United oitates Office of Air ^r ality EPA '• • /'j-83-003
Enviro<..nenuil Protection Planning and Standards f"9brr y 1983
Agency Research Triangle Park NC 27711
Air
o-EPA Review of New
Source Performance
Standards for Primary
Copper Smelters
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Review of New Source
Performance Standards for
Primary Copper Smelters
Emission Standards and Engineering Division
r;ccf'vf0
7 ° 1983
A'rSr°9>oms
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air, Noise, and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
Februarv,9S3 lifiiiii
RXOOOOOMSMO
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CONTENTS
Page
BACKGROUND 1
Existing Standard 1
Developments Since Promulgation of the Existing
Standard 1
Overview of the Copper Smelting Process 3
REVERBERATORY FURNACE EXEMPTION—S0? CONTROL 7
Alternative Smelting Technologies 8
Flash smelting 8
Electric furnace smelting 9
Continuous smelting furnaces 9
Weak S02 Offgas Stream Control 9
Flue gas desulfurization 10
Use of oxygen 12
Offgas blending 14
REVERBERATORY FURNACE EXEMPTION—PARTICULATE EMISSION
CONTROL 15
CAPACITY EXPANSION AT EXISTING SMELTERS 17
FUGITIVE EMISSIONS 19
ECONOMIC ANALYSIS 22
Basis of Analysis 22
Deletion of Reverberatory Furnace Exemption 24
Impact of Existing Standard on Expansion Capacity 27
New smelters 27
Existing smelters 28
Roaster-reverberatory furnace-converter smelting ... 28
Reverberatory furnace-converter smelting 31
Electric furnace-converter smelting 32
Flash furnace smelting 32
Impact of fugitive particulate matter control .... 32
CONCLUSIONS 33
Growth Outlook 33
Reverberatory Furnace Exemption 34
Smelter Expansion 36
Fugitive Particulate Matter Emissions 36
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STANDARDS OF PERFORMANCE FOR NEW STATIONARY SOURCES
PRIMARY COPPER SMELTERS: REVIEW OF STANDARDS
BACKGROUND
Existing Standard
The current standard of performance for primary copper smelters,
promulgated January 15, 1976 (41 FR 2338), limits S02 emissions from
new, modified, or reconstructed roasters, smelting furnaces, or copper
converters to 0.065 percent by volume (650 ppm). Reverberatory smelting
furnaces are specifically exempted from this emission limit during
periods when the total smelter charge contains a high level of volatile
impurities (i.e., a total smelter charge with greater than 0.2 weight
percent arsenic, 0.1 weight percent antimony, 4.5 weight percent lead,
or 5.5 weight percent zinc, on a dry basis). This exemption was
included in the standard because the cost of controlling S02 emissions
from reverberatory smelting furnaces was considered to be unreasonable
and because alternative smelting technologies were not available at
reasonable cost to process high-impurity materials.
Developments Since Promulgation of the Existing Standard
After promulgation of the existing standard, the exemption for
reverberatory furnaces smelting high-impurity materials was the subject
of petitions filed by the Natural Resources Defense Council (NRDC) and
by the American Smelting and Refining Company (ASARC0). The NRDC
petition alleged that available control techniques for reducing S02
and particulate emissions from reverberatory smelting furnaces
processing high-impurity materials had not been investigated adequately.
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The ASARCO petition claimed that the exemption was economically
unreasonable because it requires a new or modified reverberatory
furnace processing high-impurity materials to suspend operations when
such materials are not available.
In response to the petitions, EPA entered into negotiations with
NRDC and ASARCO that led to a court approved settlement of the petitions
in March 1982. Terms of the settlement were that EPA would review the
standard and make whatever changes were considered appropriate.
In addition to the terms of this settlement, a number of other
factors also suggested that a review of the standard was in order.
When the current standard was promulgated, analysis indicated it would
have little or no impact on the ability of existing primary copper
smelters to expand production. This analysis was based on the use of
a "bubble," which would have allowed increased emissions from modified
existing facilities, such as an expanded smelting furnace, to be
offset by an emission reduction from other existing facilities, such
as roasters or copper converters. As long as the plant's overall
emission level did not increase, the modified facilities would not be
subject to the standard. This bubble, however, was subjected to
litigation and rejected by the court in ASARCO vs EPA, 578.F.2d.319
(1978). As a result, a reassessment of the impact of the existing
standard on the ability of an existing primary copper smelter to
expand production is appropriate.
Also, emission tests conducted since promulgation of the standard
show that fugitive S02 and particulate matter emissions are generated in
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varying quantities from numerous smelting operations. The significant
quantities of these emissions indicated a need to consider fugitive
emission limitations for copper smelting operations.
Consequently, a review of the existing standard of performance
was undertaken to (1) reexamine the current exemption for reverberatory
furnaces processing high-impurity materials, (2) assess the feasibility
of controlling particulate matter emissions from reverberatory furnaces
processing high-impurity materials, (3) reevaluate the impact of the
current standard on the ability of existing smelters to expand produc-
tion, and (4) assess the technical and economic feasibility of control-
ling fugitive emissions at primary copper smelters.
Draft copies of background information that formed the bases for
the discussions in this report were provided to the litigants and inter-
veners for comment. Analysis of the information contained in the
responses indicates that no changes reached in the conclusions contained
herein are required.
Overview of the Copper Smelting Process
The conventional copper smelting process generally consists of
two or three distinct operations: roasting, smelting, and converting.
