NATIONAL INVENTORY
OF SOURCES
AND EMISSIONS:
BORON - 1969
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Water Programs
Office of Air Quality Planning and Standard*
Research Triangle Park, North Carolina 27711
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APTD-1159
NATIONAL INVENTORY
OF
SOURCES AND EMISSIONS:
BORON - 1969
by
W. E. Davis § Associates
9726 Sagamore Road
Leawood, Kansas
Contract No. 68-02-0100
EPA Project Officer: C. V. Spangler
Prepared for
ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Water Programs
Office of Air Quality Planning and Standards
Research Triangle Park, N.C. 27711
June 1972
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The AFID (Air Pollution Technical Data) series of reports is issued by
the Office of Air Quality Planning and Standards, Office of Air and
Water Programs, Environmental Protection Agency, to report technical
data of interest to a limited number of readers. Copies of APTD reports
are available free of charge to Federal employees, current contractors
and grantees, and non-profit organizations as supplies permit from
the Air Pollution Technical Information Center, Environmental Protection
Agency, Research Triangle Park, North Carolina 27711 or may be obtained,
for a nominal cost, from the National Technical Information Service,
5285 Port Royal Road, Springfield, Virginia 22151.
This report was furnished to the Environmental Protection Agency
in fulfillment of Contract No. 68-02-0100. The contents of this report
are reproduced herein as received from the contractor. The opinions,
findings? and conclusions expressed are those of the author and not
necessarily those of the Environmental Protection Agency. The report
contains some information such as estimates of emission factors and
emission inventories which by no means are representative of a high
degree of accuracy. References to this report should acknowledge the
fact that these values are estimates only.
Publication No. APTD-1159
11
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PREFACE
This report was prepared by W. E. Davis & Associates pur-
suant to Contract No. 68-02-0100 with the Environmental
Protection Agency, Office of Air Programs.
The inventory of atmospheric emissions has been prepared
to provide reliable information regarding the nature, mag-
nitude, and extent of the emissions of boron in the United
States for the year 1969.
Background information concerning the basic characteristics
of the boron industry has been assembled and included. Pro-
cess descriptions are given, but they are brief, and are
limited to the areas that are closely related to existing or
potential atmospheric losses of the pollutant.
Due to the limitation of time and funds allotted for the study,
the plan was to personally contact all of the mining and pro-
I
ducing companies and about twenty percent of those in each
major emission source group to obtain the required informa-
tion. It was knowni that published data concerning the atmos-
pheric emissions of boron were virtually nonexistent, and
contacts with industry ascertained that atmospheric emissions
ill
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were not a matter of record. The boron emissions and emis-
sion factors that are presented are based on the summation
of data obtained from production and reprocessing companies.
Additional information was acquired during field trips to in-
spect the air pollution control equipment and observe process-
ing operations.
IV
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ACKNOWLEDGEMENTS
This was an industry oriented study and the authors express
their appreciation to the many companies and individuals in
the boron industry for their contributions.
We wish to express our gratitude for the assistance of the
various societies and associations, and to the many branches
of the Federal and State Governments.
Our express thanks to Mr. C. V. Spangler, Project Officer,
EPA, Office of Air Programs, Research Triangle Park,
N. C., for his helpful guidance.
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CONTENTS
SUMMARY 1
Emissions by Source 2
Emissions by Regions 3
Emission Factors 4
MINERAL SOURCES OF BORON 6
MATERIAL- FLOW THROUGH THE ECONOMY . . 7
Chart 9
USES AND EMISSIONS OF BORON
Mining 10
Processing 12
End Product Uses of Boron 20
Glass 20
Ceramic Coatings 23
Agricultural Chemicals 27
Soaps and Detergents 29
Miscellaneous 31
SOURCES OF INADVERTENT BORON EMISSIONS
Coal 36
Oil 40
Sewage and Sludge . . i 41
UPDATING OF EMISSION ESTIMATES 42
Vii
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TABLES
Table I Emissions by Source 2
Table II Emissions by Regions 3
Table III Emission Factors 5
Table IV Typical Applications - Air Pollution
Control Equipment 18
Table V Average Minor Element Contents of
Coals from Various Regions of the
United States 38
Table VI Average Boron Content in Ash of Coal . . 39
FIGURES
Figure I Material Flow Through the Economy . . .
Vlll
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SUMMARY
The flow of boron in the United States has been traced and
charted for the year 1969 (Figure I). The consumption was
85j 864 tons, while domestic production totaled 171, 361
tons. Imports and exports were 803 and 86, 084 tons, re-
spectively.
Emissions to the atmosphere during the year were 11, 003
tons (Table I). Nearly 22 percent of the emissions resulted
from the processing of boron compounds, more than 34 per-
cent, from the manufacture and use of various end products,
and about 43 percent from the combustion of coal.
Emission estimates for processing and the manufacture of
end use products are based on unpublished data obtained
from industrial sources.
