United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S2-85/041 July 1985
v>EPA Project Summary
Parametric Evaluation of
VOC/HAP Destruction Via
Catalytic Incineration
M. A. Palazzolo, J. I. Steinmetz, D. L. Lewis, and J. F. Beltz
A pilot-scale catalytic incineration
unit/solvent generation system was
used to investigate the effectiveness of
catalytic incineration as a way to de-
stroy volatile organic compounds
(VOCs) and hazardous/toxic air pollu-
tants (HAPs). The objectives of the
study were to: (1) investigate the
effects of operating and design varia-
bles on the destruction efficiency of
VOC/HAP mixtures, and (2) evaluate
destruction efficiencies for specific
compounds in different chemical
classes. The study results verified that
the following factors affect catalyst
performance: inlet temperature, space
velocity, superficial gas velocity, cata-
lyst geometry, compound type, com-
pound inlet concentration, and mixture
composition. Tests showed that
destruction efficiencies exceeding 98
percent were possible (given suffi-
ciently high inlet temperatures/low
space velocities) for the following com-
pounds/compound classes: alcohols,
acetates, ketones, cellosolves/diox-
ane. aldehydes, aromatics, and ethyl-
ene/ethylene oxide. Destruction
efficiencies of at least 97 percent were
achieved for acrylonitrile and cresol.
Chlorinated hydrocarbons were not
effectively destroyed with the type of
catalyst used in this study.
This Project Summary was devel-
oped by EPA's Air and Energy Engi-
neering Research Laboratory. Research
Triangle Park, NC, to announce key
findings of the research project that is
fully documented in a separate report of
the same title (see Project Report order-
ing information at back).
Introduction
A test program has been completed to
investigate on an experimental scale the
effectiveness of catalytic incineration as
a way to destroy volatile organic com-
pounds (VOCs) and hazardous/toxic air
pollutants (HAPs). A pilot-scale catalytic
incineration unit and a solvent vapor gen-
eration system were used for the testing.
Prior to the completion of this study,
limited data were publicly available on
the performance of catalytic incinerators
for a large number of compounds over a
wide range of operating conditions. Thus,
objectives of this study were to (1) inves-
tigate the effects of key incinerator oper-
ating and design parameters on mixture
destruction efficiency, and (2) measure
component specific destruction efficien-
cies for compounds in different chemical
classes.
Test System
The effects of key operating and design
parameters on the destruction efficiency
of a skid-mounted catalytic incinerator
were investigated using a solvent vapor
generation system. The vapor generation
system, consisting of a pump, dry gas
meter, tube furnace, glass mixing
chamber, and motor-driven syringes,
was used to produce a spiked air stream
with the desired concentrations of
organic vapors. The skid-mounted unit,
leased from Englehard Industries, was
equipped with a blower, preheater, mass
flowmeter, catalytic reactor, and temper-
ature controls. The design gas flowrate
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Exhaust
r
Incinerator
Catalyst Electric Heater
~]
Air In
Rotary Vane
Vent
Dry Gas
Tube Furnace Mixing Chamber
Pump Activated Meter
Carbon
Figure 1. Incinerator and solvent vapor generation system.
for the catalytic test unit was 275 cfh (4.6
scfm).* Figure 1 is a schematic of the test
system.
Experimental Design
In designing the experimental pro-
gram, conditions were selected to (1) pro-
vide data on a large number of solvent
types, (2) give an indication of the operat-
ing conditions required for destruction
efficiencies near 98 or 99 percent, and (3)
represent operating conditions typically
used in industrial applications. The major
operating parameters that were varied
during the testing included: catalyst inlet
temperature, compound concentration,
space velocity, compound type, catalyst
geometry, and catalyst volume. Much of
the testing was conducted to character-
ize compound destruction across the pre-
heater and catalyst bed as a "system."
However, heater and catalyst destruction
efficiencies were also measured separ-
ately at a number of conditions.
