煤质粉末活性炭自燃和热稳定性分析

针对煤质粉末活性炭最显著的热危险特性——自燃危险性进行试验。采用粉尘层最低着火温度测定系统对煤质粉末活性炭进行自燃试验,测定煤质粉末活性炭的最低着火温度;采用SDT Q600热重分析仪测定煤质粉末活性炭在氮气和空气气氛中以20℃/min的速率升温至700℃时的热解和燃烧特性,通过TG/DTG曲线计算其着火温度,并进行热稳定性评价。粉尘层自燃试验结果表明,煤质粉末活性炭最低着火温度为400℃,具有自燃危险性,易形成阴燃;氮气气氛中热解试验表明,热解过程经历了室温~120.0℃和280.0~700.0℃两次轻缓失重阶段,646.44℃时挥发分热失重速率最大,对应热失重速率峰值为0.082 6%/℃,自燃危险性较低;空气气氛中燃烧试验表明,燃烧过程经历了室温~95.5℃和300.0~600.0℃两次剧烈失重阶段,分别为吸附水分受热蒸发和氧化生成的有机官能团分解脱附导致,565.35℃时挥发分热失重速率最大,对应热失重速率峰值为13.20%/min,粉末较强的氧气吸附效应和较低的导热系数导致其自燃倾向较高,火灾危险性较大。

On the spontaneous combustion and the thermal stability properties of the coal-based activated carbon powders

This paper is to address the spontaneous combustion risk of the activated carbon of the coal-based powder,one of the featured most distinctive thermal hazards.For the said purpose,we have identified and examined the minimal ignition temperature of the coal-base activated carbon powders via the dust layer ignition system.Furtermore,we have also tested the pyrolysis and the combustion properties of the samples in nitrogen and air atmosphere at the temperatures with the ambient temperature increased to 700 ℃ with a ramp rate of 20 ℃/min by using a SDT Q600 Thermal Gravimetric Analyzer.And,then,the TG/DTG profiles have been used to work out the ignition temperature and the needed thermal stability.The experimental results of the minimal ignition temperature of the dust layer show that the coal-based activated carbon powders can provide a typical minimalist ignition temperature of 400 ℃ and in turn set up a smoldering process easily.What is more,the experimental results of the pyrolysis properties in nitrogen also verify that the entire pyrolysis process tends to take place in two gentle stages at range from the ambient temperature to 120.0 ℃ and 280.0 ℃ to 700.0 ℃,at which the maximum mass loss rate should take place at the temperature of 646.44 ℃ with a maximum peak heat releasing rate of 0.082 6％/℃,which implies a lower-grade self-ignition risk.As to the experimental results of the pyrolysis properties in the air,it can be said that the combustion process is supposed to be made of two dramatic stages at range from the ambient temperature to 95.5 ℃ and 300.0 ℃ to 600.0 ℃.Such kinds of the combustion process are likely to be induced by the evaporation of the physically and chemically adsorbed water and/or the decompositionand adsorption of the organic functional groups from the self-oxidation.The maximum mass losing rate in the process under study tends to appear at temperature of 565.35 ℃ whereas the peak heat release rate can only reach a releasing rate of 13.20％/min,which accounts mainly for the fact that the strong adsorption effects of oxygen and low heat coefficient based on the loss and the porous structure feature of the powder,which tends to demonstrate quite a high self-ignition inclination and fire-making hazard.