Experimental study on competitive adsorption of coalbed methane power generation tail gas under variable coal seam temperatures

Under the “Dual Carbon” goals, utilizing Coalbed Methane Power Generation Tail Gas for enhanced coalbed methane (ECBM) and CO2 storage in abandoned mines shows significant potential. To investigate the influence of coal seam temperature on tail gas competitive adsorption and CO2 storage, dynamic adsorption experiments were conducted within 30–90°C using a self-developed program-controlled temperature dynamic adsorption apparatus. The results show that: (1) Dynamic adsorption of tail gas comprises three stages: rapid adsorption with massive adsorption of N2, O2, and CO2; displacement adsorption where partially adsorbed N2 and O2 are replaced by CO2; and dynamic equilibrium. (2) Elevated temperature accelerates the breakthrough and mass transfer of N2 and CO2, while the half-saturation time of O2 decreases before 70°C and increases thereafter. The mass transfer rates consistently follow k(N2) > k(O2) > k(CO2). (3) From 30°C to 90°C, N2 adsorption decreases by 82.62% and CO2 adsorption by 98.84%. However, the O2 consumption (physical adsorption + chemical consumption) shows slow linear growth (30–70°C) and exponential growth (70–90°C), with increases of 50.10% (70–80°C) and 96.14% (80–90°C). This indicates that tail gas competitive adsorption is co-regulated by temperature and the coal-oxygen reaction.