United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-82-058 August 1982
Project Summary
Environmental Considerations
for Emerging Copper-Winning
Processes
H. Dolezal, M. Hayashi, G. Potter, and J. O. Burckle
The weak SO2 emissions from
primary copper have been and con-
tinue to be the barrier to achieving SO2
emission limitations in smelter local-
ities. The ambient air quality standards
are obtained only through the SCS
(supplementary control system), that
is, by production curtailment in lieu of
constant emission controls. This doc-
ument, one of a series that addresses
the weak SO2 emission problem, was
undertaken to examine capabilities of
several alternative smelting and hydro-
metallurgical metal-winning technol-
ogies for the production of copper.
The investigation concentrated on the
comparison of the degree of sulfur
containment, energy consumption/
savings and costs of many newer,
commercially employed pyrometallur-
gical smelting processes in combina-
tion with various types of final controls
for sulfur containment. The emerging
technologies for pyro- and hydrometal-
lurgical processes are briefly discussed
but are not analyzed in great detail
owing to the lack of basic data in the
open literature.
This Project Summary was devel-
oped by EPA's Industrial Environmen-
tal Research Laboratory, Cincinnati,
OH, to announce key findings of the
research project that is fully docu-
mented in a separate report of the
same title (see Project Report ordering
information at back).
Introduction
The objective of this study was to
depict the potential of modern copper-
winning processes, to contribute to the
solution of the weak sulfur dioxide (S02
problem, and to identify potential attri-
butes or barriers to employing these
processes within the industry. The
evaluation primarily emphasized air
pollution potential, energy require-
ments, and process economics. Thirteen
processes were investigated in the first
project phase (Table 1).
As the study progressed, the main
emphasis became the evaluation of the
energy and economic aspects of the five
most developed pyrometallurgical pro-
cesses, specifically the electric furnace,
Noranda process, Outokumpu and INCO
flash furnace processes, and variations
on the conventional reverberatory fur-
nace practice for SOz control. This
approach became necessary, as the
information required for analysis of the
emerging hydrometallurgical and pyro-
metallurgical processes was not avail-
able. It was found that none of the
emerging hydrometallurgical processes
have been developed to the extent that
meaningful analyses could be per-
formed. It was also found that some of
the newer smelting methods such as
the three-furnace, oxygen-enriched re-
verberatory, converter smelting, top
blown rotary converter, and DMA SOz
processes have not yet been widely
-------
Table 1. Processes Evaluated
Phase I - Review
Pyrometallurgical Processes
Hydrometallurgical Processes
Hecla-EIPaso
Arbiter
Cymet
Duval "CLEAR"
Mitsubishi Three-Furnace System
Top Blown Rotary Converter (TBRC)
Converter Smelting
Oxygen Enriched Reverberatory Smelting
Reverb Smelting with DMA SOz Process
Electric Furnace Smelting
Outokumpu Flash Furnace
INCO Flash Furnace
Noranda Furnace
Phase II - In-Depth Evaluation
Conventional reverberatory process (five scenarios)—(1) no SOz control. (2) with
reverberatory gas vented up the stack and converter gas going to an acid plant, (3) with
converter gas going to an acid plant and reverberatory gases going to a Bureau of
Mines citrate process plant. (4) with both converter and reverberatory gases going to a
Bureau of Mines citrate process plant, and (5) using a roaster with both roaster and
converter gases going to an acid plant.
Electric arc furnace smelting (two scenarios)—(1) SQz control by an acid plant, and (2)
SOz control by a Bureau of Mines citrate process plant.
Noranda process (three scenarios)—(1) SOz control by an acid plant, (2) SOz control by
a Bureau of Mines citrate process plant, and (3) SOz control by direct reduction.
Outokumpu flash smelting (two scenarios)—(1) using preheated air with SOz control
by an acid plant, (2) using preheated air with SOz control by a Bureau of Mines citrate
process plant.
INCO flash smelting (two scenarios)—(1) using oxygen with SOz control by an acid
plant, and (2) using oxygen with SOz control by direct reduction.
used, and information was insufficient
for analysis. Quantitative data on emis-
sions and effluents in the published
literature were inadequate to account
for the distribution of minor elements in
any of the processes. Therefore, the
field of candidate processes quickly
narrowed to the five, based upon the
availability of detailed technical and
economic data. A total of 14 scenarios
were investigated for these five pro-
cesses, which are in commercial use
(see Table 1). Reverberatory smelting
with no controls was the scenario used
for the base case.
