U.S. Environmental Protection Agency Industrial Environmental Research      EPA~600/T~77~125fl
Off ice of Research and Development  Laboratory
                Research Triangle Park, North Carolina 27711 NOV€IIHX§r 1977
        ENVIRONMENTAL ASSESSMENT
        DATA BASE FOR LOW/MEDIUM-BTU
        GASIFICATION TECHNOLOGY:
        Volume I.  Technical Discussion
       Interagency
       Energy-Environment
       Research and Development
       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 seven series.
These seven broad categories were established to  facilitate further
development and application of environmental technology.  Elimination
of traditional grouping was consciously planned to  foster technology
transfer and a maximum interface  in related fields.  The seven 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

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-agehcy 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 systems.   The  goal of the Program
is to assure the rapid development of domestic  energy supplies in an
environmentally—compatible manner by providing the necessary
environmental data and control technology.  Investigations include
analyses 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 environmental 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 recommen-
dation for use.
This document is available to the public through the National Technical
Information Service, Springfield, Virginia  22161.

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                                    EPA-600/7-77-125a
                                       November 1977
   ENVIRONMENTAL ASSESSMENT
DATA BASE FOR LOW/MEDIUM-BTU
    GASIFICATION TECHNOLOGY:
    Volume I.  Technical Discussion
                       by

                  E.C. Cavanaugh, W.E. Corbet.,
                     and G.C. Page

                    Radian Corporation
                  8500 Shoal Creek Boulevard
                   Austin, Texas 78758
                Contract No. 68-02-2147, Exhibit A
                 Program Element No. EHE623A
                EPA Project Officer: William J. Rhodes

              Industrial Environmental Research Laboratory
               Office of Energy, Minerals, and Industry
                Research Triangle Park; N.C. 27711
                     Prepared for

              U.S. ENVIRONMENTAL PROTECTION AGENCY
                Office of Research and Development
                   Washington, D.C. 20460

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                            ABSTRACT
          This report was prepared as part of an overall
environmental assessment program for low/medium-Btu gasification.
The program is being directed by the Fuel Process Branch of the
Environmental Assessment and Control Division of the Industrial
Environmental Research Laboratory at Research Triangle Park,
North Carolina.  This document represents the current data base
for the environmental assessment of low/medium-Btu gasification
technology.


          The purpose of this report is to determine the pro-
cesses which can be used to produce low/medium-Btu gas from coal,
the constraints imposed upon these processes by the intended end
uses of the product gas, the multimedia discharge streams gener-
ated by these processes, and the technology required to control
these discharge streams.  Attention is focused on the processes
which appear to have the greatest likelihood of near-term
commercialization.  This type of screening provides the prelimi-
nary basis for establishing the priorities for subsequent phases
of the low/medium-Btu gasification environmental assessment
program.


          The processes required to produce low/medium-Btu gas
from coal are divided into discrete units or operations.  These
operations are coal pretreatment, gasification, and gas purifi-
cation.  Each of these operations is then further divided into
discrete modules, with each module having a defined function and
identifiable raw materials, products and discharge streams.


          This report is divided into two volumes.  In Volume I,
a discussion of the status, significant trends, major process
operations, multimedia discharge stream control strategies, and
recommendations for future program activities are presented.
Volume II contains the appendices which consist of detailed
process, environmental, and control technology data for the
processes considered to have the greatest potential for near-
term commercialization.
                               ii

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                        TABLE OF CONTENTS



                                                            Page
1.0       INTRODUCTION	    1

          1.1  BACKGROUND	    1

          1. 2  PURPOSE OF THIS DOCUMENT	    2

          1.3  METHODOLOGY OF PRESENTING THE TECHNOLOGY	    2

          1.4  CONTENTS OF THE REPORT	    3

2.0       OVERALL TECHNOLOGY STATUS	    5

          2 .1  GASIFICATION PROCESSES	    5

          2. 2  RAW MATERIALS	   11

          2. 3  PRODUCTS	   12

          2. 4  ENVIRONMENTAL IMPACTS	   14

          2. 5  STATUS OF DEVELOPMENT	   15

               2.5.1  Cost	   16

               2.5.2  Applicability of Low/Medium-Btu
                      Gasification Technology	   16

               2.5.3  Energy Efficiency	   18

               2.5.4  Extent of Development Work	   19

               2.5.5  Rate of Commercialization	   20
                          i

               2.5.6  Status Summary	   20

3.0       LOW/MEDIUM-BTU COAL GASIFICATION-PROCESS
          OPERATIONS	   24

          3.1  COAL PRETREATMENT OPERATION	   26

               3.1.1  Crushing/Sizing Module	   26

               3.1.2  Pulverizing Module	   29
                               iii

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                      CONTENTS (continued)

                                                            Page
               3.1.3  Drying/Partial Oxidation Modules	    29
               3.1.4  Briquetting Module	    29
               3.1.5  Discharge Stream and Control
                      Technology Summary -  Coal
                      Pretreatment Operation	    30
          3.2  COAL GASIFICATION OPERATION	    33
               3.2.1  Types of Gasifiers	    34
               3.2.2  Gasification Process  Prioritization.    36
               3.2.3  Effects of Feedstock and Operating
                      Parameter Changes	    44
               3.2.4  Gasification Process  Comparisons....    47
               3.2.5  Discharge Stream and Control
                      Technology Summary -  Coal
                      Gasification Operation	    53
               3.2.6  Environmentally Significant Trends
                      in Gasification Process Development
                      Activities	    63
          3.3  GAS PURIFICATION OPERATION	    63
               3.3.1  Particulate Removal Module	    66
               3.3.2  Gas Quenching and Cooling Module....    67
               3.3.3  Acid Gas Removal Module	    68
               3.3.4  Discharge Stream and Control
                      Technology Summary - Gas
                      Purification Operation	    82
4.0       POLLUTION CONTROL MODULES	    84
          4.1  AIR POLLUTION CONTROL	    85
               4.1.1  Particulate Control Module	    87
                               iv

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                      CONTENTS (continued)

                                                            Page
               4.1.2  Sulfur Control Module	    92
               4.1.3  Hydrocarbon Control Module	   102
               4.1.4  Nitrogen Oxides Control Module	   104
               4.1.5  Discharge Stream Summary	   104
          4.2  WATER POLLUTION CONTROL	   105
               4.2.1  Water Pollution Control Modules	   110
               4.2.2  Process Comparisons	   121
               4.2.3  Water Pollution Control Philosophy..   124
               4.2.4  Discharge Stream Summary	   132
          4.3  SOLID WASTE POLLUTION CONTROL	   136
               4.3.1  Sludge Reduction Module	   137
               4.3.2  Chemical Fixation Module	   137
               4.3.3  Discharge Stream Summary	   139
5.0       SUMMARY OF TECHNOLOGY ASSESSMENTS	   140
          5.1  ASSESSMENT PROGRAM PHILOSOPHY	   140
          5.2  CONTENT OF TECHNOLOGY STATUS REPORT	   142
          5. 3  SUMMARY OF 'ASSESSMENTS	   143
          REFERENCES	   155
          APPENDICES
          A    COAL GASIFICATION OPERATION            VOLUME II
          B    GAS PURIFICATION OPERATION             VOLUME II
          C    AIR POLLUTION CONTROL                  VOLUME II
          D    WATER POLLUTION CONTROL                VOLUME II
          E    SOLID WASTE CONTROL                    VOLUME II

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                             FIGURES
Number
 2-1      Coal gasification system process modules	    8
 3-1      Coal pretreatment operation	   27
 3-2      Sources of potential emissions in the coal
          gasification operation	   54
 3-3      Flow diagram for the modules in the gas
          purification operation	   65
 4-1      Flow diagram for the modules in the air
          pollution control operation	   86
 4-2      Treating sequence for example 1	   99
 4-3      Treating sequence for example 2	  100
 4-4      Treating sequence for example 3	  101
 4-5      Major process modules generating wastewater
          in a typical coal gasification plant	  106
 4-6      Flow diagram for the modules in the water
          pollution control operation	  Ill
 4-7      Wastewater treating sequence for example 1	  128
 4-8      Wastewater treating sequence for example 2	  131
 4-9      Wastewater treating sequence for example 3	  134
 4-10     Flow diagram for the modules in the solid
          waste control operation	  138
                               vi

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                             TABLES
Number                                                      Page

 2-1      U.S. AND FOREIGN STATUS OF LOW/MEDIUM-BTU
          GASIFICATION TECHNOLOGY	   6

 2-2      PROMISING LOW/MEDIUM-BTU GASIFICATION SYSTEMS	   9

 2-3      ESTIMATED CONSUMPTION OF GAS AND OIL TO SUPPLY
          DIRECT PROCESS HEAT OR CHEMICAL FEEDSTOCK NEEDS
          IN THE INDUSTRIAL SECTOR IN 1972	  17

 2-4      SUMMARY OF THE MAJOR FACTORS AFFECTING THE
          STATUS OF LOW-BTU GAS PRODUCERS	  21

 3-1      FUNCTIONS OF MODULES IN COAL PRETREATMENT
          OPERATION	  28

 3-2      EMISSION STREAM AND CONTROL TECHNOLOGY
          SUMMARY - COAL PRETREATMENT OPERATION	  31

 3-3      TOTAL POPULATION OF LOW/MEDIUM-BTU GASIFIERS	  37

 3-4      COAL GASIFIERS WITH POTENTIAL NEAR-TERM
          COMMERCIAL APPLICATION IN THE U.S	  43

 3-5      COMPARISON OF PROMISING COAL GASIFIERS	  48

 3-6      LOW/MEDIUM-BTU GASIFICATION SYSTEM PRODUCT
          GAS UTILIZATION OPTIONS	  50

 3-7      PRODUCT GAS SPECIFICATIONS FOR THE VARIOUS
          END USES FOR LOW/MEDIUM-BTU GAS	  64
                          i

 3-8      LOW-TEMPERATURE ACID GAS REMOVAL PROCESSES	  71

 3-9      COMPARISON OF LOW-TEMPERATURE ACID GAS
          REMOVAL PROCESSES	  79

 4-1      SUMMARY OF PARTICULATE CONTROL DEVICES	  91

 4-2      DIRECT CONVERSION PRIMARY SULFUR RECOVERY
          PROCESSES	  94

 4-3      SUMMARY OF SULFUR RECOVERY AND CONTROL
          PROCESSES	  97
                              vii

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                       TABLES (continued)
Number                                                      Page
 4-4      COAL GASIFICATION PLANT WASTEWATER SOURCES
          AND CHARACTERISTICS	  107
 4-5.     COMPOSITION OF GAS LIQUOR FROM SASOL
          COAL GASIFIERS	  109
 4-6.     PROMISING WASTEWATER TREATING MODULES
          FOR SASOL GAS LIQUOR	  109
 4-7      SUMMARY OF WATER POLLUTION CONTROL PROCESSES	  122
 4-8      TREATING PROCESSES FOR EXAMPLE 1	  127
 4-9      TREATING PROCESSES FOR EXAMPLE 2	  130
 4-10     TREATING PROCESSES FOR EXAMPLE 3	  133
 4-11     WATER POLLUTION CONTROL DISCHARGE STREAMS	  135
 5-1      ENVIRONMENTAL ASSESSMENT DATA REQUIREMENTS	  144
 5-2      DATA REQUIREMENTS FOR CONTROL TECHNOLOGY
          ASSESSMENT	  151
                              viii

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                       ACKNOWLEDGEMENTS
          The efforts of the following personnel in providing
technical data, along with review and preparation functions,
were instrumental in completing this document.

          Significant technical inputs and review activities
were provided by William C. Thomas, Russell L. Honerkamp, Jay
R. Hoover, Charles A. Muela, and William P. Stadig.  Mary Lou
Hoover, Rose M. Melton, and W. Jean Travis gave significant time
and effort in compiling the references and typing this report.
                                Ix

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                          SECTION 1.0

                          INTRODUCTION
1.1       BACKGROUND
          The United States has been fortunate In the past to
possess large reserves of the three major fossil-fuel energy
sources:  gas, oil and coal.  However, in recent years the
nation's energy picture has changed drastically due to increas-
ingly severe shortages of oil and natural gas.  Because of
these shortages, there has been growing interest by government
and industry in the technologies used to produce fuels from
coal.
          In response to this shift in our energy supply
priorities, the Environmental Protection Agency has initiated a
comprehensive assessment program to evaluate the environmental
impacts of synthetic fuel processes having a high potential for
eventual commercial application.  This overall assessment pro-
gram is being directed by the Fuel Process Branch of the
Envirpnmental Assessment and Control Division (EACD) of the
Industrial Environmental Research Laboratory at Research
Triangle Park (IERL-RTP).


          The primary objectives of the EPA Synthetic Fuels
Assessment Program are:


             To define the environmental effects of
             synthetic fuel technologies with respect
             to their multimedia discharge streams and
             their health and environmental effects


             To define control  technology needs for an
             environmentally sound synthetic fuel industry.


The coal conversion technologies being studied in the total
program include low/medium-Btu  gasification, high-Btu gasifica-
tion, and liquefaction.  Radian Corporation is EPA's environ-
mental assessment contractor for low/medium-Btu gasification
technology.

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1.2       PURPOSE OF THIS DOCUMENT


          This document deals specifically with low/medium-Btu
gasification and utilization technology; its purpose is to pre-
sent a description of:


             the processes which can be used to produce
             low/medium-Btu gas from coal,


             the constraints imposed upon those processes
             by the intended end uses of the product gas,


             the air, water, and solid waste streams
             generated by those processes, and


             the pollution control techniques which
             appear to be applicable to the control of
             those multimedia discharge streams.


Throughout this report, attention is focused on those processes
which appear to have the highest likelihood of near-term commer-
cialization.  This technology screening step is of considerable
importance to the overall program because it provides the
primary basis for establishing priorities for subsequent phases
of program activity.                  !


          Both low/medium-Btu gasification and product gas
utilization technologies are considered in this report.  Gasifi-
cation technology is assumed here to include the processes
required both to produce low/medium-Btu gas and to control the
resulting multimedia discharge streams.  Utilization technology
includes the processes that may use the product gas either for
direct combustion (boilers, furnaces, gas turbines, etc.) or as
a synthesis or reducing gas.


1.3       METHODOLOGY OF PRESENTING THE TECHNOLOGY


          This environmental assessment program involves the
study of a very complex technology composed of a large number of
processes which can be arranged in many different combinations.
In previous EPA sponsored programs involving technologies of
                              -2-

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this sort, it has been found useful to divide the technology
into discrete units, with each unit having well defined func-
tions and specific input and output streams.  This effort
considerably simplifies the task of analysis because it reduces
a seemingly complex system to a series of manageable components.


          In this report, low/medium-Btu gasification
technology is assumed to consist of three general process
operations:  1) coal pretreatment, 2) gasification, and 3) gas
purification.  Each of these operations is further divided into
modules, with each module having a defined function and identi-
fiable raw materials, products, and discharge streams.


1.4       CONTENTS OF THE REPORT


          A general discussion on the status of and significant
trends in low/medium-Btu gasification technology is presented
in Section 2.0.  The environmental impacts associated with this
technology are also summarized.


          In Section 3.0, the three major process operations
are defined and their anticipated environmental impacts are
described.  Attention is focused upon processes which appear
to have the highest probability of near-term commercialization.
Consideration is given to all environmental impacts associated
with each operation, but with emphasis on those that are unique
to gasification technology.  For example, the treatment of gasi-
fication process condensate is given much more attention than is
the control of air emissions from on-site steam or power genera-
tion facilities.


          In Section 4.0, environmental control strategies and
problems associated with Creating gasification plant air, water,
and solid waste discharge streams are described.  Recommendations
for future program emphasis based upon the information presented
in this report are discussed in Section 5.0.


          In the appendices, data sheets are presented which
provide detailed, yet orderly descriptions of the processes
which are identified to be of primary concern to the low/medium-
Btu gasification technology assessment program.  This information
supplements data contained in summary tables which are presented
throughout this report.  Data sheets for the processes in the
gasification and gas purification operations are presented in
                              -3-

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Appendices A and B.  Processes used to treat air, water, and
solid waste discharge streams from gasification plants are pre-
sented in Appendices C, D, and E.
                               -4-

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                          SECTION 2.0

                   OVERALL TECHNOLOGY STATUS
          The production of low/medium-Btu gas from coal has
been practiced for many years both in the U.S. and in other
countries where coal is an abundant resource.  At one time a
large number of coal gasifiers were in service in the U.S.
Most of these were retired when cheap natural gas became
available.  Now, with gas supplies dwindling and petroleum
prices escalating, there is an increasing interest by all
energy-consuming sectors in evaluating the potential for
gasification technology application.


          Discussed in this section are the general factors
that will determine which low/medium-Btu gasification processes
will be applied in the U.S.  More detailed descriptions of the
processes and their environmental impacts are presented in
Section 3.0.
2.1       GASIFICATION PROCESSES
          On the order of 68 different gasification processes
can be identified which either have been used commercially in
the past or are currently under development.  Twenty-five of
the most prominent of these gasification processes are shown in
Table 2-1.  All involve partial oxidation of coal.  Where the
system is "air blown", low-Btu gas with a heating value in the
neighborhood of 5.6 x 10s J/Nm3 (150 Btu/scf) is produced.
Where oxygen is used, medium-Btu gas with a heating value of
about 13.1 x 10s J/Nms (350 Btu/scf) is produced.


          Six of the gasifiers listed in Table 2-1 are currently
being used to satisfy some commercial demand for low/medium-Btu
gas.  These are:


             Lurgi

             Wellman-Galusha

             Woodall-Duckham/Gas Integrale
                               -5-

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      Table  2-1.    U.S.  AND  FOREIGN STATUS OF LOW/MEDIUM-BTU GASIFICATION TECHNOLOGY
Gasifler
Largi
BtllBan-Calasha
•oodall-DuckBan/
Gu Integrate
Eoppers-Totzek
Vlnkler
Chapman (Uilputte)
Uley Morgan
KG/Lurgl Slagging

Bl-Cas
Foster Uheeler/Stolc
Pressurized Uellman-
Calusha (MERC)
emc Slagging
Tezaco
KR Lov-Btu
Coaliiinclop Engineering
Hygas
Syn thane
COi Acceptor
Cogas
Foster Wbeeler
Bibcock & WUcoz
U-6as


Heating bouse
Ooalex

WellBan Incandescent
HP.
Licensor /developer
Largl Klneraloltechnik GmbH
McDowell Uellman Engineering Co.
Woodall-Duckham (USA) Ltd.

Coppers Coopany, Inc.
Davy Powergas
Wllputce Corp.
Rlley Stoker Corp.
British Gas Corp. and Lurgl
Mlneraloltechnlk GkbB
Bituminous Coal Research, Inc.
Foster Wheeler /Stole Corp.
ERDA

ERDA
Texaco Development Corp.
Bituminous Coal Research, Inc.
Combustion Engineering Corp.
Institute of Gas Technology
ERDA
ERDA
COCAS Development Co.
Foster Wheeler Energy Corp.
The Babcock & Wilcox Co.
Institute of Gas Technology,
Phillips Petroleum Corp.
Sterns-Roger
Westlnghouse Electric Corp.
Inez Resources , lac.

Applied Technology Corp.
of Mslflers currently
Lov-ltD fm» Medl
5
8(150)
(72)

-
-
2(12)
1
-

-
1«<2)
!•

-
-
1*
1*
-
-
-
-
1
1
1


1
1
(1*)
(2*)**
operation
!• 11 ii gas
(39)
-
-

-
(23)
-
-
1

1
-
_

1*
-
-
-
1
1
1
1
-
-
-


-
_

-
(no. of gaslflers built)
Synthesis gas Location
(22) Foreign
US/Foreign
(8) Foreign

(39) Foreign
6(14) Foreign
US
us
Foreign

OS
OS/Foreign
OS

US
1* US
US
US
US
us
us
us
us
us
us


us
us

US/Foreign
Scale
Commercial
Commercial
Commercial

Comoercial
Commercial
Commercial
Commercial
Demonstration

Demonstration
Deaoostratlon/CosMerclal
Demonstration

Demonstration
Demonstration
Demonstration
Demonstration
Demonstration (Hlgh-Btu)
Demonstration (High-Ben)
Demonstration (High-Btu)
Demonstration (High-Bta)
Pilot
Pilot
Pilot


Pilot
Pilot
CoBnerclal
CoBmcrclal/DeBonstration
*Under construction.
 Demonstration scale indicates 2000 to 10,000 Ib/hr coal faad.
 Pilot acale indicates 400 to 1500 Ib/hr coal feed.
**Undetermin«d number overseas

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             Koppers-Totzek

             Winkler

             Chapman (Wilputte)


A number of the remaining gasifiers listed in Table 2-1 appear
to have significant commercialization potential.  For example,
a commercial-scale Riley-Morgan system has been operated as a
development/test unit and a commercial-scale Coalex plant is
under construction.
          Gasification systems can be considered to consist of
three basic operations:  coal pretreatment, coal gasification,
and gas purification.  Each of these operations can, in turn,
be assumed to consist of process modules which are employed to
satisfy the functions of the operations.  These modules and
their interrelationships are depicted in Figure 2-1.


          From Figure 2-1, it can be seen that the coal
pretreatment processes used will vary depending upon the coal
type and the gasifier design.  Coals having excess moisture may
be dried while caking bituminous coals may be partially oxidized
to reduce their caking tendencies.  The feed coal must be
crushed and sized for fixed-bed gasifiers or pulverized for
fluid-bed or entrained-bed gasifiers.  Fines from crushing pro-
cesses which cannot be fed directly to a fixed-bed gasifier can
either be sold as a by-product, consumed to supply on-site fuel
needs, or briquetted and fed to the gasifier.


          The six gasification systems listed previously,
together with eight others which are currently under development
make up a population of fourteen systems which, on the basis of
a screening analysis presented in Section 3.2, have been
identified as the most promising candidates for satisfying near-
term commercial needs for low/medium-Btu gas.  These systems
are listed in Table 2-2.


          The fourteen gasification processes which are
considered to be members of this "most promising" group all fall
into one of six classes of processes which have unique environ-
mental impacts.  These six classes and the proprietary processes
which comprise each class are as follows:
                              -7-

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                                     COM. PRETHEATMEMT
                                        OPERATION
     COAL OASnCATION
      OPERATION
oo
 I
                             MOOT am*. A COM. HAIBUM/
                             nvuiapoHVATioM uoouts ABO A
                             COAL STORAM HOOUVC IBOHT K
                            OVtOtlO AT ANT KMT M THC
                           ntcTncATMNT nroctssixa OEOUCHCC.
                           •uo i« «am or TW A*nc inocnaa
                             no* HMHT «c Mvoirai). IA A
                           mi»i»» i «u»i« iiocuui man rmcat
                            A OAVMMIMOOUU M ANY WIN P1AIIT
                                                                                                                                                            OH-tin
                                                                                                                                                            couauanoN
^k
PKaSUROID faumcULAIC^ rvf
TK8KL™ — V--JJ- «
v_y
^^
S5" W °^.V0 V- ""vSK^"
""•~* \ \ / MUOVAL
^-^
1
-L

IOrr-aiTC
cousuano
COWIIED
CYCLE
tYNTHESU
OAS
                                                                                                  QASIFIER HUU8ER COOES •

                                                                                                      ATM08MHC M9VWH. MT ASM.
MVT TO All
                        mao-wo raciMtan OASVKR. SLAOBOB UK

                        n.U0-BC1) ATMOSPHERIC QAOTC11. OUT ASH.

                        nrnui«D-uo ATUOSFHIRIC (usvaR. ILAQOIHO ASH.

                        ENTRAIMCD4ED PMSSUR1ZED OAtmCR. SlAOOmQASK
                                      Figure  2-1.    Coal  gasification  system process  modules

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                     Table  2-2.   PROMISING LOW/MEDIUM-BTU GASIFICATION SYSTEMS
      First Group1
i
vo
i
We1Iman-Galusha

Lurgi

Woodall Duckham/
 Gas Integrals

Koppers-Totzek

Winkler

WeiIman Incandescent
        and
Foster Wheeler/Stoic
                             Second Group:
                                        Chapman (Wilputte)

                                        Riley Morgan
Third Group:
  Pressurized Wellman-
   Galusha (MERC)

  GFERC Slagging
   Gasifier

  BGC/Lurgi Slagging
   Gasifier

  Texaco

  Bi-Gas

  Coalex
       1Commercially  available;  significant  number of units  currently operating in the
       U.S.  or  in  foreign countries.
       2Commercially  demonstrated  in limited applications.
       3Commercial  or demonstration-scale  units  operating or being constructed;  technology
       is  promising  and should  be monitored.

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             Fixed-bed atmospheric dry ash gasifier;
                Wellman-Galusha
             -  Woodall-Duckham/Gas Integrale
                Chapman (Wilputte)
                Riley-Morgan
                FW/Stoic and Wellman Incandescent

             Fixed-bed pressurized dry ash gasifier;
             -  Lurgi
             -  Pressurized Wellman-Galusha (MERC)

             Fixed-bed pressurized slagging ash gasifier;
             -  BGC/Lurgi Slagging Gasifier
             -  GFERC Slagging Gasifier

             Fluid-bed atmospheric dry ash gasifier;
             -  Winkler

             Entrained-bed atmospheric slagging ash gasifier;
                Koppers-Totzek
                Coalex

             Entrained-bed pressurized slagging ash gasifier;
             -  Bi-Gas
                Texaco
          The low-Btu product gas purification scheme will vary
depending upon the desired end use of the ultimate product fuel.
Gases used for on-site boiler firing or for on-site industrial
process heat may need only particulate collection if sulfur
                              -10-

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compounds are not present in objectionable quantities.   Where
sulfur compounds must be removed for either environmental or
product quality reasons, two additional gas cleaning steps are
necessary.  Gas quenching and scrubbing are needed to cool the
gas and remove condensable tars and oils so that any one of
several commercially available low-temperature acid gas removal
processes can be used.  Sulfur removal processes are needed to
remove the reduced sulfur compounds present in the product gas.


2.2       RAW MATERIALS


          In general, any type of coal can be gasified if
appropriate coal pretreatment and gas cleaning processes are
employed.  However, the type of gasifier design and the intended
end use of the product gas will affect the selection of suitable
coals for gasification.  The properties which are important in
determining the suitability of a given coal feedstock are:


             Particle size and friability

             Caking properties

             Moisture content

             Ash content and fusion temperature

             Sulfur content


          Particle size, friability, and caking properties are
probably the most critical factors as far as the operability of
fixed-bed gasifiers is concerned.  Since "fixed-bed" gasifiers
actually have slowly gravitating beds where coal is added and
ash is withdrawn regularly, proper bed composition and uniform
gas-solid contact can be maintained only if these coal feedstock
properties are within the limits required for the gasifier.


          For most fixed-bed gasifiers, coal fines (<3 mm in
diameter) will have to be separated from the gasifier feedstock.
These coal fines can be sold as a by-product, burned in a boiler,
or briquetted for re-use as gasifier feedstock.  Fluidized- and
entrained-bed gasifiers generally require pulverized feedstock;
therefore, coal fines are not a raw material limitation.
                              -11-

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          Caking coals may cause operating problems for
fixed-bed and some fluidized-bed gasifiers.  Fixed-bed gasifiers
may require bed agitators in order to gasify caking coals.
Partial oxidation can make caking coals suitable for gasifica-
tion.  Caking properties are not a limitation for entrained-bed
gasifiers.


          Coal feedstocks with a high moisture content can cause
operational problems for coal feeding devices.   The high
moisture content may also result in low gas outlet temperature
(<420°K; 300°F) which can result in condensation of tars and
oils in the gas outlet or hot cyclone.  If the coal feedstock
must be dried, the energy requirement for drying the coal will
result in lower thermal efficiency of the overall process.  Even
if drying is not required, coals with higher moisture content
will result in lower gasification efficiency because of the
energy which must be supplied to evaporate the moisture in the
gasifier.


          Ash content and fusion temperature are important
factors for gasifiers which operate above the ash fusion  (slag-
ging) temperature.  Slagging fixed- and entrained-bed gasifiers
may require the addition of fluxing agents to the coal feedstock
in order to lower the fusion temperature of the coal ash.
Slagging fixed-bed gasifiers may also require the addition of
slag to the coal feedstock for coals with a very low ash content
in order to maintain adequate slag withdrawal rates.


          Sulfur content can be a factor in selecting acceptable
coal feedstock if no acid gas removal operations are to be used.
If the product gas is to be used as a synthesis gas, fuel for
combined-cycle turbines, or as an off-site combustion fuel trans-
ported by pipeline, acid gas removal will always be required.
For on-site combustion of the product gas, acid gas removal may
not be required if the coal sulfur content is sufficiently low.
The acceptable sulfur level will be determined by the federal,
state, and local sulfur dioxide emission regulations.


2.3       PRODUCTS


          The four potential end-use alternatives for coal
gasifier product gas are the following:
                              -12-

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             On-site combustion fuel

             Off-site combustion fuel

             Combined-cycle fuel

             Synthesis or reducing gas


          On-site combustion refers to a direct combustion
process which consumes the product gas within a relatively short
distance of the coal gasification plant.  Although any of the
fourteen gasifiers just discussed could be used to produce
on-site combustion fuel, the atmospheric pressure systems appear
to be the best suited to this end use.


          Off-site combustion refers to a direct combustion
process which consumes the product gas at a site that is not
near the coal gasification plant.  Pressurized gasifiers are
well suited to this end-use option, since it is cheaper to
compress the air or oxygen and steam feed to the gasifier than
it is to compress the product low/medium-Btu fuel gas.  Also,
air-blown gasifiers do not appear to be well suited to the pro-
duction of off-site combustion fuel because of the excessive
costs of transporting a gas with a low heating value.


          The first step in a combined-cycle operation is the
combustion of a pressurized fuel gas and the expansion of the
combustion gases through a gas turbine to provide shaft work.
Then, the sensible heat of the gas turbine exit gas stream is
recovered in a conventional steam turbine cycle to provide
additional shaft work.  Combined cycles are primarily used in
the generation of electricity.  Pressurized gasifiers are most
applicable to this end-use option, since combined-cycle gas
turbines are designed to operate at high turbine inlet gas
pressures.  Either air-blown or oxygen-blown gasifiers can be
used to produce a combined-cycle fuel.


          Synthesis or reducing gas is used as a raw material
for the production of a wide range of chemicals and metals.  In
most applications, a gas having high concentrations of hydrogen
and carbon monoxide and low concentrations of methane and other
hydrocarbons is desired.  Because of this composition require-
ment, an entrained-bed, slagging ash gasifier is probably best
suited to this end-use option.
                              -13-

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2.4       ENVIRONMENTAL IMPACTS


          The environmental impacts associated with coal
gasification operations range from conventional pollution
problems such as coal dust emissions to such ill-defined
problems as fugitive emissions which, because of their probable
noxious character, will require the design of special systems
for their control.  Emissions from coal preparation processes
generally fall in the category of problems which appear to be
solvable with available technology.  Wastes from coal storage,
handling, size reduction, and classification processes can be
handled using available techniques for controlling coal dust
emissions, disposing of mineral wastes, and handling runoff
waters from storage piles.  However, less costly or, in some
cases, more efficient controls are needed.


