Postflame Reaction Chemistry of Dichloromethane: Variations in Equivalence Ratio and Temperature

We report on the destruction pathways and byproduct formation of dichloromethane (CH2Cl2) in conditions typical of incinerator postflame regions (injection temperature 5 900–1200 K; equivalence ratio 5 0.6, 0.9, 1.0, 1.1; residence time 5 0.28–0.35 s). This is the first study to independently vary equivalence ratio and temperature, and evaluate their impacts on byproduct yield and destruction efficiency. We inject 750 ppm CH2Cl2 into postflame combustion products and measure byproducts with extractive FTIR spectroscopy. We use a detailed chemical kinetic mechanism and reaction rate analysis to predict the changes in reaction pathways as a function of equivalence ratio. The predictions for major products and several intermediate species compare well with experiments; the largest disparities are an underprediction of phosgene (CCl2O) and an overprediction of methyl chloride (CH3Cl). Both the experiment and the numerical predictions show increased destruction at lower equivalence ratios. However, the experiments reveal increased levels of stable chlorinated organics at lower equivalence ratios, opposite to the numerical prediction. We discuss reasons for this discrepancy and implications of these results for designing control strategies to promote full conversion to HCl and to reduce chlorinated byproduct emissions. © 2000 by The Combustion Institute