United States
Environmental Protection
Agency
Hazardous Waste Engineering
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-86/038 Sept. 1986
Project Summary
Interim Report on Non-Flame
Hazardous Waste Thermal
Destruction
M. Malanchuk
The thermal decomposition of toxic
organic compounds is being investi-
gated in a laboratory system dedicated
to the non-flame mode/zone of the
combustion process. The early phase of
this study has focused on three com-
pounds: pentachloronitrobenzene (a
fungicide), chloroform (a ubiquitous in-
dustrial compound) and heptane.
The results of the third compound,
heptane, are preliminary to those
sought for a mixture of two or more
compounds such as chloroform, a toxic
substance, and heptane, a combustion
process fuel.
The data of this report were collected
during the period January - June 1985.
This Project Summary was devel-
oped by EPA's Hazardous Waste Engi-
neering Research Laboratory, Cincin-
nati, OH, to announce key findings of
the research project that Is fully docu-
mented in a separate report of the same
title (see Project Report orderirtg infor-
mation at back).
Introduction
In the thermal destruction of haz-
ardous organic waste material; the in-
teractions of the gaseous components
in the post-flame or the non-flame zone
of the combustion process make an im-
portant contribution to the overall re-
sults. The thermal decomposition in
those zones can range from simple py-
rolysis in an oxygen-deficient atmos-
phere as might occur in a boiler, to a
thermal-oxidative treatment with a con-
siderable excess of oxygen as can occur
in a liquid injection incinerator sup-
ported by a secondary combustion zone
or supply of air.
A laboratory unit, identified as the
Thermal Decomposition Unit-Gas Chro-
matograph (TDU-GC), has been used to
investigate key thermal decomposition
factors of the post-flame zone, such as
time of exposure and temperature, and
their impact upon the effluent decom-
position products. The TDU-GC was de-
veloped at the University of Dayton Re-
search Institute (UDRI) and has been
applied by Institute personnel over the
past several years to study many differ-
ent organic compounds.
The TDU-GC at the U.S. Environmen-
tal Protection Agency (EPA) Center Hill
Facility has been used thus far to inves-
tigate pentachloronitrobenzene (PCNB)
and also chloroform in order to deter-
mine the level of reproducibility as mea-
sured by the comparison of these find-
ings to those reported by the UDRI for
the same compounds.
The thermal decomposition of hep-
tane was also investigated in a prelimi-
nary step to determine the effect of its
presence upon chloroform decomposi-
tion; this simulates the use of heptane
as a co-fired fuel or solvent for a haz-
ardous waste constituent such as chlo-
roform.
Experimental Procedure
The principal equipment used in this
study was the TDU-GC system, a closed
in-line system consisting of two basic
units, the thermal reactor and the ana-
lyzer, a gas chromatograph. These units
are shown in Figure 1.
1. The thermal reactor incorporates a
capillary quartz tube within a furnace
with three heating zones that are inde-
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Sample
Figure 1. Basic schematic of TDU-GC system.
pendently controlled to produce tem-
peratures up to 1150°C in the central
zone for thermally decomposing the
sample compound in its gaseous state.
A tubular quartz extension at the en-
trance of the furnace transfers the feed
gas from the larger-bore sample inser-
tion chamber. That chamber is fitted
with any one of several probes adapted
to handle gas, liquid or solid samples. A
temperature programmer controls the
heating jacket on the insertion chamber,
for converting the liquid and solid sam-
ples to the vapor phase at selected ele-
vated temperatures. The vapor or gas is
conveyed to the reactor by a controlled
flow of carrier gas which is selected ac-
cording to the nature of the atmosphere
required in the high-temperature zone
of the reactor. According to the temper-
ature and pressure measured in the re-
actor tube, the carrier gas flow is regu-
lated at the instrument console to result
in a precise residence time of the vapor-
ized/gaseous sample in the closely-
controlled high-temperature zone.
The gaseous emissions from the reac-
tor pass through a capillary tube into an
in-line tubular trap controlled to sub-
ambient temperatures as low as -50°C
and colder. The trap is located inside the
wall of the gas chromatograph (GC) and
is very short (several mm) section of the
extension of the GC capillary column
into the 30:1 splitter tubing.
2. The gas chromatograph is fitted
with a fused silica capillary column
leading to a flame ionization detector
(FID). Heating the trap transfers, via the
30:1 splitter, the smaller stream of
trapped emissions sample to the front
end of the capillary column which itself
is at the sub-ambient temperature.
Upon injection of the sample into the
GC, as initiated by the switch on the
supporting computer, the temperature
program for the capillary column con-
trols the separation of the components
of the reactor emissions sample and
their ensuing detection and measure-
ment by the FID.
The computer coupled with a re-
corder provides a means of storing the
output from the FID and of depicting it
in a chromatogram as well as in a tabu-
lation of the various peak areas.
3. The Principal Organic Hazardous
Constituent (POHC) material under in-
vestigation was introduced into the in-
sertion chamber as a gas, liquid or solid.
The more volatile, low molecular
weight compounds were generally fed
by syringe to the TDU-GC system as
gaseous samples prepared at known
concentrations.
For various organic liquids, nanoliter
quantities were injected directly into the
insertion chamber where the sample
was converted to the vapor form by a
programmed temperature increase that
provided transfer by the carrier gas into
the thermal reactor.
4. Samples of organic solids were de-
posited as measured amounts in solu-
tion onto the end of the "solids" probe.
Evaporation of the solvent left a residue
which in the confines of the insertion
chamber was transformed to the vapor
state for transfer into the thermal reac-
tor by the carrier gas.
