EMISSION FACTOR DOCUMENTATION FOR AP-42 SECTION 8.27
Feldspar Processing
1. INTRODUCTION
The document Compilation of Air Pollutant Emission Factors (AP-42) has been published by the
U.S. Environmental Protection Agency (EPA) since 1972. Supplements to AP-42 have been routinely
published to add new emission source categories and to update existing emission factors. AP-42 is
routinely updated by EPA to respond to new emission factor needs of EPA, State and local air pollution
control programs, and industry.
An emission factor relates the quantity (weight) of pollutants emitted to a unit of activity of the
source. The uses for the emission factors reported in AP-42 include:
1. Estimates of areawide emissions;
2. Estimates of emissions for a specific facility; and
3. Evaluation of emissions relative to ambient air quality.
The purpose of this report is to provide background information from test reports and other
information to support preparation of AP-42 Section 8.27, Feldspar Processing.
This background report consists of five sections. Section 1 includes the introduction to the report.
Section 2 gives a description of the feldspar processing industry. It includes a characterization of the
industry, an overview of the different process types, a description of emissions, and a description of the
technology used to control emissions resulting from feldspar processing. Section 3 is a review of emission
data collection and laboratory analysis procedures. It describes the literature search, the screening of
emission data reports, and the quality rating system for both emission data and emission factors. Section 4
details the development of pollutant emission factors for the draft AP-42 section. It includes the review of
specific data sets and the results of data analysis. Section 5 presents the AP-42 Section 8.27, Feldspar
Processing.
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2. INDUSTRY DESCRIPTION
Feldspar consists essentially of aluminum silicates combined with varying percentages of
potassium, sodium, and calcium, and it is the most abundant mineral of the igneous rocks. The two types
of feldspar are soda feldspar (7 percent or higher Na2O) and potash feldspar (8 percent or higher K2O).
Feldspar-silica mixtures can occur naturally, such as in sand deposits, or can be obtained from flotation of
mined and crushed rock. The Standard Industrial Classification (SIC) code for feldspar processing is
1459, which is designated for clay, ceramic, and refractory minerals, not elsewhere classified. The Source
Classification Code (SCC) for feldspar processing is 3-05-034.
2.1 CHARACTERIZATION OF THE INDUSTRY12
There are currently 14 feldspar processing facilities operating in the United States. In 1989, the
national production rate was 655,000 Megagrams (Mg) (720,000 tons), valued at $28 million. Table 2-1
TABLE 2-1. FELDSPAR PRODUCED IN THE UNITED STATES3
Year
1985
1986
1987
1988
1989
Hand-cobbed
Quantity
(1000
tons)
14
13
10
14
12
Value
($1000)
W
W
W
W
W
Flotation concentrate
Quantity
(1000
tons)
487
522
492
498
468
Value
($1000)
16,781
19,855
17,800
18,657
16,915
Feldspar-silica
mixtures
Quantity15
(1000
tons)
197
200
219
204
241
Value
($1000)
W
W
W
W
W
Total
Quantity
(1000
tons)
700
735
720
715
720
Value
($1000)
22,800
26,100
26,100
26,400
28,000
W = Withheld to avoid disclosing company proprietary data; included in "Total."
""Reference 2. Includes potash feldspar (8 percent K2O or higher).
bFeldspar content.
°Data may not add to totals shown because of independent rounding.
presents the annual quantity and value of feldspar produced in the United States from 1985 to
1989.
Feldspar and feldspar-silica sand are mined in seven States, led by North Carolina and followed in
descending order by Connecticut, California (estimated), Georgia, Oklahoma, Idaho, and South Dakota.
North Carolina produced 67 percent of the domestic total production for 1989. Twelve companies operate
14 beneficiating plants and 1 grinding plant, 3 of which produce potash feldspar, the remainder of which
produce soda, mixed feldspar, or feldspathic sand mixtures. North Carolina has six plants, California has
three plants, and Connecticut, Georgia, Idaho, Oklahoma, and South Dakota each have one plant.
Table 2-2 shows the producers of feldspar and feldspathic materials in 1989.