          The control of air emissions from coal dryers,
briquetting and partial oxidation processes may present more
difficult problems because of the volatile hydrocarbons which
can be liberated as the coal is heated.  The exact character of
these materials has not been determined as far as their potential
toxicities are concerned.  Hence, the limit to which they must
be controlled and the adequacy of available control technology
have not been determined.
          The coal gasification operation appears to be the most
serious source of potential gasification system pollution prob-
lems.  For all systems, the feeding of coal and the withdrawal
of ash provide opportunities for the escape of coal or ash dust
and hydrocarbons which, being products of the thermal processing
of coal, must be considered to be potentially toxic.  These
problems are similar for all gasifiers even though emissions
from some types of equipment may be limited to coal or ash dust.
Also, it is certain that gasifiers and associated equipment will
be sources of fugitive leaks from pump seals, flanges and the
like.  This leakage, unless controlled to adequate levels, can
be hazardous.


          The gas cleaning modules also appear to present
difficult control problems.  The particulate removal and gas
cooling steps will produce ash and water contaminated with
condensable hydrocarbons, many of which are toxic.  The sulfur
removal processes will produce fugitive emissions which are
similar to those generated during gasification.  Pollution
control needs for the gas cleaning area are poorly defined and
more work is needed to support judgments on the adequacy of
                              -14-

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available control technology.  EPA's current scope of activities
includes assessment of these pollution control needs.


2.5       STATUS OF DEVELOPMENT


          Low- and medium-Btu gasification technologies are in
varying stages of development.  A number of systems are now
being offered commercially.  A second group of processes which
are expected to introduce substantial improvements are currently
under development.  However, neither the older systems, such as
those offered commercially, nor the new processes, have been
proven to be satisfactory solutions to today's clean fuel supply
problems.


          While some six different gasification units are in
operation in industrial plants in the U.S., publicly available
information on their cost, fuel efficiency^ applicability to
various markets, and environmental impacts is lacking.  Further,
it is not known whether they are representative of the best
systems (from both process efficiency and an environmental
impact point of view) which could be built today.  Hence, much
more information is needed to determine the commercialization
potentials of the various candidate systems.  At present, it is
difficult to predict how the different systems will fare in
competition with each other or how low-Btu gasification will
fare in competition with other technologies such as direct coal
combustion/flue gas desulfurization, coal liquefaction, etc.


          It is possible, however, to comment on some of the
factors for judging the status of development, the most impor-
tant of these being:


             The cost of the fuel gas produced.


             The applicability of the technology to
             different end-use requirements.


             The energy efficiency of the process.


             The extent of ongoing work to develop
             and commercialize the technology.
                              -15-

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             The rate at which systems can be
             commercialized.


These factors are discussed in the following pages.


2.5.1     Cost


          Projecting the costs of low/medium-Btu fuel gas
produced from coal is difficult because of uncertainties in the
limited cost data available and because costs are sensitive to
the type and location of application.  It appears, however, that
simple atmospheric systems can produce low-Btu gas for about
$2.50/109 J (109 Joule %106 Btu) if particulate collection in a
hot cyclone is the only product gas cleaning step needed.  If
additional treatment steps are necessary (e.g., gas quenching,
sulfur removal, by-product recovery, water treatment, etc.),
this could easily add at least an estimated $1.00/109 J to the
cost of the gas.


          These figures represent large increases over costs
estimated when low-Btu systems again received serious considera-
tion in the U.S. in the early 1970*s.  Even two years ago, costs
in the general range of $1.00 to $2.00 per 109 J were considered
reasonable.  This continuing escalation is attributable to
rising construction costs, rising coal costs, and a better
understanding of problems associated with commercialization of
the technology.  Despite this apparent high cost, it appears
that low- and medium-Btu gasification systems may be competitive
in numerous critical applications where clean fuels are required
but are not available from other sources.


2.5.2     Applicability of Low/Medium-Btu Gasification
          Technology


          Low- and medium-Btu fuel gases from coal appear to be
reasonable alternatives to natural gas or distillate fuels in
certain critical applications where clean fuels are required.
These applications include synthesis gas/chemical feedstock and
combustion gas used to supply direct heat in processes such as
brick ovens, lime kilns, glass furnaces, paint drying ovens, and
food processing equipment as well as a variety of other processes
where direct coal firing may not be a viable alternative.  When
the fuels which currently supply those uses become prohibitively
expensive or are reserved for other uses by legislative mandate,
                              -16-

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a significant demand for low/medium-Btu gasification systems
could result.  The quantities of gas and oil used for these pur-
poses in the industrial sector in 1972 are shown in Table 2-3.


  Table 2-3.  ESTIMATED CONSUMPTION OF GAS AND OIL TO SUPPLY
              DIRECT PROCESS HEAT OR CHEMICAL FEEDSTOCK NEEDS
              IN THE INDUSTRIAL SECTOR IN 1972

                                  Fuel energy (10 *8 Joules)
            End Use               GaiOilTotal
Direct heat
Feedstock

3.4
.5
3.9
.9
2.5
3.4
4.3
3.0
7.3
     Total Energy Consumption,
     Industrial sector           11.2       6.0       17.2
     All End Uses

  Source:  Ref. 1   (References are listed at the end of
                    Vol. I and Vol. II.)


          Although  all of the end uses represented by the energy
consumption figures shown in Table 2-3 cannot realistically be
satisfied by low/medium-Btu gas  (for either technical or economic
reasons), the  energy use figures shown give some indication of the
significance of one potential market for low/medium-Btu gasifica-
tion systems.  Small gas and oil-fired industrial boilers of less
than a 10 MWe  equivalent capacity appear to represent another
potential market for low/medium-Btu gas.  Data published by
Battelle (Ref. 2) indicate that  these systems consume approxi-
mately 6.5 x 1018 Joules of gas  and oil per year.  In many of
these systems, the  use of low/medium-Btu gas may be a viable
alternative to the  replacement of existing units with coal-fired
systems.  This indicates a potential need for several thousand
gasifiers having annual outputs  of 0.5 to 30 x 10   J to satisfy
these energy requirements.


          Another application being considered as an important
market for low-Btu  gas is in combined cycle systems for electric-
ity generation.  It is not clear, however, whether overall cycle
efficiencies will be high enough to make this approach attractive.
As discussed in the following section, gasification process
efficiencies are low and difficult to define precisely.
                               -17-

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          The capabilities of gas turbines which could be used
in combined cycles are also poorly defined.  Manufacturers1
claims are generally more optimistic than the reported experience
of users.  It is clear, however, that present day gasifiers and
turbines would not be as efficient as a modern conventional coal-
fired power boiler.  Improved efficiencies of gasifiers and
turbines could, however, reverse this situation.


          Coal gasifiers are also being considered as sources of
replacement fuel supplies for natural-gas-fired power boilers.
It does not appear however, that these systems will be competi-
tive with replacement coal-fired boilers for base load genera-
tion.  It is possible that gasification could be competitive
when producing a fuel for peaking units, but this would require
continuous operation of the gasifier and storage of the fuel
when the boiler was not being used.  Even though this approach
appears attractive, the extent of the potential market is prob-
ably very limited.


2.5.3     Energy Efficiency


          Like costs, the energy efficiencies of the various
gasification systems being studied are difficult to determine
with certainty.  This is a significant problem.  Low efficien-
cies will tend to make the technology non-competitive with
alternative technologies serving the same need, e.g., the energy
efficiency of a low-Btu gasification/combined-cycle system may
be too low to make it competitive with coal-fired power plants
equipped with sulfur and particulate emission control hardware.


          At this point, many questions relating to the effi-
ciency of gasification systems still exist.  The confusion
associated with efficiencies which have been quoted in the
literature can be illustrated by considering some of the vari-
ables involved.  In one study (Ref. 3) it was reported that
no more than 65 percent of the heat content of the coal supplied
to an entrained-bed, slagging ash gasification system and the
associated boiler supplying electrical power could appear
as product heating value.  Also, a 4 percent penalty was asso-
ciated with the fuel used for coal drying which reduced the net
process efficiency to 61 percent.  If the boiler was assumed to
be fired with product gas instead of coal, the overall plant
efficiency dropped to 53 percent.  If the process operating
pressure was assumed to be 15 psig instead of 150 psig, the
savings in compression energy increased the base efficiency of
61 percent to 69 percent.
                               -18-

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          It would appear from these figures that the
efficiencies which have been cited for some gasification systems
are probably optimistic.  However, it is important to realize
that the efficiency of a gasification process is affected by
many process- and site-specific factors.  (These factors are
discussed further in Section 3.2).


2.5.4     Extent of Development Work


          Gasifier operating experience, as indicated earlier,
is quite extensive.  The applicability of some of this experi-
ence to current U.S. needs, however, is questionable.  This is
particularly true of the environmental aspects of gasification
technology since many of the systems which were utilized in the
past would not be environmentally acceptable by today's standards,


          Government agencies such as the EPA and ERDA, as well
as a significant number of industrial organizations, are spon-
soring research aimed at improving the capabilities of gasifica-
tion systems which are currently available or under development.
Work in this connection is being concentrated in the following
areas:


             Evaluations of advanced gasification system
             designs which utilize features enhancing the
             efficiency and/or the operability of systems
             which are representative of currently available
             technology.  In many cases, these measures will
             also enhance the environmental acceptability of
             the gasification processes involved.  This
             research has been directed toward developing
             improved:

                           l
                 Reactor designs


                 Materials of construction


                 Coal feeding and ash removal devices
                 (particularly for pressurized systems)


                 High temperature product gas cleanup
                 processes
                               -19-

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             Fundamental studies aimed at developing a better
             understanding of the reaction mechanisms involved
             in gasification processes.


             Development and use of improved analytical
             techniques for characterizing the components
             present in process and emission streams.


          Control technology applicability and development will
also be given more attention.  Many of the potential environ-
mental problems associated with coal gasification can be handled
using techniques developed to solve similar problems in related
industries.  However, many other emission problems will be
unique.  As gasification process research continues and as these
problem areas are identified, there will be an increasing empha-
sis on control technology assessment and development studies.


2.5.5     Rate of Commercialization


          The rate at which coal gasification (or any other
major energy technology) can be applied will depend primarily on
the rate at which process suppliers can respond to demands for
new units.  Up until just recently, there was a fairly small
group of process vendors who were actively marketing their gasi-
fication systems.  Generally, these systems were based on designs
which were widely used in the past.


          Awareness of the potential for the application of
gasification systems has over the past several years led to an
increase in the number of groups that are actively developing
and marketing gasification systems.  It is therefore expected
that the growth of the coal gasification industry during the
next few years will tend to be limited by the availability of
the specialized equipment required in those plants.  For this
reason, it will probably be several years before there will be
a significant increase in the number of operating gasifiers in
this country.  The number of operating gasification  systems may
increase substantially, however, during the 1980-1990  time-frame.


2.5.6     Status Summary


          The major factors affecting the development  status of
low-Btu gas producers are given in Table 2-4.  These factors are
                               -20-

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                                      Table  2-4.
                       SUM4ARY  OF  THE  MAJOR FACTORS  AFFECTING
                       THE  STATUS  OF  LOW-BTU  GAS  PRODUCERS
                    Gasifier
   Cmslfler Efficiency (1)

Cold GUI    Overall Thermal
  («            (Z)
                                                                     Applicability to Various amd Uses*
                                                                     Host Suitable
                                                                        End Use
                       Least Suitable
                          End Use
Summary of Ongoing Efforts to Develop
  and Commercialize the Technology
                                                                    On-slte combustion
                                                                                         Off-site combustion
                                                                                         Combined-cycle units
                                                                              This gaaifier has been In commercial us*
                                                                              for many years.  Current designs are
                                                                              essentially the same oa a 20-year old
                                                                              unit. Work on improved process instru-
                                                                              mentation is being done.
                Lorgi
                                     63-80
                               Off-site combustion
                               Combined-cycle tmita
                     Syntbeels/reductant gaa
This gastfler has been in commercial us*
for many years.  Recent design ioprove-
•ents include recycle tar Injection
nozzles.
 I
ro
               Uoodall-Dockho/
               Gas Integrale
                ChapBan (Wilpntte)      	
                               On-site coafaustion
                                                    Off-alte cognation
                                                    Coabined-cycle units
                               Oo-site coMOuation   Off-site coabustlon
                                                    CoBbined-cycle unit*
                                              This gasifier has been la cosoercial us«
                                              for many years.  Major improvements  1m
                                              tar collection techniques have been  mad*.
                                              This gasifier has been In
                                              for many years.
                                                                                                      commercial use
                llley Morgan
 64-68
                 71-78
                               Oo-site combustion    Off—site combustion
                                                    Combined-cycle unit*
                                              A commercial-size gasifier is being
                                              evaluated at Rlley Stoker's pilot plant
                                              facility in Dorchester, Massachusetts.
                •«*t«r MmMlsr/Stale

                Htllamn-IncaDdcBcent
                  149
                               On-slt* combuatioo    Off-site combustion
                                                    Combined-cycle units
                                              The design of this gasifier is similar
                                              to the Woodall-Duckham/Gaa Integrale
                                              gaaifier.  The improvements that have
                                              been made Include automated pokers and
                                              water—sealed ash pan.
                Pressurized
                Uellman-Galusha
                (HEBC)
  0.79
Off-sit* combustion   Syntheais/reductant
Combined-cycle units
                                                                              Gasifier design is being evaluated at
                                                                              KRDA'B Morgantown Energy Research Center
                                                                              (MERC).
                Fixed-Bed
               CTOC Slagging
                               Off-site combustion   Syntheais/reductant gaa.
                               Combined-cycle units
                                              Gulfiar design is being evaluated at
                                              EBDA'a Grand Forks Energy Research
                                              Center (GFKRC).
                BGC/Lurgi
                Slagging
                               Off-slta combuation   Syntheaia/raductant gaa
                               Combined-cycle units
                                              This gaaifier has been teated on a pilot
                                              plant scale.  A commercial scale gasifi«nt
                                              is being evaluated at U*atfield. Scotland.

-------
                                    Table  2-4.
                               SUMMARY  OF  THE MAJOR FACTORS  AFFECTING
                               THE STATUS  OF  LOW-BTU  GAS  PRODUCERS
                                                                                                                           (continued)
                                                                                                                  of Ongoing Effort* to Develop
                                                                                                            •ad CoaaerelaliM the Technology
                           (On «aa>
                                                               Oo-elta eoatraation
                    Off-ait*
                    Coablnad-cycla
                                                                                                           Thla gaalfler bM been in
                                                                                                           for May yean.
                                                                                                             •rclal UM
                                                               Syntheaia/
                                                          Oa-eite
                                                                                  Ibis gMlfier bM b«cn In co>a*rctal UM
                                                                                  for any y«ars.   Slgnlfic«at IBIIIIIUBOIII
                                                                                  la proc««> eoatrol h«v« b«m Had*.  4
                                                                                  pr«»«arlx«d (ulfl*r li currently being
rs>
10
 i
                                                  88-93
                                                                                   Oa-alta
                                                                            tioa    Of f-«lt«
                                                                                                           Th* ^*«
-------
process efficiency and applicability to various end uses.  A
brief summary of the ongoing efforts to develop and commercialize
low-Btu gasification systems is also presented in this table.
                               -23-

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                           SECTION 3.0

       LOW/MEDIUM-BTU COAL GASIFICATION-PROCESS OPERATIONS
          As indicated in the previous section, the production
of low/medium-Btu gas from coal involves three basic process
operations:  coal pretreatment, coal gasification and product
gas purification.  In this section, the optional processing
steps that may be used to accomplish the functions of these
three operations and the associated environmental impacts are
described in detail.  The objectives of this discussion are:


          1)  To identify the potential sources of emission
              from coal gasification plants


          2)  To identify the components of environmental
              concern which might be present in those streams.


          3)  To define how feedstock and process variable
              changes affect the production rates and fates
              of those components.


          Although all three of the processing operations just
mentioned are discussed to some extent in this section, the
depth of treatment given to each varies considerably.  In the
discussion of the coal pretreatment operation, for example,
emission stream sources and compositions are described in quali-
tative terms only.  This operation is included here because it
is important to consider how the emission streams generated by
coal pretreatment processes would be handled in a low/meditmi'-Btu
coal gasification plant.  On the other hand, an in-depth discus-
sion of this operation is not attempted since a detailed
environmental assessment of coal pretreatment processes is being
conducted as part of EPA's Coal Cleaning Technology Assessment
program.  Pertinent results from that program will be integrated
into future low/medium-Btu program reports as appropriate.
                                                                i

          Coal gasification and gas purification are the process
operations which are given major attention in this section.
Detailed consideration of these operations is Justified for
several reasons.  From an environmental viewpoint, these opera-
tions generally will be the sources of the most significant
                               -24-

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waste streams generated in a coal gasification plant.  These two
operations deserve detailed treatment also because of the large
choice of processes which can be used to accomplish the functions
of these operations.  In the case of the coal gasification opera-
tion, for example, 68 mechanically different gasifier designs
were identified in the literature screening study which provided
most of the background information for this document.


          Because of the large number of candidate processes
which appear to be suited to the requirements of the coal gasi-
fication and gas purification operations, it was necessary to
limit the list of processes given detailed consideration to
those that have the greatest likelihood of near-term commercial
application.  These processes were identified on the basis of
the following criteria:


              Applicability to low/medium-Btu gasification
              and utilization technology requirements,


              Development status,


              Energy efficiency,


          •   Limitations (unusual raw material needs,
              sensitivity to various feedstocks and operating
              parameters, utilization processes, etc.),


              Environmental impacts, and


              Costs.


          In this section, processes are compared with respect
to the above criteria in a series of summary tables.  In order
to understand the conclusions reached as a result of  these com-
parisons, the reader must have some knowledge of the  technical
details of the various processes.  To satisfy this need, detailed
process "fact sheets" have been prepared for most of  the impor-
tant processes described here.  These fact sheets, which contain
process descriptions, flow diagrams and summaries of  available
process and discharge stream information, are included in
Appendices A through E.
                               -25-

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          It should be emphasized that the processes which are
given detailed consideration in this section have been selected
on the basis of currently available information.  Additions to
and deletions from this list of processes are anticipated as new
information is obtained from ongoing development programs.


3.1       COAL PRETREATMENT OPERATION


          The primary function of the coal pretreatment opera-
tion is to supply a coal feedstock which satisfies the physical
specifications of the gasification operation.  Coal handling and
storage modules are almost always required in this operation.
The need for other processing modules such as grinding and
screening depends on the nature of the run-of-mine coal feedstock
and the requirements of downstream processing operations.


          Figure 3-1 is a flow diagram showing the modules which
comprise the coal pretreatment operation.  The functions of these
modules are summarized in Table 3-1.  In the following text,
these optional pretreatment modules are described and the bases
for their use are discussed.


3.1.1     Crushing/Sizing Module


          Crushing and sizing steps are needed to produce a coal
feedstock which is suitable for charging to a coal gasifier.
Particle sizes for coal feed to fixed-bed gasifiers are generally
in the range of 2-50 mm (about 0.1-2.0 inches) in diameter.
Excessive quantities of fines cannot be tolerated in fixed-bed
systems because they can cause excessive bed pressure drop, poor
gas distribution or, in extreme cases, severe channeling.  Over-
sized coal particles can reduce the maximum throughput of fixed-
bed gasifiers because of their lower reactivity (low surface
area/volume ratio).  Oversized coal particles rejected from the
sizing step are a minor problem because they can be easily re-
cycled to the crushers.  On the other hand, the fines produced
from this operation must either be burned on site (e.g., in
utility boilers), sold as a by-product, disposed of as a solid
waste (landfill) or briquetted and fed to the gasifier.
                              -26-

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K>
                 LIGNITE OR
              HIGH MOISTURE

                     COAL
                    CAKING
                BITUMINOUS
 NONCAKING

 BITUMINOUS



ANTHRACITE
               DRYING
                                                                CRUSHING
                                                                   AND
                                                                  SIZING
                                                                               TO COAL GASIFICATION
                                                                                   OPERATION
                                                                TO ON-SITE

                                                             COMBUSTION. SALE
                                                               OR DISPOSAL

                                                                (LANDFILL)
                                  IN ADDITION TO THE MODULES
                                 SHOWN ABOVE. A COAL HANDLING/
                                 TRANSPORTATION MODULE AND A
                                 COAL STORAGE MODULE MIGHT BE
                               EMPLOYED AT ANY POINT IN THE ABOVE
                                                    . ALSO THE
                                                                                              TO COAL GASIFICATION
                                                                                                  OPERATION
                                 ORDER OF THE ABOVE PROCESSING

                                 STEPS MIGHT BE INVERTED. E.G. A

                                 CRUSHING/ SIZING MODULE MIGHT
                                   PMECCM A OftVMM MODULI IN

                                        ANY CUVCN PLANT.
                                    Figure  3-1.   Coal pretreatment  operation

-------
                      Table  3-1.   FUNCTIONS  OF MODULES  IN COAL PRETREATMENT  OPERATION
           Hodule
                                              Function
                                                                   Equipment Used
        Transportation

        Storage
        Crushing/
        Sizing
 i
ro
oo
 i
        Briquetting
        Pulverizing
        Drying
       Partial
       Oxidation
Movement of coal to and from other pretreat-
ment modules and to the gasification operation.

Provides adequate reserves to allow for
supply/demand surges (mine or gasification
plant downtime) and possibly blending
capability to provide a uniform feed to
the gasification operation.

Size reduction and elimination of over- and
undersize coal particles from a fixed-bed
gasifier feed stream.  Size specifications
dictated by mechanical characteristics of
gasifier.
Compaction of coal fines to produce a
briquette of a size suitable for feed to a
fixed-bed gasifier.  Certain binders, such
as asphalt or tar, may be required, along
with a baking or curing step, to give the
briquette the required structural strength.

Size reduction to provide a feedstock for a
fluid- or entrained-bed gasifier.
Mechanical dewatering or heat treatment to
remove excess moisture from coal feed.

Method of achieving a reduction in the  caking
tendencies of a feed coal by contacting the coal
with hot air or combustion gases under  con-
trolled conditions (temperature; time)  in a
suitable reactor.
Belt conveyors
Bucket elevators

Covered/uncovered bins - up to about  1.8 x 106
kg (2000 short tons)  per bin;  uncovered piles
on ground for greater than 2.3 x 10*  kg
(250,000 short tons)                (Ref. 4)
Crushing - double and single  roll crushers,
   rotary breakers, impactors,  cage mills
Sizing - Coarse (>50 mm [2  in.]  particles) -
            grizzly screens
         Medium (>13 mm [%  in.]  particles) -
            revolving, shaking  or vibrating
            screens.
         Fine (>2 mm [0.08  in.]  particles) -
            oscillating screens

Coal fines hopper, feeder and either a rotating
or a plate-type press along with provisions for
adding a binder.  A baking  oven may also be
required.
Hammer mills
Cage mills
Impactors
Ball mills

Mechanical:  centrifugal;  filtration
Thermal:  fixed- or fluid-bed driers.

Same as thermal driers

-------
3.1^2     Pulverizing Module


          A pulverized coal feed is needed for fluid- or
entrained-bed gasifiers.  This step would normally be performed
on site in contrast to the crushing and sizing steps which could
just as easily be performed at the mine as at the site of the
gasification unit.


3.1.3     Drying/Partial Oxidation Modules


          These processes are lumped here because both generally
involve contacting the coal with hot gases.  Coal drying is
desirable when the moisture content of the coal is so high that
the efficiency of the gasification process would be adversely
affected if the coal were fed directly to the gasifier.  Partial
oxidation can be used to reduce the caking tendency and increase
the softening temperature of a coal gasifier feedstock.  This
process may be needed to prepare coal for certain fixed- and
fluid-bed gasifiers that are unable to gasify caking coals.
Usually, this oxidation is performed under controlled conditions
such that most of the volatile matter in the coal is retained.


          The 'effects of partial oxidation on the caking proper-
ties of coal vary greatly with the type of coal.  Some coals
oxidize spontaneously when held at room temperature for a few
days.  Other coals may be stored for months without any change
in caking properties.  In most cases, lower rank coals (lignite,
subbituminous) are more readily oxidized than higher rank coals
(anthracite).  By contacting coal with air or oxygen at regu-
lated temperatures, it is usually possible to reduce its caking
tendencies to any desired level (Ref. 5).


3.1.4     Briquetting Module

                      j
          In this module, coal fines are compacted into
briquettes of sizes which are suitable for feed to a fixed-bed
 fasifier.  To produce briquettes, coal fines would usually be
 ed between a pair of mated rolls with recessed surfaces.  The
fines are compacted in these recessed areas as the rolls come
together.  A binder such as asphalt or tar may be required in
order to give the briquette sufficient structural strength.  In
some cases, the briquette may also need to be baked to provide
additional structural strength.
                              -29-

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3.1.5     Discharge Stream and Control Technology Summary -
          Coal Pretreatment Operation


          Several of the process modules in the coal pretreat-
ment operation are potential sources of air emissions, liquid
effluents, and/or solid wastes.  The sources and compositions of
these discharge streams and the associated control technology
requirements are summarized in Table 3-2.


          Air Emissions -


          Air emissions may be generated by all of the modules
in the coal pretreatment operation.  From conveying, crushing,
pulverizing, sizing and briquetting equipment may come signifi-
cant quantities of coal dust produced by mechanical agitation
and windblown transport.  The storage module may also be a
source of windblown coal dust.  Minor amounts of volatile
components in the coal may be emitted from coal storage piles
or bins, due to the effects of solar or spontaneous heating.
Coal dust may be emitted from mechanical dewatering processes.
Coal dust, volatile components, and combustion products are also
possible emissions from thermal drying processes.  Air emissions
from the partial oxidation and briquetting modules may contain
coal dust and/or volatile coal components.


          Liquid Effluents -


          Liquid effluents from the coal storage module may con-
tain a wide range of organic and inorganic constituents leached
by rainfall or water spray runoff from storage piles.  Water
sprays for controlling coal dust emissions will also produce a
liquid effluent.


          Solid Wastes -


          The solid wastes generated in the crushing and pulver-
izing steps may consist of rock or other mineral matter rejected
by the equipment.  The solid waste from the sizing step may
include rock or other mineral matter as well as undersize coal
particles (fines).
                              -30-

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     Table  3-2.    EMISSION  STREAM AND  CONTROL  TECHNOLOGY -  COAL PREPARATION  OPERATION
                             tnasportatloa
                               •mfale
            Storage
                                               Storage ptlea
                                                                                   and
                       toragc bins
                                                                                      modules
   Drying and
 partial oxidation
	nodules	
Briquetting
  modal*
an BUSSIOB

                         Coal dost
Coal dust; volatile Coal drat; volatile  Coal duct
matter             matter
                                                                                                   Coal dust; volatile  Coal Dust; volatile
                                                                                                   matter;  combustion   organ!cs; combustion
                                                                                                   products           products
• Suppression
techniques
• Collection and
treatment
techniques
LIQUID EFFLUENTS
Hater sprays
Covered conveyors;
collection ducts;
transfer to air
pollution control
process
Hone
Hater sprays;
polymer coatings
Runoff /leachate
from rainfall and/
or water sprays
Covered bins
Collection hoods
and ducts; transfer
to air pollution
control process
Hone if covered;
same aa storage
piles if not
Collection hoods
and ducta; transfer
to air pollution
control process
Hone
Proper temperature
control
Collection ducts;
transfer to air
pollution control
process
Hone
Proper control of
operating conditions
Collection ducts;
transfer to air
pollution control
process
None
  Control Technologies

  • Suppression
    techniques

  • Collection and
    treatment
    techniques
Polymer coatings
Collection ditches;
reuse as spray water
for dust suppression;
transport to water
pollution control
process
SOLID HASTES
  Control Technologies
                         Hone
                                           None
                                                              Hone
                                     Rejected rock and    None
                                     mineral Batter;
                                     coal fines

                                     Landfill for
                                     rejected wastea;
                                     on-site consumption,
                                     sale, or landfill
                                     for coal finaa
                                                                                                                    None

-------
          Control Technology Requirements -


          There are two basic types of control technologies
which can be used to treat discharge streams from the coal pre-
treatment operation; suppression techniques and collection and
treatment techniques.  Suppression techniques are used to reduce
the magnitude of a discharge stream.  Collection and treatment
techniques are used to contain a discharge stream and to remove
or convert its hazardous components.  These techniques may
include direct sale or disposal, or transfer of the discharge
stream to a pollution control process.


          All of the modules in the coal pretreatment operation
may emit coal dust.  Control of this emission is one of the most
important control technology requirements associated with this
operation.  Water sprays can be used to suppress coal dust from
conveying and storage processes.  Covered bins or polymer spray
coatings can be used to suppress coal dust emissions from storage
bins and ground storage piles.  Hoods and ducts can be used to
collect and transport coal dust from any module.  Particulate
control equipment items such as cyclones, baghouse filters,
scrubbers, and electrostatic precipitators can be used to recover
the coal dust collected from these sources.


          Air emissions containing coal dust, volatile matter
and combustion products from the drying, partial oxidation and
briquetting modules, can be minimized by maintaining proper con-
trol of process operating conditions.  Hoods and ducts can be
used to collect and transport these emissions to appropriate air
pollution control processes (particulate, hydrocarbon, and/or
sulfur emission control processes).


          Rainfall runoff and leachate from the storage module
can be suppressed with polymer spray coatings.  These liquid
effluents can be collected in ditches and then either reused as
spray water for dust suppression or transported to a suitable
water pollution control process for further treatment.


          Solid wastes consisting of rejected rock and mineral
matter from crushing, pulverizing and sizing processes would
usually be disposed of in a landfill.  Undersize coal fines from
the sizing module can be sold, disposed of by landfill, consumed
on site as a fuel or briquetted for use as a gasifier feedstock.
                              -32-

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3.2       COAL GASIFICATION OPERATION


          The function of the coal gasification operation is to
produce raw low/medium-Btu gas by reacting coal with a steam/air
or steam/oxygen mixture.  Additionally, some gasification pro-
cesses may use certain additives such as dolomite or fluxing
agents in the gasifier.


          Air is used for the production of low-Btu gas while
oxygen is required to produce medium-Btu gas.  Higher heating
values of low-Btu gas are approximately 3.7 x 106 to 9.3 x 106
Joules/Nm3 (100 to 250 Btu/scf).  Medium-Btu gas has a higher
heating value of approximately 9.3 x 106 to 18.6 x 106 Joule/Nm3
(250 to 500 Btu/scf).  In addition to steam and perhaps oxygen
production facilities, any one of several other modules may be
required for the coal gasification operation.


          Numerous reactions occur during coal gasification.
Among the more important ones for product gas specifications are
(Ref. 6):

          1)  C + %02 •*• CO          4)  CO + H20 -> C02 + H2

          2)  C + 02 •*• C02          5)  2H2 + C -»• CH^

          3)  H20 + C •*• CO + H2     6)  C02 + C •*• 2CO

From an environmental viewpoint, coal devolatilization and
reactions involving the sulfur and nitrogen species as well as
the trace elements in coal are probably of greater significance
than the reactions listed above because these can result in the
formation of a variety of hazardous compounds which must be
handled in downstream processing steps.  Reactions involving
additives may also be important in some gasification processes.

                                                        (
          Many types of gasifiers have been developed to produce
low/medium-Btu gas from coal; each has characteristics that make
it unique, both from a process and an environmental viewpoint.
These differences must be taken into account in the environmental
assessment of coal gasification technology.


          The production rates and -compositions of coal gasifier
effluent streams are affected by:

          •  the mechanical features of the gasifier,
                              -33-

-------
             coal feedstock properties, and

          •   gasifier operating conditions.

