Final Report
EVALUATION OF S02 EMISSION CONTROL TECHNOLOGY
APPLICABLE TO THE EAST HELENA LEAD SMELTER
EPA Contract No. 68-02-1354 — Task 4
January 1975
Pacific Environmental Services, iimc.
1930 14th Street Santa Monica, California 90404

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0(1^
FINAL REPORT
EVALUATION OF SO EMISSION CONTROL TECHNOLOGY
"^PL^^EfTo THE EAST HELENA LEAD SMELTER
By
I.J. Weisenberg
Environmental Engineering Dept.
A. Stein, Director
EPA CONTRACT NO. 68-02-1354 - TASK 4
Project Officer: Norman Huey, Chief
Control Technology Section
Air & Water Programs Division
Environmental Protection Agency
Denver, Colorado
U.S. F.PA Region 8 Library
SOC-L
993 1 Slh SI., Suite 500
Dcrwcr. CO 80202-2466
PACIFIC ENVIRONMENTAL SERVICES, INC.
1930 - 14th Street
Santa Monica, California 90404

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TABLE OF CONTENTS
EVALUATION OF SO EMISSION CONTROL TECHNOLOGY
APPLICABLE TO THE EAST HELENA LEAD SMELTER
Page
I.	INTRODUCTION AND SUMMARY . . . .		1-1
II.	LEAD SMELTER OPERATIONS GENERATING SO
AND PARTICULATE	7		II-l
A.	GENERAL		II-l
B.	SINTERING		II-2
C.	LEAD REDUCTION		II-6
III.	SULFURIC ACID PLANT TECHNOLOGY 		III-l
A.	SYSTEM		III-l
B.	PURIFICATION OF S02 GAS		III-l
C.	CONVERSION OF S02 TO S03 AND ABSORPTION		III-5
IV.	LEAD SMELTERS WITH SULFURIC ACID PLANT S02 CONTROL ....	IV-1
A.	INTRODUCTION AND SUMMARY		IV-1
B.	ST. JOSEPH LEAD, HERCULANANEUM, MISSOURI		IV-2
C.	AMAX LEAD, BOSS, MISSOURI		IV-8
D.	BUNKER HILL, KELLOGG, IDAHO		IV-10
E.	BRUNSWICK SMELTING AND REFINING, BELLADUNE, NEW
BRUNSWICK, CANADA			IV-13
V.	SULFURIC ACID PLANT OPERATION WITH LEAD SINTER MACHINE -
PROBLEMS AND SOLUTIONS 		V-l
VI.	S02 CONTROL FOR ASARCO LEAD SMELTER, EAST HELENA, MONTANA . .	VI-1
A.	S02 CONTROL SYSTEMS	VI-1
B.	S02 CONTROL FOR EAST HELENA SMELTER	VI-1
C.	DEGREE OF S02 CONTROL EXPECTED WITH ACID PLANT ....	VI-3
D.	EAST HELENA SMELTER PLANT FLOW SHEET	VI-4
E.	SINTER MACHINE SYSTEM	VI-6
F.	SINTER MACHINE SULFUR ELIMINATION	VI-8
G.	MODIFICATION OF SINTER MACHINE SYSTEM FOR INCREASED
S02 CONCENTRATION	VI-8

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TABLE OF CONTENTS (CONT'D)	Page
VI.	SO CONTROL FOR ASARCO LEAD SHELTER, EAST HELENA,
MONTANA (CONT'D)
H.	SULFURIC ACID MANUFACTURE CAPABILITY AT EAST
HELENA	VI~13
I.	REQUIRED MINIMUM EXISTING PLANT MODIFICATIONS 		VI-13
J. COMPLIANCE SCHEDULE 		VI-15
K. COST ESTIMATE	VI-15
L. SPACE REQUIREMENTS 		VI-18
VII.	REFERENCES	VII-1
VIII.	APPENDIX 	VIII-1
LIST OF FIGURES AND TABLES
FIGURE ¦ 1. S02 CONCENTRATION VS. SINTER MACHINE LENGTH 	H-5
2.	SINGLE STREAM OPERATION 		11-7
3.	DUAL STREAM OPERATION 	H-8
4.	DUAL STREAM OPERATION WITH RECIRCULATION	11-9
5.	GAS COOLING REQUIRED FOR PRODUCTION OF 93% or 98% H SO, . . . .	111-2
2 4
6.	EFFECT OF TEMPERATURE ON THE EQUILIBRIUM CONVERSION 	III-6
7.	SINGLE AND DOUBLE CONTACT SULFURIC ACID PLANT SCHEMATIC ....	111-8
8.	ST. JOE MINERALS PLANT SCHEMATIC	IV~4
9.	ST. JOE SINTER MACHINE SO , TEMPERATURE AND PRESSURE
DISTRIBUTION			IV"6
10.	AMAX SMELTER SCHEMATIC	IV~9
11.	BUNKER HILL SINTER MACHINE SYSTEM 		IV-11
12.	EAST HELENA PLANT FLOW SHEET	VI'5
13.	EAST HELENA SINTER MACHINE SYSTEM SCHEMATIC	VI~7
14.	SULFUR ELIMINATION CURVE (CHART 3)	VI~9
15.	SULFUR ELIMINATION CURVE (CHART 4) 		VI-10
16.	PROCUREMENT SCHEDULE FOR ACID PLANT 	VI-16

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TABLE OF CONTENTS (CONT'D)
LIST OF FIGURES AND TABLES	page
TABLE 1 TYPICAL SULFUR EMISSIONS FOR A PRIMARY	H-3
LEAD SMELTER		' . .
2	AVERAGE SMELTER CONCENTRATE INPUT		IV-3
3	ST. JOSEPH MATERIAL HANDLING CAPABILITY 		IV-5
A S02 CONCENTRATION SYSTEMS 		VI"2
5	SULFUR ELIMINATION CURVE INTEGRATION 		VI-11
6	SULFURIC ACID POTENTIAL AT EAST HELENA 	
MONTANA SMELTER	VI-14
7	COMPLIANCE SCHEDULE ... 		VI-17

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I. INTRODUCTION AND SUMMARY
There are eight operating lead smelters on the North American Conti-
nent, six in the United States and two in Canada. Of these eight operating
smelters, five have installed single contact sulfuric acid plants and are
using them to partially control SO^ emissions resulting from the smelter
operations and to produce a useful byproduct. Those plants with controls
are able to limit SO2 emissions with concentrations in the range of 2000
ppm to 2600 ppm from the acid plant when it is in stable operation. Up to
90% of the input sulfur to the smelter is being fixed primarily as sulfuric
acid as well as in the solid material produced such as slag, bullion or
stored sinter.
It is the intent of this study to determine the general practicability
of applying a sulfuric acid plant to a lead smelter for SO2 control and
specifically as "reasonable available technology" for the East Helena,
Montana lead smelter. This study includes analysis of the problems that
have been'encountered in the past, current problems, design and operating
solutions to these problems, predicted SO^ control capability, cost and
practicable compliance schedules.
A brief review of the lead smelting operations normally used and the
theory and design requirements for a sulfuric acid plant are presented.
Visits and discussions by telephone were held with plant personnel from
four smelters using sulfuric acid plants. Information was collected on
operating problems and actual operating results and is summarized. An
analysis of the East Helena, Montana smelter is included with design, cost
and schedule considerations.
The greatest source of SO^ emissions from this process is the lead
sinter machine which, depending on the amount of sulfur in the concentrates,
generates as much as 85% to 94% of the SO^ emitted from the entire system.
The sinter machine is a moving metal grate upon which the lead sulfide
materials automatically react with air forming lead oxide. These machines
vary from 100 to 150 feet in length and 8 to 10 feet in width. The largest
quantity of SO^ is produced in the first 40 feet of length of the machine. All
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of the sintering machines except one are the updraft type where the main air
is forced upwards through the moving grate. Because of its mechanical com-
plexity and hot, corrosive operating environment, normal down times are as
high as 15% to 25%.
Since most of the sulfur in the concentrates processed is burned off
at the upstream end of the machine, it is possible to separate this resulting
rich stream from the lean downstream gas. In many cases this is done with
the rich stream (4% to 8% SC^) collected and ducted directly to the acid
plant. The lean stream may either be released to atmosphere or recirculated
through the sinter machine. Recirculation is possible because the oxidation
reaction is completed the first 40-60 feet of grating with the remainder of
the bed used for cooling. Thus, the air that is forced through the downstream bed
still contains a high percentage of oxygen and can be reused either to supply
oxygen for further oxidation or to provide cooling in the hot zone at the
upstream end. This recirculation has the advantage of minimizing the outflow
of lean gases. Current experience varies from no recirculation, with
separate offgas streams, to complete recirculation with only a single stream
leaving the sinter machine hood and venting to the acid plant.
There are two basic types of sulfuric acid plant designs available -
the single contact plant or double contact plant. The double contact system
takes advantage of the SO2 - SO^ kinetics by absorbing the initially genera-
ted SO^ and partially converted SO^ stream, resulting in a higher SO^ to SO^
ratio providing more efficient conversion. Acid plant manufacturers will
guarantee that emissions of SO2 from new double contact plants will not ex-
ceed 500 ppm or 2000 ppm from new single contact plants. However, a major
problem in the efficient operation of acid plants fed by the offgas from lead
sintering machines is the sensitivity to the concentration of SO2 in the in-
put gas. The single contact plant can operate with SO2 concentration of 3.5-4%
whereas, the dual contact plant requires 5-6%. Due primarily to this
characteristic all acid plants serving lead smelters are the single contact
systems, including those visited during this project.
While many design and operational problems have been encountered,
there is no single situation that cannot be remedied by engineering design or
improved operational practices. Problems such as mud like sludge material
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fouling heat exchangers and other system elements, excess moisture (water
balance), cooling capacity available for the acid plant, intermittent
operation of the sinter machine requiring frequent start-up of the acid
plant, particulate and moisture removal from the gases leaving the sinter
machine and extensive corrosion requiring frequent maintenance have all
been encountered and solved or "worked around." The best experience indi-
cates that the acid plant has caused less than 10% of the total smelter
down time (see section IV).
The application of a single contact sulfuric acid plant to the East
Helena lead smelter appears practicable to allow fixing of 70% to 80% of the
sulfur entering the plant by minimum changes to the existing equipment and
modifications to operating conditions. These reductions in emissions are
possible in part, due to the relatively large quantity of sulfur eliminated
by the sinter machine. Sulfur capture of at least 90% is technically
feasible and has been accomplished by other smelters with recirculation and
production of a single offgas stream from the sinter machine. However,
additional development work with the specific East Helena feed material and
machine would be required.
Because of considerable delays in the procurement of steel plate, the
total time to install and establish an operational acid plant and its
associated gas cleaning system is expected to take AO months. This could
be reduced by as much as 12 months if steel plate became readily available.
Cost for the acid plant and gas cleaning system are expected to be on the
order of 11-12 million dollars.
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II. LEAD -SMELTER OPERATIONS GENERATING SO,, AND PARTICULATE
A. General
Lead is usually mined as a sulfide ore containing small amounts of
copper, iron, zinc and other trace elements. It is normally concentrated
at the mine from an ore of 3 to 8 percent lead to a concentrate of 55 to 70
fiercent lead. Most U.S. smelters receive between 14 and 18 percent by weight
of the concentrate as sulfur. The ASARCO feed contains over 23% sulfur.
Normal practice for the production of lead from lead sulfide concen-
trates includes the following operations:
•	Sintering in which the concentrate lead and sulfur are oxidized
to produce lead oxide and sulfur dioxide. Simultaneously, the
charge material made up of concentrates, recycle sinter, sand
and other inert materials is agglomerated to form a dense, per-
meable material called sinter. This step is carried out with a
sinter machine.
•	Reduction of the lead oxide contained in the sinter to produce
molten lead bullion. This, step is carried out: in a blast fur-
nace.
•	Refining of the lead bullion to eliminate impurities. This
step is carried out in drossing kettles and reverberatory fur-
naces.
The sintering operation normally eliminates as sulfur dioxide up to
85'% of the concentrate sulfur. ASARCO experience indicates that they
eliminate up to 93.5% of the input sulfur based on yearly data (Reference 17).
Sintering machines are operated with either a single offgas stream, two off-
gas streams or a single offgas stream with recirculation of the weak stream.
In the case of the single stream operation, the effluent stream has an SO2
concentration of up to 2-3 percent. In dual stream operation, the strong
offgas stream has an SO^ concentration of between 4 and 7 percent and the weak
stream has an SO2 concentration of approximately 0.5 percent. Single stream
operation is accomplished by ducting all process gases under the machine hood,
via a single stream, to the emission point. In dual stream operation, the
stronger SO^ laden gases at the feed end of the machine are ducted separately
from the weaker gases at the discharge end of the machine. In dual stream
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operation with recirculation, the single offgas stream can vary from 2.5 to
6.5% (Reference 2) depending in part upon the percent recirculated.
Sinter is charged to the blast furnace periodically and typically
contains up to 15 percent of the concentrate sulfur in either a sulfide or
sulfate form. Emissions from the normal blast furnace due to oxidation of
the remaining sulfide or thermal decomposition of the sulfates typically
have concentrations of less than 1 percent SO^ and represent approximately
7 percent of the concentrate sulfur. ASARCO eliminates approximately 1%
of the smelter input sulfur at the blast furnace. The remaining sulfur is
eliminated in the stack particulates, slag, matte, speiss and baghouse
dust.
The refining process consists mainly of removing the impurities of
copper, gold, silver and antimony from the furnace lead bullion. The
furnace bullion is transferred to a series of refining kettles where
crosses are selectively removed from the bullion. The drosses, containing
various impurities, are treated in a reverberatory furnace for further
collection of lead and concentration of other metal values. The SC^
emissions from refining systems are essentially zero.
A breakdown of the sulfur emissions from a typical primary lead smelter
operation compared to ASARCO is summarized in Table 1.
B. Sintering
The basic purpose of sintering is to convert the lead sulfide concen-
trate (PbS) into an oxide or sulfate form, while simultaneously producing a
hard porous clinker material suitable for the rigid requirements of the
blast furnace, (Reference 4.)
The sintering machine is essentially a continuous steel pallet con-
vuyor belt moved by suitable gears and sprockets. Each pallet consists of
perforated or slotted grates. Beneath the moving pallets are windboxes
which are connected to suitable fans that provide large quantities of air
producing a draft on the moving sinter charge. Current practice in the
lc.ad smelter industry is to blow the air through the pallets and charge
(known as updraft). These updraft machines are of the Dwight and Lloyd
design which may be manufactured by Lurgi or McDowell-Wellman.
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Table 1. Typical Sulfur Emissions for a Primary Lead Smelter Compared To
ASARCO.
TYPICAL
ASARCO
Sintering machine
Percentage of concentrate sulfur discharged in offgases 85%
1%
0.5%
4-7%
SO2 concentration in single stream operation
SO2 concentration in dual stream operation
weak stream
strong stream
SO2 concentration in dual stream operation with
recirculation
SO2 concentration with partial recirculation
2.5-6.5%
93%
2.8%
1.5% (after
dilution
]$. Blast furnace
Percentage of concentrate sulfur remaining in feed	15%
to blast furnace
Percentage of input sulfur discharged in gas stream	7%
Percentage of input sulfur discharged in waste	8%
SO2 concentration in gas stream	0.2%
7%
1%
5%
C. Refining operations
Percentage of concentrate sulfur discharged
References * 3 and 4.
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The sinter machine has an initial ignition section which generally has
a bed, approximately 1-1 1/2 inches thick, that is ignited by gas flame.
The ignition layer burns for a distance of approximately 10' until it
reaches maximum temperature at which point it enters the main layer. The
main layer, approximately 10-14 inches thick, is laid down upon the top of
the ignition layer and is ignited as the continuous moving bed travels.
The sintering reaction is autogenous and creates temperatures of
approximately 1000°C. The temperature is basically controlled by the
sulfur content of the sinter charge mix. Years of sintering experimenta-
tion and practice have shown that best system operation and product quality
are achieved when the sulfide sulfur content of the sinter charge is
between 5 and 7 percent by weight. In order to maintain the desired
level of sulfur content, sulfide-free fluxes such as silica and limestone
plus large amounts of recycled sinter and smelter residues (usually 50%)
are added to the mix. The quality of the product sinter is usually deter-
mined by its hardness (Ritter Index) and sulfur content. There is a direct
correlation between the sulfur content of the sinter and the Ritter Index,
thus, high Ritter Indices usually indicate sufficiently low sulfur content
in the sinter. Hard quality sinter will resist crushing during discharge
from the sinter machine. Undersized sinter usually indicate insufficient
desulfurizatin and is therefore, recycled for further processing. (Reference 4)
The latter half of the machine acts as a sinter cooling zone. This
cooling zone serves three main purposes. First, it provides the metallur-
gical conditioning required for a suitable product. Second, it allows the
subsequent handling of a relatively cool material; thus, conveyor belts are
adequate to handle the discharged sinter. Third, potentially hazardous
dust formations are minimized by cooling the product.
The concentration of sulfur dioxide versus length over the sinter
machine bed is shown in the curve Figure 1. As can be seen the first
third of the sinter machine length produces the maximum concentration of
SO^. If all the gases leaving the sinter machine are mixed together a
concentration of approximately 1-2% SO2 is encountered. However, if only
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the high concentration portion of the offgases are collected separately,
then it is possible to raise the SC^ concentration to the range of 4%
to as high as 8%.
With the concentration variation of SC^ versus length in the sinter
nachine offgases, three different modes of operation of the system are
possible. The gases can be mixed into one final offgas stream, the
streams can be separated with the strong stream and weak streams going to
different locations for processing or to atmosphere and finally the strong
stream can be taken from the machine and the weak stream can be recirculated
within the sinter machine system. Figures 2, 3 and 4 are schematics showing
the three techniques.
Current practice with the three lead smelters in the U.S. using sulfuric
acid plants for partial SO^ collection incorporates a modified form of the
last two techniques. The strong and weak SC^ streams are separated, with
the strong stream going to an acid plant and the weak stream going to the
snack. Along with this stream separation the air flow systems are set up
so that partial recirculation can be accomplished. The extent of the re-
circulation is adjustable and is dependent upon operating characteristics
required to produce the required sinter products. In Canada 100% weak
stream (30% - 40% total gas volume) recirculation is accomplished. Maximum
recirculation currently encountered in the United States is 20% to 25% of
the gas volume flowing to the sinter machine in SCFM.
C. Lead Reduction
Lead reduction in the domestic industry is carried out in a blast fur-
nace. The feed material, sinter, will typically contain approximately 15% (7%
for ASARC0) of the concentrate sulfur. Approximately one half of the feed
sulfur to the blast furnace or 7 percent of the concentrate sulfur will be
emitted to the atmosphere as a weak SO^ stream.
The furnace is basically a water jacketed shaft furnace supported by a
refractory base. Tuyeres through which combustion air is admitted under
pressure are located near the bottom and evenly spaced on either side of the
furnace.
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Figure Z Single stream operation.
R£F£ft£AiC6 V
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^6.5%
•vO.5%
SINTER FEED-
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Figure 3 Dual stream operation.

