THERMAL-DESTRUCTION OF CH3CL UNDER LEAN POSTFLAME CONDITIONS

The thermal destruction of CH3Cl in the lean postflame region of a nonisothermal turbulent combustor has been studied experimentally and modeled numerically. Conditions were chosen to simulate the destruction of waste in the postflame zone of a hazardous-waste incinerator, the process believed to be responsible for the bulk of incinerator emissions. Residence times were between 0.23 and 0.28 s, and equivalence ratios were between 0.49 and 0.67. The maximum temperature in the combustor varied from 1215 to 1417 K; temperatures declined from the maximum by several hundred degrees centigrade over the reaction zone. The transition from poor to thorough destruction of CH3Cl was observed experimentally when T(max) = 1220 K. The major products of CH3Cl destruction were CO2, H2O, and HCl. In addition to these compounds, the following byproducts were observed: C2H4, C2H2, C2H3Cl, and CO. The maximum level of the C2 species was less than 2% of the initial CH3Cl level; CO was present at a maximum level of about 20 percent of the initial CH3Cl level. Numerical modeling of chemical kinetics was performed using a mechanism based on that of Karra et al. [Combust. Sci. Technol. 60: 45-62 (1988)]. The modeling underpredicted the destruction of CH3Cl, but predicted the same species as byproducts. According to the model, the C2 byproducts were formed by recombination of chloromethyl radicals, which, in turn, had been formed by H abstraction from CH3Cl by radicals. Discrepancies between model and experiment may be due to inaccuracies in modeling the initial composition or temperature history, or may indicate that the mechanism must be modified before it can make accurate predictions for fuel-lean conditions.