Results
TDU-GC test run series were made on
(1) pentachloronitrobenzene (PCNB) as
a single component feed, (2) chloro-
form, also as a single component feed,
and (3) chloroform in solution with
"fuel" heptane constituting the bulk of
the organic feed.
The results for PCNB are presented in
Figure 2 as a plot of reactor effluent con-
centrations vs. exposure temperature.
Curve A in that figure shows the in-
crease in decomposition of the POHC
material, the feed PCNB, in an oxidative
atmosphere with increasing tempera-
ture. Curves B, C, D present the concen-
trations for the more abundant PICs that
were produced in the thermal treatment
process. PIC component B was subse-
quently identified as hexachloroben-
zene (HCB).
Chloroform in the predominantly oxi-
dative atmosphere produced major
quantities of several PICs. These are
identified in Figure 3 as hexachloro-
ethane (C2CI6), tetrachloroethylene
(C2CI4) and carbon tetrachloride (CCI4).
The highest reactor temperature inves-
tigated was 625°C, at which level essen-
tially total destruction (>99.99% DE) of
the POHC (chloroform) had occurred.
Chloroform as one of several organic
compounds that might be found in a
feed mixture in an actual incinerator,
was selected for mixture (solution) in
"fuel" heptane to undergo thermal de-
composition treatment. Initially, hep-
tane alone was investigated at various
temperatures to characterize its decom-
position, Figure 4. The high tempera-
ture of 675° was considered adequate to
bracket the high for total chloroform de-
composition, namely the 625°C ob-
served in Figure 3. When a three weight
percent of chloroform was added to the
heptane, its products, as observed for
pure chloroform in Figure 3, were com-
pletely masked by the peaks of
"pollutant" components present in the
heptane. Those pollutants were domi-
nant even at a low, non-decomposing
temperature, 300°C, for heptane.
Discussion
The test runs with PCNB and with
pure chloroform were made primarily
to check for inter-laboratory reproduci-
bility.
The PCNB results from the present
study yielded a decomposition curve for
PCNB that closely matched that re-
ported by the University of Dayton
Research Institute (UDRI). The hex-
achlorobenzene formation/decomposi-
tion profile, Curve B of Figure 2 also
closely matched that reported by UDRI.
The results for pure chloroform
showed very good agreement with
those presented by UDRI in some of
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Exposure Temperature, °C
Thermal treatment of pentachloronitrobemene. PCNB (i, = 2.0 sec).
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Exposure Temperature, °C
Figure 3. Thermal treatment of chloroform (i, = 2.0 sec).
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their earlier work with toxic organic
compounds, not only for the feed mate-
rial but also for the three major PICs
shown in Figure 3. It is evident, from the
chlorine-saturated state of each of the
PIC molecules (CCI4, C2C\4, C2C\e) identi-
fied in major concentrations, that the
hydrogen atom present in the parent
chloroform molecule is being thor-
oughly eliminated from the organic
product species. Figure 5 presents the
data for chloroform on a linear scale, in
contrast to the semi-log scale of Fig-
ure 3; it readily shows the comparative
amounts of compounds present in the
emissions from the thermal reactor. It is
evident from Figure 5 that the concen-
tration of the hexachloroethane (C2Cle)
has peaked at a temperature (~570°C)
where the tetrachloroethylene (C2CI4)
and carbon tetrachloride (CCI4) are only
beginning to form.
In light of the effective masking of the
GC peaks for chloroform and its prod-
ucts by the heptane source pollutants,
the results are limited to a decomposi-
tion profile for heptane. Figure 4. The
moderate slope of the decomposition
curve at the high temperatures indi-
cates the more refractory nature of the
compound, so that by 675°C, a full 125°C
after the start of decomposition at
550°C, a little more than one percent of
the heptane still persists in the effluent
stream from the reactor.
Conclusions and
Recommendations
The Thermal Decomposition Unit-Gas
Chromatograph (TDU-GC) system has
been used in obtaining thermal decom-
position profiles for several organic
compounds associated with the inciner-
ation of toxic/hazardous organic waste
substances.
The system has been used success-
fully to demonstrate reproducibility of
results consistent with the findings of
other investigations using similar
equipment.
From the experience with heptane as
a component in the feed, it appears nec-
essary, for accurate measurement of
the effects of feed composition, to limit
mixtures to a very few, perhaps only
two, compounds that are individually
"clean" in any GC analysis.
For more fully characterizing the ther-
mal reactor emissions with respect to
PICs, more extensive procedures in-
volving additional instrumentation is
needed to identify and quantify PIC
compounds. A Mass Selective Detector
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0.
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0.1
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0.01
200 300 400 500 600
Exposure Temperature, °C
Figure 4. Thermal treatment of heptane (i, = 2.0 sec).
700 800 900
(MSD) dedicated to the TDU-GC system
is the instrument of choice, both for ac-
curacy of determinations and for vol-
ume of work that can be expedited.
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100
90
80
70
60
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200 300
400
500
500
700 SOO SOO
Exposure Temperature. °C
Figure 5. Thermal treatment of chloroform (i, = 2.0 sec).
The EPA author M. Maltnchuk is with the Hazardous Waste Engineering
Research Laboratory, Cincinnati, OH 45268.
The complete report, entitled "Interim Report on Non-Flame Hazardous Waste
Thermal Destruction," (Order No, PB 86-176 435/AS; Cost: $9.95, 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 author can be contacted at:
Hazardous Waste Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
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United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
BULK RATE
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EPA
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Penalty for Private Use $300
EPA/600/S2-86/038
0000329 PS
60604
* U S GOVERNMENT PRINTING OFFICE, 1986 — 646-017/47153
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