CFD investigation of the gas dispersion and liquid mixing in bubble columns with dense vertical internals.

Highlights • Developed and validated the CFD model of a bubble column with vertical internals. • The importance of fluctuations in the gas flow rate in the impulse tracer method. • The presence of internals reduced the gas dispersion. • The presence of internals increased liquid mixing time. • Liquid mixing time affected by the tracer injection position. Abstract Bubble columns are widely equipped with vertical internals for heat removal in slurry/bubble column reactors or providing the light source in photobioreactors. Understanding the effect of internals on the hydrodynamics of a bubble column reactor is crucial for the reactor design and scale-up. The gas dispersion and liquid mixing are two important parameters in design of bubble columns. In this study, the Eulerian-Eulerian simulation coupled with the population balance model was developed for the bubble column with dense vertical internals. The impulse tracer injection was applied to study the gas dispersion. The effect of the gas flow fluctuations, the time span of tracer injection, and the presence of internals was assessed at different superficial gas velocities. The results showed that the presence of internals has a notable effect on gas behavior. A stronger gas velocity gradient with less turbulence and dispersion were observed in the presence of internals. To study the liquid mixing, the tracer technique was applied, and the sensitivity of results to the tracer injection and detector points have been discussed. The presence of internals reduced the fluctuating liquid velocities, which led to a lower mixing performance in the bubble column. [ABSTRACT FROM AUTHOR]