EPA/600/A-92/230
DEVELOPMENT OF A LABORATORY METHOD FOR
ESTIMATION OF HYDROGEN CHLORIDE EMISSION POTENTIAL
OF INCINERATOR FEED MATERIALS
Larry D. Johnson, Robert G. Fuerst,
Thomas J. Logan, and M. Rodney Midgett
Source Methods Research Branch
Methods Research and Development Division
Atmospheric Research and Exposure Assessment Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Max R. Peterson, John Albritton, and R.K.M. Jayanty
Research Triangle Institute
Research Triangle Park, North Carolina 27709
ABSTRACT
A laboratory method has been developed to provide an estimate of the amount
of hydrogen chloride gas that will form during incineration of a waste. The
method involves heating of a sample of the waste to 900° C in a tube furnace,
removal of particles from the resulting gases by filtration, collection of
hydrogen chloride gas in a water-filled impinger, and measurement of the
collected HC1 as chloride using ion chromatography. The original goal of this
project was to develop a method which would allow accurate determination in the
laboratory, of the amount of HC1 formed upon full-scale incineration of a given
hazardous waste feed material. Although the laboratory equipment and procedures
performed as designed, the data show that results are very sensitive to materials
of construction, availability of hydrogen, and probably other factors difficult
to translate accurately from laboratory to full-scale equipment. In particular,
the incomplete and variable conversion of inorganic chlorine compounds upon
incineration makes estimation of HCl release during incineration of a real waste
highly unreliable. This same variable conversion of inorganic chlorides also
makes use of any so-called total organochlorine analysis results extremely
undependable for estimation of HCl emissions. It is recommended that the current
interim procedure of using total chlorine in the waste feed to estimate worst
case emissions be carried on as the permanent procedure. As specified in the
interim procedure, sampling for HCl before and after the scrubber will be
required for efficiency determination.

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Introduction
Permitting procedures for hazardous waste incinerators and, more recently, those
for hazardous waste burning boilers and industrial furnaces (BIF), require
information concerning the concentration of chlorine in waste feed streams(l,2).
This information is used to estimate hydrogen chloride (HC1) emissions produced
upon combustion of the waste. The estimated amount of HC1 has three important
uses. The first use is to compare with permissible emission limits for a
decision concerning the need for control technology. The second use is to set
permit limits on the concentration and feed rate of waste to keep HC1 production
within the operating envelope defined by the trial burn. The third use of the
estimated amount is to calculate the HC1 feed to the scrubber or other control
device for purposes of scrubber efficiency determination, after sampling the HC1
emissions on the downstream side of the device.
Previously, it was concluded that these three purposes could best be served by
analyzing the waste for "total organic chlorine." The key concept inherent in
this logic was that the chlorine-containing organic compounds would convert
efficiently to HCl upon combustion, and that inorganic chlorine would undergo no
significant conversion. With further experience and upon further consideration,
it became apparent that there were two major problems with the "total organic
chlorine" approach.
The first of these problems was that there was no reliable analysis method for
"total organic chlorine" except in very simple or well known mixtures. Most
reported, and many unpublished, methods for "total organic chlorine" depend on
a preliminary extraction step to separate the "organics" into one liquid phase
and the "inorganics" into an aqueous phase. Unfortunately, such a simple scheme
fails in most cases. Many water soluble organic compounds apportion into the
water phase, and numerous inorganic compounds and complexes extract into non-
aqueous solvents with high efficiency.
The second major problem with the "total organic chlorine" approach is that a
significant number of inorganic compounds and inorganic complexes can be expected
to decompose or otherwise react, upon heating to typical incinerator
temperatures. Many of these reactions can logically be expected to produce HCl
as one of the products. Any method used for estimation of HCl production upon
incineration should certainly include that produced from both organic and
inorganic sources.
Thus, it was apparent that no reliable method of measuring "total organic
chlorine" content was available, and that it would be an inadequate quantity for
the intended use even if it could be determined. Clearly, a different approach
was needed. The most nearly acceptable method available for measuring HCl
emission potential was the TOX procedure used for wastewater (3,4). The method
was designed for analysis of water samples, and includes sorption of the organic
halides onto activated carbon for separation from inorganic salts and the water
sample matrix. Following sorption and rinsing, the carbon is combusted, and the
combustion products are analyzed for halides. However, the carbon sorption step
is inappropriate for most waste samples, and TOX equipment operators were not

