' • t J Jr\ f
EPA-450/2-77-008
May 1977
(OAQPS NO. 1.2-073)
CAN COATING
AP 42
Section 4.2.2.f
Reference Number
OAQPS GUIDELINES
CONTROL OF VOLATILE
ORGANIC EMISSIONS
FROM- EXISTING
STATIONARY SOURCES -
VOLUME II: SURFACE COATING
OF CANS, COILS, PAPER,
FABRICS, AUTOMOBILES,
? AND LIGHT-DUTY TRUCKS
U.S. ENVIRONMENTAL PROTECTION AGENCY
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-O08
(OAQPSNO. 1.2-073)
CONTROL OF VOLATILE
ORGANIC EMISSIONS FROM EXISTING
STATIONARY SOURCES . VOLUME II:
SURFACE COATING OF CANS, COILS,
PAPER, FABRICS, AUTOMOBILES,
AND LIGHT-DUTY TRUCKS
Emission Standards and Engineering Division
Chemical and Petroleum Branch
I .S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Waste Management
Office of Air Quality Planning anil Standards
Research Triangle Park. North Carolina 2771 I
Mav IV77
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This report is issued by the Environmental Protection Agency to report
technical data of interest to a limited number of readers. Copies are
available free of charge to Federal employees, current contractors and
grantees, and nonprofit organizations * in limited quantities *• from the
Library Services Office (MD-35) , Research Triangle Park, North Carolina
27711.
Publication No , EPA-450/2-77-008
11
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PREFACE
This is the second in a series of reports designed to assist State
and local jurisdictions in the development of air pollution control
regulations for surface coating industries. These reports are directed
entirely at the control of volatile organic compounds (VOC) which con-
tribute to the formation of photochemical oxidants. Volume I provides
very general information on the cost and effectiveness of control
technology and guidelines for sampling and analyzing VOC emissions.
Volume II provides specific information on air pollution control of
five surface coating industries; namely, automobile and light duty truck,
can, coil, fabric and paper coating operations. For each industry,
coating systems are reviewed and various VOC control alternatives are
considered together with their costs and limitations. This volume also
provides guidance on the preparation of air pollution control reg"lation$
and test methodology suitable for their enforcement (Appendices A and C).
It must be cautioned that the limits provided below are based on
capabilities and characteristics which are general and therefore presumed
normal to these industries; the limits may not be applicable to every plant
within an industry. For example, although the level of control recommended
for the can industry is based on coatings that are generally available, those
coatings may not be suitable for every product manufactured by a can plant.
In each case the recommended limitation is stated in terms of solvent
content of the coating. This form is most applicable to situations where low
solvent coatings are employed. If an operator should choose to comply by
in
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installation of add-on control devices, it may be appropriate for the agency
to set minimal requirements on the hooding or capture system and the
efficiency of the control device.
The tables that follow provide emission limitations Mrepresent
the presumptive norm that can be achieved through the application of
reasonably available control technology (RACT). Reasonably available
control technology is defined as the lowest emission limit that a par-
ticular Source is capable of meeting by the application of control technology
that is reasonably available considering technological and economic feasibility.
It may require technology that has been applied to similar, but not necessarily
identical, source categories. It is not intended that extensive research and
development be conducted before a given control technology can be applied
to the source. This does not, however, preclude requiring a short-term
evaluation program to permit the application of a given technology to a
particular source. This latter effort is an appropriate technology-forcing
aspect of RACT.
CAN INDUSTRY
Affected Facility
Recommended Limitation
kg per liter Ibs per gal
of coating of coating
(minus water) (minus water)
Sheet basecoat (exterior
and interior) and over-
varnish; two-piece can
exterior (basecoat and
overvarnish)
Two and three-piece can interior
body spray, two-piece can
exterior end (spray or roll
coat)
Three-piece can side-seam spray
End sealing compound
0.34
2.8
0.51
0.44
4.2
5.5
3.7
IV
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The limitation for the sheet baseCOQt (exterior and interior) and
overvarnish; two-piece can exterior (basecoat and overvarnish) assumes
the average solids content of all coatings is about 25 volume percent
and the solvent is an 80 percent water, 20 percent organic mixture.
The organic-borne equivalent is 64 volume percent solids. Such coatings
are now used by some companies on part of their Production.
The limitation for two and three-piece can interior body spray,
two-piece can exterior end (spray or roll coat) oresumes all coatings
average 18 volume percent solids in an 70:30 water to organic solvent
ratio. Such coatings are now used on some beer and beverage cans.
The limitations for the three-piece can side-seam spray assumes an
increase in the solids content of typical present-day coatings by 100
percent to 25 volume percent. Water-borne coatings for some unique
products have been developed that are applied at solvent contents as low
as 0.53 kilograms per liter of coating.
The limitation on end sealing compound emissions presumes an increase
in the solids content of a typical organic-borne coating from 30 to 50
percent. Water-borne coatings for some unique products are applied at
solvent contents as low as 0.26 kilograms per liter of coating.
COIL COATING INDUSTRY
Affected Facility Recomnended Limitation
kg per liter Ibs per gal
of coating of coating
(minus water) (minus water)
Prime and topcoat or single 9.31 2.6
coat operation
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This limitation is based on incineration of the emissions from an
organic-borne coating which contains 25 volume percent solids. To comply,
90 percent of the solvent in the coating would have to be captured and
directed to the control device (afterburner) which must be at least 90
percent efficient. There are also some water-borne coatings that will
comply with this level of control without the need for add-on control
equfoment.
FABRIC COATING
Affected Facility Recommended Limitation
kg per liter Ibs per gal
of coating of coating
(minus water) (minus water)
Fabric coating line 0.35 2.9
Vinyl coating line 0.45 3.8
"Fabric coating" 'includes all types of coatings applied to fabric,
a large portion of which is rubber used for rainwear, tents and industrial
purposes such as gaskets and diaphrams. "Vinyl coatinq" refers to any
printing or decorative or protective topcoat applied over vinyl coated
fabric or vinyl sheets. It does not include the application of vinyl
olastisol to the fabric (emissions from the application of plastisol are
near zero).
The limitations for both are based on use of an add-on control device
which recovers or destroys 81 percent of the VOC introduced in the coating.
Typically, this will require that 90 percent of the VOC is captured and
delivered to the control device which also must have an efficiency of 90
percent.
vi
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The limitation for fabric coating could also be achieved by use of
an organic-borne coating which is about 60 volume percent solids or a
water-borne 80:20 coating with a solids content of about 24 volume percent.
Neither of these coatings are known to be in routine use by the industry.
PAPER COATING
Affected Facility Recommended Limitation
kg per liter' Ibs per gal
of coating of coating
(minus water) (minus water)
Coating line 0.35 2.9
These levels are for all coatings put on paper, pressure sensitive
tapes regardless of substrate (including Daper, fabric or plastic film)
and related web coating processes on plastic film such as typewriter
ribbons, photographic film, and magnetic tape. Also included are decorative
coatings on metal foil such as gift wrap and packaging. These limits can
be achieved in all cases using incineration and in many cases with coatings
that contain low fractions of organic solvents.
AUTOMOTIVE AND LIGHT DUTY TRUCK ASSEMBLY PLANTS
Affected Facility Recommended Limitation
kg per liter Ibs per gal
of coating of coating
(minus water) (minus water)
Prime application, flashoff 0. 23 1.9
area and oven
Topcoat application, flashoff 0.34 2.8
area and oven
Final repair application, 0.58 4.8
flashoff area and oven
V 1 1
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These limits apply to all objects surface coated in the plant including
the body, fenders, chassis, small parts, wheels, sound deadners, etc. It
does not apply to adhesives.
The level rSCOIHnended for prime application is based on use of an
electrophoretic system followed by a 25 percent solids water-bone "surfacer"
to build thickness and improve the adhesion of the topcoat. Water-borne
surfacer is in use at two U.S. plants. The electrophoretic system is now in
use at about half of the plants in the United States. Although several of
these were converted to electrophoretic, such a transition may not be reasonable
for an existing assembly line which uses a water-borne dip prime coating system
releasing about 0.38 kilograms per liter of coating. The moderate reduction
in emissions possible with electrophoretic coatings would be obtained at
great expense.
The level for topcoat represents a water-borne coating now in use by
two plants in the United States. Because of: (1) the large expenditures
required to convert from organic-borne coatings to water-borne coating, it may
be reasonable to grant some finite period for a source to develop low
solvent organic-borne coatings with equivalent emission characteristics.
The level for "final repair" is based on use of an organic-borne
enamel with 35 percent solids. Water-borne coatings cannot be employed
for the assembled automobile. None of the automakers are using coatings of
35 percent s 'lids at present but such use is now scheduled at one U.S. plant.
VI11
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TABLE OF CONTENTS
VOLUME II SURFACE COATING OF CANS, COILS, PAPER, FABRICS, AUTOMOBILES,
AND LIGHT-DUTY TRUCKS
PREFACE '
1,0 INTRODUCTION 1-1
2.0 CAN COATING 2-1
2.1 Summary of Control Technology 2-1
2.2 General Discussion 2-2
2.2.1 Materials Used 2-4
2.2.2 Processes and Affected Facilities. 2-6
2.3 Special Considerations 2-13
2.4 Available Control Technology. 2-17
2.4.1 Option 1 - Incineration 2-17
2.4.2 Option 2 - Water-Borne/High-Solids!Powder Coatings - - - 2-25
2.4.3 Control Option 3 - Carbon Adsorption Coating 2-28
2.4.4 Control Option 4 - Ultraviolet Curing 2-32
2.5 Comparison of Control Options and Conclusions 2-34
3.0 COIL COATING 3-1
3.1 Summary of Control Technology 3-1
3.2 -General Discussion 3-1
3.2.1 Materials Used 3-3
3.2.2 Processes and Affected Facilities 3-4
3.3 Special Considerations 3-8
3.4 Available Control Technology 3-11
3.4.1 Option 1 - Incineration 3-12
3.4.2 Option 2 • Water-Borne and High-Solids Coating 3-21
3.v Comparison of Control Options and Conclusions 3-25
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4.0 FABRIC COATING. 4 J
4.1 Summary of Control Technology 4'1
4.2 General Discussion 4-1
4.2.1 Materials Used 4-2
4.2.2 Processes and Affected Facilities 4-2
4.3 Special Considerations. 4-TJ
4.4 Aval 1 able Con trolTechnol0^ 4-12
4.4.1 Option 1 - Incineration 4-12
4.4.2 Option 2 - Carbon Adsorption 4.15
4.4.3 Option 3 - tow Organic Solvent Coatings 4-18
4.5 Comparison of Control Options and Conclusions 4-18
5.0 PAPER COATING.. 5-1
5.1 Summary of Control Technology 5-1
5.2 General Discussion. 5-1
5.2.1 Materials Used 5-4
5.2.2 Processes and Affected Facility 5-8
5.3 Special Considerations. 5-14
5.4 Available Control Technology. 5-14
5.4.1 Option 1 - Low Solvent Coatings. 5-14
5.4.2 Option 2 • Incineration. 5-21
5.4.3 Option 3 - Carbon Adsorption 5-23
5.5 Comparison of Control Options and Conclusions 5-27
6.0 AUTOMOBILE AND LIGHT DUTY TRUCK ASSEMBLY 6-1
6.1 Summary of Control Technology 6-1
6.2 General Discussion. . 6-2
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6.2.1 Materials Used ................... 6-6
€.2,2 Processes and Affected Facilities .......... 6-7
6.3 Special Considerations ................... 6-ltJ
6.4 Available Control Technology ................ 6~^
6.4.1 Option \ - Electrodeposition of Water-Borne Primer . 6-17
6.4,2 Optlw 2 <• tower Solvent Primer and Topcoat ..... €-22
6.4.3 Option 3 ~ Carbon Adsorption fur Primer and Topcoat
Spray Booths ............. 6-24
6,4,4 Option 4 - 'Incineration for Spray Booths ...... 6-29
6,4.5 Option 5 - Incineration for Priscr and
6,4,6 Option 6 - Water-Borne Topcoats ... ....... 6-36
6.5 Comparison of Control Options and Conclusions ....... 6-41
APPENDIX A - ANALYTICAL TECHNIQUES ................. A-l
APPENDIX B - RECOMMENDED POLICY ON CONTROL OF
VOLATILE ORGANIC COMPOUNDS .............. B-l
APPENDIX C - REGULATORY GUIDANCE. .................. C-l
APPENDIX D - CONVERSION METHODS ................... D-l
XI
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1.0 INTRODUCTION
The industries reviewed herein represent some of the largest and most
widespread sources of volatile organic solvents in the nation. Moreover,
their products, often with very specialized surface coatings, are interwoven
into many facets of our economy and are subject to a wide range of performance
demands. Collectively, they release about 850,000 tons of VOC annually to the
atmosphere with the largest individual sources each being responsible for
over 1,000 tons per year. The five industries employ a variety of coating
application and curing techniques, all of which impact on the viability of
alternative VOC control technologies. From the air pollution control stand-
point, it is immaterial whether VOC are removed from the coating process or
are controlled at the point of emission. Nonetheless, since solvent recovery
and/or elimination strongly influence control costs and acceptance by the
affected industries, much of this document is directed at the review of
alternative control strategies, costs, and energy impacts.
To varying degrees, four different abatement methods have been used
to reduce the contribution of surface coating VOC to the photochemical
oxidant burden. These are:
(i) "Add-on" technology \* destroy or recover VOC from
exhaust gases,
(2) Reformulation of coatings to minimize organic
solvent content,
( ') Modification of the process to f^-'uce the quantity
of VOC which escapes from a coating ]; I, and
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(4) Substitution of less photochemical ly reactive solvents
in surface coating formulations.
The first three are "positive reduction" techniques in that they
actually reduce the mass of VOC released to the atmosphere. The fourth,
solvent substitution, doesn't reduce the quantity of organic emissions
and has been only marginally effective In reducing ambient concentrations
of photochemical 0x1 dints (see Appendix 8). In preparing this document,
principal attentian has been directed at add-on control technology and
the reformulation Of coatings. These two positive reduction techniques
currently offer greeter potential for reducing organic missions than
process modifications far the five surface coating operations in question.
In previous years the primary method used to reduce organic emissions
from stationary sources has been through stack gas treatment, primarily
incineration. Incinerators or afterburners have evolved as the basic
control technique to which the efficiency of alternative methods is
often compared. Within the coating industry, however, incinerators
have, for the most part, been limited to baking and curing ovens. In
IDOSt instances, spray coating operations, which are much larger sources
of VOC than associated ovens, have gone uncontrolled. It is for these
coating sources that low-solvent coatings offer the greatest promise.
1.1 LOW-SOLVENT COATINGS
Coatings which contain relatively low fractions of organic.solvent,
the so-called "low-solvent coatings" (water-borne, high-solids, and
powder coatings), offer the advantage of saving valuable petroleum
feedstocks while also eliminating the need for abatement equipment and
its concomitant requirement for fuel and power.
The desirability of low-solvent coatings was recognized and acknowledged
by the Los Angeles County Air Pollution Control District in 1971 when
1-2
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incentives were added to Rule 66--its regulation governing use of
solvents. Under Rule 66, operators are not required to incinerate
oven exhaust gases if the surface coating meets specified limitations
(less than 20 percent organic solvent in coating by volume or an organic
solvent-to-water ratio of 20:80 or less in water-borne coatings). Many
other governmental agencies throughout the nation have adopted similar
incentives.
The low-solvent coating provisions of Rule 66 were developed at a
time when few water-borne, high-solids, or powder coatings were available.
In the six years since these incentives were first offered to the industry,
there has been only a limited shift in that direction. Currently, they
represent only about 10 percent of industrial surface coating sales. The
rest are conventional organic-borne formulations with an organic solvent
content of 60 to 90 percent or more. Lack of greater acceptance of low-
solvent coatings by the industry is attributable to many factors, some
of which are: difficulties in achieving Rule 66 specifications, relatively
low cost of solvents, and the ability to comply with air pollution regulations
by less burdensome means such as solvent substitution.
The dramatic reduction which can be achieved in switching to lov/-SOlvent
coatings is often not apparent from coating specifications. For example,
with the aid of Figure 1, it can be shown that an operator now using a 30
volume percent solids (70 percent organic solvent) coating could reduce his
VOC emissions 57 percent by rep cement with a coating containing 50 percent
solids. If he could use a coating of 70 percent solids, his VOC reduction
would be 82 percent. Even greater reductions can be realized by users of
highly jilute coatings such as lacquers. Al. ?Derat01" now using a 10 volume
percen* solids lacquer could effect a; 88 Tent VCC reduction by switching
to ? 50 iercent solids enamel. By SWltchir, to a 70 percent solids coating,
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Percent Emission Reduction Per Volume of Solids
— IM C.J ** tfl Ol ^1
O O O O O O O
(Item Coated)
00 <£> O
o o o
lb. S0lvent/
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his VOC reduction would be 95 percent. Conversion to water-borne coatings
will also significantly reduce VOC emissions. Replacement of a 30 volume
percent solids organic-borne coating with an 80:20 water-borne (80 percent
water, 20 percent organics,^ of similar solids content would yield a VOC
reduction of about 80 percent for a given industrial application.
1.2 STACK GAS TREATMENT
Founding emission limitations on low-solvent technology is not without
its drawbacks. In some instances, switching to low-solvent coatings may
not provide as much VOC control as would add-on control devices. This could
be true during any transition period as we phase into lower solvent coatings.
For certain industries, it will be more effective and possibly less costly
to employ incineration, adsorption, or other techniques to remove or destroy
VOC in the exhaust gases. Carbon adsorption should continue to find use
where the solvent has a relatively high market value and is amenable to
recovery with adsorption techniques. Incineration is expected to remain
a viable alternative where organic concentrations can be maintainei at
relatively high levels such that auxiliary fuel requirements are noi excessive
or where energy in the hot exhaust gases can be recovered and used tc offset
fuel requirements elsewhere in the plant.
A major disincentive to applying stack gas treatment to VOC sources is
the low concentration of organics often encountered. These low concentrations
mean large volumes of air or other diluents must be processed to control the
solvent. This results' in higher costs and energy requirements for control
equipment and, frequently, lower control efficiencies. Major reasons for
such low concentrations are: (1) solvents are toxic to the worker, hence,
are intentionally diluted below the thres'iold limit value (TLV); (2) concen-
trations are maintained well below the lowc - explosive limit (LEL) to reduce
1-5
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the risk of fire or explosion; (3) large dilution rdliub »'«=
accommodate fluctuations in VOC evaporation rates, and (4) the operator is
unaware of the multiple benefits of minimizing the intrusion of diluent air.
The greatest dilution and lowest VOC levels are found in hand-held
spraying operations and are attributable to TLV restrictions. No large
worker-occupied spray booths such as those used in auto assembly plants
have been controlled with VOC stack gas treatment technology. Where the
coating is applied mechanically as with a knife, roller, or electrostatic
spray gun, it is usually possible to maintain much greater VOC concentrations
in exhaust gases. Similarly, baking and curing ovens can be maintained at
VOC levels much greater than are feasible for worker-occupied spray booths.
Solvent concentrations in ovens and automated coating applications are
generally maintained below 25 percent LEL because of safety hazards associated
with higher concentrations.1 Unfortunately, many ovens are operated at
organic concentrations well below this level. For example, at 5 percent LEL,
the exhaust rate is five-fold greater than at 25 percent LEL and any add-on
control device must be five times larger. In many cases , such low concen-
trations are not necessary. Changes in system design and operating practices
can minimize air intrusion with the attendant benefit of a reduced exhaust
volume and reduced control costs.
In a few industries, operators have been notably successful in
maintaining VOC levels at greater than 25 percent LEL and effecting
major fuel economies. For example, several coil coaters have actually
reduced fuel consumption in the coating oven by use of incineration
devices and heat exchangers and maintaining VOC concentrations at 30 to
40 percent LEL. In many more applications, incineration would be a more
cost effective control option if air intrusion were minimized and VOC
levels held to 25 percent LEL or greater. This ancillary aspect of VOC
control has received only limited attention in many industries.
'Some insurers will permit operation up to 50 percent of the LEL if
appropriate monitoring and fail-safe relief systems are installed.
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1.3 EMISSION LIMITATIONS
Historically, VOC control regulations have included limitations on the
organic solvent of coatings or have stipulated that a certain percent reduction
be achieved through stack gas treatment. While either approach is acceptable
if limits are appropriate, solvent content is a more reasonable basis for
surface coating operations which are expected to employ low-solvent coatings.
For these five industries, it is recommended that emission limitations
be expressed in terms of organic solvent content since these values can be
determined with relati Vely simple analytical techniques and are directly
relatable to VOC emissions. For operators who use stack gas treatment,
alternative compliance procedures should be included.
Solvent content 1 imitations may be expressed in terms of mass or
volume and may be based on the entire coating (including solvent) or only on
paint solids. In this document, limitations are expressed as the allowable
mass of VOC per unit volume of coating (kg per liter or Ib per gallon) as it
is applied to the product. The principal advantage of this format ir 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 VOC emissions is not linear. As illustrated in
Figure D-Z of Appendix D, use of a coating containing 3 Ibs of VOC per
gallon of coating emits 4.4 tim.S as much, solvent as use of one with
1 Ib Der gallon and only 55 percent as much as one of 4.1 Ibs per gallon.
Thus, VOC emission rates could be easily misunderstood by the general public.
1-7
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The above disadvantage is eliminated if the solvent content is
expressed in terms of mass of VOC per unit volume of paint solids
(again kg per liter or Ib per gallon). Here the relationship is linear
and more readily understood by the public, e.g., a coating containing
2 Ibs per gallon of solids releases twice as much VOC as one of 1 Ib
per gallon. The disadvantage of this format is that it relies on an
analytical method which has had only limited usage in the industry and
is virtually untried by control agencies. When more experience is
developed with the procedure for measuring the volume of solids in a
coating sample (approved by the American Society for Testing and Materials),
it may be reasonable to express limitations in terms of paint solids.
Until these uncertainties are resolved, it is recommended that limitations
be based on the volume of the coating (minus water). Appendix A presents
ASTM test methods for determination of the pounds of VOC per gallon
of coating (minus water).
Other options such as Ibs or gallons of VOC per Ib 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
solids is not recommended because the specific gravity of coatings
tends to vary widely with the degree and type of pigmenting employed.
Highly pigmented paints have much greater density than unpigmented clear
coats or varnishes. Furthermore, basing limits on paint mass might
encourage users to employ a greater degree of pigmentation solely to
meet air pollution limits. Mass rather than volume of VOC is
recommended for emission limitations because measurement techniques
are simple and because VOC mass is more closely related to photochemical
oxidant formation.
1-8
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For any given industry, it may be desirable to express solvent limits
in terms other than those recommended in the Preface. In such instances,
it will be necessary to adjust numerical limits such that they provide
the desired degree of control. Appendix D provides equations and charts
through which recommended limits can be translated into other solvent
limitation formats.
The approach outlined above was designed for coating processes where
low-solvent coatings are to be employed. In those few Industries where
stack gas treatment is a more likely option, it may be more appropriate
to state emission limits in terms of control efficiency across the incinerator,
adsorber, etc* This concept is discussed 1rt Appendix C* Where limitations
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 ascertain the fraction of VOC which is directed to the
control device. in most instances, it will be more reasonable to provide
an alternative efficiency requirement for those situations where add-on
control technology is used in lieu of a complying low-solvent coating.
1-9
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2.0 CAN COATING
2.1 Summary of Control Technology
Affected Facility *
Two-Piece Can Lines
Exterior Coating:
Control Options
Interior Spray Coating:
Catalytic and
catalytic incineration
Water-Borne & High-Solids
coatings
Ultraviolet Curing
Catalytic and non-
catalytic incineration
Water-Borne & High-Solids
coatings
Powder Coating
Carbon Adsorption
Percent Reduction
90
60-90
up to 100
90
60-90
100
90
Three-Piece Can Lines
Sheet Coating Lines
Interior Coating:
Exterior Coating:
Catalytic and non-catalytic
incineration
Water-Borne & High-Solids
coatings
Catalytic and non-catalytic
incineration
Water-Borne & High-Solids
coatings
Ultraviolet curing
90
60-90
90
60-90
up to 100
2-1
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Can Fabricating Lines
Side Seam Spray Coating:
Interior Spray Coating:
Water-Borne & High-Solids 60-90
coatings
Powder (only for non-cemented 100
seams)
Catalytic and non-catalytic 90
incineration
Water-Borne & High-Solids 60-90
coatings
Powder (only for non-cemented 100
seams)
Carbon Adsorption 90
End Coating Line
Sealing Compound:
Sheet Coating
Water-Borne & High-Solids 70-95
coatings
Carbon Adsorption 90
Catalytic and non-catalytic 90
incineration
Water-Borne & High-Solids 60-90
coatings
*Any sheet, can or end coating line consists of the coater(s) and ovens(s).
2.2 General Discussion
Cans are made in one of two different ways. A "three-piece" can is
made from a rectangular sheet (body blank) and two circular ends. The
metal sheet is rolled into a cylinder and soldered, welded or cemented
at the seam. One end is attached during manufacturing, the other during
packaging of the product. The "two-piece" can is drawn and wall 1-ironed
from a shallow cup and requires only one end which is attached after the
can is filled with a product.
2-2
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Cans are used as containers for over 2500 different products ranging
from beer and other beverages, meats, fruit, vegetables and other edible
products to tennis balls, motor oil and paints. Cans are fabricated in
over 600 different shapes, styles and sizes. There are, therefore, major
differences in coating practices depending on the can and type of product
packaged in the can.
Independent and captive can manufacturers make up the industry. The
independents are a service industry that coat and fabricate cans for a
variety of customer's needs and specifications. A few olants are owned by
independent companies but manufacture cans for a single customer. Captive
can manufacturers coat and fabricate containers only for products of that
corporatjoru
Can manufacturing plants are typically located either near steel or
aluminum mills or in the vicinity of their customers. In the independent
can industry, the metal sheets for three-piece cans are usually coated near
steel mills, and the cans are usually fabricated near the customers. The
captive can industry typically coats and fabricates cans in the vicinity
of the plant that uses the cans. About 50 percent of the U.S. can
coating industry is located in California, Illinois, Ohio, Texas, Pennsylvania
and New Jersey. On a regional basis, EPA Region V has about 27 percent
of the U.S. can industry, Region IX about 16 percent and Region III about 12
percent.
Sizes of can manufacturing plants vary. Some plants coat only
the metal sheets, some fabricate only the three-piece cans from the
coated sheets', some fabricate and coat only two-piece cans.^jind some
coat and fabricate only can ends. Othe nlants perform combinations of
these processes.
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2.2.1 Materials Used - The metal sheets tyoically coated in
the three-uiece can manufacturing industry are tinplate, tin-free steel,
black plate and aluminum in gauges ranging from 0.006 to 0.015 inch and
sheet sizes ranging from 30 inches x 32 inches to 37 inches x 42 inches.
Aluminum is widely used in two-piece can manufacturing but some steel is
also used.
The interior base coat is roll coated on the sheets for three-piece
cans to provide a protective lining between the can metal and product.
It is important that the interior base coat does not react with the
product to alter the product's taste, odor, or appearance. All interior
COBtinqs for cans that will contain edible products must meet Food and
1 2
Drug Administration regulations. '
Some common resins used in the interior base coat are butadienes,
rosin esters, phenolics, epoxies, and vinyls. The coatings in which
these resins are used range from 20 to 60 percent solids by weight,
1,2
and organosols that range from 30 to 66 percent solids by weight.
The exterior base coat, usually white,IS used frequently both on two
and three piece cans to provide exterior protection to the metal and
background for the lithograph or printing operations. Some of the coating
resins used are polyesters, alkyds and acrylics. These coatings are
approximately 55 to 72 percent solids by weight.
Conventional inks used for printing or lithography contain approximately
90 to 99 percent solids by weight. ' These inks may be used for both two
and three-piece cans,with or without exterior base coat as Specified by
the customer.
24
-------
An over-varnish is usually applied directly over the inks to reduce
the coefficient of friction (to allow for proper mobility of the can on
conveyor tracks), to provide gloss, and to prbtect the finish against
abrasion and corrosion. Some common solvent-thinned coating resins
are acrylics,epoxies, alkyds, and polyesters at solids contents of 30 to 45
percent by weight. '
The orimer or size coat is roll coated before the application of the
exterior base coat or ink to provide better adhesion of the coating,
eSDecially if a coating has to withstand severe deformation during
stamoing or tooling operations or withstand high temperature processing
operations. The sizing is usually an epoxy, eooxy ester, acrylic, vinyl
or po lyester re s (i n.
Over 30 different solvents are used in interior and exterior base
coats, overvarnish and size coat. These include mineral spirits, xylene,
toluene, diacetone alcohol, methyl iso-butyl ketone, methyl et^yl ketone,
isophorone, Solvesso 100 and 150 (TM), ethylene glycol monoethyl ether
(TM under Cellosolve) ethanol, cyclohexanone, ethylene glycol monobutyl
ether (TM under Butyl Cellosolve),ethylene glycol monoethyl ether acetate
(TM under Cellosolve acetate), n-butanol, isooropanol, butyl carbinol,
oaraffins, oropylene oxide, mesityl oxide, aliphatic Petroleum hydrocarbons,
di-isobutyl ketone, di-methyl formamide, and nitrooropane.
The coating used for the sideseam on the interior and some-
times on the exterior of three-oiece cans usually contains vinyl and eDOXY-
Dhenolic resins at 10 to 40 percent solids by weight. Solvents used in
side-seam coatings are xylene, butyl acetate,paraffins, nitropropane,
Cellosolve acetate (TM), methyl iso-bu /I ketone, mineral spirits, propy-
1 4
lenr oxides and toluene. '
2-5
-------
The end sealing compound is usually a dispersion of a synthetic rubber
in heptane or hexane, and lines the edges of can ends to form a gasket.
It contains 30-45 percent solids by weight.'
2.2.2 Processes and Affected Facilities
Two-Piece Cans - The two-piece can manufacturing operation is a continuous,
high speed process and includes both fabricating and coating operations.
These cans are typically used by the beer and other beverage industries.
Figure 2-1 shows one method of fabricating and coating two-piece aluminum
cans.
Metal for two-piece cans is received in coil form and is continuously
fed into a press (cupper) that stamps and forms a shallow cup. The cups
go through an extrusion process that draws and wall-irons the cups into cans
in a lubricating solution and trims the uneven edge of the cans. The cans
are then cleansed to remove the lubricating solution, rinsed with hot water,
and dried. Some manufacturers have been required to provide water treatment
facilities to treat the cleansing process water prior to disposal.
The exterior bodies of these cans are sometimes reverse-roller
coated with a white base coat. The base coat is transferred from a feed
tray, through a series of rollers, and onto the can, which rotates on a
mandrel. The coating is cured or baked at 350 to 400°F in single or multi-
pass continuous, high production ovens at a rate of 500 to 2000 cans per
minute.
Several colors of ink are applied to printing blankets on a rotary
printer that transfers the designs and lettering to the can as it rotates
on a mandrel. A protective varnish is sometimes roll coated directly over
the inks. The decorative coating is cured or baked in single or multi-pass,
continuous, high production ovens at 325 to 400°F.
After printing, the cans are necked, flanged, and tested. Flanging
facilitates proper tnd assembly once the can is filled. Necking allows
o c
-------
use of a smaller end. Each can is tested for leakage by applying approximately
12 psig of air pressure and monitoring the can for air leakage.
The cans are spray-coated on the interior of the can body and spray
and/or roll coated on the exterior of the bottom end. The viscosity,
spray time, atomization pressure, and temperature during application of
the coating require precise control to provide a continuous protective
film between the product and the can.2
The coating is usually cured or baked in a continuous, single pass
oven at temperatures of 225 to 400°F. Coated cans are stacked on pallets
for shipment to users.
Some two-piece steel cans are sprayed with an additional interior
coating and baked prior to the application of the interior body spray.
Also the cans are necked in and flanged after the final step.
Three-Piece Cans - The three-piece can manufacturing process can be
divided into two operations: sheet coating and can fabricating. The
sheet coating operation may be subdivided further into base COeMng of
one or both sides and the printing or lithographing. The base coating
operation consists of applying an interior coating for three-piece
cans and can ends, an exterior background coating, or a size coat if the
customer so chooses.
The sheets are roll coated on one side only by transfer of the
coating from the coating tray, through a series of rollers, and onto
the sheet as shown in Figure _.2. Sheets are then picked up by the preheated
wickets and transported through a continuous, multi-zone, oven. xhe coating
is cured at temperatures of up to 425°F. Speeds are 70 to 150 sheets
per ninutei depending on the age of equipment and the type of coating.
The sheets are air cooled in the last 2(. -' of the oven. Oven exhaust
rates usually vary between 2,000 and K jQ scfm.
2-7
-------
CANS
COIL
ro
i
00
CUPPER
OVEN
WALL
IRONER
T
INTERIOR BODY SPRAY
AND EXTERIOR END SPRAY
AND/OR ROLL COATER
WASHER
LEAK
TESTER
OVEN
SECOATTRAV
EXTERIOR BASE COATER
i
CANS
HANfl
PRINTER AND OVER VARNISH
COATER
1
COLOR 4
. .COLOR 3
INTERr
COLOR 2
COLOR 1
VARNISH TRAY
NECKER AND
FLANGER
OVEN
Figure 2-1. Diagram of two-piece aluminum can fabricating and coating operation.
-------
COATING
TRAY
APPLICATION
ROLLER
WICKETS
^\
r\+T*- PRESSURE
I / \J ROLLER
SHEET (PLATE)
FEEDER
BASE COATER
WICKET OVEN
SHEET (PLATE)
STACKER
Figure 2-2. Sheet base coating operation.
