Gas-liquid mass transfer in a slurry bubble column at high slurry concentrations and high gas velocities

Abstract

The volumetric mass transfer coefficient κ_La in a 0.1  m-diameter bubble column was studied for an air-slurry system. A C₉-C₁₁n-paraffin oil was employed as the liquid phase with fine alumina catalyst carrier particles used as the solid phase. The n-paraffin oil had properties similar to those of the liquid phase in a commercial Fischer-Tropsch reactor under reaction conditions. The superficial gas velocity U_G was varied in the range of 0.01 to 0.8  m/s, spanning both the homogeneous and heterogeneous flow regimes. The slurry concentration ε_S ranged from 0 to 0.5. The experimental results obtained show that the gas hold-up ε_G decreases with an increase in slurry concentration, with this decrease being most significant when ε_S < 0.2. k_La/ ε_G was found to be practically independent of the superficial gas velocity when U_G > 0.1 m/s is taking on values predominantly between 0.4 and 0.6 s^–1 when ε_S = 0.1 to 0.4, and 0.29 s^–1, when ε_S = 0.5. This study provides a practical means for estimating the volumetric mass transfer coefficient κ_La in an industrial-size bubble column slurry reactor, with a particular focus on the Fischer-Tropsch process as well as high gas velocities and high slurry concentrations.