Synthesis system and synthesis method for lithium hexafluorophosphate

Abstract

The present invention provides a synthesis system and a synthesis method for lithium hexafluorophosphate. The synthesis system comprises a gas-liquid reaction kettle and a built-in microbubble generation unit provided in the gas-liquid reaction kettle; a material inlet and a gas inlet are formed in the side wall of the gas-liquid reaction kettle; the built-in microbubble generation unit comprises a first microbubble generator and a second microbubble generator, the first microbubble generator is provided below the liquid level in the gas-liquid reaction kettle and connected to the material inlet, and the second microbubble generator is provided at the bottom end of the gas-liquid reaction kettle and connected to the gas inlet; a plurality of layers of perforated plates are successively provided in the gas-liquid reaction kettle from top to bottom; through holes of said perforated plates are staggered, and said perforated plates are provided between the first microbubble generator and the second microbubble generator. The synthesis system of the present invention increases the area of mass transfer between lithium fluoride liquid and phosphorus pentafluoride gas, increases the reaction rate, and reduces energy consumption.

Description

A synthesis system and method of lithium hexafluorophosphate Technical Field The invention belongs to the technical field of lithium hexafluorophosphate synthesis, and in particular to a synthesis system and a synthesis method of lithium hexafluorophosphate. Background Art Lithium hexafluorophosphate (LiPF6) is a key component of modern lithium-ion battery electrolytes and is favored for its excellent conductivity and thermal stability. With the rapid growth of the renewable energy and electric vehicle markets, the demand for LiPF6 continues to increase. At present, the synthesis of lithium hexafluorophosphate mostly adopts the gas-liquid reaction method of lithium fluoride (LiF) and phosphorus pentafluoride (PF5) to synthesize LiPF6. However, this traditional production route gradually exposes the inherent technical limitations of gas. In the existing synthesis system, the efficiency of gas-liquid reaction needs to be improved. The limitation of reaction rate affects the output, which in turn affects the overall production efficiency and production cost. At the same time, the synthesis reaction needs to be carried out in a low temperature environment. Such reaction conditions not only increase the complexity of the operation, but also require relatively high energy consumption, which increases production costs. In view of this, the present invention is proposed. Summary of the invention The first object of the present invention is to provide a synthesis system of lithium hexafluorophosphate. The synthesis system increases the mass transfer area of ​​lithium fluoride liquid and phosphorus pentafluoride gas, improves the reaction rate and reduces energy consumption by arranging a built-in microbubble generating unit in a gas-liquid reactor to disperse and crush lithium fluoride liquid and phosphorus pentafluoride gas before performing a synthesis reaction. The second object of the present invention is to provide a method for synthesizing lithium hexafluorophosphate using the above-mentioned synthesis system, which is simple to operate, has milder operating conditions, and has low energy consumption, achieving a better processing effect than the existing technology process. In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted: The present invention provides a synthesis system of lithium hexafluorophosphate, comprising: A gas-liquid reactor and a built-in micro-bubble generating unit arranged inside the gas-liquid reactor; a material inlet and a gas inlet are arranged on the side wall of the gas-liquid reactor; The built-in microbubble generating unit comprises a first microbubble generator and a second microbubble generator, wherein the first microbubble generator is arranged below the liquid level in the gas-liquid reactor and connected to the material inlet, and the second microbubble generator is arranged at the bottom end of the gas-liquid reactor and connected to the gas inlet; Multiple layers of perforated plates are sequentially arranged in the gas-liquid reaction kettle from top to bottom, the through holes of the multiple layers of perforated plates are staggered, and the multiple layers of perforated plates are arranged between the first microbubble generator and the second microbubble generator. In the prior art, the following problems mainly exist when synthesizing lithium hexafluorophosphate: 1. In order to ensure the reaction efficiency, the reaction needs to be carried out in a low temperature environment, and the reaction temperature should be at least between -30℃ and -10℃, which requires more energy consumption; 2. The reaction efficiency of each raw material in the gas-liquid reactor is low, and it is difficult for PF5 bubbles to react completely from bottom to top in a single pass, resulting in a waste of raw materials. In order to solve the above technical problems, the present invention provides a synthesis system of lithium hexafluorophosphate. The overall structure of the synthesis system is simple. By arranging a built-in microbubble generating unit, the raw materials can