DA U.S. Environmental Protection Agency Industrial Environmental Research PDA £.C\C\/~7 7fi
C r M Office of Research and Development Laboratory
Cincinnati. Ohio 45268 December 1976
ENVIRONMENTAL
CONSIDERATIONS OF
SELECTED ENERGY
CONSERVING MANUFACTURING
PROCESS OPTIONS:
Vol. III. Iron and Steel
Industry Report
Interagency
Energy-Environment
Research and Development
Program Report
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S.
Environmental Protection Agency, have been grouped into seven series.
These seven broad categories were established to facilitate further
development and application of environmental technology. Elimination
of traditional grouping was consciously planned to foster technology
transfer and a maximum interface in related fields. The seven series
are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
This report has been assigned to the INTERAGENCY ENERGY-ENVIRONMENT
RESEARCH AND DEVELOPMENT series. Reports in this series result from
the effort funded under the 17-agency Federal Energy/Environment
Research and Development Program. These studies relate to EPA's
mission to protect the public health and welfare from adverse effects
of pollutants associated with energy systems. The goal of the Program
is to assure the rapid development of domestic energy supplies in an
environmentallycompatible manner by providing the necessary
environmental data and control technology. Investigations include
analyses of the transport of energy-related pollutants and their health
and ecological effects; assessments of, and development of, control
technologies for energy systems; and integrated assessments of a wide
range of energy-related environmental issues.
This document is available to the public through the National Technical
Information Service, Springfield, Virginia 22161.
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EPA-600/7-76-034c
December 1976
ENVIRONMENTAL CONSIDERATIONS OF SELECTED
ENERGY CONSERVING MANUFACTURING PROCESS OPTIONS
Volume III
IRON AND STEEL INDUSTRY REPORT
EPA Contract No. 68-03-2198
Project Officer
Herbert S. Skovronek
Industrial Pollution Control Division
Industrial Environmental Research Laboratory - Cincinnati
Edison, New Jersey 08817
INDUSTRIAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 30402
-------
DISCLAIMER
This report has been reviewed by the Industrial Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for publica-
tion. Approval does not signify that the contents necessarily reflect the
views and policies of the U.S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute endorsement or
recommendation for use.
ii
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FOREWORD
When energy and material resources are extracted, processed, converted,
and used, the related pollutional impacts on our environment and even on our
health often require that new and increasingly more efficient pollution con-
trol methods be used. The Industrial Environmental Research Laboratory -
Cincinnati (lERL-Ci) assists in developing and demonstrating new and im-
proved methodologies that will meet these needs both efficiently and
economically.
This study, consisting of 15 reports, identifies promising industrial
processes and practices in 13 energy-intensive industries which, if imple-
mented over the coming 10 to 15 years, could result in more effective uti-
lization of energy resources. The study was carried out to assess the po-
tential environmental/energy impacts of such changes and the adequacy of
existing control technology in order to identify potential conflicts with
environmental regulations and to alert the Agency to areas where its activi-
ties and policies could influence the future choice of alternatives. The
results will be used by the EPA's Office of Research and Development to de-
fine those areas where existing pollution control technology suffices, where
current and anticipated programs adequately address the areas identified by
the contractor, and where selected program reorientation seems necessary.
Specific data will also be of considerable value to individual researchers
as industry background and in decision-making concerning project selection
and direction. The Power Technology and Conservation Branch of the Energy
Systems-Environmental Control Division should be contacted for additional
information on the program.
David G. Stephan
Director
.Industrial Environmental Research Laboratory
Cincinnati
iii
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EXECUTIVE SUMMARY
In 1973, the energy consumption in the iron and steel industry accounted
for 6% of the national total and 17% of the total industrial sector. The total
capacity of the industry is expected to grow at about 2.5% a year during the
next 15 years.
It is in the manufacture of liquid steel that one finds the main areas
where tradeoffs can be considered between energy conservation and pollution
abatement. We selected four process options for study:
Recovery of carbon monoxide from BOP (Basic Oxygen Process for
steelmaking) vessels;
External desulfurization of blast furnace hot metal;
Conversion from the wet to the dry process for quenching of coke; and
Direct reduction of iron ore.
The recovery of carbon monoxide from the BOP vessels provides the steel-
maker with a new fuel source that can supplement other gaseous fuels through-
out the steel plant. The value of the fuel can make this option economically
attractive. Moreover better efficiency in gas cleaning also tends to favor
this route. The industry is expected to adopt it widely in new facilities dur-
ing the next 15 years.
External desulfurization provides the steelmaker with a way to use higher
sulfur coke in the blast furnace or alternatively to reduce the coke rate and
limestone consumption in the blast furnace. Fugitive, air and water pollution
streams are created which are, however, similar in nature to others found in
steelmaking. They will add only a small amount to the overall pollution load
and can be easily controlled with existing technology. A preliminary economic
analysis shows this option to be economically attractive when sulfur levels
in the coke exceed about 1.2%. Some steelmakers are expected to build external
desulfurization stations as a hedge against fluctuating prices and availability
of low sulfur metallurgical coal. The iron and steel industry is expected to
adopt this new option during the next 15 years although there appears to be
question on the availability of desulfurizing reagents.
Dry quenching of coke is essentially an energy-saving option. It may be
less polluting than wet quenching, although more research is needed for an
accurate assessment. Prohibitively high capital investments do not make this
option economically attractive when the recovered energy is credited on an oil
iv
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equivalent basis. Only large integrated plants are expected to consider this
option in the future in the face of changing economic conditions such as higher
energy costs or newer technology reducing dry quenching investment requirements.
The subject of direct reduction of iron ore is a very complex one. The
most proven commercial processes use gaseous reductants and are based on
reformed natural gas or other petroleum derivatives. Gasified coal can also
be used but so far this has not proved to be economically viable. The last
major remaining alternative is the direct use of coal in a rotary kiln which
was investigated in this study. The rotary kiln-electric furnace route is more
energy consuming than the conventional coke oven-blast furnace-BOP route, but
the former allows for the potential use of lower valued coals rather than pre-
mium metallurgical coals or gaseous fuels. It also eliminates the need for a
major pollution source: the coke oven. However, it is not yet technically
proven and is not expected to be widely practiced during the next 15 years in
the United States.
This report was submitted in partial fulfillment of contract 68-03-2198
by Arthur D. Little, Inc. under sponsorship of the U.S. Environmental
Protection Agency. This report covers a period from June 9, 1975 to January
30, 1976.
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TABLE OF CONTENTS
FOREWORD ill
EXECUTIVE SUMMARY iv
List of Figures ix
List of Tables x
Acknowledgments xiii
Conversion Table xv
I. INTRODUCTION 1
A. BACKGROUND 1
B. CRITERIA FOR INDUSTRY SELECTION 1
C. CRITERIA FOR PROCESS SELECTION 3
D. SELECTION OF IRON AND STEEL INDUSTRY PROCESS OPTIONS 3
II. FINDINGS AND CONCLUSIONS 5
A. RECOVERY OF CARBON MONOXIDE FROM BOP VESSELS 5
B. EXTERNAL DESULFURIZATION OF HOT METAL 7
C. DRY COKE QUENCHING 8
D. DIRECT REDUCTION (DR) 9
E. RESEARCH AREAS 11
III. INDUSTRY OVERVIEW 12
A. INDUSTRY OPERATIONS 12
B. ENERGY UTILIZATION PATTERN 14
IV. EVALUATION OF PROCESS OPTIONS 16
A. BACKGROUND 16
B. RECOVERY OF CARBON MONOXIDE FROM BOP VESSELS 18
1. Base Line Description 18
2. BOP Off-Gas Recovery 19
3. Pollutant Emissions and Necessary Abatement 22
4. Current Adoption Status 26
5. Economics of Non-Combustion and Combustion Systems 26
vii
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TABLE OF CONTENTS (Cont.)
C. EXTERNAL DESULFURIZATION OF BLAST FURNACE HOT METAL 29
1. Sulfur Problem and Base Line Technology 29
2. Methods of External Desulfurization 31
D. DRY QUENCHING OF COKE 48
1. Description of the Base Line 48
2. Description of the Dry Quenching Process 48
3. Pollutant Emissions and Necessary Abatement 50
4. Technological Factors 51
5. Energy Considerations 51
6. Economics of Dry Coke Quenching 52
7. Current Adoption Status 53
E. DIRECT REDUCTION 54
1. The Direct Reduction Route 59
2. Pollutant Emissions and Abatement Technology 64
3. Energy Usage 78
4. Investments and Operating Costs 80
5. Adoption Status 81
REFERENCES 88
viii
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LIST OF FIGURES
Number
III-l Geographical Distribution of the U.S. Iron and Steel Industry 13
IV-1 Schematic Layout of Complete Combustion BOP Gas-Cleaning System 20
IV-2 Schematic Layout of the Non-Combustion BOP Off-Gas Recovery
System (OG Process) 20
IV-3 BOP Off-Gas Recovery without Combustion (IRSID-CAFL Process) 22
IV-4 Combination of Hot Metal Mixing and External Desulfurization 32
IV-5 Schematic Representation of the ATH Injection Process for
External Desulfurization in the Torpedo Car 33
IV-6 Flow Diagram for External Desulfurization in the Torpedo Car 34
IV-7 Relationship between Cost of Ironmaking and Sulfur in Iron 43
IV-8 Schematic View of the Soviet Dry Quenching System 49
IV-9 Block Diagram of Dry Quenching Indicating Potential for
Pollutants 51
IV-10 Production and Processing of Metallized Product, July 1974 56
IV-11 Schematic Flow Diagram of the Base Line Process for Steelmaking 57
IV-12 Schematic Flow Diagram of the Direct Reduction Route 58
IV-13 The Reduction Zone of the SL/RN Process 60
IV-14 Example of Continuous Charging System 61
IV-15 Decrease of Coke Consumption by Charging Prereduced Burden
into the Blast Furnace 63
IV-16 Increase of Blast Furnace Production by Charging Prereduced
Burden 63
ix
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LIST OF TABLES
Number Page
1-1 Summary of Energy Purchased in Selected Industry Sectors, 1971 2
II-l Summary of Costs/Energy/Environmental Aspects of Process
Options in the Iron and Steel Industry 6
III-l Major Corporate Steel Producers (1973) 14
III-2 Relative Consumptions of Energy in the United States (1973) 15
IV-1 Particle-Size Distribution of Basic Oxygen Furnace Dust 24
IV-2 Particle-Size Distribution of OG Process Dust 24
IV-3 Effect of OG Process on Composition of Basic Oxygen Furnace
Dust 25
IV-4 Comparison of Energy Usage in Non-Combustion and Total
Combustion Systems 26
IV-5 Cost Structure in New Non-Combustion System 27
IV-6 Cost Structure in New Total Combustion System 28
IV-7 Definition of the Base Line and of the External Desulfurization
Option 30
IV-8 Air Pollution Control Costs for the External Desulfurization
Station 36
IV-9 Expected Composition of Treated Scrubber Water from
Desulfurization 37
IV-10 Comparison of Treated Effluent Wastewater Load 37
IV-11 Blast Furnace Wastewater Treatment Costs 39
IV-12 External Desulfurization Incremental Wastewater Treatment Costs 39
IV-13 External Desulfurization Solid Waste Disposal Costs 40
IV-14 Summary of the Pollution Costs With and Without External
Desulfurization 40
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LIST OF TABLES (Cont.)
Number Page
IV-15 Comparison of Energy Consumption With and Without External
Desulfurization 41
IV-16 Cost Comparison Between the Two Routes 43
IV-17 Cost Structure in New Blast Furnace 44
IV-18 Cost Structure in New Blast Furnace (Reduced Coke Rate) 45
IV-19 Cost Structure in New External Desulfurization 46
IV-20 Incremental Costs Incurred by a New Dry Coke Quenching Unit 52
IV-21 Classification of Direct-Reduction Processes 55
IV-22 Definition of the Base Line and Process Option Considered for
Direct Reduction 59
IV-23 Air Pollution Control for Base Case 65
IV-24 Air Pollution Costs for Three Direct Reduction Kilns 66
IV-25 Air Pollution Control Costs for an Electric Arc Furnace Shop 66
IV-26 Total Air Pollution Cost for the Direct Reduction Route 67
IV-27 Base Case Treated Effluent Waste Load 69
IV-28 Direct Reduction Treated Wastewater Load 70
IV-29 Direct Reduction Comparison of Treated Wastewater Loads 71
IV-30 Base Case Wastewater Treatment Costs 73
IV-31 Direct Reduction Kiln .Scrubber Wastewater Treatment Costs 74
IV-32 Direct Reduction vs Base Case Comparison of Wastewater
Treatment Costs 75
IV-33 Summary of Pollution Control Costs 78
IV-34 Energy Requirements of the Conventional and Direct Reduction
Steelmaking Routes 79
IV-35 Capital Costs 80
xi
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LIST OF TABLES (Cont.)
Number Page
IV-36 Cost Structure in New Coke-Making Facilities 82
IV-37 Cost Structure in New Blast Furnace Facilities 83
IV-38 Cost Structure in New Basic Oxygen Process 84
IV-39 Cost Structure in New Sponge Iron (93% Metallized) Facilities 85
IV-40 Cost Structure in New Electric Furnace Shop 86
IV-41 Operating Costs 87
xii
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ACKNOWLEDGMENTS
This study could not have been accomplished without the support of a
great number of people in government agencies, industry, trade associations
and universities. Although it would be impossible to mention each individual
by name, we would like to take this opportunity to acknowledge the particular
support of a few such people.
Dr. Herbert S. Skovronek, Project Officer, was a valuable resource to us
throughout the study. He not only supplied us with information on work
presently being done in other branches of EPA and other government agencies,
but served as an indefatigable guide and critic as the study progressed. His
advisors within EPA, FEA, DOC, and NBS also provided us with insights and
perspectives valuable for the shaping of the study.
During the course of the study we also had occasion to contact many
individuals within industry and trade associations. Where appropriate we
have made reference to these contacts within the various reports. Frequently,
however, because of the study's emphasis on future developments with compara-
tive assessments of new technology, information given to us was of a confiden-
tial nature or was supplied to us with the understanding that it was not to be
credited. Therefore, we extend a general thanks to all those whose comments
were valuable to us for their interest in and contribution to this study.
Finally, because of the broad range of industries covered in this study,
we are indebted to many people within Arthur D. Little, Inc. for their parti-
cipation. Responsible for the guidance and completion of the overall study were
Mr. Henry E. Haley, Project Manager; Dr. Charles L. Kusik, Technical Director;
Mr. James I. Stevens, Environmental Coordinator; and "Ms. Anne B. Littlefield,
Administrative Coordinator.
Members of the environmental team were Dr. Indrakumar L. Jashnani,
Mr. Edmund H. Dohnert and Dr. Richard Stephens (consultant).
Within the individual industry studies we would like to acknowledge the
contributions of the following people.
Iron and Steel; Dr. Michel R. Mounier, Principal Investigator
Dr. Krishna Parameswaran
Petroleum Refining: Mr. R. Peter Stickles, Principal Investigator
Mr. Edward Interess
Mr. Stephen A. Reber
Dr. James Kittrell (consultant)
Dr. Leigh Short (consultant)
xiii
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Pulp and Paper;
Olefins:
Ammonia:
Aluminum:
Textiles:
Cement:
Glass:
Chlor-Alkali:
Phosphorus/
Phosphoric Acid:
Primary Copper;
Fertilizers:
Mr. Fred D. lannazzi, Principal Investigator
Mr. Donald B. Sparrow
Mr. Edward Myskowski (consultant)
Mr. Karl P. Pagans
Mr. G. E. Wong
Mr. Stanley E. Dale, Principal Investigator
Mr. R. Peter Stickles
Mr. J. Kevin O'Neill
Mr. George B. Hegeman
Mr. John L. Sherff, Principal Investigator
Ms. Nancy J. Cunningham
Mr. Harry W. Lambe
Mr. Richard W. Hyde, Principal Investigator
Ms. Anne B. Littlefield
Dr. Charles L. Kusik
Mr* Edward L. Pepper
Mr, Edwin-L, Field
Mr* John W* Rafferty
Dr. Douglas Shooter, Principal Investigator
Mr* Robert M. Green (consultant)
Mr* Edward S, Shanley
Dr* John Willard (consultant)
Dr.. Richard F. Heitmiller
Dr. Paul A. Huska, Principal Investigator
Ms. Anne B. Littlefield
Mr* J.. Kevin O'Neill
Dr. D. William Lee, Principal Investigator
Mr* Michael Rossetti
Mr* R. Peter Stickles
Mr.. Edward Interess
Dr* Ravindra M. Nadkarni
Mr. Roger E. Shamel, Principal Investigator
Mr. Harry W. Lambe
Mr*. Richard P. Schneider
Mr. William V. Keary, Principal Investigator
Mr. Harry W. Lambe
Mr. George C. Sweeney
Dr., Krishna Parameswaran
Dr. Ravindra M. Nadkarni, Principal Investigator
Dr, Michel R. Mounier
Dr, Krishna Parameswaran
Mr. John L. Sherff, Principal Investigator
Mr. Roger Shamel
Dr. Indrakumar L. Jashnani
xiv
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ENGLISH-METRIC (SI) CONVERSION FACTORS
To Convert From
To
Metre2
Pascal
Metre3
t Joule
Pascal-second
Degree Celsius
Degree Kelvin
Metre
3
Metre /sec
3
Metre
Metre2
Metre/sec
2
Metre /sec
I) Metre3
Ibf/sec) Watt
.c) Watt
Watt
Metre
Joule
Metre3
Metre
Metre
Metre
Pascal-second
Newton
Kilogram
Kilogram
Kilogram
Kilogram
Kilogram
Kilogram
Multiply By
4,046
101,325
0.1589
1,055
0.001
t"c = (t° -32)/1.8
0.3048
0.0004719
0.02831
0.09290
0.3048
0.00002580
0.003785
745.7
746.0
735.5
0.02540
3.60 x 106
1.000 x 10~3
1.000 x 10~6
0.00002540
1,609
0.1000
4.448
0.4536
0.02916
1,016
1,000
907.1
1,000
Acre
Atmosphere (normal)
Barrel (42 gal)
British Thermal Unit
Centipoise
Degree Fahrenheit
Degree Rankine
Foot
3
Foot /minute
Foot
2
Foot
Foot/sec
2
Foot /hr
Gallon (U.S. liquid)
Horsepower (550 ft-1
Horsepower (electric)
Horsepower (metric)
Inch
Kilowatt-hour
Litre
Micron
Mil
Mile (U.S. statute)
Poise
Pound force (avdp)
Pound mass (avdp')
Ton (assay)
Ton (long)
Ton (metric)
Ton (short)
Tonne
Source: American National Standards Institute, '^Standard Metric Practice
Guide," March 15, 1973. (ANS72101-1973) (ASTM Designation E380-72)
xv
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I. INTRODUCTION
A. BACKGROUND
Industry in the United States purchases about 27 quads* per year, approxi-
mately 40% of the total national energy usage.** This energy is used for chem-
ical processing, raising steam, drying, space cooling and heating, process
stream heating, and miscellaneous other purposes.
In many industrial sectors energy consumption can he reduced significantly
by better "housekeeping" (i.e., shutting off standby furnaces, better thermo-
stat control, elimination of steam and heat leaks, etc.) and greater emphasis
on optimization of energy usage. In addition, however, industry can be expected
to introduce new industrial practices or processes either to conserve energy
or to take advantage of a more readily available or less costly fuel. Such
changes in industrial practices may result in changes in air, water or solid
waste discharges. The EPA is interested in identifying the pollution loads of
such new energy-conserving industrial practices or processes and in determining
where additional research, development, or demonstration is needed to charac-
terize and control the effluent streams.
B. CRITERIA FOR INDUSTRY SELECTION
In the first phase of this study we identified industry sectors that have
a potential for change, emphasizing those changes which have an environmental/
energy impact. Industries were eliminated from further consideration if the
only process changes that could be envisioned were:
energy conservation as a result of better policing or "housekeeping,"
better waste heat utilization,
fuel switching in steam raising, or
power generation.
After discussions with the EPA Project Officer and his advisors, industry sec-
tors were selected for further consideration and ranked according to:
*Quad = 1015 Btu.
**Purchased electricity valued at an approximate fossil fuel equivalence of
10,500 Btu/kWh.
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Quantitative criteria based on the gross amount of energy (fossil fuel
and electric) purchased by industry sectors, as shown in U.S. Census
figures and from information provided from industry sources: the
iron and steel industry purchased 3.49 quads of the 12.14 quads
purchased in 1971 by the 13 industries selected for study, or 13% of
the 27 quads purchased by all industry (see Table 1-1) .
Qualitative criteria relating to probability and potential for proc-
ess change, and the energy and effluent consequences of such changes.
In order to allow for as broad a coverage of technologies as possible, we
then reviewed the ranking, eliminating some industries in which the process
changes to be studied were similar to those in another industry planned for
study. We believe the final ranking resulting from these considerations identi-
fies those industry sectors which show the greatest possibility of energy con-
servation via process change. Further details on this selection process can be
found in the Industry Priority Report prepared under this contract (Volume II) .
Among the 13 industrial sectors listed, the iron an4 steel industry
appeared in first place.
TABLE 1-1
SUMMARY OF ENERGY PURCHASED IN SELECTED INDUSTRY SECTORS, 1971
1.
2.
3.
4.
5.
A.
7.
8.
9.
10.
11.
12.
13.
Industry Sector
Blast furnaces and steel mills
Petroleum refining
Paper and allied products
Olefins
Ammonia
Aluminum
Textiles
Cement
Glass
Alkalies and chlorine
Phosphorus and phosphoric
acid production
Primary copper
Fertilizers (excluding ammonia)
1015 Btu/Yr.
3.49(1>
2.96<2>
1.59
0.984(3)
0.63<*>
0.59
0.54
0.52
0.31
0.24
0.12(5)
0.081
0.078
SIC Code
In Which
Industry Found
3312
2911
26
2818
287
3334
22
3241
3211, 3221, 3229
2812
2819
3331
287
Estimate for 1967 reported by FEA Project Independence Blueprint,
p. 6-2, USCPO, November 1974.
