96
GRI87/0121 Process Description of the SASOL I Coal Gasification Plant Topical Report Gas Research Institute 8600 West Bryn Mawr Avenue Chicago, Illinois 60631
GRI87/0121
Process Description of the SASOL I
Coal Gasification Plant
Topical Report
Gas Research Institute 8600 West Bryn Mawr Avenue
Chicago, Illinois 60631
,.",
PROCESS DESCRIPTION
OF THE
SASOL I COAL GASIFICATION PLANT
TOPICAL REPORT
PREPARED BY
J. D. QUASS AND F. D. SKINNER
RADIAN CORPORATION 8501 MO-PAC BOULEVARD AUSTIN. TEXAS 78766
FOR
GAS RESEARCH INSTITUTE
CONTRACT NO. 5083-253-0936
GRI PROJECT MANAGER JAMES M. EVANS
ENVIRONMENT AND SAFETY RESEARCH
MAY 1987
•..
,.,.
GRI DISCLAIMER
LEGAL NOTICE: This report was prepared by Radian Corporation as an account of
work sponsored by the Gas Research Institute (GRI). Neither GRI. members of
GRI. nor any person acting on behalf of either:
a.
b.
Makes any warranty or representation. express or implied. with
respect to the accuracy., completeness. or usefulness of the inform
ation contained in this report. or that the use of any apparatus.
method. or process disclosed in this report may not infringe
privately owned rights; or
Assumes any liability with respect to the use of. or for damages
resulting from the use of. any information. apparatus. method. or
process disclosed in this report.
ii
50272-1ftl REPORT DOCUMENTATION 11. REPORT NO. l~
1 Recipient's Accession No.
PAGE GRI 87/0121 4- TItle and SUbtitle 5. Report OMe
Process Description of the SASOL I Gasification Plant May 1937 I.
7. Author(sl I. Perfonninc ar.anlzetion Rept. No.
J. D. Quass and F. D. Skinner GRI 87/0121 \I. Perfonnlnc Orpnizetlon Name ____ 10. ProIIlCt/Task/Work Unit No.
Radian Corporation 8501 Mo-Pac Boulevard
lL c-tnct(C) or GrantCGI No.
Austin, Texas 7.8766 (C) 5083-253-0936 (G)
12. SponsorI,. Orpniz8t1on Name and _s .11 Type 01 Report & Period Cow"",
Gas Research Institute Topical Report 8600 West Bryn Mawr Avenue Chicago, Illinois 60631 14-
15. SUppl_"'Y Notes
II. __ CUmlt: zoo _I
The SASOL I coal gasification plant is part of a highly-integrated industrial complex which produces liquid and solid hydrocarbons, petrochemicals, LPG, and J:ledium-Btu gas by Lurgi gasification followed by gas cleanup and Fischer-Tropsch synthesis. Many of the process units used in this plant are also found in the designs of a number of first generation coal gasification plants proposed for this country. Some of these projects have had tests performed at SASOL in order to obtain stream characterization data for process and control systems design. Unfortunately, much of this data is proprietary. This document provides publicly available information and data with an emphasis on environmental and health aspects. The presentation, which is the sixth in a series of documents, is arranged for each of comparison of the plant confieurations of and EH&S-data from other coal gasification plants includ.ed in this study.
17. Document _lysis a. Oacrlptors Coal Gasification SASOL I South African Coal, Oil and Gas Corporation Limited Fischer-Tropsch Synthesis EnvironJ:lental, Health, b. Iclentlfiers/Open-£nCIed T_s
and Safety
Air Emissions Control Liquid Emissions Control Solid Residuals Control/Disposal GRI Coal Gasification EH&S Information Systems c. COSAn Fleld/Groul>
II. Availability _: 11. Security CIne !ThIs Report)
Unclassified 2G. SecurIty CIa .. !ThIs ..... 1
Unclassified (See ANSI-l39.18) See Inotruct/_ on· "-
iii
-
.
21. No.oI,.....
84 22._
OP11ONAL fOlIIII 272 (4-m (F ........ rty NnS-35) Department 01 Com_
r"~
I i l~,;l
"". i , ;.,
Title
Contractor
Objective
Technical Perspective
Results
RESEARCH SUMMARY
Process Description of the SASOL ~ Gasification Plant
Radian Corporation GRI Contract Number: 5083-253-0936
The objective of this document is to present publicly available information and data on the SASOL I Gasification Plant in a manne,r which 1) gives an overview of the utility of this plant to the development of coal gasification in this country, 2) identifies process discharges of interest for environmental, health, and safety reasons, and 3) describes methods used for their control. This topical report, along with others in this series, is part of the GRI Coal Gasification Environmental, Health, and Safety (EH&S) Information System.
The SASOL I coal gasification plant is part of a highly integrated industrial complex which relies on the vast reserves of coal in South Africa to produce liquid and solid hydrocarbons, petrochemicals, LPG, and medium-Btu town gas. Many of the process operations used in this plant are also found in the designs for a number of first generation coal gasification plants proposed for this country. These include Lurgi-type pressurized, dry-ash gasification, raw gas quench and cooling, Rect~sol acid gas removal, gas liquor separation, and Phenosolvan phenol extraction. Since SASOL I is an existing operation which app'roaches the U. S. designed plants in size and complexity, there.isl the potential for obtaining useful infotmation and data for, use in designing U. S. plants, based on the experience "and technology demonstrated at SASOL I. A number of the Lurgi-base~coal ;gasification proj ects have performed tes1:lng,at SA.sOL I in order to obtain full-scale stream characteri2iation i:iata for process, control, and environme;ntal design. Unfortunately, much of this data is proprietary. This'docwllent prtrV'ides publicly available information
" ,I, " aIld data, and analyzes that data with an emphasis on environ-mental discharges.
Many of the controls at SASOL I are similar to those proposed for similar U. S. facilities. However, several of the effluent streams from the plant have the potential to adversely effect the environment. These streams include the high pressure acid gas stream from the non-selective Rectisol unit, run off from the above-ground coarse gasifier ash dump, a variety of tank
iv
j •• ,
Technical Approach
Project Implications
and equipment vents, the Phenosolvan off gas stream, coal and ash lock vents, and the treated wastewater which is discharged into the Vaal River.
This report was developed after an extensive search of the available public documents and other non-confidential sources. This information was reviewed and analyzed, and is presented in a way that lends itself to easy comparison with other gasification plants. The concept of process modules was used for this analysis as described in Section 2.2 of this report, which is the sixth ina series of r.eports which are being written on gasification plants and projects. The first five included the Great Plains Gas'ification Project, the Cool Water Gasification Project, the proposed WyCoalGas Project, the Kosovo GasificationPlant, and the KRW process Development Unit.
The purpose of assembling and summarizing the public information and data on the SASOL I facility is to define data sources and the currently available state-of-the-art information on the environmental, health, and safety aspects of this plant which should be included in the "GRI .Coal Gasification Environmental, Health, and Safety Information System." The format used in this document is designed tb illustrate the particular equipment configuration to which the EH&S data is related. This format will encourage comparison with equipment configurations for other coal gaSification plants included in this series. Such comparison will prombte interplant data comparison for determining where on~ data set may or may not be substituted for another. At the sam~time, the effort of summadzing ava,illible data has. aided', in defining those areas where additional coal gasificaitiotl. environtnental, health, and safety data are required.
v
i ;..,.
•..
TABLE OF CONTENTS
Section
1.0
2.0
3.0
4.0
5.0
OVERVIEW
1.1 Indirect Coal Liquefaction Technology 1. 2 SASOL I Plant. • • • • • • • • • • • 1.3 Major Environmental. Health. and Safety Considerations
1.3.1 Process Wastewater Treatment 1.3.2 Sulfur Recovery •••••• 1.3.3 Disposal of By-products • 1. 3.4 Disposal of Solid Wastes 1.3.5 Spills and Runoff Control 1.3.6 Occupational Health and Safety
PLANT ANALYSIS •••
2.1 Project Background. 2.2 Approach to Development of Plant Description • 2.3 Data Sources and Limitations •
MAIN TRAIN PROCESSES • •
3.1 Gasification (Lurgi-Type Dry Ash) 3.2 Gas Quench/Primary Cooling. 3.3 Secondary Gas Cooling 3.4 Acid Gas Removal (Rectisol) 3.5 Fischer-Tropsch Synthesis
AUXILIARY CONTROL AND UTILITY PROCESSES
4.1 Air Control Sulfur Recovery (Stretford) 4.2 Water Control ...•........
4.2.1 Gas Liquor Separation ••••• 4.2.2 Phenol Extraction (Phenosolvan) • 4.2.3 Ammonia Stripping • • 4.2.4 Biological Treatment ••••• 4.2.5 Cooling Towers •••••
4.3 Solids Handling (Coal Handling. Preparation. and Storage 4.4 Utilities (Steam and Power Generation) •
RESIDUALS DISPOSAL OPERATIONS
5.1 Air Emissions - Plant Flare System • 5.2 Water Effluents ••••••••••
5.2.1 Process Wastewater Residuals 5.2.2 Raw Water Treatment Residuals •
vi
1
1 2 3 4 5 5 6 6 7
8
8 11 13
19
19 25 26 27 34
42
42 45 46 49 53 54 58 58 62
64
64 65 65 65
[
-'" ,
Section
5.3
6.0
TABLE OF CONTENTS (cont.)
Solid 5.3.1 5.3.2
Wastes • Ash Handling System Disposal of Other Waste Normal Operation
REFERENCES •
vii
Produced During
65 65
70
71
LIST OF TABLES
Table
2-1 Summary of Data Availability for SASOL I Streams 17
3-1 Typical Sigma Colliery Coal Analysis • 22
3-2 Composition of Coal Lock Gas Stream 23
3-3 Non-Selective Rectisol Performance Data for SASOL I 30
3-4 Cyanic Water Composition • • • • • 33
3-5 Comparison of Fixed Bed and Fluid Bed Conditions and 'Products .. • .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 39
4-1 Gas Liquor Separation Vent Gas Stream Compositions • 50
4-2 Stripped Gas Liquor Composition 55
4-3 Composition of Biox Effluent Routed to Ash Handling 59
5-1 Composition of Treated Wastewater Discharged to Vaal River 66
5-2 Gasifier Ash Analysis .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 69
(
viii
1"'"" \
Figure
2-1
3-1
3-2
3-3
3-4
3-5
4-1
4-2
4-3
4-4
4-5
5-1·
LIST OF FIGURES
Simplified Block Diagram of the SASOL I Coal Gasification Plant .. .. • .. .. .. .. .. .. .. ..
Flow Diagram for SASOL I Gasification and Quench/Primary Cooling .. .. .. .. .. .. .. .. .. .. .. .. ..
Flow Diagram for SASOL I Rectisol Acid Gas Removal Unit
Simplified Flow Diagram for SASOL I Fischer-Tropsch Unit
Fixed-Bed Arge Reactor
Fluid Bed Synthol Reactor •
Flow Diagram for SASOL I Stretford Sulfur Recovery Unit
Flow Diagram for the SASOL I Gas Liquor Separation Unit
Flow Diagram for SASOL I Phenosolvan/Ammonia Stripper Unit
Flow Diagram for SASOL I Effluent Treatment System
Simplified Flow Diagram for SASOL I Coal Handling, Preparation, and Storage • • • • • • • • • •
Flow Diagram for SASOL I Ash Handling System
ix
14
21
29
35
36
37
43
47
52
57
61
67
, ' i
Forward
This report is one of a series of plant descriptions prepared to
provide perspective on the environmental. health. and safety (EH&S) aspects of
coal gasification operations. The report series is a part of the GRI Coal
Gasification EH£S Information System that is presently under development. All
references have been incorporated into the overall data base. For each plant
the following are presented:
• An overview of its role in the development of coal gasification
technology.
• A discussion that identifies process discharges of interest for
environmental. health and safety reasons and the proposed methods
for their control.
The overview presents the status of the technology that is being
developed (e.g •• substitute natural gas production. manufacture of gas from
coal for turbines producing electricity. etc.) and considers the intended role
of the plant in advancing that technology. The discussion of the major EH£S
considerations identifies the general nature of potential discharges and
discusses how they are handled in the specific plant that is being considered
in each report.
The discussion of plant discharges presents the results of a modular
analysis of the processes employed in each plant. The results and stream
identification are as complete as possible based on the information in the
open literature and are in a convenient form for plant-to-plant comparisons.
Composition and rate of discharge for individual discharge streams are pre
sented where data are available. Also. the control methods employed are
discussed when they are known. Where information is lacking it is noted as a
gap in the data base.
x
-The report does not provide comprehensive information on the compo
sition of discharges. control technology. economics and the like. The presen
tation is designed for use in development of programs and studies needed to 1)
identify and quantify potential environmental. health. and safety considera
tion. and 2) prioritize environmental research needs and related activities.
It was felt that inclusion of all background data would detract from. rather
than enhance. its usefulness for broad analysis. References to background
documents have been supplied for those needing more information.
xi
1.0 OVERVIEW
This report presents a description of the SASOL I plant located at
Sasolburg. Orange Free State. Republic of South Africa. This overview section
describes the technology for converting coal to liquid fuels. gaseous fuels
and petrochemicals and the potent.ial utility of the SASOL I plant data for
advancing coal conversion technology in the United States. Also discussed are
the major environmental. health and safety concerns of this plant.
1.1 Indirect Coal Liquefaction Technology
Indirect coal liquefaction involves a combination of coal gasifica
tion and chemical synthesis operations. Coal is gasified to produce a clean
synthesis gas which is catalytically converted in a chemical synthesis plant
to produce various hydrocarbon products and industrial gases.
In general. coal can be converted to synthesis gas by gasification
with an oxygen/steam mixture followed by gas cleanup to remove particulates.
condensible organics. and acid gases. Gasification involves the reaction of
coal with oxygen and steam to produce a crude gas consisting primarily of
carbon monoxide. hydrogen. carbon dioxide. water vapor. and methane. The
amount of methane produced during gasification depends on the reaction condi
tions and coal type; high methane production is promoted by high pressure.
relatively low temperature operation. and high coal volatile matter content.
Gasifiers which use high purity oxygen produce an essentially nitrogen-free
synthesis gas. This gas can be methanated to substitute natural gas CSNG) for
natural gas pipeline use or utilized in chemical synthesis processes. such as
the Fischer-Tropsch synthesis for the production of liquid hydrocarbons. In
the Fischer-Tropsch synthesis. hydrocarbons are produced by the catalytic
conversion of carbon monoxide and hydrogen using both fixed-bed CArge) reac
tors and fluidized-bed (Synthol) reactors. On site the synthesis gas can be
used immediately as a fuel gas in conventional combustion processes or gas
turbine applications.