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TABLE I
Source Category
Mining
Processing
End Product Uses
Other Emission Sources
EMISSIONS BY SOURCE
1969
Source Group
Glass
Ceramic Coatings
Agricultural Chemicals
Soaps and Detergents
Miscellaneous
Coal
Sewage and Sludge
Emissions - Tons
Emissions
100 0.9
2,400 21.8
3,783 34.5
'1,000
470
ls 800
13
500
4,720 42.8
4,700
20
N
i
TOTAL
11, 003
100.0
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TABLE II
EMISSIONS BY REGIONS
Region No. 1
Region No. 2
Region No. 3
Region No. 4
TOTAL,
Tons
3,350
3,690
2, 530
1,433
11,003
Region No. 1
Arizona
California
Colorado
Idaho
Montana
Nevada
New Mexico
Oregon
Utah
Washington
Wyoming
Illinoi s
Jndia.^a
Iowa
Kansas
Alabama
Arkansas
Delaware
Florida
Georgia
Kentucky
Connecticut
Ma ine
Massachusetts
Region No. 2
Michigan
Minnesota
Missouri
Nebraska.
Region No. 3
Louisiana
Ma ryland
Mississippi
North Carolina
Oklahoma
South Carolina
Region No. 4
New Hampshire
New Jersey
New York
North Dakota
Ohio
South Dakota
Wisconsin
Tenn.es see
Texas
Virginia
West Virginia
District of
Columbia
Pennsylvania
Rhode Island
Vermont
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EMISSION FACTORS
The emission factors presented herein are the best currently
available. They were determined through a combination of
methods consisting of: (1) direct observation of emission
data and other related plant processing and engineering data;
(2) estimates based on information obtained from literature,
plant operators, and others knowledgeable in the field; (3)
calculations based on experience and personal knowledge of
metallurgical processing operations; and, (4) specific analy-
tical results where available.
The basic data used to calculate the emission factors are
contained in the files of the Contractor.
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TABLE III
EMISSION FACTORS
Mining
Processing
End Product Uses of Boron
Glass Manufacture
Ceramic Coatings
Other Emission Sources
Coal
Sewage and Sludge
1 Ib/ton boron mined
28 Ib/ton boron processed
70 Ib/ton boron processed
80 Ib/ton boron processed
18 lb/1, 000 tons of coal
burned
55 lb/1, 000 tons of sewage
and sludge burned
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MINERAL. SOURCES OF BORON
Boron (B) is a black or brownish powder in the amorphorus
form and a black, hard, brittle solid in the crystalline form.
It melts at about 2, 300 C and has an atomic weight of 10. 82.
In nature boron occurs only in combined forms, usually as
an alkaline earth borate or as boric acid. It is widely dis-
tributed in the earth's crust, but there are only a few large
deposits that are commercially valuable. About half of the
indicated world reserves and in the sodium borate deposits
and brine lakes of California. Other important reserves are
located in Turkey and the U. S. S. R. Minor domestic deposits
occur in Oregon and Nevada.
Most of the domestic boron production comes from a mine
in Kern County, California, that is owned and operated by
the U. S. Borax and Chemical Corporation. The remain-
ing production is a by-product of mineral recovery from
Searles Lake brines.
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MATERIAL FLOW THROUGH THE ECONOMY
The domestic sources and uses of boron during 1969 are
shown in Figure I. The production was 171, 361 tons ^B
content), approximately half of which was consumed in the
United States while the other half was exported. During the
year imports were 803 tons and industry stocks were in-
creased about 216 tons.
The most important application of boron during 1969 was in
glassmaking. Nearly 34 percent of the domestic consump-
tion was used in producing glass and glassware, principally
for strengthening the product. About 16 percent was used in
soaps and detergents, and nearly 14 percent in ceramic coat-
ings applied to household and industrial appliances and pot-
tery. More than 13 percent was an ingredient in agricultural
chemicals, added to fertilizers to supply boron as an essen-
tial plant nutrient, or used in formulations for extermination
of weeds.
Other applications requiring smaller quantities included the
use of boron in fluxes, in compounds used as catalysts, in
adhesive additives for latex paints, as fire retardants in
plastics, in motor fuel additives to suppress preignition firing,
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as an absorber material in nuclear reactors, as a deoxidizing
agent in nonferrous metallurgical reactions, in compounds
for alloying steels, and numerous miscellaneous uses.
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SOURCES
171.361
BORON
MATERIAL FLOW THROUGH THE ECONOMY - 1969
(Short Tons - B Content)
USES
28.800
DOMESTIC PRODUCTION
803
IMPORTS
86.084
EXPORTS
216
85.864
INDUSTRY STOCKS
GLASS
11.700
CERAMIC COATINGS
11.700
AGRICULTURAL CHEMICAiS
13.400
SOAPS AND DETERGENTS
20.264
MISCELLANEOUS
i
sO
i
CONSUMER
Data Source - U. S. Bureau of Mines
Figure I
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USES AND EMISSIONS OF BORON
MINING
About 70 percent of the world's supply of boron is recovered
from bedded deposits and lake brines in the Mojave Desert
in southeastern California. In Kern and Inyo Counties, sod-
ium borates are mined by the major producer, United States
Borax and Chemical Corporation, employing open-pit methods.
In San Bernardino County, the borates are extracted from
Searles Lake brines by 2 companies, Kerr-McGee Chemical
Corporation and Stauffer Chemical Company.
At the large open-pit mine near Boron, California, ore is
mined using explosives and electric shovels. It is then
moved to the surface and on to the nearby concentrating and
refining plants by trucks and an automatic ore belt conveyor
system that starts in the pit at the 225 foot level.