Study Methodology
All of the processes evaluated were
similar, in that they were pyrometallur-
gical operations that produced blister
copper which was cast into anodes and
electrorefined. To enable a direct com-
parison of the various processes, each
was assumed to produce 100,000 tons
of electrorefined copper per year, start-
ing from a hypothetical standard con-
centrate, the composition of which is
given in Table 2. This hypothetical
concentrate is a composite based on
feed materials used by smelters in the
Western United States, excluding cus-
tom smelters that treat complex ores.
The basis of the hypothetical composi-
tion is given in an Appendix to the
report.
Energy requirements for the produc-
tion of a ton of copper by each of the
processes evaluated were estimated
Table 2. Chemical Composition of
Standard Chalcopyrite Con-
centrate (Dry Basis)*
Constituent Composition, pet
Cu 27.0
Fe 27.0
S 33.5
SiOz 9.0
CaO 0.5
Other^ 3.0
*Analysis of the standard concentrate
was arrived at by averaging analyses of
actual chalcopyrite concentrates used
at a number of commercial smelters.
^"Other" includes oxygen, MgO, A/zOa,
and minor elements.
with the help of reports on energy use
patterns prepared by Battelle Columbus
Laboratories. Calculation methods equiv-
alent to those used in the reports were
used to make an itemized breakdown of
total energy consumed in generating
utilities and of the energy required for
the raw materials. For raw materials,
this included energy needed for mining
and ore beneficiation, for smelting and
refining of metals, for other raw mate-
rials used as part of the production
process, and for transportation to pro-
cessing and refining plants.
The material balance, energy require-
ments, and cost estimate calculations
were produced by a computer estima-
ting program, developed by the Bureau
of Mines under a separate program,
which incorporated historic cost infor-
mation from Bureau files. The costs
reported for the evaluations performed
in this project were updated to 1980.
Flowsheets for each process evalu-
ated were developed. A material balance
for each scenario was then prepared.
The material balance indicates constant
values for the S02 content of smelter
gases and represents the average flow
for these fluctuating streams. Material
balance flowsheets for the
processes show how the major elements
in the concentrates, fluxes, and prod-
ucts are distributed. Included after all
smelting operations are electrostatic
dust precipitators in which an estimated
10 percent dilution of the gas occurs
because of leakage. Whenever available,
information concerning the minor ele-
ments is given in the text.
Cost estimates were prepared for
modifications of the smelting processes
-------
for the purpose of making relative
comparisons of capital and operating
costs. For this reason, some of the minor
operations normally conducted in a
smelter, such as recycle of dust and
scrap, have been omitted to simplify the
flowsheets and calculations. These esti-
mates do not include any interest or
other charges for invested capital or
allowances for federal taxes and profit.
Also included as part of the economic
evaluation are estimates of the total
energy requirements.
Findings and Conclusions
Estimated costs and energy require-
ments were prepared for recovering
copper from chalcopyrite concentrates
by some 14 scenarios of 5 basic pro-
cesses. The resulting estimates are
presented in Tables 3 and 4. The evalu-
ation shows that sulfur retentions
greater than 90 percent are technically
achievable and that the elimination of
the weak SO2 stream by conversion to
modern smelting furnaces combined
with acid plant control are potentially
the most effective method for S02
control and energy savings, while also
being the most cost effective.
The costs, in mid-1980 dollars, range
from a low of 34.6 cents per pound for a
conventional smelter with no S02 con-
trols to 49.4 cents per pound for a
conventional smelter using the USBM
citrate process to treat both the rever-
beratory and converter gases. If the
conventional reverberatory smelter with
no SOa controls is used as a standard for
comparison, the various systems for
controlling emissions will be found to
increase capital investment"over a range
of 30 to 34 percent and costs for
producing copper over a range of 5 to 43
percent. The lowest cost smelter with
SOz controls was an INCO flash opera-
tion with an acid plant (36.4 cents per
pound).
When smelters with acid plants for
SOz control are compared using a
reverberatory smelter with an acid plant
as a standard, the Noranda, Outokumpu,
and INCO versions require about 30
percent less energy. Sulfur dioxide
controls based on the USBM citrate
process or on direct reduction will
increase energy requirements by factors
ranging from 1.5 to 2.0.
