Detailed Process Flow of Mixer-Settler in Recycling Spent Lithium Iron Phosphate Batteries

With the arrival of large-scale retirement wave in the new energy power battery market, the stock of spent lithium iron phosphate (LFP) batteries is increasing year by year. The industry has an increasingly urgent demand for resourceful, harmless and high-value recycling and disposal of batteries. Traditional hydrometallurgical recycling processes have many industry pain points, such as low material separation purity, insufficient metal element recovery rate, poor process adaptability and high mass production operation cost, which are difficult to meet the dual standards of large-scale production and environmental compliance in the current lithium battery recycling industry. The mixer-settler, relying on its stable liquid-liquid separation performance, continuous operation advantages and process characteristics suitable for lithium battery leachate treatment, has become the core separation and purification equipment in the hydrometallurgical recycling system of spent LFP batteries. It can efficiently realize the precise separation and enrichment of valuable elements such as iron, lithium and phosphorus, simplify the subsequent purification process, and greatly improve the overall recycling capacity and resource utilization rate. It is the mainstream practical process equipment in the current lithium battery solid waste recycling field.

1. Pre-treatment Process of Spent Lithium Iron Phosphate Batteries

The complete recycling process needs to first complete the basic pre-treatment of spent LFP batteries to create a qualified raw material system for the subsequent extraction operation of the mixer-settler. First, discharge and disassemble the retired spent LFP batteries, remove non-battery pole impurities such as shells and circuit boards, and separate to obtain positive and negative active powder materials. Then, put the purified battery powder into special leaching equipment, carry out constant temperature stirring leaching treatment with acidic leaching agents, fully dissolve various valuable metal components such as lithium, iron and phosphorus in the powder, filter out insoluble solid residues, and finally prepare a battery leachate stock solution with uniform composition and stable concentration. After adjusting the pH value and preliminary filtering of impurities, the stock solution can be transported to the mixer-settler system for core separation operation, ensuring the smooth and efficient progress of the extraction process.

2. Core Extraction and Separation Process of Mixer-Settler

The lithium battery leachate completed by pre-treatment and preparation is sent into the mixer-settler according to the established flow ratio, and the supporting organic extraction reagent is fed synchronously. The two-phase liquid is fully mixed and contacted by means of the internal structure of the mixer-settler. Under the stable operation condition of the mixer-settler, different metal ions in the leachate selectively transfer to the organic phase according to the difference of distribution coefficient, completing the directional enrichment and separation of target metal elements. Relying on its own layered static structure, the equipment can quickly realize the clear stratification of water phase and organic phase, eliminate material cross-flow, maintain continuous feeding and discharging operation mode throughout, without frequent shutdown adjustment, and adapt to the use needs of industrial mass-produced lithium battery recycling production lines. Operators can flexibly adjust the operation flow rate, feed liquid ratio and reaction residence time of the mixer-settler according to the actual material composition, accurately control the extraction efficiency of various valuable elements, accurately distinguish lithium elements from iron-phosphorus components, and realize preliminary component separation.

3. Stripping Purification and Precise Component Enrichment Process

After the preliminary extraction and separation, the organic phase material carrying target metal components continues to complete the stripping treatment in the supporting process unit of the mixer-settler. Add special stripping aqueous solution into the system to break the original extraction equilibrium state, and re displace the valuable metal ions such as lithium and iron enriched in the organic phase into the water phase. Through the multi-stage series combination of mixer-settlers, multiple extraction and multiple stripping cycles can be realized, which continuously improves the purity of single metal components and effectively reduces the impurity content. After multi-stage purification treatment, different finished feed liquids such as high-concentration lithium-containing solution and iron-phosphorus mixed solution can be obtained respectively, which completely completes the refined separation of valuable elements in the leachate of spent LFP batteries and lays a high-quality material foundation for the subsequent finished product preparation.

4. Subsequent Finished Product Preparation and Material Closed-Loop Reuse Process

Various high-purity feed liquids obtained through purification and separation by the mixer-settler system enter the subsequent deep processing procedures for resource preparation respectively. The high-concentration lithium-containing solution can be directly prepared into core lithium battery raw materials such as battery-grade lithium carbonate and lithium hydroxide through concentration, crystallization, drying and other processes, and reflow to the power battery production industrial chain. The iron-phosphorus component feed liquid can be made into chemical products such as ferric phosphate raw materials and industrial iron salts through conditioning precipitation and forming treatment, realizing full resource utilization of materials. At the same time, the organic extraction reagent used in the operation process can be regenerated and recovered with the help of the mixer-settler process, realizing the cyclic reuse of reagents, effectively reducing the overall recycling production cost of spent LFP batteries and reducing the consumption of chemical auxiliaries.

5. Core Process Advantages of Mixer-Settler Applied in Lithium Battery Recycling

1. Strong Process Adaptability: The mixer-settler can perfectly fit the whole hydrometallurgical recycling process of spent LFP batteries, seamlessly connect with the front and rear processes such as leaching, filtration and concentration, without major modification of the original production line, and has low application threshold.

2. Outstanding Recycling Efficiency: The continuous and automatic operation mode greatly improves the extraction rate of valuable metals. The comprehensive recovery rate of core elements such as lithium, iron and phosphorus is far higher than that of traditional simple separation processes, maximizing the resource utilization value.

3. Stable Mass Production Operation: The equipment operates stably, can work continuously at full load for a long time, adapts to the large-scale capacity layout of large and medium-sized lithium battery solid waste recycling enterprises, and has simple operation and maintenance and low daily inspection and maintenance costs.

4. High Environmental Compliance: The whole process has a clear material flow direction, and the waste liquid and residue can be centrally disposed of, which conforms to the environmental protection discharge standards for industrial solid waste recycling, helping enterprises successfully pass environmental protection inspection and industry qualification review.

6. Summary of Industry Application and Development

Under the general trend of green and low-carbon transformation of the new energy industry, the standardized recycling of spent LFP batteries has become the mainstream trend of industry development, and the efficient, low-cost and high-purity hydrometallurgical recycling process has become the core direction of industrial upgrading. As the core equipment for liquid-liquid extraction and purification, the mixer-settler is deeply integrated into the whole process of lithium battery recycling. From the initial material leaching to the middle element separation, and then to the subsequent finished product output, it plays an irreplaceable role in separation and purification throughout the process. Relying on the mature and stable process flow and practical equipment performance, the mixer-settler effectively solves many industry problems such as low efficiency, difficult purification and high cost of traditional lithium battery recycling processes, and continuously promotes the spent LFP battery recycling industry to develop steadily towards scale, refinement and greenization. In the future, it will also have broader application space in the field of power battery echelon utilization and full-area resource recycling of retired batteries.