Eulerian simulation strategy for scaling up a bubble column slurry reactor for fischer-tropsch synthesis

Abstract

CFD simulations were carried out in the Eulerian framework using both two-dimensional (2D) axisymmetric and transient three-dimensional (3D) strategies to describe the influence of column diameter on the hydrodynamics and dispersion characteristics of the bubble column slurry reactor for Fischer-Tropsch (FT) synthesis. Interactions between the bubbles and the slurry were taken into account by means of a momentum-exchange, or drag, coefficient; this coefficient was estimated from experimental data on the bubble swarm velocity in the limit of low superficial gas velocity U. The turbulence in the slurry phase was described using the k-ε model. For an FT slurry reactor operating at U = 0.15 m/s, simulations were also carried out for columns with diameters of 0.38, 1, 2, 4, 6, and 10 m using the 3D simulation strategy to determine gas hold-up; the liquid circulation velocity; and the axial dispersion coefficient of the liquid phase, D_ax,L. The results demonstrate the strong increase of liquid circulation and D_ax,L with increasing column diameter. We conclude that 3D Eulerian simulations can provide a powerful tool for hydrodynamic scale-up of bubble columns, obviating the need for large-scale experiments.