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.

Low-temperature thermal desorption of diesel polluted soil: Influence of temperature and soil texture on contaminant removal kinetics

“…The comparison of obtained kinetic results with the literature findings, indicates that much more time (up to about 200 times) is required to successfully treat recalcitrant contaminants such as PCBs [12] or PAHs [28] compared to diesel.…”

“…Residual hydrocarbon concentration curves as a function of the desorber residence time follow a first order kinetic [1,12,28], defining an exponential decay:…”

On-site mercury-contaminated soils remediation by using thermal desorption technology

“…In recent years, the thermal desorption treatment, a kind of ex situ remedial technology which converts mercurial compounds into the volatile mercury, has been considered as a preferred treatment technology for mercury-contaminated soils remediation, due to the advantages of more safety, less emission of treating substance and less energy consuming as compared with other process [4,5]. Middle-range temperature (540-650 • C) of thermal desorption can decrease the concentration of the residual mercury to a lower level below 2 mg/kg and the mercury can be reclaimed with a purity of 99% for sale despite of its different structures and forms [4][5][6][7].…”

An investigation on the modelling of kinetics of thermal decomposition of hazardous mercury wastes

“…mercury wastes from the chlor-alkali process), almost all studies have focused on optimizing operating conditions at pilot and industrial scale [11][12][13][14][15]. Very few studies have been published on reaction mechanisms that may represent mercury behaviour during the thermal treatment [16].…”