United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park, NC 27711
Research and Development
EPA/600/SR-93/078 June 1993
&EPA Project Summary
Experimental Investigation of
PIC Formation in CFC-12
Incineration
Bruce Springsteen and Garth R. Hassel
Experiments were conducted to de-
termine the effect of flame zone tem-
perature on gas-phase flame formation
and destruction of products of incom-
plete combustion (PICs) during dichlo-
rodifluoromethane (CFC-12) incinera-
tion. The effect of water injection into
the flame zone was also studied. Tests
involved burning CFC-12 in a propane
gas flame. Combustion gas samples
were taken and analyzed for volatile
organic compounds as well as poly-
chlorinated dibenzo-p-dioxin and
dibenzofurans (PCDD/PCDF).
PCDD/PCDF were not detected at
baseline operating conditions (1204°C
and 9.3% CFC-12 by volume in fuel).
Low levels of PCDD/PCDF were de-
tected in the combustion gas at a lower
temperature (913°C). Poor combustion
conditions producing smoke and soot
may have contributed to the formation
of PCDD/PCDF. Low levels of PCDD/
PCDF were also detected at the lower
temperature with water injection into
the flame zone. Flame zone water in-
jection may have a reducing effect on
PCDD/PCDF formation during CFC-12
incineration.
Halogenated PICs including chloro-
methane, vinyl chloride, CFC-11, di-
chloroethane, chloroform, trichloro-
ethane, chlorobenzene, dichloro-
propene, carbon tetrachloride, methyl-
ene chloride, and tetrachloroethene
were detected during CFC-12 incinera-
tion. Aromatic compounds such as ben-
zene, toluene, and xylene were also
detected. Water injection into the flame
zone did not impact PIC formation. Ha-
logenated and non-halogenated PIC
compounds and levels were influenced
by flame zone temperature and com-
bustion efficiency; higher temperature
and lower carbon monoxide (CO) and
total unburned hydrocarbon (THC) flue
gas concentrations resulted in lower
PIC levels. CFC-12 destruction efficien-
cies (DE) of 99.98% were obtained. DEs
were independent of flame zone tem-
perature, stoichiometric ration, or CO
and THC flue gas concentrations.
This Project Summary was developed
by EPA's Air and Energy Engineering
Research Laboratory, Research Tri-
angle Park, NC, to announce key find-
ings 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 bench scale test program was con-
ducted in 1991 by Energy and Environ-
mental Research Corporation (EER) to
characterize combustion emissions from
chlorofluorocarbon (CFC) incineration.
CFC destruction efficiencies of 99.999%
were obtained. Chlorinated and aromatic
products of incomplete combustion (PICs)
were identified in the flue gas. Significant
levels of polychlorinated dibenzo-p-diox-
ins and dibenzofurans (PCDD/PCDF) were
also detected. The high levels of PCDD/
PCDF contrast results from CFC incinera-
tion pilot scale tests conducted recently
by T-Thermal. Preliminary results from T-
Thermal show PCDD/PCDF found at mod-
erate levels in tests with high input of CFC
and were not present in tests with low
CFC input. The T-Thermal tests were per-
Printed on Recycled Paper
-------
formed at higher temperature (1093T) and
with water injection into the combustion
zone. The higher temperature and/or wa-
ter injection were considered as possible
reasons for the difference in PCDD/PCDF
formation measured for these two pro-
grams.
The strong effects of lowering the emis-
sions of chlorinated PICs (chlorobenzenes
in particular) by water injection have re-
cently been demonstrated in a study of
thermal destruction of CFCs. Other re-
sults reported recently by the fundamental
studies of thermal destruction of
chlorohydrocarbons suggest that PIC for-
mation during the incineration of high chlo-
rine content organics, such as CFCs, oc-
curs through complex reactions. Such re-
actions will likely occur in the oxygen-
Propane
deficient regions of the incineration flame
zone created by incomplete mixing.