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TABLE 2-2. PRODUCERS OF FELDSPAR AND FELDSPATHIC
MATERIALS IN 19892
Company
APAC Arkansas, Inc.
Calspar Div. of Steelhead Resources
Inc.
CISCO
Cyprus Foote Mineral Co.
The Feldspar Corp.
The Feldspar Corp.
The Feldspar Corp.
The Feldspar Corp.
Indusmin, Inc.
KMG Minerals, Inc.
Lithium Corp. of America
Pacer Corp.
Spartan Minerals Corp.
Unimin Corp.
Unimin Corp.
U.S. Silica Co.
Plant location
Muskogee, OK
Santa Fe Springs, CA
Corona, CA
Kings Mountain, NC
Middletown, CT
Monticello, GA
Spruce Pine, NC
Montpelier, VA
Spruce Pine, NC
Kings Mountain, NC
Bessemer City, NC
Custer, SD
Pacolet, SC
Emmett, ID
Spruce Pine, NC
Oceanside, CA
Product
Feldspar-silica mixture
Soda feldspar
Feldspar-silica mixture
Feldspar-silica mixture
Soda feldspar
Potash feldspar
Soda feldspar
Aplite
Soda feldspar
Potash feldspar
Feldspar-silica mixture
Potash feldspar
Feldspar-silica mixture
Feldspar-silica mixture
Soda feldspar
Feldspar-silica mixture
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Approximately 54 percent of feldspar sold or used in the United States is used for glassmaking,
including container glass and glass fiber, and 45 percent is used in pottery and porcelain enamels. The raw
materials most often substituted for feldspar in a number of end uses are aplite and nepheline syenite.
Aplite, which contains lime-soda feldspar (plagioclase), is mined in Virginia and is used primarily for
glassmaking. Nepheline syenite is a coarse crystalline rock resembling granite but consisting essentially of
feldspathoid minerals (sodium-potassium feldspars and nepheline) with little or no free quartz. All of the
nepheline syenite used in the United States is imported from Ontario, Canada. Talc, pyrophyllite, electric-
furnace slag, and Cornwall stone may also be substituted for feldspar in the glass and ceramic industries.
2.2 PROCESS DESCRIPTION12
Conventional open-pit mining methods including removal of overburden, drilling and blasting,
loading, and transport by trucks are used to mine ores containing feldspar. A froth flotation process is used
for most feldspar ore beneficiation. Figure 2-1 shows a process flow diagram of the flotation process. The
ore is crushed by primary and secondary crushers and ground by jaw crushers, cone crushers, and rod mills
until it is reduced to less than 841 (jm (20 mesh). Then the ore passes to a three-stage, acid-circuit
flotation process.
An amine collector that floats off and removes mica is used in the first flotation step. Also,
sulfiiric acid, pine oil, and fuel oil are added. After the feed is dewatered in a classifier or cyclone to
remove reagents, sulfiiric acid is added to lower the pH. Petroleum sulfonate (mahogany soap) is used to
remove iron-bearing minerals. To finish the flotation process, the discharge from the second flotation step
is dewatered again, and a cationic amine is used for collection as the feldspar is floated away from quartz
in an environment of hydrofluoric acid (pH of 2.5 to 3.0).
If feldspathic sand is the raw material, no size reduction may be required. Also, if little or no mica
is present, the first flotation step may be bypassed. Sometimes the final flotation stage is omitted, leaving a
feldspar-silica mixture (often referred to as sandspar), which is usually used in glassmaking.
From the completed flotation process, the feldspar float concentrate is dewatered to 5 to 9 percent
moisture. A rotary dryer is then used to reduce the moisture content to 1 percent or less. Rotary dryers are
the most common dryer type used, although fluid bed dryers are also used. Typical rotary feldspar dryers
are fired with No. 2 oil or natural gas, operate at about 230°C (450°F), and have a retention time of 10 to
15 minutes. Magnetic separation is used as a backup process to remove any iron minerals present.
