1. Mine Safety Technology Branch of China Coal Research Institute,Beijing　 100083,China;2. School of Civil,Mining and Engineering,University of Wollon-gong,Wollongong,NSW 　 2500, Australia;3. Falculty of Resources & Safety Engineering, China University of Mining and Technology Beijing, Beijing 　100083,China;4. State Key Laboratory of Coal Mining and Clean Utilization(China Coal Research Institute),Beijing　 100013,China

针对瓦斯在煤中的解吸与吸附过程并非完全可逆,吸附解吸迟滞现象非常普遍,分析了以往研究中存在的问题,提出了关于吸附解吸迟滞程度的定量评价指标,通过等温吸附解吸实验考察了最高吸附压力和煤体粒径与迟滞程度的关系,并讨论了吸附解吸迟滞现象的发生机理及其对于深部煤层气开发的影响。结果表明:新的定量评价指标可以反映吸附解吸迟滞从完全可逆至完全非可逆的程度;随着最高吸附压力和煤体粒径的增加,吸附解吸迟滞程度随之增强;吸附解吸实验结果是综合了扩散作用的扩散-吸附及解吸-扩散结果,且这两个过程很难区分开来;实验发现的该现象是由于气体分子在高压作用下嵌入连通性较差的微孔中并引起孔隙变形,被吸附的气体分子受窄小的孔隙通道限制,无法从孔隙中解吸并扩散出来而导致的,即本文提出的"扩散受限"假说;深部煤层气的气体含量可能会很高,但受解吸迟滞现象影响,其真正的可采储量和产出规律需要利用等温解吸线而非等温吸附线进行评估;除了通过增透措施提升煤体的渗透率外,如何促进微尺度下的气体解吸与扩散也应该成为深部煤层气开发需要着重考虑的问题之一。

The phenomena of methane adsorption-desorption hysteresis in coal has been observed by many scholars. The results indicate that the adsorption and desorption are not fully reversible. This paper analyses the previous studies on this phenomena and proposes an improved hysteresis index ( IHI). The influences of maximum pressure and coal particle size on hysteresis degree are studied by sorption test. The mechanism of sorption hysteresis and its impact on deep coalbed methane (CBM) recovery are discussed. Results show that IHI can reflect the degree of sorption hystere- sis from a fully irreversible status to a fully reversible status. The hysteresis degree increases with growing maximum pressure and coal particle size. The result of sorption test is an integration of sorption and diffusion,and these two processes cannot be differentiated. Therefore,a 'restricted diffusion hypothesis' is proposed to explain the present phe- nomena. It is due to the diffusion restriction of narrow pore throat,which is induced by the imbedded gas molecules during high pressure adsorption. The gas content of deep CBM may be very high,however,due to the sorption hystere- sis,the minable gas content and the production perspective should be evaluated using desorption isotherm rather than adsorption isotherm. Besides enhancing coal permeability,some novel methods to increase desorption and diffusion rate should be considered for deep CBM recovery.

国家科技重大专项资助项目(2011ZX05040-001)；AustraliaCoalIndustry’sResearchProgram(C24019)；国家自然科学基金资助项目(51444006)；

Wang Gongda,Ren Tingxiang,Qi Qingxin,et al. Mechanism of adsorption-desorption hysteresis and its influence on deep CBM recovery [J]. Journal of China Coal Society,2016,41(1):49-56.