Treating contaminated soil poses a tremendous challenge for environmental specialists, but Terra Therm, an environmental services company in The Woodlands, TX, has risen to the occasion by introducing a system that takes advantage of a Des Champs air-to-air heat exchanger.

Terra Therm is an affiliate of Shell Technology Ventures, which develops commercial applications for concepts resulting from Shell Oil Company's research. Shell developed a portable soil abatement system mounted on a trailer, and Terra Therm markets it. Employing so-called In Situ Thermal Desorption (ISTD) technology, the system remediates a broad range of organic compounds such as PCBs, pesticides, petroleum wastes, and chlorinated solvents, all without excavating the soil.

At the heart of the process lies a heat source consisting of thermal blankets placed on the ground for surface soil remediation and thermal wells bores for zones extending up to several hundred feet deep. Heating elements in the blankets or wells heat the soil, causing the contaminants to vaporize. A vacuum system then draws the vapors from the ground.

The heat in the soil destroys most of the contaminants, and the rest go to a vapor treatment system. In this, a thermal oxidizer incinerates 90% of the volatile organic compounds (VOCs) and the remaining 10% pass through an activated carbon adsorption process. To work effectively, adsorption requires lower temperatures than the 1600 degree F in the incinerator exhaust gas. A Des Champs model S81CF Thermo-Z heat exchanger indirectly cools the exhaust to 230 degrees F using outside air.

With tens of thousands of contaminated sites in the U.S., Terra Therm sees a significant potential for the ISTD system and has begun limited production to meet the demand. Eventually, the company envisions several dozen units operating around the country.

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