Thermal incineration is the only tech-
nology available at a commercial scale for
CFC destruction. Therefore, it is desirable
to evaluate the risks associated with its
use. Because no significant CFC incinera-
tion test burn data are available, this test
program provides further information on
the formation of PICs and their control
during CFC incineration. Specifically, this
program investigated:
• Effects of incineration flame zone tem-
perature on the combustion gas char-
acteristics (in particular the range of
temperatures which lead to gas-phase
formation of PCDD/PCDF) in order to
determine the relation between com-
Insulation and
refractory
CEMS (O2, CO2,
THC, CO, NO)
oooooo
Water injection
nozzle
O T-2
Access ports (6)
-Q: T-
Refractory brick port
plugs
EPA Method 23
(PCDD/PCDF)
•O T 4
»
0030 (PICs)
To sodium hydroxide
yenturi scrubber,
induced draft fan,
and exhaust stack
Figure 1. Experimental controlled temperature tower (CTT) facility
bustion gas characteristics and com-
bustion conditions, and
• Effects of supplying additional (OH-)
into the flame zone through water in-
jection on PIC and PCDD/PCDF for-
mation.
Experimental
EER's Controlled Temperature Tower
(CTT) furnace was used for this study.
The furnace is shown in Figure 1. This
pilot scale facility has an inside diameter
(ID) of 8 in.* and an overall furnace length
of 94 in. The reactor entry consists of an
18 in. long quarl that diverges from 2 in.
at the burner to the full 8 in. ID.
The test matrix is shown in Table 1.
Test 1 involved firing only propane fuel to
evaluate the background organic species
that are attributable to the fuel and sys-
tem. The rest of the tests involved mixing
dichlorodifluoromethane (CFC-12) directly
with propane upstream of the burner gun.
Test 2 was performed with a mixture of
9.3% CFC-12 and 90.7% propane fuel by
volume at the same baseline temperature
as Test 1. The temperature of Test 3 was
based on PCDD/PCDF results from Test
2. If PCDD/PCDF levels were considered
to be significantly high, Test 3 would have
been performed at a higher temperature
than baseline; however, because levels
were low, Test 3 was performed at a lower
temperature. Test 4 was performed at the
same temperature as Test 3 with the ad-
dition of water injection into the flame zone
to determine the potential PIC and PCDD/
PCDF formation reduction effect.
Flue gas temperatures were measured
at the four different furnace locations,
shown in Figure 1. Temperatures were
measured with K-type thermocouples (TC).
Also, pre- and post-test temperatures were
measured using a suction pyrometer con-
taining a B-type TC to get more accurate
high temperature readings.
Flue gas was sampled for volatile or-
ganics using EPA SW 846 Method 0030
and PCDD/PCDF using EPA Method 23
during each test. Also, the flue gas was
monitored for combustion products (O2,
CO2, CO, NO, and THC) using a continu-
ous emissions monitoring system (CEMS).
The sampling locations are shown in Fig-
ure 1.
Results
Individual test conditions, including CFC-
12/fuel injection rate, water injection rate,
furnace firing rate, flame stoichiometry,
flue gas composition (O2, CO2, NO, CO,
* 1 in. = 2.54 cm.
-------
Table 1. Test Matrix
Test No.
1
2
3
4
'CFC-12/fuel ratio
(volume %)
0
9.3
10.0
10.0
Temperature
baseline
baseline
high or low '
high or low '
Water injection
no
no
no
yes
Chosen temperature depends on PCDD/PCDF results from Test 2
THC, and moisture content), and flue gas
temperature, are summarized in Table 2.
PCDD/PCDF flue gas levels are given
in Table 3, both as flue gas concentration
and generation rate based on CFC-12
burning rate. PCDD/PCDF were not de-
tected in Test 1 (system blank) or Test 2
(baseline condition of 1204°C with 9.3%
CFC-12 by volume in fuel).
