High-pressure adsorption of pure coalbed gases on dry coals

Scope and method of study. High pressure adsorption of pure methane, nitrogen, CO2 and ethane at 328.2 K (131°F) and pressures to 13.8 MPa (2000 psia) were measured on dry Illinois #6, Wyodak, Pocahontas #3, Beulah Zap, and Upper Freeport coals. Uncertainties associated with the temperature, pressure, and volume measurements as well as the calculated fluid densities were propagated to estimate the uncertainty of each adsorption datum point. The Langmuir model, Loading-Ratio correlation (LRC) and the Ono-Kondo (OK) lattice model were used to represent these pure-gas, high pressure adsorption data of the near-critical and supercritical regions.; Findings and conclusions. The model can describe the present adsorption data within their expected experimental uncertainties. Further, the one-parameter generalized OK model, which relates the model parameters to gas properties and accessible adsorbent characteristics, can represent the adsorption isotherms on dry coals with 7% average absolute deviation or twice the expected experimental uncertainties. (Abstract shortened by UMI.)...