be dispersed and broken into micron-level microbubbles, thereby increasing the mass transfer area between the gas-liquid two phases, improving the reaction efficiency and the raw material conversion rate, and reducing energy consumption; by arranging a perforated plate in the middle of the built-in microbubble generating unit, the reaction time can be extended, the liquid in the gas-liquid reactor is dispersed, the reaction is made more uniform and sufficient, and the reaction rate and the raw material conversion rate are further improved. Preferably, a baffle is provided on one side of the through hole on the upper surface of the perforated plate, and the baffles above the adjacent perforated plates are inclined in opposite directions. The baffle is provided to further extend the residence time of the reaction raw materials in the gas-liquid reactor through the barrier effect of the baffle, and at the same time, reduce the resistance for the PF5 bubbles to flow from bottom to top. Preferably, the inclination angle between the baffle and the upper surface of the perforated plate is 30-60°. The angle between the baffle and the upper surface of the perforated plate is set at 30-60° because too large an angle will cause too much resistance to the reaction raw materials and affect the flow of the raw material liquid, while too small an angle will not have the effect of extending the reaction path. Only when the angle is between 30-60° can the best effect be guaranteed. Preferably, the number of the perforated plates is four, the baffle located at the top of the four perforated plates has an inclination angle of 35° with the upper surface of the perforated plate, the two baffles located in the middle have an inclination angle of 45° with the upper surface of the perforated plate, and the baffle located at the bottom has an inclination angle of 55° with the upper surface of the perforated plate. This arrangement enables the liquid raw material coming out of the first microbubble generator to gradually increase resistance when flowing from top to bottom, further extending its flow path, thereby helping to improve the conversion rate of the raw material; at the same time, the gas raw material from bottom to top can optimize the flow path through the baffle, thereby promoting its smooth rise, and setting the baffle to a gradually decreasing inclination angle from bottom to top can effectively guide the gas flow path, avoid the generation of local vortices or dead zones, and reduce the resistance of the gas flow, increase the contact area between the gas and the liquid, and make the gas evenly dispersed inside the gas-liquid reactor, thereby increasing the reaction rate. Preferably, the diameter of the through hole is 2 mm to 5 mm. By limiting the through hole diameter to between 2 mm and 5 mm, it is possible to avoid resistance to the fluid due to a too small hole diameter, while avoiding a too large hole diameter that is not conducive to a better dispersion effect. Preferably, an agitator is provided above the first microbubble generator, the agitator is connected to the top of the gas-liquid reactor, and a stirring blade is provided at one end of the agitator close to the first microbubble generator. By providing the agitator, the unreacted gas in the upper section of the gas-liquid reactor can be further reacted with the liquid in the gas-liquid reactor, thereby improving the utilization rate of raw materials. Preferably, the agitator is arranged below the liquid surface of the gas-liquid reactor. Preferably, outlets of the first microbubble generator and the second microbubble generator are connected to distributors, and the opening direction of the distributor is close to the perforated plate. Preferably, an injection pipe is provided between the distributor connected to the second microbubble generator and the perforated plate. By providing the injection pipe and connecting it to the external circulation pipeline, the gas from the second microbubble generator and the gas-liquid mixture mixed in the gas-liquid reactor are pressurized by a circulation pump to provide power for the gas raw material to flow above the gas-liquid reactor. Preferably, an external microbubble generator is provided outside the gas-liquid reactor, and the external microbubble generator is connected to the material inlet to break and disperse the raw materials before entering the gas-liquid reactor. In the present invention, a built-in microbubble generating unit is arranged in the gas-liquid reactor, and the microbubble generating unit is composed of a first microbubble generating unit and a second microbubble generating unit. The two microbubble generating units are arranged in an upper and lower position and are used in conjunction with a distribution plate. The first microbubble generating unit is arranged in the upper section of the gas-liquid reactor, and mainly disperses and crushes the lithium fluoride liquid and phosphorus pentafluoride gas introduced into the gas-liquid reactor, and converts the pressure energy of the gas transported into the reactor or the kinetic energy of the raw material liquid into the bubble surface energy and transmits it to the phosphorus pentafluoride gas, so that the phosphorus pentafluoride gas is crushed to form micron-sized bubbles to react with the lithium fluoride liquid in the reactor, thereby increasing