Desorption of Soil Contaminants During Steam Cleaning

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This study is an investigation of the fundamentals of heat and mass transfer occurring during the steam cleaning of contaminants adsorbed in soil. The heat transfer and the condensate and gas flow are analyzed assuming local thermal equilibrium, convection, dispersion, gravity, capillarity and diffuso- and thermo-capillarity. The mass transfer among the phases (solid, liquid, and gas) are analyzed based on local non-equilibrium assumptions. The interfacial mass transfer coefficients and the specific surface areas are obtained by a direct simulation of two-phase flow in a phenomenological unit-cell. Experiments are performed in soil columns using contaminant simulants with a controlled initial equilibrium (solid-gas) condition prior to injection of steam. Transient local temperature, capillary pressure, and contaminant concentration (in liquid and gaseous phases) measurements are made. The results of the experiments will be compared to those predicted in order to examine the validity of the phenomenological unit- cell based kinetic model. The proposed research will allow for the development and critical verification of the pore-level analysis of heat and mass transfer in soil during steam cleaning. For the first time, the local velocity and local saturation dependence of the mass transfer rates among the three phases will be determined by a direct simulation and will be verified experimentally. The results will also be valuable for analysis/prediction of the isothermal remediation processes.