United States
Environmental Protection
Agency
Research and Development
Air and Energy Engineering
Research Laboratory
Research triangle Park NC 27711
JEPA/600/S7-91/010 Jan. 1992
EPA Project Summary
Experimental Investigation of PIC
Formation in CFG Incineration
Garth R. Hassel
The purpose of this study was the
collection of combustion emission char-
acterization data from chiorofluorocar-
bon (CFC) incineration. A bench scale
test program to provide emission char-
acterization data from CFC incineration,
with emphasis on products of incom-
plete combustion (PIC) formation, was
developed and performed. Tests in-
volved separately metering CFC-11 and
-12 into a propane gas primary flame.
Propane also fueled an afterburner. Si-
multaneous combustion gas samples
were taken upstream and downstream
of the afterburner. The gas samples were
analyzed for the CFCs to determine the
destruction efficiencies (DEs) of the
CFCs and for the major PICs from each
CFC. Sampling was performed one time
to screen for polychlorinated dibenzo-
p-dioxins (PCDDs), polychlorinated di-
benzofurans (PCDFs), and polycyclic
aromatic hydrocarbons (PAHs) while
incinerating CFC-12. Toluene and xy-
lene were the two most frequently oc-
curring PICs in this study. Most of the
PICs identified were non-halogenated.
PIC concentrations were independent
of the concentration of CFC in the fuel.
Flammability limits were 39 volume per-
cent CFC-11 and 58 volume percent
CFC-12 in propane. DEs of at least
99.999% can be repeatedly attained for
both CFC-11 and -12 even from a rela-
tively low temperature flame. The use of
an afterburner is not necessary to at-
tain high DEs of CFC-11 and-12. DEs of
greater than 99.999% still allow for high
generation of PCDD/PCDF. Extensive
PCDD/PCDF formation when burning
CFC-12 was apparently independent of
entrained particulate matter. The wide
variety of PICs, ranging from aliphatic
to aromatic species, observed in the
study is a strong indication that CFC
destruction during thermal incineration
occurs through complex reaction path-
ways.
This Project Summary was devel-
oped by EPA's Air and Energy Engi-
neering Research Laboratory, Research
Triangle 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
Chlorofluorocarbons (CFCs) are impli-
cated in the depletion of stratospheric
ozone, and are also contributors to global
warming. As a result of the Montreal Proto-
col and other pending international and
national agreements that will curtail the
production of the traditional CFCs and
halons, it may be necessary to thermally
destroy considerable quantities of these
materials in order to reduce their current
inventory. Thermal incineration is the only
technology available at commercial scale
for CFC destruction. Incineration may be
an appropriate technology in helping to
reduce the global inventories, if no signifi-
cant health or environmental risks result
from the combustion emissions of the
CFCs.
The environmental concerns resulting
from CFC incineration include possible for-
mation of potentially toxic products of in-
Printed on Recycled Paper -
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complete combustion (PICs), and acid and
halogen gas emissions. PIC formation, in
general, involves poorly understood phe-
nomena associated with waste incinera-
tion, which is further complicated for CFC
incineration processes since no data on
PIC formation are available.
The purpose of this study was the col-
lection of combustion emission character-
ization data from CFC incineration. The
objectives were to evaluate thermal incin-
eration as one of the appropriate technolo-
gies for the safe disposal of CFCs, and to
improve the CFC incineration technology
by Identifying the incinerator designs and
operating conditions which minimize the
formation of hazardous PICs. To achieve
the goals of this project, information was
obtained on the relationship between PIC
emissions and combustion conditions us-
ing supplemental fuels which are employed
in CFC incineration. Since no significant
test burn data are available, a test pro-
gram to provide emission characterization
data from CFC incineration, with emphasis
placed on PIC formation, was developed
and performed. The goal of the study was
to provide information on which incinerator
designs and operating conditions are
needed to maximize CFC destruction effi-
ciency and minimize PIC formation. Users
of data and findings in this report should
note that test results and conclusions are
based on experimental, not validated, pro-
cedures. A QA program implemented on
this project is reported in Appendix E of the
Final Report.
Experimental
The turbulent flame reactor (TFR) used
as the primary combustor for this study
was a swirling air/liquid spray or gas injec-
tor burner firing into a 12 in.* ID by 24 in.
long enclosure. Following the TFR was an
afterburner (AB) consisting of a 12 in. ID
refractory lined chamber with three fuel/air
injectors near its base. At the exit of the AB
was a 4 in. ID 304 stainless steel duct that
wound about 30 ft** before reaching a
scrubber.
Tests involved separate metering of
CFC-11 and -12 into a propane gas flame.
Flammability limits (maximum volume % in
the fuel) were determined for both CFCs.
The test matrix is presented in Table 1.
The baseline condition (medium concen-
tration of CFC-12 in the fuel) was repeated
twice, yielding triplicate data at baseline
conditions.
Combustion gas samples were taken
upstream and downstream of the after-
Table 1. Target Volumetric Concen-
tration of CFC in TFR Fuel
CFC-
12
11
2%
X
X
10%
XXX'
20%
X
X
Baseline condition, tested in triplicate plus
one-time sampling for dioxin.
burner simultaneously using EPA Method
18, "Measurement of Gaseous Organic
Compound Emissions by Gas Chromatog-
raphy." The gas samples were analyzed
for the CFCs to determine the destruction
efficiencies of the CFCs. An attempt was
also made at quantifying many of the ma-
jor PICs from each CFC. A system blank
was taken to evaluate the background or-
ganic species produced by the propane
fuel. Sampling was performed one time at
the baseline condition with the objective of
screening for PCDD/PCDF and PAH while
incinerating CFCs. Sampling was per-
formed according to California Air Re-
sources Board Method 428, "Determination
of Polychlorinated Dibenzo-p-dioxin
(PCDD), Polychlorinated Dibenzofuran
(PCDF), and Polychlorinated Biphenyl
Emissions from Stationary Sources." The
sample was taken downstream of the af-
terburner.
