U.S. DEPARTMENT OF COMMERCE
National Technical Information Service
PB-280 377
Emission Factors and Emission Source
Information for Primary and
Secondary Copper Smelters
Pacific Environmental Services, Inc, Santa Monica, Calif
Prepared for
Environmental Protection Agency, Research Triangle Park, N C
Dec 77
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EPA-450/3-77-051
December 1977
EMISSION FACTORS
AND EMISSION
SOURCE INFORMATION
FOR PRIMARY
AND SECONDARY
COPPER SMELTERS
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Waste Management
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
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NOTICE
THIS DOCUMENT HAS BEEN REPRODUCED
FROM THE BEST COPY FURNISHED US BY
THE SPONSORING AGENCY. ALTHOUGH IT
IS RECOGNIZED THAT CERTAIN PORTIONS
ARE ILLEGIBLE, IT IS BEING RELEASED
IN THE INTEREST OF MAKING AVAILABLE
AS MUCH INFORMATION AS POSSIBLE.
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EPA-450/3-77-051
EMISSION FACTORS
AND EMISSION SOURCE INFORMATION
FOR PRIMARY AND SECONDARY
COPPER SMELTERS
by
G.E. Umlauf and L.G. Wayne
Pacific Environmental Services, Inc.
1930 14th Street
Santa Monica, California 90404
Contract No. 68-02-1890
Task Order No. 3
EPA Project Officer: Arch McQueen
Prepared for
ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Waste Management
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
December 1977
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This report is issued by the Environmental Protection Agency to report
technical data of interest to a limited number of readers. Copies are
available free of charge to Federal employees, current contractors and
grantees, and nonprofit organizations - in limited quantities - from the
Library Services Office (MD-35), Research Triangle Park, North Carolina
27711; or, for a fee, from the National Technical Information Service,
5285 Port Royal Road. Springfield, Virginia 22161.
This report was furnished to the Environmental Protection Agency by
Pacific Environmental Services, Inc., 1930 14th Street, Santa Monica,
California 90404, in fulfillment of Contract No. 68-02-1890, Task Order
No. 3. The contents of this report are reproduced herein as received
from Pacific Environmental Services, Inc. The opinions, findings, and
conclusions expressed are those of the author and not necessarily those
of the Environmental Protection Agency. Mention of company or product
names is not to be considered as an endorsement by the Environmental
Protection Agency.
Publication No. EPA-450/3-77-051
11
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ACKNOWLEDGEMENT
Successful completion of this project depended upon the
cooperation of many individuals including, especially, personnel
of EPA Regional Offices and of the air pollution control agencies
of many states and of several cities and counties. We wish to
express our appreciation to all who participated, even though we
forbear to list their names because of the excessive length of
the roll.
111
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ABSTRACT
This document" constitutes the final report of a project,
carried out under U.S. EPA Contract No. 68-02-1890 (Task Order
No. 3), to upgrade emission factors and engineering management
information for primary and secondary copper smelters. The
main body of the report describes procedures and methodology
used in obtaining relevant information regarding these indus-
tries and the operational characteristics of process equipment
used therein. Related information regarding alloying and cast-
ing has been included in the description secondary copper smelter
processes, and information about emissions from similar furnaces
used in nonferrous foundry operations was also collected. New
information on source tests was coded for entry into the AEROS
SOTDAT files; newly identified sources were coded for entry in-
to NEDS, and information as to the precision of emission factors
was furnished for use in the SIEFA data base. New source clas-
sification codes (SCC's) were proposed for a number of processes.
Appendixes to this document are the following project de-
li verables: Appendixes A and B for inclusion in AP-42, "Compilation
of Air Pollutant Emission Factors," namely Section 7.3, Primary
Copper Smelting and Section 7.9, Secondary Copper Smelting and
Alloying; Appendix C, Primary Copper Smelting Process Compendium;
and Appendix D, Secondary Copper Smelting Process Compendium.
tv
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TABLE OF CONTENTS
Section Page
1.0 INTRODUCTION 1-1
1.1 Scope of Work 1-1
1.2 Task Description 1-1
1.3 Organization of Final Report 1-2
2.0 RESULTS AND CONCLUSIONS 2-1
2.1 Project Deliverables 2-1
2.2 Development of Emission Factors 2-1
3.0 DATA GATHERING 3-1
4.0 DATA ANALYSIS 4-1
4.1 Data Analysis Procedures 4-1
4.2 Emission Factors for Primary Smelter Processes . 4-6
4.3 Emission Factors for Participates From Furnaces
Used in Secondary Copper Smelting Processes ... 4-15
5.0 FUGITIVE EMISSIONS 5-1
5.1 Introduction 5-1
5.2 Primary Copper Smelters 5-1
5.2.1 Pollutants 5-1
5.2.2 Sources 5-3
5.3 Secondary Copper Smelters 5-6
5.4 Fugitive Emission Control 5-7
6.0 RECOMMENDATIONS FOR FURTHER SOURCE TESTING 6-1
6.1 Precision of Emission Factors 6-2
6.2 Recommendations for Additional Testing 6-6
7.0 REFERENCES 7-1
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Section
APPENDIX A. SECTION 7.3, PRIMARY COPPER SMELTING
APPENDIX B. SECTION 7.9, SECONDARY COPPER SMELTING
AND ALLOYING
APPENDIX C. PRIMARY COPPER SMELTING PROCESS COMPENDIUM
APPENDIX D. SECONDARY COPPER SMELTING PROCESS
COMPENDIUM
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LIST OF ILLUSTRATIONS
v.
Figure Page
4-1 Check List for Emission Source Information 4-3
4-2 Typical Example of Formatted Test Results 4-5
LIST OF TABLES
Table Page
2-1 Emission Factors for Particulates From Secondary
Copper Smelting and Alloying Processes Without
Controls 2-2
2-2 Emission Factors for Sulfur Dioxide for Primary
Copper Smelting Processes Without Controls 2-5
2-3 Emission Factors for Particulates From Primary
Copper Smelting Processes Without Emission Controls . 2-7
4-1 Emissions From Converters in Primary Copper Smelters . 4-7
4-2 Emissions From Reverberatory Furnaces in Primary
Copper Smelters 4-10
4-3 Combined Emissions From Multiple-Hearth Roasters and
Reverberatory Furnaces in Primary Copper Smelters . . 4-12
4-4 Emission Factors for Smelter Processes Derived From
Published Literature 4-16
4-5 Emission Factors for Particulate Matter From Furnaces
Used in Secondary Copper Smelting and Alloying
Processes ' . 4-17
5-1 Possible Fugitive Emissions From Primary Copper
Smelters 5-2
5-2 Fugitive Emission Source, Quantity and Control .... 5-9
6-1 SIEFA Standard Deviations and Precision Factors for
Primary Copper Smelting Processes (Particulate
Emissions) 6-3
6-2 SIEFA Standard Deviations and Precision Factors for
Primary Copper Smelting Processes (Sulfur Dioxide
Emissions) 6-4
6-3 Primary Copper Smelting Processes for Which Emission
Factors Should be Developed 6-7
vii
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1.0 INTRODUCTION
This report describes the methodology followed and the results
achieved by Pacific Environmental Services, Inc. (PES) pursuant to
EPA Contract No. 68-02-1890, Task Order No. 3, initiated in October
1976.
1.1 SCOPE OF WORK
The scope of work for this project called for an intensive
engineering evaluation of air pollutant emission sources at primary
and secondary copper smelters in the United States. It required
collection of reference data for primary smelters and for the
secondary smelting and alloying industry, as well as the develop-
ment of emission factors for major types of air-pollution emitting
operations and equipment.
1.2 TASK DESCRIPTION
Deliverables contemplated by the contract included a series of
documents dealing with process descriptions and emission factors for
primary and secondary copper smelter emission sources. These docu-
ments were to be prepared in formats consistent with those of the
following publications:
1. AP-42, "Compilation of Air Pollutant Emission Factors"*
2. "Engineering Support Manual for NEDS Users"(Ref. 2)
3. AP-42, Appendix C, Source Classification Codes
In addition, machine-readable data inputs were required for
updating AEROS component data systems: SOTDAT, NEDS, and SIEFA.
Subtasks designed for the implementation of the work were as
fol1ows:
Reference 1, hereafter referred to as "AP-42."
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1. Preparation of a list of information sources, including
governmental agencies, research organizations, consultants,
and nonferrous smelter industry experts, and preparation
of a bibliography.
2. Contacting the information sources to obtain information
on process descriptions for both primary and secondary
smelters and documented point source emissions data both
for criteria pollutants and for certain other non-criteria
pollutants, including arsenic, cadmium, lead, beryllium,
boron, and antimony. The best available Information on
fugitive emissions was also to be obtained.
3. Analysis of the data to determine emission factors and the
AEROS systems input elements.
1.3 ORGANIZATION OF FINAL REPORT
The remainder of this report consists of five sections (Sec-
tions 2.0 to 6.0). In Section 2.0, results and conclusions emerging from
the study are briefly summarized. In Section 3.0, experience gained
in carrying out the data-gathering task is recounted and discussed.
In Section 4.0, the methodology of data analysis is reviewed and the
results summarized and discussed, in terms of emission factors
developed for both primary and secondary smelters. Section 5.0 reviews
findings related to the nature and sources of fugitive emissions in
smelter operations and discusses suggested means of control or abate-
ment of these emissions. Finally, recommendations regarding further
source testing to improve knowledge of smelter emissions, emission
factors, and the conditions affecting them are presented and dis-
cussed in Section 6.0.
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2.0 RESULTS AND CONCLUSIONS
This section summarizes the results obtained and conclusions
derived from the study of primary and secondary copper smelting
operations.
2.1 PROJECT DELIVERABLES
Products delivered to the Project Officer, in addition to this
report and monthly progress reports, include:
1. Process Compendiums for primary and secondary copper
smelters.
2, Sections for AP-42, "Compilation of Air Pollutants
Emission Factors," for primary and secondary copper
smelters.
3. Coding forms for information for AEROS component systems
SOTDAT and NEDS, regarding primary and secondary copper
smelters. (Since coding forms for SIEFA information
have not been designed, SIEFA information is provided
only in this report, Section 6.1).
2.2 DEVELOPMENT OF EMISSION FACTORS
The primary objective of this project was to develop new or
modified emission factors for particulates from primary and secondary
copper smelters and for sulfur dioxide from primary copper smelters.
The target approach was to obtain up-to-date reliable emissions test
data from as many sources as possible, to arrange these data into
logical form, and to calculate both uncontrolled and controlled
emission factors for as many source categories as seemed reasonable.
In the case of secondary copper smelting (sometimes called
refining), a single furnace operation is almost always involved.
Several types of furnaces are utilized in this industry, and emission
factors were developed for each of the five types covered in this
study. Table 2-1 shows both the emission factors for particulates
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Table 2-1. EMISSION FACTORS FOR PARTICIPATES FROM SECONDARY COPPER SMELTING AND ALLOYING
PROCESSES WITHOUT CONTROLS, COMPARED WITH PUBLISHED FACTORS (AP-42, BRASS AND
BRONZE MELTING FURNACES)*
Type of Furnace kg/MT Ib/ton
AP-42 This Study AP-42 This Study
Crucible 6 11 12 21
Cupola 37 0.002-120 73 0.003-240
Electric Induction 1 3.5 -10 2 7-20
^ Reverberatory 35 3-18 70 5-36
Rotary 30 5-150 60 10-300
*The ranges represent variations due to charge material. Average factors for
these differing materials are given In Section 4.0.
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as developed in this project and those currently given in AP-42.
Individual test results for each type of furnace covered a fairly
wide range as shown in greater detail in Section 4.2 of this report.
Some of the factors contributing to this variation include (1)
composition of charge: presence of volatile constituents such as
arsenic, beryllium, cadmium, and zinc can substantially increase
metal oxide emissions; (2) condition of charge: insulation, oil
and grease can increase carbonaceous particulates; (3) heating
rate: high heat input can increase emissions. Therefore, emission
factors should be used with care and augmented with specific infor-
mation when available.
In the case of sulfur dioxide emissions from primary copper
smelters, PES feels that an approach should be taken on emission
factors which differs somewhat from that now used. Some of the
factors underlying that judgment are listed below:
• AP-42 currently gives factors for roasting, smelting, and
converting. These factors cannot be representative for
all smelters because emissions depend on sulfur content of
the concentrate, and because not all smelters are configured
similarly.
• Source tests at some smelters have not dealt with individual
sources but with combined effluents from two or more pro-
cessing units.
• Even for a single point source, test results are not
necessarily representative because they depend on the
current value of the variable sulfur content of concentrate.
• We have not found any measurements to indicate the actual
magnitude of sulfur loss by fugitive emissions.
• Smelting plants without roasters would naturally be expected
to have higher emission factors for their other processing
units because more sulfur must be removed in these other
units.
Consequently, in this study uncontrolled S02 emission factors
for primary copper smelters have been prepared using the following
assumptions:
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1. Sulfur content of the concentrate is 32 percent (the
national average; varies from a low of 8 percent to
a high of 38 percent).
2. Two configurations of smelters are considered - the
first including roasting, reverberatory smelting, and
converting; the second including only reverberatory
smelting and converting.
3. Sulfur dioxide emissions are allocated among the various
point sources plus fugitive emissions and slag according
to the figures given in the EPA NSPS Background Document
for Primary Copper Smelters, EPA 450/2-74-002a. (Ref. 3)
Based upon these assumptions, which are reasonably consistent
with source test data obtained in this study, uncontrolled S02
emission factors for primary copper smelting are given in Table 2-2
and compared with those currently given by AP-42. There are more
individual factors recommended than are presently given by AP-42
and there are some differences in factors for individual processes,
but the total uncontrolled S02 emissions per ton of concentrate
processed remains almost the same.
Factors for controlled sulfur dioxide emissions depend strongly
upon the type of control and the portion of the entire smelting
operation served by the controls. While there are few smelters
with controls on low concentration S02 gas streams such as from
multiple-hearth roasters and reverberatory smelting furnaces, this
situation is changing. Also, some smelters have controls on only
a portion of the emissions from any given process. Finally, the
increasing use of double contact sulfuric acid plants as control
systems has increased control efficiency in some cases from 95
percent for single contact plants to 98 or 99 percent for the
double contact plants.
In the case of uncontrolled particulate emissions from
primary copper smelters, there is no method of estimating emissions
except through the use of source test data. Because of the varia-
bility in facilities, operating conditions, feed materials, and test
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Table 2-2. EMISSION FACTORS FOR SULFUR DIOXIDE FOR PRIMARY COPPER SMELTING PROCESSES
WITHOUT CONTROLS
Configuration No. 1
S02 Emissions, kg/MT (Ib/ton) Concentrate
Process Recommended Current AP-42
Roasting 205 (410) 30 (60)
^ Reverberatory Furnace 115 (230) 160 (320)
« Converting 270 (540) 435 (870)
Fugitive Emissions 37 (74)
Total Uncontrolled 627 (1,254) 625 (1,250)
Configuration No. 2
Reverberatory 195 (390)
Converting 430 (860)
Fugitive Emissions 2 (4)
Total Uncontrolled 627 (1,254)
*In the current AP-42 only one set of emission factors are given. No distinction
is made as to smelter configuration.
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methods, it is likely that results from one group of tests will
differ from those obtained from another group unless both groups
are very large and unbiased in the parameters influencing the
results. Therefore, the results of this study were used to modi-
fy the current AP-42 emission factors on the assumption that
increasing the test base decreases the standard error.
No additional information was obtained on uncontrolled par-
ticulates from roasting or fire refining nor was information
obtained on potential additional sources of particulates not
currently covered in AP-42, such as concentrate and flux crushers
anode furnaces, and newer smelting processes - electric arc
smelting and flash smelting. Uncontrolled particulate emission
factors developed from this study are compared with those currently
given in AP-42, and recommended new factors are given in Table
2-3.
Controlled particulate emissions depend strongly upon the
type and capacity of control equipment. Electrostatic precipita-
tors are widely used in the primary copper smelting industry.
High efficiency scrubbers are used as supplementary control in
many cases where additional particulate control is required prior
to feeding exhaust gases to sulfuric acid plants. Efficiencies
from 95 percent to 99 percent can be attained.
Much additional information on emissions of S02 and particu-
lates from both primary and secondary copper smelting is given in
Section 4.0 of this report. Tables summarizing the data p'rovide
information on the range of results obtained and the number of
tests available. Fugitive emissions are discussed in Section 5.0.
Precisions of the emission factors developed in this study
and the need for additional source tests are discussed in
Section 6.0. For primary smelting processes the precision (standard
error) of the factors is generally less than 35 percent for
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ro
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Table 2-3. EMISSION FACTORS FOR PARTICULATES FROM PRIMARY COPPER SMELTING PROCESSES WITHOUT
EMISSION CONTROLS
Partlculate Emissions, kg/MT (Ib/ton) Concentrate .
Process This Study Current AP-42 Recommended
Roasting - 22.5 (45) 22.5 (45)
Reverberatory Smelting 26 (52) 10 (20) 18 (36)
Converting 12 (24) 30 (60) 21 (42)
Refining - 5 (10) 5 (10)
Total Uncontrolled - 67.5 (135) 66.5 (133)
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participates and ranges between 9 and 78 percent. Substantial
additional testing on individual processes and on sources not here-
tofore considered is recommended.
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3.0 DATA GATHERING
•t
The data gathering task for this project was performed in
order to establish a documented base for the development of emission
factors for copper smelting emission points. The task was twofold
in the sense that project engineers were required to obtain data
from all available information sources, and also were to identify
areas where current data were nonexistent. This meant that for
some emission points, the effort would have to be exhaustive, to
insure that all reasonable sources of information had been investi-
gated.
The principal objective of this task, therefore, was to gather
emission-related data in the form of source test reports, emission
inventory reports, material balances, etc. Another requirement
of the project was that the process-related information obtained be
prepared in the form of process compendiums for the primary and
secondary copper smelting industries. Data necessary for these
reports would include process flow sheets, equipment operating
parameters, and raw material and product compositions.
Initially, project personnel established five areas to be in-
vestigated for possible contributions in the data gathering phase.
These were (1) PES in-house files for 13 of the 15 primary copper
smelters, (2) trade literature, (3) professional organizations,
(4) governmental agencies, and (5) the smelters themselves. Other
sources such as control equipment manufacturers were also considered;
however, it was thought that the five identified categories would
provide the bulk of the data for the project. In support of the five
information areas, project engineers prepared an initial "Resource
Information List" which contained names of individuals and organi-
zations which would be contacted for possible information. The list
was discussed with the Project Officer and was augmented at the time
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to include a particular individual in each of the 10 EPA regional
offices who would be the initial contact for the data gathering
effort in that regi '. In many cases, this individual was the
person who had responsibility for the region's NEDS data system.
In some regions, however, PES personnel had worked with a par-
ticular person on a previous copper smelter project who had a current
understanding of the region's available smelter data. All of the
10 EPA regional offices were contacted by mail and by phone as the
first step in the process of obtaining data.
To reduce the amount of duplicated effort required for this
task, project engineers analyzed the information which was already
available in in-house files for 13 of the 15 primary copper smelters.
These data had been collected in support of six previous projects
which PES had performed or was performing for EPA. In previous
work, a large percentage of the tasks had been spent in characteri-
zing the operations of reverberatory furnaces in particular. Thus,
1t was found that a great deal of process data were available for
primary smelting sources. Also, rather extensive bibliographic
compilations had been made for these projects which assisted pro-
ject engineers in their current literature search. Emission
estimates were, in general, based upon yearly or monthly average
material balances, but in some cases, source test reports were also
included in the files.
Almost concurrently, project engineers began investigating
technical literature on the smelting processes (Refs. 4 through
17). The EPA library was consulted for reference documents on the
subjects, and technical journals were accessed at a nearby university
library. Some articles were found in the Journal of Metals. Mining
Engineering, and the Engineering and Mining Journal, and a number of
government publications were made available through the EPA library.
The Air Pollution Technical Information Center (APTIC) was called and a
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list of abstracts of publications related to copper smelting was
requested. The abstracts were not received, however. Little
information in the technical literature contained hard emission
data, but many of the documents were filled with much valuable
process information. Particularly useful were documents which
addressed new areas of process and control technology.
After reviewing literature sources, project engineers were
able to compile a list of professional organizations which could
be written to for data. The list included the following organi-
zations:
American Bureau of Metal Statistics, New York, New York
American Institute of Mining, Metallurgical, and
Petroleum Engineers, New York, New York
American Mining Congress, Washington, D.C.
Brass and Bronze Ingot Institute, Chicago, Illinois
Cast Metal Federation, Rocky River, Ohio
Colorado Mining Association, Denver, Colorado
National Association of Recycling Industries (previously
the National Association of Secondary Material
Industries), New York, New York
Non-Ferrous Foundry Society, Cleveland, Ohio
Smelter Control Research Association, Columbus, Ohio
Letters were written to each of these organizations in the hope
that they had conducted source testing at copper smelters for
research purposes. It was known at the time that the Smelter
Control Research Association (SCRA), for example, had been con-
ducting pilot plant studies of various air pollution control
devices on primary smelting processes. However, the responses
from the professional organizations did not supply any hard
emission data. The effort expended in contacting these sources was
beneficial to staff in that some of the organizations were helpful
in suggesting which people to contact at the smelter companies.
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The remainder of the effort for data gathering was concen-
trated on governmental agencies and direct contact with the plants.
In order to best access governmental file data, it was necessary
to compile a list of all of the primary and secondary copper
smelters in the country. The listing of primary smelters was a
simple task since there are only 15 plants which are operated in
the United States. To compile the listing of secondary plants,
project engineers began with a plant name listing from the NEDS
data base which was keyed on the SIC codes of 3341, 3351, 3362,
3432, 3446, and 3497. Only the 3341 code pertains uniquely to
secondary smelters; however, it was felt that other plants whose
main function might be, for instance, as a brass or bronze foundry
(3362), could also maintain operations and process equipment which
could be found at secondary smelters. To augment the 11st of
sources from NEDS, a recently published report by the Radian Cor-
poration was used. The report presented a multimedia environmental
assessment of the secondary metals Industry and included a company
directly as an appendix. From the data presented in NEDS and the
Radian report, lists were prepared of primary and secondary smelters
in each of the 10 EPA regions.