The following discussion of these factors is broken down into
six major sections.  The distinguishing mechanical features of
coal gasifiers are discussed in the first section.  The bases
used to identify the gasifiers which appear to be promising
candidates for near-term commercial application are discussed
in the second section.  This prioritization exercise was used
to select gasifiers for which detailed environmental analyses
appear to be justified.  A general discussion of how feedstock
and operating parameter changes affect gasifier performance is
presented in the third section.  In the fourth section, direct
comparisons of promising gasifiers are made on the basis of
their important process characteristics.  The fifth section
contains information pertaining to the environmental aspects of
coal gasification processes.  In that section, air emission,
liquid effluent and solid waste stream sources, quantities,
compositions and potential control methods are discussed.  Cur-
rent trends in low/medium-Btu gasification technology which are
environmentally significant and which will warrant attention
are described in the sixth section.
3.2.1     Types of Gasifiers


          Many types of gasifiers have been developed to
produce low/medium-Btu gas from coal.  These gasifiers are
usually classified according to their distinguishing mechanical
characteristics.  This basis of classification is also signi-
ficant from an environmental assessment viewpoint since varia-
tions in gasifier design account for many of the differences
which are observed in the environmental impacts of different
gasification systems.  Among the important characteristics in
this regard are the following:


             Bed type


                Fixed or supported bed
                (includes moving bed designs)


             -  Fluidized bed


             -  Entrained bed
                               -34-

-------
Operating conditions
   Pressure:  atmospheric or pressurized
-  Temperature

Gasification media
   Reactants:  steam, air, oxygen, other additives
   Coal feed/reactant ratios
   Mode of reactant introduction

Coal feeding
   Mode:   continuous or intermittent
   Mechanism:  lock hopper, slurry, screw, etc.
   Location:  top or center of gasifier

Ash removal
   Mode:   continuous or intermittent
   Ash condition:  dry or slagged  (fused)
-  Location:  from the gasifier or from the
   product gas stream

Energy input for gasification
-  Autothermic:  energy supplied by partial
   combustion of the feed coal in  the gasifier
   Electrothermic:  energy supplied by
   electrical resistance heating
   Solids circulation/heat transfer:  energy
   supplied by external heating and circulation
   of additives or inert solids
                 -35-

-------
          A total of 68 different types of gasifiers have been
identified which either have been used or are under development
to produce low/medium-Btu gas from coal.  These gasifiers are
classified in Table 3-3 according to bed type and ash removal
condition.  Most of these gasifiers are fixed-bed/dry ash,
fluidized-bed/dry ash, or entrained-bed/slagging units.


3.2.2     Gasification Process Prioritization


          Promising gasification processes (those which appear
to have the highest probability of near-term commercial
application in the United States) have been identified by a
prioritization process which is described below.  This is a
useful exercise because it also identifies those gasification
processes for which detailed environmental information will
probably be needed the soonest.


          In generating a list of priority gasifiers, the six
basic criteria discussed in the following paragraphs were con-
sidered.
          Applicability to Low/Medium-Btu Gasification -


          This criterion was applied to identify those
gasifiers that are best suited to the production of low/medium-
Btu gas from coal.  The gasifiers that have been developed
primarily to produce either high-Btu gas or liquid fuels were
not considered to be the most promising low-Btu gas producers,
even though they can also be operated to produce low/medium-Btu
gas.


          Development Status -


          There are many gasifiers which are not likely to be
used in the near future.  This includes gasifiers that have
been operated in the past but have been abandoned for various
reasons.  Other gasifiers are in such early stages of develop-
ment that their technical and economic feasibility cannot be
adequately assessed.  All gasifiers that are not either commer-
cially available or currently being tested on a demonstration
or large pilot-plant scale were not included in the list of
promising processes.
                              -36-

-------
  Table  3-3.    TOTAL  POPULATION  OF  LOW/MEDIUM-BTU  GASIFIERS
Caeifter type
   Gaslfler name
                                          Licensor/Developer
                                                  Statvs
Fixed-Bed. Dry Ash

   Lurgi

   Welloan-Galusha

   Chapman  (Hllputte)

   Woodall-Duckham/Gas Integrate

   Rlley Morgan


   Pressurized Wellman-Galusha
   (HERC)

   Foster Wheeler/Stoic

   Kllngas


   Kellogg  Fixed  Bed

   GEGAS


   Conaol Fixed Bed


   IFE Two  Stage


   Kerpely  Producer

   Harischka


   Plntsch  Hlllebrend

   U.O.I. Blue Water Gae

   Power Cei

   Vollnan  tncandeacent

   BCR/Kaiser
American Lurgi Corp. (USA)

HcDovell-Wellman Engr. Co.  (USA)

Wilputte Corp. (USA)

Woodall-Duckham, Ltd. (USA)

Riley Stoker Corp.  (USA)


Morgantown Energy Research
Center/ERDA (USA)

Foster Wheeler Energy Corp.  (USA)

Allli Chalnera Corp. (USA)


M. W. Kellogg Co. (USA)

General Ilectric Retearch and
Development (USA)

Consolidation Coel  Co.
(USA)

International Furnace Equipment
Co., Ltd.

Bureau of Mines/ERDA (USA)

Unknown


Unknown (Germany)

U.G.I. Corp./DuPont (USA)

Power Gat Co.  (USA)

Applied Technology  (USA)

Unknown
Present commercial operation

Present commercial operation

Present commercial operation

Present commercial operation

Present demonstration unit testing;
commercially available

Present development unit testing


Demonstration unit planned

Present development unit testing;
commercially available

Present development unit testing

Present development unit testing


Present development unit testing


Past commercial operation


Past commercial operation

Past commercial operation; anthracite
or coke only

Past commercial operation

Past commercial operation; coke only

Past commercial operation

Fast commercial operation

Past development unit testing
   BCC/Lurgl Slagging Ca«ifi«r


   CFERC Slagging  Gailfler


   Luena

   Thyssen Galocsy
British Gas Council  (CB)
Lurgi Mlnaraloltechnik  (W. Germany)  Preeent development unit testing
Grand Porks Energy  Research
Center/ERDA (USA)

Unknown

Unknown
Present development  unit testing;
lignite only

Fast commercial operation; coke only

Past commercial operation; coke only

                          Continued
                                                -37-

-------
 Table  3-3.    TOTAL  POPULATION  OF  LOW/MEDIUM-BTU  GASIFIEJRS   .
                                                                                              (continued)
Oaeifier typ«

   Caaitlcr name
       Licensor/Developer
                                                Status
Fluidlted-Bed. Dry Ash

   Wlnklar

   Hygaa

  •Synthane


   Hydrane


   Cogaa

   Exxon

   BCR Lov-Btu

   COj Acceptor

   Electrofluidic Gasification

   LR Fluid  Bed

   HRI FluidiMd Bed

   BASF-Flesch-Damag


   OEGB Harchwood

   Heller


fluldiaad-Bed. Agglomerating Aah

   U-Caa

   Battelle/Carbide

   Vestinghouse

   City College of NY Mark 1


   Two-stage Fluidlzed

   ICI Moving Burden



Untrained-Bed, Dry Aah

   Garrett Flash Pyrolysia


   Bianchl
Davy Powergaa Co. (USA)

Inatitute of Gaa technology (USA)

Pittsburgh Energy Research
Center/EROA (USA)

Pittsburgh Energy Research'
Center/ERDA (USA)

Cogaa Development Co.  (USA)

Exxon Corp. (USA)

Bituminous Coal Beaearch (USA)

Consolidation Coal Co. (USA)

Iowa State Univ./ERDA  (0SA)

Unknown (Germany)

Hydrocarbon Research Inc. (USA)

Badiacha Anilin und Soda Fabrlk
(Heat Germany)

Unknown

Unknown (Germany)
Institute of Gas Technology (USA)

Battelle Memorial Inatitute (USA)

Weatlnghouae Electric Corp. (USA)

Hydrocarbon Research Inc./
A.M. Squires (USA)

British Gas Council (England)

Imperial Chemical Industries,  Ltd.
(England)
Present commercial operation

Preaent development unit testing

Present development unit testing


Present development unit testing


Present development unit testing

Present development unit testing

Present development unit testing

Present development unit testing

Present development unit testing

Past commercial operation

Past development unit testing

Past development unit testing


Past development unit testing

Past development unit tasting




Present development unit testing

Present development unit testing

Present development unit testing

Present development unit testing


Present development unit testing

Past development unit testing
Garratt Research and Development    Present development unit testing
Co. (USA)
Unknown (France)
                                                                     Past development unit testing;
                                                                     lignite only
                                                                                               Continued
                                               -38-

-------
 Table   3-3.    TOTAL POPULATION  OF  LOW/MEDIUM-BTU  GASIFIEBS
	^	                                             (continued)
Gasifier type
   Gasifler name
                                         Licensor/Developer
                                               Status
   Panlndco


   USBM Annular Retort


   USBM Electrically Heated


Entrained-Bed, Slagging Ash

   Koppers-totzek

   Bi-Gas


   Texaco

   Coalex


   PAMCO/Poster Wheeler


   Combustion Engineering

   Brlghao Young  University


   Babcock and Wllcox

   Ruhrgaa Vortex

   IGT Cyclonlzer

   Inland Steel

   USBM, Morgantown


   Craat Northern Railway

   FRS Cyclone


Molten Media. Slaanlnti Ash

   Kellogg Molten Salt

   Atgae/Patgas

   Rockgas

   Rummel Single Shaft


   Sun Gasification


   ncto BiiaMl Double Shaft
Unknown (France)


Bureau of Mlnea/ERDA (USA)


Bureau of Mloea/ERDA (USA)




Koppera Co.  (USA)

Bituminous Coal Research, Inc.
(USA)

Texaco Development Corp. (USA)

Inex Resources, Inc. (USA)


Pittsburgh and Midway Coal Co./
Foster Wheeler (USA)

Combustion Engineering  (USA)

Brlghao Young University/
Bituminous Coal Research (USA)

The Babcock and Wilcox  Co.  (DSA)

Ruhrgas A. 6. (West  Germany)

Institute of Gas  Technology  (USA)

Inland Steal Co.  (USA)

Horgantown Energy Research
Center/ERDA (USA)

Great Northern Railway  Co.  (USA)

Unknown (England)
 M. W. Kellogg Co. (USA)

 Applied Technology Corp.  (USA)

 Atomic* International (USA)

 Union Rhelnlsche Braun Kohlen
 Kraftstoff A. G. (West Germany)

 Sun Resesrch and Development Co.
 (USA)

 Dr. C. Otto and Co.
Past development unit testing;
lignite only

Past development unit testing;
lignite only

Fast development unit testing
Present commercial operation

Present development unit testing


Present development unit testing

Present development unit testing;
commercially available

Present development unit testing


Present development unit testing

Present development unit testing


Past commercial operation

Past commercial operation

Past development unit testing

Past development unit testing

Paat development unit testing


Past development unit testing

Past development unit testing
 Present development unit testing

 Present development unit testing

 Present development unit testing

 Past  commercial operation


 Past  development unit testing


 Past  development unit testing
 lefsrenoeat  7. 8. 9, 10,  11, 12, 13
                                                -39-

-------
          Energy Efficiency -


          Gasifiers that have high energy requirements (or low
l[<40%] conversion efficiencies) and those with special energy
features (electric plasma arc or a molten media) were not
included on the list.


          Process Limitations -


          This criterion was used to identify the gasifiers that
have limited flexibility with respect to:


              Feedstocks

              Operating conditions

              Raw material requirements


The gas producers that were developed to use charcoal or coke
feedstocks, for instance, were not considered to be promising
gasifiers, nor were those that have low  (<100/60) turndown
ratios, unstable operating characteristics, and/or unusual raw
material requirements.


          Environmental Impacts -


          Gasifiers can be excluded from the list on the basis
that they produce uncontrollable fugitive emissions or discharge
streams containing hazardous constituents that cannot be con-
trolled with existing technology.  This criterion is somewhat
difficult to apply at the present time, however, because of the
limited information available concerning the quantities and
compositions of discharge streams and fugitive emissions from
gasification processes.


          Costs -


          This criterion should be used  to identify the gasi-
fiers that have high capital and/or operating costs, and are
therefore of questionable commercial viability.  Because of the
limited availability of accurate cost data and the dependency of
                               -40-

-------
costs on site-specific factors, this criterion was not used as a
basis for the selection of promising gasifiers.


          Ultimately, of course, economic factors will be very
significant in determining which gasifiers will be used in the
United States.  These factors include a) the rapidly changing
energy cost/supply situation, b) proposed government incentives
to switch to coal, c) the availability of currently used fuels
such as natural gas and oil, d) federal, state, and local
environmental regulations, and e) various site-specific factors
such as the type of energy required at a specific location.


          The first two economic factors, the cost/supply situa-
tion and proposed government policies are related.  If the
regulations on natural gas prices are eliminated, the cost of
natural gas will rise.  Also, if industrial use taxes on gas and
oil are implemented, the cost of using these fuels will increase.
In order to provide an incentive for companies to use coal as
their primary fuel feedstock, various economic incentives are
proposed in the National Energy Act.  These incentives include
investment credits for companies up to the amount of their
federal income taxes.  Either a dollar for dollar credit against
corporate income taxes or an additional 10 to 12 percent invest-
ment credit over and above the current 10 percent credit for
qualifying investments can be realized.  The dollar for dollar
credit is based on the amount of energy currently produced from
natural gas and oil that is replaced by using coal.


          The availability of natural gas and oil is another
significant economic factor affecting the commercialization of
low-Btu gasification.  For example, last winter there were cer-
tain areas in the U.S. that had curtailments of natural gas used
in industrial processes which caused companies to reduce or shut
down production.  These curtailments will be more widespread
once natural gas supplies are further diminished.  Therefore,
the costs associated with a cutback in production will affect
the economic viability of replacing natural gas fuel with fuels
produced from coal.


          The costs associated with controlling the multimedia
emissions from low-Btu gasification plants will also be a signif-
icant economic factor in determining the gasification systems to
be commercialized.  For example, a small gasification system
using anthracite coal to produce a low-Btu combustion gas will
require minor pollution control technology.  However, large
gasification systems using high sulfur bituminous coals will
                              -41-

-------
have significant problems in controlling gaseous, water, and
solid waste discharge streams.  Therefore, small gasification
plants will probably be the first to be commercialized in
significant quantities.


          Site-specific factors such as coal cost and avail-
ability and product gas end use will also affect the economic
viability of low-Btu gasification.  In areas where low sulfur
coal is readily available and electricity is the primary energy
need, direct coal combustion processes coupled with flue gas
cleaning will probably be more economical than combusting
low-Btu gas to produce electricity.  However, developments in
combined-cycle units may improve the economics associated with
using gasification as a means for producing electrical power.
Economic considerations of using coal gasification with an acid
gas removal process versus direct coal-fired processes with flue
gas cleaning will also affect the costs for using high sulfur
coals to produce electricity.


          Promising Gasifiers -


          Based on the above criteria, fourteen coal gasifiers
have been identified as those which appear to have the highest
potential for near-term commercial application in this country.
These gasifiers, which are listed in Table 3-4, can be divided
into three categories based on their development status.  The
first group includes the gasifiers that are commercially avail-
able and are currently being widely used in the U.S. or in
foreign countries.  Gas producers that are commercially avail-
able but are not currently in widespread use are listed in the
second group.  The third group consists of the gasifiers that
are either operating or being constructed for evaluation on a
demonstration unit scale.


          It should be emphasized that the data used to classify
these gasifiers were obtained from currently available sources
of information.  Additions to or deletions from this prioritized
list of gasifiers are anticipated as development work progresses
and more data are obtained.


          Detailed information pertaining to operating parameters;
discharge streams, control technology requirements, and flow dia-
grams for each of these "most promising" gasifiers is presented
in Appendix A.  Also shown on the flow diagrams for these gasi-
fiers are the discharge streams from the particulate removal,
                               -42-

-------
Table 3-4.   COAL GASIFIERS WITH POTENTIAL NEAR-TEBM COMMERCIAL  APPLICATION IN THE U.S
Gasifier
Lurgi
Galusha

Woodall-DucVhas/
Cas lategrale
Koppers-Totzek
Winkler
Chapman
(Wilputte)
Rlley Morgan
1
^J Coalex
1
Pressurized
Hellman-Galusha.
(KERC)
BCC/Lurgi Slagging
Gasifier
CFERC Slagging
Casifier
Texaco
Bl-Cas
Foster Wheeler/
Stoic
Wellman
Incandescent
Plant/Location*
SASOL
Salsolburg, S.A.
Glen-Gery Brick Co.
'Reading, PA
National Lime Co.
Carey, OH
Choautov Tube Works
Czechoslovakia
Azot Sanayii T.A.S.
Kutahya, Turkey
Azot Sanayii T.A.S.
Sutahya, Turkey
U.S. Army Holston
Arsenal _
Klngsport, TN
Klley Research Center
Worcester, HA
Inex Resources, Inc.
Lakevood, CO
ERDA Morgantovn
Energy Research
Center, Morgan t own, WV
West field Development
Centre
Westfield. Scotland
ERDA Grand Forks
Energy Research Center
Grand Forks, ND
Hontebello Research
Laboratory
Mcntebello, CA
Bituminous Coal
Research, Inc.
.Homer City, PA
University of Minn.
Duluth, MM
York, PA
Coal type*
tested
Bituminous
Anthracite
Bituminous
Lignite
Lignite
Lignite
Bituminous
Anthracite.
bituminous
All types
except liquids
Subbituminous,
bituminous
Bituminous
Lignite
Lignite,
bituminous
Lignite,
Subbituminous
bituminous
Subbituminous
Bituminous
Part, removal
Wash cooler
Hot cyclone
Hot cyclone
Hot cyclone/hot
ESP, wash cooler
WHB, wash cooler,
wet cyclone
WEB, hot cyclone,
vash cooler
Hot cyclone
Hot cyclone
Sone
Hot cyclone
Wash cooler
Wash cooler
Water sprays,
quench tank,
wash cooler
Hot cyclone,
wash cooler
Hot ESP, hot
cyclone
Hot ESP, cyclone
'Commercially available; significant numbers of units currently operating In the
0.8. or In forsign countries.
'CoMsrclally available or operating) MO-Ura application poatlbl*.
Quenching/cooling
Wash cooler, waste
heat boilers, trim
None
None
Wash cooler,
trim cooler
WHB, wash cooler,
wet cyclone
WHB, wash cooler
Water sprays,
wash cooler
None
None
None
Wash cooler, WHB
Wash cooler, trim
cooler
Water sprays,
quench tank,
wash cooler
Wash cooler
None
None
Acid gas
removal
Rectisol
None
None
None
Sulfinol/
Rectisol
Iron oxide,
water wash,
SaOP. wash
None
None
Checical
additive to
coal feed
None
Rectisol
None
DMA
Selexol
None
Stretford
""Location of largest
*Und«r contraet
*Proc«»» development
End Use
Synthesis gas/fuel gas for
domestic consumption
Fuel gas for brick kiln
Fuel gas for line kiln
Fuel gas for metallurgical
process
Synthesis gas for ammonia
production
Synthesis gas for ammonia
production
Fuel gas for acetic
anhydride process
PDU* - product gas flared
Fuel gas to boiler
(comercial unit under
construction)
PDU* - product gas flared
PDU* - product gas flared,
feed to nethanation demon-
stration plant
PDU* - product gas flared
PDU* - product gas flared
PDU* - product gas flared
Fuel gas steam boiler
Fuel gns
operating plant
unit
Status
1
1
1
1
1
1
2
2
2
3
3
3
3
3
3s
2

 'Operating or feeing constructed ai d«*m«tratlon units; technology !• profiting

-------
and gas quenching/cooling processes that have been proposed for
use with each gasifier.
                                                               1

3.2.3     Effects of Feedstock and Operating Parameter Changes


          Changes in:  1) the nature of the coal feedstock,
2) operating pressure, 3) operating temperature, and 4) steam/
oxygen (or steam/air) ratio can have significant effects on the
performance and environmental impact of a gasifier.  Changes in
these parameters can affect the coal throughput rate, the thermal
efficiency, arid the raw gas and ash compositions.  These composi-
tions in turn are directly related to the environmental impact
of a gasifier, since the discharge streams from coal feeding and
ash removal devices may contain ash and raw gas components.  The
composition of the raw gas can also affect the requirements for
downstream gas purification and pollution control processes.
The significant effects of feedstock and operating parameters
are summarized in the following text.


          Coal Feedstock Effects -


          The composition of the coal feedstock has little
effect on coal throughput rate or raw gas composition in en-
trained-bed gasifiers.  In fixed-bed and fluidized-bed gasifiers,
however, an increase in the amount of volatile matter in the
coal feed will tend to decrease the maximum coal throughput rate
and increase the amounts of methane, tars, and oils in the raw
gas (Ref. 14).


          For a given coal type, the method of coal feeding will
also affect the amounts of tars and oils produced in fixed- and
fluidized-bed gasifiers.  Gasifiers which feed coal at the top
of the bed will tend to produce larger amounts of tars and oils
than gasifiers which inject the coal at the center of the bed.
Feeding coal to the top of the bed allows the coal to come into
contact with rising hot gases before it reaches the gasification
zone.  This facilitates the devolatilization of tars and oils.
The types and concentrations of sulfur compounds and trace
elements in the coal feed will also directly affect the composi-
tion of the raw gas from all types of gasifiers.
                              -44-

-------
          Pressure Effects -


          The operating pressure of the gasifier affects both
the throughput rate and the raw gas composition.  For entrained-
bed gasifiers, throughput is roughly proportional to the abso-
lute operating pressure (doubling the absolute pressure will
approximately double the throughput rate).   For fixed-bed and
fluidized-bed gasifiers, throughput rate is roughly proportional
to the square root of the absolute operating pressure.  The
limiting factor in fixed-bed and fluidized-bed gasifiers is the
maximum gas velocity that can be achieved without excessive
pressure drop or solids carryover (Refs. 15, 16).


          The raw gas composition is also affected by changes in
operating pressure.  Increasing operating pressure favors methane
and carbon dioxide formation and increases the heating value of
the product gas.  Carbon monoxide and hydrogen formation are
suppressed at higher operating pressures (Ref. 17).   High pres-
sures also favor the formation of metal carbonyls and hydrogen
cyanide which are extremely hazardous and which, if formed, may
present difficult downstream removal problems.


          Temperature Effects -


          The gasification temperature affects the coal through-
put rate, the raw gas composition, and the thermal efficiency of
the gasifier.  Higher gasification temperatures are usually
obtained by increasing the 02/coal feed ratio.  Temperature has
a pronounced effect on the coal throughput rate in fixed-bed
gasifiers as the transition is made from dry ash conditions at
approximately 1255°K (1800°F) to slagging ash conditions at
greater than 1530°K (2300eF).  A temperature increase of this
magnitude has been observed to result in a fourfold increase in
the maximum coal throughput rate (Ref. 18).  This temperature
effect can be attributed to the increased rates of the gasifica-
tion reactions.  At temperatures above 1530°K (2300°F), gasifi-
cation reactions tend to become limited by mass transfer, and
therefore further increases in temperature do not increase the
maximum throughput rate appreciably (Ref. 19).


          Thermal efficiency tends, to decrease with increasing
gasification temperature because of the increased heat content
of the ash and product gas at higher temperatures.  This effect
is most pronounced for fixed-bed gasifiers as the transition is
made from dry ash to slagging conditions.  The heat carried out
                              -45-

-------
of the gasifier in the liquid slag is difficult to recover.  On
the other hand, steam consumption for this type of operation^is
lower, which tends to compensate somewhat for the heat lost in
the liquid slag.


          The composition of the raw gas is affected by changes
in gasification temperature because of shifts in the equilibrium
constants of the principal gasification reactions.  Also, the
rates of thermal cracking of tars, oils, phenols, and hydrocar-
bons increase as the temperature increases.  For fixed- and
fluidized-bed gasifiers, methane and carbon dioxide concentra-
tions in the raw gas decrease with increasing gasification
temperature while carbon monoxide and hydrogen concentrations
increase.  The heating value of the raw gas from these gasifiers
increases slightly with increasing gasification temperature
(Refs. 20, 21).  The composition of the raw gas from an
entrained-bed gasifier is not very sensitive to gasifier tempera-
ture changes.


          Steam/Oxygen and/or Steam/Air Ratio Effects -


          Changes in the ratios of reactants fed to the gasifier
can affect the coal throughput rate, thermal efficiency, and raw
gas composition.  The coal throughput rate is affected indirectly,
since lowering the steam/oxygen (or steam/air) ratio will increase
the gasification temperature which will result in an increase in
the coal gasification rate.  Fixed-bed and fluidized-bed gasifiers
that operate at temperatures below the ash fusion (slagging)
temperature require excess steam to moderate the exothermic gasi-
fication reactions; therefore, the steam/oxygen  (or steam/air)
ratio is normally higher than that required to supply the reac-
tants necessary for gasification.


          This is important from an energy efficiency point of
view.  Any excess steam used for moderation purposes ultimately
must be condensed and removed from the raw gas.  This is a loss
of useful energy and usually results in a decrease in the overall
thermal efficiency of the gasification process.  The hydrogen,
methane, and carbon dioxide concentrations in the raw gas tend
to increase with increasing steam/oxygen (or steam/air) ratios
while the carbon monoxide concentration tends to decrease.
Increasing this ratio may also favor the formation of HaS over
COS in the gasifier.  Changing this ratio has little effect on
the heating value of the raw gas.
                              -46-

-------
3.2.4     Gasification Process  Comparisons


          In this  section,  the  fourteen previously identified
"most promising" gasifiers  are  compared with respect to:


              Development status

              Thermal efficiency

              Feedstock  limitations

              Product gas end-use options


The development status,  thermal efficiencies, and coal feedstock
limitations of the fourteen priority gasifiers are summarized in
Table 3-5.  The most suitable end-use options for the low/medium-
Btu gas produced by these gasifiers are presented in Table 3-6.


          Development Status -


          Seven of the gasifiers listed in Table 3-5 are
considered to be commercially available.  These include six
gasifiers which are operating in commercial gasification plants
and one gasifier,  the Riley-Morgan, which has been tested in a
commercial scale demonstration unit.  The other seven gasifiers
listed in Table 3-5 are  classified as being demonstration scale
units.  These  include  six gasifiers which are operating at
single unit process development plants and one gasifier, the
Foster-Wheeler/Stoic, which is  presently being constructed at a
semi-commercial process  demonstration facility.


          Thermal  Efficiency -


          The cold gas and  overall thermal efficiencies listed
in Table 3-5 are defined as follows:

                    rC. *       [Product gas  energy output]   ,ftn
          Cold gas  efficiency  = -1	tCoal*ener8y ^t}     X 10°

          Overall thermal efficiency =
           [Total energy output (product gas + by-products + steam)]
             [Total energy input (coal + steam + electricity)]
                               -47-

-------
Table 3-5.  COMPARISON OF PROMISING COAL  GASIFIERS
Gasifier Development
Type Status
Bellman-Calnabm Fixed-Bed Commercial
Lmrgl Fixed-Bed Commercial
'ftn-'il 1 -mil >U«m/ Fixed-Bed Commercial
Cms Integrals
Ctapman(Uilputte) Fixed-Bed Commercial
1
00
1
tlley Morgan Fixed-Bed Commercial
Scale Demo.
Unit Tested
Pressurized Fixed-Bed Demo. Unit
tfellman-Galusha Operational
Caslfler (MERC)
CFERC Slagging Fixed-Bed Demo. Unit
Gasifier Under Const.
Feedstock Limitations
| Maximum
Cold Gas Overall Thermal, Coal Size Coal Moisture Coal Caking
Efficiency (X)" Efficiency (Z)D nm(in) Content (X) Properties
75 81 8-51(0.3-2.0) HR Requires
agitator;
reduces
throughput
63-75 76 3-38(0.1-1.5) <35 Requires
agitator;
reduces
throughput
77 88 6-38(0.25-1.5) Any Swelling in-
dex <2.5
HR HR <102(<4.0) HR Requires
agitator;
reduces
throughput
72 NR 3-51(0.1-2.0) HR Requires
agitator;
reduces
throughput
79 NR 50X<13(50X<0.5) Any Requires
agitator;
reduces
throughput
HR NR 6-10(0.25-0.75) Any Non-caking
coals only

1
Coal Ash
Content
Any
Any
NR
Any
Any
Any
Low ash or
refractory
type ash
may require
flux
                                                           (continued)

-------
             Table  3-5.   COMPARISON OF PROMISING  COAL GASIFIERS
                                                                           (continued)
Feedstock Limitations

KC/Uovl
Slagging
Casifier
IV/Stoic
Vlakler
Caslfier
Find-Bad
Fixed-Bed
Fluldized-
Bed
Eoppera-Totzek Entralned-
Bl-Gas
Texaco
Coalex
U: Hot
'told gas
kOv*rall
Entrained*
Bed
Entralned-
Bed
Entrained-
Bed
reported
efficiency - [Product
[Coal
tbanal affieiaocy - M
[1
Developawnt Cold Gaa
Status Efficiency
Deno. Unit IR
Operational
Deao. Unit KX
Under Const.
Conefclal 55-72
CoBBusrcial 65-75
Dean. Unit 69
Operational
Deao. Unit HE
Under Const.
Commercial Unit HE
Under Const.

gas energy outpotl 1nn
energy input] x iou
total an«r«y outant (»ro4»ct |
tatal anargy input (coal + at*
*•* SBtii «w**U ttenal a* Ctelaocy «f a gaslf iar my vary
•yea, fk» m41i.tr «< *•» iMiiaracai ayvfcam t« «aa UM aaaiaj
| Hndaua
Overall Thermal. Coal Six* Coal Moisture
(Z) tfflcleney «)° ••(In) Ceatent (Z)
•R 13-51(0.5-2.0) <20
Fines nay be
injected Into
tuyeres
NR TO Any
69 <9.5(<0.4) <30
68 70Z<0.1(70Z<0.0*) 2-«
65 70Z<0.1(70Z<0.04) Any
HR <0.1(<0.04) Any
88-93 <0.07(<0.003) Any


iaa •*• >r-pra ranaDS (Ivan Aa»aa«ing
eoacafcwd !• iy a»od»a.t hydr*-
Coal Caking
Proper t iaa
Requires
agitator;
reduces
throughput
Non-caking
coals only
Swelling
Index <*.0
All coals
All coals
All coals
All coala




1
Coal Aah
CoBtcmt
Low ash or
refractory
type ash
nay require
flux
HE
Any
>40X re-
factory
type ash
nay require
flux
Refractory
type aao
may raoalre
flux
NR
Any




and waste ataaau

-------
          Table  3-6.
LOW/MEDIUM-BTU GASIFICATION SYSTEM
PRODUCT  GAS  UTILIZATION OPTIONS
Qasifier type

  Gasifier name
      Significant operating
         characteristics
  Utilization option
for which each gasifier
    is best suited	
Fixed-Bed (Dry Ash)

   Wellman-Galusha

   Lurgi


   Woodal1-Duckham/
   Gas Integrale

   Chapman (Wilputte)

   Riley Morgan

   Pressurized
   Wellman-Galusha  (MERC)

   Foster Wheeler/Stoic
 Atmospheric; air or oxygen blown

 Pressurized; air or oxygen blown


 Atmospheric; air or oxygen blown


 Atmospheric; air or oxygen blown

 Atmospheric; air or oxygen blown

 Pressurized; air or oxygen blown


 Atmospheric; air blown only
On-site combustion

Off-site combustion;
combined cycle

On-site combustion
On-slte combustion

On-site combustion

Off-site combustion;
combined cycle

On-site combustion
Fixed-Bed (Slagging Ash)

   GFERC Slagging Gasifier
   BGC/Lurgi Slagging
   Gasifier
 Pressurized; oxygen blown only


 Pressurized; oxygen blown only
Off-site combustion;
combined cycle

Off-site combustion;
combined cycle
Fluidized-Bed (Dry Ash)

   Winkler
 Atmospheric; air or oxygen blown
On-site combustion
Entrained-Bed (Slagging Aah)

   Koppers-Totzek


   Texaco Gasifier


   Bi-Gas


   Coalex
 Atmospheric; oxygen blown only;
 high CO, low CH, in product  gas

 Pressurized; air or oxygen blown;
 high CO, low CHi, in product  gas

 Pressurized; air or oxygen blown;
 high CH» in product gas

 Atmospheric; air-blown; solid
 additive for sulfur removal
Synthesis/reductant gas
Synthesis/reductant gas,
combined cycle

Off-site combustion;
combined cycle

On-site combustion
Bases for selecting best utilization technology:

   1)  Atmospheric gasifiers arc limited to on-site combustion applications.