1
A number of modern derivatives of early gas producers produce a
nitrogen-rich fuel gas by partial combustion (Le •• -gasification) with air.
The nitrogen-rich fuel gas is generally called low-Btu gas and has a heating
value in the range of 100 to 150 Btu/scf.
In addition to the major species listed above. the crude gas con
tains reduced sulfur species (e.g •• hydrogen sulfide. carbonyl sulfide.
mercaptans). reduced nitrogen species (e.g •• ammonia and hydrogen cyanide).
volatile trace elements. entrained particulates (fine coal. ash. tar). and
organics. In order to produce a synthesis gas suitable for use in a
Fischer-Tropsch synthesis unit. additional processing steps are required to
remove these impurities. Treatment of the various gas. liquid. and solid
wastes produced is also required.
Excluding the three SASOL facilities. there are currently a limited
number of facilities worldwide utilizing indirect coal-liquefaction technolo
gy. Interest in this country has recently declined primarily due to economic
factors such as the drop in oil prices and difficulties in obtaining financing
to construct and operate such facilities. A number of proposed projects have
either been postponed or cancelled. However. GRI projections indicate that
synthetic fuels are still anticipated and required in the future. Present
projections are that these advanced technologies will begin to appear between
2000 and 2010 (13).
1.2 SASOL I Plant (1. 2. 3. 4)
The SASOL I coal gasification plant located in Sasolburg. South
Africa. was started up in 1955. It is part of a large industrial complex
comprised of several integrated processing units. In addition to the gasifi
cation plant. SASOL I has a coal mine - Sigma Colliery. a coal preparation
plant. an air separation plant. a Fischer-Tropsch synthesis plant. and
coal-fired steam/power plants. The gasification plant converts approximately
2
10.000 tons per day of sized coal into 330 million scfd of clean synthesis
gas. An additional 8.300 tons per day of coal fines are consumed in the power
plant. The raw gas leaving the gasifier is cooled and is then sent to a
Rectiso1 unit where it is scrubbed with cold methanol to remove the sulfur
species. carbon dioxide. and naphthas. The clean medium-Btu gas is then
routed to a Fischer-Tropschsynthesis plant where motor fuels. LPG. petrochem
icals and petrochemical feedstocks are produced. In addition. the plant is a
major supplier of medium-Btu fuel gas to other South African industrial
complexes.
SASOL I uses the Lurgi high-pressure gasification process developed
in Germany during the 1930's. In addition. the plant utilizes two Fischer
Tropsch synthesis processes: the German-developed Arge process. with pellet
ized catalysts packed in a tubular, fixed-bed reactor, and the Syntho1 process
which uses a powdered catalyst in a recirculating fluid-bed reactor system.
The Syntho1 process was developed in the United States by M.W. Kellogg Compa
ny.
1.3 Major Environmental, Health, and Safety Considerations
The SASOL I plant has been an important source of data for U. S.
companies interested in building gasification plants based on Lurgi technolo
gies. These data have been used as the basis for process/environmental
control system design and occupational health information for a number of
plants that were planned for this country. For example. SASOL data was used
to develop the Great Plains Gasification Project's Environmental Impact
Statement. Since SASOL has a long operating history with Lurgi gasification
and cleanup processes. plant personnel have provided valuable consulting
services to several project developers. Examples include. in addition to
GPGP. the WyCoa1Gas project, E1 Paso Natural Gas. Wesco, and Phillips Coal.
Unfortunately. much of the data are considered proprietary and are not
publicly available. SASOL has also provided some data and information to
3
various U. S. government agencies. The SASOL experience was an important
source of information to NIOSH in the development of proposed standards for
occupational exposures in coal gasification plants (12).
The process flow scheme at SASOL I is representative of many pro
posed U. S. Lurgi-based plant designs. However, some of the environmental
control practices followed at SASOL I could not be utilized in plants built in
this country. In fact, the more recent plants built by SASOL (SASOL II and
III in Secunda, South Africa) have modified and improved some of these prac
tices (2. 14). The following paragraphs present a general discussion of the
major EH&S concerns which have been identified at the SASOL I plant. These
are:
• Process wastewater treatment and reuse.
• Sulfur recovery,
• Disposition of organic by-products,
• Disposal of solid wastes,
• Spills and runoff control, and
• Occupational health and safety.
1.3.1 Process Wastewater Treatment
Fixed-bed gasifiers such as the Lurgi gasifiers generate process
wastewater streams as the raw synthesis gas is quenched. Unreacted gasifica
tion steam and water formed in some of the gasification reactions condense
during raw gas cooling. These wastewater streams, known as gas liquor.
contain a number of contaminants that must be removed prior to reuse or
discharge. These include dissolved and suspended organics (tars, tar oils,
phenols), dissolved acid gases, ammonia, and trace elements. At the SASOL I
plant, the gas liquor is subjected to a number of treatment steps to remove
the suspended tars, tar oils, and particulates (gas liquor separation),
dissolved organics (Phenosolvan phenol recovery). and dissolved gases (ammonia
stripping). The stripped and dephenolized wastewater is then combined with
4
,I'H'~
the Fischer-Tropsch synthesis wastewater and other wastewater streams from
outside the plant (e.g •.• domestic and industrial sewage) and is treated in a
biological treatment facility. Part of the biological oxidation effluent is
utilized in the ash-handling system where the ash absorbs some of the residual
organics. The treated wastewater is eventually discharged to the Vaal River.
1.3.2 Sulfur Recovery
Coal gasification results in the production of a number of reduced
sulfur compounds (hydrogen sulfide. carbonyl sulfide. mercaptans) that are
subsequently removed from the raw gas and the gas liquor. In 1976 construc
tion was completed on a Stretford sulfur recovery unit which was designed to
absorb and convert hydrogen sulfide to elemental sulfur to be sold as a
by-product. This Stretford unit was beset with operating problems from the
beginning of start-up. It is believed that SASOL has abandoned trying to
operate the Stretford unit and is presently incinerating the acid gases.
1.3.3 Disposition of By-Product Liquids
The SASOL I plant. like others using fixed-bed gasifiers. produces a
number of organic by-products. including tar. tar oil. crude phenols. and
naphtha (light hydrocarbons). These materials contain compounds that are
suspected carcinogens and may be considered hazardous under the Resource
Conservation and Recovery Act (RCRA). Processing and handling these materials
would be an environmental concern in a similar U. S. plant. At SASOL I. the
tar and tar oils are recovered and refined to commercial products. The light
hydrocarbons are sent to a hydrogenation unit. and the higher-boiling frac
tions are used as cresote. road tar products. and coal tar fuels. However.
due to the potential carcinogenicity of the by-products. care must be used in
handling these materials. SASOL indicates that exposures to naphtha are
minimized due to the high service factor (and therefore lowered maintenance
requirements) of the equipment used to handle it (12). No further details
5
[
were found as to any measures SASOL I incorporates into their operations to
prevent any harmful residual effects which could result from the use and
handling of these materials.
1.3.4 Disposal of Solid Wastes
The SASOL I gasification plant produces three principal solid wastes
including gasifier ash. boiler fly and bottom ash. and dusty tar. The gasifi
er ash and boiler ash are handled in a special ash-handling system. The ash
is disposed of at a surface dump. No measures are taken to prevent leachate
from entering the groundwater. However. regular sampling of groundwater in
the vici~ity of Saso1burg has reportedly shown no evidence of groundwater
contamination (4). Some fine ash remaining in the ash disposal system's
thickener overflow is handled in a slimes dam where it is used as part of
SASOL's water treatment system to absorb residual organics from wastewater.
The slimes dam has a clay surface which serves as a liner and prevents
leaching of trace components (4). The dusty tar has historically been dis
posed of by 1andfi11ing. Recent plant expansions have included provisions for
recycling the dusty tar to the gasifiers.
Stretford solution b1owdown is reportedly routed to the biological
wastewater treatment area at SASOL I. Plans for the installation of a chemi
cal recovery unit have been reported. but it is not known whether this unit
has been installed (5). There have been unofficial reports that the Stretford
unit is no longer operating.
1.3.5 Spills and Runoff Control
The slimes dam used in the wastewater treatment and ash-handling
systems at SASOL I has an extensive drainage system to recover all seepage for
return to the ash sluiceway system. The slimes dam also has an impervious
clay layer which prevents leaching of potentially toxic materials (4). The
6
'1T!" ash disposal area does n.ot have any system for preventing leachate from
enter.ing the groundwater. although monitoring has reportedly not shown any
evidence of contamination No other information has been reported on other
systems designed to prevent or control spills and runoff.
1.3.6 Occupational Health and Safety
For the majority of the process units. SASOL considers the exposures
to be similar to those in any petrochemical plant. The gasification area.
however. presents more opportunities for exposure because of the relatively
high amount of maintenance performed there. Procedures have been established
to insure safe access to process vessels by requiring lock-outs. blinding.
steam purging and other items on a detailed checklist.
Carbon monoxide leak checking is performed during each work shift.
Medical records are maintained on the plant employees.
7
2.0 PLANT ANALYSIS
2.1 Project Background (1. 2. 3. 7. 15)
The SASOL I gasification plant is part of a highly integrated
industrial complex located at Sasolburg. Republic of South Africa. The plant
is operated by the South African Coal. Oil and Gas Corporation Limited. The
complex plant produces liquid and solid hydrocarbons. a wide variety of
chemicals. and medium-Btu fuel gas to a public utility for transmission and
distribution. The SASOL I gasification plant has been in operation since
1955. The total capital investment was approximately 450 million dollars
(based on 1955 dollars).
The success of SASOL I and the expansion of the role of coal gasifi
cation as a source of liquid fuels and petrochemicals in South Africa is due
to a combination of factors. First. South Africa has no indigenous petroleum
resources and natural gas has only recently been discovered. Much of the
country's energy supply has been provided by the vast supplies of relatively
low-quality (high ash) coal. supplemented by imported oil. Second. the
country's political stance has resulted in economic boycotts by many coun
tries. including the majority of the OPEC nations. Until the Iranian revolu
tion that resulted in the overthrow of the Shah. most of South Africa's
petroleum was imported from that country. It has become increasingly impor
tant to South Africa's security that it exploit its own energy resources due
to political certainties. The third factor is the availability of cheap
labor. which lowers the cost of mining coal and operating the plant to levels
much lower than would be possible in many other industrialized nations.
Fourth. the South African government has provided SASOL with tax and other
forms of financial assistance.
SASOL was begun with funds provided by the South African government.
Although the company was formed and incorporated as an ordinary public compa
ny. the government appoints the majority of the directors. including the
8
,....
chairman. The remaining directors are appointed by the Industrial Development
Corporation. a government-owned organization whose objective is the stimula
tion of industrial development in the country. Only within the past seven
years has SASOL begun to offer stock to private investors. in order to attract
capital for the construction of SASOL II and III. The original government
loan was paid off many years ago and SASOL I has operated at a profit since
then.
Important milestones in the history of the SASOL I gasification
plant are highlighted below:
•
•
•
•
In 1935. a South African mining corporation. the Anglo
Transvaal Consolidated Investment Company (also known as Anglo
Vaal) acquired the South African rights to the Fischer-Tropsch
process and began work on developing a scheme for the produc
tion of oil from coal.
In 1937. complete specifications for a plant were drawn up.
In 1943. South Africa acquired the rights to the American
version of the Fischer-Tropsch process.
In 1946. a new study and an application to the government were
made to create a fiscal structure within which an oil-from-coal
plant could be established.
• In 1947. the Liquid Fuel and Oil Act was passed and a Liquid
Fuel Advisory Board was established.
• In 1950. the South African Coal. Oil. and Gas Corporation
Limited was formed and incorporated under the Companies Act as
an ordinary public company. Anglo Vaal rights were taken over
by the government. which provided the funds for the construc
tion of the plant. A site near the Vaal River was selected •
. 9
• In 1952. construction of the plant began.
• In 1954. the first units were put on line.
• In 1955. the first phase of the plant. comprising nine Lurgi
Mark I gasifiers began operations.
• In 1958. a tenth gasifier (Mark II) was installed.
• In 1966. a major expansion was completed comprising three
additional gasifiers (Mark III) and extensions to the coal and
ash handling facilities. gas purification. and tar and liquor
separation and treatment plants. The Mark III gasifiers have
an internal diameter of 12.4 feet. compared to 12 feet for
previous models.
• In 1975. SASOL I implemented a 65 million dollar expansion
program which increased the capacity of the gasification plant
by 40 percent and doubled the supply of industrial gas. The
expansion involved the installation of three Mark IV gasifiers
and one Mark V. The diameters of these units are 13.1 ft (4 m)
and 16.4 ft (5 m). respectively.
• In 1976. a Stretford unit began operation. The Stretford plant
was installed in order to meet new air pollution regulations
promulgated by the South African government.
SASOL decided to expand their production facilities and in 1979. a
second plant. SASOL II. was built at a cost of 2.5 billion dollars. SASOL II
is based on the same technology as SASOL I except for the exclusive use of
circulating fluid bed synthesis reactors in the Fischer-Tropsch plant. SASOL
II was originally designed to gasify 14 million tons per year using 36 Mark IV
10
_. I
!
Lurgi gasifiers, producing annually 1.5 million tons of motor fuels, 160,000
tons of ethylene, 200,000 tons of tar products, 150,000 tons of methane, and
50,000 tons of various chemicals. In 1983, a third coal-liquefaction plant,
SASOL III, began operation. SASOL III, almost an exact copy of SASOL II, was
built at a cost of 2.8 billion dollars. The three plants together produce
approximately 40-50% of South Africa's oil needs.
2.2 Approach to Development of Plant Description
In order to present the description of the SASOL I plant in a way
that lends itself to easy comparison with other gasification plants, the
concept of process modules is used for this analysis. Using this approach
each plant is considered in terms of the generic processes that it incorpo
rates. e.g., the main process train might consist of gasification. gas
quench/primary cooling. secondary cooling, acid gas removal, methanation (the
configuration used for the Great Plains SNG plant) or gasification, primary
cooling/carbon scrubbing, secondary gas cooling, and acid gas removal (the
configuration used at the Cool Water medium-Btu gasification plant). Although
both plants have a gasification process. the specific process employed is
Lurgi for Great Plains and Texaco for Cool Water. For the discussion that
follows, both generic and specific process nomenclature is used.