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optimistic about direct waste combustion in the instrument yielding meaningful
results. Major concerns were stated about capacity, heating rate, splattering
of combustion materials, and possible salt carry-over.
It was then decided that a tube furnace combustion device connected to
appropriate sampling equipment would be designed, constructed, and evaluated for
use in estimating HC1 emission potential. In the interim, it was recommended to
regulators that total chlorine measurements in waste should be used for a
conservative estimate of HC1 production and for setting waste feed rate
requirements, but not for estimating HCl on the upstream side of a scrubber. The
rationale for this recommendation is explained in the conclusions section of this
article.
Preliminary test results were reported previously, and an EPA report was
published containing complete experimental results and detailed procedural and
equipment descriptions (5,6). This paper summarizes the complete experimental
work and interprets the results in light of related papers recently discovered
in the combustion and process literature (7,8).
Experimental
The experimental approach consisted of heating a waste sample in a tube furnace,
cooling effluent gases to 120°C, filtering the gases at 120*C to remove any
chloride containing particulate matter, collecting HCl in a water-filled
impinger, collecting chlorine in an impinger filled with sodium hydroxide
solution, and measuring chloride ion in the impinger solution by ion
chromatography with conductimetric detection.
Figure 1 is a schematic drawing of the apparatus used to carry out the
experiments. Key components included a sample injection assembly, a tube
furnace, a heated filter box with filter holder, and sample collectors. The
injection assembly consisted of a rod with a sample boat on one end and a piece
of magnetic material attached to the other end. The boat mechanism and the
furnace tube were constructed of quartz for some of the experiments and Inconel
600 (Inconel is a trademark of the International Nickel Co., Inc.) for others.
A small magnet was used to slide the boat into the 0.5 in. ID furnace tube, and
to withdraw it after each sample had been heated. The furnace zone was inside
a quartz or Inconel combustion tube that was heated in the tube furnace. Waste
samples were volatilized and thermally oxidized in the furnace zone. A
thermocouple was used to determine temperature profiles of the furnace zone at
tube-center temperatures of 400"C and 900*C. The profiles indicate that (1) the
furnace zone was maintained at the desired temperature setting for at least 1 in.
on either side of the center and (2) the temperature of the gas stream at the
exit of the tube furnace was greater than 100'C. The latter condition prevented
condensation of water vapor during transfer of gases to the heated filter zone,
which was located immediately downstream from the furnace zone. The filter
apparatus consisted of a quartz-fiber filter supported by a perforated Teflon
disk and was used to remove particulate material from the gas stream. The entire
filter apparatus and associated connectors were housed in an insulated box and
maintained at a temperature of 120*C to prevent condensation.
Sample collectors were located immediately downstream from the heated filter
zone. The filtered gases were bubbled through two midget impingers connected in
series. The first impinger contained deionized water to remove gaseous HCl; the

