Characterization of thermal desorption phenomena for the cleanup of contaminated soil

The overall goal of this research is to develop an understanding of the fundamental transport phenomena associated with the evolution of hazardous constituents from several types of solid materials, in particular, soils. At the present time, incineration is a relatively costly alternative for the cleanup of contaminated soils. An understanding of the mass transfer and heat transfer limitations might lead to a more economical option, where the contaminants and other constituents are desorbed from the soil at lower temperatures in a primary combustor and then a secondary,high temperature combustor (afterburner) decomposes the potentially hazardous off-gases. This work is aimed at providing fundamental rate information which will be used to model thermal desorption of chemical constituents from soils under a Variety of thermal conditions, soil properties, and contaminants. The experimental approach is threefold. First, a bench-scale particle-characterization reactor (PCR) has been developed and is being used to characterize intraparticle transport under conditions where the bulk concentration and temperature at the particle surface are known. Following these studies, a packed-bed reactor will be used to examine interparticle transport within a well-characterized bed of particles. In the third portion of the work a 73 kW pilot-scale rotary kiln will be used to obtain time resolved measurements of trace species evolution. This paper reports recent PCR results which indicate that soil properties, type of contaminant, and temperature are important in the desorption of contaminants from soil particles.