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Types of Weak Magnetic Separators

Release time:17 October 2019

The industrial magnetic separation machine can be divided into the weak magnetic separator and strong magnetic separator (high-intensity magnetic separator).
This article mainly introduces the types of weak magnetic separators, includes dry type, wet type, and auxiliary equipment.

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types of magnetic separator in mining industry

Dry type weak magnetic separators

The dry magnetic separator requires the sorted minerals to be dry, free and loose, wet magnetic separators use liquids as diluents to improve beneficiation efficiency.

Iron remover

The iron remover is used to remove the iron lump and iron slag from the raw material, have an electromagnetic type and permanent magnet type.
Iron remover installation: fixed suspension and belt suspension.
fixed suspension iron remover
A fixed suspended iron remover is suspended above the conveyor belt to pick up iron from the material flow. The width of the magnet corresponds to the width of the belt conveyor.
It needs manually remove the iron from the magnet, so it only used in the small processing plants.

belt suspension iron remover
The belt suspension iron remover has two installation methods, as shown in the figure below.
One is that the iron remover and the conveyor belt cross at right angles, and the iron is discharged from the side of the conveyor belt; the other is that the iron remover is in the same direction as the conveyor belt, and the iron is discharged from the front end of the material stream.
It is used for extracting bulk iron materials, can be used for iron removing or iron recovering from coal, iron slag and steel slag, industrial waste and other materials.

Magnetic pulley

Magnetic pulleys, also known as magnetic rollers, are available in both electromagnetic and permanent magnets. The permanent magnet pulley has a simple structure, no power consumption, reliable work, easy maintenance, and wide application.
Magnetic pulley
1 Equipment structure—Barium ferrite constitutes a multi-pole magnetic system with a magnetic wrap angle of 360 degrees, and a rotating cylinder made of a non-magnetic material is placed outside the magnetic system.
2 Magnetic system and magnetic field characteristics—When the material size of the treated material is less than 20mm, the alternating polarity is beneficial to improve the beneficiation efficiency.
Magnetic pulley magnetic field
3 Beneficiation process— ore material evenly and constantly feed on the belt, when the ore passes through the magnetic pulley, the non-magnetic or weak magnetic ore particles are separated from the belt surface by centrifugal force and gravity; while the strong magnetic particles attracted to the belt by the action of the magnetic force and is carried by the belt to the lower part of the magnetic pulley. After the belt away the magnetic pulley, the magnetic force of the magnetic ore particles is weakened and falls into the magnetic product tank.
The yield and quality of the product are adjusted by the position of the separation baffle mounted under the magnetic pulley.

4 Application
Pre-selection for big size (10~120mm) strong magnetic ore, it usually be installed after the coarse crushing operation, separates the surrounding rock.
In some concentrating plants, the magnetic pulley is installed between the fine crushing process and the grinding process, picking up part of the tailings, which can reduce the amount of ore and improve the grade.
In the operation of the hematite ore roasting, the roasting quality is controlled by a magnetic pulley, so that the ore which is not sufficiently reduced is separated by a magnetic pulley and returned to the roasting furnace for magnetization roasting.

Drum magnetic separator

Drum magnetic separator main parts: Permanent magnet fixed magnetic system, feeding part (upper or lower feeding), discharge part, transmission and frame.
Drum magnetic separator
1 Structure—-The cylinder is made of 2mm FRP and the surface is coated with a layer of wear-resistant rubber. The magnetic system consists of a barium ferrite permanent magnet block with a magnetic envelope angle of 270 degrees. The polarity of the magnetic poles alternates in the circumferential direction and the polarities are uniform along the axial direction. The main reason for the use of FRP for cylinders instead of stainless steel is to prevent the drum from heating due to eddy currents.
The drum magnetic separator has two types of a single cylinder and double cylinder. The sorting length of the single-cylinder can be adjusted by the position of the baffle. The double-barrel machine can adjust the magnetic system declination to adapt to the needs of different sorting processes (concentrating or scavenging).

