title: Removal of NAPLs from the unsaturated zone using steam: prevention of downward migration by injecting mixtures of steam and air.
abstract: Steam injection for remediation of porous media contaminated by nonaqueous phase liquids has been shown to be a potentially efficient technology. There is, however, concern that the technique may lead to downward migration of separate phase contaminant. In this work, a modification of the steam injection technology is presented, where a mixture of steam and air was injected. In two-dimensional experiments with unsaturated porous medium contaminated with nonaqueous phase liquids, it was demonstrated how injection of pure steam lead to severe downward migration. Similar experiments, where steam and air were injected simultaneously, resulted in practically no downward migration and still rapid cleanup was achieved. The processes responsible for the prevention of downward migration when injecting steam-air mixtures were analyzed using a nonisothermal multiphase flow and transport model. Hereby, three mechanisms were identified and it was demonstrated how the effectiveness of these mechanisms depended on the air-to-steam mixing ratio.
authors: Institut für Wasserbau, Universität Stuttgart, Germany.
authors: R
authors: R
authors: Schmidt
authors: J
authors: J
authors: Gudbjerg
authors: T O
authors: TO
authors: Sonnenborg
authors: K H
authors: KH
authors: Jensen
mesh_terms: D000388:Air; D006838:Hydrocarbons; D016062:Porosity; D012822:Silicon Dioxide; D012989:Soil Pollutants / Q000032:analysis*; D013227:Steam; D014835:Volatilization; D014872:Water Movements; D014873:Water Pollutants / Q000032:analysis*; D014876:Water Pollution / Q000517:prevention & control*
chemical_list: D006838:Hydrocarbons; D012989:Soil Pollutants; D013227:Steam; D014873:Water Pollutants; D012822:Silicon Dioxide