Rotating flow characteristics in centrifugal high gradient magnetic separation and its effect on particle capture behavior

Abstract

Centrifugal high gradient magnetic separation (CHGMS) concentrates weakly magnetic minerals at high selectivity, and the rotating flow in the separating area of the CHGMS separator significantly affects its separation performance. In this work, a simulation model based on finite element method was built up to simulate the rotating flow, and the effects of two most important operating parameters affecting the flow, i.e., matrix rotation speed and feed velocity, on the matrix capture behavior were analyzed through a pilot-scale CHGMS separator in concentrating a fine ilmenite ore. The COMSOL Multiphysics simulation of the rotating flow indicates that the slurry in the separating area forms into a rotating flow as a result of the rotation of matrix, and its flow trace length of unit volume slurry prolongs with increase in the matrix rotation speed and reduces with increase in the feed velocity, thereby affecting the collision probability of matrix to particles. It was found that the slurry velocities on the upstream and downstream of magnetic wire in the matrix are significantly higher than those on the right and left sides. There is a large radial velocity gradient in the separating area, which produces a fluid shearing stress to particles in the slurry, thus improves the loosing state of particles and the capture selectivity of matrix; this velocity gradient increases with increase in the matrix rotation speed and decreases with increase in the feed velocity. The capture experiments of matrix to ilmenite particles indicate that the increased matrix rotation speed has a more significant effect on the capture behavior than that of the feed velocity, and these results are basically consistent with those of simulations. This investigation provides an important reference for the optimum development and application of CHGMS technology.