几种恒定高温下混煤燃烧反应动力学模型对比

Comparative study on several combustion dynamic models of coal blends at constant high temperature

介绍了均相反应模型、一维扩散模型及球对称收缩核模型等常用煤粉燃烧反应动力学模型,利用这几种模型对高温下混煤燃烧过程进行了动力学计算,得到了高温下不同掺混比混煤的燃烧反应动力学参数,并将模拟结果与实验结果进行了对比;同时以判定系数为指标,对上述3种模型的模拟结果进行了准确性验证。结果表明:3种模型得出的混煤燃烧反应动力学参数值呈现相同的变化趋势,即随着新疆褐煤掺混比的增大,混煤燃烧反应活化能与频率因子数值均减小;不同煤种与新疆褐煤进行掺混时,燃烧反应活化能与频率因子数值大小顺序均为神华无烟煤>大同烟煤>云南褐煤;3种模型均能在一定程度上反映高温下混煤燃烧的本质,但精度有所不同;在相同温度下(1 400℃),均相反应模型与一维扩散模型的判定系数整体较低且跨度较大,而球对称收缩核模型在各工况下的判定系数比其他2种模型高,表明球对称收缩核模型能够精确地模拟高温下混煤的燃烧过程。

Several commonly used combustion reaction kinetic models were introduced.On the basis of the co-combustion experiments of coal blends at constant high temperature,the homogeneous reaction model,one-dimensional diffusion model,and spherical symmetry shrinking core model were employed to carry out kinetic calculation for coal blends combustion at constant high temperatures.The combustion reaction dynamic parameters of the coal blends with different mixing ratios at high temperatures were obtained,and the simulated results were also compared with the experimental results.Moreover,by introducing an index called determination coefficient,the accuracy of the above three models were verified.The results show that,the dynamic parameters calculated by the above three models changed in the same trend,namely,both the activation energy and frequency factor decreased as the mixing ratio increased.For mixtures of Xinjiang lignite and other coals,the activation energy and frequency factor ranked in such order when different coals were mixed：Shenhua anthracite〉Datong bituminous〉Yunnan lignite.All the above three models can accurately reflect the nature of mixture combustion,to some extent.However,as models for solving kinetic parameters,each model had its own limitations.At the same temperature（1 400 ℃）,the maximum and minimum determination coefficients of the homogeneous reaction model and the one-dimensional diffusion model were low and the span was large.While that of the spherically symmetric shrinking core model was higher,indicating the spherically symmetric shrinking core model has higher simulation precision.