   2)  Pressurized, oxygen-blown gasifiers are best suited to off-site combustion applications.

   3)  Pressurized gasifiers, both air- and oxygen-blown, are suitable for combined-cycle
       applications.

   4)  Product gases which are high in CO and H   content, and low in CH  and hydrocarbon
       content are suitable for use as Synthesis/reductant gases.
                                         -50-

-------
Energy outputs are based on producing a quenched and cooled
product gas at a reference temperature of 300°K (80°F).


          Reported cold gas efficiencies for eight of the
fourteen gasifiers listed range from 55% to 79%.  Cold gas
efficiencies for six of the gasifiers were not reported in
available sources.  The highest cold gas efficiency reported
was for the Pressurized Wellman-Galusha Gasifier (MERC), while
the lowest was that given for the Winkler gasifier.


          Reported overall thermal efficiencies for seven of the
fourteen gasifiers range from 65% to 93%.  Overall efficiencies
for the other seven gasifiers were not reported in available
sources.  The Coalex gasifier has the highest reported overall
thermal efficiency (88-93%), although this range of efficiencies
may be somewhat optimistic.


          Feedstock Limitations -
          The coal feedstock limitations summarized in Table 3-5
include:
           •   Size requirements

           •   Moisture  content

              Caking properties

              Ash content


These  feedstock  limitations are an indication of the flexibility
of each gasifier to accommodate variations in coal feedstock
properties.  Although a feed  size requirement is not specified
for  the Foster Wheeler/Stoic  gasifier,  its size requirement is
probably  similar to that for  the Woodall-Duckham/Gas Integrale
gasifier  because of their  design and operating similarities.


           Maximum allowable moisture content is specified  for
four gasifiers.  Any moisture content is acceptable for  seven
gasifiers,  and no moisture content limitations have been
reported  for three gasifiers.
                              -51-

-------
          Caking properties are not considered limiting factors
in entrained-bed gasifiers.  The GFERC and BGC/Lurgi Slagging
Gasifiers may require the addition of flux to the coal input
when a low ash content or a high percentage of refractory type
ash is present in the feed coal.  The Koppers-Totzek and Bi-Gas
gasifiers may require the addition of flux to the coal input
when gasifying coals containing high percentages of refractory
type ash.  Three of the gasifiers do not have reported limita-
tions on ash content or composition.


          Product Gas End-Use Options -


          Of the many significant end-use options for low/medium-
Btu gas, the three uses which appear to be the most reasonable
bases for the future development of a low/medium-Btu gasification
industry in the U.S. are:


              Combustion fuel - both on-site and
              off-site (pipeline) applications


              Gas turbine fuel - including combined cycles


              Synthesis/reductant gas

                                      i
          The selection of an optimum gasifier design for each
of these end-use options involves consideration of many factors.
Atmospheric gasifiers are best suited to applications which
require a low pressure fuel gas  (on-site combustion).  Atmos-
pheric gasifiers are not competitive in applications which
require a pressurized low- or medium-Btu gas.  Since a gasifier's
product gas flow exceeds its feed gas (steam and air or oxygen)
flow on a molar or volumetric basis, it is cheaper to compress
the gasifier feed gas than the gasifier product gas whenever a
pressurized product gas is needed (e.g., for feed to a pipeline
for off-site consumption).


          Off-site consumption requirements may also justify the
use of an oxygen-blown rather than an air-blown gasifier.  For
on-site combustion fuel applications, the increased throughput
which can be realized through the use of oxygen rather than air
does not compensate for the cost of oxygen production.  The
reduced transportation costs associated with pipelining medium-
Btu gas (relative to low-Btu gas), however, may justify the use
of oxygen in a pressurized system.
                              -52-

-------
          In combined-cycle operations, the fuel gases are
burned in a pressurized system, and the combustion products are
expanded through a gas turbine which produces shaft work.  The
sensible heat of the combustion products is recovered by heat
exchange^and converted by means of a steam turbine cycle to pro-
duce additional shaft work.  Combined cycles appear to be well
suited to the generation of.electricity.  Only pressurized
gasifiers are applicable to this end-use option.  Either air-
blown or oxygen-blown gasifiers can be used to produce a
combined-cycle fuel.


          Synthesis/reducing gases are used as raw materials in
a variety of chemical processes.  In most applications, high
concentrations of hydrogen and carbon monoxide and low concen-
trations of methane and other hydrocarbons are desirable.
Because of this composition requirement, the Koppers-Totzek and
Texaco gasifiers are considered to be well suited to this end-
use option.


          As a result of these considerations, the end-use
options can be identified for which the fourteen promising
gasification systems appear to be best suited.  These options
are listed in Table 3-6.
3.2.5     Discharge Stream and Control Technology Summary -
          Coal Gasification Operation


          The types of emission problems which must be dealt
with in the coal gasification operation are shown schematically
in Figure 3-2.  From this figure, six sources of potential emis-
sions are indicated.


              02 production unit,

          •   utility (process steam; electric power)
              production facilities,

              coal handling and feeding system,

              ash removal and disposal system,

              gasifier product gas start-up vent, and

              fugitive emissions
                              -53-

-------
                           3TART-UP
                            VENT
      FUGITIVE EMISSIONS
        FROM POKEHOLES .»-
       OR LEAKING SEALS

             COAL DUST
            VENT GASES
                              PRODUCT LOW/MEDIUM-
                              BTU GAS TO GAS
                              TREATING SECTION
PRETREATED.
      COAL
     FUEL

      H2O

      AIR
             SLOWDOWN
            CONCENTRATE
      AIR

   POWER
    AIR
FRACTIONATION
    UNIT
                                       ASH DUST.
                                      VENT GASES
                                     MAKEUP
                                     QUENCH WATER
                                     SLUICE WATER
                                     OR ASH PAN
                                     SEAL WATER
                       ASH
                    (WET OR
                       DRY)
                SLUICE
                WATER
                RETURN
                                              ASH DUST,
                                             VENT OASES
°2
SLOWDOWN
SLUICE
WATER
                   N2.Ar
        Figure  3-2.
          Sources  of potential emissions
          in the  coal  gasification  operation
                               -54-

-------
Each of these environmental problem areas is discussed in the
following text along with the control methods which can be used
to minimize the impacts of emissions from these sources.


          Oxygen Production Unit -


          Current technology for generating the high purity
oxygen stream needed to produce medium-Btu gas involves the use
of a cryogenic air fractionation unit.  In such a unit, inlet
air is compressed, pre-cooled and liquefied by flash cooling and
by contact with cold product gas streams.  The only potential
direct emissions from this processing step are the high purity
nitrogen and argon streams which are produced as by-products of
the liquid air fractionation step.  Although these streams could
be vented to the atmosphere, it is more likely that they would
be used to satisfy on-site purge gas needs or sold as by-products.


          Emissions which would result from this processing step
are associated with the facility supplying the power needed by
the air fractionation unit.  These emissions are discussed in
the following section.


          Steam and/or Electric Power Production Facilities -


          The utility needs of the gasification operation will
vary considerably depending upon the nature of the gasification
process which is employed.  A high-pressure oxygen-blown gasifi-
cation system (gasifier + Oz production facility) will consume
significant quantities of high-pressure steam and/or electric
power.  An atmospheric-pressure, air-blown gasifier on the other
hand, generally will have relatively minor requirements for
steam and electric power.  In fact, the process steam require-
ments of all existing air-blown, atmospheric pressure gasifica-
tion systems are satisfied by the vaporization of water in the
gasifier cooling jacket.


          If a high pressure steam boiler is used to supply the
on-site utility needs of the gasification complex, the emission
streams and the control needs of this unit will be identical to
those of a typical utility company power plant.  The composition
of the flue gas emitted from the boiler will be a function of
the fuel which is consumed.  The best alternative environmentally
would be the consumption of product low/medium-Btu gas.  In this
instance, the boiler flue gas would have very low particulate,
                              -55-

-------
sulfur oxide and nitrogen oxide concentrations.  This option may
not be very attractive from a process efficiency or cost point
of view however, because it increases significantly the load on
the gasification unit.  A more desirable alternative from both
an energy efficiency and cost point of view is the consumption
of feed coal directly in the utility boiler.  In this case, flue
gas treatment to control particulate and perhaps sulfur emissions
would be necessary.


          The other emission streams associated with a utility
boiler which would have to be handled are boiler feed water
treatment wastes, boiler blowdown, and, if coal is used as
the boiler fuel, bottom and fly ashes.  The treatment and
disposal options which are available for these streams are
discussed in Section 4.0 in the liquid and solid waste control
discussions, respectively.


          Coal Handling and Feeding System -


          This system is a major source of potential air emis-
sions from coal gasifiers.  Emissions from coal feeding systems
may contain raw gasifier product gas components, coal or ash
dust, and, in pressurized systems, pressurizing gas components.
The rates and compositions of the vent gases from coal feeding
systems will be affected by several factors.  Among these are:


              the mechanical design of the device,


              gasification system operating and
              maintenance procedures, and


              the physical characteristics and compositions
              of the feed coal, raw gasifier product gas and
              pressurizing gas.


          Coal dust - Some coal dust will always be generated as
a result of transporting coal to the gasifier feed hopper.  Al-
though steps can be taken in the design of a coal handling system
to minimize its dust forming tendencies, some coals are inherently
more friable than others.  In most systems, the use of a covered
coal transportation system along with gas collection ducts and
particulate removal equipment would be desirable to control
the s e emi s s ions.
                              -56-

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          Vent gases - The rate of vent gas release from a coal
feeding device will be a function mainly of the design of the
device, its mode of operation and the operating pressure of the
gasifier.  The composition of the vent gas will be affected by a
variety of factors including:


              the operating procedures of the unit

              the composition of the raw product gas,
              and

              the feed system pressurizing gas, if used.


          There are four general types of coal feeding devices
which are in widespread use:


              Lock hoppers

              Rotary feeders

          •   Screw feeders

              Slurry or entrained-flow injection devices.


Lock hoppers and slurry injection devices are used to feed coal
to high-pressure gasifiers while lock hoppers, rotary feeders,
and screw feeders are used to feed coal to atmospheric pressure
gasifiers.


          Vent gases from lock hoppers and rotary feeders used
on atmospheric pressure gasifiers will contain raw gasifier pro-
duct gas components, unless steps are taken to insure that a
continuous flow of a suitable purge or blanketing gas into the
gasifier is maintained.  The composition of air emissions from
lock hoppers used on pressurized gasifiers will depend on the
method of pressurizing the lock hopper.  Various operating pro-
cedures and sources of pressurizing gas can be used:  1) Prior
to dumping the coal from the lock into the gasifier, the lock
may be pressurized to the gasifier operating pressure with a
stream of cooled raw gas or with a vent stream from an acid gas
removal or oxygen production process.  2) If the pressurizing
gas is added continuously as the coal dumps into the gasifier,
the gas remaining in the lock will have approximately the same
composition as the pressurizing gas.  3) If no gas is added as
the coal is dumped, raw gas from the gasifier will fill the void
                              -57-

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space created as the coal falls into the gasifier, and the gas
remaining in the lock will be composed of pressurizing gas and
raw gas from the gasifier.  4) If no pressurizing gas is used,
the lock will fill with raw gas as the coal is dumped into the
gasifier, and the gas remaining in the lock will be composed of
raw gas.  For any of these above cases, as raw gases pass
countercurrently through the incoming coal and into the lock,
tars, oils, water and other constituents of the raw gas may
condense on the coal feed.


          In addition to the components in the raw gas and the
lock pressurizing gases, the vent gas from a lock hopper may
also contain entrained coal dust particles.  Potential vent
gases from screw feeders will consist primarily of raw gas
although entrained coal dust particles may also be present in
this discharge stream.


          An approach to coal feeding that avoids problems
associated with gas leakage back through the feeder is to sus-
pend the feed coal in either the gasifier feed gas or a water
or oil slurry prior to its injection into the gasifier.  Although
this approach does prevent the direct leakage of raw gas back
through the feed device, it does have its problems.


          With the use of a liquid slurry; there is usually an
efficiency penalty which results from the vaporization of the
coal carrier liquid.  Also, the slurry blending step may be a
source of potential vent gas release, depending on the nature of
makeup liquid.  Gas-solid carrier systems can be difficult to
control and maintain and are limited to use with fluid- or
entrained-bed gasifiers.


          The same collection system used to contain the coal
dust generated as a result of coal transportation can also be
used to collect the vent gases from a coal feeding system.
Depending on the nature of the components present in the feed
system vent gas, this stream could either be released after
particulate cleanup or else scrubbed or incinerated prior to
its release.  The presence of tar aerosols would complicate the
handling of this stream, since heavy hydrocarbons in the aero-
sols can cause a variety of fouling problems.
                              -58-

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          Ash Removal and Disposal System -


          The initial requirement of this system is the removal
of hot ash or slag from the gasifier and the cooling or quench-
ing of that material, usually with water.  This discussion will
deal mainly with the ash handling problems of fixed- and fluid-
bed gasification systems since in entrained-bed systems the ash
must be separated from the product gas and this problem is dis-
cussed in connection with the gas purification operation.


          The ash handling devices used by fixed- and fluid-bed
gasifiers include:


              Water-sealed ash pans

              Screw conveyers

              Lock hoppers


Water-sealed ash pans and screw conveyers are best suited for
atmospheric pressure gasifiers which produce a dry or agglomer-
ated ash.  Lock hoppers can be used with any dry or agglomerating
ash gasifier.  Quench systems are used to cool the ash or slag
removed directly from the gasifier.  The quench system will
include a pressure let-down device when it is used with a high
pressure gasifier.


          Air Emissions - A problem that will be common to all
gasifiers that are not slagging or agglomerating ash units will
be the release of ash dust.  Air emissions from water sealed ash
pans and other quench systems will contain volatile materials
that evaporate from the ash pan water.  These volatiles may
either be components which enter the system with the ash pan
makeup water or they may be products of reactions between the
ash pan water and the hot gasifier ash.  The composition of the
gasifier ash will obviously have a significant affect upon the
quantities and compositions of the volatile materials released
by this mechanism.  Very little volatile material should be
derived from the quenched ash leaving a fixed-bed gasifier.
There is a greater potential for the release of hydrocarbons
from the ash leaving a fluid-bed gasifier because this material
is more "char-like" than the more completely oxidized residue
of a fixed-bed gasification process.
                              -59-

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          The composition of air emissions from lock hoppers
will be dependent on its mode of operation.  For atmospheric
pressure gasifiers which discharge a dry, unquenched ash, the
air emissions will consist of steam and air (or oxygen),  and ash
particles.  If the ash is quenched prior to discharge from the
lock hopper, products of reactions between the quench water and
the hot gasifier ash may be present in the air emissions.  Fixed-
bed, slagging ash gasifiers use a slag retaining burner and a
slag drawdown quench vessel.  Air emissions from these systems
would most likely be limited to the volatile materials present
in the quench water.  Control technologies that are applicable
to the control of air emissions from ash handling systems are
similar to those which can be employed to control coal feeding
system emissions.  Containment and collection of particulate-
laden air followed by processing in a suitable particulate control
process will be needed with dry ash systems where ash dust emis-
sions are a problem.  The control of hydrocarbon emissions from
these systems can involve:


              the use of quench or sluicing system makeup
              water that does not contain hazardous materials
              that are or will form volatile components upon
              contact with hot gasifier ash, and/or


          •   the collection and treatment or incineration
              of hydrocarbon-laden vapors which are released
              as a result of the quenching step.


Because of the considerable potential expense associated with
the second of the above options, the first alternative is
preferable.


          Liquid effluents - An ash quenching and/or sluicing
system, if used, is a major source of potential liquid effluents
from the coal gasification operation.  Ash removal devices which
discharge a dry, unquenched ash do not produce liquid effluents.
The liquid effluents produced by ash quenching sluicing systems
will contain varying amounts of suspended ash or slag particles,
and soluble components leached from the ash as well as components
initially present in the quench water makeup.  Candidate treat-
ment methods for this liquid effluent stream are discussed in
Section 4.2.


          Solid Wastes - All ash removal devices are sources of
solid wastes since the mineral matter in the gasifier ash or
                              -60-

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slag is a solid waste.  In addition to the mineral matter from
the feed coal, coal feed additives and unreacted coal may also
be present in this solid waste stream.  Components present in
the quench water input may also be present in the ash or slag.
The ultimate composition of the waste ash or slag will depend
upon the gasifier type, its operating conditions, the coal feed-
stock and additive compositions, and the makeup quench water
composition.


          Options for disposing of the ash will be determined
primarily by its chemical stability.  These options are dis-
cussed in detail in Section 4.3 that deals with solid waste
treatment and disposal methods.


          Gasifier Start-up Vent -


          When a gasifier is brought on-line from a "cold start"
position, a considerable period of time is required to bring
the gasifier up to its required operating temperature.  In a
commercial-scale unit, this period of time usually ranges from
6 to 12 hours.
          In most commercial installations, it is not possible
to utilize the low grade product gas which is produced during
the start-up period.  For this reason, a suitable method of
disposing of this gas stream must be found.


          In most systems, the flow of this stream will vary
from almost zero initially to about 50% of the design gas flow
of the producer.  Its temperature will increase steadily.  Its
composition will be similar to that of a combustion gas initially
but it will begin to assume low-Btu gas properties more and more
as the producer is brought up in temperature.


          Because of the magnitude of this stream, it must be
considered to be one of the major potential sources of air emis-
sions from a coal gasification unit, even though it is produced
only on an infrequent basis.  Current plans for most new low-
Btu gasification units call for the collection and incineration
(flaring) of this stream.  One of -the problems which must be
considered in this step is the problem of tar condensation in
the flare line.  In order to avoid problems of this nature,
some gasification unit operators use charcoal or coal char as a
start-up fuel and only start feeding coal to the system after
                              -61-

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the system is hot and the gasifier product gas has been routed
to the gas treating section.


          Fugitive Emissions -


          The whole area of fugitive emissions from coal gasifi-
cation systems is one which has received very little attention.
Because of the hazardous nature of many of the components in
the raw product gas from a coal gasifier, and from an operator
safety point of view, it is recognized that it will be necessary
to take all reasonable steps to minimize these emissions.  At
the same time, however, no meaningful documentation of the
severity of this problem has been reported in the literature.
Clearly, it is inevitable that some inadvertent release of
hazardous materials from the gasification operation will occur.
Knowledge as to the levels to which these emissions can be
controlled with current technology is a significant gap in the
existing gasification system environmental data base.


          One very likely source of product gas leakage from
these systems is represented by the pokeholes which are found in
the air-blown, atmospheric pressure, fixed-bed gasifiers which
are in current use in several industrial facilities in this
country.  These pokeholes serve several functions.  They allow
the gasifier operator to make visual inspections of the gasifier
coal bed in the event that an operating problem is suspected.
The pokeholes are also used as access ports for probing the beds
with metal rods and steam lances.  The former is used to monitor
the position of the combustion zone in the bed while either
device may be used to knock clinkers off the wall of the gasi-
fier.  Using pokeholes as a mechanism for monitoring the
performance of a gasifier is one area where improvements in
gasifier monitoring instrumentation might be justified on an
environmental basis.
          Another aspect of the fugitive emission problem which
has not been studied is the effect of pressurized operation.
It is reasonable to expect that fugitive leaks from a pressur-
ized system would exceed those of a well designed, atmospheric
pressure system.  The magnitude of this difference is hard to
estimate.
                              -62-

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3.2.6     Environmentally Significant Trends in
          Gasification Process Development Activities


          The areas in which gasification process development
work is currently being concentrated include:


              improving process efficiencies,

              improving throughput rates,

              improving feedstock flexibility, and

              improving the performance of coal feeding
              and ash removal devices.


Except for this  last category, very little research effort is
being directed toward problems which will affect the environ-
mental acceptability of gasification processes directly.
However, much of the work in other areas will yield useful
information  about how the compositions of coal gasifier product
gas vary as  functions of feedstock type and  gasifier operating
conditions.  Since process and effluent stream characterization
is one of the most significant current environmental assessment
data needs,  research efforts in all of these areas need to be
monitored.


3.3       GAS PURIFICATION OPERATION


          The purpose of the gas purification operation is to^
remove undesirable constituents such as particulates,  tars,  oils,
and acid gases from  the raw product gas.  The performance speci-
fications for the modules in this operation  are  defined by the
intended end use of  the product gas.  Product gas  specifications
with respect to  particulates and H2S for each end  use  are
summarized in Table  3-7.  Typical particulate and  H2S  ranges for
the inlet gas stream are also  shown in the  table.  The modules
needed  to satisfy  these cleanup requirements are illustrated in
Figure  3-3.  These modules include:


              particulate removal,

           •   gas  quenching and cooling, and

              acid gas removal.
                               -63-

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                            Table 3-7.
                           PRODUCT GAS SPECIFICATIONS FOR THE
                           VARIOUS END USES  FOR  LOW/MEDIUM-BTU  GAS
Product Gas
Bad Use
Direct
Conbus tton
Typical Raw Gas Composition
Particulates HjS
0.002-0.7 Kg/ltaJ 0.2-1.5 VoU
(1-300 gr/scf)
Product Gas Specifications
Particulates H2S Comments
'Low enough to
comply with HSPS
for combustion
stack gas.
2 Low enough to
comply with NSPS
for combustion
stack gas.
Gas Turbine
0.002-0.7 Kg/Nm'
(1-300 gr/scf)
0.2-1.5 VoW
Size        Concentration
<2um     <2.0x10"* Kg/Ita"
         (<0.01 gr/scf)
»2pm      2.0x10"T Kg/Ha1
         (0.0001 gr/scf)
>lO|im     None
Equivalent to less
than 100 ppmv total
sulfur
Total alkali
metals less
than 0.040 ppm
Chemical
 Synthesis or
 Reducing Gas
0.002-0.7 Kg/tat1
(1-300 gr/scf)
0.2-1.5 Vott
Essentially particulate
free
Essentially
sulfur free
<
-------
Ui
 I
                                                   ARTICULAT
                                                   FREE GAS
                 PARTICULATE
                  REMOVAL
                                                     GAS
                                                  QUENCHING
                                                     AND
                                                   COOLING
                                                                         PRODUCT
                                                                      ^LOW/MEDIUM
                                                                         BTU GAS
LOW/MEDIUM
                                                        QUENCH LIQUOR

                                                        COOLING WATER
                                                                      ACID GAS
                                                                      REMOVAL
                                          SORBENT OR REACTANT
                     LEGEND
—K
                   AIR EMISSIONS


                     LIQUID EFFLUENTS

                     SOLID WASTES
            Figure  3-3.   Flow diagram  for the  modules in  the gas  purification  operation

-------
          In this section, each of these modules and their
potential emission streams are discussed, although major empha-
sis is placed on the acid gas removal module.  The processes
within each module which appear to have a reasonable chance of
eventual commercial application are identified.  These processes
are then compared with respect to development status, contami-
nant removal effectiveness, operating characteristics, raw
material and utility requirements, and process limitations in
cases where it appears that there are a number of technically
feasible process options.


3.3.1     Particulate Removal Module


          Removal of coal dust, ash and tar aerosols entrained
in the raw product gas leaving the gasifier is the primary func-
tion of this module.  Specific processes commonly used to
accomplish this are:


              cyclones,

              electrostatic precipitators (ESP), and

              water or oil scrubbers


As shown in Table 3-4, cyclones are used as an initial cleanup
step on all of the commercial gasifiers which are currently
operating in this country.  This popularity of cyclones stems
from the fact that they are relatively inexpensive, low energy
consuming devices.  Unfortunately, they are effective in removing
only the larger particulates; other techniques are necessary to
achieve efficient removal of small particulates.  For example,
cyclone collection efficiencies for removing 10 ym particles
from a 1100°C (2000°F) gas stream have been reported to be 90%,
while the efficiency for removing 1 um particles is only about
40% (Ref. 22).


          Extremely small particulates (1 um or less) can be
removed from the raw gas stream only by using more costly and
more energy intensive devices such as electrostatic precipi-     ,
tators and/or wet scrubbers (which also serve to quench and cool
the product gas).  Collection efficiencies of over 99.9% have
been reported in removing particulates from a raw gas produced
by a Koppers-Totzek gasifier using an ESP/wet scrubber in
combination (Ref. 23).
                             -66-

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          When extensive cooling of the raw gas is not necessary
because of acid gas removal process temperature constraints, it
is not particularly useful to use wet scrubbers.   For example,
an end use involving the direct combustion of the gas may not
require sulfur removal to meet sulfur emission requirements.
Since the use of a wet scrubber lowers the temperature of the
raw gas stream, the overall process thermal efficiency is re-
duced.  In the final analysis, the increased cost of obtaining
additional particulate removal at this point must be balanced
against operating cost savings which result from decreased par-
ticulate loadings in subsequent process steps.


          A summary of gas purification equipment used in a
variety of commercial and demonstration coal gasification plants
is shown in Table 3-4.  This table gives some indication of how
the types of gas purification equipment used are dictated by the
end use of the product gas and by the gasifier and feed coal
type.  For example, fuel gas produced by gasification of anthra-
cite coal usually requires only particulate removal because of
the low sulfur content of this fuel and the negligible quanti-
ties of tars produced.  The gasification of bituminous coal or
lignite produces more tars and usually more sulfur compounds
than does the gasification of anthracite.  The need to remove
these compounds, and the extent to which they must be removed,
is again dictated by the end use; fuels used in direct combus-
tion may require only limited particulate removal while those
used as synthesis gases must be further purified.


          All particulate removal processes produce a solid
waste consisting mainly of the collected particulates (unreacted
coal fines and ash).  Liquid effluents are also produced in the
case of wet scrubbers in the form of blowdown liquids and other
materials condensed or scrubbed from the raw gas.  These liquids
will require considerable treatment to remove dissolved and
suspended organics and inorganics prior to their disposal or
reuse.  The composition and quantities of these liquids will
depend upon the nature of the raw gas and the scrubbing process
employed.


3.3.2     Gas Quenching and Cooling Module


          In the gas quenching and cooling module, tars and oils
are condensed and particulates and other impurities such as
ammonia are scrubbed from the raw product gas.  Quenching in-
volves the direct contact of the hot raw gas with an aqueous or
an organic quench liquor.  Extensive cooling of the gas stream
                              -67-

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occurs initially, primarily through vaporization of the
quenching medium.  Further gas cooling can be accomplished
using waste heat boilers followed by air- and/or water-cooled
heat exchangers.


          The choice of gas quenching and cooling processes to
be used depends upon the nature of the hot raw gas and whether
or not an acid gas removal process will be needed.  Waste heat
recovery is always desirable but fouling problems due to tar and
oil condensation in the waste heat boiler must be considered.
In addition, it may be necessary to remove tar and oil constit-
uents from the gas prior to treatment in an acid gas removal
process to prevent contamination of the solvent.  The amount of
cooling required is dictated by the acid gas removal process
temperature constraints.


          The gas quenching and cooling module is a source of
liquid effluents and solid wastes.  The liquid effluents consist
of the quench liquor and the tars and oils condensed in the
quenching process.  The composition and amounts of these tars.
and oils depends on gasifier process considerations (coal type,
pressure, temperature, etc.) and the nature of the quenching
medium (i.e., water or light oil).  The amount of condensate
produced is directly affected by the temperature to which the
gas is cooled.  This liquid effluent stream, typically referred
to as a tarry gas liquor, requires extensive treatment prior to
reuse or disposal.


          The solid wastes generated in the quenching and cool-
ing module primarily consist of coal dust and ash suspended in
the liquid effluents.  Treatment, reuse and disposal options
for the liquid effluents produced as a result of product gas
cooling processes are discussed in Section 4.2.


3.3.3     Acid Gas Removal Module


          Acid gases such as HaS, COS, CSa, mercaptans, and C02
are removed from the raw product gas in the module.  Processes
used for acid gas removal may remove both sulfur compounds and
COz or they may be operated selectively to remove only the
sulfur compounds in cases where carbon dioxide removal is not
required to meet product gas specifications.  For example, it
would not be desirable to remove COa from a pressurized, com-
bined-cycle feed gas.
                             -68-

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          There are two reasons for removing sulfur compounds
from low/medium-Btu gases.  One is to meet the emission regula-
tions for a utilization process such as direct combustion.  The
other is to meet product gas specifications which are dictated
by the end use of the gas.  In this section the acid gas removal
processes which appear to be best suited to low/medium-Btu gas
cleanup needs are identified and compared.


          The processes used for acid gas removal may be divided
into two general categories:


              High-temperature processes requiring minimal
              cooling of the feed gas before treatment; and


              Low-temperature processes requiring extensive
              cooling of the feed gas before treatment.


Each of these general categories is discussed below.  Major
emphasis is placed on low temperature processes because the high
temperature processes mentioned are still generally in early
stages of development.


          High-Temperature  Processes -


          Presently; there  are no commercially available pro-
cesses for removing acid gases from raw low-Btu gas at high
temperatures  (>420°K, 300°F).  Processes  currently under develop-
ment involve  the use of molten salts, molten metals, iron oxide,
and  dolomite  as hot sorbents.  The specific developers of these
processes are:


              Bureau of Mines  (Iron Oxide)

              Babcock and Wilcox  (Iron Oxide)

          •   Conoco (Dolomite)

              Air Products  (Dolomite)

              Battelle Northwest  (Molten  Carbonate)

              IGT-Meissner  (Molten Metal)
                              -69-

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          High temperature acid gas removal, if feasible, would
have several advantages over existing low temperature processes.
The most significant of these is the higher overall thermal
efficiency which would result from the retention of the raw gas
sensible heat.  Another potential advantage is the improvement
of gas heating value due to the reduced condensation of combus-
tible mid-boiling range hydrocarbons.  Cooling equipment fouling
by tars and oils may also be minimized or eliminated.


          Due to these advantages of high temperature cleanup,
much research and development effort in the acid gas removal
area has been aimed at developing high temperature processes.
These high temperature processes will probably be tested ini-
tially in second generation combined-cycle power generation
systems.


