Rare earth ore magnetic separation and magnetic separation equipment

Rare earth ore is a strategically important key mineral resource, and its separation technology is constantly developing. Magnetic separation plays an important role in the rare earth ore beneficiation process. It uses the magnetic field force to separate the minerals based on the difference in magnetic properties between rare earth minerals and gangue minerals. In-depth exploration of rare earth ore magnetic separation technology and supporting magnetic separation equipment is of great significance for optimizing rare earth ore beneficiation technology and improving the recycling rate of rare earth resources. Let's learn about rare earth ore magnetic separation from three aspects: process method, equipment and application environment!

1. Principle of magnetic separation of rare earth ores

Some types of rare earth minerals have certain magnetism, such as neodymium iron boron ore and monazite. The electronic structure of their internal atoms or ions enables them to be magnetized under the action of an external magnetic field and produce a magnetic response. The gangue minerals that coexist with them, such as quartz, feldspar, calcite, etc., are usually non-magnetic or weakly magnetic substances. This significant magnetic difference constitutes the basic basis for magnetic separation. When the ore pulp or ore particles pass through the magnetic field, the magnetic rare earth minerals are forced to gather in the area with higher magnetic field intensity, while the non-magnetic gangue minerals are basically not affected by the magnetic field and move along the original trajectory, thereby achieving the separation of the two.

The magnetic field force exerted by the external magnetic field on the magnetic mineral is proportional to the magnetization intensity and magnetic field gradient of the mineral. In the magnetic separation equipment, the magnetic system structure is reasonably designed, such as using magnetic poles of different shapes and arrangements to generate an uneven magnetic field, which increases the magnetic field gradient. After the magnetic rare earth minerals enter this area, they are subjected to the magnetic field force pointing in the direction of the magnetic pole, overcome the resistance such as gravity and friction, move toward the magnetic pole and adsorb on the surface of the magnetic pole or gather in a specific collection area; while the gangue minerals are carried away by other external forces such as water flow and gravity due to the extremely small magnetic field force, completing the separation process.

2. Common rare earth ore magnetic separation equipment

1. Dry magnetic separator

Dry magnetic separator is generally composed of feeding device, magnetic system, sorting drum, unloading device and other components. The feeding device is used to evenly feed the ore particles into the magnetic separation area; the magnetic system is the core component, usually composed of permanent magnets or electromagnets, and generates a magnetic field in a specific arrangement. Common ones are open magnetic systems and closed magnetic systems. The open magnetic system has a wide magnetic field distribution, which is convenient for processing large-particle ore. The closed magnetic system has a high magnetic field intensity and a large gradient, which is suitable for fine separation; the separation drum is mostly made of stainless steel, and the surface is covered with wear-resistant rubber. The drum drives the ore particles through the magnetic field during rotation, and the magnetic minerals are adsorbed on the surface of the drum; the unloading device is located below or on the side of the drum, which is used to scrape and collect the adsorbed magnetic minerals.

The ore particles are evenly fed to the rotating separation drum by the feeding device. As the drum rotates, the ore particles enter the magnetic field area generated by the magnetic system. Under the action of magnetic field force, magnetic rare earth minerals overcome gravity and centrifugal force, tightly adsorb on the drum surface, and continue to rotate with the drum to the unloading area, and are scraped and collected by the unloading device; while non-magnetic gangue minerals, due to the weak magnetic field force, are separated from the drum surface under the action of centrifugal force and gravity, and fall along the original motion trajectory to achieve separation from magnetic minerals. Dry magnetic separators are suitable for processing rare earth ores with low water content and coarse particle size, and are widely used in arid and water-scarce areas or in scenarios where ore dryness is required.

In rare earth ore beneficiation, dry magnetic separators are often used in the roughing stage of raw ore, especially in rare earth mines in some arid areas in the north. The raw ore has low water content after mining, and dry magnetic separators are directly used for preliminary screening, which can quickly remove a large amount of non-magnetic surrounding rock and waste rock, improve the grade of ore selection, and reduce subsequent transportation and processing costs. At the same time, for some rare earth minerals with strong magnetism and coarse particle size, dry magnetic separators can also play an efficient sorting role and provide high-quality raw materials for subsequent selection processes.

