Crystallization device and crystallization method

Abstract

The invention provides a crystallization device and a crystallization method, the crystallization device comprises: a first cyclone separator, the first cyclone separator having a first temperature control member; the first Taylor crystallizer is provided with a first slit; the second cyclone separator is provided with a second temperature control piece; the second Taylor crystallizer is provided with a second slit; the third cyclone separator is provided with a third temperature control piece; the third Taylor crystallizer is provided with a third slit; a fourth cyclone separator; wherein the temperature of the first temperature control part is T1, the temperature of the second temperature control part is T2, the temperature of the third temperature control part is T3, and T1 > T2 > T3. Therefore, the grain size of the crystal is accurately controlled, the content of impurities in the crystal is reduced, the purity of the crystal is improved, and the crystallization efficiency is improved.

Description

Technical Field

[0001] The present application relates to the field of materials, and in particular, to a crystallization device and a crystallization method. Background Art

[0002] Cooling crystallization is a commonly used separation and purification method, that is, crystals are precipitated from saturated solutions. By controlling the crystallization conditions, the particle size and purity of the final product can be controlled. The commonly used static crystallization method is a method in which the solution is placed under specific conditions and naturally cooled to promote crystal growth. This method has the following problems: uneven particle size distribution, high impurity content, etc. Therefore, the current crystallization device needs to be further improved. Summary of the invention

[0003] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0004] In one aspect of the present application, a crystallization device is proposed, which includes: a first cyclone separator, the first cyclone separator includes a first cyclone barrel, the first cyclone barrel has a first feed port and a first discharge port, and the first cyclone separator is provided with a first temperature control component; a first Taylor crystallizer, the first Taylor crystallizer has a first inner barrel and a first outer barrel, a first slit is formed between the first inner barrel and the first outer barrel, and the first slit is connected to the first discharge port; a second cyclone separator, the second cyclone separator includes a second cyclone barrel, the second cyclone barrel has a second feed port and a second discharge port, the second feed port is connected to the first discharge port, and the second cyclone separator is provided with a second temperature control component; a second Taylor crystallizer, the second Taylor crystallizer has a second inner barrel and a second outer barrel, the second inner barrel and the second outer barrel are connected A second slit is formed between the barrels, and the second slit is connected to the second discharge port; a third cyclone separator, the third cyclone separator includes a third cyclone barrel, the third cyclone barrel has a third feed port and a third discharge port, the third feed port is connected to the second discharge port, and the third cyclone separator is provided with a third temperature control member; a third Taylor crystallizer, the third Taylor crystallizer has a third inner barrel and a third outer barrel, a third slit is formed between the third inner barrel and the third outer barrel, and the third slit is connected to the third discharge port; a fourth cyclone separator, the fourth cyclone separator includes a fourth cyclone barrel, the fourth cyclone barrel has a fourth feed port, a fourth discharge port and an impurity outlet; wherein the temperature of the first temperature control member is T1, the temperature of the second temperature control member is T2, and the temperature of the third temperature control member is T3, and satisfies: T1>T2>T3. Thus, the particle size of the crystal is accurately controlled, the content of impurities in the crystal is reduced, the purity of the crystal is improved, and the efficiency of crystallization is improved.

[0005] According to some embodiments of the present application, the crystallization device satisfies at least one of the following conditions: -5°C ≤ T1 ≤ 20°C; -20°C ≤ T2 ≤ -5°C; -40°C ≤ T3 ≤ -20°C. Thus, the temperature gradient is precisely controlled, the size control of the orderly growth of the crystal is promoted, the content of impurities is reduced, and the purity of the crystal is improved.

[0006] According to some embodiments of the present application, the size of the first slit is a, the size of the second slit is b, and the size of the third slit is c, and they satisfy: a>b>c. Thus, the turbulence degree of the solution is increased, and the crystallization efficiency is improved.

[0007] According to some embodiments of the present application, 5 mm ≤ a ≤ 10 mm, 3 mm ≤ b ≤ 5 mm, and 1 mm ≤ c ≤ 3 mm. Thus, the turbulence of the solution is increased, and the crystallization efficiency is improved.

[0008] According to some embodiments of the present application, the first cyclone, the second cyclone, and the third cyclone are all provided with the impurity outlet, thereby improving the impurity separation efficiency, reducing the coating of impurities on the surface of the crystal nucleus or inside the crystal, and improving the crystal purity.

[0009] According to some embodiments of the present application, the crystallization device further comprises: a precooler, the precooler comprises a precooling chamber, the precooler comprises a fifth feed port and a fifth discharge port, and the fifth discharge port is connected to the first feed port. Thus, the solution is cooled in advance and the crystallization time is shortened.

