Lithium hexafluorophosphate continuous dynamic crystallization device and crystallization method thereof

Abstract

The invention belongs to the technical field of battery electrolytes, and relates to a lithium hexafluorophosphate continuous dynamic crystallization device and a crystallization method thereof.The crystallization device mainly adopts a cylinder coil crystallization device, a crystallization coil is arranged in a crystallization cylinder, so that a lithium hexafluorophosphate material spirally flows in the crystallization coil, and the crystallization coil is arranged in the crystallization cylinder. According to the present invention, the vortex can be generated at the cross section of the crystallization coil pipe, and the formation of the vortex can enhance the radial mixing of the fluid and can reduce the retention time distribution, such that the generated crystal particle size distribution is narrow, the dynamic continuous crystallization production of the lithium hexafluorophosphate can be achieved, and the high-purity lithium hexafluorophosphate crystal with characteristics of uniform crystal particle size distribution and stable yield can be obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of battery electrolytes, specifically to the technical field of lithium hexafluorophosphate, and particularly to a continuous dynamic crystallization device for lithium hexafluorophosphate and its crystallization method. Background Art

[0002] Lithium hexafluorophosphate (LiPF6) is the core component of lithium-ion battery electrolytes and has become a key material due to its excellent ion transport ability, outstanding heat resistance, and chemical compatibility. Against the backdrop of the rapid development of the electric vehicle, energy storage, and consumer electronics fields, the market's demand for high-energy-density and long-cycle-life batteries continues to grow, further driving up the industrial demand for high-purity LiPF6.

[0003] Traditional crystallization processes mostly adopt an intermittent operation mode, which has the defects of a long production cycle and insufficient batch stability, directly affecting the uniformity of electrolyte performance. This production method also leads to increased energy consumption and rising comprehensive costs due to repeated start-stop operations of equipment. In contrast, the continuous dynamic crystallization process can achieve continuous production throughout the process by continuously flowing materials and precisely controlling parameters, significantly increasing the production capacity per unit time and shortening the equipment idle cycle. This technology ensures a uniform crystal particle size distribution through real-time monitoring means, guaranteeing the stability of product quality from the source. The continuous operation mode can also significantly reduce the unit energy consumption through thermodynamic optimization and reduce human operation errors by combining an automated control system, thereby improving the production safety factor and process repeatability.

[0004] CN112340754A discloses a dynamic crystallization method that combines stepwise stirring (first stirring + second stirring) with ultrasonic assistance, and with precise temperature control and gas drying, high-purity and well-uniform crystal particles can be prepared, with a narrow particle size distribution (10 - 230 μm) and no caking. However, the equipment is complex and the energy consumption is high. Strict requirements are imposed on parameters such as the stirring rate and dropping rate, and operation errors are likely to cause fluctuations in crystal quality.

[0005] CN108147386A discloses a dynamic fractional crystallization method achieved through multiple temperature cycles. Without complex equipment, the crystal growth can be stably controlled through repeated temperature cycles, and the operation threshold is low. However, it takes a long time, the total production cycle is significantly extended, and it only relies on temperature changes and stirring, so the crystal uniformity is weaker than the ultrasonic-assisted method. At the same time, the recycling of the mother liquor is not mentioned, which may increase the waste of raw materials.

[0006] CN117466313A discloses the optimization of LiF precursor preparation by combining mother liquor recycling and temperature cycling. The mother liquor is recycled to the reaction step, reducing raw material consumption and cost. The reaction activity is improved by LiF crystallization, and the purity of LiPF6 is enhanced. However, the process is complex, requiring synchronous control of LiF crystallization and LiPF6 crystallization, and the multi-step coordination increases the management difficulty. Moreover, multiple temperature cycles are needed to reach the target purity, and the efficiency is lower than that of single ultrasonic-assisted crystallization. Mother liquor recycling requires additional pipeline and filtration system configuration, increasing the maintenance cost.

