EPA-450/2-77-032
December 1977
(OAQPSNo. 1.2-086)
GUIDELINE SEEIES
CONTROL OF VOLATILE
STATIONARY
VOLUME III:
COATING OF METAL
FURNITURE
I'.S. ENVIRONMENTAL PROTECTION AGE.NCY
Office of .Air and Waste Management
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
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EPA-450/2-77-032
(OAQPS No. 1.2-086)
CONTROL OF VOLATILE
ORGANIC EMISSIONS FROM EXISTING
STATIONARY SOURCES
VOLUME III: SURFACE COATING
OF METAL FURNITURE
Emissions Standards and Engineering Division
Chemical and Petroleum Branch
l.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Waste Management
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
December 1977
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OAQPS GUIDELINE SERIES
The guideline series of reports is being issued by the Office of Air Quality
Planning and Standards (OAQPS) to provide information to state and local
air pollution control agencies; for example, to provide guidance on the
acquisition and processing of air quality data and on the planning and
analysis requisite for the maintenance of air quality. Reports published in
this series will be available - as supplies permit - from the Library Services
Office (MD-35), U.S. Environmental Protection Agency, Research Triangle
Park, North Carolina 27711; or, for a nominal fee, from the National
Technical Information Service, 5285 Port Royal Road, Springfield, Virginia
22161.
Publication No. EPA-450/2-77-032
(OAQPS No. 1.2-086)
11
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PREFACE
This document is one of a series designed to inform Regional, State
and local air pollution control agencies of techniques available for
reducing emissions of volatile organic compounds (VOC) from existing
stationary sources. It deals with the surface coating of metal furniture.
"Metal furniture" includes any furniture made of metal or any metal part
which will be assembled with other metal, wood, fabric, plastic or glass
parts to form a furniture piece. This document describes the industry,
identifies sources and types of emissions, and applicable methods and costs
of reducing these emissions. It also discusses techniques for monitoring
the organic solvent content of coatings for purposes of determining
compliance with anticipated regulations, Detailed discussions on low
organic solvent coatings and add-on control technologies are found in
"Control of Volatile Organic Emissions from Existing Stationary Sources -
Volume I: Control Methods for Surface Coating Operations." ASTM test
methods for monitoring organic solvent technology are found in "Volume II:
Surface Coating of Cans, Coil, Paper, Fabric, Automobiles and Light Duty
Trucks,"2
The table below provides emission limitations that represent the
presumptive norm which can be achieved through the application of reasonably
available control technology (RACT). Reasonable available control technology
is defined as the lowest emission limit that a particular source is capable
of meeting by the application of control technology that is reasonably
available considering technological and economic feasibility- it may
EPA-450/2-76-028, November 1976, (OAQPS No. 1.2-067)
2EPA-450/2-77-008, May 1977, (OAQPS No. 1.2-073)
111
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require technology that has been applied to similar, but not necessarily
identical source categories. Since the definition of metal furniture
includes a wide variety of products, it must be cautioned that the emission
limits reported in this Preface are based on capabilities which are
general to this industry, but may not be applicable to every facility.
Affected Faci1ity Recommended Limitation
kg of organic solvent Ibs of organic solvent
emitted per liter of emitted per gallon of
coating (minus water) coating (minus water)
Metal Furniture Coating 0.36 3.0
Line
This emission limit is based on the use of low organic solvent coatings.
It can also be achieved with water-borne coatings and is approximately
equivalent (on the basis of solids applied) to use of an add-on control
device which collects or destroys about 80 percent of the solvent from a
conventional high organic solvent coating. Even greater reductions (up
to 90 percent) can be achieved by installing new equipment which uses
powder or electrodeposited water-borne coatings. It is believed that most
metal furniture facilities will seek to meet future regulations through
the use of coatings which are low in organic solvent.
IV
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GLOSSARY
Prime coat means, the first film of coating applied in a two-coat operation.
Topcoat means the final film of coating applied in a two-coat operation.
Single coat means, only one film of coating is applied on the metal
substrate.
Faraday caging means a repelling force generated during electrostatic
spraying of powders in corners and small enclosed areas of metal
substrate,
Blocking agent means an agent which is released from the polymer matrix
during the curing process. It is normally an organic radical and splits
from the monomer or oligmer at a predetermined temperature, thereby
exposing reactive sites which then combine to form the polymer. Such
reactions during the curing process may release additional volatile
organic compounds into the atmosphere.
Low organic solvent coating refers to coatings which contain less organic
solvent than the conventional coatings used by industry. Low organic solvent
coatings include water-borne, higher-solids, electrodeposition and powder
coatings.
v
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CONVERSION FACTORS FOR METRIC UNITS
Equivalent
Metric Unit Metric Name English Unit
Kg kilogram (103grams) 2.2046 Ib
liter liter 0.0353 ft3
3
dscm dry standard cubic meter 35.31 ft
3
scmm standard cubic meter per min. 35.31 ft /m"in
Mg megagram (10 grams) 2,204.6 Ib
metric ton metric ton (10 grams) 2,204.6 Ib
In keeping with U.S. Environmental Protection Agency policy,metric
units are used in this report. These units may be converted to common
English units by using the above conversion factors.
Temperature in degrees Celsius (C°) can be converted to temperature
in degrees Farenheit (°F) by the following formula:
t°f - 1.8 (t° ) + 32
t°f = temperature in degrees Farenheit
t° = temperature in degrees Celsius or degrees Centigrade
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TABLE OF CONTENTS
PREFACE iii
GLOSSARY v
CONVERSION FACTORS FOR METRIC UNITS , iv
1.0 SOURCES AND TYPES OF EMISSIONS 1-1
1.1 General Discussion 1-1
1.2 Processes and Emission Points 1-3
1.3 References 1-10
2,0 APPLICABLE SYSTEMS OF EMISSION REDUCTION 2-1
2.1 Powder Coating. . 2-2
2.2 Electrodeposition 2-3
2.3 Water-Borne Spray, Dip, or Flowcoat 2-4
2.5 Carbon Adsorption 2-6
2.6 Incineration. . , 2-8
2.7 References 2-10
3.0 COST ANALYSIS 3.-,
3.1 Introduction 3-1
3.1,1 Purpose 3-1
3.1.2 Scope 3-1
3.1.3 Use of Model Plants 3-2
3.1.4 Bases for Capital Cost Estimates . , 3-3
3.1.5 Bases for Annual ized Cost Estimates 3-3
3.2 Control of Organic Solvent Emissions -
Cost Estimates 3-4
3.2.1 Electrostatic Spray Line 3-6
3.2.2 Dip Line 3-10
3.3 Cost Effectiveness 3-11
3.4 Summary , 3-14
3.5 References 3-16
vn
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4.0 ADVERSE AND BENEFICIAL EFFECTS OF APPLYING
TECHNOLOGY 4-1
4.1 Powder Coatings 4-1
4,2 Electrodeposition 4-2
4.3 Water-Borne Coatings 4-4
4.4 Higher Solids Coatings. , . , 4-5
4.5 Carbon Adsorption 4-5
4.6 Incineration. 4-6
4.7 References. . , 4-8
5.0 MONITORING TECHNIQUES AND ENFORCEMENT ASPECTS 5-1
APPENDIX A - SAMPLE CALCULATIONS OF CONTROL OPTIONS A-l
References A-5
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1.0 SOURCES AND TYPES OF EMISSIONS
This chapter provides a general introduction to the metal furniture
industry, the methods by which conventional solvent-borne coatings are
applied, and volatile organic solvent (VOC) emissions which can be
expected from these coatings.
1.1 GENERAL DISCUSSION
Metal furniture is manufactured for both indoor and outdoor use, and
may be divided into two general categories; "business and institutional", and
"household" Business and institutional furniture is manufactured for use
in hospitals, schools, athletic stadiums, restaurants, laboratories and othet
types of institutions, and government and private offices. Household
metal furniture is manufactured mostly for home and general office use.
Although there are more than twice as many manufacturers of metal household
furniture, on the average, those that manufacture metal business and
institutional furniture are twice as large. About half of the metal house-
hold furniture manufacturers employ less than 20 employees. Metal furniture
includes a variety of items including tables, chairs, waste baskets, beds,
desks, lockers, benches, shelving, file cabinets, lamps, room dividers and
many other similar products.
Metal furniture plants are located throughout the United States, however,
Illinois, California, Michigan, New York and Pennsylvania contain over 50
percent of the plants in the industry. The Environmental Protection Agency's
Region V contains about 30 percent of the industry, Regions II and IV about
16 percent each, and Regions III and IX about 11 percent each. Plants vary
1-1
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in size depending on the type of furniture manufactured, the number of
manufacturing and coating lines, and the amount of assembly required.
The manufacturing markets of metal furniture facilities vary. Some
plants manufacture metal furniture to be sold directly to consumers
through retail stores. In contrast, "job shops", produce furniture on
contract. The latter facilities apply coatings on many different furniture
pieces according to the customer's specifications. The size of a metal
furniture coating line varies depending on the furniture coated, the type
of coating application used, and on how many coats are applied. The
coating line can have a steady production rate ranging from 8 to 24 feet
per minute, or the furniture pieces may be coated sporadically.