the mass transfer area between the gas and liquid phases, and increasing the conversion rate and utilization rate of the raw material. The second microbubble generating unit is arranged at the bottom of the gas-liquid reactor, and phosphorus pentafluoride gas is introduced into the bottom of the gas-liquid reactor again, so that the phosphorus pentafluoride gas flows from bottom to top to the top of the gas-liquid reactor, and reacts with the unreacted liquid again, thereby increasing the conversion rate of the raw material. A perforated plate and a baffle are also provided in the carbonization tower. The perforated plate of the present invention is multi-layered, preferably four-layered, and a baffle is provided on the upper surface of each layer of the perforated plate. The baffle is inclined, and the inclination angle of each layer of the baffle increases successively. Such an arrangement enables the liquid raw material coming out of the first microbubble generator to gradually increase resistance when flowing from top to bottom, further extending its flow path, thereby helping to improve the conversion rate of the raw material; at the same time, the gas raw material from bottom to top can optimize the flow path through the baffle, thereby promoting its smooth ascent. The baffle is set to an inclination angle that gradually decreases from bottom to top, which can effectively guide the gas flow path, avoid the generation of local vortices or dead zones, and at the same time reduce the resistance of the gas flow, increase the contact area between the gas and the liquid, and make the gas evenly dispersed inside the gas-liquid reactor, thereby increasing the reaction rate. At the same time, the baffle plate needs to be set on the upper surface of the perforated plate. This is because the gas below needs to flow from bottom to top, and setting it on the top can guide the gas flow. Those skilled in the art can understand that the microbubble generator used in the present invention has been embodied in the inventor's prior patents, such as patents with application numbers CN201610641119.6, CN201610641251.7, CN201710766435.0, CN106187660, CN105903425A, CN109437390A, CN205833127U and CN207581700U. The prior patent CN201610641119.6 describes in detail the specific product structure and working principle of the micron bubble generator (i.e., microbubble generator). The application document states that "the micron bubble generator includes a main body and a secondary crushing member, a cavity is provided in the main body, an inlet connected to the cavity is provided on the main body, the first and second opposite ends of the cavity are open, wherein the cross-sectional area of ​​the cavity decreases from the middle of the cavity to the first and second ends of the cavity; the secondary crushing member is provided at at least one of the first and second ends of the cavity, a part of the secondary crushing member is provided in the cavity, and an annular channel is formed between the secondary crushing member and the through holes open at both ends of the cavity. The micron bubble generator also includes an air inlet pipe and a liquid inlet pipe." From the specific structure disclosed in the application document, it can be known that its specific working principle is: the liquid enters the micron bubble generator tangentially through the liquid inlet pipe, rotates at ultra-high speed and cuts the gas, so that the gas bubbles are broken into micron-level microbubbles, thereby increasing the mass transfer area between the liquid phase and the gas phase, and the micron bubble generator in the patent is a pneumatic microbubble generator. In addition, the prior patent 201610641251.7 records that the primary bubble breaker has a circulating liquid inlet, a circulating gas inlet and a gas-liquid mixture outlet, and the secondary bubble breaker connects the feed port with the gas-liquid mixture outlet, indicating that the bubble breaker requires gas-liquid mixture to enter. In addition, it can be seen from the following drawings that the primary bubble breaker mainly uses circulating liquid as power, so the primary bubble breaker is actually a hydraulic microbubble generator, and the secondary bubble breaker simultaneously passes the gas-liquid mixture into the elliptical rotating ball for rotation, thereby achieving bubble breaking during the rotation process, so the secondary bubble breaker is actually a gas-liquid linkage microbubble generator. In fact, whether it is a hydraulic microbubble generator or a gas-liquid linkage microbubble generator, it is a specific form of microbubble generator. However, the microbubble generator adopted by the present invention is not limited to the above-mentioned forms. The specific structure of the bubble breaker recorded in the prior patent is only one of the forms that the microbubble generator of the present invention can adopt. In addition, the prior patent 201710766435.0 states that "the principle of the bubble breaker is to use high-speed jets to achieve mutual collision of gases", and also explains that it can be used in a micro-interface enhanced reactor, verifying the correlation between the bubble breaker and the micro-bubble generator; and the prior patent CN106187660 also has relevant records on the specific structure of the bubble breaker, see the specification for details.

