United States
Environmental Protection
Agency
Office of Air Quality
Planning and Standards
Research Triangle Park, NC 27711
EPA-453/R-94-005
February 1994
Emission Standards Division
Alternative Control
Techniques Document -
PM-10 Emissions from
Selected Processes at
Coke Ovens and Integrated
Iron and Steel Mills
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EPA-453/R-94-005
ALTERNATIVE CONTROL
TECHNIQUES DOCUMENT --
PM-10 EMISSIONS
FROM SELECTED PROCESSES
AT COKE OVENS
AND INTEGRATED IRON AND STEEL
MILLS
Emission Standards Division
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
February 1994
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ALTERNATIVE CONTROL TECHNIQUES DOCUMENT
This report is issued by the Emission Standards Division,
Office of Air Quality Planning and Standards, U.S. Environmental
Protection Agency, to provide information to state and local air
quality management agencies. Mention of trade names and commercial
products is not intended to constitute endorsement or
recommendation for use. Copies of this report are available, as
supplies permit, from the Library Services Office (MD-35), U.S.
Environmental Protection Agency, Research Triangle Park, North
Carolina 27711 (919-541-2777) or, for a fee, from the National
Technical Information Service, 5285 Port Royal Road, Springfield,
Virginia (800-533-NTIS).
11
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TABLE OF CONTENTS
Section Page
List of Figures v
List of Tables vi
1 INTRODUCTION 1-1
2 SOURCES AND POLLUTANT EMISSIONS 2-1
2.1 INDUSTRY DESCRIPTION 2-1
2.2 PROCESS DESCRIPTIONS 2-2
2.2.1 Processes Included in This Document ... 2-2
2.2.2 Process Characteristics and Feedstocks . 2-2
2.2.3 Process Summary and Overview of Mill
Operations 2-3
2.2.4 Coking 2-4
2.2.5 Sintering 2-9
2.2.6 Iron Production 2-9
2.2.7 Hot Metal Transfer and Desulfurization . 2-11
2.2.8 Steelmaking 2-11
2.2.9 Ladle Metallurgy 2-14
2.2.10 Casting 2-14
2.2.11 Finishing 2-15
2.3 PM-10 SOURCE DESCRIPTIONS 2-15
2.3.1 Processes Described 2-15
2.3.2 Coke Pushing 2-18
2.3.3 Coke Quenching 2-18
2.3.4 Coke Sizing and Screening 2-20
2.3.5 Iron Production (Casthouse) 2-20
2.3.6 Hot Metal Transfer 2-21
2.3.7 Desulfurization 2-22
2.3.8 Other PM-10 Sources 2-23
2.4 MODEL PLANTS AND EMISSIONS 2-28
2.4.1 Introduction 2-28
2.4.2 Model Plant Potential PM-10 Emissions . . 2-28
2.4.3 Model Plant Baseline Emissions 2-30
2.5 REFERENCES FOR CHAPTER 2 2-32
3 EMISSIONS CONTROL TECHNIQUES 3-1
3.1 INTRODUCTION 3-1
3.2 SOURCE REDUCTION IN IRON AND STEEL MILLS .... 3-1
3.3 CONTROL EQUIPMENT 3-4
3.3.1 Primary Control Equipment 3-4
3.3.2 Secondary Control Equipment 3-11
3.3.3 Control System Performance 3-14
3.3.4 Control Devices 3-14
3.4 NEW CONSTRUCTION CONTROLS 3-24
3.5 CONTROL METHODS FOR OPEN FUGITIVE DUST SOURCES . 3-24
3.6 REFERENCES FOR CHAPTER 3 3-25
ill
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TABLE OF CONTENTS (continued)
Section Page
4 ENVIRONMENTAL IMPACTS 4-1
4.1 INTRODUCTION 4-1
4.2 PM-10 EMISSIONS IMPACT 4-1
4.2.1 Alternative Control Techniques for Coke
Pushing, Coke Sizing and Screening,
and Casthouse Emissions 4-2
4.3 WATER POLLUTION IMPACT 4-5
4.4 SOLID WASTE IMPACT 4-8
4.5 ENERGY IMPACT 4-9
4.6 REFERENCES FOR CHAPTER 4 4-13
5 CONTROL COST ANALYSIS 5-1
5.1 INTRODUCTION 5-1
5.2 DESIGN PARAMETERS AND PURCHASED EQUIPMENT COSTS . 5-2
5.2.1 General Equipment Assumptions 5-2
5.2.2 Ductwork Cost Methodology 5-3
5.2.3 Fan/Motor System Cost Methodology .... 5-5
5.2.4 Baghouse Cost Methodology 5-6
5.2.5 Process-specific Equipment Assumptions
and Equipment Costs 5-7
5.3 BASIS FOR CAPITAL COSTS 5-15
5.4 BASIS FOR ANNUAL COST ESTIMATES 5-17
5.5 COST EFFECTIVENESS 5-24
5.6 CONTROL OPTION COSTS FROM INDUSTRY
REPRESENTATIVES 5-31
5.7 REFERENCES FOR CHAPTER 5 5-35
APPENDIX A INTEGRATED IRON AND STEEL MILLS AND BLAST
FURNACE COKE OVENS A-1
APPENDIX B SAMPLE EMISSION FACTOR CALCULATIONS B-l
IV
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LIST OP FIGURES
Number Page
2-1 General Flow Diagram for the Iron and Steel Industry . 2-5
2-2 Byproduct Coke Oven Battery with Major Emission Points 2-7
3-1 General Flow Diagram for an Emission Control System . 3-5
3-2 Casthouse with Baghouse Control 3-10
3-3 A Hot Metal Transfer and Skimming Station 3-13
3-4 Fabric Filter 3-17
3-5 Wet Venturi Scrubber 3-21
3-6 Electrostatic Precipitator 3-23
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LIST OF TABLES
Number Page
2-1 Additional References for Iron and Steel Mills .... 2-3
2-2 Uncontrolled PM-10 Emission Factors 2-16
2-3 Baseline PM-10 Emission Factors 2-16
2-4 Model Plant Operating Parameters 2-29
2-5 Uncontrolled PM-10 Emissions from Model Plants for
Selected Processes 2-29
2-6 Baseline PM-10 Emissions from Model Plants for
Selected Processes 2-31
3-1 Typical Particulate Collection Efficiencies of Control
Devices Used in Iron and Steel Mills 3-16
4-1 Controlled PM-10 Emission Factors 4-3
4-2 PM-10 Control System Efficiencies for Baseline and
Alternative Control Technique (ACT) Systems .... 4-6
4-3 Controlled PM-10 Emissions from Model Plants for
Selected Processes 4-7
4-4 Compounds Commonly Emitted at Iron and Steel Mills . . 4-8
4-5 Energy Required by Implementation of Process Control
Options 4-11
4-6 Airflows Required for Process Control Options .... 4-12
5-1 Equipment Parameter Assumptions for all Fabric Filters 5-4
5-2 Control Equipment Parameters and Purchase Costs for
Coke Pushing (Al) - Shed with Baghouse 5-8
5-3 Control Equipment Parameters and Purchase Costs for
Coke Sizing/Screening - Enclosure with Baghouse . . 5-9
5-4 Control Equipment Parameters and Purchase Costs for
Casthouse (Al) - Evacuation to Baghouse 5-10
5-5 Control Equipment Parameters and Purchase Costs for
Casthouse (A2) - Local Hooding and Baghouse .... 5-11
5-6 Control Equipment Parameters and Purchase Costs for
Hot Metal Transfer - Canopy Hood with Baghouse . . 5-12
5-7 Control Equipment Parameters and Purchase Costs for
Desulfurization - Ladle Hood and Baghouse 5-13
5-8 Conversion Factors 5-14
5-9 General Costs and Cost Factors for Fabric Filters . . 5-16
5-10 Total Capital Costs for Coke Pushing (Al) ($1,000) . . 5-18
5-11 Total Capital Costs for Coke Sizing/Screening ($1,000) 5-19
5-12 Total Capital Costs for Casthouse (Al) ($1,000) . . . 5-20
5-13 Total Capital Costs for Casthouse (A2) ($1,000) ... 5-21
5-14 Total Capital Costs for Hot Metal Transfer ($1,000) . 5-22
5-15 Total Capital Costs for Desulfurization ($1,000) . . . 5-23
5-16 Total Annual Costs for Coke Pushing (A2) ($1,000) . . 5-24
5-17 Total Annual Costs for Coke Pushing (Al) ($1,000) . . 5-25
5-18 Total Annual Costs for Coke Sizing/Screening ($1,000) 5-26
5-19 Total Annual Costs for Casthouse (Al) ($1,000) .... 5-27
5-20 Total Annual Costs for Casthouse (A2) ($1,000) .... 5-28
5-21 Total Annual Costs for Hot Metal Transfer ($1,000) . . 5-29
VI
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LIST OF TABLES (continued)
Number Page
5-22 Total Annual Costs for Desulfurization ($1,000) . . . 5-30
5-23 Cost Effectiveness for Emissions Reductions from
Uncontrolled Case 5-32
5-24 Capital and Annual Cost Comparisons from Industry
Representatives 5-34
A-l Integrated Iron and Steel Mills and Blast Furnace
Coke Ovens A-2
VII
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CHAPTER 1
INTRODUCTION
The Clean Air Act Amendments of 1990 (November 15, 1990)
authorize the Environmental Protection Agency (EPA) to designate
areas that violate the national ambient air quality standards
(NAAQS) for particulate matter nominally 10 microns or smaller in
diameter (PM-10) as nonattainment areas. [See Section 107(d) of
the Clean Air Act (Act).] Section 188(a) of the Act provides that
every designated nonattainment area for PM-10 shall be classified
as a "moderate" nonattainment at the time of designation by
operation of law. A moderate area can subsequently be reclassif ied
as "serious" if EPA determines that (1) the area cannot practicably
attain the PM-10 NAAQS by the applicable attainment date or (2) the
attainment date has already passed and the area has failed to
attain the standards.
State implementation plans (SIPs) for moderate nonattainment
areas must, among other things, provide for the implementation of
all reasonably available control measures, including reasonably
available control technology (RACT) to achieve emission reductions
from existing stationary sources. [See Sections 172(c) and
189 (a) (1) (C) .] In addition to the requirements for moderate areas,
SIPs for serious areas must include, among other things, provisions
to assure that the best available control measures, including "the
application of best available control technology (BACT) to existing
stationary sources" [H.R. Rep. No. 490, 101st Congress Sess. 267
(1990)], are implemented no later than 4 years after the areas are
reclassified as serious. [See Section 189(b) (1) (B).]
In accordance with Section 190 of the Act, EPA determined that
information for use in determining RACT and BACT was needed for the
ferrous metals industries. Therefore, EPA prepared this guideline
document on alternative control techniques (ACT) to assist States
in identifying RACT and BACT alternatives for selected process
sources of PM-10 in the iron and steel industry. Although ACT
documents review existing information and data concerning the
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technology and cost of various control techniques to reduce
emissions, they are, of necessity, general in nature and do not
fully account for unique variations within a stationary source
category. Consequently, the purpose of ACT documents is to provide
State and local air pollution control agencies with an initial
information base for proceeding with their own analysis of RACT and
BACT for specific new and existing stationary sources.
1-2
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CHAPTER 2
SOURCES AND POLLUTANT EMISSIONS
2.1 INDUSTRY DESCRIPTION
The United States iron and steel industry includes the U.S.
Government Standard Industrial Classification (SIC) codes 3312,
3315, 3316, and 3317. In 1990, domestic production of steel was
estimated to be around 78 million tons, four percent less than the
previous year. In 1989, the domestic steel industry operated at
approximately 88 percent of its capacity.1 Domestic demand for
steel is expected to remain constant through the 1990s at a level
of 90 to 100 million tons per year. If domestic demand exceeds
domestic supply, foreign imports will be used as supplements.
There will probably be increased demands for high-quality
corrosion-resistant products such as coated steel and stainless
steel.
The SIC coding system has several categories that comprise the
domestic iron and steel industry, including the steel wire and
related products category (SIC 3315), the cold finishing of steel
shapes category (SIC 3316), and the steel pipe and tubes category
(SIC 3317).2 This document is directed for coke producing
facilities and integrated mills. An integrated iron and steel
plant is one in which coke, iron ore, and other raw materials are
converted into a finished or semifinished steel product. These
facilities are contained primarily in SIC 3312, which also includes
facilities whose primary function is hot rolling iron and steel
into basic products like plates, sheets, bars, and tubing. The
majority of products produced by the domestic steel industry are
converted to final products at other facilities within SIC 3312 or
in other industries.3 A list of integrated iron and steel mills and
furnace coke ovens operating in 1991 is given in Table A-l in
Appendix A.
The majority of these iron and steel facilities are located in
states having heavy manufacturing. Fully integrated mills are
concentrated in areas that have access to coal and iron ore.
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In 1984, there were 36 operational coke plants containing 134
batteries (rows of ovens) in the United States. About 92 percent
of their coke production was used in manufacturing iron and steel.4
The largest customers of steel products are the automobile
industry and the construction industry. Manufacturing appliances,
containers, electrical equipment, and machinery also use
significant amounts of steel. The use of steel has declined
somewhat in recent years due to the increased substitution of
materials such as aluminum, plastics, glass, and ceramics. The
automobile industry also has increasingly replaced steel with
aluminum and plastics. Despite these smaller markets, demand for
steel will probably remain constant in the near future.5
2.2 PROCESS DESCRIPTIONS
2.2.1 Processes Included In This Document
This document does not discuss all the possible sources of
PM-10 emissions from integrated iron and steel plants but focuses
on emissions from two areas: the transfer of coke from the coke
oven battery to its uses at the blast furnace and EOF, and the
transfer of molten iron from the blast furnace to the EOF.
Specific sources include coke pushing (see Section 2.3.2), coke
quenching (see Section 2.3.3), coke sizing and screening (see
Section 2.3.4), casthouse emissions (see Section 2.3.5), hot metal
transfer (see Section 2.3.6), and desulfurization (see
Section 2.3.7). All of these sources are not regulated under the
New Source Performance Standards (NSPS). Other sources of PM-10
emissions are mentioned briefly. Agencies may consult references
such as those listed in Table 2-1 for more information on NSPS
processes and other processes not included in this document.
2.2.2 Process Characteristics and Feedstocks
The primary materials used in an integrated iron and steel
mill are coal, iron ore, gaseous oxygen, steel scrap, and alkaline
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TABLE 2-1. ADDITIONAL REFERENCES FOR IRON AND STEEL MILLS
U.S. Environmental Protection Agency. Electric Arc Furnaces and Argon-
Oxygen Decarburization Vessels in Steel Indus try-Background Information
for Proposed Revisions to Standards. EPA-450/3-82-020a. Office of Air
Quality Planning and Standards. Research Triangle Park, NC. July 1983.
O.S. Environmental Protection Agency. Electric Arc Furnaces in Ferrous
Foundries-Background Information for Proposed Standards.
EPA-450/3-80-020a. Office of Air Quality Planning and Standards.
Research Triangle Park, NC. May 1980.
U.S. Environmental Protection Agency. Control Techniques for Particulate
Emissions from Stationary Sources-Volume 2. EPA-450/3-81-005b. Office of
Air Quality Planning and Standards. Research Triangle Park, NC.
September 1982.
U.S. Environmental Protection Agency. Revised Standards for Basic Oxygen
Process Furnaces-Background Information for Proposed Standards.
EPA-450/2-82-005a. Office of Air Quality Planning and Standards.
Research Triangle Park, NC. December 1982.
U.S. Environmental Protection Agency. Control of Open Fugitive Dust
Sources. EPA-450/3-88-008. Office of Air Quality Planning and Standards.
Research Triangle Park, NC. September 1988.
Buonicore, A.J., and W.T. Davis, eds. Air Pollution Engineering Manual.
Van Nostrand Reinhold. New York, NY. 1992.
Lankford, W.T., et al., eds. The Making, Shaping, and Treating of Steel.
Tenth Edition. Association of Iron and Steel Engineers. Pittsburgh, PA.
1985.
fluxes such as limestone. Secondary feedstocks include water for
coke quenching, desulfurization compounds such as calcium carbonate
(CaCO3) , calcium carbide (CaC2) , or salt-covered magnesium, and
alloying agents such as nickel, silicon, and manganese.
2.2.3 Process Summary and Overview of Mill Operations
An integrated iron and steel plant is one in which iron ore,
coal, and other raw materials are converted into a finished or
semifinished steel product. First, coal is converted to coke for
use as a fuel in the production of molten iron. Fine coke
particles (breeze), which are not directly usable, may then be
burned, in the presence of iron ore fines and flux, forming a
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compound known as sinter. The ore, coke, sinter, and fluxes are
charged into the blast furnace. In the blast furnace, the iron
oxide in the ore is reduced to molten iron. Afterwards, the molten
iron is usually treated with reagents to remove any excess sulfur.
The molten iron, along with varying amounts of steel scrap, is
charged into the steel-producing furnace. In the steel furnace,
oxygen is blown into the molten iron to remove excess carbon and to
help the fluxes remove impurities in the steel. Additional
alloying steps may be conducted at a metallurgical station; then,
the molten steel is poured into ingots (teemed) or solidified into
a steel "casting" in a continuous caster. Finally, the steel
undergoes semifinishing and finishing operations such as rolling,
chipping, grinding, and scarfing. Figure 2-1 shows a general flow
diagram for the processes in a typical integrated mill.
The production processes in an integrated iron and steel mill
are generally batch processes with distinct cycles in which
materials are combined at the process station, processed or
converted, and emptied from the station. The exception is the
casting stage, where most casting currently performed is continuous
casting.
The conversion of coal to coke is a form of distillation.
Heat applied to the coal in an oxygen-deprived environment drives
off volatile compounds from the coal, leaving relatively pure
carbon. Melting in the blast furnace and in the basic oxygen
process furnace (EOF) involves two-phase reactions. In the blast
furnace, oxygen reacts with coke to form carbon monoxide. In a
reduction reaction, the carbon monoxide converts iron oxide in the
ore to metallic iron. In the basic oxygen furnace, an oxidation
reaction is used to remove excess carbon and fluxes are used to
remove other impurities from the molten iron. The oxidation
reaction also provides heat to keep the mixture molten.
2.2.4 Coking
Coke, a material that is primarily elemental carbon, is
produced by distillation of coal. The coal is heated in an oxygen-
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Coke, along with flux, iron ore, and/or scrap steel, is one of the
primary raw materials in the manufacture of steel. Integrated iron
and steel mills have coke-producing facilities on-site or nearby;
non-integrated mills are supplied with coke by rail or water.6
In 1991, the byproduct coke making process was used to produce
nearly all coke produced in the United States. In this process,
exhaust gases from the coking oven are collected and treated to
recover usable byproducts such as tar, ammonia, and light oil.
Figure 2-2 outlines a typical byproduct coke oven process
operation.4 Byproduct coke ovens are constructed in rows, or
batteries, that may contain between 19 and 102 ovens, with an
average of about 58 ovens per battery.7 Coking chambers in a
battery are heated on both sides. Typically, each individual oven
is 3.0 to 6.7 meters high (9.8 to 22 feet), 11 to 16.8 meters long
(36 to 55 feet), and 0.35 to 0.5 meters wide (1.2 to 1.7 feet),
though larger ovens may be used. The top of each oven has charging
holes and at least one additional opening, equipped with an offtake
pipe, through which volatilized byproducts are collected while the
coal is heated. The oven also has long, thin doors at each end.
When the conversion of coal to coke is complete, the coke is pushed
out of the coke oven by a powered ram which is inserted through the
"push-side" door. Coke exits the other side of the oven through
the "coke-side" door and falls into a special rail car called a
quench car.
Overhead coal bins at the battery are used to load a measured
amount of coal, which is fed into a larry car that transports the
coal to each oven. The larry car, which moves on rails along the
top of the battery, loads coal to each oven via the charging holes.
Coal is charged by gravity, assisted by a mechanical system that
employs either a screw conveyor or a revolving table discharge
arrangement.
