examined
and modified as required to meet Environmental Protection Agency objectives
Thermal efficiency is also calculated, since it indicates the amount of
waste heat that must be rejected to ambient air and water and is related to
the total pollution caused by the production of a given quantity of clean
fuel. Alternatively, it is a way of estimating the amount of raw fael
resources that are consumed in making the relatively pollution-free fuel
At this time of energy shortage this is an important consideration.
Suggestions are included concerning technology gaps that exist for techniques
to control pollution or conserve energy. Maximum use was made of the lit-
erature and information available from developers. Visits with some of the
developers were made, when it appeared warranted, to develop and update
published information. Not included in this study are such areas as cost
economics, operability, etc. Coal mining and general offsite facilities
are not within the scope of this study.
Prior to June 1, 1974 Exxon Research and Engineering Company conducted
business under the name Esso Research and Engineering Company.
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Our previous studies in this program to examine environmental
aspects of fossil fuel conversion processes covered various methods
for coal conversion to clean fuels. Reports have been issued on both gasi-
fication and liquefaction processes including Koppers-Totzek, Synthane,
Lurgi, C02 Acceptor, COED, SRC and BI-GAS processes (1,2,3,4,5,6,7). The
present report extends these studies to include chemical cleaning of coal by
the Meyers process being developed by TRW, Inc. under contract to EPA. In
this process pyritic sulfur is removed from coal by the action of a solution
of ferric sulfate. The coal is not "converted," and it essentially retains
its original heating value. The pyritic sulfur leaves the process as elemental
sulfur and iron sulfates.
We wish to acknowledge the information and assistance provided
by the Environmental Protection Agency. This study, is based, to a
large extent, on information supplied by EPA and on reports published
by TRW, Inc. for EPA.
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3. PROCESS DESCRIPTION
In the Meyers process, the pyrites in the coal are removed
by reaction with ferric sulfate in a solution containing ferric and
ferrous sulfates and sulfuric acid. The ferric ion is continuously
regenerated by reaction of oxygen and ferrous ion. The elemental
sulfur product is extracted with an organic solvent. The iron product
from the pyrites is removed as solid ferric and ferrous sulfates.
A block flow diagram of the basic Meyers process is shown in
Figure 1. The contents of the indicated streams are shown in Table 1=
This diagram and description are based on information supplied by EPA
(in the form of a process flow sheet produced by Dow Chemical U.S.A.).
and EPA reports (8,9). Later evaluations of the process may be
available but for the present study no improvement would be expected
in the results without pilot unit data. The process description is not
complete without utilities, coal preparation and storage, etc. These
items will be addressed later in this report.
A more recent design for a commercial plant has been completed
by Dow Chemical U.S. A. (12) That design has a more conservative approach
to heat integration than the one used in the present work, produces a
drier, compacted product and shows electricity to be purchased.
3d Reactor Section
Coal that has been ground to less than 100 mesh (Str. 2) is
mixed with recycled leach solution (Strs. 8, 11, 13) in a flow through
mixing tank. The mixing vessel is maintained at about 210°F. The
slurry is continually pumped from the mixing vessel to one of 10 reactor
vessels.
In the reactor vessels, the slurry is contacted with oxygen
at ©bout 300°F. The pyritic sulfur is 95% converted to elemental
sulfur and sulfate in the reactor vessels. The reactions taking place in
the reactors are shown below:
Leaching Reactions
(1) FeS2 + Fe2(S04)3 - *> 3FeS04 + 2S
(2) FeS2 + 7Fe2(S04)3 + 8H20 - £> 15FeS04 + 8H2S04
Since the net 304:8 production from FeS2 is approximately 1.5:1, the
overall leaching reaction is:
(3) FeS2 + 4.6 Fe2(S04>3 + 4.8 H20 — J> 10.2 FeS04 + 4.8 H2S04 + 0.8 S
Regeneration Reaction
(4) 9.6 FeS04 + 4.8 H2S04 + 2.4 02 — J> 4.8 Fe2(S04)3 + 4.8
Net Overall Reaction
(5) FeS2 -1-2.4 02 — $> 0.2 Fe2(S04)3 + 0.6 FeS04 + 0.8 S
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Oxygen
Feed Coal
Iron Sulfate
Product
Vent
A
Reaction
Section
Iron Sulfate
Recovery Section
Vent
Recycle Leach Sol.
Coal and Leach
Solution
Leach Sol.
Recycle Leach Sol
Water
Water
Sulfur Removal
Section
Rich
Sulfur
Solvent
Wet Coal
Solvent
and Water
Leach Sulfur
Solvent
Sulfur Recovery
Section
Product Sulfur
Solvent
Product Drying
Section
Product Coal
i
Ul
I
figure 1
Original Basic Design of Meyers Process
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Table 1
Stream 2
Coal* 188, 000
FeS2 12,000
S
FeS04
Fe2(S04)3
H2S04
H2o 20,000
Solvent
°2
Inert
Stream Identification, Original Design, Ib/hr
3 4 56789
188,000 187,800 187,800
600 600 600
2,400
30,000 18,000
122,800 200 200 73,800
6,800 4,000
662,800 47,000 3V, 600 660 466,400 200
9,400 . 200
7,296
40 40
10 11
1,000
31,600
2,200
9,400 126,600
9,400
Total 220,000 1,013,400 245,000 226,200 7,336 700 562,200 400 18,800 161,400
* Feed coal ex pyrites and moisture,
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Total
Table 1 (Cont'd)
Stream Identification, Original Design. Ib/hr
15
16
17
18
19
20
stream
Coal
S
FeSO,
H2S°4
HO
2
Solvent
°2
Inert
L£. i.-»
200
9,600 2,400
39,600 9,800
2, 200 600
231,000 50,400
200
2,400 2,400
2,400 8,600
9,800 7,400
65,400 137,800 104,400 8,400
255,800 256,000 20°
282,000 63,200 336,400 393,800 104,400 2,400 16,200 8,400
200
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The excess ferric and ferrous sulfates must be removed from the
system. The slurry is cooled by heat exchange with fresh feed and then
by cooling water and is pumped to the Sulfur Removal Section (Str. 3).