[0010] According to some embodiments of the present application, the first cyclone separator includes a first motor, the second cyclone separator includes a second motor, and the third cyclone separator includes a third motor, and the first motor, the second motor, and the third motor are independently controlled. Thus, a stepwise optimization from primary nucleation of crystals to crystal growth is achieved, and the uniformity of mass transfer and crystal growth is improved.

[0011] According to some embodiments of the present application, the crystallization device further includes: a first liquid receiving tray, which is respectively connected to the first discharge port and the second feed port; and a second liquid receiving tray, which is respectively connected to the second discharge port and the third feed port.

[0012] The second aspect of the present application proposes a method for crystallization using the crystallization device proposed in the first aspect of the present application, the method comprising: (1) allowing the solution to be crystallized to enter the first cyclone barrel of the first cyclone separator through the first feed port, and after being accelerated, forming a Taylor flow and entering the first slit of the first Taylor crystallizer for a first crystallization treatment; (2) after the first crystallization, allowing the solution obtained in step (1) to enter the second cyclone barrel of the second cyclone separator through the second feed port, and after being accelerated, forming a Taylor flow and entering the second slit of the second Taylor crystallizer for a second crystallization treatment, wherein the temperature during the second crystallization treatment is lower than the temperature during the first crystallization treatment; (3) after the second crystallization, allowing the solution obtained in step (2) to enter the third cyclone barrel of the third cyclone separator through the third feed port, and after being accelerated, forming a Taylor flow and entering the third slit of the third Taylor crystallizer for a third crystallization treatment, wherein the temperature during the third crystallization treatment is lower than the temperature during the second crystallization treatment; (4) after the third crystallization treatment, allowing the solution obtained in step (3) to enter the fourth cyclone barrel of the fourth cyclone separator through the fourth feed port for separation, and collecting crystals through the fourth discharge port. Therefore, the use of this method for crystallization can improve the purity of the crystal, accurately control the particle size of the crystal, improve the efficiency of crystallization, and reduce production costs and energy consumption.

[0013] According to some embodiments of the present application, the first cyclone separator includes a first motor, the second cyclone separator includes a second motor, and the third cyclone separator includes a third motor, the first motor has a rotation speed of 500 rpm-1000 rpm, the second motor has a rotation speed of 1000 rpm-1500 rpm, and the third motor has a rotation speed of 1500 rpm-2000 rpm. Thus, the stepwise optimization from primary nucleation of crystals to crystal growth is achieved, and the uniformity of mass transfer and crystal growth is improved.

[0014] According to some embodiments of the present application, the time of the first crystallization treatment, the time of the second crystallization treatment, and the time of the third crystallization treatment are independently less than or equal to 5 minutes, thereby improving the crystallization efficiency.

[0015] According to some embodiments of the present application, the method further comprises: precooling the solution to be crystallized before the solution to be crystallized enters the first cyclone, thereby cooling the solution in advance and shortening the crystallization time.

[0016] According to some embodiments of the present application, the method is a crystallization method for preparing lithium hexafluorophosphate crystals. Therefore, the lithium hexafluorophosphate crystals obtained by this method have the advantages of high purity, low acidity, and more uniform particle size distribution. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0018] Figure 1 A schematic structural diagram of a crystallization device according to an embodiment of the present application is shown.

[0019] Figure 2 Shows Figure 1 Diagram of the first Taylor crystallizer process.

[0020] Figure 3 Shows Figure 1 Diagram of the second Taylor crystallizer process.

[0021] Figure 4 Shows Figure 1 Method diagram of the third Taylor crystallizer.

[0022] Reference numerals:

[0023] 100: crystallization device; 1: precooler; 2: first motor; 3: first cyclone separator; 4: first Taylor crystallizer; 41: first slit; 5: first liquid receiving tray; 6: second motor; 7: second cyclone separator; 8: second Taylor crystallizer; 81: second slit; 9: second liquid receiving tray; 10: third motor; 11: third cyclone separator; 12: third Taylor crystallizer; 121: third slit; 13: fourth cyclone separator. DETAILED DESCRIPTION

[0024] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. If no specific techniques or conditions are specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used that do not specify the manufacturer are all conventional products that can be obtained commercially.

