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.

中文翻译：

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煤粉中的气体扩散是一个多速率过程

煤中的气体运移受到煤基质内吸附气体的表面扩散的强烈控制。表面扩散系数是通过对粉煤的瞬态气体解吸数据进行逆向建模而获得的。扩散系数通常被认为取决于时间和初始压力。在本文中，表明可以通过执行扩散系数和吸附等温线的联合反演来消除压力依赖性。对解吸气体生产速率随时间的对数-对数斜率的研究表明，单个煤颗粒内的扩散是一个多速率过程。扩散速率的幂律概率密度函数的应用能够确定在时间和初始压力上都恒定的单个气体扩散系数。