Liquid-waste incineration in a parallel-stream configuration: Parametric study

Abstract

Proven efficiency is a prerequisite for incineration to be accepted as a widely used destruction method for hazardous liquid wastes. The goal of this work is to use a multicomponent spray combustion model previously developed to (1) extend the investigation of injection configurations to chlorinated hydrocarbons, (2) predict the effects of initial droplet size and geometrical, volatility and chemical-kinetic parameters on the destruction efficiency in an idealized incinerator, and (3) compare the observed trends with the available experimental data. A parametric study was conducted on three liquid wastes: benzene, toluene and monochlorobenzene, somewhat representative of the range of halogen levels, volatilities and chemical kinetics prevalent in wastes. It was found that monochlorobenzene is the most incineration resistant of the three, followed by toluene and benzene. The destruction efficiency was found to be affected mainly by the waste chemical kinetics and primarily improved by initial droplet size reduction and shorter distance from the provided ignition heat-source location, whereas no dramatic amelioration was induced by initial composition variations. The results are in good qualitative agreement with the related experimental studies. Albeit simplified, this model provides a characterization of the parameters which could be controlled to obtain a more efficient incineration of the waste. Namely, small droplet sizes are needed either by enhanced primary atomization or, in the case of mixed injection, through microexplosion. For most hazardous liquid wastes (heavy with very slow chemical kinetics), mixed injection will achieve a better destruction. An auxiliary fuel significantly more volatile than the liquid waste enhances slightly the destruction because of its effect on the vaporization process, but it is believed that this feature would not be observed with a longer combustor. In the particular case of aromatic compounds however, separate injection with alternated streams of waste and fuel, was found to be better than blending of the waste and auxiliary fuel.