A secondary distillation washing water recovery and treatment system for lithium salt purification

Abstract

This utility model relates to the field of lithium salt impurity removal technology. Addressing the problem that excessive magnetic impurities in the washing water after crude lithium salt purification affect the purity of the lithium salt product during recycling, this invention specifically discloses a secondary evaporation washing water recycling system for lithium salt purification. The system includes a primary evaporation crystallization system and a secondary evaporation crystallization system connected in sequence. The discharge end of the secondary crystallization evaporation system is sequentially connected to a demagnetizer, a distiller, and a belt centrifuge. The discharge end of the belt centrifuge is equipped with a reflux pipe, the water outlet of which is connected to both the primary and secondary evaporation crystallization systems via multiple branch pipes. This further treats and removes impurities from the secondary evaporation washing water, which is then fed into both evaporation crystallization systems, enabling the reuse of the washing water and preventing the loss and waste of residual lithium elements.

Description

Technical Field

[0001] This utility model relates to the field of lithium salt impurity removal technology, and more specifically, to a secondary distillation washing water recovery and treatment system for lithium salt purification. Background Technology

[0002] In the industrial production of battery-grade lithium salts such as lithium carbonate or lithium hydroxide, crude lithium salts require deep purification to meet battery-grade material requirements. Deep purification of crude lithium salts typically involves repeated evaporation and crystallization processes. Specifically, the lithium purification solution, such as lithium sulfate, after the first evaporation and crystallization purification process still contains a small amount of calcium carbonate (Ca). 2+ Mg 2+ Na + Due to impurities, the lithium salt obtained from the solid-liquid separation in the lithium purification solution needs to be further dissolved and subjected to deep impurity removal treatments such as ion exchange / carbonization, followed by a second evaporation and crystallization to obtain battery-grade lithium salt with sufficient purity.

[0003] In the above-mentioned lithium salt purification process, the filter cake after crystallization is washed to obtain wash water containing a certain concentration of lithium. Wash water with a high lithium content can be recycled and reused to prepare lithium salts, etc. For example, patent CN221964490U proposes an MVR evaporation crystallization device for extracting lithium hydroxide, including a preheating device connected to an evaporation crystallization mechanism; the evaporation crystallization mechanism is connected to a secondary steam compression device and a salt outlet mechanism; the evaporation crystallization mechanism includes an evaporation crystallization device and a gas washing device, the evaporation crystallization device is connected to the gas washing device, the evaporation crystallization device is connected to the preheating device, the secondary steam compression device is connected to both the evaporation crystallization device and the gas washing device, and the salt outlet mechanism is connected to the evaporation crystallization device. The raw material can be preheated first, the evaporation crystallization device evaporates and crystallizes the raw material, the gas washing device removes impurities carried in the steam, the secondary steam compression device compresses and heats the steam, and the salt outlet mechanism purifies the raw material to fully heat and improve the purification effect of evaporation crystallization.

[0004] However, in actual production, technicians have found that magnetic substances often remain in the washing water, which leads to the introduction of magnetic impurities when the washing water is recycled, causing fluctuations in the magnetic content and quality of the product. Utility Model Content

[0005] The purpose of this invention is to solve the problem that the purity of lithium salt products is affected by the excessive magnetic impurities in the washing water after crude lithium salt purification during recycling. This application provides a secondary distillation washing water recycling system for lithium salt purification, which further treats and removes impurities from the secondary distillation washing water and then feeds it into two separate evaporation crystallization systems, enabling the reuse of the washing water and preventing the loss and waste of residual lithium elements in the washing water.

[0006] This utility model is achieved through the following technical solution:

[0007] This utility model provides a secondary evaporation washing water recovery and treatment system for lithium salt purification, including a primary evaporation crystallization system and a secondary evaporation crystallization system connected in sequence. The discharge end of the secondary evaporation crystallization system is connected in sequence to a demagnetizer, a distiller, and a belt centrifuge. The discharge end of the belt centrifuge is equipped with a reflux pipe, and the water outlet of the reflux pipe is connected to the primary evaporation crystallization system and the secondary evaporation crystallization system through multiple branch pipes.

[0008] Preferably, the multiple branch pipes include a first branch pipe and a second branch pipe, the water outlet of the first branch pipe is connected to the primary evaporation crystallization system, and the water outlet of the second branch pipe is connected to the secondary evaporation crystallization system.

[0009] Preferably, the discharge end of the secondary evaporation crystallization system is also connected to a washing water tank, and the discharge end of the washing water tank is connected to the demagnetizer through a pipe.

[0010] Preferably, the primary evaporation crystallization system includes a crude lithium salt storage tank, a primary evaporation dissolution tank, a primary evaporation crystallization tank, and a primary evaporation lithium salt storage tank connected in sequence.

[0011] Preferably, a purification tank is connected between the primary evaporation dissolution tank and the primary evaporation crystallization tank.