Low concentrations of octa-CDD (6.2
ng/dscm) and octa-CDF (97 ng/dscm) were
detected during Test 3. Poor combustion
conditions were present during Test 3.
Flame smoking and sooting was present
due to reduced excess oxygen, low tem-
perature, and apparently insufficient fuel/
air mixing; a layer of fine black particulate
(soot) was observed in the flue gas sam-
pling train equipment. High concentrations
of CO (270 ppmv) and THC (540 ppmv)
were present in the flue gas.
Low concentrations of hepta-CDF (6.7
ng/dscm) and octa-CDF (14 ng/dscm) were
detected in Test 4 which was performed
with water injection into the flame zone.
Sampling train filters and lines were clean;
no particulate buildup or discoloration of
the sampling equipment was observed.
High levels of CO (670 ppmv) and THC
(650 ppmv) were present.
PICs are given in Table 4. Many chlori-
nated PICs were detected at the baseline
conditions (Test 2), including chlorinated
hydrocarbons (CHCs) such as
chloromethane, dichloroethane, methylene
chloride, chloroform, and carbon tetrachlo-
ride. CFC-11 was also detected. Non-ha-
logenated aromatics including toluene, xy-
lene, and benzene were also present.
More species and higher concentrations
of chlorinated PICs were detected during
Tests 3 and 4 compared with the baseline
Test 2. PICs formed during the lower tem-
perature Tests 3 and 4 included those
detected during the baseline Test 2; also,
CHCs such as chloroethane, vinyl chlo-
ride, trichloroethane, tetrachloroethene,
dichloropropene, and chlorobenzene were
identified. Higher levels of benzene were
detected in the lower-temperature Tests 3
and 4.
Tentatively identified compounds (TICs)
identified from the EPA SW 846 Method
0030 sampling train are given in Table 5.
Relatively high levels of dichlorodifluo-
romethane (CFC-12) were detected in the
flue gas during all three tests which in-
volved CFC-12 incineration. CFC-12 DEs
of 99.982, 99.985, and 99.980% were ob-
served for Tests 2, 3, and 4, respectively.
Other halogenated TICs that were identi-
fied in Tests 3 and 4 include difluoro-
dimethylsilane, fluorotrimethylsilane, and
chloropropene.
Conclusions
PCDD/PCDF were not detected at fur-
nace baseline temperature and operating
conditions (1204°C, 15.8 kW, and 9.3%
CFC-12 by volume in fuel). At these CFC-
12 incineration conditions, there is no ten-
dency for PCDD/PCDF to form within the
primary flame. PCDD/PCDF levels de-
tected by another study during CFC-12
incineration were very likely due to cata-
lytic formation in the metal exhaust duct in
the presence of copper at a flue gas tem-
perature range of 149-371 °C.
Low levels of PCDD/PCDF were de-
tected at lower temperature operating con-
ditions (954°C, 9.38 kW). Poor combus-
tion conditions producing smoke and soot
may have contributed to the formation of
PCDD/PCDF. Low levels of PCDD/PCDF
were also detected at lower temperatures
with water injection into the flame zone.
PCDD/PCDF formation may be attribut-
able to homogeneous flame gas-phase
reactions or heterogeneous reactions be-
tween precursors on soot and fine par-
ticulate matter. Water injection reduced
PCDD/PCDF levels by a factor of 5; how-
ever poor combustion conditions during
the test without water may have been
responsible for the higher levels of PCDD/
PCDF.
Halogenated PICs such as chloro-
methane, vinyl chloride, CFC-11, dichloro-
ethene, chloroform, trichloroethane, car-
bon tetrachloride, and tetrachloroethene
were observed during CFC-12 incinera-
tion. Water injection into the flame zone
did not have an effect on volatile PIC
formation. Halogenated and non-haloge-
nated PIC species and concentration lev-
els were influenced by flame conditions;
higher temperature and lower CO and THC
flue gas concentrations resulted in forma-
tion of a fewer number of PIC species at
lower concentrations. CFC-12 DEs of
99.98% were obtained. DEs were inde-
pendent of flame zone temperature, sto-
ichiometric ratio, or CO and THC flue gas
concentrations.