In roasting, the copper ore concentrates, which consist primarily of
copper, iron, and sulfur, are heated in the presence of air to drive
off a portion of the sulfur as sulfur dioxide (S02) gas. Roasting may
or may not be included at a copper smelter, depending on factors such
as the sulfur and volatile impurity levels (e.g., arsenic, antimony)
contained in the copper ore concentrates processed by the smelter.
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Two different types of roasters are used by the industry:
multihearth roasters and fluid-bed roasters. Multihearth roasters
generally are used when removal of volatile impurities during roasting
is a prime consideration and when the composition of the copper ore
concentrates processed may fluctuate widely. Either multihearth or
fluid-bed roasters are used when removal of "excess" sulfur during
roasting is a prime consideration. The S02 concentration in the
offgases from these two types of roasters differs substantially, with
that for multihearth roasters generally in the range of 4 to 5 percent
and that for fluid-bed roasters generally in the range of 9 to 15 percent.
Offgas volume is from 550 to 1,700 normal cubic meters per minute
(Nm3/min) (20,000 to 60,000 standard cubic feet per minute [scfm]) for
multihearth roasters and 300 to 1,300 Nm3/min (10,000 to 45,000 scfm)
for fluid-bed roasters.
The roasted materials (calcine) or the raw copper ore concentrate
(if roasting is not used) then are melted in a smelting furnace to
form two molten layers: a slag layer and a matte layer. All of the
rock and a portion of the iron combine with the fluxing agents to form
the slag layer which is drawn off and discarded. The matte layer,
composed of copper, iron, and sulfur, is transferred in ladles to the
converters for further processing.
Three different types of smelting furnaces are used by the industry:
reverberatory furnaces, electric furnaces, and flash furnaces. The
reverberatory smelting furnace is a rectangular structure typically
11 meters (36 feet) wide and 40 meters (130 feet) long. Calcine or
raw copper ore concentrates are fed into the furnace through the roof
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or sidewalls and smelted by heat generated by combustion of fossil
fuel (i.e., natural gas, oil, or coal) introduced through burners in
the end wall. Matte is removed through ports in the sidewalls.
Typical S02 concentration in the offgases is low, between 0.5 and
2.0 percent, and the volume of offgas ranges between 1,700 and
4,500 Nm3/min (60,000 and 160,000 scfm).
The electric smelting furnace is a rectangular structure typically
10 meters (33 feet) wide and 35 meters (115 feet) long. With electric
smelting furnaces, calcine or raw copper ore concentrates are charged
through the furnace roof and melted by the heat generated by passing
an electric current through the molten bath. The electric current is
provided by a series of electrodes that passes through the roof of
the furnace and extends into the molten bath maintained in the furnace.
Typical S02 concentrations in the offgas are between 4 and 6 percent.
Offgas volume is usually between 400 and 800 Nm3/min (15,000 and
30,000 scfm).
In contrast to the reverberatory and electric smelting furnaces,
which use fossil fuel and electrical energy, respectively, to melt
their charge, the flash furnace uses the heat generated by "combustion"
or oxidation of some of the sulfur contained in the copper ore
concentrate. The flash furnace is a rectangular structure typically
7 meters (23 feet) wide and 20 to 25 meters (65 to 80 feet) long.
Dried copper ore concentrates, together with fluxing material and
preheated air, and a mixture of oxygen and air or oxygen alone are
injected into the furnace. A portion of the sulfur contained in the
charge is oxidized to S02, generating sufficient heat to melt the
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charge. Depending on the amount of oxygen used, the offgases contain
from 10 to 80 percent S02, with offgas volume ranging from 125 to
2,250 Nm3/min (4,600 to 80,000 scfm).
As mentioned earlier, the matte produced in the smelting furnace
is transferred to copper converters for further processing. In the
converters, air is blown through the molten matte to oxidize the
remaining iron and sulfur. The iron combines with fluxing agents to
produce a slag, which is removed from the converter. The remaining
sulfur is eliminated as S02 in the offgases. The product of converting
is blister copper approximately 99 percent pure.
Unlike roasting and smelting, which are continuous operations,
converting is a batch process. Converting is a cyclic process
consisting of charging, blowing, and removal of slag and blister
copper. An average converter cycle is about 12 hours. The volume and
S02 concentration of the offgases fluctuates widely depending on the
operation taking place.
Generally, from two to four converters are required to process
the matte produced in a single smelting furnace. These converters are
located in a converter aisle. Operation of the converters may be
scheduled to smooth out the fluctuation in offgas flow from the
converter aisle as a whole. Offgases from the converter aisle contain
from 4.0 to 6.5 percent S02. Offgas volumes vary from 1,700 to
3,400 Nm3/min (60,000 to 120,000 scfm).
Sulfuric acid plants are used to control S02 emissions at domestic
smelters by converting the S02 to sulfuric acid. The offgas streams
produced by each of the copper smelting operations generally are
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classified as either strong S02 streams, which contain S02 in
concentrations greater than 3.5 percent, or weak S02 streams, which
contain S02 in concentrations less than 3.5 percent. A strong gas
stream can be processed in a sulfuric acid plant for removal of the
S02 without adding heat (i.e., autothermal operation), whereas a weak
gas stream requires the addition of heat to be processed in an acid
plant. Weak gas streams, however, may be mixed with strong gas streams,
and the mixed stream sent to a sulfuric acid plant for processing
without adding heat, providing the S02 concentraton of the mixed gas
stream is above 3.5 percent.