Coatings applied in each plant vary with personal preference, type of
furniture, application technique, pretreatment, and end use. Conventional
coatings are applied at 0.7 to 1.5 mils thickness. Most of the coatings
are enamels although some lacquers are also used. Some metal furniture
pieces are coated with metallic coatings. The most common coatings are
a'lkyds, epoxies and acrylics containing various mixtures of ketones,
aromatic, aliphatic, terpene, ester, ether and alcohol solvents. The coatings
are often purchased at higher solids contents but are thinned for application
to about 25 to 35 volume percent solids.
The coatings applied to metal furniture must protect the metal from
corrosion, be it indoor or outdoor furniture. They must have good adhesion
properties to avoid peeling or chipping, must be durable and must meet
customer standards of appearance.
1-2
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1.2 PROCESSES AND EMISSION POINTS
Figure 1-1 depicts a typical metal furniture line. Unassembled,
semi-assembled or totally assembled furniture pieces first are transported
on a conveyor through a cleansing process. Here an alkaline cleaner
removes mill scale, grease arid oil. After a hot rinse, iron phosphate or
other pretreatment often is employed to improve coating adhesion and prevent
rusting. Following a cold rinse, the pieces are dried at 130°-180°C
(250°-350°F). In some cases, the entire wash section is omitted and the
pieces are cleaned in a shot-blasting chamber or organic solvent cleaning
operati on.
Most metal furniture is finished with a single-coat operation. Some
pieces, however, require a prime coat application due to the topcoat
formulation or the end-use of the piece. The prime coat may be applied by
electrostatic or conventional spray, dip or flowcoating techniques. The
substrate with the prime coat then goes through a flashoff period to avoid
popping of the film when the coating is baked. The prime coat is usually
baked in an oven at about 160° to 200°C (300°-400°F).
The topcoat or a single coat may be applied by spraying, dipping or
flowcoating. If a Dlant manufactures furniture in a variety of colors,
necessitating frequent color changes, the coating is usually sprayed either
electrostatically or by conventional airless or air spray methods. If a
plant manufactures furniture in only one or two colors, the coating often
is applied either by flowcoating or by dipping.
Electrostatic spray coating may be performed either manually or auto-
matically although most spray coating in metal furniture facilities is done
manually. The paint particles are negatively charged, move along the path
1-3
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FROM
MACHINE SHOP
CLEANSING AND
PRETREATMENT
PRIME COAT, FLASHOFF AREA
AND OVEN
(OPTIONAL)
ELECTROSTATIC, OR
CONVENTIONAL AIR OR
AIRLESS SPRAY COATING
i
-"*"" "T
no
DIP COATING
nr
FLOW COATING
TOPCOAT OR SINGLE
COAT APPLICATION
Figure 1-1 Common techniques used in the coating of metal furniture nieces
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of an electric force field created between the spray gun and the grounded
metal furniture piece, and coat the piece. This method of application is
more efficient than the conventional air or airless spray methods because
there is less overspray thereby reducing the amount of paint that must be
sprayed and the VOC that evaporates.
Spray coating is performed in a booth to contain overspray and prevent
surface contamination, Two kinds of spray booths are usually found in
the metal furniture industry, down draft or side draft. Air flow rates
from spray booths vary depending on whether it is occupied by people,on type
of spray booth, and on size of spray booth and openings. The minimum air
velocities are prescribed by OSHA to assure capture of paint
particles and insure the VOC concentration does not exceed the threshold
limit values.
Dip coating is the immersion of pieces into a coating bath. After
withdrawal, the excess coating is allowed to drain back into the tank.
Flowcoating involves conveying the piece over an enclosed sink, and
allowing pumped streams of coating to hit the piece from all angles, flow
over the piece and coat it. Excess coating drains back into the sink, is
filtered and pumped hack into a coating holding tank.
The coated furniture is usually baked in an oven but in some cases is
air dried. The flashoff area lies between the coating application area
and the oven. This allows solvents to rise slowly in the coating film,
thus avoiding popping of the film when the coating is baked. The fraction
of the solvent which evaporates in this area will depend on the type
of coating used, line speed and the distance between the application area
and oven.
1-5
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The baking oven may contain several zones at temperature ranges of
160° to 230°C (300-450°F). The exhaust air flow rate from the ovens will
depend on the type and size of the oven, and the size of the oven openings
through which the parts enter and exit. Fire Underwriters Insurance
typically requires that the atmosphere within industrial baking ovens
not exceed 25 percent of the lower explosive limit (LEL) of the evaporating
solvents. This means that about 10,000 scf of air is required to evaporate
1 gallon of solvent. Some facilities have been allowed to operate at higher
LF.L's (around 50 percent), however, if proper LEL monitoring equipment is
used. Many metal furniture baking ovens presently operate between 5-15
percent of the LEL. The principle reason for maintaining such low concen-
tration levels is that the oven must be maintained under negative pressure to
avoid spillage of fumes into the plant. This requires a 15 mpm (50 fpm)
to a 45 fpm (150 fpm) air velocity through the oven openings. The lower
velocities are common to ovens which use air curtains to contain spillage.
Since the openings are often large to accommodate the variety of coated metal
furniture pieces, the air flow required to maintain the oven under negative pres-
sure may exceed the air flow required to maintain the oven below 25 percent LEL.
Volatile organic compounds are emitted from the coating area, the flash-
off area and the oven. It is estimated that in spray applications, about
65-80 percent of the VOC are released from the spray booth and the flashoff
area, and the remaining 20-35 percent from the oven. For a dip or flowcoat
application, it is estimated that about 50-60 percent of the VOC are emitted
from the coating and flashoff area, and the other 40-50 percent from the oven.
1-6
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Table 1-1 summarizes estimated VOC emissions from metal furniture coating
operations. Note that emissions will vary from line to line due to its
construction and the type of coating applied.
Figure 1-2 displays the relationship between VOC emissions and flow-
rate with isopleths of organic concentrations (LEL). Note that for a given
emission rate, the exhaust flowrate at one percent LEL concentration is
10 times that at 10 percent LEL. The flowrate and resulting concentrations
are a function of many factors; open or enclosed spray booths, dip or
flowcoater, flashoff area or an oven. Unfortunately, flowrates are often
designed for the worst situation and may be excessive for the typical
piece coated by the facility.
1-7
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oo
Table 1-1 DISTRIBUTION OF VOC EMISSIONS FROM METAL FURNITURE
COATING LINES3
Appl i cat ion
Method
Appl icati
Flashoff
on and
Area
Oven
Electrostatic Spray
Conventional Ai r or
65
80
35
20
Airless Spray
Dip 50 50
Flow 60 40
The base case coating is applied at 25 volume percent solids, 75 volume percent organic solvent
which is equivalent to a VOC emission factor of 0.66 kg of organic solvent per liter of coating
(5.5 Ibs/gal) minus water.
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40
Ol
S-
o
30
20
10
0
T r
i r
20 40 60 80 100 120 140 160 180 200
Ibs of organic solvent (VOC) emitted per hour
Figure 1-2. Relationship between VOC emission, exhaust flowrates and
VOC concentrations.
1-9
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1.3 REFERENCES
1. Sherman, Michael, S., Director of Economic and Market Research,
Summer and Casual Furniture Manufacturers Association, letter to
V. Gallagher in comment to draft of this document. Letters dated
August 5, 1977 and August 12, 1977.
1-10
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2.0 APPLICABLE SYSTEMS OF EMISSION REDUCTION
This chapter discusses low polluting coatings and add-on equipment
for the control of VOC from conventional coating applications used in the
metal furniture industry. It also discusses other methods of applying
coatings (powder and electrodeposition) which result in low VOC emissions.
Table 2 SUMMARY OF APPLICABLE CONTROL TECHNOLOGY
FOR METAL FURNITURE
Control Technology
Coating Application
Percent Reduction In
Organic Emissions
Powder (spray or dip)
Water-borne (electro-
deposition)
Water-borne (spray, dip
or flowcoat)
Higher solids (spray)
Carbon adsorption
Incineration
Top or single coat
Prime or single coat
Prime, top or single coat
Top or sing! e coat
Prime, top or single
coat (application
and flashoff areas)
Prime, top or single coat
(ovens)
95-99c
90-95C
60-90C
50-80C
90b
90L
The base case against which these percent reductions were calculated is a
high organic solvent coating which contains 25 volume percent solids and 75
volume percent organic solvents. The transfer efficiencies for liquid coatings
were assumed to be about 80 percent for spray and 90 percent for dip or flow-
coat, for powders about 93 percent, and for electrodeposition 99 percent.
bThis percent reduction in VOC emissions is only across the control device, and
does not take into account the capture efficiency.
2-1
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2.1 POWDER COATING
Powder coatings may be applied electrostatically by spraying or dipping,
or by dipping the preheated metal into a fluidized bed. Electrostatic
spraying of powder is used more widely in metal furniture than fluidized bed
because of its ability to coat the pieces with thinner films of coating.
Electrostatic sprayed powders can be applied at film thicknesses of 2 mils
or greater while fluidized bed powders are limited to 6 mils or greater.
After application, the powder particles are melted and cured in the oven to
form a continuous ,sol id film. Although powders appear to be 100 percent
solids, it is not unusual for them to contain small quantities of entrapped
organic solvent. Powders can release up to 10 weight percent of VOC during
the curing process. Therefore, the reduction in emissions for powders may
range from 95 to 99 percent over conventional systems. Powder coatings are
presently being applied on some furniture such as outdoor and indoor furniture,
234
bed and chair frames, shelving and stadium seating. ' '
Electrostatic powder spray coating may be performed either manually or
automatically. Powder particles are charged as they pass through the spray
gun, and subsequently are attracted to the grounded metal furniture piece.
