Anti-solvent crystallization device and crystallization system

Abstract

The utility model belongs to the field of crystallization devices, and particularly relates to an anti-solvent crystallization device and an anti-solvent crystallization system. The anti-solvent crystallization device comprises a separator with an inner cavity, the separator is provided with an anti-solvent inlet, a liquid salt solution introduction mechanism and a stirring mechanism, the separator is further provided with a good solvent outlet for discharging a good solvent in the liquid salt solution, and the good solvent outlet is located at the boundary position of the good solvent and the anti-solvent; the anti-solvent crystallization device further comprises an anti-solvent outlet used for discharging the anti-solvent after the good solvent is discharged. The anti-solvent crystallization device disclosed by the utility model does not generate a large amount of solvent needing to be distilled and separated, so that the solvent recovery energy consumption of a traditional anti-solvent crystallization method is greatly reduced, the idle running of a good solvent in the production process is avoided, and the production energy consumption of a high-purity compound is reduced.

Description

Technical Field

[0001] This utility model belongs to the field of crystallization apparatus, specifically relating to an antisolvent crystallization apparatus and crystallization system. Background Technology

[0002] Antisolvent crystallization is a common method for compound purification. It generally involves passing a liquid salt solution formed by crude salt of the compound and a good solvent into a large amount of antisolvent of the compound (for example, the mass ratio of liquid salt solution to antisolvent can reach about 1:10~20). As the solubility of the compound decreases sharply in its antisolvent, the relatively pure compound precipitates out in crystal form, while the impurities in the crude salt of the compound remain dissolved in the solvent. After solid-liquid separation, a high-purity compound can be obtained.

[0003] Taking lithium bisfluorosulfonylimide, an additive for lithium-ion battery electrolytes, as an example, the synthesis of lithium bisfluorosulfonylimide involves three steps: chlorination, fluorination, and salt formation. It involves a large number of raw materials, reaction steps, and equipment. The synthesized bisfluorosulfonylimide salts are crude salts with high levels of water, acid, chloride ions, and solubility residues. They need to be purified to obtain crystalline salts that meet all the requirements and can be used in electrolytes.

[0004] When purifying crude lithium bis(fluorosulfonyl)imide using antisolvent crystallization, the crude salt is first dissolved by stirring with a good solvent (such as dimethyl carbonate) and an acid remover. After filtration, a clear and transparent liquid salt solution is obtained. This liquid salt solution is then added to a large amount of antisolvent (such as dichloromethane) for crystallization. After separating the solvent, the pure product is obtained. The separated solvent is generally separated again by distillation to achieve the recycling of both the good solvent and the antisolvent. This solvent recovery process generates a large amount of distillation energy, increasing the production cost of lithium bis(fluorosulfonyl)imide and reducing solvent utilization efficiency and production economics. Utility Model Content

[0005] The purpose of this invention is to provide an antisolvent crystallization device that solves the problem that antisolvent crystallization generates a large amount of solvent that needs to be separated by distillation and results in high energy consumption during production.

[0006] The second objective of this invention is to provide an antisolvent crystallization system to solve the problem of decreased crystal yield due to increased antisolvent reuse.

[0007] To achieve the first objective mentioned above, the technical solution adopted by this utility model is as follows:

[0008] An antisolvent crystallization apparatus includes a separator with an inner cavity, wherein the separator is provided with an antisolvent inlet, a liquid salt solution inlet mechanism and a stirring mechanism, and a good solvent outlet for discharging good solvent from the liquid salt solution, the good solvent outlet being located at the boundary between the good solvent and the antisolvent; the antisolvent crystallization apparatus further includes an antisolvent outlet for discharging antisolvent after discharging the good solvent.

