Dynamic Performance of Continuous-Flow Mixing of Pseudoplastic Fluids Exhibiting Yield Stress in Stirred Reactors

The core objectives of this work were to characterize and optimize the continuous-flow mixing of pseudoplastic fluids exhibiting yield stress in stirred reactors. To achieve these objectives, the effects of impeller type (for the seven axial-flow impellers A100, A200, A310, A315, A320, 3AH, and 3AM and the four radial-flow impellers R500, RSB, RT, and Scaba), impeller speed (50-800 rpm), impeller diameter (T/3.2-T/1.6, where T is the tank diameter), impeller off-bottom clearance (H/3.4-H/1.7, where H is the fluid height in the vessel), inlet and outlet locations (for the four configurations top inlet-top outlet, top inlet bottom outlet, bottom inlet-bottom outlet, and bottom inlet-top outlet), pumping directions for axial-flow impellers (upward and downward pumping), fluid height in the vessel (T/1.06-T/0.83), residence time (257-328 s), and jet velocity (0.317-3.24 m s(-1)) on the dynamic performance of the mixing vessel were explored. To identify nonideal flows, dynamic tests were conducted using the frequency-modulated random binary input of a brine solution with the feed. The mixing quality in the vessel was substantially improved by increasing the impeller diameter, increasing the residence time, optimizing the impeller off-bottom clearance, decreasing the fluid height, optimizing the jet velocity, and using the up-pumping axial-flow impeller. Applying these findings will lead to improved quality of products and more efficient use of power in continuous-flow mixing of yield-pseudoplastic fluids.