The effect of vertical internals on the hydrodynamics and phase dispersions in bubble columns: CFD simulation and population balance model

Abstract

Vertical internals are widely installed in the bubble columns as heat exchangers or illuminating tubes. This research aims to investigate the effect of dense vertical internals (rods) on the performance of bubble columns. The Eulerian-Eulerian model coupled with the population balance model was used to develop the CFD simulation. The effect of interfacial forces on the results was studied by applying different models. The results indicated that just by choosing the appropriate interfacial forces, the numerical model agrees well with the experimental data. A sharper gas holdup, a stronger gas velocity gradient, and a more intense liquid recirculation were observed as important impacts of the internals. Moreover, three circular internals’ arrangements were considered to study the effect of wall and core clearance distances on the bubble column hydrodynamics. The results revealed that by increasing the wall clearance distance, flatter gas holdup and velocity distributions could be achieved. Furthermore, the capability of the population balance model in the prediction of the bubble size distribution in the presence of internals was assessed, and a modification factor for the population balance kernels was proposed. Moreover, the impulse tracer injection was applied to study the gas dispersion in the bubble column. The results showed that the presence of internals has a notable effect on the gas behavior. Less turbulence and dispersion were found in the presence of internals. To study the liquid mixing, the tracer technique was applied. The presence of internals reduced the fluctuating liquid velocities, which led to a lower mixing performance in the bubble column.