EPA-600/2-80-168
July 1980
INDUSTRIAL PROCESS PROFILES
FOR ENVIRONMENTAL USE:
CHAPTER 27
PRIMARY LEAD INDUSTRY
by
PEDCo Environmental, Inc.
11499 Chester Road
Cincinnati, Ohio 45246
Contract No. 68-03-2577
Project Officer
John 0. Burckle
Energy Pollution Control Division
Industrial Environmental Research Laboratory
Cincinnati, Ohio 45268
INDUSTRIAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the Industrial Environmental Research
Laboratory-Cincinnati, U. S. Environmental Protection Agency, and approved
for publication. Approval does not signify that the contents necessarily
reflect the views and policies of the U. S. Environmental Protection Agency,
nor does mention of trade names or commercial products constitute endorse-
ment or recommendation for use.
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TABLE OF CONTENTS
INDUSTRY DESCRIPTION
Raw Materials
Products
Companies
Environmental Impact
References
INDUSTRY ANALYSIS
Process No. 1,
Process No. 2,
Process No. 3,
Process No. 4,
Process No. 5,
Process No. 6,
Process No. 7,
Process No. 8,
Process No. 9,
Process No. 10,
Process No. 11,
Process No. 12,
Process No. 13,
Process No. 14,
Process No. 15,
Process No. 16,
Process No. 17,
Process No. 18,
Process No. 19,
Process No. 20,
Process No. 21,
Process No. 22,
Mining
Concentrating
Sintering
Contact Sulfuric Acid Plant
Blast Furnace
Slag Fuming Furnace
Dressing
Dross Reverberatory Furnace
Cadmium Recovery
Reverberatory Softening
Kettle Softening
Harris Softening
Antimony Recovery
Parkes Desilverizing
Retorting
Cupelling
Vacuum Dezincing
Chlorine Dezincing
Harris Dezincing
Debismuthizing
Bismuth Refining
Final Refining and Casting
1
1
3
3
7
7
9
12
16
23
31
35
42
47
50
52
53
56
58
60
62
64
65
67
69
70
72
74
75
m
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LIST OF TABLES
Table Page
.. _. Ji..
1 Lead Minerals, By Name and Composition 2
2 Twenty-Five Leading Lead-Producing Mines in the United
States in 1976, in Order of Output 4
3 Principal Statistics for the Primary Lead Industry in
the United States in 1978 5
4 U.S. Primary Lead Producers 6
5 Analysis of a Missouri Mine Water 14
6 Analysis of an Idaho Mine Water 14
7 Typical Southeastern Missouri Lead Concentrate
Analyses 17
8 Western Lead Concentrate Analyses 18
9 Flotation Chemicals 20
10 Lead Mill Wastewater Analysis 21
11 Sinter Analysis 24
12 Sinter Machine Feed 25
13 Grain Loading and Weight Analysis of Input Feed and
Emissions Updraft Lead Sintering Machine 26
14 Typical Size Profile of Emissions, Updraft Lead
Sintering Machine 26
15 Analysis of Sinter Machine Exhaust Gases (Missouri
Lead Operating Company) 28
16 Atmospheric Control Systems on Primary Lead Sintering
Machines 29
17 Wastewater Treatment at Primary Lead Acid Plants 34
IV
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LIST OF TABLES (Continued)
Table Page
18 Scrubber Wastewater Treatment at Primary Lead Plants 34
19 Lead Bullion Composition 36
20 Typical Blast Furnace Slag Analysis 37
21 Typical Blast Furnace Charge 38
22 Exhaust Gas Analysis After Air Dilution and CO
Combustion 39
23 Atmospheric Control Systems on Primary Lead Blast
Furnaces 41
24 Waste Effluents from Slag Granulation 43
25 Effluent Concentrations with Neutralization and
Clarification 44
26 Primary Lead Slag Granulation Wastewater Treatment 45
27 Lead Bullion Analysis 48
28 Typical Compositions of Softened Lead Bullion and Slag
(Amounts in Weight Percent) 54
29 Typical Retort Analysis 64
LIST OF FIGURES
Figure
1 Primary U.S. Lead Smelting and Refining Locations 8
2 Lead Industry Flowsheet 10
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LEAD INDUSTRY
INDUSTRY DESCRIPTION
Although primary lead refinery production increased somewhat in 1978,
mine production and consumption declined. Curtailed use of lead antiknock
compounds in gasoline accounts for a significant portion of this reduction
in spite of the fact that such use still represents 15 percent of lead
consumption (1). Other areas of lead consumption have also decreased. Lead
pigments are now rarely used in paints, and lead has been partially replaced
in such applications as plumbing, battery manufacture, packaging, protective
coatings, and construction.
Although new methods of production are being developed, few techno-
logical changes have occurred in domestic commercial operations; lead is
still being produced with the same pyrometallurgical techniques introduced
75 years ago. The one major exception to this lack of innovation is the
replacement of all downdraft sinter machines with the updraft type.
The most significant recent development in the U.S. lead industry was
the discovery and development of the "New Lead Belt" in southeastern
Missouri. Mining of this deposit began in 1967 and now more than 80 percent
of the ore mined in the United States specifically for lead comes from this
region. A portion of this deposit consists of almost pure galena, analyzing
at over 70 percent lead with only very small amounts of other metals.
Three of the six U.S. lead smelters are near the New Missouri lead
belt; the others are located in Idaho, Montana, and Texas. The industry
employs about 7000 people; two-thirds of this number are employed in mining
and concentrating operations (1).
Raw Materials
Lead is most often found in nature as galena (PbS), the primary sulfide
of lead. Deposits are rarely pure since the lead-bearing compound is usu-
ally mixed with pyrite, sphalerite, and pyrrhotite. Most of these deposits
contain very little copper.
Oxidized lead ores also occur and are composed primarily of anglesite
and cerussite, the weathered products of galena. Table 1 lists the impor-
tant lead ore minerals, together with others in which the lead is combined
with phosphorus, vanadium, and other elements.
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TABLE 1. LEAD MINERALS, BY NAME AND COMPOSITION
Mineral
Galena
Angles ite
Cerussite
Pyromorphite
Vanadinite
Crocoite
Wu If en ite
Linarite
Composition
PbS
PbS04
PbC03
Pb5Cl(P04)3
Pb5ci(vo4)3
PbCr04
PbMo04
PbO-CuO-S03 H20
Lead, %
88.6
68.3
77.5
76.3
73.0
63.9
56.4
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Domestic production of lead pomes chiefly from ores mined primarily for
their lead content. Additional lead is derived from ores in which lead and
zinc are comparably valued as coproducts and it is also recovered as a
byproduct from ores mined for copper, gold, silver, zinc, or fluorine.
Complex ores mined in the Rocky Mountains are greatly dependent for eco-
nomical recovery on the values of the lead, zinc, silver, and gold content
and not the value of just one metal (2). Table 2 list the 25 leading lead
producing mines in the United States in 1976.
Most lead produced in this country is from domestic ores. Little is
produced from imported concentrates. General imports of lead represented 20
percent of total consumption in 1978 (3). A considerable quantity is pro-
duced first at zinc smelters, the residues then being sent to lead smelters
for recovery of lead.
In the production of lead metal, the industry requires various other
raw materials. Explosives, water, and various organic chemicals are used in
mining and concentrating operations; pyrometallurgical smelting and refining
require various fluxing materials such as limestone and silica and fuel in
the form of coke, oil, or natural gas.
Energy requirements for lead production involving mining, concentrat-
ing, smelting, and refining are lower than any of the other major metals.
The production of 1 ton of lead is estimated to require 6.8 x 106 kilo-
calories; this figure is about one-fourth that for refined copper and less
than one-half that of zinc (2).
Products
Lead bullion more than 99.9 percent pure is the primary product of this
industry. Antimonial lead, a less ductile metal, is also produced. In
1976, the processing of lead ores and concentrates accounted for 100 percent
of domestic bismuth production, as well as 56 percent of antimony, and
sizable quantities of zinc, silver, tellurium, copper, and gold. Appreci-
able quantities of sulfur and sulfuric acid are also recovered as byproducts
of lead production. Byproduct and coproduct associations in lead production
in the rest of the world are similar to those found domestically (2).
Table 3 provides basic 1978 statistics of the lead industry.
Companies
The United States leads the world in lead production, accounting for
about 15 percent of the total world mine production in 1978 (3). In that
year, the domestic mining industry was comprised of about 35 mines in 11
states with production valued at $398 million (3). The seven leading mines,
all in Missouri, produced 88 percent of the year's total mine production of
recoverable metal (1).
Domestic primary smelters are located in Missouri, Montana, Texas, and
Idaho. As shown in Table 4, four companies operate four integrated lead
smelters/refineries, two lead smelters, and one lead refinery. Each of
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TABLE 3. PRINCIPAL STATISTICS FOR THE
PRIMARY LEAD INDUSTRY IN THE UNITED STATES IN 1978 (3)
Primary lead produced, metric tons
Mine (recoverable) 529,661
Refinery (refined lead) 566,417
Refinery (antimonial lead, lead content) 4,296
Exports, metric tons
Lead materials excluding scrap (lead content) 8,225
Lead ore and concentrates (lead content) 54,231
Imports, metric tons
Ores and concentrates (lead content) 52,985
Refined metal 225,620
Consumption, metric tons
Reported 1,432,744
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these companies also operates a zinc smelter; however, the zinc and lead
operations are not located near each other except in Kellogg, Idaho. Figure
1 indicates the locations of domestic primary lead smelters and refineries.
In 1978 approximately 2,400 persons were employed at lead smelters and
refineries. Approximately 4700 persons were employed at domestic mines and
mills producing lead, lead-silver, or lead-zinc ores or concentrates (3).
Many of the companies producing primary lead are vertically integrated
and therefore are involved in two or more process segments. These firms may
process other metals such as zinc, copper, and gold, with recovery of these
metals often making the mining and processing of lead economically feasible.
Environmental Impact
The primary lead industry emits fine particulate and sulfur dioxide to
the atmosphere. The particulate contains metals such as lead, cadmium, and
arsenic and originates from sinter machines, blast furnaces, slag fuming,
dressing, cadmium recovery, reverberatory softening, and antimony recovery
operations. Control of sulfur dioxide emissions is a significant problem
for the industry because of all the sources only one gas stream produced by
the sintering machine is amenable to sulfuric acid production.
Unlike the copper industry, most lead smelters are located in areas
where rainfall exceeds evaporation and consequently recycle of process
waters is not completely practicable. Therefore, water pollution can be a
problem at lead mines, mills, and smelters. Toxic flotation agents may be
discharged from mills, and runoff from smelter property can contain heavy
metals. Holding ponds are used for treatment of these waste streams; how-
ever, some escape is inevitable.
References
1. Commodity Data Summaries. 1979. U.S. Department of the Interior,
Bureau of Mines. Washington, D.C. 1979.
2. Mineral Commodity Profiles, Lead-1977. U.S. Department of Inte-
rior, Bureau of Mines. Washington, D.C. 1977.
3. Mineral Industry Surveys, Lead Industry Monthly. June 1979. U.S.
Department of the Interior, Bureau of Mines. Washington, D.C.
August 1979.
4. Minerals Yearbook 1976. U.S. Department of Interior, Bureau of
Mines. Washington, D.C. 1978.
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INDUSTRY ANALYSIS
This industry analysis examines each production process to define its
purpose and its environmental effects. Each process is analyzed as follows:
1. Function
2. Input Materials
3. Operating Conditions
4. Utilities
5. Waste Streams
6. Control Technology
7. EPA Classification Code
8. References
This section includes only the processes that are now operating in the
United States or that are under construction. Figure 2 is a flowsheet
showing the processes, their interrelationships, and their major waste
streams.
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REFINERY SLAGS -
COKE
FLUX
COM. OR COtt-]
OTHER INOR6ANIC J
ADDITIVES
SLAG
FUMINC
FUR
IIACt „
6
T
I AIR
V SOLID
Figure 2. Lead industry flowsheet.
10
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Figure 2 (continued)
11
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PRIMARY LEAD PRODUCTION
PROCESS NO 1
1. Function - Ore deposits containing economically recoverable amounts of
lead are excavated and transported to an ore concentration plant. Most lead
ore is obtained from underground mines that use normal stoping methods (1 2)
rut *M f-n C?+;n2' room-and-P111ar> Wlth and without rock bolting; and'
cut-and-fill with timber supports. After the ore is cut from the deposit,
belt, ™de?< ?h tSU rface,b^ ra11 tram> trackless shuttle cars, or conveyor
+1 I K ,1 transported to ore concentrating facilities by rail car
truck, belt conveyor, or a combination thereof.
2'
- The major Jead-containing minerals, with composition
Presented ln Tab1e I- The most common are galena
no H if-H - re gaena
(lead sulfide), cerussite (lead carbonate), and anglesite (lead sulfate)
n±tna °™ ^it* n™ the most abundant ^ nature and are the most fre:
quent y used in the United States as a source of lead. The deposits usually
b?±th Ot?nr 1ementS SUC,h aS ZinC' 9°ld' Cadmium' antimony Trsen?c a ^
bismuth. In a few areas, however, such as southeastern Missouri, the ore
other minerals d ^ Slmpl6 mineral1zation and virtual exclusion of
The economically important deposits of lead ore in the United States
asso'cia'te^i'h CatVlt^fi11. in9s ^ replacements, the origin of which is
associated with intrusive igneous masses.
