A modelling approach to investigate the performance of slurry bubble column reactors implementing Fischer-Tropsch synthesis

A reliable estimation of the reactor performance is a crucial aspect of slurry bubble column reactor design. Hydrodynamics, mass transfer, and reaction rate are the main parameters influencing the overall performance. A new hydrodynamic model was adopted in this study to properly predict the effect of solids loading, particle size, pressure, and temperature on the gas holdup, bubble size distribution, and mass transfer coefficient. The reactor was divided into small cells with individual hydrodynamic parameters. The results were compared with the experimental data and showed that the model can acceptably predict the hydrodynamic and mass transfer parameters in various process situations. A parametric study was accomplished to understand the effect of catalyst loading, superficial gas velocity, H-2/CO ratio, L/D ratio, pressure, temperature, and catalyst attrition on the conversion rate, catalyst productivity, and space-time yield. A cobalt/silica catalyst was adopted in this study. Based on the obtained results, the syngas conversion increases by catalyst loading, L/D, and temperature, while it decreases by U-g and pressure. The H-2/CO ratio results in a maximum conversion somewhere between 2 and 2.5. Three different scenarios were determined to study the effect of catalyst attrition on the reactor performance. The results show that the attrition decreases the syngas conversion due to the decrease in the catalyst size and the catalyst loss. Also, the performance remains constant if a sufficient amount of fresh catalyst is added to the system continuously.

Automated summary

A reliable estimation of the reactor performance is achieved using a new hydrodynamic model to predict the effect of various parameters on gas holdup, bubble size distribution, and mass transfer coefficient. The study also investigates the influence of catalyst loading, gas velocity, H-2/CO ratio, L/D ratio, pressure, temperature, and catalyst attrition on conversion rate, catalyst productivity, and space-time yield. The results show that catalyst loading, L/D ratio, and temperature increase syngas conversion, while gas velocity and pressure decrease it. The H-2/CO ratio has a maximum conversion at around 2 to 2.5. Catalyst attrition decreases syngas conversion, but constant performance can be maintained with continuous addition of fresh catalyst.