          Low-Temperature Processes -


          For purposes of this discussion, acid gas cleanup
processes that operate below 420°K (300°F) are defined as low-
temperature processes.  Processes of this type are widely avail-
able, having been used in both the natural gas and chemical
process industries.  The low-temperature processes considered
here can be further divided into the following categories:


              Physical Solvent Processes

              Chemical Solvent Processes

              Combination Chemical/Physical Solvent Processes

              Direct Conversion Processes

          •   Catalytic Conversion Processes

              Fixed-bed Adsorption Processes


Table 3-8 presents the total population and development status
of the low-temperature acid gas removal processes which were
identified from available information.  The following text pre-
sents a brief description of the processes in the six categories
listed above.
                              -70-

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    Table 3-8.   LOW-TEMPERATURE  ACID  GAS  REMOVAL  PROCESSES
    Process  Category
Process Name and Status*
    Physical Solvent
    Chemical Solvent
       Amine Solvent
    -  Alkaline Salt Solution
Selexol a
Fluor solvent a
Purisol a
Rectisol a
           o
Estasolvan
Union Oil b

Monoethanolamine (MEA) a
Diethanolamine (DEA) a
Triethanolamine (TEA) a
Methyldiethanolamine (MDEA)
             Q
Glycol-amine
Diisopropanolamine  (DIPA) a
Diglycolamine  (DGA) a
Caustic Wash a
Seaboard °
                 Q
Vacuum Carbonate
Hot Potassium Carbonate a
Catacarb a
Tripotassium Phosphate c
Benfield a
Alkazid a
Sodium Phenolate
T     a
Lucas
                                                  Continued
a Commercially Available
  Under Development
c Obsolete/Inactive
d Pilot Plant
                            -71-

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Table 3-8.   Continued
      Process Category
Process Name and Status*
         Ammonia Solution
      Combination Chemical/Physical
      Solvent
      Direct Conversion
      -  Dry Oxidation
         Liquid Oxidation
Chemo Trenn
Collins a
Amisol
Sulfinol a

Iron Oxide (Dry Box) a
                 Q
Activated Carbon
Glaus
Great Lakes Carbon Co.
Burkheiser
Ferrox
Konox
Gludd c
Manchester c
Cataban
Thylox c
Giammarco-Vetrocoke a
Fischer a
Staatsmijnen-Otto/ a
Autopurification
Perox c
Stretford a
Takahax a
CAS d
    Commercially Available
    Under Development
    Obsolete/Inactive
    Pilot Plant
                                                    Continued
                              -72-

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Table 3-8.  Continued
      Process Category
Process Name and Status*
         Liquid Oxidation (Cont.)
Townsend
Wiewiorowski
Sulfonly d
Nalco d
Sulphoxide
Permanganate and Bichromate
Lacey-Keller
Sulfox d
Direct Oxidation a
      Catalytic Conversion
         Organic Sulfur  to H2S
       -   Organic  Sulfur  to  H2S
          and  SO2
Carpenter Evans
                St
Peoples Gas Co.
Holmes-Maxted
British Gas Council
                     a
Iron Oxide Catalysts
Chromia-Aluminum Catalysts
Copp er-Chromium-Vanadium
Oxide Catalysts
Cobalt Molybdenum Catalysts
Appleby-Frodingham
Katasulf a
North Thames Gas Board
Soda Iron a
                                                      Continued
   a  Commercially Available
   k  Under  Development
   0  Obsolete/Inactive
   d  Pilot  Plant
                              -73-

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Table 3-8.   Continued
      Process Category
Process Name and Status*
      Fixed-Bed Adsorption
Activated Carbon
Raines d
Molecular Sieve e
Zinc Oxide a
    Commercially Available
    Under Development
    Obsolete/Inactive
    Pilot Plant
References:  24, 25, 26, 27, 28, 29, 30, 31, 32, 33,
             34, 35, 36, 37, 38, 39, 40, 41, 42
                              -74-

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          Physical Solvent Processes - remove acid gases from
the raw product gas by physical absorption in an organic sol-
vent. ^  These processes must operate at high pressures since the
solubilities of acid gases in the solvents are not sufficiently
high at low pressures.  Most of the solvents used in these
processes have an appreciably higher affinity for H2S than for
C02,  and can therefore be used in a manner that allows for
selective removal of H2S.


          Chemical Solvent Processes - remove acid gases by
forming chemical complexes.In most of these processes the sol-
vent is regenerated by thermal decomposition of the chemical
complex.  These processes are generally identified by the type
of solvent used.  Amine, ammonia, and alkaline salt solutions
are the three solvents in common use.


          Combination Chemical/Physical Solvent Processes - use
a physical solvent together with an alkanolamine chemical sol-
vent additive.  The physical solvent absorbs acid gases such as
082>  mercaptans, and COS, which are not easily removed by chemi-
cal solvents, while the chemical solvent removes the bulk of the
C02,  H2S, and HCN.


          Direct Conversion Processes - produce elemental sulfur
from H2S by oxidation.Some of these processes, such as the
Glaus and Stretford processes, are not classified as acid gas
removal processes in this report; however, they could be used as
such.  These direct conversion processes are divided into two
general categories; dry oxidation and liquid phase oxidation.


          Catalytic Conversion Processes - are divided into two
categories"!  a) those that convert organic sulfur to H2S, and
b) those that convert organic sulfur and H2S to S02.  Most of
these processes are generally not considered to be acid gas
removal processes; however, they can be used to convert hard-to-
remove acid gases such as COS, CS2, and mercaptans into com-
pounds such as H2S and S02, which can then be handled by other
acid gas removal processes.


          Fixed-Bed Adsorption Processes - remove acid gases by
adsorption on a fixed sorbent bed.The amount of acid gases
removed is dependent on the surface area available for adsorp-
tion.  Regeneration of the sorbent is accomplished by thermal
methods or by chemical reaction.
                              -75-

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          Low-Temperature Process Prioritization -


          The low-temperature acid gas removal processes
presented in Table 3-8 were screened to identify those processes
which have the highest probabilities of near-term application in
low/medium-Btu gasification systems.  The following criteria
were used as bases to identify these processes.


              Applicability to low/medium-Btu gasification

          •   Development status

              Environmental impacts

              Energy requirements

              Costs

              Process limitations
In the following text a discussion of how these criteria were
applied to the low-temperature acid gas removal processes is
presented.


          Applicability to low/medium-Btu gasification - This
criterion was used to eliminate those processes which are not
capable of reducing acid gas concentrations to levels which
will meet specific end use product gas specifications and to
determine which processes have operated successfully in coal
gasification systems.  At present, only two processes, Rectisol
and Benfield, have been used in commercial coal gasification
processes.  However, many other processes have been successfully
operated in the natural gas and refinery industries and should
be technically acceptable for removing acid gases from coal
gasification product gas.


          Development status - This criterion was used to
determine whether a process is under development, commercially
available, or in declining use.  Only those processes which are
currently commercially available were given detailed considera-
tion.


          Environmental impacts - This criterion involved
characterizing the discharge streams from each process and
                              -76-

-------
investigating potential control technologies for the hazardous
constituents in those streams.  There are commercially available
techniques for controlling all of the discharge streams from the
processes which appear, to be applicable to low/medium-Btu gasi-
fication process cleanup needs.


          Energy requirements - Processes that require excessive
amounts of energy or special utilities were eliminated from
further consideration for purposes of this analysis.


          Costs - Costs were not used specifically as a basis
for the elimination of any acid gas removal processes, however,
it was assumed that commercially available processes are gener-
ally competitive with respect to capital and operating costs.


          Process limitations - Process limitations with respect
to unusual raw materials requirements, sensitivity to variations
in feedstocks and operating parameters, and ability to achieve
required product gas specifications are important considerations
in the selection of a process.  These limitations can take
several forms including unfavorable economics and actual process
operating problems.  For example, certain compounds which may be
present in the raw gas feed can be the cause of solvent degrada-
tion problems.  This is both an economic and operating problem
because of the cost of replacing the solvent and because the
degradation products may adversely affect the process perfor-
mance.  Another example of an operating parameter limitation is
the high acid gas partial pressure required for economical
operation of physical solvent type processes.


          Promising processes - Using the criteria described
above, the following were identified to be the processes which
appear to have the greatest likelihood of near-term commercial
application:


              Physical Solvent Processes

                 Rectisol              -  Estasolvan

                 Selexol               -  Fluor Solvent
                                   *
              -  Purisol
                             -77-

-------
              Chemical Solvent Processes

              -  MEA                   -  DIPA

              -  MDEA                  -  DGA

              -  DEA                   -  Benfield


              Combination Chemical/Physical Solvent Processes

              -  Amisol                -  Sulfinql


              Direct Conversion Process

              -  Stretford


          A detailed discussion of the Stretford, Glaus and
other prioritized sulfur emission control processes is presented
in Section 4.1.2.  It should be emphasized that the acid gas
removal processes listed above were selected using currently
available data.  Additions to or deletions from this list are
likely as new information is obtained.


          Low-Temperature Process Comparison -


          In this section, the acid gas removal processes just
discussed are compared on the basis of their similarities,
advantages, and limitations.  Important considerations in this
comparison include feed gas composition, operating conditions,
and ability to meet required product gas specifications.  The
primary acid gas removal processes are compared in Table 3-9
with respect to:


              Control effectiveness,

              Ability to be operated selectively
               (removal of H2S),

              Utility requirements,

           •   Discharge streams requiring further control,

              By-products, and

              Process limitations.
                              -78-

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              Table  3-9.    COMPARISON  OF  LOW TEMPERATURE
                                 ACID GAS REMOVAL  PROCESSES

Control Effectiveness
• H2S
• C02
• COS/CS2
• R-SH
• HCN
• NIlj
MEA

99.9+Z
99+Z
D
D
DNA
DNA
HDBA

99.9+Z
99+Z
DNA
DNA
DNA
DNA
DEA

99.9+Z
95+Z
90-99Z
DNA
DNA
DNA
DIPA

99.9+Z
DNA
DNA
DNA
DNA
DNA
DGA

99.9+Z
99+Z
D
D
D
DNA
Benfleld

99.9+Z
99.9+Z
75-99Z
68-92Z
99+Z
DNA
Capable of Being             DNA         yes          DNA         yes         DNA           yes
Operated Selec-
tively (to remove
HjS without CO2


Operating Requirements

  • Steam                   /           /           /           /           /            /

  • Electricity              /           /           /           /           /            /
  • Cooling Water             /           /           S           /           /            /

  • Fuel Gas

  • Chemicals                                                                            S


Discharge Streams
Requiring Further
Control
  • Caseous                  /           /           /           /           /            /

  • Aqueous                  /          NR          NR          NR           /            /
  . Solid                  NR          NR          NR          NR          NR           NR


By-Products                 NR          NR          NR          NR          NR           NR


Process Limitations         Organic      Corrosion    Corrosion                Organic
                         •ulfur       problems     problems                sulfur
                         compounds    greater      greater                 compounds
                         degrade      than MEA     than MEA                degrade
                         solvent                                         solvent
                                            -79-

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               Table  3-9.
             COMPARISON  OF  LOW  TEMPERATURE
             ACID  GAS  REMOVAL  PROCESSES
                                                                                      (continued)
                      	Physical solvent processes	   Combination processes
                      Rectlftol   Stlexol   Purlool   Estasolvan  Fluor solvent   Sulflnol       Aniaol
Control EffectivcnPHfl
  • H,8
  • CO,
  • C08/CS,
  • R-SII
  • HCN
  • HH|
 99.9+Z
 V9.94Z
 99.9+2
 99.9+Z
  DNA
  DNA
          99.9+Z
99. 9
 DMA
 DNA
99.9+Z
99.9+Z
 99+Z
 DNA
 DMA
 DNA
99.9+Z
99.9+Z
 98+Z
 97+Z
 DNA
 DNA
99.9+Z
99.9+Z
 DNA
 DNA
 DNA
 DNA
99.9+Z
 99+Z
 90+Z
 90+Z
 DNA
 DNA
99.9+Z
 99+Z
 99+Z
 DNA
 DNA
 DNA
Capable of Being
Operated Selec-
tively (to remove
H2S without C02
  yes
           yes
                    yes
                               yes
                                           yes
                                                        yes
                                                                                            DNA
Operating Requirements
  •  Steam                 /        /         /
  •  Electricity            /        /         /
  •  Cooling Water          /        /         /
  •  Fuel Can              /        /         /
  •  Chemicals             /        /         /
Dlichargn Streams
Ruquirlno Furthpr
Control
  •  Gaieou*
  •  AqueouR
  •  Solid
   /
   /
  NR
 NR
 NR
                                           NR
            NR
            NR
              NR
              NR
              NR
              NR
              NR
              NR
By-Products
Napbtha
                                  NR
                                           HI
                                                     NR
                                                                  NR
                                                                               NR
                                                                                            NR
Process Limitations
                       Low trap.
                       required
                       to limit
                       solvent
                       lostea;
                       retains
                       heavy hy-
                       drocarbons ,
                       high
                       pressure
          Rataina
          haavy
          hydro-
          carboos,
          high
          pressure
         Retains     Retains       Retains
         heavy hy-   heavy hydro-  heavy hy-
         drocarbons, carbons,      drocarbone,
         high       high         high
         pressure    pressure      pressure
                                   Solvent is
                                   expensive
NR  - none reported
DNA - data not available
0   - solvent dogrndcB forming nonrcgonsrablc compounds
/   - indicates presence of a utility requirement or discharge stream
                                                -80-

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The following text summarizes the major conclusions derived from
the information presented in this table.


          Control effectiveness - The control effectiveness is
reported in Table 3-9 as the percentage removal of an input
species that can be obtained by the process.  In some cases a
compound may be removed but in a nonregenerable manner.  This is
indicated in the table by the symbol (D) indicating solvent degra-
dation.  An example of this is the removal of COS, CS2, and R-SH
with the MEA process.  All of the processes can meet the most
stringent H2S product gas specification of 4 ppmv or less and
most can meet a C02 specification of less than 1.0 vol. %.


          Selective H2S removal - The need for selective removal
of H2S depends on the end use of the cleaned, desulfurized gas.
Most product gas utilization options require extensive desulfur-
ization of the raw gas.  If the gas is to be used for combined
cycle power generation, the removal of C02 is not desirable
since it would reduce the amount of useful work which would be
recovered in the gas turbine section.  For simple combustion
applications, removal of C02 will increase the heating value of
the gas.  However, this advantage must be weighed against the
added cost of removing the C02.


          Utility requirements - The entries in this section of
the table are intended to show how the processes compare with
respect to utility requirements.  This is important in process
selection as some utilities may not be readily available at all
sites.  The presence of a check  (/) indicates the types of
utility required by the processes.  These utility requirements
have not been quantified at this point.


          Discharge streams requiring further control - The
purpose of this section is to indicate the types of discharge
streams, gaseous, aqueous, or solid produced by each process
which require further control prior to disposal.  All of these
processes produce gas streams which must be treated further to
remove H2S and other sulfur compounds before the streams may be
discharged to the atmosphere.  While most of the processes do
not report an aqueous effluent stream, all require periodic
solvent blowdown to prevent buildup^ of contaminants and solvent
degradation products.  Some of the'processes, such as Rectisol
and Purisol do produce a condensate or blowdown stream which
will require further treatment prior to disposal.  Solid wastes
removed from these processes would include coal fines and ash
                               -81-

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entrained in the process gas feed and solvent degradation
products.  These wastes will be contained in the solvent blow-
down stream.
          By-products - In this entry, by-products from the acid
gas removal processes are shown.  While only one process,
Rectisol, is known to produce a naphtha by-product, many of the
other processes should produce similar by-products when used in
coal gasification systems.


          Process limitations - In this section, major process
limitations specific to each process are briefly listed.  In
some cases these limitations may be serious enough to eliminate
the process from consideration for a particular application.
For example, if the gas to be treated contains large amounts of
organic sulfur compounds (>150 ppmv),  serious consideration must
be given to the economics and potential operating problems which
may occur if the MEA process is selected.  In other cases, the
limitation may present a problem which is not serious enough to
eliminate a process.  For example, the corrosion problems which
have been experienced with the DEA and other processes may be
eliminated by a careful selection of materials of construction.


          Another limitation which affects acid gas removal
process selection is the pressure of the cooled gas stream.  Low
pressures, less than 1.7 MPa (250 psia), eliminate physical sol-
vent processes from prime consideration since they require
significant acid gas partial pressures to be economical.  At
pressures greater than 1.7 MPa, all of the processes can be used
successfully but the physical solvent processes become more
economical at high pressures.


3.3.4     Discharge Stream and Control Technology Summary -
          Gas Purification Operation


          Air Emissions -
          The modules in the gas purification operation are
sources of hazardous air, water, and solid waste emission
streams.  The air emissions from the acid gas removal module
may contain C02, H2S, COS, mercaptans, NH8, hydrocarbons, and
other toxic constituents.  These emissions require treatment
before being vented to the atmosphere.  Treatment methods for
these pollutants, primarily hydrocarbon control and sulfur
                              -82-

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control processes, are commercially available and are discussed
further in the Air Pollution Control Section.


          Liquid Effluents -


          Liquid effluents from this operation may contain a
variety of pollutants such as tars, oils, phenols, dissolved
acid gases and hydrocarbons, and trace elements.  These effluents
will therefore require treatment prior to reuse or disposal.
The composition of these liquid effluents will depend upon the
nature of the raw gas from the gasifier, the method of raw gas
cooling used, and the specific acid gas removal process employed.
All of the acid gas removal processes mentioned here, except for
the Benfield process, use some type of organic solvent which
will be present to some extent in these streams.  In addition,
solvent degradation products will be present which may be diffi-
cult to treat with currently available water pollution control
processes.  The Benfield process uses an inorganic potassium
carbonate solvent which will be present to some extent in the
blowdown stream from this process.  Treatment of this stream
using processes currently available should present minimal prob-
lems.  Processes available to treat these effluents are discussed
in the Water Pollution Control Section.
          Solid Wastes -


          Solid wastes are generated by all of the modules in
this operation.  These solid wastes are composed primarily of
unreacted coal fines and ash entrained in the raw product gas.
These solids may be collected dry by cyclones or electrostatic
precipitators or they may be collected wet in the quenching and
acid gas removal process.  In the case of wet collection, the
solids may be suspended in the quench liquor and/or the acid gas
removal process solvent.  These solid wastes may be a usable
by-product or they may require ultimate disposal which is dis-
cussed in the Solid Waste Pollution Control Section.


          In addition to the solid wastes discussed above, some
of the solvent degradation products may exist in solid form.
These contaminants will be removed in the solvent blowdown
stream.  Proper treatment of these compounds may represent a
significant research and development need since they may not be
compatible with existing wastewater treatment processes.
                              -83-

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                          SECTION 4.0

                   POLLUTION CONTROL MODULES
          Air emissions, liquid effluents, and solid wastes from
the process operations described in Section 3.0 will require
pollution control modules.   The function of these modules is to
achieve levels of control that are consistent with environmen-
tally acceptable plant practices.


          Air pollutants from low-Btu gasification processes are
primarily coal dust, coal feeder vent gases, combustion gases,
process tail gases and tank vents.  These streams are processed
in various combinations of control modules to achieve particu-
late control, sulfur control and recovery, hydrocarbon control
and nitrogen oxides control.  These modules and their use are
described in Section 4.1.


          Water pollution control includes treating modules
designed to separate oils from aqueous liquids and to remove
solids, and organic and inorganic compounds from wastewaters.
The ultimate design philosophy for water pollution control
systems embodies the concept of zero liquid discharge in which
all used water is treated then recycled to the process operations
and their supporting auxiliaries.  Solid wastes and by-products
are removed from the wastewater and sold or disposed of.  The
rationales for the selection and arrangement of wastewater
treating systems are described in Section 4.2.


          Reducing solid wastes to unobjectionable, nonpolluting
products and by-products also requires the use of specific pro-
cessing modules.  These modules are described in Section 4.3.


          The multimedia waste streams and the pollution control
modules are described in the following section only in such
detail as to characterize the waste streams and the control     '
module designs.  More detailed descriptions of the pollution
control modules are provided in Appendices C, D, and E.
                              -84-

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4.1       AIR POLLUTION CONTROL


          The air pollution control modules receive contaminated
gaseous emissions from the various process operations within low/
medium-Btu coal gasification plants and reduce the concentrations
of these contaminants in the gas streams to levels acceptable for
discharge to the environment.  There are four basic control
modules:
              Particulate Control

              Sulfur Control  .

              Hydrocarbon Control

              Nitrogen Oxide Control


          A flow diagram of these modules is presented in
Figure 4-1.  In this figure, the gaseous effluents which may be
directed to these four modules and potential flow paths between
the modules are identified.  The nature of the contaminated
gaseous effluents dictate which modules are required to treat
the gases.


          The gaseous effluents of major concern in this environ-
mental assessment program are the process tail gases from the
acid gas removal module and wastewater stripping process.  These
streams contain the bulk of the sulfur originally present in the
coal feedstock along with substantial quantities of hydrocarbons.
Sulfur and hydrocarbon control techniques are therefore given
prime emphasis in this section.


          There are many proven processes available for use in
the sulfur control module.  A list of sulfur control processes
which are or will be of primary interest in low/medium-Btu
gasification technology was prepared.  The prioritization cri-
teria discussed in Section 3.0 were also used in classifying
these processes.


          Because of the importance of the sulfur and hydro-
carbon control modules, detailed process and discharge stream
data sheets for the high-priority sulfur control processes and
the hydrocarbon control processes were prepared.  These data
sheets, which are included in Appendix C, contain the following
types of information for each process:


                              -85-

-------
00
o\
             MREM33MNS


              UO«P EFFIUEMTO


           •^VSOUO WASTES
        Figure 4-1.  Flow diagram  for the modules in the air pollution  control operation

-------
              Flow diagrams

              Commercial applications

              Operating parameters

              Raw material and utility requirements

              Process advantages and limitations

              Discharge stream compositions


          In the following sections, each of the air pollution
control modules are discussed with respect to a) the types of
gaseous effluents to be treated, b) the processes capable of
treating these effluents, and c) the operating principles and
waste streams associated with each process.  The advantages and
disadvantages of the processes and their applicability to low/
medium-Btu gasification are also addressed.


4.1.1     Particulate Control Module
          Coal dust from the coal pretreatment and coal gasifi-
cation operations are the principle particulate emissions
requiring control.  Other emission sources include the ash
handling system and the permanent coal storage pile.  The
severity of the particulate emission problem will vary from
site to site.  Water sprays are used at coal conveying transfer
points at some sites; however, these may or may not be effective
control devices.


          The control of particulate emissions actually entails
three steps.  First, the particulate containing gases must be
collected and directed to the control process.  For example, a
coal conveyor belt might be completely enclosed, with the vapor
space vented to the control process.  Next, the particulates
are removed from the gases; and finally, the collected particu-
lates are removed from the control process.


          The many processes and variations of processes that
could be used to control particulate emissions from coal gasi-
fication processes are generally divided into the following
four categories, based on the collection mechanism used:
                              -87-

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              Mechanical Collectors

              Electrostatic Precipitators

              Wet Collectors

              Afterburners


          Mechanical Collectors -


          Mechanical collectors remove particulate matter from
gas streams by the actions of physical forces such as gravity,
centrifugal force, impingement, and diffusion.  Three types of
mechanical collectors which are widely used to control particu-
late emissions from industrial processes include:


              Settling chambers

              Cyclones

              Filters


The effectiveness of each of these types of collectors depends
mainly upon the size distribution of the particulate matter and
the flow rate and physical properties of the gas stream.  Fil-
ters generally provide better collection efficiencies than the
other two types of collectors, especially if very small par-
ticles (<5 urn) must be collected.


          Electrostatic Precipitators -


          Electrostatic precipitators (ESP's) remove particulate
matter from gas streams by the action of an electrical field on
charged particles.  Two types of ESP's (high- and low-voltage)
are commercially available.


          High-voltage ESP's are used most frequently when pre-
dominantly small particles (<20 ym) must be removed from large /.
volumes of gas.  Collection of particulate matter by high-voltage
ESP's involves three basic steps:


              Transmitting an electrical charge
              to the particulate matter.
                              -88-

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              Collecting the charged particles
              on a grounded surface.


              Removing the collected particulates
              from the precipitator.


Because of the high collection efficiencies associated with
high-voltage ESP's they are generally applicable to control of
particulate emissions from coal gasification plants.


          Low-voltage ESP's are two-stage devices which were
originally designed to purify the inlet air to air-conditioning
systems.  They are used only to treat small volumes of gas con-
taining nonsticky liquid particulates, and they do not collect
solid particulate matter.  For this reason, it does not appear
that low-voltage ESP's will play an important role in low/medium-
Btu gasification technology.


          Wet Collectors -
          Wet collectors use a liquid, usually water, either to
remove particulate matter from a gas stream by direct contact or
to increase collection efficiency by preventing reentrainment of
the collected particles.  There are many types of wet collectors,
all of which are some variation of a spray chamber or a wet
scrubber.  The principal mechanisms by which particulate matter
is contacted with the liquid in these collectors are:


              Interception            •   Diffusion

              Gravitational force     •   Electrostatic forces

              Impingement             •   Thermal gradients


          Wet scrubbers are relatively high energy using devices.
This is especially true in those designed for highly efficient
particulate removal.  For this reason, wet scrubbers often do
not compare favorably with mechanical collectors or ESP's, in
applications where particulate removal is the only control re-
quired.  Scrubbers can be useful when dealing with troublesome
particulates (e.g., a sticky metal fume) or when concurrent
removal of another pollutant such as S02 is required.  Therefore,
while a baghouse or ESP's might be better suited to the removal
                              -89-

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of coal and ash dust from gas streams which are collected in the
vicinity of solids handling operations,  wet scrubbers appear to
have application in the removal of particulates and S02 from on-
site combustion stack gases.


          Afterburners -


          Direct flame afterburners can be used to remove combus-
tible particulates from gas streams.  Generally, they are used to
control fumes,  vapors, and odors when relatively small quantities
of combustible matter are present.


          Process Comparison -


          The relative merits of these particulate control
devices are summarized in Table 4-1.  Baghouse filters and high-
voltage ESP's appear to be best suited to the requirements of
coal gasification plants because of their high efficiencies in
the collection of fine particulate matter.  However, final
selection of a particulate control device will also depend on
its capital and operating costs, and on how effectively the
device can be integrated into a particular gasification plant.
Particulate emissions from portions of the gasification plant,
such as the ash handling system, are not completely combustible;
afterburners would be ineffective in controlling this emission.
Also, direct flame afterburners usually require supplemental
fuel.
          Particulate Control Module Discharge Streams -


          The particulate control module can be a source of air
emissions, liquid effluents and solid wastes.  Properly treated
air emissions are essentially particulate-free gases which may
or may not require additional treatment for control of sulfur
compounds, hydrocarbons, or nitrogen oxides.  For example, the
coal dust-laden air collected from the vicinity of the coal
handling operations can generally be vented to the atmosphere
after the particulates have been removed.  Combustion gases from
on-site power generation facilities, on the other hand, may     '
require additional treatment, e.g., for S02 removal.
                              -90-

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                                         Table  4-1.    SUMMARY  OF  PARTICULATE  CONTROL DEVICES
                     Device
                                                     Advantage*
                                                                                Disadvantage*
                                                                                                                                      Contents
            Mechanical Collectors

              1.  Settling Chambers
                                 Low Energy Devices
                                         Large size due to high
                                         residence time and low
                                         flow requirements
                                         Low removal efficiency for
                                         fine participates
                                     Does not appear to be well suited
                                     to coal gasification plant parti-
                                     culate control applications.
              2.  Cyclones
               3.  Filters (Baghouses)
                                 Mechanically Staple
                                 LQW Cost
                                 High collection efficiency
                                         Not an effective  collector
                                         of fine participates
                                         Caking/Plugging problems
                                         incurred with wet, saturated
                                         gases
                                     Is a low energy device  for large
                                     participates,  but requires higher
                                     energy dissipation to remove fine
                                     particulates.

                                     Medium Energy  Device.

                                     Of Che mechanical collectors,
                                     probably the best suited to the
                                     control of gasification plant coal
                                     and ash dust emissions.
VO
f-1
 i
Electrostatic Precipitators

  1.  High-Voltage
               2.  Low-Voltage
            Wet Collectors (Scrubbers)
            Afterburners

              1.  Direct Plane
High collection efficiency
Suitable for fine particulate
collection

High gaa flows  can be treated
Can collect liquid and solid
particulate matter

Low voltages required
                                 High efficiency can be obtained
                                 with certain scrubber types
                                             High removal efficiency
                                             Simple construction and low
                                             maintenance
High voltages  required
Sticky liquids can collect on
the collection electrode and
decrease efficiency
                                                                                      Cannot handle solid or sticky
                                                                                      liquid particulate natter
                                                                                      Liquid wastes  are produced
                                                                                      To obtain high collection effi-
                                                                                      ciencies requires high energy
                                                                                      dissipation
                                                                         Requires auxllllary fuel

                                                                         Can handle only combustible
                                                                         particulates

                                                                         Fir* hoiarda
Very effective  device for removing
fine particulates  from large gas
flows.   Typical applications have
been on coal  fired boiler flue gave*
                                     Since only application is to non-
                                     sticky liquid particulates,  this de-
                                     vice does not appear to be suited to
                                     coal gasification plant parciculate
                                     control applications-

                                     The need for treating the resultant
                                     liquid waste detracts from wet scrub-
                                     bers as a particulate-only control
                                     device.
                                                                             The fuel  penalty associated with par—
                                                                             ticulate-removal-only afterburner*
                                                                             detracts  from  their applicability.

-------
          Liquid effluents are generated only when wet
collectors are utilized for particulate control.  These
effluents are directed to the water pollution control operation
for treatment.  Solid wastes mainly consist of coal dust and
ash.  The coal dust may be disposed of (e.g., as landfill), used
as a fuel, or sold as a by-product, while the ash is generally
used as landfill.
4.1.2     Sulfur Control Module


          All operations in low/medium-Btu coal gasification
plants are potential sources of sulfur-bearing gaseous effluents.
Examples of these effluents are:


              Tail gases from the acid gas removal module,

              On-site power generation flue gases,

              Vent gases from the water pollution
              control module,

              Coal feeder vent gases from the coal
              gasification module, and

              Gases from the particulate module.


The function of the sulfur control module is to reduce the con-
centrations of the sulfur compounds such as H2S, COS, CS2„ and
S02 to levels acceptable for discharge to the environment.


          The processes capable of removing sulfur compounds
from gas streams can be divided into three general categories.


              Primary sulfur recovery processes

              Tail gas cleanup processes (secondary recovery)

              Sulfur oxides control processes                   (


          The principles of operations of the sulfur control
processes are discussed in the following paragraphs.  A priority
list, based on the merits of each process, is presented.
                               -92-

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          Primary Sulfur Recovery Processes -


          There are numerous processes based on removal of
sulfur compounds from gas streams, followed by recovery of the
sulfur as a by-product.  These direct conversion processes can
be classified as either dry oxidation or liquid phase oxidation
and are listed in Table 4-2.  The principle of operation in-
volves the oxidation of sulfur compounds to elemental sulfur,
which is a salable by-product.  The two most widely used direct
conversion processes are the Glaus (dry oxidation) and the
Stretford (liquid phase oxidation) processes.


          Tail Gas Cleanup Processes -


          Tail gas cleanup processes are used to remove and, in
some cases, recover the sulfur compounds remaining in the tail
gases of primary sulfur recovery processes.  These processes,
when combined with a Glaus unit for example, can provide an
overall sulfur removal effectiveness of up to 99.9+%.  Commer-
cially available tail gas cleanup processes are classified as
follows:
               Process Type              Process Name

          Removal of sulfur compounds     Beavon
          and recovery of elemental       Cleanair
          sulfur                          CBA
                                          Sulfreen
          Reduction  of  sulfur compounds   SCOT
          to H2S which  is recycled  to a   Trencor-M
          Glaus unit
           Sulfur Oxides  Control Processes  -


           Sulfur oxides  control processes  are not major  func-
tions within  coal  desulfurization plants.  They are primarily
flue gas desulfurization processes  and  are generally used  to
control sulfur  emissions from on-site coal-fired heaters and
boilers.   Therefore,  these processes are not discussed in
detail in  this  report.
                              -93-

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Table 4-2.  DIRECT CONVERSION PRIMARY SULFUR RECOVERY PROCESSES

                   Dry Oxidation Processes
                   Iron Oxide (Dry Box)
                   Activated Carbon
                   Glaus
                   Sulfreen
                   Great Lakes Carbon

                  Liquid Oxidation Processes
         Burkheiser
         Ferrox
         Konox
         Gludd
         Manchester
         Cataban
         Thylox
         Giaromar co-Vetro coke
         Fischer
         Staatsmijnen-Otto
         Autopurification
         Perox
Stretford
Takahax
C.A.S.
Townsend
Wiewiorowski
Sulfonly
Nalco
Sulphoxide
Permanganate and Dichromate
Lacey-Keller
Sulfox
Direct Oxidation
References:  43, 44, 45
                              -94-

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          There are three primary types of sulfur oxides
control process:  nonregenerable, regenerable, and catalytic
conversion.  Nonregenerable processes remove SOX from gas
streams by sorbing and/or reacting the SOX with an alkali salt.
The products formed from these processes are not suitable for
reuse and require disposal.  Regenerable processes remove SOX
by absorption, reaction, and/or adsorption, and produce salable
or reusable products.  SOX control processes using catalytic
conversion either oxidize or reduce the SOX to form solid or
liquid by-products.


