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<p>This study explores the re-ignition characteristics of overfired coal derived from three typical low-rank coals prone to spontaneous combustion: Zhalainuoer (ZH) lignite, Zhungeer (ZC) long-flame coal, and Shenfu-Dongsheng (DB) non-caking coal. The influence of pyrolysis reactions at varying temperatures on the formation of overfired coal was systematically analyzed, followed by an assessment of its re-ignition properties. The results reveal consistent pyrolysis behavior across all three coals, characterized by critical transitions around 500&#xa0;°C. While the volatile release rate increases with temperature, it diminishes beyond 500&#xa0;°C due to the formation of semi-coke. Higher-rank coals exhibit greater residual mass, and prolonged pyrolysis intensifies macromolecular reactions. Pyrolysis also induces significant alterations in functional group composition, with reductions in hydroxyl and aliphatic hydrocarbons and an increase in aromatic hydrocarbons. During re-ignition, ignition point temperatures initially decrease and then increase with rising pyrolysis temperatures, with ZC overfired coal demonstrating the highest sensitivity to these changes. Combustion intensity is most pronounced in ZC overfired coal, with heat release peaking at 500&#xa0;°C before declining. Among the three coals, DB overfired coal exhibits the highest total heat release, followed by ZH and ZC, which is attributed to structural transformations and the breakdown of weak bonds during pyrolysis. These findings offer critical insights into the re-ignition behavior of overfired coal, providing a foundation for improved spontaneous combustion risk management strategies.</p>

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Pyrolysis-induced transformations and re-ignition behavior of overfired low-rank coals under oxygen exposure

  • 期刊论文

  • 发表日期：

    2025年9月18日

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  • Liangzhou Chen,
  • Wei Lu,
  • Xuyao Qi,
  • Jinhu Li,
  • Jinliang Li

摘要

This study explores the re-ignition characteristics of overfired coal derived from three typical low-rank coals prone to spontaneous combustion: Zhalainuoer (ZH) lignite, Zhungeer (ZC) long-flame coal, and Shenfu-Dongsheng (DB) non-caking coal. The influence of pyrolysis reactions at varying temperatures on the formation of overfired coal was systematically analyzed, followed by an assessment of its re-ignition properties. The results reveal consistent pyrolysis behavior across all three coals, characterized by critical transitions around 500 °C. While the volatile release rate increases with temperature, it diminishes beyond 500 °C due to the formation of semi-coke. Higher-rank coals exhibit greater residual mass, and prolonged pyrolysis intensifies macromolecular reactions. Pyrolysis also induces significant alterations in functional group composition, with reductions in hydroxyl and aliphatic hydrocarbons and an increase in aromatic hydrocarbons. During re-ignition, ignition point temperatures initially decrease and then increase with rising pyrolysis temperatures, with ZC overfired coal demonstrating the highest sensitivity to these changes. Combustion intensity is most pronounced in ZC overfired coal, with heat release peaking at 500 °C before declining. Among the three coals, DB overfired coal exhibits the highest total heat release, followed by ZH and ZC, which is attributed to structural transformations and the breakdown of weak bonds during pyrolysis. These findings offer critical insights into the re-ignition behavior of overfired coal, providing a foundation for improved spontaneous combustion risk management strategies.