REVERBERATORY FURNACE EXEMPTION—S02 CONTROL
Copper smelting and refining operations must produce a copper
end-product with minimal levels of impurities such as arsenic and
antimony. Impurity removal occurs at each stage of the smelting
process: roasting, smelting, and converting.
As mentioned above, the existing standard exempts reverberatory
smelting furnaces that process high-impurity materials (i.e., those
processing a total charge with more than 0.2 weight percent arsenic,
0.1 weight percent antimony, 4.5 weight percent lead, or 5.5 weight
percent zinc). This exemption was provided in the existing standard
because the cost of controlling S02 emissions from reverberatory
smelting furnaces was considered unreasonable and because alternative
smelting technologies capable of processing high-impurity materials
were considered too costly or not demonstrated. Since the existing
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standard was promulgated, however, there have been a number of
developments in the area of alternative smelting technologies and the
control of weak S02 streams.
Alternative Smelting Technologies
Three alternative smelting technologies were examined during the
review of the existing standard to determine their suitability for
processing high-impurity materials: flash smelting, electric smelting,
and continuous smelting.
Flash smelting. Two flash smelting furnace designs were studied:
Inco and Outokumpu Oy. Analysis of the data and information collected
show that while both furnace designs are capable of processing copper
concentrates with a higher than average impurity levels, experience to
date has been insufficient to judge whether they are capable of
processing materials with impurity levels in excess of those specified
in the exemption to the existing standard.
Outokumpu Oy has developed a procedure for removing impurities
prior to flash smelting. In this process, dried and preheated concen-
trates are fed to a rotary kiln in an atmosphere of sulfur and nitrogen.
Arsenic and antimony sulfides in the feed are vaporized and recovered
from the offgas by condensation. Laboratory tests indicate in excess
of 99 percent arsenic removal from concentrates containing up to 11.4
percent arsenic and from 50 to 80 percent antimony removal from
concentrates containing up to 1.5 percent antimony.
Small-scale pilot tests in a 10- to 100-kilograms-per-hour (kg/h)
(22- to 220-pounds-per-hour [lb/h]) facility indicate that the use of
sulfidizing roasting prior to the flash smelting could result in
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impurity elimination comparable to that obtained by multihearth roasting
followed by reverberatory furnace smelting. Although promising,
Outokumpu Oy feels that full-scale pilot tests of the technology in a
1,000-kg/h (2,200-lb/h) facility is required before it could be commer-
cial ized.
Electric furnace smelting. Although electric furnace smelting is
considered technically demonstrated for processing high-impurity
materials, the costs associated with the use of this technology, due
to the high cost of electrical power, are considered unreasonable.
Continuous smelting furnaces. While the continuous smelting
furnace technologies have processed some high-impurity materials, they
have not been shown to be capable of producing copper of acceptable
quality from materials with impurity levels in excess of those specified
in the existing standard. Therefore, continuous smelting furnace
technologies are not considered demonstrated for processing high-impurity
materials.
Weak SO? Offgas Stream Control
Offgases from reverberatory smelting furnaces have an S02 content
too low to be processed directly in a sulfuric acid plant without the
addition of large amounts of heat. Other alternatives available
for the control of these offgases include application of flue gas
desulfurization systems (FGD) directly to the weak S02 offgas stream
(which either remove the S02 in the form of a throwaway by-product or
provide a strong SO offgas stream); use of oxygen in the reverberatory
furnace to increase S02 concentration; and blending the offgases with
strong S02 offgas from converters and/or roasters.
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Flue gas desulfurization. Since promulgation of the existing
standard, several FGD systems have been applied to weak metallurgical
S02 offgas streams, including copper smelter streams, on either a
pilot- or a full-scale basis. Two types, a calcium-based system and a
magnesium-oxide-based system, have been applied to full-scale reverbera-
tory furnace offgas streams at a copper smelter in Japan. A third
system, ammonia-based, has been used commercially to remove S02 from
weak S02 offgas streams produced at lead and zinc smelters.
The calcium-based system removes and "fixes S02" from the weak
S02 offgas stream as a solid or slurry. There has been no application
of this system at copper smelters in the United States; however, a
calcium-based system has been successfully controlling a weak S02
offgas stream (<0.6 percent) from a molybdenum roaster in Arizona
since 1972.
The most significant application of calcium-based FGD technology
has been at a copper smelter in Japan. Operating experience at this
smelter has demonstrated that calcium-based FGD systems are capable of
removing S02 from reverberatory furnace offgas. System reliability is
high, over 99 percent, while an S02 absorption efficiency of 99.5 percent
has been achieved. Analyses indicate that calcium-based FGD systems
can accommodate the fluctuations in flow and S02 content of reverbera-
tory furnace offgas streams while maintaining a minimum 90-percent S02
removal efficiency. Consequently, calcium-based FGD's are considered
demonstrated for control of S02 emissions contained in reverberatory
furnace S02 offgas streams.