Includes captive consumption of energy from process byproducts
(FEA Project Independence Blueprint)
Olefins only, includes energy of feedstocks: ADL estimates
*4)Amonia feedstock energy included: ADL estimates
*5)ADL estimates
Source: 1972 Census of Manufactures, FEA Project Independence Blueprint,
USGPO, November 1974, and ADL estimates.
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C. CRITERIA FOR PROCESS SELECTION
In this study, we focused on identifying changes in the primary production
processes which have clearly defined pollution consequences. In selecting
those to be included in this study, we considered the needs and limitations of
the EPA as discussed more completely in the previously mentioned Industry
Priority Report. Specifically, energy conservation is broadly defined to
include, in addition to process changes, conservation of energy or energy form
(gas, oil, coal) by a process or feedstock change. Natural gas has been con-
sidered as having the highest form value of energy, followed in descending
order by oil, electric power, and coal. Thus, a switch from gas to electric
power would be considered energy conservation because electric power could be
generated from coal, whose reserves in the United States, in comparison to
natural gas, are abundant. Moreover, pollution control methods resulting ,in
energy conservation have been included within the scope of this study. Finally,
emphasis was placed on process changes with near-term rather than long-term
potential within the 15-year span of time of this study.
In addition to excluding from consideration better waste heat utilization,
"housekeeping," power generation, and fuel switching, as mentioned above, cer-
tain other options were excluded to avoid duplication of work being funded
under other contracts and to focus this study more strictly on "process
changes." Consequently, the following have also nojt been considered to be
within the scope of work:
Carbon monoxide boilers (however, unique process vent streams yield-
ing recoverable energy could be mentioned);
fuel substitution in fired process heaters;
mining and milling, agriculture, and animal husbandry;
substitution of scrap (such as iron, aluminum, glass, reclaimed tex-
tiles, and paper) for virgin materials;
production of synthetic fuels from coal (low- and high-Btu gas,
synthetic crude, synthetic fuel oil, etc.); and
all aspects of industry-related transportation (such as transporta-
tion of raw materials).
D. SELECTION OF IRON AND STEEL INDUSTRY PROCESS OPTIONS
Within each industry the magnitude of energy use was an important crite-
rion in judging where the most significant energy savings might be realized,
since reduction of energy use reduces the amount of pollution generated in the
energy production step. Guided by this consideration, candidate options for
in-depth analysis were identified from the major energy-consuming process steps
with known or potential environmental problems.
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After developing a list of candidate process options, we assessed sub-
jectively the:
pollution or environmental consequences of the change,
probability or potential for process change, and
energy conservation consequences of the change.
Even though all of the candidate process options were large energy users,
there was wide variation in energy use and estimated pollution loads between
options at the top and bottom of the list. A modest process change in a major
energy-consuming process step could have more dramatic consequences than a more
technically significant process change in a process step whose energy consump-
tion is rather modest. Process options were selected for in-depth analysis
only if a high probability for process change and pollution consequences in the
alternative process steps was perceived.
Because of time and scope limitations for this study, we have not attempted
to prepare a comprehensive list of process options, or to consider all economic,
technological, institutional, legal, or other factors affecting implementation
of these changes- Instead, we have relied on our own background experience,
industry contacts, and the guidance of the Project Officer and EPA advisors
to choose 16 reasonably promising process options (with the emphasis on near-
term potential) for analysis.
After discussion with the EPA Project Officer, his advisors, and industry
representatives, we narrowed the list of candidates to four:
Recovery of carbon monoxide from BOP (basic oxygen process) vessels,
External desulfurization of blast-furnace hot metal,
Conversion from wet to dry coke quenching, and
Direct reduction of iron ore.
We discarded options, for example, if it appeared that:
the technology seemed to have limited use in terms of the type of
product produced and the expected production volume, or
the practice of the technology implied a manifestly unattractive
pattern of energy consumption.
Recognizing that capital investments and energy costs have escalated
rapidly in the past few years and have greatly distorted the traditional basis
for making cost comparisons, we developed costs representative of the first
half of 1975 using constant 1975 dollars for our comparative analysis of new
and current processes.
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II. FINDINGS AND CONCLUSIONS
The main characteristics of the four options analyzed in depth are sum-
marized in Table II-l.
A. RECOVERY OF CARBON MONOXIDE FROM BOP VESSELS
The basic oxygen process (BOP) off-gases consist largely of carbon mon-
oxide and are thus highly combustible. In conventional practice, since there
is no provision to prevent air from entering, these hot gases combust spontan-
eously in the gas-collecting hood.
Non-combustion systems prevent this air infiltration; they cool and clean
the CO-rich gases without burning them and thus make them available as a gaseous
fuel for general purpose.
Two U.S. firmsAmerican Air Filter in Louisville, Kentucky and Chemico
in New York Cityoffer engineered collection systems. The former offers a
system based on a French process (IRSID-CAFL)* and the latter one is based on a
Japanese process (OG).**
The main findings relating to carbon monoxide collection are:
The recovered gas has a heating value of about 200 to 250 Btu/scf.***
This represents about 0.4 to 0.5 x 10^ Btu per ton of raw steel.
In recent years more than 100 CO collection installations have been,
or are being, built largely in the United States, Europe and Japan.
In the United States the gas recovered from 59 reported non-combustion
systems (Stone 1976) is temporarily flared rather than utilized.
The dust content in the CO collection system is less oxidized than
in the conventional combustion system, contains a smaller percentage
of submicron particles, and is easier to collect. Treatment of water
used in scrubbing is facilitated because of the more rapid settling
characteristics that result. Solid waste disposal methods are
unaffected.
*IRSID-CAFL - Institut de Recherche de la Siderurgie-Compagnie des Atelias
et Forges de la Loire.
**OG = oxygen converter gas recovery process.
***scf = standard cubic foot.
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TABLE II-l
SUMMARY OF COSTS/ENERGY/ENVIRONMENTAL ASPECTS
OF PROCESS OPTIONS IH THE IRON AND STEEL INDUSTRY
PROCESS OPTION
Process/
Factor
Recovery of Carbon Monoxide
from BOP Vessels
External Desulfurization
of Blast-Furnace Hot-Metal
Conversion of Hot Coke Quenching
from the Wet to the Dry Process
Direct Reduction
Environment
1) easier particulate collec- Virtually no change in
tion steel plant overall
2) easier treatment of scrubber emissions.
water
3) solid waste disposal un-
affected
1) Eliminates emissions from the
wet quenching process.
2) Additional potential for part-
iculate emission, but control
of such emissions is part of
dry-quench design.
Absence of the coke ovens
points toward significant
reduction in pollutant emissions.
Pollution Control Costs
Fixed Investment
Operating Costs
$ 4.40 vs $ 2.70
$ 0.66 vs $ 1.12
per ton of steel
if 6.32 vs $ 5.65
$ 4.42 vs $ 4.57
per ton of hot metal
U.S.
U.S.
$ 11.57 vs $ 17.41
$ 7.94 vs $ 9.26
per ton of steel
Energy
Makes available 0.44 x 10
Btu/ton of steel in the form
of a combustible gas. (220
Btu/Scf.)
Allows shift from low-
sulfur to higher-sulfur
metallurgical coal.
Energy credit from the partial
recovery of the sensible heat
of the incandescent coke.
However, less breeze is made
available for sintering, etc.
Less efficient process,
but permits use of abundant
non-metallurgical coal.
Economics
Process Economics
Fixed Investment
Operating Costs
Necessity of a gas holder
results in higher capital
costs. Operating costs are
lower because of energy
credit.
(see pollution control costs)
(see pollution control costs)
Main capital expenditure
is for pollution control
equipment. Main operating
expenditure is for the de-
sulfurizing agent. Eco-
nomically favored when the
sulfur content of the coke
is greater than 1.2%
N.S.
N.S.
Capital and operating costs
significantly higher than
for wet quenching.
Economics would favor DR
mini-mills if the technology
were reliable enough for the
process to operate according
to specifications.
$ 9.5 (incremental)
$ 1.18 (incremental)
per ton of coke
$ 151.92 vs $ 135.09
$ 147.83 vs $ 143.40
per ton of steel
Remarks - Fixed investment costs are given in US dollars per annual ton of capacity
- Operating costs are given in US dollars per ton of product, including 20% pretax ROI.
- Costs are given as cost of option versus cost of base line, unless otherwise stated
- N.S. - Non Significative
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Compared with a total combustion system, the CO collection system
with a gas holder will cost about 60% more in capital, mainly because
of the need for a separate and independent hood and scrubber for each
furnace.
If the collected gas can be utilized and credited at $2/million Btu,
the non-combustion collection system offers lower operating costs
than the conventional BOP pollution control equipment.
The cyclic pattern of generation, the need for a gas holder of
several million cubic feet capacity or larger, the land needs asso-
ciated with the gas holder, and the logistical problems in piping a
collected gas to end-users combine to make industry regard this
source of fuel gas as supplemental to its other fuel sources.
In view of these findings, the iron and steel industry is expected to
implement non-combustion and recovery of the fuel value in BOP off-gases in
the new installations built over the next 15 years. A large proportion of the
remaining open-hearth capacity will be replaced by BOP, and the total capacity
of the industry will increase at an average rate of about 2.5%/yr. Thus, by
1990 industry BOP capacity may be expected to increase 80-100 million tons
above the level in 1973. A significant fraction of such capacity can be
expected to be achieved by "rounding out" (i.e., capacity increases achieved
by going from a two-vessel to a three-vessel BOP shop). Logistical factors,
such as plant layout and existing facilities, are likely to have a major
influence on the actual number of plants adopting the non-combustion recovery
system.
B. EXTERNAL DESULFURIZATION OF HOT METAL
This additional step is an alternative method of controlling the sulfur
content of blast furnace hot metal. In conventional practice, blast furnace
sulfur content is completely controlled by adding limestone to form a sulfur
bearing slag and by limiting the sulfur content of the metallurgical coke.
External desulfurization is achieved by injecting sulfur retaining reagents
(e.g., calcium or magnesium compounds in an inert gas such as nitrogen) into
high sulfur hot metal from a blast furnace. These compounds form a sulfide
slag that must be skimmed off prior to charging the hot metal into the BOP. Use
of external desulfurization either permits limestone and coke rates to be
reduced, or alternately allows the sulfur content in the coke to be increased
without increasing the limestone charge to the blast furnace. An experimenta-
tion period to establish operating conditions specific to each plant seems
appropriate, despite considerable experience with this practice overseas.
The main findings relating to external desulfurization follow:
Fugitive, air, and water pollution problems are created. They are,
however, similar in nature to other pollutants found in steelmaking.
Moreover, they add only a small increment to the overall steelmaking
pollution load and can be controlled with existing technologies.
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The sulfur content in finished steels, according to changing specifi-
cations, are decreasing slowly with time. Bulk contents ranging from
0.025-0.030% are common nowadays. This sulfur level depends on the
amount of sulfur entering the blast furnace and on the fluxing prac-
tice adopted in running the blast furnace. An important decision
parameter, therefore, is the quality of the coke (or coal) supply
available to each plant. When the coke contains more than 1.2 - 1.5%
sulfur, we believe that external desulfurization becomes economical.
Aside from coke-rate implications, external desulfurization permits
a better consistency to be obtained in the sulfur level of the hot
metal charged to the BOP, thereby smoothing the steelmaking operation
and increasing its yield.
From an energy usage viewpoint, this option allows substitution of
higher-sulfur metallurgical coal for less plentiful low-sulfur metal-
lurgical coal, thus expanding the domestic reserves.
In view of these findings, several external desulfurization installations
can be expected to be built during the next 15 years. The driving force is a
gradual increase in the sulfur content of available metallurgical coals.
C., DRY COKE QUENCHING
This option is an alternative to wet quenching involving a water quench
to cool the incandescent coke. In dry coke quenching, the coke is cooled by
an inert gas stream. The sensible heat transferred to the inert gas can then
be partially recovered for useful purposes.
The facilities involved in either method of quenching are physically
separate from the coke ovens in that the incandescent coke is pushed from the
oven and falls into a tracked car in which it is transported to the quenching
area.
The main findings relating to dry quenching are:
There are no such installations in the United States. Dry quenching
of coke is practiced to some extent in the U.S.S.R. One company, the
American Waagner Biro Company of Pittsburgh, designs and offers to
install dry-quenching facilities through an associated engineering
firm. Both the Russian design (offered by Licensintorg) and the
Austrian design (American Waagner Biro) are based on an old Sulzer
Bros, process (Hersche, 1946).
There has been acceptance that when clean water is used in wet quench-
ing the magnitude of the air emissions is significantly reduced,
perhaps to the point where these can meet anticipated standards.
According to Linsky (1975), dry quenching is claimed by Russian
authors to produce a higher-grade coke, thus reducing the coke rate
in the blast furnace. However, this claim needs to be demonstrated
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for U.S. coals. In addition, less production of coke breeze is
claimed for dry quenching, thus increasing the coke yield. A research
program would be appropriate to verify these claims. Thus the only
demonstrated benefit of dry coke quenching to date is the significant
amount of energy recoverable.
The physical installation is more complex than that for wet quenching,
and this complexity increases the capital cost significantly. The
difference between a dry coke-quenching station with the associated
tracked vehicle and a wet coke-quenching station is about $7 million
for an annual production of 1 million tons of coke. Moreover, it
appears that a standby coke-quenching station would have to be avail-
able to ensure reliable operations. This requirement could add
another $2.5 million to the capital cost if the less costly wet quench
unit is chosen as the standby unit. Only very large plants, using
several quenching towers, could waive the requirement for a standby
coke-quenching unit.
Therefore, the iron and steel industry probably will not adopt dry quench-
ing of coke on any significant scale during the next 15 years. This situation
could change if the economics of the process can be improved or it can be demon-
strated that dry quenched coke measurably reduces blast furnace coke rates.
Supporting experimental evidence so far is lacking.
D. DIRECT REDUCTION (DR)
New iron units (oxide pellets, lump ore, etc.) can be partially reduced
in the solid state by reaction with a reducing gas mixture (CO and H2> at tem-
peratures ranging from 1470 to 2000°F. These prereduced materials are called
sponge-iron or metallized materials, because up to 95% of their iron content
is in the metallic state. They can partially or wholly replace purchased scrap
in the steelmaking electric arc furnace. (The prereduced pellets may also be
charged to the blast furnace to increase its productivity or be used in the
oxygen steelmaking shop in lieu of scrap and as a cooling agent.) Many firms
will design, engineer, and construct direct reduction plants; and interest in
making steel by this route is intense worldwide.
The main findings related to direct reduction are:
The most advanced direct reduction technology is based on the use of
natural gas or a petroleum-based hydrocarbon as the energy source.
Technology based on coal, employing the rotary kiln, is also avail-
able (SL/RN*, Krupp, etc.), but demonstration on an industrial scale
for acceptance in the United States is still at least several years
away. A successful large demonstration is vital for widespread
application of this technology in the United States.
*SL/RN = Stelco-Lurgi/Republic Steel, National Lead.
9
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The alternative use of coal for direct reduction purposes would be
a gas-oriented process utilizing a coal gasification step to produce
the necessary high-temperature reducing gases. Although the tech-
nological approaches are clear and research and development are
active, commercial demonstration of this alternative lies further in
the future because it has not proven economically attractive.
The direct-reduction electric-furnace steelmaking route eliminates
dependence on metallurgical coal, but consumes a larger quantity of
energy per ton of steel than the blast furnace-coke oven-basic oxygen
furnace route. Its energy conservation potential is one of form
rather than quantity.
Pollution control problems with the direct-reduction electric-furnace
route are generally less severe than with the blast-furnace route.
A major factor in this respect is the elimination of the need for
coke ovens.
The two routes (conventional coke oven-blast furnace-BOP vs. direct
reduction-electric furnace) are about equally costly, in terms of
both capital and operating expenses. Transportation costs and other
site-specific economic conditions, together with reliability expecta-
tion differences, presently favor the traditional approach for the
bulk of the steel industry. Because these total cost estimates are
relatively small differences between large numbers, it will be worth-
while to re-examine this judgment periodically.
The installation of a direct-reduction-electric furnace steelmaking
sequence in the iron and steel plant may add flexibility in meeting
changes in demand and decrease dependency on fluctuations in scrap
prices.
Certain locations in the world have the potential for low-cost manu-
facture of semi-finished products via direct reduction and electric
furnace steelmaking, e.g., Venezuela with iron ore and surplus
natural gas resources and the Middle East with surplus natural gas
resources. Long-distance movement of metallized pellets, or even of
semi-finished products in international trade, could become of major
importance in facilities planning within the next 15 years.
The use of partially metallized pellets in the electric furnace would
produce a net increase in electricity consumption per ton of produc-
tion as compared to all-scrap practice, because of the need to melt
the oxide content of the pellet and to add lime to flux the gangue.
The saving in energy consumption permitted by continuous charging of
the pellets does not entirely compensate for this.
In view of these findings, the industry should be expected to treat the
subject of direct reduction and the production of metallized iron units
cautiously. It may be more realistic to expect that the U.S. industry within
the next 15 years will import increasing quantities of metallized or partially
reduced pellets. While a few plants may be built, the prospects for large-scale,
direct-reduction processing in the United States within the next decade do not
look optimistic.
10
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E. RESEARCH AREAS
Five specific areas have been identified in this study where additional
research is needed:
1. The possibility of cyanide formation under the following circum-
stances should be investigated:
injection of nitrogen during external desulfurization of hot
metal, and
continuous recirculation of a CO-N2 mixture over incandescent
coke during dry quenching.
2. Quantitative measurements of fugitive and source emissions of carbon
monoxide with non-combustion BOP gas collection systems should prove
the acceptability of these hoods, including those taken during the
transition periods at the beginning and the end of the blow, when
the off-gases are not collected as a fuel.
3. A comparison of available equipment (lances, bells, etc.) for exter-
nal desulfurization should be made to determine the economics and
exact nature of the gaseous effluents as a function of the desulfur-
izing reagent used. The availability of desulfurizing agents (calcium
carbide, magnesium, etc.) and the pollution/energy implications for
industries supplying these products should not be neglected.
4. An increase in the quality of coke due to dry rather than wet quench-
ing has been reported in the Russian literature. Should this be the
case, a more efficient operation of the blast furnace would result
and allow substantial savings, both in terms of coke rate and furnace
productivity. A demonstration program is needed to substantiate this
claim using U.S. coals.
5. The chemistry of the rotary kiln (e.g., SL/RN) is still not well-known.
The pollution implications mentioned in this study are "best engi-
neering judgment" and lack actual proof. The composition of the
off-gases and the leaching properties of the coal, ash, and fine
metallic discarded particles should receive the attention of research
organizations.
11
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III. INDUSTRY OVERVIEW
A. INDUSTRY OPERATIONS
Although its share of world production has decreased, the United States
has consistently ranked first or second among the world producers of steel.
In 1950, the United States produced almost 50% of the world steel supply, but
by 1973 its share had shrunk to barely 20%. During that same period, however,
production increased from 90-100 million tons to about 150 million tons of raw
steel.
The United States lost its self-sufficiency in iron ore production about
the end of World War II, and imports have risen since to recent levels equiva-
lent to almost 50% of domestic production, i.e., almost a third of domestic
consumption of iron ore. The nation, however, is self-sufficient in the pro-
duction of metallurgical coals needed for coke production and, in fact, is a
major exporter of metallurgical coals to foreign steelmaking centers. The
major fluxes for slagging the nonmetallic content, limestone, and dolomite are
in adequate supply.
The industry comprises some 400 steel production and fabrication plants
employing more than 500,000 people in 37 states. About 130 of these plants
produced 146 million short tons of raw steel in 1974. The remainder are steel
rerolling, finishing, fabrication plants. These figures exclude the mining
operations for the raw materials and transportation and warehousing operations
associated with the consumption of finished products. Figure III-l shows the
geographical distribution of the U.S. iron and steel industry. The major
concentration of the industry operations occurs in the Ohio River Valley and
states bordering the Great Lakes.
Ten major corporations accounted for about 80% of U.S. steel production
in 1973. The largest of them, U.S. Steel Corporation, accounted for 23.2% of
the national total, while the smallest in this group accounted for 2.1%. The
details are shown in Table III-l. About half of the production in the "all
others" category may be attributed to 19 smaller companies.
Two technological approaches are employed in the manufacture of raw steel,
one using iron ore and one using scrap. In the iron ore-based technology, the
blast furnace burns coke to produce iron in molten form as a high-carbon con-
tent hot metal which is further refined to steel by the selective oxidation 6f
its impurities in a steelmaking furnace and by alloying additions. The molten
steel is then cast as desired for rolling. Fluxes are added in the blast
furnace to combine with the nonmetallic content of the iron ore to produce a
molten slag. In 1974, about 80% of the raw steel was produced with this
technology.
12
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U)
Legend:
RAW STEEL - Producing Centers
" IRON ORE - Deposits Currentiv or Recently
Minod or Presently Being Developed
COKING COAL - Coked at Present Time ot
Has Been Coked in the Past
SOURCE: Arthur D. Little and American Iron and Steel Institute, "Geography of Iron and Steel in the United States."