Atmospheric emissions of boron at the mine are in the form
of sodium borate with the size ranging from, about 01.5 to 20
microns, the principal emissions occurring in connection
with blasting, loading, unloading, hauling, conveying, and
crushing. Air pollution control equipment consists oŁ ba,g
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filters for the primary and secondary crushers.
Searles Lake consists of a salt body with an area of more
than 30 square miles. About 45 percent of the volume of the
deposit consists of a saturated brine that fills spaces between
clusters of salt crystals. The surface of the lake is usually
dry, but the brine level never falls more than a few inches
below the surface.
Wells have been drilled in the lake to the desired depths and
the brine is pumped from them to the processing plants.
During mining, the boron is always in solution in the brines
and there are no detectable emissions to the atmosphere.
The Contractor's estimate of boron emissions to the atmos-
phere from sources of mining is 100 tons for the year 1969.
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PROCESSING
The borate minerals currently mined in Kern County, Cali-
fornia, are principally borax (tincal - Na2B^OylO HoO), a
sodium borate with 10 molecules of water, and kernite
(Na2B>Oy-4 I^O), a sodium borate with 4 molecules of
water. Both these minerals must be processed to remove
impurities during the production of the primary commercial
compounds sodium tetraborate decahydrate (NaoB^Oy-l
sodium tetraborate pentahydrate (Na^B^O '5 H?O), and an-
hydrous sodium tetraborate (Na2B^O_).
Since the ore in Kern County arrives at the processing plant
in a dry form, the refining starts with ore dissolving and
impurity removal, followed by recrystallization and drying.
Some of the material is crystallized and produced as deca-
hydrate, some as pentahydrate, and the remainder fused in
a furnace to the anhydrous state.
When the crushed ore is received it is mixed with a weak
borax liquor from the refinery and heated to near the boiling
point in steam-jacketed tanks. As the borax is dissolved
insoluble impurities are removed by screening, sedimenta-
tion, and filtration.
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The hot, muddy liquor then enters the first of 4 thickeners.
The underflow from the first thickener goes successively to
the second, third, and fourth, each time being washed with
a more dilute borax solution. The overflow from the first
thickener is filtered and pumped to vacuum crystallizers to
produce sodium tetraborate decahydrate or sodium tetrabo-
rate pentahydrate. Crystals are separated from the slurry
of borax pentahydrate or decahydrate in automatic centrifuges.
From the centrifuges the crystals "are dried in 3 rotary
driers and 7 Wysmont Turbo driers equipped with revolving
trays in which the borax is raked from one to the next. The
dried borax crystals are stored prior to sale or shipment to
other divisions for production of boric oxide, boric acid, an-
hydrous borax, and specialty products.
At Searles Lake the first processing steps are somewhat
different than in Kern County. When the sodium borate is
received it is already dissqlved. It is in the brine pumped
from the lake and the average concentration is about 1. 5
percent. The dissolving step is not required but there is an
excess of water that must be removed.
The principal processing steps are evaporation, crystallization,
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recrystallization, and drying. In the evaporation process,
brines are fed into evaporators where sodium salts crystal-
lize and are removed, leaving only potassium and borate com-
ponents of the brine in the liquor. The liquor is then cooled
in continuous vacuum crystallizers to crystallize potassium
chloride. During this period, the solution becomes super-
saturated with respect to borax. It is sent through crystal-
lizers, thickeners, and centrifuges. Moist borax then goes
to driers which discharge dried borax ready for any further
processing into boron chemicals.
Anhydrous sodium tetraborate may be produced from either
wet or dry sodium tetraborate decahydrate. In one process
the decahydrate is first calcined, which creates some dust-
ing. These dust-laden exhaust gases pass through a cyclone
separator and into wet scrubbers. The dust collected in the
separator is added to the calciner discharge which then goes
to the fusion furnaces. Each fusion furnace is cylindrical
in shape and has a gap of about 8 inches between the bottom
edge of the furnace firebox and the inner edge of the water-
cooled furnace bottom. The calcined borax is fed continu-
ously into this bottom area of the furnace, where it becomes
molten and can flow out the furnace tap. Anhydrous borax
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usually remains in the amorphous form when it is cooled
by running the molten borax between large water-cooled
rolls. This operation forms thin sheets which are crushed
and screened to desired particle size. Some crystalline
anhydrous borax is desired by manufacturers and it is pro-
duced by cooling the molten borax in bucket molds to form
ingots, then crushing the ingots.
Other compounds made at some of the primary refineries
include boric acid (H3BO3).and boric oxide (B2O3). Boric
acid is an important compound because it is the raw mater-
ial for making boron carbide, metal borides, boron alloys,
and ferro-boron. It also has a wide range of industrial uses.
By one method of manufacture, granulated borax or a hot
saturated solution of borax from the refining plant is
charged into a reaction vessel. Then sulfuric or hydro-
chloric acid is added to produce an acidic solution. When
the solution is cooled, bori^c acid crystals can be removed
by filtration. This crude boric acid may be further refined
by one or more recrystallizations from water. Other man-
ufacturing methods are similar to the one described as they
involve solutions which are crystallized in evaporators.
