EPA-450/3-73-002
         FIELD SURVEILLANCE
           AND ENFORCEMENT
                         GUIDE
                 FOR PRIMARY
METALLURGICAL INDUSTRIES
     U.S. ENVIRONMENTAL PROTECTION AGENCY
         Office of Air and Water Programs
     Office of Air Quality Planning and Standards
     Research Triangle Park, North Carolina 27711

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                             EPA-450/3-73-002
     FIELD  SURVEILLANCE
  AND ENFORCEMENT GUIDE
          FOR PRIMARY
METALLURGICAL  INDUSTRIES
                  by

           Engineering-Sciences, Inc.
             7903 Westpark Drive
            McLean, Virginia 22101

           Contract Number 68-02-0627
           Program Element No .  2A5137
        EPA Project Officer: Bruce Hogarth
               Prepared for

       ENVIRONMENTAL PROTECTION AGENCY
         Office of Air and Water Programs
      Office of Air Quality Planning and Standards
        Research Triangle Park, N.C. 27711

              December 1973

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This report is issued by the Environmental  Protection Agency to
report technical  data of interest to a limited number of readers.
Copies are available free of charge to Federal employees, current
contractors and grantees, and nonprofit organizations - as supplies
permit - from the Air Pollution Technical  Information Center,
Environmental Protection Agency, Research  Triangle Park, North Carolina
27711, or from the National  Technical  Information Service, 5285
Port Royal Road,  Springfield, Virginia  22151.
This report was furnished to the Environmental Protection Agency
by Engineering-Sciences, Inc., McLean, Virginia, in fulfillment of
Contract No. 68-02-0627.  The contents of this report are reproduced
herein as received from Engineering-Sciences, Inc.   The opinions,
findings, and conclusions expressed are those of the author and not
necessarily those of the Environmental Protection Agency.  Mention of
company or product names is not to be considered as an endorsement
by the Environmental Protection Agency.
                   Publication No. EPA-450/3-73-002
                                11

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                                ABSTRACT






     This manual covers a step-wise enforcement procedure intended for




use by state and local air pollution control agencies.  This manual




focuses on the primary metallurgical industry and includes a process




description, a discussion of emission sources, typical control devices,




stack gas and process monitoring instrumentation, and Inspectors Work-




sheets for operations in the iron and steel, aluminum, copper, lead,




and zinc industries.  All major operations in each of those industries




were analyzed including an enforcement procedure for the storage and




handling of raw materials.   Upset conditions and abnormal operating




circumstances were examined in relation to their role in air pollution.






     All major pollutants from these five industrial catagories were




examined.  Generally the pollutant of most concern was particulate




matter.  Sulfur oxides and fluorides are unique to specific metals




operations and were discussed accordingly.  The manual includes sections




on the inspection of pertinent air pollution control devices.
                                   iii

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                            ACKNOWLEDGEMENTS






     In completing this investigation many people other than the principal




authors made significant contributions.  We wish to acknowledge the guidance




and direction provided by the Program Guideline and Information Branch




project officers and other engineers including Messrs. Geoffrey Stevens,




Hal Richter, and Norman Edmisten.  They were able to provide data which




was not readily available from other sources and have reviewed copies of




this manual.






     Throughout the project, assistance was obtained  from several trade




associations, large corporations, and state agencies.  These included:




the Aluminum Association, the American Mining Congress, the Department of




Interior, U. S. Steel, Bethlehem Steel, Kaiser Steel, Alcoa, Kaiser




Aluminum and Chemical, Intalco, Eastalco, New Jersey Zinc, and others.




Visits to these offices and plants provided an additional insight into




the current technology of air pollution control in these various industries.




The state air pollution control agencies of Maryland, Washington, and




California also provided valuable information which helped make this




project a success.






     The principal investigator for Engineering-Science, Inc. was M. Dean




High; Michael E. Lukey was Project Manager.  Other staff members contributing




to this project included:  J. Kenneth Allison, Terrence A. Li Puma, and




Mark L. Mercer.  Mr. Robert A. Herrick and Stanley Berger of General




Environments and Mr. Charles A. Licht of Charles Licht Engineering




Associates also contributed to the manual.
                                    iv

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                                FOREWORD






     From time to time it will become necessary for air pollution control




officials to make plant visits t^ the primary metals industries to assure




that emission levels from these operations comply with existing air




pollution regulations.






     This Enforcement Guide was published in anticipation of the problems




which state, local and Federal air pollution control officials may




encounter in reviewing and understanding several primary metallurgical




operations as they affect emissions to the atmosphere.  As the name of




this manual indicates, it is intended to serve as a fundamental reference




on air pollution emissions from five different primary metal process




industries:  iron and steel production, aluminum reduction, and copper,




lead, and zinc smelting.  The manual has been designed to:  (a) provide




a process description which illustrates basic operating principles and




variations, (b) discuss the significant operating variables which affect




air pollution emissions, and (c) provide a stepwise approach which an




enforcement official should follow when inspecting a primary metallurgical




source.






     This manual was prepared under contract with the U. S. Environmental




Protection Agency; Office of Air Programs, Program Guideline and Informa-




tion Branch, currently located at Research Triangle Park, N.C. 27711.




The project was initiated on August 17, 1972 and scheduled to last 7




months.  A portion of the task involving the iron and steel industry was




subcontracted to General Environments Corp. Springfield, Va.  Early in




the Study it was deemed vital that plant visits would provide a first-




hand understanding of the field activities of an enforcement official.

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Permission was requested to visit metallurgical operations at selected




nationwide locations and general cooperation was received from industry.




Some plant officials showed some reluctance to participate in the engineer-




ing, whereas other officials did participate, but remained anonymous.  Visits




to state agencies provided invaluable guides with respect to the structure




of this manual.






     Generally the pollutant of most concern (on the basis of mass emission




rate) is particulate matter.  Sulfur oxides and fluorides are unique to




certain metals operations yet particulates emanate from nearly every




operation in the primary metals industry.  Each section (Chapter) includes




a discussion of the process, operating variables, and the procedure that




should be followed when inspecting a site.  It is not intended that this




manual should be a substitute for source testing in determining compliance,




nor is it anticipated that the enforcement official's Field Data File




would take the place of an air pollution permit system.  This study examines




the type of air pollution regulations which exist for the industries and




defines the stepwise approach that could be used to establish compliance/




non-compliance on a routine schedule.  In many cases the pollutant emission




rate is a function of feed ore composition, e.g., sinter plant sulfur




dioxide emissions.  For those processes, a simple calculation procedure




is described to determine emissions based on process weight by obtaining




an assay of the raw ore for sulfur content.  A similar type of calculated




emission rate for particulate matter from these sources is not plausible.




At this stage in controlling air pollution, almost all particulate sources




wiJ,j. be controlled to some degree.  For this reason a complete section




was devoted to air pollution control devices (Part VI) in which is
                                    VI

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discussed the operating principles and operating variables of air pollution




abatement systems.  In order to assess stack gas particulate levels,




invariably some measuring device will have to be used.  Consequently,




this manual includes a section (Part VII) on the test equipment and




method that could be used to measure particulate emissions, as well as




sulfur dioxide, fluorides, hydrocarbons, and exhaust eas parameters in a




manner not consistent with the EPA testing procedure, but adequate to




obtain an estimate using a simplistic/quick method approach.






     Since many of the operations inherent in the primary metals industry




already have air pollution abatement devices installed, the task of en-




forcement becomes (among others) one of properly maintaining and operating




control equipment at or near design specification.  Furthermore, for many




of the larger metals operations, stack tests will be made on the abatement




equipment and the data will be submitted to control agencies.  Based on




the emission results, plant operators may have to provide additional or




better controlled systems.  For the metals operations it is likely that




"upsets" in the operation can cause higher emissions, exceeding the design




of control systems, and result in neighborhood complaints to the agency.




It is anticipated that the enforcement official will be called upon im-




mediately to respond to these complaints.  For this reason this manual




examines several factors that would demonstrate a properly maintained




control device (such as spark rate, pressure drop, etc.) and factors that




cause an upset condition, including what can and should be done to enable




a return to normal.






     This manual was prepared by Engineering-Science, Inc., Washington, B.C.




offices.  The EPA/OAP project officers were Geoffrey Stevens and Bruce Hogarth.
                                   vii

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                           TABLE OF CONTENTS
Abstract
Acknowledgements
Foreword
List of Abbreviations
                                                  Page
                                                   iii
                                                    iv
                                                     v
                                                  xviii
PART I
PART II
PART III
PART IV
PART V
IRON AND STEEL INDUSTRY
   1.  Pelletizing
   2.  Receiving, Storing and Handling of
       Material
   3.  Coking
   4.  Sintering
   5.  Blast Furnace
   6.  Pigging of Iron
   7.  Iron Casting
   8.  Open Hearth Furnace
   9.  Basic Oxygen Furnace
  10.  Electric Furnace
  11.  Steel Shaping and Finishing
  12.  Slag

PRIMARY ALUMINUM INDUSTRY
  13.  Receiving, Storage and Handling of
       Raw Materials
  14.  Preparation of Alumina
  15.  Anode Manufacturing
  16.  Reduction Operations
  17.  Cast House Operations
  18.  Cryolite Manufacture and Recovery
  19.  Anode and Cathode Reclaiming

COPPER SMELTING
  20.  Receiving, Storing and Handling of
       Raw Materials
  21.  Concentrating
  22.  Concentrate Roasting
  23.  Concentrate Smelting
  24.  Converting,

LEAD SMELTING
  25.  Material Handling
  26.  Concentrate Drying
  27.  Concentrate Sintering
  28.  Ore Reduction - Blast Furnace
  29.  Ore Refining - Reverberatory

ZINC SMELTING
  30.  Material Handling
  31.  Concentrate Drying
  32.  Concentrate Roasting
  1
  6

 18
 21
 33
 40
 47
 49
 51
 59
 72
 82
 93

103

110
115
118
131
161
166
172

175

184
188
191
199
212

225
227
239
241
251
261

269
274
281
284

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                      TABLE OF CONTENTS (Continued)
PART V (Continued)
PART VI
PART VII

PART VIII
ZINC SMELTING (Continued)
  33.  Concentrate Sintering
  34.  Zinc Metal Production

AIR POLLUTION CONTROL SYSTEMS
  35.  Electrostatic Precipitators
  36.  Fabric Filters
  37.  Wet Scrubbers
  38.  Cyclones

FIELD ENFORCEMENT EQUIPMENT

FIELD ENFORCEMENT PROCEDURE
294
301

311
315
324
330
344

347

355
PART I

Figure No.

Figure 1.1



Figure 1.2


Figure 1.3


Figure 1.4


Figure 3.1

Figure 4.1

Figure 5.1

Figure 5.2

Figure 6.1

Figure 8.1
        LIST OF FIGURES

IRON AND STEEL INDUSTRY

        Title                               Page

SIMPLIFIED FLOW DIAGRAM ILLUSTRATING
PRINCIPLE OF THE PELLETIZING PROCESS
USING THE TRAVELING GRATE METHOD              11

SCHEMATIC DIAGRAM OF THE TRAVELING GRATE
SYSTEM FOR PRODUCING PELLETS                  11

SCHEMATIC DIAGRAM OF THE SHAFT FURNACE
SYSTEM FOR PRODUCING PELLETS                  11

PILOT PLANT PELLETIZING MACHINE -
CIRCULAR GRATE SYSTEM                         12

BY-PRODUCT PLANT FLOW SHEET                   27

SINTERING PROCESS                             35

BLAST FURNACE                                 42

TAPPING                                       45

PIG CASTING MACHINE                           48

CROSS SECTION OF AN OPEN HEARTH FURNACE,
SHOWING REGENERATIVE CHECKER CHAMBERS
PREHEATING INCOMING AIR                       52

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LIST OF FIGURES (Continued)
PART I (Continued)
Figure No.
Figure 8.2
Figure 8.3
Figure 8.4
Figure 9.1
Figure 9.2
Figure 9.3
Figure 10.1
Figure 10.2
Figure 10.3
Figure 11.1
Figure 11.2
Figure 11.3
Figure 11.4
Figure 11.5
PART II
Figure No.
Figure II-l
Figure 14.1
Figure 15.1
Figure 15.2
Figure 15 . 3
IRON AND STEEL INDUSTRY (Continued)
Title
OPEN HEARTH FURNACE OPERATING WITH HOT
METAL PRACTICE CONSISTING OF 60% HOT METAL
AND 40% SCRAP (OXYGEN PRACTICE)
FLOW DIAGRAM FOR CLEANING OPEN HEARTH FURNACE
GAS WITH AN ELECTROSTATIC PRECIPITATOR
TYPICAL PRECIPITATOR MAINTENANCE RECORD
BASIC OXYGEN FURNACE
VENTURI SCRUBBER FOR BOF SHOP
BOF MANUAL HEAT LOG - PULPIT INFORMATION
ELECTRIC FURNACE
EXAMPLE OF ELECTRIC FURNACE STEELMAKING
USING A CHARGE OF COLD STEEL SCRAP
(OXYGEN PRACTICE)
ELECTRIC FURNACE CONTROL SYSTEM
TEEMING OF INGOTS
SOAKING PITS
ROUGHING MILL
CONTINUOUS CASTING
HOT SCARFING MACHINE
PRIMARY ALUMINUM INDUSTRY
Title
ALUMINUM REDUCTION PLANT
THE ALCOA COMBINATION PROCESS
SODERBERG ANODE PASTE PRODUCTION PROCESS
PREBAKE ANODE FLOWSHEET
OVEN RING FURNACE OR BAKING POT

Page
53
54
60
62
67
69
74
75
77
83
83
84
85
86

Page
107
116
119
120
123
             XI

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PART II (Continued)

Figure No.

Figure 16.1

Figure 16.2

Figure 16.3

Figure 16.4

Figure 16.5


Figure 16.6

Figure 16.7


Figure 18.1
LIST OF FIGURES (Continued)

  PRIMARY ALUMINUM INDUSTRY (Continued)

     Title                                Page

PREBAKE REDUCTION CELL                     136

VSS SODERBERG CELL                         139

HSS SODERBERG CELL                         141

TYPICAL HSS POT(S) WITH HOOD(S)            144

ROOM COLLECTION SYSTEM SIDEWALL AND
BASEMENT ENTRY                             145

ALCOA 398 REACTOR                          149

FLOATING BED SCRUBBER DEVELOPED FOR
HORIZONTAL STUD SODERBERG CELL EXHAUSTS    154

CRYOLITE RECOVERY FLOW DIAGRAM             169
PART III

Figure No.

Figure III-l


Figure III-2


Figure HI-3

Figure III-4

Figure III-5

Figure III-6

Figure 22.1

Figure 23.1

Figure 24.1

Figure 24.2
  COPPER SMELTING

     Title                                Page

BASIC STEPS - COPPER ORE TO FINISHED
PRODUCT                                    179

PRODUCTION OF BLISTER COPPER FROM
SULFIDE CONCENTRATES                       181

CONCENTRATION AND SMELTING OF A COPPER ORE 182

COPPER SMELTING EMISSION SOURCE DIAGRAM    183

COPPER SMELTER                             185

SCHEMATIC CROSS-SECTION OF A SMELTER       186

MULTIPLE HEARTH ROASTER                    194

SECTION OF REVERBERATORY FURNACE           202

ELEVATION OF A PIERCE-SMITH CONVERTER      215

CONVERTER AISLE CROSS-SECTION              216
                                   xii

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PART IV
Figure No.
Figure 25.1
Figure 25.2
Figure 26.1
Figure 27.1
Figure 28.1
Figure 29.1
PART V
Figure No.
Figure V-l
Figure 30.1
Figure 33.1
Figure 34.1
PART VI
Figure No.
Figure VI-1
Figure 35.1
Figure 35.2
Figure 35.3
Figure 36.1
Figure 36.2
Figure 37.1
LIST OF FIGURES (Continued)
LEAD SMELTING
Title
LEAD PLANT EMISSION SOURCE DIAGRAM
LEAD PRODUCTION PROCESS FLOW DIAGRAM
LEAD CONCENTRATE PLANT
LEAD SINTER PLANT
LEAD BLAST FURNACE
LEAD REVERBERATORY FURNACE
ZINC SMELTING
Title
ZINC PLANT FLOW DIAGRAM
ZINC RETORT PLANT EMISSION SOURCE DIAGRAM
SINTER PLANT FLOW SHEET
ELECTROTHERMIC ZINC METAL FURANCE
AIR POLLUTION CONTROL SYSTEMS
Title
CHARACTERISTICS OF PARTICLES AND PARTICLE
DISPERSIONS
A SINGLE-STAGE VERTICAL WIRE AND PIPE UNIT
PARALLEL PLATE PRECIPITATOR

Page
233
235
240
245
254
262

Page
273
280
297
305

Page
314
316
317
EFFECT OF NON-UNIFORM VELOCITY ON PRECIPITATOIl
COLLECTION EFFICIENCY 320
TYPICAL SIMPLE FABRIC FILTER BAGHOUSE DESIGN
BAGHOUSE CONFIGURATIONS
CALIBRATION CURVE FOR A BLAST FURNACE
325
329

VENTURI SCRUBBER
332
               xiii

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PART VI (Continued)

Figure No.

Figure 37.2


Figure 37.3


Figure 37.4



Figure 37.5

Figure 37.6

Figure 37.7

Figure 37.8


Figure 38.1

Figure 38.2
   LIST OF FIGURES (Continued)

     AIR POLLUTION CONTROL SYSTEMS (Continued)
              Title                          Page

PERFORMANCE OF A VENTURI SCRUBBER ON AN
OPEN HEARTH FURNACE FUME                      334

PERFORMANCE OF A VENTURI SCRUBBER ON A
METALLURGICAL FUME                            335

VENTURI SCRUBBERS MAY FEED LIQUID THROUGH
JETS (A), OVER A WEIR (B), OR SWIRL THEM
ON A SHELF (C)                                337

WET IMPINGEMENT COLLECTORS                    338

FLOODED BED SCRUBBER                          339

CENTRIFUGAL FAN SCRUBBER                      340

FAN HORSEPOWER REQUIREMENTS FOR VARIOUS
SIZE SCRUBBERS                                342

CONVENTIONAL REVERSE-FLOW CYCLONE             345

TYPICAL FRACTIONAL EFFICIENCY CURVE OF A
CYCLONE                                       345
PART VII

Figure No.

Figure VII-1

Figure VII-2

Figure VII-3
     FIELD ENFORCEMENT EQUIPMENT

              Title

PITOT TUBE AND MANOMETER

FILTER HOLDER ASSEMBLY AND PROBE

MIDGET AIR SAMPLER
Page

 349

 351

 351
                                   xiv

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                            LIST OF TABLES

PART I       IRON AND STEEL INDUSTRY

Table                            Title                           Page

1-1          STEEL COMPANIES                                      3-6

1.1          IRON ORE PELLET PLANTS IN THE UNITED STATES            8

1.2          PHYSICAL FORM OF IRON ORE CONSUMED IN THE
             UNITED STATES AND ESTIMATES TO 1980                    9

9.1          BASIC OXYGEN FUEwACX INSTALLATIONS AND ASSOCIATED
             AIR POLLUTION CONTROL EQUIPMENT                       63

12.1         ANNUAL U. S. STEEL INDUSTRY SULFUR BALANCE (1967)     94
PART II      PRIMARY ALUMINUM INDUSTRY

Table                            Title                           Page

II-l         U. S. PRIMARY ALUMINUM REDUCTION PLANTS          104-105

II-2         FEED MATERIALS PER TON OF ALUMINUM                   108

16.1         PREBAKE REDUCTION CELL EFFLUENTS                     137

16.2         EFFICIENCIES OF CONTROL EQUIPMENT IN CURRENT USE
             FOR PREBAKE POTLINE EFFLUENTS                        147

16.3         ESTIMATED EFFICIENCIES OF CONTROL EQUIPMENT
             APPLICABLE TO PREBAKE POTLINE EFFLUENTS              147

16.4         FUME CONTROL PERFORMANCE OF ALCOA 398 SYSTEM         150



PART III     COPPER SMELTING

Table                            Title                           Page

III-l        U. S. COPPER SMELTERS                                176

III-2        COMMON COPPER BEARING MINERALS                       177

23.1         RKVERBERATORY SMELTING DATA                      206-209

24.1         TYPICAL OPERATING SCHEDULE FOR A CONVERTER
             BATCH USING A 40% MATTE                              219
                                   xv

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                       LIST OF TABLES (Continued)

PART IV      LEAD SMELTING

Table                            Title                           Page

IV-1         SURVEY OF UNITED STATES LEAD PRODUCTION IN 1968      226

25.1         LEAD BLAST FURNACE DATA                          230-231

25.2         SINTERING DATA                                       232

25.3         PRINCIPAL MATERIALS OF LEAD PRODUCTION AND
             THEIR ESTIMATED RELATIVE QUANTITIES                  236

27.1         EMISSIONS FROM LEAD SINTERING MACHINES               243

28.1         LEAD BLAST FURNACES CAPACITIES, EMISSION RATES AND
             WASTE GAS TEMPERATURES                               253

28.2         AUXILIARY LEAD SMELTER OPERATIONS, EMISSIONS, AND
             OPERATING CONDITIONS                                 256

29.1         TYPICAL ANALYSES OF DROSS REVERBERATORY FEED AT
             ONE LEAD PLANT                                       264

29.2         TYPICAL REVERBERATORY FEED AND PRODUCT WEIGHT RATES
             AND COMPOSITIONS AT ONE LEAD PLANT                   264
29.3
LEAD DROSS REVERBERATORY EMISSION DATA AND
OPERATING CONDITIONS
                                                                  265
PART V       ZINC SMELTING

Table                            Title                           Page

V-l          UNITED STATES ZINC CONSUMPTIONS                      269

V-2          SURVEY OF UNITED STATES LEAD AND ZINC PRODUCTION
             IN 1968                                              270

V-3          DUST-IN OFF GAS RATES FOR SOME PRIMARY ZINC PLANT
             OPERATIONS                                           272

V-4          PRINCIPAL MATERIALS OF ZINC PRODUCTION AND THEIR
             ESTIMATED RELATIVE QUANTITIES                        274

30.1         PROCESS AND MATERIAL FLOW PRIMARY ZINC
             PRODUCTION                                       278-279
                                   xvi

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PART V (Continued)

Table
32.1

32.2


33.1


33.2

33.3
          LIST OF TABLES (Continued)

          ZINC SMELTING (Continued)

                    Title
TYPICAL ZINC ROASTING OPERATIONS

ZINC ROASTERS CAPACITIES, EMISSION RATES AND
WASTE GAS TEMPERATURES

ZINC SINTERING MACHINES CAPACITIES, EMISSION
RATES AND WASTE GAS TEMPERATURES

ZINC SINTERING OPERATIONS

DUST-IN OFF GAS RATES FOR SOME ZINC PLANT
OPERATIONS
Page

 286


 289


 295

 295


 298
PART VI      AIR POLLUTION CONTROL SYSTEMS

Table                            Title

VI-1         USE OF PARTICULATE COLLECTORS BY INDUSTRY

36.1         FILTER FABRIC CHARACTERISTICS
                                                   Page

                                                    312

                                                    326
                                  xvii

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                         LIST OF ABBREVIATIONS
Common Units
acf
acf/hr or acfh
acfm
atm
bbl
bbl/day
Btu
Btu/gal
Btu/hr
Btu/ ton
°C
cf
cfm
cfm/ft2
day
EA
°F
fps
ft
g
gal.
gpm
gr/cf
gr/scf
hp
in.
in. Hg
in. H20
in. wg
j
actual cubic feet
actual cubic feet per hour
actual cubic feet per minute
atmospheres
barrels
barrels per day
British thermal units
British thermal units per gallon
British thermal units per hour
British thermal units per ton
degrees Centigrade
cubic feet
cubic feet per minute
cubic feet per minute per square foot
days
excess air
degrees Fahrenheit
feet per second
feet
grains
gallons
gallons per day
gallons per minute
grains per cubic foot
grains per standard cubic foot
horsepower
inches
inches of mercury
inches of water
inches water gauge
3 oules
                                       xviii

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Common Units (Continued)
kcal
kv
kw
kwh
Ib
long ton
m
ma
mcf
mps
mwh
ohm-cm
psi
°R
scf
scfh or scf/hr
scfm
spm
sq ft
ton or short ton
tons/day
wg
U
Ug
pg/m
106Btu
kilo calories
kilovolts
kilowatts
kilowatt hours
pounds
2,240 pounds
meters
milliampere
millions cubic feet
meters per second
megawatt hours
ohm centimeter
pounds per square inch
degrees Rankine
standard cubic feet
standard cubic feet per hour
standard cubic feet per minute
sparks per minute
square feet
2,000 pounds
tons per day
water gauge
microns
micrograms
micrograms per cubic meter
million British thermal units
percent
Chemical Elements
Al
As
Ag
Au
aluminum
arsenic
silver
gold
                                  xix

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Chemical Elements
Ca
Cd
Co
Cu
Fe
Hg
Mg
N
Na
Ni
0
Pb
S
Sb
Sn
Zn
Common Symbols
A
C
d
m
M
P
Q
R
T
u
V
P
(Continued)
calcium
cadmium
cobalt
copper
iron
mercury
magnesium
nitrogen
sodium
nickel
oxygen
lead
sulfur
antimony
tin
zinc

area
concentration
diameter
molecular weight
mass , weight
pressure
flow rate
gas constant
temperature
speed
volume
density
Subscripts
s
w
standard conditions; 70°F and 29.92 in. Hg
water vapor
                                         xx

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                PART I.   IRON AND STEEL INDUSTRY









       Steel is the most widely used  single  industrial material for the




manufacture of transportation equipment,  construction materials, durable




goods, defense hardware and metal containers.   The U.S.  industry is the




world's largest producer of steel,  accounting  for 20 percent of the total




world production.






       The steel industry in this country is highly concentrated.  Four




companies account  for more than 50 percent of  production and the eight




largest companies  produce 75 percent  of the  steel output.  The major




steel markets are  located in the Midwest  and Northeast and five states




in these regions account for almost 70 percent of the raw steel production.






       The making  of steel involves steps ranging from the mining of raw




materials from the ground to the shaping  and treating of finished products.




The basic raw materials needed for the production of steel are iron ore,




coke and limestone.  Ore is received  at the  steel plant  in bulk or in




some cases processed into pellet form, but bulk ore is commonly crushed




and sintered into  lumps.  The use of  pelletized or sintered ore facilitates




furnace operation.






       Coke is produced at the plant  site by heating coal in the absence




of air.  It is the basic source of heat in the blast furnace and provides




the carbon which acts as the reducing agent.  The limestone is used in the




same form as -mined except for crushing and provides a means for removing




impurities from the iron being made.
                                 -I-

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       The blast furnace smelts ore to produce pig iron.   Ore,  coke and




limestone are combined in the blast furnace and hot air is injected,




igniting the coke and providing oxygen for combustion.  The impurities




are removed separately from the iron in the form of slag.






       The steel making furnaces that convert pig iron, scrap and alloys




into steel of the desired composition are open hearth, basic oxygen and




electric.  The open hearth furnace is relatively slow.  The amount of raw




steel produced by this method has decreased from 84 percent in 1962 to




37 percent in 1970.  The basic oxygen furnace converts molten pig iron




and scrap to steel by blowing large quantities of oxygen into the charge.




This process has a high production rate and is replacing the open hearth




process.  Basic oxygen furnace production has increased from 7 percent of




the raw steel produced in 1962 to 48 percent in 1970.  Electric furnaces




are generally charged with cold scrap and alloys to produce a variety of




steels.  Heat is produced by electricity flowing through the metal.  Steel




production by electric furnaces has increased from 9 percent in 1962 to




15 percent in 1970.






       Primary shaping of the molten steel is most commonly accomplished




by pouring ingot molds.  After solidifying, the steel ingot is reheated and




rolled to a convenient size for further processing.  These shapes, depend-




ing on the dimensions, are called billets, blooms or slabs.  A newer method




for shaping the steel is the continuous casting process.  Molten steel is




continuously formed into shapes similar to those produced by primary roll-




ing of ingots.






       The primary shape is reduced to final dimensions by a series of




rolling operations.  The steel can then be treated by a variety of  surface





                                    -2-

-------
coatings or conditioning processes depending on the particular pro-




duct need.






      There are about 200 steel producing companies (Table 1-1) but




only 25 are integrated from the blast furnace through the rolling mills.




There are 61 companies that produce raw steel from scrap only.  The




remainder process semi-finished steel into finished products.






                              TABLE 1-1




                            STEEL COMPANIES
Company
Alan Wood Steel Co.
Allegheny Ludlum Steel Corp.
Allison Steel Mfg. Co.
American Compressed Steel Corp.
Armco Steel Corp.
National Supply Division
Atlantic Steel Co.
Babcock & Wilcox Co.
Baldwin-Lima-Hamilton Corp :
Standard Steel DJ,v.
Bethlehem Steel Corp.
Border Steel Rolling Mills, Inc.
Borg-Warner Corp:
Calumet Steel
Ingersoll Steel Div.
Braeburn Alloy Steel Div.
Cabot Corp.
Cameron Iron Works, Inc.
Carpenter Technology Corp.
Ceco Corp:
Lemont Manufacturing Corp.
Milton Manufacturing Co.
Southern Electric Steel Co.
CO

o 6
X
X
X



Blast
Furnaces
X
X
X



Steelmaking Furnaces
4J
§1-1
n)
(X 
-------
         TABLE 1-1
STEEL COMPANIES (Continued)




Company





C F & I Steel Corp.
Columbia Tool Steel Co.
Continental Steel Corp.
Copperweld Steel Co.
Crucible Inc.
Cyclops Corp:
Empire Reeves Steel Div.
Universal-Cyclops Spec. Steel Div.
Detroit Steel Corp.
Eastern Stainless Steel Corp.
Edgewater Corp.
Latrobe Forge & Spring, Inc.
Etiwanda Steel Producers, Inc.
Florida Steel Corp.
Ford Motor Co.
Georgetown Steel Corp.
Granite City Steel Co.
Harper Co. , H. M.
Harrisburg Steel Co.:
Division Harsco Corp.
Hawaiian Western Steel Ltd.
Heppenstall Co.
Midvale-Heppenstall Co.
Inland Steel Co.
Inter coastal Steel Corp.
Inter lake Inc.
International Harvester Co.:
Wisconsin Steel Div.
Jessop Steel Co.
Green River Steel Corp.
Jones & Laughlin Steel Corp.
Jones & McKnight Corp.
Jorgensen Co., Earle M.
Joslyn Stainless Steels Div.
Judson Steel Corp.
Kaiser Steel Corp.





in

jrf 4)
O >
u 6
X



X



X





X

X






X

X

X


X




X




0)

-------
        TABLE 1-1
STEEL COMPANIES (Continued)
Company
Kentucky Electric Steel Co.
Keystone Consolidated Ind., Inc.:
Key e tone Steel & Wire
Laclede Steel Co.
Latrobe Steel Co.
Le Tourneau, Inc., R. G.
Lone Star Steel Co.
Lukens Steel Co.
McLouth Steel Corp.
Mesta Machine Co.
Mississippi Steel Div. of Magna Corp.
National Forge Co.
National Steel Corp.:
Great Lakes Steel Div.
Hanna Furnace Corp.
Weir ton Steel Div.
Newport News Shipbuilding & Drydock Co.
North Star Steel Co.
Northwest Steel Rolling Mills, Inc.
Northwestern Steel & Wire Co.
Owen Electric Steel Co. of South Carolina
Pacific States Steel Corp.
Phoenix Steel Corp.
Pollak Steel Co.
Porter Co., Inc., H. K. :
Connors Steel Div.
Republic Steel Corp.
Finkl & Sons Co. A.
Roblin Steel Co.
Sharon Steel Corp.
Carpentertown Coal & Coke Co.
M
3§
8&






X






X

X










X


X
X
Blast
Furnaces






X

X




X
X
X










X


X

Steelraakins Furnaces
f
w
a M
« «
£5


X



X
X

X



X

X





X
X



X


X

Electric
X

X
X
X
X

X
X
X
X
X

X


X
X
X
X
X

X
X

X
X
X
X
X

Basic Oxygen
Process








X




X

X










X


X

            -5-

-------
                                   TABLE 1-1
                            STEEL  COMPANIES  (Continued)
Company
Shenango Incorporated
Simonds Steel Div.
(Wallace-Murray Corp.)
Soule Steel Co.
Southwest Steel Rolling Mills
Structural Metals, Inc.
Tennessee Forging Steel Corp.
Texas Steel Co.
Timken Co.
Tonawanda Iron Division, American
Standard Inc.
Union Electric Steel Corp.
United States Pipe & Foundry Co.
United States Steel Corp.
Vasco Metals Corp.
Washburn Wire Co.
Washington Steel Corp.
Wheeling-Pittsburgh Steel Corp.
Woodward Co . :
Woodward Iron Div.
Youngstown Sheet and Tube Co.
0)
.38
s$
X


X
X
X
X
X
Blast
Furnaces
X

X
X
X
X
X
X
Steelmaking Furnaces
4-1
C M

-------
extended period of time because of its adverse effect on product quality.




Outloading can be a major source of fugitive dust.






1.1    Process Description




       Pelletizing is the agglomeration of finely ground iron ore into a




fairly uniform size ball-shape.  Pelletizing plants are usually located




at or near the mine site (see Table 1.1).  The finished pellets are shipped




to the steel plant for use directly in the blast furnace.  Productivity




of the blast furnace is increased when the charge is made up of high




grade, uniform burden such as pellets as opposed to unsized raw ore.  Fines




generated from the crushing and grinding of high grade lump ore during




sizing operations and beneficiated low grade ore are utilized to form




pellets.  The use of pellets is increasingly becoming a significant mode




of operation in the iron and steel industry, as shown in Table 1.2.






       Pellets are made by rolling fine iron ore mixed with a binder to




form "green" pellets (about 3/8 inch to 1 inch in diameter) which are then




heated.  Bentonite, the usual clay binder, is the principal additive.




Other additives such as soda ash, limestone, or dolomite are sometimes




used to improve pellet strength.  The most widely used devices for forming




pellets are the balling drum and the disc pelletizer.
                                   -7-

-------
                                 TABLE 1.1
                IRON ORE PELLET PLANTS IN THE.UNITED STATES
     Company
     Location
Annual Capacity
 (gross tons)
Bethlehem Steel Corporation
  Cornwall
  Grace

The Cleveland-Cliffs Iron Company
  Empire Iron Mining Co.
  Humboldt Mining Co.
  Marquette Iron Mining Co.
  Marquette Iron Mining Co.
  Pioneer Pellet Plant

The Hanna Mining Company
  Butler Taconite
  Groveland
  National Steel Pellet Co.
  Pilot Knob Pellet Co.

Inland Steel Company
  Jackson County Iron Co.

Kaiser Steel Corporation
  Eagle Mountain

Meramee Mining Company
  Pea Ridge

Oglebay Norton Company
  Eveleth Taconite Company

Pickands Mather & Co.
  Erie Mining Company

Reserve Mining Company
  E. W. Davis Works

United States Steel Corporation
  Atlantic City Ore
  Minntac
Cornwall, Pennsylvania          700,000
Morgantown, Pennsylvania      1,500,000
Palmer, Michigan              3,200,000
Humboldt, Michigan              800,000
Eagle Mills, Michigan           800,000
Republic, Michigan            2,000,000
Eagle Mills, Michigan         1,200,000
Nashwauk, Minnesota           2,000,000
Iron Mountain, Michigan       2,100,000
Keewatin, Minnesota           2,100,000
Ironton, Missouri             1,000,000
Black River Falls, Wisconsin    750,000
Eagle Mountain, California    2,000,000
Sullivan, Missouri
Eveleth, Minnesota
Hoyt Lakes, Minnesota
Silver Bay, Minnesota
     2,000,000
     1,600,000
     10,300,000
     10,700,000
Atlantic City, Wyoming         1,500,000
Mountain Iron, Minnesota       4,500,000
                            Total United States Annual Capacity   51,050,000
                                          -8-

-------
                                 TABLE 1.2
                 PHYSICAL FORM OF IRON ORE CONSUMED IN THE
                    UNITED STATES AND ESTIMATES TO 1980
Year
1960
1967
1975
1980
Lump
Millions
of Tons
62.0
46.7
31.7
34.9
Ore
Percent
54.1
35.3
20.0
19.5
Sinter Fines ta)
Millions
of Tons
41.5
42.2
46.0
48.3
Percent
36.3
31.9
29.0
27.0
Pellets
Millions
of Tons
11.0
43.4
80.8
95.8
Percent
9.6
32.8
51.0
53.5
Total
Millions
of Tons
114.5
132.3
158.5
179.0
Percent
100.0
100.0
100.0
100.0
(a) Includes only iron-ore fines used for making sinter.  For example, sinter
    production in 1967 was 51.6 million net tons but required only 42.2 million
    tons of iron-ore fines.  The remainder was supplied as mill scale, dust,
    fluxes, and the like.


       The disc has a greater possibility of adjustment and produces a more

uniform pellet size which simplifies screening of the product, but the capacity

of the disc is lower than the drum and generally requires closer control.

In the pellet-forming process a small amount of pulverized coal may be added

to the pellet mix or coated on the pellets to supply part of the heat re-

quired during the firing step.  Oxidation of the pelletized magnetite

(FejO^) concentrate to hematite (Fe20j) may also supply a significant

proportion of the process heat requirement.


       The three most important pelletizing systems are the traveling-

grate (updraft and/or downdraft) system, the shaft-furnace system, and the

grate-kiln system.  In the first method, green pellets coated in a balling

drum with a fine layer of fuel are continuously fed to a traveling grate,

Figure 1.1.  The first few of the wind boxes below the grate are used to

dry and preheat the moist pellets.  After ignition of the bed, a downdraft

of air is continued until all the fuel is consumed and substantially all


                                    -9-

-------
the magnetite is oxidized to hematite, Figure 1.2.  An updraft of air is




then applied to cool the pellets.  Fuel requirements are about 700,000 Btu




per long ton of pellets with another  300,000  Btu obtained from the oxidation




of magnetite.  An advantage of this system is the close control that can




be maintained over each step of the pellet-hardening process.






     In the shaft-furnace system, Figure 1.3, the fuel is mixed inside




the pellet rather than as a coating on the outside, as in the traveling-




grate process.  The green pellets are distributed at the top of the shaft




furnace.  As the pellets pass down through the furnace they are first




dried and then heated to the pelletizing temperature of approximately




2,400°F in the top portion of the unit.  From here down to the bottom of




the furnace the pellets are cooled by an upward-rising stream of air.




At the bottom of the shaft, the pellets are discharged through a chunk-




breaker.  Difficulty can arise if a uniform combustion zone is not main-




tained and hot spots develop.  This will cause the pellets to fuse together




into large masses and, in addition to discharge problems, a sudden shift




of the pellets will produce heavy particulate emissions.  Advantages of




the shaft-furnace are simplicity of design and a high degree of heat




recuperation.  Fuel requirements are about 500,000 Btu per ton of pellets




with a magnetite concentrate.  The shaft furnace is unsuitable for hema-




tites, primarily because of the "hanging" or sticking that results from




the additional heat input that must be supplied in the hardening of




hematite pellets.






     The grate-kiln system, Figure 1.4 combines the advantages of the




traveling grate with a rotary kiln.   In this system the pellets are dried




and preheated on a traveling grate and then hardened by high temperature






                                  -10-

-------
                                               BCNTONITE FEED.
                                      BALLING DR
                                                             .CONCENTRATE FEED
              PULVERIZER COAL FEED
                                    VIBRATING SCREEN
                                      CLASSIFIER
                                                                  DRY! NO HOOD
      TO PELLET.
       STORAGE
 FIGURE 1,1  SIMPLIFIED FLOW DIAGRAM  ILLUSTRATING PRINCIPLE
OF THE PELLETIZING  PROCESS  USING  THE TRAVELING GRATE METHOD
   OREEN
  PELLET
   FEED          IGNITION
    j     OWNS ANO  |
         SRE>-EA7,N3   I    B.SVN8     COCHINS
       \pj\j\l\j\j\l\l\i\j\j\j\j ^r^
  FIGURE  1,2   SCHEMATIC  DIAGRAM
 OF THE  TRAVELING GRATE SYSTEM
  FOR PRODUCING PELLETS
                                                              —PELLET FEED
                                                               MOT GAS INLET
DRYING AND HEATING
    ZONE
                                                               COOLING ZONE



                                                               CHUNKBREAKER

                                                               COOLING AIR INLET
                                        FIGURE  1,3   SCHEMATIC DIAGRAM OF THE
                                     SHAFT  FURNACE SYSTEM FOR PRODUCING PELLETS
                                         -11-

-------
                                             CO
                                             >-
                                             CO

                                             UJ
                                             CD
                                            Q_

                                            t—
                                            CD


                                            Q_


                                            cr

                                            r-\

                                            UJ
                                            Di

                                            CD
-12-

-------
heating in a rotary kiln.  Hot gases discharged from the kiln are used




in the downdraft drying and preheating section of the grate.  No solid




fuel is added to the pellets with this method.  About 1 million Btu per




ton of pellets is required and is generally supplied by fuel oil.






       Ore concentrates received at the pelletizing plant are normally




moist, thus dust generation during receiving is not a problem.  Bentonite




is received in covered hopper cars and is unloaded into special bins that




meter the material into the pelletizing operation.  Particulate emissions




of magnetite, hematite, or bentonite are possible.  Dusts produced in the




materials handling portion of the plant are sometimes controlled by medium




energy wet scrubbers and although finished pellets are strong and abrasion




loss is low, a considerable amount of dust can be released during loading




for shipment because of the very large amount of material being handled.






       There is a possibility of some sulfur dioxide emissions during the




firing operation.  Sulfur is sometimes found in the ore concentrate in




the form of pyrites and the amount of SQ~ formation would be proportional




to the sulfur content of the ore.  A small amount of sulfur might be in




the pulverized coal but because of the small amount used the effect would




be minimal.  The iron and steel industry tries to keep the amount of




sulfur-bearing ore to a minimum because some of the sulfur becomes sulfate




(SOT) in the pellets and this is undesirable in the steel making process.






1.2    Process Control Operation




       The strength and hardness of finished pellets is maintained in




order to minimize degradation by breakage and abrasion during handling.




A check on these physical characteristics is conducted by exposing a
                                  -13-

-------
control sample of pellets to compression and tumbling tests.  In addition




to the properties of the ore concentrate, pellet quality is affected by




additives, balling method, firing technique and temperature,  test pro-




cedure and size.  Depending on these variables, pellet compressive strengths




have been reported between 250 and 5,000 Ibs.  A commercially acceptable




1/4-inch pellet has a minimum strength as low as 300 Ibs while it is 800




to 1,500 Ibs for a 1-inch pellet.  The tumbler test consists of a drum




tumbler (ASTM D 294-50) operating at 25 rpm for 200 revolutions with 25




to 50 Ibs of plus 3 mesh  (3/8 inch) pellets.  After screening the product,




satisfactory commercial pellets should contain not more than 6 percent of




minus 28 mesh fines and at least 85 percent of plus 3/8 inch size.  It




is also desired there be a minimum of broken pellets between these sizes.




It is advantageous to the production of steel to use strong, hard, uniform




pellets.  Sub-standard pellets, i.e. those that tend to crumble and create




dust, are inefficient for steel making.






       Although materials flowing into the pelletizer are metered and



monitored, the easiest check of the production rate is the pellet weight-




meter at the end of the process.  This record-keeping instrument is located




near the transfer point where finished pellets are placed on the product




conveyor belt.






       Air flows in the firing and cooling sections of the pellitizing



process are monitored with pressure gauges and recorders.  A record is




kept of the pressure drop and suction in the windbox which  is located under




the grate in both the grate-kiln and traveling-grate systems.  In the




shaft-furnace process, air flow into the furnace is recorded at both the




hot gas inlet and the cool gas inlet.  Individual  shaft furnaces are






                                   -14-

-------
commonly coupled to a single tall stack.  Other plants utilize hoods




over each furnace which direct the exhaust gas into multi-cyclones prior




to release to the atmosphere.






       For plant production record purposes major air volumes and static




pressures are metered and continuously recorded.  At shaft furnaces, for




example, the volumetric air flow and the inlet static pressure of the




combustion air supplied to the top of the furnace are recorded.  Should




the pellet bed hang up, the pressure would increase and/or the air flow




would decrease.  When the bridged mass of pellets breaks free an open




channel could develop which would cause a sudden drop in pressure and/or




increase in flow and would be evident on the charts.  During this period




particulate emissions increase because of the increased gas velocity




through a small portion of the bed.  A review of the charts would in-




dicate whether the plant has had this sort of difficulties with any




frequency over a given period of time.






       The situation described previously where the gases are passing




through a small section of the bed at high velocity is called a "blow"




in a shaft furnace.  A bad blow might throw red hot pellets as far as




fifty feet onto the charging floor.  Production rate and pellet quality




are both adversely affected during operation of the furnace under blow




conditions.






       Typical emission controls consist of multiple small diameter




cyclones for the capture of particulate matter from the process gas




streams.  There may be a manometer across the cell plate or between the




upstream and downstream duct of these dust collection units.
                                  -15-

-------
       Pellet dust is quite abrasive and the temperature of the gas




streams can have excursions to over 1,000°F during upset conditions at




the furnace.  The major elements which would contribute to these collectors




operating at less than design efficiency are abrasive wear and warpage,




both of which cause short circuiting between the dirty and clean side of




the collector.  The pressure-drop/gas-volume relationship for multi-




cyclones is not sensitive enough to record these problems until they




develop to major proportions.  An increase in visible emission intensity




over a period of time would suggest this type of deterioration of the




cyclones.  The only certain way to identify the presence or absence of




minor leakage of air at multi-cyclone dust collectors in a pellet plant




is to visually inspect the unit.  Furnace shut-downs are generally not




scheduled more than 2 or 3 times a year, so cyclone inspection can not




be a routine procedure.






1.3    Enforcement Procedure




       Emissions from the pellet plant consist of sulfur dioxide and



particulates.  Air pollution abatement equipment is used at all plants




to control particulate emissions.






       The objective of pellet plant inspections is to establish com-




pliance with  the particulate and sulfur dioxide emission regulations.




In order to accomplish the above objectives, the enforcement official




needs  to determine:




       1.  Current production levels and operating conditions,




       2.  Design production levels and operating conditions,




       3.  Current controlled and uncontrolled particulate and sulfur




           dioxide emission levels,





                                    -16-

-------
       4.  Efficiency and adequacy of emission control equipment




           at current and design levels.






       Both plant and emission control equipment design capacities and




operating conditions can be obtained from design drawings and plans.




These data should be obtained from the company representative prior to




plant inspection.  Production levels, feed weight rates and emission




control equipment operating conditions are monitored by the plant operator




and are either recorded in the operator's daily log or are displayed on




instrument panels.






       Make a visual inspection of the entire plant, tracing the material




flow from raw material storage to finished pellet outloading.  Look




closely at conveyor belt transfer points for excessive amounts of dust




formation.  Loading of finished pellets into railroad cars or barges




can be a major fugitive dust source.  If wetting sprays are used to




reduce dust emissions during material handling see that they are operating




properly with sufficient volume and pressure.






       Observe the collection hoods to see if they are properly located



and that their capture velocities are adequate.  If dust is escaping




the hood it is an indication that the collection system is undersized,




out of adjustment, or not located close enough to the point of emission.




Check the general condition of the system looking for holes and leaks




in the ducting due to wear, corrosion, and excessive fan vibration.




These conditions contribute to inefficient operation of control equipment.






       If shaft furnaces are being used for the pelletizing process,




check the air flow and/or the pressure records to establish the frequency
                                  -17-

-------
of upset conditions (blows).   Ask the operator what happens during blow




conditions.






       Compare the operating levels of the control devices being used




against design conditions.  The procedures described in Part VI of this




manual can be used to estimate emissions.






       Visible emissions are the simplest means for estimating particulate




control equipment performance.  The enforcement official should estimate




the percent opacity of dust control equipment stack plume and, if in excess




of allowable limits, take appropriate action.






       Building openings should be observed for evidence of escape of




inadequately captured process dust.  If noted, determine point(s) of




origin and require corrective action.






       Of  importance for the enforcement of air pollution emission regu-




lations is the process weight.  With the mass rate and sulfur content of




the feed and product, SC>2 emissions can be estimated.






       Compare these estimated emissions with allowable levels in the




regulations.  Take appropriate action.






2.     RECEIVING, STORING AND HANDLING OF MATERIAL




       Possible emissions will be particulate matter.  Fugitive dust regu-




lations will govern.






2.1    Process Description




       Raw materials arrive at steel plants by water or rail with some




minor amounts of materials arriving by truck.  The raw materials are unloaded
                                   -18-

-------
to open stockpiles, with the exception of a few materials such as lime




which is shipped in closed hoppers or container cars and then transferred




to enclosed hoppers without exposure to the atmosphere.  Most of the




materials received are in a presized condition; i.e. the crushing and




sizing was already accomplished at the mine, quarry or pelletizing plant.






     Transfer of the materials into and out of storage and to the pro-




cessing centers creates a persistent dust problem, due to the fine




material always associated with bulk handling of ore, coal and limestone.






     Coal storage piles are susceptible to spontaneous combustion so




they must be "turned over" from time to time.






2.2  Process Control Operation




     Open stockpiles may reach a height of 100 feet and cover up to ten




acres.  Because stockpiles of raw materials are exposed to the weather




and can be dusty, various techniques have been attempted to suppress




dusting.  These methods have ranged from simple wetting with water to




spraying with special plastic materials.  The large tonnages and available




methods of material handling for stockpiling and reclaiming make it econom-




ically impractical to house or shroud the stockpiles.






     Transfers from stockpiles usually are by means of overhead clam-




bucket gantries to bottom-dump cars, or by endless conveyor belts for




upward movement and gravity chutes for downward movement.  Dust is generally




created at each transfer point.  Outdoor belts normally are covered but




not enclosed and dusting can occur during windy weather.  Emission of




particulates to the atmosphere from materials in the building usually can be




controlled and emission control at indoor transfer points is often controlled
                                   -19-

-------
by cyclone dust collectors.  Coal dust inside a building can be controlled




at transfer points by the use of wetting agents and water sprays.






       No record keeping is maintained by the steel industry on the amount




of raw materials lost by dusting.






       While methods of receiving, storing and handling of raw materials




affect the amount of fugitive dust, the inherent dustiness of the materials




and the meteorological conditions of the area are the most significant fac-




tors.






2.3    Enforcement Procedure




       The following enforcement procedure describes general observations




which can be made for the materials handling at steel plants.  Due to the




non-uniformity of the raw materials, the following general guides for this




type of inspection are suggested:




       1.  Trace the flow of raw material from the time it arrives at the




           plant until it enters the process.




       2.  From a distance, observe the raw material and processed materials




           for dust clouds either from roadways, stock piles, transfer points,




           crushers or screening operations, slag dumping, plant construc-




           tion activities, etc.  These sources are generally not continuous




           emitters, but depend on the individual activity schedule.




       3.  Make records of the dusty areas for a close-up inspection.  These




           observations should be made from beyond the plant perimeter on




           a hillside overlooking the entire complex, if possible for a




           period of several hours.




       A.  Observe the raw material stock piles when the wind is blowing




           and note any entrained dust.





                                    -20-

-------
       5.  Observe the material-moving methods at the stockpile.




       6.  If the material is brought in on bulk transporters, note any




           dust emissions during handling.




       7.  If cranes, belts, or bulldozers are used to move the raw




           materials, note any major dust clouds.




       8.  Make notes on the lengths and locations of unpaved roadways.




           Ask what frequency these roadways receive dust preventive




           treatment such as water, oil or calcium chloride.  Observe the




           traffic on these roadways, and note whether or not a significant




           cloud is generated by vehicular movement.  Observe the paved,




           macadamized and gravel roads for latent dust.  Occasionally




           these roads may become burdened with dust and result in another




           source for fugitive dust.




       9.  Observe the transfer points along belt haulage ways.  If no




           dust is noted, no further inspection is required here.






       The Inspector's Worksheet which follows may be useful for record




keeping.  Interpretation of these observations is heavily dependent upon




the pertinent regulations governing fugitive dust emissions.  Since many




of these plants are located on large plots of land, it is important to




discriminate between in-plant housekeeping problems and emissions which




cross the property line.  If fugitive dust violations are apparent, take




appropriate action.






3.     COKING




       This is a major source of particulate emissions.  Other emissions




include  hydrocarbons, sulfur dioxide and odors.  Emissions are mainly a




function of facility design.
                                   -21-

-------
                             INSPECTORS WORKSHEET
            FOR RECEIVING,  STORING AND HANDLING OF RAW MATERIALS
Plant Id.
Date of this Inspection^

Type of Plant	
               _Date of last Inspection
Capacity of Plant
Source Location
                 Wind
              Direction
  Type        Wind Speed                      Preventive
Material        (mph)	Plume Description    Measures
Sample
Coal stacking
conveyor
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
coal














SW/20














Moderate black
dusting














Telescoping
chute














                                          -22-

-------
3.1  Process Description




     Coke is a cellular form of carbon produced by thermal distillation




of coal. As crushed coal is slowly heated in the absence of air to a




temperature above 2,000 F over a period of 10-30 hours the moisture,




volatile hydrocarbons, and about one-half of the sulfur are driven off.




