subject: The Development And Usage Of Magnetic Separation [print this page] The magnetic separator is one of commonly used preparation equipments in magnetic separation factory. It has dry and wet two types. According to types of magnets, it can be divided into permanent magnet type and electromagnet type. It is also can be divided into strong magnet type, middle magnet type and weak magnet type according to the magnetic field strength. Different magnetic separators have different characteristics and performance.
Since the 19th century, the magnetic separation process has been used for beneficiation. In the 1970s, the more economic magnetic separator was discovered. In addition, iron ore magnetic separation is used in many mineral processing.
Working principle of magnetic separator
The pulp enters into the tank by the ore box. Under the action of sprinkler pipe, the loose mineral particles pass into the feeding area. The magnetic mineral particles form magnetic group or magnetic chain under the influence of magnetic field. The magnetic group or magnetic chain move to the magnetic pole in the pulp and be adsorbed on the cylinder. For the polarity of magnetic separator alternately arranged along the direction of cylinder rotation and fixed at work, the gangue and other non-magnetic minerals mixed in the magnetic group and chain will spilt away in the rotation of cylinder. At last the magnetic group or magnetic chain which is sucked in the surface of cylinder is the concentrate. The concentrate will be discharged in the concentrate trough by the rinse water from unloading pipe when the concentrate moves to the weakest magnet place following the rotation of cylinder. If there is magnetic roller, it needs brush roll to unload the ore. The non-magnetic or weakly minerals are left in the pulp and discharged with pulp, which form the tailings.
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Advantages of high strength magnetic separator: high strength magnet in the surface of cylinder, big magnetic wrap angle, stable magnetic strength and reliable driveline; it can significantly improve the ore grade.
Magnetic characteristics of weak magnetic minerals
Magnetite can be used as a classic representative of strong magnetic minerals, it belongs to ferrous magnetic material; it have more complex magnetism due to its internal magnetic structure (namely Spontaneous magnetization over small area), the magnetic characteristics can be summed up in the following:
Magnetic strength and magnetized coefficient is very big, with the phenomenon of magnetic saturation, and can be saturated in the lower external magnetic field intensity.
There are curvilinear relationship between Magnetic strength, magnetized coefficient and the external magnetic field intensity, and magnetized coefficient is not a constant. Strength of minerals is in relevant with its properties, but also to the historical change of external magnetic field.
There are hysteresis of minerals, it still retain some residual magnetism when it deviate from magnetized materials; To remove residual magnetism, a reverse magnetic field should be added to completely remove the magnetic field intensity H, which is called coercive force
The magnetism change with temperature, there will exist the phenomenon of paramagnetism when the temperature is higher than the critical temperature-Curie and its internal magnetic structure is small.
The magnetism changes with the strength of magnetic field in the outside, but also with shape and size of its own particle and degree of oxidation.
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