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The furnace is charged with a mixture of sinter and metallurgical coke.
Other materials added include limestone, silica, litharge, and slag-forming
materials. Coke makes up from 8-14% of the charge, and sinter makes up from
80 to 90 percent. The remaining constituents are recycled and clean-up
materials. The blast furnace takes the charge materials and reduces the
sinter to lead bullion with most of the impurities being eliminated in the
slag.
The principal reactions which take place in the blast furnace are:
PbO + CO + heat —Pb + C02
C + 02 — C02 + heat
C + C02 + heat — 2C0
The blast furnace products separate into as many as four layers, depen-
dent upon the charge constituents and the processing circumstances. These
include, from lightest to heaviest, matte (made up essentially of copper
sulfide and other metal sulfides), speiss (basically arsenic and antimony),
slag (largely silicates) and lead bullion. Normally, the collected slags at
domestic smelters are made up of the first three layers and are collected
continually from the blast furnace. The slag is either processed at the smel-
ter for its metal content or shipped to slag treatment facilities.
Since the sintering process is not 100 percent efficient in the conver-
sion of lead sulfide (PbS) to lead oxide (PbO), some PbSO^ and small amounts
of lead sulfide (PbS) remain in the product sinter. Therefore, within the
blast furnace shaft there are additional lead-forming reactions involving
Lead sulfides and sulfates. It is these reactions which generate S02 during
blast furnace operations. The reactions are principally:
2Pb0 + PbS — 3Pb + S02
PbSO. + PbS — 2 Pb +. 2S0o
4	2
As a result, the effluent from a blast furnace normally contains S02 in
concentrations ranging from a few hundred ppm to as much as 2500 ppm.
However, not all sulfur in the sinter feed to the blast furnace is
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eliminated as SC^- A major portion is captured by the slag. This is depen-
dent in part upon copper and other impurities in the sinter. Part of the
isulfur in the sinter becomes fixed with the copper present, and is eliminated
as slag. Thus, sulfur emissions as SC^j from the blast furnace are in part
dependent upon the amount of sulfur that becomes fixed with copper and other
impurities and is captured by the slags.
Typical sulfur balances from domestic installations indicate that from
10 to 20% of the concentrate sulfur is eliminated in the blast furnace for
ASARCO this value is 7%. Fully 50 percent captured by the slags. ASARCO
captures 71% of the furnace sulfur in the slag. The overall sulfur eliminated
from the blast furnace may seem high compared to the relatively low outlet
SO2 concentration experienced, but this is mainly due to the high volume of
dilution air injected into the emission stream from the furnace. The di-
lution air serves two important purposes. First, it provides oxygen to allow
combustion of the carbon monoxide in the discharged gas stream from the fur-
nace shaft. If the carbon monoxide were not reacted to carbon dioxide a
potentially dangerous situation would arise due to the explosive nature of
carbon monoxide. Second, large volumes of air are also required to cool the
e:cit gases from an estimated 750°C to approximately 140°C which then allows
baghouse treatment for particulate removal.
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III. SULFURIC ACID PLANT TECHNOLOGY
A.	System
The process for the manufacture of sulfuric acid from lead smelter
*
offgases consist of three principal steps, namely:
•	Purification of the sulfur dioxide (SO2) gas from the lead
sinter machine.
•	Conversion of the sulfur dioxide (S0_) gas to sulfur
trioxide (SO^) gas.
•	Absorption of the sulfur trioxide (SO.) in sulfuric
acid (H2S04).
B.	Purification of SO^ Gas
The sinter machine gas can normally contain combinations of metallic
fume, dust, sulfur trioxide, hydrocarbons and carbon monoxide. The S0o
i.
gas stream entering the acid plant must be clean and dry to minimize
operational problems.
The gas is usually cooled from approximately 750°F to 250°F by water
sprayed in at locations varying from the sinter machine hood to a downstream
spray chamber. The gases are cooled sufficiently to enter a baghouse or
precipitator for major particulate removal. Then the gases pass to a spray
chamber or cooling tower where water removes many of the remaining impuri-
ties and further cools the gas. Scrubber equipment has also been used for
this purpose.
The gas must be cooled to reduce its moisture content. Final cooled
temperature (saturation) is determined by the SO2 concentration, product
acid strength desired and the elevation of the plant above sea level. This
characteristic can be seen in Figure 5 showing gas cooling required for pro-
duction of 93% or 98% ^SO^ versus mole percent SO^ on a dry basis. An
allowance has been made in these curves to permit the addition of some water
to the strong acid system to provide more flexible control of acid strength.
Shell and tube type gas coolers can be used for final cooling to 100°F or less.
*
See Schematic Figure 7.
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UAS COSIING requires for
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The water discharged from the spray chamber or cooling tower will
contain the impurities removed from the gas and will also be saturated
with SO2 from the gas. To recover sulfur values and reduce effluent
nuisance, this water may be passed through a stripping column where a
stream of air removes most of the SO^ from the water. The SO^ gas so
recovered is fed back to the tower. The water from the stripping column
then may be either neutralized or discharged.
The gas leaving the cooling section is passed through a mist
precipitator in which most of the remaining particles of acid mist,
metallic fume and dust are removed by electrical precipitation.
Sulfuric acid mist generally contains particles less than 5 microns and
is very difficult to remove from the gas stream except with an electro-
static precipitator. If this mist is allowed to enter the contact
section of the acid plant it will cause corrosion problems in carbon
steel ducts, heat exchangers and the main blower.
The usual "mist precipitator is a tube type with vertical tubes 6-10"
in diameter made of lead. High voltage discharge electrodes are suspended
in the center and run the entire length of the tubes. The mist particles
are attracted to the tube walls, flow downward and are collected in the
lower header in the form of 5-10% H^SO^. Two mist precipitators installed
in series can provide 99% removal efficiency. The reason for two preci-
pitators is because the entrained acid in the gas stream tends to produce
arcing and requires a reduced input voltage lowering the efficiency
of the unit. With two units in series the voltage is reduced only to the
first unit so the overall efficiency is affected only slightly. In most
cases, only one precipitator is used to minimize capital expenditures.
The gas passes from the mist precipitator to the drying tower where
it moves up through a bed counter current to the flow of 93% acid. The
acid absorbs whatever moisture is present and the gas is dried to a maxi-
mum water vapor content of 5 mg/SCF. The heat generated by the absorption
of water in the circulating acid is removed in heat exchangers cooled with
water reducing the acid temperature to approximately 105°F.
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For good SO^ to SO^ conversion efficiency the converter entrance
gas should contain at least 1.3 volumes of oxygen for every volume of
sulfur dioxide. This ratio maximizes the gas strength at the converter
and determines the required volume of gas handled per ton of sulfuric
acid produced. (Air is usually added to increase this ratio.)
The main gas blower usually follows the drying tower to provide
sufficient suction to pull the air required through the purification
system and sufficient pressure to blow the gas through the converter
heat exchanger system and the absorption tower. Blower static pressure
capability is typically 150" W.C.
The gas leaves the blower at about 130°F and flows through a
series of heat exchangers in which its temperature is raised to 820°F
which is the required temperature for entering the first catalyst
layer in the converter.
The dry gas leaving the blower passes through the shell side of
three (usually) shell and tube heat exchangers in series in which its
temperature is raised to 820°F. In the cold heat exchanger, the SO^
gas is heated to approximately 480°F as it flows counter-current to
the SO^ gas leaving the converter. In the intermediate exchanger, the
SO2 gas is further heated to about 555°F by cooling the gas leaving the
second bed of the converter. Further heating of the SC^ gas to 820°F
is accomplished in the hot, or converter, heat exchanger by cooling the
partially converted gas leaving the first catalyst bed from about 1075°F
to 820°F. Suitable by-passers are provided around these exchangers to
permit maintaining optimum temperatures to the converter. An S0^ cooler
utilizing forced air may also be provided to further cool the SO^ gases
leaving the cold heat exchanger before they enter the absorption tower.
Operation of the plant can be maintained with any of the three heat
exchangers blanked and taken out of service by the use of the SO^
cooler for heating the SO^ gas and the introduction of quench sulfur
dioxide gas at strategic points for temperature adjustment.
046
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C. Conversion of S02 to SO^ and Absorption.
The conversion of SO^ to SO^ takes place in the converter. The
converter contains several layers of a vanadium pentoxide catalyst, the
purpose of which is to accelerate the reaction between SO^ and oxygen
to form SOy The converter is normally of the three stage four bed
type, designed to provide maximum conversion efficiency.
The heat of reaction generated in the first stage of conversion
where 70-75% of the SC^ reacts with 0^ in the gas stream is removed
from the gas in the external converter heat exchanger. The temperature
rise may be 250-300°F. The rise in temperature reduces the conversion
equilibrium. See Figure 6 . The partially converted gas, cooled to
820°F in the converter heat exchanger, is returned to the second stage.
The heat of reaction in the second mass is also removed in an external
intermediate exchanger. Heat from the third and fourth beds is removed
in the external cold heat exchanger and SO^ gas cooler. As indicated
above, the SO^ gas leaving the converter is cooled in the tube side
of the cold heat exchanger and SO^ cooler by preheating the SC^ gas
leaving the blower and by forced air respectively.
An indirect air cooler reduces the SO^ temperature to 300-350°F
before going to the 98% absorption tower where its SO^ content is
absorbed in the 98% sulfuric acid recirculating over the tower. The
heat rise in the acid resulting from (a) the transfer of 93% acid,
(b) heat of absorption of SO^, and (c) from the sensible heat in the
incoming gas, is removed from the acid as it flows by gravity through
the 98% acid cooling heat exchangers to the pump tank. The exchangers
are designed to reduce the acid temperature to 150°F. A vertical
submerged pump recirculates the 98% acid over the absorption tower and
also delivers the product 98-99% acid to the acid storage coolers or to
the 93% acid system for dilution.
For heating up the converter system, valved ductwork is provided
from the blower discharge to a heat source, either a separate gas fired
heater or from some other source in the plant.
046
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Figure 6 Kffcct of temperature on the equilibrium conversion of sulfur di-
oxide to sulfur trio.xide. (Initial sulfur dioxide concentration 8.0 per cent by vulume.)
REFZRENC£ 1
mmu L 046
III-6

