Dynamic capture and accumulation of multiple types of magnetic particles based on fully coupled multiphysics model in multiwire matrix for high-gradient magnetic separation

Abstract

High-gradient magnetic separation (HGMS) effectively separates fine weakly magnetic minerals using a magnetic matrix. The basic principle of single-wire capture of magnetic particles in HGMS has received considerable attention. In practice, however, a real matrix is made of numerous magnetic wires. Transport of magnetic particles inside a multiwire matrix under various operating conditions has not been sufficiently investigated, and it is not clear whether single-wire and multiwire matrices differ significantly. A fully coupled multiphysics model based on the idealized capture model was developed to investigate the 2D capture and accumulation of multiple types of particles in single-wire and multiwire matrices. In this model, the properties of multiple types of particles were defined. Then, particle tracing via the fluid flow model was used to calculate the dynamic capture and accumulation of particles under the determined magnetic and flow fields. The time-dependent dynamic capture mode used in this study can reveal the details of particle capture and accumulation in single-wire and multiwire matrices. All the calculations and analyses indicate that single-wire and multiwire matrices both exhibit basically the similar capture tendency as the particle size, slurry feed velocity, and magnetic induction are gradually increased, and a single-wire matrix always has a much higher capture selectivity than a multiwire matrix. This difference in selectivity between the single-wire and multiwire matrices results mainly from magnetic coupling between magnetic wires in the multiwire matrix, where the fluid flow is also quite complicated. In addition, adjacent columns of wires are staggered vertically, increasing the probability of collisions between the particles and the wires; thus, intergrowth particles that are not captured by the upstream wires are more easily captured by the downstream wires. By comparing the experimental results with the simulation results, the correctness of the HGMS recovery and grade prediction results was verified.