-------
The sheet printing or lithograph operation (graphic arts) usually
consists of applying one or two colors of ink either on the exterior base
coat, the size coat, or directly on the metal. A varnish is applied directly
over the wet inks. Inks are applied by a series of rollers transferring the
design first to a blanket cylinder, then onto the metal sheet as shown in
Figure 2-3. The transfer of inks is influenced by environmental factors
such as temperature, draft and humidity because the inks can become
emulsified in the presence of water. Varnish is applied to the metal sheets
by a direct roll coater. Inks and overvarnish are cured in a wicket oven
similar to but usually smaller than the base coat oven; exhaust rates are
1,500 to 8,000 SCfttl. If the required design has more than two colors, the
first set of inks is dried in an oven. Another set of inks is then applied
followed by an overvarnish and then baking in an oven.
During the past several years, ultraviolet light curable inks have
been developed which permit the application of up to 4 colors in a single
pass. In addition, some printing inks have been developed that do not
require an overvarnish.
The can fabricating process is the forming of cans from the coated
sheets. Some of these cans have flat surfaces and some are beaded
for extra strength. Figure 2-4 describes a beer and other beverage three-piece
can fabricating line. Sheets are slit into can body size blanks and fed into
a "body maker" in which the body blank is formed into a cylinder. The seam
is welded, cemented, or soldered, and sprayed on the exterior and interior
of the seam with usually an air-dry lacquer to protect the exposed metal.
On some cans other than beer or other beverage containers, the coating is usually
sprayed only on the interior. The cylinders are flanged to provide proper
can end assembly and may be necked-in depending on the customer's specifications.
2-10
-------
BLANKET
CYLINDER
SHEET (PLATE)
FEEDER
INK
APPLICATORS
LITHOGRAPH
COATER
OVER-VARNISI
COATER
WICKET OVEN
SHEET (PLATE)
STACKER
Figure 2-3. Sheet printing operation.
-------
CAN END, AND THREE-PIECE BEER AND BEVER/GE CAN FABRICA™G OPERATION
ro
SHEET (PLATE) STACK
ENDSEAMER
BODY
BLANKS
SCROLL
STRIP SHEARER
FORMED
SOLDERED
OR CEMENTED
BODY MAKER
SIDE SEAM
SPRAY
OVEN
INSIOIr NECKEA AND FL.ANGER
BODY
SPRAY
PALLETIZED LOAD
LEAK TESTER
Figure 2-4. Can end, and three-piece beer and beverage can fabricating operation.
-------
The interior of the cylinder is sprayed with a coating to ensure
a protective lining between the beer or other beverage and the can. Cans
used for other products are typically not spray coated.
The spray coating is usually cured or baked in single pass vertical
or horizontal ovens at temperatures of up to 425°F. The oven exhaust
rate is approximately 2,000 SCfm.
Open cylinders pass through an "end double seamer" that attaches one
end onto the cylinder. The cans are tested for leakage, then stacked and
palletized for shipment.
Can ends are stamped from coated sheets of metal in a reciprocating
press and the perimeter coated with a synthetic rubber compound that functions
as a gasket when the end is assembled on the can. Solvent-based compounds are
usually air dried and water-based compounds oven dried at approximately 110°F.
The oven exhaust rate is about 300 SCfm.
Table 2-1 summarizes some typical oven exhaust rates, organic solvent
concentrations, type of fuel used for the curing or baking operations, and
control methods used in the can industry.
Typical organic emission rates for can coating lines are listed in
Table 2-2. For sheet coating lines,88 to _9|jiercent-0f ^thfi solvent:_ i S^ estimated
to be evaporated in the Oyen._ For interior coating, side seam and coating
and end sealing compound line , most of the solvent evaoorates in the
1 4
coating operation. '
2.3 Special Considerations
Independent manufacturers have less "ontrol over the coatings used
thar captive manufacturers because the ""dependents must satisfy a broad
range of customers' product needs and Specifications. An independent may
Ure as many as 300 different coating for jlations.
2-13
-------
TAME 21 OPERATIOH OF TYPICAL CM COATING FACILITIES
EXHAUST GAS
SOLVENT
_ PLANT
ShWt Coating
Two-Piece Cans
Sheet Coating
Sheet Coating,
ro
£ Three- Piece Cans,
Two-Piece Cans
Sheet Coating,
Three- Piece
Cans and Ends
'hree-Piece Can
Fabrication (only
beer and beverage
PROCESS
Shget Base Coating
(fiJteriOr * interior)
Sheet Printing
Side Seam
Interior Body Spray
Exterior Base Coat
Lithograph, and
Overvarnish
Interior Body and
Exterfor End Spray
Exterior and Interior
Base Coat
Sheet Lithograph
Sheet Exterior and
Interior Base Coat
Sheet Printing
Side Seam
Interior Body Spray
Two-Piece: Exterior
Base Coat
Lithograph
Interior Body Spray
and End Spray/Rollcoat
Sheet Coating
Side Seam
Ends
Side Seam
'nterior Body Spray
OVEN
TEMPERATURE (*F)
400
380
Air dried
300-350
385
385
365
400
380
350-400
315
Air-dried
300
400
325
225
350-4Z5
Air -dried
Air -dried
Air-dried ,
300-350
OVEN EXHAUST
HATE IN SCW
8,000-10,000
4,000-5,000
2,000-3,000
6,800
4,000
2,000
6,000-6,00^
3,500-4,008
4,900
3.508
2,200
2.200
2,000
2,200
8,000-9,000
7,000
CONCENTRATION
tia
12
10-12
lo-12
8-15
8-15
8-15
5-10
5-10
5-15
3-12
10-15
5-15
5-15
10-15
10-15
-
10-15
FUEL
Itotural Gas
Natural Sas
Natural fits
natural
Gas
And
Propane
Backup
Natural
fiat And
Propatw
Backup
Natural
Gas
And
Propane
Backup
Satural
Gas
AM
Propane
Backup
Natural
Gas
CONTROL ftETHOO(S)
Each oven has a thermal incinerator
All OVtni ducted into one
incinerator.
None.
Some water-borne.
Single 20,000 ScflR thermal
incinerator, primary and
S«COndary heat recovery.
Use some water-borne; plan on
gO in) to water-borne, high-
solids and UV coatings. Use
WV for SOT* Inks.
CrUlytic incineration, plan
on goinQ to water-borne and
high-solids.
Plan on going to water-borne.
tV1gh-Sol1ds, and no-var Inks.
None.
Water-borne on some lines
Plan on going to water-borne
and high-solids.
Plan on going to water-borne
varnish or no-var inks.
Wse water-borne on some lines.
Carbon adSOrtar (feting replaced
by a catalytic inc1n»rator).
None.
Use some water-borne coatings.
None.
"Ion,-.
-------
Table 2-2 ORGANIC SOLVENT EMISSIONS FROM CAN COATING PROCESSES
Sheet
Sheet
Beer
Process
>".cJ coating line
lithographic coating line
and beverage can- side
Typical volatile organic
emissions from coating
line, lb/hr
112
. 65
12
Estimated fraction
of emissions from
Coater area
9-12
8 11
100
Estimated fraction
of emissions from
oven
88-91
89-92
air-dried
Typical organic
emissions,
tons/yr"
160
50
18
seam spray coating process
Beer and beverage can-interior
body spray coating process
54
75-85
15-25
80
Two-piece can coating line
End sealing compound line
86
8
uncertain
100
uncertain
air-dried
260
14
•r.-ip-ii . solvent emissions will vary from line to line as a result of line speed, size of can or sheet being
* 'PS of coating used.
upon normal operating conditions.
\
V
-------
Interior coatings must comply with (J. S. Food and Drug Administration
(FDA) Regulation No. 121.2514 if the cans are to contain edible products.
The FDA determines compliance with the regulation through a lengthy test
program. First, the coating must be tested to verify that all of the
components in that coating are specified in the FDA list of approved components.
Other tests must be performed to verify that extractables from that coating
are less than 50 ppm. If a coating contains new components not previously
tested by the FDA, an extended period may be required for suitable testing.
Frequently, the customer also performs long-range storage tests (as
long as 18 months) with the interior coating in contact with the product to
determine if there is any change in the product. Interior coatings must prevent
the product from reacting with the can,and the coatings must not react with
the product to alter its taste, odor, or color. Exterior coatings must meet
requirements for flow, gloss, color, hiding, adhesion, fabrication, blocking,
pasteurization, and retorting temperature resistance. Both exterior and interior
coatings are applied in very thin films, usually round 0.0003 inches. In the
can industry, film thickness is expressed in mg/sq. inch; most range from 1 to
15.
Plants subject to interruptions in natural gas suooly tynically use
liquefied petroleum gas (LPG) as backup fuel for can ovens. Sulfur dioxide
and other products of combustion of fuel oil may contaminate the coating
and affect product taste. However, if less efficient indirect fired ovens
are employed, fuel oil is acceptable.
Most can (coating ovens are designed to operate at 25 percent of the
lower explosive limit (LEL). Some can manufacturers, especially independents,
operate their ovens at only 5 to 15 percent of the LEL. This is less efficient
from both an energy and air pollution control standpoint because larger
volumes of air must be handled and processed. Some of the reasons cited for
2-16
-------
operating at lower LEL levels are: the variety of temperatures and speeds
required for different coatings, diverse sheet sizes, air volume distribution
requirements, uneven evaporation rates, and the tendency of LEL sensing devices
to foul. Coaters that use uniform coatings and coat uniform sizes of cans or
sheets are more likely to operate their ovens closer to 25 percent of the LEL
than COaters which use a large variety of coatings.
Equipment used for can coating and fabricating varies with age and type
of cans coated and manufactured, therefore, the ease of application of pollution
control technology will vary. Some existing equipment can apply low solvent
coatings without major costs and alterations; other equipment must be replaced
or extensively modified. Also, add-on control equipment is more costly to
retrofit to some lines than others depending on the extent of line equipment
alterations and structural changes.
The following sections discuss the use of incineration and carbon
adsorption, and conversion to water-borne, high-solids, powder, and ultraviolet
curable coatings to reduce organic emissions.
2.4 Available Control Technology
2.4.1 Option 1 - Incineration
Achievable Reductions - Reductions of organic emissions of 90 to 98 percent
from can coating ovens are achievable using non-catalytic incinerators.
At least 90 percent control is attainable by catalytic incineration systems.
Technical Analysis: Catalytl Incineration - Catalytic incineration frequently
can oxidize organic emissions efficiently at catalyst inlet gas stream
temperatures of 500 to 600°F and outlet gas temperatures of 750 to 1 ,000°F.
2-17
-------
Catalysts used in catalytic incineration are usually made of
platinum and therefore,are relatively expensive and may be poisoned.
Its activity or effectiveness is adversely affected by normal aging,
high temperature, and participate matter, sulfur oxides, and other
contaminants. Natural gas or propane are the preferred fuels for catalytic
incineration because their combustion products will not adversely affect
the catalysts. Normal catalyst life on a can coating line can be 2 to 4
years if the catalyst is not subjected to overheating, due to higher inlet
temperatures and/or higher concentrations,and is not poisoned.
Catalyst efficiency may be monitored by a hydrocarbon analyzer or in
terms of temperature rise and/or pressure drop across the bed. Routine
inspection and periodic cleaning are needed to insure optimum oxidation
of volatile organics.
For details on catalytic incineration, refer to Volume I, Section
3.2.2 of this series.
Table 2-3 presents a comparison of burner fuel requirements for
catalytic incineration with and without heat recovery for two flow rates:
5,000 and 15,000 scfm. As shown in Table 2-3, fuel requirements decrease
with the use of heat recovery. When using both primary and secondary heat
recovery, a net line fuel savings is possible with use of incineration
if all the energy available for recovery can be utilized. As the temperature
of the inlet process gas stream increases and/or the concentration of organics
in the gas stream increases above 15 percent LEL, the potential net fuel
savings using both primary and secondary heat recovery would even be greater.
As the gas stream concentration approaches 25 percent LEL, the fuel value of
the oven exhaust stream increases. If all other factors remain constant,
2 18
-------
TABLE 2-3 BURNER REQUIREMENTS FOR CATALYTIC INCINERATION
WITH VARYING DEGREES OF HEAT RECOVERY
a,5
Method
Process gas flow rate into
i nc i nerator, SC fm
5,000
15,000
Catalytic incineration, no heat
recovery
Burner requirements, 10 BtU/hr
Net
Gross
Catalytic incineration with
primary heat recovery
Primary heat exchanger efficiency,
percent
Burner requirements, 10 Btll/hr
Net
Gross
Catalytic incineration with primary
and secondary heat recovery
1.69
1.80
36.8
0.26
0.27
5.07
5.39
36.8
0.77
0.82
Secondary air flow, scfm
Secondary heat exchanger efficiency,
percent
Heat recovered, 10 BtU/hr
Net fuel savings, 10 BtU/hr
15,000
53.8
1.33
1.07
45,000
53.8
3.99
3.22
300°F process inlet gas stream, 15 percent LEL concentration.
Energy that may be used for energy using facilities other than an
incinerator.
2-19
-------
the temperature of the catalyst bed will increase and its design
temperature may be exceeded. Therefore, the operator may not always
be able to utilize all of the energy potentially recoverable with a
primary system.
Technical Analysis: Non-Catalytic Incineration - Many organic emissions
will oxidize at temperatures of 1,100°F to 1,250°F. Cellosolves (TM), toluene,
xylene, and some other organics, however, require 1,400°F to 1»500°F. Effective
Oxidation is also dependent on residence time and mixing in the incinerator.
Partially oxidized compounds can be formed 1f non-catalytic incinerators are
not maintained at proper oxidation temperatures and residence times. Non-
Catalytlc incineration will also increase NO, levels somewhat over those
experienced with Catalytic units.
For details on non-catalytic incinerators, refer to Volume I, Section
3,2.2.
Table 2-4 presents a comparison of incinerator fuel requirements for
two flow rates (!5,000 and 15,000 scfm) and two cases: with and without
heat recovery. Fuel requirements decrease with primary heat recovery,more so
with both primary and secondary heat recovery. A net fuel savings may accrue
by using both primary and secondary heat recovery if all of the recovered
energy can be utilized. Moreover, as the temperature or organic concentration
of the inlet process gas stream increases, there will be an even greater net
fuel savings if the available heat can be utilized. However, the can
coaters may often apply a variety of coatings on a line at various organic
solvent contents resulting in varied emission concentrations and variable
fuel requirements.
As shown in Table 2-1, some can coaters are presently using incineration,
typically with 45 percent efficient primary heat recovery, to control emissions
from sheet coating facilities and two-piece can coating facilities. Some
2-20
-------
TABLE 2-4 BURNER REQUIREMENTS FOR NON-CATALYTIC INCINERATORS
WITH VARYING DEGREES OF HEAT RECOVERY3'5
Method
Process gas flow rate into
incinerator, scfm
5,000
15,000
Thermal incineration, no heat
recovery
Burner requirements, 10 BtU/hr
Net
Gross
Thermal incineration with
primary heat recovery
Primary heat exchanger
efficiency, percent
Burner requirements, 10 Btu/hr
Net
Gross
Thermal incineration with primary
and secondary heat recovery
Secondary air flow, scfm
Secondary heat exchanger
efficiency, percent
Btu recovered, 10 Btu/hr
Net fuel savings, 106 Btu/hrb
4.05
4.30
38.5
1.56
4.73
15,000
55.2
1.90
0.34
12.16
12.93
38.5
1.66
5.03
45,000
55.2
5.69
0.66
300°F process inlet gas stream; 15 percent LEL concentration.
Energy that may be used for eneryy using facilities other than
an incinerator.
2-21
-------
secondary heat recovery is used for preheating the wickets on sheet coating
lines, and for the washers and dryers on two-piece can coating lines.
Costs of Control Option. - The value of recovered energy does not completely
compensate for added operating costs, Table 2«5 provides a comparison of
estimated annual operating costs for various degrees of heat recovery. '
These costs were derived for "ideal" facilities using 5,000 and 15,800 scfm
flow rates at 15 percent of the LEI concentration. It was assumed that the
cost of installation is about 40 percent of the equipment costs. However,
the varying degrees of difficulty of retrofitting an incinerator to an existing
facility could increase installation costs by a factor of 2 to 4. The age
and type of can coating equipment, the price of fuel and electricity, labor,
wat«*"» engineering costs and the percent operating time where there is solvent
Input will cause operating costs to vary for each facility.
Catalytic incineration as shown in Table 2-5, 1s less costly than thermal
incineration in all cases for 5,000 scfm flow rates and for two cases with 15,000
scfm flow rates. However, catalytic incineration is almost equal in cost to
thermal incineration for the 15,000 scfffl primary and secondary heat recovery
cases. As more energy is recovered, operating costs of either type incinerator
decrease.
For detailed costs of thermal and catalytic incineration, see Valuma I,
section 4 of this series.
Effects and Limitations * Adverse environmental effects from incinerators
are mostly dependent on fuels and compounds present in the gas stream, If
sulfur or nitrogen compounds are present, their oxides can be generated.
If halogens are present, their a-cids will be formed, Sulfur oxides will be
generated by sulfur in the fuel oil or in the oven gases. Some nitrogen oxides
are always generated by air fixation.
2-22
-------
TABLE 2-5 ESTIMATED ANNUAL OPERATING COSTS FOR
THERMAL AND CATALYTIC INCINERATION9'b'5
FLOW RATE INTO INCINERATOR:
Type of Incineration
5,000 SCFM
Annual operating Cost per ton of
cost range, organics removed
dollars range, dollars
15,000 SCFM
Annual operating Cost
cost range, "•"*"
dollars
per ton of
organics removed
range, dollars
168,560-225,560 169-752
99,560-156,560 100-522
t\3
CO
Thermal, no heat recovery
Thermal, primary heat recovery
only
Thermal, primary and secondary
heat recovery
Catalytic, no heat recovery
Catalytic, primary heat
recovery only
i ,\ »,. . (i- i>wv and secondary
heat recovery
72,810-91,800
52,550-70,550
39,870-57,850
55,040
45,000-49,950
37,310-45,310
218-918
158-706
120-579
165-550
135-500
112-453
52,680-109,680
120,390
85,450-102,450
55,060-82,090
53-366
121-401
86-342
55-274
a300°F process inlet gas temperature; 5-15 percent LEl_ concentration range; $2.00/10 Btu fuel cost; tube and
b
shell heat exchangers.
these calculations are based on continuous 5000 hours per year operating time. However, due to the variety
of coatings applied, and often frequent coating changes in non-captive facilities, the actual operating time
when organic solvents are being emitted may not be 5000 hours per year.
-------
The can industry has generally avoided using fuel-oil-fired ovens
because of potential sulfur contamination that may affect the product
taste. Using fuel oil in the incinerator would necessitate indirect
heat-exchangers to ensure that sulfur compounds do not reach the ovens.
It is important to note that the energy contribution of the oven exhaust
will vary considerably. Solvent will actually enter an incinerator from
many sheet and can coating facilities rarely more than 75 percent of the
operating time of that facility due to coating changes, preparation period,
etc. During this time, the oven and incinerators must be maintained at
operating temperatures, thus using additional fuel. In addition, the
solvent concentration will vary due to coating composition-, film thickness,
line speed, sheet size, etc. To compensate for these variations, it is
common tc install a bypass around the primary heat exchanger. Then during
periods when the exhaust gas contains less organics, the bypass can be
throttled to maximize the inlet temperature to the incinerator.
Incineration is applicable for sheet coating facnitieSj_iwo-piece can
facilities and three-piece interior body spray coati-ng facilities,because
of their relatively high oven temperature and organic concentration
(around 10 percent of the LEL). Caoturing and incinerating the volatile
organics from side seam spray coaters and end sealing compound anolicators
is more costly and energy intensive because: the exhaust is usually at
ambient temperatures, gas volumes would be large and would contain relatively
low concentrations of organics , and since these coatings are air-dried, there
may be no nearby energy using facilities that can benefit from the
recovered energy.
2-24
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2.4.2 Option 2 » Water-Borne/High-Solids/Powder Coatings
Achievable Reduction, - The potential reduction of organic emissions from
converting to water-borne coatings and high-solids coatings is 60 to 90
percent. This depends on the solvent content of the original coating.
The reduction from conversion to powder coating approaches 100 percent.
Technical Analysis: Water-Borne Coatings • Water-borne coatings contain
a polymer or resin base, water, some organic "cosolvent" and solubilizing
agent. The presence of some organic solvent in water-borne coatings is
necessary to improve stability, flow-out, appearance, as well as to
depress foaming, and control the evaporation rate.
Problems associated with conversion to water-borne coatings often
vary due to application characteristics and the type of equipment available.
The replacement of certain existing equipment is usually necessary to
protect against corrosion.
Water-borne coatings may be applied by conventional techniques and
other newer methods. One. newer-^t4w>dy—currently, jus ed..forsome tK'Q-piece
beer cans is to apply a_water.rJbtonie base coat on the, entire can. during-the
final-stages of the cleansing section, then bake the coating in an oven.
Another method, in the experimental stages, is to coat the interior of
two-piece cans by filling them with a water-borne coating, apolyinq
a charge and electrodepositing the coating particles onto the can. This
method of apoli cat ion, however, is relatively slow and might require
several such units on each line. This could be a disadvantage to an older
plant which does not have enough room to install these applications.
The temperatures Of the oven zones have to be adjusted to avoid
"Ditt^nq" the water-borne coating film. 1 though some water-borne coatings
may require higher curing temperatures, this increase in energy consumption
2-25
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may be balanced by a significant reduction in oven exhaust flow because
Of the reduced input of volatile organics.
Water-borne coatings are often difficult to clean up after thev have
dried because they do not remain soluble in their carrier. Also, water-
borne coatings should be protected in transport and storage during winter
and summer months. For details on water-borne coatings, see Volume I,
section 3.3.1 of this series.
Technical Analysis: High-SoUds Coatings • "High-solids" coatings have
been defined by various agencies as those with volatile solvent contents of
only 20 or 30 percent by volume. To convert a process to a high-solids
coating may present application difficulties because of the high viscosity
of the material. To lower viscosity, it may be necessary to raise the
application temperature by installing a heating unit as well as changing
the application equipment. For details on high-solids coatings, see
Volume I, Section 3.3.2 of this series.
Technical Analysis: Powder Coatings - Powder coatings approach 100 oercent
solids. Converting to powder coatings necessitates a major change of
application equipment. Powder coating application technology is being pursued
in the can industry for two-piece can interiors, and has been used for the
sjde seam coating of nonHcemented three-piece cans. Powder coatings may
also be applicable as an overvarnish on two-piece cans. However, present
powder coating application technology has not been perfected to produce
the thin continuous film on the can at high speeds, as with solvent or
water-borne. For details on powder coatings, see Section 3.3.3 of Volume
I of this series.
2-26
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Cost of Control Options - The cost of converting to water-borne, high-
solids, or powder coatinqs will vary from Dlant to plant depending on
the type of cans, and the age and design of application equipment.
Some application equipment may require only small adjustments or the
replacement of a spray nozzle; others will require much more extensive
modification.
Water-borne, high-solids and powder coatings are often more expensive
than the pure organic solvent-borne coatings. With increased consumption,
further development and the increasing costs of organic solvents, the overall
cost of low solvent coatings may become less than conventional organic
solvent-borne coatings.
Secondary costs for conversion to low solvent coatings include:
refinements needed to meet customer's specifications and Federal Food
and Drug Administration standards. One independent can company reportedly
has spent more than $4iiOOO,000 in the last 3 years in the development
and testing of water-borne, high-solids, powder and "exempt" solvent
coatings. 4'8'9
Effects and Limitations - Some water-borne, high-solids and powder coatings
have been developed for the can industry that are comparable in performance
to solvent-borne coatings; they also comply with FDA standards. Since
these coatings are new to th«=» industry, many customers require extensive
testing because their differer friction characteristics may affect the
mobility of the cans during packaging or they may change the taste of
the oroduct. Many customers conduct independent tests to determine effects
of a coating on their product.
2-27
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The can industry applies very thin films of coating. Many of these
coatings,such as the side seam spray and interior body spray coatings,
are low solids (10-18 volume percent) coatings at 6.8 to 6.6 pounds of
organic solvent for each gallon of coating (minus water). Water-borne
coatings available for some of those applications contain 3.5 to 4.0 pounds
per gallon (minus water). ' This represents about an 80 percent reduction
in organic emissions over conventional organic coatings. Available water-
borne and high-solids sheet and can exterior base coats and overvarnishes
can contain about 2.2 pounds per gallon (minus water). The sheet interior
water-borne or high-solids base coats may contain 2.2 to 2.8 pounds per gallon
(minus water).
Water-borne,high-solids or powder coatings are not available to
replace all the present organic solvent-borne formulations used in the
can industry. Therefore, this option is not universal. However,
availability of these systems is predicted to increase substantially
over the next several years.
2.4.3 Control Option 3 - Carbon Adsorption
Achievable Reductions «• Carbon adsorption units can be used to control
organic emissions with an efficiency of 85 to 90 percent.'
Technical Analysis • A single carbon adsorption unit may be installed on
one can coating facility or on several coating lines together depending
on the location of the coating lines and the type of coating being performed.
Carbon adsorption is most adaptable to"low temperature" processes
using a limited number of solvents such as the can end sealing compound or
the interior body spray coater for beer and beverage cans, because
collecting mixtures of solvents can be difficult.
2128
-------
Coatings in the can industry may contain as many as ten solvents.
Because of the difficulty in separating-them, the recovered solvent is
probably best used as boiler fuel for generating steam for the regeneration
of the carbon bed. If the solvent is recovered for reuse, additional
distillation would probably be necessary to render it acceptable for reuse
in can coating.
Process gas streams must be cooled below 100°F for carbon adsorption
to be effective. Also particulate collection may be required since
particulate matter will coat the carbon bed and reduce its adsorption
efficiency. Carbon adsorption systems are not practical if non-filterable
matter is present in the gas stream. For example, silicone coatings
will coat the carbon bed and prevent adsorption. Corrosion of equipment
can occur if the solvents contain acid-forming compounds. If the carbon
adsorption units are located out of doors, improper operation may be
encountered on cold winter days unless care is taken in the design.
An experimental carbon adsorption system that uses the reco\'Qtd solvent
as fuel to produce steam for the regeneration of the carbon bed is known to
have been retrofitted to one can coating facility, a sheet coating line.
This unit has not been successful due to plugging of the carbon bed by
condensables and polymerization of some solvents.
Other cited Dr obi ems are: h'gh operating costs, water-soluble solvents
causing-water pollution, con 'ling of the carbon support screen, short useful life
of the carbon, and large fuel and water usage for steam regeneration. This
system is reportedly being replaced with a catalytic incinerator. Many of
the? a problems causing the carbon adsorber to function improperly were
2-29
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related to the relatively higher operating temperatures of the oven
and the mixtures of solvents used. Carbon adsorption is technically
feasible for "lower" temperature operations such as the end sealing
compound, side seam spray or the interior body spray of both two and
three-piece cans. However, capture of the volatile emissions from the
sealing compound and the side seam application areas may be difficult
and costly. This technique, although technically feasible, has not been
commercially demonstrated. For details on carbon adsorption, see Volume
I, Section 3.2.1 of this series.
Cost of Control Option » The costs of carbon adsorption systems to control
organic emissions are summarized in Table 2-6. These costs were derived
for an "ideal" facility, where the installation cost is about 40 oercent
of the cost of equipment. Installation costs will vary depending on
the pi ant involved and will be higher when retrofitting a carbon adsorber
on an existing facility.
The cost figures are for carbon steel equipment, although some solvents
such as ketones will require more costly alloys to avoid corrosion, costs
will increase also if distillation equipment or filtration of the process
gas stream is necessary. For additional cost data, see Volume I, section
4 of this series.
2-30
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TABLE 2-6. CUST OF CARBON AUSuRPTIOfi. IN CAN COATING
INDUSTRY a*
ro
Costs
Installed cost, $
5,000 scfm
15,000 scfm
No credit
for recovered
solvent
162,000
302,000
Recovered
solvent
credited at
fuel value
162,000
302,000
Recovered
solvent
at market
chemical value
162,000
302,000
Annual operating
cost, $
5*000 scfm
15,003 scfn
rr"t of collected
sol "'N» hs > '• " >n
15,'000 scfm
60,000
142,000
145
42,000
90,000
215
105
15,000
1,000
100
-5C
300 F inlet process gas temperature; 15 percent of LEL concentration.
Installation cost assumed to be 40 percent of equipment cost.
'Cost indicates a net qaitl.
-------
Effects and Limitations - The oven gas stream may contain not only the organic
vaoors from the coating but also other products such as from thermal
degradation and volatilization of resin. Some of these may condense to
sticky tar-like particulates. In such a case, the gas stream must be filtered
or scrubbed upstream of the adsorber and the solid waste-must be disposed
in an environmentally acceptable manner. If the filter does not remove
these particulates, the carbon bed will foul. When solvents that are
miscible in water are used, the condensate from the steam used to regenerate
the carbon bed may have to be heated to remove the solvents to avoid a
water pollution problem. Any boiler operating on recovered solvent must be
supplementally fired because of the typically low organic concentrations
of the process gas and the potential water loss of any miscible organics
during steam regeneration of the carbon bed.
2.4.4 Control Potion 4 - Ultraviolet Curing
Achievable Reductions - The curing chamber is lighted by special lamps
such as mercury vapor lights. Some ultraviolet curing lamps in the can
industry are water cooled and some air cooled. The air cooled systems
exhaust at about 3000 scfm. These ultraviolet curable coatings are specially
formulated to cure in the presence of ultraviolet light. These coatings
although totally organic, may be considered the equivalent of near zero
percent solids since little vaporization takes place during the near
instantaneous curing. Theoretically, UD to 100 Percent reduction of organic
emissions is achievable when using ultraviolet curing technology, however,
2-32
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there may be some volatilization of low molecular weight compounds during
the curing process. The amount emitted will depend on the coating
formulation; In addition, ozone generated by the lamps, is also emitted.
(The ozone concentration will likely never exceed 1 ppm in the exhaust
12
air for the ultraviolet systems in the can industry.} Rapid curing,
which can take place in less than one second, make the process attractive
13
for high soeed can coating ooerations.
Technical Analyses
Ultraviolet curing technology is becoming more attractive to the can
industry partially due to natural gas shortages. Ultraviolet curing
technology was first applied on sheet coating lines to dry the first two
colors (set) of ink quickly such that another-two colors of ink could be
applied in the same pass, thereby eliminating the need for oven drying the
first set. Research efforts report some progress in ultraviolet curing of
the exterior base coat, the inks and the overvarnish in a single pass,
followed sometimes by oven baking the coatings to achieve the dtsired
coating film properties. This would not only eliminate individua" oven
baking of the base coat and inks, but would also eliminate almost a^l
organic emissions from the oven since all the coatings would be ul T3-
violet sensitive and set before entering the oven. >L,\3t\'l
Ultraviolet light curing technology is also being considered and in
some cases used on a limited basis in other areas of the can industry such
as the curing-of the exterior ">f two-piece beer and beverage cans. Progress
in the acceptance of ultraviole coatings for can interiors will likely be
slow because each must await Federal Food anc Drug Administration aooroval
before they can be used.
2-33
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For further technical details on ultraviolet curing, see Volume I
section 3.3.8 of this series.
Cost of Control Options « The cost of ultraviolet curable coatings is
about twice as much as conventional coatings because their use is not wide-
spread, and the chemistry of ultraviolet coatings is more complex.
On the other hand, ultraviolet curing reduces energy usage by 60 percent.
The cost of curing equipment for ultraviolet coatings is about one-fifth
that of conventional ovens. The line speed for ultraviolet curing is
15
comparable to if not greater than that for conventional coating.
Effects and Limitations - Ultraviolet curing technology is presently
limited to thin semi-transparent coating films although they are being
tested for additional uses in the can coating industry. There are, however,
coating apn 11 cations (such as some can interiors) that will require a
matter of years before acceptable ultraviolet curable coatings are available.
2.5 Comparison of Control Options and Conclusions
Incineration is a proven retrofit control system that can reduce
organic solvent emissions from can coating facilities. Although inci-
neration can require significant amounts of fuel, installation of primary
and secondary heat recovery systems when feasible, will significantly reduce,
if not eliminate the incremental energy requirements.
Mater-borne, high-solids, powder and ultraviolet curable coatings can
reduce organic solvent emissions to the same degree as incineration and
may use less energy than solvent-borne coatings. Conversion to water-borne,
high-solids, powder and ultraviolet curable coatings has been successful
on some can coating formulations; however, many coatings are still in the
development stages or are undergoing tests for Food and Drug
2-34
-------
Administration and the packaging customer approval. The ability to convert to
water-borne, high-solids, oowder and ultraviolet curable coatings as a
control option will vary from plant to plant depending on the product.
Carbon adsorption can be feasi fa] e for reducing organic emissions on
the interior body and end spray area and oven, the end sealing compound
application area and the side seam spray area. Measures may be needed
in soiac cases to clean the process gas stream first. Because different
solvent mixtures are used, the recovered organics may have little market
value. However, they can be used as boiler fuel or be incinerated.
Costs of controlling organic emissions from the can coating industry
using low solvent coatings is difficult to determine because of the many
variable factors in the manufacturing process. Incineration is the most
economical retrofit control option when combined with heat recovery.
Control costs for carbon adsorption are greater than incineratic/i but approach
that of incineration if recovered solvent can be used as fuel.
It may be costly to collect and retrofit add-on control devices to
reduce organic emissions from side seam spray coaters, beer and beverage
can interior spray coaters and ovens, and the can end sealing compound
coaters because 75-100 percent of the organic solvent vapors are now
emitted as fugitive emission: within the plant. Conversion to water-borne,
high-solids or powder coatings is the best control option for those systems.
Moreover, conversion to water-borne, high-solids, powder or ultraviolet
curable coatings for the two-piece can coat nq lines and the sheet coating
lines would be the economical options i* ^ceptable. Otherwise, incineration
i*with heat recovery) or carbon adsoroti' vwith solvent recovery for fuel)
is re<- jrnmended.
