United States
Environmental Protection
Agency
Hazardous Waste Engineering
Research Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/S2-86/091 Feb. 1987
&EPA Project Summary
Incinerator Operating
Parameters Which Correlate
with Performance
Laurel J. Staley, Mart a K. Richards, George L Huffman, and Daniel P. Y.
Chang
A research project entitled "A Study of
Incinerator Operating Parameters Which
Correlate With Performance" was con-
ducted by the Thermal Processes Re-
search Staff of the Hazardous Waste
Engineering Research Laboratory. This
project evaluated how closely carbon
monoxide (CO) reflected incinerator per-
formance as measured by emission levels
of unburned or incompletely burned sim-
ulated chemical waste. The results of this
research are contained in a report entitled
"Incinerator Operating Parameters Which
Correlate With Performance."
Within this report are results of two dif-
ferent sets of tests; in the first set, a series
of six experiments were conducted in
which five different chemicals frequently
found in hazardous waste streams were
diluted in heptane and burned in a water-
jacketed pilot-scale combustor under a
series of excess air levels which span the
range from fuel-rich to fuel-lean combus-
tion. In the first five experiments, com-
pounds were diluted with heptane and
burned individually (either 1.1,2,2,-
tetrachloroethane, 1,1,2-trichloroethylene,
carbon tetrachloride, chlorobenzene or
Freon-113). In the sixth experiment,
Freon-113 and chlorobenzene were burned
together to test for mixture effects. Car-
bon monoxide levels in the combustor ex-
haust were continuously monitored as
was exhaust temperature. Emission levels
of unburned and incompletely burned
hydrocarbons were determined by sam-
pling the combustor exhaust using Tenax-
GC® filled sorbent traps which were
subsequently analyzed by a gas chromato-
graph equipped with a Hall Detector. In the
second set of tests, CO concentration and
Destruction Efficiency (DE) were meas-
ured as a function of Swirl Number and
fuel nozzle position. The second set of
tests was accomplished using a GC/MS
(gas chromatograph/mass spectrometer)
for analysis.
In general, the results of these experi-
ments indicated that CO levels in the
research combustor exhaust did not di-
rectly reflect the exhaust emissions of un-
burned and incompletely burned chlori-
nated hydrocarbon. Rather, these emis-
sions were more directly affected by the
specific nature of the chemical being
burned and by the combustor operating
temperature.
This Project Summary was developed
by EPA's Hazardous Waste Engineering
Research Laboratory, Cincinnati, OH, to
announce key findings of the research pro-
ject That is fully documented in a separate
report of the same title (see project report
ordering information at back),
Introduction
Performance standards developed under
the Resource Conservation and Recovery
Act require that hazardous waste inciner-
ator operators achieve 99.99% Destruc-
tion and Removal Efficiency (DRE) on the
Principal Organic Hazardous Constituents
(POHCs) present in the waste streams
they burn. (POHCs are generally waste
chemicals designated by the permit writer
on the basis of their concentration, toxi-
city and non-combustibility relative to the
other constituents of the waste stream.)
Compliance with this standard is usually
determined in a trial burn in which a waste
stream representative of what the inciner-
ator would usually receive is incinerated.
Extensive sampling is done at the inciner-
ator's stack to measure POHC emission
levels. These samples are analyzed to
determine the level of POHC in the ex-
-------
haust. This information, along with infor-
mation on the composition of the feed, is
then used to determine ORE and ultimately
compliance with the RCRA incineration
regulations.
Not only is this method of determining
compliance time-consuming and expen-
sive, it only provides information on the in-
cinerator's performance during the time of
the test. Since an incinerator's waste feed
may vary widely in composition, it may not
be valid to assume that if the incinerator
is operated as it was during the trial burn,
it will continue to be in compliance with
the RCRA regulations regardless of varia-
tions in waste feed. Therefore, there is a
need for some way to continuously mon-
itor incinerator performance, to immedi-
ately warn the operator of the onset of
performance deterioration so that correc-
tive action can be taken before an air pollu-
tion problem results.
One method being considered involves
using CO levels in the exhaust to indicate
ORE. Readily available and inexpensive
methods exist to monitor CO levels in in-
cinerator exhaust. If the level of CO in the
exhaust could in some way be tied to the
levels of unburned POHCs in the exhaust
and, ultimately, to ORE, then CO could be
used as a continuous indicator of ORE
which would alleviate the above-
mentioned uncertainties.