3.2 Sulfur Removal Section
In the Sulfur Removal Section, approximately 6070 of the leach
solution is removed in hydroclones and recycled to the Reaction Section
(Str. 8). The remaining leach solution is removed by filtration and is
passed to the Iron Sulfate Recovery Section (Str. 12).
The wet filter cake is washed with water and then mixed with
recycle solvent (e.g., light naphtha) at 160°F and most of the elemental
sulfur is dissolved. The resulting slurry is filtered to remove the
cleaned coal which passes to the Product Drying Section (Str. 4). The
sulfur-rich solvent is separated from water by decantation and passes to
the sulfur recovery section (Str. 14).
3.3 Product Drying Section
The treated coal, containing about 257, moisture and 57» solvent
(dry basis), is conducted to the drying section (Str. 4). The coal is
partially dried under vacuum; the sensible heat of the coal is sufficient
to remove all the solvent and about 2070 of the water. The vapors are returned
to the Sulfur Removal Section (Str. 10) where they are condensed in a
water cooled vessel. The water and solvent are separated by decantation
and reused in the process. The coal product, containing 207» moisture
(dry basis) then leaves the process (Str. 5).
3.4' Sulfur Recovery Section
The sulfur-laden solvent and miscellaneous solvent and water
streams are passed to the Sulfur Recovery Section (Str. 14). The solvent
is removed from the sulfur by distillation and the sulfur leaves the pro-
cess (Str. 17). Water and rich solvent are separated by decantation. The
water is recycled to the Reaction Section (Str. 13) and the solvent is
returned to tha Sulfur Removal Section (Str. 15). Makeup water and solvent
(Strs. 19 and 20) are added to the system through the Sulfur Recovery Section.
3.5 Iron Sulfate Recovery Section
The water filtrate from filtration in the Sulfur Removal Section
passes to the Iron Sulfate Recovery Section (Str. 12). Since the process
produces iron from the pyrites, it is necessary to remove iron from the
system. The filtrate is heated to about 265°FS and some of the water is
flashed overhead. Part of the steam thus formed is returned to the
Reaction Section (in Str. 11) and part passes to the Sulfur Recovery Section
in stream 16. The remaining slurry of iron sulfates is filtered at 215°F
to produce an iron sulfate filter cake for disposal. The filtrate is returned
to the Reaction Section.
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4. MODIFIED PROCESS DESIGN INCLUDING
UTILITIES AND EFFLUENTS
To more carefully assess the pollution potential and the thermal
efficiency of the Meyers Process, an oxygen plant, coal preparation and
storage and utilities have been included in the design and other slight
changes have been made. The complete block diagram for the plant is shown
in Figure 2 and the streams are identified in Table 2. An asterisk (*)
indicates streams released to the environment.
4.1 Major Design Modifications
The plant has been made self sufficient with regard to all
utilities. Steam and power are generated internally, water treatment
facilities have been included, a cooling tower has been added to allow
recycling the cooling water, the coal storage and preparation section
was added and an oxygen plant has been assumed.
The coal analysis assumed in the present study is given in
Table 3. This analysis corresponds to that of the Lower Kittanning coal
given on page 10 of reference 8 except the pyritic sulfur content has
been assumed to be 3.21% (dry basis) instead of 3.58% and the moisture
has been assumed to be 10% to conform to previous design studies of the
process (e.g., stream 1, Table 29, p. 120 of Ref. 8). Reference 9,
p. 126, gives a pyritic sulfur content of 3.09%. Such changes will have
little effect on the conclusions of this study.
4.2 Effluents to Air
4.2.1 Coal Storage and Preparation
ROM coal, 8 in. X- 0, is received at the plant and stored. Three
days storage (7920 tons, wet) has been suggested. This quantity of coal
would probably be stored in silos with nitrogen blanketing. It would
probably be advisable to store more coal (e.g., 30 days supply) in a
"permanent" pile for emergency use. This pile could be covered with
asphalt and used only in case of mine outage.
The ROM coal is conveyed to pulverizers where the coal is reduced
to 80% less than 200 mesh. (This size is smaller than previous designs
and is used to enhance reaction rates as well as to provide a product
size suitable for combustion). The coal from the pulverizers is then fed
to the Reaction Section.
It is not necessary to dry the coal as it is subsequently
slurried in a water solution. It is assumed that covered conveyers will
be used throughout to minimize dust problems. The coal dimunition
equipment can be enclosed, with air vented to bag filters. This will
reduce outside noise as well as provide for dust containment.