Figure III-l. Geographical Distribution of the U.S. Iron and Steel Industry
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TABLE III-l
MAJOR CORPORATE STEEL PRODUCERS
(1973)
Raw Steel Total National
Company Production Production
(million tons) CQ
United States Steel Corporation 34.97 23.2
Bethlehem Steel Corporation 23.70 15.8
National Steel Corporation 11.32 7.5
Republic Steel Corporation 11.29 7.5
Armco Steel Corporation 9.46 6.3
Inland Steel Company 8.16 5.4
Jones and Laughlin Steel Corp. 7.99 5.3
Youngstown Sheet and Tube Co. 5.85 3.9
Wheeling Pittsburgh Steel Corp. 4.41 2.9
Kaiser Steel Corporation 3.17 2.1
All others 30.10 20.1
Total U.S. Production 150.42 100.0
Source: Steel Industry Financial Analysis for 1973, Iron Age
The scrap-based technology accounts for about 20% of the steel made in
the United States. It uses selected iron and steel scrap in electric arc
furnaces. In addition, a newer technological development involves directly
reducing lump ore or pellets to provide a synthetic scrap for electric furnaces.
B. ENERGY UTILIZATION PATTERN
The U.S. steel industry uses about 6% o'f all the energy consumed in the
nation, or 17% of the total industrial energy requirements (see Table III-2).
About 24 x 10 Btu are consumed in the production of a net ton of raw steel.
Thus, the total energy consumption required to produce 150 million tons of raw
steel in 1973 was 3.6 x 1015 Btu (3.6 quads).
Coal is the major fuel consumed in the U.S. steel industry; specifically,
coals suited to the preparation of coke for the blast furnace. In 1974, about
90 million tons of coal were consumed by the industry. As energy byproducts
the production of coke yields a gaseous fuel (coke-oven gas), plus liquid tars
and pitches.
In addition to coal, the industry purchases natural gas, fuel oil, and
electricity. About 17% of -the energy consumption in 1973 was natural gas, 5%
purchased electricity, and 1.5% fuel oil. Coal and coal-derived fuels accounted
for the balance. The recent changes in fuel prices and availability are gen-
erating pressures to use more coal wherever this is technically feasible.
14
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TABLE III-2
RELATIVE CONSUMPTIONS OF ENERGY IN THE UNITED STATES (1973)
Percentage
10 Btu
(quads) of Nation of Industrial
Total Nation 75.560 100.0
Total Industrial 21.357 28.2 100.0
Steel Slabs from Ore 3.072* 4.1 14.4
Aluminum Ingots 1.120 1.5 5.3
Portland Cement 0.646 0.9 3.0
Gray Iron Castings 0.365 0.5 1.7
Copper Cathodes and Shapes 0.271 0.4 1.3
Glass Containers 0.217 0.3 1.0
Magnesium Metal 0.042 0.1 0.2
*The 3.072 x 10!5 figure is based on an average energy consumption of 24 x 106
Btu and 1973 production of 128 million tons. The tonnage discrepancy may be
accounted for in the definition of crude steel and slabs from ore.
Source: Arthur D. Little, Inc., estimates.
The major consumption bf energy occurs in the reduction of the iron ore to
remove its oxygen content. This process step in the blast furnace sequence
accounts for about 75% of the energy consumption per ton of raw steel. If the
iron ore is directly reduced rather than smelted in the blast furnace, and the
product is then smelted in an electric furnace to produce crude steel, the
energy consumption increases substantially as discussed in Chapter IV. On the
other hand, selected lower valued steam coals may be the basis for direct-
reduction/electric-furnace steelmaking, whereas high valued metallurgical coals
are a prerequisite for the blast-furnace method. Thus, fuel form, price, and
availability may characterize energy conservation rather than actual consump-
tion as energy units.
The two major sources of recycled fuel gas within the steel manufacturing
complex are: coke-oven gas, a sulfur-containing, medium-Btu fuel gas pro-
duced in the manufacture of coke; and blast-furnace gas, a low-sulfur, low-Btu
value fuel. A portion of the coke-oven gas is often utilized to provide the
heat input to the ovens in which the coking reactions occur. A large portion
of the blast furnace off-gas is employed to preheat the blast air in the regen-
erative stoves and fire the coke ovens. Gas streams not used in these processes
may provide fuel for reheating and soaking furnaces or for the boiler house. Tar
and pitch produced as byproducts from coke-making operations can be either sold
or used as a fuel (e.g., by injection in the blast furnace).
15
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IV. EVALUATION OF PROCESS OPTIONS
A. BACKGROUND
The major process steps in iron and steelmaking are: agglomeration of
iron ore, cokemaking, blast furnace production of hot metal (molten pig iron),
refining of the hot metal in a steelmaking furnace, and casting. The solidi-
fied product is then heated, rolled, heat-treated and, at times, coated to
form a wide variety of end-products, such as steel plate, heavy structurals,
rails, wire and wire products, cold finished bars, seamless pipe and tube,
welded pipe, hot rolled sheet and strip, galvanized products, tin plate, and
other plated products.
Although energy-conservation measures will prompt process changes in the
steel-forming step, the major pollution consequences arising from process
changes will be felt in the raw steelmaking sequence.
In addition to the integrated steel industry, which manufactures semi-
finished and finished products from virgin raw materials supplemented by
scrap, there is a semi-integrated industry based upon the electric furnace,
which uses scrap as a raw material and manufactures the same type of prod-
ucts. The major pollution problems of this industry are associated with
the electric furnace. These problems are discussed in connection with the
melting of synthetic scrap made by the direct reduction process.
Of the many processes considered in the iron and steelmaking industry,
the following four were chosen for analysis:
Recovery of carbon monoxide from the basic oxygen process (BOP)
vessel for its fuel value,
Dry quenching of coke,
Direct.,reduction of iron ore, and
External desulfurization ofxblast furnace hot metal.
To compare the pollution characteristics, energy consumption, and
economic attractiveness of these newer technological options, we developed
a base line technology for each process option. Recognizing that there may
be differences of opinion about the proper selection of a base line tech-
nology, we chose to define the smallest process sequence that would be a
clear-cut design alternative, starting with similar raw materials and
finishing with similar products. Thus, for the four process options selected,
the base line technologies were defined as follows:
16
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Recovery of Carbon Monoxide from BOP Vessels. We chose the conventional
practice of burning the gas issuing from the BOP vessels in the collecting
hood and then scrubbing the burned gases to remove particulates. The
fuel value of the BOP off-gas is, therefore, lost in the base line. In
the alternative process investigated, the COcontaining gases are pre-
vented from burning, cleaned, and collected for their fuel value.
Dry Quenching of Coke (starting with hot coke as it is pushed from the
coke oven). The base line technology chosen was the conventional wet
quenching of coke. In both cases the coke is cooled to close to ambient
temperature.
Direct Reduction. We chose the conventional coke oven-blast furnace-BOP
vessel route for the base line. The direct reduction route includes the
direct reduction units and electric furnaces. We started with iron ore
pellets and finished with molten steel in both cases, with the same
amount of scrap being reciirculated to the steelmaking furnaces. We
might have considered a direct reduction-blast furnace-BOP route.
External Desulfurization of Blast Furnace Hot Metal. Because of a
growing demand for low-sulfur metallurgical coal, there has been con-
siderable pressure to use higher-sulfur metallurgical coals for making
coke. The most meaningful way of evaluating the desulfurization process
would include:
Establishing a base line technology whereby the blast furnace
uses low sulfur coke (say, 0.8% S) and produces 2.6 million
tons of hot metal annually, while meeting sulfur specifications
(0.025% S in hot metal).
Considering as an alternative technology the same blast furnace
using a higher sulfur coke (say, 1.2% S) and producing also
2.6 million tons of hot metal per year. All other things being
equal, the sulfur content of the hot metal would be higher
(0.050%). To reduce this sulfur content, an external desulfuri-
zation station would be considered.
Because of the unprecedented recent demand for low-sulfur coal, it has
become a premium-priced commodity compared to other coals being sold on the
market. Premiums that are being paid for such low-sulfur coal depend upon the
geographical considerations within the United States, demand for such low-
sulfur coal in the industrial and utility sectors, the need of a steel company
to get maximum productivity out of existing blast furnaces which, in turn,
depends upon the demand for steel in a given year, and the like. Thus,
setting a long-term value on coal depending upon sulfur content is a rather
difficult exercise. Prices and price differences existing today would have
probably little significance in the long term. Thus, to demonstrate that
external desulfurization is an economically viable process to be considered
when sulfur levels in the coke rise to 1.2% or higher, we chose an alterna-
tive way to indicate the competitive nature and economics of external
desulfurization.
17
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For purposes of this study, we assumed that a blast furnace designer
would have two methods of coping with the higher-sulfur coals: (a) design
a blast furnace for a given production of hot metal to accommodate a suffi-
cient limestone fraction in the burden so the sulfur specifications would be
met in the blast-furnace hot metal as tapped (0.025% sulfur), or (b) design
a slightly smaller furnace with smaller limestone and coke rates and desul-
furize the hot metal partially in the blast furnace (0.050% sulfur as tapped)
and partially outside of the blast furnace, bringing the sulfur content to
the 0.025% specification. Such a process is known as external desulfurization.
While such an approach has its deficiencies, it provides a clear and con-
sistent basis for comparing the economics of both options while using the
same type coal for both base line and alternative process.
Each of these four process options was then evaluated on the basis of
its energy conservation potential and the impact on pollution control that
its implementation would generate. Capital and operating costs were developed
and compared with the base line for both production and pollution equipment.
In each of the above comparisons, the focus was on new installations,
even though many of the applications might be in old facilities (retrofitting).
In older facilities the economic attractiveness depends upon the specific
plant situation, location of the facilities within the plant, the amount of
available land, logistical problems, and the like. Hence, it is difficult
to generalize about the applicability of such processes to older facilities
without doing a plant-by-plant analysis for each steel mill in the United
States.
B. RECOVERY OF CARBON MONOXIDE FROM BOP VESSELS
1. Base Line Description
Our base line is a complete combustion system. The gases issuing from
the mouth of the furnace are collected in a hood with a considerable infil-
tration of air, burned in the hood, and cooled and cleaned of particulates
before being released to the atmosphere. The hood is steam- or water-cooled.
The hot gases leaving the basic oxygen furnace have a calorific value of
approximately 350 Btu/scf and after collection and cooling will have a value
of about 200-250 Btu/scf. In the United States, however, steelmakers have
had little incentive to recover this heat, because they have had an adequate
supply of inexpensive fuel. Thus, until 1961, most BOP installations used
panel-type hoods that cool hot gases, but have no provision to recover the
waste heat for reuse. More recently, a significant proportion of newer
installations have utilized pressurized hood systems with membrane tube con-
struction. These lend themselves to increased cooling water temperatures,
or the generation of steam. However, waste heat recovery in the form of
steam from these gases is difficult because the gas flow from the basic
oxygen process is intermittent.
18
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Although either electrostatic precipitators or wet scrubbers can be used
for cleaning combustion products, fire and explosion hazards make the electro-
static precipitator system unsuitable for the collection of the carbon monoxide
off-gas. Therefore, to ensure consistency in analysis, both base line and
alternative technology include a wet scrubber system.
With conventional membrane hoods, the gases from the basic oxygen fur-
nace are cooled to 1850°F and quenched in a venturi scrubber where they are
further cooled to approximately 170°F. The quenched gases immediately enter a
separating elbow where most of the liquid is separated from the gas stream.
They are then led through a refractory-lined duct to the venturi scrubber.
The scrubber is equipped with restricted throats which maintain a pressure
drop in the range of 40 to 65 inches of water. The cleaned gas contains less
than 0.05 grain of dust per cubic foot (0.11 gm/m^). The cleaned gases leaving
the scrubbers pass through an extraction fan and stack to the atmosphere.
The water treatment circuit consists of a thickener, a cooling tower,
and a filter. The dust entrained in the water settles out as a sludge.
Normally the cleaned water will contain less than 5 grains per gallon (100 mg/
liter) of suspended solids. (Some steel companies claim less than 1 grain/
gallon in the cleaned water.)
The schematic layout of such a plant is shown in Figure IV-1.
2. BOP Off-Gas Recovery
The BOP off-gas recovery systems collect and recover CO gas without com-
bustion. The two prominent systems are the OG process and the IRSID-CAFL
process.
a. The OG System
Figure IV-2 presents a schematic layout of an OG system. The gap between
the vessel mouth and the collecting hood is minimized by a movable skirt. In
the initial OG design, any space remaining between the skirt and the mouth of
the furnace was closed off by a nitrogen seal. In recent installations, no
nitrogen curtain seal is used. The space between the skirt and the vessel's
mouth is closed as much as possible by lowering the skirt into the furnace
nose section. During the oxygen blow, a slight negative pressure is main-
tained inside the hood.
In the process described ,by Rowe (1970), the skirt is attached to the
lower section of the hood which subsequently leads the gases into the cooler.
The upper section, which is equipped with the flux chute hole and the oxygen
lance entry hole, is mounted on a carriage and may be moved away from its
operating position to facilitate entry of the brick relining elevator. The
necessary process fluxes are added to the BOP during the oxygen-blowing
period through a system of gas seals.
19
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I HIST ELIMINATOR I
I
(FAN }
Figure IV-1. Schematic Layout of Complete Combustion
BOP Gas-Cleaning System
IVENTURI
SCRUBBER
T
I SLBOWSSPAHAT
/INDUCED*
I OBAFT
.FAN ,
TO GAS HOLDER ' ^ TO STACK
Figure IV-2. Schematic Layout of the Non-Combustion BOP
Off-Gas Recovery System (OG Process)
20
-------
The gases pass through the upper section of the hood at a temperature
of 2300°F and are cooled to approximately 1850°F in the hot gas cooler before
entering the gas cooling plant. The gas-cooling section consists of a series
of nested tubes supported in a mild steel, circular outer jacket. The wet
scrubber used to clean the gas from the OG system is similar to that used in
a plant with complete combustion.
The gases leaving the radiant section of the hood pass into a venturi
quencher where they are cooled to an outlet temperature of about 170°F. At
the same time, some 85% of the dust entrained in the gases is removed. The
cooled gases leaving the venturi quencher pass through an elbow separator into
a variable-throat venturi scrubber.
The adjustable throat acts both as a highly efficient dust-collecting
unit and as a means of controlling the pressure in the waste gas hood. This
system maintains a constant hood pressure during the oxygen blow by opening
and closing the movable throat inside the venturi. The dust particles remaining
in the waste gases after leaving the quencher are removed in the venturi scrub-
ber. Finally, the cleaned gases pass through a second elbow separator and
through a mist eliminator before being piped away as a clean fuel.
b. The IRSID-CAFL Process
The IRSID-CAFL process, described by Manbon (1973), is quite similar in
concept to the OG process in that gas combustion is prevented by regulating
the draft precisely. The gas collection equipment is comprised of a hood with
a movable skirt. The pressure inside the hood is regulated so that the pres-
sure differential between the flowing gases and the atmosphere is about
0.04-0.08 inch of water. The pressure in the system is regulated by a butter-
fly valve located upstream of the fan or by an adjustable venturi. The gases
leave the hood and enter a spark box where entrained pieces of slag, refractory,
ore, and such, drop out by gravity. The hoods and solids traps are water-
jacketed, the heat being removed as low-pressure steam. The gas is then
sprayed with water in a horizontal duct and vertical risers. Dust is removed
in a venturi scrubber. The water treatment circuit consists of a thickener
and cooling towers. The thickened material is dewatered in centrifuges or
filters.
If the gas is collected in a gas holder, the system is purged at the
beginning and end of each blow by controlling the position of the movable
skirt. The skirt is in its raised position during charging and during the
first two or three minutes of the blow. The raised skirt permits enough air
to enter to ensure the complete combustion of relatively small amounts of gas
coining from the converter. The skirt is then lowered and gas collection pro-
ceeds without combustion. At the end of the gas blow, as the flow of gas
begins to decline, the skirt is again raised and the blowing is finished
with complete combustion. This method of purging ensures process safety by
preventing the accumulation of explosive gas mixtures.
21
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3. Pollutant Emissions and Necessary Abatement
A generalized flowsheet illustrating the potential for pollutant emissions
is shown in Figure IV-3.
a. Air Pollution Control
The non-combustion system is an alternative method for air pollution con-
trol. In the conventional system, along with the BOP off-gas, there is a
considerable amount of air infiltration that results in combustion in the
hood. A major advantage of a non-combustion system is that the volume of
gases to be treated is reduced as much as 80%, since air infiltration is
reduced. Because both gas volume and thermal load to the gas cooling system
are reduced as combustion is eliminated, the gas-handling equipment can be
considerably smaller than that of the combustion systems. This is also true
during the start-up and finishing phases: although the gases are burned
during these phases, they are generated at a much smaller rate than during
the recovery phase.
Basic oxygen furnace dust, as it issues from the vessel, is black and is
composed primarily of iron in varying stages of oxidation. It also includes
small amounts of tramp elements, such as zinc, that come from the scrap
charged to the furnace.
BOP OFF-GAS
1
COOUNO Y
WMBkH . V-| SKIRT |
o.5x iii8 u mi
1 HOOD
1
CAS COOLER
I
JCT LOADING; 1
,.6GRAtNS/Kl LOW-VELOCITY
FIRST OUST VENTURI
COLLECTOR AND ELBOW
SEPARATOR
t
SSST «°-
COLLECTOR SEPA|,ATOB
*
SLURRY
0
SLURRY
1
i (*}
/NDUCEn
1 DRAFT 1
V"FAN_/ *
DUST LOAOINQ P*"; \Y
O.MI ORAIN/ ul 1 1 »
t_ TOOA5MOLOER __
WATER
ii.u x io> oni
CLEAN WATER
1 COOLING TOWER
VACUUt
OVERFLOW
(ENER
THICK SLURRY
,f|LTER| IF PRODUCT ISL
«HLT[R| FOR SINTER
-n.
CAKE TO SINTER PLANT
GO AIR POLLUTION
@ WATIR POLLUTION
[T] ULIDWAITIOimiAL
Figure IV-3. BOP Off-Gas Recovery without Combustion (IRSID-CAFL Process)
22
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About 55 pounds of dust are produced per ton of steel in the BOP. When
the carbon monoxide is burned with entrained air in the fume hood, the CO/C02
ratio becomes very low and the dust particle surfaces are subjected to high
oxygen potentials causing oxidation and giving the dust a red color. Since
the particles are swept and quenched before being oxidized completely, the
dust has an outer surface of hematite surrounding a core of magnetite.
In the non-combustion processes the dust is composed mainly of FeO,
magnetite, and small amounts of metallic iron. Because FeO and magnetite
agglomerate more easily than hematite, the dust particles are larger than
those obtained in conventional practice.
Tables IV-1 and IV-2 show the particle-size distribution for basic oxygen
furnace dust with complete combustion and with non-combustion (OG) gas-
cleaning systems. Although variations may be the result of operating practice,
and analytical techniques, it is notable that OG dust contains only about
9% material below 5 microns compared with more than 25% below 1 micron in a
combustion system.
Table IV-3 compares the dust composition in systems with and without
combustion. Notable is the change in degree of oxidation represented by
increased amounts of FeO and metallic iron in the OG dust. The metallic
particulate material is cooled as it contacts the hood and stack walls and
falls back into the converter. Yawata (1964) reports higher yields of metal
for non-combustion systems in Japanese practice. One can speculate that this
higher yield can be attributed to the lower gas volume in the non-combustion
system, which results in more particles falling back into the converter. In
the combustion systems, with their larger volumes of air infiltration, these
particles would be carried away with the gases. However, some U.S. users of
non-combustion systems state that these systems do not improve yields.
In both non-combustion and combustion systems, the dust collection equip-
ment, consisting of high-energy scrubbers, gives a similar outlet concentra-
tion of dust. However, because the gas volumes are much reduced in the
non-combustion case, the emission rate to the environment will be lower.
b. Water Pollution Control
Water pollution in BOP operations arises from the removal of air pollu-
tants. The principal pollutant parameters are pH, suspended solids, and
fluorides.
The water treatment circuits for both non-combustion and combustion gas
treatment options are quite similar. Because of the lesser amount of fines
in the non-combustion case - 9% material below 5 microns compared with more
than 25% in a combustion system - settling characteristics are likely to be
better, furthermore, the water usage is lower in the non-combustion process.
We have not seen any data that would indicate a substantial difference in
the weight of dust generated in the combustion and non-combustion processes,
so the size of solids/water separation equipment is not likely to change
significantly.
23
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TABLE IV-1
PARTICLE-SIZE DISTRIBUTION OF BASIC OXYGEN FURNACE DUST
Particle Diameter Weight Percent
(microns)
<1 25
1-65 15
65-90 20
90-110 15
25
Source: Skelly (1966)
TABLE IV-2
PARTICLE-SIZE DISTRIBUTION OF OG PROCESS DUST
Particle Size Weight Percent
(microns)
<5 8.7
5-10 9.0
10-20 39.5
20-30 28.8
>3° 14.0
Source: Yawata (1964)
24
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TABLE IV-3
EFFECT OF OG PROCESS ON COMPOSITION OF BASIC OXYGEN FURNACE DUST
(weight percent)
Component Normal Practice OG Process
Fe total 59 75
Fe metal 10
Fe as FeO 1.6 62
Fe as Fe304, Fe203(a) 57.4 3
CaO 2 2
SiO« 1 1
(a) Calculated by difference.
Source: Cavaghan (1970)
c. Solid Waste Disposal
Solid wastes from this air pollution control equipment consist of wet
scrubber sludges. The composition of the dust is influenced by the nature
of the scrap charged to the BOP. If clean uncoated home scrap is used, the
dust consists primarily of iron oxides and can be recycled to the sinter
strand. If purchased scrap is used, it may not be possible to control the
composition closely; as a result, the dust and resultant sludge can contain
Pb, Zn, Sn and so forth. Suitable care has to be taken in the disposal of
this sludge to prevent leaching of hydroxide precipitates by groundwater.
Despite the change in the oxidation state of non-combustion dust, there are
no data to suggest significant changes in treatment and handling of the
wastewaters and resultant sludges. The sludges are expected to be alkaline
and should be amenable to disposal into appropriately designed and operated
landfills.
