Separation characteristics of dilute slurry in horizontal flow type of a high gradient magnetic separator

The characteristics of high gradient magnetic separation (HGMS), where strongly magnetic suspensoids are extracted from a dilute slurry flowing through a horizontal, cuboid chamber with a ferromagnetic element on its bottom, are examined using Fe3O4 particle-water mixtures. For different slurry flow rates, slurry concentrations and average solid diameters, the effects of applied magnetic fields on both separation rate and efficiency are studied. When the extraction force due to gravity and magnetic field is much larger than the viscous drag due to slurry flow, the separation rate and efficiency of fine-size suspensoids increase linearly with elapsed time. The smaller the diameter of suspended solids, the lower the velocity of the slurry stream and the stronger the magnetism acting on the solids, the higher is the average rate and efficiency of separation for all slurry concentrations used. These behaviors of HGMS can be related simply to a number of operating variables in view of the fact that the magnetic-effect factor (defined as the ratio of magnetic to gravitational separation efficiency) can be expressed substantially as a unique function of the controlling parameter composed of the strength of the magnetic field and the magnetization of solids. Also presented is a description of how high magnetism, created by the formation of fine-size solids layer on the magnetic element, can be used effectively to remove submicron-sized suspensoids from slurry fed at a fairly high rate.