For analytical purposes, the processes that make up each plant are
classified as main train or auxiliary control processes that are used for
pollution control or to provide utilities. Residuals disposal operations
receive streams from main train or auxiliary control processes. and either
convert them to an environmentally acceptable form or prevent their release to
the environment.
Main train processes are those needed to produce the principal
product of the plant. The raw materials are brought together in the gasifier
to form the crude product which is then treated to produce a final product
11
r"'''''
p-"'" , I I
l .. ,
"'~ , I I li.-""
having the composition and purity required for sale or consumption. The
SASOL I plant main train processes are as follows:
• Gasification (Lurgi-type dry ash).
• Gas quench/primary cooling.
• Secondary gas cooling,
• Acid gas removal (Rectisol), and
• Fischer-Tropsch synthesis.
Auxiliary control processes operate on streams routed to or removed
from the main process train. They may serve to prepare feeds for the main
train process. or may recover by-products which aid the overall plant econom
ics or minimize waste disposal. Auxiliary control processes are further
subdivided. according to the phase of the principal stream they treat, into
air, water. and solid auxiliaries. The SASOL I plant contains the following
auxiliary control processes:
• •
Air Control: Sulfur recovery (Stretford)
Water Control: Gas liquor separation Phenol extraction (Phenosolvan) Ammonia stripping and recovery Biological treatment
• Solid Handling: Coal handling. preparation. and storage.
Utility processes provide steam. electricity. cooling water. oxygen,
etc •• utilized in the plant. Since the analysis is limited to processes with
significant potential for environment. health. and safety impacts, only one
utility is considered. i.e •• :
• Steam generation/superheating
12
r" L",
The primary purpose of residuals disposal operations is to protect
the environment and the health and safety of plant personnel and the public.
These operations receive streams from the main processes and either convert
potentially harmful pollutant species to less harmful forms or prevent their
release into the environment. These operations are subdivided into air
emissions, water effluents, and solid waste disposal operations. The SASOL I
plant has the following residual disposal operations:
• Air Emissions: Flaring/Incineration
• Water Effluents: Discharge
• Solid Wastes: Surface Disposal Slimes Dam
The processes that compose the SASOL I plant are shown in Figure 2-1
as a series of process modules. Process and discharge streams relevant to the
analysis are shown. Each process is discussed individually in Section 3.0
(Main Stream Processes), or Section 4.0 (Auxiliary Control and Utility Pro
cesses). Residual disposal operations are presented in Section 5.0.
2.3 Data Sources and Limitations
Although a ,number of organization have sponsored sampling and
analysis programs at SASOL in support of design activities for specific plants
planned for this country, a large fraction of these data have not been made
available in the public domain.
The primary references used in compiling this topical report were:
Assessment of Discharges from SASOL I Lurgi-Based Coal Gasification Plant (1);
Trip Report: Four Commercial Gasification Plants November 6-18. 1974 (2); and
Sasol: South Africa's Oil from Coal Story - Background for Environmental
Assessment (4). All three sources provided descriptive process information.
However. Reference 1 contained the most recent data and was the only source to
provide a detailed material balance for a major portion of the plant. These
13
r 'I
....
.j>o
OKYGEN fROM AIR SEPARATION
COAL LOCK GAS to STEAM
$UPEflHEAT£R
STl:r':=:~~'ON"""'-..-_-,.-J
RUN· OF· MINE COA'
SIZED COA'
COAL fiNES
GASifiER
""
"
I
""
TAR, fAA OIL 10 OISTILLATIOH
oum ACETATE
CRUDE PHENOLS
j (f""
1--------__ ~.IIIIYs~~~CT
HIGH PRESSURe FLASH GAS to fUEl,.
SOLUTION PUAGE TO
"'OX
METHANOl •• o---i .. ..--'-_L._-,
GAS CONDENSATE' CYANIC WATER
.-____ ~.IIM~~M~U
co"
FUEL OIL I PETROCHEMICALS
DISCHARGE TO RIVER
, -. TO ~~~~N~~UM SULfATE PLANT
COMBINED ASH
.... ., TO AS:Y~:E~lING
~--------------------------------------------------.,:i~~~~E~
Figure 2-1. Simplified Block Diagram of the SASOL I Coal Gasification Plant
[
sources. however. were augmented by several other sources since they did not
include significant details such as process flow diagrams.
The stream characterization data were obtained from References 1 and
2. The data in these references were, for the most part, obtained from the
SASOL I personnel. Reference 1 supplemented the SASOL data with material
balances and pollutant distribution evaluations which were based largely on
engineering estimates and calculations, since there were gaps in the data
provided. The available flow rate data appear to be from the period prior to
the latest plant expansion, when there were thirteen gasifiers operating.
Process flow diagrams were obtained from several additional sources
since no one source contained diagrams for all of the units at the plant.
Flow diagrams were provided by Reference 3 (gasification, quench/primary
cooling, Rectiso1), Reference 7 (gas liquor separation, ash handling, coal
handling), Reference 5 (Stretford), Reference 10 (Phenoso1van), and Reference
8 (Fischer-Tropsch synthesis). Additional details were also obtained from the
NIOSH Criteria Document for Coal Gasification (12).
The biggest difficulty in assembling the flow rate information for
SASOL I was that a number of sources had to be used and it is possible that
differences in the plant's flow rate basis due to the various plant expansions
are reflected in the data presented in each source. Every effort has been
made to maintain consistency among the descriptions for the various plant
modules, but it should be recognized that there may still be discrepancies.
It is not likely that such discrepancies will impact the overall conclusions
of the report. In addition, the available data do not appear to reflect the
latest expansions to the plant. The section on gasification. for example. is
written as if there were thirteen gasifiers in operation.
Another difficulty was in trying to recognize contraditions in the
various process descriptions found in the literature. In most cases. the most
recent source was used, together with knowledge of personnel who have visited
SASOL I.
15
....
report.
Table 2-1 summarizes all the SASOL I processes addressed in this
Input streams. destinations of output streams. and availability of
engineering and stream composition data are indicated. The data themselves
are presented in tabular format in the process descriptions in subsequent
sections of this report.
The table shows that a substantial amount of flow rate and stream
composition data are available for emission streams not only for the main
train processes but also for the air and water auxiliary control processes
throughout the plant. Some of the stream flow rates and compo,sitions shown
were derived from engineering estimates and calculations made in order to
close material balances (1). For other streams. such as the Stretford purge.
composition data are not available in public data sources because of the
proprietary nature of the technologies.
16
L
~-
c lI<_"
r , , :!..~-,"
,tII'''''''''
F-I i
."
r~
I '--
Process Area
Gasification
Gas Quench/ Primary Cooling
Secondary Gas Cooling
Ac:id Gas Removal (Rectiaol)
Fischer-Tropscb Synthesis
Sulfur Recovery (Stretford)
Gas Liquor Separation
TABLE 2-1. SUMMARY OF DATA AVAILABILITY FOR SASOL I
Stream
Input: Sized Coal Oxygen (96.4%) Steam Coal lock fill gas Water to ash lock scrubber
Output: Hot raw gas
Gasifier ash H. P. coal lock gas L. P. coal lock gas Ash lock "lent gas
Input: Hot raw gas Recycled quench liquor Cooling' water
Output; Cooled raw gas Quench liquor (gas liquor)
Input: Cooled raw gas
Output: Cooled crude product gas
Oily gas liquor
Input, Cooled crude product gas Makeup methanol Water
Output: Pure synthesis gas
Acid gases: - High pressure flash gas
- Low pressure and atmospheric flash gas
Cyanic water Gas condensate Naphtha
Input: Pure synthesi.s gas
Output: Gaseous products -LPG - Medium-Btu fuel gas Other products - Medium and hard waxes - Gasoline
Diesel oil - Alcohols/ketones Wastewater
Input: Acid gsses Stretford chemicals Caustic Water Oxidizer air
Output: Molten and flaked sulfur Stratford tail gas Oxidizer vent gas Stretford solution purge
Input: Raw gas liquor feed: - Quench liquQr - Oily gas liquor from
secondary cooling - Cyanic water from
Rectisol - Rectisol wastewater
(gas condensate)
Flow Rate Temperature Pressure Composition
X X X X X X X X X X
X X
X X X X X
X X
X X X
X X X
X X X X
X X X X
X X X X
X
X X X X
X X
X
X X
,
X
(continued)
17
STREAMS
Destination
Gas quench/primary cooling
Ash handling Steam .superheater Atmosphere Atmosphere
Secondary gas cooling Gas liquor separation
Acid gas removal (Rectisol)
Gas liquor separation
Fischer-Tropsch synthesis
Plant fuel gas system
SulfUr recovery (Stretford)
Gas liquor separation Gas liquor separation Hydrogenation
Product storage
Product storage
Biological treatment
Byproduct storage Atmosphere Atmosphere Biological treatment
~'~ TABLE 2-l. (continued) Process Flow
Area Stream Rate Temperature Pressure Composition Destination
"'"" Gas Liquor Output: Flash gas (expansion gas) X Plant fuel gas Separation system (cont:.) Dusty tar X X Recycle to gasifiers
Clear tar and tar oil X Tar/oil distillation Vent gases: X
f"'~' - Surge tank vent Atmosphere - Primary ~ar separator X X Atmosphere
vent: - Secondary tar separator X X Atmosphere
vent - Oil separator vent X X Atmosphere Gas liquor Phenosolvan
It"..".!
Phenol Input:: Gas liquor Extraction Makeup ,solvent (Phenosolvan) (butyl acetate)
Output: Crude phenols X Byproduct storage Phe'nol pitch X Tar and taroil
distillation Dephenolized gas liquor Ammonia stripper Vent gas X Atmosphere or
Stretford unit
Alua.onia Input: Dephenolized gas liquor Stripping Steam
Output: Stripper overhead gases Ammonium sulfate plant
Stripped gas liquor Biological treatment
.. ~ Biological Input: Wastewater feed: Treatment - Stripped gas liquor
- Fischer-Tropsch ~"." wastewater
- Process wastewater from other sources
Oxygen PO;;
Output: Biox effluent X Ash handling/ discharge
r"· Excess biox sludge Anaerobic digestion
t Cool Handling. Input: Run-of-mine coal X ilion"" Preparation.
and Storage Output: Sized coal X X Gasification Fines X Power plant Fugitive dust Atmosphere Storage vent gas Atmosphere
Steam and Input: Coal fines X Power Fuel gas (coal lock gas) Generation Boiler feedwater
Air
Output: Steam - From boilers Process - From superheaters Process Electricity Process Flue gas Atmosphere Boiler ash X t Ash handling
Flare System Input: Excess coal lock gas X Rectisol high pressure X X X X flash gas
Startup raw gas
Output: Flare offges Atmosphere
Asb Handling Input: Gasifier ash X X X System Power plant ash X
Recycle sluicewater
Output: Ash sluiceway vent gas Atmosphere r-_ Combined ash Surface disposal r Thickener overflow Slimes Dams , l...,
18
•..
, ),.,,,.,.
3.0 MAIN TRAIN PROCESSES
This section contains descriptions of the main train processes
identified in Section 2.2 - i.e., gasification; gas quench/primary cooling;
secondary gas cooling; acid gas removal; and Fischer-Tropsch synthesis. For
each process a general process description and flow sheet are given followed
by specific process information and waste stream characterization.
3.1 Gasification (Lurgi-TYpe Dry Ash) (1, 2, 3, 4, 7)
The SASOL I plant uses Lurgi dry-bottom gasifiers. The plant has a
total of 13 gasifiers in parallel, 10.8 of which are in service on an annual
basis. Several different gasifiers sizes are used: the oldest units (Lurgi
Mark I and II) have an inside diameter of 12 ft,while the more recently
installed Mark III gasifiers have a diameter of 12.4 ft. These gasifiers
combined produce an average of 330 million scfd of raw synthesis gas. The
input and output stream for the gasification processes are as follows:
Input:
Sized coal Oxygen (96.4%) Steam Coal lock fill gas Water to ash lock scrubber
Output:
Hot raw gas Gasifier ash (dry) High pressure coal lock gas Low pressure coal lock gas Ash lock vent gas
Flow Rate (lb/hr)
848,800 282,500
1.225,000
265,600
16,900*
318 750
850 392
P(psig)
420 550
370
*Flow rate shown is the "total coal lock gas". Approximately 98% of this amount is high pressure lock gas.
19
Process Information
Figure 3-1 presents a flow diagram for the Lurgi gasification
process. Gas quench and primary cooling are also included in the figure
because of the close relationship between these processes. The Lurgi gasifi
ers consume up to approximately 10.000 tons per day of coal from the coal
preparation plant where it has been crushed to an approximate size range of
0.5 to 1.5 inches (2). The published references report the size range of coal
to the gasifiers from 3/8 to 1/2 inch for the smaller size and 1 1/2 to 3
inches on the large end. The coal is a non-caking. low-grade coal supplied
from the plant's own coal mine. Sigma Colliery. A typical analysis of the
coal along with a trace e1em~nt analysis is presented in Table 3-1. The coal
is fed to the top of each gasifier through lock hoppers. After the coal has
been charged to the lock hopper. the upper valve is closed and the lock is
pressurized to the gasifier operating pressure (370 psig) with cooled and
quenched product gas (i.e •• fill gas). After the coal has been emptied into
the gasifier. the lock hopper is depressurized in a single stage for the next
charging cycle. The lock hopper is depressurized to approximately 0.3 psig.
with the lock gas being routed to gas holder. This represents approximately
98 percent of the total coal lock gas. The recovered coal lock vent gas is
used as fuel in the power plant steam superheater. Because of the sequencing
of the fill and vent cycles of the plant's gasifiers. excesses and shortages
of the coal lock gas result depending on the demands of the superheater. The
excess gas is sent to the plant flare system. The remaining low-pressure coal
lock gas and the residual gas displaced as the lock hopper is refilled with
coal. is evacuated by means of a steam ejector. and is vented directly to the
atmosphere. Since cooled and quenched product gas is used as pressurant in
the gasifiers. the composition of the coal lock gas is essentially the same as
the cooled raw gas; Table 3-2 presents the composition of this gas.
Oxygen (at 96.4% purity) and superheated steam required for the
gasification reactions are mixed and distributed through the rotating ash
20
N ....
LURGI GASIFIER
\
COAL FEED
V" ~~ ") " fJ
FEED l JBUNKER
TO LOCK GAS4--l RECOVERY
JACKET STEAM
OXYGENtL-f...._ .... -}
H.P. STEAM
ASH
RECYCLE GAS LIQUOR
QUENCH SCRUBBER
35 PSI STEAM
WASTE HEAT EXCHANGER
~ l ""> ,
TO START-UP FLARE
COOLED RAW GAS TO SECONDARY
COOLING
PRE COOLER
COOLING WATER
GAS LIQUOR
Figure 3-1. Flow Diagram for SASOL I Gasification and Quench/Primary Cooling
'" -=~
;1
1
I f ~
I I
I I I ! I I ~ :I
i I i
"'",,(
I
L ..
