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ACTIVATED CARBON REGENERATION <br /> Granular activated carbon (GAC) can be used for final "polishing" of the soil-gas <br /> by adsorption of low concentration VOC's being recycled. This is achieved by placing <br /> the GAC in the closed loop flow path of the Cyclo-Purgo system. The use of the CP in <br /> this arrangement reduces the relative humidity of the airaentoering capacity ty is With <br /> t e <br /> preconditioning of the evil-gases entering the GAC, the rP <br /> tio <br /> enhanced. In the case of highly contaminated soil formations, such as the <br /> 0gventing% he <br /> the capillary fringe above a water table with floating gasoline product, <br /> VOC is eliminated from the soil gas as a condensed liquid before it reaches the GAC. <br /> GAG inc <br /> This feature alone ion <br /> will allow a tremendous reduction in the size <br /> ahour medium sized <br /> required during the initial months of remediation. With the use <br /> G need <br /> unit, the recovery of up to 24 gallons VOC per day can be a T he A <br /> gremainin after passing <br /> only be concerned with the adsorption solvent <br /> 1 vapor <br /> %of the raw sol gas• <br /> through the cold heat exchanger, e.g. approximately <br /> When saturation of the GAC does occur, regeneration of the GAC can be <br /> accomplished, in place, by rerouting the flow path of closed-loop gas (which might be <br /> inert gaseous nitrogen when recells from <br /> overing flammable vapors) to excludearmthe <br /> ir from the <br /> the modified closed loop flow path. This rearrangement allows t <br /> l` CP t° enter the GAC canister, of <br /> wl=ere the high temperature encourages desoh®ti GAC <br /> the VOC from the GAC. An auxiliary heat source is beneficial9 <br /> se. The VOC saturated vapors leaving the <br /> tAor�.canister <br /> recare <br /> culthen <br /> regeneration pha <br /> ted <br /> passed into the OF, where condensation removes the VOC frac <br /> o strip <br /> gas is reheated after "cold drying" and reintroduced into the GAG <br /> nister�s tplaced <br /> additional VOC, until regeneration is completed.. The GAC ca then <br /> on <br /> e for a 200 <br /> back on line in the soil venting flow path arra <br /> ngement. The desorptihoursClincurring a <br /> pound canister of GAC can easily be achieved in less than eight <br /> total electrical power cosi of approximately $6.00. Time and costs will vary with the <br /> nature of the VOC material and the size of the GAC canister. However, the <br /> 03 per pound of GAC may be considered a conservative <br /> regeneration cost ratio of $0. <br /> estimate. <br /> i <br /> 4 <br />