[0007] Currently, the industrial crystallization process of lithium hexafluorophosphate mainly relies on the batch static operation mode, and its limitations are reflected in many aspects. Due to the lack of a continuous regulation mechanism during the crystallization process, the nucleation and growth of crystals are easily affected by local environmental fluctuations, resulting in poor crystal shape regularity and wide particle size distribution, thereby weakening the batch stability of the product and its downstream application performance. In addition, batch 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 consumption due to repeated start-stop of the equipment. In contrast, dynamic crystallization technology can significantly improve production capacity and optimize crystal quality by introducing a continuous process flow. However, existing dynamic crystallization processes still have problems such as insufficient mass transfer efficiency of equipment and lack of accuracy in key parameters, and it is necessary to optimize the flow channel structure design and other means to achieve fine adjustment of process parameters and improvement of process stability.

[0008] Therefore, it is necessary to develop a new type of continuous dynamic crystallization device for lithium hexafluorophosphate and its crystallization method. 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 its crystallization method. The crystallization device mainly adopts a cylindrical coil crystallization device, and a crystallization coil is arranged inside the crystallization cylinder, so that the lithium hexafluorophosphate material flows spirally inside the crystallization coil, and an eddy current will be generated at the cross-section of the crystallization coil. The formation of this eddy current enhances the radial mixing of the fluid, can reduce the residence time distribution, so the resulting crystal particle size distribution is narrower, and the dynamic continuous crystallization production of lithium hexafluorophosphate can be realized, obtaining high-purity lithium hexafluorophosphate crystals with uniform crystal particle size distribution and stable output.

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

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

[0012] 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 at least two crystallization temperature control intervals, and each crystallization temperature control interval is respectively provided with independent refrigerant inlets and outlets, so that along the flow direction of the lithium hexafluorophosphate material, the temperatures of adjacent two crystallization temperature control intervals decrease in sequence; between the crystallization coils of adjacent two crystallization temperature control intervals, they are connected by a quasi-right-angle pipe.

[0013] The continuous dynamic crystallization device for lithium hexafluorophosphate of the present invention mainly realizes the production of high-quality lithium hexafluorophosphate crystals by optimizing the flow field control. Specifically, first, the lithium hexafluorophosphate material is introduced into a precooling device for precooling treatment, and then introduced into the cylindrical coil crystallization device. Specifically, through the spiral flow channel design of the crystallization coil, a radial vortex effect is induced in the cross-section of the pipe, significantly enhancing the fluid mixing uniformity and narrowing the material residence time distribution, thereby realizing the precise control of crystal particle size. Finally, the solid-liquid mixture after crystallization is subjected to sedimentation separation and filtration treatment by a separation device, and the obtained solid-phase material is dried again 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 arranged between the precooling device and the cylindrical coil crystallization device.

[0016] And / or, along the flow direction of the lithium hexafluorophosphate material, a seed addition port is opened on the crystallization coil corresponding to the first crystallization temperature control interval. During actual operation, lithium hexafluorophosphate seeds can be selectively added, and the mass of the lithium hexafluorophosphate seeds is 0.1-0.5% of the mass of lithium hexafluorophosphate in the precooled liquid after precooling treatment.

[0017] And / or, the separation device includes a horizontal scroll centrifuge. During actual operation, the rotational speed of the horizontal scroll centrifuge is 1000 rpm - 2000 rpm.

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

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

[0020] Experimental verification has shown 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 size distribution.

[0021] As a preferred technical solution of the present invention, it is characterized in that the angle of the quasi-right-angle 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 arranged 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 to ensure continuous and stable operation of the crystallization process.

[0023] And / or, a nitrogen inlet is provided in the right-angle pipeline to introduce nitrogen to enhance the vortex. Nitrogen is introduced into the crystallization coil, and the fluid state in the tube is controlled by changing the flow rate of the gas. Uniform bubbles appear in the fluid, which can not only regulate the size distribution of the crystals, but also avoid clogging of the pipeline. Generally, the nitrogen introduction flow rate is controlled at 0.5-5L / 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 vortex effect.