-------
The double contact acid plant is the same as a single contact with
the exception that the partially stripped gases at a higher SO^ to SO^ ratio
;ire again passed through a portion of the converter and a second absorption
Cower. With this approach a 500 ppm acid plant (new) emission can be
guaranteed compared to 2000 ppm for a single Contact. Figure 7 shows a
Siingle and double contact sulfuric acid plant schematic.
A clear discussion on the relative merits between single and double
contact systems for metallurgical plants is presented below from Reference
16.
"High sulfur dioxide concentrations are advantageous because they
produce more acid for a given size plant. However, oxygen concentrations
decrease as sulfur dioxide concentrations increase, and the oxygen concen-
tration has a significant effect on catalyst performance and yield. For
this reason, optimum sulfur dioxide concentration in a conventional metallur-
gical type contact plant is approximately 7.0 to 7.5% by volume. In the
double contact or "interpass absorption" type plants first developed by
Bayer in Germany, the optimum concentration is approximately 9.0% S02*
However, equipment must be added to handle this stronger gas.
As sulfur dioxide concentration decreases, small fractions of the
reaction heat are available to preheat incoming cold gases. At approxi-
mately 3.5 to 4.0% SO2 the single contact acid plant is thermally balanced
and any lower concentrations require the addition of external heat. The
preheater provided for plant start-up can be used for this purpose but its
continuous operation adds extra maintenance and fuel costs to the cost of
acid production. It should also be noted that heat exchanger sizes increase
rapidly as sulfur dioxide concentration decreases. With the double contact
process, thermal balance occurs at approximately 6.0 to 7.0% SO2 with 7.5%
preferred as a practical lower limit."
046
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$/NGL£ AN£> DOUBLE CONTACT SULFUR/C AC//) P/JA/T J C H&/W T/C*
F/
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IV. LEAD SMELTERS WITH SULFURIC ACID PLANT SO., CONTROL
A. Introduction and Summary
There are six lead smelters currently operating in the United
States and two in Canada. Of these eight smelters, five are using
sulfuric acid plants to obtain partial or nearly complete SO2 control
from the major source, the sinter machine. This evidence conclusively
proves that the technique is now "reasonably available technology.11
Many specific problems have been encountered and have been
solved with varying degrees of success at each smelter. Available
knowledge and experience throughout the industry, however, is
sufficient to permit engineering design and operational techniques to
obviate major problems that have arisen in the past.
Three lead smelters using, sulfuric acid plants were visited and
data from a fourth obtained by telephone and from the EPA. Operating
problems were discussed with plant personnel. Similar problems were
encountered by most of the smelters. In no case, was a problem en-
countered that could not be resolved by engineering design or worked
around by suitable operating procedures. Many of the problems that
still exist are the result of lack of recognition during the initial
design phase or poor equipment selection. Additionally, economic
considerations tend to minimize capital expenditures requiring opera-
ting personnel to "make do" with the equipment available as long as
possible with consequent more frequent breakdowns with age or opera-
tion at below design capability.
During normal operation single contact sulfuric acid plants have
been measured at maximum tail gas concentrations of 2,000 PPM. This
value is guaranteed by the plant designers for new plants.
Significant factors relating to each smelter are included in
this section. Complete notes from each of the discussions with
smelter personnel and acid plant vendors are included in the Appendix
046
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to this report.
The average lead, sulfur and zinc contained in the input con-
centrate for each of the smelters is shown in Table 2. The lead to
sulfur ratio varies significantly from 1.0 to 4.2. This factor
will have a significant effect on the operation of the sinter
machine system and should be considered when comparing results.
Plant input sulfur recovery, or fixing, with a single contact
sulfuric acid plant directly receiving sinter machine offgas can
normally be at least 66% as manufactured sulfuric acid and an
additional 4% leaving slag, bullion or stored sinter. Each of these
plants only use the rich SC^ stream from the sinter machine for the
acid plant, with lean stream to atmosphere. Lower percent sulfur
fixed as acid can also occur depending on the plant operating
conditions.
In one case where the smelter is operating with complete re-
circulation of the sinter machine lean gas and only a single stream
is removed, 86% of the plant input sulfur is fixed as manufactured
sulfuric acid. With the additional 4% sulfur fixed in the slag,
bullion or stored sinter, overall plant input sulfur fixing reaches
90%. This again is based on yearly production figures.
B. St. Joseph Lead, Herculaneum, Missouri
The St. Joseph Minerals Corporation Lead Smelter at Hercu-
laneum, Missouri has a conventional updraft sintering machine with
a 300 ton per day acid plant to collect strong stream, only, SO2
rich gases. The usual material mixing systems and blast furnace with
refinery kettle systems are also used. The plant schematic is shown
in Figure 8. All of the gas streams from the plant are combined to
flow through a single baghouse capable of handling 550,000 ACFM.
Concentrate analysis is shown in Table 2. The following Table
3 shows material process capability.
046
IV-2
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TABLE 2
AVERAGE CONCENTRATE INPUT TO SMELTER
Pb	Zn	S	Pb/S
%	%	%	
Brunswick 35	9	30	1.2
Bunker Hill 65	6	18	3.6
St. Joe 72	17	4.2
Amax 70	15	A.7
ASARCO. E. Helena 22	8.5	23	1.0
046
IV-3
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TABLE 3
ST. JOSEPH MATERIAL HANDLING CAPABILITY
Units	Design	Normal	Max
TPD	TPD	TPD
Sinter	3,336	3,504	4,392
Furnace	1,536	1,632	2,040
Dross Reverb	144	168	216
The 10 feet wide by 105 feet long sinter machine offgas flow rate is
approximately 40,000 SCFM. The sinter machine has thirteen windboxes.
Figure 9 is a sketch showing the SO^. temperature and pressure distribu-
tion at various points along the length of the sinter machine. The dis-
tribution curves are typical of this type of machine with maximum sulfur
and temperature at the upstream end. A downdraft system is used for igni-
tion. After adding slag consisting of iron oxide, carbon dioxide and
calcium oxide to the concentrate, the sulfur content is reduced by approx-
imately 17». 52% recycle material is added resulting in a 46% lead and a
127o sulfur feed to the sinter machine. Recycle sinter material consists
of 46%, lead and 1%, sulfur. Final sulfur content consisting of 12%, of the
original concentrate plus 1% from the recycle is 6.5%. This percentage
is required to maintain proper bed temperature during burning of the
material.
A large amount of water is sprayed in at the sinter machine hood
very close to the off take to the acid plant. Input water is approximately
120 lbs/min. It is estimated that there is approximately 4%, moisture in
the charge which adds an additional 207 lbs/min. A total of 12% water is
included in the gases from the sinter plant. The injected water is re-
quired to cool the gases to approximately 150°F before entering a baghouse
for particulate collection. Acrylic bags are used. This baghouse is in-
sulated to minimize corrosion.
046
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The single absorption acid plant produces 93% acid. An SC^ gas
stream temperature reduction to 93 - 96°F is required to eliminate
sufficient moisture for this plant to operate satisfactorily. This re-
quires 1500 GPM of cooling water for the heat exchangers.
3.5 - 3.6% SC>2 is required in the gas for autogenous operation.
There is not sufficient heat available in the acid plant to use in any
other part of the plant. It is estimated that approximately 557» of the
input sulfur goes to the sulfuric acid plant. Approximately 53% of the
input sulfur is converted to sulfuric acid.
Problems encountered at this plant appeared to be greater than at
any of the other lead smelters using sulfuric acid SC^ control. The
major problem appears to be excessive moisture (water) present within the
sinter machine offgas and acid systems. This excessive water causes a
water balance problem with difficulty in maintaining acid product concen-
tration as well as introducing corrosion as a result of condensation in
various parts in the system.
The flotation reagent problem (see Section V), also seems to be
present to a greater extent in this plant. They have measured approxima-
tely 1.2 lbs. of flotation reagent oil in one ton of concentrate. The
"mud" deposits form in many places especially in the heat exchanger systems
requiring frequent (almost daily) cleanout of these heat exchangers. Since
the heat exchangers are not designed for easy disassembly, excessive down-
time is encountered.
Excessive corrosion has resulted in heat exchanger being completely
retubed after five years of operation. Condensation within the baghouse
results in excessive corrosion even though insulated. Corrosion is en-
countered in the screw conveyor and the shaker mechanism. In addition,
only one year bag life has been obtainable. Condensation in the baghouse
at times has included some free sulfur particularly with a deficiency of
oxygen at the sinter bed.
The start of the sinter machine takes approximately one half hour
046
IV-7
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before the off gases are sufficiently atabilized to allow passing them to
the acid plant.
The water supply to the heat exchangers contains some impurities
which further cause plugging on the cooling side of these units.
C. Amax Lead, Boss, Missouri
The Amax Lead Smelter at Boss, Missouri is a conventional lead smelter
using a Lurgi sinter machine. The sinter machine uses 40,000 SCFM gases
(air) of which 22,000 SCFM is passed through the acid plant. The gas
stream to the acid plant contains an average of 5.5% SO2 varying from
4.9% to 7%. Input concentrate contains 70% lead and 15.0% to 15.5% sulfur.
Half of the sinter machine feed is recycle sinter. Total sinter machine
feed is approximately 670,000 TPY.
Some recirculation of the gas from the downstream end of the sinter
machine is accomplished. The gases from the upstream end of the machine
are at 600°F and go to the spray chamber. Gases from the downstream end
of the machine leave the hood at 350°F. The gases going to the acid
plant are reduced in temperature at the spray chamber from 600°F to 250°F.
Approximately 25 GPM (200 lbs/min) of water is used in the spray chamber.
The original acid plant installed in 1968 was designed for 200 TPD
and they are presently running at 240 to 250 TPD. Original cost was
$2,500,000. The plant has a 4 pass converter.
After the spray chamber the gases have been passed through a bag-
house. This has resulted in considerable problems in bag maintenance.
They are presently building a precipitator to replace the baghouse. A
Venturi scrubber will be used downstream of the precipitator. A schematic
of the plant is shown in Figure 10.
Operating experience with the sinter machine is the same as in other
plants with frequent shutdowns for maintenance. Two days per week, Tues-
days and Thursdays are used for standard maintenance downtime. It is
estimated that at no other time is the sinter machine down for more than
046
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AM*	7^"/?
W*£ ;o_046
IV-9
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8 hours per day. The sinter machine on time is approximately 757». How-
ever, start and shut down of the acid plant does not appear to be a seri-
ous problem.
One sixth of the acid plant operating cost is expended in the annual
3-4 week shutdown for maintenance. This maintenance includes the following:
•	Screening the catalyst bed
•	Cleaning the cooling coils and heat exchangers
•	Clean out gas ducts of dust
•	Mist precipitator maintenance
•	Packed tower cleanout (every two years)
•	Spray chamber repair and leak elimination
A mist eliminator was required downstream of the mist precipitator. It
completely solved the mist emission problem.
D. Bunker Hill, Kellogg, Idaho
The Bunker Hill Smelter uses a conventional Lurgi updraft sinter machine
8 feet wide and 96 feet long. Capacity of the sinter machine is approxi-
mately 2700 wet tons per day. Operating on time experience is 75%-85%.
The sinter machine was installed in 1970. Part of the off-gases are
passed to a sulfuric acid plant and the remainder to the stack.
Burn through on the sinter machine occurs at approximately 40 feet and
complete sulfur burnout at 60 feet. From 60 feet to 96 feet cooling occurs.
The acid plant is a 300 ton per day single absorption plant. The 700°F
gases pass from the sinter machine hood, where no water is injected, into a
water spray chamber where they are cooled to approximately 230°F. The
gases then enter a baghouse for particulate removal. After the baghouse
they enter a packed tower which is used as a cooling device as well as an
additional particulate collector. From the cooling tower the gas is
passed into a mist precipitator and then into the acid plant drying tower.
The smelter system is shown in Figure 11.
732,000 TPY of concentrate are used in the lead smelter. The concen-
trate contains 65% lead, 6% zinc and 18% sulfur. The concentrate comes
046
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PLANT OPERATION
Input Charge
M
o
«
^ w	w ^
rH co	u a
£ ATMOSPHERE^ u
SOLID PRODUCTS
BUNKER HILL
SULFUR BALANCE - LEAD SMELTER
FIGURE 11
046
IV-11
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from various locations. At least 30 different types of concentrate
are encountered during one year. The acid plant handles approximately
32,000 SCFM.
Startup and shutdown of the sinter machine and acid plant has been
handled with reasonable success.
The 75%-85% on time for the sinter machine appears to be normal
experience in the industry. On startup of the sinter machine it takes
from 5-20 minutes to be able to obtain autogenous operation of the acid
plant. During this low startup flow condition chanelling of the gases
through much of the equipment such as the towers and the precipitators
occurs. This chanelling reduces the efficiency of the equipment, to a
point where it may be as low as 82%. It takes from 20-40 hours to get
the third pass out of the converter up to a maximum heat.
They do encounter the black "mud" deposit and believe it is the hydro-
carbon flotation reagent material in the concentrate. This material
builds up in various places in the system and must be cleaned out periodi-
cally. They do get a build up of mud at the bottom of inlet side of the
tubes in the precipitator and it is necessary to keep these clean to
obtain efficient precipitator operation.
They use a preheater for start up of the converter but it has given
them problems because of the moisture in the ambient air introduced and
resultant corrosion in the system.
They have encountered excessive corrosion in the inlet duct of the
blower and in the blower itself. They believe that there is still some
acid mist coming in at this point.
Mist corrosion is also encountered in the outlet duct from the bag-
house to the fan and in the fan housing.
They change bags in the baghouse at least once a year.
They are able to detect when plugging occurs in the heat exchangers
by increase in the drip acid at a drain pipe which is located at the inlet
to the blower. This drain pipe is checked every 24 hours.
046
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E. Brunswick Smelting and Refining, Belladune, New Brunswick, Canada
This lead smelter was built in 1967. It has a 10 ft. wide by 150 ft.
long Lurgi sinter machine operating with complete recirculation. This
results in a single off-gas stream leaving the machine of 50,000 SCFM at
a temperature of 550°F to 575°F with 4% to 6% SO^. Gases go directly to a
single contact acid plant by way of a hot gas precipitator, three
Venturi scrubbers in parallel and twelve mist precipitators in parallel.
No water is injected into the gases until they reach the Venturi
scrubbers. These scrubbers have a very low pressure drop and are used
primarily for cooling and some mist elimination.
The high sulfur content of the concentrate (30%) requires a 5:1 sinter
recycle to machine feed mix. Complete air supply to the sinter machine is
produced by three fans with one additional fan for ignition air. Ignition of
the ignition layer is accomplished by No. 6 fuel oil burners.
No evidence of "mud" deposits is encountered. They do find a sludgy
grayish yellow, non oily material that is readily washed out with water.
Sea water is used for cooling. An acid plant water balance problem is
encountered in the summer only. Additional heat exchange surface is
being added to resolve this problem.
With the recirculation sinter machine system,86% of the smelter input sulfur
is captured as sulfuric acid. Additional sulfur capture in the solid
materials leaving the plant such as slag and lead raises the total to
90%.
They do not have any major problems with frequent starts on the acid
plant. A preheater and insulation are used to maintain temperatures for
start. Constant maintenance is required on the mist precipitators. Each
unit is taken off the line every 7 to 10 days for cleaning. Sinter
machine availability averages 80%. Downtime due to acid plant problems
is less than 10% of the total downtime for the entire smelter. Two para-
llel cooling towers in the plant allow alternation for cleaning purposes.
046
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V. SULFURIC ACID PLANT OPERATION WITH A LEAD SINTER
MACHINE - PROBLEMS AND SOLUTIONS
Many difficulties have been encountered with the operation of
sulfuric acid plants using offgases from a lead sinter machine.
However, currently, production of sinter and acid has been sustained
over long operating periods. This experience has been obtained at
St. Joseph Lead, Herculaneum, Mo., AMAX, Voss County, Mo., and
Bunker Hill, Kellogg, Idaho in the United States and Cominco and
New Brunswick Smelters in Canada.
In general, it can be said that since the first acid plant was
used in conjunction with a lead smelter, considerable experience has
been obtained and all of the problems can be solved by good engineering
design and operational procedures. These problems will be discussed.
Normal operation of a lead sinter machine encounters consider-
able maintenance problems. This results in scheduled and unscheduled
down times for the sinter machine of approximately 15% to 25%. These
problems seem to be inherent in the operation of a moving mechanical
device in conjunction with the high temperature lead sinter material
and the general complexity of the machine. In addition, the control
of the metallurgical properties of the sinter must predominate and is
dependent upon sinter composition, available oxygen at various points
along the bed and sulfur content. The complexity of the air supply
system, with from 4 to 8 fans supplying air each with damper or speed
controls, further complicates the adjustment of the machine. There
does not, at this time, appear to be a solution to reducing the down
time of existing design sinter machines to less than 15%.
Therefore, it becomes necessary to accept the fact that the SO^
stream will be interrupted to the acid plant as long as there is no
auxiliary source. (Cominco uses an intermediate concentration pro-
cess before sending offgas to the acid plant.) The acid plant is
normally a steady state system because of internal process characteristics.
046
V-l
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In starting an acid plant., it is necessary to build up the flow to
converter to allow autogenous operation. It usually takes from
twenty minutes to half an hour to start up an acid plant once the
sinter machine has established equilibrium operation and sufficient
SC>2 stream concentration. Frequent starts and shutdowns of the
acid plant can result in cooling down all the acid system and thereby
causing corrosion due to passage through the dew point and slow
start-up of the converter. The addition of insulation and preheaters
supplying auxiliary heat can minimize or eliminate both the start-
up time and corrosion in the associated acid plant. Start-up and
shutdown with present plant experience does not appear to be a major
