Numerical simulation of bubble characteristics in bubble columns with different liquid viscosities and surface tensions using a CFD-PBM coupled model

Abstract

Most liquids in gas–liquid phase reactions are organic solvents; hence, it is particularly important to study the effect of liquid properties on fluid dynamic parameters in bubble columns. In this study, the correction of surface tension and viscosity were used to determine the influence of different liquid properties on the hydrodynamic parameters of bubble columns. These were implemented based on the minimum energy model proposed by Li (Li et al., 1999; Li and Kwauk, 2003; Xu and Li, 1998), our previous work (Zhang et al., 2018), the drag model of atmospheric pressure from Xiao et al. (2017) and that from Yan et al. (2019). According to previous studies (Syed et al., 2017), because liquid properties significantly influence the bubble size distribution in a bubble column, the density correction term and gas holdup of large bubbles were utilized to optimize the coalescence coefficient (Ce). Computational fluid dynamics coupled with the population balance model were used to simulate the effects of liquid viscosities and liquid surface tensions on the hydrodynamic parameters of the bubble column. The simulation results showed that when the liquid viscosity or surface tension increases, there is a higher probability of coalescence between two bubbles, resulting in the formation of a large bubble. The collision of large bubbles with turbulent eddies can increase the energy required to break up large bubbles into small ones; large bubbles in a bubble column are more stable, and the gas holdup of large bubbles increase. Moreover, the gas holdup of small bubbles, total gas holdup in the bubble column, and contact area between gas and liquid in the bubble column decrease, which leads to the decrease of the mass and heat transfers between the two phases.