Adsorption and Desorption of CO2 on Korean Coal under Subcritical to Supercritical Conditions

Coal seams have been reported as possible storage sites for CO2 to help mediate the global greenhouse gas problem. The adsorption and desorption characteristics of CO2 on dry and wet (3.64 wt %) Korean coal (Kyungdong, anthracite coal) were studied using a static volumetric method at 298 and 318 K, and up to 150 atm. The adsorption of CO2 was favorable at low temperatures and dry coal conditions. The hysteresis of coal swelling through adsorption, desorption, and readsorption of CO2 was observed at subcritical condition. Hysteresis between adsorption and desorption isotherms occurred in both dry and wet coals. The crossover between adsorption and desorption isotherms in dry coal was observed near the critical region, while the excess amount of adsorbed CO2 on wet coal was lower during desorption than during adsorption. Structural variations of the coal after the wet experiment were significant compared to those in the dry coal. In wet coal, the dissolution of H2O in the CO2 phase, absorption of CO2 in the aqueous phase, and coal structure changes affected the estimation of adsorption amount, especially under supercritical condition.