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The magnesium oxide (MgO) scrubbing system absorbs the S02 present
in weak S02 offgas streams in a MgO slurry to form hydrated crystals
of MgS03 and MgS04. These crystals are then dried and calcined to
generate a strong S02 offgas stream (i.e., ~10 percent S02) that can
be treated directly in a sulfuric acid plant. The MgO system has been
applied to copper reverberatory furnace offgases on a full-scale basis
at the Japanese smelter referred to earlier. An MgO system processes
a portion of the gases generated by the reverberatory furnaces at this
smelter. Offgases that exit the MgO absorber generally exhibit an S02
concentration of about 200 ppm, reflecting a 99-percent S02 removal
efficiency. Experience has shown that the MgO system has considerable
capability to handle fluctuations in the reverberatory furnace offgas
S02 concentration. Thus, the MgO system is also considered demonstrated
for the control of weak S02 offgas streams from reverberatory furnaces.
The Cominco process absorbs the S02 contained in weak S02 offgas
streams in an ammonia solution to form ammonium bisulfite. The ammonium
bisulfite is then reacted with sulfuric acid to form ammonium sulfate,
S02) and water. The S02 is stripped from solution to generate a
strong S02 offgas stream (i.e., ~25 percent S02) for treatment in an
S02 control facility, such as a sulfuric acid plant. While the Cominco
system has not been applied to offgases from copper smelting reverbera-
tory furnaces, it has been applied to other pyrometal1urgical offgas
streams with characteristics similar to those from copper smelter
reverberatory furnaces. Offgases from a lead sintering plant and a zinc
roaster, for example, have been treated by the Cominco process at a lead
smelter in Canada. The system has exhibited S02 removal efficiencies
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ranging from 91 to 98 percent and has shown that it can accommodate
the fluctuations encountered in both flow rate and S02 concentration
normally associated with copper smelting reverberatory furnaces while
maintaining an S02 removal efficiency of at least 90 percent. Thus,
the ammonia-based Cominco system is also considered demonstrated for
controlling weak S02 offgas stream from copper reverberatory furnaces.
While the use of each of the scrubbing systems described above
produces solid and liquid waste materials, disposal methods currently
in use at numerous S02 scrubbing installations demonstrate that techniques
are available for the disposal of these waste products in an environ-
mentally acceptable manner.
Use of oxygen. The use of oxygen in a reverberatory furnace
involves the substitution of commercial oxygen for some or all of the
combustion air fed to the furnace. A number of techniques related to
the use of oxygen in reverberatory furnaces have been developed and
are in use at a number of locations outside the United States. These
techniques increase the S02 concentration in reverberatory furnace
offgas by reducing the amount of nitrogen introduced with the combus-
tion air and by reducing fuel consumption. Production capacity of the
reverberatory furnace also increases, with increases of up to 122 per-
cent reported with this furnace modification. In addition, the use of
oxygen also results in a reduction in the size and cost of downstream
gas handling and processing equipment because of reduced offgas volumes.
Three distinct means of oxygen use in reverberatory furnaces currently
in use or under development were reviewed: oxygen enrichment, oxy-fuel
burners, and oxygen sprinkle.
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Oxygen enrichment involves increasing the oxygen content of the
combustion air introduced to the reverberatory furnace. An increase
in the oxygen/nitrogen ratio of the combustion air from 21:79 to 25:75
can result in an increase in the S02 concentration of the reverberatory
furnace offgas after gas treatment and cleaning of 0.9 percentage points.
Experience on full-scale and pilot-scale demonstrations indicate that
this performance can be sustained with no adverse effects on the
reverberatory furnace. Consequently, oxygen enrichment is considered
a demonstrated technique for increasing S02 concentrations in reverber-
atory furnace offgases.
Oxygen enrichment will not necessarily increase the S02 content
of reverberatory furnace offgas to the level necessary to operate a
sulfuric acid plant autothermally. On the other hand, its use does
increase the S02 concentration of reverberatory furnace offgases to a
level that facilitates blending of these offgases with other strong
streams (i.e., roasters and/or converters) and subsequent treatment in
a sulfuric acid plant. Oxygen enrichment can be used with conventional
burner systems and sidewall charging systems.
The use of oxy-fuel burners on reverberatory furnaces involves
the use of commercial oxygen to provide 100 percent of the oxygen
required for fuel combustion in these burners. Fuel and oxygen are
introduced through vertically positioned, roof-mounted burners rather
than the conventional horizontally positioned, end-wall burners.
Increases in reverberatory furnace offgas S02 concentrations in the
range of 2.5 to 5.5 percentage points have been reported. Experience
on full-scale demonstrations at both copper and nickel smelters indicate
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that this performance can be sustained with no adverse effect on the
reverberatory furnace. Oxy-fuel burners, therefore, are considered a
demonstrated technique for increasing the S02 concentration of the
reverberatory furnace offgases above the minimum level required for
autothermal operation of a sulfuric acid plant.
The oxygen-sprinkle system differs from other oxygen enhancement
systems in that it results in reverberatory furnace operation on the
same principle as a flash furnace. This system is currently under
development at a copper smelter in Arizona. Oxygen-sprinkle smelting
is expected to result in S02 concentration of 15 to 30 percent in the
reverberatory furnace offgas. Although preliminary results appear
promising, this system cannot be considered demonstrated at this time.
Offgas blending. Offgas blending involves mixing the reverberatory
furnace offgases with converter and/or roaster offgases to produce a
blended stream that can be treated in a sulfuric acid plant. Although
no copper smelter in the United States is currently using this technique
as a means of controlling reverbatory furnace offgases, it is considered
a demonstrated control technique for reverberatory furnaces. Varia-
tions in converter offgas flow rate and S02 concentration can result
in S02 concentrations in the blended gas stream below that required
for autothermal sulfuric acid plant operation. In such cases, supple-
mentary heat must be supplied to the sulfuric acid plant.
