SERJV
United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-81 -244 Mar. 1982
Project Summary
Organic Emissions
Evaluation of a Paint Bake
Oven with Catalytic Incineration
Bruce C. DaRos, Richard Merrill, and William C. Kuby
This report describes sampling
methods and results of a field test
program conducted at the Mack Truck,
Inc., paint bake oven facility located in
Allentown, Pennsylvania. The purpose
of the test program was to measure
total hydrocarbon (THC) concentra-
tions at the inlet and outlet of an incin-
erator with heat recovery used to
reduce organic solvent emissions.
Data were also collected to evaluate
the energy efficiency and economics
of the system compared to other THC
control alternatives.
The incinerator system was de-
signed by Schweitzer Industrial of
Madison Heights, Wisconsin, and incor-
porates DuPont's Torvex catalyst with
platinum to enhance hydrocarbon
reduction in the process stream. The
incinerator fuel is No. 2 distillate oil
injected through a Model 500, com-
bination overpack gas/oil burner manu-
factured by Maxon of Muncie, Indi-
ana. The incineration system includes
a heat exchanger following the cata-
lyst bed. The gas stream being heated
is circulated to the electrodeposition
(E-coat) oven, thus replacing a direct
heat source otherwise required. The
heat exchanger "effectiveness" of
this configuration was 82 percent,
allowing for a recovery of 35.1 per-
cent of total thermal energy from the
gas stream.
An analysis of the annualized costs
of thermal and catalytic incineration
and carbon adsorption was performed.
Because the concentration of hydro-
carbons to the control device was
small, the annualized cost of carbon
adsorption was less than other control
devices.
Measurements conducted at the
inlet and outlet of the incinerator indi-
cated an average reduction in organic
emissions of approximately 86 per-
cent. Bypassing the incinerator with a
fraction of the total gas stream resulted
in an emissions reduction to the atmos-
phere of 70 percent.
This Project Summary was devel-
oped by EPA's Industrial Environ-
mental Research Laboratory, Cin-
cinnati, 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
The painting and paint baking of new
automobiles represents a major station-
ary source of volatile organic carbon
(VOC) emissions from the transporta-
tion industry. These emissions, when
destroyed efficiently, have the potential
to be utilized as a fuel supplement and
aid in significantly reducing the energy
requirements of paint baking.
A catalytic incineration system with
heat recovery and gas recirculation
(Figure 1), designed to control hydro-
carbon emissions from paint bake ovens.
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vent to
Atmosphere
(Roof)
Flow Regulator Damper
Fuel and Air
O *Sample Locations
Figure 1. Schematic of the Mack Truck. Inc., incineration system.
was tested and evaluated to determine
its organic solvent emissions reduction
efficiency.The system incinerates off-
gases from three ovens while supplying
heat through a heat exchanger to a
fourth oven (E-coat). The system normally
operates throughout the first and second
shifts, 6 days/week. A Dupont Torvex
catalyst bed with platinum was installed
Table 1. Summary of Emission Rates
Sample
Location
Description
in late 1976 to enchance the incinerator
system's reduction efficiency. When
this test program was conducted, less
than 20 percent of the catalyst life
remained (regeneration was rescheduled
for 1980).
In three one-hour tests at the Mack
Truck, Inc., facility in Allentown, Penn-
sylvania, THC concentrations were
Emission Rate
kg/hr ppm
(as methane) (as methane)
Paint bake oven off-gas
(inlet to incinerator)
Incinerator exhaust gas
(outlet of incinerator)
Paint bake oven incinerator
bypass
1.55
0.214
0.360
195
25
195
determined at the inlet and outlet of th
incineration system using a Beckma
Model 400 Hydrocarbon Analyzer wit
a flame ionization detector. Prior i
sampling, measurements were taken 1
determine gas phase conditions at eac
test location as well as at the inlet an
outlet of the heat exchanger followin
the incinerator. THC concentration
were recorded as equivalent methan
and are summarized in Table 1. He£
exchanger performance was evaluate
using mass and energy balances. Sine
the heat exchanger bypass stream join
the exchanger outlet flow prior to th
sampling point, actual exit condition
were computed by assuming flow prop
erties identical to those of air. The fol
lowing balance was determined:
Fuel inflow
Air inflow
Off-gas inflow
Exchanger bypass flow
Exchanger inflow
Total outflow
Exchanger outflow
2.37 kg/mi
53.8 kg/mi
237 kg/mii
136 kg/mii
157 kg/mii
255 kg/mii
119 kg/mii
To aid in understanding the discre
pancy between the computed inflov
and outflow of the heat exchanger, tra
versing techniques and profile result:
were examined at each sampling loca
tion. The higher velocity profiles am
flowrates were determined to be due t<
flow stratification. The off-gas inflow
although also high, appeared suff icienth
reliable to be used in the remaining
computations.
