煤堆自燃升温规律与漏风特征的数值模拟

Numerical simulation of heating up and air leakage distribution for spontaneous combustion of coal pile

为了研究露天煤堆内部的漏风分布特征以及漏风特征对煤自燃升温的影响,在考虑风压、热压和质量扩散等驱动力的情况下建立了二维干燥煤堆传热传质数学模型,利用FLUENT软件对煤堆内部漏风分布与升温规律进行分析。计算结果表明:煤堆在迎风面漏风风速最高,背风面最低,中间递减,高温区位于迎风坡附近漏风强度适中,氧气充足的蓄热区。大气风速越低煤堆升温速率越慢,低于临界风速,煤堆可以安全存放。风速较高时,风速对煤堆自燃的影响主要体现在高温区位置,而非升温速率。现场可根据风速、煤堆松散度、堆放方式等因素事先评估自燃危险性,以便及时采取措施,提高防火工作效率。

In order to investigate the air leakage characteristics and heating up law of the spontaneous combustion in an exposed coal pile,a two-dimensional mathematical model for heat and mass transfer of a coal pile was established based on three influential factors that were air pressure,thermal pressure and mass diffusion.Then the air leakage and temperature distribution were analyzed by software Fluent. The results show that the high temperature region always lies in the windward slope where appropriate air velocity and sufficient oxygen supply are available. The reason is that the windward slope has the highest air velocity and oxygen supply in a coal pile,but they decrease far from the windward slope. The case of the leeward slope is contrary. Slow air velocity reduces heating up rate,and a coal pile can be kept safe when the air velocity drops into a critical value. When air velocity rises to a certain value,the effect of air velocity on coal pile spontaneous combustion does not focus on heating up rate but on the high temperature region instead. Several factors such as air velocity,coal pile porosity and stack model should be considered to evaluate coal pile risk. Therefore,fire protection should be strengthened by timely measurement of the factors.