Competitive adsorption characteristics of N2 and CH4 gas mixtures on coal and its geological significance

Abstract

Coalbed methane (CBM) is an important unconventional natural gas resource and has achieved great advances in recent years. In this study, single and binary component adsorption experiments of N2 and CH4 on dry coal from eastern Yunnan and western Guizhou area were conducted on a high-pressure isothermal adsorption equipment to investigate the competitive adsorption characteristics of N2 and CH4. The results show that absolute adsorption capacity of methane is higher than that of nitrogen for coal samples in this area. Moreover, maximum mixture gas adsorption isotherms lie between the pure N2 isotherms and pure CH4 isotherms. There is an obvious increasing trend for PL as the content of nitrogen increases, it can be ruled out that critical desorption pressure increases along with the increasing nitrogen content in coal seam. This investigation is significative to understand CBM recovery processes considering N2 injection.