Because of the high metal content, special attention should be given to
preventing acidic leaching conditions from occurring, and appropriate efforts
should be taken to mitigate percolation and run-off from the disposal site.
d. Energy Aspects
The non-combustion collection system, as a result of the lower gas volumes
handled, generally consumes less electrical energy than the combustion system,
as shown in Table IV-4.
25
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TABLE IV-4
COMPARISON OF ENERGY USAGE IN NON-COMBUSTION
AND TOTAL COMBUSTION SYSTEMS
Total
Non-Combustion Combustion
Electricity, kWh/ton steel 8 14
Energy recoverable as gas,
10 Btu/ton steel 0.44 none
Source: Rowe (1970)
The main advantage of the non-combustion process is that it permits about
half of the off-gases to be recovered. This represents 2000 cu ft/ton steel
of a fuel gas with a calorific value of about 220 Btu/cu ft and a low-sulfur
content. Such a gas, with proper burner design, may be used in a variety of
steel mill applications - e.g., soaking pits and power generation.
4. Current Adoption 'Status
More than 100 units using non-combustion systems are either operating or
being built in Japan, France, the United States, the United Kingdom, Belgium,
and the U.S.S.R. At almost all of the U.S. installations the collected gas
is presently flared but increasingly consideration is being given to collec-
tion, storage, and use of this low-Btu gas.
5. Economics of Non-Combustion and Combustion Systems
We have compared the capital and operating costs for the two systems for
a three-vessel BOP shop with an annual raw steel capacity of 5.25 million tons.
Both systems use high-energy wet scrubbers. Current designs call for a separate
gas-cleaning facility for each converter for safety reasons. The total com-
bustion system needs two gas-cleaning facilities for three converters.
The costs for the two systems are presented in Tables IV-5 and IV-6.
Capital investment for the non-combustion system is high ($4.4 vs. $2.7/annual
ton of capacity). With the recovered gas used as a fuel and priced at
$2/million Btu, the total operating costs of the non-combustion system are
lower than those of the combustion system ($0.66 vs. $1.12/ton of steel,
respectively).
26
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TABLE IV-5
COST STRUCTURE IN NEW NON-COMBUSTION SYSTEM
Annual Design Capacity; 5.25 x 106 tone
Capital Investment: $23 x Id6 (S4.4/annual ton)
Location: Great Lakes
VARIABLE COSTS
Energy [Details on Table IV-4]:
Electric Power Purchased
Energy Credits: Gas
Direct Operating Labor (Wages)
Direct Supervisory Wages L
Maintenance Labor +
Maintenance Supervision S
Maintenance Materials and Supplies
Labor Overhead
FIXED COSTS
Plant Overhead
Local Taxes and Insurance
Depreciation 18 years
TOTAL PRODUCTION COSTS
Return on Investment (pretax)
TOTAL (Rounded)
Units Used in
Costing or
Annual Cost
Basis
kUh
105 Btu
Man-hr
Man-hr
Man-hr
Man-hr
(2% of Investment)
(35X L + S)
-
(65X L + S)
(2% Investment)
(20X)
$/Unit
0.016
2.00
7.00
7.00
7.00
7.00
Units Consumed
per Ton of
Product
8
-0.44 x 106
0.005
0.001
0.002
~
S/Ton of
Product
O.L28
-0.880
O.M5
0.007
0.014
0.088
0.020
0.036
0.088
0.244
-0.22
0.88
0.66
27
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TABLE IV-6
COST STRUCTURE IN NEW TOTAL COMBUSTION SYSTEM
Annual Design Capacity: 5.25 x 10 tons
Capital Investment: $1A x 10 (?2.7/annual ton)
Location: Great Lakes
VARIABLE COSTS
Energy [Details on Table IV-4):
Electric Power Purchased
Direct Operating Labor (Wages)
Direct Supervisory Wages L
Maintenance Labor S
Maintenance Supervision
Maintenance Materials and Supplies
Labor Overhead
FIXED COSTS
Plant Overhead
Local Taxes and Insurance
Depreciation
TOTAL PRODUCTION COSTS
Return on Investment (pretax)
TOTAL (Rounded)
Units Used In
Costing or
Annual Cost
Basis
kWh
Man-hr
Man-hr
Han-hr
Man-hr
(21 Investment)
35Z (L + S)
65Z (L + S)
(2Z Investment)
5.55Z Investment
(20Z)
$/Unlt
0.016
7.00
7.00
7.00
7.0
Units Consumed
per Ton of
Product
14
0.005
0.001
0.002
S/Ton of
Produc t
0.224
0.035
0.007
0.014
0.053
0.020
0.036
0.053
O.U8
0.59
0.533
1.12
28
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C. EXTERNAL DESULFURIZATION OF BLAST FURNACE HOT METAL
1. Sulfur Problem and Base Line Technology
Coke, containing some of the sulfur found in the coal used, is the major
contributor to the total amount of sulfur entering the blast furnace. Other
sources of sulfur in the blast furnace include fuel injections, the scrap
mixed with the burden, and the minerals themselves (ore, limestone).
Only a negligible portion of the sulfur is found in the off-gases; most
of the sulfur leaving the blast furnace appears in the liquid slag and hot
metal. The capacity of the slag to retain sulfur is governed by its basicity.
Detailed thermodynamic studies of this subject can be found in the literature
(e.g., Ward, 1962); generally an increase in the basicity of the slag by
adding more limestone increases the sulfur retaining capacity of the slag.
The sulfur enters the slag as calcium sulfide. Since such limestone addi-
tions must be brought to temperature and calcined in the blast furnace, they
increase the coke consumption, which in turn introduces more sulfur. Clearly,
then, there is a limit to the amount to which this "internal" desulfurization
process is viable. It may be advantageous to tap a hot metal containing more
sulfur than specified, and to add to the process sequence a new step: the
injection of desulfurization agents into the molten iron during its transfer
from the blast furnace to the steelmaking furnace. These agents react with
the dissolved sulfur and form a sulfide slag that can be disposed of. This
new step is called external desulfurization.
There are other steps in the iron and steelmaking sequence where sulfur
can be controlled to some extent. In the BOP or open-hearth shop, sophisti-
cated slagging techniques can be used. However, they are expensive as they
interfere with other chemistry adjustments and considerably decrease the
productivity of the shop. Prior to casting, one may still make sulfur-
controlling additions. However, such reagents are expensive, the yield
decreases again, and the chemistry of the steel can easily be shifted beyond
the final specifications.
Except for some special grades of free-machining steel in which a high
sulfur content (0.1 - 0.33 wt%) is specified for ease of cutting, sulfur is
largely a deleterious element that should be kept at a minimum. It causes
(Ward, 1962) red shortness* and susceptibility to overheating in wrought steels
and ingot cracking and low ductility in cast steels. It also tends to form
solid inclusions with oxides andj alloying elements. It has strong interaction
coefficients with other alloying elements and, therefore, displaces the entire
physical chemistry of the steel. Most steel specifications call for a sulfur
content of 0.020 - 0.030 wt%, and there has been a tendency to reduce this
range, as customers require better and better qualities of steel. Therefore,
the most favorable condition occurs when the sulfur in the hot metal already
is in the proper range (0.020-0.030 wt%).
*The expression "red shortness" refers to poor formability at red temperature.
29
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Unfortunately, some operators find it more and more difficult to obtain
low-sulfur metallurgical coal. Unless they own mines of such coal,, they find
themselves many times using coal containing over 1.5% sulfur. The resulting
coke typically contains 1.2% sulfur and the hot metal which they tap may con-
tain 0.050 wt% sulfur and more. At this point, the cost of adding an external
desulfurization step must be balanced against greater productivity of the
blast furnace and savings in fuel and limestone.
Table IV-7 shows the basis for our comparison as explained at the
beginning of this chapter: in both bases, we produce 2.6 million tons of hot
metal per year, using coke containing 1.2% sulfur. In both bases, the hot
metal brought to the BOP contains 0.025% dissolved sulfur. In the base case,
this specification is achieved in the blast burnace. With external desulfur-
ization, the hot metal contains 0.050% sulfur when it is tapped. It is further
reduced to 0.025% sulfur on its way to the BOP at the desulfurization station.
Both blast furnaces call on exactly the same technology. As stated
earlier, we considered new plants in both cases for purposes of consistency
in our comparison. The greater productivity gained with external desulfuriza-
tion implies an economy of scale in the design of a blast furnace of same
capacity; coke and limestone costs are reduced, as well as BF gas credits.
Customarily, the gas-cleaning system of the blast furnace does not
appear as a pollution-abatement device, as it is, in fact, a step in the
production of a low-Btu fuel gas. The only air-cleaning technology of con-
cern will therefore be associated with the external desulfurization station.
TABLE IV-7
DEFINITION OF THE BASE LINE AND OF THE EXTERNAL DESULFURIZATION OPTION
Base Case Option
Blast Furnace Capacity (million annual tons) 2.6 2.6
Coke Rate (Ib/ton of hot metal) 1,060 1,030
Limestone Rate (Ib/ton of hot metal) 665 450
Sulfur content of the coke (%) 1.2 1.2
Sulfur content of the hot metal, as tapped (%) 0.025 0.050
Desulfurizing agent per ton hot metal _0- 1.4 Ib of Mg
Sulfur content of the hot metalt delivered 0.025 0.025
to BOP (%)
30
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The scrubbing water of both the blast furnace and the external desul-
furization station can be treated in the same plant.* Therefore, the
wastewater treatment plant of the sequence blast furnace and external
desulfurization station will be designed as one unit. The same base line
technology is assumed as for the blast furnace described in this chapter under
Section E (Direct Reduction).
2. Methods of External Desulfurization
a. Reagents
A number of solid reactants have been proposed and used, with calcium-
and magnesium-based compounds being those most seriously considered.
Calcium has been used in various forms - in the metallic state (it boils
at 2432°F), and as CaO, CaC2 and Ca(CN)2 - to desulfurize pig iron. Powdered
lime reacts with sulfur in the presence of carbon and silicon to give CaS,
CO and some form of lime-silica compound. Calcium carbide is the most
effective. However, it has to be ground to less than 150 mesh, which is
difficult and expensive. The powder must be kept dry, because it reacts
readily when brought into contact with water. Finally, it generates con-
siderable quantities of black fumes during this reaction.
Magnesium metal has been used in England in wire form with nitrogen as a
carrier. This metal causes tremendous turbulence in the bath, essentially
because it boils at quite a low temperature, 1157°F. However, the most com-
mon application of magnesium is through the Mag-Coke process. In the Mag-Coke
process, the desulfurizer is prepared by preheating coke and immersing it in
molten magnesium. Lumps weighing 2-5 Ib and containing 45% Mg are produced,
and these are stored in sealed drums to prevent hydration. The Mag-Coke is
added under a graphite plunging bell to keep it at the bottom of the bath as
long as possible. Magnesium sulfide floats to the surface and tends to
thicken the slag.
Finally, magnesium aluminum alloys injected through nitrogen lances have
proven to be effective desulfurizers, with considerably less fuming than
carbon-bearing products.
b. Implementation and Technological Factors
Practical methods are continuously being sought by which this new opera-
tion can be integrated into the overall handling procedure of the hot metal
between tapping and pouring into the BOP vessel. Agarwal (1971) proposed to
combine hot metal mixing and external desulfurization in the arrangement shown
in Figure IV-4. This idea certainly is interesting, but no current engineering
*This is our choice of a base line. Depending on the layout of the plant, the
scrubbing water of the external desulfurization operation may actually be
treated together with the BOP's scrubber water.
31
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TO
THICKENER
BALLING DRUM
WATER
SPRAYS
SLAG DISPOSAL
SOURCE: Agarwal (1971).
Figure IV-4. Combination of Hot Metal Mixing and External Desulfurization
design of such arrangement exists. The reason probably is that simpler schemes
are more appealing in an industry where productivity and reliability are key
words. A few such schemes are discussed below:
Desulfurization in the ladle has the advantage of:
A large contact area between the hot metal and the slag, which
accelerates the rate of sulfur removal; and
A favorable location for operation, the point where the torpedo
car is poured into the ladle, because some air pollution con-
trol equipment is already likely to be in place there.
Some problems can arise for the following reasons:
The ladles and crane? would be tied up longer, so larger capital
expenditures for cranes and ladles would be necessary;
It is more difficult to prevent the dilution of the gaseous
effluents, so air pollution controls may have to be signifi-
cantly larger, depending on the practice followed.
32
-------
August Thyssen Hutte, among others, proposed to build a station over the
railroad and to inject the desulfurizer through the narrow mouth of the
torpedo car. Whenever practical, a lance is used to inject the reagent with
nitrogen as a carrier. Such a design is shown in Figure IV-5. One major
advantage is that a hood can be tightly fitted to the opening of the torpedo,
so that gaseous emissions are easily collected. Drawbacks include the short
life of the lances in the violently agitated metal bath, and the difficulty
of using plunging graphite bells. Also, the slag formed may be difficult to
remove as it tends to solidify or at least to be very viscous.
As graphite bells are not very convenient - they break and are difficult
to operate through the opening of a torpedo car - the more likely injection
system to be accepted is lancing with a nitrogen carrier a few feet from the
bottom of the vessel. The nitrogen flow provides a beneficial stirring
action. The lining of the vessel, however, has to be repaired more frequently
because of the increased turbulence and larger exposure to hot metal. Never-
theless injection in the torpedo car seems to have gained a large audience,
and we have used it as our external desulfurization option.
STORAGE
SITE
DISPENSER
WORKING PLATFORM
SOURCE: Meichsner(1974).
Figure IV-5.
Schematic Representation of the ATM Injection Process
for External Desulfurization in the Torpedo Car
33
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c. Materials Balance
While variations can be expected, typically 2 to 5 Ib of desulfurizer are
required per ton of hot metal. The products and emissions include:
The desulfurized steel, with a slightly lower silica content, on
the order of 230 tons of hot metal for a torpedo car.
A very viscous or solid slag. This slag amounts to 1 to 3% of the
hot metal by volume. To reduce viscosity some thought has been
given to additions of fluorspar, but it is not considered here as
part of the process.
Black smoke emissions and solid carbon in the slag when carbide
is used.
Possibly some cyanides when nitrogen is used as a carrier in the
presence of carbon saturation. This is a potential area open to
research, as no data has been brought to our attention on this
subj ect.
Various amounts of particulate emissions to the air because of
turbulence and incomplete reactions.
Figure IV-6 shows a tentative flow chart of the process.
DESULFURIZATION
ATM.
LEGEND: f A > POLLUTED GAS STREAM
f W 1 POLLUTED WATER STREAM
I S I SOLID WASTE
CfJ FUGITIVE
Figure IV-6. Flow Diagram for External Desulfurization in the Torpedo Car
34
NOTE 1:
The water treatment It Incremental to the blut furnace icrubber wanawater trtatrgent.
-------
d. Pollution Control
(1) Air Pollution Control
The gaseous emissions from desulfurization are essentially a nitrogen
exhaust that contains particulates such as iron oxides, unreacted desulfurizer,
and product slag. Since lancing with nitrogen is not a combustion process, the
particulates which are produced should be more the result of entrainment than
of metal condensations. Hence, the mean median diameter of the particulates
is expected to be larger than that of BOP or blast furnace particulates, for
example. This larger size should make the particulates easier to remove from
the gas stream. Since nitrogen lancing generates an inert gas rather than a
combustible gas, as found in blast furnace or BOP exhausts, problems of
designing and maintaining a collection hood for the system should be greatly
reduced and should result in a high degree of collection before the air pol-
lution control equipment.
Finally, cyanide or traces of other nitrogen compounds might be present
in the exhaust gas as they are in blast furnace gases. However, since nitrogen
is relatively inert at the desulfurizing temperatures, we believe these com-
pounds are not likely to be present in the exhaust of external desulfurization
processes.* Therefore, an adequate control system should consist of a
refractory-lined hood over the torpedo car opening, connected with a high-
energy venturi scrubber to remove the particulates.
The design bases for such a system are taken as 26,500 actual cu ft/min
(ACFM) for 50% of the total operating time and no flow the remaining time.
With an estimated dust loading of 0.0025 Ib/scf, this system should be capable
of meeting present process weight-based emissions limitations. The capital
and operating costs of such a system are shown in Table IV-8.
(2) Water Pollution Control
The wet scrubber chosen to control exhaust gas emissions from the desul-
furization step will generate a wastewater stream. Based on the previous
estimates (0.0025 Ib of dust per cubic foot of gas, and an actual gas flow
rate through the scrubber of approximately 26,500 cu ft/min for 50% of total
operating time), the untreated scrubber water will be as follows:
flow rate - 381,600 gpd (instantaneous)
- 190,800 gpd (actual 24-hour flow)
suspended solids - 29,900 mg/liter (47,700 Ib/day).
*In the absence of specific data, we are unable to confirm this hypothesis,
and this may well be an open area for research.
35
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TABLE IV-8
AIR POLLUTION CONTROL COSTS FOR THE EXTERNAL DESULFURIZATION STATION
(Basis: 2.6 million tons of hot metal/yr)
CAPITAL INVESTMENT (CI) $1,.241,000
ANNUAL OPERATING COST
Variable Coses
Labor, (incld Supr + Overhead) 3 ^QQ
(Total)
Maintenance @ 5% of CI 62,100
Utilities
Electric Power 220 kWh/10 scf 200
$/Ton of Steel 0.17
For purposes of this study it has been assumed that gravity settling for
removal of suspended solids in a mechanical clarifier will be adequate to meet
effluent limitations. (Furthermore, it is assumed that water from the clari-
fier will be recycled to the scrubber.) Although there might be some sulfides
in the scrubber water (expected to be in the form of relatively insoluble
compounds rather than free ions) and it is uncertain if cyanides would be
present, the estimated capital and operating costs for wastewater treatment
do not include processes for filtration or cyanide or sulfide removal.
Because virtually no hydrogen is present in the desulfurization process,
phenol and ammonia will not be present in the scrubber water and no fluorides
are expected. The expected condition of the treated desulfurization scrubber
water is shown on Table IV-9.
To properly assess the water pollution control implications of an external
desulfurization operation, it is necessary to compare the treated wastewater
effluent from the base line blast furnace with the treated effluent from a
blast furnace, plus an external desulfurization unit. A comparison of treated
effluents is shown in Table IV-10. In this comparison the blast furnace
scrubber water is subjected to the "Best Available Technology Economically
Achievable (BATEA)," the 1983 treatment level recommended in the EPA Develop-
ment Document. This basis was chosen because it is anticipated that any
installations would not be completed before either the effective date of the
1983 standards, or that new source performance standards would be equally as
stringent. This treatment level consists of clarification with a high degree
36
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TABLE IV-9
EXPECTED COMPOSITION OF TREATED SCRUBBER WATER FROM DESULFURIZATION
Flow Rate 76,300 gpd (instantaneous)
(20Z blowdovn from recycled
scrubber water) 38,150 gpd (actual 24-hr flow)
Parameter Waste Load
(Ib/day)
Suspended Solids 16
Cyanide Small amounts may be present
Phenol Not present
Ammonia Not present
Fluoride Not present
Sulfides May be present as insoluble compounds
An estimation of the incremental costs of treating the desulfurization
scrubber water is shown in Table IV-12. The wastewater treatment system
consists of clarification plus sludge dewaterlng via vacuum filtration.
Eighty percent of the treated water is recycled to the scrubber.
TABLE IV-10
COMPARISON OF TREATED EFFLUENT WASTEWATER LOAD
Paraneter
Suspended Solids
Cyanlde(5)
Phenol
Annonla (as NH.)
Sulfide
Fluoride
Flow Rate
Blast Furnace (D
(Base Case)
(Ib/day)
74
1.9
3.7
74
2,2
143
890,000 g
(mg/1)
10
0.25
0.5
10
0.3
20
pd
Blast Furnace (L)
plus
External DesulfurizationC2)
(Ib/day)
90
>1.9<3)
3.7
74
>2.2
148
928,000
(ms/l)
11.6
>0.24
0.48
9.6
>0.29
19.2
gpd
Notes: 1. Blase furnace scrubber water la both cases is subjected to "Best
Available Technology Economically Achievable" (1933).
2. External desulfurizatlon scrubber water is subjected only to
clarification for suspended solids removal.
3. Cyanide nay be present in external desulfurization scrubber water, but
has been assumed absent or inconsequential.
4. Low-solubility sulflde conpounds may be present in external
desulfurization water.
5. Cyanide amenable to alkaline chlorination.
37
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of treated effluent recycle (97%). The blowdown stream from the scrubber
water recycle loop is then subjected to alkaline chlorination for the
removal of cyanide followed by neutralization, filtration, and carbon
adsorption. The overall purpose of the treatment is to remove cyanide,
phenol, ammonia, fluorides, and sulfides. As can be seen from Table IV-10,
the additional waste load imposed by the incorporation of external desul-
furization is a very small increment of the base line blast furnace.
An estimation of the wastewater treatment costs of the base line furnace
is shown in Table IV-11, and the external desulfurization incremental waste-
water treatment costs are presented in Table IV-12. The wastewater treatment
system for external desulfurization consists of clarification plus sludge
dewatering via vacuum filtration with eight percent of the treated water
recycled to the scrubber.
(3) Solid Waste
There are two sources of solid waste from the external desulfurization
process: slag and sludge from the wastewater treatment. With the same sulfur
content in the coke, incorporation of external desulfurization in the steel-
making sequence permits a lower limestone usage rate in the blast furnace.
Lower limestone usage results in less slag generation. It is estimated that
a blast furnace, coupled with external desulfurization, will produce 120 Ib
less slag/ton than a blast furnace without external desulfurization. Since
the external desulfurization process itself produces an estimated 9 Ib/ton of
slag, net reduction in slag generation is about 111 Ib/ton. Thus, an opera-
tion of 2.6 million ton/yr capacity employing external desulfurization will
reduce overall slag generation by approximately 144,300 ton/yr.
