ABSTRACT

Coal fires are very typical hazards caused most significantly by uncontrolled spontaneous combustion processes in coal mines, seams, and the like. By thermogravimetry (TG) experiments, evolution behaviors and properties of thermal oxidation processes at low temperature of a bituminous coal with five microscale particle sizes (L1 215.20 μm; L2 151.90 μm; L3 80.22 μm; L4 43.71 μm; and L5 19.21 μm) were investigated. A two-step reaction model was developed by using Coats–Redfern method and pyrolysis kinetics parameters were calculated. Results show that in stage 1 (65.0–160.0°C) segments of water evaporation and gas desorption dominate, while in stage 2 (160.0–320.0°C) segments of generation of coal–oxygen complex and structure oxidation contribute most. Five macro-characteristic temperatures (critical temperature T₁, xerochasy temperature T₂, activity temperature T₃, mass peak temperature T₄, and ignition temperature T₅) move to the low temperature direction with decreasing particle sizes except T₄. Reaction processes during coal–oxygen interactions are proposed. Activation energies decrease as particle sizes reduce during both stage 1 (15.01–32.47 kJ·mol⁻¹) and stage 2 (64.29–96.34 kJ·mol⁻¹) since specific surface areas are augmented and more active groups are exposed. This work is expected to better monitoring of temperature thresholds for coal spontaneous combustion processes.

摘要

煤火是非常典型的危害，主要由煤矿、煤层等不受控制的自燃过程引起。通过热重（TG）实验，研究了五种微尺度（L1 215.20 μm；L2 151.90 μm；L3 80.22 μm；L4 43.71 μm；L5 19.21 μm）烟煤低温热氧化过程的演化行为和性质调查。使用 Coats-Redfern 方法建立了两步反应模型，并计算了热解动力学参数。结果表明，在阶段 1 (65.0–160.0°C) 中，水蒸发和气体解吸环节占主导地位，而在阶段 2 (160.0–320.0°C) 中，煤氧络合物的生成和结构氧化环节贡献最大。五宏观特征温度（临界温度T ₁, 干法温度T ₂ , 活性温度T ₃ , 质量峰温度T ₄ , 引燃温度T _{5 )除T 4}外均向低温方向移动,粒径减小。提出了煤-氧相互作用过程中的反应过程。^{在第 1 阶段 (15.01–32.47 kJ·mol -1} ) 和第 2 阶段(64.29–96.34 kJ·mol ^-1 )期间，随着粒径减小，活化能降低，因为比表面积增加，更多活性基团暴露。这项工作有望更好地监测煤自燃过程的温度阈值。