Blending with multihearth roaster offgases may result in production
of "black" sulfuric acid in the acid plant due to contamination with
trace amounts of organic flotation agents not completely decomposed in
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the roaster. Although "black" acid must generally be sold at a price
lower than that for clear acid, the income from the sale of this acid
covers transportation and sales costs.
REVERBERATORY FURNACE EXEMPTION—PARTICULATE EMISSION CONTROL
The existing standard does not address control of particulate
matter emissions from reverberatory furnaces which are exempt from S02
emission limitations when they process high-impurity materials. Lack
of such a requirement has no impact when such materials are not being
processed. In this situation, S02 emissions from new, modified, or
reconstructed reverberatory furnaces must be controlled to comply with
the existing standard and particulate matter emissions are removed
from the reverberatory furnace offgas stream during the gas treatment
and conditioning associated with the control of S02 emissions.
Fabric filtration is a well-demonstrated technology for control
of particulate matter emissions. Although fabric filtration has not
been used by the domestic copper smelting industry to control particu-
late matter emissions from reverberatory furnaces, it has been used to
control particulate matter emissions from fluid-bed and multihearth
roasters, electric furnaces, and converters at copper smelters. For
example, a fabric filter used to remove particulate matter emissions
from a gas stream composed of offgases from a fluid-bed roaster, an
electric furnace, and several converters at a domestic copper smelter
was tested in 1980. The fabric filter operated at approximately
110° C (230° F) and processed about 4,700 Nm3/min (165,000 scfm) of
gas. A spray chamber was used to cool the gases prior to their entry
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to the baghouse. Emission tests results indicated a particulate
matter removal efficiency of 99.7 percent and an average outlet grain
loading of 47 mg/Nm3 (0.020 grain/dry scf).
Electrostatic precipitators (ESP's) also may be used for
reverberatory furnace particulate matter emission control. ESP's are
well demonstrated throughout the domestic copper smelting industry for
control of particulate matter in offgases from reverberatory furnaces,
roasters, and converters. Tests at domestic copper smelters indicate
show that ESP's are capable of achieving a removal efficiency of
96.7 percent and outlet grain loadings on the order of 98 mg/Nm3
(0.04 grain/dry scf).
The presence of volatile metal oxides that remain in the vapor
phase at gas-stream temperatures between 315° to 430° C (600° to
800° F), but which condense in the range of 120° to 300° C (250° to
570° F) and below necessitates gas cooling to achieve efficient removal
of particulate matter emissions from reverberatory furnace offgases.
This was confirmed by particulate matter emission tests at the reverbera-
tory furnace ESP outlets of four domestic copper smelters. These data
indicate that particulate matter removal efficiency, as measured by
EPA Method 5, decreases to less than 50 percent if the reverberatory
furnace offgas stream is not cooled to 110° C (230° F) or less prior to
the control device.
In summary, both fabric filters and ESP's are considered
demonstrated control techniques for control of particulate matter
emissions from reverberatory furnace offgases.
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CAPACITY EXPANSION AT EXISTING SMELTERS
Standards of performance apply to new or modified sources of air
pollution. At the time of promulgation of the existing standard, the
definition of "modification" was amended by authorizing a "bubble"
under which sources of air pollution could alter facilities within the
source to increase capacity and not be considered "modified" if total
emissions from the source did not increase. The analysis of the
impact of the existing standard on the ability of domestic copper
smelters to expand production was based on the use of this "bubble."
This amendment to the definition of modification was litigated, however,
and rejected by the court [ASARCO v. EPA 578 F.2d.319 (1978)].
Under the current modification provisions, which apply to all
standards of performance, many physical or operational changes to an
existing facility are considered modifications. A domestic copper
smelter may expand capacity and not be subject to the modification
provisions if the cost of the physical or operational change as a
percentage of the original cost of the facility exceeds the annual
guideline repair allowance specified in the latest edition of "Internal
Revenue Service Publication 534." In addition, a facility may expand
capacity and not be subject to the modification provision if the
offgas stream from the facility is partially controlled so that there
is no increase in emissions from the facility.
Traditionally, domestic primary copper smelters have satisfied
increased demand by expanding existing facilities. Generally, the
capacity of the smelting furnace is the primary factor limiting
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production at a copper smelter. Roaster and converter capacities
normally exceed that of the smelting furnace and generally can accom-
modate increased throughputs of up to 20 percent.
To analyze the impact of the existing standard on the ability of
domestic copper smelters to expand production, a number of expansion
scenarios (i.e., an expansion option coupled with an alternative
control technique to achieve preexpansion levels) for each domestic
smelter configuration were identified. The expansion options selected
include the use of oxygen enrichment, oxy-fuel burners, tHe conversion
of existing green-charge smelting furnaces to calcine charge (i.e.,
use of roasting at reverberatory and electric furnaces that do not
currently employ roasting), and the replacement of reverberatory
furnaces with flash furnaces. Capacity expansions for these options
range from as little as 10 to 20 percent to as much as 100 percent.
Emission controls selected for the expansion scenarios include
the application of FGD systems, offgas stream blending, and sulfuric
acid plants. In scenarios involving reverberatory furnaces, a suf-
ficient fraction of the reverberatory furnace weak S02 offgas stream
is treated by the control system to ensure that emissions from the
furnace following expansion are equal to or less than emissions from
the furnace prior to expansion. For scenarios in which only strong
S02 offgas streams are involved, the strong streams are treated directly
in a sulfuric acid plant. Increased emissions from existing converters
and/or roasters are treated in the same control facility following the
expansion as they were before the expansion. Emissions from new
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converters and/or roasters are treated in a sulfuric acid plant. A
detailed description of the expansion scenarios analyzed is included
in the Background Information Document (BID).
