Lithium is an element valuable for the production of glass, aluminum products, and batteries. With the development of technology, electronic equipment, and new energy industries, the demand for lithium ore has increased rapidly. Therefore, lithium ore is known as the “energy metal that drives the progress of the world”.
Lithium is mined from ores of petalite LiAl(Si2O5)2, lepidolite K(Li,Al)3(Al,Si,Rb)4O10(F,OH)2, spodumene LiAl(SiO3)2 and also subsurface brines.
Typical lithium minerals are Spodumene (containing 5.80%-8.10% Li2O), Lepidolite (containing 3.20%-6.45% Li2O), Amblygonite(containing Li2O 7.10%-10.10%), Petalite(also called castorite, containing 2.90%-4.80% Li2O), and Zinnwaldite(containing Li2O 1.10%-5.00%). The more common ones are Spodumene and Lepidolite.
The three minerals, spodumene, petalite, and lepidolite, can be used for various purposes after beneficiation and concentration. The cut-off grade and industrial grade of lithium deposits are divided into manual beneficiation and machine beneficiation, and the grade indicators are determined respectively. The division between manual and machine beneficiation is based on practical experience in production (the spodumene particle size in the ore body is greater than 3cm, and the ore grade is above 2%~3%). For example, the particle size of a green column stone is larger than 0.5cm, and Stones with a grade of 0.1%~0.2% above are suitable for manual beneficiation. The tailings of hand beneficiation stones that have value in machine beneficiation and those that are not suitable for hand beneficiation belong to machine beneficiation stones.
Lithium ore beneficiation methods include manual selection, flotation, magnetic separation, chemical or chemical-flotation combined method, thermal cracking, radioactive beneficiation, particle flotation, etc.
In the early days, the development of the beneficiation industry was lagging behind and the technical level was low. Since most of the lithium ore comes from pegmatite deposits, the main industrial minerals selected are spodumene, beryl, and other large crystals, which are easily selected. Therefore, in the 1850s and 1960s, almost all of them were hand-selected lithium ore. In 1962, the world’s beryl concentrate production was 7400t, of which hand-selected concentrate accounted for 91%.
However, the manual separation method has great defects, such as high labor intensity, low production efficiency, serious waste of resources, etc. With the continuous development of mineral processing technology, the flotation method has gradually replaced the manual separation method to process lithium ore.
The treatment of lithium ore by flotation method has been applied abroad since the 1930s, but the treatment of lithium ore by flotation method in my country began in the late 1950s. There are two commonly used spodumene flotation methods, positive flotation and reverse flotation.
Lepidolite Flotation
Lepidolite mostly adopts positive flotation. Its working principle is that according to the characteristics of lepidolite easy flotation, positive flotation is often used in the beneficiation process to obtain lithium concentrate.
Spodumene Flotation
Spodumene processing can be used for positive flotation or reverse flotation. The positive flotation process is the process of preferential flotation of spodumene. The method is to add sodium hydroxide to the slurry at the beginning to stir and scrub to remove the pollutants on the surface. After desliming and washing, then follow the following three methods to deal with
(1) First float mica, then float spodumene, and finally float feldspar.
(2) First float spodumene, then float mica, then float feldspar.
(3) Mixed flotation of spodumene and mica, and finally pumice.
The reverse flotation operation process is carried out in alkaline pulp, with dextrin, starch, etc. as spodumene inhibitors, terpineol oil as a foaming agent, and amine cationic collectors for flotation of quartz, feldspar, mica, etc. Gangue mineral, after the iron is removed from the product in the tank, it is spodumene.
The magnetic separation method is usually suitable for lithium ore containing iron impurities, and the magnetic separation method is selected according to the magnetic strength of the iron material in the ore. The beneficiation mainly for iron-lithium ore can effectively improve the quality of lithium concentrate, and finally obtain higher-grade lithium concentrate.
This method is suitable for salt lake lithium mines, from which lithium salts are extracted. The process is to evaporate the brine on the drying field, precipitate the sodium salt and potassium salt, increase the concentration of lithium chloride to about 6%, and then enter it into the factory to convert the lithium chloride into lithium products.
Lithium ore beneficiation technology, after years of technical iteration and innovation, the current beneficiation method is very mature, it is difficult to achieve a high beneficiation recovery rate with a single beneficiation method, so we often use a combination of multiple processes. For example, hand selection-magnetic separation process, flotation magnetic separation process, flotation, gravity separation, combined magnetic separation process, the combined process of mineral processing-chemical treatment, the combined process of beneficiation-metallurgy, etc. Each process has its own characteristics, and it can be selected according to the composition and properties of the lithium deposit and the main products.
After crushing, the material enters the ball mill for grinding to produce uniform fine particle size. It is said that the rod mill has proven extremely satisfactory for grinding such pegmatitic minerals as feldspar and spodumene.
An effective lithium ore processing plant mainly includes crushing, grinding, beneficiation, and some auxiliary equipment.
The lithium ore is fed to the primary jaw crusher through the vibrating feeder for coarse crushing, and then the cone crusher is used for fine crushing.
After crushing, the material enters the ball mill for grinding to produce uniform fine particle size. It said that the rod mill has proven extremely satisfactory for grinding such pegmatitic mineral as feldspar and spodumene.
As proper grinding fineness is crucial to the flotation results, the particle size of lithium ore generally needs to be ground to less than 0.15 mm for a better flotation effect.
The ore slurry comes to the mix tank for mixing, and flotation by flotation machines. Lithium ore often contains complex components, and the lithium concentrate obtained by flotation sometimes contains more iron. In order to improve the grade of lithium concentrate, the magnetic separation method is used as an auxiliary method.
The most commonly used production equipment is crushers (jaw crushers, impact crushers, cone crushers), ball mills, flotation machines, or magnetic separators.
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