The metallurgical coke which is produced is used in blast furnaces as a




source of carbon.  Approximately 65 million tons of coke are produced




annually in the United States.






     An individual slot-type coke oven is a long, tall narrow chamber




with doors at each end.  Older ovens may be 10 feet high, 30 feet long




and 14 inches wide.  New ovens might be 18 feet high, 60 feet long and




20 inches wide.   For material handling purposes coke ovens are con-




structed in batteries of as many as 100 ovens.






     In its simplest form, the process consists of filling the oven with




crushed coal.  The oven is then sealed to prevent air infiltration and




heat is applied to the exterior walls and the by-products piped to a re-




covery system.  When the coking cycle is completed both end doors are




removed and the coke is pushed out.






     Actual coking practice is complicated because of the need for pre-




cise controls and  sophisticated mechanical equipment, but the basic




process is as described.






     Coke oven batteries are designed so that refractory side walls of




the oven taper slightly from end to end to prevent sticking of the




charge during pushing.  The walls between the ovens form refractory




brick combustion chambers, designed to allow even heating of the ovens.
                                -23-

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Since the oven operating temperatures are within a few hundred degrees




of the working limit for the refractories the temperature control sys-




tem has many safeguards.  Protection of the refractories is an important




maintenance factor in a coke plant as these refractories are susceptible




to total failure if subjected to thermal shock.  Once initially heated,




many batteries are not cooled through their entire working life.






     Thermal economy demands that some of the heat supplied to the com-




bustion chambers be recovered before venting to the stack.  Regenerators




consist of large brick checker chambers.






     Uniform heating over the entire oven wall area is a prime considera-




tion in quality control of coke.  Non-uniform heating is usually caused




by air infiltration at the ends of the oven which leads to a plug of in-




completely coked material at the ends of the charge.  This causes a heavy




black smoke cloud as the remaining volatiles burn.  This is known as a




"green push."






     Coking proceeds from the walls toward the center.  The ends take




longer to coke than the middle because the end doors are unheated.






     The preparation of coal requires considerable effort.  Coal of dif-




ferent volatile contents usually must be blended to get a mixture with




proper thermal coefficient of expansion.  Coals must be crushed  to 85 to 90




precent below 1/8-inch before blending.






     Sulfur is an undesirable element in steelmaking.  Metallurgical




grade coal is nearly always below 1 percent sulfur content.






     Blended coal is sent by conveyor belt to large silos atop the coke




oven battery.  The ovens are charged by a wide-gauge vehicle called a



                                         -24-

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larry car, which traverses the entire battery.  The larry car carries a




precisely weighed single charge of coal to individual ovens.







      Each oven has three to five charging ports on the top.  The end




doors are in place during charging.  The charge of 10 to 30 tons of coal




is dropped into the oven in less than a minute in most cases.  Surface




moisture and some light hydrocarbons are vaporized as the fine coal comes




in contact with the hot refractories.  A cloud of steam, brown smoke, and




some dust is generated during charging.







      The top of the coal charge is leveled by a long bar inserted from




the pushing side of the battery.  The leveling rod goes through a small




"chuck door" located on the oven door.  The leveling bar is part of the




pushing machine.







      After the charging is completed, the charge-port lids are replaced.




This is accomplished manually or, at newer plants, by a machine on the




larry car.  The heavy round tapered lid seats against a steel sealing




ring embedded in the oven brickwork.  The machine-placed lids are spun




in place and generally seat much better than hand-positioned lids.  If




the mating surfaces do not meet due to wear or warpage, tarry deposits




or particles of coal eventually complete the seal.  Coal dust left on the




seat or swept around the lid will smoke as the lid gets hot.  Sometimes a




clay sealer material is applied around the port cover to reduce emissions.







      Sealing of the end doors of the ovens is an important but difficult




step in the coking process.  Some older ovens have luted doors which are




sealed by the application of a mud-like troweled material around the peri-




phery of the door.  Operating personnel apply this luting material by




hand.  Newer ovens have knife edge seals.  These doors have a thin metal




                                 -25-

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strip around the edge which butts against the door jamb of the furnace.




They have some degree of manual adjustment, allowing them to fit worn or




warped jambs.  A positive seal is not actually made until a tar deposit




builds along the hairline crack at the mating edges.  Even clean doors




in good condition will leak for some period of time until a seal is formed




by the accumulation of tar from the leaking vapors.  It is necessary that




the doors and jambs be scraped clean of this tar deposit between each cok-




ing cycle to allow the doors to seat properly.  This cleaning is accom-




plished by machines and/or by hand.  Generally, machine cleaning must be




supplemented by hand cleaning.






     Each oven has one or two evacuation pipes at the top corner for the




recovery of volatiles.  Called stand pipes or ascension pipes, they carry




the gases to a collecting main which runs the length of the battery.




This is the start of the by-product recovery  system shown by Figure 3.1.






     The collecting main is held at a controlled slight negative pressure




by an exhauster.  Sprays of flushing liquor cool the gas and condense a mix-




ture of tars and high boiling organic and inorganic chemicals.  Flushing




liquor is recirculated.  Depending upon whether the system has one or two




collecting mains, between 1,000 and 2,000 gallons of liquor are used per




ton of coke.






     A tar precipitator removes mist to prevent plugging of the remainder




of the system.  A weak-sulfuric acid scrubber removes ammonia and forms




ammonium sulfate.  Light and heavy organic chemicals are recovered in a




series of steps similar to refinery processes.  Some sulfur is usually




recovered for making the sulfuric acid used in the ammonia scrubber.
                                    -26-

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                       <4   COKE OVENS  ~)

                                   I  Cote]
                         _L
                     | COLLECTING MAIN • DOWNCOME*
                    Cat and
                   Condcniatc
      Fluihlflg Liquor
       and Tar
               I PRIMART COOLER  I
               _  f~—~r
               1 CM I    |  CooJtmii,  |
               ^r           H
            [tXHAUSTtR ]


           | PRECIPITATOR  |
|  HOT TAR DRAIN TANKS |
           [REIIEATER J


LsJ

Liqua

Ammonia and
Phenoli
FIGURE 3,1   BY-PRODUCT PLANT FLOW  SHEET
                                  -27-

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     The resulting coke oven gas has a heating value of about 550 Btu/cf




and is an important fuel in a steel plant.  Coke oven gas supplies about




70 percent of the fuel for heating the ovens;  the balance is supplied by




blast furnace gas and small amounts of natural gas or oil.






     Raw coke oven gas contains from 3.5 to 4.5 grains of hydrogen sul-




fide per standard cubic foot.  This is a fuel sulfur content equivalent




to coal containing 1.2 to 1.6 percent sulfur.   Some plants have desulfuri-




zation processes which reduce the hydrogen sulfide content to below 0.5




grains per standard cubic foot.






     The coke plant operator has some degree of control over his pro-




duction rate because coking is a time and temperature related process.




Lower temperatures mean longer coking times.  If, for example, a 60-oven




battery was on a 15 hour coking cycle this would mean that an oven would




be charged every 15 minutes.  Extending coking time to 20 hours would




mean a charge every 20 minutes.  Most plants schedule their charging and




pushing times so that lunch breaks and shift changes are periods of




light activity.






     At the completion of the charge both end doors are removed and the




incandescent coke is pushed out of the oven by a large ram on the pushing




machine into a quench car.  This is a slope-bottom car which is self-




propelled on a track.  When the hot coke drops into the quench car a




strong thermal updraft is created, lofting dust into the air.






     The quench car travels to the battery quench tower, a large brick




or wooden chimney.  A large amount of water - typically about 4,000




gallons - deluges the hot coke in a period of about two minutes.  Roughly




one-half of the water is vaporized forming a heavy steam plume.  Some of




                                  -28-

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the water droplets from this plume fall in the immediate vicinity of the




quench tower.






     The quench car dumps the coke on a coke wharf, a sloping surge area




which feeds a belt conveyor.  The finished coke goes through a rough




crushing stage to break up large lumps and is screened.  Coke fines,




called breeze, are undesirable in blast furnaces because they impair the




porosity of the burden.  Coke breeze is used in the sinter plant as a




source of carbon.







3.2  Process Control Operation




     Coal is sent from the stockpiles to the crushing and blending station.




This operation will have a dust collection system for control of particu-




late emissions.  Some plants add oil to the coal at this point as a final




adjustment to the density of the blended coal, but it is becoming less




common.  Oil reduces dusting during handling.







     Long runs of belt conveyors carry the coal to the silos above the




ovens; the weigh bins below the silos drop the coal into the larry car.




The dust created at this point might be considered fugitive dust or a




housekeeping burden.







     The charging of the ovens is a major point-source of visible emis-




sions.  Several new emission control systems are being investigated.




Barring changes in the mechanical design of the system, control practice




consists primarily of reducing the total time of the charging.  This means




getting the lids back on as soon as possible.  Stand pipes must be closed




off during pushing and before charging to prevent air entering the main.




The oven should be "on the main" before charging is completed.  This sig-




nificantly reduces the emissions from the charging ports and chuck door




                                   -29-

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while they are open.  The sealing of the lids should be complete within




one-half hour after charging.  Some plants pour a mud slurry sealer




around the lids to provide a seal.






     Coal dust should be swept away from the lid before it gets hot and




beings to smoke.  The top of a coke oven is a hot, dirty place to work.






     During the coking cycle, there are two sources of leakage from the




end doors, whether they are the self-sealing or luted type.  The first is




leakage due to doors that are not properly cleaned and adjusted, or be-




cause of excessive warpage of seal strips or jambs.  Improper application




of the luting compound has the same result.  The emissions are a heavy




brown smoke during the first stages of coking and continue as yellowish




smoke for many hours.  The second type of leak is inherent as the positive




seal forms through the accumulation of tars along the mating edges of




the doors and jambs.  This light brown or yellowish smoke will stop .after




about an hour of coking.  Long time emissions are undesirable and prevent-




able.  Light emissions for less than one hour are the best which can be




attained at this time.  The amount of emissions from end door leakage is




heavily dependent on the operating personnel.






     Green coke is the greatest source of emissions during the pushing




operation.  The amount of smoke is directly related to the amount of in-




sufficiently coked coal.  Green coke performs poorly in the blast furnace;




thus it is rarely made deliberately, although in some cases pressure to make




up lost time or provide material ahead of schedule can lead to a decision




to push ahead of the normal  cycle time.  A small reduction in the coking




time can result in a large increase in the amount of emissions.
                                         -30-

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     Operators are sometimes surprised by a green push which is caused

by defective burners or flues.  This is most apt to happen in old deteri-

orating batteries.  Overfilling an oven is another cause of a green push.


     In the by-product recovery section of the plant, odors will be pre-

sent where flushing liquor sumps and tar decanters are sources of both

ammonia and organic odors.


     In newer plants the handling systems for foul water and recovered

chemicals are designed to reduce odorous point sources.  Older plants

face problems with pump and valve seals, leaky gaskets, and occasional

spills.  Maintenance is the most important factor short of total re-

design in controlling organic emissions in by-product plants.


     The steam plume rising from the quenching tower carries dust ranging

from 1/16-inch down to micron sizes into the atmosphere.  This is unavoid-

able with the towers currently being used.  In a few plants, baffles in

the tower contain some of the grit emissions.  In some cases, contaminated

water is disposed of in the quenching process, but this undesirable prac-

tice can result in emissions of ammonia, phenol and other air pollutants.


     At the coke screening station, transfer points and screens have dust

collection systems.  Dusting during coke handling is generally not a

problem.


3.3  Enforcement Procedure

     A visual inspection should be made of the entire plant facilities.

Trace the material flow from receiving the crushed coal in the storage

bin above each battery of ovens to the delivery of coke to the blast fur-

nace.  Also trace the by-product process from the coke ovens to finished

product.
                                  -31-

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     Record the weight of the batch charge, the length of time for the




coking cycle, and the temperature range maintained in the oven.  These




items are controlled and monitored by the plant.  The frequency,  degree




and cause of green pushes are probably not recorded but possibly can be




established by talking to operating personnel.  Observe if good house-




keeping practices are maintained around the charging ports and that lids




are properly seated and sealed to eliminate unnecessary smoking during




coking.






     Inquire if there is an established maintenance program to keep oven




doors in proper adjustment and learn how the doors and jambs are cleaned




of tar deposits and observe the battery during the coking cycle to de-




termine the effectiveness of the door seals.  Compare the amount of leak-




age at the beginning of the cycle to the leakage a few hours later.






     Determine if waste water and/or weak liquors are being fed to the




quench tower sump for disposal by evaporation.  Follow the by-product




recovery system, noting any odor or fume emissions.  Take note of vents




from scrubbers and exhaust fans and inquire if the sulfur content of the




coke-oven gas is checked and recorded.  In some plants hydrogen sulfide




is stripped  from the gas and either converted to sulfuric acid or vented.




Newer processes produce pure sulfur from the  stripped l^S.  Determine




the process  being employed, if any, by  the particular plant and what




form of emissions are being released to the atmosphere.






     Visible emissions are the simplest means for estimating particulate




and control  equipment performance.  The enforcement  official should esti-




mate the percent opacity of dust  control equipment stack plumes and if




in excess of allowable  limits, take appropriate action.




                                   -32-

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     With the sulfur content and volume of coke oven gas used as fuel,
the approximate S0~ emissions can be calculated.  Take note of the ulti-
mate disposition of any sulfur stripped by recovery plants.  Gaseous pro-
ducts, if burned, should be included in the emissions calculation.  Com-
pare with allowable emission levels and take appropriate action.

     Short of changes in plant design, maintenance and housekeeping are
the two factors which affect emissions from coke ovens.  After a few
visits to a plant over a period of months it will be possible to make
a qualitative judgment concerning deteriorating or improved performance.

4.   SINTERING
     This is a major particulate and minor gaseous emission source.
Emissions are mainly a function of control system design and
operations.

4.1  Process Description
     Sintering is the principal in-plant recycling process.  Ore dust,
blast furnace flue dust, turnings and borings, and various otherwise un-
usable materials are converted into a high quality blast furnace feed
material in the sinter plant.  There are about 50 sinter plants in the
United States.

     In the early 1900's, unsized raw ore was used as the principal iron-
bearing raw material in blast furnaces.  Researchers found that higher
production rates were possible if the raw materials were stipped of fines.
Sinter plants were developed to recover the iron in flue dust and ore
fines.

     As the supply of high quality domestic ore dwindled, pelletizing was
developed as a beneficiation method for the available lower grade ores.
                                   -33-

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The size of pellets was held within close limits and blast furnace opera-




tors found that even better production rates were possible.






     Current blast furnace research indicates that sized-sinter (as op-




posed to unsized) is a very good raw material.  Sintering is a flexible




process and some blast furnace raw materials can be added to the sinter




mix with cost savings.  These factors, in combination with the recycling




aspects of the sintering process, indicate that sinter plants will be a




permanent part of an integrated steel plant.






     The sintering process.depicted in Figure 4.1, requires blending of




the iron-bearing materials with flux and solid fuel as a first step.




This mixture is deposited on a bed up to 18 inches deep and 13 feet wide.




This bed is supported on an endless belt of grate-type pallets which




move slowly to carry the raw material through the process.






     The bed of raw materials is leveled before it passes under a com-




bustion zone.  Suction under the grate creates a downflow of air. Com-




bustion in the bed is initiated by a gas-fired heater a few inches above




the top of the sinter.  Coke oven gas is the most common combustion fuel.






     At this point, the top surface of the bed has been ignited.  As the




sinter moves slowly down the sinter line, air is downdrafted through the




bed to maintain combustion, producing a fused, porous material.  At the




discharge end of the sinter line the bed is discharged from the grates




by gravity.  The large chunks are broken by a tooth and comb breaker and




fines are removed by a hot screen for recycling to the feed.






     The hot sinter goes to an air cooler, from which it is belt-conveyed




to screens.  Finished sinter is transported from storage bins to the blast






                                   -34-

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FIGURE 4,1  SINTERING PROCESS
             -35-

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furnace by railroad car.  The sinter mix must contain a carefully blended




amount of carbonaceous material to give the correct combustion temperature




and burning rate.  Coke breeze is the preferred material, with anthracite




coal an alternative.






     A flux, such as limestone, must be included in the mix for fusion of




the burned sinter.  An important new aspect of sintering is the inclusion




of excess limestone in the sinter mix.  Limestone added in the sinter re-




duces this addition at the blast furnace.  Normal limestone rates for




standard sinter plant operation is on the order of 200 Ib/ton while




"high lime" or "superUJuxed" sinter takes up to 700 Ib/ton.






     The feed must be thoroughly blended and of uniform bulk density on




the grate to prevent uneven air distribution.  If hot spots develop, or




if the bed develops holes, the operation is disrupted and poor quality




sinter results.






     Suction under the bed is developed by a high pressure induced draft




fan.  Under the sinter bed are a series of "wind boxes" which exhaust into




a plenum.  The wind box stack gases are the principal air pollution emis-




sion source at the sinter plant.  They contain particulates and a variety




of gases.  About two-thirds of the sulfur in the feed materials is trapped




in the sinter by the flux.  If mill scale, turnings, or other oily feed




materials are used there can be oil in the stack gases.  Nitrogen oxide




concentrations are generally not significant because of the relatively




low combustion temperature.  Typical stack temperatures are about 300 F.






     Cyclones are used upstream of the fan to provide protection from the




highly abrasive sinter dust.  The dust caught by this cyclone becomes part




of the sinter plant feed.




                                  -36-

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     At the discharge end of the sinter machine there is a significant




thermal head.  Dust is created as the sinter falls to and through the




breaker, passes over the hot screen and drops to the pan conveyor.  From




this point in the process the only air pollutant is particulate matter.






     Sinter coolers come in various sizes and shapes.  Some are updraft,




some downdraft, and a few are shaft-type designs.  Depending on the de-




sign and the degree of hot screening, the cooler can be a substantial to




minimal point source of particulate emissions.






     Once cooled, sinter is crushed and screened to appropriate size.




The conveyor transfer points and the screens are all potential sources of




particulate emissions.






4.2  Process Control Operation




     Careful records are kept of raw material mixes and the production




rate, but instrumentation at sinter plants is generally unsophisticated.




Wind box suction is a useful indicator of the stability of the process




but it may not be recorded.






     The maintenance rate is high at sinter plants and they are typically




shut down one shift per week to perform necessary work.






     Air pollution control systems for wind box gases, in addition to the




cyclones mentioned above, are usually precipitators.   Scrubbers or bag-




houses may also be used.   With the process change to  high lime sinter many




plants with precipitators found that efficiency was drastically reduced.




The lime dust altered the resistivity of the particulate matter.






     Scrubbers have problems of high corrosion and erosion as well as




scaling in water lines and a water pollution problem.




                                 -37-

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     Sinter plant wind box air pollution control is a difficult problem




because of process flexibility.  Changes in feed material or process




operation can have a drastic effect on the air pollution control equip-




ment efficiency.






     Control equipment throughout the rest of the process is much more




straightforward.  The design of hoods and ductwork must be adequate to




capture the particulates at the source operations.  Once captured,




collection of the particulate is not difficult.






     At the discharge end of sinter machines the air is hot and the dust




particles may still be glowing red; therefore, glass fabric baghouses




and medium energy wet scrubbers must be used to collect this dust.  Bag-




house problems center around broken bags and scrubber problems,including




plugging of water lines and the erosion of scrubber internals.






     The dust from sinter handling and screening is usually collected by




baghouses.  The dry dust can be directly recycled to the feed of the sin-




ter line.






4.3  Enforcement Procedure




     Emissions from sinter plants consist principally of particulate




matter, with some sulfur dioxide.  Particulate control abatement equip-



ment is used on all plants.






     The objective of sinter plant inspections is to establish compliance




with the particulate and sulfur dioxide emission regulations.  In order




to accomplish the above objectives, the enforcement official needs to




determine:
                                  -38-

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        1.  Current production levels and operating conditions,




        2.  Design production levels and operating conditions,




        3.  Current controlled and uncontrolled particulate and  sulfur




            dioxide emission levels,




        4.  Efficiency and adequacy of emission control equipment at cur-




            rent and design levels.




     Both plant and emission control equipment design capacities and op-




erating conditions can be obtained from design drawings and plans.  These




data should be obtained from the company representative prior to plant




inspection.  Production levels are monitored by the plant operator and




are either recorded in the operator's daily log or are displayed on in-




strument panels.






     Familiarization with the process is a necessary preliminary step.




Walk through the entire process from the mix house to the loadout bins and




become familiar with the process control instrumentation.






     Trace all ducts which are part of the air pollution control system.




Make a record of the type of control equipment used and take special note




of its instrumentation.






     Make a detailed flow chart or obtain one from the plant to better




understand the process.






     Inquire about maintenance and operational problems with the pollution




control systems.  A site visit during a maintenance shutdown would be use-




ful in clarifying any situations which are confusing when the plant is in




operation.






     A precipitator on the wind box gases will have an efficiency which




is sensitive to gas volume, temperature, and particulate composition.



                             -39-

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Establish whether control devices are operated above,  at,  or below design




capacity.






     Since changes in the feed material may drastically affect wind box




emissions, discuss this point with operating personnel.  If the sinter




mix is different from that for which a precipitator was designed, pre-




cipitor efficiency may be adversely affected.






     Visible emissions are the simplest means for estimating particulate




control equipment performance.  The enforcement official should estimate




the percent opacity of dust control equipment stack plumes and if in ex-




cess of allowable limits, take appropriate action.






     Building openings should be observed for evidence of escape of in-




adequately captured process dust.  If noted, determine point(s) of origin




and require corrective -action.






5.   BLAST FURNACE




     The furnace is a minor emission source.  The ancillary operations are




minor sources of particulate and sulfur dioxide emissions.






5.1  Process Operation




     The blast furnace is the primary production unit  in the iron and




steel industry for the conversion of iron-bearing raw materials to high




carbon pig iron, commonly known as hot metal.  This pig iron contains




roughly 4 percent carbon, 0.05 percent sulfur, 1.5 percent silicon, 0.4




percent phosphorous and 1.5 percent manganese.  It is  used almost exclu-




sively as a raw material in steelmaking furnaces where further purifica-




tion and alloying produces steel of the desired composition.  The steel-




making process reduces the concentration of the elements noted above,




which are considered impurities in most steel specifications.  A small




                                   -40-

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quantity of the hot metal produced is cast directly as pig iron.  There




are a few blast furnaces in the United States which produce ferroalloys.






     Ironmaking technology has advanced rapidly in the last fifteen years,




with great attention to the economy of scale attained by larger blast fur-




naces.  Blast furnaces are generally over 100 feet tall and may be 30 feet




or more in hearth diameter.  The blast furnace, Figure 5.1, is roughly




pear-shaped, with the hot metal and slag formed at the hearth.  The blast




furnace uses more air than any other raw material, by weight.  Thermal




economy demands that this air be preheated before it is injected into the




hearth through a series of nozzles calle "tuyeres."






     The metallurgy of the blast furnace involves reducing iron oxides




to elemental iron.  Carbon, added in the form of coke, acts as the re-




ducing agent.  Limestone is added as a flux so that a slag can be formed




for the separation and retention of sulfur, phosphorous and silicon.  Air




is provided to burn the coke to attain the necessary reduction tempera-




tures.  The gases produced during this smelting process consist of about




25 to 30 percent carbon monoxide, water vapor, nitrogen, carbon dioxide




and hydrogen.  The gases also contain particulate matter.  The gas is used




as fuel following the removal of particulate matter.






     Approximately 30 percent of the cleaned blast furnace gases are uti-




lized to preheat the air supplied through the tuyeres, the balance of the




gas is used throughout the steel plant.  It has a low heating value of




about 75 to 100 Btu/cf.  The burners used for blast furnace gas are speci-




ally designed to maintain combustion.  Many of the applications where blast




furnace gas is burned involve heating of chambers containing refractory




bricks; trace amounts of iron-bearing particulate matter can cause






                             -41-

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FIGURE 5,1  BLAST FURNACE
           -42-

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slagging of these refractories.  The slagging problem and the difficulties




in burner maintenance with dirty gas have led to common industry practice




of cleaning the blast furnace gases to a particulate content of less than




0.01 gr/cf in almost all cases, and to as low as 0.001 gr/cf in some new




installations.






     Raw materials are introduced to the blast furnace through a system




of two or three pressure sealing bells at the top of the furnace.  Re-




search has shown that blast furnace production can be increased by opera-




ting the furnace under high positive pressures of approximately 100 in. H_0




as measured at the top of the furnace.  This high top pressure must be




dissipated before the cleaned blast furnace gas is distributed to plant




fuel use; however, high energy venturi scrubbers can accomplish the par-




ticulate removal concurrently with reduction of gas pressure.  In some




plants a combination of wet scrubbers and wet electrostatic precipitators




are used.  High efficiency gas cleaning devices are preceded by an iner-




tial or cyclone dust collector (dust catcher) to collect some of the par-




ticulate matter in the dry state.  This is recycled to the sinter plant.






     As raw materials are introduced at the top of the blast furnace they




fall to the top of the burden of raw materials already in the furnace.




The hottest temperature zone in the blast furnace is at the hearth level,




where the burden is molten.  One operating problem with blast furnaces is




maintaining an even downward flow of the burden toward the hearth.  At




times the burden does not slide downward uniformly because of an arch of




partially melted raw material.  If this arch breaks precipitously or




"slips", the furnace top pressure increases abruptly.  This results in




heavy particulate discharges from the top of a blast furnace as a safety




valve opens to prevent rupturing of furnace components.  Improved control





                                  -43-

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of  furnace operation and improved raw materials have reduced the  frequency


of  these slips to the point where they are now an unusual occurrence.



      The raw materials are delivered to the bell system at the furnace


top by conveyor belts or skip cars.  Particulate emissions from material


handling depend upon the design of the system at any particular plant.



      Hot metal and slag are drawn from the furnace at regular intervals


through separate tap holes at the hearth levels and are directed  through


refractory runners to slag pots or hot metal transfer cars.  A large  shower


of  sparks (Figure 5.2), generally accompanies the opening of a tap hole.


Emissions of sulfur dioxide and particulate matter are inevitable as  the


material passes through the open runners in transit to the receiving  vessels.



      Particulate emissions during hot metal tapping consist of iron  oxide


fumes, manganese fumes, and "kish".  Kish  is a platelet-shaped graphite ma-


terial released as the temperature of the  carbon-saturated hot metal  is re-


duced.  Kish particles tend to be oily and cause a general housekeeping prob-


lem in the tapping area.



      Sulfur emissions released from the slag as its temperature  is re-


duced are mainly in the form of sulfur dioxide, although some hydrogen sul-


fl.de is formed.



      Nearly all of the hot metal produced is used in steelmaking furnaces;


however, minor amounts are consumed by foundries within the steel plant for


the manufacture of heavy castings such as  ingot molds.  At some plants hot


metal is cast into pigs as a finished product.



5.2 Process Control Operations


     Accurate records of furnace top pressure and temperature are kept at


all blast furnaces.
                                         -44-

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FIGURE 5,2  TAPPING
           -45-

-------
     In some plants frequent tests are conducted for the particulate




content of the cleaned blast furnace gas, and if so, these data should




be available.  In other plants records may be kept of the venturi pres-




sure drop and water flow rates.  These serve as an adequate substitute




for frequent measurements of particulate content to monitor the cleanli-




ness of the fuel gas.  The dust content of the cleaned gas is not a ma-




jor factor in the evaluation of air pollutant emissions from blast fur-




naces since process operating upsets (burner fouling and refractory slag-




ging) are so serious that the condition would not be allowed to exist in




an uncorrected state.






     Tapping fumes may escape the cast house as visible emissions (Chapter




7).  The dumping of dust catcher hoppers is another point of potential




particulate emissions.






     Raw material composition and feed rate records, as well as records




of hot metal and slag production, are maintained.  Frequency and duration




of slag and hot metal taps are also recorded.






5.3  Enforcement Procedure




     The blast furnace is a minor contributor to air pollution so that




only a cursory inspection is needed.  The major items to be evaluated




are the adequacy and condition of the dust control systems at the raw ma-




terials handling area, frequency of slips which cause emissions, and dust




catcher dumping.






     A large quantity of process data on raw materials, operating pressures,




temperatures, and production rate are available.  These will be of little




value unless there is an effect on emissions.
                                  -46-

-------
     A change in raw material composition or rate can, in some cases,




cause slips.  The furnace-top pressure charts can be reviewed for "spikes"




to verify the occurrence of slips.




     Visible emissions are the simplest means for estimating particulate




emissions.  The enforcement official should estimate the percent opacity




of these emissions, and if in excess of allowable limits, take appropriate




action.




     Building openings should be observed for evidence of escape of in-




adequately captured process dust, and if noted, determine point(s)  of




origin and require corrective action.




     Inspect the dust catcher during dumping of the dust.  Some plants




have found it necessary to treat the dust before loading it into transfer




cars (going to the sinter plant) because of heavy dusting.




     Slag disposal (Chapter 12) is closely allied with blast furnace op-




eration.  These inspections can logically be made concurrently.






6.   PIGGING OF IRON




     This is a minor potential particulate emission source.






6.1  Process Operation




     The high-carbon pig iron produced by the blast furnace can be cast




directly into "pigs" ranging from 30 to 100 pounds each.  These pigs are




used for small castings in iron foundries and provide carbon additions in




electric furnace or open hearth steelmaking furnaces.




     Hot metal is poured from a transfer car into a small basin located




above one or two endless belts of pig molds, (Figure 6.1).  The line of




molds travels slowly to the head pulley, where the solidified pigs drop




out.  Water-sprays cool the pigs.  On the return (under) side of the end-




less belt the molds are sprayed with a lime water wash, used as a mold





                             -47-

-------
FIGURE 6,1  PIG CASTING MACHINE
                -48-

-------
release.  Iron pigs represent only a small percentage of blast furnace




production.  Where pig casting machines are installed, they are seldom




used for more than a few hours a week to meet product demand.






6.2  Process Control Operation




     The pouring of hot metal generates minor amounts of iron oxide fumes




and the rapid cooling of the hot metal creates kish, causing a local house-




keeping problem.  The water-sprays result in a heavy steam cloud at pig




casting machines.




     The only potential emissions are particulate matter, and this is




slight because of the nature of the process and the low percent utili-




zation of pig machines.  Air pollution control equipment is not used.






6.3  Enforcement Procedure




     Observe the area of the pig casting machine to note the presence of




visible emissions of particulate matter.  If required, take appropriate




action.






7.  IRON CASTING




     This is a minor source of particulate emissions.






7.1  Process Description




     Periodically, the pig iron is tapped from the blast furnace and passed




through runners to submarine-type open-top ladles.  When the molten iron is




released from the blast furnace, kish is emitted due to the rapid cooling




of the carbon-saturated hot metal.  The kish consists of graphite flakes,




and due to its shape and low density can be carried long distances by a




light breeze.  Its  oily tenacity makes it difficult to remove after it has




settled.  Other substances which are emitted during the tapping operation




include manganese oxide and sulfur dioxide.  The particle size of the





                                   -49-

-------
metallic fumes is in the sub-micron range.




     Slag is tapped from the blast furnace and passed through runners to




slag pits or ladles.  Emissions from the slag tapping operation include




sulfur dioxide, hydrogen sulfide, and fine particulate matter consisting




of metallic oxides.






7.2  Process Control Operation




     Very few blast furnace cast houses will have air pollution control




systems.






7.3  Enforcement Procedure




     The enforcement official should make an overall inspection of the




blast furnace from the exterior of the building during the casting opera-




tion as air pollution control devices are not commonly used for casting




operations.




     The process weight can be determined from the production data.




     If pollution control ventilation hoods exist at the tapping location,




over the runners and/or at the ladle filling station, inspection should




be made during tapping.  Such systems should control the fumes.  The



control equipment should be evaluated and operating data obtained.




Personnel and plant safety considerations must also be observed at all




times.




     Visible emissions are the only means for estimating particulate emis-




sions.  The enforcement official should estimate the percent opacity of




the emissions and if in excess of allowable limits, take appropriate action.




     Building openings should be observed for evidence of escape of in-




adequately captured process dust and if noted, determine point(s)  of ori-




gin and require corrective action.






                                   -50-

-------
8.   OPEN HEARTH FURNACE
     This is a major potential particulate emission source.  Emissions
are mainly a function of control system design and operation.

8.1  Process Description
     Steelmaking is the conversion of pig iron, scrap steel, and other
ingredients into specification steel.  The "open hearth" furnace (Figure 8.1)
consists of a large hearth, fully enclosed, that is used to bring the in-
terior temperature to 3000°F.  The furnace is lined with refractory.  An
open hearth is heated with oil, natural gas, tar, or coke oven gas.  The
type of refractory material has little effect on the quantity of emissions
from these installations.  Typical capacities of open hearth furnaces
range from 100 to 400 tons per heat.   The time required to produce a
heat is usually about eight hours.  High purity oxygen can be blown into
the bath to accelerate production.
     The basic raw materials in open hearth steelmaking are hot pig iron
from the blast furnace and steel scrap.  Figure 8.2 indicates the ma-
terials used in the production of one ton of steel in an open hearth fur-
nace using oxygen.  Process variables such as the amount of scrap, hot
metal, fluxes, fuel, etc. are usually recorded on the operators daily log.
These logs are generally kept in the control booth.  Combustion air is
preheated by a checker system (Figure 8.1) located adjacent to the fur-
nace.
     Pollutant emissions include particulates, sulfur dioxide and pos-
sibly fluorides.  Most plants have a waste heat boiler to produce pro-
cess steam.
     The exhaust gases from the furnace pass through the checker system
and waste heat boiler to the air pollution control devide.  Figure 8.3
shows an open hearth furnace with an electrostatic precipitator.
                             -51-

-------
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-52-

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8.2  Process Control Operation




     The most important process control variables which affect air con-




taminant emissions rates are:




       1.  Type of fuel used,




       2.  Oxygen blowing rate,




       3.  Quality of raw material charged.




     Emission level variations from different types of fuel are insignifi-




cant when compared to the increased emissions resulting from oxygen lanc-




ing.  With oxygen lancing, variations in blowing rate (over the normal




ranges found in practice) do not markedly affect particulate emissions.




     Since even an open hearth furnace which does, not use oxygen cannot




meet current particulate emission standards, air pollution evaluations




center on the abatement equipment.




     As production rates at individual furnaces are increased, the system




air volume must also be increased.  This can cause an overload of the con-




trol equipment unless it was designed with over-capacity.




     Production records detailing total production rate, charge composition,




and other information will be available.




     Air pollution control systems will normally serve several furnaces




located in a single open hearth shop.  Precipitators (Figure 8.3) and high-




energy wet scrubbers are in use at open hearth shops.  A stack opacity




meter may be installed.




     As hot metal is received in the open hearth shop it is transferred




to a large holding vessel known as the mixer.  From the mixer, hot metal




is poured into individual ladles for transfer to the furnace. Some emis-




sions of kish and iron oxide fume will be generated.




     When the furnace is tapped, the hot metal and slag are poured into




separate ladles, generating fumes.




                                  -55-

-------
     The molten steel is generally poured or "teemed" directly into ingot




molds in the open hearth shop.   Emissions from teeming are minimal, but




when lead is added to r.he molds, a separate ventilation system and bag-




house are usually operated.







8.3  Enforcement Procedure




     The objective of open hearth shop operation inspections is to estab-




lish compliance with particulate emission regulations.  In order to ac-




complish the above objective, the enforcement official needs to determine:




       1.  Current production levels and operating conditions,




       2.  Design production levels and operating conditions,




       3.  Current controlled and uncontrolled particulate emission levels,




       A.  Efficiency and adequacy of emission control equipment at current




           and design operating levels.




     Emission control equipment design capacities and operating conditions




can be obtained from design drawings and plans.  These data should be ob-




tained from the company representative prior to plant inspection.  Pro-




duction  levels and emission control equipment operating conditions are




monitored by the plant operator and are either recorded in the operator's




daily log or are displayed on instrument panels.




     The shop may have a control booth near the units for monitoring pur-




poses so the enforcement official should have little difficulty assessing




the current operating status of r.he furnaces by observing the many re-




corders, gauges and  logs which  are normally kept.




     For those open  hearth shops which use  electrostatic precipitators  to




reduce atmospheric- emissions, the problem of enforcement becomes one of




maintenance on  the electrostatic precipitators.  Most of the  time  the prob-




lem with precipitators will  be  dead sections  (Part VII discusses the







                                   -56-

-------
                         INSPECTORS WORKSHEET
                           FOR STEEL PLANTS
GENERAL
     Plant Id.
     Date of this Inspection
    _Date  of  last  Inspection
     Type Furnace:  Open Hearth, EOF, Electrical Arc
OPERATING VARIABLES
     Steel Production Rate
     No. of Heats per day
tons/heat
     No. of Furnaces Operating	
     This Heat:  pounds of scrap metal	
     Oxygen Blow	scf/heat
     Total Oxygen Clock Time	min.
     Spar Addition Rate	Ibs/heat
           _, pounds of hot metal
ABATEMENT EQUIPMENT
^\Unit
Parameter\^^ 1234
Particulate
Efficiency (%)
Scrubber Pressure
Drop (in. H20 )
Scrubber Water Flow
Rate f gpm N
^1000 Scfm )
Precipitation
Spark Rate, spm
Primary Voltage
Primary Amps
Flow Rate, (scfm)
Inlet temp, ( F)
Opacity or
Ringleman No.




































Average in
Industry
95+%
60+
5 to 10
50 to 400
20 to 100 kv
1
30,000 to
300,000
300°
0
                             -57-

-------
ACTUAL EMISSION DATA
     Particulates	Ib/ton of Steel Produced    Tested by:_
     Sulfur Dioxide	Ib/ton                    Date:	
     CO	Ib/ton
     Fluorides	Ib/ton

GENERAL OBSERVATIONS
     Plume Capture	
     Scrap and Hot Metal Addition
     Pouring	
     Duct Work
     Age of Control Equipment	years

     Time In                                              Time Out
                                         -58-

-------
impact of dead sections on reducing emissions).   Most steel plants will




keep records on the operation of a precipitator.   Figure 8.4 indicates




the type of report that has been prepared at one  steel manufacturing




plant for the electrostatic precipitators.  If  similar records are not




kept by plant operators, the enforcement official should suggest that




these type of records be kept on a daily basis.




     Visible emissions are the simplest means for estimating particulate




control equipment performance.  The enforcement  official should estimate




the percent opacity of control equipment stack  plumes and if in excess of




allowable limits, take appropriate action.




     Building openings should be observed for evidence of escape of in-




adequately captured process dust and if noted,  determine point(s) of ori-




gin and require corrective action.




     The enforcement official should complete the Inspector's Worksheet




during his visit for future comparisons.






9.   BASIC OXYGEN FURNACE




     This is a major potential particulate emission source.  Emissions are




mainly a function of control system design and  operation.






9.1  Process Description




     Steel is produced by lowering the carbon,  manganese, and silicon




contents of iron by oxidation to levels desired for the type of steel re-




quired.  Impurities such as sulfur and phosphorous are also lowered by




using fluxes of appropriate composition.  Steel scrap, flux, and hot metal




are charged into a furnace lined with refractory material.  The basic oxy-




gen furnace process (BOF) is also known as oxygen-blown steelmaking.  High




purity oxygen (95 percent or better) is blown onto or into the molten




metal bath in the furnace.  There are three basic designs in use:




                                  -59-

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(1) the basic oxygen process, (2) the Stora-Kaldo process, and (3) the




rotor process.




     The EOF process was developed to full scale operations in the early




1950's at Linz-Donawitz, Austria, and is also known as the L-D process.




The basic oxygen furnace is a pear-shaped steel shell, lined with refractory,




in an upright position (Figure 9.1).  The vessel is tilted for charging and




tapping.  Most of the installations in the United States are of this type.




Sixteen steel companies have 34 of the 36 EOF installations in the United




States  (Table 9.1).




     Tie basic EOF process consist of charging, blowing, metal testing,




tapping and slagging.  The charge is generally 25 to 35 percent scrap metal




and 65 to 75 percent molten pig iron.  The scrap is charged first and may




be preheated by the combustion of natural gas introduced into the furnace




by the lance.  Charging is completed by the addition of flux and molten




pig iron.  Blowing is the introduction of oxygen into the molten charge




through the lance.  The amount of oxygen varies slightly and depends on




the quantity of impurities.  The oxygen combines with iron in an exothermic




reaction.  No additional fuel is required.  Blowing is done at sonic vel-




ocity providing sufficient agitation of the molten charge to melt the scrap




and provide good heat contact.  The blowing lasts about 20 minutes, at




which time the steel composition is determined.  Additions and further




blowing are determined by this analysis.  When the desired composition is




reached, the finished steel is tapped into ladles.  Slag is tapped into a




separate ladle.  The complete cycle, called a heat, is then repeated.




     Fumes and gaseous emissions emanate from the mouth of the vessel and




enter a hood during the oxygen blow.  Exhaust gases leave the hood and run




through a series of water sprays before going to an air pollution device.
                                  -61-

-------
                                            Movable or
                                          Combustion Hood
                                            Retractable
                                           Oxygen Lance
                                           Tapping Port
                                            Refractory
                                              Lining
                                            High Purity
                                             Oxygen at
                                          Supersonic Speed
                                              onverter
                                              Vessel
FIGURE 9,1   BASIC  OXYGEN  FURNACE
               -62-

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The temperature of the gases leaving the furnace is several thousand de-




grees and must be cooled before entering any air pollution control de-




vice.  The fumes generally consist of fine reddish brown iron oxide and




carbon monoxide.  For combustion type hoods, the iron is oxidized to




^^2^3 while in shops using a movable hood, the iron is partially oxidized




to FeO.  The iron oxide particulate ranges from 0.01 to 10 microns for




combustion hoods and 0.5 to 30 microns for movable hoods.  Other emissions




from the EOF occur during charging, fluxing, slagging, metal testing, and




tapping.  The vessel is tilted when charged with the scrap and, as a




result, some visible particulate escapes the hood and passes to the roof




monitors.  The vessel is also tilted for charging of the molten iron.




When the iron comes in contact with cool scrap material in the vessel,




iron oxide and kish are emitted.  Visible emissions occur during tapping




and slagging.  The hood over the vessel has little control over emissions




when the vessel is tilted.




     All EOF installations in the United States have air pollution control




systems.  Electrostatic precipitators or high energy venturi scrubbers are




used.




     A movable hood is one that is lowered securely over the mouth of the




vessel during oxygen blowing.  Because this hood is closer to the mouth,




the required inspiration rate and exhaust flow volume are considerably




less than that required for a combustion hood.  The gases are rich in CO.




     The hot gases must be cooled before going to the control equipment.




Most EOF shops will have automatic hood and/or duct water spray systems




which  are activated at certain gas temperatures.  Occasionally, the  spray




system cannot control the temperature so a bypass is placed in the exhaust




stream.  This would allow gases from the vessel to bypass the control de-




vice and be  emitted directly to the atmosphere.  If this occurs, a dense




                                   -64-

-------
reddish brown p^ir.e goes to the atmosphere.  EOF plants will usually have




a slightly visible (less than 20 percent opacity) plume which can be seen




about the time the oxygen lance is lowered and blowing initiated.  A




steam plume can be seen throughout the blow for units with high energy




scrubbers.  A CO flare may be seen at the top of the stack for plants




which employ a movable hood.






9.2  Process Control Operation




     The most important operating variable which affects emission levels




is steel production rate.




     Emissions occur mainly during the oxygen blowing period.  The emis-




sions from the EOF are governed by the oxygen blowing time and the oxygen




blowing rate, major factors determining production rate.  To a lesser de-




gree, the ratio of molten iron to scrap and flux additives will also affect




the quantity of particulate emissions.  Different types of steel will re-




quire different amounts of oxygen.  To produce low carbon steel, the oxy-




gen usage is increased.  Often after the hot metal is analyzed, a reblow,




lasting several minutes, is necessary to achieve the desired structural




properties.




     The reladling station, where hot metal is received and transferred




to BOF shop ladles, is a source of iron oxide and kish emissions.  Many




plants will hood this reladling station and clean the gases.  Baghouses




are normally used as control equipment.  The major problem from the BOF




steelmaking process is particulate matter.  High energy venturi scrubbers




and electrostatic precipitators have been used to reduce particulate emis-




sions from BOF shops.  Generally, the use of electrostatic precipitators




is accompanied with a fixed hood and an inspiration flow rate of about




200,000 cfm.  Depending on the availability of water and the secondary





                                   -65-

-------
treatment that must accompany the water from scrubbers,  high energy ven-




turi units have also been used to clean exhaust gases from the EOF shop.




Both of these types of control systems can reduce or nearly eliminate par-




ticulate emissions from the EOF shop if designed and operated correctly.




     One of the factors which applies to either control  device is the




entering gas temperature.  Cooling is required before the gases enter a




precipitator or a venturi scrubber.  This is usually accomplished with




water sprays.  This gas temperature to the precipitator  is important in




that the BOF dust resistivity is dependent upon that temperature.




     There are several operational control features of an electrostatic




precipitator which are important in cleaning particulate matter (Chapter 5).




In order to attain good removal efficiency, all sections of the precipi-




tator must be operating as designed.




     Venturi scrubbers, Figure 9.2, have fewer operating control variables




than a precipitator.  Pressure drop is the principal variable as some ven-




turi scrubbers may be equipped with variable throats.  Chapter 36 of this




manual discusses some of the important operating variables of various type



scrubbers that could be used in BOF installations.  To a lesser degree,




water flow rate within the scrubber is important.  Most steel plants will




have monitoring systems that will record air flow rate,  pressure drop,




and water flow rate in a scrubber.  The fan house for these scrubbing units




generally have volt meters and ammeters.  Many steel plants will have an




opacity meter on the BOF stack as well as monitors in the duct for CO, HC,




moisture, and temperature.






9.3  Enforcement Procedure




     The  objective  of BOF  shop  operation  inspection  is  to establish, com-



pliance with particulate and carbon monoxide emission regulations.   In





                                   -66-

-------
Iron Oxide Fume,
Particles of Slag. .
and Metallic Shot
                       Large Dia Water Jets
                      With Automatic Reamers
                    and Automatically Controlled
                         Variable Throat
 Water Cooled
Stack and Hood
      Oxygen Furnace
Large Particles of Slag end
Metallic Shot Drain Off
Here With Quencher
Water
                          Bleed Contains 2%
                          Solids, Phis Particles
                           ol Slag and Shot
                                                                                     Clean Qas Discharge
                                                                                       to Atmosphere
                                                                           Spent. Clean
                                                                            Cooling
                                                                           Water Out
                                                                           To Sewer
                                                                                   w
                                                                                  Qw
                                                                                    Fan
                                                                         Make-up Water
                                             Slurry Pump
                                                                                           Slack
                                       To Sludge
                                     Recovery Plant
                                                               Separator
                  FIGURE 9,2    VENTURI  SCRUBBER  FOR  BOF  SHOP
                                                 -67-

-------
order to accomplish the above objectives, the enforcement official needs




to determine:




        1.  Current production levels and operating conditions,




        2.  Design production levels and operating conditions,




        3.  Current controlled and uncontrolled particulate and carbon




            monoxide emissions levels,




        4.  Efficiency and adequacy of emission control equipment at cur-




            rent and design operating levels.




     Emission control equipment design capacities and operating conditions




can be obtained from design drawings and plans.  These data should be ob-




tained from the company representative prior to physical plant inspection.




Production levels and emission control equipment operating conditions are




monitored by the plant operator and are either recorded in the operator's




daily log or are displayed on instrument panels.




     The shop will have a control booth near the units for monitoring.




The enforcement official should have little difficulty assessing the cur-




rent operating status of the vessels by observing the many recorders,




gauges and log sheets which are normally kept.




     Emissions from a EOF installation depend on the operating condition




of the control equipment.  Part VI of this manual provides detailed an-




alyses of the air pollution control devices.




     The enforcement official should observe one complete heat cycle from




tap to tap.   Certain types of operational data should be recorded on the




Inspector's  Worksheet and, if possible, this data should be compared to




other plant  records for other heats to diagnose whether this is any un-




usual heat,  especially with respect to capacity and CL blow rate.  Figure




9.3 is an example of the kinds of operating logs that are normally  kept




at BOF shops.




                                   -68-

-------
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-------
                          INSPECTORS WORKSHEET
                            FOR STEEL PLANTS
GENERAL
     Plant Id.
     Date of this Inspection_
      JDate of last Inspection_
     Type Furnace:  Open Hearth, EOF, Electric Arc
OPERATING VARIABLES
     Steel Production Rate_
     No. of Heats per day	
tons/heat
     No. of Furnaces Operating	
     This Heat:  pounds of scrap metal	
     Oxygen Blow	scf/heat
     Total Oxygen Clock Time	min.
     Spar Addition Rate	
            ,  pounds of hot metal
     Ibs/heat
ABATEMENT EQUIPMENT
Parameter^^11 1234
Particulate
Efficiency (%)
Scrubber Pressure
Drop (in. H20)
Scrubber Water Flow
Rater gpm \
(lOOO scfmy
Precipitation
Spark Rate, (spm)
Primary Voltage
Primary Amps
Flow Rate, (scfm)
Inlet temp, (°F)
Opacity or
Ringlemann No.




































Average in
Industry
95+%
60+
5 to 10
50 to 400
20 to 100 kv
1
30,000 to
300,000
300°
0
                                        -70-

-------
ACTUAL EMISSION_J3ATA




     Parciculates
     Sulfur Dioxide




     CO
     Fluorides
_lb/ton of Steel Produced




 Ib/con




_lb/ton




_lb/ton




        Tested by:	




        Date:
GENERAL OBSERVATIONS
     Plume Capture
     Scrap and Hot Metal Addition_




     Pouring_	




     Duct Work
     Age of Control Equipment
      years
Time In
             Time Out
                                 -72-

-------
     The enforcement official should make a visual inspection of the EOF
vessel with the purpose of assessing the adequacy of the collection sys-
tem.  For movable type hoods it is necessary that the hood come in close
proximity to the mouth of the vessel.  Otherwise dense smoke may emanate
from the vessel and escape the hood, especially during the first part of
the blow.  For fixed hoods, a check should be made to determine whether
or not the inspiration flow rate is adequate.  If any plume escapes the
hood, it may be an indication that the collection system is undersized,
the fans are not operating, there is a leak in the duct work, ducts are
clogged, etc.
     It is not only important that the control equipment be operating
correctly during the inspector's visit, but operating continuously.  The
routine maintenance of control equipment should be verified as for effec-
tive air pollution control, it is mandatory that EOF operators carry out
a regular maintenance program.
     Since air pollution emissions depend primarily on the abatement
equipment, the enforcement official should spend most of his time assess-
ing the operating condition of the air pollution control devices.
     Visible emissions are the simplest means for estimating particulate
control equipment performance and the enforcement official should estimate
the percent opacity of control equipment stack plumes.   If in excess of
allowable limits, take appropriate action.
     Building openings should be observed for evidence of escape of in-
adequately captured process dust and if noted, determine point(s) of
origin and require corrective actions.

10.  ELECTRIC FURNACE
     This is a major potential particulate emission source.  Emissions
are mainly a function of control system design and operation.
                                  -72-

-------
10.1  Process Description




      There are approximately 200 electric arc steelmaking furnaces in




the United States having a combined capacity of about 20 million tons per




year.  The size of furnaces vary from a few tons per heat up to 400 tons




per heat.  These furnaces are refractory lined cylindrical vessels with a




top diameter of up to 22 feet (Figure 10.1).




      The major component of the charge is steel scrap  (Figure 10.2).




Other ingredients charged to the furnace include alloying compounds, fluxes




and coke breeze.  Basically, there are two types of furnaces:  movable roof




(top charging) and fixed roof (door charging).  The top charging furnace




permits more rapid charging of scrap, while the side door charging furnace




provides better fume control and improved refractory life.  An oxygen lance




is used in the electric furnace to increase production rate.  The chemistry




involved in this steelmaking process is the same as that for the open hearth




and the EOF processes.  Electric furnaces derive heat from electrical energy.




The scrap is usually segregated by type for the production of special steels.




Scrap is usually classified as clean or dirty scrap, depending on the rust




and combustible content.  More particulate emissions occur with the dirty




scrap than the clean scrap.




      Scrap may be preheated prior to charging into the furnace.  Melt time




is reduced with heated scrap.  Emissions from scrap preheaters are not gen-




erally controlled by air pollution control systems.