The powder can wrap around the edges of complicated forms and is self-leveling
on flat pieces. Film thickness may be controlled by voltaqe^and a thickness of
3 to 4 mils can easily be achieved. Film thicknesses of 2 to 3 mils can be
achieved with special attention and a very close control. Thinner films, however,
have been achieved only in the laboratories and not on production lines.
Powder spray coating requires a booth as does spray coating with
conventional coatings. However, ventilation requirements are greatly reduced
from those of solvent borne spray booths mainly because the booths are not
occupied. This obviates the need to heat or air condition air going into the
2-2
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spray booth and saves energy. Most powder overspray may be reclaimed and
reused. Some overspray, however, has to be removed and reprocessed because
it consists of larger and heavier granules which are not suitable for reuse.
The ability to collect overspray can provide a high coating utilization. To
change colors in a powder coating system, the booth and recovery units must
be cleaned thoroughly to avoid color contamination. To shorten the time
required for a color changeover, some plants have several recovery units that
may be easily connected to the spray booth. Some have also purchased multiple
mobile spray booths with associated recovery equipment.
Powder coating may also be applied by dipping metal pieces into a fluidized
bed. In the metal furniture industry, dipping has the disadvantage of apply-
ing powder only in thick films (at least 6 mils). The metal furniture piece
is preheated to the melting point of the powder, dipped into the bed and
held there until the desired film thickness is achieved. In electrostatic
fluid bed coating, the powder particles are charged and become attracted to
the grounded,usually unheatedimetal piece moving through the bed. The latter
method is limited to simple shapes.
Powder coatings are baked at temperatures of 180° to 230°C (300-450°F).
Since the concentrations of organics are almost insignificant compared to
conventional coatings and no flashoff zones are required, smaller ovens may be
installed. Further technical details on the use of powder coating's may be
found in Volume I, Sections 3.3.3 and 3.3.5.
2.2 ELECTRODEPCS IT ION
Electrodeposition (EDP) is being used at several facilities to coat metal
furniture with 0.5 to 1.2 mils of film thickness. ' The thickness may
be adjusted somewhat by varying voltage and immersion time. Electrodeposition
2-3
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provides increased corrosion protection and applies thin coatings more
uniformly and at a greater transfer efficiency than any other application
system. Although electrodeposition was previously limited to one to two
colors, a new installation will be applying four different colors.
EDP coatings are applied from an aqueous bath which contains about
10-15 volume percent solids and 2-4 volume percent organic solvents. A
direct current is applied in the bath causing the solids to become attached
to the grounded metal piece. Electrodeposition can be performed either
anodically or cathodically. The metal emerges from the bath with a coating
containing about 90 volume percent solids, 1 to 2 percent organic solvent and
the balance water. It is rinsed to eliminate excess paint particles and
baked at 160° to 180°C (300-350°F). The rinsing water is often obtained from
the discharge from the ultrafilter. Ultrafiltration purges most of the
soluble organics, amines and contaminating ions from the rinse residue and
returns the solids portion to the bath.
For further technical details in the use of electrodeposition coating
12
technology, see Volume, Section 3.3.1.
2.3 WATER-BORNE - SPRAY, DIP OR FLOWCOAT
Since water-borne coatings have similar characteristics to organic
solvent-borne coatings, they can often be substituted for existing solvent-
borne coatings without requiring major changes to existing coating equipment.
There may be however, some necessary alterations in equipment or the coating
line to protect the equipment from corrosion,to lengthen the flashoff area
and sometimes to control the humidity in the application and flashoff areas.
Several metal coating facilities have been successful in converting their
existing flow, dip and spray (both electrostatic and conventional) operation
to apply water-borne coatings.
2-4
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Some organic solvents must be a part of a water-borne coating to
temper the evaporation rate,and to provide film coalescence and the necessary
film properties. A reduction of 60-90 percent in VOC emissions may be
obtained by conversion to a water-borne coating.
Water-borne coatings may be sprayed electrostatically on small coating
limes if the entire coating system is electrically isolated. On larger lines,
however, where the paint storage areas are hundreds or even thousands of
feet away from the application areas, electric isolation of the entire
system becomes difficult and sometimes financially impractical. ' Color
changes often require only that the application system be flushed out with
water. Coating with water-borne coatings may require more attention to the
coating process since temperature, humidity, gun-to-metal distance and
flashoff time may change the looks and performance of the coating. Conventional
air and airless spray techniques may also be used to apply water-borne coatings.
Further technical details on the use of water-borne coatings may be found in
Volume I, Sections 3.3.1 and 3.3.5.15
2.4 HIGHER SOLIDS SPRAY
The achievable VOC emission reduction by switching to higher solids
coatings may range from 50 to 80 percent depending on the type of coating
used previously and the volume percentage of solids. Higher solids coatings
are being used on both pilot and full production lines.
Higher solids coatings can be applied most efficiently by automated
electrostatic spraying although manual and conventional spraying techniques
can also be used. Some minimal increase in energy may be required to raise
the pressure of the spray gun, heat the coating, or power electrostatic spray
2-5
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equipment in order to pump and atomize these coatings due to their higher
viscosities. Transfer efficiencies of higher solids coatings are often
better than those of conventional coatings, particularly when sprayed
18
electrostatically.
As the solids content is increased in a coating, less solvent is
released for each dry mil of coating. This may permit some reduction in
air flow to the booth (if the air flow was originally'determined by the threshold
1 g
limit of organic solvents) resulting in an energy savings. This reduction
however, will be limited by the successful collection of overspray particles. The
lower solvent content may also allow the air flow from the oven to be reduced.
Further technical details on the use of high solids coatings may be
20
found in Volume I, Section 3.3.2.
2.5 CARBON ADSORPTION
As discussed in Chapter 1, from 50 to 80 percent of the volatile organic
compounds from metal furniture coatings are emitted from the application
and flashoff areas. The use of carbon adsorption can reduce emissions from these
areas by 75 to 90 percent depending on the capture efficiency into the control
device.
Carbon adsorption is considered a viable control option for the
application and flashoff areas because exhaust gases are at ambient temperature
and contain only small amounts of particulate matter that could contaminate
the carbon bed. Although there are no known installations of a carbon
21
adsorption system in a metal furniture plant, it is technically feasible,
and no new invention would be required. Pilot studies will be necessary,
however.
2-6
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The size of a carbon adsorption unit is dependent on the exhaust flow
rate, its desorption period and VOC concentration. The flow rates and
volatile organic concentrations will vary from each facility because of
the wide variety of metal furniture manufactured. If any reduction in
the flow rate of the exhaust air (within compliance with safety regulations)
can be achieved, a smaller and less expensive carbon adsorber can be used.
This reduces both capital and fixed operating costs. In order to optimize
application of an add-on control device, the flashoff areas must be enclosed
to minimize intrusion of air.
In conventional spray booths, some particulate matter from overspray is
captured by dry filters, or water or oil wash curtains at about 95 percent
22
efficiency. Additional particulate removal, however, may be necessary to
prevent contamination of the carbon bed. Although there is little possibility
that the recovered solvents may be directly recycled (because of the complex
solvent mixtures), they may be valuable as supplementary fuel for boilers or
heaters.
Carbon adsorption systems can be large and require a large amount of
floor space. Some large metal furniture facilities may require several dual-bed
carbon adsorption units in parallel operation. Availability of the requisite
space is an important consideration. The metal furniture operator may have
to construct an addition to the plant.
Further technical details on the use of carbon adsorption may be found
23
in Volume I, Section 3.2.1.
2-7
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2.6 INCINERATION
There are no serious technical problems associated with the use of
either catalytic or noncatalytic incinerators on metal furniture facilities.
Incineration has been used to reduce VOC emissions from ovens in metal
24
furniture facilities.
Incinerators are more efficient than carbon adsorbers for reducing VOC
emissions from metal furniture ovens. Although some energy is. required to bring
the oven exhaust to incineration temperature, this incremental energy can
be minimized by the use of primary heat exchangers. The concentration of organic
vapors is usually higher in the oven exhaust (5-15 percent of LEL) than in
the application and flashoff areas and provides some fuel for the incinerator.
Particulate and condensible matter that is often found in the exhaust from
higher temperature baking ovens will not affect an incinerator, whereas, it
will coat a carbon bed and render it ineffective. Incineration can also be
used to reduce VOC from application and flashoff areas. It will normally
be necessary (but not always possible) for the operator to incorporate heat
recovery systems to reduce fuel consumption to an acceptable level. Otherwise
incineration of ambient temperature, low VOC concentration, gas streams is
often energy intensive.
If the exhaust rate can be lowered, within the limits of health and
fire safety regulations, less fuel will be required in the incinerator. Also
higher VOC concentration will provide a greater fraction of the total fuel
requirement. Thus, increasing the VOC level not only reduces the size of
the required incinerator and its capital and fixed operating cost, but also
the fuel requirements. The degree of difficulty in retrofitting incinerators
2-8
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to existing metal furniture facilities will vary depending on the age of the
equipment and facility, and where the equipment is located.
In the past, most incinerators were fired with natural gas. Due to
the energy shortages, some incinerators have been converted to No. 2 fuel
oil, and more energy recovery methods have been used to reduce energy
consumption.