Because of variations in local condi-
tions, the effect of byproduct credits was
not included in the computer program.
The actual overall cost would depend on
the availability of a market, either inter-
nal or external, for the acid and/or
sulfur produced. In most cases, where
the use or sale of byproducts is possible,
costs would be reduced by some inde-
terminate amount that would depend on
local conditions. It should be recognized,
however, that in instances where little
or no use or sale of byproducts is
possible, costs would be increased
owing to the cost of storage or disposal.
In the cases where neutralization of
sulfuric acid is necessary, the disposal
cost could make a significant change in
the economics of the process. In these
evaluations no credits or penalties were
applied for disposal of byproducts, so
that all the processes could be compared
on the same basis. However, a rough
comparison of these effects was made
based on assigned values of $20 per ton
for sulfuric acid and $100 per ton for
elemental sulfur. The effect of these
byproduct values is shown in Table 5. As
expected, byproduct values shift the
unit production costs of copper to a
lower range of 33 to 43.8 cents per
pound, but they also have a leveling
effect, in that costs for the Noranda
smelter with an acid plant and the INCO
and Outokumpu flash smelter with acid
plants were in the lower end of the cost
range (33.4 to 33.6 cents per pound).
When a reverberatory smelter without
pollution controls is used as a standard
for comparison with alternative pro-
cesses, the following conclusions are
reached:
• unit production costs in cents per
pound of copper, without byprod-
uct credit, will increase from 34.6
to a range of 36.4 to 49.4, with an
INCO flash smelter in an acid plant
giving the lowest increase,
• estimates for byproduct credit shift
unit production costs to a lower
range of 33.0 to 43.8 cents, with
INCO, Noranda, and Outokumpu
flash smelters in acid plants giving
cost in the lower end of the range,
• sulfur retention increased from
2.4 percent to a range of 64.5 to
96.2 percent, with both an electric
furnace in an acid plant and a
reverberatory smelter treating re-
verberatory and converter gases
in a citrate plant giving the highest
retention, and
• energy requirements in million
Btu per ton copper are 38.46 for
the standard and range from 30.13
to 90.67, with both the Noranda
and INCO smelters in acid plants
using the least energy.
-------
Table 3. Estimated Capital Cost, Operating Cost, and Energy Requirements*
Process
Noranda process
Do.
Do.
Outokumpu flash
Do.
INCO flash
Do.
Electric smelting
Do.
Reverberatory
Do.
Do.
Do.
Do.
Type of
SOz Control
Acid plant
Citrate plant
Direct reduction
Acid plant
Citrate plant
Acid plant
Direct reduction
Acid plant
Citrate plant
None
Converter gas to
acid plant
Converter gas to
acid plant,
reverberatory gas
to citrate plant
Converter and
reverberatory gases
to citrate plant
Roaster and
converter gases to
acid plant
Fixed
Capital,
Dollars
305,118.000
341,002,000
304.701.000
300,992.000
330,456.000
286,086.000
311,605,000
300,529,000
315,140,000
261,028,000
313,267,000
348,784,000
334,686,000
307,077,000
Working
Capital,
Dollars
16,613,000
21,185,000
20,979,000
16,639,000
21,320,000
16,426,000
22,049.000
18,211,000
22,027,000
15,679,000
18,250,000
21,204,000
22,768,000
17,918.000
Annual
Operating
Cost,
Dollars
74,101,000
92,978,000
91,550,000
74.122,000
93,022,000
72,891,000
96.065,000
80,021,000
95.350.000
69,193,000
80,747,000
93,241,000
98,725,000
79,257,000
Energy
Requirement,
Million
Btu/ton Cu
30.13
66.90
85.14
30.88
68.07
33.19
90.67
44.97
81.69
38.46
43.56
58.38
81.67
41.93
'Estimates are based on 1980 costs without allowance for escalation during construction period and do not include interest on
invested capital, federal taxes, or prof it. Capacity basis is 100,000 tons per year of electrorefined copper.
-------
Table 4. Summary of Processes Evaluated*
Process
Noranda process
Do,
Do.
Outokumpu flash
Do.
INCO flash
Do.
Electric smelting
Do.
Reverberatory
Do.
Do.
Do.
Do.