[0025] The cooling crystallization process in the related art usually uses a static or simple stirring method to cool the solution, and indirectly reduces the solution temperature through natural convection or external cooling medium to promote crystal precipitation. This method often has the following limitations: First, the crystallization rate and particle size distribution are difficult to accurately control: due to the uncontrollable nucleation rate of crystals in the solution, a large number of crystal nuclei may be generated, thereby forming small crystals with a wide particle size distribution. During the crystal nucleation process, insoluble impurities dissolved in the solution are easily captured on the crystal nuclei or deposited on the surface of the crystal, increasing the insoluble content in the product and reducing the purity of the crystal; second, due to limited heat transfer efficiency and poor mixing effect, local supersaturation may fluctuate greatly, affecting product quality and yield; third, for solutes with poor solubility (such as lithium hexafluorophosphate), secondary crystal nuclei are easily generated during the crystallization process, thereby producing fine particles or even powder, which is not conducive to subsequent filtration separation and electrochemical performance.

[0026] In a first aspect, the present application provides a crystallization device 100, referring to Figure 1 The crystallization device 100 includes a first cyclone separator 3, a first Taylor crystallizer 4, a second cyclone separator 7, a second Taylor crystallizer 8, a third cyclone separator 11, a third Taylor crystallizer 12 and a fourth cyclone separator 13.

[0027] The first cyclone separator 3 includes a first cyclone barrel, the first cyclone barrel has a first feed inlet and a first discharge outlet, and a first temperature control element is provided on the first cyclone separator 3, and the temperature of the first temperature control element is T1. The first temperature control element can cool the first cyclone separator 3, and the solution enters the first cyclone barrel through the first feed inlet.

[0028] The first Taylor crystallizer 4 has a first inner cylinder and a first outer cylinder, a first slit 41 is formed between the first inner cylinder and the first outer cylinder, and the first slit 41 is connected to the first discharge port. The solution cooled in the first cyclone is accelerated into the first slit 41 through the first discharge port, and a stable liquid film and liquid droplets are formed in the first slit 41 to perform initial nucleation. For example, when the crystal is lithium hexafluorophosphate, the Taylor vortex effect in the first slit 41 can promote the effective collision and aggregation of lithium hexafluorophosphate molecules to form fine crystal nuclei.

[0029] The second cyclone separator 7 includes a second cyclone barrel, the second cyclone barrel has a second feed port and a second discharge port, the second feed port is connected to the first discharge port, and a second temperature control component is provided on the second cyclone separator 7. The temperature of the second temperature control component is T2, and T2<T1. The second temperature control component can cool the second cyclone separator 7 so that the temperature inside the second cyclone separator 7 is lower than the temperature inside the first cyclone separator 3.

[0030] The second Taylor crystallizer 8 comprises a second inner cylinder and a second outer cylinder, a second slit 81 is formed between the second inner cylinder and the second outer cylinder, and the second slit 81 is connected to the second discharge port. The solution cooled in the second cyclone separator 7 is accelerated into the second slit 81 through the second discharge port. Since T2<T1, the temperature of the solution in the second slit 81 is lower, and the lower temperature environment can make the crystals continue to grow without condensing too quickly, thereby improving the uniformity of the crystal size.

[0031] The third cyclone separator 11 includes a third cyclone barrel, the third cyclone barrel has a third feed port and a third discharge port, the third feed port is connected to the second discharge port, and the third cyclone separator is provided with a third temperature control component. The temperature of the third temperature control component is T3, and T3<T2. The third temperature control component can cool the third cyclone separator 11, so that the temperature inside the third cyclone separator 11 is lower than the temperature inside the second cyclone separator 7.

[0032] The third Taylor crystallizer 12 has a third inner cylinder and a third outer cylinder, a third slit 121 is formed between the third inner cylinder and the third outer cylinder, and the third slit 121 is connected to the third discharge port. The solution cooled in the third cyclone separator 11 is accelerated into the third slit 121 through the third discharge port. Since T3<T2, the temperature of the solution in the third slit 121 is lower, and the crystal undergoes the most efficient growth and size optimization at this stage.

[0033] The fourth cyclone separator 13 includes a fourth cyclone barrel, and the fourth cyclone barrel has a fourth feed port, a fourth discharge port, and an impurity outlet. The solution in the third slit 121 enters the fourth cyclone separator 13 through the fourth feed port, and under the action of strong centrifugal force, impurities are discharged from the fourth cyclone separator 13 from the impurity outlet, and crystals are deposited at the bottom of the fourth cyclone separator 13 under the dual action of gravity and centrifugal force, and can be collected through the fourth discharge port. For example, when cooling and crystallizing lithium hexafluorophosphate, hydrofluoric acid can be discharged from the fourth cyclone separator 13 through the impurity outlet, and lithium hexafluorophosphate is deposited at the bottom of the fourth cyclone separator 13, and lithium hexafluorophosphate crystals can be collected through the fourth discharge port.