2-35
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If incineration or carbon adsorotion is used to reduce emissions,
the coater can either be covered with a hood which is ducted to the oven
exhaust stream or the coater may be enclosed up to the oven entrance so
that the coater emissions are drawn directly into the oven.
The control of orqanic emissions from can COatinq facilities will
most likely require a combination of several control technologies because
of the complexity of coatings used and their annlication, and the economic
and energy considerations in any Particular plant.
2-36
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References
1. Gallagher, V. N., Environmental Protection Agency, Research Triangle
Park, N.C. Reoorts of trips to various can coating facilities in
1975 and 1976.
2. Read, R.T., Recent Developments in Protective Finishes for Metal
Containers, Part I: Internal" Organic Coatings. Oil Colour and
Chemists Assoc. 58: 51-56, 1975.
3. Holt, J.C., Recent Developments in Protective Finishes for Metal
Containers, Part II: External Organic Finishes. Oil Colour and
Chemists Assoc. 58: 57-61, 1975.
4. Personal communication between Environmental Protection Agency and
a representative of American Can Company, December 1975.
5. Combustion Engineering Inc., Wellsville, N.Y. Report on Fuel Require-
ments, Capital Cost and Operating Expense for Catalytic and Thermal
Afterburners, prepared for the U.S. Environmental Protettion Agency
under Contract No. 68-02-1473, (Task No. 13) EPA-450/3-76-031.
6. Ansfield, J., Powders Competition. Canadian Paint and Finishing.
December 1974.
7. Henning, C.C., and M.J. Krupp., Compell ing Reasons for the Use of
Water Reducible Industrial Coetings. Metal Finishing. October 1974
po 57-61.
a. Water-Borne Coatings Developed for Beer, Soft Drink Can Interiors.
Industrial Finishing, December 1974. p 76.
9. Landauer, L., and C.E. Scruggs, New Can Coatings to Meet Air Quality
Standards - Status Report. American Can Company, Barrington, Illinois
10. LeBras, L.R., PPG Industries, Pittsburgh, Pa., Letter to Vera Gallagher
in comment to draft of this document. Dated August 13, 1976.
11. Carlson, D.T., Coors Container Corporation, Golden, Colorado. Letter
to Vera Gallagher in comment to draft of this document. Dated
September 13, 1976.
12. Sal lee, Elgin D., Ultraviolet and Other Metal - Decoration Processes,
American Can Company, September 24, 1975.
13. Shahidi, I.K., J.C. Trebellas, and J.A. Vona. Improving UV Cured Can
Coatings. Celanese Chemical Company; Modern Paint and Coatings; Summit,
New Jersey, July 1375. pp 21-26
14. Capron, J.W. and R.C. Heininger. Continental Can Corporation, Thor
V Solventless Metal Decorating for Three-Piece Cans, Background.
Preoared for the U.S. Environmental Protection Agency, 1976.
Series 600/2-76-011
15. Radiation Curing Goes Begging for Coaters. Iron Age. August 18, 1975
pp 43-52
2-37
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3.0 COIL COATING
3.1 Summary of Control Technology
Affected Percent
facility Control Option Reduction
Coil coating line Therial incineration 90-98
Catalytic incineration 9 0
Water-borne & high- 70-95
solids coatings
Coil coating line consists of tbe coater(s), the oven(s) and the quench area(s),
3.2 fienera^ tHstnrsstQn
Coil coating is the coating of any flat metal sheet or strip that
comes in rolls or coils.1 The metal is typically roll coated on one or
both sides on a continuous production line basis. The metal may also
be printed or embossed. The coated metal is slit and fabricated by
drawing, stamping, roll -forming, or other shaping operations into
finished products to be used for cans, appliances, roof decks, shelvinq,
industrial and residential siding, cameras, culvert stock, cars, gutters,
and many other items'.
"Toll" and "captive" coaters represent the two basic divisions of the
industry. The toll coater is a service coater who accepts orders to
coat metal according to his customers' needs and specifications. The
captive coater both coats the letal and fabrisates the product from the
coated metal within the same plant or corporation. Some coil coaters are
both captive and toll coaters.
Coil coating plants are tyoically lo ited near industrial areas to
reduce raw material shipping time and cr . About half of the U.S. coil
coatv ] plants are located in Peimsylvan , Illinois and Ohio. On an EPA
3-1
-------
regional basis, Region V comprises about 46 percent of the coil coalers
and Region III about 28 percent. Plants vary in size based on the
number and the size of the coil coating lines.
Coil coating lines vary in the maximum width of metal they are capable
of coating. The lines can coat metal widths ranging from 0,50 to ?2 inches
and thickness ranges of approximately 0,005 to 0.090 Inches, 11 ne speeds
can range yp to 400 feet per minute with plant to go as high as 800 feet
per minute. Some common coil coating line sizes are 18, 26, 48, 54, 60
and 66 inches.
Coil coating line emissions come from the Coating area, the preheat
and baking zones of the oven, and the Cjueneh area, These emissions are
mainly volatile organics and other compounds, such as aldehydes, that
result from thermal degradation of volatile organics, Emissions from the
combustion of natural gas, which is typically used to heat the ovens, are
carbon monoxide, unburned fuel, nitrogen oxides, and aldehydes. If fuel
oil is used to heat the ovens, sulfur oxides and greater quantities of
2
nitrogen oxides,and partiClllates may also be emitted.
The major emissions from a typical coil coating operation are
summarized in Table 3-1.
TABLE 3-1 EMISSIONS MEASURED F-ROM AN UNCONTROLLED NATURAL GAS FIRED COIL
COATING OPERATION USING SOLVENT-BORNE COATINGS
Pollutant Amount emitted
Hydrocarbons 1.0 Ib/lb of coating apolied
Carbon monoxide 1,10 lb/103 ft3 gas fired
Nitrogen oxides 0.20 lb/103 ft3 gas fired
(as N)2)
Aldehydes 0.020 Ib/lb coating volatiles
(as formaldehyde) applied when water quench is used
Aldehydes 0.027 Ib/lb coating volatiles
(as formaldehyde) applied when air quench is used
3-2
-------
3.2.1 Materials Used- - The metals coated in the coil coating industry
include various aluminum alloys; steel; plated steel; steel alloys; and
some zinc, brass and copper.
Some plants may use as many as 900 different coatings, each containing
four to ten different solvents, and some use as much as 40,000 gallons of
coatings oer month. ADDfOXimate weight percentages of volatiles in
coatings most often applied in the coil coating industry are shown in
Table 3-2.
TABLE 3-2 COATINGS USED IN COIL COATING4'5
Volatile
Coatings (weight percent)
Acrylics 40-45
Adhesives 70-80
Alkyds 50-70
Epoxies 45-70
Fluorocarbons 55-60
Organosols 10-15
Phenol ics 45-50
Plastisols 0-50
Polyesters 45-50
Silicones 35-50
Vinyls 60-75
Dacromet (TM)
The solvents most often used in the coil coating industry include
xyl ene» tol uene , methyl ethyl ketone, Cellosolve Acetate (TM) , butanol ,
diacetone alcohol, Cellosolve (TM) , Butyl fellosolve (TM) , SolveSSO 100
and 150 (TM), isophorone, butyl carbine"1 mineral spirits, ethanol ,
nitrOD,X>Dane, tetrahydrofuran, Panasolv ?TM) , methyl isobutyl ketone,
Hisol 100 (TM), Tenneco T-125 TM)t isopi -panol »bd di isoamyl ke ^ne.
3-3
-------
3.2.2 Processes and Affected Facilities - Configurations of coil coating
lines differ from one another. On some lines, the metal is uncoiled at
one end of the line and recoiled at the opposite end. On other lines, called
"wrap around" lines, the metal is uncoiled and recoiled at about the same
point on the line. Some coil coating lines have a single COater and one
curing or baking oven; others called "tandem" lines, have several successive
COaterS each followed by an oven so that several different coatings may be
applied in a single pass. Figure 3-1 is a schematic of a "tandem" coil
coating line.
The metal on the coil coating line is moved through the line by power-
driven rollers. It is uncoiled as the process begins and goes through a
splicer, which joins one coil of metal to the end of another coil for
continuous, nonstop production. The metal is then accumulated so that
during a splicing operation, the accumulator rollers can descend to pro-
vide a continuous flow of metal throughout the line. The metal is cleaned
at temperatures of 120°F to 160°F» brushed, and rinsed to remove dirt,
mill scale, grease, and rust before coating begins, The metal is then
treated for corrosion protection and for proper coating adhesion with
various pretreatments,depending on the type of metal being coated and the
type of coatings applied.
The first or "prime" coat may be applied on one or both sides of the
metal by a set of three or more power-driven rollers. The "pick-up"! roll,
partially immersed in the coating, transfers the coating to the applicator
roll. The metal is coated as it passes between the applicator roll and
the large back-up roll. The metal is typically reverse roll coated.
3-4
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ACCUMULATOR
ACCUMULATOR
OJ
i
PRIME
COATER
PRIME
OVEN
PRIME
QUENCH
METAL CLEANING PRETREATMENT
/T
UNCOILING
METAL
TOPCOAT
COATER
TOPCOAT
OVEN
TOPCOAT
QUENCH
SHEAR
LJ U
RECOILING
METAL
Figure 3-1. Diagram of coil coating line.
-------
Figure 3-2 is a schematic of a typical rollcoater. A third roll, Called
a "doctor" rol1,may be used to control film thickness when applying a nigh
viscosity coating,by making contact with the "pick-up" roll.
The applied coating is usually dried or baked in continuous, mul ti -
zone, high production cateaary, flotation, or double-pass oven. The
temperatures of the preheat, drying or baking zones may range from 100°F to
1000°F depending on the type and film thickness of coating used, and the
type of metal being coated. The flow rates of the ovens' exhaust may vary
from approximately 4000 SCfm to 26,000 scfm. Many of these ovens are
designed for operation at 25 percent of the room-temperature lower
explosive level when coating at rated solvent input. As the metal exits
the oven, it is cooled in a quench chamber by either a spray of water or a
blast of air followed by water cooling.
A second coat or "topcoat" may be applied and cured in a manner similar
to the prime coat. The topcoat oven, however, is usually longer than the
prime coat oven and contains more zones.
Another method of applying a prime coat on aluminum coils or a Single
coat on steel coils is to electrodeposit a water-borne coating to either one
or both sides of the coil. The coil enters a V-shaped electrocoating bath
that contains a roll on the bottom. As the metal goes around the roll,
electrodes on each side can be activated and permit the coagulation of the
paint particles on either one or both surfaces of the coil. The coated coi ]
is then rinsed and wiped by squeeges to remove the water and excess paint
particles. For steel coils, the electrodeposited coating must be baked in
an oven. For aluminum coils, however, the prime coat is stable enough to
3-6
-------
INTO OVEN
APPLICATOR ROLL
PICKUP ROLL
FLOW OF METAL INTO COATER
Figure 3-2. Typical reverse roll coater.
3-7
-------
immediately go over rolls to the topcoat coater without destroying the
6
finish, and then be baked as a two-COdt system.
After cooling, the coated metal passes through another accumulator, is
sheared at the spliced section, usually waxed, and finally recoiled. The
accumulator rolls rise during the shearing process, collecting the coated
metal to ensure continuous production. Table 3-3 summarizes the ooeration of
typical coil coating facilities.
Organic vapors are emitted in three areas of a coil coating line:
the area where the coating is applied, the oven, and the quench area. The
oven emits approximately 90 percent of the organic vapors and a majority
of the other pollutants. Of the remaining 10 percent of hydrocarbons emitted,
approximately 8 percent are emitted from the coater area and approximately
two percent are emitted from the quench area. » Organic vapor emissions
from a tested uncontrolled coil coating facility, reported as methane, are:
117
coater arek 480 ppm; oven, 4950 ppm; and quench area 100 ppm. Considerable
amounts of aldehydes are also emitted from the thermal degradation and
oxidation of volatiles in the ovens. Carbon monoxide emissions mainly result
3
from improper adjustments of oven burners.
3.3 Special Considerations - The coil coating industry has exhibited about
15 percent annual growth rate over the past decade compared with the 4 to 5
8 9
percent annual growth rate for most other industrial coating industries. '
The reasons for this rapid growth include the high speed at which the metal ma;
be coated, the low labor costs, the small amount of waste that occurs during
the coating process, the uniformity of film thickness (al though the range of
thickness that can be applied may be limited), the savings on plant space,
the Wide variety of coatings and designs available, and the short changeover
times needed when changing coatings.'
3-3
-------
Line Size Ovens
(in width;
18 inch Prime
Topcoat
26 inch Prime
Topcoat
31 inch Single
31 inch Single
w 48 inch Prime
I'D Topcoat
54 inch Prime
Topcoat
54 inch Prime
Topcoat
60 inch Prime
Topcoat
60 inch Prime
Topcoat
Flow Rate
scfm
4,900
3,400
7,400
12,000
5,000
5,600
25,900
11,700
6,500
12,500
24; 000
24,000
26,000
35,000
Operating solvent
Ternperature°F concentration
(in % LEL)
10-20
600 10-20
?00
700 25 and less
Zoned at Near 25
400-600
Zoned at 25 and less
300-600
900-1100 25 and less
725
Zoned at fjear 25
3CO-600
750 10-15
775 15-25
600 Near 25
Zoned at 25 and less
300-800
Type of
fuel used
Natural
gas
Natural
gas
Natural
gas
Electric
Natural
gas
Electric
and gas
Natural
gas
Natural
gas
Natural
gas
Control Method
NONE
Thermal
incineration
Going water-borne
Plan on going to
water-borne
Catalytic
incinerator
Plan on going to
water-borne
Thermal
incineration
Thermal
incineration
Thermal
incineration
Mme 24,000
Topcoat 24,ooc
Less than 25
Propane
Thermal
incineration on
each oven
-------
The captive coil coater, because he fabricates his own product, tends
to have more control over the coatings used than the toll coater, v.'ho
must meet the needs and specifications of customers. New uses for coil
coated metal are being found continuously as are new coatings.
Because of the different post-forming operations that coated coils
must undergo, coatings must survive many "acceptance tests", including adhesion,
impact resistance, film thickness, color, sheen, gloss, hardness and resistance
4
to salt spray and abrasion. Approximately 65 percent of the coil coated
production is used by the building industry: therefore, the coatings often
must be resistant to weathering, must provide durable finishes, and must
satisf" a product warrant.1'. Extensive testing (as long as 5 years) may be
6
required before a coating can be commercialized,
Natural gas is the primary fuel used in coil coating, and propane is
the primary backup fuel during curtailments of natural gas or V.'here natural
gas is not available. The coil coating industry consumes less than 1 percent
of the U.S. total gas usage. Production has been curtailed in some plants
because of the shortages of natural gas and the lack of availability of
propane as backup fuel!' In some areas of the country, the gas companies
are not accepting new orders of natural gas. This, couoled \.ith increasing
demands for propane are causing some coil coaters to use other forms of fuel
such as oil and electricity to heat the ovens, or oil to fire the incinerators.
Others are T0okincj into more efficient methods of baking.
The coil coaters typically try to operate the ovens around 25 ercent
of the lower explosive limit (LEL) as permitted by the insurance companies.
Some are permitted to operate at higher LEL'S under special conditions and
3-10
-------
reliable LEL monitoring equipment. However, present LEL monitoring
equioment reoortedly requires a high degree of maintenance because
condensate fouls the sensing device.
It is not always possible to operate at a high LEL. Coil coaters
are not always able to vary the exhaust flow rates dynamically from each
oven to maintain high LEL's at a given line SDeed when applying a tWO-
coat system.
On some coil coating lines, the coater is isolated in a room.
[-^
! Since the oven is maintained at negative pressure, the organic vapors
from the coater room are Dulled into the oven. Others have hoods over the
coater to exhaust the organic vapors into the atmosphere. f
Coil coaters are also faced with controlling the water pollution from
their metal cleaning ooerations. Many have been required to install water
treatment systems and have faced the associated sludge disposal oroblems.
Thus, coil coaters are faced with water pollution control and S\,lid waste
4
disoosal costs as well as those of air pollution control.
3.4 Available Control Technology » The followinq discusses incineration,
water-borne and high-solids coatings, all of which reduce organic vapor
emissions. Other technically feasible control options may be used on coil
coating lines that coat metal for a specific purpose, but they are not
yet applicable to the industry as a whole.
Electrostatically sprayec DOWder coating is limited because a complete
selection of acceptable resins is not yet available for use in the coil
industry, and the present aoolication technology cannot adequately control
film thickness and edge overlap.
The use of electron beam ClirirK is .ited because coating formulations
have P't yet been developed to satisfy f requirements of the coil coating
industry. The deficiencies may be relat. to the chemistry presently used
3 11
-------
12
for these coating formulations. ""Ultraviolet curing is limited because it
is presently restricted to thin semi-transparent coatings. Moreover, an
acceptable variety of such coatings has not yet been developed for use by
the coil coating industry.
The use of carbon adsorption is limited because the high oven discharge
temperatures necessitate a large decree of cooling upstream of the adsorber.
Further pretreatment would be required because cracking and nolytnenzation
of organics form condensable products that can foul or poison the adsorbent.
(Pretreatment by water scrubbing may produce a potential water pollution
problem). Moreover, even after pretreatment by scrubbing or filtering, some
products may still foul the carbon bed, resulting in an inefficient collection
of organic vapors. In addition, there would be little market value for solvents
recovered by this industry because of the mixtures of solvents used and the
expense required to separate them.
Carbon adsorption may be applicable to certain coil COatGPS who operate
low temperature ovens and use uniform coating formulations. However, because
the industry is finding new uses for coated coil as well as new coatings that
may poison the carbon, adsorption is not widely applicable, especially for
independent coil coating operations. If carbon adsorption is considered, it
is advisable to analyze the gaseous and condensable organics in the gas stream
vented from the ovens to assure such control is practical. For further details
on carbon adsorption, see Volume I, section 3.2.1 of this series.
3.4.1 Option 1 - Incineration . A reduction of over 90 percent in organic
emissions from a coil coating line is achievable using either noncatalvtlC
or catalytic incineration.
3-12
-------
Technical Analysis - Catalytic incineration oxidizes organic emissions
efficient!; at catalyst inlet gas stream terrueratures over 500 to 600°F and
Catalyst outlet gas stream temperatures of 750 to 1000°F.
The platinum catalysts usually used in catalytic incineration can be
deactivated by: aging or high temperatures, coating with particulate
matter, or poisoning with contaminants. Natural gas or propane is the
preferred fuel for preheating the gases (if necessary) because of its
cleanliness.
The life of a catalyst on a coi? coating line is about 1 to 2 years,
depending on the inlet gas stream temperature, on the inlet concentration
of organics, and on other pollutants in the gas stream. At higher inlet
temperatures and organic concentrations, the temperature rise from combustion
of the organic vapors increases; thus, the exit temperature in the catalyst
may become too high for normal catalyst life.
The catalyst can be poisoned by certain materials or coated 5} particulate
such as that from si 1 iconized coatings. These will reduce its efficiency if
they are not removed effectively ahead of the catalyst bed.
Catalyst efficienctmay be monitored by a hydrocarbon analyzer or in
terms of temperature rise and pressure drop across the bed. Such routine
inspection and periodic cleaning can insure optimum reduction efficiency of
volatile organics and possibly a longer catalyst life.
For further technical details on catalytic incineration, refer to
Volume I, section 3.3.2 of this series.
Table 3-4 presents a comparison of calculated catalytic incinerator burner
requirements for three systems: simple catalytic incineration, catalytic
incineration with "primary" heat recovery, | ~eheat of gases into the
>r) and catalytic incineration wft1 Tl'mary and "secondar*'" h=>at
3-13
-------
TABLE '3-4 FUEL REQUIREMENTS FOR CATALYTIC INCINERATORS WITH
AND WITHOUT HEAT RECOVERS
I LEL
15
25
Gas
twnperature to
catalyst, °F
600
500
Catalytic
Incineration
mo t-teat recovery
Fuel
Requirements
WBtu/hr
Net Gross
1.69
0
1.80
0
Catalytic Incineration with
primary heat recovery
Heat exchanger
efficiency, %
20
-
Fuel
Requirements ,
10 Btti/hr
net eross
0
0
0
0
Catalytic
and
bat exchanger
efficiency, %
5 5
55
Incineration with primary
secondary heat recovery
Heat recovered
by secondary
heat exchanger,
10 Btu/hr
5.58
6.76
Net fuel
rate,
10° Bfu/h
-5.88
-6.76
Process gas flow rate of 15,000 scfm; process gas inlet temperature of 500*F
-------
recovery (recovery of heat from the incinerator exhaust for prOGSS heat).
As can be seen from Table 3-4, when the concentration of the qas stream
approaches 25 percent of the LEL, and the inlet gas stream temperdture
to the combustion chamber is maintained at about 500°F, a coil coating
line equipped with a catalytic incinerator may use little, if any,
additional energy for the operation of the burner, even without primary
heat recovery. A primary heat exchanger without a bypass may not save much
energy because the efficiency of the heat exchanger is limited by the upper
temperature limitations of the catalyst. Klien catalytic incineration with
only 55 percent efficient secondary heat recovery is used, there is a net
fuel savings , assuming the recovered heat can be used for process heat.
Coil coating facilities are currently using catalytic incinerators to
reduce organic emissions from their surface coating operations.
Technical Analysis: Noncatalytic (Thermal) Incineration - Noncatalytic
incinerators will oxidize most organics at temperatures of 1100 tc 1250°F.
Some organics, however, such as Cellosolves, (TM), toluene and xyl£fl3
require 1400 to 1500°F incineration temperatures for oxidation. Proper
oxidation is also dependent on residence time (usually 0.4 to 0.6 seconds)
and sufficient mixing. If noncatalytic incinerators are not maintained
at proper oxidation temperatures or residence times, partially oxidized com-
pounds can be formed. Such compounds,in some cases, may be harmful.
Noncatalytic incineration may also increase NO levels from a source. For
further technical details on noncatalytic incineration, refer to Volume I,
section 3.2.2 of this series.
As can be seen from Table 3-5, a significant amount of energy is consumed
"'hen n -ncatalytic incineration is used t^, educe organic emissions. As the
organic concentration of the gas stream " ,reaS6S from 15 percent to 25
Percent of the LEL, the burner requirements are reduced by almost
3-15
-------
\
TABLE 3-5 FUEL REQUIREMENTS FOR NONCATALYTIC INCINFRATORS WITH
AND WITHOUT HEAT RECOVER?
% LEI
15
25
JMoncata-iytic
Incinerator
10 heat, recovery
Burner
Requirements,
10 Btu/hr
Net Qress
9.95
5.59
10.58
5.95
Noncatalytic Incinerator with
primary heat recovery
Heat exchanger
efficiency, %
35
25
Fuel
Requirements ,
KTTJtu/hr
Net
3.14
1.5
Gross
3.36
1.65
Noncatalytic Incinerator with primary
and secondary heat recovery
Heat exchanger
efficiencv, %
55
55
Heat recovered
by secondary
heat exchanger,
10DBtu/hr
6.12
6.73
Net fuel
gate,
10 TTtu/hr
-2.76
-5.23
Process gas flow rate of 15,000 scfm; process gas inlet temperature of 500°F; Incinerator temperature of 1 »400°F.
CO
I
-------
50 percent because of the fuel value of organics. The incinerator would
have to heat only 60 percent as much gas with no change in fuel value.
Primary heat recovery (preheating the incoming gas into the incinerator)
will decrease the burner fuel requirements in the noncatalytic incinerator
as shown in Table 3-5. At a gas stream concentration of 15 percent of
LEL, the energy usage will decrease by about 30 percent with a 35 percent
efficient primary heat exchanger. At 25 percent of LEL concentration,
the energy usage will be the minimum required for noncatalytic incineration
using only a 25 percent efficient heat exchanger. Installation of both
35 percent efficient primary and 55 percent efficient secondary heat
recovery system will result in a net fuel savings if all the recovered heat
is used as process heat. Greater heat exchanger efficiencies will result
in even greater fuel savinqs.
Many coil coating facilities have successfully used either retrofit
or integrated noncatalytic incinerators and both orimary and SE ondary
heat recovery systems.
Cost of Control Option - Table 3-6 provides a comparison of estimated
annual operating costs and operating costs per ton of emissions removed
by incineration alone and with various degrees of heat recovery, providing
sufficient recovered energy can be used. Operating costs are based on
an assumed inlet process temoerature of 500°F. For further details on
the cost of controlling orgari"*" vapor emissions with noncatalytic and
catalytic incineration, see section 4 of Volume I of this series.
The ooeratinq costs for a coi? coatincj facility using incineration
wiV decrease as the organic concentratior increases, and as more
is r-covered from the incinerators to [ JSed for other energy-usinq
roc ses, as can be seen from Table 3-p The difference in 00
3-17
-------
TABLE 3-6 COMPARISON OF ESTIWTED ANNUAL ABATING COST
FOR COIL COATING INCINERATION'3 a
Type of Annual Operating Cost
Incineration at 15% LEL,
dollars
Noncatalytiq
no heat recovery
Noncatalytic,.
primary heat
recovery only
Noncatalytic*
primary and
secondary heat
recovery
Catalytic,
no heat recovery
Catalytic, primary
heat recovery only
Catalytic, orimary and
secondary heat recovery
Catalytic, secondary
heat recovery only
122,580
74,100
34,800
78,850
75,030
39,690
42,710
Ooerating Cost
per ton of
organ! cs removed
at 15% LEL,
.dollars/ton
153
93
44
98
94
50
53
Annual operating
cost per year at
25% LEL
dollars
85,540
61,100
16,910
64,450
not applicable
n
II
19,670
Operating cost
per ton of
organics removec
at 25% LEL,
dollars/ton
71
51
14
54
not applicable
11
16
Process gas flow rate of 15,000 scfm at 500°F, 4,000 hr/yr operating time, $2.00/10° BTU fuel cost, tube and shell heat
exchangers.
-------
costs for catalytic incinerators with and without primary heat recovery
is minimal orovided that organ!cs constitute at least 15 percent of
the LEL and oven exhaust temperatures are at least 500°F.
For aoncatalytic incineration, the smallest annualized operating
cost is realized when both orimary and secondary heat recovery are used.
Catalytic incineration without heat recovery was found to have lower
annualized operating cost than noncatalytic incineration without heat
recovery.
If the energy can be recovered and used, incineration with heat
recovery can reduce net energy consumption compared to a line without
an incinerator. The value of this recovered energy does not, however,
completely compensate for other operating costs, and incineration will
invariably increase overall operating costs. In addition, there is 40
percent more gas to be treated for a given solvent amount, with resultant
increased capital cost, at 15 percent of the LEL than at the same plant
at 25 percent of the LEL.
These costs did not include enclosing the coater area or installing
hoods to duct the coater exhaust into the oven exhaust. Also, these costs
were based on an "ideal" facility where the cost of installation was about
40 percent of the cost of equipment. The degree of difficulty of retrofitting
an incinerator to an existing facility will likely increase the installation
and engineering costs, therefore, increasing the cost oer ton of organics
removed ,.
Effects and Limitations -Adverse environmental effects from incinerators
are mostly dependent, on the compounds nr .. _:it in the inlet gas stream. If
sul, T comoounds are present in the in! ^as stream or in the fuel, their
;xid? will be generated; ff halogens c ^ present, their acids may be
termed. Also, nitrogen oxides are gen? red from the nitrogen present in
the gas stream.
-------
Some of the particulates found in the gas stream, for example, from
si1iconized coatings may corrode or foul the heat exchanger tubes. If
the incinerator is not preheated before the operation begins, condensate
and other particulate matter formed in the tubes during shutdown may ignite
and warp the heat exchanger. In addition, catalytic incineration may have
limitations because of catalyst poisoning from some coatings used in
the coil coating industry.
It was assumed in the cost and fuel usage calculation that the
exhaust from both the prime and toncoat ovens Is ducted to one incinerator.
Actual solvent input into an incinerator will rarely exceed 85 oercent of
the operating time of a coil coating line due to coating and color changes,
running out a coil of rejected metal, etc. During this time, the ovens
12
and incinerator must be maintained at ooerating temperatures. In
addition, it is difficult to maintain an optimum percentage of the LEL
exhaust from each oven. The concentrations can vary wjjftcompositions of
the primer and topcoat, film thickness and line speed. At higher LEL's
high heat exchanger efficiencies can cause the incinerator to exceed its
design temperature limits. To minimize fuel usage, the primary heat
exchanger should be designed to handle such varying concentrations, i.e.,
to maximize the heat exchanger efficiency as the solvent input decreases
and lower the efficiency as the solvent input increases. One method of
achieving this is to design a bypass around the beat exchanger. To
ontimize investment and minimize fuel usage and operating costs, each
coil coating ooeration should be studied individually to determine
the most effective heat exchanger efficiency. However, the coil
3-20
-------
COater will still have to base the choice of an incinerator with optimum
heat exchanger efficiencv on the most critical situation.
The use of tube and shell heat exchangers was assumed in the cost
calculations. There are, however, other types of heat exchangers used j '
the coil CQaterS. These heat exchangers will var' in net efficiencies
and in cost; and include the rotating ceramic wheel , packed ceramic beds, air
to liquid heat exchangers and some others. In addition, there are other
methods of operating ovens and incinerators to achieve optimum heat recover-:
and fuel savings such as; inert atmosphere baking systems with rich fume
incinerators, and the recycling of solvent rich exhaust through zoned inci-
nerators .
3.4.2 Option 2 - Water-Borne and High-Solid Coatings
Achievable Reduction - Water-borne coatings are defined as coatings that
contain a polymer or resin base, water and often some organic solvent or
"CDSOlvent" that is miscible with water. The presence of a certain per-
centage of organic solvents in water-borne coatings is necessary tc
improve stability, appearance, reduce the "orange-peel" effect, depress
14
foaming and improve edge-pull. Water-borne coatings typically used in
coil coating are water-isoluble coatings.
High-solids coatings contain a solid composition up to 70
or 80 percent by volume. The remaining portion is organic solvent
necessary for proper application and optimum curing characteristics.
Table 3-7 lists the potential percentage reduction, in pounds of
organic solvent per unit volume of coating,which could be realized by
to water-borne and high-solids coatings.
3-21
-------
TABLE 3-7 POTENTIAL REDUCTIONS FROM USE OF WATER BORNE
AND HIGH SOLIDS COIL COATINGS
Pounds of organic solvent Potential reduction
Coatinq formulation per gallon of coating by using water-borne
(by volume) (minus water) coatings, percent
Water-borne
32% solids
54.4% water
13.6% organic solvents 2.2
Orq anlc solvent-borne
20% solids
80% solvent 5.9 90
50% solids
50% solvent 3.7 58
70% solids
30% solvent 2.2 0
3-22
-------
Technical Analysis - Water-borne and high-solids coatings are easily applicable
with roller coating Systems because the; have application characteristics
similar to organic solvent borne coatings. Converting to these COStinciS,
however, could present some difficulties.
High-solids coatings are difficult to apply due to high viscosity and may
necessitate heating of the rolls to reduce the viscosity. This may cause a build-
up of resin in the rolls unless a three-roll roller coating system is used.
Progress is being made in commercializing medium high to high-solids coatings
for the coil coating industry.
Water-borne coatings have different flow and wetting properties from
solvent-borne coatings. Evaporation of water from an applied coating
cannot be controlled as well as from a solvent mixture. Sometimes coil
coating line speeds must be reduced to avoid popping of the film.
Care must be taken to thoroughly clean the metal prior to coating
because any grease will result in lack of adhesion and edge-covering,
and formation of craters. Also, care must be taken in using certain pre-
treatments, such as chromic acid, that may cause water-borne coatings to gel.
Tubes, shafts, bearings and other movable parts on a COater must be
replaced or somehow protected from the water-borne coating to avoid corrosion.
In addition, all the pipes and pumps must be replaced with non-corrosive
materials if the coating is pumped from a separate storage or mixing area.
However, since there exists little fire hazard with water-borne coatings,
it is possible to use"tote-bins"inside the plant.
Cleaning dried water-borne coatings is difficult because they do
not remain soluble in their carrier. Water-borne coatings are difficult to
dispose of, and are difficult to transnort ard store during the winter
n
surlier months.
3-23
-------
Electrodeposited water-borne coatings have been successfully applied
on aluminum and some Steel coils. The electrodeposited coated steel is
baked directly after application of the coating. The electrodeposited
coated aluminum can be coated immediately with a topcoat then baked in an
oven. This system not onl ' reduces volatile organic emissions but also
the fuel usage and the costs of a prime coat oven.
For further details on water-borne and high-solids coatings, see
Volume I, section 3.3.1 and 3.3.2 respectively, of this series.
Cost of Control Option - The cost of converting to water-borne or high-
solids coatings will vary from plant to plant. Some secondary costs will
result from the necessity to test the coating and its performance on the
line, during forming and during the use of the end-product. It may also be
necessary to alter or adjust the equipment with which the metal is formed
into its final shape.
Some water-borne coatings may require higher curing temperatures than
organic solvent-borne coatings; however, many do not. Increases in
energy maybe counteracted by a reduction in aiir flow through the oven
necessary in organic solvent systems to maintaiin the organic vapor con-
centration below 25 percent of the LEL. It is estimated that in con-
verting to water-borne coatings , d COll COater may reduce the dilution air
14
by a factor of four, therefore reducing energy COnSUfflDtlOn by 50 percent.
Water-borne coatings may be more costly than organic solvent borne
coatings because industrial consumption is not widespread. With increased
consumption, further improvements in water-borne coatings and increasing
cost Of organic solvents, water-borne coatings may become tess 'jxpensfve than
3-24
-------
organic solvent-borne coatings. High-solid coatings are generally equal
to or more exoensive than equivalent high-solvent coatings.
Effects and Limitations • Water-borne primers, backers,and some low to
medium gloss tODCOatS that equal the performance of organic solvent borne
coatings have been develooed for aluminum but have not achieved full line
speed in all cases.'[ For other metals, such as steel, the uses are so
varied that water-borne coatings have not been developed to provide
properties equivalent to all of the present organic solvent-borne coatings
and which can withstand all post-forming operations. Some, however, are
in the early stages of development, but have not reached commercial status.