          While there are numerous sulfur oxides control pro-
cesses available, most of them have not been completely proven
in commercial applications and are still in a developmental
stage.  For this reason data on removal efficiency, utility
usage, reliability and costs are not available for many of the
processes.


          Process Prioritization -


          The sulfur control processes with the highest likeli-
hood of being used in future coal gasification plants were
selected using the criteria discussed below.


          Applicability - Sulfur emissions consist mainly of
H2S, COS, CS2 and mercaptans.  Flue gas desulfurization (SOx
removal) is not a principle process need.


          Development status - Only commercially available
processes were considered.


          Environmental impacts - Processes producing troublesome
secondary effluent streams were not considered to be promising.
For example, the Phylox and the Giammarco-Vetrocoke processes,
use arsenic-based solutions and purge streams from these pro-
cesses would contain arsenic compounds.  They were not included
among the promising sulfur control processes.


          Energy requirements - This criterion was used to
eliminate processes requiring excessive amounts of energy.
                              -95-

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          Costs - Limited economic data were available for these
processes.  It was assumed that all "promising" processes are
competitive on a cost basis.


          Process limitations - This criteria was used to
identify special raw material requirements, sensitivity to varia-
tion in feedstock and operating parameters, and the ability to
meet sulfur emission requirements.  Some processes simply cannot
remove contaminants to desired levels.  For example, the
Stretford process, while effective in removing HaS, does not
remove organic sulfur compounds such as COS and CS2.


          Promising processes - Using the above criteria, the
following sulfur control processes were identified as those that
will most likely be used in coal gasification plants in the near
future:


              Primary Sulfur Recovery Processes

                 Glaus

              -  Stretford
              Tail Gas Cleanup Processes

                 Beavon

              -  SCOT
These processes are compared in Table 4-3.  Detailed information
on each promising sulfur recovery and control process is pre-
sented in Appendix C.  It must be emphasized that no process has
been totally eliminated from consideration.  As new data become
available, it may be necessary to add or delete processes from
the above list.
          Sulfur Control Philosophy -


          The combinations of sulfur control processes that
might be used to treat three types of contaminated gases are
discussed in the following paragraphs.  The three example gas
streams are characterized as those containing:
                               -96-

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Table  4-3.    SUMMARY  OF  SULFUR RECOVERY  AND  CONTROL  PROCESSES
                                  Sulfur recovery process
                              Tall gas cleanup processes
                                    Claus
                                              Stretford
                                                            Beavon
                                                                          SCOT
                                                                                   Wellman-Lord
           Development Status
                                 Commercial
                                                  rcial
                                                           Commercial   Commercial
                                                  Commercial
           Control Effectiveness
             •   H2S                 90-951
             •   COS/CSj              901
             •   R-SH                 95X
             •   HCH                 . DNA
             •   NHi                  DNA
             •   Hydrocarbons         90Z
              99.9+1
                           99.9+Z
                            98+Z
                            DNA
                             D
                            DMA
                           99.8+Z
                            98+Z
                            DNA
                            DNA
                            DNA
99.0+Z
 99+Z
 99+Z
 DBA
 DNA
           Operating Requirements
             •  Steam
             •  Electricity
             •  Cooling Water
             •  Fuel Gas
             •  Chemicals
                (Including
                 catalyst)
             •  Process Water
           Discharge Streams
             Requiring Further
             Control
             •  Gaseous              /
             •  Aqueous
             •  Solid                /
                              /*
            By-Products
              •  Sulfur
              •  Other
                                                      SteaB
            Applicability To
            Coal Gasification
              •  Proven
              •  Technically
                  Feasible
            Process Limitation*
High hydro-
carbon  feed
can result
In formation
of organic
sulfur  coo-
pounds
Does not
remove
organic
sulfur
compounds
            *If organic aulfur compoundo ara present  in food atresn
          D - Solvent degrades forming nonregenareble compounds
          DNA - Data not available
          / - Indicates presence of an operating requirement, discharge stream,
              by-product, or applicability characteristic
                                                 -97-

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              small amounts of H2S and organic
              sulfur compounds,


              large amounts of organic sulfur and
              small amounts of H2S, and


              large amounts of H2S and small amounts
              of organic sulfur compounds


If high concentrations of hydrocarbons are present in any of
these streams, further treatment by the hydrocarbon control
processes discussed in Section 4.1.3 will be required.  The
following are examples of control schemes that are capable of
removing 99.9+70 of the sulfur compounds from the three gas
streams listed above.


          Example 1 - Figure 4-2 shows a potential control
scheme for a feed gas containing small amounts of H2S and
organic sulfur compounds.  This stream may be treated in a
Stretford unit for sulfur recovery.  However, it may be neces-
sary to incinerate the Stretford tail gas to control hydrocarbon
emissions or to convert the remaining sulfur species to S02
prior to release into the atmosphere.


          Example 2 - For a feed gas containing large amounts of
organic sulfur but little H2S, the control scheme shown in
Figure 4-3 may be used.  This is basically the same as that
described in Example 1 except that an organic sulfur compound
conversion process step is added before the Stretford unit.  In
this process step, organic sulfur compounds such as COS, CS2,
and mercaptans are catalytically converted to H2S.  The H2S can
then be removed by the Stretford unit.


          Example 3 - Gas streams containing large amounts of
H2S but low hydrocarbon and organic sulfur contents, such as
might be produced from a selective acid gas removal process,
can be controlled using the scheme presented in Figure 4-4.  At
high concentrations of H2S Qll5 vol %) a Glaus unit becomes
economically attractive for sulfur recovery.  The tail gas from
the Glaus unit would still contain significant quantities of
sulfur and would need further control.  Because of the low hydro-
carbon content of the feed gas, little organic sulfur is formed
in the Glaus process; therefore, a Stretford process is suitable
for tail gas cleanup.  This is desirable since a selective acid
                               -98-

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                                                      SULFUR (D
                                                     RECOVERY
I
«*>
                                                 PROCES
                                                 CONDEN-
                                                   SATE
TO INCINERATION
                                              TOWASTEWATER
                                                TREATMENT
                              LOW ORGANIC SULFUR AND LOW H2S. EITHER PRODUCT GAS FROM GAS COOLING
                                 OR ACID GAS FROM ACID GAS REMOVAL PROCESS

                              STRETFORD PROCESS SUITABLE
                                Figure 4-2.   Treating  sequence  for example 1

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                                     ORGANIC
                                      SULFUR
                                    CONVERSION
O
O
                                                               ROCESS
                                                              CONDEN-
                                                                SATE
    TO
INCINERATION
                                                           TO WASTEWATER
                                                             TREATMENT
                          HIGH ORGANIC SULFUR AND LOW HgS. EITHER PRODUCT GAS FROM GAS COOLING
                            OR ACID GAS FROM AN ACID GAS REMOVAL PROCESS

                          STRETFORD PROCESS SUITABLE
                               Figure  4-3.   Treating sequence for example  2.

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SULFUR
RECOVERY
)
(2)
w
I
l-»
o
 ROCESS
CONDEN-
 SATE
PROCES
CONDEN
 SATE
                                                                                               TO

                                                                                           INCINERATION
                                               TOWASTEWATER

                                                 TREATMENT
                     ® LOW HYDROCARBON AND LOW ORGANIC SULFUR, HIGH H2S


                     (2) GLAUS PROCESS SUITABLE


                     (3) STRETFORD PROCESS SUITABLE
                                Figure 4-4.  Treating  sequence for example  3

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gas removal process also generates a lean HjS stream which can
also be treated in the Stretford unit.


          Sulfur Control Module Discharge Streams -


          The sulfur control module can be a source of air
emissions, liquid effluents, and solid wastes.  The air emis-
sions consist of essentially sulfur-free gases which may require
hydrocarbon and NOx control before b.eing vented to the atmosphere.
Liquid effluents include spent scrubbing solutions and reaction
liquors which may contain dissolved and suspended organics and
inorganics.  Since further treatment of these materials will
almost always be required, these liquid effluents are sent to
the water pollution control section.  The solid wastes include
spent catalysts, sorbents, and by-products.  If necessary, these
solid wastes are sent to the solid wastes control section for
further treatment and/or ultimate disposal.


          Discharge Streams Requiring Further Control -


          The tail gases from the Glaus and SCOT process require
further control of sulfur compounds.  If high concentrations of
organic sulfur compounds are present in the fuel gas, the tail
gas from the Stretford process may need further treatment.
Liquid effluents consisting of spent sorbents, scrubbing liquors,
or sour condensates are discharged from all of the processes
except the Glaus process.   (The Glaus process generates a solid
waste stream containing spent catalyst).


4.1.3     Hydrocarbon Control Module


          The function of this module is to reduce the hydro-
carbon content of process tail gases, vent streams and other
waste streams to levels acceptable  for discharge to the environ-
ment.  There are two basic methods of hydrocarbon control:
afterburners and adsorbers.  Afterburners simply convert hydro-
carbons to COz and HzO by oxidation.  Adsorbers use sorbents
such as activated carbon to remove  the hydrocarbons from the gas
stream.  Fact sheets containing detailed information on the
hydrocarbon control processes are presented in Appendix D.
                             -102-

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          Afterburners -


          Two types of afterburners are used to control
hydrocarbon emissions, direct flame and catalytic.  These are
essentially identical to the particulate control afterburners
discussed in Section 4.1.1.  The direct flame afterburners
depend upon direct contact of the hydrocarbons with a relatively
high-temperature flame.  High temperatures are required to insure
complete combustion.  This may be accomplished in a steam or
utility-type boiler or a separate combustion chamber may be
required.  In catalytic afterburners, the hydrocarbons are first
preheated and then passed over an oxidizing catalyst bed.


          Afterburners can provide very high hydrocarbon control
efficiencies (>99+%), but they have some disadvantages.  First,
if the hydrocarbon content of the gas stream is too low to support
combustion, a supplemental fuel must be fired to maintain the
required high operating temperatures in direct flame units.  In
catalytic afterburners, the catalyst is susceptible to poisoning
by components likely to be present in the gas stream and may
require frequent reactivation.


          Adsorbers -


          Adsorptive hydrocarbon control processes can be used
to remove organic vapors present in dilute concentrations in gas
streams.  Two basic steps are required for these processes:
first is collection of the vapors on adsorbents such as activated
carbon; second is thermal regeneration of the sorbent.  While
adsorptive control processes provide effective control of hydro-
carbons  (>99+%), the desorbed hydrocarbons emitted from the
regeneration step require further control.  The desorbed hydro-
carbon vapors can be partially recovered via condensation, or
they may be burned, usually without the need for supplemental
fuel firing.


          Hydrocarbon Control Module Waste Streams -


          The hydrocarbon control module can be a source of both
gaseous emissions and solid wastes.  The gaseous emissions are
essentially hydrocarbon-free gases which can usually be discharged
to the atmosphere.  The solid wastes primarily consist of spent
sorbents or catalyst  (from catalytic afterburners).
                              -103-

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4.1.4     Nitrogen Oxides Control Module


          A nitrogen oxide control strategy for the combustion
 fases emitted from coal or low/medium-Btu gas-fired boilers and
 urnaces may be required.  NOx formation in the gasification
module is expected to be low since the raw gas passes through a
reducing atmosphere before leaving the gasifier.  The nitrogen
that does react in the gasifier should form NH9, HCN, thiocya-
nates, and other nitrogen-containing organics rather than
nitrogen oxides (Ref. 46).


          There are three basic processes that can be used to
control NOx emissions from boilers and furnaces:


              Combustion modifications

              Post-combustion flue gas cleaning

              Fluidized-bed combustion


These are processes which would not be considered central to
those in coal gasification plants; therefore, no further atten-
tion is given to them in this report.  These processes are being
assessed by EPA via other contractors and with in-house studies.


4.1.5     Discharge Stream Summary


          The air pollution control modules are sources of air,
liquid, and solid waste discharge streams.  These secondary
discharge streams may require further treatment before being
discharged to the environment or they may be salable by-products.


          The air emissions from these modules  consist of
treated gases which are either discharged directly to the atmo-
sphere or sent to another air pollution control module for
further treatment.  Most of the air pollution control processes
have not been used to treat the air emissions from low-Btu gas
production.  Also, adequate control of minor hazardous constit-;
uents such as hydrogen cyanide, COS, CSz, mercaptans, thiophenes,
trace elements, etc. has not been completely demonstrated.
                               -104-

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          Liquid effluents from air pollution control modules
include spent sorbents (sulfur control module),  scrubbing liq-
uors (particulate, sulfur, and nitrogen oxide control modules)
and sour condensates (sulfur control module).   These effluents
will contain varying levels of pollutants and would be treated
in water pollution control modules before being discharged or
reused.


          All of the air pollution control modules produce
solid wastes.  These include coal fines, ash,  sulfur, and spent
sorbents and catalysts.  The sulfur and coal fines can be sal-
able by-products.  Ash and spent sorbents and catalysts would
be treated in solid waste control modules.


4.2       WATER POLLUTION CONTROL


          In a coal gasification facility, the specific sources
which generate wastewaters will determine the type of contami-
nants that are present in those streams.  Wastewater sources in
a coal gasification plant are shown in Figure 4-5 along with
descriptions of the particulate type of wastewaters they gener-
ate.  The types of contaminants these streams contain are
briefly described in Table 4-4.


          The suspended solid contaminants are primarily coal
particulates that are generated when the coal is crushed and
sized and/or ash is quenched as it is discharged from the gasi-
fier.  Dissolved organics are volatile hydrocarbons that are
condensed in the quench liquor during the subsequent raw gas
cooling step.  Dissolved inorganic gas contaminants such as C02,
HaS, and NHs are produced in the same manner as the dissolved
organics.  Dissolved salts accumulate when reuse of the upgraded
wastewaters is maximized.  At higher concentrations, salts begin
to scale-out on exchanger surfaces; consequently, close monitor-
ing of dissolved solids in the wastewater will be an essential
control practice.


          The composition of coal gasification wastewater is
highly dependent upon certain process variables.  For instance,
lignite coals have substantially different moisture, volatile
hydrocarbon, and inorganic contents, than do bituminous or sub-
bituminous coals.  Therefore, the amounts of tars, oils, phenols,
and other volatile organics that appear in the wastewaters are
greatly affected by the type of coal used.  The type of gasifier
used can also affect the wastewater produced.  A Lurgi gasifier
                              -105-

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                  WATER SPRAY
RUN-OF-MINE
  COAL
              CLEAN
              PRODUCT
              GAS
        BOILER SLOWDOWN
        AND WATER TREAT-
        MENT WASTES
                       COAL PILE RUNOFF;
                       COAL WASHING/
                       CLEANING PROCESS
                       WASTES
                                        ASH QUENCHING/
                                        SLUICING WATER
BY-PRODUCT
TARS AND OILS
TO STORAGE
                                                        COOLING TOWER
                                                        SLOWDOWN
                                                                        PROCESS
                                                                        CONDENSATE
                                                                                 __ RECOVERED BY-PRODUCT.
                                                                                    NH3 AND PHENOLS
                                                                   RECLAIMED
                                                                     WATER
             Figure  4-5.   Major process  modules generating  wastewater
                              in a typical coal gasification plant.

-------
    Table  4-4.   COAL GASIFICATION  PLANT WASTEWATER SOURCES
                          AND CHARACTERISTICS
 Process Module
       Source
                                                        Contaminant
Coal Pretreatment
and Storage
Gasifier
Coal-pile runoff;
coal crushing/
cleaning wastes

Ash quench/sluice
water
Suspended solids;
dissolved organics
Suspended solids;
dissolved inorganics
Particulate Removal;
Gas Quenching and
Cooling; Acid Gas
Removal
Gas liquor;  process
condensate;
unrecoverable solvent
Suspended solids;  non-
emulsified oils;  dis-
solved organics and
inorganics; spent
solvent
Cooling Tower
Slowdown
Suspended solids;  dis-
solved organics and
inorganics (volatiles
and salts)
Utility System
Slowdown
Dissolved inorganics;
suspended solids
Organics Separation
Process condensate
Suspended solids; dis-
solved organics and
inorganics
Wastewater Treatment
 Sludges
                                                   Semisolids
                                  -107-

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which operates at high pressures and relatively low temperatures
will produce wastewaters containing condensed volatile organics
which have been carried overhead in the gasification process.
However, the same volatile organics are cracked in Koppers-Totzek
gasifiers, which operate at higher temperatures and lower pres-
sures.  The result is a wastewater that is essentially free of
dissolved organics.

                                                                  i
          Gas Liquor -


          Gas liquor is just one of several wastewaters from a
typical gasification facility, however, it is the wastewater
that has been the most extensively investigated.  The composi-
tion of the gas liquor produced at the SASOL gasification plant
is presented in Table 4-5 and shows some of the contaminants and
relative concentrations that might be expected for a gasification
gas liquor.  This gas liquor composition was used as a screening
standard for the various process modules whose applicability to
coal gasification wastewaters was evaluated.  Those process
modules shown on Table 4-6 were determined to be the most promis-
ing in terms of control effectiveness, operating cost, reliability,
and energy consumption, for treating a wastewater similar to
SASOL's gas liquor.


          Zero Discharge -


          Because water quality standards have not been estab-
lished, several companies considering construction of coal
gasification plants are planning to achieve zero discharge of
aqueous effluents.  This will allow them to meet any future
standards that may be established.  Unfortunately, the costs
of obtaining zero discharge are usually high.


          To successfully attain zero discharge, the wastewater
treating steps must produce an effluent of a quality that may be
reused in the process or discharged to an evaporation pond.  The
treating modules necessary to accomplish this include:


              removal of suspended solids and non-
              emulsified oils,


              removal of dissolved organic contaminants,
                              -108-

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 Table  4-5.   COMPOSITION OF  GAS LIQUOR FROM SASOL COAL  GASIFIERS
              Component
            Approximate
            Composition
          Phenols

          Ammonia (free)

          Ammonia (fixed)

          Sulfides (total)

          Suspended Tar, Oil

          Cyanides

          CO 2

          Fatty Acids
         3,000 - 4,000 ppm

           500 -   750 ppm

           100 -   200 ppm

           200 -   250 ppm

                ^5,000 ppm

                   <50 ppm

                 <1.0%

                 <.05%
(Ref.  47)
         Table  4-6.   PROMISING WASTEWATER TREATING MODULES
                       FOR SASOL GAS  LIQUOR
        Process Module
             Process
 Suspended  Solids Removal
Filtration,  Flocculation and
Flotation, and Oil-Water Separator
 Dissolved Organics Removal
Phenosolvan, Carbon Adsorption,
Biological Oxidation, Cooling Tower
Stripping (Oxidation)
 Dissolved Volatile Inorganics
 Removal
Acid Gas Stripping, WWT Acid Gas
Stripping
 Dissolved Salts Removal
Forced Evaporation
 Ultimate Disposal
Evaporation Ponds
                                  -109-

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              removal of dissolved salts and inorganic
              volatile contaminants,  and


          •    use of an ultimate disposal process
              (evaporation pond) to facilitate final
              disposition of any wastewater that cannot
              be economically upgraded.


4.2.1     Water Pollution Control Modules


          In addition to the unique problems associated with gas
liquor treating and zero discharge attainment, standard indus-
trial water treating problems (such as treatment of cooling tower
and boiler blowdowns) must also be considered in coal gasifica-
tion plants.  Certainly the types of contaminants present in a
waste stream will determine the treatment required to upgrade
that stream.  Typical wastewaters and the modules required to
treat them are shown schematically in Figure 4-6.


          The water pollution control modules generally consid-
ered for use in coal gasification plants are discussed in the
following text.


          Oil/Water Separation and Suspended Solids
          Removal Modules -


          The functions of these modules are to remove suspended
solids and oils from process wastewater.  The processes generally
used in these modules are:
              Oil-Water Separation

              Filtration

          •   Flocculation/Flotation (dissolved air)


          Oil-water separator - An oil-water separator utilizes
the difference in the densities of the contaminants and the
water to achieve separation of nonemulsified oils and suspended
solids from the wastewater.  Oil-water separation processes have
a history of successful application in the petroleum industry.
These oil/water separation processes are highly reliable, have
                              -110-

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                                                                                                                  p
   SPENT
 /SORBCMT8 \
   AND
  REACTION
 \UQOOHS /
OH/WATER
SEPARATION
SEPARATED
 WATER
   ASH
  QUENCH
   UOUOR
                                                                                  EVAPORATION
                                                                                     PONDS
                                     SUSPENDED
                                      SOLIDS
                                     REMOVAL
                                                                                                      WATER RECYCLE
                                                                                                       TO COOLING
                                                                                                       TOWERS OR
                                                                                                       ASH QUENCH
                                                    DISSOLVED
                                                    OROAMCS
                                                    REMOVAL
                                                                   DISSOLVED
                                                                   MORGAMCS
                                                                    REMOVAL
   STEAM
   SYSTEM
  SLOWDOWN
                                                                                                        AIR EMISSIONS

                                                                                                     ~~|~~°UOIHD EFFLUENTS

                                                                                                     —K  SOLID WASTES
Figure  4-6.   Flow diagram  for the  modules  in the  water pollution control  operation

-------
demonstrated good control effectiveness, and are low cost
operations compared to other oil-water separation techniques.


          There are several disadvantages associated with this
process.  These include its sensitivity to oil droplet density
and size and to the types of solids in the wastewater.  These
variables influence the control effectiveness of a separator and
significant variations in these parameters from those which were
the basis for the design of the separator will affect the degree
of contaminant removal.  To remove small/emulsified oil droplets,
it is sometimes necessary to use a coalescer/separator.


          Filtration - These processes rely on the adherence of
suspended particles to the filter media and/or entrapment of the
particles in the filter interstices to remove suspended contami-
nants from wastewaters.  The major types of filters used in
industries requiring treatment of large volumes of wastewaters
are hay and sand filters.  Backwashing is used to "regenerate"
the filtration media.


          Filtration is a highly reliable means of reducing the
suspended contaminant loading in the wastewater.  It has proven
successful in treating the wastewaters generated at the SASOL
coal gasification complex in South Africa.


          The major disadvantage of the filtration process is
the backwashing process that is required to regenerate the spent
filter media.  This procedure generates an additional contaminated
water effluent whose final disposition must be further considered.
This effluent has been disposed of in the past by incineration
or landfilling.  However, these procedures may create significant
problems if they are not closely controlled.  An alternative
disposal scheme would be to separate the effluent by gravity,
send the bottoms liquid to a mechanical dewatering system, dis-
pose of the solids in an evaporation pond, and treat the waters
from the gravity separator and dewatering system for possible
reuse.


          Flocculation-flotation - This process involves the
addition of chemicals to the wastewater in order to coagulate
and subsequently accelerate the ascension of fine oil droplets
that are present in the water.  Water from the flocculating
chamber flows into a vessel where the oil droplets are floated
to the surface by air bubbles.  These bubbles are skimmed off
to achieve final separation of the oil from the water.  The  air
                              -112-

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                      a sparger at the bottom of the vessel.
Addition ot the flocculant also removes suspended solids by
increasing the rate at which the solids settle.


          The effluents from a flocculation-flotation process
are the oily scum skimmed from the surface of the water, the
settled sludge, and the wastewater free of suspended contami-
nants.  Both the oily scum and the sludge can be sent to an
evaporation pond.  The effluent wastewater will require further
processes prior to its reuse or final disposal.


          Flocculation-flotation is a promising water treating
process.  It is a proven and highly reliable process.  It has
exhibited good control effectiveness in other industrial appli-
cations, and it is a simple operation.  While flocculation can
be combined with other separation techniques such as gravel-bed
or sand-bed filters to remove suspended solids and oils, the
advantage of combining flocculation with air flotation is that
there is minimal contamination of additional water since no
backwashing is required.  Its major disadvantage is the high
cost of the chemicals used.  The oil separation step is also
sensitive to temperature and oil density.


          Dissolved Organics Removal Module -


          The processes in this module are normally considered
to be secondary or tertiary wastewater treatment techniques.
These processes remove dissolved organics by the following
mechanisms:
              Extraction

              Adsorption

              Biological treatment

              Cooling tower oxidation (stripping)


          Extraction processes - These processes are often used
to remove phenols from process wastewater.  These processes con-
sist of two steps:  an extraction step in which the solvent
extracts the phenols from the wastewater and a regeneration step
in which the phenols are separated from the solvent.  Counter-
current extraction columns,  mixers,  and distillation columns are
                              -113-

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used in these processes.  A wide variety of solvents can be
employed in phenol extraction processes, including:


              Benzene

              Tricresyl phosphate

          •   Isopropyl ether

              Aliphatic esters

              Light oils (tar base)

              Light aromatics (tar base)

              Sodium hydroxide solutions

              Various proprietary solvents


          The Phenosolvan process was developed by Lurgi.  It is
a liquid-liquid extraction process involving contacting the
wastewater in which phenols are dissolved with a suitable sol-
vent.  During regeneration of the solvent, the phenols are
recovered as a by-product.   The dephenolized wastewater is
treated for the removal of dissolved inorganics and any residual
contaminants before it is recycled for reuse.


          Phenosolvan is considered to be a very promising
process for application in coal gasification plants because:


              It is very effective in removing the phenols
              from the wastewater.
              This process has been successfully applied
              in the SASOL coal gasification plant, plus
              some 32 other industrial installations since
              1940.  (Lurgi includes this process as part
              of its overall gasification technology.)
              The phenols are recovered as by-products
              from the process.
                             -114-

-------
The major disadvantage of this process is that the solvent is
slightly soluble in water; therefore, it is necessary to remove
the solvent thoroughly to prevent contamination of the phenol-
free wastewater.


          Adsorption processes - These processes utilize a solid
sorbent to remove dissolved organics from wastewater.  After the
sorbent has become saturated, it is regenerated and returned to
service.  The major types of adsorbents used are:


              Aluminas

              Siliceous materials

              Carbonaceous materials

              Synthetic polymers


If the wastewater contains phenols, activated carbon or synthetic
polymer sorbents are normally used to treat the wastewater.  How-
ever, in instances when the flowrates of the wastewater are high,
only activated  carbon can be used economically.


          There are several possible regeneration techniques
available.  Aluminas and siliceous and carbonaceous sorbents are
thermally regenerated.  Polymer sorbents are regenerated by a
solvent wash in which the spent solvent is separated from the
organics by distillation.


          Activated carbon adsorption has been extensively used
to remove contaminants from air and water.  When the carbon bed
becomes saturated with the organic contaminants, it is usually
regenerated by heating the carbon to a high temperature (1140-
1260°K, 1600-1800°F) in the presence of a gas with a low oxygen
content.  Under these conditions the adsorbed organics are
selectively oxidized.  The carbon is then cooled with quench
water and readied for reuse.


          Carbon adsorption of dissolved organics in wastewater
is considered a promising process because it:


              has been successfully applied to upgrading
              wastewaters from coke oven plants,
                              -115-

-------
              has been proven to have a high operating
              reliability and good control effectiveness,


              is simple to operate, and


              is insensitive to organic loading,
              toxicity and temperature change.


The disadvantages of this process are:


              phenols cannot be readily recovered from
              activated carbon, and


              regeneration of the carbon generates a
              contaminated aqueous stream and a poten-
              tially contaminated gaseous emission.


          Biological treating processes - Biological treating
processes use the natural metabolic processes of bacteria and
other microbes to remove dissolved organics from wastewaters.
Overall reactions associated with the two basic types of bio-
logical treating systems, aerobic and anaerobic, are represented
in the equations below.


          Aerobic;

          Organic matter + microbes + 02 •*•
            more microbes + C02 + H20 + waste energy


          Anerobic:

          Organic matter + microbes + NOx 4- SOx •*•
            more microbes + HC03 + N2 + CH^ + H2S +
            C02 + H20 + waste energy


There are several techniques which are based on biological
oxidation; they are:  a) activated sludge, b) trickling  filters,
c) aerated lagoons, and d) aerobic and anaerobic waste stabili-
zation ponds.  Since these techniques all have a 90-99%  phenol
removal efficiency, the selection and use of any of these
techniques will depend on the process to which it is applied.
                             -116-

-------
          Biological oxidation is considered a promising process
because:


              It has been successfully used to upgrade
              wastewater from coke oven plants.


              It has good control effectiveness for
              the removal of phenols.


              Although its primary function is the removal
              of dissolved organics, it also removes some
              trace metals, ammonia, sulfides, BOD, and
              cyanides that the wastewater may contain.


The major disadvantages of this process are its sensitivity to
temperature, wastewater pH, oxygen concentration, and organic and
hydraulic loadings.  It also requires that nitrogen and phos-
phorus nutrients be present to maintain an optimum oxidation
level; this requirement increases the costs and maintenance
involved with this process.


          Cooling tower oxidation (air stripping) - Cooling
towers have been used in the refinery industry as a means of
removing phenols from wastewater.  This process involves the
normal countercurrent contact of air and wastewater in a
cooling tower.  Phenols and other dissolved contaminants are
removed from the wastewater as a secondary function while the
primary function (cooling) is occurring.


          The mechanism by which the contaminants are removed is
uncertain.  There are claims that the phenols and other contami-
nants are destroyed by a biological oxidation mechanism.  However,
the residence time in a cooling tower is short compared to other
biological oxidation processes; therefore, there is some specu-
lation that the dissolved contaminants are removed to some
degree by stripping.  There is a basic difference between these
two mechanisms.  Biological oxidation reduces the contaminants
to harmless compounds while the stripping mechanism simply
transports the contaminants from the wastewater to the air
leaving the cooling tower.  Therefore, a potentially hazardous
air emission may be created.
                              -117-

-------
          Cooling tower oxidation was selected as a promising
process because:


              phenol removal efficiency is high,


              operating costs are low (cooling towers
              are normally required plant equipment; no
              additional expense is incurred in using
              them for phenol removal), and


              this method for treating gas liquor
              has been used successfully at SASOL.


          Dissolved Inorganics Removal Module -


          The function of this module is removal of dissolved
inorganics from wastewater.  There are four basic types of pro-
cesses available:


              Stripping

              Brine concentration

              Ion exchange

              Membrane desalination


Effluents requiring the removal of dissolved inorganics include
process condensates, cooling tower blowdown, ash quench water,
coal-pile runoff, and spent scrubbing liquors.


          Stripping processes -  These processes are used to
remove dissolved inorganic gases (H2S, C02, and NH3) from process
wastewaters and are generally classified as sour water or acid
gas stripping processes.  Acid gas stripping has been extensively
used in the refinery industry for the removal of the inorganic
gases plus phenols and cyanides.  In coal gasification, this
process would be primarily used to remove H2S and NH9 from the
water effluent.
                             -118-

-------
          Removal of acid gases is usually achieved in a
two-stage process.  In the first stage the wastewater is con-
tacted countercurrently with steam and the least soluble of the
two gases (H2S) is removed.  The NH3-rich effluent is then fed
to the second stage where it is, again, contacted counter-
currently with steam to remove NH3.   The overhead gases from
the two stages can be further processed to yield elemental
sulfur and liquid ammonia, which are potential by-products.
The sulfur recovery processes used are discussed in Section
4.1.2.


