450289002
United States
Environmental Protection
Agency
Office of Air Quality
Planning And Standards
Research Triangle Park, NC 27711
August 198!?
AIR
LOCATING AND ESTIMATING
AIR EMISSIONS
FROM SOURCES OF
CHROMIUM (SUPPLEMENT)
Note: The material herein on electroplating, chromic acid anodizing and
cooling towers supersedes the material in EPA-450/4-84-007g.
MC-II
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EPA-450/2-89-002
August 1989
LOCATING AND ESTIMATING AIR EMISSIONS FROM
SOURCES OF CHROMIUM
SUPPLEMENT
By
Midwest Research Institute
Suite 350
401 Harrison Oaks Boulevard
Gary, North Carolina 27513
EPA Project Officer: Dallas W. Safriet
U. S. Environmental Protection Agency
Office of A1r and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
August 1989
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This report has been reviewed by the Office of A1r Quality Planning And
Standards, U. S. Environmental Protection Agency, and approved for
publication. Any mention of trade names or commercial products 1s not
Intended to constitute endorsement or recommendation for use.
EPA-450/2-89-002
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TABLE OF CONTENTS
Page
LIST OF FIGURES ill
LIST OF TABLES 111
SECTION 1.0 PURPOSE OF DOCUMENT 1
SECTION 2.0 OVERVIEW OF DOCUMENT CONTENTS 3
SECTION 3.0 CHROMIUM EMISSION SOURCES 5
3.1 CHROMIUM ELECTROPLATING AND CHROMIC ACID
ANODIZING OPERATIONS 5
3.1.1 Background Information 5
3.1.2 Uncontrolled Chromium Emissions 17
3.1.3 Emission Reduction Techniques 21
3,1.4 Nationwide Emission Estimates 23
3.2 COOLING TOWERS ... 26
3.2.1 Background Information 26
3.2.2 Potential Emission Reduction Techniques... 29
3.2.3 Cooling Tower Emissions 34
3.2.4 Nationwide Emissions Distribution by
Industry 38
SECTION 4.0 SOURCE TEST-PROCEDURES.. 41
4.1 CHROMIUM ELECTROPLATING 41
4.2 COOLING TOWERS 41
SECTION 5.0 REFERENCES 43
APPENDIX A. ADDITIONAL CHROMIUM ELECTROPLATING EMISSION DATA
OBTAINED AND EVALUATED DURING DEVELOPMENT OF THIS
REPORT A-1
ii
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LIST OF FIGURES
Page
Figure 1. Flow diagram for a typical chromic acid anodizing
process 11
Figure 2. Internals of crossflow and counterflow cooling towers... 30
Figure 3. Designs of various drift eliminators. 33
LIST OF TABLES
Page
TABLE 1. TYPICAL OPERATING PARAMETERS FOR HARD CHROMIUM
ELECTROPLATING 7
TABLE 2. TYPICAL OPERATING PARAMETERS FOR DECORATIVE CHROMIUM
PLATING 9
TABLE 3. CHROMIC ACID/SULFURIC ACID ETCH SOLUTION 9
TABLE 4. TYPICAL OPERATING PARAMETERS FOR CHROMIC ACID
ANODIZING 13
TABLE 5. HEXAVALENT AND TRIVALENT CHROMIUM DEPOSIT COM! OSITIONS 16
TABLE 6. UNCONTROLLED EMISSION DATA FOR TOTAL AND HEXAVALENT
CHROMIUM FROM CHROMIUM PLATING OPERATIONS 18
TABLE 7. TANK PARAMETERS AND PROCESS OPERATING PARAMETERS
MONITORED DURING CHROMIUM PLATING TESTS 20
TABLE 8. PERFORMANCE LEVELS OF INDIVIDUAL CONTROL DEVICES 24
TABLE 9. NATIONWIDE NUMBER OF OPERATIONS AND ESTIMATED HEXAVALENT
CHROMIUM EMISSIONS FROM CHROMIUM ELECTROPLATING AND
CHROMIC ACID ANODIZING OPERATIONS 25
TABLE 10. MODEL COMFORT COOLING TOWERS AND HOURLY BASELINE Cr+S
EMISSIONS 28
TABLE 11. EMISSION FACTORS FOR HEXAVALENT CHROMIUM FROM
COOLING TOWERS . 36
TABLE 12. NATIONWIDE COOLING TOWER CHROMIUM EMISSIONS SUMMARY.... 40
TABLE A-l. ADDITIONAL CHROMIUM ELECTROPLATING EMISSION DATA
OBTAINED AND EVALUATED DURING DEVELOPMENT OF THIS
REPORT A-l
111
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1.0 PURPOSE OF DOCUMENT
The U. S. Environmental Protection Agency (EPA), States, and local
air pollution control agencies are becoming Increasingly aware of the
presence of substances 1n the ambient air that may be toxic at certain
concentrations. This awareness, in turn, has led to attempts to identify
source/receptor relationships for these substances and to develop control
programs to regulate emissions. Unfortunately, very little information is
available on the ambient air concentrations of these substances or on the
sources that may be discharging them to the atmosphere.
To assist groups interested in inventorying air emissions of various
potentially toxic substances, EPA is preparing a series of documents that
compiles available information on the sources and emissions of these
substances. This document was prepared as a supplement to a previous EPA
document that addressed chromium emissions, "Locating and Estimating Air
Emissions From Sources of Chromium," EPA-450/4-84-007g. The supplement
updates technical information and presents new emission data upon which
emission factors are based for chromium emissions from cooling towers and
chromium electroplating operations. The reader should use both the
original document and this supplement to obtain the most complete
assessment of emissions from these two sources of chromium emissions. The
information in this supplement was obtained by EPA's Emission Standards
Division for use in development of National Emission Standards for a
Hazardous Air Pollutant (NESHAP) for chromium used in electroplating
operations and for regulation of chromium emissions from comfort cooling
towers under the Toxic Substances Control Act.
The reader is strongly cautioned against using the emissions
information contained in the original document or this supplement to
develop an exact assessment of emissions from any particular facility.
Because of insufficient data, no estimate can be made of the error that
could result when these factors are used to calculate emissions from any
given facility. It is possible, in some extreme cases, that orders-of-
magnltude differences could result between actual and calculated
emissions, depending on differences in source configurations, control
equipment, and operating practices. Thus, in situations where an accurate
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assessment of chromium emissions 1s necessary, source-specific information
should be obtained to confirm the existence of particular emitting
operations, the types and effectiveness of control measures, and the
Impact of operating practices. A source test and/or material balance
should be considered as the best means to determine air emissions directly
from an operation.
Possible sources of plant-specific information that would be useful
in estimating air emissions of hexavalent chromium include the National
A1r Toxics Information Clearinghouse database maintained by EPA or the
Toxics Release Inventory (TRI) data resulting from Section 313 of the
Superfund Amendments and Reauthorization Act (SARA). In the absence of
specific Information about the locations of facilities, State Departments
of Commerce, trade associations, or references such as the Thomas Register
of American Manufacturers may be sources of information.
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2.0 OVERVIEW OF DOCUMENT CONTENTS
This section outlines the information presented in the remaining
sections of this report and indicates whether the information is new or
whether It is a revision of Information presented in the original
document.
Section 3.1 presents process descriptions for five kinds of
plating/anodizing operations. New information is included for decorative
chromium electroplating of plastics, chromic acid anodizing, and trivalent
chromium plating. Additional process information is provided to
supplement the discussion of hard and decorative chromium electroplating
presented in the original document. New emission data are presented for
hard and decorative chromium electroplating operations; the results of an
engineering mass balance to obtain an emission estimate for chromic acid
anodizing are also presented. A significant change from the original
document is 1n the format of the chromium emission factors for hard and
decorative plating operations, which have changed from kilograms per hour
per square foot of tank area to milligrams per ampere-hour. Supplemental
Information has been Included on emission control techniques for' reduction
of chromic add mist from plating operations. New information 1s
presented on nationwide chromium emission estimates" for three types of
plating operations: hard plating, decorative plating, and chromic acid
anodizing.
Section 3.2 presents updated information about the distribution of
industrial process cooling towers that use chromium-based water treatment
chemicals and presents new information about comfort cooling towers. New
information also is presented on emission reduction techniques for
chromium emissions from cooling towers. New emission data are presented
for cooling towers equipped with low- and high-efficiency drift
eliminators. A significant change from the original document is in the
format of the chromium emission factor, which has changed from picograms
per joule of thermal energy input to the power plant associated with the
cooling tower to percentage of the recirculating chromium that is
emitted. New information is presented on nationwide chromium emission
estimates for industrial cooling towers in eight industries.
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Section 4.0 summarizes the procedures used for source sampling and
analysis of chromium 1n emission streams from electroplating operations
and cooling towers.
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3.0 CHROMIUM EMISSION SOURCES
3.1 CHROMIUM ELECTROPLATING AND CHROMIC ACID ANODIZING OPERATIONS
3.1.1 Background Information
Plating and anodizing operations range in size from small shops,
with one or two tanks that are operated only a few hours per week, to
large shops with several tanks that are operated 24 hours per day, 7 days
per week. Many plating and anodizing -operations are captive shops that
perform chromium electroplating or chromic acid anodizing as one operation
within or for a manufacturing facility, while others are job shops that
provide custom plating or anodizing services for many different clients.
Captive and job shops may perform hard or decorative chromium plating or
chromic add anodizing or any combination of these three operations.
The estimated number of electroplating shops nationwide is
1,540 hard chromium plating facilities and 2,800 decorative chromium
plating facilities. The estimated number of chromic acid anodizing shops
nationwide is 680. Electroplating and anodizing shops typically are
located 1n or near industrial centers 1n areas of high population
density. States with large numbers of chromium electroplaters include
California, Illinois, Massachusetts, Michigan, New York, Ohio, and
Pennsylvania.