[0009] This invention is pioneering. Antisolvent is added to the separator cavity through an antisolvent inlet. A liquid salt solution inlet mechanism introduces a good solvent solution of the crude salt to be purified into the antisolvent. A stirring mechanism mixes the liquid salt solution and the antisolvent. During settling, the less dense good solvent migrates to the top of the antisolvent. Separation of the good solvent and antisolvent is achieved by sequentially discharging the good solvent and then the antisolvent. The separated antisolvent can be recycled, while the good solvent can be used for secondary crystallization, dissolving the crude salt, or distillation. This antisolvent crystallization device avoids the generation of large amounts of solvent requiring distillation, significantly reducing the energy consumption for solvent recovery in traditional antisolvent crystallization methods, preventing the good solvent from idling during production, and lowering the energy consumption for producing high-purity compounds.

[0010] Preferably, the liquid salt solution inlet mechanism includes an inlet pipe extending into the inner cavity of the separator, and the position of the good solvent outlet is higher than the outlet of the inlet pipe.

[0011] More preferably, the stirring mechanism includes a stirrer, which is disposed near the outlet of the inlet pipe.

[0012] More preferably, there are multiple agitators arranged at intervals on the same circumference of the inner wall of the separator, and each agitator includes an agitator shaft and agitator blades, with the axis of the agitator shaft perpendicular to the axis of the separator.

[0013] Preferably, the separator is a vertical structure with a height greater than its inner diameter, and the inlet pipe is a central pipe extending vertically.

[0014] Preferably, the lower part of the separator is provided with a filtration mechanism, and the outlet of the filtration mechanism is connected to the antisolvent outlet.

[0015] More preferably, the filtration mechanism includes a filter screen disposed on the outer wall of the separator, a solvent storage chamber surrounding the filter screen is disposed on the outer side of the filter screen, and the antisolvent outlet is disposed on the solvent storage chamber.

[0016] More preferably, the bottom of the separator is provided with a crystal discharge port, and a discharge valve is provided on the crystal discharge port.

[0017] To achieve the second objective mentioned above, the technical solution adopted by this utility model is as follows:

[0018] An antisolvent crystallization system includes two or more stages of the above-mentioned separators, wherein the good solvent outlet of the previous stage separator is connected to the liquid salt solution inlet mechanism of the next stage separator.

[0019] When the number of times a defective solvent is reused increases and its purity decreases, it will affect the product yield. The antisolvent crystallization system of this invention consists of two or more separators connected in series. Through secondary antisolvent crystallization, it can promote the full precipitation of crystals and improve the product yield.

[0020] Preferably, the antisolvent outlet of the preceding stage separator is connected to the antisolvent inlet of the following stage separator via a connecting pipeline; a cooler is installed on the connecting pipeline. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the antisolvent crystallization apparatus according to Embodiment 1 of this utility model;

[0022] Figure 2 This is a schematic diagram of the antisolvent crystallization system of Embodiment 3 of this utility model;

[0023] Figure 3 This is a schematic diagram of the antisolvent crystallization system of Embodiment 4 of this utility model;

[0024] Among them, 1-Separator; 2-Resolvent inlet; 3-Good solvent outlet; 4-Central tube; 5-Agitator; 6-Discharge port; 7-Discharge valve; 8-Filter screen; 9-Solvent storage bin; 10-Resolvent outlet; 11-Cooler; 12-Refrigerant inlet pipe; 13-Refrigerant outlet pipe. Detailed Implementation

[0025] The technical concept of this utility model is to select a high-density antisolvent and a low-density good solvent during antisolvent crystallization. A liquid salt solution (i.e., a good solvent solution of crude salt) is introduced into the antisolvent. After crystallization, the good solvent migrates upwards to the antisolvent due to the density difference. The good solvent outlet position of the separator is adapted to the amount of good solvent. After the good solvent (also known as mother liquor, which may contain a small amount of antisolvent but does not affect subsequent use) is discharged through the good solvent outlet, the separator is left with antisolvent and crystalline salt. At this time, the antisolvent and crystalline salt can be discharged in sequence. That is, the separation and recovery of good solvent and antisolvent are achieved simultaneously during antisolvent crystallization, which changes the traditional approach of solvent recovery in antisolvent crystallization, reduces the energy consumption of distillation separation, and improves solvent operation efficiency.

