A lithium hexafluorophosphate continuous dynamic crystallization device and crystallization method

Abstract

The present invention belongs to the technical field of battery electrolytes and relates to a continuous dynamic crystallization device for lithium hexafluorophosphate and a crystallization method thereof. The crystallization device mainly adopts a cylindrical coil crystallization device. A crystallization coil is arranged inside a crystallization cylinder so that lithium hexafluorophosphate material flows in a spiral inside the crystallization coil. Eddy currents are generated at the cross section of the crystallization coil. The formation of the eddy currents enhances radial mixing of the fluid and can reduce residence time distribution. Therefore, the particle size distribution of the generated crystals is narrower, and dynamic continuous crystallization production of lithium hexafluorophosphate can be realized, thereby obtaining high-purity lithium hexafluorophosphate crystals with uniform crystal size distribution and stable output.

Description

Technical Field

[0001] The present invention relates to the technical field of battery electrolytes, in particular to the technical field of lithium hexafluorophosphate, and in particular to a lithium hexafluorophosphate continuous dynamic crystallization device and a crystallization method thereof. Background Art

[0002] Lithium hexafluorophosphate (LiPF6), a core component of lithium-ion battery electrolytes, is a key material due to its excellent ion transport capabilities, outstanding temperature resistance, and chemical compatibility. Amid the rapid development of electric vehicles, energy storage devices, and consumer electronics, market demand for high-energy-density, long-cycle-life batteries continues to grow, further driving industry demand for high-purity LiPF6.

[0003] Traditional crystallization processes mostly use intermittent operation modes, which have the disadvantages of long production cycles and insufficient batch stability, which directly affect the uniformity of electrolyte performance. This type of production method will also lead to increased energy consumption and overall costs due to repeated starting and stopping of equipment. In contrast, the continuous dynamic crystallization process can achieve continuous production throughout the entire process through continuous material flow and precise parameter control, greatly improving production capacity per unit time and shortening equipment idle cycles. This technology uses real-time monitoring to ensure uniform crystal particle size distribution, ensuring product quality stability from the source. The continuous operation mode can also significantly reduce unit energy consumption through thermodynamic optimization, and combine with automated control systems to reduce human operation errors, thereby improving production safety factors and process repeatability.

[0004] CN112340754A discloses a method for producing high-purity, uniform crystals with a narrow size distribution (10-230 μm) and no agglomeration by combining step-by-step stirring (primary stirring + secondary stirring) with ultrasonic-assisted dynamic crystallization, along with precise temperature control and gas drying. However, the equipment is complex and energy-intensive, with strict requirements on parameters such as stirring rate and dripping rate. Operating errors can easily lead to fluctuations in crystal quality.

[0005] CN108147386A discloses dynamic fractional crystallization achieved through multiple temperature cycles. This method, which requires no complex equipment and allows stable control of crystal growth through repeated temperature cycles, has a low operational threshold. However, it is time-consuming, significantly extending the total production cycle, and relies solely on temperature changes and stirring. Crystal uniformity is inferior to that achieved by ultrasonic-assisted methods. Furthermore, the method does not mention the recycling of mother liquor, which may increase raw material waste.

[0006] CN117466313A discloses combining mother liquor recycling with temperature cycling to optimize LiF precursor preparation. The mother liquor is reused in the reaction step, reducing raw material consumption and lowering costs. LiF microcrystallization is used to increase reaction activity and improve LiPF6 purity. However, the process is complex and requires simultaneous control of LiF microcrystallization and LiPF6 crystallization. The multi-step collaboration increases management difficulty. In addition, multiple temperature cycles are required to achieve the target purity, which is less efficient than single ultrasonic-assisted crystallization. Mother liquor reuse requires additional piping and filtration systems, increasing maintenance costs.