Most of the test work involved the mea-
surement of destruction efficiencies for
low concentrations of VOC/HAP mix-
tures in air. A short series of tests was
also conducted with a low oxygen gas
stream, intended to simulate the off-gas
from an ethylene oxide production pro-
cess. Components of the VOC/HAP mix-
tures and compositions of the simulated
ethylene oxide off-gases are shown in
Tables 1 and 2, respectively. For the
VOC/HAP mixtures, total system inlet
concentrations were typically main-
tained near 1200 ppm carbon (by
volume). Mixtures were generally pre-
pared to provide equal amounts of each
component on a per carbon or ppm car-
*1 ft3 = 28.3 L.
bon (by volume) basis. At all test condi-
tions, total mixture destruction
efficiencies were measured with EPA
Method 25A, and component specific
efficiencies were determined by EPA
Method 18.
The ranges of incinerator operating
conditions tested during this study are
summarized in Table 3. As shown in
Table 3, space velocities, based on total
catalyst volume and standard gas flow
rates, were varied from 15,000 to 80,000
hr° with catalyst inlet temperatures
ranging from 500 to 800 F.* Two
volumes of two different catalyst types
were tested. Both catalyst types had the
same precious metals formulation. How-
ever, the ceramic honeycomb substrates
had different cell sizes and, hence, differ-
ent catalyst surface areas.
*5/9(°F-32) =
Table 1. Lists of Components in Multi-
component VOC/HAP Mixtures
Mixture 1 - Control Mixture
Isopropanol
Methyl ethyl ketone
Ethyl acetate
Benzene
n-Hexane
Mixture 1A - Hexane Substitution
Isopropanol
Methyl ethyl ketone
Ethyl acetate
Benzene
Cyclohexane
Mixture IB - Hexane Substitution
Isopropanol
Methyl ethyl ketone
Ethyl acetate
Benzene
Iso-octane
Mixture 1C - Hexane Substitution
Isopropanol
Methyl ethyl ketone
Ethyl acetate
Benzene
n-Octane
Mixture 2 - Industrial Mixture
Methyl ethyl ketone
Toluene
Mixture 3 - Alcohols/Acetates
Methanol
Ethanol
Isopropanol
n-Butanol
Ethyl acetate
n-Propyl acetate
Isobutyl acetate
Mixture 4 - Ketones/Miscellaneous
Oxygenated Compounds
Acetone
Methyl ethyl ketone
Methyl isobutyl ketone
Cyclohexane
Ethyl cellosolve
Butyl cellosolve
Dioxane
Mixture 5 - Aldehydes
Propionaldehyde
Isobutyl aldehyde
Isovaleraldehyde
n-Butyl aldehyde
n-Valeraldehyde
Mixture 6 - Alkanes/Aromatics
n-Hexane
n-Octane
n-Decane
Benzene
Toluene
m-Xylene
Isopropyl benzene
Mixture 7 - Non-Chlorinated HAPs
m-Cresol
Acrylonitrile
Mixture 8 - Chlorinated HAPs
Methylene chloride
Carbon tetrachloride
Ethylene dichloride
Trichloroethylene
Tetrachloroethylene
1,1 -Dichloroethane
1,1,2-Trichloroethane
Test Results
Results from the pilot-scale catalytic
incineration testing identified and/or
verified the effects of a number of operat-
ing and design parameters on catalytic
incinerator performance. Parameters
found to have the greatest effect on
destruction included catalyst inlet
temperature, space velocity, compound
type, catalyst geometry, and catalyst
volume. Other parameters generally
showing a lesser effect included inlet
concentration and mixture composition.
