Gas holdup and volumetric mass transfer coefficient in a slurry bubble column

Abstract

The gas holdup, ϑ, and volumetric mass transfer coefficient, k_La, were measured in a 0.051 m diameter glass column with ethanol as the liquid phase and cobalt catalyst as the solid phase in concentrations of 1.0 and 3.8 vol.-%. The superficial gas velocity U was varied in the range from 0 to 0.11 m/s, spanning both the homogeneous and heterogeneous flow regimes. Experimental results show that increasing catalyst concentration decreases the gas holdup to a significant extent. The volumetric mass transfer coefficient, k_La, closely follows the trend in gas holdup. Above a superficial gas velocity of 0.04 m/s the value of k_La/ϑ was found to be practically independent of slurry concentration and the gas velocity U; the value of this parameter is found to be about 0.45 s⁻¹. Our studies provide a simple method for the estimation of k_La in industrial-size bubble column slurry reactors.