Coupling of adsorption and strain in coal
Résumé
The swelling of coal induced by an adsorption of CO2 impedes a large scale deployment of carbon storage projects in coal fields. How adsorption can lead to a strain of a porous material is theoretically explained by poromechanical equations extended to microporous media. The adsorption-induced stress depends on the amount adsorbed per unit undeformed volume, in particular how this amount varies with strain. In this work we study the coupling between adsorption and strain in coal in two different ways: by molecular simulation of adsorption in a realistic molecular model of the coal matrix and by analyzing results of immersion experiments in which both the adsorbed amount and the swelling of the sample are measured. For positive strains, the adsorption depends linearly on the strain and the derivative of the adsorbed amount with respect to the strain is almost proportional to the adsorbed amount at zero strain. However, carbon dioxide exhibits a peculiarity for temperatures and pressures close to the critical temperature and pressure, which can be explained by the molecular aggregation which occurs in such conditions. These adsorption behaviors combined with the poromechanical equations enable us to estimate the differential swelling of coal for coalbeds at various depths.
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11_ALERT_Coupling of adsorption and strain in coal.pdf (1.87 Mo)
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11_ALERT_Coupling of adsorption and strain in coal_extended abstract.pdf (24.94 Ko)
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