v>EPA
United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S2-81-017 Oct. 1981
Project Summary
Catalytic Incineration of Low
Concentration Organic Vapors
Norman A. Martin
Catalytic abatement of low concen-
tration hydrocarbon vapors has been
demonstrated. This report presents
the results of the demonstration
conducted on both a pilot and full-
scale system. The tests were conduct-
ed on industrial exhausts which con-
tained carbon monoxide as well as
volatile hydrocarbons. Utilizing this
data an economic comparison was
made between thermal and catalytic
abatement systems.
The pilot data was obtained in a
plastic printing plant in which the
major solvents were ethanol, n-propyl
acetate, and heptane. Test data was
obtained for a 5-month period.
The full-scale data was obtained
from the exhaust of a Formox* formal-
dehyde plant. The exhaust contained
carbon monoxide, dimethyl ether,
methanol, and formaldehyde. Test
data was gathered over a 9-month
period.
The pilot and full-scale units were
able to convert 97%-99% of the
pollutants to carbon dioxide and
water.
This report was submitted in fulfill-
ment of Contract No. 68-02-3133 by
the Systems Department of the Engel-
hard Industries Division of Engelhard
Minerals & Chemicals Corporation
under the sponsorship of the U.S.
Environmental Protection Agency.
This report covers the period October
1, 1978 to March 31,1980, and was
completed November 15,1980.
'Trademark of Reichhold Chemical Company
This Project Summary was developed
by EPA's Industrial Environmental
Research Laboratory, Research Tri-
angle 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
ordering information at back).
Introduction
A study of catalytic incineration of low
concentration organic vapors has been
conducted. The scope of the study
included both pilot-scale and full-scale
demonstration testing of catalytic
abatement systems. In addition to the
assessment of the catalytic system's
abilities to reduce organic emissions, an
economic comparison was made be-
tween catalytic and thermal air pollu-
tion abatement systems.
Catalysis is the process of changing
the velocity of a chemical reaction by the
presence of a substance (catalyst) that
remains apparently chemically unaf-
fected throughout the reaction.
The catalyst used in this study is a
precious metal formula evenly distri-
buted over a high-surface-area alumi-
num oxide support material. The support
material comes in two forms, pellet and
honeycomb. High catalyst surface area
is a major contributing factor in catalyst
activity in that it assists in exposing a
maximum number of active catalytic
sites to the flowing gas. Many catalyst
formulas using platinum, paladium, or
other precious metals are used in
combination with surface preparation to
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give the properties necessary for each
application. Selection of a catalyst
formulation and operating temperature
depends on many interrelating factors.
These include the organic materials to
be removed, the outlet concentration to
be achieved, the operating temperature,
and the catalyst life which in itself is
dependent on temperature, solid particles
concentration in the gas, and elements
(such as sulfur) which reduce catalyst
life.
Pelletized catalyst makes for easy
loading and unloading and is less
expensive than honeycomb catalyst. It is
used in pressurized chemical processes.
Honeycomb catalyst, with itsfixed direct
flow-through passages, has a much
lower pressure drop resulting in a
smaller reactor vessel and lower power
consumption by the gas moving device.
Honeycomb catalyst is used in the
catalytic abatement systems.
Organic vapors as well as carbon
monoxide can be removed effectively
from many kinds of off-gas streams by
oxidation in catalytic reactors. When the
off-gases containing these pollutants
are heated to suitable temperatures at a
given space velocity, the combustible
components react with oxygen from the
air to form harmless carbon dioxide and
water vapor. The term "space velocity"
is defined as the volume of gas flowing
through the catalyst per hour, divided by
the volume occupied by the catalyst.
Space velocity replaces the term "con-
tact time" used in thermal incinerators.
As a frame of reference, contact times in
thermal units are usually 0.3 to 0.5 sec-
onds. A space velocity of 50,000 hr "1 is
equivalent to a contact time of 0.072
seconds.
In a thermal incinerator, pollutants
are oxidized directly in the residence
chamber at high temperature—typically
above 704°C. Because of the high fuel
consumption required to maintain these
temperatures in a thermal incinerator,
the alternative of catalytic reaction is
often preferable.
