Effect of supercritical-CO2 interaction time on the alterations in coal pore structure

摘要: Abstract The supercritical CO2 (S-CO2) interaction time is a vital parameter in geo-sequestration coal seams, which under-evaluated up to date. Through this study, we provide an experimental insight into aspect by evaluating the effect of S-CO2 on pore structural alterations. results revealed that pre-exposure has notable impact adsorption capacity coal, short-term (order hours) and long-term weeks) S-CO2-treated show less higher capacities, respectively, compared untreated coal. characterisation infer both surface area volume are decreased about 20% after treatment then approximate linear increment with further longer time. Based observations, propose conceptual model explain temporal alterations, elucidate complex alterations morphology occur due combined multiple factors: 1) adsorption-induced matrix swelling consequent shrinkage, causes physical constriction pores, reducing volume, 2) S-CO2-induced plasticization extracts mobilizes low-molecular-weight hydrocarbons, entrapped mouths or necks, increasing number accessible pores. resultant overall alteration at given depends competitive behaviour significance processes. proposed supported measuring volumetric matrix, concludes 70% already been completed within 24 h coal-S-CO2 interaction, causing shrinkage and, analysing FT-IR spectrums, confirms bond dissociation substitution, confirming re-arrangement macromolecular structure possibly leads hydrocarbon mobilization