Further technical details on the use of incineration may be found in
Volume I, Section S.2.2.26
2-9
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2.7 REFERENCES
1. LeBras, Louis R., Technical Division Director, PPG Industries, Pittsburgh,
Pa. Letter to Vera Gallagher in comment to draft of this document.
Letter dated September 22, 1977.
2. Springborn Laboratories, Inc., (formerly DeBell & Richardson, Inc.)
Trip Report Nos. 57,72,85,86,100,108, General Surface Coating Study
Contract by EPA 68-02-2075.
3. "Powder System Cuts Finishing Costs at Westinghouse" and "Powder Coating
Seating Scores at Iowa State's New Statium": Powder Finishing World.
Pages 20-22 and 50-52. Second quarter, 1975.
4. Besselsen, John, Painting With Powder. Technical Paper presented at the
Association for Finishing Processes of Society of Manufacturing Engineers
in Cincinnati, Ohio, 1975. (FC 76-431).
5. LeBras, Op. Cit.
6. Dornbos, David L. Sr., Steelcase Incorporated, Grand Rapids, Michigan.
Letter to Vera Gallagher in comment of this document. Letter dated
August 31, 1977.
7. OAQPS Guidelines "Control of Volatile Organic Emissions From Existing
Stationary Sources-Volume I" Control Methods for Surface Coating Operations",
EPA - 450/2-76-028; November 1976.
8. Springborn Laboratories, Trip Report No. 103. General Surface Coating Study,
Contract by EPA 68-02-2075.
9. Schrantz, Joe, Twin Electrostatic Tanks Add Versatility at Star Industries.
Industrial Finishing, pages 20-26. January 1976.
10. Two Electrocoating Tanks Boost Production at Waterloo Industries, Industrial
Finishing, pages 34-36. June 1975.
11. LeBras, Op. Cit.
12. Volume I, Op. Cit.
13. Dornbos, Op. Cit.
14. Zimmt, Werner S., Research Fellow, E.I. DuPont de Nemours & Company.
Letter to Vera Gallagher in comment to draft of this document. Letter
dated August 25, 1977.
15. Volume I, Op. Cit.
16. Springborn Laboratories Trip Report No. 41. General Surface Coating Study
under Contract by EPA 68-02-2075.
2-10
-------
17. DeVittorio, J. M., Application Equipment for High-Solids and Plural
Component Coatings. High-Solids Coatings, Volume I, No. 2, April 1976.
18. LeBras, Op. Cit.
19. Lunde, Donald I., Aqueous and High-Solids Acrylic Industrial Coatings.
High-Solids Coatings, Volume I, No. 2, April 1976.
20. Volume I, Op. Cit.
21. Johnson, W.R., General Motors Corporation, Warren, Michigan. Letter
to Radian Corporation commenting on "Evaluation of a Carbon Adsorption
Incineration Control System for Auto Assembly Plants." EPA Contract
No. 68-02-1319, Task No. 46, January 1976. Dated March 12, 1976.
22. Johnson, W. R., General Motors Corporation, Warren, Michigan. Letter
to James A. McCarthy dated August 13, 1976.
23., Volume I, Op. Cit.
24, Springborn Laboratories, Inc. Trip Report No. 57, General Surface
Coating Study Contract by EPA 68-02-2075.
25. Volume I, Op. Cit.
2-11
-------
3.0 COST ANALYSIS
3.1 INTRODUCTION
3.1.1 Purpose
The purpose of this chapter is to present estimated costs for con-
trolling solvent emissions from existing coating lines at metal furni-
ture plants.
3.1.2 Scope
Estimates of capital and annualized costs are presented for control-
ling VOC (Volatile Organic Compounds) from application areas and curing
ovens associated with electrostatic spray and dip coating lines applying
a single coat to metal shelves. The control alternatives considered
applicable to a coating line using the conventional solvent thinned
coating and for which cost estimates are developed include:
Alternative I - Process Modification
Conversion to a coating system applying one of the following
low solvent coating materials:
1. Higher solids (70% or above)
2. Waterborne
3. Powder
Alternative II - Exhaust Gas Treatment
Installation of hydrocarbon control equipment:
1. Carbon adsorption for application exhausts
2. Thermal incineration for oven exhausts
3-1
-------
Detailed control costs estimates are developed for existing coating
? 2
lines with annual production rates of 278,000 m/yr. and 4,000,000 m/yr.
2 ?
for electrostatic spraying and 650,000 m /yr. and 2,100,000 m/yr. for
dip coating. The cost: effectiveness (annualized cost (credit) per metric
unit weight of VOC controlled) for the alternative control measures
considered are estimated and graphically displayed for the range of pro-
duction rates analyzed.
3.1.3 Use of Model Plants
The cost analysis provided in this chapter relies upon the use
of model coating lines that are basically defined by an annual product
coverage rate (square meters/year) for 1920 hours operation. In general,
no attempt has been made to consider detailed design characteristics
for the model lines in terms of process equipment requirements, line
speed, etc. However, it was necessary to estimate the number of spray
booths, required coating thickness, transfer efficiencies, oven and
booth exhaust rates in order to estimate capital and operating costs for
the control alternatives considered.
It is emphasized that model coating lines used in this analysis are
particularly simple in that a one color single coat is applied to metal
shelves. Analyzing multi-color coating systems is beyond the scope of
this analysis although some general cost implications will be summarized
later. Other factors influencing cost analyses of coating lines dif-
ferent than the models chosen will be covered in the discussion of the
bases for model line cost estimates. Finally, although control cost
3-2
-------
estimates based upon the model plant approach may differ with actual
costs; incurred, they are considered to be the best means of comparing
the relative costs and cost-effectiveness of alternative control measures.
3.1.4 Bases for Capital Cost^ Estimates
Capital cost estimates are intended to represent the total capital
required to purchase and install necessary control or process equipment.
For coating lines converting to low solvent coatings, capital costs
for control are generally incremental investments required to apply the
different coatings. It has been assumed throughout the model cost analysis
that existing pre-treatment and curing equipment will not require modi-
1 2
fication in going to low-solvent coatings. " This should not be interpreted
to mean that such modifications are unnecessary in all cases. Rather,
factors such as finish specifications and the condition of existing equip-
ment will dictate how capital investments for actual lines will compare
with the model estimates. The cost estimates provided were developed
from EPA contractor studies and by contacting facilities that have im-
plemented coating line conversions. ' ' All capital costs are intended
to reflect second quarter 1977 dollars.
3.1.5 Bases forAnnualized Cost Estimates
Annualized cost estimates for the control alternatives considered
are developed to reflect annual charges for capital required to purchase
and install process equipment or control systems, operating and maintenance
costs and miscellaneous recurring costs such as taxes, insurance and admin-
istrative overhead. Capital charges are calculated using the "capital
3-3
-------
recovery factor" formula. Operating costs include costs for materials,
utilities, labor and waste disposal. Net annualized costs for process
changes, i.e. line conversions, are the incremental costs in going from
the conventional solvent coating to the low solvent coating. As evidenced
later in this chapter, some conversions are projected to result in net
annualized savings while others appear to result in increased annual costs.
The bases for these projected incremental costs or savings were provided
in References 1 and 2. Again it is emphasized that these model coating
line analyses are provided as a means of comparing the relative costs of
alternative control measures. The area of estimating incremental annual
costs (savings) for alternative coatings is one in which all coating
suppliers have devoted considerable resources. Unsurprisingly, varying
some key assumptions can alter the conclusions drastically. Annual
coating material costs appear to have the greatest impact on annual costs
(savings) when comparing different coatings. Differences in coating
thickness requirements, transfer efficiencies, raw material costs and solids
content all influence this cost element. Assumptions used in this analysis
are provided later in Table 3-2 which lists technical assumptions associated
with the model coating lines. General cost factors used to estimate an-
nualized costs for the model coating lines are provided in Table 3-1. All
annualized cost estimates are current.
3.2 CONTROL OF SOLVENT EMISSIONS FROM METAL FURNITURE SURFACE COATING
- COST ESTIMATES
The technical parameters used in developing the control cost estimates
3-4
-------
II.
Table 3-1. COST FACTORS USED IN COMPUTING ANNUALIZED COSTS
Direct Operating Costs
A. Materials (As purchased):
*
- Alkyd conventional solvent coating (40% solids)
*
- Polyester high solids coating (70% solids)
*
- Alkyd Waterborne coating (40% solids)
- Epoxy powder coating
- Electrodeposition waterborne (60% solids)
- Carbon
2. Utilities
- Electricity 0.03/kw-hr
- Natural gas
- Steam
$2.00/liter ($8/gal)
$3.70/liter ($14/gal)
$2.40/liter ($9/gal)
$3.30/kg ($1.50/lb)
$2.90/liter ($ll/gal)
$2.20/kg ($1.00/lb)
$1.90/thousand joules
($2.Do/million Btu)
$5.50/thousand Kg
($2.50/thousand Ib)
- Boiler feed water
3. Direct Labor
4. Maintenance Labor
- Process modifications
- Add-on systems
5. Maintenance Materials
6. Waste Disposal
- Electrodeposition
- All others
Annualized Capital Charges
1. Depreciation and interest
2. Taxes, insurance, administrative charges
* By volume
$0.13/thousand liters
($0.50/thousand gal)
$10/man-hour
$10/man-hour
0.02 x Capital Cost
0.02 x Capital Cost
$0.008/1 Her coating ($0.03/gal)
$0.03/liter coating ($0.11/gal)
0.1468 x Capital Cost
0.04 x Captial Cost
3-5
-------
provided in Tables 3-3 and 3-4 are summarized in Table 3-2. Additional
information regarding the expected range for many of these parameters is
included in Chapters Two and Three of this document.
