Increasing Gas-Liquid Mass Transfer in Stirred Power Law Fluids by Using a New Energy-Saving Impeller

M. Martinov and S. D. Vlaev

Abstract
The gas-liquid mass transfer performance of a stirred vessel equipped with a novel impeller, has been studied. The device is presented as means to increase gas-liquid mass transfer rate in stirred non-Newtonian media of fermentation vessels. The impeller is of the fluid foil type that is suitable for power law fluids. Mass transfer rates for power law liquids are determined by measuring KLa in model pseudoplastic CMC and xanthan gum solutions at moderate shear. The effects of geometry, gas flow rate, rheology, and impeller speed are illustrated. The results are compared with similar data reported for the disc-style flat blade Rushton (RT) turbine, used conventionally in industrial vessels. The mass transfer coefficient is correlated with gas linear velocity and specific mixing power. An equation for KLa is proposed. In comparison with the conventional case, significant energy saving is demonstrated.

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Keywords
mass transfer, stirred vessel, fluid foil impeller, pseudoplastic media