Having tabulated the smelters by region, project engineers
initiated contacts by letter and by telephone with govenmental
agency personnel to ascertain whether relevant data might be
available. Federal-, state-, and local-level agencies responded to
the data requests by either sending available source test and pro-
cess information or by indicating that data were available in their
fields and project engineers could access the data in their offices.
Based upon an evaluation of the number of possible sources in an
area and the probable quantity and quality of data to be obtained,
the following governmental agency offices were visited by PES
personnel:
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EPA, Region III, Philadelphia, Pennsylvania
Philadelphia ?-'••" Management Services, Philadelphia, Pennsylvania
New Jersey Department of Environmental Protection,
Trenton, New Jersey
New Jersey Department of Environmental Protection, Metro
field office, Springfield, New Jersey
New Jersey Department of Environmental Protection,
Newark field office, Newark, New Jersey
New York State Department of Environmental Conservation,
New York, New York
The City of New York Department of Air Resources, New
York, New York
EPA, Region V, Chicago, Illinois
Cook County Department of Environmental Control, Maywood,
Illinois
Wayne County Department of Health, Air Pollution Control
Division, Detroit, Michigan
City of Cleveland Department of Public Health and Wel-
fare, Division of Air Pollution Control, Cleveland, Ohio
State of Ohio Environmental Protection Agency, Columbus,
Ohio
City of Chicago Department of Environmental Control,
Chicago, Illinois
EPA, Region IX, San Francisco, California
Arizona Department of Health Services, Phoenix, Arizona
South Coast Air Quality Management District, Los Angeles,
California
Other agencies which provided information by mail were:
EPA, National Enforcement Investigations Center, Denver,
Colorado
EPA, Region IV, Atlanta, Georgia
EPA, Region VII, Kansas City, Missouri
Texas Air Control Board, Austin, Texas
Tennessee Department of Public Health, Division of Air
Pollution Control, Nashville, Tennessee
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Montana State Department of Health and Environmental
Sciences, Helena, Montana
Puget Sound Air Pollution Control District, Seattle,
Washington
Bay Area Air Pollution Control District, San Francisco,
California
New Mexico Environmental Improvement Agency, Santa Fe,
New Mexico
In some cases, the types of data items which were being re-
quested from these agencies were considered to be potentially con-
fidential in nature, and the agencies were reluctant to release
the data to a private consultant. In particular, this problem was
encountered in EPA, Region IX offices and in the South Coast Air
Quality Management District (SCAQMD). Since these two sources were
expected to be able to provide a great deal of source test data,
special provisions had to be arranged to obtain the information.
After many discussions with the SCAQMD, a rather simple solution
to the problem was agreed upon. The SCAQMD provided copies of the
complete test reports for secondary copper smelters in their juris-
diction, but company names and addresses were deleted in all tests.
Eight tests were made available from this source.
The data availability problem in EPA, Region IX, required a
great deal more time and effort than was initially expected, but
the efforts were rewarded by the acquisition of a large number of
pertinent source tests. A request for data was first made to
Region IX in early February 1977. PES personnel were informed,
at that time, that EPA had done testing at several of the primary
smelters in Arizona, but due to impending court decisions, the
tests were not immediately available. On March 8, 1977, project
engineers visited EPA offices in San Francisco to again discuss
the acquisition of the test data. At that time, however, it was
decided that a modification to the contract would be necessary
to allow PES to access potentially confidential material. Upon
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approval of the Project Officer, and in accordance with the speci-
fications set forth by Region IX, the PES contract was suitably modi-
fied, and the test results were received on April 29, 1977.
It was apparent at this point in the data gathering task that
a great deal of source test data were not going to be available
through governmental agencies. It was also apparent most of the
testing which had been done by the agencies was performed for com-
pliance determination purposes. As such, most of the emission
measurements were taken downstream of control equipment and were
often measured in gas streams which had been combined from a number
of processes. Project engineers contacted other governmental agencies
which were thought to be more inclined to do research testing rather
than compliance testing, such as the U.S. Bureau of Mines OAQPS,
and the Industrial Environmental Research Laboratory of EPA. No
usable test data were obtained from these sources, however.
After making contact with 37 governmental agencies, in all,
project personnel began concentrating their final efforts of this
task on the smelting plants themselves. Initially, plant managers
at a few of the primary smelters were written to and called. As a
standard company policy, however, the plant managers referred our
requests, in all cases, to central company offices. PES then con-
tacted personnel who were in charge of environmental matters for
an entire copper company. In general, the position that was taken
by the copper companies was that all testing which had been per-
formed had already been submitted to the proper governmental agency
and would have to be obtained through their offices. It is not
known how much of the test data presumably submitted by the smelters
ultimately was obtained from the governmental agencies contacted.
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4.0 DATA ANALYSIS
4.1 DATA ANALYSIS PROCEDURES
In order to facilitate the review of the data which had been
gathered, a filing system was organized to alloy; ready access to
individual items of information. Preparation of the project
deliverables basically required a progression of four steps as out-
lined below:
1. Identification of processes
2. Writing of process descriptions
3. Analysis of source tests
4. Development of emission factors
With this framework in mind, project engineers classified the data
into a series of process files. From the process file system,
project personnel could withdraw data to be used in the writing of
a process description or the development of an emission factor for
a particular smelting process. These files ultimately were destined
to serve as backup data for NADB.
The identification of processes to be included for study in
this project was straightforward. The previously referenced multi-
media assessment report by Radian (Ref. 18) listed the significant air pollu-
tion sources at secondary smelters. Based upon this report, the
secondary smelter data were organized into files for the following
processes:
1. Reverberatory furnaces
2. Electric induction and arc furnaces
3. Crucible furnaces
4. Pot furnaces
5. Insulated wire burners
6. Oil removal processes (dryers)
4-1
-------
7. Rotary furnaces
8. Cupola (shaft and blast) furnaces
9. Converters (BOF)
Primary smelter data elements were also organized into files for
the following operations:
1. Concentrate and flux preparation processes
2. Multiple-hearth roasters
3. Fluidized-bed roasters
4. Reverberatory smelting furnaces
5. Electric arc smelting furnaces
6. Flash smelting furnaces
7. Converters
8. Fire-refining furnaces
9. Electrolytic refining processes
10. Continuous smelting furnaces
11. Hydrometallurgical smelting processes
12. Sulfuric add manufacturing plants
Separate files were also maintained for information on fugitive
emissions and noncriteria pollutant emissions at primary and
secondary smelters.
Process information in the files could be accessed without
much difficulty. Project engineers began to compose the various
process descriptions, and the process data appeared to be complete,
current, and readily usable. In order to better organize the
emission data in the files, project engineers developed a check-
list for emission source test information (Figure 4-1). Recording
the test results in a standardized format expedited accessing the
data and simplified the task of coding. A typical example of a
recorded source test report in the PES standardized format is shown
in Figure 4-2. Use of this format could greatly simplify future
projects in which data are to be gathered and eventually coded into
4-2
-------
Finn's Name and Address
Source involved; contaminants involved
Process information:
Products and production rates (specify units)
Raw materials and charging rates (specify units)
Maximum annual capacity (specify units)
If batch process, maximum batch capacity (specify units)
Typical batch time
If continuous, maximum daily capacity
maximum hourly capacity
Seasonal variation (typical) in activity
Control equipment:
Type, model, operating parameters
Rated efficiency for various pollutants
Configuration in relation to source
Emission point(s):
Stack parameters
Configuration in relation to sources and control units
Comments:
Report of source test
Sampling position; pollutant
Number of samples taken at this sampling position
Fraction of batch, cycle, or day represented by sampling periods
Weighted pollutant concentration in effluent gases
Implied emission rates, hourly
daily
annually
Implied emission factors per SCC unit
(specify SCC unit)
Comments:
Sampling information
Date
Pollutant
Sampling method
Sampling position (related to stack, control device, and source
configuration)
Number of samples taken at this sampling position
Figure 4-1. Check List for Emission Source Information
4-3
-------
Sample number (entry made for last sample)
Production rat- and condition at time of sampling, including
fuel and fer ~ compositions if relevant
Sampling time in relation to batch, cycle, or day
Sampling period, minutes
Sampling flow rate or total volume sampled (specify)
Total pollutant found in sample (specify units)
Pollutant concentration in gas sampled (specify units)
Comments:
Figure 4-1. Check List for Emission Source Information (Concluded)
4-4
-------
Firm: J- Doe Refining
Source: Arc furnace
Process: Producing molten high-temperature alloys
Raw materials: Cu-Ni pit scrap, iron ore, limestone,
fluorspar
Maximum batch capacity: 5,000 pounds
Typical batch time: 2 hours
Control Equipment:
Baghouses: 10,000 ACFM, 2,500 fpm, 175°F
Efficiency: rated 99.9 percent
Configuration: 3 baghouses serving a swing-away hood via fixed
intake point in duct above hood
Emission Point:
Stack: no data
Configuration: one of three serving baghouses
Sampling Information:
Date: 052671 Run No: 01
Sampling Position: stack top (emission control)
Production Rate: ca 20,000 pounds/day
Sample Results:
Total particulates: controlled, reported at 1.36 Ib/hr;
uncontrolled, reported at 2.5 Ib/hr.
Corresponding annual figures cited at
0.34 and 0.63 tons/yr, respectively.
Comments:
It is assumed, although not stated, that the values cited are
averaged over an entire batch period. It is not clear whether
more than 1 baghouse serves a single hood, and whether there
are other stacks serving other baghouses.
Figure 4-2. Typical Example of Formatted Test Results
4-5
-------
SOTDAT, since the information could be transcribed directly from
the data source onto the PES form.
The task of coding the source test data into SOTDAT, while
simplified by the standard test result format, still required a
great deal of effort. For the most part, source test information
was incomplete. Most of the reports presented only information
such as pollutant tested, date of sample, measured emission rate,
gas flow rate and temperature, and occasionally isokinetic sampling
percentages. To provide a complete analysis, project engineers
coded all tests onto SOTDAT coding forms (Ref. 19). In all, about 120 tests
were coded for primary smelting sources and about 70 tests coded
for secondary smelting processes.
Finally, all emission results were compiled in tables for
each of the individual processes. These tables included source
test results, as well as other types of emission estimates (from.
material balances, for instance). The results derived from these
tables will be discussed in more detail in following sections for
the primary and secondary smelting processes.
4.2 EMISSION FACTORS FOR PRIMARY SMELTER PROCESSES
Tables 4-1 through 4-3 present emission factors for primary
copper smelting sources. All entries in the tables are given in
weight of emissions per unit of concentrate which enters the smelter.
The emission results are shown for various smelter configurations
and for various control systems to detail the effect of these para-
meters on the emissions. Average emission factors for each case
are unweighted, and maximum and minimum values are included to indi-
cate the range of emissions observed.
The tables show far more tests to determine controlled emissions
than uncontrolled. This is consistent with the fact that no test
results were received from the smelters or from professional
4-6
-------
Table 4-1. EMISSIONS FROM CONVERTERS IN PRIMARY COPPER SMELTERS
A. Participates, kilograms per metric ton and pounds per ton of concentrate processed by smelter
Smelter8
Configuration
1
2
All
1
1
2
3
All
Control b
Equipment
0
0
0
1
2
2
2
2
Emissions
kg/MT
Avg.
15
8.5
12
1.5
0.19
0.14
0.55
0.20
Range
11-20
0.7-13
0.7-20
0.55-3.5
0.085-0.38
0.025-0.55
0.50-0.70
0.025-0.70
Ib/ton
Avg.
30
17
24
2.9
0.38
0.28
1.1
0.39
Range
21-40
1.4-25
1.4-40
1.1-6.9
0.17-0.76
0.05-1.1
1.0-1.4
0.05-1.4
No. of
Tests
4
4
8
14
7
19
3
29
No. of Plants
Tested
1
3
4
2
2
3
1
6
Configuration 1, converter follows multiple-hearth roaster and reverberatory furnace
Configuration 2, converter follows reverberatory furnace, no roaster
Configuration 3, converter follows flu1d1zed-bed roaster and reverberatory furnace
i
Control equipment: 0 signifies none operated
1, electrostatic predpltator
2, electrostatic predpltator with add plant particulate control
-------
-p.
I
00
Table 4-1. Continued. EMISSIONS FROM CONVERTERS IN PRIMARY COPPER SMELTERS
fl. Oxides of sulfur: S02§ and S03 (as H2S04). In kilograms per metric ton and pounds per ton of concentrate processed.
Smelter'
Configuration
1
1
2
All
1
1
2
2
All
All
1
Control11
Equipment
0
0
0
0
2
Pollutant
S02
S03
S02
S02
S02
so3
so2
SOj
so2
so3
so2
Emissions
kg
Avg.
350
0.65
650
600
31
0.07
14
0.03
16
0.04
0.31
im
Range
_
-
60-1.500
60-1.500
12-50
-
1.4-23
0.01-0.06
1.4-50
0.01-0.07
0.16-0.45
Ib/ton
Avg.
700
1.3
1.300
1.200
61
0.14
27
0.06
31
0.07
0.62
Range
_
-
120-3.000
120-3,000
23-99
-
2.8-46
0.01-0.11
2.8-99
0.01-0.14
0.31-0.89
No. of Tests
1
1
5
6
2
1
14
13
16
14
4
No. of Plants
Tested
1
1
1
2
2
1
2
2
4
3
1
aSee footnote a, Table 4-1A
Control equipment: 0 signifies none operated
1 single-contact add plant
2 double-contact add plant
-------
Table 4-1. Continued. EMISSIONS FROM CONVERTERS IN PRIMARY COPPER SMELTERS
C. Oxides of nitrogen (NOX) as nitrogen dioxide (M^), kilograms per metric ton and pounds per
ton of concentrate processed by smelter.
Smelter configuration 2: converter follows reverberatory furnace; no roaster. No control
equipment operated. One test only.
U3
Emissions
Smel ter
Configuration
2
kq/MT
Avg.
0.025
Ib/ton
Avg.
0.05
-------
Table 4-2. EMISSIONS FROM REVERBERATORY FURNACES IN PRIMARY COPPER SMELTERS
A. Participates, kilograms per metric ton and pounds per ton of concentrate processed by smelter.
Smelter3
Configuration
2
2
3
All
Control b
Equipment
0
1
1
1
Emissions
kQ/MT
Avg.
26
11
1.2
7.5
Range
21-34
0.9-34
0.13-6.5
0.13-34
Ib/ton
Avg.
52
22
2.4
15
Range
42-67
1.7-68
0.25-13
0.25-68
No. of
Tests
4
32
18
50
No. of Plants
Tested
2
3
2
5
_*>
Configuration 2, converter follows reverberatory furnace, no roaster
Configuration 3, converter follows flu1d1zed-bed roaster and reverberatory furnace.
Control equipment: 0 signifies none operated
1, electrostatic precipltator
-------
Table 4-2. Continued. EMISSIONS FROM REVERBERATORY FURNACES IN PRIMARY COPPER SMELTERS
B. Oxides of sulfur: S02, and S03 (as H2S04), In kilograms per metric ton
and pounds per ton of concentrate processed. No control equipment operated.
Smelter3
Configuration
2
2
3
3
All
All
Pollutant
so2
so3
so2
so3
so2
so3
Emissions
kg/MT
Avg.
115
0.41
33
0.11
110
0.31
Range
25-310
0-0.85
19-55
0-0.30
19-310
0-0.85
Ib/ton
Avg.
230
0.81
66
0.22
220
0.61
Range
50-620
0-1.7
38-110
0-0.60
38-620
0-1.7
No. of Tests
19
14
7
7
26
21
No. of Plants
Tested
3
2
1
1
4
3
aSee footnote a, Table 4-2A
C. Oxides of nitrogen (NOx) as nitrogen dioxide (N02K kilograms per metric ton and pounds per ton of
concentrate processed by smelter.
Smelter configuration 2: converter follows reverberatory furnace; no roaster. No control equipment operated.
Smel ter
Configuration
2
Emissions
kg/MT
Avg.
0.045
Range
0.035-0.06
Ib/ton
Avg.
0.09
Range
0.07-0.12
No. of
Tests
3
No. of Plants
Tested
1
-------
Table 4-3. COMBINED EMISSIONS FROM MULTIPLE-HEARTH ROASTERS AND REVERBERATORY FURNACES IN
PRIMARY COPPER SMELTERS
A. Participates, kilograms per metric ton and pounds per ton of concentrate processed by smelter.
Control
Equipment
1
2
Emissions
kq
Avg.
2.4
0.70
rm
Range
0.35-8.4
0.37-0.96
Ib/ton
Avg.
4.8
1.4
Range
0.70-17
0.74-1.91
No. of
Tests
38
15
No. of Plants
Tested
2
2
B. Oxides of sulfur: SO*, and $03 (as H2S04), In kilograms per metric ton and pounds per ton of
concentrate processed. No control equipment operated.
Pollutant
so2
S03
Emissions
ka
Avg.
220
0.75
rMT
Range
180-330
1
Avg.
450
1.5
p/tpn
Range
360-660
No. of
Tests
8
1
No. of Plants
Tested
3
1
-------
organizations for use in this project. Since the majority of the
tests were obtained from governmental agencies, they were primarily
run for compliance determination purposes. As such, results were
measured at points of emission to the atmosphere, after combining
gas streams from various processes and after application of control
systems.
The following specific comments apply to the information in
the tables:
1. Converters
• ESP control achieves an average control efficiency of
88 percent for particulates, while ESP's combined with
the gas cleaning systems included in sulfuric acid
plants yield 98 percent efficiency.
• Particulate emissions can potentially be as high as
40 pounds per ton of concentrate and can be controlled
to a level of 0.05 pounds per ton.
• Particulate emissions from converters are potentially
slightly larger in smelter configurations which include
roasters.
• S02 emissions are reduced by approximately 97.4 percent
by single contact sulfuric acid plants, and by 99.9 per-
cent by double contact plants.
• Potential SO? emissions from converters are smaller in
smelting configurations which include a roasting step.
• Although only one test result was recorded for NOX, it
indicates that these emissions are very small.
2. Reverberatory Furnaces
• No results were recorded for reverberatory furnaces
which are operated in conjunction with a multiple-hearth
roasting furnace. In all cases in this configuration,
reverberatory furnace gases are combined with those of
the roaster before exhausting the atmosphere (see Roaster/
Reverb).
• S02 emissions from the reverberatory furnace depend on
smelter configuration, since roasting will remove a por-
tion of the sulfur in the feed to the furnace. Listed
4-13
-------
results show that these emissions are 4 times greater
when no roasting is done as compared to the case where
a fluid-bed roaster is used.
• S02 emissions from reverberatory furnaces alone are not
controlled emissions shows only 60 percent collection
efficiency for an average ESP.
• Potential NOX emissions appear to be very small, based
upon a limited number of tests.
3. Multiple-Hearth Roaster/Reverberatory Furnace Combined Stream
• As mentioned previously, test results in all of the
smelters which operate multiple-hearth roasters and rever-
beratory furnaces were measured after the two exhaust
streams had been combined and after the application of
particulate control equipment.
• At present there are no S02 controls applied to these
gases at U.S. smelters.
• Particulatfr emission factors for the combined stream
cannot be analyzed into the component contributions.
The reported emission factor with control by electro-
static precipitator seems Inconsistent with the factor
(Table 4-2) for the reverberatory furnace alone with
similar control.
One would expect the combined gases to have a higher
particulate emission, but the figures Indicate that the
gases from the furnace alone have emissions almost 5
times greater. Both figures are based upon a comparable
number of test results taken at a number of different
plants. A possible explanation would be that the ESP's
applied to the furnace gases were older, less efficient,
or poorly maintained units.
Data Items were also gathered for other emission points in the
smelter, but were not sufficient to warrant tabulation. These data
can be found in the background files (Ref. 20) for the following
operations:
• Concentrate and Flux Preparation
• Multiple-Hearth Roasters
• Fluidized-Bed Roasters
« Electric-Arc Smelting Furnaces
• Fire-Refining Furnaces
4-14
-------
Table 4-4 contains emission factor information which has
been compiled from other data sources(Refs. 21 and 22).
4.3 EMISSION FACTORS FOR PARTICIPATES FROM FURNACES USED IN
SECONDARY COPPER SMELTING PROCESSES'
Table 4-5 presents emission factors for participates for
secondary copper smelting sources.
The emission factors listed have been estimated from the
results of source tests, or from rates of production and waste
accumulation according to material-balance principles, or by other
means which, in some instances, have not been identified.
Records available for inspection regarding these facilities
were almost always fragmentary and unverifiable, and their inter-
pretation in terms of emission factors therefore involved a sub-
stantial component of engineering judgment. Further, estimates
regarding potential emissions from uncontrolled equipment have in
some cases been estimated by applying a nominal emission control
efficiency factor to the observed level of emissions from the con-
trol equipment.
Another problem was that in some of the reports of emissions
tests, while it was evident that emissions measured were derived
from two or more processes controlled by the same systems, it was
not clear which units were being operated at the time of the test.
Because of these and other difficulties, the emission factors
presented can be given a rating no higher than average.
Where not otherwise specified, it is reasonable to assume
that a major fraction of the particulate matter (50 percent or
more) consists of oxides of heavy metals, commonly zinc, copper,
lead,and tin. The detailed composition of the particulate matter
is related to the composition of the material charged into the fur-
nace; smelting of alloys containing zinc is especially likely to
4-15
-------
Table 4-4. EMISSION FACTORS FOR SMELTER PROCESSES DERIVED FROM PUBLISHED LITERATURE
I
_^
o>
Process
Ore Crushing
Roasting
Reverberatory
Furnace
Converters
F1re Refining
Materials Handling
Acid Manufacture
(single-contact)
(double-contact)
Material
Basis
Ore
Concentrate
Copper
Concentrate
Concentrate
Copper
Concentrate
Concentrate
Copper
Concentrate
Concentrate
Copper
100% add
Pollutant
TSP
TSP
TSP
S02
TSP
TSP
S02
TSP
TSP
S02
TSP
TSP
TSP
so2
S02
so2
Emission Factor
kg/MT Ib/ton
1
23
84
30
10
103
160
30
120
435
5
5
0.6-3.7
14-35
19
2
2
45
168
60
20
206
320
60
235
870
10
10
1.2-7.4
27-70
38
4
Ref.
