Thermal Desorption

Thermal desorption is a technology that is based on the application of heat to volatilise and/or break down the organic compounds that are adhered to soil.

Detailed description

Thermal desorption is a non-destructive process causing the physical separation by heating soil to temperatures ranging between 90 ºC and 540 ºC, in order to volatilise and/or decompose adhered organic pollutants and/or volatile heavy metals (such as mercury), without altering the soil structure. The result is that the soil treated with this technology can be used later for several purposes, such as fill material at the site itself or be deposited in landfills for inert waste.

Thermal desorption differs substantially from incineration because in addition to operating at a lower temperature, the process does not modify the physical structure of the soil, a crucial aspect for its reuse.

Thermal Desorption Unit property of Emgrisa

Thermal Desorption Unit property of Emgrisa

Operation of the Thermal Desorption Unit

A typical thermal desorption plant has the following elements:

  • Pre-treatment system consisting of processes that optimise the subsequent heat treatment, such as reducing the natural moisture content in soil, screening, disintegration, etc. This is dependent on the type and conditions of the soil to be treated.
  • The actual desorption equipment, which heats the material to be treated and maintains it at a sufficient temperature for the necessary time to transfer the pollutants adsorbed in the soil to a gaseous phase. This usually has a revolving furnace where heat is applied directly or indirectly.
  • Gas treatment system. This is the most complex system of the unit, where the gases generated are oxidised at temperatures above 1,000 ºC. This system is associated with the processing of particulates and the condensates generated in the process.

The material treated, once cooled, is analysed to verify the treatment objectives. The percentage of reduction obtained by this technique is more than 95%.


  • It is a widely proven technique that offers results with high efficiency and speed.
  • Treatment suitable for soils with a high load of organic contamination and hydrocarbons composed of heavy and long-chain fractions with low potential biodegradation.
  • Treated soil can be used as fill material as the desorption process does not damage the internal structure of the soil.
  • The treatment uses the hydrocarbon compounds absorbed to the soil as part of the treatment process, lowering the use of external fuel sources in the process.


  • It does not treat inorganic compounds, such as heavy metals (except for volatile metals, including mercury).
  • Excessive moisture from the material to be treated can increase energy costs or pre-treatment costs as well as increasing the time required for treatment.

The Thermal Desorption Unit of Emgrisa

Since 2008 Emgrisa owns a mobile thermal desorption unit that has been used to treat hydrocarbon impacted soils on site and provided a quick, economical and environmentally appropriate solution to contaminated land, sludge and other hydrocarbon wastes.

The Thermal Desorption Plant for Emgrisa was designed in-house: Patent of Invention Nº 200702870/C of 16/06/2010, by “system of thermal decontamination of soils”, with a design characterised by its high capacity (up to 30 t/h) and yields exceeding 95%, as well as low energy consumption (less than 60-70% compared with conventional technology) and an advanced gas treatment system capable of complying with the most stringent emissions regulations.

This plant has been used in large projects for the recovery of sites, both nationally and internationally.


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Publicado el 22/02/16

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