problem and can be controlled. This is being done at Amax, Bunker
Hill and Brunswick with direct connected acid plants.
One of the most difficult problems presently encountered
appears to be that of formation of a "mud" that travels through the
entire system all the way through to the final product acid. It
is believed that the black material comes from a flotation reagent
oil that remains in the concentrate as delivered to the plant. It
should be noted that this theory is somewhat speculative, but is
generally agreed to by both the acid plant vendors and the smelter
operators. In some cases it has been found that 1.2 lbs of oil
per ton of concentrate has been present.
The main output of this oil or hydrocarbon in the offgases
comes from the down draft ignition area. Here the temperature is
low and the hydrocarbons do not get a chance to burn completely to
CO^. In some cases, a large quantity of water is sprayed in almost
immediately above the hot zone of the sinter machine just downstream
of the ignition zone, further reducing the chance of reacting any
unburned hydrocarbons that may be present. The unburned or partially
burned hydrocarbon flows through the gass collection system into the
catalyst converter. Here the temperature is about 820°F and may go
up to 1000°F. This is within the ignition limit of some hydrocarbons.
046
V-2
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Ignition in the converter occurs resulting in the formation of
CO2 and water. This produces water in the area where it is not
desired since the SO^ conversion should be done with dry gas for
maximum efficiency. In addition, the "mud" can coat the catalyst
and other portions of the system before the converter, particularly
heat exchanger surfaces.
It would appear highly desirable to first inject cooling water
as far downstream from the sinter machine hood as possible to maxi-
mize the temperature of the offgases in and adjacent to the ignition
area. This will allow time and temperature for the reaction of the
hydrocarbon to CO^. Secondly, some means should be provided to
increase the temperature of the ignition offgases, perhaps with an
auxiliary burner, to promote oxidation of hydrocarbon. In one case,
where no mud like deposits are encountered the ignition layer is
ignited by six steam ejected fuel oil burners. A third approach
would be to inject oxygen at this point to further promote the re-
action of the hydrocarbon by raising the temperature of the gas
and providing an excess oxygen environment. Existing plants do seem
to be able to operate with this problem, even though it does require
some maintenance effort. Furthermore, the experience at one smelter
implies that almost complete elimination of the black material is
possible with high temperature ignition zone and no water injection
near the sinter machine.
Acid manufactured from lead sinter machine gases tends to be
black. It is believed that this black or, in some cases, straw
color results from colloidal carbon that comes through the system
also due to the flotation reagent. This material has been noted for
many years and is more in the form of a dye, which is extremely
difficult, if not impossible to move. This then somewhat limits
the market for the acid produced since some users such as food
manufacturers require clean "white" acid. However, the markets for
fertilizer and leaching acids which can accept "black" acid are the
046
V-3
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major expanding markets at the present time.
The "water balance" problem in the acid plant has been en-
countered by some operators particularly in the summer time. This
means that the water used for spray cooling plus whatever water is
generated from the reaction of the flotation reagent, results in
more water in the acid plant system than is needed to make either
93 or 98% acid. This problem can be easily cured by reducing the
temperature of the SC^ gas stream to a point where sufficient water
has been eliminated. This has been shown in the curves of Figure
5 which are based on saturation conditions. If this cannot be
done with conventional heat exchangers, refrigeration to reduce the
temperature of the gas to as low as 40°F can be provided. This
approach has been used in Japan and is discussed in Reference 6.
SO2 concentrations as low as 1.5% sent directly to an acid plant
can be tolerated with reduced feed temperatures.
It is extremely important to clean the particulate and acid
mist from the SO^ gases as soon after they leave the sinter machine
as possible. High temperature (600 F-700 F) precipitators immediately
downstream of the sinter machine appear to make the best match for
reducing most of the particulate. Baghouses immediately downstream
of the sinter machine introduce the problems of gas cooling, corro-
sion and bag blinding.
Mist precipitators and mist eliminators have been used to re-
duce the sulfuric acid mist which is caused by mixing of all small
percentage of SO^ formed with water vapor. As long as no acid mist
is present, no corrosion will occur and mild steel material can be
used for construction of the acid plant. In one case, a Venturi
scrubber has been placed downstream of a precipitator to improve
the mist collection.
Conventional mist precipitators and baghouses have been used
and work satisfactorily. Considerable maintenance is required both
for the baghouse and the precipitator. Problems of the baghouse
046
V-4
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include plugging and tears of the bags and usual replacement of
the bags within one year, which is approximately one half of the
"normal" bag life. Iron sulfate and sulfuric acid tend to cement
dust with resultant blinding. The mist precipitator tends to get a
buildup of material at the bottom of the tubes and these must be
cleaned frequently (weekly) to maintain precipitator efficiency.
High capacity, multiple mist precipitators are beneficial to allow
alternate on time-and maintenance.
Additional steps that can be taken to improve acid plant
operations basically involve enhancement of the sulfur dioxide con-
version to sulfur trioxide as follows (Reference 7):
•	Reduce the initial sulfur dioxide concentrations entering
the converter
•	Reduce the ratio of SC^ to 0
•	Increase the number of converter stages
•	Increase the volume of catalyst
•	Change catalyst more frequently and improve distribution
•	Improve uniformity.of feed conditions
•	Reduce feed gas impurities
•	Provide additional interstage cooling in converter and
improve temperature control throughout the plant
•	Reduce throughput rate
•	Exercise additional care during plant start-up
Most of these steps tend to increase costs and therefore, must
be considered in relation to the overall plant performance.
Since intermittent operation of the sinter machine cannot
be avoided and since the conventional acid plant operates more
efficiently and with less maintenance problems on a continuous basis,
it appears that some method should be introduced to provide an
auxiliary SO^ source when the sinter machine is not producing.
This approach is somewhat beyond the scope of this study and cannot
be considered "current state of the art" but should be considered to
046
V-5
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minimize the intermittent SC^ supply problem. The Cominco lead
smelter is using an ammonium hydroxide with SC^ reaction which
eventually produces ammonium sulphate and concentrated SC^ which is
then sent to the acid plant (Reference 8).
Concentration schemes such as Wellman-Lord (Reference 9) or the
ASARCO DMA can be used to produce liquid SO^ that can be conveniently
stored for use when the sinter machine is down. DMA concentration
and production of liquid SC^ has been conducted by ASARCO from lead
sinter machine gases at the Selby Smelter.
Another alternative to obtain constant acid plant operation is
to use a sulfur burner to generate SC^ and heat when the sinter
machine is not producing maximum acid plant feed. This scheme would
allow the use of lower percentage concentrations of SC^ in the feed
gas as well as provide for complete sinter machine shutdown.
Additional SC^ and heat facilities autogeneous operation in the con-
verter at a lower concentration. Ignition and turndown ratio (4:1
maximum in some cases) of the sulfur burner are possible problem
areas unless it can be operated at a continuous fixed level.
The additional capital costs of the auxiliary systems would
be partially returned by the reduction in acid plant size. With
any auxiliary system only part of the sinter machine offgas stream
would go to the acid plant with the remainder to the auxiliary
supply system. A 75% sinter machine on time with 100% SO^ (avail-
ability storage or generation) will allow a 25% reduction in acid
plant size and provide a system with constant or more normal acid
plant operation.
It should again be noted, that intermittant operation of
acid plants can be and is currently being accomplished without
auxiliary systems. However, more constant operation of these plants
will improve sulfur capture efficiency and minimize maintenance.
Furthermore, availability of a supply of SO2 to increase concentration
046
V-6
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will allow the use of a double contact acid plant with its con-
siderable reduction in emissions compared to the single contact
plant.
046
V-7
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VI. SO CONTROL FOR ASARCO LEAD SMELTER, EAST HELENA, MONTANA
	2	'	1	1	
A. SO^ Control System
There are perhaps a total of as many as 100 different methods for SO^
control, if all modifications of basic systems are included, References 10
and 11. These systems may be divided into two major categories:
1.	Primary systems for conversion of SO^ to a saleable or
throwaway product.
2.	Secondary or concentrating systems.
The Type 1 SO^ control systems may be classified as those systems that
can handle relatively high percentage of S0„ from approximately 3% up to as
4L
high as 18%. The Type 2 systems are essentially concentration systems that
will increase extremely low percentages of SO^ from 0.1% up to 3% to the
point where the Type 1 systems can be used. There are some Type 2 systems
that do produce a useful product such as the ammonium hydroxide system that
can produce ammonium sulfate fertilizer along with a concentrated stream of
£102. Table 4 lists some of these systems.
I!. SO^ Control for East Helena Lead Smelter
Since all operating lead smelters in North America have used either the
"tall stack" or the sulfuric aeid route for SO2 control (Section IV)
an acid plant can be considered as "reasonably available technology." The
following discussion will therefore, review the use of a sulfuric acid plant
applied to the East Helena, Montana lead smelter. As discussed in Section
III the single contact sulfuric acid plant can operate on an SO^ concen-
trated stream of approximately 3.5% to 8%. Too low a concentration requires
additional heat to be supplied for SO^ to S0^ conversion and to high a
concentration requires an excessive increase in heat exchange surface. It
is; therefore, desirable to adjust the stream coming from the sinter machine
to increase the SO2 concentration from the present 2.9% to 5-6%.
046
VI-1
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TABLE 4
Typical SC>2 Concentration Systems
•	ASARCO DMA System (Dimethylaniline)
•	Cominco (Ammonium Sulfite-Bisolfite)
•	Wellman Lord (Sodium Sulfite)
•	Lurgi Sulphidine (xylidine)
•	Imperial Chemical Industries (Aluminum Sulfate)
•	Magnesium Oxide (Magnesium Sulfite)
046
VI-2
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C. Degree of SO,, Control Expected with Acid Plant
Total sulfur in the concentrates entering the lead smelting plants
will vary from 14% to 33% throughout the industry. Generally 80-85% of
the total sulfur entering the lead smelter as concentrate will be
emitted as SO^ from the sinter machine. An additional 7% will leave in
the form of slag, stored sinter or dross. The remaining will leave from
the blast furnace either as gas or fixed in the solid material. The
1971-1973 ASARCO records show that 92% to 94% of the total sulfur entering
the smelter was emitted as SC^ from the sinter machine (Reference 17)
The sulfur content in the total material processed by the sinter
machine will vary from 4.5% to 7.0%. This is controlled to obtain proper
flame temperature so that the desired physical characteristics of the sin-
ter will be obtained. The sinter machine feed will be a mixture of initial
concentrates, slags, fluxes, and recycled sinter. Generally the recycled
material will be approximately 50-60% of the total sinter machine feed
although in one case it is as high as 83% because of high sulfur content
in the concentrates.
With no recirculation or limited recirculation of the weak SO2 stream
and processing of only the rich stream in the acid plant, typically 64%
of the smelter input sulfur will be converted to sulfuric acid. 6% of the
input sulfur will be fixed in solids resulting in a combined typical total
of 70% sulfur capture.
With complete recirculation of the weak stream sinter machine gases
(e.g. the use of only a single offgas stream from the sinter machine) as
much as 86% of the smelter input sulfur has been captured as sulfuric
acid with a single contact acid plant, (Section IV and Appendix). With the
additional sulfur captured in the slag, etc. a maximum 90% overall input
sulfur capture can be expected. The plant has a high (30%) sulfur content
Ln the concentrate which would tend to show the potential for ASARCO at
23% sulfur content (both values are higher than normal - Table 2). Thus, the
range of sulfur capture from no recirculation to full recirculation (par-
tial is possible) should be from 70% to 90% as reasonable values. Plant
046
VI-3
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operating conditions and condition of equipment will, of course, also be
of significance in determining overall sulfur capture.
D. East Helena Smelter Plant Flow Sheet
Figure 12 shows a schematic plant flow sheet of the American Smelting
and Refining Company, East Helena Smelter, East Helena, Montana. The con-
centrated ore, coke, scrap iron, purchased dross, siliceous ores and lime
rock are brought into the plant by rail. The first step in the process is
to prepare a feed for the blast furnace. The concentrates, coke - breeze,
siliceous ores and lime rock are mixed to make up the sinter machine feed
and pass through an impactor and nodulizing drum to provide thorough mixing
and proper physical characteristics.
Primary feed from the nodulizing drum is then fed into a pelletizing
drum along with recycled sinter that has passed through the sinter machine
product classification system. This recycle sinter is primarily fines not
suitable for the blast furnace. The total pelletized mix is fed onto the
81 by 72' updraft sintering machine (activated bed dimensions).
Material from the sinter machine is fed to a series of classification
roles to separate the acceptable sinter material and the fines. Blast fur-
nace feed consists of the sinter from the sinter machine, coke, recycled
dust and direct smelting ores. Two blast furnaces are used.
The sinter machine offgases have water injected directly above the
hood and also in a spray chamber following the hood to reduce the temperature
to 175°F. They then pass to a Cottrell precipitator which cannot operate
above 175°F. This unit has 180 six inch diameter by 12' long pipes.
After the gases have had the acid mist and particulate removed in the
precipitator they are heated to approximately 250°F to raise the temperature
above the dew point. The gases must be raised to 250°F for sufficient
margin above the dew point because the 400' stack is concrete lined and
cannot withstand any acid environment. The heating also aids in updraft.
The blast furnaces convert the lead oxide to lead. The hot material
from the blast furnace enters the drossing plant where there are five 90
ton kettles. These kettles are used to separate the dross from the lead. The
046
VI-4
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lead is then cast in suitable shape (bullion) for shipment.
Separate operations for" zinc fuming to produce zinc oxide and addi-
tional smelting in a reverberatory furnace for preparation of speiss also
take place within the smelter. Gases from the blast furnace, drossing
plant and reverberatory furnace all pass through three baghouses. The
dust collected in the baghouses passes back to dust bins and is used as
part of the feed for the blast furnace (or separated as a useful product
for shipping for further refining).
E. Sinter Machine System
The primary source of SO^ at the plant is the sinter machine. This
machine has an active bed 8' wide and 72' long. Its total length is 100'
with the capability of handling a process weight of at least 2200 TPD at
7.5% sulfur content.
A schematic of the sinter machine system is shown in Figure 13. The
ignition system consists of one downdraft bed with one windbox and fan
handling approximately 5,940 CFM. The gases from the ignition bed are
vented from the windbox hood through vent fan to the stack.
The 72' long active bed has nine updraft windboxes with basically
three air feed systems. Windbox 1 and 2 are fed by fan #1 handling 17,700
SCFM. Windboxes 3, 4, 5 and 6 are fed by #4 fan handling 29,100 SCFM.
Windboxes 7, 8 and 9 are fed by //3 and #2 fans at 33,350 SCFM.
The flow rates shown in Figure 13 are estimates for various parts of
the sinter machine system based upon the data in reference 3, and the
information obtained during the visit to the smelter (Appendix). The flow
rates in SCFM can only be considered approximations because the plant flows
are continuously adjusted during operation to obtain desired metallurgical
properties of the sinter.
As can be seen, partial recirculation of the oxygen richer gases from
the downstream end of the sinter machine is obtained. Approximately 19% of
the total flow in SCFM leaving the sinter machine is recirculated.
The top hood of the sinter machine has water spray heads at the down-
046
VI-6
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stream end placed approximately 4' apart on both sides of the machine to
cool the gases. Vented air from the sinter machine tunnel and the crush-
ing system is recirculated back to the sinter machine. During operation
the system is adjusted to provide sufficient air, bed depth, machine
speed, dust collection and metallurgical characteristics of the sinter.
At present this is being done simply by adjusting the airflow through
the various windboxes and the physical location of the downstream exhaust
takeoff point in relation to the main stack. Typical temperatures leaving
the machine at the main duct are 550°F and at the downstream recirculating
duct.of 250°F. Cooling of the gases is accomplished by water spray injec-
tion at the sinter machine hood in the downstream end of the sinter machine.
F.	Sinter Machine Sulfur Elimination
The sulfur elimination curve showing percent SO^ versus length along
the main sinter bed is shown in Figures 14 and 15 taken from Reference
3. The absolute values of percent SO^ will vary, depending upon the
various operating conditions such as airflow at the various windboxes,
sulfur concentration in the bed, speed of the machine, thickness of the
sinter bed, lead percentage and particle size distribution. As can be
seen, the first 40 feet of the machine emits the major portion of the SO^.
The SC>2 average concentration was measured and determined to be 2.81%
for curve Figure 14, and 2.99% for curve Figure 15. A numerical integra-
tion of these curves Table 5 results in an average SO^ content of 3.58%
(compared to measured 2.99%). The average of the integrated value is
2.66% and the measured value 2.90%.
The difficulties in taking measurements and the variation in the
operating conditions above the sinter bed make the data spread somewhat
large and therefore, the agreement is considered reasonably good.
G.	Modification of Sinter Machine System For Increased S0^ Concentration
The SO2 concentration can be increased by separation of the high and
low concentration streams out of the sinter machine with recirculation of
the low SO2 stream. Recirculation of low SO2 concentration stream was
046
VI-8
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TABLE 5
SULFUR ELIMINATION CURVE INTEGRATION
CHART 3
POSITION
—2
POSITION
so2
POSITION
so2
L-FT.
1°
L-FT.
1
L-FT.
1
2.5
1.7
27.5
1.0
52.5
.6
5.0
3.5
30.0
.9
55.0
.6
7.5
5.2
32.5
.9
57.5
.55
10.0
6.3
35.0
.85
60.0
.5
12.5
6.3
37.5
.8
62.5
.5
15.0
5.4
40.0
.8
65.0
.4
17.5
4.1
42.5
.75
67.5
.4
20.0
2.7
45.0
.7
70.0
•
(jO
00
22.5
1.75
47.5
.7
72.5
.35
25.0
1.25
50.0
.65