The heat exchanger outlet tempera
ture was not measured but computec
based on the bypass, incinerator outlet
and total inlet stream measurements
The result was 504°K, with the unrelia
bility of the exchanger bypass anc
incinerator outflow measurement:
making this a maximum value. The
computed heat recovery rate was sub-
sequently 0.740 x 106 joules/hr, with a
total energy flowrate for the heal
exchanger inlet of 2.09 x 106 joules/hr.
Thus, 35.1 percent of the energy flux
was recovered in the exchanger. To
complete the energy balance, the cold-
side recovery was determined to be
0.712 x 106 joules/hr, the difference
being attributed to losses and/or data
uncertainties. Using the actual heat
transfer rate obtained earlier, the heat
transfer effectiveness was computed to
be 82 percent.
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Results
Data Analysis
The emission rates for each incinera-
tor THC sampling location were calcu-
lated using average concentrations for
the tests and the measured volumetric
flowrate. These emission rates along
with the emission rate for the incinera-
tor bypass are recorded in Table 1. (This
bypass is vented directly to the atmos-
phere from the oven off-gas duct and
therefore affects the overall control
effectiveness.) The average THC con-
centration at the incinerator inlet was
used to calculate the emission rate to
the incinerator and the resulting control
effectiveness. Using overall test aver-
ages for THC concentrations allowed for
fluctuations in concentration at the
incinerator inlet and outlet. The incin-
erator emission control effectiveness in
reducing THC concentrations was com-
puted to be 86 percent. Likewise, the
overall system effectiveness (including
the bypass) was determined to be 70
percent.
An energy balance to determine heat
exchanger effectiveness was developed
as outlined in Figure 2. Heat fluxes were
calculated to be as follows:
6,,r= 82 x 106 joules/hr
Qexhaust = 5,864 x 106 joules/hr
= 2,731 x 106 joules/hr
To implement THC concentration
emission control requires additional
energy (Qluei, CU.r, Wwo*). The heat
exchanger recovers a portion of this
energy from the E-coal oven. The effec-
tiveness of this heat recovery system
(/7c) is measured as the percent recovery
of the additional energy required by the
control device, expressed as:
n = Qaxchanoer
Qa,r + Qfu.1 + Wwork
Qgas is not included since the tempera-
ture of the gas from the other paint bake
ovens to the incinerator is below that of
the E-coat oven and would exist for both
controlled and uncontrolled systems.
The recovery efficiency computed above
is 41.5 percent; if Q^s were included to
give the overall recovery efficiency, that
value would be 32.7 percent.
Process Analysis
As cited earlier, the THC concentra-
tion emission control effectiveness for
the catalytic incinerator tested was 86
percent, which was assumed to be the
Control
Volume
QlO.W.
Wwork
I r=r
QfU»l
F/A = Fuel/air ratio
Our,
Figure. 2 Control volume for heat balance.
maximum possible for this system opera-
ting with less than 20 percent of the
catalyst life remaining.
An advantage of this system is its
insensitivitytofluctuations in one absorb-
ing and one regenerating bed.
While carbon adsorption can result in
near total THC concentration control,
the adverse effect of variations in types
and concentrations of contaminants re-
quires that its application in facilities
similar to the Mack Truck, Inc., paint
bake ovens be qualified by similar appli-
cations presently in operation.
Cost Analysis
The installed capital costs of thermal
and catalytic incineration systems consist!ng
of catalyst beds, preheat burners, duct-
work, fan, and controls are $111,100
and $132,000, respectively. The addi-
tion of a heat exchanger increases the
capital cost approximately 25 percent.
The operating cost differential between
each pollution control device is impacted
further by utility costs, capital recovery
costs, and other indirect operating costs
(taxes, insurance, administration).
Estimates of the annualized costs in
1977 dollars for thermal and catalytic
incineration were $348,000 and
$105,000, respectively, and fuel costs
were 95 and 78 percent, respectively, of
these totals. Thus, reduction in fuel
consumption yields high economic
returns. Instead of transferring heat to
the E-coat oven stream from the incin-
erator outlet stream, this energy could
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be used to preheat the incinerator inlet
stream. For this configuration and
assuming an 82 percent exchanger
efficiency as before, the heat recovery
would be 38.6 percent as compared to
35.1 percent for the current application.