TABLE 3-1. TYPICAL SIGMA COLLIERY COAL ANALYSIS
Ultimate Analysis (wt%)
Moisture
Ash
Carbon
Hydrogen
Nitrogen
Oxygen
Sulfur
HHV. Btu/lb
As received
Dry
8.5
30.3
44.5
2.8
0.95
9.5
0.5
7.860
8.980
Trace Elements. ppmv
As
Be
Cd
Hg
Mn
Ni
Ph
Sb
Source: References 1 and 2
22
3
2
0.1
0.1
500
40
15
0.05
fEl'li TABLE 3-2. COMPOSITION OF COAL LOCK GAS STREAM r , '"~
)I''ltIt"
Component Composition. (vol%)
CO2 27.93
CO 20.66
y''''''- H2 40.32
CH4 9.05
r'*" C2H4 O.OS
C2H6 O.lS
C3H6 0.06
C3HS 0.04
C4HS 0.09 p"'*' C4H10 0.06 "-~- CSH12 0.05
C6H6 0.04
~HS 0.04
CH3
0H 0.36
N2 + Ar 0.74
H2S 0.30
Total 100.00%
H2O Saturated
Source: Reference 1
23
.l''':t4
grate at the bottom of the coal bed. These reactants flow upward counter
current to the coal. As the coal descends slowly in the gasifier. it passes
through several zones: preheat. drying. devolatilization. gasification. and
combustion. These zones operate at progressively higher temperatures. Hot
ash generated during gasification is cooled by the incoming reactants (steam
and oxygen) and is removed by a rotating grate. The ash is collected in a
steam-pressurized ash lock located at the bottom of the gasifier. The ash is
then periodically discharged into an enclosed ash sluiceway which is described
in Section 5.3 of this report. Steam released during the ash lock hopper
blowdown cycle is scrubbed with water to condense the steam and remove any
entrained solids.
The gasifiers operate at about 370 psi and at a maximum temperature
less than the fusion temperature of the ash; the gas leaves the top of the
gasifier at about 850°F. The hot raw gas leaving the gasifiers has a
composition similar to that presented in Table 3-2 for the coal lock gas and
consists primarily of hydrogen. carbon monoxide. methane. carbon dioxide.
hydrogen sulfide. and water. In addition. the gas contains low molecular
weight hydrocarbons. tars. oils. phenols. organic sulfur and nitrogen
compounds. ammonia. cyanide compounds. and entrained coal particles. The hot
raw gas is routed to gas quench/primary cooling.
Waste Streams
The gasification process produces the following waste streams:
1)
2)
Coal lock hopper gases. Approximately 98 percent of the coal lock gas is used as fuel in the steam superheaters. The remaining low pressure lock gas is vented directly to the atmosphere.
Gasifier ash. This stream contains the majority of the coal mineral matter and trace elements. The ash is conveyed from the gasification area via a sluiceway system. This waste stream is further discussed in Section 5.3 (Solid Wastes).
24
3) Ash lock hopper vent gas. The ash lock vent gases are scrubbed with water to remove entrained particles and to condense steam. This stream is discharged into the ash sluiceway. No characterization data are available for this stream. However, it will consist primarily of water vapor and some entrained particles.
3.2 Gas Quench/Primary Cooling (1, 2, 3, 7)
The gas quench/primary cooling process at SASOL I as shown in Figure
3-1 consists of direct spray. quench scrubbers mounted to each of the 13
gasifiers, waste-heat boilers in which the quenched gas is cooled by generat
ing 35 psig steam, and shell and tube precoolers associated with each unit.
The inputs and outputs for this unit are as follows:
Input:
Hot raw gas Recycled quench liquor Cooling water
Output:
Cooled raw gas Quench liquor (gas liquor)
Process Information
Flow Rate (lb/hr) P(psig)
850 370
The hot raw gas leaving each gasifier is cooled and scrubbed in a
direct spray quench scrubber with a stream of recycled gas liquor from the gas
liquor separation unit. In the scrubber, the gas is cooled and saturated and
a portion of the entrained particles are removed. This cooling results in the
condensation of some of the heavy tar. The gas leaving the scrubber enters a
waste-heat exchanger where it is cooled by raising 35 psig steam. The waste
heat exchanger also removes entrained dust and condenses additional tar,
25
water vapor. and organics; more gas dissolution'also occurs. Further cooling
and condensation are achieved in a shell and tube precooler. The crude gas
enters the precoolers from the waste he.at boilers and is cooled by heat
exchange with process cooling water.
The gas liquor streams leaving the quench scrubbers. waste heat
exchangers. and precoolers are combined and sent to a primary tar separator in
the gas liquor separation unit. The cooled raw gas is routed to secondary
cooling.
Waste Streams
The quench/primary cooling unit produces a single waste stream: the
gas quench liquor. This stream consists of the gas liquor leaving each of the
units comprising the quench/primary cooling module. No analysis of this
stream is available but it will contain suspended particles. tar. tar oil.
dissolved organics. and dissolved gases including NH3 and H2S. The gas quench
liquor is routed to the gas liquor separation unit.
3.3 Seconda~ Gas Cooling (1. 2. 3. 7)
Secondary gas cooling is used to further lower the temperature of
the crude gas prior to entering the acid gas removal (Rectisol) unit. At
SASOL I. this consists of a series of shell and tube heat exchangers in which
cooling of the gas leaving the quench/primary cooling is achieved using
cooling water. As a result. additional condensing of gas liquor and organics
occurs. The input and output streams for this unit are as follows:
Flow Rate P(psig)
Input:
Cooled raw gas
26
Flow Rate P(psig)
Output:
Cooled crude product gas Oily gas liquor
86 365
Process Information
The cooled raw gas leaving the precoolers in quench/primary cooling
are combined and enter the secondary gas cooling shell and tube exchangers
where it is cooled using process cooling water. The temperature of the gas
leaving the final coolers is approximately 86°F (30 0 e).
As a result of this cooling. additional gas liquor is condensed.
This condensate. known as oily gas liquor. contains tar oil. phenols. other
dissolved and suspended organics. and dissolved gases. The oily gas liquor is
routed to the oil separator in the gas liquor separation unit. The cooled raw
product gas is sent to the acid gas removal unit.
Waste Streams:
Secondary gas cooling produces a single waste stream:
1) Oily gas liquor. No composition data is available for this stream. However. it will contain tar oil. phenols. other dissolved and suspended organics. and dissolved gases such as NH3 and H2S. It is routed to the gas separation unit.
3.4 Acid Gas Removal (Rectisol) (1. 2. 3. 4. 6)
The SASOL I plant uses a non-selective configuration of Lurgi's
Rectisol process for the removal of carbon dioxide. hydrogen sulfide. carbonyl
sulfide. organic sulfur compounds. hydrogen cyanide, ammonia, and condensable
hydrocarbons from the cooled raw product gas. Rectisol is a proprietary
27
L
process which removes acid gases by physical absorption in cold methanol at
elevated pressure. The non-selective process configuration differs from a
"selective" configuration in that all acid gas constituents are absorbed
simultaneously and no special process is used to p.roduce high purity CO2 vent
gas. The methanol solvent is regenerated by pressure reduction and distilla
tion. A simplified flow diagram for the SASOL I Rectiso1 unit is illustrated
in Figure 3-2. The Rectiso1 unit at SASOL I is designed to remove essentially
all of the sulfur compounds and nearly all of the CO2 from the cooled raw
product gas. Design specifications call for the pure synthesis gas to contain
less than 1.5 mol % CO2 and 0.1 ppmv H2S. Lurgi's first Rectiso1 plant is the
one built at SASOL I. The input and output streams for this unit are as
follows:
Input:
Cooled crude product gas Makeup methanol Water
Output:
Pure synthesis gas Acid gases:
high pressure flash gas - low pressure and
atmospheric flash gas Cyanic wate.r Gas condensate Naphtha
Process Information
Flow Rate P(psig)
86 365
227.800 scfm 59 330
4.700 scfm 32 180 32 55
88.600 scfm 23 1
10.000 1b/hr
The cooled crude product gas from secondary gas cooling enters the
acid gas removal unit at a temperature of 86°F and a pressure of 365 psig.
Table 3-3 presents composition data for this stream. The crude product gas is
then split into three streams which are cooled in two stages. Both stages
28
N 10
METHANOL
NH3 NH3 MAIN WASH
({'fa ( ? REFRIG.
TOWERI-I __ --'
METHANOL
FINE WASH
TOWER
SVNT~~~~GAS· I'· \ I"<j ~ \ \ \ \ \.
WATER
NAPHTHA TO HYDAOGENATION & DISTILLATION
CONDENSATE
Figure 3-2.
CYANIC WATER
LIQUOR
MeOHfWATEA DISTILLATION
COLUMN
COLD WATER RICH
METHANOL
FLASH GAS
ATMOSPHERIC FLASH GAS
) • ACID GAS • • TO STRETFOAD
LOW PRESSURE flASH GAS
Flow Diagram for SASOL I Rectisol Acid Gas Removal Unit
-" -"-.~ ----'--~-~ .----""---,--.---~ ~-~~-------.
<~j
! 1 ! • , , ;!
~
I J , i ~
I
I I I
w 0
-1 'iF , r -, -~-
• ,l ii '- ':l:
TABLE 3-3. NON-SELECTIVE RECTI SOL PERFORMANCE DATA FOR SASOL I
Rectisol Feed Synthesis High-Pressure Gas Component Gas. Mole % Gas. Mole % Flash Gas
H2 40.05 57.30 21.4
CO 20.20 28.40 18.2
CH4 8.84 11.38 11.4
C+ 0.54 0.7 2 CO2 28.78 0.93 46.7
N2 + Ar 1.59 1.77 1.5
H2S 0.28 ND 0.30
COS 10 ppmv NA NA
CS2 NA NA NA
RSH 20 ppmv NA NA
Total Sulfur (as S) NA 0.04 ppmv NA
Source: Reference 2
Notes: ND = not detected (detection limits not given in source) NA = not available
Offgases. Mole %
Low~Pressure
Flash Gas
2.6
4.8
7.2
1.1
83.4
0.8
0.46
NA
NA
NA
NA
,,-_ ..... ~ ¥ ,
Atmospheric Flash Gas
0.14
0.0
0.9
0.7
97.2
0.03
0.83
30 ppmv
2 ppmv
280 ppmv
NA
I"~ ,
have identical' cooling trains. Cooling of the first stream is achieved by
evaporation of high pressure amm~nia. Cooling of the second stream is
achieved by heat exchange with high pressure flash gas. Cooling of the third
stream is achieved by heat exchange with the cold product gas. Following the
first stage. the gas streams which are at a temperature of approximately 40 0 F
are comoined. condensed moisture and hydrocarbons are recovered. and methanol
is added to prevent ic'ing in the second stage. Following the second stage.
the cold crude product gas streams. which are at a temperature of approximate
ly -30oF. are recombined and the condensed gas liquor is recovered and sent to
the naphtha separator ,for methanol and by-product recovery. The gas enters
the prewash tower where the last traces of condensible organics along with
some H2S. CO2, and organic sulfur compounds are removed. The methanol used in
this stage enters at -70oF and leaves at approximately -20 oF. The rich
methanol from this stage is combiiIled with condensate from the second stage
coolers land is sent to the naphtha separator. The feed to the separator is
flashed ,and extracted with water. An aqueous methanol phase and a by-product
naphtha phase containing sulfur compounds result. The aqueous phase is
dist,i1le,d and methanol is recovered. The bottom cyanic water mixture. con
taining l,less than 0.1 percent methanol but some phenols and cyanide. is sent
to the tiar and oil separation unit for hydrocarbon removal. The naphtha is
routed to a hydrogenation unit for further processing. The naphtha consists
primarily of benzene. toluene. xy1enes. and other aromatics. together with
organic sulfur compounds (e.g •• thiophenes). and other organics (12). Another
referenc~ indicated that the naphtha is greater than 80 percent aromatics and
contains 0.34 percent sulfur (2).
The main wash tower is used to remove most of the CO2 and the H2S.
Here again the gas is washed with cold methanol. The desired temperature in
the column is achieved using low pressure ammonia evaporation in cooling
coils.
31
The gas leaving the main wash tower enters a fine wash tower where
it is contacted with methanol at -SooF. The resulting product gas contains
less than 1.S percent CO2
and 0.1 ppm H2S. Table 3-3 presents available data
for the product and offgas streams. The cold synthesis gas is used to cool
the Rect~sol feed gas and is then sent to the Fischer-Tropsch synthesis unit
for further processing.
Rich methanol from the pre-wash tower is combined with that from the
main wash tower and is sent to a six-stage expansion tower for regeneration
and reuse in the wash towers. A high pressure CO2 flash gas containing
primarily carbon dioxide. hydrogen. carbon monoxide. and methane is produced
and is utilized within the plant as a fuel gas at SASOL I. In addition a low
pressure flash gas is also produced.
Regeneration of the fine wash methanol results in an atmospheric
flash gas: which is combined with the low pressure flash gas; the combined acid
gas stream is sent to the sulfur recovery unit.
Waste Streams
The Rectisol unit produces the following waste streams:
1) Acid gases. This stream is made up of the atmospheric flash gas from the hot regenerator and the low pressure flash gas from the expansion tower. It consists primarily of CO
2, H2S.
and other reduced sulfur species. hydrocarbons. hydrogen. and carbon monoxide. The combined stream is routed to the Stretford sulfur recovery unit when operating. Prior to the installation of the Stretford unit. the atmospheric flash gas was routed to the power plant stack and the low pressure flash gas was flared (2). Although none of the available sources specify what is done in the event that the Stretford unit is not operating. it is possible that the former routing scheme applies to these streams. Table 3-3 presents composition data for each of the individual streams.
2) High pressure flash gas. This stream contains primarily hydrogen. carbon monoxide. methane. and carbon dioxide. It is used in the plant fuel gas system at SASOL I (1.2). Table 3-3 presents composition data for this stream.
