不同热分析方法求解无烟煤燃烧反应动力学参数的研究

Study on Dynamic Reaction Parameters of Anthracite Combustion by Using Different Thermoanalytical Methods

利用热天平实验测试数据,分别采用Freeman-Carroll微分法、改良Coats-Redfern积分法和Flynn-Wall-Ozawa法等热分析手段求解4种无烟煤的燃烧动力学参数。结果表明:分析方法、升温速率、拟合区域等因素对热分析的结果有影响。尽管不同热分析方法的求解结果都能反映出不同煤种燃烧的差异,但具体计算方法不同,结果相差很大。对于微分法,当选取的反应区域不同时,拟合的结果不一样。而积分法对于在不同升温速率条件下所得实验数据的计算结果不同。当采用Freeman-Carroll法求解时,其热天平实验的升温速率取得越小,计算结果越可能接近真实平均值;在升温速率较大的情况下,用改进Coats-Redfern方法计算所得到的动力学参数会较多地偏离实际值。因煤的燃烧机理在不同的反应阶段是变化的,通过热分析手段所得的动力学参数反映的是整个燃烧区域的平均值。

Several thermoanalytical methods such as the Freeman-Carroll differentiation method, the improved CoatsRedfern integration method and the Flunn-Wall-Ozawa method are adopted to calculate the dynamic parameters of four kinds of anthracites by using experimental data obtained from TGA tests. Results indicate that the thermoanalytical results are influenced by the thermoanalytical method used, by rate of heating and the section chosen for correlation, etc. Although the results obtained by the different methods can all show combustion diversities of different kinds of coal, but the discrepancy among results is remarkable, depending on the specific method of calculation used. With the differentiation method, correlation results vary with the reaction section selected. Whereas with the integration method, results vary with the heating rate under which the experimental data were obtained. With the Freeman-Carroll method, the smaller the heating rate of the TGA tests, the nearer the calculated results get to the real mean values. In case of a higher heating rate, the dynamic parameters obtained by the improved Coats-Redfern method deviate from the real values.Since the combustion mechanism of coal varies during the different stage of reaction, the dynamic parameters obtained by thermoanalytical methods are mean values of the whole combustion section. Figs 5, tables 4 and refs 12.