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Rare earth elements are of various types, with complex mineral compositions, and contain a lot of useful minerals and gangue minerals. Therefore, rare earth ores are difficult to be separated. According to the physical and chemical properties of the minerals, associated gangue and other minerals, suitable beneficiation processes can be selected. The equipment required in the beneficiation process mainly includes the following:
Gravity separation is achieved by using the density difference between rare earth minerals and their gangue minerals. Usually, there is a significant density difference between rare earth and gangue minerals such as quartz, feldspar, and calcite. Therefore, gravity separation is more suitable for handling this type of rare earth separation. Generally, it is often used in the roughing stage. In the early stage of beneficiation, a large amount of gangue minerals can be removed by gravity separation. The gravity separation equipment required for gravity separation mainly includes jigs, shaking tables and spiral chutes.
Jig: Utilize the upward movement of the diaphragm to form internal pressure, achieve sedimentation of ore particles, and complete gravity separation. It is generally used for coarse particle gravity separation of ≥0.04mm.
Shaking table: Based on the reciprocating movement of the bed surface, the mineral gravity separation is achieved. It is mostly used for the gravity separation of fine-grained rare earth ores below 0.02mm.
Spiral chute: Suitable for processing rare earth ores with a wide particle size range (generally -1mm), especially when processing medium and fine particle size raw ores or re-selected rough concentrates.
Flotation is the main method for rare earth beneficiation. It uses the difference in physical and chemical properties between it and the associated mineral surface, and by adding reagents, it makes its surface hydrophobic. After adding bubbles, it floats on the bubbles at any time, thereby achieving separation. Generally, flotation is suitable for selecting rare earth ores with finer ore particle size, and its process is mostly a flotation process of one roughing-two fines-two sweeps. The equipment required for this stage is mainly a flotation machine and a stirring tank.
Flotation machine: According to the different gas supply methods, there are two types of flotation machines: mechanical stirring flotation machines and aerated stirring flotation machines. The equipment are xcf type flotation machine, kyf type flotation machine, sf type flotation machine, jjf type flotation machine, bf type flotation machine, etc.
Mixing tank: Mainly used for the flotation machine to fully mix the reagent and slurry before separation. There are reagent mixing tanks, high-efficiency mixing tanks and ordinary mixing tanks.
Magnetic separation is mainly used to select magnetite ores or remove iron-containing impurities. For some rare earth ores containing weak magnetic or semi-ferrous minerals, magnetic separation can be used to remove iron. In the flotation of rare earth ores, in order to simplify the flotation process and save flotation reagents, strong magnetic separation technology is sometimes used to pre-enrich the rare earth ores. Commonly used magnetic separators include dry magnetic separators, magnetic drums, and wet strong magnetic separators.
Dry magnetic separator: 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 little 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.
Magnetic drum: In rare earth mines, it can be used for roughing of raw ore, concentrating of medium ore, etc., but most of them are mainly used as pre-selection operations before flotation, with a selected particle size of 300mm.
Wet high-intensity magnetic separator: It is mostly used for the selection of medium and fine-grained ores in rare earth ore selection, and can play an important role in both roughing and concentrating. In the roughing stage, the ore pulp after crushing and grinding can be subjected to preliminary magnetic separation to enrich magnetic rare earth minerals; in the concentrating stage, the magnetic minerals remaining after the previous selection can be further purified by adjusting the magnetic field strength of the wet magnetic separator.
The leaching method for selecting rare earth ores can be divided into three methods: barrel leaching, pool leaching and heap leaching. Among them, pool leaching has a lower cost, but the overall work efficiency is low; heap leaching uses ammonium sulfate as a leaching agent, which can effectively reduce the leaching of harmful metal ions such as Ca2+ and Ba2+, but the use of leaching agents will affect the surrounding environment. The equipment required for this link mainly includes leaching stirring tanks, heap leaching equipment, etc.
Leaching stirring tank: rare earth ore crushed to a certain particle size and pre-adjusted concentration of leaching agent are added to the stirring leaching tank from the feed port in a certain proportion, stirred to make the particles fully contact with the agent, and start chemical reaction to achieve leaching. Leaching stirring tank is widely used in rare earth ore dressing plants of various sizes.
Heap leaching equipment: mainly includes heap leaching site, spraying system, liquid collection system and other parts. The process is to pile the minerals crushed to a certain particle size in the heap leaching site, and spray the prepared leaching agent from top to bottom evenly on the ore pile through the spraying system, so that it slowly penetrates through the ore layer and reacts with the rare earth minerals in the mineral. The seeping solution flows into the liquid collection tank along the liquid collection ditch at the bottom of the ore pile to complete the initial collection.
Pre-selection pretreatment mainly involves grinding the large pieces of ore after mining to a certain particle size through some processes, so that the monomers between the minerals can be dissociated to meet the selection requirements. At the same time, it may also be necessary to remove the fine mud components in the ore through operations such as desludging. The required equipment is as follows:
Crushing equipment: jaw crusher is usually used as coarse crushing equipment (generally, large ore with a diameter of about 1m can be crushed to 10-30cm), cone crusher is used as medium crushing equipment (it can crush ore to 3-10cm), and hammer crusher is used as fine crushing equipment (ore particle size is crushed to less than 3cm).
Screening equipment: circular vibrating screen is usually used for coarse particle screening or classification; linear vibrating screen is used for fine particle screening or desludging; automatic center vibration is used for fine particle screening.
Grinding equipment: according to the coarseness of the processed material, it can be divided into grid type ball mill and overflow type ball mill, and rod mill and other equipment are occasionally used. Among them, the grid type is mainly used for coarse particle grinding, while the overflow type is used for fine particle grinding.
Classification equipment: there are two types of equipment, cyclone and spiral classifier. The former is used in conjunction with overflow type ball mill for fine grinding and classification; the latter is used in conjunction with grid type for coarse grinding and classification.
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