Water-borne coatings can contain on the average about 2.2 pounds of
volatile organic per gallon of coating (minus water) as applied. Medium
high solids coatings can contain on the average of 3.1 pounds per gallon
of coating applied (minus water).
3.5 Comparison of Control Options and Conclusions •
Incineration and conversion to water-borne or high-solids coatings
appear to be the most reasonable control options for reducing
organic emissions from coil coating lines because of the typically high
curing temoeratures and the various mixtures of organic solvents found in
the coatings used by this industrv. Incineration, coupled with various
types of heat recovery, has be°n successfully anplied to existing coil
coating lines. Similarly, water-borne coatings have been successfully applied,
within limits, to several existing coil coating lines. Over 90 percent
reduction of organic emissions is achievable with incineration and 70-95
Dercent reduction is achievable with WfttPr-bom8 coatings, depending on the
Processes and the solvent level of the O1' inal solvent-borne coatings
used.
3-25
-------
There are limitations on the options from which to choose. Some
coatings used in the industry can poison incinerator catalysts. There
is a lack of water-borne and high-solids coatings equivalent to organic
solvent-borne coatings for many metal uses, especially where resistance
to corrosion or wear is critical, where severe forming operations are performed
or where a high gloss finish is required. Incineration, especially HOD*
catalytic, will increase the use of natural gas or other fuels if no nearby
operations can use the recovered energy.
Ooerating costs of incineration for each ton of volatile organic com-
pounds removed are reduced by one half when the concentration of volatiles
is increased from 15 oercent of the LEL to 25 percent of the LEL. Cost
per ton removed for noncatalytic incineration could be reduced further if
concentrations were increased above 25 percent of the LEL. Such high con-
centrations, however, for catalytic incinerators would exceed their design
temperature limits. If incinerator heat is recovered, costs per ton removed
can be reduced by a factor of 2 to 5 depending on the extent of recovery
and tyne of incineration. The most cost effective systems shown in this
document are noncatalytic incinerators with both Primary and secondary
heat recovery and catalytic incinerators with only secondary heat recovery;
both oxidizing exhausts at 25 percent of the LEL.
If incineration is chosen as a control option, the coater may be
enclose! in a room. Since the ovens are maintained at negative pressure,
the volatile organ!cs will be pulled into the oven through the oven opening.
A hood may also be installed over the coater area to collect the volatile
organ!cs and exhaust them into the incinerator.
3-26
-------
There does not appear to be a single best control system for the entire
coil coating industry; therefore, each coil coating facility must be con-
sidered separately to determine the most applicable system.
3-27
-------
REFERENCES
1. National Coil Coaters Association; Fact Sheet 1974. National Coil
Coaters Association, Philadelphia, Pa.
2. A Study of Emissions from the Coil Coating Process, Volume I. Scott
Research Laboratories, Inc., Plumsteadville, Pa., December 1970,
Prepared for the National Coil Coaters Association.
3. Cosden, W. B., The Ecology of Coil Coating, Metal Finishing, November
1974. op 55-58
4. Gallagher, Vera N., U.S. Environmental Protection Agency, Research
Triangle Park, N.C. Reports Hf visits to coil coating facilities.
5. A Study of Gaseous Emissions from the Coil Coating Processes: Volume II
Survey Results, Scott Research Laboratories, Inc., Plumsteadville, Pa.
March 1971, Prepared for the National Coil Coaters Association.
6. LeBras, L. R., PPG Industries, Pittsburgh, Pa,, Letter to Vera N. Gallagher
in comment to draft of this document, letter dated August 13, 1976.
7. A Study of Gaseous Emissions from the Coil Caoting Process and their
Control, Scott Research Laboratories, Plumsteadville, Pa. October 1971,
Prepared for the National Coil Coaters Association.
8. Hughes, T. W., D. A. Horn, C. W. Sandy, and R. W. Serth, Source
Assessment: Prioritization of Air Pollution from Industrial Coating
Operations, Monsanto Research Corporation, Dayton, Ohio. Prepared
by U.S. Environmental Protection Agency, Research Triangle Park, N.C.
under contract No. 68-02-1320 (Task No. 14). Publication No. 650/2-75-019a.
February 1975.
9. Why Coil Coating Growth Continues. Products Finishing, November 1974.
pp 60-61.
10. Moorsman, R., Coil Coating - Past and Present. Products Finishing,
November 1974. pp 163-165
11. Messing, R., Outlook for Natural Gas Suoply. (Presented at National
Coil Coaters Association Convention, Chicago, Illinois - October 3,
1Q75.)
123. Mil on, C. L., Rnner Eastern, Columbia, Md., Letter to Vera Gallagher
in comment to draft of this document. Letter dated August 10, 1976.
13. Combustion Engineering, Inc., Wellsville, N.Y. Report of Fuel
Requirements, Caoital Cost and Operating Exnense for Catalytic and
Thermal Afterburners. Prepared for the U.S. Environmental Protection
Agency, Research Triangle Park, N.C. under contract no. 68-02-1473
(Task No. 13). Publication No. 450/3-76-031.
14. An is field, J., Powders Competition. Canadian Paint and Finishing,
December 1974. pp 41-44
3-28
-------
15. Heiming, C. C. and M. J. Krunp, Compelling Reasons for the Use of
Water-Reducible Industrial Coatings. Metal Finishing, October 1674,
DO 57-61
3-29
-------
4.0 FABRIC COATING
4.1 Summary of Control Technology
Affected Control system Percentage
facility or strategy reduction
Coating line Incineration 95
Carbon adsorption 90+
Low solvent coatings 80-100
(A coating line consists of the application area and the drying oven.
The application technique may be a roll, knife or rotogravure coater.)
4.2 General Discussion
Fabric coating involves the coating of a textile substrate with a
knife or roller spreader to impart properties that are not initially
present, such as strength, stability, water or acid repel 1 ancy or
appearance.'
The fabric coating industry is diverse, concentrated in the
northeastern and southeastern portions of the United States, With a wide
variation in products and plant sizes. The industry consists mal'.ly of
small to moderate size plants each of which specializes in a limited
product line.
Most of the industrial facilities located in the northeast are old;
some are over 40 years of age. (These can be difficult to modify to
achieve an air pollution standard.) Plants in this industry, which is
highly competitive, are usually located near either the textile raw
material producers or industries usinq the coated fabric.
Coating solutions may be either aqueous or organic base. It is the
latter that produces the organic emissions into the atmosphere. It is
estimated that 36 x 10 kilograms per v r (80 x 10 Ibs per year) are
emitted in the United States by the VIP1 coated fabric segment of the
2
industry.
4-1
-------
Rubber, coating of fabrics is also a large scale of solvent emissions,
although nationwide emissions from this source are not currently known.
ADD!ications for coated textiles include industrial and electrical
taoes, tire cord, utility meter seals , imitation leathers, tarpaulines,
shoe material, and upholstery fabrics.
4.2.1 Materials Used • Substrates (textile materials used to suonort
the coating) can be either natural or man-made. Coating of polyvinyl
chloride (PVC) substrates is covered in this section.
Coatings include latexes, acrylics, polyvinyl chloride, DOlyurethanes,
and natural and synthetic rubbers.
4.2.2 Processes and Affected Facilities - The coating line is the largest
source of solvent emissions in a fabric coating plant, and the most
readily controllable. Some coating plants report that over 70 percent
of solvents used within the plant are emitted from the coating line.
Other plants, especially those involved in vinyl coating, report that only
40 to 60 percent of solvents purchased by the plant are emitted from the
o
coating line. Remaining solvents are lost as fugitive emissions- from
other stages 6f processing and in cleanup. These fugitive losses are
generated by:
1. Transfer from rail cars or tank trucks to storage tanks,
and subsequent transfer to processing tanks.
2. Breathing losses from vents on storage tanks.
3. Agitation of mixing tanks which are vented to the
atmosphere.
4. Solvent evaporation from clean up of the coating applicator
when coating color or tyoe is changed.
4-2
-------
5. Handling, storage and disposal of solvent soaked
cleaning rags.
6. Waste ink disposal. Waste ink is usually distilled
to recover much of solvent. After distillation the sludge,
which still contains some solvent, is usually dumoed in a
landfill.
7. Losses from drums used to store coatings which are being
bumped onto coating applicator. These are usually 55 gallon
drums which a re not hooded and may not even be covered.
8. Cleaning of empty coating drums with solvent.
9. Cleaning coating lines with solvent.
10. Evaporation of solvent from the coated fabric after it leaves
the coating line. From two to three percent of total plant
solvent usage remains in the product. Half of this may
eventually evaporate into the air.
Control techniques for the above types of sources include tightly
fitting covers for ooen tanks, collection hoods for areas where solvent
is used for clean up, and closed containers for solvent wiping cloths.
Figure 4-1 shows a general outline of a fabric coating operations.
The following discussions describe these ooerations and control options
for the coating line.
4-3
-------
RUBBER
PIGMENTS
CURING AGENTS
SOLVENT
MILLING
1
MIXINB
DRYING AND
CURING
COATING
APPLICATION
FAifilC
COATED PRODUCT
Figure 4-i. typical fabric coating operation.
-------
COATING
KNIFE
COATED FABRIC TO DRYER
EXPANDED COATED FABRIC
COATING
SUBSTRATE
SUBSTRATE
i
OT
HARD RUBBER OR STEEL ROLLER
Figure 4-2. Knife coating of fabric. 1
-------
Milling .Milling is primarily restricted to coatings containing rubber.
Natural and synthetic rubbers are usually milled with pigments, curing
agents, and fillers to produce a homogeneous mass that can be dissolved
in a suitable solvent. Organic solvents are not usually involved in
the milling process; thus, there are seldom any orqanic emissions from this
operation.
Mixing - Mixing is the dissolution of solids from the milling process
in a solvent. The formulation is usually mixed at ambient temperatures.
Sometimes only small fugitive emissions occur. However, some vinyl
COdters estimate that as much as 25 percent of plant solvents are lost
in mixing operations.
Spreading or coating » Fabric is usually coated by either a knife or a
roller coater. Both methods are basically spreading techniques used for
high speed application of coatings to flat surfaces. In some unique
situations, dip coating may be used.
In knife coating, probably the least expensive method, the substrate
is held flat by a roller and drawn beneath a knife that spreads the
viscous coating evenly over the full width of the fabric, Knife coating
may not be appropriate for coating materials such as certain unstable
•i
knitgoods,1 or where a high degree of accuracy in the coating thickness
is required. Figure 4-2 illustrates knife coating.
In 'roller coating, the coating material is applied to the moving
fabric, in a direction opposite to the movement of the substrate, by
hard rubber or steel rolls. The depth of the coating is determined by
the gap between rolls (A and B as shown in Figure 4-o). The coating
that is transferred from A to B is then transferred to the substrate
4-6
-------
u
5
CO
01
'•£
s
u
o
O)
u
E
CD
<
BC
CO
CO
-------
from roll B. Unlike knife coaters, roller coaters apply a coating
of constant thickness without regard to fabric irregularities.
Rotogravure printing is widely used in vinyl coating of fabrics
and is a large source of solvent emissions. Rotogravure printing uses
a roll coating technique in 'which the pattern to be printed is etched
as a series of thousands of tiny recessed dots on the coating roll.
Ink from a reservoir is picked up in these recessed dots and is transferred
to the fabric surface. Shadow prints are used to simulate leather grain
A variety of patterns are printed on such Items as vinyl wall paper
A transparent protective topcoat over the printed pattern is also applied
with rotogravure techniques.
Solvent emissions from the coating applicator account for 25 to
35 percent of all solvent emitted from a coating line. This solvent
may be collected by totally enclosing the coating applicator in a small
room or booth and sending all booth exhaust to a control device.
However, a total enclosure of the coater may be difficult to retrofit
on many existing lines. Another alternative is to cover the coater
with a hood which can collect most of the solvent emissions.
Drying and Curing • Solvent emissions from the ovens account for 65 to 7b
percent of all solvent emitted from a coating line. In most ovens, almost
all solvent emissions are captured and vented with exhaust gases. On
some coating lines tne emissions from tne coating anpltcator nood are
ducted to the oven and included with the oven exhaust.
4-8
-------
Estimated and reported solvent concentration levels from drying operations
456
range between 5 and 40 percent of the LEL. ' ' Typically drying ovens
are designed to process fabric on a continuous basis operating with a web
or conveyor feed system. Ovens can be enclosed or semi enclosed and,
depending on size, may exhaust from a few thousand to tens of thousands of
7
cubic feet per minute of air. Obviously, if an add-on control device is
to be installed, it is in the owners best interest to minimize the volume
of air which must be treated.
The oven heat increases the evaporation rate of the solvent and, with
some coatings, will produce chemical changes within the coating solids to
give desired properties to the product. In many cases, evaporation rates are
controlled to give the desired properties to the coated fabric.
High air velocities distribute heat uniformly over the fabric surface,
facilitate heat transfer to the coating and substrate (by minimizing the
laminar zone next to the coated surfaces), and remove the evaporated solvents
from the oven at a rate that will prevent their buildup to explosive levels.
Ovens are heated by natural gas, steam, or electricity. Those heated
by gas may be either direct or indirect-fired. In the direct-fired oven,
the products of combustion are combined with fresh air and circulated over
the material. Indirect-fired, steam heated ovens are the most common
method for heating most existing facilities, although they are less
fuel efficient than direct-fireo ovens. They are also limited
in the maximum temperature achievable. One advantage of indirect-
fired ovens is that the fuel or combustion products cannot
contaminate the product. In electrically htated ovens makeup
air peases over resistance heaters before posure to the fabric.
4-9
-------
TABLE 4-1 FABRIC AND PAPER COATING OPERATIONS
USING CARBON ADSORPTION
Company
Alden Rubber
Company
Tuck Industries
(two plants)
Nashua Corporation
(two plants)
DenniSOn Manu-
facturing Company
Anchor Continental
Company
Product
Rubber coated fabric
Specialty tapes
(fabric and paper)
Specialty tapes
(fabric and paper)
Paper
Paper
Sol vent
Toluene
Toluene
Toluene
Toluene
Exhaust
*cfra
14,000
43,000
20,000
48,000
55,000
Carbon
adsorption
recovery
percent
85
95
85
96
70
Operating
percent
of LEL
50
45
45
(one)
25
18
I
—«J
o
-------
Many drying ovens in older plants are only semienclosed. As a
consequence they draw in excessive dilution air. Solvent concentrations
range between 5 and 12 percent of the LEL according to both calculations
and reports by industry. Newer installations are reported to be
4,5
operating with exhaust concentrations up to 40 percent of the LEL.
Levels of up to 50 percent of the LEL are possible if proper safety
devices are used according to recent publications. When ODeratinq at
at 50 percent of the LEL, the total exhaust rate is only one-fifth (20%) of
that at 10 percent of the LEL. This greatly reduces the cost of a control
system. As shown in Table 4-1, at least three plants in the United States
are operated at 40 to 50 Dercent of LEL. 4»5,8,9,10
4.3 Special Considerations
The fabric coating industry has a number of unique considerations that
affect the technical and economic feasibility of organic emission control.
Although a number of the larger facilities specialize in a specific product,
many plants produce a variety of products or operate on contract to coat
products to a customer's specifications. The latter type, often called
"commission coaters", must use a variety of coating formulations to comply
with the customer's specifications. The coating may be specified or even
supplied by the customer. The variety of coating specifications causes
variations in emissions which present problems in designing the control
system. Even if the COdtfir knows the solvent compositions, it is necessary
to base exhaust volume and controls upon the most critical or difficult
situation. The number of solvents used al S3 affects the owner's ability
4 11
-------
to recover and reuse the solvent. Thus the coating type is an important
factor in the cost of controlling emissions from a fabric coating plant.
Not only are insurance costs sensitive to the maximum solvent concentration
achieved but also the availability and cost of fuel also affect the djMiign
and cost of control.
These considerations all emphasize that one must define and specify control
technology for many existing plants in the fabric coating industry on a
case-b/-case basis.
4.4 Available Control Technology
Although few companies have elected to use organic emission controls,
there are alternative systems available that are technically feasible.
These are carbon adsorption and incineration. Another approach to reducing
organic emissions is to switch to lower organic solvent coatings such
as aqueous emulsion coatings. These alternatives are discussed in
the following sections.
4.4.1 Option 1 - Incineration - Both catalytic
and thermal incinerators (afterburners) can destroy'95 percent
of the organic emissions introduced to them. Since the effectiveness of
the capture and containment system varies from plant to plant, the overall
reduction in coating plant emissions may be less than 90 percent.
Technical Analyses - Incinerators convert organic vapors to carbon dioxide
and water. They have been used by fabric COaters for a number of years to
control V latile OrganiCS. A detailed description of incineration is given
in Volume I, Section 3.2.2 of this series of reports.
Incinerators can consume large amounts of energy. Fortunately, the
heat they generate frequently can be used within the olant. A number
4 12
-------
of heat recovery schemes are possible including preheating of the
incinerator inlet stream (so called primary heat recovery). Another is
to transfer the heat from the incinerator exhaust gases to supply process
needs (secondary recovery). Primary heat recovery alone can provide
approximately 50 percent of the energy necessary to incinerate gases from
a typical fabric coating system. If the oven exhaust is operated at
greater than 25 percent of the LEL, both primary and secondary heat recovery
can actually decrease overall plant fuel requirements. Fabric COflterS usually
can generate all of their steam requirements with secondary heat recovery.
Since the economics of incineration improve with higher solvent concentrations,
the cost of modifying an existing system to maximize the concentration of
solvent in the oven exhaust must be explored when considering retrofitting
a control system. Higher concentrations of solvent also decrease the fuel
requirements for the oven. The prospect of future energy shortages, and ever
increasing fuel costs 'will render such modifications of an oven desirable
form a cost effectiveness standnoint.
Cost Of Control Options . The cost of installing and operating an incinerator
for an exhaust stream of 15,000 scfm at 25 Percent of the LEL and
300°F is given in Table 4-2. Note that a noncatalytic incinerator (afterburner)
with primary and secondary heat recovery has the lowest annualized operating
cost. If the stream is at a lower inlet temperature, more auxiliary fuel
would be required and operating costs would be higher. Chrpter 4 of Volume
I details the assumptions made in calculating these costs. In assessing
fuel reqrirementS one must consider that coating operations usually operate
intc -mitiently and that qreater quantities r. fuel are required to
Stan up i incinerator than to operate at „•> ?ady state.
4 13
-------
TABLE 4-2 INCINERATION COSTS FOR A TYPICAL FABRIC
COATING OPERATION3
Device
Installed
cost, $
Incineration
No heat recovery
Catalytic
Noncatalytic
155,000
125,000
Annualized
jsost,_$/yr_
100,000
105,000
Control cost
$/ton of solvents
recovered
51
54
Incineration
Primary heat
recovery
Catalytic
Noncatalytic
(Afterburner)
180,000
150,000
75,000
66,000
39
34
Incineration -
Primary and
secondary heat
recovery
Catalytic
Noncatalytic
(Afterburner)
220,000
183,000
54,000'
26sOOOfc
28L
13'
aProcess rate of 15,000 scfm; temperature of 300°F, operation at 25
percent of LEL. See Volume I, Chapter 4 for costs for other
operating parameters.
Assumes heat is recovered and used.
4 14
-------
Effects and Limitations - Energy consumption is a disadvantage of inci-
neration but as discussed both in this Section and in Volume I, recovery
of the heat generated can eliminate or minimize the disadvantage.
Other adverse environmental effects are mostly dependent on the
compounds present in the inlet gas stream. If nitrogen or sulfur-
containing compounds are present in fuel or exhaust gas, their oxides
will be generated. Nitrogen oxides will also be generated from oxidation
of nitrogen present in the combustion air. If halogens are present, acids
will be formed. For a further discussion, see Volume I of this series.
4.4.2 Option 2 • Carbon Adsorption - A carbon
adsorber can remove over 90 percent of the organic vapors from the gases
that pass through it. Oftencollection efficiency across the carbon bed is
greater than 95 percent. Just as with the incinerator, the inability to
capture 100 percent of the emissions will result in a lower overall plant
reduction. Experience has shown that in plants that use activatec carbon, the
greatest losses occur in handling of solvent. As care is taken to
minimize handling losses, the overall solvent recovery increases. It ha!: been
reported that 95 percent of the captured solvent vapor can be recovered. '
Table 4-1 identifies some sources that use carbon adsorbers and presents
their effectiveness. These companies all have one factor in common: they
are able to recycle recovered solvent. The importance of this fact can be
seen below under "Cost of Contrc Option."
Technical Analyses - Activated carbon is used not only by fabric COdters but by
a number of industries in a variety of coating applications. Carbon
adsorbers are particularly attractive for tK >^* sources which use a single
Solvenc or which constantly use the same Si ;ent blend. This permits the
owr.cr tc recycle the solvent without first rjrifyir»g the recovered material.
4-15
-------
For those nlants that must use many solvents or a variety of mixtures,
the recovered material would probably have to be distilled. The
recovered solvent could, of course, always be used as fuel but its fuel
value would always be much lower than its value as a solvent.
Historically, the decision to recover solvent has been based upon
cost effectiveness (return on investment) rather than air pollution
considerations.
Cost of Control Option - Table 4.3 summarizes installation and operating
costs for a 15,000 scfm carbon adsorption unit operating at 170°F and
25 percent of the LEL. Tnree cases are oresented: (1) the solvent has
no value, (2) credit at fuel value and (3) credit at replaceaent value.
Notice that only where the recovered solvent can be recycled does the
investment pay for itself.
Effects and Limitations - Recovered solvent may be sufficiently water-
miscible to Dose a water pollution problem if the condensate from the
steam is not treated before discharge. This is not likely to be a
problem with adsorbers on tke discharge stream from lost fabric coating
ovens. In cases where this problem exists, it can be solved by treating
the condensate or incinerating the condensate-solvent stream. One
fabric coating operation that uses a water soluble organic solvent is
Vinyl coating which uses methyl ethyl ketone.
4-16
-------
TABLE 4-3 CARBON ADSORPTION COSTS &OR A TYPICAL FABRIC
COATING OPERATION '
Installed
cost, $
Annualized
operating
cost $/yr
Control cost
$/ton of solvents
recovered
Case with no credit for
recovered solvent
Case with recovered
solvent credited at
fuel value
Case V.'ith solvent
credited at market
chemical value
320,000
320,000
320,000
127,000
60,000
(100,000)°
72
34
(57)'
aProC6SS rate of 15,000 SCflTl, temperature of 170°F, operation at 25 percent LEL
See Volume I, Chapter 4 for cost for other operating parameters.
See Volume I, Chapter 4 for details on cost estimates
'Costs in parenthesis indicate a net gain
4-17
-------
4.4.3 Option 3 • Low Organic Solvent Coatings • Organic emissions can
be reduced 80 to 1_00_ Dercent through use of coatings which inherently
have low levels of organic solvents. Both high-sol ids and water-borne
coatings are used. The actual reduction achievable depends on the organic
solvent contents of the original coating and the new one.
Teabnical Analyses - Using a coating which has a low organic solvent
content may preclude the need for an emission control device. Often
the coating equipment and procedures need not be changed when a plant
converts to coatings low in organic solvent.
There is only a limited number of cases for which information is
available to compare the resulting coating to its organic solvent
counterpart. Although a number of companies have converted to low
solvent coatings, either in part or in total, one may not Presume them
to be a universal control measure. Each coating line is somewhat unique
and many coated fabricshave different soecifications.
Cost of Control Option - The cost of converting to a low organic solvent
coating and the cost effectiveness of such a strategy is dependent aoon a
number of factors. Research and develooment costs for the coatings may
be high and al though the unit cost will be lowered as use increases, some
users are so specialized that consumption will be small and developmental
costs oer unit volume will remain high.
4.5 Comparison of Control Options and Conclusions
lach control ootion discussed in Section 4.4 is a viable alternative
and probably the best choice for some sources. Th- most desirable strategy
for all parties concerned is probably the conversion to low solvent
4-18
-------
coatings. Unfortunately, this option may not be available at present for
all situations.
Carbon adsorotion and incineration are possible for those sources
that cannot use low polluting coatings. Carbon adsorotion is probably the
most economical for sources that use a single solvent or solvent mixture,
but the larqe caoital investment required is appreciably greater than for
incineration.
Incineration.; Preferably with primary and secondary heat recovery,
is most aoolicable at those sources that use a variety of solvents. Fuel
costs can be reduced by increasing the organics level in-exhaust gases,
i.e., by reducing dilution air.
4-19
-------
References
1. Smith, J C, Coating of Textiles. The Shirley Link, The Shirley
Institute, England, pp. 23-27
2. Telephone communication between W. I. Johnson, U.S. Environmental
Protection Agency and Paul Johnson, Executive Secretary of Chemical
Fabrics and Film Association, August 20, 1976,
3. letter to James McCarthy, U.S. Environmental Protection A
-------
5.0 PAPER COATING
5.1 Summary of Control lecnnolugy
Percentage
Affected facility Control technique reduction
Coating line Incineration 95
Carbon adsorption 90+
Low solvent coatings 80-99
(A coating line consists of the application area and the drying ovens. The
application technique may be a roll, knife or rotoqravure coater.)
5.2 General Discussion
Paoer is coated for a variety of decorative and functional purposes,
using water-borne, organic solvent-borne, or solventless extrusion type
materials. Because the organic solvent-borne coating process is a
source of hydrocarbon emissions, it is an air pollution concern. Among
oroducts that are coated using organic solvents are: adhesive tapes;
adhesivelabels ; decorated, coated, and glazed paper; book covers;
office copier paper (zinc oxide coated); carbon paper; typewriter ritbons;
and photograph i c fi1ms.
In organic solvent paper coating, resins are dissolved in an organic
solvent or solvent mixture and this solution is applied to a web (con-
tinuous roll) of paper. As the coated web is dried, the solvent evaporates
and the coating cures. An organic solvent has several advantages: it will
dissolve organic resins that are not soluble in water, its components can
be changed to control drying rate, and organic base coatings show suoerior
water resistance and better mechanical prone ties than some types of water-
borne coatings. In addition, a large varie of surface textures can
be ohtair 3d using solvent coatings.1
5-1
-------
Most organic solvent-borne coating is done by paper converting com-
panies that buy paper from the mills and apply coatings to produce a
final product. The paper mills themselves sometimes applv coatings
but these are usually water-borne coatings consisting of a pigment such
2
as clay and a binder such as starch or casein. These water-borne
coatings are not normally sources of organic emissions.
Mo$t companies that coat paper using organic solvents are listed
in the U.S. Department of Commerce's Standard Industrial Classification
(SIC) grouping 2641, Paper Coating and Glazing. This group includes
establishments primarily engaged in manufacturing of coated, glazed or
3
varnished papers from purchased paper Stock. Also included are
establishments primarily manufacturing nressure-sensitive tane with backing
of any material other than rubber. Establishments primarily engaged in
manufacturing carbon paper are classified in Industry Code 3955 and nhO-
tographic and blue-printed paper in Industry Code 3861, Some tyDG
of paper coating with organic solvents, however, may not fall into ail"
of these groups.
4
The 1967 Census of Manufacturers gives the following information
about companies in SIC 2641:
Total employment in industry: 37,100
Number of oroduction employees 27,000
Total plants by geographic region:
New England 61
Mid-Atlantic 122
North Central 117
South 44
We s t 53
Total plants in top ten states for paper coating:
New York 57
California 41
Massachusetts 40
New Jersey 40
Illinois 34
Ohio 27
5-2
-------
Pennsylvania 25
Wisconsin 17
Michigan 16
Rhode Island 7
Nationwide emissions of organic solvents from paper coating have been
estimated to be 0.56 million tons/year. This estimate includes resin
emissions from solventless polyethylene extrusion coatings applied to
milk cartons and resin emissions from water emulsion coatings. Also
included are solvent emissions from rubber adhesives used to glue paper
bags and boxes. A more conservative estimate based on solvent emissions
from the type of coating operations found in SIC 2641 is 0.35 million tons/yr.
This is slightly less than 2.0 percent of the estimate of 19 million tons/yr
of hydrocarbon emissions from all stationary sources reported in Volume I
nf this series. Manufacturing of pressure sensitive tapes and labels, the
largest solvent source in SIC 2641, alone accourts for 0.29 million tons/yr.
Solvent emissions from an individual coating facility will vary with
the size and number of coating lines. A plant ma ' have only one or as
many as 20 coating lines. Uncontrolled emissions from a single line may
vary from 50 to 1000 Ibs/hr depending on the line size. The amount of
solvent emitted also depends on the number of hours the line operates each
day.
Table 5-1 gives tyoical emission data from various D3Der coating
ano Heat ions.
5-3
-------
TABLE 5-1 EMISSION DATA FROM TYPICAL PAPER COATING PLANTS
Plant
A
B
c
D
E
Number
of coating
lines
2
5
a
2
10
Solvent
usage ,
Ib/day
10,000
15,000
9,000
1,200
24,000
Solvent
emissions
Ib/day
10,000
15,000
9,000
1,200
950
Control *
efficiency, %
0
0
0
0
96
Control
device
None
None
None
None
Carbon
adsorptton
20
55,000
41,000
90
G
H
I
5,000
21,000
10,500
1,500
840
500
90
96
96
Car&on
adsorption
(not all lines
control led)
Carbon
adsorption
Carbon
adsorption
Afterburner
*Neglecting emissions that are not captured in the hooding system.
5.2.1 Materials Used - The formulations usually used in organic solvent-borne
paper coatings may be divided into the following classes: film-forming
materials, plasticizers, pigments, and solvents. Dozens of organic solvents
are used., The major ones are: Toluene, xylene. methyl ethyl ketone, 1SO-
propyl alcohol, methanol, acetone, and ethanol.
Although j single solvent is frequently -used, often a solvent mixture
is necessary to obtain the optimum drying rate. Too rapid drying results in
bubbles and an "orgnge peel" effect in the coating; whereas, longer drying
coatings require longer ovens or slower production rates. Variations in the
solvent mixture also affect the solvent qualities of the mix.
54
-------
The main classes of film formers used in paoer coating are cellulose
derivatives and vinyl resins. The most commonly used cellulose derivative,
nitrocellulose has been used for paper coating decorative paper, book
covers and similar items since the 1920's. It is relatively easy to formulate
and handle, and it dries quickly, allowing lower oven temperatures than
vinyl coatings. The most common vinyl resin is the copolymer of vinyl
chloride and vinyl acetate. These vinyl copolymers are superior to
nitrocellulose in toughness, flexibility and abrasion, resistance. They
also show good resistance to acids, alkyds, alcohols and greases. Vinyl
coatings tend to retain solvent, however, so that comparatively high
temperatures are needed. In general, nitrocellulose is most applicable to
the decorative paner field, whereas vinyl copolymers are used for functional
"i
papers such as some DackagintJ materials.'
Plasticizers are often added to a coating to improve its flexi-
bility. Three common plasticizers are dioctyl phthalate, tricrer 1
phosphate, and castor oil. Each type of resin has an optimum nlasticizer
concentration. As plasticizer concentration increases, the coating becomes
more flexible until it begins to be too soft and tacky.
In the production of pressure sensitive tapes and labels, adhesives
and silicone release agents are applied using an organic solvent carrier.
The adhesive layer is usually based on one of the following organic
solvent-borne resins: natural or synthetic rubber, acrylic or silicone.
Because of their low cost, natural and synthetic rubber compounds are the
main film formers used for adhesives in pressure sensitive tapes and
labels, although acrylic and silicone adhesives offer DerfOftTiance advantages
for certain apolications.
5-5
-------
01
I
a\
HEATED AIR
FROM BURNER
REVERSE ROLL
CDATER
UNWIND
ZONE 1
EXHAUST
t
n
L
ZONE
2
EXHAUST
T
n
^< "—" 1
t^ D u
"ir ii — *•.
p n -
OVEN
HOT AIR NOZZLES
tension MtitLS
REWIND
figure 5 t. Typical paper coating line.
-------
PAPER WEB
Figure 5-2. Knife coating of paper.
5-7
-------
The oaoer on which adhesive labels are attached until use are treated
with a release agent so that the adhesive tag may be easily removed.
This is usually a silicone coating that is dDDlied with a solvent.
Release agents are also annlied to the backside of pressure sensitive
taoes with organic solvents so that the tapes will unwind easily.
5,2.2 Processes and Affected Facilities 'Figure 5-1 shows a typical oaoer
coating line, Components include an unwind roll, a coating applicator
(knife, reverse roll, or gravure), an oven, various tension and chill rolls,
and a rewind roll. The unwind, rewind and tension rolls display various
degrees of complexity depending on the design of the line.
The coating applicator and the oven are the main areas of-organic
emission in the paper coating facility.
Coatings may be applied to paper in several ways. The main application
devices are knives, reverse rollers, or rotogravure devices.
A knife coater (Figure 5-2) consists of a blade that scrapes off
excess coating on the paoer. The position of the knife (relative to the
paper surface) can be adjusted to control the thickness of the coating.
The knife coater is simply constructed and easy to clean.
The reverse roll coater (Figure 5-3), applies a constant thickness
of coating to the caper web, usually by means of three rolls -- each
rotating in the same direction. A transfer roll picks up the coating
solution from a trough and transfers it to a coating roll. (Sometimes
there IS no transfer roll and the coating is pumped directly onto a
coating roll.) A "doctor roll" removes excess material from the coating
roll. The gao between the doctor roll and the coating roll determines
the thickness of the coating. The web is supported by a rubber backing
roll where the coating roll contacts the paper. The coating roll turns
in a direction opposite to that of the paper, hence the name "reverse
5-8
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DOCTOR ROLL
METERING GAP
TRANSFER ROLL
COATED PAPER WEB
BACKING ROLL
COATING RESERVOIR
Figure 53. Four-roll reverse roll coater for paper.
