IN-SITU DELIVERY OF HEAT BY THERMAL CONDUCTION AND STEAM INJECTION FOR IMPROVED DNAPL REMEDIATION

ABSTRACT: Thermal Conduction Heating (TCH) is a major component of In Situ Thermal Desorption (ISTD), a soil remediation technology in which heat and vacuum are applied simultaneously. Heat flows into the soil primarily by conduction from heaters typically operated between 1000 and 1500ºF (540 and 815ºC). The heaters are installed in wells at regular intervals within the soil. As the soil is heated, water is boiled and dense non-aqueous phase liquid (DNAPL) constituents in the soil are vaporized. The resulting steam and vapors are drawn toward extraction wells for in-situ and aboveground treatment. Compared to fluid injection processes, the conductive heating process is very uniform in its vertical and horizontal sweep. Field project experience at numerous TCH/ISTD sites has confirmed that maintaining target temperatures for several days results in extremely high destruction and removal efficiency of chlorinated volatile organic compounds (CVOCs), polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and other DNAPLs. Provided that water influx is managed, the effectiveness of the TCH/ISTD process is not limited by the presence of heterogeneous soil conditions or clay, and can be applied effectively below the water table. Despit