Title: Effects of ethanol-mixed supercritical CO₂ fluid on CO₂ adsorption on coals: implications for CO₂ geologic storage in coal seams

Authors: Dengfeng Zhang; Zichao Hu

Addresses: Faculty of Chemical Engineering, Kunming University of Science and Technology, No. 727 Jingming South Road, Chenggong District, 650500 Kunming, China ' Faculty of Chemical Engineering, Kunming University of Science and Technology, No. 727 Jingming South Road, Chenggong District, 650500 Kunming, China

Abstract: The coal matrix swelling induced by CO₂ decreases the permeability of the target coal seams, and it will trigger disadvantages to CO₂ storage in deep coal reservoirs. In order to mitigate such swelling effect, the addition of ethanol into CO₂ is proposed. The effects of ethanol-mixed supercritical CO₂ on the adsorption equilibrium and kinetics behaviors of CO₂ adsorption on coals are studied in this paper. The results indicate that the ethanol-mixed supercritical CO₂ fluid could increase CO₂ adsorption capacity of two coals with low metamorphic degree, but decrease that of two coals with high metamorphic degree. The addition of ethanol into CO₂ fluid remarkably enhances the diffusion and adsorption rate of CO₂ within the micropores and macropores of coals. The alterations of pore system of various rank coals could account for the changing law of CO₂ adsorption equilibrium and kinetics behaviors on coals after interacting with ethanol-mixed supercritical CO₂.

Keywords: coal; CO₂ storage; adsorption; ethanol; supercritical CO₂ fluid.

DOI: 10.1504/IJGW.2020.108675

International Journal of Global Warming, 2020 Vol.21 No.3, pp.274 - 286

Received: 19 Sep 2019
Accepted: 25 Jan 2020
Published online: 24 Jul 2020 *

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