Presented by the members of Superior Engineering Solutions: Mike Najera Dong Hoon Kim Seth Maher

1. Thermal Desorption • Presented by the members of Superior Engineering Solutions: • Mike Najera • Dong Hoon Kim • Seth Maher • Priya Heerwani

2. Definition Thermal means heat and desorption refers to the removal of a contaminant from a surface. Thus, thermal desorption is defined as a treatment technology whereby contaminants are removed from a surface by the application of enough heat to turn the contaminant into a gas and the gas is then removed. The focus of this presentation is how thermal desorption applies to contaminated soils.

3. Why and when do we use thermal desorption? Thermal desorption is a fast method for cleanup. We use it at a polluted site which needs to be cleaned up quickly for reuse of that site. Thermal desorption works well at sites where soil is contaminated with volatile and semi-volatile chemicals. These include compounds like:

4. BTEX (benzene, toluene, ethyl benzene and xylene) which are aromatic compounds commonly found in gasoline • chlorinated volatile organic carbons (VOC’s) • low molecular weight polychlorinated aromatic hydrocarbons (PAH’s)

5. Where to use thermal desorption? Thermal desorption can be carried out where the contaminant is found (in-situ) or the contaminated substance can be removed and treated elsewhere (ex-situ). Cost predominantly dictates where to use it.

6. How does the process of thermal desorption work? Thermal desorption works by heating a contaminated substance (soil, for example). A gas is passed over the top of the substance and as the contaminants are heated up, they turn into a gas and enter the gas stream. The gas stream leaves the thermal desorption chamber and is collected for further treatment.

7. Example A large amount of gasoline, which contains benzene, spills onto the ground thus contaminating the soil. Using thermal desorption to clean the soil means the soil would be put into a thermal desorption unit where it would be heated. The heat would turn the benzene into a gas. As the gas stream flows over the soil, the now gaseous benzene joins the stream and is carried out of the unit and into another area for further treatment. Now the soil is clean provided there aren’t any contaminants that the heating couldn’t remove.

8. Time frame for the process of thermal desorption • Thermal desorption systems can clean over 20 tons • of polluted soil per hour. The time it takes to clean up • a site using thermal desorption depends on: • the amount of polluted soil • the condition of the soil (Is it wet or dry? Does it contain a lot of debris?) • type and amounts of harmful chemicals present

9. Advantages and disadvantages of thermal desorption: • Advantages • Process is simple and well established. • Only a small amount of gas is generated and the removed organics (contaminants) can be held for further treatment if necessary. • Temperatures are relatively low compared to • incineration and can be made lower with • the use of a vacuum.

10. Disadvantages • Organics (contaminants) are not destroyed in the process unless operated at high temperatures. • High clay, humic material (natural organic material), or moisture content increases costs. • Highly abrasive substances can potentially damage the thermal desorption equipment. • Dust and organic matter in the soil increases the difficulty of treating the gas stream. • Debris greater than 60 mm in diameter typically must be removed prior to processing.

11. Conclusions • Simple process compared to other treatment • methods. • Thermal desorption is a viable technology at • relatively-small project sites. • Contaminated sites can be reused and soil • which can’t be cleaned entirely is sent to a landfill. • Cost effective compared to other treatments. • Thermal desorption systems remove volatile organic compounds (VOC’s), semi-volatile organic compounds (SVOC’s), fuels, pesticides and some • metals from soil. • High temperature units are more effective removing volatile metals and SVOCs.