Thermal destruction of methyl chloride, ethyl chloride, and 1,1,1-trichloroethane in the post-flame zone of a turbulent combustor.

摘要

The bulk of organics emissions from hazardous waste incinerators are attributed to off-design operating conditions. In experiments simulating these nonoptimal conditions, or "failure modes", three chlorinated hydrocarbons {dollar}CHsb3 Cl,Csb2 Hsb5 Cl{dollar}, and 1,1,1{dollar}- Csb2 Hsb3 Clsb3{dollar}, decomposed to produce byproducts more toxic than themselves.; The compounds were injected as gases into the post-flame region of a tubular (5.1-cm-OD) turbulent combustor with equivalence ratios between 0.4 and 0.7 and residence times between 0.2 and 0.55 s. The temperature range for each compound covered the transition from poor to thorough destruction. Samples from the combustor were analyzed using a Fourier Transform Infrared (FTIR) spectrometer.; Injection of {dollar}CHsb3 Cl{dollar} produced {dollar}CO{dollar}, {dollar}Csb2 Hsb3 Cl{dollar}, {dollar}Csb2 Hsb2{dollar}, and {dollar}Csb2 Hsb4{dollar} as byproducts. For a combustor maximum temperature of 1215 K, the {dollar}Csb2 -{dollar} species reached levels as high as 0.017 moles per mole of elemental chlorine detected. At 1000 K, {dollar}Csb2 Hsb5 Cl{dollar} had the same byproducts, but with the {dollar}Csb2 -{dollar} species at levels an order of magnitude higher. The byproducts of 1,1,1{dollar}- Csb2 Hsb3 Clsb3{dollar} were 1,1{dollar}- Csb2 Hsb2 Clsb2{dollar} (peaking at 997 K at 0.27 moles per mole elemental chlorine), and {dollar}CO{dollar}, {dollar}Csb2 Hsb2{dollar}, and {dollar}CClsb2 O{dollar} (peaking at 1123 K). Among these byproducts, {dollar}Csb2 Hsb3 Cl{dollar} (vinyl chloride), 1,1{dollar}- Csb2 Hsb2 Clsb2{dollar}, and {dollar}CClsb2 O{dollar} (phosgene) are far more toxic than their parent compounds.; Detailed chemical kinetics modeling for {dollar}CHsb3 Cl{dollar} and {dollar}Csb2 Hsb5 Cl{dollar} made use of an extension of the reaction mechanism of Karra et al. (1988) that distinguishes between isomers of chlorinated species. The combustor was modeled as a plug-flow device, using experimentally measured centerline temperature profiles. Modeling predicted the byproduct peaks for {dollar}CHsb3 Cl{dollar} and {dollar}Csb2 Hsb5 Cl{dollar} to occur at 1345 and 1006 K, respectively. Calculations indicated that {dollar}CHsb3 Cl{dollar} decomposes mainly as a result of {dollar}Cl{dollar} and {dollar}OH{dollar} attack. Chloromethyl radicals formed in this process recombine to create {dollar}Csb2 -{dollar} byproducts. {dollar}Csb2 Hsb5 Cl{dollar} decomposes both unimolecularly to {dollar}Csb2 Hsb4{dollar} and {dollar}HCl{dollar}, and by {dollar}H{dollar} abstraction followed by {dollar}beta{dollar}-scission, creating {dollar}Csb2 Hsb4{dollar} or {dollar}Csb2 Hsb3 Cl{dollar}.