Effect of gas distributor on gas–liquid dispersion and mass transfer characteristics in stirred tank

Abstract

Aiming at the fact that the function of gas distributor is often neglected in the case of high viscosity conditions, a novel spherical micro-orifice gas distributor was proposed and investigated experimentally in water system and non-Newtonian viscous system, respectively. The comparisons of gas–liquid dispersion and mass transfer performance between novel spherical micro-orifice gas distributor and traditional ring distributor were also done. Furthermore, the effects of gas distributors on the gas–liquid dispersion and mass transfer characteristics of three wide-viscosity-range impellers including LDB impeller, FZ impeller and MB impeller were also researched, and an impeller-distributor configuration with good gas–liquid dispersion and mass transfer performance was achieved. The results show that, compared with ring gas distributor, the bubbles dispersed by novel spherical micro-orifice gas distributor are smaller, and the gas holdup and volumetric mass transfer coefficient are relatively higher under the same power consumption per unit volume. Meanwhile, the significant effect of gas distributor geometry on gas dispersion was found for high-viscosity liquid, but not relevant for low-viscosity batches. In addition, compared with other impeller-distributor configurations, the configuration consisting of FZ impeller and novel spherical micro-orifice gas distributor can achieve greater global gas holdup and higher oxygen mass transfer rate, which is recommended especially in viscous system with high gas flow rate. The research is beneficial to promote the application of novel spherical micro-orifice gas distributor in stirred tanks.