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<p>Carbon dioxide emissions from coal fired power plants are a major contributor to the greenhouse effect. As a sustainable negative emissions technology, injecting CO₂ into underground coal mine goafs for long-term storage offers both environmental and economic benefits. However, the dynamic chemical processes governing the long-term interactions within the multiphase system of coal, rock, water, and CO₂ in goafs remain poorly understood. To address this gap, under actual goaf conditions (308&#xa0;K, ambient pressure), this study conducted a 28-day experiment on the interactions of CO₂ and water with coal and coal-rock mixture samples. Changes in mineral composition and functional groups before and after the reaction were analyzed by TG-MS, FTIR, and SEM-EDS. The results reveal that water exerts a dual effect during coal-CO₂ interaction. In the early stage (≤ 14 days), water promotes CO₂ hydrolysis and the dissolution of minerals, accelerating the precipitation of carbonate minerals. However, in the later stage, water intensifies the dissolution of carbonates. It also promotes the hydrolysis of functional groups in the coal. In the coal-rock mixture system, Al-OH and Si-OH groups on clay mineral surfaces stabilize carbonates by consuming H<sup>+</sup>. Organic acids complex with Al<sup>3+</sup> and Si<sup>4+</sup>, improving the pore structure. And significantly enhances CO₂ adsorption capacity. At 28 days, the CO₂ uptake of the dry coal and the water-containing coal samples reached 16.14&#xa0;g/kg and 20.32&#xa0;g/kg, respectively. Compared with the coal sample, the coal-rock mixture and the water-containing sample exhibited increases in total CO₂ adsorption of 33.20&#xa0;g/kg and 37.65&#xa0;g/kg. This study elucidates the dynamic mechanisms governing the long-term evolution of the multiphase system of coal, rock, water, and CO₂. It confirms that coal gangue plays an active role in the long-term CO₂ storage in goafs. These findings provide a theoretical foundation for the resource utilization of coal gangue and the enhancement of CO₂ storage in goafs.</p>

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Study on the dynamic mechanism of long-term CO₂-water-coal-rock system interactions in underground coal mine goafs of the Tashan coal mine, Datong

  • 期刊论文

  • 发表日期：

    2026年7月22日

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  • Yansheng Wang,
  • Jun Li,
  • Ling Qiao,
  • Cunbao Deng,
  • Qingsheng Xu,
  • Zhixin Jin

摘要

Carbon dioxide emissions from coal fired power plants are a major contributor to the greenhouse effect. As a sustainable negative emissions technology, injecting CO₂ into underground coal mine goafs for long-term storage offers both environmental and economic benefits. However, the dynamic chemical processes governing the long-term interactions within the multiphase system of coal, rock, water, and CO₂ in goafs remain poorly understood. To address this gap, under actual goaf conditions (308 K, ambient pressure), this study conducted a 28-day experiment on the interactions of CO₂ and water with coal and coal-rock mixture samples. Changes in mineral composition and functional groups before and after the reaction were analyzed by TG-MS, FTIR, and SEM-EDS. The results reveal that water exerts a dual effect during coal-CO₂ interaction. In the early stage (≤ 14 days), water promotes CO₂ hydrolysis and the dissolution of minerals, accelerating the precipitation of carbonate minerals. However, in the later stage, water intensifies the dissolution of carbonates. It also promotes the hydrolysis of functional groups in the coal. In the coal-rock mixture system, Al-OH and Si-OH groups on clay mineral surfaces stabilize carbonates by consuming H+. Organic acids complex with Al3+ and Si4+, improving the pore structure. And significantly enhances CO₂ adsorption capacity. At 28 days, the CO₂ uptake of the dry coal and the water-containing coal samples reached 16.14 g/kg and 20.32 g/kg, respectively. Compared with the coal sample, the coal-rock mixture and the water-containing sample exhibited increases in total CO₂ adsorption of 33.20 g/kg and 37.65 g/kg. This study elucidates the dynamic mechanisms governing the long-term evolution of the multiphase system of coal, rock, water, and CO₂. It confirms that coal gangue plays an active role in the long-term CO₂ storage in goafs. These findings provide a theoretical foundation for the resource utilization of coal gangue and the enhancement of CO₂ storage in goafs.