In order to study the internal self-heating theory of low-rank coal in piling state, the theory of critical self-ignition temperature and the Frank-Kamenetskii model were applied to study the internal heat generation and heat dissipation balance theory in the coal pile and the phenomenon of heat transfer on the surface of coal pile.The self-developed experimental device and the measurement method on thermal diffusivity and temperature of coal pile were applied to evaluate the critical critical self-ignition temperature of low-rank coal samples (lignite and sub-bituminous coal) effectively.The results showed that the critical self-ignition temperature of coal samples in piling state could be obtained through the measurement and analysis on the self-heating curves of screen frames with different volume under different environmental temperatures in the laboratory.The critical critical self-ignition temperature increased with the improvement of coal rank under the same volume.When the environmental temperature was 140 ℃, the temperature change trends of 1#, 2# and 3# coal samples were similar in the first 20 minutes of rapid heating.When the environmental temperature was in the range of 60 ℃-65 ℃, the temperature turning point appeared for all the three coal samples, and the heating rate began to slow down.The spontaneous combustion tendency and critical self-ignition temperature of large volume coal samples could be predicted by the coupling relational expression between the piling volume and the ignition temperature, which was obtained according to the critical self-ignition temperature of coal samples combined with the Frank-Kamenetskii thermal ignition boundary conditions.%为了研究低品质煤炭堆积状态下内部自热理论,采用临界自燃着火点理论和Frank-Kamenetskii 模型研究了煤堆内部热产生与热散失平衡理论以及煤堆表面的换热现象;并应用设计研发的煤堆热扩散率及温度监测实验装置和测定方法来评估低品质煤样(褐煤以及亚烟煤)临界自燃温度.结果表明:煤样堆积状态下临界自燃着火点温度可通过实验室内测定分析不同体积网框在不同环境温度条件下自热曲线得出;同体积条件下,临界自燃着火点随着煤品质的升高而增加;在140 ℃ 环境条件下,1#,2# 和3# 煤样在快速升温的前20 min内,温度变化趋势相似;在60~65 ℃,3种煤样出现温度转折点,升温速率开始减缓;根据煤样临界自燃着火点温度结合F-K热发火边界条件理论得出的堆积体积与着火点耦合关系式可预测大体积煤样自燃倾向性及临界自燃温度.
展开▼