[0007] At present, the industrial crystallization process of lithium hexafluorophosphate mainly relies on an intermittent static operation mode, and its limitations are reflected in many aspects. Due to the lack of a continuous control mechanism during the crystallization process, the nucleation and growth of the crystals are easily affected by local environmental fluctuations, resulting in poor crystal regularity and a wide particle size distribution, which in turn weakens the batch stability of the product and downstream application performance. In addition, intermittent production requires frequent interruption of equipment operation to complete discharging and cleaning operations, which not only prolongs the production cycle, but also causes additional energy loss due to repeated start and stop of the equipment. In comparison, dynamic crystallization technology can significantly increase production capacity and optimize crystal quality by introducing a continuous process flow. However, the existing dynamic crystallization process still has problems such as insufficient equipment mass transfer efficiency and lack of accuracy of key parameters. It is necessary to achieve fine adjustment of process parameters and improve process stability through means such as optimizing flow channel structure design.

[0008] Therefore, it is necessary to develop a novel lithium hexafluorophosphate continuous dynamic crystallization device and a crystallization method thereof. Summary of the Invention

[0009] In view of the problems existing in the prior art, the present invention provides a continuous dynamic crystallization device for lithium hexafluorophosphate and a crystallization method thereof. The crystallization device mainly adopts a cylindrical coil crystallization device. A crystallization coil is arranged inside the crystallization cylinder, so that the lithium hexafluorophosphate material flows spirally inside the crystallization coil, and vortices are generated at the cross-section of the crystallization coil. The formation of the vortex enhances the radial mixing of the fluid and can reduce the residence time distribution. Therefore, the generated crystal particle size distribution is narrower, and dynamic continuous crystallization production of lithium hexafluorophosphate can be realized, and high-purity lithium hexafluorophosphate crystals with uniform crystal particle size distribution and stable output are obtained.

[0010] To achieve this object, the present invention adopts the following technical solutions:

[0011] One of the purposes of the present invention is to provide a lithium hexafluorophosphate continuous dynamic crystallization device, which includes a precooling device, a cylindrical coil crystallization device and a separation device connected in sequence.

[0012] The cylindrical coil crystallization device includes a crystallization cylinder, and a crystallization coil is arranged inside the crystallization cylinder, so that the lithium hexafluorophosphate material flows spirally inside the crystallization coil; along the flow direction of the lithium hexafluorophosphate material, the inner cavity of the crystallization cylinder is divided into at least two crystallization temperature control zones, and each of the crystallization temperature control zones is respectively provided with a mutually independent refrigerant inlet and outlet, so that along the flow direction of the lithium hexafluorophosphate material, the temperature of the two adjacent crystallization temperature control zones decreases successively; the crystallization coils of the two adjacent crystallization temperature control zones are connected by a quasi-right-angle pipe.

[0013] The lithium hexafluorophosphate continuous dynamic crystallization device described in the present invention primarily achieves the production of high-quality lithium hexafluorophosphate crystals by optimizing flow field control. Specifically, the lithium hexafluorophosphate material is first introduced into a pre-cooling device for pre-cooling treatment, and then introduced into a cylindrical coil crystallization device. The spiral flow channel design of the crystallization coil induces a radial vortex effect in the cross-section of the tube, significantly enhancing the fluid mixing uniformity and narrowing the material residence time distribution, thereby achieving precise control of the crystal particle size. Finally, the solid-liquid mixture after crystallization is subjected to sedimentation separation and filtration in a separation device. The resulting solid phase material is then dried to obtain high-purity lithium hexafluorophosphate crystals with uniform particle size.

[0014] As a preferred technical solution of the present invention, the precooling device includes a precooling kettle.

[0015] And / or, a pressurized peristaltic device is provided between the pre-cooling device and the cylindrical coil crystallization device.

[0016] And / or, a seeding port is provided on the crystallization coil corresponding to the first crystallization temperature control zone along the flow direction of the lithium hexafluorophosphate material. In actual operation, lithium hexafluorophosphate seed crystals can be selectively added, with the mass of the lithium hexafluorophosphate seed crystals being 0.1-0.5% of the mass of the lithium hexafluorophosphate in the precooling liquid after the precooling treatment.

[0017] And / or, the separation device comprises a horizontal spiral centrifuge. In actual operation, the rotation speed of the horizontal spiral centrifuge is 1000 rpm to 2000 rpm.

