Process for producing high-purity lithium hexafluorophosphate

Abstract

The present application relates to the technical field of lithium hexafluorophosphate production, and discloses a production process of high-purity lithium hexafluorophosphate, which comprises the following process flow: dry base lithium fluoride is obtained by dehydrating and drying lithium fluoride; under the protection of nitrogen, hydrofluoric acid reacts with diaphosphorus pentoxide to generate lithium hexafluorophosphate; the obtained lithium hexafluorophosphate solution further reacts with sulfur trioxide at room temperature under the condition that the pressure is controlled to be 0.02 MPaG to generate phosphorus pentafluoride gas; the gas is introduced into a lithium fluoride mixed solvent to react with lithium fluoride, and the target crude product lithium hexafluorophosphate solution is obtained, and the reaction is ensured to be carried out under the protection of nitrogen; the lithium hexafluorophosphate solution is further purified, crystallized, crushed and dried, and the high-purity product lithium hexafluorophosphate crystal can be obtained, which can effectively save raw materials, improve the preparation efficiency of lithium hexafluorophosphate, adapt to the demand of mass production, improve the purity, reduce the requirement of preparation and processing procedures, and reduce the preparation cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium hexafluorophosphate production, in particular to a production process of high-purity lithium hexafluorophosphate. BACKGROUND

[0002] Lithium hexafluorophosphate is the most common electrolyte, and lithium hexafluorophosphate is one of the important components of lithium ion battery electrolyte, and the purity of lithium hexafluorophosphate is particularly high when used in electrolyte.

[0003] The Chinese patent application No. 201010550107.5 discloses a preparation method of lithium hexafluorophosphate, which utilizes the reaction of hydrogen fluoride and phosphorus pentachloride to obtain a mixed gas of phosphorus pentafluoride and hydrogen chloride, and the mixed gas is introduced into hydrogen fluoride and lithium fluoride to react to obtain a lithium hexafluorophosphate solution; finally, lithium hexafluorophosphate product is obtained by crystallization separation, filtration and drying, but the method has the disadvantage that hydrogen fluoride and phosphorus pentachloride are used to obtain phosphorus pentafluoride, and phosphorus pentafluoride is used as a raw material for synthesizing lithium hexafluorophosphate, but the reaction is extremely violent and can easily explode if not handled properly.

[0004] The patent CN101570327A discloses a method for producing lithium hexafluorophosphate, which uses high-purity lithium fluoride as a raw material, resulting in high production cost, and the quality stability of domestic high-purity lithium fluoride is poor, which is difficult to ensure product quality.

[0005] Meanwhile, lithium hexafluorophosphate needs to be crystallized when preparing lithium hexafluorophosphate, and the crystallization kettle is a crystallization equipment for the product, at present, the crystallization is completed based on the existing crystallization kettle during the lithium hexafluorophosphate crystallization operation, but the crystallization kettle on the market is natural crystallization, which is easy to cause caking, so it is necessary to carry out crushing and screening treatment after the subsequent drying process to ensure the uniformity of the crystallization particle size, which makes the process complex.

[0006] Therefore, it is necessary to invent a production process of high-purity lithium hexafluorophosphate to solve the above problems. SUMMARY

[0007] The present application aims to provide a production process of high-purity lithium hexafluorophosphate to solve the problems in the background art.

[0008] To achieve the above-mentioned purpose, the present application provides the following technical solution: a production process of high-purity lithium hexafluorophosphate, comprising the following process flow:

[0009] S1, under the condition of room temperature, the pressure is controlled to be 0.02 MPaG, and lithium carbonate and hydrofluoric acid are fully reacted in liquid-solid phase under the protection of nitrogen to obtain lithium fluoride, and the lithium fluoride is dehydrated and dried to obtain dry lithium fluoride;

[0010] S2, under the condition of room temperature and controlled pressure of 0.02 MPaG, hydrogen fluoride reacts with phosphorus pentoxide under nitrogen protection to generate hexafluorophosphoric acid;

[0011] S3, the obtained hexafluorophosphoric acid solution further reacts with sulfur trioxide under the condition of room temperature and controlled pressure of 0.02 MPaG to generate phosphorus pentafluoride gas;

[0012] S4, the gas is introduced into a lithium fluoride mixed solvent to react with lithium fluoride to obtain a target crude product of lithium hexafluorophosphate solution, and the reaction is ensured to be carried out under nitrogen protection;

[0013] S5, the lithium hexafluorophosphate solution is further purified, crystallized, crushed and dried to obtain high-purity lithium hexafluorophosphate crystals.

[0014] Preferably, in the step S5, the specific steps of purifying the lithium hexafluorophosphate solution are as follows:

[0015] S501, the crude material in the intermediate tank is pumped into a concentration kettle by a centrifugal pump to recover the solvent, and is distilled under the condition of normal pressure and a temperature of 70°C for 8-9 hours; the fraction collected from the top of the kettle is condensed by a primary and a secondary condensers and then recycled; and then dichloroethane is introduced to further displace the solvent, so that the purification process is completed;

[0016] S502, the material at the bottom of the column is pumped into a crystallization kettle by a centrifugal pump for crystallization treatment, the crystallization kettle is controlled to cool and crystallize under the condition of a pressure of 0.03 MPaG and a temperature of 0°C for 3-4 hours; after the crystallization is completed, the mother liquor is collected from the bottom of the kettle into a mother liquor tank for reuse; dichloroethane is introduced into the crystallization kettle at a ratio of solid:dichloroethane of 1:2 to further wash the impurities in the crystals; after washing for 3-4 hours, the washing liquid is pumped from the bottom of the kettle into a washing liquid tank for second washing; and direct screening treatment is performed to ensure that the particle size of the lithium hexafluorophosphate after crystallization is uniform to avoid the occurrence of caking during the crystallization process, and the crushing of the crystals can be realized during the crystallization process;

[0017] S503, the lithium hexafluorophosphate crystals after washing and purification are introduced into a drying kettle to be vacuum dried under the condition of a micro-negative pressure and a temperature of 70°C, and the drying time is 10 hours.

