Abstract
The complex flow of gases from the coal matrix is basically controlled by (1) diffusion of gas from coal following Fick’s law and (2) Laminar flow of gases through the fractures in coal following the Darcy’s law or pressure-dependent flow. The slower of the two processes decides the net flow because they work in series. Diffusion process is fully explained. Methane is stored on coal (molecule) surfaces adsorbed in a monolayer. A new parameter that controls the rate of diffusional flow is defined as (Da2) second−1 where D is the coefficient of diffusivity and a is the hypothetical coal particle radius where methane is adsorbed. In mining parlance, the value of (Da2) is not easily realized and hence a new parameter, τ, was created that is sorption time of coal. During this time, the coal will diffuse about 63% of the total gas contained on its surface.
Published Version
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