煤氧化特性的STA-FTIR实验研究

采用同步热分析-红外联用技术(STA-FTIR),以4种不同变质程度的新鲜煤样为研究对象,从特征温度点、热量变化、逸出气体、氧化反应动力学等多角度分析煤的氧化放热特性及其规律。研究结果表明,随着煤变质程度降低,煤中挥发分含量增高,煤氧化过程特征温度点逐渐减小;各个阶段反应活化能逐渐变小,最大热释放速率和放热量相应增加;同时,氧化过程中所释放的CO,CO2,H2O,CH4等气体的初始温度和峰值温度均呈现出逐渐减小趋势,生成CO量减少,CO2和水量增加;此外,不同煤样在水分蒸发及脱附阶段、吸氧增重阶段的反应机理接近。实验结果说明不同煤样的氧化反应过程具有相似性,变质程度越低的煤,发生氧化和燃烧反应越容易,自燃危险性越高。应根据煤样存储、开采、运输环境,针对初始放热温度较低的低变质煤样,及时采取冷却降温、封堵裂隙、阻化剂阻化等措施预防煤自燃发生和发展。

Oxidation characteristics of coal by STA-FTIR experiment

The aim of this study was to use the simultaneous thermal analysis-Fourier transform infrared spectroscopy (STA-FTIR) technique to analyse the oxidation and exothermic behaviours for four types of fresh coals based on various critical factors,such as characteristic temperatures,change of heat,releasing gases,reaction kinetics.A foundation of prevention and control technology in spontaneous combustion of coal was established.In accordance with experimental results,with the decrease of metamorphic grade of coal,the volatile matters,heat releasing rate,and the total heat release were also increased.The characteristic temperature gradually reduced,and the initial temperature and peak temperature in gases releasing of H2O,CO2,CO,and CH4 during the non-isothermal oxidation process were lower,decreasing in the generation of CO.By contrary,the great amounts of CO2 and H2O were increased.In addition,the function of reaction mechanism in water evaporation,oxygen desorption,and mass gain process are similar.This demonstrates that the different coals have a similar reaction process.When the metamorphic grade of coal is lower,the oxidation and combustion reaction is easier and the hazard of spontaneous combustion of coal is more serious.Therefore,according to different storage,mining,or transportation conditions,the cooling system,sealing off the cracks,or suitable inhibition agent should be adopted to prevent the spontaneous combustion in the lower metamorphic grade of coal with low initial temperature.