The composition of the coal charged to the ovens is important
for several reasons. Coke in the blast furnace is used both as a
fuel and as a structural matrix that allows air to flow through the
blast furnace. Because the coke chunks (around one or two inches
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in size) must support great weights in a stacked blast furnace, the
coke must be reasonably strong. Maximum strength of the coke is
achieved by crushing the feed coal, then adjusting the bulk density
of the product by blending it with oil. Water can also be added to
increase the bulk density of the coal.8 This "wet" charging of coal
typically contains 6 to 11 percent moisture by weight. "Dry"
charging is used in some batteries. In this type of system the
coal is preheated to remove moisture and then fed into the coke
oven by conveyor or pipeline.6 However, industry representatives
indicate that pipeline charging was a theory that did not work well
in practice and has generally been abandoned.9
The coal in wet coal batteries is heated in the coke oven for
15 to 18 hours in the absence of oxygen. Approximately 2/3 Mg of
coke can be produced from one Mg of coal, excluding the coke fines,
which are referred to as "breeze."4
After the coke is pushed, it is usually cooled by a wet
quenching process in which the quench car is placed under a quench
tower and the coke doused with water.10 Typically, approximately
9-18 Mg (10-20 tons) of hot (800°C/~1,500°F) coke are quenched by
22,700-45,400 liters (6,000-12,000 gallons) of water in a process
lasting two to three minutes for blast furnace coke.11 A. final
moisture content of 2.5-5.0 percent results.9'10 After quenching,
the coke is removed from the car, drained, further cooled, and
sized. This sizing and screening is performed in order to yield a
controlled size of coke for the blast furnace.11
The properly sized coke is used in the production of iron.
The dust-like particles, or breeze, that result from the coke
handling process are used in sintering or elsewhere in the mill.
The gases formed by baking the coal are collected and sent to the
byproduct recovery plants. Water sprays cool the gases to a
temperature of 80-lOO°C (~200°F). The gases are then treated to
remove valuable byproducts for use or sale. These byproducts
include light oil, tar, and ammonia. The gas that remains after
the byproduct recovery processes contains significant amounts of
methane and hydrogen and has a heating value of approximately 20.5
MJ/Nm3 (Megajoules per normal cubic meter).4 This gas is returned
2-8
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to the coke ovens for use as fuel or may be used as fuel elsewhere
in the plant.6
2.2.5 Sintering
Sintering fuses raw materials such as iron ore fines, coke
breeze, and flux (an alkaline material such as limestone) into a
solid product of sufficient size and strength to be charged into
the blast furnace. The materials to be sintered are mixed with
water or are left dry. The mixture is placed on a movable grate
known as a sinter strand and the coke breeze is ignited by a
natural gas or fuel oil burner. The burning coke breeze in the
mixture generates enough heat to sustain combustion at
1,300-1,480°C (~2,400-2,700°F) and achieve the desired level of
fusion of iron particles. The large volume of combustion gases is
drawn through the burning mixture into windboxes below the strand,
then into a common duct that leads to a gas cleaner. The fused
mass is cooled with air or a water spray, crushed, and screened
prior to being charged into the blast furnace. Undersized sinter
is recycled through the sintering process. Generally, 2.5 Mg of
raw materials, including water and fuel, will yield 1.0 Mg of
product sinter.12
2.2.6 Iron Production
2.2.6.1 Blast furnace
The production of iron for steel-making is achieved by the
reduction of iron ore to iron in a refractory-lined blast furnace.
Iron in the ore is typically found as hematite (Fe203) or magnetite
(Fe304) . In addition to the iron ore, coke, sinter, flux, and other
materials are charged into the furnace by either skip hoist or
continuous conveyor. The materials added to the furnace are
collectively known as the "burden." The typical blast furnace
operates at temperatures greater than ~1,650°C (3,000°F) in the
lower part of the furnace.8 Heated air (-300-1,100°C, 600-2,000°F)
is injected into the furnace, where it heats and reacts with the
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coke to form carbon monoxide. In the hot reduction environment,
the carbon monoxide reacts with the iron oxide to produce molten
metallic iron and carbon dioxide. The metallic iron flows to the
bottom of the furnace. Impurities and other materials in the blast
furnace collect in a liquid slag layer on top of the molten iron,
which is now termed "hot metal."
The hot metal and slag are removed from the blast furnace by
"tapping," which releases the material through a taphole drilled
through a clay plug located at the base of the furnace. The hot
metal and slag flow from the blast furnace into a trough. The
slag, which floats on the hot metal, is skimmed off the flowing
iron and directed to slag runners, which carry the slag to a
repository such as a slag pit. Later, the slag is transported for
further processing.8 The hot metal flows from the trough into
runners that guide the hot metal to a torpedo car. The torpedo car
is essentially a refractory-lined tubular container mounted on a
railcar base. At the conclusion of the tapping process, the
taphole is replugged with clay.
Producing one Mg of hot metal typically requires the following
raw materials: 1.4 Mg of iron ore, 0.5 to 0.65 Mg of coke, 0.25 Mg
of flux and 1.8 Mg of air. Byproducts include 0.2 to 0.4 Mg of
slag and 2.5 to 3.5 Mg of blast furnace gas that contains
approximately 0.05 Mg of dust and a significant amount of carbon
monoxide. Blast furnace gas has a low heating value but may be
used after cleaning for supplemental fuel.12
2.2.6,2 Direct reduction--an alternate method
There are alternatives to the traditional blast furnace method
of producing iron. The most widely known is direct reduction, in
which natural gas is reformed into hydrogen and carbon monoxide,
then contacted with iron ore at 800 to 900°C (-1,500 to ~1,700°F),
which strips the oxygen from the iron. The result is a spongy form
of metallic iron known as directly reduced iron (DRI). Currently
there is only one DRI plant in the United States because the cost
of natural gas has limited the implementation of this process. One
company, Hylsa S.A. of Monterrey, Mexico, is attempting to develop
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a pneumatic transport system which would move DRI from the
reduction facility to the steel-making furnace while still hot,
resulting in a significant savings in energy costs and thereby
making the DRI process more affordable. Midrex, Inc., of
Charlotte, North Carolina has developed a coal-based DRI process
known as Fasmet®. In this process, ground iron ore and coal are
mixed with water and bentonite, which serves to bind the mixture
together. The mixture is then formed into pellets, which are
predried and heated to produce the reduction gases. DRI is
generally used at smaller capacity "minimills, " which produce steel
with electric arc furnaces.13
2.2.7 Hot Metal Transfer and Desulfurization
From the blast furnace, the torpedo car carries the hot metal
to the EOF shop. At the EOF shop, the torpedo car is tilted to
transfer the hot metal into a transfer ladle. Typically, the
transfer ladle is then moved to the desulfurization station, where
high-pressure nitrogen or argon is used to inject powdered reagents
through a lance into the hot metal. The reagents react with the
sulfur in the metal and draw the sulfur-compounds into a slag that
floats on the surface of the hot metal. The slag layer is then
skimmed off the metal. Desulfurization reagents used have included
calcium carbide (CaC2) , calcium carbonate (CaC03) , and salt-covered
magnesium.n
Desulfurization is used to improve the properties of the steel
in several ways. Desulfurized steel generally is cleaner and has
fewer surface defects than steel that does not undergo the process.
The process also tends to increase the malleability, strength, and
ductility of the steel. Finally, welds on desulfurized steel are
less porous and are therefore stronger.14
2.2.8 Steelmaking
After desulfurization, the molten iron is transported to a
furnace for conversion to steel. In EOF Steelmaking, steel scrap
2-11
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is fed into the furnace along with the molten iron. Flux is added
to aid in the formation of a slag that removes excess silicon and
manganese and reduces the levels of sulfur and phosphorus.
Fluorspar is also added to increase the fluidity of the molten
mixture. Once the furnace is fully charged, oxygen is blown into
the molten metal to remove excess carbon and other impurities.
In the last few decades, the open hearth furnace and EOF have
been the predominant furnace types used to make steel from hot
metal. However, open hearth furnaces have recently been supplanted
by BOFs; by 1977, open hearth furnaces had virtually disappeared
from the domestic steel industry, accounting for less than five
percent of production.5 There are currently no operating open
hearth furnaces in the United States. A brief discussion of the
open hearth furnace process is included here for comparison with
the EOF process.
2.2.8.1 Open hearth furnace
The open hearth process employs a furnace with a relatively
shallow refractory-lined basin. Scrap and flux are fed into the
furnace through doors in its front, while molten iron is poured
from a ladle through the door. The feed varies but is typically an
equal mixture of scrap and fresh molten iron. Heat for the process
is furnished by gas, oil, or tar burners below and on the sides of
the furnace. Oxygen is often injected below the surface of the
melt to speed the process and to remove excess carbon, silicon, and
manganese. The carbon is removed as gaseous carbon monoxide and
carbon dioxide, while the manganese and silicon form oxides that
are removed with the slag. When the steel has reached the desired
composition and temperature, it is tapped from the bottom of the
furnace. The time required to produce a "heat" (batch) of steel in
this manner ranges from eight to twelve hours, with some older
models requiring up to 20 hours. Some later models, which employ
a water-cooled oxygen lance to add oxygen to the furnace, have
produced heats in as little as four to five hours.12
2-12
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2.2.8.2 Basic oxygen process furnace
Currently, the BOF is the most widely used process to convert
hot metal into steel. In 1989, this process produced 60 percent of
the domestic steel industry's output, the remainder being supplied
from steel scrap melted in electric arc furnaces.5 The furnace
consists of an open-mouthed, pear-shaped vessel with an alkaline
refractory lining. The mouth of a standard vessel usually ranges
from 3.7 to 4.3 meters (12 to 14 feet) in diameter, while the
vessel itself can be -6.1 to 9.1 meters (20 to 30 feet) high. A
BOF can produce up to 440 Mg (~485 tons) of steel in a single heat.
The feed to a BOF is typically 70 percent or more hot metal and the
remainder scrap. After the feed is charged, high-purity oxygen is
blown into the furnace in one of two ways. The most prevalent
method involves the use of a water-cooled lance to inject oxygen
into the top of the furnace. In the newer Quelle process, or QBOP
furnace, oxygen and fluxing agents are injected into the bottom of
the furnace through tubes known as tuyeres. The Quelle process has
several advantages over the standard top blown technique. A Quelle
furnace fits into many facilities originally designed for open
hearth furnaces, thus enabling firms to avoid excessive capital
costs in replacing open hearth furnaces. Quelle furnaces also
produce slightly higher yields of steel and allow a slightly higher
ratio of scrap to molten iron in the initial charge.3
Oxygen is blown into the furnace in a part of the cycle called
the "oxygen blow" which lasts for approximately 8 to 20 minutes.
The carbon and silicon in the molten steel are oxidized and removed
during this period. No additional fuel is necessary, as the
reaction of the oxygen with the carbon in the hot metal provides
all the heat needed to sustain oxidization in the furnace. Flux
and fluorspar are added after the beginning of the oxygen blow.
Following the completion of the blowing period, the composition of
the molten steel is tested in the "turndown" period. A second,
shorter, oxygen blow is conducted if necessary. Next, the molten
steel is poured into a teeming ladle through a taphole in the side
of the furnace. It is at this point in the process that alloying
agents are usually added.3 After the steel has been removed, the
2-13
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teeming ladle is removed, and the slag remaining in the vessel is
dumped into a slag car and removed. A typical run in a EOF lasts
25 to 45 minutes.12
2.2.9 Ladle Metallurgy
In some facilities, the steel in the teeming ladle may be
taken to a ladle metallurgy station for further treatment. Argon
stirring, alloying, and other metallurgical processes may be
performed on the metal at the ladle metallurgy station.
2.2.10 Casting
From the BOF or ladle metallurgy station, the molten steel
moves to the casting stage. Traditionally, molten steel was
poured, or teemed, into large cast iron ingot molds and allowed to
solidify in these molds. The steel was then removed, reheated, and
tested to ensure that the temperature was constant throughout the
entire ingot. The ingots were then rolled into billets, blooms, or
slabs depending on their ultimate destination.12 The current
prevailing method of casting is known as continuous casting. In
1990, 67.1 percent of the steel produced in the United States
underwent continuous casting; Japan and Europe used continuous
casting for about 80 or 90 percent of their steel production.5 In
this process, the molten steel is poured into a water-cooled mold.
The steel emerges from the bottom of the mold in a continuous slab,
bloom, or billet that is then cut into appropriate lengths for
rolling. The process is more efficient than traditional ingot
casting since it casts steel into shapes already suitable for
rolling, thus eliminating the need for reworking.3 The trend in the
United States is to roll billets and blooms from steel produced in
electric arc furnaces while producing slabs with steel from BOFs.
Pressure casting is a third, seldom-used method of forming steel
that uses pressure from the outside air to force molten steel into
a slab-shaped ceramic mold. The steel is then solidified, removed
from the mold, and sent off for rolling.15
2-14
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2.2.11 Finishing
Steel in bloom, billet, or slab form can have surface defects
that could lower the value of the finished product if allowed to
remain. To remove these defects, the steel is often subjected to
chipping, grinding, or scarfing. Chipping and grinding are
relatively simple processes used with minor imperfections.
Scarfing is used for more serious defects. In scarfing, high-
velocity streams of oxygen, along with acetylene or natural gas as
fuel, are applied to the steel surface until it reaches a
temperature of approximately 870°C (1,600°F). This causes the
steel at the surface to melt slightly. Roughly three millimeters
of steel are then removed from each side of the piece.6 Scarfing
is used primarily to remove defects caused by rolling ingots into
semifinished forms, i.e., slabs, billets and blooms, and is
therefore not typically used when continuous casting is employed.8
2.3 PM-10 SOURCE DESCRIPTIONS
2.3.1 Processes Described
This section discusses emission factors for coke pushing, coke
quenching, coke sizing/screening, casthouse process fugitives, hot
metal transfer, and desulfurization. Emissions from air pollution
control devices that collect pollutants from coke pushing, coke
quenching, coke sizing/screening, hot metal transfer, and
desulfurization are considered "process" emissions that are emitted
by a specific process and controlled by capture devices assigned to
each process. Uncaptured emissions from the above processes are
considered "process fugitive" emissions, i.e., emissions that
escape individual capture devices or are emitted from uncontrolled
processes. Emissions from other processes are discussed briefly.
References listed in Table 2-1 may be consulted for more
information on processes not included in this document.
Tables 2-2 and 2-3 present uncontrolled and baseline PM-10
emission factors for the processes examined in this document.
2-15
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Baseline emissions are those resulting from a prescribed or
reference method of air pollution control, not necessarily the
predominant method. The emission factor data quality ratings are
given if available. The ratings were taken from the U.S. EPA's
Compilation of Air Pollutant Emission Factors (AP-42), which rates
the quality of emission factors from A to E, with A being the
highest quality. AP-42 indicates that high ("A") ratings were
given to emission factors based on multiple observations at many
different plants, while low ("D" or "E") ratings were given to
emission factors based on single observations of questionable
quality or extrapolated from other emission factors from similar
processes. The ratings given in AP-42 are considered a general
indicator of the accuracy and precision of a given factor used to
estimate emissions from a large number of sources. If different
ratings are given for the total particulate emission factor and the
size distribution (used to estimate a PM-10 emission factor from a
total particulate emission factor), the lower quality rating is
shown.
For several processes in Table 2-3, emission factors vary
slightly for different plant sizes. Emission factors represent the
composite of fugitive and process emissions. In general, well-
operated fabric filters can remove more than 99 percent of the PM-
10 contained in the emission stream. However, it is generally
agreed that, regardless of the amount of PM-10 in the emission
stream, the airstream exiting the fabric filter will contain some
minimum concentration of dust, on the order of 0.003 gr/dscf (for
typical inlet streams with concentrations higher than 0.003
gr/dscf) .9'16
To calculate emissions from a specific process, it is
appropriate to calculate the fugitive emissions and process
emissions separately. The fugitive emissions can be calculated
using an uncontrolled emission factor and the capture efficiency of
the ventilation system. The process emissions (emissions that pass
through the control device) may be calculated one of two ways: by
either using the capture and control efficiencies in conjunction
with the uncontrolled emission factor; or by multiplying the
2-17
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control device's minimum exit grain loading by the volume of air
moving through the control device. The final emission figure
should be the sum of (a) the fugitive emission calculation and (b)
the larger of the process emission estimates. The emission factors
presented in Table 2-3 reflect the typical airflows associated with
different types of iron and steel mills.
2.3.2 Coke Pushing
Coke pushing produces varied amounts of emissions depending on
the execution of the coking process. Most coke pushing emissions
consist of coke dust. Coke that is "green," or not fully coked,
emits far more particulates to the atmosphere than does fully coked
coal. The remaining volatile components of the coal burn or
vaporize as the coke is pushed and exposed to the atmosphere. The
emissions from the pushing of green coke consist of coal dust, coke
dust, and condensed tars. Optimization of the coking period can
significantly reduce these emissions.6
Coke pushing emissions, if uncontrolled, have a total
particulate emission factor of 0.58 kg/Mg (1.15 Ib/ton) of coal
charged. Of this amount, 0.25 kg/Mg (0.50 Ib/ton) is PM-10.12
Typical control systems for coke pushing include fixed duct
systems, sheds or moveable hoods vented to venturi scrubbers or
baghouses, and mobile scrubber cars. The AP-42 PM-10 emission
factor for hoods venting to a wet venturi scrubber is 0.08 kg/Mg
(0.16 Ib/ton).12 An alternate emission factor provided by an
industry source is approximately 0.054 kg/Mg (0.11 Ib/ton).9 The
alternate emission factor was used for calculations in this
document.
2.3.3 Coke Quenching
During wet quenching, water is sprayed onto the newly pushed
coke. The thermal shock that occurs when the quench water contacts
the hot coke fractures and shatters the coke, resulting in the
emission of coke dust. Testing emissions from coke quenching is
2-18
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difficult because of the formation of a steam cloud when the quench
water contacts the hot coke. One test showed particulate emissions
from quenching ranging from 0.29 to 1.22 kg of total particulate
per Mg of coal charged. The amount of particulate emissions varied
noticeably with the cleanliness of the quench water. When clean
quench water was used instead of recycled water, the average amount
of particulate emitted dropped from 1.1 to 0.68 kg/Mg (2.2 to 1.36
Ib/ton).n Another reference noted that emissions for recycled
quench water were 1.5 to 3 times greater than those for clean
quench water.6 The percentage of total emissions that are
classified as PM-10 emission also varies, depending on whether
clean or recycled quench water is used in this operation. When
clean water is used for the quench operation, the mass percentage
of PM-10 emissions as a fraction of the total particulate emissions
is 30.1 percent. For recycled quench water, the mass percentage of
PM-10 emissions is 22.8 percent.12 In general, coke manufacturers
use recycled quench water, adding clean water only as makeup for
the water lost as steam or held in the coke. Quenching is normally
conducted with "relatively clean water" (less than 1500 mg/L total
dissolved solids); however, at some facilities, water containing
over 5000 mg/L total dissolved solids may be used (often called
"dirty water quenching") ,16
Aside from the use of less dirty water, the primary control of
quench-tower emissions is accomplished with baffles as inertial
control devices. The baffles typically cover the entire area
inside of the quench tower. The effectiveness of baffles in
controlling emissions varies from 50 to 95 percent depending on the
type.6
The AP-42 emission factors reflect the effects of water
cleanliness and baffle use on the amount of emissions that result
from quenching. Uncontrolled quenching with dirty water has a
PM-10 emission factor of 0.60 kg/Mg (1.19 Ib/ton) of coal charged.
In one series of tests, the use of baffles with recycled water with
"typical" particulate loading reduced the PM-10 emission factor for
coke quenching to 0.21 kg/Mg (0.42 Ib/ton) of coal charged. Use of
clean makeup water reduces the emission factor to 0.17 kg/Mg (0.34
2-19
-------
Ib/ton) of coal charged. For comparison, the use of both clean
makeup water and baffles reduces PM-10 emissions by 95 percent, to
0.03 kg/Mg (0.05 Ib/ton) of coal charged; however, it is not
expected that this technique would be used in ordinary practice.12
Other options, such as the Kress Indirect Dry Cooling (KIDC)
system and quenching with inert gas have been tried in limited
efforts within the U.S. or outside the U.S.16 These methods are
described in Chapter 3.
2.3.4 Coke Sizing and Screening
Reference 17 gives an uncontrolled PM-10 emission factor of
0.04 kg/Mg coal charged (0.08 Ib/ton) for coke handling operations.
This emission factor is assumed to be an appropriate emission
factor for coke sizing and for coke screening operations. As in
the case for coke pushing emissions, the emission factor given in
Table 2-3 for coke sizing and screening is a composite of a
fugitive emission calculation and a process emission calculation.
