Gas migration and vent design at landfill sites

Abstract

Abstract, A finite element model has been developed to simulate the migration of gases in soil from a buried source such as a landfill. Using quadratic elements, the diffusion convection equation coupled with the mass conservation equation of a binary mixture of gases is solved under a combination of Dirichlet, Neumann and flux type of boundary conditions. The model is compared with an analytical solution and a set of field measurements. The model is used to display the influence of seasons on the migration of gases. The effectiveness of venting trenches in containing such migrations is examined and a method for the determination of trench depth is presented.

Computer simulation of gas generation and transport in landfills II: Dynamic conditions

“…Since the 1970s, gas migration in landfills has also been studied theoretically (Mohsen et al, 1980;Moore et al, 1982;McOmber et al, 1982;Alzaydi, 1986;Metcalfe and Farquhar, 1987;Ishii et al, 1989), assuming that the gas is homogeneous. Others (Findikakis et al, 1988;El-Fadel et al, 1995;Young, 1992;Lee et al, 1993) developed models assuming equal rates of convective and diffusive transport, while several models were developed for emission from landfills of volatile organic compounds (Shen, 1982;Baker and Mackay, 1985;Seigneur et al, 1989;Cernuschi and Giugliano, 1989;Thomas et al, 1992;Lin and Hildemann, 1995) for which diffusion is the dominant transport process.…”

Buoyant Advection of Gases in Unsaturated Soil

“…A number of these models have simulated forced advection of dilute gases in soils, including Mohsen et al (1980) and Metcalfe and Farquhar (1987), who address methane release from landfills; Loureiro et al (1990), who model radon transport into the basement of buildings, and a number of models related to the transport of volatile organic solvents in unsaturated soil (Abriola and Pinder 1985;Baehr and Corapcioglu 1987;Gierke et al 1990). With the recognition that volatile organic liquids become trapped in the subsurface following their release, gas transport models have included the effects of volatilization and buoyancy-induced advection (Sleep and Sykes 1989;Falta et al 1989;Mendoza and Frind 1990;Mendoza and McAlary 1990).…”

Auxiliary analyses in support of performance assessment of a hypothetical low-level waste facility: Two-phase flow and contaminant transport in unsaturated soils with application to low-level radioactive waste disposal. Volume 2

“…Galerkin finite element methods were applied by Mohsen et al (1980), Metcalf andFarquhar (1983, Dotgarten (1989), Mendoza andFrind (1990), andCulver et d. (1991). The deficiencies of the finite element method for solving the transport equation are well known.…”