The presence of gas content in medium- and high-rank coal poses a threat to safety production. Safe gas extraction is based on a correct understanding of the pore structure of coal. This work investigates the pore structure characteristics of medium- and high-rank coal and evaluates their fractal structure. The coal samples were collected from Huainan Coalfield and Qinshui Coalfield, and divided into four types, according to the difference in surface bright characteristics. Through adopting low-temperature liquid nitrogen adsorption and desorption, and applying Kelvin equation, we obtain the main pore structure types and main pore size distribution characteristics of various coal briquettes. Electron microscope scanning structure and scientific analysis were used for special adsorption and desorption curves and hysteresis to find the dynamic reason. According to the different adsorption mechanism and Frenkel–Halsey–Hill-based model, with P/P₀ = 0.4 as the dividing point of fractal dimension analysis, the pore structure of coal samples is classified into five grades. The fractal evaluation results are consistent with the results of curve analysis and pore size analysis.

中高阶煤中瓦斯的存在对安全生产构成威胁。安全采气的基础是正确认识煤的孔隙结构。这项工作研究了中高阶煤的孔隙结构特征并评估了它们的分形结构。煤样取自淮南煤田和沁水煤田，根据地表光亮特征的不同，分为四种类型。通过采用低温液氮吸附解吸，并应用开尔文方程，我们得到了各种型煤的主要孔隙结构类型和主要孔径分布特征。针对特殊的吸附解吸曲线和滞后现象，通过电子显微镜扫描结构和科学分析，寻找动态原因。根据不同的吸附机理和基于 Frenkel-Halsey-Hill 的模型，有P / P ₀  = 0.4 作为分形维数分析的分界点，将煤样孔隙结构分为五个等级。分形评价结果与曲线分析和孔径分析结果一致。