32
TABLE 3-4. CYANIC WATER COMPOSITION
pH 9.7
Phenol 18
Cyanide (as CN) 10.4 - including Thiocyanate
Ammonia (as N) 42
Sulfides (as S) Trace
Oxygen (absorbed) 286
COD 1.686
Conductivity 1.111
Note: Units are mg/l except for conductivity (umhos/cm) and pH
Source: Reference 2
33
3) Cyanic water. This stream represents the aqueous stream from the MeOH/water distillation column used for methanol regeneration. Table 3-4 presents composition data for this stream. It is routed to the gas liquor separation unit for processing.
4) Gas condensate. This stream represents the condensate formed during cooling of the crude product gas in the first stage coolers. Composition data are not available but it will contain mainly water and. hydrocarbons.
3.5 Fischer-Tropsch Synthesis (4, 8, 11)
The purified synthesis gas leaving the Rectisol unit undergoes
Fischer-Tropsch synthesis whereby hydrocarbons are produced by catalytic
conversion of carbon monoxide and hydrogen. As shown in Figure 3-3, SASOL I
utilizes two types of Fischer-Tropsch reactors. The first, as shown in Figure
3-4, is a German-developed fixed-bed process (Arge) which produces mainly
heavy hydrocarbons and waxes. At SASOL I five fixed-bed reactors operate in
parallel, each with a shell diameter of 10 feet (3 meters) and a height of 42
feet (13 meters). Each reactor contains 2,000 tubes having a diameter of 2
inches (5 cm). The catalyst pellets, manufactured at SASOL I, consist of
silica with precipitated iron and promoters. The second reactor type used at
SASOL I, as shown in Figure 3-5, is an American-developed circulating fluid
ized bed system (Synthol) which produces primarily gaseous hydrocarbons and
gasoline. Three Synthol reactors operate in parallel, each with an inside
diameter of 7 feet (2 meters) and a height of 120 feet (37 meters). Finely
divided iron with promoters is used as a catalyst. The input and output
streams for Fischer-Tropsch synthesis are as follows:
Flow Rate P(psig)
Input:
Pure synthesis gas 227,800 scfm 59 330
34
U> V1
1
HYDROFINE
• ARGE REACTOR
SEPARATION
t---l1. . :
PURE SYNTHESIS
GAS
r ALCOHOL
KETONE
t OXYGENATE WORK-UP
SYNTHOL REACTOR
r-1 CONDENSATION I
SEPARATION I--
/1 GAS REFORMING
Cl & C2
• • MEDIUM HARD ~ Cl &C2 J J J J • MEDIUM BTU
FUEL GAS
WAX WAX C3 & C4
OIL
DISTILLATION t:GASOLINE
DIESEL '----r--~
TO BIOLOGICAL TREATMENT
.C3 & C4
~ ISOMERIZATION OLIGOMERIZATION
• GASOLINE LPG
Figure 3-3. Simplified Flow Diagram for SASOL I Fischer-Tropsch Unit
-
:}
1 , i I
l ! , 1 I I I
I i , , ~
f I i -, J :!
I I l I I (
STEAM 'COLLECTOR
TUBE BUNDLE
==I--a. STEAM OUTLET
FEEDWATER INLET
INNER SHELL
-1--I~ GAS OUTLET
ll::'-" WAX OUTLET
Figure 3-4. Fixed Bed Arge Reactor
36
TAIL GAS & SYNTHESIS ""1--1:===;-;:: PRODUCTS
CATALYST SETTLING HOPPER
SLIDE VALVES
COOLER GROUPS
COOLING OIL INLET
FRESHFEED~-I-C~~==~~::::::~ & RECYCLE'
Figure 3-5. Fluid Bed Synthol Reactor
37
COOLING OIL OUTLET
GAS & CATALYST MIXTURE
r l .. tr'ff,
I . \,."
Flow Rate P(psig)
Output:
Gaseous products:
- LPG
- Town gas
Other products:
Medium and hard waxes
- Gasoline
- Diesel oil
- Alcohols and ketones
Wastewater
Process Information
The Fischer-Tropsch synthesis can be generalized by the following
chemical equations:
at an H2 to CO ratio of 2.0:
nCO + 2nH2 ---I.~ (-CH2-)n + nH
20 (3-1)
at an H2 to CO ratio of 0.5:
(3-2)
These reactions are linked by the water gas shift reaction:
(3-3)
38
TABLE 3-5. COMPARISON OF FIXED BED AND FLUID BED CONDITIONS AND PRODUCTS
Conditions
Temperature Pressure CO + H2 Conversion. % H2/CO Ratio in Feed
Product Composition. Vol %
Liquefied Petroleum Gas (C3
-C4
) Petroleum (C5-C
ll)
Middle Oils \diesel. furnace) Waxy Oil Medium Wax. mp 135-140oF (59°C) Hard Wax. mp 203-206°F (96°C) Alcohols and Ketones Organic Acids
Product Selectivity. Vol %
Paraffins Olefins Aromatics Alcohols Carbonyls
Source: Reference 4
Fixed Bed (Arge)
430-490 0 F (220-255°C) 360 psig (2500 kPa)
65
39
1.7
5.6 33.4 16.6 10.3 11.8 18.0
4.3 trace
Fluid Bed (Synthol)
625°F (330°C) 330 psig (2300 kPa)
85 2.8
7.7 72.3 3.4 3.0
12.6 1.0
C11-C14
15 60 15 5 5
Pure synthesis gas from the Rectiso1 unit is split into two streams.
About one-third of the total amount of synthesis gas is mixed with recycle gas
and is fed to the top of the fixed bed reactors. Table 3-5 presents typical
operating conditions and product compositions for the reactors. At the bottom
of the reactors, the heaviest hydrocarbons (primarily waxes) separate out as
reactor condensate and the hot gases are cooled in condensers. The hydrocar
bon condensate is sent to the. SASOL ref.inery for further processing. The
aqueous condensate from the coolers is sent to the oxygenate work-up unit for
alcohol and ketone recovery. The residual wastewater that results is sent to
biological treatment. A part of the tail gas is used for recycle and the rest
is sent to oil absorption towers. The G3 's and C4 's are recovered and sent to
catalytiC polymerization reactors for further processing. The C2 ' sand
methane are recovered as medium-Btu fuel gas which is sold to local industries
gas or are sent to the gas reforming unit where they are reacted with steam
and oxyg~n over a nickel catalyst at l8000F to form additional CO and H2
•
The remaining two-thirds of the pure synthesis gas is routed to the
Syntho1 reactors, where it is combined with recycle gas and is fed to the
bottom of the fluid bed reactors. Table 3-5 presents typical operating
conditions and product compositions for these reactors. The tail gas from the
reactors enters a scrubber where the gas is cooled and high molecular weight
hydrocarbons are condensed, separated, and sent to the oil recovery facility.
The scrubbed gas is cooled further and lighter hydrocarbons are condensed,
separated. and sent to the oxygenate work-up unit for alcohol and ketone
recovery. Most of the non-condensible product gas is recycled to the reactor
inlet at a rate such that the feed contains one volume of fresh feed and two
volumes of recycle. The remaining gas, containing lighter hydrocarbons, is
sent to an absorber where all the C4 's and most of the C3 's are combined with
those from the fixed-bed reactor system and are further processed. The C2's
and methane are combined with those of the fixed bed system and are reformed
or used as blending components for the medium-Btu fuel gas.
40
I~
rI' , j"" .. "
Waste Streams
The Fischer-Tropsch process produces a single waste stream: re
sidual wastewater. This stream consists of the wastewater from the oxygenate
work-up unit. The principal contaminants are carboxylic acids. Fischer
Tropsch wastewater is sent to the biological wastewater treatment facility at
the SASOL I plant.
41
i l ...
.. ~ ! I I,,,,,,,,
4.0 AUXILIARY CONTROL AND UTILITY PROCESSES
4.1 Air Control Sulfur Recovery (Stretford) (I, 5)
At SASOL I, a Stretford sulfur recovery unit was installed in 1976
to convert the hyd.rogen sulfide in the acid gas from the Rectisol unit to
elemental sulfur. Two parallel trains were built. It is believed that SASOL
I no longer operates the Stretford sulfur recovery process due to operating
difficulties. This section describes the Stretford unit as it was designed to
be operated. The input and output streams include the following:
Input:
Acid gases from Rectisol Stretford chemicals Caustic Water Oxidizer air
Output:
Molten and flaked sulfur Stretford tail gas Oxidizer vent gas Stretford Solution purge
Process Information
Flow Rate (lb/hr) P(psig)
88.600 scfm
3,815 lb/hr
Figure 4-1 presents a flow diagram for the SASOL I Stretford unit.
The Stretford process utilizes an aqueous solution of sodium carbonate, sodium
bicarbonate, sodium vanadate, and 2,7-anthraquinone disulfonic acid (ADA) and
a buffering compound. The H2S in the entering acid gas stream is absorbed by
the alkaline solution in absorption columns forming bisulfide ions. The
bisulfide is then oxidized to elemental sulfur by the vanadium; this reaction
continues in the delay tank at the bottom of the absorber. The solution is
42
f' if ~ -~
t;
" i
TAIL GAS TO ~---II.~ ATMOSPHERE
ACID • J f----l GASES FROM t-t---II'I I
RECTI SOL
HYDROGEN SULFIOE
ABSORBER
AIR
OXIOIZER AIR COMPRESSOR
OXIDIZERS
SLURRY TANK
CHEMICALS TANK
WASH WATER
SULFUR TANK
CAUSTIC TANK
STEAM
Figure 4-1. Flow Diagram for SASOL I Stretford Sulfur Recovery Unit
,
FLAKER
SULFUR PIT
L--_--II.~FlAKED SULFUR
~_-I~ LIQUID r< • SULFUR
'-
1 , ~ j ,j
\
i 1 ! ~ I I
I ~ ~
i , "
I ~ 'I j I ~ i I ~ I " ! !
.'. i
regenerated by catalytic oxidation of the vanadium from V+4 to V+
5 by sparging
with air in the oxidizer tanks, with ADA acting as a catalyst. The sparging
also forms a froth and floats the sulfur to the top of the solution. The
froth overflows into a slurry tank, from which it is pumped to a centrifuge.
The Stretford solution is separated from the sulfur and returned, via a
balance tank, to the absorber. The sulfur is then sent to an autoclave where
it is melted and water is driven off; the molten sulfur is stored in a tank
prior to being routed either to a flaker or a liquid sulfur storage pit.
A portion of the aqueous stream from the autoclave, which contains
small amounts of Stretford chemicals as well as unregenerable salts
(thiocyanates and thiosulfates), is returned to the Stretford absorber. The
remainder is reportedly routed to the plant's aqueous effluent treatment unit.
Future plans call for the implementation of a processing unit to recover the
Stretford chemicals (5).
The feed stream to the Stretford unit consists of the combined
low-pressure and atmospheric flash gas streams from Rectisol. The gas is
compressed prior to entering the Stretford absorber to overcome the pressure
drop in the absorber. The tail gas remaining after absorption is simply \
vented to the atmosphere at SASOL I. "The design specifications call for this
tail gas to contain less than 50 ppmv of H2S. This represents an improvement
over plant emissions prior to the installation of the Stretford unit, when the
acid gas streams were routed to the power plant stacks and vented directly
into the atmosphere.
Potential problems with the Stretford process include less than
design sulfur removal, absorber plugging, foaming in the oxidizer sulfur
flotation tanks, mercaptan emission from the oxidizer, excess solids buildup,
and excess chemical usage. Severe plugging problems in the Stretford tower
have caused SASOL I to test and use absorbents different than that normally
used in such units. No authoritative data are available on how satisfactory
44
these alternate adsorbent solutions have been. Presumably the high CO2 level
in the Rectisol acid gas has contributed to this problem. In addition, CO2 absorption by the Stretford solution lowers the pH which in turn lowers the
H2S absorption eff.iciency.
4.2
Waste Streams
The Stretford unit produces the following waste streams:
1) Stretford tail gas. This stream contains unconverted reduced sulfur species, hydrocarbons, and CO2• At the SASOL I plant, the tail gas stream is vented to the atmosphere.
2)
3)
Stretford solution purge. This stream contains species present in the absorber solution including undegradable thiosulfates and thiocyanates. Specific details are not available as to the composition of this stream. It is reportedly routed to the biological treatment facility (5).
By-product sulfur. The sulfur recovered in the Stretford unit is sold as a by-product in both liquid and solid form. Approximately 95 percent of the H2S in the Rectisol acid gas is recovered as sulfur.
4) Oxidizer tank vent. This stream consists primarily of air, water vapor, and CO2 • However. some COS, CS2' mercaptans and ammonia may also be present. This stream is vented to the atmosphere.
Water Control
The SASOL I facility has the following water control processes which
are described in this section:
• Gas liquor separation.
• Phenol extraction (Phenosolvan),
• Ammonia stripping,
• Biological treatment.
These processes are discussed in the following text.
45
4.2.1 Gas Liquor Separation C1. 2. 7)
The gas liquor separation unit receives the gas liquor stream from
the quench/primary cooling and secondary cooling process units along with
cyanic water and gas condensate from the Rectisol unit. A simplified flow
diagram for this process is presented in Figure 4-2. This unit is designed to
separate t,he gas liquor into dusty tar. clear tar. tar oil. and aqueous liquor
phases. The input and output streams are as follows:
Input:
Raw gas liquor feed: Quench liquor Oily gas liquor from secondary cooling Cyanic water from Rectisol Rectisol wastewater (gas condensate)
Output:
Flash gas (expansion gas) Dusty tar Clear tar and tar oil Vent gases:
Surge tank vent - Primary tar separator vent
Secondary tar separator vent Oil separator vent
Gas liquor
Process Information
Flow Rate Clb/hr)
Flow Rate (lb/hr)
1,025 1,102
20.000
31 32 41
PCpsig)
PCpsig)
The gas liquor streams produced in the quench/primary cooling and
secondary cooling units and the cyanic water and gas condensate produced in
the Rectisol unit contain a number of dissolved and suspended components
46
f- ,. r
t
Figure 4-2.
"I
I VENT GAS TO ATMOSPHERE L......-..I
TAR
TARRY LIQUOR
AQUEOUS LIQUOR
T DUSTY
TAR
t-,
EXPANSION GAS
WATER SCRUBBER
VENT GAS TO ATMOSPHERE ,
TAR
VENT GAS TO ATMOSPHERE
TAR OIL
LIQUOR
r1
VENT GAS TO • ATMOSPHERE
TAR TANK
TAR TO • OISTILLATION
GAS LIQUOR TO PHENOSOLVAN
VENT GAS TO • ATMOSPHERE
TAR OIL TANK
TAR OIL TO L-__ .... DISTILLATION
Flow Diagram for the SASOL I Gas Liquor Separation Unit
.... ,,:.
i
'-
I i , ~.
