CO_2对受限空间煤明火燃烧的灭火机理

Fire-Extinguishing Mechanism of CO_2 on Coal Flame Combustion in Confined Space

为探究不同体积分数CO_2对受限空间煤明火燃烧的灭火机理和灭火效率,采用自主研制的煤明火燃烧实验装置,对平煤八矿煤样进行了通入3种不同体积分数CO_2和持续时间条件下的煤明火燃烧灭火实验,测定了煤燃烧过程中温度、标志性气体(O_2、CO和CH_4)组分体积分数以及热释放速率的变化规律;同时利用化学动力学软件CHEMKIN模拟了不同体积分数CO_2熄灭CH_4/O_2火焰中主要自由基体积分数、反应物与燃烧产物体积分数随火焰高度的变化关系,以此分析了CO_2抑制煤有焰燃烧的作用机理.结果表明:CO_2体积分数越高,在煤有焰燃烧阶段,CH_4燃烧火焰中的自由基H、O和OH的生成速率越低,因此火焰熄灭得越快,煤体温度上升速度、耗氧量和热释放速率越低,同时,CO和CH_4体积分数的下降速度越小;而在煤阴燃熄灭阶段,煤体温度、CO和CH_4体积分数的下降速度越快,耗氧量和热释放速率则进一步减小.由此说明CO_2的体积分数越高,对煤明火燃烧熄灭全过程的灭火效率越高,但只通入CO_2 10,min,则会发生复燃.

In order to thoroughly investigate the fire-extinguishing mechanism and efficiency of different concentrations of CO2 on coal fire combustion in confined space,the self-designed experiment device of coal flame combustion was used to conduct the fire-extinguishing experiment on coal flame combustion,using coal samples in Ping Dingshan coal mine,by importing CO2 of three different concentrations and durations,and the changing laws of temperature,index gas formation(O2,CO and CH4)and heat release rate obtained from the experimental stages of coal flame combustion and smoldering extinguishment were measured.Meanwhile,CHEMKIN program was utilized to simulate the change of concentration of main free radicals,reactants and combustion products with flame height in the extinguishment of CH4/O2 flame by CO2 of different concentrations,so as to analyze the mechanism of CO2 inhibiting coal flame combustion.The results show that,in coal flame combustion stage,the higher the CO2 concentration,the lower the generation rate of free radicals H,O and OH,the faster the extinguishment coal flame,and the smaller the rising rate of coal temperature,the lower the oxygen consumption and heat release rate,and the smaller the declining speed of CO and CH4 concentration.In the smoldering extinguished stage,the faster the falling speed of coal temperature,concentration of CO and CH4,the smaller the oxygen consumption and heat release rate.It is shown that the higher the concentration of injecting CO2,the greater the fire-extinguishing efficiency,but if injection time is too short,coal mine fire will occur again.