Abstract
ABSTRACT
Emission of waste compounds and byproducts from thermal treatment systems is generally recognized to be due to limitations in the transport processes. A relatively small fraction of the feed material experiences an environment in which complete waste destruction cannot occur within the time available. These environments involve low temperatures, short times (i.e., high quench rates), oxygen-starved conditions, and possibly combinations of these. The research reported here examines waste compound destruction under the short reaction times that are representative of flame zone extinction processes. An externally fired stirred reactor system is used to study the behavior of toluene, chlorobenzene, 1,2-dichloroethane, 1,1,1-trichloroethane, and chloroform. Each of these is added to the reactor at a rate equivalent to a concentration of 10,000 ppm of carbon atoms. Major byproducts include the light paraffin and olefin hydrocarbons and species that are specific to the individual parent compounds.
Tests also evaluated the influence of reactor residence time and initial concentration on toluene behavior, and a published mechanism for toluene destruction was compared with the data. Additional tests focused on mixture effects (toluene and 1,1,1-trichloroethane fired together). At 1200–1350 K, 1,1,1-trichloroethane fired alone results in no measurable emissions. In a mixture, however, the presence of toluene prevents the complete destruction of the more reactive 1,1,1-trichloroethane under these same conditions. Kinetic analysis shows that the additional free radicals generated by the toluene act in a complex way to increase 1,1,1-trichloroethane concentrations in the reactor, illustrating the difficulties encountered in predicting the behavior of complex waste mixtures.
Key words:
Incineration; toluene; byproducts; DRE; wastes; thermal oxidation
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