S02 MEAN = 5^53 = 1.74%	S02 MEAN MEASURED = 2.81%
(REFERENCE 3 )
CHART 4
POSITION
S02
POSITION
S02
POSITION
so2
L-FT.
1
L-FT.
1°
L-FT.
1
2.5
2.5
27.5
6.4
52.5
.45
5.0
4.95
30.0
4.6
55.0
.45
7.5
7.25
32.5
2.8
57.5
.45
10.0
8.80
35.0
1.5
60.0
.40
12.5
9.9
37.5
.8
62.5
.40
15.0
10.4
40.0
.6
65.0
.40
17.5
10.4
42.5
.5
67.5
.40
20.0
10.1
45.0
.48
70.0
.40
22.5
9.3
47.5
.46
72.5
.40
25.0
8.0
50.0
.45


D2 mean =
= 3*587°


S02 mean measured =
2.99%
S02 AVERAGE OF INTEGRATED VALUES = 1,74 + 3,58 = 2.66%
2 81 + 2 99
S02 AVERAGE MEASURED = ———-—— = 2.90%
046
VI-11
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conducted by ASARCO as early as March 1914. This work was done at their
California Selby Smelter. Additional tests on recirculation were carried
out at Trail and at Kellogg, Idaho smelters. This work is summarized along
with preliminary and commercial experience with recirculation in Reference
12. While most of the work was done with a downdraft sinter machine and
most present smelters have updraft, it did conclusively prove that recircu-
lation did provide an increase in the SC^ concentration.
Separation of the rich stream as seen from the sulfur elimination
curve Figure 14 such that only this stream will go to the acid plant will
materially increase the SC^ percent. For example, a step by step integra-
tion of the sulfur elimination curve assuming the stream going to the acid
plant is taken from the first five windboxes, (covering the initial 40'
of the sinter machine) results in an SC>2 concentration of 6.14%. (If this
is corrected to adjust for the difference between the integration and the
actual measurement, this percentage would reduce to 5.3%).
In addition, the total gas volume going to the acid plant would be
41,295 SCFM if the downdraft ignition stream is included. Thus, 64.5% of
the gas being emitted from the sinter machine would go to the acid plant
and 36.5% would be recirculated. It should be emphasized that the exact
numbers in this case are only representative, and are used as an indication
of what can be done with this particular equipment. Actual smelter ex-
perience (Appendix and Section VI) indicates that this is a practical method
of operation under the proper .conditions. Experience with the specific
equipment and feed material is required to determine optimum operating
conditions.
Furthermore, it appears that a significant reduction in total air flow
(with consequent increase in SC^ concentration) is possible. One smelter
uses a total air flow of 50,000 SCFM to process approximately 600 TPD of 33%
s;ulfur rich concentrate. This compares with nearly twice this amount of
£:ir with approximately 700 TPD of concentrate at 23% sulfur at East Helena.
(The other smelter has a larger machine so the data are not directly comparable
but indicative only).
A potential problem that may be encountered with recirculation is lack
046
VI-12
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of available oxygen. This can be corrected by so-called oxygen enrichment
providing an external supply of additional oxygen is available. The deve-
lopment of this technique again must be done for each particular sinter
machine operation and will take some development effort to obtain a satis-
factory system. Particular care must be taken to minimize excessive
temperatures and hot spots when oxygen is used. In a two windbox downdraft
system early recirculation experiments resulted in the actual extinguising
of the burning of the sinter because of lack of oxygen. In addition, if
sufficient oxygen is not present it is possible to obtain elemental sulfur
which can be passed throughout the entire downstream system causing con-
tamination problems.
H.	Sulfuric Acid Manufacture Capability At East Helena
Based upon current thruput it appears that a 400 TPD sulfuric acid
plant should be capable of handling the maximum amount of SO^ generated
at East Helena. See Table 6.
I.	Required Minimum Existing Plant Modifications
If it is assumed that the minimum effort be expended on plant
modifications and equipment additions, the basic approach to SC>2 control
at East Helena would be to install a gas cleaning system and a single con-
tact sulfuric acid plant to handle rich SC^ stream gases from the existing
sinter machine. Lean stream gases would be passed to atmosphere. Exper-
ience has indicated that a maximum effluent SO^ concentration of 2000-2600
ppm can be maintained under these conditions.
The following major plant modification steps would be required:
•	Partial removal of existing brick duct to existing precipitator.
•	Install hot gas precipitator and its output dust handling system.
e Connect sinter machine hood outlet duct to hot gas precipitator
•	Install scrubbers, cooling tower, mist precipitators and
associated ductwork and fans.
•	Install remainder of single absorption sulfuric acid plant with
product storage tanks.
•	Reconnect remainder of dust emission points to existing precipitator.
(Replacement of this precipitator with a modern unit is certainly
adviseable).
046
VI-13
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Table 6 . Sulfuric Acid Potential
at East Helena, Montana
Smelter

