Impact of water contents on the chemical composition and structure of coals under supercritical CO2 (ScCO2)

作者：Xiao Hui Zhang, Zeyuan Sun, Z. H. Zhang, Shuo ZHANG, Yanli Li, Zhigang Du · 发表于：DOAJ (DOAJ: Directory of Open Access Journals) · 年份：2026 · DOI：10.13225/j.cnki.jccs.2024.1350 · 研究领域：Coal Properties and Utilization、Thermochemical Biomass Conversion Processes、Hydrocarbon exploration and reservoir analysis

In the process of CO2 sequestration in deep coal seams, CO2 usually exists in a supercritical state (ScCO2) and undergoes complex physicochemical reactions with water and coal, resulting in changes of coal chemical composition and structure and thus affecting the CO2 sequestration efficiency. To study the influence laws of ScCO2 on coal chemical composition and structures under different water contents, ScCO2-coal reaction experiments were conducted using coking coal samples. Then, the differences in coal composition and structure before and after the reaction were discussed. Finally, the influencing mechanism of water contents on the ScCO2-coal reaction was revealed. The results show that: ScCO2 dissolves carbonate minerals in coal more effectively than clay minerals, and the mass fraction of carbonate minerals in the residual coal increases and then decreases with the increase of water content; at higher water content, the reaction between ScCO2 and carbonate minerals in coal is stronger than that of clay minerals, thus causing a more significant depletion of carbonate minerals. ScCO2 and H2O exert a significant influence on the oxygen-containing functional groups, but they give a weak impact on aromatic and aliphatic hydrocarbons; specifically, ScCO2 reduces the content of oxygen-containing functional groups in coal. Furthermore, as the water content increases, the oxygen-rich index (I2) increases significantly, while the hydrogen-rich index (I1), aromaticity (I3), and con...