Following the drying process, dry grinding is sometimes performed to reduce the feldspar to less than 74
(jm (200 mesh) for use in ceramics, paints, and tiles. Drying and grinding are often performed
simultaneously by passing the dewatered cake through a rotating gas-fired cylinder lined with ceramic
blocks and charged with ceramic grinding balls. Material processed in this manner must then be screened
for size or air classified to ensure proper particle size.
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AMINE
HF
*
CONDITIONER
i
CRUSHING, GRINDING
1
VIBRATING SCREEN
HYDROCLASSIFIER
*
CONDITIONER
i
FLOTATION CELLS
*
*
CONDITIONER
*
FLOTATION CELLS
FLOTATION CELLS
*
DRYER
SCC: 3-05-034-02
GLASS PLANTS
MAGNETIC SEPARATION
PEBBLE MILLS
OVERFLOWSLIME
TO WASTE
AMINE, H SOy
PINE OIL, FUEL OIL
- OVERFLOW (MICA)
- OVERFLOW (GARNET)
DRYER
soo. 3_o5_o34-02
I
GLASS PLANTS
Figure 2-1. Feldspar floatation process.1
5
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2.3 EMISSIONS13
The primary pollutant of concern that is emitted from feldspar processing is participate matter
(PM). Participate matter is emitted by several feldspar processing operations, including crushing, grinding,
screening, drying, and materials handling and transfer operations.
2.4 CONTROL TECHNOLOGY
Emissions from dryers typically are controlled by the combination of a cyclone or a multiclone and
a scrubber system. Particulate matter emissions from crushing and grinding generally are controlled by
fabric filters.
REFERENCES FOR CHAPTER 2
1. Calciners and Dryers in Mineral Industries-Background Information for Proposed Standards. EPA-
450/3-85-025a, U.S. Environmental Protection Agency, Research Triangle Park, NC, October 1985.
2. Feldspar, Nepheline Syenite, and Aplite: U.S. Minerals Yearbook 1989. pp. 389-396.
3. Air Pollution Control Techniques for Non-Metallic Minerals Industry. EPA-450/3-82-014. U.S.
Environmental Protection Agency, Research Triangle Park, NC, August 1982.
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3. GENERAL DATA REVIEW AND ANALYSIS
3.1 LITERATURE SEARCH AND SCREENING
Data for this investigation were obtained from a number of sources within the Office of Air Quality
Planning and Standards (OAQPS) and from outside organizations. The docket for the development of new
source performance standards (NSPS) for dryers in the mineral industries was reviewed for information on
the industry, processes, and emissions. The Crosswalk/Air Toxic Emission Factor Data Base Management
System (XATEF) and VOC/PM Speciation Data Base Management System (SPECIATE) data bases were
searched by Source Classification Code (SCC) for identification of the potential pollutants emitted and
emission factors for those pollutants. A general search of the Air CHIEF CD-ROM was also conducted to
supplement the information from these two data bases.
Information on the industry, including number of plants, plant location, and annual production
capacities, was obtained from the Minerals Yearbook and Calciners and Dryers in Mineral Industries.
A number of sources of information were investigated specifically for emission test reports and data.
A search of the Test Method Storage and Retrieval (TSAR) data base was conducted to identify test
reports for sources within the feldspar processing industry. Copies of these test reports were obtained from
the files of the Emission Measurement Branch (EMB). The EPA library was searched for additional test
reports. Using this information and information obtained on plant location from the Minerals Yearbook
and Calciners and Dryers in Mineral Industries. State and Regional offices were contacted about the
availability of test reports. However, the information obtained from these offices was limited. Publications
lists from the Office of Research and Development (ORD) and Control Technology Center (CTC) were
also searched for reports on emissions from the feldspar processing industry.
Because of the limited amount of information available on emissions from feldspar processing, the
following criteria were used in assessing the usefulness of the data:
1. Emissions data should be from a primary reference. However, secondary references were used if
the document included emission data by run, rather than data averaged for the entire test. In such cases, the
data were downrated to account for the fact that a secondary reference was used.
2. The referenced report should contain more than one test run. When only one valid test run was
conducted, the data were downrated to account for this fact.
3. The report must contain sufficient data to evaluate the testing procedures and source operating
conditions.
