Gas—liquid mass transfer in external-loop airlift columns with newtonian and non-newtonian fluids

Abstract

Gas—liquid mass transfer in external-loop airlift columns has been examined. The measurements have been carried out in two external-loop airlift columns and a bubble column with newtonian and non-newtonian fluids. The experimental results indicate that the volumetric mass transfer coefficient k L a decreases with increasing downcomer-to-riser cross-sectional area ratio and its dependence increases with non-newtonian flow behaviour or shear thinning. A theoretical model for volumetric mass transfer coefficient has been also developed. It is based on a combination of Higbie's penetration theory and Kolmogoroff's theory of isotropic turbulence. The capability of the proposed correlation for k L a was examined using the present data and the available results in the literature. Reasonable agreement between the predicted and experimental results for newtonian and inelastic non-newtonian (pseudoplastic) fluids suggests applicability of the proposed model.