Coal microstructural and mechanical alterations induced by supercritical CO2 exposure: Role of water

• Published in: Fuel (Guildford) 2023-11, Vol.352, p.128952, Article 128952
• Main Authors: Yang, Yongbo, Xing, Pengchao, Dai, Linchao, Liu, Xianfeng, Nie, Baisheng
• Format: Article
• Language: English
• Subjects: Coal microstructures; Mechanical strength; Pore distribution; ScCO2-water interaction
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2023.128952

•ScCO2-water interaction has significant influence on coal structures and mechanical properties.•Approximately 62.75–85.92% of aliphatic groups within coal are extracted by ScCO2-water.•The UCS is reduced by  800 m are the potential reservoirs for CO2 sequestration, and CO2 is stored in the form of supercritical state. The interactions between supercritical CO2 (ScCO2) and coal are a complex process, which has influence on coal structures and strength. Recent studies are rarely reported regarding the impact of ScCO2-coal-water reactions on coal microstructures and mechanical strength. In this paper, comparative analysis was conducted on the microstructural changes and mechanical degradation of coal induced by ScCO2 treatment and ScCO2-water saturation. The results show that water has great influence on coal pore structure, functional groups, mineral compositions and mechanical properties during the reaction. ScCO2 saturation only triggers a small decline of 11.27–17.65% in aliphatic groups in coal, while approximately 62.75–85.92% of aliphatic groups are extracted by ScCO2-water. The largest hysteresis loops are found in samples saturated by ScCO2-water, followed by the specimens treated by ScCO2, illustrating that the complexity of coal pore structure is enhanced by ScCO2 interaction, and the presence of water can further increase the pore roughness. The UCS is reduced by