Li Fengli, Jiang Bo, Cheng Guoxi, Song Yu
Key Laboratory of Coalbed Methane Resource & Reservoir Formation Process, Ministry of Education, China University of Mining & Technology, Xuzhou 221116, China.
School of Resources and Geosciences, China University of Mining & Technology, Xuzhou 221116, China.
ACS Omega. 2022 Jan 11;7(3):2737-2751. doi: 10.1021/acsomega.1c05383. eCollection 2022 Jan 25.
This paper aims to reveal the methane adsorption characteristics of brittle tectonically deformed coal (TDC) under high temperature and high equilibrium pressure and the surface free energy changes during methane adsorption. Taking the anthracite of the Yangquan mining area of China as the research object, methane adsorption tests of high temperature and high pressure were conducted to discuss the influences of coal deformation, temperature, and pressure on the gas adsorption behaviors of coal under the in situ conditions of deep coal seams. Results indicated that coal deformation and pressure had positive effects on the methane adsorption capacity of coal, whereas temperature showed negative effects. Meanwhile, the negative influences of temperature rise on gas adsorption gradually increased with the equilibrium pressure and the enhancement of coal deformation. In a given adsorption system, the adsorption potential decreased with increasing pressure while increased with temperature. In contrast, the adsorption space increased with increasing pressure and decreased with temperature rise. Meanwhile, adsorption potential decreased with the increase in adsorption space. In the process of methane adsorption, with increasing adsorption pressure, the cumulative reduction of surface free energy gradually increased, whereas the surface free energy reduction at each pressure point decreased. The cumulative and incremental reduction of surface free energy at each pressure point gradually decreased with the increase in temperature. The reduction of adsorption space and cumulative surface free energy and the changes in surface free energy at each pressure point of brittle TDCs were higher than those of primary structure coal, and the changes in the strongly deformed coal (granulitic and mortar coal) were more significant than those of the weakly deformed coal (cataclastic coal). Based on the adsorption potential theory, we drew the adsorption characteristic curves and established adsorption capacity prediction models of primary structure coal and brittle TDCs.
本文旨在揭示高温高压下脆性构造变形煤（TDC）的甲烷吸附特性以及甲烷吸附过程中的表面自由能变化。以中国阳泉矿区无烟煤为研究对象，进行高温高压甲烷吸附试验，探讨煤层深部原位条件下煤变形、温度和压力对煤瓦斯吸附行为的影响。结果表明，煤变形和压力对煤的甲烷吸附能力有正向影响，而温度则有负面影响。同时，温度升高对瓦斯吸附的负面影响随着平衡压力和煤变形程度的增强而逐渐增大。在给定的吸附体系中，吸附势随压力升高而降低，随温度升高而升高。相反，吸附空间随压力升高而增大，随温度升高而减小。同时，吸附势随吸附空间的增大而降低。在甲烷吸附过程中，随着吸附压力的增加，表面自由能的累积降低逐渐增大，而各压力点的表面自由能降低则减小。各压力点表面自由能的累积和增量降低随温度升高而逐渐减小。脆性TDC的吸附空间减小、表面自由能累积降低以及各压力点表面自由能变化均高于原生结构煤，强变形煤（粒状煤和糜棱煤）的变化比弱变形煤（碎裂煤）更为显著。基于吸附势理论，绘制了吸附特性曲线，建立了原生结构煤和脆性TDC的吸附量预测模型。