21
1
t .
1
1
21
1
1
21
1
1
21
1
1
22
1
-------
Table 4-5. EMISSION FACTORS FOR PARTICIPATE MATTER FROM FURNACES USED IN SECONDARY COPPER SMELTING
AND ALLOYING PROCESSES
A. Cupolas
Type of Charge
Scrap Copper
Insulated Copper Wire
Insulated Copper Wire
Scrap Copper and Brass
Scrap Copper and Brass
Control
Equipment
0
0
1
0
1
Emissions
ka/K
Avg.
0.002
120
5
35
1.2
T lb/tnn
Range
-
-
-
30-40
1.0-1.4
Avg.
0.003
230
10
70
2.4
Range
-
-
-
60-80
2.0-2,8
No. of
Units
Tested
1
1
1
2
2
No. of
Plants
Tested
B. Reverberatory Furnaces
Type of Charge
Copper
Copper
Brass and Bronze
Brass and Bronze
Control
Equipment
0
2
0
2
Emissions
kg/MT Ib/ton
Avg.
2.6
0.2
18
1.3
Range
0.4-15
0.1-0.3
0.3-35
0.03-2.5
Avg.
5.1
0.4
36
2.6
Range
0.8-30
0.2-0.6
0.6-70
0.05-5
No. of
Units
Tested
2
2
2
No. of
Plants
Tested
12
2
2
2
I
-~l
Control equipment: 0 signifies none operated
1 Indicates electrostatic preclpltator used
2 Indicates baghouse filter systems
-------
Table 4-5. Continued. EMISSION FACTORS FOR PARTICULATE MATTER AMD ALLOYING FROM FURNACES USED IN
SECONDARY COPPER SMELTING AND ALLOYING PROCESSES
C. Rotary Furnaces
Type of Charge
Brass and Bronze
Brass (Foundry)
Control
Equipment
0
1
0
2
Emissions
kg/MT
Avg.
150
7
5
2.5
Range
50-260
3-10
-
0.1-5
Ib
Avg.
300
13
10
5
/ton
Range
100-500
6-19
-
0.1-10
No. of
Units
Tested
2
3
1
3
No. of
Plants
Tested
2
3
1
1
i
00
D. Crucible and Pot Furnaces
Type of Charge
Brass and Bronze
Control
Equipment
0
1
Emissions
kg/MT
Avg.
11
0.5
Range
1-20
0.1-1
Ib/ton
Avg.
21
1
Range
2-40
0.1-2
No. of
Units
Tested
17
5
No. of
Plants
Tested
13
3
-------
Table 4-5. Continued.
EMISSION FACTORS FOR PARTICULATE MATTER AND ALLOYING FROM FURNACES USED IN
SECONDARY COPPER SMELTING AND ALLOYING PROCESSES
E. Electric Arc Furnaces
Type of Charge
Copper
Brass and Bronze
Control
Equipment
0
2
0
2
Emissions
kg/MT
Avg.
2.5
0.5
5.5
3
Range
1-4
0.02-1.0
2-9
-
Ib
Avg.
5
1
11
6
/ton
Range
2-8
0.04-2
4-18
-
No. of
Units
Tested
3
2
3
1
No. of
Plants
Tested
2
1
2
1
•c*
_J
IO
F. Electric Induction Furnaces
Type of Charge
Copper
Brass and Bronze
Control
Equipment
0
2
0
2
Emissions
kg/MT
Avg.
3.5
0.25
10
0.35
Range
-
-
0.3-20
0.01-0.65
lb>
Avg.
7
0.5
20
0.7
'ton
Range
-
-
0.5-40
0.01-1.3
No. of
Units
Tested
1
1
No. of
Plants
Tested
1
1
18
6
-------
produce large quantities of particulate matter which, in this case,
contains a high proportion of zinc oxide.
Other circumstances which affect the rates of emission and
the composition of the particulate matter are the type of furnace
used, the operational procedures, the rate of heating and the tem-
perature attained, the physical form of the materials fed to the
furnace, and others. Available information is not sufficient to
permit complete evaluation of the quantitative effects of these
variables on emission rates. The emission factors listed In
Table 4-5 below are, therefore, classified only with respect to the
type of furnace involved and to whether the feed metal contains
or does not contain zinc.
Types of furnaces encountered in secondary copper smelting
are:
1. Cupola (or blast furnace)
2. Reverberatory
3. Rotary
4. Crucible (or pot)
5. Electric Arc
6. Induction (electric, high or low frequency)
The following sections discuss emission factors for furnaces of
these types as indicated by emissions data and production data for
both zinc-free and zinc-bearing feed metals. Where the information
is available, PES reports emission factors both for actual and poten-
tial emissions, the latter corresponding to weights of material
which would be emitted to the atmosphere if no emission control
equipment were provided.
The following notes apply to the information shown in
Table 4-5 for specific furnace types.
4-20
-------
• Cupolas
230 pounds per ton was estimated (by state personnel)
for a smelting operation in which insulated copper wire
was recycled. Presumably most of the particulate matter
generated originated from the insulation materials and
contained little copper oxide. An appropriate emission
factor for copper oxide alone would be much smaller than
120 pounds per ton.
• Reverberatory Furnaces
Of 12 facilities reviewed, only one indicated potential
emissions larger than 10 pounds per ton.
• Rotary Furnaces
The lower emission rates from control equipment at the
foundries apparently reflect higher efficiency of con-
trol by baghouses, which were in use at some foundries,
than by the equipment used at the smelters, which in-
cluded scrubbers and electrostatic precipitators.
• Crucible and Pot Furnaces
Constituents more volatile than copper included arsenic
and cadmium in one case, beryllium in another. The largest
factor for potential emissions occurred with a copper-arsenic
alloy containing no zinc.
• Electric Arc Furnaces
Products include refined copper (castings and shot) and
various copper alloys, including bronze, tinsel bronze,
beryllium copper, and high-temperature alloys containing
cobalt, nickel, chromium, molybdenum, tungsten, and
manganese. Beryllium emission factors appear to be about
0.002 kg/MT or 0.004 Ib/short ton.
• Electric Induction Furnaces
This table includes both high-frequency and low-frequency
induction furnaces.
Emission control was effected, in all cases cited, through
the use of fabric collectors (or baghouses).
4-21
-------
5.0 FUGITIVE EMISSIONS
5.1 INTRODUCTION
Both gaseous and participate fugitive emissions arise from
operations at primary copper smelters while those from secondary
smelters are essentially limited to particulates. Generally,
these emissions result from materials handling and storage, from
process equipment and industrial exhaust from system leakage, and
from unconfined operations such as furnace tapping and metal pouring.
Problems of the respective industries are discussed below.
5.2 PRIMARY COPPER SMELTERS
5.2.1 POLLUTANTS
All the pollutants discharged from primary point sources, such as
uncontrolled stacks, particulate control equipment, and acid plants,
are also found as fugitive emissions. These include mechanically
generated dusts from storage and transfer of ore concentrate, fluxes,
and slag; metallurgical fumes from furnace operations, sulfur dioxide,
and sulfur trioxide (also in form of acid fume). Table 5rl lists
many of the materials and compounds which are found as fugitive
emissions.
These fugitive emissions are generally released at or near
ground level and are difficult to quantify. The quantification is
particularly difficult in the case of particulates because there
is not good material-balance approach for estimating losses and
almost no direct tests have been conducted. In the case of sulfur
oxides, fugitive emissions have been estimated as the difference
between the total sulfur charged to the smelting process and the
total sulfur known to be collected as acid by product, discharged
through stacks, and present in slag. The amount of fugitive sul-
fur-compound emission has been estimated by this technique to be
approximately 6 percent of the total sulfur charged (Ref. 3).
5-1
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Table 5-1. POSSIBLE FUGITIVE EMISSIONS FROM PRIMARY COPPER SMELTERS
Dusts
Concentrates
Ferric Oxide (Fe203)
Magnetite (Fe304)
Refractory Dust (Alumina, Magnesia)
Slag
Zinc Oxide (ZnO)
Disturbed Soil
Fumes3
Arsenic Trioxide
Antimony Trioxide (Sb203)
Lead Oxide (PbO)
Zinc Oxide (ZnO)
Sulfuric Acid Mist
Sul fates
Gases
Carbon Monoxide
Sulfur Dioxide
Nitrogen Oxides
aSmall amounts of other elements and compounds such as mercury,
selenium, chlorides, and fluorides may be present depending upon
concentrate source.
Generally will condense on waste heat boilers if present.
5-2
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Sometimes, primary copper smelter fugitive emissions have been
characterized as "ground smoke," because of the smoky appearance or
opacity of the emissions. This appearance is likely due to the pre-
sence of small aerosols, in the 0.4-1.0 micrometer diameter size
range, which are very effective in scattering visible light. Many
metallurgical fumes are known to be in this size range. These fume
particles are small in diameter because the metals or metal oxides
of which they are composed are condensed from the vapor state.
Another mechanism of "ground smoke" formation is thought to
involve the reaction of a small fraction of the fugitive sulfur
dioxide emissions with atmospheric oxygen to form sulfur trioxide.
As the trioxide is formed it combines rapidly with water vapor to
form small aerosols. This combination takes place even at low
relative humidities.
The submicron sized fugitive emissions are easily capable of
being transported over long distances, while at least some of the
mechanically generated dusts will settle rather rapidly.
5.2.2 SOURCES
Potential sources of fugitive emissions from primary copper
smelters are listed herein:
• Roaster
Hot calcine transfer points
• Reverberatory Furnace
Matte tap holes
Matte launders
Slag tap holes
Slag skim bays
Slag launders
Charging points
View ports
Brick work leaks
5-3
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• Converters
Converter r th
End joints
Hood
• Miscellaneous
Ladles (matte and slag)
Matte and slag handling operations
Leaking ducts, flues,and stacks
Other leaking process equipment
Holding and refining furnaces
The principal source of fugitive emissions from roasters is the pro-
cess of removing hot solid calcine from the roaster. Both dust and
residual sulfur dioxide can be released. When the process involves
dumping the calcine into cars for transfer to the reverberatory
furnace, as is the case with some multiple-hearth roasters, the
sudden dissipation of kinetic energy as the calcine strikes the car
causes the generation of a puff of dust and trapped gases. Emissions
from leaks in the roaster can also be present; the losses from fluidized-
bed roasters are generally smaller than those from multiple-hearth
roasters because of differences in construction. Because internal
pressures are higher in fluidized-bed roasters, leakage can become sig-
nificant in a fluidized-bed roaster if leakage points exist.
Reverberatory furnaces produce molten matte from either "green"
charge or calcine. Charging and tapping of the furnace for the
matte both are carried out intermittently while melting continues.
Even though the furnace operates at slightly less than atmospheric
pressure (generally about -0.05 to -0.1 inch w.c.), the charging
operation is conducted through openings in the furnace from which
some dust, fume, and sulfur dioxide may escape.
Molten matte is removed from the furnace through tap holes
which are normally plugged. During tapping these are opened and the
5-4
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matte flows through channels called launders to ladles. Most fur-
naces have two or three matte tap holes on each side. Because the
matte is still close to furnace temperature as it is removed, the
remaining sulfur in the form of sulfides can continue to oxidize
outside the furnace for a time, forming sulfur dioxide. Oxides
of volatile metals may also be emitted from the launders and the
ladle. As the ladle is transported to the converters, emissions
can continue. These emissions produce the earlier-described ground
smoke. The less dense slag which floats on top of the matte in the
reverberatory furnace is also removed periodically through slag
tap holes and launders. Some emissions result from this operation
but they are not generally as intense as those from the matte.
Reverberatory furnaces are constructed of refractory bricks.
Because of the need to allow room for thermal expansion, it is
difficult to achieve a leakproof condition. Also, in the case of
furnaces built with suspended roofs, a gap exists between the fur-
nace walls and the roof which must be packed with a heat-resistant
material. Any imperfections in this packing will result in leak
points. The sealing problem is not as difficult with sprung-arch
roof construction. Leaks may be sealed by spraying on a slurried
refractory.
Fugitive emissions associated with copper converting generally
result from ineffective capture of fumes and sulfur dioxide during
certain phases of the converter operation. During blowing, the
exhaust hood placed over each converter generally fits rather tightly
and emissions are exhausted with little loss. The fit is not perfect,
however, as there must be some gap between the hood and the opening
to prevent freezing of the hood to the converter as a consequence of
splashing of molten copper. A chain-curtain closure is sometimes used
at the edge of the hood to minimize the opening while still providing
5-5
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durability and flexibility. A metal skirt is sometimes used to
improve the seal and minimize deterioration of the converter. In
a properly designed system it is possible to collect nearly all
the emissions during the "roll-in" and blowing phase.
Automatic damper controls are generally used to prevent excess
dilution air from being drawn into the system while at the same
time maintaining effective fume collection from most phases of con-
verter operation. If the damper control point is improperly set
or if the charge level in the converter is higher than normal,
fugitive emissions can result.
When the converter is rolled out for pouring either slag or
blister copper, the hood draft is usually shut off by dampers. The
main reason for this is to maintain a higher concentration of sulfur
dioxide in gases that are fed to the by-product acid plant (if such
a plant is provided). When the dampers are closed the converter.
emissions are uncaptured and discharged directly to the atmosphere.
The roll-out operational phase can amount to 3 to 6 hours out of
every 24-hour period for each converter.
A variety of other fugitive emission sources can be present
in a smelter, most of which involve leaks in waste heat boilers,
heat exchangers, and flues and ducts. Another minor source of
fugitive emissions is fire refining. The residual sulfur content
of blister copper is only about 2 percent and any small amounts of
impurities remain. Therefore, when final blowing is conducted the
potential quantity of emissions is small. These furnaces are,
therefore, not hooded and any emissions resulting from the operation
can be classified as fugitive.
5.3 SECONDARY COPPER SMELTERS
Fugitive emissions from secondary copper smelters are generally
limited to dusts, fumes, and smoke because the sulfur content of the
5-6
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scrap charge is very low. As in the case of primary smelters,
larger participates classified as dust can be expected from materials
handling and from furnace charging. Because these materials settle
rather rapidly, the impact depends upon how well these operations
are protected from the wind.
The other fugitive emissions result from uncaptured or uncon-
trolled contaminants generated by the furnaces. These include metal
fumes (zinc and other volatile metal oxides) and smoke from oily or
insulation-covered scrap. Most of these emissions arise during
charging, slag removal, metal tapping or pouring, chage mixing, and
air lancing. Because a wide variety of furnace types are used,
hood design and effectiveness can vary substantially.
5.4 FUGITIVE EMISSION CONTROL
Fugitive emissions control techniques can be divided into two
major categories: (1) process changes to eliminate or minimize
generation of emissions, and (2) installation of equipment to collect
the emissions. A requirement in either case is that process equip-
ment and industrial ventilation be designed and maintained to con-
trol leakage.
In primary copper smelting, several types of process changes
are possible. To reduce emissions while charging reverberatory
furnaces, automatic control of furnace pressure could be incorporated.
This could involve the installation of pressure transducers to pro-
duce a signal which would control dampers or fans to maintain the
desired negative pressure. In the case of converters, techniques
might be devised to reduce the time during which the converter
opening is rolled out away from the hood opening. Fluidized-bed
roasters could be substituted for multiple-hearth roasters.
Installation of additional or improved systems for collecting
emissions would involve changes in some present industry practices.
5-7
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At present most furnace operations are located in large buildings
with some open sides and openings (monitors or other vents) in the
roof. Installation of additional hoods and ventilation equipment
could be complicated by existing support structures and cranes.
On the other hand, reduction of emissions inside these buildings
could improve the work environment.
The collection of fugitive emissions does not necessarily
mean that all current discharge of fugitive emissions would be
eliminated. The actual reduction of emissions would be influenced
by the overall abatement plan for each source and applicable regu-
lations. In the case of collected but uncontrolled emissions, it
is still likely that ambient pollutant concentrations would be
reduced because of the discharge through elevated stacks in place
of ground level discharge.
Table 5-2 summarizes fugitive emission points, quantities
emitted,and possible control techniques for primary copper smelting
sources. While controls for secondary smelters have not been
directly discussed in this section, many of the same techniques
considered for primary smelters would be applicable.
5-8
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Table 5-2» FUGITIVE EMISSION SOURCE, QUANTITY AND CONTROL
Fugitive Emission Source
Quantity Emitted
Control
01
10
Roaster Hot Calcine Transfer Points
Roaster Leakage
Furnace Matte Taps and Launders
Furnace Slag Taps, Launders, and Skim Bay
Furnace Charging Points and Leaks
Converter Mouth
Converter End Leakage
Ladles - Matte and Slag Handling
Leakage at Ducts and Equipment
Minor
Major (possibly)
Major
Significant but
not as great as
from matte
Major (possibly)
Major
Major (possibly)
Major
Major (possibly)
Evacuated room-type enclosure
Repair or replace
Evacuated room-type enclosure
or separate evacuated hoods
Separate evacuated hoods
a. Pressure control systems to
maintain negative pressure
at all times
b. Reduce firing rate during
charging
a. Separate hood and evacuation
system
b. Completely enclose converter
with removable hood
c. Feed cold materials through
hood
Repair
Hoods at launder pouring points
Continuous maintenance and
repair
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6.0 RECOMMENDATIONS FOR FURTHER SOURCE TESTING
Both the primary and secondary copper smelting industries
involve a rather wide variety of processes and equipment types.
In the case of primary copper smelting the sulfur content of the
ore varies significantly. In the secondary smelting industry the
nature and composition of scrap feed varies widely. An attempt
was made to develop emission factors for the major processes and
combinations of processes in these industries. Insufficient
valid test data were available to cover all the possibilities of
feed composition, nature of specific process or equipment, and
type of air pollution; therefore accurate emission factors could
not be developed for all these combinations. Many tests had been
done, but often important data elements were missing, such as feed
rate or composition. Another complication with primary smelters
is that tests were performed on combined gas streams and not on
streams from individual items of equipment.
Because of these difficulties, it was decided that emission
factors for uncontrolled sulfur dioxide emissions should be based
upon an average sulfur content in copper concentrate and on a dis-
tribution of this sulfur found in a large number of tests. The
sulfur content used is specified so that corrections can be made
where sulfur content differs and is known. However, there are
only 15 primary copper smelters in the United States, each one
having a different configuration. Therefore, these emission factors
should probably not be used to estimate potential emissions from
any given plant. (Latest data specific to the plant should be
used instead.)
Emission factors for particulates and for controlled emissions
must be based upon testing. As will be discussed in more detail in this
section, it is obvious that a major program of testing smelter sources
is needed if precision and accuracy of these factors is to be improved.
6-1
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6.1 PRECISION OF EMISSION FACTORS
To formulate any program to supplement the existing tables
of emission factors, it is important to examine the precision of
the data in those tables. A system for examining precision has
been promulgated by EPA. Called "Source Inventory and Emission
Factor Analysis" (SIEFA), it is intended to provide estimates of
the precision of all the elements of an emissions inventory, inclu-
ding, in particular, the emission factors which may be necessary in
quantifying industrial emissions.
Tables 6-1 and 6-2 provide estimates of standard deviation
and precision for the emission factors (presented in Section 4.0) for
primary copper smelting processes. For particulate emissions,
estimates of the precision of the emission factors range from 0.07
to 0.34; that is, the standard error of the emission factor is
between 7 and 34 percent of the factor. (The standard error is
equal to the standard deviation divided by the square root of the
number of observations accepted.) For sulfur dioxide emission
factors, precision estimates range from 0.09 to 0.73 - somewhat
larger, on the whole, than those for particulates.
Considered solely in the light of these precision estimates,
it may be reasonable to suggest that additional attention be
directed toward those factors with precision poorer - i.e., larger
- than 25 percent. These would include uncontrolled particulate
emissions from converters in the configuration, reverberatory
furnace followed by converter, and from reverberatory furnaces in
another smelter configuration; also, sulfur dioxide emissions un-
controlled and from single-contact acid plants.
However, the precision of the emission factor is not usually
the most important error-bearing item in determining the accuracy
of emission estimates, since the precision is, basically, inde-
pendent of accuracy. That is, an estimate can be quite precise
6-2
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Table 6-1. SIEFA STANDARD DEVIATIONS AND PRECISION FACTORS FOR PRIMARY COPPER SMELTING
PROCESSES (PARTICULATE EMISSIONS)
Process
Unit
Converter
Reverberatory
Furnace
Combined
Stream of
Roaster and
Reverberatory
Furnace
Smel tera
Configuration
1
2
1
1
2
3
2
2
3
1
1
Control b
Equipment
0
0
1
2
2
2
0
1
1
1
2
E.F.
kg/MT
15
8.5
1.5
0.19
0.14
0.55
26
11
1.2
2.4
0.7
S.D.
kg/MT
4.6
5.8
0.75
0.11
0.14
0.13
6.1
6.9
1.8
1.7
0.19
E.F.
Ib/ton
30
17
2.9
0.38
0.28
0.11
52
22
2.4
4.8
1.4
S.D.
Ib/ton
9.2
11.5
1.5
0.22
0.28
0.25
12.1
13.7
3.5
3.3
0.37
Estimated
Precision
0.15
0.34
0.13
0.22
O.?'*
0.1-'
0.12
0.11
0.34
0.11
0.07
Configuration 1, converter follows multiple-hearth roaster and reverberatory furnace
Configuration 2, converter follows reverberatory furnace, no roaster
Configuration 3, converter follows fluid1zed-bed roaster and reverberatory furnace
Control equipment:
0 signifies none operated
1, electrostatic precipltator
2, electrostatic precipltator with acid plant particulate control
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Table 6-2. SIEFA STANDARD DEVIATIONS AND PRECISION FACTORS FOR PRIMARY COPPER SMELTING
PROCESSES (SULFUR DIOXIDE EMISSIONS)
Process
Unit
Converter
Reverberatory
Furnace
Combined
Stream of
Roaster and
Reverberatory
Furnace
Smel tera
Configuration
1
2
1
2
1
2
3
1
Control5
Equipment
0
0
1
1
2
0
0
0
E.F.
kg/MT
350
650
31
14
0.31
140
33
230
S.D.
kg/MT
-
620
33.7
6.7
0.14
96
13.3
53
E.F.