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Boric oxide, practically an anhydrous form of boric acid,
can be made by heating finely ground boric acid slowly to
about 500 F in a vacuum and maintaining the temperature
for 6 hours. Another form of boric oxide may be produced
by heating boric acid in a loosely covered container at 440
to 480 F for several days.
Boron carbide and metal borides account for about 16 per-
cent of the boron used during 1969. Because of its self-
bonding characteristic, boron carbide can be molded in graph-
ite and pressed at temperatures up to 4, 300 F into high-
density, non-porous shapes. Lower density shapes may be
prepared by cold-molding and sintering.
The most common method of producing boron carbide is
the reduction of boric oxide by carbon at temperatures be-
tween 2, 500 and 4, 200 F. The reaction can be accelerated
by using fine carbon particles, such as carbon black, and
by intimate mixing of the boric oxide and carbon. The re-
duction of boric oxide with magnesium in the presence of
carbon also yields boron carbide, but the product must be
washed free of magnesium oxide with hydrochloric acid and
then further purified by boiling in hydrofluoric and nitric
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acids. The other production methods are unprofitable for
commercial quantities and are used to produce very small
amounts of a high-grade product.
The metal borides may be made by a number of general
methods. One of the most economical and widely used is
the reduction of boric oxide and the metal oxide with a reduc-
ing agent such as aluminum, silicon, magnesium, carbon,
boron, or boron carbide. There can be a direct reduction
of metallic boron with the metal at temperatures between
2, 000 to 3, 600 F. Other methods include electrolysis of
fused-salt mixtures containing metal and boron oxides, and
deposition from, the vapor phase.
While this study was in progress, information was obtained
from the 3 companies that produce commercial borax and
other boron compounds. Meetings were held with 2 and data
were received by correspondence from all 3. The informa-
tion included details concerning the use of air pollution con-
trol equipment, as shown in Table IV, and data regarding
particulate emissions. During the processing of borax the
boron emissions that occur are sodium borate in various de-
grees of hydration, primarily from one to 3 mols hydrate.
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TABLE IV
TYPICAL APPLICATIONS
AIR POLLUTION CONTROL EQUIPMENT
Procedure
Borax refining
Anhydrous borax
Borax calcining and melting
Boric acid drying
Borax drying
Borax screening
Borax dehydration
Borax packing
Dehydrated borax packing
Dehydrated borax grinding
Boric oxide production
Boron trichloride production
Boron tribromide production
Control Equipment
Cyclone, scrubber, and baghouse
Cyclone, scrubber, and baghouse
Cyclone, baghouse, and electro-
static precipitator
Cyclone and scrubber
Baghouse
Baghouse
Cyclone and electrostatic
precipitator
Cyclone and baghouse
Baghouse
Baghouse
Scrubber and baghouse
Scrubber
Scrubber
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Other emissions that occur are boric oxide, boric acid, and
sodium pentaborate as those compounds are being produced.
Particulate size has been reported to range from less than
one to as much as 45 microns.
Boron emissions have been reported to vary considerably
from plant to plant, ranging from 0, 2 to 40 pounds per ton
of product. During 1969 emissions to the atmosphere re-
sulting from the production of commercial borates and boron
compounds totaled 2,400 tons.
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END PRODUCT USES OF BORON
Glass
Borates, including borax, boric acid, and boric oxide, are
important as raw materials for the glass industry. They
make glass more brilliant and more resistant to breakage
from impact or sudden temperature change. The inclusion
of borates in glass batches has been found to facilitate pro-
duction by lowering the liquidus temperature, increasing the
rate of melting and refining, and increasing the furnace pro-
duction. Borates are also used in fiber glass products such
as glass cloth, boat hulls, insulating materials, automobile
bodies, containers, building panels, aircraft sections, and
numerous molded articles. Currently, the glassmaking in-
dustry is the largest single user of boron in the United States.
Raw materials for glass manufacture are shipped in packages
or in bulk and unloaded by manual labor, vibrator-gravity,
drag shovels, or vacuum systems. Methods of material stor-
age vary widely, but in large installations the raw materials
for the glass mix are often stored in gravity feed storage
hoppers and are fed directly to the weighing and mixing room.
Minor ingredients are usually stored in their original
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containers. Gullet (waste glass or rejected ware to be re-
melted) must be transported to an area where it may be seg-
regated by type.
Glass batch mixing systems range from full automation to
hand operations. Most mixers are of the rotating-barrel
type which tumble the batch upon itself in a revolving drum.
During a batch mixing process the materials are dry or
nearly dry, which results in a loss by dusting. The glass
furnace charging may be done manually or automatically,
and continuously or intermittently.
Basically, the manufacture of glass is a high-temperature
conversion of raw materials into a homogenous melt for the
fabrication of useful articles.
There are 3 types of melting units used in the glass industry.
Clay "pots", which may be open or covered, are used where
quantities or special compositions do not justify the use of a
i
tank. This process involves a relatively high proportion of
manual handling, The day tank handles batches up to sev-
eral tons. Finally, most glass .is melted in large, direct-
fired, regenerative type furnaces. Raw materials are charged
at one end of the furnace and molten glass is pulled from the
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other end. Glass temperatures are as high as 2, 700 F in
the furnace, but usually 2, 220 F at the discharge.
