6t/h aluminum electrolyte lithium extraction MVR evaporation crystallization system

I. Project Background

Under the "dual carbon" goal, the recycling of retired lithium-ion batteries has become a key area for ensuring the supply of strategic resources such as lithium, nickel, and cobalt. Aluminum electrolyte (cathode carbon block + electrolyte), as a byproduct of lithium battery recycling, contains soluble Li₂CO₃ 6–8 g/L, NaF/KF 200 g/L, Al³⁺ 20 g/L, and trace amounts of heavy metals, exhibiting four high characteristics: high fluoride, high salt content, high lithium content, and strong corrosiveness. Traditional triple-effect evaporators suffer from high steam consumption, large lithium entrainment, and short equipment lifespan, making it difficult to meet the requirements for front-end enrichment of battery-grade lithium salts.

The client's procurement requirements are as follows: Primary concentrate Li₂CO₃ ≥ 80 g/L, enrichment ratio ≥ 12; Battery-grade Li₂CO₃ purity ≥ 99.2%, primary yield ≥ 90%; No mother liquor discharge from the system; power consumption per ton of water ≤ 42 kWh; Equipment material resistant to 30% HF and long-term operation at 85℃.

II. Process Route

1. Pretreatment for Impurity Removal

"CO₂ aluminum removal + heavy metal capture + resin deep impurity removal": CO₂ bubbling at pH 8.0, Al³⁺ to Al(OH)₃, Al ≤ 3 mg/L after ceramic membrane filtration; Novel thiol chelating resin selectively adsorbs Ni/Co/Mn, total heavy metal ≤ 0.05 mg/L, avoiding evaporation foaming and catalyst poisoning.

2. MVR Forced Circulation Evaporation Crystallization: Utilizing an integrated module of "two-stage preheating + single-effect forced circulation evaporation + centrifugal steam compressor + Oslo DTB crystallizer": Evaporation temperature 78℃ (vacuum -0.080MPa), compressor temperature rise 20℃, compression ratio 1.75; 100% secondary steam reuse, requiring only 0.5t of live steam for initial replenishment; Circulation pump flow rate 2000m³/h, pipe velocity 3.8m/s, inhibiting fluoride scaling; DTB crystallizer controls slurry solid content to 30%, average particle size 0.55mm, and water content ≤2% after centrifugation.

3. Freeze-Heat Melt Salt Separation and Purification: Concentrated Li₂CO₃ 80g/L and NaF 220g/L enter a -5℃ freeze crystallizer, precipitating NaF·KF mixed salts, which are returned to the front end after centrifugation; the frozen mother liquor is heated to 95℃, achieving Li₂CO₃ crystal purity ≥99.2%, with a first-pass yield of 90%. 4. Mother Liquor Drying and Fluoride Recovery: A thin-film dryer for lithium-rich mother liquor achieves a dry solids content of ≤3% and a mixed salt content of 0.25 t/d, which is then sent to the industrial park for hazardous waste co-processing, achieving zero mother liquor discharge.

III. Key Equipment and Materials

IV. Operating Data (2024.05-2024.11 Continuous 200-day Average)

• Processing Capacity: 6.3 t/h (Load Rate 105%)

• Electricity Consumption per Ton of Water: 39 kWh (Including Compressor, Circulating Pump, and Drying)

• Steam Makeup: 0.02 t/t Water (On-Duty Only)

• Lithium Enrichment Ratio: 13 times, Li₂CO₃ Concentration: 82 g /L Lithium recovery rate: 91%, NaF mixed salt recovery rate: 94%

• Condensate F⁻: 4mg/L, reuse rate: 97%

• System uptime: 98.7%, unplanned shutdown once per year

• Cleaning cycle: 100 days (3 hours of online acid circulation)

V. Technical Innovations

1. Fluorine-resistant material system: The corrosion rate of TA10 titanium alloy in the tube side is ≤0.008mm/a under 30%HF and 80℃ conditions, increasing the lifespan by 8 times compared to 316L.

2. High-temperature centrifugal MVR: Single-stage temperature rise of 20℃, pressure ratio of 1.75, power consumption of 28kWh per ton of water compression, 18% energy saving compared to the two-stage Roots system.

3. Oslo DTB particle size controllable: Circulation rate 3-4, average particle size 0.55mm, centrifugal dehydration power consumption reduced by 20%, battery-grade lithium salt first-pass yield increased by 15%.

4. Freeze-Heat Melting Salt Separation: Utilizing the solubility difference between NaF and Li₂CO₃, low-temperature nitrification and hot melting are performed at the front stage, achieving a 92% sulfate removal rate and an 85% reduction in impurities.

VI. Environmental and Economic Benefits

1.Environmental: Annual reduction of 52,000 tons of high-salinity wastewater, 8.5 tons of F⁻ emissions, and 88% reduction in hazardous waste and impurities.

2.Economic: Annual savings of 50,000 tons of primary water and 6,500 tons of live steam, with a byproduct of 3,300 tons of battery-grade Li₂CO₃. At 150,000 yuan/ton, this translates to annual sales revenue of 495 million yuan.

VII. Conclusion

The 6t/h aluminum electrolyte lithium extraction MVR evaporation crystallization system successfully solves the three major challenges of "high fluoride, high salt, and high lithium loss." With "corrosion-resistant titanium materials + high-temperature MVR + controllable DTB particle size + freeze-separation" as its core, it achieves high-level enrichment of lithium resources and zero wastewater discharge. This case study provides the lithium battery recycling industry with a standardized module that is efficient, low-consumption, and has a long cycle, marking a new stage in the large-scale application of MVR technology in the field of new energy strategic resource extraction.