Ib/ton
700
1,300
61
27
0.62
280
66
450
S.D.
Ib/ton
-
1,240
67.4
13.4
0.28
191
26.6
106
Estimated
Precision
0.25
0.42
0.78
0.13
0.23
0.16
0.15
0.09
Configuration 1, converter follows multiple-hearth roaster and reverberatory furnace
Configuration 2, converter follows reverberatory furnace, no roaster
Configuration 3, converter follows fluidized-bed roaster and reverberatory furnace
Control equipment:
0 signifies none operated
1, single-contact acid plant
2, double-contact add plant
-------
and nevertheless wrong, because of errors and uncertainties not
related to precision. In particular, with respect to sulfur
emissions, a large and irreducible source of variation in uncon-
trolled emissions can be due to variations in the composition of
the ore or other feed material. It follows that, for improved
accuracy, sulfur emissions should be expressed in relation to com-
position of the feed. Although emissions from fuel-burning have
long been routinely expressed in this manner, emissions from copper
smelters have not been so expressed.
Unfortunately, the data made available to PES in this project
were far too fragmentary to permit the utilization or even explora-
tion of this approach. None of the data for this study were fur-
nished directly by smelter firms. Nevertheless, it seems likely
that some smelter companies may have obtained such data for their
own use in private studies unrelated to air quality compliance
testing. Tests conducted to verify control equipment efficiencies,
for example, would be very valuable as a supplement to the existing
data base.
Of interest as indicating a special need for new source tests
is a recently discovered problem relating to sulfur compounds in
the copper smelter stack gases and their relationship to the
measurement of particulate matter. When compliance tests were per-
formed on primary smelters in Arizona in late 1975 (Ref. 23), it was
found that the EPA Method 5 test for determination of particulate matter
suffered serious interference from sulfuric acid mist which con-
densed in the probe and filter holder or passed through the filter
as a mist. Two questions arose from this circumstance. First,
should this acid material be counted as particulate matter? This
would depend on whether the material was in a gaseous form in the
stack and was later condensed in the probe and filter or whether it
was in the form of acid mist, which is considered particulate.
Second, how can reproducibility in the use of Method 5 be assured?
6-5
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With this volatile material condensing in the testing apparatus
it was difficul • if not impossible, to secure reproducible
test results.
A joint research program is being carried out by the Arizona
Bureau of Air Quality Control CRef. 24}., the Magma Copper Company,
and the Phelps Dodge Corporation to discover some method of testing
which will separate, quantify, and identify the condensible and solid
particulate matter.
6.2 RECOMMENDATIONS FOR ADDITIONAL TESTING
Based on scrutiny of the emission factors reported above,
together with consideration of the estimated precision of those
factors and the application of engineering judgment, it is
recommended that the processes listed in Table 6-3 be studied.
Particular attention should be given to the problem of determin-
ing potential uncontrolled emissions, I.e., the emissions which
would enter the atmosphere if no control systems were in use.
Table 6.2-1 also lists primary smelter plants which are known
to operate the particular processes mentioned and which might,
therefore, be considered as possible test sites.
Additional testing would also be desirable for secondary
copper smelting and alloying plants. Because of the large
number of plants in the United States the development of statis-
tically valid average emission factors for various types of furnaces
seems appropriate. The priority of this work will have to be deter-
mined 1n consideration of available resources and the impact of any
improvement in factor accuracy that might result.
Determination of fugitive emissions represent yet another
problem, regarding which little information is available. Because
of the difficulty of measuring them, little effort has been made
by the Industry to quantify these emissions. Sulfur dioxide
6-6
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Table 6-3. PRIMARY COPPER SMELTING PROCESSES FOR WHICH EMISSION
FACTORS SHOULD BE DEVELOPED
Process
Pollutant to be
Tested
Possible Test Sites
Concentrate and
Flux Crushers
Multiple-Hearth
Roasters
Fluldized-Bed
Roasters
Electric-Arc
Smelting Furnaces
Flash Smelting
Furnaces
Anode Furnaces
Particulates
Particulates
and S02
Particulates
and S02
Particulates
and S02
Particulates
and S02
Particulates
Kennecott, Hayden, Arizona and others
1. ASARCO, Tacoma, Washington
2. ASARCO, Hayden, Arizona
3. ASARCO, El Paso, Texas
4. Phelps Dodge, Douglas, Arizona
1. Phelps Dodge, Morenci, Arizona
2. Kennecott, Hayden, Arizona
3. Anaconda, Anaconda, Montana
4. Cities Service, Copperhill, Tennessee
1. Cities Service, Copperhill, Tennessee
2. Inspiration, Miami, Arizona
Kennecott, Hurley, New Mexico
ASARCO, Tacoma, Washington, and others
-------
fugitive emissions are usually estimated by a material balance.
All measurable sulfur outputs are summed and compared to the total
sulfur input, with the difference being assumed to represent fugi-
tive emissions.
Three basic strategies can be considered for sampling of
fugitive emission sources. These strategies, in order of decreasing
probable accuracy, are:
1. Mock-up Stack: Emissions are captured in a temporary
hood-duct-fan system and measured by essentially standard
stack sampling methods.
2. Roof Monitor: Roof monitors and other vent openings in
buildings containing fugitive emissions are evaluated
with appropriate instrumentation to determine airflows
and material balances through these openings.
3. Environmental Sampling: Outdoor air is monitored during
prescribed meteorological conditions using a network
of sampling sites upwind and downwind of the source to
determine pollutant flux.
Of these three approaches, the first is preferred from an
engineering standpoint because it offers the most direct and veri-
fiable accounting for the effluents to be measured. At the same time,
it requires the highest degree of cooperation and assistance from
the smelter operating staff and causes the greatest difficulties
in avoiding interference with normal process operations. Sampling
at roof monitors is less direct and more difficult, but involves
less interference with plant operations. Outdoor sampling is typically
a last-resort measure, which would only be attempted if it were
necessary to estimate emissions from a plant to which no access could
be obtained; very low accuracy would be expected from this technique.
6-8
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Third Printing. , .$. Environmental Protection Agency, Research
Triangle Park, N.C. Publication No. AP-42. February 1976.
2. Engineering Support Manual for NEDS Users, in preparation by
U.S. Environmental Protection Agency.
3. Background Information for New Source Performance Standards:
Primary Copper, Zinc, and Lead Smelters, Volume 1: Proposed
Standards. U.S. Environmental Protection Agency, Research
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1974.
4. Air Pollution Control Field Operations Manual, Volume III.
Final Report for EPA Contract No. CPA 70-122. February 1972.
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Pollution Control Technology. Arizona Department of Health
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6. Biswas, A.K. and W.G. Davenport. Extractive Metallurgy of
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10. Oglesby, Sabert, Jr., et al. A Manual of Electrostatic Preci-
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and Volume II: Hydrometallurgy and Electrowinning. The Metallur-
gical Society of AIME, New York, New York. 1976.
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Industry. Brass and Bronze Ingot Institute and National Air
Pollution Control Administration. PB 190295. November 1969.
13. Air Pollution Engineering Manual, Second Edition. EPA Publi-
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7-1
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14. Development Document for Proposed Effluent Limitations Guide-
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-------
23. Weisenberg, I.J., and G.E. Umlauf. Evaluation of the Control-
lability of S02 Emissions from Copper Smelters in the State
of Arizona. Pacific Environmental Services, Inc., Final Report
for EPA Contract No. 68-02-1354 Task Order No. 8, Santa Monica,
California, June 1975.
24. Personal communication with Carl H. Billings, Arizona State
Department of Health, Phoenix, Arizona.
7-3
-------
APPENDIX A
SECTION 7.3
PRIMARY COPPER SMELTING
Prepared by
PACIFIC ENVIRONMENTAL SERVICES, INC.
EPA Contract No. 68-02-1890
Task Order No. 3
Project Officer: Arch A. McQueen
Prepared for
ENVIRONMENTAL PROTECTION AGENCY
National Air Data Branch
Research Triangle Park, North Carolina
Fbcific Environmental Services. INC.
CORPORATE AND ENGINEERING 1930 14th Strut Santa Monica. California 90404 Telephone (213) 393-9449
MIDWEST OPERATIONS Suiti228N 2625 Butterfield Road Oak Brook, Itlinoit 60521 Telephone (312) 325-5586
-------
7.3 PRIMARY COPPER SMELTING
7.3.1 Process Description
Pyrometallurgical smelting methods are utilized extensively
in the United States to produce copper from sulfide ores. These
ores usually contain less than 1-percent copper when mined and
therefore must be concentrated before being transported to the
smelter. Concentration to 15- to 35-percent copper is accom-
plished by crushing, grinding, and flotation operations at the
mine site. Sulfur content of the concentrate is generally
25 to 35 percent. Most of the remaining concentrate is iron
(25 percent) and water (10 percent). Some concentrates also con-
tain significant quantities of arsenic, cadmium, lead, boron,
antimony, and other heavy metals.
The most common configuration of operations for pyrometallur-
gical smelters in the United States includes roasting, reverbera-
tory or electric furnace smelting, and converting to produce
blister copper (99+ percent pure copper) from concentrate. The
remaining impurities are usually removed by fire refining and
electrolytic refining. A generalized flowsheet for this com-
bination of operations is illustrated in Figure 7.3-1. About
half of the smelters in the United States do not use the roasting
step and instead feed wet or "green" charge directly to the
smelting furnace.
In roasting, concentrate is heated in air, eliminating 20
to 50 percent of the sulfur as S02- Relatively volatile impuri-
ties such as antimony, arsenic, and bismuth are also driven off,
and some of the iron is converted to oxides which combine with
slag in ensuing processes. Concentrate is mixed with a siliceous
-------
ENTERING THE SYSTEM
Raw concentrates
Fuel
Air
Flux
Fuel
A1r
Siliceous flux
A1r
Miscellaneous miterlal high
In copper
Reducing git/fuel
A1r
ROASTER
(Multiple-Hearth or Fluidlzed Bed)
SMELTING FURNACE
(Reverbtritory or Electric-Arc)
CONVERTER
FIRE-REFINING FURNACE
I
CASTING MH£EL
ELEOmiYTlC REFINING
LEAVING THE SYSTEM
Eases, dust and volatile oxides
to control equipment «nd stack
Gases and dust to xaste heat
boilers, control equipment and stack
Slag to dump
Gases to control equipment
and stack
Gases to stack
Slag to converter
Copper to fabrication
Figure 7.3-1. Typical Primary Copper Smelter Flowsheet
X}-2-
-------
flux (often a low-grade ore) to produce the roaster charge material.
The roasted product, called calcine, serves as a dried and pre-
heated charge for the smelting furnace. Either multiple-hearth or
fluidized-bed roaster furnaces are used for roasting copper concen-
trate. Because there is less air dilution, higher S02 concentra-
tions are present in fluidized-bed roaster gases than in multiple-
hearth roaster gases.
The second step is smelting. In this process, hot calcines
from the roaster, or raw, unroasted concentrate are fused with
limestone and siliceous flux, in reverberatory or electric-arc
furnaces,to produce copper matte. Copper matte is primarily
miscible liquid sulfides and some heavy metals. In reverberatory
furnace operation, heat is supplied by combustion of oil, gas, or
pulverized coal, and is reflected from the roof of the furnace onto
the charge. As the charge is melted, copper, iron, and sulfur form
cuprous sulfide (Cu2S) and ferrous sulfide (FeS). Other minerals
combine with fluxes forming slag. Slag floats on top of the molten
bath and is removed continuously. Copper matte remains in the
furnace until poured. Normal smelting furnace operations produce
a matte which contains 40- to'45-percent copper.
For smelting 1n electric-arc furnaces, heat is generated by
an electric current passing through carbon electrodes which are
lowered into the slag layer of the molten bath. Electric furnaces
do not produce fuel combustion gases, therefore, gas flow rates
are lower and S02 concentrations are higher 1n electric furnace
effluent streams than those 1n reverberatory furnace gases.
The final step in the production of blister copper is con-
verting. Converting is normally performed in Peirce-Smith con-
verters. The converter consists of a cylindrical steel shell.
The shell is mounted on trunnions at either end and rotated about
Its major axis. An opening 1n one side of the converter functions
-------
as a mouth through which molten matte, siliceous flux, and scrap
copper are charged to the converter and gaseous products are
vented. Air or oxygen-enriched air is blown through the metal;
FeS 1s oxidized and combined with the flux to form a slag which
floats on the surface. Relatively pure Cu2S (called "white
metal") is collected 1n the bottom of the converter. After re-
moval of slag, a renewed air blast oxidizes the sulfide sulfur
to S02 leaving blister copper in the converter.
Hoboken converters have recently been installed at one U.S.
smelter to replace the standard Peirce-Smith converters. The
metallurgical operations of the Hoboken unit are the same as those
of the Peirce-Smith unit. However, to prevent dilution air from
entering the exhaust gas stream, the Hoboken converter is fitted
with a stationary side flue instead of a movable hood.
In a newer process, roasting and smelting are combined in one
operation to produce a high-grade copper matte from concentrates
and fluxes, using a flash furnace. Fuel 1s supplied to sustain
combustion reactions, but most of the heat necessary for smelting
is generated autogenously by the oxidation of the sulfides in the
concentrate.
The flash smelting operation has also been applied to the
oxidation of matte to blister copper in the continuous smelting
process. Continuous smelting systems which have been operated at
foreign smelters include the Noranda, WORCRA, Mitsubishi, and
TBRC (top-blown rotary converter) processes.
Blister copper usually contains from 98.5- to 99.5-percent
pure copper. Impurities may include gold, silver, antimony,
arsenic, bismuth, Iron, lead, nickel, selenium, sulfur, tellurium,
and zinc. To further purify the blister copper, fire refining
and electrolytic refining are used. In fire refining, air is
blown through the metal to oxidize remaining impurities; these
-------
are removed as a slag, and the remaining metal bath is subjected
to a reducing at phere to reconvert cuprous oxide to copper.
The fire-refined Copper is cast into anodes and further refined
electrolytically.
Electrolytic refining involves separation of copper from
impurities by electrolysis in a solution containing copper sul-
fate and sulfuric acid. Metallic impurities precipitate from
the solution and form a sludge which is removed and treated for
recovery of precious metals. The copper produced is 99.95- to 99.97-
percent pure.
Hydrometallurgical processes are usually applied to recovery
of copper from oxide ores, but their application in U.S. plants
is limited.
7.3.2 Emissions and Controls
Particulates and sulfur dioxide are the principal air con-
taminants emitted at primary smelters. In some cases, these
emissions are generated directly as a result of the processes
involved, as in the liberation of sulfur from the ore as S02
emissions, or the volatilization of trace-elements to oxide
fumes. Significant quantities of fugitive emissions are genera-
ted from material handling operations and during the charging
and tapping of furnaces. Actual quantities of emissions from a
particular smelter unit depend upon the configuration of equip-
ment 1n the smelting plant and the operating parameters employed.
Table 7.3-1 summarizes the emission factors for the major units
for various smelter configurations. Other potential emission
sources, which have not been quantified, include ore crushing
and preparation, flux crushing, ore storage, concentrate drying,
slag dumping, fire refining, and copper casting.
-5-
-------
Table 7.3-1. EMISSION FACTORS FOR PRIMARY COPPER SMELTERS
a,d
Smelter
Configuration
Reverberatory furnace
followed bv
converters
Multiple- hearth roaster
followed by reverber-
atory furnace and
converters
F1u1d1zed-bed roaster
followed by reverber-
itory furnace and
converters
Flu1d1zed-bed roaster
followed by electric
furnace and
converters
Unit
Reverb.
Converter
Roaster
Roaster am
reverb.'
Converter
Reverb.
Roaster
Converter
Roaster
Electric
furnace
Converter
Total uncontrolled smelter
Control11
PartlculatesC
Ib/ton
Hone . 36
ESP 22
None
ESP
ESP +
SCAP
None
Baghouse
42
2.5
0.28
45
0.2
None
ESP 4.8
Spray
Chamber •*•
ESP ' 1.4
None
ESP
ESP +
SCAP
ESP +
ESP
None
Baghouse +
SCAP
ESP + SCAP
None
Baghouse +
SCAP
None
None
None
42
2.9
0.38
0.38
2.4
55
0.1
1.1
55
0.1
-
135
kg/MT
18
11
21
1.3
0.14 j
22.5
0.1
2.4
0.7
21
1.5
0.19
0.19
1.2
28
0.5
0 55
28
0.05
66.5
*>2C
Ib/ton
390
860
27
410
450
540
61
0.62
66
540
2
_
540
?
131
444
1.254
kg/KT
195
430
14
205
230
270
31
0.31
33
270
1
Z70
1
66
72
627
S03 (as H2S04)C
Ib/ton
0.81
0.06
-
1.5
0.14
0.22
-
•
-
-
kg/MT
0.41
0.03
0.75
0.07
0.11
N0x(as N02)c
Ib/ton
0.09
0.05
-
-
-
.
-
-
-
-
kg/KT
0.045
0.025
'Emission factors are expressed as units per unit weight of concentrated ore processed by the smelter. Approximately
4 unit weights of concentrate are required to produce 1 unit weight of copper metal.
^SP • electrostatic preclpUator
SCAP • single contact add plant
OCAP • double contact add plant
'References 2. 4, 5. 6.7. and 9. Additional Information was furnished by the following agencies:
Arizona Department of Health Services. Phoenix, Arizona
Montana State Department of Health and Environmental Sciences. Helena, Montana
Puget Sound Air Pollution Control District, Seattle, Washington
New Mexico Environmental Improvement Agency. Santa Fe, New Mexico
Ore storage, crushing and handling; flux crushing and handling; concentrate drying and handling; slag dumping; fire
refinery and copper casting are potential emission sources but emission rates have not been quantified.
Roaster and reverbentory furnace emissions are combined and therefore a single set of emission factors 1s provided.
// -6-
-------
Multiple-hearth and fluidized-bed roasters are sources of
both particulates and sulfur oxides. Particulates consist of
oxides of the metals which are found In the concentrate. Copper
and Iron oxides are the primary constituents, but other oxides
such as those of arsenic, antimony, cadmium, lead, mercury, and
zinc may also be present with metallic sulfates and sulfuric
acid. Combustion products from fuel burning also contribute
to the partlculate emissions from multiple-hearth roasters. It
is standard practice 1n the Industry to control particulates from
roaster gases because of the recovery value of the copper in the
dust and because of the presence of toxic particulates such as
arsenic. Cyclones and scrubbers may be used for coarse parti -
culate removal and are usually followed by electrostatic pre-
cipitators (ESP's) or fabric filters for collection of fines.
Smelting furnaces also emit significant quantities of oxi-
dized metal particulates and S02- Particulate collection systems
for smelting furnaces are similar to those used for roasters.
Reverberatory furnace offgases are usually routed through low-
velocity balloon flues and waste heat boilers to recover large
particles and heat, then routed through electrostatic precipi-
tators. Overall collection efficiencies of 95 to 99 percent for
ESP systems are normal for these applications. Efficiencies as
high as 99.7 percent have been reported.
Converter flue gases also contain particulates and S02- In
the standard Pelrce-Smith converter, flue gases are captured
during the blowing phase by movable hooding which covers the con-
verter mouth opening. To prevent freezing of the hood to the
converter (caused by splashing of molten metal), there is a gap
between the hood and the vessel. Sophisticated draft control
devices have been developed which maintain a negative pressure
at the gap to draw air in for cooling and to prevent fugitive
f\ -7-
-------
emissions. During charging and pouring operations, significant
fugitive emissions may occur when the hooding is removed to allow
crane access.
Remaining smelter processes handle material which contains
very little sulfur. Hence, SO^ emissions from these processes are
relatively insignificant. Particulate emissions from fire-refining
operations, however, may still be of concern. Electrolytic refining
does not produce emissions unless the associated sulfuric acid
tanks are open to the atmosphere. Crushing and grinding systems
used in ore, flux, and slag processing also contribute to fugitive
dust problems.
Control of S02 emissions from smelter sources 1s most
commonly performed in a single or double-contact sulfuric acid
manufacturing plant. Use of a sulfuric add plant on copper
smelter effluent gas streams requires that gas be free from par-
ticulate matter and that a certain minimum SOg concentration be maintained.
Table 7.3-2 shows typical average S02 concentrations for the
various smelter unit offgases. These offgas streams may be
treated Individually, or weak and strong concentration streams
may be blended. Typically, single-contact add plants achieve
96.5- to 97-percent conversion of S02 to acid with approximately
2,000 parts per million (ppm) of S02 remaining in the acid plant
effluent gas. Double-contact acid plants collect 98 percent of
the S02 and emit about 500 ppm S02. Absorption of the S0£ in
dimethylaniline (DMA) solution has also been used in U.S. smelters
for production of liquid S02-
Emissions from hydrometallurglcal smelting plants are gene-
rally small in quantity and easily controlled. In the Arbiter
process, ammonia gas escapes from leach reactors, mixer-settlers,
thickeners, and tanks. For control, all of these units are covered
and vented to a packed-tower scrubber which recovers the ammonia
and recycles it.
4-8-
-------
Table 7.3-2. AVERAGE SOe CONCENTRATIONS IN OFFGASES FROM PRIMARY
COPPER SMELTING SOURCES
Unit %S02
Multiple-Hearth Roaster 1.5-3
Fluidized-Bed Roaster 10-12
Reverberatory Furnace 0.5-1.5
Electric-Arc Furnace 4-8
Flash-Smelting Furnace 10-20
Continuous Smelting Furnace 5-15
Peirce-Smith Converter 4-7
Hoboken Converter 8
Single Contact H2S04 Plant 0.2
Double Contact H2S04 Plant 0.05
-9-
-------
No control practices are currently utilized in U.S. smelters
for NOX, CO, or hydrocarbon emissions, which are found in the
offgas streams from units requiring fuel combustion. Multiple-
hearth roasters, reverberatory furnaces, converters, and
refining furnaces are sources of these contaminants. Data are
available for assigning emission factors for NOX emissions from
reverberatory furnaces and converters in only one smelter con-
figuration (Table 7.3-1), Data for assigning emission factors
for CO and hydrocarbons are unavailable.
f\ -10-
-------
References for Section 7.3
1. Air Pollutio: agineering Manual. Air Pollution Control
District, County of Los Angeles. U.S. DHEW, Public Health
Service. PHS Publication No. 999-AP-40. 1967.