I i ~
I I i
I I i
i I ~ I ! i , .!
I I
t ,~ I
! !
condensed from the raw gasifier gas. These consist of dust, tar (heavier
than-water suspended organics), tar oil (lighter-than-water suspended
organics), phenols, ammonia, sulfides, cyanides, and naphtha. Each of these
streams enter an expansion vessel where the pressure is reduced to near
atmospheric. The resulting flash gas (expansion gas) streams are combined,
sent to a vapor cooler, and scrubbed with water before being routed to the
plant's fuel gas system (1,7). The expansion gas consists primarily of CO2,
but als.o contains significant concentrations of hydrogen, carbon monoxide,
methane, and H2S.
The raw gas liquor from the quench/primary cooling units along with
the cyanic water from the Rectisol unit leave the expansion vessel and enters
a primary tar separator where tar and dust are allowed to settle. This
separator produces several streams. A clear tar stream is taken off and is
sent to a storage tank prior to being distilled. A dusty tar stream contain
ing heavy tar and dust is also produced. This stream was formerly disposed in
a sludge dump. One reference claims that dusty tar is now recycled to the
upper part of the newer gasifiers and is distributed over the coal (7). It is
not known with certainty whether all of the dusty tar is presently recycled.
Two gas liquor streams are taken off. The first is routed to a secondary tar
separator, which produces additional clear tar and gas liquor. The tar is
combined with that from the primary tar separator and is sent to the distilla
tion unit. The gas liquor stream is sent to a storage tank. The other gas
liquor stream from the primary separator is combined with the gas liquor from
secondary cooling and the gas condensate from the Rectisol unit and is sent to
an oil separator. Here tar oil and gas liquor are separated. The tar oil
stream is routed to the distillation unit. The gas liquor stream is combined
with that of the secondary separator and is routed to a sand filter for final
removal of suspended solids. The filtered gas liquor is sent to the
Phenosolvan solvent extraction unit.
48
4.2.2
Waste Streams
1) Pressure reduction flash gas. This stream consists primarily of CO
2, with smaller amounts of CO. hydrogen. methane. and H2S.
It is combusted in the plant's fuel gas system.
2)
3)
Gas liquor. The combined gas liquor stream contains residual amounts of suspended organics (e.g •• tar and tar oil). dissolved organics (e.g •• phenols. fatty acids. amines). dissolved gases (e.g •• CO2 , NH3 • H2S. HCN) and trace elements. It is routed to the Plienosolvan unit.
Vent gases. sludge sump. atmosphere. presented in
The vent gases from the three separators. the and the tar storage tanks are vented to the Composition data for several of these streams is Table 4-1.
Phenol Extraction (Phenosolvan) (1. 2. 10)
The Phenosolvan process at SASOL I is designed to remove dissolved
organics (especially phenolic compounds) from the aqueous liquor stream
leaving the gas liquor separation unit. Approximately 4.000 lb/hr of crude
phenols are recovered from this gas liquor. A multistage horizontal extractor
containing an organic solvent. butyl acetate. is used to remove the majority
of the phenolic compounds from the gas liquor. [Most U. S. plant designs are
based on the use of another solvent. diisopropyl ether (DIPE).] SASOL claims
that there are several advantages to the use of butyl acetate. including a
lower required solvent-to-feed radio. higher flash point. and lower toxicity
compa;red to DIPE (12). The input and output streams for this module are as
follows:
Input:
Gas liquor from gas liquor separation
Makeup butyl acetate
Flow Rate (lb/hr) P(psig)
49
TABLE 4-1. GAS LIQUOR SEPARATION VENT "GAS STREAM COMPOSITIONS
Gas Composition (dry gas basis)
Fixed Gases, vol %
Sulfur Species, vol %
Source: Reference 1
Primary Tar Separator
Vent
8.00
15.60
58.64
1.84
4.22
11.21
0.14
50
Secondary Tar Separator
Vent
4.18
17.55
66.02
0.95
2.28
8.48
0.20
Tar Oil Separator
Vent
1.33
2.16
8.11
2.55
0.61
83.87
0.83
Output:
Crude phenols Phenol pitch Dephenolized gas liquor Vent gas
Process Information
Flow Rate (lb/hr)
4.000 500
P(psig)
Figure 4-3 presents a simplified flow for the SASOL I Phenosolvan
and ammonia stripping units. Phenosolvan is a proprietary solvent extraction
process developed by Lurgi for the removal of phenols from coke oven and coal
gasification process wastewaters. The process is based on the preferential
solubility of phenolics (as well as some other organics) in a organic solvent.
such as butyl acetate or DIPE. and the immiscibility of the solvent and the
aqueous phase. Contacting the wastewater with solvent in a multistage extrac
tor results in the transfer of phenolics to the solvent phase. The remainder
of the process equipment serves to recover residual solvent from the
dephenolized gas liquor. and separate the crude phenols from the solvent.
The gas liquor stream from the gas liquor separation unit is con
tacted with acid gas (primarily CO2 with some H2S) from the solvent stripper
in order to adjust the pH of the gas liquor to the optimum for extraction.
Excess gas is vented to the atmosphere. The saturated liquor is fed to a
horizontal multistage extractor where it is contacted with butyl acetate.
Following extraction. the rich solvent stream. which contains the majority of
the phenolic components. is pumped to a series of solvent distillation columns
where the solvent and phenols are separated; the crude phenols are recovered
and stored for subsequent use or sale. Most of the phenols are reportedly
exported to Europe (7). In the course of the final cleanup of the butyl
acetate-phenol mixture. phenolic pitch comprised of heavy hydrocarbons is
recovered and is sent to the tar/oil distillation unit. The recovered solvent
is cooled and returned to the extractor.
51
• VI t-.>
FROM GAS LIQUOR
SEPARATION
OJ , "1'
OFFGAS TO ATMOSPHERE
SATURATION TOWER
BUTYL ACETATE 0
PHENOL
SOLVENT STRIPPER~
GAS LIQUOR
AMMONIA - RICH GAS TO AMMONIA SULFATE PLANT
AMMONIA STRIPPER
PHENOSOLVAN STRIPPED LIQUOR
STEAM
STRIPPED GAS LIQUOR TO
BIOLOGICAL OXIDATION
CRUDE PHENOLS
Figure 4-3. Flow Diagram for SASOL I Phenosolvan/Ammonia Stripper Unit
J
!i...
i G
I
I i i
I I
i i I ! I t 1 i I I
I I ~ I I
The aqueous stream from the Phenoso1van extractor is steam stripped
in order to recover the trace amounts of butyl acetate in the stream and is
then sent to a stream stripper for the recovery of ammonia. The solvent
stripper overheads consist of noncondensib1e gases. steam and solvent vapors;
the stream is cooled and routed to a three-phase separator. The gas phase,
consisting primarily of CO2 with some H2S is routed to the feed saturation
tower. Solvent is returned to the solvent tank for recycle to the extractor.
The aqueous phase is recycled to the solvent stripper.
Waste Streams
The Phenoso1van wastewater extraction process produces the following
waste streams:
4.2 .• 3
1) Depheno1ized gas liquor. This stream contains ammonia and residual amounts of other dissolved gases including hydrogen sulfide. hydrogen cyanide. CO • and other components of the crude gas; residual phenols; tatty acids; and other organics. It is routed to the ammonia stripper for further treatment.
2) Vent gas. The Phenoso1van off gas contains approximately 90 percent CO2 and some H2S. The exact composition is not available. SASOL planned to route this stream to the Stretford unit. It is reportedly vented to the atmosphere when the Stretford unit is not in operation (2).
Ammonia Stripping (1. 2. 4)
Ammonia is recovered from the depheno1ized gas liquor prior to
entering the wastewater treatment facility. As shown in Figure 4-3. this is
done by steam stripping. The input and output streams for this process are as
follows:
Input:
Depheno1ized gas liquor Steam
Flow Rate (lb/hr) P(psig)
53
[
Output: Flow Rate (lb!hr) P(psig)
Stripper overhead gases Stripped gas liquor
5,000 948,000
Process Information
The aqueous stream from the Phenosolvan extraction unit is fed to
the top of a stripping column. Steam is fed to the bottom of the column and
flows countercurrently up through the column. The majority of the dissolved
gases in the aqueous stream are stripped and exit the top of the column. This
stream, which contains water vapor, 6 percent ammonia. and 0.1 percent sulfur
containing species, is sent to the ammonium sulfate plant for fertilizer
production. Stripped gas liquor is recovered from the bottom of the column
and is routed to the biological treatment facility.
4.2.4
Waste Streams
The ammonia stripper produces two waste streams:
1)
2)
Stripper overhead gases. This stream contains water v~por, 6 percent ammonia, and 0.1 percent sulfur species (e.g., H2S). It is routed to an ammonium sulfate plant for fertilizer production.
Stripped gas liquor. The available composition data for this stream are given in Table 4-2. It is routed to the biological treatment facility.
Biological Treatment (1, 2, 9)
Process wastewater comprised of the effluent streams from the
Phenosolvan plant, the residual wastewater from the Fischer-Tropsch synthesis,
various other aqueous waste effluent streams, SASOL and other petrochemical
industrial effluents, and domestic waste from area townships are all treated
by the biological treatment facility at the SASOL I plant. A flow sheet
54
TABLE 4-2. STRIPPED GAS LIQUOR COMPOSITION
pH 8.6
NH+ 4 125
t"';' t
CN- 0.05 L.,~b SCN- 40
-S 2 -
F 50 -C1 20
COD 1.190
TOC 400
TSS 8
Phenols 150
Note: Units are mg/l except pH
Source: Reference 1
.. ~ i
55
.I""'"
summarizing all process and wastewater handling is presented in Figure 4-4.
The input and output streams are as follows:
Input:
Wastewater: - Stripped gas liquor
Fischer-Tropsch wastewater Process wastewater from other sources Oxygen P04
Output:
Biox effluent Excess biox sludge
Process Information
Flow Rate (lb/hr) P(psig)
948.000
Stripped gas liquor from ammonia stripping is first routed to a pond
where it is cooled to about 140°F by spraying it into the air (9). The
stripped gas liquor is combined with neutralized wastewater from the
Fischer-Tropsch unit in the spray pond. The combined wastewater stream is
then routed to the biological filters. Wastewater streams from other sources
are also routed to the same biological treatment unit. including flocculated
oily· wastewater from the SASOL and other petrochemical industries in the area
and the SASOL petroleum refinery. and settled domestic sewage from townships
and factories.
Biological treatment is performed using trickle filters. Each of
the biological filter tanks is filled with gravel which serves as a substrate
for the biological organisms. The treated effluent is sand filtered and
recycled to the ash sluiceways. where it is used to convey the ash to the
slime dams. Contacting the biox effluent with ash results in the removal of
56
lJ'o -..J
, - r -, I
Source:
f~"~-"1l
Figure 4-4.
Reference 2
SASOl FISCHER· TAOPSCH
ACIDS
SLUDGE
OilY WATER
SWDGE
r~ ~ .~
~ VAAL RIVER ~
Flow Diagram for SASOL I Effluent Treatment System
'- - j
L
-'
j i
i
i t t
I I ~ ! I l , ~ I ! i ~\
I I i f I i I ~ , iI
r-:
additional residual organics by adsorption on the ash. After settling most
the water goes to large maturation dams where it is held for a period of 10 to
12 days; it is then discharged to the Vaal River. Some of the settled water
from the slimes dams is recycled to the ash handling system.
Excess biological sludge is sent to anaerobic digestors where it is
combined with domestic sewage sludge. The digested sludge is sent to concrete
"drying bogs".
4.2.5
Waste Streams
The biological treatment facility produces two waste streams:
1) Biox effluent. This stream represents the discharge from the sand filters in the biological treatment unit. The limited data available on the composition of the treated wastewater at this point are shown in Table 4-3. Biox effluent is routed to ash handling at SASOL I.
2) Excess sludge. This stream contains suspended solids (biological organisms) and trace metals. It is sent to anaerobic digestors at SASOL I. The treated sludge is then dried and used at selected farms in the area as fertilizer.
Cooling Towers
A forced-draft cooling tower system is used at SASOL I to provide
cooling water for a number of process streams. Treated raw water is used as
the source of makeup for this system. A portion of the stripped gas liquor is
used for Phenosolvan unit cooling tower makeup.
4.3 Solids Handling (Coal Handling. Preparation. and Storage)
(1. 2. 4. 7)
Coal is supplied from SASOL's own Sigma Colliery coal mine. Several
processes including transportation of the coal from the mine and crushing and
screening are required before it can be used in the Lurgigasifiers and the
58
TABLE 4-3. COMPOSITION OF BIOX EFFLUENT ROUTED TO ASH HANDLING
pH 8.2
Ammonia as N 20.0
r~~ Phenols (steam volatile) 0.2
! Fatty acids (as Benzoic acid) 22.0 I,,,,,
Fluoride 17.0
COD 165
Note: Units as mg/L except pH
Source: Reference 2
59
[
[
power plant. Figure 4-5 illustrates the coal handling procedure. The input
and output streams are as follows:
Input:
Run-of-mine coal
Output:
Sized coal Fines
Process Information
Flow Rate (lb/hr)
1.543.300
848.800 694.500
P(psig)
Run-of-mine coal is transported via conveyors to primary crushers
located at the bottom of inclined coal hauling shafts. The coal is carried to
the. surface by conveyor and discharged into storage bunkers of 12.000 tons
total capacity. Surface conveyors transport the coal from the bunkers to
secondary crushers and screens. Here the coal is separated into two sizes.
less than about 0.5 inch and between 0.5 - 1.5 inches. All the fines up to
0.5 inch are conveyed to storage bunkers above the power plant boilers. The
available literature sources are not in agreement to the size ranges produced
by the screens. The larger sizes are transported via conveyor to storage
bunkers for use in the Lurgi gasifiers. The coal used at SASOL I reportedly
releases methane upon storage. Explosions in storage bunkers are currently
avoided by assuring adequate ventilation of the bunkers. Originally the
bunkers were nitrogen blanketed. but ventilation has been more successful.
The temperature of stored coal is monitored closely; any coal showing a
temperature rise is immediately fed to the plant and the storage bin is
emptied.
Fugitive dust is reduced by keeping the coal damp on the conveyors
with water sprays (1).
60
C7> I-'
COAL FROM MINE
')
'-PRIMARY
CRUSHERS
VENTILATED COAL STORAGE ..