3.1.1.1 Hard Chromium Electroplating of Metals. In hard plating, a
relatively thick layer of chromium is deposited directly on the base metal
(usually steel) to provide a surface with wear resistance, a low
coefficient of friction, hardness, and corrosion resistance, or to build
up surfaces that have been eroded by use. Hard plating is used for items
such as hydraulic cylinders and rods, industrial rolls, zinc die castings,
plastic molds, engine components, and marine hardware.
Tanks used for hard chromium electroplating usually are constructed
of steel and lined with a polyvinyl chloride sheet or plastisbl. The
anodes, which are Insoluble, are made of a lead alloy that contains either
tin or antimony. The substrate to be plated, the cathode, is suspended
from a plating rack that is connected to the cathode bar of the
rectifier. The plating rack may be loaded in the tank manually, by a
hoist, or by an automatically controlled hoist system.
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The plating tanks typically are equipped with some type of heat
exchanger. Mechanical agitators or compressed air supplied through pipes
on the tank bottom provide uniformity of bath temperature and
composition. Chromium electroplating requires constant control of the
plating bath temperature, current density, plating time, and bath
composition.
Hexavalent chromium plating baths are the most widely used baths to
deposit chromium on metal. Hexavalent chromium baths are composed of
chromic add, sulfurlc add, and water. The chromic add 1s the source of
the hexavalent chromium that reacts and deposits on the metal and that is
emitted to the atmosphere. The sulfurlc add 1n the bath catalyzes the
chromium deposition reactions. Typical operating parameters are given in
Table I.1*
The evolution of hydrogen gas from chemical reactions at the cathode
consumes 30 to 90 percent of the power supplied to the plating bath,
leaving the remaining 10 to 20 percent for the deposition reaction. When
the hydrogen gas evolves, 1t entrains chromic add and causes misting at
the surface of the plating bath.
3,1.1.2 Decorative Chromium Electroplating of Metals. In decorative
plating, the base material (e.g., brass, steel, aluminum, or plastic)
generally 1s plated with a layer of nickel followed by a relatively thin
layer of chromium to provide a bright surface with wear and tarnish
resistance. Decorative plating 1s used for Items such as automotive trim,
metal furniture, bicycles, hand tools, and plumbing fixtures. The purpose
of decorative chromium plating is to achieve a combination of the
following surface properties:
1. Blue-white color;
2. High reflectivity;
3. Tarnish resistance;
4. Corrosion resistance;
5. Wear resistance; and
6. Scratch resistance.
Decorative electroplating baths operate on the same principle as
that described for the hard chromium plating process: the metal substrate
is immersed in a plating solution, and direct current is passed from the
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TABLE 1. TYPICAL OPERATING PARAMETERS FOR HARD CHROMIUM ELECTROPLATING
Plating thickness, ym (mil) 1.3-762 (0.05-30)
Plating time, mina 20-2,160
Chromic add concentration, g/a (oz/gal )b 225-375 (30-50)
Temperature of solution, °C (°F) 49-66 (120-150)
Voltage, volts c
Current, amperes (A) d
Current density, A/m2 (A/ft2)6 1,600-6,500
(150-600)
* minutes.
- grams per liter, oz/gal « ounces per gallon.
Depends on the distance between the anodes and the Items being plated.
Dep^nds on the amount of surface area plated.
A/m = amperes per square meter (-square foot) of surface area plated.
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anode through the plating solution causing the desired metal (copper,
nickel, chromium) to deposit out of the solution onto the metal substrate
(cathode).
Decorative chromium plating requires shorter plating times and
operates at lower current densities than does hard chromium plating to
achieve the desired properties of the chromium plate. Some decorative
chromium plating operations use fluoride catalysts instead of sulfuric
add because fluoride catalysts, such as fluosillcate or fluoborate, have
been found to produce higher bath efficiencies.8 Typical operating
parameters are shown in Table 2.
3.1.1.3 Decorative Chromium Electroplating of Plastics. Most plastics
that are electroplated with chromium are formed from the polymer composed
of acrylonitrlle, butadiene, and styrene (ABS).8 The process for chromium
electroplating of ABS plastics consists of the following steps:
1. Chromic acid/sulfuric acid etch;
2. Dilute hydrochloric add dip;
3. Colloidal palladium activation;
4. Dilute hydrochloric acid dip;
5. Electroless nickel- plating or copper plating; and
6. Chromium electroplating cycle.
After each process step, the plastic 1s rinsed with water to prevent
carry-over of solution from one bath to another. The chromic acid/
sulfuric acid etch solution (see Table 3) renders the ABS surface
hydrophlHc and modifies the surface to provide adhesion for the metal
coating.9 The dilute hydrochloric acid dips are used to clean the surface
and remove palladium metal from the plating rack, which is Insulated with
a coating of polyvinyl chloride. The colloidal palladium activation
solution deposits a thin layer of metallic palladium over the plastic
surface.10 The metallic palladium induces the deposition of copper or
nickel, which will not deposit directly onto plastic. The electroless
nickel and copper plate are applied to impart electrical conductivity to
the part; otherwise, the insulating surface of the plastic could not be
electroplated with chromium. The electroless nickel plating or copper
electroplating baths develop a film on the plastic about 1.0 micrometer
(pin) (3.9xlO"s inch [1n.]) thick. The plating time for electroless nickel
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TABLE 2. TYPICAL OPERATING PARAMETERS FOR DECORATIVE CHROMIUM PLATING
Plating thickness, utn (mil) 0.003-2.5 (0.0001-0.1)
Plating time, min 0.5-5
Chromic add concentration, g/i (oz/gal) 225-375 (30-50)
Temperature of solution, °C (°F) 38-46 (100-115)
Voltage, volts a
Current, A b
Current density, A/m2 (A/ft2)c 540-2,400 (50-220)
^Depends on the distance between the anodes and the items being plated.
DDepends on the amount of surface area being plated.
GAmperes per square meter (square foot) of surface area plated.
TABLE 3. CHROMIC ACID/SULFURIC ACID ETCH SOLUTION
Concentrated sulfurlc add, g/4 (oz/gal) 172 (23)
Chromic acid, g/a (oz/gal) 430 (57)
Temperature, 8C (°F) 60-65 (140-149)
Immersion time, min 3-10
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plating and electroless copper plating ranges from 10 to 15 minutes and 15
to 30 minutes, respectively, at temperatures ranging from 25° to 35°C (77°
to 95°F). The components of the plating baths Include the metal salt
(nickel or copper), a reducing agent, a complexing agent, a stabilizer,
and a pH buffer system. The electroplating of plastics follows the same
cycle as that described for decorative chromium electroplating.
3.1.1.4 Chromic Add Anodizing. Chromic acid anodizing 1s used primarily
on aircraft parts and architectural structures that are subject to high
stress and corrosion. Chromic acid anodizing is used to provide an oxide
layer on aluminum that imparts the following properties:
1. Corrosion protection;
2. Electrical insulation;
3. Ease of coloring; and
4. Improved dielectric strength.
Figure 1 presents a flow diagram for a typical chromic add anodizing
process.
There are four primary differences between the equipment used for
chromium electroplating and that used for chromic add anodizing:
(a) chromic acid anodizing requires the rectifier to be fitted with a
rheostat or other control mechanism to permit starting at about 5 V,
(b) the tank is the cathode in the electrical circuit, (c) the aluminum
substrate acts as the anode, and (d) sldewall shields typically are used
instead of a liner in the tank to minimize short circuits and to decrease
the effective cathode area. Types of shield materials used are
hercullte glass, wire safety glass, neoprene, and vinyl chloride
polymers.
The following pretreatment steps typically are used to clean the
aluminum before anodizing:
1. Alkaline soak;
2. Desmut;
3. Etching; and
4. Vapor degreaslng.
The pretreatment steps used for a particular aluminum substrate depend
upon the amount of smut and the composition of the aluminum. The aluminum
substrate is rinsed between pretreatment steps to remove cleaners.
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SUBSTRATE TO BE PLATED
PRETREATMENT STEPS
Alkaline soak
D«smut
Etching
Vapor degreaaing
RINSE
CHROMIC ACID ANODIZING
RINSE
SEALING
FINAL PRODUCT
CHROMIC ACID
EMISSIONS
Figure 1. Flow diagram for a typical chromic acid anodizing process
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The alkaline soak is the primary preparatory step In cleaning the
aluminum; Its purpose 1s to dislodge soil from the aluminum surface. The
solutions for alkaline cleaning are typically made up of compounds such as
sodium carbonate, sodium phosphate, and sodium hydroxide and usually
contain a small amount of silicate to prevent metal attack. The
alkaline soak consists of Immersing the metal 1n the alkaline solution
that 1s mildly agitated with air.
The purpose of desmuttlng 1s to remove soil or grease films that
cleaners and etchants leave behind. Desmuttlng baths typically consist of
a cold nitric acid solution mixed with water at a concentration ranging
from 5 to 50 percent acid by volume. The nitric add bath also 1s used
either as a bleaching treatment to remove dyes from faulty coatings or as
part of the technique of producing multicolor coatings. Other
desmuttlng treatments use combinations of chromic, phosphoric, and
sulfuric adds depending upon the amount of smut to be removed or the
aluminum composition.
When a dull finish 1s desired, the aluminum 1s etched before
anodizing. Etching baths consist of a dilute solution of soda ash,
caustic soda, or nitric add.18 The degree of etching desired and the
composition of the aluminum being treated determine the concentration of
the etch solution, temperature of the bath, and duration of the etch.
The vapor degreaslng step removes any residual oil or grease on the
surface of the aluminum prior to the anodizing operation.
