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Durham University

Department of Engineering

Staff Profile

Publication details for Professor Simon Mathias

Mathias, Simon, Dentz, Marco & Liu, Qingquan (2020). Gas diffusion in coal powders is a multi-rate process. Transport in Porous Media 131: 1037-1051.

Author(s) from Durham

Abstract

Gas migration in coal is strongly controlled by surface diffusion of adsorbed gas within the coal matrix. Surface diffusion coefficients are obtained by inverse modelling of transient gas desorption data from powdered coals. The diffusion coefficient is frequently considered to be dependent on time and initial pressure. In this article, it is shown that the pressure dependence can be eliminated by performing a joint inversion of both the diffusion coefficient and adsorption isotherm. A study of the log–log slope of desorbed gas production rate against time reveals that diffusion within the individual coal particles is a multi-rate process. The application of a power-law probability density function of diffusion rates enables the determination of a single gas diffusion coefficient that is constant in both time and initial pressure.