4.2.2 Reaction Section
Except for minor vents, which will be discussed later, no air
effluents are emitted from the reaction section.
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46
A
47
A
Coal Storage and
Preparation Section
Note: Heavy dashed lines are
effluent streams; others
are used in plant or
are products.
30 31
Oxygen
Plant
t
21
Reaction
Section
Iron Sulfate
Recovery Section
32 33 34
35
A
Makeup
Water
Treatment
Sulfur Removal
Section
Sulfur
Recovery
Section
1L
36 37 38 39 40
A
Cooling
" Tower
25
26
Product
Drying
Section
42 43
44
£
Steam and
Power
Generation
29
Figure 2
Flow Diagram - Modified Meyers Process
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TOTAL
Table 2
Stream Identification for Modified Process, Lb/Hr
10
Stream 1 *
Coal* 188,000 188,000
FeS2 12,000 12,000
S
FeS04
H 0 20,000 20,000
Solvent
°2
Inert
188,000 187,800 187,800
602 602 602
2,438
30,060 18,°°°
122,798 200 200 73,800
6,800 4>°°°
662,800 47,000 37,600 660 466,400 200 9,400
9,400 20° 9>400
7,296
40 40
220,000 220,000 1,013,498 245,020 226,220 7,336 700 562,200 400 18,800
* Feed coal, ex pyrites and moisture.
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Table 2 (Continued)
Stream
Coal
FeS2
S
FeS04
H2S°4
Solvent
°2
Inert
TOTAL
Stream Identification for Modified Process, Lb/Hr,
n 12 13 14 15 16 17 18 19 20
200 20°
2,438 2,438
1,000 9,660 2,400 2,400 8.660
31,600 38,998 9,800 9,800 7»398
2,200 2,200 600 600
126,600 231,000 50,460 65,400 137,800 104,400 18,460
255,800 256,000 20°
161,400 282,058 63,260 336,438 393,800 104,400 2,438 16,258 18,460 200
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- 13 -
Table 2 (Continued)
Stream Identification for Modified Process, Lb/Hr
21 - Air to 0. Plant
22 - Chemicals
23 - Water
24 - Air
25 - Water
26 - Water
27 - Product Coal
28 - Air
29 - Water
30 - Water
*31 - Nitrogen
*32 - Sludge
33 - Boiler Feed
Water Makeup
34 - Cooling Water
*35 - Backwash
*36 - Air From Cooling
Tower
*37 - Drift Loss Water
*38 - Water Vapor
31,520
153,850
12,700,000
(4 X 109 scfd)
135,560
7,083,600
13,234 (Dry)
141,229
126,000
170
24.050
5,830
129,560
12,700,000
(4 X 109 scfd)
14,160
100,000
Air to Cooling Tower
Makeup Water to Cooling
Tower at 85°F
Water plus makeup recirc.
to Cooling Tower at 105°
Product Coal to Utility
Boiler
Air to Boiler
Boiler Feed Water (Includes
6000 Ih/hr makeup water)
Moisture from Air to Boiler
Feed Water
Vent from 02 Plant, can be
used is coal silos
From Treating Makeup Water
To Steam Generation
Makeup
Air from Cooling Tower
Water Mist to Air
Water Evaporated from
Cooling Tower
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- 14 -
Table 2 (Continued)
Stream Identification for Modified Process, Lb/Hr
*39 - Slowdown Water
40 - Cooling Water
*41 - Flue Gas
42 - Blow Down Water
43 - Steam
*44 - Ash
45 - Rain**
*46 - Rain Run Off**
*47 - Dust
21,400
7,083,600
154,570
6,000
120,000
2,541
e.g. 6" Rain in
24 Hours
e.g. 6" Rain in
24 Hours
Purge from Cooling Tower
to Holding Pond
From Utility Boiler
To Cooling Tower Makeup
Rain on Coal Storage
and Preparation Area
From Coal Storage
and Preparation Area
From Coal Preparation
Collect in Bag Filters
* These streams are emitted to the environment.
** Not applicable if all storage-is in silos.
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- 15 -
Table 3
Feed Coal Analysis (Dry Basis)
Proximate Analysis, Wt. %
Fixed carbon 53.48
Volatile matter 20.66
Ash 20.R6
Moisture = 1070 wt. dry coal
(assumed)
Heating value
HHV (dry) - 12140 Btu/lb
Ultimate Analysis, Wt.
Carbon
Hydrogen
Nitrogen
Chlorine
Sulfur
Ash
Oxygen (difference)
68.53
3.85
1.20
0.08
3.92
20.86
1.56
Sulfur Forms
Pyritic
Sulfate
Organic
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- 16 -
4.2.3 Sulfur Removal Section
The only effluents in the Sulfur Removal Section come from vents
which are discussed later. Pressure filtration is used, thus vapors are
e nclosed.
4=2.4 Product Drying Section
The naphtha solvent and a portion of the water are removed from
the product coal by vacuum. The resulting vapors are condensed and returned
to the process system.
The dry product coal heating value has been increased by ca 570
(Ref. 8), from 12,140 Btu/lb to 12,747 Btu/lb due to ash removal. With added
sulfate and elemental sulfur the product contains approximately 0.95% sulfur
in the following forms:
Sulfur Form
Pyritic
Elemental
Sulfate
Organic
0.95%
(This is the analysis used in Ref. 8 but corrected for the decrease in
coal weight in processing.)
