Date of Award
Master of Science in Mechanical Engineering - (M.S.)
Mechanical and Industrial Engineering
Stevens, John G.
Remediation of contaminated subsurface sites at lower cost and time than currently used technologies are being demonstrated for a systems concept using new technology developed at the Hazardous Substance Management Research Center at New Jersey Institute of Technology. A technique for pneumatic fracture is employed to "open" subsurface passages to enhance vacuum extraction of contaminants. Economical and environmentally sound destruction of these contaminants is then accomplished using catalytic oxidation followed by scrubbing to remove air pollutants. The hot gas from this phase of the process is then injected into the subsurface formation after being used to preheat the fuel/air mixture to catalyst operating temperature, to increase contaminant temperature, hence vapor pressure leading to increased contaminant mass removal rates.
A computer based model of the subsurface heating process has been developed to provide for engineering design. Using the heat injection well as the radial center for a cylindrical coordinate system, a non-steady state numerical heat transfer model is utilized to predict ground temperature in three dimensions assuming uniform gas flow along the fracture planes.
Extension of the above model has been made to include contaminant mass removal. The change in rate of evaporation of chlorocarbon contaminants and low vapor pressure organic liquids in the vadose zone is related to the computed temperature increases. This connection allows assessment of the expected change in the measured mass removal rates of contaminants as a result of hot gas injection into the sub-surface.
It was found that trichloroethylene (TCE) is removed from the surface of the formation cracks at gas temperatures of 635 °F and redeposits further downstream as the temperature drops to 60 °F. If the formation is heated for a sufficiently long time then the TCE would be transported to the extraction well. For accurate predictions of temperature distribution and mass removal rates, the model must be calibrated on the actual site of the clean-up.
Jayabal, Sanjay, "Remediation of contaminated sites using hot gas injection" (1994). Theses. 1627.