          Acid gas stripping is a promising process because:


              it is a reliable process with a history
              of successful application in the coke and
              oil refining industries, and


              it has exhibited good control effectiveness
              for removal of H2S and NH3.


Its major disadvantages are:


              the removal efficiency is related to stripping
              steam rates; it can therefore have high
              operating costs,


              removal of NHs and cyanide is sensitive
              to pH level, and


              the overhead and bottom effluents from the
              process require further environmental control.


          Brine concentration processes - Dissolved salts can be
removed from wastewater using brine concentrators or forced
evaporators.  In the brine concentrator, the water is vaporized
from an aqueous stream containing a high concentration of
dissolved salts.  The salts are accumulated as a concentrated
brine or sludge, then sent to an ultimate disposal system.  The
evaporated water is recirculated as heating steam to an earlier
stage in the evaporator.  The steam is condensed and used as
boiler feed water.  Other reasons for selecting this as a
promising process are:
                             -119-

-------
              it requires less energy input than
              thermal drying, and


              it can be used in geographical locations
              where it is impractical to use solar
              evaporation ponds.


          Ion-exchange processes - Ion-exchange processes
utilize solid resins to replace undesirable ions with IT" and
OH~ ions.  The ion-exchange resins can be a variety of high
molecular weight, cross-linked polymers that contain numerous
sites for ion exchange.  During ion-exchange, cations such as
Mg~H~ and Ca"*"* replace H+ ions on the polymer while anions such
as SO = and Cl" replace OH" ions.   As the resin exchange capa-
city decreases, a point is reached where regeneration of the
resin is required.  During regeneration the ion-exchange polymer
is backwashed with strong acids (sulfuric acid) and bases
(sodium hydroxide) to replace the undesirable ions with H+ and
OH-.
          Membrane desalination processes - Membrane desalina-
tion processes are divided into two categories:   reverse osmosis
and electrodialysis.  Reverse osmosis uses semipermeable mem-
branes which allow essentially pure water to pass through the
membrane, but not water impurities, which are rejected.  Electro-
dialysis processes employ membranes with cation and anion
selective characteristics.  These processes produce dilute water
and concentrated brine streams.
          Ultimate Disposal Module -


          The final treatment of wastewater which contains
residual organic and inorganic contaminants, and semi-solid
contaminants, and which cannot be economically upgraded is
usually the evaporation pond.  In this ultimate disposal tech-
nique, wastewater is simply evaporated in place.  This process
has been included as part of the wastewater treating scheme in
a number of preliminary coal gasification plant designs.  It
can be an inexpensive and effective technique for disposing of
unprocessable wastes, and it requires minimum maintenance.


          This method also has some disadvantages.  It requires
substantial land area and it is not generally effective in an
area that has an annual evaporation rate of less than 20 inches
                             -120-

-------
Also, these ponds may require an impermeable lining to prevent
leaching of contaminants into the groundwater.


4.2.2     Process Comparisons


          Water treating processes described in this section are
likely to be utilized in first-generation coal gasification
plants for the following reasons:


              All are commercially available processes
              with histories of successful industrial
              application.


              All have demonstrated good control effec-
              tiveness for wastewater treating applications
              similar to those required for coal gasifica-
              tion plants.


              All have exhibited good operating
              reliability.


A fact sheet for each of the processes of interest is included
in Appendix D.  Specific information about the various water
pollution control processes is summarized in Table 4-7.  Factors
to be considered in  selection of thqse wastewater treating pro-
cesses are summarized below.


              Development status - All are commercially
              available.


              Coal gas applicability - All the processes
              shown  in Table 4-7 are being used or poten-
              tially can be used in coal gasification plants.


              Control effectiveness - These are statements as
              to the removal efficiency that can be expected
              for a  given contaminant using a given process.
                              -121-

-------
                    Table 4-7.    SUMMARY  OF  WATER POLLUTION  CONTROL  PROCESSES
Dissolved
Suspended solids and Inorganics Ultimate
Treatment fraction oils removal Dissolved organlcs removal removal Residual contaminant removal disposal

rlocculation
Flotation
Oil-water
separation
Filtration
Liquid-liquid
extraction
(Phenosolvan)
Activated
carbon
adsorption
Biological
oxidation
(activated
sludge)
Acid gas
• stripping
Forced
evaporation
Activated
carbon
adsorption
Cooling
tower
oxidation
Evaporation
ponds
Development Status



Coal Gas Applicability
Commercial Commercial  Coaoercial   Commercial   Commercial  Commercial  Commercial   Commercial  Commercial Commercial  Commercial
• Presently used yes yes yes yes
- Potential future
use yes yes yes yes
Control Effectiveness
• Suspended solids
reaoval 1.75Z ^OZ 52-83Z
• Free oil removal t-97Z t90Z S2-83Z
• Phenol removal t<25Z >94Z
• Total organics
reaoval VOZ
• BOD removal -x*OZ 36Z
• Sulfide removal
• NHs reaoval
• Cyanate reaoval
• COD removal 801 >v50 ppm <_ 25-44Z
• Trace element "
removal J
• Total dissolved
solids removal
Utility Requirements
• Steam /
• Electricity / / r /
• Cooling/backwash
no yes yes no no yes no

yes yes yes yes yes yea yes


%90Z 70Z *v90Z
^93Z 80Z fl7Z *>49Z
15Z ^OZ
MZ -X.70Z " 1Z
•\-90Z 
-------
                               Table  4-7.    SUMMARY  OF WATER  POLLUTION  CONTROL PROCESSES
                                                                                                                                 (continued)
Dissolved
Suspended solids and inorganics Ultimate
Treatment fcactlca oils removal Dissolved organics removal removal Residual contaminant removal disposal

Flocculation
Flotation
Oil-water
separation
Liquid-liquid
I extraction
Filtration 1 (Phenoeolvan)
Activated
carbon
adsorption
Biological '
oxidation
(activated
sludge)
Acid gas
• stripping
Forced
Bvaporation
Activated
carbon
adsorption
Cooling
tower
oxidation
Evaporation
ponds
I
I-1
N>
law Materials Beqolred

  • Solvent
  • Chesical additives

Allovs By-Product to be
lecovered

Generates Effluents
leqniring Further
Control

  • Gaseous
  • Aqueous
  • Treated effluent
  • Solid/senisolid

Process Limitation/
Sensitivity

  • Teoperature change
  • pE level
  • Contaainant size
     distribution
  • Requires
     regeneration
  • Adversely affected
     by trace elements
  • Nutrients required
  • Chenical additives
     required
  • Hydraulic loading
             - Although It cannot be quantified, it Is a factor to be considered for the processes.

-------
              Utility  requirements - The various types  of
              utilities  required by the respective processes
              are  shown  under this heading (little or no
              information is available on the quantities  of
              utilities  required).
              Raw materials  required - Processes requiring
              solvents  or chemical additives are indicated.
              By-product  recovery - Processes recovering
              contaminants  of commercial value are  identi-
              fied under  this heading.
              Effluents  requiring further control -  Contami-
              nant  streams  subject to further treatment are
              indicated.  Examples of sources and types of
              contaminant streams are:
                 Contaminated    Contaminated
                   Effluent        Effluent       Specific
                   Source           Type        Effluent

                 Flocculation -   Aqueous         Oily scum
                 flotation

                 Activated       Solid/semi-      Excess sludge
                 sludge          solid

                 Activated       Gaseous         Flue gas from
                 carbon                         regeneration
                 adsorption/                    heater
                 regeneration


4.2.3     Water Pollution Control Philosophy


          No  single  process can remove all of the impurities
required to yield  an acceptable wastewater.   It  is usually
necessary to  combine several processes to achieve the  desired
effluent quality.


          The sequence  of wastewater  treating processes selected
will depend upon the overall treating philosophy.   In  coal gasi-
fication it is likely this philosophy will be to achieve zero
                              -124-

-------
discharge and to recover contaminants as by-products whenever
economically feasible.  For example, the following sequence of
treatment processes reflects this philosophy.


              1st Step - Separate tar and oil from the
              wastewater.  (The tar and oil can subse-
              quently be separated from one another and
              recovered as by-products.)


              2nd Step - Remove suspended solids and oils.
              This is to insure that the subsequent waste-
              water treating processes will not be plugged
              or fouled.
              3rd Step - Remove dissolved phenols and, if
              possible, recover them as a by-product.  Maxi-
              mum removal of the phenols at this point will
              reduce the amount that could be present as a
              contaminant during subsequent acid gas strip-
              ping operations.
              4th Step - Remove acid gases from the waste-
              water by a two-stage steam stripping process.
              HaS is less soluble in water than is NHa.   It
              is stripped out in the first stage; NHs is
              removed in the second stage.
              5th Step - Remove residual contaminants.  The
              acid gas stripping effluent will contain small
              amounts of the major contaminants which must
              be removed to achieve desired effluent water
              quality.


              Ultimate Disposal - Evaporation ponds are
              normally required for the disposal of waste-
              waters that cannot be economically upgraded.
              The general climate of the region in which
              the coal gasification plant will be located
              will determine whether solar evaporation ponds
              are feasible.  Sanitary landfills are used for
              ultimate disposal of solids or semisolids
              (sludge) from the wastewater treating processes
                             -125-

-------
          Treating Sequence Selection - Examples
          The logic for selection of treating sequences is
illustrated by three examples described below.  The concentra-
tions of various contaminants determine, in part, the processes
chosen.  For the three example cases, the contaminants are
characterized as follows:
           Contaminant
          Concentration

          phenols

          dissolved acid gases

          dissolved solids
        Example
 high

 high

 low
low

high

low
low

low

high
          Example 1 - The approach to achieving zero discharge
would probably consist of recovery phenols as by-products and
recovering acid gases for further processing to elemental sulfur
and liquid ammonia.  The treating processes are described on
Table 4-8 and the treating sequence is shown on Figure 4-7.
          Three processes can be used in Example 1 for removing
the residual organic and inorganic contaminants in the waste-
water.  These processes and the criteria for their selection are
as follows:
          Treating Process

          Carbon Adsorption



          Cooling Tower




          Forced Evaporation
   Criteria for
Selecting Processes

should be used when an
effluent of high quality
is desired.

this is a low cost process;
however, its effectiveness
in removing dissolved
inorganics is unknown.

useful where it is
impractical to use solar
evaporation ponds and where
the wastewater contains a
high concentration of
dissolved solids.
                             -126-

-------
                              Table 4-8.   TREATING PROCESSES FOR EXAMPLE  1
Contaminant
Throughput
Probable Approach
to Attain
Zero Discharge
Treating
Sequence
Treating
Process
          High amounts of
          phenols; high
          amounts of  dis-
          solved acid gases;
          low quantity of
          of dissolved solids
Recover phenols as by-
products.  Recover acid
gases for further pro-
cessing to sulfur and
liquid ammonia
Tar, oil/HaO separation
Removal of suspended
solids and oils
                                                            Phenol recovery
        separator
Flocculation-
flotation
                                                        • Phenosolvan
                                                          • Acid gas removal
I
M
N>

I
                                                            Removal of residual
                                                            organic and inorganic
                                                            contaminants
                                                          Acid gas
                                                          stripping
                                                                                          Carbon adsorption
                                                          Cooling tower
                                                          Oxidation
                                                                                          Forced evapora-
                                                                                          tion
                                                            Ultimate disposal
                                                            of sludge
                                                                                          Evaporation pond
                                                                                          Sanitary landfill

-------
             OH. TAR.
           WATER INFLUENT "
N>
00
I
TREATED EFFLUENT
  RECYCLED TO
   PROCESS
                                                                                 	FEASIBLE TREATING PROCESSES

                                                                                 	 BEST TREATING PROCESS
                          Figure 4-7.   Wastewater treating  sequence  for  example 1

-------
          Evaporation ponds and sanitary landfills are commonly
used for the ultimate disposal of sludges.  Evaporation ponds
are used whenever possible for the disposal of wastewaters that
cannot be economically treated.  Sanitary landfills are gener-
ally used for the ultimate disposal of any solids or semisolids
(sludge) generated in the plant; however, before sludges can be
disposed.of in a landfill they must be mechanically dewatered so
that any possible leaching is minimized.


          Example 2 - The approach to achieving zero discharge
would probably consist of removing and destroying phenols, and
recovering acid gases for further processing to elemental sulfur
and liquid ammonia.  The treating processes are described on
Table 4-9 and the treating sequence is shown on Figure 4-8.


          Two processes can be used for phenol removal in
Example 2.  The criteria for selecting these processes are dis-
cussed below.
    Removal Processes          Criteria for Selecting Processes

  • Carbon Adsorption          - has good control effectiveness,
                                 but not the most economical
                                 process for this example.  It
                                 would yield a higher quality
                                 effluent than is required for
                                 recycling to the process.


  • Biological Oxidation       - would be good process for this
                                 example.  It requires no re-
                                 generation and is easily main-
                                 tained.  Effluent pH must be
                                 controlled between 5.5-9.5.
                                 The optimum pH level is 7.0.
                                 A high concentration of sul-
                                 fides can adversely effect this
                                 process; therefore, biological
                                 oxidation should follow acid
                                 gas stripping in this example.


          Three processes  can be used in Example 2 for removing
residual organics  and  inorganic contaminants.
                              -129-

-------
                             Table  4-9.   TREATING PROCESSES FOR EXAMPLE 2
o
I
Contaminant
Throughput
Probable Approach
to Attain
Zero Discharge
Treating
Sequence
Treating
Process
          Low  amounts of
          phenols; high
          quantity of dis-
          solved  gases; low
          quantity of dis-
          solved  solids
Phenol recovery uneco-
nomic, therefore, remove
phenols.  Recover acid
gases for further pro-
cessing to elemental
sulfur and liquid
ammonia
Tar, oil, water separa-
tion
Removal of suspended
solids and oils
                                                            •  Phenol removal
                                                            •  Acid gas  removal
  Oil/HaO separator
•  Flocculation-
  flotation
                                                        • Carbon adsorption

                                                        • Biological oxida-
                                                          tion
                                                          Acid gas strip-
                                                          ping
                                                              Removal  of residual
                                                              organic  and  inorganic
                                                              contaminants
                                                        • Carbon adsorption

                                                        • Forced evaporation

                                                        • Cooling tower
                                                          oxidation
                                                              Ultimate disposal of
                                                              sludge
                                                        • Evaporation pond

                                                        • Sanitary landfill

-------
  oa. TAR.  _

WATER INFLUENT
I
h-«
(j)
                                                                                    1


                                                                          ,   FORCED   t	|

                                                                          | EVAPORATION |


                                                                          I
                                                                                                     THCATEO EFFLUENT

                                                                                                      RECYCLED TO

                                                                                                        PROCESS
                                                                      	FEASIBLE TREATING PROCESSES


                                                                      	 BEST TREATING PROCESS
               Figure 4-8.   Wastewater treating sequence  for  example 2

-------
    Removal Processes

    Carbon Adsorption
                     Criteria for Selecting Processes

                     - after the biological oxidation
                       and acid gas treating steps,
                       the residual contaminants in
                       the wastewater should primarily
                       be dissolved NH3  and H2S.
                       Carbon adsorption is most effec-
                       tive in removing  dissolved
                       organics,  which are not present
                       in great quantity in this
                       example.
    Cooling Tower Oxidation
    (Air Stripping)
                     -  would be effective for treating
                       waters with low contaminant
                       concentrations and is economical
                       if air emissions are within
                       allowable limits.
    Forced Evaporation
                     - is the least desired process
                       because of its high operating
                       costs.
          Example 3 - The approach to achieving zero discharge
would probably consist of completely removing and destroying
phenols and acid gases; their recoveries would not be economi-
cally justified.  The treating processes are described on
Table 4-10 and the treating sequence is shown on Figure 4-9.


          Carbon adsorption and forced evaporation can be used
to remove residual contaminants.  For this example, forced
evaporation is best choice because of the relatively large
quantities of dissolved solids to be removed from the waste-
water.
4.2.4
Discharge Stream Summary
          The water pollution control modules are sources of
air, liquid and solid waste discharge streams.  A summary of
these discharge streams is presented in Table 4-11.


          Air emissions - Air emissions from these modules con-
tain organic vapors, ammonia, and acid gases (H2S, C02, COS, etc)
                              -132-

-------
                              Table  4-10.   TREATING PROCESSES  FOR EXAMPLE 3
            Contaminant
            Throughput
 Probable Approach
     to Attain
  Zero Discharge
       Treating
       Sequence
  Treating
  Process
          Low quantity phenols;
          low quantity of dis-
          solved acid gases;
          high dissolved
Uneconomical to recover
either phenols or acid
gases; consequently, re-
move both from the
wastewater
Tar, oil, water separa-
tion
                                                              Removal of suspended
                                                              solids and oils
Oil/H20 separator
                             Flocculation-
                             flotation
                                                             • Phenol and dissolved
                                                              acid gas removal
                                                         Biological
                                                         oxidation
u>
 i
                                                             • Residual contaminant
                                                              removal
                                                         Carbon adsorption

                                                         Cooling tower
                                                         oxidation

                                                         Forced evapora-
                                                         tion
                                                              Ultimate disposal of
                                                              sludge
                                                         Evaporation pond

                                                         Sanitary landfill

-------
                   OIL. TAR.
                 WATER INFLUENT
CO
-P-
 I
 TREATED EFFLUENT
f RECYCLED TO
   PROCESS
                                                                          	FEASBLE TREATING PROCESSES
                                                                          	 BEST TREATING PROCESS
                          Figure  4-9.   Wastewater treating  sequence for example  3

-------
      Table  4-11.   WATER POLLUTION CONTROL DISCHARGE STREAMS

                                                  Probable and Potential
  Process Module              Processes                 Waste Streams
Suspended solids      Filtration,  flocculation-    Aqueous - treated waste-
removal               flotation, oil-water            water, oily scum,
                      separator                      backwash water

                                                  Solid - sludge


Dissolved organics    Liquid-liquid extraction,    Aqueous - Regeneration
removal               activated carbon adsorp-        quench, blowdown,
                      tion, biological oxidation,     spent solvent,
                      cooling tower stripping         treated wastewater

                                                  Solid - sludge

                                                  Gaseous - vent gases,
                                                     cooling tower outlet,
                                                     regeneration flue gas
Dissolved volatile    Acid gas stripping          Aqueous - treated waste-
inorganics removal                                   water

                                                  Gaseous - potential HjS
                                                     and NHa emissions
Dissolved salts       Forced evaporation,          Aqueous - concentrated
removal               ion exchange, membrane          brine, spent ion
                      desalination                    exchange regenera-
                                                      tion solution

                                                   Gaseous - vent gases

                                                   Solids - spent ion
                                                      exchange resins
                                  -135-

-------
These emissions are either recycled to air pollution control
modules for treatment or they are collected as a by-product.


          Liquid effluents - The liquid effluents from water
pollution control modules consist of tar, oil, and phenol by-
products, spent regeneration solutions, concentrates,  stripper
condensates, and treated wastewater.  The tar, oil, and phenols
are useful by-products.   Concentrates, sludges,  and condensates
are sent to a dewatering system and then to an evaporation pond
for ultimate disposal.   The treated water is either sent to
evaporation ponds, recycled to other processes,  or used as
cooling tower feed.  There are predictable air emissions from
evaporation ponds and cooling towers.  Improper evaporation-pond
operation may result in water runoff which could contaminate
surface waters.  Groundwater contamination may occur if the pond
is not properly lined.   Liquid effluents (blowdown streams) from
cooling towers are sent to evaporation ponds or to ash quench.


          Solid wastes - The solid wastes consist of coal fines,
ash, spent sorbents, biological sludge, spent ion-exchange
resins, and evaporation pond sludge.  These wastes are sent to
the solid waste control modules for disposal.


4.3       SOLID WASTE POLLUTION CONTROL
          The solid waste pollution control module treats and
disposes of the following classes of wastes:


              Ash

              Coal residue

              Biological oxidation sludge

              Spent catalysts and filter media

          •   Coal fines

              Sulfur
Coal fines may be collected and burned on site; coal fines and
sulfur may be sold as by-products.  The other wastes may or may
not require treatment before disposal, depending upon their
composition.  Chemical fixation and sludge reduction modules
                             -136-

-------
can be used to treat these solid wastes.  Figure 4-10 is a flow
diagram of the modules for solid waste control.  Landfill, by
definition, is the ultimate disposal technique for these wastes.
The functions of and waste streams generated by these modules
are described in the following paragraphs.


4.3.1     Sludge Reduction Module


          The function of the sludge reduction module is to
reduce the volatile matter and to destroy or detoxify the haz-
ardous constituents in biological oxidation sludge.  This can be
accomplished either by incineration or by pyrolysis.  Multiple-
hearth and fluidized-bed incinerators are the types in common use.


          In multiple-hearth incinerators, the sludge enters the
top of the unit where it is dried.  The dried sludge is then
burned as it moves slowly down through the lower hearths.  In
fluidized-bed incinerators, sludge is combusted in a hot, sus-
pended bed of sand.


          Pyrolysis of biological oxidation sludge is a controlled
thermal process that reduces sludge volumes and detoxifies solid
residues.  The carbon and volatiles in the sludge are not com-
busted because the pyrolysis takes place in an oxygen-deficient
environment.  The resulting pyrolysis gas may be used as a com-
bustion fuel or it may be condensed to recover tars and oils.


          The sludge reduction module is a source of both air
and solid waste pollution.  Air emissions which consist of par-
ticulates, combustion gases, and odors, require control.  The
solid waste generated by this module primarily consists of ash,
which may either be sent to the chemical fixation module or to
landfill.


4.3.2     Chemical Fixation Module


          The chemical fixation module treats solid wastes to
produce environmentally safe materials that can be used for
either landfill or salable by-products.  Most fixation processes
consist of mixing proprietary chemicals with solid wastes and
pumping the resulting mixture onto the land where solidification
occurs in several days to weeks.
                             -137-

-------
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                                                                                         LEGEND	



                                                                                        AfflEM3SK)M8



                                                                                         UOUID EFFLUENTS



                                                                                         SOLO) WASTES
                                                                                        I COM. FINES '.

                                                                                      ~*1 AND SULFUR )
             Figure  4-10.   Flow  diagram  for the modules in  the solid waste control operation.

-------
          The only waste stream generated by the chemical
fixation module is the treated solid waste.   This solid waste is
either disposed of in landfill or can be sold as a soil condi-
tioner.


4.3.3     Discharge Stream Summary


          The solid waste pollution control module is a source
of air and solid waste emissions.  Air emissions are from the
sludge reduction module.  They consist primarily of volatile
organics, combustion products and particulate matter.  These
emissions require further treatment before being vented to the
atmosphere.  The solid wastes generated by this module consist
of "fixed" solids from chemical fixation and ash from sludge
reduction.  For ultimate disposal, these wastes may be sent to
landfills or sold as by-products.


          Landfilling solid wastes may also be a source of water
pollution because of the potentially toxic compounds that can be
leached from the solid wastes.  These toxins may contaminate
surface and/or ground waters depending upon the quality and
quantity of runoff water at the landfill and the ground perme-
ability characteristics.


          With the exception of the spent filter media and coal
residues, virtually all of the solid wastes generated during the
production of low-Btu gas from coal are potentially salable
products.  The sludge from the biological wastewater treatment
process can be sold as a soil conditioner or as fertilizer if
trace elements or toxic compounds are not present in significant
concentrations.  Coal fines can be sold or recycled as a fuel
for combustion processes.  The spent catalyst can, in some cases,
be sold to catalyst manufacturers for regeneration.  The sulfur
recovered from the air pollution control operation can be sold
to sulfur users.
                              -139-

-------
                          SECTION 5.0

               SUMMARY OF TECHNOLOGY ASSESSMENTS
          This report has been prepared as a reference and
planning document for use in a comprehensive multimedia environ-
mental assessment of coal conversion processes which produce
low/medium-Btu gases.  Control techniques needed to guarantee
environmental acceptability of these technologies are also
identified in this document.
5.1       ASSESSMENT PROGRAM PHILOSOPHY


          For successful execution of a comprehensive environ-
mental and control technology assessment program, it is required
that specific information about the processes and pollution
control technologies in question be gathered.  A logical manner
to gather this information is as follows:


          a)  Characterize the technology - This is a factual
              description of how each process works, its
              operating conditions, its history of perfor-
              mance, economics of operation, how the plants
              are assembled section by section, and so forth.
              This is the type of information that would be
              of prime importance to parties interested in
              designing and building low/medium-Btu coal
-gn
[fT
              gasification plants.
          b)  Identify problem areas - The next step is to
              identify specific sections of the processes
              where environmental problems are most likely
              to occur.  To do this"] the investigators must
              first have a thorough knowledge of the design
              of equipment being used in these process plants,
              They must also have specific knowledge of the
              compositions, physical properties, and sizes
              of streams flowing into and out of each process
              operation or module, and of the operating condi-
              tions (temperature, pressure, etc.) in these
              process units.
                             -140-

-------
    Finally,  the investigators must develop
    the capability to judge the potential
    environmental problems associated with
    any-given process.   This judgment sense
    includes  the ability to determine if any
    environmental problem exists;  specifically
    where it  is occurring; why it  is occurring;
    and whether or not more information will
    be needed.  Some of the information needed
    to develop this judgment comes from the
    literature; some from engineering assess-
    ment of the processes; and some will
    come from inspection of operating plants.
c)  Develop and execute test programs - Much
    of the essential.information is simply
    not available from known sources.  It
    will have to be obtained from actual
    tests in pilot units and commercial
    plants.  These tests are costly.  It is
    therefore critical that investigators
    determine early in the program just
    what information is most critically
    needed and what test work can reasonably
    be deferred.
    Much of the cost in these test programs
    is related to chemical analyses.   Complete
    analysis of some streams can be very
    expensive because of the large number of
    organic compounds and/or trace elements
    that may be present in these streams.
    EPA is working on various methods to
    obtain maximum useful environmental data,
    while holding analytical costs to a
    practical level.  One approach has been
    identified as Level 1.  This involves a^
    screening procedure which allows investi-
    gators to qualitatively identify groups
    of compounds and to broadly assess the
    health effects of pollutants (by bioassay
    testing) at relatively low costs.
                    -141-

-------
          d)  Perform environmental assessment - The
              combined results of the engineering
              assessment, problem definition, and
              testing program will provide the basis
              for an environmental assessment.  There
              are two primary questions to be answered
              in this step.  What parts of these pro-
              cesses are environmentally unacceptable,
              and what is required to make them environ-
              mentally sound?


          e)  Recommend control technology - In the final
              analysis, a process is judged environmentally
              acceptable, or it is not.  In many cases, it
              may be made acceptable by adding available
              and practical control equipment.  It may be
              possible in some cases to reduce pollutants
              to a suitable level by altering operating
              conditions (gasification temperature can be
              raised; feedstock characteristics can be
              modified, and so forth).   In still other
              cases, principle changes in the plant design
              may produce the desired pollution control.


5.2       CONTENT OF TECHNOLOGY STATUS REPORT


          This report was prepared to provide investigators with
an up-to-date source of information on low/inedium-Btu coal gasi-
fication technology.  Special emphasis has been placed on matters
which might be considered environmentally and commercially
significant.  This is important in that it gives proper direc-
tion to investigators in subsequent studies and test programs.


          In Sections 1.0 through 4.0, technologies are dis-
cussed in a conceptual manner.  This is to acquaint investigators
with the nature of commercially available processes and control
systems.  The practical problems and the characteristics of
emissions that would be expected are also presented.


          The appendices (Appendix A through E) contain detailed /
fact sheets for those process modules and control system modules
that have been judged to be significant elements of the technology.
                             -142-

-------
          All information in this report and its appendices is
related to these specific flow processes.  Major processing steps
such as coal gasification are identified as operations.   Each
operation has well defined input and output streams and performs
a specific function.  Smaller, but equally distinct process
steps, are defined as modules.  One or more of these modules may
be combined to form either a major process operation or a pollu-
tion control technique.


5.3       SUMMARY OF ASSESSMENTS


          As test programs are developed, investigators will
continue to search out those matters of principle concern such
as environmental impacts, economic factors, pollution control
efficiency, and so forth.  The following tables are summaries of
such items which, based on results to date, are considered areas
of concern.
          Table  5-1  contains data requirements for environmental
assessments.  Input  and output  streams at major pollution sources
are characterized.   What is or  is not known about each stream
cited is listed  under Remarks.  This, in many cases, is the most
important information on the table.  Table 5-2 is a comparable
summary for control  technology  assessments.


          It  is  expected that these  tables will be expanded to
include new problem  areas.  Fugitive emissions, for example,
while referred to  only briefly, are  an acknowledged emission
problem that  currently suffer from lack of definition.  Better
definitions of health effects and ecological effects attributable
to specific pollutants are being made; these judgments will
certainly alter  the  areas of concern in these tables.
                              -143-

-------
                                        Table   5-1.    ENVIRONMENTAL  ASSESSMENT  DATA  REQUIREMENTS
             Discharge Str
                 Source
Fcaamtoek awl Discharge
   Streams Requiring
   Characterization
Current Status of
Environmental Data
                                                                                                                                       arks
            Coal  Pretreatmeat

            Storage, Bandling,
            •mi Cniahlag/SUIng
   Raw coal  feedstock
                                     Dust  emissions
                              There are many data on the major species
                              in coal feedstock.  However, there are
                              little data on Minor constituents such as
                              trace elements and the types of sulfur
                              in the coal.

                              The air emission from coal storage piles,
                              crushing/sluing and handling will consist
                              primarily of coal dust.  The amount of
                              these emissions will vary from site to
                              site depending on wind velocities and
                              coal size.
                                      More data on the trace constituents In the coal
                                      are needed.
                                                                                                                Asphalt  and various polymers have been used to
                                                                                                                control  dust  emissions from coal storage piles.
                                                                                                                Water sprays  and enclosed equipment have been
                                                                                                                used to  control coal handling emissions.  Enclosures
                                                                                                                and hoods  have been used for coal crushing/sizing.
-P-
 I
                                     Water runoff
                                     Solid wastes from
                                     crashing and sizing
                              The amount of data on dissolved and
                              suspended organics and Inorganics in
                              runoff water produced from coal storage
                              piles and dust control or supression
                              processes is minimal.

                              This stream consists of rock and mineral
                              matter rejected from crushing and sizing
                              coal.  There are few data concerning the
                              trace components in this stream and the
                              potential of these components to con-
                              taminate surface and groundwaters is
                              not known.
                                                                                                                Proper  runoff water management techniques have been
                                                                                                                developed.  More data on the characteristics of this
                                                                                                                wastewater need to be obtained to determine the
                                                                                                                need for  treating this effluent.
                                     This waste has been disposed of  in landfills.
                                     Leaching data need to be obtained.
            Coal Drying. Partial
            Oxidation and Bri-
            quettlng Modules
                                     Coal feedstock
                                    Vent gases
            Coal Gasification
            Coal Feeding Device
                                    Pretreated coal feed
                              Same as  for the raw coal feedstock for
                              the coal storage, crushing/sizing, and
                              handling modules.

                              These emissions will contain coal dust  and
                              combustion gases along with a variety of
                              organic  compounds liberated as a result of
                              coal devolitillzatlon reactions.  There are
                              currently few data on the characteristics
                              of these organic species.
                              There are many data on the major components
                              in the pretreated coal; however, there  is
                              little or no data on trace elements,  the
                              distribution of sulfur compounds, and the
                              alkalinity of the coal ash.
                                      Same ae for the raw coal feedstock for the coal
                                      storage, crushing/Sizing, and  handling modules.


