Mechanisms of Flame Quenching by Chlorine in Well-Stirred Reactorś

Abstract

An evaluation of chlorine inhibition effects on the hydrocarbon combustion process was made using an elementary reaction mechanism consisting of 305 reactions and 77 species. The evaluation was conducted, by adding 1% (mole basis) elemental chlorine to fuel-lean and fuel-rich, C₂H₄ air mixtures, and running numerical simulations based on a perfectly-stirred reactor configuration. The evaluation included analysis of: chlorine-catalyzed free radical recombination cycles, carbon flux pathways, principal chain branching reactions, free radical flux pathways, chlorine flux pathways, and reaction exotherrnics. Additionally, the evaluation incorporated the use of a hypothetical molecule “deuterium” that possessed thermodynamic properties similar to hydrogen and chemical properlies similar to chlorine. From this evaluation, it was determined that both chemical and thermal effects result from the addition of chlorine. The primary chemical effect results from suppression of the O-atom concentration. The primary thermal effect results from suppression of the highly exothermic H₂O formation channel due to competition from HCl formation channels. Thermal effects were determined to be the mechanism primarily responsible for flame quenching in a well-stirred reactor.