[0026] Furthermore, by adjusting the location of the good solvent outlet on the separator and the configuration of the filtration mechanism, the crystallization efficiency and the recovery efficiency of good solvent, antisolvent, and crystal salt can be further improved, thereby enhancing the smoothness of the antisolvent crystallization process.

[0027] By connecting two or more separators in series, the problem of declining crystal yield can be further solved. The overall process can avoid the intervention of hot processes such as distillation, and truly achieve energy saving, consumption reduction and scientific production.

[0028] The implementation process of this utility model will be described in detail below with reference to specific embodiments.

[0029] Example 1

[0030] The antisolvent crystallization apparatus of this embodiment is shown in the schematic diagram below. Figure 1 As shown, it includes a separator 1, which has a sealed inner cavity, in which antisolvent crystallization and separation of good solvent and antisolvent are realized.

[0031] The separator 1 is equipped with an antisolvent inlet 2 and a good solvent outlet 3 at its upper part. The antisolvent inlet 2 is used to add antisolvent into the separator 1. There are no special restrictions on the location of the antisolvent inlet 2; in other implementations, it can also be located at the lower part of the separator 1 or at other locations, as long as it facilitates the addition of antisolvent. The good solvent outlet 3 is located at the boundary between the good solvent and antisolvent. The good solvent outlet 3 is used to discharge the good solvent. The location of the good solvent outlet 3 is adapted to the amount of good solvent in the added liquid salt solution. That is, by calculating the amounts of antisolvent and good solvent, after crystallization is complete and the good solvent migrates above the antisolvent, the valve at the good solvent outlet 3 is opened, and the good solvent should be almost completely discharged. At this time, the liquid discharged from the good solvent outlet 3 is mainly good solvent (which may contain about 10% antisolvent). Since the amount of antisolvent added is often more than 10 times that of the liquid salt solution, the location of the good solvent outlet 3 is often in the upper middle part of the separator 1.

[0032] Separator 1 is equipped with a liquid salt solution inlet mechanism, which is used to introduce a liquid salt solution (i.e., a good solvent solution of crude salt) into the antisolvent of separator 1. The liquid salt solution can be introduced through conventional piping. Figure 1 In this structure, separator 1 is a vertical structure with a height greater than its diameter. The liquid salt solution mechanism includes a central tube 4 extending vertically. The outlet of the central tube 4 is close to the bottom of separator 1. At this time, the position of the good solvent outlet 3 is higher than the position of the outlet of the central tube 4. The liquid salt solution first enters the interior of the antisolvent. The good solvent in the liquid salt solution comes into full contact with the antisolvent and then migrates upward to the top of the antisolvent. This process involves a long contact and exchange time between the two solvents, which is beneficial for filling the crystals.

[0033] To promote thorough mixing of the introduced liquid salt solution and the antisolvent, a stirring mechanism is installed at the outlet of the central tube 4. Figure 1In this configuration, the stirring mechanism includes multiple stirrers 5 evenly arranged on the same circumference of the inner wall of the separator 1. Each stirrer 5 includes a stirring shaft and stirring blades mounted on the stirring shaft. The axis of the stirring shaft is perpendicular to the axis of the separator 1, and the stirring blades rotate in a plane perpendicular to the axis of the stirring shaft, enhancing the mixing degree of liquids at different heights. In other implementations, a conventional stirring method can also be used, where the axis of the stirring shaft coincides with the axis of the separator 1, and multiple sets of stirring blades are arranged at intervals along the height direction of the stirring shaft. In this case, the stirring blades rotate around the axis of the stirring shaft to achieve mixing of liquids at different heights. In this case, the shape or position of the inlet pipe of the liquid salt solution mechanism should be adapted accordingly. The outlet of the inlet pipe should preferably be close to the bottom of the separator 1, and the inlet pipe should avoid interfering with the stirring action of the stirring mechanism.