3.2.1 Electrostatic Spray Lijie^
Capital and annual ized costs for control alternatives applicable to
electrostatic spray coating lines are presented in Table 3-3. Capital costs
for converting lines to higher solids coatings (70% and above) or to waterborne
coatings are related to application equipment modifications only. Sources
estimated conversion costs at between $10,000-$15,000 per automatic station
and about $1,000 for manual booths. ' The above estimates change radically
for waterborne if paint sources are not located close to application equipment
and if stainless steel piping is required for paint recirculation systems.
Additionally, as mentioned in Chapter Three, attempting to insulate the remote
paint source configuration from ground to comply with OSHA requirements creates
technical problems. Capital costs for converting to a powder coating are
associated with installation at powder application and recovery systems. Since
models considered are one color lines, only one recovery system is included
in capital cost estimates. Multi-color lines with production rates comparable
to model lines may realize higher costs for additional recovery systems in
order to minimize the longer times associated with powder color changes.
Capital costs for achieving VOC emission reductions comparable to low solvent
coatings (i.e., 80% and greater) using exhaust gas treatment appear to be
greater than line conversion costs.
3-6
-------
Table 3-2. TECHNICAL PARAMETERS FOR MODEL COATING LINES
Electrostatic Spray Line
Number of Booths
Automatic
Manual
Dry Coating Thickness, i,m (mils)
Conventional solvent
Higher solids
Waterborne
Powder
Transfer efficiencies
o
Exhaust gas volumes, N_ m /sec (scfm)
Oven(s)
Booth(s)
Dip Line
Dry Coating Thickness, nm (mils)
Conventional solvent
Waterborne
Electrodeposition
Transfer Efficiencies
TI
Exhaust gas volumes, NnT'/sec. (scfm)
Oven
Dip Tank
278.000 nT/yr.
1
2
25(1)
25(1)
25(1)
50(2)
Same as Table 2
0.24
(500)
4.25
(9000)
650,000 m2/yr.
25(1)
25(1)
17.5(0.7)
4,000.000 nr/yr.
4
2
25(1)
25(1)
25(1)
50(2)
Chapter 2
3.30
(7000)
20.8
(44,000)
2,100,000 m2/yr.
25(1)
25(1)
17.5(0.7)
Same as Table 2 - Chapter 2
.94
(2000)
1.41
(3000)
1.41
(3000)
3.76
(8000)
3-7
-------
Table 3-3. CONTROL COSTS FOR WDEL EXISTING ELECTROSTATIC SPRAY COATING LINES
Alternative I - Process Change:
Installed Capital Cost ($000)
Direct Operating Costs (savings)
($000/yr)f
Capital Charges ($000/yr.)
Net Annualized Cost (credit)($000/yr)
Solvent Emissions Controlled (Mg/yr)-
Percent Emission Reduction
Cost(credit) per Mg of VOC
controlled (S/Mg)
278,000 Square Meters/Veara
(3.000,000 Square Feet/Year)
Baseline Costs Incremental Costs for Conversion^
25% solids
255b
175
48
223
NA
NA
Higher
Solids
15C
(6)
3
(3)
19
86
Waterborne
15d
5
3
18
80
NA (158) 444
Powder
60e
17
11
28
22
97
1273
4,000,000 Square Meters/Year3
(48,000,000 Square Feet/Year)
Baseline Costs Incremental Costs for Conversion
25% solids
l,200b
1,113
224
1 ,337
NA
NA
NA
Higher
Solids
62C
(81)
12
(69)
305
86
(226;
1
Waterborne
62d
50
12
62
285
80
217
Powder
317e
343
59
402
345
97
1165
!
Alternative II - Exhaust Gas Treatment
Installed Capital Cost ($000)h
Direct Operating Costs ($000/yr)h
Capital Charges (SOOO/yr)
Net Annualized Cost (SOOO/yr)
Solvent Emissions Controlled (Mg/yr)
Percent Emission Reduction (Total)
Cost per Mg of VOC controlled ($/Mg)
- - ' - -
(Oven)
Thermal Incinerator
with Primary
Heat Recovery
36
5
7
12
4
18
3,000
(Spray Booth)
Carbon Adsorption
Solvent at
Fuel Valve
92
17
17
..
34
15
68
2,266
Oven
and
Booth
128
22
24
46
19
86
2,421
(Oven)
Thermal Incinerator
with Primary
Heat Recovery
150
31
28
59
64
18
922
(Spray Booth)
Carbon Adsorption
Solvent at
Fuel Value
500
82
93
175
241
68
723
Oven
and
Booth
650
113
121
234
305
86
767
One color system operating 1920 hours/year and coating metal shelves - single coat.
Excludes metal pre-treatment equipment and dry-off oven costs for line (reference 1,2)
Application and paint circulating equipment modifications (references 3, 10).
Better insulation from ground to prevent electrical shock and corrosion protection (references 3,4)
eBooths and recovery system (reference 6).
References 1,2.
9Mg = megagram = 1 metric ton
References 1,2.
-------
Table 3-4. CONTROL COSTS FOR MODEL EXISTING DIP COATING LINES
Alternative I - Process Change:
Installed Capital Cost ($000)
Direct Operating Costs (Savings)
($000/yr)
Capital Charges (SOOO/yr)
Net Annual ized Cost (credit) (SOOO/yr)
Solvent Emissions Controlled (Mg/y)9
Percent Emission Reduction
Cost (credit) per Mg of VOC
controlled ($/Mg)
650,000 Square Meters/Year0
(ZipOO.OOO Square Meters/YearJ
Basel ine Costs
25% Solids
105b
135e
20
155
NA
NA
NA
Increniental Costs for Conversion
Waterborne
3C
10e
1
1]
25
80
440
EDP
124d
2f
23
25
38
92
657
2,100,000 Square Meters/Year
(22,500,000 Square Feet/Year|
Baseline Costs
25% Solids
215^
450e
40
Incremental Costs for
Waterborne
5C
!7e
i
490 18
NA
NA
NA
111
80
162
a
Conversion
EDP
208d
7f
39
46
128
92
359
(Dip Tank)
Alternative II - Exhaust Gas Treatment
Installed Capital Cost ($000)h
Direct Operating Cost ($000/yr)
Capital Charges ($000/yr)
Net Annual ized Cost ($000/yr)
Solvent Emissions Controlled (Mg/yr)
Percent Emission Reduction (Total)
Cost per Mg of VOC Controlled ($/Mg)
(Oven)
Thermal Incinerator
with Primary
Heat Recovery
93
8
17
25
18
45
1,388
Carbon Adsorption
Solvent at
Fuel Valve
150
6
28
34
18
45
1,888
Oven
and
Tank
243
14
45
59
36
90
1,638
(Oven)
'hermal Incinerator
with Primary
Heat Recovery
119
12
22
34
63
45
540
Carbon Adsorption
Solvent at
Fuel Valve
270
9
50
59
63
45
936
Oven
and
Tank
389
21
72
93
126
90
738
One color system operating 1920 hours/year and coating metal shelves - no primer.
Excludes metal pre-treatment and dry-off oven costs (references 1,2).
cExisting tank cleaned and corrosion protection (reference 5).
Existing solvent dip coating system replaced by EDP system (references 1,2,7).
References 1,2.
Reference 8.
9Mg = Megagram = 1 metric ton
^References 1,2.
-------
Net annual savings appear possible by converting to higher solids
coatings due mainly to the estimated lower applied film cost when compared
to conventional solvent coatings.
As noted in Table 3-1, coating material costs for waterborne are
slightly higher than solvent coatings for the same volume solids. This
results in higher annual costs when converting to waterborne coatings. For
lines converting to powder coatings some energy, waste disposal and direct
1 2
labor savings were estimated. ' However, as indicated in Table 3-2, it is
assumed that metal furniture requires a coating thickness of 50 ym (2 mils)
when coating with powders. This factor greatly diminishes any materials cost
savings normally expected with powder coatings when compared to conventional
solvent coatings.
In the case of incineration of oven emissions, annualized costs are
mainly costs for fuel required to raise the temperature of the oven exhaust
from 160°C to 760°C and capital charges. Annual costs for carbon adsorption
of spray booth exhausts are slightly reduced (less than 2%) by crediting recovered
solvent at fuel value. Large capital investments required for carbon
adsorption systems are reflected in high capital charges. In general, net
annualized costs for controlling VOC emissions from electrostatic spray coating
lines appear to be lowest when converting to higher solids or waterborne
coatings and greatest when combining incineration and carbon adsorption
of oven and spray booth exhausts, respectively.
3.2.2 Dip Line
Capital and annualized costs for the control alternatives considered
for existing dip lines are summarized in Table 3-4. The incremental capital
costs for converting the dip line to waterborne appear to be small when compared
to the baseline investment. Costs assume that the existing dip tank is used
3-10
-------
and some corrosion protection is required. On the other hand, dip lines
converting to the waterborne electrocoat will require significant investments
when installing the electrodeposition application system. Capital costs for
oven exhaust incineration and carbon adsorption of dip tank exhausts for the
model dip lines are approximately two times greater than converting to
electrodepos i ti on.