H- ammo"iul'1 m'trate and fuel oil (AN-FO) is used for blasting
powe (3) " added t0 the ml'XtUre t0 increase Casting
3. Operatinci Conditions - Mining is performed under ambient conditions.
4. Utilities - Electricity is used for operation of equipment in under-
ground mining and transport. Diesel fuel and electricity are required for
ore transport equipment at the surface. Specific energy requirements fo?
the mining equipment are not reported. requirements ror
A small quantity of water is required for miscellaneous uses such as
equipment washing, dust control spraying, and sanitation facilities
5. Waste Streams - The mining of lead ore generates dust in drillinq
dust ImL nn ic9i'innd transport operations. Estimated average fugitive
?rom severll tvn J10f9ram? per metnc ton of ore' based "P™ observations
rrom several types of nonferrous mining.
Wastewater from lead mining results from several sources the worst of
which is.probably seepage of surface water through spo 1 piles- others
our ots1? 5%TPti2n °f,^uifers and wate^ sent into'the Sine for utility
purposes (5,6). The water is pumped from the mine at a rate necessary to
maintain mining operations. The required pumping rate bears no relatior J to
12
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the ore output and is subject to seasonal variation. The rate can range
from a few cubic meters to thousands of cubic meters per day.
Along with small amounts of oil and hydraulic fluid resulting from
spills or leaks, the wastewater contains dissolved and suspended solids that
reflect the composition of the ore being mined. Analysis of wastewater from
a Missouri and an Idaho mine are given in Tables 5 and 6. In general,
chemical characteristics of the water are typical of those from any sulfide
mine in the same geographic area.
Substantial amounts of solid waste result from underground mining
operations, the estimated average for 1973 being 0.13 ton per ton of ore
mined (4). This waste material consists of the country-rock surrounding the
ore body plus low-grade lead ore contained in it. The normal method of
disposal is to pile this waste in a location near the mouth of the mine.
6. Control Technology - Fugitive dust emissions are controlled by the
manual use of water sprays or oil as needed.
Wastewater is generally treated with lime and impounded as practiced in
copper mining. Since water from Missouri mines is already basic, liming may
not be required for pH adjustment. Water from western lead mines is acidic
and is treated similarly to that from copper mines. After treatment, the
wastewater is reused in ore milling operations.
The solid waste or spoil generated by the mining operation is often
used as support and landfill material for highway construction. When it
cannot be so used, it is placed in a waste dump located so that it should
not contaminate a stream or underground aquifer. Prevention of water seep-
age is important in this regard.
7. EPA Source Classification Code - None
8. References -
1. Mineral Facts and Problems. U.S. Department of the Interior,
Bureau of Mines. Washington, D.C. 1970.
2. Minerals Yearbook. U.S. Department of the Interior, Bureau of
Mines. Washington, D.C. 1973.
3. Encyclopedia of Chemical Technology. Interscience Publishers, a
division of John Wiley and Sons, Inc. New York. 1967.
4. Development Document for Interim Final and Proposed Effluent
Limitations Guidelines and New Source Performance Standards for
the Ore Mining and Dressing Industry. Point Source Category
Volumes I and II. Environmental Protection Agency. Washington,
D.C. EPA-1-75/032-6. February 1975.
13
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TABLE 5. ANALYSIS OF A MISSOURI MINE WATER (7,8)
Component
Mercury
Cadmi urn
Chromium
Manganese
Iron
Sulfate
Chloride
Fluoride
Concentration, mg/1
0.001 to 0.002
<0.002 to 0.058
<0.010 to 0.17
<0.02 to 57.2
<0.02 to 2.5
63.5 to 750
<0.01 to 57
0.063 to 1.2
TABLE 6. ANALYSIS OF AN IDAHO MINE WATER (6)
Constituent
pH
Sulfate as SO/
Total iron
Zinc
Nickel
Copper
Manganese
Aluminum
Lead
Cadmium
Concentration,
ppm
2.2
63,000.0
16,250.0
14,560.0
4.8
13.4
2,625.0
347.0
0.8
22.5
Constituent
Magnesium
Calcium
Potassium
Sodium
Chromium
Chloride
Nitrate as NO?
\j
Electrical con-
ductivity
(micromhos @ 25°C)
Concentration,
ppm
1,500.0
31.6
0.7
0.5
0.3
38.0
77.5
48,000.0
14
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5. Hawley, J.R. The Problem of Acid Mine Drainage in the Province of
Ontario. Ontario Ministry of the Environment. Toronto. 1977.
6. Williams, R.E. Waste Production and Disposal in Mining, Milling,
and Metallurgical Industries. Miller Freeman Publications, Inc.
San Francisco. 1975.
7. Wixon, B.G., et al. An Interdisciplinary Investigation of Envi-
ronmental Pollution by Lead and Other Heavy Metals From Industrial
Development in the New Lead Belt of Southeastern Missouri.
University of Missouri, Rolla and Columbia, Missouri. June 1974.
8. Hallowell, J.B., et al. Water Pollution Control in the Primary
Nonferrous Metals Industry - Volume I. Copper, Zinc, and Lead
Industries. Environmental Protection Agency. Washington, D.C.
EPA-R2-73-274a.
15
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PRIMARY LEAD PRODUCTION PROCESS NO. 2
Concentrating
!• Function - Concentrating is the process whereby the lead-containing
portions of the ore produced by the mine are isolated from the fractions low
in desirable mineral content. Except for high-grade galena ore produced in
southeastern Missouri, ore concentration is required to produce feed mate-
rial ^suitable for subsequent metal recovery processes. The process consists
of milling the ore by crushing and grinding, followed by separation into two
or more fractions. The fractions rich in desired minerals are called con-
centrates, and the fraction^ low in mineral content are called gangue.
Reparation is achieved by gravity and froth flotation methods. The
gravity method achieves separation because of differences in specific
gravity of the lead-rich minerals and the gangue particles. The flotation
method achieves separation by the use of compressed air and chemical addi-
tives that create a froth in which finely divided mineral particles are
floated from the gangue. In some applications, the flotation method serves
as a supplement to gravity separation to improve the concentrate.
Lead producers of the Mississippi Valley and the eastern United States
use^gravity separation because there are considerable differences in spe-
cific gravities of the ore minerals and the gangue. Since the milled ore
particles need not be as small as those required for flotation, the milling
costs are lower. Two modes of gravity separation are commonly used, jigging
and float-sink. In jigging, the crushed ore particles are fed to an agi-
tated, water-filled jigging chamber, where the heavier ore particles gravi-
tate to the bottom and the lighter gangue is displaced to the top and
removed. ^ The float-sink mode utilizes a liquid medium, such as an aqueous
ferrosilicon suspension, with a specific gravity between that of the lead
mineral and the gangue. The mineral particles sink, while the gangue floats
to the top for removal by skimming.
Flotation is practiced chiefly by lead mines in the western United
States. The concentrate recovered from the flotation cells contains 45 to
78 percent lead, the percentage depending on the type and grade of crude ore
and its susceptibility to flotation. The concentrate also contains varying
amounts of other valuable elements.
Ore concentrate from the flotation cells requires dewatering before
shipment to smelters. The slurry is fed to thickeners, and flocculating
agents such as alum are added to improve the settling rate and fines collec-
tion. The thickened slurry of about 50 percent solids is vacuum-filtered
and dried to a product containing 6 to 15 percent moisture (1).
Typical analyses of southeastern Missouri and western lead ore concen-
trates are presented in Tables 7 and 8, respectively.
16
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TABLE 8. WESTERN LEAD CONCENTRATE ANALYSES (4)
Constituent
Pb
Zn
Au
Ag
Cu
As
Percent
45-60
0-15
0-0.05 kg/ ton
0-1.4 kg/ton
0-3
0.01-0.40
Constituent
Sb
Fe
insolubles
CaO
S
Bi
Percent, weight9
0.01-2.0
1.0-8.0
0.5-4.0
tr-3.0
10-30
tr-0.1
tr = trace,
18
-------
2. Input Materials - Lead content of the sulfide ores fed to concentrating
plants ranges from 3 to 8 percent, except for the high-grade Missouri ores
in which lead content exceeds 70 percent (2).
Table 9 lists the flotation chemicals and amounts required for process-
ing lead ore; included also are some of the less commonly used agents.
3. Operating Conditions - All concentrating operations take place at
atmospheric pressure and ambient temperatures.
4. Utilities - Water usage varies with the degree of processing and is
approximately 4 cubic meters per metric ton of ore processed (3).
Electricity is used to operate grinding equipment and generate com-
pressed air.
5. Waste Streams - Fugitive dust emissions are the only type of atmo-
spheric pollutant warranting consideration. Compositions of the dust are
not specified. Crushing operations generate, on the average, 3.2 kilograms
of particulate emissions per metric ton of ore processed; 0.9 kilogram is
attributable to the crushing and grinding operations, and 2.3 kilograms to
material transport and storage (3,4,5).
Liquid waste from the concentrating operation is in the form of a
tailings slurry discharged to the tailings pond. Approximately 4 cubic
meters of tailings slurry is discharged per metric ton of ore processed
(3,6).
Flotation and conditioning chemicals are present in the wastewater
either as a floating layer or a solute. In general, lead sulfide flotation
is run at an elevated pH level (8.5 to 11) requiring frequent pH adjustments
with hydrated lime or sodium carbonate (7). This alkaline wastewater dis-
solves only small amounts of heavy metals, but can carry mineral particles
in suspension.
Wastewaters leaving a concentrating operation contained metals as shown
in Table 10. These were the only metals investigated; others may have been
present in greater than normal concentrations. Concentrations of calcium,
magnesium, sodium, and potassium in mill waters are significantly higher
than those in surface water.
Water content of the gangue material from flotation is adjusted to
facilitate hydraulic transport to a tailings pond. Tailings contain
residual solids from the ore, dissolved solids, and excess mill reagents.
Typical quantities are 0.9 to 1.1 tons per ton of ore milled. The main
component is dolomite, with small quantities of such constituents as lead,
zinc, copper, mercury, cadmium, manganese, chromium, and iron.
6. Control Technology - Dust from the crushing operations is generally
reduced by drawing air "through the equipment and collecting the dust with
cyclone separators. This is both a dust control and an integral part of the
process since it allows these small particles to bypass one or more crushing
19
-------
TABLE 9. FLOTATION CHEMICALS (8)
Chemical
Amount used,
kg/metric ton of ore
Na^CO^ (conditioner)
CaO (conditioner)
CuS04 (activator)
Sodium isopropol xanthate (collector)
Pine oil (frothers)
NaCN (depressant)
0.45 - 0.9
0.9 - 18.
0.36 - 0.55
0.0045 - 0.09
0.09
0.045 - 0.14
LESS COMMON FLOTATION REAGENTS
Reagent
Purpose
Methyl isobutyl-carbinol
Propylene glycol methyl ether
Long-chain aliphatic alcohols
Potassium amyl xanthate
Dixanthogen
Isopropyl ethyl thionocarbonate
Sodium diethyl-dithiophosphate
Zinc sulfate
Sodium dichromate
Sulfur dioxide
Starch
Frother
Frother
Frother
Collector
Collector
Collectors
Collectors
Zinc depressant
Lead depressant
Lead depressant
Lead depressant
20
-------
TABLE 10. LEAD MILL WASTEWATER ANALYSIS (6)
Component
Concentration, mg/1
Mercury
Lead
Zinc
Copper
Cadmium
Chromium
Manganese
Iron
<0.001
0.107 to 1.9
0.12 to 0.46
0.014 to 0.36
0.005 to 0.011
0.002 to 0.02
0.03 to 0.169
0.03 to 0.53
21
-------
and grinding operations. Fugitive dust is usually uncontrolled unless the
amount being lost economically justifies the installation of equipment for
its recovery.
To preserve the Ozark area of Missouri where the New Lead Belt is
located, special attention has been given to wastewater treatment. Flota-
tion reagents in the wastewater are biologically degraded by algae growth.
Use of meandering streams before final discharge to receiving waters in-
creases exposure to the algae and provides good conditions for algae growth.
The algae sink to the bottom of the stream and act as a solids collector, as
well (6). Disposal of algae in event of excessive growth is not discussed
in the literature.
7. EPA Source Classification Code - 3-03-010-04
8. References -
1. Development Document for Interim Final Effluent Limitations Guide-
lines and Proposed New Source Performance Standards for the Lead
Segment of the Nonferrous Metals Manufacturing Point Source Cate-
gory. Environmental Protection Agency. EPA-440/l-75/032-a.
February 1975.
2. Mineral Facts and Problems. U.S. Department of the Interior,
Bureau of Mines. Washington, D.C. 1970.
3. Development Document for Interim Final and Proposed Effluent
Limitations Guidelines and New Source Performance Standards for
the Ore Mining and Dressing Industry. Point Source Category
Volumes I and II. Environmental Protection Agency. Washington,
D.C. EPA-1-75/032-6. February 1975.
4. PEDCo-Environmental Specialists, Inc. Trace Pollutant Emissions
from the Processing of Metallic Ores. August 1974.
5. Jones, H.R. Pollution Control in the Nonferrous Metals Industry.
Noyes Data Corporation. Park Ridge, New Jersey. 1972.
6. Wixon, B.C., et al. An Interdisciplinary Investigation of Envi-
ronmental Pollution by Lead and Other Heavy Metals from Industrial
Development in the New Lead Belt of Southeastern Missouri.
University of Missouri. Rolla and Columbia, Missouri. June 1974.