FUGITIVE EMISSIONS
The existing standard does not limit fugitive emissions from
primary copper smelters. Emission tests at several domestic smelters
indicate that multihearth roasters and converters are the major sources
of particulate matter emissions, while copper converters are the major
source of S02 emissions.
Capture of S02 and particulate matter fugitive emissions, with
release of these emissions to the atmosphere through "tall" stacks, is
generally necessary at new smelters to comply with State, local, and
Occupational Safety and Health Administration (OSHA) workplace and
ambient air requirements. Capture of these fugitive emissions results
in a high volume of gas with low concentrations of particulate matter
and S02. Control systems such as ESP's and fabric filters, which are
not necessarily required by State or local regulations, are available
for the removal of the particulate matter from these gas streams.
Systems for removal of S02, however, have not been demonstrated.
Consequently, analysis of the alternatives for control of fugitive
emissions from copper smelters focused on control of particulate
matter emissions.
Calcine discharge and transfer are the primary sources of fugitive
particulate matter emissions from multihearth roaster operations.
Calcine is normally discharged from the bottom of the roaster and
distributed through a hopper to vehicles (larry cars) for transportation
19
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to the smelting furnace. Various systems of enclosing the hopper and
larry car coupled with local hoods have been used to capture fugitive
emissions. Visible emission observations of systems now in use for
the capture of fugitive emissions from calcine discharge operations at
four domestic copper smelters indicate that these systems have a
capture efficiency of about 90 percent.
Converter fugitive emissions occur during converter charging,
skimming, pouring, and blowing operations. During the first three
operations, the mouth of the converter is no longer under the primary
hood used to capture process emissions and, as a result, significant
amounts of emissions are discharged to the atmosphere. During blowing
operations, substantial quantities of emissions escape from around the
primary hood. Two systems have been demonstrated for capture of these
converter fugitive emissions: air curtain/secondary hood and building
evacuation (general ventilation).
An air curtain and secondary hood system for capture of converter
fugitive emission is currently in use at a Japanese copper smelter.
Visible emission observations evaluating the performance of this
system indicate a capture efficiency of about 90 percent. In addition,
an air curtain and secondary hood system is currently being installed
at one converter at a domestic copper smelter. The system will be
undergoing testing and evaluation during 1983. If the outcome of
these tests indicates the system is successful in capturing fugitive
emissions, similar systems may be installed on the other converters
at this smelter.
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A building evacuation system is currently being used at one
domestic copper smelter to capture fugitive emissions from the converter
aisle. Based on visual observations of the system, engineering judgment
indicates that this system has a capture efficiency of about 95 percent.
Regardless of the capture system used, removal of particulate
matter emissions from the fugitive gas streams prior to discharge to
the atmosphere requires the use of either an ESP or a fabric filter.
Tests on the fabric filter serving the building evacuation system
mentioned above indicate a 99-percent removal of particulate matter
from the captured fugitive gas stream. Tests conducted on the fabric
filter serving the multihearth roaster calcine discharge at one of the
domestic copper smelters mentioned earlier also indicated a 99-percent
removal of particulate matter from the captured fugitive gas stream is
achievable.
No test data are available on control of particulate matter
contained in the fugitive gas stream captured by an air curtain/
secondary hood system on a converter. Particulate matter grain
loading in this stream, however, would lie between that of the
converter fugitive gas stream captured by a building evacuation system
and that of a roaster calcine discharge fugitive gas stream.
Consequently, the use of a fabric filtration system on fugitive
particulate matter emissions captured by an air curtain/secondary hood
should also achieve 99.0 percent control.
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ECONOMIC ANALYSIS
Basis of Analysis
As international markets and trade have grown and expanded,
foreign copper smelters, particularly those in Japan, have begun to
compete with domestic smelters for sources of copper ore concentrates.
Perhaps the most vivid example of this competition is the current
agreement between Anaconda Company and a consortium of Japanese copper
smelting companies to ship copper ore concentrates previously
processed at Anaconda's smelter in Montana to Japan for processing.
This agreement illustrates the point that if the cost of producing
copper in domestic smelters rises above the cost of producing copper
in foreign smelters, the domestic copper industry could begin to focus
on the mining and milling of copper ores. Concentrates would then be
shipped to foreign smelters for processing rather than to domestic
smelters. The cost of producing copper in foreign smelters, therefore,
can be used as a yardstick against which to measure the impact of the
increased costs of producing copper at new or modified domestic smelters
due to compliance with the standard of performance.
The Japanese currently have established themselves as the lowest
cost copper producers in the world. Consequently, their costs establish
the yardstick or "trigger" beyond which domestic smelters would no
longer be able to compete with Japanese smelters for the processing of
domestic copper ore concentrates.