5-9
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roll". This reverse direction of the coating roll reduces striations in
the coating that can form if the coating roll is turned in the same
direction as the paper web.
Knife coaters can apply solutions of much higher viscosity than roll
coaters, thus less solvent is emitted per pound of coating applied.
Knife coaters handle coatings with viscosity up to 10,068 centipose(co).
Reverse roll coaters operate best in a much «»ore dilute range where
viscosity is 300 to 1500 cp. Roll coaters, however, can usual ly operate
at higher speeds, and show less tendency to break the pa^er. Both kinds
of coaters apply coatings of good uniformity.
Rotogravure, another type of application method used by paper coaters,
is usually considered a printing operation, Uith it, the image area on
the coating or rotogravure roll is recessed relative to the OOflifliage area.
The coating is picked up in the recessed areas of the rol1 and transferred
directly to the substrate. The gravure printer can print patterns or a
solid sheet of color on a paper web. Rotogravure can also be used to
apply materials such as silicone release coatings for pressure sensitive
tapes and labels. Because of the similarities, this Study is appropriate
for gravure as well as knife and roll coating.
Most solvent emissions from coating paper come from the dryer or oven.
Ovens range from 20 to 200 feet in length and may be divided into two to
five temperature zones. The first zone, where the coated paper enters the
oven, is usually at a low temperature {^ 110°F). Solvent emissions are
highest in this zone. Other zones have progressively higher temperatures that
cure the coating after most of the solvent has evaporated. The typical
curing temperature is 250°F, although in some ovens temperatures of 400°F
are reached. This is generally the maximum because higher temperatures
5-10
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can damage tne paper. Exhausts streams from oven zones may be discharged
independently to the atmosphere or into a common header, and sent to
some type of air pollution control device. The average exhaust temperature
is about 200°F.
Oven heaters are either direct or indirect fired. With direct-fired
heaters, combustion products contact the coated web inside the oven. The
burners themselves may be inside the oven chamber. More commonly, the
burners are mounted external to the oven. In this case, heated air
(along with products of combustion) is blown directly from the burner to
the oven chamber.
Although natural gas is the fuel most often used for direct-fired
ovens, fuel oil is sometimes used. Some of the heavier grades of fuel
oil can create problems because SCL and particulate may contaminate the
paper coating. Distillate fuel oil usually can be used satisfactorily.
Indirect-fired oven heaters are arranged so that products of com-
bustion do not enter the oven chamber. A heat exchanger of some t} pe
is used to transfer heat from the burner to the oven ehamber. Because
combustion products do not enter the oven chamber in the indirect-fired
heater, there is no chance for contamination of the naper coating, and
dirtier fuels can be burned. Fuel is not used as efficiently in the
indirect-fired oven, so more '-jel will be required than if direct-firing
is used.
Steam produced in gas or oil-fired boilers is sometimes used to
heat ovens in the paper industry because a^er coating ovens operate
. r Tairly low temperatures. (Such boile ;ou!d also burn solvent
( Elected by a carbon adsorption system Typically, the steam is
piped to the oven, and fresh air drawn i :o the oven is heated by
5 11
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passing it over the steam coils.
Most paper coaters try to maintain air flow through their ovens so
the solvent concentration will be 25 percent of the LEL, although many
ovens are run at much lower solvent concentrations. As the energy shor-
tages intensifies, coaters are making greater efforts to minimize
dilution air and thus raise solvent concentrations.
Although 25 percent of the LEL is often regarded as the maximum
allowable solvent concentration in the oven discharge because of safety
considerations, insurance and safety requirements will sometimes permit
even higher solvent concentrations. The Handbook of Industrial Loss
Prevention notes that flammable vapor concentrations of up to 50 percent
of the LEL may be tolerated if approved continuous vapor concentration
o
indicator controllers are used. The controller must sound an alarm
when concentrations reach 50 percent, and shut the oven down automatically
when concentrations reach 60 percent of the LEL.
Precise methods are available for calculating the amount of dilution
air needed to maintain the exhaust solvent concentration at a given LEL
level. However, most of the paper-converting industry uses the estimation
method of assuming 10,000 ft of fresh air, referred to 70°F, per gallon
7
of solvent evaporated in the oven. This method will give a solvent
concentration of approximate!:' 25 percent of LEL for most solvents, but
the r^nge may vary from 10 percent to 32 percent of the LEL for some
solvents.
The exhaust flow rates from paper coating ovens vary from 5000 to
35,000 scfm depending on size. Average exhaust rates are 10,000 to
20,000 scfm. Paper coating ovens vary in cost depending on web width,
5-12
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line speed, and complexity of coating and associated equipment. For
example, some lines have two coating stations SQ that the paper web
may be coated on both sides. Paper coating lines have an installed
cost of $100,000 to $1,000,000. A typical line would cost about $300,000.
In a typical paper coating plant about 70 percent of all solvents
used are emitted from the coating line. The emphasis in this chapter is
on control of the coating line. However, about 30 percent of plant emissions
are from the other sources. These include solvent transfer, storage, and
mixing operations. In order to control solvent emissions from these
areas, provisions must be made to insure that solvent containing vessels
have tight fitting covers and are kept closed. Another often overlooked
source of solvent loss is use of solvents for cleaning various coatings
and sludges from the coating line. This must be done before ever" color
change. Areas of the coating line that are frequently cleaned with
solvent can be hooded so that solvent fumes are caotured and sent to
a control device. Dirty cleanup solvent can be collected, distilled and
reused. Solvent soaked wiping rags should be kept in closed containers.
Almost all emissions of the solvent from the.coating line itself
can be collected and sent to a control device. Many plants report that
96 percent of solvent introduced to the coating line is recovered. Most
of the coating line emissions are from the.oven and the coating application
area. The oven emissions can be exhausted directly to a control device.
Part of the solvent remains with the finished product after it has
cured in the oven. For example, certain types of jressure-sensitive tapes
have 150 to 2,000 ppm by weight of solvent in the adhesive mass on the
finished tape. Some COaterS estimate th t 2 or 3 percent of solvent
remai; S in the product.
5-13
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5.3 Special Considerations
The manufacture of photographic film pPtttCntS SDecial solvent control
problems. Four or more layers of coatings may be applied to a photo-
graphic film, using equipment and coating techniques similar to those
used for other paper coatings. Because the coatings on the photographic
film later undergo chemical reactions, the composition and quality of
the coatings must be tightly controlled. Because of the nature of these
coatings, certain control options ma.y not be practical. For example, it
may be impossible to recover solvents in a carbon adsorption unit and then
reuse these solvents in new photographic coatings since the reclaimed
solvents may contain enough impurities to contaminate the film.
5.4 Avai1ab1e Contro1 Techno1ogy
5.4.1 Option 1 » Low Solvent Coatings
Achievable Reductions - These are shown in Table 5-2.
TABLE 5-2 ACHIEVABLE SOLVENT REDUCTIONS USING
LOW SOLVENT COATINGS IN PAPER COATING INDUSTRY
Type of low solvent coating Reduction achievable.%
Water-borne coatings 80-99
Plastisols 95-59
Extrusion coatings 99+
Hot melts 99+
Pressure sensitive adhesives
Hot melt 99
Water-borne 80-99
Prepolymer 99
Silicone release agents
Water-borne emulsions 80-99
100 percent nonvolatile coatings 99+
Based on comparison with a conventional coating containing 35 percent
solids by volume and 65 percent organic solvent by volume.
5-14
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Technical Analysis - Low Solvent Paper Coatings - A variety of low
solvent coatings have been developed for coating paper. These coatings
form organic resin films that can equal the properties exhibited by
typical solvent-borne coatings for some uses.
Water-borne coatings have long been used in coating paper to
improve printability and gloss. The most widely used types of water-borne
coatings consist of an inorganic pigment and nonvolatile adhesive. Such
older water borne coatings are useful but cannot compete with organic
solvent coatings in properties such as weather , scuff and chemical
resistance. Newer water-borne coatings have been developed in which a
synthetic insoluble polymer is carried in water as a colloidal dispersion
or an emulsion. This a two-phase system in which water is the continuous
phase and the polymer resin is the dispersed phase. When the water is
evaporated and the coating cured, the polymer forms a film that has pro-
perties similar to those obtained from organic solvent based COftings.
Plastisols and organisols are low solvent coatings. Plastiscls are
a colloidal dispersion of a synthetic resin in a plasticizer. When the
plasticizer is heated, the resin particles are solvated by the ^lasti-
cizer so that they fuse together to form a continuous film. Plastisols
usually contain little or no solvent, but sometimes the addition of a
filler or pigment will change the viscosity so that organic solvents
must be added to obtain desiraole flow characteristics. Uhen the
volatile content of a plactisol exceeds 5 percent of the total weight, it
is referred to as an organisol.
Plastisol technology began in the 19 's and was first applied to
", vinyl upholstery in automobiles i' n example of a plastisol
iri" Paper is coated with plastisols to make products such as
5-15
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artificial leather goods, book covers, carbon paper and components of
automobile interiors, Plastisals may be applied by a variety of means,
but the most common method is probably reverse roll coating, One
advantage of plaStUoU 1s that thiy ean &« applied In layers UP te 1/8
inch thick. This avoids the neee§i1t > of multiple panes through a coating
machine,
Although orpnle solvents an net evipprated from plastlsels, some
of the pHstieUir my volit1l1« In th« oven, This p1§st1e1ier win
condense when I!fll1tt0d frQW the exhaust Stick to form a visible emission.
Companies that ult pU»t1|Ql* Often have a small electrostatic precipitator
to remove these droplets from the GVin exhaust
Hot melt coatings contain no solvent; the polymer resins are applied
in a molten state to the pager surfaces. All the materials deposited on
the paper remain as part of the coating, Because the hot melt cools to
a Golid coating soon after it is applied, a drying oven is not needed
to evaporate solvent or to cure the coating, Energy-that would have been
used to heat an oven and to heat makeup air to replace oven exhaust
is therefore saved. Considerable floor space is also saved when an oven
is not used. In addition, the paper line speed can be increased because
the hot melt coating cools faster than a solvent coating can dry.'
One disadvantage with hot melt coatings is that materials that char
or burn when heated cannot be applied by hot melt. Other materials will
slowly degrade when they are held at the necessary elevated temperatures.
Hot melts may be applied by heated gravure or roll coaters and are
usually applied at temperatures from 150°F to 4509F. The lower melting
point materials are generally waxy type materials with resins added to
5-16
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increase gloss and hardness. The higher melting point materials form
films that have superior scuff resistance, transparency and gloss.
These coatings form excellent decorative finishes. One Particular
advantage of hot melts is that a smooth finish can be applied over a
rough textured paper. This is possi ble because the hot melt does not
penetrate into the pores of the paper.
A type of hot melt coating, plastic extrusion coating is a solvent-
less system in which a molten thermoplastic sheet is discharged from
a slotted dye onto a substrate of paper, paperboard, or synthetic
material. The moving substrate and molten plastic are combined in a
nip 'between a rubber roll and a chill roll. A screw type extruder
extrudes the coating at a temperature sometimes as high as 600°F. Low
and medium density polyethylene are used for extrusion coating more than
3
any other type resins.
More than 260 extrusion coating lines now produce materials for
Paper, paperboard, and flexible packaging applications.' Hundreds of
products are coated with extrusion coatings. Food packaging materials
are often coated by extrusion coatings because a good moisture barrier
can be formed. A well known extrusion coated product is the polyethylene-
coated milk carton, which became popular in the 1960's. Before that
time, milk cartons were coated with wax.
Pressure sensitive adhesives are an area in which 1 ov solvent tech-
nology is being applied. Because this is a large industry, the potential
for solvent emission reduction is great. In 1974, sales of pressure-
sensitive adhesives in the United States y.ere over $1 billion, and the
5-17
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growth rate about 15 percent per year. Products using pressure sensitive
adhesives include tapes and labels, vinyl wall coverings, and floor
tiles. Nationwide organic solvent emissions from pressure sensitive
tape and label manufacture is 580 million pounds per year.
The three types of low solvent coatings applicable for use as
presstire sensitive adhesives are: hot melts, water-borne systems, and
prepo 1 yme r tyi terns.
Pressure-sensitive hot melts currently being, marketed consist mostly
of styrene " butadiene rubber block copolymers. Some acrylic resins are
used, but these are more expensive. The capital expense of hot melt
coating equipment is a problem for paper coaters that have already invested
heavily in conventional solvent coating equipment. There are currently
four manufacturers of hot melt coating application equipment for pressure
sensitive adhesives.
Water-borne adhesives have the advantage that they can be applied
with conventional coating equipment. Water-borne emulsions, which can
be applied less expensively than can solvent-borne rubber-based adhesives,
are,'already in use for pressure sensitive labels, A problem with water
borne adhesives is that they tend to cause the paper substrate to curl
and wrinkle. Some companies have overcome this wrinkle problem, but
many smaller companies have not.
Pre-polymer adhesive coatings are applied as a liquid composed of
monomers containing no solvent. The monomers are polymerized by either
heat orradiation. These pre-polymer systems show promise, but they are
presently only in a developmental stage.
5-18
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Silicone release coatings, usually solvent-borne, are sometimes
used for oressure-sensitive, adhesive-coated products. Two low-solvent
alternatives are currently on the market. The first is a 1 00 percent
nonvolatile coating which is usually heat-cured, but may be radiation cured.
This is a pre-polymer coating which is applied as liquid monomers that
are cross-linked by the curing process to form a solid film. The second
system is water emulsion coatings,
Products are being developed that will allow solvent recovery from
solvent-borne silicone coatings using carbon adsorption. Currently, there
are difficulties with recovering solvent from silicone coatings because
some silicone is carried into the adsorber where it fouls the carbon and
lowers collection efficiency.
TABLE 5-3 CAPITAL COST OF SILICONE COAXING SYSTEMS IN
PAPER COATING INDUSTRY1"
' Net sost $/lb of
Coatinq systems silicone sclids on paper
Solvent Cwith sol vent recovery) 8.20
Solvent (with solvent incineration) 7.33
Solventless (heat cure) 7.11
Solvent (with no recovery) 6.69
<
Water emulsion System 5.28
The emulsion system is the lowest in cost, but the 100 percent
solventless (pre-polymer) process may prove to be the most practical system
in the long run. It may be difficult for ^aper COaters that are familiar
V/ith organic solvent-borne systems to swi^fl to a water-borne system because
of V*» nkl ing of the paper and other appi ation problems.
5-19
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Cost of Control Option - Costs will vary for low solvent systems depending
on the type of low solvent coating and the particular end use. The low
solvent coatings will be economical once the technology has been
established, but there can be large costs involved in initially developing
the coatings, purchasing new application equipment and learning to use
the new systems.
Cost comparisons between various low solvent coatings are not as easy
to make as are cost comparisons between various types of add-on control
systems. However, a detailed cost comparison has been made between
10
various types of silicone application systems. This comparison is
shown in Table 5-3. The cost of learning to apply water-borne systems
to paper could be very large.
Additional costs will be associated with switching to 100 percent
nonvolatile (pre-polymer) coatings. Most organic solvent-borne silicone
release coatings are currently applied by gravure or reverse roller
fione °f these are suitable for solventless coatings. Solvent
less coatings must be applied with 3-roll or 4-roll offset gravure presses.
These cost from $25,000 to $200,000 per coating line. A cost of $100,000
would be about average. Because of these costs, availability of capital
can be an impediment to the adoption of solventless silicone coatings.
Effects and Limitations • Most of the low solvent coatings listed here
are currently being used for certain types of products, However, organic
solverit-borne coatings have been developed over the course of decades,
whereas the low solvent coatings are only now being ipplied to many
products. Continued research will expand the number of applications
for these low solvent coatings; however, at present, low solvent coating
systems are not available for all paper coating applications.
5-20
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5.4.2 Option 2- -Incineration
Achievable reductions--Thermal (noncatalytic) incinerators may be used to
control organic vapors from paper coating operations. Catalytic incinerators,
widely used for printing operations, have rarely been applied to control
paper coating operations using roll coating or blade coating but certainly
are applicable.
Incinerators, if properly operated, can be over 95 percent efficient
in controlling organic vapors which are directed to the incinerator. The
overall control for the entire plant will be less because of the emissions
which escape captured.
Technical analysis- -Incinerators have been retrofitted to a large number
of oven exhausts from paper coating lines to use primary and even secondary
heat recovery. A recent article describes how five paper coating lines
for producing office copier paper were fitted with incinerators, which
were equipped with ceramic wheel heat exchanger.'' xhe recovered heat
was used to heat the ovens. Total fuel consumption for the lines actually
decreased after the incinerators were installed. For a discussion OT the
capabilities .and limitations of heat recovery, see Section 3.2.2 of
Volume I.
Cost of control option--Section 4 of Volume I provides cost data for
incineration at various gas flow rates and temperatures. Exhaust rates from
typical paper coating ovens range from 8,000 to 20,000 scfm at exhaust
temperatures of 175°F to 300°F. Costs for catalytic and noncatalytic incinera-
tors onerating on a 15,000 gas stream at 300°F and at 25 percent of the LEL
are given in Table 5-4.
6-21
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TABLE 5-4 INCINERATION COSTS FOR A TYPICAL PAPER
COATING 'OPERATION"
Device
Incineration-
No Heat Recovery
catalytic
nancatalytic
(afterburner)
Incineration- -
Primary Heat Recovery
catalytic
noncatalytic
( afterburner)
Incineration- -
Primary and Secondary
Heat Recovery
catalytic
noncatalytic
(afterburner)
Installed
$cost,
155,000
125,000
180,000
150,000
220,000
183,000
Annual! zed
cost. $/yr
100,000
105,000
75,000
66,000
h
26,'OQOb
Control
•cost, $/ton
of solvent
tmrnpH
51
51
39
34
K
28h
aProcess rate of 15,000 scfm; temperature of 300°F, operation at 25
percent of LEL.
Assuming recovered heat can be used.
'5-22
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Effects and limitations--The major problem associated with the
use of afterburners to control organic vapor emissions from paper coating
lines is the limited availability of natural gas. If heat recovery is
used and the system is operated properly, no additional fuel may be
necessary.
Primary heat recovery refers to using the incinerator exhaust
to preheat oven gases going to the incinerator. Secondary heat recovery
means using heat from the incinerator for plant operations such as heating
the oven or for room heatiing. Thermal (noncatalytic) incinerators can be
operated at lowest annual expense if both primary and secondary heat
recovery are used. It is possible, however, that the heat recovered from
the secondary heat recovery unit cannot be totally utilized at some P3P&F
coating plants. Paper coating line ovens operate at relatively low
temperatures, usually around 250°F and rarely over 400°F so the heat
available to the secondary heat exchanger from the incinerator may be more
than needed by the oven. If some other use for the excess heat C^FIOt be
found, the full cost savings of secondary heat recovery will not be achieved.
When silicone-release coatings are being applied, silicone compounds
may be emitted. These will foul the heat transfer surface of a shell and
tube heat exchanger and the heat transfer efficiency will decrease,
5.4.3 Option 3 - Carbon Adsorption
Achievable reductions--Carbon adsorption units can be over
90 percent efficient in controlling organic solvent vapors that are drawn
into the carbon bed.
5-23
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Technical Analysis - Carbon adsorption has been used since the
1930's for collecting solvents emitted from paper coating operations.
Most operational systems on paper coating lines were installed because
they were profitable. Pollution control has usually been a minor concern.
Carbon adsorption systems at existing paper coating plants range in size
from 19,000 to 60,000 SCfllh Exhausts from several paper coating lines are often
manifolded together to permit one carbon adsorption unit to serve several
coating lines. Paper products that are now made on carbon-adsorption-
control led lines include pressure sensitive tape, office copier paper,
and decorative paper.
Carbon adsorption is Imost adaptable to single solvent
processes. Many COdtePS using carbon adsorption have reformulated
their coatings so that only one solvent is required. Toluene, probably
the most widely used solvent for paper coating, is readily captured in
carbon adsorption systems.
The greatest obstacle to the economical use of carbon adsorption
is that in some cases reusing solvent may be difficult. In many coating
formulations, a mixture of several solvents is needed to attain the desired
solvency and evaporation rates. If this solvent mixture is recovered, it
sometimes cannot be reused in formulating new batches of coatings. Also
if different coating lines within the plant use different solvents and are
all ducted to one carbon adsorption system, then there may be difficulty
reusing the collected solvent mixture. In this case solvents must
be separated by distillation.
5 24
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Separation of solvent mixtures by distillation is well established
technology and several plants are already doing this. One paper coating
plant has been using such distillation procedures since 1934. Distillation
equipment can be expensive, however, and it is hard to build flexibility
into a distillation system. Flexibility is needed because many paper
ceaters, especially those who do custom work for others, are constantly
changing solvent formulations.
Cost of Control Option « The cost of using carbon adsorption to control
hydrocarbons emissions is outlined generally in Chapter 4, Volume I.
The costs for a plant operating with an exhaust of 15,000 scftn of gas
at '170°F and 25 percent of LEL are given in Table 5-5
TABLE 5-5 CARBON ADSORPTION COSTS FOR PAPER COATING INDUSTRYa'b
(15,000 scfm, 170°F, 25% of LEL)
Control
cost, $/ton
Installed Annualized of solvent
cost,$ cost, $/yr recovered
No credit for recovered 320,000 127,000 125
solvent
Recovered solvent credited 320,000 60,000 40
at fuel value
Solvent credited at market 320,000 (100,000)°
value
aProcess rate of 15,000 scfm, temperature of 170°F, operation at
25 percent of LEL.
See Volume I, Chapter 4 for details on cost estimates.
'Costs in parenthesis indicate a net qain.
5-25
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The installed cost qiven above is for a carbon steel adsorber. Certain
solvents such as ketones and ethyl acetate require that the vessel be made
of SDecial alloys. These solvents form acids when exposed to steam, and
can corrode carbon steel. Stainless steel alloys are normally used in
these cases, For materials of other than carbon steel, the cost of equipment
increases significantly.
If a distillation unit must be included, the installed cost of the
carbon adsorption system will increase significantly. The installed cost
of the distillation unit will deuend on the number of distillation
columns, the complexity of the separation, and the size of the columns.
These factors will be determined by the quantity, complexity and physical
prooerties of the solvents to be separated.
An example of distillation costs encountered is the separation of a
mixture of 50 percent methyl ethyl ketone (MEK), 25 percent toluene and
25 percent methyl isobutyl ketone (MIBK) into a pure dry MEK stream and
a dry toluene •* MIBK mixture. The separation system consists of a
decanter, neutralizing tank and two distillation columns together with
necessary heat exchangers, pumps, structural supports and instrumentation.
The system handles a solvent feed rate of 1.5 gallons per minute which
corresponds to a coating oven exhaust of 15,000 cfm at solvent concentration
of 25 percent of LEL. The cost of this separation system is approximately
12
$125,000 in carbon steel construction.
-------
Impacts and Limitations - The only adverse environmental effect of carbon
adsorotion is the possibility of small amounts of organic solvent
remaining in the water phase after the carbon bed is steam stripped.
Water pollution has not been reported as a problem by paper coaters
currently using carbon adsorption.
5.5 Comparison of Control Sptions and Conclusions
The two proven add-on control devices for controlling organic
solvent emissions from paper coating lines are incinerators and carbon
adsorbers. Both have been retrofitted onto a number of paper coating
lines and are being operated successfully.
The main constraint to the use of incinerators is the possible
shortage of natural gas. However, in many cases the combination of
afterburner and oven will use no more fuel than the oven alone if proper
heat recovery is used. Incinerators can be operated on LPG or distiHated
fuel oil if natural gas is not available.
The major drawback to the use of carbon adsorption is that in some
cases solvent mixtures may not be economically recoverable in usable form.
If the recovered solvent has no value, it is more economical to incinerate
and recover heat than install a carbon adsorber. However, if the recovered
solvent can be used as fuel, carbon adsorption compares favorably in
operating cost with an incinerator. If the solvent can be recovered as
usable solvent, use of carbon adsorption represents an economic advantage
to the paper coater.
It IS more difficult to estimate costs for low solvent coatings,
because the cost will vary depending on chc type of coating. Low organic
5-27
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solvent coatings will usually cost less in dollars per pound of coatings
solids applied than will conventional organic solvent coatings with
some type of add-on control device.
5-28
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REFERENCES
1. Mosher, R. H., and D. Davis. Industrial and Specialty Papers,
Vol. I - Technology. New York, Chemical Publishing Co., 1968.
2. Cairns, C. W., Evolution of Raw Materials, TAPPI Journal.
Vol. 57, No. 5, page 85, May 1974.
3. 1972 Standard Industrial Classification Manual. U. S. Government
Printing Office. Washington, B.C., p. 1.
4. 1967 Census of Manufacturers, U. S. Department of Commerce,
Washington, D.C
5, Hughes, T. W., et al, Source Assessment: Prioritization of Air
Pollution from Industrial Surface Coating Operations, Monsanto
Research Corporation, Dayton, Ohio. Prepared for U. S. Environ-
mental Protection Agency, Research Triangle Park, N. C., under
Contract No. 68-02-1320 (Tech. 14) Publication No. 650/2-75-019a.
February 1975.
6. Industrial Ovens and Driers, Handbook of Industrial Loss Prevention,
Hightstown, N.J., McGraw-Hill Book Co,, 1967.
7. Standards for Ovens and Furnaces, Design, Location, and Equipment,
National Fire Protection Association, NFPA No. 86A, Boston, MA, 1973.
8. Modern Plastics Encyclopedia - 1973-74; Vol. 50, No. IDA, New York,
N.Y., McGraw-Hill, Inc., 1974.
9. State-of-the-Art in Hot Melt Coating Equipment; Paper, Film and
Foil Converter, September 1975, page 51.
10, Comparison of Alternatives by Incremental Basis - Cost Per Pound of
Silicone Solids, Dow-Corning, Midland, Mich.
11. Heat Recovery: Pays for Air Incineration and Process Drying,
Pollution Engineering, Vol. 7, No. 9, pages 60-61, September 1975.
12. Personal communication between W. L. Johnson, U.S. Environmental
Protection Agency and John W. Drew, Chem-Pro Equipment Corp.,
March 16, 1976.
5-29
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6.0 AUTOMOBILE AND LIGHT DUTY TRUCK ASSEMBLY
6.1 Summary of Control Technology
Affected
Facility9
Control Option
Percentage
Reduction
Prime application,
and flashoff area
Prime cure oven
Topcoat app1i cati on
and flashoff area*
Topcoat cure oven
Water-borne (electrodeposition)9
>50 volume percent solids primer
Incineration
Carbon adsorption
Water-borne (electrodeposition)
>50 volume percent solids primer
Incineration
Water-borne topcoat9
>50 volume percent solids topcoat
Incineration
Carbon adsorption
Water-borne topcoat
volume percent solids topcoat
Incineration
_
0C-65d
90+
85+
Oc-65
40
90+
c,f Q:)e ,f
90+
85+
_
Oc-86
90+
(a) These options reduce emissions from application, flashoff and
cure. The percentage reduction given is the reduction from all
of these sources.
(b) Applicable but not costed in this report since water-borne primer
is likely the preferred method.
(c) Based on an original coating with 50 volume percent solids. (3.7 1
(d) Based on an original coating with 26 volume percent solids.
Surfacer (guidecoat) is included. (5.5 Ibs/gal)
Based on an original coating with 12 volume percent solids. (6.5 1
Based on a water-borne topcoat with 2.76 pounds of organic solvent
Per galIon Of coating minus water (e.g., 25 volume percent solids,
15 volume percent organic solvent and 60 volume percent water).
\9/ These control options are applicable to all assembly and subassembly
lines in the plant including those for frames, small parts, wheels,
and main bod.V parts.
*The application area(s) is (are) the
applied by dip or spray. The flashoff
the annl icatinn ar*>a and
OV°P.
s) where the coating is
is the space between
6-1
-------
6.2 General Discussion
For purposes of this study, "automobiles" includes all passenger
cars or passenger car derivatives capable of seating 12 or fewer pas-
sengers. "Light duty trucks" includes any motor vehicles rated at 8500
pounds gross vehicle weight or less which are designed primarily for
purposes of transporation of property or are derivatives of such vehicles.
This is intended to include pick-ups, vans and window vans.
The automobile and light duty truck assembly industry receives
parts from a variety of sources and produces finished vehicles ready for
sale to vehicle dealers. Various models may be built on one line, but
they usually are of the same general body style. A plant may have more
than one line. This chapter is intended to apply to assembly plants
only and not to customizers, body shops or other repainters.
Although faster production is possible, automobile and light truck
assembly lines typically produce from 30 to 65 units per hour using two
(or rarely three) worker shifts per day. Plants are usually shut down
on holidays and for several weeks during the model changeover period.
Most plants operate about 4000 hours per year, ' depending on demand.
Locations of U.S. automobile and light duty truck assembly plants
include: American Motors--Kenosha, WI, and Toledo, OH; Checker Motors--
Kalamazoo, MI; Chrysler Corporation--Belvidere, IL, Hamtramck, MI,
Detroit, MI (2), Newark, DE, and St. Louis, MO; Ford Motor Company--
Atlanta, GA, Chicago, IL, Dearborn, MI, Kansas City, MO, Lorain, OH, Los
Angeles, CA, Louisville, KY, Mahaw, NJ, Metuchen, NJ, Norfolk, VA, St.
Louis, MO, San Jose, CA, Minneapolis - St. Paul, MN, Wayne, MI, and
Wixom, MI; General Motors--Arlington, TX, Baltimore, MD, Detroit,
6-2
-------
MI, Doraville, GA, Fairfax, KS, Flint, MI, Framingham, MA, Fremont, CA,
.Janesville, WI, Lakewood, GA, Lansing, MI, Leeds, MO, Linden, NJ,
Lordstown, OH, Norwood, OH, Pontiac, MI, St. Louis, MO, South Gate, CA,
Tarrytown, NY, Van Nuys, CA, Willow Run, MI and Wilmington, DE; and
International--Springfield, OH. A plant is under construction by Volks-
wagen in Pennsylvania. Volvo, who had planned a new Plant in Virginia,
recently announced their plant has been postponed "indefinitely".
Although no "typical" automobile or light truck assembly line
exists, features common to all are shown in Figure 6-1. As the process
begins, an automobile body emerges from the body shop and undergoes
metal treatment (usually a phosphate wash cycle) to improve paint
2 3
adhesion and corrosion resistance. ' The first coat, a primer, is
applied by dip and/or spray methods, then the unit is baked. The
topcoat is then applied in one to three steps, usually with a bake step
after each. The painted body then goes to the trim shop where assembly
is completed.
Coatings which are damaged during the trim step are repainted in a
repair spray booth. Because the automobile now contains heat sensitive
materials such as plastics and rubbers, repair is generally limited to
solvent-borne coating, which can be dried in low-temperature ovens.
(Water-borne coatings usually require high curing temperatures.)
Production volume in the repair area is intermittent, making add-on
emission control devices less cost-effective than for the primary
coating area. Emission controls, therefore are generally not practical
for the repair spray booth and its oven. Considerable reductions in
emissions can be accomplished by the use of a higher solids repair coating.
6-3
-------
FROM BODY SHOP
METAL
PRETREATMENT
DRY-OFF OVEN
PRIME
APPLICATION
AREA
PRIMECURE OVEN.
FIRST TOPCOAT
APPLICATION AREA
FIRST TOPCOAT
CURE OVEN
SECOND TOPCOAT
APPLICATION AREA
(IF ANY)
SECOND TOPCOAT
CURE OVEN
(IF ANY)
COATED PARTS FROM
OTHER LINES
:• THIRD TOPCOAT
APPLICATION AREA
(tf ANY)
THIRD TOPCOAT
CURE OVEN
-------
Cost estimates and pollutant emissions presented in this chapter
are based on coating main body parts including hoods and fenders. In
some plants (particularly those building larger vehicles), hoods and
fenders are coated separately and joined to the body after coating. The
total cost of controlling emissions may be more if the coating is done
on several lines instead of one line.'
Some automobiles and most trucks have a separate frame that is
joined to the body after coating. Frames and small parts such as wheel
rims may arrive at the assembly plant already coated or may be coated at
the assembly plant. These sources of emissions are liable to the same
control measures as those for the main body and this report applies.
Parts that are not visible from the exterior of the vehicle may be
dipped in a viscous coating that can be either water-borne or solvent-
borne. Headlight frames and other visible small parts may arrive at the
assembly plant already coated, be coated after assembly to main body
parts, or be coated on a separate line. As with the other vehicle
components, the coating process for these parts is liable to the same
control measures used for the main body.
Uncontrolled organic emissions from coating vehicles with organic
solvent-borne surface coatings can range from less than 600 pounds per
hour (lb/hr) to more than 4000 lb/hr for an assembly line. This wide
range is caused by variations in the surface area coated for different
vehicles, the number of vehicles coated per hour, and, most importantly,
the solvent content of the coatings. There may be more than one assembly
line at a plant.
6-5
-------
Other sources of organic emissions from a vehicle assembly plant
that are not included in this study include the application of adhesives
and sound-proofing materials. These account for about 10 to 30 percent
of total organic emissions from the plant.
6.2.1 Materials Used - Two types of coatings are used in this
industry: lacquers and enamels. Lacquers are resin-pigment combinations
dissolved in a high solvent-power solvent. Drying occurs by evaporation
of the solvent and deposition of the resin and pigment, rather than by ,
cross-linking. Enamels are highly pigmented drying oils thinned with a
low-solvent-power solvent. The coating is formed by polymerization.
The uses of coatings can be divided into primers and topcoats.
Acrylic coatings may be either lacquers or enamels and are widely used
for topcoats. Topcoats currently used contain from about 14 to 35
percent solids by volume. Primers are usually enamels and are complex
polymers prepared from epoxy and drying oil acids. Primers are usually
either solution epoxies (cross-linked with a urea or melamine) or
2
electrodeposition primer resins. A typical solids content of a solvent-
borne primer enamel would be 26 volume percent for General Martf and
19
30-35 volume percent for Ford.