[0018] Preferably, the crystallization kettle used in the crystallization process in the step S502 comprises a basic assembly, a driving assembly is installed in the basic assembly, a scraping assembly provided in the basic assembly is fixedly assembled at the bottom of the driving assembly, a screening assembly adapted to the scraping assembly is assembled in the basic assembly, a pressurizing assembly is attached and assembled at the top of the screening assembly, and a limiting assembly is fixedly installed at the bottom of the screening assembly.

[0019] The driving assembly comprises a threaded cylinder, a driving screw is threadedly connected in the threaded cylinder, and a first locking assembly is fixedly installed at the top end of the driving screw.

[0020] The scraping assembly comprises a mounting plate fixed at the bottom end of the driving screw, both sides of the mounting plate are provided with accommodating grooves, the first half tooth plate is rotatably assembled in the accommodating grooves, the telescopic rod is integrally formed on the first half tooth plate, the scraping plate is fixedly assembled at the other end of the telescopic rod, the second half tooth plate is engagedly assembled on the inner side of the first half tooth plate, and the servo motor is fixedly assembled in the inner cavity of the mounting plate, and the output end of the servo motor and the second half tooth plate are fixedly assembled.

[0021] The screening assembly comprises a fixing ring assembled on the inner side wall of the base assembly, the top of the fixing ring is uniformly provided with buffers, and the top of the buffer is fixedly provided with a screen plate.

[0022] The limiting assembly comprises a second locking assembly fixed at the bottom of the screen plate, and the limiting plate is clampedly assembled in the second locking assembly.

[0023] Preferably, the base assembly comprises a kettle body, the bottom of the kettle body is fixedly provided with a supporting column, the bottom of the kettle body is fixedly provided with a discharge pipe in the middle, and the bottom right side of the kettle body is fixedly provided with a liquid discharge pipe.

[0024] Further preferably, the kettle body is provided with a kettle cover at the top, the top of the kettle cover is provided with a pressure relief valve and a pressure pump, and the control panel is fixedly assembled on the outer side wall of the kettle body.

[0025] Preferably, the driving assembly comprises a driving motor fixed at the top of the kettle cover, the output end of the driving motor is fixedly assembled through the top end of the kettle cover and the threaded cylinder, the threaded channel adapted to the driving screw is formed in the threaded cylinder, the length of the driving screw is the same as the depth of the threaded channel, and the size of the first locking assembly is smaller than the inner diameter of the threaded channel.

[0026] Preferably, the telescopic rod comprises an outer rod integrally formed with the first half tooth plate, the other end of the outer rod is insertedly assembled with an inner rod, the supporting spring is fixedly connected to the inner rod at one end of the inner rod extending into the inner cavity of the outer rod, the other end of the supporting spring is fixed on the inner side wall of the outer rod, and the other end of the inner rod is fixed on the scraping plate.

[0027] The first half tooth plate and the second half tooth plate are oppositely arranged, the front and rear widths of the accommodating grooves are the same as the width of the outer rod, the accommodating grooves are open grooves through the top and bottom, and the shaft seal is assembled at the assembly position of the output end of the servo motor and the mounting plate.

[0028] Preferably, the scraping plates are symmetrically arranged on both sides of the driving screw, the scraping plates are stainless steel rectangular plates, the end of the stainless steel rectangular plate is arc-shaped and connected with an arc-shaped plate, and the end of the arc-shaped plate is arc-shaped.

[0029] Preferably, the pressurizing assembly comprises a sliding plate slidingly assembled on the limiting plate, a bottom of the sliding plate is fixed with an outer cylinder sleeved outside the limiting plate, an inner side of the outer cylinder is installed with a supporting spring sleeved outside the limiting plate, and left and right sides of the bottom of the sliding plate are symmetrically fixed with protrusions.

[0030] Further preferably, the protrusions are semispherical, and the protrusions are matched with the scraping plate, and a transverse distance of the protrusions to the containing groove is 1 / 2 of a length of the scraping plate.

[0031] Preferably, the limiting assembly further comprises a circular channel opened in a middle position of the sieve plate, the limiting plate is a rectangular plate, and the sliding plate, the mounting plate and the driving screw are all provided with a guide channel matched with the limiting plate, and a length of the limiting plate is greater than a distance between the sieve plate and the threaded cylinder.

[0032] Preferably, the buffer comprises a base fixed on a top of the fixed ring, a top of the base is insertedly assembled with an inner cylinder, the inner cylinder is fixedly connected with a reset spring inside, and a bottom end of the reset spring is fixed on an inner side wall of the base.

[0033] Technical effects and advantages of the present application:

[0034] 1. The present application can effectively save raw materials, improve the preparation efficiency of lithium hexafluorophosphate, adapt to mass production demand, reduce the preparation process, reduce the preparation cost, solve the problem of taking out a large amount of hydrogen fluoride and phosphorus pentafluoride gas into the tail gas system in the synthesis reaction process, effectively recover hydrogen fluoride and continue to pass into the synthesis reaction kettle for recycling.

[0035] 2. The cooperation of the driving assembly, the first locking assembly and the scraping assembly can complete the stirring operation of the liquid in the kettle body, at this time, the scraping plate is purely used as a stirring structure.

[0036] 3. The driving assembly can promote the scraping assembly to scrape the crystals on the inner side wall of the kettle body every time the height adjustment is started, thereby increasing the scraping range of the crystals on the inner side wall of the kettle body, preventing the crystals from adhering to the inner side wall of the kettle body, and at the same time, the scraping plate can also play a stirring role during rotation, accelerating the crystallization speed of the crystals.