      The scrap is charged to the furnace using an overhead crane.  Visible




emissions are generated during charging.  In terms of emissions, the type




of scrap charged is quite important.  The inclusion of large quantities of




low boiling point non-ferrous metallic impurities will lead to high par-




ticulate concentration." in the fume.  Oil and grease on the scrap will burn






                                   -73-

-------
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-75-

-------
off at relatively low temperatures and result in significant amounts of




carbonaceous particulate matter.  Most of the fume generated during the




melt cycle is FeJ),,.  Other significant fume constituents include oxides




of the alloys and deoxidizers.  The dust is reddish-orange in color.






10.2  Process Control Operation




      The process variables which affect emissions are:




         1.  Quality of the scrap,




         2.  Oxygen lancing,




         3.  Steel production rate.




The highest emissions will be encountered when dirty scrap is used.  Oxy-




gen lancing reduces heat time and increases particulate emissions.  The




weight of material charged to the furnace (process weight) is recorded




in the operator's daily log.




      For the relatively few fixed roof electric furnaces, emission con-




trol is accomplished by evacuation of the furnace shell.  Tapping will




cause some emissions which may be hooded and exhausted to the dust col-




lector.




      For the movable roof furnaces, the most common type, capture of




charging fumes presents a major engineering control task.  Several elec-




tric furnace shops have totally enclosed the building and evacuate to




dust collectors through the roof monitor.  While air volumes are large,




this approach captures fumes from tapping, charging and any other particu-




late -generating operations in the shop.




      In many cases there will be some type of evacuation of fumes from




the furnace shell during the melt.  One system is shown in Figure 10.3.




      Baghouses, electrostatic precipitators and high energy wet scrubbers




have been used at electric furnaces.  Particulate emissions range from







                                  -76-

-------
0)
in
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                                 =D
                                 C-D
   -77-

-------
10 to 40 pounds per ton, depending principally on the cleanliness of the



scrap.



     An operating variable which affects air pollution control equipment



is the inlet temperature to the abatement unit.   The gases leave the fur-



nace at an elevated temperature and are cooled either through heat ex-



changers, air dilution or water sprays.  Most baghouses will have a by-



pass system to prevent hot gases from destroying the bags.  The most com-



mon bag fabric used in electric arc furnace installations are made of


       (R)
DacronS' Other synthetic fibers have also been used.  Fabric bags are



not common because fluorspar, when used as a flux, generates fluoride



gases which may deteriorate the bags.  Electrostatic precipitators are



uncommon at electric arc furnaces.  Dust resistivity is unfavorable and



the varying gas volume is difficult to handle.





10.3 Enforcement Procedure



     The objective of electric steel shop operation inspections is to



establish compliance with particulate emission regulations.  In order to



accomplish the above objectives, the enforcement official needs to de-



termine :



     1.  Current production levels and operating conditions,



     2.  Design production levels and operating conditions,



     3.  Current controlled and uncontrolled particulate emission



         levels,



     4.  Efficiency and adequacy of emission control equipment at



         current and design operating levels.



     Emission  control equipment design capacities and operating conditions



can be obtained from design drawings and plans.  These data should be ob-



tained from the company representative prior to plant inspection.



                                   -78-

-------
Production levels and emission control equipment operating conditions are




monitored by the plant operator and are either recorded in the operator's




daily log or are displayed on instrument panels.




     The shop may have a control booth near the units for monitoring.




The enforcement official should have little difficulty assessing the cur-




rent operating status of the furnaces by observing the many recorders,




gauges and logs which are normally kept.




     The enforcement official should observe the electric furnace during




charging, oxygen lancing and pouring.  During oxygen blowing, air pollu-




tion emissions are expected to be the highest.  If the control system in-




cluding the ducts and hoods have been adequately designed, no plume should




escape the hood.  For those plants which capture fumes at the roof monitor




there should be no visible emissions from the building.  The capture sys-




tem is the most important aspect of controlling air pollution from the




electric arc steelmaking process.




     The enforcement official should complete the Inspectors  Worksheet  for




electric furnaces as the data on that sheet can be used as a comparison




of the operating variables from inspection to inspection.   As usual, the




enforcement official should verify that the ducts, fans, and abatement




equipment are maintained regularly and are functioning properly.




     Visible emissions are the simplest means for estimating particulate




control equipment performance.  The enforcement officer should estimate




the percent opacity of control equipment stack plumes and, if in excess




of allowable limits, take appropriate action.




     Building openings should be observed for evidence of escape of in-




adequately captured process dust and, if noted, determine  point(s)  of




origin and require corrective action.
                                 -79-

-------
                           INSPECTORS WORKSHEET
                             FOR STEEL PLANTS
GENERAL
     Plant Id.
     Date of this Inspection
      _Date of last Inspection
     Type Furnace:   Open Hearth, EOF, Electric Arc_

OPERATING VARIABLES
     Steel Production Rate
     No. of Heats per day	
tons/heat
     No. of Furnaces Operating_
     This Heat:   pounds of scrap metal	
     Oxygen Blow	scf/heat
     Total Oxygen Clock Time	min.
     Spar Addition Rate	Ibs/heat
          _, pounds of hot metal
ABATEMENT EQUIPMENT
Parameter^^^ 1234
Particulate
Efficiency (%)
Scrubber Pressure
Drop (in. HO)
Scrubber Water Flow
Ratef gpm "\
V/1000 scfm )
Precipitation
Spark Rate, (spm)
Primary Voltage
Primary Amps
Flow Rate, (scfm)
Inlet temp, (°F)
Opacity or
Ringlemann No.




































Average in
Indus try
95+%
60+
5 to 10
50 to 400
20 to 100 kv
1
30,000 to
300,000
300°
0
                                           -80-

-------
ACTUAL EMISSION DATA




     Particulates	Ib/ton of Steel Produced




     Sulfur dioxide	Ib/ton




     Carbon monoxide	Ib/ton




     Fluorides	Ib/ton




                                          Tested by:	




                                          Date:
GENERAL OBSERVATIONS
     Plume Capture
     Scrap and Hot Metal Addition_




     Pour ing	
     Duct Work
     Age of Control Equipment	years






Time In                                        Time out
                                   -81-

-------
11.   STEEL SHAPING AND FINISHING




      In general, emission potential from these operations is minimal in




comparison to other steel plant operations.






11.1  Process Description




      Following the refining operation at the steelmaking furnaces the




steel is converted to semi-finished shapes before manufacturing into fin-




ished products.  The two principal methods of converting the molten steel




into semi-finished products are ingot casting followed by rolling, and




continuous casting.




      The major portion of the steel produced in this country is teemed




(poured) into large cast iron molds (Figure 11.1).  Upon solidification




these steel castings are called "ingots".  After removal from,the molds




the ingots are placed in furnaces called "soaking pits" (Figure 11.2).




The soaking pit heats the ingot to a uniform temperature to facilitate




rolling.  The hot ingots are then transported to the roughing mill (Figure




11.3), where they are rolled into billets, blooms, or slabs for subsequent




processing into finished products.  Billets are normally 2 to 5 inches




square while blooms are square or slightly oblong shapes 6 to 12 inches




on a side.  Slabs are oblong, generally between 2 and 9 inches thick and




24 to 60 inches wide.  All the shapes have rounded corners and dimensions




are approximate.




      Continuous casting of steel is a relatively new process that elimi-




nates much of the handling necessary in ingot casting.  In continuous




casting (Figure 11.4), the molten steel is transported from the furnace




in a ladle and poured into a water-cooled bottomless mold.  The metal




cools quickly to the shape of the mold and the solidified steel is extrac-




ted from the bottom of the mold continuously in one or several strands.






                                  -82-

-------
FIGURE 11.1  TEEMING OF INGOTS
 FIGURE 11,2  SOAKING PITS
          -83-

-------
FIGURE 11,3  ROUGHING MILL
              -84-

-------
Traveling
 Torch
Cut-Off
           Reheat
Sizing Mill  Furnace
   \          \ ._
                                             Mold
                                           Discharge-
                                             Rack

                                            Vertical
                                           Guide-Roll
                                             Rack
                          Water
                      a    .Spray
                      %/Headers
                      I  /
   Pinch Rolls—^i
    Bending Clusterijj]j2~
          Curved
        Guide Rack
   Slab
Straightener
   i
                        O O O U U O U"
          FIGURE 11,4  CONTINUOUS  CASTING
The cast bar is cut to a predetermined length  for  further  processing.

Continuous casting machines can produce billets, blooms, or  slabs depend-

ing on the final products of the plant.

     Prior to forming into final shapes, the billets,  blooms,  and slabs

are gound, chipped or scarfed to remove surface defects.   Grinding and

chipping are hand operations.  Scarfing removes surface defects by burning.

It can be either a hand or machine operation.   In  hand scarfing the defect

is spot-heated by a fuel-oxygen torch, speeded by  use  of a starting rod.
                                  -85-

-------
              FIGURE  11,5   HOT SCARFING MACHINE
Once the reaction has started,  the  heat of oxidation is sufficient to con-




tinue the reaction so fuel is no  longer needed.  Mechanical scarfing uses




rows of torches to burn all the surfaces  of  the steel slab as it passes




through the machine.   The scarfer (Figure 11.5), is usually directly in




the mill line so that the steel is  at  a sufficiently high temperature to




eliminate the need for starting rods.  The hot scarfing machine removes a




thin layer (one-eighth or less) of  metal.




     After conditioning, the billets,  blooms, or slabs are soaked  (heated)




in reheat furnaces.  When the  required uniform temperature is reached, the




semi-finished products are taken  to the hot  rolling mills where they are
                                  -86-

-------
processed into rods, bars, angles, pipe, channels, plate, sheet, or




strip.  These are finished products in most cases.




     Sheet and strip steel can be further processed by cold rolling.




A pickling operation is the first step in this process.  Sulfuric or




hydrochloric acid treatment cleans the oxidized surface formed during




the hot rolling.  The steel can be bath-dipped or passed continuously




through this bath.




     Annealing of sheet or strip is a heat treating operation to




improve the strength characteristics of the steel.  This is accom-




plished in either a batch or continuous furnace.  In the batch opera-




tion the coiled steel is enclosed in a removable shell.  The shell




is heated by combustion gases while an inert or protective atmosphere




inside the shell prevents oxidation of the steel coil.  In the con-




tinuous process the steel passes through an annealing furnace.  The




heating, holding, and cooling sections of the furnace have a controlled




atmosphere to prevent oxidation.




     The final step in the production of a small percentage of the steel




industry's products is surface coating.  These coatings include zinc,




tin, terne (lead alloy), aluminum, chromium, nickel, copper, phosphate




and a broad spectrum of paints and other organic materials.  Prior to




coating, the continuous strip is cleaned with a hot alkaline solution




or heated to remove grease or oil films.  The lightly oxidized sur-




face then is acid-cleaned or annealed.




     Zinc, aluminum, and terne coat are applied by a dip coating pro-




cess.  The preheated strip is treated with a flux or passed through




a flux layer on top of the metal bath.  Electrolytic processes can be
                                   -87-

-------
employed to surface-coat the steel with zinc,  chromium, nickel, or copper.




In this operation, clean strip enters directly into the particular plat-




ing bath.  Another process for coating with chromium or nickel involves




coating the steel with a chemical solution of  the desired material.  The




solution coating is then reduced in a hydrogen atmosphere to produce the




final metal coating.




     Phosphate coatings are accomplished by dipping the steel in a dilute




acid-phosphate solution which is saturated with a metal such as zinc,




cadmium, aluminum, or lead.  This results in the metal surface being




converted into an insoluble crystalline phosphate coating.




     An electrocoating (electrophoretic deposition) process is one method




employed to apply paint to the steel surface.   This is accomplished in




either a dip tank or by roller coating.  An electrical charge is applied




to a solution of paint in water which causes the paint resins to move




to the oppositely charged steel immersed in the solution.  After washing,




the paint coating is baked.  Spray or dip coating with solvent-based




paints is more common than electrocoating.






11.2 Process Control Operation






     Minor amounts  of iron oxide fume are generated when  the molten steel




is poured into the  ingot molds.  The coating applied  to the inner  sur-




 faces  of  the  ingot  mold  to  reduce  surface  imperfections of  the  steel




casting  is  the primary  source  of  emissions.   One  general  type  of  mold




coating  is  nonvolatile,  relying  on surface  texture  to accomplish  the




desired  surface  improvement.   The  other general  type  of coating relies
                                  -88-

-------
on volatilization to shield against metal splashing.   This type includes




coal-tar products and petroleum derivatives resulting in carbonaceous




gas emissions.




     Pouring is done in a large area of the shop floor and emission




controls are normally not used.  In some cases where free-machining




steel is being produced, lead is added to the steel during pouring




resulting in the generation of lead oxide fumes.  Where leaded steel




is produced, ventilation systems for fume collection are usually pro-




vided because lead fumes present a potential employee health hazard.




     Emissions generated during the pouring of ingots varies at each




plant depending on the particular practice.  Visible amounts of par-




ticulate emissions range from light to heavy.  Where entire furnace




shops are ventilated through the roof monitor, as in some electric




furnace shops, emissions may be controlled by a baghouse.




     Emissions during continuous casting are markedly lower than when




teeming ingot molds.  Continuous casting is done at a single location




as opposed to the large area necessary for ingots.  This allows for




the efficient use of a localized fume-collecting system.  The pouring




tundish may be enveloped with a reducing gas to minimize oxidation




of the steel.  Mold lubricants are used to prevent seizure and re-




sult in a small amount of smoke.  Some operations use torch cut-off




machines which generate minor to moderate amounts of iron oxide par-




ticulates, depending on the amount of material cut.  Where shears




are used there are no air pollutant emissions.
                                  -89-

-------
     Hand grinding, chipping, and scarfing result in small amounts of




localized particulate emissions.   Usually no emission controls are utili-




zed except where shop practice calls for extensive amounts of grinding




or hand scarfing and then collection hoods might be used.   Particulate




emissions from machine scarfing are substantial and usually are controlled




with electrostatic precipitators or high energy scrubbers.  About 50 per-




cent of all hot rolled steel is surface conditioned by machine scarfing.




Emissions are iron oxide fumes and would present a visible emission




source if a control system were not employed.




     Emissions from soaking pits or reheat furnaces are the normal pro-




ducst of combustion.  The furnaces are often fired with relatively clean




blast furnace gas.  In some cases natural gas or oil are used as the fuel.




Carbon dioxide, trace quantities of carbon monoxide, and low concentra-




tions of nitrogen oxides are present as in all combustion products.  If




any sulfur is present in the fuel, sulfur dioxide emissions will also




be present.  Induction heating of the steel billets, blooms, or slabs



is used.




     The iron oxide scale formed on the steel during reheating is broken



off by high pressure water sprays as the steel enters the first rolling




stand.  Some quantities of fine iron oxide are generated at the strip




finishing stands.  At some mills these emissions are collected and con-




trolled with high-energy scrubbers.




     The major potential emissions from cold working and surface treating




are from cleaning operations which prepare the surface of hot rolled strip




for cold rolling.  The pickling operation provides the metal with a clean




surface for cold rolling.  A sulfuric or hydrochloric acid bath is maintained




                                   -90-

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in the pickling tank.  The tanks are generally hooded and exhausted to a




fume control system.  Wet scrubbers or packed towers are used to remove




acid mist from the exhaust air.  In some cases where only small quantities




of steel are pickled, the exhaust may be vented directly to the atmosphere.




     Cold rolling is accomplished by high speed rolls.  Emissions from




this operation consist of small amounts of water-oil mist which is gen-




erated by the roll lubricant.  Mechanical mist eliminators or wet scrub-




bers are used to collect these emissions.




     Surface coating of steel for protection and appearance is tending




toward continuous-line operation for economic reasons.  Emission controls




are also easier to apply to continuous lines.  Prior to galvanizing, cold




rolled steel is heat-treated.  The galvanizing pot is covered with a flux




which generates some emissions as the steel passes through it.  This flux




may be ammonium chloride or zinc ammonium chloride.  Particulate emissions




tend to agglomerate, causing gum in the ductwork.  Control of these emis-




sions is accomplished by a baghouse or wet scrubber.




     Coating installations for the application of other metals, paints




and plastics are essentially the same as already discussed.




     Vapors from electroplating baths are collected by hoods and treated




like the acid vapors from pickling.




     Solvent vapors are emitted from painting operations.  These are gen-




erally collected in an exhaust system and in most cases vented to the




atmosphere outside the plant building.  Some of the vapors evolved during




the baking of painted surfaces are combusted in direct-fired ovens.  The




remainder are vented.






11.3 Enforcement Procedure




     The objective of steel-shaping and finishing operation inspection




is principally to establish compliance with particulate emission regulations.



                                   -91-

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In order to accomplish the above objective,  the enforcement  official needs




to determine:




     1.  Current production levels and operating conditions,




     2.  Design production levels and operating conditions,




     3.  Current controlled and uncontrolled emissions levels,




     4.  Efficiency and adequacy of emission control equipment  at




         current and design operating levels.




     Emission control equipment design capacities and operating conditions




can be obtained from design drawings and plans.  These data should be ob-




tained from the company representative prior to physical plant  inspection.




Production levels, feed weight rates and emission control equipment oper-




ating conditions are monitored by the plant operator and are either re-




corded in the operator's daily log or are displayed on instrument panels.




     Become familiar with the processes and where the control equipment




is applied and make a visual inspection of the complete process.  Follow




the flow of material from casting to final product for each of the plant's




product lines.  Become familiar with the process operation at each station.




While following the product flow, points of visible emissions should be




noted and, if possible, identified.  Check control equipment locations




against the points of observed emissions to determine if any controls are




not operating or are only partially effective.




     Observe all collection hoods, especially at the hot scarfing machine,




to determine if the collection rate is sufficient to capture the generated




emissions.  If  a significant amount of dust  is escaping it  is an indication




of an  inefficiently operating or  under-designed  collection  system.   Take




special notice  of  the collection  hoods at the pickling tank and note any




escaping fume or badly corroded ducts allowing fume  leakage.






                                    -92-

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     Visible emissions are the simplest means for estimating particulate




control equipment performance.  The enforcement official should estimate




the percent opacity of control equipment stack plumes and, if in excess




of allowable limits, take appropriate action.




     Building openings should be observed for evidence of escape of in-




adequately captured process dust and if noted, determine point(s) of




origin and require corrective action.






12.  SLAG




     Hydrogen sulfide and particulate emissions are possible.  Hydrogen




sulfide is the principal pollutant.






12.1 Process Description




     Slag is a by-product of the blast furnace and the steelmaking pro-




cesses.  The quantitites, properties, and end uses of these two types of




slag are quite different.  Blast furnace or iron slag is the dominant




factor, accounting for 24.8 million of the 33.3 million tons of slag




produced in the United States in 1971.




     The two air pollution factors to be considered in slag processing




are dust and sulfur gases.  Blast furnace slag has an average sulfur con-




tent of about 1.8 percent, while steel slag averages about 0.1 percent



sulfur.  Table 12.1 shows a gross sulfur balance for the steel industry




based on 1967 data, and puts the importance of slag as a sulfur disposal



point in the steelmaking process in perspective.




     The combined chemical form of the sulfur in cold blast furnace slag




is permanently bound in non-reative forms.  Sulfur emissions from slag




are associated with the processes used to cool the slag from its original




temperature of about 2,700°F.
                                   -93-

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      Table 12.1 ANNUAL U. S. STEEL INDUSTRY SULFUR BALANCE (1967)


Sulfur In
Coal to:    Coke Oven Gas                                    196,000
           Coke                                             455,000
           Coke Plant (Other)                                69,000
                                                            720,000
Fuel Oil                                                     90,000
Ore                                                          93,000
Scrap                                                        20,000
Fluxes                                                       21,000
Other                                                        11,000
                                                            955,000
Sulfur Out
Blast Furnace Slag                                          518,000
Steel and Scrap                                              39,000
Steel Slag                                                   14*,000
Fuels                                                       374,000
Other                                                        10,000
                                                            955,000 Tons

     There are three types of slag, each manufactured by a different pro-
cess.  These are air cooled, granulated, and expanded slag.  Granulated
and expanded slag are produced only from blast furnace slag.  All steel
slag is air cooled.

12.1.1  Air Cooling
        Air cooling of blast furnace slag accounts for two-thirds of the
total slag production.  It is the single most important individual process.

                                    -94-

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Molten slag is poured into pits or diked areas to solidify.  Once cooled,




it is removed by power machinery.  The slag can be sold as is, or it can




be crushed and screened to desired aggregate sizes.




     While some steel plants operate their own slag plant, it is common




for the molten slag to be sold to an independent operator whose facility




is usually located on steel plant property.  The supply of molten slag is




controlled by the steel plant as blast furnace or steel furnace production




is paramount.  The slag plant gets slag as it is produced.  Slag ladles




are transported by a plant-operated railroad system to a slag processing




area some distance from the furnace.  Delays in transit cause freezing of




a "skull" of slag on the sides and surface of the ladle, making it difficult




to remove the slag; therefore, if the supply of slag ladles at the furnaces




is short, slag plant operators will have to pour rapidly to prevent delays




at the furnaces.




     Because of limited space and time, water sprays may have to be ap-




plied to partially cooled slag to accelerate cooling.






12.1.2  Granulated Slag




        When molten slag is poured into direct contact with large quan-




tities of water, the result is a glassy, granular material with a lower




bulk density than air-cooled slag.  The jet process uses high-pressure




water jets to break up the molten slag stream before it reaches the pit.




Jet-granulated slag has a finer size gradation than pit-granulated slag.






12.1.3  Expanded Slag




        The ASTM definition of expanded slag is:  "the light-weight cellu-




lar material obtained by controlled processing of blast furnace slag with




water, or with water and other agents such as steam or compressed air, or




both."  More processes will be encountered in expanded slag plants than in




                                  -95-

-------
air cooled or granulated slag plants because of the mechanical process




variations which are possible.




        The amount of water, or less commonly air or steam, used to expand




the molten slag is carefully controlled to provide expansion but prevent




granulation.  The pit is not flooded with water.






12.2    Process Control Operations






12,2.1  Sulfur Gas Emissions




        As slag cools from the molten state some sulfur is released.  When




the slag is dry and atmospheric humidity is low, most of these emissions




are in the form of sulfur dioxide.  As moisture increases, either in direct




contact with the cooling slag or as' high ambient humidity, the reactions




change and hydrogen sulfide can become the principal form of sulfur gas




emissions.




        The rate of cooling and the presence of moisture are both factors




in the quantity of these emissions.  Total emissions will be at their low-




est with a long cooling time  in the absence of moisture.  Accelerated cool-




ing in the presence of moisture maximizes both the total quantity and the




concentration of sulfur gas emissions.




        On this basis, the  granulation process represents the least desirable




and air cooling the most desirable slag process from the standpoint of sul-




fur emissions.  This  is true  with some exceptions.  If air cooling  is prac-




ticed where substantial water spraying is necessary, total emissions could




be nearly as great as with  granulation.




        Even though  sulfur  gas emissions are a very small percentage of  the




total sulfur burden  of  the  slag,  they can present  a localized air pollution




problem.  Both  the American Iron  and Steel  Institute and  the National Slag






                                    -96-

-------
Association have researched possible solutions to emission reduction.
Results to date are not encouraging.  The best recommendations to operators
are to extend cooling time and minimize water contact.

12.2.2  Particulate Emissions
        The operations of expansion, granulation, pit digging, magnetic
iron recovery, crushing, screening, and handling at various transfer points
all present potential particulate emissions.  Slag forms dust rather than
fine fume.
        Most plants use water sprays as their primary dust control measure.
Baghouses have been used and then abandoned because the dust cakes and
blinds the bags.  Some wet scrubbers are used, but the highly abrasive
nature of slag dust reduces the life of the scrubbers.
        Water use in pit digging varies.  Hot spots require a lot of water
to cool the slag to protect the processing equipment.  Water should be
sprayed in small streams over a large area rather than deluging a single
spot.  There is a tradeoff required when digging hot slag.  Water mini-
mizes dusting but increases sulfur emissions.
        Loading and hauling practices are important in terms of particulate
emissions as the height of the drop of material during loading will affect
dusting.  Front-end loader operators have a great deal of control over this
step.  Trucks should not be overloaded, preventing spillage on the road-
ways.  Dust from coarse screened material will not blow much in transit,
but water spraying of fines or mixed grades of slag is desirable to re-
duce blowing dust.

12.3    Enforcement Procedure
        First, determine whether the slag processing plant is owned and/or
operated by the steel producer or a private firm.
                                 -97-

-------
        For air cooled slag,   observe the operating practices.   Thin pouring




is preferred since it discourages hot spots which must be sprayed heavily




on digging, increasing sulfur emissions.




        Walk through the crushing, screening,  and shipping areas to observe




the use of water spray dust control.




        Granulation plants produce a large plume as the hot slag is poured




into the pit.  Particulates and the odors of sulfur dioxide and hydrogen




sulfide will be noted in this plume.




        Expanded slag plants are similar to granulation plants in that the




emissions occur during the expansion step.




        Slag processing plants have some control over particulate emissions;




air cooled plants have limited operational control over water spraying and




pit digging schedules, which are related to sulfur gas emissions; and granu-




lation and expansion plants, by their design,  have very little control over




their sulfur gas emissions.




        Hydrogen sulfide is the major cause of complaints and control is dif-




ficult.




        The stepwise enforcement procedure, which follows, outlines general




observations which can be made at slag plants.




        1.  Trace the flow of raw materials from the time it arrives at the




            plant until it leaves.




        2.  From a distance, observe the raw material and processed ma-




            terials for dust clouds either from roadways, stock piles,




            transfer points, crushers, or screening operations.  These




            sources are generally not continuous emitters, but are depen-




            dent on the individual activity schedule.




        3.  Make records of the probable dusty areas for a close-up in-




            spection.  These observations should be made from beyond the



                                   -98-

-------
            plant perimeter on a hillside overlooking the entire complex,




            if possible, over a period of several hours.




        4.  Observe the material stock piles when the wind is blowing and




            note any entrained dust.




        5.  Observe the methods of moving material at the stockpile.




        6.  Note dust emissions at the loading stations.




        7.  If cranes, belts or bulldozers are used to move the materials,




            note any major dust clouds.




        8.  Make notes on the lengths and locations of unpaved roadways.




            Ask what frequency these roadways receive dust preventive




            treatment such as water, oil, or calcium chloride.  Observe




            the traffic on these roadways, and note whether or not a sig-




            nificant cloud is generated by vehicular movement.  Observe




            the paved, macadamized, and gravel roads for  latent dust.




            Occasionally these roads may become burdened  with dust and




            result in another source of fugitive dust.




        9.  Observe the transfer points along belt haulage ways.  If  no




            dust is noted, no further inspection is required here.




        Interpretation of these observations is heavily dependent upon the




pertinent regulations governing fugitive dust emissions.   Since many of




these plants are located on large plots of land, it is important to dis-




criminate between in-plant housekeeping problems and emissions which cross




the property line.  If fugitive dust violations are apparent, take appro-




priate action.
                                  -99-

-------

-------
                             BIBLIOGRAPHY
Oglesby, Sabert, Jr., A Manual of Electrostatic Precipitator Technology,
     Part I., The National Air Pollution Control Administration, 1970.

Schueneman, Jean J., Air Pollution Aspects of the Iron and Steel Industry,
     U. S. Department of Health, Education and Welfare, 1963.

Xavier, J. A., Survey of Air Pollution from the Kaiser Steel Plant,
     State of California Air Resources Board, 1971.

Air Pollution Manual, Part II, Control Equipment,  American Industrial
     Hygiene Association, Detroit, Michigan, 1968.

The Making, Shaping and Treating of Steel,  United States Steel
     Corporation, 1971.

Varga, J., et. al., A Systems Study of the Integrated Iron and Steel
     Industry.  Battelle Memorial Institute, 1969.

Barnes, T. M., et. al., Evaluation of Process Alternatives to Improve
     Control of Air Pollution from Production of Coke.  Battelle Memorial
     Institute, 1970.

Gowland, William, The Metallurgy of the Non-Ferrous Metals, Charles
     Griffin and Company, Strand, W. C., 1921.

Stern, Arthur, Air Pollution,  Academic Press, New York; London, 1968.

Edwards, J. D., Aluminum and Its Production,  McGraw-Hill, New York;
     London,  1930.

Cook, C. C.,  Evolution of Fluoride Recovery Processes ALCOA Smelters,
     Aluminum Company of America, Pittsburgh, Pennsylvania.

Rossano, A. T., Recent Developments in the Control of Air Pollution from
     Primary Aluminum Smelters in the United States,  Second International
     Union of Air Pollution Prevention Association, Washington, D. C.,
     1970.

First, M. W., Field Evaluation of Web Fiber Filters for the Treatment of
     Air Contaminants,  Journal of the Air Pollution Control Association,
     May 1956.

Bohlen, Dr. B., Fluorine Emissions at Aluminum Works, The Chemical
     Engineer, September, 1968.

Shreve, R. Norris, Chemical Process Industries,  McGraw-Hill, New York,
     1967.

Ott, Ronald R., Control of Fluoride Emission at Harvey Aluminum, Inc.-
     Soderberg Process Aluminum Reduction Mill, Presented at the 29th
     Annual Pacific Northwest Pollution Control Association Meeting, 1962.

                                  -101-

-------
Hayward, Carle R.,  An Outline of Metallurgical Practice,   D.  Van Nostrand
     Company, Inc., New York.

Singmaster & Breyer, Air Pollution Control in the Primary Aluminum Industry,
     VI, October,  1971.

Cook, Swany, and Colpitts, Operating Experience with the Alcoa 398 Process
     for Fluoride Recovery,  paper presented at Annual Meeting of the
     Pacific Northwest International Section APCA, November,  1970
                                  -102-

-------
          PART  II.  PRIMARY ALUMINUM INDUSTRY



     The annual production of aluminum  in the United States, amounting to

over 45 percent of the world total,  is  increasing.  In 1972, approximately

5.1 million tons  of the metal were produced, an increase of nearly 40 per-

cent since 1968.   It has been predicted that by 1984 the production of

aluminum will triple.   One reason for the increased production is the

improving technology that  allows for lower prices and better products.

In 1854, the metal sold for $100 per pound.  By 1898, the price had

plummeted to $0.31 per pound, and in 1968, the price was $0.25 per pound.

A major reason for aluminum's use is its remarkable physical character-

istics.  The metal is  light, strong, an excellent conductor of heat and

electricity, corrosion resistant, highly reflective, has low toxicity,

and is easy to cut, mold,  extrude, machine, or polish.


     In 1972, there were 31 primary  aluminum smelters, operated by 13
                                                         <
companies in the  United States.  Their  capacities ranged from 35,OOC

tons per year to  275,000 tons per year.  These plants are listed in

Table II-l.


     Aluminum is  abundant,  making up one-twelfth of the eartbjs crust.

Bauxite, a hydrated oxide  of aluminum,  is the main ore resource for alum-

inum production.   Most of  the ore is mined abroad.  Jamaica is the largest

free-world producer of the crude ore.   Other sources are Surinam, France,

Guyana, and the United States.
                                -103-

-------











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     In 1967, bauxite usage was 13.1 million tons of imported and 1.8 mil-




lion tons of native bauxite.  Domestic sources are located in Arkansas and




Alabama.






     Alumina (Al^O,,) is produced from bauxite by refining, extracting, and




calcining the crude ore.  The bauxite is dried and then ground in ball




mills.  A sodium hydroxide solution is added, forming an aluminum hydroxide




precipitate which is later calcined to form alumina.






     Primary aluminum metal is extracted from the oxide by means of the




Hall-Heroult electrolytic process.  The alumina is dissolved in a fused




bath of sodium aluminum fluoride (cryolite) in carbon-lined pots, which




serve as the cathode.  Carbon anodes are immersed in the bath to make the




electrical contact.  The alumina is electrolytically reduced to aluminum




and oxygen.  Ninety to 240 cells are connected electrically in series to




form a potline.  Figure II-l illustrates the operations required to pro-




duce aluminum from alumina.






     Approximately  7.5 kwh of dc current is  consumed per pound of alu-




minum metal produced.  Table II-2 contains this information and other




facts concerning materials consumed.






     There are two types of reduction cells:  prebake and Soderberg.  The




primary difference in the two pots is the manner in which the anode is




prepared.  In the prebake cell, the anode is manufactured in the anode




plant prior to placing it in the pot.  In the Soderberg process, a paste




mix of pitch and petroleum coke is poured into a rectangular steel shell




which is immersed in the bath and baked by the heat of the pot.
                                    -106-

-------

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-107-

-------
                              TABLE II-2
                  FEED MATERIALS PER TON OF ALUMINUM
Alumina (Al 0 )                                                3860 lb


                                                                 40 lb
Cryolite (Na.AlF^)
            jO

Aluminum Fluoride (AlF )                                         70 lb



Fluorspar (CaF )                                                  6 lb



Anode Carbon                                                   1000 lb



Cathode Carbon                                                   40 lb



Electric Power                                                 14-16 mwhr






     Prebake anodes are replaced approximately every 10 to 20  days.  The



butts are recycled through the anode plant, which is usually located on



the reduction plant site.  The petroleum coke is crushed, mixed with



ground spent anode butts and combined with pitch to produce the green



(uncured) anodes, or, in the case of the Soderberg cell, to form the



anode paste.  The green anodes are baked and electrical connectors are



inserted.





     Soderberg anodes are completely consumed during the reduction pro-



cess.  Baking the paste in the cell causes hydrocarbons to be  evolved.



The hydrocarbons, which are not present in prebake cell effluent, require



modification in the air pollution control systems.





     Cryolite is absorbed into the carbon cell lining and must be replen-



ished from time to time.  The molten bath has a crust on top   that must



be broken to feed the bath.   Fluoride gases and particulates are emitted



whenever the pot is charged.
                                   -108-

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     The high cost of cryolite makes recycling economically advantageous.




The cell effluents are sometimes scrubbed with caustic to produce cryolite.




Fluorides in the cathode are recovered by crushing and grinding the old




lining then leaching with caustic at the cryolite recovery plant.






     Emissions and sources in the reduction of aluminum include particulates




from materials handling and preparation, and particulates and gases from the




potlines.  The anode plant emits dusts and gases.  Particulates are emitted




during the anode baking operation.  Anode and cathode recovery also gen-




erates some particulates and fluorides.






     The pollutants of most concern are fluorides.  The major source of




fluorides is the potline.  Controls that have been used include scrubbers,




wet and dry electrostatic precipitators, and fluid bed dry filters.






     After reduction  has occurred, aluminum metal is siphoned from the pots




into crucibles for transport to the alloying and holding furnaces.  These




furnaces are refractory-lined fuel-fired reverberating furnaces.






     In these furnaces, various alloying elements are added to produce




specific alloys of aluminum.  In some cases, alloying elements are added




in the pots as well, usually heavy elements such as manganese, copper and



iron.  When pure aluminum is delivered to the alloying furnaces, these




elements will be added as required.  Other metals such as magnesium, zinc,




nickel and titanium are added in the reverberatory furnace.






     Chlorine gas is "blown" through the metal to remove suspended oxides




and cryolite.  After blowing and before pouring the oxide and cryolite,




the surface is skimmed.  The aluminum is transferred to the holding fur-




naces and poured after temperature and alloy constituents are stabilized.
                                        -109-

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     The skims from the alloying and holding furnaces, unless quickly




cooled, may ignite.  This generates a dense white aluminum oxide particu-




late.  Burned or not, there is a significant quantity of skims which must




be handled in some way.  Particulate emissions will be generated by spread




cooling, dross barrel processing, or any other technique used to handle




the skims.






     The evaluation of air pollution control systems at primary aluminum




smelters is a two-step process.  The efficiency of the air pollution con-




trol device(s) must be determined, as well as the capture efficiency of




the ventilation system.






     Emissions from primary aluminum plants are heavily dependent upon




the adequacy of routine operating and maintenance procedures.






13.  RECEIVING, STORAGE AND HANDLING OF RAW MATERIALS




     The possible emissions will be particulates.  Fugitive dust regula-




tions will govern.






13.1   Process Description




       There are four basic raw materials necessary in the reduction of




aluminum which represent potential sources of airborne particulates when




handled.  These include coke, coal tar pitch, cryolite and alumina.  The




coke and coal tar pitch usually arrive at the plant in railroad cars with




a nugget size of about one-half inch.  On the other hand, the alumina and




cryolite are fine white particulates which will pass through a 200 mesh




screen.  Because of its fine size, the alumina material handing system




must be fully enclosed to prevent excess loss, especially during high




winds.  Aluminum reduction plants located inland will usually have the




alumina delivered by fully enclosed railroad cars.  Those plants which






                             -110-

-------
have access to water transportation are likely to have their alumina




shipped by completely enclosed barges or freighters.  The material handling




system used to transfer the alumina from the transportation vessel to the




storage silo is always enclosed and usually has a baghouse at the trans-




fer points.  Alumina must be moisture free, precluding any use of water




sprays to control dust.






     Once inside the plant the alumina is transferred by fully enclosed




conveyor systems to the pot room.  At the pot room, the alumina is loaded




into movable storage bins (distributing hoppers) which serve various pot




lines.  Depending on the plant, these movable storage bins may or may not




be fully enclosed.  Those bins which have an open top are likely to have




dust loss during movement from pot to pot.  Particulate losses from this




operation can be prevented with the use of canvases or shrouds.  When the




alumina is charged to the pot, a small dust plume can be observed.  Some




plants have the hooding and ventilation system designed such that very




little dust escapes into the pot room during the charging operation.






     The coke and the coal tar pitch are transferred from the storage




bins to the prebake anode or paste plant.  Because of its physical size




it can be handled by front-end high lift loaders.  Conveyor systems are




not usually covered.  Almost all plants will have air pollution abatement




equipment connected to the grinding, crushing and screening operations




that are required for the production of paste (Chapter 15).   Water can




be used as a dust suppressant for these raw materials.






     These materials are made up of fine particulates which have the




potential of causing a hazardous dust explosion.  Generally speaking,




fugitive dust emanating from aluminum reduction plants is almost thwarted
                                       -111-

-------
because of the concern over industrial safety, spillage losses and air
pollution regulations.

     Scrap use is an important aspect of plant economics.   All plants
recycle a substantial portion of their internally generated scrap.  Pur-

chased scrap is another raw material which is handled by the plant.
                     t
13.2  Process Control Operation
      The high unit cost of the raw materials dictates good control pro-
cedures to prevent potential handling losses.  The use of enclosed systems
for alumina essentially eliminates escape of the raw material.  There is

a potential for losses of coke dust, but process ventilation is almost
universally applied to coke handling systems.

13.3  Enforcement Prodecure
      The following enforcement procedure describes general observations
to be made at primary aluminum plants.
         1.  Trace the flow of raw materials from the time they arrive at
             the plant until they enter the pots.
         2.  From a distance observe the raw material and processed ma-
             terials for dust clouds either  from roadways, stock piles,
             transfer points, crushing and  screening  operations,  dross
             handling, plant construction activities, etc.  These  sources
             are generally not continuous emitters, but depend on  the
             individual activity schedule.

         3.  Make records of the dusty areas for a close-up inspection.

             These observations should be made from beyond the plant per-
             imeter on a hillside overlooking the entire complex,  if pos-

             sible for a period of several hours.
                              -112-

-------
                4.  Observe the raw material stock piles when the wind is




                    blowing and note any entrained dust.




                5.  Observe the material moving methods at the stockpiles.




                6.  Note any dust emissions at the bulk unloading stations.




                7.  If cranes, belts or bulldozers are used to move the




                    raw materials, note any major dust clouds.




                8.  Make notes on the lengths and locations of unpaved




                    roadways.  Ask if and at what frequency these road-




                    ways receive dust preventive treatment such as the




                    application of water, oil or calcium chloride.  Ob-




                    serve the traffic on these roadways, and note whether




                    or not a significant dust cloud is generated by ve-




                    hicular movement.  Observe the paved, macadamized




                    and gravel roads for latent dust.  Occasionally these




                    roads may become burdened with dust and result in an-




                    other source for fugitive dust.




                9.  Observe the transfer points along belt haulage ways.




                    If no dust is noted, no further inspection is re-




                    quired here.






     The Inspector's Worksheet which follows may be useful for record




keeping.  Interpretation of these observations is dependent upon the per-




tinent regulations governing fugitive dust emissions.  Since many of these




plants are located on large plots of land, it is important to discriminate




between in-plant housekeeping problems and emissions which cross the prop-




erty line.
     If
fugitive dust violations are apparent, take appropriate action.
                                        -113-

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                             INSPECTORS WORKSHEET

             FOR RECEIVING. STORING AND HANDLING OF RAW MATERIALS
Plant Id.	

Date of this Inspection^

Type of Plant	
Capacity of Plant_
                 Date of last Inspection_
  Source Location
              Wind
           Direction
  Type     Wind Speed                     Preventive
Material      (mph)   Plume Description    Measures
Alumina elevator
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
alumina














SW/10














slightly visible-
white














baghouse used














                                        -114-

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14.  PREPARATION OF ALUMINA

     The possible emissions will be particulate.  Likelihood of emissions

is remote.


14.1  Process Description

      The principal ore used in the production of aluminum is bauxite, and

although large deposits of the ore are found in Alabama, Georgia, Mississippi,

Tennessee, Virginia and Arkansas, much of the better grade ore is imported.

A preliminary process of converting bauxite into pure alumina, which is used

in the reduction process, is necessary for the production of high quality

aluminum.

      Most of the world's aluminum is reduced from alumina, which is pro-

duced from bauxite by the Bayer process.  Generally, there are two types

of domestic bauxite; hard or rock bauxite and soft or clay-like bauxite.

In addition to the aluminum oxide, bauxite ore will contain roughly 10 to

30 percent of iron oxide, 4 to 18 percent silica and 2 to 5 percent titania.

Figure 14.1 shows the process involved in the preparation of alumina from

bauxite.  After being mined in open pits, the ore is first dried and ground

to pass through a 100 mesh screen.  Soda ash and lime are mixed with bauxite

in proper proportion and treated in digesters at elevated temperature and

pressure.  Because of the chemical properties of the various impurities

found in the bauxite, most of the alumina goes into solution as sodium

aluminate during the reaction.  Iron oxide and titanium oxide are virtually

unaffected.

      When this digestion is completed the sodium aluminate liquor is sep-

arated from the suspended "red mud" by settling and filtration.  Red mud

carried over with the liquor is an impurity and must be removed, otherwise

the iron oxide will cause difficulty and contamination in the electrolytic

reduction process.
                                        -115-

-------
                                       CO
                                       CO
                                        _
                                       CD
                                       CXL
                                       Q_
                                       CD

                                       H^
                                       «=C


                                       5

                                       CD
                                       
-------
     The sodium aluminate  liquor is pumped to tanks where  it  is "seeded"




with a small amount of aluminum hydroxide.  The liquor  is  slowly cooled




over a period of about 30  hours.  Aluminum hydroxide precipitates from




the sodium aluminate liquor.  The aluminum hydroxide precipitate is washed




to remove any soda and then calcined in rotary kilns at a  temperature of




about 1,000 C.  The resultant alumina is cooled.  It contains at least




99.6 percent aluminum oxide.




     The alumina is sent to the reduction plants in enclosed bulk trans-




porters as a minus 200 mesh white powder.




     Scrubbers, or baghouses, controlling effluents at the aluminum hy-




droxide kiln can be expected to be high efficiency control devices.




     The mining, drying and grinding of bauxite is generally conducted at




the mine.  Processing from bauxite to alumina is a separate operation which




may be carried out at a separate plant site or at a reduction plant.







14.2  Process Control Operation




      The operational variable which would affect air pollution emissions




from the calcining of aluminum hydroxide is the adequacy of the control




equipment.




      The major source of  emissions will be from the kiln, and from the




material handling of the ore and alumina.  Scrubbers are commonly used to




control the effluents from the aluminum hydroxide calcining kilns.   Scrub-




bers are similar to those  used in the cryolite recovery plants.  The slurry




that is generated is recycled directly into the process.  Another factor




which affects air pollution emissions is the condition of the collection




hood at the discharge end  of the kiln.   A factor which would affect the




amount of air pollution emissions emanating from the kiln is the process




feed rate.






                                 -117-

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     Natural gas is the principal fuel used to calcine the alumina in the




kilns.  The major pollutant associated with the calcining of aluminum hy-




droxide is particulate matter, in the form of fine white Al_0 .






14.3  Enforcement Procedure




      Visible emissions are the simplest means for estimating particulate




control equipment performance.  The enforcement official should estimate




the percent opacity of dust control equipment stack plumes.  If in excess




of allowable limits, take appropriate action.






     Building openings should be observed for evidence of escape of in-




adequately captured process dust.  If noted, determine point(s)  of origin




and require corrective action.






15.   ANODE MANUFACTURING




      This is a major potential particulate and minor sulfur dioxide, hy-




drocarbon and fluoride emission source.  Particulate emissions are mainly




a  function of the adequacy of the control system.






15.1   Process Description




      Anodes for prebake pots weigh approximately 500 pounds and are con-




sumed in less than a month.  In Soderberg pots an equivalent amount of




paste must be supplied.  Substantial tonnages of anode material must be




processed at aluminum smelters.






      Carbon paste preparation consists of crushing, grinding, screening




and classifying, combining of carefully sized fractions with a pitch binder,




and mixing.  The preparation plant is termed the "green mill" by the in-




dustry and may produce anode paste for Soderberg cells, cathode paste, or




green pressed anodes for prebake treatment.  Figure 15.1 shows a typical





flowsheet for a Soderberg paste plant and Figure 15.2 shows a typical




                                   -118-

-------
    CALCINED
    PET. COKE
     HAMMER
      MILL
    VIBRATING
     SCREEN
    FINE COKE
    BALL MILL
   CLASSIFIER
          Steam
          Steam
MEDIUM
 COKE
COARSE
 COKE
                           1
                           BATCHING SCALE
                                 1	L
      BLADE  MIXER
                COAL TAR
                 PITCH
                               ANODE
                               PASTE
FIGURE 15,1   SODERBERG ANODE  PASTE  PRODUCTION PROCESS
                               -119-

-------
-120-

-------
flowsheet for the paste preparation and green anode pressing of pre-




bake anodes.  Forming of the green anodes is accomplished either by hydrau-




lic molding or vibratory jolting of the stiff anode paste into dimensionally




stable blocks ready for baking and rodding.






     Solid raw materials (calcined petroleum coke, anthracite coal, solid




pitch, and green petroleum coke, as required for various kinds of paste




mixes) are received in bulk and conveyed to carbon plant storage.  Wetting




agent sprays are used in some green mills to reduce dusting conditions in-




herent in materials handling.






     Material is reclaimed from storage, usually by front-end loaders with




enclosed cabs, and fed to combinations of crushing equipment in closed cir-




cuit with vibrating screens followed by grinding units.  Sized fractions




of crushed and ground material are separated and stored in mix bins for




make-up of paste composition.






     Cleaned reclaimed spent anodes and anode scrap from prebake plant op-




erations are similarly crushed and sized for recycle to prebake anode




preparation.






     Dry solids are drawn from the mix bins in weighed proportions to pro-




vide batches of carefully controlled size distribution and composition,




which are then transferred to steam-jacketed hot mixers.  For baked anode




pastes the mixer feed contains either solid crushed coal tar pitch which




is softened and blended in the mixers or hot liquid pitch to provide the




paste binder.  For Soderberg paste, a liquid pitch is used, metered to the




mixers.






     The hot Soderberg paste is either discharged directly from the batch




mixers to transfer cars which  convey  it  to  the  cell rooms for anode re-





                                  -121-

-------
plenishment, or it may be cooled and briquetted.






     The prebake paste, less fluid than the Soderberg material, is trans-




ferred from the mixers to anode molds, in which the self-supporting green




anode is formed by compaction.






     Green anodes are delivered to the baking plant.  Ring furnaces,




Figure 15.3, are sunken baking pits with surrounding interconnecting flues.






     Anodes are packed into the pits, with a mixture of green coke and cal-




cined petroleum coke filling the space between the anode blocks and the




walls of the pits.  A 10 to 12 inch blanket of calcined petroleum coke




fills the top of each pit above the top layer of anodes.






     The pits are heated with natural gas or oil-fired manifold burners




for a period of about 40 hours.  The flue system of the furnace is ar-




ranged so that hot gas from the pits being fired is drawn through the next




section of pits to gradually preheat the next batch of anodes before they




are fired, in turn, when the manifold is progressively moved.  The cycle




of placing green anodes, preheating, firing, cooling, and removal is ap-




proximately 28 days.






     The ring type furnaces use outside flues under draft.  The flue walls




are of dry-type construction.  Volatile materials released from the anodes




during the baking cycle pass through the walls and mix with the flue gases.






     Air contaminants from the ovens include tarry hydrocarbons, particu-




lates, sulfur dioxide, and fluorides.  Some prebake oven installations use




scrubbers to control emissions.






     Another source of particulate emissions at the ring furnace occurs




when coke or anthracite  is placed over each ditch.  This layer acts as  a




                                   -122-

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                      TOP
    CAS PRODUCER
                                              SCRUBBER
                                        CROSS-SECTION
                                            FRONT
                                       CROSS-SECTION
                                           SIDE
FIGURE 15,3   OVEN RING FURNACE OR BAKING POT

-------
seal and insulator for keeping heat in the pit.   The coke is a fine




granulated material less than a 1/4-inch in diameter.  When the coke bed




is removed, after the anodes have been baked, fine particulates can be-




come airborne.






     A second type of furnace, the tunnel kiln,  has been developed for




baking anodes.  The kiln is an indirect fired chamber in which a con-




trolled atmosphere is maintained to prevent oxidation of the carbon




anodes.  Green anode blocks are loaded on transporter units which enter




the kiln through an air lock, pass successively through a preheating zone,




a firing zone, and a cooling zone, and leave the kiln through a second air




lock.  The refractory beds of the cars are sealed mechanically to the kiln




walls to form the muffle chamber, while permitting movement of the units




through the kiln.






     The muffle chamber is externally heated by combustion gases, and the




products of combustion are discharged through an independent stack system.







     Effluent gases from the kiln may be introduced into the fire box to




recover the fuel value of hydrocarbons and reduce the quantity of unburned




hydrocarbon to approximately 1 percent of that coming from a ring furnace.




Further reduction of solid and gaseous effluent may be achieved by the use




of scrubbers or electrostatic precipitators.






     While the tunnel kiln presents mechanical problems in design and




operation, it is reported to have several appreciable advantages over the




ring-type of furnace.  Baking cycle from green to finished anode is much




shorter.  Anode baking is more uniform.  Space requirements for equal ca-



pacity furnaces are less.  Smaller gas volumes are handled through the




furnace emission control system.







                              -124-

-------
     Baked anodes are delivered to air blast cleaning machines utilizing




fine coke as blasting grit.  Fins, scarfs, and adherent packing are re-




moved by this treatment.  The baked anodes are then transferred to the




rodding room.






     Steel bars or pins are inserted in the anodes to provide the electri-




cal connection between the bus and the carbon block.






15.2   Process Control Operation




       There are  several operating variables which will  affect air pollu-




tion emissions from the anode plant:




       1.  Adequacy of the crushing,  grinding and screening hoods,




       2.  Fluoride, content of anode butts,




       3.  Sulfur content of petroleum coke,




       4.  Temperature of the ovens,




       5.  Method used for covering and uncovering anodes in ring furnaces,




       6.  Efficiency of air pollution control equipment.






     Air pollution control devices are usually installed on many of the




material handling, crushing, screening, and mixing operations to capture




valuable raw materials.  Since the coal tar pitch may be a fine fluffy




material it is easily entrained by air.  In almost all plants, it will be




transported by a fully enclosed pneumatic conveying system.  Nearly every




anode plant will have a control booth to monitor the transport system, the




crushing and screening system, the mixing, and precision weighing operations.




The indicators on the control booth may only be lights which indicate that




chutes are open, that conveyors are in motion, or that pressure is being




applied to a press.
                                        -125-

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     The control booth may also include monitors of the control systems.




The controls may indicate flow rates, temperatures, and fan amperage.




Particulates captured by dry collectors are usually sent directly into




the bins for reprocessing.  On the other hand, slurry from butt grinding




control scrubber is dried before returning to the butts bin.






     Plants which use no control systems or have only selected operations




with abatement devices will usually have soot on the floor or suspended




in the air of the anode building.  Some soot can be expected in the best




controlled plants.






     Fluoride gases are a major concern in emissions from the oven baking




process.  Other emissions from the oven baking process include hydrocarbons




and sulfur dioxide.  The hydrocarbons come from the coal tar pitch follow-




ing the breakdown from tar products.






     Another operation procedure which affects particulate emissions is




the method used to cover and uncover the anodes in the ring furnace.




Some plants use no control system for handling the coke and as a result




dust is apparent in the room.  For those plants which do control coke dust,




operators will have a small baghouse attached to the crane which, charges




the coke to the furnace pits.  The baghouse acts as a "vacuum cleaner"




in controlling particulates from becoming airborne.






15.3  Enforcement Procedure




      The objective of anode plant operation inspection is to establish,



compliance with gaseous and particulate emission regulations.  In order




to accomplish these objectives, the enforcement official needs to determine:




      1.  Current production levels and operating conditions,




      2.  Design production levels and operating conditions,





                            -126-

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      3.  Current controlled and uncontrolled particulate and gaseous emission
          levels,
      4.  Efficiency and adequacy of emission control equipment at current
          and design operating levels.

