Study on the Thermodynamic Characteristics of Methane Adsorption–Desorption in Coal under Infrared Radiation Heating

Coalbed methane (CBM) is unconventional natural gas. In this study, the thermodynamic characteristics of the coal adsorption-desorption methane process under infrared radiation heating (IRH) conditions were investigated. These findings indicate that as the infrared radiation power increases, the lag effect of methane desorption significantly decreases. The methane desorption process exhibits nonspontaneous endothermic entropy-increasing characteristics, and the required energy is significantly higher than that of the spontaneous exothermic adsorption process. Infrared radiation increases the thermodynamic energy of the system, which disrupts the adsorption potential equilibrium and effectively induces methane desorption. The difference in adsorption-desorption volume work decreases with increasing infrared power, whereas the increase in critical desorption pressure reduces the proportion of desorption lag volume energy in the total energy, increasing CBM extraction efficiency. This study reveals the thermodynamic mechanisms of methane desorption lag under infrared heating conditions, providing a theoretical basis for the development of CBM.