Coal pores not only serve as the storage space for coalbed methane but also provide channels for gas migration. The accurate characterization of coal pore structures is of significance to study the methane adsorption behaviors. In this work, the quantitative relationship between gas adsorption and pore characteristics was investigated in depth for bituminous coals. Results of scanning electron microscopy showed that the surface morphological characteristics of these samples differ greatly. Some typical pore types including cylindrical pores and conical pores were found in these samples. The remarkable hysteresis loop was observed, which is attributed to the bottle-shaped pores with poor connectivity. Fractal theory was introduced to quantitatively evaluate the surface roughness of coal. Pore fractal dimensions, D₁ and D₂, were calculated using low-pressure N₂ gas adsorption data, and their values were in the range of 2.125–2.721 and 2.084–2.461, respectively. D₁ was larger than the corresponding D₂ for the same sample, suggesting that micropore structures in coal were more complex when compared with mesopores and transition pores. Both D₁ and D₂ were enhanced with increase in micropore specific surface area, but they were reduced with increase in mesopore specific surface area. Gas adsorption in coal was estimated from the perspective of fractal dimension. Judging from the fitting degree, the influence of D₁ on adsorption capacity of coal was remarkably greater than that of D₂. D₁ is expected to be used as one of the major adsorption indicators in the future study.

煤孔不仅是煤层气的储存空间，也是瓦斯运移的通道。煤孔隙结构的准确表征对于研究甲烷吸附行为具有重要意义。在这项工作中，深入研究了烟煤的气体吸附和孔隙特征之间的定量关系。扫描电镜结果表明，这些样品的表面形态特征差异很大。在这些样品中发现了一些典型的孔隙类型，包括圆柱孔和圆锥孔。观察到显着的滞后回线，这归因于连通性差的瓶状孔。引入分形理论定量评价煤的表面粗糙度。孔隙分形维数，D₁和D ₂是使用低压N ₂气体吸附数据计算的，它们的值分别在2.125-2.721和2.084-2.461的范围内。对于相同的样品，D ₁大于相应的D ₂，表明与介孔和过渡孔相比，煤中的微孔结构更复杂。既d ₁和d ₂与在微孔比表面积增加而增强，但它们与中孔比表面积增加而减小。从分形维数的角度估计了煤中的瓦斯吸附。从拟合程度来看，D ₁对煤的吸附能力明显大于D ₂。D ₁有望作为未来研究的主要吸附指标之一。