页岩气煤层气典型气体吸附模型分析

Analysis on typical gas adsorption models for shale gas or coalbed methane

对大量实验数据描绘出的气体吸附等温线分析认为,Langmuir方程形式简单,可以计算气体的吸附气量,但是对固体表面均一性的假设和单分子层吸附使其应用局限;BET方程是计算比表面积的常用模型,但同样需假设固体表面均一性;BJH模型较好地反映毛细凝聚现象和滞后环,但由于毛细凝聚只能在中孔中出现,不能解释存在微孔的样品;DR/DA方程只能在地压条件下对微孔吸附进行描述。

After analyzing the gas isothermal adsorption curves described by a large number of experimental data,some conclusions were shown as follows：（ 1） although Langmuir equation has simple form and may calculate gas adsorption amount,the application of the equation is limited by the assumption of uniform solid surface and single layer adsorption;（ 2）BET equation is a common model for calculating specific surface area,but requires the assumption of uniform solid surface;（ 3） although BJH model can better reflect the phenomenon of capillary condensation and hysteresis loop,it can not explain the micro porous sample because the phenomenon of capillary condensation only exists in the medium pore;（ 4） DR / DA model can only describe the gas adsorption of micro pore under the low- pressure condition. The results have great guiding significance to study on the gas adsorption / desorption mechanisms.