      Emission control equipment design capacities and operating conditions
 can be obtained from design drawings and plans.  This data should be obtained
 from the company representative prior to plant inspection.  Production levels,
 feed weight rates, and emission control equipment operating conditions may
 be monitored by the plant operator and may be recorded in the operator's
 daily log or displayed on instrument panels.

     The pollutant of most concern in the paste shop is particulate matter.
An immediate tip-off regarding the adequacy of air pollution abatement sys-
tems would be the soot lying on the floor and hanging on the walls.
Those plants which have good air pollution capture systems will usually be
fairly clean and have no build up of the black fluffy material.  The grind-
ing, crushing, screening and mixing operations should be examined thoroughly
for capture efficiency at the hoods and equipment openings.

     Anode paste shops may not operate continuously.   It is possible that
the paste shop will not be in operation during a routine periodic inspec-
tion.

     The enforcement official should check past records to determine whether
or not the air pollution abatement equipment has been operating satisfactorily.

     Visible emissions are the simplest means for estimating particulate
control equipment performance.  The enforcement official should estimate
the percent opacity of dust control equipment stack plume.  If in excess of
allowable limits, appropriate action should be taken.
                                         -127-

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     Building openings should be observed for evidence of escape of in-




adequately captured process dust.  If noted, determine point(s) of origin



and require corrective action.






     Baking furnaces will always operate three shifts per day continuously,




even on the weekends.  As background data it is important to establish the




anode baking rate and cycle, the number of furnaces in operation, and the




maximum temperature of the furnace.  When the temperature is increased,



curing time is reduced and air pollution emissions increase.  The enforce-




ment official should check the operating circumstances during his visit




with design and typical operating characteristics as obtained prior to his




visit.






     Certain observations need to be made at the furnaces.  If the en-




forcement official notices strong odors of sulfur dioxide or hydrocarbon,




it may be an indication that the ventilation system is not adequate, may




have severe leaks, or may be plugged.






     The enforcement official should observe the method of charging anodes




to the oven and removing anodes from the ovens.  The granulated coke or




anthracite used to cover anodes can become a fugitive dust problem.  Some




plants have pneumatic systems which act as a vacuum cleaner to minimize




dust during the charging and removing operation.  The amount of natural




gas fired in the ring furnaces is not important.






     Because of the fluoride emissions from the ovens, low energy scrubbers




may be used.  The enforcement official should note the operating parameters




of the scrubber and check past records of its performance.







     The enforcement official should complete the Inspector's Worksheet




for prebake anode plants and perhaps make some quick checks for particulates,



                             -128-

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                              INSPECTORS WORKSHEET
                            FOR PREBAKE ANODE PLANTS
GENERAL
     Plant Id.
     Date of this Inspection	
OPERATING VARIABLES
     Paste Shop
     Raw material feed rate:  coal tar pitch
                	Ib/day, butts	
                                            Date of last Inspection_
                                           Ib/day, r.a.lcined petroleum
coke
_lb/day.
     Percent Sulfur in Coke
     No. of Anodes Produced per Shift	
     No. of Shifts Anode Plant Operates
     Furnaces :  RingD   TunnelD   	
     No. of Anodes Baked per Day	
     No. of Furnaces
                                    .D
     Maximum Temperature of Furnace
     Baking Time	hours
                    , operating this inspection_
                                     o
AIR POLLUTION ABATEMENT EQUIPMENT
     Devices used at Paste Shop	
     Devices used at Furnaces
Parameters
Pressure drop, in.H-0
Scrubber water flow rate, gpm
Exhaust Flow Rate, scfm
Exhaust Gas Temperature, F
Paste Shop




Furnaces




AIR POLLUTION TESTS
     Paste Shop - Particulates
     Furnace - Particulates	
   HC	ppm
                                      Ib/hr
                                            , SO.
                                                  _pptn, HF_
                            _ppm,
Tested by_
                                 Dated
                                        -129-

-------
VISUAL OBSERVATIONS
     Mixing Hoppers_
     Presses
     Appearance of Building Interior
     Odors
     Charging Coke to Furnace
     Extracting Anodes from Furnace
Time In                                                Time Out
                                   -130-

-------
fluoride, and sulfur dioxide emissions.  These procedures are described




in Part VII of this manual.






16.  REDUCTION OPERATIONS




     This is a major potential fluoride and particulate emissions process.




Sulfur dioxide is a minor emission.  Emissions are mainly a function of




ventilation and collector design and maintenance.  Operating practices and




routine maintenance can have a major effect on emissions.






16.1  Process Description




      The Hall-Heroult process is the electrolytic reduction of alumina




to aluminum in a fused cryolite electrolyte.  A carbon-lined steel vessel




serves as both the cell body and cathode.  The cell anodes are carbon




blocks, suspended above the cell body and immersed in the electrolyte.






     In operation, electric current passes through the fused cryolite




electrolyte.  Alumina in solution is reduced at the cathode to metallic




aluminum.  The aluminum, which is liquid at cell temperatures, collects




on the bottom of the cell since it is more dense than the electrolyte.




At the anodes, carbon is consumed by oxidation.  The cell reaction is:




                 2 A1203 + 3C  	»•  4 Al + 3C02




This reaction theoretically requires approximately 2.5 kwh of energy




per pound of aluminum produced.  Due to heat loss through the pot, sensible




heats of reaction and unwanted electrode reactions, 6 to 9 kwh per pound




of aluminum are consumed.






     The reduction cell, or pot, is a reinforced steel container, insulated




to retain heat.  The pot contains an inner  carbon lining which forms  the




cathode of the cell.  The lining varies from 6 to 18 inches in thickness



and consists of either  a rammed mixture of  pitch and coke or prepaked






                                       -131-

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cathode blocks laid in place with pitch sealing.  The resulting cathode


box measures about 12 to 20 inches deep, 30 feet long and 10 feet wide.


Steel cathode current collectors are embedded in the lining and connect


to a cathode buss.  Between 90 and 240 cells are connected in series


forming a pot line.  Each pot line requires 4 to 6 volts per pot and 50,000


to 200,000 amperes.



     During the reduction process, the anodes are steadily consumed thus


liberating oxygen from the alumina.  Ten to twenty days is a typical life


for an anode.  Cathodes, on the other hand, usually last two to four years


before relining is necessary.



     The cell bath is approximately 85 percent  cryolite (Na A1F ), 8 to 10


percent fluorspar (CaF-), and 2 to 6 percent alumina  (Al.O ).  A  crust con-


sisting of alumina and frozen cryolite forms over the bath preventing air

                                                           o
oxidation of the anode and helping retain heat  in the 1,750 F bath.  Two


tons of alumina are required for each ton of aluminum produced.  Every


five or six hours the crust is broken and fresh alumina is added.



     Periodically, usually daily, the aluminum  collected on the cell bot-


tom is siphoned off.  A  thermally insulated steel crucible with a vacuum


line siphons the molten  metal.  Usually three or four cells are tapped


into a crucible.  The metal is transferred to the cast house where it  is

used.



     Aluminum pots must  be run within closely controlled operational para-


meters.  Emissions can increase sharply when a  pot is "sick".  The two


main causes of a "sick"  pot are poor current distribution and abnormal


bath temperatures.  In one case, when alumina concentration of the bath


is depleted, a buildup of CF, gas forms on the  anode.  Voltage and bath
                              -132-

-------
temperature rise, the latter causing the elevated emissions.  The pot must
then be stirred and alumina added to return the pot to normal operation.
Causes of "sick" pots include:
          1.  Voltage too low,
          2.  Bath and metal violently agitated while putting out an
              anode effect or preparing pot for tap,
          3.  Muck formations due to either too much ore or too low bath
              temperature,
          4.  Unlevel anode due to faulty jack system,
          5.  Grounds such as anode spikes and long ends on anodes,
          6.  Too much metal,
          7.  Faulty voltmeter,
          8.  Too little metal.

     The engineering design and maintenance of ventilation systems is the
most critical factor in air pollution control at a primary aluminum plant.
Although the capture systems for prebake, vertical stud Solderberg (VSS)
and horizontal stud Soderberg (HSS) are different, there are several factors
which apply throughout.

     Pots cannot be completely hooded (shielded) at all times because
several operations must be routinely conducted within the confines of the
hood.  The crust on the pot must be broken every few hours to add alumina.
"Sick" pots must be stirred.  Anodes must be replaced (prebake) or studs
must be moved (Soderberg).  Other operations such as gas-hole punching
also require access to the pot.  The important point is that the shields
must be opened at frequent intervals.

     Some of the factors leading to the deterioration of the efficiency
of capture ventilation are:
                                        -133-

-------
1.  Anode blocks handled from cranes often swing into shields




    used as hoods on prebake cells, denting and deforming them.




2.  "Sick" cells may get so hot that some or all shields actually




    melt down; some shields partially damaged this way may im-




    properly be kept in service.




3.  Shields removed for anode replacement, bath sampling, and




    other routine work may be replaced haphazardly, leaving gaps




    between some shields.




4.  Ducts should be balanced for uniform collection from all




    cells, and damper positions should be marked; if dampers are




    closed when a cell is removed, or opened to provide better




    collection under non-normal operation, the damper should be




    carefully reset.




5.  When reduction cells age, the cell lining (cathode) absorbs




    bath and deforms the steel shell so that it "bows out",




    perhaps as much as a foot on each side.  This impairs the




    gas seal, especially on HSS cells.




6.  HSS cells evolve tars in considerable quantity, and these




    condense and deposit in ductwork, sometimes plugging it com-




    pletely.  Regular cleaning of the ductwork, especially of




    small ducts near the cells, is a requirement.




7.  General housekeeping is extremely important  - a pot room




    can be a clean and attractive place to work  - but if house-




    keeping is poor, doors and shields will be left open un-




    necessarily, damaged doors and shields will  appear part of




    the "normal" appearance, and capture effectiveness will de-




    teriorate more than in direct proportion.




                                -134-

-------
Procedures for controlling some of these conditions have been developed.


In a prebake plant, inspectors tour each pot line, noting for each cell



the "equivalent shields" misplaced, damaged, or missing, recording obser-



vations to the "nearest 1/8 shield."  The number of equivalent shields is



totalled for each pot line and becomes a performance criterion.  Observer



error is large, but differences between pot lines may be larger, and the



system has proven effective.  Objective criteria may be developed, espe-



cially as improved measurement techniques are evolved.





16.1.1  Prebake Pot Operations



        Anodes which have been pre-formed and baked are used in these



pots.  The prebake cell, Figure 16.1, uses up to 24 anode assemblies.



These are clamped to the anode buss, which has a vertical travel of 10 to 14



inches.   As the anode is consumed it is moved down to maintain proper po-



sition in the pot.  New anodes are installed using an overhead crane.




        The air pollutants generated by prebake pots consist of fairly



coarse alumina dust, condensed metallic fumes, sulfur dioxide, fluorides



in both gaseous and particulate form.  There are virtually no hydrocarbons,



these having been baked out at the anode furnaces.




        Most of the particulate emissions originate during the charging



of fresh alumina and other materials to the cell.  This is a result of



the breaking of the cell crust (usually with a jack hammer) and subse-



quent agitation of the bath.  Some carbon particles are emitted during



anode replacement operations.   Other particulates include aluminum fluoride



(AlFO,  cryolite (Na AlF,), fluorspar (CaF-), iron oxide (Fe20 ), and



chiolite (Na0Al F7).
            3  34
                                       -135-

-------
       ALUMINA (ORE) BIN
                                    I— ANODE  BUS
          ANODE  ROD

             ClAMP
CRUST BREAKER
RISER BUS  TO
NEXT CELL
SIDE HOOD FOR
VENT CONTROL


ALUMINA

 CRUST
 CRYOLITE BATH
                    STEEL  CRADLE
          STEEL CATHODE
         "COLLECTOR  BAR
          FIGURE 16,1   PREBAKE  REDUCTION  CELL
                         -136-

-------
     The high fluoride electrolytic bath is the source of the emitted




fluorine compounds.  Hydrogen fluoride gas is caused by the hydrolysis




of vaporized fluoride salts.  This is the most harmful of the pollutants




emitted due to its high toxicity and extreme corrosiveness.






     The consumption of the carbon anodes liberates significant quantities




of sulfur dioxide (SO.)•   The source of the sulfur is the petroleum coke




used in the manufacturing of the anodes.  The average sulfur content in




the coke used today is 3 percent.  Sulfur dioxide effluent for 1,000




pounds of aluminum produced ranges from 15 to 50 pounds, depending upon




the exact sulfur content of the coke.






     A typical analysis of the emissions from a single prebake cell are




shown in Table 16.1.






             Table 16.1 PREBAKE REDUCTION CELL EFFLUENTS




                      (Quantity - lb/1,000 Ib Al)
Component
co2
CO
SO-
2
F (gaseous fluorides)
F (solid fluorides)
Total Fluorides (F)
Total Solids
European U.S.
1,500 	
250 	
6.5 30(1)

10.3 13.1
6.3 8.8
16.6 22.5
25 to 63 45.6
(1)
   Estimate based on 3 percent sulfur in anode cokes.
                                  -137-

-------
16.1.2  Vertical Stud Soderberg Pot Operations




        The Soderberg pot operation uses a coke and pitch paste to form




the cell anodes during cell operation.  The paste is fed into a steel




casing and baked in place by the heat of the electrolytic bath eliminating




the necessity of anode forming and baking operations.






        The materials used, pot specifications, and tapping methods of the




Soderberg cells are identical to those of tne prebake operations.  The dif-




ference between them is solely in the type of anode used, types of air




pollution emissions (hydrocarbons are present in Soderberg cells), and




control systems.






        There are two kinds of Soderberg cells: the "horizontal stud" or




"side pin" (HSS) and the "vertical stud" (VSS).  Figure 16.2 shows the




typical layout of the vertical stud pot.  The "vertical" notation refers




to the electrical connection by means of steel studs to the anodes as the




vertical studs enter the anode mass from the top.  The "green anode paste"




is poured into the top of an open end steel casing and baked by cell heat.




In effect, there is a continuous anode without the need for replacement




as in the prebake operation.  As a stud tip comes close to the cell bath




it is fepositioned upward.






16.1.3  Horizontal Stud Soderberg Pot Operations




        The Soderberg pot operation uses a coke and pitch paste to form




the cell anodes during cell operation.  The paste is fed into a steel




casing and baked in place by the heat of the electrolytic bath eliminating




the necessity of anode forming and baking operations.






        The materials used, pot specifications, and tapping methods of the




Soderberg cells are identical to those of the prebake operation.  The





                                   -138-

-------
                                                ANODE BUSS
                                                     TO EFFLUENT
                                                     COLLECTION
                                                     SYSTEM
        ANODE  ROD
          STEEL ANODE
             STUD
    ANODE  CASING
GAS COLLECTING
SKIRT
     MOLTEN
     ELECTROLYTE
     CRUST
  ALUMINA
                                                     VSTEEL CATHODE
                                                       COLLECTION BAR
                                                STEEL
                                                CRADLE
        -CATHODE BUSS
           FIGURE  16,2   VSS  SODERBERG  CELL
                                -139-

-------
difference between them is solely in the type of anode used, types of air




pollution emissions (hydrocarbons are present in Soderberg cells), and




control systems.






       There are two kins of Soderberg cells;  the "horizontal stud" or




"side pin" (HSS) and the "vertical stud" (VSS).  Figure 16.3 show the




typical layout of the horizontal stud pot.   The "horizontal" notation




refers to the electrical connection by means of steel studs to the anodes.




The horizontal studs enter the anode mass from the sides.  The "green




anode paste" is poured into the top of an open end steel casing and baked




by cell heat.  In effect, there is a continuous anode without the need




for replacement as in the prebake operation.  As a stud comes close to




the cell bath it is removed.  To remove the stud, the pot hood doors are




opened and the steel channel containing these studs is forcibly removed.






16.2   Process Control Operation




       Both particulate and gaseous air pollution control aspects must




be considered.  Fluorides, the gaseous constituent of primary interest,




are soluble in water and also can be reacted with solids.  Particulates



consist of alumina dust, condensed metallic fumes and hydrocarbon tars




(Soderberg).






       The varying composition and wide spread of particle sizes of the




particulate matter have led to the application of several types of con-




trol equipment.  Historically, cyclones and wet scrubbing towers were the




first devices used.  Electrostatic precipitators, baghouses, medium energy




wet scrubbers and dry reactor/baghouses are in current use.






Control methods for aluminum reduction cells include the following:
                           -140-

-------
ALUMINA HOPPERS
                                PASTE  COMPARTMENT
                               "COVER
 REMOVABLE
 CHANNELS
    ALUMINA
   CRUST
 STEEL  SHELL
                                                        PASTE  COMPARTMENT
                                                        CASING
                       POT ENCLOSURE
                       DOOR
                                                          GAS AND FUME
                                                          EVOLVING
        INSULATION

        CARBON  LINING
 MOLTEN
'ALUMINUM
                      CATHODE
                      COLLECTOR BAR
        FIGURE  16,3   HSS  SODERBERG CELL
                               -141-

-------
Wet Scrubbers - Spray towers can remove a high percentage of hydrogen




fluoride since this contaminant is highly soluble in water.  These




devices, however, have a poor collection efficiency for fine particu-




lates.  Recent improvements include a floating-bed type of wet scrubber




on horizontal Soderberg cells.  This type of scrubber tends to over-




come the problem of tar fouling that occurs in scrubbers with station-




ary packings.






Electrostatic Precipitators - Wet electrostatic precipitators are be-




ginning to be used in controlling reduction cell emissions.  These




include vertical counterflow precipitators employing plywood collection




plates which are irrigated with a falling film of water supplied from




troughs at the top of the plates.  Another application utilizes con-




tinuous spray washing of the collection plates and discharge elec-




trodes .






Reactor/Baghouse - The method consists of the chemisorption of hydrogen




fluoride on  a  finely divided alumina and removal of the sorbed fluoride




by means of  a  fabric collector.  Particulate fluorides are also re-




moved by simple filters.  The system requires effective local exhaust



hooding on each pot.  Particulate emissions as low as 3 pounds of




hydrogen fluoride per ton of aluminum produced are claimed.  Contami-




nation of liquid streams and solid waste disposal problems are avoided




and spent alumina from the collector system is recycled to the pots




and the sorbed fluoride is added to the cryolite make-up.






Roof Monitor Scrubber. - In this procedure gases and dust are allowed




to enter the workroom atmosphere.  Large exhaust blowers at the ceiling




induce an inward flow of outside air, through open louvres on the out-




side walls of the building, across the cells and  into an overhead ex-




                                -142-

-------
    haust system to the  gas cleaning equipment,  usually wet scrubbing.


 16.2.1  HSS

         In order  to trap  the  fumes  escaping  from  the pots,  hoods are

 usually  used  to capture most  of  the pot  emissions (see Figure 16.4).

 From the hood,  gases  and  particulates  are ducted  to various emission  con-

 trol equipment.   Hoods  do not capture  all of the  pot effluents.  This  is

 largely  due  to  the need to open  the hoods for pot maintenance,  charging,

 anode replacement, and  aluminum  tapping.  Pots  designed for crust  breaking

 and charging  in the middle between  anode rows are usually equipped with

 hoods which  are  only  opened for  anode  replacement and  metal tapping.

 Typical  hood  exhaust  flow rates  range  from 2,000  to 4,000 cfm per  pot.


         A few prebake pot lines  in  the United States do not use hoods.

 All of the pot  line effluent  and room  ventilation air  passes through  roof

 monitors, where  the emission  control equipment  is located.   Room venti-

 lation air is regulated by adjustable  louvers located  in the building
              fib
 wall and situated to  minimize worker exposure.  Under  certain wind con-

 ditions, this ventilation scheme allows  pot  line  effluents  to escape

 through  building  openings instead of through the  monitors.   Another scheme

 is  to have the ventilation air enter through floor gratings. The  air  then

 passes up through the floor by each cell and out  the monitors.  Figure  16.5

 illustrates these systems.  Large amounts of air  must  be handled by con-

 trol equipment  (30,000  to 60,000 cfm per cell).   Monitor controls  are

 usually  filament  mats or  screens wetted  by water  sprays.   Gaseous  fluoride

 collection efficiency is  reported at 60  to 70 percent.   Efficiencies  for

 particulate collection  have not  been reported.


         Factors which may influence emissions from the prebake pot lines

include:

                                  -143-

-------
                                     GO
                                     N_X

                                     §
                                     o
                                      o
                                      Q_


                                      CO
                                      CO
                                      Q_
                                      CO
-144-

-------
                        CZI
                                           INDUCED DRAFT FAN
                                                   ROOF MONITOR SPRAYS
 X
 X
 X



i
                                          REDUCTION

                                            CELLS
 FLOOR GRATING-
FIGURE  16,5  ROOM COLLECTION  SYSTEM SIDEWALL AND  BASEMENT ENTRY
                             -145-

-------
         1.   Adequacy of control equipment,




         2.   Maintenance and operation of equipment,




         3.   Anode effects,




         4.   Bath composition,




         5.   "Sick pots",




         6.   Charging frequency.






     Various types of control equipment have been used for recovery of




particulate and gaseous emissions from prebake cells.  Tables 16.2 and




16.3 compare these different types of control equipment, their efficiencies




and operating conditions.






     Multiple tube cyclones .are applicable to prebake operations since




there are no tars in the gases to plug the equipment.






     Reactor/baghouse systems have an advantage in that they remove both




gaseous and particulate fluorides.  The recovered effluents can be re-




used in the reduction process.  The coated filter dry scrubber has shown




efficiencies of 98 percent for solids and 90 percent for gaseous fluorides.




This process involves the injection of finely ground alumina into the gas




stream.  The alumina forms a coating on the fabric bags and absorbs hydro-




gen fluoride passing through it.






     Wet spray scrubbers are the most common type of control equipment used




in aluminum reduction plants.  Efficiencies are high for gaseous fluorides




but lower for particulates.  Particulate recovery can be greatly increased




by preceding the scrubbers with small diameter cyclones.  In prebake pot




lines, spray scrubber gas volumes can range from 38,000 to 630,000 acfm.
                                    -146-

-------
TABLE 16.2
EFFICIENCIES OF CONTROL EQUIPMENT IN
CURRENT USE

Primary Collection
Multiple Cyclone
Fluid Bed Reactor/Baghouse
Coated Filter Reactor/Baghouse
Injected Alumina Reactor/Baghouse
Dry Electrostatic Precipitator
Spray Tower
Secondary Collection
(No Primary Collection)
Spray Screen
Crossflow Packed Bed (3 ft. Bed)

FOR PREBAKE POTLINE EFFLUENTS

Reported and Derived
Efficiencies (%) Operating
Participate Fluoride Gas HP/MCF
77.9 to 85 - 0.8 to 1.6
91.8 to 98.3 99.2 to 99.5 4.4
98 76 to 92 1.5
98 98 1.5
89 to 98 - 0.26 to 0.68
80 88.9 to 98.4 0.4 to 0.9
50 93 0.15 to 0.25
87 93 0.5
TABLri 16.3

Conditions
Gal/MCF
1.7 to 10
1.3 to 10
10

ESTIMATED EFFICIENCIES OF CONTROL EQUIPMENT
APPLICABLE

Primary Collection
Baghouse
Wet Electrostatic Precipitator
High Pressure Spray Screen (3 Stage)
Wet Centrifugal
Venturi
Wet Impingement
Orifice Type
Crossflow Packed Bed (5 ft. Bed)
Secondary Collection
(No Primary Collection)
High Pressure Spray Screen (1 Stage)
Floating Bed
Secondary Collection
(With Primary Collection)
High Pressure Spray Screen (1 Stage)
Spray Screen
Crossflow Packed Bed (3 ft. Bed)
Floating Bed
TO PREBAKE POTLINE EFFLUENTS

Estimated Efficiencies (%) Operating
Particulate Fluoride Gas HP/MCF
98 to 99 - 1.6
90 to 99 - 0.66 to 1.36
93 98 6.1
92 to 97 85 to 92 2.0 to 3.2
96 99 9.0 to 10.0
96 to 97 90 1.9 to 3.1
93 96 3.3
87 98 1.5 to 1.8
82 95 2.0
70 87 to 95 0.3 to 1.0
82 95 2.0
45 93 0.15 to 0.25
87 93 0.5
70 87 to 95 0.3 to 1.0

Conditions
Gal/MCF
5 to 10
26
6 to 10
6 to 10
6 to 10
6 to 10
10+
5 to 10
3 to 10
5 to 10
10
10
3 to 10
    -147-

-------
Spray rates are from 2 to 10 gallons of liquor per 1000 cf of gas.






     Fluidized beu. reactors have shown good success in controlling alu-




minum plant effluents.  Gaseous and particulate fluorides from reduction




cells pass through a fluidized bed of finely divided alumina particles in




the Alcoa Process 398, (Figure 16.6).  The particulate, including alumina




bed particles, are removed from the gas stream by fabric collectors lo-




cated above the bed.  Gaseous fluorides react with the bed-forming alu-




minum fluoride.  The filter bags are cleaned periodically by reversing




the gas flow.  The accumulated filter cake falls back into the bed.  Alu-




mina is fed into the bed on one end and the reacted bed material is re-




moved from the other end.  The reacted bed material is conveyed to the




pot lines for use in the cells.  Table 16.4 shows the performance of this




scrubbing scheme.  It has been reported that the process should leave no




visible plume.  With this process there is no solid or liquid waste.  Pol-




lutants are captured and returned for reuse.  Alumina particulates become




charge to the pots and the adsorbed fluorides are reincorporated in the




cell electrolyte.






16.2.2  VSS




        Because of the baking of the anode paste during pot operation,




hydrocarbons are emitted in addition to other pollutants normally asso-




ciated with aluminum reduction.  Tars cause a major problem in effluent




control since they tend to clog and gum up some types of control equip-




ment intended for particulates and fluorides.






        In the VSS pot, the studs are in a vertical position.  A metal




skirt is attached to the bottom of the anode jacket to effectively trap




cell effluents.  The skirt reaches to the crust, thereby allowing little






                                   -148-

-------
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-------
dilution air to mix with the effluent gases.  Burning the hydrocarbons  in




the effluent gases reduces  their  concentration up to 97 percent,  i.e.,




from about 3 to 0.1 percent by volume.  This control method has the added




advantage of converting fluoridated carbon  compounds to simpler fluoride




gases.  Each pot has its own burner.  Pot fumes from approximately 15




cells are collected and exhausted to control equipment.  Cell burners




convert effluent hydrocarbons to  CCL and water vapor.  The flame  burns




continuously when the cell  is operating properly.






     Variations in pot operation  can cause  the flame to extinguish unless




igniters or auxiliary fuel  is used.  An average of 5 to 10 percent of the




burners on a pot line may be out  at any instant which allows unburned




hydrocarbons to enter control equipment downstream intended for particu-




late and fluoride control.  Main  combustion variables are hydrocarbon




concentrations of the effluent gases, and the amount of combustion air




supplied to the burners.  Combustion air quantity is regulated by the




shape, size and location of the air inlet opening.  This duct between the




skirt and burner should be  large  enough to  permit a sufficient flow even




when the bath splashes.






     For particulate control after hydrocarbon combustion, cyclones have




a collection efficiency of  only about 40 to 50 percent.






     Reactor/baghouse control equipment as  well as scrubbers are  in use




with vertical stud Soderbergs.   The dry process requires self-supporting




combustion burners and gas  cooling to 275°F prior to the fluid bed.   Chapter




16.1.2,  particularly Tables 16.2 and 16.3,   is generally applicable.






     In VSS operations,  crust breaking and pot charging are conducted




outside of the gas collecting skirt, releasing some effluents to  the pot




                                        -151-

-------
room.  The top of  the anode casing releases a visible amount of heavy




hydrocarbons and some sulfur dioxide from the baking of the paste.  These




emissions are not  captured by the pot ventilation system and escape the




building through the roof monitor.






16.2.3  HSS




        Due to the baking of the anode paste during pot operation, hydro-




carbons are emitted in  addition to other pollutants normally associated




with  aluminum reduction.  Tars cause a major problem in effluent  control




since they tend to clog and gum up ducts and many types of control equip-




ment.






        Capture of horizontal stud Soderberg pot effluents is extremely




difficult because  of the large emission potential during crust breaking,




pot stirring, stud removal, and other routine operations which require




access to the surface of the pot.  At these times the hoods must  be open.






        Frequent opening of doors presents several serious problems af-




fecting the capture of  pot effluents.  When the door is open the  substantial




thermal head carries the effluents out of the control zone of the hoods.




With  frequent use  the doors warp, become bent, and otherwise fit  poorly.




High  pot temperatures can warp the doors, door support  frames and the pot




body.






        It is significant that HSS pots probably have the poorest capture




efficiency of the  three types of aluminum smelting pots.  This is due to




the doors being open for longer periods of time to carry out the  necessary




pot operations.






        Effluent  recovery is a complicated problem.  A  gas skirt  cannot




be connected to the anode casing because the casing shell is composed of





                             -152-

-------
removable sections that are changed as the anode is consumed.  Hoods are




suspended above the cells entraining large volumes of dilution air.  The




resulting dilute effluent gases will not support combustion and with burn-




ing impossible, ducts and control equipment are fouled by the tars.  Cy-




clones and baghouses would be rapidly clogged and electrostatic precipi-




tator plates must be flushed with water to remove accumulated tars and




other particulates.  High velocity spray scrubbers are usually used but




even they tend to clog without mechanical collectors or combustion units




because the tars tend to resist wetting.






     A floating bed scrubber (Figure 16.7), however, has been used to




overcome the problem of tar fouling.  The bed consists of polyethylene




spheres and during operation, liquor flows down the floating bed, absorbing




gases and cleaning the spheres.  The collection efficiency of total fluor-




ides (particulate and gaseous) is better than 95 percent.  Soluble fluor-




ides are recovered with better than 98 percent efficiency.






16.3  Enforcement Procedure




      The objective of aluminum reduction plant inspection is to establish




compliance with fluoride, sulfur dioxide, and particulate emission regu-




lations.  In order to accomplish the above objectives, the enforcement




official needs to determine:




         1.  Current production levels and operating conditions,




         2.  Design production levels and operating conditions,




         3.  Current controlled and uncontrolled particulate and sulfur




             dioxide emission levels,




         4.  Efficiency and adequacy of emission control equipment at




             current and design levels.
                                        -153-

-------
                                  CLEAN GAS
MIST ELIMINATOR
FROM
RECIRCULATION
PUMP
SCRUBBING  LIQUOR
RETAINING GRID

FLOATING  BED OF
LOW-DENSITY SPHERES
MAKEUP LIQUOR

TO
RECIRCULATION-*
PUMP
                             ooooooooooo
                              oooooooooo
RETAINING GRID
                                                                 FEED  GAS
                                                                TO DRAIN
                                                                OR RECOVERY
             FIGURE 16,7  FLOATING BED  SCRUBBER DEVELOPED FOR

                 HORIZONTAL STUD SODERBERG CELL EXHAUSTS
                                 -154-

-------
     Emission control equipment design capacities and operating conditions




can be obtained from design drawings and plans.  These data should be ob-




tained from the company representative prior to physical plant inspection.




Production levels and emission control equipment operating conditions are




monitored by the plant operator and are either recorded in the operator's




daily log or are displayed on instrument panels.






     Pot lines will have  a control booth in the plant for monitoring pur-




poses.  The enforcement official should have little difficulty assessing




the current operating status of the pot line by observing the many re-




corders, gauges, and the log sheets which are normally kept.






     The contaminants of  most concern from aluminum reduction plants are




fluorides and particulates.  In general, the fluoride emissions occur con-




tinuously, while particulate emissions are highest when there is some ac-




tivity at the pot such as crust breaking, charging, siphoning, or respond-




ing to an anode effect.






     Aluminum pot lines are operated continuously and are rarely taken




out of service.   The Inspector's Worksheet indicates the operating vari-




ables which need to be recorded during the enforcement official's visit.




Aside from the data indicated on the worksheet, the enforcement official




should observe certain operations and plant practices.






     The enforcement official should observe the pot activities.  It




should be pointed out that these activities usually occur during the early




part of the work shift.   Therefore, it is suggested that the enforcement




official arrive at the plant near the beginning of a work shift  to carry




out an effective inspection.
                                  -155-

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     At those plants which use hoods on the pots the official should




check for leaks and adequacy of the exhaust volume.   He should walk com-




pletely around several of the pots, selected at random, and check for




visible particulate escape when the doors on the hood are closed.  If




any particulate matter escapes the hood, it is an indication that the ex-




haust volume is not adequate for this particular cell or that the exhaust




volume is not in balance with other pots on this line.






     When the doors are open on the hoods for activities such as crust




breaking, charging, siphoning, or controlling an anode effect, the en-




forcement official should observe how much of the plume escapes the hood




system.  Plant operators can increase the exhaust volume of any pot by




damper adjustments.






     It is recommended that the enforcement official visit at least two




lines during his visit.  While observing the plume leaks and balance on




selected pots, the enforcement official should also note the number of




anode effects which will occur on this particular line during this in-




spection.  All aluminum plants have lights or bells on each pot which,




when lit or ringing, will denote an anode effect.  A walk up each aisle




of a pot line will indicate the number of anode effects that exist on




this line.  Anode effects cause the highest particulate emissions.  Emis-




sions will continue at an elevated level until the anode effect is con-




trolled.  Anode effects are controlled both automatically and manually.




Whatever the plant method for responding to an anode effect, the enforce-




ment official should note the time it takes to respond and return the




pot to normal operation.






     The enforcement official should note the number of doors left open




and unattended  on a particular  pot line.   From visit to visit the en-



                                   -156-

-------
forcement official will develop a "feel" for the amount of emission es-




caping to the roof monitor based on the visibility inside the pot room.






     Some plants may not use hoods on the pots to control emissions.  In




these plants, the enforcement official should check to verify that the




plume rises to the roof monitor instead of escaping the building through




the louvered walls.  If it does not go to the monitor, it is an indication




that the emissions may be excessive.






     Particulate and fluoride emissions from aluminum reduction pot lines




will depend on the adequacy of the design maintenance, and operation sys-




tems and the pots.  Scrubbers and/or dry adsorption baghouses may be




used to reduce particulate and fluoride emissions from pot lines.  There




is little data that an enforcement official can gather relative to the




operation of the air pollution abatement systems.  The enforcement of-




ficial should, however, note the pressure drop on scrubber and the scrub-




ber water flow rate, if available.  At some plants, review of recorded




pH control data will give an indication of scrubber effectiveness.  Ab-




norma-lly low pH is an indication of plant upset with attendant elevated




fluoride emission potential.






     The enforcement official should ascertain that the scrubber is op-




erating and that water is circulating.  Because of freezing temperatures,




some plant operators will not or cannot operate their scrubbers at low




ambient temperatures.  Instead, the units are turned off, the water is




drained and the exhaust gases pass uncontrolled to the atmosphere.  If




this occurs,, the enforcement official should take proper action.  It is




possible that these exhausts will have been diverted to standby control




devices.
                                  -157-

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     For dry adsorption processes, it is likewise difficult to ascertain




that the control equipment is operating satisfactorily.   In the dry ad-




sorption process, reactant must be charged to the control device in order




to control fluoride emissions.  Some devices pipe the powdered reactant




directly into the duct while one process has a fluidized bed of alumina.




If reactant is not in the control system, then no fluoride reduction is




taking place.  The enforcement official should observe the entire dry




adsorption process and determine that the reactant is being used.  Bag-




houses are used in the dry adsorption system.  Plants will generally




have manometers and continuous recorders on these baghouses.  A check




of the manometer and a review of recorded pressure drop data will indi-




cate the baghouse operability.






     If desired, the enforcement official can make quick determinations




for hydrogen fluoride, sulfur dioxide, and particulate emission levels.




(See Part VII).






     With the mass rate and sulfur content of the anodes, an estimate




of SO- mass emissions can be computed.  It should be pointed out that many




state regulations restrict sulfur emissions from the entire smelter and




not just the pot room.  For determining compliance with the regulations,




sulfur emissions from each operation must be summed.






     Visible emissions are the simplest means for estimating particulate




control equipment performance.  The enforcement official should estimate




the percent opacity of control equipment stack plumes.  If in excess of




allowable limits, take appropriate action.






     Building openings should be  observed for evidence of escape of in-




adequately captured process dust.  If noted, determine point(s) of origin





                                   -158-

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                         INSPECTORS WORKSHEET
                     FOR ALUMINUM REDUCTION PLANTS
GENERAL
Plant Id.
Date of this Inspection_
     _Date of last Inspection_
Type Plant: VSS, HSS, Prebake_
OPERATING VARIABLES
Aluminum Production Rate	
No. of lines running	
tons/day
No. of pots running today_
Anode, sulfur content	
         ,  Usage_
tons/day
Average anode effects per pot line per day
Cryolite addition rate	
Flow rate per cell this line_
ABATEMENT EQUIPMENT
   lbs/1,000 Ibs of Aluminum
       scfm;  Line No.
^\ Unit
Parameter^^ 123456
Particulate
efficiency 7o
F efficiency %
Pressure drop,
in. H20
Scrubber water
flow rate, gpm
Dry adsorption
feed rate, Ib/hr
Flow rate, scfm
o
Inlet temp, F
Opacity, %
















































Average








                                  -159-

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ACTUAL EMISSION DATA




     Particulates	lb/ton of Aluminum




     Fluorides (gaseous)	lb/ton of Aluminum




     Sulfur Dioxide ppm	, Ib/hr	
                                                   Tested by:




                                                        Date:




GENERAL OBSERVATIONS
Time In                                            Time out
                                    -160-

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and require corrective action.


     Systems and equipment for controlling aluminum reduction emissions

will require constant upgrading in the years ahead to meet increasingly

stringent emissions standards.  Emissions which may now range from 40 to 50

Ibs/ton aluminum processed will have to be reduced to something like 15

Ibs/ton and #1 Ringelmann.  Bag filters and improved electrostatic pre-

cipitators may be the only types of control systems that will help to re-

alize this goal.  Such design improvements as larger pot capacities, auto-

mated ore feeding, and roof scrubbers should also help to achieve these

goals.

     Much of the inspector's function will be to help assure that compli-

ance schedules are met, that control systems are conscientiously operated

and maintained, and plant facilities are operated and maintained in a

manner which takes into account air pollution control, and prevents en-

vironmental damage in the vicinity of and downwind from the plant.

     The enforcement official should complete the Inspector's Worksheet.

17.  CAST HOUSE OPERATIONS

     This is a minor but highly visible source of particulate emissions

and chlorine.  Emissions are mainly dependent on control system design

and plant operational practices.

17.1 Process Description

     The metal siphoned from the pots is transported from the pot room

to another part of the plant where it is then poured into an alloying

furnace.  The alloying furnace is a fuel-fired reverberatory furnace,

either rectangular or circular.  Metal is usually poured into the furnace

through a funnel port on the side.
                                  -161-

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      Scrap may be charged into the alloying furnaces.  If scrap is charged,




it is often done prior to "pot" metal additions so that the excess heat in




the pot metal can be utilized to melt the scrap.  Pot metal is at 1,750 F




while alloy furnace operation is at 1,400°F to 1,500°F.






      The circular units have removable roofs so that scrap is top-loaded.




The rectangular unics are charged through side doors.  Some rectangular




units have external hearths into which scrap can be charged into the




molten bath without direct flame impingement.






      After the furnace has been partially filled with scrap and pot metal,




it is sampled to establish analysis.  Additions are made to conform to




alloy requirements.  In some plants partial alloying is done in the pots,




particularly elements such as copper, silicon, iron, and manganese.  If




not, then they are added in the alloying furnaces as are zinc and magnesium.






      During the alloying process the bath may be "blown" with nitrogen,




chlorine gas, chlorine-nitrogen or chlorine-nitrogen-carbon monoxide mix-




tures to carry to the surface suspended oxides and to degas.






      After alloying is finished, the furnace is again deoxidized and de-




gassed with chlorine, or other gases, or by use of chloride fluxes.  It is




then skimmed.  The finished alloy is then laundered into holding furnaces.






      The holding furnace is a rectangular fuel-fired reverberatory furnace.




It is usually quite shallow since temperature in the bath must be closely




controlled.






      Final degassing and deoxidizing is accomplished, temperatures are




stabilized, analysis is checked, and the metal is poured into:





                                  -162-

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           1.  Billets,




           2.  Rolling ingots,




           3.  Sows,




           4.  Casting ingots,




           5.  Pigs.






      Various pouring systems are used.  Rolling ingot and billet are cast




in continuous casters or direct chill Casters and sows are poured from




ladles filled at the furnace and taken to the pouring floor where the




cast iron sow molds are lined up for filling.  Casting ingot and pig is




either poured into conveyors equipped with cast iron molds or into con-




tinuous casting units.






      The furnaces are skimmed as necessary to remove drosses.  The drosses




on the surface interfere with heat transfer and must be removed before




they get so thick as to allow "thermit reaction" to occur on the bath or




to reduce heating efficiency.  The drosses are skimmed into skim pans and




in some plants these pans are taken to a dross barrel where the drosses




are heated and spun in a refractory lined drum.  The excess metal drains




and is poured off and the remaining dross is dumped into a pan or onto a




conveyor and taken to a cooler, then to tote boxes and indoor storage.






      In some plants the skim pans are taken to a dross cooling area where




they are dumped, manually or mechanically spread and hosed down to cool,




and then collected and taken to indoor storage.  Later, the drosses are




loaded into trucks or railroad cars for shipment to other plants for




processing.
                                  -163-

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17.2  Process Control Operation




      The operations in the cast house generate gaseous and particulate




emissions.  Mechanical operations such as transfer of metal, scrap charg-




ing, stirring, and skimming may also result in emissions.







      If scrap is dirty, i.e., oily, painted, or laquered, carbonaceous




effluents may be generated.  In the furnaces where scrap is charged in




the melting zone much of the smoke is burned but in the "open-hearth"




charging furnaces pickup hoods must be in place and connected to control




equipment to prevent emissions







      During alloying few emissions occur except when magnesium is not




properly handled.  This can crea,te a magnesium fire with attendant emission




of aluminum and magnesium particulates.







      During degassing or during the process for removing suspended solid




oxides from the melt (deoxidizing) gases or salt chemicals are fluxed into




the bath.  This generates emissions of fine particulates and gases.  When




chlorine or chlorine-nitrogen is used there will be emissions of aluminum




chloride and chlorine, but when chlorine-nitrogen-carbon monoxide or tri-




gas is used there is less visible emission.  The chlorine-nitrogen or tri-




gas emissions will contain very little chlorine and when nitrogen is used,




only particulate emissions result.







      The use of hexachlorethane, aluminum chloride, or magnesium chloride




involves the mechanical insertion of the powdered salts into the melt using




iron tools.  The salts react and vaporize.  They react with dissolved gases




and suspended solids to bring them to the surface, which will result in the




formation of copious visible emissions.  The chlorides will react on cooling






                                    -164-

-------
and mixing with atmospheric moisture to form HCl which can be detected




by its pungent odor.







      If the skim pans are not removed quickly to further process activity,




the aluminum will burn, resulting in the emission of large quantities of




aluminum oxide.  These thermally-generated particulates, less than 0.5




microns, are in the particle size range of maximum light scattering.







      Pouring processes may result in discharge of steam plumes from the




cooling operation.







      The gaseous additives flow rates are usually controlled by flowmeters




and pressure gauges and the salt additions are weighed but reaction rates




are not consistent.







      Air pollution control practices vary widely at cast houses, depend-




ing principally upon the emission potential and the gas volume to be




treated.  Scrubbers or baghouses are the usual control devices used.







17.3  Enforcement Procedure




      The objective of cast house operation inspection is to establish




compliance with particulate emission regulations.  In order to accomplish




the above objective, the enforcement official needs to determine:




         1.  Current production levels and operating conditions,




         2.  Design production levels and operating conditions,




         3.  Current controlled and uncontrolled particulate emission




             levels,




         4.  Efficiency and adequacy of emission control equipment at




             current and design operating levels.
                                  -165-

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      Emission control equipment design capacities and operating conditions



can be obtained from design drawings and plans.  These data should be ob-



tained from the company representative prior to the physical plant inspection.



Production levels and emission control equipment operating conditions are



monitored by the plant operator and are either recorded in the operator's



daily log or are displayed on instrument panels.





      The cast house may have a control booth near the units for monitoring.



The enforcement official should have little difficulty assessing the current



operating status of the furnaces by observing the many recorders, gauges and



logs which are normally kept.





      Visible emissions are the simplest means for estimating particulate



control equipment performance.  The enforcement official should estimate the



percent opacity of control equipment stack plumes and if in excess of allow-



able limits, take appropriate action.





      Building openings should be observed for evidence of escape of inade-



quately captured process dust.  If noted, determine the point(s) of origin



and require corrective action.




18.   CRYOLITE MANUFACTURE AND RECOVERY



      The potential emissions are particulates.  This is a minor source.




18.1  Process Description



      Cryolite is essential in the production of aluminum since it acts



as the solvent in which powdered alumina is dissolved in a bath and elec-



trically reduced to molten aluminum.




                      A10, + C    C7°lite.  . Al + CO,
                        2 3        electricity         2
                                   -166-

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Cryolite occurs naturally and is found in large enough quantities to mine




only in Greenland.  Most cryolite used today is manufactured or "synthetic".






      In the process of aluminum reduction, fluorides are vaporized causing




a depletion in the fluoride content to the cryolite electrolyte.  Fluoride




compounds which are rich in sodium are absorbed by the carbon cathodes of




the pot.  Aluminum fluoride, soda ash, fluorspar, and cryolite are added




to the pots on an "as-needed" basis.  About 40 to 80 pounds of cryolite




must be added to the bath per ton of aluminum produced.






      Because of the high value of the fluoride compounds captured in




air pollution control systems and/or the pot linings, some primary re-




duction plants have facilities for recovering cryolite from pot linings




and scrubber effluent.






      When the carbon lining becomes decomposed and needs to be replaced




(typical average pot life is 3 years), it is removed from the pot line




and the lining is stripped from the steel shell.  Outdoor storage of the




pot linings may result in water pollution.  If rain comes in contact with




the fluoride laden linings, some of the fluoride will be washed away.




Several aluminum plants have built concrete storage facilities with suit-




able drains and treat the rainwater discharge.  The composition of the




pot linings when taken off-line is:




                             Carbon               30%




                             Cryolite             30%




                             Alumina              25%




                             Fluorspar             5%




                             Sodium Carbonate      7%




                             Silicon Oxide         2%



                             Ferric Oxide          1%



                                  -167-

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      To recycle, pot linings are crushed and ground to 80 percent minus



100 mesh and are reacted in a digester with sodium hydroxide.  The slurry



is further processed through a variety of thickeners and mixers where var-



ious chemical reagents are added to produce a slurry composed of Na A10 .



The cryolite is precipitated in a carbonator by bubbling CO  through the



solution which yields cryolite, Na A1F,.   The cryolite is then dried in
                                  j   o


a rotary diln and returned to the pot room.  Kilns are usually fired with



natural gas to prevent any contamination from other fuels in the "synthetic"



cryolite.





      Because of the economics involved in cryolite recovery, efficient



air pollution control devices are used.  Medium energy wet scrubbers are



usually used.  The slurry from the kiln scrubber is recycled directly into



the thickener.  Figure 18.1 illustrates the basic steps involved in cryolite



recovery.





18.2  Process Control Operation



      Two factors which influence emission levels from cryolite recovery



operations are:  capacity of plant and adequacy of the collection system.



There are few operating variables at a cryolite plant which would affect



air pollution emissions.  The quantity of particulate emissions will be



determined by the process weight rate of the kiln and the adequacy of the



control equipment.





      Process information available at cryolite recovery plants includes



kiln temperature, feed rate, scrubber pressure drop, water flow rates, and



tank levels.  Little variation in operating conditions and emissions levels



will be noted from day to day.





                                   -168-

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         TO CaC03 POND
FIGURE 18,1   CRYOLITE RECOVERY FLOW DIAGRAM
                     -169-

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18.3  Enforcement Procedure




      The objective of cryolite recovery operation inspection is to estab-




lish compliance with particulate emission regulations.  In order to accomp-




lish the above objective, the enforcement official needs to determine:




         1.  Current production levels and operating conditions,




         2.  Design production levels and operating conditions,




         3.  Current controlled and uncontrolled particulate and sulfur




             dioxide emission levels,




         4.  Efficiency and adequacy of emission control equipment at




             current and design operating levels.






      Both plant and emission control equipment design capacities and




operating conditions can be obtained from design drawings and plans.




These data should be obtained from the company representative prior to




the physical plant inspection.  Production levels and emission control




equipment operating conditions are monitored by the plant operator and




are either recorded in the operator's daily log or are displayed on in-




strument panels.






      The plant may have a control booth for monitoring.  The enforcement




official should have little difficulty assessing the current operating




status of the plant by observing the recorders, gauges and log sheets




which are normally kept.






      Visible emissions are the simplest means for estimating particulate




control equipment performance.  The enforcement official should estimate




the percent opacity of dust control equipment stack plumes and if in ex-




cess of allowable limits, take appropriate action.
                            -170-

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                          INSPECTORS WORKSHEET
                      FOR CRYOLITE RECOVERY PLANTS
GENERAL
     Plant Id.
     Date this inspection
                                        Date last Inspection_
OPERATIONAL
     Cryolite plant process rate
                                          tons /day
ABATEMENT EQUIPMENT
     Pressure drop, in.
     Scrubber flow rate, gpm_
     Exhaust flow rate, scfm_
     Particulate efficiency	
     Inlet temp.  F	
     Opacity %	
ACTUAL EMISSION DATA
     Particulates
                                 Ib/hr
                                                Tested by
                                                Date
GENERAL OBSERVATIONS
Time In
                                  Time Out
                                       -171-

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      Building openings should be observed for evidence of the escape of




inadequately captured process dust and if noted, determine point(s) of




origin and require corrective action.






19.   ANODE AND CATHODE RECLAIMING




      This is a minor potential source of particulate emissions and odors.






19.1  Process Description




      Soderberg pots have a continuous anode and therefore the anode re-




claiming operation is not associated with these operations.  As stated in




Chapter 16, the prebake plant manufactures the anode in a separate facility




away from the pots.  Most of the carbon in the anode is consumed during the




reduction process.  The prebake anodes have a life of about 10 to 20 days at




which time the "butts" are removed and sent to the anode and cathode reclaim-




ing center.






      When the anode is first installed in a cell, the dimensions include




a height of about two feet.  When the butts are removed, the height has




been reduced to about six inches.  When the butts are extracted from the




cell they are contaminated with alumina, aluminum fluoride, and cryolite.




The operators try to knock off the laden material.  After the anode is




removed from the pot, residual crusty material is knocked off and returned




to the pot.






      The anode butts are carried to the anode and cathode reclaiming




center where jack hammers and other  devices are used to separate the steel




studs from the remaining carbon block.  Some plants use hydraulic presses.




The spent carbon is ground and reused in making new anodes; the steel studs




are returned for further cleaning and then reused in anode assembly.




                                   -172-

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      The major source of emissions at an anode and cathode reclaiming




center occur during the use of jack hammers which remove the carbon from




the stud.  Compared to other sources at an aluminum reduction plant, this




is considered a minor source.  None of the aluminum reduction plants con-




trol air pollution emissions from the anode and cathode reclaiming center.







      Although all aluminum reduction plants have cathodes, not all plants




recycle them.  Once the cathodes have been removed from the pot line, they




are taken to a separate building (reclaiming center) where cranes handle




the steel jacketed cells.  Some plants will use water, steam, and some




chemicals to assist in the process of removing the carbon lining from




the steel jacket.  If water is used, there is the possibility of the re-




lease of ammonia and carbides.  Particulate emissions and odors from the




cathode reclaiming shop emanate during the handling of the large cathode.




At best, this could only be considered a minor source of particulate




emissions.  The spent carbon may be returned to the anode shop for making




paste or to cryolite reclamation.







19.2  Process Control Operation




      There are no operating variables which affect air pollution emissions




from this source.







19.3  Enforcement Procedure




      Anode and cathode reclaiming shops are a minor source of air pollu-




tion emissions.  Fugitive dust is generated during anode and cathode han-




dling, but because of the frequency of these operations and the amount of




particulate emitted, no further inspection is required at an anode and




cathode reclaiming shop.
                                 -173-

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      Interpretation of these observations is heavily dependent upon the




pertinent regulations governing fugitive dust emissions.   Since many of




these plants are located on large plots of land,  it may be important to




discriminate between in-plant housekeeping problems and emissions which




cross the property line.
                                   -174-

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                      PART III.  COPPER SMELTING






     Copper was first produced in  the United States  at  Simsbury, Conn,  in




1709.  Further discoveries of ore  deposits were made in Vermont in  1820




and in Michigan in the early 1840's.   Extensive ore  bodies were found  in




Arizona and Montana during the period from 1860 to 1880,  and  by 1880




smelter production from domestic mines had reached 30,000 tons per  year.