2. Weisenberg, I.J. and Umlauf, G.E. Evaluation of the Control-
lability of S02 Emissions from Copper Smelters in the State
of Arizona. Final Report for EPA Contract No. 68-02-1354,
Task Order No. 8. June 1975.
3. Field Surveillance and Enforcement Guide for Primary Metal-
lurgical Industries. U.S. Environmental Protection Agency,
Research Triangle Park. Publication No. EPA-450/3-73-002.
December 1973.
4. Background Information for New Source Performance Standards:
Primary Copper, Zinc and Lead Smelters, Volume 1: Proposed
Standards. U.S. Environmental Protection Agency, Research
Triangle Park. Publication No. EPA-450/2-74-002a. October
1974.
5. Billings, Carl H. First Annual Report on Arizona Copper
Smelter Pollution Control Technology. Arizona Department
of Health Services. April 1977.
6. Compilation of Air Pollution Emission Factors. Second Edi-
tion, Third Printing. U.S. Environmental Protection Agency,
Research Triangle Park. Publication No. AP-42. February
1976.
7. Control of Sulfur Dioxide Emissions in Copper, Lead, and
Zinc Smelting. U.S. Bureau of Mines, Washington, D.C.,
Information Circular 8527. 1971.
8. Yannopoulos, J.C, and Agarwal, J.C. (ed). Extraction Metal-
lurgy of Copper, Volume I: Pyrometallurgy and Electrolytic
Refining, and Volume II: Hydrometallurgy and Electrowinnlng.
The Metallurgical Society of AIME, New York, New York. 1976.
9. Atmospheric Emissions from Sulfuric Acid Manufacturing Pro-
cesses. U.S. DHEW. NAPCA Publication No. 999-13. 1966.
-11-
-------
APPENDIX B
SECTION 7.9
SECONDARY COPPER SMELTING AND ALLOYING
Prepared by
PACIFIC ENVIRONMENTAL SERVICES, INC.
EPA Contract No. 68-02-1890
Task Order No. 3
Project Officer: Arch A. McQueen
Prepared for
ENVIRONMENTAL PROTECTION AGENCY
National Air Data Branch
Research Triangle Park, North Carolina
facific Environmental Services, INC.
CORPORATE AND ENGINEERING 1930 14th Strtct Santa Monica, California 90404 T«ltQhone (213) 393-9449
MIDWEST OPERATIONS Suitt228N 2625 ButteHield Road Oak Brook. Illinois 60521 Telephone (312) 325-5586
-------
7.9 SECONDARY COPPER SMELTING AND ALLOYING
7.9.1 Process Description
The secondary copper industry processes scrap metals for the
recovery of copper. Products include refined copper or copper
alloys in forms such as ingots, wirebar, anodes, and shot.
Copper alloys are combinations of copper with other materials,
notably, tin, zinc, and lead. Also, for special applications,
combinations include such metals as cobalt, manganese, iron,
nickel, cadmium, and beryllium and nonmetals such as arsenic and
silicon.
The principal processes involved in copper recovery are
scrap metal pretreatment and smelting. Pretreatment includes
cleaning and concentration processes necessary to prepare the
material for the smelting furnace. Smelting involves heating
and treating the scrap to achieve separation and purification
of specific metals.
The feed material used in the recovery process can be any
metallic scrap containing a useful amount of copper, bronze
(copper and tin), or brass (copper and zinc). Traditional forms
are punchings, turnings and borings, defective or surplus goods,
metallurgical residues such as slags, skimmings, and drosses,
and obsolete, worn out, or damaged articles including automobile
radiators, pipe, wire, bushings and bearings.
The type and quality of the feed material determines the
processes the smelter will use. Due to the large variety of
possible feed materials available, the method of operation varies
greatly between plants. Generally, a secondary copper facility
deals with less pure raw materials and produces a more refined
product, whereas brass and bronze alloys processors take cleaner
scrap and do less purification and refining. A flowsheet depicting
the major processes that can be expected in a secondary copper
-------
smelting operation 1s shown In Figure 7.9-1. A brass and bronze
alloying operation is shown in Figure 7.9-2.
Pretreatment of the feed material can be accomplished using
several different procedures, either separately or in combination.
Feed scrap is concentrated by manual and mechanical methods such
as sorting, stripping, shredding, and magnetic separation. Feed
scrap 1s sometimes brlquetted in a hydraulic press. Pyrometallur-
gical pretreatment may include sweating, burning of insulation
(especially from wire scrap), and drying (burning off oil and
volatiles) 1n rotary kilns. Hydrometallurglcal methods include
flotation and leaching, with chemical recovery.
In smelting, low-grade scrap is melted in a cupola furnace,
producing "black copper" (70- to 80-percent Cu) and slag; these
are often separated in a reverberatory furnace, from which the
melt is transferred to a converter or electric furnace to produce
"blister" copper which 1s 90- to 99-percent Cu.
Blister copper may be poured to produce shot or castings, but
1s often further refined electrolytically or by fire refining. The
fire-refining process 1s essentially the same as that described in
the primary copper smelting industry (refer to Section 7.3.1).
sequence of events 1n fire-refining 1s (1) charging; (2) melting
in an oxidizing atmosphere; (3) skimming the slag; (4) blowing
with air or oxygen; (5) adding fluxes; (6) "poling" or otherwise
providing a reducing atmosphere; (7) reskimming; and (8) pouring.
To produce bronze or brass rather than copper, an alloying
operation 1s required. Clean, selected bronze and brass scrap 1s
charged to a melting furnace with alloys to bring the resulting
mixture to the desired final composition. Fluxes are added to
remove impurities and to protect the melt against oxidation by
air. A1r or oxygen may be blown through the melt to adjust the
composition by oxidizing excess zinc.
-2-
-------
ENTERING THE SYSTEM
LEAVING THE SYSTEM
Low-grade scrap
(slags, skinning;,
drosses, chips, _
borings)
A1r
Flux.
Fuel.
Air_
Flux.
Fuel.
A1r_
Flux.
Fuel.
A1r_
PYROMETALLURGICAL
PRETREATMENT
(Drying)
CUPOLA
SMELTING FURNACE
(Rtverberatory)
P
CONVERTER
A1r_
Fuel.
Reducing medium,
(poling)
Gases, dust, metal oxides
"to control equipment
Carbon monoxide, paniculate dust,
.metal oxides, to afterburner and
partlculate control
•Slag to disposal
.Gases and metal
equipment
oxides to control
.Gases and metal oxides to control
equipment
CASTINGS AND SHOT
PRODUCTION
Fugitive metal oxides from
..pouring to either hooding
or plant environment
FIRE REFINING
1
-•-Gases, metal dust, to control device
Figure 7.9-1. Low-Grade Copper Recovery
B-3-
-------
ENTERING THE SYSTEM
LEAVING THE SYSTEM
High-gride scrap
(wire, pipe, bearing,.
puncMngs. radiators)
MANUAL AND MECHANICAL
PRETREATMENT
(Sorting)
Flux.
Fuel.
Alloy material (zinc,tin. etc)
MELTING AND
ALLOYING FURNACE
.Fugitive dust to atmosphere
.Undeslred scrap to sale
Gases, metal oxides to control equipment
Lead, solder, babbitt metal
Particulates, hydrocarbons, aldehydes, fluorides,
and chlorides to afterburner and partlculate
control
Metal oxides to control equipment
Sl»g to disposal
Fugitive metal oxides generated during
pouring to either plant environment or
hooding
Figure 7.9-2. High-Grade Brass and Bronze Alloying
-------
With zinc-rich feed such as brass, the zinc oxide concen-
tration in the exhaust gas is sometimes high enough to make re-
covery for its m • ' value desirable. This process is accomplished
by vaporizing the zinc from the melt at high temperature and
capturing the oxide downstream in a process baghouse.
The final step is always casting of the suitably alloyed
or refined metal into a desired form. This form may be shot,
wirebar, anodes, cathodes, ingots, or other cast shapes. The
metal from the melt is usually poured into a ladle or a small pot,
which serves the functions of a surge hopper and a flow regulator,
then into a mold.
7.9.2 Emissions and Controls
The principal pollutants emitted from secondary copper
smelting activities are particulate matter in various forms.
Removal of insulation from wire by burning causes particulate
emissions of metal oxides and unburned insulation. Drying of
chips and borings to remove excess oils and cutting fluids can
cause discharges of large amounts of dense smoke consisting of
soot and unburned hydrocarbons. Particulate emissions from the
top of a cupola furnace consist of metal oxide fumes, dirt, and
dust from limestone and coke.
The smelting process utilizes large volumes of air to oxidize
sulfldes, zinc, and other undesirable constituents of the feed.
This procedure generates much particulate matter in the exit gas
stream. The wide variation among furnace types, charge types,
quality, extent of pretreatment, and size of charge is reflected
in a broad spectrum of particle sizes and variable grain loadings
in the escaping gases. One major factor contributing to differences
in emission rates is the amount of zinc present in scrap feed
materials; the low-boiling zinc evaporates and combines with air
oxygen to give copious fumes of zinc oxide.
h -5-
-------
Metal oxide fumes from furnaces used in secondary smelters
have been controlled by baghouses, electrostatic precipitators,
or wet scrubbers. Efficiency of control by baghouses may be better
than 99 percent, but cooling systems are needed to prevent the
hot exhaust gases from damaging or destroying the bag filters.
A two-stage system employing both water jacketing and radiant
cooling is common. Electrostatic precipitators are not as well
suited to this application, having a low collection efficiency
for dense particulates such as oxides of lead and zinc. Wet
scrubber installations are also relatively ineffective in the
secondary copper industry. Scrubbers are useful mainly for
particles larger than 1 micron, but the metal oxide fumes genera-
ted are generally submicron in size.
Particulate emissions associated with drying kilns can be
similarly controlled. Drying temperatures up to 150°C (SOOT)
produce relatively cool exhaust gases, requiring no preceding
for control by baghouses.
Wire burning generates much particulate matter, largely
unburned combustibles. These emissions can be effectively con-
trolled by direct-flame afterburners, with an efficiency of 90
percent or better 1f the afterburner combustion temperature is
maintained above 1,000°C (1,800°F). If the insulation contains
chlorinated organics such as polyvinyl chloride, hydrogen chloride
gas will be generated and will not be controlled by the afterburner.
One source of fugitive emissions in secondary smelter opera-
tions 1s charging of scrap Into furnaces containing molten metals.
This often occurs when the scrap being processed is not sufficiently
compact to allow a full charge to fit into the furnace prior to
heating. The introduction of additional material onto the liquid
metal surface produces significant amounts of volatile and com-
bustible materials and smoke which can escape through the charging
-6-
-------
door. Briquettlng the charge offers a possible means of avoiding
the necessity of such fractional charges. When fractional charging
cannot be eliminated, fugitive emissions are reduced by turning
off the furnace burners during charging. This reduces the flow of
exhaust gases and enhances the ability of the exhaust control
system to handle the emissions.
Metal oxide fumes are generated not only during melting, but
also during pouring of the molten metal into the molds. Other
dusts may be generated by the charcoal, or other lining, used in
association with the mold. Covering the metal surface with ground
charcoal is a method used to make "smooth-top" ingots. This pro-
cess creates a shower of sparks, releasing emissions into the
plant environment at the vicinity of the furnace top and the molds
being filled.
Emission factor averages and ranges for six different types of
furnaces are presented in Table 7.9-1.
fo-7-
-------
Table 7.9-1. EMISSION FACTORS FOR PARTICIPATE MATTER AND ALLOYING FROM FURNACES USED IN SECONDARY
COPPER SMELTING AND ALLOYING PROCESSES3
A. Cupolas
Type of charge
Scrap copper
Insulated copper wire
Insulated copper wire
Scrap copper and brass
Scrap copper and brass
Control
equipment
0
0
1
0
1
Emissions
Avg
(kg/MT)
0.002
120
5
35
1.2
Range
(kg/MT)
-
-
-
30-40
1.0-1.4
Avg
(Ib/ton)
0.003
230
10
70
2.4
Range
(Ib/ton)
-
-
-
60-80
2.0-2.8
No. of
units
tested
1
1
1
2
2
No. of
plants
tested
1
1
1
1
1
00
I
B. Reverberatory Furnaces
Type of charge
Copper
Copper
Brass and bronze
Brass and bronze
Control b
equipment
0
2
0
2
Emissions
Avg
(kg/MT)
2.6
0.2
18
1.3
Range
(kg/MT)
0.4-15
0.1-0.3
0.3-35
0.3-2.5
Avg
(Ib/ton)
5.1
0.4
36
2.6
Range
(Ib/ton)
0.8-30
0.3-0.6
0.6-70
0.05-5
No. of
units
tested
2
2
2
No. of
plants
tested
12
2
2
2
aAll factors given 1n terms of raw materials charged to unit.
Control equipment:
0 signifies none operated
1 Indicates electrostatic preclpltator used
2 indicates baghouse filter system
-------
Table 7.9-1.
EMISSION FACTORS FOR PARTICULATE MATTER AND ALLOYING FROM FURNACES USED IN SECONDARY
COPPER SMELTING AND ALLOYING PROCESSES (CONTINUED)3
C. Rotary Furnaces
Type of charge
Brass and bronze
Control
equipment
0
1
Emissions
Avg
(kg/MT)
150
7
Range
(kg/MT)
50-250
3-10
Avg
(Ib/ton)
300
13
Range
(Ib/ton)
100-500
6-19
No. of
units
tested
2
3
No. of
plants
tested
2
3
D. Crucible and Pot Furnaces
Type of charge
Brass and bronze
Control b
equipment
0
1
Emissions
Avg
(kg/MT)
11
0.5
Range
(kg/MT)
1-20
0.1-1
Avg
(Ib/ton)
21
1
Range
(Ib/ton)
2-40
0.1-2
No. of
units
tested
17
5
No. of
plants
tested
13
3
All factors given In terms of raw materials charged to unit,
Control equipment:
0 signifies none operated
1 Indicates electrostatic preclpltator used
2 Indicates baghouse filter system
-------
Table 7.9-1. EMISSION FACTORS FOR PARTICIPATE MATTER AND ALLOYING FROM FURNACES USED IN SECONDARY
COPPER SMELTING AND ALLOYING PROCESSES (CONCLUDED)3
E. Electric Arc Furnaces
Type of charge
Copper
Brass and bronze
Control6
equipment
0
2
0
2
Emissions
Avg
(kg/MT)
2.5
0.5
5.5
3
Range
(kg/MT)
1-4
0.02-1.0
2-9
-
Avg
(Ib/ton)
5
1
11
6
Range
(Ib/ton)
2-8
0.04-2
4-18
-
No. of
units
tested
3
2
3
1
No. of
plants
tested
2
1
2
1
j^ F. Electric Induction Furnaces
Type of charge
Copper
Brass and bronze
Control6
equipment
0
2
0
2
Emissions
Avg
(kg/MT)
3.5
0.25
10
0.35
Range
(kg/MT)
-
-
0.3-20
0.01-0.65
Avg
(Ib/ton)
7
0.5
20
0.7
Range
(Ib/ton)
-
-
0.5-40
0.01-1.3
No. of
units
tested
1
1
-
-
No. of
plants
tested
1
1
18
6
Vll factors given 1n terms of raw materials charged to unit.
Control equipment:
0 signifies none operated
1 Indicates electrostatic preclpltator used
2 Indicates baghouse filter system
-------
Additional footnotes to Table 7.9-1.
The information fc ."able 7.9-1 was based on unpublished data furnished
by the following:
Philadelphia Air Management Services, Philadelphia, Pennsylvania
New Jersey Department of Environmental Protection, Trenton, Mew
Jersey
New Jersey Department of Environmental Protection, Metro field
office, Springfield, New Jersey
New Jersey Department of Environmental Protection, Newark field
office, Newark, New Jersey
New York State Department of Environmental Conservation, New
York, New York
The City of New York Department of Air Resources, New York,
New York
Cook County Department of Environmental Control, Maywood,
Illinois
Wayne County Department of Health, Air Pollution Control
Division, Detroit, Michigan
City of Cleveland Department of Public Health and Welfare,
Division of Air Pollution Control, Cleveland, Ohio
State of Ohio Environmental Protection Agency, Columbus, Ohio
City of Chicago Department of Environmental Control, Chicago,
Illinois
South Coast Air Quality Management District, Los Angeles,
California
-------
References for Section 7.9
1. Air Pollution Aspects of Brass and Bronze Smelting and Refining
Industry. U.S. DHEW, PHS, EHS, National Air Pollution Control
Administration, Raleigh, N.C. Publication No. AP-58. November
1969.
2. Air Pollution Engineering Manual. Air Pollution Control District,
County of Los Angeles. U.S. DHEW, Public Health Service. PHS
Publication No. 999-AP-40. 1967.
0-12-
-------
APPENDIX C
PRIMARY COPPER SMELTING PROCESS COMPENDIUM
Prepared by
PACIFIC ENVIRONMENTAL SERVICES, INC.
EPA Contract No. 68-02-1890
Task Order No. 3
Project Officer: Arch A. McQueen
Prepared for
ENVIRONMENTAL PROTECTION AGENCY
National Air Data Branch
Research Triangle Park, North Carolina
toific Environmental Services. INC.
CORPORATE AND ENGINEERING 1930 14th StrMt S«nti Monic*. California 90404 Telephone 1213) 393-9449
MIDWEST OPERATIONS Suit*228N 2625 Butttrfi»W Ro»d O»k Brook, Illinoil 60521 Telephone (312) 325-5586
-------
TABLE OF CONTENTS
Section Page
PRIMARY COPPER SMELTING 1
PROCESS DESCRIPTION 1
PYROMETALLURGICAL SMELTING 1
Raw Materials 3
Feed Preparation 3
Roasting 5
Smelting 7
Converting 10
Refining 13
Fire Refining 13
Electrolytic Refining 13
New Processes 14
Flash Smelting 14
Continuous Smelting 15
HYDROMETALLURGICAL SMELTING 15
EMISSIONS 18
PYROMETALLURGICAL SMELTING 18
Emissions From Bedding Plants 18
Roaster Emissions . . . 18
Emissions From Smelting Furnaces 19
Converter Emissions 20
Other Sources 20
HYDROMETALLURGICAL SMELTING 22
CONTROL PRACTICES 22
CODING NEDS FORMS 25
CODING EIS/P&R FORMS 39
GLOSSARY 40
REFERENCES 42
-------
LIST OF ILLUSTRATIONS
Figure Page
1 Composite Flow Diagram for Pyrometallurgical Smelting
and Refining in the Primary Copper Industry 2
2 Multiple-Hearth Roaster 6
3 Fluidized-Bed Processing 8
4 Copper Converter 11
5 Copper Converter Operation 12
6 Outokumpu Flash Smelting Furnace 16
7 Noranda Continuous Smelting 17
8 Fluctuations in Converter Off-Gas Volume and Sulfur
Dioxide Concentrations 21
9 Standard NEDS Form for Primary Copper Smelting:
Multiple-Hearth Roaster 26
10 Standard NEDS Form for Primary Copper Smelting:
Fluidized-Bed Roaster 27
11 Standard NEDS Form for Primary Copper Smelting:
Concentrate Dryer 28
12 Standard NEDS Form for Primary Copper Smelting:
Reverberatory Smelting Furnace Without Roaster 29
13 Standard NEDS Form for Primary Copper Smelting:
Reverberatory Smelting Furnace With Roaster 30
14 Standard NEDS Form for Primary Copper Smelting:
Electric Smelting Furnace 31
15 Standard NEDS Form for Primary Copper Smelting:
Converter Furnace Without Roaster 32
16 Standard NEDS Form for Primary Copper Smelting:
Converter Furnace With Roaster 33
17 Standard NEDS Form for Primary Copper Smelting:
Fire-Refining Furnace 34
18 Standard NEDS Form for Primary Copper Smelting:
Electrolytic Refining 35
19 Standard NEDS Form for Primary Copper Smelting:
Flash Smelting Furnace 36
20 Standard NEDS Form for Primary Copper Smelting:
Continuous Smelting Furnace 37
LIST OF TABLES
Table Page
1 Common Copper-Bearing Minerals 4
2 IPP Codes for SIC Number 3331 (Primary Copper Smelting) . 38
-------
PRIMARY COPPER SMELTING
PROCESS DESCRIPTION
PYROMETALLURGICAL SMELTING
Pyrometallurgical smelting 1s a process for recovering metal
from ore by techniques involving heating to very high temperatures.
As applied to the production of copper, pyrometallurgical tech-
niques are commonly employed in smelting sulfide ores which, when
oxidized by air, furnish much heat because of the conversion of
their component sulfur to sulfur dioxide.
The most common configuration for pyrometallurgical smelters
in the United States comprises four distinct high-temperature
techniques:(1) roasting, in which a concentrated ore is heated
with fluxes to eliminate some sulfur and produce a calcine suit-
able for smelting; (2) smelting proper, in which the calcine is
heated to produce a liquid matte containing sulfides of copper and
iron; (3) converting, in which the matte reacts with oxygen form-
ing iron oxide, sulfur dioxide, and a nearly pure product known
as blister copper; and (4) fire refining, in which blister copper
is melted, partially oxidized, then reduced, generating a still
purer product. Newer processes combine some of these steps. The
final purification, when required, is done by electrolytic
refining.
A composite illustration of the roasting, reverberatory or
electric furnace smelting, and converting configuration options
for pyrometallurgical smelting is shown in Figure 1.
Concentrated ore can be fed directly to a reverberatory
smelting furnace, or the smelting step may be preceded by
roasting. In some installations, the concentrate is dried
(without roasting) before being fed to the reverberatory furnace.
