Simulation of Cleanup of Contaminated Soil by Steam Injection

by
Md. Rashidul Hassan, MSE

University of Texas at Austin, 1997
Supervisor: Mark A. Miller
Kamy Sepehrnoori

A simulation study is conducted to investigate the feasibility of using steam injection for an effective cleanup of dense non-aqueous phase liquids (DNAPLs) in contaminated soils. The study investigated soils contaminated with perchloroethylene (PCE) and trichloroethylene (TCE). These compounds are denser than water and are commonly referred to as DNAPLs. The primary benefit of injecting steam into the contaminated zone is the elevation of the vapor pressures of the contaminants, leading to improved recovery rates. Condensing steam releases its latent heat, thereby increasing in soil temperature.

Computer Modeling Group's STARS 97 simulator is used for conducting this research. The simulator is a thermal compositional model capable of a 3D simulations involving up to six components. The simulator was run for a 3D case study with a combination of both horizontal and vertical wells. The hypothetical site was a high permeability sand zone with a very low permeability clay zone below, followed by a sand zone. For the base case studied, the percentage recover was 99.3%. Remaining contaminants in this case were diffused in the clay zone in a gaseous phase. The success of this project is due to the several mechanisms: a) displacement of all mobile fluids form the pore space by steam, b) elevation of the vapor pressures and thus vaporization of contaminants due to the increase in temperature. All of these are possible by effectively placing the injection wells to heat the contaminants and placing the production wells in crucial locations.

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