Li Zhe, Gao Baobin, Lei Wenjie, Ma Shujun, Liu Hao
Henan Provincial Key Laboratory of Gas Geology and Gas Control, Henan University of Technology-The Cultivation Base of State Key Laboratory Jointly Built By the Province and the Ministry, Jiaozuo, Henan 454000, China.
School of Safety Science and Engineering, Henan University of Technology, Jiaozuo, Henan 454000, China.
ACS Omega. 2024 Sep 27;9(40):41923-41935. doi: 10.1021/acsomega.4c06774. eCollection 2024 Oct 8.
The study of isothermal adsorption models for coal and methane under supercritical conditions helps us to understand the gas content distribution in coal seams and improve gas management in coal mines. Coal samples from the Hebi mine and Longshan coal mine were selected for this research. Using the weight method, isothermal adsorption curves of supercritical methane at temperatures of 308, 313, and 318 K were measured. The adsorption phase density of supercritical methane was obtained by using the intercept method and model fitting, and the absolute adsorption capacity of methane was calculated. Simultaneously, the pore volume and specific surface area of the coal samples were tested, and the isothermal adsorption model for supercritical methane was studied and optimized. The results indicate that using mercury intrusion, low-temperature N, and low-temperature CO adsorption methods for testing coal sample pore structures allows for multiscale characterization of the coal pore structure. Based on the Gibbs excess adsorption theory, the phase density of methane obtained from the intercept method and model fitting effectively represent the isothermal adsorption curve of supercritical methane. By combination of the specific surface area and pore volume distribution of the coal with the absolute adsorption capacity of methane, the number of methane adsorption layers on the coal surface was calculated to be between 1.11 and 1.3 layers. This suggests that the isothermal adsorption model for supercritical methane on coal is not solely micropore filling or single molecular layer adsorption but primarily single molecular layer adsorption with concurrent micropore filling adsorption. Based on this adsorption mechanism, an L-DA isothermal adsorption model for supercritical methane on coal was established. The L-DA isothermal model shows good fitting results and effectively explains the adsorption characteristics of supercritical methane on coal.
超临界条件下煤与甲烷等温吸附模型的研究有助于我们了解煤层瓦斯含量分布并改善煤矿瓦斯治理。本研究选取了鹤壁矿和龙山煤矿的煤样。采用重量法测定了308、313和318K温度下超临界甲烷的等温吸附曲线。通过截距法和模型拟合得到了超临界甲烷的吸附相密度，并计算了甲烷的绝对吸附量。同时，对煤样的孔隙体积和比表面积进行了测试，并对超临界甲烷的等温吸附模型进行了研究和优化。结果表明，采用压汞法、低温N₂和低温CO吸附法测试煤样孔隙结构，可实现对煤孔隙结构的多尺度表征。基于吉布斯过剩吸附理论，通过截距法和模型拟合得到的甲烷相密度有效地表征了超临界甲烷的等温吸附曲线。结合煤的比表面积和孔隙体积分布与甲烷的绝对吸附量，计算得出煤表面甲烷吸附层数在1.11至1.3层之间。这表明超临界甲烷在煤上的等温吸附模型并非单纯的微孔填充或单分子层吸附，而是主要为单分子层吸附并伴有微孔填充吸附。基于该吸附机理，建立了超临界甲烷在煤上的L-DA等温吸附模型。L-DA等温模型拟合效果良好，有效解释了超临界甲烷在煤上的吸附特性。