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Table 2. Components and Concentrations in the Ethylene Oxide Off-Gas
Test Parameter Conditions or Values Tested
Stream Composition 1
(percent by volume)
Stream Composition II
(percent by volume)
Ethylene
Ethane
Ethylene oxide
Nitrogen
Carbon dioxide
Oxygen
Ethylene
Ethane
Ethylene oxide
Nitrogen
Carbon dioxide
Oxygen
0.43%
0.09%
0.01%
86.0%
12.0%
1.5%
0.64%
0.09%
0.01%
85.3%
11.5%
2.5%
Table 3. Ranges of Operating Conditions Tested
Catalyst
Geometry/
Volume"
A/0.006 ft3
B/ 0.006 ft3
A/0.012 ft3
A/0.012 ft*
B/ 0.01 2 ft3
Mixture(s)
Tested
1 through 8
plus pure
compounds11
1,6
1,2,4,6
Ethylene
Oxide
Ethylene
Oxide
Range of
Space
Velocity
hr~'
20,000 to
80,000
30,000 and
50,000
15,000 to
50,000
30,000 and
50,000
30,000 and
50,000
Inlet
Concentrations
ppmCc
1.200/6.000
10,000
1,200
1.200
/,//d
/"
Catalyst Inlet
Temperatures
°F
500 to 800
600 to 800
600 to 800
500 and 600
500 and 600
Catalyst A had a catalyst surface area of 270 ft2/ft31 and Catalyst B had an area of 660 ft2/ft3.
Sixteen single components tested with this catalyst.
ppmC = parts per million by volume as carbon.
Compositions shown in Table 2.
ft2 = 0.0929m2
The test results provided data on: (1)
potential partial oxidation products, (2)
carbon monoxide emissions, and (3) cata-
lyst temperature rise relationships. The
capability of catalytic incineration to
achieve destruction efficiencies in the 98
to 99 percent range was also verified for
compounds in seven different chemical
classes.
Multi-component mixture effects on
compound specific destruction efficien-
cies were evaluated by comparing pure
compound destruction efficiencies with
efficiencies of these compounds as com-
ponents of the VOC test mixtures. In addi-
tion, destruction efficiencies for
compounds tested in more than one mix-
ture were compared. A mixture effect
was found on pure compound destruc-
tion efficiencies for 6 of 13 compounds.
In most cases, these compounds showed
higher destruction efficiencies as mix-
ture components than as pure com-
pounds. However, two linear alkanes,
n-hexane and n-octane, showed
decreased destruction as components of
one mixture.
An effect of mixture composition was
also found for two of five compounds
tested in more than one mixture. This
effect appeared to be greatest at lower
catalyst inlet temperatures.
The effects of catalyst inlet tempera-
ture and space velocity on system de-
struction efficiency are shown for
Mixture 1 in Figure 2. The trends shown
in Figure 2 of increasing destruction with
increasing inlet temperature and
decreasing space velocity are typical of
those observed for the other mixtures.
System destruction efficiencies for Mix-
ture 3 (alcohols and acetates) showed a
particularly strong dependence on cata-
lyst inlet temperature at a space velocity-
of 50,000 hr"1. In addition, system
destruction efficiencies for Mixtures 3
and 6 (alkanes and aromatics) showed a
strong dependence on space velocity.
Test Mixture 5, which consisted of dif-
ferent aldehyde compounds, generally
showed the highest system destruction
efficiencies of the mixtures tested. Mix-
ture 8, which contained seven chlori-
nated hydrocarbons, showed by far the
lowest destruction. Except for Mixture 8,
all mixtures showed system destruction
efficiencies ranging from 85 to 99 per-
cent for the conditions tested in this
study. Mixture 8 destruction efficiencies
ranged from 0.0 to 80 percent.
The preheater on the test unit con-
sisted of a pipe or tube wrapped with a
high temperature electrical resistance
heater element. At low space velocities
and/or high inlet temperatures with the
small catalyst volumes, heater (thermal)
destruction efficiencies were as high as
80 to 90 percent for some mixtures. With
the larger catalyst volume, gas flow rates
through the system were doubled at a
given space velocity and heater destruc-
tion decreased to between 10and 76 per-
cent. The degree to which the heater
destruction efficiencies observed on the
test unit may represent destruction in the
natural gas burner zones of full-scale
incinerators is not known. However,
burner designs that provide direct con-
tact of the waste gas with the flame are
expected to provide an opportunity for a
significant amount of compound
destruction.