The fugitive emission portion of this emission factor is calculated
using an assumed capture efficiency of 90 percent and the reference
17 uncontrolled emission factor. The process emission portion of
this emission factor is calculated using typical airflows
(10,000-40,000 cfm) and a minimum exit grain loading of 0.003
gr/dscf.9-17
2.3.5 Iron Production (Casthouse)
Emissions from the blast furnace casthouse occur primarily
during tapping. When the molten iron and slag are exposed to
ambient air, particulates, primarily iron oxides, are formed that
may escape to the ambient air through the sides and roof of the
casthouse. Opening the taphole, particularly if it is clogged, is
also a significant source of emissions.12 Approximately 75 percent
of the casthouse emissions from iron production consists of iron
oxides, the remainder being manganese, silicon, and sulfur
compounds.18 Casthouse emissions are sometimes uncontrolled. In
2-20
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other cases, hoods above the taphole vented to a baghouse are used
to control emissions. Many blast furnace operations reduce the
initial formation of particulates by preventing the molten metal
from contacting the outside air. Some operations use metal covers
over the trough and runners to prevent the hot metal from
contacting the atmosphere. Flame suppression (removing oxygen from
the trough and runner areas via a natural gas flame) can also be
used to reduce iron oxidation. Some new blast furnaces feature
runners covered by hoods vented to baghouses to control the
emissions at their source. Uncontrolled casthouse emissions
measured at the roof monitor have an AP-42 PM-10 emission factor of
0.15 kg/Mg (0.31 lb/ton).12
2.3.6 Hot Metal Transfer
The hot metal transfer process occurs when molten iron is
transferred from a torpedo car to the charging ladle or a hot metal
mixer for the EOF. Emissions from this transfer operation include
small iron oxide particles as well as larger flakes of graphite
("kish"). Approximately 42 percent by weight of hot metal transfer
emissions are kish, with the remaining 58 percent consisting of
particles of iron oxides. Since the kish generally has a diameter
of greater than 75 microns, it is not considered in this evaluation
of PM-10 emissions. The iron oxides, however, generally are less
than three microns in diameter. A baghouse is usually employed to
help control these emissions. The baghouse is fitted with a
sparkbox to protect the bags from accidental ignition by hot
particles emitted from the ladle. Capture device options include
close-fitting ladle hoods, canopy hoods and partial building
evacuation.14
Reference 17 gives a PM-10 emission factor of 0.045 kg/Mg
(0.09 lb/ton) hot metal for uncontrolled emissions at the transfer
station. As in the case for coke sizing and screening, the
emission factor given in Table 2-3 for hot metal transfer is a
composite of a fugitive emission calculation and a process emission
calculation. The fugitive emission portion of this emission factor
2-21
-------
is calculated using an assumed capture efficiency of 90 percent and
uncontrolled emission factor from reference 17. The process
emission portion of this emission factor is calculated using
typical airflows (150,000-300,000 cfm) and a minimum exit grain
loading of 0.003 gr/dscf.9'17
2.3.7 Desulfurization
Desulfurization also results in particulate emissions. This
process is most often performed in the charging ladle and uses the
previously mentioned baghouse control system. The injection of the
desulfurization reagents causes turbulence in the molten iron,
which results in emissions. These emissions typically consist of
iron oxides, sulfur oxides, and oxides of the reagents. The
removal of the slag formed by desulfurization also results in
particulate emissions. A hood such as the one located over the
charging ladle is often used to control emissions from the skimming
of slag. Several firms use various types of hoods to control
emissions from desulfurization. Few quantitative data of
uncontrolled emissions are available.14
A study of emissions from the desulfurization of molten iron
was performed at the Kaiser Steel facility in Fontana, California.
At this plant, CaC2 and CaC03 were injected into the molten iron by
means of a nitrogen lance. Fumes from the process were collected
by side draft hoods and then vented to a baghouse. Tests were
conducted on the exhaust prior to the collection system and on the
dust collected in the baghouse in order to determine the
composition of the exhausts. The testing revealed a particulate
emissions rate of 0.637 kg/Mg (1.27 Ib/ton) of metal treated. Of
this material, 0.319 kg/Mg (0.64 Ib/ton), or 50 percent by weight,
was PM-10. The dust was mainly iron oxides, with concentrations of
arsenic, strontium, and chromium possibly high enough to preclude
landfilling without treatment for heavy metals.19 This dust is
often recycled through a sinter plant.9
An uncontrolled emission factor for desulfurization is given
in AP-42. For this study, the baseline control system is assumed
2-22
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to be a close-fitting hood vented to a fabric filter. Assuming a
close-capture hood efficiency of 95 percent, a minimum exit grain
loading as described earlier, and typical airflows for
desulfurization (50,000—100,000 cfm) generates the emission factor
given in Table 2-3.
2.3.8 Other PM-10 Sources
Several potential PM-10 sources are not covered in this
document, including captured emissions such as those from the blast
furnace and steel furnaces as well as process fugitive sources.
The references listed in Table 2-1 provide more information on
those emissions sources. Other activities that may produce PM-10
emissions are discussed briefly in the following sections.
2.3.8.1 Coal storage and handling
Emissions resulting from the conversion of coal to coke can be
classified into two types: fugitive emissions resulting from the
handling of materials, and emissions caused by the process itself.
Emissions can result from the transportation, unloading, handling,
piling, crushing, and screening of coal as well as from the
handling, screening, and crushing of coke. Methods used to control
or reduce these emissions include collection (coke handling,
crushing, screening) and wet suppression (storage piles). For wet
suppression, water or chemicals are sprayed in a mist over
potential emission sources to prevent particles from becoming
airborne. Generally, emissions from coal storage piles might be
reduced as much as 90 percent with such a system.9'20
2.3.8.2 Charging and oven emissions
Charging the coal into the coking oven causes the formation of
smoke and combustion gases. These products will leave the oven at
any place that is open to the atmosphere, including the charge door
and the combustion stack from the battery. An estimated 40 to 95
percent of this particulate matter has a diameter smaller than one
2-23
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micrometer. On the average, 90 percent of the particles have a
diameter of less than three micrometers.6
The charging of wet coal from a larry car, if uncontrolled,
emits about 0.24 kg of particulate per Mg (0.48 Ib/ton) of coal
charged.12 Most modern larry cars also can include the use; of a
jumper pipe which provides suction to control charging emissions.
Modern larry cars also employ staged charging and steam aspiration
that keep charging emissions to a minimum. Stage charging is a
process which uses steam or liquor aspiration at the offtake piping
to create a vacuum in the oven being charged. Material that would
otherwise be emitted is evacuated to the collector main and cleaned
in the by-product plant. Scrubber equipped larry cars, used for
some time but no longer in wide use, proved less effective than
stage charging.9 Door leakage can also cause noticeable emissions.
Most doors leak during the initial portion of the coking cycle when
oven pressures and gap sizes are greatest; the doors seal more
effectively later in the cycle.4
2.3.8.3 Sintering
Sintering also contributes to PM-10 emissions. The windbox
exhaust is the major source of sintering emissions. The emissions
from a typical windbox average 5.6 kg/Mg (11.1 Ib/ton) of sinter
produced. The PM-10 emissions factor for sinter windbox emissions
is 0.83 kg/Mg (1.67 Ib/ton) of finished sinter. Most sintering
processes have a mechanical collector such as a cyclone to remove
the larger particles in the exhaust. The exhaust then goes to a
secondary collector such as a scrubber, fabric filter,
electrostatic precipitator, or gravel bed filter.6 Most U.S.
operations currently use scrubbers, while some use baghouses. ESP
use has been declining since changes were made in flux addition to
the sinter feed.
2.3.8.4 Flux handling
Handling and transporting flux also releases particulates into
the atmosphere. The composition of these emissions naturally
depends on the composition of the flux, which is usually limestone,
2-24
-------
dolomite, or another alkaline material. The flux is normally
received in bulk lots by truck or rail and is moved by conveyor
belt to storage areas until it is needed. Hoods cover areas having
a serious risk of material loss. These hoods normally vent to a
baghouse.3 No emission factors are available for flux handling.
2.3.8.5 Steelmaking
EOF operations produce two types of emissions: "primary
emissions" generated during the oxygen blow and "secondary
emissions" associated with charging and tapping. Primary emissions
generally consist of iron oxides, slag particles, carbon, and
carbon monoxide. These fumes are mostly captured by a primary hood
located over the furnace mouth. The fumes must undergo a cleaning
process to remove excess particulate matter. The most common types
of cleaning processes employed are the open hood with electrostatic
precipitator (ESP), open hood with wet scrubber, and closed hood
with scrubber.3 If an ESP is used, the carbon monoxide must first
be combusted by addition of excess air at the furnace mouth to
avoid the risk of explosion.
For more information on BOFs, their emissions, methods of
control, and relevant regulations, agencies should consult the
sources listed in Table 2-1.
Emissions from the secondary sources associated with a EOF are
usually not captured by the primary hood. Most of these secondary
sources may also be present in a shop employing an open hearth or
electric arc furnace.
2.3.8.6' Charging of molten iron and of steel scrap
The charging of the molten iron and the steel scrap into the
steel producing furnace may cause fairly significant emissions of
particulates. Emissions are greater if the scrap is dirty or
contains excess moisture. In some shops with an open hood, these
emissions are controlled to an extent by slowing the iron feed rate
and reducing the furnace tilt in order to capture as much of the
emission stream as possible with the hood. Bottom blown or Quelle
furnaces produce greater quantities of emissions than standard top
2-25
-------
blown furnaces due to the continuous gas flow through the tuyeres
in a bottom blown furnace.3
2.3.8.7 Tapping, slag pouring, and turndown
Iron oxides are emitted when the hot steel is tapped from the
furnace into ladles. When alloying materials such as nickel,
silicon, or manganese are added, emissions increase noticeably. In
some BOFs, the ladle is enclosed and the fumes are captured by the
hood system on the furnace: in some shops, the hood system is also
used to attempt to control emissions from the tilting or "turndown"
of the furnace. Turndown may be performed to check the composition
of the molten steel or to pour slag from the top of the molten
steel. A few furnaces have sliding doors in front of the furnace
that can be closed to improve the collection efficiency of the
primary hood.3 Flame suppression can be used to remove oxygen from
the tapping area, thereby reducing oxide formation and emission.
2.3.8.8 Scarfing
Very few data are available on the quantity and composition of
emissions that result from scarfing. The scarfing process may be
carried out either by hand with torches or by jets of oxygen from
a machine similar in design to a rolling mill. Machine scarfing
emissions are normally controlled by either an electrostatic
precipitator or a scrubber. Emissions from hand scarfing are
almost always uncontrolled. It is estimated that uncontrolled
machine scarfing produces 0.05 kg/Mg (0.1 Ib/ton) total particulate
emissions.12
2.3.8.9 Slag handling
The molten slag from steel making is dumped either in the shop
or at a dump site elsewhere in the mill area, allowed to solidify,
and then removed for disposal. The pouring and cooling of slag
emits particles to the atmosphere. In addition, the use of heavy
equipment to remove the slag produces large quantities of dust.
Usually, neither of these emission sources is controlled.
Slag recycling and materials recovery also may generate
2-26
-------
fugitive emissions. Magnets remove the metallic components of the
slag for reuse. Portions of the slag that are especially basic may
be reused as flux. The remaining, unusable portion of the slag is
landfilled. This operation generates emissions from materials
transportation and storage. Measures must be taken to prevent
components of the slag from leaching into nearby groundwater.3 No
firm emission factors are available for slag handling and disposal.
2.3.8.10 Deskulling
Both transfer ladles and torpedo cars build up crusts of
solidified metal around their edges after repeated use. This
buildup is known as "skull" and may eventually prevent proper
operation of the ladles and cars. Oxygen lances are used to burn
off skulls on transfer ladles; iron oxides are emitted from this
process. Torpedo cars are deskulled with jackhammers rather than
with oxygen lances; this process is also likely to emit dust to the
atmosphere.3 There are no established emission factors for the
deskulling processes.
2.3.8.11 Waste disposal
Two sources of dust result from the disposal of solid wastes
from the steelmaking process. First, the dust collected by the
various control devices on or around the EOF must be removed. In
some cases the dust may be recycled to the blast furnace for use in
iron production. However, the dust often has high concentrations
of tin and zinc oxides, which would adversely affect the quality of
metal if fed into the furnace. In these cases, the dust must be
dumped onto an open pile or into a landfill. While the
transportation and subsequent storage of this dust allows some of
it to escape into the atmosphere, a more significant problem is the
possibility of metals leaching into groundwater from the dust.3 No
reliable emissions data have been compiled for disposal of waste
and slag.
2-27
-------
2.4 MODEL PLANTS AND EMISSIONS
2.4.1 Introduction
This section describes operating parameters and PM-10
emissions from the processes listed in Section 2.2.1 for model
plants representing typical integrated iron and steel mills that
use BOFs. The model plant operating parameters and emissions
estimates are based on data collected from published literature or
on engineering estimates.
The small plant includes two 136 Mg (150 ton) BOFs in its
steel making shop; this model is representative of some older mills
and of mills that produce some specialty steels. The large plant
includes three 272 Mg (300 ton) furnaces, typical of a modern high-
volume steel production facility. The medium plant includes two
272 Mg (300 ton) furnaces, midway between the small and large
facilities in size. The small and large model plants' furnace
complement and production data were taken or developed from
Reference 3. Metal production figures in Reference 3 are not
necessarily proportional to the number of furnaces and furnace
capacity. According to the reference, the production numbers
reflect the variations in the operating schedules possible with
multiple furnaces (e.g., a two furnace facility may alternate
operation of each furnace, or a three-furnace shop may operate one
or two furnaces while the third is idle). Table 2-4 contains
operating parameters assumed for these model plants. Emission
factors also were taken from the literature and/or based on
engineering estimates as described earlier in this chapter.12
2.4.2 Model Plant Potential PM-10 Emissions
Table 2-5 lists PM-10 emission estimates for uncontrolled
model plants. These calculated emissions are often referred to as
"potential emissions." The potential PM-10 emissions for each
process and model plant are calculated using the model plant
parameters given in Table 2-4 and the emissions factors given in
2-28
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Table 2-2. Potential PM-10 emissions estimates are given for all
processes where reasonable operating parameter and emission factor
data were available or could be estimated.
2.4.3 Model Plant Baseline Emissions
Table 2-6 is similar to Table 2-5, but Table 2-6 lists
emission estimates for model plants that use pollution control
methods assumed to be in use at typical iron and steel facilities.
These calculated emissions are often referred to as "baseline
emissions" because they represent the emissions expected from
plants that use currently accepted pollution control techniques.
The baseline emissions for each process and model plant were
calculated using the model plant parameters in Table 2-4 and the
emission factors given in Table 2-3.
The emissions estimates given in Tables 2-5 and 2-6 are
considered representative of typical plants; however, process
parameters and pollution control practices will be different for
each integrated mill. Extreme caution should be exercised in
interpreting the emissions estimates in Tables 2-5 and 2-6 because
they are calculated from very general operating parameters given
for the model plants and general emission factors. Any assessment
of emissions from existing plants should be made on an individual
site-specific basis for each integrated mill examined. Sample
calculations of two baseline emission figures are given in
Appendix B.
2-30
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2.5 REFERENCES FOR CHAPTER 2
1. U.S. Department of Commerce. 1990 U.S. Industrial Outlook.
Chapter 16: Ferrous Metals. Washington, B.C.
2. Gale Research, Inc. Ward's Business Directory of U.S. Private
and Public Companies-1991. Volume 4. Detroit, MI. 1991.
3. U.S. Environmental Protection Agency. Revised Standards for
Basic Oxygen Process Furnaces- Background Information for
Proposed Standards. EPA-450/3-82-005a. Office of Air Quality
Planning and Standards, Research Triangle Park, NC. December
1982.
4. U.S. Environmental Protection Agency. Coke Oven Emissions
from Wet-Coal Charged By-Product Coke Oven Batteries-
Background Information for Proposed Standards.
EPA-450/3-85-028a. Office of Air Quality Planning and
Standards, Research Triangle, Park, NC. April 1987.
5. Standard and Poor's Industry Surveys. Steel and Heavy
Machinery. Volume 158, No. 30. August 9, 1990.
6. U.S. Environmental Protection Agency. Control Techniques for
Particulate Emissions from Stationary Sources - Volume 2.
EPA-450/3-81-005b. Office of Air Quality Planning and
Standards, Research Triangle Park, NC. September 1982.
7. Letter from David C. Ailor, American Coke and Coal Chemical
Institute, to James H. Maysilles, U.S. Environmental
Protection Agency. Comments on draft ACT document for PM-10
emissions from iron and steel mills. Letter dated September
25, 1992.
8. Lankford, W.T., et al., eds. The Making, Shaping, and
Treating of Steel. Tenth Edition. Association of Iron and
Steel Engineers. Pittsburgh, PA. 1985.
9. Letter from Thomas W. Easterly, Bethlehem Steel Corporation to
James H. Maysilles, U.S. Environmental Protection Agency.
Comments on draft ACT document for PM-10 emissions from iron
and steel mills. Letter dated August 19, 1992.
10. U.S. Environmental Protection Agency. Industrial Process
Profiles for Environmental Use. Chapter 24: The Iron and
Steel Industries. EPA-600/2-77-023x. Office of Research and
Development, Research Triangle Park, NC. February 1977.
11. U.S. Environmental Protection Agency. Coke Quench Tower
Emission Testing Program. EPA-600/2-79-082. Industrial
Emissions Research Laboratory, Research Triangle Park, NC.
April 1979.
2-32
-------
12. U.S. Environmental Protection Agency. Compilation of Air
Pollutant Emission Factors. AP-42, Fourth Edition with
Supplements. Office of Air Quality Planning and Standards,
Research Triangle Park, NC. September 1985.
13. Parkinson, G. "Steelmaking Renaissance." Chemical
Engineering, Volume 98, No. 5. New York, NY. May 1991.
14. U.S. Environmental Protection Agency. Fugitive Emissions from
Integrated Iron and Steel Plants. EPA-600/2-78-050. Office
of Research and Development, Washington, D.C. March 1978.
15. Varga, Jr. and H.W. Lownie, Jr. A Systems Analysis Study of
the Integrated Iron and Steel Industry. HEW Contract No.
22-68-65. Battelle Memorial Institute, Columbus, Ohio. May
1969.
16. Buonicore, A.J., and W.T. Davis, eds. Air Pollution
Engineering Manual. Van Nostrand Reinhold. New York, NY.
1992.
17. U.S. Environmental Protection Agency. A IRS Facility Subsystem
Source Classification Codes and Emission Factor Listing for
Criteria Air Pollutants. EPA-450/4-90-003. Office of Air
Quality Planning and Standards, Research Triangle Park, NC.
March 1990.
18. Jeffery, J. and J. Vay. Source Category Report for the Iron
and Steel Industry. EPA-600/7-86-036. U.S. Environmental
Protection Agency, Research Triangle Park, NC. October 1986.
19. U.S. Environmental Protection Agency. Hot Metal
Desulfurization, EOF (Basic Oxygen Furnace) Charging and
Oxygen Blowing: Level 1 Environmental Assessment.
EPA-600/2-82-036. Research Triangle Park, NC. March 1981.
20. U.S. Environmental Protection Agency. Control Techniques for
Particulate Emissions from Stationary Sources - Volume 1.
EPA-450/3-81-005a. Office of Air Quality Planning and
Standards, Research Triangle Park, NC. September 1982.
2-33
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CHAPTER 3
EMISSIONS CONTROL TECHNIQUES
3.1 INTRODUCTION
This chapter contains descriptions and data for various PM-10
alternative control techniques (ACTs) for the specific emission
sources described in Chapter 2 of this document. Also, pollution
prevention (source reduction) techniques, which can prevent or
reduce emissions from mills and associated fugitive area sources,
are provided. Finally, typical emission reductions are discussed.
The emission control techniques discussed are emission capture
and collection devices that are considered to be ACTs for PM-10
sources. This chapter focuses on retrofit control techniques,
where a retrofit is considered to be the replacement of, or
addition to, pre-existing equipment, and provides additional
information on ACTs for newly constructed facilities. The
discussion of each control technique addresses design parameters,
operating parameters, and variables affecting operation.
