(193c) Performance of a Dual Shaft Mixer for Gas-Viscous Liquid Processing

A novel mixer configuration consisting of independently-driven dual off-centered impellers has been studied extensively during gas-viscous liquid mixing. A mixing kinetics method based on image analysis of a fast acid-base coloration-decoloration reaction was used for the determination of the mixing times as well as to reveal the presence of compartmentalization and communication between the mixed zones. It is shown that for viscous Newtonian and non-Newtonian liquids the dual shaft mixer can eliminate compartmentalization and reduce the mixing time when compared to the classical single shaft arrangement with two impellers. This reduction can be achieved when the collaboration between the impellers is favoured by adjusting the impellers speed and rotation direction. In gas-liquid processing the effects of the rotational speed, gas flow rate, and impeller type on the volumetric mass transfer coefficient (kla) were investigated in polymeric non-Newtonian solutions.