[0018] And / or, a mother liquor tank is provided at the liquid outlet of the separation device for collecting the crystallization mother liquor and circulating it to the lithium hexafluorophosphate production process.

[0019] As a preferred technical solution of the present invention, the crystallization coil in a particular crystallization temperature control zone is divided into at least two sections of crystallization secondary coils, with adjacent sections of the crystallization secondary coils connected by a quasi-right-angle pipe. For example, the crystallization coil in a particular crystallization temperature control zone is bent 90 degrees twice at equal intervals along the flow direction of the lithium hexafluorophosphate material, forming a C-shape, thereby dividing the crystallization secondary coils into three sections of equal length. This changes the direction of the centrifugal force, generating vortices at the cross-section of the tube, enhancing radial mixing of the fluid and reducing the residence time distribution.

[0020] Experimental verification shows that compared with conventional curved pipes, artificially set right-angle pipes can enhance the vortex effect, strengthen the radial mixing of the fluid, and reduce the residence time distribution, thus producing a narrower crystal particle size distribution.

[0021] As a preferred technical solution of the present invention, it is characterized in that the angle of the right-angle-like pipe is 60 to 90 degrees, such as 60 degrees, 65 degrees, 70 degrees, 75 degrees, 80 degrees, 85 degrees or 90 degrees.

[0022] As a preferred technical solution of the present invention, an ultrasonic transducer is provided on the outside of the crystallization cylinder, corresponding to the position of the quasi-right-angle pipe. Through high-frequency vibration, scaling on the inner wall of the pipe can be effectively suppressed, thereby ensuring the continuous and stable operation of the crystallization process.

[0023] Alternatively, a nitrogen inlet may be provided in the quasi-right-angle pipe to introduce nitrogen to enhance vortex flow. Nitrogen is introduced into the crystallization coil, and the flow rate is varied to control the fluid state within the coil. This results in uniform bubbles in the fluid, which not only regulates the crystal size distribution but also prevents pipe clogging. Typically, the nitrogen inlet flow rate is controlled at 0.5-5 L / min.

[0024] It should be noted that the setting of the right-angle pipe can easily lead to the retention of crystal particles and even cause crystal scale on the inner wall of the pipe. Therefore, the introduction of ultrasound and / or nitrogen can not only avoid the retention of crystal particles, but also enhance the eddy current effect.

[0025] A second object of the present invention is to provide a method for continuous dynamic crystallization of lithium hexafluorophosphate, wherein the method uses the lithium hexafluorophosphate continuous dynamic crystallization device described in the first object and comprises the following steps:

[0026] (1) adding lithium hexafluorophosphate material to a precooling device for precooling to obtain a precooling liquid;

[0027] (2) transporting the pre-cooling liquid of step (1) to the crystallization coil, so that the lithium hexafluorophosphate material flows in a spiral manner inside the crystallization coil, and is gradually cooled through at least two crystallization temperature control zones, thereby precipitating lithium hexafluorophosphate crystals and obtaining a crystal liquid;

[0028] (3) The crystal liquid in step (2) is transported to a separation device to obtain lithium hexafluorophosphate crystals through separation.

[0029] It should be noted that the lithium hexafluorophosphate material refers to the lithium hexafluorophosphate reaction solution obtained by the reaction, such as the lithium hexafluorophosphate anhydrous hydrogen fluoride solution obtained by the reaction.

[0030] The lithium hexafluorophosphate continuous dynamic crystallization method described in the present invention introduces the lithium hexafluorophosphate material into a pre-cooling device for preliminary cooling. This pre-cooling treatment can effectively narrow the temperature control range in the crystallization stage, thereby reducing the energy consumption load and hardware cost of the temperature control equipment. During the crystallization process, the spiral flow channel structure induces a radial vortex effect in the coil cross section, which significantly narrows the residence time distribution of the material in the crystallizer by enhancing the radial mixing uniformity of the fluid, thereby achieving precise control of the crystal particle size. After the crystallization is completed, the solid-liquid mixed phase is subjected to sedimentation, filtration and drying to finally obtain a high-purity lithium hexafluorophosphate product with uniform particle size.

