An integrated CFD methodology for tracking fluid interfaces and solid distributions in a vortexing stirred tank

Abstract

Distribution of solid phase in a solid–liquid suspension being mixed in a vortexing, unbaffled stirred tank is difficult to model numerically. The need is to be able to predict the shape of the vortex (air–water interface) and the distribution of solids in the liquid domain. Typically, the problem is approached with assumptions about the shape of the interface to capture the solid distribution through a multi-phase Eulerian model (doi: 10.1016/j.ces.2018.07.023). In this work, a multi-step modelling framework for multi-phase systems that have a free surface along with the dispersion of secondary phase(s) in the liquid domain is proposed. To demonstrate the method, it is applied to a laboratory-scale vortexing unbaffled system reported in the literature (doi: 10.1021/ie071225m) and a pilot-scale tank (doi: 10.1016/j.cej.2018.10.020). The predictions from the computational fluid dynamics model are compared with the experimental profiles of solid volume fractions. Using the model, the effects of solid density, particle size, particle loading, and impeller speed are investigated for the laboratory-scale system. An interesting self-similar nature in the axial distribution of solid is observed when the loading is varied from 0.5 to 10 volume percent.