1971
1972
1973
Sulfur input to plant, TPY*
51,728
49,329
40,753
Operating days*
319.8
320.8
314.2
Sulfur input to plant TPD
161.8
153.8
129.7
Sulfuric acid (100%) potential TPD
494.8
470.3
396.6
Miiximum expected sulfuric acid 100% production TPD
395.8
376.2
317.3
(£i0% plant input S from sinter machine to acid plant)
* Data received from EPA (6-4-74)
046
VI-14
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Additional development effort to improve the gas supply system to the
sinter machine should materially improve operations. Significant reduction
of the total air flow through the sinter machine appears possible consider-
ing experience at other smelters.
J. Compliance Schedule
Procurement of a single contact acid plant in the 400 TPD size range
is shown by major steps in Figure 16. These estimates were obtained from
References 13, 14 and 15. (Appendix).
Completed plant, including start-up, can be supplied in 25 to 31.
months. The largest delay or rate determining step at this time is in the
procurement and fabrication of steel platework. Availability of steel has
extended plant procurement times by as much as 12 to 14 months. This situa-
tion cannot be predicted but some improvement has recently been noted.
Purchased items such as electric motors that normally are stock items are
also not readily available at this time.
Gas cleaning equipment such as precipitators and scrubbers can be ob-
tained in the same time period and are influenced by the same constraints
as the acid plant.
Assuming installation of a single absorption acid plant with its
associated gas cleaning system at East Helena and using existing water,
power and fuel systems the increments of progress are shown in Table 7.
Starting July 1, 1974 it is expected that the new system can be in normal
operation by November 1, 1977. This allows a three month "shakedown" to
phase operation of the new equipment with the rest of the plant.
K.. Cost Estimate
Wide ranges of costs for a sulfuric acid plant can be obtained depen-
ding upon the minimum input of SO2 concentration (converter size), the
maximum temperature of the cooling water for the heat exchangers (heat
exchange surface) and the degree of gas cleaning carried out (particulate
collector size). In addition, special design features, such as parallel
mist precipitators, can be included to minimize maintenance downtime by
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u
w
M	T3
4J	M
C	(fl
°	5
MONTH
ENGINEERING
SITE PREP. & FOUND.
PURCHASED EQUIPMENT
FABRICATED EQUIPMENT
ERECTION
START-UP
ACID PLANT PROCUREMENT SCHEDULE
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34
NOTE: Each line represents a different vendor estimate
3 vendors supplied information (not in this order)
Monsanto Envirochem
Ralph L. Parsons
Chemical Construction Co.
^	_	FIGURE 16
<	o
M	-t-
I	O
t-1
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TABLE 7
COMPLIANCE SCHEDULE
ASARCO - E. HELENA, MONTANA LEAD SHELTER
INCREMENTS OF PROGRESS:
Date of Submittal - final control plan	11-4-74
Date of Contract Award for Equipment	2-3-75
Date of Initiation of On-Site Construction	1-5-76
Date of Completion of Equipment Installation	8-1-77
Date of Final Compliance	11-1-77
ASSUMPTIONS:
1.	A complete new gas cleaning system will be installed to
handle gases from sinter machine.
2.	A single absorption acid plant will be used.
3.	Acid plant design will be subcontracted.
4.	Gas cleaning system consists of (in order used)
a. Hot gas precipitator
I?. Scrubber - cooler
c. Mist precipitator
5.	Existing water, power and fuel systems can be used.
6.	Work initiated July 1, 1974.
7.	Steel plate continues in short supply.
046
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providing by-pass modes of operation to allow removal of components from
the system during operation.
As an estimating range,the single absorption plant in the 400 TPD
range will cost $4,000,000 to $5,000,000. Gas cleaning systems will range
from $5,000,000 to $6,000,000 and will be dependent upon gas volume flow
which can be minimized by sinter machine operating techniques. Total
capital costs should range from $9,000,000 to $11,000,000. With possible
escalation this would result in a maximum estimate of $11,000,000 to
$12,000,000.
Operating costs exclusive of depreciation have been estimated at $7.00
to $13.00 per ton of acid, based on vendor and operator estimates. The plant
can be depreciated over a 15 year period resulting in approximately a $9.00/T
additional cost. Maximum cost of acid could be as high as $22/T.
A double contact acid plant would increase acid plant cost by
approximately 10%. Refrigeration to increase cooling efficiency for further
moisture removal would increase acid plant cost by 15%.
L. Space Requirements
An acid plant in the 600TPD size range can be designed to the following
overall dimensions (Reference 14):
Acid Making System	77' x 200'
Gas Cleaning System	46' x 200'
Elevation Maximum Less Stack 70'
It would be expected that a 400 TPD plant would use somewhat less space
f?uch as:
Acid Making System	70' x 190' = 13300 sq. ft.
Gas Cleaning System	44' x 190' = 8350 sq. ft.
Because the plant is composed of many components the arrangement of the major
items is somewhat flexible in terms of the overall plan geometry. The gas
cleaning system should be located as close to the sinter machine as
possible and the acid making section as close to this as possible.
046
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Based on preliminary information there appears to be 70' x 300'
available adjacent to the sinter machine at East Helena for the acid
plant. Additional space AO' x 300' appears available beyond this.
The estimated 21,650 sq. ft. required could be arranged within the
available space if the existing brick flue is removed.
046
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VII. REFERENCES
1.	"The Manufacture of Sulfuric Acid" W.W. Duecker, J.R. West, ACS
Monograph No. 144, Reinhold Publishing Corp., 1959
2.	"Concentration of the SO Content of Dwight-Lloyd Sintering
Machine Gas by Recirculation", W.S. Reid, Aime Metals Transactions
April, 1949, pp. 261-266.
3.	"East Helena Sinter Plant Volumes", C.R. Counts, M.J. Belich, ASARCO
Memo to Mr. J.J. Donoso, June 21, 1972.
4.	"Background Information-Proposed New Source Performance Standards
for Primary Copper, Zinc and Lead Smelters, EPA. Draft, August 1973.
5.	"Sulfuric Acid Plants for Copper Converter Gas" J.B. Rinckhoff ACS
Paper, April 4, 1974.
6.	"Japanese Copper Smelter Strives for Total SO- Emission Control"
E/MJ pp. 69-71, August, 1972.
7.	Air Pollution Control Field Operations Manual, TM-4870/000/00, Control
Agency Procedures Branch, Office of Air Programs, EPA, February, 1972.
8.	"Cominco Collects 1970's Dividend from 1920s Pollution Control Effort"
pp 121-124, E/MJ, September 1973.
9.	"Recent Experience of the Wellman Lord SO2 Recovery Process", W.J.
Osborne, ACS Paper March 31-April 5, 1973 Meeting.
10.	"Control of Sulfur Oxide Emissions from Primary Copper, Lead and Zinc
Smelters - A Critical Review" K.T. Semrao, Jrnl. Air Pollution Control
Association, Vo. 21, No. 4, April, 1971.
11.	"Controlling the "Other" Sulfur Oxides Sources" K. Semrau, 167th ACS
National Meeting April 4-5, 1974.
12.	"Concentration of the SO Content of Dwight-Lloyd Sintering Machine
Gas by Recirculation" W.S. Reid, Metals Transactions pp 261-266, April,
1949.
13.	Discussion with Mr. M.E. Doyle, Sales Manager, Process Plants, Monsanto
Envirochem, St. Louis, Mo.
14.	Discussion with Mr. T. Browder and Mr. R.E. Warner, Sulfuric Acid Process
Managers, Ralph M. Parsons Co., Los Angeles, Calif.
046
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REFERENCES (Continued)
15.	Discussion with Mr. R. Berger, Chemico, New York, N.Y.
16.	"Sulfuric Acid Production from Ore Roaster Gases" J.R. Donovan, P.J.,
Stuber, pp. 45-50, Jrnl. of Metals, November 1967.
17.	"Environmental Impact Statement For The Air Pollution Variance Requested
By: The American Smelting And Refining Company For Its East Helena Lead
Smelter" Montana Department of Health and Environmental Sciences, May
20, 1974.
046
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VIII. APPENDIX
Visit and telephone conversation notes
St Joseph Lead, Herculaneum, Ho.
Amax Lead, Boss., Mo.
Bunker Hill Smelter, Kellogg, Idaho
ASARCO Smelter, East Helena, Montana
Brunswick Smelting & Refining, Beladune,
New Brunswick, Canada
Monsanto Envirochem, St. Louis, Mo.
Ralph M. Parsons Co., Los Angeles, Calif.
Chemical Construction Co., New York, N.Y.
EPA Meeting Region VI
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I. SUMMARY OF THE VISITS TO ST. JOSEPH LEAD SMELTER
AMAX LEAD SMELTER
MONSANTO CHEMICAL CORPORATION
The visits to the St. Joseph Lead Smelter at Hurculaneum, Mo. and the
Amax Lead Smelter at Boss., Mo., were made to obtain experience data on
the use of sulfuric acid plants for SO^ control for a lead smelter. The
visit to Monsanto Chemical Corporation, Envirochem Division, was made to
obtain updated information on acid plant design as applied to lead
smelters. A preliminary meeting at EPA Region VI offices in Kansas City
was held and some detailed information on the smelters to be visited as
well as the E. Helena Smelter was obtained.
In general, the experience at St. Joseph Lead indicated a very marginal
operation of the acid plant as a result of most of the problems mentioned
by ASARCO in the objections they have made to using acid plants on their
lead smelters. However, all of these operating problems are the result
of either not recognizing and allowing for them during the design phase
or not modifying the smelter operation to match the acid plant require-
ments. It appears that the smelter (at least originally) did not recog-
nize the acid plant problems and vice versa.
As further confirmation of the feasibility of applying an acid plant for
SO^ control for a lead smelter, the Amax Plant is operating with considera-
bly less difficulty and while still having some problems, are able to opera-
te very consistently to produce and market sulfuric acid. They are even
considering adding to and increasing the capacity of their acid plant.
In both cases, a market is available to sell the acid product produced.
However, St. Joseph is under a long term contract and cannot adjust their
price to meet market conditions whereas Amax is able to raise prices as
the market changes.
Monsanto confirmed the above and further indicated that making acid from
lead smelter tail gases was more difficult than from other non-ferrous
metal smelting because of the carbon coming through the system from the
flotation reagent used to concentrate the ores. This carbon tends to
react resulting in the formation of water which causes serious corrosion
problems. They believe that an acid plant can be specifically designed for
a lead smelter to solve the problems being encountered.
046
VIII-1
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II. EPA, REGION VI MEETING
A meeting was held at EPA, Region VI offices in Kansas City, Mo., on
April 23 to discuss SO^ control for smelters, particularly the ASARCO
plants at East Helena, Montana and Glover Mo. The following people
attended:
Tom Jacobs, EPA, Region VI
Mike Sanderson, EPA, Region VI
Norm Huey, EPA Region VIII
Charles 0'Boyle, EPA, Region VIII
Bud Weisenberg, PES
A general discussion of EPA position on SC^ control indicated that dis-
persion control either by tall stacks or intermittant operation (ICS) was not
considered acceptable by EPA as a long term solution to the problem.
Questions on the smelters raised by PES and Region VIII were discussed to
f,et as much of the background from Tom Jacobs and the EPA, Region VI ASARCO
files as possible. Considerable data from ASARCO (that neither Region VIII
or PES had seen) was made available. Much of the significant data (i.e.
cost studies on various control means for the East Helena Smelter) was taken
by Norm Huey for duplication. He will send copies to PES and return to
Region VI.
The St. Joseph Lead Smelter combines all streams from the sinter machine
blast furnace, ventilation air and acid plant to one stack. (Approximately
400,000 SCFM). Tests were conducted indicating they were meeting 2000 ppm
requirement at stack.
Amax has also conducted tests indicating they meet the 2000 ppm requirement.
They have a sinter machine designed to recirculate the weak stream but have
never operated this way.
III. ST. JOSEPH LEAD SMELTER, HURCULANEUM, M0
Attendees at the meeting after the plant tour were:
Tom Jacobs, EPA, Region VI
Bud Weisenberg, PES
Charlie 0'Boyle, EPA, Region VIII
Maurie A. Pickard, St. Joseph Minerals Corp.
J.W. Sherman, Manager, St. Joseph Minerals Corp.
H.R. Bianco, Assistant Manager, St. Joseph
Minerals Corp.
D.H. Beilstein, Chief Metallurgist, St. Joseph
Minerals Corp.
OA 6
VIII-2
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R.T. Jacobs, Jr., EPA, Region VII
Byron Taylor, EPA, Region VII
Bruce Clark, Assistant Superintendent Acid
Plant, St. Joseph Minerals Corp.
The St. Joseph operation uses one sinter machine to feed one acid plant.
They combine all off-gas streams to one stack with total flow of 550,000
SCFM. Data obtained follows:
•	550,000 ACFM to baghouse
•	Concentrate 50-55% lead 15-16% sulfur
•	On sinter machine - charge 1\ inches - 10% raw chg to ignition
thick	90% to burden
Burden Layer to 10 inches thick
Blast furnace charge 1600-1650 TPD 10.7%-11% coke
Concentrate	CFM ^ ^
1268	27200 5.0 830 249
1263	34800 4.9 498 220
•	Sinter plant time on always tends to be longer than acid plant
time/on. Time difference ranged from zero to up to 4 hours for a
one month study.
•	Heat exchangers cause 8-12 hours acid plant shutdown/day.
2
•	40-120 BTU/Ft average heat exchange rate for Carbate heat
Exchangers^	2
350 BTU/Ft design - reduction due to fouling - 40 BTU/Ft .
•	Design	Normal	Max.
TPH	TPD TPH	TPD XPH	TPD
Sinter	139 x 24 = 3336 146 x 24 = 3504 183 x 24 = 4392
Blast furnace 64 x 24 = 1536 68 x 24 = 1632 85 x 24 = 2040
Dross Revert^.	6 x 24 = 144. 7 x 24 = 168 9 x 24 = 216
• Exhaust gas volume range 820,000 SCFM to 370,000 SCFM
Sinter Machine	St. Joseph Lead Smelter
f" irter
I mdraft
SO2 and temperature curve
Pressure inches H^O above atmospheric
13 updraft windboxes (all not shown)
16-20" H^O at precipitator
046
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• Feed Mix
Original Concentrate
After adding slag
After Adding Recycle (52%)
Slag consists of FeO, SiO^,
72% Pb
72% Pb
46% Pb
CaO
17% Sulfur
16% Sulfur
12% Sulfur
Recycle sinter consists of
46% Pb
1% Sulfur
•	Off-gas Mix
Final sulfur content 12% (original because of dilution) + 1% (Sinter)
t 50% = 6.5%
Water in gases to sinter plant 12% (added in part by cooling sprays
over sinter bed).
•	Requires 1/2 hour from start of sinter machine to build up to full
SO^ stream concentration.
•	Sinter machine 10 ft. wide x 105 feet long
•	Problems:
At .St". Joe the problems of operating the acid plant in conjunction
with the sinter machine has been extensive. These problems are listed as
follows:
o High moisture content of gases.
•	Flotation oil contamination
•	Gaseous condensation after baghouse (sulfur)
•	Water supply contains 1.5 ppm iron which tends to plug the
inside of the heat exchangers.
•	93% acid requires a gas temperature of 93°-96°F which requires
1500 GPM for cooling
•	There is approximately 1.2 lbs of oil in one ton of concentrate
(flotation)
•	3.5-3.6% SO^ required in the gas for autogenous operation.
•	Heat exchangers have been completely retubed after 4-5 years of
operation.
•	Source of water is as follows:
046
VIII-4
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4% moisture in the charge
Ambient air
Spray in water
Natural gas 70 CFM per ton of feed
•	40,000 wet SCFM to	the acid plant which is equivalent to 32,000
DSCFM.
120 lbs per minute	water enters from the sprays
270 lbs per minute water from the charge
•	Gases are cooled to 150°F to enter the baghouse which uses
acrylic bags. The baghouse is insulated.
e Considerable corrosion has been encountered around the baghouse
screw conveyor and shaker mechanism. They have obtained only
one year life on the bags.
o They are able to capture 80% of the sulfur from discharge from
the sinter machine.
•	1400°F is required for the sintering temperature.
e They stated that about 50% of the sulfur goes to the acid plant.
•	They need to minimize the amount of water in the acid on the
sinter machine shutdown which requires shutting down the acid
plant. It takes one half hour to ensure that the sinter machine
is started before the main acid plant blowers are turned on. This
blower is 1250 hp.
•	There is not enough heat available from the acid plant to use in
any part of the process.
•	Iron sulfate condensation causes welding problems.
•	They tried a fiberglass flue but this failed because it was not
strong enough.
IV. VISIT TO AMAX LEAD SMELTER, BOSS. MO
Those present were the following:
R.C. Harban, Plant Manager
G.H. Carr, Environmental Engineer
Charles 0'Boyle, EPA, Region VIII
Bud Weisenberg, PES
046
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Two days per week (Tuesday and Thursday) are used for standard maintenance,
for the sinter machine and acid plant. Maximum off time is 8 hours each day.
They have a 200 foot stack where the monitors are placed in strategic areas
ensure meeting SO^ requirements which the State of Missouri says they do meet.
They handle 40,000 SCFM total gases to the sinter machine. They handle
.22,000 SCFM to the acid plant. The gas stream to the acid plant contains
¦an average of 5.5% SO^ with a range of 4.9 to 7.0%.
They have a Lurgi sinter machine. (22,000-25,000 SCFM to acid plant). The
original acid plant was designed for 200 TPD and they are presently running
at 240-250 TPD.
"j^hey do recirculate some of the cold gas. Gases coming off the upend of the
winter machine at 600 F and at 350 F off the cold end.
The gases leave the sinter machine and go to a spray chamber where 25GPM of
water is sprayed in. The temperature drops from 600 F to 250 F.
They use 98% acid in the drying tower.
They estimate that due to maintenance problems sinter machine is on only
75% of the time. However, start and shutdown of the acid plant does not
appear to be tooserious a problem.
Bag life on the baghouse is one year.
Iciput concentration contains 70% lead and 15-15.5% sulfur.
The original cost of 200 TPD acid plant was $2,500,000. Operating cost here
is approximately $718,000. (?)
At 52,000 TPY acid operating cost here is $13.83 per ton producing 94% acid.
Added to this is approximately $5 per ton for depreciation.
One-sixth of the operating cost is extended in the annual 3-4 week shut-down
maintenance for the acid plant. This maintenance includes the following:
•	screening the catalyst bed.
•	clean the cooling coils in the heat exchangers,
o	clean out gas ducts of dust.
•	mist precipitator maintenance.
•	pack tower clean out (every two years)
046
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• spray chamber repair and leak elimination
The acid plant manufacture guaranteed 96% conversion with the four pass
converter. They are considering putting in a double contact plant.
They investigated the responsibility of using processes to clear up the
black acid but have found that this is not possible to do without going
to extensive cost. In addition, iron and lead may be present in this
acid, eliminating its purchase by many users. They have also encountered
plugging of the heat exchangers where they white sulfate material.
The total number of men operating the plant are 305. This processes
150,000 tons per year of lead with 1 oz of silver per ton and 50,000 TPY
Hulfuric acid. The pay scale is in the range of $2.55 to $4.65 per hour.
046
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V. BUNKER HILL SMELTER, KELLOGG, IDAHO
A. Meeting with EPA, Region X and VIII to discuss data from the Bunker Hill
Smelter for Project 046.
A meeting was held at EPA Region X Headquarters in Seattle, Washington
to obtain data on the Bunker Hill Smelter on May 5, 1974. The following
people were in attendance:
EPA Region X: Ben Eusebio
Chuck Findley
Dean Wilson (Regional Meteorologist)
EPA Region VIII: Norm Huey
C. J. 0'Boyle
PES:	Bud Weisenberg
The PES work statement was reviewed. Region X personnel indicated that
they were presently "negotiating" with the Bunker Hill Smelter on a new
regulation and did not want any further EPA visits. They attempted to
answer all questions. Some additional information was required specifi-
cally in the areas of operating problems encountered. EPA Region X will
obtain this information and transmit.
During my discussion with N. Huey after the meeting I indicated and he
agreed, that we should, if at all possible, talk to the people at Bunker
Hill directly. This is particularly important because they have both zinc
and lead smelters with acid plants. They have little or no problems with
the acid plant on the zinc smelter, but considerable with the lead smel-
ter. N. Huey will try to arrange. The following information was re-
ceived on the Bunker Hill Smelter:
•	Lead sinter machine 8 ft. wide x 96 ft. long.
e Water is not sprayed into sinter machine. Gas cooling
done in separate spray chamber.
•	They use their product acid in fertilizer plant.
•	79% of SO2 is captured in acid plant.
•	70% of input sulfur is captured.
•	They can hold heat in acid plant for 12-24 hours with
auxiliary and no SO2 flow.
•	732,000 TPY concentrate to lead smelter 40 oz/ton silver.
046
VIII-8
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•	236,000 TPY concentrate to zinc smelter 6 oz/ton silver.
•	Acid Elant Size = 300 TPD.
Acid Plant Cost = $6.5 x 10^.
•	Gas stream diverted during acid.
•	Answers to the list of questions (Attachment A) following
Attachment B.
•	Plant block diagram Attachment C.
B. Telephone Conversation with Mr. Gene Baker, Plant Engineer, Bunker Hill,
Kellogg, Idaho, on May 20, 1974.
At the request of Mr. Norman Huey, Project Officer, Mr. Gene Baker, Plant
Engineer of the Bunker Hill Smelter was contacted by telephone (area code
208-784-1261, Ext. 216).
The purpose of the call was to obtain additional information that was
not available at the meeting with Region X people in Seattle.
The Bunker Hill Smelter Lead Sinter Machine has no water injection in
the hood of the machine. Gases averaging 700°F pass from the hood of the
sinter machine to the water spray chamber. The spray chamber reduces
the temperature of gases to a minimum of 250°F. They normally try to
operate at 280-290°F inlet temperature to the baghouse located downstream
of the spray chamber. This keeps a batter temperature margin above the
dew point.
The baghouse is completely insulated. In addition, there are heaters on
the collecting hopper and collecting screw conveyor. These electric
heaters will be turned on automatically when the temperature drops to
below 250°F.
Baghouse maintenance problems in terms of corrosion have been negligable.
They do have a relatively high maintenance on the bags. There is a
material which tends to crystalize on the bags causing both cracking and
plugging. They change the bags completely approximately once per year,
which is only approximately % of "normal" life.
The acid plant was started up about June, 1972. The entire hot section
including all pipes and ducts is completely insulated on the acid plant.
including essentially everything downstream of the drying tower. The
exceptions to this are the cold heat exchanger and blower. It is possi-
ble with this arrangement to maintain the acid plant at temperature for
periods of from 12-18 hours.
Corrosion has only been noted on the cold portions of the plant where
046
VIII-9
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there is no insulation such as on the down corner from the drying towers,
the duct to the cold heat exchanger and the acid plant blower. The cold
heat exchanger has been retubed once since start-up of the plant.
They have noted deposits of the black organic material which is believed
to be the flotation reagent from the ores. They have also noted some
sulfate deposits.
They are able to detect when plugging occurs by the incrase in drip acid.
This is detected by checking a drain pipe every twenty four hours which
is located at the inlet to the blower.
There is an insulated duct from the drying tower to the blower to the
cold heat exchanger.
Corrosion has been detected on the main blower. The main blower uses a
1200 horsepower blower and is capable of operating at 150 inches w.c.
He believes that they have collected over a one year period 49% of the
input sulfur to the plant. He feels that the number 79% of the SO2 from
the sinter machine is a little high.
The acid plant is bypassed until it is determined by visual inspection
of the instrument that sufficient SO2 is produced to allow acid plant
start-up. Once the minimum amount of SO2 is being generated the acid
plant is manually turned on.
C. Telephone conversation with Mr. Ron Johnson, Manager, Lead Smelter,
Bunker Hill Smelter, Kellogg, Idaho on May 22, 1974.
Mr. Johnson is the manager of the lead smelter at the Bunker Hill facil-
ity. They also have a zinc smelter.
(In a previous conversation with Mr. Gene Baker (the same day) he stated
that the sulfuric acid plant on the zinc smelter can be operated contin-
uously and they do not have the same problems as encountered with the
acid plant on the lead smelter. The two major problems he cited as
occuring with the lead smelter are 1) the continuous starting up of the
sinter machine and 2) the black material deposited within the system.
On the zinc smelter they do not have a sinter machine and they use flash
smelters and are able to operate continuously. Also, the acid produced
from the zinc plant is white acid and is not discolored.)
Mr. Johnson was initially quite reticent in answering questions and
wanted to know in detail why we were asking for this information. I
assured him that we only wanted to obtain experience data on the parti-
cular equipment that he had at his plant and were not in anyway concerned
with applying regulations to his operation.
046
VIII-10
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He then quite willingly answered all questions put to him.
The Bunker Hill lead smelter takes the gases from the sinter machine and
passes them through a water spray chamber where they are cooled to approx-
imately 230°F. The gases then enter the baghouse for particulate removal.
After the baghouse they enter a packed tower which is used as a cooling
device as well as additional particulate collector. From the cooling
tower gases pass into one mist precipitator and then into the acid
plant drying tower.
During start-up they build up flow of gases to the acid plant to allow
generation of enough heat for autogenous operation. This start-up time
might be carried over a period of from 5-20 minutes. It takes, in some
cases, as much as AO hours before the entire acid plant has reached
thermal equilibrium.
During the low start-up flow condition channeling of the gases through
much of the equipment such as the tank tower and the mist precipitator
occurs. This channeling reduces the efficiency of the equipment. In
fact, during some start-up the whole plant efficiency may be down as
low as 82%. It takes 20-40 hours to get the third pass out of the con-
verter at maximum efficiency.
The sinter machine is on approximately 75% of the time. During start-
up, if they introduce toomuch cold gas into the system heat will not be
generated at a sufficient rate to reach autogeous operation. This is
particularly true if they are down for 15-16 hours. They will bypass
the acid plant during the start-up phase.
Mr. Johnson believes that part of the problem at Herculaneum is because
of their injecting water into the hood of the sinter machine.
He believes quite strongly that the black "mud" deposited throughout
the system is a hydrocarbon material. However, he could not specifically
site any tests that had been run on this although he said that they had
done so. He seemed quite sure that the back material was not lead or
lead sulfates.
He said that it is possible to get material coming all the way through
the system as proved one time when they were trying some experimemts with
reduced oxygen present over the sinter machine. This caused elemental
sulfur to be formed which actually came all the way through and was
found in the acid.
They operate at approximately 800°F gases on top of the sinter machine.
They try to maintain 235°F gases going into the baghouse. They have not
encountered any excessive corrosion in the baghouse.
They have encountered excessive corrosion at the inlet duct to the
046
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blower and in the blower itself. They believe that there is Still some
acid mist coming through at this point.
They have a preheater for the start-up of the converter but it is not
too satisfactory because it uses outside atmospheric air. This air con-
tains;:enough moisture to cause additional corrosion in the system.
They have tried to change the system to minimize this acid mist. They
have added a knockout tower and in addition a dam and weir set up which
seems to be working well.
Mr. Johnson was quite strong in his statement that it was very necessary
to have both the baghouse and the mist precipitator operating at peak
efficiency. He said that they did get a build up of the "mud" material
at the bottom or inlet side of the tubes in the precipitator. It was
necessary to keep this clean to obtain efficient precipitator operation.
They change bags in the baghouse at least once a year or somewhat less intervals.
He believes that bags made in Europe from acrylic thread appeared to be
the best at this time.
Mist corrosion is in the outlet duct from the baghouse to the fan and in
the fan housing.
They have been experimenting with a KREBS scrubber which uses a jet of
high velocity water impinging on a plate. They have found this, in small
scale experimental work, to be very efficient. This design comes from
South Africa.
Mr. Johnson said that they were experiencing $75,000 permanent loss
because of the operation of their acid plant. He did not think that it
would be practical to add either a sulfur burner or liquid SO2 supply to
smooth out and maintain constant operation of the acid plant, because
of this fact.
The following data on the Bunker Hill smelter were obtained from EPA
Region X.
046
VIII-12
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1.	Brief history of SO2 control at Bunker Hill.
Zinc plant: 1954 wedge roasters converted to flash roaster
Monsanto Plant #1 acid plant installed.
1968 zinc production increased - new flash roaster
Chemico plant //2 acid plant installed.
Pb smelter: 1970 new Lurgi updraft sinter machine and
Monsanto acid plant installed for strong stream.
2.	Plant input
Sources of ore
-	custom smelters: accepts ores of various concentration
-	also uses ores from Bunker Hill mines
-	uses about 30 different types of concentrates per year.
(70% local sources)
Ore sulfur content and variation.
Pb cone: 65% Pb, 6% zinc, 18% S ) .	..
Zn cone: 54% Zn, 1%% Pb, 30% S ) Aug* ValueS
Small amounts of Cadmium, Hg, Cu, etc.