7. Hawley, J.R. The Use, Characteristics and Toxicity of Mine-Mill
Reagents in the Province of Ontario. Ontario Ministry of the
Environment. Toronto. 1977.
8. Encyclopedia of Chemical Technology. Interscience Publishers, a
division of John Wiley and Sons, Inc. New York. 1967.
22
-------
PRIMARY LEAD PRODUCTION PROCESS NO. 3
Sintering
1. Function - The ore concentrate is treated by sintering to make it
suitable for subsequent blast furnace operation. Sintering is the roasting
of blended and pelletized ore concentrate mixtures. The purposes of sinter-
ing are as follows:
1) To provide a feed of proper ratio of lead, silica, sulfur, and
iron for smelting;
2) To convert metallic oxides into oxides or sulfates amenable to
smelting;
3) To drive off volatile oxides such as S02, S03, As203, and Sb203;
and
4) To produce a firm, porous clinker that is easily fed to a blast
furnace (1).
The process consists of three consecutive steps:
1) Blending of ore concentrates with direct-smelting ores, sinter
recycle, flue dust, and fluxes;
2) Pelletization of the blended mixture; and
3) Roasting of pelleted material.
Blending balances the smelter charge and permits control of impurity
levels of zinc, copper,, arsenic, antimony, and bismuth. Pelletizing is
achieved by mixing the blended charge with 6 to 8 percent by weight water in
a pug mill and feeding the mix to a rotating pelletizing drum. Resulting
pellets are 3 to 5 millimeters in diameter.
The pellets are spread evenly over a horizontal metal belt which takes
them through an updraft sintering machine. The only remaining downdraft
sintering machine was scheduled for replacement early in 1979. As the
pellets proceed through the sintering machine, they are heated and undergo
oxidizing reactions that convert sulfides to oxides and sulfates. Lead
silicate forms, and oxides combine to form low-melting-point silicate com-
plexes, which bind the ore particles together.
The resulting sinter is broken into pieces ranging up to 25 millimeters
diameter (2). The crushed sinter is screened for removal of fines, which
are recycled to the charge blending step. The screened product is stored
for blast furnace reduction. Table 11 gives typical ranges of components in
the sintered product.
23
-------
TABLE 11. SINTER ANALYSIS (1,3,4)
Component
Ag
Cu
Pb
S
Fe
Si02
CaO
Zn
Sb
Cd
Weight,
percent
0.03-0.07
0.3-4.5
28-50.0
0.75-2.0
12-15.5
10.0-15.6
9.0-10.5
4.0-12.5
0.01-1.5
Tr-0.04
24
-------
2. Input Material - Lead concentrates are the main input material for
sintering. Typical analyses of western and Missouri lead concentrates are
presented in the concentrating process description (Process No. 2). Col-
lected flue dusts, recycled sinter, and smelter residues also are part of
the charge for sintering. Sulfide-free fluxes are added to maintain a
specified sulfur content (5 to 7 percent by weight) in the charge. Silica
and limestone are used as needed. Coke fines, in the amount of I percent by
weight of the total charge, are mixed with the charge (5).
Typical feed sources to a sinter machine are presented in Table 12.
TABLE 12. SINTER MACHINE FEED (10)
Ore concentrate
Misc. lead materials
Flux diluent
Sinter recycle
Weight, percent
31.47
12.44
19.86
36.20
3. Operating Conditions - Temperatures in both updraft and downdraft
sinter roasting machines reach approximately 800°C. Pressure is atmo-
spheric.
4. UtilIities - In updraft sintering machines gas- or oil-fired burners are
used to ignite the charge. Energy consumed in the sintering process amounts
to 0.5 million kilocalories per ton of lead produced. A breakdown allocates
40 percent to coke consumption and 60 percent to gas or oil consumption, gas
being used more than oil (6).
Water may be added for pelletizing the charge if the moisture content
is below required limits. Air is injected through the charge while oxidiz-
ing in the sintering machines. No quantities are given for air injection.
Electricity is the power source for fans, feed conveyors, and general
operating equipment. Approximately 20 percent less power is required for
the updraft fans than for downdraft (7).
5. Waste Streams - Particulate emissions are approximately 100 to 250
kilograms per metric ton of lead produced in sinter machines (9). Analysis
of the flue dust shows roughly 40 to 70 percent lead, 10 to 20 percent zinc,
and 8 to 12 percent sulfur (8). Depending upon concentrate composition, the
flue dust contains various amounts of antimony, cadmium, germanium, sele-
nium, tellurium, indium, thallium, chlorine, fluorine, and arsenic (7).
Tables 13 and 14 give weight analysis and size distribution of particulate
emissions.
25
-------
TABLE 13. GRAIN LOADING AND WEIGHT ANALYSIS OF INPUT FEED AND
EMISSIONS UPDRAFT LEAD SINTERING MACHINE (11)
Grain
loading, g/Nm3 (0°C)
16.3
Weight
Pb
Si02
Fe
CaO
MgO
Zn
S
Cu
As
Cd
Se
inerts
analysis, %
35-50
8-11
9-13
7-10
0.7-1
4-6
0.7-1
tr
tr-30
tr
tr
6-8
TABLE 14. TYPICAL SIZE PROFILE OF EMISSIONS
UPDRAFT LEAD SINTERING MACHINE (11)
Size,
micron
20-40
10-20
5-10
< 5
% weight
15-45
9-30
4-19
1-10
26
-------
Sintering is the only step in the lead smelting process that emits
enough S02 to create a serious air pollution control problem. About 85
percent of the sulfur is removed from the concentrate during sintering.
Approximately 50 percent of the remainder is discharged as S02 from subse-
quent operations; the balance goes into the slag as sulfates (7,9).
In the sintering process most of the sulfur is eliminated at the front
end of the conveyor. By the time the charge reaches the end of the machine,
little S02 is being emitted. If the exit gases are removed in a single
stream, the S02 concentration is about 2 percent (7,8). In an updraft
machine, the exit gases can be split into two streams, one predominantly
from the front and the other from the rear. This procedure produces both a
weak and a strong S02 stream, 0.5 and 5.7 percent S02 respectively (7).
Off-gases also contain organic vapors from flotation reagents or their
combustion products. The compounds formed from these flotation chemicals by
reactions caused by the sintering temperatures are not known. Traces of HF
and SiF4 may be found in these gases. The volume of gases emitted is a
function of machine size and material throughput and ranges from 0.25 to
0.50 normal cubic meters per minute per square meter of bed area (8).
Temperatures of the gases normally range from 150° to 400°C (5,8). Flow
rates may vary between 58,000 and 66,000 standard cubic meters per hour (8).
Table 15 gives a typical analysis of gases from a sintering machine. A
small but variable amount of arsenic trioxide in the gaseous form may also be
present.
6- Control Technology - Particulates from the sinter machine are collected
by several different methods. Table 16 lists current atmospheric controls on
lead sintering processes. Efficiencies range from 95 to 99.8 percent.
The strong gas stream collected from separation of updraft exit gases
is the only stream amenable to sulfuric acid production. In both the weak
stream and the combined single stream, concentrations are too low for such
treatment. At least one smelter has installed a recirculation system for
the weak stream, which allows S02 to be removed in the strong stream exit
for subsequent treatment. Certain foreign operations have successfully made
use of this technique for some time.
Three plants are now controlling S02 in sinter machine off-gases by use
of single-contact sulfuric acid plants, which reduce total S02 emissions by
70 to 80 percent. Another plant is planning to add an acid plant to its new
updraft machine.
Currently no lead smelters practice control on weak S02 streams. The
best available control technology for these streams would be chemical scrub-
bing.
27
-------
TABLE 15. ANALYSIS OF SINTER MACHINE EXHAUST GASES
(MISSOURI LEAD OPERATING COMPANY) (12)
so2
°2
co2
N2
so3
Dust content
Temperature
Moisture content
Range, % by volume
4-7
4-9
3-4
84-85
0.05-0.2
57 g/Nm3
200-350°C
25 percent by vol .
28
-------
TABLE 16.
Plant
Control system
Bunker Hill/Kellogg, Idaho
AMAX/Boss, Missouri
St. Joe/Herculaneum, Missouri
ASARCO/E. Helena, Montana
ASARCO/Glover, Missouri
ASARCO/E1 Paso, Texas
Updraft sintering machine produces
two gas streams: strong gas stream
to acid plant. Weak gas stream com-
bined with blast furnace and hygiene
air, then goes to a baghouse and out
the stack.
Updraft sintering machine produces
two gas streams: strong gas stream
to acid plant. Weak gas stream com-
bined with blast furnace gas before
discharge through stack.
Updraft sintering machine produces
two gas streams: strong gas stream
to acid plant. Weak gas stream joins
other gases, then thru baghouses
and to stack.
Updraft sintering machine. Gases to
water spray, ESP, then dilution air
added and released to stack.
Updraft sintering machine. All gases
to water spray and baghouse, then
out stack.
Updraft sintering machine. A new con-
trol system is planned, making use of
an acid plant for the strong stream.
29
-------
7. EPA Classification Code - 3-03-010-01.
8. References -
1. Development Document for Interim Final Effluent Limitations Guide-
lines and Proposed New Source Performance Standards for the Lead
Segment of the Nonferrous Metals Manufacturing Point Source Cate-
gory. Environmental Protection Agency. EPA-440/l-75/032-a.
February 1975.
2. Davis, W.E. National Inventory of Sources and Emissions: Copper,
Selenium, and Zinc. U.S. Environmental Protection Agency (NTIS),
Research Triangle Park, North Carolina. PB-210 679, PB-210 678
and PB-210 677. May 1972.
3. Encyclopedia of Chemical Technology. Interscience Publishers, a
division of John Wiley and Sons, Inc. New York. 1967.
4. Hallowell, J.B., R.H. Cherry, Jr., and G.R. Smithson, Jr. Trace
Metals in Effluents from Metallurgical Operations. In: Cycling
and Control of Metals. U.S. Environmental Protection Agency.
Cincinnati, Ohio. November 1972. pp. 75-81.
5. Fejer, M.E., and D.H. Larson. Study of Industrial Uses of Energy
Relative to Environmental Effects. U.S. Environmental Protection
Agency. Research Triangle Park, North Carolina. July 1974.
6. Copper Hydrometallurgy: The Third-Generation Plants. Engineering
and Mining Journal. June 1975.
7. Background Information for New Source Performance Standards:
Primary Copper, Zinc, and Lead Smelters. Volume I, Proposed
Standards. Environment Protection Agency. Research Triangle
Park, North Carolina. EPA-450/2-74-002a. October 1974.
8. Jones, H.R. Pollution Control in the Nonferrous Metals Industry
Noyes Data Corporation. Park Ridge, New Jersey. 1972.
9. Calspan Corporation. Assessment of Industrial Waste Practices in
the Metal Smelting and Refining Industry. Volume II - Primary and
Secondary Nonferrous Smelting and Refining. Draft. April 1975.
10. Arthur G. McKee & Co. Systems Study for Control of Emissions
Primary Nonferrous Smelting Industry. U.S. Department of Health,
Education, and Welfare. June 1969.
30
-------
PRIMARY PRODUCTION PROCESS NO. 4
Contact Sulfuric Acid Plant
!• Function - An acid plant catalytically oxidizes S02 gas to sulfur
trioxide, and absorbs it in water to form sulfuric acid. The sintering
machine produces the only lead smelter exit gases that are amenable to
production of sulfuric acid.
Contact sulfuric acid plants are continuous steady-state processing
units that are operated in other industries using S02 made by burning
elemental sulfur. They may be used with waste S02 streams if the gas is
sufficiently concentrated, is supplied at a reasonably uniform rate, and is
free from impurities.
The heart of a sulfuric acid plant is a fixed bed of vanadium pentoxide
or other special catalyst which oxidizes the S02. All other components of
the plant are auxiliary to this catalytic converter. The other components
clean and dry the stream of gas, mix the proper amount of oxygen with it
(unless sufficient oxygen is present), preheat the gas to reaction tempera-
ture, and remove the heat produced by the oxidation.
The plant incorporates one or two absorbers to contact the gas with
water to form the acid. If only one absorber is provided, this is described
as a single-contact sulfuric acid plant. If two are provided, the second is
placed between stages of the converter, and this is a double-contact plant.
The second absorber allows a larger proportion of the S02 to be converted
into acid, and thus removes more S02 from the gas stream if the initial
concentration is high.
2. Input Materials - Most contact sulfuric acid plants operate most ef-
ficiently with a constant gas stream that contains 12 to 15 percent S02.
Performance almost as good can be achieved in plants that are designed for 7
to 10 percent S02 content. The ability of a plant to convert most of the
S02 to sulfuric acid declines either as gas streams become weaker in S02 or
as the flow rate or concentration becomes less consistent. A concentration
lower than 4 percent S02 is extremely inefficient, since sufficient catalyst
temperature cannot be maintained (1). Certain modifications of the process,
which add heat by combustion of fuel, can provide better conversion at low
S02 concentrations.
The gas that enters the catalyst bed must be cleaned of all particulate
matter, be almost completely dried, and contain no gases or fumes that act
as poisons to the catalyst. The acid plant is always supplied with special
scrubbers to remove final traces of objectionable materials.
Clean water is required to react with the S03 to form sulfuric acid.
It may be necessary to deionize the water in a special ion exchange system
in order to avoid excessive corrosion or to meet acid quality specifica-
tions. Steam condensate may also be used.
