Investigation of the Solids Suspension and Dispersion in Newtonian and Non-Newtonian Fluids With the Coaxial Mixers

Abstract

Achieving a high degree of solid dissemination at optimum power consumption in a liquid-solid system is a challenging task. No information is available in the literature regarding slurry suspension in dense systems, slurry suspension and dissemination in non-Newtonian fluids, and suspension and distribution of poly-disperse solids in Newtonian and non-Newtonian fluids, using coaxial mixers. The prime objectives of this study were aimed at assessing the mixing capability of a coaxial system comprised of a central axial-flow impeller with a high rotating speed and an outer anchor with a low rotating speed in suspending and dispersing solid particles in water (Newtonian) and carboxymethyl cellulose (CMC) solutions (non-Newtonian) using flow visualization (electrical resistance tomography), numerical (computational fluid dynamics), and statistical (response surface methodology) techniques. The goal also included examining the suitability of a coaxial mixer in suspending the polydisperse particles in Newtonian and non-Newtonian fluids. The 2D images acquired by ERT and CFD methodologies were utilized in creating solid concentration profiles. Different mixing indexes were employed to analyze the impacts of both solid concentration gradients (axial and radial) on the degree of solids distribution. The mixingcapability of thecoaxial mixingsystemwas comparedtothat of a traditional single impeller system in terms of the degree of axial homogeneity with respect to total power drawn. RSM was utilized to determine the optimum design parameters and conditions to achieve the best suspension quality inside the coaxial reactors. The effects of different factors namely solids content, central impeller speed, anchor speed, CMC concentration, central impeller types, central impeller spacing, poly-disperse ratio, particle size, solid specific gravity, and rotating mode on the suspension and dispersion phenomena were comprehensively analyzed. The results demonstrated that the coaxial mixer facilitated