Power Consumption Characterization of Energy-Efficient Aerated Coaxial Mixers Containing Yield-Stress Biopolymer Solutions

Abstract

The operations of mixing systems utilized in a variety of industrial applications for dispersing gas in non-Newtonian fluids are complex. The main challenge is to maintain a homogeneous medium throughout the vessel. In fact, coaxial mixers have demonstrated an energy-efficient performance for systems containing rheologically complex fluids. However, the accurate characterization of the power demand for gas dispersion in yield-stress fluids using coaxial mixers remains unclear. Hence, the objective of the present work was to investigate the power characteristics of a coaxial mixing system comprising the xanthan gum solution, which is a shear-thinning fluid possessing yield stress. The power consumption of an Anchor-PBT mixing configuration was measured experimentally at different central and anchor impeller speeds, rotation modes, and aeration rates. The main effects of the operating variables and their interactions were quantified using a central composite design of experiments. Significant effects of the central impeller speed and the interaction between the anchor speed and the aeration rate were identified. Also, a generalized power curve for this mixing system was proposed based on a predefined equivalent impeller speed and impeller diameter expressions to develop the novel power number and Reynolds number. The findings of this work provide an asset in designing and scaling up of energy-efficient aerated coaxial mixers by rapidly estimating the power demand.