There are 2 principal sources of particulate matter in the
furnace exhaust gases: raw materials entrained in combus-
tion gases, and materials from the melt. Particulates ex-
pelled from the furnace are the result of many physical and
chemical reactions that occur during melting. The reactions
are so complex that prediction of losses cannot be based on
temperature and vapor pressure data alone. One significant
factor affecting the quantity of particulates is the production
rate. As the production rate of the furnace is increased, the
particulates also increase in quantity.
Following melting there are several ways to accomplish the
forming of glass. Glass may be blown, pressed, cast, rolled,
or drawn. Glass fibers may be made continuously by mechan-
ical drawing, and a glass to be pulverized is dribbled or
ladled into water to produce "dry gage" glass.
Final glass operations are principally finishing and secondary
forming. Finishing operations may include any one or com-
bination of the following: flame cut-off, sawing, score and
break, score-thermal crack off, drilling, grinding, polishing,
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engraving, acid etching, glazing, and sealing. Secondary
forming operations may then be used to produce difficult
shapes. Before the glass becomes a finished product, a
final treatment of tempering or staining may be required.
Many of the people in the glass industry who were contacted
during this study provided general information concerning
glassmaking, the use of boron compounds, methods of opera-
tion, and air pollution control equipment, but only one com-
pany provided specific data regarding boron emissions to the
atmosphere.
Based on emission data obtained from this one company,
boron emissions to the atmosphere during 1969 are esti-
mated at 70 pounds per ton of boron used in the manufacture
of glass. In the United States, boron emissions during the
year totaled approximately 1, 000 tons.
Ceramic Coatings
\
Porcelain enamel is a bright, colorful ceramic coating that
is applied on metal to provide both decoration and surface
protection. It is a finish commonly used on many household
and industrial products such as stoves, refrigerators,
freezers, washing machines, sinks, bath tubs, and building
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panels. The coating called enamel slip is essentially a water
suspension of clay and frit. It is applied to the metal and
fired in a furnace at high temperature to produce a hard glass-
like finish. Ceramic glaze is a similar ceramic coating ap-
plied to glass or pottery.
The frit is a shattered glass which is the chief component of
porcelain enamels and ceramic glazes. It is manufactured
on customer order for specific end uses and the composition
of the production mix varies widely. In most mixes borates
are added in varying amounts to make the coating brighter,
more resistant to cracking, and easier to apply.
From the standpoint of air pollution, the principal emissions
of boron from the production and use of ceramic coatings are
those that occur during the manufacture of the frit. The most
significant dust and fume emissions are due to the smelting
operation. In the fritting process, inorganic chemicals and
minerals are removed from storage in weighed increments
according to formula, .dry mixed in a rotary blender, and
charged into smelting furnaces. The minerals and chemi-
cals fuse and react to form a glass. When the glass in the
furnace reaches a predetermined physical and chemical
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state, it is removed and shattered either by passing it through
a bath of cold water or by passing it through water-cooled
rolls. The final production steps include either drying or
cooling, and then bagging. There are dust emissions due to
handling the raw materials as they are received, stored, mea-
sured, and mixed prior to charging the smelter. The ingred-
ients in the charge are mostly refractories, including quartz,
feldspar, and clay, plus mineral fluxes such as borax, soda
ash, fluorspa.r, litharge, and cryolite. These fluxes react
with the refractories to form the molten glass.
The atmospheric emissions of boron during frit smelting
consist primarily of oxides in vapor form and in particulates.
The magnitude of emissions varies considerably depending
upon the amount of boron in tb.e charge, the combination of
ingredients, and the type of smelter. As the boron content
of the mix is increa.sed, the boron emissions also increase.
However, as larger proportions of fluorspar and other simi-
lar ingredients are added, they react with boron reducing
the emissions.
Rotary and crucible smelter emissions are somewhat more
difficult to control than those from a smelter of the hearth
type. The rotary unit is cylindrical, can be rotated in
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either direction, and can be tilted vertically. It is open at
one end for the introduction of fuel and combustion air. It is
open at the opposite end for the discharge of flue gases and
for charging raw materials. Smelters of this type require
a detached canopy hood properly suspended above the unit so
that exhaust gases will be trapped and prevented from escap-
ing into the manufacturing plant.
The crucible smelter is a refractory or fireclay container
mounted within a circular steel shell that is insulated and
supported by trunnions in a manner which allows it to be
tilted for the pouring operation. A canopy hood is required
if the discharge gases are to be collected and vented through
air pollution control equipment.
The hearth smelter does not require a hood. It is a station-
ary unit with an exhaust gas outlet that may be directly con-
nected to a dust collecting system.
Several people in the ceramic industry were contacted during
this study and information was obtained regarding the fritting
process, the use of boron compounds and other ingredients,
the types of smelters, and air pollution control equipment.
Two industrial sources provided specific data regarding
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boron emissions to the atmosphere from smelting furnaces.
Based on the emission data obtained from these 2 companies,
boron emissions to the atmosphere during 1969 are estimated
at an average of 80 pounds per ton of boron used in ceramic
coatings. In the United States boron emissions during the
year totaled about 470 tons.