31
-------
3. Operating Conditions - The catalyst bed operates properly only if
temperatures are maintained between 450° and 475°C. Pressures do not
usually exceed 2 kilograms per square centimeter. The plants are usually
not enclosed in a building.
4. Utilities - Noncontact cooling water is required. At one plant pro-
ducing 1500 metric tons of acid per day, about 12 million liters of water is
required each day (2).
A small amount of electricity is required for pumps and blowers. This
may be generated on site in some cases, where recovery of waste heat is
maximized.
In certain patented modifications, heat from combustion of natural gas
is used to provide better efficiency at low S02 concentrations. Natural gas
or oil is also required to heat any acid plant to operating temperature
following a shutdown.
5. Waste Streams - Single-contact sulfuric acid plants using weak gas
streams can at best absorb only 96 to 98 percent of the S02 fed to them.
The remaining quantity passes through to the atmosphere. Efficiencies as
low as 60 percent have been reported (3).
Double-contact acid plants provide a higher percentage of S02 removal
if they are fed gas with a higher S02 content. Efficiencies higher than 99
percent have been reported. Exit gas S02 concentration is still usually
within the same range as shown above, although one recently developed
process claims stack emissions of less than 0.005 percent S02 (4).
In sulfuric acid plants, it is difficult to prevent some loss of S03,
in the form of a fine mist of sulfuric acid, with the absorber exit gases.
This is usually 0.02 to 0.04 kilogram of S03 per metric ton of 100 percent
acid produced.
The scrubbing columns that clean the waste gas stream create off-grade
weak acid that cannot be sold. The amount is estimated as 4 to 8 liters for
each 10 cubic meters of gas treated (5).
In this industry, most particulate matter from gas cleaning equipment
is recycled to the metallurgical processes. The small quantities of partic-
ulate removed by the acid scrubbing operations, however, are mixed with a
stream of weak sulfuric acid and cannot readily be recycled. They are
discharged with the acid plant blowdown.
In some sections of the country it is difficult to sell the product
acid, even for less than the cost of manufacture. Therefore, it may be less
expensive to neutralize and discard the acid than to absorb the costs of
shipment to a distant user. Thus, the product acid can itself become a
waste stream.
An acid plant does not produce solid wastes directly, but the gypsum
formed in neutralization of acid can constitute a significant solid waste.
32
-------
6. Control Technology - In this country the S02 in the tail gas from the
sulfunc acid plant is not controlled. When S02 emissions are large, the
best control may be to increase operating efficiency by adding additional
catalyst stages or by adding heating equipment to maintain proper catalyst
temperature. Changes in the metallurgical operations to produce a stream of
higher S02 concentration at a more uniform rate are also good controls, if
this is possible. Scrubbing of the weak S02 stream for final S02 absorption
may also be necessary.
Mist eliminators in the form of packed columns or impingement metal
screens can minimize acid mist emissions. Manufacturers claim elimination
of all but 35 to 70'milligrams of mist per cubic meter of gas, and the units
at times perform better. To prevent formation of plumes of mist during
periods of abnormal operations, however, electrostatic precipitators are
often used. Better regulation of feed rate and quality also minimizes acid
loss.
Tables 17 and 18 give the treatments now practiced at lead smelters for
the control of acid plant blowdown and scrubber water (1).
If volumes of strong acid must be neutralized, treatment with limestone
is followed by more precise pH adjustment with lime, and discharge to a pond
for in-perpetuity storage of the resulting gypsum is the only tested and
economical method of disposal.
7. EPA Source Classification Code - None
8. References -
1. Jones, H.R. Pollution Control in the Nonferrous Metals Industry.
Noyes Data Corporation. Park Ridge, New Jersey. 1972.
2. Hallowell, J.B., et al. Water Pollution Control in the Primary
Nonferrous Metals Industry - Volume I. Copper, Zinc, and Lead
Industries. EPA-R2-73-274a. U.S. Environmental Protection
Agency. Washington, D.C. September 1973.
3. Confidential information from EPA.
4. Browder, T.J. Advancements and Improvements in the Sulfuric Acid
Industry. Tim J. Browder Co. San Marino, California.
5. Vandergrift, A.E., L.J. Shannon, P.G. Gormena, E.W. Lawless, E.E.
Sal lee, and M. Reichel. Particulate Pollutant System Study - Mass
Emissions, Volumes 1, 2, and 3. PB-203 128, PB-203 522, and
PB-203 521. U.S. Environmental Protection Agency. Durham, North
Carolina. May 1971.
6. Development Document for Interim Final Effluent Limitations Guide-
lines and Proposed New Source Performance Standards for the Lead
Segment of the Nonferrous Metals Manufacturing Point Source Cate-
gory. Environmental Protection Agency. EPA-440/l-75/032-a.
February 1975.
33
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TABLE 17. WASTEWATER TREATMENT AT PRIMARY LEAD ACID PLANTS (6)
Plant
Liquid effluent treatment
Discharge
Enters water treatment plant,
limed, thickened, and filtered,
and sent to reservoir for
recycle.
Recycled to slag granulation.
Enters liming sump, then
passed to lime bed, then
to a cool ing pond.
0
0
273 nT/day
TABLE 18. SCRUBBER WASTEWATER TREATMENT AT PRIMARY LEAD PLANTS (6)
Plant
Treatment
Discharge
Enters water treatment plant,
limed, thickened, filtered,
and then sent to reservoir for
recycling.
Recycled from a cooling tower.
Sent to a lime sump then
to a settling pit. Most
is recycled.
0
Undetermined
34
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PRIMARY LEAD PRODUCTION PROCESS NO. 5
Blast Furnace
1. Function - Sintered feed is reduced in the blast furnace to produce a
crude lead bullion. Specified amounts of coke, limestone, and other fluxing
materials are charged with the sinter through a water-jacketed shaft at the
top of the furnace. The material settles to the furnace bottom, which is
supported by a heavy refractory material.
Air is injected into the charge through side-mounted tuyeres to effect
a more complete formation of metallic oxides and thereby raise the tempera-
ture of the charge. At the operating temperature of the furnace, coke and
resulting carbon monoxide reduce most of the metallic oxides to yield a
molten mass of metal. Some of the metallic impurities interact with the
flux to form a slag composed mainly of iron and calcium silicates. Depend-
ing upon the composition of the charge, material in the blast furnace can
separate into as many as four distinct liquid layers.
Copper, if present in lead ores, reacts with residual sulfur to form a
matte that separates into a layer beneath the slag. The matte typically
assays 44 to 62 weight percent copper, 10 to 20 percent lead, and up to 13
percent sulfur (1). If the charge is high in arsenic and/or antimony con-
tent, a speiss layer will form under the matte. Speiss compounds are
arsenides and antimonides of iron and other metals. The bottom layer of
lead bullion is 94 to 98 weight percent lead plus varying amounts of other
metals such as copper, tin, arsenic, antimony, silver, and gold. Typical
ranges of composition are shown in Table 19.
Upon completion of the process, the crude bullion is charged to dross-
ing kettles (2), the matte and speiss are sold to a copper smelter, and the
slag is discharged to a fuming furnace. A typical slag analysis is shown in
Table 20.
The capacity of most large blast furnaces is 1360 metric tons of charge
materials per day.
2. Input Materials - The blast furnace charge is made up of sinter,
fluxes, coke, and sundry materials recycled from other smelting operations.
The relative amounts of these materials are presented in Table 21.
Normally, coke comprises 8 to 15 weight percent of the furnace charge.
If the blast air is enriched with oxygen, coke consumption is reduced 10
percent with a 10 to 20 percent increase in smelting rate.
3. Operating Conditions - Temperatures in a blast furnace range from 215°C
for the charge near the top of the furnace to 1220°C in the slag zone. Slag
temperatures range from 1000° to 1220°C, and bullion temperatures from 900°
to 950°C.
Because of the exhaust gas configuration, the blast furnace operates at
a pressure slightly above atmospheric.
35
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TABLE 19. LEAD BULLION COMPOSITION (2,3,4)
Component
Ag
An
Cu
c
o
Pb
Fe
Zn
Sn
As
Sb
Bi
Wt. percent
0.13-0.31
1.6-3.13
1.0-2.5
0.25
94-98
0.6-0.8
tr.
tr.
0.7-1.1
1.0-1.75
0.01-0.03
Value for Au in g/metric ton.
tr. - trace
36
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TABLE 20. TYPICAL BLAST FURNACE SLAG ANALYSIS (2,3,4)
Component
Ag
Cu
Pb
FeO
CaO
Zn
insol
MnO
As
Sb
Cd
F
Cl
Ge
S
Weight percent
1.56-4.693
0.10b
1.5-3.5
25.5-31.9
14.3-17.5
13.0-17.5
22. 6-26. 5d
2.0-4.5
0.10
0.10
0.10
trc
trc
trc
0.5-1.0
a Values for Ag in grams per metric ton.
Variable, depending on the furnace charge.
c tr = trace.
Insolubles include MgO - A10 - Si02 phases.
37
-------
TABLE 21. TYPICAL BLAST FURNACE CHARGE (2)
Component
Sinter
Coke
Miscellaneous products
(zinc plant residues)
Slag (dross)
Silica
Lime rock
Cadmium residue
Refinery dross
Baghouse product
Weight, kg
1250-1650
125-165
0-90
0-225
0-36
0-27
0-9
0-35
0-35
38
-------
4. Utilities - Air is injected into the charge at a pressure of 0.1 to 0.3
kilogram per square centimeter (2). Consumption of 140 to 175 cubic meters
per hour is required for a charge of 1360 metric tons per day (2).
Cooling water circulates through jacketed shafts to control furnace
temperatures. Quantities are unreported.
5. Waste Streams - Participate emission rates in blast furnace exhaust gas
range from 125 to 180 kilograms per metric ton of bullion produced (3,5).
Particle sizes of the dust range from 0.03 to 0.3 micron (5). The dust is
composed of oxides, sulfates, and sulfides of the various metals present in
the furnace charge, plus chlorides, fluorides, and coke dust (5,6).
Undiluted gas temperatures are estimated to be 650° to 750°C (3,5),
with theoretical flue gas rates of 170 to 400 normal cubic meters per
minute. After dilution by air and water vapor, however, volume typically
increases from 9 to 12 times the theoretical flow (1).
Exhaust gas analysis after- air dilution and CO combustion is reported
in Table 22.
TABLE 22. EXHAUST GAS ANALYSIS AFTER
AIR DILUTION AND CO COMBUSTION (5,7)
Component
C02
02
C0a
S02
N2
Percent by volume
15
15
5
0.05
Remainder
CO concentration estimated to be 25 to 50
volume percent prior to combustion.
Other reports indicate that CO and S02 concentrations, although highly
variable, average 2.0 and 0.01 to 0.25 volume percent, respectively (1,5).
An estimated 10 to 20 weight percent of total sulfur in the feed concentrate
is removed in the blast furnace, half emitted as S02 and the rest retained
in the slag or matte (8).
Slag from the blast furnace is generally discharged and granulated
with cool ing water.
39
-------
6. Control Technology - The dilute S02 emissions from the blast furnace
are not controlled at lead smelters. The best available control technology
is chemical scrubbing.
Particulates in blast furnace exhaust gases are controlled at all
smelters by means of baghouses. Control efficiency ranges from 95 to 99.9
percent. Table 23 describes controls for blast furnace gases.
Current practice for slag disposal is to convey it hydraulically with
the granulating water stream to a dump or tailings pond. Recommended tech-
nology includes use of concrete settling pits, ground sealing of disposal
area, and diversion of runoff to a water treatment lagoon.
7. EPA Classification Code - 3-03-010-02
8. References -
t
1. Arthur G. McKee & Co. Systems Study for Control Emissions Primary
Nonferrous Smelting Industry. U.S. Department of Health, Educa-
tion, and Welfare. June 1969.
2. PEDCo-Environmental, Specialists, Inc. Trace Pollutant Emissions
from the Processing of Metallic Ores. August 1974.
3. Encyclopedia of Chemical Technology. Interscience Publishers, a
division of John Wiley and Sons, Inc. New York. 1967.
4. Development Document for Interim Final Effluent Limitations Guide-
lines and Proposed New Source Performance Standards for the Lead
Segment of the Nonferrous Metals Manufacturing Point Source
Category. Environmental Protection Agency. EPA-440/l-75/032-a.
February 1975.
5. Jones, H.R. Pollution Control in the Nonferrous Metals Industry.
Noyes Data Corporation. Park Ridge, New Jersey. 1972.
6. Phillips, A.J. The World's Most Complex Metallurgy (Copper, Lead,
and Zinc). Transactions of the Metallurgical Society of AIME
Volume 224. August 1962. pp. 657-668.
7. Arthur G. McKee & Co. Systems Study for Control of Emissions
Primary Nonferrous Smelting Industry. U.S. Department of Health
Education, and Welfare. June 1969.
8. Background Information for New Source Performance Standards:
Primary Copper, Zinc, and Lead Smelters. Volume I Proposed
Standards. Environmental Protection Agency, Research Triangle
Park, North Carolina. EPA-450/2-74-002a. October 1974
40
-------
TABLE 23. ATMOSPHERIC CONTROL SYSTEMS ON PRIMARY
LEAD BLAST FURNACES (7)
Plant
Control system
Bunker Hill/Kellogg, Idaho
AMAX/Boss, Missouri
St. Joe/Herculaneum, Missouri
ASARCO/E. Helena, Montana
ASARCO/Glover, Missouri
ASARCO/E1 Paso, Texas
Blast furnace gas stream joined
to weak sinter gas stream and
hygiene air, then to baghouse
then to stack.
