Description of the thermal indirect desorption plant (DTI)

Mobile unit for indirect thermal desorption (ITD)

Further to the experience gained in treatment and disposal of contaminated soils, at the end of a complex program for research, design, execution with own labor as well as technological tests, SETCAR put into operation the first mobile unit for indirect thermal desorption in Romania.
The unit separates the volatile toxic substances from contaminated soils at temperatures higher than the boiling point of these substances, therefore being designed to decontamination of soils contaminated with HCH, mercury, various volatile substances, phenols, PCB etc.

Operation, stages, results:

  • soil conditioning in order to be introduced in thermal desorption plant – coarse screening for foreign matters separation (stones, roots, wooden pieces etc.), followed by drying until moisture decreases below 20%;
  • introducing contaminated soil in the desorber, on a conveyor belt after a fine screening up to a granulation of max. 3 mm;
  • in the first stage of the process, by heating the contaminated soil in desorber, vapors of water and toxic substances contaminated in soil are released, which, together with non-condensing gases, are extracted by vacuum and sent to the next stage of the process;
  • in the second stage, the contaminants are trapped by condensation;
  • in the third stage, the gaseous phase is purified by eventual traces of contaminants – by absorption in specific solutions and filtration through active coal, then released in the air;
  • the soil decontaminated in the first stage is cooled, checked by specific laboratory analyses and stored for being reused;
  • the pollutants resulted from the process are put separately and will follow the normal steps of packaging, labelling, authorized transporttemporary storage and disposal.

The big advantage of the plant is that contaminated soil does not come into contact with hot gases from the process, this way their contamination being avoided. Moreover, any possibility for environment pollution by gas release in the air is out of question because the entire gas circuit is under vacuum. Thermal desorption under vacuum reduces the boiling point of volatile compounds, the energy consumption being reduced this way.

Mobile unit for indirect thermal desorption is equipped with all measure and control devices needed for monitoring and adjusting in real time of flow parameters.
The unit consists in 6 portable modules mounted on metal structures container type, this way having mobility, a reduced time for mounting – demounting in an area close to contaminated site and a significant reduction of contaminated soil transport costs.