Investigation of gas-liquid mass transfer in slurry systems driven by the coaxial mixer

Abstract

The coaxial mixer was applied to the gas-liquid mass transfer process in slurry systems containing up to 8 vol% solids. The effects of impeller type, impeller speed, solid content, and gas flow rate were examined, and a correlation for the volumetric mass transfer coefficient was established. The findings indicate that at identical impeller speeds, the combination of an anchor and Rushton turbine exhibited the highest volumetric mass transfer coefficient and gas hold-up among coaxial mixers. However, when the pitched blade turbine with a down-pumping direction was utilized as the inner impeller, the coaxial mixer demonstrated superior performance under the same power consumption conditions. Additionally, the lower anchor speed was found to improve gas-liquid mass transfer, whereas a higher speed would lead to poor dispersion of gas phase, thereby deteriorating the performance of coaxial mixers. Increasing solid content caused a continuous decline in both the volumetric mass transfer coefficient and gas hold-up, while a rise in gas flow rate had the positive effect. Finally, the correlation developed for the volumetric mass transfer coefficient in slurry systems showed a deviation of less than 20% between predicted and measured values.