As part of our efforts to model enhanced coalbed methane recovery and CO2 sequestration in coalbeds, we have investigated the equilibrium, pure-gas adsorption behavior of five wet Argonne premium coals: namely, Illinois #6, Wyodak sub-bituminous, Pocahontas, Beulah Zap, and Upper Freeport coal; in addition, adsorption was measured on wet F-400 Calgon activated carbon. Using a volumetric technique, isotherms of CO2, methane, and nitrogen were measured at a temperature of 131°F and pressures to 2000 psia at select moisture contents of the adsorbents. Through the simplified local density (SLD) model for adsorption, comparisons are made between the new adsorption measurements on wet adsorbents and the previous adsorption measurements on dry adsorbents.

We have previously used the SLD model to describe isotherm component adsorptions (binary and ternary gas) at temperatures from 113°F to 131°F and for pressures to 2000 psia; the adsorbents were either dry or water-saturated. Here, the SLD model is used to describe how the water content of the adsorbent affects the gas adsorption. The SLD model incorporates a hard-sphere equation of state and a fluid-solid potential function to calculate the local fugacity of the fluid confined in a slit pore.