(244d) High Pressure Adsorption of CO2 On Dry and Wet Coals

The coal seam is reported as one of favorable storage candidates for CO₂. When CO₂ is stored in the coal seam, CO₂ will be compressed from subcritical condition to supercritical condition. This study measured adsorption and desorption isotherms of CO₂ on dry and wet coals (South Korean Anthracite) by a static volumetric method. In addition, the swelling of coal by CO₂ adsorption was also monitored by a high pressure view cell.

The adsorption isotherms on dry coal were measured at 278.15 K, 298.15 K, 318.15 K and 338.15 K from 0 to 150 atm, while the desorption isotherms were measured at the supercritical temperature conditions (318.15 K and 338.15 K). The supercritical excess adsorbed amounts of CO₂ on coal were fitted by Modified Dubinin-Radushkevich (M-DR) and M-DR+k models. The adsorption isotherm was significantly changed in the range of CO₂ phase transition, such as gas to liquid and gas to supercritical fluid.

Swelling test of coal was done on a dry coal plate at 318.15 K. The swelling and shrinkage of coal during adsorption, desorption and readsorption processes were analyzed. The adsorption capacity of coal was re-evaluated by the swelling effect

In addition, the effect of moisture on the CO₂ adsorption capacity of Korean coal was investigated. The CO₂ adsorption and desorption isotherms on wet coal at 318.15 K and 338.15 K were compared to the results of dry coal. The thermodynamic calculations of CO₂ absorption in water and H₂O vaporization in CO₂ were considered in order to explain the wet coal isotherms.