Lithium industry chain develops lithium extraction technology

The application of lithium in the battery industry has opened a new era of lithium resource application and stimulated the rapid development of the entire lithium industry chain. How to extract lithium from lithium ore efficiently, environmentally friendly, low-energy and low-cost is the focus of many companies.

1. Lithium extraction by limestone roasting method

Limestone roasting method is the oldest method of extracting lithium from ore, that is, limestone and lithium ore are ball-milled and mixed in a ball mill at a weight ratio of 3:1, and then roasted at 800-900℃ to obtain clinker, which is then quenched with water, finely ground, leached, filtered or centrifuged to obtain leachate and residue. The leachate is evaporated, crystallized and centrifuged to obtain monohydrate lithium hydroxide, or prepared by CO2 carbonation to prepare lithium carbonate.

The limestone roasting method has a simple process and low raw material price, but it has low lithium content in the leachate, high evaporation energy consumption and low lithium recovery rate.

2. Lithium extraction by sulfuric acid method

The sulfuric acid method is currently the most mature method for extracting lithium. This method requires high-temperature roasting of lithium ore to change its structure from dense to loose, then mixing it with excess sulfuric acid after ball milling, roasting and dissolving it at 250°C in a rotary furnace, and obtaining a crude lithium sulfate solution after water leaching. After purification, lithium precipitation, evaporation and concentration, lithium carbonate products are obtained. The sulfuric acid method is mature and is still the mainstream method for producing lithium products at home and abroad.

The disadvantages of the sulfuric acid method are high impurity content in the leached solution, heavy subsequent purification load, high technical difficulty, and large-scale use of sulfuric acid, which requires high anti-corrosion performance of the equipment.

3. Lithium extraction by sulfate auxiliary roasting method

The sulfate method is often used to treat silicate minerals, but when it is used to extract lithium from lithium ore, α spodumene and potassium sulfate are mixed and roasted to replace the lithium in the ore with soluble lithium sulfate, leached with 10% dilute sulfuric acid, and the leachate is purified and precipitated to obtain lithium carbonate. The sulfate method has a simple process flow, and has the advantages of low roasting temperature, short roasting time, high lithium concentration in the leaching solution, and low energy consumption. However, this method consumes a lot of potassium salt.

4. Lithium extraction by sodium carbonate pressure leaching

This process is to mix spodumene and sodium carbonate solution, strengthen the leaching of lithium at a certain temperature and pressure, use Na to replace Li, and then introduce CO2 into the water leaching slurry to convert lithium carbonate into LiHCO3 with higher solubility. After separating the residue, heat the solution to precipitate lithium carbonate products.