[0037] 4、The application can promote the scraping plate to scrape the crystalline crystals on the surface of the screen plate with the rotation of the scraping plate, prevent the crystals from being gathered and bonded on the surface of the screen plate to affect the screening effect of the crystals, and realize the extrusion and crushing of the large particles by the scraping plate cooperating with the screen plate, so that the homogenization treatment of the particle size is realized, the consistency of the crystal particle size is ensured, the screening of the crystal particles is facilitated, and the stirring effect is also achieved during the rotation of the scraping plate to speed up the crystallization speed of the crystals. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 It is a production process workflow diagram of the application.

[0039] Figure 2 It is a whole structure diagram of the application.

[0040] Figure 3 It is a whole structure diagram of the application.

[0041] Figure 4 It is a whole structure diagram of the application.

[0042] Figure 5 It is a whole structure diagram of the application.

[0043] Figure 6 It is an enlarged structure diagram of A part of the application.

[0044] Figure 7 It is an enlarged structure diagram of C part of the application.

[0045] Figure 8 It is an enlarged structure diagram of B part of the application.

[0046] Figure 9 It is a buffer structure diagram of the application.

[0047] In the figure: 11, kettle body; 12, kettle cover; 13, support column; 14, pressure pump; 15, pressure relief valve; 16, liquid discharge pipe; 17, discharge pipe; 18, control panel; 21, driving motor; 22, threaded cylinder; 23, driving screw; 24, first locking assembly; 31, mounting plate; 32, containing groove; 33, first half tooth plate; 34, telescopic rod; 35, scraping plate; 36, second half tooth plate; 37, servo motor; 41, fixed ring; 42, buffer; 421, base; 422, inner cylinder; 423, reset spring; 43, screen plate; 51, second locking assembly; 52, limiting plate; 53, circular channel; 61, sliding plate; 62, outer cylinder; 63, supporting spring; 64, protrusion. DETAILED DESCRIPTION

[0048] With reference to the accompanying drawings: the technical solutions in the embodiments of the present application will be apparently and completely described, obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments, based on the embodiments in the present application, all other embodiments obtained by the ordinary skilled in the art without creative labor belong to the protection scope of the present application.

[0049] First embodiment

[0050] The present application provides a production process of high-purity lithium hexafluorophosphate as shown in Figure 1 The process flow is as follows:

[0051] S1, lithium fluoride synthesis: self-made pure water is pumped into a synthesis kettle, bagged lithium carbonate is slowly added into the LiF synthesis kettle through the feeding port by appropriate control, then hydrofluoric acid is directly pumped into the high tank from the storage tank area by a pump (centrifugal pump) and then added into the LiF synthesis kettle, so that lithium carbonate and hydrofluoric acid are fully reacted in a liquid-solid phase under the condition of room temperature and 0.02 MPaG pressure and nitrogen protection, lithium fluoride is obtained, and the lithium fluoride is dehydrated and dried to obtain dry lithium fluoride, and the reaction equation is as follows:

[0052] Li2CO3+2HF——→2LiF+H2O+CO2

[0053] The reaction temperature is room temperature, the pressure is set to 0.03 MPaG, the reaction of hydrofluoric acid and lithium carbonate is an exothermic reaction, the temperature in the kettle gradually rises to about 30℃, the reaction lasts for 3.5h, after the reaction is completed, the reaction kettle is slowly vented for about 2h, and the CO2 waste gas generated in the reaction enters the total plant tail gas absorption main pipe.

[0054] Then the lithium fluoride is refined, that is, the lithium fluoride suspension obtained by the synthesis reaction is discharged into a centrifuge and centrifuged for about 20 minutes, the filtrate is returned to the LiF synthesis kettle for reuse, and the LiF filter residue is discharged into a drying machine and dried at a temperature of 120℃ for 12h.

[0055] S2, preparation of phosphorus pentafluoride gas: bagged phosphorus pentoxide is continuously fed into the HPF6 synthesis kettle through the feeding port at an appropriate speed, the synthesis kettle is cooled to normal with refrigerated brine, the inside air of the device is discharged with nitrogen first, then the HF metering tank (anhydrous hydrofluoric acid is pumped into the metering tank from the HF pump), and at the same time, the HPF6 synthesis kettle is entered in a quantitative form, the pressure is controlled to be 0.02 MPaG under the condition of room temperature, and the hydrofluoric acid and the phosphorus pentoxide are reacted under the protection of nitrogen, the reaction generates hexafluorophosphoric acid, and the reaction equation is as follows:

[0056] P2O5+12HF——→2HPF6+5H2O

[0057] The chemical reaction is an exothermic reaction, and the control pressure is 0.02 MPaG.

[0058] S3, the obtained hexafluorophosphoric acid solution is further reacted with sulfur trioxide at room temperature under the condition of a control pressure of 0.02 MPaG to generate phosphorus pentafluoride gas, that is, after the di-phosphorus pentoxide is fully reacted, the sulfur trioxide is pumped from the storage tank area into the metering tank and then continuously fed into the synthesis kettle at a speed (the control speed is 100-120 kg / h, and the dropping time needs to be determined according to the single batch input amount) to promote the obtained hexafluorophosphoric acid solution to fully react with the sulfur trioxide, and the further reaction is carried out at room temperature under the condition of a control pressure of 0.02 MPaG to generate phosphorus pentafluoride gas, and the reaction equation is:

[0059] HPF6+H2O+SO3→PF5+H2SO4+HF

[0060] The chemical reaction is controlled to be carried out at a pressure of 0.02 MPaG and room temperature, and the reaction time is 2 h. After the reaction is completed, the material is discharged into the intermediate tank, and then the mixed acid is fed into the intermediate reaction kettle by a centrifugal pump. Under the condition of room temperature and a control pressure of 0.02 MPaG, the hexafluorophosphoric acid is decomposed into PF5 and HF. After the reaction is completed, the mixed gas is fed into a condenser. Under the condition of a secondary condenser at a temperature of-20℃, PF5 and HF, SO3 are separated. PF5 is separated in the form of gas and fed into the LiPF6 synthesis kettle. HF and SO3 are discharged in the form of liquid to the HF intermediate reaction kettle. The sulfuric acid (mixed with a small amount of HF) generated in the intermediate reaction kettle is transported to the sulfuric acid intermediate tank by a delivery pump, and the transportation process takes about 2 h.