3.2 SOURCE REDUCTION IN IRON AND STEEL MILLS
Source reduction techniques are practices that reduce the
amount of any hazardous substance, pollutant, or contaminant
entering any waste stream prior to recycling, treatment, or
disposal. Process improvements may reduce the number of process
steps, and their implementation can result in reduced energy
consumption and/or materials use. These reductions in energy and
resources use may translate directly or indirectly into lower
pollutant emissions.
Because of their design, non-recovery coke ovens inherently
release less particulate matter to the atmosphere. Non-recovery
coke ovens are operated under negative pressure, which minimizes
the emission of particulate from the oven. Only one non-recovery
coke oven is currently used in the United States.
3-1
-------
Coke pushing operations provide some opportunity for source
reduction. Coke pushing is the operation in which hot coke is
removed or "pushed" from the coking oven. The PM-10 emissions from
coke pushing are greater if the coal is not fully coked before
pushing. Optimizing the coking period can significantly reduce the
pushing emissions. An increase in the temperature of the coking
oven, an increase in the coking period, and a more even
distribution of heat in the coking oven can all increase coking
efficiency and decrease pushing emissions. The first two steps are
related, with the temperature of the oven walls and the amount of
time required for proper coking being interdependent. There is an
upper temperature limit above which the refractory lining of the
oven will be damaged by increased heating. Uneven heat
distribution in the oven can cause areas within the coal charge to
receive less heat than necessary for full coking. If a flue or gas
nozzle is closed or defective in one section of the oven, then the
coal in that section may not coke completely, resulting in
increased emissions when it is pushed. Moisture pockets within
charges of coal can also cause "greenness" or undercoking, as some
of the heat provided by the oven must be used to heat and evaporate
the excess moisture.1
Controlling the level of suspended solids in the coke quench
water is another example of source reduction. In general, water
not evaporated or caught by the coke is collected in the quench
tower sump and recycled for later quenches. Makeup water can be
supplied by clean water or by wastewater from other plant processes
such as the coal chemical plant. One test showed particulate
emissions from quenching that ranged from 0.29 to 1.22 kg of total
particulate matter per Mg of coal originally charged. When clean
makeup water was used instead of coal chemical plant makeup water,
the average amount of particulate matter emitted dropped from 1.1
to 0.68 kg/Mg.2 Another source confirmed this observation, noting
that when clean quench makeup water was used instead of coal
chemical plant wastewater, average emissions were 1.5 to three
times smaller.1
3-2
-------
Some firms are attempting to reduce their need for coke.
Furnaces may be modified to allow powdered coal injection (PCI)
directly into the combustion area. One reference indicates that up
to 50 percent of the coke used in steelmaking could be replaced by
coal.3
Another emission reduction alternative may be to entirely
eliminate coke production from the steelmaking process. The German
firm Deutsche Voest-Alpine Industrieanlagenbau has developed a two-
step iron production process that uses non-coking coals. First,
the iron ore is reduced in a shaft furnace. The reduced ore is
then melted in a "melter-gasifier, " which both melts the ore and
produces the reducing gas for the reduction furnace. This process
reportedly avoids the emissions normally generated by coke-making
in addition to lowering operating costs up to 25 percent. This
process is in commercial use in South Africa but has not yet been
adopted by U.S. steel producers. As of 1991, one unit had been
designed (in South Africa) with an operating capacity of 800,000 to
1,000,000 tons per year. Several American firms are currently
examining the viability of the process.3
Emissions from the casthouse area may also be reduced by
employing pollution prevention practices. Some new blast furnaces
feature covered runners or other devices that prevent contact
between the molten pig iron and the ambient air. Thus, the
formation of particulate pollutants may be inhibited.4 Another
approach is to blanket the troughs and runners with a natural gas
flame that consumes the local oxygen, thus suppressing the
formation of iron oxides.
Changes in some work practices can prevent or reduce
particulate emissions from open dust sources. These work practices
focus on the operation of equipment used to transport, store, and
transfer materials. In the case of unpaved and paved travel
surfaces, emissions can be reduced by decreasing vehicle speed and
weight, using dust suppressants, and/or employing road sweeping.
For materials handling operations, emissions can be reduced by
decreasing drop height and increasing bucket capacity. Finally,
3-3
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emissions from wind erosion can be reduced by decreasing the size
of the active area of a storage pile or exposed ground surface.5
3.3 CONTROL EQUIPMENT
Iron and steel mill process PM-10 emissions can be controlled
by systems consisting of two basic components, a capture device and
a collection device. (The collection device is also known as a
control or removal device.) Figure 3-1 shows a typical emissions
control scheme. The particulate matter is captured in the local
air stream by a hood or other capture equipment and sent, to a
control device, which separates the particulate matter from the air
stream and sends the cleaned air into the stack. The recovered
particulate matter is then removed and recycled, landfilled, or
reused.
This section discusses equipment used to capture both primary
and secondary emissions. By definition, primary emissions in the
EOF shop are those generated by the furnace and related equipment
while the furnace is operating. Primary capture equipment is
designed to capture these primary emissions and consists of various
types of hoods and enclosures. Secondary emissions are defined as
emissions from process steps that are not collected by primary
emissions control systems. Secondary capture involves using
building evacuation, booths and/or hooding, and enclosures. The
control devices discussed here are those most frequently employed
in the industry and include fabric filters (baghouses), wet
scrubbers, and electrostatic precipitators (ESPs).
3.3.1 Primary Control Equipment
The operations generating primary emissions that are examined
in detail in this document include coke pushing, coke quenching,
coke sizing and screening, hot metal transfer, and desulfurization.
Primary control equipment is designed to capture emissions from
these areas and direct them to collection systems. Also, a brief
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discussion is provided on primary furnace emissions and various
capture and collection equipment associated with them.
3.3.1.1 Primary control of BOF emissions
Fumes from the BOF generally consist of iron oxides, slag
particles, and carbon monoxide. These fumes can be captured by a
hood located over the furnace mouth and routed to a control device
for PM-10 collection. The most common types of control systems
employed are the open hood with ESP, open hood with scrubber, and
closed hood with scrubber.6
The particulate emissions from open hearth furnaces are mainly
(up to 90 percent) iron oxides, primarily in the form of Fe20;J. Due
to the predominance of small particles in these emissions, high-
efficiency controls such as wet venturi scrubbers and ESPs must be
used in conjunction with appropriate hooding. Fabric filter
baghouses may also be used if the exhaust gases are cooled to
reduce the risk of accidentally igniting a bag.1
3.3.1.2 Primary control of other process emissions
Control systems for non-furnace primary emissions vary
substantially in design between different sources. Some systems,
such as those for coke pushing and coke quenching, are unique to
the specific operation. Systems for casthouses are also somewhat
site-specific. The following sections describe control methods
that are available for each type of source.
3.3.1.2.1 Coke Pushing-. Three methods are commonly used for
controlling emissions from coke pushing. The first method is the
use of a mobile scrubber car, which consists of an enclosed quench
car coupled with a wet venturi scrubber car. The enclosed car
captures any exhaust gases and particulates that result from the
pushing operation, then vents them into a specially equipped
exhaust gas cleaning car for treatment.l An advantage of the
enclosed quench car is the relatively low gas flow rate required
for operation, which results in lower utility costs. However, the
3-6
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added weight of the control system may require that the tracks and
support system for the car be strengthened before use.8 Also,
industry representatives indicate that the enclosed quench car
requires frequent maintenance, leading many in the coke industry to
abandon its use.9
The second available method uses a full-length shed over the
exits from the oven. The shed traps the pushing emissions and
prevents their escape into the atmosphere. The emissions are then
drawn into a control device such as a scrubber or baghouse.1 One
advantage of the shed system is that its continuous operation also
captures emissions from coke oven door leaks. It does, however,
require large volumes of airflow to be effective.8
The third method is the traveling hood. This system consists
of a mobile hood that is attached to the quench car or to the coke
guide. The mobile hood with quench car combination can result in
very good capture efficiency, nearly at the same level as the shed
with baghouse, and with lower airflows.10 The emissions from the
hood are vented to a fixed duct exhaust main, which is routed to a
collection device such as a scrubber or a baghouse. A disadvantage
of the traveling hood is frequent downtime (5 percent) for
maintenance and repairs.9
3.3.1.2.2 Coke Quenching. After pushing, the coke is hot
enough to burn in the presence of air. To prevent the coke from
burning, most coke production facilities cool the coke with water
in a quench tower. In the quench tower, water is sprayed onto the
hot coke. Emissions from quenching are typically larger-sized
particulates created by the breakup of the hot coke when the quench
water contacts the coke. The particulate is carried up the quench
tower on the steam plume.
Quenching is normally conducted with relatively clean water
(less than 1500 mg/L total dissolved solids) ; however, at some
facilities, water containing over 5000 mg/L total dissolved solids
may be used (often called "dirty water quenching").16
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Other options have been used in the past to prevent
particulate emissions from coke cooling. The Kress Indirect Dry
Cooling system is unique in that it eliminates the need for
particulate control. In the Kress system, coke is pushed into a
large box that mates directly to the door jamb. Once the coke is
in the box, the box is sealed and taken to a cooling rack. When
the coke in the box has been cooled (by thermal transfer through
the box) , it can be handled as dry, cool coke. There are
essentially no pushing or quenching emissions from this system.16
The system has not been tried widely in the United States.
Quenching of coke with inert gas under controlled conditions
can also eliminate quenching emissions and recover heat energy from
the hot coke. While this process has been used in Europe and
Japan, it has not been tried in the United States.
3.3.1.2.3 Coke Handling. Coke handling consists of several
operations, including sizing, screening, and conveying. Emissions
from coke sizing and screening are typically controlled by a hood
or enclosure vented to a baghouse.
Emissions from conveyors may be controlled in the same manner.
Coke conveyors often need no controls as the coke is a strong solid
and, unless it is extremely dry, does not release particulate when
being conveyed. Conveyors carrying dusty materials are often
covered, and any dust that may be generated falls back onto the
material being conveyed. Conveyor transfer points are sometimes
controlled by an enclosure, which, for very dusty materials, may be
vented to a baghouse.10
The crushing operation may be controlled by wet suppression
(see Reference 12) with a particulate matter control efficiency of
around 95 percent. However, most steel producers avoid adding
additional moisture to the coke. Foggers that wet the emissions
only and not the coke itself may be preferable for control.
Alternatively, these emissions can be controlled like coke sizing,
screening, and crushing emissions by enclosing the area and venting
3-8
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to a baghouse. This type of system would control the PM-10
emissions without adding excess moisture.13
3.3.1.2.4 Casthouse. Casthouse emissions may be controlled
by any of three methods. The first method involves local hoods
vented to a baghouse, which can capture emissions from various
sources within the casthouse. These local hoods can have a capture
efficiency up to 95 percent or greater depending on their design
and location. A second option for casthouse emissions control is
total building evacuation of the casthouse area exhausted to a
baghouse.
These control systems can have an overall collection
efficiency of 95 percent or greater for PM-10. One advantage of
total building evacuation is the absence of bulky structures (i.e.,
hoods and ductwork) near the casthouse operations, leading to
greater ease of casthouse operations and maintenance.6 Figure 3-2
shows a casthouse with an emissions control system.14
A third method for casthouse emissions reduction involves the
use of suppression techniques. Suppression techniques are designed
to limit or control the formation of particulate (metal oxide)
emissions by either reducing contact between the hot metal and
ambient air/oxygen or disallowing formed particulate from escaping
the casthouse. The major techniques used today include flame
suppression, steam suppression, and covers. Any combination of
these three types can be integrated into one suppression system for
a given facility.
Flame suppression is accomplished by directing natural gas
fired from a nozzle (or nozzles) toward the surface of the hot
metal. The gas is ignited by the high temperature of the metal and
burns away the oxygen near the surface of the metal so that metal
oxide formation is hampered. Flame suppression has been shown to
be effective on particulate emissions from troughs, runners, and
ladles.
Steam suppression can control PM-10 emissions in one of two
demonstrated methods. As one example, taphole emissions are
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controlled by steam agglomeration of particulate into larger sizes
which then settle inside the casthouse. As a second example, iron
runner emissions can be controlled by a steam blanket that covers
the hot metal and prevents contact with oxygen. Steam suppression
has been shown to be somewhat effective on particulate emissions
from the taphole, trough, runners, and ladles.
Cover suppression involves the use of tight fitting covers
that prevent the hot metal from contacting ambient air. These
covers have proven effective for controlling particulate emissions
from the trough and runners. However, PM-10 emissions can escape
when the trough covers are removed for such activities as taphole
drilling.
3.3.2 Secondary Control Equipment
This section discusses control of emissions from hot metal
transfer and desulfurization and from secondary control of EOF
emissions during charging, tapping, and slagging.
3.3.2.1 Secondary control of EOF emissions
The primary emission control system for a EOF is designed to
capture emissions released during the oxygen blow, in which the
furnace is in the vertical position with the mouth at the top.
This primary hood may not effectively capture emissions from
furnace charging, steel tapping, and slag pouring operations,
during which the furnace is rotated or tilted and its mouth is no
longer completely under the hood.7
Two secondary control options currently used are close-in or
local capture hoods and roof-mounted hoods, with the latter option
being more frequently employed. Secondary hoods may be designed to
capture charging, tapping, and slag pouring emissions. Along with
secondary hood design, which is usually facility-specific,
operating practices, particularly for furnace charging, are
critical to effective secondary emissions control. The furnace is
tilted towards the transfer ladle no more than is necessary to
3-11
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begin hot metal pouring. As the transfer ladle is emptied, the
ladle and furnace are progressively rotated towards each other only
as much as necessary to transfer metal while keeping the ladle and
furnace under the secondary hood as much as possible.7
The secondary hood is typically evacuated through a fabric
filter. This secondary control system is sometimes part of a more
comprehensive system in which other secondary hoods that capture
emissions from non-furnace operations, including hot metal transfer
and desulfurization, may be evacuated through the same filter.
3.3.2.2 Control of other process emissions
This section contains control options for the hot metal
transfer and desulfurization processes. Typically, the emission
control systems for these processes are site-specific and thus are
inherently different. Figure 3-3 shows a typical hot metal
transfer station.6 There are several options for collecting
emissions from the hot metal transfer operation. The first capture
option is the installation of a close-fitting ladle hood around the
ladle at the transfer station. The second alternative is the use
of a canopy hood, which is generally placed several feet above the
transfer station.4 Due to this positioning, the canopy hood may
require a larger volume of air to capture emissions as effectively
as close fitting hoods. However, emissions from the hot metal
transfer are carried upward by the buoyant pressure of the heated
air. Also, if a baghouse is used, the gas from a close-fitting
hood may be too hot and will require dilution air to cool the gases
for the baghouse. Hoods for non-furnace emissions may be either
fixed or movable, depending on the application. Fixed hoods are
less burdensome from an operational standpoint since they can be
located farther away from the process being controlled. However,
they require larger airflows. Movable hoods must be in close
proximity to the process they control and are therefore more likely
to be an operational hindrance, but they require less airflow than
fixed hoods. In some facilities, emissions from hot metal transfer
and desulfurization are captured by a side draft hood.15 Regardless
3-12
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Exhaust to
baghouss
Figure 3-3. A hot metal transfer and skimming station.
3-13
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of the hood type employed (canopy, movable, close-fitting, side
draft, etc.), the emissions are normally vented to a baghoiise or
scrubber. Since the hot metal transfer and desulfurization
operations are often conducted at the same station within a mill,
emissions from both operations may be captured and collected by the
same control system. Flame suppression (see discussion in Section
3.3.1.2.4) is another control option at the hot metal transfer
station.7
3.3.3 Control System Performance
The effectiveness of the control systems discussed here
depends mainly on the capture system's performance. In order to
effectively collect emissions they must first be routed, via a
capture system (composed of a capture device and ductwork), to the
collection device. The capture efficiencies of hood designs used
for primary and secondary emissions vary widely. A single system
efficiency value cannot be assigned to these designs because
capture depends upon installation and site-specific parameters such
as the hood placement and design face velocity. This variability
makes site-specific capture efficiency determination virtually
mandatory to ensure a high level of emissions capture.
3.3.4 Control Devices
The primary and secondary devices that capture PM-10 emissions
from iron and steel mill processes comprise the first part of an
effective control system. The second half of the system is the
control (collection) device. The control equipment cleans (or
removes) PM-10 from the air streams before exhausting to the stack.
The fabric filter is the most common control device for
primary and secondary particulate emissions. However, some mills
employ high efficiency wet scrubbers or ESPs for EOF shop primary
emissions and other processes depending on the emissions'
characteristics. For example, EOF primary emissions are hot
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(1,650-3,000°F) and contain carbon monoxide (CO), providing the
opportunity for energy recovery from CO combustion for use within
or outside the plant. These emissions are normally controlled by
an ESP or wet scrubbing device. Emissions from casthouse
operations may contain CO, sulfur dioxide (S02) , or high humidity,
which would require the use of a wet scrubbing device.16 Table 3-1
lists the particulate removal efficiencies of various control
devices.4 The reasons for the predominance of fabric filtration use
in mills for PM-10 emissions control are discussed below.
3.3.4.1 Fabric filters
The fabric filter is a versatile type of equipment used to
collect solid particulates from an air stream. For PM-10
emissions, a collection efficiency of 99 percent or greater can be
expected. As the filter medium becomes caked with particulate, the
collection efficiency actually increases, as does the proportion of
smaller particles collected.17 This section discusses the basic
principles of operation for a fabric filter and how collection
efficiency can be maximized.
A fabric filter system (baghouse) consists of several
filtering elements (bags) and a bag cleaning system all contained
in a main shell structure that is equipped with dust hoppers
(Figure 3-4).18 Particulate-laden gases are passed through the bags
so that particles are retained on the fabric in a filtering dust
layer that enhances the fabric filter's performance. The major
fabrics used in iron and steel mill bags are polyester, woven and
felted fiberglass, and Teflon fluorocarbon materials, though the
specific choice of material depends on the application.16
Typically, a baghouse is divided into several compartments or
sections, each containing several bags. In larger installations,
an extra section is often provided to allow one compartment to be
out of service for cleaning at any given time without affecting the
overall efficiency of the system.18
The basic mechanisms used for cleaning particulate-laden gases
in a fabric filter are inertial impaction, diffusion, direct
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TABLE 3-1. TYPICAL PARTICULATE COLLECTION EFFICIENCIES OF CONTROL
DEVICES USED IN IKON AND STEEL MILLS4'3
Efficiency (percent)
by Particle Size
(micrometers)
Type of Device
Wet scrubber
- high efficiency
- medium efficiency
- low efficiency
Gravity collector
- high efficiency
- medium efficiency
- low efficiency
Centrifugal collector
- high efficiency
- medium efficiency
- low efficiency
Electrostatic precipitator
- high efficiency
- medium efficiency
- low efficiency
Fabric filter
- high temperature
- medium temperature
- low temperature
0 - 2.5
90
25
20
3.6
2.9
1.5
80
50
10
95
80
70
99
99
99
2.5 - 6
95
85
80
5
4
3.2
95
75
35
99
90
80
99.5
99.5
99.5
6 - 10
99
95
90
6
4.8
3.7
95
85
50
99.5
97
90
99.5
99.5
99.5
Data represent an average of actual efficiencies. Efficiencies are representative of well-
designed and well-operated control equipment. Site-specific factors (e.g., type of
particulate being collected, varying pressure drops across scrubbers, maintenance of
equipment, etc.) will affect overall control efficiencies. Efficiencies shown are intended
to provide guidance for estimating control equipment performance when source-specific data
are not available.
interception, and sieving. The first three mechanisms are
prevalent during the first few minutes of cleaning with new or
recently cleaned bags. However, the sieving action of the dust
layer accumulating on the fabric surface soon predominates.. This
3-16
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SHAKER
MECHANISM
OUTLET
PIPE
INLET
PIPE
3AFFLE
DLATE
1USTY AIR
.IDE
FILTER,
BAGS
CELL
".PLATE
HOPPER
Figure 3-4. Fabric filter.18
3-17
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sieving mechanism leads to high efficiency collection of
particulates unless defects such as pinhole leaks in the bags or
cracks in the filter cake appear.19
In fabric filtration, both the collection efficiency and the
pressure drop across the bag surface increase as the dust layer on
the bag builds up. Since the system cannot continue to operate
efficiently with the pressure drop increasing without limit, the
bags are cleaned periodically by a reverse airflow, pulse-jet, or
shaker mechanism. The dust is collected below the filters in
hoppers and is either recycled or sent to a landfill.
