In this study, a three-dimensional computational fluid dynamics model is established in Ansys Fluent to describe the biodegradation of toluene in an internal loop airlift reactor (IALR). The Euler-Euler approach is used with the standard k-ε method to predict the hydrodynamics of the reactor, and the population balance model is used to describe the bubble size distribution in the reactor. The recently developed concentration variance $\overline{c^2}$ and its dissipation rate ε_c formulations are adopted to close the turbulent mass transfer differential equations, so that the turbulent mass diffusivity can be determined without using empirical methods. There is a good agreement between the simulated dissolved oxygen concentrations obtained by the proposed model and the experimental data reported in the literature. As the predicted turbulent mass diffusivity is found to be unevenly distributed and the calculated turbulent Schmidt number Sc_t is not a constant but varies, it may not be appropriate to use a constant Sc_t or an experimentally determined dispersion coefficient. In addition, the maximal shear stress is found in the top region of the IALR and the liquid flow are very uniform in the riser and downcomer.

在这项研究中，在Ansys Fluent中建立了一个三维计算流体动力学模型来描述甲苯在内部回路气升式反应器 (IALR) 中的生物降解。Euler-Euler方法与标准k-ε方法一起使用来预测反应器的流体动力学，并使用种群平衡模型来描述反应器中的气泡尺寸分布。最近开发的浓度方差$\overline{C^2}$并采用其耗散率ε _c公式来封闭湍流传质微分方程，从而无需使用经验方法即可确定湍流质量扩散率。通过所提出的模型获得的模拟溶解氧浓度与文献中报道的实验数据具有良好的一致性。由于发现预测的湍流质量扩散率分布不均匀，并且计算的湍流施密特数Sc _t不是常数而是变化的，因此使用常数Sc _t可能不合适或实验确定的色散系数。此外，最大的剪切应力出现在 IALR 的顶部区域，上升管和下降管中的液体流动非常均匀。