Table 2. Summary of Test Conditions
Primary flame
Flue gas composition
Flue gas temperature
CFC-12
in fuel
vol
Test No. %
1 0.0
2 9.3
3 10.0
4 10.0
Wt
0.0
22.0
23.4
23.4
Water
injection
g/min
0
0
0
40
Firing
rate
MM
Btu/hr "
0.054
0.054
0.032
0.032
SRb
1.4
1.4
1.1
1.7
* Btu/hr = 0.293 W.
b Stoichiometric ratio.
c @7%O2
d °C = 5/9(°F-32).
dry
vol%
6.1
6.1
2.0
9.4
C02
dry
vol%c
7.6
7.2
6.6
6.1
CO
dry
ppmvc
58
56
267
671
NO
dry
ppmvc
66
63
30
29
THC
dry
ppmv0
11
12
540
650
H20
wet
vol%
6.0
8.4
3.5
7.1
T-1
T-2
T-3
T-4
opd op op op
2200
2130
1675
1400
1850
1700
1086
1040
1500
1430
860
795
1200
1130
716
660
-------
Table 3. Summary of PCDD/PCDF Flue Gas Levels
Flue gas concentration (ng/dscm)'
Generation rate (ng/g of CFC-12)
Species
PCDD
TCDD
PeCDD
HxCDD
HpCDD
OCDD
Total PCDD
PCDF
TCDF
PeCDF
HxCDF
HpCDF
OCDF
Total PCDF
Total PCDD/PCDF
Testl
nd"
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
Test 2
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
Test3
nd
nd
nd
nd
6.2
6.2
nd
nd
nd
nd
97
97
103
Test 4
nd
nd
nd
nd
nd
nd
nd
nd
nd
6.7
14
21
21
Testl
n/a°
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
Test 2
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
Tests
nd
nd
nd
nd
0.47
0.47
nd
nd
nd
nd
7.4
7.4
7.9
Test 4
nd
nd
nd
nd
nd
nd
nd
nd
nd
0.5
1.1
1.6
1.6
@ 7% O2.
Not detected in sample (below method detection limit).
Not appropriate.
Table 4. Summary of PIC Flue Gas Levels •
Flue Gas Concentration (\ig/dscm)'
Generation Rate (\ng/g of CFC-12)
Compound
Chloromethane
Vinyl Chloride
Bromomethane
Chloroethane
Trichlorofluoromethane
1, 1 -Dichloroethene
Acetone
Methylene Chloride
Trans- 1, 2-Dichloroethene
1, 1 -Dichloroethane
Chloroform
1, 1, 1 -Trichloroethane
Carbon Tetrachloride
Benzene
1 ,2-Dichloroethane
Trichloroethene
1 ,2-Dichloropropane
Bromodichloromethane
Cis- 1, 3-Dichloropropene
Toluene
Trans- 1, 3-Dichloropropene
1, 1 ,2-Trichloroethane
Te trachloroe thene
Dibromochloromethane
Chlorobenzene
Ethyl Benzene
M,P-Xylene
O-Xylene
Testl
150
ndc
2.6
nd
51
0.8
18
110
nd
nd
nd
1.3
nd
15
nd
nd
nd
nd
nd
20
nd
nd
nd
nd
nd
nd
4.15
nd
Test 2
1600
nd
8
nd
130
2.3
8.4
78
nd
nd
6.5
nd
5.6
13
nd
nd
nd
nd
nd
16
nd
nd
nd
nd
nd
nd
1.7
nd
Tests
1700
234
4.4
5.5
4.1
5
50
130
nd
nd
14
2.2
7.9
650
nd
nd
nd
nd
1.4
49
0.87
nd
2.5
nd
2.8
0.82
2
0.7
Test 4
1100
170
1.5
4.2
6.8
8.7
9.2
15
nd
nd
10.5
1.8
8.5
580
nd
nd
nd
nd
6.6
27
1.9
nd
4.4
0.72
2.7
0.81
2.1
0.34
Testl
n/a"
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
