ABSTRACT

A good understanding of the intrinsic relationship between heat evolution and mass change induced by coal–oxygen oxidation reaction is critical for accurately predicting the behaviour of spontaneous combustion. In this study, thermal subtraction method and six sets of characteristic temperatures were introduced to explore the intrinsic reaction between coal and oxygen which provides the main heat source responsible for coal self-heating. The heat evolution and mass change during coal spontaneous combustion were measured in real time using a sensitive differential scanning calorimeter (DSC) and a thermogravimetric analyzer (TG), respectively. The DSC and TG subtraction curves obtained from subtracting the results of nitrogen atmosphere from those of air atmosphere can reveal the heat change and mass change due only to the reaction between coal and oxygen. The term of q/m defined as the amount of heat release by the change of per unit of coal mass was introduced to study the intrinsic relationship between heat evolution and mass change during coal spontaneous combustion. The q/m values of the three coals show different evolution trends as coal temperature increases and are related to the mechanism of coal spontaneous combustion. The kinetics analysis of this intrinsic relationship was also carried out based on experimental data. Moreover, q/m can be used in the evaluation of spontaneous combustion propensity with respect to different coal types.

摘要

充分理解煤-氧氧化反应引起的放热和质量变化之间的内在关系对于准确预测自燃行为至关重要。本研究引入热减法和六组特征温度，探索煤与氧气之间的内在反应，氧气为煤自热提供主要热源。分别使用灵敏的差示扫描量热仪 (DSC) 和热重分析仪 (TG) 实时测量煤自燃过程中的放热和质量变化。从空气气氛中减去氮气气氛的结果得到的DSC和TG减去曲线可以揭示仅由于煤与氧气反应而引起的热量变化和质量变化。期限q / m定义为单位煤质量变化释放的热量，用于研究煤自燃过程中放热与质量变化的内在关系。三种煤的q / m值随着煤温升高呈现不同的演化趋势，与煤自燃机理有关。这种内在关系的动力学分析也是基于实验数据进行的。此外，q / m可用于评估不同煤种的自燃倾向。