United States
Environmental Protection
Agency
Hazardous Waste Engineering Researcf
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-84-179 Dec. 1984
Project Summary
Environmental and Energy
Benefits of Microprocessor
Control of Oven Airflows from
a Coil Coating Operation:
A Case Study
I n most industrial coating operations,
the percentage of the lower explosive
limit (LEL) of volatile organic com-
pounds (VOC) emissions typically re-
main at below 5 to 10 percent LEL.
Although monitors are available to
determine solvent concentration in the
oven, most existing ovens require man-
ual corrective action when potentially
explosive oven atmospheres are gener-
ated. In 1982, a project was completed
that developed and demonstrated the
viability of using microprocessor tech-
nology to make VOC control of paint
curing ovens less expensive and safer
than present operations. This would be
accomplished by lowering oven ventila-
tion air flow, safely increasing LEL
concentration to a maximum 50 percent
and providing automatic control of
oven ventilation systems. The demon-
stration system, however, was not
operated at maximum LEL concentra-
tion; thus, the versatility of the system
to operate at high LEL concentration
was not determined. This project eval-
uates the system at a commercial facil-
ity while operating at higher concentra-
tions approaching 50 percent LEL.
Included in the report is a description
of the oven modification at the Prior
Coated Metals Coil Coating facility in
Allentown, Pennsylvania, and the oven
operating conditions before and after
the modifications. Also included are the
operating economics of the oven and
VOC control system.
This Project Summary was developed
by EPA's Hazardous Waste Engineering
Research Laboratory. Cincinnati, OH,
to announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
Industrial paint curing ovens utilize
significant volumes of ventilation or dilu-
tion air to keep the solvent concentration
within the oven at below its LEL. This
dilution, however, must be heated to
curing temperature and finally to incin-
eration temperature. The requirement to
raise the oven exhaust temperature to the
incineration temperature in order to meet
VOC emissions regulations adds signif-
icantly to the cost of manufacturing
coated products. By reducing the volume
of VOC-laden gases emitted from the
curing oven, environmental control costs
can be reduced.
The full report presents an evaluation
of a commercial installation utilizing
microprocessor technology to reduce the
volume of VOC-laden gases that are
emitted from the curing oven. The site of
this evaluation was the Prior Coated
Metals Coil Coating facility at Allentown,
Pennsylvania. The system represents an
extension of the microprocessor tech-
nology concept demonstrated in early
1982 at the Mack Trucks, Inc. facility in
Allentown, Pennsylvania, which is pre-
sented in another report, EPA-600/S7-
83-037. The Mack Trucks program de-
signed, developed, and demonstrated the
basic concept of microprocessor control
for oven applications; however, the sys-
tem was not operated at its maximum
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solvent concentration potential of 50
percent LEL during that program due to
limitations in the production schedule
and the bake oven design. Therefore,
demonstration of the system operating at
high solvent evaporation rates, composi-
tions, and LEL concentrations was re-
quired to totally prove the capability of the
concept.
This report describes an installation
that operates over a range of solvent
evaporation rates and compositions that
can reach the control set points of 50
percent LEL and demonstrates the vers-
atility of the technology. It also presents
the pollution reduction results of the
modified oven and resulting operating
economics of the system.
The Chemical Coaters Association, the
Department of Energy, and the Environ-
mental Protection Agency jointly spon-
sored the original technology develop-
ment program conducted at Mack Trucks
and this commercial evaluation program
at Prior Coated Metals.
System Operation
Prior Coated Metals is a coil coating
facility whose curing oven is typically
operated over a range of solvent evapora-
tion rates which result in variable oven
solvent concentrations.
Typical oven operating conditions and
fuel demands are presented in Table 1. As
shown, the percent LEL within the oven is
5 to 6 percent with a flow rate of 5.75 to
7.3 std mVsec. With the installation of
the microprocessor system, four condi-
tions had to be met: (1) optimize the
emissions control system operation; (2)
reduce total energy demand; (3) reduce
inplant VOC levels; and (4) provide safety
and curing oven process control.
The oven modifications included the
installation of a microprocessor, VOC
analyzers, appropriate dampers, air seals,
and duct modifications. Final installation
and check-out was completed in Decem-
ber 1983, although the system had been
operated successfully minus one air seal
since May 1983.
Results
The microprocessor system modifica-
tion to the oven resulted in a major
reduction in VOC emissions, which sig-
nificantly reduced pollution control and
manufacturing costs. Table 2 summarizes
operating conditions after the installation
of the microprocessor system. The results
of the evaluation indicated consistent
achievement of greater than 95 percent
VOC destruction efficiency based on
760°C (1400°F) incinerator operating
temperature. The ventilation air flow rate
was reduced approximately 60 percent
and resulted in a total fuel demand
reduction of approximately 60 percent.
Conclusions
The evaluation indicated that an oven
utilizing microprocessor technology can
be operated at high LEL concentration
without adverse effects on system per-
formance of product quality. With reduced
air flow, capital expenditures for pollution
control and operating costs are reduced
because of the smaller volume of gas that
must be processed by the oven and
control system. The use of microprocessor
technology is thus considered to be a
versatile and important tool to assist in
eliminating or reducing VOC pollution
and associated control costs.
Table 1. Typical Operating Conditions and Fuel Demand Before Retrofit*
Curing Oven Conditions
Oven Air Flow Rates, std rrf/sec (std ft3/mini
Solvent Evaporation Rates. m3/s (gal/min)
Oven Exhaust Temperature, °C (°FJ
Average Fuel Demand, MW (Million BTU/h)
Percent LEL %
Incinerator Conditions
Air Flow Rates*, std m3/sec (std ft3/min)
Incinerator Exhaust Temperature. °C (°F)
Average Fuel Demand. MW (Million BTU/h)
5.76 to 7.27 (12.200 to 15.400)
.00001 to.0001 (0.1 to 1.0)
249 to 382 (480 to 720)
2.43 to 3.31 (8.3 to 11.3)
5 to 6
6.53 to 8.04 (13.800 to 17,000)
538 to 649 (1.000 to 1.400)
1.76 to 3.16 (6.0 to 10.8)
•Includes air flow from coater room and quench air.
Table 2. A verage 0 ven and Incineration A fter Retrofit
Curing Oven Conditions
Oven Air Flow Rates, std rrf/sec (std ft3/min)
Solvent Evaporation Rates, rrf/s (gal/min)
Oven Exhaust Temperature. °C (°F)
A verage Fuel Demand. MW (Million BTU/h)
Incinerator Conditions
Air Flow Rates, std rrfl/sec (std ft3/min)
Incinerator Exhaust Temperature, °C (°F)
A verage Fuel Demand. MW (Million BTU/h)
VOC Destruction EH.. %
3.1 (6500)
.00005 (.5)
280 (535)
1.52 (5.2)
3.1 (6500)
760(1400)
1.21 (4.1)
99.9
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The Project Summary was prepared by staff of Chemical Coalers Association,
Wheaton, IL 60181.
Charles Darvin is the EPA Project Officer (see below).
The complete report, entitled "Environmental and Energy Benefits of Micro-
processor Control of Oven Airflows from a Coil Coating Operation: A Case
Study," (Order No. PB 85-121 135; Cost: $8.50, subject to change) will be
available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Hazardous Waste Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
U S GOVERNMENT PRINTING OFFICE; 559-016/7870
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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Penalty for Private Use $300
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