Increased annualized costs for controlling dip coating lines by conversion
to waterborne are primarily a result of higher material costs for the water-
borne coating. For electrodeposition, lower applied film costs for the
electrocoat material help over-ride increased electrical costs associated
"I Q
with the electrodeposition system. ' Although incremental direct operating
cost increases for the electrodeposition system appear to be minimal in
Table 3-4, capital charges associated with the large capital investment
requirements are much higher than waterborne conversion. Total annualized
costs for incineration and carbon adsorption presented in Table 3-4 are about
two times greater than incremental annualized costs for electrodeposition and
about five times greater than waterborne annualized costs.
3.3 COST-EFFECTIVENESS
The cost-effectiveness of the alternative control measures considered for
electrostatic spray and dip coating lines are summarized in Table 3-5. For
electrostatic spray lines it appears to be more cost effective to reduce VOC
emissions by converting to a low solvent coating, either waterborne or higher
solids. Conversion to powder coating will result in the highest emission
reduction achievable yet is not nearly as cost-effective as waterborne or
3-11
-------
Table 3-5. COST EFFECTIVENESS OF ALTERNATIVE CONTROL METHODS
CO
I
Spray Coating Line:
A. Conversion to Higher Solids Coating
B. Conversion to Waterborne coating
C. Conversion to Powder Coating
D. Thermal Incinerator on Oven &
Carbon Adsorber on Spray Booths
E. Carbon Adsorber on Spray Booth
F. Thermal Incinerator on Oven
Dip Coating Line:
G- Conversion to Waterborne
H. Conversion to Electrodeposition
I- Thermal Incinerator on Oven &
Carbon Adsorber on Spray Booths
(Dip Tank)
J. Carbon Adsorber on Spray Booths
(Dip Tank)
K. Thermal Incinerator on Oven
$/Mg of VOC Controlled
278,000 m2/yr.
(158)*
444
1273
2421
2266
3000
$/Mq of VOC
650,000 m2/yr.
440
657
1638
1888
1388
4,500,000 m2/yr.
(226)
217
1165
767
723
922
Controlled
2,100,000 m2/yr
162
359
738
936
540
% Reduction in VOC
86
80
97
86
68
18
% Reduction in VOC
80
92
90
45
45
*Parenthesis indicates credit
-------
Figure 3-1. Cost-Effectiveness versus Surface Area Coated
(Baseline=25% Solids Conventional Coating)
3000
2000
-o
O)
o
o
o
en
i.
O)
Q.
O)
i.
u
LO
O
O
1000
Electrostatic Spray
Dip
NOTE: Refer to Table 3-5
for code to letters
(500)
234
Million Square Meters/Year
3-13
-------
higher solids conversions. In fact, at higher production rates the results
appear to indicate that it is more cost-effective to incinerate oven exhausts
and treat booth exhausts by carbon adsorption than convert to powder coatings.
For dip coating lines, converting to an alternative coating appears to be a more
cost-effective measure for reducing VOC emissions than incineration and carbon
adsorption. Although the model analysis estimates a 92% reduction in VOC by
converting to electrodeposition, the cost per megagram of VOC controlled is
higher than waterborne conversion over the range of sizes studied. Cost-
effectiveness values from Table 3-5 and an additional estimate of cost-effective-
ness for each application method were plotted and the results are displayed
in Figure 3-1. Smooth curves drawn through the points depict how cost-
effectiveness is expected to vary with square feet coated per year.
3.4 SUMMARY
Based upon the model analyses performed on electrostatic spray and dip
coating lines applying finishes to metal shelves, VOC reductions of 80 percent
or greater can be achieved at the least cost per unit weight of VOC controlled
when using existing (modified) application equipment while applying low solvent
coatings. For electrostatic spray lines, converting to higher solids coatings
(70% or greater) or a waterborne coating appears to be the most cost effective
control alternative. The latter alternative, however, may have limited application
due to the technical arid cost implications associated with some line configurations.
For clip coating lines conversion to waterborne, where applicable, seems the
most cost-effective alternative. Controlling VOC emissions by incineration
and carbon adsorption appears to be the least cost-effective alternative for
3-14
-------
the model lines considered.
Finally, it is stressed that the results of this analysis are intended
only to serve as guidance in assessing the relative costs of alternative
control schemes. Individual requirements and specifications of a particular
coating line may require analysis when determining costs for that specific
coating line.
3-15
-------
3.5 REFERENCES
1. Second Interim Report on Air Pollution Control Engineering and
cost study of the General Surface Coating Industry Prepared by
Springborn Laboratories, Inc. under EPA contract no. 68-02-2075
August 23, 1977
2. Second Interim Report on Air Pollution Control Engineering and
Cost Study of the General Surface Coating Industry - Appendices
A & B. Prepared by Springborn Laboratories, Inc. under EPA contract
no. 68-02-2075, August 23, 1977
3. Personnal communication to John Pratapas, USEPA/SASD, from Bill
White - DeVilbiss, Toledo, Ohio, November 29, 1977
4. Trip Report - Keller Industries, Mil ford, Va. from W.B. Kloppenburg
of Springborn Laboratories to David Patrick, USEPA/ESED, February
23, 1976
5. Personnal communication to John Pratapas, USEPA/SASD, from Margo
Oge - Springborn Laboratories, April 29, 1977
6. DeVilbiss Case History - Powder coating Technical Handbook PC-1001
July 15, 1974
7. Personnal communication to John Pratapas, USEPA/SASD, from James
Johnson, The Shaw-Walker Co. Muskegon, Michigan, November 29, 1977
8. Personnal communication to Vera Gallagher, USEPA/ESED, from L.R.
LeBras, PPG Industries, Pittsburgh, Penn. , September 22, 1977.
9. Personnal communication to John Pratapas, USEPA/SASD, from Frank
Merlotti - Steelcase, Inc. Grand Rapids, Michigan, June 9, 1977.
10. Personnal communication to John Pratapas, USEPA/SASD, from Clyde
Speir - Lyon Metals, Aurora, Illinois, December 8, 1977.
11. High Solids Coatings Volume 2, No. 2, Technology Marketing Corporation
Stamford, Conn., April 1977
12. Capital and Operating Costs of Selected Air Pollution Control
Systems, GARD, Inc., Niles, Illinois, EPA contract no. 68-02-2072,
May 1976
13. Control of Volatile Organic Emissions from Existing Stationary
Sources - Volume I: Control Methods for Surface-coating operations.
3-16
-------
4.0 ADVERSE AND BENEFICIAL EFFECTS OF APPLYING TECHNOLOGY
4.1 POWDER COATINGS
There are several advantages obtained after a facility is converted to
apply powder coatings besides the substantial reduction in emissions.
There are almost none of the solid or liquid waste disposal costs
or problems that are often encountered when using solvent-borne coatings.
Powders do not require the purchase of additional solvents to
control viscosity or to clean equipment.
Conversion to powder coatings will reduce energy requirements of
the spray booth because the large volumes of fresh air required for solvent-
borne coatings are not required. (Although the lower explosive limit is
higher than for solvent, the reduction in air volumes is possible mostly
because the spray booth is not occupied.) By using an efficient particulate
collector, the spray booth air may be recycled into the working area,further
reducing energy usage for air conditioning or heating. It has been estimated
that a 35-50 percent overall reduction in energy consumption can be achieved
when a single coat application is replaced with one coat of powder, and a
55-70 percent reduction is possible when a two-coat application is replaced
with a single coat of powder.
Powder coatings also have an advantage in providing good coverage
of the metal piece and masking imperfections or welds in the metal.
Although powder overspray can be reclaimed at about 98 percent
efficiency, not all the reclaimed powders can be reused. Reclaimed powder
containing a buildup of powder fines will have to be discarded, and the
larger and heavier granules will have to be reprocessed again before they
are suitable for reuse. '
4-1
-------
There are disadvantages encountered when applying powder coatings.
All application equipment, spray booths and associated equipment
(and often ovens) used for liquid systems must be replaced. This will then
limit the coating flexibility of the metal furniture manufacturer because he
will only be able to apply powders.
- Coating film thickness of less than 2 mils has not been successfully
obtained with powders on a production line basis.
Color changes for powder require about half an hour downtime. Metal
furniture facilities requiring numerous color changes during the day would
have to greatly curtail production capacity. Color changes may be shortened
if the powders are not reclaimed in their respective colors resulting in a
coating usage efficiency of about 50 to 60 percent. Those facilities which
apply many colors but can schedule their operations to run a single color
for a given time period may still find powder an economically acceptable
alternative.
. No one can yet provide the so-called metallic coatings in powder,
Color matching during manufacturing of powder is difficult.
Powder films have appearance limitations.
Recesses are difficult to cover effectively due to the Faraday caging
effect.
. Excessive humidity during storage or application can affect the
performance of powder.
Powder coatings are also subject to explosions,as are many particulate
4
dusts-
4.2 ELECTRODEPOSITION
Several other advantages, in addition to reduced VOC emissions, accrue
from converting to electrodeposition.
4-2
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The major one is good quality control as a consequence of the fully
automated process.
It provides a very high transfer efficiency.
* It also provides excellent coating coverage and corrosion protection
because the paint particles penetrate into the smallest recesses. (However,
because the coverage is so uniform, electrodeposition does not mask
imperfections in the substrate as well as other application techniques).
The low solvent content permits lower ventilation rates resulting in
reduced energy consumption.
