煤及其显微组分热解过程中的半焦收缩动力学

采用显微热台对煤显微组分微粒进行热解, 通过在线拍摄的显微图片能够直观揭示出煤粒热解时呈现的两个阶段——脱挥发分和半焦收缩. 通过对显微图片的图像分析, 获得了煤粒面积随温度变化的热解曲线. 结果表明, 半焦收缩过程由缓慢收缩、过渡收缩和快速收缩三个阶段构成, 活化能、指前因子及速率常数皆随三个阶段依次增大, 其原因在于各段的化学键断裂种类及其键能、生成的自由基碎片及缩聚反应存在不同特点. 就半焦收缩而言, 镜质组的速率常数大于惰质组; 变质程度较低的神东煤及其显微组分的速率常数大于平朔煤及其对应显微组分,即前者显示出较强的半焦收缩反应性.

Semicoke Contraction Kinetics of Coal and Its Macerals in Pyrolysis

The thermal behavior of maceral particles was investigated using the micro heating stage. The phenomena of devolatilization and semicoke contraction on pyrolysis of the particles were observed directly in the micro-picture taken online. The curve of the particle area which changed with increasing the temperature was obtained by means of image analysis on the micro-picture. The results of the above processes showed that three stages were involved in the process of semicoke contraction: slow contraction stage, transitional contraction stage, and rapid contraction stage. The values of the apparent activation energy, pre-exponential factor, and reaction rate constant might increase in the three stages as a result of different features shown by the chemical bond breakage types, its bond energy as well as the free radical pieces, and condensation reaction in each stage. In terms of semicoke contraction, the reaction rate constant of vitrinite was bigger than that of inertinite; the reaction rate constants of ShenDong coal and its macerals with lower metamorphic grade were bigger than those of PingShuo coal and its corresponding macerals, namely, the former had better semicoke contraction reactivity.