[0031] -

[0041] , as well as the attached drawings, provide a detailed description of the specific working principle of the bubble breaker S-2. The top of the bubble breaker is a liquid inlet, and the side is a gas inlet. The liquid phase coming in from the top provides suction power, thereby achieving the effect of crushing into ultra-fine bubbles. It can also be seen in the attached drawings that the bubble breaker has a conical structure, and the diameter of the upper part is larger than that of the lower part, so that the liquid phase can better provide suction power. Since the microbubble generator was just developed in the early stage of the prior patent application, it was named micron bubble generator (CN201610641119.6), bubble breaker (201710766435.0), etc. in the early stage. With the continuous technical improvement, it was later renamed as microbubble generator. Now the microbubble generator in the present invention is equivalent to the previous microbubble generator, bubble breaker, etc., but the name is different. In summary, the microbubble generator of the present invention belongs to the prior art. Preferably, the above-mentioned synthesis system also includes a dissolver, a heat exchanger, a separation tank, a crystallizer and a tail gas washing tower; the dissolver is connected to the heat exchanger; the separation tank is connected to the material outlet at the bottom of the gas-liquid reactor to separate the unreacted gas and liquid products, and part of the unreacted gas is sent to the tail gas washing tower, and the other part is circulated back to the reaction system to continue the reaction; the crystallizer is connected to the separation tank to further purify the liquid product. Preferably, a gas outlet is provided at the top of the gas-liquid reactor, and the gas outlet is connected to the tail gas washing tower. Preferably, the dissolver is connected to a solid raw material storage tank and a liquid raw material storage tank; and a stirring paddle is provided in the dissolver to stir the raw materials in the dissolver. Preferably, the heat exchanger is connected to a gas storage tank, and the gas and the liquid from the dissolver enter the gas-liquid reactor after heat exchange in the heat exchanger. In addition, the present invention also provides a method for synthesizing lithium hexafluorophosphate. Systematic preparation of lithium hexafluorophosphate. Preferably, the synthesis method comprises the following steps: dissolving solid LiF in a hydrofluoric acid solution to prepare a suspension, introducing PF5 gas into the reaction to obtain a LiPF6 solution, and then obtaining the product lithium hexafluorophosphate through crystallization, separation, and drying. The preparation method of the invention is simple to operate, can effectively improve the conversion rate of reactants and the yield of products, and at the same time, reduces the reaction time, increases the reaction temperature, and significantly reduces the cost. Compared with the prior art, the present invention has the following beneficial effects: (1) By setting up a built-in microbubble generating unit, the raw materials can be dispersed and broken into micron-level microbubbles, thereby increasing the mass transfer area between the gas and liquid phases, improving the reaction efficiency and raw material conversion rate, and reducing energy consumption; (2) By setting a perforated plate in the middle of the built-in microbubble generating unit, the reaction time can be extended, the liquid in the gas-liquid reactor can be dispersed, the reaction can be more uniform and sufficient, and the reaction rate and raw material conversion rate can be further improved; (3) By setting up baffles, the barrier effect of the baffles is utilized to further extend the residence time of the reaction materials in the gas-liquid reactor, and at the same time, the resistance for the PF5 bubbles to flow from bottom to top is reduced. BRIEF DESCRIPTION OF THE DRAWINGS Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings: FIG1 is a schematic structural diagram of a synthesis system of lithium hexafluorophosphate provided in Example 1 of the present invention; FIG. 2 is a schematic diagram of the structure of the perforated plate provided in Example 1 of the present invention. in: 1-gas-liquid reaction kettle; 101-material inlet; 102-gas inlet; 103-material outlet; 104-gas outlet; 2-built-in micro bubble generating unit; 201-a first microbubble generator; 202-a second microbubble generator; 3-perforated plate; 301-through hole; 302- baffle; 4- agitator; 401-stirring blade; 5-distributor; 6-jet pipe; 7-external microbubble generator; 8-dissolver; 801-stirring paddle; 9-heat exchanger; 10-separation tank; 11-crystallizer; 12-tail gas washing tower; 13- solid raw material storage tank; 14- liquid raw material storage tank; 15- Gas storage tank. DETAILED DESCRIPTION The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially. In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance. In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" 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 or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. In order to more clearly explain the technical solution of the present invention, it is described in the form of specific embodiments below. Example 1 Referring to FIGS. 1-2 , a synthesis system of lithium hexafluorophosphate according to an embodiment of the present invention is shown, wherein, referring to FIG. 1 , it includes a gas-liquid reactor 1 and a built-in microbubble generating unit 2 disposed inside the gas-liquid reactor 1; a material inlet 101 and a gas inlet 102 are disposed on the side wall of the gas-liquid reactor 1; specifically, the built-in microbubble generating unit 2 