The fabric filter capacity can be varied widely with little
effect on efficiency. This inherent flexibility permits an
increase in capacity within reasonable limits by increasing system
fan horsepower. An oversized unit is more desirable than an
undersized unit because the dust loading and gas volume can surge
during many mill operations. A sudden increase in volume flow rate
may decrease the dust collection efficiencies on other types of
collectors but, within limits, does not affect the performance of
a fabric filter. Sporadic overloading can be readily accommodated
by a baghouse but this does not mean that a fabric filter should be
operated at wide variations from the equipment manufacturer's
recommendations .20
Fabric filters have the disadvantage of being unable to
control high-temperature gas streams. Often dilution air is
required to cool certain gas streams to a temperature for
sufficient baghouse operations. Also, baghouses may not be the
most suitable control device for all gas streams (i.e., high
moisture content, condensing organics) even though they have a
theoretical control efficiency advantage.
As the data in Table 3-1 indicate, the collection efficiency
of a fabric filter typically exceeds that of any other applicable
control device. Fabric filters also have many other advantages
that make them suitable for control of particulate emissions.
Fabric filters consume less energy (lower pressure drop, less fan
horsepower required) than either scrubbers or ESPs for equivalent
3-18
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outlet particulate concentrations. They are efficient collectors
of very fine emissions and are tolerant of fluctuations in the
inlet particle size distribution (which affects ESPs). Finally,
fabric filters collect particulate emissions as a dry dust, which
is easier to handle or recycle than the wastewater and sludge
collected from scrubbers. However, if desired, the dust from a
fabric filter can be wetted in a pug mill or pelletized before it
is recycled or landfilled, decreasing handling problems associated
with the fine dust.
Two types of fabric filter systems used in the industry are
the positive-pressure type and the negative-pressure type. They
are distinguished by how the exhaust air stream is moved through
the baghouse. Positive-pressure fabric filter systems are those in
which the effluent gases are forced through the fabric filter by a
fan placed between the emissions capture system and the fabric
filter. Bag inspections and maintenance are easier to perform than
on negative-pressure fabric filters. The compartments can be
entered while the positive-pressure fabric filter is in operation,
assuming that the temperature inside the compartments is low enough
for worker safety. Uncleaned air entering the fabric filter is
filtered through the cloth and then vented to the atmosphere
through louvers, a stack, stub stacks, or a ridge vent (monitor) .20
The alternative to the positive-pressure system is a negative-
pressure or suction-type fabric filter. In this system, the fan is
placed on the clean air side of the fabric filter and effluent gas
is drawn through the fabric. These negative-pressure filters
usually require less fan maintenance and less operating horsepower
than the pressure type; however, there are disadvantages.19 They
need to withstand the suction created by the fans, and good sealing
is necessary to prevent the introduction of dilution air. Despite
these disadvantages, negative-pressure systems are dominant in the
iron and steel industry because of the large-size particulates
sometimes present in mill emissions, which can quickly destroy fan
blades if not filtered before entering the fan.11 It may be
necessary to precoat the bags with another material in order to
3-19
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prevent them from being fouled or plugged by tar from the coke
pushing operation.1
3.3.4.2 Wet scrubbers
Another type of particulate collection device is the wet
scrubber. Wet scrubbers are broadly employed in industry for
particulate control. Generally, mechanically generated dust can be
handled with medium or low energy scrubbers, but fine particulates
can only be collected efficiently with higher energy scrubbers, as
shown by the data in Table 3-1.
No wet scrubbing device, however, is comparable to a fabric
filter for overall particulate control efficiency. The most
frequently employed wet scrubbing design for PM-10 control is the
high energy venturi scrubber. In the venturi scrubber, shown in
Figure 3-5, the water is injected into the inlet gases, which are
<*"
passed through a venturi throat. In spite of the relatively short
residence time, the extreme turbulence in the venturi throat
promotes very intimate contact between the particulate and the
water. The wetted particles and droplets are collected in a
cyclone spray separator.11
Properly designed plant-size high-energy wet venturi scrubbers
are capable of collecting up to 99 percent of total particulate
emissions from various processes in integrated mills, including
those from the steelmaking furnace (EOF). The efficiency of these
scrubbers is greater than 90 percent for particulate removal
regardless of the process or type of particle being collected.21
One disadvantage of wet scrubbers is that most require
settling equipment of appreciable size, in which the solids can
separate from the water, and a recirculating system to reuse the
water because raw overflow from the scrubber system cannot be
discharged into streams or sewers. Scrubber wastes include mill
PM-10 emissions considered hazardous to the environment that must
be treated. Currently, wet scrubbing technologies are addressing
the wet waste problem by recovering some reusable material from the
waste stream, thereby reducing material and energy costs.
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3.3.4.3 Electrostatic precipitators
The ESP is a third type of particulate collection device.
Figure 3-6 shows a single-stage ESP, which is the type most
applicable to the iron and steel mill industry due to the
industry's typically high flow rates.18 The ESP uses electrical
forces to deflect particulates out of the effluent stream and onto
collector plates. In the ESP, the emission stream is passed
through a region in which the gases are ionized. Particles pick up
the charge from the ionized gas and are captured on the polarized
collector plates.16
The plate-wire precipitator is the most common single-stage
ESP in current use. It is well-suited for handling large airflow
volumes. The ESP housing encases several electrically grounded
plates set at specific intervals with rows of discharge electrode
wires between the plates. These electrodes are long wires weighted
and hanging between the plates or wires supported there by rigid
frames.16 High voltages at the discharge electrodes ionize gas
molecules as the air stream flows through the ESP. The
electrically grounded plates function as collection electrodes and,
by electrostatic attraction, capture the charged particles.22
After time, particulate builds into a layer on the collection
plates and must be removed without reentrainment in the gas
stream.16'23 In a "dry" ESP, the collector plates are cleaned by
rapping; in a "wet" ESP, the plates are cleaned by a water spray.
If water is used, it must be cleaned before it can be recirculated
or discharged.20
Wet scrubbers and fabric filters are the dominant particulate
control devices in the industry, partly because ESPs often cost
much more to install and maintain than high energy venturi
scrubbers or baghouses with similar capacity.19 Recent enhancements
to precipitators have increased their efficiency while reducing
capital and operating costs. Pulse energization and intermittent
energization apply a cyclic high voltage to the base voltage,
allowing the base voltage to be reduced. These high voltage bursts
3-22
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Ml RAPPERS
HT CABLE FROM
RECTI FIER
.COLLECTING
'PLATES
HOPPERS
•»IRE-TENSIONING
WEIGHTS
HOPPER BAFFLES
Figure 3-6. Electrostatic precipitator.
is
3-23
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result in better collection efficiency while the base voltage
reductions provide energy cost savings. Also, wider plate spacing
and the reduction in the number or discharge electrodes has
resulted in capital cost savings of 10-20 percent. These
improvements may eventually make ESPs a more viable option for use
in the iron and steel industry.11
3.4 NEW CONSTRUCTION CONTROLS
There is no substantial technological difference between ACT
capture and control systems for new construction and ACT retrofit
technology for most integrated iron and steel mills. However, the
retrofit installation of a PM-10 control system in an existing mill
is typically more expensive than new construction at a new or
expanding facility. New construction costs are lower since the new
control system can be designed and installed without adjusting or
changing existing equipment. Typical industry estimates indicate
a 25 to 50 percent increased cost for retrofit versus new
construction.16'23 As a result, the cost per ton of controlled
particulate can be lower for new construction than it is for the
retrofit of a complete control system. Note, however, that the 25
to 50 percent increased cost is only an estimate and may be higher
(or lower) on a case-by-case basis. Additional information on ACT
system costs is presented in Chapter 5 of this document.
3.5 CONTROL METHODS FOR OPEN FUGITIVE DUST SOURCES
Fugitive dust sources refer to non-process generated air
pollutants that enter the atmosphere without first passing through
a stack or duct designed to direct or control their flow. Several
non-furnace mill activities generate these fugitive emissions,
including vehicular travel on paved and unpaved roads, wind erosion
from storage piles, and materials transfer to or from vehicles or
storage piles. Reference 12 describes control methods designed to
reduce PM-10 emissions from these sources.
3-24
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3.6 REFERENCES FOR CHAPTER 3
1. U.S. Environmental Protection Agency. Control Techniques for
Particulate Emissions from Stationary Sources - Volume 2.
EPA-450/3-81-005b. Office of Air Quality Planning and
Standards, Research Triangle Park, NC. September 1982.
2. Laube, A.H., and B.A. Drummond. Coke Quench Tower Emission
Testing Program, EPA-600/2-79-082. Industrial Environmental
Research Laboratory, U.S. Environmental Protection Agency,
Research Triangle Park, NC. April 1979.
3. Parkinson, Gerald. "Steelmaking Renaissance." Chemical
Engineering. Vol. 98, No. 5, pp 30-35. May 1991.
4. U.S. Environmental Protection Agency. Compilation of Air
Pollutant Emission Factors - AP-42. Fourth Edition with
Supplements. Office of Air Quality Planning and Standards,
Research Triangle Park, NC. September 1985.
5. Cowherd Jr., C. and Kinsey, J.S. Identification, Assessment,
and Control of Fugitive Particulate Emissions.
EPA-600/8-86-023. Office of Air Quality Planning and
Standards, U.S. Environmental Protection Agency, Research
Triangle Park, NC. August 1986.
6. U.S. Environmental Protection Agency. Revised Standards for
Basic Oxygen Process Furnaces - Background Information for
Proposed Standards. EPA-450/3-82-005a. Office of Air Quality
Planning and Standards, Research Triangle Park, NC. December
1982.
7. Telephone discussion with J. Maysilles (Office of Air Quality
Planning and Standards, U.S. Environmental Protection Agency)
and S. Snow (Alliance Technologies Corporation). October 17,
1991. Discussed Maysilles' observations of iron and steel
mill controls from plant trips.
8. Goldman, L.J. and D.W. Coy. Technical Support for Control of
Co^e Pushing. Contract No. 68-01-4141, Task 33. Research
Triangle Institute, Research Triangle Park, NC. Undated.
9. Letter from David C. Ailor, American Coke and Coal Chemical
Institute, to James H. Maysilles, U.S. Environmental
Protection Agency. Comments on draft ACT document for PM-10
emissions from iron and steel mills. Letter dated September
25, 1992.
10. Letter from Thomas W. Easterly, Bethlehem Steel Corporation to
James H. Maysilles, U.S. Environmental Protection Agency.
Comments on draft ACT document for PM-10 emissions from iron
and steel mills. Letter dated August 19, 1992.
3-25
-------
11. U.S. Environmental Protection Agency. Coke Net Quenching-
Background Information for Proposed Standards--Draft EIS.
Office of Air Quality Planning and Standards, Research
Triangle Park, NC. March 25, 1982.
12. Cowherd, C., G.E. Muleski, and J.S. Kinsey, Control of Open
Fugitive Dust Sources. EPA-450/3-88-008. Office of Air
Quality Planning and Standards, U.S. Environmental Protection
Agency, Research Triangle Park, NC. September 1988.
13. Ohio Environmental Protection Agency. Reasonably Available
Control Measures for Fugitive Dust Sources. Columbus, Ohio.
September 1980.
14. Nicola, Arthur G. "Blast Furnace Casthouse Emissions
Control." Jron and Steel Engineer, 56 (8). Association of
Iron and Steel Engineers. Pittsburgh, PA. August 1979.
15. U.S. Environmental Protection Agency. Hot Metal
Desulfurization, EOF (Basic Oxygen Furnace) Charging and
Oxygen Blowing: Level 1 Environmental Assessment.
EPA-600/2-82-036. Industrial Environmental Research
Laboratory, Research Triangle Park, NC. March 1981.
16. Buonicore, A.J., and W.T. Davis, eds. Air Pollution
Engineering Manual. Van Nostrand Reinhold, New York. 1992.
17. Foundry Ventilation and Environmental Control. American
Foundrymen's Society Inc., Des Plaines, IL. 1972.
18. U.S. Environmental Protection Agency. Air Pollution
Engineering Manual - AP-40. Second Edition. Office of Air
Quality Planning and Standards, Research Triangle Park, NC.
May 1973.
19. Fennelly, P.P. and P.O. Spawn. Air Pollution Control
Techniques for Electric Arc Furnaces in the Iron and Steel
Foundry Industry. EPA-450/2-78-024. Office of Air Quality
Planning and Standards, U.S. Environmental Protection Agency,
Research Triangle Park, NC. June 1978.
20. Foundry Ventilation Manual. American Foundrymen's Society,
Des Plaines, IL. 1985.
21. Strauss, W. Industrial Gas Cleaning. Second Edition.
Pergamon Press, New York. 1975.
22. U.S. Environmental Protection Agency. Control Techniques for
Particulate Emissions from Stationary Sources - Volume 1.
EPA-450/3-81-005a. Office of Air Quality Planning and
Standards, Research Triangle Park, NC. September 1982.
3-26
-------
23. U. S. Environmental Protection Agency. Control Technologies
for Hazardous Air Pollutants. EPA-625/6-86-014. Air and
Energy Engineering Research Laboratory, Research Triangle
Park, NC. 1986.
3-27
-------
CHAPTER 4
ENVIRONMENTAL IMPACTS
4.1 INTRODUCTION
The primary purposes of this chapter are to identify
alternative control techniques (ACTs) in addition to those
discussed in Chapter 3 for the iron and steel processes discussed
in Chapter 2 and to estimate PM-10 emissions from model plants
employing each option. The chapter presents the alternative
control techniques and their respective PM-10 emission factors,
emissions, and emission reduction efficiencies from the
uncontrolled case. Since implementation of these air emission
control techniques may have secondary environmental impacts on
water pollution, solid waste disposal, and energy consumption,
these topics are discussed briefly.
4.2 PM-10 EMISSIONS IMPACT
Many capture systems discussed in Chapter 3 can attain high
capture efficiencies. Hoods, enclosures, and building evacuation
systems can attain capture efficiencies in excess of 90 percent.
Of the collection devices discussed in Chapter 3, fabric filters
and wet venturi scrubbers are well-suited for use in iron and steel
mills. Total PM-10 control efficiencies of 90 percent or greater
can be attained by control systems using these devices if the
capture and collection devices are properly designed, constructed,
and operated. Note that the capture efficiencies and control
efficiencies used in the calculations here are hypothetical
efficiencies thought to be within the realm of actual control
system performances. The efficiencies assumed in this document are
not represented as necessarily typical or recommended for actual
facilities.
In this chapter, two alternative control techniques (ACTs) are
presented for coke pushing, one ACT is presented for coke sizing
and screening, and two ACTs are presented for controlling emissions
4-1
-------
from the casthouse. The ACTs for the casthouse and for coke sizing
and screening result in improved PM-10 control from those emission
points in comparison to the baseline cases presented in Chapter 2.
The ACTs for coke pushing are comparable to the baseline control
option for PM-10 control efficiency and presented for comparison.
The ACTs presented here reflect the variety of techniques that are
in current use within the industry, but are not comprehensive.
Other techniques may be used successfully within the industry.
No ACTs are presented for coke quenching, hot metal transfer,
or desulfurization. The control methods presented in the baseline
case were considered the principally feasible control methods
available for these processes. Therefore, any ACTs presented for
these processes would either be significantly less efficient than
the assumed baseline, or prohibitively expensive.
It is emphasized that the PM-10 calculations in this chapter
are made for the model plants given in Chapter 2 using emission
factor data taken from various sources; they should not be directly
applied to operating sources that possess unique operating
practices and conditions. The emission information presented here
is intended to provide a basis for understanding emission factor
calculation methods and relative magnitudes of emission sources in
example plants. Assessment of emissions from existing plants must
be made on the basis of operating information for the actual
plants, rather than on the operating information assumed for the
model plants in this document.
4.2.1 Alternative Control Techniques for Coke Pushing, Coke Sizing
and Screening, and Casthouse Emissions
Emission factors for the baseline and alternative control
techniques are summarized in Table 4-1. The baseline control
technique assumed for coke pushing is a moveable hood (also known
as a "traveling hood" or "fixed duct" system) vented to a wet
venturi scrubber. ACTs considered for coke pushing are the use of
a shed vented to a fabric filter ["Coke pushing (Al)"] in the
tables] and a mobile scrubber car ["Coke pushing (A2) "] .. The
4-2
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baseline emission factors are discussed in Section 2.3.2. The
emission factors given in Table 4-1 for coke pushing controlled by
a shed vented to a fabric filter are composites of fugitive
emission calculations and process emission calculations. The
fugitive emission portion of these emission factors is calculated
using an assumed shed capture efficiency of 97 percent and the
uncontrolled PM-10 emission factor for AP-42.1 The process emission
portion of these emission factors is calculated using typical
airflows (350,000-1,000,000 acfm) and an assumed minimum grain
loading of 0.003 gr/dscf.2'3 The emission factor for the mobile
scrubber car is based on performance ratings provided by an
industry representative.2
The baseline control technique assumed for coke sizing and
screening is a hood vented to a fabric filter. The ACT presented
for coke sizing and screening is a total enclosure vented to a
fabric filter. The ACT emission factors for coke sizing and
screening are based on an uncontrolled emission factor of 0.04
kg/Mg coal charged (0.08 Ib/ton) taken from Reference 4, an assumed
total enclosure capture efficiency of 98 percent, and an assumed
fabric filter minimum exit grain loading of 0.003 gr/dscf.2'3'4
In the baseline case, emissions from the casthouse are assumed
to be uncontrolled and emitted through the casthouse roof monitor.
The AP-42 PM-10 emission factor for uncontrolled casthouse
emissions is 0.15 kg/Mg hot metal produced (0.31 Ib/ton).' Two ACTs
are presented for controlling emissions from the casthouse. The
first casthouse ACT ["Casthouse (Al)"] is total building evacuation
to a fabric filter. The assumed building evacuation capture
efficiency is 95 percent, and the assumed minimum exit grain
loading is 0.003 gr/dscf.2'3 Historically, building evacuation has
been rarely used, due to cost and operating drawbacks, but this ACT
option is presented here for comparison of emission reductions and
(in Chapter 5) control system costs.
The second casthouse ACT ["Casthouse (A2)"] is a combination
of local hoods over the trough and runners vented to a fabric
filter. The assumed capture device efficiency is 80 percent, and
4-4
-------
the assumed fabric filter minimum exit grain loading is 0.003
gr/dscf ,2'3
The above assumptions in combination with the AP-42
uncontrolled PM-10 emission factor are used to generate the
casthouse ACT emission factors in Table 4-1.
Table 4-2 summarizes the control system efficiencies for the
processes and control systems in Table 4-1; these efficiencies
represent the PM-10 emission reduction from the uncontrolled case.
Emissions from each process in Table 4-1 are summarized in
Table 4-3.
4.3. WATER POLLUTION IMPACT
Of the control techniques presented here, coke pushing and
coke quenching operations use water for control of airborne
particulate. Disposing of the used water can create potential
water quality impacts that should be considered when evaluating the
environmental impact of implementing these options. These impacts
are briefly discussed in this section.
Used water from coke pushing and coke quenching particulate
control contains solid emissions from these processes. These
emissions may include coke (carbon), crude tar, crude light oil,
ammonia, phthalates, and other volatile organic gases.5'6
Wastewater composition differences between the baseline and
alternative control technique cases are expected to be a function
of quantity more than type of substance. All control options
presented use water for control of coke quenching operations. The
baseline and second alternative control options for coke pushing
use water, but the first alternative control option uses a fabric
filter for control of coke pushing emissions. Therefore, model
plants under the first alternative technique would generate less
wastewater than those using the baseline or second alternative
technique controls.
