Methane Adsorption Characteristics in Low-Permeability Coal Seams of Huainan and Huaibei Mining Areas

为探究两淮低渗煤层的甲烷吸附特征，本研究选取淮南和淮北矿区共五个煤样开展等温吸附实验，结合Langmuir模型及优化后的Langmuir模型、优化后的DBET模型和优化后的DA模型进行拟合分析。实验结果表明，甲烷过剩吸附量随压力增大呈先快速上升后线性下降的趋势；优化后的Langmuir模型和DA模型能准确地拟合甲烷在煤中的过剩吸附量，而优化后的DBET模型无法拟合甲烷在煤中的过剩吸附量；甲烷在煤中的吸附只存在单分子层吸附和微孔充填吸附，而不存在多分子层吸附，且在低压条件下煤中甲烷以单分子层吸附为主，而随着吸附压力的增大，吸附方式发生变化，由单分子层吸附转变为微孔充填吸附；煤中甲烷的吸附量受煤样的镜质组反射率(Ro, max)、有机碳含量(TOC)影响，且随镜质组反射率(Ro, max)、有机碳含量(TOC)增大而增大。To investigate the methane adsorption characteristics of low-permeability coal seams in the Huainan and Huaibei mining areas, this study selected five coal samples from these regions for isothermal adsorption experiments. The experimental data were analyzed using the Langmuir model, the optimized Langmuir model, the optimized DBET model, and the optimized DA model. The results indicate that: (1) The methane excess adsorption initially increases rapidly and then decreases linearly with rising pressure; (2) The optimized Langmuir and DA models accurately fit the methane excess adsorption in coal, while the optimized DBET model fails to describe the adsorption behavior; (3) Methane adsorption in coal involves only monolayer adsorption and micropore filling, with no multilayer adsorption observed. At low pressures, monolayer adsorption dominates, whereas adsorption mechanisms transition to micropore filling as pressure increases; (4) Methane adsorption capacity is positively correlated with vitrinite reflectance (Ro, max) and total organic carbon content (TOC), showing an increasing trend with higher Ro, max and TOC values.