BUNKERS
SECONDARY 1/2" - 1 . 11 2"
SIZE COVERED CRUSHERS & COAL STORAGE SCREENING BUNKER
LESS THAN 1/2" SIZE
COVERED COAL FINES TO STORAGE SILOS - POWER PLANT
SIZED COAL TO COAL
GASIFICATION
Figure 4-5. Simplified Flow Diagram for SASOL I Coal Handling. Preparation. and Storage
I I
I i
I ~
f I i i it
I ~
f"""'11
Waste Streams
Waste streams for the coal handling. preparation. and storage
activities consist of the following:
1) Fugitive coal dust. These streams consist of fine coal particles which may escape the water spray dust suppression units and enter the atmosphere.
2) Storage vent gas. This stream consists primarily of air with smaller amounts of methane which is produced during coal storage. It is vented to the atmosphere.
4.4 Utilities (Steam and Power Generation) (1. 2. 3. 4)
The stream and electricity power requirements of the SASOL I plant
are provided by a power plant which consumes 8.300 tons per day of coal or
approximately 45 percent of the total coal supplied to the SASOL I plant. The
input and output streams consist of the following:
Input:
Coal fines Fuel gas (coal lock gas) Boiler feedwater Air
Output:
Steam - From boilers - From superheaters
Electricity Flue gas Boiler ash
Flow Rate (lb/hr) P(psig)
694.460
Flow Rate (lb/hr) P(psig)
221.300
62
r~
I, .. ,
... i i I. .
L ...
Process Information
Little information is available for the power plant. However_ it is
known that the plant utilizes powdered fuel boilers designed to also burn oil
and refinery gas as well as coal. Steam superheaters are also present which
are fueled by raw gasifier gas and coal lock gas. The plant supplies steam
and power used in the entire SASOL I complex in addition to the gasification
plant.
following:
Waste Streams
Waste streams for the steam and power plant module consist of the
1) Boiler ash. No composition data are available for this stream although it will contain most of the mineral matter originally contained in the feed coal. Boiler ash is combined with the gasifier ash and is sent to the ash handling system.
2) Flue gas. No composition data are available for the power plant stack gas. The stack gas form the boiler is treated with three stage of electrostatic precipitation. This results in a particulate loading of 0.1 grams per cubic meter of effluent. The stream superheater flue gas consists of approximately 20 percent CO2 and small quantities of CO. NO _ SO _ and other contaminants with the remainder being N2- 02' afld H20 •
63
... ,
5.0 RESIDUALS DISPOSAL OPERATIONS
5.1 Air Emissions - Plant Flare System (1. 2)
Air emissions control at the SASOL I plant in provided by the
plant's flare system. Various gaseous discharge streams are flared in order
to limit the amount of reduced sulfur compounds and organics emitted into the
atmosphere. The input and output streams for this residual disposal operation
are as follows:
Input:
Excess coal lock gas Startup raw gas Air Supplemental fuel
Output:
Flare offgas
Process Information
Flow Rate P(psig)
Few details are available describing the flare system. Its purpose
as stated above is the destruction of reduced sulfur species and organics that
would otherwise be emitted into the atmosphere with some of the plant's
discharge streams. It is likely that additional treatment would be required
prior to flaring of such streams in similar U. S. proposed plants •
Waste Streams
The flare system produces an offgas which contains the products of
combustion of the various waste gas streams routed to it. No characterization
data are available for this stream. However. it will contain sulfur oxides.
64
carbon monoxide and carbon dioxide. unburned hydrocarbons. and reduced sulfur
compounds. It is discharged to the atmosphere.
5.2 Water Effluents
5.2.1 Process Wastewater Residuals
Process wastewater (treated gas liquor) is used in the ash handling
sluiceway and eventually discharged to the Vaal River. Treatment steps are
provided to reduce the concentration of suspended organics (gas liquor separa
tion). dissolved organics (Phenosolvan). ammonia (ammonia stripping). and
trace organics (biological treatment). These water treatment processes and
any associated waste streams are described in detail in Section 4.2. Water
Control. Data on the composition of the treated wastewater discharge stream
are presented in Table 5-1.
5.2.2 Raw Water Treatment Residuals (8)
At SASOL I treated raw water is used for cooling tower or boiler
feed water uses. No details were available for the raw water treatment
processes. The boiler and cooling tower blowdown streams are sent to 'the
slimes dams at the biological treatment facility.
5.3 Solid Wastes
5.3.1 Ash Handling System (2. 4. 7. 12)
Figure 5-1 presents a flow scheme for the ash handling and removal
system. There are discrepancies in the available sources as to the configura
tion of parts of the ash handling system. The scheme shown here is consistent
with the more recent literature sources. The inputs and outputs for this unit
are as follows:
65
{""'"
TABLE 5-1. COMPOSITION OF TREATED WASTEWATER DISCHARGED TO VAAL RIVER
pH
Suspended Solids
Total Dissolved Solids
Ammonia (as N)
Arsenic
Boron
Total Chromium
Copper
Phenolic Compounds (steam volatile)
Lead
Cyanides
Fluoride
Zinc
Sodium
Phosphates (as P)
COD
Soap. Oil. and Grease
Note: Units are mg/L except pH
Source: Reference 2
66
8.5
31.0
959
7.45
0.05
4.40
0.01
0.04
0.03
0.02
0.11
5.87
0.07
158
0.29
82
0.13
0-
"
--, ~
WRGI GASIFIER
ASH
POWER PLANT ASH
ASH SWICEWAYS
-. I
Figure 5-1.
'ASH SUMP
SLIMES DAM
.. l
FINE ASH SLURRY
THICKENERS
THICKENED FINE ASH
'';", .,"" "
I ,
Flow Diagram for SASOL I Ash Handling System
r· ~''-- ljo -, ,i !
+ f
~
I i
I ~ , ! ~
! i , 1 I l !
~
I I ,
Input:
Gasifier ash Power plant ash Recycle sluicewater
Output:
Ash sluiceway vent gas Coarse ash Fine ash slurry
Process Information
Flow Rate (lb/hr)
265.600 220.500
P(psig)
392
The ash discharged from the Lurgi gasifier ash locks falls into
hoppers below ground level. Table 5-2 presents composition data for the
gasifier ash. These hoppers are covered with hoods reaching to the bottom of
the ash locks and are connected to a ventilation system for removal of fumes
and dust. High pressure water jets are used to remove the ash from the
hoppers into an enclosed sluiceway. The power plant ash is also fed to this
sluiceway. The ash slurry passes through a clinker grinder into a sump. From
the sump. the ash-water slurry is pumped through an overhead aqueduct to an
ash dewatering installation. The coarse ash is removed by screens and ash
classifiers and is transported by conveyor belts to the ash dump. The fine
ash slurry is concentrated in conventional thickeners. The thickener overflow
is pumped to a slimes dam for dewatering while the overflow is combined with
the rest of the ash for disposal. The slimes dam has an impervious clay layer
which prevents water seepage. Any water drainage from the slimes dam is
collected via an extensive drainage system and is returned to the ash sluice
way. The slimes dam also serves as part of the water treatment facility since
the ash ~bsorbs residual organics.
68
TABLE 5-2. GASIFIER ASH ANALYSIS
Mineral Concentration (wt%)
Si02 A1203 Fe
20
3 CaO
C
MgO
K2
0
Na2
0
S04
P04
Melting Properties. OF
Softening Point
Melting Point
Fluid Point
Trace Elements (ppmw)
As
B
Be
Cd
F
Hg
Mn
Ni
Ph
Sb
V
Source: Reference 2
69
52
28
5
7
3
1.7
0.5
0.7
0.2
0.3
2.507
2.687
2.732
1.7
133
<0.05
<0.1
150
<0.1
2,000
183
50
<0.5
1,000
5.3.2
Waste Streams
The ash handling system produces the following waste streams:
1)
2)
3)
Ash sluiceway vent gas. This stream consists primarily of water vapor. air. and some fine ash particles and low concentrations of other lockhopper vent gas constituents. No composition data are available for this stream. It is vented to the atmosphere through a ventilation system.
Combined ash. The combined gasifier and power plant ash is sent to an above-ground ash dump. No evidence of seepage from the ash dump has been found and no measures are taken to guard against it. Regular samples of ground water in the vicinity of Saso1burg have indicated no evidence of underground water pollution (4).
Thickener overflow. The thickener overflow is sent to slimes dams. The dams have a clay surface which serves as a liner and prevents leaching of trace components. The slimes dams are used as part ·of the water treatment facility since the ash absorbs residual organics from the biox effluent used as sluicing water.
Disposal of Other Waste Produced During Normal Operation (2)
The dusty tar. representing the bottom stream from the primary tar
separator of the gas liquor separation unit was sent to a landfill until the
installation of newer gasifiers which are designed for dusty tar recycle. It
is not known if all of the dusty tar is presently recycled or if some of it is
still 1andfi11ed.
No details were found which discussed the disposal of other plant
solid wastes.
70
~,~
{"''''t
6.0 REFERENCES
1. Themsen. S.J •• G. Kasper. J.F. Nagy. A Tzeu. L.S. Pernet. Assessment ef Discharges Frem SASOL I Lurgi-Based Cea1 Gasificatien Plant. EPA/600/7-83-044. Industrial Envirenment Research Laberatery. Research Triangle Park. N.C •• August 1983. (L-21788)
2. Bertrand. R.R •• E.M. Magee. T.K. Janes. W.J. Rhedes. Trip Repert:
3.
4.
5.
FeurCemmercia1 Gasificatien Plants Nevember 6-18. 1975. Exxen Research and Engineering Co. •• Linden. N.J .• and EPA. Office ef Research and Deve1epment NERC-RTP. Centre1 Systems Laberatory. Research Triangle Park. N.C. EPA Centract No.. 68-02-0629. (L-07888)
Heegendeern. J.C. and J.M. Sa1emen. "SASOL: Wer1d's Largest Oi1-frem-Cea1 Plant." British Chem. Engr. ~(5). (May. 1957). (L-00676)
Anastai. J.L •• SASOL: Seuth Africa's Oil frem Cea1 Stery - Backgreund fer Envirenmental Assessment. EPA-600/8-80-002. TRW. Inc •• Redondo. Beach. CA. January 1980. (L-14487)
Jurenka. K •• "Removal of Hydrogen Sulfide frem Waste Gases at SASOL". in: Proceedings: International Conference on Air Pollution. Pretoria. South Africa. April 1976. (L-21668)
6. Envirenmental Protection Agency. Po11utien Contre1 Technical Manual for Lurgi-Based Indirect Coal Liguefaction and SNG. EPA-600/8-83-006. Washington. D.C •• April 1983. 625 p. (L-21455)
7. Tisdall. G.e •• "SASOL Operating Experience in Large Scale Pressure Gasification". in: Proceedings of the Second Synthetic Pipeline Gas Symposium. Pittsburgh. PAs November 1983. (L-02007)
8. Dry. M.E •• "The Saso1 Fischer-Tropsch Processes." Applied Industrial Catalysts. ~(5). 167-213. (1983). (L-22616)
9. Hoogendoorn. J.C •• "Gas from Coal with Lurgi Gasification at SASOL." in: Symposium Papers: Clean Fuels Frem Cea1. Chicago. IL. 10-14 September. 1973. 111-125. (L-00677)
10. Graefe. K •• "Kohleverede1ung in der Sudafrikanischen Union."
11.
Frieberger Forsch A 264. 103-128 (1963). (L-00612)
Hoogendoorn. J.C •• "Experience with Fischer-Trepsch At Saso1." in: Symposium Papers: Clean Fuels Frem Coal. Chicago. IL. 10-14 SePtember. 1973. 353-365. (L-00678)
12. National Institute fer Occupatiena1 Safety and Health. Criteria for a Recommended Standard ••• Occupationa1 Exposures in Coal Gasificatien Plants. DHEW/PUB/NIOSH-78-191. September 1978. (L-11751)
71
L.
13. Roltberg. P.D •• Woods. T.J •• and Ashby. A.B •• "1986 GRI Baseline Projection of U.S. Energy Supply and Demand to 2010." Strategic Analysis and Energy Forecasting Divsion, Gas Research Institute. December 1986.
14. Kronseder, J.G., "SASOL II: South Africa's Oil-from-Coal Plant." Hydrocarbon Processing. 55(7), July 1976. (L-5790)
15. , "SASOL Synfuel Plants Now Publicly Owned." Cameron Synthetic Fuels Report, ~(3). September 1981.
72
-1"''!
L
GRI COAL GASiFICATION EH&S INFORMATION SYSTEM DOCUMENT CATALOG
STIC No. L-217'3'3
Title: Assessment of Discharges from SASOL I Lurgi-Based Coal Gasification Plant.
Corporate Author: Fluor Engineers and Constructors, Inc. Sponsor: Environmental Protection Agency, lERL-RTP
First Personal Author: Thomson, S.J. Additional' Personal Authors: Kasper, G.; Nagy, e. F.; Tzoll, H.; Pernot, L,8. Publi sher: Date: 1)'3-00- i 983 Source: Volume/Number: f Beginning Page: Document Type: Report Identifying Nos: PB83 253740; EPA-600!7-83-044
Keywords: A1l910 C10000 C20000 [30000 010000 D20000 F20200 F42000
Supplementary Note:
Summary/Comments:
SASOL I Gaseous streams Liquid streams Solid streams Inorganics Organics Material & energy balances Test results
Total Pages: 28
This report presents information obtained from Sasol I. on emission and effluent streams. These are supplemental engineering estimates and calculations performed by Fluor using publicly~available information (e.g., Kosovo STER)s About 89% of the coal sulfur is found in gas streams, 4% in liquids and the rest in ash. Most trace elements (from a selected list including Sb, As, Pb, Cd, Ni, 8e, Hg, and Mnl remain in the ash and have low solubility (exception-As). Caution should be exercised in using these data they should be confirmed by test runs prior to use with design, cost estimates, Dr environmental control studies.
SRI Hardcopy? Yes Rea50n: Source of emissions data/estimateci for Sasol I. Evaluation: Completeness 5 Referencing 5 Methodology ~ Documentation 5 Reviewer: FDB
73
GRI COAL GASIFICATION EH&S INFORMATION SYSTEM DOCUMENT CATALOG
STIC No. L-(;7B88 CONTAINS PROPRIETARY INFORMATION
Title: Trip Report: Four Commercial Gasification Plants=
Corporate Author: Exxon Research and Engineering Co., Linden, NJ Sponsor: E~vironmental Protection Agency
First Personal Author: Bertrand, R. R. Additional Personal Authors: Magee, E. M. Publi sherI Source: Volume/Number: Beginning Page: Doc¥ment Type: Report Identifyin~ Nos:
Keywords: Ai i 150 A11910 B21112 B21121 821235 B25507 832211 B40000 C10000 C20001) F20000 F60000
Kutakya; Turkey SASOL I Koppers-Totzek Lurgi Winkler Rectisol Phenosolvan Residuals Disposal Operations Gaseous streams Liquid streams Engineering description Environmental impact/assessment
Date: i)i)-i)i)-i 975
Total Pages: 5()
Supplementary Note: Trip report; Lurgi (dry ash) plant in Westfield.
