Gas-solid heterogeneous photo-catalytic oxidation (PCO) has been shown to be effective in its ability to oxidize dilute volatile chlorinated organics as well as other volatile organic compounds (VOCs) in humid air streams. A good example of an application for this technology is the incorporation of a PCO reactor downstream of an air stripper at a groundwater remediation pump-and-treat site to completely oxidize the organics in the air stripper off gases. Unfortunately, several factors make the air stripper application less than ideal. First, air strippers generally employ large air/water flow rations, leading to a relatively high air flow to treat for the volume of water remediated. Second, a high level of water vapor in the air significantly inhibits the photo-catalytic oxidation rate for several classes of VOCs including the chlorinated ethylenes. This rate-inhibition forces the design of larger, and hence more costly PCO reactors to achieve the desired VOC destruction and removal efficiency (DRE).Researchers at Arizona state University have designed, built and tested a new vacuum VOC stripping technique that significantly reduces the air-to-water ratio while achieving the same VOC removal in the air stripper. This new technology offers a significant advantage for PCO, or any air abatement technique since a lower volume of air needs to be treated. In fact, higher oxidative conversions were obtained in spite of a reduction in the residence time accompanying the lower pressure operation.There are other possible uses of this technology besides that mentioned above. For instance, Vacuum PCO could also be employed in association with soil vapor vacuum extraction in which the contaminants in the soil are volatilized by means of convective forces generated by an applied vacuum. This technology could also be used in a VOC control system incorporating physical adsorption beds with downstream PCO in which the adsorption beds would capture emitted VOCs during the operation of a chemical process. During thermal regeneration of the beds, a vacuum would be applied and the off-gases would be treated in the PCO unit.
|Original language||English (US)|
|State||Published - Jan 1 1900|