Simulation of a commercial-scale slurry bubble column reactor using cobalt catalysts

Abstract

A user-friendly simulator based on a comprehensive computer model for slurry bubble column reactor (SBCR) developed in our laboratory was used to predict the performance of a conceptual commercial-scale (9-m ID and 50-m height) SBCR for indirect coal conversion using Fischer-Tropsch (F-T) synthesis in the presence of a cobalt catalyst. New correlations for predicting the hydrodynamic and mass transfer parameters and three different kinetic rate expressions from the available literature specifically for cobalt catalysts were incorporated in the simulator. The effects of operating conditions, including catalyst concentration, pressure, temperature, H2/CO ratio, and superficial gas velocity on the SBCR performance were predicted using the simulator. The predictions showed that the performance of the SBCR was strongly dependent on the kinetic rate expression used. At low catalyst concentration, the reactor operated in a kinetic-controlled regime with increased syngas conversion and catalyst productivity; however, increasing catalyst concentration drove the reactor to operate in a mass transfer-controlled regime with decreased syngas conversion and catalyst productivity. The transition from kinetic-controlled regime to mass transfer-controlled regime occurred at different solid concentrations depending on the kinetic rate expressions employed. High H2/CO ratios in the inlet feed gas to the SBCR led to high syngas conversion. Increasing the superficial syngas velocity in the reactor decreased the gas residence time, which decreased the syngas conversions. High operating temperature always resulted in high syngas conversion. Also, the effect of operating pressure on the SBCR performance was not clear, since increasing pressure resulted in low or high syngas conversion depending on the catalyst and kinetic rate expressions used.