A final set of reference materials was compiled after a thorough review of the pertinent reports,
documents, and information (according to these criteria).
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3.2 EMISSION DATA QUALITY RATING SYSTEM
As part of the analysis of the emission data, the quantity and quality of the information contained in
the final set of reference documents were evaluated. The following data were excluded from consideration:
1. Test series averages reported in units that cannot be converted to the selected reporting units;
2. Test series representing incompatible test methods (i.e., comparison of EPA Method 5 front half
with EPA Method 5 front and back half);
3. Test series of controlled emissions for which the control device is not specified;
4. Test series in which the source process is not clearly identified and described; and
5. Test series in which it is not clear whether the emissions were measured before or after the control
device.
Test data sets that were not excluded were assigned a quality rating. The rating system used was that
specified by the Emission Inventory Branch (EIB) for preparing AP-42 sections. The data were rated as
follows:
A~Multiple tests that were performed on the same source using sound methodology and reported in
enough detail for adequate validation. These tests do not necessarily conform to the methodology specified
in EPA reference test methods, although these methods were used as a guide for the methodology actually
used.
B~Tests that were performed by a generally sound methodology but lack enough detail for adequate
validation.
C~Tests that were based on an untested or new methodology or that lacked a significant amount of
background data.
D~Tests that were based on a generally unacceptable method but may provide an order-of-magnitude
value for the source.
The following criteria were used to evaluate source test reports for sound methodology and adequate
detail:
1. Source operation. The manner in which the source was operated is well documented in the report.
The source was operating within typical parameters during the test.
2. Sampling procedures. The sampling procedures conformed to a generally acceptable methodology.
If actual procedures deviated from accepted methods, the deviations are well documented. When this
occurred, an evaluation was made of the extent to which such alternative procedures could influence the
test results.
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3. Sampling and process data. Adequate sampling and process data are documented in the report, and
any variations in the sampling and process operation are noted. If a large spread between test results
cannot be explained by information contained in the test report, the data are suspect and are given a lower
rating.
4. Analysis and calculations. The test reports contain original raw data sheets. The nomenclature
and equations used were compared to those (if any) specified by EPA to establish equivalency. The depth
of review of the calculations was dictated by the reviewer's confidence in the ability and conscientiousness
of the tester, which in turn was based on factors such as consistency of results and completeness of other
areas of the test report.
3.3 EMISSION FACTOR QUALITY RATING SYSTEM
The quality of the emission factors developed from analysis of the test data was rated using the
following general criteria:
A-Excellent: Developed only from A-rated test data taken from many randomly chosen facilities in
the industry population. The source category is specific enough so that variability within the source
category population may be minimized.
B-Above average: Developed only from A-rated test data from a reasonable number of facilities.
Although no specific bias is evident, it is not clear if the facilities tested represent a random sample of the
industries. The source category is specific enough so that variability within the source category population
may be minimized.
C—Average: Developed only from A- and B-rated test data from a reasonable number of facilities.
Although no specific bias is evident, it is not clear if the facilities tested represent a random sample of the
industry. In addition, the source category is specific enough so that variability within the source category
population may be minimized.
D-Below average: The emission factor was developed only from A- and B-rated test data from a
small number of facilities, and there is reason to suspect that these facilities do not represent a random
sample of the industry. There also may be evidence of variability within the source category population.
Limitations on the use of the emission factor are noted in the emission factor table.
E—Poor: The emission factor was developed from C- and D-rated test data, and there is reason to
suspect that the facilities tested do not represent a random sample of the industry. There also may be
evidence of variability within the source category population. Limitations on the use of these factors are
always noted.
The use of these criteria is somewhat subjective and depends to an extent upon the individual reviewer.
Details of the rating of each candidate emission factor are provided in Chapter 4 of this report.
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REFERENCES FOR CHAPTER 3
1. Technical Procedures for Developing AP-42 Emission Factors and Preparing AP-42 Sections (Draft).
Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research
Triangle Park, NC, March 6, 1992.
