Thermal Desorption Treatment of Contaminated Soils in a Novel Batch Thermal Reactor

Abstract

Low-temperature thermal desorption, in which thermal energy is used to vaporize and physically separate volatile and semivolatile organic contaminants from soil, is among the most promising and economic ex situ soil remediation alternatives. Experiments were performed using a bench-scale thermal desorber, the batch thermal reactor, which was developed as a prototype to commercial desorbers. A treatability study using four representative samples of industrial contaminated soil was followed by a fundamental study of the thermal desorption process using three controlled samples prepared by mixing a soil with binary mixtures of selected polynuclear aromatic hydrocarbons. For the industrial samples, the effect of desorber residence time, temperature, and several pretreatments on contaminant removal was investigated. Three of the five samples were successfully treated to the legislated soil remediation limits. Using the prepared samples, the effects of sample porosity, contaminant molar mass, desorber residence time, and temperature on thermal desorption were investigated. The experimental results were fitted to an exponential desorption equation, and the desorption rate curves were generated to provide a basis for scale-up.