Volumetric mass transfer coefficient in a slurry bubble column operating in the heterogeneous flow regime

摘要

We report the results of an experimental study of the gas holdup, epsilon(G), and volumetric mass transfer coefficient, k(L)a, in a bubble column slurry reactor of 0.1 m diameter operated at ambient temperature and pressure conditions. The superficial gas velocity U was varied in the range 0-0.4 m/s, spanning both the homogeneous and chum-turbulent flow regimes. Air was used as the gas phase. The liquid phase used was C-9-C-11 paraffin oil containing varying volume fractions (epsilon(S) = 0, 0.05, 0.10, 0.15, 0.20 and 0.25) of porous catalyst (alumina catalyst support, 10% < 10 mum; 50% < 16 mum; 90% < 39 mum). With increasing slurry concentrations, epsilon(G) is significantly reduced due to enhanced bubble coalescence. For superficial gas velocities U > 0.10 m/s the volumetric mass transfer coefficient per unit volume, k(L)a/epsilon(G), was found to be practically independent of U and has values in the range 0.36-0.55 s(-1). From estimations of the sizes of the bubble size from literature correlation it is found that the "large" bubble mass transfer coefficient is about one order of magnitude higher than predicted by literature correlations. (C) 2004 Elsevier Ltd. All rights reserved.