In a catalytic reactor, the catalyst
induces oxidation at lower temperatures,
typically at 316-427°C.
Lower operating temperatures mean
lower fuel consumption. Lower equip-
ment costs from smaller reactors and
heat exchangers help balance the
additional cost of catalyst, making the
overall equipment cost comparable to
thermal systems.
In some cases, the heat generated by
the chemical reaction within the catalytic
reactor permits self-sustained operation:
depending on concentration and other
factors, a well-designed catalytic abate-
ment system equipped with a heat
recuperator may be self-sufficient after
initial lightoff. Lower operating temper-
atures also have the advantage of
preventing NO, formation.
The study was divided into four
phases. Phase I was the process
selection. Phase II was the preparation
and installation of a pilot demonstration
unit on a plastic printing plant. Phase III
was a full-scale demonstration of a
catalytic air pollution abatement system
installed on a Formox type formalde-
hyde plant. Phase IV is this final report
in which the data are presented and
analyzed.
Conclusions
Pilot Test Unit
The catalytic abatement of low level
hydrocarbons from the slip stream of a
plastic printing press exhaust has
resulted in low level emissions in that
stream.
1. The catalytic abater at a space
velocity of 50,000/hr"1 and an
exhaust temperature of 315°C
would reduce total hydrocarbons
from the plastic printing plant 95%
or more for a period of 3 years.
2. Increased conversion efficiency
may be obtained by increasing
temperature or reducing space
velocity.
3. Increased catalyst life may be
obtained by increasing temperature.
4. Conversion efficiency varies for
the different components of the
exhaust.
Full-Scale Unit
The catalytic abatement system has
been operating on the exhaust of a
Formox formaldehyde plant for a year.
1. The removal efficiency of the
catalytic abatement system has
remained in the range of 97.9% to
98.5%. There is no trend in the
data points which would predict a
maximum catalyst life. A minimum
of 3 to 5 years is indicated.
2. The catalytic abatement system
was not receiving any appreciable
(1 ppm) NOX nor was any NOX
produced by the system.
Pilot Test
Process Description
The test was conducted on the
exhaust stream of a plastic film printing
press manufactured by the Paper
Converting Machine Company. It is a
six-station, 60-in. (152-cm) wide central
impression cylinder flexographic printing
press. The press contains dryers which
evaporate volatile organic solvents from
the plastic film after printing.
The inks employed are solvent based
polyamid printing inks which are
approximately 78% by weight volatile at
the proper printing viscosity. The major
volatile components of the inks are
ethanol, n-propyl and 2-propyl alcohol,
heptane, and n-propyl and 2-propyl
acetate. Ethanol is the major solvent
component but the percentage of all
components varies widely with different
colors as does the amount of additional
solvent added to the original inks to
bring them to the proper printing
viscosity.
Pilot Test Unit Description
The pilot test unit consists of a blower,
electric heater, catalytic reactor, and
temperature, flow and pressure instru-
mentation. A flow schematic of the unit
is shown in Figure 1. The reactor
contains Engelhard's proprietary cata-
lyst. The catalyst is a precious metal t
formula on a unitary ceramic substrate. "
The Pilot Test Unit contains two catalyst
elements, each 1.5 in. (3.8 cm) in
diameter by 3 in. (7.6 cm) deep. The total
volume of the bed is 0.006 ft (170cm3).
Pilot Test Program
The test program was conducted over
a period of 6 months (July-December
1979). Five tests were conducted during
the 6-month period. The tests were all
performed at three temperatures and
three space velocities. A target for
conversion efficiency of 95% for a 3-
year period was chosen. These numbers
were chosen arbitrarily from past
experience but proper selection of the
data would make it possible to alter
these numbers to meet a specific appli-
cation.
During the initial testing periods, the
inlet and outlet were sampled to
determine the content of n-propyl
acetate, ethanol, and n-propyl alcohol.