The purpose of this preliminary study
was to examine the usefulness of CO as
an indicator of ORE under well-controlled
laboratory conditions.
Description of the Research
Conducted
In the first set of tests, a series of
five compounds, common constituents of
waste streams and often chosen as
POHCs, were burned in a water-jacketed
pilot-scale research combustor under a
range of excess air levels. The compounds
chosen were 1,1,2,2-tetrachloroethane
(TCA), 1,1,2-trichloroethylene (TCE),
carbon tetrachloride (CCI4), chloroben-
zene (CLBZ), and Freon-113, F113 (1,1,2-
trichloro-1,2,2-trifluoroethane). Each com-
pound was tested separately. In each run,
the compound was diluted in normal hep-
tane to produce a two-mole percent solu-
tion. In a sixth run, chlorobenzene was
burned with Freon-113 (CB/F), each at 2
mole percent. For each run, the combus-
tion air flow rate was varied while fuel flow
was held constant, thus producing differ-
ent excess air levels and causing the CO
levels in the combustor exhaust to span
the range of observable values. At five or
sometimes six different sets of operating
conditions, incinerator exhaust samples
were drawn through Tenax-GC® sorbent
traps for purposes of determining the
levels of unburned POHC being emitted
from the incinerator under these various
conditions. These traps were analyzed by
a gas chromotograph equipped with a Hall
Detector. In the second set of tests, CO
concentration and DE were measured as
a function of Swirl Number and fuel noz-
zle position. A GC/MS was used for the
analyses required by the second set of
tests.
The Turbulent Flame Reactor (TFR)
shown in Figure 1 was the experimental
combustor used for this study. Fuel en-
tered the TFR through a Delavan pressure-
atomizing nozzle located at the bottom of
the reactor. Combustion air also entered
at the bottom of the TFR through an Inte
national Flame Research Foundation win
box which was designed so that tf
amount of angular momentum ("swirl'
imparted to the incoming air could t
closely controlled. A water jacket su
rounded the entire combustion chamb
and removed approximately 45,OC
BTU/hr from the system. All samples we
taken from probes in the exhaust port
In addition to taking Tenax-GC® trs
samples, the exhaust was also contini
ously monitored for CO, carbon dioxid
oxygen, and Total Unburned Hydrocarbo
Non-dispersive infra-red analyzers we
used to monitor CO and carbon dioxic
levels. A paramagnetic analyzer was USE
for monitoring oxygen level and a Flarr
lonization Detector was used to monit
Turbulent Flame Reactor
To CO. C02 + O2
Monitors _
To TENAX
(Heated Line)
,i
Air
(From
Compressor)
EC
—»• to THC monitor
' T.C. for Exhaust
Gas Temp.
Swirl Vane
Adjustment
Heptane &
Waste Compound
Figure 1. Turbulent Flame Reactor (TFRI.
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unburned hydrocarbon level. Exhaust tem-
perature was monitored through the use
of a type-K (chromel-alumel) thermo-
couple.
Summary of Test Results and
Recommendations
Continuous sampling for conventional
measures of incinerator performance such
as CO, CO2, O2 and integrated sampling
of POHC DE and PIC (Products of Incom-
plete Combustion) formation were per-
formed under conditions of strong thermal
quenching and variable levels of excess air.
Preliminary studies of the effects of mix-
ing resulting from changes in inlet air swirl
and nozzle position were also carried out.
A summary of the results obtained is
presented below, as are recommendations
for future research.
1. Over the range of excess air ex-
amined (120% < Percent Theoretical Air
[%TA] < 230%), CO concentration and
exhaust gas temperature were functions
of the %TA in the TFR (see Figure 2 for
a pictorial representation of the former).
The CO functional dependence was non-
linear and non-monotonic, exhibiting a
minimum at about 140% TA. CO produc-
tion as a function of theoretical air ap-
peared to be relatively insensitive to the
particular POHC mixed with the fuel at the
level tested, two mole percent. The be-
havior of CO as a function of excess air
could plausibly be attributed to poor mix-
ing leading to locally fuel-rich pockets
under conditions of low excess air, and to
thermal quenching under conditions of
high excess air. Exhaust temperature was
a monotonically decreasing function of
%TA over the range tested.
