A lithium sulfate MVR forced circulation evaporator with a processing capacity of 30t/h for the lithium battery industry.

I. Project Overview
As the new energy vehicle industry enters a stage of large-scale development, the stable supply and quality assurance of upstream lithium salt materials have become crucial links in the industrial chain. Lithium sulfate, as a core precursor for the preparation of lithium carbonate, lithium hydroxide, and lithium battery cathode materials, directly determines the purity, particle size distribution, and subsequent processing costs of the product through its evaporation and crystallization process.

This project is an evaporation and crystallization section配套 (supporting) a new lithium salt production line with an annual capacity of tens of thousands of tons for a leading lithium battery material company. The designed processing capacity is 30 t/h of lithium sulfate solution for forced circulation MVR evaporation concentration and continuous crystallization. Located in Southwest China, the project uses pure lithium sulfate solution after extraction and impurity removal. The system is required to have a continuous and stable production capacity of no less than 8000 hours per year, and the crystallized product must meet the front-end raw material standards for battery-grade lithium salts.

II. Process Challenges and Technical Difficulties

The evaporation and crystallization of lithium sulfate solution is not a simple dehydration process. Before implementation, this project mainly faced the following technical challenges:

1. Thermosensitivity and Scaling Tendency: The solubility of lithium sulfate changes significantly at high temperatures. Local supersaturation easily leads to scaling on the heat exchanger tube walls, affecting heat transfer efficiency and continuous operation cycle.

2. Crystal Quality Control: Lithium-ion battery materials have strict requirements for the particle size, uniformity, and purity of lithium sulfate crystals, necessitating the avoidance of fine crystal formation and impurity inclusions.

3. High-Load Continuous Operation: A processing capacity of 30t/h constitutes a medium-to-large-scale lithium salt evaporation unit, placing high demands on the stability of the steam compressor, the net positive suction head (NPSH) of the circulating pump, and the precision of automated control.

4. Corrosion-Resistant Material Selection: The feed pH is approximately 4-5, containing trace amounts of sulfate ions, posing a challenge to the corrosion resistance of the equipment's flow-through components during long-term operation.

III. Solution and Process Route

To address the above requirements, our company adopts an integrated process of "MVR forced circulation evaporation + continuous crystallization," with the core flow as follows:

1. Pretreatment and Preheating: After precision filtration to remove suspended solids, the lithium sulfate solution undergoes multi-stage preheating using the system's secondary steam condensate and non-condensable gas waste heat, reducing subsequent evaporation energy consumption.

2. MVR Forced Circulation Evaporation Concentration: The preheated solution enters the MVR forced circulation evaporator. The core of the system is a high-efficiency steam compressor, which compresses and heats the secondary steam generated by evaporation and then reuses it as a heat source, forming a near-closed-loop thermal energy cycle. The evaporator uses an axial flow circulation pump to ensure high-speed flow of the solution within the heating tubes, effectively inhibiting scaling.

3. Continuous Crystallization and Crystal Slurry Separation: The solution, concentrated to near saturation, enters a continuous crystallizer. Through precise control of evaporation temperature and pressure, lithium sulfate is uniformly nucleated and grown under stable supersaturation. The crystal slurry is discharged into a thickener for thickening, and then separated into solid and liquid components by a centrifuge. The mother liquor is returned to the system for circulation, while the crystals enter the downstream drying section.

4. Condensate and Waste Heat Recovery: The condensate generated by evaporation is treated and reused in the production system, achieving water resource recycling. The latent heat of the secondary steam is efficiently recovered by the compressor, significantly reducing the amount of external steam required.

IV. Key Equipment and Technical Parameters

1. Design Processing Capacity: 30t/h (evaporation water volume)

2. Feed Lithium Ion Concentration: Approximately 6-7g/L (adjustable according to upstream processes)

3. Evaporation Process: MVR forced circulation evaporation

4. Crystallization Method: Continuous crystallization + thickener + centrifugal separation

5. Main Body Material: 2205 duplex steel/316L stainless steel for flow components

6. Steam Compressor: High-efficiency centrifugal/Roots-type steam compressor

7. Power Consumption per Ton of Evaporated Water: Approximately 30-45kWh

8. Design Annual Operating Time: ≥8000h

9. Automation Control: PLC + DCS full-process automatic monitoring

V. Project Highlights

1. Significant Energy Saving and Consumption Reduction: Compared to traditional multi-effect evaporation processes, the MVR system achieves a comprehensive energy saving rate of over 60% through secondary steam recompression technology, significantly reducing operating costs.

2. Anti-Scaling Design: The forced circulation evaporator, combined with a reasonable circulation flow rate and online cleaning interface, effectively extends the continuous operating cycle and reduces the frequency of downtime maintenance. 

3. Controllable Crystal Quality: Continuous crystallization process combined with stable supersaturation control results in lithium sulfate crystals with uniform particle size and high purity, meeting the requirements of downstream battery-grade lithium salt production.

4. Reliable and Durable Materials: Key flow components are made of 2205 duplex steel or titanium, possessing excellent resistance to chloride ions and sulfuric acid corrosion. The main equipment is designed for a lifespan of no less than 10 years.

5. High Degree of Automation: The system is equipped with comprehensive online monitoring of temperature, pressure, liquid level, and density, enabling unattended automatic operation and reducing human intervention and operational risks.

VI. Operational Results

1. Evaporation capacity is stable within 70%–110% of the design load of 30t/h, with flexible adjustment.

2. Condensate quality meets reuse standards, significantly improving the system's water recycling rate.

3. Lithium sulfate crystals exhibit concentrated particle size distribution, reasonable mother liquor circulation volume, and low lithium loss rate.

4. The equipment's continuous operation cycle meets the stringent requirements of the lithium battery industry for production line stability.

The successful implementation of this project has verified the reliability and economy of MVR evaporation crystallization technology in the production of high-volume, high-value-added lithium battery materials. From process design and equipment manufacturing to system integration and commissioning, our company, with solid engineering experience and strict quality control, provided customers with evaporation crystallization solutions that meet the high standards of the new energy industry, helping lithium salt production achieve the dual goals of energy saving, consumption reduction, and quality upgrading.