Since most manufacturers apply about a 3.0 to 3.5 mils thick
coating, the mass of solvent emitted per unit surface area Is propor-
tional to the ratio of solvent to solid material in the coating. The
relationship between pounds of solvent (assuming a solvent density of
6.6 Ibs/gal) emitted per gallon of solids applied and the percentage
6-6
-------
of organic solvent present is shown in Figure 6-2. The relative
positions of the various types of coatings emphasize the great dif-
ferences in emissions between coatings of different solids content,
e.g., between lacquers and enamels. Even though the positions Of
lacquers and enamels on this figure do not represent absolute numbers
(since exact percent solids and solvent density can vary), the dif-
ference is striking. The amount of organic solvent contained per unit
of solids (as used) factor is a convenient comparative tool because it
is independent of vehicle size, line speed, and coating thickness.
6.2.2 Processes and Affected Facilities • Four types of facilities are
affected: (1) prime application area(s), including flashoff area
(evaporation area prior to the oven); (2) prime cure; (3) topcoat
application area(s), including flashoff area but excluding repair
application area; and (4) topcoat cure, excluding repair oven.
The prime coat serves the dual function of protecting the surface
from corrosion and providing for good adhesion of the topcoat. A
combination of manual and automatic spray methods, with or without the
use of electrostatic techniques, is usually used to apply organic
solvent-borne primer. Because workers are in the spray area; health
regulations require solvent concentrations be kept low. At some plants,
vehicle hoods and fenders may have their own prime spray booth and OVSH.
In 'rare cases, primers may be applied in more than one step with each
fo11owed by cur i ng.
Primers may also be applied by dipping techniques. The Chrysler
Corporation, for example, uses water-borne dip primers for underbodies
6-7
-------
POUNDS OF ORGANIC SOLVENT EMITTED PER GALLON OF SOLIDS APPLIED
w to
w c
|3
•o °»
< 3
C8 r+
o. to
» o_
i. a
F* «A
0)
r+
CD
a>
a.
T3
CD
-^
CO
3
o^
E
D)
•a
CD
a.
•o
m
x
OJ<2 «
b>5 g
— T3 o
^ O 5b
"g 3 5
c:Q- ^
r^ en <
O
I
o'
m
x
o
C
5 S
z
o
m
3D
NONAQUEWWB
DISPERSION ENAMEL (40% SOLIDS)
NONAQUEOUS
DISPERSION ENAMEL (50% SOLIDS)
URETHANE (60 PERCENT SOLIDS)
32 PERCENT SOLIDS, WATER-BORNE SPRAY (80/20)
1 40 PERCENT SOLIDS, WATER-BORNE SPRAY <80/20>
HIGH SOLIDS (80 PERCENT SOLIDS)
50 PERCENT SOLIDS, WATER-BORNE SPRAY (80/20)
ELECTRODEPOSITION (PRIMING ONLY)
I
POWDER COATING
1 I I
I 1 I I
6-8
-------
at some of its plants. Because the dip-coated primer is not smooth, the
coating must be sanded or else be used only on areas where appearance is
not important.
Of most interest from a pollution control standpoint is total body
priming by electrophoretic (electrodeposited) water-borne dip. In this
system the object to be coated is immersed in a water-borne coating and
an electric potential difference is induced between the vehicle and the
coating bath. By correctly setting the electrical potential and the
time in the bath, the coating thickness can be controlled as desired.
Corrosion protection is excellent because coverage is more complete than
can ever be obtained by spray priming alone. Additional primer may be
sprayed on rough or sanded areas. This additional primer, called
"surfacer" or "guidecoat", can be either water-borne or organic SOlvent-
borne.
The paint in the electrophoretic bath consists of 5 to 15 volume
percent solids, 80 to 90 volume percent water, and about 5 volume
percent organic co-solvent. The coating solids displace solvent as they
are deposited and solvent is squeezed out. As the vehicle component
emerges from the bath, its coating is 90 volume percent solids, 9 volume
percent water and 1 volume percent organic co-solvent. Excess coating
is returned to the bath by washing with makeup and ultra-filtered water.
Because of the extremely low solvent usage (about 7 1b/hr), the exhaust
from this oven does not require further emission control unless it
presents an odor problem. The electrophoretic dip process is used at
over 40 percent of U.S. assembly plants and is very widely used in
r 1,5,6,7
turope.
6-9
-------
An option suitable for some plants is to spray a water-borne
primer.
Organic solvent-borne primers are usually spray applied. When
using organic solvent-borne spray, 85 to 90 percent of the solvent
evaporates in the booth and flashoff area; the remaining 10 to 15
percent evaporates in the oven.
Water-borne coatings contain relatively small quantities of organic
solvents, principally to improve leveling and gloss. They are less
volatile organics than those from organic solvent-borne coatings and
consequently a lower proportion evaporates in the booth(s) and flashoff
area(s). For water-borne topcoats, the calculations here assume that 50
percent evaporates in the spray booth(s) and flashoff area(s) and 50
percent in the cure area(s). Note that maximum humidity limitations
(for proper curing), the necessity of an adequate air flow at oven
entrance, and avoidance of explosive mixtures, all affect required oven
exhaust volume for water-borne coatings,
A relatively new system of coatings called "autophoretic" has been
used for frames and parts. This system has been proven for these
applications but has not been applied to primers or topcoats. »^° H
is unknown at this time if the system can be used for parts of the
vehicle that are normally visible.
6.3 Special Considerations
With respect to the coating process, the automobile and light truck
assembly industry has characteristics that make it unique. The companies
involved are large and possess a great deal of expertise in coatings
6-10
-------
(unlike some other companies that coat their products), the entire
process is under their control, and they are free to change coatings,
within the limits of their equipment, (unlike toll coaters that often
have no choice in the coatings they use). These tend to facilitate
control, especially the use of low-solvent coatings. The process can,
and usually does, run at a relatively high percentage of capacity and at
a constant rate-which tends to make control more cost-effective. The
industry produces a product that is expensive to inventory, must be
responsive to customer whim, and is available with a large number of
optians and colors. These make frequent color change a necessity and
hence the use of powder coating difficult. The industry has strong
competition from foreign imports , and produces a product that is exposed
to a wide range of climates and is judged critically by its appearance.
These considerations make the use of unproven coatings more difficult.
Special considerations drastically affect the cost of control. To
Obtain acceptable appearance and coverage on a complex shape SUCn as a
car or truck, manufacturers have found it necessary to apply topcoats by
a combination of manual and automatic spray. Multiple applications are
necessary to achieve the necessary thickness, and sufficient time must
be allowed between applications for adequate drying. Sufficient space
also must be provided between vehicles on a moving assembly line to
allow the operator to complete his task. All of these factors cause
spray booths to be as much as several hundred feet long. Because the
booth is occupied, OSHA requires a minimum air velocity away from the
workers to protect them. This requirement is normally met by main-
taining a minimum air movement from .top to bottom of the booth. This
air flow, in conjunction with the long Spt 3y booths characteristic of
the industry, results in exhaust volumes of hundreds of thousands of
6-11
-------
cubic feet per ainute. The concentrations of organic vapors range from
50 to 200 ppm (equivalent to less than 2 percent of the lower explosive
limit, i.e., the LEL) at temperatures of 60°F to 90°F. This combination
of high volume and low concentration makes add-on devices very expensive
for spray booths.
Ovens are not restricted to the same low organic concentrations
since they are not occupied. Their allowable concentrations are governed
by three factors: explosivity limits (usually to less than 25 percent
of LEL), the necessity to maintain adequate air inflow at openings to
prevent escape of oven gas , and the necessity to prevent condensation of
high boiling compounds on the inner surfaces of the oven. Although
improved oven entrance design can help in the future, the problem of
adequate inlet flow presently limits motor vehicle assembly plant ovens
to a maximum of about 10 percent of the LEL. The condensation problem
7
may begin to occur at higher concentrations. With many older ovens,
modifications may be necessary to raise the concentrations even to 10
percent of the LEL.
Besides minimizing the size and fuel requirements of the control
equipment, operating ovens at the higher concentrations has the additional
advantage of minimizing the fuel requirements of the oven itself by
decreasing the quantity of makeup air to be heated. The higher temper-
ature and the higher concentration (with correspondingly lower exhaust
flow rates) makes incineration much less costly for an oven than for a
spray booth.
Some special considerations make powder coating difficult. These
are the necessity to change colors often and the desirability of "metallic"
coatings. It would be desirable both from a manufacturing and air
6-12
-------
pollution standpoint to switch colors as seldom as possible. Manufac-
facturers would like to schedule many vehicles of one color through the
line in sequence for convenience and to save the paint that must be
purged from spray nozzles each time a color is changed. Unfortunately,
vehicles are built with a large number of available options, of which
color is only one. Air conditioners, power brakes, power steering,
etc., are each installed on a given percentage of the production volume.
Each of these subassembly operations has a production capacity that may
be less than the line speed and each has a finite storage capacity.
Vehicles are largely built to dealer or customer orders which must be
filled within a limited time. The scheduling of vehicles on the assembly
line is, therefore, constrained by many factors and color change is
often necessary between each vehicle. The capability must exist to
change colors quickly in the booth, or else separate application areas
must be available for each color. Because an assembly plant usually
applies in excess of 15 colors, the latter choice is economically
prohibitive.
Spraying powders of different color in one booth also has problems.
In the conventional spray system, each color is delivered through a
separate hose and the operator manually switches his spray nozzle among
the hoses. The former color is first flushed out of the nozzle with the
new color and then coating with a new color begins. Inertial deposition
is the primary coating mechanism although electrostatic attraction may
assist. Once the coating material strikes the surface it agglomerates
and is not then susceptible to reentrainment. High air velocities are
6-13
-------
maintained in the booth to meet health requirements and to prevent
overspray from one vehicle to another. In contrast to this, powder does
not coalesce: the sole force holding the powder is electrostatic
attraction. Furthermore, the small particle size makes it impractical
to use the high sweep velocities required for worker safety (because of
entrainment). Exhaust velocities must be kept low. These low exhaust
velocities make it necessary to use largely automated coating systems
and require face masks where workers are essential. The low velocities
can result in carryover. Any carryover of coating in a powder system
shows up as discrete specks on a differently colored product since there
is no opportunity for dilution of carryover paint specks as in liquid-
borne coatings.
Metallic coatings, much in demand for automobiles, obtain their
name from platelets of aluminum added to give a reflective appearance.
In a powder system, the platelets cannot move after application and are
thus set in a random order. The appearance is less aesthetically
pleasing than that achieved with liquid-borne coatings where the platelets
orient parallel to the surface.
To date these problems have been an obstacle to the adoption of
powder coatings as topcoats in this industry.
6.4 Available Control Technology
For ease of comparing control technology, a flowchart of a typical
plant is shown in Figure 6-3. As outlined at the beginning of this
section, certain technologies are limited to certain affected facilities
and some will reduce emissions from more than one affected facility
6-14
-------
COATINGS,
SOLIDS, b. v.
SOLVENTS,
AND TYPE
12% SOLUTION
LACQUER
18% DISPERSION
LACQUER
32% ENAMEL
50% ENAMEL
WATER-BORNE
PRIME APPLICATION
SOLVENT
EXHAUST
RATE, Ib/hr
380
170
NEGLIGIBLE
FLOW
RATE,
x 103 $cfm
262
123
SMALL
PRIME OVEN
SOLVENT
EXHAUST
RATE, Ib/hr
64
30
40
FLOW
RATE,
x 103 scfm
4.5
1.6
1.6
TOPCOAT APPLICATION
SOLVENT
EXHAUST
RATE, Ib/hr
2490
1546
720
340
85
FLOW
RATE,
x 103 scfm
1815
1129
525
248
525
TOPCOAT OVEN
SOLVENT
EXHAUST
RATE, Ib/hr
438
212
127
60
85
FLOW
RATE,
x 103 scfm
25.0
15.5
6.0
3.4
3.4
I
en
1
PRIME
APPLICATION
(AREAS)
k
t .
PRIME
OVEN(S)
k
1
TOPCOAT
APPLICATION
AREA(S)
I
r i
TOPCOAT
OVEN(S)
ASSUMPTIONS: SOLVENT CORRESPONDS TO SO-SO mote percent HEXANE-BENZENE; 85 percent OF EMISSIONS ARE IN APPLICATION AREA(S)
FOR SOLVENT-BORNE COATINGS; 50 percent OF EMISSIONS ARE IN APPLICATION AREA(S) FOR WATER-BORNE TOPCOAT; 30 gal/hr OF SOLIDS
ARE APPLIED FOR PRIME COAT; 60 gal/hr OF SOLIDS ARE APPLIED FOR TOPCOAT; APPLICATION AREA EXHAUST AT 100 ppm WAS 0.0228 lb/103
scf; OVEN EXHAUST AT 10 percent OF LEL WAS 0.296 lb/103 scf; ORGANIC SOLVENT DENSITY WAS 6.665 Ib/gal. FOR WATER-BORNE, percent OF
LEL WAS LOWER.
Figure6.3 Typical plant for assembling intermediate-sized automobiles and light-trucks at rate of 60 per hour. (For
different vehicles, the values would correspond to different production rates.)
-------
(e.g., transition to water-borne coatings will result in reduced emissions
from both the application and curing areas). Some technologies can be
combined (e.g., incineration will further decrease emissions even after
a plant changes to coatings with higher solids content).
Caution must be used in applying the cost estimates below to specific
plants, since retrofitting costs can vary greatly depending on the
specific situation. In some cases the assumptions used herein are for
an almost 'ideal cafe; any deviation will increase the cost. One should
carefully analyze each situation to determine if the assumptions are
valid or the deviations essential (for example the cost of control for a
given amount of organic material is roughly inversely proportional to
concentration but exhaust gases in most ovens are far more dilute than
necessary), The paint usage assumptions can also vary considerably
i o
between plants. In all cases, the assumptions (and where possible the
effects on costs of different assumptions} are listed, either In this
Section or in Section 4 of Volume I
The control options described have varying levels of current use in
assembly plants. Water-borne primers are currently used in almost half
of the plants. Water-borne topcoats are being used at two plants and
their use is planned at a third. Incineration of oven exhaust has been
used at a number of plants. Topcoats with greater than 50 volume
percent solids have not yet been used but this level is being approached.
One compa.iy plans to use topcoats with greater than 70 percent solids
or
before 1981. Incineration or adsorption of spray booth exhaust,
although technically feasible, has not been used at any plant. Carbon
6-16
-------
adsorption of spray booth exhaust would require pilot studies because of
known potential problems. Thus the timetable and cost of compliance are
more uncertain using carbon adsorption than for other methods.
Finally, it should be noted that inclusion of a discussion of a
technology in this report indicates it is technically feasible, that is
that no invention is required for its implementation. No judgement is
made as to its reasonability or advisibility for a given situation, from
a standpoint of either cost or energy.
6.4.1 Option 1 - Electrodeposition of Water-Borne Primer - This option
assumes electrophoretic (electrodeposited or electrocoated) application
of primer to the vehicle. Spraying of water-borne primers is possible,
but it does not achieve the same coverage or lend itself to automation
as well as the electrophoretic method does. Water-borne spray priming
is used at some plants and it is a viable option for many plants. It is
important to evaluate the ratio of organic solvent to solids for spray
primers and the losses due to overspraying to determine the effective-
ness of this option.
Achievable Reduction - The amount of organic solvent in an electrophoretic
coating is less than 0.15 Ibs per gallon (minus water). However, solvent
emitted from evaporation in the tank and from the "surfacer" used after the
dip increases the overall total to about 1.9 Ibs per gallon (minus water).
The percentage reduction achieved by a change to electrophoretic coatings
depends on the original system. For example, if the change is from a 32
volume percent solids primer (about 5.3 Ibs of organic solvent per gallon
of coating) to electrophoresis (about 1.9 Ibs of organic solvent per gallon
of coating), the reduction is 80 percent.
6-17
-------
Technical Analysis - A description of electrophoretic priming (electro-
deposition or electrocoating) is provided in Section 3.3.1 of Volume I.
As discussed earlier, electrophoretic priming requires better precleaning
of the metal than does an organic solvent-borne primer and it requ i res a
final rinsing with deionized water before priming.
With an organic solvent-borne system, the assembly line can be
stopped overnight, on weekends, or during shift changes and breakdowns.
This is not possible with electrophoretic primer or with other water-
borne systems because of the potential for rusting and dirt pick-up (due
to the longer time it stays wet). Thus, vehicles covered with water-
borne coatings cannot be left for long periods of time before being
baked and the assembly lines must have the capability of carrying coated
vehicles through the oven after assembly line shutdowns. Accommodations
must also be made for storage of these vehicles or parts until the line
starts up again. This necessity for surge storage areas and independent
conveyor chains for each of the spray booths results in additional
conveyor controls and costs.
The major limitation of electrophoretic dip coating is that it can
be used only directly over metal or other conductive surfaces. It is
limited to one-coat applications or primer finishes, and there is a
practical maximum thickness that can be achieved.' A bath can only
contain one color so a separate bath would be necessary for each color.
None of these problems adversely affects the use of electrophoretic dip
for primer, but they do make it unusable for motor vehicle topcoats.
13
Electrophoretic dip coating is a fully demonstrated technology.
6-18
-------
A consideration for any control option is natural gas usage. In
electrophoretic dip priming, gas is used in the ovens. Although higher
temperature must be maintained for a longer time period than when
curing conventional primers, organic solvent emissions are far less.
Thus,, required air flow may be reduced (this is limited by the ventil-
1ation necessary to keep oven gases from escaping and to remove reaction
products from the oven). Unlike organic solvent-borne primer, no dry-
off of the body after cleansing is required prior to the electrophoretic
coating, therefore it eliminates fygl usage for this purpose.
Electrical requirements increase by about 1400 kilowatts by a
switch to electrophoretic coatings. Electrical requirments for applying
the coating are about 1000 amps at 400 volts (400 kilowatts). Ford
reports that their plants use 1500 amps at 200 volts (300 kilowatts).
Cooling requirements for the bath are about 150 tons of refrigeration,
equivalent to about 1300 kilowatts. Some additional power is av50
required for the agitation and ultrafiltration steps. Note that ;0 to a
300 kilowatt credit in power usage can be taken because most of the
120,000 to 260,000 SCfm exhaust from replaced spray booths is no longer
required. ($ome spray booths may still be needed for surfacer.)
Depending on climate, this air would have to be heated in the winter,
usually by natural gas, steam or propane. Finally, there is no increase
in pumping requirements since the circulation in the bath that is
necessary in electrophoretic systems for mixing and water circulation is
offset by elimination of the water which would be required in the spray
booths for collecting particulate,
6-19
-------
In summary, since an assembly line applying organic solvent-borne
primers uses about 12,000 KW of electricity, the 1400 kilowatt increase
caused by electrophoresis represents a 12 percent increase.
Cost of Control Option » The principal disadvantage of electrophoretic
dip priming is its high capital cost. Maintenance costs are equal to or
less than those for conventional spray systems and operating labor is
'reduced. More coating is applied per vehicle than when spray is used
because coverage is better but total paint usage is about equal to spray
coating because there is almost no waste.
The installed cost of an electrophoretic system for a typical
vehicle assembly plant would be about $8 million. Costs can, of course,
vary considerably depending on what building alteration and relocation
of existing equipment is necessary. Table 6-1 gives increased operating
costs for electrophoretic primer, based on electricity at $0.03/KWhr,
interest and depreciation at 12 percent of capital costs, and operation
for 4000 hours per year.
Effects and Limitations - Electrophoretic dip coatings contain amines
that are driven off during the curing step. Some plants have found it
necessary to incinerate the oven exhaust gas to eliminate the visible
emission and nialodors associated with these amines. No other adverse
environmental effects appear to result from a change to electrophoretic
dip coatings, and no apparent safety problems exist, assuming normal
industrial procedures are followed. The energy impact was discussed
earlier in this section.
6-20
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TABLE 6-1. INCREASED ANNUAL OPERATING COST
FOR ELECTROPHORETIC DIP PRIMERS COMPARED TO SOLVENT-BORNE PRIMER
Utilities:
Electricity $.03/kWhr x4000 hrs/vr x 1400KK 168,000
Direct labor: 8hrs/shift x 500 shift./yr -180,000a
Savings of 3 workers/ shift $15/hr
Interest and 12 percent x ^1^000,000 120,000
depreciation to 8,000,000} ' to 960,000
Total increased operating cost — 108,000 to 948,000 $/yr
There is a net credit for labor cost for electrophoretic dip coating.
The calculation is for the difference between one operator VeTSU^ four
in a conventional SDrav booth applying organic solvent-borne primer.
Assuming 20 year life, 10 percent interest.
The range of values is for different ages of the existing prime line.
The lower value represents the increased total installed cost of an
electrophoretic dip line over an organic solvent-borne crime line for a
plant with an old prime line ready for replacement. The higher value
represents the total installed cost for a plant with a new sol vent -
borne pr i me 1 i ne .
6-21
-------
§.4.2 Option 2 - Lower Solvent Primer and Topcoat - This option is the
use of lower solvent (higher solids) organic solvent-borne systems (not
to be confused with "high-solids" coatings discussed in Volume I,
Section 3.3.2). At many of its plants, General Motors uses lacquers for
the topcoat. Lacquers have very low solids content (^14 volume percent).
Ford, American and Chrysler use topcoat enamels with 22 to 35 percent
solids by volume {^33 to 45 weight percent). Volkswagen expects to use
25
topcoats with ^70 volume percent solids (80 weight percent) by 1981.
Current solvent-borne prime coats vary from 26 volume percent4 to 37
volume percent (sealer at new Volkswagen plant). European and Japanese
H
manufacturers use enamels almost exclusively.
This option examines the general effect that raising the solids
content of coatings has on emissions. The choice of 50 volume percent
solids as a base is intended as an example only since any increase in
solids content can dramatically reduce emissions, as shown Figure 6-2.
An obvious improvement would be a change from a low solids lacquer
system to a higher solid enamel system.
Any regulation calling for a minimum solids content should be based
on an average over at least an hour since the solids of different
colors and coatings can vary within a plant. Distinction between weight
percent and volume percent solids is also necessary.
Achievable Reduction « The achievable reduction again depends on both
the old dating and its replacement. For example, the 50 volume percent
coating achieves an 86 percent reduction if it replaces a lacquer with
12 volume percent solids, but only a 53 percent reduction if it replaces
an enamel with 32 volume percent solids. Obviously, even further
reductions can be achieved if an add-on control device is also installed.
6-22
-------
Technical Analysis - There are no significant changes in operating
requirements necessary to switch to lower solvent coatings. Nozzles
would have to be slightly modified as would procedures for application
and curing, but generally, the same equipment would be used. Oven
exhaust volumes could be reduced considerably, as could the number of
spray booths, if lacquers were replaced with enamels.
There are no unresolved technical problems associated with this
option. At present only General Motors uses lacquer for vehicles, but
even they apply enamel to many of their light trucks and some of their
automobiles. General Motors recently converted their Kansas City
assembly plant from applying lacquers to enamels on a trial basis.
Cost of Control Option • Typical capital costs for this option are
difficult to assess because they depend completely on the specific plant
situation. We estimate a change from lacquer to enamel would require a
capital cost (including engineering) of $1,000,000. (General Motors
claims that it would be higher.) Based on a rule of thumb 12 percent of
capital investment, annualized operating costs could be as high as
$120,000 per year although this would be affected by the lower manpower
required to apply enamels and the increased manpower which would be
4 14
needed to repair damaged coatings. '
Effects and Limitations - The chief impact of this option would be on
General Motors (GM) Corporation, the only company still predominantly
using the lacquer system.
The energy required to cure enamels should be less than for ITacquers
because of lower exhaust flow rates (since fewer coats are needed,, fewer
6-23
-------
booths are used and less solvent is evaporated). This potential energy
savings is partially offset by the higher temperature required for
curing enamels.
6.4.3 Option 3 - Carbon Adsorption for Primer and Topcoat Spray Booths -
As discussed in Section 6.2 of this volume, 85 to 90 percent of the
solvent emissions from organic solvent-borne coatings occur in the spray
booth and flashoff area and only about 10 to 15 percent in the ovens.
This option considers installation of carbon adsorbers to control organic
emissions from the spray booths and flashoff areas where it is assumed
85 percent of the emissions occur.
Achievable Reduction * Reductions of greater than 85 percent can be
achieved using carbon adsorption to control emissions from primer and
K ^ 15,16,17
topcoat spray booths.
Technical Analysis - Spraying processes for topcoats and primers are
subject to the same health-related constraints on concentration because
an operator is required in the booth. Thus the organic concentrations
in the exhaust typically average about 100 ppm and can be lower. Some
areas, such as the booth for two-tone coating jobs, have significantly
lower average concentrations.
There are problems in the application of carbon adsorption for
automotive and light duty truck spray booths. These problems, which
arise from the presence of particulate matter and water miscible organics
in the inlet stream and from high humidity, are solvable. General
Motors has acknowledged that activated carbon can be effectively used" on
spray booths and ovens to reduce solvent emissions by 90-95 percent if
16 '
the carbon adsorption system is properly engineered and regularly maintained. '
6-24
-------
For instance, although excessive particulate matter can reduce carbon
life, spray booths generally already use some type of particulate
control. In smaller booths this may be a panel filter, although in the
more typical larger booths, 95 percent efficient water scrubbers (water-
wash booths) are used to give a low particulate concentration level.'
The remaining 5 percent could still have a significant effect on an
adsorber but additional particulate removal can be used if necessary.
Such particulate removal has not been included in cost estimates. A
humidity problem, if any, can be solved by reheat of the gases. About a
10 F reheat may be necessary to reduce the relative humidity below 80
percent. Solvents that are deleterious to carbon can be avoided. Spray
booth temperatures are too low to degrade coimon solvents or vaporize or
break down any of the resins into compounds that can cause problems.
As with any add-on control device, the capital cost is largely
dependent on the flow rate. Generally anything that decreases flew
rates of exhaust will decrease capital and fixed operating cost. Possib le
methods of reducing flow rates include reduction of velocities past the
workers (yet remaining in compliance with health requirements) and
recirculation of cleaned exhaust air from manned spray areas to unmanned
areas using automatic spray. ' Improved automatic spray machines
under development will enable the use of a wider variety of coatings and
4
also decreased ventilation. Another avenue that might be profitably
explored is to protect workers with breathing masks supplied with an
exterior source of clean air. This would permit reduced exhaust flow
rates limited only by the necessity of providing adequate ventilation to
avoid cross-contamination of vehicles on the line and by health regu-
6-25
-------
lations. An attractive possibility, especially for users of lacquers,
is to switch to higher solids material to reduce flow rates before
applying carbon adsorption; the lower the flow rate, the lower the
cost.
Questions that have been raised in comments to drafts of this
report as to the validity of the assumptions on which we predicate
carbon adsorption can be satisfactorily answered. Therefc, of course,
no one "typical solvent fnixtare^for^nc||^^ i & -.
& "' -4V "" '
The important factor in assuming a solvent for cost estimation purposes
is that it be representative of the actual solvents used (to the greatest
degree possible) in the characteristics important to the control technology
being evaluated. The mixture of hexane and benzene meets these criteria
for carbon adsorption. This mixture was chosen because it represents
the two largest classes of solvents (aliphatic and aromatic hydrocarbons)
used, because the molar volumes of these compounds are representative of
most solvent blends (see Section 3.2.1 of Volume I of this series for
the importance of this), and because cost data were available. The
question of the miscibility of the solvents will be covered in the next
section.
Although carbon adsorption is technically feasible, (i.e., no new
inventions are needed for its implementation), no full-scale instal-
lations are presently in operation on automobile or truck assembly plant
paint spi ay booths. As noted earlier, pilot studies would be necessary
for use of this technology.
Cost of Control Option - These costs were estimated assuming adsorber
modules, each capable of handling 50,000 cubic feet per minute.. Total
costs for a system would be a multiple of the cost for one. Special
6-26
-------
designs for high volume low concentration flows are possible to lessen
capital costs, but were not investigated for this study.
Three cases are costed in Table 6-2. (Note that although these
estimates include installation, actual costs could be higher for difficult
retrofit situations. Ford estimates that capital costs would be about
80 percent higher. ) The first is with solvent recovery and no credit
for solvent. The second case, which is for solvent recovery with credit
as fuel only, is probably the most reasonable assumption for assembly
plants. The third case is credit for the solvent at its solvent value.
Assembly plants general ly use multi-component solvents and reuse would
be difficult.4
Impacts and Limitations - Due to the pressure drop associated with gas
flow through a carbon adsorber and the large volumes of air through
spray booths, the electrical requirements for handling air are large.
Steam consumption for desorption is also large because of the laroe
amounts of low concentration gas. (See Section 3.2.1 of Volume I of
this series for details.) Some solvent used in assembly plants are
sufficiently water miscible to pose a water pollution problem if regene-
4 14
ration steam is condensed and discharged untreated. * Many of these
compounds (e.g., alcohols, esters and ketones) are primarily in the
formulation to comply with regulations based on photochemical reactivity
such as contained in the former Los Angeles APCD Rule 66 (now Southern
California Air Pollution Control District Rule 442). With effective
add-on controls, less expensive water-immiscible solvents could be
employed. Carbon adsorption of these "non-exempt" solvent blends
6-27
-------
TAB'LE 6 2. COST ESTIMATES FOR AUTOMOBILE AND LIGHT TRUCK ASSEMBLY
PLANTS WITH CARBON ADSORPTION FOR TOPCOAT SPRAY BOOTHS AND
FLAS'IOFF AREA?
CASE 1
CASE 2
CASE 3
cost
No credit
for solvent
Fuel value
for solvent
Solvent at b
solvent prices
Capital cost
per 1000 ft3 /min '10,820
Total capital c
cost, $ x 106 2.7 -
Annualized
operating cost
per 1000 SCfm, $ 4,162
otal annualized r ,
operat 1 ng cost, 1.0 -7.3
t if in6
Total annualized
operat
$ x 10
Steam use,,
Ib/hr x 1(
7c-55d
Cost per ton of
organic removed,$ 1,153
10,820
2.7C - 19.6d
4,003
- 7.26
7c-55d
1,110
10,820
2.7C -
3,643
n.90C - 6.61d
7c-55d
1,005
'Based on 100 ppm of hexane-benzene - 90 percent removal and 5840 hrs per year
ooeration. Correction factors for different operating hours assumptions and
a list of other assumptions can be found in Chapter 4 of Volume I. Note tint
costs for condensate stripping [if necessary) are not included.
It is very unlikely that recovered organiCS could be reused as solvents.
'Based on 50 percent solids topcoat (248,000 SCfm).
Based on 12 norcent solids toncoat (1,815,000 scfm).
6-28
-------
14
(e.g., toluene and xylene) would be less difficult although some
treatment of the condensate might still be necessary. In cases where
such a problem is unavoidable, the uncondensed steam (or hot air if hot
air regenerated ) and solvent can be incinerated together ' ' '
or the condensate can be stripped and the miscible solvent disposed of
' V - . , '• ! ''
properly. The size, fuel usage and the cost of this incinerator is many
times less than if incineration were used alone. There will, of course,
be extra' costs associated with these solutions:" These costs are,
'••''•'• -r.T'r-M IT.'" '••••!,!! -if!' virrdi.:'' "; vi/ , v. ;.,'..'.. . 'Li1 ., ; .tin ifiili ... l' i ", -..>*' 0 J'-> '
An important factor which must be considered before selecting
. b9V 1 nv'l"!! V i n'j | lt>
carbon adsorption as a means of control is space. The exhaust from
assembly plant topcoat spray booths and flashoff areas may need as many
as 6 to 37 dual-bed carbon adsorption units in parallel operation. The
floor area required by the adsorbers would be comparable to that'occupied
by the spray booths.
6.4.4 Option 4 - Incineration for Spray Booths
Achievable Reductions - Reductions in volatile emissions of 95 percent
are achievable with incineration.
:., I "j ! • i • l - I . .
'Technical Analysis • The basic requirement for noncatalytic incineration
is to maintain sufficient temperature to combust the gases. For the
cost estimates presented here, an exit temperature of 1400 F has been
assumed. Depending on the solvents used, however, the operator may be
able to lower this somewhat and still achieve sufficient oxidation of
the organics.
6 -29
-------
ec bfucsv ;3nsi\A bus ensure? ,.?.9;
the
Important operating requirements for catalytic incineration are
^tHw 29?5j n i -v'f&229D9rt sd ' i U £ trio rr; s^Scfisbnoo srij ?ro 7 nsmj nS'fj
necessity to preheat and, periodically clean or replace the catalyst.
, ,•' •"'' "U£ Jon ID; mn9Jd be ansbnoofuj erlj t 91 jab rovsnu 2 i fne i'dc^q e fiou?
Moni ^pring or periodic testing of the exhaust eases is necessary to
' ustS'ianrDfif sd n&z tnevFoa bn& I bsj sisrisrisi i rb
assure that combustion is complete.
TO Dsaoqa'rb- .tnsvfoa sfdroarm srtt brie bsqq'ma sd nso sjfiansbnoo 9 fit 10
Although there are no major technical problems associated with
Y, -rr. " ^ ;T' _t~"
(e.g., for odors).
ni'j --" , v u anc ir».iU'-H - sr* • '<"$ w :••*' •- .'.- ~ /
Cost of Control Option - Incineration was only considered for topcoat
( ^e't&n'rjfii -J rw 9 Fdsve !;'„•? tr*;.
related streams since the advantages of electrophoretic dip coatings are
'
such that this would likely be the preferred control method of reducing
•• ' ;i ro. .: i r;rn oj : r
emissions from application of the prime coat.
ji/wi i-j.tr.-. i-r*q ssJsrnrJ.?^ JSOD
The following three options were considered in estimating the cost
of control .