Typical operating parameters for chromic add anodizing baths are
presented in Table 4*19*20 The voltage 1s applied step-wise (5 V per
minute) from 0 to 40 V and maintained at 40 V for the remainder of the
anodizing time. A low starting voltage (i.e., 5 V) minimizes current
surge that may cause "burning" at contact points between the rack and the
aluminum part. The process Is effective over a wide range of voltages,
temperatures, and anodizing times. All other factors being equal, high
voltages tend to produce bright, transparent films, and lower voltages tend
to produce opaque films. Raising the bath temperature increases current
density to produce thicker films 1n a given time period. Temperatures up
to 498C (120°F) typically are used to produce films that are to be colored
by dyeing. The amount of current varies depending on the size of the
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TABLE 4. TYPICAL OPERATING PARAMETERS FOR CHROMIC
ACID ANODIZING
Chromic add concentration, g/*, (oz/gal) 50-100 (6.67-13.3)
Temperature, *C (°F) 32-35 (90-95)
Plating time, min 30-60
pH 0.5-0.85
Current density, A/m2 (A/ft2)a 1,550-7,750 (144-720)
Voltage (step-wise), volts 30-40
Film thickness, ym (mil) 0.5-1.27 (0.02-0.05)
aAmperes per square meter (square foot) of surface area
plated.
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aluminum parts; however, the current density typically ranges from 1,550
to 7,750 A/m2 (144 to 720 A/ft2).
The postanodizlng steps include sealing and air drying. Sealing
causes hydratlon of the aluminum oxide and fills the pores in the aluminum
surface. As a result, the elasticity of the oxide film increases, but the
hardness and wear resistance decrease. Sealing is performed by
immersing aluminum in a water bath at 88° to 99°C (190° to 210°F) for a
minimum of 15 minutes. Chromic add or other chromates may be added to
the solution to help improve corrosion resistance. The aluminum is
allowed to air dry after it is sealed.
3.1.1.5 Trtvalent Chromium Plating. Trlvalent chromium
electroplating baths have been developed primarily to replace decorative
hexavalent chromium plating baths. Development of a trivalent bath has
proven to be difficult because trivalent chromium solvates in water to
form complex stable ions that do not readily release chromium. The
trivalent chromium baths that have been developed are proprietary baths.
There are two types of trivalent chromium processes on the market:
single-cell and double-cell. The major differences 1n the two processes
are that (1) the double-cell process solution contains m1nimal-to-no
chlorides whereas the single-cell process solution contains a high
concentration of chlorides; and (2) the double-cell process utilizes lead
anodes that are placed in anode boxes that contain a dilute sulfuric add
solution and are lined with a permeable membrane whereas the single-cell
process utilizes carbon or graphite anodes that are placed in direct
contact with the plating solution.25
The advantages of the trivalent chromium processes over the
hexavalent chromium process are (1) fewer environmental concerns,
(2) higher productivity, and (3) lower operating costs. In the trivalent
chromium process, hexavalent chromium 1s a plating bath contaminant. .
Therefore, the bath does not contain any appreciable amount of hexavalent
chromium, which is more toxic than trivalent chromium. The total chromium
concentration of trivalent chromium solutions 1s approximately one-fifth
that of hexavalent chromium solutions. As a result of the chemistry of
the trivalent chromium electrolyte, misting does not occur during plating,
as it does during hexavalent chromium plating. Use of trivalent chromium
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also reduces waste disposal problems and costs. Waste treatment of
hexavalent chromium is a two-stage process. The hexavalent chromium is
first reduced to the trivalent chromium ion; then it can be precipitated
as chromium hydroxide. Trivalent chromium plating solution wastewaters
are already in the reduced trivalent state and require only the chromium
hydroxide precipitation step.
Productivity is increased when trivalent chromium processes are used
because less stripping and replating of parts are required, more parts can
be placed on a rack, and more racks can be placed on a workbar.
The cost of operating a trivalent chromium process is less than that
of a hexavalent chromium process because of the lower wastewater treatment
costs and lower operating costs due to a reduction in rejects and high
productivity.
The disadvantages of the trivalent chromium process are that the
process is more sensitive to contamination than the hexavalent chromium
process and the trivalent chromium process cannot plate the full range of
plate thicknesses that the hexavalent chromium process can.29 Because it
is sensitive to contamination, the trivalent chromium process requires
more thorough rinsing and tighter laboratory control than the hexavalent
chromium process. Trivalent chromium baths can plate thicknesses ranging
up to 0.13 to 25 micrometers (urn) (0.005 to 1.0 mils).28 The hexavalent
chromium process can plate thicknesses up to 762 pm (30 mils). Therefore,
trivalent chromium solutions cannot be used for most hard chromium plating
applications.
The plating efficiency of a trivalent chromium bath, approximately
20 to 25 percent, is slightly higher than that of a hexavalent chromium
plating bath. The color, hardness, and corrosion resistance of triva-
lent chromium deposits are comparable to those of hexavalent chromium
deposits. However, the composition of the trivalent chromium deposit is
significantly different than that of the hexavalent chromium deposit.
Table 5 presents the composition of trivalent and hexavalent chromium
1*. 3l
deposits.
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TABLE 5. HEXAVALENT AND TRIVALENT CHROMIUM DEPOSIT COMPOSITIONS
Chromium deposit Carbon, % wt Oxygen, % wt Chromium, % wt
Hexavalent 0.0 0.4 99+
TMvalent 2.9 1.6 95+
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3.1.2 Uncontrolled Chromium Emissions
Emissions of chromic acid mist from the electrodeposition of
chromium from chromic acid plating baths occur because of the inefficiency
of the hexavalent chromium plating process; only about 10 to 20 percent of
the current applied actually is used to deposit chromium on the Item
plated. Eighty to ninety percent of the current applied is consumed by
the evolution of hydrogen gas at the cathode with the resultant, liberation
of gas bubbles. Additional bubbles are formed at the anode due to the
evolution of oxygen. As the bubbles burst at the surface of the plating
solution, a fine mist of chromic acid droplets is formed.
3.1.2.1 Hard Chromium and Decorative Electroplating Operations.
Uncontrolled emission data for 10 hard chromium plating operations and
2 decorative chromium plating operations are presented in Table 6. These
data were obtained from 11 EPA tests and 1 non-EPA test. Table 7 presents
tank parameters and process operating parameters monitored during each of
the 12 tests. The process parameters monitored during testing include
current supplied to the plating baths, voltage, chromic acid concentration,
and temperature of the plating baths. The chromic add concentration and
temperature did not vary significantly within each type operation for the
emission tests and appeared to be representative of typical operating
values for conventional hard and decorative chromium plating operations.
The amount of current supplied during testing varied considerably because
of the different types and quantities of parts plated.
Based on the existing test data, an uncontrolled emission factor of
10 milligrams of hexavalent chromium per ampere-hour (mg/Ah) (0.15 grain
per ampere-hour [gr/Ah]) 1s considered to be representative of uncon-
trolled emissions from a hard chromium electroplating operation, and an
uncontrolled hexavalent chromium emission factor of 2 mg/Ah (0.03 gr/Ah)
1s considered representative of uncontrolled emissions from a decorative
chromium electroplating operation.
The emission factor for uncontrolled chromium emissions from
decorative chromium plating operations is based on EPA-approved test data
from two plants whose tanks represent the extremes in tank size for
decorative chromium plating. Although the sizes of these tanks may not be
17
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TABLE 6. UNCONTROLLED EMISSION DATA FOR TOTAL AND HEXAVALENT CHROMIUM FROM
CHROMIUM PLATING OPERATIONS*
CO
Process conditions
Plant
Hard chroaiiM plating
Plant Ab'32
Plant Bc'33
Plant Cd'34
Plant Dc'35
Plant E0'36
Plant Ff'37
Plant G*'38
Plant Hc»39
Plant I1'40
Plant Jc»41
Average
Total tank
No. of surface area,
tanks «2 (ft2)
1 5.8
(63)
2 2.5
(27)
4 8.4
(90)
1 5.2
(56)
1 3.4
(37)
1 1.8
(20)
1 1.4
(1.5)
1 5.5
(60)
2 9.0
(99)
3 6.6
(71)
Aapere-
hours
14,000
14.400
20,000
19,800
11,700
12,200
8,900
3,440
8,530
8,790
Actual
gas flow
rate,
(ft3/«in)
226
(7,970)
152
(5,390)
339
(12,000)
177
(6,260)
190
(6,670)
126
(4,540)
95
(3,360)
242
(8,540)
290
(10,300)
512
(18,100)
Mass en 1 ss ion
rate, kg/h (Ib/h)
Total Cr
0.029
(0.064)
0.008
(0.018)
e
0.076
(0.167)
e
e
e
0.009
(0.019)
0.100
(0.221)
0.044
(0.097)
Cr*°
0.026
(0.057)
0.015
(0.033)
0.039
(0.085)
0.076
(0.168)
0.031
(0.069)
0.083
(0.183)
0.024
(0.053)
g
g
0.090
(0.199)
0.046
(0.102)
Process Cr emission
rate, «g/A-h (gr/A-h)
4.0 (0.06)
3.2 (0.05)
4.6 (0.07)
9.1 (0.14)
6.3 (0.10)
16.3 (0.25)
6.5 (0.10)
3.6 (0.06)h
22.5 (0.35)
15.5 (0.24)
9.6 (0.15)
(continued)
-------
TABLE 6. (continued)
Actual
Process conditions gas flow
Plant
Total tank
No. of surface area,
tanks m2 (ft2)
rate,
Ampere- « /m I n
Mass emission
rate, kg/h (Ib/h)
hours (ft3/min) Total Cr Cr*°
Process Cr*6 emission
rate, mg/A«h (gr/A'h)
Decorative chromium plating
Plant Kc»42
Plant Lc'43
Average
1 22.6
(240)
1 2.9
(30.8)
97,000 683
(24,100)
6,500 70
(2,470)
e 0,066
(0.145)
e 0.004
(0.008)
2.0 (0.03)
1.3 (0.02)
1.6 (0.02)
All tests were performed by EPA except for the Plant H test which was performed by the Naval Energy and Environmental Support
.Activity, Port Hueneme, California.
