A finite difference approach for mathematical simulation of soil vapor extraction from unsaturated zone.

摘要

The soil vapor extraction technique is a very cost-effective technique for in-situ subsurface remediation. The soil vapor extraction process involves volatilization, gas advection, gas diffusion, liquid diffusion, residual saturation, vapor-liquid equilibrium, and mass transfer. The variable mass transfer coefficient is governed by the diffusion process. Currently available models can be classified in two broad categories of equilibrium models and non-equilibrium models.;This dissertation proposes a non-equilibrium model that solves a set of partial differential equations for two-dimensional gas flow and advective-dispersive vapor transport in variably saturated porous media with a finite difference approach. The initial-boundary value problem is solved by using Crank-Nicolson scheme and Successive Over Relaxation method. The unique features of model include calculation of changes in the air permeability of the porous media and the amount of residual liquid after every time step. The model is intended for field-scale application to aid in design, development, and operation of high-efficiency soil vapor extraction systems.