Agricultural Chemicals
Boron in the soil is essential to healthy plant growth, and
most soils under cultivation for a long period of time have
become deficient in this element. A lack of boron in the soil
may cause corkiness in apples, cracked stems in celery,
deformed heads of cauliflower, low yields, stunting, and
discoloration in many crops and trees. In very small quan-
tities it is an ingredient of complete, balanced, artificial
fertilizers: however, care must be used in adding boron,
for when it is used in large amounts it acts as a nonselect-
ive herbicide.
I
Certain borates are widely used on railroad rights-of-way,
airport runways, factory sites, lumber and oil storage
yards, and other places where plant growth is a nuisance
and a fire hazard. A new development is to use boron for
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growth control rather .than growth elimination. By stopping
growth without killing the vegetation, freeway borders, cen-
ter strips, and other similar areas may be maintained at the
desired growth level without pruning or mowing, thereby
saving the cost and the danger of performing these operations
in heavy traffic.
Borates are used in solutions as a wash for certain citrus
fruits to.inhibit the formation of molds. They are also used
as insecticides in the control of fly larvae in the poultry in-
dustry, and of dog and swine hookworm larvae.
Emissions to the atmosphere due to the use of boron in ag-
ricultural chemicals occur principally when the products
are applied as sprays or dusts. The various factors affect-
ing the application have been discussed in the literature at
great length: the droplet size, the spray drift, the fluid
properties, the meteorological factors, the air movement,
the nozzle types, the evaporation, and numerous other sub-
jects. A wealth of general information has been published,
but there is virtually none that is specific regarding the a-
mount of spray or dust that is not effective. The pesticide
industry merely replies that there are too many factors
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involved to estimate overall emissions with any degree of
accuracy; however, one manufacturer did indicate that less
than 2 percent of the recommended dosage is required for
effective application. Obviously., it is expected that a large
part of the spray or dust will not contact the vegetation or
the insects. Most of it will evaporate, drift, or fall on the
ground.
In order to estimate emissions, the problem was discussed
with people knowledgeable in the field of pesticide applica-
tion. In most instances they were reluctant to estimate at-
mospheric emissions; however, a few did express an opin-
ion. As a result, the Contractor's estimate of boron emis-
sions to the atmosphere due to the use of agricultural chem-
icals during 1969 is 1, 800 tons including losses during
formulation, spraying, and dusting.
Soaps and Detergents
Borax adds to the cleaning power of .soaps and detergents.
It controls alkalinity, freshens and deodorizes, aids in ie-
moval of certain stains, and is mildly antibacterial. It is
used in detergents, scouring cleansers, liquid cleaners,
shaving cream, tooth paste, and talcum powder.
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Sodium borates are one of the components used in the form-
ulation and manufacture of some household synthetic deter-
gents. These spray-dried detergents are made by mixing
formula quantities of the various components as a slurry.
Some ingredients are wet and others are dry as they are fed
to the process. The slurry from the mixer is pumped at
high pressure to the spray drying tower where it is sprayed
into a stream of drying air. As the slurry falls through the
air, most of the moisture is removed and detergent granules
are formed. Effluent air from the drying operation is dis-
charged through wet scrubbers and/or bag collectors.
Scouring cleansers and talcum powder are manufactured by
dry mixing formula quantities of the required ingredients
prior to packaging. Manufacturers advise there are no air
emissions from these processes and dusting is not a prob-
lem. Air pollution control equipment is not used in connec-
tion with these processes.
Liquid cleaners are formulated by agitating measured quan-
tities of wet and dry components together in a. tank. Batches
are transferred to holding tanks and then delivered to the
filling operation. Atmospheric emissions, if any, are
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negligible and air pollution control equipment is not required.
Both shaving cream and tooth paste are products that are
produced in a similar manner and they may contain boron.
However, their production is relatively unimportant from the
standpoint of air pollution. Most of the processing is done
with the ingredients in a wet or damp condition.
While this study was in progress, emission data and related
information was obtained concerning 21 soap and detergent
manufacturing facilities. Sodium perborate, sodium tetra-
borate, and sodium borohydride are reported to be the boron
compounds in the particulate emitted to the atmosphere, and
the particle size is thought to be within a range of one to 10
microns. Based on data from 4 manufacturing plants, the
boron emissions to the atmosphere during 1969 averaged 2
pounds per ton of boron processed. Based on this emission
factor, the atmospheric emissions of boron in the United
\
States during the year totaled approximately 13 tons.
Mis cellaneous
In addition to the major applications discussed above, boron
is used for many miscellaneous purposes. It is found in
many lubricating oil additives and in certain gasoline additives
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where it is clainaed to prevent preignition, help prevent
formation of sludge in the engine, and give extra power.
It has been considered as a high energy jet and missile fuel,
but that development program has been discontinued. How-
ever, it is used as a jet fuel additive to kill bacteria and
fungus in fuel tanks and lines. It is also an ingredient in
additives for antifreeze and hydraulic brake fluids where
its purpose is to act as a corrosion inhibitor.
Other than in the transportation field applications of boron
include those in pharmaceuticals, cosmetics, photographic
chemicals, termite control, flameproofing for building
materials, fluxes, adhesives, glues, starches, sizing, wire
drawing, extra hard abrasives, leather tanning, treatment
of brain tumors, soldering, brazing, welding, anodizing
aluminum., electrolytic condensers for electronic equip-
ment, r.uclear reactors, alloy steels, wash solutions for
citrus fruits, plastics, paints, and nonferrous metallurgy.