10
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4. AP-42 SECTION DEVELOPMENT
4.1 DEVELOPMENT OF SECTION NARRATIVE
This draft AP-42 section is a new section addressing feldspar processing. The draft section is based
on information gathered from the references cited and includes a description of the industry, a process flow
diagram, and emission factors for drying in the feldspar processing industry.
4.2 POLLUTANT EMISSION FACTOR DEVELOPMENT
A total of six test reports were documented and reviewed in the process of developing the section on
feldspar processing. All six tests took place at facilities in Spruce Pine, North Carolina. The tests reported
in References 1 through 4 were used to determine compliance with the North Carolina Emission Control
Standard, 15 NCAC 2D .0509, "Particulates from Mica and Feldspar Processing Plants." The test
reported in Reference 5 was performed to determine PM emissions. The test reported in Reference 6 was
performed to establish NSPS for the nonmetallic minerals industry. Reference 4 was not used in
calculating emission factors because of problems with equipment failures and high sampling velocities that
resulted in data of inadequate quality for AP-42 emission factors. Reference 5 was not used because
process data were insufficient to calculate emission factors. Reference 6 was not used because no
production rates or process information was provided.
4.2.1 Review of Specific Data Sets
4.2.1.1 Reference 1. This test measured PM emissions from the scrubber stack that served the drying
process. After the flotation process, a rotary dryer, fueled with 50 gallons per hour of No. 2 fuel oil, was
used to reduce the moisture content of the feldspar. Exhaust gases from the dryer passed through a
multiclone, a scrubber (type and pressure drop not specified), and a fan and out the stack to the
atmosphere. Method 5 was used to measure filterable PM emissions at 20 sampling points throughout the
stack. Sample point locations and velocity measurements were made by EPA Methods 1 and 2, and flue
gas composition was determined by Fyrite on Run 1 and by integrated bag samples on Runs 2 and 3 with
an Orsat analyzer. The Fyrite measurement of the CO2 concentration was less than half of the Orsat
measurements. Fyrite is not considered a valid method for CO2 measurements, as data from this report
show.
A rating of B was assigned to the test data for filterable PM. The methodology appeared to be sound
and no problems were reported, but the report lacked adequate detail to warrant a higher rating. A rating
of B was assigned to Runs 2 and 3 of the carbon dioxide (CO2) test data. The test methodology is sound
but lacks adequate detail for documentation. Data from Run 1 were not used to develop emission factors
because it was conducted using unsound test methodology.
4.2.1.2 Reference 2. This test measured PM emissions from the drying process. Crushed feldspar
that had been separated from the ore by froth flotation was dewatered and routed to a direct-fired rotary
dryer. The dust-laden exhaust gases from the dryer were then cleaned in a scrubber (type and pressure
drop not specified) and routed through a demister to an induced draft (ID) fan, from which they exited the
stack. Method 5 was used to test filterable PM emission rates. Sampling port locations and number of test
ports to be used were determined according to Method 1. Instead of using Method 3 to determine flue gas
composition, a dry molecular weight value of 29.0 was used for flue gas composition because of the large
11
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quantities of air relative to combustion products. No other data regarding flue gas composition were
provided.
A rating of B was assigned to this test data. Although a sound methodology was used, the report lacks
adequate detail for documentation.
4.2.1.3 Reference 3. This test measured PM emissions from a feldspar dryer and a quartz dryer.
Only the emissions data for the feldspar dryer were used to calculate emission factors for the feldspar
processing industry, however. For each dryer, ductwork carried the dust-laden gases from the outlets to a
cyclone, then through a scrubber (type and pressure drop not specified) to an ID fan. Sampling was
performed at the outlet from the fan. A back-up system was attached to this system by ductwork between
the cyclone and the scrubber but was isolated from the primary system by blind flanges in the ductwork.
Method 5 was used to test filterable PM emission rates. Sampling port locations and number of test
ports to be used were determined according to Method 1. The composition of the flue gas was determined
by the following method: CO2 measurements were taken periodically during the run with a Fyrite
instrument. Percent O2 was determined from a nomograph (not included in the data sheets). Carbon
monoxide was assumed to be zero, and the percent N2 was determined by subtracting the percentages of
CO2 and O2 from 100 percent.
