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不同升温速率下烟煤的低温氧化放热特性研究

Study on low temperature oxidation heat release characteristics of bituminous coal at different heating rates

  • 摘要: 煤自燃是威胁开采、储存和利用过程的重要因素之一,而煤在低温阶段的氧化放热反应也是导致煤自燃的主要因素。为了研究烟煤在低温条件下的放热特性,选取3种不同变质程度的烟煤进行研究,煤样分别为曹家滩(CJT)的长焰煤、大佛寺(DFS)的不黏煤和东滩(DT)的气煤。采用微量热仪(C80)实时监测煤样在30~300 ℃温度区间内升温过程中的热流变化,从而探究不同烟煤低温氧化过程的热流变化规律以及放热情况,得到低温氧化过程的分段热流特征以及相应的数学模型。为了进一步研究升温速率对烟煤放热特性的影响,试验分别设置在0.2、0.4和0.6 ℃/min的不同升温速率下进行,通过热流模型和热量公式建立判定自燃倾向性的指数γ,从而分析不同升温速率对烟煤低温氧化过程放热特性和煤自燃倾向性的影响规律。结果表明:烟煤低温氧化分为了吸热、缓慢放热、加速放热和快速放热4个阶段,随着升温速率的升高,特征温度点有着向后推移的趋势,放热量呈现减小的趋势,3个放热阶段的放热量占比没有明显变化,约为1%、30%、70%。并且发现升温速率越低,活化能值越小,煤自燃倾向性指数γ值变大。通过研究烟煤的放热特性和不同升温速率对烟煤放热特性的影响,能够对烟煤氧化放热情况有着更清晰的认识,从而针对性的研究防灭火材料,对煤自燃的预防和治理作出相应的贡献。

     

    Abstract: Coal spontaneous combustion is one of the important factors threatening the process of mining, storage and utilization. The oxidation exothermic reaction of coal at low temperature stage is also the main factor leading to coal spontaneous combustion. In order to study the heat release characteristics of bituminous coal at low temperature, three kinds of bituminous coal with different metamorphic degree were selected to study. Caojiatan (CJT) long flame coal, Dafosi (DFS) non caking coal and Dongtan (DT) gas coal were used as the coal samples. The micro calorimeter (C80) was used to monitor the change of heat flow of coal samples in the temperature range of 30~300 ℃, so as to explore the heat flow change law and exothermic situation of different bituminous coal low-temperature oxidation processes, and obtain the staged heat flow of the low-temperature oxidation process. features and corresponding mathematical models. In order to further study the effect of heating rate on the heat release characteristics of bituminous coal, the experiments were conducted at different heating rates of 0.2, 0.4 and 0.6 ℃ / min, respectively. Based on the heat flow model and heat formula, the index γ for judging the spontaneous combustion tendency was established, and the influence of different heating rates on the heat release characteristics and spontaneous combustion tendency of bituminous coal in low temperature oxidation process was analyzed. The results show that the low temperature oxidation of bituminous coal can be divided into four stages: endothermic, slow exothermic, accelerated exothermic and fast exothermic stages. With the increase of heating rate, the characteristic temperature point tends to move backward and the heat release decreases. The proportion of exothermic heat in the three exothermic stages did not change significantly, about 1%, 30%, and 70%. It was found that the lower the heating rate is, the smaller the activation energy value is, and the γ value of coal spontaneous combustion tendency index increases. By studying the heat release characteristics of bituminous coal and the influence of different heating rates on the heat release characteristics of bituminous coal,, this subject can have a clearer understanding of bituminous coal oxidation heat release so as to study fire extinguishing materials, and prevent and control coal spontaneous combustion.

     

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