No information is available on techniques available for drying
the product coal. It is assumed that the product coal will be burned as is.
Part of the coal (13,234 Ib/hr, dry basis) is used in the steam plant.
Thus, net product is 175,366 Ib/hr (dry).
4.2.5 Iron Sulfate Recovery Section
Except for minor vents, there are no air effluents from the iron
sulfate section., The filter is assumed to be enclosed to prevent vapors
from escaping. It is also assumed that the product iron sulfates will be
handled in a moist form to avoid dusting.
4.2.6 Sulfur Recovery Section
Again, this section is completely enclosed except for vents and
there are no effluents to the air. If the sulfur product is stored as a
liquid, there will be no emissions since the storage and handling facilities
will be enclosed. If the product is handled and stored as a solid, then
control of dust is necessary.
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- 17 -
4.2.7 Auxiliary Facilities
The auxiliary facilities in the complex include an oxygen plant,
raw water treatment, cooling towers and steam and power generating
facilities. These auxiliary units must be considered to evaluate effluent
problems and overall thermal efficiency.
The oxygen plant is a major consumer of power and there is a
large gaseous effluent. It has been assumed in the present design that
an extraction turbine, using 600 psig steam, is used to drive the air com-
pressor in the oxygen plant. The extraction steam, at 115 psig, is utilized
in the rest of the plant. The effluent to the air consists of 24,050 Ib/hr
(5435 cu ft/min) of relatively pure nitrogen which requires no cleaning.
Moisture containing air from the cooling tower represents the
largest effluent to the atmosphere. In this particular plant the cooling
water should be relatively free of volatile materials; pressures on the
heat exchangers are low and, except for the organic solvent, no volatile
organics have been reported as being present in the reaction system. Fog
formation can sometimes represent a problem with cooling towers. The extent
of this problem is determined in large part by the plant location. Drift
loss from the cooling tower can cause dust problems when the solids in the
cooling water are deposited. It is expected that cooling tower blowdown
will be sent to an evaporation pond. Due to the nature of the present
process, there should be no noxious fumes from this pond if there are no
leaks in the naphtha heat exchangers.
A raw water treatment system is provided to furnish makeup water
to the steam boiler and cooling tower. No air effluents are expected from
this unit.
Product ccal is burned in the steam plant and the flue gas
represents the largest quantity of noxious contaminants emitted to the
atmosphere. The combustion gas contains dust, NOX, CO and sulfur compounds
and these must be controlled. The use of product in the boiler furnace
also affects the thermal efficiency of the overall plant. Control of
particulate matter can be effected by the use of commercial electrostatic
precipitators, cyclones and/or scrubbers. The use of excess air should
reduce the CO content of the stack gas. NOX emissions can be reduced by
careful control of combustion conditions and staged firing. The ultimate
limit on NO* reductions has not been reached as considerable work is in
progress on techniques for NOX control. It is expected that a technique
will be developed eventually for direct removal of WO^ from stack gases or
for its conversion to W2a Thls problem, however, could exist for a long
time.
Sulfur in the flue gas represents a problem. The sulfur in the
product coal produces 1.49 Ib of S02 per million Btu. This is higher than
the present Federal limit of 1.2 Ib S02/MM Btu for large power plants. The
major part of this sulfur in the fuel is in the form of organic sulfur
(0.717. out of Oo95%) which is not resaoved in the process. In many coals,
the organic sulfur content (and total sulfur in the product coal) is much
higher than that shown here (Ref, 9, Appendix D). It is thus expected that,
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- 18 -
for most coal feeds, the total sulfur in the product coal will be higher
than that used here. Though the total sulfur has been decreased remarkably,
the content would indicate the need for stack gas scrubbing on the boiler
furnace stack. This, however, would defeat the purpose of using product
coal for boiler fuel.
For some coals, the product may be used as fuel so that emissions
meet Federal regulations for new installations. It has been estimated (10)
that the percentage of Appalachian coals meeting the requirement of 1.2 Ib
S02 emissions per million Btu could be increased from about 10% to 40%.
Due to variations in pyrites removal and increase in sulfate content, these
coals would, of course, have to be tested. That some coals can be desulfurized
to meet existing regulations has been recently reported (11).
4.2.8 Minor Vents
It is expected that the effluents from minor vents in the process
will be collected. The moisture and solvent vapor will be condensed and
returned to the system. The net vent gas can be incinerated in the utility
furnace.
4.3 Liquid and Solid Effluents
4.3.1 Coal Storage and Preparation
The major liquid and solid effluents from this area consist of
rain runoff and wash water from coal dust removal. This water should be
sent to a storm pond where solids can settle out. If there are no spills
of organic materials in the process area, storm drainage from this area can
also be sent to this holding pond. After sufficient settling time, the
water from this pond can be used as raw process water. The pH of the pond
water can be corrected for acid content by limestone addition to the pond
circuit or the treatment can be accomplished in the makeup Water Treatment
Section. The pond should be large enough to prevent contamination by
overflow and, if the soil is such that seepage would be a problem, the
bottom of the pond should be lined with clay, concrete or other impervious
material.
4.3.2 Reaction and Sulfur Removal Sections
There are no liquid or solid plant effluent streams from the
Reaction and Sulfur Removal Sections.