Summ~ry/Comments: Detailed descriptions of SASOL I gasification, gas purification and water treatment facilities are given. Composition and flow rate data provided along with typical operating data for the above units. Analysis of effluent returned to river along with analytical capabilites at SASOL I are also included. This facility was one of four commercial gasifiers visited in November 1974 and documented by a group composed of members of EPA and Exxon Research and Engineering. Other gasifiers visited were: Westfield, Scotland (Lurgi); and Kutahya~ Turkey (Koppers-Totzek and Wink12r)~
SRI Hardcopy? No Reason: Some details sketchy. Evaluation: Completeness 5 Referencing N Methodology N Documentation N Reviewer: JDQ
74
GRI COAL GASIFICATION EH~S INFORMATION SYSTEM DOCUMENT CATALOG
STIC No. L-00676
Title: Sasol: World's Largest Oil-from-Coai Plant.
Corporate Author: South African Coal, Oil and Gas Corp., Ltd .. Sasolburg Sponsor:
First Personal Author: Hoogendoorn, J. C. Additional Personal Authors: Salomon, J. M. PLlbli sherI Source: British Chemical Engineering Volume/Number: 2 15 Beginning Page: 238 Document Type: Journal article Identifying Nos:
Keywords: A11910 821121 825000 825507 F20000
Supplementary Note:
Summary/Comments:
SASOl I Lurgi Acid Gas Removal Processes Rectisol Engineering description
Total Pages: 7
This journal article is a fairly detailed description of the acid gas removal svstem at SASOL I including equipment and operating conditions. It also includes a desciiption of the gasification process.
SRI Hardcopy? No Reason: Dated. Evaluation: Completeness 7 Referencing N Methodology N Documentation N Reviewer: JDQ
75
t,;' .• ".
GRI COAL GASIFICATION EH~S INFORMATION SYSTEM DOCUMENT CATALOG
STIC No. L-14487
Title: SASOL: South Africa's Oil from Coal Story -- Background for Environmental Assessment.
Corporate Author: TRW. Inc., Redondo Beach, CA Sponsor: Environmental Protection Agency
First Personal Author: Anastai, J. L. Additional Personal Authors: Publisher: Source: Volume/Number: ! Beginning Page: Document Type: Report Identifying Nos: EPA-600!8~80-002; PB80-148752
Keywords: AI0000 A11910 A 11920 821121 B25507 B26300 B32211 B33200 B43000 F20000 F80000
Project/Plant Information SASOL I SASOL II Lurgi Redisol Fischer-Tropsch synthesis Phenosolvan Coal handling and transport Solid waste disposal Engineering description Economics
Supplementary Note: Fischer-Tropsch
Summary/Comments:
Date: 01-0\)-1':';-81
Total Pages: 36
This paper conatins a brief history of BASOl and describes processing units that comprise BASOL I .. Included are typical conditions, production rates:; and equipmerl't used. The major focus is placed on Fischer-Tropsch synthesis. SABOL II is briefly described and compared with SASOL I. An economic analysis is included.
GRI Hardcopy? No Reason: Limited scope. Evaluation: Completeness 5 Referencing 5 Methodology N Documentation N Reviewer: JDQ
76
, \,."j
GRI COAL GASIFICATION EH.S INFORMATION SYSTEM DOCUMENT CATALOG
STIC No. L-21668
Title: Removal of Hydrogen Sulphide from Waste Gases at 5a501=
Corporate Author: South African Coal, Oil & Gas Corp., Ltj, Sponsor:
First Personal Author: Jurenka, K. Additional Personal Authors: Publisher: Date: (;4-00-1976 Source: Proe. Inta Confa on Air Poli.;; Univ. of Pretori-3.~ South Africa; Volume/Number: ! Beginning Page: Total Pages: 11 Document Type: Conference paper Identifying Nos:
Keywords: Al1920 B31204 B32000 C11000 C15000 C21000 D13000 F20000 F201!)!) F20600 F80000
BASOl II Stretford/Holmes-Stretford Water control processes Main process gas streams Fugitive emissions Wastewater Sulfur species Engineering description Flow shee!s Feeds, products, byproducts Economics
Supplementary Note: Source (cont'dl: April 26 - 29, 1976. Qverview of SASCL Stretford (Bischoff) program during construction, Bischoff Stretford.
Summary/Comments: Design values for BASOl Stretford (total for two units); 175,000 cu. ffi:!n Rectisol expansion gas, 53 TID sulfur produced (99.8% purity~ molten or flaked form).
GRI Hardcopy? No Reason: Summarized in Stretford Status Report IL-23288). Evaluation: Completeness ~ Referencing ~ Methodology N Documentation N Revi ewer: DAD
77
SRI COAL GASIFICATION EH.s INFORMATION SYSTEM DOCUMENT CATALOG
STIC No. L-21455
Title: Pollution Control Technical Manual for Lurgi-Based Indirect Goal Liquefaction and SNGg
Corporate Author: Radian Corp", Au.stin, TX; TRW 1 Inc: ~ 8.edD/ido B?3Ch; LP= Sponsor: Environmental Protection Agency, RTP, NC~
First Personal Author: Additional Personal Authors: Publisher: Date: ,)4-(;(;-1%:)
Source: Volume/Number: j Beginning Page: Total Pages: 651 Document Type: Report Identifying Nos: EPAt600!8-83-006; PBB3 214478.
Keywords: A11130 A11910 A12310 B21121 B25507 B26000 CI0000 C20000 C30000 F2000!) F80Qi)i) F97200
Kosovo Coal Gasification Plant, Yugoslavia SASOL I Westfield Slagging Gasifier Test Facility Lurgi Rectisol Catalytic Upgrading Gaseous streams Li qui d streams Solid streams Engineering description Economics Pollution Control Technical Manuals (PCTM)
Supplementary Note: See L-21941 for Control Technol~gy Appendices for Control Technical Manuals.
Summary/Comments:
-. - ~ .. \--;JllutlOii
Excellent coverage of available information on process modules and waste stream characteristics~ Numerous tables of chemical data, well documented, The manual proceeds through a description of the hypothetical base plant, characterizes. the waste streams produced in each medium, and diSCUSSES the array of commercially available controls which can be applied to the base plant waste streams~ From these generally characterized controls, several examples are constructed for each medium in order to illustrate typical control technology applications. Then, example control trains are constructed for each medium, illustrating the function of integrated control systems.
SRI Hardcopy? Yes Reason: Basic reference in synfuels area. Evaluation~ Completeness 9 Referencing 9 Methodology N Documentation N Reviewer: NPM
78
I~F""'1 , , I , \i,,~<
,.,," ,
, .... "1
GRI COAL GASIFICATION EH&S INFORMATiON SYSiEM DOCUMENT CATALOG
SilC No. L-02;)07
Title: Sasal Operating Experience in Large Scale Pressure Gasification~
Corporate Author: South African Coal, Oil, and Gas Corp., Ltd" Sasolburg, a.F.S. Sponsor:
First Personal Author: Tisdale, G. C. Additional Personal Authors: Publisher: American Gas Association Date: 00-00-1968 Source~ Pr!oceedings of the 2nd Synthetic Pipeline Gas Symposium Volume/Num'ber: i Beginning Page: 61 Total Pages: 13 Document ~ype: Conference paper IdentHyin!g Nos:
Keywords: A11910 B21121 B32100 B33200 F20000 F20700
Supplementary Note:
Summary/Comments:
SA SOL I Lurgi Gas liquor separation Coal handling and transport Engineering description Operating and maintenance
Brief description of SASOL I operation. The main focus is on the problems associated with gasification and gas liquor separation units and how SASOL I has tried to resolve them.
eRr Hardcopy? No Reason: Brevity. Evaluation: Completeness 5 Referencing N Methodology N Documentation N Reviewer: JDQ
79
--I
_. I
GRI COAL GASIFICATION EH.S INFORMATION SYSTEM DOCUMENT CATALOG
STIC No. L-22616
Title: The Sasel Fischer-Tropsch Processes:
Corporate Author: Sasol Technology Sponsor:
(PT'.{) Limited, Sasolburg, South
First Personal Author: Dry, Mark E. Additional Personal Authors: Publisher: Academic Press, Inc., New YorK, NY So·urce: Applied Industrial Catalysis Vol ume/Number: 2 / Beginning Page: 167 Document Type: Journal article Identifying Nos:
SASOL I Fischer-Tropsch synthesis Catalysts Engineering description Chemical reactions and mechanisms Kinetics
Date: 00-00-1983
Total Pages: 47
Keywords: A11910 826300 C36000 F200!)!) F30000 F3100!) F92000 Bibliographies and Literature Reviews
Supplementary Note: Fischer-Tropsch
Summary/Comments: Brief history and overview of SASOL I is given, along with a detailed engineering description of Fischer-Tropsch reactors. The major emphasis is placed on catalysts, mechanisms, selectivity and alternative process schemes.
SRI Hardcopy? No Reason: Too detailed. Evaluation: Completeness 7 Referencing 7 Methodology N Documentation N Revi ewer: J DQ
80
'''''' i GRI COAL GASIFICATION EH.S INFORMATION SYSTEM DOCUMENT CATALOG
STIC No. L-00677
Title: Gas from Coal with Lurgi Gasification at SASOL.
Corporate Author: SDuth African Coal, Oil and Gas Corporation, LTD~, Sasolburg Sponsor:
First Personal Author: Hoogendoorn, Jan C. Additional Personal Authors: Publisher: Institute of Ga~ Technology, Chicago! IL Date: 12-(;:)-1973 Sour-ern Proceedings of Clea.fi Fuels from Coal, ChicalJo, ILr 1973 Volume/Number: f Beginning Page: il1 Total Pages: 15 Document Type: Conference pap~r Identifying. Nos:
Keywords: Ai0000 A11910 821121 825507 B26300 B32211
Supplementary Note:
Summary/Comments:
Project/Plant Information BASOl I lurgi Rectisol Fischer-Tropsch synthesis Phenosolvan
General overall description of SABOL I operation is presented in this conference paper. Typical operating and production data are included.
GRI Hardcopy? No Reason: limited scope. Evaluation: Completeness 5 Referencing 5 Methodology N Documentation N Reviewer: JDQ
81
I ]0<,..,
GRi COAL GASIFICATION EH~S INFORMATION SYSTEM DOCUMENT CATALOG
STlC No. [,,-00612
Title: Upgrading of Coal in the South African Union.
Corporate Author: Sponsor:
First Personal Author: Graefe, Karl Additional Personal Authors: Publisher: Source: F~eiberger Forschungsh
Date: 00-00-1963
Volume/Nu~ber: A 1264 Beginning Page: 103 Total Pages: i,s Document Type: Journal article Identifying Nos:
Keywords: Ai i 910 821121 B25507 B26300 B32211 F20000 F20100
Supplementary Note:
Summary/Comments:
SASOL I Lllrgi Rectisol Fischer-Tropsch synthesis Phenosolvan Engineering description Flow sheets
This document provides a detailed description of SASOL I, incorporating DrOC2SS flow diagrams for Lurgi gasification, Rectisol and Phenosoivan processes. However, this paper has limited utility since it is written in German.
SRI Hardcopy? No Reason: Evaluation: Completeness 7 Reviewer: JDQ
Written in German. Referencing N Methodology N
82
Document;.ti on N
GRI COAL GASIFICATION EH~S INFORMATION SYSTEM DOCUMENT CAiALOG
STlC No. L-00678
Title: Experience with Fischer-Tropsch Synthesis at SASOL~
Corporate Author: South African Coal, Oil and Gas Corp:, Ltd:~ Sasclburg Sponsor:
First Personal Author: Hoogendoorn, Jan C. Additional Personal Authors: Publisher: Institute of Gas Technology Date: 12-00-1973 Sou'fee: Proceedings of Clean Fuel from Coal, Chicago, IL, 1973 Volume/Number: ! Beginning Page: 354 Total Pages: 12 Document Type: Conference paper Identifying Nos:
Keywords: A11910 B26300 F20000 F20600
SASOL I Fischer-Tropsch synthesis Engineering description Feeds, products, byproducts
Supplementary Note: Fischer-Tropsch
Summary/Comments: A general description of the SASOL I Fischer-Tropsch Synthesis is provided in this conference papera Major focus is placed on Synthol reactor scheme. A review of the operating results, product properties, scope for further development, and application for synthesis of liquids and for synthesis of light hydrocarbons are included.
SRI Hardcopy? No Reason: Limited scope. Evaluation: Completeness 5 Referencing 5 Methodology N Documentation N Reviewer: JDQ
83
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GRI COAL GASIFICATION EHlS INFORMATION SYSTEM DOCUMENT CATALOG
STIC No. l-11751
Title: Criteria for a Recommended Standard •. , Occupational E;{posures "" Coal Gasification Plants.
Corporate Author: National Institute for Occupational Safety and Health Sponsor: Environmental Protection Agency
First Personal Author: Additional Personal Authors: Publ iSher: Date: 09-01)-1978 Source:
Beginning Page: Total Pages: 195 Volume/Number: ! Document Type: Report Identifying Nos: P880-<164874j DHEWINIOSHI Publication No. 78-191
Keywords: B211)00 823(;1)0 825507 826100 Clt)i)i)O C20000 C30000 F20000 F50000 F52(1)0 F53000 F53230
Coal Basification Proc~ss~s CO shift/conversion Rectisol Methanation Gaseous streams Li qui d strea.ms Solid streams Engineering description Occupational Health and Safety Employee exposure controls Occupational hazards Toxics/hazardous materials
Supplementary Note: Occupational exposure. Criteria document. Stream characterization.
SummarY/Comments: REVISED 7/24/86. Detailed standards for occupation~l exposures in coal gasiiication plants. Includes process descriptions with potential employee hazards, monitoring and work practices, engineering controls and standard development. Numerous tables of stream characterization data for various plants (estimated and actual) as reported in public documents.
SRI Hardcopy? Yes Reason: Basic health Evaluation: Completeness 7 Referencing 7 Reviewer: DSD
84
and safety document~ Methodology N DocumentatiDn N
