An Extended Technique for Predicting the Mixing Times of High-Viscosity Liquid in a Mixer—Mixing Systems with Molecular Diffusion and Reaction of Solutes—

Abstract

This paper presents an extended technique for predicting the mixing time of high-viscosity liquids in a mixer. The molecular diffusion and reaction between solutes each dissolved in the liquids are analyzed during the mixing. Concentration profiles are obtained by solving simultaneously the diffusion and reaction differential equation and a model equation representing the decrease of scale of segregation with time. The calculated mixing time is predicted as the elapsed time until the local maximum concentrations of the solute become less than a chosen criterion of mixing. Mixing experiments were carried out with helical screw/draft tube mixers and helical ribbon-impeller mixers filled with corn syrups prepared at various viscosities. The chemical reactions were the reduction of I₂ to 2I^– in the presence of either Na₂S₂O₃ or Na₂HPO₄. It was found that the predicted mixing times were in fairly good agreement with those determined experimentally. The mixing time was found to depend mainly on the reaction rate of reactants as well as the operational conditions of the mixer.