Institute of Public Safety Research, Department of Engineering Physics, Tsinghua University, Beijing, 100084, China.
School of Emergency Management & Safety Engineering, China University of Mining and Technology-Beijing, Beijing, 100083, China.
Environ Sci Pollut Res Int. 2023 Aug;30(36):85953-85967. doi: 10.1007/s11356-023-28583-w. Epub 2023 Jul 3.
Revealing the characteristics of spontaneous combustion and re-combustion of oxidized coal is of great significance for the coal fire prevention and control. Synchronous Thermal Analyzer (STA) and Fourier Transform Infrared Spectrometer (FTIR) were used to measure the thermal kinetics and microscopic characteristics of coal samples with different oxidation degrees (unoxidized, 100 ℃, 200 ℃ and 300 ℃ oxidized coal). It is found that the characteristic temperatures decrease first and then increase with the increasing degree of oxidation. The ignition temperature of 100 ℃-O coal (oxidized at 100 ℃ for 6 h) is relatively the lowest at 334.1 ℃. Pyrolysis and gas-phase combustion reactions dominate the weight loss process, while solid-phase combustion reactions are relatively minor. The gas-phase combustion ratio of 100 ℃-O coal is the highest at 68.56%. With the deepening of coal oxidation degree, the relative content of aliphatic hydrocarbons and hydroxyl groups gradually decreases, while that of oxygen-containing functional groups (C-O, C = O, COOH, etc.) increases first and then decreases, reaching the highest value of 42.2% at 100 ℃. Moreover, the 100 ℃-O coal has the minimum temperature at the point of maximum exothermic power of 378.5 ℃, the highest exothermic power of -53.09 mW/mg and the maximum enthalpy of -18,579 J/g. All results show that 100 ℃-O coal has the highest risk of spontaneous combustion than the other three coal samples. This suggests that there is a maximum point of spontaneous combustion risk in the range of pre-oxidization temperatures of oxidized coal.
揭示氧化煤自燃和复燃的特性对于煤炭火灾的防治具有重要意义。采用同步热分析仪（STA）和傅里叶变换红外光谱仪（FTIR）对不同氧化程度（未氧化、100℃、200℃和 300℃氧化煤）的煤样进行热动力学和微观特性测试。结果表明，特征温度随氧化程度的增加先降低后升高。100℃-O 煤（在 100℃下氧化 6 小时）的着火温度相对最低，为 334.1℃。热解和气相燃烧反应主导了失重过程，而固相燃烧反应相对较小。100℃-O 煤的气相燃烧比最高，为 68.56%。随着煤氧化程度的加深，脂肪族烃和羟基的相对含量逐渐减少，而含氧官能团（C-O、C=O、COOH 等）的相对含量先增加后减少，在 100℃时达到 42.2%的最高值。此外，100℃-O 煤在最大放热功率点的温度最低，为 378.5℃，最大放热功率为-53.09 mW/mg，最大焓值为-18,579 J/g。所有结果表明，与其他三个煤样相比，100℃-O 煤自燃风险最高。这表明在氧化煤的预氧化温度范围内存在自燃风险的最高点。