In the steel industry boron has become an important alloy-
ing element to increase the hardenability of steels. Ferro-
boron is generally used for this purpose since it dissolves
rapidly in molten steel, providing better distribution and
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more accurate additions. Boron is usually added in ferrous
alloys in amounts up to 0. 003 percent, but higher amounts
may be used in the production of very hard cutting tools. As
little as 0. 001 percent boron accelerates the annealing time
of malleable iron castings.
In nonferrous metallurgical operations boron is used as a
deoxidizer and degasifier. It is an especially good cleans-
ing agent for refining gold and silver, and also a good grain
refiner for aluminum.
Borax, boric acid, and sodium metaborate all find varied
and special applications in the manufacture of photographic
supplies. Borates are components of photographic develop-
ing chemicals for film and paper; however, wet processes
are used during manufacture.
Boron nitride finds use in the manufacture of crucibles and
heat-resistant products. It is found in thermal insulation
I
in high-frequency induction furnaces, in electrical insulators
for high voltages, and as a coating on electrode holders in
automatic welding. It may be prepared by heating boric
oxide or boric acid with sodium cyanide, potassium cyanide,
calcium cyanide, calcium cyanamide, ammonium chloride,
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or by heating boric oxide with ammonia.
Water solutions of borax are commonly used in dyeing
leather and textiles, in cleansing hides and skins, to pre-
vent mildew in plasters, and to give a high gloss to starches.
Other preservative applications are found in the cosmetic
and pharmaceutical industries where boron compounds are
used in face creams, talcum powder, medicated gauzes,
and special medicines.
Boron carbide is useful as an abrasive and refractory ma-
terial. Because of its thermal properties many jet aircraft,
rocket, and gas turbine parts are made of this compound.
The metal borides have high thermal and chemical stability
and are suitable for cutting equipment, nuclear control de-
vices, long-lasting cathodes, and electronic devices.
Although more than 100 industrial companies were contacted
during this study regarding the reprocessing of boron and
boron compounds, very little information was available con-
cerning the magnitude of emissions resulting from the mis-
cellaneous uses of boron.
The Contractor's estimate of boron emissions to the atmosphere
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-35-
due to miscellaneous uses totaled 500 tons for the year 1969.
Information obtained from 7 companies was used as a basis
for this estimate. Even though they did not report emissions,
the information furnished concerning processing was helpful.
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-36-
SOURCES OF INADVERTENT BORON EMISSIONS
COAL
In order to estimate boron emissions due to the burning of
coal it has been necessary to determine the boron content
of the coal, the quantity of boron in the fly ash, and the a-
mount of coal fired, as well as the degree of application and
the efficiency of air pollution control equipment in service
during 1969.
Numerous samples of coal from various regions of the United
States have been analyzed and the results reported by sev-
eral investigators. The data shown in Tables V and VI are
from 2 of the published reports which show the boron concen-
tration in domestic coal averages about 59 ppm.
When firing coal, part of the ash is discharged from the furn-
ace as fly ash and part as bottom ash. The fly ash averages
about 65 percent of the total ash and is carried from the furn-
ace by the flue gas, usually through a cyclone-type dust col-
lector or an electrostatic precipitator, then discharged to
the atmosphere. It is estimated that 90 percent of the coal
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-37-
is fired in units that are equipped with some type of air pol-
lution control system, and the average efficiency of control
is 85 percent.
Calculations have been made based on:
(a) 516, 084, 000 tons of bituminous and anthracite coal
consumed in the United States during 1969 /;
(b) an average boron content of 59 ppm;
(c) fly ash 65 percent of total ash;
(d) 85 percent efficiency of control; and
(e) 90 percent application of control.
The boron emissions in the United States during 1969 calcu-
lated by this method totaled 4, 700 tons.
516, 084, 000 x 59 x 10'6 x 0. 65 [l - (0. 85 x 0. 90)] = 4, 700
1- Minerals Yearbook; Bureau of Mines; 1969.
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-38-
TABLE V
1;
AVERAGE MINOR ELEMENT CONTENTS OF COALS
FROM VARIOUS REGIONS OF THE UNITED STATES - PPM
Region
Northern Great Plains
Eastern Interior
Appalachian
Western and Southwestern
Ash Content
of Coal - %
13.42
6.16
6.11
NR*
B Content
of Coal - ppm
116
96
25
33
Average Boron Content in Coal 67
Not reported
NOTE - The above table based on Geological Survey Bulle-
tins 1117-C and 1117-D; 1966 and 1967.
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TABLE VI
AVERAGE BORON CONTENT IN ASH OF COAL
Region Frequency of B Content Ash Content
Detection - % of Ash - % of Coal - %
Eastern Province 100 0.0265 9.3
Interior Province 100 0.0731 10.5
Western States 100 0.0529 9.8
Average Boron Content of Coal
B Content
of Coal - %
0.0025
0.0077
0. 0052
0.0051
I
w
NOTE - The above table based on "Spectrochemical Analyses of Coal Ash for Trace
Elements"; Bureau of Mines RI 7281; Table 1; July, 1969.