Ampere-hour and mass emission rate values are based on an average of four test runs.
Ampere-hour and mass emission rate values are based on an average of three test runs.
Ampere-hour and mass emission rate values are based on an average of six test runs.
TTotal chromium emissions were not determined.
Ampere-hour and mass emission rate values are based on an average of five test runs.
PHexavalent chromium emissions were not reported.
.Not included in average value because data are based on total chromium.
Ampere-hour and mass emission rate values are based on an average of 11 test runs.
-------
TABLE 7. TANK PARAMETERS AND PROCESS OPERATING PARAMETERS MONITORED DURING CHROMIUM PLATING TESTS
ro
o
Average process parameters monitored
Tank parameters
Plant
Hard chromium plating
Plant A32
Plant B33
Plant C34
Plant D35
Plant E36
Plant F37
Plant G38
Plant H39
Plant I40
Plant J41
Decorative chromium plating
Plant K42
Plant L43
Ho. of
tank(s)
1
2
4
1
1
1
1
1
2
3
1
1
Total tank
surface area.
•2 mV
5.8 (63)
2.5 (27)
8.4 (90)
5.2 (56)
3.4 (37)
1.8 (20)
1.4 (15)
5.5 (60)
9.0 (99)
6.6 (71)
22.6 (240)
2.9 (31)
Total tank
capac i ty ,
I (gal)b
10,710 (2,830)
4,130 (1,090)
35,000 (9,250)
15,820 (4,180)
9,270 (2,450)
4,810 (1,270)
5,720 (1,510)
7,190 (1,900)
11,210 (2,960)
6,090 (1,610)
61,170 (16,160)
3,860 (1,020)
Current ,
amperes
6,220
1,610
2,660
8,390
4,970
2,640
3,480
2,480
1,140
1,150
21,320
2,700
Voltage,
volts
9.0
12.3
7.9
7.4
7.0
4.9
4.9
6.6
7.7
6.1
22.4
5.1
Chromic
acid
concen-
tration.
3/1
(oz/gal)
254 (34)
208 (28)
250 (33)
156 (21)
250 (33)
210 (28)
210 (28)
210 (28)
225 (30)
173 (23)
300 (40)
241 (32)
Bath
temp..
•C CF)
52 (125)
62 (145)
54 (130)
52 (125)
54 (130)
56 (133)
55 (131)
60 (140)
59 (138)
49 (120)
54 (130)
48 (119)
m = square meters, ft = square feet.
al = liters, gal = gallons.
-------
typical of the sizes of other decorative plating tanks, there is
insufficient evidence to show that emissions are directly proportional to
tank size. In any case, the uncontrolled emissions have been normalized
to account for tank size using the ampere-hours term in the emission
factor. Because the data are limited, a conservative approach was taken
in selecting the emission factor for decorative plating. Thus, a value of
2 mg/Ah was selected instead of the average value for the two tests.
3.1.2.2 Chromic Acid Anodizing Operations. Uncontrolled emission
data for chromic acid anodizing operations were not obtained through an
EPA source test at an anodizing facility. Instead, an estimate of the
amount of hexavalent chromium emissions was made by performing a mass
balance on a scrubber used to control emissions from a chromic acid
anodizing operation. Outlet scrubber water grab samples were analyzed to
determine the amount of hexavalent chromium in the sample, and a mass
balance was performed on the scrubber to determine the inlet hexavalent
chromium emission rate. The results of this mass balance indicate that an
uncontrolled of emission factor of 6.0xlO~ kilogram of hexavalent
chromium per hour per square meter of tank surface area (1.2x10" pound
per hour per square foot of tank surface area) 1s appropriate to
characterize emissions from chromic add anodizing. Alternatively, if
the tank surface area is unknown, uncontrolled emission rates can be used
to approximate the level of uncontrolled chromium emissions. The results
of the mass balance at the small anodizing operation (tank capacity
-1,900 liters [500 gallons!) and results from a non-EPA emission test at a
large chromic acid anodizing operation (tank capacity -17,600 liters
[4,600 gallons]) indicate uncontrolled emission rates range from 0.0012 to
0.0028 kg/h (0.0026 to 0.0062 Ib/h), respectively/4 At this time, there
are insufficient data from anodizing operations to determine conclusively
that one emission factor format is more appropriate than the other.
3.1.3 Emission Reduction Techniques
The principal techniques used to control emissions of chromic acid
mist from decorative and hard chromium plating and chromic acid anodizing
operations include add-on control devices and chemical fume
suppressants. The control devices most frequently used are mist
eliminators and wet scrubbers that are operated at relatively low pressure
21
-------
drops. Because of the corrosive properties of chromic acid, control
devices typically are made of polyvinyl chloride (PVC) or fiberglass.
Chemical fume suppressants are added to decorative chromium plating
and chromic acid anodizing baths to reduce chromic add mist. Although
chemical agents alone are effective control techniques, many plants use
them 1n conjunction with a control device.
Chevron-blade and mesh-pad mist eliminators are the types of mist
eliminators most frequently used to control chromic add mist. The most
Important mechanism by which mist eliminators remove chromic acid droplets
from gas streams 1s the 1nert1al 1mpact1on of droplets onto a stationary
set of blades or a mesh pad. M1st eliminators typically are operated as
dry units that are periodically washed down with water to clean the
Impaction media.
The wet scrubbers typically used to control emissions of chromic
acid mist from chromium plating and chromic acid anodizing operations are
single and double packed-bed scrubbers. Other scrubber types used less
frequently include fan-separator packed-bed and centrifugal-flow
scrubbers. Scrubbers remove chromic add droplets from.the gas stream by
humidifying the gas stream to increase the mass of the droplet particles,
which are then removed by Impingement on a packed bed. Once-through water
or redrculated water typically Is used as the scrubbing liquid because
chromic add 1s highly soluble 1n water.
Chemical fume suppressants are surface-active compounds that are
added directly to chromium plating and chromic add anodizing baths to
reduce or control misting. Fume suppressants are classified as temporary
or as permanent. Temporary fume suppressants are depleted mainly by the
decomposition of the fume suppressant and dragout of the plating solution,
and permanent fume suppressant are depleted mainly by dragout of the
plating solution. Fume suppressants, which are manufactured 1n liquid,
powder, or tablet form, include wetting agents that reduce misting by
lowering the surface tension of the plating or anodizing bath, foam
blankets that entrap chromic acid mist at the surface of the plating
solution, or combinations of both a wetting agent and foam blanket.
22
-------
The performance capabilities of the control devices used to control
chromic acid mist are presented in Table 8. The air pollution control
devices tested include four mist eliminators, three packed-bed scrubbers,
and one packed-bed scrubber in conjunction with a mist eliminator used to
control emissions from hard chromium plating operations. In addition, one
emission test was conducted at a decorative chromium plating facility to
determine the performance of chemical fume suppressants in controlling
chromic acid mist.
The average hexavalent chromium removal efficiency of mist
eliminators was 98 percent for nrist eliminators with double sets of
blades, 90 percent for mist eliminators with single sets of blades, and
98 percent for mesh pad units. The average hexavalant chromium removal
efficiency of scrubbers was 98 percent. The hexavalant chromium removal
efficiency of the scrubber in conjunction with the mist eliminator was
95 percent.
For decorative chromium plating operations, the performance
efficiency of both chemical fume suppressants tested (a foam blanket and a
combination of a foam blanket and wetting agent) was greater than
99 percent. This performance efficiency is achievable as long as vendor
recommendations on the makeup and use of the fume suppressants are
followed rigorously.
3.1.4 Nationwide Emission Estimates
Table 9 presents the estimated number of operations and the
nationwide annual emission rate for each type of operation. The
assumptions regarding the existing control levels for each type operation
were derived from data obtained during the development of the NESHAP for
chromium electroplating operations. The nationwide emission rate for hard
chromium electroplating operations was based on the assumption that
30 percent of operations are uncontrolled, 30 percent of operations are
controlled by mist eliminators with single sets of blades (90 percent
efficient), and 40 percent are controlled by single packed-bed scrubbers
(97 percent efficient). The nationwide emission rate for decorative
chromium electroplating operations was based on the assumption that
15 percent of operations are uncontrolled, 80 percent are controlled by
chemical fume suppressants (97 percent efficient), and 5 percent are
23
-------
TABLE 8. PERFORMANCE LEVELS OF INDIVIDUAL CONTROL DEVICES
Plant Plant
cade name
Description of control device
Ho. of
runs
averaged
Concen-
tration, mo/ ds cm
Inlet Outlet
Hass Mission
rate, ka/h
Inlet
Outlet
Efficiency.
percent*
Process emission
rate. jo,/Ah
Inlet
Outlet
ro
HARD CHROMIUM HATING
Chevron-blade mist eliminators
A
B
D
Single set of overlapptng-type blades
Single set of overlapping type blades
Double set of overlapping type blades
4
3
3
2.030
1.760
7.690
0.306
0.149
0.124
0.0260
0.01 51
0.0763
0.0033
0.0013
0.0012
fi7.9
91.3
98.4
3.96
3.16
9.06
0.65
0.27
0.15
Mesh-pad mist eliminators
F
a
t?