The wastewater treatment system will produce a dewatered sludge estimated
to contain 35% solids. It is estimated that 24,000 tons of sludge will be
generated annually. If cyanide is present in the scrubber water, it will also
be present in the liquid fraction of the sludge, because the common practice
is to effect solids removal prior to cyanide destruction. Although the
chemical form of the cyanides is not known, care should be taken to dispose
of the sludge in a manner that will avoid groundwater contamination.
Solid waste disposal costs for the external desulfurization are given in
Table IV-13. Use of the external desulfurization process will reduce overall
solid waste generation by 120,300 ton/yr, which in turn will reduce solid
waste disposal cost by $0.23/ton of steel, based on an estimated cost/ton of
sludge and slag disposal of $5.
Total pollution control costs at the external desulfurizing station are
$0.36/ton of hot metal. About half of these costs are attributable to air
pollution control costs. Table IV-14 compares the total pollution control
costs of both alternatives.
38
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TABLE IV-11
BLAST FURNACE WASTEWATER
(Basis: 2.6 million tons
Capital Investment:
Annual Operating Costs;
Direct Operating S Maintenance
Labor (L) @ $7 man-hr.
Supervision (S) 15*(L)
Maintenance @ 4% of CI
Chenicals Include:
Sulfuric Acid
Electric Power
Labor Overhead (L+S) 35 Z
TOTAL VARIABLE COSTS
FIXED COSTS
Plant Overhead (L+S) 65*
Taxes S Insurance
(@ « of CI)
Depreciation (18 years)
TOTAL FIXED COST
TOTAL ANNUAL COST
RETURN ON INVESTMENT
(Pretax) (? 20Z of CI)
Cost/Unit Quantity/Ton
Quantity of Product
$ 7.00/ 0.00292/
man-hr man-hr
--
551. 30/ ton 0.11 Ib
$0.01cVkWh 0.138 kUh
..
__
.-
S/Ton of
hot metal
0.0205
0.0030
0.0099
0.0028
0.0022
0.0082
0.0466
0.0153
0.0039
0.0109
0.0301
0.0767
0.0392
TOTAL
0.1159
39
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TABLE IV-13
EXTERNAL DESULFURIZATION SOLID WASTE DISPOSAL COSTS
(Basis: 2.6 million tons of hot metal/yr)
Material
Wastewater Treatment
Sludge (35% Solids)
External Desulfuriza-
tion Slag
Annual
Quantity
(ton )
24,900
11,700
Disposal
Cost
($/ton)
5.00
5.00
Quantity/
Ton of Product
0.0096
0.0045
$/Ton
of Product
0.048
0.022
TOTAL SOLID WASTE
36,600
5.00
0.0141
0.070
TABLE IV-14
SUMMARY OF THE POLLUTION COSTS WITH AND WITHOUT EXTERNAL DESULFURIZATION
(Basis: 2.6 million tons of hot metal/yr)
BASE CASE
Mr Pollution Control
Blast Furnace *
Desulfurizing Station
Wastewater Treatment
Blast Furnace
Desulfurizing Station
Solid Waste Disposal
Blast Furnace
Desulfurizing Station
Capital
Cost
($)
Operating
Cost
S/ton
-0-
-0-
-0-
-0-
14,700,000 2.91
-0- -0-
-0-
-0-
1.66
-0-
OPTION
Capital
Cost
($)
Operating
Cost
$/ton
-0- -0-
1,241,000 0.17
14,700,000
510,000
-0-
-0-
2.91
0.12
1.15
0.07
TOTAL 14,700,000 4.57 16,451,000 4.42
*No air production control cost is shown here for the blast furnace
because the gas cleaning devices are considered productive equipment
in the generation of a low-Btu fuel gas. (See text.)
40
-------
e. Energy Considerations
The hot metal that has been externally desulfurized is only slightly
cooler (15-30°F) than when it was tapped, because the heat of desulfurization
partly compensates for the heat losses from the time delay. Its silicon and
possibly its manganese content are lower, but the extent of this depletion
does not significantly affect the ability of the BOP to melt scrap. Thus,
except for the energy going into the preparation of the desulfurizing agent
and into the preparation of nitrogen, the desulfurization station cannot be
considered an energy-consuming unit.
Consequently, the energy implications of the process lie entirely with
the blast furnace operation. The amount of limestone charged to the blast
furnace is basically a function of the gangue and sulfur coming with the iron
oxides and coke as well as the desired sulfur and silica level required in
the hot metal. Increasing the limestone flux to control increased amounts
of sulfur requires additional coke to meet the corresponding heat require-
ment. Since calcium sulfide has a limited solubility in slag, it may even
be necessary to add silica. The additional coke, in turn, brings more sulfur
that must be controlled. This is quantified in an example shown in Table IV-15.
If the coke contains 1.2% sulfur, then the hot metal can be produced with
0.050% sulfur and externally desulfurized to 0.025% sulfur. To obtain the
same sulfur level in the blast furnace would require an estimated additional
30 pounds of coke. External desulfurization, therefore, allows high-sulfur
metallurgical coal to be used without any penalty on a Btu basis.
TABLE IV-15
COMPARISON OF ENERGY CONSUMPTION WITH AND WITHOUT EXTERNAL DESULFURIZATION
Base Case Option
106 Btu 106 Btu
Blast Furnace:
Coke1 , 13.25 12.87
Electricity 0.26 0.25
BF Gas Credit (3.80) (3.69)
Total Production: 9.71 9.43
Pollution Controls
Wastewater Treatment:
Fuel 2 0.07 0.07 (3)
Electricity 0.22 0.22 (3)
Air Pollution Control:
Electricity2 0.004
Total Pollution 0.29 0.294
Total: 10.00 9.724
Notes: 1. i ton of coke 25 * 106 Btu
2. 1 kWh = 10,500 Btu at the power source.
3. The energy required to treat scrubbing water from the
desulfurizing station is negligible.
41
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f. Cost Factors
As mentioned earlier, external desulfurization is linked to blast furnace
practice. An economic evaluation of this option was made recently by Ward
(1975) for a particular plant of the British Steel Corporation (Appleby-
Frodingham). His results are summarized in Figure IV-7. They show that
meeting common sulfur specifications (0.020-0.030) in the blast furnace is
increasingly difficult and expensive when the sulfur content of the coke
reaches 1-1.2 wt%. Similar conditions were chosen for this study, and indeed
they appear to represent the point of indifference where either technology
seems to be equally attractive. We expect that less favorable conditions
regarding the price and quality of the blast furnace feedstock (coke and
limestone) or more stringent hot metal specifications would favor external
desulfurization, whereas more lenient conditions would favor the traditional
practice.
(1) Capital Costs
The blast furnace of the base line was estimated at $156 million. As
the alternative practice increases the productivity of a blast furnace of this
category by 3.6%, a slightly smaller blast furnace was associated with the
external desulfurization station to produce the same quantity (2.6 x 10 ton/yr)
of hot metal. Its investment cost is estimated to be about $152 million.
The capital cost estimates of the desulfurizing station include $900,000
for the station itself, and $1,240,000 for the air pollution abatement equip-
ment (wet scrubber). These costs do not include investments for intra-
structure such as additional railway track for a desulfurizing station. The
wastewater treatment plant is common to the blast furnace and the desulfur-
izing station. The latter incurs an incremental capital investment of
$510,000 to a base case of $14,700,000. The difference between the two routes
is summarized in Table IV-16 and is not significant.
(2) Operating Costs
The operating costs of the base line blast furnace, the alternative opera-
tion with a smaller blast furnace and external desulfurizing station are
detailed in Tables IV-17, IV-18 and IV-19, respectively.
The new option reduces the cost of hot metal as tapped from the blast
furnace from $105.99 to $103.28 per ton. The cost of operating the desul-
furizing station is $2.07 and the associated pollution control cost is
$0.36/ton of hot metal, so that the cost of a ton of hot metal delivered to
the BOP shop is $105.71 with the new route. The difference between the two
routes is $0.28/ton of hot metal. This is well within the accuracy of these
calculations, but does suggest that cost would not be an obstacle to imple-
mentation under the assumptions made in this analysis.
42
-------
0.01 0.02 0.03 004 0.05 0.06 007
SULPHUR CONTENT. <%)
Figure IV-7.
NOTE: Mtx S2.03
SOURCE: Waid (19751.
Relationship between Cost of Ironmaking and Sulfur in Iron
TABLE IV-16
COST COMPARISON BETWEEN THE TWO ROUTES
(with and without external desulfurization)
Capital Cost ($)
Blast Furnace
Desulfurization Station
Pollution Control
Total
Base Line
156,000,000
14,700,000
170,700,000
Operating Costs2 ($/ton of hot metal) $105.99
Option
152,000,000
900,000
16.451.000
169,351,000
$105.71
(1) Basis: 2.6 x 10 ton/yr of hot metal
(2) Includes 20% ROI and pollution control costs
43
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TABLE IV-17
COST STRUCTURE IN NEW BLAST FURNACE
Annual Design Capacity: 2.6 x 10 tons hot metal
Capital Investment (CI): $156 million
Location: Great Lakes
VARIABLE COSTS
Raw Materials: Pellets
Limestone
Energy: Purchased Coke
Electrical Power Purchased
Energy Credits: Blast Furnace Gas
Water; Process (Consumption)
Cooling (circulating Rate)
Direct Operating Labor (Wages) L
Direct Supervisory Wages +
Maintenance Labor and Mat'l. S
Labor Overhead
Misc. Variable Costs/Credits:
slag sampling
scrap credit
TOTAL VARIABLE COSTS
FIXED COSTS
Plant Overhead
Local Taxes and Insurance
Depreciation
TOTAL PRODUCTION COSTS
Return on Investment (pretax)
POLLUTION CONTROL
TOTAL
* long ton unit - 22.4 Ib of coal con
Units Used in
Costing or
Annual Cost
Basis
ltu(a>
ton
ton
kWh
106 Btu
o
103 gal
Man-hr
15% Labor
5Z Inv.
35% L + S
ton
65% L + S
2Z Inv.
5.55%
20% CI
tained Fe.
5/Unit
0.45
5.00
90.0
0.016
2.0
0.05
7.00
80.00
Units Consumed
per Ton of
Product
84.7
0.332
0.53
25.
3.8
11
0.10
0.01
$/Ton of
Product
38.11
1.66
47.70
0.40
(7.60)
0.55
0.70
0.11
3.00
0.28
0.25
(0.80)
84.36
0.53
1.20
3.33
89.42
12.00
4.57
105.99
44
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TABLE IV-18
COST STRUCTURE IN NEW BLAST FURNACE
(Reduced Coke Rate)
Annual Design Capacity; 2.6 x 10 tons hot metal
Capital Investment (CD: $152 million
Location: Great Lakes
VARIABLE COSTS
Raw Materials: Pellets
Limestone
Energy: Purchased Coke
Electric Power Purchased
Energy Credits: Blast Furnace Gas
Water: Coollr.g (Circulating Rate)
Direct Operating Labor (Wages) L
Direct Supervisory Wages +
Maintenance Labor S
Maintenance Materials and Supplies
Labor Overhead
Misc. Variable Costs/Credits
-------
TABLE IV-19
COST STRUCTURE IN NEW EXTERNAL DESULFURIZATION
Annual Design Capacity: 2.6 x 10 tons hot metal
Capital Investment (CD: $900.000
Location: Great Lakes
VARIABLE COSTS
Raw Materials: Desulfurizer
Nitrogen
Hot Metal (S-0.0483)
Direct Operating Labor (Wages) L
Direct Supervisory Mages (S)
Maintenance Materials and Supplies
Labor Overhead
TOTAL VARIABLE COSTS
FIXED COSTS
Plant Overhead
Local Taxes and Insurance
Depreciation
TOTAL PRODUCTION COSTS
Return on Investment (pretax)
POLLUTION CONTROL
TOTAL
Units Used in
Costing or
Annual Cost
Basis
Ib
1,000 scf
ton
Man-hr
L
CI
L + S
L + S
CI
CI
$/Unit
0.67
0.16
7.00
Units Consumed
per Ton of
Product
2
0.870
0.0066
15ZL
4X CI
35* (L + S)
65X (L + S)
2% CI
5.6% CI
$/Ton of
Product
1.71
0.14
103.28
0.047
0.007
0.014
0.02
105.22
0.035
0.007
0.02
105.22
0.07
0.36
105.71
46
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g. Current Adoption Status and Future Outlook
The average sulfur content of the hot metal has been continuously
increasing and can be expected to reach 0.060 - 0.070 wt% in the next 15 years.
External desulfurization is most likely to be used, therefore, to bring
sulfur from 0.050% or more down to 0.020-0.030% for production of ordinary
steels.
Various forms of external desulfurization have been practiced in Europe
for many years. Soda ash was used at first; erratic results, pollution
problems, wear of refractory lining and difficulty in deslagging prompted
a switch to calcium-and magnesium-based processes. The process studied in
some detail in this study might be the one with the. widest conceptual accept-
ance: a reagent (magnesium alloy, calcium compound) is injected in the
torpedo car through a nitrogen lance.
The concept of external desulfurization is not new to American steel-
makers. However, they have started partial and temporary pilot tests and
operations only recently. The general feeling is that the industry will
adopt this practice more widely in the 15 years to come because:
low-sulfur metallurgical coal may well be at a premium;
it is not a very capital-intensive investment; and
it has the potential to be retrofitted to existing facilities.
Where space is available and it is logistically feasible to set up a desul-
furizing station, older blast furnaces can easily accommodate external
desulfurization. This can be an interesting option for a steel company faced
with the prospects of using higher-sulfur coal. In this way, productivity
can be maintained at a relatively small capital investment. However, in
order to assess more accurately how many steel mills will use higher-sulfur
metallurgical coals and which of these mills can retrofit external desulfurizing
stations into the present plant layout a detailed economic assessment on a
plant-by-plant basis would be required.
47
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D. DRY QUENCHING OF COKE
1. Description of the Base Line
Current technology involves wet quenching of coke and forms the base
line for this analysis. In wet quenching, hot coke (at 1900-2000°F) is
delivered in a coke car to a tower where the coke is quenched with water,
thereby producing large quantities of steam that are vented to the atmosphere.
The coke car is designed to allow the excess water to drain. This water is
often recirculated. Wet quenching results in coke with an average moisture
content of 2.5%.
Wet quenching of coke creates air pollution if the quenching water con-
tains contaminants, e.g., flushing liquor from the coke byproduct recovery
plant. In such cases, pollutants are vaporized and carried off in the "cloud"
or "plume." The use of clean water minimizes the emission of objectionable
organic vapors, and the installation of baffles in the quench tower is claimed
to remove solid particulates satisfactorily (A.D. Little, Inc., 1975)
2. Description of the Dry Quenching Process
In dry quenching of coke, the hot coke pushed from the ovens is cooled in
a closed system. Dry quenching uses "inert" gases to extract heat from incan-
descent coke by direct contact. The heat is then recovered in waste heat
boilers or by other techniques. The inert gases can be generated from an ini-
tial intake of air which reacts with the hot coke to form a quenching gas of
the following composition: 14.5% OL, 0.4% 02, 10.6% CO, 2% H£ and 72.5% N£
(Linsky, 1975).
Except for the periodic introduction of hot coke with entrained gases, dry
quenching is a closed-cycle operation on the gas side. Because oxygen is
largely absent, the danger of explosion is minimized. Nevertheless, explosion
precautions must be taken and the composition of circulating gases must be
monitored and controlled by the addition of nitrogen.
Quenching plants in the U.S.S.R. are comprised of independent "tower
boiler" blocks. Each block includes a cooling tower, a waste-heat boiler, dust
collectors, and a gas-blower. The following process description is based on
an article by Linsky (1975) with the flow diagram shown in Figure IV-8. The
incandescent coke, which is between 1900°F and 2000°F, is initially pushed
from the coke oven into a special car bucket designed to receive coke from only
one oven at a time. An electric locomotive transports the bucket^to the cooling
tower, and a vertical hoist lifts the bucket from the locomotive to the tower's
cl urging hole (near the top of the tower). As the hoist approaches the charg-
ii hole, it automatically opens and a coke guide hopper is placed over the
pi hamber so the bucket and the charging hole are sealed. Automatic gates
oj <.n the bottom of the bucket and the red hot coke enters the prechamber.
D\ this time, the pressure at the charging hole is between 0.02 and 0.03
ir /ater gauge. After the prechamber is charged, the coke guide hopper is
r ed, the charging hole closes automatically, and the bucket is returned to
t lectric locomotive. After 40-50 minutes, according to Linsky, the coke
48
-------
CLEANED COOLER CAS
FINE DUST CYCLONE
SUPER-HEATED
STEAM 820" F
590 PM
\V*S)W,\\\\\\\\\
/ «j
,/TRANSPORT *J
SOURCE: L,mk»(l975)
Figure IV-8. Schematic View of the Soviet Dry Quenching System
drops through the prechamber and begins to fall into the cooling zone. As the
coke falls through the cooling zone, circulating gases cool the coke to between
400°F and 500°F.
Periodically, a discharge gate, which can be adjusted according to the
required capacity of the cooling chamber, allows batches of coke to fall from
the bottom of the cooling zone onto conveyors running under the quenching unit
described above. Between 2 and 2-1/2 hours are required for the coke to pass
through the quench unit and onto the conveyors.
The discharge gate, which is a double gas-tight structure, operates auto-
matically and interlocks mechanically to ensure proper opening sequences.
Approximately 100 seconds separate consecutive discharges of 1-1/2 to 2 tons.
The maximum number of discharges possible per hour, as stated in the Linsky
article, is 35 (average throughput 60 ton/hr). The Soviet system uses a blower
to circulate the quenching gases through the "tower-boiler" system. To reach
the cooling chamber, quenching gases are initially forced into distribution
ducts, where they pass through peripheral slots and a central divider into the
cooling chamber.
As the gases rise in the cooling chamber, heat is transferred from the
hot coke to the circulating gases. After the gases are heated to between
1380°F and 1470°F, they pass from the cooling chamber into dust dropout chambers.
49
-------
In the dust dropout chambers, coarse particulates are removed so that
the boiler elements will be protected from erosion. Once the coarse partic-
ulates have been removed (200-400 Ib/hr collected), the gases pass from the
dust dropout chamber into the waste-heat boiler where they are cooled to
between 350°F and 390°F and high-pressure steam is raised.
After cooling in the waste-heat boiler, the gases pass through two dust
recovery cyclones. In the cyclones, finer particulates are removed so that
the gas blower, which forces the gases through the dry quenching system, will
be protected from erosion. (Particulates are collected here at a rate of 400-
600 Ib/hr.) Dusts removed from the circulating gases are periodically removed
by pneumatic transport. They are mainly carbon dusts that can be burned as a
solid fuel.
After the finer particulates are removed, nitrogen may be added to the
gases so that their composition will meet operational safety regulations.
Finally, the gases are sent to the blower to repeat the gas cycle. Instruments
control the operations of cooling towers, charging and discharging coke, and
monitor the temperature of the cooled coke, pressure and rate of circulating
gas, and so forth.
3. Pollutant Emissions and Necessary Abatement
Figure IV-9 is a block diagram of the process showing potential pollutant
emissions. Coke dust could be discharged to the ambient air since potential
dust emission sources are located at points where the quenched coke is dis-
charged onto the conveyor from the dry quenching unit, and also where coke dust
is discharged from the dust dropout chamber and cyclone dust separators on to
the conveyor belts that carry the dust to storage. The designs of dry quench-
ing units considered in this study have provisions for hooding at coke/coke
dust discharge points. Air collected at such points is being exhausted through
a bag house, and the dust, mainly coke breeze, is collected in a dust hopper.
It is likely £o be used as a fuel on the plant site.
There is some potential for dust emission during coke transfer and coke
charging to the dry quenching unit. However, according to discussions with
American Waagner Biro, the transfer car and charging side of the unit can be
designed so as to minimize such emissions.
There have been references in the literature (Linsky, 1975) concerning the
addition of nitrogen to control the gas composition and to prevent the forma-
tion of an explosive CO-rich mixture. This would imply as well a bleed stream
containing carbon monoxide and particulates.
The emissions during pushing operations are another matter. While we
recognize that current design concepts claim a relationship between pushing
emissions control and the type of track vehicle used to transport the incandes-
cent coke, we believe that pushing emissions can be equally controlled in wet
or dry quenching.
50
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COKE OVEN/
BYPRODUCT PLANT
HOODED
COKE
GUIDE
[Al AIR EMISSIONS
HOT
COKE
BUCKET
G)
DRY COKE
QUENCHING
UNIT
1 _
^
DUST DROP
OUT CHAMBER
* flG^ V^f
COKE
DUST
-]
50-55X I03scfm
DRY COKE
WASTE HEAT
BOILER
- WATER
STEAM
COKE DUST
Figure IV-9. Block Diagram of Dry Quenching Indicating Potential for Pollutants
4. Technological Factors
Dry quenching is reported (Kemmetmueller, 1973) to yield a better quality
of coke .in comparison with wet quenching because of even cooling which results
in more uniformly sized coke. Two percent increase in usable coke output per
ton of coal charged has been reported, reflected by a similar reduction in coke
breeze. Better mechanical strength, dryness of product, uniform distribution
of volatile constituents, and less adhering breeze are said to contribute to
smoother blast furnace operation with dry quenched coke. Moreover, in the
Russian literature there are reports of decreases in coke rates of 2-3% in
Soviet blast furnace trials with dry quenched coke. We have yet to come across
any published data that will substantiate such claims for dry quenched coke
using U.S. coking coals.
5. Energy Considerations <
In wet quenching the sensible heat in the hot coke is lost to the water
used in quenching. When the hot coke is cooled to 400°F in a dry quenching
unit, about 1.1 x 10^ Btu/ton of coke are recoverable.
Conceptually, the recovered energy can be put to a variety of uses. For
instance, the 1.1 x 106 Btu/ton that dry quenching is capable of recovering is
equivalent to about 940 Ib of superheated steam. Under the right economic and
51
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logistical circumstances, the recovered energy can be used to produce electricity
or mechanical power, or to preheat coal, combustion air, and/or feed water sup-
plies to fuel-fired boilers. As an example, this recoverable energy is suffi-
cient to cover the needs of the byproduct plant.
