%0 Journal Article
%T Volumetric Measurements of Methane-Coal Adsorption and Desorption Isotherms¡ªEffects of Equations of State and Implication for Initial Gas Reserves
%J Energies | An Open Access Journal from MDPI
%D 2019
%R https://doi.org/10.3390/en12102022
%X This study presents the effects of equations of state (EOSs) on methane adsorption capacity, sorption hysteresis and initial gas reserves of a medium volatile bituminous coal. The sorption experiments were performed, at temperatures of 25 ¡ãC and 40 ¡ãC and up to 7MPa pressure, using a high-pressure volumetric analyzer (HPVA-II). The measured isotherms were parameterized with the modified (three-parameter) Langmuir model. Gas compressibility factors were calculated using six popular equations of state and the results were compared with those obtained using gas compressibility factors from NIST-Refprop £¿ (which implies McCarty and Arp¡¯s EOS for Z-factor of helium and Setzmann and Wagner¡¯s EOS for that of methane). Significant variations were observed in the resulting isotherms and associated model parameters with EOS. Negligible hysteresis was observed with NIST-refprop at both experimental temperatures, with the desorption isotherm being slightly lower than the adsorption isotherm at 25 ¡ãC. Compared to NIST-refprop, it was observed that equations of state that gave lower values of Z-factor for methane resulted in ¡°positive hysteresis¡±, (one in which the desorption isotherm is above the corresponding adsorption curve) and the more negatively deviated the Z-factors are, the bigger the observed hysteresis loop. Conversely, equations of state that gave positively deviated Z-factors of methane relatively produced ¡°negative hysteresis¡± loops where the desorption isotherms are lower than the corresponding adsorption isotherms. Adsorbed gas accounted for over 90% of the calculated original gas in place (OGIP) and the larger the Langmuir volume, the larger the proportion of OGIP that was adsorbed. View Full-Tex
%U https://www.mdpi.com/1996-1073/12/10/2022