In order to grasp the effect of soft and hard coal pore structure on gas adsorption characteristics, based on fractal geometry theory, low-temperature nitrogen adsorption and constant temperature adsorption test methods are used to test the pore structure characteristics of soft coal and its influence on gas adsorption characteristics. We used box dimension algorithm to measure the fractal dimension and distribution of coal sample microstructure. The research results show that the initial nitrogen adsorption capacity of soft coal is greater than that of hard coal, and the adsorption hysteresis loop of soft coal is more obvious than that of hard coal. And the adsorption curve rises faster in the high relative pressure section. The specific surface area and pore volume of soft coal are larger than those of hard coal. The number of pores is much larger than that of hard coal. In particular, the superposition of the adsorption force field in the micropores and the diffusion in the mesopores enhance the adsorption potential of soft coal. Introducing the concept of adsorption residence time, it is concluded that more adsorption sites on the surface of soft coal make the adsorption and residence time of gas on the surface of soft coal longer. Fractal characteristics of the soft coal surface are more obvious. The saturated adsorption capacity of soft coal and the rate of reaching saturation adsorption are both greater than those of hard coal. The research results of this manuscript will provide a theoretical basis for in-depth analysis of the adsorption/desorption mechanism of coalbed methane in soft coal seams and the formulation of practical coalbed methane control measures.

中文翻译：

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软硬煤孔隙结构对瓦斯吸附特性影响的研究

为掌握软硬煤孔隙结构对瓦斯吸附特性的影响，基于分形几何理论，采用低温氮气吸附和恒温吸附试验方法，测试软煤孔隙结构特性及其对瓦斯吸附特性的影响。气体吸附特性。我们使用盒维数算法来测量煤样微观结构的分形维数和分布。研究结果表明，软煤的初始氮吸附量大于硬煤，且软煤的吸附滞后回线比硬煤更明显。并且吸附曲线在高相对压力段上升得更快。软煤的比表面积和孔容比硬煤大。孔隙数量远大于硬煤。特别是微孔内吸附力场与中孔内扩散的叠加增强了软煤的吸附势。引入吸附停留时间的概念，得出软煤表面吸附位点越多，气体在软煤表面的吸附停留时间越长。软煤表面的分形特征更为明显。软煤的饱和吸附容量和达到饱和吸附的速率均大于硬煤。