Membrane process for selective separation of black powder acid total immersion liquid of lithium iron phosphate battery

Abstract

The invention relates to a membrane process for selective separation of lithium iron phosphate battery black powder acid total immersion liquid, which is used for high-purity recovery of lithium, phosphoric acid and iron in lithium iron phosphate black powder, and advances the extraction of lithium ions from the last step to the acid leaching in the traditional hydrometallurgy process, so that the extraction efficiency is greatly improved. And lithium ions are separated from other metals through an acid-resistant nanofiltration separation membrane physical method. The new process comprises a complete process system including separation, concentration, circulating water replenishing and the like. The method for extracting lithium from iron phosphate through a non-leaching process (hereinafter, hereinafter, hereinafter) is not related to the range of the process.

Description

TECHNICAL FIELD

[0001] The new process belongs to the field of material regeneration in waste battery material recycling, and specifically relates to a membrane process for separating lithium from other metals in a full leaching solution of waste lithium iron phosphate battery black powder acid BACKGROUND

[0002] With the vigorous development of the global new energy vehicle market and the wide application of energy storage technology, lithium iron phosphate (LFP) batteries have occupied half of the market due to their high safety, long service life and low cost. However, the disposal of a large number of retired batteries has become a problem. How to efficiently and environmentally recycle valuable metals, especially lithium, has become the key to sustainable development of the industry chain.

[0003] After grading and screening, the batteries that cannot be used are usually regenerated. The general regeneration methods are as follows: hydrometallurgy, pyrometallurgy, and emerging direct regeneration technology. On the basis of considering environmental protection and economic benefits, hydrometallurgy is currently the mainstream production process. After pretreatment, black powder is obtained and acid leaching is carried out: sulfuric acid (H2SO4), hydrochloric acid (HCl) or organic acid (such as citric acid) is used to dissolve lithium and iron, and some processes usually add H2O2 as an oxidizing agent to improve leaching efficiency. Separation and purification: FePO4 and Li2CO3 are precipitated step by step by adjusting pH to realize full-element recovery of Li, Fe and P.

[0004] The biggest pain point of the traditional process is that a large amount of chemicals are added during the removal of various metals at the front end, resulting in a large accumulation of sodium. The subsequent concentration of lithium ions faces great Na interference, making it very difficult to achieve a concentration concentration. It is necessary to use MVR for evaporation. At the same time, due to the increase of sodium, the treatment of sodium in wastewater will bring higher treatment cost. This is the main problem of the current traditional process.

[0005] The new process mainly adjusts the process of sulfuric acid or phosphoric acid mixed acid full leaching solution (including but not limited to additional folic acid, phosphoric acid, hydrogen peroxide, hydrochloric acid, etc.). The process of lithium ion leaching only in lithium iron phosphate acid leaching solution is not discussed in the new process. The reason is that iron ions and phosphate ions are not leached separately, and the final purity of iron phosphate is too low, which has very low value and is not suitable for the value concept of recycling. SUMMARY

[0006] A membrane process for selective separation of lithium iron phosphate battery black powder acid leaching solution is disclosed. This new process is applicable to waste lithium iron phosphate battery black powder. After acid leaching in a wet process (where iron, phosphoric acid, lithium, and other metals exist in ionic form), lithium and iron are separated. The separated liquid is divided into two streams: one stream containing iron and other impurities, which enters the existing wet process for further extraction; the other stream is a solution of sulfuric acid, phosphoric acid, and lithium. This innovative process significantly shortens the lithium extraction process. After impurity removal, the separated lithium-containing solution enters a lithium precipitation process to obtain battery-grade lithium iron phosphate, lithium carbonate, or lithium hydroxide. The process also maximizes phosphorus utilization, reducing future phosphorus treatment costs in wastewater.

[0007] This new process eliminates the need for pH adjustment before separation at the lithium extraction stage, preventing the premature entry of large amounts of sodium ions into the liquid. This lays a solid foundation for reducing the cost of subsequent concentration of the lithium-containing solution, shortening the process and significantly lowering lithium extraction costs. The separation utilizes a pressure-resistant acid-resistant nanofiltration membrane module, a physical method that reduces energy consumption and the use of large amounts of chemical reagents, achieving energy saving, environmental protection, safety, and stable continuous operation. The pH of the acid leaching solution is between 0.5 and 2, and the separation module uses a self-produced acid-resistant nanofiltration membrane suitable for pH 0-6. The implementation of this new separation process creates a significant foundation for low-cost and environmentally friendly lithium-ion extraction in the future of lithium iron phosphate battery recycling.

[0008] A membrane process for selective separation of the acid-containing total immersion solution of lithium iron phosphate battery black powder mainly consists of, for example,... Figure 1 The modules shown are composed of... Attached image description: Figure 1 This is a membrane process flow diagram for the selective separation of acid-containing immersion liquid from lithium iron phosphate battery black powder.

[0009] Appendix Figure 1 Explanation: In Process 1, the lithium iron phosphate full immersion solution, after meeting the full immersion standard, enters Process 2 – an acid-resistant nanofiltration membrane. In Process 2, it is separated into Process 3 – a lithium, sulfuric acid, and phosphoric acid solution, and Process 4 – a solution containing iron and other metallic impurities. Processes 3 and 4 then undergo further concentration and recovery. Simultaneously, purified water enters Process 5, achieving water recycling and reducing water consumption.

