Due to its low energy consumption, MVR evaporation has become the mainstream process for resource recovery and wastewater volume reduction of salt-lake lithium-precipitated mother liquor. However, many ongoing salt-lake projects are facing common challenges: after commissioning, hard scales composed of calcium, magnesium and silicates rapidly form on heat exchange tube walls, reducing the system heat transfer efficiency by 20%~50%. The specific power consumption for evaporation keeps rising. The originally designed energy consumption of 35~42 kWh per ton of water surges to 55~70 kWh per ton of water in actual operation. In addition, the cleaning cycle of some projects is shortened to 15~30 days, and a single shutdown cleaning takes 8~12 hours. Severe unplanned shutdown losses throughout the year directly drag down the overall lithium recovery rate of the whole production line. The root cause of this pain point usually lies not in MVR hardware selection, but in the neglect of the complex ionic system of lithium-precipitated mother liquor. MVR is treated as a standalone unit without collaborative design of upstream impurity removal and full-process material balance.
Lithium-precipitated mother liquor has a special composition, with lithium concentration generally ranging from 5 to 20 g/L, while enriched with calcium, magnesium, boron, silicon and sodium ions. For many projects, mother liquor is directly fed into MVR. As the concentration factor increases, calcium sulfate and silicates reach supersaturation and precipitate on heat transfer surfaces, forming dense and hard scale that cannot be completely removed by conventional acid washing. Field measurements taken at a project before BICHEM’s technical retrofitting show that the feed mother liquor contained only 30 mg/L Ca²⁺ and 45 mg/L SiO₂. Under 4-fold concentration conditions, continuous enrichment of calcium and silicon components doubled the heat transfer resistance after 30 days of operation, the evaporation capacity declined by nearly 40%, and O&M costs far exceeded figures estimated in the feasibility study. Simply increasing circulation flow velocity and raising the frequency of online cleaning can only provide temporary relief and cannot eradicate the root cause of scaling.
According to BICHEM’s investigations, most project owners only focus on hardware indicators such as evaporation capacity and installed power, while neglecting upstream water quality control. Suspended solids, colloidal silica and residual carbonates carried over from the lithium-precipitated section act as seed crystals and accelerate scale deposition. If impurity interception in the upstream extraction, adsorption and refining sections fails to meet requirements, the downstream MVR will inevitably suffer severe scaling pressure. Working conditions at high-altitude salt lakes further amplify such risks. In the Latin American Lithium Triangle, high elevations lead to a rise in boiling point, pushing the MVR compressor pressure ratio away from the design range and causing an additional 10%–15% increase in energy consumption. Many production lines adopting designs copied from plain regions face excessive energy consumption right after commissioning.
As a full-process DLE solution provider, BICHEM innovatively integrates the MVR concentration section into the overall mass balance system of salt-lake lithium extraction to control feed quality at the beginning to resolve scaling and energy consumption challenges. Comprehensive brine component analysis combined with long-term bench-scale concentration tests are conducted to define mother liquor pre-treatment specifications. Chelating resins are used for in-depth calcium and magnesium removal, and membrane is adopted to retain colloidal silica, maintaining Ca²⁺ and Mg²⁺ in the feed to MVR at low levels and mitigating the risk of hard scale precipitation. Meanwhile, based on the brine ionic model, BICHEM simulate salt crystallization behavior under different concentration factors and optimize operating parameters including pH, circulation flow rate and feed load, directing crystal formation inside the crystallization chamber instead of deposition on heat exchange tube walls.
For the implemented salt-lake project in South America, after process optimization by BICHEM, the MVR section achieves an extended stable operating cycle of 60–90 days, with specific power consumption for evaporation stably controlled below 40 kWh per ton of water. The concentrated lithium-rich mother liquor is recycled back to the main process. The overall comprehensive lithium recovery rate of the project steadily exceeds 95%, and the condensate water reuse rate surpasses 90%, realizing a closed cycle loop. For existing projects, BICHEM offers lightweight technical retrofits. There is no need to replace the main MVR equipment; only optimization of upstream pre-treatment and operating regimes can mitigate scaling and cut evaporation energy consumption.
The efficiency of MVR concentration for salt-lake lithium-precipitated mother liquor hinges not on equipment specifications, but on full-process process coupling and working-condition adaptability. Against the backdrop of increasingly stringent green mining compliance requirements, suppressing scaling and controlling evaporation costs through systematic process design can recover residual lithium resources in mother liquor to boost economic returns while reducing wastewater volume, enabling salt-lake projects to achieve a win-win outcome between economic benefits and environmental compliance.