In 1906, the exploitation of the large, low-grade porphyry deposits in




Utah was begun, and with the development of froth flotation concentrating




technology in the early part of the  century, low-grade  deposits became




economically attractive.






     Today, virtually al\ domestic mining operations are  conducted  in




seven states, producing 170 million  tons of copper ore.   Concentrates  from




this ore and imported concentrates are processed at  16  primary copper  smel-




ters with a total annual charge capacity of 9.2 million tons  of copper con-




centrate, representing 1.8 million tons of copper.   Table III-l lists  these




16 copper smelters and their locations and capacities.






     Mineralogically, copper ores  are divided into three  ore  groups: sul-




fide, oxide, and native.  In the United States, sulfide ores  comprise  85




to 95 percent of the total primary production.   The  deposits  of the Lake



Superior district (Lake Copper) are  the only ones of economic importance



in which metallic copper is the chief ore mineral.   This  native metal  is




very pure, containing 98 to 99 percent copper with small  amounts of silver




and minor quantitites of arsenic.  Table III-2 lists the  composition of




the more important sulfide and oxide minerals from which  copper is  extracted.






     These minerals are usually associated with siliceous and other min-




erals, so that most copper ores consist partly of one or  more copper




                                  -175-

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                    Table III-l U.S.  COPPER SMELTERS
                   (Thousands of Short Tons Charge*)
COMPANY
Asarco
Asarco
Asarco
Anaconda Company
LOCATION
El Paso, Texas
Hayden, Arizona
Tacoma, Washington
Anaconda, Montana
CAPACITY
420
420
600
1000
Inspiration Consolidated
  Copper Co.
Magma Copper Company
  Magma Division
  San Manuel Division
Kennecott Copper Corp.
  Nevada Mines Division
  Chino Mines Division
  Ray Mines Division
  Utah Copper Division
Phelps Dodge Corp.
  Douglas Smelter
  Morenci Branch
  New Cornelia Branch
Tennessee Corporation
  Tennessee Copper Co.
  Division
Miami, Arizona              450

Superior, Arizona           150
San Manuel, Arizona         403

McGill, Nevada              400
Hurley, New Mexico          400
Hayden, Arizona             420
Garfield, Utah             1000

Douglas, Arizona           1250
Morenci, Arizona            900
Ajo, Arizona                300
Copperhill, Tennessee        90
White Pine Copper Co.
Total
White Pine, Michigan
*  Stated in tonnage of annual capacity for smelting materials that yield a
   product.
+  Thousands of tons of copper.
                                   -176-

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              Table III-2 Common Copper Bearing Minerals
Mineral
Theoretical Formula
Cu(%)
Chalcopyrite




Chalcocite




Bornite




Covellite




Malachite




Azurite




Cuprite




Chrysocolla
   CuFeS,
   CuS
   CuC03 - Cu(OH)2




   2CuC03 - Cu(OH)2
 34.5




 79.8




 63.6




 66.5




 57.3




 55.1




 88.8




 36.2
34.9




20.2




25.6




33.5




 0




 0




 0




 0
                                 -177-

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containing minerals and partly of earthy matter.   The sulfide ores are also




generally associated with iron sulfides.  The type of copper ore and its




tenor, i.e., percentage of copper content, determines the method of ex-




traction.






     There are two methods of copper extraction from concentrated ores:




          1.  Dry methods consisting of smelting followed by treatment of




              the copper-bearing mineral in a converter,




          2.  Wet methods consisting of leaching and precipitation or




              electrowinning of the copper from solution.




Leaching is the term applied to the process of recovering the valuable metal




from an ore by dissolution with an aqueous solvent, leaving the gangue or




waste material virtually unaffected.  Subsequent recovery of the metal from




solution is accomplished by chemical or electrolytic precipitation.  For




copper, these processes are limited largely to copper-bearing materials




that, because of grade, composition or other consideration, are not amenable




to concentration and pyrometallurgical extraction.  Generally, hydrometal-




lurgical methods are used to treat low-grade ores containing native copper,




oxide, or mixed oxide-sulfide minerals because costs of other types of




treatment are too high per unit of copper recovered.  There are no air pollu-




tion problems associated with leaching itself, although as in other materials




handling activities, the problem with fugitive dust is a recurring one.






     Since most of the world copper production is extracted from low-grade




sulfide ores, smelting is the dominant method of recovery of the metal.




Figure III-l shows the basic steps in copper production, one of which is




the pyrometallurgical process of separating copper trom the iron, sulfur,




and gangue.  The strong affinity of copper for sulfur and its weak affinity
                                    -178-

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            Blasting
            The ore body is broken up by
            blasting.

    MILLING
             IORE
                               Loading
                               The ore. averaging about 1 per-
                               cent copper, is loaded into ore
                               cars by electric shovels
               Hauling
               The cars ol ore are hauled to
               the mill.
            Crushing
            The ore is crushed to pieces
            the size of walnuts

   SMELTING
            ICOPPER CONCENTRATES^
                               Grinding
                               The crushed ore is ground to
                               a powder
               Concentrating
               The mineral-bearing  particles
               in the powdered ore  are con-
               centrated
Roosting
The copper concentrates (av
eragmg about 30  percent
copper) are roasted to remove
sulfur
    REFINING
              BLISTER
                                           Reverberotory Furnace
                                           The  roasted concentrate is
                                           smelted and a matte, contain
                                           ing 3242 percent  copper, is
                                           produced
                Converter
                The matte is converted  into
                blister copper with a purity of
                about 99  percent
                                                         OTHM tr-MOOUCTS
            Refining Fumoce
            Blister  copper is  treated in a
            refining furnace.*

      FABRICATING
            (REFINED  COPPER
                               Electrolytic Refining
                               Copper requiring further treat-
                               ment is sent to the electrolytic
                               refinery **
                                                                           HWien the lire refined copper meets Ihc specr
                                                                          ficationsol litnrcitors it is used •ithout further
                                                                          ielimn|.
                * Copper is further refined e ectroiyticalry *hen
                It* icecul properties ol eiecvohiK copper in
                required eg when the coppt' is to be used tor
                eteclncil conductors, indjor when precious
                Rwtots ire present in sufficient quintities lo
                mike recovery dffcribte
C  REFINE




      *
 tolling
                                           Drawing

             Fire refined or electrolytic copper and/or brass
             la mixture of copper and zmci is made into
             sheets tubes rods and wire
                Extruding

Sheets, tubes, rods and wire are further fabricated
into the copper articles you see in even/day use
FIGURE  III-l    BASIC   STEPS  -   COPPER  ORE  TO  FINISHED  PRODUCT
                                                 -179-

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for oxygen, compared with iron,  sulfur and ether base metals of the ore,




form the basis for the three primary steps in smelting - roasting,  re-




verberatory furnacing, and converting.  Although particularly adapted




to the reduction of sulfide ores,  high grade oxide ores may be used as




part of the charge to the furnace, or if siliceous, may be fed direct




to the converters as fluxing material.






     The treatment of the Lake Copper ores of the Lake Superior district




departs from the general smelting  process, in that the matte-forming and




converting stage are combined and, consequently, the smelting process is




more akin to copper refining and is not a part of this manual.






     Figure III-2 illustrates the  three primary steps in copper smelting




and the materials entering and leaving the system at each step.  Figure




III-3 shows representative quantities involved in each step.  Figure III-4




is a simplified flow diagram of the smelting process with emission points




noted.






     Virtually all copper ore is beneficiated at the mine.  Although some




ores are sufficiently high grade for direct smelting and some oxide ores




are treated directly by leaching,  the average tenor of ores mined in the




United States is less than 1 percent.  Beneficiation, or ore dressing,




comprises the two steps of comminution in which the ore is crushed and




ground to liberate the individual  mineral particles, and concentration by




means of which the comminuted ore  is mechanically separated into waste




material or tailings and the copper concentrate.  The concentrate, on the




order of 30 percent copper, is delivered to the smelters by rail, barge,




or conveyor belts.






     Several plants are in operation which produce satisfactory matte without





                                    -180-

-------
    ENTERING THE SYSTEM
LEAVING THE SYSTEM
     Raw concentrates
    Fuel
    Air
Flux  and
fettling material
Fuel
Air
Si Iiceous flux
Miscellaneous
material high in  copper
Air
                                     ROASTER
                                   REVERBERATORY
                                    CONVERTER
Gases, volatile oxides,
and dust to dust  recovery
and stack
    Gases and dust
    to  waste heat  boi lers,
    dust  recovery,  and stack
                                                         Slag to dump
   Gases to  stack
                                                        Blister  copper
                                                        to refinery
          FIGURE 111-2   PRODUCTION  OF  BLISTER COPPER FROM
                            SULFIDE CONCENTRATES
                                     -181-

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           Concentration
            2000 Ib ore
                5%
Concentrate
  365 Ib
 96 Ib Cu
  26%
                             -Tailings
                              1635 Ib
                              4 Ib Cu
                              0.25% Cu
                                                      •Slag
                                                      215 Ib
                                                     1 Ib Cu
                                                     0.55% Cu
         Roasting
                Reverberatory
                   Smelting
                            frjii   !ii::;a:;;.
                                                Gas 50 Ib
                                                          Slag
                                                          126 Ib
                                                          0.5 Ib Cu
 Gas  62  Ib
  1  Ib Cu
Calcine
303 Ib
95 Ib Cu
31% Cu
Matte
202 Ib
94 Ib Cu,
46% Cu|
                                            98.9% Cu\  99.4%  Cu
Copper \
93.5 lbA
Gas ting
Anodes
93 Ib Cu
     FIGURE 111-3  CONCENTRATION AND SflELTING  OF A COPPER  ORE
                                      -182-

-------
                                      a
                                      CD
                                      00
                                      CO
                                      00
                                      00
                                      UJ
                                      Q_
                                      Q_
                                      -=r
                                       i
                                      a:
-183-

-------
roasting.  In these cases, the concentrate may either be dried before




smelting or the raw, moist concentrate may be fed to the reverberatory




furnace.  Figure III-5 provides an overall view of a copper plant and




Figure III-6 shows typical cross section.






     All smelters have waste heat boilers utilizing the waste heat from




the reverberatory furnaces for power production and in some cases for air




preheating and economizers.






     Electrostatic precipitators were used extensively at copper smelters




to prevent product loss, long before air pollution control regulations were




promulgated.  The dust from the converter may contain up to 45 percent cop-




per.  At some smelters an arsenious oxide by-product is recovered, primarily




from the roaster and furnace gases.






     Sulfuric acid plants may be considered add-on pollution control devices.




Such plants are not integral parts of the smelter complex, and, consequently




are not considered in this manual.  However, as leaching of copper ores be-




comes more widespread, the on-site demand for sulfuric acid will increase




and the production of sulfuric acid will become more attractive.






20.  RECEIVING, STORING AND HANDLING OF RAW MATERIALS




     The possible emission will be particulates.




20.1 Process Description




     Copper ores are mined by underground methods and by open pit mining




operations.  From the mine, it is  loaded onto railroad cars and shipped to




the processing plant.  The ore arrives at the plant  in the form of small




nuggets usually less than  2 inches in diameter.  The ore is unloaded from




the car  and placed  into storage bins for further processing.  The ore is




crushed, ground, screened, and then sent to  the concentrator.  From the




concentrator the ore goes  to roasters and then to the reverberatory smelting





                                    -184-

-------
__ CB
T3 w
C D
Main office a
change ho
0
0
+j
Sampling sta
(5)
>
Reverberator
(in


furnaces



Converters
(3)


c
co
Q.
•O
'5
<
(^)


Acid storage
(™)


Slag dump
(*)


a
o
c.
tn
15
0}
55
(D


Warehouse
©
                                    OO
                                    Q_
                                    Q_
                                    O
                                    tn
-185-

-------
                                    REVERBERATORY
                                      FURNACE
                                                      COPPER
                                                       TRACK
0      50     100
I  I I  I I  I I  I I  I I
  Scale  in Feet
 FIGURE  111-6  SCHEMATIC CROSS-SECTION OF A SMELTER
                           -186-

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furnaces.  Once the copper leaves the reverberatory furnace,  the matte is




transferred to the converter.  Finally, the copper goes through several




refining stages before leaving the plant.






      The major air pollution problem associated with the handling of the




raw materials for a copper production plant occurs at the transfer points




when the ore is first brought to the plant.  Depending on operational




practices at the plant, some of the ore may be stockpiled for future pro-




cessing.  The transfer of ore to and from storage, whether in fully en-




closed containers or on open fields, has the potential of becoming a




source of fugitive dust.






20.2  Process Control Operation




      There is some plant motivation to reduce fugitive dust-type emis-




sions from the transfer points of the material handling scheme at copper




smelters.  Dust losses represent product losses and in addition, dust at




appropriate concentration can become a potential explosion hazard.  For




occupational safety-considerations then, it is undesirable for copper




plant operators to have a dusty working environment.  If any air pollution




control schemes are used to remove the dust, they will likely consist of




small baghouses.  Water sprays are sometimes used to suppress dusting.




Essentially, there are no operating variables that the enforcement official




should be concerned with at this point that would affect air pollution




emissions.






20.3  Enforcement Procedure




      The enforcement official should inspect the material handling scheme




at a copper smelter on a windy day.  If any noticeable plumes exist on a




windy day from any of the transfer points, storage hoppers, or stockpiles,




it would indicate a deficiency of the plant's control procedure of





                                  -187-

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reducing or minimizing fugitive-type dust.   On the other hand,  if no dust




is noticeable on a windy day, it is safe to assume that the plant has ade-




quate preventive measures for handling the  raw ore.






     The overview for the material handling scheme should be done on a




hillside overlooking the coper smelting.  At that point, the enforcement




official should observe the precise sources of dust and identify them as




being either from stacks or fugitive sources.  The air pollution code




which deals with materials handling, storage, and receiving of materials




is one that applies to fugitive dust emissions.  The enforcement official




should subjectively observe the transfer points, storage hoppers, conveyors,




and stockpiles.  The enforcement official should fill out the Inspector's




Worksheet for future reference.






     The Inspector's Worksheet which follows may be useful for record keep-




ing.  Interpretation of these observations is heavily dependent upon the




pertinent regulations governing fugitive dust emissions.  Since many of




these plants are located on a large plot of land, it may be important to




discriminate between in-plant housekeeping problems and emissions which




cross the property line.






21.   CONCENTRATING




      Fugitive dust regulations will govern.






21.1  Process Description




      Concentration is a process used in many of these  smelting operations




to mechanically separate minerals in a  raw-feed ore into the ore constit-




uents.  The concentration process is accomplished in a  variety of means,




based on differences in various mineral properties, such as, specific




gravity, magnetic properties, and chemical properties.  The flotation process






                                    -188-

-------
                            INSPECTORS WORKSHEET

                                     FOR

              RECEIVING.  STORING AND HANDLING OF RAW  MATERIALS
Plant Id.
Date of this Inspection

Type of Plant	
               Date of last Inspection
Capacity of Plant_
Source Location
  Type
Material
   Wind
Direction
Wind Speed
   mph      Plume Description
Preventive
 Measures
Sample
Receiving hopper
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
Copper ore














SW/10














Brown














Baghouse used














                                       -189-

-------
is now the most generally used concentration method.  A weak slurry




of ore is introduced to a vessel.  Flotation agents cause the copper-




bearing minerals to rise as a froth as the bath is agitated.  The froth




is skimmed and dried for use in the subsequent smelting operations.  The




flotation cell must have particles less than 
-------
processed through the concentrator building.  These records can be used for




future comparisons to determine whether any Increase of production occurs




at this plant.  These daily operating records are likely to be kept by




plant officials as part of their overall monitoring of the plant operation.






        The enforcement official should observe the material transport system




and note if there are any dust plumes generated especially at the transfer




points.  Water sprays can be used as a dust suppressant for many of these




material handling schemes.  From outside the building, note whether any




plume escapes through the roof monitors.  Finally, record the moisture




content of the concentrate leaving the process.






22.     CONCENTRATE ROASTING




        This is a major point of sulfur emissions in the copper smelting




process.  It is also a possible major source of particulate emissions if




control equipment is not functioning properly.  Individual plants may not




have sulfur recovery units.






22.1    Process Description




        Roasting is the pyrometallurgical process in which an ore or con-




centrate is heated in a specific atmosphere to a high temperature (but




below the melting points of the constituents) in order to effect a desired




chemical change and usually to eliminate, by volatilization, unwanted im-




purities.  As distinguished from calcining, which is a chemical decomposi-




tion process, roasting is a chemical combination process.  Although funda-




mentally different, the roasted product is called calcine.






        In the roasting of sulfide copper ore or concentrates, the material




is heated in an oxidizing atmosphere to eliminate a portion (but not all)




of the sulfur as S02J to remove detrimental volatile impurities such as




                                  -191-

-------
antimony, arsenic, and bismuth; and to convert a portion of the iron into

iron oxides in which form it will be removed in the slag from the matte
furnace.  The amount of sulfur and iron to be oxidized in the roasting

operation depends upon the desired quality of the charge to the reverbera-
tory furnace.  With a given concentrate to treat, the smelter personnel

must decide how much sulfur, if any, to remove by roasting in order to put
the reverberatory and converter operation in the best economic position.

        The desired reduction in the sulfur content is normally effected in
a roasting furnace of which there are two types:  multiple-hearth and fluid

bed.  The two are similar in metallurgical principle and involve the follow-

ing considerations:

        1.  Roasting is an oxidation of the copper and iron sulfides with

            oxygen in the air as the oxidizing agent.  An adequate supply

            of air is necessary.  Representative reactions would include,
            among others:
                       4FeS2 + H02 - *• 2Fe203  + 8S02
                       4CuFeS2 + 1302 - *>4CuO  + 2Fe203 + 8S02

        2.  The principal combustion product is S02 which must be cleared

            from the roaster atmosphere to continue the reaction.  At

            high S02 concentrations the reaction virtually ceases.

        3.  No part of the roaster charge nor the calcine becomes liquid;

            hence the reaction occurs only when particle surfaces are ex-

            posed, necessitating a finely milled concentrate charge.

        4.  Temperatures must be maintained high enough to ignite the

            sulfide charge and maintain combustion temperatures.  Self

            roasting ores, i.e., at least 24 percent sulfides, release

            enough heat to maintain the proper temperature without added

            fuel.
                                    -192-

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22.1.1  Multiple Hearth Roasting Furnace




        Figure  22.1 is a sectional drawing of a typical multiple hearth




furnace.  This older type roaster is gradually being replaced by the more




modern fluid bed roaster.






        The hearths are constructed of refractory brick with a slight




arch.  The external portion of the furnace is a brick-lined, steel shell




with hinged doors and inspection plates at each level.  The moist concen-




trate enters the roaster proper through an annular opening to the top-most




or dryer hearth.  Rabble arms, attached to the hollow central shaft, are




rotated as the shaft turns and plow through the charge to continually ex-




pose fresh surfaces to the oxidizing air.  The rabble blades are set at




an angle and, in addition to stirring the material, move it alternately




either to the center of the hearth or to the periphery where it falls to




the next lower hearth.  Finished calcine is discharged through holes on




the circumference of the bottom hearth.






        The air required for roasting is admitted through the central




shaft and by means of valves the air supply to each hearth may be regulated.




Roaster gases are drawn off through gas outlets located just below the drier




hearth.  A luted discharge from the dryer hearth to the top roasting hearth




prevents escape of gas from the interior of the roaster.






        Burners for fuel oil, gas, or pulverized coal are set in the side




wdll to preheat the roaster to combustion temperature upon start up and




when the concentrate does not contain enough sulfur to be self-roasting.






        Multiple hearth roaster off gases contain variable amounts of SCL




because of the wide variation in concentrate constituents and desired matte




quality.  For low sulfur concentrates requiring continuous auxiliary fuel,





                                  -193-

-------
                              Air Inlet to Arms;
Feed Scraper

Feed Raceway

 Feeder Arm

 Feed Plate
 and Apron

    Air
 Control Valve

 Arm Locking
   Device  "
  Lute Cap
   Supply
  Air Duct
  Discharge
   Air Duct
  Inspection
    Door
 Hinged Door
 Master Gear
 Bevel Pinion'
  Safety Pin
Speed Reducer
                  Upper Bearing

                       3
                                             Outlet from Arms
                                                                Removable
                                                                 Bearing
      FIGURE  22,1    MULTIPLE  HEARTH  ROASTER
                                    -194-

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values as low as 1 percent S0? may occur.  On the other hand, values up




to 10 percent may result from completely self-roasting concentrates.  In




general, the average would be in the range of 4 to 5 percent.






     Particulate gas loadings are high with the countercurrent air flow,




ranging from 3 to 6 percent of feed depending upon the size distribution




of the concentrate.  The flue dust may contain anything that was in the




original concentrate charge and, if pulverized coal is used as the firing




fuel, a certain amount of ash.  Since the dust contains an average of




about 7 percent copper, it is economically attractive to recover the dust




for feed to the reverberatory or converter.  Preliminary dust collection




in a cyclone is followed by gas cooling and final dust collection in an




electrostatic precipitator.






22.1.2  Fluid Bed Roasting Furnace




        With the increased concern for sulfur dioxide air pollution con-




trol at smelters, there is a revival of interest in the roasting of cop-




per concentrate in a manner which produces SO  rich gas.  New installa-




tions are almost invariably fluid-bed roasters.






        The fluid-bed roaster is similar in appearance to a multiple




hearth roaster but does not include the intricate internal mechanical




systems.  Finely ground material (60 percent minus 200 mesh) passes over




a drying hearth and through a chute and feeder into a ball-mill to break




up agglomerates formed in drying, or is introduced as a slurry.  The feed




is continuously delivered into the combustion chamber.  Roasting occurs




as the sulfide particles are falling through the oxidizing air.






        Combustion air from the windbox passes up through distribution




plates at the bottom of the chamber into the combustion zone.  Because





                                  -195-

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of the large surface area of the finely ground material exposed to the air




stream the residence time in the oxidizing atmosphere is short.  The re-




action is self-sustaining.  Oil, gas, or pulverized coal burners are re-




quired only to preheat the roaster to combustion temperature.






        Roaster gases are drawn off through flues at the top of the chamber




and pass immediately to cyclone collectors, followed by cooling and final




dust collection.  As much as 85 percent of the feed is carried with the




gas stream and, hence, the cyclones are an integral part of the roasting




operation.  Screw conveyors collect this 'finished calcine and that from




the bottom of the combustion chamber for discharge into hoppers.






        S02 concentrations are considerably higher than for multiple hearth




roasters due to the lower total air volume.  Average stack gas S02 concen-




tration is about 12 percent with maximums near 18 percent.






22.2    Process Control Operation




        For either type roaster there are three operating variables:  feed




rate, combustion air flow rate, and  temperature.  Day-to-day operation of




the roaster will depend upon the chemical and physical characteristics of




the feed concentrate,  the quality of the calcine desired for the reverber-




atory furnaces, and whether or not the off gasses are being treated for




sulfur removal.  It would be expected  that some variation in operation




will occur at any one  smelter and that large variations will occur between




several smelters that  have  roasting  operations.  Typical operating ranges




are given below:




                               Multiple Hearth            Fluid Bed




Feed rate  (tons/day)              150 to  800              700 to 1,500




Air Flow Rate  (103  scfm)          100 to  130                6 to 25




Temperature  (°F)                1,200 to  1,800         1,200 to 1,750
                                    -196-

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     For economic reasons the three operating variables are carefully




controlled.  The furnace operator can regulate rate-of-feed, air supply,




and temperature in such a way as to obtain the maximum efficiency for the




material being treated.  Hourly values are usually recorded.






22.3  Enforcement Procedure




      The objectives of copper concentrate roasting operation inspections




are to establish compliance with the sulfur dioxide and particulate emis-




sion regulations.  In order to accomplish the above objectives,  the en-




forcement official needs to determine:




         1.  Current production levels and operating conditions,




         2.  Design production levels and operating conditions,




         3.  Current controlled and uncontrolled particulate and sulfur




             dioxide emission levels,




         4.  Efficiency and adequacy of emission control equipment at




             current and design operating levels.




      Both roaster and roaster emission control equipment design capacities




and operating conditions can be obtained from design drawings and plans.




These data should be obtained from the company representative prior to




physical plant inspection.   Production levels, roaster feed weight rates,




roaster and roaster emission control equipment operating conditions are




monitored by the plant operator and are either recorded in the operator's




daily log or are displayed on instrument panels.






      All copper roasters will have a control booth near the roaster for




careful monitoring.  The enforcement official should have little diffi-




culty in assessing the current operating status of the roaster by observing




the many recorders, gauges, and log sheets which are normally kept for the




roaster.




                                   -197-

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      Of primary importance for the enforcement of air pollution emission
regulations is the process weight rate and the sulfur content.  With the
mass rate and sulfur content of the feed and calcine, a sulfur mass balance
can be calculated.  From this, SC^ emissions can be computed.  It should
be pointed out that many state regulations restrict sulfur emissions from
the entire copper smelter and not just the copper roaster.  For deter-
mining compliance with the regulations, sulfur emissions from each opera-
tion must be summed, then compared.

      Many copper roasters have a sulfuric acid plant to treat exhaust
gases from the roaster.  These plants monitor SC^ gases continuously.
The enforcement official should note the flow and concentration of the
acid plant inlet and outlet gas for subsequent inspections.  There should
be little deviation (± 20) from visit to visit because of the fixed design
of acid facilities.

      There is little that can be noted on instrument panels regarding the
amount of particulates emitted to the atmosphere.  Some plants will have
a smoke density meter which may be used to determine relative particulate
emissions from one visit to another.  The enforcement official should
note the pressure drop, spark rate, flow rate, and the operational para-
meters of the air pollution control devices.

      Visible emissions are the simplest means for estimating particulate
control equipment performance.  The enforcement official should estimate
the percent opacity of dust control equipment stack plume and if in excess
of allowable limits, take appropriate action.

      Building openings should be observed for evidence of escape of inade-
quately captured process dust.  If noted, determine points of origin and
require corrective action.
                                   -198-

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     The enforcement official should subjectively analyze the appearance
of the copper roaster and note any leaks, SCL odors, condition of the
duct, etc.  Finally, some attention should be given to the dust emission
from the material handling of the feed ores and calcine to and from the
roasting machine.

23.  CONCENTRATE SMELTING
     This is a major potential particulate emission and moderate sulfur
emission process.  Particulate emissions are mainly a function of the
adequacy of the control system.
23.1  Process Description
      Smelting is the pyrometallurgical process in which solid material
is melted and subjected to certain chemical changes.  In the smelting of
copper, hot calcines from the roaster or raw unroasted concentrate with
siliceous or limestone flux are melted in a reverberatory furnace.  Con-
verter slag, collected dust, ladle skulls, refinery slag, oxide ores, and
any other material rich in copper may be added to the furnace charge.  The
copper and iron which are present in the charge combine with sulfur to
form cuprous sulfide, Cu9S, and ferrous sulfide, FeS.  For example, covel-
lite and pyrite, upon being heated to a high temperature, will decompose
according to the equations:
                            2 CuS—>-Cu S + S
                            FeS 	>-FeS + S,

and the oxides according to:
                         2 Cu 0 + 33	>2 Cu2S + SO

                         2 FeO + 3S	*2 FeS + SO^
The more complex associations of copper, iron and sulfur break down in a
similar way:
                                  199-

-------
                       2 Cu FeS2—»-Cu2S + 2FeS + S




The net result is the formation of the two stable compounds and the




volatilization of some sulfur which is immediately oxidized to S02.




The two sulfides are miscible in all proportions in the liquid state,




and the mixture, whether liquid or solid, is known as copper matte.  In




practice, the matte contains about 95 percent copper and iron sulfides,




with sulfides of various other metals and arsenic, antimony, selenium,




and tellurium accounting for the remainder.  The precious metals remain




dissolved in the matte and are recovered later in the refining process.






     The amount of matte produced as a percentage of the total charge is




called the matte fall; the percent of copper is the grade of the matte.




Bluish-purple mattes containing 40-45 percent are best for efficient con-




verter operation.  Low grade matte, a dull bronze in color and containing




20-40 percent copper, makes the converting process economically unattrac-




tive.  High grade matte, a whitish color, containing more than 70 percent




copper, although economically converted, requires excessive roasting, re-




sults in high copper loss, as well as insufficient matte to collect  the




precious metals, and difficulty in converter operation.






     The purpose of the smelting process is the separation of the  gangue




minerals in the charge  from the matte.  The material which contains  these




minerals is called  slag.   Essentially slags are a molten solution  of com-




plex ferrous silicates  in  which are dissolved  smaller  amounts of other




basic oxides  (A^O^, CaO,  and MgO).  The slag  also contains a small  amount




of  copper  and sulfur.






     The fluxes used to form  the  slag are  mixed to a composition and




quantity to combine with all  the  gangue present  in the copper-rich mater-




ial and  to produce  a slag  of  suitable properties  and volume.  Although
                                    -200-

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in some cases a  charge may be  self-fluxing,  it  is generally necessary  to




add either siliceous materials or  limestone  according to  the nature of the




deficiency.  Silica is often added in  the  form  of siliceous copper ores.




The iron-rich slag from  the converters  is  almost invariably charged into




the reverberatory furnaces and this material also exerts  a fluxing action




by providing iron oxide,  and is  thus useful  in  counteracting any excessive




slag acidity.






     Reverberatory furnaces are  long room-like  structures from 80 to 130




feet long and 10 to 35 feet wide.   Figure  23.1  is a  sketch of such a fur-




nace.  Capacities range  from 50  to 1,500 tons of charge per day.  Oil,




natural gas, or  pulverized coal  is  burned  in a  separate compartment from




which the flame  and hot  gases pass  over the  molten mass.  Heating of the




charge is principally accomplished by  radiation from the  roof and side




walls rather than by'direct contact with the hot gases.   There is little




reaction between the gases in the  furnace  atmosphere and  the material  on




the hearth.  It  is possible to get some oxidation of the  charge by using




a large excess of air for combustion,  but  this  is uneconomical and is  sel-




dom, practiced.   The principal chemical  reactions that take place in the re-




verberatory furnace are  between  the various  constituents  of the charge to




form the matte and the slag.






     The concentrates, hot calcines and fluxes  are brought in cars on




tracks or on conveyor belts above  the  reverberatory  furnace and charged




to hoppers.  In  some of  the latest construction, the roaster is placed dir-




ectly above the  furnaces  where the  roasters  discharge directly into the




charge hoppers,  flow being gate-controlled.






     The contents of the  hoppers are charged above and along the sides of




the furnace forming charge piles on each side of the central molten bath




                                   -201-

-------
                                «c
                                cE
                                gj
                                o

                                CD
                                H^
                                LU
                                oo
                                1—I

                                CNI
                                LU

                                CD
-202-

-------
 of matte and slag.  Water-cooled gun feeders allow the charge to flow




 over the surface with minimum disturbance.  At one plant using raw con-




centrate the moist charge is introduced by means of high-speed belt sling-




 ing machines which deliver a ribbon-like thin layer over the surface of




 the bath.






      As new charge is added and fuses into the bath, the volume of molten




 matte and slag increases.  The depth of the bath at the firing end may be




 three feat ^uU i_hc slag,, i.ecau^v. ^_ j.^ lower density, floats on top and




 is usually allowed to overflow continuously from the skimming door or slag




 notch located near the exhaust end of the furnace.  Launders lead to slag




 cars which then carry the slag to the slag pit.  The matte is tapped inter-




 mittently from tap holes near the bottom toward the firing end of the fur-




 nace and conveyed in a molten condition to the converter plant.






      The furnace is fired by high capacity burners located in one end of




 the furnace.  In some cases, auxiliary burners are set in the side walls




 near the back.  Rapid and complete mixing of air and fuel is necessary in




 order to liberate the maximum amount of heat close to the burners where




 most of the heat is required.  Secondary air is drawn in around the




 burner to provide about 5 percent excess air.  Waste heat boilers are




 almost universally used.  The boilers are constructed without baffles to




 prevent draft loss and to maintain negative pressure which prevents gas




 escape,  up to 40 percent of the flue gas sensible heat is recovered in



 the waste heat boiler and, in some cases, an additional 10 percent may be




 recovered in combustion gas preheaters.  These heat recovery systems not




 only reduce overall fuel requirements but also serve to cool the gases be-




 fore entering the primary dust recovery system.






      Combustion gases will contain from 15 to 30 percent of the sulfur in




 the original charge depending primarily upon whether or not the concentrate





                                    -203-

-------
was roasted, but because of the high volume of combustion air, SC>2 con-




centrations are low, varying from 0.5 percent to 3.5 percent.  These




lean SC^ mixtures, unlike off gases from the roasters and converters, are




not economically utilized as feed for sulfuric acid plants or other sul-




fur recovery methods.






        Particulate loading in the combustion gas will vary from 2 to 5




gr/scf which, for a large furnace at maximum production rate, would pro-




duce 80 tons of particulates per day.  Dusting within the furnace is




greatly reduced where moist concentrate is used as the charge, and where




furnace feeding operations are carefully controlled.  Pulverized coal




will result in a certain amount of ash contained in the flue gases.






        Heavy particulate matter settles out below the waste heat boilers




or in the balloon flues leading to the primary dust collection system,




from which it is collected and returned to the system to recover copper.




Final dust collection is performed by an electrostatic precipitator.




Table 23.1 lists the operating parameters of the reverberatory furnaces




in the United States.






23.2   Process Control Operation




       There are three operating variables for a reverberatory furnace:




(1) feed rate,  (2) combustion air flow rate, and (3) furnace  temperature.




Although the furnace operation is continuous, the through-put rate must




be varied  to match  the availability  of converter capacity.   The matte  is




transferred  to  the  converters in the molten  state in ladles; hence,  the




matte formation and, consequently, the feed  rate is adjusted  to meet con-




verter requirements.  Further, on occasion,  an upset may occur upstream




in the system and limit the availability of  furnace charge.
                                   -204-

-------
     The feed rate, in turn, determines the air flow rate and fuel feed




rate.  If converter capacity has been reduced through breakdown or other




cause, furnace charge is reduced and the fuel feed rate and combustion air




are reduced to that required only to maintain the correct temperature re-




quired for the molten bath.  This temperature may vary to a limited degree,




but it is economically important that it be carefully controlled.  At the




firing end of the furnace, a temperature of around 2,800 F is required to




maintain the desired fluidity of the matte.  Depending upon furnace length




and charge rate, the exhaust end temperature must be sufficiently high to




permit free-running matte and slag with efficient separation.  Temperatures




higher than required are wasteful of fuel.  Exhaust-end temperatures are




around 2,000°F.






     Listed below are typical operating ranges for reverberatory furnaces




operating at designed capacity.




                 Feed rate (tons/day)           400 to 1,500




                 Air flow rate (103 scfm)        26 to 155




                 Temperature (°F)              2,000 to 2,800





     Exhaust gas temperatures from the furnace average near 2,600 F.  Gas




temperatures following the waste heat boilers average 700 F with further




cooling by dilution air to 600 F before the precipitator.






     In the past it was necessary to shut down the reverberatory furnace




periodically for repair of the refractory material.  Since the adoption




of hot patching methods, furnace campaigns have been extended almost in-




definitely and furnace shut downs are rare.  Upset conditions may occur in




feed mechanisms or burner operation, but the result of such upsets is merely




to reduce the through-put rate.
                                   -205-

-------
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                                         -208-

-------

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Where and How Is
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Product Data

5


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In Matte
-209-

-------
        While the major source of particulate and sulfur dioxide emissions




is the furnace stack, there are three other sources.   Dust can be gener-




ated during loading and unloading of charging equipment.  The slag launder




and handling equipment are minor sources of sulfur dioxide.  The matte




launder and transfer ladle are another source of sulfur dioxide and




particulates.






23.3    Enforcement Procedure



        The objective of copper smelting operation inspection is to es-




tablish compliance with the sulfur dioxide and particulate emission regu-




lations.  In order to accomplish the above objective, the enforcement




official needs to determine:




        1.  Current production levels and operating conditions,




        2.  Design production levels and operating conditions,




        3.  Current controlled and uncontrolled particulate and sulfur




            dioxide emission levels,




        4.  Efficiency and adequacy of emission control equipment at




            current and design operating levels.






        Both furnace and emission control equipment design capacities and




operating conditions can be obtained from design drawings and plans.




These data should be obtained from the company representative prior to




plant inspection.  Production levels, roaster feed weight rates, roaster




and roaster emission control equipment operating conditions are monitored




by  the plant operator and  are either recorded in the  operator's daily




log or are displayed on instrument panels.






        The furnaces will  have a control booth nearby for careful monitor-




ing.  The enforcement official should have little difficulty assessing  the






                                   -210-

-------
current operating status of the furnace by observing the many recorders,




gauges and log sheets which are normally kept.






     Of primary importance for the enforcement of the air pollution emission




regulations is the process weight rate and the sulfur content.  With the




mass rate and sulfur content of the feed, slag and matte, a sulfur mass




balance can be calculated.  From this, S02 emissions can be computed.




Compare the computed emissions with allowable levels in the regulations.




If required, take appropriate action.






     It should be pointed out that many state regulations restrict sulfur




emissions from the entire smelter and not separate processes.  For deter-




mining compliance with the regulations, sulfur emissions from each oper-




ation must be summed, then compared.






     There is little that can be noted on instrument panels regarding the




amount of particulates emitted to the atmosphere.  Some plants will have




a smoke density meter which may be used to determine relative particulate




emissions from one visit to another.  The enforcement official should




note the pressure drop, spark rate, and flow rate and operational para-




meters of the air pollution control devices.






     The enforcement official should subjectively analyze the appearance




of the roaster and note any leaks, SC>2 odors, condition of the duct, etc.




Finally, some attention should be given to the dust emission from the




material handling of the feed to the furnace.  The enforcement official




should inspect the dust handling system below the boilers and the flues




and also trace out and inspect the balloon flues leading to the final dust




collection system.
                                 -211-

-------
     Two sources of effluent at the reverberatory furnace occur at the




tap hole and the slag notch.  Matte is drawn off intermittently into matte




pots resulting in a rather significant source of smoke and dust which,




if not collected, will be emitted through the roof monitors.  Matte pots




generally have ventilating hoods which collect the emissions and vent to




ducting system.






     No control is attempted for the slag skimming operation.  The launders




usually lead to slag cars outside the building.  This and the continuous




nature of the skimming process results in low mass emission rates and




rapid dilution of the effluent.






     Visible emissions are the simplest means for estimating particulate




control equipment performance.  The enforcement official should estimate




the percent opacity of dust control equipment stack plume and if in ex-




cess of allowable limits, take appropriate action.






     Building openings should be observed for evidence of escape of in-




adequately captured process dust.  If noted, determine point (s) of origin




and require corrective action.






24.  CONVERTING




     This' is the principal source of sulfur emissions in the copper smelt-




ing process.  Individual plants may have recovery units.  It may be a




major source of particulate emissions, depending on the adequacy of the




control equipment.






24.1  Process Description




      Converting  is the final pyrometallurgical process in  the production




of blister copper ready for refining.  The process consists essentially in
                                    -212-

-------
blowing air through the molten matte from the reverberatory furnace.  The




ferrous sulfide is oxidized to ferrous oxide and slagged off and the copper




sulfide is oxidized to blister copper.  Sulfur from both reactions goes off




in the flue gases as sulfur dioxide.




          Two types of converters are used:




          1.  The upright or Great Falls converter ,




          2.  The horizontal or Fierce-Smith converter.




The operation is similar with both.  The general procedure is directed into




two stages:  the slag-forming blow and the copper blow.






     About 20 tons* of molten matte at about 1,100°C are charged together




with about 5 tons* of siliceous flux, either relatively pure quartz or a




siliceous ore of copper.  The blast is then turned on and the converter




rotated until the tuyeres are covered.  During the early stages of the




blow (the slagging period) the ferrous sulfide in the matte is oxidized




preferentially, because of its lower free energy of formation as compared




with cuprous sulfide:
                       2FeS + 302 - *-2FeO + 2S02




The ferrous oxide produced combines with the siliceous flux to form a slag:




                       FeO + Si02 - »-FeO + Si02




The reaction furnishes sufficient heat to maintain the desired temperature




and, in fact cold copper bearing material in the form of scrap, or matte




skulls are added to prevent overheating and damage to the converter lining.






     At the end of the slagging period, when all the ferrous sulfide has




been oxidized and slagged, the bottom of the bath contains nearly pure






* These approximate figures apply to large horizontal converters.  Quanti-




ties are smaller with upright converters which are rare today.






                                   -213-

-------
cuprous sulf ide (white metal) .   In normal practice the charge is blown




almost to white metal (30 to 180 minutes) and the converter is then rotated




and most of the slag poured off.  A new charge and fresh flux are then




added and blowing and pouring of slag are repeated until the converter is




filled with white metal.  The last of the iron is removed as completely




as possible, and the copper blow started.






     The copper blow converts the white metal to blister copper:
                       Cu2S + 02 - ^2Cu + S02




the sulfur oxidizing preferentially to the copper.  If the blow is con-




tinued too long, the copper begins to oxidize; if too short, the sulfur




is not completely oxidized.






     The Fierce-Smith converter consists of a cylindrical steel shell




mounted on trunnions at either end which permits rotation of the converter




around the long axis.  Figure 24.1 is a picture of a 13 by 30 foot con-




verter, a common size.  Figure 24.2 is a sketch of a typical converter




aisle cross section.  Air enters through tuyeres connected to the wind




box by air pipe and flexible coupling.  The tuyeres are usually 1 to 1-1/2




inches in diameter and 8 to 12 inches apart.  They are placed high enough




above the bottom to clear the level of the metal at the finish of the con-




version.  Frequent punching of the tuyeres is necessary to keep the air



inlets clear.






     Siliceous  flux may be added to the converter in three ways:




     1.  By a steel scoop or boat handled by a crane which pours the




         material into the mouth of the converter,




     2.  By a chute from an overhead bin,
                                    -214-

-------
FIGURE 24,1  ELEVATION OF A FIERCE-SMITH CONVERTER
                       -215-

-------
                                   LU
                                   GO
                                   GO
                                   CD
                                   cc:
                                   oo
                                   cc:
                                    CM

                                    ^r
                                    CNl

                                    LU
                                    ceZ
                                    ^D
                                    CD
-216-

-------
     3.  By a Gar gun which blows finely crushed silica into the con-

         verter through a tube inserted at one end.

     When the converter cycle is finished the converter is tilted to dis-

charge the copper metal into ladles.  It is then transferred to the anode

furnace and casting machines.  The products of the converter are blister

copper containing 99 percent copper, slag, and flue dust and gas.  Con-

verter slags are essentially iron silicates with some alumina and magnesia,

but contain up to 5 percent copper.  To avoid the loss of this copper,

converter slags are used to flux the reverberatory furnaces or are solidi-

fied, broken up, and added to the furnace charge.

     Flue gases laden with dust and fumes are captured at the converter

mouth by either air-cooled or water-cooled hoods.  Sufficient dilution air

is introduced to cool the gases before entrance into large balloon flues

leading to the primary gas cleaners.  The gases consist principally of

N2, C>2> an<^ SO™.  The production of SO. varies within the converter cycle

and occurs only during the blowing periods.  During the slagging blow,

SO^ concentration may be as high as 12 percent at the converter mouth, and

during the finish blow as high as 18 percent.  After dilution, SO. concen-

tration varies from 2 to 10 percent at different stages of the converter

cycle with an average of about 4 to 6 percent.

     Fumes present in the flue gases are volitalized oxides of arsenic,

antimony and lead and certain metallic sulfates and sulfuric acid.  The

dust from the converter contains as much as 45 percent copper.  This copper

and by-product arsenious oxide are collected in the flues and the primary

dust collector.  Dust concentration in the converter off gasses may average

as high as 12 gr/scf, which for a large converter would produce 15 tons of

particulates per day.
                                  -217-

-------
24.2  Process Control Operation




      The converter operation is a batch process.  The parameters depend




upon the converter size and the matte tenor.  For instance, a 13-by-30




foot Fierce-Smith converter holds 200 tons of matte.  With 40 percent




matte the capacity is about 120 tons of copper per day with 12-hour oper-




ating cycles.  Table 24.1 shows a typical operating schedule.  Within mod-




erate limits, the daily capacity increases 5 tons for each 1 percent in-




crease in matte tenor and decreases 5 tons for each 1,000 ft. increase in




altitude.






      The theoretical quantity of oxygen per ton of copper produced can be




calculated.  However, excess air of around 50 percent at 12 to 15 psi is




supplied to the converter and the volume is approximately 150,000 acf/ton




of blister produced.  Both the theoretical and actual amount vary with the




g.'ade of matte used.  For' the converter schedule outlined in Table 24.1,




approximately 9,000,000 acf of air are required per cycle with an average




flow rate of 15,000 acfm during the 10.1-hr blow period.  The use of oxygen




enriched air results in a substantial decrease in air requirements.






      Infiltration of dilution air is permitted at  the hood covering the




mouth of the converter in order to cool the hot gases.  For air cooled




hoods, dilution air can be as much as four times the actual converter gas




volume.  In the case of tight fitting water cooled  hoods, the dilution air




may be only half the volume of the converter gas.






      Operating temperatures within the converter are closely controlled




in the range from 2,200 to 2,300°F by adding cold material to the oxidizing




material as required.  After dilution the flue gas  temperatures are  in the




range 600 to 700°F with properly adjusted hoods.  With excess dilution the




temperatures are lower.



                                      -218-

-------
                                  TABLE 24.1
                     TYPICAL  OPERATING SCHEDULE  FOR A
                     CONVERTER BATCH USING A 40% MATTE
Work Done
Charge 6 tons matte shells
Charge 6 ladles (72 tons) matte
Charge 12 tons ^^ij-ca flax
Skim 3 pots (27 tons) slag
Charge 2 ladles (24 tons) matte
Charge 4 tons converter cleanup
Charge 8 tons silica flux
Skim 2 pots (18 tons) slag
Charge 2 ladles (24 tons) matte
Charge 6 tons copper slag
Charge 7 tons silica flux
Skim 2 pots (18 tons) slag
Charge 1 ladle. (12 tons) matte
Charge 3 tons matte shells
Charge 6 tons silica flux
Skim 2 pots (18 tons) slag
Charge 1 ladle (12 tons) matte
Charge 5 tons silica flux
Skim 1 ladle (9 tons) slag
Final Blow
Skim 1 ladle (9 tons) slag
Charge 4 tons scrap copper
Blowing to copper
Charge 1 ton 90% silica flux (to remove lead)
Blow to high blister
Skim oxidized slag (6 tons) .
Transfer copper to pouring ladle
Cleaning tuyeres, silica gun and adding new matte
charge
„ v t Cumu-
Converter Not . .
Blowing Blowing Time
Hr.


1
-


1
-


1
-


-
-

1
-
-
-

3

-
-
-
-
Min.


30
-


15
-


05
-


55
-

-
-
20
-

45

15
-
-
-
Hr.


-
-


-
-


-
-


-
-

-
-
-
-

-

-
-
-
-
Min.


-
15


-
10


-
10


-
10

-
5
-
10

-

-
5
15
20
Hr.


-
1


3
3


4
4


5
5

6
6
6
7

10

11
11
11
11
Min.


-
45


-
10


15
25


20
30

30
35
55
05

50

05
10
25
45
Total time
Total matte
Total silica flux
Total cold material
Total blister produced
Total slag produced
                                                 10
05
                                                                           11
1    40
 144 tons
  38 tons
  17 tons
  60 tons
  11 pots or 99 tons
                                                                                 45
                                      -219-

-------
     The operating variables for a given converter and gas recovery system


are the quantity and tenor of the matte, the converter charging and blowing


schedule, operating temperature and quantity of dilution air.   All but the


last of these are carefully controlled by the metallurgist in charge to


produce the most desirable and economical product.  Only the quantity of


dilution air is outside the purview of the metallurgist and subject to


other considerations.  With acid plant SO. recoverv systems dilution air


will be reduced to a minimum commensurate with the requirement for cooling,


but without acid plant recovery systems dilution air will increase to a


maximum commensurate with flue and air cleaning capacity.



24.3 Enforcement Procedure


     Emissions from the converter consist of sulfur dioxide gas and par-


ticulates.  The gas composition is on the order of 4 to 6 percent SO™.


The dust loading is on the order of 3 to 10 gr/scf.  Air pollution abatement

  i
equipment is used on almost all plants  to remove the dust and many plants


have sulfuric acid recovery facilities  to remove sulfur dioxide from  the


gas stream.



       The objective  of copper  converter operation  inspection is to estab-

lish compliance with the  sulfur dioxide  and particulate emission regulations.


In order to  accomplish the  above  objective, the enforcement official  needs


to determine:


     1.  Current production  levels and  operating  conditions,


     2.  Design production  levels  and operating conditions,


     3.  Current controlled  and uncontrolled particulate  and sulfur


         dioxide emission levels,


     4.  Efficiency  and adequacy  of emission control  equipment at  current


         and design  levels.


                                    -220-

-------
     Converter and converter emission control equipment design capacities




and operating conditions can be obtained from design drawings and plans.




These data should be obtained from the company representative prior to




plant inspection.  Production levels, converter feed weight rates and




emission control equipment operating conditions are monitored by the




plant operator and are either recorded in the operator's daily log or are




displayed on the instrument panels.






     Converters may have a control booth near the unit for process moni-




toring.  The enforcement official should have little difficulty assessing




the current operating status of the converter by observing the many re-




corders, gauges and log sheets which are normally kept.






     Of primary importance for the enforcement of air pollution emission




regulations is the process weight.  With the mass rate and sulfur content




of the feed, the SC^ emissions can be computed (assume negligible content




in copper and slag).






     There is little that can be noted on instrument panels regarding the




amount of particulates emitted to the atmosphere, although some plants




will have a smoke density meter which may be used to determine relative




particulate emissions from one visit to another.  The enforcement official




shouls note the operational parameters of the air pollution control devices.






     Visible emissions are the simplest means for estimating particulate




control equipment performance.  The enforcement official should estimate




the percent opacity of dust control equipment stack plumes and if in ex-




cess of allowable limits, take appropriate action.
                                   -221-

-------
     Building openings should be observed for evidence of escape of in-




adequately captured process dust and if noted, determine point(s) or origin




and require corrective action.






     The enforcement official should complete the Inspector's Worksheet




for the converter.
                                    -222-

-------
                         INSPECTORS WORKSHEET
                         FOR COPPER CONVERTERS
Plant Id.
Date of this Inspection	Date of  last  Inspection	
No. of converters	
Total capacity	tons/hr Feed	tons/hr  copper
Type of converter	
Sulfur content of feed          %
ABATEMENT EQUIPMENT - Particulates
Pressure Drop	in. 1^0
Flow rate	scfm
Inlet Temperature	°F
Spark Rate	spm
Collection Efficiency	7°   Grain loading	gr/scf
Year Installed	
Opacity reading on stack	%

DIAGRAM OF CONVERTER, PARTICIPATE CONTROL EQUIPMENT S02 PLANT AND STACK
                  (Use separate sh^et if necessary.)
GENERAL OBSERVATIONS:
Is hood volume adequate"?_
S02odor?	
LeaksP holes, etc.?_
Time In                                      Time Out
                                  -223-

-------

-------
                     PART  IV.  LEAD SMELTING







     Lead mining and refining ranks as  the fifth largest basic metallur-



gical industry.  Lead is one of the most useful metals,  its major uses




include automobile storage batteries, gasoline additives, building and




construction, and small arms ammunition.  Lead is also considered to be




a strategic and critical material and is one of the stockpiled metals.




Essentially all lead ores are mined underground and are  concentrated, or




beneficiated, at the mine site.   The common lead minerals are galena




(lead sulfide), cerussite (lead carbonate), and anglesite (lead sulfate).




Galena is the most abundant lead mineral and is usually  found associated



with zinc, silver, gold, iron, and other minerals.






     The domestic lead supply is derived from domestic mine production,




imported ores and concentrates,  imported metal, and secondary domestic




production.  The 1968 apparent demand of 1.4 million tons was supplied




as follows:  domestically refined primary lead - 35 percent, imports -




24 percent, secondary domestic production - 39 percent,  and the remaining




2 percent from government stockpile releases.






     Table IV-1 shows the 1968 U.  S. lead smelters and refineries and



their salient process identification.






     The anticipated annual demand growth rate is about  two percent and




the forecast demand for the year 2000 ranges between 2.5 to 4.1 million




tons.  Environmental and economic considerations and changing use patterns




could have major impact on the consumption patterns and  demand rates.
                                 -225-

-------
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                             -226-

-------
     Copper, gold, silver, and zinc are the major co- or by-products of

lead production.  The minor by-products consist of antimony, bismuth,

cadmium, arsenic, sulfur, tellurium, gallium, germanium, indium, selenium,

and fluorspar.  Concentrator tailings may be used for highways, railroads

and agriculture.  Smelter slags are valued as construction material.


