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How Dry Magnetic Separators Reach Maximum Efficiency?

Published time:30 January 2023

The dry magnetic separator is an essential magnetic separation equipment in mineral processing equipment. It is a magnetic separation machine for separating dry magnetic minerals. It is especially suitable for the magnetic separation of magnetite, pyrrhotite, roasted ore, ilmenite, and other materials with particle sizes below 3mm. It is also used for iron removal of coal, non-metallic minerals, building materials, and other materials.

 

Dry Magnetic Separator
Dry Magnetic Separator

 

Please pay attention to the following three main points to ensure that the dry magnetic separator achieves a good magnetic separation effect.

 

1. Thickness of the 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 dealing with coarse grades, the feeding thickness should not exceed about 1.5 times of the maximum particle size.
  • When dealing with medium grades, the thickness of the feeding layer can reach about four times of the maximum particle size.
  • When processing fine grades, the thickness of the feeding layer can reach about ten times of 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 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. Gravity and inertial force dominate the mechanical force acting on the ore particles. Gravity is a constant, and the inertial force increases or decreases proportionally to the square of the velocity. 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 specific limit, the magnetic force will not be enough to attract them well due to the sharp increase of inertial force. Therefore, weakly magnetic minerals The moving speed in the magnetic field of the magnetic separator should be lower than that of the strong magnetic minerals.

  • When selecting, there are many monomer minerals in the raw materials, and their magnetism is stronger, so the vibration speed of the vibrating tank can be higher;
  • When scanning, the raw materials contain more cognates, and the magnetism of the cognates is weaker. To improve the recovery rate, the speed of the vibrating tank should be lower.
  • When dealing with fine-grained raw materials, the frequency of the vibrating tank should be slightly higher (beneficial to loose mineral particles), and the amplitude should be smaller;
  • When dealing with coarse-grained raw materials, the frequency should be slightly lower, and the amplitude should be larger.

According to the properties of raw materials and sorting requirements, the appropriate operating conditions are determined through practice.

 

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 power of the magnetic field depends on the magnetic properties and operating requirements of the processed raw materials.

  • Use a weaker magnetic field strength when dealing with minerals with stronger magnetism and beneficiation operations.
  • Use a stronger magnetic field strength when dealing with weaker magnetic minerals and scanning operations.

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 crack are not 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 selecting, 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 mineral particles to the disc teeth. To increase the selectivity of separation and improve the grade of magnetic products, 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.

 

Other Tips

Adjust the distance between the magnetic roller and the distribution plate

The distance between the material plate and the magnetic drum is essential in pre-selection. The smaller the space between the material partitions, the poorer magnetite nuggets cannot be recovered, which reduces the utilization rate of ore resources; the distance between the material partitions The bigger it is, the gangue minerals will not be separated well, and the grade of the grinding will drop, which is not conducive to the efficiency of grinding. According to the properties of the ore and the distance between the distribution plate and the drum is adjusted so that the gangue can entirely throw out and ensure the full recovery of magnetic products and the recovery rate of dry beneficiation concentrate. Adjusting the height of the dry-type magnetic separator material separation plate The magnetic separator material separation plate directly affects the separation effect of the magnetic separator. If the separation plate is too low, the extremely poor magnetite blocks cannot be recovered well. The utilization rate of ore resources is reduced; the separation plate is too high, and the gangue minerals are not thrown out completely, which affects the separation effect of the dry magnetic separator. Adjust the height of the dry separation separating plate according to the specific conditions so that the dry separation can not only ensure a certain ratio of tailings but also enable the non-magnetic minerals to be thrown out better.

Increase the flat feeder, and try to make the dry material layer thin and uniform

Generally speaking, the farther the magnetic separator is from the drum surface, the stronger the magnetic attenuation will be. If the material flow is too thick, the magnetic and non-magnetic particles will be mixed with each other, affecting the ore’s separation effect. Layer distribution is ideal if the particles can be separated on the belt. Increasing the material layer leveling device before dry selection and using the effective width of the belt to make the dry selection material layer thin and uniform to ensure the dry selection effect.

 

JXSC Mine Machinery Factory has many years of experience in producing magnetic separators. The dry magnetic separators produced by JXSC have deep surface magnetic field strength, large magnetic system wrap angle, stable magnetic field strength, and stable and reliable transmission system. They can significantly improve the grade of ore entering the mill. You can ask for more information about magnetic separators or consult mineral ore solutions.

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