The influence of mineral magnetism on the magnetic separation process
The fundamental reason for the magnetic properties of minerals is the result of electron transport in the molecules or atoms within the substance. The electron movement forms a molecular loop and thus generates a magnetic field. The electron motion is either orbital motion around the nucleus or the spin motion of the electron itself. The magnetic moment produced by the orbital motion is weak and negligible, while the magnetic moment produced by the spin motion is stronger and is the main source of magnetism in matter. Before magnetization, minerals do not show magnetic properties because their internal magnetic moments are disordered. When placed in a magnetic field and magnetized, the internal magnetic moment orientation of minerals is consistent and thus show magnetic properties. Mineral magnetism can be classified as antimagnetic, paramagnetic and ferromagnetic.
The magnetic separation process is used to select the separation conditions with the help of the magnitude of the magnetization strength of the minerals under the action of the external magnetic field. In mineral magnetic separation classification, comparison, description of the hysteresis curve and magnetic saturation, remanence, coercivity and other principles are commonly used to explain the behavior of minerals in magnetic separation.
The magnetic properties of minerals have a great influence on the magnetic separation process. The magnetization coefficient of the mineral grains that should be recovered into the magnetic product determines the choice of magnetic field strength of the magnetic separator (of weak or strong magnetic field). The influence of mineral magnetism on the magnetic separation process is as follows:
1. Due to the strong magnetic properties of strong magnetic minerals such as magnetite, recovering them can be achieved with a lower magnetic field.
2. Magnetite particles retain remanent magnetism as soon as they are magnetized. When the particle size is fine, the particles will attract each other into magnetic clusters or magnetic chains. The magnetic clusters are not easily dispersed, and if they contain vein particles, they will reduce the grade of the magnetic product. If magnetic agglomerates are present in the feed to the classification operation, the classification efficiency will be reduced. This is the adverse effect of magnetic agglomeration. In this case demagnetizer can be used to eliminate the remanent magnetism and destroy the magnetic agglomeration.
3. Weak magnetism of the magnetite particles of microfine grains, magnetic separator while moving in water with high resistance, so recovery requires a large magnetic force, and the water flow is easy to wash it away, resulting in metal loss. It can be seen that the grinding process should be minimized over-grinding.
4. If the monomer dissociation of the grinding process is not sufficient, congeners of magnetite and veinlets particles will appear. Although the veins are mostly non-magnetic minerals, but because the magnetism of magnetite is very strong, it is subjected to magnetic force enough to bring the veins with its congeners to the magnetic product, which reduces the grade of the magnetic product. If you want to separate this part of the conjoined body from the magnetic product, you need to use fine sieve regrinding, flotation, re-election or other sorting methods.
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