[0061] S4, according to the mass ratio of acetonitrile, toluene, and lithium fluoride: 25:15:1, acetonitrile and toluene are filled into the synthesis kettle, and the dried lithium fluoride is metered and continuously fed into the LiPF6 synthesis kettle by an electric hopper. LiF is dissolved and distributed in acetonitrile and toluene. Five fluorophosphorus gas is gradually introduced into the lithium fluoride mixed solvent and reacts with lithium fluoride to obtain the target crude product lithium hexafluorophosphate solution. The reaction is carried out under the protection of nitrogen, and the reaction equation is:

[0062] LiF+PF5→LiPF6

[0063] The reaction pressure is controlled to be 0.02 MPaG, and after the reaction is carried out at room temperature for 4 h, the excess PF5 is removed by nitrogen, and the nitrogen flushing time is about 2 h. Then, the material is discharged into the intermediate tank.

[0064] S5, purification of lithium hexafluorophosphate: the lithium hexafluorophosphate solution is further purified, crystallized, crushed, and dried to obtain high-purity lithium hexafluorophosphate crystals.

[0065] In the S5 step, the specific steps for purifying the lithium hexafluorophosphate solution are as follows:

[0066] S501, the coarse material in the intermediate tank is pumped into the concentration kettle by a centrifugal pump to recover the solvent, and is distilled at normal pressure and at a temperature of 70 DEG C for 8-9 hours, the distillate collected from the kettle top is condensed by a primary and secondary condenser and then recycled, and then dichloroethane is introduced to further displace the solvent, so that the purification process is completed;

[0067] S502, the material at the bottom of the tower is pumped into the crystallization kettle by a centrifugal pump for crystallization treatment, the crystallization kettle is controlled to cool and crystallize at a pressure of 0.03 MPaG and a temperature of 0 DEG C for 3-4 hours, after the crystallization is completed, the mother liquor is collected from the bottom of the kettle into a mother liquor tank for reuse, dichloroethane is introduced into the crystallization kettle at a ratio of solid:dichloroethane of 1:2 to further wash the impurities in the crystals, and the washing liquid is pumped from the bottom of the kettle into a washing liquid tank for second washing after being washed for 3-4 hours, and is directly subjected to screening treatment to ensure that the particle size of the lithium hexafluorophosphate after crystallization is uniform, so that the caking during crystallization is avoided, and the crushing of the crystals during crystallization is realized.

[0068] S503, the lithium hexafluorophosphate crystal after washing and purification is introduced into a drying kettle to be vacuum dried at a temperature of 70 DEG C under a slight negative pressure, and the drying time is 10 hours.

[0069] S504, the packaging process

[0070] The lithium hexafluorophosphate crystal dried under nitrogen protection is packaged by a packaging machine under nitrogen sealing protection, so that the purification of the product lithium hexafluorophosphate is completed.

[0071] Second embodiment

[0072] The present application provides a crystallization kettle as shown in Figures 2 to 9 The crystallization kettle comprises a base assembly, a driving assembly is installed in the base assembly, a scraping assembly is fixedly assembled at the bottom of the driving assembly and arranged in the base assembly, a screening assembly is assembled in the base assembly and matched with the scraping assembly, a pressurizing assembly is matched and assembled at the top of the screening assembly, and a limiting assembly is fixedly installed at the bottom of the screening assembly.

[0073] Please refer to Figure 2, the base assembly comprises a kettle body 11, a support column 13 is fixedly arranged at the bottom of the kettle body 11, a discharge pipe 17 is fixedly arranged at the middle of the bottom of the kettle body 11, a liquid discharge pipe 16 is fixedly arranged at the right side of the bottom of the kettle body 11, a kettle cover 12 is arranged at the top of the kettle body 11, a pressure relief valve 15 and a pressure pump 14 are arranged at the top of the kettle cover 12, a control panel 18 is fixedly arranged on the outer side wall of the kettle body 11, a liquid inlet pipe is fixedly arranged at the top of the rear side of the kettle body 11, and the liquid inlet pipe and the output end of the centrifugal pump are fixedly arranged, so that the material can be punched into the kettle body 11 through the liquid inlet pipe by the centrifugal pump after the lithium hexafluorophosphate is purified, a liquid guide pipe is communicatively arranged on the kettle cover 12, so that the introduction of the displacement solvent can be realized, and an electromagnetic valve is arranged on the liquid guide pipe.

[0074] In use, under the premise that the sealing installation between the kettle cover 12 and the kettle body 11 is ensured, then the centrifugal pump is controlled to work through the control panel 18, the material is punched into the kettle body 11 through the liquid inlet pipe by the centrifugal pump, at the same time, the pressure pump 14 works to adjust the pressure in the kettle body 11, the control pressure is 0.03 MPaG, and the pressure relief valve 15 can realize pressure relief operation when the pressure in the kettle body 11 increases, so that the relatively stable pressure value in the kettle body 11 is ensured, then the mother liquor is introduced through the liquid guide pipe.

