Multiphase Analysis for High-Pressure Adsorption of CO2/Water Mixtures on Wet Coals

Abstract

Traditional modeling of gas adsorption on wet coals does not consider water as a separate adsorbed component and treats the adsorbed water as a “pacifier” of the coal matrix. In a recent work, we presented a new modeling approach for investigating the competitive adsorption of gas/water mixtures in high-pressure systems. We used the simplified local-density (SLD) model to investigate the effect of including the competitive adsorption of water present in coals on gas adsorption under the conditions encountered in coalbed methane (CBM) and CO2 sequestration applications. In continuation of that work, we present here a new multiphase algorithm to investigate the three-phase adsorption equilibrium of CO2/water mixtures on wet coals. When water is treated as one of the adsorbed components in a high-pressure gas adsorption system, as many as three fluid phases may coexist at equilibrium (gas, adsorbed, and liquid phases). A new algorithm is presented in this work to facilitate a Gibbs energy-driven multiphase a...