[0034] The crystallization device 100 proposed in the present application has the following advantages: ① Segmented control of crystallization temperature: by respectively arranging temperature control components on the first cyclone separator 3, the second cyclone separator 7 and the third cyclone separator 11, the temperature of the three-stage cyclone separators can be independently controlled to achieve three-stage continuous cooling, effectively utilizing the solubility difference of crystals at different temperatures, promoting the orderly growth of crystals, and controlling the particle size of crystals; ② Optimizing mass transfer and mixing: by introducing Taylor flow crystallization technology, a high-speed fluid is sprayed into the cyclone device to form a special flow field environment, so that the solution forms a stable and efficient mass transfer interface during high-speed rotation, thereby enhancing The uniform mixing of the components within the solution ensures the consistency of nucleation and crystal growth; ③ Efficient graded crystallization: Through the design of a unique multi-stage cyclone separation structure, light and heavy components can be effectively separated at different cooling stages, which not only reduces the impurity content, but also realizes crystal grading based on density and solubility differences; ④ Improve yield and purity: By introducing Taylor flow crystallization technology, the separation effect between solute and solvent can be optimized, and the coating of impurities on the surface of the nucleus or inside the crystal can be reduced, thereby effectively reducing the insoluble content in the final product, significantly improving the purity and yield of the crystal, and reducing production costs and energy consumption.

[0035] According to some embodiments of the present application, the first temperature control component, the second temperature control component and the third temperature control component can be independently temperature control jackets.

[0036] According to some embodiments of the present application, -5°C≤T1≤20°C, for example, it can be -5°C, 0°C, 5°C, 10°C, 15°C or 20°C, etc., or it can be a range consisting of any of the above numerical values.

[0037] According to some embodiments of the present application, -20°C ≤ T2 ≤ -5°C, for example, it can be -20°C, -15°C, -10°C or -5°C, etc., or can be a range consisting of any of the above numerical values.

[0038] According to some embodiments of the present application, -40°C ≤ T3 ≤ -20°C, for example, it can be -40°C, -35°C, -30°C, -25°C or -20°C, etc., or can be a range consisting of any of the above numerical values.

[0039] Therefore, through three-stage continuous and precise cooling during the crystallization process, the solubility difference of crystals at different temperatures is effectively utilized to promote the orderly growth and size control of crystals and improve the uniformity of crystal particle size.

[0040] It should be noted that those skilled in the art can select the specific temperatures of T1, T2 and T3 according to the type of crystal.

[0041] According to some embodiments of the present application, reference Figure 2-Figure 4, the size of the first slit 41 can be a, the size of the second slit 81 can be b, and the size of the third slit 121 can be c, and they satisfy: a>b>c. Thus, during the crystallization process, the size of the Taylor slits decreases step by step, the turbulence degree of the solution when entering the second slit 81 is greater than the turbulence degree when entering the first slit 41, and the turbulence degree of the solution when entering the third slit 121 is greater than the turbulence degree when entering the second slit 81. As the turbulence degree increases, the crystallization efficiency increases, thereby achieving a step-by-step optimization from primary nucleation to crystal growth, and improving the uniformity of mass transfer and crystal growth.

[0042] According to some embodiments of the present application, reference Figure 2 , 5mm≤a≤10mm, for example, it can be 5mm, 6mm, 7mm, 8mm, 9mm or 10mm, etc., or it can be a range consisting of any of the above values.

[0043] According to some embodiments of the present application, reference Figure 3 , 3mm≤b≤5mm, for example, it can be 3mm, 3.5mm, 4mm, 4.5mm or 5mm, etc., or it can be a range consisting of any of the above values.

[0044] According to some embodiments of the present application, reference Figure 4 , 1mm≤c≤3mm, for example, it can be 1mm, 1.5mm, 2mm, 2.5mm or 3mm, etc., or it can be a range consisting of any of the above values.

[0045] It should be noted that those skilled in the art can select specific sizes of the first slit 41 , the second slit 81 and the third slit 121 according to the type of crystal.

[0046] According to some embodiments of the present application, the first cyclone, the second cyclone, and the third cyclone are all provided with the impurity outlet. Impurities separated in the cyclone separator can be directly discharged through the impurity outlet, thereby improving the purity of the crystal.

[0047] According to some embodiments of the present application, reference Figure 1 The crystallization device 100 further includes a precooler 1, the precooler 1 includes a precooling chamber, the precooler 1 includes a fifth feed port and a fifth discharge port, and the fifth discharge port is connected to the first feed port. The solution can be precooled in the precooler 1 before entering the first cyclone separator 3, thereby shortening the cooling time in the first cyclone separator 3 and improving the crystallization efficiency.

[0048] As an example, the temperature of the solution after being cooled by the precooler 1 may be 0°C-5°C.

