外来水分对煤自燃过程影响及作用机制研究

通过浸泡方法制备一系列不同外来水分含量的煤体,利用程序升温氧化实验模拟煤自燃过程,研究外来水分对煤自燃特性的影响;结合热分析和孔结构表征实验,探讨外来水分对煤自燃过程影响作用机制。外来水分对煤自燃过程的作用机制随着煤自燃状态发展而发生变化,主要表现出四个阶段。在缓慢氧化阶段,外来水分主要隔离煤与氧气的接触反应,对煤自燃起到物理抑制作用;在加速氧化阶段,水分可直接参与煤氧反应,起到化学促进作用;经过缓慢氧化阶段和加速氧化阶段,大量外来水分的蒸发导致煤颗粒表面裂隙增大,水分越大的煤生成的活性点位会更多,当煤自燃进入快速氧化阶段,外来水分对煤氧化反应的影响表现出延迟促进效应;当煤体温度达到180℃后,随着煤体温度进一步升高,不同初始外来水分含量的煤体自燃特征逐渐趋于一致。

Study on the effect and mechanism of foreign moisture on coal spontaneous combustion

A series of coal bodies with different foreign moisture was prepared by soaking a long flame coal with low water content. The effects of foreign moisture on the rate of temperature rising and the release of CO and CO₂ were studied by simulating coal spontaneous combustion. Moreover, the action mechanism of foreign moisture on the spontaneous combustion of coal was discussed in combination with the characterization of thermal analysis and the pore structure. The action regime of foreign moisture varies with the development of coal spontaneous combustion. At the slow oxidation stage, the foreign moisture plays a physical inhibition effect on coal spontaneous combustion mainly by isolating the contact reaction of coal and oxygen. At the accelerated oxidation stage, the water may involve in the process of the coal-oxygen reaction, promoting the rate of coal self-heating. After entering the rapid oxidation stage, due to the large amount of external water removal during the first and second stages, the pore structure and specific surface area of the coal body are increased; the higher the moisture content of coal, the more active sites will be generated, and the external water presents an indirect promoting effect. When the coal body temperature reaches 180 ℃, with the further increase of coal body temperature, the spontaneous combustion characteristics of coals with different initial external moisture content gradually tend to be consistent.