CFD modeling of slurry bubble column reactor for Fischer-Tropsch synthesis

Industrial bubble column reactor for Fischer-Tropsch (FT) synthesis includes complex hydrodynamic, chemical and thermal interaction of three material phases: population of bubbles of different sizes, liquid and catalyst particles suspended in liquid. To simulate FT bubble column, a Computational Fluid Dynamics model is described here. The model is based on Eulerian multifluid formulation and accounts for the following important phenomena. Turbulence is modeled by ε − k model. Bubble size distribution is predicted by the Population Balance (PB) method. Experimentally observed influence of catalyst particle concentration on bubble size distribution is theorized to be linked to catalyst particle induced modification of turbulent dissipation rate. A simple scaling modification to dissipation rate is proposed to model this influence. Additional mass conservation equations are introduced for chemical species associated with phases. Heterogeneous and homogeneous reaction rates representing simplified FT synthesis are taken from literature and incorporated in the model. The model has been tested against experimental results on lab scale bubble columns. Good agreement was observed for bubble size distribution and gas holdup for bubble columns operating in bubble and churn turbulent regimes. Finally, a full model including chemical species transport was applied to industrial scale bubble column. Predicted hydrocarbon production rate was compared to one dimensional lumped parameter model.