[0010] Step 1: Acid-resistant nanofiltration membrane separation module, using membrane sheets with a pH of 0-6. The company's own acid-resistant nanofiltration module is used for the assembly.

[0011] Step 2: The lithium concentration module concentrates the lithium solution to above 10 g / L, achieving a lithium separation and recovery rate of ≥95%. Subsequent processes include impurity removal and phosphorus extraction.

[0012] Step 3: Iron and metal liquid concentration module, highly concentrate iron and metal solution, reduce the use of other solvent materials in the subsequent traditional new process, the interception rate is ≥98%, and then enter the traditional wet process Water circulation module, clear water forms a circulating water supply. Reduce water consumption.

[0013] PLC logic control system, online monitoring and setting of various parameters.

[0014] LI recovery rate calculation: lithium recovery rate = 【1- gold concentration flow × lithium content ÷ (original liquid flow × lithium content) 】 × 100% Metal interception rate calculation: metal interception rate = 【1- lithium concentration flow × any other metal content ÷ (original liquid × any other metal content) 】 × 100% In this new process, step 1, adopts a two-stage, 3+1 segment mode, and the metal concentrated water adopts a two-stage, 3+1 segment mode, and the clear water lithium solution adopts a two-stage, 3+1 segment mode.

[0015] In this new process, step 1, the lithium content in the metal solution is controlled below 200 mg / L. The metal impurities in the lithium solution are controlled below 50-100 mg / L In this new process, step 1, the water supply system circulates water according to the PLC process.

[0016] In this new process, step 1, the PH value remains the PH value of the original liquid, and the PH value changes by about 0.1-0.2 due to water supply In this new process, step 1, the content of iron is close to 30 g / L, and the PH value is controlled below 1.5 to prevent the formation of ferrous hydroxide precipitate.

[0017] In this new process, step 1, the 8040 standard module structure is adopted, the single membrane area is 35 m², and the total water inflow is 800 m³ / H.

[0018] In this new process, step 1, the separation pressure is kept at 25-30 kg In this new process, step 1, the frequency of the pump is about 20-28 HZ.

[0019] In this new process, step 2, the lithium separation liquid enters the concentration stage, and the acid-removing membrane is used for acid-removing treatment In this new process, step 2, the lithium separation liquid enters the concentration stage, and can be easily concentrated to about 10 g / L. If super concentration is used, it basically reaches 19-21 g / L In this new process, step 2, the lithium separation liquid enters the concentration stage, and the lithium ion is used as the interception body at the concentrated water end, and the clear water is recycled.

[0020] In this new process, step 2 involves a pressure of approximately 50 kg. In this new process, in step 2, the pump frequency is around 20Hz. In this new process, in step 3, the heavy metal separation solution enters the concentration stage, and acid removal is performed first. In this new process, step 3 involves acid removal followed by concentration. In this new process, in step 3, the heavy metal separation liquid enters the concentration stage, where the heavy metals are retained at the concentrate end, and the purified water is recycled.

[0021] In this new process, step 3 involves a pressure of approximately 70 kg. In this new process, in step 3, the pump frequency is around 20Hz. A membrane process for selective separation of lithium iron phosphate (LFP) battery black powder acid immersion solution offers advantages for LFP battery regeneration: While ensuring the recovery of valuable materials, it selectively separates lithium, thus reducing the use of chemicals and concentrating the lithium solution to the most economical recovery value range of 19 g / L. This significantly reduces MVR energy consumption, making the product competitive. This membrane separation process is primarily a physical separation process, driven by pressure. Energy consumption mainly comes from the power of the transfer pump.

[0022] Separation Case:

[0023] Based on the measured data, the following calculations were performed: Lithium recovery rate calculation: Lithium recovery rate = [1 - Gold concentration flow rate × Lithium content ÷ (Current solution flow rate × Lithium content)] × 100% = [1 - 110 * 0.11 / (162 * 6.73)] * 100% = 98.92% Metal Retention Rate Calculation: Metal Retention Rate = [1 - Lithium Concentration Flow Rate × Content of Any Other Metals ÷ (Current Solution × Content of Any Other Metals)] × 100% = [1 - 300 * 0.10 / (162 * 29.3)] = 99.37% Data analysis shows that the separation efficiency is fully met. Most of the separated phosphorus remains in the lithium-ion fraction, which is highly beneficial for subsequent processing.

[0024] The biggest advantages of membrane separation are low energy consumption, stable operation, and environmental friendliness. It reduces the use of chemical reagents. Generally, under stable parameters, the material difference in membranes is 20-50% within a certain number of years, which has almost no impact on the overall process performance.

Claims

1. In the recycling and regeneration of waste lithium iron phosphate batteries, after acid leaching with sulfuric acid or phosphoric acid (including but not limited to folic acid, phosphoric acid, hydrochloric acid, hydrogen peroxide, etc.), nanofiltration pressure membrane technology is used for separation. Lithium is separated from other metals such as iron using membrane technology, with the pH range of 0-4.

2. Setting the separation parameters and designing the number of stages for the acid-resistant separation mold.

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