A lithium hexafluorophosphate segmented continuous static crystallization column

Abstract

The application relates to the technical field of crystallization equipment, and particularly discloses a lithium hexafluorophosphate segmented continuous static crystallization tower, which comprises a crystallization kettle with a crystallization jacket, the upper end of the crystallization kettle is connected with a vertically arranged cooling tower, the cooling tower is connected with the inside of the crystallization kettle, the upper end of the cooling tower is provided with a feeding port, the bottom of the crystallization kettle is provided with a discharging port, and a plurality of partition jackets are arranged on the cooling tower. The technical problem that lithium hexafluorophosphate pretreatment tanks encounter a large temperature difference in low temperature when entering the crystallization tank, rapidly precipitate to form amorphous powder, easily wrap impurities and reduce the purity of products is solved.

Description

Technical Field

[0001] This utility model relates to the field of crystallization equipment technology, specifically to a segmented continuous static crystallization tower for lithium hexafluorophosphate. Background Technology

[0002] Crystallization is the process by which solid substances precipitate as crystals from vapor, solution, or melt. Thousands of years ago, it was used to extract salt from seawater. Statistics show that in modern society, approximately two-thirds of bulk chemical products are solid products. In particular, in modern chemical production, 90% of products are solid, and the production processes of these solid products are inseparable from crystallization.

[0003] Lithium hexafluorophosphate is a key raw material for lithium-ion battery electrolytes. Due to its many excellent properties, such as high specific energy, low self-discharge, long cycle life, fast charge and discharge, high discharge power, and no memory effect, it has become the preferred high-performance battery material for modern new energy and is widely used in 3C, power batteries, energy storage and other fields.

[0004] The production of lithium hexafluorophosphate also requires a crystallization process. Traditional crystallization processes often use crystallization tanks with jackets, through which a coolant is passed to lower the temperature. This method only has one crystallization chamber. However, the crystallization environment for lithium hexafluorophosphate synthesis liquid needs to be as low as -50°C. This results in the crystallization tank inlet temperature being too low. When the lithium hexafluorophosphate synthesis liquid is suddenly subjected to a low temperature of tens of degrees below zero at the inlet of the crystallization tank, some lithium hexafluorophosphate precipitates out and adheres to the inlet, causing blockage.

[0005] To address the aforementioned issue of blockage at the feed inlet, existing technologies typically incorporate a pretreatment tank before the crystallization tank. For example, patent document CN220860700U describes a lithium hexafluorophosphate crystallization device that includes a pretreatment tank. The pretreatment tank's outlet is connected to the crystallization tank's inlet. The low temperature within the crystallization tank affects the pretreatment tank through thermal radiation, allowing it to slowly cool the lithium hexafluorophosphate in advance. This method can, to some extent, prevent the lithium hexafluorophosphate synthesis solution from frosting and sticking to the feed inlet. However, when the lithium hexafluorophosphate pretreatment tank enters the crystallization tank, it encounters a significant temperature difference. The solute molecules do not have time to arrange themselves in an orderly manner, resulting in numerous tiny crystal nuclei. This leads to small crystal sizes, sometimes even amorphous powder. The formation of nanoscale crystals or irregular dendritic crystals results in small particles that are prone to agglomeration and have poor flowability. Rapid crystallization easily traps solvent (HF) and impurities (such as phosphorus-containing compounds), leading to reduced product purity. Utility Model Content

[0006] The purpose of this invention is to provide a segmented continuous static crystallization tower for lithium hexafluorophosphate, which solves the technical problem mentioned above in the prior art where lithium hexafluorophosphate pretreatment tanks encounter extremely low temperatures with large temperature differences when entering the crystallization tank, resulting in rapid precipitation of amorphous powder, which easily encapsulates impurities and leads to a decrease in product purity.

[0007] To solve the above problems, the technical solution adopted by this utility model is as follows: a segmented continuous static crystallization tower for lithium hexafluorophosphate, including a crystallization vessel with a crystallization jacket, a vertically arranged cooling tower connected to the upper end of the crystallization vessel, the cooling tower being connected to the interior of the crystallization vessel, a feed inlet at the upper end of the cooling tower, a discharge outlet at the bottom of the crystallization vessel, and several partitioned jackets on the cooling tower.

[0008] The beneficial effects of this implementation plan are as follows: 1. In the prior art, the ambient temperature for the crystallization of lithium hexafluorophosphate synthesis solution needs to be as low as -50℃. This results in the temperature at the inlet of the crystallization tank being too low due to the influence of the internal low temperature. When the lithium hexafluorophosphate synthesis solution flows through the inlet of the crystallization tank, some lithium hexafluorophosphate precipitates out and adheres to the inlet, causing blockage. However, this application is equipped with a cooling tower column with several partitioned jackets. By using the different partitioned jackets on the cooling tower column, the temperature of the inlet at the upper end of the cooling tower column is set above zero. Then, the temperature is gradually reduced by using the partitioned jackets. Therefore, it effectively avoids frost formation and blockage of the inlet.