4.3.3 Product Drying Section
The only effluent stream from the Product Drying Section is the
product itself. This product contains part of the sulfur input to the plant,
much of the minor element input and the major part of the trace element
input. The water and solvent removed from the coal in this section are
returned to the process. The further transportation, use or storage of the
product is not specified, but enclosed transport should be used to prevent
dusting problems.
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4.3.4 Irou Sulfate Recovery Section
The effluent ^ from the Iron Svil fate Recovery Section consists mainly
of ferrous and ferric sulfate; " The moisture content of this material as
well as its Disposition, are unspecified. There doesn't seem to be a simple
solution to the disposition problem as the material is water soluble and
will be acidic. This problem is considered further under Potential
Improvements .
4.3.5 Sulfur Recovery Section
l
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- 20 -
5. THERMAL EFFICIENCY
The basic thermal efficiency of the Meyers' Process, using the
present design, is estimated to be 92,1% (see Table .4). This is the heat-
ing value of the net product (total product less 13,234 Ib/hr (dry) that is
burned to generate steam) divided by the heating value of input coal. If the
heating value of the by-product sulfur is included, the thermal efficiency
rises to 92.5%. Results are summarized in Table 4.
It will be necessary to remove dissolved solids (other than iron
sulfates) from the reaction section water circuit. One way of accomplishing
this is to remove the iron sulfates in a water purge stream instead of
filtering. It is then unnecessary to evaporate a large amount of water and
the total thermal efficiency rises to about 92.6%. Debits (mainly, sulfuric
acid makeup) occur, however, in this type of iron sulfate removal; these
are discussed in Section 8.
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Table 4
Thermal Efficiency
Net thermal e'fficiency 92.1%
Including sulfur product 92.'5%'
Without water evaporation 92.6%
in iron sulfate removal*
* See Section 8 for a description of this
alternative and the debits thereby incurred.
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- 22 -
6. SULFURBALANCE
A detailed sulfur balance for the Meyers' process is shown in
Table 5. In the present design, most of the sulfur exits the plant in
solids; the boiler stack is the only source of gaseous sulfur emission.
As indicated earlier, most of the sulfur in the coal product, is in the
form of organic sulfur not removed in the processing.
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Table 5
Sulfur Balance
Ib/hr
Sulfur Into Plant
In coal feed 7,836
Pyritic 6416
Sulfate 80
Organic 1340
Sulfur Out of Plant
In product coal 1, 788
Net product coal 1,663
Boiler stack gas 125
In coal loss 2
In FeSO^ 1,828
In Fe2(S04)3 1,780
Product sulfur 2,438
Total sulfur from plant 7,836
Percent
100.0
81.9
1.0
17.1
22.82
21.22
1.60
0.03
23.33
22.72
31.11
100.0
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- 24 -
7. TRACE' ELEMENTS
The Meyers process offers an excellent example of how potentially
hazardous trace elements can buildup in a coal treating plant. Reference to
Figure 2 shows that the only egress of water from the process (other than
minor vents) occurs with the product coal in Stream 5. (An unknown amount
of water leaves with the iron sulfate in stream 18 as surface moisture and
water of hydration.) The concentration of trace elements that are soluble
will build up in the water recycled to the Reaction Section. Although the
concentration can be limited by withdrawing a purge stream from the cir-
cuit, as indicated in a later section, the concentration level of dissolved
solids is still somewhat arbitrary.
Analyses furnished by EPA for minor and trace elements in a Lower
Kittanning coal are shown in Table 6 for both treated and untreated coal.
The table indicates significant reductions in calcium, copper, iron,
magnesium, manganese, nickel, potassium, sodium, sulfur, titanium and zinc.
Some elements of interest, such as arsenic, are below the limits of analysis
and whether or not these are dissolved is unknown.
Table 7 shows analyses for trace elements in a treated and
untreated Lower Kittanning coal (reference 8, p. 189). Elements that are
depleted by-action of the pyrites leach solution are arsenic, boron,
beryllium, chromium, copper, fluorine, manganese, nickel, selenium and zinc.
From the viewpoint that the product coal contains less of some
potentially hazardous elements, leaching of these elements is beneficial.
It should be kept in mind, however, that this leaching will concentrate
these elements in a small area (depending on the method used for disposing
of the purge from the reaction water circuit). More work is necessary to
define potential problems from trace elements. A recycle system would be
advantageous in ascertaining the extent of dissolved solids buildup.
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- 25 -
Table 6
Minor and Trace Elements In
Coal Feed (Lower Kittanning)
and Product Coal (from EPA), .ppm
Element Method Untreated
Aluminum
Antimony
Arsenic
Beryllium
Bismuth
Boron
Cadmium
Cadmium
Calcium
Chloride
Chromium
Chromiium
Cobalt
Copper
Copper-
Fluoride
Germanium
Iron
Iron
Lead
Lead
Lithium
Magnesium
Manganese
Manganese
Mercury
Mercury
Molybdenum
Nickel
Nickel
Nitrogen
Potassium
ES 19000.
ES <2.
ES <2.
ES Kl.
ES *1.
ES 66 .
AA 2.4
ES <5.
ES 1100.
NA 8600.
AA 30.
ES 44.
ES 11.
AA 12.
ES 40.
IE 17.
ES 22.
AA 40000.
ES 33000.
AA 21.
ES 80.
