焦煤氧化燃烧特性参数与热动力学特征

Oxidation combustion characteristic parameters and thermodynamic of coking coal

煤氧化自燃是矿井火灾的主要原因之一。为了探明煤氧化燃烧的特点和规律,采用TG-DTG试验研究了沙曲一号煤矿焦煤氧化热解过程,对不同升温速率下煤样的特征温度和燃烧特性参数进行了计算,并根据改进的Starink法计算了缓慢失重阶段和燃烧失重阶段的热动力学参数,确定了这2个阶段的动力补偿效应。结果表明:特征温度点随升温速率的增大出现了后移现象,并且反应结束后的残余物质比例随着升温速率的增大而增加;燃烧特性参数随升温速率增大呈现显著增大趋势,升温速率越大,煤粉可燃性越好,燃烧越稳定,但反应也越不充分;表观活化能在缓慢失重阶段呈现逐渐增大的趋势,最大值188.47 kJ/mol在着火点T_(3)附近;在燃烧失重阶段当转化率小于0.3时,表观活化能逐渐增大,之后逐渐减小,最大值173.65 kJ/mol在最大失重速率温度点T_(4)附近;指前因子整体变化规律与表观活化能基本一致,动力学补偿效应在燃烧失重阶段更大。

Coal oxidation and spontaneous combustion is one of the main causes of mine fires.In order to explore the characteristics and laws of coal oxidation and combustion,TG-DTG experiments was adopted to study the oxidation and pyrolysis process of coking coal in No.1 coal mine in Shaqu.The characteristic temperature and combustion characteristic parameters of coal samples at different heating rates were calculated,and the thermodynamic parameters of the slow weight loss stage and the combustion weight loss stage were calculated using the improved Starink method,with the kinetic compensation effects of these two determined.The results show that the characteristic temperature points exhibit a backward shift phenomenon with the increase of heating rate,and the proportion of residual substances after the reaction increases with the increase of heating rate;at the same time,the combustion characteristic parameters show a significant increasing trend with the increase of heating rate,indicating that the higher the heating rate,the better the combustibility of coal powder and the more stable the combustion,but the reaction is also less sufficient;the apparent activation energy shows a gradually increasing trend during the slow weight loss stage,with the maximum value near the ignition point T_(3),which is 188.47 kJ/mol;When the conversion rate is less than 0.3 during the combustion weight loss stage,the apparent activation energy gradually increases and then gradually decreases.The maximum value is near the temperature point T_(4)of the maximum weight loss rate,which is 173.65 kJ/mol;the overall variation pattern of the pre-exponential factor is basically consistent with the apparent activation energy,and the dynamic compensation effect is greater at the combustion weight loss stage.