Abstract To analyze the secondary oxidation of the active structures of pulverized coal and reduce risks of coal spontaneous combustion, free radical theory and functional group analysis were combined to study the effects of particle size and oxidation temperature on the active structure of coal molecules. This process was based on electron paramagnetic resonance (EPR) and Fourier-transform infrared (FTIR) technology. The results show that the reduction in pulverized coal particle size can enhance the secondary oxidation activity of coal and that the reactivity is the strongest when the particle size is 0.074−0 mm. The smaller the coal particle size is, the shorter the aliphatic side chain is after secondary oxidation. The reaction in which the side chain breaks to form a stable chain structure is also more intense. A smaller coal particle size also makes it easier to produce −OH after secondary oxidation, resulting in a large increase in the Average A (−OH) in the Coal 1# and Coal 3# at the minimum particle size range of 0.074−0 mm. The −C=O and −C−O− in Coal 1# with a lower metamorphic grade are greatly affected by temperature and particle size, and the consumption of −C=O during oxidation plays a dominant role in the secondary oxidation process. The −C=O and −C−O− in Coal 2# and Coal 3# are less affected by temperature and more affected by particle size, and −C−O− is the main group driving the secondary oxidation reaction.

中文翻译：

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粒径和低温二次氧化对煤结构活性基团的影响

摘要 为分析煤粉活性结构的二次氧化，降低煤自燃风险，结合自由基理论和官能团分析，研究了煤粉粒径和氧化温度对煤分子活性结构的影响。该过程基于电子顺磁共振 (EPR) 和傅里叶变换红外 (FTIR) 技术。结果表明，减小煤粉粒径可提高煤的二次氧化活性，粒径为0.074-0 mm时反应性最强。煤的粒径越小，二次氧化后脂肪族侧链越短。侧链断裂形成稳定链结构的反应也更加激烈。较小的煤粒径也使得二次氧化后更容易产生-OH，导致煤1#和煤3#在最小粒径0.074-0 mm范围内的平均A（-OH）大幅增加. 变质品位较低的煤1#中-C=O和-CO-受温度和粒径的影响很大，氧化过程中-C=O的消耗在二次氧化过程中起主导作用。Coal 2#和Coal 3#中的-C=O和-CO-O-受温度影响较小，受粒径影响较大，-CO-是驱动二次氧化反应的主要基团。变质品位较低的煤1#中-C=O和-CO-受温度和粒径的影响很大，氧化过程中-C=O的消耗在二次氧化过程中起主导作用。Coal 2#和Coal 3#中的-C=O和-CO-O-受温度影响较小，而受粒度影响较大，-CO-是驱动二次氧化反应的主要基团。变质品位较低的煤1#中-C=O和-CO-受温度和粒径的影响很大，氧化过程中-C=O的消耗在二次氧化过程中起主导作用。Coal 2#和Coal 3#中的-C=O和-CO-O-受温度影响较小，受粒径影响较大，-CO-是驱动二次氧化反应的主要基团。