Blast furnace gases join sinter
weak gases, then to baghouse,
and then out the stack.
Blast furnace gases join sinter
weak gases and other gases pass
thru baghouses and stack.
Blast furnace gases join reverb
and ventilation gases, then pass
thru three baghouses in parallel
with stack for each house.
Blast furnace gases to water
spray, baghouse, and three
stacks.
Blast furnace and dross furnace
gases mix, then pass thru a
spray chamber and a baghouse,
then out six stacks.
41
-------
PRIMARY LEAD PRODUCTION PROCESS NO. 6
Slag Fuming Furnace
1. Function - A slag fuming furnace is used to recover metal values other-
wise lost in the slag. Blast furnace slag contains appreciable concentra-
tions of lead and zinc oxides created through reoxidation of the metals in
the bottom portion of the blast furnace.
The slag is fed to the fume furnace in the molten state, and pulverized
coal is used with a stream of primary combustion air to supply heat and to
maintain a reducing environment. The metallic oxides are first converted to
metals, then are reoxidized with a stream of secondary air added above the
slag surface. Lead and zinc are discharged from the slag fuming furnace as
finely divided participates entrained in the furnace gases.
A matte is sometimes separated from the slag in this operation for
recovery of substantial amounts of copper and silver from the dezinced slag
When fuming has subsided, the slag is dumped and cooled with water.
2. Input Materials - Composition of the blast furnace slag charged to the
fume furnace is shown in Table 20 of Process No. 5. Two tons of slag are
generated per ton of crude lead bullion produced by the blast furnace.
Pulverized coal is added to maintain temperature by combustion. The amount
is not specified in the literature.
3. Operating Conditions - The slag temperature range is 1000° to 1200°C
Atmospheric pressure is used (1).
4. Utilities - Air is injected into the furnace for combustion of the
coal. Quantities are not cited in the literature (2).
onn .uWaneL!S used for slag C0o1l"n9 and granulation in amounts ranging from
200 to 8,200 cubic meters per day (3), the amount depending upon the design
of cooling water circuit at a given plant. A typical analysis is given in
5. Waste Streams - The exhaust gas from the furnace typically has a low
S02 concentration. The literature (2) cites a value of 0.02 volume percent
for a flow rate of 5,660 normal cubic meters per minute. Gas stream temper-
ature is about 1200°C.
The exit gas also contains high concentrations of particulate and fume
composed of the volatile components of the blast furnace slag. The litera-
ture does not cite quantities or composition.
The dumped slag and water used for granulation constitute the major
waste stream from the process. The slag is made up of various compounds of
iron, calcium, silicon, aluminum, magnesium, and other elements. The water-
soluble portions are leached by the cooling water. Table 24 presents analy-
ses of the intake and outflow streams of water used for slag granulation
42
-------
TABLE 24. WASTE EFFLUENTS FROM SLAG GRANULATION
Parameter
pH
Alkalinity
COD
Total solids
Dissolved solids
Suspended solids
Oil and grease
Sulfate (as S)
Chloride
Cyanide
Aluminum
Arsenic
Cadmium
Calcium
Chromium
Copper
Iron
Lead
Magnesium
Mercury
Molybdenum
Nickel
Potassium
Selenium
Silver
Sodium
Tellurium
Zinc
Total
plant
intake
mg/1
7.6
203
8
-
408
3
-
145
18
-
-
-
-
70
-
0.02
1.70
0.12
.31
-
-
0.03
-
-
-
-
-
0.05
Total
plant
discharge
mg/1
8.3
186
8
-
500
36
-
215
-
-
-
-
-
-
-
0.02
-
0.30
-
-
-
0.04
-
-
-
-
-
0.12
Net
change,
mg/1
-
-17
0
-
92
33
-
70
-
-
-
-
-
-
-
0
-
0.18
-
-
-
0.02
-
-
-
-
-
0.38
Net loading
kg/ton
-
NLCa
0
-
0.89
.32
-
0.67
-
-
-
-
-
-
-
0
-
0.0018
-
-
-
0.00018
-
-
-
-
-
0.0037
Process water flow: 6 million liters/day.
Production: 695 metric tons/day.
Source: This contract and 1971 RAPP data.
Notes:
NLC = no load calculable.
43
-------
6. Control Technology - The exhaust gas from the fuming furnace is cooled
by waste heat boilers or cooling chambers before being sent to baghouses for
removal of particulate and condensed volatiles. Baghouse operation is
limited to a maximum temperature of 285°C. Particulate removal efficiency
ranges from 95 to 99 percent (4). It is preferable to operate the baghouse
at the lowest possible temperature to allow removal of volatile matter
contained in the gas stream.
Slag disposal is the same as described in Process No. 5, involving
conveyance with the granulating water stream to a dump or tailings pond, use
of concrete settling pits, ground sealing, and diversion of runoff.
Normally, it is desirable to recycle slag granulation water after
cooling and clarification. A smaller stream is bled off to neighboring
surface water to control buildup of water-soluble components. The best
available control technology for wastewater treatment is a combination of
neutralization and clarification; the resulting effluent concentrations are
presented in Table 25. The control methods in use are presented in Table
26.
TABLE 25. EFFLUENT CONCENTRATIONS WITH
NEUTRALIZATION AND CLARIFICATION
Component
Cadmium
Lead
Mercury
Zinc
Concentration,
mg/1
0.5
0.5
0.005
5.0
These values are currently being met by five of the six lead smelters.
7. EPA Classification Code - None
8. References -
1. Encyclopedia of Chemical Technology. Interscience Publishers, a
division of John Wiley and Sons, Inc. New York. 1967.
2. Arthur G. McKee & Co. Systems Study for Control of Emissions
Primary Nonferrous Smelting'industry. U.S. Department of Health,
Education, and Welfare. June 1969.
3. Hallowell, J.B., et al. Water Pollution Control in the Primary
Nonferrous Metals Industry. Volume I, Copper, Zinc, and Lead
Industries. Environmental Protection Agency. Washington, D.C.
EPA-R2-73-274a. September 1973.
44
-------
TABLE 26. PRIMARY LEAD SLAG GRANULATION
WASTEWATER TREATMENT (5)
Plant
1
2
3
4
5
6
Treatment
Sent to cooling pond.
Sent to settling pit then to
a cooling pond.
Sent to settling pond and
recycled.
Sent to two settling ponds in
series.
Sent to a slag pile.
No data.
Discharge
8,230 m3/day
(2,200,000 gpd)
273 m3/day
(72,000 gpd)
0
Discharge is present
but no quantities
are available.
No apparent discharge
to surface. Leaching
is not mentioned.
No data
45
-------
Vandergrift, A.E., L.J. Shannon, P.G. Gorman, E.W. Lawless, E.E.
Salle, and M. Reichel. Particulate Pollutant System Study - Mass
Emissions, Volumes 1, 2, and 3. U.S. Environmental Protection
Agency (NTIS). Durham, North Carolina. PB-203 128, PB-203 522,
and PB-203 521. May 1971.
Development Document for Interim Final Effluent Limitations Guide-
lines and Proposed New Source Performance Standards for the Lead
Segment of the Nonferrous Metals Manufacturing Point Source Cate-
gory. Environmental Protection Agency. EPA-440/l-75/032-a.
February 1975.
46
-------
PRIMARY LEAD PRODUCTION PROCESS NO. 7
Crossing
!• Function - Dressing is the initial step in refining lead bullion.
Molten bullion from the blast furnace is placed into dressing kettles of 90
metric-ton capacity where submerged air lances provide agitation and oxida-
tion. The kettle and molten bullion are cooled to a temperature at which
lead is still a liquid but oxides of the common impurities and oxides of
lead solidify. The term "dross" refers to any solid scum floating on top of
a metal bath. Dross may contain varying amounts of lead, copper, tin,
indium, arsenic, antimony, and bismuth. Because of the high specific
gravity of molten lead, these solid oxides float and are easily skimmed off
the molten lead. Dressing of the blast furnace bullion always occurs before
the lead is sent to the refinery.
For more complete removal of copper, sulfur is added to the dressing
kettle. This sulfur combines with the remaining copper forming cuprous
sulfide (CU2S), which floats and is skimmed off with the rest of the dross.
By dressing, a bullion with copper content as high as 2 percent can be
reduced to approximately 0.005 percent copper (1).
The dross is sent to a dross reverberatory furnace for further treat-
ment and recovery of marketable products. Dross may typically contain 90
percent lead oxide, 2 percent copper, and 2 percent antimony, in addition to
other values such as gold, silver, arsenic, bismuth, indium, zinc, telluri-
um, nickel, selenium, and sulfur. The collected dross amounts to 10 to 35
percent of the blast furnace bullion (1). A typical assay of drossed bul-
lion is shown in Table 27.
2. Input Materials - Lead bullion is the principal input. During the dross-
ing procedures sulfur is added in a ratio of approximately 1 kilogram per ton
of bullion from the blast and dross reverberatory furnace. Various amounts of
coal or coke, ammonium chloride, soda ash (Na2C03), and litharge or baghouse
fume (PbO) are added to the kettles as needed.
3. Operating Conditions - The molten bullion is cooled to a temperature of
370° to 500°C and maintained within that range. Pressures are atmospheric
(1).
4. Utilities - Most of the dressing kettles are heated with natural gas.
About 1.1 million kilocal ories per metric ton are consumed during this
stage, of which 90 percent is allocated to gas and 10 percent to oil (2).
Conveyors, agitators, pumps, and similar equipment are powered by elec-
tricity. Air is injected by submerged lances for supplementing oxidation
and agitation (1,5,6). Quantities of electrical and air consumption are not
given in the literature.
5. Waste Streams - The dressing operation generates small amounts of air
pollutants and slag. The air pollutants are S02 and volatile components of
the lead bullion. A typical analysis of the bullion was presented in Table
19. Varying quantities of copper, iron, arsenic, zinc, cadmium, antimony,
and bismuth may be volatilized; it is believed that the quantities are very
47
-------
TABLE 27. LEAD BULLION ANALYSIS (1,3,4)
Basis: As drossed
Element
Ni
Ag
Au
Cu
Fe
Te
As
Sb
Bi
Se
Sn
Wt. percent
tr.
0.13-0.31
1.2-3.19
0.08-0.005
0.7-0.8
0.01-0.03
0.7-1.1
1.0-1.75
0.01-0.03
tr.
tr.
Value of Au in g/metric ton.
tr. = trace.
48
-------
small because of the low temperatures. The S02 content of the off-gas is
very low, usually less than 0.05 percent by volume. Flow rates of exit
gases from a blast furnace are typically 5,100 to 5,500 normal cubic meters
per minute. Temperatures of these gases are low, approximately 200° to 300°C
(6). The particulate loading has been quantified by one source as being
between 1.0 and 21.7 grams per cubic meter of off-gas (7). Another source
cites the emission rate as 10 kilograms per metric ton of lead produced.
6. Control Technology - No control methods are presently applied to the
weak S02 stream emitted from the dressing operation. The best available
technology is chemical scrubbing.
Particulates and fumes from the dressing kettles are combined with the
blast furnace off-gas at all plants. See Process No. 5.
7. EPA Source Classification Code - None
8. References -
1. Encyclopedia of Chemical Technology. Interscience Publishers, a
division of John Wiley and Sons, Inc. New York. 1967.
2. Fejer, M.E., and D.H. Larson. Study of Industrial Uses of Energy
Relative to Environmental Effects. U.S. Environmental Protection
Agency. Research Triangle Park, North Carolina. July 1974.
3. Development Document for Interim Final Effluent Limitations Guide-
lines and Proposed New Source Performance Standards for the Lead
Segment of the Nonferrous Metals Manufacturing Point Source Cate-
gory. Environmental Protection Agency. EPA-440/l-75/032-a.
February 1975.
4. PEDCo-Environmental Specialists, Inc. Trace Pollutant Emissions
from the Processing of Metallic Ores. August 1974.
5. Background Information for New Source Performance Standards:
Primary Copper, Zinc, and Lead Smelters. Volume I, Proposed
Standards. Environmental Protection Agency. Research Triangle
Park, North Carolina. EPA-450/2-74-002a. October 1974.
6. Arthur G. McKee & Co. Systems Study for Control of Emissions
Primary Nonferrous Smelting Industry. U.S. Department of Health,
Education, and Welfare. June 1969.
7. Jones, H.R. Pollution Control in the Nonferrous Metals Industry.
Noyes Data Corporation. Park Ridge, New Jersey. 1972.
49
-------
PRIMARY LEAD PRODUCTION PROCESS NO. 8
Dross Reverberatory Furnace
1. Function - Dross removed from the lead bullion requires further treat-
ment for separation of components. As cited in Process No. 7, the dross is
composed of about 90 percent lead oxide, 2 percent copper, 2 percent
antimony, and small amounts of other elements. Prior to smelting, the
dross may be treated with soda ash, litharge or baghouse fumes, coke, and
sulfur to produce matte and speiss containing high ratios of copper to lead.
Whether treated or not, the dross is charged into a reverberatory furnace
along with pig iron and silica. Lime rock may also be used.
During smelting, the charge separates into four layers: slag
on top, matte and speiss intermediate, and molten lead at the bottom.