A rating of B was assigned to the test data for filterable PM emissions. Although a sound
methodology was used, the report lacks adequate detail for documentation. Carbon dioxide emission data
were not used to develop emission factors because Fyrite is not valid for measuring CO2 concentrations.
4.2.2 Review of XATEF and SPECIATE Data Base Emission Factors
The XATEF and SPECIATE data bases do not contain emission factors for feldspar processing.
4.2.3 Results of Data Analysis
Emission factors were developed for filterable PM and for CO2 emissions from feldspar dryers. For
filterable PM, emission factors were developed for emissions controlled by scrubbers and by scrubbers in
combination with cyclones/multiclones (mechanical collectors). The emission factors for cyclones and
multiclones were combined because the emission factor for the multiclone and scrubber combination is
higher than the cyclone and scrubber factor. Presenting these factors separately would be misleading
because a multiclone should be more efficient than a cyclone. Also, no details on the control systems were
supplied in the test reports. For CO2, the emission factors were developed for dryers with multiclones and
scrubbers. Scrubbers may achieve incidental control of CO2 emissions, and multiclones do not control CO2
emissions.
Because the emission factors for filterable PM and CO2 emissions controlled by scrubbers are based
on only one test, the emission factors are rated D. The emission factors for filterable PM emissions
controlled by a combination of mechanical collectors and scrubbers are based on two tests. Because of the
relatively small number of domestic feldspar plants (12), tests from 2 facilities may be representative of the
industry. However, because the emission factors from the two tests differ by an order of magnitude, this
average emission factor is rated D.
12
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Table 4-1 summarizes the emission data and emission factors developed from References 1, 2, and 3.
Table 4-2 summarizes the emission factors to be included in the draft AP-42 section for feldspar
processing.
To estimate emission factors for products of combustion, refer to AP-42 Chapter 1, External
Combustion Sources.
TABLE 4-1. SUMMARY OF TEST DATA FOR FELDSPAR DRYERS
Type of
control3
Scrubber and demister
Multiclone and
scrubber
Cyclone and scrubber
Multiclone and
scrubber°'d
Pollutant
Filterable
PM
Filterable
PM
Filterable
PM
CO2
No. of
test runs
3
3
3
2
Data
rating
B
B
B
B
Emission factorb
Range
kg/Mg (Ib/ton)
0.54-0.64
(1.1-1.3)
0.063-0.093
(0.13-0.19)
0.0048-0.0073
(0.0095-0.015)
47-55
(93-110)
Average
kg/Mg (Ib/ton)
0.60
(1.2)
0.075
(0.15)
0.0061
(0.012)
51
(102)
Ref
No.
2
1
3
1
3Control devices are listed in the order of their location in the flue gas stream.
bEmission factor in units of pollutant weight per weight of feldspar dried.
°Scrubbers may achieve incidental control of CO2 emissions. Multiclones do not control CO2
emissions.
dFuel usage is the preferred method for estimating CO2 emissions.
13
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TABLE 4-2. SUMMARY OF EMISSION FACTORS FOR FELDSPAR PROCESSING
Process
Dryer
Type of
control3
Scrubber and demister
Scrubber and mechanical
collector
Multiclone and scrubberc>d
Pollutant
Filterable
PM
Filterable
PM
CO2
No. of
tests
1
2
1
Average
emission factor,
kg/Mg (lb/ton)b
0.60
(1.2)
0.041
(0.081)
51
(102)
Emission
factor
rating
D
D
D
Ref
No.
2
1,3
1
3Control devices are listed in the order of their location in the flue gas stream.
bEmission factor in units of pollutant weight per weight of feldspar dried.
°Scrubbers may achieve incidental control of CO2 emissions. Multiclones do not control CO2 emissions.
dFuel usage is the preferred method for estimating CO2 emissions.
REFERENCES FOR SECTION 4
1. Source Sampling Report for The Feldspar Corporation: Spruce Pine. NC. Environmental Testing
Inc., Charlotte, NC, May 1979.