6. Economics of Dry Coke Quenching
We compare the costs of wet and dry quenching starting from the point coke
is pushed out of the ovens. Capital requirements for a system with a capacity
of 2750 tons of coke per day (1.0 x 10° tons coke annually) is estimated at
$9.5 million.* The projected savings in operating costs arise from the signifi-
cant amount of byproduct energy recovery possible. Current plant designs in
the U.S.S.R. recover the byproduct energy as high-pressure steam. The attrac-
tiveness of the process depends on the value attributed to the recoverable
energy. As it may be used to generate power, preheat gases, or raise steam,
it was credited in this study with a dollar value set by competitive low-sulfur
fuels at $2/106 Btu. Table IV-20 shows the costs on an incremental basis,
viewing dry quenching as a mechanism to recover heat.
At present, this energy credit alone does not seem to justify the substan-
tial capital investment involved. If, however, it can be demonstrated in U.S.
blast furnace practice that dry quenching yields a better quality of coke so
that the coke rate in the blast furnace is reduced, then there is likely to be
a greater driving force for the adoption of the process. Further research is
needed to establish this point.
TABLE IV-20
INCREMENTAL COSTS INCURRED BY A NEW DRY COKE QUENCHING UNIT
Annual Design Capacity: 1.0 x 10 tons
Capital Investment: JJ9.5 jin annual ton)
Location: Creac Lakes
VARIABLE COSTS
Electric Pouer Purchased
Energy Credits
Direct Operating and Maintenance
Labor (Wages)
Direct Supervisory Wages
Maintenance Materials and Supplies
Labor Overhead
FIXED COST
Plant Overhead
Local Taxes and Insurance
Depreciation
TOTAL PRODUCTION COSTS
RETUTUJ ON INVESTMENT (PRETAX)
TOTAL
Units Used in
Costing or
Annual Cost
Basis
XWh
106 Btu
L Han-hr
*S Man-hr
5Z Investment
(35Z L6S)
(65X L&S)
(2Z Investment)
$/Unit
0.016
2.00
7.00
7.00
Units Consumed
per Ton of
Product
8.4
-1.1 x 106 Btu
0.008
0.003
S/Ton of
Product
0.134
-2.20
0.056
0.021
0.68
0.027
0.050
0.19
0.530
0.712
1.900
1.188
*Estimates supplied to us by AISI (1976) late in this study indicate these
investments are probably low. This would have the effect of making dry quench-
ing even a less favorable economic alternative than indicated in this study.
52
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7. Current Adoption Status
Dry quenching was developed by the Sulzer Brothers shortly after World
War I. Over 70 coke plants in gas works and some steel mills were equipped
with dry coke quenching units up to 1950, but most of these gas-works installa-
tions were closed as low-cost natural gas became readily available. Only two
of these are still in operation: one is in England at the Ford Dagenham plant;
the other one is located at Wendel-Sidelor, Homecourt, France.
Linsky (1975) observed that, in 1960, the Soviet Union commissioned its
first dry quenching pilot plant at Cherepovets Integrated Iron and Steel Works,
north of Moscow. Because of its success in a relatively cold climate where
wet quenching may be difficult, more than 40 dry quenching towers have been
built in the Soviet Union which quenched approximately 15 million tons of coke
in 1973. Apparently dry quenching facilities are mandatory in the U.S.S.R. for
all new coke oven batteries as well as for rebuilt batteries if space permits.
We understand that in the U.S.S.R., with centralized planning, many of the
steel facilities are quite large and produce more than 5 million tons of steel
annually. Several dry quenching systems can be installed in an integrated
facility. The reliability question is, therefore, not a critical issue. Barker
(1976) reports that one Russian-designed installation is now operating in Japan
at Nippon's Steel Tobata Works. Nippon Steel has reportedly filed 16 patent
applications on modifications of the Russian design. Completion of another
dry-quenching installation based on the Russian design is expected in 1977 at
the Chiba Works of Kawatetsu Chemical Industry in Japan.
Two designs, both of which are based on the old Sulzer patent, are
presently offered to U.S. steelmakers. One is offered by Licenzintorg (U.S.S.R.)
and the other one is offered by Waagner Biro, an Austrian firm which acquired
the patent from Sulzer in 1971.
There is probably little future for dry quenching with coke ovens that
produce in the order of 1,000,000 tons a year. For such facilities only one
dry quenching station is needed, and the reliability issue then becomes critical.
Our discussions with steelmakers that have seen dry quench facilities in the
Soviet Union indicate that they would have real concerns about installing such
a facility without a backup to quench the coke. Without such a backup and with
the failure of a fairly complex system, such as a dry quenching facility is
reported to be, the complete steel facility would be in danger of closing for
lack of coke. It would then take several weeks, even months, to bring produc-
tion back into line. Thus prudent business practice would call for a backup
quench facility, and the lowest cost backup that is currently available and
that would meet current environmental regulations would be a wet quench tower.
Thus the U.S. steelmakers look upon dry quenching for many of their applications
as equipment that has to be installed in addition to their wet quench system.
For this reason, we have figured the costs on an incremental basis and looked
upon the dry quenching system as a mechanism to recover heat.
53
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For larger steel facilities, those producing 5,000,000 or more tons of
steel a year where multiple dry quenching towers would be needed, one could,
of course, eliminate the wet quench backup system. In such an instance, one
might be able to save about 10% of the estimated cost of $25 to $30 million
for three dry quench systems. Therefore, the applications for dry quenching
seem to be in large steel plants which will be undoubtedly re-examining on a
periodic basis the dry quenching option in the face of changing economic con-
ditions such as energy costs and dry quench facility investments.
E. DIRECT REDUCTION
The blast furnace is now - and will remain for decades to come - the
primary way of reducing iron ores, if only because most existing units are far
from the end of their useful lives. However, oxygen has been successfully
removed from solid iron oxides by gaseous reduction in a number of instances.
Traditionally, direct reduction units have been considered only where
special conditions have made them appear economically attractive as an alterna-
tive to the blast furnace (small production, unavailability of coke, special
incentives, etc.). The economic situation of industrialized countries is such
that the treatment of metallized ores in electric furnaces or in blast furnaces
may become an alternative to the conventional blast furnace practice.
Several processes, as shown in Table IV-21, have been proposed. Although
most of them have not been commercialized, a few are presently receiving con-
siderable attention in North America and in other parts of the world. For
example:
fluidized-bed direct reduction (FIOR process),
static bed process (HyL process),
shaft furnace (moving bed) processes (MIDREX, Armco), and
kiln-type processes (SL/RN*, Krupp, Kawasaki).
The first three processes require a gaseous reductant, while the kiln
processes generally operate with a solid fuel (coal) supplemented by liquid or
gaseous fuel injection. For the gaseous reduction processes, the reducing gas
normally has been generated from natural gas and occasionally from naphtha.
The shortages of these types of feedstocks cast some doubt about whether such
a gas-based process can be built in the United States.
Alternatively, heavier petroleum feedstocks or coal could be gasified
and the resultant gases, if of the proper quality, can be used in direct
reduction. Unfortunately, with such feedstocks, a considerable amount of sul-
fur usually enters into the reducing gas stream, normally as I^S or COS. To
utilize these gases in direct reduction, the sulfur-containing species would
*SL/RN comes from the name of the companies who developed this process;
Stelco-Lurgi/Republic Steel, National Lead.
54
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TABLE IV-21
CLASSIFICATION OF DIRECT-REDUCTION PROCESSES
1. PROCESSES USING SOLID REDUCTANTS
Kiln Processes
Krupp-Renn
R-N, SL-RN
Bassett
Sturzelberg
Domnarfvet
Hornsey-Wills
Retort Processes
Hoganas
Chenot
Larkins
DuPuy
Lang
Electric-Furnace Smelting Processes
Tysland-Hole
Lubatti
Elektrometall
D. L. M. (Dwight-Lloyd-McWane)
S trategic-Udy
Edwin-Elektrokemisk
Low-Shaft Blast-Furnace Processes
Ougree-Liege
Demag-HumboIdt
Weber
Miscellaneous Solid-Reductant
Process
RudoIph-Landin
Leckie
Gerhardt
PROCESSES USING GASEOUS REDUCTANTS
Kiln Processes
Maier-Mococo
Azincourt
Scortecci
Shaft-Furnace Processes
Wiberg-Soderfors
Norsk-Staal
U. S. Bureau of Mines
Skinner Multiple-Hearth
Cape-Brassert
United Verde
Norwegian H-Iron
Galluser
Purofer
Armco Steel
Midland-Ross
Fluidized-Bed Processes
Nu-Iron
H-Iron
A. D. L. (Esso Research-Little)
Stalling
Bubble-Hearth
Novalfer-Ouia
Retort Processes
Madaras-Mexican
Hyl
Jet-Smelting Process
0. R. F. (Ontario Research Foundation)
DIRECT-STEEL PROCESSES
0. R. F. Direct-Steel (Cavanagh)
Flame-Smelting (Cyclosteel)
Twyman
Source: Making, Shaping and Treating of Steel, U.S. Steel Corp., Pittsburgh, Pa.,
1971
55
-------
have to be scrubbed out. At present, there are no economical high-temperature
(1500-2000°F), sulfur-removal processes. If the gases have to be cooled in
order to scrub out the sulfur-containing species and then reheated, energy
costs and capital investments make such an alternative economically unattrac-
tive. For this reason we have focused here on the last alternative, namely,
the coal-based kiln processes, most of which use limestone, if necessary, for
sulfur control.
Since large plants have been - and are being - built using the SL/RN
process, we have used this particular process as the basis for out analysis.
Because 90 percent of the metallized products from direct reduction units is
charged to electric furnaces, as shown in Figure IV-10, we have chosen the use
of direct reduced material in electric arc furnaces (EAF) rather than using
direct reduced product in a blast furnace followed by the BOP for steelmaking.
As stated earlier, we have retained, for the base line technology, the conven-
tional coke oven-blast furnace-basic oxygen process. A schematic flowchart
of the base line is shown on Figure IV-11 with the alternative direct reduction-
electric arc furnace route shown on Figure IV-12. Examination of Figures IV-11
and IV-12 for the base line and alternative processes shows both using oxide
pellets to produce an equivalent end-product, namely 1,710,000 tons of molten
steel per year, as shown in Table IV-22.
SHAFT FURNACES
28%
STATIC BED
59%
FLUIDIZEDBED
4%
ROTARY KILNS
9%
1 1
PRODUCTION TO JULY, 1974
11.0 MILLION TONS OF METALLIZED PRODUCT
I
9%
BLAST
FURNACES
I
90%
ELECTRIC-ARC
FURNACES
I
0.6%
OPEN HEARTH
FURNACE, BOF
BALANCE
OTHERS
(CUPOLA, ETC.)
Source: Rollinger, B., "Steel via Direct Reduction," Electric Furnace
Proceedings, Vol. 32., p. 5, Pittsburgh, 1974
Figure IV-10. Production and Processing of Metallized Product, July 1974
56
-------
OXIDE PELLETS
METALLURIGCAL
COAL
Ul
COK
GAS
COKE OVEN
1
GAS
BYPRODUCT
PLANT
EOVEN
(FUEL)
COKE
(CLEANED BATEA)
(F
OTHER BYPRODUCTS (SOLID)
LEGEND: (A) AIR POLLUTION
(w) WASTE WATER
0 SOLID WASTE
0 FUGITIVE EMISSIONS
* OPTIONAL
t '
LIMESTONE
(FUEL)*
'iL
BLAST
FURNACE
^ l
1
BOP SHOP
\
ST
s)
MAKE-UP WATER
WET
SCRUBBER
1
WATER
TREATMENT
1
^0 SLUDGE
1 MAKE-UP WATER
I
i
T0
SLAG
(LANDFILL)
= EL
WET
SCRUBBER
i i
l
WATER
TREATMENT
CLEAN BF GAS (FUEL)
(LANDFILL)
CLEAN BOP GAS (FUEL!
Figure IV-11.
,S) SLUDGE
(LANDFILL)
Schematic Flow Diagram of the Base Line
Process for Steelmaking
-------
©
FLARED
Ui
00
OXIDE PELLETS
COAL
MAKE-UP WATER
WET
SCRUBBER
WATER
TREATMENT
SLUDGE
(LANDFILL)
©
LEGEND:
(A) AIR POLLUTION
@ WASTEWATER
(s) SOLID WASTE
(?) FUGITIVE EMISSIONS
OPTIONAL
RETURN COAL
LIMESTONE
((FUEL)" _.
1 ©
3 KILNS
ASH. FINES, USED LIMESTONE
PREREDUCED
PELLETS
SEPARATION
UNITS
SCRAP
©
ELECTRIC AIR
FURNACES
LANDFILL
ASH
BURNED LIME
BLEED COAL
FILTERS
©
ATMOSPHERE
SLAG
(LANDFILL)
DUST
(LANDFILL)
STEEL
Figure TV-12. Schematic Flow Diagram of the Direct Reduction Route
-------
TABLE IV-22
DEFINITION OF THE BASE LINE
AND PROCESS OPTION CONSIDERED FOR DIRECT REDUCTION
Base Line
Process
Step
'oke Oven
Jlast Furnace
SOP Shop (2)
Product
Coke
Hot Metal
Steel
Capacity
(annual tons
product)
660*000
1,200,000
1,710,000
Process Option
Process
Step
DR Plant ^
(2)
EAF Shopv '
Product
Reduced
Pellets
Steel
Capacity
(annual tons
product)
1,200,000
1,710,000
EAF = Electric Arc Furnace
NOTE 1: The coke consumption of the blast furnace is 1,100 Ib/ton of
hot metal.
NOTE 2: Both routes use 30% scrap in their steelmaking vessels.
NOTE 3: The direct reduction plant consists of three SL/RN units having
an annual capacity of 400,000 tons each.
The following pages on direct reduction are broken down into four main
sections:
1. Description of the direct reduction route to steelmaking.
2. Pollutant emissions, abatement technology, and costs.
3. Energy use of the two process routes to steelmaking.
4. Investments and operating costs.
1. The Direct Reduction Route
a. Description of the SL/RN Process
Each existing plant is unique in its design and application; however,
Figure IV-12 shows a typical flow sheet for the treatment of high-grade pellets
or lump ore and solid reductants with a low content of volatile matter. Iron
oxides, coal, and lime for desulfurizing are mixed and charged into a rotary
kiln. Coal provides the reducing gas (CO) and the sensible heat for the reduc-
tion of iron oxides. Air is admitted at the lower end of the kiln and, through
several blowers, is distributed along the length of the kiln. Supplementary
fuel can be supplied by oil burners. The temperature, measured by thermocouples,
is regulated to around 1922°F by the air and fuel rates. The spent gases
exit at the charging end of the kiln at about 1200°F. It is therefore a
countercurrent process, although other units have been designed as concurrent
reactors.
59
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Theoretically, a wide variety of charge characteristics is acceptable;
lump ore, green balls, indurated pellets, and even wet concentrates have been
considered. The acid gangue content, however, should be less than 2-4% so
that the product will be acceptable as feedstock for a blast furnace or
electric arc furnace. Also, any reductant is acceptable as long as the ash
does not fuse or form low-melting compounds with other species present, such
as the desulfurizing agent and the gangue coming with the iron oxides. The
softening point of the coal should be at least 210°F above the maximum temper-
ature in the kiln. Thus, the type of coal has an important bearing on the
successful operation of the kiln.
Figure IV-13 shows a section of the kiln in the reducing zone. The
rotary movement facilitates the heat and mass transfers. The product is highly
metallized; that is, 93-95% of the total iron is present as metal.
CO-FLAME
INTERMEDIATE LAYER OF \^^^>, OXIDIZING
THE OXIDES OF CARBON fj\ ^C^ FURNACE
APPEARING ON THE /OV ^ GAS
CHARGE SURFACE
REDUCTION OF THE IRON
OXIDES IN THE INTERIOR
OF THE CHARGE
Source: Johannsen, quoted in L.v. Bogdandy and
H.J. Engell, "The Reduction of Iron Ore,"
Springer Verlag, Berlin, 1971.
Figure IV-13. The Reduction Zone of the SL/RN Process
After the reduction has taken place, the products pass into a cooling drum
where they are cooled to below 210°F to prevent reoxidation. The cooler
discharge, consisting of coarse- and fine-grain sponge-iron excess coal, coal
ash and desulfurizing agents, is split into the individual components by screen-
ing and magnetic separation. They may also be separated by electrostatic sepa-
ration, flotation, and air jig. At times, difficulty has been experienced in
separating the coal from the ash; extreme care and skill must be used to avoid
either excessive coal usage or excessive ash buildup. The unburned or excess
coal is largely recycled.
If pellets are fed the metallized products are produced in the form of
pellets along with some fines. The pellets are not pyrophoric and they do not
reoxidize, so long as they are not brought into contact with condensed water.
Moreover, any excessive air draft through a pile of prereduced pellets should
be avoided. If a steelmaking plant is adjacent to the kiln, the fines and
pellets can be charged continuously. If the product has to be shipped, the
fines must be briquetted or otherwise agglomerated, which increases their cost.
60
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b. Uses for Prereduced Materials in Iron and Steelmaking
Prereduced materials are an intermediate product since they cannot be
thought of as either an ore or a metal in the common sense. They are being
considered today as a feedstock to both blast furnaces and electric furnaces.
(1) Use in Electric Arc Furnaces
Ninety percent of the prereduced materials produced in the world is fed to
electric arc furnaces (EAF). Although the operating conditions vary signifi-
cantly from plant to plant (composition of the feedstock, capacity, power,
charging method, end-product), one may characterize the process as follows.
The EAF usually melts scrap (home and/or purchased) together with the
prereduced materials. Whereas the roof must be open in order to charge scrap,
the prereduced materials are more often charged continuously (Figure IV-14).
With direct reduced materials, coke is often used and three pounds of limestone
are added for each pound of silica contained in the prereduced materials to
operate the EAF under normal basic conditions.
The utilization of prereduced materials has a good potential for minor
element control. Elements that tend to build up in steel because of scrap
recirculation (Cu, Ni, Cr, Sn) undergo some dilution. The phosphorus content
depends largely on the ore quality, because direct reduction processes are not
likely to remove it in significant proportions. The sulfur content depends on
the ore quality and the reduction practice. Should the sponge iron be suffi-
ciently low in sulfur and phosphorus, either lower grades of scrap could be
used in conjunction with prereduced materials or the refining period could be
shortened.
In conclusion, EAF's of traditional design can accommodate prereduced
materials with no limitation on the grade of steel produced.
SCATTER BOX
THREE
RETRACTABLE
TUBES
SOURCE: Lurgi Publication No. 166.
Figure IV-14. Example of Continuous Charging System
61
-------
(2) Use in Blast Furnaces
Ten percent of the prereduced iron units produced in the world is
charged to blast furnaces.
As shown in Figures IV-15 and IV-16, coke consumption decreases by 0.5%
and the production increases by 0.7% with each percent of burden metallization.
The production of a blast furnace plant with an annual capacity of 2 million
tons of pig iron, for example, can be raised by 25% to 2.5 million tons by
premetallizing the burden to approximately 35%. A sponge-iron plant with an
annual capacity of about 1 million tons would be needed to achieve the same
increase with equal ores.
Should prereduced materials become available on the U.S. market, some
flexibility in blast furnace productivity could be gained. However, they would
probably introduce no new pollution control problems around the blast furnace.
Thus, for purposes of this study, we focused on the direct reduction/electric
furnace route to steelmaking and compared it to the conventional coke oven-
blast furnace-basic oxygen process.
c. Technological Problems
(1) The SL/RN Process.
Although it may seem a relatively simple device, a rotary kiln is very
difficult to operate. Some attrition of the charge is bound to occur. Further-
more, the dust particles tend to overheat and sinter in "dam rings" against the
shell of the furnace. These rings slowly build up to the point of completely
obstructing the furnace, forcing a complete shutdown of the operations.
The control of the temperature profile in the kiln is complex and critical.
Without going into a detailed discussion of the heat and mass transfers
involved, one must emphasize this point as the one on which extensive R&D is
still proceeding. The reaction zone is actually very narrow and non-uniform,
so that the formation of pasty or liquid products that eventually solidify on
colder regions and force a shutdown of the kiln is difficult to avoid.
(2) Electric Arc Furnaces
These process units are usually similar to the traditional scrap melting
units. However, refractory consumption is a problem in electric arc furnace
operations in which metallized products are used. Generally, it is 20 to 60%
higher than that for all-scrap practice. This increased refractory consumption
results principally from continuous charging of prereduced material with full
power; the furnace walls are unshielded by scrap and the radiation of the arc
damages the walls, especially in the areas of the hot spots. A second factor
is the increased slag volume, which has a corrosive effect on the walls. The
decrease in the roof-lining life can be attributed to the fines generated
during handling and charging of the sponge iron. These fines penetrate the
refractories and form low-melting eutectics. These problems are partially
controlled by
62
-------
100
90
g
z
2 80
I
8
70
60
50
40
10
_L
J L
_L
_L
_L
20 30 40 50 60 70 80 90
J L
100
-^- METALLIZATION OF BURDEN (%)
0,A
U.S. BUREAU OF MINES DATA
STEEL COMPANY OF CANADA LTD. DATA.
SOURCE: USBM and Lurgi, Publication No. 166
Figure IV-15. Decrease of Coke Consumption by Charging Prereduced
Burden into the Blast Furnace
180 -
10
20 30 40 50 60 70 80 90 100
^- METALLIZATION OF BURDEN (%)
0,4
U.S. BUREAU OF MINES DATA
STEEL COMPANY OF CANADA LTD. DATA.