Ec
Packed -bed
I
J
C
DECORATIVE
Two mesh pads In series
Iwo mesh pads in series
One aesh pad
Two sets of chevron -blades followed by two aesh pads
scrubbers
Single packed-bed scrubber
Double packed-bed scrubber
Double packed-bed scrubber followed by chevron-blade list
eliminator with * double set of wave-type blades
CHROMIUM PLATING
S
3
3
3
11
3
6
11.400
4.410
0.609
3.070
5.510
1.670
2.040
0.0326
0.0435
0.0257
0.040
0.0302
0.0523
0.081
0.0829
0.0241
0.0087
0.0313
0.0900
0.0464
0.0388
0.0002
0.0003
O.OOOS
0.0004
0.0005
0.0015
0.0015
99.7
98.9
94.5
98.7
99.4
96.2,
95. 4d
16.3
6.52
3.60
6.33
22.5
15.5
4.57
0.04
0.07
0.18
0.08
0.14
0.56
0.14
Fume suppressants
L
1. Foam blanket
2. Foaa blanket In combination with wetting agent
3
3
0.916
0.916
0.0041
0.0021
0.0036
0.0036
0.00002
0.00001
*99.5
*99.8
1.34
1.34
0.006
0.003
Efficiencies are based on the average of efficiencies from each run. Therefore, they My not agree with the values obtained by calculating the efficiency from the average
.Inlet and outlet rate.
"Results are for total chromium. Hexavalent chromium analyses were not performed.
CA aolsture extractor preceded the mist eliminator unit. However, the eaissio* data for the combined control techniques were attributed to the mist eliminator unit only.
Any droplets caught by the aoisture extractdr would have been collected by the altt eliminator unit, if the aoisture extractor was eliminated fro* the systea.
"The efficiency presented is the combined efficiency of both units.
-------
TABLE 9. NATIONWIDE NUMBER OF OPERATIONS AND ESTIMATED
HEXAVALENT CHROMIUM EMISSIONS FROM CHROMIUM ELECTROPLATING
AND CHROMIC ACID ANODIZING OPERATIONS
Operation
No. of plants
nationwide
f*jat1onwide
Cr+ emissions,
(tons/yr)
Hard chromium plating
Decorative chromium plating
2
Chromic acid anodizing
1,540
2,800
630
145 (160)
10 (11)
3.6 (3.9)
25
-------
controlled by single packed-bed scrubbers (95 percent efficient). The
nationwide annual emission rate for chromic acid anodizing operations was
based on the assumption that 40 percent of operations are uncontrolled,
10 percent are controlled by mist eliminators with single sets of blades
(90 percent efficient), 30 percent are controlled by chemical fume
suppressants (97 percent efficient), and 20 percent are controlled by
single packed-bed scrubbers (95 percent efficient).
3.2 COOLING TOWERS
3.2.1 Background Information
Cooling towers are devices that cool warm water by contacting 1t
with ambient air that is drawn or forced through the tower. This cool
water is used to remove heat from a process or an HVAC chiller and 1s then
redrculated to the cooling tower. Chemicals are added to this
recirculatlng water to Inhibit heat exchanger corrosion. One of the many
classes of corrosion Inhibitors used is chromium based. Air emissions of
chromium occur when water droplets (and the chemicals they contain)
entrained in the air stream that 1s drawn through the tower are emitted to
the atmosphere. These droplet emissions are referred to as "drift." .All
cooling towers that are used to remove heat from an Industrial process or
chemical reaction are referred to as industrial process cooling towers
(IPCT's). Towers that are used to cool heating, ventilation, and air
conditioning (HVAC) and refrigeration systems are referred to as comfort
cooling towers (CCT's).
3.2.1.1 Industrial Process Cooling Towers. Major users of IPCT's
that also use chromium-based water treatment chemicals are chemical
manufacturing plants, petroleum refineries, and primary metals
facilities. Several miscellaneous manufacturing industries (textiles,
tobacco products, tire and rubber products, and glass products) and
utilities use chromium-based water treatment chemicals to a lesser
degree. It is estimated that IPCT's are used at approximately 190 petro-
leum refineries, 1,800 chemical manufacturing plants, 240 primary metals
plants, and 730 plants in the miscellaneous Industries/5 In addition,
the percentage of cooling towers using chromium-based water treatment
chemicals 1n each industry is estimated as 70 percent at petroleum
refineries, 40 percent at chemical manufacturing plants, 20 percent at
26
-------
primary metals facilities, 15 percent at plants in the tire and rubber
Industry, and 5 percent at plants in the other miscellaneous industries.
In the utilities Industry, it was reported that chromium-based water
treatment chemicals are used at two electric power plants. When
combined with data from plant responses to EPA information requests in
each of these industries, these estimates result in a total of about
2,855 IPCT's using chromium-based water treatment chemicals: 476 at
petroleum refineries, 2,039 at chemical plants, 224 at primary metals
plants, 110 at miscellaneous plants, and 6 at utilities. The nationwide
baseline Cr* emissions from these towers are estimated to be 85 megagrams
per year (Mg/yr) (94 tons per year [tons/yr]).
3.2.1.2 Comfort Cooling Towers. Comfort cooling towers are used in
all States 1n the U.S., primarily in urban areas. Major users of CCT's
with HVAC systems Include hospitals, hotels, educational facilities,
office buildings, and shopping malls. Refrigeration systems that may
operate with CCT's include 1ce skating rinks, cold storage (food) ware-
houses, and other commercial operations. The EPA estimates that the
nationwide population of CCT's 1s 250,000 units and that 15 percent of
CCT's (about 37,500) use chromium-based water treatment chemicals. These
CCT's are estimated to emit between 7.2 and 206 Mg/yr (8 to 227 tons/yr)
of chromium. Chromium*use 1n CCT's appears to be distributed randomly
across the country.
In the preparation of the proposed rule for CCT's under the Toxic
Substances Control Act (TSCA) (see 52 FR 10206), EPA developed model tower
parameters and estimates of chromium emissions per model tower to
represent the population of CCT's 1n the U.S. Table 10 presents the model
parameters and baseline (i.e., low efficiency drift eliminator [LEDE])
emission estimates/
The emission estimates in Table 10 are based on an emission factor
developed from EPA- and Industry-sponsored cooling tower emission tests.
Because the emission factors developed to estimate Cr+s emissions from
cooling towers are Independent of tower operating parameters (recirculation
rate, chromate concentration, cooling range), the factors are applicable
to both CCT's and IPCT's. Section 3.2.3.1 of this document discusses
specific emission factors to use for estimating Cr+6 emissions from
cooling towers on a case-by-case basis. [Note: The proposed TSCA rule
27
-------
TABLE 10. MODEL COMFORT COOLING TOWERS AMD HOURLY BASELINE Cr*6 EMISSIONS
ro
oo
Model
tower
1
2
3
4
5
6
Model
building
•^(ft8)
673
(7,240)
1,460
(15,720)
3,405
(36.650)
6,224
(66,990)
12,338
(132,800)
37.626
(405,000)
Flow rates, ft /rain (gal/mln)
Model tower
cooling requirements
W (Btu/h)
95,400
(325,800)
207,100
(707,400)
482,900
(1,649,000)
882,900
(3,015,000)
1,750,000
(5,976,000)
5,338,000
(18,230,000)
Tons
27
59
137
251
498
1.520
Reclrcu-
1 at Ion
rate
246
(65)
534
(141)
1,250
(330)
2.280
.(602)
4,520
(1*194)
13.800
(3.642)
Evapora-
tion rate
2.08
(0.55)
4.54
(1.20)
10.6
(2.80)
19.4
(5.12)
38.4
(10.15)
117.0
(30.96)
Chromium
emissions
Slowdown per tower,
rate mg/h (lb/1,000 h)
0.53
(0.14)
1.14
(0.30)
2.65
(0.70)
4.85
(1.28)
9.61
(2.54)
29.3
(7.74)
19.9
(0.044)
43.2
(0.095)
101
(0.222)
184
(0.406)
365
(0.804)
1,110
(2.45)
Assumptions:
Wet bulb temperature = 23.9°C (75°F)
Hot water temperature = 29.4°C (85"F)
Cooling range = 5.6°C (10°F) 2
Cooling requirements = 142 W/m floorspace (45 Btu/ft /h)
Cycles of concentration - 5
Latent heat/total heat = 0.8
Chromate concentration = 10 ppm
Chromium emission factor = 0.0003 mg Cr*1" /(ppm Cr* Xlltet H20) .
(2.504x10 Ib Cr* /ppm Cr+
/gal H20)
-------
would prohibit the use of chromium-based chemicals in CCT's. If
promulgated, this rule would have the effect of reducing Cr+s emissions
from CCT's to zero.]
3.2.1.3 Cooling Tower Fundamentals. Schematics of typical cooling
u a
tower designs are shown in Figure 2. The major cooling tower components
include the fan(s), fill material, water distribution deck or header,
drift eliminator, structural frame, and cold water basin. Other
components that affect tower operation include the pumps and pipes
necessary to circulate the cooling water through the cooling tower and
heat exchanger loops.
Most IPCT's are designed with induced-draft airflow, but many have
forced-draft airflow, and some (especially 1n the utilities industry) have
natural-draft airflow. Induced draft is provided by a propeller-type
axial fan located in the stack at the top of the tower. Forced-draft
towers are usually smaller than induced-draft towers and have either
centrifugal fans located at the base of the tower, which 1s constructed as
a plenum to provide positive-pressure airflow through the fill material,
or axial fans located on the side of the tower. Natural-draft airflow
relies on air currents created by temperature differences between the air
1n the tower and the atmosphere. When the cooling demands are minimal and
the air temperature is low enough, water can be circulated through the
tower and cooled sufficiently without using the fans. In these Instances,
a natural draft Is created in the cooling tower.
The direction of the airflow through a mechanical draft tower is
either crossflow or counterflow. Crossflo./ refers to horizontal airflow
through the fill, and counterflow refers to upward vertical airflow. Fill
material is used to maintain an even distribution of water across the
horizontal plane of the tower and to create as much water surface as
practical to enhance evaporation and sensible heat transfer.