[0034] Figure 1 In this separator, separator 1 comprises a straight cylindrical section and a conical section connected vertically. The diameter of the conical section gradually decreases from top to bottom. A discharge port 6 is located at the bottom of the conical section, and a discharge valve 7 is installed at the discharge port 6. A filter screen 8 is installed on the conical section, and a solvent storage chamber 9 surrounds the filter screen area outside the filter screen 8. The solvent storage chamber 9 is fitted onto the outside of separator 1, forming an annular liquid storage cavity between itself and the corresponding outer wall of separator 1. A reverse solvent outlet 10 is located at the bottom of the solvent storage chamber 9. The purpose of the filter screen 8 and the reverse solvent outlet 10 is that after the good solvent in separator 1 is discharged, the remaining reverse solvent and crystalline salt in separator 1 are discharged. When the reverse solvent outlet 10 is opened, the reverse solvent can be discharged through the filter screen 8, leaving only crystalline salt in separator 1. After being discharged through the discharge port 6, high-purity product can be obtained after conventional treatment such as drying.

[0035] The working principle of the antisolvent crystallization device in this embodiment is as follows: First, a certain amount of antisolvent (for example, about 2 / 3 of the container volume) is injected into the separator 1 through the antisolvent inlet 2. Then, liquid salt solution is introduced into the antisolvent through the liquid salt solution inlet mechanism. Stirring is started. After standing for a certain period of time, the good solvent will migrate to the top of the antisolvent due to the density difference. Then, the good solvent is discharged from the good solvent outlet 3, and then the antisolvent in the separator 1 is discharged from the antisolvent outlet 10. Finally, the crystal salt is discharged from the discharge port 6.

[0036] Taking lithium bis(fluorosulfonyl)imide as an example, the overall processing technology is as follows:

[0037] 1) Add 50 kg of crude salt containing lithium difluorosulfonylimide to a dissolving tank (the crude salt has the following test results: moisture: 800 ppm, acidity: 250 ppm, chloride ion: 49 ppm, and insoluble matter: 1%). Then add dimethyl carbonate, a good solvent, with a mass ratio of crude salt to dimethyl carbonate of 1:0.6. Then add 5‰ of the crude salt mass of lithium carbonate. Maintain the temperature at 25±5℃ and stir thoroughly to dissolve for 4 hours.

[0038] 2) After the mixture is fully dissolved, it is filtered and the turbidity of the filtrate is controlled to be ≤10 NTU, resulting in 79.5 kg of clear and transparent liquid salt solution.

[0039] 3) The antisolvent dichloromethane, after pre-cooling to 10°C, enters separator 1 through antisolvent inlet 2. Once the container is 2 / 3 full, the clear, transparent liquid salt solution obtained from filtration in step 2) is introduced into separator 1 through central tube 4. The mass ratio of liquid salt solution to antisolvent is 1:20. After the liquid salt solution is introduced, the agitator on the side wall of separator 1 is activated (the liquid salt solution introduction rate is generally 40~50 kg / min). After the introduction is complete, the agitator is stirred for another 40 minutes. Then, the agitator is stopped, and the mixture is allowed to stand for 30 minutes. The good solvent outlet 3 is then opened to discharge the mother liquor (the mass of the discharged mother liquor is 42% of the mass of the introduced liquid salt solution). The dichloromethane content in the mother liquor is measured to be 10%.

[0040] Open the antisolvent outlet 10 to discharge dichloromethane, which can be used as an antisolvent. The precipitated crystal salt is discharged from the discharge port 6. After centrifugation, nitrogen purging for 10 hours, and drying at 30°C for 10 hours, 48.6 kg of finished crystal salt is obtained, with a yield of 98.2%.

[0041] Example 2

[0042] In this embodiment of the antisolvent crystallization apparatus, the antisolvent inlet, good solvent outlet, central tube, and stirring mechanism on the separator are the same as in Embodiment 1, but the filtration mechanism is different from that in Embodiment 1.

