Process for producing lithium carbonate from spodumene as raw material

1. Sulfuric acid method

The sulfuric acid method produces lithium carbonate with a high yield and can process ores with Li2O content of only 1.0-1.5%. However, a considerable amount of sulfuric acid and soda ash have been converted into lower value Na2SO4, and the dosage of sulfuric acid should be minimized as much as possible. The process flow is as follows:

The major advantage of this method is that the solution obtained by leaching and sintering contains 110-150g/L lithium sulfate, and a relatively pure solution can be obtained after leaching. The sulfuric acid method can also be used to treat lithium mica and phosphoaluminate.

2. Mixed sintering method of spodumene and sulfate

Mix spodumene concentrate with K2SO4 (or CaSO4 or a mixture of both) and sinter at a certain temperature. After a series of physical and chemical reactions, the metal elements in the prepared sulfate replace lithium in the ore to form soluble sulfate, while the main impurities form insoluble compounds. Then, the sintered clinker is leached and separated, and lithium ions are introduced into the solution. After purification, concentration, and precipitation, lithium carbonate product is obtained. When processing spodumene, first convert the α - type to the more loosely structured and easily reactive β - type. This phase transition actually occurs simultaneously during the sintering process. The process flow is as follows:

The advantage of the mixed sintering method of spodumene and sulfate is that it has universality and can decompose all lithium ores. The disadvantage is that during the production process, if K2SO4 is used as a sulfate, a large amount of potassium salt will be consumed, resulting in high production costs and frequent potassium contamination of the product.

3. Sodium carbonate pressure leaching method

The process of sodium carbonate pressure leaching method is:

(1) The β - spodumene produced by processing spodumene is crushed and ground to an average particle size of 0.074mm;

(2) Add 3.5-7 times the amount of Li2O to sodium carbonate and mix well. In the reactor, leach under pressure at 200 ℃ and introduce CO2 gas to generate soluble LiHCO3;

(3) Filter to remove residue (zeolite), heat to 95 ℃ to remove CO2, precipitate, filter, and dry the filter cake to prepare lithium carbonate product. Lithium carbonate production line, pressure vessel, Jiangxi Zongheng Special Equipment Co., Ltd

The advantage of the carbonization process for producing lithium carbonate is that it eliminates the processes of product washing and sodium precipitation, simplifies operations, and saves energy consumption. Therefore, the carbonization process is superior to the sulfuric acid method.

4. Chlorination roasting method

This process mainly uses chlorinating agents to convert lithium and other valuable metals in ores into chlorides for extraction. There are two production processes for chlorination roasting: one is the medium temperature chlorination method. Produce chloride containing sintered blocks at temperatures below the boiling point of alkali metal chlorides, and separate them from impurities through dissolution; Another method is high-temperature chlorination or chlorination volatilization roasting. Roast at a temperature higher than its boiling point to volatilize chloride into a gaseous state and separate it from impurities. Both methods can be used to process various lithium containing ores. Chlorination agents are chlorides of potassium, sodium, ammonium, and calcium.

The advantages of chlorination roasting method are: simple process and no consumption of valuable reagents. The disadvantage is that it is difficult to collect LiCl and the furnace gas has strong corrosiveness.

5. Production process of limestone roasting method

The main advantage of the lime method is its widespread practicality, as it is suitable for decomposing almost all lithium minerals. The reaction process does not require scarce reagents (natural product limestone is used for decomposition); Media, oil, or gas can be used as fuel. The disadvantage is that the lithium content in the leaching solution is low, the evaporation energy consumption is high, the lithium recovery rate is low, and the obtained mineral slurry after leaching has cohesiveness, which brings difficulties to equipment maintenance.