Assessing the performance of an industrial SBCR for Fischer-Tropsch synthesis: Experimental and modeling

The main objective of this study is to predict the performance of an industrial-scale (ID=5.8 m) slurry bubble column reactor (SBCR) operating with iron-based catalyst for Fischer-Tropsch (FT) synthesis, with emphasis on catalyst deactivation. To achieve this objective, a comprehensive reactor model, incorporating the hydrodynamic and mass-transfer parameters (gas holdup, epsilon(G), Sauter-mean diameter of gas bubbles, d(32), and volumetric liquid-side mass-transfer coefficients, k(L)a), and FT as well as water gas shift reaction kinetics, was developed. The hydrodynamic and mass-transfer parameters for He/N-2 gaseous mixtures, as surrogates for H-2/CO, were obtained in an actual molten FT reactor wax produced from the same reactor. The data were measured in a pilot-scale (0.29 m) SBCR under different pressures (4-31 bar), temperatures (380-500 K), superficial gas velocities (0.1-0.3 m/s), and iron-based catalyst concentrations (0-45 wt %). The data were modeled and predictive correlations were incorporated into the reactor model. The reactor model was then used to study the effects of catalyst concentration and reactor length-to-diameter ratio (L/D) on the water partial pressure, which is mainly responsible for iron catalyst deactivation, the H-2 and CO conversions and the C5+ product yields. The modeling results of the industrial SBCR investigated in this study showed that (1) the water partial pressure should be maintained under 3 bars to minimize deactivation of the iron-based catalyst used; (2) the catalyst concentration has much more impact on the gas holdup and reactor performance than the reactor height; and (3) the reactor should be operated in the kinetically controlled regime with an L/D of 4.48 and a catalyst concentration of 22 wt % to maximize C5+ products yield, while minimizing the iron catalyst deactivation. Under such conditions, the H-2 and CO conversions were 49.4% and 69.3%, respectively, and the C5+ products yield was 435.6 ton/day. (c) 2015 American Institute of Chemical Engineers