Lithium Hard Rock Processing Overview
Hard rock lithium deposits, primarily spodumene (LiAlSi2O6), are a major source of the world's lithium supply. Processing spodumene ore involves multiple stages — from beneficiation to chemical conversion — to produce battery-grade lithium hydroxide or carbonate. This guide covers the complete processing chain.
Ore Sorting and Pre-Concentration
Before crushing, modern lithium operations use ore sorting technologies to reject waste:
- Sensor-based sorting: XRT, color and laser sorting to remove dilution
- Dense Media Separation (DMS): Heavy liquid separation at 2.7-3.0 SG
- These steps typically reject 30-50% of feed as waste, reducing downstream processing costs
Crushing and Grinding
Spodumene is harder than most lithium-bearing minerals, requiring careful crushing:
- Primary jaw crushing: Reduce ROM ore to -200mm
- Secondary cone crushing: Achieve -30mm product
- Ball mill grinding: Produce -150 micron feed for flotation
- Note: Spodumene crystals are friable — avoid over-grinding
Lithium Processing — From Spodumene Ore to Battery Grade
Spodumene Flotation
Flotation is the primary concentration method for spodumene:
- Desliming: Remove -20 micron slimes before flotation
- Conditioning: Alkaline conditioning with NaOH (pH 10-11)
- Collector: Oleic acid or tall oil fatty acids
- Depressants: Starch or dextrin for gangue depression
- Typical concentrate grade: 5.5-7.0% Li2O
Thermal Treatment (Conversion)
The natural alpha-spodumene must be converted to beta-spodumene by thermal treatment at 1000-1100°C. This conversion is essential because beta-spodumene is more amenable to sulfuric acid digestion.
Hydrometallurgical Processing
Sulfuric Acid Route (Lithium Carbonate):
- Beta-spodumene roasted with concentrated H2SO4 at 250°C
- Water leaching of the calcine
- Impurity removal (Ca, Mg, Fe precipitation)
- Lithium carbonate precipitation with Na2CO3
Lithium Hydroxide Production:
- Li2CO3 causticization with Ca(OH)2
- Crystallization to battery-grade LiOH·H2O
- Preferred for high-nickel battery cathodes
Key Design Considerations
- Spodumene is abrasive — use wear-resistant materials
- Fine grinding creates difficulty in flotation — optimize grind size
- DMS feed preparation must avoid crystal breakage
- Thermal conversion is energy-intensive — optimize fuel efficiency
WSHT offers complete lithium processing solutions from beneficiation testwork to full EPC delivery. Contact our team to discuss your lithium project requirements.