includes a first microbubble generator 201 and a second microbubble generator 202, the first microbubble generator 201 is disposed below the liquid level in the gas-liquid reactor 1 and connected to the material inlet 101, and the second microbubble generator 202 is disposed at the bottom end of the gas-liquid reactor 1 and connected to the gas inlet 102. By providing a built-in microbubble generating unit 2, the raw materials can be dispersed and broken into microbubbles of micron level, thereby increasing the mass transfer area between gas and liquid phases, improving the reaction efficiency and raw material conversion rate, and reducing energy consumption. In this embodiment, a plurality of perforated plates 3 are sequentially arranged from top to bottom in the gas-liquid reactor 1, and the through holes 301 of the plurality of perforated plates 3 are arranged in a staggered manner, and the plurality of perforated plates 3 are arranged between the first microbubble generator 201 and the second microbubble generator 202. By arranging the perforated plate 3 in the middle of the built-in microbubble generating unit 2, the reaction time can be prolonged, the liquid in the gas-liquid reactor 1 can be dispersed, the reaction can be more uniform and sufficient, and the reaction rate and the raw material conversion rate can be further improved. As shown in Fig. 2, a baffle plate 302 is provided on one side of the through hole 301 on the upper surface of the perforated plate 3, and the baffle plates 302 above the adjacent perforated plates 3 are inclined in opposite directions. The baffle plates 302 are provided to further extend the residence time of the reaction raw materials in the gas-liquid reactor 1 through the barrier effect of the baffle plates 302, and at the same time, reduce the resistance for the PF5 bubbles to flow from bottom to top. Specifically, the inclination angle between the baffle 302 and the upper surface of the perforated plate 3 is 30-60°. The angle between the baffle 302 and the upper surface of the perforated plate 3 is set at 30-60° because too large an angle will cause too much resistance to the reaction raw materials and affect the flow of the raw material liquid, while too small an angle will not have the effect of extending the reaction path. Only when the angle is between 30-60° can the best effect be guaranteed. In this embodiment, the number of perforated plates 3 is four, and the inclination angle between the baffle plate 302 located at the top and the upper surface of the perforated plate 3 is 35°, the inclination angle between the two baffle plates 302 located in the middle and the upper surface of the perforated plate 3 is 45°, and the inclination angle between the baffle plate 302 located at the bottom and the upper surface of the perforated plate 3 is 55°. This arrangement enables the resistance of the liquid raw material coming out of the first microbubble generator 201 to gradually increase when it flows from top to bottom, further extending its flow path, thereby helping to improve the conversion rate of the raw material; at the same time, the gas raw material from bottom to top can optimize the flow path through the baffle plate 302, thereby promoting its smooth rise. Setting the baffle plate 302 to a gradually decreasing inclination angle from bottom to top can effectively guide the gas flow path, avoid the generation of local vortices or dead zones, and reduce the resistance of the gas flow, increase the contact area between the gas and the liquid, and make the gas evenly dispersed inside the gas-liquid reactor 1, thereby increasing the reaction rate. In order to prevent material blockage and ensure better dispersion effect, the diameter of the through hole 301 of the present invention is 2 mm-5 mm. Continuing to refer to FIG. 1 , an agitator 4 is provided above the first microbubble generator 201, and the agitator 4 is connected to the top of the gas-liquid reactor 1. A stirring blade 401 is provided at one end of the agitator 4 close to the first microbubble generator 201. The agitator 4 is provided below the liquid surface of the gas-liquid reactor. By providing the agitator 4, the unreacted gas in the upper section of the gas-liquid reactor 1 can be further reacted with the liquid in the gas-liquid reactor 1, thereby improving the utilization rate of the raw materials. In this embodiment, the outlets of the first microbubble generator 201 and the second microbubble generator 202 are connected to a distributor 5, and the opening direction of the distributor 5 is close to the perforated plate 3. Specifically, a spray pipe 6 is provided between the distributor 5 connected to the second microbubble generator 202 and the perforated plate 3. The gas-liquid reactor 1 of this embodiment is provided with an external micro-bubble generator 7 outside, and the external micro-bubble generator 7 is connected to the material inlet 101 to break and disperse the raw materials before entering the gas-liquid reactor 1 . As shown in FIG1 , the synthesis system of this embodiment further includes a dissolver 8, a heat exchanger 9, a separation tank 10, a crystallizer 11 and a tail gas washing tower 12; the dissolver 8 is connected to the heat exchanger 9; the separation tank 10 is connected to the material outlet 103 at the bottom of the gas-liquid reactor 1 to separate the unreacted gas and the liquid product, and part of the unreacted gas is sent to the tail gas washing tower 12, and the other part is circulated back to the reaction system to continue the reaction; the crystallizer 11 is connected to the separation tank 10 to further purify the liquid product. A gas outlet 104 is provided at the top of the gas-liquid reactor 1, and the gas outlet 104 is connected to the tail gas washing tower 