【摘要】 为详细研究分级气化技术的流场特点及气化性能,采用Fluent软件对山西某分级气化炉进行三维数值模拟。计算采用贴体六面体网格划分计算域以降低数值扩散,采用Realizablek-ε模型封闭湍流方程,应用离散相模型(dispersed phased model,DPM)和随机轨道模型(stochastic tracking method,STM)分别模拟颗粒气化过程和考察颗粒受湍流脉动的影响;计算根据简化PDF模型建立燃烧表以建立温度、组分等标量同混合分数间的关系,并由此计算同相气化反应过程。除此之外,还引入用户自定义函数改进了焦炭异相反应模型。通过对分级气化炉流场特性和温度等值面特征的分析,发现分级气化炉中由于二次对冲给氧射流的引入,造成了二次卷吸效应以及冲击射流效应,加强了炉内混合过程,有利于碳转化率的进一步提高。更多还原

【Abstract】 In order to study the character of the flow field and the gasification performance of staged gasification technology, numerical simulation for a staged entrained flow coal gasifier located in Shanxi province was conducted based on Fluent. Body fitted hexahedron mesh was used to minimize the numerical diffusion due to mesh quality. Realizable k-ε model was adopted to make a closure for turbulence equations. dispersed phase model (DPM) and stochastic tracking method (STM) were used to describe the coal particle gasification process and to predict the turbulent disturbance effects on particle motion. A combustion table was built by presumed PDF model to describe the relationship between mixture fraction and the scalars of temperature, species, et al. In addition, User Defined Functions was used to modify the heterogeneous char gasification reaction model in Fluent. The analysis of the flow field and the contours of temperature of the staged entrained flow coal gasifier show that the engulfment and the counter flow aroused by the secondary injection strengthen the mixing process in the staged gasifier. This had a positive effect on the improvement of coal conversion rate.更多还原