[0009] 2. In existing technologies, the lithium hexafluorophosphate synthesis solution is directly introduced into a -50°C low-temperature environment. When encountering such extreme temperature differences, the solute molecules do not have enough time to arrange themselves in an orderly manner, resulting in numerous tiny crystal nuclei. This leads to small crystal sizes or even amorphous powder. Nanoscale crystals or irregular dendritic crystals are formed, with small particle sizes that are prone to agglomeration and poor flowability. Rapid crystallization easily encapsulates solvent (HF) and impurities (such as phosphorus-containing compounds), leading to reduced product purity. In contrast, this application uses a cooling tower column with partitioned jackets. The partitioned jackets of the cooling tower column gradually lower the temperature, slowly forming crystal nuclei. After entering the bottom crystallization vessel, the ambient temperature reaches -50°C, allowing the crystal nuclei to grow fully. Ultimately, large, uniformly sized crystals precipitate in the bottom crystallization vessel, resulting in large, high-purity lithium hexafluorophosphate particles.

[0010] Furthermore, the cooling tower includes several cooling tower columns, which are fixed and connected to each other using connecting flanges.

[0011] Furthermore, the ratio of the inner diameter of the cooling tower column 2 to the inner diameter of the crystallization vessel 1 is 1:2-3.

[0012] Furthermore, the cooling tower is equipped with two cooling tower columns, each of which has three partitioned jackets. Each partitioned jacket, corresponding to a specific location on the cooling tower column, is equipped with a PFA sight glass for observing the formation of lithium hexafluorophosphate crystal nuclei within that partitioned column. This facilitates observation of the crystal nucleus formation in the lithium hexafluorophosphate synthesis solution within the cooling tower column, and allows for adjustment of the temperature in each partitioned jacket, controlling the formation and growth rate of crystal nuclei.

[0013] Furthermore, the crystallization jacket includes a crystallization jacket inlet and a crystallization jacket outlet, with the inlet located on the lower end face of the crystallization vessel. The ambient temperature at the outlet is maintained at -50°C to prevent the lithium hexafluorophosphate crystals from redissolving due to temperature increases when exiting the crystallization tower along with the solvent.

[0014] Furthermore, the cooling tower column has a through hole at the PFA sight glass mounting location, and a reinforcing support frame is installed inside the through hole. A movable flange is used for connection at the through hole, and a fluoroplastic gasket is installed on the contact surface between the movable flange and the PFA sight glass for isolation. The reinforcing support frame can isolate the external forces on the tower column itself, preventing the PFA sight glass from deforming due to external forces from the tower column. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of this utility model. Detailed Implementation

[0016] The following detailed description illustrates the specific implementation method: The reference numerals in the accompanying drawings include: crystallizer 1, crystallization jacket inlet 11, crystallization jacket outlet 12, cooling tower column 2, first cooling tower column 21, second cooling tower column 22, connecting flange 23, partitioned jacket 3, refrigerant inlet 31, refrigerant outlet 32, feed inlet 4, discharge outlet 5, and PFA sight glass 6.

[0017] Implementation, for example, attached Figure 1 As shown: A segmented continuous static crystallization tower for lithium hexafluorophosphate includes a crystallization vessel 1. The crystallization vessel 1 has arc-shaped upper and lower ends and a barrel-shaped body in the middle. A crystallization jacket is provided outside the body. The inlet 11 of the crystallization jacket is located at the bottom of the crystallization vessel 1, vertically downward, and the outlet 12 is located on the uppermost circumferential surface of the barrel-shaped part of the crystallization vessel 1. Therefore, when the crystallization vessel 1 is working, a coolant is introduced into the crystallization jacket to maintain a low temperature. The temperature of the coolant entering the crystallization jacket from the inlet 11 is controlled at -50°C, and the temperature of the coolant exiting from the outlet 12 is also controlled at 50°C. Thus, the internal temperature of the crystallization vessel 1 can be controlled at -50°C. A discharge port 5 for lithium hexafluorophosphate crystals is located at the center of the lower arc-shaped surface of the crystallization vessel 1, and the discharged product is a mixture of crystals and solvent.

[0018] The upper end of the crystallization vessel 1 is connected to a vertically arranged cooling tower, which is composed of several cooling tower columns 2 spliced ​​together. The number of cooling tower columns can be selected according to the actual production output of lithium hexafluorophosphate and the required cooling time. The ratio of the inner diameter of the cooling tower column 2 to the inner diameter of the crystallization vessel 1 is 1:2-3. In this embodiment, the inner diameter of the cooling tower column is 600mm, the inner diameter of the crystallization vessel 1 is 1600mm, and the height of the crystallization vessel 1 is 1900mm.