After testing, the actual temperature
rise was compared to the calculated
temperature rise. It was found that the
calculated rise from the measured
hydrocarbon contact was less than
actual temperature rise. This indicated
that additional unmeasured hydrocarbon
was probably present and that additional i
testing was necessary. As a result, it '
was decided to also monitor total
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Legend
F1 Flow Indicator
TIP Overtemp. Shut Off
TIC Temp. Controller
PI Press. Indicator
DPI Differential Press Indicator
FV Control Valve
Damper ~£_
Inlet
Sample
Point
txi
Element
TIP\ fVariac
•---•££/
Shell
Catalytic Reactor
Figure 1. Flow schematic pilot test unit.
organic carbon and heptane in the
exhaust. Heptane monitoring began on
September 25. Total hydrocarbon moni-
toring began on October 30.
Results
A summary of the results of the pilot
test program is provided in Tables 1, 2,
and 3.
Full Scale Catalytic Unit
Installation
The full-scale unit is an Engelhard
Deoxo Catalytic Pollution Abatement
System, Model PAS-4, installed on a
formaldehyde plant using the Formox
process under license from Reichhold
Chemicals, Inc. The process makes
formaldehyde by passing preheated air
and recycled process gas mixed with
methanol through a Formox catalyst.
The reaction without balancing the
equation is:
CH3OH
02
inerts -
methanol oxygen
HCHO + CH3OCH3 + CO + inerts
formal- dimethyl carbon
dehyde ether monoxide
Table 1. Pilot Test Data Summary, Preliminary
Recycling takes place with sufficient air
addition to keep the inlet oxygen level at
about 10%. It is, therefore, necessary to
withdraw approximately 25% of the
exhaust gas to remove the inerts; i.e.,
nitrogen, dimethyl ether, and carbon
monoxide.
The catalyst is contained in a multiple
tube converter where a controlled
reaction takes place. Formaldehyde is
absorbed in multiplate columns which
produce an essentially methanol-free
product.
Process Description
The catalytic incinerator (Figure 2) is
used to reduce hydrocarbon emissions
being exhausted in the off-gas from a
Formox formaldehyde plant. The gas
stream, under saturated conditions,
exits the plant at a rate of 4500-6000
m3/h entering the catalytic incinerator
at 32-43°C. The entering gas passes
through a gas-to-gas recuperative heat
exchanger to raise the temperature to
232°C minimum. The gas then proceeds
through a gas-fired preheater which is
used to start the system or add heat if
the incoming exhaust is low in heat
content. It then passes through a mixing
section to ensure even distribution of
the heat before entering the catalyst
bed. After combustion, the temperature
rises to 427-621 °C, depending on
hydrocarbon loading, and the hot
exhaust gas passes through the heat
exchanger to the exhaust stack. A
bypass of the inlet gas around the heat
exchanger permits regulation of the
incoming gas stream temperature.
The exhaust stream inlet has the
following composition on a dry basis
(actual gas is saturated at 25-38°C):
Carbon Monoxide 3000-8000 ppm
Methanol 100-900 ppm
Test
Date
Time
Measurement No.
Flow Rate (m*/h)
Space Velocity x 1000
Catalyst Inlet Temp. (°C)
Catalyst Outlet Temp. (°C)
Catalyst Press. Drop (Pa)
Removal %
Ethanol
N-Propanol
N-Propyl Acetate
Total
Preliminary Testing
7/17
0929
1
8.3
49
371
402
622
99.7
99.8
97.8
99.7
7/17
1001
2
11.9
70
371
406
846
99.6
99.8
97.8
99.6
7/17
1030
3
15.3
90
371
407
1120
99.6
99.4
93.1
99.4
7/'17
1305
4
14.6
86
316
360
996
99.6
99.1
94.6
99.3
7/17 7/17
1400 1430
5 6
11.9 8.5
70 50
316 316
362 362
871 572
99.6 99.6
99.2 99.6
97.1 97.2
99.4 99.5
7/17
1500
7
5.1
30
313
360
373
99.8
99.9
99.4
99.8
7/17
1643
8
5.1
30
260
316
249
99.6
99.8
97.5
99.6
7/18
1320
9
11.9
70
266
316
747
98.6
98.7
99.4
98.6
7/18 7/18
1352 1515
10 11
8.5 5. 1
50 30
291 277
313 311
498 249
99.0 99.8
99.3 99.9
92.2 97.7
99.0 99.8
7/19
1021
12
5.1
30
338
354
249
99.8
99.8
94.4
99.7
7/19 7/19
1200 1115
13 14
8.5 12.2
50 72
346 340
371 368
498 747
99.4 98.9
99.6 99.1
97.7 90.8
99.4 98.9
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Table 2. Pilot Test Data Summary, Months 1 and 2
Test
Date
Time
Measurement No
Flow Rate (irf/ht
Space Velocity x WOO
Catalyst Met Temp (°CI
Catalyst Outlet Temp /°CI
Catalyst Press Drop (Pa!
