Column-based magnetic separation can concentrate magnetite while preventing magnetic particle agglomeration. Changes in the force characteristics during this process greatly affect the separation of different magnetite components. Here, the mechanical characteristics of magnetite with different particle sizes during column-based magnetic separation are studied. Upon reducing the particle size (passing 74 μm) from 45% to 90%, the magnetic force ( $HgradH$) required to separate the magnetite concentrate gradually increased. The difference in the magnetic force required to capture magnetite concentrate and rich interlocking concentrate by a magnetic field decreased from 39.53% to 13.92%. The difference in the magnetic force required to capture lean interlocking concentrate and gangue minerals by a magnetic field decreased from 75.87% to 54.26%. Verification tests showed that pre-separating magnetite concentrate and gangue from individual coarse particles reduced the workload of subsequent grinding and separation, making it easier to separate magnetite from the concentrate.

The magnetism of minerals plays an important role in magnetic agglomeration. In this paper, the relationship between the magnetism of magnetite ore and particle size was revealed by mineral liberation analyzer (MLA) and vibrating sample magnetometer (VSM) tests. With decreasing fineness, the specific susceptibility of the liberated magnetite decreased and its coercivity increased, and the difference in magnetism between liberated magnetite and rich interlocking particles decreased. Based on the above conclusion, a three-product magnetic separator with rotatable magnetic system, dispersed screen, and fluid drag was developed to simultaneously separate liberated magnetite and discard gangue minerals in a short process.

The settlement characteristics of magnetite particles are one of the key factors affecting the separation performance of column magnetic separator. This paper reports on the settlement characteristics of different magnetite particles under the action of complex force field measured by using a particle settlement device with an applied magnetic field. The results show that under the combined effect of fluid drag force and magnetic field, the differences in magnetite particle density and particle size are reduced, the differences in magnetic properties are amplified, and particles with different magnetic properties are separated. Based on these results, a three-product magnetic-separation column with mutually independent magnetic and fluid field structures for different magnetic particles was developed. Using this separator, the TFe grade and recovery of the concentrate were 67.93% and 92.9%, respectively. The results show that the equipment is effective in separating the liberated magnetite and other interlocking particles, thereby improving the sorting efficiency. This provides a theoretical basis for the development of column magnetic separation equipment and the improvement of magnetic separation accuracy.