Lithium mica calcination process for producing lithium carbonate
Published time:
2023-02-10 10:39
Source:
Process Flow
Conversion Calcination:
Lepidolite is crushed and ball-milled to <178μm, and mixed evenly to obtain primary ore powder; spodumene concentrate is manually sent from the concentrate warehouse to a bucket elevator to the concentrate warehouse, then added to the tail end of the lithium carbonate rotary kiln via a rotary feeder and a screw feeder. The concentrate is dried using the high-temperature gas in the preheating section of the kiln tail. The lithium carbonate rotary kiln has a certain inclination, and as the kiln continuously rotates, the material slowly moves from the high end to the low end. Natural gas is injected from the kiln head and burned in the lithium carbonate rotary kiln, the heat is absorbed by the material, and the concentrate undergoes crystal transformation roasting at a temperature of about 1200℃ in the calcination section, converting from α-type (monoclinic, density 3150kg/m3) to β-spodumene (tetragonal, density 2400kg/m3, i.e., roasted material), with a conversion rate of about 98%, and discharged from the lower end of the lithium carbonate rotary kiln cylinder.
Acid Roasting:
After the roasted material is cooled by a cooler, it is discharged from the kiln head, naturally cooled, and milled to 0.074mm (more than 90% of the particle size) using a ball mill, then transported to the acid roasting kiln tail ore warehouse, and then added to the acid mixing machine via a feeder and a screw conveyor, mixed evenly with concentrated sulfuric acid (more than 93%) at a certain ratio (concentrated sulfuric acid is calculated based on 35% excess lithium equivalent in the roasted material, about 0.21t of concentrated sulfuric acid is required per ton of roasted material), and added to the acid roasting chamber for closed acid roasting at a temperature of 250～300℃ for 30～60min. The β-spodumene in the roasted material reacts with sulfuric acid, and the hydrogen ions in the acid replace the lithium ions in the β-spodumene, so that Li2O combines with SO42- to form Li2SO4 soluble in water, obtaining acidified sintered material. Then, through a series of separation and impurity removal processes, lithium carbonate is obtained.
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