[0049] As an example, the precooling time may be 3s-20s, for example, 3s, 5s, 10s, 15s or 20s, etc., or may be a range consisting of any of the above values.

[0050] As an example, the pressure in the precooler 1 may be 0-0.6 MPa, for example, 0 MPa, 0.3 MPa, 0.6 MPa, etc., or may be in a range consisting of any of the above values.

[0051] According to some embodiments of the present application, reference Figure 1 , the first cyclone separator 3 includes a first motor 2, the second cyclone separator 7 includes a second motor 6, and the third cyclone separator 11 includes a third motor 10, and the first motor 2, the second motor 6 and the third motor 10 are independently controlled. Therefore, the first motor 2, the second motor 6 and the third motor 10 are independently controlled, and the Taylor flow in the first cyclone separator 3, the second cyclone separator 7 and the third cyclone separator 11 can be controlled respectively to meet the crystallization requirements of different crystallization stages, realize the step-by-step optimization from primary nucleation to crystal growth, and enhance the uniformity of mass transfer and crystal growth.

[0052] According to some embodiments of the present application, reference Figure 1 The crystallization device 100 further includes: a first liquid receiving tray 5, the first liquid receiving tray 5 is connected to the first discharge port and the second feed port respectively; a second liquid receiving tray 9, the second liquid receiving tray 9 is connected to the second discharge port and the third feed port respectively. Specifically, the solution in the first Taylor crystallizer 4 enters the second cyclone separator 7 after passing through the first liquid receiving tray 5, and the solution in the second Taylor crystallizer 8 enters the third cyclone separator 11 after passing through the second liquid receiving tray 9.

[0053] The second aspect of the present application proposes a method for crystallization using the crystallization device 100 proposed in the first aspect of the present application, the method comprising: (1) allowing the solution to be crystallized to enter the first cyclone barrel of the first cyclone separator 3 through the first feed port, and after being accelerated, forming a Taylor flow and entering the first slit 41 of the first Taylor crystallizer 4 for a first crystallization treatment; (2) after the first crystallization, allowing the solution obtained in step (1) to enter the second cyclone barrel of the second cyclone separator 7 through the second feed port, and after being accelerated, forming a Taylor flow and entering the second slit 81 of the second Taylor crystallizer 8 for a second crystallization treatment, The temperature during the second crystallization is lower than the temperature during the first crystallization; (3) after the second crystallization, the solution obtained in step (2) enters the third cyclone barrel of the third cyclone separator 11 through the third feed port, and after acceleration, forms a Taylor flow and enters the third slit 121 of the third Taylor crystallizer 12 for a third crystallization treatment, and the temperature of the third crystallization is lower than the temperature of the second crystallization; (4) after the third crystallization, the solution obtained in step (3) enters the fourth cyclone barrel of the fourth cyclone separator 13 through the fourth feed port for separation, and collects crystals through the fourth discharge port. Therefore, the method for crystallization can improve the purity of the crystal, accurately control the particle size of the crystal, improve the efficiency of crystallization, and reduce production costs and energy consumption.

[0054] The following is a detailed description of this method using lithium hexafluorophosphate as an example:

[0055] The crude solution containing lithium hexafluorophosphate enters the first cyclone separator 3 and is accelerated and cooled in the first cyclone separator 3 before entering the first Taylor crystallizer 4. The first crystallization treatment is performed in the first slit 41 to perform initial nucleation. After the first crystallization treatment, the solution enters the second cyclone separator 7 and is accelerated and cooled in the second cyclone separator 7 before entering the second Taylor crystallizer 8. The second crystallization treatment is performed in the second slit 81. The temperature of the second crystallization treatment is lower than the temperature of the first crystallization treatment. The lower temperature promotes the continuous growth of the crystals without condensing too quickly, thereby obtaining crystals with more uniform particle size distribution. After the second crystallization treatment, the solution enters the third cyclone separator 7. The solution enters the third Taylor crystallizer 12 after being accelerated and cooled in the third cyclone separator 11, and undergoes a third crystallization treatment in the third slit 121. The temperature of the third crystallization treatment is lower than that of the second crystallization treatment. The lower temperature promotes the continuous growth of the crystal. The lithium hexafluorophosphate crystals undergo the most efficient growth and size optimization process during the third crystallization treatment. After the third crystallization treatment, the solution enters the fourth cyclone separator 13. Under the action of centrifugal force, hydrofluoric acid is discharged from the impurity outlet. The solution containing lithium hexafluorophosphate crystals is deposited at the bottom of the fourth cyclone separator 13 under the dual action of gravity and centrifugal force, and the lithium hexafluorophosphate crystals are collected through the fourth discharge port.