     There are several terms and grades that define lead in terms of

degree of purity, composition of impurities, and the size and shape of

the product marketed.


     Refined lead is 99.85 percent pure and is marketed in seven grades:

corroding lead, chemical lead, acid lead, copper lead, and common de-

silverized lead; also antimony and tin alloys are classified as anti-

monial or hard-lead, white metals, fusible alloys, and copper alloys as

leaded brasses or bronzes.  The final product may be 1-ton blocks, 100-

pound lead pigs, 25-pound caulking lead strings, powder form such as

litharge and red lead oxide, or liquid tetraethyl lead.


     Primary lead production is a sequence of physical-chemical processes

that involves the mining and concentrating of the naturally occurring

lead mineral, mostly as sulfide, the preparatory steps that are necessary

for reducing lead to the metal form, the pyro-reduction process itself

and the subsequent lead purification or refining.


25.  MATERIAL HANDLING

     The possible emissions will be particulates.  Fugitive dust regula-

tions will govern.


25.1  Process Description

      Material handling is an important aspect of lead production in

terms of bulk, diversity of equipment as well as the magnitude of the
                                 -227-

-------
problem associated with airborne particulates and their control.  Lead




production is the process of separating 5 to 7 pounds of lead from about




100 pounds of mine ore.






     Lead ore is mined underground and then transported to the surface




where the first and most substantial bulk reduction, ore concentration,




normally occurs.  The concentrating, or milling operation consists of




ore size reduction by grinding, crushing, and separation.  Feeders con-




vey the ore to large bins for blending and storing.  Further size reduction




takes place in wet-ball mills.  The silt-like ore from the ball mill is




classified and separated from coarse material and is pumped as a water




slurry to flotation cells where the pulp is conditioned by additives.




Large propellers stir the solution and the lead bearing minerals separate




and float to the surface where they are skimmed off.  The non-lead portion




of the slurry, called tailings, is treated in cyclone separators to re-




move fines from the sand.  The clean sand then may be pumped back into




the mine and the fines to a settling pond.






     Once separated, the ore concentrates are thickened in settling tanks




and the slurry is fed to vacuum drum filters which reduce the moisture




content to about seven percent.  The concentration is now complete and




the lead content has been upgraded from an average of 5 to 7 percent to



about 65 percent.






     The concentrates are transported to the smelter site and are stored




in bins.  Proper proportions of concentrates, fluxes, coke breeze, sinter




dust, and crude ore, as necessary, are mixed and pelletized.  Conveyor




belts carry the pelletized mixture to the sintering unit, which removes




most of the sulfur by roasting, and agglomerates it into a porous mass







                                   -228-

-------
called sinter.  The fused sinter is crushed and the dust recovered and re-




cycled.  The sinter, now ready for the blast furnace, is mixed with coke




and is conveyed to the blast furnace.






     Blast furnace products consist normally of four liquids that are dis-




charged from the bottom: lead metal, matte, speiss, and slag.  The lead




usually goes to refining, and the matte and speiss to the dross  furnace.




Slag is removed separately to the fuming furnace for recovery of lead




and zinc.  Some slag from the fuming furnace may be recycled, the rest




goes to waste.  The dross, matte and sepiss from the lead refinery goes




to the reverberatory furnace where lead is recovered and recycled; matte




and speiss are then shipped to a copper smelter for copper recovery.




Lead metal is further refined in kettles where other metals and  trace




materials are recovered.  The final product is refined lead.






     Some lead smelters operate such other equipment as cadmium  roasters,




deleading kilns, and slag fuming furnaces.  Some slag from the fuming fur-




nace, where lead and zinc are recovered, may be recycled but the rest goes




to waste.






     The material handling equipment may include such primary means of



transportation as rail, truck, ships, barges, and pipelines.  The secon-




dary and more highly specialized equipment includes conveyors, overhead




cranes, clamshell loaders, and cars.  Modes of material storage  include




piles, bins, hoppers, kettles, settling tanks, and ponds.  Process equip-




ment includes crushers, grinders, ball mills, vibrating screens, vacuum




filter drums, sinter machines, and furnaces.  Figure 25.1 depicts princi-




pal emission points.  Tables 25.1 and 25.2 summarize the pertinent lead
                                 -229-

-------
                            TABLE  25.1
                      LEAD BLAST  FURNACE  DATA

Furnace Data
Length and width at
stock line, inside
Length and width at
tuyere line, inside
Height, tuyeres to
feed door
Distance, tuyeres
to slag tap
Depth of hearth
Suiglt; or double
tier of jackets
Height of water
Jacket zone
Number and size
of tuyeres
Type of top
Number of settlers
before stag pot
Operating Data
Volume of blast
per minute
Pressure of blast
Volume of cooling
water
Temperature of
water overflow
Charge Data
Total wt. per 24 hr.
exclusive of coke
Per cent sinter
in charge
Per cent lime rock not
included in sinter
Other constituents of
charge, kind and wt.
Per cent of lead
In charge
exclusive of coke
Per cent of coke
per .cent of charge
Product Data
Slag, wt. per 24 hr.
Method of disposing
of slag
AS.fcR.
No. 1

16 ft. 10 in. x 8ft.
16 ft. 10 in. x 48 in.
27 ft. 10-1/2 in.
13-1/2 In.
6 in. below slag tap
Double
8 ft 6 in.
15 per side, 4 in.
Thimble
Two

7500-9000 cu. ft.
35-50 oz.
1500 gal. per min.
100-110° F.

440 tons
70-80
5-10
Leady siliceous ore
10-12 pet.
Scrap Iron 3.5 pet.
26-28
13

275 metric tons
Dumped hot
AS.&R.
No. 2

16ft. x 6 ft. 9 in.
16ft. x 48 In.
24 ft. 1 in.
11 in.
3 ft. 7 in. (2 furnaces)
3ft.l in (1 furnace)
Single
6ft 4-1/2 in (2furnaces)
6ft. 6 in. (1 furnace)
28 4-1/2 in.(2 furnaces)
24:4-1/2 in (1 furnace)
Open
Two

7200 cu. ft.
40 oz.
250 gal per min.
100° F.

470 tons
86
None
Settler slag 4 pet
Plant byproducts3pct.
Zinc plant residues
7 pet.
24
10 regular
3 scrap

3 10 tons
Zinc fuming furnace
A.S.&R,
No. 3

15 ft. 3 in. x5 ft. 8 in.
15 ft. 3 in. K 5(1.6 in.
27ft.
14 in.
21 in.
Double
9 ft.
24-4 in.
Thimble
Two

7500 cu. ft.
40-45 oz.
850 gal. per mm.
140-160° F.

450 tons
85
None
Foul slag 15 pet.
Scrap iron 3 pet.
30
11

275-300 tons
Zinc fuming furnace
AS &R.
No. 4

16 ft. 10 in.xS ft. 6 in.
16 ft. 10 in. x 4 ft.
28 ft. 3 in.
9 in.
2 ft. 3 in.
Single
6ft. 9 In.
29 - 2-1/2 in.
Thimble
Two

0000 cu ft.
46 oz.
500 gal. per min.
100° F.

457 tons
458
11.9 pet.
Scrap iron 3 8 pet.
Siliceous ores 29 2 pet.
Foul slag 9 3 pet.
17.4
12.5

290 tons
Dumped hot
A.S 4R.
No. 5

15 ft. 3 in x6 ft 2 In.
15 ft. 3 in.x4 ft. 6 in.
24 ft. 6-1/2 in.
15 in.
2 ft. 6 in.
Single
7 ft.
24 - 4 in.
Thimble
Two

7200 cu ft.
45 oz.
"
190° F.

550 tons
95
0.2 pet. of total
lime rock used
Foul slag
16 tons - 24 hr.
Scrap iron
8 tons - 24 hr.
30
9.5

245 tons
Dumped hot
Bullion, total wt.
  per 24 hi
Before dross ing
After dressing
Wt. dross per 24 hr.
What additions are
made to dressing
kettle?
Wt. primary matte.
If any
Wt primary speiss,
if any
Dross Furnace Data
Wt dross charged
per 24 hr.
Kind and wt. of
other additions
per24hr.
Wt. matte -speiss
produced per 24 hr.
Wt. slag produced
per 24 hr.
—
110 tons
85 tons
Soda ash, coke,
litharge, sulfur,
for decoppenzing
None
3 tons per day

85 tona
Additions made
In dross ing kettle
45 tons
30 tons
None
115 tons
90 tons
25 tons
300 Ib. S
for decopperlzing
per 60 tons bullion
None
7 tons per day

70 tons
4 pet soda ash
1 pet. coke breeze
45 tons
8 Ions matte
15 tons speiss
None
265-275 tons
175 tons
90-100 tons
Salt cake 5 pet.
crushed coke 3 pet.
None
None

00-100 tons
Additions made
in dressing kettle
60 tons
25 tons matte
23 tons apeiss
None
188 tons
150 tons
38 tons
130 Ib. 3
per 55 tons bullion
Sawdust
None
3 tons per 24 hr.

43 tons
Miscellaneous furnace
speiss 22 tons
siliceous ore 1.5 tons
23 tons
35 tons
6 tons
220 tons
151 tona
68 tons
Petroleum coke
Soda ash
None
10 tons per 24 hr.

77 tons
Additions to dressing
kettle + 1/2 ton
litharge
50 tons
21 tons
None
                               -230-

-------
Bunker Hill
Ktllon, IiUho
Furnace No. 3
Bunker Hill
Kellogg. Idaho
Furnaces 2 & 4
CM. 8,3.
Trail, B.C.
International
Tooele, Utah
St. Joseph Lead
Herculaneum, Mo.
VS. Smelting
Mldvale, Utah
21 It. X 5 ft. 8-1/2 In.
21 It. x 5 (t. 9-1/2 In.
11 It. 4 In.
10 In.
1 ft. 8 In.
Triple. 2 vertical
1 Inclined
19 R.
SB - 2-1/2 In.
Vertical center gas
take-off charge fed at
sides of take-off
One when slag goes
to fuming furnace.
Two when dumped
15 It. X 3 II. 9 In.
15 ft. X 4 ft.
19 ft. 4 In.
14 In.
1ft. 2 In.
Double tier
boshed out
13ft.
20 - 4 In.
End gas take-off.
Center dump feed.
Splitting rail
Same as No. 3

11,000 cu.lt.
26 - 34 02.
ISO gal. per min.
reclrculated
175° F.

350-650 tons
10-80
1-1/2 - 3 pet.
6000 cu. ft.
18 - 24 oz.
350-450 gal.
per min.
75-175" F.

240-370 tons ' •
70-80
1-1/2 -3 pet..
Foul slag 0 - 1/2 pet. Reverb. dross 0-1 pet.
Misc. 0-5 pet. Zinc plant residue 10 - 25 pet.
Dump slag 5-10 pet.
25-40
10-12
25-40
10-14

400-450 tons (2 furnaces)
To slag fuming or dumped hot
Length, 3 8 15 ft.
2 S 22 ft. 6 In
Width, 29 6ft. 4 In.
2 0 6 ft. 10 In.
1 § 10 ft.
Length, 3815 ft.
2 ft 22 ft. 6 In.
Width, 1 6 4 ft.
2 § Sit. 5 In.
lg 611.8 in.
10 84-96 In.
17 ft.
14 In,
2 ft. below bottom
of tuyeres at lead
well only
4 with 2
1 with 1-1/2
4 8 13 ft.
1 9 9-1/2 ft.
2 with 48 - 2-1/2 In.
2 with 72 - 2-1/2 In.
1 with 59 - 2-1/2 In.
Hooded with
central off-take
One
IS ft. X 7 ft. 9 In.
15 ft. x 4 It. 4 in.
24 ft. 8 In.
13 In.
2 It. 7-3/4 In.
Double
15ft.
24-4 In. on sides
2 - 3 In. at back
1-2 In. at front
Open
Two

2g1000cu.lt.
1 6 8000 cu. ft.
2 S 9000 cu. ft.
34 - 36 oz.
50 gal. per min.
Nesmlth Vaporizer
1760 F.

350-550 tons
depends on furnace size
87
None
Pot shells 6.3 pet.
Settler cleanings 1 .9 pet
Miscellaneous 4.8 pet.
31.2
11.5

675 tons new slag
930 total
Zinc fuming furnace
8500 cu. ft.
45 - 54 oz.
"
150-180° F.

• 550-590 tons
90
0-4 pet.
B.F. cleanings 3 pet.
Bag house fume
1-1/2 pet. Conv.slag
1 pet. Ore 4 pet.
Scrap ironO 5-2.5pct.
20-30
10 - 11-1/2

325-360 tons
Zinc fuming furnace
16 ft. x 6 ft.
16 ft. x 5 ft.
19 ft. 5 In.
14 In.
2 ft. 4-3/4 In.
Single
12ft.
24 - 5 In.
Open
One

7000 cu. ft.
32 - 36 oz.
205 gal. per min.
-

486 tons
71.5'
None
Slag 24 pet.
Wind box lead 20 pet.
Dross 50 pet.
Pore hearth clean ings 5.
49
8.5

195 tons
Granulated
15 ft. 4 In. x 5 ft. 5 In.
13 ft. 4 In. x 4 ft.
24 ft. 7-1/4 in.
11 In.
2 ft. 9 In.
Single
( ft.
20 - 5 In.
Open
Two

8000 cu. ft.
40 oz.
480 gal. per min.
1470 p.

575-625 tons
60-96
1-3 pet.
Scrap iron 4 pet.
Siliceous gold ore
1 - 5 pet.
24-28
9-10

375-425 tons
Granulated
180-265 tons (2 furnaces)
170-240 tons (2 furnaces)
10-25 tons (2 furnaces)
15-25 tons coal per 100 ton kettle
100 Ib. S per 90 tons bullion
None
4-10 tons per 24 hr. (2 furnaces)

60 tons
1-3 pet. silica 1 1 Pet. coke. Add
antimony skim to soften crusts
when necessary
25-95 tons
15-20 tons
5-10 tons
415 tons
400 tons
15 tons
None
None
None

45 tons
Dross furnace operated
3-4 months yearly
None
13 tons
15 Ions
9.5 tons
150-230 tons
110-180 tons
50-85 tons
Salt cake ,coke breeze
Finish with 500 Ibs.
to 120 tons Pb
None
None

50-80 tons
Added in dross
kettle
30-45 tons
4-4-1/2 tons speiss
5-5-1/2 tons matte
Kone
217 tons
168 tons
49 tons
None
19 tons per day
None

No dross furnace
--
<
--
-
130-170 tons
105-134 tons
33-39 tons
Pyritc and sulfur
None
4-8 tons per day

33-39 tons
400 Ib. S + 300 Ib.
pyrlte per 30 tons,
stirred in kettle.
24 Ions
10-12 tons
2 tons
-231-

-------
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i








I
in
w

a
s
i.
1
•=

-
J-3 pet. limestone*
13-16pet.llme8and
41 pet C»0

M
O

(ft

^1



S
0

*8
if
sl
in r]
*

3
3 Pet. of to
limestone
S


'

to






s

a|
•a
1
1
- «
00
& '
                                           -232-

-------
                                     CO


                                     Q
                                     CD
                                     OD
                                     CO
                                     CO
                                     LTt
                                     Csl

                                     LU
         38
          I
                           fl
-233-

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blast furnace and sintering machine equipment data, respectively, by




companies for 1968.





     Figure 25.2 shows a typical material flow diagram of the total pro-




cess involved in lead production.





     Of primary concern in material handling is the containment and con-




trol of fugitive dusts which are generated when sufficiently fine size




material is exposed to moving air.  Such material may be stationary or




in transit.  Most dusts become airborne during periods of loading and




unloading at points of transfer.





25.2 Process Control Operation




     There are two effective and widespread imethods of dust control:




water sprays and physical capture and confinement by such means as hoods




and other enclosures.





     Some of the most important variables affecting dust emission into




the air are particle size and density, the relative velocity between par-




ticle and air, and the surface area exposed to air per unit volume of




dust.  Total emission control includes, in the final analysis, the manip-




ulation of all the variables affecting emission rates.





     Table 25.3 is a summary of the principal materials involved in lead




production.  It is relatively simple to identify the major material




handling process variables, namely mass flow rates, composition, size




distribution, plant physical layout, and material flow paths at an




individual plant.
                                  -234-

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     Lead      -   Siliceous         Crude       Zinc plont
   concentrate  I     ore*    I      ere*    I   residue     1    Limerock

r "~
AUTCX
1
L


j 	 1
Pressure leochinq •
1
1 ^ CuSO^, ZnSOj solution I
I LAVE extraction and electrolytic!
1 ' 1
jPbSO^ residue
|

1 , i
* These products ore all crushed ond
ground in a rod mill to -1/8 in. size
*
                          Return
                          sinter
                         Coke
                                     ITHARGE PBFPARATION  |
                                     [PELLETIZING    ]
                          t
                 Slogshell
                                              Sinter
                                                 Refinery drossei

                                                	t
   Low-grade ZnO
                   Cool
 Leaded
zinc oxide
to market
                     FUMING PLANT
                      "Zinc oxide
                          _L
TT=HDE LEADING KILN!
PbO  I—— ...... . -    J
                      Deleoded zinc
                     oxide to market
       Dezinced granulated ^
         slog to storage
                           •J BLAST FURNACE^


                           -Slag
                                                                                    ^ Puff
                                                   Bullion
                                     Concentration for cadmium-.
                                     extraction electric furnace
                                                              Copper dross
DROSS KETTLES
                                  I
                                Bullion
                     Bullion
                                  BY-PRODUCT FURNACE
                              Slag to
                            blast furnace
                                          Matte
Speiii
 Slag to blast furnace
                        [SOFTENING FURNACE}
                             I         ^
                          Bullion       Joe
                                                                                       Granulation
               -Parkes gold crust-
                   Parkes silver crusr-
                             Slog to
                             blatt furnace
       Gold dor<   Fine silver
       to market    to market
1 —


A
Antimony skim
i
rialle and sp
to market
Coke
Ir
                                                               Fume
Baghoute


 Stock
                                                                                                    Fume •
                                                               [ELECTRIC FURNACE!
                                                                  t          T~^
                                                                Slag to      Bullion
                                                              blast furnace
                                                                               PbO
                                                                                                      | STORAGE
                                                                                                      {.EACH
                                                                                              TANkj
                                                               |  REFINING KETTLE  |
                                                                        J
                                                                     Casting


                                                                    Hard lead
                                                                    to mart*!
                                                                         Cadmium sponge to 4
                                                                         electrolytic refining
                                                                                                         FILTER "I



Zinc
J
t«b
furn,

PRECIPITATION
TANK
          FIGURE  25,2    LEAD  PRODUCTION  PROCESS  FLOW  DIAGRAM
                                                     -235-

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         Table 25.3 PRINCIPAL MATERIALS OF LEAD PRODUCTION AND

                  THEIR ESTIMATED RELATIVE QUANTITIES


     Material                                             Weight
                                                          (tons)

     Lead ore                                            100

     Ore concentrate                                     15 to 20

     Ore tailings                                        80 to 85

     Lead metal                                           5 to 7

     Blast furnace slag                                   8 to 15

     Slag fuming furnace slag                             7 to 14

     Fluxes and additives                                  	

     Coke                                                 1 to 2

     Speiss and matte                                     2 to 3

     Other                                                2 to 3


25.3 Enforcement Procedure

     The following enforcement procudure lists general observations which

can be made of materials handling schemes at lead plants.  At many integrated

plants, fugitive dust losses may account for more atmospheric emission of

particulate matter than the sintering and blast furnaces which have air

pollution control equipment.  Because of the different methods of handling

raw materials, product, and tailings, the following general guides are

suggested:

         1.  Trace the flow of raw materials from the time they arrive at

             the plant until they enter the blast or reverberatory furnaces.

         2.  From a distance observe the raw material and processed materials

             for dust clouds either from roadways, stock piles, transfer

             points, crushing and screening operations, slag dumping,


                                  -236-

-------
           plant construction activities,  etc.   These  sources  are




           generally not continuous emitters, but  depend  on the  activity




           schedule.




       3.  Make records of the dusty areas for a close-up inspection.




           These observations should be made from beyond the plant peri-




           meter on a hillside overlooking the entire  complex, if possible.




       4.  Observe the raw material stock piles when the wind is blowing




           and note any entrained dust.




       5.  Observe the material moving methods at  the  stockpiles.




       6.  Note any dust emissions at the bulk unloading stations.




       7.  If cranes, belts, or bulldozers are used to move the  raw ma-




           terials, note any major dust clouds.




       8.  Make notes on the lengths and locations of  unpaved roadways.




           Ask if, and at what frequency, these roadways receive dust




           preventive treatment such as the application of water,  oil, or




           calcium chloride.  Observe  the paved, macadamized and gravel




           roads for latent dust.  Occasionally these  roads may  become




           burdened with dust and result in another source for fugitive




           dust.




       9.  Observe the transfer points along belt  haulage ways.   If no




           dust is noted, no further inspection is required here.







     The Inspector's Worksheet which follows may be useful for record




keeping.  Interpretation of these observations  is  dependent upon the per-




tinent regulations governing fugitive dust emissions.   Since many  of these




plants are located on large plots of land, it is important to discriminate




between in-plant housekeeping problems and emissions which cross the prop-




erty line.




                                -237-

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                             INSPECTORS WORKSHEET
             FOR_RECEIVING. STORING AND HANDLING OF RAW MATERIALS
Plant Id.
Date of this Inspection_
Type of Plant	
   Date of last Inspection
Capacity of Plant_
                     Type
Source Location    Material
   Wind
Direction
Wind Speed                      Preventive
  (mph)	Plume Description    Measures
Sample
Concentrate belt
loading
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
ore
concentrate














SW/10














slightly visible
dust














none














                                 -238-

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26.  CONCENTRATE DRYING




     The possible emissions will be participates.  Likelihood of emissions




is remote.





26.1 Process Description




     The concentration operation for these various smelting processes is




employed to separate sulfide minerals from waste rock.  The drying mechanisms




used to remove moisture from concentrate ores for lead production are gen-




erally not heated.  Thus, the air pollution potential from this source is




minimized.  Most of the concentrate drying processes at lead plants use fil-




tration drums to draw as much water from the concentrated ores as possible.




This is done at room temperature and with no heat being added to the drum.







      The raw ore arrives at the plant and is stored in various silos and




bins for further processing.  The ore may come from barges, shipping ves-




sels, underground mines, or railroad cars.  The material handling system




is likely to have the most air pollution emissions at the concentrate




building.  Moisture content for the raw material is about 3 percent.  The




raw ore is then screened, crushed, and ground and sent through a flotation




process to separate zinc ore and lead ore.  Figure 26.1 shows a typical




concentrator at a lead production plant.  The final lead concentrate will




assay about 67 percent lead, 5 percent zinc.  The average moisture content




of the filtered lead concentrate is 7 percent.  Tailings from the lead




concentrate assay will average about 55 percent zinc.  The zinc concen-




trate filter cake has an average moisture content of about 10 percent.







26.2  Process Control Operation




      Very few air pollution emissions occur from the lead concentrate




operation.  The concentrator plant is usually located away from the blast





                                 -239-

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                                           CO
                                           CNJ

                                           UJ
-240-

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furnace and sintering operations in a separate building.  The few emis-
sions that do occur from this operation are the result of the material
handling of the bulk ores.  Generally speaking, no air pollution control
devices are installed at the concentrator plant.  There are no detrimental
off gases of any concern from the concentrate operation.  The concentrate
dewatering takes place on a filter drum at room temperature and emits
nothing to the atmosphere.

26.3  Enforcement Procedure
      The enforcement official should make a subjective type evaluation
of the material handling system for the concentrate building.  It is un-
likely that any of the ore will be entrained by air and present a fugitive
dust problem.  The enforcement official should check the transfer points
and the enclosed system of the storage hoppers.

      The enforcement official should make note of the amount of material
processed through the concentrate building for future comparisons.  No
atmospheric testing needs to be done at this particular process during the
enforcement official's inspection visit.

      If fugitive dust violations are apparent, take appropriate action.

27.  CONCENTRATE SINTERING
      This is the major point of sulfur emissions in the lead smelting
process; however, individual plants may have sulfur recovery units.  It
is also a possible major source of particulate emissions if control equip-
ment is not functioning properly.

27.1  Process Description
      Sintering is a chemical and physical process that converts metal
sulfides to metal oxides and fuses the concentrate into a porous mas's,
                                 -241-

-------
called calcine, that is suitable for reduction in a blast furnace.  The




main chemical reaction taking place on the sintering machine is the oxi-




dation of lead and other metal sulfides.  Heat is generated by these re-




actions and the oxidation is self-sustaining.  Fuel, usually natural gas,




is required to initiate the reaction.   Process temperatures are kept below




1,400 F to prevent excessive loss of metals by vaporization, fusion of the




clinker, and damage to the grating of the pallets.






     The feed to the sintering machine consists of pelletized mixture of




lead sulfide concentrate, high silica lead ores, recycled dust, coke




breeze and fluxes.  The flux usually consists of high grade limestone,




silica and some steel scrap.  The lead concentrate generally has 55 to




70 percent lead, 13 to 18.5 percent sulfur, up to 6.5 percent zinc, 0.5




to 4.0 percent copper, up to 5.0 percent iron and minor amounts of silica,




lime, silver, gold, arsenic and others, depending on the source.






     The pelletized feed is loaded on the continuous conveyor, is ignited




and combustion is sustained by supplying air to the pellets.  Combustion




gases are removed, usually through sectionalized wind boxes, and the clinker




cakes drop to a coarse breaker and screen at the discharge end of the ma-




chine.  The oversized material is crushed and the fines are recycled to




the feed end of the machine.  The product is a fused porous sinter which




contains most of the metals as oxides.






     Off gases may contain 0.8 to 1.8 percent sulfur dioxide.  This repre-




sents about 85 percent of the total sulfur present in the feed; solid




b,-products account for about 14 percent and the remaining one percent is




distributed between blast and dross furnace effluents.  In addition to




sulfur oxides, the gases may contain air, water vapor, carbon dioxide,






                                  -242-

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hydrogen fluoride, silicon tetra-fluoride and traces of other gases.  Or-




ganic vapors from flotation reagents are also present.  Fumes include the




more volatile metal oxides such as arsenic, cadmium, selenium, and tellur-




ium.  Elemental sulfur may also be present.  Fumes are condensed and col-




lected with the dust.  If the cadmium content reaches 12 percent or more,




portions of the dust may be diverted to cadmium furnace.  Off gas flow




rates vary from 100 to 220 scfm per square foot of bed area.






     Table 27.1 shows some emission rates from lead sintering machines.
            Table 27.1 EMISSIONS FROM LEAD SINTERING MACHINES
                                                              Emission Rates


Plant No. (a)
326.09
1st stage
2nd stage
326.10
326.17
326.18
326.33
326.34
Estimated
Capacity for
Lead Production
(tons/yr)
76,000
n.a.
n.a.
122,000
198,000
120,000
91,000
42,000
Off Gas
Flow Rate
(scfm)

8,200
n.a.
32,400
34,000
35,500
n.a.
n.a.
Temperature
(°F)

300
n.a.
400
300
350
300
350
Sulfur
Equivalent
of Sulfur
Oxides
(tons/yr)
19,200


36,200
39,100
28,500
33,800
13,500
Dust
Recovered

(tons /day)

--
--
22
—
--
--

      (a)  From Systems Study of Arthur McGee.







      A sectionalized windbox is installed beneath or above the pallet grate




 to regulate burning rates.  Gases are drawn through the windbox into




 ducts leading to dust collection equipment.  The reported sinter off gas




 temperatures range between 300  and 400 F.  The collected sinter gases




 may be cooled by air dilution and conditioned by water quenching to pre-




 pare for dust collection by filtration or precipitation.  After the dust




 collector the gases are either vented or fed to a sulfuric acid plant, in




 which case the high sulfur dioxide content gas is processed separately.






                                -243-

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     Sintering machines range in size from 3.5 by 22 feet to 10 by 103 feet

and in capacities from 1.5 to 2.75 tons  of charged material, 12 to 18

inches deep, per square foot of bed area per day.  In most of the older

and smaller machines, air is introduced from above and flows through the

ore bed on the conveyor and captured in the windbox and duct system un-

derneath.  These are known as down-draft machines.  The newer and larger

machines, in which the air flow is the reverse, are known as up-draft

machines„  Figure 27.1 shows the process of a sintering unit.

     Following the sinter machine the sinter is crushed to usable size

and transported to storage or to the blast furnace.  The fines are re-

turned to the feed-end of the sinter machine where they are blended into

the feed.


27.2  Process Control Operation

      The most important process variable in the sinter machine is the

temperature.  Temperatures exceeding 1,400 F are to be avoided to prevent

excessive loss of metals by volatilization, fusion of the clinker and

damage to the grating of the pallets.  To a limited extent, temperature

control is achieved by limiting the sulfur content between 6 and 12 per-

cent.  Once oxidation is started, it becomes self-sustaining because the

process is exothermic.  Sulfur content is regulated by mixing with sulfur-

free fluxes, such as silica, limestone, fume furnace slag and sinter.

Excess air flow regulation provides additional control.


      Relatively high dust carry-over is expected during the period of ig-

nition and initial stages of the oxidation , especially if high or excess

flow rates occur.  Initially, when the feed is relatively cool, sufficient

air (oxygen) is required for optimum reaction and later, when the feed

fuses and reaches the upper temperature limit (1,400 F) , excess air is
                                  -244-

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                                   csi

                                   LU
                                   a:
                                   :^
                                   CD
                      OJ
                      O
                      CO

                      o
-245-

-------
required to provide cooling.  Volatilization of most metals occurs in
the upper temperature ranges which is most likely to occur at low air
flow rates.  Sulfur dioxide emission is expected to reach maximum then
tail off toward the end of the process.  This process characteristic
may be utilized to isolate high sulfur dioxide gases for acid plant
processing.

     Emission rates and concentrations can be expected to vary with feed
composition, type of equipment used and operating skill.  Particulate
size distribution is also influenced by these factors.

     The sinter crushing and screening operations at the machine-discharge
have enormous particulate emission potential.  These operations  ill be
hooded and ducted to a control device.

27.3  Enforcement Procedure
     The objectives of lead concentrate sintering operation inspection
are to determine sulfur dioxide and particulate emission levels from the
sintering operation and to evaluate the pollutant emission potential of
this operation  for varying production rates and operating conditions.
In order to accomplish the above objectives, the enforcement official needs
to determine:
        1.  Current production levels and operating conditions,
        2.  Design production levels and operating conditions,
        3.  Current controlled and uncontrolled particulate and sulfur
            oxide emission levels,
        4.  Efficiency and adequacy of emission control equipment at cur-
            rent and design operating levels.
     Both sintering machine and emission control equipment design capa-
cities and operating conditions can be obtained from design drawings and
                                    -246-

-------
plans.  These data should be obtained from the company representative

prior to physical plant inspection.  Production levels, sintering machine,

and emission control equipment operating conditions are monitored by the

plant operator and are either recorded in the operators' daily log or are

displayed on instrument panels.


     The enforcement official should obtain specific information regarding

the plant layout and plant capacity prior to his inspection of a sintering

operation.  Some of the operating variables of importance are:

        1.  The total feed rate to the sinter machine - these data are

            necessary in comparing process weight rate to allowable par-

            ticulate emissions from industrial operations,

        2.  The percent sulfur content of the feed ore - most sintering

            plants will have these data readily available from previous

            ore assays, and,

        3.  The percent sulfur content of the sinter.

                                                           t
     Many sintering plants will have sulfur oxide monitoring equipment

on the sintering machines at various stages along the bed.  This infor-

mation may be used as a check against the sulfur oxide emissions calcu-

lated from the feed concentrate and sinter product sulfur mass balance.

When sulfur recovery systems are used, performance data are needed.  If

valid information is not available from the plant operator, the enforce-

ment official may elect to spot test the recovery system efficiency by

means of indicator tubes (Part VII).


     Visible emissions are the simplest means for estimating particulate

control equipment performance.  The enforcement official should estimate

the percent opacity of the dust control equipment stack plumes and if in

excess of allowable limits, take appropriate action.  Building openings
                                  -247-

-------
should be observed for evidence of the escape of inadequately  captured
process dust.  If noted, determine poin't(s) of origin and require cor-
rective adtion.

     The enforcement official should obtain off gas temperatures, tlow
rates, sulfur oxide concentration, particulate concentration,  opacity,
and other operating data that he can relate from one visit  to  another.

     Upset renditions at Wintering machines can cause elevated notential
emissions,  depending on tht parfclcuiate control eauipmeatrused,  this
could result in elevated particulate emissions.  For example,  a hole may
develop in the sinter bed as a/result of an improper distribution of t-he
ore on the sinter bed.  |.tiis hole will prevent complete  sulfur ojx-tdation
and result in a small quantity of high sulfur content sinter.   Continuous
strip charts which record bed pressure on  each wind box  are available  at
most sintering ptaflts.  A sharp decrease in pressure on  the strip pftarts
wotrlcf indicate that a hole has occurred.   The major potential  problem
with frequent holes in  the bed, over a** fvfcetided period,  is elevated par-
ticulate emission potential.  TJie''operating record strip  charts can be re-
viewed tc est'ablish^this'otJerating problem/.  If a baghouse  is  used  as  the
control device there is 1 it-tie likelihood  of exceeding allowable  emissions.
If an electrostatic precijpitator is the /jontrol device, stack  tests may bi
required to ^stablish emission data.

     The enforcement official should complete the Inspector's  Worksheet
for IjKaJ sinter plants  and make the calculations for total  sulfur1 emis-
sio'ns rrutn this oper/ation.  It should be pointed oflt that although  most
of the sulfur from lead smelting is emitted trom the .winter plants,
many state air pollution emissions standards are Rased on total
sulfur emission from the sme^tiijg^eperation.  Th&  total  smelting operation
                                  -248-

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                              INSPECTORS WORKSHEET
                             FOR LEAD SINTER PLANTS
GENERAL
     Plant Id,
     Date of this Inspection
          _Dat$ of last Inspection_
OPERATING VARIABLES
     Sinter Machine Feed Rate, including ore,
       concentrate flux cok;e, etc.	
     Sulfur Content of Feed Ore
     Sinter Sulfur Content
     Moisture Content of Feed Ore
     Temperature of Off Gases	
     Sinter Machine Bed Speed	
     Number of Windboxes
     Exhaust Gas Flow Rate
      ft/hr
,  No.  Updraft_
	scfm
                  _ton/hr  Output Rate_
                                  ton/hr
             , No. Downdraft
Pressure Drop at Each Windbox; (in. H.O)
                                                                          10
Number of "Holes" Recorded in last day
Sulfur Dioxide Concentration: hi SO
                                     gas.
                %,  remaining gas
Type of SO. Control Device	
Percent of Exhaust Gases Treated by S0_ Control Dev'ce_
Particulate Control Device
Control Efficiencies:
                        dO,
    %
Particular
Inlet Temperature of -Exhaust Gases to Control Device
Pressure Drop Across Control Device^	
              in./H20
VISUAL OBSERVATIONS
Physical condition of equipment:
                                     -249-

-------
     Describe ductwork
Maintenance Program
Develop a diagram indicating gas flow from the sinter machine to atmosphere.
CALCULATIONS
     % sulfur in feed x feed rate  ^lb/hr) - 	 	Ib/hr of  sulfur.
hi S02 gas
     concentration (!) x flQO - 7, efficiency of acid'plant! x flow rate  (scfm) x
                         L      '           ItfO            J
      	Ib/hr sulfur in acid stack.
remaining SO^ gas
     concentration (%) x flow rate (scfm) x 5 =	|	sulfur,  Ib/hr.
If concentration is not available, take
     (% S feed ore - % S calcine) x feed rate  (Ib/hr), =	Ib/hr net  sulfur
     from sinter machine.
[net sulfur, (Ib/hr) ]-[ hi SO  concentration x  (collection eff. °L  ) x
                                                               100
flow rate  (scfm) x 5] =	Ib/hr sulfur from sinter plant.
Time In                                     Time Out
                                          -250-

-------
would include not only the sinter machines but also tl"* blast  furnace  and



the reverberator furnacesJ_=jCE^4i«s''been estimated that about  90 percent



of all sulfur emitted to the atmosphere will occur as  a result of  the  sin-



tering operation.  The remaining 10 percent is divided between the blast



furnace and the reverberatory operations.





     On his first visit the enforcement official should develop a  dia-



gram indicating the gas flow or sulfur oxide gas streams  from  the process



equipment to the atmosphere.  Many lead manufacturing  plants will  combine



the exhaust gas streams from the, winter plant, lead blast  furnace, rever-



beratory furnaces, and^e-cHer ancillary operations into one large abate-



ment facility".  Electrostatic precipitators or baghouses are frequently



used to reduce particulate emissions from these operations.





28.  ORE REDUCTION - BLAST FURNAC&



     This is a major potential particulate emissions and minor sulfur



emission process.  Particulate emissions are mainly a  function of  the



adequacy ot the control system.





28.1  Process Description



      Lead oxide is reduced to metallic lead using carbon monoxide as  a



reducing agent.  The process heat required is derived  from coke combustion.



The major chemical reaction^ that take place are:



                           C + 0  -> CO  + heat



                           C + CO  + heat -+ 2CO



                           PbO + CO + heat -> Pb -t^eO,
                                                   ~-£



Some iron, zinc and other oxides are also" reduced.  Liquid lead collects



at the bottom of the furnace -wliere it is drawn off.  Slag floats on top



of the metal and prevents further oxidation of lead.   Other metal oxides




                                 -251-

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react with silTca to form slag.  The blast furnace charge is a mixture




of sinter, coke and some fluxes.  Air is introduced through tuyeres at




low pressure and ambient temperature near the furnace bottom.  The air




flow rate is related to furnace capacity and varies between 5,000 and
     The products from the blast furnace consist of liquids and gases.




The liquids are drawn off at the bottom and the gases are vented at  the




top.  There are four distinct liquids that comprise the bottom products:




lead, matte, speiss and slag.  Lead may be separated from matte and




speiss and sent directly to the refinery or to the dross furnace with




the matte and speiss.  Slag is removed separately and is conveyed  to a




fuming furnace for recovery of lead and zinc.







     Slag is a siliceous amalgam of many constituents.  It contains  10




to 20 percent zinc, up to 2 percent lead and 3 percent sulfur.







     Matte (metallic sulfides) contains 44 to 62 percent lead, lo  to 20




percent zinc, up to 13 percent sulfur, and lesser amounts of  iron, copper




and silica.







     Speiss (metallic arsenides) contains 55 to 64 percent copper, 8 to




18 pei-'-p.nt lead, up to 1 percent zinc, 0.5 percent each of iron and  sil-




ica and lesser quantities of sulfur and arsenic^
     Theoretical flue-gas rates vary with t-he size of the furjiace




6,000 to 14,000 scfm, bu*~ is usually diluted to several times this  flow




rate by air entering at the top of the furnace.






     The flue gases, before uilution and  combustion, maV contain 25  to




50 percent carbon monoxide, significant amounts of carbon dioxide and





                                  -252-

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 nitrogen.  They also contain dusts and fumes from chemical  reactions  as

 they become entrained in the air from the tuyeres as it sweeps  through

 the charge.  The fumes include cadmium, lead, and zinc oxides.

      Table 28.1 contains some reported emission rate& ^or lead  blast  fur-

 naces.  Gas flow rate and temperature values are ,after air  dilution and
 cooling.

                    Table 28.1 LEAD BLAST FURNACES
CAPACITIES, EMISSION RATES AND WASTE GAS TEMPERATURES


Plant
1.
2.
3.
4.
5.
6.
Estimated
Lead Production
Capacity
(tons/year)
76,000
122,000
198,000
120,000
91,000
42,000
Waste Gas

Temperature
(°F)
400
450
350
300
350
300


Flow Rate
(scfia)
8,500
11,100
26,200
23,300
20,400
— —


Dust Recovery
(tons /day)
12
9.7
	
___
	
26
     Blast furnaces (Figure 28.1) have rectangular horizontal cross-sections.

There are tuyeres in each side, and above these the two long sides slope
outwards for a third of the shaft heights.  In the upper two-thirds of the
shaft, the outward slope is less.  Shaft sides and ends are water-cooled
steel panels.

     The flue gas ducts and charge openings are at the top of the furnace

shaft.  Below the hearth is a crucible or, in newer furnaces, a trough,
sloped toward one end where liquids from the furnace flow continuously to

an external settler-separator.  Hearth widths range from 4.5 to 6.0 feet
and lengths from 15 to 28 feet.  The furnace charge is 600 to 1,200 tons/day
for hearth areas from 80 to 150 sq. ft.
                                   -253-

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5 Ton Charge
   Bucket
                                      Gas Offtake
                                  FURNACE DIMENSIONS

                                  Between Tuyeres = 1 meter
                                  Length         = 7 meters
                                  Height         = 8 meters
  Slag
Bullion
                                                             Blower
  1-5 Ton
Button  Mold
                FIGURE 28,1   LEAD  BLAST  FURNACE
                                -254-

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28.1.1  Lead refining is the process of recovery of valuable by-products
from blast furnace lead and the removal of impurities.  Molten lead is

first treated in dressing kettles for copper removal.  Cooling causes

the copper to separate and rise to the surface as a dross.  The dross is

skimmed off and is smelted in the dross reverberatory furnace.  A con-

tinuous softening process removes arsenic and antimony through oxidation.

The skim may be treated in an electric furnace to produce an arsenical-

antimonial lead known as hard-lead.  Gold and silver are removed by the

addition of zinc metal.  The zinc amalgam forms a dross on the surface

which is removed.  Gold and silver are extracted from the skim by cupel-

lation and retorting.  The residual zinc in lead is removed by vacuum

distillation.  Addition of sodium hydroxide, or caustic soda, removes

the last traces of impurities and the final product, corroding lead, is

cast out for marketing.


28.1.2  Other smelter operations include dross reverberatory furnaces,

cadmium roasters, slag fuming-furnaces and deleading kilns.


        A natural gas-fired dross reverberatory furnace separates the re-

maining lead in the dross skim, matte and speiss from the blast furnace

at temperatures of 1,400 to 1,800°F.   The lead is sent to the refinery,  the

matte and speiss to the copper smelter.


        The off gases consist mainly of combustion products and average

less than 0.05 percent sulfur dioxide, except for short time periods

when sulfur is added to the furnace charge when it may go as high as 0.2

percent.  Off gas flow rates are relatively low, 1,000 to 3,000 scfm;

only sufficient draft is provided to remove the smoke and fumes and still

allow as much heat retention as possible over the hearth.  Flue dust re-

covery averages 0.75 tons/day at one plant which is believed to be primarily
                                 -255-

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metal oxides.  The speiss and matte compositions are not believed to be




altered significantly.







     Other lead smelter operations emission data and operating conditions




are presented in Table 28.2







        Table 28.2 AUXILIARY LEAD SMELTER OPERATIONS, EMISSIONS
AND OPERATING CONDITIONS
Operation

Plant 1
Dross reverb
Plant 2
Dross reverb
Slag fuming
Plant 3
Slag fuming
Plant 4
Dross reverb
Slag fuming
Deleadihg kiln
Plant 5
Dross reverb
Slag fuming
Deleading kiln
Lead Waste Gas
Production Temperature
Capacity ( F )
(tons /year)
76,000
1,700
122,000
1,400
600

2,200
91,000
1,700
600
2,500
42,000
1,650
2,200
1,500

(scfm)


1,100

8,500
59.3

9,000


19,700
4,000

6,000
50,000

Dust
recovered
(tons /day)





67




100
11

0.75
50
10
     These operations are  auxiliary to the primary lead  smelting process




and even though they constitute a significant portion of lead plant oper-




ations, they are not fully treated here.






28.2  Process Control Operation




      The basic chemical reactions define the important  process variables




                                         -256-

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and can readily be identified as the coke and lead content of the charge

and the air (oxygen) flow rate.  Temperature control plays an important

but less critical part than in sintering.  In order to reduce lead oxide,

1,100 to 1,300°F is required but temperatures may go higher in portions of

the furnace and cause some distillation and carry-over of lead and zinc

oxides.  Sinter, coke, flux and other dust carry-overs are governed by

size distribution and air flow rates, especially during the initial part

of the blasting cycle.  Good air flow rate control is also important for

the production of the reducing agent, carbon monoxide.


     The flue gases are collected in a hood and duct system where the

carbon monoxide is burned by excess air to carbon dioxide.  The volumes

of dilution air are large enough to also cool the gas.  Further cooling is

accomplished by quenching with water.  The diluted and conditioned gas is

ready for particulate removal by either filtration or precipitation.  The

clear flue gas is vented through a stack.


28.3  Enforcement Procedure

      The objectives of lead blast furnace operation inspection are to

determine sulfur dioxide and particulate emission levels from the reduc-

tion operation and to evaluate the pollutant emission potential of this

operation for varying production rates and operating conditions.  In

order to accomplish the above objectives, the enforcement official needs

to determine:

         1.  Current production levels and operating conditions,

         2.  Design production levels and operating conditions,

         3.  Current controlled and uncontrolled particulate and sulfur

             dioxide emission levels,

         4.  Efficiency and adequacy of emission control equipment at

             current and design operating levels.
                                 -257-

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     Both blast furnace and blast furnace emission control equipment




design capacities and operating conditions can be obtained from design




drawings and plans.  These data should be obtained from the company




representative prior to physical plant inspection.  Production levels,




blast furnace feed weight rates, furnace, and furnace emission control




equipment operating conditions are monitored by the plant operator and




are either recorded in the operator's daily log or are displayed on




ins trument panels.






     Prior to physical inspection of a lead blast furnace, the enforcement




official should obtain specific information regarding the number of loca-




tion of blast furnaces.  The enforcement official should compare the feed




weight rate that is indicated on the operator's log during his visit with




what is considered normal operation for this particular furnace.  This will




help establish whether the furnace is being overburdened because of in-




creased production or whether a light load has been charged to the furnace




because of the inspector's visit.  The most important process variable




with a lead blast furnace is the process weight rate, which is the sum of




ore, fluxes, concentrates, coke and coke breeze charged to the furnace.




The enforcement official should also record the sulfur content of the sin-




ter and of the furnace products.  Calculate sulfur emissions from these data.






     The enforcement official should examine the air pollution collection




hood at the blast furnace to see whether the inspiration volume is ade-




quate to encompass the entire plume during the heaviest particulate emis-




sions.  Additional particulate matter may emanate during the slagging and




tapping operations.  Plants will generally have hoods to capture the par-




ticulate from these operations.
                                   -258-

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                         INSPECTORS WORKSHEET
                        FOR LEAD BLAST FURNACE
GENERAL
     Plant Id.
     Date of this Inspection	Date of last lnspection_
OPERATING VARIABLES
     Blast Furnace Feed Rate,	Ib/hr
     Sulfur Content of Feed Ore	%
     No. of Blast Furnaces	Capacity of Blast Furnaces, total	tons/day
     Sulfur Content of Slag	%
     Exhaust gas Flow Rate	scfm,  	scfm,  etc.
                         (Furnace 1)       (Furnace 2)
     Type of Control Device
     Efficiency of Control Device	%
     Inlet Temperature	^F
     Pressure Drop Across Control Device	in. H^O
     Spark Rate	spm
     No. of Dead Sections	

EMISSION TESTS
     Par t iculate s	Ib /hr
     S02	Ib/hr, expressed as S	Ib/hr
     Tested by	Dated_

VISUAL OBSERVATIONS
     Capture Efficiency	

     Ducts
                                       -259-

-------
DIAGRAM OF EXHAUST GAS FLOWS
 NOTE:   For comparison with regulations,  total smelter emissions may include
        sinter plant and reverberatory operations as well as the blast furnaces,
 Time In                                    Time Out
                                       -260-

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     There is little telltale evidence on a lead blast furnace that would




indicate any upset condition has occurred.  Occasionally a crust may form




over the hot metal and below the cold ore.  A slip may occur when the




crust finally breaks and drops into the hot pool, resulting in a heavy




particulate emission.  The enforcement official should observe the air




pollution control system during a slip if possible, and note whether the




abatement facility is capable of handling the heavy emissions.







     Compare calculated sulfur emissions to applicable regulations.  If




the calculated value exceeds limits, a stack test should be conducted




to verify the calculation estimate.







     On the basis of stack opacity and/or visible particulate losses




from the building, due to inadequate process ventilation, there may be




cause for issuing a citation or requiring more definitive tests to deter-




mine compliance.







29.  ORE REFINING - REVERBERATORY




     This is a major potential particulate emission and minor sulfur




emission process.  Particulate emissions are mainly a function of the




adequacy of the control system.







29.1 Process Description




     The reverberatory furnace is a high temperature separation process




unit where the high lead content of dross skim is separated as lead bullion




from the copper matte and slag and, on occasion, nickel bearing material.







     The reverberatory furnace is a refractory lined vessel that radiates




heat from its burner flame, roof and walls onto the dross charge.  Figure




29.1 is a graphical depiction of a representative dross reverberatory





                                  -261-

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-------
furnace.  Fuel, usually natural gas or fuel oil, and combustion air are
introduced into the furnace where the combustion occurs directly above
the molten bath; the walls and roof receive radiant heat from the hot com-
bustion products and, in turn, reradiate this heat to the surface of the
charge.  The process temperature is normally between 1,700 and 1,800°F.

     The feed to the furnace may include the following components:  dross,
soda ash, coke breeze, coal, sawdust, sulfur, ores, and silica.  Lead
bullion from the blast furnace is sometimes included in the charge as an
additional step in the refinery operation.  The reverberatory products
consist primarily of lead, copper matte, slag, and possibly nickel matte.
Tables 29.1 and 29.2 contain some typical reverberatory charge and product
weight rates and compositions.

     The off gases consist mainly of combustion products and normally
average less than one percent sulfur dioxide which may be higher for short
periods when sulfur is added to the furnace charge.  Off gas flow rates
are relatively low, 1,100 to 8,500 scfm, because only sufficient draft is
provided to remove the smoke and fumes and still allow as much heat reten-
tion as possible over the hearth.  Table 29.3 is a listing of some dross
reverberatory emission data and operating conditions.

29.2 Process Control Operations
     The basic process parameter is temperature, which must be sufficiently
high to permit liquefaction of the charge and phase-separation of the
liquid lead bullion from by-products that float on top of the molten bath.
The method of temperature control is fuel rate adjustment.

     The off gases are essentially combustion by-products of either natural
gas  or fuel oil,  slight quantity of excess air,  less than one percent
                                  -263-

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                               Table 29.1
TYPICAL ANALYSES OF DROSS
REVERBERATORY FEED AT
ONE LEAD
PLANT

Material Reverb
(%) Bullion
Pb
Cu 1.4
S
Ni
Insol
FeO
Zn
Co
Cd
Bi
Ag
Copper Ni
Matte Matte
15 35
60 35
20
15
-
-
-
-
-
-
-
Dross
60
13
4.5
3
3
1.5
4.3
0.5
-
-
-
Lead
-
0 .010
-
-
0.004
-
0.001
-
0.0000
0.0000
0.031
                               Table 29.2
  TYPICAL REVERBERATORY FEED AND  PRODUCT WEIGHT RATES AND  COMPOSITIONS
                            AT ONE LEAD PLANT
               Weekly Summary of Reverberatory Operations
Material Charged
Tons
% of Charge
Dross
Soda Ash
Coke Breeze
Silica sand
835
 45
 16
 10
    92
     5
     2
     1
Material Tapped
Lead Bullion
Copper Matte
Slag
Ni bearing material
590
164
 81
 10
    65
    18
     9
     1
                                   -264-

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                              Table  29.3
LEAD
DROSS REVERBERATORY EMISSION DATA AND OPERATING CONDITIONS


Plant ,
1
2
3
4
Lead
Production
Capacity
(tons/yr)
76,000
122,000
91,000
42,000



Waste Gas
Temperature
( F)
1,700
1,400
1,700
1,650
Flow Rate
(scfm)
1,100
8,500
-
6,000
Sulfur Dioxide
(%)
0.99
0.02
neg.
0.52

Dust
Recovered
(tons /day)
-
-
-
0.75
sulfur dioxide, and some entrained dusts and fumes.  The fumes are believed




to be primarily metal oxides.






     The off gases are collected in a hood and duct system and may be




cooled to about 150 to 300°F by heat exchangers, air dilution, or water




spray, before treatment in baghouses.  The reverberatory off gases may be




combined with other process off gases before particulate removal.






29.3 Enforcement Procedure




     The objectives of dross reverberatory furnace operation inspection




are to determine sulfur dioxide and particulate emission levels from the




furnace operation and to evaluate the pollutant emission potential of this




operation for varying production rates and operating conditions.  In order




to accomplish the above objectives, the enforcement official needs to




determine:




          1.  Current production levels and operating conditions,




          2.  Design production levels and operating conditions,




          3.  Current controlled and uncontrolled particulate and sulfur




              dioxide emission levels,




                                  -265-

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          4.   Efficiency and adequacy of emission control equipment at




              current and design operating levels.






     Both furnace and furnace emission control equipment design capacities




and operating conditions can be obtained from design drawings  and plans.