It common practice for coke oven facilities and iron and steel
mills to recycle water used in pollution control systems. For
water discharged from the facility, the Clean Water Act, along with
4-5
-------
TABLE 4-2. PM-10 CONTROL SYSTEM EFFICIENCIES FOR
BASELINE AND ALTERNATIVE CONTROL
TECHNIQUE (ACT) SYSTEMS
Process
Control
Efficiency%
Control system
Coke pushing (B)a
Coke pushing (Al)
Coke pushing (A2)
Coke quenching (B)
Coke sizing/screening
(B)
Coke sizing/screening
(A)
Casthouse (B)
Casthouse (Al)
Casthouse (A2)
Hot metal transfer (B)
Desulfurization (B)
78b
88°
79b
90b
86b
96C
0
85C
72C
72C
88C
Hood vented to venturi scrubber
Shed (97%) vented to fabric
filter
Mobile scrubber car
Clean makeup water and baffles
Hood (90%)d vented to fabric
filter
Total enclosure (98%) vented to
fabric filter
Uncontrolled
Building evacuation (95%)
vented to fabric filter
Local hood (80%) vented to
fabric filter
Hood (90%)d vented to fabric
filter
Hood (90%)d vented to fabric
filter
•»(B)" - baseline control system.
"(A)" - alternative control technique system.
"(Al)" - 1st of two alternative control technique systems presented for single process.
"(A2)" - 2nd of two alternative control technique systems presented for single process.
bCalculated from AP-42 controlled and uncontrolled emission factors. No efficiencies
given for individual capture and collection devices.
°Control efficiency calculated from assumed capture efficiency and a fabric filter minimum
exit grain loading of 0.003 gr/dscf (References 2 and 3).
""specific capture device not given in AP—42. Capture efficiency assumed
Note: percentages calculated from unrounded figures used in Table 4-3.
any local or State regulatory standards, require that facilities
limit their release of such compounds as oil and grease and other
organics. In addition, there are generally limits on the amount of
total suspended solids (TSS) in wastewater released from the mills.
Facilities must also adjust wastewater pH where necessary to comply
with applicable regulations. Wastewater from iron and steel mills
is not expected to exhibit biochemical oxygen demand (BOD) and
therefore should not need secondary treatment for that condition.
4-6
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4.4 SOLID WASTE IMPACT
For many of the processes examined here, fabric filters are
used to control particulate emissions. Nearly all materials
(especially coke recovered from the coke pushing operation using
the first control technique) recovered from fabric filters can be
reused in the mill or sold for reprocessing.7 If wastewater
treatment ponds or tanks are used, sludge from the ponds must also
be recycled or discarded. Where materials are discarded, these
operations generate an additional solid waste impact from the mill.
Table 4-4 lists some materials commonly found in the particulate
generated by iron and steel mill operations.
TABLE 4-4. COMPOUNDS COMMONLY EMITTED AT IRON
AND STEEL MILLS*'b
Coking Emissions
Coke (C)
Crude tar
Crude light oil
NH3
CO
CH4
Phthalates
Blast
Fe
Fe203
Si02
A1203
CaO
ZnO
P4
S
Mn
C
Furnace Emissions
MgO
Cr203
MnO
V205
Na2O
Ti02
Pb
BaO
K2O
"Reference 1.
^Reference 6.
Sludge volumes can sometimes be reduced if the sludge is
dewatered by gravity settling, filtering, or other techniques.
Solid waste from mills is usually classified as nonhazardous and is
managed at nonhazardous waste landfills. However, solid waste
generated from capture of desulfurization emissions may contain
significant concentrations of toxic metals, necessitating disposal
at a hazardous waste landfill. Testing at Kaiser Steel's Fontana,
4-8
-------
CA mill revealed significantly high concentrations of lead,
mercury, barium, antimony, strontium, arsenic, copper, manganese,
and chromium in the desulfurizing process air stream.8 However, an
industry commenter indicates that the Kaiser results may be
atypically high for the industry.9 Regulatory limits for solid
waste and hazardous waste disposal are typically provided within
legislation such as the Resource Conservation and Recovery Act
(RCRA), the Superfund Amendments and Reauthorization Act (SARA) ,
and various State and local rules.
4.5 ENERGY IMPACT
Nearly all particulate control techniques require energy to
induce airflow, pump water, or perform other tasks. Table 4-5
summarizes the energy impacts associated with implementing the
alternative control techniques at the model plants. Energy impacts
are calculated for fans (used for fabric filters and wet scrubbers)
and water pumps (used for wet scrubbers), the two principal energy
users within the air pollution control systems. Energy impacts for
fabric filters and wet scrubbers were estimated using techniques
presented in EPA guidance.10'11 Reference 10 contains an energy
consumption equation for fans that is based on airflow, system
pressure drop, hours of operation, specific gravity of air, and
fan/motor efficiency:
E = 0.746xQxPDxsx HRS
6,356ri
where
E = energy consumption in kwh/yr
Q = airflow rate in acfm
PD = system pressure drop in inches H20
s = specific gravity of gas relative to air
HRS = hours of operation per year
Tj = combined fan and motor efficiency
For these calculations, PD was assumed to be 15 inches H20,
specific gravity was 1.0, hours of operation were 8,760, and r\ was
equal to 0.65.
4-9
-------
Coke pushing (A2) power requirements were derived from
Reference 11, where energy consumption figures of 400-600 kW to
power the scrubber car transport are reported. An industry
reference provided other data indicating that the combined power
requirement for the scrubber car transport and scrubber operation
was on the order of 3,500 kw.2 The energy requirements for the
mobile scrubber car in Table 4-5 were calculated using this energy
consumption factor, the coke throughput specified for the model
plants, and an assumed operating time of 8,760 hours per year. All
other process energy requirements were calculated using the
equation from Reference 10. It should be noted that energy
requirements for emissions control from both primary and secondary
sources are typically less than one percent of the total energy
used for all mill operations.12
Energy use for an air pollution control system is directly
proportional to the air flow rate through the system and the
pressure drop necessary to induce the airflow. The flow rates used
to estimate energy consumption are summarized in Table 4-6. These
airflows were derived from published reports (reference numbers
given in the table) that provided specific airflows or ranges of
airflows based on either a model plant size or throughput. These
airflows were adapted to the throughputs and plant sizes in this
document to determine the ACT model plant and process flow rates.
Pressure drops for fabric filters may range from 0.75 to 4 kPa
(3 to 16 in. H20), while pressure drops for wet-venturi scrubbers
may range from 1.5 to 20 kPa (6 to 80 in. H20) . As stated
previously, the energy requirements for fabric filter systems in
Table 4-5 were estimated assuming a static pressure drop of 4 kPa
(15 in. H20).
4-10
-------
TABLE 4-5. ENERGY REQUIRED BY IMPLEMENTATION OF PROCESS
CONTROL OPTIONS
Process
Coke pushing (Al)a
(shed with fabric filter)
Coke pushing (A2)b
(mobile scrubber car)
Energy Consumed (kWh/yr)
Small Medium Large
Plant Plant Plant
8.3 x 106 17 x 106 24 x 106
10.5 x 10s 15.8 x 10s 26.3 x 106
+87.6 x 109 +131 x 109 +219 x 109
Btuc Btu Btu
Coke quenching
(baffles with clean makeup
water)
Coke sizing/screening (A)
(enclosure with fabric
filter)
Casthouse (Al)a
(building evacuation with
fabric filter)
Casthouse (A2)a
(local hoods with fabric
filter)
Hot metal transfer
(canopy hood with fabric
filter)
Desulfurization
(close-fitting ladle hood
with fabric filter)
n/avd
n/av
n/av
0.2 x 106 0.5 x 106 1.0 x 106
7.1 x 106 14 x 106 21 x 106
4.8 x 106 9.5 x 106 14 x 106
3.6 x 106 7.1 x 106 11 x 106
1.2 x 10s 2.4 x 106 3.6 x 10*
•"(A)" - alternative control technique system.
"(Al)" - 1st of two alternative control technique systems presented for single process.
"(A2)" - 2nd of two alternative control technique systems presented for single process.
"See Reference 11
°The mobile scrubber car uses electricity to move the car, and uses petroleum fuel (typically
No. 2. fuel oil) to heat water for the scrubber system.
''n/av - not available
4-11
-------
TABLE 4-6. AIRFLOWS REQUIRED FOR PROCESS CONTROL OPTIONS
Airflow (acfm)
Process
Coke pushing (Al)a
(shed with fabric filter)
Coke pushing (A2)b
(mobile scrubber car)
Coke quenching
Small
Plant
350,000
n/avc
n/appd
Medium
Plant
700,000
n/av
n/app
Large
Plant
1,000,000
n/av
n/app
(baffles with clean make-up
water)
Coke sizing/screening (A)e
(enclosure with fabric filter)
Casthouse (Al)e
(building evacuation with fabric
filter)
10,000
300,000
20,000
600,000
40,000
900,000
Casthouse (A2)a
(local hoods with fabric filter)
Hot metal transfer6
(canopy hood with fabric filter)
Desulfurization6
(close-fitting ladle hood with
fabric filter)
200,000
150,000
50,000
400,000
300,000
100,000
600,000
450,000
150,000
•Reference 2.
''Reference 11.
cTypical flowrates are on the order of 10,000 acfm per ton of coke (Reference 3). Reference
10 gives energy consumption in IcWh; this figure is used for the energy consumption
calculations in Table 4-7.
dnot applicable. This control technique does not require an induced airflow.
•Reference 3.
4-12
-------
4.6 REFERENCES FOR CHAPTER 4
1. U.S. Environmental Protection Agency. Compilation of Air
Pollutant Emission Factors. AP-42. Fourth Edition with
Supplements. Office of Air Quality Planning and Standards,
Research Triangle Park, NC. September 1985.
2. Letter from Thomas W. Easterly, Bethlehem Steel Corporation to
James H. Maysilles, U.S. Environmental Protection Agency.
Comments on draft ACT document for PM-10 emissions from iron
and steel mills. Letter dated August 19, 1992.
3. Buonicore, A.J., and W.T. Davis, eds. Air Pollution
Engineering Manual. Van Nostrand Reinhold, New York. 1992.
4. U.S. Environmental Protection Agency. AIRS Facility Subsystem
Source Classification Codes and Emission Factor Listing for
Criteria Air Pollutants. EPA-450/4-90-003. Office of Air
Quality Planning and Standards, Research Triangle Park, NC.
March 1990.
5. U.S. Environmental Protection Agency. Control Techniques for
Particulate Emissions from Stationary Sources.
EPA-450/3-81-005b. Office of Air Quality Planning and
Standards, Research Triangle Park, NC. September 1982.
6. Laube, A.M., and B.A. Drummond, Coke Quench Tower Emission
Testing Program. EPA-600/2-79-082. U.S. Environmental
Protection Agency, Industrial Emissions Research Laboratory,
Research Triangle Park, NC. April 1979.
7. Letter from R. Wade Kohlmann, Indianapolis Coke, to James H.
Maysilles, U.S. Environmental Protection Agency. Comments on
draft ACT document for PM-10 emissions from iron and steel
mills. Letter dated August 44, 1992.
8. U.S. Environmental Protection Agency. Hot Metal
Desulfurization, EOF (Basic Oxygen Furnace) Charging and
Oxygen Blowing: Level 1 Environmental Assessment.
EPA-600/2-82-036. Industrial Emissions Research Laboratory,
Research Triangle Park, NC. March 1981.
9. Letter from Robert E. Sistek, LTV Steel Company to James H.
Maysilles, U.S. Environmental Protection Agency. Comments on
draft ACT document for PM-10 emissions from iron and steel
mills. Letter dated August 25, 1992.
10. U.S. Environmental Protection Agency. OAQPS Control Cost
Manual. Fourth Edition. EPA 450/3-90-006. Office of Air
Quality Planning and Standards, Research Triangle Park, NC.
January 1990.
4-13
-------
11. U.S. Environmental Protection Agency. Envirotech/Chemico
Pushing Emissions Control System Analysis. EPA-340/1-83-019.
Office of Air Quality Planning and Standards, Washington, DC.
April 1983.
12. U.S. Environmental Protection Agency. .Revised Standards for
Basic Oxygen Process Furnaces—Background Information for
Proposed Standards. EPA-450/3-82-005a. Office of Air Quality
Planning and Standards, Research Triangle Park, NC. December
1982.
4-14
-------
CHAPTER 5
CONTROL COST ANALYSIS
5.1 INTRODUCTION
This chapter presents cost analyses of the ACT options for
PM-10 control from the model iron and steel mill processes
presented in Chapter 4. Equipment costs, capital costs, annual
costs (including operation and maintenance) , and cost effectiveness
are calculated for each process control option and model plant
size. Also included in this chapter are the comments of industrial
representatives who reviewed the draft version of this document.
All cost estimates given here apply only to the emission sources
described in Chapter 4, and not to other PM-10 sources that may
exist in the mills. Section 5.2 summarizes the design parameters
assumed for each process control system and the associated
purchased equipment costs. Section 5.3 describes and summarizes
the capital costs for each process control option, including cost
algorithms used in the calculations. Section 5.4 describes and
summarizes the annual costs for each process control option,
including cost algorithms used in the calculations. Section 5.5
summarizes the cost effectiveness estimates for each process ACT
option and model plant size. Finally Section 5.6 contains cost
comparisons provided by industry representatives (asked to review
a draft version of this document) for most of the control option
costs presented in this chapter. These cost comparisons are
provided to show the variability of cost estimates within the iron
and steel industry. To assist readers interested in completing
their own cost estimates for existing facilities, this chapter
makes detailed reference to the texts, tables, figures, and
equations used to develop the cost estimates contained in
Sections 5.2, 5.3, and 5.4.
5-1
-------
5.2 DESIGN PARAMETERS AND PURCHASED EQUIPMENT COSTS
The process ACT system options presented in Chapter 4 achieve
PM-10 emissions control by the addition of capture and collection
equipment. These additions increase both the capital and annual
costs for operating each controlled process. To develop purchased
equipment costs for each process control option, detailed
assumptions were made about the types and sizes of equipment needed
and the operation of the equipment. These assumptions were based
on cost algorithms presented in the EPA cost manuals titled Capital
and Operating Costs of Selected Air Pollution Control Systems and
OAQPS Control Cost Manual.1"2 Note that the costs and estimating
methodologies given here are directed towards a "study" estimate of
30 percent accuracy. Study estimates are used to roughly evaluate
the economic feasibility of a project using relatively small
amounts of data and without expending great effort. Other general
classifications of estimates include the "order-of-magnitude"
estimate, less accurate than a study estimate; "scope," "budget
authorization" or "preliminary" estimates, nominally of 20 percent
accuracy; "project control" or "definitive" estimates, nominally of
10 percent accuracy; and "firm," "contractor's," or "detailed"
estimates, nominally of 5 percent accuracy.2 Study estimates have
been extensively used in regulatory development, while the more
detailed techniques have been more typically used in actual plant
practice. This section presents the design parameters and costing
methodologies as well as the associated equipment costs derived
from them.
5.2.1 General Equipment Assumptions
Two types of equipment parameter assumptions were used for
this study: general and process-specific. General assumptions are
described in this section and apply to all process control
equipment discussed herein. Process-specific assumptions are
described in subsequent sections and are dependent on the process
and model process size being controlled.
5-2
-------
Table 5-1 lists the general equipment assumptions that were
made for each type of control equipment including ductwork, fan and
motor system, and baghouse parameters. Each of these assumptions
is required as an input into the cost methodologies presented in
the cost manuals.1-2 The ductwork and fan/motor system costs were
developed from Reference 1; baghouse, capital, and annual costs
were derived from Reference 2. Equipment assumptions for the
mobile scrubber car were not necessary because the costs were given
directly in Reference 3.
5.2.2 Ductwork Cost Methodology
The cost algorithm for determining ductwork costs depends on
two key input variables: airflow and duct length. Each of these
parameters is process-specific and was chosen based on the given
model plant sizes. This section describes the ductwork cost
algorithm contained in Reference 1. Therefore, the page numbers,
tables, and figures cited in this section refer to the page
numbers, tables, and figures contained in Reference 1. They are
italicized to avoid confusion with tables and figures appearing in
this ACT document.
First, a duct velocity of 20.3 m/s (4,000 fpm) was chosen
based on the dust type to be captured (page 4-16). Duct velocity
and airflow were then used to calculate the required diameter of
the ductwork from a given equation (page 4-17). Duct diameter
determines the costs for straight steel duct, elbows, and dampers.
Using general ductwork assumptions from Table 5-1, namely carbon
steel construction and 0.476 cm (3/16 in.) duct thickness, the
straight steel duct, elbow, and damper costs were read from cost
curves given in Figures 4.7, 4.10, and 4.14, respectively. Note
that the cost for straight steel duct is given as dollars/linear
foot and therefore must be multiplied by duct length to calculate
the total straight steel duct cost. Also, elbow and damper costs
are per item and must be multiplied by the number of elbows and
dampers to determine their total costs. The sum of straight steel
5-3
-------
TABLE 5-1.
EQUIPMENT PARAMETER ASSUMPTIONS FOR ALL FABRIC
FILTERS
Equipment
Assumption
Ductwork
Material of construction
Duct thickness (cm)
Elbows
Radius/diameter
Angle (degrees)
Material of construction
Pressure drop across ductwork (kPa)
Dampers
Fan/Motor
System pressure drop (kPa)
Material of construction
Fan/motor efficiency (%)
Motor cover
Starter
Fan type
Location of fan
Altitude of plant (m)
Inlet/outlet dampers
Baghouse
Gas inlet temperature (°C)
Baghouse life/individual bag life (yrs)
Operator time (hours/shift)
Maintenance time (hours/shift)
Pressure drop across baghouse (kPa)
Bag material
PM-10 removal efficiency (%)
Baghouse maintenance (man-minutes/bag)
Pulse-jet
Carbon steel
0.476
1.5
90
Carbon steel
1.25
Automatic control
3.75
Carbon steel
65
Drip proof
Magnetic
Backward curved
After the fabric filter
0
1 each
66
10/2
8
1-2
2.5
Polyester
99
10
5-4
-------
duct, elbow, and damper costs determines the total purchased
equipment cost of ductwork.
5.2.3 Fan/Motor System Cost Methodology
The cost algorithm for determining the fan/motor system cost
depends primarily on two key input variables: airflow and system
pressure drop. Airflow is a process-specific parameter chosen
based on model plant size, while pressure drop was assumed to be
the same for all process control systems discussed in this document
(see Table 5-1). This section describes the fan/motor system cost
algorithm contained in Reference 1. Therefore the page numbers,
tables, and figures cited in this section refer to the page
numbers, tables, and figures contained in Reference 1. They are
italicized to avoid confusion with tables and figures appearing in
this ACT document.
First, a fan sizing factor must be determined from Table 4.10
for the assumed airflow temperature and facility altitude. Next,
the pressure drop is divided by the fan sizing factor to estimate
the pressure drop at standard conditions. By combining the
pressure drop at standard conditions with airflow, the fan price
can be read from Figure 4.33. Also, inlet and outlet damper costs
can be found in Figure 4.35 with the same inputs.
Similarly, the motor and starter costs are found in Figure
4.34 as a function of airflow and pressure drop at standard
conditions. The motor and starter costs, however, require an extra
iteration. When brake horsepower (bhp) is found in Figure 4.34, it
must be multiplied by the fan sizing factor to determine the actual
bhp requirement. Motor and starter costs are then found based on
the actual bhp. The total purchased equipment cost for the
fan/motor system is the sum of fan, inlet and outlet damper, motor,
and starter costs.
5-5
-------
5.2.4 Baghouse Cost Methodology
The cost algorithm for determining baghouse costs depends on
two key input variables: airflow and air-to-cloth (A/C) ratio.
Each of these parameters is process-specific and was chosen based
on a given process model size. This section describes the baghouse
cost algorithm contained in Reference 2. Therefore, the page
numbers, tables, and figures cited in this section refer to the
page numbers, tables, and figures contained in Reference 2. They
are italicized to avoid confusion with tables and figures appearing
in this ACT document.
First, an air-to-cloth ratio must be either assumed from Table
5.1 or calculated from equation 5.11. Table 5.1 lists A/C ratios
for different dust types based on the baghouse and filter material
used to control a process. For iron compounds, the A/C ratio
ranges from 2.0 to 11.0 feet/minute. The actual airflow is then
divided by the A/C ratio to determine the net cloth area required
of the filtering media. Table 5.2 is a guide to estimating, based
on net cloth area, the gross cloth area required for such things as
downtime and cleaning.
Next, the type of baghouse, either shaker, pulse-jet, or
reverse air, must be determined. The gross cloth area is then
applied to the appropriate cost curve given in Figures 5.2 through
5.7. Any additional costs, such as those for a stainless steel
frame or insulation add-on, are also determined from the cost
curves. The costs for the baghouse were developed using the field-
construction curves in the manual rather than the prefabricated
construction to reflect the likelihood of extra costs associated
with custom fitting or retrofitting existing equipment.