[0012] Preferably, the secondary evaporation crystallization system includes a secondary evaporation dissolution tank, an ion exchange filter column, a secondary evaporation crystallization tank, and a centrifuge kettle connected in sequence, and the discharge end of the primary evaporation lithium salt storage tank is connected to the feed end of the secondary evaporation dissolution tank, and the discharge end of the centrifuge kettle is connected to the feed end of the washing water tank.

[0013] Preferably, the centrifuge is further provided with a mother liquor pipe at the discharge end, and the discharge end of the mother liquor pipe is connected to the first-stage dissolving tank.

[0014] Preferably, the discharge end of the belt centrifuge is also equipped with a solid material pipe, and the discharge end of the solid material pipe is sequentially connected to a drying tower and a secondary distillation lithium salt storage tank.

[0015] The technical solution of this utility model has the following beneficial effects:

[0016] The lithium salt purification double-distillation washing water recovery and treatment system of this utility model further treats the washing water after double distillation to remove impurities, and then passes it to the two evaporation crystallization systems to achieve the reuse of washing water and avoid the loss and waste of residual lithium elements in the washing water. This results in the final lithium salt product with the advantages of low magnetic impurity content and stable quality purity. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the secondary distillation washing water recovery and treatment system for lithium salt purification in Example 1;

[0018] Figure 2 This is a schematic diagram of the single-evaporation crystallization system in Example 1;

[0019] Figure 3 This is a schematic diagram of the secondary evaporation crystallization system in Example 1.

[0020] Figure labels: 1-Primary evaporation crystallization system, 11-Crude lithium salt storage tank, 12-Primary evaporation dissolution tank, 121-Purification tank, 13-Primary evaporation crystallization tank, 14-Primary evaporation lithium salt storage tank, 2-Secondary evaporation crystallization system, 21-Secondary evaporation dissolution tank, 22-Ion exchange filter column, 23-Secondary evaporation crystallization tank, 24-Centrifuge kettle, 25-Mother liquor pipe, 26-Washing water tank, 3-Demagnetizer, 4-Distiller, 5-Belt centrifuge, 51-Solid material pipe, 52-Drying tower, 53-Secondary evaporation lithium salt storage tank, 6-Reflux pipe, 61-First branch pipe, 62-Second branch pipe. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions of this utility model will be clearly and completely described below. Where specific conditions are not specified in the embodiments, they are performed according to conventional conditions or conditions recommended by the manufacturer; where the manufacturers of instruments, equipment, reagents, or raw materials are not specified, they are all conventional products that can be purchased commercially. The following are specific embodiments in conjunction with the accompanying drawings.

[0022] like Figures 1 to 3 As shown, this embodiment provides a secondary evaporation washing water recovery and treatment system for lithium salt purification, including a primary evaporation crystallization system 1 and a secondary evaporation crystallization system 2 connected in sequence. The discharge end of the secondary evaporation crystallization system 2 is connected in sequence to a demagnetizer 3, a distiller 4, and a belt centrifuge 5. The discharge end of the belt centrifuge 5 is equipped with a reflux pipe 6. The water outlet of the reflux pipe 6 is connected to the primary evaporation crystallization system 1 and the secondary evaporation crystallization system 2 through multiple branch pipes. The multiple branch pipes include a first branch pipe 61 and a second branch pipe 62. The water outlet of the first branch pipe 61 is connected to the primary evaporation crystallization system 1, and the water outlet of the second branch pipe 62 is connected to the secondary evaporation crystallization system 2.

[0023] This lithium salt purification system uses a secondary distillation washing water recycling system to further treat and remove impurities from the washing water after the secondary distillation, and then feeds it into the two evaporation crystallization systems to achieve the reuse of the washing water and avoid the loss and waste of residual lithium elements in the washing water. This results in the final lithium salt product having the advantages of low magnetic impurity content and stable quality purity.

[0024] In this embodiment, the primary evaporation crystallization system 1 includes a crude lithium salt storage tank 11, a primary evaporation dissolution tank 12, a purification tank 121, a primary evaporation crystallization tank 13, and a primary evaporation lithium salt storage tank 14 connected in sequence.

[0025] In this embodiment, the secondary evaporation crystallization system 2 includes a secondary evaporation dissolution tank 21, an ion exchange filter column 22, a secondary evaporation crystallization tank 23, and a centrifuge kettle 24 connected in sequence. The discharge end of the primary evaporation lithium salt storage tank 14 is connected to the inlet end of the secondary evaporation dissolution tank 21, and the discharge end of the centrifuge kettle 24 is connected to the inlet end of the washing water tank 26. The discharge end of the centrifuge kettle 24 is also equipped with a mother liquor pipe 25, and the discharge end of the mother liquor pipe 25 is connected to the primary evaporation dissolution tank 12. The discharge end of the secondary evaporation crystallization system 2 is also connected to the washing water tank 26, and the discharge end of the washing water tank 26 is connected to the demagnetizer 3 through a pipeline. By performing demagnetization and distillation filtration on the washing water after secondary evaporation crystallization, the quality of the final battery-grade lithium salt can be guaranteed to better meet the requirements of subsequent industrial production and practical applications.

