Experimental study on micromixing characteristics of novel large-double-blade impeller

Abstract

Large-double-blade (LDB) impeller is a new type of agitator based on Fullzone (FZ) impeller and Maxblend (MB) impeller. To investigate its micromixing characteristics in rapid-reaction situations, we conducted experiments in a 380mm diameter stirred tank. The effect of feeding time, feeding location, agitating speed and viscosity on micromixing characteristics of the novel large-double-blade impeller was investigated, adopting the iodide–iodate parallel competing reaction system. The micromixing characteristics of the novel large-double-blade impeller were also compared with that of double helicon ribbon (DHR) impeller and FZ impeller, which were widely used in process industries. The results indicate that segregation index decreases with increasing feeding time, and won׳t stabilize until the feeding time is greater than its critical value, when macromixing effects can be neglected. In addition, it is favorable for micromixing effects to feed in the impeller regions with high local energy dissipating rate. Segregation index is negatively correlated with stirring speed, whereas the rate of decline tends to be smaller at higher stirring speed, which means that the strengthening effect of improving rotation speed on micromixing efficiency decreases. Moreover, whether the systematic viscosity is high or not, the novel LDB impeller has the advantage of better micromixing effects over FZ and DHR impellers with the same power consumption per unit volume (Pv ).