2. Particulate Emission Test Report for a Scrubber Stack at International Minerals Corporation: Spruce
Pine. NC. North Carolina Department of Natural Resources & Community Development, Division of
Environmental Management, September 1981.
3. Particulate Emission Test Report for 2 Scrubber Stacks at Lawson United Feldspar & Mineral
Company: Spruce Pine. NC. North Carolina Department of Natural Resources & Community
Development, Division of Environmental Management, October 1978.
4. Particulate Emission Test Report for a Scrubber Stack at The Feldspar Corporation: Spruce Pine.
NC. North Carolina Department of Natural Resources & Community Development, Division of
Environmental Management, July 1978.
5. Source Sampling Report for Indusmin Incorporated: Spruce Pine. NC. Pace Laboratories. Inc..
Charlotte, NC, January 1990.
6. Air Pollution Emission Test. International Minerals and Chemical Company: Spruce Pine. NC. EMB
Report 76-NMM-l, U. S. Environmental Protection Agency, Research Triangle Park, NC, September
1976.
14
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5. AP-42 SECTION 8.27
8.27 FELDSPAR PROCESSING
8.27.1 General1
Feldspar consists essentially of aluminum silicates combined with varying percentages of potassium,
sodium, and calcium, and it is the most abundant mineral of the igneous rocks. The two types of feldspar
are soda feldspar (7 percent or higher Na2O) and potash feldspar (8 percent or higher K2O). Feldspar-
silica mixtures can occur naturally, such as in sand deposits, or can be obtained from flotation of mined
and crushed rock.
8.27.2 Process Description 1>2
Conventional open-pit mining methods including removal of overburden, drilling and blasting, loading,
and transport by trucks are used to mine ores containing feldspar. A froth flotation process is used for
most feldspar ore beneficiation. Figure 8.27-1 shows a process flow diagram of the flotation process. The
ore is crushed by primary and secondary crushers and ground by jaw crushers, cone crushers, and rod mills
until it is reduced to less than 841 (jm (20 mesh). Then the ore passes to a three-stage, acid-circuit
flotation process.
An amine collector that floats off and removes mica is used in the first flotation step. Also, sulfuric
acid, pine oil, and fuel oil are added. After the feed is dewatered in a classifier or cyclone to remove
reagents, sulfuric acid is added to lower the pH. Petroleum sulfonate (mahogany soap) is used to remove
iron-bearing minerals. To finish the flotation process, the discharge from the second flotation step is
dewatered again, and a cationic amine is used for collection as the feldspar is floated away from quartz in
an environment of hydrofluoric acid (pH of 2.5 to 3.0).
If feldspathic sand is the raw material, no size reduction may be required. Also, if little or no mica is
present, the first flotation step may be bypassed. Sometimes the final flotation stage is omitted, leaving a
feldspar-silica mixture (often referred to as sandspar), which is usually used in glassmaking.
From the completed flotation process, the feldspar float concentrate is dewatered to 5 to 9 percent
moisture. A rotary dryer is then used to reduce the moisture content to 1 percent or less. Rotary dryers are
the most common dryer type used, although fluid bed dryers are also used. Typical rotary feldspar dryers
are fired with No. 2 oil or natural gas, operate at about 230°C (450°F), and have a retention time of 10 to
15 minutes. Magnetic separation is used as a backup process to remove any iron minerals present.
Following the drying process, dry grinding is sometimes performed to reduce the feldspar to less than 74
(jm (200 mesh) for use in ceramics, paints, and tiles. Drying and grinding are often performed
simultaneously by passing the dewatered cake through a rotating gas-fired cylinder lined with ceramic
blocks and charged with ceramic grinding balls. Material processed in this manner must then be screened
for size or air classified to ensure proper particle size.