2. The existence of two limbs to the CO
concentrations versus %TA curve sug-
gested correlating CO with POHC DE for
one limb of the curve at a tima Adequate
data were only available for the high ex-
cess air case. For the high excess air limb,
POHC penetration appeared to increase as
CO increased, but was dependent upon
the POHC burned (see Figure 3). Qualita-
tive agreement with the thermal stability
incinerability ranking scale was observed
for the POHCs: TCE, CLBZ, CCI4 and
TCA. Freon-113 exhibited anomalous be-
havior which possibly was related to an in-
ability of the analytical method employed
to distinguish Freon-113 from chloroform
(a common PIC). The utility of CO as a
continuous measure of POHC DE appears
to be limited by the multiple-valued nature
of the CO versus excess air curve as well
as by dependence upon the POHC burned.
Thus, it follows that the relationship be-
tween CO and ORE could be even more
tenuous. Increase of CO emission did.
CO vs. %TA
1
•-?
it
U
O *^-
Q
0
a TCE
1.3 -
1.2 -
1.1 -
1 -
0.9 -
0.8 -
07 -
06 -
0.5 -
0.4 -
0.3 -
0.2 -
0.1 -
o v
\ A
\ /
\ 0 /
»x' /
\°
\ /
>'"
\ /
\ I-, /
\ D '
« +/
\ / X
^ a o.^
X \ '
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\ + C* s
*^ ^' x & v
V
0_
110 130 150 170 190 210 230
% Theoretical Air
+ CCU O TCA A CLBZ xF113 V CB/F
however, precede or occur simultaneously
with the increase in POHC penetration
above about 130% to 140% of theoretical
air. Therefore, CO concentration might still
serve as a useful upper bound for pur-
poses of incinerator permitting, but will
likely be combustor dependent. Further
research investigating the low excess air
limb of the curve needs to be pursued.
3. The formation of PICs was observed
to increase as a function of excess air
under conditions of high excess air. For an
example of this, see Figure 4. The relative
amounts of a given PIC formed was de-
pendent upon the POHC burned, but nu-
merous PICs were common to all POHCs
tested. As shown in Figure 4, it was
observed that a recalcitrant PIC, TCE,
could be formed from a relatively easily
destroyed POHC, TCA. In fact, the PlC-to-
POHC ratio was observed to be greater
than unity in that instance, consistent with
larger pilot-scale combustor tests under
similar conditions of strong thermal
quenching. The potential importance of
this finding applied to boilers co-firing
waste is evident.
4. The common occurrence of PICs
(benzene, chloromethane, dichlorometh-
ane, chloroform, carbon tetrachloride and
chlorobenzene) formed from the fuel and
chlorinated POHCs may contribute to an
understanding of the previously found
phenomena of increasing DE with increas-
ing POHC concentration in the waste feed.
POHCs which could also be formed as
PICs would appear to be more difficult to
destroy. The same phenomenon could be
one possible explanation for the difficulties
in using incinerability ranking scales to
predict destruction efficiency. As a prac-
tical application of these findings, it is sug-
gested that, for trial burns, one select
recalcitrant POHCs which are not likely to
be formed as PICs, but which also yield
readily identifiable recalcitrant PICs as
well. Further research to better understand
the role of radical recombination in the for-
mation of PICs should be pursued.
5. Hardware-related parameters such
as degree of mixing produced by inlet air
swirl and nozzle position were found to af-
fect flame stability and CO emissions in
preliminary testing. More comprehensive
tests of the influence of such parameters
on POHC DE should be carried out in the
future.
Figun 2. CO vs. % Theoretical Air (%TA): All compounds.
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Log (POHC Penetration} vs. CO
.o
1
1
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The EPA authors LaurelJ. Staley (also the EPA Project Officer, see belo w), Marta
K. Richards, and George L. Huffman are with the Hazardous Waste
Engineering Research Laboratory. Cincinnati, OH 45268; and Daniel P. Y.
Chang is with the University of California, Davis, CA 95616.
The complete report, entitled "Incinerator Operating Parameters which Correlate
with Performance," (Order No. PB 87-104 626/AS; Cost: $9.95, 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:
Hazardous Waste Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
6250109 I
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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