[0075] It is worth noting that the kettle body 11 is sleeved with a cooling channel, a water guide pipe that communicates with the cooling channel is fixedly arranged on the kettle body 11, the water guide pipe is connected with an external pump, a temperature sensor is arranged in the kettle body 11, the temperature in the kettle body 11 can be monitored in real time, the delivery control of the cooling liquid can be realized through the control panel 18, the cooling liquid can be introduced into the cooling channel through the external pump, the temperature in the kettle body 11 can be controlled, and the temperature of the cooling liquid is controlled to be minus 8-5 degrees, so that the temperature in the kettle body 11 is controlled through heat exchange between the cooling liquid in the cooling channel and the kettle body 11, the internal temperature of the kettle body 11 is controlled to be about 0 during the crystallization process of the kettle body 11, the cooling and crystallization time is 3-4 hours, the problem that the reaction is violent and explosion is caused due to large heat production during the reaction process can be solved, the reaction conditions can be controlled, and a safe working environment is provided for the reaction.

[0076] In addition, an electric control valve is arranged on the liquid discharge pipe 16, so that the mother liquor can be discharged by opening the electric control valve through the control panel 18 after the crystallization is completed, the mother liquor can be collected from the bottom of the kettle body 11 into a mother liquor tank for reuse, at the same time, a washing solvent is introduced through the liquid guide pipe, the impurities in the crystalline crystal are further washed, the washing solvent is pumped into a washing liquid tank from the bottom of the kettle body 11 after being washed for 3-4 hours for second-time washing, and finally the crystalline crystal is discharged through the discharge pipe 17.

[0077] Please refer to Figures 2-5The driving assembly comprises a threaded cylinder 22, a driving screw 23 is threadedly connected in the threaded cylinder 22, a first locking assembly 24 is fixedly installed at the top end of the driving screw 23, the driving assembly comprises a driving motor 21 fixed at the top of the kettle cover 12, the output end of the driving motor 21 is fixedly assembled through the top end of the kettle cover 12 and the threaded cylinder 22, a threaded channel is formed in the threaded cylinder 22 and is matched with the driving screw 23, the length of the driving screw 23 is the same as the depth of the threaded channel, and the size of the first locking assembly 24 is smaller than the inner diameter of the threaded channel.

[0078] Please refer to Figure 5 and Figure 8 The limiting assembly comprises a second locking assembly 51 fixed at the bottom of the sieve plate 43, a limiting plate 52 is clamped and assembled in the second locking assembly 51, the limiting assembly further comprises a circular channel 53 formed in the middle position of the sieve plate 43, the limiting plate 52 is a rectangular plate, and a guide channel matched with the limiting plate 52 is formed in the sliding plate 61, the mounting plate 31 and the driving screw 23, and the limiting plate 52 is slidingly assembled with the sliding plate 61, the mounting plate 31 and the driving screw 23, the hole diameter of the circular channel 53 is larger than the size of the limiting plate 52, and the length of the limiting plate 52 is greater than the distance between the sieve plate 43 and the threaded cylinder 22.

[0079] When the device is in use, the second locking assembly 51 is started and the first locking assembly 24 is closed at the same time through the control panel 18, so that the second locking assembly 51 can limit the limiting plate 52, so that the limiting plate 52 can limit the axial direction of the driving screw 23, so that the driving screw 23 cannot rotate relative to the axis, so that the threaded cylinder 22 can be driven to rotate when the driving motor 21 works, so that the driving screw 23 is driven to move up and down on the limiting plate 52 through the threaded connection of the threaded cylinder 22 and the driving screw 23 (i.e. the driving screw 23 moves up when the driving motor 21 rotates in the positive direction, otherwise the driving screw 23 moves down), and the action process is recorded as the height adjustment action.

[0080] In addition, when the second locking assembly 51 is closed and the first locking assembly 24 is opened at the same time through the control panel 18, the first locking assembly 24 can prevent the driving screw 23 and the threaded cylinder 22 from rotating relative to each other, and the limiting plate 52 is out of the limiting action of the second locking assembly 51, so that the threaded cylinder 22, the driving screw 23 and the scraping assembly can be driven to rotate synchronously when the driving motor 21 works, and the action process is recorded as the rotation action.

[0081] Please refer to Figures 3-6The scraping assembly comprises a mounting plate 31 fixed at the bottom end of the driving screw 23, and a containing groove 32 is formed on the left and right sides of the mounting plate 31, and a first half-toothed plate 33 is rotatably assembled in the containing groove 32, and an extension rod 34 is integrally formed on the first half-toothed plate 33, and a scraping plate 35 is fixedly assembled at the other end of the extension rod 34, and a second half-toothed plate 36 is meshingly assembled on the inner side of the first half-toothed plate 33, and a servo motor 37 is fixedly assembled in the inner cavity of the mounting plate 31, and the output end of the servo motor 37 is fixedly assembled with the second half-toothed plate 36, and the extension rod 34 comprises an outer rod integrally formed with the first half-toothed plate 33, and an inner rod is insertedly assembled at the other end of the outer rod, and a supporting spring is fixedly connected to the inner rod and extended into the inner cavity of the outer rod, and the other end of the supporting spring is fixed on the inner side wall of the outer rod, and the other end of the inner rod is fixed on the scraping plate 35.

[0082] The scraping assembly can be in three different working states in actual use, namely:

[0083] (1) When the scraping assembly is used as a stirring structure, the servo motor 37 is controlled to rotate in the forward direction through the control panel 18, so that the second half-toothed plate 36 is driven to rotate, and the extension rod 34 is driven to rotate counterclockwise around the rotating shaft through the meshing action of the second half-toothed plate 36 and the first half-toothed plate 33, so that the scraping plate 35 at the end of the extension rod 34 can rotate upward, and the scraping plate 35 and the inner side wall of the kettle body 11 are separated from each other, so that the scraping plate 35 is driven to rotate together with the mounting plate 31 when the driving motor 21 drives the scraping plate 35 on the mounting plate 31 to rotate through the threaded cylinder 22 and the driving screw 23, and the scraping plate 35 completes the stirring operation of the liquid in the kettle body 11 together with the mounting plate 31, and at this time, the scraping plate 35 is purely used as a stirring structure.