Finally, the costs for bags and bag mounting hardware must be
calculated. Initially, bag diameter and type of material are
chosen from Table 5.7, which determines the cost per square foot of
bag area. Also, the type and cost of mounting hardware are found
in Table 5.7. The total purchased equipment cost of a baghouse is
the sum of baghouse, additions, bags, and mounting hardware costs.
5-6
-------
Polyester bags were assumed for the examples in this study, but
Nomex bags are another typical bag type used in the industry.
5.2.5 Process-specific Equipment Assumptions and Equipment Costs
This section contains the detailed process-specific parameters
that were used to determine purchased equipment costs. Tables 5-2
through 5-7 contain the specific equipment parameters for each
process control option. Also contained in the tables are the
purchased equipment costs that were derived from the equipment
parameters.
Table 5-2 contains data for the first ACT for coke pushing
["coke pushing (Al) " in the table] , which utilizes a shed vented to
a baghouse. The shed serves as a partial enclosure of the coke
pushing operation that reduces PM-10 emissions and lowers airflow
requirements. No process-specific data are given in this section
for the second ACT for coke pushing due to the unavailability of
such data from the published information used for mobile scrubber
car costs.3
Table 5-3 lists the parameters and costs for the coke
sizing/screening option. This option utilizes a total enclosure of
the sizing/screening area vented to a baghouse. The total
enclosure ensures high capture efficiencies while keeping the
volumetric flow rate relatively low.
Table 5-4 contains data for the first ACT for casthouse
emissions ["casthouse (Al) " in the table], which is the evacuation
of the casthouse to a baghouse. Building evacuation captures PM-10
emissions from all areas of the casthouse, including the taphole,
troughs, and runners. This type of control system requires large
airflows to control large volumes of space and therefore large and
costly fans, motors, ducts, and baghouses. Data for the second ACT
for casthouse emissions ["casthouse (A2)" in the table], which
incorporate local hooding to a baghouse, are contained in
Table 5-5. Local hoods reduce the required airflow volumes from
building evacuation; however, they require more space around the
blast furnace and can be difficult to retrofit.
5-7
-------
TABLE 5-2. CONTROL EQUIPMENT PARAMETERS
FOR COKE PUSHING (Al) - SHED
AND PURCHASE COSTS
WITH BAGHOUSE
Equipment Parameters
Ductwork
Number of takeoffs
Length per takeoff (m)
Diameter (m)
Duct velocity (m/sec)
Number of elbows
Number of autodampers
Fan/Motor
Number of motors
Motor size (kW)
Gas temperature (°C)
Fan sizing factor
(correction for
temperature)
Baghouse
Gross cloth area required
(m2)
Air-to-cloth ratio (m/min)
Total flow rate (actual
thousand m3/h)
Equipment Purchase Costs
($1,000)*
Capture devices
Ductwork
Fan/motor system
Baghouse
Total Purchase Costs ($1,000)
Small
4
60.96
3.22
20.3
4
2
10
119
66
0.869
7,876
1.37
594
184
338
218
1,071
1,811
Plant Size
Medium
8
60.96
3.22
20.3
8
4
20
119
66
0.869
15,752
1.37
1,188
368
676
436
2,142
3,622
Large
15
60.96
3.22
20.3
15
7
37
119
66
0.869
28,945
1.37
2,183
676
1,242
801
3,936
6,655
Costs are in April 1991 dollars.
5-8
-------
TABLE 5-3.
CONTROL EQUIPMENT PARAMETERS AND PURCHASE COSTS FOR
COKE SIZING/SCREENING - ENCLOSURE WITH BAGHOUSE
Equipment Parameters
Ductwork
Number of takeoffs
Length per takeoff (m)
Diameter (m)
Duct velocity (m/sec)
Number of elbows
Number of autodampers
Fan/Motor
Number of motors
Motor size (kW)
Gas temperature (°C)
Fan sizing factor
(correction for
temperature)
Baghouse
Gross cloth area required
(m2)
Air-to-cloth ratio
(m/min)
Total flow rate (actual
thousand m3/h)
Equipment Purchase Costs
($1,000)»
Capture devices
Ductwork
Fan/motor system
Baghouse
Total Purchase Costs ($1,000)
Small
1
22.86
0.54
15.2
1
1
3
13.4
66
0.869
413
1.37
17
8
9
17
399
433
Plant Size
Medium
2
22.86
0.77
15.2
2
1
3
26.8
66
0.869
619
1.37
34
15
21
24
418
478
Large
3
22.86
1.09
15.2
3
2
3
52.2
66
0.869
1,239
1.37
68
27
47
35
473
582
Costs are in April 1991 dollars.
5-9
-------
TABLE 5-4. CONTROL EQUIPMENT PARAMETERS AND PURCHASE COSTS FOR
CASTHOUSE (Al) - EVACUATION TO BAGHOOSE
Plant Size
Equipment Parameters
Ductwork
Number of takeoffs
Length per takeoff (m)
Diameter (m)
Duct velocity (m/sec)
Number of elbows
Number of autodampers
Fan/Motor
Number of motors
Motor size (kW)
Gas temperature (°C)
Fan sizing factor
(correction for temperature)
Baghouse
Gross cloth area required
(m2)
Air-to-cloth ratio (m/min)
Total flow rate (actual
thousand m3/h)
Equipment Purchase Costs ($1,000)*
Capture devices
Ductwork
Fan/motor system
Baghouse
Total Purchase Costs ($1,000) 1,
Small
3
22.86
2.98
20.3
3
2
10
89
66
0.869
6,813
1.37
509
160
128
183
975
446
Medium
4
22.86
4.21
20.3
4
2
10
179
66
0.869
13,006
1.37
1,019
296
260
382
1,533
2,471
Large
5
22.86
5.16
20.3
5
3
10
268
66
0.869
19,324
1.37
1,528
418
414
593
2,101
3,526
a Costs are in April 1991 dollars.
5-10
-------
TABLE 5-5.
CONTROL EQUIPMENT PARAMETERS AND PURCHASE COSTS
FOR CASTHOUSE (A2) - LOCAL HOODING AND BAGHOUSE
Plant Size
Equipment Parameters
Ductwork
Number of takeoffs
Length per takeoff (m)
Diameter (m)
Duct velocity (m/sec)
Number of elbows
Number of autodampers
Fan/Motor
Number of motors
Motor size (kW)
Gas temperature (°C)
Fan sizing factor
(correction for
temperature)
Baghouse
Gross cloth area required
(m2)
Air-to-cloth ratio (m/min)
Total flow rate (actual
thousand m3/h)
Equipment Purchase Costs ($1,000)*
Capture devices
Ductwork
Fan/motor system
Baghouse
Total Purchase Costs ($1,000)
Small
3
22.86
2.43
20.3
3
2
8
82
66
0.869
4,645
1.37
340
112
101
136
780
1,129
Medium
4
22.86
3.44
20.3
4
2
8
127
66
0.869
8,919
1.37
679
210
202
195
1,165
1,772
Large
5
22.86
4.21
20.3
5
3
8
179
66
0.869
13,006
1.37
1,019
296
325
306
1,533
2,460
a Costs are in April 1991 dollars.
5-11
-------
TABLE 5-6. CONTROL EQUIPMENT PARAMETERS AND PURCHASE COSTS
FOR HOT METAL TRANSFER - CANOPY HOOD WITH BAGHOUSE
Equipment Parameters
Ductwork
Number of takeoffs
Length per takeoff (m)
Diameter (m)
Duct velocity (m/sec)
Number of elbows
Number of autodampers
Fan/Motor
Number of motors
Motor size (kW)
Gas temperature (°C)
Fan sizing factor
(correction for temperature)
Baghouse
Gross cloth area required (m2)
Air-to-cloth ratio (m/min)
Total flow rate (actual
thousand m3/h)
Equipment Purchase Costs ($1,000)*
Capture devices
Ductwork
Fan/motor system
Baghouse
Total Purchase Costs ($1,000)
Plant Size
Small Medium
2 3
22.86 22.86
2.11 2.98
20.3 20.3
2 3
1 2
6 6
89 179
66 66
0.869 0.869
3,623 6,813
1.37 1.37
255 509
85 160
56 128
110 229
688 975
939 1,492
Large
3
22.86
2.98
20.3
3
2
6
179
66
0.869
6,813
1.37
509
160
128
229
975
1,492
a Costs are in April 1991 dollars.
5-12
-------
TABLE 5-7. CONTROL EQUIPMENT PARAMETERS AND PURCHASE COSTS
FOR DESULFURIZATZON - LADLE HOOD AND BAGHOUSE
Equipment Parameters
Ductwork
Number of takeoffs
Length per takeoff (m)
Diameter (m)
Duct velocity (m/sec)
Number of elbows
Number of autodampers
Fan/Motor
Number of motors
Motor size (kW)
Gas temperature (°C)
Fan sizing factor
(correction for temperature)
Baghouse
Gross cloth area required
(m2)
Air-to-cloth ratio (m/min)
Total flow rate (actual
thousand m3/h)
Equipment Purchase Costs ($1,000)*
Capture devices
Ductwork
Fan/motor system
Baghouse
Total Purchase Costs ($1,000)
Small
2
22.86
1.22
20.3
2
1
3
67
66
0.869
1,548
1.37
85
32
30
42
501
605
Plant Size
Medium
3
22.86
1.72
20.3
3
2
3
127
66
0.869
2,581
1.37
170
62
67
71
594
794
Large
3
22.86
1.72
20.3
3
2
3
127
66
0.869
2,581
1.37
170
62
67
71
594
794
a Costs are in April 1991 dollars.
5-13
-------
Table 5-6 lists the parameters for the hot metal transfer
control option of a movable canopy hood. This movable canopy
reduces the required airflow by allowing the hood to travel with
the transfer ladle, thus reducing the emissions coverage area
versus a fixed canopy hood.
Table 5-7 contains data for the desulfurization control option
of a close-fitting ladle hood evacuated to a baghouse. A ladle
hood is ideal for capturing emissions from the desulfurization
process since desulfurization takes place while the hot metal is in
the ladle.
All Tables 5-2 through 5-7 contain process-specif ic parameters
which were estimated via other documents, industry contacts, and
engineering judgement. Table 5-8 lists conversion factors used to
convert the design parameters given in Tables 5-1 through 5-7 from
metric to English (inch-pound) units.
TABLE 5-8. CONVERSION FACTORS
Original Unit
meters
meters
centimeters
square meters
meters per
second
cubic meters
per hour
liters
Megagrams
degrees Celsius
kilopascals
kilowatts
Multiplied by
3.281
39.370
0.394
10.764
196.9
0.589
0.264
1.102
9/5 + 32
4.015
1.341
Yields
feet
inches
inches
square ft .
feet per minute
cubic feet per
minute
gallons
short ton
degrees
Fahrenheit
inches of water
brake horsepower
These control device parameters and plant sizes may be
different from any given facility in the United States; however,
they were developed for cost comparison purposes only. The costs
5-14
-------
given in Tables 5-2 through 5-7 are in April 1991 dollars and may
be updated with cost indices obtained from Chemical Engineering.4
5.3 BASIS FOR CAPITAL COSTS
Capital costs represent the costs associated with purchasing
and installing new or retrofitted equipment (see Section 5.2).
These costs are usually divided into three categories: (l) the
base costs of purchasing the control equipment and some auxiliary
equipment; (2) the costs of installing the equipment; and (3) the
indirect labor costs of retrofitting and testing the equipment.
Capital costs were estimated by obtaining base equipment costs from
EPA cost manuals or from background sources, then adding
installation and indirect costs derived from the base costs using
algorithms provided in EPA cost manuals.1'2 It was recognized that
retrofitting new control equipment in an existing plant is more
expensive than installing new equipment in a new plant. Therefore,
the total retrofitted capital costs are assumed to be equal to the
total new capital cost of new installation plus a "retrofitting
effort" of 25 percent of the total new capital cost.5
Table 5-9 lists the costs and cost factors derived from
Reference 2 for fabric filter capital and annual operating costs.
Capital cost factors are described here while annual cost factors
are discussed in Section 5.4. Capital costs were determined by
summing the capital cost factors and multiplying by the total
purchased equipment cost. The total purchased equipment cost
includes the costs of equipment (control device, fan/motor,
ductwork) and freight and sales tax. The following equation shows
the calculation:
TCI = ( EC + FST ) x Sum of CCF
where TCI = total capital investment
EC = equipment costs (from Tables 5-2 through 5-7)
FST = freight and sales tax
Sum of CCF = sum of capital cost factors
5-15
-------
TABLE 5-9 GENERAL COSTS AND COST FACTORS FOR FABRIC FILTERS8
Parameter Factor or Cost
Capital Costs
Factor of Equipment Costs
Freight and sales tax 0.08
Direct Installation Cost Factors
Foundation and supports 0.04
Handling and erection 0.35
Electrical 0.08
Piping 0.01
Insulation for ductwork 0.07
Painting 0.02
Indirect Installation Cost Factors
Engineering and supervision 0.10
Construction and field expenses 0.20
Contractor's fee 0.10
Start-up and performance tests 0.02
Contingencies 0.03
Annual Costs
Direct Costs
Electricity ($/kWh) 0.075
Compressed air ($/m3/hour) 0.094
Operator labor rate ($/hour) 13.41
Supervisor rate (fraction of operator 0.15
labor)
Maintenance labor rate ($/hour) 14.75
Material (fraction of maintenance 1.00
labor)
Indirect Costs
Annual interest rate (%) 10.0
Overhead (fraction of operator, 0.60
supervisor, maintenance and material
costs)
Property tax (factor of TCI) 0.01
Insurance (factor of TCI) 0.01
Administration (factor of TCI) 0 .02
a See Reference 3 for mobile scrubber car cost factors.
5-16
-------
The estimated total and retrofit capital costs for the process
control options are given in Tables 5-10 through 5-15.
5.4 BASIS FOR ANNUAL COST ESTIMATES
In contrast to capital costs, which represent the costs
associated with purchasing and installing new equipment, annual
costs represent yearly disbursements for operating and maintaining
the control systems and the annualized costs of capital recovery.
Annual costs are usually divided into direct and indirect annual
costs. Direct annual costs include utilities, operating labor,
maintenance labor, maintenance material, dust disposal and sludge
disposal. Indirect annual costs include overhead, property tax,
insurance, general administration and annualized capital recovery
charges. Annual costs were derived by using cost algorithms given
in Reference 2 for fabric filters.
Table 5-9 lists the costs and cost factors used to determine
annual operating costs for fabric filters. As shown, annual costs
are the sum of direct and indirect costs. The following equation
shows the calculation for total annual costs:
TAC = UT + OML + RP + OH + CR + GAC
where TAC = total annual cost
UT = utilities cost
OML = operating and maintenance labor and materials
RP = replacement parts
OH = overhead (60 percent of OML)
CR = capital recovery
GAC = general administrative costs (property tax, etc.)
Capital recovery costs were based on a 10 percent interest rate
with a 10-year equipment life. The annual costs for the process
control options, assuming capital equipment expenditures on a
retrofit basis, are given in Tables 5-17 through 5-22. Annual
costs published in Reference 3 for the mobile scrubber car were
given in a different format than those of the fabric filter given
in Reference 2, and appear separately in Table 5-16. Capital
recovery costs given in Table 5-16 are estimates of the annual
5-17
-------
TABLE 5-10. TOTAL CAPITAL COSTS FOR COKE PUSHING (Al) ($1,000)
Plant Size
Purchased Equipment Costs
Removal & auxiliary equipment
Freight & sales taxes
Subtotal
Direct Installation Costs
Foundation & supports
Handling & erection
Electrical
Piping
Insulation for ductwork
Painting
Subtotal
Indirect Costs
Engineering & supervision
Construction & field expenses
Contractors fee
Start-up and performance test
Contingencies
Subtotal
Total New Capital Costs
Total Retrofit Capital Costsb
Small
1,811
145
1,956
78
685
156
20
137
39
1,115
196
391
196
39
59
881
3,952
4,940
Medium
3,622
290
3,912
156
1,369
313
39
274
78
2,229
391
782
391
78
117
1,759
7,900
9,875
Large
6,655
532
7,187
288
2,516
575
72
503
144
4,098
719
1,438
719
144
216
3,236
14,521
18,151
a Costs are in April 1991 dollars.
b For retrofit capital costs multiply new capital costs by 1.25.
5-18
-------
TABLE 5-11. TOTAL CAPITAL COSTS FOR COKE
SIZING/SCREENING ($1,000)*
Plant Size
Purchased Equipment Costs
Removal & auxiliary equipment
Freight & sales taxes
Subtotal
Direct Installation Costs
Foundation & supports
Handling & erection
Electrical
Piping
Insulation for ductwork
Painting
Subtotal
Indirect Costs
Engineering & supervision
Construction & field expenses
Contractors fee
Start-up and performance test
Contingencies
Subtotal
Total New Capital Costs
Total Retrofit Capital Costsb
Small
433
35
468
19
164
37
5
33
9
267
47
94
47
9
14
211
946
1,182
Medium
478
38
516
21
181
41
5
36
10
294
52
103
52
10
15
232
1,042
1,303
Large
582
47
629
25
220
50
6
44
13
358
63
126
63
13
19
284
1,271
1,589
a Costs are in April 1991 dollars.
b For retrofit capital costs multiply new capital costs by 1.25.
5-19
-------
TABLE 5-12. TOTAL CAPITAL COSTS FOR CASTHOUSE (Al) ($1,000)*
Plant Size
Purchased Equipment Costs
Removal & auxiliary equipment
Freight & sales taxes
Subtotal
Direct Installation Costs
Foundation & supports
Handling & erection
Electrical
Piping
Insulation for ductwork
Painting
Subtotal
Indirect Costs
Engineering & supervision
Construction & field expenses
Contractors fee
Start-up and performance test
Contingencies
Subtotal
Total New Capital Costs
Total Retrofit Capital Costsb
Small
1,446
116
1,562
62
547
125
16
109
31
890
156
312
156
31
47
702
3,154
3,943
Medium
2,471
198
2,669
107
934
214
27
187
53
1,522
267
534
267
53
80
1,201
5,392
6,740
Large
3,526
282
3,808
152
1,333
305
38
267
76
2,171
381
762
381
76
114
1,714
7,693
9, 616
a Costs are in April 1991 dollars.
b For retrofit capital costs multiply new
capital costs by 1.25.
5-20
-------
TABLE 5-13. TOTAL CAPITAL COSTS FOR CASTHOUSE (A2) ($1,000)*
Plant Size
Purchased Equipment Costs
Removal & auxiliary equipment
Freight & sales taxes
Subtotal
Direct Installation Costs
Foundation & supports
Handling & erection
Electrical
Piping
Insulation for ductwork
Painting
Subtotal
Indirect Costs
Engineering & supervision
Construction & field expenses
Contractors fee
Start-up and performance test
Contingencies
Subtotal
Total New Capital Costs
Total Retrofit Capital Costsb
Small
1,129
90
1,219
49
427
98
12
85
24
695
122
244
122
24
37
549
2,463
3,079
Medium
1,772
142
1,914
77
670
153
19
134
38
1,091
191
383
191
38
57
860
3,865
4,831
Large
2,460
197
2,657
106
930
213
27
186
53
1,515
266
531
266
53
80
1,196
5,368
6,710
a Costs are in April 1991 dollars.
b For retrofit capital costs multiply new capital costs by 1.25.
5-21
-------
TABLE 5-14. TOTAL CAPITAL COSTS FOR HOT METAL TRANSFER
($l,000)a
Purchased Equipment Costs
Removal & auxiliary equipment
Freight & sales taxes
Subtotal
Direct Installation Costs
Foundation & supports
Handling & erection
Electrical
Piping
Insulation for ductwork
Painting
Subtotal
Indirect Costs
Engineering & supervision
Construction & field expenses
Contractors fee
Start-up and performance test
Contingencies
Subtotal
Total New Capital Costs
Total Retrofit Capital Costsb
a Costs are in April 1991 dollars.
b For retrofit capital costs multiply new
Small
939
75
1,014
41
355
81
10
71
20
578
101
203
101
20
30
455
2,047
2,559
capital costs
Plant Size
Medium
1,492
119
1,611
64
564
129
16
113
32
918
161
322
161
32
48
724
3,253
4,066
by 1.25.