Removal %
Ethanol
N-Propanol
N-Propyl Acetate
Heptane
Total
Month 1
8/15
1221
1
119
70
327
365
747
98 8
990
96 1
—
987
8/15
1301
2
85
50
327
368
622
992
994
978
—
992
8/15
1346
3
51
30
333
368
373
997
998
998
—
997
8/15
1542
4
11 9
70
230
260
622
994
980
586
—
970
8/15
1614
5
85
50
232
260
373
994
99 1
683
—
982
8/15
1642
6
5 1
30
227
260
249
998
997
82.0
—
99 1
Month 2
8/16
1112
7
11 9
70
285
316
747
984
965
91 7
_
974
8/16
1138
8
85
50
288
316
498
988
978
945
—
983
8/16
1303
9
5 1
30
282
316
249
998
996
992
—
997
9/17
1420
1
12 1
71
337
371
747
994
997
965
969
995
9/17
1445
2
85
50
335
371
809
995
999
990
973
996
9/17
1545
3
5 1
30
326
371
373
999
999
996
974
999
9/18
0925
4
11 7
69
285
316
747
982
979
935
88 1
978
9/18
0957
5
85
50
288
316
498
989
988
958
840
989
9/18
1005
6
49
29
285
313
249
993
994
99 1
980
993
9/18
1208
7
11 7
69
232
260
622
969
970
548
347
95 1
9/18
1253
a
85
50
229
263
373
98 1
972
598
580
959
9/18
13S7
9
51
30
241
257
249
99 7
998
933
927
994
Table 3. Pilot Test Data Summary, Months 3 and 5
Test
Date
Time
Measurement
Flow Rate Irrf/h)
Space Velocity x WOO
Catalyst Inlet Temp I°CI
Catalyst Outlet Temp I°C)
Catalyst Press Drop (Pal
Removal %
Ethanol
N-Propanol
N-Propyl Acetate
Heptane
Total
Total Orgamcs"
"A verage of three or more tests
**As analyzed
Month 3
10/10
*
1
119
70
337
371
647
983
999
962
—
989
977
10/10
*
2
85
50
337
37?
498
99 1
999
996
—
995
980
to/w
*
3
51
30
327
362
299
998
999
997
—
999
980
10/10
*
4
119
70
279
316
647
972
963
865
833
962
943
1O/10
*
5
85
50
285
316
498
980
973
930
638
973
950
10/10
"
6
5 1
30
271
316
249
997
998
985
977
996
952
10/10
*
7
119
70
238
266
622
957
950
529
577
930
826
10/10
*
8
85
50
230
260
373
976
972
51 0
620
959
858
1O/10
'
9
5 1
30
232
260
249
997
997
61 5
780
989
875
12/11
1458
1
119
70
330
371
560
987
986
962
—
985
12/11
1615
2
85
50
330
371
436
995
995
998
—
99 5
12/12
1019
3
5 1
30
319
365
249
998
998
998
990
998
Month 5
12/12
1117
4
11 9
70
260
321
498
978
973
850
853
96.9
12/12
1230
5
85
50
260
319
373
989
988
93 1
91 9
985
12/12
1318
6
5 1
30
252
319
249
997
998
990
983
997
12/12
1453
7
11 9
70
221
260
436
960
955
442
24 1
907
12/12
1515
a
85
50
224
265
324
975
975
596
504
940
12/12
1540
9
5 1
30
221
260
199
996
998
780
770
979
7. Burner
2. Catalyst Bed
3. Heat Exchanger
4. Bypass Valve
5. Stack
6. Bypass Duct
7. Warm Gas Duct
8. Mixing Section
Figure 2. Full scale catalytic system.