[0056] According to some embodiments of the present application, reference Figure 1 , the first cyclone separator 3 includes a first motor 2, the second cyclone separator 7 includes a second motor 6, and the third cyclone separator 11 includes a third motor 10. The rotation speed of the first motor 2 is 500rpm-1000rpm, the rotation speed of the second motor 6 is 1000rpm-1500rpm, and the rotation speed of the third motor 10 is 1500rpm-2000rpm. Specifically, in the process of preparing lithium hexafluorophosphate crystals, the Taylor flow in the first cyclone separator 3 is driven by the first motor 2, the Taylor flow in the second cyclone separator 7 is driven by the second motor 6, and the Taylor flow in the third cyclone separator 11 is driven by the third motor 10. According to the requirements of different crystallization stages, the rotation speed of the motor is different. From primary nucleation to crystal growth, the motor speed gradually increases, thereby enhancing the uniformity of mass transfer and crystal growth.

[0057] As an example, the rotation speed of the first motor 2 may be 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm or 1000 rpm, etc., or may be a range consisting of any of the above values.

[0058] As an example, the rotation speed of the second motor 6 may be 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, 1400 rpm or 1500 rpm, etc., or may be a range consisting of any of the above values.

[0059] As an example, the rotation speed of the third motor 10 may be 1500 rpm, 1600 rpm, 1700 rpm, 1800 rpm, 1900 rpm or 2000 rpm, etc., or may be a range consisting of any of the above numerical values.

[0060] According to some embodiments of the present application, the time of the first crystallization treatment, the time of the second crystallization treatment, and the time of the third crystallization treatment are each independently less than or equal to 5 minutes, thereby improving the efficiency of crystallization.

[0061] According to some embodiments of the present application, the method may further include: precooling the solution to be crystallized before the solution to be crystallized enters the first cyclone. Specifically, the solution to be crystallized may be precooled by the precooler 1 before entering the first cyclone separator 3, and the cooled solution enters the first cyclone separator 3, which can reduce the time of the first crystallization process.

[0062] According to some embodiments of the present application, the method is a crystallization method for preparing lithium hexafluorophosphate crystals. Specifically, the method for preparing lithium hexafluorophosphate crystals may include: pre-treating a crude solution containing lithium hexafluorophosphate, filtering to remove mechanical impurities; pumping the pre-treated solution into a precooler 1 to cool the solution to 0°C-5°C, and the pressure in the precooler 1 may be 0-0.6MPa; then, the cooled solution is introduced into a first cyclone separator 3, and the first cyclone separator 3 is cooled by a first temperature control component, and the temperature of the first temperature control component may be -5°C-20°C, and the liquid is accelerated to enter the first slit 41 of the first Taylor crystallizer 4 for a first crystallization treatment, and the size of the first slit 41 is 5mm-10mm, and the speed of the first motor 2 may be 500rpm-1000rpm; after the first crystallization treatment, the solution enters a second cyclone separator 7, and the second cyclone separator 7 is cooled by a second temperature control component, and the temperature of the second temperature control component may be -20°C--5°C, and the solution enters the second of the second Taylor crystallizer 8 after acceleration. A second crystallization treatment is carried out in the slit 81, the size of the second slit 81 can be 3mm-5mm, and the rotation speed of the second motor 6 can be 1000rpm-1500rpm; after the second crystallization treatment, the solution enters the third cyclone separator 11, and the third cyclone separator 11 is cooled by the third temperature control component, and the temperature of the third temperature control component can be -40℃--20℃. After acceleration, the solution enters the third slit 121 of the third Taylor crystallizer 12 for a third crystallization treatment, the size of the third slit 121 can be 1mm-3mm, and the rotation speed of the third motor 10 can be 1500rpm-2000rpm; after the third crystallization treatment, the liquid enters the fourth cyclone separator 13, and under the action of centrifugal force, hydrofluoric acid is discharged from the impurity outlet, and the solution containing lithium hexafluorophosphate crystals is deposited at the bottom of the fourth cyclone separator 13 under the dual action of gravity and centrifugal force, and the lithium hexafluorophosphate crystals are collected through the fourth discharge port.

[0063] According to some embodiments of the present application, the volume average particle size Dv50 of the lithium hexafluorophosphate crystals obtained by the method proposed in the present application is 240μm-340μm, the purity of the lithium hexafluorophosphate is 99.9%-99.99%, and the acidity of the lithium hexafluorophosphate is less than or equal to 15ppm.

[0064] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. If no specific techniques or conditions are specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used that do not specify the manufacturer are all conventional products that can be obtained commercially.