Green (undried, unroasted) concentrate may be fed to a reverbera-
tory smelter, but not to an electric smelting furnace.
c1 -1-
-------
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Figure 1. Composite Flow Diagram for Pyrometallurgical Smelting and Refining in the Primary Copper Industry
-------
Raw Materials
The bulk of the world's copper ore reserves are found as
either copper sulfides, copper oxides, or native copper. The
most widely used ores in pyrometallurgical smelting are the sul-
fides such as chalcopyrite (CuFeS2) and bornite (CUgFeSj. These
ores usually contain less than 1-percent copper when mined and
therefore must be concentrated before being transported to the
smelter. Concentration to 15- to 35-percent copper is accomplished
by crushing, grinding, and flotation operations at the mine site.
Oxide ores also may contain less than 1-percent pure copper, but
can be processed in hydrometallurgical leaching operations and
are generally not concentrated. Table 1 shows the sulfide and
oxide minerals from which copper is extracted.
Due to the availability of sulfide ores, pyrometallurgical
smelting has been utilized extensively 1n this country for many
years. To a certain extent, the choice of smelting equipment
used for the recovery of copper from ores 1s influenced by the
chemical composition of the concentrate feed. For example, a
high sulfur content in the concentrate usually dictates the use
of a roasting stage for partial sulfur removal prior to charging
to a smelting furnace. As mentioned previously, concentrate
material can vary over a wide range of copper contents. Sulfur
percentages can also vary between 25 to 35 percent for concentrate
materials. The remainder of the material 1s composed, for the
most part, of Iron (-25 percent) and water (10 percent). Some
concentrates also contain significant quantities of arsenic,
cadmium, lead, boron, antimony, and other heavy metals.
Feed Preparation
Concentrate material arriving at the smelter is mixed with
a flux material 1n a bedding plant. The flux is usually made of
low-grade siliceous ore, sand, and gravel. The bedding plant
consists of several pads of concrete where an overhead crane is
used to deposit proper quantities of concentrate and flux. The
material 1s then mixed by a front-end loader to produce the
roaster charge.
-------
Table 1. COMMON COPPER-BEARING MINERALS
Mineral
Chalcopyrite
Chalcocite
Bornlte
Covellite
Malachite
Azurite
Cuprite
Chrysocolla
Theoretical formula
CuFeS2
Cu2S
CuS
CuCOs - Cu(OH)2
2CuC03 - Cu(OH)2
Cu20
CuSi03 - 2H20
34.9
20.2
25.6
33.5
0
0
0
0
<* -4-
-------
Roasting
Roasting is the heating of concentrated ores to produce
partially oxidized calcines. In this process, the charge is
heated in air; sulfide sulfur combines with oxygen to form sul-
fur oxides; and some sulfide metals from metal oxides. In the
typical roaster-furnace-converter smelter, roasting eliminates
20 to 50 percent of the sulfur in the charge. Roasting can,
however, be used to eliminate all the sulfur ("dead" roasting)
or only a very small percentage of the sulfur. The amount re-
moved depends on the volume of air supplied to the process per
unit of charge and the roasting temperature. Roasting also
serves to dry and preheat the product (called "calcine") before
charging to the smelting furnace. During roasting, a portion of
the iron in the charge is converted to ferric oxide (Fe203), in
which form it will be removed in the slag from the smelting fur-
nace. Some of the iron will also be oxidized to magnetite (FegO.)
which can lead to problems in the smelting furnace, such as slags
of high copper content, reduced smelting rate, and furnace bottom
buildup. If any impurities such as arsenic, antimony, or bismuth
are present in the ore, they will be volatilized in the roasting
step. These factors, with the added costs of operating a roaster,
must be considered at each smelter when deciding whether to uti-
lize a roasting step or to feed a wet or "green" concentrate
directly to the smelting furnace.
The multiple-hearth furnace is commonly used for roasting.
This is a cylindrical, brick-lined vessel divided from top to
bottom by horizontal brick hearths. Feed is dropped into the top
drying hearth near the central shaft and is moved outward on the
hearth by rotating rabble arms until it is dropped to the hearths
below. Air and auxiliary fuel are added as needed at various
levels of the furnace. Temperatures range from 400°F in the top
hearths to 1,400°F at the bottom level where the hot calcine pro-
duct is removed (see Figure 2).
f -5-
-------
RABBLE
ARM
RABBLE
BLADE
HOT AIR
TO EXHAWST
Figure 2. Multiple-Hearth Roaster
•«. -6-
C-
-------
A more recent development in roaster technology has produced
the fluidlzed-bed roaster. The fluidized-bed roasting process is
characterized by a gas-solid reaction in a dense suspension of
solids maintained in a turbulent mass by the upward flow of gases
that affect the reaction. The roaster is essentially a cylindri-
cal refractory lined steel shell used to contain the suspended
solids, Figure 3.
Air is forced into the roaster through tuyeres in a refrac-
tory lined steel constriction plate that is placed at the bottom
of the shell. The two best known types of fluidized-bed roasters,
the Lurgi and the Dorr-Oliver, are characterized by different tuyere
design.
Reaction rates in fluidized-bed roasting are rapid, and in-
dustrial copper smelters treat 1n the order of 15 to 50 tons of
concentrate per square meter of hearth area per day. An important
consequence of the high reaction rates 1s the high efficiency of
oxygen utilization by the roasting reactions. This leads to an
air requirement only slightly in excess of stolchometric and it
results in high S02 concentrations in the effluent roaster gases.
Roasting 1s not applicable to blast furnace, flash, or single-
step smelting, all of which incorporate the roasting reactions
(and their heats of oxidation) in the smelting step.
Smelting
Smelting 1n the furnace is the next process in a typical
pyrometallurglcal facility. Smelting 1s the heating of calcines
accompanied by a chemical change resulting in the formation of
liquid metallic sulfldes, termed matte. Most of the plants in
the United States use reverberatory furnaces for this step. Hot
calcine or raw unroasted concentrate is charged to hoppers with
siliceous or limestone flux and dropped into the furnace through
-7-
-------
OFF-MS
SLURRY
FEED
TUYERE
HEADS
PRODUCT
Figure 3. Flu1d1zed-Bed Processing
-------
staggered holes 1n the roof. Heat 1s supplied by combustion of
oil, gas, or pulverized coal and is reflected from the roof of
the furnace onto the charge. About 4-million Btu are required
per ton of hot calcine. Although reverberatory furnaces have
low thermal efficiencies, almost all are equipped with waste heat
boilers to recover approximately 50 percent of the heat as super-
heated steam.
The principal purpose of the smelting operation using the
reverberatory furnace is the separation of minerals such as iron,
aluminum, calcium, and magnesium from the copper to produce the
copper "matte." This is accomplished by combining the copper and
iron which are present in the charge with sulfur to form cuprous
sulfide (Cu2S) and ferrous sulfide (FeS). These two sulfides are
miscible in the molten state and make up 95 percent of the copper
matte which is produced. Heavy metals can also be present in the
matte layer. Gangue minerals are removed as complex ferrous sili-
cates. These silicates contain dissolved small amounts of the
basic oxides (AlgOj, CaO, MgO). A slag material is formed which
floats on top of the molten bath and is removed continuously into
slag pots. Copper matte is tapped intermittently from tap holes
near the bottom of the furnace and 1s conveyed in a molten con-
dition to the converters. Mattes containing 40- to 45-percent
copper are generally best for efficient converter operation.
Some plants use an electric-arc smelting technique as an
alternative to the reverberatory furnace. The feed to the elec-
tric furnace may or may not be roasted, but must at least be dried
to prevent explosions due to rapid expansion of steam. Heat is
generated in the furnace by an electric current passed through
carbon electrodes in the slag layer of the molten bath within the
furnace, smelting the new charge which covers the bath. As the
copper concentrates and fluxes are smelted, they settle into the
bath, form slag and matte layers, and are tapped.
C-9-
-------
Converting
The final step in the production of blister copper is con-
verting. This p -ess is normally performed in Peirce-Smith con-
verters. The converter consists of a cylindrical steel shell.
The shell is mounted on trunnions at either end and rotated about
its major axis. An opening in one side of the converter functions
as a mouth through which molten matte is charged and gaseous pro-
ducts are vented. Blowing air is supplied through a header along
the back of the converter, from which a horizontal row of tuyere
pipes extend into the interior of the vessel. (See Figure 4.)
Typically, several of these vessels are maintained at a facility
with each converter running through a 9- to 12-hour cycle per
batch.
The copper converting cycle consists of two phases. In the
first phase, molten matte, highly siliceous ore flux, and scrap
copper are charged to the converter. The vessel 1s rotated until
the tuyeres are covered and a hood is lowered over the converter
opening. Air or oxygen-enriched air is blown through the tuyeres
into the metal. During the early stages of this first blowing
period, FeS is oxidized and combined with the siliceous flux. A
slag is formed which floats on the surface. Relatively pure
Cu2S (called "white metal") is collected 1n the bottom of the con-
verter. At intervals, the operator discontinues blowing and skims
slag from the unit. A series of "slag blows" may be performed
until sufficient white metal is accumulated so that the tuyeres
are covered when the converter is rotated Into position for the
"copper blow." At that point, the air blast 1s again started
and the white metal 1s oxidized to blister copper. A typical
cycle for a Peirce-Smith converter showing the copper operation
is diagrammed in Figure 5.
-10-
-------
OFF-GAS
TUYERE
PIPES
SILICEOUS
FLUX
Figure 4. Copper Converter
-------
CHARGING
BLOWING
SKHMING
Figure 5. Copper Converter Operation
-12-
-------
Hoboken converters have recently been installed at a U.S.
smelter to replace the standard Peirce-Smlth converters. The
metallurgical operations of the Hoboken unit are the same as
those of the Peirce-Smith: copper matte is charged to the unit;
air is blown through matte; slag is removed; and blister copper
is produced. However, to prevent dilution air from entering
the exhaust gas stream, the Hoboken converter is fitted with a
stationary side flue and with rotating seals instead of a movable
hood.
Refining
Blister copper usually contains from 98.5- to 99.5-percent
copper. Impurities which may occur in blister copper include
gold, silver, antimony, arsenic, bismuth, iron, lead, nickel,
selenium, sulfur, tellurium, and zinc. To further purify the
blister copper, fire refining and electrolytic refining are used.
*
Fire Refining
A fire-refining furnace can be of the reverberatory or cylin-
drical converter type. In a cylindrical furnace, air is first
blown through the metal to oxidize all of the impurities and a
portion of the copper. When the copper oxide content reaches
about 1 percent, blowing is stopped, and a slag layer 1s skimmed
off the unit. The metal bath 1s then subjected to a reducing
atmosphere either by fuel-rich combustion of pulverized coal, oil
or gas, or by poling. In poling, green logs are forced into the
metal bath, and are destructively distilled. However, this pro-
cess is not common in modern smelters. The resulting atmosphere
in the furnace causes the reduction of the cuprous oxide to copper.
The fire-refined copper still may contain small quantities
of gold, silver, and other Impurities. These impurities may have
value, 1f recovered, and also reduce the strength, electrical
-------
conductivity, and ductility of the copper. For chemical manu-
facturing purposes, such as the production of copper sulfate for
agricultural use, fire-refined copper may be used without further
processing. However, for most applications, including metallur-
gical, the fire-refined copper is cast into anodes and is further
treated by electrolytic refining.
Electrolytic Refining
Electrolytic refining involves separation of copper from
impurities by electrolysis. Fire-refined anodes are immersed in
a solution bath containing copper sulfate and sulfuric acid.
Metallic impurities precipitate from the solution and form a
sludge which is removed and treated for recovery of precious
metals. Cathode copper (99.95- to 99.97-percent pure) is removed
from the remelted and made Into bars, Ingots, or slabs for
marketing purposes.
New Processes
The sequence of operations described previously is utilized
in most copper smelting Installations in the United States. In
part, because of air pollution control regulations, new processes
have been developed to be used in primary smelting. These areas
of new technology include flash smelting furnaces and continuous
smelting units.
Flash Smelting
Flash furnace smelting combines the operations of roasting
and smelting to produce a high-grade copper matte from concentrates
and flux. Charge material must be fine-grained and essentially
"bone-dry" to ensure an even and homogeneous distribution as it
1s injected into the furnace and mixed with preheated (up to 930°F)
-------
air or oxygen. Oil is supplied to the furnace to sustain flash
combustion reactions, but most of the smelting heat is generated
autogenously by the oxidation of the sulfides in the concentrate.
This heat smelts the particles as they fall through the reaction
section into a settler section where molten matte is separated
from slag. Since high-grade mattes are normally produced (50-
to 60-percent Cu), flash smelter slag is also high in copper and
must be treated for metal recovery. This is normally accomplished
by flotation. Use of flash smelting furnaces also requires modi-
fications to the operations of the converters to accommodate the
higher grade matte. Figure 6 shows a typical flash smelting
furnace.
Continuous Smelting
Continuous pyrometallurgical smelting processes have been
developed and implemented at foreign smelters but have not as yet
been utilized in U.S. plants. Processes which have been developed
include Noranda, WORCRA, Mitsubishi, and TBRC (top-blown rotary
converter) smelting. Basically, these operations combine the
flash-smelting principal of autogenous smelting with an additional
step of Injecting gas to oxidize the copper matte to blister copper
in the same vessel. The Noranda continuous smelting process is
illustrated 1n Figure 7.
HYDROMETALLURGICAL SMELTING
Hydrometallurgical processes have been successfully applied
to the recovery of copper from oxide ores. These involve leaching
of copper from ore into a solution which is then purified and
treated to recover the copper. Processes have also been developed
to recover copper from sulfide ores using hydrometallurgical
techniques, but their application in U.S. plants has been limited.
One such system, the Arbiter process, utilizes an anhydrous
ammonia leaching reaction, followed by organic solvent extraction
and electrowinning to produce high purity copper cathodes.
-15-
-------
PREHEATED
AIR
CONCENTRATE
J.
, CONCENTRATE BURNER
:— OIL
SLAG
•ATTE
SLAG MATTE SETTLER
Figure 6. Outokumpu Flash Smelting Furnace
-16-
-------
FEEDER
$02
OFF-GAS
CONCENTRATE
•PELLETS AND FLUX
MR TUYERE
COPPER
REDUCING GAS
TUYERE
Figure 7. Noranda Continuous Smelting
C7-17-
-------
EMISSIONS
PYROMETALLURGICAL SMELTING
The principal air contaminants emitted from primary smelters
are sulfur dioxide and particulates. Sulfur dioxide is a major
product inevitably generated in the pyrometallurgical process, as
previously explained. Particulates, on the other hand, are genera-
ted mainly in the manipulation of materials or in combustion of
fuel, and are not inherent products of the smelting process. A
significant fraction of the particulate emissions may be represen-
ted by fugitive emissions from crushing and grinding operations
and from charging and tapping of furnaces.
The following paragraphs describe emissions from processes
and equipment common in pyrometallurgical smelters which process
concentrates of sulfide ores.
Emissions From Bedding Plants
The preparation of the concentrate feed in the bedding plant
can be a source of fugitive particulate emissions. The extent
to which these emissions become a problem depends on the type of
cover or enclosure which 1s used 1n the bedding area and the
method of transporting the materials from the bedding plant to
the smelting or roasting furnace. Local wind conditions are a
factor in determining whether these emissions cause 1n-plant
housekeeping problems or affect areas outside of plant property.
Roaster Emissions
Multiple-hearth and fluidized-bed roasters are sources of
both particulates and sulfur oxides. Particulates consist of
oxides of the metals which are found in the concentrate. Copper
and iron oxides are the primary constituents, but other metals
I? -18-
-------
such as arsenic, antimony, cadmium, lead, mercury, and zinc may
also be present with metallic sulfates and sulfuric acid.
Combustion products from fuel burning also contribute to the
particulate emissions from multiple-hearth roasters. Fluidized-
bed roaster gases typically contain 10- to 15-percent S02 as
compared to 0.5 to 6 percent in multiple-hearth roaster gases.
Both types of roasters generate about the same amount of
sulfur oxides per unit of charge, but the concentrations of S02
in the effluent gases are quite different due to the excessive
leakage often associated with the multiple-hearths. Fluidized-
bed roasters are completely enclosed and operate at a positive
internal pressure (2 to 4 psig). Due to the positive internal
pressure, any openings in the roaster walls can be large sources
of fugitive emissions. Proper maintenance is effective in keeping
these emissions to a minimum.
Emissions From Smelting Furnaces
Reverberatory and electric smelting furnaces also emit sig-
nificant quantities of particulates and S02« A slight negative
pressure is usually maintained within a reverberatory smelting
furnace and infiltration air combines with combustion gases to
produce large gas flow rates out of the unit. Occasionally,
positive pressure surges, especially during charging, cause
large quantities of fugitive particulates and S02 to escape through
the furnace roof and walls. Electric smelting furnaces, on the
other hand, do not produce combustion gases and do not utilize
outside air leakage. Hence, effluent gas flow rates and fugitive
emissions are reduced, and S02 concentration in the effluent gas
is higher. Both furnace types produce fugitive emissions when
tapping and pouring matte or slag into launders and ladles.
-19-
-------
Converter Emissions
Emissions from converter operations follow a pattern genera-
ted by the air-blowing cycle, as shown in Figure 8. In the opera-
tion of a standard Peirce-Smith converter, the flue gases con-
taining participates and S02 are captured during the blowing phase
by movable hooding which covers the converter mouth opening. Most
hooding arrangements are fairly effective in capturing the effluent
gas stream from the converter. To prevent freezing of the hood to
the converter, caused by splashing of molten metal, there is a gap
between the hood and the vessel. Fairly sophisticated draft con-
trol devices have been developed to maintain a negative pressure
at the gap to draw air in for cooling and prevent excessive fugi-
tive emissions. During charging and pouring operations, the
hooding is removed to allow crane access, and significant fugitive
emissions occur. These fugitive emission problems should theoreti-
cally be eliminated when using Hoboken converters* since the
stationary side flues are in place during charging and pouring to
collect the exhaust gases. However, in the only U.S. application
of these converters, design problems have caused positive pressure
buildups at the opening between the converter vessel and the flue.
Therefore, it cannot at this time be said that the use of Hoboken
converters 1s completely effective 1n eliminating fugitive emissions.
Other Sources
Remaining smelter processes handle material which is over
98-percent copper and contains very little sulfur. Hence, S02
emissions from these processes are Insignificant when compared to
roasters, smelting furnaces, and converters. Particulate emissions
from fire-refining operations, however, may still be of concern.
Fire-refining furnaces do not vent to a stack but are open and
vent directly Into the smelting building. If poling is used,
(« -20-
-------
so?
CONTENT,
OFFGAS
VOLUME,
scfm
CONVERTER'
AIR BLOW,
scfm
10
t
6
4
2
0
40,000
35,000
30,000
25,000
20,000
15,000
10,000
5,000
0
20,000
15,000
10,000
5,000
0
Figure 8. Fluctuations in Converter Offgas Volume and
Sulfur Dioxide Concentrations
-21-
-------
black smoke can be generated, but in general, participate and
S02 emissions from this type of furnace are minimal. Electro-
lytic refining c •; not produce emissions unless sulfuric acid
tanks are open to the atmosphere.
Auxiliary functions at the smelter, such as slag processing,
may also contribute to fugitive dust problems through the opera-
tion of crushing and grinding systems.
HYDROMETALLURGICAL SMELTING
Emissions from hydrometallurgical smelting plants are
generally small in quantity and easily controlled. In the Arbiter
process, ammonia gases are generated by leach reactors, mixer-
settlers, thickeners, and tanks. All of these units are routinely
covered and vented to a packed-tower scrubber. The scrubber
removes the ammonia and recycles it into the system.
CONTROL PRACTICES
Control of particulate emissions from certain sources has
been practiced for many years because of the recovery value of
the copper contained in the dusts. Electrostatic precipitators
have been used for control of particulates from roasters, smelting
furnaces, and converters. Cyclones and scrubbers, however, are
more commonly applied to control of particulates from the con-
centrate dryers.
In a fluidized-bed roaster, 70 to 90 percent of the solids
are carried out through the top of the roaster with the effluent
gases. The offgases from the fluidized-bed roaster are passed
through a series of primary and secondary cyclones to collect the
particulate which 1s then fed to the smelting furnace. The
fraction of the particles carried out with the effluent gases
depends principally upon the velocity of the gases in the roaster
and the size range of the particles in the concentrate feed.
v! -22-
-------
In the control of particulate emissions from smelting
furnaces, standard practice has been to employ balloon flues or
cyclones for pretreatments. These devices are used in conjunction
with waste heat boilers and water spray chambers not only to
recover large particles but also to cool the gases before further
treating. Cooling of the gases helps to condense volatilized
metals so that they can be collected by electrostatic precipi-
tators (ESP's). ESP's are ideally suited to this type of appli-
cation because of their'ability to achieve high collection
efficiencies when handling gases with high-temperature, high-
volume, and low-grain-loading conditions. Overall collection
efficiencies of 90 to 95 percent for ESP systems are normal for
these applications. Efficiencies as high as 99.7 percent have
been reported. In special Instances where arsenic oxides are
present in the effluent gases, additional cooling equipment,
followed by baghouses, are normally used to prevent the emission
of toxic substances.
Control of S02 emissions from smelters has been a more recent
development. The most common form of S02 treatment presently
utilized in U.S. smelters 1s the single-contact sulfuric acid
manufacturing plant. Use of a sulfuric acid plant on copper
smelter effluent gas streams requires that the gas be free from
particulate matter and sufficiently rich in S02- The first
consideration requires the installation of high-efficiency scrubbers
and mist-eliminators which handle the large gas flow rates genera-
ted by smelter processes. The requirement for a sufficient SOg
concentration in the treated gas has, 1n the past, limited the
use of sulfuric add manufacture to only converter off gases.
The offgases typically average about 4- to 7-percent S02 by
volume. Gases from reverberatory smelting furnaces and multiple-
hearth roasters have not been treated by themselves in sulfuric
acid plants because S02 concentrations are low (0.5- to 6-
percent S0£) and concentration procedures or preheating would
have to be used.
