PB90-246349
Laminar Methane-Air Diffusion Flame with Chlorine Impurities
Preliminary Results
(U.S.) Environmental Protection Agency, Research Triangle Park, NC
1990

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NOTICE
This document has been reviewed in accordance with
U.S. Environmental Protection Agency policy and
approved for publication. Mention of trade names
or commercial products does not constitute endorse-
ment or recommendation for use.
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EPA/600/0-90/051
Pti90-2<46J49
Laminar Methane-Air Diffusion Flame with Chlorine Impurities:
Preliminary Result*
S. Venkatesh, K. Saito, and J. M. Stcncel
Deportment of Mechanical Engineeering, University of Kentucky, Lexington, KY 40506
'Center far Applied Energy Research, University of Kentucky, Lexington, KY 40511
and
P. M. Lemieuz and R. E. Halt
Combustion Research Branch, Air and Energy Engineering Research Laboratory
U S E P A, Research Triangle Park, N.C. £7711
ABSTRACT
Formation of products of incomplete combustion (PICs) during the thermal destruction of
chlorinated compounds is of current interest. To study the fundamental processes accompanying the
combustion of chlorinated hydrocarbons, exploratory tests have been conducted by adding chlorine to
the fuel side of a well characterized methane-air laminar diffusion flame. The preliminary observa-
tions are concerned with the soot emissions and the flame temperature. The structure of the soot par-
ticles is examined under a Scanning Electron Microscope (SEM). The SEM studies and the tempera-
ture measurements are compared to similar studies on a methane-air diffusion flame. Results indicate
no change in the temperature field between the methane-air and chlorine/methane-air diffusion
flames. The SEM analysed soot indicated the absence of chlorine, although in one case the soot exhi-
bited a porous structure possibly due to chlorine induced attack.
INTRODUCTION
Products of incomplete combustion are of concern during incineration of municipal and hazar-
dous wastes. Chlorinated hydrocarbons and other chlorine compounds are potential sources in aiding
the formation of chlorinated dioxins and furans. Therefore there is a need to conduct systematic fun-
damental studies on the combustion of chlorinated compounds. Although there have been studies on
the flame destruction of halogenated compounds focused on kinetic studies, very little is known
regarding the physical and chemical structure of soot produced during the combustion of chlorine
compounds. Soot and other particles that exit the flame are condensation sites for chlorinated materi-
als and could potentially form chlorinated dioxins and furans. We intend to conduct detailed studies
connected with the formation of soot and gaseous products during the combustion of chlorinated
methanes. Combustion of chlorinated compounds should result in either Clg or HCI as final products.
Although HCI is not known to donate CI atoms for the formation of chlorinated PICs, researchers
suspect Cl2 to be a donor |l,2). In such cases, besides the gaseous species in the flame and post-flame
zone, the soot formed may also indicate the presence of chlorine.
Here we present preliminary results obtained by the addition of Clj to the fuel side of a laminar
coflow methane-air diffusion flame. Soot samples collected from various regions of the flame were
analyzed for the presence of chlorine using SEM. Following tnis we are in the process of obtaining
detailed gaseous species concentrations in the flame and post-flame regions using microsampit g tech-
niques [3].
EXPERIMENTAL METHOD
A detailed description of the experimental methods used has been reported elsewhere (3,4]. A
brief description of the temperature measurement and soot sampling procedure is given here. The
flame examined is a laminar coflow methane-air diffusion flame. The burner consists ol* two concen-
tric lubes of 7 and 1.6 cm diameter. The fuel flows through the inner tube while air flows in the outer
I.

