Effect of Equation of States on High-Pressure Volumetric
Measurements of Methane–Coal Sorption IsothermsPart
1: Volumes of Free Space and Methane Adsorption Isotherms
posted on 2019-01-24, 00:00authored byJamiu M. Ekundayo, Reza Rezaee
High-pressure volumetric
analysis (HPVA) experiments were carried
out using Particulate System’s HPVA-II 200 at temperatures
of 25 and 40 °C and pressures up to 7 MPa to quantify methane
adsorption capacities of a coal sample. Six well-known equations of
state (EOSs), namely, Peng–Robinson (PR), Soave–Redlich–Kwonk
(SRK) and their volume translated forms (PR-Peneloux and SRK-Peneloux),
Soave modified Benedict–Webb–Rubin (SBWR), and Lee–Kesler
(LK) were used for data interpretation, and the results were compared
with those calculated by the equipment using Z-factors
from NIST-refprop software implementation of McCarty and Arp EOS for
helium and Setzmann and Wagner EOS for methane. Because of variations
in the Z-factors of helium and supercritical methane
obtained from the different EOSs, large variations were observed in
calculated isotherms and Langmuir parameters with the PR-Peneloux
and PR-EOS family showing the largest relative deviations, while SRK-EOS
and SRK-Peneloux gave more negative adsorption for each temperature.
All the EOSs gave significantly lower density for the adsorbed phase
at 40 °C compared to the value at 25 °C. This is consistent
with the negative effect of temperature on adsorption.