Modeling and simulation on extraction of rare earth by computational fluid-particle dynamics in a batch reactor

Abstract

The reaction mechanism for a leaching process was described in a slurry consisting of Rare earth ore (REO) particles and magnesium-sulfate solution. An inner diffusion control shrinking core model was adopted to describe reactant migration within the REO particle, and the outer diffusion layer was modeled by considering a thin diffusion layer to capture the convection effect on the particle surfaces. This reaction mechanism was implemented in a Computational fluid-particle dynamics (CFPD) simulation coupled with a Coarse-grained particle model (CGPM) for a liquid-solid leaching reactor equipped with a mixing impeller. The simulations of batch reactor were carried out to predict leaching efficiency with various impeller speed and REO particle sizes. The simulation results show that inefficient leaching of REO particles was caused by solute depletion due to incomplete mixing. This magnesium ion depletion intensified in packed-particle regions due to poor species transfer from the bulk solution. This CFPD study also demonstrates that the REO particle size has a major effect on the leaching process.