CFD Modeling: An efficient tool to optimize the design and operation of aeration systems

This paper exemplifies the beneficial use of CFD models coupled to mass transfer equations to optimize fine bubble aeration systems in closed-loop reactors. The models, previously validated at different scales (Fayolle et al. 2007), allow assessing the impact of the design and operating parameters on the oxygenation performances. In this article, the impact of different parameters is investigated: the arrangement of the grids of diffusers, the surface air flow rate and the axial liquid velocity. The increase in the thrust velocity of the mixers or in the distance between two consecutives grids of diffusers induces an increase in the oxygen transfer coefficient. An increase in the surface air flow rate induces a decrease in the oxygen transfer performance of the system. In each cases, computations results agree with experimental ones and allows interpreting these variations thanks to the local representation of liquid velocity flow fields and gas hold-up profiles.