SOURCE: USBM and Lurgl, Publication No. 166
Figure IV-16. Increase of Blast Furnace Production by
Charging Frereduced Burden
63
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shielding the walls with unmelted scrap as much as possible;
utilizing special refractory material in the area of the hot spots,
with the corresponding cost differential; and
cooling the walls with waterwith corresponding increase in energy
consumption.
Electric energy consumption is higher than with an all-scrap practice as
a result of the:
energy required to reduce the residual oxygen content of the metal-
lized product; and
heating and melting requirements for the additional slag generated
by the gangue from the product.
If the metallized material requires significantly more lime, the total
slag volume increases, and therefore more electric energy is used. Additional
heat losses in the fumes leaving the furnace also must be compensated for.
2. Pollutant Emissions and Abatement Technology
The sizes and types of process units used for this evaluation are those
previously mentioned (Table IV-22). We anticipate no pollutional difference
due to the pellets between the two alternative technologies being considered
here. In both cases, we anticipate that there will be fugitive emissions and
dusting from the pellets being unloaded and stored on the steel mill grounds.
Similarly, the amount of coal that is used in the two technologies is about the
same. One uses metallurgical coal and the other steam coal, but we have come
across no data to indicate a significant difference in the dusting problems
and water run-off from the coal piles from these two types of coals. The prob-
lems associated with coal storage are thus not addressed within the iron and
steel sector of this study.*
a. Air Pollution
The air pollution costs of the base line (BATEA** technology) are shown
in Table IV-23. They amount to $2.62 per ton of steel.
The direct reduction route generates air pollution of the following types:
Point sources: exhausts of the kilns and electric furnaces; and
Fugitive sources: from magnetic separators and transfer operations.
*This is discussed in the "Ammonia" report also prepared under this contract
(Chapter IV, "Ammonia Production" based on Coal Gasification).
**BATEA = Best Available Technology Economically Achievable.
64
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TABLE IV-23
AIR POLLUTION CONTROL FOR BASE CASE
(Basis: 1.2 million ton/yr Iron)
Capital Cost, $
Blast Furnace
Coke Oven
Basic Oxygen Furnace
Total
Operating Cost, $/ton
Variable Costs
Labor (total)
Maintenance @ 5% of Capital
Utilities
Electric Power @ $0.016/kWh
Water @ $0.20/103 gal
Total
Fixed Costs, $/ton
Depreciation, 18 years
Insurance & Taxes @ 2%, Capital
Total
Total Production Cost, $/ton
Return on Investments (pre-tax) @ 20%
Total Unit Cost, $/ton
-0-
6,411,000
4,669.000
11,080,000
0.07
0.46
0.53
0.13
1.19
0.51
0.18
0.70
1.89
1.85
$ 3.74/ ton hot metal or
$ 2.62/ton steel
The gas flow rate from each kiln is estimated to be 57,000 scfm at
1200°? with a composition of 64% N2, 2% C02, and 34% CO. In addition, S02, in
a very low concentration, will be present in the gases arising from the fuel's
sulfur content and from the ore. The estimated particulate loading will be
0.95 Ib/ton of product. The chemical nature of the particles is Fe, ^304, C,
Si02, ash, CaO, and tramp elements. The large particulates in the exhaust will
be removed in the cyclone and recycled. The smaller particulates including
some submicron particulates will be removed using a high-energy venturi scrub-
ber. The exhaust from the scrubber is a clean gas which can be flared. Lurgi
(Dec., 1975) has claimed that the off-gases have a supplemental fuel value of
70 Btu/scf, but this depends on operating practice and cannot be generalized.
It may be even lower.
The electric arc furnace exhausts are not significantly different from
those of conventional units, except that their dust load may be 10 - 20%
higher. Electrostatic precipitators will be installed and should suffice.
Table IV-24 summarizes the air pollution costs of the direct reduction
plant and Table IV-25 for the electric furnaces. For a fair compairson of the
two routes, it must be remembered that the gas-cleaning devices of the blast
furnace are considered process equipment, because they continuously deliver
blast furnace gas (80-90 Btu/scf) to the stoves and other facilities. There-
fore, they do not appear as a pollution control device.
65
-------
TABLE IV-24
AIR POLLUTION COSTS FOR THREE DIRECT REDUCTION KILNS
(Basis: 1,200,000 ton/yr)
Capital Cost:
$ 5,658,000
Operating Costs:
Variable Costs: $
Electric Power @ $0.016/kWh 95,400
Water
-------
Table IV-26 shows that the cost of air pollution control in the direct
reduction route is $3.21/ton of steel.
TABLE IV-26
TOTAL AIR POLLUTION COST FOR THE DIRECT REDUCTION ROUTE
$/ton Steel
DR Kiln Air Control: $1.12(1)
EAF Air Control: 2.09
Total $3.21/ton steel
b. Effluent Wastewater
(1) The Base Case
As previously discussed, the base case consists of a byproduct coke oven,
a blast furnace, and a basic oxygen furnace shop, all of which generate waste-
water streams. Wastewaters from byproduct coke operations contain high con-
centrations of ammonia, oil and grease, and phenol (all three of which exert a
biochemical oxygen demand), plus cyanide, sulfide, and suspended solids. Waste-
water characteristics of blast furnace scrubber water have been described in the
discussion of the direct-reduction alternative. The basic oxygen furnace gener-
ates a wastewater containing suspended solids and fluorides. The three treat-
ment systems chosen in the EPA Development Document (1974) for the attainment
of the BATEA treatment levels have been used in estimating the capabilities
and costs of treatment. These treatment systems are:
Byproduct Coke
1) Distillation (with ammonia recovery) of waste ammonia liquor,
2) Alkaline ammonia stripping,
3) Neutralization,
4) Settling,
5) Air flotation,
6) Two-stage chlorination,
7) Clarification (with vacuum filtration of sludge),
8) Filtration, and
9) Carbon adsorption:
(1)
The feed to the EAF is a mix of sponge iron and scrap.
67
-------
Blast Furnace
(See direct reduction discussion); and
Basic Oxygen Furnace
1) Clarification (97% recycle of effluent),
2) Neutralization,
3) Lime precipitation,
4) Clarification (with vacuum filtration of sludge), and
5) Final neutralization.
An estimate of the treated effluent characteristics is presented in
Table IV-27. Column D of Table IV-27 lists the total treated effluent waste
load for the entire base case.
(2) Direct Reduction Alternative
There is one significant wastewater stream from the direct reduction
process: the kiln exhaust gas scrubber water. (The direct reduction process
requires non-contact cooling water at the rate of about 4,000 gal/ton of iron,
but this water is comparable in volume and composition to that of the blast
furnace it replaces, and thus will not be included in the comparison.)
The exact composition of the kiln exhaust gas is not known. In view of
the chemistry of this process, the exhaust gas and its associated scrubber
water should be similar to that of a conventional blast furnace. The composi-
tion of blast furnace scrubber water has been established reasonably well. The
major pollutants of concern in blast furnace scrubber water are:
suspended solids, ammonia,
cyanide, sulfide, and
phenol, fluoride.
Due to the reducing atmosphere in the solid bed in the reduction kiln and
the abundance of carbon, nitrogen, and sulfur in the coal, it is reasonable to
expect that the exhaust gas scrubber water will contain cyanide, phenol, ammonia,
and sulfide. Since no fluorspar fluxing agent is used in the direct reduction
process, there would not normally be any fluoride in the exhaust gas scrubber
water. This is an important environmental advantage of the direct reduction
process over the base case.*
*If fluorspar appears in the raw materials (limestone or coal), fluorides can
be expected in the exhaust gases and the scrubber water is treated accordingly.
68
-------
TABLE IV-27
BASE CASE TREATED EFFLUENT WASTE LOAD
Basis: Coke Oven - 660,000 ton/yr
Blast Furnace -1,200,000 ton/yr
Basic Oxygen Furnace-1,710,000 ton/yr
Parameters
Suspended Solids
BOD5
Oil & Grease
Cyanide (2)
Phenol
Ammonia (as NH.)
Sulfide
Fluoride
Flow Rate
Treated Byproduct
Coke Oven Effluent
(Ib/dav
15.1
30.2
15.1
0.38
0.75
15.1
0.45
-
(mg/1)
10
20
10
0.25
0.5
10
0.3
-
180,800 gpd
Treated Blast
Furnace Effluent
(Ib/dav)
34.3
-
0.86
1.72
34.3
1.0
68.6
(mg/1)
10
NIL
NIL
0.25
0.5
10
0.3
20
411,000 gpd
Treated Basic
Oxygen Furnace Effluent
Mh/Hav)
48.8
-
0
-
-
39.1
(mg/1)
25
-
0
-
:
20
234,000 gpd
Total Treated Effluent
Waste Load
(Ib/dav)
98.2
30.2
15.1
1.24
2.47
49.4
1.45
107.7
825,800 gpd
Notes: 1) All effluents are subjected to "Best Available Technology Economically Achievable1' (1983).
2) Cyanide is amenable to alkaline chlorination.
-------
Since the wastewater from the direct reduction process is expected to be
similar to blast furnace wastewater, it is reasonable to expect that the direct
reduction scrubber water will have to be subjected to the same treatment as
blast furnace scrubber water. The BATEA (Best Available Technology Economically
Achievable) treatment level, to be implemented by 1983, is envisioned to require
the following treatment steps:
Clarification of the once-through scrubber water with vacuum filtra-
tion of the solids;
Cooling and recycling (upwards of 97%) of the clarifier effluent; and
Treatment of the recycle loop blowdown by
1) alkaline chlorination,
2) neutralization,
3) clarification,
4) filtration, and
5) carbon adsorption.
Each direct-reduction kiln, with an estimated exhaust gas flow rate of
57,000 scfm, is equivalent (in terms of gas volume) to a blast furnace having
a capacity of 1,296 ton/day. Application of the BATEA treatment level is expected
to result in a treated effluent wastewater discharge of 125 gal/ton, or 162,000
gpd. Based on the expected effluent concentrations set forth in the EPA Iron
and Steel Development Document, (1974), Table IV-28 presents an estimation of
the treated effluent wastewater load from the direct reduction process. Table
IV-29 summarizes the comparison of the two routes.
TABLE IV-28
DIRECT REDUCTION TREATED WASTEWATER LOAD
(Basis: 1,200,000 ton/yr)
Parameter
Suspended Solids
BODj
Oil & Grease
Cyanide
Phenol
Ammonia
Sulfide
Fluoride
Treated Effluent
Concentration
(mg/1)
10
MIL
NIL
0.25
0.50
10
0.3
Treated Effluent
Waste Load
( Ib/ton)
58.5
1.02
2.04
57.15
1.23
Not Present
Flow Rate
Remarks :
486,000 gpd
1) Direct reduction-treated effluent Is expected to be very nearly
the same as the treated effluent from a blast furnace.
2) Direct reduction kiln scrubber water is subjected to "Beat Avail-
able Technology Economically Achievable" (1983) specified for
blast furnace scrubber water.
3) Cyanide amenable for alkaline chlorination.
70
-------
TABLE IV-29
DIRECT. REDUCTION COMPARISON OF TREATED WASTEWATER1 LOADS
Parameter
rf
Suspended Solids
BOD5
Oil & Grease
Cyanide
Phenol
Ammonia
Sulfide
Fluoride
Flow Rate
Total Base Case Treated
Effluent (Based on:
1,200,000-ton/day
Blast Furnace Capacity)
(Ib/day)
98.2
30.2
15.1
1.24
2.47
49.4
1.45
107.1
825,800 gpd
Direct Reduction
Treated Effluent
(Based on 1,200,000-ton/day [3 kilns] capac
(Ib/day)
98.2
nil
nil
1.24
2.04
58.5
1.45
NIL
486,000 gpd
NOTES: 1) All treated effluents are subjected to the "Best Available Technology
Economically Achievable" (1983).
2) Cyanide amenable to alkaline chlorination.
-------
(3) Wastewater Treatment Costs
Wastewater treatment cost estimates for attaining the BATEA treatment level
have been developed for both the base case and the direct-reduction alternative.
The base case cost estimates are presented in Table IV-30, the direct-reduction
cost estimates in Table IV-31, and the comparison of the two in Table IV-32.
As can be seen from the comparison presented in Table IV-32, the direct-
redoetion alternative has a unit treatment cost that is approximately 54% of
the base case. Most of the reduction in cost is due to the absence of the
wasfewater-generating coke oven and BOP alternative.
c. jtolid Waste Disposal
(1) Base Case
Each of the production units within the base case produces large volumes of
solid waste, which are:
Byproduct Coke - Solid wastes include coke dust and wastewater treat-
ment sludge;
Blast Furnace - Solid wastes include furnace slag and wastewater treat-
ment sludge; and
Basic Oxygen Furnace - Solid wastes include furnace slag and wastewater
treatment sludge.
Estimated quantities and disposal costs are presented below:
Yearly Total Yearly Unit ,^
Parameter Quantity Disposal Cost^^ Disposal Cost
(ton/yr) ($/yr) ($/ton output)
Byproduct Coke 13,200 66,000 0.04
BlastTFurnace 240,000 1,200,000 0.70
Basic-ftxygen Furnace 256,500 1,282,500 0-75
TOTAL SOLID WASTE 509,700 $2,548,500 $1.49/ton steel
(1) ^Disposal cost @ $5.00 per actual^ton.
(2) ^Based on 1,710,000 ton of steel/year.
72
-------
TABLE IV-30
BASE CASE WASTEWATER TREATMENT COSTS
(Basis: 1,200,000 ton of Hot Metal/yr)
CAPITAL INVESTMENT - $18,700,000
VARIABLE COSTS
Operating Labor (L)
Supervision (S)
Labor Overhead
Maintenance
(Labor + Materials)
Chemicals
includes :
lime
chloride
acid
activated carbon
Electrical Power
Fuel
TOTAL VARIABLE COST
FIXED COST
Plant Overhead
Taxes & Insurance
Depreciation (@ 5.6%)
TOTAL FIXED COST
TOTAL ANNUAL COST
Annual
Quantity
84,000 hr
15% (L)
35Z (L+S)
-
_
Cost per
Unit Quantity
$ 7.00/man-hr
-
12,700,000 kWh $0.016/kWh
435,600 x 1C
65Z (L+S)
-
2% CI
18 years
RETURN ON INVESTMENT 20Z CI
6Btu $2.00A06Bti
Quantity per
Ton of Product
0.07
-
_
10.62
0.363
-
$ per Ton
of Hot Metal
0.49
0,07
0.20
0.77
0.26
0.17
0.73
2.68
0.36
0.31
0.87
1.54
.4.22
3.12
TOTAL
$7.34/ton hot metal
or
$5.IS/ton steel
NOTES: 1) Base Case includes byproduct coke, blast furnace, and basic oxygen
furnace.
2) Cost estimates are for the ground-up implementation of the "Best
Available Technology Economically Achievable" treatment level (1983).
3) Cost does not include wastewater treatment sludge disposal.
However, this cost is included in the discussion of solid waste
disposal.
73
-------
TABLE IV-31
DIRECT REDUCTION KILN SCRUBBER WASTEWATER TREATMENT COSTS
(Basis: 1,200,000 ton of sponge iron/yr)
CAPITAL INVESTMENT- $8,535,360 (CI)
VARIABLE COSTS
Operating Labor (L)
Supervision (S)
Labor Overhead
Maintenance
(Labor & Materials)
Chemicals includes:
lime
chlorine
acid
activated carbon
Electrical Power
Fuel
TOTAL VARIABLE COST
FIXED COST
Plant Overhead
Taxes & Insurance
Depreciation 18 yrs
TOTAL FIXED COST
TOTAL ANNUAL COST
Annual
Quantity
48,000 man-hr
15% (L)
35% (L+S)
10,500,000 kWh
320,000 106 Btu
65% (L+S)
2% CI
r-
Cost per
Unit Quantity
$ 7. 00 /man-hr
$ 0.016/kWh
$ 2.00/106Btu
_
;
Quantity per
Ton of Product
0.03
8.77
0.266
-
-
$ per Ton
of Product
0.28
0.04
0.11
0.41
0.28
0.14
0.53
1.79
0.21
0.14
0.40
0.75
2.54
RETURN ON INVESTMENT
TOTAL
20% CI
1.42
$3.96/ton sponge
lro:a or
$2.77/ton steel
NOTES: 1) Cost estimates are for the ground-up implementation of the "Best Available
Technology Economically Achievable" treatment level (1983).
2) Cost does not include wastewater treatment sludge disposal.
74
-------
TABLE IV-32
DIRECT REDUCTION VS BASE CASE COMPARISON OF
WASTEWATER TREATMENT COSTS
($/ton of Product)
VARIABLE COSTS
Operating Labor (L)
Supervision (S)
Labor Overhead
Maintenance
(Labor & Materials)
Chemicals includes :
lime
chlorine
acid
activated carbon
Electrical Power
Fuel ;
TOTAL VARIABLE COST
FIXED COST;
Taxes & Insurance
Depreciation
TOTAL FIXED COST
TOTAL ANNUAL COST
RETURN ON INVESTMENT
BASE CASE
0.49
0.07
0.20
0.71
0.26
0.17
0.72
2.68
0.31
0.87
1.54
4.22
3.12
DIRECT REDUCTION
0'.-28
0.04
0.11
0.41
0.28
0.14
0.53
1.79
0.14
0.40
0.75
2.54
1.42
TOTAL
$7.34/ton hot metal $3.96/ton sponge iron or
$5.15/ton steel $2.77/ton steel
NOTES: 1) Cost estimates are for the ground-up implementation of the "Best
Available Technology Economically Achievable" treatment level (1983) .
2) Costs do not include wastewater treatment sludge disposal.
3) Both routes use about 30% scrap in the steelmaking step.
75
-------
(2) Direct Reduction
The direct-reduction process produces four sources of solid waste:
Direct reduction kiln waste,
Wastewater treatment sludge,
Electric furnace slag, and
Electric furnace air pollution control dust.
The direct reduction kiln waste consists of the following components:
lime - 140 Ib/ton of output
coal ash - 125 Ib/ton of output
discarded coal* - 100 Ib/ton of output
Total solid waste = 365 Ib/ton of output
This is equivalent to 219,600 ton/yr from a 1,200,000-ton/yr direct-
reduction facility.
Wastewater treatment sludge is estimated to be generated at a rate of
187,000 ton/yr of dewatered sludge (@ 35% solids). The wastewater treatment
sludge should be similar to blast furnace scrubber water sludge in that the
liquid fraction of the sludge will probably contain cyanide, ammonia, phenol,
and sulfide. However, there should not be any fluoride present in the waste-
water treatment sludge from the direct-reduction alternative. As in the case
of the blast furnace wastewater treatment sludge, care must be taken in its
disposal to avoid groundwater contamination.
Electric furnace slag is estimated to be generated at the rate of 239,400
ton/yr, and electric furnace air pollution control dust is estimated at 8,600
ton/yr. In a qualitative sense, the environmental problems associated with
the disposal of solid waste from the direct-reduction process are very nearly
the same as those associated with the conventional base case operations. An
estimation of the total yearly solid waste disposal cost for the direct reduc-
tion process is:
*A major part of the larger sized coal particles can be separated from the ash
and recycled. Coal fines that cannot be screened from the ash are discarded.
76
-------
Yearly Total Yearly Unit
Waste Stream Quantity Disposal Cost^) Disposal Cost
(ton/yr) ($/yr) ($/ton of steel)
Kiln Waste 219,600 1,098,000 0.64
Wastewater Treatment 187,800 939,000 0.55
Sludge
Electric Furnace Slag 252,000 1,260,000 0.74
(2)
Electric Furnace Dustv ' 9,000 45.000 0.03
TOTAL SOLID WASTE 668,400 3,342,000 $1.96/ton steel
(1) Disposal cost @ $5.00 per actual ton
(2) The air pollution control for the arc furnace is a bag house.
While it is not considered in detail here, we understand that fines may be
generated by abrasion of the iron oxide pellets in the direct-reduction units
leading to iron losses. If a direct-reduction unit were in an integrated steel
plant having a sinter strand, such fines could be fed to this unit. Alterna-
tively, a limited amount of fines could be fed into the electric arc furnaces.
However, if a significant quantity of fines were generated in a non-integrated
plant, it may cause a pollution problem, either of dusting to the atmosphere,
or the fines being entrained in rain water run-off. Further research is needed
to define the magnitude of this problem.
From these estimates it appears that the direct-reduction process has a
slightly higher solid waste disposal cost. The quantities of solid wastes from
the various operations included in this comparison can vary considerably from
plant to plant. It is conceivable that in certain instances the direct-reduction
process could generate the same or even less solid waste than the base case. On
the whole, the solid waste disposal problems and cost for the two alternatives
are very nearly the same and certainly not different enough in quantity, cost,
or impact to serve as a deciding factor.
d. Summary of the Pollution Control Comparison
In conclusion to the preceding paragraphs:
The direct-reduction route creates less severe pollution problems,
as the coke plant weighs heavily in the total amount of pollutants
generated in the base case.
Consequently, pollution control costs are significantly lower with
the direct-reduction route. Capital costs are reduced by one-third
($20 million versus $30 million) and operating costs are 15% lower
($7.94 versus $9.26 per ton of steel); see Table IV-33.
77
-------
TABLE IV-33
SUMMARY OF POLLUTION CONTROL COSTS
Base Line Direct Reduction Route
Capital Costs:
Air $11,080,000 11,258,000
Water $18,700,000 8,535,360
Solid
Total $29,780,000 $19,793,360
Operating Costs ($/ton of steel)
Air 2.62
Water 5.15
Solid 1.49
Total $9.26
3. Energy Usage
Table IV-34 summarizes the energy usage of the conventional and direct-
reduction routes for making steel. Clearly the direct-reduction route uses more
energy (18.45 Btu/ton) than the conventional route (11.84 Btu/ton).* The base line
has the advantage that the blast furnace is a remarkably efficient device
against which several smaller direct-reduction vessels have a net thermal dis-
advantage. This is aggravated by the fact that the pellets must: be substan-
tially (if not completely) cooled before being transferred to the electric
furnace.