[0025] The second object of the present invention is to provide a continuous dynamic crystallization method for lithium hexafluorophosphate, wherein the continuous dynamic crystallization method for lithium hexafluorophosphate uses the continuous dynamic crystallization device for lithium hexafluorophosphate 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) conveying the precooling 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 in at least two crystallization temperature control zones in sequence, so that lithium hexafluorophosphate crystals are precipitated to obtain a crystal liquid;

[0028] (3) Deliver the crystal liquid described in step (2) to a separation device, and 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 reaction, such as the anhydrous hydrogen fluoride solution of lithium hexafluorophosphate obtained by reaction.

[0030] In the continuous dynamic crystallization method of lithium hexafluorophosphate of the present invention, the lithium hexafluorophosphate material is introduced into a precooling device for preliminary cooling. This precooling 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 cross-section of the coil. By strengthening the radial mixing uniformity of the fluid, the residence time distribution of the material in the crystallizer is significantly narrowed, realizing precise control of the crystal particle size. After crystallization, the solid-liquid mixed phase is subjected to sedimentation, filtration and drying treatments, and finally a high-purity lithium hexafluorophosphate product with uniform particle size is obtained.

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

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

[0033] And / or, stirring is carried out during the precooling treatment described in step (1), and the stirring speed is 50 - 150 rpm, such as 50 rpm, 60 rpm, 80 rpm, 100 rpm, 110 rpm, 130 rpm or 150 rpm, etc.

[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°C, such as 0°C, -1°C, -3°C, -5°C, -6°C, -8°C or -10°C, etc.; the temperature of the second crystallization temperature control interval is -10 - -15°C, such as -10°C, -11°C, -12°C, -13°C, -14°C or -15°C, etc.; the temperature of the third crystallization temperature control interval is -15 - -20°C, such as -15°C, -16°C, -17°C, -18°C, -19°C or -20°C, etc.

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

[0036] And / or, between the crystallization coils in adjacent two crystallization temperature control intervals, they are connected by a quasi-right-angle pipe, and an ultrasonic transducer is correspondingly arranged. The frequency of the ultrasonic transducer is 20-80 Hz, such as 20 Hz, 30 Hz, 40 Hz, 50 Hz, 60 Hz, 70 Hz or 80 Hz, etc.

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

[0038] (1) The present invention provides a lithium hexafluorophosphate continuous dynamic crystallization device. 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. An eddy current will be generated at the cross-section of the crystallization coil. The formation of this eddy current enhances the radial mixing of the fluid, can reduce the residence time distribution, so the crystal particle size distribution produced is narrower. The lithium hexafluorophosphate crystal particle size D50 is 120-220 μm, and the 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 can be obtained.

[0039] (2) In the crystallization device of the present invention, through the design of the quasi-right-angle pipe, the eddy current effect can be further enhanced, the radial mixing of the fluid can be strengthened, and the residence time distribution can be reduced. Therefore, the crystal particle size distribution produced is narrower; due to the setting of the quasi-right-angle pipe, it is easy to cause the retention of crystal particles and even cause crystallization scale on the inner wall of the pipe. Therefore, by means of ultrasonic wave and / or nitrogen introduction, not only can the retention of crystal particles be avoided, but also the eddy current effect can be enhanced. Description of the Drawings

[0040] Figure 1 is a schematic structural diagram of the lithium hexafluorophosphate continuous dynamic crystallization device described in Embodiment 1 of the present invention.

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

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

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

[0044] In the figure: 1 - precooling kettle; 2 - nitrogen inlet; 3 - ultrasonic transducer; 4 - seed addition port; 5 - horizontal scroll centrifuge; 6 - mother liquor tank. Specific embodiments

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

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

[0047] Embodiment 1

[0048] This embodiment provides a lithium hexafluorophosphate continuous dynamic crystallization device, and the lithium hexafluorophosphate continuous dynamic crystallization device includes a precooling device, a cylindrical coil crystallizer, and a separation device connected in sequence.