[0065] Example 1

[0066] The crude solution containing lithium hexafluorophosphate is filtered, and the pretreated solution is pumped into the precooler to quickly reduce the solution temperature to 0°C while maintaining the pressure in the system at 0.3MPa. The cooled solution is introduced into the first cyclone separator, and the liquid is accelerated into the first slit where the inner cylinder rotates and the outer cylinder is stationary. The size of the first slit is set to 8mm, the temperature of the first temperature control jacket is -5°C, the first motor speed is 800rpm, and the time is 4.5min. The solution after the first crystallization treatment enters the second cyclone separator through the first liquid receiving tray, the temperature of the second temperature control component is -15°C, the size of the second slit is reduced to 5mm, the second motor speed is 1200rpm, and the time is 4min. The solution after the second crystallization treatment enters the third cyclone separator, the temperature of the third temperature control component is -30°C, the third slit is further reduced to 3mm, the third motor speed is 1600rpm, and the time is 4min; the liquid after the third crystallization treatment enters the fourth cyclone separator tangentially through the baffle, and the hydrofluoric acid is discharged from the top of the system under the action of strong centrifugal force, while the wet material containing lithium hexafluorophosphate crystals is deposited at the bottom under the dual action of gravity and centrifugal force and collected through the fourth receiving port.

[0067] The crystallization methods of lithium hexafluorophosphate in Examples 2 to 13 and Comparative Examples 1 to 6 are the same as those in Example 1, and the differences are detailed in Table 1.

[0068] Table 1

[0069]

[0070] Performance Testing

[0071] 1. Lithium hexafluorophosphate purity test method

[0072] The content of lithium hexafluorophosphate was measured using ICP.

[0073] 2. Lithium hexafluorophosphate acidity test method

[0074] Coulometric titration was performed.

[0075] 3. Lithium hexafluorophosphate size test method

[0076] Laser particle size analyzer was used.

[0077] The test results of lithium hexafluorophosphate in Examples 1 to 13 and Comparative Examples 1 to 6 are shown in Table 2.

[0078] Table 2

[0079]

[0080]

[0081] It can be seen from the comparison between Examples 1 to 13 and Comparative Examples 1 to 6 that the lithium hexafluorophosphate obtained by the crystallization device proposed in the present application has higher purity, larger Dv50 and lower acidity, indicating that the present application can promote the orderly growth of crystals, control the particle size of crystals, enhance the mixing uniformity of the components inside the solution, and improve the purity of the product through segmented crystallization and segmented control of crystallization temperature.

[0082] It can be seen from the comparison between Examples 1 to 13 and Comparative Example 1 that the two-stage crystallization has limited improvement on the purity and acidity of lithium hexafluorophosphate. The present application can significantly improve the purity of lithium hexafluorophosphate, increase the Dv50 of lithium hexafluorophosphate, and reduce the acidity of lithium hexafluorophosphate by three consecutive cooling crystallizations.

[0083] It can be seen from the comparison between Examples 1 to 13 and Comparative Examples 2 to 6 that when three-stage crystallization is adopted, by making T1>T2>T3, the purity of lithium hexafluorophosphate can be significantly improved, the Dv50 of lithium hexafluorophosphate can be increased, and the acidity of lithium hexafluorophosphate can be reduced. This shows that the present application can effectively utilize the solubility difference of crystals at different temperatures by adopting three-stage continuous cooling, promote the orderly growth of crystals, control the particle size of crystals, enhance the mixing uniformity of various components in the solution, and achieve efficient fractional crystallization.

[0084] It can be seen from Examples 7 to 12 that, under the premise of segmented crystallization and controlling the temperature of segmented crystallization, by selecting different first slit sizes, second slit sizes and third slit sizes, lithium hexafluorophosphate with higher purity, larger Dv50 and lower acidity can be obtained.

[0085] It can be seen from Examples 7 to 13 that whether the first slit size, the second slit size and the third slit size are the same or different, lithium hexafluorophosphate with higher purity, larger Dv50 and lower acidity can be obtained.