./!:*:>i>.'s. . . , •!;• v-/9,:, £ ; : 32
1. Option one is use of incineration without heat recovery.
'
2. Option two is use of incineration with primary heat recovery,
that is preheating of exhaust gases prior to incineration. The
efficiency of heat recovery is 35 percent.
&s- a
6-30
-------
3" Option three is the use of a noncatalytic incinerator with 85
percent efficient primary heat recovery. This option was costed based
on captial costs and fuel and electricity rates given in Reference 22.
Labor cost were assumed to be the same as Option 2 and fuel costs were 23
reduced. This option is being used on a coil coating line in Wisconsin.
Heat recovery efficiencies of up to 90 percent are available.
Cost estimates for these three options are summarized in Table 6-3.
Secondary heat recovery was not costed as there is no apparent use for
this energy.
Effects and Limitations - Small quantities of oxides of nitrogen will
normally be formed during incineration (from atmospheric Np). If there
are nitrogen or sulfur-containing compounds present in the waste gas,
higher levels of their oxides may be formed. Halogenated compounds will
form acids upon combustion. The nitrogen oxides are formed primarily at
high temperatures such as found in a burner flame and are thus minimized
with high degrees of heat recovery. Thus, the heat recovery mandated by
cost and energy considerations should minimize nitrogen oxide emissions.
The chief adverse effect of incinerating spray booth exhaust ''s
hl'Qh energy consumption. This can be reduced through the use of: coatings
with lower solvent content, catalysts, and primary and secondary hec.t
recovery. Before requiring incineration for spray booths one should
contact local fire protection agencies for their approval.
6.4.5 Option 5 - Incineration for Primer and Topcoat Ovens
Achievable Reductions - Reductions in volatile organic emissions of 95
percent are achievable using catalytic or noncatalytic incineration on
oven exhausts.
6-31
-------
TABLE 63. COST ESTIMATES FOR INCINERATION OF EXHAUST FROM L
AUTOMOBILE AND LIGHT DUTY TRUCK ASSEMBLY TOPCOAT SPRAY BOOTHS'L '
Costs
Capital cost per
1000 scfm, $
Total capital cost,
$ x 106
Annual ized operating
cost per 1000 scfm,$
Total operating cost,
$ x 10°
Fuel, Btu/hr x 10
Electrical
requ i rements , k W
No heat recovery
Option 1
Catalytic
6,814
i.6a-11.9b
8,674
2.1a-15.3b
182a-1332b
447a-3262b
Cost per ton of 2,!lr;
Organ 1CS removed, $
Noncatalytic
4,985
1.3a-9.4b
16,447
4.1a-29.8b
494a-3612b
349a-2553b
4,12n
38 percent efficient
Primary heat recovery
Option 2
Catalytic
8,050
2.0a-14.5b
7,306
1.8a-12.8b
118a'b-862b'c
7233-5280b
1,820
Yoncatalytic
6,435
1.5a-11.0b
11,578
2.9a-21.3b
314a'c-2300b'C
719a-5250b
2,910
85 oercent efficient
Primary
. heat recovery
Option 3
Noncatalytic
8,575
2.1a-15.5"
1,598
0.4a-2.6b
53a-384b
645a-4715b
a n
I
CO
ro
Based on 50 volume percent solids, 248,000 Scfm from tODCOat booth(s).
Based on 12 volume nercent solids (lacquer), 1,815,000 Scfm from topcoat booth(s).
Net energy usaqe considering recovered energy.
Based on 95 nercent removal efficiency.
-------
Technical Analysis - There are no serious technical problems with the
use of incineration for oven exhaust and incineration has been used on
automobile and light truck assembly plant ovens.
Cost of Control Option - The control devices for the topcoat and the
primer ovens -would most likely be separate. Primer ovens have exhaust
rates ranging from 1600 SCflTl to 4500 and are assumed to operate at 10
percent of the LEL. Topcoat ovens have exhaust rates ranging from 3400
SCfm to 25,000 scftn, and are also assumed to operate at 10 percent of
the LEL.
Table 6-4 shows estimated costs for primer and topcoat ovens
operating at 10 percent of the LEL. Table 6-5 shows the cost for 15
percent of the LEL. Note that the exhaust volumes are 33 percent lower
for 15 percent of the LEL for the same solvent volume. The 15 percent
of the LEL case is included to show the benefits of minimizing dilution.
It is important to note that most existing ovens are operated at " fSS
than 10 percent of the LEL. No cost was assigned to the modificati n$
necessary to reduce air flow to achieve this concentration, however.
The modifications would vary considerably and it is difficult to estimate
a "typical" cost. Since reduction of exhaust flow has a dramatic effect
on consumption of increasingly scarce and expensive natural gas,this
modification would seem to be mandated, even without, pollution control
cons i derat i ons.
Effects and Limitations . As illustrated by Tables 6-4 and 6-5, the fuel
consumed by incinerators for ovens need not be excessive if the ovens
operate above 10 percent of the LEL. If ovens were operated at
6-33
-------
TABLE 6-4. COST ESTIMATES FOR INCINERATION Oh tXHAUbl ur fiunt miu
OVENS FOR AN AUTOMOBILE LIGHT TRUCK ASSEMBLY Pt
(AT 10 PERCENT OF THE LOWER EXPLOSIVE i
i Flow rate3
and option
Lower
Option 1
Catalytic
Noncatalytic
Option 2
Catalytic
Noncatalytic
Option 3
" Catalytic
^ Noncatalytic
Higher
Option 1
Catalytic
Noncatalytic
Option 2
Catalytic
Noncatalytic
Option 3
Catalytic
Noncatalytic
i 1
Capital cost
for prime
oven , *
52,800:
31,400
79,40 b
69,20
-------
r\nu
PLANT (AT 15 PERCENT LOWER EXPLOSIVE LIMIT)'
F low vtcH
and opt ! o r
Lower
Option 1 (No heat recovery)
Catalytic
Noncatalytic
Option 2 (Primary heat
recovery)
Catalytic
Noncatalytic
Option 3 (Primary and
secondary Heat recovery)
Catalytic
Noncatalytic
Higher
0"! >on ' 'r-1' heat recovery)
(itai,/ I*.
Noncatalytit
Option 2 (Primary heat
recovery)
Catalytic
Noncatalytic
Option 3 (Primary and
secondary heat recovery)
Catalytic
T Nuncatalytic
Capital cost
for pri me
oven, $b
42,100
41,000
49,000
48,800
56,700
57,400
122,000
112,000
146,000
126,000
170,000
158,000
Total
capital
cost, $ e
106,000
106,600
123,500
122,800
142,700
144,500
281,000
239,000
340,000
281,000
400,000
343,000
Annual total
operating
cost, $/yr e
48,600
58,800
42,500
48,500
42,500
44,000
197,400
254,000
147,000
163,000
105,000
102,000
Net energy
used,
xlO6 Btu/hre
1.2
2.8
.2
1.13
••"1
- .13d
9.0
21.5
1.5
8.5
-5.0d
-1.0d
Electrical
requirements,
kWe
10.6
8'. 2
13.3
12.2
16.0
16.2
80
62
100
92
120
122
Cost per ton
of organics
removed, F/ton^
195
236
171
195
171
177
108
139
81
89
58
56
l ower flow rate: 1,100 scfm for prime oven: ?,20n *r\lit for topcoat oven. Higher flow rate: 8,333 scfm for prime
oven , 16,666 SCfm for topcoat oven.
Calculated from data for 5^00 SCfm using six-tenths rule.
Based on 95 percent removal.
Recovered energy is greater than energy input.
Prime and Topcoat
-------
15 percent of the LEL, incinerators can actually save energy by recovery
of the fuel value from the solvents that would have been exhausted.
This energy can displace natural gas or other fuels that otherwise would
be needed for the oven, for metal cleaning, for building heat, or for
other uses in the plant. Note that distillate oil as well as natural
gas can be used as fuel for noncatalytic incinerators. Incinerators
with higher heat recovery efficiency can be used to minimize fuel usage
even of streams with lower LEL values.
6.4.6 Option 6 * Water-Borne Topcoats
Achievable Reductions - Reductions in organic solvent emissions of up to
92 percent from topcoat spray booths and ovens are achievable using
water-borne topcoats. The exact reduction depends on both the original
coating and the replacement. If, for example the original coating were
12 volume percent solids lacquer (6.5 Ibs of organic solvent per
gallon of coating) and the water-borne had 2.8 Ibs of organic solvent
per gallon of coating (as do GM coatings in California), reduction would
be 92 percent. If the original coating were 33 volume percent solids,
reduction would be 70 percent.
Technical Analysis - Water-borne topcoats are currently being used at
two General Motors automobile assembly plants in California on a full-
scale basis. Although there can be no argument as to the technical
feasibility of water-borne topcoats, a number of major process modifications
are necessary to retrofit this technology to an existing plant. '
These are:
6*36
-------
1. Lengthening of flash tunnel and ovens • Water-borne coatings
require a longer flash tunnel prior to curing. Temperatures must also
be raised more slowly in order to evaporate the water slowly enough to
avoid pitting the coating. This necessitates longer ovens, which in
turn may force equipment relocations.
2. Cleanliness - Water-borne coatings do not "touch dry" (dry to
the point where the surface can be handled) as quickly as solvent-borne
coatings. Thus they are more susceptible to dirt pick-up. This necessi-
tates filtration of incoming spray booth air. Overhead conveyors may
also be unacceptable because of potential for dropping dirt on newly
painted parts.
3. Humidity and temperature- Because the major solvent being
evaporated is water, proper temperature and humidity conditioning of the
make-up spray booth air is vital. If the humidity is too high or the
temperature too low, the solvent will not dry quickly enough an' the
coating will sag on vertical surfaces. If the humidity is too If./ or
the temperature too high, the water will evaporate too rapidly and the
coating will have "orange peel" or pits. Each coating must be for-
mulated for a narrow humidity range, but formulations for different
humidities (within limits) are possible. Water can be removed from
incoming air by chemical or mechanical means. The chemical means
involves the use of a hydrosccpic solution. The mechanical means
involves the use of refrigeration cycle. The most economical choice
depends on both the climate and the availability of energy at the plant.
The chemical method is more complex, but requires less energy.
6-37
-------
The chemical method uses steam as its energy source while the mechanical
method uses electricity. Thus, steam availability favors the chemical
choice. Both methods have been used. '
4. Shutdown * Because of the potential for rusting and dirt pick-
up, vehicles coated with water-borne coatings cannot be left wet over-
night or even during shift change. The assembly line must have facilities
for carrying painted vehicles through the following oven after a line
shuts down. Accommodations must also be made for storage of these
vehicles until the line starts up again. These requirements necessitate
surge storage areas and independent conveyor chains for each of the
spray booths with resultant controls and costs.
5. Cleanup - Unlike overspray from organic solvent-borne coating,
water-borne coating overspray does not dry in the air before being drawn
through the particulate collector. This causes increased cleanup
problems and costs.
6. Sludge handling - Water-borne coatings do not harden in the
water-wash particulate collectors , sludge handling is more difficult.
7. Corrosion - The pipe commonly used to convey organic solvent-
borne coatings from central mixing areas to the spray booth are not
suitable for water-borne coatings and must be replaced with a corrosion
resistart material. The lifetime of carbon steel spray booths may also
be lessened when water-borne coatings are used.
8. Maintenance - Maintenance costs will increase because of the
new air conditioning and humidity control systems required.
6-38
-------
9. Repair of coatings - Repair of coatings damaged during assembly
is more difficult than for lacquers but no more difficult than for other
enamels.
Cost of Control Option - The cost of converting to water-borne topcoats
for an existing plant will vary. A major variable will be the age of
the existing coating equipment. If near retirement, it may be better to
build entirely new spray booths and ovens. This was done at one of two
automobile plants which converted to water-borne coatings. In this
case:, costs should be adjusted to give credit for the value of the
improved facilities.
If the coating equipment is still relatively modern, however,
retrofitting will entail lengthening of ovens and modification of spray
booths and conveyors. This was the approach taken at the other auto-
mobile plant using water-borne topcoats and is the basis for the cost
calculations presented here. Capital costs for a switch to water-borne
5
topcoats for the model plant are estimated to be about $20 million.
For a plant where the entire coating line is replaced, capital COSIS are
about twice this.
Incremental operating costs include increased electrical require-
ments and increased maintenance labor. Coating material costs are
approximately the same. Higher oven temperature causes an increase in
natural gas usage. Annualizea operating costs for the model are given
in Table 6-6.
Effects and Limitations - The effluent water from water-borne coating
processes will require the same treatment methods as that from SOlvent-
borne systems. The treated effluent is acceptable to sewer authorities
6-39
-------
TABLE 6-6. INCREASED ANNUAL OPERATING COST ESTIMATt FOR
WATER-BORNE TOPCOATS OVER ORGANIC SOLVENT-BORNE
TOPCOATS
T - f
Utilities:
Electricity
Direct labor:
Maintenance \
Building overhead \
(
Taxes and insurance j
Interest, and i
depreciation I
Total increased
operating cost
$.03/KWhr x AOOOhrs x 50QOKW
y*
20 additional hrs/shift x
500 shifts/vr $15/hr
21 percent x capital costs =
0.21 x $20,000,000
$6on,noo
$150,000
$4,200,000
$4,950,000/yr
Assuming a 20 year life and 10 percent interest charge
6-40
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at the two California plants now using the coatings. Water-borne
coatings do not precipitate and dewater as well in the overspray col-
lection water as do some other paints and this lack of dewatering
creates an increased solid waste disposal problem.
The additional electrical energy consumption to apply water-borne
coatings is about 5000 KW. Since a typical plant uses about 12,000 KW,
a change to water-borne topcoats increases electrical usage by 42 percent.
6.5 Comparison of Control Options and Conclusions
Prime Line • For prime application and cure, several control measures
are applicable. Electrophoretic priming and water-borne surfacer is the
most effective control system. The corrosion advantages of this system
is such that at least one company is replacing their priming systems
with electrophoretic systems as they are ready for replacement. Water-
borne spray primer may also be used. Although emission reductions
through increased solids content are more limited than for tOpCOfl.S
(enamels are very widely used), this option is worth consideration since
there is still a substantial range of solids contents used. Incineration
of ovens is effective and not energy intensive but it's benefit is limited
since only 5-15 percent of the solvent evaporates there. Add-on devices
for prime spray booths are technologically feasible but probably would
not be installed because of the advantages of a transition to an electrophoretic
coating.
Topcoat Line * Over two-thirds of uncontrolled emissions from the
coating line come from the topcoat application and cure areas. Considerable
reduction in emissions can be achieved at many plants by increasing the
6-41
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solids content. This is especially true for plants using lacquers.
Incineration of an oven exhaust is effective for those emissions and
energy consumption is minor if the resultant heat is recovered, but it
has limited impact since only 5-15 percent of the solvent evaporates
there. Carbon adsorption of spray booth exhaust is technically feasible
but pilot studies are needed to overcome the difficulties. Incineration
of spray booth exhaust is technically feasible but it uses substantial
quantities of energy, even with good heat recovery. Water-borne top-
COdtS are proven and reduce emissions considerably, but they are substan-
tial users of electrical energy and require substantial capital investment.
Unlike water-borne electrophoretic dip priming, there are no product
quality advantages to the use of water-borne topcoats.
Generally, different control options require different lead times
to implement and utilize the technology. The consideration of timing
(the time by which reductions are sought) should be included in determining
the degree of control required.
€-42
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References
1. Sussman, Victor, H., Ford Motor Company, Dearborn Michigan.
Letter to James McCarthy in comment to draft of this report.
Letter dated August 6, 1976.
2. LeBras,L.R., PPG Industries, Pittsburgh, Pa., Letter to
Vera Gallagher in comment to draft of this report. Letter
dated August 13, 1976.
3. Schrantz, Joe, Hitchcock Publishing Company, Wheaton, Illinois.
Letter to James McCarthy in comment to draft of this report.
Letter dated July 22, 1976.
4. Johnson, W. R., General Motors Corporation, Warren, Michigan.
Letter to James McCarthy in comment to draft of this report.
Letter dated August 13, 1976.
5. McCarthy, James, A., U.S. Environmental Protection Agency, Research
Triangle Park, N.C., Report of trip to General Motors assembly
plants in South Gate and Van Nuys, California. Report dated
November 17, 1975.
6. McCarthy, James A., U.S. Environmental Protection Agency, Research
Triangle Park, N.C., Report of trip to assembly plant in Framingham,
Mass. Report dated November 17, 1975.
7. Conversation with John Stockholm, St. Gobi an Company in Paris,
France, September 20, 1976.
8. Stockbower, E.A., Amchem Products, Inc., Ambler, Pa. Letter to
James McCarthy in comment to draft of this report. Letter dated
August 2, 1976.
9. Schrantz, Joe, How Autodeposited Coating Benefits Chrysler.
Industrial Finishing, November 1975, page 14.
10. Anonymous, "Electroless Electrocoat" Now in Production at Chrysler.
Products Finishing, October 1975, page 72.
11. Conversation with Fred Port?r, Ford Motor Company, Dearborn, Michigan,
September 23, 1976.
12. Johnson, W. R. , General Motors Corporation, Warren, Michigan.
Letter to James McCarthy in COHItient to draft of this report. Letter
dated November 12, 1976.
13. Kachman, N. C., General Motors Corporation, Warren, Michigan.
Letter to Gerald M. Hansler, Region II U.S. Environmental Protection
kg OCy. Letter dated February 11, 19 1.
6-43
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14. Bullitt, Orville H., E. I. DuPont de Nemours & Company, Wilmington,
Delaware. Letter to William Johnson in comment to draft of this
report. Letter dated August 12, 1976.
15. Sussman, Victor, H., Ford Motor Company, Dearborn, Michigan,
Letter to James McCarthy dated August 6, 1976.
16. Radian Corporation, Austin, Texas, Evaluation of a Carbon Adsorption
Incineration Control System for Auto Assembly Plants. EPA Contract
No. 68-02-1319, Task No. 46, January 1976.
17. Johnson, W. R., General Motors Corporation, Warren, Michigan,
Letter dated to Radian Corporation commenting on Reference 16.
Letter dated March 12, 1976.
18. Roberts, R. W. and IB. Roberts, E. I DuPont de Nemours and Company,
Wilmington, Delaware. An Engineering Approach to Emission Reduction
in Automotive Spray Painting. Presented to 67th Annual Meeting of
the Air Pollution Control Association, Denver, Colorado, June 1974.
Paper No. 74-279.
19. Sussman, Victor H., Ford Motor Company, Dearborn, Michigan ,
Letter to James McCarthy in COlHnent to draft of this report. Letter
dated November 15, 1976.
20, MSA Research Corporation, Package Sorption Device Systems Study.
EPA Contract Report No. EPA-R2-73-202. April 1973.
21. Grandjacques, Bernard, Calgon Corporation, Pittsburgh, Pa., Air
Pollution Control and Energy Savings with Carbon Adsorption Systems,
Report No. APC 12-A. July 18, 1975.
22, Mueller, James H., Reeco, Morris Plains, New Jersey. Letter to
James McCarthy dated October 1, 1976.
23. Inryco, Inc., Mel rose Park, Illinois. Inryco's Solution to Paint
Fume Pollution. Inryco Today 1976/2.
24. Combustion Engineering Air Preheater, Wellsville, New York, Report
of Fuel Requirements, Capital Cost and Operating Expense for Catalytic
and Thermal Afterburners, EPA Contract Report No. EPA-450/3-76-031,
September 1976.
25. Volkswagen submittal to Commonwealth of Pennsylvania, Summer 1976-
644
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APPENDIX A
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APPENDIX A
ANALYTICAL TECHNIQUES
All analytical techniques used in the determination of compliance
in the surface coating industry have oreviously been published by the
American Society of Testing Materials (ASTM) or the U.S. Government
SlIDply Agency. This Aooendix details the applicability and procedures
for using these methods. When used on certain coating products, however,
the methods may yield erroneous results. Therefore, any emission control
regulations which WOllld rely on these methods should also provide authority
for the source to request and the control agency to approve alternative
techniques. During development of such alternatives, the source should be
encouraged to coordinate with ASTM Committee D-l which is responsible for
the three ASTM test methods of interest, numbers D 1644-59, D 1475-60 and
D 2369-73. The procedure that follows yields results in the units of mass
per volume of coating. If units of mass per volume of solids are C4~sired»
the source should refer to ASTM test method D X97-73.
A-l
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DETERMINATION OF VOLATILE CONTENT OF PAINT, VARNISH,
LACQUER, OR RELATED PRODUCTS
1. Principle and Applicability
1.1 Principle. The weight of nonaqueous volatile matter per unit volume
of a paint, varnish, lacquer, or related surface coating is calculated after
using standard methods to determine the density, nonvolatile matter content,
and (if necessary) water content of the surface coating.
1.2 Applicability. This method is applicable to paint, varnish, lacquer,
and related products, which are air-dried or force-dried; it is not applicable
to any coating system which requires a special curing process such as exposure
to temperatures in excess of 110% to promote thermal cross-linking or exposure
to ultraviolet light to promote cross-linking.
There may be other specific cases where the ASTM methods are not applicable.
In general, these cases will occur when the evaporation temperature is so high
as to produce thermal degradation of the nonvolatile matter in the surface
coating or when the temperature is too low to produce complete evaporation of
the volatile matter. The former will generally be indicated by a discoloration
of the solid residue, while the latter will be indicated by incomplete drying
of the residue (visible liquid or tackiness).
Whenever it is determined that the ASTM methods are not applicable,
alternative methods subject to the approval of the State or local agency, must
be used.
2. Classif'zation of Surface Coatings
For the purposes of this method, the applicable surface coatings are divided
into three classes. They arc:
2.1 Class I: General Solvent-Type Paints. This class includes white
A 2
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linseed oil outside paint, white soya and phthalic alkyd enamel, white linseed
o-phthalic alkyd enamel, red lead primer, zinc chromate primer, flat white
inside enamel, white epoxy enamel, white vinyl toluene modified alkyd, white
amino modified baking enamel, and other solvent-type paints not included in
Class II.
2.2 Class II: Varnishes and Lacquers. This class includes clear and
pigmented lacquers and varnishes.
2.3 Class III: Water Thinned Paints. This class includes emulsion or
Idtex paints and colored enamels.
3. Applicable Standard Methods
3.1 ASTM D 1644-59 Method A: Standard Methods of Test for Nonvolatile
Content of Varnishes. Do not use Method B.
3.2 ASTM D 1475-60: Standard Method of Test for Density of Paint, Varnish,
Lacquer, and Related Products.
3.3 ASTM D 2369-73: Standard Method of Test for Volatile Content of Paints.
3.4 Federal Standard 141 a, Method 4082.1: Water in Paint and Varnishes
(Karl Fischer Titration Method).
4. Procedure
4.1 Classification of Samples. Assign the coating 'to one of the three
classes discussed in Section 2 above. Assign any coating not clearly belonging
to Class II or III to Class I.
2
4.2 Analyses and Calculations. Determine the density D (in 9/cm ) of
the paint, varnish, lacquer, or related product according to the procedure
outlined in ASTM D 1475-60. Then, depending on the class of the coating, use one
of the following specified procedures to determine the volatile content:
A3
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4.2.1 Class I. Use the procedure in ASTM D 2369-73; record the following
information:
W-j = Weight of dish and sample, g.
W,, s Weight of dish and sample after heating, g.
S = Sample weight, g.
Calculate the volatile matter content Cv (in g/1 of paint) as follows:
r
lv = 1
To convert g/1 to Ib/gal, multiply Cy by 8.3455 x 10 .
4.2.2 Class II. Use the procedure in ASTM D 1644-59 Method A; record the
following information:
A = Weight of dish, g.
B = Weight of sample used, g.
C = Weight of dish and contents after heating, g.
Calculate the volatile matter content Cv (in g/1) as follows:
(A + B -C)(Dm)(103)
"V ~ B
To convert g/1 to Ib/gal, multiply C by 8.3455 x 10 .
4.2.3 Class III. Use the procedure in ASTM D 2369-73; record the same
information as specified in Section 4.2.1. Determine the water content P (in
percentwater) of the paint according to the procedure outlined in Federal
Standard 14"1!, Method 4082.1. Calculate the nonaqueous volatile matter content
C (in g/1) as follows:
(Hj - W2 . 0.01 PS)(Dfn)(103)
Cv = S
To convert g/1 to Ib/gal, multiply Cv by 8.3455 x 10~3.
A 4
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5. Bibliography
1. Standard Methods of Test for Nonvolatile Content of Varnishes. In:
1974 Book of ASTM Standards, Part 27. Philadelphia, Pennsylvania. ASTM
Designation D 1644-59. 1974. p. 285-286.
2. Standard Method of Test for Density of Paint, Varnish, Lacquer, and
Related Products. In: 1974 Book of ASTM Standards, Part 27. Philadelphia,
Pennsylvania. ASTM Designation D 14X-60. 1974. p. 231-233.
3. Standard Method of Test for Volatile Content of Paints. In: 1974
Book of ASTM Standards, Part 27. Philadelphia, Pennsylvania. ASTM Designation
D 2369-73. 1974. p. 441-442.
4. Federal Test Method Standard No. 141 a, Paint, Varnish, Lacquer, and
Related Materials; Methods of Inspection, Sampling, and Testing. General Semises
Administration, Business Service Center. Washington, D, C. 1965.
A 5
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APPENDIX B
RECOMMENDED POLICY ON CONTROL OF
VOLATILE ORGANIC COMPOUNDS
-------
ENVIRONMENTAL PROTECTION AGENCY
Air Quality
RECOMMENDED POLICY ON CONTROL OF
VOLATI LE ORGAN1 C COMPOUNDS
PURPOSE
The purpose of this notice is to recommend a policy for States to
follow on the control of volatile organic compounds (VOC), which are a
constituent in the formation of photochemical oxidants (smog). This
notice does not place any requirements on States; State Implementation
Plan (SIP) provisions which offer reasonable alternatives to this policy
will be approvable. However, this policy will be followed by EPA whenever
it is required to draft State Implementation Plans for the control of
photochemical oxidants.
BACKGROUND
Photochemical oxidants result from sunlight acting on volatile
organic compounds (VOC) and oxides of nitrogen. Some VOC, by their
nature, start to form oxidant after only a short period of irradiation
in the atmosphere. Other VOC may undergo irradiation for a longer
period before they yield meas'Table oxidant.
In its guidance to States for the preparation, adoption, and
submittal of State Implementation Plans published in 1971, the
Environmental Protection Agency emphasized reduction of total organic
Compound emissions, rather than substitution. (See 40 CFR Part 51;
Appendix B.) However, in Appendix B, £F stated that substitution of
B-l
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one compound for another might be useful where it would result in a
clearly evident decrease in reactivity and thus tend to reduce photo-
chemical oxidant formation. Subsequently, many State implementation
Plans were promulgated with solvent substitution provisions similar to
Rule 66 of the Los Angeles County Air Pollution Control District. These
regulations allowed exemptions for many organic solvents which have now
been shown to generate significant photochemfcal oxidant.
On January 29, 1976, EPA published its "Policy Statement on Use of
the Concept of Photochemical Reactivity of Organic Compounds 1n State
Implementation Plans for Oxidant Control." The notice of availability
of this document appeared In the FEDERAL REGISTER on February 5, 1976
(41 FR 5350).
The 1976 policy statement emphasized that the reactivity concept
was useful as an interim measure only, and would not be considered a
reduction in organic emissions for purposes of estimating attainment of
the ambient air quality standard for oxidants. The document also
included the following statement:
Although the substitution portions of Rule 66 and similar
rules represent a workable and acceptable program at the
present time, better substitution regulations can be
developed, base3oiicurrentknowledgeof reactivity and
industrial capability. EPA in collaboration with State
and industry representatives will formulate in 1976 an
improved rule for national use.
SUMMARY
Analysis of available data and information show chat very few
Volatile organic compounds are of such low photochemical reactivity that
they can be Ignored in oxidant control programs, for this reason,
B-2
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EPA's recommended policy reiterates the need for positive reduction
techniques (such as the reduction of volatile organic compounds in
surface coatings, process changes, and the use of control equipment)
rather than the substitution of compounds of low (slow) reactivity in
the place of more highly (fast) reactive compounds. There are three
reasons for this. First, many of the VOC that previously have been
designated as having low reactivity are now known to be moderately or
highly reactive in urban atmospheres. Second, even compounds that are
presently known to have low reactivity can form appreciable amounts of
oxidant under multlday stagnation conditions such as occur during summer
in many areas. Third, some compounds of low or negligible reactivity
may have other deleterious effects.
Of the small number of VOC which have only negligible photochemical
reactivity, several (benzene, acetonitrile, chloroform, carbon tt ra-
chloride, ethylene dichloride, ethylene dibromide, and methylene c^oride)
have been identified or implicated as being carcinogenic, mutagenic, or
teratogenic. An additional compound, benzaldehyde, while producing no
appreciable ozone, nevertheless, forms a strong eye irritant under
irradiation. In view of these circumstances, it would be inappropriate
for EPA to encourage or support increased utilization of these compounds.
Therefore, they are not recommended for exclusion from control. Only
the four compounds listed in Table 1 are recommended for exclusion from
SIP regulations and, therefore, it is not necessary that they be inventoried
or controlled. In determining reductions required to meet oxidant
, these VOC should not be included ir ;he base line nor should
B-3
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reductions in their emission be credited toward achievement of the
\AAQS .
It is recognized that the two halogenated compounds listed in Table
1 (methyl chloroform and Freon 113) may cause deterioration of the
earth's ultraviolet radiation shield since they are nearly unreactive in
the lower atmosphere and all contain appreciable fractions of chlorine.
The Agency has reached conclusions on the effects of only the fully
halogenated chlorofluoroalkanes. The Agency on May 13, 1977 (42 FR
24542), proposed rules Under the Toxic Substances Control Act {TSCA) to
prohibit the nonessential use of fully halogenated cblorofllioroalkanes
as aerosol propellants. The restrictions were applied to all members of
this class, including Freon 113, since they are potential substitutes
for Freon 11, Freon 12, Freon 114, and Freon 115, which are currently
used as aerosol propellants. The Agency is planning to investigate
control systems and substitutes for nonpropellant uses under TSCA, as
announced on May 13. Methyl chloroform is not a fully halogenated
chlorofluoroalkane. Rather, it is among the chlorine-containing compounds
for which the Agency has not completed its analysis; EPA has not yet
concluded whether it is or is not a threat to the stratospheric ozone.
Therefore, it has been placed on this list as an acceptable exempt
compound. As new information becomes available on these compounds, EPA
will reconsider the recommendation.
The volatile organic compounds listed in Table 2, while more
photochemical ly reactive than those in Table 1, nevertheless do not
contribute large quantities of oxidant under many atmospheric conditions.
B 4
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Table 1
Volatile Organic Compounds of Negligible Photochemical
Reactivity That Should Be Exempt From Regulation Under
State Imp]ementation Plans
Methane
Ethane
*l,1,1-Trichloroethane (Methyl Chloroform)
*Trichlorotrifluoroethane (Freon 113;
*These compounds have been implicated as having deleterious effects on
stratospheric ozone and, therefore, may be subject to future controls.
B 5
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Table 2
Volatile Organic Compounds of Low
Photochemical Reactivity
Propane
Acetone
Methyl Ethyl Ketone
Methanol
Isopropanol
Methyl Benzoate
Tertiary Alkyl Alcohols
Methyl Acetate
Phenyl Acetate
Ethyl Amines
Acetylene
N, N-dimethyl formamide
B-6
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Only during multlday stagnations do Table 2 VOC yield-significant
oxidants. Therefore, if resources are limited or if the sources are
located in areas where prolonged atmospheric stagnations are uncommon,
priority should be given to controlling more reactive VOC first and
Table 2 organics later. Table 2 VOC are to be included in base line
emission inventories and reductions in them will be credited toward
achievement of the NAAQS. Reasonably available control technology
should be applied to significant sources of Table 2 VOC where necessary
to attain the NAAQS for oxidants. New sources of these compounds will
also be subject to new source review requirements.
Perchloroethylene, the principal solvent employed in the dry
cleaning industry, is also of low reactivity, comparable to VOC listed
in Table 2. It was not included in Table 2 because of reported adverse
health effects. Uses, environmental distribution, and effects Q"
perchloroethylene currently are being studied intensively by occupational
health authorities and EPA. Findings from these investigations may have
major impact on industrial users. In designing control regulations for
perchloroethylene sources, particularly dry cleaners, consideration
should be given to these findings as well as industry requirements and
the costs of applying controls. Available control technology is highly
cost effective for large perchloroethylene dry cleaning operations.
However, for coin-operated and small dry cleaners, the same equipment
would represent a heavy economic'burden.
As part of its continuing program, EPA will review new information
relative to the photochemical reactivity, *"OX"icity, or effects on
stratospheric ozone of volatile organic COnipOUflds. Where appropriate,
B 7
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additions or deletions will be made to the lists of VOC in Tables 1 and
2.
DISCUSSION
Most air pollution control regulations applicable to stationary
sources of VOC in the United States are patterned after Rule 66 of the
Los Angeles County Air Pollution Control District (presently Regulation
442 of the Southern California Air Pollution Control District). Rule 66
and similar regulations Incorporate two basic strategies to reduce
ambient oxidant levels, i.e., positive VOC reduction and selective
solvent substitution based on photochemical reactivity. Positive
reduction schemes such as Incineration, adsorption, and the use of low-
solvent coatings are acknowledged means of reducing ambient oxidant
levels; they should be retained in future VOC control programs. In
contrast, the utility of solvent substitution strategies has been
questioned as more information on photochemical reactivity has emerged.
EPA acknowledged the shortcomings of solvent substitution based on
Rule 66 reactivity criteria in a 1976 policy statement (41 FR 5350).