The increased heat transferred per unit
heat exchanger area results from the
increased temperature differential. This
configuration also would eliminate the
need for a bypass stream.
The capital cost of a carbon adsorp-
tion device is based on the total weight
of carbon required for efficient control
of the organic material being controlled
and the configuration of the system.
Based on these assumptions, the annu-
alized costs are $34,000. Since the
concentration of pollutants being
removed is small, operating costs are
negligible compared to the cost of inlet
THC concentrations and changes in
contaminants. This is assuming the
species entering the incinerator do not
blind the catalyst or generate paniculate
matter requiring further control. A
disadvantage of the system is the large
energy requirement to raise the gas
temperature sufficiently for effective
catalyst performance. In general, how-
ever, increases in the combustible con-
tent of the entering gas stream reduce
the energy requirement offset.
Thermal (noncatalytic) incineration
requires temperatures in excess of
1500°F and residence times from 0.5 to
1.5 seconds; thus, higher energy input
to reach operating temperature and
construction with heat-resistant
materials are required. This energy re-
quirement can be reduced by preheating
the gas stream entering the incinerator
using heat exchangers or hot gas
recirculation. A heat recovery of 35
percent is typical and similar to the 35.1
percent calculated for this catalytic
system.
Thermal or catalytic incineration can
be used to control THC concentration in
a gas stream. Selection of this technol-
ogy over carbon adsorption is influenced
by the economic burden of the additional
energy requirement and the potential
use of the solvent being controlled.
Replacement parts (such as the catalyst)
are not included in such determinations.
Incineration also precludes recovery of
organic species in the gas stream.
Carbon adsorption, on the other hand,
uses a bed of activated carbon to absorb
organic species, which means its effi-
ciency is impacted by the organic con-
stituents; methane, for example, cannot
be effectively controlled by carbon
adsorption. The energy requirements
(exclusive of gas-moving equipment and
instrumentation), however, is low com-
pared to incineration, consisting of
stream generation for regenerating the
beds and production of cooling water. If
organics are not to be recovered, a
water effluent would be generated which
may require treatment and/or disposal.
Carbon, like the catalyst, can be regen-
erated, having a useful life of five years.
Typically, a system consists of removing
higher pollutant concentrations. There-
fore, although carbon adsorption may
appear to be more attractive than incin-
eration for the Mack Truck, Inc., applica-
tion, it may be economically unattrac-
tive in applications with higher
concentrations. Also, since Mack Truck,
Inc., operates two shifts a day, which
allows them to use one catalyst bed and
regenerate during the third shift, annu-
alized costs using adsorption may also
be reduced further by eliminating the
dual adsorption bed design.
Conclusions and
Recommendations
The catalytic incineration system
tested at Mack Truck, Inc., was effective
in reducing organic emissions from the
small parts bake ovens. Based on the
average emission rates calculated for
the three 1 -hour tests, the incinerator
was capable of reducing organic emis-
sions by 87.2 percent. Bypassing the
incinerator with a fraction of the total
gas stream resulted in an emissions
reduction to the atmosphere of only 70
percent.
The effectiveness of the heat ex-
change/, used to heat air for the E-coat
oven, was 82 percent, allowing for a
recovery of 35.1 percent of the total
thermal energy from the gas stream
entering the heat exchanger. Larger
fuel savings may be possible for Mack
Truck, Inc., if the combustion air and gas
stream being incinerated are preheated
(rather than the E-coat oven air) since
more energy can be transferred to these
streams, thus allowing reduced fuel
requirements. A further analysis of the
heat exchanger showed that 38.6 per-
cent of the energy required to operate
the incineration system could be
recovered.
The primary disadvantage of thermal
or catalytic incineration is the cost
associated with the fuel requirements.
Carbon adsorption has lower operating
costs than the incinerators but highc
capital costs. Since all of these prc
cesses can reach near total control (
the THC emissions, the major diffei
ence between incineration and adsorp
tion is the annualized cost of each.
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Bruce C. DaRos, Richard Merrill, and William C. Kuby are with A cur ex Corpora-
tion. Mountain View, CA 94042.
M. Lynn Apel is the EPA Project Officer (see below).
The complete report, entitled "Organic Emissions Evaluation of a Paint Bake
Oven with Catalytic Incineration." (Order No. PB 82-116 872; Cost: $9.00.
subject to changeI 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:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
6USGPO: 1982—559-092/3382
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