[0031] As a preferred technical solution of the present invention, the mass concentration of lithium hexafluorophosphate in the lithium hexafluorophosphate material in step (1) is 10-30%, for example, 10%, 13%, 15%, 18%, 20%, 22%, 25%, 27% or 30%.

[0032] And / or, the temperature of the pre-cooling treatment in step (1) is 0-5°C, such as 0°C, 1°C, 2°C, 3°C, 4°C or 5°C.

[0033] And / or, stirring is performed during the pre-cooling treatment in step (1), and the stirring speed is 50-150 rpm, for example, 50 rpm, 60 rpm, 80 rpm, 100 rpm, 110 rpm, 130 rpm or 150 rpm.

[0034] As a preferred technical solution of the present invention, three crystallization temperature control intervals are set in step (2), the temperature of the first crystallization temperature control interval is 0~-10℃, for example, 0℃, -1℃, -3℃, -5℃, -6℃, -8℃ or -10℃, etc., the temperature of the second crystallization temperature control interval is -10~-15℃, for example, -10℃, -11℃, -12℃, -13℃, -14℃ or -15℃, etc., and the temperature of the third crystallization temperature control interval is -15~-20℃, for example, -15℃, -16℃, -17℃, -18℃, -19℃ or -20℃, etc.

[0035] As a preferred technical solution of the present invention, the speed of the spiral flow in step (2) is 200~500g / min, for example, 200g / min, 250g / min, 300g / min, 350g / min, 400g / min, 450g / min or 500g / min.

[0036] And / or, the crystallization coils in two adjacent crystallization temperature control zones are connected by quasi-right-angle pipes, and ultrasonic transducers are correspondingly arranged, and the frequency of the ultrasonic transducer is 20~80Hz, for example, 20Hz, 30Hz, 40Hz, 50Hz, 60Hz, 70Hz or 80Hz.

[0037] Compared with the existing technical solutions, the present invention has at least the following beneficial effects:

[0038] (1) The present invention provides a continuous dynamic crystallization device for lithium hexafluorophosphate. The crystallization device mainly adopts a cylindrical coil crystallization device. A crystallization coil is arranged inside the crystallization cylinder, so that the lithium hexafluorophosphate material flows spirally inside the crystallization coil. A vortex is generated at the cross section of the crystallization coil. The formation of the vortex enhances the radial mixing of the fluid and can reduce the residence time distribution. Therefore, the generated crystal particle size distribution is narrower, so that the lithium hexafluorophosphate crystal particle size D50 is 120~220μm, which can realize the dynamic continuous crystallization production of lithium hexafluorophosphate and obtain high-purity lithium hexafluorophosphate crystals with uniform crystal particle size distribution and stable output.

[0039] (2) In the crystallization device of the present invention, the design of the quasi-right-angle pipeline can further enhance the vortex effect, strengthen the radial mixing of the fluid, and reduce the residence time distribution, so that the resulting crystal particle size distribution is narrower; since the setting of the quasi-right-angle pipeline is prone to cause the retention of crystal particles and even cause crystal scale on the inner wall of the tube, the introduction of ultrasonic waves and / or nitrogen can not only avoid the retention of crystal particles, but also enhance the vortex effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the structure of the continuous dynamic crystallization device of lithium hexafluorophosphate described in Example 1 of the present invention.

[0041] Figure 2 It is a structural schematic diagram of the cylindrical coil crystallization device in the continuous dynamic crystallization device of lithium hexafluorophosphate described in Example 2 of the present invention.

[0042] Figure 3 It is a structural schematic diagram of the cylindrical coil crystallization device in the continuous dynamic crystallization device of lithium hexafluorophosphate described in Example 3 of the present invention.

[0043] Figure 4It is a structural schematic diagram of the cylindrical coil crystallization device in the continuous dynamic crystallization device of lithium hexafluorophosphate described in Example 4 of the present invention.