ES 9.
ES 1300.
AA 28.
ES 40.
AA 0.5
ES <0.2
ES 220.
AA 50.
ES 88.
COU 3000.
ES 6600.
AA - Atomic Absorption
ES - Emission Spectrochemical
NA - Neutron Activation
IE - Ion Electrode
COM - Combustion
COU - Coulometric
G - Gravimetric
Treated
22000.
66.
2,0
440.
8500.
32.
42.
15.
7.0
12.
18.
22.
16700.
19000.
29.
82.
9.
880.
15.
12.
0.6
•c-0.2
220.
30.
44.
3000.
4400.
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- 26 -
Table 6 (Cont'd)
Minor and Trace Elements In
Coal Feed (Lower Kittanning)
and Product Coal (from EPA), ppm
Element Method
Samarium
Selenium
Silicon
Silver
Silver
Sodium
Strontium
Sulfur
Tellurium
Thorium
Tin
Titanium
Vanadium
Vanadium
Zinc
Zinc
Zirconium
ES
ES
ES
AA
ES
ES
ES
COM
ES
ES
ES
ES
NA
ES
AA
ES
ES
Untreated
X10.
<10.
66000.
0.98
1.
660.
44.
33000.
<10.
<10.
2.
440.
22.
44.
32.
40.
<4.
AA - Atomic Absorption
ES - Emission Spectrochemical
NA - Neutron Activation
IE - Ion Electrode
COM - Combustion
COU - Coulometric
Treated
68000.
0.97
1.
400.
44.
14000.
2.
400.
28.
44.
20.
22.
4.
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Element
Ag
As
B
Be
Cd
Cr
Cu
F
Hg
Li
Mn
Ni
Pb
Sb
Se
Sn
V
Zn
Table 7
Trace Element Analysis
Fox Mine
Lower Kittanning Seam,
Clarion County, Pennsylvania (From Ref. 9)
Average Values, oorn
ffntreated
<.l
23.5 + 1.5
16 + 1.7
2.0 +0.6
<.5
94+4.3
25 + 2.4
93.5 + 2.1
0.07 + 0.01
4 + 0.1
24 + 2.5
147 + 5.1
5 + 2.9
<1
17 + 7.2
"C2.5
94 + 11.8
105 + 7.1
Treated
1.1 + 1.1
1.4 + 1.2
13+0
0,6 + 0.2
<.5
40 + 4.5
14 + 0.6
82+0
0.15 + 0.02
15 + 0.6
9 + 1.2
11 + 1.1
12 + 0.6
< 1
X2.5
<2.5
115 + 10
11 + 0.6
ppm. Change
+1.1 + 1.1
-22.1 + 1.9
-3 + 1.7
-1.4 + 0.6
Ind
-54 + 6.2
-11 + 2.5
-11.5 + 2.1
+0.08 + 0.02
+11 + 0.6
-15 + 2.8
-136 + 5.2
+7 + 3
Ind
-15 + 7.2
Ind
+21 + 15
-94 + 7.1
Change
N.D.
-94 + 5
19+9
-70 +
Ind
-58 + 5
44 + 6
-12 + 2
Gain
Gain
63 + 6
-93 + 1
Gain
Ind
-85%
Ind
Gain
-90 + 1
14
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8. PROCESS ALTERNATIVES AND IMPROVEMENTS
One process alternative is the use of a settling tank instead of
hydroclones to reduce the water content of the solids from the reactor
prior to filtration. This technique was suggested in.reference 8. The
use of a settling tank allows part of the reaction to take place in the
tank and reduces the size of the reactors. A cost/efficiency analysis
would be required to determine the best solids concentration technique.
Another process alternative discussed in reference 8 is the use
of submerged combustion instead of steam to evaporate water before filter-
ing the iron sulfates in the Iron Sulfate Recovery Section. Although a
detailed cost comparison would be necessary to decide which method of
evaporation is cheapest, it is felt that the use of steam would be the
better of the two. Low pressure steam can be made available from the
utilities area to give1a steam balance and condensation of moisture from
the large volume of combustion gas is then unnecessary.
It is felt that recovery of sulfur in a fractionation unit is
preferable to the use of a pressure filter as suggested in Reference 8.
Very little additional heat input is necessary for evaporation of the
solvent. Again, however, a cost/efficiency evaluation would be necessary
before a choice of units could be made.
If the Meyiers. process were located near a large power plant,
steam and power requirements might be purchased. Since the plant location
is, unknown, the production of steam and power has been included in the
present design.
As indicated previously, it will be necessary to prevent excessive
buildup.of solids dissolved from the coal. It is possible that the soluble
materials can be allowed to buildup to the point where they begin to
precipitate with the iron sulfates in the Iron Sulfate Removal Section. If
this steady-state concentration does not affect the operability of the
process, then the minor and trace elements can be disposed of with the
iron sulfates. Otherwise, a purge stream from the process water circuit
must be included. One simple method of accomplishing this is to replace
the Iron Sulfate Recovery Section shown in figure 2 with the system shown
in figure 3. The composition of the streams in figure 3 are given in
Table 8.
