Impact of incinerator internal hydrodynamics on hazardous organic waste destruction efficiency

Abstract

The results of a study concerning the influence of internal hydrodynamics of incinerators on the principal organic hazardous constituents (POHCs) destruction efficiency are presented in this paper. A model of two tanks-in-series is used to describe internal hydrodynamics of incinerators via residence time distributions (RTD). Two cases corresponding, respectively, to the presence of a short-circuit and a deadwater zone within the internal flow are examined in detail. The results indicate that the incinerability ranking, based on plug-flow laboratory experiments for thermal stability determination, is disrupted. Temperatures required to obtain a conversion rate of 99.99% in a perturbed flow are higher. Simple relationships allow calculation of the temperature requirement deviation from the plug-flow case knowing the kinetic parameters of the waste combustion and the characteristics of the reactor hydrodynamics. This study shows that the selection of compounds to be spiked in the waste feed of an incinerator during a trial burn should be coupled to a direct determination of the residence time distribution of the incinerator itself for a proper selection of the compound that is more difficult to burn than any other organic expected in the actual waste. Methane, chlorobenzene and methyl chloride, which are characterized by a high stability whatever the species residence time distribution in the incinerator, are good candidates for trial burns.