4
Dimethyl Ether
Formaldehyde
Nitrogen
Oxygen
2500-4500 ppm
50-500 ppm
90-92%
6-7%
Test Program
The test program began in July 1979,
and is now part of a continuous
monitoring system of the process. The
program was conducted so that samples
were obtained once or twice a week.
Each test reading is an average of two
samples. Grab samples were used on
both the inlet and exhaust from the
abatement system. Difficulty in separat-
ing the hydrocarbon components in the
packed columns of the gas chromato-
graph prevented acceptable data from
being obtained until October; the
program was extended until February
1980 to achieve a 6-month program.
Testing on the full-scale system,
compared to the pilot systems, was
restricted. Very little variation of
temperature or flow was obtained: the
system was abating a plant under
steady state conditions. Minor variations
in feed conditions and plant operating
conditions varied the inlet pollutant
concentrations as shown in the data.
Within these ranges, little or no effect
was found in the outlet or abated
concentrations.
Results
Results of the full-scale demonstration
are provided in Table 4.
Economic Comparison
The economic comparison of a ther-
mal and catalytic system presented here
is limited to a comparison of units with
similar efficiencies of operation, reduc-
tion of pollutants, and material costs.
The capital and annual costs of operating
an air pollution abatement system are (
shown in Table 5.
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Table 4. Full-Scale Test Data Summary
Removal Efficiency (%)
Test Flow Rate Outlet Temp.
Date (rrP/h) (°C) CO CH3OH CH3OCH3 HCHO
1 1/30/79 4945
12/18/79 5149
1/11/80 2957
3/13/80 —
3/18/80 4124
3/25/80 4590
540
432
540
505
510
98.9 97.2 96.8
99.1 98.6 97.2
99.3 99.2 96.6
99.0 93.2 96.6
99.0 98.9 96.7
99.0 97.1 96.5
95.0
98.6
97.0
98.6
99.1
98.7
Overall
97.9
98.5
98.3
97.9
98.3
98.0
Table 5. Capital and Annual Costs {$)
Plastic Printing
Catalytic
Capacity
(m3/h)
Purchase
Installed
Capital Cost
Capital Recovery*
(16.3%)
Catalyst Repl.
Maintenance (2%)
Fuel
Annual Cost
16,992
186,000
186,000
372,000
60,600
19,300
7,500
36,500
123,900
33,984
271,000
271,000
542,000
88.300
38,600
10,800
73,000
210,700
Thermal
16,992
177,000
177.000
354,000
57,700
7,100
107,500
172,300
33,984
247,000
274,000
494,000
80,500
9,900
214,000
304.400
Formaldehyde
Catalytic
8,496
150,000
150,000
300,000
48,900
10,500
6,000
65,400
16,992
207.000
207,000
414,000
67,500
20,900
8,300
96,700
Thermal
8,496
135,000
135,000
270,000
44,000
5,400
198,000
247,400
16,992
174,000
174,000
348,000
56,700
7,000
370,000
433,700
*Capital Recovery Factor of 16.3% is based on 10% interest over a 10-year period.
Norman A. Martin is with 'Engelhard Minerals and Chemicals Corporation,
2655 U.S. Route 22, Union, NJ 07083.
Bruce A. Tichenor is the EPA Project Officer (see below).
The complete report, entitled "Catalytic Incineration of Low Concentration
Organic Vapors," (Order No. PB 81 158 446; Cost: $9.50, 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:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
•&U. S. GOVERNMENT PRINTING OFFICE: I98I/559-092/3328
-------
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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Fees Paid
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