23. Pyrolysis

Pyrolysis is the application of heat in the absence of oxygen to extract volatile and semi-volatile pollutants from the soil by volatilization (figure 23 ). The technique is increasingly competitive with incineration.

• Principle

  Once the contaminated soil has been excavated, pyrolysis involves introducing it into a pyrolysis unit, where it is heated in the absence of oxygen to temperatures generally ranging from 150 to 540°C. This increase in temperature serves two purposes:

  • promote the desorption of contaminants strongly adsorbed on soil particles,

  • increase the vapor pressure of low-volatility compounds so that they can be volatilized and...