Through the use of suitably placed taps on the furnace, each layer can be
removed separately. The slag, amounting to 2 to 4 weight percent of the
dross charge, is returned to the blast furnace for smelting. The slag
typically assays 6 percent copper, 38 percent lead, 11 percent zinc, 11
percent FeO, and 16 percent Si02 (1). The matte and speiss are tapped
separately, granulated, and shipped to copper smelters for recovery of
copper and precious metals. The matte amounts to 10 to 14 weight percent of
the dross charged; the speiss, 20 to 30 percent. The collective assay of
these materials is 42 percent copper, 38 percent lead, 16 percent sulfur, 1
percent iron, and 0.6 percent arsenic, plus small amounts of zinc, rare
earths, and precious metals (1). The lead layer is 94 to 98 percent lead
and comprises 50 weight percent of the dross charged. It is returned to the
blast furnace.
2: Input Materials - Along with the dross, the process requires the addi-
tion of pig iron, silica, and limestone. The amounts of these materials
vary with each charge, depending upon dross composition. If soda treatment
is used, equal amounts of soda ash, litharge, coke, and sulfur are added.
Each is 3 to 5 percent by weight, of the dross charged.
3- Operating Conditions - Smelting temperatures are the same as those in
the blast furnace, ranging from 1000° to 1200°C. Smelting is done at atmo-
spheric pressure.
4. Utilities - Gas or oil fuels are used for heating and maintaining
temperature. Quantities are not given in the literature.
5. Waste Streams - Atmospheric emissions are the only form of pollution
from the dross reverberatory furnace. Particulate emission rates are 10
kilograms per metric ton of lead produced (2). The reference does not
indicate whether this emission includes condensed fume. Sulfur dioxide,
carbon dioxide and monoxide, sulfur trioxide, and nitrogen and its compounds
are released to the atmosphere as products of combustion. The exit gas
volume from a dross reverberatory ranges from 30 to 170 normal cubic meters
per minute (2,3). The S02 content of this gas is usually below 0.05 per-
cent. Exhaust gases are about 760° to 980°C (2).
50
-------
Water used in matte and speiss granulation is evaporated before trans-
port.
All solids are recycled or marketed.
6. Control Technology - No control methods are used for the weak S02
stream emitted from the dressing reverberatory. The best available tech-
nology is chemical scrubbing.
Particulates and fumes from the dressing reverberatory are combined
with the blast furnace off-gas at all plants. See Process No. 5.
7. EPA Source Classification Code - None
8. References -
1. Encyclopedia of Chemical Technology. Interscience Publishers, a
division of John Wiley and Sons, Inc. New York. 1967.
2. Jones, H.R. Pollution Control in the Nonferrous Metals Industry.
Noyes Data Corporation. Park Ridge, New Jersey. 1972.
3. Arthur G. McKee & Co. Systems Study for Control of Emissions
Primary Nonferrous Smelting Industry. U.S. Department of Health,
Education, and Welfare. June 1969.
51
-------
PRIMARY LEAD PRODUCTION PROCESS NO. 9
Cadmium Recovery
1. Function - The flue dusts generated by lead smelting are processed to
recover cadmium values. Since dust from blast furnace exhaust gases is
recycled to the sintering machine, sinter dust becomes enriched in cadmium,
thallium, and zinc. When cadmium content in the dust reaches 12 weight
percent or greater, the dust is subjected to a separate roasting operation
for cadmium separation and recovery (1).
Roasting is performed in one of several different types of small en-
closures (2). The objective is to selectively volatilize certain of the trace
elements, including cadmium, thallium, indium, and selenium and to carry
these fumes out of the roaster in a stream of air. The less-volatile elements,
including lead, zinc, and antimony, remain in the roaster residue which is
recycled to the sintering machine feed preparation equipment.
2. Input Materials - Flue dust collected from the sintering machine ex-
haust gases is the only input material.
3. Operating Conditions - Operating temperature has not been reported; it
is, however, carefully controlled to provide optimum separation of the trace
elements.
4- Utilities - Many of these roasters are heated electrically and others are
heated with oil or gas. The energy consumption of these units has not been
reported.
5. Waste Streams - Fume emissions from the roaster are cooled and
recovered as product. The roaster residue is recycled. Data for fume
capture are not furnished in the literature.
There are no liquid or solid wastes from cadmium recovery.
6. ControltTechnology - The flue dust and fume emitted from the roaster
can be contained by further cooling with water sprays and collection in a
Dagnouse.
?• EPA Source Classification Code - None
8. References -
1. Arthur G. McKee & Co. Systems Study for Control of Emission
Primary Nonferrous Smelting Industry. U.S. Department of Health
Education, and Welfare. June 1969.
2. Hallowell, J.B., et al. Water Pollution Control in the Primary
Nonferrous Metals Industry. Volume I, Copper, Zinc, Lead Indus-
tries. Environmental Protection Agency. Washington, D C
EPA-R2-73-274a. September 1973.
52
-------
PRIMARY LEAD PRODUCTIONS PROCESS NO. 10
Reverberatory Softening
1. Function - The drossed lead bullion is further purified by a process
termed "softening", which entails removal of the elements that make lead
hard, notably arsenic, antimony, and tin. Several other softening processes
can be used (Process No's. 11 and 12) (1,2).
The reverberatory method is similar to the dressing procedure and is
particularly applicable to processing bullion with a wide range of impuri-
ties. The bullion is charged into a reverberatory furnace, melted, and
blown with air to effect oxidation of the arsenic, antimony, tin, and other
impurities. If hardness of the feed bullion is greater than 0.3 to 0.5
weight percent antimony equivalent, litharge is added to increase the rate
of impurity oxidation (1).
Furnaces with capacities of up to 300 metric tons are used for the
process. The oxides rise to the surface to form a slag that is skimmed off
and further treated to recover contained values. The softened lead is
tapped from the bottom of the furnace and pumped to the desilverizing
process. Table 28 presents typical analyses of the softened bullion product
and the softened slag. Hardness of the softened bullion is less than 0.03
weight percent antimony equivalent.
2. Input Materials - An analysis of drossed lead was presented in Table 27
(Process No. 7).[Ttharge is added only when especially hard bullion is
processed. Coke or coal may be added to inhibit the oxidation of lead.
3. Operating Conditions - Temperatures during softening reach 700°C.
Pressures are atmospheric (1).
4. Utilities - Electricity is the power source for mechanical agitators,
pumps, and conveyors. Most of the heat is supplied by the exothermic oxi-
dation of impurities. Any fossil fuel can be used to begin the reaction and
maintain the temperature. Air is injected through lances or pipes into the
bath. Air consumption is not reported.
5. Waste Streams - The air blow from the furnace is the only waste stream
for the process. No data are reported for fume emissions.
There are no liquid or solid wastes from reverberatory softening.
6. Control Technology - No controls of atmospheric fume emissions are
reported. The exhaust gas could be routed to blast furnace baghouses.
7. EPA Source Classification Code - None
53
-------
TABLE 28. TYPICAL COMPOSITIONS OF SOFTENED LEAD BULLION AND SLAG (1)
(AMOUNTS IN WEIGHT PERCENT)
Constituent
Pb
Cu
Se
Te
As
Sb
Sn
Ag
Au
Softened lead
bullion
0.004
0.001
0.025
0.15
1.25a
Softened slag
(liquid dross)
75.
0.005
tr
tr
1.7
12.0
tr
tr
tr
Value for gold in grams per metric ton.
tr - trace.
54
-------
8. References -
1. Encyclopedia of Chemical Technology. Interscience Publishers, a
division of John Wiley and Sons, Inc. New York. 1967.
2. Development Document for Interim Final Effluent Limitations Guide-
lines and Proposed New Source Performance Standards for the Lead
Segment of the Nonferrous Metals Manufacturing Point Source Cate-
gory. Environmental Protection Agency. EPA-440/l-75/032-a.
February 1975.
55
-------
PRIMARY LEAD PRODUCTION PROCESS NO. 11
Kettle Softening
1. [unction - Arsenic, antimony, and tin may be removed from the drossed
lead bullion by kettle softening. Other softening methods are reverberatory
(Process No. 10) and Harris (Process No. 12). Unlike the reverberatory
method, in which air is blown through molten bullion, the kettle method
entails addition of oxidizing agents to remove impurities. Application is
usually limited to treating bullion with a relatively low impurity content
0.3 weight percent or less antimony equivalent (1,2).
Drossed bullion is charged to a kettle and melted. Oxidizing fluxes
such as caustic soda (NaOH) and niter (NaN03) are then added while the
charge is agitated. The fluxes react with the impurities to form a series
of salts such as sodium antimonate (NaSb03) (1,3). A slag containing the
oxidized impurities results. When the reactions are complete, agitation of
the kettle is stopped, and the slag rises to the top of the kettle, where it
is skimmed off; the purified lead bullion is sent to the desilvering proc-
ess. Composition of the softened bullion is similar to that shown in Table
28 (Process No. 10); residual hardness is less than 0.03 weight percent
antimony equivalent.
2. Input Materials - In addition to the drossed lead bullion, caustic soda
and sodium nitrate (niter) are required for fluxing. Amounts depend upon
the impurity content of the feed bullion; a slight excess over stoichio-
metric requirements is desirable fo'r effective removal of impurities.
3- Operating Conditions - A kettle temperature of 700°C is required
Pressure is atmospherical).
4. Utilities - Electricity is used to power the process equipment, such as
agitators and conveyors. Gas or oil are used to heat the kettle and main-
tain temperature.
5. Waste Streams - Atmospheric emissions containing oxides of nitrogen are
released during kettle softening. Details are unreported.
There are no liquid wastes from this process.
The slag containing oxidized impurities is discarded. This material
contains lead as well as water-soluble sodium oxide salts of arsenic, tin,
and antimony. The amount of slag generated is not reported.
6- Control Technology - The controls used for atmospheric emissions are
not known.
Slag is dumped with that generated in either the blast furnace or
fuming furnace (2). There is no recognized control technology for disposi-
tion of this slag. Substitution of Harris softening (Process No 12) is
recommended.
56
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7. EPA Source Classification Code - None
8. References -
1. Encyclopedia of Chemical Technology. Interscience Publishers, a
division of John Wiley and Sons, Inc. New York. 1967.
2. Hallowell, J.B., et al. Water Pollution Control in the Primary
Nonferrous Metals Industry - Volume I. Copper, Zinc, and Lead
Industries. Environmental Protection Agency. Washington, D.C.
EPA-R2-73-274a. September 1973.
3. Development Document for Interim Final Effluent Limitations Guide-
lines and Proposed New Source Performance Standards for the Lead
Segment of the Nonferrous Metals Manufacturing Point Source Cate-
gory. Environmental Protection Agency. EPA-440/l-75/032-a.
February 1975.
57
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PRIMARY LEAD PRODUCTION PROCESS NO. 12
Harris Softening
1. Function - In addition to reverberatory and kettle softening, removal of
arsenic, antimony, and tin from drossed lead bullion can also be accomplished
by the Harris process. As with kettle softening, the process is most applica-
ble in treating bullions containing 0.3 percent or less antimony.
The process consists of two operations. The initial pyrometallurgical
step is the same as the kettle softening process. The drossed bullion is
charged to a kettle, melted, and agitated. Sodium nitrate and sodium hydrox-
ide are added to react with the impurities and form metallic salts which float
on top of the bath in a mixture with sodium oxide. These salts are skimmed
off, and the purified lead is sent to the desilverizing process (1).
The second operation is a hydrometallurgic'al treatment of the cooled
skimmings, in which hot water is used to dissolve the valuable constituents.
Most of the skimmings will be dissolved and will form a strongly alkaline so-
lution. Any undissolved residue is filtered from the mixture and discarded.
The clear solution is then cooled to preferentially precipitate sodium antimo-
nate. After separation by filtration, the antimony-rich filter cake is sub-
jected to further processing (Process No. 13), and the filtrate is mixed with
lime to precipitate calcium salts of arsenic and tin in separate operations.
Upon removal from solution, the calcium arsenate is reported to be sold
to insecticide manufacturers, and the calcium stannate is shipped to tin
producers. The residual sodium hydroxide solution is evaporated to produce
dry sodium hydroxide, which is recycled to the softening process.
2. Input Materials - Aside from the drossed lead bullion, sodium hydroxide
and sodium nitrate are required in slightly more than stoichiometric amounts
for fluxing. Unspecified amounts of process water are fed to the operation
for leaching. Lime is required in quantities sufficient to precipitate salts
of arsenic and tin.
Use of sodium chloride and lead oxide in this process has also been
reported.
3. Operating Conditions - Maximum temperatures are 700°C for the pyrometal-
lurgical operation, 100°C for hydrometallurgical processing, and more than
200°C for sodium hydroxide evaporation (2). Atmospheric pressure is main-
tained during all operations.
4- Utilities - Process equipment, such as agitators, pumps, and conveyors,
are powered by electricity.
Gas or oil is utilized for kettle heating, temperature maintenance, and
sodium hydroxide recovery.
58
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5. Waste Streams - Atmospheric emissions containing oxides of nitrogen will
result from the use of sodium nitrate as an input material.
The quantity of insoluble residue created from the leaching step has not
been reported. Its composition is also unknown, but it has been reported to
be insoluble in water (1).
6. Control Technology - No control of air emissions from this process is
employed. The leaching residue is apparently discarded along with blast
furnace or fuming furnace slag.
