The study of gas sorption characteristics is important for practical assessment of coal bed methane(CBM)production and CO2 sequestration in coal seam.Adsorption isotherm is one of the critical parameters for the establishment of production as well as injection well.Adsorption isotherm provides information about the reservoir conditions and critical desorption pressure as well as volume of gas that can be sequestered in deep coal seam.Alteration in sorption isotherm reflects the increase or decrease of the gas production as well as CO2 sequestration.Therefore,in this paper,experimental investigation was carried out to determine the CO2/CH4 sorption capacity of five different coal samples taken from different locations of Jharia coalfield(Moonidih area)of Gondwana basin.Gas sorption capacity was determined at 27 ℃ temperature and up to 7.5 MPa pressure.CO2 adsorption was observed to be higher than that of the CH4.The sorption ratio of CO2/CH4 varied from 1.6:1 to 1.2:1 for all coal samples.Furthermore,the experimental results were correlated using established Langmuir,Freundlich,Temkin and D-R isotherm models.Experimentally obtained values satisfactorily fitted to the Langmuir and Freundlich model with comparable accuracy.The excess adsorption capacity of coal was also compared with different rank parameters to understand the variation of sorption capacity with rank of coal.
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