CO_2对受限空间煤明火燃烧的灭火机理
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摘要
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 CO_2 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 CO_2 of three different concentrations and durations,and the changing laws of temperature,index gas formation(O_2,CO and CH_4) 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 CH_4/O_2 flame by CO_2 of different concentrations,so as to analyze the mechanism of CO_2 inhibiting coal flame combustion.The results show that,in coal flame combustion stage,the higher the CO_2 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 CH_4 concentration.In the smoldering extinguished stage,the faster the falling speed of coal temperature,concentration of CO and CH_4,the smaller the oxygen consumption and heat release rate.It is shown that the higher the concentration of injecting CO_2,the greater the fire-extinguishing efficiency,but if injection time is too short,coal mine fire will occur again.
In order to thoroughly investigate the fire-extinguishing mechanism and efficiency of different concentrations of CO_2 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 CO_2 of three different concentrations and durations,and the changing laws of temperature,index gas formation(O_2,CO and CH_4) 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 CH_4/O_2 flame by CO_2 of different concentrations,so as to analyze the mechanism of CO_2 inhibiting coal flame combustion.The results show that,in coal flame combustion stage,the higher the CO_2 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 CH_4 concentration.In the smoldering extinguished stage,the faster the falling speed of coal temperature,concentration of CO and CH_4,the smaller the oxygen consumption and heat release rate.It is shown that the higher the concentration of injecting CO_2,the greater the fire-extinguishing efficiency,but if injection time is too short,coal mine fire will occur again.
引文
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[4]邵昊,蒋曙光,吴征艳,等.二氧化碳和氮气对煤自燃性能影响的对比试验研究[J].煤炭学报,2014,39(11):2244-2249.Shao Hao,Jiang Shuguang,Wu Zhengyan,et al.Comparative research on the influence of dioxide carbon and nitrogen on performance of coal spontaneous combustion[J].Journal of China Coal Society,2014,39(11):2244-2249(in Chinese).
[5]徐晓楠.灭火剂与应用[M].北京:化学工业出版社,2006.Xu Xiaonan.Fire Extinguishing Agent and Application[M].Beijing:Chemical Industry Press,2006(in Chinese).
[6]Janssens M.Measuring rate of heat release by oxygen consumption[J].Fire Technology,1991,27(3):234-249.
[7]孙金华,王青松,纪杰,等.火焰精细结构及其传播动力学[M].北京:科学出版社,2011.Sun Jinhua,Wang Qingsong,Ji Jie,et al.Flame Fine Structure and Its Propagation Dynamic[M].Beijing:Science Press,2011(in Chinese).
[8]吴仕生,曾玺,任明威,等.含氧/蒸汽气氛中煤高温分解产物分布及反应性[J].燃料化学学报,2012,40(6):660-665.Wu Shisheng,Zeng Xi,Ren Mingwei,et al.Product distribution and reactivity of coal pyrolysis at high temperature and in atmospheres containing O2/steam[J].Journal of Fuel Chemistry and Technology,2012,40(6):660-665(in Chinese).
[9]赵丽红,郭慧卿,马青兰.煤热解过程中气态产物分布的研究[J].煤炭转化,2007,30(1):5-9.Zhao Lihong,Guo Huiqing,Ma Qinglan.Study on gaseous products distributions during coal pyrolysis[J].Coal Conversion,2007,30(1):5-9(in Chinese).
[10]Saso Y,Zhu D,Law C K,et al.Laminar burning velocities of trifluoromethane-methane mixtures:Experiment and numerical simulation[J].Combustion and Flame,1998,114(3/4):457-468.