How to optimize the effect of dry magnetic separator? - Halbach array

Dry magnetic separator is a magnetic mineral separation machine for sorting dry magnetic minerals, especially suitable for magnetic separation of magnetite, pyrrhotite, roasted ore, ilmenite and other materials with a particle size of less than 3mm. It is suitable for iron removal operations of coal, non-metallic minerals, building materials and other materials. There are three main points to ensure that the dry magnetic separator achieves good magnetic separation effect: the thickness of the feed layer, the vibration speed of the vibrating tank, the magnetic field strength and the working gap.

1. Thickness of feeding layer

The thickness of the feed layer is related to the particle size of the processed raw material and the content of magnetic minerals. Coarse-grained raw materials are generally thicker than fine-grained feed layers. When processing coarse grades, the thickness of the feed material should not exceed about 1.5 times the maximum particle size, while when processing medium grades, the thickness of the feed layer can reach about 4 times the maximum particle size, and the thickness of the feed layer can reach about 10 times the maximum particle size. When the content of magnetic minerals in the raw material is not much, the feeding layer should be thinner. If it is too thick, the magnetic ore particles in the bottom layer will not only receive less magnetic force, but also be subjected to the pressure of the non-magnetic ore particles above in addition to their own weight, which will reduce the recovery rate of magnetic products. When the content of magnetic minerals is large, the feeding layer can be appropriately thicker.

2. The vibration speed of the vibration tank

The vibration speed of the vibrating tank determines the time that the ore particles stay in the magnetic field and the magnitude of the mechanical force they receive. The greater the product of the vibration frequency and the amplitude of the vibration tank, the greater the vibration speed, and the shorter the residence time of the ore particles in the magnetic field. The mechanical force acting on the ore particles is dominated by gravity and inertial force. Gravity is a constant, and the inertial force increases or decreases proportional to the square of the speed. The magnetic force suffered by weakly magnetic minerals in the magnetic field is not much greater than the gravitational force. Therefore, if the speed of the vibrating tank exceeds a certain limit, the magnetic force is not enough to attract them well due to the sharp increase of inertial force. Therefore, weak magnetic minerals The moving speed in the magnetic field of the magnetic separator should be lower than that of the strong magnetic minerals.

Generally speaking, when selecting, there are many monomer minerals in the raw material, and their magnetism is stronger, so the vibration speed of the vibrating tank can be higher; Weak, in order to improve the recovery rate, the speed of the vibration tank should be lower. When dealing with fine-grained raw materials, the frequency of the vibrating tank should be slightly higher (beneficial to loose ore particles) and the amplitude should be smaller; while for coarse-grained raw materials, the frequency should be slightly lower and the amplitude should be larger. Appropriate operating conditions should be determined through practice according to the nature of the raw materials and the requirements for sorting.

3. Magnetic field strength and working gap

The magnetic field strength and working gap are closely related to the particle size, magnetism and operation requirements of the processed raw materials. When the working gap is constant, the magnetic field strength between the two magnetic poles is determined by the ampere-turns of the coil, and the number of turns is not adjustable, so the magnetic field strength is adjusted by changing the magnitude of the current. The strength of the magnetic field depends on the magnetic properties and operating requirements of the processed raw materials. When dealing with strong magnetic minerals and beneficiation operations, a weaker magnetic field strength should be used. When dealing with minerals with weaker magnetic properties and sweeping operations, a stronger magnetic field strength should be used.

When the current is constant, changing the size of the working gap can make the magnetic field intensity and magnetic field gradient change simultaneously. Therefore, the effects of changing the current and the working gap are not exactly the same. Reducing the working gap causes a sharp increase in the magnetic field force. The size of the working gap is determined by the particle size of the raw material being processed and the job requirements. Larger for coarser levels and smaller for finer levels. When sweeping, adjust the working gap to the minimum as much as possible to improve the recovery rate; when beneficiating, it is best to increase the working gap to reduce the non-uniformity of the magnetic field distribution between the two poles and increase the magnetic ore particles to the disc teeth. To increase the selectivity of separation and improve the grade of magnetic products, but at the same time, it is necessary to increase the current appropriately to compensate for the reduced magnetic field strength due to the increase of the working gap.