3.2.2 Potential Emission Reduction Techniques
Techniques to control chromium emissions from cooling towers involve
two different strategies: modification of chromium addition to the
reclrculatlng water, and improved reduction of drift. The first technique
involves reducing the concentration of chromium in the water treatment
program, thereby reducing the concentration of chromium in the drift
29
-------
WATER
INLET
FAN
WATER
INLET
"*« DRIFT
^.ELIMINATORS
WATER OUTLET
MECHANICAL DRAFT
CROSS-FLOW TOWER
AIR
OUTLET
DRIFT
ELIMINATORS
WATER OUTLET
MECHANICAL DRAFT
COUNTER-FLOW TOWER
Figure 2. Internals of crossflow and counterflow cooling towers
(reprinted from Reference No. 48).
30
-------
emitted. The second technique Involves retrofitting towers that normally
have LEDE's with high-efficiency drift eliminators (HEDE's) to reduce
drift emissions to the lowest possible rate.
3.2.2.1 Alternative Water Treatment Programs. Responses to 28 EPA
Information requests and a survey of the Chemical Manufacturers Associa-
tion Indicate that the average chromate concentration for those IPCT's
using chromium-based corrosion inhibitors 1s 13 ppm.1*5'*9 One potential
chromium emission reduction technique involves alternative water treatment
programs such as programs with lower chromate levels or nonchromate
treatments.
A low-chromate treatment program would reduce Cr"1"6 emissions from
IPCT's by limiting the chromate concentration 1n cooling water. Water
treatment programs are available that maintain average chromate concentra-
tions of 0*5 to 4 ppm 1n the recirculatlng water, but these programs have
not always been successful in industrial applications. Low-chromate
programs that have provided acceptable results in a number of cases
maintain chromate concentrations 1n the range of 4 to 6 ppm.
Because of National Pollution Discharge Elimination System (NPDES)
chromium restrictions and other regulations, nonchromlum treatments are
now more widely used than chromium treatments. The most common
nonchromium treatment program 1s phosphate based, but others include
molybdates, zinc, and all-organic treatments (primarily organo-phosphorus
compounds). However, these alternative programs may not perform corrosion
Inhibition functions as well or as cheaply as chromates depending on the
Individual cooling tower system. The performance of any treatment program
is dependent on water quality parameters (pH, alkalinity, hardness, and
conductivity) and operating conditions (water temperature, flow velocity,
Inhibitor concentration, and the presence of contaminants such as H2S,
S02, NH3, and N02) that are specific to each cooling system.
3.2.2.2 Low- and High-Efficiency Drift Eliminators. Water droplets
entrained in the air and the dissolved and suspended sol Ids contained in
the droplets that are emitted from cooling towers are referred to as
drift. Drift eliminators can be Installed at the exit of the fill
sections to reduce the amount of drift 1n the exiting airflow.
Historically, the purpose of drift reduction has been to alleviate the
31
-------
nuisance deposition of water drift and Its dissolved sol Ids on nearby
buildings or on personal property such as automobiles. More recently, the
concern has focused on the environmental Impact caused by the compounds
contained 1n the drift and, thus, on the deposition of these compounds.
Drift eliminators are designed with pressure drops lower than those of
other air pollution control equipment and rely primarily upon the
1mpact1on of water droplets on drift eliminator surfaces to reduce the
concentration of drift from the exit air of cooling towers. The drift
eliminator blades are configured to force directional changes 1n the
airflow such that the momentum of the water droplets causes them to
Impinge onto the blade surfaces. The number of directional airflow
changes, the spacing between the blade surfaces, the angle of directional
change, and the capability to return the collected water to a quiescent
area of the plenum are the major design features (parameters) 1n drift
eliminators that affect efficiency. Drift eliminators are constructed of
wood, PVC, metal, asbestos-cement, polystyrene, or cellulose. The
material most often specified 1s PVC.
Figure 3 presents schematics of the three major drift eliminator
designs: herringbone (blade-type), waveform, and cellular (or honey-
comb). Low-efficiency drift eliminators Include herringbone, some
waveform (sinusoidal), and some cellular designs. Herringbone designs are
constructed to create two or three major directional changes 1n the
airflow. The blades are sloped 1n opposing directions 1n a manner that
provides drainage of the accumulated drift Into the fill area. The blades
typically are constructed of wood, but other materials (e.g., metal and
asbestos cement board) also are used. Waveform drift eliminators are
configured 1n a sinusoidal wave pattern such that two major directional
changes 1n the airflow are created. The sinusoidal blades are constructed
of asbestos cement board or PVC material. Cellular drift eliminators are
configured with thinner blades 1n a honeycomb pattern. The airflow
passages 1n the cellular drift eliminators, which are narrower than
passages 1n other designs, reduce the distance a droplet must travel
across the stream to Impact on the surface. Drainage of the collected
water to prevent reentralnment 1s not a design criteria of LEDE's.
32
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.wood Lath
Staaos
HERRINGBONE
(BLADE-TYPE)
ELIMINATOR
WAVEFORM
ELIMINATOR
CELLULAR
ELIMINATOR
Figure 3. Designs of various drift eliminators (reprinted
from Reference No. 50).
33
-------
High-efficiency drift eliminators include a few of both cellular and
sinusoidal designs. The cellular HEDE's that achieve the higher
efficiencies are designed with complex configurations that contain
numerous, closely constructed airflow passages. Thin materials of
construction are used to reduce the area of blockage to the airflow and
minimize the pressure drop that is created by the eliminator. For
sinusoidal drift eliminators, the blades are placed closer together in
high-efficiency designs than in low-efficiency designs, and the exit is
configured with a tip for draining captured water that would otherwise be
partially reentralned in the airflow. Typically, drainage of water into a
quiescent area of the tower 1s a major design consideration of HEDE's. A
few drift eliminators installed 1n towers built in recent years are more
likely to be higher efficiency waveform or cellular units, but the vast
majority of older towers still have lower efficiency herringbone and
waveform eliminators.
The performance of a drift eliminator is affected primarily by the
droplet or particle size and the airflow velocities through the drift
eliminator. Small droplets are created both from evaporation of larger
droplets and the physical breakage of larger droplets Into small
droplets. Parameters that affect the rate of evaporation and the size of
droplets created include the water distribution system, the type of fill,
the type of tower, the meteorological conditions, and the temperature of
the redrculatlng water.
A drift eliminator manufacturer indicates that HEDE's can remove
80 to 90 percent or more of the drift discharged from low-efficiency
herringbone drift eliminators. * These drift eliminator efficiencies,
however, are based on data collected with a test method that has not been
submitted to EPA for approval.
3.2.3 Cooling. Tower Emissions
Three series of emission tests were conducted by EPA on IPCT's
equipped with low- and high-efficiency drift eliminators. The results of
these tests are presented 1n the next section.
34
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3.2.3.1 Drift and Chromium Emissions. The drift rate (rate of
water lost by entrainment in the cooling air drawn through the tower) is
often expressed as the percentage of the recirculating water flow rate
that is emitted. Likewise, the chromium emission rate can be expressed as
a percentage of the recirculating chromium rate. However, the chromium
emission rate from towers should not be confused with the drift rate.
Based on test results, a drift eliminator manufacturer claims that the
achievable drift rates range from 0.001 to 0.06 percent of the
recirculating water. The approximate dividing line between drift rates
for higher and lower efficiency drift eliminators is 0.008 percent. Those
achieving a lower percentage are "higher efficiency," and those that
cannot achieve 0.008 percent are "lower efficiency."
Drift can be estimated by measuring the emission rate of an element
(such as sodium, calcium, manganese, chromium, lithium or bromine) and
assuming that the percentage of water emitted as drift is the same as the
percentage of the recirculating element emitted. However, a claimed drift
rate may or may not be equivalent to the element's emission rate depending
on the way the drift rate was measured. Also, drift rate measurement
results are highly dependent on the measurement method; therefore,
achievable drift rate claims may not be comparable 1f they are based on
different measurement methods.
The EPA-sponsored emission tests of IPCT's at three facilities used
an isokinetic test method for chromium which is still under development.
Emission factors relating the chromium emission rate to the chromium
recirculation rate were developed from each of these emission tests. The
average baseline (LEDE) and controlled (HEDE) emission factors for each
test site are presented in Table 11. In addition, five industry-sponsored
drift performance tests conducted by Midwest Research Institute and two
chromium emission tests conducted by Mobil are included. The emission
factors express the emission rate as a percentage of the recirculating
rate (milligrams of chromium emitted per milligram of chromium
recirculating in the tower multipled by 100). The most comprehensive
emission tests were conducted at Plant B. At this plant, two towers of
similar design located side-by-side were tested simultaneously under the
same meteorological conditions. One tower was equipped with an LEDE and
the other was equipped with an HEDE.
35
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TABLE 11. EMISSION FACTORS FOR HEXAVALENT CHROMIUM FROM
COOLING TOWERS33'5
Test site
Chromium emission
factor, percent3
Standard deviation
(percent relative
standard deviation,
percent)
EPA-sponsored tests
A (HEDE)
C (HEDE)
B (HEDE)
B (LEDE)
A (LEDE)
Industry-sponsored tests
MRI No., 3 (HEDE)
MRI No. 4 (HEDE)
MobH-PTR Tower No. 5
(LEDE)
Mobil -North Tower No. 6
(LEDE)
MRI No. 1 (LEDE)
MRI No. 2 (LEDE)
MRI No. 5/6 minerals
test (LEDE)
0.0037
0.028 w/outl1ers
0.0038
0.0087
0.0267
0.0318
0.141 w/outT1ers
0.01
0.007
0.0334
0.0321
0.0305
0.034
0.018
0.021 w/out11ers
0.0020 (54)
0.035 w/outl1ers
0.0044 (116)
0.0037 (43)
0.0168 (63)
0.0292 (92)
0.192 w/outHers
NA (--)
NA (»)
0.0306 (92) .
0.0156 (49)
NA <--)
NA (--)
0.0045 (25)
0.0094 w/outllers
(126)
(136)
(45)
^Percentage of redrculatlng chromium that 1s emitted.