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second impinger contained 0,1 N NaOH solution to remove any chlorine gas present
in the gas stream.
The heating and sampling procedure for each sample consisted of eight steps: (1)
the impingers were attached; (2) the air flow, which served as a sampling carrier
as well as a combustion oxygen source, was turned on; (3) the gas flow path of
the apparatus was tested for leaks; (4) the waste sample was injected into the
boat; (5) the boat was moved into the furnace zone; (6) after 15 min. , the
impingers were disconnected; (7) after an additional 15 min., the boat was
removed from the furnace zone; and (8) at the end of 30 additional min. (60 min.
from the beginning of step 5), the air was turned off. These steps were repeated
for each sample injection.
Water samples from the first impinger were diluted to 25 mL and analyzed on a
Dionex Model 14 Ion Chromatograph with conductimetric detection. A quaternary
ammonium resin separator column and an anion fiber (acid form) suppressor column
were used for the separation. A bicarbonate/carbonate buffer solution was used
as the eluent. The conductivity meter had a detection limit of 0.01 ppm CI".
The compounds selected for use in synthetic wastes were methylene chloride and
dichlorobenzene, both organohalogen compounds; ferric chloride, a predominantly
molecular inorganic compound; and sodium chloride and potassium chloride, two
very ionic inorganic compounds. Table I gives the composition and chlorine
concentration of the synthetic wastes used in the study. Inorganic compounds
were dissolved in water, and the organic compounds were dissolved in ethanol.
Four different test atmospheres were investigated*. (1) 100% zero grade air, (2)
zero grade air containing 0.5% propane, (3) zero grade air containing 2.4% water
vapor, and (4) zero grade air containing 5.0% water vapor. The last three
atmospheres were investigated to determine if the presence of a hydrogen-
containing species would affect the recovery of inorganic chlorine as HC1.
An airflow of 200 mL/min. was used to sweep material through the furnace tube and
sampling train. This flow rate gave a residence time of 3-4 sec. in the hottest
part of the tube. At the 900°C setting, residence time in the region heated
above 700"C was 8-10 sec. For a more detailed description of equipment and
procedures, refer to the EPA report (6).
Results and Discussion
The recovery results of a preliminary set of runs is shown, along with waste
composition, in Table I. The test atmosphere for this run was 100% zero grade
air, and the furnace zone temperature was 900"C. Conversion efficiency to HCl
was high for organic compounds and generally low for inorganic chlorides,
although the KCl conversion was higher than expected.
To provide more favorable conditions for inorganic chloride conversion, water or
propane was added to the gas stream in a test series summarized in Table II. All
runs were carried out at furnace temperature of both 900°C and 1000°C. The
concentrations of propane and water vapor for this series gave approximately the
same concentration of hydrogen in the test atmosphere and resulted in very
similar recoveries of HCl. Increasing the water vapor concentration to 5,0% had
no appreciable effect on recovery of HCl.

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Conversion of NaCl to HCl at the efficiencies shown in Table II was surprising,
since NaCl was assumed to be the most thermodynamically stable form for the
thermally activated chlorine to assume upon cooling to room temperature. One
possible explanation for this behavior was that a reaction was occurr-ing in the
hot zone, which removed major portions of the activated sodium atoms from the
material balance. That, in turn, would favor HCl formation when sufficient
hydrogen was present.
Further support for this hypothesis was observed in the form of degradation of
quartz components when water vapor was present. The tube and boat took on a
frosted appearance, and a white crust formed on the inside of the tube. The boat
was brownish-red at the end of the ferric chloride runs, presumably because of
the presence of iron in the degraded quartz. The evidence suggests that sodium
and iron ions remained, perhaps as silicates, on the walls of the tube and boat
following conversion of chlorides to HCl.
The presence of significant amounts of HCl gas in the sample stream during this
series was confirmed with an HCl monitor based on gas-filter correlation infrared
spectroscopy. This evidence, plus a 14:1 ratio of chloride to sodium ions found
in the sample collector liquid, eliminated any concern that the chloride found
in the sample collectors was caused by NaCl migration through the entire
experimental apparatus.
Since degradation of the quartz apparatus was more severe at 1000°C than at
900®C, and HCl recoveries were similar at the two temperatures, all subsequent
experiments were carried out at 900°C.
It was observed that the quartz was involved in some form of chemical reaction
during the experiments, and it was suspected that the reaction played a key role
in promoting HCl formation. Therefore, a series of runs was conducted using a
furnace tube and sample boat constructed of Inconel 600 to observe any
differences in recovery caused by the change in construction materials. Inconel
600 contains 76.0% nickel, 15.5% chromium, and 8.0% iron.
The Inconel tube withstood the 900'C temperatures of the furnace without sagging;
however, the interior of the tube became discolored after several runs. The
surface of the Inconel boat mechanism slowly deteriorated during the study. The
boat eventually became pitted and cracked, and material resembling iron filings
collected in the tube. This material was attracted to a magnet, while the
Inconel components were not.
Table III presents the results of experimental runs conducted at 900°C with
quartz components and with Inconel components, with and without water vapor
present. The test solutions are the same as those shown in Table I. The
following observations may be made about the results in Table III.
1. In all cases, hydrogen deficient compounds gave higher conversion to HCl
when water vapor was added and, except for FeCl3, gave very little recovery
when water vapor was not added. Water in which the KCl and NaCl were
dissolved and injected was thought to evaporate or boil so early in the
test sequence that it was not available as a hydrogen source for critical
stages of the test. Perhaps the small recoveries that were achieved in
the zero air tests were the result of a small portion of this solution
water still being available.

