Large Eddy Simulations of a Mixing Tank with Axial Flow Turbine

Abstract

An understanding of solid-liquid mixing, with many aspects of mixing, dispersing and contacting, is critical to the efficient preparation of brine from sodium formate and other processes, such as agitated leaching, in the mining industry, rubber crumb, crystallization and precipitations. Generally speaking, solids can be porous catalysts for catalytic reactions, active agents for adsorption, polymers and co-polymers for suspension polymerization or particles that need to be dissolved or coated. In the present attempt, large-eddy simulations of a turbulent flow of a mixture of solid liquid in a baffled, cylindrical mixing vessel, with a large number of solid particles, were formulated to obtain insight into the fundamental aspects of a solid-liquid mixing. The impeller-induced flow at the blade tip radius of an axial turbine was modeled using the dynamic-mesh Lagrangian method. The simulations were four-way coupled, which implies that both solid liquid and solid-solid interactions are taken into account. By using a phenomenological model, based on the modified Kelvin-Maxwell model, normal and tangential forces were calculated acting on a particle, due to viscoelastic contacts with other neighboring particles. Simulations were performed for the special case of dissolving solids, whose dissolution rate was assumed to be mass transfer controlled. The results suggest that the granulated form of dissolving solids, such as sodium formate, may provide a mixture that allows faster and easier preparation of formate brine in a mixing tank.