3/93 Feldspar Processing 8.27-1
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CRUSHING, GRINDING
i
VIBRATING SCREEN
*
HYDROCLASSIFIER
*
CONDITIONER
i
FLOTATION CELLS
|
CYCLONE
1
CONDITIONER
*
FLOTATION CELLS
^^ ^^\
>20MESH
^, OVERFLOWSLIME
TO WASTE
^ AMINE, H SO2, 4
"^ PINE OIL, FUEL OIL
^- OVERFLOW (MICA)
•^ H SO 4PETROLEUM SULFONATE
^- OVERFLOW(GARNET)
--^
DRYER
CYCLONE SCC: 3-05-034-02
t
I
AMINE fc. CONDITIONER GLASS PLANTS
HF ^
*
FLOTATION CELLS
I
DRYER
SCC: 3-05-034-02
^^ ^\^
GLASS PLANTS
MAGNETIC SEPARATION
1
PEBBLE MILLS
T
8.27-2
Figure 8.27-1. Feldspar flotation process.1
EMISSION FACTORS
3/93
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8.27.2 Emissions and Controls
The primary pollutant of concern that is emitted from feldspar processing is particulate matter (PM).
Participate matter is emitted by several feldspar processing operations, including crushing, grinding,
screening, drying, and materials handling and transfer operations.
Emissions from dryers typically are controlled by a combination of a cyclone or a multiclone and a
scrubber system. Particulate matter emissions from crushing and grinding generally are controlled by
fabric filters.
Table 8.27-1 presents controlled emission factors for filterable PM from the drying process. Table
8.27-2 presents emission factors for CO2 from the drying process. The controls used in feldspar processing
achieve only incidental control of CO2.
TABLE 8.27-1 (METRIC UNITS). EMISSION FACTORS FOR
FILTERABLE PARTICULATE MATTER
All Emission Factors in kg/Mg Feldspar Dried
Ratings (A-E) Follow Each Factor
Process (SCC)
Dryer with scrubber and demister3 (3-05-034-02)
Dryer with mechanical collector and scrubber^0 (3-05-034-02)
Emission factor
0.60
0.041
D
D
TABLE 8.27-1 (ENGLISH UNITS). EMISSION FACTORS FOR
FILTERABLE PARTICULATE MATTER
All Emission Factors in Ib/Ton Feldspar Dried
Ratings (A-E) Follow Each Factor
Process (SCC)
Dryer with scrubber3 (3-05-034-02)
Dryer with mechanical collector and scrubber^0 (3-05-034-02)
Emission factor
1.2
0.081
D
D
3 Reference 4.
b Reference 3.
0 Reference 5.
3/93
Feldspar Processing
8.27-3
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TABLE 8.27-2 (METRIC UNITS).
EMISSION FACTOR FOR CARBON DIOXIDE3
Emission Factor in kg/Mg Feldspar Dried
Rating (A-E) Follows the Factor
Process (SCC)
Dryer with multiclone and scrubber3 (3-05-034-02)
Emission factor
51 | D
TABLE 8.27-2 (ENGLISH UNITS). EMISSION FACTOR
FOR CARBON DIOXIDE3
Emission Factor in Ib/Ton Feldspar Dried
Rating (A-E) Follows the Factor
Process (SCC)
Dryer with multiclone and scrubber3 (3-05-034-02)
Emission factor
102
D
3Scrubbers may achieve incidental control of CO2 emissions. Multiclones do not control
CO2 emissions.
REFERENCES FOR SECTION 8.27
1. Calciners and Dryers in Mineral Industries-Background Information for Proposed Standards. EPA-
450/3-85-025a, U.S. Environmental Protection Agency, Research Triangle Park, NC, October 1985.
2. US Minerals Yearbook 1989: Feldspar, Nepheline syenite, and Aplite: US Minerals Yearbook 1989,
pp. 389-396.
3. Source Sampling Report for The Feldspar Corporation: Spruce Pine. NC. Environmental Testing Inc..
Charlotte, NC, May 1979.
4. Particulate Emission Test Report for a Scrubber Stack at International Minerals Corporation: Spruce
Pine. NC. North Carolina Department of Natural Resources & Community Development, Division of
Environmental Management, September 1981.
5. Particulate Emission Test Report for Two Scrubber Stacks at Lawson United Feldspar & Mineral
Company: Spruce Pine. NC. North Carolina Department of Natural Resources & Community
Development, Division of Environmental Management, October 1978.
8.27-4 EMISSION FACTORS 3/93
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