Large
1,492
119
1,611
64
564
129
16
113
32
918
161
322
161
32
48
724
3,253
4,066
5-22
-------
TABLE 5-15. TOTAL CAPITAL COSTS FOR DESULFURIZATION ($1,000)*
Plant Size
Purchased Equipment Costs
Removal & auxiliary equipment
Freight & sales taxes
Subtotal
Direct Installation Costs
Foundation & supports
Handling & erection
Electrical
Piping
Insulation for ductwork
Painting
Subtotal
Indirect Costs
Engineering & supervision
Construction & field expenses
Contractors fee
Start-up and performance test
Contingencies
Subtotal
Total New Capital Costs
Total Retrofit Capital Costsb
Small
605
48
653
26
229
52
7
46
13
373
65
131
65
13
20
294
1,320
1,650
Medium
794
64
858
34
300
69
9
60
17
489
86
172
86
17
26
387
1,734 1,
2,168 2,
Large
794
64
858
34
300
69
9
60
17
489
86
172
86
17
26
387
734
168
a Costs are in April 1991 dollars.
b For retrofit capital costs multiply new capital costs by 1.25.
5-23
-------
TABLE 5-16. TOTAL ANNUAL COSTS FOR COKE PUSHING
(A2) ($l,000)a
Plant Size
Direct Costs
Power cost
Heat
Maintenance
Subtotal
Indirect Costs
Capital recovery
Subtotal
Total Annual Costs
Small
788
787
332
1,907
500
500
2,407
Medium
1,185
1,177
498
2,860
1,000
1,000
3,860
Large
1,973
1,968
830
4,771
1,250
1,250
6,018
a Costs are in April 1991 dollars.
maintenance required to successfully operate a mobile scrubber car
already in use. These costs do not represent the capital recovery
of an investment in a new mobile scrubber car system. The costs
given in Reference 3 were indexed from 1974 dollars to 1991
dollars. It is recognized that this method may not yield an
accurate representation of current annual costs; however, other
references were not readily available. Agencies interested in
conducting a more detailed estimate of mobile scrubber car costs
should consult with an air pollution control equipment vendor.
5.5 COST EFFECTIVENESS
Cost effectiveness is defined as the total annual costs per Mg
of PM-10 emissions reduced. The cost effectiveness is calculated
by dividing the incremental cost of implementing a new process
control option (the annualized cost of control system
modifications) by the additional mass of PM-10 removed by the new
5-24
-------
TABLE 5-17. TOTAL ANNUAL COSTS FOR COKE PUSHING (Al)
($1,000)*
Plant Size
Direct Costs
Utilities
Operating labor
Maintenance
Replacement parts
Bags
Subtotal
Indirect Costs
Overhead
Property tax
Insurance
Administration
Capital recovery
Subtotal
Total Annual Costs
Small
682
135
129
129
29
1,104
236
49
49
99
796
1,229
2,333
Medium
1,364
270
258
258
58
2,208
472
98
98
198
1,592
2,458
4,666
Large
2,507
496
474
474
107
4,058
867
180
180
364
2,926
4,517
8,575
a Costs are in April 1991 dollars.
5-25
-------
TABLE 5-18. TOTAL ANNUAL COSTS FOR COKE SIZING/SCREENING
($1,000)*
Plant Size
Direct Costs
Utilities
Operating labor
Maintenance
Replacement parts
Bags
Subtotal
Indirect Costs
Overhead
Property tax
Insurance
Administration
Capital recovery
Subtotal
Total Annual Costs
Small
20
34
16
16
1
87
40
12
12
24
192
280
367
Medium
39
34
16
16
2
107
40
13
13
26
212
304
411
Large
78
34
16
16
5
149
40
16
16
32
257
361
510
a Costs are in April 1991 dollars.
5-26
-------
TABLE 5-19. TOTAL ANNUAL COSTS FOR CASTHOUSE (Al) ($1,000)*
Plant Size
Direct Costs
Utilities
Operating labor
Maintenance
Replacement parts
Bags
Subtotal
Indirect Costs
Overhead
Property tax
Insurance
Administration
Capital recovery
Subtotal
Total Annual Costs
Small
584
135
129
129
25
1,002
236
39
39
79
635
1,028
2,030
Medium
1,169
135
129
129
47
1,609
236
67
67
135
1,083
1,588
3,197
Large
1,753
135
129
129
71
2,217
236
96
96
192
1,545
2,165
4,382
a Costs are in April 1991 dollars.
5-27
-------
TABLE 5-20. TOTAL ANNUAL COSTS FOR CASTHODSE (A2)
($1,000)*
Plant Size
Direct Costs
Utilities
Operating labor
Maintenance
Replacement parts
Bags
Subtotal
Indirect Costs
Overhead
Property tax
Insurance
Administration
Capital recovery
Subtotal
Total Annual Costs
Small
400
135
129
129
17
810
236
31
31
62
496
856
1,666
Medium
779
135
129
129
32
1,204
236
48
48
97
111
1,206
2,410
Large
1,169
135
129
129
47
1,609
236
67
67
134
1,078
1,582
3,191
a Costs are in April 1991 dollars.
5-28
-------
TABLE 5-21. TOTAL ANNUAL COSTS FOR HOT METAL TRANSFER
($1,000)*
Plant Size
Direct Costs
Utilities
Operating labor
Maintenance
Replacement parts
Bags
Subtotal
Indirect Costs
Overhead
Property tax
Insurance
Administration
Capital recovery
Subtotal
Total Annual Costs
Small
292
135
129
129
13
698
236
26
26
51
413
752
1,450
Medium
584
135
129
129
25
1,002
236
41
41
81
655
1,054
2,056
Large
584
135
129
129
25
1,002
236
41
41
81
655
1,054
2,056
* Costs are in April 1991 dollars.
5-29
-------
TABLE 5-22. TOTAL ANNUAL COSTS FOR DESULPURIZATION ($1,000)*
Plant Size
Direct Costs
Utilities
Operating labor
Maintenance
Replacement parts
Bags
Subtotal
Indirect Costs
Overhead
Property tax
Insurance
Administration
Capital recovery
Subtotal
Total Annual Costs
Small
97
135
129
129
6
496
236
17
17
33
267
570
1,066
Medium
195
135
129
129
9
597
236
22
22
43
350
673
1,270
Large
195
135
129
129
9
597
236
22
22
43
350
673
1,270
a Costs are in April 1991 dollars.
5-30
-------
process control option (amount of emissions reduced from baseline
emissions). The cost effectiveness for each process control option
and model plant site is listed in Table 5-23.
5.6 CONTROL OPTION COSTS FROM INDUSTRY REPRESENTATIVES
The cost comparisons in this section are provided to
illustrate the variability in control option cost estimates for the
iron and steel industry. These comparative costs were provided to
EPA by industry representatives who reviewed a draft version of
this document. The discussion here focuses on reviewers' comments
on the methodology used to derive control option costs in
Sections 5.2, 5.3, and 5.4 of this document and their own field
experience with costing these control options.
The costing methodologies (derived from EPA guidance) used in
this chapter were sound according to one reviewer's comments;
however, certain parameters used ' in the methodology were
questioned. For example, the assumed control system pressure drop
of 15 inches H^O was stated to be low as pressure drops on some
systems often exceed 20 inches H2O. This same reviewer questioned
the airflow rates that were assumed for each process size and
control option. The airflow rates have since been revised to be in
line with the reviewers' comments; however, the control system
pressure drop assumption remains at 15 inches water column. The
reviewer also stated that the assumed air-to-cloth ratio of
4.5 feet/minute in Tables 5-2 through 5-7 was somewhat low for
modern baghouse designs; however, this value was left unchanged in
the costing methodology.6 (The effect of changing the air-to-cloth
ratio is relatively small.) Changes in these parameters noted by
reviewers could either increase or decrease the capital and annual
costs derived in this document.
Other comments on the parameters used in the costing
methodology focused on various capital and annual cost factors that
are given in Table 5-9. General comments were that Freight and
Sales Tax (8%) , Foundation and Supports (4%) , and the assumed
annual interest rate (10%) were too low for most iron and steel
5-31
-------
TABLE 5-23. COST EFFECTIVENESS FOR EMISSIONS REDUCTIONS FROM
UNCONTROLLED CASE
PM-10
Reduction
Annual Coats from
($1,000)' Uncontrolled Cost Eff.
(Mg/yr) ($l,000/Mg)
Coke Pushing (Al)
Small
Medium
Large
Coke Pushing (A2)
Small
Medium
Large
Coke Sizing/Screening
Small
Medium
Large
Casthouse (Al)
Small
Medium
Large
Casthouse (A2)
Small
Medium
Large
Hot Metal Transfer"
Small
Medium
Large
Desulfurizationb
Small
Medium
Large
2,333
4,666
8,575
2,407
3,860
6,018
367
411
510
2,030
3,197
4,382
1,666
2,410
3,191
1,450
2,056
2,056
1,066
1,270
1,270
230
450
830
200
410
750
39
79
150
150
300
550
130
270
490
39
78
140
120
230
420
10
10
10
12
9.5
8.0
9.3
5.2
3.5
14
11
8.0
12
9.0
6.5
37
26
14
9.3
5.5
3.0
' Costs are in April 1991 dollars.
b Control options for desulfurization and hot metal transfer are considered to
be baseline.
5-32
-------
applications. One reviewer stated that specifically for the Coke
Pushing (Al) control option (shed with baghouse), Foundation and
Supports are very expensive due to the massive structure associated
with a shed. Other specific comments were that Engineering and
Supervision costs are more likely near 20 percent rather than the
10 percent factor used in the calculations. Also the reviewer
stated that contingency costs may be at least 10 percent as opposed
to the 3 percent factor used in the methodology. Finally, the
reviewer stated that from their experience, annual
Maintenance/Replacement costs typically run at 10 percent of each
facility's total annual replacement costs. However, the costing
methodology assumed that replacement costs equal 100 percent of the
maintenance costs plus fabric filter bag purchases. For one
example given in Table 5-17, coke pushing (Al), a small facility's
maintenance/replacement costs would be $1.3 million in the
reviewer's example; however, these costs sum to $287,000 using the
OAQPS costing methodology.6
Several industry reviewers provided comments relating their
actual costing experience to the control costs estimated in this
chapter.6-7'8 These comments were consolidated and are presented in
Table 5-24. Nearly all the cost comments provided by reviewer's
related their own retrofit capital cost experience instead of total
annual costs. These reviewer's costs were up to 4 times greater
than the retrofit capital costs estimated in this chapter. These
differences may result from several factors, including the
differences in capital cost estimating factors discussed earlier in
this section and the "study" estimate error inherent in the cost
methodology discussed in Section 5.2. Also, as noted earlier in
this document, several site-specific parameters may impact the
control costs derived in this chapter. These costs may include
building and site preparation costs, stack costs, or downtime
losses. It is therefore re-emphasized that the costs presented
here are provided for comparative purposes only; evaluation of
actual facility costs should be developed specifically for each
individual site.
5-33
-------
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-------
5.7 REFERENCES FOR CHAPTER 5
1. Neveril, R.B. Capital and Operating Coats of Selected Air
Pollution Control Systems. EPA 450/5-80-002. Office of Air
Quality Planning and Standards, U.S. Environmental Protection
Agency, Research Triangle Park, NC. December 1978.
2. U.S. Environmental Protection Agency. OAQPS Control Cost
Manual. Fourth Edition. EPA 450/3-90-006. Office of Air
Quality Planning and Standards, U.S. Environmental Protection
Agency, Research Triangle Park, NC. January 1990.
3. McClelland, R.O. Coke Oven Smokeless Pushing System Design
Manual. EPA 650/2-74-076. U.S. Environmental Protection
Agency, September 1974.
4. "Chemical Engineering Plant Cost Index and Marshall & Swift
Equipment Cost Index," in Chemical Engineering, Vol. 98,
No. 7. July 1991.
5. U.S. Environmental Protection Agency. Control Technologies
for Hazardous Air Pollutants. EPA 625/6-86-014. Air and
Energy Engineering Research Laboratory, U.S. Environmental
Protection Agency, Research Triangle Park, NC. June 1986.
6. Letter from Thomas W. Easterly, Bethlehem Steel Corporation,
to James H. Maysilles, U.S. Environmental Protection Agency.
Comments on draft ACT document for PM-10 emissions from iron
and steel mills. Letter dated August 19, 1992.
7. Letter from R. Wade Kohlmann, Indianapolis Coke, to James H.
Maysilles, U.S. Environmental Protection Agency. Comments on
draft ACT document for PM-10 emissions from iron and steel
mills. Letter dated August 4, 1992.
8. Letter from David C. Ailor, American Coke and Coal Chemicals
Institute, to James H. Maysilles, U.S. Environmental
Protection Agency. Comments on draft ACT document for PM-10
emissions from iron and steel mills. Letter dated
September 25, 1992.
5-35
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APPENDIX A
INTEGRATED IRON AND STEEL MILLS
AND BLAST FURNACE COKE OVENS
A-l
-------
TABLE A-l.
INTEGRATED IRON AND
FURNACE COKE OVENS
STEEL MILLS AND BLAST
Plant
Location
Acme Steel
Armco Inc.
Armco Inc.
Bethlehem Steel
Bethlehem Steel
Bethlehem Steel
Bethlehem Steel
Geneva Steel
Gulf States Steel
Inland Steel
LTV Steel
LTV Steel
LTV Steel
LTV Steel
McClouth Steel
National Steel
National Steel
Rouge Steel
Sharon Steel
USS Division of USX
USS Division of USX
USS Division of USX
USS/Kobe Steel
Warren Consolidated
Industries
Weirton Steel
Wheeling-Pittsburgh Steel
Wheeling-Pittsburgh Steel
Chicago, IL
Middletown, OH
Ashland, KY
Bethlehem, PA
Burns Harbor, IN
Lackawanna, NY
Sparrows Point, MD
Provo, UT
Gadsden, AL
East Chicago, IL
Cleveland, OH
Pittsburgh, PA
Indiana Harbor, IN
East Chicago, IN
Trenton, MI
Ecorse, MI
Granite City, IL
Dearborn, MI
Parrel1, PA
Fairfield, AL
Clairton, PA
Gary, IN
Lorain, OH
Warren, OH
Weirton, WV
Mingo Junction, OH
East Steubenville, WV
References:
U.S. Environmental Protection Agency. Cost Analysis for the Coke Oven NESHAP.
Office of Air Quality Planning and Standards, Research Triangle Park, NC, April
1992.
"Blast Furnace Roundup." 33 Metal Producing, Volume 29, No. 5. Penton
Publishing, Inc., Cleveland, OH. May 1991. Inc., Cleveland, OH. May 1991.
A-2
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APPENDIX B
SAMPLE EMISSION FACTOR CALCULATIONS
B-l
-------
Example Calculation for Derived Emission Factors
If controlled emission factors were not available from published texts,
an emission factor was derived using the following methodology:
1) Calculate fugitive emission factor (emissions not captured at the source) using:
(a) controlled emission factor from published source
(b) assumed capture system efficiency
2) Calculate process emission factor (emissions released at control device outlet) using:
(a) assumed minimum exit grain loading
(b) assumed inlet temperature
(c) assumed hours of operation
(d) assumed flowrate (for each size model plant)
(e) assumed throughput (for each size model plant)
(f) if flowrates and throughputs are not linearly proportionate, use the average
process emission factor for step 3
3) Add fugitive emission factor to the average process emission factor to obtain total emission factor.
The following example illustrates the use of this procedure to generate
a controlled emission factor for the hot metal transfer process.
1) Calculate fugitive emission factor:
(a) controlled emission factor 0.09 Ib/ton
(b) assumed capture efficiency 90 percent
Fugitive e.f. = 0.09 Ib PM-10 emitted x (100%-90%)
ton hot metal produced
Fugitive e.f. = 0.009 Ib PM-10 emitted
ton hot metal produced
B-2
-------
2) Calculate process emission factor:
(a) assumed minimum exit grain loading (assume all is PM-10).. 0.003 gr/dscf
(b) assumed inlet temperature 100 C
(c) assumed hours of operation 8,760
(d) assumed flowrate for each size model plant (acfm) small 150,000
medium 300,000
large 300,000
(e) assumed throughput for each size model plant (tons/yr) small 1,316,276
medium 2,632,552
large 4,856,604
(f) calculate average process emission factor
Process e.f. = 150,000 acfm x 273 C x 0.003 gr x 60 min x 8,760 hr x year x 115
(small) 373 C dscf hr year 1,316,276 tons 7,000 gr
Process e.f. = 0.0188 Ib PM-10 emitted
(small) ton hot metal produced
Process e.f. = 300,000 acfm x 273 C x 0.003 gr x 60 min x 8,760 hr x year x 1 Ib
(medium) 373 C dscf hr year 2,632,552 tons 7,000 gr
Process e.f. = 0.0188 Ib PM-10 emitted
(medium) ton hot metal produced
Process e.f. = 300,000 acfm x 273 C x 0.003 gr x 60 min x 8,760 hr x year x 1 Ib
(large) 373 C dscf hr year 4,856,604 tons 7,000 gr
Process e.f. = 0.0102 Ib PM-10 emitted
(large) ton hot metal produced
Process e.f. = (0.0188 + 0.0188 + 0.0102) / 3
(average)
Process e.f. = 0.0159 Ib PM-10 emitted
(average) ton hot metal produced
3) Calculate total emission factor (fugitive emission factor plus average process emission factor):
Total e.f. = Fugitive e.f. + Process e.f. (avg)
Total e.f. = 0.009 + 0.0159
Total e.f. = 0.249 Ib PM-10 emitted
ton hot metal produced
or
0.125 kg PM-10 emitted
Mg hot metal produced
Note that derived emission factor values in Table 2-3 and Table 4-1 are reported with only one significant figure.
B-3
-------
REPORT DOCUMENTATION PAGE
rOr.T ~~c :,. -rC
OMB No 3704-0188
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1. AGENCY USE ONLY (Leave blank)
2. REPORT DATE
February
1994
3. REPORT TYPE AND DATES COVERED
Final
4. TITLE AND SUBTITLE
Alternative Control Techniques Document --
PM-10 Emissions From Selected Processes at
Coke Ovens and Integrated Iron and Steel Mills
6. AUTHOR(S)
Philindo J. Marsosudiro and W. Scott Snow
5. FUNDING NUMBERS
68-DO-0121
WA 2/117
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)
TRC Environmental Corporation
100 Europa Drive, Suite 150
Chapel Hill, NC 27514
8. PERFORMING ORGANIZATION
REPORT NUMBER
9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)
U.S. Environmental Protection Agency
Emission Standards Division (MD-13)
Office of Air Quality Planning and Standards
Research Triangle Park, NC 27711
10. SPONSORING / MONITORING
AGENCY REPORT NUMBER
EPA-453/R-94-005
11. SUPPLEMENTARY NOTES
EPA Work Assignment Manager:
James H. Maysilles 919-541-3265
12a. DISTRIBUTION/AVAILABILITY STATEMENT
Release unlimited
12b. DISTRIBUTION CODE
13. ABSTRACT (Maximum 200 words)
The purpose of this document is to provide guidance to state and loc
air quality management agencies for determining reasonably available
control technologies (RACT) and best available control technologies
(BACT) that apply to PM-10 sources in the iron and steel industry.
Emission sources addressed are coke pushing, coke quenching, coke
sizing and screening, casthouse operations, hot metal transfer, and
desulfurization. These sources were selected for analysis because
they are not presently regulated under New Source Performance
Standards (NSPS). Emission control system descriptions, environment
and energy impact assessments, and control cost analyses are
presented. The principal emission collection devices used are the
fabric filter and wet venturi scrubber.
14. SUBJECT TERMS
Iron production Iron and steel industry Cost of
Steel production Fabric filter PM-10
Coke oroduction Wet venturi scrubber control
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OF REPORT
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18. SECURITY CLASSIFICATION
OF THIS PAGE
UNCLASSIFIED
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OF ABSTRACT
UNCLASSIFIED
15. NUMBER OF PAGES
128
16. PRICE CODE
20. LIMITATION OF ABSTF
UL
NSN 7540-01-280-5500
Standard Form 298 (Rev
Prescnoed by ANSI Std Z39-18
298-102
2-!
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