[0019] In this embodiment, the cooling tower is as follows: Figure 1 As shown, it is equipped with two cooling tower columns 2, namely a first cooling tower column 21 and a second cooling tower column 22. The first cooling tower column 21 and the second cooling tower column 22 are connected as one unit by a connecting flange 23. Each cooling tower column 2 is equipped with three partition jackets 3, and each partition jacket 3 is equipped with a refrigerant inlet 31 and a refrigerant outlet 32. Therefore, different refrigeration units can be connected to introduce refrigerants of different temperatures to control the temperature of different areas of the cooling tower column 2, so as to achieve the purpose of partition temperature control. In this embodiment, there are two cooling tower columns with six partition jackets. The partition temperature control from bottom to top is as follows: -50 to -45℃, -40 to -35℃, -30 to -25℃, -25 to -20℃, -10 to -5℃, and 0 to 3℃. A synthesis liquid inlet 4 is located on the upper end face of the cooling tower column at the top of the cooling tower. Therefore, when the lithium hexafluorophosphate synthesis liquid enters the cooling tower, its temperature is still above zero degrees Celsius, and it gradually cools down as it descends the cooling tower, slowly forming crystal nuclei. This application can control the flow rate of the lithium hexafluorophosphate synthesis liquid entering through the inlet 4 and the flow rate of the mixture exiting through the outlet 5, achieving material balance between inlet and outlet, thereby realizing continuous crystallization production.

[0020] Each section jacket 3 of the cooling tower column 2 is equipped with a PFA sight glass 6. The cooling tower column 2 has a through hole at the installation location of the PFA sight glass 6. The through hole passes through the jacket and enters the inner cavity of the cooling tower column 2. The position through the jacket is sealed to ensure that the refrigerant flowing inside the jacket does not leak. A reinforcing support frame is set in the through hole to ensure that the PFA sight glass 6 does not deform due to the external force of the tower column. It is installed using a movable flange. The flanges at both ends of the PFA sight glass tube are embedded into the groove of the movable flange (the movable flange is composed of two semi-circular flanges mating together) and fixed with bolts. When the PFA sight glass 6 is embedded into the groove of the movable flange, a fluoroplastic gasket is installed on the contact surface of the movable flange for isolation. When the bolt is threaded, polytetrafluoroethylene sealing tape is wrapped around the thread to ensure that the lithium hexafluorophosphate synthetic liquid inside the cooling tower column does not leak.

[0021] The PFA sight glass 6 allows direct observation of the interior of the cooling tower. Therefore, the crystallization of lithium hexafluorophosphate in each cooling zone can be observed using the PFA sight glass 6. By adjusting the control temperature of different zones, the crystal nuclei of lithium hexafluorophosphate synthesis liquid are gradually generated during the descent process, and slow growth is achieved.

[0022] The above descriptions are merely embodiments of this utility model, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of this utility model, and these should also be considered within the scope of protection of this utility model. These modifications will not affect the effectiveness of the implementation of this utility model or the practicality of the patent. The scope of protection claimed in this application shall be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A segmented continuous static crystallization tower for lithium hexafluorophosphate, characterized in that: It includes a crystallization vessel with a built-in crystallization jacket. The upper end of the crystallization vessel is connected to a vertically arranged cooling tower, which is connected to the interior of the crystallization vessel. The upper end of the cooling tower is provided with a feed inlet, and the bottom of the crystallization vessel is provided with a discharge outlet. The cooling tower is provided with several partitioned jackets.

2. The segmented continuous static crystallization tower for lithium hexafluorophosphate according to claim 1, characterized in that: The cooling tower includes several cooling tower columns, which are fixed and connected by connecting flanges.

3. The segmented continuous static crystallization tower for lithium hexafluorophosphate according to claim 2, characterized in that: The ratio of the inner diameter of the cooling tower column to the inner diameter of the crystallization vessel is 1:2-3.

4. The segmented continuous static crystallization tower for lithium hexafluorophosphate according to claim 2, characterized in that: The cooling tower is provided with two cooling tower columns. Each cooling tower column is provided with three partitioned jackets. Each partitioned jacket is provided with a PFA sight glass at the position of the cooling tower column to observe the lithium hexafluorophosphate crystal nuclei inside the partitioned cooling tower column.

5. The segmented continuous static crystallization tower for lithium hexafluorophosphate according to claim 1, characterized in that: The crystallization jacket includes a crystallization jacket inlet and a crystallization jacket outlet, with the crystallization jacket inlet located on the lower end face of the crystallization vessel.

6. The segmented continuous static crystallization tower for lithium hexafluorophosphate according to claim 4, characterized in that: The cooling tower column has a through hole at the PFA sight glass mounting location, and a movable flange is used for connection at the through hole. A fluoroplastic gasket is installed on the contact surface between the movable flange and the PFA sight glass for isolation.

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