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-40-
OIL,
In order to estimate boron emissions to the atmosphere due
to the combustion of fuel oil, it is necessary to determine
the boron content and the quantity of oil received from num-
erous foreign and domestic sources. Information was located
showing the analyses of 120 samples of domestic crude; how-
ever, the situation was different with respect to residual oils
and foreign crude. The only reliable information available
on residual oil was that regarding nickel and vanadium.
Due to the lack of reliable data, there is no estimate of emis-
sions set forth in this report other than a suggested range of
values. Based on the Contractor's studies of other metal
emissions due to the burning of fuel oil, boron emissions
should range between 2 and 40 tons for the year 1969.
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SEWAGE AND SLUDGE
A recent report concerning the burning of sewage and sludge
indicates the present burning rate in the United States is a-
bout 2, 000 tons per day _/. Based on a boron content of 30
O
ppm /, the atmospheric emissions currently are about 20
tons of boron per year.
1- Private communication from the Federal Water Pollution
Control Authority.
2- International Research Group on Refuse Disposal; Infor-
mation Bulletin No. 8; Mar., I960.
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-42-
UPDATING OF EMISSION ESTIMATES
The emissions and emission factors presented in this report
are the result of calculations based principally on informa-
tion obtained from industrial sources. They are specifically
for the year 1969, but may be updated at any time when addi-
tional information is available. Either of the 2 methods de-
scribed herein may be used for updating; however, the long-
er procedure, referred to as Method A, will yield results
that are much more reliable.
The procedures to be followed with Method A are essentially
the same as those used during the original study, which are
described briefly as follows. More than 130 inquiries were
sent to processing and reprocessing companies by mail or
delivered during personal visits to plant sites. There was
no reply from 56 companies. Another 38 companies answer-
ed but did not provide data. There were 36 companies that
furnished all or part of the data requested, and that informa-
tion was the basis for emission factors and emission esti-
mates set forth in this report.
All of the companies that produce boron were requested to
provide the essential data required for the study. Information
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-43-
was obtained from all of them. The manufacturers of end
products that provided information represented about 30
percent of the industry capacity.
Regardless of the method selected, the first step to be taken
when updating the emission estimates is to contact the United
States Bureau of Mines to obtain the latest information con-
cerning tonnages for domestic production, imports, exports,
and the domestic uses.
When using Method A, the emission factors must be revised
by contacting industry to determine the improvements in air
pollution collection equipment efficiency and other process-
ing changes affecting boron emissions. The revised emission
factors may then be used with the production quantities ob-
tained from the Bureau of Mines.
Method B is considerably shorter than Method A, and less re-
liable. The only requirement is to revise the material flow
i
chart according to the most recent Bureau of Mines data and^
apply the emission factors shown in this report. In reality
this method is only a partial updating. There is no determi-
nation regarding improvements in air pollution control, a
shift in production to more efficient plants, or any other
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-44-
c on side rations affecting emission factors. The advantage
is that the report can be updated within a few days, rather
than several months.
To update boron emissions from processing, glass produc-
tion, ceramic coatings, and agricultural uses, it is prefer-
able to use Method A. The remaining emissions shown in
this report may be updated by Method B without introducing
an appreciable error into the results.
*U.S. Government Printing office: 1973-746-770/4177
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BIBLIOGRAPHIC DATA
SHEET
1. Report No.
APTD-1159
4. Tide and Subtitle
National Inventory of Sources and Emissions: Boron - 1969
3. Recipient's Accession No.
5. Report Date
June 1972
6.
7. Author(s)
W. E. Davis
8. Performing Organization Rept.
No.
9. Performing Organization Name and Address
W. E. Davis & Associates
9726 Sagamore Road
Leawood, Kansas
10. Project/Task/Work Unit No.
11. Contract/Grant No.
68-02-0100
12. Sponsoring Organization Name and Address
ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Water Programs
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
13. Type of Report Sc Period
Covered
14.
15. Supplementary Notes
16. Abstracts
Information is provided regarding the nature, magnitude, and extent of the emissions
of boron. Background information concerning the basic characteristics of the boron
industry has been assembled and included. Process descriptions ara given, but they
are brief, and are limited to the areas that are c-losely related to existing or
potential atmospheric losses of the pollutant. The consumption of boron during 1969
was 85,864 tons, while domestic production totaled 171,361 tons. Imports and exports
were 803 and 86,084 tons, respectively. Emissions to the atmosphere during the year
were 11,003 tons. Nearly 22 percent of the emissions resulted from the processing of
boron compounds, more than 34 percent from the manufacture and use of various end
products, and about 43 percent from the combustion of coal. Emission estimates for
processing and the manufacture of end use products are based on unpublished data
obtained from industrial sources.
17. Key Words and Document Analysis. 17o. Descriptors
Air pollution Fertilizers
Inventories Spraying
Industrial wastes Glass
Coal
Combustion
Boron inorganic compounds
Processing i
Mining
Herbicides
17b. Identifiers/Open-Ended Terms
17c. COSATI Field/Group
13B
18. Availability Statement
FORM NTIS-35 (REV. 3-72)
Unlimited
19.. Security Class (This
Report)
UNCLASSIFIED
20. Security Class (This
Page
UNCLASSIFIED
21- No. of Pages
51
22. Price
USC O MM- DC 1 < 932 - P72
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