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High-density magnetic separators prevent ferrous and paramagnetic particle contamination from non-metallic dry minerals. However, the design of the separation system determines the final product purity and product losses. The two most common designs of dry high density magnetic separator are Induced Magnetic Roll Separator (IMRS) and Rare Earth (RE) Roll. These magnetic separators are widely used in the mineral processing industry to purify non-metallic minerals such as silica sand, feldspar, and in the ceramics industry to clean raw materials.
Induced Roll Magnetic Separator AKSA MAGNET usually determines the optimum system as a result of controlled laboratory tests. Representative samples are tested on lab scale versions of the IMR and RE Roll and their capacity and separation performance are confirmed.
The Induced Magnetic Roll Separator (IMRS) uses electromagnetically generated high-intensity magnetic fields to separate small paramagnetic particles from materials with a particle size ranging from -2 mm to 45 microns. The highest magnetic field produced in the role of IMRS is 2.2 Tesla (22,000 Gauss).
During the process, a controlled rate of material is fed by induced magnetic roll from a feeding unit or vibratory feeder. The weak magnetic material is attracted by the roll and held on the surface. The orbit of non-magnetic material, on the other hand, is unobstructed and discharges away from the magnetic material. The captured magnetic material is separated from the roll at a point of lower magnetic density, usually with the aid of a brush. A separator plate is placed between the two product streams to ensure clean separation. The IMRS is usually set up to produce "middling" (material with very weak magnetic properties mixed with non-magnetic) by adding a second separator plate to the equipment. It is also possible to design systems consisting of double rolls on the same unit for improved separation efficiency and process performance.
The flexible working performance of IMRS is the reason of choice among many mineral processing engineers. The magnetic field strength is variable due to the adjustable electromagnetic coil, and the roll speed is adjustable. Additionally, the spacing between the induced roll and the magnetic poles can be adjusted to accommodate different feed size ranges.
Apart from this, one of the important advantages of IMRS is; It is the ability to process hot minerals (up to 80-100°C) without sacrificing separation efficiency. This is different from Rare Earth Roll Separators that use permanent magnets. In addition, since very little static charge is formed on the induced roll surface, dusting and agglomeration caused by light particles are minimized. In this way, mineral losses due to the process are prevented.
Typical capacities for a meter wide unit vary with mineral type, density and particle size distribution and are ideally determined by laboratory test trials. Typical capacities per meter width are as follows.
Concentrated Ilmenite: 4 t/h
Concentrated Chromite: 5 t/h
Silica: 5 t/h
Roll Magnetic Separator (Rare Earth)
The Roll Magnetic Separator has a magnetic roll consisting of high-density permanent NdFeB magnets placed on a short conveyor belt. Magnets built into the unit align to generate intense magnetic forces across the entire width of the roll. The system is suitable for processing materials with a particle size range between 15 mm and 75 microns, but optimum separation performance is related to the grain size of the material and is obtained from material with a narrow scale.
During the process, a thin and evenly spread layer of material is fed from a vibrating feeder to a short center thin conveyor belt. While the magnetically sensitive material is held by the high magnetic field created by the roll, the non-magnetic material continues in its orbit and leaves the system.
Magnetic strength of Roll Magnetic Separators can be adjusted using different tape thicknesses. Material trajectories are determined by varying the conveyor speed and adjusting the separator troughs. The magnetic array in the magnetic roll is designed to handle different particle size ranges and material properties.
Roll Magnetic Separators have roll diameters of 75 mm, 150 mm and 200 mm and widths up to 1.5 m. Its multiple configurations provide enhanced separation performance.
Typical Applications include removing iron contamination from silica sands, feldspar and other industrial minerals. It is used in granular slag processing, concentrated ilmenite, sand processes and recycling applications such as crushed glass. Typical capacities range from 2 to 5tph depending on size.
Both Induced Roll Magnetic Separator and Rare Earth Roll Magnetic Separator generate high intensity magnetic fields to separate ferro and paramagnetic minerals. Electromagnetic IMR offers greater magnetic field flexibility and can handle high-temperature materials. Roll Magnetic Separators, on the other hand, have a permanent magnetic role and therefore consume a low power. The design is also more compact and reduces the amount of space used in a processing plant.
Understanding the magnetic properties of minerals or material is crucial when optimizing a magnetic separation system in all industries. A wide variety of magnetic separation designs use different strengths and types of magnetic fields to create effective separation. Various magnetic separator designs can be found in a single mineral processing process.
Ultimately, separation performance will determine which magnetic separator is chosen for a particular application.