[0043] refer to Figure 1 Instead of installing a filter screen and solvent storage chamber on the conical section of the separator, a filter plate is installed between the lower outlet of the conical section and the discharge valve. During operation, after the good solvent is released from the good solvent outlet, the discharge valve is opened and the reverse solvent is released. The crystal salt is trapped on the filter plate. Then the filter plate is opened to release the crystal salt.

[0044] Of course, in other implementation scenarios, a filtration mechanism may not be required. After the good solvent is released from the good solvent outlet, an antisolvent extraction pipeline can be installed to extract the clear liquid above the crystal salt, thereby achieving the separation of the antisolvent and the crystal salt.

[0045] Example 3

[0046] The antisolvent crystallization system of this embodiment, such as Figure 2As shown, the system includes two-stage separators 1 connected in series, with the structure of separator 1 being the same as in Example 1. When the two-stage separators 1 are connected in series, the good solvent outlet 3 of the upper-stage separator is connected to the liquid salt inlet mechanism of the lower-stage separator, allowing the good solvent (or mother liquor) separated by the upper-stage separator to continue entering the lower-stage separator for crystallization. The antisolvent outlet 10 of the upper-stage separator is connected to the antisolvent inlet 2 of the lower-stage separator, meaning the antisolvent separated by the upper-stage separator continues to be used in the lower-stage separator, improving antisolvent utilization efficiency and crystal yield.

[0047] The two-stage separators are used after the antisolvent has been reused multiple times. At this time, the purity of the antisolvent decreases (for example, the purity of the antisolvent drops below 95%), and a single crystallization cannot achieve a good yield.

[0048] The purification process of lithium bis(fluorosulfonyl)imide based on this embodiment is as follows:

[0049] 1) Add 50 kg of crude salt containing lithium difluorosulfonylimide to a dissolving tank (the crude salt has the following test results: moisture: 800 ppm, acidity: 250 ppm, chloride ion: 49 ppm, and insoluble matter: 1%). Then add dimethyl carbonate, a good solvent, with a mass ratio of crude salt to dimethyl carbonate of 1:0.6. Then add 5‰ of the crude salt mass of lithium carbonate. Maintain the temperature at 25±5℃ and stir thoroughly to dissolve for 4 hours.

[0050] 2) After the mixture is fully dissolved, it is filtered and the turbidity of the filtrate is controlled to be ≤10 NTU, resulting in 79.5 kg of clear and transparent liquid salt solution.

[0051] 3) The antisolvent, dichloromethane, is a recovered solvent (94.8% main content and 5.2% remaining dimethyl carbonate). After pre-cooling to 10°C, it enters the primary separator through antisolvent inlet 2. Once the container is 2 / 3 full, the clear, transparent liquid salt solution obtained from filtration in step 2) is introduced into the primary separator through the central tube 4. The mass ratio of liquid salt solution to antisolvent is 1:20. Stirring is started while introducing the liquid salt solution. After the solution is introduced, stirring continues for 30-40 minutes. Stirring is then stopped, and the mixture is allowed to stand for 30 minutes. The good solvent outlet 3 of the primary separator is opened, and 45.67 kg of mother liquor is discharged (the mass of the discharged mother liquor is 57% of the mass of the introduced liquid salt solution; the proportion of non-polar solvent dichloromethane in the mother liquor is 10%). This mother liquor is then discharged into the secondary separator through the central tube.

[0052] Open the antisolvent outlet 10 of the primary separator to discharge dichloromethane. After being cooled by the cooler (optional), it enters the secondary separator through the antisolvent inlet 2. If the amount of defective solvent entering is less than 2 / 3 of the container, it is replenished by the antisolvent inlet 2 of the secondary separator. Then, repeat the operation of the primary separator.