At a given space velocity, catalyst
destruction efficiencies for the mixtures
were found to be higher for the larger
catalyst volume. The higher destruction
for the large volume results from a higher
gas velocity through the catalyst cells,
which apparently improved mass
transfer and increased the overall reac-
tion rate. With the larger catalyst volume,
catalyst destruction efficiencies of 98
percent or higher were obtained for Mix-
tures 1, 3, 4, and 6.
The effect of catalyst inlet temperature
and space velocity on component
destruction efficiencies varied consider-
ably for the different compounds. Com-
pounds of the same chemical class often
showed similar destruction efficiencies
and trends with inlet temperature.
Other results from the catalytic incin-
eration testing included:
- Tests with the chlorinated hydrocar-
bon mixture were found to have par-
tially deactivated the catalyst.
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- Higher destruction efficiencies were
observed for the catalyst type with
the higher surface area (catalyst B),
as expected.
- Inlet concentration was found to
slightly affect destruction, with
higher efficiencies at higher
concentrations.
- Tests with the simulated ethylene
oxide off-gas showed VOC destruc-
tion efficiencies in excess of 99 per-
cent at all conditions tested.
- The pilot-scale efficiencies for Mix-
ture 2 agreed well with those for a
full-scale unit treating this same mix-
ture in exhaust gas from a foil coil
coating line.
- Mass spectroscopy analysis identi-
fied partial oxidation products from
the catalytic combustion test unit.
- Carbon monoxide emissions from
catalytic combustion were found to
be less than 5 ppmv for most test
conditions.
- Catalyst bed temperature rise was
found to be directly related to the
mass of solvent destroyed in the cata-
lyst bed.
- Method 25A and Method 18 mixture
destruction efficiencies were in very
good agreement, with Method 25A
efficiencies being 2.4 percent lower
on average for the entire test effort.
Conclusions
Results from this study identified or
verified that the following factors affect
the performance of catalytic incinerators:
- catalyst inlet temperature;
- space velocity;
- superficial gas velocity (at the
catalyst inlet);
- catalyst geometry;
- compound type;
- inlet VOC concentration; and
- mixture composition.
In addition, the testing verified that
destruction efficiencies in the 98 to 99
percent range are achievable with cata-
lytic incineration for the following com-
pounds or classes at sufficiently low
space velocities and/or high enough
catalyst inlet temperatures:
- alcohols;
- acetates;
- ketones;
- cellosolve compounds/dioxane;
- aldehydes;
- aromatics; and
- ethylene/ethylene oxide.
Destruction efficiencies of at least 97
percent are also achievable for acryloni-
trile and cresol, while chlorinated hydro-
carbons appear unsuitable for control
700 _
•a 90
80
CO
70
/
L
©
O 80.000 hr'1
A 50,000 hr''
[•] 30,000 hr~1
(•} 20,000 /ir'1
Hi Shaded - Method 25A
I I Open-Method 18
Ht
500
600 700
Catalyst Inlet Temperature, °F
800
900
Figure 2.
Mixture 1 system destruction efficiency vs. inlet temperature for small volume
catalyst A.
with the type of catalyst tested in this
study. Other catalyst formulations might
be more favorable for destroying chlori-
nated hydrocarbons.
M. A. Palazzolo, J. I. Steinmetz, D. L. Lewis, and J. F. Beltz are with Radian
Corporation, Research Triangle Park, NC 27709.
Bruce A. Tichenor is the EPA Project Officer (see below).
The complete report, entitled "Parametric Evaluation of VOC/HAP Destruction
Via Catalytic Incineration," (Order No. PB 85-191 187/AS; Cost: $25.00,
subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, V'A 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
U. S. GOVERNMENT PRINTING OFFICE: 1985/559-111/20613
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