As noted earlier the exhaust gases from the kiln may represent a heating
value of 70 Btu/scf. This, however, can vary with time and is subject to vari-
ous operating parameters. Since the gases have a low heating value we believe it
would be difficult to use them economically and thus no energy credit is taken
in this analysis. The energy advantage of the direct reduction is its ability
to use non-coking coal, a resource that is much more plentiful and cheaper than
metallurgical coal.
*These numbers do.not include the power consumption of ancillary equipment such
as handling, etc.
78
-------
TABLE IV-34
ENERGY REQUIREMENTS OF THE CONVENTIONAL AND
DIRECT REDUCTION STEELMAKING ROUTES
10 Btu/ ton steel
Direct Reduction
Kiln
Coal 10.96
Electric Power W 0.41
Electric Arc Furnace
Electric Power*-1* 6-30
Total Production 17.67
Pollution Controls;
Air: Kiln (electric power) 0.036
EAF (electric power) 0.487
Water: Kiln (electric power) 0.065
Kiln (fuel) 0.187
Total Pollution O-78
Total: ______________________________ 18.45
Base Line
Coke Oven I-85
Blast Furnace ,^ 9.45
Basic Oxygen Process^ ' (0.13)
Total Production 11.17
Pollution Controls:
Air (electric power) f °-34
Water (electric power) 0.08
Water (fuel) °-25
Total Pollution
Total :
(1) 1 kWh = 10,500 Btu fuel equivalent at power source.
(2) Includes 0.44 x 106 Btu credit for CO recovery.
Remark: This table assumes that both the base case and the direct
reduction alternative . use 30% scrap with a zero energy content.
79
-------
4. Investments and Operating Costs
a. Capital Costs
The same production capacities were adopted for comparing the base line
and the option. Table IV-35 summarizes the capital costs of the two routes.
Modern direct-reduction facilities often consist of one or several 400,000
ton/yr modules. One such SL/RN facility includes the raw materials intake and
the handling facilities for the shipment of products. The economy of scale
realized with three kilns is small and rests largely with the raw materials
and products handling capacity. A direct-reduction plant, including three
SL/SN kilns, was estimated to cost about $168 million. The electric arc fur-
nace shop has a capacity for melting 30% scrap and 70% prereduced materials.
Its capital cost is $65 million, bringing the total capital associated with the
production costs to $233 million. For comparison the base line investments are
estimated to be $195 million. Due to the absence of the coke oven and the
simpler pollution technology required by electric furnaces (as compared to
BOP's), the cost of pollution of the DR route is 2/3 that of the base line
($20 million versus $30 million).
TABLE IV-35
CAPITAL COSTS
BASE CASE;
Process Unit
Coke Oven
Blast Furnace
EOF Shop
Total Production
Wastewater Treatment
Air Pollution Control
Total Pollution
TOTAL BASE CASE
Capacity (ton/yr)
660,000 (coke)
1,200,000 (iron)
1,710,000 (steel)
Investment ($10 )
60
90
45
18.70
11.08
195
29.78
$224.78
DIRECT REDUCTION;
Process Unit
Three Kilns
Kiln Air Treatment
EAF Shop
Total Production
Wastewater Treatment
Air Pollution Control
Total Pollution
TOTAL DIRECT REDUCTION
Capacity (ton/yr)
1,200,000 (iron)
1,710,000 (steel)
Capital ($10°)
168
65
8.53
11.26
233
19.79
$252.79
80
-------
The total capital costs of the DR route are $253 million, or 10% more than
that of the base case ($225 million). Such a difference is well within the cost
estimating procedure; thus both routes can be considered equally capital-
intensive. From the viewpoint of minimizing investments, much larger facilities
would favor the blast furnace route, because of the economy of scale. Conversely,
much smaller facilities would favor the direct-reduction approach.
b. Operating Costs
Tables IV-36 through IV-38 give the breakdown of the operating costs of the
three process units of the base line sequence. The pollution control costs are
excluded, as they have been reported separately. On this basis, raw steel costs
$134.l4/ton. The pollution control costs are $9.26/ton, so that the total charge
against raw steel production is $143.40/ton.
Tables IV-39 and IV-40 give the breakdown of the operating costs of the
two process units of the DR route: raw steel costs $139.89 a ton. Lower pol-
lution costs still add $7.94, giving a total charge against raw steel production
of $147.83.
The 3% difference between the two routes shown in Table IV-41 is well within
the cost estimate uncertainty and does not favor either route. Operating costs
again do not constitute a significant decision factor.
5. Adoption Status
Table IV-42 gives the nominal characteristics of existing SL/RN facilities
around the world as communicated by Lurgi (1975).
The SL/RN process has had a history of operating difficulties. While some
of our industry contacts clearly question whether these technical problems can
ever be solved with a kiln based process, others are more optimistic. Construc-
tion of an SL/RN kiln 19.7 ft in diameter and 410 ft long has just been com-
pleted at Griffith Mine in Northern Ontario. It has a design capacity of
400,000 net tons of prereduced pellets per year. The solid reductant is a
subbituminous coal from Alberta; the prereduced pellets (95% Fe) will possibly
be shipped, by the same rail cars bringing the coal, to a 500,000-ton/yr steel
mill in Alberta featuring three electric furnaces. Any objectionable (more
than 1%) repxidation of the pellets during transportation is expected to be
effectively prevented by use of covered railroad cars. The degree of success
with which this facility will operate will be closely watched by the iron and
steel industry as a new test of the viability of the process.
The results of this new plant cannot be judged before a few years of success-
ful operation have passed. Moreover, the success of such a plant is closely
related to its feed material and is, therefore, site specific. Given the
historical experience of similar operations in the past, we do not expect the
steel industry to adopt this process extensively in the near-term future. Suc-
cessful testing of the Griffith Mine facility would go far in alleviating the
concerns about the technical viability of a coal-based rotary kiln process.
81
-------
TABLE IV-36
COST STRUCTURE IN NEW COKE-MAKING FACILITIES
Annual Design Capacity: 660.000
Capital Investment: S60 million
Location: Great Lakes
VARIABLE COSTS
Raw Materials
metallurgical coal
Byproduct Credits
ammonium sulfate
Energy
Purchased Steam
Electric Power Purchased
Energy Credits (Specify form)
coke oven gas
BTX
tar
coke breeze
Water
Cooling (Circulating rate)
Direct Operating Labor (Wages)
Direct Supervisory Wages
Maintenance Labor and materials
Labor Overhead
Operating supplies
TOTAL VARIABLE COSTS
FIXED COSTS
Plant Overhead
Local Taxes and Insurance
Depreciation 18 years
TOTAL PRODUCTION COSTS
Return on Investment (pretax)
TOTAL
Units Used, in
Costing or
Annual Cost
Basis
ton
ton
1000 Ib
kUh
106 Btu
gal
gal
ton
man-hr
151 labor
6% CI
35Z (L&S)
65Z (L&S)
2% CI
203! CI
$/Unit
50.00
94.00
3.00
0.016
2.00
0.70
0.43
40.00
0.05
7.00
Units Consumed
per Ton of
Product
1.43
0.02
0.67
25.00
4.5
3.0
10
0.05
5
0.25
$/ton of
Product
71.43
(1.88)
2.01
0.40
(9.00)
(2.10)
(4.30)
(2.00)
0.25
1.75
0.26
5.45
0.70
1.00
67.97
1.31
1.82
5.00
72.10
18.13
90.28
82
-------
TABLE IV-37
COST STRUCTURE IN NEW BLAST FURNACE FACILITIES
Annual Design Capacity: 1.22 x 10 tons hot metal
Capital Investment: $90 million
Location: Great Lakes
VARIABLE COSTS
Raw Materials
Pellets
limestone
Energy (Details on Table B)
Purchased coke
Electric Power Purchased
Energy Credits (Specify form)
blast furnace
Water
Cooling (Circulating rate) '
Labor (Wages) (1)
Direct Supervisory Wages (s)
Maintenance Labor and Material
Labor Overhead
Misc. Variable Costs/Credits(a>
slag sampling
scrap credit
TOTAL VARIABLE COSTS
FIXED COSTS
Plant Overhead
Local Taxes and Insurance
Depreciation 18 years
TOTAL PRODUCTION COSTS
Return on Investment (pretax)
TOTAL
Units Used in
Costing or
Annual Cost
Basis
Btu
ton
ton
kWh
106 Btu
103 gal
man-hr
15% labor
5Z CI
35% (L&S)
ton
652 (L&S)
2% CI
20% CI
1
$/Unit
0.45
5.00
90.25
0.016
2.0
0.05
7.00
80.00
Units Consumed
per Ton of
Product
84.7
0.25
0.53
25.00
3.8
11
0.15
0.01
$/Ion of
Product
38.11
1.25
47.85
0.40
(7.60)
0.55
1.05
0.16
3.69
0.42
0.25
(0.80)
85.33
0.79
1.48
4.06
86.21
14.76
106.42
83
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TABLE IV-38
COST STRUCTURE IN NEW BASIC OXYGEN PROCESS
Annual Design Capacity: 1.71 million tons steel
Capital Investment: $45 million
Location: Great Lakes
VARIABLE COSTS
Raw Materials
Hot Metal (93? Fe)
Scrap (96% Fe)
Energy
Electric Power Purchased
Energy Credits (Specify term)
Carbon monoxide
Hater
Cooling (Circulating rate)
Direct Operating Labor (Wages)
Direct Supervisory Wages
Maintenance Labor and materials
Labor Overhead
Misc. Variable Costs/Credits
oxygen
FeMn, lime, spar
Slag disposal, hot metal,
scrap treatment
TOTAL VARIABLE COSTS
FIXED COSTS
Plant Overhead
Local Taxes and Insurance
Depreciation 18 years
TOTAL PRODUCTION COSTS
Return on Investment (pretax)
TOTAL
Units Used in
Costing or
Annual Cost
Basis
ton
ton
kWh
106 Btu
1000 gal
man-hr
15* labor
8Z CI
35* (L&S)
ton
65% (L&S)
2% CI
20Z CI
$/Unit
106.42
80.00
0.016
2.00
0.05
7
10
Units Consumed
per Ton of
Product
0.83
0.35
30
0.44
2
0.25
0.08
$/Ton of
Product
88.33
28
0.48
088)
0.10
1.75
0.26
2.09
0.70
0.80
3.00
1.00
125.63
1.31
0.52
1.45
128.90
5.23
134.14
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TABLE IV-39
COST STRUCTURE IN NEW SPONGE IRON (93% METALLIZED) FACILITIES
Annaul Design Capacity: 1,200,000 tons
Capital Investment: $168 x 10
Location: Great Lakes
VARIABLE COSTS
Raw Materials
pellets
limestone
Energy (Details on Table B)
Purchased Fuel
Coal
Purchased Steam
Electric Power Purchased
Misc.
Water
Process (Consumption)
Cooling (Circulating rate)
Direct Operating Labor (Wages) (L)
Direct Supervisory Wages (S)
Maintenance Materials and Supplies
Labor Overhead
TOTAL VARIABLE COSTS
FIXED COSTS
Plant Overhead
Local Taxes and Insurance
Depreciation 18 years
TOTAL PRODUCTION COSTS
Return on Investment (pretax)
TOTAL
Units Used in
Costing or
Annual Cost
Basis
Ltu
ton
fi
10 Btu
ton
105 Btu
kUh
103 gal
103 gal
man-hr
L
4Z CI
35Z (L&S)
652 (L&S)
22 CI
20Z CI
$/Unit
0.45
5.00
2.00
25.00
3.00
0.018
0.50
0.05
7.00
Units Consumed
per Ton of
Product
8.5
0.140
0.625
56.0
4
0.20
152 L
$/Ton of
Product
38.25
0.70
15.62
0.90
0.20
1.40
0.21
5.60
0.56
63.44
1.05
2.80
7.84
35.83
28.00
102.88
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TABLE IV-40
COST STRUCTURE IN NEW ELECTRIC FURNACE SHOP
Annual Design Capacity: 1.71 x 10 tons
Capital Investment: $65 million
Location: Great Lakes
VARIABLE COSTS
Raw Materials
reduced pellets
scrap
Energy
Electric Power Purchased
electrodes
Water
Process (Consumption)
Cooling (Circulating rate)
Direct Operating Labor (Wages).
Direct Supervisory Wages
Maintenance Labor and Materials
Labor Overhead
Misc. Variable Costs/Credits
refractories
fluxes, oxygen, misc.
nonmetallics
metallic additions
TOTAL VARIABLES COSTS
FIXED COSTS
Plant Overhead
Local Taxes and Insurance
Depreciation 18 years
TOTAL PRODUCTION COSTS
Return on Investment (pretax)
TOTAL
Units Used in
Costing or
Annual Cost
Basis
ton Fe
ton
kUh
Ib
man-hr
15% Labor
5% CI
35% (LSS)
65% (LSS)
2Z CI
20% CI
$/Unit
102.88
80
0.016
0.55
7.00
Units Consumed
per Ton of
Product
0.75
0.32
600
10
0.3
$/Ton of
Product
77.16
25.60
9.60
5.50
2.10
0.32
2.27
0.85
2.00
1.00
1.50
127.90
1.57
0.76
2.10
131.83
7.56
139.89
86
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TABLE IV-41
OPERATING COSTS
($/ton of steel)
Production Costs:
Pollution Costs:
GRAND TOTAL
Base Case
134.14
9.26
$143.40
Direct Reduction
139.89
7.94
$147.83
TABLE IV-42
SL/RN PLANTS AND ROTARY KILNS FOR PREREDUCTION
TO FEED ELECTRIC REDUCTION FURNACES
(PLANTS BUILT OR UNDER CONSTRUCTION)
Company
Plant
size
Ore
Through-
put
Raw
Materials.
Ore
Coal
Product
and
Further
Proces-
sing
Remarks
Hlghveld Steel and
Vanadium Corp.
South Africa +
6 kilns
4 x 60 m
kiln nos. 7/8
under construction
start-up, late
1976
2,000,000 mtpy
Lump ore
M-25 mm
55Z Fe
1.6Z V,0
high-volatile
45% pre-reduced
ore
smelter
PIG IRON
VANADIUM SLAG
No SL/RN
process
Lurgi
designed and
delivered the
kilns
New Zealand
Steel Ltd.
New Zealand
1 kiln
4 x 75 m
190,000 mtpy
Iron sand
concentrate
58.0% Fe
8X TiO,
sub-
bituminous
High-met .
concentrate
arc furnace
STEEL
Western Titanium
Corporation
Australia
1 kiln
2.4 x 30 m
20,000 mtpy
Ilmenlte
concentrate
bituminous
High-met .
concentrate
leaching
ARIIFICAL
RUTILE
Acos Finos
Plratlni
Brazil
1 kiln
3.6 x 50 m
95,000 mtpy
lump ore,
pellets
67. OX Fe
high-vola-
tile
High-met.
ore, pel-
lets
,- arc fur-
nace STEEL
Nippon
Kokan KK
Fukuyama
Japan
1 kiln
6 x 70 m
with pre-
hardening
grate
250 sqm
525,000
mtpy
Bf, BOF-
dust and
Ore fines
pellets
bituminous
High-met.
pellets,
Zn, Pb
blast
furnace
PIG IRON
Start-up
early
1975
Hecla Mining
Arizona
USA
1 kiln
3.6 x 50 n
separate
pellet In-
durating
machine
95,000 mtpy
Leach-Resi-
due pellets
50-53Z Fe
sub-bitumi-
nous
High-met.
pellets
copper
cementation
Start-up
mid
1975
Steel Corp.
of Canada
Canada
1 kiln
6 x 125 m
520,000 mtpy
Pellets
66.51 Fe
sub-bitumi-
nous
High-met.
pellets
arc fur-
nace STEEL
Start-up
mid
1975
Source: Lurgi, September 1975
87
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REFERENCES
Adam, R.W., "High Energy Wet Gas Cleaning for the Basic Oxygen OG Process,"
Metal Progress, 98 (6), December 1970, pp 68-69.
Agarwal, J.C., and Elliot, J.F., "High Sulfur Coke for Blast Furnace Use,"
paper presented at the Iron Making Conference of AIME, April 19, 1971.
American Iron and Steel Institute, Wash., B.C., "Annual Statistical Report,"
1974.
American Iron and Steel Institute, Wash., B.C., "Energy Conservation in the
Steel Industry," 1976.
Ashton, M.C., et al., "Use of Magnesium Wire Injection for the Desulfurization
of Pig Iron"," Iron Making and Steelmaking, No. 2, 1975, p. 111.
Barker, J.E., "The Case for Dry Cooling," paper presented at a joint meeting
of the Midland Section of the Coke Oven Manager's Association and the East
Midland Section of the Institute of Fuel in Britain, March 11, 1976.
Battelle, Final Report to the Federal Energy Administration, "Potential for
Energy Conservation in the Steel Industry," Columbus, Ohio, May 1975.
Cavaghan, N.J., et al, "Utilization of In-Plant Fines," Journal of Iron and
Steel Institute, 208, June 1970, pp. 538-542.
"Coke Quenching from IHI," Iron Age, November 10, 1975.
Fisher, P.A., "Magnesium Desulfurization of Blast Furnace Iron," Metals and
Minerals, September 1973, p. 501.
Hersche, W., "Sulfur Dry Coke Cooling Plants," Sulfur Technical Review
3(1), 1946.
Industrial Gas Cleaning Institute, Inc., "Air Pollution Control Technology and
Costs in Nine Selected Areas," Report No. APTD-1555, Environmental Protection
Agency, Durham, No. Carolina, September 1972.
Kemmetmueller, R., "Dry Coke Quenching - Proved, Profitable, Pollution-Free,"
Iron and Steel Engineer, 50 (10), October 1973, pp. 71-78.
Linsky, B., et al., "Dry Coke Quenching, Air Pollution and Energy: A Status
Report," Journal of Air Pollution Control Association, 25(9), September 1975,
pp. 918-924.
88
-------
A.D. Little, Inc., "Steel and the Environment: A Cost Impact Analysis," Report
to the American Iron and Steel Institute, May 1975.
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Huttenwesen, MBH, Frankfurt am Main, Sept. 1975.
Lurgi, Canada Ltd., Toronto, Canada, personal communication, Dec. 1975.
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pp. 85-97.
Meichsner, W.E., et al., "Desulfurization of Hot Metal," Journal of Metals,
April 1974, p. 55.
Roederer, C., et al., "Gas Collection Without Combustion - IRSID-CAFL Process
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Rowe, A.D., et al., "Waste Gas Cleaning Systems for Large Capacity Basic Oxygen
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Trans. American Institute Min. (Metall.) Engrs., 1952, 194, pp. 597-602.
Skelly, J.S., "Profits in BOP Gas Collection," Iron and Steel Engineer, 43(3),
March 1966, p. 82.
Stone, J.K., "Worldwide Roundup of Basic Oxygen Steelmaking," I&SM, April 1976,
p. 31.
Swindell-Dressier Company, "Gas Cleaning and Recovery in Oxygen Steelmaking -
The IRSID-CAFL Process," December 1967.
Ward, M.D., "Consistent Iron, the Steelmaker's Viewpoint," Iron Making and
Steelmaking, No. 2, 1975, p. 89.
Ward, R.G., An Introduction to the Physical Chemistry of Iron and Steelmaking,
Edward Arnold (Publishers) Ltd., London, 1962.
Yawata Iron and Steel Co. Ltd., OG Process, 1964.
Yawata Iron and Steel Co. Ltd., New Improved OG, 1966.
Development Document for Proposed Effluent Limitation Guidelines and New Source
Performance Standards for Steel Making Segment of the Iron and Steel Point
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89
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/7-76-034c
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE ENVIRONMENTAL CONSIDERATIONS OF
SELECTED ENERGY CONSERVING MANUFACTURING PROCESS
OPTIONS. Vol. III. Iron and Steel Industry Report
5. REPORT DATE
December 1976 (Issuing Date)
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Arthur D. Little, Inc.
Acorn Park
Cambridge, Massachusetts 02140
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-03-2198
12. SPONSORING AGENCY NAME AND ADDRESS
Industrial Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
FINAL
14. SPONSORING AGENCY CODE
EPA-ORD
15. SUPPLEMENTARY NOTES Vol. IV-XV, EPA-600/ 7~76-034d through EPA-600/7-76-034o, refer to
studies of other industries as noted below; Vol. I, EPA-600/7-76-034a, is the
Industry Summary Report and Vol. II, EPA-600/7-76-034b, is the Industry Priority Repor
16. ABSTRACT
This study assesses the likelihood of new process technology and new practices being
introduced by energy intensive industries and explores the environmental impacts of
such changes.
Specifically, Vol. Ill deals with the iron and steel industry and examines four
alternatives: (1) recovery of carbon monoxide from BOP (basic oxygen process),
(2) external desulfurization of blast-furnace hot metal, (3) conversion from wet to
dry coke quenching, and (4) direct reduction of iron ore, all in terms of relative
process economics and environmental/energy consequences. Vol. IV-XV deal with the
following industries: petroleum refining, pulp and paper, olefins, ammonia,
aluminum, textiles, cement, glass, chlor-alkali, phosphorus and phosphoric acid,
copper, and fertilizers. Vol. I presents the overall summation and identification
of research needs and areas of highest overall priority. Vol. II, prepared early
in the study, presents and describes the overview of the industries considered
and presents the methodology used to select industries.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Energy; Pollution; Industrial Wastes;
Iron; Steels
Manufacturing Processes;
Energy Conservation;
Dry Quenching; Direct
Reduction; Desulfuriza-
tion; Carbon Monoxide
13B
13. DISTRIBUTION STATEMENT
Release to public
19. SECURITY CLASS (ThisReport)
unclassified
21. NO. OF PAGES
106
20. SECURITY CLASS (This page)
unclassified
22. PRICE
EPA Fotm 2220-1 (9-73)
90
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