7. EPA Source Classification Code - None
8. References -
1. Hallowell, J.B. et al. Water Pollution Control in the Primary
Nonferrous Metals Industry - Volume I. Copper, Zinc, and Lead
Industries. Environmental Protection Agency. Washington, D.C.
EPA-R2-73-274a. September 1973.
2. Encyclopedia of Chemical Technology. Interscience Publishers, a
division of John Wiley and Sons, Inc. New York. 1967.
59
-------
PRIMARY LEAD PRODUCTION PROCESS NO. 13
Antimony Recovery
1. Function - Slags from the softening processes (Process No's. 10, 11
12) are treated in order to separate and recover the contained mineral
values, notably arsenic, tin, and antimony. Two methods are commonly used
to recover antimony, depending upon the product desired.
If antimonial lead or "hard lead" is desired, the softening slag is
subjected to a reduction process. The slag is charged to a furnace and
heated with a reducing agent and slagging fluxes. Since the oxidation
potential of the other minerals in the charge is higher, the oxides of lead
and antimony are preferentially reduced. Slag is formed and skimmed off
while the metallic mixture of lead and antimony is tapped as a marketable
product. If the slag is rich in tin, it may be sold to a tin producer-
otherwise, it is recycled to the sintering process or blast furnace (1).
If the desired product is antimony trioxide (Sb203), the softening slag
teed is treated by a volatilization process. The slag is fed to a furnace
where it is heated to volatilize arsenic trioxide and antimony trioxide
Since arsenic trioxide is more volatile, it is driven off first and is
separated from the antimony trioxide by selective condensation (2) Col-
lection of the oxides consists of condensing the volatilized fume and
capturing it in an electrostatic precipitator or a baghouse. The recovered
antimony trioxide is sent to antimony refining plants, usually located
nearby. Recovered arsenic trioxide may be sold to arsenic processors The
nonvolatilized furnace residue, containing appreciable lead values is
returned to the blast furnace or sintering process.
2. Input Materials - Slag from the softening processes is the main input-
it contains primarily lead, arsenic, antimony, and tin. A typical analysis
is presented in Table 28 (Process No. 10). For production of hard lead!
coke or charcoal is used as a reductant, the quantity dependent on feed slag
composition. Soda ash or silica is used as a flux. No quantitative data
are reported.
3- Operating Conditions - Temperatures range from 800° to 900°C Pres-
sures are atmospheric (2).
4 Utilities - Gas or oil is used to maintain furnace temperatures
Electricity is required for operation of conveyors. In antimony trioxide
production, cooling water is required for fume condensation. No quanti-
tative data are furnished in the literature.
5 Waste Streams - In the volatilization process, the airstream carrying
the oxide fume is released to the atmosphere after condensation and collec-
tion.
There are no liquid wastes from antimony recovery.
60
-------
The arsenic tri oxide, if it cannot be sold, represents the only solid
waste from the process.
6. Control Technology - In the volatilization and condensation process,
the fume stream passes through an electrostatic precipitator or baghouse
No established control for excess arsenic trioxide has been developed.
7. EPA Source Classification Code - None
8. References -
1. Hallowell, J.B., et al. Water Pollution Control in the Primary
Nonferrous Metals Industry. Volume I, Copper, Zinc, and Lead
Industries. Environmental Protection Agency. Washington, D.C.
EPA-R2-72-274a. September 1973.
2. Encyclopedia of Chemical Technology. Interscience Publishers, a
division of John Wiley and Sons, Inc. New York. 1967.
3. Development Document for Interim Final Effluent Limitations Guide-
lines and Proposed New Source Performance Standards for the Lead
Segment of the Nonferrous Metals Manufacturing Point Source Cate-
gory. Environmental Protection Agency. EPA-440/l-75/032-a.
February 1975.
61
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PRIMARY LEAD PRODUCTION PROCESS NO. 14
Parkes Desilverizing
1. Function - Gold and silver are removed from the softened lead bullion
by the Parkes desilverizing process. These metals do not oxidize easily,
and they are not removed by any of the previous refining steps. The Parkes
desilverizing process is based on the fact that gold and silver have a
greater affinity for zinc than for lead. Therefore, zinc is added to the
molten lead bullion to form alloys with the copper, gold, and silver con-
tained in the bullion. These alloys are insoluble in the lead and rise to
the surface, forming a crust that is skimmed off.
To simplify subsequent recovery processes, the gold and silver are
often recovered in separate steps. Since gold and most of the copper are
first to combine, zinc is added in two steps. The initial addition results
in a crust rich in gold values (1,2). Following removal of this crust, the
second addition of zinc is made to allow the removal of silver. Although
these steps are not totally exclusive for either gold or silver, they do
effect a good degree of segregation.
Because other metallic impurities, notably arsenic, can interfere with
this process, they must be removed prior to this operation. Arsenic content
in the bullion must be less than 0.10 weight percent (1).
2. Input Materials - Softened lead bullion is required for the process.
Hardness equivalent to less than 0.03 combined weight percent of arsenic,
antimony, and tin is desirable. A typical analysis for a softened bullion
is presented in Table 28, Process No. 10.
Zinc is the only additive. The amount is 1 to 2 percent in excess of
the amount required to saturate the lead bullion, i.e., 0.55 weight percent
of bullion weight.
3- Operating Conditions - The bullion charge is heated to 540°C and then
cooled to 40" to 93UC (1,3). Pressure is atmospheric.
4. Utilities - Gas or oil is used to heat the charge. Electricity is used
to operate pumps and agitators. Utility quantities are not given in the
literature.
5. Waste Streams - None
6. Control Technology - None
7. EPA Source Classification Code - None
8. References -
1. Encyclopedia of Chemical Technology. Interscience Publishers, a
division of John Wiley and Sons, Inc. New York. 1967.
62
-------
2. Hallowell, J.B., et al. Water Pollution Control in the Primary
Nonferrous Metals Industry. Volume I, Copper, Zinc, and Lead
Industries. Environmental Protection Agency. Washington, D.C.
EPA-R2-73-274a. September 1973.
3. Development Document for Interim Final Effluent Limitations Guide-
lines and Proposed New Source Performance Standards for the Lead
Segment of the Nonferrous Metals Manufacturing Point Source Cate-
gory. Environmental Protection Agency. EPA-440/l-75/032-a.
February 1975.
63
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PRIMARY LEAD PRODUCTION
PROCESS NO. 15
Retorting
1. Function - Crusts from the Parkes process are retorted to recover zinc
for reuse in the desilvering process and to form a purified Dore metal.
Dross is placed in graphite crucibles of 600 tp 640 kilograms capacity;
these are heated in a special
vaporized. The zinc vapor is
to bars or blocks for recycle
kilograms Dore per metric ton of dross (1).
analysis of this retort metal.
Faber-du-Faur-type furnace, and the zinc is
condensed in a cooling chamber and then tapped
The remaining retort metal assays 140 to 400
Table 29 presents a typical
TABLE 29. TYPICAL RETORT ANALYSIS (1)
Constituent
'
Dore
Zinc
Arsenic
Antimony
% weight
15.6-43.8
1.5-2.5
0.4
1.0
Constituent
Copper
Tel lurium
Bismuth
Lead
% weight
1.5-4.0
0.2
0.25
Remaining
percentage
2. Input Materials - Crusts from the desilverizing process are the only
input materials for this process. This dross is basically a gold-silver-
zinc compound with small amounts of impurities such as antimony, copper,
tellurium, bismuth, and lead.
3. Operating Conditions - Operating temperatures during retorting are
between 1260° and 1320°C (1). Pressure is atmospheric.
4. Utilities - The retort furnaces are gas- or oil-fired.
consumed by transport apparatus. No quantities are cited.
Electricity is
5. Waste Streams - The only waste stream consists of small quantities of
metallic fume escaping the condensing chamber. This fume is believed to be
composed predominately of zinc, arsenic, antimony, and lead. No data were
found on emission factors or constituents.
6. Control Technology - Several smelters control fume and particulate
emissions with baghouses. Destruction of baghouse fabric at high tempera-
tures is prevented by routing the gases through tubular cooling chambers
prior to entering the baghouse. Control efficiencies of more than 98 per-
cent are claimed. The collected flue dusts are recycled to the sintering
machine. Other smelters use no control devices on retorts.
7. EPA Source Classification Code - None
8. References -
1. Encyclopedia of Chemical Technology.
division of John Wiley and Sons, Inc.
Interscience Publishers,
New York. 1967.
64
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PRIMARY LEAD PRODUCTION PROCESS NO. 16
Cupel ling
1. Function - Retort metal is purified in the process called cupelling.
In a furnace called a cupel, the molten metal charge is successively blown
with air and slagged to remove impurities and produce a relatively pure
Dore. The difference in oxidation potentials of the impurities allows
sequential removal of slags with distinct characteristics.
Zinc, arsenic, and antimony are oxidized first and removed; most of the
lead content oxidizes next, forming a product called "good litharge." Upon
removal, it is recycled to the softening process for use as an oxidizer.
Bismuth, copper, and tellurium accumulate in the Dore until the final stages
of cupelling, when they oxidize to a slag called "coppery litharge" because
the copper content may be as high as 10 weight percent. Oxidizing agents
are^required to remove the last traces of copper and tellurium from the
Dore. These latter slags are returned to smelting for further processing.
Cupels are rated according to Dore output. Usual capacities range from
2,850 to 11,300 kilograms per charge. When impurity removal is complete,
the remaining gold-silver alloy is cast into bars for marketing. Purity is
99.9 percent.
2. Input Materials - Retort metal is the basic feed to the process. A
typical analysis of the metal is given in Table 29, Process No. 15.
Sodium nitrate and silica flour are added to remove the last traces of
copper and tellurium from the Dore. Amounts depend upon residual levels of
the impurities.
3. Operating Conditions - Temperature of the cupel reaches 1150°C (1).
Pressure is atmospheric.
4. Utilities - Gas or oil is used to heat the furnace. Pumps and agita-
tors are electrically powered. Cooling water is pumped through jacketed
furnace sections. Compressed air is injected into the charge for oxidation
of impurities. A cold air stream is also blown across the face of the bath
at a pressure of 70 to 87 grams per square centimeter to cause rippling,
which hastens oxidation. No additional quantitative data are given.
5. Waste Streams - Process exhaust gases range in temperature from 1000°
to 1100°C and contain metallic vapors (fume) as well as particulates. Zinc,
lead, arsenic, and antimony comprise the fume. Particulates may contain any
of the components listed in Table 29 (Process No. 15). Emission data are
not present in the literature.
6. Control Technology - Several smelters control exhaust gases, cooling
them by passage through tubular cooling chambers before routing them to
baghouses. Collection efficiency greater than 98 weight percent is claimed.
Collected dust is recycled to the smelter for further processing. Other
smelters do not control cupel emissions.
65
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7. EPA Source Classification Code - None
8. References -
1. Encyclopedia of Chemical Technology. Interscience Publishers, a
division of John Wiley and Sons, Inc. New York. 1967.
66
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PRIMARY LEAD PRODUCTION PROCESS NO. 17
Vacuum Dezincing
1. Function - Zinc added to the bullion in the desilverizing process is
removed by dezincing. The vacuum distillation method is used most widely in
the industry because the recovered metallic zinc can be directly recycled to
the desilvering process. Alternate methods are chlorine dezincing (Process
No. 18) and Harris dezincing (Process No. 19).
Desilverized lead is charged into a kettle and heated. An inverted
bell is placed on top of the kettle with its skirt projecting into the
molten lead to form a vacuum seal. A vacuum is drawn in the bell and is
held for about 2.5 hours, during which the bath is agitated to bring the
zinc to the surface. The zinc vaporizes and is condensed on the water-
cooled dome of the bell.. On completion of the process, the vacuum is
broken, the bell removed, and the solidified zinc peeled from the surface of
the bell.
The product bullion typically is analyzed as less than 0.001 weight
percent zinc, 0.0003 weight percent antimony, and 0.15 weight percent
bismuth (1). The bullion is sent for debismuthizing or for casting if
bismuth content is low (2).
2. Input Materials - Desilverized lead bullion typically containing 0.5 to
1.0 weight percent zinc is the only feed material (3).
3. Operating Conditions - The molten lead bath is maintained at 580° to
595°C (1,2) with an operating pressure of 50 to 60 micrometers absolute (1).
4- Utilities - Gas or oil is used to maintain the kettle temperature.
Pumps, agitators, and conveyors are electrically powered. Cooling water is
used to remove heat from the jacketed bell surface. Although no quantita-
tive data are given in the literature, energy consumption is higher than in
other dezincing processes because of the higher temperature requirements.
5. Waste Streams - None
6. Control Technology - None
7. EPA Source Classification Code - None
8. References -
1. Encyclopedia of Chemical Technology. Interscience Publishers, a
division of John Wiley and Sons, Inc. New York. 1967.
2. Hallowell, J.B., et al. Water Pollution Control in the Primary
Nonferrous Metals Industry. Volume I, Copper, Zinc, and Lead
Industries. Environmental Protection Agency. Washington, D.C.
EPA-R2-73-274a. September 1973.
67
-------
Development Document for Interim Final Effluent Limitations Guide-
lines and Proposed New Source Performance Standards for the Lead
Segment of the Nonferrous Metals Manufacturing Point Source Cate-
gory. Environmental Protection Agency. EPA-440/175-032a
February 1975.