[0084] (2) When the scraping assembly acts as a scraping structure, the servo motor 37 is controlled to move by the control panel 18, and the second half-toothed plate 36 and the first half-toothed plate 33 are engaged to drive the telescopic rod 34 to rotate clockwise around the rotating shaft. In the rotating process, the scraping plate 35 first contacts the inner wall of the kettle body 11. In this process, as the telescopic rod 34 continues to rotate, the extrusion force of the kettle body 11 on the scraping plate 35 increases, which can cause the telescopic rod 34 to shrink, and then the scraping plate 35 can rotate with the telescopic rod 34 until the telescopic rod 34 is in a horizontal state. At this time, the scraping plate 35 is attached to the inner wall of the kettle body 11, and then the height adjustment action is completed by the control panel 18. This can adjust the height position of the scraping assembly, facilitate the height adaptation range of the scraping assembly, and complete the rotation action by the control panel 18 after the height adjustment is completed. This can drive the scraping assembly to scrape the crystalline crystals on the inner wall of the kettle body 11, preventing the crystals from adhering to the inner wall of the kettle body 11. This can provide auxiliary action for preventing crystalline crystal agglomeration. At the same time, each time the height adjustment is performed by the driving assembly, the rotation action is started again to cause the scraping assembly to scrape the crystals on the inner wall of the kettle body 11, thereby increasing the scraping range of the crystals on the inner wall of the kettle body 11, preventing the crystals from adhering to the inner wall of the kettle body 11. At the same time, the scraping plate 35 can also play a stirring role during rotation, accelerating the crystallization speed of the crystals.

[0085] (3) When the scraping assembly acts as a structure for improving the granularity of the crystals, the height adjustment action is completed by the control panel 18, so that the scraping assembly is in the lowest position. At this time, the servo motor 37 is controlled to rotate counterclockwise, which can drive the second half-toothed plate 36 to rotate counterclockwise, thereby synchronously driving the first half-toothed plate 33 to rotate clockwise, synchronously driving the telescopic rod 34 and the scraping plate 35 to rotate clockwise. In the process of the scraping plate 35 separating from the inner wall of the kettle body 11, because the distance between the middle position of the scraping plate 35 and the rotating shaft is less than the distance between the outer end of the scraping plate 35 and the rotating shaft, the telescopic rod 34 is in a continuous shrinking state before the outer end of the scraping plate 35 reaches a position where the rotating shaft is in a horizontal line. When the end of the scraping plate 35 is below the horizontal line where the rotating shaft is located, as the rotation angle of the telescopic rod 34 increases, the extrusion force between the scraping plate 35 and the inner wall of the kettle body 11 gradually decreases. At this time, the telescopic rod 34 is extended until the scraping plate 35 and the inner wall of the kettle body 11 are separated. The length of the telescopic rod 34 is reset, and then the scraping plate 35 continues to rotate with the rotation of the first half-toothed plate 33.

[0086] Please refer to Figure 5 and Figure 7 The screening assembly includes a fixed ring 41 assembled on the inner wall of the base assembly. The top of the fixed ring 41 is uniformly provided with a buffer 42, and the top of the buffer 42 is fixedly provided with a sieve plate 43.

[0087] Thus, as the telescopic rod 34 drives the scraper 35 to rotate, when the bottom end of the scraper 35 contacts the sieve plate 43, the sieve plate 43 will generate a pressing force on the scraper 35, which will promote the telescopic rod 34 to shrink synchronously, and the pressing force will act on the buffer 42 synchronously to promote the buffer 42 to shrink, so that the telescopic rod 34 and the buffer 42 are compressed synchronously until the scraper 35 is completely attached to the sieve plate 43, at which time the telescopic rod 34 and the buffer 42 are in a compressed state and are in a static state, which facilitates the pressing force of the scraper 35 on the sieve plate 43, and facilitates the scraping effect of the scraper 35 on the crystal materials on the sieve plate 43, and then the control panel 18 is rotated to drive the telescopic rod 34 and the scraper 35 to rotate, which can promote the scraper 35 to scrape the crystal on the surface of the sieve plate 43 during the rotation of the scraper 35, preventing the crystal from being aggregated and bonded on the surface of the sieve plate 43 to affect the screening effect of the crystal, and at the same time, the use of the scraper 35 with the sieve plate 43 can achieve the pressing and crushing of large particles, which facilitates the homogenization treatment of the particle size and ensures the consistency of the crystal particle size, facilitating the screening of the crystal particles, and during the rotation of the scraper 35, the stirring effect can also be achieved to accelerate the crystallization speed of the crystal.

[0088] Referring to Figures 5-6 , the first half tooth plate 33 and the second half tooth plate 36 are oppositely arranged, and the front and rear widths of the accommodating groove 32 and the width of the outer rod are the same, and the accommodating groove 32 is an open groove penetrating from top to bottom. The output end of the servo motor 37 and the assembly position of the mounting plate 31 are assembled with a shaft seal, which can drive the telescopic rod 34 and the scraper 35 to achieve position adjustment between positive ninety degrees and negative ninety degrees under the drive of the servo motor 37, facilitating different use effects when the scraper 35 is in different positions, and greatly increasing the crystallization effect of the material.

[0089] Referring to Figure 5 , the scraper 35 is symmetrically arranged on the left and right sides of the drive screw 23, and the scraper 35 is a stainless steel rectangular plate, and the end of the stainless steel rectangular plate is arc-shaped and connected with an arc-shaped plate, and the end of the arc-shaped plate is arc-shaped. Thus, when the two groups of scraping assemblies are used, the use state of the two groups of scraping assemblies can be adjusted according to actual needs, the functions of the two groups of scraping assemblies can be freely combined according to actual needs, and the crystallization speed and crystallization particle uniformity of the crystallization kettle are greatly improved.