In this disposal scheme, a fraction (0.3635) of stream 12, leach
solution from filtration in the Sulfur Removal Section, sufficient to remove
the necessary iron, is purged as stream B in figure 3. The remainder is passed
to a reactor where sulfuric acid and oxygen are added to convert sufficient fer-
rous sulfate to ferric sulfate to give the iron compositions of stream 11 in
figure 2. Sufficient water is flashed to give the water content of stream 11
and this stream is then returned to the Reaction Section. Make-up water (Stream
G) is added to the overhead from the flash tank (stream F) to give stream 16
of figure 2 and this is passed to the Sulfur Recovery Section. Alternatively,
stream A of figure 3 could go first to the Water Flash Tank and the bottoms
could be returned to the Reaction Section. In this case, the aulfuric
acid and extra oxygen would be added directly to the Reaction Section.
-------
Makeup
Purge to
Water
Evaporation Pond
from Sulfur Removal
Section of Figure 2
Sulfuric Acid
Oxygen —
^>
Ferrous Sulfate
Oxidation Unit
Stream 16 To. Sulfur
Recovery Section
of Figure 2
Water
Flash
Stream 11 To
Reaction Section
of Figure 2
NJ
VO
Figure J
Flow Plan for Removal of Dissolved
Solids and Iron from Meyers Process
-------
Stream —* 12
Chemical
FeS04
H2S°4
- 30 -
Table 8
Material Balance for Removal of Dissolved Solids
A
6,149
24,824
1,400
B C D E F
3,511 -- -- 1,000
14,174 -- -- 31,600
800 2,462 -- 2,200
G 11 16
1,000
31,600
2,200
231,000 147,038 83,962 -- -- 147,343 20,743 83,657 126,600 104,400
02 -- -- -- .. 271
TOTAL 281,858 179,411 102,447 2,462 271 182,143 20,743 83,657 161,400 104,400
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- 31 -
The debits incurred by this scheme are:
• An increase in oxygen consumption of 271.Ib/hr
• An additional 83,657 Ib/hr. of process water
'. Addition of 2462 Ib/hr of H2S04
• An evaporation pond for the purge
The credits for this scheme are:
• Savings of cooling water
• Steam savings for evaporation of approximately
31,000 Ib/hr of water
• No filter required for iron removal
It is assumed that the purge stream will go to an evaporation pond for con-
tainment of the solids and acid. If naturalization of the acid is necessary,
then limestone will be required.
The concentration of dissolved solids will be the weight of solids
dissolved from the entering coal divided by the quantity of water purged in
stream 2 of figure 3 (83,962 Ib/hr of water). Thus, if 1% (ex P^"^
of the feed coal is dissolved, the concentration in stream 2 is 23,820 ppm.
The concentration of dissolved solids will vary with the coal feed used.
Thus, it has been found that the quantity of ash removed other than that
representing pyrites, varys over a ten-fold range (Ref. 8, Table 13). To
increase the dissolved solids content of the recycle water stream, "would
be necessary to remove part of the iron sulfate by precipitation and filtration
as in the basic case. To decrease the solids content it would be necessary
to purge a larger stream from the system. The iron content could be madeup
by precipitation of part of the iron from the purge stream, filtering it
and returning it to the system.
A different technique for removing dissolved solids has been
suggested in a recent design for the Meyers process'^). This involves
evaporation of a portion of the sulfate stream to essentially dryness
whereupon the dissolved solids are removed with the iron sulfate.
The process alternatives and improvements are summarized in
Table 9.
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- 32 -
Table 9
Process Alternatives and Improvements
Use settling tank rather than hydroclones to increase
solids content in stream from reactor.
• Use submerged combustion to evaporate water from
iron sulfates solution.
• Use of a filter to remove elemental sulfur rather
than fractionation.
• Purchase steam and electricity.
• Purge iron from system in solution form to remove other
dissolved solids.
• Evaporate a portion of the iron sulfate to dryness and
remove solids.
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- 33 -
9. PROCESS DETAILS
Power and steam production and requirements are shown in Table 10,
The plant water balance is given in Table 11.
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- 34.-
Table-10
Power and Steam Balance
Electricity
Utilities kW 600 psia Steam 115 psia Steam
~"Ib/hr. Ib/hr.
Consumed
Coal Preparation 2,740
Steam to vaporize H20 in plant -* 120,000
Oxygen Plant 23,000
Power generation 97,000
Cooling water pumps 420
Cooling tower fans 260
Boiler feed water pumps 110
Rest of plant 1,000
4,530 120,000 120,000
Produced
Power generation 4,530
Steam plant 120,000
From 600 psia Steam 120»000
4,530 120,000 120,000
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- 35 -
Table 11
Water Balance*
Into Plant
To makeup water treatment
In feed coal
In air to 02 plant
TOTAL IN
Out of Plant
Cooling tower
Evaporation 100,000
Drift 14,160
Blow Down 21,400
Ib/hr
153,850
20,000
170
174,020
135,560
In total product coal
Vents
Iron sulfate product
TOTAL OUT
37,600
860
(Unknown)**
174,020
* Excluding potable water and sanitary sewer.
** Any positive value would necessitate increased makeup,
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- 36 -
10. TECHNOLOGY NEEDS
In order to more clearly define and quantify potential pollution
problems, certain areas will have to be investigated in more detail.than
has been done heretofore. The major items requiring further investigation
are discussed here.
One major item that may need further work involves overall sulfur
removal from coal.: As indicated previously, some coals
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- 37 -
The quantity of water in the product coal requires quantification.