C -23-
-------
Process and equipment substitutions offer opportunities
for improving control of 862 emissions. Thus, fluidized-bed
roasters normally produce offgases containing 10- to 15-percent
SOg, whereas multiple-hearth roaster gases contain much less
(0.5 to 6 percent). Again, electric smelting furnaces can
produce effluents containing 4- to 8-percent S02» in contrast
to reverberatory smelting furnaces, which usually yield 0.5 -
1.5-percent SOg. Effluents from multiple-hearth roasters and
reverberatory smelting furnaces can be reduced in volume and,
thereby, enriched in S02 concentration, by careful control of
operating conditions. Reduction of infiltration air by closing
furnace wall holes, close monitoring of internal furnace pressure
conditions, and use of oxygen-enriched combustion air are
expedients which have been found to increase S02 concentration
by reducing the volume of effluent gas. Such S02-n'ch streams
can be treated individually or blended with low-S02 streams
prior to treatment in an acid plant.
Typically, single-contact acid plants can achieve 96.5- to
97-percent conversion of 502 *° ac^- Approximately 2,000 parts
per million (ppm) of S02 remains in the acid plant effluent gas.
Double-contact acid plants collect 98 percent of the S02 and
emit about 500 ppm S02- Absorption of the S02 in dimethylani-
line (DMA) solution has also been used in U.S. smelters for pro-
duction of liquid S02-
No control practices are currently utilized in U.S. smelters
for NOX, CO, or hydrocarbon emissions. NOX> CO,and hydrocarbons
are found 1n the offgas streams from units requiring fuel combus-
tion. Multiple-hearth roasters, reverberatory furnaces, conver-
ters, and refining furnaces are sources of air contaminants.
Data are available for assigning emission factors for NO
emissions from reverberatory furnaces and converters in only one
smelter configuration. Data are unavailable for assigning
emission factors for CO and hydrocarbon.
-------
CODING NEDS FORMS
The sources of emissions in a primary copper smelter are:
SCC
Pollutants
3-03-005-02
3-03-005-03
3-03-005-04
3-03-005-05
3-03-005-06
3-03-005-08
3-03-005-09
3-03-005-10
3-03-005-11
3-03-005-12
3-03-005-13
Particulate,
Particulate,
Particulate,
Particulate,
Particulate,
Particulate
Particulate,
Particulate,
Particulate
Particulate,
Particulate,
S02,
S02,
S02,
S02,
NOX,
S02,
S02,
so2,
so2,
NO
NO
x»
x»
NOX,
NO
HC
NO
NO
NO
NO
x»
,
X'
X'
X'
X'
HC,
HC,
HC,
HC,
CO
HC,
HC,
HC,
HC,
CO
CO
CO
CO
CO
CO
CO
CO
Source
Multiple-Hearth Roaster
Reverberatory Smelting
Furnace
Converter Furnace
Fire-Refining Furnace
Concentrate Dryer
Finish Operations, General
Fluidized-Bed Roaster
Electric Smelting Furnace
Electrolytic Refining
Flash Smelting
Continuous Smelting
Standard NEDS forms for each of the sources, Figures 9 through 20 show
entries for the SCC's and other codes. Entries in the data fields give
information common to the designated equipment in primary copper smel-
ters. Information pertinent to coding the source is entered on the
margins of the forms and above or below applicable data fields. Entries
for control equipment codes, other optional codes, emission factors,
and required comments minimize the need to refer to code lists.
Data entered in EIS/P&R and NEDS must be actual values specific
to and reported by the plant, rather than typical values.
IPP codes as shown in Figures 9 through 20 are taken from the
AEROS Manual of Codes, Volume V, Section on NEDS Specific Codes,
Chapter on Implementation Planning Program Process Identification,
items for SIC code 3331. In IPP coding, a distinction is made,
for both reverberatory furnaces and converters, as to whether a
roaster is included in the smelter configuration; however, the roas-
ter, if present, has its own separate code. These codes are listed
in Table 2.
e -25-
-------
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-------
Table 2. IPP CODES FOR SIC NUMBER 3331 (PRIMARY COPPER SMELTING)
Process Code
Combustion XX
Roaster 01
Reverberatory furnace (w/o roaster) 02
Reverberatory furnace (w/roaster) 03
Converter (w/o roaster) 04
Converter (w/roaster) 05
Refining 06
Materials handling 07
(T-38-
-------
For smelters which combine exhausts from roasters and smelting
furnaces in a single stack or control system, it is acceptable to
combine the sources as a single emission point, coded on one NEDS
form. The point would be defined by the three SCC's, 3-03-005-02,
3-90-OOX-01, and 3-03-005-03.
CODING EIS/P&R FORMS
The BEC's for use in EIS/P&R forms are shown herein:
Source BEG
Multiple-Hearth Roaster OMX (x-fuel)
Fluidized-Bed Roaster OMX (x=fuel)
Concentrate Dryer OMX (x=fuel)
Reverberatory Smelting Furnace 162
Electric Smelting Furnace 122
Converter Furnace 192
Fire-Refining (Anode) Furnace 192
Electrolytic Refining (no code)
Flash Smelting Furnace 192
Continuous Smelting Furnace 192
Finish Operations, General (no code)
In the above list, x refers to fuel according to the following
code:
x a 1 Natural gas
2 Liquid petroleum
4 Distillate oil
5 Residual oil
6 Wood
8 Coal
-39-
-------
GLOSSARY
Anode Copper - Slabs of blister copper used as anodes in electro-
lytic refining.
Autogenous Smelting - Smelting in which heat is self-generated
by the reactions of the ore sulfur (as sulfide) without use
of auxiliary fuel.
Balloon Flues - Low-velocity furnace exhaust venting which causes
heavy particulate matter to settle into hoppers at the bottom
of the flue.
Blister Copper - Impure copper (98.5 to 99.5 percent) product of
converters,having a blistered appearance.
Btu - British thermal unit.
Calcine - Partially oxidized copper material produced by roasting.
Concentrate - Input material to the smelter which has been con-
centrated from raw copper ore by flotation to reduce the
amount of material which must be transported from the mine
to the smelter.
Converter - A furnace in which impurities are oxidized out of
copper matte to produce blister copper by blowing air or
oxygen-enriched air through the material.
Copper Blow - The cycle of converter operation during which cuprous
sulfide 1s oxidized to blister copper.
Flux - A siliceous material added to smelting furnaces and con-
verters to combine with Iron materials for removal as slag.
Furnace Bath - The molten metal which is collected in the bottom
of the furnace.
Gangue - Stony or earthy minerals found in metallic ore.
Green Charge - Unroasted, wet concentrate which is fed to the
reverberatory smelting furnace.
Hydrometallurgical - Treatment of ore to recover pure metal by
wet processes.
Launder - An Inclined channel or trough for the conveyance of
molten metal or slag from a furnace to a ladle.
Leaching - Dissolving soluble minerals out of an ore by use of
percolating solutions such as acids.
Matte - An impure metallic sulfide produced by the smelting fur-
nace.
Poling - A process of inserting into a molten metal bath wood
poles which by destructive distillation produce refining
gas.
0 -40-
-------
Pyrometallurglcal - Treatment of ore to recover pure metal by
high-temperature processes.
Reverts - Scrap brass, bronze, and copper material which is added
to converter charge.
Roasting - Heating of concentrate material to produce partially
oxidized calcine material.
Siliceous - Describing a material containing abundant silica.
Slag - A nonmetallic product resulting from the interaction of
flux and impurities in melting furnaces.
Slag Blow - The cycle of converter operation during which matte
is oxidized to pure cuprous sulfide and slag.
Smelting - The heating of ore mixtures accompanied by a chemical
change resulting in the formation of liquid metal matte.
Tapping - Opening the pouring hole of a melting furnace to remove
molten material.
Tuyere - An opening in the shell and refractory lining of a
furnace through which air is forced.
White Metal - pure copper sulfide.
-------
REFERENCES
Air Pollution Control Field Operations Manual, Volume III. Final
Report for EPA Contract No. CPA 70-122. February 1972.
Atmospheric Emissions from Sulfuric Acid Manufacturing Processes.
Public Health Service Publication No. 999 - AP-13. April 1965.
Background Information for New Source Performance Standards: Primary
Copper, Zinc and Lead Smelters, Volume 1: Proposed Standards. U.S.
Environmental Protection Agency, Research Triangle Park. Publica-
tion No. EPA-450/2-74-002a. October 1974.
Billings, Carl H. First Annual Report on Arizona Copper Smelter
Pollution Control Technology. Arizona Department of Health
Services. April 1977.
Biswas, A.K. and W.G. Davenport. Extractive Metallurgy of Copper.
Pergamon Press, Oxford.1976.
Compilation of Air Pollutant Emission Factors. Second Edition,
Third Printing. U.S. Environmental Protection Agency, Research
Triangle Park. Publication No. AP-42. February 1976.
Control of Sulfur Dioxide Emissions in Copper, Lead, and Zinc
Smelting. U.S. Bureau of Mines, Washington, D.C. Information
Circular 8527. 1971.
Field Surveillance and Enforcement Guide for Primary Metallurgical
Industries. U.S. Environmental Protection Agency, Research Triangle
Park. Publication No. EPA-450/3-73-002. December 1973.
Guides for Compiling a Comprehensive Emission Inventory. U.S.
Environmental Protection Agency, Research Triangle Park. Publica-
tion No. APTD-1135. March 1973.
Oglesby, Sabert, Jr., et al. A Manual of Electrostatic Precipitator
Technology, Part II, Application Areas. Final Report for National
Air Pollution Control Administration Contract No. CPA 22-69-73.
Weisenberg, I.J. and G.E. Umlauf. Evaluation of the Controllability
of SOg Emissions from Copper Smelters 1n the State of Arizona.
Final report for EPA Contract No. 68-02-1354, Task Order No. 8.
June 1975.
Yannopoulos, J.C. and J.C. Agarwal (ed). Extractive Metallurgy
of Copper, Volume I: Pyrometallurgy and Electrolytic Refining, and
Volume II: Hydrometallurgy and Electrowinning. The Metallurgical
Society of AIME, New York, New York. 1976.
-42-
-------
APPENDIX D
SECONDARY COPPER SMELTING PROCESS COMPENDIUM
Prepared by
PACIFIC ENVIRONMENTAL SERVICES, INC.
t
EPA Contract No. 68-02-1890
Task Order No. 3
Project Officer: Arch A. McQueen
Prepared for
ENVIRONMENTAL PROTECTION AGENCY
National Air Data Branch
Research Triangle Park, North Carolina
Pacific Environmental Services, INC.
CORPORATE AND ENGINEERING 1930 14thStiwt Sent* Monica. California 90404 Tctaphont (213)393-9449
MIDWEST OPERATIONS Suitt228N 2626 ButttrfMd ROM* Oak Brook. Illinois 60521 Trttphon* <312) 325-5586
-------
TABLE OF CONTENTS
Section Page
SECONDARY COPPER SMELTING AND ALLOYING 1
PROCESS DESCRIPTION 1
Secondary Copper Smelting 1
Scrap Metal Pretreatment 3
Smelting 4
Refining 6
Melting and Alloying 7
Casting 9
Furnace Types 9
Blast Furnace or Cupola 10
Reverberatory Furnaces 10
Rotary Furnaces 11
Converters 11
Crucible Furnaces 16
Pot Furnaces 16
Electric Furnaces 16
Direct-Arc Furnaces 17
Indirect-Arc Furnaces 17
Induction Furnace 19
EMISSIONS 19
Scrap Metal Pretreatment 19
Cupola Furnaces 21
Reverberatory Furnaces 21
Converter Emissions 22
Emissions 1n Fire Refining 22
CONTROL EQUIPMENT 23
CODING NEDS FORMS 24
CODING EIS/P&R 27
GLOSSARY 38
REFERENCES 40
-------
LIST OF ILLUSTRATIONS
Page
1 Low-Grade Copper Recovery 2
2 A Cupola Furnace 5
3 High-Grade Brass and Bronze Alloying 8
4 Gas-Fired, Cylindrical Reverberatory Furnace 12
5 Rotary-Tilting-Type Reverberatory Furnace
Venting to Canopy Hood and Stack Vent 13
6 Copper Converter 14
7 Copper Converter Operation 15
8 Principles of Operation of Direct-Arc and
Indirect-Arc Furnaces 18
9 Low-Frequency Induction Furnace With Fixed Hood 20
10 Systems Cooling Exhaust Gas Prior to
Baghouse Entry 25
11 Standard NEDS Form for Secondary Copper Smelting:
Scrap Dryer 29
12 Standard NEDS Form for Secondary Copper Smelting:
Scrap Wire Burner 30
13 Standard NEDS Form for Secondary Copper Smelting:
Blast Furnace 31
14 Standard NEDS Form for Secondary Copper Smelting:
Cupola Furnace 32
15 Standard NEDS Form for Secondary Copper Smelting:
Reverberatory Furnace ... 33
16 Standard NEDS Form for Secondary Copper Smelting:
Rotary Furnace 34
17 Standard NEDS Form for Secondary Copper Smelting:
Crucible Furnace 35
18 Standard NEDS Form for Secondary Copper Smelting:
Electric Arc Furnace 36
19 Standard NEDS Form for Secondary Copper Smelting:
Electric Induction Furnace 37
LIST OF TABLES
Table Page
1 IPP Codes for SIC Number 3341 (Secondary Copper,
Brass, and Bronze) 28
-------
SECONDARY COPPER SMELTING AND ALLOYING
PROCESS DESCRIPTION
In the secondary copper Industry, copper 1s recovered from
scrap metal, which Includes both copper and copper alloys. The
processes used are determined by the type and quality of the feed
material. Low-grade copper scrap, which contains less than 30-
percent recoverable metal, 1s usually utilized in secondary smel-
ting, whereas clean, selected scrap Including brass and bronze
may be melted (without smelting) to produce alloys. Generally,
a secondary copper facility processes the less metal-rich feed
and produces a more refined product. Alloy processors perform
fewer refining operations.
Secondary Copper Smelting
Processes Involved 1n copper recovery may be classified as
pretreatment, smelting, and refining. Figure 1 presents a flow-
sheet depicting the major processes typically employed 1n a
secondary copper smelter, producing refined copper from low-grade
scrap.
Copper-bearing scrap, for Industry purposes, has been classi-
fied as either new or old. New scrap 1s that produced 1n fabri-
cating finished products; for example, turnings, borings, and
other waste from machining copper, brass, and bronze. Old scrap
consists mainly of obsolete, wornout, or salvaged articles such
as wire, plumbing fixtures, parts from electrical machinery,
automobiles, and domestic appHcances. Other materials with
copper values Include slags, drosses, foundry ashes, and sweepings
from smelters and copper processing Industries. A detailed classi-
fication of copper-bearing scrap materials has been published
by the National Association of Secondary Materials Industries.
-------
ENTERING THE SYSTEM
LEAVING THE SYSTEM
Lou-grade scrap
-------
Specifications for the various classes have also been defined.
Copper wire and tubing constitute almost half of the scrap used
in the Industry.
Scrap Metal Pretreatment
Feed scrap may contain a great deal of nonmetallic material
Including oil, grease, paint, Insulation, rubber, and even
chemicals such as antifreeze. The scrap 1s segregated for further
treatment by a variety of processes adapted to the considerable
number of Input materials. Generally, it is sorted according to
Its copper content and cleanliness; clean scrap may be manually
sorted for charging directly to a melting and alloying furnace.
It 1s not unusual for this segregation to be performed prior to
shipment to the smelter, but a complete facility provides for
this operation.
In general, pretreatment processes may be classified as
mechanical, pyrometallurgical (Involving heat), or hydrometallur-
gical (Involving water). Their purpose is to concentrate the
valuable metals prior to smelting, refining, and alloying.
Mechanical methods are as follows:
1. Hand sorting - Individuals sort the scrap as it 1s
unloaded before being routed to storage.
2. Stripping - Any process Involving the mechanical
removal of Insulation from copper cable.
3. Shredding - Insulated wire is reduced In size in a
hammermlil, and conveyed pneumatically to a cyclone
where the metal and Insulation are gravity-separated.
4. Magnets • Magnetic pulleys convey brass and bronze
scrap and trap loose iron particles.
5. Briquetting - A powerful hydraulic press is used to
reduce bulky scrap to small bales (briquettes).
Pyrometallurgical methods are as follows:
.2-3-
-------
1. Sweatlng - The separation of low-melting point
metals, such as lead, solder, and babbitt metal
from the desired materials by heating.
2. Burning - The removal by Incineration of Insula-
tlon from wire scrap which, for some reason,
cannot be mechanically separated.
3. Drying - A process employing a rotary kiln to
vaporize excess cutting fluids from machine
shop chips or borings.
Hydrometallurglcal methods Include gravity separation by
flotation, leaching with ammonium carbonate or sulfuHc add,
and recovery of copper from the leachate by chemical processing.
Smelting
Pretreated scrap containing between 10- and 30-percent copper
1s normally smelted 1n a cupola furnace (Figure 2). A cupola
furnace 1s essentially a vertical, refractory-Hned cylinder open
at the top and equipped with airports at the bottom. A1r 1s
supplied by a forced-draft blower. Alternate charges of scrap,
coke, and limestone are placed on top of a burning bed of coke;
the metal melts and 1s drawn off through a tap-hole and spout
at the bottom of the furnace. Oxides of copper and heavy metals
are chemically reduced. Various Impurities, such as Iron, combine
to form a slag, which collects on top of the molten metal and can
be drawn off separately. A typical cupola furnace has a capacity
of about 55 to 65 metric tons per day, producing so-called
"black" copper of about 70- to 80-percent purity. The Impurities
may be sulfides of copper and Iron, as well as other metals and
their oxides: tin, zinc, lead, and others.
In the typical system of Figure 1, further smelting and
refining are accomplished using a reverberatory "holding" furnace,
a converter, and a reverberatory or rotary refining furnace.
These operations are similar to those used 1n primary copper
smelting (q,v.). The contents of reverberatory furnaces are furnaces
T-4-
-------
Figure 2. A Cupola Furnace
3-5-
-------
by radiation heat from burner flames, refractory walls and roofs.
The function of the holding furnace is to retain the melt until
a sufficient batch is accumulated as a charge to the converter
and to allow for tapping the slag. (An electric-arc furnace can
also be used for this purpose.)
The converter consists of a cylindrical steel shell which
can be rotated about its longtudinal axis. An opening in one
side admits the molten charge and vents gases. Air is blown
through the melt by means of a horizontal row of pipes, with
openings (called "tuyeres") which are below the liquid metal
when the furnace is rotated. A silica flux is added to remove
iron from the metal, while zinc and any sulfur are converted to
their respective oxides by the air which is blown in.
The product from the converter is "blister" copper, usually
90- to 99-percent pure. This material may be poured and cast,
or it may be transferred in the molten state to another furnace
for a final pyrometallurgical process known as "fire refining."
Feed containing low-copper values can also be smelted in
electric crucible furnaces, using oxygen 1n place of air for
oxidation.
Ref1n1nq
Blister copper 1s,typically, further purified by fire
refining, to about the level of 99,9-percent purity. Electroly-
tic refining may be done as an additional step to produce elec-
trolytic copper. These processes are essentially the same In
secondary smelting as in primary smelting of copper.
F1re-ref1n1ng furnaces are, typically, reverberatory fur-
naces, often of a rotary type. Capacities usually range from
about 100 to 35C metric tons. In the furnace, air 1s blown
through the molten metal to oxidize impurities which, as oxides,
J -6-
-------
are removed 1n the slag which 1s skinned or poured off. Copper
oxide, formed to the extent of less than 1 percent of copper, 1s
reduced by "poling" (submerging wooden poles 1n the molten metal)
or by supplying a reducing atmosphere of gas (by fuel-rich combus-
tion). The usual sequence of events 1n fire refining is (1)
charging; (2) melting; (3) skimming; (4) blowing; (5) adding
fluxes; (6) reducing; (7) reskimming; and (8) pouring.
Electrolytic refining separates Impurities from the copper
by electrolysis in a solution bath containing copper sulfate and
sulfuric acid. Metallic Impurities form a sludge ("slime") which
is removed and may be treated for recovery of precious metals.
Melting and Alloying
To produce bronze or brass rather than copper, an alloying
operation 1s required. Where high-grade scrap is used, smelting
may be unnecessary. Figure 3 presents a flow diagram for a
typical operation of this kind.
In the case Illustrated, scrap as received 1s manually and
mechanically sorted to segregate pure copper, especially copper
wire, from copper alloys. Insulated wire 1s fed to a wire-burner,
an Incinerator in which combustible insulation 1s removed. Brass
and bronze scrap is sweated to remove low-melting metals such as
solder, lead, and babbitt metal. The cleaned copper and alloys
are then melted in an alloying furnace. Zinc and other metals
may be added to bring the resulting mixture to the desired final
composition. Fluxes are added to the mixture to remove Impuri-
ties and to protect the melt against oxidation. Air or oxygen may
be blown through the melt to adjust the composition by oxidizing
excess zinc. With zinc-rich feed, the zinc oxide particulate
loading 1n the exhaust is often recovered in a process baghouse.
Tj-7-
-------
ENTERING THE SYSTEM
LEAVING THE SYSTEM
High-grid* scrip
(«rtr«, pipe, btirlng,-
puncMngs. radiators)
MANUAL AM) MECHANICAL
rlETREATMENT
(Sorting)
Fins.
Fuel.
Alloy Material (zinc,tin. *tc)
MELTING AND
ALLOYING FURNACE
.Fug1t1v* dust to aaaospher*
.Undeslred scrap to sal*
MS. e»ta! oxides to control equipment
•ad. soldtr, babbitt Mtal
fartlculatM. hydrocarbnm, aldehydes, fluorldts.
and chlorides to afterburner and partlculate
oildes to control eaulpMnt
S1*« to dltpoul
FMg1tl«t Mttal oildes fenerated during
pouring to either plant envlroneant or
hooding
Figure 3. High-Grade Brass and Bronze Alloying
-8-
-------
Brass and bronze shapes for working, such as slabs and
billets, are usually produced 1n large reverberatory furnaces,
of the type also used for secondary smelting and copper recovery.
In smaller operations and to make commercial castings, the metals
are melted 1n crucible furnaces, pot furnaces, or electric fur-
naces, both arc and Induction types.
Casting
The final step 1s always casting of the metal Into desired
form. Blister copper 1s sometimes poured Into water for quenching
to produce copper shot, but 1s usually either transferred In the
molten state to a refining furnace or cast Into Ingots. Fire-
refined copper Is cast Into wlrebar, anodes, and cathodes as
well as Ingots.