Temperatures were measured by ther-
mocouples protruding to the centerline of
the furnace. Pretest temperatures were
also taken using a suction pyrometer. The
flue gas was continuously monitored down-
stream of the AB for combustion products.
The continuous monitoring system (CMS)
included oxygen (O2), carbon dioxide (CO,,),
carbon monoxide (CO), nitrogen oxides
(NOX) as nitric oxide (NO), and total
unburned hydrocarbons (THCs).
The TFR was fired at 73,000 Btu/hr* at
a stoichiometric ratio of 1.1 (2% O2). Com-
bustion air for the primary flame was pre-
heated to 375°F.** The target AB
conditioners were 1800°F and 7% excess
O2. Attaining 1800°F at 7% O2 required
that AB be fired at 91,000 Btu/hr, with the
O2 being supplied by compressed O2 in-
stead of air.
Results
Flammability limits were determined by
slowly increasing the flow of CFC into the
steady stream of propane fuel leading to
the TFR until the flame was extinguished.
11n. • 2.54 cm
1 ft-0.3
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DEs of greater than 99.999% still allow
for high generation of PCDD/PCDF. Ex-
tensive PCDD/PCDF formation when burn-
ing CFC-12 was apparently independent
of entrained particulate matter. PCDF con-
centration was 6.6 times the PCDD con-
centration.
Most PICs are non-halogenated spe-
cies. PIC concentrations were indepen-
dent of the concentration of CFC in the
fuel. PAHs were not detected. The wide
variety of PICs, ranging from aliphatic to
aromatic species, observed in the study is
a strong indication that CFG destruction
during thermal incineration occurs through
complex reaction pathways.
TC-3Q
Mizzou
Refractory
Block Mix
Insulation TC-2&
t
Secondary EPA Method 18
and CMS Sample Ports
AB Pyrometer Port
Secondary Fuel and
Oz Injectors
1784°F, 0.7Sec at
AB Pyrometer
Sampling Port
Primary EPA Method
18 Sample Port
TFR Pyrometer Port
Ignition Port
Variable Swirl
Burner
Figure 1. System diagram indicating average operating temperatures and cumulative AB residence times.
3
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Tabla 2. Destruction Efficiencies and Tentatively Identified Products of Incomplete Combustion
CFC-12
Vol. % CFG in Fuel 8.3 8.3
8.3
Primary Rame
CFG, ngJL
DE,%
T1Cs,*ng/L
Secondary Flama
CFC, ng/L
Overall DE,%
TlCs,ngJL
<63
>99.9996
ND2
<63
>99.9994
unknown, 69
toluene, 31
xylene, 19
<63
>99.9996
CFC-11,81
<63
>99.9994
hexafluoropropene, 781
unknown HC, 1000
<63
>99.9996
ND
>99.9994
hexafluoropropene, 2400
Unknown compound, 494
carbon disulfide/
trichlorotrifluoroethane, 438
Vol. % CFC in Fuel
Primary Flame
CFG, ngfi-
DE, %
TlGs'ngn.
14
93
99.9997
CFC-11, 81
unknown HCs, 44, 256, 25
unknown compound, 225
toluene, 488
bicyclo[4,2,0]octa-1,2,5-triene, 644
CFC-12
1.3
<63
>99.997
chloroform, 213
pentane,225
toluene, 50
xylene, 50
Secondary Flame
CFC, ngIL
OvoraHDE, %
TICs,ng/L
<63
>99.9997
CFC-11, 250
methyl propene, 550
pentane, 581
trichlorotrifluoroethane, 325
toluene, 219
ethyl benzene, 113
xylene, 369
<63
>99.996
chloroform, 213
System
Blank
Vol. % CFC in Fuel
Secondary Flame
CFG, ng/l
Overall DE, %
7IGs,ngA.
<63
NA
ND
CFC-11
1.3
13
Primary Rama
CFC, ngn.
DE, %
TICs,'ng/L
<63
NA3
ND2
181
99.993
unknown HCs, 550, 806, 5600
^4
<63
>99.9998
ND
trichlorotrifluoroethane, 413
cyclohexane, 556
ethylbenzene, 144
xylene, 450
<63
>99.997
unknown HCs, 44,81
toluene, 19
xylene, 31
<63
>99.9997
ND
' tentatively Identified compounds
* not dotoctod
* not appKcabla
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Table 3. PCDD/PCDF Results for 8.3% by Volume CFC- 12 in Propane
Flue Gas
Concentration
Generation
Rate
\ig/gofCFC
Total PCDD
Total PCDF
ars
20.70
1.82
PCDD/PCDF
23.80
2.09
•fru.S. GOVERNMENT PRINTING OFFICE: 1992-648-080/40148
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r
Garth R. Hassefls with Energy and Environmental Research Corporation, Irvine, CA
92718.
C.W. Lee is the EPA Project Officer, (see below).
The complete report, entitled "Experimental Investigation of PIC Formation in CFC
Incineration" (Order No. PB92-126952/AS; Cost: $26.00, 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
Official Business
Penalty for Private Use $300
EPA/600/S7-91/010
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