湍动流化床气固传质行为的CFD模拟

Simulation of the gas-solid mass transfer behavior in turbulent fluidized beds

利用基于稀密两相结构的湍动流化床传质模型(基于结构的传质模型),结合稀密两相间的传质系数(相间传质系数)求解关联式对湍动流化床的传质行为进行了CFD模拟,以分析各关联式对模拟结果的影响。结果表明,采用以聚团为基础的Foka关联式求解相间传质系数时,基于结构的传质模型的模拟结果最好,而采用其他关联式的模拟结果均存在较大偏差,原因可能是反应主要发生在聚团相,并且相间传质系数求解关联式的特征结构与传质模型的基础结构不一致时会引入较大误差。随着气速增加,由于传质行为的强化,气穴相的臭氧浓度变化不大,而聚团相的臭氧浓度明显增加且主要发生在颗粒含量较少的床层上部。此外,还分析了传质行为与聚团尺寸的关系。

The gas-solid mass transfer behavior in turbulent fluidized beds （TFBs） was studied numerically with the mass transfer model based on the heterogeneous structure and the correlations for interphase mass transfer to validate the simulation results of the different correlations. The simulation with the correlation of Foka which based on the cluster phase achieves the best predictions, while others produce large errors. The likely reasons are that the reactions in TFBs mainly occurs in the cluster phase and that the basic structure of correlation for the interphase mass transfer differs from that of the mass transfer model. With the increase of the inlet gas velocity, the ozone concentration in the void phase varies slightly due to the enhanced mass transfer behavior, while that in the cluster phase increases significantly especially in the upper dilute region. Besides, the relationship between the mass transfer behavior and the average cluster diameter was also analyzed.