68
-------
PRIMARY LEAD PRODUCTION PROCESS NO. 18
Chlorine Dezincing
1. Function - Desilverized lead bullion requires removal of the zinc added
during the desilverizing process. A process known as chlorine dezincing, or
the Betterton process, can be used, as well as vacuum dezincing (Process No.
17) and Harris dezincing (Process No. 19).
Molten lead is pumped from a heated kettle to a reaction chamber into
which gaseous chlorine is injected from a chlorine tank. Since reactivity
of zinc with chlorine is greater than that of lead, zinc chloride is formed
in the reactor and subsequently collects on the surface of the molten lead.
The material skimmed from the lead contains small amounts of lead chloride
and mechanically entrained lead prills. After treatment with metallic zinc
for lead removal and recovery, a marketable byproduct analyzed as 99 percent
zinc chloride is obtained. The dezinced lead bullion is sent for debis-
muthizing or casting.
A 180-metric-ton kettle with an overall cycle of about 8 hours
typically produces 16,300 metric tons of dezinced bullion per month. The
bullion contains 0.005 weight percent zinc (1).
2. Input Materials - The desilverized lead bullion feed contains 0.5 to
1.0 weight percent zinc.
Chlorine is injected at a rate of 180 to 225 kilograms per hour into
molten lead recirculated at a rate of 7 to 11 metric tons per minute (1).
3. Operating Conditions - A temperature of 370°C maintains the lead in a
molten condition. Pressure is atmospheric (1).
4. Utilities - The kettle is heated with oil or gas. Electricity is used
for pumps, agitators, and conveyors. No quantitative data regarding con-
sumption are cited.
5. Waste Streams - None
6. Control Technology - None
7. EPA Source Classification Code - None
8. References -
1. Encyclopedia of Chemical Technology. Interscience Publishers, a
division of John Wiley and Sons, Inc. New York. 1967.
69
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PRIMARY LEAD PRODUCTION PROCESS NO. 19
Harris Dezincing
1. Function - Zinc added to the lead bullion for desilverizing requires
removal by a dezincing process. The Harris dezincing process consists of a
pyrometallurgical step followed by a hydrometallurgical procedure. Alter-
nate dezincing processes are vacuum (Process No. 17) and chlorine (Process
No. 18).
The pyrometallurgical equipment is the same as for Harris softening
(Process No. 12), i.e., a charging kettle, a reaction cylinder, and a molten
lead pump. In a typical cycle, desilverized lead bullion is charged to the
kettle and then pumped, in a molten state, through the reaction cylinder,
which contains a small amount of caustic soda saturated with lead oxide.
The saturated caustic remains from the previous dezincing cycle. Upon
contact with the molten lead, the lead oxide in the caustic reacts with the
zinc to form zinc oxide, which in turn reacts with caustic to form sodium
zincate. After 30 minutes of lead recirculation, pumping is stopped, fresh
caustic is added to the cylinder to maintain salt fluidity, and the contents
of the cylinder are emptied into a granulator tank. Fresh molten caustic is
again pumped to the cylinder, and recirculation of the lead bullion is re-
sumed. The final caustic addition will become saturated with zinc and lead
oxide and is held over for the next cycle. When dezincing is complete, the
product contains less than 0.001 weight percent zinc and 0.0003 weight
percent antimony. The dezinced lead is pumped from the kettle for debis-
muthizing or casting.
The spent salts from the granulation tank are treated hydrometal-
lurgically. After granulation and solution in hot water, sodium zincate
hydrolyzes to zinc oxide and sodium hydroxide. The zinc oxide precipitates
from the solution and is recovered by filtration. It is subsequently dried
and sold. The sodium hydroxide solution is evaporated, and the resulting
anhydrous caustic recycled (1).
2. Input Materials - Desilverized lead containing 0.5 to 1.0 weight per-
cent lead is charged to the process. Anhydrous sodium hydroxide is
required, the amount dependent upon the zinc content of the feed bullion.
Water is used for the hydroextraction of byproducts. No data as to quanti-
ties are given.
3. Operating Conditions - A temperature of 540°C is required for the
pyrometallurgical operation. The temperature for hydroextraction is 100°C.
Evaporation of the sodium hydroxide solution requires temperatures above
200 C. All operations are performed at atmospheric pressure (1).
Utilities - Kettle heating and soda evaporation of caustic require gas
il as fuel. Electricity is used to operate pumps, agitators, and con-
4.
or oil as fuel.
veyors.
70
-------
5. Waste Streams - None
6. Control Technology - None
7. EPA Source Classification Code - None
8. References -
1. Encylopedia of Chemical Technology. Interscience Publishers, a
division of John Wiley and Sons, Inc. New York. 1967.
71
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PRIMARY LEAD PRODUCTION PROCESS NO. 20
Debismuthizing
1. Function - When the dezinced lead bullion contains 0.15 weight percent
or more bismuth, it must be debismuthized before the final refining and
casting process. The debismuthizing procedure is called the Betterton-Kroll
process.
Calcium and magnesium are added to the molten lead to form ternary
compounds (e.g., CaMg2Bi2) with the bismuth (1). The compounds have a
higher melting point than lead and a lower density. Therefore, when the
temperature of the mixture is reduced to just above the melting point of
lead, the metallic compounds solidify to form a dross that can be skimmed
from the lead. To enhance physical separation, antimony or organic agents
are sometimes added. Chlorine steam may also be used.
The purified lead is pumped to the casting operation, and the skimmed
metallic compound is sent to bismuth recovery.
Cupel slags rich in bismuth may be similarly treated; the residual lead
is returned to smelting.
2. Input Materials - Dezinced lead bullion fed to the process typically
assays 0.001 weight percent zinc, 0.0003 weight percent antimony, and 0.15
weight percent bismuth (2). The quantities of calcium and magnesium added
depend on the amount of bismuth to be removed. Twice as much calcium is
added as magnesium. Cupel slags are added when bismuth content is high
enough (20 to 25 weight percent) to warrant recovery. Antimony or organic
compounds are added as needed to improve bismuth separation. The literature
does not specify the organic compounds or the amounts.
3. Operating Conditions - The molten lead bath is maintained at 500° to
550°C (1,3) for calcium-magnesium addition and is cooled to 350°C for dross
separation. Pressure is atmospheric.
4. Utilities - A small amount of gas or oil is required to maintain the
lead bath temperature. Pumps and agitators are electrically powered.
5. Waste Streams - None
6. Control Technology - None
7. EPA Source Classification Code - None
8. References -
1. Development Document for Interim Final Effluent Limitations Guide-
lines and Proposed New Source Performance Standards for the Lead
Segment of the Nonferrous Metals Manufacturing Point Source Cate-
gory. Environmental Protection Agency. EPA-440/l-75/032-a.
February 1975.
72
-------
2. Encyclopedia of Chemical Technology. Interscience Publishers, a
division of John Wiley and Sons, Inc. New York. 1967.
3. Hallowell, J.B., et al. Water Pollution Control in the Primary
Nonferrous Metals Industry. Volume I, Copper, Zinc, and Lead
Industries. Environmental Protection Agency. Washington, D.C.
EPA-R2-73-274a. September 1973.
73
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PRIMARY LEAD PRODUCTION PROCESS NO. 21
Bismuth Refining
1. Function - The dross generated by debismuthizing is processed for bismuth
recovery. The material is placed in a furnace, where it is melted. Chlorine
gas is injected, and the calcium, magnesium, zinc, and lead combine with the
chlorine to form chlorides more readily than does bismuth. The chlorides form
a solid slag that is skimmed from the surface of the molten bismuth. Air is
then blown through the bismuth, and a caustic soda flux is added to oxidize
any residual impurities. After slag removal, the metal, which is now 99.99
percent bismuth, is cast into marketable shapes and sold (1).
Alternate methods of bismuth refining are also in use involving wet
chemical processing; these methods are not addressed in this report.
2. Input Materials - The slag from the debismuthizing process is chiefly
composed of ternary compounds of calcium, magnesium, and bismuth. Chlorine
constitutes about 25 weight percent of the slag charged to the furnace.
Caustic soda flux is used in varying amounts for oxidation of impurities.
Charcoal is used as a cover during casting to maintain the bismuth in a
reduced state.
3. Operating Conditions - Bath temperature during chlorination is 500°C.
Subsequent temperatures for oxidation and casting are lower. Pressure is
atmospheric (1).
4. Utilities - Gas or oil is used for heating and maintaining temperature.
Electricity is used to run pumps and agitators. Compressed air is furnished
to oxidize impurities. The literature does not state the quantities required.
5. Waste Streams - Exhaust gases to the atmosphere contain chlorine and
fume. No emission quantities were found.
There are no liquid wastes from the process.
Slag composed of chlorides of calcium, magnesium, zinc, and lead is 40
weight percent of the dross fed to the process. Final oxidation generates a
soda slag in unspecified amounts.
6. Control Technology - Control of atmospheric emissions is not practiced.
Slags are discarded with those generated in smelting. Further infor-
mation is given in Process No's. 5 and 6. The chloride salts contained in
the slag are very water-soluble and easily leached into adjacent water
supplies. Existing practice does not represent good control technology.
7- EPA Source Classification Code - None
8. References -
1. Encyclopedia of Chemical Technology. Interscience Publishers, a
division of John Wiley and Sons, Inc. New York. 1967.
74
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PRIMARY LEAD PRODUCTION PROCESS NO. 22
Final Refining and Casting
1. Function - Refined lead bullion from dezincing or debismuthizing is
given a final purification and cast into ingots. The refined lead is fluxed
with oxidizing agents to remove remaining impurities such as lead oxide and
magnesium or calcium residues. After slag removal by skimming, the lead,
assayed as 99.999 percent purity, is reheated and sent to the casting opera-
tion, where it is formed into ingots or pigs. Most casting is performed by
fully automated machines. Slag is recycled to the blast furnace (1).
2- Input Materials - Refined bullion containing a small amount of impuri-
ties is fed to the process. Caustic soda and sodium nitrate are used as
oxidizing flux in amounts varying with the impurity of the lead (1,2).
Water is used to cool the cast lead ingots by direct contact, at rates
ranging from 300 to 1,500 liters per minute (3).
3. Operating Conditions - Temperatures for final purification range from
370° to 500UC; casting is at 540°C (1,4). Pressure is atmospheric.
4- Utilities - Gas or oil is required for heating. Pumps and agitators
are electrically operated. The literature gives no data on quantities.
5. ^ Waste Streams - Small amounts of atmospheric emissions are released
during refining and casting operations. Emission factors and constituents
have not been reported.
Direct-contact cooling water becomes contaminated with particulate
matter, including lead and lead oxides.
6. Control Technology - There are no controls on the atmospheric emis-
sions.
Several methods are used to handle the contaminated cooling water. The
water is either recycled for use in slag granulation or is sent to a tail-
ings pond for settling of suspended solids. A variation of the latter
method, liming the effluent for precipitation of solids, is also practiced
7. EPA Source Classification Code - None
8. References -
1. Encyclopedia of Chemical Technology. Interscience Publishers, a
division of John Wiley and Sons, Inc. New York. 1967.
2. Development Document for Interim Final Effluent Limitations Guide-
lines and Proposed New Source Performance Standards for the Lead
Segment of the Nonferrous Metals Manufacturing Point Source Cate-
gory. Environmental Protection Agency. EPA-440/l-75/032-a.
February 1975.
75
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO. 2.
EPA-600/2-80-168
4. TITLE AND SUBTITLE
Industrial Process Profiles for Environmental Use:
Chapter 27 Primary Lead Industry
7. AUTHOR(S)
Same as Below
9. PERFORMING ORGANIZATION NAME AND ADDRESS
5EDCo Environmental, Inc.
L1499 Chester Road
Cincinnati, Ohio 45246
12. SPONSORING AGENCY NAME AND ADDRESS
Industrial Environmental Research Laboratory
)ffice of Research and Development
I. S. Environmental Protection Agency
Cincinnati, Ohio 45268
3. RECIPIENT'S ACCESSION NO.
5. REPORT DATE
July 1980 issuing date
6. PERFORMING ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO.
10. PROGRAM ELEMENT NO.
1AB604
11. CONTRACT/GRANT NO.
68-03-2577
13. TYPE OF REPORT AND PERIOD COVERED
One of Series
14. SPONSORING AGENCY CODE
EPA/600/12
15. SUPPLEMENTARY NOTES — —
'reject Officer: John 0. Burckle
The catalog of Industrial Process Profiles for Environmental Use was developed
is an aid in defining the environmental impacts of industrial activity in the United
States. Entries for each industry are in consistent format and form separate chap-
ters of the study.
The primary lead industry as defined for this study consists of mining bene-
iciation, smelting, and refining. A profile of the industry is given including
lant locations, capacities, and various statistics regarding production and con-
traption of lead, co-products,- and by-products. The report summarizes the various
ommercial routes practiced domestically for lead production in a series of process
low diagrams and detailed process descriptions. Each process description includes
available data regarding input materials, operating conditions, energy and utility
requirements, waste streams produced (air, water, and solid waste), and control
technology practices and problems.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
Hxhaust Emissions
Smelting
Trace Elements
Pollution
XIDENTIFIERS/OPEN ENDED TERMS
Lead Production
c. COS AT I Field/Group
13B
19. SECURITY CLASS (This Report)
Unclassified
Release to Public
20. SECURITY CLASS (Thispage)
Unclassified
21. NO. OF PAGES
82
22. PRICE
EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION is OBSOLETE
76
PRINTING OFF 1CE:1°8n.-P57- 1fi5/nna4
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