Effect of drag correlation and bubble‐induced turbulence closure on the gas hold‐up in a bubble column reactor

Abstract

AbstractBACKGROUNDGas–liquid hydrodynamics play an important role in processes across a wide range of applications in chemical technology and biotechnology. In most of these applications, gas is bubbled in the bottom of the reactor to conduct physical mixing or mixing‐induced chemical reaction. In either case, the gas bubble hydrodynamics play a critical role on the overall performance of these processes. In the present study, the gas–liquid multiphase system is simulated using a Eulerian–Eulerian two‐fluid Computational Fluid Dynamics (CFD) model.RESULTSThe physical model is a cylindrical bubble column contactor wherein gas is sparged into liquid through a perforated sparger with a superficial gas velocity of ≈3–40 cm s−1. The CFD model for the contactor is built using the free and open source tool OpenFOAM v.4.0 to simulate the gas–liquid system. The time‐averaged volume fraction distribution was studied at different heights in the column. The effect of drag force and bubble‐induced turbulence are studied to arrive at appropriate closures for the CFD model. The results obtained from the numerical simulations were validated against available experimental results found in literature.CONCLUSIONThe recommended models, based on the present CFD study of the bubble column reactor, are the Ishii–Zuber drag closure with the modification that the parameter p is set to 2 for superficial gas velocities ≤20 cm s−1 and is set to 4 for 40 cm s−1 superficial gas velocity) and the mixed k–ϵ model to account for drag correlation and bubble‐induced turbulence closure, respectively. © 2019 Society of Chemical Industry