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<p>To investigate the thermal properties and microscopic mechanisms of secondary oxidation, water-immersed coal (WIC) and WIC subjected to pre-oxidized at 90–180&#xa0;°C were prepared. Low-temperature nitrogen adsorption, simultaneous thermal analysis, and in situ Fourier-transform infrared spectroscopy were employed to study the pore structure, thermal behavior at different stages, and the dynamic changes of functional groups in coal. The findings show that, with increasing pre-oxidation temperature, the specific surface area and pore volume of coal subjected to water immersion initially rise and subsequently decline. Meanwhile, parameters <i>D</i><sub>1</sub> and <i>D</i><sub>2</sub> exhibit an increase. Sample #2 exhibited the maximum heat release (1749.49&#xa0;J/g), the lowest activation energy, and the most vigorous combustion response. Water immersion and pre-oxidation alter the distribution and thermal stability of oxygen-containing functional groups. Sample #2 exhibited a notably greater –OH concentration compared with the other coal samples, enhancing oxidation and elevating both carbonyl content and C–O single bond levels throughout the dehydration and weight loss phases. The active functional groups, including carbonyl, carboxyl, and carbon–oxygen single bonds, are swiftly depleted by interconversion during the pyrolysis phase, while the buildup of heat expedited spontaneous combustion. The experimental results determined an optimal pre-oxidation temperature range responsible for coal spontaneous combustion (CSC) initiation, explained the interactive effects of water immersion and pre-oxidation on CSC characteristics, and supplied theoretical guidance for CSC control and coal mine safety management.</p>

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Chemical Structure Evolution and Thermodynamic Characteristics of Coal Under Water–Heat Coupling Effect

  • 期刊论文

  • 发表日期：

    2026年1月10日

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  • Xiaolu Liu,
  • Haiyan Wang,
  • Huiyong Niu,
  • Gongda Wang,
  • Zhuangzhuang Shao,
  • Yanxiao Yang,
  • Yikang Liu,
  • Haoliang Zhu

摘要

To investigate the thermal properties and microscopic mechanisms of secondary oxidation, water-immersed coal (WIC) and WIC subjected to pre-oxidized at 90–180 °C were prepared. Low-temperature nitrogen adsorption, simultaneous thermal analysis, and in situ Fourier-transform infrared spectroscopy were employed to study the pore structure, thermal behavior at different stages, and the dynamic changes of functional groups in coal. The findings show that, with increasing pre-oxidation temperature, the specific surface area and pore volume of coal subjected to water immersion initially rise and subsequently decline. Meanwhile, parameters D1 and D2 exhibit an increase. Sample #2 exhibited the maximum heat release (1749.49 J/g), the lowest activation energy, and the most vigorous combustion response. Water immersion and pre-oxidation alter the distribution and thermal stability of oxygen-containing functional groups. Sample #2 exhibited a notably greater –OH concentration compared with the other coal samples, enhancing oxidation and elevating both carbonyl content and C–O single bond levels throughout the dehydration and weight loss phases. The active functional groups, including carbonyl, carboxyl, and carbon–oxygen single bonds, are swiftly depleted by interconversion during the pyrolysis phase, while the buildup of heat expedited spontaneous combustion. The experimental results determined an optimal pre-oxidation temperature range responsible for coal spontaneous combustion (CSC) initiation, explained the interactive effects of water immersion and pre-oxidation on CSC characteristics, and supplied theoretical guidance for CSC control and coal mine safety management.