Study on capture radius and efficiency of fine weakly magnetic minerals in high gradient magnetic field

•The capture limit of fine weakly mineral particles was numerically computed.•The capture process is clearly shown by the motion trajectories of the particles.•The capture efficiency of particles is analyzed based on the capture radius.•Generalized relation between capture radius and influencing factor is derived.•Optimizations of the HGMS system are demonstrated.

The recovery of ultrafine weakly magnetic minerals using HGMS is proved a tough issue in industrial practice. Optimization of HGMS parameters determines the recovery result. The capture limits of weakly magnetic particles of diameter range 1–30 μm in high gradient magnetic field are studied using a numerical computation method. The matrix size and slurry velocity as well as the magnetic induction show great influence on the capture radius. The capture radius decreases rapidly with the decrease of particle size, the increase of matrices diameter and slurry velocity. For generalized condition, the capture radius is largely dependent on the ratio of slurry velocity V0 to the so called magnetic velocity Vm. The capture efficiency decreases with the increase of the matrices arrangement value of d/a (the ratio of half the spacing between matrices to the matrix radius). The relationship between capture efficiency and V0/Vm as well as d/a is obtained. This relationship can provide a guidance of choosing matrices of the perfect size and arrangements or configuring the HGMS system to work with high capture efficiency. It is also demonstrated how to regulate the HGMS system from a working point of low capture efficiency to a working point of high capture efficiency.