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2.	Even without added water vapor, the FeCl3 was converted to HCl with 76.8%
efficiency. Since it is not possible to form HCl without a hydrogen
source, some form of hydrogen capture was operative in the FeCl3 conversion
that was absent during NaCl and KC1 tests. One possibility is that the
hygroscopic nature of FeCl3 and its ability to form a hexahydrate might
delay test solution water loss just enough for a higher concentration of
the water to participate in conversion than in the NaCl and KC1 tests.
3.	Methylene chloride conversion was lower with water vapor present in the
quartz test equipment, but was higher in the Inconel apparatus. It is
possible to speculate somewhat about reasons for the Inconel results, but
the lower yield in quartz is puzzling. The 75.0% value given is the
result of six injections which produced a data set with only a 3% relative
standard deviation.
In the absence of unexpected effects, a recovery of very close to 100%
would be expected when methylene chloride is combusted, whether in quartz
or Inconel. Obviously, some unexpected effects were at work during the
test series. Since the methylene chloride in Inconel series showed
recovery patterns similar to NaCl or KC1 in quartz, perhaps some undefined
reaction caused a hydrogen deficiency. Since CH2C12 only contains the
minimum amount of hydrogen for HCl formation, the effect would be more
critical than during combustion of a more hydrogen-rich compound. What
the hydrogen consuming mechanism might be is not apparent, although the
degradation of the Inconel equipment certainly shows that chemical
reaction of some sort had occurred.
One obvious, but probably incorrect, explanation for low HCl recoveries
from the Inconel equipment would be reaction of the HCl with the metallic
surface. This seems unlikely, since the NaCl runs show an increased
recovery in metal equipment rather than a decrease.
4.	NaCl conversion to HCl was higher in Inconel equipment, especially with
water present. Two of the three runs yielded recoveries of better than
83%, but one was only slightly higher than the quartz run.
Approximately a year after the EPA report(6) summarizing this project had been
published, two earlier papers by Uchida, et. al.(7,8) were discovered. These
papers report that production of HCl from inorganic chlorides during combustion
in municipal incinerators is therraodynamically possible, and give results of tube
furnace experiments similar to those reported in this article. Their experiments
were carried out in alumina equipment, but various materials including silica,
alumina, and iron oxide were added to the NaCl in the reaction boat. Residual
HCl formation when the boat contained only NaCl was explained by reaction with
alumina surfaces of the tube and boat. Conjugate reactions were hypothesized to
explain the interaction of the various metal oxides with the basic HCl formation
reaction.
It is not possible to make direct quantitative comparisons between the data
reported here and that of Uchida without considerably more effort than is
warranted, but the trends in the data are very consistent between the two studies
which tend to strongly support each other.
The effect of increased water in the vapor phase in the current work levels off