These data should be obtained from the company representative  prior to




physical plant inspection.  Production levels, furnace feed weight rates,




furnace, and furnace emission control equipment operating conditions are




monitored by the plant operator and are either recorded in the operator's




daily log or are displayed on instrument panels






     Obtain sulfur content data on both feed and product.  Calculate




possible sulfur emissions.  This could be verified using indicator tubes




(Part VII).  If these estimates indicate that emissions exceed allowable




limits, definitive stack testing and/or a compliance program are in-




dicated.






     On the basis of stack opacity and/or visible particulate losses




from the building, due to inadequate process ventilation, there may be




cause for issuing a citation or requiring more definitive tests to de-




termine compliance.
                                   -266-

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                              BIBLIOGRAPHY
American Bureau of Metal Statistics Yearbook, Maple Press Company,
     York, Pennsylvania, 1971

Dennis, W. H., Metallurgy in the Service of Man. Pitman Publishing
     Company, New York, 1961.

Smith, B. W., The World's Great Copper Mines, Hutchinson, London, 1967.

Bray, J. L., Non-Ferrous Production Metallurgy, John Wiley & Sons,
     New Yorl;, 1947

Liddell, D. M., Handbook of Non-ferrous Metallurgy. McGraw-Hill Book
     Company, New York, 1945.

Hayward, C. R., Outline of Metallurgical Practice, D. Van Nostrand Com-
     pany, New York, 1952.

Ruddle, R. W., Physical Chemistry of Copper Smelting. Institution of
     Mining and Metallurgy, London, 1953.

U. S. Department of the Interior, Bureau of Mines, Copper: A Materials
     Survey. 1965.

Newton, J. and Wilson, C. L., Metallurgy of Copper. John Wiley and Sons,
     Inc., New York, 1942.

Fluor Utah, Inc., The Impact of Air Pollution Abatement on the Copper
     Industry, San Mateo, California, 1971.

U. S. Department of the Interior, Bureau of Mines, Information Circular,
     Control of Sulfur Oxide Emissions in Copper, Lead, and Zinc Smelting,
     1971.

Engineering-Science, Inc.  Exhaust Gases from Combustion and Industrial
     Processes, Washington, D. C. 1971.

Davis, W. E., National Inventory of Sources and Emissions Barium. Boron,
     Copper, Selenium, and Zinc.(Section III Copper)  Environmental
     Protection Agency, 1972.

Arthur G. McKee and Company, Systems Study for Control of Emissions
     Primary Non-ferrous Smelting Industry, National Air Pollution Control
     Administration, 1969.

Semrau, K. T. Control of Sulfur Oxide Emissions  from Primary Copper, Lead
     and Zinc Smelters. - A Critical Review, Journal of the Air Pollution
     Control Association, 21-4, 1971.

U. S. Department of the Interior, Bureau of Mines, Mineral Facts and
     Problems, 1970.
                                  -267-

-------
American Smelting and Refining Company, Hayden, 1972.

Smith, P. R., Bailey, D. W. and Soane, R. E., Minerals Processing:  Where
     We Are - Where We're Going, Engineering and Mining Journal, 173-6,
     1972.
                                   -268-

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                    PARTY.  ZINC SMELTING





     Zinc is a strategic and critical  material  and, as such, is one of the




government stockpiled  metals.  The  zinc  industry  is one of the primary




metallurgical industries and ranks  fourth  in production of tonnage after




steel, aluminum and copper.




     The United States is the world leader in both metal production ana




consumption.  Consumption patterns,  both usage  and temporal trends, are




given in Table V-l below.






              Table V-l  UNITED STATES ZINC CONSUMPTIONS
Total Consumption, percent

Galvanizing
Brass
Castings
Rolled Zinc
Other
1940
40
32
16
8
4
1950
46
14
30
7
3
1960
43
11
39
4
3
1968
36
12
42
4
6
                                       100      100      100       100






Total Consumption,




    Short Tons                      719,000  967,100  877,900 1,333,700








     Table V-2 presents  the 1968 United States zinc plants and their sal-




ient process identification.




     The United States relies  on zinc metal supply from domestic primary




and secondary plants,  imporcs  of metal  and its concentrate, and industry
                                -269-

-------
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                                          -270-

-------
and government stocks.  Of the 1968 consumption, 529,400 tons, or about




40 percent, were produced domestically.




     Zinc is a bluish-white metal highly valued  for its corrosion resis-




tivity.  It is used extensively to galvanize iron and steel products




against corrosion.  Zinc produced from newly mined ores is termed primary,




or virgin zinc, and when it is produced from scrap or residue it is termed




secondary, redistilled, or remelt zinc.  Primary zinc may be referred to




as electrolytic or distilled zinc according to the reduction process used.




The final product may be in the oxide form as a  powder or in the metal




form cast into slabs, usually of 55 pounds.  Slab zinc is produced in five




standard grades ranging from 98.3 to more than 99.99 percent zinc with




certain limits on maximum impurity contents.




     The most abundant zinc ore is the sulfide,  called "blende", but a




composite form of oxides, silicates and other, is also significant.




Zinc ores also contain varying amounts of other  valuable and recoverable




materials, including cadmium, copper, fluorspar, gallium, germanium, gold,




indium, lead, manganese, silver, sulfur, and thallium.  Other commercially




significant sources of zinc include lead ores where zinc is found as a




by- or co-product.  Zinc is recovered from ore by a combination of pyro-




metallurgical processes, such as roasting and distillation, or an electro-




lytic process in lieu of distillation.




     Significant industrial uses of zinc include transportation, construc-




tion,  electrical equipment and supplies, pigments and compounds and others.




     Demand for primary zinc is expected to increase to,  and range from




about,  a low of two million to a high of four million tons by the year




2000.   The corresponding growth rates for the possible zinc demand are




between one and three percent per annum.
                                  -271-

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      The nonmetallic zinc by-products, such as concentrate tailings,  are




valued by such diverse industries as highway, railroad and agriculture.




      Primary zinc production is a sequence of physical-chemical processes




that involve the mining and concentrating of the naturally occurring zinc




mineral, mostly as sulfide, the preparatory steps that are necessary for




reducing zinc to the metal form, the reduction process itself (either elec-




trolytic or pyrometallurgical), and the subsequent zinc purification.   Figure




V-l is a simplified process flow diagram of a zinc plant and Tables V-3 and




V-4 list plant emissions and products.






                                Table V-3




       DUST-IN OFF GAS RATES FOR SOME PRIMARY ZINC PLANT OPERATIONS

,, „ . Feed Capacity
Process Equipment , , , ,.
H ^ (tons/day)
1. Roasters
Multihearth 50 to 120
Ropp 40 to 50
Fluid Bed (2) 240 to 350
(Door Oliver)
Suspension 120 to 350
Fluid Column 225
2. Sinter Machines
Plant 1 240 to 300
Plant 2 400 to 450
Plant 3 550 to 600
Dust-in Off Gas Dust-in Off Gas
(% of feed) (tons/day)

5 to 15 2.5 to 18
5 2.0 to 2.5
75 to 85 180 to 300

50 60 to 175
17 to 18 38 to 40

5 12 to 15
5 to 7 20 to 32
5 to 10 28 to 60
                                       -272-

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                H
CD

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                                Table V-4




       PRINCIPAL MATERIALS OF ZINC PRODUCTION AND THEIR ESTIMATED




                            RELATIVE QUANTITIES
          Material                                     Weight




          Zinc Ore                                      100




          Gangue                                      60 to 70




          Zinc Concentrate                            10 to 15




          Tailings                                    15 to 30



          Retort Furnace Residue                       5 to IQ




          Zinc Metal                                   5 to 6




          Coke and Coal                                4 to 5




          Fluxes and Additives                         4 to 5




          Other                                        4 to 5







     This section on zinc smelting, is divided into five chapters (Chap-




ters 30 through 34): material handling, concentrate drying, concentrate




roasting, sintering, and zinc metal production.  Each chapter is sub-




divided into three parts, namely process description, process control




operation and enforcement procedure.  This system of subdivision serves




as a structure that incorporates   sic process and emission control de-




scriptions and operating principles that serve as a foundation for ef-




fective monitoring and enforcement.






30.  MATERIAL HANDLING



     The possible emissions will be particulates.  Fugitive dust regula-




tions will govern.
                                  -274-

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30.1  Process Description




      Material handling is an important aspect of zinc production in




terms of tonnage of material.  Zinc production is the process of separa-




ting mechanically and chemically 4 to 5 pounds of zinc from about 100




pounds of mine ore.




      Most ore is mined underground and then transported to the surface.




The first and most substantial bulk reduction, ore concentration, normally




occurs here.  Concentrating consists of separating the desirable mineral




constituents in an ore from the unwanted impurities by various mechanical




processes.  Ore size is reduced bv crushing and wet grinding.  Size separ-




ation is accomplished by vibrating or trommel screens and classifiers to




give properly sized feed.  Heavy-medium cones, jigs and tables separate




the zinc minerals from a low specific gravity gangue.  Conveyors trans-




port the ore to large bins for blending and storing.  The ore is next




pumped as an aqueous slurry to flotation cells where it is conditioned




by additives.  Large propellers stir the solution and the zinc-bearing




minerals separate and float to the surface where they are skimmed off.




The unprofitable part of the slurry, called tailings, may be treated in




cyclone type separators to remove fines from the sand.




      Once separated, the metal concentrates are thickened in settling




tanks and the slurry is fed to vacuum drum filters which reduce the




moisture content to a small percent.  At completion of the concentration




process, the zinc content has been upgraded to about 55 to 60 percent.




Thermal drying may be used to further reduce the moisture content of the




concentrates.




      The concentrates are transported to a storage site and stored in




bins.  Usually, the first step of zinc smelting is the conversion of zinc
                                  -275-

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sulfides to zinc oxide by roasting.  The sulfur is converted to sulfur




dioxide and is driven off in the off gases.  The reduction of zinc ores




and concentrates to zinc is accomplished either by electrolytic deposition




from a solution or by retorting.




     The low sulfur calcine is weighed in hoppers and introduced into




tanks where it is leached with dilute sulfuric acid solution.  Most me-




tals, among them zinc, copper, cadmium, arsenic, antimony, cobalt and




nickel, enter the solution as sulfates.  Insolubles suspended in this mix-




ture include lead, silver, gold, iron, silica and calcium which are re-




moved by filtration.  Most of the soluble metals are removed from solu-




tion by selective precipitation and filtration until the zinc sulfate




solution is ready for electrolysis.  Zinc is finally electrodeposited on




aluminum cathodes.  The high purity zinc is removed from the cathodes and




the sulfuric acid (generated during electrolysis) leaching solution is




recycled.




     Pyrometallurgical extraction employs different processes and reduc-




tion principles.  The preparation of calcined zinc oxide for pyro-chemical




reduction involves agglomeration, either by sintering or by nodulizing and




blending with coke, fluxes and additives.  The blended feed is ready for




retorting, in some cases, after briquetting.  Zinc is finally reduced to




zinc metal in retort furnaces and the distilled metal is recovered from




the effluent by condensation.  The liquid zinc may be cast into slabs or




further refined by distillation.  The magnetic content of the retort resi-




due may be recovered and further processed, the rest goes to waste.




     The material handling equipment may include such primary means of




transportation as rail, trucks, ships, barges and pipelines.  The sec-




ondary, or more highly specialized equipment includes conveyors,  overhead
                                  -276-

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cranes, clamshell loaders and cars.  Modes of material storage include:


piles, bins, hoppers, kettles, settling tanks and ponds.  Material


handling process equipment include crushers, grinders, vibrating screens,


clarifiers, heavy-medium cones, jigs, tables, flotation cells, vacuum


filters, electrolytic cells, leaching tanks, roasters, sintering machines,


nodulizers, retort furnaces.  Table 30.1 summarizes the major process and


material flows involved in primary zinc production.  Figure 30.1 depicts


principal retort process emission points.


    Of primary concern in material handling is the containment and con-


trol of fugitive dusts which are generated when sufficiently fine size

material is exposed to moving air.  Such material may be stationary or


in transit.  Most dusts become airborne during periods of loading and un-


loading at points of transfer.



30.2  Process Control Operation


      There are two effective and widespread methods of dust control:

                                                            «
water or other chemical sprays and physical capture and confinement by


such means as hoods and other enclosures.


      Some of the most important variables affecting dust emission into


air are particle size and density, the relative velocity between particle


and air, and the size of the surface area exposed to air per unit volume


of dust.  Total emission control includes, in the final analysis, the


manipulation of all the variables affecting emission rates.


      It is relatively simple to identify the major material handling


process variables, namely mass flow rates, composition, size distribution,


plant physical layout and material flow paths at an individual plant.
                                 -277-

-------











































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                                             -280-

-------
30.3 Enforcement Procedure




     The enforcement official should make a subjective type evaluation




of the material handling system for the concentrate building.   It is un-




likely that any of the ore will be entrained by air and present a fugitive




dust problem.  The enforcement official should check the transfer points




and the enclosed system of the storage hoppers.




     The enforcement official should make note of the amount of material




processed through the concentrate building for future comparisons.  No




atmospheric testing needs to be done at this particular process during the




enforcement official's inspection visit.




     If fugitive dust violations are apparent, take appropriate action.






31.  CONCENTRATE DRYING




     The possible emissions will be particulates.  Likelihood of emissions




is remote from the wet part of the system.  The dryer can be a major par-




ticulate source if control equipment is not functioning properly.






31.1 Process Description




     The preparation of the zinc concentrate is usually done wet by grav-




ity or flotation methods.  Flotation is usually used to eliminate as much




of the lead as possible.  The concentrated zinc ore usually contains about




sixty percent zinc.




     Depending on the type of sintering and/or roasting operation that




may accompany a zinc plant, some of the raw zinc orp may be dried.  The




drying process  takes place in direct-fired rotary dryers.  Concentrate en-




tering the dryer contains about 11 percent moisture and leaves at about




3 percent moisture.  Below about 3 percent moisture, the concentrate becomes




quite dusty.  It is stored in a concentrate silo for future processing in the




flash roaster or sintering plant.



                                  -281-

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                         INSPECTORS WORKSHEET
         FOR RECEIVING, STORING AND HANDLING OF RAW MATERIALS
Plant Id.
Date of this Inspection_

Type of Plant	
   Date of last Inspection
Capacity of Plant
                     Type
Source Location    Material
   Wind
Direction
Wind Speed
  (mph)	Plume Description
Preventive
 Measures
Sample
Concentrate
belt unloading
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
Ore
Concentrate














SW/10














slight visible dust














Water spray














                                 -282-

-------
     Dust emissions occur as the hot air passes over the moving bed of




concentrate.  Most plants will have some type of particulate abatement




equipment at the dryer as dust caught in the air pollution device can




easily be recirculated into the storage bin for further use.  Cyclones




and low-to-medium energy scrubbers are likely to be used to remove the




particulate matter from the exhaust gas stream.  Cyclones operate on a




dry principle and could remove much of the large particles for reuse dir-




ectly into the flash roaster with no further processing.  Particulates




caught in the scrubbers will need to be dried before reuse in the roasters



or sintering plants.  Since the specific purpose of this dryer is to re-




duce the moisture content of the ore, a water plume will be noted at the




stack outlet.  Not all zinc plants will have an ore drying operation;




virtually no sulfur dioxide is driven off during this process.






31.2  Process Control Operation




      Emission to the atmosphere from this process will depend on the




adequacy of the air pollution control system.  There is likely to be a




corporate motivation to include air pollution control systems oi\ this




process since the raw ore can easily be reused at another stage in the




zinc reduction process.  Pollution control efficiencies for this type of




system will require about 90 percent removal efficiency.  This can be




accomplished with the use of low energy scrubbers and multicyclone de-




vices.  Operating factors likely to affect air pollution emissions are




process feed rate and product moisture content.




      The concentrate drying operation is a continuous one and will nor-




mally operate 24 hours per day.  Very few operating instruments are likely




to be found for this particular process.   If any, the gas feed rate and




the ore feed rate would be recorded on a daily basis.  Analysis of the






                                -283-

-------
moisture  that  is  sent  to  the sintering plant or the  flash roaster  is




critical and  would be recorded  at  the  control booth.







31.3   Enforcement Procedure




       The enforcement  official should obtain data  on the process feed




rate,  moisture contents,  and the  fuel firing rate  for the dryer.   This




data would be  used for future  comparisons  to determine whether  any change




in  production  rate has occurred for this particular  plant.  The enforce-




ment official  should record the operating  variables  for the air pollution




control device.   These include the:




          1.  Gas  pressure drop across the  scrubber or cyclone,




          2.  Water flow rate,




          3.  Air  flow  rate.




       The enforcement  official should check the hood capture  system used




at  the tail  end of the dryer.   Any dust plumes are an indication of a




poorly designed unit,  clogged  ducts,  or malfunctioning control  equipment.




The enforcement official  should observe the plume  for visible emissions.




A water vapor  plume will  be noted at  the stack outlet.  The enforcement




official  should check  for any  visible plume noticeable beyond the  vapor




plume. A visible plume would  indicate that the control device  may not




be  operating satisfactorily.   Reference to allowable emissions  and opacity




regulations  must  be made. If  opacity of plume downwind of the  steam plume




is  excessive,  appropriate action  should be taken.







32. CONCENTRATE  ROASTING




     This is the  major point of sulfur emissions  in  the zinc  smelting




process.   Individual plants may have  sulfur recovery units.   It is also




a possible major  source of particulate emissions  if  control equipment  is




not functioning properly.






                                  -284-

-------
32.1 Process Description




     Roasting zinc concentrate is a preparatory step to zinc extraction.




It consists of a high temperature exothermic process that converts metal




sulfides to metal oxides and fuses the concentrate into a porous mass




called calcined oxide.   This oxide may require further processing prior




to zinc extraction, either by electrolytic or pyrometallurgical methods.




If extraction is by pyrometallurgy, further calcining of the oxides is




usually necessary.




     Fuel combustion is required to initiate the reaction which, if the




sulfide concentration is high enough, becomes self-sustaining.




     Reaction temperatures vary from plant to plant between 1,200 and




1,900°F depending on the type of roaster, concentrate composition and the




specific use of the calcine (see Table 32.1).  Roaster calcine size also




depends on the same factors and can vary from fine powder to walnut sized




chunks.




     Differing requirements have resulted in a great diversity of roaster




machine forms, the most important of which are the multiple hearth furnace,




flash roaster, and fluid bed roaster.




     Multiple hearth roasters are some of the oldest and most popular.




The roaster consists of a brick lined cylindrical steel shell through




which runs a central shaft with two rabble arms attached for each hearth.




There may be from four to sixteen hearths in each roaster.  The motor




driven shaft contains cooling pipes and rotates slowly, about one-half




to two revolutions per minute.  Seven to nine rakes or rabbles are at-




tached to each arm.  Their arrangement is such that the ores introduced




into and dried in the upper chamber are gradually moved from the outer




edge toward the center and fall through a drop hole onto the first hearth.
                                  -285-

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               Table 32.1 TYPICAL ZINC ROASTING OPERATIONS
Type of Roaster
Multihearth
Multihearth
Ropp
Fluid Bed (4)
(Dorr-Oliver)
Fluid Bed (2)
(Dorr-Oliver
Fluid Bed
(Lurgi)
Suspension
Fluid Column
Operating
1,200-1,350
1,600-1,650
1,200
1,640

1,650

1,700

1,800
1,900
Feed
Capacity
(tons /day)
50-120
250
40-50
140-225

240-350

240

120-350
225
Dust -in
Off Gas
(% of feed)
5-15
5-15
5
70-80

75-85

50

50
17-18
Off Gas
(S02%)
4.5-6.5
4.5-6.5
0.7-1.0
7-8

10-12

9-10

8-12
11-12
(1)   Dead roast except where noted otherwise.
(2)   First stage is a partial roast in multihearth,  second stage
     is a dry-feed dead roast in Dorr-Oliver fluid bed.
(3)   Partial roast.
(4)   Slurry Feed.

     The ore then moves across this hearth to a slot near the outer edge
     and drops to the second hearth.  The ore progresses through the furnace
     in this zig-zag fashion until it drops into a car or conveyor beneath the
     lowest hearth.  There are doors for visual observation, repairs and ad-
     mission of air for each hearth.  Multihearth roaster feed capacities vary
     between 50 and 250 tons per day.
                                       -286-

-------
     Suspension, or flash roasting, resembles the burning of powdered coal




in furnaces wherein finely ground concentrates are sprayed into a combustion




chamber in a stream of combustion air.  The reaction usually proceeds without




the addition of fuel unless the sulfide content is too low, in which case




fuel addition, normally undesired is required.  The roaster itself resembles




multihearth roasters.  It is made up of a refractory-lined cylindrical steel




shell.  The upper portion contains the combustion chamber and the lower por-




tion two to four hearths, similar to those of the multiple hearth furnace.




The feed concentrate is introduced into the lower one or two hearths to dry




before final grinding in an auxiliary ball mill.  The dried and ground con-




centrate is then introduced into the combustion chamber.  Rotating rabble




arms move the material on the hearths.  Flash roaster feed capacities vary




from 120 to 350 tons per day.




      Fluid-bed roasters are continuous operating fluidized concentrate feed




 combustion chambers.  The closely size-regulated, dry, pelletized or slurry




 feed is introduced to the usually rectangular cross-section reactor.  Low




 pressure air is introduced into a windbox and passes through the perforated




 bottom, which acts as an air distribution plate.  The feed is lifted and  flui-




 dized.  Additional air may be introduced through inlets on each side of  the




 bed.  The roasted material overflows into a collection system and the gases




 go to waste heat boilers for heat recovery and to g£.s cleaning equipment.




 Table 32.1 shows some typical roaster capacities and operating conditions.




      Agglomeration of the calcined oxide from the roaster is usally re-




 quired before retorting which may be done by either sintering or nodu-




 lizing.  Both of these processes involve high temperature fusion and some




 additional sulfide conversion (see Chapter 33).




      The roaster feed is zinc concentrate consisting of 52 to 60 percent




 zinc, 30 to 33 percent sulfur, 4 to 11 percent iron and lesser quantities






                                  -287-

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of lead, cadmium, copper and other.  Franklinite ore requires special




processing to recover iron and manganese in addition to zinc.  Additional




fuel may be required and therefore it may be included in the process




weight, depending on the type of fuel and applicable regulations.




     The roasting process converts 93 to 97 percent of the sulfur in the




concentrate to sulfur dioxide.




     The roaster products consist of the calcined oxides and the off gases.




Since the solid products' size distribution includes significant portions




of fines, a substantial portion of the feed is carried over by the off




gases requiring major dust recovery operations.  Metal fumes, especially




that of cadmium, constitute an appreciable portion of the waste gas par-




ticulate carry over.




     The volumes of off gases produced range from 5,000 to 6,000 scfm




for multiple hearth roasters, 10,000 to 15,000 scfm for suspension




roasters and 6,000 to 10,000 scfm for fluid-bed roasters.  Sulfur dioxide




content of off gases ranges from 4.5 to 6.5 percent for multiple hearth




roasters and 7 to 12 percent for suspension and fluid-bed roasters.




     Tables 32.1 and 32.2 contain more specific operation information.






32.2  Process Control Operation




      The basic chemical reactions define the important process variables,




which are:   feed composition, feed mass rate, and air flow rate.  Roaster




configuration and concentrate size distribution also affect particulate




emission potential.  Operating conditions vary greatly from plant to plant




depending on the feed composition, type of roaster and the specific use




of the roaster calcine.  Process temperature plays an important, but not




critical, role in monitoring.  It varies between 1,200 and 1,900 F for




all plants although the range for a specific roaster is considerably
                                  -288-

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                        Table 32.2 ZINC ROASTERS
CAPACITIES, EMISSION RATES AND
WASTE GAS TEMPERATURES




Estimated Zinc
Production Capacity
Plant (tons /year)
1 252,000
2 88,000
3 88,000
4 59,000
5 92,000
6 44,000
7 215,000
8 53,000
9 56,000






Waste Gas

Temperature Dust Recovery
(°F) Flowrate (scfm) (tons/day)
1,600
1,600
1,900
2,000
n.a.
1,200
—
700
900
94,500 n.a.
32,000 n.a.
22,200 80
16,000 n.a.
23,000 n.a.
9,500 n.a.
--
123,000 n.a.
166,000 n.a.
Sulfur
Equivalent
of Sulfur
'Oxide
Emission Rate
(tons /year)
159,000
49,900
50,100
33,600
52,100
23,400
124,000
27,000
26,500
narrower.  Higher roasting temperatures distill more cadmium and increase




formation of ferrites.  Temperature control is usually achieved by air flow




rate control.  The combination of air flow rate, particulate size distri-




bution and equipment configuration affect the quantity of dust carry over.




The composition of the distilled metal fumes is determined primarily by the




concentrate composition and the operating temperature.




     Roaster off gases require cooling and conditioning before particulate




emission control.  Emission control is usually accomplished in two stages.




The first stage is cooling (normally by dilution) and removal of coarse




particulates in cyclones.  The secondary stage is a high efficiency control




device, such as a filter or precipitator.






32.3  Enforcement Procedure




      The objective of the zinc concentrate roasting operation inspection




is to establish compliance with sulfur dioxide and particulate emission




                                        -289-

-------
regulations.  In order to accomplish the above objective, the enforcement




official needs to determine:




          1.  Current production levels and operating conditions,




          2.  Design production levels and operating conditions,




          3.  Current controlled and uncontrolled particulate and  sulfur




              dioxide emission levels,




          4.  Efficiency and adequacy of emission control equipment at




              current and design operating levels.




     Both roaster and roaster emission control equipment design capacities




and operating conditions can be obtained from design drawings and  plans.




These data should be obtained from the company representative prior to




physical plant inspection.  Production levels, roaster feed weight rates,




roaster, and roaster emission control equipment operating conditions are




monitored by the plant operator and are either recorded in the operator's




daily log or are displayed on instrument panels.




     All zinc roasters will have a control booth near the roaster  for




careful monitoring.  The enforcement official should have little difficulty




assessing the current operating status of the roaster by observing the




many recorders, gauges and logs which are normally kept for the roaster.




     Of primary importance for the enforcement of air pollution emission




regulations is the process weight rate and the sulfur content.  With the




mass rate and sulfur content of the feed and calcine, a sulfur mass balance




can be calculated.  From this, SO  emissions can be computed.  If  an acid




plant is used to treat the gases, acid production data must be obtained.




The calculated SO- mass equivalent scrubbed out by the acid plant  must be




subtracted from the computed emissions based on the mass balance.   Compare




the net computed emissions with allowable levels in the regulations and
                                  -290-

-------
take appropriate action if necessary.  It should be pointed out that many




state regulations restrict sulfur emissions from the entire zinc smelter




and not just the zinc roaster.  For determining compliance with the regu-




lations, sulfur emissions from each operation must be summed, then compared.




Almost 90 percent of the sulfur is removed in the roasting process.  If an




approximation of compliance is desired, the calculated sulfur emissions




from the zinc roaster may be used.  Many zinc roasters will have a sulfuric




acid plant to treat exhaust gases from the roaster.  These plants will




monitor SO. gases continuously.  The enforcement official should note the




flow and concentration of the acid plant inlet and outlet gases for subse-




quent inspections.  There should be little deviation (± 20 percent) from




visit to visit because of the fixed design of acid facilities.




     There is little that can be noted on instrument panels regarding the




amount of particulates emitted to the atmosphere.  Some plants will have




a smoke density meter which may be used to determine relative particulate




emissions from one visit to another.  The enforcement official should note




the operational parameters of the air pollution control devices.




     Visible emissions are the simplest means for estimating particulate




control equipment performance.  The enforcement official should estimate




the percent opacity of dust control equipment stack plume and if in excess




of allowable limits, take appropriate action.  Building openings should also




be observed for evidence of escape of inadequately captured process dust




and if noted, determine point(s) of origin and require corrective action.




     The enforcement official should subjectively analyze the appearance




of the zinc roaster and note any leaks, SO  odors, and condition of the




duct, etc.  Finally, some attention should be given to the dust emission




from the material handling of the feed ores and calcine to and from the




roasting machine.






                                  -291-

-------
                           INSPECTORS WORKSHEET

                             FOR ZINC ROASTING

GENERAL
    Plant Id.
    Date of this Inspection	Date of last Inspection
OPERATING VARIABLES
    Roaster Feed Rate	Ib/hr  Calcine Product Rate	Ib/hr
    Sulfur Content of Feed Ore	?„
    No. of Roasters	Capacity of Roaster	tons/day
    Moisture Content of Feed Ore	%
    Sulfur Content of Calcine	%
    Exhaust Gas Flow Rate	
    Type of Control Device	
    Efficiency of Control Device:  Part.	%, SO 	%
    Inlet Temperature	.	F
    Pressure Drop Across Control Device	in. H.O
    Spark Rate	spm
    No. of Dead Sections	

EMISSION TESTS
    Location of Test Ports	
    Particulates	Ibs/hr
    SO 	Ib/hr, expressed as S	Ib/hr
    Tested by	Dated	
VISUAL OBSERVATIONS
    Capture Efficiency
    Ducts
    SO2 Odor_
    Other
                                          -292-

-------
DIAGRAM OF EXHAUST GASES AND PROCESSES
Time In                             Time Out
                     -293-

-------
33.   CONCENTRATE SINTERING




      This is a major potential particulate emission and minor sulfur




emission process.  Particulate emissions are mainly a function of the




adequacy of the control system.






33.1  Process Description




      Sintering is a process that converts remaining metal sulfides to




metal oxides.  It eliminates residual lead and cadmium and densifies or




fuses the roasted calcine to make it suitable for retorting.




      The feed to the sintering machine consists of a pelletized mixture of




roasted calcine and coal, or coke, and sinter dust.  The pelletized mixture




is fed uniformly across the grates of the sintering machine on top of a




shallow returning sinter layer consisting of coarse particles.  The feed




is ignited as it enters the natural gas-fired ignition box and combustion




is sustained by supplying air to the pellets.  Combustion gases are re-




moved, usually through sectionalized wind boxes.  Just before the discharge




end of the machine, the top layer of the sinter bed is shaved off by a ro-




tating scalper.  This top layer, from which about 80 percent of the cadmium




and 40 percent of the lead may have been eliminated, constitutes the sinter




product containing approximately 60 percent zinc, 0.4 percent lead and 0.05




percent cadmium.  The lower portion of the bed, not removed by the scalper,




is discharged at the end of the machine to a set of crushing rolls and then




the coarser material may be separated on a vibrating screen.   The oversized




particles are returned to the sinter machine while the undersize material




is incorporated with the sinter feed mix.




      The off gases contain usually less than 1 to 2 percent sulfur dioxide.




This represents, depending on the roaster sulfur removal efficiency, only
                                    -294-

-------
1 to 5 percent of the sulfur originally present in the feed.  In addition




to sulfur oxides, the gases contain air, water vapor, carbon dioxide, and




traces of other gases.  The fumes consist primarily of cadmium, lead, zinc,




and arsenic oxides.  Other metals and other compounds are also present in




lesser quantities.  The fumes condense and are collected with the dust.




      Some plant capacities, emission rates, and operating conditions are




shown in Table 33.1.  Table 33.2 summarizes some zinc sintering operations.







            Table 33.1 ZINC SINTERING MACHINES
CAPACITIES, EMISSION

Estimated
RATES AND WASTE GAS TEMPERATURES

Waste Gas
Zinc Production Temperature (°F) Flowrate (scfm)
Capacity
Plant (tons/year)
1 88,000
2 92,000
3 215,000
4 53,000
5 56,000
Table 33.2
Case
New feed material
400 23,200
200 150,000
400 58,500
200 95,000
300 22,200
ZINC SINTERING OPERATIONS
1 2
calcine calcine
Total charge capacity (tons per day) 240 to 300 400 to 450
Machine size (ft)
Fuel added to feed (%)
Total sulfur in new feed (%)
Recycle (% of new feed)
Dust-in off gas (% of feed)
Off gas S02 content (%)
3.5 x 45 6 x 97
6 to 7 10 to 11
8 2
35 to 75 40 to 70
5 5 to 7
1.5 to 2.0 0.1

Sulfur Equivalent
of Sulfur Oxide
Emission
(tons /year)
200
60,100
4,400
5,800
7,800
3
concentrate
550 to 600
12 x 168
0 to 2
31
80
5 to 10
1.7 to 2.4
                             -295-

-------
     Sintering machines,  known as Dwight-Lloyd machines,  range in size




from 3.5 ft wide x 45 ft  long to 12 ft wide x 168 ft long and from




100 to 2,000 square feet  of bed area.   The loading capacity variation




is from 0.75 to 1.75 tons per day/square foot of bed area.  Figure 33.1




is a graphical depiction  of a sintering machine and process flow.  In




some machines air is introduced from above and flows through the ore




bed OP the conveyor and captured in the wind box and duct underneath.




These are known as downdraft machines and are most widely used in the




zinc industry.  Tn other  machines, the air flow is the reverse.  These




are known as updraft machines.  The temperature of the combined exit




sinter gases vary from 500 to 700°F which may be cooled by air dilution




and water sprays in preparation for gas cleaning.  The primary collection



means of particulate removal may be by cyclones and settling chambers




followed by secondary removal in electrostatic precipitators or baghouses.






33.2 Process Control Operation




     The most important process variable is temperature.   Temperature




control is achieved by limiting the coke and coal content and the sulfur




content of the sinter mix.  Once oxidation is started it becomes self-




sustaining.  Air flow regulation provides additional temperature control.




     Sulfur dioxide emission is dependent on the sulfur content of the




roasted calcine or zinc concentrate.  It may be assumed that all of the




1 to 5 percent of the original sulfur content of the zinc concentrate re-




maining in the roasted calcine is driven off as sulfur dioxide in the




sinter off gases.




     The sinter crushing  and screening operations have enormous particu-




late emission potential.   These operations will be hooded and ducted to




a control device.






                                   -296-

-------
                              LJ
                              o_
-297-

-------
      Table 33.3 shows some feed capacities,  dust-in off gas and dust




recovery rates for some zinc plant operations.




      Table 33.3 DUST-IN OFF GAS RATES FOR SOME ZINC PLANT OPERATIONS

Sintering Machine
Plant 1
Plant 2
Plant 3
Feed Capacity Dust-in Off Gas
(tons/day) (% of feed)
240 to 300. 5
400 to 450 5 to 7
550 to 600 5 to 10
Dust-in Off Gas
(tons/day)
12 to 15
20 to 32
28 to 60
      Emission rates and concentrations are expected to vary with feed compo-




sition, type of equipment used, and operating skill.






33.3  Enforcement Procedure




      Sintering plants are traditionally dusty.  The enforcement official




is likely to find the sintering operation the dirtiest building at a pri-




mary zinc manufacturing plant.




      The wind box fan operates at a high negative pressure in order to




pull combustion air through the bed.  Leakage between the bed and the fan




will draw in a substantial amount of dilution air and increase the system




gas volume.  If a precipitator is used, its performance will be degraded




when gas volume exceeds the design capacity.




      Zinc sinter dust is very abrasive.  Ducts can develop holes and the




seals between the wind boxes and the bed can deteriorate causing a major




maintenance problem at older plants.




      The enforcement official must take particular note of the stack opacity




for elevated visible dust levels.  If noted, one probable cause is dilution




air drawn into the system through leaks.  The plant inspection should include




observation of the system of wind boxes and ducts leading to the dust collector.



                                        -298-

-------
                         INSPECTORS WORKSHEET

                        FOR ZINC SINTER PLANTS
GENERAL

Plant Id.
Date of this Inspection
                        «
            _Date of last Inspection
OPERATING VARIABLES

      Sinter Machine Feed Rate,  including ore,
        concentrate flux coke, etc.	ton/hr
      Sulfur Content of  Feed Ore_

      Calcine Discharge  Rate	

      Calcine Sulfur Content
               ton/hr
     Moisture Content of Feed Ore_

     Temperature of Off Gases	
     Sinter Machine Bed Speed

     Number of Windboxes
                 ft/hr
     Exhaust Gas Flow Rate
             scfm
  Pressure Drop at Each Windbox; in. H«0

   12345678
                                  10
ABATEMENT EQUIPMENT

     Type of Unit	
     Pressure Drop

     Spark Rate	
spm
     Primary Voltage_

     Water Flow Rate
     kv
                            gpm
                                 -299-

-------
VISUAL OBSERVATIONS




     Note leaks on sinter machine
     Is SO  odor present?	Strong, Detectable, Barely detectable




     Describe Ductwork
     Maintenance Program_
Develop a diagram indicating gas flow from the sinter  machine to atmosphere.
Time In                                           Time Out
                                   -300-

-------
Good maintenance is a major part of plant operation,  so records will




likely be available.  The precipitator should likewise be inspected




for its general condition.  Particular note should be made on the adequacy




of dust control when dust hoppers are emptied.




    Compare calculated emissions to applicable regulations.  If the cal-




culated value exceeds limits, a stack test should be  conducted to verify




the calculation estimate.




    On the basis of stack opacity and/or visible particulate losses from




the building due to inadquate process ventilation there may be cause for




issuing a citation or requiring more definitive tests to determine com-




pliance.




    There are not likely very many monitoring instruments for the sin-




tering operation, and at best, the control booth will monitor the pressure




drop in each of the wind boxes.  Occasionally, a hole may result in the bed




and cause excessive particulate generation.  The enforcement official




should ask how many holes occurred in the sinter bed  for the preceding




day for subsequent comparisons.  The enforcement official should also fill




out the Inspector's Work Sheet for this operation.






34. ZINC METAL PRODUCTION




    Emissions from the electrolytic process may contain minor amounts




of sulfuric acid mist.  The pyrometallurgical processes emit particulates.




Emission levels are a function of control equipment adequacy.






34.1 Process Description




     The reduction of roasted zinc calcine to metallic zinc is accom-




plished either by electrolytic depostion from a solution or by pyrometal-




lurgical reduction.
                                  -301-

-------
34.1.1  Electrolytic extraction - This process consists of dissolving the




calcined metal oxides in a sulfuric acid solution and separating the various




soluble and insoluble metals from this solution by selective precipitation




and filtration until the zinc sulfate solution is ready for electrolytic




reduction of sine.  The high purity zinc is removed from the cathodes and




the electrolyte (aqueous solution containing the sulfuric acid generated




during electrolysis) is recycled to the leaching tanks.




        The roasted sulfur-free calcine is weighed in hoppers and appor-




tioned into leach tanks.  The dilute sulfuric acid electrolyte, returned




from the cell room, is mixed with the calcine in the leaching tank and




the ensuing chemical reaction converts the metal oxides to the respective




metal sulfates.  The soluble metal sulfates, among them zinc, copper, cad-




mium, arsenic, antimony, cobalt, and nickel are dissolved and go into so-




lution.  The insolubles suspended in this aqueous mixture include lead,




silver, gold, iron, silica, and calcium.  The insolubles are first sepa-




rated from the solution by filtration.  The dewatered residue from the




settling tank contains the lead, gold and silver which are sent to the




smelter and recovered.




        The filtered zinc sulfate solution is piped to an agitator tank and




enough zinc dust  is added to precipitate the copper.  The copper precipi-




tate is removed from solution by filtration.  This same process is repeated




through several stages.  Other metals such as cadmium, cobalt, nickel,




antimony, and arsenic are precipitated out of the solution.  The residues




from the first two  filtrations are put into water to form a  slurry which




is leached with electrolyte from the cell room and the copper is filtered




out.  Zinc dust is  added to the remaining solution and the cadmium is re-




moved by filtration.  The spongy cadmium product  is refined  by dissolving
                                    -302-

-------
it in a cadmium cell electrolyte from which the cadmium metal is recovered




by electrolysis, melted, and cast into various shapes.




        The remaining zinc sulfate solution is treated in a cell where the




zinc is removed by electrolysis and deposited on aluminum cathodes.  The




spent electrolyte is returned to the leaching tanks for reuse, and the




zinc is stripped from the cathodes and sent to the primary melting fur-




naces.  The 99.99+ percent pure zinc metal is tapped from the furnaces




and cast into blocks.






34.1.2  Pyrometallurgical zinc reduction - This process is a high-tem-




perature carbon monoxide reduction process.




        The reduction temperature is between 1,800 and 2,AOO°F and the




pyroreduction may be done in horizontal or vertical retorts, or in open




or submerged electrothermal arc furnaces.  Horizontal retorts are small




ceramic cylinders that are mounted horizontally in racks that hold several




rows of these retorts in layers.  Vertical retorts are large, refractory-




lined vessels with external gas combustion chambers.  The retorting process




is continuous and highly mechanized.  The feed consists of a briquetted




mixture of the following approximate composition:  60 percent roasted zinc




concentrate, 25 percent bituminous coal, 5 percent anthracite fines, 10




percent plastic refractory clay and 1 percent sulfite liquor.  The bri-




quets are charged into the upper unheated extension of the retort, known




as the charge column, and the residue briquets are continuously discharged




at the bottom. Air is introduced at the bottom of the retort at a low




rate, and the oxygen is converted to carbon monoxide.  The retort is heated




by combustion in the firing chamber external to each sidewall.  Good heat




conduction is essential through both the sidewalls and the briquetted charge.
                                   -303-

-------
     The gaseous-reaction products formed in the retort, which rise up




through the charge column, have the approximate composition of 40 percent




zinc vapor, 45 percent carbon monoxide, 8 percent hydrogen, 7 percent




nitrogen and some carbon dioxide.  These gases exit near the top of




the charge column through a zinc vapor condenser.  In the condensation




process, a back oxidation reaction is responsible for the production of




3 to 5 percent partially oxidized zinc powder.  This zinc oxide, known as




blue powder, floats on top of the zinc bath and is periodically skimmed




off.  A scrubber system may be used to scrub out the entrained blue powder




from the flue gases and this cleaned gas may be used as supplementary fuel




or flared.  The zinc thus produced may be further refined.  About one-half




of the zinc produced in vertical retorts is refined to 99.99 percent purity




by means of continuous fractional distillation.




     Electrothermic furnaces, such as the one graphically depicted in




Figure 34.1, may be used for either zinc or zinc oxide production.  Pre-




heated coke and zinc-bearing sinter are continuously fed to the furnace;




electricity is introduced through graphite electrodes and coke serves as



the principal electrical conductor so the developed electric heat provides




the energy required for smelting.  Zinc is recovered through condensation




by bubbling through a molten zinc bath and zinc oxide may be produced by




oxidizing  zinc vapors with air.  The zinc oxide fume-laden gases are cleaned




by cyclones to remove oversized particles and foreign material, then zinc




oxide is removed either by bag filtration or high energy wet scrubbing.






34.2 Process Control Operation




     Atmospheric emission of pollutants from electrolytic  zinc reduction




is limited  to minor amounts of sulfuric acid mist but disposal of liquid
                                    -304-

-------
                            Granules
                       Cone   Briquets  Sinter
          CO  Gas Burner
               Batch Fed Dross
    Gas Washer
  Carbon
 Monoxide
To Vacuum
  Pumps
  Liquid
   Zinc
                   Charge Level
                     Detector
Zinc Vapor
 & Carbon
 Monoxide,
     Cooling
      Well
        Condenser
             Water Ring
          Rotary  Discharge
               Table
                                                               Rotary
                                                             Preheater
   Rotary
Distributor
                                                              Gamma  Ray
                                                               Source
                                                          Graphite
                                                         Electrodes
                                                             Vapor Ring
                                   Water Cooled
                                      Jackets
                                          Graphite
                                         El-ectrodes
                                                          Residue
                                        Pan  Conveyors
                                        to  Recovery
                                           System
        FIGURE 34,1  ELECTROTHERMIC ZINC  METAL FURNACE
                                 -305-

-------
wastes can create a significant water pollution problem.  Emissions from




retort furnaces are of minor significance compared to other operations




like concentrate roasting and sintering.  Of the total sulfur in the raw




concentrate, only 0.2 to 0.3 percent is emitted from retort furnace oper-




ations.  Particulate emission, which consists primarily of metal and metal




oxide fumes, is minor because economics dictate a high-efficiency metal




recovery.  Because the retort off gases are rich in carbon monoxide, they




are used as auxiliary fuel either in the retort furnaces themselves, or




in other smelter operations.  Retort off gases are commingled with combus-



tion by-products, thus seldom are they directly vented.




     The important process variables are the zinc and coke content of the




feed, the feed, and air flow rates.  Proper air flow rate is important for




the production of carbon monoxide, the reducing agent, since too much air




might result in nearly complete combustion of coal.




     The most important process parameter is temperature.  Process tem-




perature is regulated by fuel rate adjustment for conventional retort fur-




naces and by regulating current flow to the electrodes for electrothermic




furnaces.  The normal process temperature range is between 1,800 and 2,400




     The gases leaving the furnace at essentially atmospheric pressure




bubble through the molte.n condensed zinc.  Gas cleaning consists of par-




ticulate removal which may be cyclone removal of oversized particles fol-




lowed by bag filtration after cooling, or high energy wet scrubbing.  The




cleaned gases, rich in carbon monoxide, are recycled and used as auxiliary




fuel.






34.3  Enforcement Procedure




      Zinc oxide is a fine, highly-visible white particulate, the major




pollutant emitted from the retort furnaces.  The retort furnace is an
                                     -306-

-------
entirely closed system except during charging or when a hole occurs in




the wall of the furnace.  There are many retort furnaces at a zinc pro-




duction facility and most of these are older furnaces where leaks can occur




if not maintained properly.  The enforcement official should ask about the




maintenance schedule used on the furnaces and specifically the maintenance




schedule for the furnace walls.




     The enforcement official should also observe the stack plume.  If a




white cloud is present, it is an indication that the air pollution control




equipment may not be operating satisfactorily.  Most plants will have an




opacity meter located on the stack to warn of any upsets in the furnace




condition.  Opacity meter charts (if available) 5' juld be reviewed, as




well as dust collector maintenance records.




     The enforcement official should obtain information from the operator's




daily logs on the process operation.  The important variables are listed




on the Inspector's Work Sheet shown on the next page.  There is little




telltale evidence that can be collected while standing on the floor of the




plant; therefore, the enforcement official should carry out his inspection




program at the control booth for the retort furnaces and at a distance




from the building so that he can observe the stack plumes for this opera-




tion.  Observations of the opacity of the stack plumes should be made and




if opacity exceeds allowable levels, appropriate action should be taken.
                                  -307-

-------
                          INSPECTORS WORKSHEET
                        FOR ZINC RETORT FURNACES
Plant Id.
Date of this Inspection	Date of last Inspection_




Type of Retorts	




No. of Retorts, entire plant	
No. of Stacks for Retort furnaces
No. of Retorts out of service this day
Process feed rate, entire retort plant	tons/hr






ABATEMENT EQUIPMENT (fill out for each device)




Pressure drop	in. FUO




Spark rate	spm




Flow rate	scfm




Inlet Temperature	°F




Opacity Meter Reading	%
DIAGRAM OF RETORTS, ABATEMENT EQUIPMENT AND STACKS
GENERAL OBSERVATIONS:
Time In                                             Time Out

-------
                              BIBLIOGRAPHY

                          LITERATURE REFERENCES
Rausch, D. 0. and Mariacher, B. C., AIME World Symposium on Mining and
     Metallurgy of Lead and Zinc,  The American Institute of Mining,
     Metallurgical, and Petroleum Engineers, Inc., 1970.

Hayward, C. R., An Outline of Metallurgical Practice, D. Van Nostrand
     Company, New York, 1952.

Arthur G. McKee and Company, Systems Study for Control of Emissions
     Primary Nonferrous Industry,  National Air Pollution Control
     Administration, 1969.

Engineering-Science, Inc.,  Exhaust Gases from Combustion and Industrial
     Processes,  Washington, D. C., 1971.

System Development Corporation, Air Pollution Control Field Operations
     Manual,  Environmental Protection Agency, Office of Air Programs,
     Raleigh, N. C., 1972.

Midwest Research Institute,  Emissions, Effluents, and Control Practices
     for Stationary Particulate Pollution Sources, National Air Pollution
     Control Administration, Cincinnati, Ohio, 1970.

U. S. Department of the Interior, Bureau of Mines, Mineral Facts and
     Problems,  1970.

Strauss, W.,  Air Pollution Control, Wiley--Interscience, New York, 1971.

Los Angeles County Air Pollution Control District, Air Pollution Engineer-
     ing Manual,  U. S. Department of Health, Education and Welfare,
     National Center for Air Pollution Control, Cincinnati, Ohio, 1967.

Stern, A. C.,  Air Pollution,  Academic Press, New York, 1968.

Southern Research Institute,  Manual of Electrostatic Precipitator
     Technology,  National Air Pollution Control Administration,
     Cincinnati, Ohio, 1970.

GCA Corporation, Handbook of Fabric Filter Technology,  National Air
     Pollution Control Administration,  1970
                                   -309-

-------

-------
           PART VI.  AIR POLLUTION CONTROL SYSTEMS





     Particulates are the principal pollutant from the five metal indus-




tries covered in this report.  The air pollution control devices which




have been  used to abate particulate emissions include electrostatic pre-




cipitators, fabric filters, wet scrubbers, and cyclones.  In the copper,




lead, and  zinc industries, sulfur dioxide emissions are significant.




The most effective method for reducing sulfur dioxide emissions to the




atmosphere has been with sulfuric acid plants.  However, this particular




type of "abatement device" is not part of the scope of work for this  par-




ticular project and will not be treated in this section.  In the aluminum




industry,  the major air pollutant is fluoride.  Two different types of




controls have been used to reduce fluoride gases from these operations,




low energy wet scrubbers and dry adsorption processes.  The low energy




wet scrubbers are discussed as part of this section ind the dry adsorption




process is discussed in Chapter 16.  Table VI-1 is a list of the common




particulate control devices used by these major metals industries.




     There are several factors which affect the selection of the gas




cleaning unit for a particular operation.  These include the volumetric




flow rate, the variability of the gas flow, particulate concentration,




allowable pressure drop, product quality requirements, and the required




collection efficiency.  Particle size gradients in the inlet gas stream




are also an important factor in selecting the proper abatement device.




Particles larger than about 15 microns are usually removed effectively




by inertial separators such as cyclones.   For those sources which have




particles smaller than 15 microns and with many of them being smaller




than one micron (submicron), medium and high energy scrubbers, fabric
                                  -311-

-------
            Table VI-1.  USE OF PARTICULATE COLLECTORS  BY INDUSTRY
    Industrial  classification
                                      Process
                                                        EP
                                                              MC
                                                                    FF
                                                                         ws
                                          Other
Rock products






Steel










Mining and metallurgical














Cement 	
Phosphate 	
Gypsum 	
Alumina 	
Lime 	
Bauxite — --------------
Magnesium oxide 	 --
Blast furnace 	
Open hearth 	
Basic oxygen furnace 	
Electric furnace 	
Sintering 	 ' 	
Coke ovens 	
Ore roasters----- 	 	 —
Cupola 	
Pyrites roaster 	
Taconite 	
Hot scarfing 	
Zinc roaster 	
Zinc smelter 	
Copper roaster 	 	 	
Copper reverb 	
Copper converter 	 	 	
Lead furnace 	
Aluminum 	
Elemental phos 	
Ilmenite 	
Titanium dioxide 	
Molybdenum 	
Sulfuric acid 	
Phosphoric acid 	
Nitric acid 	
Ore benef iciation 	
0
0
0
0
0
0
+
0
0
0
+
0
0
0
+
0
+
0
0
0
0
0
0

0
0
0
+
+
0


+
0 0
0 0
0 0
0 0
0 +
0 	
+ 	



	 0
0 	

0 	
	 +
0 	
0 	

0 	

0 	


	 0


0 	
	 0




+ +
+
0
0
+
	


0
+
0
0


+
0
0

+





0
0


	

0
0
0
+

	
	
	
	
	
	
+
+
	
	
	
+
	
	
	
	
	
	
	
	
	
	

+
	
	
	
	
0
0
0
+
Key:
    0 = Most common
    + = Not normally used
   EP = Electrostatic Precipitator
   MC = Mechanical Collector
   FF = Fabric Filter
   WS = Wet Scrubber
Other = Packed  towers
        Mist  pads
        Slag  filter
        Centrifugal exhausters
        Flame incineration
        Settling chamber
                                          -312-

-------
 filters,  or electrostatic precipitators will have  to  be  used to clean




 the gas  stream.   Figure VI-1 indicates  the type of control systems  that




 can be used on various  size particles.




      Once the  technological considerations have been  made  for selecting




 control  systems,  general operating factors play an important role  in final




 selection.   For  example, the disadvantages of wet  scrubbers include the




 potential water  pollution problem, high power costs,  and the presence of




 a visible plume.   Fabric filters  and  electrostatic precipitators capture




 particles without any physical  modification and the collected material




 can readily be reused in the process.   However, fabric filters have a




 temperature limitation  and are  sensitive to process conditions.  Electro-




 static precipitators  have few moving  parts and low power requirements




 but are  sensitive to  variable dust loadings and variable flow rates.   Be-




 cause of  the wide variations in process operating  conditions,  different




 types of  control  devices may be found on the same  source at different




 plants.