12; The dissolver 8 is connected to the solid raw material storage tank 13 and the liquid raw material storage tank 14; a stirring paddle 801 is provided in the dissolver 8 to stir the raw materials in the dissolver 8; The heat exchanger 9 is connected to a gas storage tank 15 , and the gas and the liquid from the dissolver 8 enter the gas-liquid reactor 1 after heat exchange in the heat exchanger 9 . The method for preparing lithium hexafluorophosphate by the synthesis system of this embodiment is as follows: solid LiF is dissolved in a hydrofluoric acid solution to prepare a suspension, PF5 gas is introduced into the reaction to prepare a LiPF6 solution, and the product lithium hexafluorophosphate is obtained after crystallization, separation, and drying. Example 2 The only difference between this example and Example 1 is that the inclination angles of the upper surfaces of the baffle and the perforated plate are both 10°. Example 3 The only difference between this example and Example 1 is that the inclination angles of the upper surfaces of the baffle and the perforated plate are both 45°. Example 4 The only difference between this example and Example 1 is that no external microbubble generator is provided. Comparative Example 1 The only difference between this example and Example 1 is that no baffle is provided on the upper surface of the perforated plate. Comparative Example 2 The only difference between this example and Example 1 is that no perforated plate is provided. Comparative Example 3 The only difference between this example and Example 1 is that no built-in microbubble generating unit is provided. Comparative Example 4 The only difference between this example and the first embodiment is that no injection pipe is provided. Comparative Example 5 This example adopts the existing technology to directly introduce the dissolved lithium fluoride liquid and phosphorus pentafluoride gas into the gas-liquid reactor for reaction, and the generated reaction product is subjected to subsequent separation and purification stages. Experimental Example 1 Lithium hexafluorophosphate was prepared by using the synthesis systems of Examples 1-4 and Comparative Examples 1-4, respectively. The specific experimental conditions were as follows: 150 kg of lithium fluoride solid was dissolved in 300 kg of hydrofluoric acid solution to prepare a lithium fluoride suspension, and then the lithium fluoride suspension was introduced into a gas-liquid reactor, and 100 kg of phosphorus pentafluoride gas was slowly introduced into the gas-liquid reactor. The reaction results are shown in the following table: Table 1 Experimental results When lithium hexafluorophosphate is prepared by the prior art, the yield of lithium hexafluorophosphate is 62% and the purity of lithium hexafluorophosphate is 78%. As can be seen from Table 1, compared with the prior art reactor, the yield of lithium hexafluorophosphate in each embodiment of the present invention is significantly increased, and the yield of lithium hexafluorophosphate in Example 1 is increased by 37%. The reaction temperature of the reaction system of each embodiment of the present invention is higher than -10°C, which is 10°C higher than the prior art, and the reaction time of each embodiment of the present invention is shorter than the prior art. As can be seen from Table 1, Example 1 of the present invention is the best example. The reaction temperature of the synthesis system of this example is significantly higher than the reaction temperature of preparing lithium hexafluorophosphate in the prior art, and the reaction time is significantly shortened, while still having a good raw material conversion rate and product yield. This shows that the microbubble generator setting method of Example 1 and the use of a perforated plate can achieve the best reaction effect. It can be seen that the synthesis system of this example has low reaction energy consumption and good preparation effect. Among them, the yield of lithium hexafluorophosphate in Comparative Example 3 is lower than that in Example 1. This is because Comparative Example 3 does not have a built-in microbubble generating unit, which cannot fully crush and disperse the lithium fluoride suspension and phosphorus pentafluoride gas in the gas-liquid reactor. It can be seen that Example 1 improves the yield of lithium hexafluorophosphate by setting the arrangement of the microbubble generator of the gas-liquid reactor. In summary, compared with the prior art, the synthesis system of lithium hexafluorophosphate of the present invention has an easy-to-achieve reaction temperature, a short reaction time, a high raw material conversion rate, and a high product yield, and is worthy of wide promotion and application. Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A synthesis system of lithium hexafluorophosphate, characterized in that: include: A gas-liquid reactor and a built-in micro-bubble generating unit arranged inside the gas-liquid reactor; a material inlet and a gas inlet are arranged on the side wall of the gas-liquid reactor; The built-in microbubble generating unit comprises a first microbubble generator and a second microbubble generator, wherein the first microbubble generator is arranged below the liquid level in the gas-liquid reactor and connected to the material inlet, and the second microbubble generator is arranged at the bottom end of the gas-liquid reactor and connected to the gas inlet; Multiple layers of perforated plates are sequentially arranged in the gas-liquid reaction kettle from top to bottom, the through holes of the multiple layers of perforated plates are staggered, and the multiple layers of perforated plates are arranged between the first microbubble generator and the second microbubble generator.

