3-D simulations of an internal airlift loop reactor using a steady two-fluid model

Three-dimensional (3-D) simulations of an internal airlift loop reactor in a cylindrical reference frame are presented, which are based on a two-fluid model with a revised k-epsilon turbulence model for two-phase bubbly flow. A steady state formulation is used with the purpose of time saving for cases with superficial gas velocity values as high as 0.12 m/s. Special 3-D treatment of the boundary conditions at the axis is undertaken to allow asymmetric gas-liquid flow. The simulation results are compared to the experimental data on average gas holdup, average liquid velocity in the riser and the downcomer, and good agreement is observed. The turbulent dispersion in the present two-fluid model has a strong effect on the gas holdup distribution and wall-peaking behavior is predicted. The CFD code developed has the potential to be applied as a tool for scaling up loop reactors.