      The  following discussion on  electrostatic precipitators,  fabric




filters, wet scrubbers,  and cyclones provides some  background with respect




 to the technological  considerations applicable to  an  abatement system.




 Air pollution  control systems for a single source  may include  different




 control devices  in series and in  parallel.  Particulates coming from




 roasters  in a  lead smelter will often go through cyclones  to remove the




 large particulate matter prior  to entering electrostatic precipitators.




 Non-ferrous sintering machines  may have the wind boxes divided into sev-




 eral sections  with the  primary  combustion gases going to one kind of




 control device,  say a sulfuric  acid plant, and the secondary combustion




 zone ga-ses  going  to a different kind  of collector.
                                   -313-

-------
Particle Oamcter. microns (p)
,1m,! drum! lleml
00001 0001 001 01 1 10 100 1.000 10.000
Equivalent
Sito*
«.«£
WflVM
Technical
Definition
Common Atmospheric
Dnporeoid*
Typical Particle*
and
Gu Ditporsoidl
M.thodi tor
Pirllcle Sin
Anjlytii
TypMot
Gu Ctoaninc
Equipment
Terminal
Gravitational
Sottimf-
fforiDlwrM.]
I IP fr. 2.0 J
Particla Diffusion
Coefficient.'
cm '/we.


fepnods
Sal




hi AM
•j»-c
latm
In WMrf
X
arc
In Air
ai2vc
lafm
1



) K
IngstrOm Units. '


	
Merber| or Inlcrrutiorul SW ClHWhuMn S
AdopMd by Internal Soc Sod So S"K< 1934

0, CO,
H, 1 f, \ Cl,
^wi
I N, I CM. j
CO HX) HO
•Molecular darnel
from viscosity dat


Reynolds Number
Setibnc Velocity
cm/we
Reynolds Number
Sefl*«f Velocity,
Cm/SK



J
G*> r
Molecules'
tl
OHi.
ten ukutated
J.tO'C

H 	 Vi

1












10 •'' 10"" 1
1
• ) > 10
,O;,O-;MO;'
10 10 10?
1 , , , I II
.., ' ^'oy,,10-;,,10-
mwttar I . 1 ,
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FIGURE VI-1  CHARACTERISTICS OF PARTICLES AND PARTICLE DISPERSIONS
                                 -314-

-------
     There are many existing air pollution control regulations which apply



to the maintenance of air pollution control systems.  Generally speaking,



the laws will require that all air pollution control devices be maintained



in good operating condition.  Thus, unbalanced fans, excessive spark rates,



holes in the ducts and water entrainment are indications that the control



system has not been maintained in good operating condition.  Observations



of concern to an enforcement official when inspecting an air pollution



control system are included in the following chapters.





35.  ELECTROSTATIC PRECIPITATORS



     The theory of the successful operation of the electrostatic precipi-



tator will not be discussed in detail in this chapter, since it has been



carefully documented academically.   Interest is in the actual field ap-



plication of the precipitator.   Basically,  there are two types of precipi-



tators used in these five industries:   wire-in-plate and wire-in-cylinder.



Because of the nature of the air contaminants, plate-type precipitators



are predominantly used to reduce particulate emissions.  The wire-in-



cylinder type precipitator is best applied to wet gas cleaning, which is



uncommon in these industries.  Figures 35.1 and 35.2 are diagrams of the



wire-in-cylinder and wire-in-plate type precipitators.



     There are several parameters which are important in selecting the



size of precipitator.  These include the volume of gases to be treated,



the resistivity of the particulate, particulate size, and dust loading.



Of these, resistivity and dust loading are the most important.  The resis-



tivity is dependent upon the nature of the pollutant.  Most of the pollu-



tants associated with these five industries have resistivity values be-


        7       9
tween 10  and 10  ohm-cm.  Dust loadings may range from several hundreths



to 100 gr/scf depending on the manufacturing process.





                                  -315-

-------
                                                        High Voltage
                                                          Insulator
                                                        Compartment
   Support
  Insulator
  Steam
 Collector
High Tension
Support  Frame
 Collecting
  Electrode
    Pipes
    Shell
High Tension
  Electrode
  Electrode
   Weight
                                                                Clean Gas
                                                                   Main
Gas Deflector
    Cone
                                 Collected
                                 Dust Out
      FIGURE 35,1  A SINGLE-STAGE VERTICAL WIRE AND  PIPE UNIT
                                     -316-

-------
FIGURE 35,2  PARALLEL PLATE PRECIPITATOR
                  -317-

-------
     An equation which relates efficiency with gas flow rate and collec-




tion area of the precipitator is:




           E - 1 - e ' <* A/V)




           Where:   A = Area of collecting surface




                    V = Gas flow rate




                    w = Precipitator rate parameter




                    E « Efficiency percent




                    e = Base of natural logarithm




This equation can be used to calculate the collecting surface area re-




quired for a specified volume of gases.  The critical parameter in that




equation is "w", the precipitation rate.  The precipitation rate is an




indication of the speed at which particles will migrate to the collecting




electrode.  Precipitation rate varies with respect to each individual ap-




plication.  For smelters, the precipitation rate is 0.35 fps.  For  open




hearth steel making furnaces it is 0.06 fps.  For EOF furnaces it ranges




between 0.20 and 0.46 with an average of about 0.36 fps.  Other precipi-




tator parameters which are important for the effective removal of particu-




lates from a gas stream include spark rate and corona power.  Typical




spark rates for these heavy metal industries will usually range between




50 and 250 sparks/minute.  At no time should a precipitator for these




industries be operating with a spark rate in excess of 400 sparks/minute.




To a certain degree, spark rate will depend on the physical condition of




the precipitator.  Corrosion, reduced electrical insulation, and particu-




late build-up may cause excessive sparking.  On the other hand, a low




spark rate, on the order of 10 to 20 sparks/minute, would indicate a de-




ficiency in precipitator power, therefore, reduced efficiency.




     The electrical energy necessary to charge a particle and bring it in
                                   -318-

-------
contact with a collecting surface is unique to each specific application.




Generally speaking, the corona power will range from 200 to 300 watts per




1,000 cfm of gases treated for these metals industries.



     Once the particle has been deposited on the collecting surface, it




must be removed.  A dust build-up would prevent further ionization and re-




duce the overall efficiency of the precipitator.  Particulate is removed




from the plates and the wire by vibrators or rappers.   These are mechani-



cal means for removing the dirt from the electrodes.  The rappers and vi-




brators will knock the agglomerated particulates to the bottom of the pre-




cipitator where it is collected in hoppers.  There is no set rapping rate




or average rapping rate that can be associated for each of these large




metals industries.  Each precipitator will have its own rapping or vi-




brating sequence.




     Another critical operating parameter of a precipitator is the gas




flow rate.  In most cases, the gas is preconditioned to meet the design




specifications of the electrostatic precipitator.  Often, the gas comes




from a furnace at extremely high temperatures and is cooled by water




sprays or dilution air to a temperature of 500 F on the inlet side of the




unit.  It is very important that the distribution of the gas through the




precipitator be uniform.  This is usually accomplished by straightening




vanes and distribution vanes.  Figure 35.3 illustrates the poor effici-




encies associated with the irregular flow velocity.  At a flow velocity




of 0.5 meters per second (mps) there is an efficiency of 99.4 percent.




While in another section of the precipitator, where the flow velocity is




1.5 mps the efficiency is only 91 percent.




     Depending on the specific installation, the precipitator may be




designed to have several sections or several units.  A unit connotes par-




allel gas flow and a section connotes gas flow in series; therefore, for





                                 -319-

-------
»*


o

Ul
I—•
o
                                           Weighted

                                           Average

                                            94.5
                     VELOCITY, meters/sec
    FIGURE 35,3   EFFECT OF NON-UNIFORM VELOCITY  ON

                  PRECIPITATOR COLLECTION EFFICIENCY
                          -320-

-------
 a precipitator  installation which has  two  units,  50 percent  of  the  gas




 will be  treated by  one  unit,  and  50  percent  of  the gas will  be  treated




 by the other  unit.  A unit may have  several  sections and  for these  heavy




 metals industries it is common to find up  to four sections for  each of




 the precipitators.  The principal advantage  of  sectionalizing is with




 respect  to  down-time of the precipitator.  For  example, if one  section




 of a four sectional precipitator  became  inoperative, the  remaining  three




 could control particulate levels, although not  as efficiently.




      The type of monitoring instruments that are available  for an electro-




static precipitator installation will include meters to measure spark rate,




voltage and,current.  Typical voltages for these  industries will be on the




order of 20 to 100 kv and the average current is  about 1000 ma or 1 amp.






35.1  Precipitator Inspection




      Manufacturers of electrostatic precipitators have usually designed




precipitators for specific applications.  It is unlikely that identical




precipitators would be found, even in the same metals application.  Such




things as corona power,  precipitation rate, type  of plates, and gas tem-




peratures will vary from furnace to furnace and also from plant to plant.




It is the intent of this sub-section of this chapter to identify those




general operating characteristics and inspection points which can be ob-




served when a precipitator is in operation.  Observation of marked increase




in plume opacity is one  indication that the precipitator may not be oper-




ating properly.




      Causes for precipitator malfunction include:  electrical,  gas flow,




and physical.  Most electrostatic precipitator service men have indicated




that it is the electrical system of the precipitator which is most often




the cause of malfunction.  If there is any doubt  as to the operability of






                                  -321-

-------
the precipitator the electrical meters should be checked first.  Older




precipitators will have problems with the rapping or vibrating scheme




and the physical abrasion caused by the pollutants.  If the precipitator




monitoring instruments, spark rate meter, primary voltage meter and pri-




mary ammeter indicate that the precipitator is operating normally, yet




visual observations indicate poor precipitator efficiency, then it is im-




perative that the enforcement official obtain the design specifications




from the plant operator.




     The following step-wise procedure should be used to detei-uiine the




effective operability of a precipitator.   Many items on this check list




came from "The Manual of Electrostatic Precipitator Technology."




     1.  Observe the electrical monitoring instruments for the precipi-




tator.  If the spark rate is less than 400 sparks/minute this is con-




sidered normal operation; however, a spark rate in excess of 400 sparks




minute is an indication that the precipitator section has shorted out.




Record the primary voltage and primary amperage to each of the sections,




if a precipitator has four sections, this inspection procedure must be




carried out on each individual section.  A marked voltage drop in one sec-




tion of a precipitator is an indication of a dead section and the unit




is not operating correctly.




     2.  Record the gas inlet temperature and gas flow rate.  The gas




temperature should be between 250 and 500 F.  If the temperature is less




than 250 F, it is likely that condensation will form in the precipitator,




causing malfunction.  Temperatures in excess of 500 F cause the plates




and wires to warp within the precipitator.  Observe the ducts entering




the precipitator for corrosion.  Corrosion at the exterior ducts is an




indication of corrosion on the interior of the precipitator.
                                  -322-

-------
      3.  Open the hatch on several of the precipitator sections.  Observe




dust deposits on collecting plates, and wires before cleaning.  A 1/4-




inch deposit is normal, but if the metal plates are clean there is a pos-




sibility that a section is shorting out.  If more than 1/4-inch of dust is




on the plates the rappers and vibrators are not working properly.  Observe




the amount of corrosion adjacent to the door.  Leakage to the interior of




the precipitator through the doors could cause non-uniform gas flow and




reduce efficiency.  Check plate alignments for equal spacing between plates,




also check for broken wires at the top of the precipitator.




      4.  Open the hopper access door for this inspection.  Check for leak-




age into the precipitator around the door and for dust build-up in upper




corners of hoppers.  Check the high tension weights, if one has dropped




more than 3 inches, it is an indication that the wire has broken.  Check




the hopper bottom for broken precipitator parts, like wires, insulators




and plates.




      5.  Check the electrical distribution center by examining the high




tension lines, insulators, bushing, terminals, and arresters for broken




parts.  Some minor sparking should be noted in this area.




      6.  Listen to the rapper or vibrating mechanism which cleans the dust




from the plates and wires.  A uniform, rhythmic tapping, of metal to metal,




should be noted.  Any irregular sounds are an indication that the rapper




mechanism is not operating correctly.




      7.  If necessary, make the calculations, which relate efficiency




collection area, gas flow rate and precipitator rate.  Compare the calcu-




lated results to design specifications and ask whether any alterations




have been made to the process which might affect precipitator performance.




      8.  Ask about the routine maintenance schedule for the precipitators,




and to see logsheets for any repairs.






                                  -323-

-------
36.  FABRIC FILTERS




     Fabric filter collectors are commonly referred to as baghouses and




are perhaps the oldest and most reliable methods of removing dry particu-




late matter from an air stream.  Baghouses have traditionally been de-




signed with a collection efficiency in excess of 99 percent.  As mentioned




in the previous chapters, these five metals industries are commonly as-




sociated with fine particulates (minus 10 microns in diameter).   Fabric




filters are effective in collecting particulates as small as 0.1 micron




and some investigators have measured and collected particulates  smaller




than 0.01 micron in size.  The size of these systems range from one or two




bags to as many as many several thousand bags for one system.  Figure 36.1




is an illustration of a typical baghouse.




     The operating principle of a baghouse is simple, the filter itself




acts as a collection medium.  When air is passed through the fabric, par-




ticles come in direct contact with the fabric and are caught.  The air




stream or gas is not affected by the fabric filter and passes without in-




terruption to 'the outlet side of the unit.  There are several factors which




are special to the design of a fabric filter system.  Different fabrics




will have different permeabilities.  Permeability is associated with the




ease at which a gas passes through a fabric.  The American Society for




Testing and Materials (ASTM) has developed a standard procedure for meas-




uring permeability through new cloth; by keeping the pressure differential




to 0.5 in. wg, the flow rate is recorded that passes through a square




foot of cloth.  Table 36.1 indicates the fabric filter characteristics




including air permeability for selected fibers.




     The pressure drop commonly found in baghouses in these metals appli-




cation ranges from 2 to 8 in. of water during normal operation.   Average
                                   -324-

-------
CLEAN AIR
 OUTLET
 DIRTY AIR
  INLET
CLEAN AIR
  SIDE
                                                     CELL PLATE
FIGURE 36,1   TYPICAL  SIMPLE FABRIC FILTER BAGHOUSE DESIGN
                              -325-

-------


















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-326-

-------
 flows  are between  1.5  and  3.0  cfm/ft2  of cloth.   This  is  known as


 the air-to-cloth-ratio.  Baghouses  traditionally  found in these five

metals industries have a maximum filtering ratio, air-to-cloth-ratio,


which  ranges between 2.0 and 3.5.   However, when  the bags are  cleaned  with

                                                                             2
a reverse air jet  stream,  the  air-to-cloth-ratio  increases to  about 9  cfm/ft .


     Moisture and gas  temperature are  the most critical operating variables


for baghouse  installation.  It is  desirable to keep the  temperature of  the


gas 50 to 75 F above the dew point  to  prevent condensation within the  unit.


Moisture would cause mud cakes to form on the bags and cause high resis-


tance  and ultimate rupture.  Because of  the physical and  thermal charac-


teristics of each of these fibers,  the bags will  fail  at  elevated tempera-


tures.  The long and short term operating exposure of  selected fibers  is
also shown in Table 36.1.  Dacron-^ is the most popular bag used  in these


metals industries.  Its normal operating temperature  is about  270 F.  Gases


coming from melting and smelting operations from these industries at high


temperatures must be cooled before entering the baghouses.   Heat exchangers


and water spray systems are used to cool the gases.   Each of* these gas  cool-


ing systems must be well designed to prevent moisture and excess temperature


in the baghouses.


     There are three types of baghouse  designs commonly used  today:  open


pressure, closed pressure, and closed suction.  Open-pressure  baghouses


do not have a stack, instead the gases are exhausted  through the walls  or


sides of the baghouse  installation.   Closed-pressure baghouses  are con-


structed with the fan  supplying a positive pressure and the dirty gas to


the unit.  Because the fan is on the inlet side, it is subjected to the


abras,ion and wear caused by the air pollutants.  In a closed-suction bag-


house, the fan is located on the outlet side of the unit, thus  the gases
                                 -327-

-------
at the fan are cleaned and free of abrasive pollutants.  One of the




problems encountered with a closed-suction baghouse is the tight seal




required for the entire installation.  Air leaks around access doors,




vibrators, and walls may reduce the efficiency of the unit or cause con-




densation at "cold spots".




     There are several types of manual shaking systems used to clean the




bags once they become dirty.  The cleaning cycle is based on pressure




drop across the bag or a timed cycle.  Figure 36.2 illustrates some of




the schemes used to remove dust from the fabrics.  Each cleaning scheme




has its advantages for a specifically designed baghouse.  Often bag-




houses are sectionalized, that is, having several compartments so that




one compartment may be cleaned while the others continue to operate.




For those baghouses which clean on a pressure drop response, the clean




cycle may begin when the pressure drop across the compartment reaches



3 and 4 in. wg.  On the other hand, time cycles vary widely, from once a




minute to once a day.




     Bag life for these metallurgical industries ranges between 18 months




and 2 years.  There are few operational adjustments which can be made to




a baghouse once it has been installed and most likely, the only monitoring




instrument for baghouses will be a manometer measuring pressure drop




across the entire system.  Bags are changed on a regular schedule, also




when they rupture.






36.1  Enforcement Procedure




     The following step-wise procedures should be used to assess the opera-




ability of a baghouse abatement installation:




     1.  Prior to, or upon entry to the plant, obtain design specifications




of the baghouse installation.   Ask what type of bags are being used and
                                  -328-

-------
                            JET
        UNI-BAG
      INSIDE OUT
      FILTERING
                                   SIDE VIEW
                                                                        COMPRESSED AIR
                                                                       OUTSIDE IN
                                                                       FILTERING
  Bubble cleaning of dust collector bags.
                                                                     SIDE VIEW

                                                         Jet pulse dust collector bag cleaning.
X


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/
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rj EXHAUST


	 3


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REPRESSURING
   VALVE
URING\       /
                     SIDE VIEW
                                                   SIDE VIEW
                                                                                     , INLET
                                                                                     Q VALVE
              FILTERING                  COLLAPSING
                     Reverse air flexing to clean dust collector bags by repressuring
                                                                       SIDE VIEW

                                                                CLEANING
                           AIR HORN
     FILTER BAG
                                                          TOP ENTRY
                                                                      \
                                                                   HIGH PRESSURE
                                                                 -»-AIR BLOW
                                                                   RING
                  DUST--
                   " >•_* !•*/.'

       • Sonic cleaning of dust collector bags.
                                                                    INSIDE OUT
                                                                   "FILTERING
                                                                           CROSS-SECTION
                                                   Reverse jet cleaning of dust collector bags.
                   FIGURE  36,2   BAGHOUSE  CONFIGURATIONS
                                           -323-

-------
ask for historical records which would indicate fan size, inlet tempera-




ture through the baghouse and pressure drop across the unit.  Determine




the number bags and collection area of this installation and compare this




data to the data in Table 36.1.




    2.  Observe the cleaning cycle for this particular installation.




Determine whether a pressure or time cleaning cycle is used to remove




the dirt from the fabric.  For a pressure control system, check the con-




trols and their operability to insure that when the pressure drop is




reached, cleaning is initiated.  For time-cycle cleaning schemes, observe




the rhythm for a given period to assure its operability.




    3.  Check for air leakage into the ducts, fans, access door, bag-




house structure, and hopper.  For closed-suction baghouses, check the




seals on doors, hatches, and hoppers for a tight seal.




    4.  Observe the unit for an entire cleaning cycle.  If the light or




dark plume is noted emanating from the stack, it is likely that a rupture




or bag failure has occurred but has not been replaced.




    5.  Measure the wet bulb and dry bulb temperature of the inlet gas




stream.  Use the section in Part VIII of this manual to determine the dew




point of the inlet stream.  The dew point should be at least 50 F above




the inlet temperature to prevent moisture build-up on the bags.




    6.  Observe the manometer or pressure drop across the baghouse sec-




tions.  After cleaning, the pressure drop across the fabric should be




less than when dirty.




    7.  Observe during the hopper clean out operation.







37.  WET SCRUBBERS




    There are many types of scrubbers in use in these five metals indus-




tries today.  The types vary from the most simple design of a water spray







                                 -330-

-------
in stack to high energy venturi scrubbers.  Each manufacturer has his




own design on the method for impacting particulate matter in a liquid




film.  Basically, there are low, medium and high-energy scrubber systems.




The energy requirement refers to the amount of power needed to obtain se-




lected pressure drops across the scrubbing system.  Low energy scrubbers




typically have a pressure drop of up to 12 in. wg pressure.  High energy




venturi scrubbers can go up to 100 in.  wg pressure.  For these five




metals industries, we are primarily interested in the high-energy capa-




city scrubber systems.  This is mainly due to the nature of the pollu-




tants from these industries.  As we have seen in previous chapters, the




particle diameter of much of the metal fume is less than one micron.




This requires the use of high energy venturi scrubbers on most of these




industrial applications.  Neither cyclones nor settling chambers have been




effective in removing the submicron particle inherent in these metals




applications.





     The collection principle of wet scrubbing systems  is  accomplished




by  impaction of dust  with  liquid droplets.  The particles  come  in  contact,




enlarge  in size and finally settle out.   Once the particle  is trapped,  it




is  then washed away.   There are no universally  accepted equations  which




relate scrubbing parameters with collection efficiency.  Much of the ex-




isting scrubber technology has  been defined and presented  in  the reference




entitled, "Scrubber Handbook."  Basically, the collection  efficiency of




a scrubber system will depend on the size of  the particle.  Of particular




importance is the particle size and inlet dust loading.  Figure 37.1




shows a relationship  between pressure drop and outlet grain loading.




     Several investigators have tried to  relate input power to efficiency.




Power refers to the amount of energy necessary to overcome  the resistance
                                  -331-

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     100
  o
  CM
  a.
  o
      10
  a.

  »—4

  cc
       1
                                                   I
                                                               J	I   I
0.001                 0.01                   0.1


        CLEAN GAS DUST LOADING GRAINS PER STANDARD CUBIC FOOT
                                                                       10
FIGURE  37,1  CALIBRATION CURVE  FOR A BLAST FURNACE VENTURI SCRUBBER
                                    -332-

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caused by a scrubbing system, such as a contracting throat or high pres-




sure sprays.  Figures 37.2 and 37.3 show this relationship of contacting




horsepower and efficiency for selected metallurgical operations.  These




curves were developed for specific industrial applications.  Generally




speaking, it will require about 7 hp/1000 cf of exhaust gases to obtain




an efficiency of above 99 percent for the particle diameter typically found




in these industries.  These relationships were developed for high energy




venturi scrubbing systems.  Less efficient systems like the impingement




plate scrubber does not have the high collection efficiency commonly as-




sociated with venturi units; however, a lower efficiency would not require




as much contacting horsepower.  It is because of the similarity of the




metal fume generated in each of these metals industries that these curves




supply "ball-park" figures for power requirements for scrubbing systems.




As mentioned in the previous chapters, these fumes are fine and many are




submicron in size.  The pressure drop, which corresponds to the contacting




power, will represent the most important scrubber operating variable used




to assess the collection efficiency of a unit.




     Another fundamental operating parameter of wet scrubber systems is




the liquid flow rate in the unit.   This parameter is usually expressed in




terms of gallons of water per 1000 cf of gas processed.  For the high en-




ergy venturi systems on these particular applications the flow rate re-




quirement varies between 3 and 10 gal/1000 cf of gas processed.  For




plate or impingement type scrubbers (low energy units) the flow rate is




something less; on the order of 1 to 2 gal/1000 cf of exhaust gases pro-




cessed.  Under normal operation, high energy venturi units have been




shown to reduce particulate levels to an exit loading of less than 0.01 gr/




scf.  Typical throat velocities for venturi units are on the order of 200
                                 -333-

-------
 I

to
tx.
Ul
u.
a   2
                OXYGEN  IN
                                            I     III
                                                                 99.9






                                                                 99.5



                                                                 99



                                                                 98
                                                                      4)
                                                                 95   if
                                                                      
-------
 I

to
    0.9


    0.8


    0.7


    0.6



    0.5




    0.4
1
                                         O
                                   O,
                                      O
                              O
                   O
                                     I
J	I
                                                                98
                                                                95
                                                                90
                                                         80   S

                                                              
-------
to 600 ft/sec.  Packed bed or impingement type scrubbers typically have




pressure drops less than 5 in. wg pressure.  Figures 37.4 and 37.5 are




illustrations of a venturi scrubber and a wet impingement scrubber.



     The principal disadvantage of using a venturi unit in lieu of an




electrostatic precipitator, fabric filter, or other collection devices is




its high annual operating cost.  Once installed, the cost of water is




much cheaper than that for electrical energy for precipitators, and, in




many cases, much cheaper than replacement of bags for the fabric filter




systems.  The immense horsepower requirements soon offset these savings.




Venturi systems in these metals industries typically operate about 60 to




80 in. wg pressure.  These systems have a collection efficiency in excess




of 99 percent.  Packed bed and plate type scrubber systems have an ef-




ficiency of between 80 and 90 percent.






37.1  Medium Energy Scrubbers




      Medium energy scrubbers refer to those control devices which op-




erate with a pressure drop of up to 14 in. H~0.  Compared to the other




types of control systems, these scrubbers usually require a minimum of




space.  Typical efficiencies for these units will be on the order of up




to 90 percent for large dust.  Their major application in these metals




industries is in the material handling segment of production.  These type




units are found on transfer points from conveyor systems, and at the end




of crushing, screening and grinding operations.  In the aluminum industry,




low energy scrubbers (up to 8 in. H«0 wg) are the primary air pollution




control systems.  Hydrogen fluoride gas, which emanates from anode curing




ovens, prebake pot and Soderberg pot operations, is very soluble in water




and can be effectively controlled by passing it through these scrubber




systems.  Figures 37.6 and 37.7 are illustrations of a flooded-bed
                                  -336-

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                                                    B
                        A
FIGURE 37,4  VENTURI SCRUBBERS MAY FEED  LIQUID  THROUGH JETS (A),
             OVER A WEIR  (B), OR SWIRL THEM ON  A  SHELF (C)
                              -337-

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               Gas Outlet
                                Water
                                Eliminator
                                Impingement
                                Baffle Plate
                  Drain
     CLEAN AIR OUT
                                    -ENTRAPMENT
                                     SEPARATOR
FIGURE  37,5   WET  IMPINGEMENT COLLECTORS
                       -338-

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GAS OUTLET
                                                           MIST
                                                           ELIMINATOR
GLASS SPHERES
      SPRAY
      WATER INLET
               FIGURE 37,6  FLOODED BED SCRUBBER
                             -339-

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DIRT AND WATER
DISCHARGED AT
BLADE TIPS
DIRTY GAS
INLET
                                CLEAN GAS
                                OUTLET
       WATER AND
       SLUDGE OUTLET
     FIGURE  37,7  CENTRIFUGAL FAN SCRUBBER
                          -340-

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scrubber and a centrifugal fan wet scrubber.  Flooded-bed scrubbers sim-




ilar to Figure 37.6 are the ones that are used to remove hydrogen fluor-




ide gas.  The centrifugal wet scrubber is the type of system that would




be used on many material handling sources.  Figure 37.8 will provide some




idea of the fan horsepower required for various sized installations.






37.2  Enforcement Procedure




      In this subsection it is impractical to discuss typical operating




parameters for each industrial application because of the numerous scrubber




designs.  Certain things are similar for scrubbers applied to these in-




dustries.  One of the easiest parameters used in assessing the performance




of a scrubber is the contacting horsepower and corresponding flow rate.




The horsepower rating is available on nearly every motor in the form of a




name plate on the frame of the motor housing.  Flow rate can be measured




or obtained from fan curve data.  A scrubber installation will contain a




manometer which would indicate the pressure drop across the scrubber.




Amperage of the fan, line voltage and water flow rate in the system are




necessary parameters in assessing the operability of the scrubbing system.




      The following step-wise procedure will assist the enforcement offi-




cial in determining whether or not a scrubbing system is working effec-




tively:




      1.  Obtain the horsepower rating of the motor or motors involved in




moving the gas stream through the scrubbing system.  Determine the fan ca-




pacity for each of the fans in the system, in terms of  scfm.   Compare this




power/flow rate ratio to the above mentioned figures for these type indus-




tries.   Ascertain that this unit has been properly sized for this particular




installation.




      2.  Inspect the fan for vibration.   Excessive vibration may cause the




fan, ducts,  and scrubber components to rupture.





                                   -341-

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O
O.
UJ
CO
o:
o
a:
o
                               ce
                               LLJ
CO
OL
O
                               O
       1  23456789 10

   SATURATED GAS VOLUME CFM x 1000
900




800





700





600





500


450


400


350


300


250


200


150

125
100
 75
 50
 25
  0
       10      20       30       40       50

         SATURATED GAS VOLUME CFM x  1000
         FIGURE 37,8   FAN HORSEPOWER  REQUIREMENTS FOR
                        VARIOUS  SIZE SCRUBBERS
                                    -342-

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     3.  Check for the distribution of water at the throat or in the




packed bed system.  Some venturi systems will have gauges which indicate




the pressure supply to each nozzle or each section of a particular throat.




Observe and insure that these pressures are nearly the same for each sec-




tion or each nozzle.  A deficient pressure indication for a nozzle or




section would indicate that the proper amount of water is not being sup-




plied for the ensuing air stream, thus reducing the overall efficiency




of the collection system.




     4.  Record the temperature of the inlet gas stream to the scrubber.




Temperatures to the scrubber will be on the order of 250 to 500 F.  If




the inlet temperature is less than 250 F, it is likely that condensation




will form in the ducts, causing plugging.




     5.  Inspect the interior of the scrubber for scaling and particulate




build-up.  For venturi systems, inspect the interior of the throat care-




fully for caking and other particulate build-up.  Any caking that causes




an uneven distribution of the gas stream across the throat would reduce




the overall collection efficiency of the scrubber.  Inspect the mist elim-




inator for mud build-up.




     6.  Observe the water effluent from the scrubber system.  A mud




slurry should be noted.  Compare the water flow rate for this scrubber




installation with the values mentioned above.




     7.  Obtain the pressure drop across the entire scrubbing system.




Compare this pressure drop to those values cited for typical installations.




If possible, obtain design specifications for the scrubber installations




and compare the operating parameters,  flow rate, horsepower, pressure  drop




and water flow rate,  to the design specification.
                                 -343-

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38.   CYCLONES




     Cyclones are the least efficient air pollution collection device that




has  been used in these metallurgical industries.  Cyclones work on a prin-




ciple of centrifugal force and gravitational settling to remove large par-




ticulate matter from gas streams.  Cyclones work well in removing particu-




lates greater than 10 microns in diameter.  With that size particle, cy-




clones and multicyclones have shown an excess of 80 percent removal




efficiency.




     Figure 38.1 illustrates the conventional reverse-flow cyclone.  The




inlet gas stream is tangentially applied to the cyclone.  The exhaust gas




is removed through the center of the unit.  The centrifugal action in the




cyclone causes large particles to settle to the base of the cyclone where




they are removed periodically.  Figure 38.2 indicates the kind of effici-




ency that can be found in various mechanical collectors which may have a




load of 4.6 gr/cf.




     Cyclones are still used in modern air pollution abatement systems.




Generally they serve as a preliminary knock-out chamber to remove the very




large particles from many of these metallurgical operations.  Precipitators




may encounter operational problems if varying loads of fine and large dusts




are cleaned in these systems.  In these systems, cyclones may be only 50




percent effective, yet remove virtually all of the large particles.  The




 particle size range for these metals operations is normally considered to




be fine particulate.  This would include particles down to 0.1 microns.




As can be seen from Figure 38.2, cyclones have little effect on particles




in this size range.







38.1  Cyclone Inspection




      The successful operation of a cyclone depends on its physical con-




dition.  Power requirements, pressure drop, temperature, and moisture have






                                   -344-

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                ZONE OF INLET
                INTERFERENCE
                 TOP VIEW
                         INNER
                         VORTEX
                         GAS
                         INLET
                 SIDE VIEW
                          OUTER
                          VORTEX
                            INNER
                            VORTEX
   OUTER
   VORTEX
GAS OUTLET
  INNER
  CYLINDER
  (TUBULAR
  GUARD)
                                           CORE
                                       \-DUSTOUTLET
        FIGURE 38,1  CONVENTIONAL REVERSE-FLOW CYCLONE
                                       M> a 70* F       	
                                       RESISTANCE 30 IN WG
                                       LOAD 4 6 GRAMS PER CU FT.,
                                       SP GR 21
                                     1O    Z9

                              PARTICLE DIAMETER. MICRONS
                                                 JS   40
FIGURE 38,2   TYPICAL FRACTIONAL EFFICIENCY  CURVE  OF A CYCLONE
                              -345-

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little effect on the operating performance of a cyclone.  The major prob-




lem attributed to cyclone deficiency is normal wear and abrasion.  Par-




ticles can be abrasive and actually wear through the shell of a cyclone.




The enforcement official  should observe the cyclone in its entirety for




rust and leaks in the duct work and cyclone shell.




     It is unlikely that cyclones will have air pollution monitoring




instrumentation associated with them.  At best, a manometer may indicate




the pressure drop across the unit.  If the manometer is available the




enforcement official should record this pressure drop for future com-




parisons.  A lower pressure drop noticed from visit to visit may indi-




cate that the cyclone performance is deteriorating.  For cyclones which




have outlets to the atmosphere, the enforcement official should note the




plume opacity.  Finally, the enforcement official should ask what schedule




is used to remove the collected particulate from the cyclone hopper.
                                  -346-

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            PART VII.  FIELD ENFORCEMENT EQUIPMENT








     The enforcement official is  expected to be  able to  perform  some




direct and simple field tests and measurements.   These tests  should indi-




cate gaseous volumetric flow rates and pollutant concentrations.  Particu-




lates, sulf - J-'"y?de,  --.rlror. r.cr-•-;-:•'  .  3nd  fluorides are  of  special in-




terest.  It is anticipated that  other  pollutants may become subjects of




interest from time  to time.






     The purpose of  the enforcement official's field testing  is  to deter-




mine the need for complete source-emission testing  in accordance with




rigorous testing procedures.  The simple tests performed by the  enforcement




official have inherent limitations and provide only an estimate  of emission




rates.  Most of the information sought by the enforcement  official will be




available from plant operating records and instruments and therefore it is




believed that direct field tests for estimating  emission rates  seldom  will




be required.






     Source testing considerations must include  the adverse field conditions




under which the field tests are to be  performed.  These  include  high temper-




atures, presence of noxious gases and, possibly, poor accessibility.






     The enforcement official's field  testing equipment  inventory needs




to include:




     1.  A pitot tube, inclined manometer, and high and  low temperature




         thermometers for gaseous emission volumetric flow rate  deter-




         mination,
                                  -347-

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     2.  A stack particulate sampling assembly that Is to include a probe,



         a particulate filter,  a flow meter,  and a pump,



     3.  A kit of direct-reading colorimetric indicators  primarily for



         the concentration determination of sulfur dioxide,  carbon mon-



         oxide and hydrogen fluoride.





     Gaseous emission volumetric flow rates can be obtained  by the direct



measurement of the average flow rate by pitot tube.  The  product of the



average gas velocity and the cross-sectional area of the  stack at the



place of measurement gives the gas flow rate.





     The pitot tube is a simple probe that is inserted in the stack.  It



permits the direct reading of the velocity head of the flowing gas stream



at the tip of the pitot tube on an inclined manometer (Figure VII-1).





     A simple mathematical relationship correlates velocity head to gas



velocity.  This relationship is defined for gases of density equal to air



at one atmosphere by:
          V_,7 = 2.90    "V Ah T
           d V
where:    Vav = gas velocity, fps



         Ah = velocity head, in. 1^0



          T = gas temperature, °R (°F + 460)





     A correction factor (normally 0.8) must be introduced into the equa-



tion for a type-S pitot tube because it slightly overstates the velocity,



whereas the standard type pitot tube requires no correction.  The average



stack gas velocity is determined by measuring the velocity in the stack



at several places and then obtaining the arithmetical average velocity.
                                     -348-

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r
                                                  §


                                                  o
                                                  I—I
                                                  o.
IX)

I—

I—
CD


Q_


i—I
 I
                           -349-

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     Weight concentration determination of particulate matter in the gas-




eous effluent requires the withdrawal of a known volume of gaseous efflu-




ent from the stack and determining the quantity of particulates in the




effluent sample taken by removing the particulates by filtration and weigh-




ing the collected particulates.  The net weight gain of the filter is the




weight of the particulate strained from the effluent sample taken.  The




particulate weight concentration of the effluent is obtained by dividing




the weight of the particulates collected by the volume of gas sampled,




corrected to standard temperature and pressure.  The usual unit of weight




concentration is grains per standard cubic foot (gr/scf).






     The desired goal is to obtain a representative average effluent par-




ticulate concentration.  In order to achieve this aim as closely as pos-




sible without conducting rigorous tests under isokinetic conditions, the




sample size should be at least 10 to 15 cf collected at an approximate




rate of 1 scfm.






     The sampling train is used for particulate concentration determina-




tion.  It consists of a probe, housing the sampling nozzle and particulate




filter, a flow meter and a pump.  Figure VII-2 shows a Joy Manufacturing Co.




filter holding assembly,, including the probe.  It is desired that the meter




and air mover connected to the probe be lightweight, durable, and compact.




For example, an air moving unit, the RAC Midget Air Sampler, manufactured




by the Research Appliance Company, shown in Figure VII-3, is well suited




for this purpose.






     After determining the particulate loading  (weight concentration) and




the average velocity, it is possible to determine the mass emission rate




in terms of Ibs/hr or tons/day.  Temperature pressure, cross-sectional




                                   -350-

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FIGURE VII-2  FILTER HOLDER ASSEMBLY AND PROBE
      FIGURE VI1-3  MIDGET AIR SAMPLER
                     -351-

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area, and the proportion by volume of water vapor in the gas are also



required.  The temperature, pressure, and cross-sectional area are easily



obtained by simple methodology.  The proportion by volume of water vapor



(Bwo) is more difficult to obtain.  Hence, in some cases such as for a



dry gas or where accuracy is not of great importance, the term BWQ can be



taken as zero, thus simplifying the equation.





     Mass emission rate equation:



              Q = 60 (1 - Bwo) Vav A







where:



     Q    = Volumetric flow rate, scfm



     BWO  = Proportion by volume of water vapor in the gas stream



     Vav  = Velocity Average, fps



     A    = Cross-sectional area of stack at test point, sq ft



     Tstd = StaTldard temperature, 530°R



     Tav  = Average temperature of stack gases, °R



     Pav  = Average pressure of stack gases, in. Hg



     pstd = Standard pressure, 29.92 in. Hg



     All values should be measured at the test port.
     Q(scfm)  x particulate loading  (gr/scf) x 0.0086  / min./lbi

                                                       Ur/gr  J



              Mass emission rate  (Ib/hr)
                         (Ib/hr) x 0.012  /ton/hr J     =    Mass  emission
                                         I -. "-- .-. ~— I                   • ^   .
     Mass emission rate                  	

                                        lib/dayj         rate (ton/day)





     Effluent gaseous pollutant concentrations, such as carbon monoxide,



sulfur dioxide and hydrogen fluoride, can be conveniently estimated by
                                   -352-

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direct reading colorimetric indicators.  The most common indicators are




the solid chemical-in-glass indicator tubes.  The underlying principle




of these direct reading indicators is a selective chemical reaction be-




tween the chemical reagent in the tube and the pollutant of interest




(different tubes for different pollutants) that produces a color change.




The resulting color change can be directly correlated to the concentra-




tion of pollutant causing the color change by comparing either the color




shade to standardized color-concentration correlation charts or the length




of the colored tube to a calibration curve.  The concentration is read




in parts per million (ppm).  The use of detecting tubes is extremely




simple.  The tubes are placed, after breaking off the sealed ends, in




holders provided by the manufacturer which are fitted with a calibrated




squeeze bulb or piston pump.  The recommended volume of gaseous sample




is then drawn through the tube at a low rate.  For a few gases, a variable




volume of sample is drawn through the tube until the first visible dis-




coloration is noted.  When sampling hot gases, cooling the sample is




essential because of distortions introduced at high temperatures into




calibration and gas volumes.






     Indicator-tube gas analysis is very rapid, convenient, and inexpen-




sive.  The best accuracy that can be expected from indicator tubes is on




the order of plus or minus 20 percent.






     Various detector tubes are available to measure SC^, CO, I^S, HF,




NC>2, 0.,, etc.  Although the detector tubes are not accurate, they are




suitable for making an estimate of the gases by an inspector.






     Opacity is an index of particulate emission and it is assumed that




the enforcement official will be a certified smoke reader.





                                  -353-

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         PART VIII.  FIELD ENFORCEMENT PROCEDURE








     The type of  air pollution, regulation  that has been adopted for




these primary metallurgical operations  include codes which set a maxi-




mum allowable particulate emission rate based on process weight rate,




codes which restrict total sulfur  emission as a function of sulfur (in




ore) feed rate, and codes which regulate the mass emission rate of




fluorides.   Other types of air pollution regulations also apply to these




primary metallurgical operations.   Almost  all agencies will have visible




emission regulations which are applicable  to these processes.  A few




state agencies also have a concentration type regulation for these




industries independent of process  weight rate.






     From the types of air pollution codes that have been developed for




these industries, it might be expected  that the only measurement for




determining compliance with the codes would be source sampling.  The




source sampling results could provide engineers with the exact emission




levels of any pollutant and any operation; however, source testing is




quite expensive,  completion time is lengthy, and involves prior




scheduling before testing.  Any of these three criteria can become a




deterrent for local air pollution  control  agencies in their enforcement




of air pollution codes.  The field enforcement procedures  that have been




developed for each of the metallurgical operations in this manual take




these factors into consideration and attempt  to  minimize  the  amount  of




source testing needed for determining whether or not a source is in




compliance with the existing codes.  In order to meet the  objectives of




the Clean Air Act of 1970, many sources need to be controlled all of the






                                 -355-

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time, not only when the air pollution official arrives on plant for a




visit.  The procedures that have heen developed in each of these




chapters will allow the enforcement official to make periodic checks at




selected sources, and from the process operating parameters and air




pollution control variables, assess whether or not a source is in com-




pliance.  It has provided guidelines for the enforcement official to




determine whether or not the process is operating correctly and has




identified what variations in operating circumstances affect air pollu-




tion emissions.






     In order to develop a viable field enforcement procedure, a control




official must first establish baseline conditions for each of the opera-




tions in his jurisdiction.  The baseline conditions must include the




stack sampling data 'which relates the process operating conditions




during the stack test to air pollution control equipment parameters




(eg., spark rate, pressure drop, flow rate, etc.).  An enforcement




official who makes periodic visits to certain plants must know what




relationship exists between the source test results and the operating




circumstances at the time of the test.  If the enforcement official




returns to the plant at a later date and finds some deviation in the




operating variables  (i.e., a higher production rate or lower pressure




drop on scrubber), he can expect some increase or decrease in atmos-




pheric emissions.  For example, if a pressure drop across the venturi




scrubber of 60 in. wg provided an atmospheric emission rate of 2 Ibs/hr




from a process feed rate of 500 tons/hr, a subsequent pressure drop of




35 in. wg would  likely result in a several-fold increase  in particulate




emissions to the atmosphere.  Some operating variables are not
                                   -356-

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important at all as far as the air pollution control official is con-




cerned.  In these chapters it has been noted which variables affect and




which variables do not affect air pollution emissions.






     The enforcement official can use the worksheets for establishing




the baseline conditions.  A special worksheet should be identified as




the baseline condition.  On subsequent visits to the plant, the enforce-




ment official will take along the worksheets for a particular metal




operation of his concern and fill out the worksheet as he conducts his




tour of a plant.  The enforcement official should then compare the




operating variables of his most recent visit with the baseline condi-




tions and identify any changes which have occurred which might affect




air pollution emissions.  It should be pointed out that published emis-




sion factors were based on industry-wide surveys and cannot be applied




to one specific source.  At best, the emission factors indicate the magni-




tude of selected emission levels for the metallurgical operations.






     For establishing baseline conditions of emission levels or any




metallurgical operation, an air pollution control agency must have




certain general information relative to the plant.  This will include




the name of the plant operator and specifically the personnel to be




contacted when an inspection is required.  The general information would




include these data:  plant address, phone number, and visiting procedures




including visitor's passes and security clearances.  Many control agencies




will have an air pollution permit system.  As part of the permit system,




enforcement officials have requested plant layout and blueprints for all




operations which emit pollutants into the atmosphere.  The blueprints and




design specifications for the machinery and air pollution control devices
                                   -357-

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are important to the enforcement official in assessing design operating




conditions.  If process flow sheets are available,  this background data will




also be helpful and should be incorporated in the field enforcement file.




Information on the process equipment or machinery should include a general




description of the unit, design specifications, meter readings,  capacity and




the operating time.  The description of the process should identify whether




this is a batch or continuous operation.






     The information on air pollution abatement equipment would  include




a general description of the device, the design specification, meter




readings, and collection efficiency.  Design parameters such as  the gas




flow rate, temperature, pressure drop, water flow rate, and spark rate




are critical factors that should be identified and kept on record.






     At this stage of air pollution control in the United States, plant




officials will have made air pollution emissions tests on nearly every




one of their processes and/or stacks.   Some of the testing informa-




tion will have already been submitted to the agency in applying  for an




air pollution permit.  The stack sampling data is of strategic importance




to the enforcement official and inspector who will routinely visit these




plants.  Plant operating data are routinely collected with stack tests.




Ask for them.  Parameters like pressure drop, spark rate, inlet  tempera-




ture, water flow rate, and opacity will help the enforcement official in




his routine inspection.  Many plants will use stack opacity meters as a




means of monitoring air pollution control device performance.  Enforce-




ment officials will be able to use the same opacity meters and continuous




records for assessing the operability and emission levels.  If stack




tests are made on  those operations which have opacity meters, and if
                                   -358-

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parallel readings were taken, the enforcement official will have




some idea of emission load when he visits the plant.






     Each time an enforcement official visits a plant, he will fill out




the Inspector's Worksheet.  That information will be kept as a con-




tinuous record on emissions and operating parameters for given certain




operations of a plant.  Also included in the field data file would be




the records of complaints that have been received relative to a specific




source.  These complaints might precipitate plant visits.  If the




plant visits are successful and there are no complaints, then perhaps




a frequency of once-per-year is adequate.  If the plant is frequently




in violation and complaints exist, more frequent inspections would be




necessary.






     The U. S. Environmental Protection Agency has developed a computer-




ized system entitled, "Enforcement Management System Users Guide, APPD




1237."  The bulk of the information included in the field enforcement




file may be applied to this computerized system for an up-to-dqte and




speedy method to retrieve data on selected sources.






     Personnel requirements for air pollution control agencies will




vary depending upon the type of sources in its jurisdiction.  To inspect




primary metals installations and maintain records of plant activities




would require an individual with an engineering background.  Many of




the calculations that have been included in this manual are relatively




simple and could be completed by an individual with several years of




college engineering.  Direct working experience in any of the metals




operations would be a tremendous asset for carrying out the objectives




of an enforcement program.
                                -359-

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                                   TECHNICAL REPORT DATA
                            (Please read Instructions on the reverse before completing)
1. REPORT NO.
 EPA-450/3-73-002
                                                           3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
 Field Surveillance and Enforcement Guide  for
 Primary Metallurgical Industries
             5. REPORT DATE
               December 1973
             6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
                                                           8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
 Engineering-Science,  Inc.
 7903 Westpark Drive
 McLean, Virginia  22101
             10. PROGRAM ELEMENT NO.
               2A5137
             11. CONTRACT/GRANT NO.
                                                             68-02-0627
12. SPONSORING AGENCY NAME A.ND ADDRESS
 Environmental  Protection Agency
 Office of Air  and Water Programs
 Office of Air  Quality Planning and  Standards
 Research Triangle Park, N.C.  27711
             13. TYPE OF REPORT AND PERIOD COVERED
               Final
             14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT

      This manual covers a step-wise  enforcement procedure intended for use by
 state and local air pollution control  agencies.  This manual  focuses on the
 primary metallurgical industry and includes a process description,  a discussion
 of emission sources, typical control devices, stack gas and process monitoring
 instrumentation, and inspectors worksheets for operations in  the iron and steel,
 aluminum, copper,  lead, and zinc  industries.  All major operations in each of
 those industries were analyzed including an enforcement procedure for the storage
 and handling of raw materials.  Upset  conditions and abnormal operating circumstances
 were examined in relation to their role  in air pollution.

      All major pollutants from these five industrial categories  were examined.
 Generally the pollutant of most concern  was particulate matter.   Sulfur oxides
 and fluorides are unique to specific metals operations and were  discussed
 accordingly.  The manual includes sections on the inspection  of  pertinent air
 pollution control devices.
                               KEY WORDS AND DOCUMENT ANALYSIS
                  DESCRIPTORS
                                              b.IDENTIFIERS/OPEN ENDED TERMS  C.  COS AT I Field/Group
                                                                          13B
18. DISTRIBUTION STATEMENT
  Unlimited
19. SECURITY CLASS (ThisReport)
     N/A
                                                                         21. NO. OF PAGES
                                                                          380
                                              20. SECURITY CLASS (Thispage)
                                                                        22. PRICE
                                                  ML.
EPA Form 2220-1 (9-73)
                                         -361-

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                                                         INSTRUCTIONS

    1.   REPORT NUMBER
        Insert the EPA report number as it appears on the cover of the publication.

    2.   LEAVE BLANK

    3.   RECIPIENTS ACCESSION NUMBER
        Reserved for use by each report recipient.

    4.   TITLE AND SUBTITLE
        Title should indicate clearly and briefly the subject coverage of the report, and be displayed prominently.  Set subtitle, if used, in smaller
        type or otherwise subordinate it to main title. When a report is prepared in more than one volume, repeat the primary title, add volume
        number and include subtitle for the specific title.

    5.   REPORT DATE
        Each report shall carry a date indicating at least month and year. Indicate the basis on which it was selected (e.g., date of issue, date of
        approval, date of preparation, etc.),

    6.   PERFORMING ORGANIZATION CODE
        Leave blank.

    7.   AUTHOR(S)
        Give name(s) in conventional order (John R. Doe, J. Robert Doe, etc.).  List author's affiliation if it differs from the performing organi-
        zation.

    8.   PERFORMING ORGANIZATION REPORT  NUMBER
        Insert if performing organization wishes to assign this number.

    9.   PERFORMING ORGANIZATION NAME AND ADDRESS
        Give name, street, city, state, and ZIP code. List no more than two levels of an organizational hirearchy.

    10.  PROGRAM ELEMENT NUMBER
        Use the program element number under which the report was prepared. Subordinate numbers may be included in parentheses.

    11.  CONTRACT/GRANT NUMBER
        Insert contract or grant number under which  report was prepared.

    12.  SPONSORING AGENCY NAME AND ADDRESS
        Include ZIP code.

    13.  TYPE OF  REPORT AND PERIOD COVERED
        Indicate interim final, etc., and if applicable, dates covered.

    14.  SPONSORING AGENCY CODE
        Leave blank.

    15.  SUPPLEMENTARY NOTES
        Enter information not included elsewhere but useful, such as: Prepared in cooperation with, Translation of, Presented at conference of,
        To be published in, Supersedes, Supplements, etc.

    16.  ABSTRACT
        Include a brief (200 words or less) factual summary of the most significant information contained in the report. If the report contains a
        significant bibliography or literature survey, mention it here.

    17.  KEY WORDS AND DOCUMENT ANALYSIS
        (a) DESCRIPTORS - Select from the Thesaurus of Engineering and Scientific Terms the proper  authorized terms that identify the major
        concept of the research and are sufficiently specific and precise to be used as index entries for cataloging.

        (b) IDENTIFIERS AND OPEN-ENDED TERMS - Use identifiers for project names, code names, equipment designators, etc.  Use open-
        ended terms written in descriptor form for those subjects  for which no descriptor exists.

        (c) COSATI FIELD GROUP - Field and group assignments are to be taken from the  1965 COSATI Subject Category List. Since the ma-
        jority of documents are multidisciplmary in nature, the Primary Field/Group assignment(s) will be  specific discipline, area of human
        endeavor, or type of physical object. The application(s) will be cross-referenced with secondary Field/Group assignments that will follow
        the primary posting(s).

    18.  DISTRIBUTION STATEMENT
        Denote releasability to the public or limitation  for reasons other than security for example "Release Unlimited."  Cite any availability to
        the public, with address and price.

    19. &20. SECURITY CLASSIFICATION
        DO NOT submit classified reports to the National Technical Information service.

    21.  NUMBER OF PAGES
        Insert the  total number of pages, including this one and unnumbered pages, but exclude distribution list, if any.

    22.  PRICE
        Insert the price set by the National Technical Information Service or the Government Printing Office, if known.
EPA Form 2220-1 (9-73) (Reverse)

                                                                362

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