The dry off oven that normally follows the pretreatment step is no
longer required although an additional rinse with deionized water is essential.
Conversion to electrodeposition may also result in lower insurance costs
because of reduced fire and toxicity hazards.
There are several disadvantages to the electrodeposition process.
One is that it requires a unique type of application equipment. As
a result, electrodeposition can be capital intensive when used on small
scale production lines.
If the hooks which hold the metal furniture pieces are not properly
cleaned or hung, the electrical contact may be faulty and the coating will
not adhere to the metal.
Conversion to electrodeposition coating will increase electrical con-
sumption. The amount, however, will depend on the former application system,
size of the electrodeposition bath, type of furniture pieces coated, and
thickness of the coating. Energy is required for the coating system,
refrigeration (to overcome the heat generated by the electrical process), to
circulate the bath, and purification of the bath. If a spray operation is
4-3
-------
replaced by electrodeposition, some credit may be allowed for decreased
solid and liquid wastes and the reduced energy requirements attributable to
elimination of the spray booth.
4.3 WATER-BORNE COATINGS
There are several advantages to converting to water-bome coatings.
The greatest is that existing equipment, whether for rpray, flow, ordip
coatinq, can be used. (Some parts of the coating equipment, however, may have
to be protected from corrosion).
* Water-borne coatings may be thinned with water,and coating equipment
can be cleaned or flushed with water rather than organic solvent. Unlike
with organic coatings, however, water-borne coatings must be cleaned off
application equipment when still wet since they are not soluble in their
carriers when they become dry making cleanup with organic solvents necessary.
A potential disadvantage of water-borne coatings is that energy con-
sumption may increase because some water-borne coatings must be flashed off
under controlled humidity, and the ovens may have to be lengthened to
several stages to compensate for the slower evaporation rate. However, this
energy increase is partially offset by the reduced oven exhaust and perhaps
the lower curing temperature typical of many water-bome coatings.
The water-borne coating is more sensitive to temperature and humidity,
both during application and flashoff. The flashoff air circulation may need
to be increased to allow a uniform evaporation rate of water during high and
low humidity conditions.
Disposal of solid or liquid waste may be difficult.
- In dip or flow coating processes, an additional rinse may be required
to avoid contamination of the coating bath.
4-4
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Overspray from water-borne does not harden as rapidly making sludge
handling more difficult.
Proper pretreatment is critical to prevent flash rusting of metal
furniture.
4.4 HIGHER SOLIDS COATINGS
Higher solids coatings can be applied with existing spray equipment.
These coatings are presently limited to about 65 volume percent solids,
although research is being done; both on high solids (65-80 percent)
coatings and on improved application equipment. Conversion to higher solids
coatings can reduce energy requirements. Air flow in the spray booth can be
reduced because less organic solvent is applied for each dry mil of coating.
The oven energy requirements may also be reduced. Solid and liquid waste
may decrease since less coating is applied per dry mil. However, the tackiness
of some high-solids coatings may make cleanup more difficult. Although the
solvent content is reduced, thus reducing the level of toxicity, there is a
potential health hazard associated with isocyanates used in some high-solid,
two-component systems.
4.5 CARBON ADSORPTION
There are no metal coating facilities known to use carbon adsorbers to
reduce VOC from application and flashoff areas. This technology, however,
is technically feasible for such applications and is well documented. A
potential disadvantage is that it will increase the requirements for electrical
and fuel energy. The amount will depend on application, size of adsorber,
and concentration of the organics entering the carbon bed. Any decrease in
air flow and accompanying increase in VOC concentration from the coating
application and flashoff areas will reduce the energy demands.
4-5
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af!d liauid wastf generated by use of a carbon
siOhs ' TOPI i"! uw ;ind dip coating operations do not
: and v/ill not require filtration or scrubbing.
',, however, it'dv roqu i; < some filtration due to
!. ne gas strean, Water unsrible solvents pose a
:i , nn^nervted strain is condensed and discharged
;,:;? bn sr-'ved o»/ inc i ne^atinc) the steam
'r;e1:her, o* by stripping the condensate and disposing
'. i i increase the costs and energy consumption of
; widely applicaMe technique used for the reduction
;-ir : r-'-TSti on. i!(iweve>", one potential disadvantage
- ';'' i;ijel oil s u:-iP
-------
ji!w>-y aid 55'! E *+' -j e
Heat Pecove^
CATALYTIC INCINERATOR:
f,'o hed' Recovery
50D° sr frr
TABLL '1-1
BURNER REQUIREMEJTS FOR £Njj I HERITORS
A. * 4 t L, f' J L;. .' ' i ' -'
5 percent LEL
5.82
1 7 . 4R
34.95
3,32
10.09
19.97
1.42
4.40
8.67
1 .69
5.07
10.14
0.79
2.38
4 . 76
-0.21
-0.62
- 1 . 24
4.05
1? .16
24.31
1.56
4.73
9.38
-0.34
-0.66
-1.82
1.69
5.07
10.14
0.26
0.77
1.54
-1.07
-3.22
-6.46
:vpr, o,,ti ;t lernoprature; l^OOT outlet tenperature for non-catalytic
rcn-sp' - *'.. -:i> for catalvtlr iio
incinerators.
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4.7 REFERS Nab
1. "Economic. Justi M cation of Powder Coating. Powder Finishing World.
Pages 13-22, 4th quarter, 1976.
2. LeBras, Louis R. Technical Director, PPG Industries, Inc., Pittsburgh,
Pa. Letter fc W:ra Gillagher in comment of this document. Letter
dated September ?2', 1977.
3. Dornbos, javid L. M\ , Steelcase, Incorporated, Grand Rapids, Michigan.
Letter to Vero. ^an^aner in comment of this document. Letter dated
August 31, '977
4. Op. Cit. LeBras
5. "Water-Borne clow Coat and Dip," Products Finishing. Pages 73-76.
February 1977.
6. "Question Corner/1 High-Solids Coatings, Volume I, No. 3. July 1976.
7. Combustion Engineering Air Preheater, Wellsville, New York, Report of
Fuel Requirements, Capital Cost and Operating Expenses for Catalytic
and Thermal Afterburners. EPA Contract Report No. EPA-450/3-76-031.
September 1976,
4-8
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5.0 MONITORING TECHNIQUES AND ENFORCEMENT ASPECTS
This chapter discusses the recommended emission limit, the monitoring
techniques and enforcement aspects of low polluting coatings and add-on
control equipment.
As stated in the preface, there is no universal VOC emission control
technique applicable for the industry as a whole because of the variety of
metal furniture products manufactured. However, metal furniture facilities
have certain similarities which permits grouping them for use of certain
control techniques. For example, if a facility has no difficulty with
Faraday caging, applies a limited number of colors, can run a single color
for a given time period, and a coating film thickness of greater than two
mils is not objectionable, powder could be the best control technique.
If a facility runs only a few colors on a large production basis, electro-
deposition would be the best control technique. However, if a facility must
color match or change colors frequently, water-borne or higher-solids coatings
would be the best choice. The recommended emission limit(3.0 Ibs of organic
solvent per gallon of coating, less water), as stated in the Preface,is based
on the application of water-borne or higher solids coatings. Sample calculations
to verify compliance with this emission limit are shown in Appendix A.
Previous control regulations for VOC have included limitations on the
reactive organic solvent or have stipulated that a minimal reduction be
achieved through add-on control equipment. While either approach is acceptable,
maximum solvent content is a more practical basis for those surface coating
operations where use of low-solvent coatings will generally be the compliance
technique.
5-1
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For metal furniture industries, it is recommended that emission
limitations be expressed in terms of organic solvent content since these
values can be determined with relatively simple analytical techniques.
Limitations in VOC may be expressed in terms of mass or volume and
may be based on the entire coating (including organic solvent) or only on
paint solids. In this guideline, limitations are expressed as the allowable
mass of organic solvent per unit volume of coating (kgs per liter of coating
or Ibs per gallon of coating) as it is delivered to the coating applicator.
Water in the coating is subtracted. The principal advantage of this format is
that enforcement is relatively simple. Field personnel can draw samples and
have them analyzed quickly. A disadvantage is that the relationship between
the solvent fraction and organic emissions is not linear. If the solvent
content is expressed in terms of mass of organic solvent per unit volume of
paint solids (kgs per liter of solids or Ibs per gallon of solids), the
disparity disappears. The relationship is linear and more readily understood
e.g., a coating containing 2 Ibs of organic solvent per gallon of solids
releases twice as much organic solvent as one of 1 Ib per gallon. The
disadvantage of this format, however, is that the analytical methods are more
complex. Appendix A in "Control of Volatile Organic Emissions from Existing
Stationary Sources - Volume II: Surface Coating of Cans, Coils, Paper,
Fabrics, Automobiles and Light Duty Trucks" presents ASTM method^ for
determination of the pounds of organic solvents per gallon of coating (minus
water).
Other options such as pounds or gallons of organic solvent per pound of
coating are generally less desirable although they may be entirely appropriate
for a given industry. Basing limitations on the mass of coating or paint
5-2
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solids is not recommended because the specific gravity of coatings tends
to vary widely with the degree and type of pigment employed, Highly
pigmented paints have much greater density than unpigmented clear coats
or varnishes.
This limitation for coatings assumed the facility merely converts
from use of an organic-borne coating to a coating low in organic solvent.