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at lower water concentrations than reported by Uchida, probably because much
smaller amounts of NaCl were injected into the furnace in the EPA study. Uchida
clearly shows that the presence of silica or alumina greatly increases HC1
production from NaCl compared to that when no metal oxides are available. He
hypothesizes formation of complex silicates which effectively remove the sodium
ion from the material balance and promote HC1 formation. This interpretation is
in complete agreement with the explanation and data given earlier in this
article.
Conclusions
The results of this study have shown that the formation of hydrogen chloride from
waste incineration depends on the nature of the waste, the presence of hydrogen
in the gas stream, and the composition of the walls and other surfaces in the
furnace zone. Reasonable explanations have been discussed for some of the
increases and decreases in conversion efficiency observed under different
conditions, but other observed effects remain unexplained.
From a practical standpoint, these data show that the incomplete and variable
conversion of inorganic chlorine compounds upon incineration makes estimation of
HC1 release during incineration of a real waste highly unreliable. A complex
system of reactions and interactions with waste feed, fuel, materials of
construction of the hot zone, temperature, and probably residence time makes any
simulation likely to be undependable.
Because of the unreliable nature of any waste test method-based HC1 emission
estimates, the interim procedure described in the introduction is recommended as
permanent. That is, a total chlorine measurement should be used for a
conservative estimate of HC1 production for setting waste feed rates and
approximating uncontrolled emissions, but not for estimation of HC1 levels on the
upstream side of a control device. The latter situation differs from the other
two since the HC1 value is used in the denominator of the efficiency calculation.
A high estimate for HC1 thus makes control device efficiency appear higher than
the correct value.
Acknowledgement
The authors are grateful to Kevin R. Bruce of Acurex Corporation for informing
us about the work of Uchida, et.al.
Disclaimer
The information in this document has been funded wholly or in part by the United
States Environmental Protection Agency under Contracts 68-02-4442 and 68-02-4550
to Research Triangle Institute. It has been subjected to the Agency's peer and
administrative review, and it has been approved for publication. Mention of
trade names or commercial products does not constitute endorsement or
recommendation for use.

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References
1.	"Guidance On Setting Permit Conditions and Reporting Trial Burn Results,"
EPA-625/6-89-019, U.S. Environmental Protection Agency, January 1989.
2.	"Hazardous Waste Burned in Boilers and Industrial Furnaces," Code of
Federal Regulations, 40CFR Part 266, Subpart H, U.S. Government Printing
Office, Washington, DC, 1991.
3.	"Method 9020," in Test Methods for Evaluating Solid Waste,
Physical/Chemical Methods. SW-846 Manual. 3rd ed. Document No. 955-001-
0000001, U.S. Government Printing Office, Washington, DC, November 1986.
4.	"Total Organic Halogen" in Standard Methods for Examination of Water and
Wastewater, 16th ed. , American Public Health Association, Washington, DC,
pp 516-525, 1985.
5.	M.R. Peterson, J.R. Albritton, R.K.M. Jayanty, R.G. Fuerst, T.J. Logan,
and L.D. Johnson, "Laboratory Method to Estimate Hydrogen Chloride
Emission Potential Prior to Combustion of a Waste," in Proceedings of the
1989 EPA/A&WMA International Symposium: Measurement of Toxic and Related
Air Pollutants, Raleigh, NC, May 1989, Document VIP-13, Air and Waste
Management Association, Pittsburgh, PA, 1989.
6.	M.R. Peterson, J.R. Albritton, and R.K.M. Jayanty, "Laboratory Method to
Estimate Hydrogen Chloride Emission Potential Before Incineration of a
Waste," EPA-600/3-90-054, PB90-235854/AS, U.S. Environmental Protection
Agency, August 1990.
7.	S. Uchida, H. Karoo, H. Kubota, and K. Kanaya, "Reaction Kinetics of
Formation of HC1 in Municipal Refuse Incinerators," Ind. Eng. Chem.
Process Des. Dev., 22, pp 144-149, 1983.
8.	S. Uchida, H. Kamo, and H. Kubota, "The Source of HC1 Emissions from
Municipal Refuse Incinerators," Ind. Eng. Chem. Res., 27, pp 2188-2190,
1988.