Brass and bronze are more often cast Into special shapes.
The mold, made of cast Iron or similar material, 1s dusted with
charcoal before filling, to facilitate removal of the solid
casting. After the mold 1s filled, exposed metal surfaces are
sometimes dusted with charcoal, to reduce skin oxidation due to
oxygen from the air.
Furnace Types
Furnaces of many types are used 1n secondary copper operations
and 1n brass and bronze melting and alloying. In recovery of copper
from scrap having relatively low copper content, the charge Is
commonly treated 1n a blast furnace or cupola, where heavy-metal
oxides and sulfides are reduced. Reverberatory furnaces are used
as holding furnaces for the cupola melt, and sometimes 1n fire
refining. Converters are used to oxidize sulfides, zinc, and base
metals by blowing air through the melt. These and various other
types of furnaces, frequently encountered 1n the secondary copper,
brass, and bronze Industries, are described 1n the following para-
graphs.
-------
Blast Furnace or Cupola
Although these names are sometimes used Interchangeably,
the cupola 1s generally considered to be a smaller variety of
blast furnace. The principles of operation are essentially the
same* but the larger furnaces are more common 1n primary smelting,
where metal 1s recovered by reducing oxide or sulfide ores. The
cupolas, commonly used 1n the secondary copper Industry, recover
metal from skimmings, slags, and scrap metal 1n a reducing atmos-
phere provided by the combustion of coke.
Blast furnaces and cupolas consist essentially of vertical,
refractory-lined cylindrical shells (also known as "shafts," from
which these furnaces are sometimes called "shaft furnaces") open
at the top and equipped with air blowers at the bottom. The scrap
1s Intermingled or layered with coke and limestone and heated by
combustion. Molten metal and slag may be tapped separately from
the base of the furnace, but more commonly both are continuously
tapped Into a "holding" furnace where they are separated. This 1s
usually a stationary reverberatory furnace.
Reverberatory Furnaces
A reverberatory furnace operates by radiating heat from Its
burner flame, roof, and walls onto the material being heated.
Combustion of fuel occurs directly above the molten bath; transfer
of heat 1s accomplished almost entirely by radiation.
Reverberatory furnaces are available 1n many types and
designs. Their use will depend on specific job requirements,
such as the nature and quantity of the charge to be handled.
The largest such units are open-hearth furnaces, which range 1n
]Mo-
-------
capacity from about 40 to about 500 metric tons. In the
secondary copper, bronze, and brass Industry, such units are often
used as holding furnaces to accumulate and separate the molten
metal ("black" copper) and slag tapped from the cupola furnace.
They may also be used 1n fire refining.
Large open-hearth furnaces are built with heat regenerators,
consisting of brick checker-work, which absorb heat from the
effluent gases and transfer 1t to Incoming air. The fuel 1s oil
or gas. The charge 1s Introduced through refractory-lined doors
in the front wall; molten metal and slag are removed through tap-
holes in the rear.
For melting and holding smaller amounts of copper, brass,
and bronze, cylindrical reverberatory furnaces are common. (See
Figure 4.) These are fired through tangential nozzles and charged
through end doors on top openings. They usually utilize rotary
tilting mechanisms to facilitate pouring of the molten contents.
Rotary Furnaces
A more elaborate type of reverberatory furnace, commonly
called a "rotary" furnace, not only tilts for charging and pouring,
but also rotates during the melting period to Improve heat
transfer. (Figure 5.) Two types are common. One 1s charged
through the furnace, opposite the burner. The other has a side
charge door at the center through which charging, skimming, and
pouring operations are conducted.
Converters
A converter 1s basically a cylindrical reverberatory furnace,
mounted to tilt about Its longitudinal axis and modified to permit
blowing air through the melt. Illustrations of the copper conver-
ter and copper converter operation are shown 1n Figures 6 and 7,
respectively. A side charge door 1s used for charging, skimming,
and pouring. Air 1s supplied through a header along the back of
the cylinder (opposite the charge door) from which a horizontal
row of tuyere pipes extend Into the Interior of the vessel.
p-n-
-------
Figure 4. Gas-Fired Cylindrical Reverberatory Furnace
T-1Z-
-------
Fum'ce
'J5-13-
-------
OFF-GAS
TUYERE
PIPES
SILICEOUS
FLUX
Figure 6. Copper Converter
-------
Exhaust Hood
CHARGING
BLOWING
SKMI1NG
Figure 7. Copper Converter Operation
-------
Crucible Furnaces
Crucible furnaces are 1nd1rect-f1red furnaces having capaci-
ties of about 10 to 1,000 kilograms. They are used to melt metals
having melting points not above 1,400°C (2,500°F). The covers
of the crucible furnaces are constructed of materials similar to
the Inner shell lining and have a small hole over the crucible
for charging metal and exhausting the products of combustion. The
crucible rests on a pedestal 1n the center of the furnace and 1s
commonly constructed of a refractory material such as a clay-graphite
mixture or silicon carbide.
Crucible furnaces are classified as tilting, pit, or stationary
furnaces. All types are provided with one or more gas or oil
burners mounted near the bottom of the unit. Flames are directed
tangentially around the Inside of the furnace. The crucible 1s
heated both by radiation and by contact with the hot gases.
Pot Furnaces
Pot furnaces are 1nd1rect-f1red furnaces used to melt metals
having melting points not above 800'C (1,400°F). These furnaces
may be cylindrical or rectangular and consist of an outer shell
lined with refractory material, a combustion chamber, and a pot.
The pots are made of pressed steel, cast steel, or cast Iron with
flanged tops. The flange rests on the furnace wall, holds the
pot above the furnace floor, and seals the contents of the pot
from the products of combustion of the fuel used. The shape of
the pot depends upon the operation to be conducted.
Electric Furnaces
Most pyrometallurglcal operations can be conducted with the
use of electricity rather than fuel for heating. Major advan-
tages of the electric furnace over fuel-fired furnaces are furnace
JM6-
-------
atmosphere control and high-temperature operation. Temperatures
as high as 6,000*F are possible for special processes.
Resistance furnaces are used mainly for ferroalloys. The
other three types of electric furnaces are described 1n following
paragraphs.
Direct-Arc Furnaces
In the direct-arc furnaces, many and varied arrangements are
used to heat the metal charge, but radiation between arc and the
metal bath 1s the principal method. Here, the heat is generated
by radiation from the arc as well as from the resistance heat
effect with the bath, as shown in Figure 8. Graphite and carbon
electrodes are usually used and are spaced just below the surface
of the slag cover. The current passes from one electrode through
the slag, the metal charge, the slag, and back to the other elec-
trode. In some arrangements, the current 1s carried from the
metal charge to the earth. The slag serves a protective function
by shielding the metal charge from vaporized carbon and the
extremely high temperatures at the arc.
Indirect-Arc Furnaces
In the indirect-arc furnaces, the metal charge is placed
below the electrodes, and the arc is formed between the electrodes
and above the charge (Figure 8). Indirect-arc furnaces are used
mainly in the steel Industry. One of the common smaller furnaces
is the Indirect-arc rocking furnace, 1n which an automatic
rocking action of the furnace is employed to ensure a homogeneous
melt. This 1s done by mounting the refractory-lined steel shell
on cog bearings so that the furnace may be rocked through a 200°
range. Radiated heat from the Indirect arc and conduction from
the preheated refractory lining Initially melt small scrap,
forming a pool of molten metal at the bottom of the furnace. Then
'p-17-
-------
EUCTIOOES.
IIKCT
"CHMSE
IMIKCT
Figure 8. Principles of Operation of Direct-Arc and
Indirect Arc Furnaces
-------
the rocking action 1s Initiated, and the molten metal washes
against the refractory, picking up additional heat, which 1s trans-
ferred by convection and radiation to the larger pieces of metal.
During the heat, the rocking action 1s advanced gradually to
avoid a sudden tumbling of cold metal, which could fracture the
graphite electrodes.
Induction Furnace
The Induction furnace consists of a crucible within a water-
cooled copper coll (Figure 9). An alternating current 1n the coll
around the crucible Induces eddy currents 1n the metal charge and
thus develops heat within the mass of the charge, Heating 1s
rapid and uniform and temperature can be accurately controlled.
High-frequency Induction furnaces are well adapted to copper-rich
alloys (bronzes), but low-frequency Induction furnaces are more
suitable for z1nc-r1ch alloys (brass).
EMISSIONS
The principal air contaminants emitted 1n secondary copper
smelting and recovery are various forms of partlculate matter.
These Include organlcs from the pretreatment and metal oxides from
the pyrometallurglcal processes. Some gases, Including hydrogen
chloride and sulfur dioxide, may be released by burning of Insula-
tion. Carbon monoxide 1s emitted 1n the operation of cupola fur-
naces .
Scrap Metal Pretreatment
Copper reclamation from Insulated wire 1s commonly accomplished
1n single-chamber Incinerators such as tepee burners, which may be
portable to cover piled scrap, A great variety of materials com-
poses the combustible Insulation: rubber, paper, cotton, silk,
plastics, paint and varnish, and others. During combustion, 1n the
-------
&*.* -~<~'x*l*
Figure 9. Low-Frequency Induction Furnace
H1th Fixed Hood
-------
absence of control equipment, black smoke is not uncommon, accom-
panied by disagreeable odors, inorganic materials, and oxygenated
hydrocarbons. If the insulation contains polyvinyl chloride,
hydrogen chloride is emitted. Sulfur dioxide is one product of
the burning of rubber insulation and of some synthetic rubbers.
In published results of one test, particulates recovered from
wire-burning in a single-chamber incinerator amounted to 178 kilo-
grams per metric ton (356 pounds per ton) of combustibles. The
combustibles constituted 35 percent of the charge.
Scrap driers consisting of rotary kilns are ofterv used to
burn off oil and volatiles from turnings, borings, and other waste
from machining. This process can cause discharge of dense smoke
accompanied by volatile hydrocarbons and oxygenated materials.
Mechanical pretreatment, such as stripping, shearing, crushing,
shredding, and briquetting, is likely to be a source of fugitive
dust in copper recovery operations, both for secondary smelters
and for alloying operations. Such emissions have not been quanti-
tatively evaluated.
Cupola Furnaces
Air contaminants emitted from cupola furnaces are (1) gases,
(2) dust and fumes, and (3) smoke and oil vapor. Typically, the
gases may contain 10 percent or more of carbon monoxide. Dust in
the discharge gases arises from dirt in the feed material and from
fines in the coke and limestone charge. Smoke and oil vapor arise
primarily from, the partial combustion and distillation of oil
from greasy scrap charged to the furnace.
Reverberatory Furnaces
Reverberatory furnaces are used both for holding the melt
from the cupola furnace preparatory to loading the converter
with molten copper, and for melting and alloying in the production
of brass or bronze.
-------
Air contaminants from reverberatory furnaces include gases,
smoke, fumes, and dusts. The particulate matter varies according
to the fuel, alloy composition, melting temperature, type of fur-
nace, and various operating procedures. In addition to fly ash, carbon,
and mechanically produced dust, the emissions generally contain
fumes resulting from condensation and oxidation of the more vola-
tile elements, including zinc and lead.
Converter Emissions
Emissions of air contaminants from converter operations occur
predominantly during the air-blowing process, in which zinc and
sulfur are oxidized. In secondary smelting, sulfur is usually
a rather minor constituent of the melt, in contrast to the major
fraction encountered in primary smelting of sulfide ores. Fuel
use in this operation 1s also relatively minor, as the oxidation
of zinc, iron, and sulfur provides most of the necessary heat;
fuel-associated contaminants are therefore minimal. However, if
the material charged to the converter is not in the molten state,
fuel combustion is required 1n order to melt it and typical fuel-
combustion contaminants (i.e., sulfur dioxide, nitrogen oxides,
carbon monoxide, fly ash) are emitted during melting.
During charging and pouring, significant fugitive emissions
are likely to occur. These emissions have not been quantitatively
evaluated.
Emissions in Fire-Refining
Fire-refining generates relatively little sulfur dioxide or
metallic oxide particulates, since the blister copper charged is
at least 90-percent pure. Poling, however, often produces black
soot, which may be of concern.
-------
CONTROL EQUIPMENT
Due to the wide variety of participates emitted, many
different control strategies are used.
Wire burning generates large amounts of particulate matter
in the form of unburned combustibles. These emissions are most
effectively controlled by a direct flame afterburner. If the
afterburner combustion temperature is maintained at a minimum of
1,000°C (1,800°F), an efficiency of 90 percent can be expected.
If the insulation contains polyvinyl chloride, hydrogen chloride
gas will be a contaminant. An afterburner will not control this
contaminant, but it can be reduced by a water scrubber.
Particulate emissions associated with the drying process
are controlled by a variety of control devices. Drying tempera-
tures of 70° to 150°C (150° to 300°F) are low enough to allow a
baghouse to operate without precooling of inert gases. Baghouse
efficiencies of 99 percent and above can be anticipated. Other
means of control used include cyclones (60-. to 75-percent
efficiencies) and wet (venturi) scrubbers with efficiencies of
approximately 65 percent.
Emissions associated with the charging of scrap to melting
furnaces can be reduced by turning off the burners during charging.
The technique has several effects. It reduces the volume of
escaping air which can entrain contaminants. If the furnace
operates in conjunction with a baghouse, the operation of the
baghouse blower with the burner off actually produces a negative
pressure in the furnace, further reducing emissions. The escaping
fumes from charging and pouring are commonly captured by being
drawn upward through ducts to the same control equipment which
services the furnace exhaust gases.
There are many possible systems for the control of the metal
oxide fumes escaping from the furnace during melting. Baghouses,
J>23-
-------
electrostatic precipitators, and wet scrubbers are most common.
Due to the small size of the metal oxide particles to be captured
(0.3 to 0.5 microns), the baghouse is the most effective device,
reaching efficiencies well in excess of 99 percent.
The temperature of the exit gas from the melting furnace is
approximately 1,2009C, which would destroy a baghouse. Several
practices are used to cool the gases to temperatures the baghouse
can handle (below 260°C). Figure 10 shows a two-stage cooling
system consisting of water-jacketed coolers followed by radiant
cooling which reduces the baghouse outlet temperature to 180°C
(350°F).
Although electrostatic precipitators are reputed to be
extremely effective for collecting particles 1n the size range
exhibited by these metal oxides, experience has shown that collec-
tion efficiency for lead and zinc oxides 1s low, perhaps due to
unusual resistivity 1n these systems. Electrostatic precipitators
have been little used in control of furnace emissions, as their
optimum application appears to be for larger gas flow rates.
Wet scrubber Installations must be restricted to applications
where the particle size range 1s above 1 micron and even then
collection efficiencies are only 1n the 50- to 65-percent range.
CODING NEDS FORMS
The emissions sources in a secondary copper smelter and in
brass or bronze alloying are:
Source SCC Pollutants
Blast furnace 3-04-002-01 Particulates, SOg, CO, HC, NOX
Crucible furnace 3-04-002-02 Particulates, S02, CO, HC, NOX
Cupola 3-04-002-03 Particulates, S02, CO, HC, NOX
Electric induction 3-04-002-04 Particulates, S02, CO, He, NOX
furnace
7-24-
-------
Emergency
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— »
f f « (,
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1 |60*C(140*F]
\ /
\ /
\ /
\ /
\ /
\ /
^V
482*C(900*F)
Exhaust Manifold 177'C(350*F)
260*C(SOO*F)
n . n n.
/
Utter Cooling Tower Radiant Cooler!
Figure 10. Systems Cooling Exhaust Gas Prior to Baghouse Entry
Htgh-TeT?erature
Modular baghouse
Exhaust Stack
Suction Fan
-------
Source SCC Pollutants
Reverberatory furnace 3-04-002-05 Particulates, SOg, CO, HC, NOX
Rotary furnace 3-04-002-06 Particulates, S02, CO, HC, NOX
Scrap dryer 3-04-002-07 Particulates, S02, CO, HC, NOX
Wire burner 3-04-002-08 Particulates, S02, CO, HC, NOX
Electric arc furnace 3-04-002-09 Particulates, S02, CO, HC, NOX
Standard NEDS forms for each of these sources are shown in Figures 11
through 19, with entries for the SCC's and other codes. Entries in
the data fields give information common to the designated equipment
in secondary copper smelting and brass and bronze alloying. Infor-
mation pertinent to coding the source is entered on the margins of
the forms and above or below applicable data fields. Entries for
control equipment codes, other optional codes, emission factors, and
required comments minimize the need to refer to code lists.
Data entered in NEDS and in EIS/P&R must be actual values
specific to and reported by the plant, rather than typical values.
IPP codes as shown in Figures 11 through 19 are taken from
AEROS Manual of Codes, Volume V, section on NEDS specific codes,
chapter on Implementation Planning Program Process Identification,
items for SIC code 3341. These codes are listed in Table 1.
If one or more in-process fuels are used, the appropriate
in-process fuel SCC code must be entered, together with the fuel
use rate. The codes which apply to the various fuels are:
Fuels §CC_
Coal 3-90-003-05
Residual oil 3-90-004-05
Distillate oil 3-90-005-05
Natural gas 3-90-006-05
Coke 3-90-008-05
Wood 3-90-009-05
"D-26-
-------
CODING EIS/P&R FORMS
The BEC's for use in EIS/P&R forms are shown herein:
Source EEC
Blast furnace 112
Crucible furnace 102
Cupola furnace .. 112
Electric induction furnace 132
Reverberatory furnace 162
Rotary furnace 172
Electric arc furnace 122
Scrap dryer 192
Wire burner 192
-27-
-------
Table 1. IPP CODES FOR SIC NUMBER 3341 (SECONDARY COPPER, BRASS
AND BRONZE)
Process Code
Combustion XX
Scrap preparation 01
Blast furnace 06
Crucible furnace 07
Electric induction furnace 08
Cupola 09
Reverberatory furnace 11
Rotary furnace 12
'JJ-28-
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GLOSSARY
Alloy - Any substance having metallic properties and consisting
of two or more elements; with few exceptions the components
are usually metallic elements.
Anode - The positive terminal of an electrolytic cell; cast in
copper for use 1n electroplating or for electrolysis.
Arc Furnace - A furnace used to heat materials by the discharge
of electricity from electrodes.
Black Copper - The more or less impure metallic copper (70- to
99-percent copper) produced in blast furnaces.
Blister Copper - Impure copper (98.5 to 99.5 percent) product
of converters, having a blistered appearance.
Crucible - A refractory vessel or pot used in a furnace for
melting or calcining.
Cupola - A vertical cylindrical furnace for foundry use; the
metal, coke, and flux are put into the top of the furnace
onto a bed of coke through which air is blown.
Dross - An Impurity, usually an oxide, formed on the surface of
a molten metal.
Flotation - A process used to separate particulate sol Ids by
causing one group of particles to float; utilizes differences
in surface chemical properties of the particles, some of
which are entirely wetted by water while others are not.
Flux - A substance used to promote the fusing of minerals or
metals, and certain chemical reactions.
Hydrometallurglcal - Treatment of ore to recover pure metal by
wet processes.
Indirect-fired furnace - A fuel-fired furnace in which melt is
contained in a heated vessel and 1s not contacted by the
flame.
Induction Furnace - An electric furnace in which heat is produced
in a metal charge by electromagnetic Induction.
Ingot - A solid metal casting suitable for remelting or working.
jp-38-
-------
Leachate - The material removed from a mixture by leaching.
Leaching - Dissolving soluble minerals out of an ore by use of
percolating solutions such as acids.
Poling - Insertion of wood poles into a molten metal bath,
producing a reducing atmosphere by destructive
distillation.
Pyrolysis - The breaking apart of complex molecules into simpler
units by the use of heat, as in the pyrolysis of heavy oil
to make gasoline.
Pyrometallurgical - Treatment of ore to recover pure metal by
high-temperature processes.
Refining - Any process used to improve the purity of a metal to
meet product specifications.
Reverberatory Furnace - A furnace in which the charge is heated
by direct contact with flame and by radiation from furnace
walls.
Rotary Furnace - A cylindrical furnace which can be rotated about
its (horizontal) cylindrical axis.
Shaft Furnace - A vertical, refractory-lined cylinder in which a
fixed bed (or descending column) of solids is maintained
and through which an ascending stream of hot gas is forced.
Shot - Product made by pouring metal in finely divided streams;
particles solidifying during descent and are cooled in a
tank of water.
Slag - A nonmetallic product resulting from the interaction of
flux and Impurities in the smelting and refining of metals.
Smelting - The heating of ore or scrap metal mixtures accompanied
by a chemical change resulting in the formation of liquid
metal matte.
Tuyeres - An opening in the shell and refractory lining of a
furnace through which air is forced into the melt.
Wirebar - Cast copper ingots used for the manufacture of wire.
7) -39-
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REFERENCES
Air Pollution Aspects of Brass and Bronze Smelting and Refining
Industry.Brass and Bronze Ingot Institute and National Air
Pollution Control Administration. PB 190295. November 1969.
Air Pollution Engineering Manual, Second Edition. EPA Publication
No. AP-40. May 1973.
Development Document for Proposed Effluent Limitations Guidelines
and New Source Performance Standards for the Secondary Copper Sub-
category of the Copper Segment of the Nonferrous Metals Manufacturing
Point Source Category. U.S. Environmental Protection Agency, Office
of Water and Hazardous Materials, Effluent Guidelines Division,
Washington, D.C. November 1974.
Lauber, D.W. Conley, and D. Barshield, Air Pollution Control of
Aluminum and Copper Recycling Processes. Pollution Engineering,
p. 23-26. December 1973.
Multimedia Environmental Assessment of the Secondary Nonferrous
Metal Industry, Volume II. Industry Profile. Final Draft. Radian
Corporation, Austin, Texas. Prepared for the U.S. Environmental
Protection Agency, Industrial and Environmental Research Laboratory,
Cincinnati, Ohio under Contract No. 68-02-1319. June 21, 1976.
Particulate Pollutant System Study, Volume III: Handbook of
Emission Properties. Midwest Research Institute, Kansas City,
Missouri. Prepared for the U.S. Environmental Protection Agency,
Air Pollution Control Office, Durham, North Carolina under Contract
No. CPA 22-69-104. May 1, 1971.
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