2 Beneficiation process
The fine dry ore particles are firstly fed into the upper drum by the electric vibrating feeder, the magnetic ore particles are attracted on the cylinder surface and be discharged.
The non-magnetic ore particles are thrown away from the cylinder surface by gravity and centrifugal force, and enter the lower drum for sorting. The non-magnetic ore particles enter the tailings trough, the rich aggregate enters the concentrate tank.

3 Applications
Dry tye separation for fine-grained strong magnetic ore;
Removing magnetic impurities and purifying magnetic materials from powdery materials, widely used in metallurgy, machinery, chemical, electric power, building materials and so on.
Foreign dry-type weak magnetic cylinder magnetic separators include the former Soviet Union’s cylindrical magnetic separator and the Sala Mortsell magnetic separator.

drum magnetic separator magnetic filed

Wet type weak drum magnetic separator

The wet type weak magnetic field magnetic separator has electromagnetic type and permanent magnets type, and the latter one is more often used.

Permanent magnetic cylinder magnetic separator

The permanent cylinder magnetic separator is widely used for magnetite sorting, magnetic medium recovery, and preparation for wet strong magnetic beneficiation.

Permanent magnetic cylinder magnetic separator main parts: cylinder, magnetic system, sorting tank, feeding port, discharging and overflowing part.
The cylinder can transport the adsorbed magnetic particles and prevent the slurry from immersing in the magnetic system. The cylinder and end cap are made of non-magnetic, high resistivity and corrosion-resistant materials. The tank in the magnetic field is made of austenitic stainless steel and is lined with synthetic material to prevent wear.
Magnetic pole of permanent magnet drum separator
Adding auxiliary magnetic pole to the gap of the main magnetic pole of the permanent magnetic cylinder magnetic separator, which can increase the magnetic field strength and the depth of action, and improve the production capacity and the sorting effect.
The wet cylindrical magnetic separator has three tank structures: a forward flow, a reverse flow, and a semi-reverse flow.

Auxiliary magnetic equipment

Auxiliary magnetic equipment includes pre-magnetic, demagnetizer, magnetic desilting tank, magnetic drum filter and selective magnetic flocculator.

Magnetic desilting tank

The magnetic desilting tank is also called a magnetic dewatering tank. It is a dressing device that combines gravity and magnetic effect, widely used in the magnetic separation process to remove slime and fine-grained gangue, and also as a concentrator before filtration.
Advantages of simple structure, no moving parts, convenient maintenance, simple operation, large processing capacity and good beneficiation effect.

The magnetic desilting tank is composed of an inverted flat-bottomed conical tank, magnetic system, feeding, discharging and a water supply device.

In the magnetic desilting tank, the forces that the ore particles receive are gravity, magnetic force and water flow force.
Gravity causes the ore particles to settle, and the magnetic force accelerates the sedimentation of the magnetic ore particles and adheres on the surface of the magnetic system. The rising water flow can prevent the sedimentation of the non-magnetic fine-grained gangue and the slime, and cause them to flow into the overflow. Thus, separate from magnetic ore particles from gangue. The ascending water flow can also make the magnetic ore particles loose, flush out and improve the concentrate grade.
desilting tank

Pre-magnetizer

In order to improve the beneficiation effect of the magnetic desilting tank, the ore particles are pre-magnetized before being selected, so that the fine-grained ferromagnetic materials are condensed into larger magnetic agglomerates. The sedimentation velocity of the magnetic agglomerates is faster than that of the non-magnetic particles, which is conducive to subsequent magnetic deliming and the like.
Pre-magnetizer Magnetic field strength

Demagnetizer

The demagnetizer disperses the ferromagnetic agglomerates. The commonly used demagnetizer structure is shown in the figure below. It is a tower-shaped coil that is placed on a non-magnetic material tube and works by alternating current.
When the ferromagnetic mass passes through an alternating magnetic field whose magnetic field strength is changed from large to small, the magnetic particle has repeatedly magnetized a plurality of times, so that the magnetic energy product of the magnetic particle is smaller than once, and finally, the residual magnetism is lost.

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