Presence of Chlorine Radicals and Formation of Molecular Chlorine in the Post-Flame Region of Chlorocarbon Combustion

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 radi...