Type of
SOz Control
Acid plant
Citrate plant
Direct reduction
Acid plant
Citrate plant
Acid plant
Direct reduction
Acid plant
Citrate plant
None
Converter gas to
acid plant
Converter gas to
acid plant.
reverberatory gas
to citrate plant
Converter and
reverberatory gas
to citrate plant
Roaster and
converter gas to
acid plant
Total
Sulfur
Retention^
437.8
437.5
398.0
364.6
364.3
367.2
333.8
368.3
357.3
9.1
246.9
368.3
367.8
292.5
Sulfur
Recovered,^
pet
95.6
95.5
86.9
95.9
95.8
95.9
87.2
96.2
93.3
2.4
64.5
96.2
96.1
76.4
Byproduct Produced,
tpd
Sulfuric
Acid
1.269.4
0
0
1,050.6
0
1,054.0
0
1.O43.2
0
0
690.8
690.8
0
823.0
Sulfur
0
410.5
375.2
0
339.8
0
311.6
0
337.1
0
0
114.1
337.O6
0
Estimated
Overall Cost,
cents/lb/Cu
(No Byproduct
Credit)
37.1
46.5.
45.8
37.1
46.5
36.4
48.0
40.0
47.7
34.6
40.4
46.6
49.4
39.6
* Estimates are based on 1980 costs without allowance for escalation during construction period and do not include interest on
invested capital, federal taxes, or profit. Capacity basis is 100,000 tons per year electrorefined copper.
^TotaI sulfur retention includes sulfur in HtSO*, CaSO* slag, tailings, sulfur product,
-------
Table 5. Estimated Effect of Byproduct Credit on Operating, Cost
Process
Noranda process
Do.
Do.
Outokumpu flash
Do.
INCO flash
Do.
Electric smelting
Do.
Reverberatory
Do.
Do.
Do.
Do.
Type of
SOZ Control
Acid plant
Citrate plant
Direct reduction
Acid plant
Citrate plant
Acid plant
Direct reduction
Acid plant
Citrate plant
None
Converter gas to
acid plant
Converter gas to
acid plant,
reverberatory
gas to citrate
plant
Converter and
reverberatory
gas to citrate
plant
Roaster and
converter gas
to acid plant
Annual
Operating
Cost.
Dollars
74,101,000
92,978.000
91.550,000
74,122,000
93,022,000
72,891.000
96.065.000
80.021.000
95.350,000
69.193,000
80.747,000
93,241,000
98.725,000
79.257,000
Byproduct*
Credit,
Dollars
6,956.000
1 1.248,000
10,281,000
6.934.000
11.213,000
6,956,000
10.283,000
6.885.000
11,124,000
-
4,559,000
8,325,000
1 1, 123,OOO
5.432,000
Annual
Operating
Cost With
Byproduct
Credit,
Dollars
67,145,000
81,730,000
81,259,000
67,188.000
81.809,000
65,935,000
85,782,000
73, 136,000
84,226,000
69, 193,000
76,188,000
84,916,000
87,602.000
73.825.000
Estimated
Overall Cost,
Cents/ Ib Cu
No
Credit
37.1
46.5
45.8
37.1
46.5
36.4
48.0
40.0
47.7
34.6
40.4
46.6
49.4
39.6
With
Credit
33.6
40.9
40.6
33.6
40.9
33.0
42.9
36.6
42.1
34.6
38.1
42.5
43.8
36.9
Reduction
In Cost
Cents
3.5
5.6
5.2
3.5
5.6
3.4
5.1
3.4
5.6
0
2.3
4.1
5.6
2.7
Percent
9.4
12.0
11.4
9.4
12.0
9.3
10.6
8.5
11.7
0
5.7
8.8
11.3
6.8
*Based on $20.00 per ton for HzSO* and $100.00per ton for elemental sulfur for a production basis of 100.000 tons per year o)
electrorefined copper.
H. Dolezal, M. Hayashi, and G. Potter are with the U.S. Bureau of Mines, Salt
Lake City Research Center. Salt Lake City, UT; the EPA author J. O. Burckle
(also the EPA Project Officer, see below) is with the Industrial Environmental
Research Laboratory, Cincinnati, OH 45268.
The complete report, entitled "Environmental Considerations for Emerging
Copper-Winning Processes," (Order No. PB 82-227-794; Cost: $12.OO.
subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati. OH 45268
*USGPO: 1982 — 559-092/0474
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