Hot air injection for removal of dense, non-aqueous-phase liquid contaminants from low-permeability soils
The performance of soil vapor extraction systems for the recovery of volatile and semi-volatile organic compounds is potentially enhanced by the injection of heated air to increase soil temperatures. The soil temperature increase is expected to improve soil vapor extraction (SVE) performance by increasing target compound vapor pressures and by increasing soil permeability through drying. The vapor pressure increase due to temperature rise relieves the vapor pressure limit on the feasibility of soil vapor extraction. However, the system still requires an air flow through the soil system to deliver heat and to recover mobilized contaminants. Although the soil permeability can be increased through drying, very low permeability soils and low permeability soils adjacent to high permeability air flow pathways will be treated slowly, if at all. AR thermal enhancement methods face this limitation. Heated air injection offers advantages relative to other thermal techniques, including low capital and operation costs. Heated air injection is at a disadvantage relative to other thermal techniques due to the low heat capacity of air. To be effective, heated air injection requires that higher air flows be established than for steam injection or radio frequency heating. Heated air injection is not economically feasible for the stratified soil system developed as a standard test for this document. This is due to the inability to restrict heated air flow to the clay stratum when a low-resistance air flow pathway is available in the adjoining sand. However, the technology should be especially attractive, both technically and economically, for low-volatile contaminant recovery from relatively homogeneous soil formations. 16 refs., 2 tabs.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- OSTI ID:
- 447169
- Report Number(s):
- ORNL/TM-13305; ON: DE97050722; TRN: 97:001173-0010
- Resource Relation:
- Other Information: PBD: Aug 1996; Related Information: Is Part Of In situ remediation of DNAPL compounds in low permeability media fate/transport, in situ control technologies, and risk reduction; PB: 318 p.
- Country of Publication:
- United States
- Language:
- English
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