[0086] In the present invention, unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0087] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A crystallization device, characterized in that: include: A first cyclone separator, wherein the first cyclone separator comprises a first cyclone barrel, the first cyclone barrel has a first feed inlet and a first discharge outlet, and the first cyclone separator is provided with a first temperature control element; A first Taylor crystallizer, wherein the first Taylor crystallizer comprises a first inner cylinder and a first outer cylinder, a first slit is formed between the first inner cylinder and the first outer cylinder, and the first slit is communicated with the first discharge port; A second cyclone separator, wherein the second cyclone separator comprises a second cyclone barrel, the second cyclone barrel has a second feed inlet and a second discharge outlet, the second feed inlet is connected to the first discharge outlet, and a second temperature control element is provided on the second cyclone separator; A second Taylor crystallizer, wherein the second Taylor crystallizer comprises a second inner cylinder and a second outer cylinder, a second slit is formed between the second inner cylinder and the second outer cylinder, and the second slit is communicated with the second discharge port; A third cyclone separator, the third cyclone separator comprising a third cyclone barrel, the third cyclone barrel having a third feed inlet and a third discharge outlet, the third feed inlet being connected to the second discharge outlet, and the third cyclone separator being provided with a third temperature control element; A third Taylor crystallizer, the third Taylor crystallizer comprises a third inner cylinder and a third outer cylinder, a third slit is formed between the third inner cylinder and the third outer cylinder, and the third slit is communicated with the third discharge port; A fourth cyclone separator, the fourth cyclone separator comprising a fourth cyclone barrel, the fourth cyclone barrel having a fourth feed inlet, a fourth discharge outlet and an impurity outlet; The temperature of the first temperature control component is T1, the temperature of the second temperature control component is T2, the temperature of the third temperature control component is T3, and the following conditions are satisfied: T1>T2>T3.

2. The crystallization device according to claim 1, characterized in that Satisfy at least one of the following conditions: -5℃≤T1≤20℃； -20℃≤T2≤-5℃； -40℃≤T3≤-20℃。 3. The crystallization device according to claim 2, characterized in that: The size of the first slit is a, the size of the second slit is b, and the size of the third slit is c, and they satisfy: a>b>c.

4. The crystallization device according to claim 3, characterized in that 5mm≤a≤10mm, 3mm≤b≤5mm, 1mm≤c≤3mm.

5. The crystallization device according to claim 1, characterized in that: The first cyclone barrel, the second cyclone barrel and the third cyclone barrel are all provided with the impurity outlet.

6. The crystallization device according to any one of claims 1 to 5, characterized in that: Also includes: A precooler, the precooler includes a precooling chamber, the precooler includes a fifth feed port and a fifth discharge port, and the fifth discharge port is connected to the first feed port.

7. The crystallization device according to any one of claims 1 to 5, characterized in that: The first cyclone separator includes a first motor, the second cyclone separator includes a second motor, and the third cyclone separator includes a third motor. The first motor, the second motor, and the third motor are independently controlled.

8. The crystallization device according to any one of claims 1 to 5, characterized in that: Also includes: A first liquid receiving pan, the first liquid receiving pan being connected to the first discharge port and the second feed port respectively; A second liquid receiving pan, wherein the second liquid receiving pan is connected to the second discharge port and the third feed port respectively.

9. A method for crystallization using the crystallization device according to any one of claims 1 to 8, characterized in that: include: (1) allowing the solution to be crystallized to enter the first cyclone barrel of the first cyclone separator through the first feed inlet, and after being accelerated, forming a Taylor flow, entering the first slit of the first Taylor crystallizer for the first crystallization treatment; (2) After the first crystallization, the solution obtained in step (1) enters the second cyclone of the second cyclone separator through the second feed port, and after being accelerated, forms a Taylor flow and enters the second slit of the second Taylor crystallizer for a second crystallization treatment, wherein the temperature during the second crystallization treatment is lower than the temperature during the first crystallization treatment; (3) After the second crystallization, the solution obtained in step (2) enters the third cyclone barrel of the third cyclone separator through the third feed port, and after being accelerated, forms a Taylor flow and enters the third slit of the third Taylor crystallizer for a third crystallization treatment, wherein the temperature of the third crystallization treatment is lower than the temperature of the second crystallization treatment; (4) After the third crystallization treatment, the solution obtained in step (3) is passed through a fourth feed port into a fourth cyclone drum of a fourth cyclone separator for separation, and crystals are collected through a fourth discharge port.

10. The method according to claim 9, characterized in that The first cyclone separator includes a first motor, the second cyclone separator includes a second motor, and the third cyclone separator includes a third motor. The rotation speed of the first motor is 500rpm-1000rpm, the rotation speed of the second motor is 1000rpm-1500rpm, and the rotation speed of the third motor is 1500rpm-2000rpm.

11. The method according to claim 9, characterized in that The time of the first crystallization treatment, the time of the second crystallization treatment and the time of the third crystallization treatment are each independently less than or equal to 5 minutes.

12. The method according to any one of claims 9 to 11, characterized in that: Further including: Before the solution to be crystallized enters the first cyclone, the solution to be crystallized is precooled.

13. The method according to any one of claims 9 to 11, characterized in that: The method is a crystallization method for preparing lithium hexafluorophosphate crystals.

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