[0026] In this embodiment, the discharge end of the belt centrifuge 5 is also equipped with a solid material pipe 51, and the discharge end of the solid material pipe 51 is connected in sequence to the drying tower 52 and the secondary distilled lithium salt storage tank 53.

[0027] The wash water after secondary evaporation and crystallization contains magnetic impurities (such as Fe) and residual lithium, and direct reuse would contaminate subsequent products. The demagnetizer 3, as the core processing unit, removes ferromagnetic impurities (such as iron oxide) from the wash water through magnetic adsorption, preventing impurities from entering the circulation system. The distiller 4 distills the demagnetized wash water, evaporating water and separating volatile impurities (such as organic solvents and ammonia), further purifying the water. In the belt centrifuge 5, the lithium-containing solid material is dried in the drying tower 52 and stored in the secondary distillation lithium salt storage tank 53 to recover residual lithium salt, while the purified water after separation enters the circulation system through the reflux 6. One branch pipe 61 directs purified water to the primary evaporation crystallization system (for dissolving crude lithium salts). Since the primary evaporation has lower water quality requirements, it can efficiently utilize recycled water containing trace impurities. The second branch pipe 62 directs high-purity purified water to the secondary evaporation crystallization system (for purifying battery-grade lithium salts). This avoids impurities affecting high-purity products and allows for differentiated reuse based on process water quality requirements, balancing safety and economy. The mother liquor pipe 25 returns the mother liquor from the secondary evaporation crystallization centrifuge 24 back to the primary evaporation dissolution tank 12 to recover uncrystallized lithium ions. This reduces lithium loss, increases lithium recovery rate, reduces water consumption, and lowers raw material replenishment costs.

[0028] The above are merely preferred embodiments of this utility model and are not intended to limit the scope of this utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A double distilled washing water recovery treatment system for purification of lithium salt, characterized by, It includes a primary evaporation crystallization system (1) and a secondary evaporation crystallization system (2) connected in sequence. The discharge end of the secondary evaporation crystallization system (2) is connected in sequence to a demagnetizer (3), a distiller (4) and a belt centrifuge (5). The discharge end of the belt centrifuge (5) is equipped with a reflux pipe (6), and the water outlet end of the reflux pipe (6) is connected to the primary evaporation crystallization system (1) and the secondary evaporation crystallization system (2) through multiple branch pipes.

2. The lithium salt purification secondary distillation washing water recovery and treatment system according to claim 1, characterized in that, The multiple branch pipes include a first branch pipe (61) and a second branch pipe (62). The outlet end of the first branch pipe (61) is connected to the primary evaporation crystallization system (1), and the outlet end of the second branch pipe (62) is connected to the secondary evaporation crystallization system (2).

3. The lithium salt purification secondary distillation washing water recovery and treatment system according to claim 1, characterized in that, The discharge end of the secondary evaporation crystallization system (2) is also connected to a washing tank (26), and the discharge end of the washing tank (26) is connected to the demagnetizer (3) through a pipe.

4. The lithium salt purification secondary distillation washing water recovery and treatment system according to claim 3, characterized in that, The primary evaporation crystallization system (1) includes a crude lithium salt storage tank (11), a primary evaporation dissolution tank (12), a primary evaporation crystallization tank (13), and a primary evaporation lithium salt storage tank (14) connected in sequence.

5. The lithium salt purification secondary distillation washing water recovery and treatment system according to claim 4, characterized in that, A purification tank (121) is also connected between the primary evaporation dissolution tank (12) and the primary evaporation crystallization tank (13).

6. The lithium salt purification secondary distillation washing water recovery and treatment system according to claim 4, characterized in that, The secondary evaporation crystallization system (2) includes a secondary evaporation dissolution tank (21), an ion exchange filter column (22), a secondary evaporation crystallization tank (23), and a centrifuge (24) connected in sequence. The discharge end of the primary evaporation lithium salt storage tank (14) is connected to the feed end of the secondary evaporation dissolution tank (21), and the discharge end of the centrifuge (24) is connected to the feed end of the washing water tank (26).

7. The lithium salt purification secondary distillation washing water recovery and treatment system according to claim 6, characterized in that, The centrifuge (24) is also equipped with a mother liquor pipe (25) at the discharge end, and the discharge end of the mother liquor pipe (25) is connected to the first-stage dissolution tank (12).

8. The lithium salt purification secondary distillation washing water recovery and treatment system according to claim 1, characterized in that, The discharge end of the belt centrifuge (5) is also equipped with a solid material pipe (51), and the discharge end of the solid material pipe (51) is connected in sequence to a drying tower (52) and a secondary distilled lithium salt storage tank (53).

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