甲烷及二氧化碳在不同煤阶煤内部的吸附扩散行为

摘要

The adsorption and diffusion behaviors of methane（CH4）and carbon dioxide（CO2）on various rank coals were investigated with a volumetric method at temperature range from 35 ℃ to 65 ℃ and a pressure of 1.4 MPa.The experimental results show that the second Fick＇s Law can well describe the diffusion behaviors of CH4 and CO2 on various rank coals under the experimental conditions.The effective diffusivities of CH4 and CO2 increase with an increase of temperature and present a U-shaped trend with coal rank,which is indicated by maximum vitrinite reflectance coefficient,Ro,max.The effective diffusivity of CO2 is larger than that of CH4 under the same conditions.The diffusion of CH4 and CO2 on various rank coals is mainly dependent on surface diffusion in micropore.%采用容量法确定吸附量的方法,基于Fick第二定律,在吸附平衡压力约为1.4 MPa,温度为35～65℃的实验条件下,研究了甲烷（CH4）和二氧化碳（CO2）在不同煤阶煤内部的吸附扩散行为。研究结果表明：Fick第二定律能够很好地描述CH4及CO2在不同煤阶煤内部的扩散行为;CH4和CO2有效扩散系数随着吸附温度的升高而增大,同时有效扩散系数和煤阶（利用镜质组最大反射率Ro,max表征）之间呈现＂U＂形关系;相同条件下,同种煤样的CO2有效扩散系数高于CH4;CH4和CO2在不同煤阶煤内部的扩散主要受微孔内部的表面扩散控制。