Table I summarizes the best estimates available to EPA of key
components of Japanese smelting and refining costs for the case in
which copper ore concentrates are purchased in the United States and
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TABLE I. KEY COMPONENTS OF JAPANESE
SMELTING AND REFINING COSTS
(t/kg)
Freight for concentrate
Smelting
Refining
Freight to United States
Profit margin
29.5
23.5
17.6
5.9
6.5
Total cost plus profit margin
83.0
shipped to Japan for smelting and refining with the resulting copper
being returned to the United States for sale. The 83.0
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Most domestic smelters discharge weak S02 streams through "tall"
stacks, suspending or curtailing operations when necessary to comply
with the NAAQS for S02. While existing copper smelters will eventually
have to control weak S02 offgas streams to comply with the Clean Air
Act, the current status of S02 control at existing copper.smelters was
selected as the "baseline" against which to assess the impact of the
existing standard of performance. Therefore, the baseline for the
economic analysis assumes full control of all strong S02 offgas
streams and capture, but no control, of all weak S02 offgas "streams.
Although this overstates the impact of the existing standard of
performance, it clearly represents an absolute minimum, in terms of
emission control, that any new, modified, or reconstructed copper
smelter would have to achieve in the absence of the standard of
performance.
Deletion of Reverberatory Furnace Exemption
The cost of smelting high-impurity materials in a new greenfield
reverberatory furnace smelter under the baseline (i.e., control of S02
emissions from the multihearth roaster and converter, no control of
S02 or particulate matter from the reverberatory furnace, and no
particulate matter control on captured converter fugitive gas streams)
is estimated to be 97.8
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The use of oxy-fuel burners on the reverberatory furnace at a new
greenfield smelter to increase the concentration of S02 in the
reverberatory furnace offgas followed by gas stream blending and a
sulfuric acid plant is the most cost-effective and, coincidentally, the
least-cost S02 control alternative for controlling S02 emissions from
the reverberatory furnace. If the exemption is removed, control of
S02 in the reverberatory furnace offgas stream would add 2.8
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expenditure and emissions from the reverberatory furnace increased.
An examination of the various alternatives for expanding the capacity
of reverberatory furnace smelters processing high-impurity materials
indicates that capacity expansions of about 20 percent are technically
feasible through the use of oxygen enrichment of the combustion air in
the reverberatory furnace.
If the exemption is retained, the costs of the incremental copper
production associated with a 20-percent expansion at an existing
reverberatory furnace smelter processing high-impurity materials under
the baseline would be about 59.5
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copper. Cost-effectiveness for these controls is $126/Mg ($115/ton)
of particulate matter removed. In all three cases--no control, partial
S02 control, and partial particulate matter control of emissions from
the reverberatory furnace—the cost of the incremental copper production
remains less than the trigger. Deletion of the exemption for reverbera-
tory furnaces processing high-impurity materials, therefore, would
have little impact on the expansion capability of the domestic copper
smelting industry to process high-impurity materials.
With or without the exemption, the copper production costs of new
reverberatory furnace smelters processing high-impurity materials are
not competitive on world markets. Only small expansions of up to
20 percent at existing reverberatory furnace smelters processing
high-impurity materials are technically feasible. These expansions
are competitive on the world market and would remain so whether the
exemption were retained or deleted.
Impact of Existing Standard on Expansion Capacity
The impact of the existing standard on the expansion capability
of the domestic copper smelting industry to process high-impurity
materials is discussed above. Consequently, the following discussion
focuses on the impact of the existing standard on the expansion
capability of the domestic copper smelting industry to process
low-impurity materials.
New smelters. Three basic smelting technologies are available
for new smelter construction: reverberatory furnaces; electric
furnaces; and flash furnaces. Because of the limited availability of
the large blocks of electric power and the high costs of this power,
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electric furnace smelting generally is not considered a viable option
for new smelters. In addition, a substantial cost differential exists
between flash furnace smelting and reverberatory furnace smelting
(i.e., 61.0
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smelter capacity: roaster-reverberatory furnace-converter, 43 percent;
reverberatory furnace-converter, 24 percent; electric furnace-converter,
9 percent; and flash furnace-converter, 24 percent.
Roaster-reverberatory furnace-converter smelting. Capacity
expansions of up to 20 percent are technically feasible at smelters of
this configuration through the use of oxygen enrichment 'of the
combustion air in the reverberatory furnace. In addition, capacity
expansions of up to 100 percent are technically feasible by replacing
a reverberatory furnace and multihearth roasters with a flash furnace,
and capacity expansion of up to 60 percent are technically feasible by
replacing a reverberatory furnace and fluid-bed roasters with a flash
furnace.
The incremental copper production costs associated with a
20-percent expansion, under the baseline, range from 42.4
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reverberatory furnace offgas stream to avoid the modification provision
and can be attained at a cost-effectiveness of $47/Mg ($43/ton) to
$166/Mg ($151/ton) of S02. The cost-effectiveness for reverberatory
furnaces with fluid-bed roasters is at the lower end of the scale and
the cost-effectiveness for smelters with multihearth roasters is at
the higher end.
The cost of partial S02 control of the reverberatory furnace for
20 percent expansion ranges from 2.1
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Reverberatory furnace-converter smelting. Capacity expansions of
up to 20 percent are technically feasible at smelters of this configura-
tion through the use of oxygen enrichment of the combustion air in the
reverberatory furnace. In addition, capacity expansions of up to
100 percent are technically feasible by replacing the reverberatory
furnace wit'h a flash furnace.
The incremental copper production costs for the 20-percent
expansion scenarios under the baseline are about 57.7
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costs associated with the 50- and 100-percent expansion scenarios are
well below the trigger. Therefore, the existing standard does not
preclude capacity expansions at existing reverberatory furnace-converter
smelters.