[0044] In the figure: 1-pre-cooling kettle; 2-nitrogen inlet; 3-ultrasonic transducer; 4-seed crystal addition port; 5-horizontal spiral centrifuge; 6-mother liquor tank. DETAILED DESCRIPTION

[0045] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.

[0046] To better illustrate the present invention and facilitate understanding of the technical solutions of the present invention, typical but non-limiting embodiments of the present invention are as follows:

[0047] Example 1

[0048] This embodiment provides a lithium hexafluorophosphate continuous dynamic crystallization device, which includes a pre-cooling device, a cylindrical coil crystallization device, and a separation device connected in sequence.

[0049] Among them, the cylindrical coil crystallization device includes a crystallization cylinder, and a crystallization coil is arranged inside the crystallization cylinder, so that the lithium hexafluorophosphate material flows spirally inside the crystallization coil; along the flow direction of the lithium hexafluorophosphate material, the inner cavity of the crystallization cylinder is divided into three crystallization temperature control zones, and each of the crystallization temperature control zones is respectively provided with an independent refrigerant inlet and outlet, so that along the flow direction of the lithium hexafluorophosphate material, the temperature of the two adjacent crystallization temperature control zones decreases successively.

[0050] like Figure 1 As shown, the pre-cooling device includes a pre-cooling kettle 1; a pressurized peristaltic device is provided between the pre-cooling device and the cylindrical coil crystallization device; a seed feeding port 4 is provided on the crystallization coil corresponding to the first crystallization temperature control zone along the flow direction of the lithium hexafluorophosphate material; the separation device includes a horizontal spiral centrifuge 5; a mother liquor tank 6 is provided at the liquid outlet of the separation device for collecting the crystallization mother liquor and circulating it to the lithium hexafluorophosphate production process.

[0051] The crystallization coils of two adjacent crystallization temperature control zones are connected by a quasi-right-angle pipe; the crystallization coil of a certain crystallization temperature control zone is divided into three sections of crystallization secondary coils, and the two adjacent sections of the crystallization secondary coils are connected by a quasi-right-angle pipe; the angle of the quasi-right-angle pipe is 90 degrees; on the outside of the crystallization cylinder, corresponding to the position of the quasi-right-angle pipe, an ultrasonic transducer 3 is set, or a nitrogen inlet 2 is opened for introducing nitrogen to enhance the vortex.

[0052] Example 2

[0053] This embodiment provides a continuous dynamic crystallization device for lithium hexafluorophosphate, such as Figure 2 As shown, compared with Example 1, the only difference is that for the crystallization coil in a certain crystallization temperature control zone, a secondary crystallization coil is no longer provided, but a whole section of crystallization coil is provided, that is, only the crystallization coils in two adjacent crystallization temperature control zones are connected by a quasi-right-angle pipe.

[0054] Example 3

[0055] This embodiment provides a continuous dynamic crystallization device for lithium hexafluorophosphate, such as Figure 3 As shown, compared with Example 1, the only difference is that all right-angle pipes are replaced with smooth arc pipes.

[0056] Example 4

[0057] This embodiment provides a continuous dynamic crystallization device for lithium hexafluorophosphate, such as Figure 4 As shown, compared with Example 1, the only difference is that: all right-angle pipes are omitted, that is, the crystallization cylinder is a single line, and a single line crystallization coil is arranged inside it; along the flow direction of the lithium hexafluorophosphate material, the inner cavity of the crystallization cylinder is divided into three crystallization temperature control zones by regional division, and each of the crystallization temperature control zones is respectively provided with a mutually independent refrigerant inlet and outlet.

[0058] Application Example 1

[0059] This application example provides a method for continuous dynamic crystallization of lithium hexafluorophosphate, using the lithium hexafluorophosphate continuous dynamic crystallization device described in Example 1, including the following steps:

[0060] (1) Adding a lithium hexafluorophosphate material into a precooling device and performing a precooling treatment at 3°C and a stirring speed of 80 rpm to obtain a precooling liquid; the lithium hexafluorophosphate material is a lithium hexafluorophosphate-hydrogen fluoride solution, and the mass concentration of the lithium hexafluorophosphate is 20%.

