氧气体积分数对楔形热板煤自燃特性的影响

Influence of Oxygen Volume Fraction on Coal Spontaneous Combustion on Wedge Hot Plate

为了研究氧气体积分数对楔形热板煤自燃特性的影响,建立了二维瞬态煤自燃楔形热板模型,考虑了自燃着火和阴燃蔓延结合的平行反应,具体研究了不同氧气体积分数下煤自燃的温度变化、煤氧化反应速率以及煤体高温点的运移过程。结果表明:建立的模型与实验结果有较好的一致性,随着氧气体积分数的增加煤体易发生热失控,并且对应的最小着火时间在推前;随着氧气体积分数的增加,煤氧化反应速率的峰值大小在逐渐增加,反应速率的极值点大小与氧气体积分数呈指数相关;对于煤氧化反应初期,由于氧气较为充足,煤氧化反应不剧烈,高温点始终位于楔形热板夹角处;随着煤氧反应的加剧,煤体受温度以及氧气浓度的约束,煤氧反应表现竞争氧气的现象,高温点由夹角向自由表面移动,并且低氧部位也向上移动。

To study the influence of oxygen volume fraction on the coal spontaneous combustion characteristics on wedge hot plate, a two-dime nsional transient model was established. The parallel reaction of spontaneous ignition and smouldering spread were considered in the simulation. The temperature, coal oxidation reaction rate and the migration process of hot spot under different oxygen volume fractions were studied. The results show that the established model was in good agreement with the experimental results. As the oxygen volume fraction increased, the coal was prone to thermal runaway, and the corresponding minimum ignition time was in advance;with the increase of oxygen volume fraction, the peak value of coal oxidation reaction rate increased gradually, and the extreme value of reaction rate was exponentially correlated with the oxygen volume fraction. For the initial stage of coal oxidation reaction, due to sufficient oxygen, the coal oxidation reaction was not violent, and the high temperature point was always located at the corner of the wedge-shaped hot plate;as the coal oxygen reaction intensified, the coal body was restricted by temperature and oxygen concentration. The coal oxygen reaction exhibited a phenomenon of competing for oxygen, and the high temperature point moved from the angle to the free surface. With the increase of time, the hypoxic parts also moved up.