Electric furnace-converter smelting. This smelter configuration
can be expanded by up to 40 percent by converting the smelting furnace
to calcine charging through the use of roasting. The incremental
copper production costs associated with this expansion scenario under
the baseline are 88.1
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or reverberatory furnace smelting due to the substantial cost advantages
associated with flash smelting. Although flash smelting employs
copper converters, this process does not require roasters. Consequently,
fugitive emission control at new smelters will focus on copper converters.
Control systems are available for the control of fugitive particulate
matter emissions from converters at new flash furnace smelters at a
cost effectiveness of $1,970/Mg ($l,790/ton) of particulate matter
removed. Including the cost of a system to control particulate matter
from fugitive converter offgases would increase smelting costs at a
new flash furnace smelter by 1.3
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have fallen below the 1973 level and have shown no signs of returning
to it. The absence of growth in copper smelter production as a result
of a flat demand curve for copper in recent years suggests that demand
is not likely to increase significantly over the next 5 years.
Current domestic copper smelting capacity in place is about
1,700,000 Mg of blister copper per year. Possible shutdowns through
1988 could amount to about 225,000 Mg. Announced expansions through
the same period amount to about 25,000 Mg. The net effect of these
changes would leave the domestic copper smelting industry with a
capacity of about 1,500,000 Mg in 1988. Average copper production
over 5 previous typical years, not including the periods of low
production due to the 1980 strike and the 1982 recession, was
1,400,000 Mg. Thus, it appears that, barring unforeseen upward
increases in demand, the demand for copper over the next 5 years can
be met by existing domestic copper smelting capacity without the need
for smelter expansion.
Reverberatory Furnace Exemption
As previously discussed, the cost of producing copper from high-
impurity materials at a new reverberatory furnace smelter exceeds the
^r>
trigger cost by about ISt/kg (7
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at a cost substantially below the trigger cost. Deletion of the
reverberatory furnace exemption would increase the cost of producing
copper slightly but not to the extent that it would exceed the trigger
cost.
The primary sources of domestic high-impurity materials are
copper ores mined in the Northwest and lead smelter by-products. Over
the past two decades, growth and expansion of copper ore mining capacity
has concentrated in the Southwest. Most of the copper ores mined in
the Southwest, however, are characterized by low impurity levels.
Because future growth and expansion of copper ore mining capacity will
probably continue to occur in the Southwest, the copper ore concentrates
produced by growth or expansion in copper ore mining will most likely
contain low impurity levels. In addition, the domestic primary lead
industry projects a decline in production, with a resulting decrease
in lead smelter by-products that could be processed in domestic copper
smelters. Thus, there appears to be no need for additional smelter
capacity to process high-impurity materials.
With no anticipated increase in demand for copper over the next 5
years and, more specifically, no anticipated need for additional
capacity to process high-impurity materials, the question of whether
to delete or retain the exemption for reverberatory furnaces processing
high-impurity materials appears academic. Therefore, it appears
appropriate to leave the standard as it is and reexamine the question
of the exemption during the next review of the standard.
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Smelter Expansion
Although there is no increase in the demand for copper expected
over the next 5 years, any unexpected increases in demand through
1988 could be satisfied by an expansion of existing smelting capacity.
As discussed above, the existing standard allows for the expansion of
existing smelters through the use of oxygen enrichment of the
combustion air in the smelting furnace or replacement of existing
reverberatory furnaces with flash smelting furnaces at smelters
processing low-impurity materials. Domestic smelting capacity could
be increased from 200,000 Mg to 900,000 Mg through the use of these
techniques. As a result, potential annual smelting capacity at
existing smelters ranges between 1,700,000 and 2,400,000 Mg, well above
the projected demand of about 1,400,000 Mg/yr over the next 5 years.
The existing standard also imposes no constraints on expansion of
domestic smelting capacity through construction of new greenfield
smelters. Consequently, there is no need to revise the existing
standard to accommodate expansion of domestic copper smelting capacity.
Fugitive Particulate Matter Emissions
Revising the existing standard of performance to require control
of fugitive particulate matter emissions from multihearth roasters and
copper converters would have little or no impact on the cost of
producing copper. In none of the cases examined would the cost of
c
fugitive particulate matter control cause copper production costs to
exceed the trigger costs.
Fugitive particulate matter emission control technology is
demonstrated. Fugitive particulate matter emission capture technology,
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however, is still evolving. Over the past 5 years, fugitive particulate
matter emission capture systems have been installed on copper converters
at a few domestic smelters to evaluate their performance. To date,
however, these systems generally have failed to live up to expectations.
More recently, a new fugitive particulate matter emission capture
system, modeled on a design that has been employed successfully at a
number of Japanese copper smelters has been installed for testing on
one copper converter at a domestic smelter. This system holds great
promise for capture of fugitive particulate matter emissions and its
performance will be evaluated in a joint program between EPA and the
smelter during 1983. Until the tests are completed and evaluated, no
basis is available for developing emission limits. While design
specifications probably could be developed at this time, equipment
specifications tend to constrain innovation and inhibit cost
improvement. As a result, standards based on equipment design
specifications generally are considered as a last resort.
For this reason and because of the lack of growth projected for
the domestic copper industry over the next 5 years, it is considered
appropriate to defer incorporating fugitive particulate matter emission
limitations until the next review of the standard. At that time it is
anticipated that sufficient data will be available to support the
development of specific limits for fugitive particulate matter emissions
from primary copper smelters.
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