[0061] (2) The pre-cooling liquid in step (1) is transported to the crystallization coil, so that the lithium hexafluorophosphate material flows in a spiral inside the crystallization coil, and is gradually cooled through three crystallization temperature control zones in sequence, lithium hexafluorophosphate crystals are precipitated, and a crystal liquid is obtained.

[0062] Among them, the set temperature of the first crystallization temperature control zone is -5°C, the set temperature of the second crystallization temperature control zone is -12°C, and the set temperature of the third crystallization temperature control zone is -18°C; by controlling the pressurized peristaltic device, the spiral flow speed of the lithium hexafluorophosphate material is 300g / min; the nitrogen introduction flow rate is controlled at 1L / min.

[0063] (3) The crystal liquid in step (2) is transported to a separation device, and lithium hexafluorophosphate crystals are obtained after separation, which are then dried to obtain a finished lithium hexafluorophosphate product. The mother liquor obtained by separation enters a mother liquor tank for collecting the crystallization mother liquor and recycling it to the lithium hexafluorophosphate production process. Therefore, the yield of this application example is 100%.

[0064] Application Example 2

[0065] This application example provides a method for continuous dynamic crystallization of lithium hexafluorophosphate. Compared with Application Example 1, the only difference is that the continuous dynamic crystallization device for lithium hexafluorophosphate described in Example 2 is used.

[0066] Application Example 3

[0067] This application example provides a continuous dynamic crystallization method for lithium hexafluorophosphate. Compared with Application Example 1, the only difference is that the continuous dynamic crystallization device for lithium hexafluorophosphate described in Example 3 is used.

[0068] Application Example 4

[0069] This application example provides a method for continuous dynamic crystallization of lithium hexafluorophosphate. Compared with Application Example 1, the only difference is that the continuous dynamic crystallization device for lithium hexafluorophosphate described in Example 4 is used.

[0070] Performance testing:

[0071] The finished lithium hexafluorophosphate product was analyzed according to HG / T 4066-2015 to calculate the purity, acid content, and moisture content. The crystal particle size of the finished lithium hexafluorophosphate product was analyzed using a laser particle size analyzer to obtain D50. The test results are shown in Table 1.

[0072] Table 1

[0073]

[0074] In summary, the present invention provides a continuous dynamic crystallization device for lithium hexafluorophosphate. The crystallization device mainly adopts a cylindrical coil crystallization device. A crystallization coil is arranged inside the crystallization cylinder, so that the lithium hexafluorophosphate material spirally flows inside the crystallization coil. Eddy currents are generated at the cross section of the crystallization coil. The formation of the eddy currents enhances the radial mixing of the fluid and can reduce the residence time distribution. Therefore, the generated crystal particle size distribution is narrower, so that the lithium hexafluorophosphate crystal particle size D50 is 120~220μm, which can realize the dynamic continuous crystallization production of lithium hexafluorophosphate, and obtain high-purity lithium hexafluorophosphate crystals with uniform crystal particle size distribution and stable output.

[0075] In addition, in the crystallization device described in the present invention, the design of the right-angle pipeline can further enhance the vortex effect, strengthen the radial mixing of the fluid, and reduce the residence time distribution, so that the resulting crystal particle size distribution is narrower; due to the setting of the right-angle pipeline, it is easy to cause the retention of crystal particles and even cause crystal scale on the inner wall of the tube. Therefore, by introducing ultrasonic waves and / or nitrogen, not only can the retention of crystal particles be avoided, but the vortex effect can also be enhanced.

[0076] While the present invention is described through the above-described embodiments to illustrate the detailed structural features of the present invention, the present invention is not limited to these detailed structural features, nor does it necessarily rely on these detailed structural features for implementation. Those skilled in the art should understand that any improvements to the present invention, equivalent replacements for selected components, additions of auxiliary components, and selection of specific embodiments, etc., fall within the scope of protection and disclosure of the present invention.