[0049] Among them, the cylindrical coil crystallizer 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 intervals, and each of the crystallization temperature control intervals is provided with independent refrigerant inlets and outlets, so that along the flow direction of the lithium hexafluorophosphate material, the temperatures of adjacent two crystallization temperature control intervals decrease in sequence.

[0050] As Figure 1 shown, the precooling device includes a precooling kettle 1; a pressurized peristaltic device is arranged between the precooling device and the cylindrical coil crystallizer; a seed addition port 4 is opened on the crystallization coil corresponding to the first crystallization temperature control interval along the flow direction of the lithium hexafluorophosphate material; the separation device includes a horizontal scroll centrifuge 5; a mother liquor tank 6 is arranged at the liquid outlet of the separation device for collecting crystallization mother liquor and recycling it to the lithium hexafluorophosphate production process.

[0051] The crystallization coils between adjacent two crystallization temperature control intervals are connected by a quasi-right-angle pipe; for the crystallization coil of a certain crystallization temperature control interval, it is divided into three crystallization secondary coils, and the adjacent two crystallization secondary coils are connected by a quasi-right-angle pipe; the included angle of the quasi-right-angle pipe is 90 degrees; outside the crystallization cylinder, at the position corresponding to the quasi-right-angle pipe, an ultrasonic transducer 3 is arranged, or a nitrogen inlet 2 is opened for introducing nitrogen to enhance the eddy current.

[0052] Embodiment 2

[0053] This embodiment provides a lithium hexafluorophosphate continuous dynamic crystallization device, asFigure 2 As shown, compared with Embodiment 1, the difference is only that: for the crystallization coil in a certain crystallization temperature control range, instead of setting a secondary crystallization coil, it is an integral section of crystallization coil, that is, only between the crystallization coils in adjacent two crystallization temperature control ranges, they are connected by a quasi-right-angle pipe.

[0054] Embodiment 3

[0055] This embodiment provides a lithium hexafluorophosphate continuous dynamic crystallization device, as Figure 3 shown. Compared with Embodiment 1, the difference is only that: all quasi-right-angle pipes are replaced with smooth arc-shaped pipes.

[0056] Embodiment 4

[0057] This embodiment provides a lithium hexafluorophosphate continuous dynamic crystallization device, as Figure 4 shown. Compared with Embodiment 1, the difference is only that: all quasi-right-angle pipes are omitted, that is, the crystallization cylinder is in a single linear shape, and a crystallization coil in a single linear shape is arranged inside it; along the flowing direction of the lithium hexafluorophosphate material, through area division, the inner cavity of the crystallization cylinder is divided into three crystallization temperature control ranges, and each of the crystallization temperature control ranges is respectively provided with independent refrigerant inlets and outlets.

[0058] Application Example 1

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

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

[0061] (2) Transport the precooled liquid described in step (1) to the crystallization coil, so that the lithium hexafluorophosphate material spirally flows inside the crystallization coil, and gradually cools down through three crystallization temperature control ranges in sequence to precipitate lithium hexafluorophosphate crystals, obtaining a crystal liquid.

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

[0063] (3) The crystal solution described in step (2) is transported to a separation device. Lithium hexafluorophosphate crystals are obtained through separation and dried to obtain the finished product of lithium hexafluorophosphate. The mother liquor obtained through separation enters the mother liquor tank, which is used to collect the crystallization mother liquor and recycle it to the lithium hexafluorophosphate production process. Therefore, the yield of this application example is counted as 100%.

[0064] Application Example 2

[0065] 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 2 is adopted.

[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 adopted.

[0068] Application Example 4

[0069] 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 4 is adopted.

