煤自燃程序升温实验及其在实验教学中的应用

Experiment on the programmed temperature rise in a spontaneous combustion of coal and its application in experimental teaching

该文利用程序升温实验系统,对三种氧气浓度(20.9%、10%和7%)所代表的采空区散热带、氧化带、窒息带进行了煤样自燃发火实验,采集了不同温度阶段的气体产物,分析了温度及氧气浓度对气体产物浓度的影响,并对指标气体进行了详细分类和评估。实验结果表明:交叉点温度CPT随着氧气浓度的升高而降低,干空气的交叉点温度为144.6℃,由经验关系计算得到的CPT值与实验数据相差仅6.08%;氧气浓度越高,临界温度越低,所产生的气体浓度越高;CO气体在不同的含氧环境下都是主要的氧化产物,可作为判断煤自燃发火的主要指标,C_(2)H_(4)和C_(3)H_(6)的产生表示煤体进入加速氧化状态,可作为判断煤自燃发火的辅助指标。

[Objective]As the main energy source in China,coal has an important strategic position in the country’s economic development.China’s coal-based energy structure model will not change in the short term,but coal mine accidents occur frequently.Mine fire is a major disaster that threatens safe coal mine production,which incurs huge economic losses and threatens the personal safety of miners and coal mine production.However,coal spontaneous combustion primarily causes mine fires.The occurrence mechanism of coal spontaneous combustion is highly complex and is affected by the inherent combustion characteristics of coal and external environmental factors.Therefore,it is necessary to comprehensively analyze various phenomena and characteristics in the process of coal spontaneous combustion and apply quantitative indicators to express to predict the risk and ensure the safe production of the mine.[Methods]Oxygen concentration is an important factor influencing coal oxidation reaction.In this paper,the temperature-programmed experimental system is used to conduct the spontaneous combustion experiment of coal samples with three oxygen concentrations of 20.9%,10%,and 7%regarding the heat dissipation,oxidation,and asphyxiation zones in the goaf.The gas products at different temperature stages are collected,the effects of temperature and oxygen concentration on the concentration of gas products are analyzed,and the index gases are classified and evaluated in detail.[Results]The results show the following:(1)The cross-point temperature(CPT)decreases with the increase in the oxygen concentration.The cross-point temperature under dry-air conditions is 144.6℃.The error between the CPT value calculated by the BM empirical relationship and the experimental data is only 6.08%.The higher the oxygen concentration,the smaller the critical temperature,and the higher the gas concentration.(2)The content of oxidation products increases with the oxygen concentration.When heating commences,minimal CO and CH4 gases are generated,but with the increase in the temperature,C_(2)H_(4) and C2H6 gases appear gradually.The oxidation reaction of coal samples is primarily affected by temperature and oxygen concentration.At a certain temperature,the higher the oxygen concentration,the more intense the coal-oxygen composite reaction,and more gas products appear.(3)For different oxygen concentration environments,the regularity of generating CO gas is highly significant,which can be used as an indicator gas to evaluate the spontaneous combustion of coal.In dry air,the temperature of C_(2)H_(4) is earlier than that of C_(3)H_(6),implying that the existence of C_(2)H_(4) indicates that the coal oxidation process has entered an accelerated stage.The emergence of C_(3)H_(6) gas marks the transformation of the coal oxidation into strong oxidation.Recently,the programmed temperature rise experiment has become an important research field.[Conclusions]Through indoor experiments,students can deeply understand the mechanism of coal spontaneous combustion and the process of establishing the prediction index system and introduce the experiment into the classroom.This practical teaching approach not only helps students to apply theoretical knowledge to practical problems but also broadens their horizons and improves their interest in scientific research,achieving better teaching results.