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ACTIVATED CARBON REGENERATION Granular activated carbon (GAC) can be used for final "polishing"of the soil-gas by adsorption of low concentration VOC's being recycled. This is achieved by placing the GAC in the closed loop flow path of the Cyclo-Purge System The use of the CP in this arrangement reduces the rdlative humidity of the air entering the GAC. With the preconditioning of the soil-gases entering the GAC, the adsorption capacity Is greatly enhanced In the case of highly contaminated soil formations, such as the venting of the capillary fringe above a water table with floatingF gasobne product, over 9090 of the i VOC is eliminated from the soil gas as a condensed liquid before It reaches the GAC. This feature alone will allow a tremendous reduction in the size of the GAC installation reqi,..:Z4 during the initial months of remediation With the use of our medium sized snit, the recovery of up to 24 gallons VOC per day can be achieved The GAC need only be concerned with the adsorption of solvent vapors remaining after passing through the colt' heat exchanger, a g. approximately 10% of the raw soil gas. When saturation of the GAC does occur, regeneration of the GA � 9 C can be accomplished, in place, by rerouting the flow path of closed-loop gas (which might be inert gaseous nitrogen when recovering flammable vapors) to exclude the wells from the modified closed loop flow path This rearrangement allows the warm air from the CP to enter the GAC carim'er, where the high temperature encourages desorption of the VOC from the GAC An auxiliary heat source is beneficial during the GAC fregeneration phase The VOC saturated vapors leaving the GAC canister are then i passed into the CI~, where condensation removes the VOC fraction. The recirculated gas is reheated after "cold drying" and reintroduced into the GAC canister, to strip i additional VOC, until regeneration is completed The GAC canister is then placed back on line in the sod venting flow path arrangement The desorption cycle for a 200 T pound canister of GAC can easily be achieved in less than eight hours, incurring a total electrical power cost of approximately $6 00 Time and costs will vary with the ' nature of the VOC material and the size of the GAC canister However, the regeneration cost ratio of $0 03 per pound of GAC may be considered a conservative estimate i 4