36
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Since the completion of the emission tests at Plant B, additional
methods development investigations have been conducted. These
investigations have revealed that the chromium sampling method is subject
to substantial error due to potentially severe problems associated with
chromium recovery and cross-over contamination from sample run to sample
run. The extent to which these problems appear in the test results
obtained at Plants A, C, and Mobil 1s uncertain. As a result, the data
presented in Table 11 should be used with caution.
The EPA believes that the tests at Plant B provide the best
available data on the relative performance of HEDE's. The EPA Method 13-
type testing at Plant B Indicated a Cr+6 emission factor of 0.03 percent
of the redrculatlng Cr+fi for LEDE's and 0.0087 percent for HEDE's. As
discussed in Section 3.2.1.2, these factors can be used for both IPCT's
and CCT's.
The current factors are based on the assumption that the ratio of
hexavalent to total chromium 1n the emissions 1s the same as that in the
cooling water. The test program conducted by the Agency has not
conclusively Identified the speciatlon of emissions (i.e., Cr+ versus .
Cr+3). For purposes of estimating Cr+ emissions, the conservative
assumption is that all of the chromium is Cr+ .
3.2.3.2 Sample Calculation of Chromium Emissions. The chromium
emission rate for any tower can be estimated by multiplying the emission
factor by the recirculating rate of water and the chromium concentration
1n the recirculating water as shown 1n Equation (1).
ECr = K'R'cCr (D
where:
E^r - chromium emission rate, mg Cr/min
K » chromium emission factor, percent of recirculating chromium
that is emitted
R = recirculating ra;e of cooling water, liters/rain
C,£r = concentration of chromium in the recirculating water, mg
Cr/liter = ppm (multiply CrO^ concentration by 0.448 to obtain
Cr concentration)
For example, the following calculation estimates the emissions from a
10,000-gallon-per-minute (gal/min) IPCT with a recirculating chromate
37
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concentration of 10 parts per million (ppm), equipped with a low-
efficiency drift eliminator.
R - (10,000 gal/m1n)(3.785 liters/gallon) * 37,850 Uters/mlnute
C^r » 10 ppm as CrOu 3 4.48 ppm Cr
K * the emission factor for towers with low-efficiency drift
eliminators; use K = 0.03 percent.
ECr - K'R«CCr - (0.03J£)(37t850)(4.48) - (0.0003)(37,850)(4.48) -
50.9 mg Cr em1tted/m1n
To estimate the emissions from the same IPCT equipped with a high-
efficiency drift eliminator, use K » 0.0087.
Therefore:
ECr - K«R«CCr * (0.0087SS)(37,850)(4.48) » (0,000087)(37,850)(4.48) =
14.8 mg Cr em1tted/m1n
Thus, the emission reduction achieved by a HEDE compared to a LEDE 1s:
71 percent.
The following example calculation estimates the emissions from a
500-gal/m1n CCT with a reclrculatlng chromate concentration of 10 ppm,
equipped with a low-efficiency drift eliminator.
R - (500 ga1/m1n)(3.785 Uters/gal) - 1,892.5 11ters/m1n
C£r « 10 ppm as CrO,, » 4.48 ppm Cr
K » 0.03 percent
ECr » K»R«CCr - (0.03*)(1,892.5)(4.48) -
(0.0003)(1,892.5)(4.48) - 2.5 mg Cr emitted/rain
3.2.4 Nationwide Emissions Distribution by Industry
In developing the NESHAP for chromium emissions from IPCT's, EPA has
generated Industry-by-lndustry estimates of the total number of cooling
towers, the number of towers using chromate treatments, and chromium
emissions. Table 12 presents these estimates as currently known. The
data show that the Industries of greatest concern are chemical manufac-
turing (43 Mg/yr [47,5 tons/yr]), petroleum refining (31.8 Mg/yr
[35.1 tons/yr]), and primary metals production (8.4 Mg/yr [9.3 tons/yr]).
38
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Together, these industries represent 98.2 percent of nationwide chromium
emissions from IPCT's. Tabli
chromium emissions from CCT's.
emissions from IPCT's. Table 12 also presents nationwide estimates of
39
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TABLE 12. NATIONWIDE COOLING TOWER CHROMIUM EMISSIONS SUMMARY
Industry
Chemical manufacturing
Petroleum refining
Primary metals
Tobacco products
T1re and rubber
Textile finishing
Glass manufacturing
Utilities
Subtotal (IPCT only)
Comfort cooling towers
TOTAL
Total No.
of cooling
towers
5,096
680
1,118
336
267
1,018
58
775
9,348
250,000
259,350
No. of
cooling towers
using cnromate
2,039
476
224
16
40
51
3
6
2,855
37,500
40,360
Cr*6
Mg/yr
43.13
31.82
8.39
0.23
0.18
0.08
0.01
0.95
84.8
33
118
em1ssionsa
Tons/yr
47.54
35.08
9.25
0.26
0.20
0.09
0.01
1.05
93.5
34
128
aBased on use of low-efficiency drift eliminators.
40
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4.0 SOURCE TEST PROCEDURES
4.1 CHROMIUM ELECTROPLATING
During the standards support study for hexavalent chromium emissions
from hard and decorative chromium electroplating facilities, samples to be
analyzed for hexavalent and total chromium were obtained in accordance
with EPA Method 5 (40 CFR Part 60-Appendix A), also referred to as
Modified Method 13-B in test reports. The only modification to the sample
collection method was the elimination of the filter and the replacement of
H20 in the impingers with 0.1 Normal sodium hydroxide. Method 5 provides
detailed procedures and equipment criteria and other considerations
necessary to obtain accurate and representative emission samples. In
order to sample for chromium emissions, Methoas 1 through 4 must also be
used.
After collection, the samples were analyzed for hexavalent and total
chromium (total chromium is the sum of hexavalent chromium plus other
chromium). Concentrations of hexavalent chromium were determined using
spectrophotometric analysis while total chromium was determined using
inductively coupled argon plasmography (ICAP). At the present time,
sample analysis has been performed in accordance with the tentative method
"Detection of Hexavalent Chromium from Stationary Sources (December 13,
1984)," and a draft method: "E.P.A. Protocol for Emission Sampling for
Both Hexavalent and Total Chromium (February 22, 1985)."
4.2 COOLING TOWERS
During the standards support study for chromium emissions from
cooling towers, testing was conducted according to two draft test methods
developed from previously conducted methods development testing:
"Method —Determination of Chromium Emissions from Cooling Towers" and
"Method —Direct Measurement of Gas Velocity and Volumetric Flowrate
Under Cyclonic Flow Conditions (Propeller Anemometer)." The cooling tower
method is similar to EPA Method 13 (40 CFR Part 60-Appendix A) with the
following exceptions: (1) a Teflon"1 filter is used in place of a paper
filter, (2) a propeller anemometer is used in place of the pitot tube for
gas velocity and flowrate measurements, (3) the determination of the
measurement site does not follow EPA Method 1, and (4) the chemical
41
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analysis for total chromium 1n the emission samples 1s performed using
Neutron Activation Analysis (NAA), Graphite Furnace Atomic Absorption
(GFAA), or ICAP. In conjunction with the emissions testing, repre-
sentative cooling tower water samples were collected to determine the
ratio of hexavalent to total chromium 1n the cooling water; these samples
were analyzed for total chromium by NAA, GFAA, or ICAP and for hexavalent
chromium by the dlphenylcarbazlde colorlmetrlc method (1n "EPA Draft
Method-Determination of Hexavalent Chromium Emissions from Stationary
Sources," December 13, 1984). The ratio was used to calculate the amount
of hexavalent chromium 1n the cooling tower emissions.
Preliminary material balance calculations were performed on the
cooling water at several towers to compare the apparent chromium loss In
the drift emissions with the emission measurements obtained during the
standards support study. Variables used 1n these calculations Included:
cooling water flow rates to the towers, riser cells, and/or fan cells;
blowdown rates; makeup water flow rates; addition(s) of chemicals to the
cooling water; and chemical analysis of the cooling water samples taken
during testing.
Two major modifications were made to the draft test method for
cooling towers based on problems encountered and knowledge gained during
the testing program. Initially, the draft method specified the use of NAA
to determine the total chromium content of the 1mp1nger train samples and
the cooling water samples. Because of the length of time required for
sample analysis and the limited availability of commercial NAA services,
two additional analytical techniques, GFAA and ICAP, were utilized and
were added as options to the draft test method. Unlike NAA, both of these
techniques require acid solubilization of the chromium 1n the sample prior
to analysis. In assessing the chromium recovery efficiency for the
concentrated 1mp1nger samples from the first test, it was discovered that
a significant residue remained in the beakers used to concentrate the
samples. The concentration procedure was modified to require an acid
rinse of the beakers used for sample concentration with the rinse being
added to the concentrated sample.
42
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5.0 REFERENCES
1. Memo from Hester, C., MRI, to Smith, A., EPA/ISB. Bases for Risk
Assessment Inputs for Chromium Electroplating Operations. June
1988. pp. 6-7, 10.
2. Memo from Hester, C., MRI, to Smith, A., EPA/ISB. Bases for Risk
Assessment Inputs for Chromic Add Anodizing Operations. June
1988. pp. 8-9.
3. Logozzo, A., and Schuwartz, M. Hard Chromium Plating. American
Electroplaters Society, Inc. p. 9.
4. Vervaert, A. Preliminary Assessment of Chromium from Chromium
Electroplating Facilities. Research Triangle Park, North Carolina.
U. S. Environmental Protection Agency, p. 3.
5. Decorative Chromium Electroplating. American Electroplaters
Society. 1980. p. 2.
6. Dennis, J., and Such, T. Nickel and Chromium Plating, Butterworth
and Company. University Press. Cambridge, England, Second
Edition. 1986. p. 179.