[0090] Third embodiment

[0091] When the scraper 35 is in the negative ninety-degree position, the scraper 35 only rotates in the circumferential direction to complete the scraping of the crystalline crystal, prevent the crystal from being aggregated on the sieve plate 43, and can play a role in scraping the crystal, and during the rotation of the scraper 35, the crystal particles can be conveniently discharged and screened, but the screening effect of the material is limited. Based on this, the applicant proposes the following improvement scheme:

[0092] Referring to Figure 5 and Figure 8 The pressing assembly comprises a sliding plate 61 slidingly assembled on the limiting plate 52, the bottom of the sliding plate 61 is fixed with an outer cylinder 62 sleeved on the outer side of the limiting plate 52, the inner side of the outer cylinder 62 is provided with a supporting spring 63 sleeved on the outer side of the limiting plate 52, the bottom of the sliding plate 61 is symmetrically fixed with protrusions 64 on the left and right sides, the protrusions 64 are semispherical, the protrusions 64 are matched with the scraping plate 35, and the transverse distance from the protrusions 64 to the containing groove 32 is 1 / 2 of the length of the scraping plate 35.

[0093] During the rotation of the scraping plate 35, when the end of the scraping plate 35 rotates to correspond to the protrusions 64 on the bottom of the sliding plate 61, the arc-shaped end of the scraping plate 35 can impact the protrusions 64, so that the protrusions 64 and the arc-shaped end of the scraping plate 35 are extruded to drive the sliding plate 61 to move upward along the limiting plate 52 by a length against the stretching and rebounding force of the supporting spring 63, the length is the length of the protrusions 64 and the arc-shaped end of the scraping plate 35 in the vertical direction, when the scraping plate 35 and the protrusions 64 are separated, the supporting spring 63 drives the sliding plate 61 to move downward, which can impact the screen plate 43, so as to drive the buffer 42 to be compressed, so that the screen plate 43 is driven to move downward, so that the pressing assembly can extrude the screen plate 43 frequently by the frequent lifting action of the scraping plate 35 on the pressing assembly, and then the screen plate 43 is reset under the action of the buffer 42, so as to complete the vibrating and screening effect of the screen plate 43, facilitate the screening effect of the screen plate 43 on the material scraped by the scraping plate 35, and facilitate the screening of the crystalline material.

[0094] Referring to Figure 9 The buffer 42 comprises a base 421 fixed on the top of the fixed ring 41, the top of the base 421 is insertedly assembled with an inner cylinder 422, the inner cylinder 422 is fixedly connected with a reset spring 423, and the bottom end of the reset spring 423 is fixed on the inner side wall of the base 421.

[0095] It is worth mentioning that when the scraper 35 is completely attached to the screen plate 43, the telescopic rod 34 and the buffer 42 are in a compressed state and in a static state, when the scraper 35 is lifted up to the pressing assembly, the scraper 35 is subjected to a squeezing force, the squeezing force acts on the buffer 42 and in turn drives the screen plate 43 to move downward again, and the telescopic rod 34 is compressed again, and then the screen plate 43 is quickly lifted up to reset under the action of the buffer 42, and the telescopic rod 34 also moves downward to drive the scraper 35 to reset, that is, the scraper 35 and the screen plate 43 are in contact and still in the initial static state, which is convenient for the convex 64 on the pressing assembly to be lifted up again when the scraper 35 rotates, and the cycle is repeated, the pressing assembly applies pressure to the screen plate 43, and the screen plate 43 is vibrated to complete the screening of the material.

[0096] Finally, it should be pointed out that the above only describes the preferred embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent replacements to some technical features, as long as they are within the spirit and principles of the present application. Any modification, equivalent replacement, improvement, etc. shall be included in the protection scope of the present application.