• Pb plant: Zn	oxide, Cu, Silver, Gold, Antimony
Zn plant: Dd	Zinc alloys, Cu,
both plants:	Hg
3. Sinter production
•	capacity or prod, rate of sinter machine
2700 wet tons/day (approx. 2300 dry tons/day
on time operating factor = 85% annual basis
approx. 1300 TPD sinter storage
blast furnace
1000 TPD return as fines to prep plant
down time once every 7 days for standard maintenance.
•	Capacity of acid plant: Approximately 400 TPD. 32,000 SCFM (1800-32,000)
min. SO2 - 5% can get down to 3.5% . Efficiency 97.5% (varies 92% to 97.5%)
046
VIII-13
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• Amount of sinter recycled.
No sinter recycled, goes back to return prep plant.
The machine uses gas recycle. Figures not available as to percent-
age. but if4fan can handle 40,000 ACFM which includes a) combustion
air (8000 CFM) b) recycle gas and additional ambient air if neces-
sary i. e., approx. 32,000 ACFM recycle possible.
•	Air flow diagram - refer to schematic of sinter machine and flow
chart, Figure 13.
•	Lead plant (Hi strength) calls for:
27,900 SCFM dry gas @ 600°F - 700°F
10,000 SCFM H20 vapor @ 600°F - 700°F
5% SO2 by volume of dry gas
usual weak stream 30,500 SCFM (dry)
.9% S by vol dry gas.
Sample calculation:
Strong gas from sinter machine 63,800 ACFM (600°F)
(incl. 8,000 ACFM H^0 vapor)
At spray chamber gas cooled to 250°F
(dry gas 37,400 ACFM at 250° F
H2O vapor 5,360 ACFM @ 250°F
Water added at spray chamber = 8,050 ACFM @ 250°F
• Variation of SO2 across length of sinter machine
Ignition	Layer	Sulfur burn-
layer	bum thru	out complete
0'	40'	60'	92'
^	cooling 	>
•	Air vol and S conc. to main stack
30,500 SCFM 0.9% by vol. from sinter machine
goes into main baghouse (no spray chamber)
•	Lurgi 1970 updraft sinter machine
046
VIII-14
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•	No exceptional sinter machine maintenance problem noted.
•	Acid plant reliability very poor - to date has had functional
failure with most of the present equipment on stream 50 to 70% of
the time.
•	B. H. now conducting these experiments - results not in yet.
-	part of State regulation. Recycle low SO2 thru sinter machine.
Acid disposal	O2 enrichment
Reduced SO2 loss	Limestone and scrubbing on tail gas
•	No power generation from sinter offgas -
none for lead smelter - do for zinc smelter
•	Quality of acid produced
-	discoloration, high Hg content prior to purification and Hg
removal - suitable for use in NH3 phosphate plant.
• Actual capture of SO^ limited in past by
a)	reliability of plant
b)	markets
9 Acid plant tail gas concentration.
1100 PPM to 4000 PPM
97.5% Eff. 92% Eff
Source test data shows
1800 PPM 37000 SCFM
650 PPM 25000 SCFM
660 PPM
046
VIII-15
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VI. VISIT TO ASARCO EAST HELENA, MONTANA
SMELTER FOR PROJECT 046.
A visit was made to the American Smelting and Refining Corporation, ASARCO,
in East Helena, Montana on May 13, 1974 to obtain data for the study on SO
control for their lead smelter.
Those interviewed were:
Stan Lane, Plant Manager
Bob Hearst, Superintendent
Elden Lindstrom, Assistant Superintendent
A preliminary discussion, with all present, covered the general problems of
operating an acid plant with a lead smelter, experience at St. Joe and Amax,
the June 21, 1972 summary memo of sinter machine flows and the confirmation
and update of this information.
Mr. Lane indicated (as does material given us by Norm Huey) that their
studies have shown no local markets for sulfuric acid. He said that this
problem is further compounded by the close proximity of large supplies of
low cost Canadian sulfur which could be converted to sulfuric acid.
The author was asked and noted that St. Joe experience with their acid plant
was marginal but Amax seemed to be able to operate reasonably well. Also,
that all of the evidence seems to indicate that most of the problems
encountered were the results of not sufficiently modifying the "standard"
acid plant design to specifically match the lead smelter needs and operating
characteristics.
ASARCO comments on sulfuric acid plant - sulfuric acid market is strongly
influenced by the close proximity of Canadian sulfur. Anaconda in Anaconda,
Montana makes more sulfuric acid in their plant than they can use. Stan Lane
indicated they would not want to get into the fertilizer market because it is
a special product requiring an entirely new technology.
They noted that the "new" No. 3 fan (mentioned in the June 21, 1972 memo) did
not perform as they had expected and produces only 40,000 CFM instead of
5i>000 CFM as expected. This caused some additional modification and margi-
nal performance of their recirculation system.
A review of the sinter machine schematic was conducted with Eldon Lindstrom.
He said that no further test data had been obtained since the 1972 tests.
Additions and corrections to update this material were obtained and are
summarized below. An inspection of the sinter machine system completed the
interview.
The ASARCO sinter machine was one of the first updraft units installed in this
046
VIII-16
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country. It is 100 feet long and 8 feet wide. The updraft section is 72
feet long. It uses a IV thick ignition layer and a 14" to 16" final sinter
Layer.
Normal maintenance on the sinter machine is 8 hours down time per week. This
is exclusive of any unforeseen down times. The machine had been shut down
for approximately 4 hours for unforeseen maintenance during the day of this
visit. Also, the blast furnace had been banked for lack of sinter feed.
Correction of the "old" system schematic shown was made and the "new" system
schematic defined in Figure 13. Dust from the cyclone handling
gases from several exhaust points is sent back to the sinter machine instead
of being collected because of handling difficulties.
From the flow system balance it appears that gases leaving the sinter machine
are at a rate of approximately 98,000 SCFM based upon the June 16, 1972 flow
data. There has not been any additional tests made since that time and after
the plant was modified.
Water spray heads are inserted at 4 foot intervals on both sides of the sinter
machine hood just downstream of the main outlet flue. About 18 spray heads
located on each side (total 36) supply enough water to cool the outlet gases
to 550°F. Each spray head flows 50-70 GPM at 500 PSI feed pressure.
The cooled outlet gases then flow to the main exhaust fan (200,000 ACFM at
500 F). The reason for providing water injection upstream of this fan is
to reduce the volume of the gas so as to match the capacity capability of
the fan. In addition it is necessary to humidify the gases before they enter
the Cottrell precipitator to 50-60% humidity so that the precipitator can
operate efficiently.
After tlie gases pass through the main exhaust fan they enter a rectangular
concrete flue which is approximately 300 feet long before entering the
precipitator. This precipitator was built in the early 1920s and is an
extremely old design. The upper limit of operation was stated to be 175 F
because of gas resistivity and the wooden roof. It seems to collect particu-
late more efficiently below this temperature. At the present time only the
precipitator is used for particulate control.
After the gases have passed through the precipitator they are heated again
with auxiliary gas heat to raise the temperature well above the dew point
before flowing through the stack and out into the atmosphere. The main
reason for heating the gases before they enter the stack is to ensure that
no acid will be formed which would rapidly erode the cement lined stack.
There is 14-16% sulfur in the new concentrate entering the plant. This quanti-
ty of sulfur is reduced to approximately 7% by mixing with recycled sinter
and moisture. There is approximately 6-7% moisture in the sinter feed.
VIII-17
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Fan operating points are shown in the following table:
I^an
Volume Flowrate
ACFM
Gas
Temperature
Speed
RPM
Static
Pressure
in W.C.
Power
BHP
Main Fan
Down Draft
n
H
i'/2 Westing-
house
#40370
//3 (Expected)
#3 (Actual)
200,000
10,000
30,000
50,000
33,000
55,000
40,000 (Approx.)
500
300
100
100
100
100
440
1170
1750
1770
1770
2
5
20
25
15
10
116.6
13.7
108.7
94.3
116.8
13(Approx.)
Altitude 4,200 Ft. - East Helena, Montana
Most of these fans are Westinghouse. Where the data are not shown it was
not available.
046
VIII-18
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VII. VISIT TO BRUNSWICK MINING AND SMELTING CORP. LTD.
NEW BRUNSWICK, CANADA ON JUNE 12 AND 13.
The Brunswick Mining and Smelting Corporation, Limited, Smelting Division,
Belledune, New Brunswick, Canada was visited on June 11 and 12 to discuss
the operation of their sulfuric acid plant in conjunction with the lead
smelter. This smelter uses complete sinter machine gas recirculation,
collecting a single stream for direct flow to a single contact sulfuric
acid plant. This results in more complete collection of SO^ emissions
than any lead smelter in the United States.
Personnel taking part in the discussions were as follows:
Brunswick Mining and Smelting:
Alan Young, Smelter Manager
Mike Street, Production Superintendent
Peter Dugdale, Technical Services Superintendent
(Environmental and Metallurgy)
Bob Nutten, Sinter and Acid Plant General Foreman
Stewart Norton, Sinter Plant General Foreman
Eldon Hickey, Maintenance Coordinator for
Sinter and Acid Plants
Bunny Legacy, General Foreman, Acid Plant.
Bud Weisenberg, PES
This is a relatively new smelter having been started up in 1967. It was
established to handle ores from a mine located approximately 35 miles away.
The entire input to the smelter is received from this mine. The original
process in the smelter produced low lead and zinc bullion until about 1970.
At this point the cost of coke became so high it was decided to only produce
lead and ship zinc concentrate overseas.
The entire operation is presently owned by Noranda Mining & Minerals Corpora-
tion. It consists of the mine, the lead smelter (silver, copper, arsenic),
the sulfuric acid plant, and a fertilizer plant making super phosphate
fertilizer.
The smelter is organized as follows:
046
VIII-19
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The actual operating crew consists of approximately 15 men per shift with
¦4 shifts covering a 24 hour 7 day week period. The cleanup crew consists
of about 10 men who work only during the day. The entire smelter has
.a total of 550 personnel. Noranda also maintains a research center at
Montreal. They serve as consultants to the smelter.
The concentrate.handled is unique to this particular smelter containing
30-40% lead, 30-35% sulfur and 8-10% zinc. This concentrate is lower in
lead content and considerably higher in sulfur content than processed by
iQost smelters. The concentrate is produced by a concentrating plant located
at the mine site. They use the normal flotation reagents such as the
Jrollowing:
H-31 Starch
Dow Chemical Z-200 -Dithionocarbonate
242 Cyanimide-Dithiophosphate
Amyl Xanthate
Isopropyl Xanthate
The material enters the plant by rail from the concentrating plant. It passes
through a thaw shed which in the winter time thaws out the entire rail car
lor 1-4 days. The new material may be stored in open stock or placed
directly in . the feed bins.
The feed bins consist of 5 concentrate storage bins of 200-250 tons each,
an additional storage bin contains sand (silica) and an additional storage
bin containing lime rock.
The feed material loaded on to a belt in proper proportions to obtain a new
feed mix consisting of concentrate, lime and silica. The lime to silica
ratio is approximately .7.
046
VIII-20
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For every 3 tons of sinter manufactured they produce approximately 2 tons of
acid.
The mix is added to recycled sinter material to produce a sinter machine
feed containing 6-8% sulfur. This is common to all lead smelters. The sinter
machine recirculates the gases generated from the downstream end of the machine
and produces a single gas stream which flows to the acid plant. This gas stream
normally contains approximately 5% SO^. A concentration of 6% is preferable for
good acid plant operation.
The concentrate containing approximately 30% sulfur is mixed with return sinter
containing approximately 2%. Five parts of return sinter are mixed with 1 part of
concentrate. Output sinter contains approximately 1.5% sulfur.
The Lurgi sinter machine can handle 1.45 tons of sulfur per 24 hours per square
meter. The bed is 120 square meters in area which results in 174 tons per day
of sulfur being burned as the rate limit. At 30% sulfur in the concentrate this
produces a total maximum input concentrate load of 580 tons per day.
The feed from the feed bins, dust from the precipitator hopper and returns
are proportioned and transferred by a series of belts to a mixing drum. Water
is added to this drum to maintain a moisture content of 5% by weight, total.
The feed is then passed to a balling drum where additional mixing takes place.
The sinter machine is 150 feet long and 10 feet wide with a bed area above
the updraft windboxes of 120 square meters. An ignition layer of 1%" is used
and is ignited by five oil burners using No. 6 fuel oil. Steam injection with
the oil improves the combustion efficiency. Ignition length is approximately
6 feet and ignition time 1^ minutes. The bed travel 4-5 feet per minute. The
main layer adds an additional 10-11" thickness of material.
A sketch of the sinter machine system is shown below:
-------
The air supply system consists of one ignition fan and three main fans with
11 windboxes. The following table summarizes the fans and flows:
Fan No.
Windbox No.
Volume Flowrate SCFM
Air Source
Fan No. 1
Fan No. 2
Fan No. 3
Ignition
1-4
5-7
8-11
Ignition
18,000
9,000
15,000
21,000
14,000
20,000
6,000
100% Atmosphere
100% Atmosphere
Recirculation +
some atmosphere
100% Atmosphere
A maximum recirculation gas temperature of 300°C is used. If this temperature
is exceeded then the volume of the other fans is increased by damper control.
The entire air flow is controlled by dampers at each of the windboxes.
The following table shows the gas volume passed to the acid plant with
average SO^ content for various months.
Mon th
Gas Flow To Acid Plant
SCFM
Average SO2 Percent
January
February
March
April
40,000
48,000
49,000
45,000
4.0
5.5
5.6
5.2
Typical loading history for the Brunswick Smelter is as follows:
Concentrate 67,000 TPY
Lime and sorter mix 17,350 TPY
Total new material 84,350 TPY
Total process weight 422,000 TPY
Recycle sinter 337,650 TPY
The sinter containing 1.5% sulfur produced is approximately 62,000 TPY.
62% of the sulfur produced goes to slag at 1.75% sulfur. The lead produced
contains 0.5% sulfur. 67,000 tons of concentrate produces 50,000 tons of 100%
sulfuric acid. The concentrate at 30% sulfur contains 20,100 tons of sulfur
arid the sulfuric acid at 32.7% sulfur contains 17,310 tons of sulfur.
The additional sulfur mixed in the lead and slag will raise the total overall
sulfur collection to approximately 90%. Typical monthly production shows the
following:
14,300 tons of concentrate producing 4,340 tons of sulfur
11,353 tons of 100% sulfuric acid
046
VIII-22
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The sulfur content is shown in the following sketch:
30% S
6-8% S
Acid
Output sinter 1.5% S
Return sinter 2% S
The gases from the sinter machine pass directly to a hot gas precipitator.
There is no water or air injection beyond the sinter machine output. From
the hot gas precipitator the gases pass to venturi scrubbers and proceed as
shown by the following acid plant basic material flow sheet (Page VIII-24)
046
VIII-23
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< O
H ¦>
M ON
I
N>
nmce LIQUOR TO
SOjiTRl^tR CON*
MEAT

