Numerical analysis of the effect of gas sparging on bubble column hydrodynamics

A discrete bubble model (DBM) has been used to study the effect of gas sparger properties on the hydrodynamics in a bubble column. As a first step the performance of the model was evaluated by comparison with experimental data. Subsequently, four different perforated plates with different sparged areas were used as a gas sparger. Distributions of liquid velocity, turbulent kinetic energy, and void fraction in the central plane were compared for the four different systems. Furthermore, the effect of the sparger location was also investigated. It was found that the liquid-phase circulation becomes more pronounced as the sparged area location is more distant from the center of the bottom plate. Finally, gas-phase residence time distributions (RTD) were obtained from the simulations. By employing standard axial dispersion model, the gas-phase mixing in the bubble column was characterized. Results show that the extent of mixing increased when the sparged area decreased. The axial dispersion coefficient increased as the sparged area was shifted to the edge of the bottom plate.