7. Reference 4, p. 2.
*
8. Reference 6, p. 287.
9. Reference 6, p. 289.
10. Reference 6, p. 290.
11. Reference 6, pp. 272, 294-295.
12. Locating and Estimating Air Emissions From Sources of Chromium.
U. S. Environmental Protection Agency, Research Triangle Park, North
Carolina. EPA Publication No. 450/4-84-007g. July 1984. p. 83.
13. Graham, K. Electroplating Engineering Handbook. Reinhold Book
Corp., New York. 1962. p. 427.
14. Reference 13, p. 432.
15. Reference 13, p. 432.
16. Reference 13, pp. 162» 427.
17. Brace, A. The Technology of Anodizing Aluminum. Robert Draper,
Ltd. Teddington, 1968. p. 54.
18. Darrln, M., and Tubbs, L. "Dyeing Chromic Acid Anodized Aluminum."
Metal Finishing. September 1984. p. 550.
43
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19. Schwartz, M. Anodlzed Aluminum and Its Alloys. American
Electroplaters Society. 1985. p. 15.
20. Wernlck, S., and Pinner, R. "Surface Treatment and Finishing of
Light Metals." Metal Finishing. June 1955. p. 92.
21. Reference 13, p. 429.
22. Reference 13, p. 429.
23. Br1m1, M.f and Luck, J. Electroflnlshlng. American Elsevler
Publishing Company. New York. 1981, p. 77.
24. Reference 13, p. 430.
25. Snyder, D. "THvalent Chrom'lum Plating: The Second Decade."
Product Finishing. March 1988. p. 57.
26, Reference 25, pp. 59-60.
27. Reference 25, p. 63.
28. Reference 25. p. 65.
29. TMvalent Chromium Cost Enclosure: Harshaw/FHtrol Partnership.
Prepared for IK S. Environmental Protection Agency, Research Triangle
Park, North Carolina, by Dennis Maserlk, Manager of Technical
Services. June 22, 1987. p. 3.
30. Tomaszewskl, T., and Fischer, R. "Trlvalent Chromium: A
Commercially Viable Alternative." Occidental Chemical Crop. p. 5.
31. Reference 30, p. 5-6.
32. Chromium Electroplaters Test Report: Greensboro Industrial Platers,
Greensboro, North Carolina. Entropy Environmentalists, Inc.,
Research Triangle Park, North Carolina. Prepared for U. S.
Environmental Protection Agency, Research Triangle Park, North
Carolina. EM8 Report 86-CEP-l. March 1986.
33. Chromium Electroplaters Test Report: Consolidated Engravers
Corporation, Charlotte, North Carolina. Peer Consultants, Inc.,
Rockvllle, Maryland, Prepared for U. S. Environmental Protection
Agency, Research Triangle Park, North Carolina. EMB
Report S7-CEP-9. May 1987.
34. Chromium Electroplaters Test Report: Roll Technology, Greenville,
South Carolina. Peer Consultants, Inc., Dayton, Ohio. Prepared for
U. S. Environmental Protection Agency, Research Triangle Park, North
Carolina. EMB Report 87-CEP-6. September 1987.
44
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35. Chromium Electroplaters Test Report: Able Machine Company, Taylors,
South Carolina. PEI Associates, Inc., Cincinnati, Ohio. Prepared
for U. S. Environmental Protection Agency, Research Triangle Park,
North Carolina. EMB Report 86-CEP-3. June 1986,
36. Chromium Electroplaters Test Report: Roll Technology Corporation,
Greenville, South Carolina. Peer Consultants, Dayton, Ohio.
Prepared for U. S. Environmental Protection Agency, Research Triangle
Park, North Carolina. EMB Report 88-CEP-13. August 1988.
37. Chromium Electroplaters Test Report: Precision Machine and
Hydraulic, Inc., Worthington, West Virginia. Peer Consultants,
Dayton, Ohio. Prepared for U. S. Environmental Protection Agency,
Research Triangle Park, North Carolina. EMB Report 88-CEP-14.
September 1988.
38. Chromium Electroplaters Test Report: Hard Chrome Specialists, York,
Pennsylvania. Peer Consultants, Dayton, Ohio. Prepared for U. S.
Environmental Protection Agency, Research Triangle Park, North
Carolina. EMB Report-89-CEP-15. January 1989.
39. Emission Test Report: Norfolk Naval Shipyard, Norfolk, Virginia.
Naval Energy and Environmental Support Activity, Port Hueneme,
California. Source Emission Testing of the Building 195 Plating Shop
at Norfolk Naval Shipyard, Portsmouth, Virginia. March 11-18,
1985. NEESA 2-124. May 1985.
40. Chromium Electroplaters Test Report: Piedmont Industrial Platers,
Statesville, North Carolina. Entropy Environmentalists, Inc.,
Research Triangle Park, North Carolina. Prepared for U. S.
Environmental Protection Agency, Research Triangle Park, North
Carolina. EMB Report 86-CEP-04. September 1986.
41, Chromium Electroplaters Test Report: Steel Heddle, Inc., Greenville,
South Carolina. PEI Associates, Inc., Cincinnati, Ohio. Prepared
for U. S. Environmental Protection Agency, Research Triangle Park,
North Carolina. EMB Report 86-CEP-2. June 1986.
42. Chromium Electroplaters Test Report: GMC Delco Products Division,
Livonia, Michigan. Peer Consultants, Inc. Rockville, Maryland.
Prepared for U. S. Environmental Protection Agency, Research Triangle
Park, North Carolina. EMB Report 87-CEP-7. May 1987.
43. Draft Chromium Electroplaters Test Report: A Plant in the Midwest.
Prepared for U. S. Environmental Protection Agency, Research Triangle
Park, North Carolina. April 1988.
44. Memo from Barker, R., MRI, to Vervaert, A., EPA/ISB. Engineering
Analysis - Reliable Plating and Polishing Company. May 1987.
pp. 5-7.
45
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45. Chromium Emissions from Industrial Process Cooling Towers-Background
Information for Proposed Standards. Draft. Prepared for LI. S.
Environmental Protection Agency. Research Triangle Park, North
Carolina. May 1988.
46, Telecon. P. BelUn, MRI, with C. Bergesen, Utility Data Institute
(UDI), March 5, 1986. UDI study on chromate use 1n electric
utilities Industry.
47. Chromium Emissions from Comfort Cooling Towers-Background Information
for Proposed Standards. Prepared for U. S. Environmental Protection
Agency. Research Triangle Park, North Carolina. March 1988.
EPA-450/3-87-010a.
48. Holmberg, J. 0., and 0. L. Klnney. Drift Technology for Cooling
Towers. The Marley Company, Mission, Kansas. 1973.
49. Letter and attachments. Mayer, A., Chemical Manufacturers
Association, to Cuffe, S., EPA:ISB. September 27, 1986. Summary of
CMA member survey on corrosion Inhibitors used 1n process cooling
towers Including average ppm in redrculatlng water.
50. Telecon: C. Clark, MRI, with J. Holmberg, Marley Cooling Tower
Company. April 2, 1985. Drift eliminator efficiency.
51. Telecon: P. BelUn, MRI, with J. Holmberg, Marley'Cooling Tower
Company. July 19, 1985. Drift eliminator efficiency.
52, Kelly, G. M. A System Efficient-Approach to Cooling Tower Energy
Modifications. Cooling Tower Institute Technical Paper.
No. TP-85-18. New Orleans, Louisiana. January 1985,
53. Emission Test Report: National Bureau of Standards, Galthersburg,
Maryland. EMB Report 85-CCT-4. October 1986.
54. Emission Test Report: Exxon Company Petroleum Refinery, Baytown,
Texas. EMB Report 85-CCT-3. November 1986.
55. Emission Test Report: Southeastern Manufacturing Facility. EMB
Report 87-CCT-5. Draft. September 1987.
56. Abstracts of six confidential emission test reports conducted by MRI
for Industrial clients.
57. Letter and attachments. Hawes, R., Mobil 011 Corp., to Randall, D.,
MRI. August 24, 1987, Emission test results.
46
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TECHNICAL REPORT DATA
'• TSX7SS8-2-89-002 i2' X«C,«.NT,ACC«».ONNO.
4. TITLE AND SUBTITLE
Locating And Estimating Air Emissions From Sources
of Chromium (Supplement)
7. AUTHOfl(S)
Jeff Shular, Robin Barker, Bruce Nicholson,
David Randall
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Midwest Research Institute
401 Harrison Oaks Boulevard
Gary, North Carolina 27513
12. SPONSORING AGENCY NAME ANO ADDRESS
U. S. Environmental Protection Agency
OAR, OAQPS, AQMD, PCS (MD-15)
Research Triangle Park, North Carolina 27711
5. REPORT DATE
August 1989
6. PERFORMING ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO.
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-02-4395
13. TYPE OF REPORT ANO PERIOD COVERED
Fi na 1
14. SPONSORING AGENCY CODE
i
15. SUPPLEMENTARY NOTES
EPA Project Officer: Dallas U. Safriet
16. ABSTRACT
To assist groups inventorying air emissions of potentially toxic substances, EPA
is preparing a series of documents that compiles available information on sources
and emissions of toxic substances. This document deals specifically with methods to
estimate chromium (Cr+6) emissions from cooling towers and electroplating operations.
17. KEY WORDS ANO DOCUMENT ANALYSIS
a. DESCRIPTORS
Chromium (Cr+6)
Estimating Air Emissions
Air Toxic
Cooling Towers
Electroplating
18. DISTRIBUTION STATEMENT
Unlimited
b.lOENTIFIERS/OPEN ENDED TERMS
19. SECURITY CLASS (Tfiis Report!
Unclassified
20. SECURITY CLASS / This page)
Unclassified
c. COSATI Field/Group
21. NO. OF PAGES
50
22. PRICE
EPA F«* 2220-1
». 4— 77) PACV1OU3 EDITION t* OBSOLETE
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