Production process of lithium hydroxide

1、 The use of lithium hydroxide

Lithium hydroxide plays a very important role in basic lithium salt products.

Lithium based grease prepared from lithium hydroxide has a particularly long service life, strong oxidation resistance, and high temperature stability. 

As an additive for alkaline batteries, lithium hydroxide can also increase the storage capacity and extend the battery's service life. 

It is mainly used to produce lithium based grease and can also be used to produce other lithium compounds. 

It is an additive for alkaline battery electrolytes.

Lithium hydroxide has significant effects in metallurgy, atomic energy, chemical reagents, aerospace, defense industry, and other fields.

2、 What are the preparation processes of lithium hydroxide

1） Lithium carbonate causticization method.

The main method is to mix lithium carbonate and refined lime milk in a ratio of 1:1.08, adjust the concentration of the solvable solution to 18-20g/l, 

heat it to boiling state and stir vigorously,and control the causticization time to about 30 minutes. 

After centrifugal separation, CaCO3 precipitate and lithium hydroxide mother liquor with a concentration of 3.5% can be obtained. 

After evaporation, concentration, crystallization and drying of the mother liquor, monohydrate lithium hydroxide product can be obtained.

2） Lithium sulfate causticization method.

The main process is to transform and roast spodumene concentrate at 950-1100 ° C, followed by acid roasting at 250-300 ° C, 

and then neutralize and leach to obtain an 8.5% lithium sulfate leaching solution.

Force evaporate it to a concentration of 17%, add the corresponding amount of caustic soda solution according to the lithium content in the leaching mother liquor, 

freeze it to -10 ℃ to precipitate saltpeter, centrifuge and dehydrate the frozen slurry, deeply remove impurities, 

and then force evaporate to obtain monohydrate lithium hydroxide product.

3） Soda ash pressure leaching method

The pressure leaching method of caustic soda is to use spodumene concentrate (Li2O content 5.5-7.5%) as raw material, roast it in a rotary kiln at 1050-1100 ℃, 

convert the crystal structure of spodumene from α - type to β - type that is easy to produce and process,

 and then add 3.5-7.0 times the amount of caustic soda according to the Li2O content. 

The pressure leaching is carried out in a high-pressure reaction kettle at 200 ℃. 

The leachate is carbonized to remove insoluble impurities in the minerals, and refined lime milk is added for causticization to prepare lithium hydroxide.

The lithium hydroxide product prepared by the pressure leaching method of soda ash has high purity and overall lithium recovery rate. 

However, due to the use of a high-pressure reaction kettle as the core leaching equipment in this process, with a pressure of up to 2.5 MPa, 

the operating conditions are relatively strict, and the unloading process is cumbersome, making it impossible to achieve continuous feeding and discharging, 

resulting in low equipment capacity and low production efficiency.

4） Limestone roasting method.

The main method is to mix lithium mica and limestone in a mass ratio of 1:3 and grind them finely, 

then roast them at high temperature for more than 4 hours at 850 ℃. 

By leaching the roasted product, the monohydrate lithium hydroxide product is obtained. 

By improving the grade of lithium concentrate and the concentration of leachate, and adopting methods such as triple effect evaporation, 

the goal of energy conservation and production increase can be achieved.