It does not consider any small or significant reduction in VOC emissions
which may result from a decrease in film thickness or an increase in
transfer efficiency of a coating. One example of such reduction may be
where a facility is applying a conventional coating at 1.2 mils film
thickness, and converts to a coating containing less organic solvent than
the conventional coating but which does not quite meet the recommended
emission limit. However, if the new coating has better hiding power and can
be applied at only 0.8 mils film thickness, the decrease in film thick-
ness can still result in a proportional reduction in VOC emissions as
compared to a coating which meets the recommended emission limit. Other
examples would be if a facility converts from a manual conventional spray
application (at a transfer efficiency of 40-70 percent) to an automated
electrostatic spray system (at a transfer efficiency of 70-90 percent), or
from any spray system to a flow or dip coat system (at a transfer efficiency
of at least 90 percent). Some incremental reduction in VOC emissions will
be realized. This reduction in VOC content can be included in the overall
system to provide the equivalent reduction in emissions.
In those few facilities where add-on control equipment is a more likely
option, it may be more appropriate to state emission limits in terms of
control efficiency across the incinerator, adsorber, etc. Where limitations
5-3
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are expressed only in terms of the coating content, it will be necessary
to determine mass emissions from the control system and relate them to
the quantity of coatings applied during the test period. It is often
difficult to determine the consumption of coatings during any given period
and to determine the amount of organic solvent directed to the control
device. Chapter 5 of "Control of Volatile Organic Emissions from
Existiny Stationary Sources - Volume I: Control Methods for Surface
Coating Operations" presents test methods for add-on control devices.
When add-on type devices are selected as the compliance method, the air
pollution control agency should require that the coating lines be equipped
with an approved capture device to assure effective control. The capture
system will likely have to be custom designed to accommodate the plant-to-
plant variables which affect performance. When reviewing the design of
such a system, however, the air pollution control official must consider
requirements imposed by the Occupational Safety and Health Administration
and the National Fire Prevention Association.
Some coatings will emit a greater amount of VOC than merely its
solvent content. This incremental VOC may come from three possible sources.
The first is the possibility that some of the monomer may evaporate. Also,
if it reacts by the condensation polymerization, the evolution of by-
product compounds may be a compounding factor. Finally, it has been reported
that the industry is using increasing quantities of "blocking agents" which
are released from the polymer matrix during the curing process.
There are now no approved analytical methods certified by the agency
for determining the quantity of VOC emitted by such reactions, although
certainly the organic mass emission rate could be determined by expensive
5-4
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and sophisticated analytical techniques. The more practical means of
quantifying the contribution of the polymerization reaction to the
overall emission problem would be by contacting the manufacturer of
the coating. Certainly, his knowledge of the fundamental chemical
mechanisms involved would allow calculation of an emission rate based
on the chemical reaction.
This emission will occur during the cure (if at all) which is usually
temperature initiated by the oven. If the oven is controlled by an
incinerator, then verification of the efficiency of the device should be
sufficient to assure compliance with the coating regulation.
5-5
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APPENDIX A
SAMPLE CALCULATIONS OF CONTROL OPTIONS
This appendix aids the local agency in determining if a coating pro-
posed for use by a metal furniture facility will meet the recommended
emission limit of 0.36 kilograms of VOC per liter of coating applied,
(3.0 Ibs/gal) excluding any water that the coating may contain. The
purpose of excluding water is to preclude compliance through dilution with
water. This appendix also explains how to compare the actual VOC emissions
from a facility regardless of the type of low-polluting coating or add-on
control device used.
The purpose of all coating operations is to cover a substrate with a
film that provides both corrosion resistance to the substrate and esthetic
appeal. Therefore, the rational basis for specifying an allowable VOC
emission limit would be in units of coating volume ( e.g, grams of VOC per
square meter (Ibs/sq.ft) per unit thickness of film). However, the
complexity of any analytical method which would provide a measurement of the
volume of a cured coating precluded this approch. As a compromise, the
recommended limitations were developed in kilograms (Ibs) of VOC per unit
volume of uncured solids and organic solvent. Mathematically, then, the
emission factor (ef) for a coating would be expressed as:
n] f (volume fraction organic sol vent)(average^organic solvent density)
^ ' volume fraction of solids + volume" Traction of organic solvent
or
(2) ef = (volume fraction organic solveatj(average organic solvent density)
T - volume" fraction of water
A-l
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The following examples show the use of these equations to determine
the emission factor for both organic solvent-borne and water-borne coatings.
CASE 1: Determine the emission factor for an organic solvent-borne coating
which contains 40 percent organic solvent.
Therefore: ef - (..40)$0.88 kg/liter*?
= 0.35 kg/liter (2.94 Ibs/gal)
Since the emission factor is less than the recommended limit of
0.36 kg/liter (3.0 Ibs/gal), this coating is in compliance.
CASE 2: Determine the emission factor for a water-borne coating containing
75 percent solvent.
Since 80 percent of the solvent is water, the respective volumes of
water and organic solvent may be calculated as shown:
Volume water= .80 x .75 liter = .6 liter
Volume organic solvent^ 0,75 liter - .6 liter = .15 liter
Therefore: ef - (0.15H0..88 kg/Hter*)
I - U.b
= 0.32 kg/liter (2.64 Ibs/gal)
This coating also has an emission factor less than the recommended limit
and would comply.
The level of control represented by 0.36 kg/liter of coating
(3.0 Ibs/gal) less water can also be achieved with a conventional high
organic solvent coating if suitable add-on control equipment is installed.
However, this method of determining the equivalvent emission limit factor
is not as straightforward as the previous two cases and must also consider
the volume of solids in the coating.
*This' density is considered typical and is equal to 1.36 Ibs/gal.
A-2
-------
CASE 3: Determine the emission factor for a conventional organic-borne
coating containing 75 percent organic solvent.
Therefore: ef = (.75)(.88, kg/liter*)
= 0.66 kg/liter (5.5 Ibs/gal)
However, this liter of coating contains only 0,25 liter (gallon of
solids whereas the coating which represents the recommended emission limit
of 0.36 kg/liter (3,0 Ibs/gal) contains 0.60 liter (gallon) of solids.
(This can be back calculated from the recommended emission limit in this
manner,)
i.e. 0.36-= j;x)(0.88, kg/liter)
x = 0.40 volume percent organic solvent.
Therefore fraction of solids =1 - x = 0.60
On a unit volume of solids basis, the conventional coating contains:
0.66 kg organ i r sol vent _ 2.64 organic solvent 22 Ibs VOC
0.25 liter solids liter solids ~ gal .solids
And the recommended limit reference coating contains
0.36 kg organic solvent _ G.6 kg organic solvent 5 Ibs VC
CT.6 Titer solids ~ liter solids gal solicTs
A-3
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Consequently, in order for the conventional coating to emit no more VOC
than the reference coating, the add-on control device must capture and
destroy (or collect) 2.04 kg of solvent per liter of solids applied
(2..64 - 0.6). This will require a control system that is at least 78
percent efficient. Since the add-on control devices can often operate at
90 percent efficiency or greater, the agency must insure that at least
85 percent of the VOC emitted by the coating is captured and delivered to
the add-on control device. Since it will normally not be practical to
attempt the complex analytical program essential to develop a
material balance around the coating application and flashoff areas and ovens,
the agency will normally certify an acceptable capture system based on good
engineering practice.
A-4
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APPENDIX A REFERENCE
1. Young, Dexter E., Environmental Protection Agency, memorandum concerning
requirements for ventilation of spray booths and ovens. Dated March 10,
1977.
A-5
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4. TITLE ANOSUBTITLE
Control of Volatile Organic Emissions from Existing
Stationary Sources - Volume III: The Surface Coating
of Metal Furniture
9 PERFORMING ORGANIZATION NAME ANQ ADDRESS
U.S. Environmental Protection Agency
Office of Air and Waste Management
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing/
W-480/2-77-032
3. RECIPIENT'S ACCESSION-NO.
5. REPORT DATE
December 1977
6. PERFORMING ORGANIZATION CODE
7. AUTHORIS)
8. PERFORMING ORGANIZATION REPORT NO.
OAQPS No. 1 .2-086
12. SPONSORING AGENCY NAME AND ADDRESS
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
This report provides the necessary guidance for development of regulations
to limit volatile organic compound (VOC) emissions from the coating operations
of metal furniture industry. This auidance includesan emission limit which
represents Reasonably Available Control Technology (RACT), methods by which
RACT can be achieved, and monitoring and enforcement aspects.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
Air Pollution
VOC Emission Limits
Metal Furniture Industry
Regulatory Guidance
b.IDENTIFIERS/OPEN ENDED TERMS
Air Pollution Control
Stationary Sources
Organic Vapors
c. COSATI Field/Group
18. DISTRIBUTION STATEMENT
INSECURITY CLASS (ThisReport)
unclassifiecT
21. NO. OF PAGES
63
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
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ENVIRONMENTAL PROTECTION AGENCY
General Services Division (MD-28)
Office of Administration
Research Triangle Park, North Carolina 27711
POSTAGE AND FEES PAID
ENVIRONMENTAL PROTECTION AGENCY
EPA-335
OFFICIAL BUSINESS
AN EQUAL OPPORTUNITY EMPLOYER
Return this sheet if you do NOT wish to receive this material [~1
or if change of address is needed I I (Indicate change, including
ZIP code.)
PUBLICATION NO. EPA-450/2-77-032
(OAQPS No. 1.2-086)
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