Findings were cited which indicated that almost all VOC eventually react
in the atmosphere to form some oxidant. Concurrently, EPA Initiated an
investigation to consider implications-of revising the solvent substitution
aspect: of Rule 66. Three separate forums were conducted with repre-
sentatives of State and local air pollution control agencies, university
professors, and industrial representatives with knowledge and expertise
in the fields of atmospheric chemistry and industrial solvent applications,
In addition, numerous discussions were held with acknowledged experts in
B-8
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the field. Topics of particular concern were:
. Whether Rule 66 substitution criteria could be revised
consistent with available reactivity data and yet be
compatible with industrial processes and with product
requirements.
. Whether some compounds are of sufficiently low reactivity
that they are not oxidant precursors and can be exempted
from control under State Implementation Plans.
• Whether the imposition of reactivity restrictions in
addition to positive emission reductions will delay
the development or implementation of promising
technologies, particularly the use of water-borne
and high-solids surface coatings.
Investigation showed that:
1. Solvent substitution based on Rule 66 has been directionally
correct in the aggregate and probably effects some reductions in peak
oxidant levels. However, because of the relatively high reactivity of
most of the substituted solvents, the reduction is small compared to
that which can be accomplished with positive reduction techniques.
Revision of Rule 66 consistent with current knowledge of reactivity
would eliminate the solvent substitution option for most sources in
which substitution is now employed. Many of the organic solvents which
have been categorized as having low photochemical reactivity are, in
fact, moderately or highly reactive; they yield significant oxidant when
subjected to irradiation in smog chambers Designed to simulate the urban
atmosphere.
B-9
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2. A few VOC yield only negligible ozone when irradiated in smog
chambers under both urban and rural conditions. Experiments conducted
to date indicate that only methane and ethane, a group of halogenated
paraffins, and three other organics--benzene, benzaldehyde, and aCEtO-
nitrile--can be so classified. These compounds react very slowly yielding
little ozone during the first few days following their release to the
atmosphere. Available data suggest that none of the listed compounds
contribute significant oxidant even during extended irradiation under
Hiultiday stagnation conditions.
The broad group "halogenated paraffins" includes important industrial
solvents, most of which are chlorinated methanes and ethanes and Chloro-
fluoroethanes. They find use as metal cleaning and dry cleaning solvents
and as paint removers. Halogenated paraffins also serve as building
blocks in the manufacture of other halogenated organics; these processes
do not necessarily release significant VOC to the atmosphere.
3. Besides focusing on VOC of negligible reactivity, smog chamber
studies show that a few additional VOC generate oxidant at a relatively
slow rate. Under favorable atmospheric conditions, these VOC releases
may not form oxidant until they have been transported substantial
distances and become greatly diluted. However, under multiday stagnation
conditions such as occur during summer in many areas of the middle and
eastern United States, there is the potential for these organiCS to
undergo appreciable conversion to oxidant. The more important VOC in
this category are acetone, methyl ethyl ketone, perchloroethylene,
methanol, isopropanol, and propane. All except propane are industrial
B-10
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solvents.. The latter, a gas under normal conditions,-is associated
principally with crude oil and liquefied petroleum gas operations.
4. The vast number of volatile organic compounds--particularly
nonhalogenated VOC--yield appreciable ozone when irradiated in the
presence of oxides of nitrogen. While there are measurable variations
in their rates of ozone formation, all are significantly more reactive
than VOC listed in Table 2. Quickly reactive VOC include almost all
aliphatic and aromatic solvents, alcohols, ketones, glycols, and ethers.
5. Low photochemical reactivity is not synonymous with low bio-
logical activity. Some of the negligible or slowly reactive compounds
have adverse effects on human health. Benzene, acetonitrile, carbon
tetrachloride, chloroform, perchloroethylene, ethylene dichloride,
ethylene dibromide, and methylene chloride have been implicated as
being carcinogens, teratogens, or mutagens. In addition, bfifizal^hyde,
which produces no appreciable ozone, nevertheless forms a strong eve
irritant under irradiation. While their use might reduce ambient oxidant
levels, it would be unwise to encourage their uncontrolled release.
Additional halogenated Organics are being investigated for possible
toxicity.
Most of the related health information available at this time
concerns acute toxicity. Thre;- !0ld limit values (TLV's) have been
developed for many VOC. They are appropriate for the healthy, adult
work force exposed eight hours a day, five days a week. Experts suggest
that more stringent levels should be estsb.ished for the generalpopuld-
tion. Hazards represented by chronic and r 'bchronic exposure are much
i^Oi'B diTicult to quantify than acute toxicity. Adverse health effects
of the VOC cited above are generally recognized although not completely
B 11
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quantified. Chlorinated solvents currently are under-intensive study.
6. Some VOC are of such low photochemical reactivity that they
persist in the atmosphere for several years, eventually migrating to the
stratosphere where they are suspected of reacting and destroying ozone.
Since stratospheric ozone is the principal absorber of ultraviolet (UV)
light, the depletion could lead to an increase in UV penetration with a
resultant worldwide increase in skin cancer. The only in-depth analysis
of this potential problem has focused on the chlorofluoromethanes (CFM),
Freon 11 and Freon 12, because of their known stability and widespread
use in aerosol containers. A report of the National Academy of Sciences
concerning environmental effects of CFM1S concluded that:
"... Selective regulation of CFM uses and releases is
almost certain to be necessary at some time and to some
extent of completeness."
In response to the report of the National Academy of Sciences and other
studies, EPA on May 13, 1977 (42 FR 24542) proposed rules to prohibit
nonessential usage of fully halogenated chlorofluoroalkanes as aerosol
propellants. The restrictions were applied to all members of this class
including Freon 113 since they are potential substitutes for Freon 11,
Freon 12, Freon 114, and Freon 115 which are currently used as aerosol
propellants.
Other stable halogenated solvents which are released in volumes
comparable to the chlorofluoroalkanes also are suspected of depleting
the earth's UV shield. Of major concern is the widespread substitution
of methyl chloroform (1,1,1 trichloroethane) for the photochemically
B-12
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reactive degreasing solvent trichloroethylene. Such substitution under
Rule 66 generation regulations has already influenced industrial degreasing
operations to the extent that methyl chloroform production has surpassed
that of trichloroethylene in the United States. Any regulation in the
area will have a marked effect on the production and atmospheric emissions
of both solvents. Endorsing methyl chloroform substitution would increase
emissions, particularly in industrial States that have not, heretofore,
implemented Rule 66. On the other hand, disallowing methyl chloroform
as a substitute or banning it altogether would significantly increase
emissions of trichloroethylene even if degreasers were controlled to the
limits of available technology. Presently, technology is only able to
reduce emissions by approximately 50 percent. In metropolitan areas
which have already implemented Rule 66, a return to trichloroethylene
would have an adverse effect on ambient oxidant levels. In addit on to
being highly reactive, trichloroethylene has been implicated as a
carcinogen.
Alternatives to the above-cited choices would be (1) development
and application Of highly efficient degreaser control systems and (2)
replacement with an intermediate solvent which is neither reactive nor
detrimental to the upper atmosphere. Major revisions would be needed to
degreaser designs to improve vapor capture above the current best level.
Anticipated design changes could add materially to degreaser costs. No
alternative solvent is clearly acceptable from the standpoints of
photochemical oxidant and stratospheric ozone depletion. Neither
methylc.ne chloride nor trichlorotrifluoroe ane are reactive, but, like
B-13
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methyl chloroform, are suspected of causing damage to'the stratospheric
ozone layer. In addition, methylene chloride is a suspect mutagen.
Perchloroethylene, the principal dry cleaning solvent, does not present
a hazard to the stratosphere but has been implicated as being a carcinogen
and also reacts slowly in the atmosphere to form oxidant.
7. Organic solvents of low or negligible photochemical reactivity
have only limited use in many industries. Most are chlorinated orcjaniCS
that find principal applications as cleaners for metals and fabrics. A
few nonhalogenated VOC such as acetone, methyl ethyl ketone, and isopropanol
are of low reactivity but these can't possibly satisfy all the myriad
needs of the paint, plastics, pharmaceutical, or many other industries.
While users of reactive VOC usually can employ effective control equipment
to recover or destroy VOC emissions, they seldom have the option of
applying reactivity considerations in choosing solvents. Applying
reactivity restrictions to the surface coating industry would be especially
disadvantageous since it would greatly inhibit the development of low-
solvent coatings; essentially all of the organic solvents used to constitute
high-solids coatings and water-borne coatings are, in fact, highly
reactive.
8. It is recognized that smog chamber studies conducted to date
are incomplete because many organic compounds have not been examined and
it has teen impossible to duplicate all atmospheric situations. por
example, there has been only limited examination of oxidant formation
under relatively high ratios of VOC to NO, (30:1 and greater), comparable
to rural conditions. Any policy on photochemicai reactivity necessarily
B-14
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has to be open to revision as new infonnation is devel'oped which may show
specific organic compounds to be more or less photochemically reactive
than indicated by current data.
Dated::
Acting Assistant Administrator
for Air and Waste Management
B-15
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APPENDIX C
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APPENDIX C
REGULATORY GUIDANCE
1. INTRODUCTION
This section serves to facilitate the preparation of regulations
for the control of volatile organic compound (VOC) emissions from the
surface coating operations discussed in this document. This guidance is
not intended to prescribe specific regulatory language. Responsibility
for developing regulations and the associated emission limitations
clearly rests with the respective States.
2. GENERAL DISCUSSION
The recommended regulatory approach is predicated on the concept of
positive emission reduction rather than the substitution of compounds
Of-lower reactivity as the means of reducing ambient levels of photochem-
ical oxidant. This is in keeping with EPA's recent policy statement on
reactivity.
The facility to be controlled in each of the five coating operations
discussed in this document is the coating line. In general, the recommended
control approach is to reduce emissions from the coating line by means of
low solvent coating technology. This approach is recommended since, in
addition to reducing emissions at the applicator, it also serves to reduce
fugitive and flash area emissions while at the same time eliminating the
C-l
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need for add-on control equipment. It should be recognized, however, that
for certain source categories or coating lines it may be preferable to use
add-on controls, particularly when heat or VOC recovery techniques can be
employed. Therefore, the regulations should not preclude the employment
of add-on devices such as incinerators and adsorbers with appropriate
capture systems.
Before developing regulations, States should carefully evaluate the
sources to be regulated within their jurisdiction to determine whether
the emission limitations cited in this document truly reflect reasonably
available control technology (RACT) for them. In some instances, it may
be found that the guidance is not appropriate for a particular coating
material or coating operation.
The employment of low solvent coatings may be technology forcing for
certain products or applications. Under such circumstances, an extended
time period may be required to evaluate the low solvent coatings both in
the laboratory and the field, prior to placing them into production. In
comparison, the application of add-on control devices is well demonstrated
and the only constraint is the time necessary to purchase, install, and
start up such equipment. In view of these factors, compliance schedules
should be flexible, taking into consideration the specific problems
associated with a given plant. Consideration may also have to be given
Reasonably available control technology (RACT) 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 require technology that
has been applied to similar, but not necessarily identic"*"!, SOUfC"?
categories. It is not intended that extensive research and development
be conducted before a given control technology can be-applied to the
source. 'This does not, however, preclude requiring a short-term evalu-
ation program to permit the application of a given technology to a particu-
lar type of source. This latter effort is a legitimate technology-foreing
aspect of RACT.
c-2
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to the cumulative impact of other jurisdictions promulgating stmilar
regulations, which may limit the availability of control
equipment, etc.
Even though the regulatory requirements are based on control
technology that has been determined to be reasonably available for the
source category as a whole, some individual plants may not be able to
comply with them. In order to forestall future problems of compliance,
the States should review their various authorities at the time regulations
are developed. If it is found that existing authorities do not provide
sufficient flexibility to accommodate such problems, consideration should
be given to developing regulatory provisions which will provide adequate
relief.
To assist in developing regulations, the Office of Air Quality
Planning and Standards (OAQPS) has identified several areas that should
be taken into consideration. These are discussed below.
COITITIOn Terminology
When developing regulations it is important that a degree of
commonality exists in the definition of key terms. This will provide a
greater degree of understanding on the part of source owners and operators
and remove some of the confusion that presently exists for owners that
have multi-State operations. With this in mind, the following definitions
were developed for commercial an' industrial surface coating operations:
a. Coating applicator means an apparatus used to apply a surface
coating..
b. Oven means a chamber within which heat is used to bake, cure,
polymerize, and/or dry a surface coating.
(• Coating line means one or more apparatus or operations com-
prised of a coating applicator, flash-off a> ,, and oven wherein a
surface coating is applied, dried, and/or ci. i.
c-3
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d. Owner or operator means any person who owns, leases, operates,
controls, or supervises a surface coating operation or a
plant of which a sufface coating operation is a part.
e. Standard conditions mean a temperature of 20°C (68°F) and pressure
of 760 mm of Hg (29.92 inches of
f. Volatile organic compound is any compound of carbon (excluding
carbon monixide, carbon dioxide, carbonic acid, metallic carbides or
carbonates, and aHmonium carbonate) that has a vapor pressure greater
than 0.1 tnm of Hg at standard conditions.
g. Day means a 24 hour period beginning at midnight.
h. Capture system means the equipment (including hoods, ducts,
fans, etc.) used to contain, capture, or transport a pollutant to a
control device.
1, Control device means equipment (incinerator, adsorber, or the
like) used to destroy or remove a pollutant from a discharge gas stream.
j. Approved means approved by the designated air pollution control
official.
Expression of Requirements
When developing regulations, the language used to express the
requirement must be carefully weighed. As noted on page 1-5, the
decision to express emission limitations for coating operations in
terms of weight of VOC per volume of coating, less water, was chosen
after much deliberation. A change in the manner of expression without
an adjustment in the limit could materially affect the stringency of
the requirements. Therefore, if it is found desirable to express the
limitation in different terms, such as pound of VOC per pound of coating
solids, reference should be made to Appendix D so the recommended emission
limit can be properly adjusted.
Similar care must be exercised when specifying requirements for
incinerators and other add-on control devices. At present, there are
c-4
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no standardized test methods that can be universally applied to determine
mass rates of emission or concentrations of VOC. In view of this,
requirements for incinerators and most other add-on devices should be
expressed in terms of efficiency of removing organics expressed as
combustible carbon.
In view of the above, OAQPS developed the following language for
expressing an emission limitation based on the guidance contained in
this document:
"No owner or operator subject to the provisions of this regulation
shall discharge or cause the discharge into the atmosphere from a
coating line any volatile organic compound in excess of pounds
per gallon of coating, excluding water, delivered to the coating applicator.
"The emission limit prescribed above shall be achieved by:
a. Low solvent coating technology,
b. Incineration, provided that 90 percent of non-methane volatile
organic compounds (VOC measured as total carbon) which enter the incinerator
are oxidized to carbon dioxide and water; or
c. Processing the discharge in a manner determined by control
official to be not less effective than that of b obove."
When providing for the use of add-on devices as a means of
complying with the requirements of the regulation, the States should also
require that such control devices be equipped with an approved capture
system in order to assure effective control. When examining the need for
such a provision, OAQPS staff explored whether it was feasible to prescribe
performance or design specifications for capture systems. After examining
the situation, it was concluded that effective capture systems must be
custom designed to accommodate plant-to-plant variables which affect
performance. An alternative approach of testing to determine whether VOC
c-5
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is escaping capture was also dismissed for the want of suitable testing
techniques. In view of these findings, it is recommended that case-by-case
design review be performed to assure installation of effective capture
systems.
When reviewing capture system designs , air pollution officials must
take into consideration requirements imposed by the Occupational Safety
and Health Administration and the National Fire Prevention Association,
as well as State and local health and safety officials. The publication
"Industrial Ventilation, A Manual of Recommended Practice" prepared by the
American Conference of Governmental Industrial Hygienists is one source of
guidance on the proper design of capture and ventilation systems.
Need for flexibility
As was discussed earlier, the employment of low solvent coatings
may be technology forcing for certain products or applications. Under
such circumstances-additional time should be afforded sources faced with
real technological problems, provided they move as expediently as prac-
ticable toward compliance. During this period it may be appropriate for
the State to require interim controls such as solvent substitution.
OAQPS does not necessarily recommend the installation of add-on control
devices, particularly incinerators, i f the interim period is to be of
relatively short duration. In many instances, to do so would be a
disincentive for the source to continue its efforts to develop low
solvent coatings.
An alternate approach that has been the subject of discussion is to
allow the source to develop a plant-wide emission reduction plan. Under
such an approach, the source owner would have to demonstrate that any
£-6
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emissions in excess of those allowed for a given coating line would be
compensated for. Compensation would be achieved by either reducing VOC
emissions from other coating lines below the allowable level or by
controlling non-regulated sources within the surface coating facility.
The plant-wide emission reduction plan provides flexibility by affording
the source owner the-Opportunity to select the most cost-effective
means of providing the desired VOC reduction. In addition, it promotes
innovation by encouraging the control of sources that have not been
previously regulated and by providing the source owner an incentive to
control certain coating lines to a greater degree than that required
by the emission limitation. While this approach has been favorably viewed
by industry, enforcement officials have expressed reservations as to its
enforceability. If the problems of enforceability can be overcome, the
plant-wide emission reduction approach would appear to be a very useful
tool.
Seasonal Operation of Natural Gas-Fired Afterburners
As an energy conservation measure, it is also recommended that
provision be made for the seasonal operation of natural gas-fired
afterburners. The basic rationale for seasonal operation of natural
gas-fired afterburners and the criteria for designating time periods
within which the devices may be shut down was set forth in the July 28,
1976, policy statement "Seasonal Operation of Natural Gas-Fired
Afterburners" issued by the Assistant Administrator of Air and Waste
Management (see attachment). The following language is offered if a
State determines that the best method of implementing this policy is by
incorporation into its regulation:
C 7
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"The operation of natural gas-fired incinerator and associated
capture systems installed for the purpose of complying with this regulation
will not be required in (specify AQCR) during the month 4or months) of
provided that the operation of such devices is not required
for purposes of occupational health of safety or for the control of
toxic substances, malodors, or other regulated pollutants."
Disposal of Waste VOC
Consideration should also be given to restricting the manner by
which waste volatile organic compounds are disposed. To accomplish
this objective, OAQPS suggests the following regulatory language:
"No owner or operator shalfl dispose of or permit the disposal of
BlOre than gallons per day of volatile organic compounds by
any means which will permit the evaporation of such compounds to the
IT,
atmosphere."
Small Source Exemption
States should also consider for inclusion in their regulation a
provision to exempt certain coating lines from control due to their
small quantity of emissions. When determining which coating lines to
exempt, States should assess the sources within their jurisdiction to
determine a lower cut off level which will result in the most effective
control strategy.
Finally, when developing regulations the States should be cognizant
of EPA policy statements and other guidance on overall strategy for oxidant
control such as photochemical reactivity, seasonal control, and the
pnortttzation of geographical areas jfor which reductions in volatile
ff, ».* , .
organic emissions are required.
C-8
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ATTACHMENT
\ UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
*
* WASHINGTON, D.C. 20460
JUL 2 8
OFFICE OF
AIR AND WASTE MANAGEMENT
SUBJECT: Seasonal Operation of Natural
Gas-Fired Afterburners
MEMO TO: Regional Administrators
It has been estimated that the use of afterburners for control of
air pollutants required 0.4 percent of the total 22 trillion cubic feet
of natural gas consumed in 1975 in the U.S.. While not a high percentage,
this is a substantial amount of natural gas—equivalent, for example, to
the annual amount required to heat 62,000 homes in Washington, D.C.
Many of these afterburners are required solely to reduce emissions
of hydrocarbons to control ambient oxidant levels. However, results
from both statistical analyses of ambient data and smog chamber tests
show that oxidants do not readily form at temperatures below about 59°F.
Thus, in many parts of the U.S., the operation of afterburners required
for oxidant control may not be needed during the winter months. This
fact and t-fto expectation tnat natural gas wil i be in aiiui '\, ^UPH"^ dm luy
the coming winter support an EPA policy of allowing states to permit
natural gas-fired afterburners to be shut down during the coming winter
season p.roVi
-------
concentrations during the winter season. This observed seasonal phe-
nomenon is consistent with the theory of oxidiant formation:; high ambient
temperatures and strong sunlight assist is the prodoction of oxidants
from a complex photochemical reaction involving hydrocarbons and
nitrogen oxi dfes.
A recent analysis of oxidant air quality data and meteorological
data* identifies areas of the country which, during specified months,
experience low oxidant concentrations:. This analysis; shows a high
correlation between maximum daily temperatures and maximum nearly
axidtnt concent rations, with concentrations above tine Rational standard
becoming highly improbable when fflixiHun daily temperatures are consist-
ently below SS*F. The analysis suggests that the maximum daily tem-
perature can, be used as. a reasonably reliable indicator of the potential
for oxidant formation and supports a policy which would permit seasonal
use of natural gas-fired afterburners in wany dress.
Figure 1 is a nap of the U.S. on which sttxty results art sumaHzed.
It shows general areas (or zones) in which seasonal shutoff of natural
gas-fired afterburners cowld be considered. However, it is important
to note that local conditions may obviate seasonal control even though
shutdown otherwise may appear to be acceptable. If, for example, winter-
time oxidant concentrations in a particular area are in violation of
th o amiiiiaaii ». r~r. .!_..' i~\r + *•" -• /- - , - -t»*v»->+>* •*>*•* -»•••> f,,££j ,,S ^l \t K-Snh 4'
n e cunuierti itaiiufU ur »,nc vuii\»«.uwi uwi«.._ — .* - ._..._T.-.V __ Tr
afterburner shutdown could create violations, you should neither encourage
nor allow seasonal afterburner operation even though the area is in a
theoretically acceptable zone.
A policy to seasonally control afterburners can only be implemented
through the SIP process -- by establishing new oxidant SIPS or by revising
existing SIPs. Of course, the enforceability of the policy must be care-
fuliy considered in reviewing each specfic regulation. The approval of
SIP changes to permit seasonal afterburner operation need not require
detailed, time-consuming analyses of air quality impacts if the seasonal
shutdown time period is consistent with the zones delineated in Figure. 1 ,
and if existing air quality data shows no past violations in the month
during which the afterburners will be shutdown. The attached staff study,
supported by air quality data where available, normally should be adequate
technical support for a decision to approve the seasonal operation of
afterburne"S in a given location. If an occasional high oxidant concentra-
tion has been noted during the winter months but the gas savings to be
achieved by afterburner shutoff appears to warrant favorable consideration
*See attached OAQPS "Staff Study: Oxidant Air Quality and Meteorology,"
dated February 6, 1976.
C--10
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of a variance request, a short trial period to test the impact on oxidant
concentrations may be suggested. If it is found that ambient violations
persist or are exacerbated, the trial program must be terminated.
It is recommended that you notify those state agencies in your
Region which may be eligible to implement this program that EPA sup-
ports a policy which would permit sources to shut off afterburners
during cold weather months this year when oxidant concentrations are
below the ambient standard. In discussing this policy with state agency
personnel , it is important to emphasize that the policy pertains only to
oxidant control strategy and that EPA is not encouraging a wide-spread in-
crease in hydrocarbon emissions. Moreover you must make it clear that,
consistent with §116 of the Clean Air ^Act, the state is not required in
any way to relax its strategy.
Roger Jrcrelw
Assistant Administrator
for Air and Waste Management
Enclosure
c c: Stan LearO
William Prick
0-11
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NOVEMBER JHROU 5H MARCH
ER THROUGH 1FE8RUARY
•«-««i. Figure 1. Areas for1 Which theProbablHty of Maximjm Daily Tenperature > S9°Mft < 5X During Monthly Ranges
Indicated (Based on 5 Years of Temperature Data).
-------
STAFF STUDY: OXIDANT AIR QUALITY AND METEOROLOGY
* * «<
February 6, 1976
Prepared By
Honitoring and Reports Branch
Monitoring and Data Analysis Division
Office of Air Quality Planning and Standards
c-13
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Oxidant Air Quali ty arid Meteorology
An analysis was performed of the seasonal: variation of days
with violations of the oxidant standard at sites across the nation
with sufficient data for all fowr quarters of 1974. Depicted in
Figures 2 tfon&wgh 4 are the percent »f diayswitfe hourly coicentra-,
titins exceeding the HAAQS of 16& m§/m3 for three periods: (1} Dec-
«lai; (2J Ptov-Oec-Jan-Fefc-Mar; and, ,{3} Apr through Oct. The '
analysis shows conclusively that for the two sets of monthly ranges
dwring the cold season, oxidant NAAQ5 violations decrease substantial-
ly from the warmer mon-ths. This is consistent with the seasonal
cycTe of temperatures and solar radiation that has a pronounced ef-
• . ^«_^JL „__.._,»•• "
. U<,.L, i/n o^.vflic ^jr ll l-ilCi I 5 .
. Air quality data for some states were not available in EPA's
data bank. Also,.'in some states only a few monitoring "sites had
sufficient data for all quarters or those stations with sufficient
amounts of data may not have been located where maximum concentra-
tions occur. Therefore, because of some deficiencies inherent in
the air quality data base, an additional parameter was used as an
indicator of significant ozone formation potential, xhis para-
meter, tnav'imurii daily temperature, was used as a surrogate for oxidant/
ozone data in areas without such data and as a supplement in areas
1 •
with insufficient data. High maximum daily temperatures have been
-------
associated with hi gh ozone concentrations in field and smog chamber
Studies.1* 2* 3 Our best estimate is that nearly all oxidaht/ozone
concentrations above the HAAQS occur with maximum daily temperatures
above about 58-59°F. This was corroborated by an independent analy-
sis of 1973 ozone/oxidant data.1*
In the current analysis, the frequency of maximum daily tempera-
turai exceeding 59 "f at Selected National Weather Service Sites was
. . • •
tabulated for each month over a 5-year climatic period. Assuming that
maximum da''ly temperatures above 59 F indicate high ozone formation
potential, the ranges of months that have less than a 5 percent proba-
bility of this condition were noted. Since sll days with temperatures.
higher than 59 F will no-i; have all other'conditions (solar radiation,
air mass characteristics, wind speed, etc.) conducive to formation of
high ozone concentration, the 5 percent value represents a reasonably
• Tow risk. Accordingly, the geographical areas.meeting this criterion
•for the two sets of cold month ranges December through February and
November through March are shown in Figure 1.
Considering the analyses of. the.two factors, air quality and
maximum daily temperature., the areas of the nation with low seasonal
incidence of, and low potential for NAAQS violations are well defined.
, The only possible exceptions are the Milwaukee, Wisconsin area and
parts of Massachusetts where oxidant violation frequencies that may
H
be considered appreciable occur despite the temperature data indicat-
ing the contrary during colder months. Possible factors that may
C-15
-------
have causod these anomalies include instrumental
transport, stratospheric intrusions, or S'o«* other
local condition.
, long range
-------
NO'MBER THROJGH
/ DECEMR • THROUGH \FEBRUARY
•:> Figure 1. Areas for Which the ProbabiVy of Maxinum Daily Temperature > 59°F is < 5% During Monthly Ranges
Indicated (Based on 5 Years < Tempera tire Data).
-------
Oxidant D^ta in Parenthesis
Figure 2.. Percent of Days with Maximum Hourly (Lone Concentrations > 160 vg/m3 January, February, and
December 1974. -,
-------
\ i * <>=
/ < ^J-T-.j''
Cxidant Da'ta in Parenthesis
:3 Figure 3. Percent of Days with Maximum Hourly Ozone Concentrations > 160 yg/m3 Jarjuary, February, March, and
November-December 1974. '• '
-------
idant Data in Parenthesis
Figure 4. 'Percent of Days with Max mum Hourly C20ne Concentrations > 160 yg/m* April .through October 1974.'
-------
REFERENCES
1. Bach, W. D., "Investigation of Ozone and Ozone Precursor
Concentrations at Non^rban Locations in the Eastern United States,"
Phase II, Research Triangle Institute, prepared for Environmental
Protection Agency, Research Triangle Pat-k, N. C., EPA Report No.
450/3/74-034a> February 1975.
2. . Lovelace, D. E., Kapsilis, T., Bourke, R. C., and Cook,
P. P., "Indianapolis 1974 Siirr.-ner Ozone Study," Indianapolis Center
for Advanced Research, Indianapolis, Ind., 1975.
. 3. Jefferies, H. E., University of Not-th Carolina, Chapel
Hill, Personal Cornmunication to Dinitriades, B., Environmental Pro-
tection Agency, Research Triangle Park, N. C., November 1974.
4. Neligan, R. E., Memorandum to Walsh, R. T., "High Ozone-
0x1 dan t Concentrations and Associated Maximum Daily Temperatures
During Cold Season," Environmental Protection Agency, Research
Triangle Park, H. C., November 3, 1974
-------
APPENDIX 0
-------
APPENDIX D
CONVERSION METHODS
Presented below are techniques which will permit ready conversion
between alternative terms which may be used for emission control
regulations:
. * English Units - Metric Units
b) Multiply «{$gSS. by 8.23 to get
c) Gallons _ Liters
Gallon " Liter
• o Water-borne coatings, equivalent organic solvent-borne coatings, volume
percent solids, and pounds of solvent per gallon of coating (minus V^ter).
a) From volume percent solids in coating, draw vertical line to
appropriate line in Figure D-l (depending on ratio of water to organic-
solvent in coating). From the point of intersection, draw a horizontal
line. Where this line intersects the ordinate, read the pounds of solvent
per gallon of coating (minus water). Where this line intersects the
"Or§anic- Bome" line, a vertical line yields the solids content of the
equivalent organic-borne coating.
b) To convert organic-borne coating to equivalent water-borne, draw
a vertical line in Figure D-l from the volume percent solids to the
"Organic -Borne" line. From this intersectior . ^raW a horizontal line.
D-l
-------
Where this intersects the appropriate water-borne line, draw a vertical line
to yield the solids content of the equivalent water-borne coating. The
continuation of the horizontal line yields the pounds of solvent per
gallon of coating (minus water} of the organic-borne coating and its
equivalent water-borne coating.
** Weight percent solids - Volume percent solids
Multiply Weight Percent Solids by figffi ff jffiffi to get ^erofnt
The density of the solvent may be assumed to be 7.36 pounds per gallon
(0.89 kg per liter) unless better information 1s available, the density
of the solids may be calculated from the composition and density of the
coating:
Density of _ (100 x density of coating) • (% solvent x 7.36) • (% water x 8.34)
Solids " Percent Solids
Densities of coating solids may range from 7 to 35 pounds per gallon
(0.84 to 4.2 kg per liter).
• o Pounds of Solvent per Gallon of Solid * Pounds of Solvent per Pound of Solid
a) Divide Pounds of Solvent by Density of Solid to get Pounds of Solvent
'Gallon of SolidIn Pounds Per Pounds of Solid
Gallon
b) Multiply Pounds of Solvent by Density of Solid to get Pounds of Solvent
Pounds of Solid In Pounds Per Pounds of Solid
Gallon
. o Pounds of So1vent Pounds of Solvent
Gallon of Coating " (SalTon of" Solid
(minus water)
D-2
-------
FIGURE D-l
s-
QJ
4->
re
in
i/i
QJ
C. i—
•i— IO
-M c:
re *~s.
o =tfe
o
o
o
to
6 -^
5
4
3
2
1
Weight of Organic
Solvent Per Gallon for
3 Coatings As A Function
of Solids Content
10 20 30 40 50 60 70 80 90
100
Volume % solids in coating
D-3
-------
90
riyure u-c
80
70
O
VI
o
-------
Fiqure D-3
8 L
a 6
•a 5
fi 3
2 L_
1 I—
Pounds of solvent per gallon
of coating solids
vs,
Pounds of solvent oer gallon
of coating (minus water)
Pounds of solvent oer gallon of coating
(minus water)
D-5
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TECHNICAL REPORT DATA
[Please read /nstructions on the reverse before Completing/
REPORT NO.
EPA-450/Z-77-008
3. RECIPIENT'S ACCESSION-NO.
TITLE AND SUBTITLE
Control of Volatile Organic Emissions from Existing
Stationary Sources-Volume II: Surface Coating of Cans,
Coils, Paper, Fabric, Automobiles & Light Duty Trucks
5. REPORT DATE
MAV 1971
S. PERFORMING
May m//
ORGANIZATION
CODE
AUTHOR(S)
3. PERFORMING ORGANIZATION REPORT NO,
OAQPS NO. 1.2-073
PERFORMING ORGANIZATION NAME AND ADDRESS
J.S. Environmental Protection Agency
3ffice of Air and Waste Management
3ffiC6 of Air Quality Planning and Standards
Research Trianq1e Parkr North Carolina 27711
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
2. SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
5. SUPPLEMENTARY NOTES
6. ABSTRACT
This report provides the necessary guidance for development of regulations to
limit emissions of volatile organic sources (VOC) of hydrocarbons, especially
from the coating operations of five industries: can, coil, paper, fabric and
automobile and light duty trucks. This guidance includes an emission limit which
represents Reasonably Available Control Technology (RACT) for each df the five,
analytical techniques for determining the solvent content of coatings, EPA's
policy on the control of VOC, and a monograph on how these components can be used
to develop a State regulation.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c . COS AT I Field/Group
Air Pollution
Cm, Coil, Paper, Fabric, Automobile and
Light Duty Truck Industries
Solvent Substitution
Emission Limits
Regulatory Guidance /
Air Pollution Control
Stationary Sources
Organic Vapors
8. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (This Ht-pnrl)
Unclassified
N O . Ol T'
232
20. SECURITY CLASS (TMs P
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ENVIRONMENTAL PROTECTION AGENCY
Technical Publications Branch
Office of Administration
Research Triangle Park, North Carolina 27711
OFFICIAL BUSINESS
AN EQUAL OPPORTUNITY EMPLOYER
«•? ' t
.r-V
POSTAGE AND FEES PAID
ENVIRONMENTAL PROTECTION AGENCY
EPA • 335
- -
f ^
Return this sheet if you do NQT wjsh foi
or if change of address is needed I '
ZIP code.)
|tn is materialL-J
'-1----->, including
,'fefV • > V*,, ^' *. "*
•*n • •'• j., . »• >•
PUBLICATION NO, EJR
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