Claims

1. A production process for high-purity lithium hexafluorophosphate, characterized in that: The process includes the following steps: S1. Under room temperature conditions and with a controlled pressure of 0.02 MPaG, lithium carbonate and hydrofluoric acid undergo a liquid-solid phase reaction under nitrogen protection to obtain lithium fluoride. The lithium fluoride is then dehydrated and dried to obtain dry-based lithium fluoride. S2. Under room temperature conditions and with a controlled pressure of 0.02 MPaG, hydrofluoric acid reacts with phosphorus pentoxide under nitrogen protection to produce hexafluorophosphoric acid. S3. The obtained hexafluorophosphoric acid solution reacts with sulfur trioxide at room temperature and under a controlled pressure of 0.02 MPaG to produce phosphorus pentafluoride gas. S4. Gas is introduced into the lithium fluoride mixed solvent to react with lithium fluoride, and the reaction yields the target crude product lithium hexafluorophosphate solution. Ensure that the reaction is carried out under nitrogen protection. S5, after further purification, crystallization, pulverization and drying of the lithium hexafluorophosphate solution, can yield high-purity lithium hexafluorophosphate crystals; In step S5, the specific steps for purifying the lithium hexafluorophosphate solution are as follows: S501. The coarse material in the intermediate tank is pumped into the concentration kettle by a centrifugal pump to recover the solvent. It is distilled for 8-9 hours under normal pressure and 70℃. The fraction taken from the top of the kettle is condensed and recycled after being condensed by the first and second stage condensers. Then, dichloroethane is introduced to further displace the solvent, thus completing the purification process. S502. The material at the bottom of the tower is pumped into the crystallization kettle by a centrifugal pump for crystallization. The crystallization kettle is controlled to cool and crystallize for 3-4 hours under the conditions of 0.03 MPaG pressure and 0℃ temperature. After crystallization, the mother liquor is collected from the bottom of the kettle into the mother liquor tank for reuse. Dichloroethane is introduced into the crystallization kettle at a ratio of 1:2 (solid:dichloroethane) to further wash the impurities in the crystals. After washing for 3-4 hours, the washing liquid is pumped from the bottom of the kettle into the washing liquid tank for a second washing and reuse. It is then directly screened to ensure that the lithium hexafluorophosphate particles after crystallization are of uniform size and to avoid agglomeration during the crystallization process. The crystals can be crushed during the crystallization process. S503. After washing and purifying, the lithium hexafluorophosphate crystals are placed in a drying kettle and vacuum dried under slight negative pressure and at a temperature of 70°C for 10 hours. The crystallization vessel used in step S502 crystallization process includes a base component, a drive component installed inside the base component, a scraper component fixedly mounted at the bottom of the drive component and installed inside the base component, a sieve component adapted to the scraper component, a pressure component fitted to the top center of the sieve component, and a limit component fixedly mounted at the bottom of the sieve component. The drive assembly includes a threaded cylinder (22), which is internally threaded with a drive screw (23), and a first locking assembly (24) is fixedly installed at the top end of the drive screw (23). The scraping assembly includes a mounting plate (31) fixed to the bottom of the drive screw (23). The mounting plate (31) has receiving grooves (32) on both the left and right sides. A first half-tooth plate (33) is rotatably mounted in the receiving groove (32). A telescopic rod (34) is integrally formed on the first half-tooth plate (33). A scraper plate (35) is fixedly mounted on the other end of the telescopic rod (34). A second half-tooth plate (36) is meshed with the inner side of the first half-tooth plate (33). A servo motor (37) is fixedly mounted in the inner cavity of the mounting plate (31). The output end of the servo motor (37) is fixedly mounted with the second half-tooth plate (36). The screening assembly includes a fixing ring (41) mounted on the inner wall of the base assembly, and buffers (42) are evenly distributed on the top of the fixing ring (41), and a screen plate (43) is fixedly mounted on the top of the buffers (42). The limiting assembly includes a second locking assembly (51) fixed to the bottom of the sieve plate (43), and a limiting plate (52) is engaged within the second locking assembly (51).

2. The production process for high-purity lithium hexafluorophosphate according to claim 1, characterized in that: The basic components include a vessel body (11), a support column (13) is fixedly mounted at the bottom of the vessel body (11), a discharge pipe (17) is fixedly mounted in the middle of the bottom of the vessel body (11), and a drain pipe (16) is fixedly mounted on the right side of the bottom of the vessel body (11). The top of the vessel body (11) is fitted with a vessel lid (12), and the top of the vessel lid (12) is fitted with a pressure relief valve (15) and a pressure pump (14). A control panel (18) is fixedly fitted on the outer wall of the vessel body (11).

3. The production process for high-purity lithium hexafluorophosphate according to claim 2, characterized in that: The drive assembly includes a drive motor (21) fixed to the top of the lid (12). The output end of the drive motor (21) passes through the lid (12) and the top of the threaded cylinder (22) and is fixedly assembled. The threaded cylinder (22) has a threaded channel that matches the drive screw (23). The length of the drive screw (23) is the same as the depth of the threaded channel. The size of the first locking assembly (24) is smaller than the inner diameter of the threaded channel.

4. The production process for high-purity lithium hexafluorophosphate according to claim 1, characterized in that: The telescopic rod (34) includes an outer rod integrally formed with the first half toothed plate (33), an inner rod is inserted and assembled at the other end of the outer rod, and a support spring is fixedly connected to one end of the inner rod into the inner cavity of the outer rod, and the other end of the support spring is fixed on the inner side wall of the outer rod, and the other end of the inner rod is fixed on the scraper plate (35). The first half-tooth plate (33) and the second half-tooth plate (36) are arranged opposite to each other, and the front and rear width of the receiving groove (32) is the same as the width of the outer rod. The receiving groove (32) is an open groove that runs through the top and bottom. The output end of the servo motor (37) and the assembly point of the mounting plate (31) are equipped with a shaft seal.

5. The production process for high-purity lithium hexafluorophosphate according to claim 4, characterized in that: The scraper (35) is symmetrically arranged on the left and right sides of the drive screw (23), and the scraper (35) is a stainless steel rectangular plate, and the end of the stainless steel rectangular plate is connected to an arc plate with an arc transition, and the end of the arc plate is arc-shaped.

6. The production process for high-purity lithium hexafluorophosphate according to claim 1, characterized in that: The pressurizing assembly includes a slide plate (61) slidably mounted on a limiting plate (52). The bottom of the slide plate (61) is fixed with an outer cylinder (62) sleeved on the outside of the limiting plate (52). The inner side of the outer cylinder (62) is fitted with a support spring (63) sleeved on the outside of the limiting plate (52). The bottom of the slide plate (61) is symmetrically fixed with protrusions (64) on the left and right sides. The protrusion (64) is hemispherical and is adapted to the scraper (35). The lateral distance from the protrusion (64) to the receiving groove (32) is 1 / 2 of the length of the scraper (35).

7. The production process for high-purity lithium hexafluorophosphate according to claim 6, characterized in that: The limiting component also includes a circular channel (53) located in the middle of the sieve plate (43). The limiting plate (52) is a rectangular plate, and the sliding plate (61), the mounting plate (31) and the drive screw (23) are all provided with guide channels that are compatible with the limiting plate (52). The length of the limiting plate (52) is greater than the distance between the sieve plate (43) and the threaded cylinder (22).

8. The production process for high-purity lithium hexafluorophosphate according to claim 1, characterized in that: The buffer (42) includes a base (421) fixed to the top of the fixing ring (41), an inner cylinder (422) is inserted into the top of the base (421), a return spring (423) is fixedly connected inside the inner cylinder (422), and the bottom end of the return spring (423) is fixed to the inner side wall of the base (421).

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