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Table	I. Synthetic Wastes and Recoveries
Chlorine Source	Chlorine Content. % Chlorine Recovery. X
NaCl	5.8 0.6
KC1	5.6 8.4
FeCl3	4.1 *
C6H<,C12	6.6 85.5
CHZC12	5.5 103.5
*Not determined in preliminary test.

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Table II. Recovery from Sodium Chloride
Zero Grade Air Containing	Recovery. %
Propane Water	900"C 10Q0°C
No No	0.6 5.1
0,5% No	30.7 48.5
No 2.4%	38.5 38.5

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Table III. Recovery of Chlorine as HCl at 900°C
Water
Vapor	Quartz:
Chlorine Source Cone.. %	Recovery. 1
CH2C12 0	103
2.4	75,0
PaCl 0	2.0
0.55
2.4	38.5
KC1 0	0.56
2.4	23.7
FeCl3 0	76.8
2.4	92.8
Inconel:
Recovery. %
2.6
1.0
35.6
40.6
64.1
5.0
45.4
83.1
83.4
1.8
18.6
5.2
68.1

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Infection
AMembly
Figure 1. Laboratory apparatus used in the study.

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TECHNICAL REPORT DATA
1. REPORT NO.
EPA/600/A-92/230
2.
3.
4. TITLE AND SUBTITLE
Development of a Laboratory Method for Estimation of
Hydrogen Chloride Emission Potential of Incinerator
Feed Materials
5.REPORT DATE
6.PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Larry D. Johnson, Robert G. Fuerst, Thomas J. Logan,
and M. Rodney Midgett
8.PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Research Triangle Institute
Research Triangle Park, NC 27709
10.PROGRAM ELEMENT NO.
D 109
11. CONTRACT/GRANT NO.
68-02-4550
12. SPONSORING AGENCY NAME AND ADDRESS
U.S. Environmental Protection Agency
ORD/AREAL/MRDD/SMRB
Research Triangle Park, NC 27711
13.TYPE OF REPORT AND PERIOD COVERED
Symposium Paper
14 . SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
A laboratory method has been developed to provide an estimate of the amount of
hydrogen chloride gas that will form during incineration of a waste. The method
involves heating of a sample of the waste to 900° C in a tube furnace, removal of
particles from the resulting gases by filtration, collection of hydrogen chloride
gas in a water-filled impinger, and measurement of the collected HCl as chloride
using ion chromatography. The original goal of this project was to develop a
method which would allow accurate determination in the laboratory, of the amount of
HCl.-formed upon full-scale incineration of a given hazardous waste feed material.
Although the laboratory equipment and procedures performed as designed, the data
show that results are very sensitive to materials of construction, availability of
hydrogen, and probably other factors difficult to translate accurately from
laboratory to full-scale equipment. In particular, the incomplete and variable
conversion of inorganic chlorine compounds upon incineration makes estimation of
HCl release during incineration of a real waste highly unreliable. This same
variable conversion of inorganic chlorides also makes use of any so-called total
organochlorine analysis results extremely undependable for estimation of HCl
emissions. It is recommended that the current interim procedure of using total
chlorine in the waste feed to estimate worst case emissions be carried on as the
permanent procedure. As specified in the interim procedure, sampling for HCl '
before and after the scrubber will be required for efficiency determination.
17.	KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
b.IDENTIFIERS/ OPEN ENDED TERMS
C.COSATI



18. DISTRIBUTION STATEMENT
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19. SECURITY CLASS (This Report)
21.NO. OF PAGES
13
7.0. SECURITY CLASS (This PaRe>
22. PRICE

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