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2020 Issue 10

Micropore structure of outburst coal seam in Guizhou Area and its effect on gas flow

Author:

LI Xijian XUE Haiteng CHEN Liuyu SHEN Zhonghui XU Mingzhi XU Shiqing

Author Unit:

Mining College,Guizhou University Engineering Center for Safe Mining Technology Under Complex Geologic Condition Institute of Gas Disaster Prevention and Coalbed Methane Development of Guizhou University State Key Laboratory for the Coal Mine Disaster Dynamics and Control,Chongqing University State Key Laboratory of Coal Mine Disaster Dynamics and Control,Chongqing University

Key Words:

outburst coal seam; gas adsorption; pore structure; coal seam permeability; coal seam fractal dimension;
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The gas flow law of coal seam is closely related to the pore structure of coal. In order to reveal the micropore structure characteristics of outburst coal s eams in Guizhou and its effect on gas flow,six outburst coal seams in typical mines in Guizhou Area were taken as the research objects, and the adsorption capacity of s ix coal samples was tested by the high pressure capacity method. At the same time, according to the high-pressure mercury test,the fractal dimension of the coal sample was obtained by the fractal method,and the fractal characteristics of the micropore structure of the coal and its relationship with the coal material composition were anal yzed. On this basis,the law of gas flow in multi-scale pores was discussed, and the effect of adsorption on gas flow was analyzed. The results show that Guizhou outbur st coal seams are dominated by micropores,which are the main contributors to the specific surface area and pore volume. The micropore fractal dimension D1 ,small por e fractal dimension D2 and mesopore fractal dimension D3 of the same coal sample increase sequntially,and the fractal characteristics are obvious. D1 and the integra ted fractal dimension Dkare negatively correlated with moisture,the volatile matter is negatively correlated with D2 and D3,and the ash yield is negatively correlated with D3. The gas diffusion mode in outburst coal is mainly Knudsen type and transition type. In the Knudsen difusion zone and transition difusion zone,the permeabllity is le ss affected by temperature and pressure; in the Fick diffusion zone,under the same Knudsen number( Kn) and temperature,the permeability decreases with increasing p ressure and decreases with increasing temperature. The higher the pressure,the smaller the pore size,and the more the permeability is affected by adsorption.

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No.05
May 15th,2022

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