Title: Gas emission through coal particles using instantaneous gas diffusion coefficients: experimental and modelling study

Authors: Guangshan Shi; Tianxuan Hao; Pengfei Bai; Yugui Zhang

Addresses: School of Safety Science and Engineering and State Key Laboratory Cultivation Base for Gas Geology and Gas Control, Henan Polytechnic University, Jiaozuo, Henan, 454000, China; Collaborative Innovation Center of Central Plains Economic Region for Coalbed/Shale Gas, Henan, 454000, China ' School of Safety Science and Engineering and State Key Laboratory Cultivation Base for Gas Geology and Gas Control, Henan Polytechnic University, Jiaozuo, Henan, 454000, China; Collaborative Innovation Center of Central Plains Economic Region for Coalbed/Shale Gas, Henan, 454000, China ' School of Safety Science and Engineering, Henan Polytechnic University, Jiaozuo, Henan, 454000, China ' School of Safety Science and Engineering and State Key Laboratory Cultivation Base for Gas Geology and Gas Control, Henan Polytechnic University, Jiaozuo, Henan, 454000, China; Collaborative Innovation Center of Central Plains Economic Region for Coalbed/Shale Gas, Henan, 454000, China

Abstract: Similarity theory and the second law of diffusion were used to develop a diffusion model to accurately characterise the behaviour of gas emissions from coal particles. A method for calculating instantaneous diffusion coefficients, D(t), was established. These were incorporated into the diffusion equation and its analytical solution obtained via separation of variables. The results indicated that changes of D(t) as a function of time were described by a power function. The model accurately characterises the entire process of gas emission from coal particles and reflects the complexities of pore size. It provides a new calculation method and theoretical reference for determination and prediction of parameters for gas emission from coal seams. [Received: August 10, 2017; Accepted: January 9, 2018]

Keywords: coal particles; methane; diffusion coefficient; similarity theory; Fick's law; instantaneous diffusion; diffusion model; unipore model; pore structure; mean free.

DOI: 10.1504/IJOGCT.2019.102786

International Journal of Oil, Gas and Coal Technology, 2019 Vol.22 No.2, pp.269 - 290

Received: 10 Aug 2017
Accepted: 09 Jan 2018
Published online: 07 Oct 2019 *

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