Experimental Study on Methane Diffusion Characteristics of Different Metamorphic Deformed Coals Based on the Counter Diffusion Method

Jiangang Ren; Liang Gao; Zhihui Wen; Hongbo Weng; Jianbao Liu; Runsheng Lv; Yanwei Qu; Zhimin Song; Yongwang Zhang; Bing Li

LAPSE

Living Archive for Process Systems Engineering

LAPSE:2024.0265

Published Article

LAPSE:2024.0265

Experimental Study on Methane Diffusion Characteristics of Different Metamorphic Deformed Coals Based on the Counter Diffusion Method

Jiangang Ren, Liang Gao, Zhihui Wen, Hongbo Weng, Jianbao Liu, Runsheng Lv, Yanwei Qu, Zhimin Song, Yongwang Zhang, Bing Li

February 19, 2024

The diffusion coefficient (D) is a key parameter that characterizes the gas transport occurring in coal seams. Typically, D is calculated using the desorption curve of particle coal. However, this method cannot accurately reflect the diffusion characteristics under the stress constraint conditions of in situ coal seams. In this study, different metamorphic deformed coals of medium and high coal rank were considered based on Fick’s law of counter diffusion. The change laws of D under different confining pressures, gas pressures, and temperature conditions were tested and analyzed, and the influencing mechanisms on D are discussed. The results showed that D of different metamorphic deformed coals exponentially decreased with an increase in confining pressures, and exponentially increased with increases in gas pressures and temperature. There is a limit diffusion coefficient. The influence of the confining pressure on D can essentially be determined by changes in the effective stress, and D negatively affects the effective stress, similar to permeability. The effect of gas pressure on D involves two mechanisms: mechanical and adsorption effects, which are jointly restricted by the effective stress and the shrinkage and expansion deformation of coal particles. Temperature mainly affects D by changing the root-mean-square speed and average free path of the gas molecules. Under the same temperature and pressure conditions, D first increased and then decreased with an increase in the degree of deformation. D of the fragmented coal was the largest. Under similar deformation conditions, D of the high-rank anthracite was larger than that of the medium-rank fat coal. Porosity is a key factor affecting the change in D in different metamorphic deformed coals.

Record ID

LAPSE:2024.0265

Keywords

confining pressure, counter diffusion method, diffusion coefficient, gas pressure, temperature

Subject

Energy Systems

Suggested Citation

Ren J, Gao L, Wen Z, Weng H, Liu J, Lv R, Qu Y, Song Z, Zhang Y, Li B. Experimental Study on Methane Diffusion Characteristics of Different Metamorphic Deformed Coals Based on the Counter Diffusion Method. (2024). LAPSE:2024.0265

Author Affiliations

Ren J: School of Environmental and Biological Engineering, Henan University of Engineering, Zhengzhou 451191, China; Engineering Research Center of Resources and Ecological Environment Geology of Henan Province, Zhengzhou 451191, China [ORCID]
Gao L: No. 2 Geological Team, Hebei Coal Geology Bureau (Hebei Dry Hot Rock Research Center), Xingtai 054001, China [ORCID]
Wen Z: State Key Laboratory Cultivation Base for Gas Geology and Gas Control, Henan Polytechnic University, Jiaozuo 454000, China [ORCID]
Weng H: School of Environmental and Biological Engineering, Henan University of Engineering, Zhengzhou 451191, China [ORCID]
Liu J: School of Environmental and Biological Engineering, Henan University of Engineering, Zhengzhou 451191, China; Engineering Research Center of Resources and Ecological Environment Geology of Henan Province, Zhengzhou 451191, China
Lv R: State Key Laboratory Cultivation Base for Gas Geology and Gas Control, Henan Polytechnic University, Jiaozuo 454000, China [ORCID]
Qu Y: School of Environmental and Biological Engineering, Henan University of Engineering, Zhengzhou 451191, China; State Key Laboratory Cultivation Base for Gas Geology and Gas Control, Henan Polytechnic University, Jiaozuo 454000, China [ORCID]
Song Z: School of Environmental and Biological Engineering, Henan University of Engineering, Zhengzhou 451191, China; Engineering Research Center of Resources and Ecological Environment Geology of Henan Province, Zhengzhou 451191, China; State Key Laboratory Cult [ORCID]
Zhang Y: School of Environmental and Biological Engineering, Henan University of Engineering, Zhengzhou 451191, China [ORCID]
Li B: School of Environmental and Biological Engineering, Henan University of Engineering, Zhengzhou 451191, China; Engineering Research Center of Resources and Ecological Environment Geology of Henan Province, Zhengzhou 451191, China [ORCID]

Journal Name

Processes

Volume

11

Issue

9

First Page

2808

Year

2023

Publication Date

2023-09-21