(694e) Measurements and Modeling of in-Situ Gas Densities and Adsorption Isotherms for CO2 On Wet Coals

High-Pressure gas adsorption isotherms on wet coals are typically measured without the aid of an in situ gas density meter. As a result, the densities of bulk gas-phase are inferred either volumetrically or gravimetrically with the assumption that the gas-phase free from water vapor (or dry). However, the effect of the presence of water vapor in the gas-phase for adsorption isotherms of a supercritical gas such as CO₂ may be an over-simplification and may lead to significant errors in the data reduction of the adsorption isotherms. To test this hypothesis, a vibrating tube density meter was installed within a high-pressure adsorption apparatus to measure the in situ gas densities for CO₂ isotherms on wet coals. Further, a new data reduction method was implemented that utilizes the accurate measurements of wet gas densities rather than the densities of pure CO₂ (or dry gas density). In this manner, the adsorption isotherm measurements were aided by the inclusion of a gas-phase density meter.

Two data reduction approaches can be formulated and applied for adsorption isotherms based on these new measurements. The two approaches differ in the manner in which the effect of moisture on gas adsorption is taken into account. The two approaches and their relative merits will be presented. Further, the adsorption isotherm data obtained from the two approaches were modeled with the simplified local density (SLD) adsorption model. An analysis and interpretation of the SLD model results based on these two approaches will also be presented for these systems.