2. The synthesis system of lithium hexafluorophosphate according to claim 1, characterized in that: A baffle is provided on one side of the through hole on the upper surface of the perforated plate, and the baffles above the adjacent perforated plates have opposite inclination directions.

3. The synthesis system of lithium hexafluorophosphate according to claim 2, characterized in that: The inclination angle between the baffle plate and the upper surface of the perforated plate is 30-60°.

4. The synthesis system of lithium hexafluorophosphate according to claim 2, characterized in that: There are four perforated plates, the top baffle plate among the four perforated plates has an inclination angle of 35° with the upper surface of the perforated plate, the two baffle plates in the middle have an inclination angle of 45° with the upper surface of the perforated plate, and the bottom baffle plate has an inclination angle of 55° with the upper surface of the perforated plate.

5. The synthesis system of lithium hexafluorophosphate according to claim 1, characterized in that: The diameter of the through hole is 2mm-5mm.

6. The synthesis system of lithium hexafluorophosphate according to claim 1, characterized in that: An agitator is arranged above the first microbubble generator, the agitator is connected to the top of the gas-liquid reactor, and a stirring blade is arranged at one end of the agitator close to the first microbubble generator; preferably, the agitator is arranged below the liquid surface of the gas-liquid reactor.

7. The synthesis system of lithium hexafluorophosphate according to claim 1, characterized in that: The outlets of the first microbubble generator and the second microbubble generator are connected with distributors, and the opening direction of the distributors is close to the perforated plate; preferably, an injection pipe is arranged between the distributor connected to the second microbubble generator and the perforated plate.

8. The synthesis system of lithium hexafluorophosphate according to claim 1, characterized in that: An external micro-bubble generator is arranged outside the gas-liquid reactor, and the external micro-bubble generator is connected with the material inlet to break and disperse the raw materials before entering the gas-liquid reactor.

9. The synthesis system of lithium hexafluorophosphate according to claim 1, characterized in that: It also includes a dissolver, a heat exchanger, a separation tank, a crystallizer and a tail gas washing tower; the dissolver is connected to the heat exchanger; the separation tank is connected to the material outlet at the bottom of the gas-liquid reactor to separate the unreacted gas and the liquid product, and part of the unreacted gas is sent to the tail gas washing tower, and the other part is circulated back to the reaction system to continue the reaction; the crystallizer is connected to the separation tank to further purify the liquid product; Preferably, a gas outlet is provided at the top of the gas-liquid reactor, and the gas outlet is connected to the tail gas washing tower; Preferably, the dissolver is connected to a solid raw material storage tank and a liquid raw material storage tank; a stirring paddle is provided in the dissolver to stir the raw materials in the dissolver; Preferably, the heat exchanger is connected to a gas storage tank, and the gas and the liquid from the dissolver enter the gas-liquid reactor after heat exchange in the heat exchanger.

10. A method for synthesizing lithium hexafluorophosphate, characterized in that: Lithium hexafluorophosphate is prepared using the synthesis system described in any one of claims 1 to 9.

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