ex

CHANCER




CON-

OENSCR

CONVCATC*
CAS TO
¦frfTAC*
TO rcriTILIZCA PLANT
ACID PLANT BASIC MATERIAL FLOW SHEET
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Tht: gases-leaving the sinter machine are at approximately 300°C (571°F). This is
'somewhat lower than machines without recirculation and is probably due to the
reduction in temperature from the mixing of the cold recirculated gas with hot
gases coming off the burning bed. A maximum upper limit of 400 C (751 F) is used
as a control point for gases entering the precipitator. At this point an alarm
will sound and readjustment of the gas flow will be required. The hot gas pre-
cipitator is located close to the sinter machine to facilitate the return of the
dust removed to the feed bin for recycle.
The: gases pass from the hot gas precipitator to three Venturi Scrubbers. These
Venturi Scrubbers use weak acid as the fluid. Since the pressure drop across
these scrubbers is very low (1" of water) very little particulate removal is
obtained at this point. From the Venturi Scrubbers the gases pass to a cooling
tower and into 12 mist precipitators. From the mist precipitators they pass
into a conventional Lurgi single absorption acid plant. A sketch showing tem-
peratures at the various points through the acid plant follows:
046
VIII-25
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Pressure drops throughout the acid plant system are shown in the following
table:
Unit	Pressure Drop, " H^O
Fan Outlet	60
Fan Inlet	14
Venturi	1.0
Cooling Tower	1.5
Mist
Precipitator	4
Dryer	6
Fan-Con-
vertor	15
Converter	35
An auxiliary oil fired heating unit is used for start up of the system. This
unit will handle 20,000 SCFM which is sufficient to preheat the converter
and other parts of the system for startup to autogenous operation.
It is necessary to crush a significant portion of the output sinter to make
sufficient material for return.
Sinter machine availability which also takes into account scheduled main-
tenance down time is as follows:
January	78.5%
February	79.8%
March	80.7%
April	83.8%
May	75.7%
Usually 12 hours per week are established as scheduled sinter machine
maintenance down time. They expect to raise the sinter machine availability
to 85%.
Sulfur elimination from the sinter machine covered approximately 95% going
t:o the acid and 5% to the sinter. For April 4,130 tons of sulfur eliminated
iirom 14,308 tons of concentrate. For February 3,670 tons of sulfur was elimin-
ated from 11,259 tons of concentrate.
Problems and Solutions
• Sinter machine downtime as has been seen, varies from 10-15^.
Startup and shut down of the sinter machine and acid plant do not
appear to result in undue problems. The acid plant generally will
take from one half hour to one hour for startup after being shut
down for a relatively long period of time (8 hours).
046
VIII-26
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The 20,000 SCFM gas heater (Peabody) has encountered problems in cracking
of the tube sheet. Cracking resulted from the frequent variation in tem-
perature and the original selection of the wrong material. In some cases
when the acid plant has been down for a long time the auxiliary heater will
be turned on two hours ahead of sinter machine startup to preheat the con-
verter and the remaining portions of the system.
The acid plant can be operated with a crew of 2 men per shift. One man is
in the control room, which is separate from the sinter machine control room,
and one man is out in the plant.
The 12 mist precipitators tend to get a build up of solid material at the
bottom end of the tube. It is necessary to clean out this build up once a
week to maintain sufficient precipitator operation. This is done by taking
one off the line each day or less. With continuous maintenance on a regular
basis of each of the mist precipitators good operation and no problems are
¦encountered.
There is no "mud" like or oily deposit encountered anywhere in the system.
They do see a sludgy greyish yellow deposit that does seem to be encountered
in the heat exchanger. However, this deposit can easily be washed out with
water. There at no time is a necessity to completely dismantle any heat
exchanger. They are usually taken out of the line and water is forced through
i:o clean out any deposits when the pressure drop becomes too high.
'•There are two cooling towers in the gas input system. These towers are used
alternately and when the pressure drop in one reaches to high a value because
c>f partial plugging they switch to the other then clean out or wash down the
high pressure drop side.
Very little downtime has been required as a result of problems with the acid
plant. For example, in an elapsed time period when the sinter machine was
operating for 744 hours a total machine downtime of that time was 180 hours.
Only 10 hours of the 180 hours was due to the acid plant problems.
Sea water is used for heat exchanger cooling. They do not have a water
balanced problem at this plant except in several months in the summer. They
are presently awaiting receipt of an additional p.late and frame heat exchanger
to add sufficient heat transfer capacity, to eliminate their water balance
problem in the summer.
They have had a considerable amount of failure problems recently with their
baghouses. Bags have been failing however, total life has been 14 months
which is actually somewhat longer than most of the lead smelters in the
United States.
046
VIII-27
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A. VISIT
VIII. MONSANTO ENVIROCHEM SYSTEMS, INC.
A visit was made to the Monsanto Envirochem Systems, Inc. in St. Louis
Missouri. Those present at the meeting were:
Mr. M.E. Doyle, Sales Manager Process Plants
Mr. Frank Smith, Engineer
A discussion of sulfuric acid plants as applied to lead smelters for SO^
control was conducted. Mr. Doyle indicated that for a single absorption
plant a minimum of 3.0-3.5% SO^ concentration is required for autogenous
operation. For the double absorption plant, a 5% minimum SO^ stream is
required.
The converter requires an 800°F operating temperature which usually occurs
with a temperature rise of the inlet of 500 F to the outlet of 800 F. The
heat exchanger will use acid or water from 180 F which will rise to 300 F
when the gases are cooled to 500 F.
It is necessary to cool the gas in the drying tower to remove water under
che following conditions:
100°F removes water with 9% SO2
80qF removes water with 5% S0£
60 F removes water with 2% SO^
No water needs be removed when 76% acid is being made. Monsanto has built
it sulfuric acid plant (600 TPD) for a 2% SO^ stream in Chile. A 600 ton
refrigerating unit was used to cool the gases down sufficiently for drying
purposes. In addition 2 GPM of fuel was used to heat the catalyst bed
continuously for the SO2 to SO^ conversion. This plant used 30,000 SCFM gas
stream.
Buring sulfur to manufactured sulfur acid considerably simplifies the problem
because this not only provides a controllable maximum SO^ content but also
provides heat.
E. TELEPHONE CONVERSATION WITH MR. M.E. DOYLE, SALES MANAGER, PROCESS IN
PLANTS, MONSANTO ENVIROCHEM SYSTEMS CORPORATED ON TUESDAY MAY 28, 1974
Kr. Doyle was contacted from Columbus, Ohio.
Mr. Doyle had called PES to answer questions in our letter of
May 17, to him regarding sulfuric acid plants.
The following comments relate to this letter.
046
VIII-28
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Additional heating systems could be provided to maintain plant temperatures
during a sinter machine shutdown, however, additional capital costs would be
required and probably could not be justified. Sulfur burning plants produce
98% acid with SO gas feed cooling down to only 165 F. This means that the
gases are saturated at 165°F and naturally contain more moisture than with
a sulfuric acid plant used for a lead smelter. Here the gases are cooled
¦down to 100 to 125 F to remove more moisture for making 93% acid.
Monsanto believes that the primary problem causing corrosion is the organics
from the lead concentrate that come through this system to the converter.
The converter breaks down the organics since it is at about 800 F and causes
the organics to burn. Since they are in the presence of oxygen they form
CO2 and water. This water is the primary source of corrosion.
Monsanto uses 93% .acid for drying in all wet gas systems.
Bunker Hill has been finding a yellow deposit in their acid plant attached
1:0 their zinc smelter. They believe it is a mercury compound.
Spent acid regeneration plants used refrigeration for cooling down the input
leases to remove additional moisture. This is done to maintain the water
balance. They use steam ejector or mechanical refrigeration.
A 400 ton per day acid plant would probably handle approximately 30,000 to
35,000 SCFM. The volume flow rate primarily determines size and cost of the
};as cleaning section. Battery limit capital costs for the conversion section
would be approximately 3.9 million dollars for a single contact plant.
For a dual contact plant, this price would go up to 4,6 million dollars.
A .6 factor can be used for scaling up this capital cost. These costs are
exclusive of the gas cleaning system which may be 1.1 to 1.5 times the cost
of the conversion section.
Maintenance costs are estimated at approximately 4-1/2% of capital investment.
No guaranteed plant life is given.
They estimate a sulfuric acid plant should last up to fifteen years. Engineer-
ing design in time will cover a six to eight month period. It will take six
weeks from go-ahead to order platework. Total erection time is expected to
be 30 to 36 months at the present time.
The 30-36 months include 22-28 months steel vessels only. This is primarily
because of the availability of steel plate. It used to take 12-13 months
=nd now takes 22-28 months for erection of steel vessels.
lour months after erection of steel vessels the plant is ready for startup.
Startup usually takes approximately two weeks.
046
VIII-29
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A sulfur burner to provide SO^ during sinter machine shutdown and also to
provide additional heat, is a technically feasible method of minimizing
acid plant shutdown. However, the turndown ratio of a sulfur plant is
probably 4 to 1. This means that the sulfur burner must be continued in
operation at all times or the sulfur will solidify and startup problems
on the sulfur burner will be encountered.
Cost of the sulfur burner would add approximately 5% to capital cost, for
a 400 ton per day acid plant.
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IX. RALPH M. PARSONS COMPANY, LCS ANGELES, CALIFORNIA.
DISCUSSION ON SULFURIC ACID PLANTS FOR LEAD SMELTERS
A. VISIT
On April 19, 197h a visit was made to the Ralph M. Parsons Company in Los
,Angeles, California to discuss the work, they have done in design and installa-
tion of single and double absorption sulfuric acid plants. The following
Parsons personnel took part in the discussion.
Mr. Tim Browder, Sulfuric Acid Process Manager
Mr. Dick (R.E.) Warner, Assistant Sulfuric Acid
Process Manager.
A general discussion of the Parsons Sulfuric Acid Manufacturing System
indicated that while they are similar, each plant is uniquely designed to
neet its feed and product requirements.
Parsons not only believes that current technology is available to apply
an acid plant to a lead smelter but are actually in the initial stages of
construction of a single contact plant for Met Mex Penoles, Mexico City,
Mexico (Headquarters). This plant is sized for approximately 600 TPD which
is only slightly smaller than a unit required for the East Helena Smelter.
Enough costs were quoted as follows:
Single contact H^SO^ plant 	 $5,000,000
(Exclusive of initial cleaning baghouse)
This could be capitalized over 10 years
at approximately 		700,000/year
(2,000/day)
With production of 600 TPD
Capitalized cost = $2000 = $3.33 per ton acid
600
Operating cost	= $7.00 to $8.00 per ton acid
Flourine is present in the gas at the Mexican lead smelter requiring a water
spray chamber (tank with spray heads) as an initial gas conditioning step.
A scrubber is also used downstream of this unit for further elimination of
particulates.
The plant was designed for a 5% to 6% SO^ stream. It is capable of being
expanded to a double contact system with only minor addition and modification.
Parsons believes the difference in cost between double and single absorption
to be very small - much less than 10%.
046
VIII-31
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Catalytic conversion of SO,, to SO will be affected if concentration is
reduced below 2.5%. Some plants will burn sulfur to compensate during
lean periods. Low SCL concentration can be used, but plant costs go up
rapidly because of additional heat exchangers required to maintain
reaction temperature.
Indirect heat must be used to minimize water content. Drying is
accomplished to allow 98 + % H SO, manufacture. If lower acid concen-
2 A
tration is required, more water in the treated gas stream can be tolerated.
The Climax smelter in Ft. Madison, Iowa uses an oil fired sinter machine
and must handle carbon that comes over., Their exact procedure is not known,
but they do form carbon at the initial end of the sinter machine. They
have a double contact acid plant.
Parsons recently received an order for sulfuric acid plant for Valley
Nitrogen Company in California. They will use the sulfuric acid to make
phosphate fertilizer. Most of the phosphate fertilizer manufacturers
are located in Florida near the major phosphate deposits in the U.S. It
is interesting that a western company should be producing this product
which is a superior fertilizer to ammonium sulfate and has a much larger
market. Parsons did not know where the phosphate was being mined but
did know of some deposits in Wyoming and Montana.
Parsons indicated that they were in the process of installing or up™
grading additional sulfuric acid plant capacity of 19,700 TPD; this is
mostly new plants. They believe sulfuric acid will be selling for $60
$80 per ton within the next 18 months. One of the major reasons
for this is that they believe most existing acid plants will be required
to reduce their present thruputs to meet environmental regulations.
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B. TELEPHONE DISCUSSION WITH MR. DICK WARNER, RALPH M. PARSONS CO.
ON 5/16/74
•	He had just talked to Kennecott in Salt Lake City and they can
sell all the acid they can make.
•	Climax Molybdenum is buying a plant to operate @ 2.7% SO2 -
will use sulfur burner to supply heat and SO^ - could be auto-
matically controlled.
•	He would try to use two sinter machines to even out SO2 flow -
on sulfur burner (2).
Gas to gas heat exchangers
Use scrubber to reduce gas temperature as well as remove
particulate.
He said you could go to refrigeration probably add 10% to 15%
to cost of plant.
Could design heat exchangers to be opened by manhole and washed
out.
Could also put in nozzles to wash out.
For 400 TPD 6% SO,
Electrical
2000 HP Blower
200 HP Pumps
Water
Schedule
7000 GPM
Month Number
Eng. Design	1-9
Purchase	3-12
Site Prep.	12-16
Construction	16-24
Startup	25
Cool down after precipitator and then reduce temperature to condense
out moisture before entering drying tower minimum AT = 2-3 F.
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X. TELEPHONE CONVERSATION WITH MR. BOB BERGER
CHEMICO, NEW YORK, N.Y. ON JUNE 6, 1974
(212) 239-5856
Scheduling for fabrication and installation of an acid plant is as
follows:
Operation	Month
Process Engineering	3
Equipment Engineering	5
Foundation Design	5-9
Structural	4-7
Buildings and Services	7-8
Piping Engineering (Drafting)	4-11
Electrical	4-11
Instrumentation	3-13
Specs, and Standards	10-11
Construction	11-26
Startup	5
There contracts generally call for five consecutive days of satisfactory
operation and production as an acceptance requirement.
Mr. Berger could not answer the other questions we asked.
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