                                      The organic compounds need to  be characterized
                                      to determine whether this discharge stream needs
                                      to be controlled.  Afterburners In addition to
                                      particulate collection devices may be required.
                                      Data needs to be obtained on  the distribution of
                                      sulfur species and trace elements in the pretreated
                                      coal.  The characteristics of the coal ash need to
                                      be determined to assess the potential for the ash
                                      retaining coal sulfur species.

-------
                            Table  5-1.     ENVIRONMENTAL  ASSESSMENT  DATA  REQUIREMENTS
                                                                                                                                     (continued)
 Discharge Stream
     Sontee
Feedstock and Discharge
   Stream Requiring
   Characterization
            Current Status of
            Environmental Data
                                                                                                                             arks
ash
            Device
Coal Gaalfler
                         Input pressurizing gas
                         for lock hoppers  and
                         transport gaaes for
                         entraiaed-flov
                         injection devices

                         Vent gases
                         Ash quench water
                         Vent gases
                         Spent ash quench
                         water
                         Ash or slag
                         Coal, additives,
                         steam, and air/oxygen
                         feedstocks
                         Start-up vent strean
There are very few data on  the character-
istics of these input  streams.  The con-
stituents in these streams  will exit In
the gasifier output streams or be vented
to the atmosphere.

There are currently no data on the charac-
teristics of these gases.   These vent gases
nay contain hazardous  species found in the
raw product gas exiting the gasifier.
                             There are currently few data on process
                             coodenaates that are used  for ash quench
                             water.
                             There are currently no data on the charac-
                             teristics of this discharge strean.  This
                             stream May contain hazardous species found
                             in the raw product gas and nay require
                             control.

                             There are currently no data on this dis-
                             charge streaa.  This strean will contain
                             dissolved and suspended organlcs and In-
                             organics and will require control.

                             There are United data on the character-
                             istics of the ash and slag especially con-
                             cerning the anount of unreacted coal, trace
                             elements and total organics.

                             The coal characterization needs are the sane
                             as for Pretreated Coal. Additives to the
                             coal will affect the characteristics of the
                             discharge streaa and there are currently
                             few data on the composition of these
                             additives.

                             There are currently no data on the composi-
                             tion of start-up vent strean.  Depending on
                             the coal feedstock, there »*y, be tar and oil
                             aerosols, sulfur species, -.yv  tides, etc. in
                             this strean; therefore, control of pollu-
                             tants generated during start-up is required.
                                                                              In medlmt-Btu gasification plants, the use of
                                                                              the nitrogen vent strean  fron oxygen production
                                                                              is a good candidate for these gas input streans
Vent gases fron coal feeders can represent
a significant environmental and health problem.
Control of these emissions is required; however,
the characteristics of  these gases need to be
determined to implement an adequate control device.

Hany sources of contaminated water may be used  as
ash quench water.   Characterization of these waste
waters will be required to determine the potential
effect of the ash  removing some of the organics
contained in these waters.

The type of ash removal device and the character-
istics of the quench water will determine the
characteristics of this stream.
                                                 The magnitude of this strean can  be minimized by
                                                 designing an ash quench water recycle process.
                                                 Leaching tests need to be done on this solid
                                                 waste to determine whether further treatment is
                                                 necessary before ultimate disposal.
                                                 Characterization of these  input streams will pro-
                                                 vide a basis for correlating  the characteristics
                                                 of  the gasifier discharge  streams and raw product
                                                 gas for various typea of coal and coal additives.
                                                Thia strean can be controlled using a flare to burn
                                                the combustible constituents.  The amount of heavy
                                                tars and coal partlculatea  in this strean will affect
                                                the performance of the  flare.  Problems with tars
                                                and coal particles can  be minimized by using char-
                                                coal or coke as the start-up fuel.
                                                                                                                                           (Contimiwt)

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                            Table  5-1.     ENVIRONMENTAL  ASSESSMENT  DATA  REQUIREMENTS
Operation

 Discharge Stream
      Source
Feedstock and Discharge
   Streams Requiring
   Characterization
            Current  Status of
            Environmental Data
                                                                                                                         Remarks
                         Rav product gas
                         Fugitive emissions
Gas Purification

Partlculate Removal
Gas Quenching and
Cooling
Acid Gas Removal
                         Rav product gas
                         from the gasiflers
                         Collected partlculate
                         matter
 Spent quench liquor
                         Tail gases
                         Spent sorbents and
                         reactants
                            There are many data on the major constituents
                            in this stream; however, few data are avail-
                            able on the minor components such as HtS,
                            COS, NHj, NCH, trace elements, tar and par-
                            tlcnlate loadings, etc.

                            There are no data available on these emissions.
                            These emissions will contain hazardous species
                            that are in the raw product gas.
                            The characteristics of the partlculate matter
                            entrained  In  this stream need to be determined.
                            There are  few data reported on these charac-
                            teristics.
                            There are  few data on the characteristics  of
                            this solid waste stream.  This stream will
                            contain unreacted carbon, sulfur species,
                            organics,  and trace elements.
There are few data on  the composition of
this stream;  however,  current data indicate
that there are significant quantities of
suspended and dissolved organics (primarily
phenols)  and  inorganics present in this
stream.

There are few data on  the composition of
these tail gases.  These gases will contain
sulfur species and hydrocarbons.
                            No data have been reported on these streams.
                            These  streams will contain hazardous species
                            such as cyanides, heavy metals, organics,
                            etc. and will require further treatment
                            before disposal.
                                                 The concentrations of these minor gas constituents
                                                 will affect the types of gas purification techniques
                                                 (i.e., acid gas removal processes) used to treat
                                                 the raw product gas.
                                                 These  emissions will determine the  extent of worker
                                                 exposure to hazardous species and define the need
                                                 for  continuous area monitoring of toxic compounds
                                                 and  personal protection equipment.
The nature of the entrained particulate matter de-
pends upon the coal  feedstock and gaslfier operating
parameters.  The partlculate characteristics will
affect the performance of partlcnLate removal de-
vices such as cyclones and electrostatic preclpt-
tators.

Characterization of  this stream is needed to
determine whether it can be used as a by-product
or whether further treatment is necessary before
disposal.  Current data indicate that there is a
significant amount of unreacted carbon In this
stream and It may be used as a combustion fuel.

Characterization of  this stream will determine
the type of water pollution control techniques
required to treat the spent quench liquor.  These
control techniques will vary depending upon the
quantity and composition of this effluent stream.
These gases are  the primary feedstock to the
sulfur recovery  and control processes.   Trace
constituents such as hydrocarbons, trace elements,
and cyanides will affect the performance of these
sulfur recovery  processes.

Characterization of this stream is required
If It is to be treated using on-slte pollution
control devices.
                                                                                                                                           (Comtlowed)

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                                       Table  5-1.     ENVIRONMENTAL  ASSESSMENT  DATA  REQUIREMENTS
                                                                                                                                                (condoned)
             Discharge Stream
                 Scarce
feedstock and  Mochmrge
   Streams Requiring
   Characterization
            Current Status of
            Environmental Data
                                                                                                                                     Remarks
            4ir Pollution Control

            Partlculate Removal
                                     Partlculate-free gas
                              Thece are many data oo the  collection of
                              partlculates using a variety of devices.
                              The efficiency of these devices depends
                              upon the nature of Che partlculate
                              •alter and gas stream to be treated.
                                                 These  devices are mainly used to collect coal
                                                 dusts  from the coal pretreatment and  feeding
                                                 processes.  The particulate-free gas  is a discharge
                                                 stream from the gasification plant  and is usually
                                                 vented to the atmosphere.
            Sttlfnr Recovery
            and Control
   Coal dust


   Treated gases
 I
I-1
   Spent sorbents and
   reactants
                                     Sulfur
            Hydrocarbon R
   Treated gases
                                     Liquid streams from
                                     regenerating activated
                                     carbon or polymers
The physical characteristics (particle
size) needs to be determined.

There are few data on  the characteris-
tics of the treated-gases from sulfur
recovery and control processes used in
lov-Btu gasification systems.  These
gases will contain small amounts of
sulfur species and hydrocarbons.

There are no data on the composition
of these blovdovn streams.  These
streams will contain hazardous species
such as organics, heavy metals,
cyanides, etc.

There are no data concerning the amount
of trace elements In the by-product
sulfur.
There are no data  on  hydrocarbon removal
processes used in  lov-Btu gasification
systems.  These gases are vented to the
atmosphere and may contain sulfur and
nitrogen oxides along with trace elements.

No data are reported  on the characteristics
of these effluents for coal gasification.
These streams will contain suspended  and
dissolved organics and inorganics and will
require further treatment.
This stream Is a usable by-product.  It may be
combusted on-site, briquetted, or sold.

Kany data are available on the treated gases from
processes that are used In other industries
(petroleum, petrochemical,  natural gas, etc.).
These data should be applicable to lov-Btu gasi-
fication.
These streams need to  be characterized to determine
the treatment processes required before they are
disposed of.
The amount and kinds of trace elements in the  by-
product sulfur will determine Its usefulness in
the production of various products such as ferti-
lizer, chemicals, etc.  In certain Instances,  the
sulfur nay be disposed of In a landfill rather
than being sold.  Therefore, the environmental
acceptability of landfilling sulfur may need to
be evaluated.

Kany data have been reported for controlling hydrocarbon
ealssions from other industries.  These data should he
applicable to low-Btu gasification systems.
                                                                              Characterization  of  these streams Is needed  to
                                                                              determine the processes required to control  the
                                                                              pollutants in these  effluents.
                                                                                                                                                       (Continued)

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                                        Table   5-1.    ENVIRONMENTAL  ASSESSMENT  DATA  REQUIREMENTS
                                                                                                                                                (continued)
             Discharge Stream
                  Scarce
Feedstock and Discharge
   Streams Requiring
   Characterization
            Current  Status of
            Environmental Data
                                                                                                                                        arks
                                     Spent sorbent and
                                     catalysts
-P-
00
            Water Pollution Control
            Oll/Vater Se|>aratloa      Separator vent gases
                                     By-product tar/oil
                                     Sludge and sol-
                                     solids
            Floccalatlon-
            Flotation
            Mmaolved Organlcs
            ••n il (Liquid
            Extraction)
            Dlaaolved Organlcs
            Kamoval (Biological
            Oblation)
   Vent  gases


   Oily  SCUM

   By-product phenols




   Treated wastewater
   Treated vastewatcr

   Sludge and semisolids
                              Ho data are reported on the characteristics
                              of these solid wastes.  These wastes will
                              contain organic  species, heavy metals, and
                              other hazardous  constituents and need to
                              be treated before being disposed of.
                              No data have been reported on the composition
                              of these gases.  These gases will contain
                              sulfur species,  cyanides, and hydrocarbons.

                              There are few data on the composition of
                              major components In  this stream and no data
                              on the minor constituents such as dissolved
                              gases and trace  elements.
Ho data have been reported on this solid
waste stream for  gasification plants.
This stream will  contain hazardous organics
and inorganic species and will need to be
treated before disposal.

Same as for separator vent gases.
Same as for spent  quench liquor.

There are few data on  the composition of
this stream.  This stream will contain
a variety of phenolic  compounds along with
other organlcs and trace elements.

Few data are available on the major
components In this stream and no data
are available on the minor components
such as trace metals,  chlorides, fluorides,
ammonia, and organlcs.

Sane as for the above  treated wastewater.

Ho data are available on the character-
istics of this solid waste stream from coal
gasification.  This stream will contain
hazardous pollutants such as organlcs,
cyanides, trace elements, etc. and will
require further treatment.
                                                 Characterization of these solid wastes and leaching
                                                 tests need to be made to determine  the treating
                                                 processes and disposal techniques required.
Characterization of  these gases are required to
determine the processes necessary to control these
emissions before they are vented to the atmosphere.

The characterization of this stream is necessary
to evaluate the type of end uses for the by-product
tar/oil.   Using the  tar/oil as a combustion fuel
may require flue gas treating processes if the
concentration of sulfur in the tar is excessive.

Characterization of  this stream is needed to
determine the processes required to control the
pollutants In this solid waste stream.
     as for separator vent gases.
Characterization of this stream is needed to
help evaluate the phenol removal efficiency of
these processes and to evaluate the potential
end-uses of  the phenol by-product.

Characterization of this stream is necessary
to determine the types of processes required
to further treat this effluent.
Characterization of this stream is necessary
to determine the processes required to control
the pollutants  before disposal.  Data on the
treatment of coke oven effluents should be
applicable.
                                                                                                                                                        (Continued)

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                                       Table   5-1.    ENVIRONMENTAL  ASSESSMENT  DATA  REQUIREMENTS
                                                                                                                                                (continued)
            Operating

             Discharge Sere
                  Source
Feedstock and Discharge
   Streams Requiring
   Characterization
            Current  Status of
            Environmental Data
                                                                                                                                        arks
            Unsolved Organ Ics
            limuiil  (Carbon
            Adsorption)
            Dissolved Organlcs
            it< •mil (Cooling
            rover Oxidation)
   Regeneration gases
                                     Gaseous emissions
            Dissolved Organlcs
            •amoral (Acid Gas
            and Ammonia Strlp-
   Cooling tover blowdov


   Stripped gases
VO
 I
            Dissolved Organlcs
            •/••oval (Forced
            Evaporation)
            Evaporation Ponds
   Treated uastevater


   Vent gases




   Treated vaatevater


   Slodge or concentrate


   Gaseous emissions




   Sludge
Ho data are currently available on the
composition of these gases for coal
gasification.   These gases will contain
organlcs and inorganics  that need to
be controlled.

Ho data are available on the composition
of the gaseous emissions from cooling
tovers that are used to  control dissolved
organlcs from coal gasification.  These
emissions may contain partially oxidized
organlcs, cyanides,  sulfur species, and
trace elements.

Same as for the treated  vastewater for
Liquid Extraction.

There are few data on the composition
of major and minor species in these gases.
These gases will contain H2S, COS, CS2,
mercaptans, thiopenes, ammonia, trace
elements, and cyanides.
'iimi  as for the treated vastevater for
Liquid Extraction.

Ho data have been reported on the compo-
sition of these gases.  These gases will
contain organic vapors, cyanides, ammonia,
and trace elements and need to be controlled.

Same as for the treated vastewater for
Liquid Extraction.

Same as for the sludge for Biological
Oxidation.

Ho data are currently available on the
gaseous emissions fron evaporation ponds.
These emissions will contain volatile
organlcs and sulfur species.

Same as for the sludge from Biological
Oxidation.
 Data on the characteristics of these gases have been
 reported for using carbon adsorption in other Indus-
 tries.  The applicability of these data to coal
 gasification is uncertain.
                                                                               Characterization of these emissions is required to
                                                                               determine whether the dissolved organlcs are actually
                                                                               oxidized or stripped from the aqueous effluent in
                                                                               cooling towers.
The gases from acid  gas stripping provide a portion
of the feed to the sulfur recovery and control  pro-
cess.  The composition of trace constituents in this
stream will affect the performance of the recovery
process.  The stripped aaaonia represents a by-
product.  The characteristics of this strean will
determine whether  additional ammonia purification
processes are required.
Characterization of these gases Is needed  to
determine the processes required to control
these emissions before venting to the atmosphere.
Characterization of these gases is  required to
determine  the environmental acceptability of using
evaporation ponds as an ultimate disposal technique.
                                                                                                                                                       (Continued)

-------
                                       Table  5-1.    ENVIRONMENTAL  ASSESSMENT DATA  REQUIREMENTS
                                                                                                                                              (continued)
           Omcutiom
            Discharge Stream
                 Source
                      Feedstock and Discharge
                         Streams Requiring
                         Chacac ter1ratloo
                                      Current Status of
                                      Environmental Data
                                                                                                                                      arks
           Solid Hastes Control

           Sludge Reduction
           (Incineration and
           Pyrolysls)
                         Gaseous emissions
               ical Fixation
                                    Reduced sludge
                                    Fixed Solids
Ul
O
 I
Product Gas End Uses

Direct Combustion In
Process Beaters and
Boilers
           Direct Combustion
           1m Gas Turbines for
           Combined Cycle Units
           Synthesis/Reductant
           Gas
Combustion  gases
                         Combustion gases
                         Process vent gases
                                                    Ho data are currently available on these
                                                    emissions for coal gasification processes.
                                                    These  emissions nay contain organics,
                                                    chlorides, fluorides, sulfur  species,
                                                    and nitrogen oxides and may require
                                                    control.

                                                    Same as for sludge produced from
                                                    Biological Oxidation.

                                                    No data have been reported on the
                                                    characteristics of this solid waste
                                                    for coal gasification systems.  Leaching
                                                    and stability studies are needed to
                                                    evaluate the feasibility of this
                                                    process.
There are few data on the composition
of these floe gases.  These Elue gases
may contain significant amounts of HHs,
HOI, and trace  elements depending upon
the operating characteristics of the
combustion process.

Mo data are currently available; however.
because of the  strict specification for
gas purity, there should be minimal pollu-
tion from these emissions.

Because of strict specifications on the
purity of the low-Btu fuel gas, the
pollution attributable to the low-Btu
gas should be negligible.
                                                                           Characterization of these gages Is needed to
                                                                           determine whether further treatment Is required
                                                                           before venting to the atmosphere.
                                                                                                               Data  on fixed solid wastes have been reported
                                                                                                               for other Industries such as  the petroleum,  petro-
                                                                                                               chemical, oonferrous metal, and utility industries.
                                                                                                               The applicability of these data is uncertain.
Characterization of these gases Is required to
determine the type of process required to adequately
combust the  trace constituents In the product low-
Btu gas.
                                                                           There are strict specifications for particulate
                                                                           loading and sulfur and alkaline metal compounds
                                                                           for using low-Btu gas in combined cycle units.

-------
                              Table  5-2.     DATA  REQUIREMENTS  FOR CONTROL  TECHNOLOGY  ASSESSMENT
             Operation
              Discharge Stream
                   Source
                            Screams to be
                            Characterized
  Applicable Control
     Technologies
     Data Requirements
                                                                             Remarks
 I
l-«
Ul
t->
 I
             Coml Pretreatment

             Coal Handling and
             Storage
             Coal Crushing and
             String
             Coal Drying,  Partial
             Oxidation,  and Bri-
             quet ting

             Coal Gasification

             Coal Feeding
             Unices
Ash Removal Devices
                         Partlcnlate emissions
                         and aqueous effluents
                         from water runoff
                         Emissions and hood
                         collection efficiency
                         Coal  fines, organic
                         binder, and air
                         emissions
                         Vent  gases
                         Vent  gases
                                      Ash quench water
                                      Ash or slag
                                      Start-up vent  stream
                                      Raw product gas
                                      Fugitive emissions
Coal dust control using
water sprays,  waetewater
treatment
Coal dust control using
hoods,  cyclones, bag
houses  or ESP's

Hydrocarbon control using
afterburners or adsorp-
tion
Particulate collection.
Incineration,  recycle


Particulate collection,
cooling.  Incineration,
recycle

Recycle,  wastewater
treatment processes
                                                    Landfill, chemical
                                                    fixation, by-product
                                                    Incineration, participate
                                                    collection (cyclone,  ESP)
                                                    See  gas purification
                                                    operation
                                                    New designs, automatic
                                                    pokers, good maintenance
Particulate characterization
and emission rates of trace
elements, solids, and organlcs
In the water runoff.

Particulate collection effi-
ciencies.
Particulate, hydrocarbon, and
trace element emission rates.
Particulate and gaseous com-
ponents from various coal
feeding mechanisms.

Particulate and gaseous com-
ponents from various ash
removal devices.

Data on suspended and dissolved
organlcs and Inorganics are
needed.

Data on organics, unreacted
carbon, and trace elements
along with leaching tests are
needed.

Data on the amount and type
of organlcs,  HjS, COS, S02,
HCN, HHs,  and trace elements
are needed along with incin-
eration and particulate
collection efficiencies.

Data on acid  gases, particu-
late and tar  loadings, NHi,
HCN, sulfur species, and
trace elements are needed.

Same as for the  raw product
gas stream.
Data from coal-fired power plants
should be applicable.
Data from coal-fired  power plants
and particulate control devices
should be applicable.

Limited data is available
for these emissions.
No data are  available on these
emissions.
No data are available on these
emissions.
                                                                                                                   No data are currently available
                                                                                                                   on this effluent.
                                                               Limited data are available on
                                                               this solid waste stream.
                                                               No data are  available on this
                                                               emission.
                                                               Limited or no data on particulate
                                                               and tar loadings, HjS, C055.  CS?.
                                                               mercaptans,  thlopenes, NH«,  HCN,
                                                               and trace elements are available.

                                                               No data are  available.
                                                                                                                                                        (Continued)

-------
                  Table  5-2.    DATA  REQUIREMENTS  FOR  CONTROL  TECHNOLOGY  ASSESSMENT
                                                                                                                                   (continued)
OpKratiam
 Discharge Sere
      Source
    Streams to be
    Characterized
  Applicable Control
     Technologlea
                                                                                      Data Requirements
                                                                                                                                  arks
Cu Purification
Partlcolate Removal
Gas Quenching and
Cooling
Acid Gas Removal
                         Inlet and outlet  gas
                         and collected partleu-
                         la tes
Inlet and outlet gas
and collected tar
and partlculates
                         Spent quench liquor
                         Inlet and outlet  gas
                         streams and blowdovn
                         sorbent or solvent
                           Cyclones, ESP
Spray chambers,  hydro-
carbon, packed or plate
towers, air and  water
heat exchangers

Recycle or waetevater
treatment processes
                           Chemical or physical
                           sorptlon and direct con-
                           version processes
Data on the partlculate
loadings and size distri-
butions In each gas stream
and the physical character-
istics of the collected
partlculates are needed to
determine collection
efficiencies.

Data on the collection effi-
ciency of partlculates, tars,
oils, NHj. UCM, B2S, COS, CS2,
and trace elenents are needed.

Data on dissolved and sus-
pended organics and inorganics
along with trace elements are
needed.

Data are needed to determine
the acid gas removal effi-
ciencies, the solvent or
solvent degradation character-
istics, composition of the tall
gases, and aolvent/sorbent
blowdovn.
                                                                Limited  data are available on
                                                                these streams.  Characteristics
                                                                of the partlculate matter will
                                                                effect the performance of
                                                                particulate removal devices.
Limited or no data are available
on the removal efficiencies for
these species.
Limited data are available for
this effluent.   These data will
be used to determine the waatewaeer
for treatment processes required.

Limited data have been reported
on most of the acid gas removal
processes used to treat low/medium-
Btu gas.
Air Foliation Control
Participate Control
Sulfur Recovery
and Control
Hydrocarbon control
                         Partlculate generating
                         sources such as coal
                         handling and storage
                         processes
Inlet and outlet gas
streams, sulfur by-
product characteristics,
and blowdovn sorhents
or reactants

Inlet and outlet gas
streams, and spent
sorbents and catalysts
                           Cyclones, ESP,  baghouses,
                           wet scrubbers
Direct conversion and
Claua tall gas cleanup
processes
Afterburners and carbon
adsorption
Data are needed  to determine
the effective means of collect-
Ing these emissions so they may
be treated by typical partlcu-
late control  techniques.

Data are needed  to determine
the sulfur removal efficiencies,
the sorbent or resctant degra-
dation characteristics, and
blowdown stream  composition.

Data are needed  to determine
the hydrocarbon  removal effec-
tiveness and  sorbent and
catalyst degradation charac-
teristic*.
                                                                The methods of controlling these
                                                                emissions are currently available;
                                                                however, collecting the participates
                                                                from the source may be difficult.
Limited data are available on most
of these processes for treating
sulfur laden gases in gasification
plants.
No data on these processes for
controlling hydrocarbon emissions
from gasification plants have been
reported.
                                                                                                                                           (Continued)

-------
                              Table   5-2.    DATA REQUIREMENTS  FOR  CONTROL  TECHNOLOGY  ASSESSMENT
                                                                                                                                               (continued)
           Omajcmtlnm
            Discharge Stre
                 Source
    Streams to be
    Characterized
                                                       Applicable Control
                                                         Technologies
                                                                                                  Data Requirements
                                                                                                                                              arks
•ater Folio t loo Control

Oil/Hater Separation
            Suspended Solids
            Removal
            Maaolved Organlcs
                •al
            Dlsmulved Orgaaies
Of
            Dittolved Organlcs
Inlet and outlet waste-
water streams and  sludge
Inlet and outlet  waste-
water streams and oily
SCO*
Inlet and outlet waste-
water streams,  by-
product phenols, and
solvent blowdown

Inlet and outlet waste-
water streams and the
semisolld wastes
Inlet and outlet waste-
water streams and the
spent sorbent
                                                                Filtration,  separators
                                                                Flocculation—flotation
                                                     Liquid-liquid extraction
                                                     Biological oxidation
                                                     Carbon adsorption
Data are needed to determine
the oil removal effectiveness.
                                                                                   Data are needed  to determine
                                                                                   the suspended  solid removal
                                                                                   effectiveness.
Data are needed to determine
the phenol recovery effective-
ness and solvent degradation
characteristics.

Data are needed to determine
the organic removal efficiency
and the wastewater composition
effects on the microorganisms.

Data are needed to determine
the organic removal efficiency
and the sorbent degradation
characteristics.
 Limited  data have been reported
 for gasification plants.  Coke
 oven and refinery data may be
 applicable.

 No  data  have been reported for this
 process  in treating gasification
 vastewater.  Data from other  indus-
 tries may be applicable.

 Limited  data are available on this
 process  because of  its proprietary
 nature.
Limited data have been reported
for treating gasification waste-
waters by this process.
No data have been reported for
treating gasification wastewaters
by this process.
            Dissolved Organlca
            Removal
            Dissolved Inorganic
            Dissolved  Inorganic
                •al
Inlet and outlet waste-
water streams and the
air emissions from
the cooling tower

Inlet and outlet waste-
water streams and tail
gases
Inlet and outlet waste-
water streams and the
concentrated liquor
                                                     Cooling  tower oxidation
                                                     Acid  gas and ammonia
                                                     stripping
                                                     Forced evaporation
Data are needed to determine
the amount of organlcs that are
either oxidized or stripped in
the cooling tower.

Data are needed to determine
the acid gas and anaonla re-
moval efficiency and the compo-
sition of the acid gas and
ammonia by-product tail gases.

Data are needed to determine
the amount of volatile constit-
uents In the vaporized water
and the efficiency of reducing
dissolved solids.
Ho data have been  reported on the
amount of organics oxidized or
stripped in cooling towers.
Limited data have been reported on
treating gasification wastewaters
by this process.
Limited data are available on
treating gasification wastewaters
by this process'.
            Evaporation ponds
Inlet wastewater streams
and the bottom sludge
                                                                                   Data are needed to determine
                                                                                   the amount of air emissions
                                                                                   generated by evaporation ponds
                                                                                   and the potential need for
                                                                                   treating the sludge before
                                                                                   dtapoul.
                                  No data have been reported for
                                  evaporation ponds for disposing
                                  of wastewaters generated from
                                  gasification plants.

-------
                              Table  5-2.    DATA REQUIREMENTS  FOR  CONTROL  TECHNOLOGY ASSESSMENT
                                                                                                                                       (continued)
             Discharge Stre
                  Source
    Streams to be
    Characterized
Applicable Control
   Technologies
                                                                                             Data  Requirements
            Solid Waste Control
            Slodge Redaction and
            Chemical Fixation
            Undf tiling
Gaalfler ash, sludge,
spent  sorbents,  and
other  solid wastes
Gaslfler ash,  sludge,
spent sorbents, and
other solid wastes
Incineration, pyrolysis,
chemical fixation pro-
cesses
Data are needed to determine
the need for further treat-
ment by sludge reduction or
chemical fixation of the solid
wastes before ultlnate disposal.

Leachate tests for trace ele-
ments and for dissolved organics
and inorganics are needed.
                                                          Limited data have been reported on
                                                          the characteristics of these solid
                                                          wastes.  Data from refineries and
                                                          coal-fired power plants may be
                                                          applicable.

                                                          Limited data have been reported
                                                          on gasification process solid wastes.
                                                          Data fro* coal-fired power plants
                                                          and refineries may be applicable.
I-1
in

-------
                           VOLUME I

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                              -158-

-------
47        Personal Communications with W. J. Rhodes
          L-7888
                                -159-

-------
EPA-600/7-77-12 5a
4. TITI.I' A\U SUIIl II Lli  r-i          i  i  A          j. i-v  j.  t-«
                 Environmental Assessment Data Base
for Low/Medium-Btu Gasification Technology: Volume
I.  Technical Discussion
                                TECHNICAL REPORT DATA
                             trail Imiritr in ait nil the ri".'cr'.i' hi-furi' cmnplrting)
\. HI iMiU NO
T
7. AUTHOR(S)
E.C.Cavanaugh, W. E.Corbett, and G. C. Page
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Radian Corporation
8500 Shoal Creek Boulevard
Austin, Texas  78758
12. SPONSORING Af!l NCY NAMC AND AOOI1FSS
 EPA, Office of Research and Development
 Industrial Environmental Research Laboratory
 Research Triangle Park, NC  27711
                                                      1. FU CIPII.NVS ACCF-SSION NO.
                             5. REPORT DATE
                              November 1977
                             6. PERFORMING ORGANIZATION CODE
                                                      8. PERFORMING ORGANIZATION REPORT NO.
                             10. PROGRAM ELEMENT NO.
                             EHE623A
                             11. CONTRACT/GRANT NO.

                             68-02-2147, Exhibit A
                             13. TYPE OF REPORT AND PERIOD COVERED
                             Task Final: 8/76-6/77	
                             •"4. SPONSORING AGENCY CODE
                               EPA/600/13
                   IERL-RTP project officer for this report is William J. Rhodes,
Mail Drop 61, 919/541-2851.
16. ABSTRACT
              repOr(; represents the current database for the environmental assess-
ment of low- and medium-Btu gasification technology. Purpose of the report is to
determine: processes that can be used to produce low/medium -Btu gas from coal,
uses of the product gas, multimedia discharge streams generated by the processes,
and the technology required to control the discharge streams.  Attention is on the
processes that appear to have the greatest likelihood of near-term commercialization.
This type of screening provides the preliminary basis for establishing priorities for
subsequent phases of the low/medium-Btu gasification environmental assessment pro-
gram. Processes required to produce low/medium-Btu gas from coal are divided into
discrete operations: coal pretreatment, gasification, and gas purification.  Each oper-
ation is divided into discrete modules,  each having a defined function and identifiable
raw materials, products,  and discharge streams. This volume includes  a discussion
of the status, significant trends, major process operations, multimedia discharge
stream control strategies, and recommendations for future program activities.  Vol-
ume II contains appendices including detailed process, environmental, and control
technology data for the processes considered to have the  greatest potential for near-
term commercialization.
17.
1.
Air Pollution
Assessments
Coal
Gasification
Treatment
Gas Purification
                             KF Y WORDS AND DOCUMENT ANALYSIS
IB. m , f Uli'.i; I H;N :, I A 11 Ml l-J I
 Unlimited
                                          b.lDENTIFIfcRS/OPEN ENDED TERMS
                                           Air Pollution Control
                                           Stationary Sources
                                           Environmental Assess-
                                            ment
                                           Pretreatment
                                          19. SECURITY CLASS (Tlih Hi-port)
                 .             ___ __
                 20. SLCu'niT Y BLAG'S (Tlii.~pa'KeJ'
                 Unclassified
                                          c.  COSATI Held/Group
                                          13B
                                          14B
                                          21D
                                          13H,07A
                                                                   21. NO. OF CAGES
                                                                        169
                                                                   712. PRICE
                                         -160-

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