[0077] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0078] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0079] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A lithium hexafluorophosphate continuous dynamic crystallization device, characterized in that: The lithium hexafluorophosphate continuous dynamic crystallization device comprises a pre-cooling device, a cylindrical coil crystallization device and a separation device connected in sequence; The cylindrical coil crystallization device includes a crystallization cylinder, a crystallization coil is arranged inside the crystallization cylinder, so that the lithium hexafluorophosphate material flows spirally inside the crystallization coil; along the flow direction of the lithium hexafluorophosphate material, the inner cavity of the crystallization cylinder is divided into at least two crystallization temperature control zones, each of which is provided with a mutually independent refrigerant inlet and outlet, so that along the flow direction of the lithium hexafluorophosphate material, the temperature of two adjacent crystallization temperature control zones decreases successively; the crystallization coils of two adjacent crystallization temperature control zones are connected by a quasi-right-angle pipe; The angle of the right-angle pipe is 60 to 90 degrees; An ultrasonic transducer is provided on the outside of the crystallization cylinder, corresponding to the position of the quasi-right-angle pipeline; and / or a nitrogen inlet is opened in the quasi-right-angle pipeline for introducing nitrogen to enhance the vortex.

2. The lithium hexafluorophosphate continuous dynamic crystallization device according to claim 1, characterized in that: The precooling device includes a precooling kettle; and / or, a pressurized peristaltic device is provided between the pre-cooling device and the cylindrical coil crystallization device; and / or, a seed crystal addition port is provided on the crystallization coil corresponding to the first crystallization temperature control zone along the flow direction of the lithium hexafluorophosphate material; and / or, the separation device comprises a horizontal spiral centrifuge; And / or, a mother liquor tank is provided at the liquid outlet of the separation device for collecting the crystallization mother liquor and circulating it to the lithium hexafluorophosphate production process.

3. The lithium hexafluorophosphate continuous dynamic crystallization device according to claim 1, characterized in that: The crystallization coil in a certain crystallization temperature control zone is divided into at least two sections of crystallization secondary coils, and two adjacent sections of the crystallization secondary coils are connected by a quasi-right-angle pipe.

4. A continuous dynamic crystallization method for lithium hexafluorophosphate, characterized in that: The lithium hexafluorophosphate continuous dynamic crystallization method uses the lithium hexafluorophosphate continuous dynamic crystallization device according to any one of claims 1 to 3, comprising the following steps: (1) adding lithium hexafluorophosphate material to a precooling device for precooling to obtain a precooling liquid; (2) transporting the pre-cooling liquid of step (1) to the crystallization coil, so that the lithium hexafluorophosphate material flows in a spiral manner inside the crystallization coil, and is gradually cooled through at least two crystallization temperature control zones, thereby precipitating lithium hexafluorophosphate crystals and obtaining a crystal liquid; (3) The crystal liquid in step (2) is transported to a separation device to obtain lithium hexafluorophosphate crystals through separation.

5. The continuous dynamic crystallization method of lithium hexafluorophosphate according to claim 4, characterized in that: The mass concentration of lithium hexafluorophosphate in the lithium hexafluorophosphate material in step (1) is 10-30%; And / or, the temperature of the pre-cooling treatment in step (1) is 0-5°C; And / or, stirring is performed during the pre-cooling treatment in step (1), and the stirring speed is 50-150 rpm.

6. The continuous dynamic crystallization method of lithium hexafluorophosphate according to claim 4, characterized in that: In step (2), three crystallization temperature control intervals are set, the temperature of the first crystallization temperature control interval is 0~-10°C, the temperature of the second crystallization temperature control interval is -10~-15°C, and the temperature of the third crystallization temperature control interval is -15~-20°C.

7. The continuous dynamic crystallization method of lithium hexafluorophosphate according to claim 4, characterized in that: The speed of the spiral flow in step (2) is 200-500 g / min; And / or, the crystallization coils in two adjacent crystallization temperature control zones are connected by a quasi-right-angle pipe, and ultrasonic transducers are correspondingly provided, and the frequency of the ultrasonic transducers is 20-80 Hz.

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