Presence of chlorine radicals and formation of molecular chlorine in the post-flame region of chlorocarbon combustion

Document Type

Article

Publication Date

11-1-2000

Abstract

This study is concerned with the formation and persistence of atomic and molecular chlorine in the late stages of chlorocarbon combustion under fuel-lean conditions as well as in postcombustion cooling stages, since chlorine-containing hazardous organic pollutants including dioxin precursors can be formed through reactions involving these active forms of chlorine. In bench-scale experiments with a chlorine-containing fuel mixture (C2H4/CH3Cl or CH4/CH3Cl, with Cl/C in the range of 0 to 2.2%) the fuel is oxidized in a relatively short time (10-20 ms). The major chlorine-containing product is HCl; however, the cooled combustion gases contain significant concentrations of Cl2 (up to 18% of the total chlorine load), with the exact amount depending on the fuel equivalence ratio, the residence time in the combustor, the H/C ratio of the fuel, and the rate of cooling of the gas products. Calculations indicate that the Cl2 measured in the cold exhaust gas is formed by recombination during the quenching of Cl radicals present at high temperature. The model predicts that, under conditions found in practice, Cl radicals can likewise be present in significant concentrations (1 to 5% of the total chlorine) in combustion products at the exhaust. Due to kinetic constraints, Cl radicals can then persist at surprisingly low temperatures (down to ca. 500 K) before recombining to form Cl2.

Identifier

0034332525 (Scopus)

Publication Title

Environmental Science and Technology

External Full Text Location

https://doi.org/10.1021/es001051z

ISSN

0013936X

First Page

4565

Last Page

4570

Issue

21

Volume

34

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