(234x) CFD Simulation of Bubble Columns Operating in Heterogeneous Regime
Bubble columns are widely used for gas-liquid contact, applied in several chemical process, they are often used for promoting high heat and mass transfers rates combined with low operating and implantation costs. For most industrial applications the multiphase flow occurs with high superficial gas velocities consequently, the column operates at a heterogeneous regime. The main difference between the homogeneous and heterogeneous regimes lies within the superficial velocity magnitude, while low superficial velocities characterize homogeneous regime with low presence of breakage and coalescence the heterogeneous flow presents a higher superficial velocity and grater turbulence, and so the breakage and coalescence phenomena have a significant importance. The heterogeneous regime flow characteristically allows the achievement of higher heat and mass transfer rates, which makes it industrially relevant. Bubble columns have a large application as well as a great potential use as multiphase contactors and multiphase reaction systems at several industrial areas. Therefore, the correct scale-up of this equipment is crucial to the plants operation. The successful scale-up is highly dependent of the correct prediction of the mixing and of fluid dynamics. A brief literature assessment allows the conclusion that besides the fact that heterogeneous regime is largely verified in industrial operations few are the studies focused on such regime. Therefore, several issues remain unanswered so far. In this way, the investigation of bubble columns fluid dynamics is proposed for the heterogeneous regime. Numerical simulations were conduct with a CFD commercial code using an Euler-Euler methodology. The biggest problem of fluid dynamics simulation for this kind of systems by CFD technics is the dynamic bubble behavior. For that, a population balance is solved applying a class method. The numerical results of holdup and bubble velocities were compared with literature experimental data of a bubble column operating with high superficial velocity.