Test 2
122
nd
0.6
nd
9.5
0.2
0.6
6
nd
nd
0.5
nd
0.4
0.9
nd
nd
nd
nd
nd
1.2
nd
nd
nd
nd
nd
nd
0.1
nd
Tests
130
1.8
0.3
0.4
0.3
0.4
3.8
9.9
nd
nd
1.1
0.2
0.6
49
nd
nd
nd
nd
0.1
3.7
0.07
nd
0.2
nd
0.2
0.06
0.15
0.05
Test 4
85
13
0.1
0.32
0.53
0.7
0.7
8.9
nd
nd
0.81
0.14
0.65
45
nd
nd
nd
nd
0.5
2
0.15
nd
0.34
0.06
0.2
0.06
0.16
0.03
-------
Table 4. Summary of PIC Flue Gas Levels' (continued)
Flue Gas Concentration (\ig/dscm)"
Generation Rate fag/g of CFC-12)
Compound
Bromoform
1, 1 ,2,2-Tetrachloroethane
1 ,2-Dichlorobenzene
1 , 4-Dichlorobenzene
1 ,3-Dichlorobenzene
Test 1
nd
nd
nd
nd
nd
Test 2
nd
nd
nd
nd
nd
Test3
nd
nd
nd
nd
nd
Test 4
nd
nd
nd
nd
nd
Testl
n/a
n/a
n/a
n/a
n/a
Test 2
nd
nd
nd
nd
nd
Tests
nd
nd
nd
nd
nd
Test 4
nd
nd
nd
nd
nd
From SW 486 Method 0030 flue gas sampling train and SW 846 8240 Analytical Method.
@ 7% O2.
Not detected in sample (below Method detection limit).
Not appropriate.
Table 5. Summary of TIC Flue Gas Levels'
Flue Gas Concentration (\ig/dscm)b
From SW 846 Method 0030 flue gas sampling train.
@ 7% O2.
Not appropriate.
Generation Rate (\ig/g of CFC-12)
Compound
Dichlorodifluoromethane
Difluorodimethylsilane
Methylpropane
Sulfur Dioxide
Methanethiol
Fluorotrimethylsilane
Dichloroethyl Ether
Chlorotrimethylsilane
Thiobismethane
Chloropropene
Methoxytrimethylsilane
Hexane
Dihydrofuran
Methylfuran
Nitromethane
Ethylbenzene
Me thylethylbenzene
Trifluoro Ester
Naphthalene
Testl
78
12
33
26
22
24
3.3
7.3
1.9
4.8
Test 2
2400
798
98
430
28
57
9
11
3.9
Test3
1900
10
4.6
15
21
26
Test 4
2600
12
41
51
18
53
1
10
Testl
n/a°
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
n/a
Test 2 Tests
180 150
60 0.8
0.4
74
32 1.1
2.1
4.3
0.7
1.6
0.8
0.3
2
Test 4
200
0.9
3.1
3.9
1.4
4.1
0.07
0.8
•ffV.8. GOVERNMENT PRINTING OFFICE: 1993 - 75»47I/«M33
-------
-------
-------
B. Springsteen and G.R. Hasset are with Energy and Environmental Research
Corp., Santa Ana, CA 92705.
C.W. Lee is the EPA Project Officer (see below).
The complete report, entitled "Experimental Investigation of PIC Formation in CFC-
12 Incineration," (Order No. PB93-191294/AS;Cost: $27.00, 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:
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati, OH 45268
BULK RATE
POSTAGE & FEES PAID
EPA PERMIT NO. G-35
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Penalty for Private Use $300
EPA/600/SR-93/078
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