The suitability of the product for furnace fuel could be affected consider-
ably if the product is sticky. If the moisture in the product is too
great, drying may have to be provided and this would decrease the thermal
efficiency.
A better method of disposal of the iron sulfates is needed since
the quantity of this byproduct for the present case is almost 200 "tons
per day. Although a holding pond has been assumed in this study for iron
sulfate disposal, it would be preferable if a method were available to
recover the iron and sulfur values from the material. In any case, the
quantity of surface moisture and water of hydration leaving with the iron
sulfates should be defined as this will affect the quantity of make up
water.
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- 38 -
11. QUALIFICATIONS
As pointed out, this study does not consider cost or economics.
Also, areas such as coal mining and general offsites are excluded. These
will be similar and common to all conversion operations.
The study is based on a specific process design and coal type,
with modifications as discussed. Plant location is an important item of
the basis and is not always specified in detail. It will affect items
such as the air and water conditions available, and the type of pollution
control needed. For example, this study is based on high sulfur eastern
coal, although it can be used on low sulfur western coal. Because of
variations in such basis items, great caution is needed in making compar-
isons between coal conversion processes since they are not on a completely
comparable basis.
Some other conversion processes are intended to make SNG or
low-Btu gas fuel, and may make appreciable amounts of by-products, such
as tar, naphtha, phenols, and ammonia. Such variability further increases
the difficulty of making meaningful comparisons between processes.
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- 39 -
12. BIBLIOGRAPHY
1. Magee, E. M., Jahnig, C. E., and Shaw, H., "Evaluation of Pollution
Control in Fossil Fuel Conversion Processes, Gasification; Section 1*:
Koppers-Totzek Process," EPA-650/2-74-009a. (PB-231-675/AS, NTIS,
Springfield, Va., 22151), Jan. 1974.
2. Kalfadelis, C. D., and Magee, E. M., "ibid. Synthane Process,"
EPA-650/2-74-009b, (PB-237-113/AS, ibid), June 1974.
3. Shaw, H., and Magee, E. M., "ibid. Lurgi Process," EPA-650/2-74-009c
(PB-237-694/AS, ibid), July 1974.
4. Jahnig, C. E., and Magee, E. M., "ibid. C02 Acceptor Process,"
EPA-650/2-74-009d, December 1974.
5. Kalfadelis, C. D., and Magee, E. M., "ibid. Liquefaction: Section 1
COED Process," EPA-650/2-74-009e, January 1975.
6. Jahnig, C. E., "ibid. Section 2, SRC Process'," EPA-650/2-74-009f,
March 1975.
7. Jahnig, C. E., "ibid. Section 5, BI-GAS Process/1 EPA-650/2-74-009g,
May 1975.
8. Hamersma, J. W., et al., "Chemical Desulfurization of Coal: Report of
Bench-Scale Developments, Vol. 1," EPA-R2-73-173d, February 1973.
.9. Hamersma, J. W., et al., "Applicability of the Meyers Process for
Chemical Desulfurization of Coal: Initial Survey of Fifteen Coals,"
EPA-650/2-74-025, April 1974.
10. Lorenzi, Jri, L., et al., "Preliminary Commercial Scale Process Engineering
and Pollution Control Assessment of the Meyers Process for Removal of
Pyritic Sulfur From Coal," 32nd Ironmaking Conference, American Institute
of Mining, Metallurgical, and Petroleum Engineers, Cleveland, Ohio,
April 9-11, 1973.
11. Meyers, R. A., Hydrocarbon Processing, p. 73, June 1975.
12. Nekervis, W. F. and Hensley, E. F., "Conceptual Design of a Commercial
Scale Plant for Chemical Desulfurization of Coal," Parts 1 and 2, EPA
Report No. EPA-650/2-75-051, October 1975.
* The section numbers of" references 1, 2, 3, and 4 have been changed to 1
through 4, respectively.
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- 40 -
TECHNICAL REPORT DATA
(Please read Inunctions on the reverse before completing)
1. REPORT NO.
EPA-650/2-74-009-k
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE E valuation of Pollution Control in
Fossil Fuel Conversion Processes; Coal Treatment:
Section 1. Meyers Process
5. REPORT DATE
September 1975
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
E.M. Magee
8. PERFORMING ORGANIZATION REPORT NO.
EXXON/GRU.10DJ.75
9. PERFORMING ORSANIZATION NAME AND ADDRESS
Exxon Research and Engineering Company
P.O. Box 8
Linden, NJ 07036
10. PROGRAM ELEMENT NO.
1AB013; ROAP 21ADD-023
11. CONTRACT/GRANT NO.
68-02-0629
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
The report gives results of a review of the Meyers process being developed by TRW,
Inc. , from the standpoint of its potential for affecting the environment. The quan-
tities of solid, liquid, and gaseous effluents have been estimated, where possible,
as well as the thermal efficiency of the process. For the purpose of reduced envi-
ronmental impact, a number of possible process modifications or alternatives which
could facilitate pollution control or increase thermal efficiency have been proposed,
and new technology needs have been pointed out.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
COSATI Field/Group
Air Pollution
Coal
Treatment
Coal Preparation
Fossil Fuels
Thermal Efficiency
Air Pollution Control
Stationary Sources
Clean Fuels
Meyers Process
Fuel Gas
Research Needs
13B
21D
081
20M
18. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
46
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
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