[0053] The crystalline salt precipitated from the primary separator is discharged from the discharge port 6 of the primary separator. After centrifugal separation, nitrogen purging for 10 hours, and drying at 30℃ for 10 hours, 37.1 kg of finished crystalline salt is obtained, with a yield of 75%. The crystalline salt precipitated from the secondary separator is discharged from the discharge port 6 of the secondary separator. After centrifugal separation, nitrogen purging for 10 hours, and drying at 30℃ for 10 hours, 9.55 kg of finished crystalline salt is obtained, with a yield of 77%. The overall yield is 94.2%.

[0054] The salt content of the mother liquor discharged from the secondary separator is less than 5 kg, so there is no need for tertiary separation. It can be returned to the dissolving tank to continue preparing the next batch of materials.

[0055] Example 4

[0056] The antisolvent crystallization system of this embodiment, such as Figure 3 As shown, a cooler 11 is installed on the connecting pipeline between the antisolvent outlet 10 of the primary separator and the antisolvent inlet 2 of the secondary separator. The cooler 11 is connected to a refrigerant inlet pipe 12 and a refrigerant outlet pipe 13 to cool the flowing antisolvent using refrigerant.

[0057] During the antisolvent crystallization process, precooling the antisolvent can promote the crystallization process. For example, the antisolvent needs to be precooled to 0~10℃ to achieve the best crystallization efficiency. When the temperature of the antisolvent flowing out of the antisolvent outlet 10 of the primary separator exceeds 10℃, the cooler 11 can cool the antisolvent to reduce the temperature entering the secondary separator back to below 10℃, thereby ensuring the crystallization effect in the secondary separator.

[0058] Finally, it should be noted that the above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Although the present utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. An antisolvent crystallization apparatus, characterized in that, The apparatus includes a separator with an internal cavity, which is provided with an antisolvent inlet, a liquid salt solution inlet mechanism, and a stirring mechanism. It is also provided with a good solvent outlet for discharging the good solvent in the liquid salt solution, and the good solvent outlet is located at the boundary between the good solvent and the antisolvent. The antisolvent crystallization apparatus also includes an antisolvent outlet for discharging the antisolvent after discharging the good solvent.

2. The antisolvent crystallization apparatus as described in claim 1, characterized in that, The liquid salt solution inlet mechanism includes an inlet pipe extending into the inner cavity of the separator, and the good solvent outlet is located higher than the outlet of the inlet pipe.

3. The antisolvent crystallization apparatus as described in claim 2, characterized in that, The stirring mechanism includes a stirrer, which is located near the outlet of the inlet pipe.

4. The antisolvent crystallization apparatus as described in claim 3, characterized in that, The agitators are multiple and spaced apart on the same circumference of the inner wall of the separator. Each agitator includes a stirring shaft and stirring blades, and the axis of the stirring shaft is perpendicular to the axis of the separator.

5. The antisolvent crystallization apparatus as described in claim 2, characterized in that, The separator is a vertical structure with a height greater than its inner diameter, and the inlet pipe is a central pipe whose length extends vertically.

6. The antisolvent crystallization apparatus as described in claim 1, characterized in that, The lower part of the separator is provided with a filtration mechanism, and the outlet of the filtration mechanism is connected to the antisolvent outlet.

7. The antisolvent crystallization apparatus as described in claim 6, characterized in that, The filtration mechanism includes a filter screen disposed on the outer wall of the separator, a solvent storage chamber surrounding the filter screen, and an antisolvent outlet disposed on the solvent storage chamber.

8. The antisolvent crystallization apparatus as described in claim 7, characterized in that, The separator is provided with a crystal discharge port at the bottom, and a discharge valve is provided on the crystal discharge port.

9. An antisolvent crystallization system, characterized in that, The separator includes two or more stages as described in any one of claims 1 to 8, wherein the good solvent outlet of the preceding stage separator is connected to the liquid salt solution inlet mechanism of the following stage separator.

10. The antisolvent crystallization system as described in claim 9, characterized in that, The antisolvent outlet of the preceding stage separator is connected to the antisolvent inlet of the next stage separator via a connecting pipeline; a cooler is installed on the connecting pipeline.

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