2. Wet magnetic separator

The main structure of the wet magnetic separator includes a tank body, a magnetic system, a stirring device, a feeding device, a tailings discharge device, etc. The trough provides space for the slurry and is generally made of corrosion-resistant materials; the magnetic system is installed inside or at the bottom of the trough and is also composed of permanent magnets or electromagnets. The magnetic field strength and gradient are designed according to the separation requirements. Some wet magnetic separators use a multi-layer magnetic system structure to improve the separation effect; the stirring device is used to keep the slurry in a suspended state to ensure that the mineral particles are fully exposed to the magnetic field and evenly distributed in the trough; the feeding device stably feeds the slurry with the reagent (if necessary) into the trough; the tailings discharge device is located at the bottom or side of the trough to discharge the gangue mineral tailings that have not been magnetically separated.

The adjusted slurry is slowly injected into the trough through the feeding device. Under the action of the stirring device, the slurry is in a uniform suspension state. When the slurry flows through the magnetic field area generated by the magnetic system, the magnetic rare earth minerals are attracted by the magnetic field force, move toward the magnetic pole direction and adsorb on the surface of the magnetic pole or gather near the magnetic pole to form a magnetic concentrate; and the non-magnetic gangue minerals are driven by the water flow and discharged from the tailings discharge device. Compared with dry magnetic separators, wet magnetic separators reduce the friction resistance between ore particles due to the presence of slurry media, which is conducive to improving magnetic separation efficiency. They are especially suitable for processing fine-grained and viscous rare earth ores, and can effectively prevent ore particles from agglomerating and ensure separation accuracy.

Wet magnetic separators are widely used in the selection of medium and fine-grained ores in rare earth ore beneficiation, and can play an important role in both roughing and concentrating. In the roughing stage, the slurry after crushing and grinding can be subjected to preliminary magnetic separation to enrich magnetic rare earth minerals, providing a basis for subsequent combined processes such as flotation and gravity separation; in the concentrating stage, for the magnetic minerals remaining after the previous selection, the magnetic field strength of the wet magnetic separator and the addition of reagents can be adjusted to further purify the rare earth concentrate, improve product quality, and meet the application needs of high-end rare earths.

III. Application environment of rare earth magnetic separation

For rare earth ores with obvious magnetic differences, magnetic separation can quickly and efficiently separate magnetic rare earth minerals from gangue minerals, with large processing capacity and high beneficiation efficiency. Compared with some beneficiation methods that require complex reagent regulation, the magnetic separation process is relatively simple, and the equipment operation and maintenance are relatively easy, which can effectively save time and labor costs.

Moreover, it can not only process coarse-grained rare earth ores, but also directly conduct preliminary enrichment by magnetic separation after coarse crushing; it can also adapt to the separation of ores within a certain fine-grained range. It only needs to adjust the magnetic field strength and equipment parameters according to the particle size, which can effectively broaden the particle size applicable range of rare earth ore beneficiation.

When rare earth ores contain a large amount of highly magnetic minerals such as NdFeB ore, magnetic separation can be used as the preferred process. In the early stage of mining, the raw ore can be directly roughed through equipment such as dry magnetic separators, and a large amount of non-magnetic waste rock can be quickly discarded, which greatly improves the grade of the selected ore, reduces the workload of subsequent processing, and reduces the cost of mineral processing. In the complex rare earth ore beneficiation process, magnetic separation is often used in conjunction with flotation, gravity separation and other methods.

Rare earth ore magnetic separation technology relies on the use of mineral magnetic differences and uses magnetic separators to achieve mineral processing. It plays an irreplaceable role in the field of rare earth ore beneficiation. It can be used independently as an efficient roughing method to quickly enrich magnetic rare earth minerals, and it can also work closely with other beneficiation methods to build a complete rare earth ore beneficiation system and realize the recycling of rare earth resources.