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tube. Before entering the burner a mixture of nitrogen and chlorine is well mixed with methane (62%
Na, 37% CH4, and 1% Cl3). When the fuel velocities are 3.85 and 4.025 cm/s, the respective flame
heights are 4,0 and 5.5 cm. Temperatures were measured using a Pt-l3%Rh/Pt thermocouple. The
wire diameter of the thermocouple was 0.05 mm (bead diameter 0.1 mm), and it was coated with a
uniform layer of silica. Soot samples were collected using a metallic filament 0.25 mm in diameter.
Soot was allowed to aggregate on the probe for 7-8 minutes.
RESULTS AND DISCUSSION
The Rames were studied in over-ventilated, laminar, and non-smoking conditions. Both the 4.0
and the 5.5 cm flames exhibited a blue zone which was 1.0 cm in height for the smaller flame and 1.5
cm in height for the larger flame. The blue tone was followed by a bright yellow-orange zone associ-
ated with the production of soot. This bright zone was followed by a light orange zone at the tip
which was about 2 mm thick. The orange zone is associated with the oxidation of soot produced in
the yellow-orange region, and no soot deposits occurred on the probes. Further details of the two
colored soot regions have been presented by Saito et.al |5]. Soot samples were collected mainly in the
yellow-orange zone. Soot was collected from the 4.0 cm flame at axial heights of 2.85 and 3.85 cm
from the burner port. For the 5,5 cm flame, soot was collected from axial heights of 2.85, 4.0, and
4.4 em. Scanning electron photographs of the soot samples magnified 7500 times are presented along
with elemental analysis spectrographs (Figs. 1-5). All the spectrographs show that there is no chlorine
on the soot. A peak for chromium appears since the probe contains chromium. A rather striking
result is the porous structure of soot exhibited in Fig. 4. We have not observed similar porous struc-
tuics while studying soot formation in other hydrocarbon flames. The SEM photographs indicate
that the soot aggregates consist of individual blocks which are spherical in shape and, for a given
location within the flame, of nearly uniform diameter, similar to the results reported for pure hydro-
carbon flames [5,6],
Temperature measurements were obtained from the 5.5 cm flame for conditions with and
without chlorine addition. Figs. 6 and 7 depict the measured temperature profiles in a three dimen-
sional fashion. There are no significant differences in temperature between the chlorinated and non-
chlorinated flames. This is consistent with observations made by other researchers, that there is no
appreciable change in the flame temperature on the addition of a small amount of chlorinated hydro-
carbons (2|.
SUMMARY
Our preliminary investigation on the addition of Cl2 to the methane-air diffusion flame has
shown no significant effect on the temperature profiles as compared to the methane-air flame.
Chlorine was not observed on the soot based on an SEM analysis. It may be speculated that CU is
being converted to HC1 in the flame and hence refraining from any further reactions. A detailed gase-
ous species analysis in progress will reveal the fate of chlorine in the flame and post-flame regions.
Analysis of soot produced from other chlorinated methanes is also currently in progress. We believe
tli.il, in addition to gaseous species, studies on the history of soot from early stages in the flame to the
cooler post-flame regions are important to understand the formation of solid PIC's.
ACKNOWLEDGEMENTS
The review and comments by W. P. Linak and B. K. Gulletl are deeply appreciated. We wish
to thank R. Gonsalez of UKCAER for SEM analyses of the soot, and J. Sievo of Princeton University
for providing the excellent thermocouple. The project was supported (P.O,#9D4637NAEX) by
the U. S. Environmental Protection Agency, Combuston Research Branch, Air and Energy Engineer-
ing Research Laboratory, Research Triangle Park, NC 27711,
2

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RKPKRl'lNCKS
I- 11 Caruer, H Four, A 1 Ciaham, and A. liadakashan, Pro'- ;,ixth symposium (Intl.), The
Combustion Institute, l!)5(j, pp HO'-i-NOf).
<• C Lee and C L Huffman, Fn viro.imental Progress, Vol 8, No.3, 1989, pp. 143-151.
K. Saito, A. S. Cordon, and F A. Williams, Transactions of A.SME, Journal of Heat Transfer
Vol 108, 1980, pp. 0'I0-(>48.
K. Saito, A S. Cordon, and F A. Williams, Combustion Science and Technology Vol 45 1986
pp. 117-138.
k. Sait< F. A. Williams, W. F. Stickle, and A. S. Gordon, Central States Secilon Meeting / The
Combustion Institute, May 1988.
k Saito, F A Williams, and A. S. Cordon, Combustion Science and Technology Vol 51 1987
pp. 291-312
Figure 1 (a) SEM of soot collected at axial height
2.8 cm from 4.0 cm flame.
C L
Figure I (h) Spectrograph of soot in Figure I in
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Figure 2 (a) SEM of soot collected at axial height
4^	2.8 cm from 5.5 cm flame.
C ft
CL
1«K>CT <**V»
Figure 2 (b) Spectrograph of soot in Figure 2 (a).
Figure J (a) SEM of soot collected at axial height
4.0 cm from 5.5 cm flame.
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a e
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Figure 3 (b) Spectrograph of soot in - - *