[0070] Performance Test:

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

[0072] Table 1

[0073] In summary, the present invention provides a continuous dynamic crystallization device for lithium hexafluorophosphate. The crystallization device mainly adopts a cylindrical coil crystallization device, and a crystallization coil is arranged inside the crystallization cylinder, so that the lithium hexafluorophosphate material flows spirally inside the crystallization coil, and eddy currents will be generated at the cross-section of the crystallization coil. The formation of these eddy currents enhances the radial mixing of the fluid, can reduce the residence time distribution, so the resulting crystal particle size distribution is narrower, and the crystal particle size D50 of lithium hexafluorophosphate is 120 - 220 μm. It 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.

[0074] In addition, in the crystallization device of the present invention, through the design of the quasi-right-angle pipeline, the eddy current effect can be enhanced, the radial mixing of the fluid can be strengthened, the residence time distribution can be reduced, and thus the crystal particle size distribution generated is narrower; due to the setting of the quasi-right-angle pipeline, it is easy to cause the retention of crystal particles and even lead to the crystallization scale on the inner wall of the pipeline. Therefore, by means of ultrasonic wave and / or nitrogen introduction, not only can the retention of crystal particles be avoided, but also the eddy current effect can be enhanced.

[0075] The present invention uses the above embodiments to illustrate the detailed structural features of the present invention, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent replacement of the components selected by the present invention, the addition of auxiliary components, and the selection of specific methods, etc., all fall within the protection scope and the disclosure scope of the present invention.

[0076] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of 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 belong to the protection scope of the present invention.

[0077] In addition, it should be noted that, in the above specific embodiments, the various specific technical features described can be combined in any suitable way without contradiction. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods.

[0078] In addition, any combination can be made between various different embodiments of the present invention, as long as it does not violate the idea of the present invention, and it should also be regarded as the content disclosed by the present invention.

Claims

1. A continuous dynamic crystallization device for lithium hexafluorophosphate, characterized in that, The lithium hexafluorophosphate continuous dynamic crystallization device comprises a precooling device, a cylindrical coil crystallization device and a separation device which are connected in sequence; 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 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 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.

2. The lithium hexafluorophosphate continuous dynamic crystallization device according to claim 1, characterized in that, The precooling device comprises a precooling kettle; and / or, a pressurized peristaltic device is provided between the precooling device and the cylindrical coil crystallization device; And / or, a seed feeding port is opened 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 to collect the crystallization mother liquor and circulate it to the lithium hexafluorophosphate production process.

3. The lithium hexafluorophosphate continuous dynamic crystallization device according to claim 1, wherein 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 pipeline.

4. The lithium hexafluorophosphate continuous dynamic crystallization device according to claim 1 or 3, characterized in that, The included angle of the quasi-right-angle pipe is 60 to 90 degrees.

5. The lithium hexafluorophosphate continuous dynamic crystallization device according to claim 1 or 3, characterized in that, An ultrasonic transducer is arranged on the outer side of the crystallization cylinder, corresponding to the position of the quasi-right-angle pipeline; And / or, a nitrogen inlet is provided in the quasi-right-angle pipeline for introducing nitrogen to enhance the vortex.

6. 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 5, comprising the following steps: (1) adding lithium hexafluorophosphate material to a precooling device for precooling to obtain a precooling liquid; (2) conveying the precooling 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 in at least two crystallization temperature control zones in sequence, so that lithium hexafluorophosphate crystals are precipitated to obtain a crystal liquid; (3) The crystal liquid of step (2) is transported to a separation device to obtain lithium hexafluorophosphate crystals through separation.

7. The continuous dynamic crystallization method of lithium hexafluorophosphate according to claim 6, 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 precooling treatment in step (1), and the stirring speed is 50-150 rpm.

8. The continuous dynamic crystallization method of lithium hexafluorophosphate according to claim 6, 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.

9. The continuous dynamic crystallization method of lithium hexafluorophosphate according to claim 6, wherein 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 an ultrasonic transducer is correspondingly arranged, and the frequency of the ultrasonic transducer is 20-80 Hz.

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