The International Information Center for Geotechnical Engineers

Thermal Desorption - Main Concept

Thermal desorption is a remediation method used to clean contaminated soils. This method uses heat to vaporize the contaminants, and as such only works for volatile contaminants. These include mostly organic wastes composed of hydrocarbons, such as oil refining wastes, coal tar wastes, wood-treating wastes, creosotes, chlorinated solvents, fuels, PCBs, mixed wastes, synthetic rubber processing wastes, pesticides, and paint wastes (Sharma et al., 2004). By applying heat to the contaminated soils, the wastes with low boiling points are forced to turn into a vapor which can be collected and treated in an off gas treatment unit. This allows the soil to be used again for other purposes without any issues of contamination. This advantage is often considered valuable since landfill space can usually be preserved and the soil can simply be replaced rather than transporting it offsite.

 

In order to use thermal desorption, several soil characteristics must be taken into account. These include the moisture, the plasticity, heat capacity, particle size, and bulk density of the influent soil. If the moisture content of the soil is too high (usually above 20%), the cost of treatment is significantly greater due to the extra energy used to dry the soil beforehand. Soils made up of a large percentage of fines (i.e. clays and silts) are also undesirable for this process as these materials generally emit the fine particles as dust which is prone to clogging and destroying the machinery used to collect the vaporized contaminants (Sharma et al., 2004).

 

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