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igure 4 (a) SEM of soot collected at axial height
3.85 cm from 5.5 cm flame.
IIIBQT (KKV)
Figure 4(b) Spectrograph of eoot in Figure 4 (a)
Figure 5 (a) SEM of soot collected at axial height
4.A cm from 5.5 cm flame.
CL
SISR61 (CSV|
Figure 5 (b) Spectrograph of soot in Figur

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SO 0
Figure 6 Temperature distribution of the methane-air
diffusion flame with chlorine addition.
711 i
525 0
21' 5
SO 0
Figure 7 Temperature distribution of the methane-air
diffusion flame without chlorine addition.
6

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a riMi t n fltA TECHNICAL REPORT DATA
A U»tjKL' r" DOU wstfImiuuetitmi on the rt verse before comple"
1 REPORT NO, 2,
EPA/600/D-90/051
3.
4. TITLE AND SUBTITLE
Laminar Methane- Air Diffusion Flame with Chlorine
Impurities: Preliminary Results
6. REPORT DATE
A. PERFORMING ORGANIZATION COD6
7 AMTHOn(S)
S. Venkatesh, K. Sailo, and J. M. Stencel (University of
Kentucky); and P.M. Lemieux and E. E. Hall (EPA)
S. PERFORMING ORGANIZATION REPORT NO.
9, PERFORMING ORO AN 12 ATI ON NAME AND ADDRESS
University of Kentucky
Lexington. Kentucky 40506/40511
10. PRCiQWaS I'LiftfiNT NO,
11. cdtotftACT/dnANf S6.
EPA P.O. 9D4637NAEX
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Air and Energy Engineering Research Laboratory
Research Triangle Park, NO 27711
13. TYPE Of REPORT AND PERIOD COVERED
Extended abstract; 9/89-3/90
14. SPONSORING AGENCY CODE
EPA/600/13
is. supplementary notes ^EERL project officer is Paul M. Lemieux, Mail Drop 65, 910/
541-0962. For presentation at Central States Section meeting/The Combustion Insti-
tute. Cincinnati. CH. 5/20-22/90.
The extended abstract gives preliminary results of exploratory tests, con-
ducted by adding chlorine to the fuel side of a well characterized methane-air flame,
to study the fundamental processes accompanying the combustion of chlorinated hy-
drocarbons. (NOTE: Formation of products of incomplete combustion during the
thermal destruction of chlorinated compounds is of current interest.) The prelimin-
ary observations are concerned with soot emissions and flame temperature. The
structure of the soot particles is examined under a scanning electron microscope
(SEM). The SEM studies and the temperature measurements are compared to simi-
lar studies on a methane-air diffusion flame. Results indicate no change in the tem-
perature field between the methane-air and chlorine/methane-air diffusion flames.
The SEM analyzed soot indicated the absence of chlorine, although in one case the
soot exhibited a porous structure, possibly due to chlorine induced attack.
17. KEY WORDS AND DOCUMENT ANALYSIS
*. DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COsati f->eUl/Group
Pollution Temperature
Flames
Soot
Chlorine
Methane
Chlorohydrocarbons
Combustion
Pollution Control
Stationary Sources
13B 14G
21B
07 B
07 C
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (Thh Report)
Unclassified
21. NO. OF PAGES
*
20, SECURITY CLASS (Thin page)
Unclassified
22, PRICE
EPA Form >220-1 (•-?])
1

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